Biofilters

Water Res, 2001 Sep, 35(13), 3097 - 108
Biofilter treatment of aquaculture water for reuse applications; Yang L et al.; Biotreatment of aquaculture water for recirculation purposes is a sensible mean to support the further growth of aquaculture industry without excessive water demands that are environmentally unsustainable . This study evaluates the efficacy of biofilter treatment of an eel (Anguilla japonica) culture pond water using different filter media and flow scheme arrangements . The experimental results demonstrate that biofilter systems packed with suitable filter media are capable of improving the quality of effluents for recirculation applications . The characteristics of the filter media appear to be more critical than biofilter flow scheme arrangements in affecting the efficacy of the biofilter treatment . Filter media with surface and structural characteristics are conducive to the development of biofilms and the capture of organic suspended matter are desirable to ensure good and consistent biofilter performance . Under such circumstances the bacterial "consortia" in the biofilter are capable of utilizing the captured organic suspended matter as an alternative substrate to support their metabolic activities when the concentration of the primary substrate (i.e., BOD) is low . For the eel pond water, a biofilter packed with filter media having cross-link structures and a high bed porosity, followed by another biofilter packed with a type of filter media having rough surfaces, produced the best results under the conditions tested . Moreover, a preliminary cost-benefit analysis confirms its cost advantages.

Waste Manag, 2001, 21(6), 489 - 98
Treatment of methylacetate waste gas using a trickle-bed air biofilter; Lu C et al.; The trickle-bed air biofilter (TBAB) performance for methylacetate (MA) removal from waste gases was evaluated under different gas flow rates and influent concentrations . In the pseudo-steady-state conditions, the elimination capacity increased but the removal efficiency decreased with the increase of MA loading . More than 95 and 90% removal efficiencies were achieved for influent MA loadings below 390 and 727 g/m3/h, respectively . The TBAB appears to be a very effective treatment process for controlling MA emission under low to high loading conditions, and the effectiveness could be maintained over 190 days of laboratory operation.

J Ind Microbiol Biotechnol, 2001 Apr, 26(4), 196 - 202
Microbial treatment of a styrene-contaminated air stream in a biofilter with high elimination capacities; Juneson C et al.; A styrene-utilizing mixed microbial culture was isolated and utilized in a biofilter for the biological treatment of a contaminated air stream . Biofilter media consisted of composted wood bark and yard waste . The biofilters were acclimated at 120 s residence time and further evaluated at 60 and 30 s gas residence times . The biofilters received organic loading rates of up to 350 g/m(3) h . The styrene volumetric removal rate was a function of the organic loading rate and increased with increasing loading rates . Average volumetric removal rates of 69-118 g/m(3) h observed in our studies were higher than reported values for styrene biofilters . Average styrene removal efficiencies ranged from 65% to 75% (maximum 100%) . Axial analysis of styrene concentration along the column indicated that the bulk of the styrene removal occurred in the first section of the biofilter . Analyses of the media indicated that the moisture content of the first section (50-55% w/w) was significantly lower than in the second and third sections (65-70% w/w) . The pressure drops across the biofilter were low due to the high concentration of large media particles . The total pressure drops were 1-3, 4-6, and 10-16 mm for the 120-, 60-, and 30-s residence time periods, respectively.

Hepatogastroenterology, 2001 May-Jun, 48(39), 752 - 6
The intracorporeal autoorganic biofilter of portal blood in portal hypertension surgery; Kakabadze Z et al.; BACKGROUND/AIMS: The authors present the new surgical treatment method for portal hypertension by means of intracorporeal autoorganic biofilter of portal blood at the portosystemic shunt pathway . The hepatized spleen is used as the organic biofilter of portal blood . METHODOLOGY: The experiments were carried out on 20 mongrel dogs, both sexes, 18-20 kg of body weight . The animals were divided into the four equal groups . The comparative evaluation of portal hypertension treatment efficiency by means of several vascular portosystemic shunts were performed after the portal hypertension modeling . On the animals of groups I and II, the mesenterico-caval and splenorenal shunts were performed, respectively . The hepatized autospleen was involved in the portosystemic shunt pathway in the animals of group III . The animals of group IV served as controls . RESULTS: The reduction in perfusional pressure of the blood which flows to the liver led to damage of the organ's functional possibilities, significant disturbances to the hemodynamics and reduction of the liver detoxification possibilities, respectively, for several portocaval shunt creations during the portal hypertension model . On the other hand, the undetoxificated portal blood entrance into the system blood flow via the created shunt over the liver increased . CONCLUSIONS: The hepatized autospleen insertion into the portosystemic bloodflow gave us the opportunity to perform the dosage passing of portal blood into the systemic bloodflow and to maintain the pressure of the portal blood, which flows to the liver . Moreover, the hepatized autospleen has shown such specific liver functions as glucogenesis, albumin synthesis and others.

Chemosphere, 2001 Jul, 44(2), 173 - 80
Treatment of N,N-dimethylacetamide waste gas by a trickle-bed air biofilter; Lu C et al.; The system performance of a trickle-bed air biofilter (TBAB) for treating N,N-dimethylacetamide (DMAC) waste gas was investigated under different gas flow rates and influent concentrations . In the pseudo-steady-state conditions, the DMAC elimination capacity increased but the removal efficiency decreased as the influent loading increased . More than 90% and 80% DMAC removal efficiencies are achieved for influent loadings below 20.2 and 34.5 g DMAC/m3/h, respectively . The TBAB appears to be an effective treatment process for controlling DMAC emission with low-to-medium loadings and the effectiveness could be maintained over a long-period operation.

Water Sci Technol, 2001, 43(11), 35 - 42
Polyurethane foam based biofilter media for toluene removal; Moe WM et al.; Polyurethane foam medium was manufactured and analyzed to determine its suitability as a solid support medium for use in gas-phase biofilters . Physical and chemical studies were conducted to determine the medium's characteristics . The medium's ability to support an active biofilm capable of degrading volatile organic compounds was assessed using a laboratory scale biofilter fed a model waste stream containing toluene for more than 250 days with empty bed residence times (EBRTs) ranging from two to four minutes . Results are presented that show how a polyurethane foam medium with high porosity, suitable pore size, low density, and an ability to sorb water was able to remove over 99% of the influent toluene when fed at a concentration of 200 ppm . An operating strategy is described which effectively prevented two problems common to conventionally operated biofilter systems: nutrient limitations and biosolid accumulation.

Environ Manage, 2001 Jul, 28(1), 131 - 40
The environmental impact of shrimp aquaculture: causes, effects, and mitigating alternatives; Paez-Osuna F; Attracted by the demand for shrimp in the developed countries, shrimp aquaculture has expanded rapidly, mainly in the subtropical and tropical lowlands of America and Asia . This work provides a global review and viewpoint on the environmental impacts of shrimp aquaculture, considering the causes and effects of the siting and operation of shrimp ponds and abandonment of farm facilities . Additionally, mitigating alternatives are discussed . To date, approximately 1-1.5 million ha of coastal lowlands have been converted into shrimp ponds, comprising mainly salt flats, mangrove areas, marshes, and agricultural lands . The impact of shrimp farming of most concern is the destruction of mangroves and salt marshes for pond construction . Compatibility with other users, the presence of buffer zones, maintaining an acceptable balance between mangroves and shrimp pond area, improved pond design, reduction of water exchange, and an improved residence time of water, size and capacity to assimilate effluents of the water body, are examples of ways to mitigate the adverse effects . The use of mangroves and halophytes as biofilters of shrimp pond effluents offers an attractive tool for reducing the impact in those regions where mangrove wetlands and appropriate conditions for halophyte plantations exist . Healthy seed supply, good feed with the use of prophylactic agents (including probiotics), good water quality, and lower stocking densities are examples of actions suggested to control disease in shrimp farming . Finally, in the context of integrated management, research priorities are suggested.

Int J Hyg Environ Health, 2001 May, 203(4), 335 - 45
Reduction potential of microbial, odour and ammonia emissions from a pig facility by biofilters; Martens W et al.; The intention of this study was the determination of the potential to reduce specific microbial bioaerosol (cultivable bacteria and fungi, total cell counts of microbes, airborne endotoxins and microbial volatile organic compounds, MVOC), odour and ammonia emissions from a pig facility by biofilters . Five identical biofilter units in half technical scale were filled with different filter materials (Biochips, coconut-peat, wood-bark, pellets + bark and compost) and connected in parallel to a piggery . The results showed obvious differences between the filter materials . Numbers of airborne cultivable bacteria were decreased by ca . 70 to 95% and the total counts of bacterial cells from ca . 25 to (>) 90% . The total amount of fungal cells was reduced by at least 60%, although the percentage of cultivable moulds in the air after passing the filters was sometimes higher than before . Airborne endotoxins and MVOC were effectively reduced by all filter materials to at least 90% . Regarding odour, the average reduction was between 40 and 83%, whereas only one of the filters proved to be capable of slightly reducing the ammonia emissions . No relationships between odour/ammonia and microbial bioaerosols with regard to the reduction efficiency of the different filter materials or the total load of the emitted air could be established . A tendency could be shown, that biofilters best capable to reduce odour emitted slightly more airborne bacteria, both cultivable and total cell counts.

Huan Jing Ke Xue, 2001 Mar, 22(2), 31 - 5
{Biological removal of VOCs emissions}; Li G et al.; The designed test conditions were following: vacancy velocity was from 0.7 cm/s to 3.5 cm/s, retention time was from 30 s to 80 s . Column activated carbon was selected as the filler of the reactor and toluene was taken as representative of VOCs . The biodegradation of toluene using biofilter reactor and the influence of concentration, flow and humidity on the toluene removal were investigated and the removal model was set up . The experimental results showed that the biofilter reactor had higher toluene removing ability . The observation of biotic community demonstrated that the microbes consisted of fungi, bacillus and spore bacillus . Of them spore bacillus was dominant.

J Ind Microbiol Biotechnol, 2001 Mar, 26(3), 127 - 33
Themophilic biofiltration of methanol and alpha-pinene; Dhamwichukorn S et al.; Biofiltration systems utilizing thermophilic (55 degrees C) bacteria were constructed and tested for the removal of methanol and alpha-pinene--two important volatile organic compounds (VOCs) in the forest products industry . Thermophilic bacterial mixtures that can degrade both methanol and alpha-pinene were obtained via enrichment techniques . Two bench-scale thermophilic biofiltration systems (1085 and 1824 cm3) were used to examine compound removals at different residence times, with influent concentrations of 110 ppmv methanol and 15 ppmv alpha-pinene . At a residence time of 10.85 min, the smaller system had removal efficiencies of >98% for methanol, but only 23% for alpha-pinene . The larger system was operated with the same parameters to evaluate residence time and surfactant effects on compound removals . At a residence time of 18.24 min, both methanol and alpha-pinene removal rates were > or = 95% . However, a-pinene removal dropped to 26% at a residence time of 6.08 min; methanol removal was not affected . Subsequent addition of a surfactant mixture increased a-pinene removal to 94% at the shortest residence time . No residual alpha-pinene was detected with the support medium Celite R-635, indicating that the surfactant may increase mass transfer of alpha-pinene.

Sci Total Environ, 2001 Jun 12, 273(1-3), 41 - 52
Exergy analysis in the assessment of the sustainability of waste gas treatment systems; Dewulf J et al.; This study focuses on the sustainability of different technological options for the treatment of waste gases from a waste water treatment plant loaded with volatile organic compounds . The options considered are biofiltration, active carbon adsorption and catalytic and thermal oxidation . The amount of resources and utilities to construct and operate each system have been investigated from the point of view of the Second Law of thermodynamics . The unit in which all resources are treated is Joules of exergy . It was concluded that biofiltration was the most exergetically efficient system . The cumulative exergy consumption of the resources and utilities for construction and operation have been quantified in exergy terms . Further on, the requirements for the abatement of emissions generated by operating the waste gas treatment systems and the amount of renewables have been taken into account in the assessment of the sustainability of the waste gas treatment technologies . Finally, a comparison between exergy analysis and life cycle analysis in assessing the sustainability of the waste gas treatment options, is presented.

J Air Waste Manag Assoc, 2001 Jun, 51(6), 895 - 902
A fungal vapor-phase bioreactor for the removal of nitric oxide from waste gas streams; Woertz JR et al.; Ground-level O3 formation is becoming a major concern in many cities due to recent tightening of O3 regulations . To control O3 formation, more efficient treatment processes for O3 precursors, such as NOx and volatile organic compounds (VOCs), are needed . One promising new technology for removing both NOx and VOCs from off-gas streams is biofiltration, a simple process whereby contaminated air is passed through a biologically active packed bed . In this study, a toluene-degrading fungal bioreactor was used to treat an aerobic gas stream contaminated with NO . The fungal bioreactor removed 93% of the inlet 250-ppmv NO at an empty bed contact time (EBCT) of 1 min when supplied with 90 g/m3/hr toluene . The presence of NH4+ concentrations greater than 0.4 mg NH3/g dry packing medium, however, resulted in poor NO removal . The bioreactor achieved a maximum toluene elimination capacity of 270 g/m3/hr and maintained greater than 95% toluene removal efficiencies over the 175-day study period.

Biotechnol Bioeng, 2001, 76(1), 77 - 85
Possible complication regarding phosphorus removal with a continuous flow biofilm system: diffusion limitation; Falkentoft CM et al.; Diffusion limitation of phosphate possibly constitutes a serious problem regarding the use of a biofilm reactor for enhanced biological phosphorus removal . A lab-scale reactor for simultaneous removal of phosphorus and nitrate was operated in a continuous alternating mode of operation . For a steady-state operation with excess amounts of carbon source (acetate) during the anaerobic phase, the same amount of phosphate was released during the anaerobic phase as was taken up during the anoxic phase . The measured phosphorus content of the biomass that detached during backwash after an anoxic phase was low, 2.4 +/- 0.4% (equal to 24 +/- 4 mg P/g TS) . A simplified computer model indicated the reason to be phosphate diffusion limitation and the model revealed a delicate balance between the obtainable phosphorus contents of the biomass and operating parameters, such as backwash interval, biofilm thickness after backwash, and phase lengths . The aspect of diffusion is considered of crucial importance when evaluating the performance of a biofilter for phosphate removal .

Biotechnol Bioeng, 2001, 76(1), 61 - 9
Toluene biofiltration by the fungus Scedosporium apiospermum TB1; Garcia-Pena EI et al.; The performance of biofilters inoculated with the fungus Scedosporium apiospermum was evaluated . This fungus was isolated from a biofilter which operated with toluene for more than 6 months . The experiments were performed in a 2.9 L reactor packed with vermiculite or with vermiculite-granular activated carbon as packing material . The initial moisture content of the support and the inlet concentration of toluene were 70% and 6 g/m3, respectively . As the pressure drop increased from 5-40 mm H2O a strong initial growth was observed . Stable operation was maintained for 20 days with a moisture content of 55% and a biomass of 33 mg biomass/g dry support . These conditions were achieved with intermittent addition of culture medium, which permitted a stable elimination capacity (EC) of 100 g/m3(reactor)h without clogging . Pressure drop across the bed and CO2 production were related to toluene elimination . Measurement of toluene, at different levels of the biofilter, showed that the system attained higher local EC (200 g/m3(r)h) at the reactor outlet . These conditions were related to local humidity conditions . When the mineral medium was added periodically before the EC decreases, EC of approximately 258 g/m3(r)h were maintained with removal efficiencies of 98% . Under these conditions the average moisture content was 60% and 41 mg biomass/g dry support was produced . No sporulation was observed . Evaluation of bacterial content and activities showed that the toluene elimination was only due to S . apiospermum catabolism .

Water Sci Technol, 2001, 43(3), 283 - 90
Strategies to enhance the biodegradation of toxic compounds using discontinuous processes; Buitron G et al.; This study presents two strategies used to enhance the biological degradation of phenolic wastewaters . In the first one the operation of a sequencing batch biofilter added with granular activated carbon (SBB-AC) was studied . The second strategy presents the results of the automation of a sequencing batch reactor in order to optimize the reaction phase . In this case, the dissolved oxygen was employed to monitor and control the reactor . The results of the SBB-AC system, based on the configuration of the reactor, type and size of activated carbon and size of the packing material, are discussed . The system biodegraded efficiently (total phenol removals as high as 97%) high concentrations (600 mg/l) of a mixture of phenol, 4-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol . Maximal eliminated loads of 4.33 kg COD/m3-d were achieved . For the second strategy, the applicability of an optimal control for a SBR using the dissolved oxygen as the measured variable was demonstrated . When the reactor was operated under the time-optimal control strategy, the degradation time of 4-chlorophenol was reduced . A very satisfactory operation of the reactor was observed, since the removal efficiencies were around 99%.

Water Sci Technol, 2001, 43(3), 241 - 8
Intracellular dynamics of ribonucleic acid (RNA) and protein in microorganisms from periodically operated biofilters; Moe WM et al.; Conventional biofilters are designed and operated as continuous flow processes where the reactors receive a constant stream of contaminated air . Recent research has shown that periodically operated biofilters can remove a greater mass of contaminants during shock loads than equally sized continuously loaded biofilters . Preliminary experiments were conducted to investigate effects of periodic operation on physiological state of biofilter microorganisms . Relative concentrations of two macromolecular components of microbial cells, RNA and protein, were quantified in biosolids samples removed from biofilters operated under different periodic and continuous loading strategies . Preliminary studies presented herein suggest that the physiological state of the microbial population present in the periodically operated biofilter differs from that of those present in the biofilter operated continuously supplied air.

Water Sci Technol, 2001, 43(3), 231 - 9
Period biofilter operation for enhanced performance during unsteady-state loading conditions; Irvine RL et al.; In conventional biofilter operation, contaminated air is passed continuously through packed beds containing microbial consortia capable of contaminant biotransformation . This paper describes how biofilters can be designed and operated as controlled unsteady-state, periodic processes for the destruction of gas-phase contaminants . Such operation, previously limited to applications in wastewater treatment and soil remediation, increases an operator's ability to control the physiological state, "robustness," and spatial distribution of the microbial communities established within the biofilter and, thus, minimizes uncertainties that often accompany design and operation of biological systems . Results are presented from toluene degrading biofilters that used polyurethane foam packing medium . These studies demonstrate how controlled periodic operations can enhance contaminant removal during transient periods of elevated contaminant load.

Water Sci Technol, 2001, 43(1), 285 - 93
Biofilm structure and mass transfer in a gas phase trickle-bed biofilter; Zhu X et al.; Mass transport phenomena occurring in the biofilms of gas phase trickle-bed biofilters are investigated in this study . The effect of biofilm structure on mass transfer mechanisms is examined using experimental observation from the operating of biofilters, microelectrode techniques and microscopic examination . Since the biofilms of biofilters used for waste gas treatment are not completely saturated with water, there is not a distinguishable liquid layer outside the biofilm . Results suggest that due to this characteristic, gas phase substrates (such as oxygen or volatile organic compounds) may not be limited by the aqueous phase because transport of the compound into the biofilm can occur directly through non-wetted areas . On the other hand, for substrates that are present only in the liquid phase, such as nitrate, the mass transfer limitation is more serious because of the limited liquid supply . Microscopic observations show that a layered structure with void spaces exists within the biofilm . Oxygen concentration distributions along the depth of the biofilms are examined using an oxygen microelectrode . Results indicate that there are some high dissolved oxygen zones inside the biofilm, which suggests the existence of passages for oxygen transfer into the deeper sections of the biofilm in a gas phase trickle-bed biofilter . Both the low gas-liquid mass transfer resistance and the resulting internal structure contribute to the high oxygen penetration within the biofilms in gas phase trickle-bed biofilters.

Chemosphere, 2001 Jun, 43(8), 1043 - 50
Biological elimination of H2S and NH3 from wastegases by biofilter packed with immobilized heterotrophic bacteria; Chung YC et al.; Biotreatment of various ratios of H2S and NH3 gas mixtures was studied using the biofilters, packed with co-immobilized cells (Arthrobacter oxydans CH8 for NH3 and Pseudomonas putida CH11 for H2S) . Extensive tests to determine removal characteristics, removal efficiency, removal kinetics, and pressure drops of the biofilters were performed . To estimate the largest allowable inlet concentration, a prediction model was also employed . Greater than 95%, and 90% removal efficiencies were observed for NH3 and H2S, respectively, irrespective of the ratios of H2S and NH3 gas mixtures . The results showed that H2S removal of the biofilter was significantly affected by high inlet concentrations of H2S and NH3 . As high H2S concentration was an inhibitory substrate for the growth of heterotrophic sulfur-oxidizing bacteria, the activity of H2S oxidation was thus inhibited . In the case of high NH3 concentration, the poor H2S removal efficiency might be attributed to the acidification of the biofilter . The phenomenon was caused by acidic metabolite accumulation of NH3 . Through kinetic analysis, the presence of NH3 did not hinder the NH3 removal, but a high H2S concentration would result in low removal efficiency . Conversely, H2S of adequate concentrations would favor the removal of incoming NH3 . The results also indicated that maximum inlet concentrations (model-estimated) agreed well with the experimental values for space velocities of 50-150 h(-1) . Hence, the results would be used as the guideline for the design and operation of biofilters.

J Air Waste Manag Assoc, 2001 May, 51(5), 756 - 65
Removal of ammonia from contaminated air by trickle bed air biofilters; Sorial GA et al.; A trickle bed air biofilter (TBAB) was evaluated for the oxidation of NH3 from an airstream . Six-millimeter Celite pellets (R-635) were used for the biological attachment medium . The efficiency of the biofilter in oxidizing NH3 was evaluated using NH3 loading rates as high as 48 mol NH3/m3 hr and empty-bed residence times (EBRTs) as low as 1 min . Excess biomass was controlled through periodic backwashing of the biofilter with water at a rate sufficient to fluidize the medium . The main goal was to demonstrate that high removal efficiencies could be sustained over long periods of operation . Ammonia oxidation efficiencies in excess of 99% were consistently achieved when the pH of the liquid nutrient feed was maintained at 8.5 . Quick recovery of the biofilter after backwashing was observed after only 20 min . Evaluation of biofilter performance with depth revealed that NH3 did not persist in the gas phase beyond 0.3 m into the depth of the medium (26% of total medium depth).

Environ Sci Technol, 2001 May 1, 35(9), 1765 - 70
Biodegradation of metal-{S,S}-EDDS complexes; Vandevivere PC et al.; The {S,S}-stereoisomer of ethylenediaminedisuccinic acid (EDDS), a biodegradable strong metal chelant, has substituted traditional chelants in a number of consumer products . However biodegradability of metal-EDDS complexes has remained largely undocumented . In the present study, activated sludge fed with EDDS as sole C and N source, was shown to readily biodegrade 1 mM pulses of Ca-, Cr(III)-, Fe(III)-, Pb-, Al-, Cd-, Mg-, Na-, or ZnEDDS (the latter only after extensive lag phase) . On the other hand, the Cu-, Ni-, Co-, and Hg-complexes remained essentially undegraded . Only in the case of HgEDDS was lack of biodegradation due to metal toxicity . Speciation analysis revealed free HEDDS3- concentration was higher than 10(-5.4) M for all readily biodegradable metal-EDDS complexes and smaller than 10(-9.0) M for all recalcitrant complexes at pseudo-steady-state (i.e . after initial rise of aquo metal concentration at onset of biodegradation) . The rate of metal-EDDS degradation may be modeled with a Monod expression with HEDDS3- as substrate (half-saturation constant ca . 10(-6) M) . This model explains the drastic effect of additional metal ligands, e.g . phosphate or iron, on biodegradation rate of several recalcitrant metal-EDDS complexes . Continuously fed aerated biofilters removed 10 mM Pb- or ZnEDDS at a rate of ca . 0.4 mM h-1.

Environ Sci Technol, 2001 Jan 1, 35(1), 240 - 6
The biofiltration of indoor air: air flux and temperature influences the removal of toluene, ethylbenzene, and xylene; Darlington AB et al.; An alternative approach to maintaining indoor air quality may be the biofiltration of air circulated within the space . A biofilter with living botanical matter as the packing medium reduced concentrations of toluene, ethylbenzene, and o-xylene concurrently present at parts per billion (volume) in indoor air . The greatest reduction in concentrations per pass was under the slowest influent air flux (0.025 m s(-1)); however, the maximum amount removed per unit time occurred under the most rapid flux (0.2 m s(-1)) . There was little difference between the different compounds with removal capacities of between 1.3 and 2.4 micromol m(-3) biofilter s(-1) (between 0.5 and 0.9 g m(-3) biofilter h(-1)) depending on influent flux and temperature . Contrary to biofilters subjected to higher influent concentrations, the optimal temperatures for removal by this biofilter decreased to less than 20 degrees C at the most rapid flux for all three compounds . Microbial activity was decreased at these cooler temperatures suggesting the biofilter was not microbially limited but rather was limited by the availability of substrate . The cooler temperatures allowed greater partitioning of the VOCs into the water column which had a greater impact on removal than its reduction in microbial activity.

Appl Microbiol Biotechnol, 2001 Mar, 55(2), 254 - 8
Parameters affecting performance and modeling of biofilters treating alkylbenzene-polluted air; Veiga MC et al.; Both short-term and long-term biofiltration experiments were undertaken with a biofilter inoculated with a defined microbial consortium and treating an alkylbenzene mixture . The results obtained with such a biofilter in short-term experiments were very similar to those obtained with a biofilter inoculated with a non-defined mixed culture, in terms of maximum elimination capacities (70-72 g m(-3) h(-1)) and the corresponding removal efficiencies (>95%) . However, in long-term experiments, a better performance was reached, with a maximum elimination capacity of 120 g m(-3) h(-1), corresponding to a removal efficiency >99% after 2 years of operation . Inoculation proved to be useful for shortening the start-up period . In the long term, it appeared that biomass distribution was not homogenous along the biofilter, which in some cases resulted in a bad fit between simple model equations and experimental data.

Environ Sci Technol, 2001 Apr 15, 35(8), 1610 - 5
Biofiltration of residual fertilizer nitrate and atrazine by Rhizobium meliloti in saturated and unsaturated sterile soil columns; Mehmannavaz R et al.; This study was undertaken to investigate whether microbial bioaugmentation of subsurface soil with subsurface irrigation could be used as a biofiltration/biocontrol technology for agricultural pollutants . Nine Plexiglas columns, 458 mm long x 139 mm in diameter, were packed with a sterilized sandy loam soil . Subsurface irrigation, through a controlled water table management system, was used to deliver bacteria, Rhizobium meliloti A-025, to the soil and to maintain aerobic (unsaturated) or anaerobic (saturated) conditions in the columns . Nitrate and atrazine, a fertilizer and a corn herbicide, were applied to the soil surface, and leaching was affected by simulated rainfall events . The soil and drainage waters were analyzed for nitrate and atrazine residues after each rainfall simulation throughout the experimental period during which the soil was kept saturated for a total of 80 days and unsaturated for a total of 70 days . The monitoring of transport and survival of the implanted bacterial strain (A-025) showed that subsurface irrigation was successful in introducing and transporting the bacteria throughout the soil columns . During the saturated period, significantly more (95% probability) nitrate-N leached into the drainage waters from the control columns than from the bioaugmented columns; the increase being 450% or more for the abiotic control columns . The amount of atrazine that leached into the drainage waters during the unsaturated period was also significantly more from control columns as opposed to bioaugmented columns, with the increase being 262%.

Environ Microbiol, 2001 Mar, 3(3), 220 - 5
Isolate PM1 populations are dominant and novel methyl tert-butyl ether-degrading bacterial in compost biofilter enrichments; Bruns MA et al.; The gasoline additive MTBE, methyl tert-butyl ether, is a widespread and persistent groundwater contaminant . MTBE undergoes rapid mineralization as the sole carbon and energy source of bacterial strain PM1, isolated from an enrichment culture of compost biofilter material . In this report, we describe the results of microbial community DNA profiling to assess the relative dominance of isolate PM1 and other bacterial strains cultured from the compost enrichment . Three polymerase chain reaction (PCR)-based profiling approaches were evaluated: denaturing gradient gel electrophoresis (DGGE) analysis of 230 bp 16S rDNA fragments; thermal gradient gel electrophoresis (TGGE) analysis of 575 bp 16S rDNA fragments; and non-denaturing polyacrylamide gel electrophoresis of 300-1,500 bp fragments containing 16S/23S ribosomal intergenic transcribed spacer (ITS) regions . Whereas all three DNA profiling approaches indicated that PM1-like bands predominated in mixtures from MTBE-grown enrichments, ITS profiling provided the most abundant and specific sequence data to confirm strain PM1's presence in the enrichment . Moreover, ITS profiling did not produce non-specific PCR products that were observed with T/DGGE . A further advantage of ITS community profiling over other methods requiring restriction digestion (e.g . terminal restriction fragment length polymorphisms) was that it did not require an additional digestion step or the use of automated sequencing equipment . ITS bands, excised from similar locations in profiles of the enrichment and PM1 pure culture, were 99.9% identical across 750 16S rDNA positions and 100% identical across 691 spacer positions . BLAST comparisons of nearly full-length 16S rDNA sequences showed 96% similarity between isolate PM1 and representatives of at least four different genera in the Leptothrix subgroup of the beta-Proteobacteria (Aquabacterium, Leptothrix, Rubrivivax and Ideonella) . Maximum likelihood and parsimony analyses of 1,249 nucleotide positions supported isolate PM1's position in a separate lineage within the Leptothrix subgroup.

Water Res, 2001 Apr, 35(6), 1469 - 77
Measurement of biomass activity in drinking water biofilters using a respirometric method; Urfer D et al.; A simple respirometric method was developed and applied for the measurement of biomass activity in bench-scale drinking water biofilters . The results obtained with the new method, i.e . biomass respiration potential (BRP), indicated a high sensitivity allowing the quantification of the activity of low amounts of biomass . The analysis of duplicate samples showed a reasonable reproducibility, i.e . average coefficient of variation of 14% (n = 19) . The calculation of the ratio between biomass activity and the amount of viable biomass (phospholipid) at different filter depths indicated a substantial increase of this ratio with filter depth . This indicated an increased biomass activity per unit amount of viable biomass deeper in the biofilters, where biofilm thickness is low . The comparison of the filter profiles of biomass activity and dissolved biodegradable organic matter (BOM), expressed as theoretical oxygen demand, showed a high correlation between these profiles . Consequently, BRP results appear to be good indicators of the BOM removal capacity of the filter biomass . Therefore, BRP results can potentially be used in certain cases instead of BOM measurements for the assessment of the BOM removal capacity of drinking water biofilters, operated under different conditions . This is important because of the relative complexity of the measurements of BOM surrogates, e.g . assimilable organic carbon and biodegradable dissolved organic carbon, and BOM components.

Water Res, 2001 Apr, 35(6), 1407 - 14
Effect of nitrogen limitation on performance of toluene degrading biofilters; Moe WM et al.; The literature reports conflicting observations regarding the need for nutrient addition to biofilters treating contaminated gases . Such conflicts are often based on quasi-steady-state performance data collected on biofilters operated under continuous loading conditions . In the studies described herein, the impact of nitrogen limitations on two toluene-fed biofilters was assessed over a 97-day period . The biofilters were packed with polyurethane foam medium and contained different initial levels of nitrate-nitrogen . Toluene and CO2 concentration profiles were monitored during both normal steady loading conditions and short-term, unsteady-state transient loading conditions (e.g., shock loads) . Packing medium samples were periodically removed and analyzed to quantify changes in nitrate-nitrogen content over time . Data are presented which show that over long-time periods (several months), nutrient-induced kinetic limitations diminished biofilter performance during transient, unsteady-state conditions even when performance during normal steady loading was not adversely affected . Elemental analysis of biomass removed from the biofilters support nitrate-nitrogen and CO2 concentration profile data and clearly illustrate how kinetically limited biofilters fail during shock loads even when there is an overall stoichiometric excess of nutrients.

Environ Technol, 2001 Jan, 22(1), 47 - 56
Evaluation of porous ceramic as microbial carrier of biofilter to remove toluene vapor; Lim JS et al.; Three kinds of porous ceramic microbe media are fabricated from fly ash, diatomite and a mixture of fly ash and diatomite powders . Water holding capacity, density, porosity, pore size and distribution, compressive strength and micro-structure of each of the fabricated media are measured and compared . The fly ash and diatomite mixture ceramic is evaluated as the best biofilter medium among the three media because of its high compressive strength . It is selected as an experimental biofilter medium inoculated with thickened activated sludge . The laboratory scale biofilter was operated for 42 days under various experimental conditions varying in inlet toluene concentration and flow rate of contaminated air stream . The experimental result shows that the removal efficiency reaches up to 96.6% after 4 days from the start-up . Nutrient limitation is considered as a major factor limiting biofilter efficiency . Biofilter efficiency decreases substantially at the build-up of backpressure, which is largely due to the accumulation of excess VSS within the media . Periodic backwashing of the biofilter is necessary to remove excess biomass and attain stable long-term high removal efficiency . The bed needs to be backwashed when the overall pressure drop becomes greater than 460.6 Pa at space velocity of 100 h-1 . A maximum flow rate of 444.85 g m-3hr-1 of toluene elimination by the mixture ceramic biofilter, which is higher than the previously reported values . This indicates that the fly ash and diatomite mixture ceramic biofilter can be effectively applied for removing toluene vapor.

Biotechnol Bioeng, 2001 May 20, 73(4), 282 - 94
Dynamic volume-averaged model of heat and mass transport within a compost biofilter: I . Model development; Mysliwiec MJ et al.; Successful, long-term operation of a biofilter system depends on maintaining a suitable biofilm environment within a porous medium reactor . In this article a mathematical study was conducted of the spatial and temporal changes of biofilter performance due to interphase heat and mass transport . The method of volume averaging was used to spatially smooth the three-phase (solid, liquid, and gas) conservation equations over the biofilter domain . The packing medium was assumed to be inert, removing the solid phase mass continuity equation from the system . The finite element method was used to integrate the resulting nonlinear-coupled partial differential equations, tracking eight state variables: temperature, water vapor, dry air, liquid water, biofilm, gas and liquid phase organic pollutant, and nutrient densities, through time and space . A multiphase, gas and liquid flow model was adapted to the biofilter model from previous studies of unsaturated groundwater flow . Newton's method accelerated by an LU direct solver was used to iterate the model for solutions . Effects of packing media on performance were investigated to illustrate the utility of the model . The moisture dynamics and nutrient cycling are presented in Part II of this article .

J Biotechnol, 2001 May 4, 87(2), 123 - 30
Removal of ethylacetate vapor from waste gases by a trickle-bed air biofilter; Lu C et al.; Biofilter system is a relatively new process that has been proven to be more cost-effective than traditional technologies such as carbon adsorption, liquid scrubbing, condensation, thermal incineration, and catalytic incineration for removing low-strength volatile organic compounds from waste gases . The trickle-bed air biofilter (TBAB) performance for ethylacetate (EA) removal was evaluated under different influent loadings . In the pseudo-steady states, the elimination capacity increased, but the removal efficiency decreased with increased influent loading . More than 95 and 90% removal efficiencies could be achieved for EA loadings below 490 and 810 g m(-3) h(-1), respectively . The TBAB appears to be very effective for controlling EA emission under low to high loading conditions, and the effectiveness could be maintained over 190 days of laboratory operation.

Bioresour Technol, 2001 May, 77(3), 257 - 74
Biofiltration--the treatment of fluids by microorganisms immobilized into the filter bedding material: a review; Cohen Y; Biofiltration is distinguished from other biological waste treatments by the fact that there is a separation between the microorganisms and the treated waste . In biofiltration systems the microorganisms are immobilized to the bedding material, while the treated fluid flows through it . In recent decades, a vast amount of literature has been written on single experiments involving the treatment of fluids by immobilized microorganisms . Several artificial immobilization methods have been examined and impressive results have been achieved in the treatment of fluids with one of the artificial immobilization methods the entrapment of microorganisms within polymer beads . This method, even though it needs to be improved, seems to have a future potential in commercial biofiltration systems . The methods of artificial immobilization of microorganisms within biofiltration systems have several advantages, but also suffer from several disadvantages in comparison to the treatment of fluids by naturally attached microorganisms . Understanding the mechanisms and forces responsible for the attachment of microbes to the bedding material, in attempt to improve this attachment, is of the utmost importance . Further improvement of the artificial entrapment of microorganisms within polymers will allow the exploitation of the advantages of this method in the treatment of fluids . The aim of this review essay is to introduce the main principles of two immobilization processes - the self-attachment of microorganisms to the bedding material and the artificial entrapment of microorganisms within polymer beads . Both treatments of liquids and gases with each immobilization process are discussed . The advantages and disadvantages of each immobilization process are pointed out and different aspects of the fluid treatment with the two immobilization processes are compared.

J Air Waste Manag Assoc, 2001 Mar, 51(3), 387 - 92
Carbon disulfide and hydrogen sulfide removal with a peat biofilter; Hartikainen T et al.; Simultaneous removal of H2S and CS2 was studied with a peat biofilter inoculated with a Thiobacillus strain that oxidizes both compounds in an acidic environment . Both sulfurous gases at concentrations below 600 mg S/m3 were efficiently removed, and the removal efficiencies were similar, 99%, with an empty bed retention time (EBRT) of more than 60 sec . Concentrations greater than 1300-5000 mg S/m3 caused overloading of the filter material, resulting in high H2SO4 production, accumulation of elemental sulfur, and reduced removal efficiency . The highest sulfur removal rate achieved was 4500 g-S/day/m3 filter material . These results indicate that peat is suitable as a biofilter material for the removal of a mixture of H2S and CS2 when concentrations of gases to be purified are low (less than 600 mg/m3), but it is still odorous and toxic to the environment and humans.

Water Res, 2001 Jan, 35(1), 211 - 23
Non-steady state simulation of BOM removal in drinking water biofilters: applications and full-scale validation; Hozalski RM et al.; A biofilter model called "BIOFILT" was used to simulate the removal of biodegradable organic matter (BOM) in full-scale biofilters subjected to a wide range of operating conditions . Parameters that were varied included BOM composition, water temperature (3.0-22.5 degrees C), and biomass removal during backwashing (0-100%) . Results from biofilter simulations suggest a strong dependence of BOM removal on BOM composition . BOM with a greater diffusivity or with faster degradation kinetics was removed to a greater extent and also contributed to shorter biofilter start-up times . In addition, in simulations involving mixtures of BOM (i.e . readily degradable and slowly degradable components), the presence of readily degradable substrate significantly enhanced the removal of slowly degradable material primarily due to the ability to maintain greater biomass levels in the biofilters . Declines in pseudo-steady state BOM removal were observed as temperature was decreased from 22.5 to 3 degrees C and the magnitude of the change was significantly affected by BOM composition . However, significant removals of BOM are possible at low temperatures (3-6 degrees C) . Concerning the impact of backwashing on biofilter performance, BOM removal was not affected by backwash resulting in biomass removals of 60% or less . This suggests that periodic backwashing should not significantly impact biofilter performance as observed biomass removals from full-scale biofilters were negligible . In general, the simulation results were in good qualitative and quantitative agreement with experimental results obtained from full-scale biofilters.

Water Res, 2001 Jan, 35(1), 198 - 210
Non-steady state simulation of BOM removal in drinking water biofilters: model development; Hozalski RM et al.; A numerical model was developed to simulate the non-steady-state behavior of biologically-active filters used for drinking water treatment . The biofilter simulation model called "BIOFILT" simulates the substrate (biodegradable organic matter or BOM) and biomass (both attached and suspended) profiles in a biofilter as a function of time . One of the innovative features of BIOFILT compared to previous biofilm models is the ability to simulate the effects of a sudden loss in attached biomass or biofilm due to filter backwash on substrate removal performance . A sensitivity analysis of the model input parameters indicated that the model simulations were most sensitive to the values of parameters that controlled substrate degradation and biofilm growth and accumulation including the substrate diffusion coefficient, the maximum rate of substrate degradation, the microbial yield coefficient, and a dimensionless shear loss coefficient . Variation of the hydraulic loading rate or other parameters that controlled the deposition of biomass via filtration did not significantly impact the simulation results.

J Air Waste Manag Assoc, 2001 Feb, 51(2), 163 - 72
Biotreatment of hydrogen sulfide- and ammonia-containing waste gases by fluidized bed bioreactor; Chung YC et al.; Gas mixtures of H2S and NH3 are the focus of this study of research concerning gases generated from animal husbandry and treatments of anaerobic wastewater lagoons . A heterotrophic microflora (a mixture of Pseudomonas putida for H2S and Arthrobacter oxydans for NH3) was immobilized with Ca-alginate and packed into a fluidized bed reactor to simultaneously decompose H2S and NH3 . This bioreactor was continuously supplied with H2S and NH3 separately or together at various ratios . The removal efficiency, removal rate, and metabolic product of the bioreactor were studied . The results showed that the efficiency remained above 95% when the inlet H2S concentration was below 30 ppm at 36 L/hr . Furthermore, the apparent maximum removal and the apparent half-saturation constant were 7.0 x 10(-8) g-S/cell/day and 76.2 ppm, respectively, in this study . The element sulfur as a main product prevented acidification of the biofilter, which maintained the stability of the operation . As for NH3, the greater than 90% removal rate was achieved as long as the inlet concentration was controlled below 100 ppm at a flow rate of 27 L/hr . In the NH3 inlet, the apparent maximum removal and the apparent half-saturation constant were 1.88 x 10(-6) g-N/cell/day and 30.5 ppm, respectively . Kinetic analysis showed that 60 ppm of NH3 significantly suppressed the H2S removal by Pseudomonas putida, but H2S in the range of 5-60 ppm did not affect NH3 removal by Arthrobacter oxydans . Results from bioaerosol analysis in the bioreactor suggest that the co-immobilized cell technique applied for gas removal creates less environmental impact.

J Hazard Mater, 2001 Apr 20, 82(3), 233 - 45
Removal of styrene vapor from waste gases by a trickle-bed air biofilter; Lu C et al.; The trickle-bed air biofilter (TBAB) performance for the removal of high-strength styrene was evaluated under different gas flow rates and influent concentrations . Under pseudo-steady-state conditions, the elimination capacity increased but the removal efficiency decreased with the increase of styrene loading . More than 90 and 80% removal efficiencies were achieved for influent styrene loadings below 32 and 55g/m(3)/h, respectively . The TBAB appears to be an effective treatment process for controlling high-strength styrene emission under low-to-medium loading conditions, and the effectiveness could be maintained over 140 days of laboratory operation.

Appl Microbiol Biotechnol, 2001 Jan, 55(1), 122 - 8
BTEX catabolism interactions in a toluene-acclimatized biofilter; du Plessis CA et al.; BTEX substrate interactions for a toluene-acclimatized biofilter consortium were investigated . Benzene, ethylbenzene, o-xylene, m-xylene and p-xylene removal efficiencies were determined at a loading rate of 18.07 g m(-3) h(-1) and retention times of 0.5-3.0 min . This was also repeated for toluene in a 1:1 (m/m) ratio mixture (toluene: benzene, ethylbenzene, or xylene ) with each of the other compounds individually to obtain a final total loading of 18.07 g m(-3) h(-1) . The results obtained were modelled using Michaelis-Menten kinetics and an explicit finite difference scheme to generate vmax and Km parameters . The Vmax/Km ratio (a measure of the catalytic efficiency, or biodegradation capacity, of the reactor) was used to quantify substrate interactions occurring within the biofilter reactor without the need for free-cell suspended and monoculture experimentation . Toluene was found to enhance the catalytic efficiency of the reactor for p-xylene, while catabolism of all the other compounds was inhibited competitively by the presence of toluene . The toluene-acclimatized biofilter was also able to degrade all of the other BTEX compounds, even in the absence of toluene . The catalytic efficiency of the reactor for compounds other than toluene was in the order: ethylbenzene > benzene > o-xylene > m-xylene>p-xylene . The catalytic efficiency for toluene was reduced by the presence of all other tested BTEX compounds, with the greatest inhibitory effect being caused by the presence of benzene, while o-xylene and p-xylene caused the least inhibitory effect . This work illustrated that substrate interactions can be determined directly from biofilter reactor results without the need for free-cell and monoculture experimentation.

Water Res, 2001 Mar, 35(3), 736 - 44
Inter-relationship between adsorption and pH in peat biofilters in the context of a cation-exchange mechanism; McNevin D et al.; A mathematical model of biofiltration McNevin and Barford (1998) has been augmented to include speciation, acid/base equilibria and pH dependence of adsorptive equilibria . It accurately predicts qualitative aspects of dynamic transients observed in an experimental perfusion column and supported a mechanism of adsorption by cation exchange with acidic functional groups on the surface of peat . It mirrored the buffering capacity of peat when solutions of high and low pH flow over the peat surface . This is a direct result of cation exchange where adsorption of cations increases with pH . This buffering capacity makes peat an attractive medium for engineered biological systems which must often operate within narrow pH bands to optimise biological activity.

J Air Waste Manag Assoc, 2001 Jan, 51(1), 78 - 85
Development and performance of an alternative biofilter system; Lee DH et al.; Step tracer tests were carried out on lab-scale biofilters to determine the residence time distributions (RTDs) of gases passing through two types of biofilters: a standard biofilter with vertical gas flow and a modified biofilter with horizontal gas flow . Results were used to define the flow patterns in the reactors . "Non-ideal flow" indicates that the flow reactors did not behave like either type of ideal reactor: the perfectly stirred reactor {often called a "continuously stirred tank reactor" (CSTR)} or the plug-flow reactor . The horizontal biofilter with back-mixing was able to accommodate a shorter residence time without the usual requirement of greater biofilter surface area for increased biofiltration efficiency . Experimental results indicated that the first bed of the modified biofilter behaved like two CSTRs in series, while the second bed may be represented by two or three CSTRs in series . Because of the flow baffles used in the horizontal biofilter system, its performance was more similar to completely mixed systems, and hence, it could not be modeled as a plug-flow reactor . For the standard biofilter, the number of CSTRs was found to be between 2 and 9 depending on the airflow rate . In terms of NH3 removal efficiency and elimination capacity, the standard biofilter was not as good as the modified system; moreover, the second bed of the modified biofilter exhibited greater removal efficiency than the first bed . The elimination rate increased as biofilter load increased . An opposite trend was exhibited with respect to removal efficiency.

J Air Waste Manag Assoc, 2001 Jan, 51(1), 11 - 6
Oxidation of gas mixtures containing dimethyl sulfide, hydrogen sulfide, and methanethiol using a two-stage biotrickling filter; Ruokojarvi A et al.; A biofiltration technique was developed for removing a mixture of hydrogen sulfide (H2S), methanethiol (MeSH), and dimethyl sulfide (Me2S) from waste gases . Since H2S, especially at high concentrations, disturbs the removal of Me2S, two biotrickling filters with different microbes and operating pH levels were connected in series to create a two-stage system . Different loads of these gases were studied in order to determine their impact on the removal capacity of the system . The microbial consortia for these filters were enriched from the sludge of a Finnish refinery with bubbling H2S or Me2S . Acclimation for Me2S took 2 weeks, though no acclimation time was needed for the other gases . The first filter, at a pH of 2, removed most of the H2S and some of the MeSH and Me2S . The second filter, at a pH of approximately 6.5, removed the rest of the MeSH and most of the Me2S . The total maximum loads of the whole two-stage biotrickling filter were 1150 g/m3/day for H2S-S (suffix S indicates the results are counted as sulfur amounts), 879 g/m3/day for Me2S-S, and 66 g/m3/day for MeSH-S treated in a gas mixture . The average removal efficiencies for all gases tested were 99% or higher.

Biotechnol Bioeng, 2001 Feb 20, 72(4), 389 - 401
Modeling the removal of VOC mixtures in biotrickling filters; Baltzis BC et al.; A mathematical model was derived for describing removal of mixed VOC vapors in biotrickling filters (BTFs) . The model accounts for potential process rate limitation by the availability of oxygen as well as for potential kinetic interactions among pollutants during their biodegradation . Without using any fitted parameter, the model was found capable of predicting experimentally obtained removal rates of mono-chlorobenzene (m-CB) and ortho-dichlorobenzene (o-DCB) vapors . Experimental results reported here show that m-CB removal is better than that of o-DCB . The two compounds were known to be involved in a kinetic cross-inhibition interaction when degraded in suspended culture . However, model sensitivity studies showed that cross-inhibition does not affect BTF performance due to the low pollutant concentrations involved . For the same reason, the influence of oxygen on BTF performance was found to be minimal under the conditions tested . The model was found to predict experimentally obtained values with less than 10% error in the majority of cases . Computations with an earlier model describing VOC removal in conventional biofilters showed that, for the model mixture used in this study (m-CB/o-DCB), removal rates obtained with BTFs are one to more than two orders of magnitude higher than those obtained with conventional biofilters . This is attributed to the larger active specific biofilm surface area in BTFs, obtained through the creation of favorable growth conditions for the biomass, and better moisture control .

Artif Organs, 2000 Dec, 24(12), 981 - 4
The effect of biofiltration on red blood cells 2.3-diphosphoglycerate and pH; Umimoto K et al.; To investigate the effect of biofiltration (BF) on the ability of blood to supply oxygen to the peripheral tissues, a 2 week crossover study was conducted with bicarbonate hemodialysis (BcHD) and BF using 5 male patients with diabetic renal failure as subjects . BcHD and BF were performed for 4 h and 3.5 h per session, respectively . Blood gases, the pH of red blood cells (RBC-pH), and 2 . 3-diphosphoglycerate in RBC (RBC-2.3DPG) were measured during each treatment . After a 2 week BF treatment, the plasma HCO3- at the beginning of BF was significantly higher than that of BcHD (p < 0.01), and the blood pH improved with an elevated plasma bicarbonate level (p < 0.05) . The RBC-pH at the beginning of BF was higher than that of BcHD (p < 0.05) although the RBC-pH at the end of both therapies increased to similar levels . The RBC-2.3DPG during BcHD remained unchanged, but during BF significantly increased (p < 0.05) . Metabolic acidosis was significantly improved by BF with its effect reaching to the RBC intracellular level . The improved metabolic acidosis might occur as a result of the increase in RBC-2.3DPG during BF . This increase in RBC-2.3DPG has the effect of reducing the affinity of oxygen for hemoglobin and allows more oxygen to be delivered to the peripheral tissues although the increase in RBC-pH by dialysis restricts the dissociation of oxygen from hemoglobin.

J Hazard Mater, 2001 Jan 29, 81(1-2), 115 - 22
Pressure-drops control strategy in a fixed-bed reactor; Thalasso F et al.; This paper presents a strategy to control pressure-drops (head loss) in a biofilter designed according to the "Mist-Foam" concept . This concept is based on the mixing of the gaseous substrate and a liquid nutrient solution with an atomization nozzle to generate a mist passing subsequently through a synthetic polyurethane foam . In this type of bioreactor, the microbial growth reduces progressively the empty bed volume of the biofilter and causes an increase in the pressure-drops . This phenomenon can result in a complete clogging of the biofilter . The strategy of pressure-drops control presented here consists of successive interruption of the liquid flow, automatically controlled, resulting in a drying effect of the biomass . Tested during a 160 days experiment, this system has permitted to reduce and stabilize the pressure-drops in a biofilter in which the carrier exhibited a high likelihood of clogging.

Biotechnol Bioeng, 2001 Jan 20, 72(2), 156 - 65
Development of a novel bioreactor system for treatment of gaseous benzene; Yeom SH et al.; A novel, continuous bioreactor system combining a bubble column (absorption section) and a two-phase bioreactor (degradation section) has been designed to treat a gas stream containing benzene . The bubble column contained hexadecane as an absorbent for benzene, and was systemically chosen considering physical, biological, environmental, operational, and economic factors . This solvent has infinite solubility for benzene and very low volatility . After absorbing benzene in the bubble column, the hexadecane served as the organic phase of the two-phase partitioning bioreactor, transferring benzene into the aqueous phase where it was degraded by Alcaligenes xylosoxidans Y234 . The hexadecane was then continuously recirculated back to the absorber section for the removal of additional benzene . All mass transfer and biodegradation characteristics in this system were investigated prior to operation of the integrated unit, and these included: the mass transfer rate of benzene in the absorption column; the mass transfer rate of benzene from the organic phase into the aqueous phase in the two-phase bioreactor; the stripping rate of benzene out of the two-phase bioreactor, etc . All of these parameters were incorporated into model equations, which were used to investigate the effects of operating conditions on the performance of the system . Finally, two experiments were conducted to show the feasibility of this system . Based on an aqueous bioreactor volume of 1 L, when the inlet gas flow and gaseous benzene concentration were 120 L/h and 4.2 mg/L, respectively, the benzene removal efficiency was 75% at steady state . This process is believed to be very practical for the treatment of high concentrations of gaseous pollutants, and represents an alternative to the use of biofilters.

Biotechnol Bioeng, 2001 Jan 5, 72(1), 34 - 40
An optimal operating strategy for fixed-bed bioreactors used in wastewater treatment; Benthack C et al.; Optimization of a fixed-bed bioreactor used in wastewater treatment is addressed . The objective of optimization is to maximize the treatment efficiency of the biofilter by manipulating the feed flow rate while satisfying operational constraints . Numerical results indicate that the optimal input is characterized as being on the boundary of the admissible region . Thus, the characterized optimal solution is implemented using a simple feedback control law, which provides the optimal input profile despite variations in substrate inlet concentration and biomass growth rate .

J Hazard Mater, 2000 Dec 30, 80(1-3), 259 - 69
Long-term results of ammonia removal and transformation by biofiltration; Liang Y et al.; In this paper, long-term (>8 month) results of ammonia removal in biofilters was studied . Compost was used as the biofilter medium and activated carbon as an added material . The ammonia removal was normally >95% at influent ammonia concentrations of 20-500ppmv . According to the test results, the influent ammonia concentration should be <200ppmv (0.1570g ammonia/kg media per day) so that the effluent concentration of ammonia is <1.0mg/m(3) (the emission standard of China), and the biofiltration system can achieve good long-term performance . In the biofiltration system utilized in this study, the shortest retention time that the system could attain was 0.532min . However, the retention time can be decreased further without decreasing the ammonia removal efficiency . Countercurrent flow is favorable, as it enhances the moisture retention ability of the media . In the bioreactors, ammonia can be converted into the nitrate . The bioreactors have a stratification phenomenon for ammonia removal over the biofiltration depth, which implies that different parts of the bioreactor play different roles in the ammonia removing process.

Biodegradation, 1999, 10(6), 399 - 404
Dolomite limits acidification of a biofilter degrading dimethyl sulphide
Smet E, Van Langenhove H, Philips G.
The applicability of dolomite particles to control acidification in a Hyphomicrobium MS3 inoculated biofilter removing dimethyl sulphide (Me2S) was studied . While direct inoculation of the dolomite particles with the liquid microbial culture was not successful, start-up of Me2S-degradation in the biofilter was observed when the dolomite particles were mixed with 33% (wt/wt) of Hyphomicrobium MS3-inoculated compost or wood bark material . Under optimal conditions, an elimination capacity (EC) of 1680 g Me2S m(-3) d(-1) was obtained for the compost/dolomite biofilter . Contrary to a wood bark or compost biofilter, no reduction in activity due to acidification was observed in these biofilters over a 235 day period because of the micro environment neutralisation of the microbial metabolite H2SO4 with the carbonate in the dolomite material . However, performance of the biofilter decreased when the moisture content of the mixed compost/dolomite material dropped below 15% . Next to this, nutrient limitation resulted in a gradual decrease of the EC and supplementation of a nitrogen source was a prerequisite to obtain a long-term high EC (> 250 g Me2S m(-3) d(-1)) for Me2S . In relation to this nitrogen supplementation, it was observed that stable ECs for Me2S were obtained when this nutrient was dosed to the biofilter at a Me2S-C/NH4Cl-N ratio of about 10.

J Appl Microbiol, 2000 Oct, 89(4), 580 - 6
Physiology and taxonomy of thiobacillus strain TJ330, which oxidizes carbon disulphide (CS2); Hartikainen T et al.; A bacterium (strain TJ330) capable of using carbon disulphide (CS2) as its sole energy source in an acidic environment was isolated from a peat biofilter used in experiments to remove CS2 and hydrogen sulphide (H2S) from air . Its physiology and taxonomy are described here . The strain oxidized CS2, H2S and elemental sulphur to sulphate chemolithotrophically . The rate of sulphate production was highest at pH 2 . The maximum growth rate constant (micromax) using CS2 as a substrate was 3.9 x 10(-2) h(-1) (generation time 18 h) and the Monod constant (Ks) was 0.97-2.6 micromol l(-1) CS2 (74-198 microg l(-1)), corresponding to an equilibrium with 15-40 ppm CS2 in the headspace . The optimum growth temperature using elemental sulphur as a substrate was 28 degrees C . The strain bears morphological and physiological similarities to Thiobacillus thiooxidans, but the latter is incapable of oxidizing CS2 . The strain TJ330 (DSM 8985) showed only 44.2 + 11.8% DNA homology with the type strain T . thiooxidans ATCC 19377, while its homology with T . ferrooxidans ATCC 23270 was 17.1 + 3.4% . The strain TJ 330 represents a high-affinity bacterium which can effectively remove low CS2 concentrations in an acid environment . These properties can be utilized in biotechnological purification applications.

Appl Microbiol Biotechnol, 2000 Aug, 54(2), 248 - 54
Toluene vapour removal in a laboratory-scale biofilter; Zilli M et al.; A bench-scale biofilter with a 0.5-m high filter bed, inoculated with a toluene-degrading strain of Acinetobacter sp . NCIMB 9689, was used to study toluene removal from a synthetic waste air stream . Different sets of continuous tests were conducted at influent toluene concentrations ranging over 0.1-4.0 g m(-3) and at superficial gas velocities ranging over 17.8-255 m h(-1) . The maximum volumetric toluene removal rate for the biofilter (242 g m(-3) h(-1)) was obtained at a superficial gas velocity of 127.5 m h(-1) (corresponding to a residence time of 28 s) and a toluene inlet concentration of 4.0 g m(-3) . Under these operating conditions, toluene removal efficiency was only 0.238, which suggested that effective operation required higher residence times . Removal efficiencies higher than 0.9 were achieved at organic loads less than 113.7 g m(-3) h(-1) . A macro-kinetic study, performed using concentration profiles along the bioreactor, revealed this process was limited by diffusion at organic loads less than 100 g m(-3) h(-1) and by biological reaction beyond this threshold.

Appl Environ Microbiol, 2000 Sep, 66(9), 3878 - 82
Ethylene removal at low temperatures under biofilter and batch conditions; Elsgaard L; Removal of the plant hormone ethylene (C(2)H(4)) is often required by horticultural storage facilities, which are operated at temperatures below 10 degrees C . The aim of this study was to demonstrate an efficient, biological C(2)H(4) removal under such low-temperature conditions . Peat-soil, acclimated to degradation of C(2)H(4), was packed in a biofilter (687 cm(3)) and subjected to an airflow ( approximately 73 ml min(-1)) with 2 ppm (microl liter(-1)) C(2)H(4) . The C(2)H(4) removal efficiencies achieved at 20, 10, and 5 degrees C, respectively, were 99.0, 98.8, and 98.4% . This corresponded to C(2)H(4) levels of 0.022 to 0.032 ppm in the biofilter outlet air . At 2 degrees C, the average C(2)H(4) removal efficiency dropped to 83% . The detailed temperature response of C(2)H(4) removal was tested under batch conditions by incubation of 1-g soil samples in a temperature gradient ranging from 0 to 29 degrees C with increments of 1 degrees C . The C(2)H(4) removal rate was highest at 26 degrees C (0.85 microg of C(2)H(4) g {dry weight}(-1) h(-1)), but remained at levels of 0.14 to 0.28 microg of C(2)H(4) g (dry weight)(-1) h(-1) at 0 to 10 degrees C . At 35 to 40 degrees C, the C(2)H(4) removal rate was negligible (0.02 to 0.06 microg of C(2)H(4) g {dry weight}(-1) h(-1)) . The Q(10) (i.e., the ratio of rates 10 degrees C apart) for C(2)H(4) removal was 1.9 for the interval 0 to 10 degrees C . In conclusion, the present results demonstrated microbial C(2)H(4) removal, which proceeded at 0 to 2 degrees C and produced a moderately psychrophilic temperature response.

Blood Purif, 2000, 18(3), 177 - 82
Homocysteine as a cardiovascular risk factor; Biasioli S et al.; Hyperhomocysteinemia (HH), a known risk factor for vascular diseases, is a frequent condition in hemodialysis (HD) patients . HH induces an oxidant stress to the vascular endothelium, causing a failure of vasodilation and an impairment of the antithrombotic properties . Vitamins B(6), B(12) and folic acid are important cofactors for the enzymes in the catabolism of homocysteine (Hcy) . Failure of Hcy catabolism forces the cell to export Hcy into the plasma . The kidney is an important metabolic site for removal (up to 70%) of plasma Hcy (P-Hcy) . HD lowers the P-Hcy concentration by 29 and 41% with cellulosic and noncellulosic membranes, respectively, yet values return to normal in only a few patients . Clearly, we must decrease the dangerous high levels of Hcy in different ways . Vitamin Supplementation: Vitamins B(6), B(12) and folic acid decreased the basal level of Hcy by about 40%, starting from the sixth month . Membranes: Some membranes performed better than the others . Techniques: On the chronic basis, in our 1-year experience, paired filtration dialyis led to the best results, when compared to bicarbonate dialysis and acetate-free biofiltration . Finally, as in HD patients no one type of treatment can normalize the P-Hcy concentration, we should try other, different strategies such as absorption, the use of liposomes and new types of supplementation .

Appl Biochem Biotechnol, 2000 Spring, 84-86, 469 - 78
Design and performance of a fibrous bed bioreactor for odor treatment; Chua H et al.; Biological processes have become popular for odor treatment . In this study, a novel fibrous bed bioreactor was applied for treatment of odorous gas . The column reactor was packed with spirally wound fibrous sheet material on which a consortium of microorganisms selected from activated sludge was immobilized . The first stage of this work comprised a preliminary study that aimed at investigating the feasibility of the fibrous bed bioreactor for treatment of odorous volatile fatty acids (VFAs) . In this stage, the performance of a fibrous bed bioreactor at increasing mass loadings ranging from 9.7 to 104.2 g/(m3.h) was studied . VFA removal efficiencies above 90% were achieved at mass loadings up to 50.3 g/(m3.h) . At a mass loading of 104.2 g/(m3.h), removal efficiency was found to be 87.7% . In the second stage of the work, the process was scaled up with design and operational considerations, namely, packing medium, process condition, and configuration selections . A trickling biofilter with synthetic fibrous packing medium was selected . It was operated under countercurrent flow of gas and liquid streams . The effects of inlet concentration and empty bed retention time on bioreactor performance were studied . The bioreactor was effective in treating odorous VFAs at mass loadings up to 32 g/(m3.h), at which VFAs started to accumulate in the recirculation liquid, indicating that the biofilm was unable to degrade all the VFAs introduced . Although VFAs accumulated in the liquid phase, the removal efficiency remained above 99%, implying that the biochemical reaction rate, rather than gas-to-liquid mass transfer rate, was the limiting factor of this process . The bioreactor was stable for long-term operation; no clogging and degeneration of the packing medium was observed during the 4-mo operation.

Indoor Air, 2000 Mar, 10(1), 39 - 46
The biofiltration of indoor air: implications for air quality; Darlington A et al.; An alternative method of maintaining indoor air quality may be through the biofiltration of air recirculating within the structure rather than the traditional approach of ventilation . This approach is currently being investigated . Prior to its acceptance for dealing with volatile organic compounds (VOCs) and CO2, efforts were made to determine whether the incorporation of this amount of biomass into the indoor space can have an (negative) impact on indoor air quality . A relatively large ecologically complex biofilter composed of a ca . 10 m2 bioscrubber, 30 m2 of plantings and a 3,500 litre aquarium were established in a 160 m2 'airtight' room in a recently constructed office building in downtown Toronto . This space maintained ca . 0.2 air changes per hour (ACH) compared to the 15 to 20 ACH (with a 30% refresh rate) of other spaces in the same building . Air quality parameters of concern were total VOCs (TVOCs), formaldehyde and aerial spore counts . TVOC and formaldehyde levels in the biofilter room were the same or significantly less than other spaces in the building despite a much slower refresh rate . Aerial spore levels were slightly higher than other indoor spaces but were well within reported values for 'healthy' indoor spaces . Levels appeared to be dependent on horticultural management practices within the space . Most genera of fungal spores present were common indoors and the other genera were associated with living or dead plant material or soil . From these results, the incorporation of a large amount of biomass associated with indoor biofilters does not in itself lower indoor air quality.

Biochem, Eng . J. . 2000 Jul 1, 5(3), 231 - 242
Biofiltration as an odour abatement strategy; McNevin D et al.; The chemical, physical and biological processes occurring in biofiltration are reviewed . A survey of operating biofilter performances is also presented and includes some novel comparative methods . It is concluded that biofiltration is a simple and cost-effective technology for odour removal and that an understanding of the many interactions occuring within the biofilter is essential for the optimal performance of the biofilter.

Schriftenr Ver Wasser Boden Lufthyg, 1999, 104, 685 - 701
{Determining the emission of microorganisms from biofilters and emission concentrations at the site of composting areas}; Schilling B et al.; In order to assess source emissions and dispersal of airborne culturable microorganisms from composting plants, measurements at three composting plants have been carried out . The downwind concentrations of dispersed microorganisms differed greatly, depending on the type of plant design . At 200 metres downwind from the totally enclosed composting plant, levels of spore concentrations of thermotolerant fungi and Aspergillus fumigatus, which may be regarded as characteristic for composting operations, were not above the magnitude of background concentrations . In contrast, spore concentrations in excess of the background level occurred within 500 metres of the partly open plant . Moreover, the ranges of airborne concentrations at similar distances from the enclosed plant were much smaller relative to the partly open plant . Measurement of source emissions from biofilters showed concentrations in the raw and purified gases in the range of up to three orders of magnitude . The operational characteristics of the plants generally contributing to bioaerosol emissions on-site were found to have an influence on the concentration levels in the raw gas . A decrease in the microbiological parameters which may be regarded as specific for composting operations, was attributed to a reduced rate of passage through the biofilters . The magnitude of reduction as well as the concentrations varied greatly.

Int J Artif Organs, 2000 Mar, 23(3), 173 - 80
The effect of hemodialysis and acetate-free biofiltration on anemia; Eiselt J et al.; The authors monitored, for a period of 12 months, anemia-, nutrition-, and free radical-related parameters and the rHuEPO dose required to maintain target hemoglobin (Hb) in 20 patients with chronic renal failure . Ten patients each were randomized for treatment by either acetate-free biofiltration (AFB) or low-flux hemodialysis (HD) . At baseline, Hb levels were 102+/-2 (AFB) vs . 98+/-2 g/L (HD) (not significant difference, NS), the rHuEPO dose was 4050+/-976 vs . 5100+/-1538 lU/week (NS) . Compared with baseline and with HD, lower rHuEPO doses were required during AFB at months 8, 9, 10 and 11, and 12 when they were 2100+/-510 (AFB) vs . 6000+/-1153 (HD), p=0.008 . Prealbumin, transferrin and cholinesterase levels rose in the AFB group . Kt/V, albumin, transferrin saturation, aluminium, bicarbonate in serum, superoxide dismutase and glutathione peroxidase in erythrocytes, and malondialdehyde and antioxidant capacity in plasma did not differ between the AFB and HD groups . In terms of anemia control, AFB using an AN69 membrane was found to be more advantageous than low-flux HD, AFB improves some nutritional parameters . The compared methods do not differ in their effect on lipid peroxidation and the antioxidant system.

Syst Appl Microbiol, 1999 Dec, 22(4), 626 - 34
Characterization of microbial communities of biofilters by phospholipid fatty acid analysis and rRNA targeted oligonucleotide probes; von Keitz V et al.; The microbial community of a biofilter for waste gas treatment of an animal rendering plant was characterized by the analyses of the phospholipid fatty acids (PLFAs) of the filter material . For these analyses five samples of one filter were taken in intervals between one and two months . The main components of the PLFA profiles were straight chain saturated, monounsaturated and cyclopropyl fatty acids . Terminally branched and 10-methyl branched fatty acids were present in minor amounts . The structure and succession of the microbial community was interpreted by the presence and quantitative changes of diagnostic fatty acids . The stability of diagnostic fatty acids in relation to varying incubation parameters was tested for a number of bacterial isolates from biofilters representing different phylogenetic branches . For two samples, the data from the PLFA-analyses were compared with data obtained by hybridization with fluorescently labeled, rRNA-targeted oligonucleotide probes specific for the alpha-, beta- and gamma-subclass of the Proteobacteria, the Actinobacteria (Firmicutes with high G+C content) and the Firmicutes with low G+C content . These data indicated a dominating number of Proteobacteria (54% and 35% of DAPI-stained cells), in which the gamma-Proteobacteria represented the main fraction . Actinobacteria were detected in minor amounts, the number of Firmicutes with low G+C content was near the detection limit of the method . About half of the cells detected with a probe specific for Bacteria did not hybridize with the probes specific for the alpha-, beta- and gamma subclass of the Proteobacteria and the two subgroups of the Firmicutes . The results of both methods, the fluorescence in situ hybridization (FISH) and the PLFA analyses corresponded well and were best suited to confirm and complement each other.

Environ Health Perspect, 2000 Apr, 108(4), A178 - 80
The trickle-down theory of cleaner air; Frazer L; The 1990 Clean Air Act Amendments prompted an increased urgency to find new ways to treat airstreams containing volatile organic compounds, which affect the nitrogen photolytic cycle and help produce ground-level ozone, hazardous air pollutants, and odorous air emissions such as hydrogen sulfide . Scientists at the New Jersey company Envirogen have adapted traditional biofiltration technology to perform airborne waste stream cleanup . Preliminary research on pollutants such as phenol, methylene chloride, benzene, and toluene indicates that Envirogen's biotrickling filter may remove an average of about 94% of total hazardous air pollutants . Scientists are working to identify microbes that will clean up more stubborn pollutants.

Biotechnol Bioeng, 2000 May 20, 68(4), 448 - 55
Influence of mixing and water addition on the removal rate of toluene vapors in a biofilter; Auria R et al.; The effects of successive mixing (homogenization) of packing material (peat), with or without water addition, on the removal of toluene vapors in a biofilter were studied . Over a period of 50 days, an increase in the Elimination Capacity (EC) of approximately 240% was obtained by successive mixing and water additions . After each mixing, a high EC of toluene was maintained only for a short period of 3-4 days . After this time, decreased biofilter performance was observed, probably associated with the development of dried and/or clogged zones . In the long-term experiments, an attenuation of the EC recovery was observed after successive mixing . In this case, an increase of 110% over 4 months of experiment was obtained . The global reduction of EC over time could be explained by the colonization of the biofilter by filamentous fungi which was facilitated by the mixing of the packing material . The most frequently observed fungi were identified as Scedosporium sp . and Cladosporium sp .

J Air Waste Manag Assoc, 2000 Mar, 50(3), 411 - 7
Removal of BTEX vapor from waste gases by a trickle bed biofilter; Lu C et al.; The system performance of a trickle bed biofilter for treating single and mixed benzene, toluene, ethylbenzene, and o-xylene (BTEX) vapors from waste gases was investigated under different gas flow rates and influent BTEX concentrations . When a single substrate was fed, removal efficiencies of greater than 90% could be achieved for the loads below 64 g benzene/m3/hr, 110 g toluene/m3/hr, 53 g ethylbenzene/m3/hr, and 55 g o-xylene/m3/hr . When a mixed substrate was fed, removal efficiencies of each compound could be above 90% at BTEX loads below 96 g/m3/hr . The trickle bed biofilter appears to be an effective treatment process for removing both single and mixed BTEX vapors with low to high loads . Under similar substrate loads, BTEX vapors were preferentially biodegraded in the order of toluene, benzene, o-xylene, and ethylbenzene . The volumetric removal rates (elimination capacities) of BTEX vapors for a single-substrate feed were higher than those for a mixed-substrate feed under similar substrate loads; these differences were enhanced at higher substrate loads and less significant for a preferred substrate.

J Microbiol Methods, 2000 Apr, 40(2), 181 - 91
The measurement of toluene dioxygenase activity in biofilm culture of Pseudomonas putida F1; Woo H et al.; Toluene dioxygenase (Tod) enzyme activity can be measured by the conversion of indole to indigo . Indigo is measured spectrophotometrically at 600 nm . However, this method is inadequate to measure the whole-cell enzyme activity when interference by suspended biomass is present . Indoxyl is a highly fluorescent intermediate in the conversion of indole to indigo by Tod . A fluorescence-based assay was developed and applied to monitor Tod activity in whole cells of Pseudomonas putida F1 biofilm from a continuously operated biofilter . Suspended growth studies with pure cultures indicated that indoxyl, as measured by fluorescence, correlated with indigo production (r(2)=0.89) as measured by spectrophotometry . Whole-cell enzyme activity was followed during growth on a minimal medium containing toluene . The maximum normalized whole cell enzyme activity of 19+/-1.5x10(-4) mg indigo (mg protein)(-1) min(-1) was reached during early stationary phase . P . putida F1 cells from a biofilm grown on vapor phase toluene had a normalized whole-cell enzyme activity of 5.0+/-0.2x10(-4) mg indigo (mg protein)(-1) min(-1) . The half-life of whole-cell enzyme activity was estimated to be between 5.5 and 8 h in both suspended and biofilm growth conditions.

J Hazard Mater, 2000 Feb 1, 72(1), 77 - 90
Comparison of organic and inorganic packing materials in the removal of ammonia gas in biofilters; Kim NJ et al.; Two organic and two inorganic packing materials were compared with regard to the removal of ammonia gas in a biofilter inoculated with night-soil sludge . By gradually increasing the inlet load of ammonia, the complete removal capacity, which was defined as the inlet load of ammonia that was completely removed, and the maximum removal capacity of ammonia, which was the value when the removal capacity leveled off for each packing material, were estimated . Both values which were based on a unit volume of packing material, were higher for organic packing materials than inorganic ones . By using kinetic analysis, the maximum removal rate of ammonia, V(m), and the saturation constant, K(s), were determined for all packing materials and the values of V(m) for organic packing materials were found to be larger . By using the kinetic parameters, the removal rates for ammonia were compared among the four packing materials, and the organic packing materials showed superior performance for the removal of ammonia in the concentration range of 0-300 ppm as compared to inorganic packing materials.

Berl Munch Tierarztl Wochenschr, 1999 Dec, 112(12), 444 - 7
{Reduction efficiencies of a biofilter and a bio-scrubber as bio-aerosols in two piggeries}; Seedorf J et al.; Biofilters and bioscrubbers are ultimate tools to control odour emissions from animal houses in pig and poultry production . Little is known about the efficiency of these devices to remove airborne particulate pollutants such as dust, microorganisms and endotoxins from the exhaust air of animal houses . Preliminary results of a one year field campaign in two piggeries show that the biofilter reduces the number of particles in the exhaust air by 79 to 96% . The efficiency of the bioscrubber was 22% only . The biofilter reduced the amount of mesophilic bacteria by 11% and 71%, respectively, the amount of thermotolerant fungi by 71% . The concentration of endotoxin and mesophilic fungi in the clean air after the bioscrubber was 3.8 times resp . 2.7 times higher than in the air of the piggery . The washing water which is regularly recirculated in both systems was highly contaminated with varying amounts of air contaminants . It seems that the quality of the washing water distinctly influences the reduction efficiency of both systems.

J Nephrol, 1999 Nov-Dec, 12(6), 375 - 82
A prospective randomised European multicentre study of medium-long run mortality and morbidity comparing acetate-free biofiltration and bicarbonate dialysis; Santoro A et al.; In recent years, the progressive increase in the mean age of the population entering chronic dialysis treatment has been responsible, on the one hand, for the growing number of patients undergoing regular dialysis, and on the other, for the high number of "critical" patients, both as a result of their age and the presence of concomitant morbidity . Thus, dialysis treatment today is not only aimed at waste removal and water-electrolyte homeostasis, but also at a reduction in morbidity and mortality, and at improving the patients' quality of life, thanks to the use of biocompatible materials and the achievement of good cardiovascular tolerance to treatment . Consequently, diffusive-convective dialysis procedures have been on the increase, since they combine better depuration with the use of biocompatible high-flux membranes . Acetate-free biofiltration (AFB) is a diffusive-convective dialysis procedure which utilises a high-flux membrane, AN69, post-dilution infusion of a sodium bicarbonate solution (NaHCO3), and a dialysate which is completely free of any buffer, and thus also free of acetate, which may have various negative effects on the patient . A number of studies have already shown the better hemodynamic stability and the reduction of intradialytic side-effects during AFB . All these, however, were short-term studies . To verify the beneficial effects of AFB in the long run, a three year multicentre randomised European trial has been proposed to compare bicarbonate hemodialysis (BD), a technique used in nearly 80% of the world's dialysis population, and AFB . The specific aim of the investigation is to verify, in a large number of patients, the results of hemodialysis treatment in terms of morbidity, mortality and quality of life . The study involves 80 hemodialysis units across Italy, France, Germany, Spain, Slovenia and Croatia, with enrollment of about 400 patients considered "critical" for at least one of the following reasons: age, diabetes, dialysis cardiovascular instability . Fifty percent of the patients are to undergo AFB with the AN69 membrane and bicarbonate solution infusion (NaHCO3 145 or 167 mEq/lt), and the other fifty percent are to be treated by BD, with any membrane except the nonmodified cellulosic one . Biochemical, cardiological, and nutritional parameters will be considered throughout the study . Mortality, morbidity both in terms of intra- and interdialysis symptoms - and hospitalisation rate, as well as the patients' quality of life, evaluated by the SF36 questionnaire, will be analysed.

Appl Microbiol Biotechnol, 1999 Nov, 52(6), 863 - 8
Analysis of the relative abundance of different types of bacteria capable of toluene degradation in a compost biofilter; Juteau P et al.; A microbial community of a compost biofilter treating toluene vapors was investigated using serum-bottle assays and mineral-agar plates . Toluene was not consumed in the absence of oxygen . However, filter-bed extracts exposed to toluene vapor as the only carbon source produced distinct colony types (phenotypic groups) that were counted separately . Strains from each group were isolated and checked for toluene-degradation activity in serum bottles . Only 15% of colonies were true toluene degraders . This population was divided into 11 genotypic groups based on DNA fingerprints . Identification of a member of each group using 16S rRNA gene-sequence comparison showed that they belonged to seven genera: Acinetobacter, Azoarcus, Mycobacterium, Nevskia, Pseudomonas, Pseudonocardia and Rhodococcus . Together, members of the genera Pseudonocardia and Rhodococcus were 34 times more numerous than all the others . We hypothesized that these two organisms are K-strategists (adapted to a resource-restricted and crowded environment) and that the compost biofilter is a K-environment . This would explain why they are not outnumbered by faster growers like Pseudomonas or Acinetobacter species, which would be r-strategists (adapted to a resource-abundant and uncrowded environment).

Appl Environ Microbiol, 1999 Nov, 65(11), 4788 - 92
Biodegradation of methyl tert-butyl ether by a bacterial pure culture; Hanson JR et al.; A bacterial strain, PM1, which is able to utilize methyl tert-butyl ether (MTBE) as its sole carbon and energy source, was isolated from a mixed microbial consortium in a compost biofilter capable of degrading MTBE . Initial linear rates of MTBE degradation by 2 x 10(6) cells ml(-1) were 0.07, 1.17, and 3.56 microg ml(-1) h(-1) for initial concentrations of 5, 50, and 500 microg MTBE ml(-1), respectively . When incubated with 20 microg of uniformly labeled {(14)C}MTBE ml(-1), strain PM1 converted 46% to (14)CO(2) and 19% to (14)C-labeled cells within 120 h . This yield is consistent with the measurement of protein accumulation at different MTBE concentrations from which was estimated a biomass yield of 0.18 mg of cells mg MTBE(-1) . Strain PM1 was inoculated into sediment core material collected from a contaminated groundwater plume at Port Hueneme, California, in which there was no evidence of MTBE degradation . Strain PM1 readily degraded 20 microg of MTBE ml(-1) added to the core material . The rate of MTBE removal increased with additional inputs of 20 microg of MTBE ml(-1) . These results suggest that PM1 has potential for use in the remediation of MTBE-contaminated environments.

Sci Total Environ, 1999 Sep 1, 235(1-3), 169 - 78
Comparison of the heavy metal content of motorway stormwater following discharge into wet biofiltration and dry detention ponds along the London Orbital (M25) motorway
Hares RJ, Ward NI.
The Surrey section of the London Orbital M25 motorway uses mainly detention pond facilities for the treatment of stormwater runoff . A majority of these implement the use of dry detention basins . However, in a few locations biofiltration facilities operate through the use of reed bed systems . An assessment of the removal efficiencies for both wet biofiltration and dry pond treatment facilities was undertaken . Motorway-derived contaminants, including V, Cr, Mn, Co, Ni, Cu, Zn, Mo, Cd, Sb and Pb, were measured in unfiltered stormwater collected during the initial stages of a storm event using inductively coupled plasma mass spectrometry (ICP-MS) . Results suggest that a higher level of motorway-derived heavy metal contamination exists in stormwater runoff from a road section with a higher average daily traffic density . In addition, a comparison of both sites shows a higher percentage removal efficiency of heavy metals in stormwater from the biofiltration facility.

J Air Waste Manag Assoc, 1999 Sep, 49(9), 1068 - 74
Removal of low concentrations of carbon tetrachloride in compost-based biofilters operated under methanogenic conditions; Lee BD et al.; Research was performed to demonstrate the removal of carbon tetrachloride (CT) using compost biofilters operated under methanogenic conditions . Biofilters were operated at an empty-bed residence time of 2.8 minutes using nitrogen as the atmosphere . Hydrogen and carbon dioxide were supplied as an electron donor and carbon source, respectively, during acclimation of the bed medium microbes . Once methanogenesis was demonstrated, CT flow to the biofilter was established . Biofilters were operated over a CT concentration range from 20 to 700 ppbv for 6 months . Bed medium microbes were able to remove up to 75% of the inlet CT . At excessively high CT concentrations (> 500 ppmv), methane production and hydrogen utilization by the bed medium microbes appeared to be inhibited . CT removal by the biofilter decreased when the hydrogen supply was removed from the biofilter inlet, indicating that hydrogen acted as the electron donor for reductive dechlorination . The removal efficiency and relatively low empty bed residence times demonstrated by these laboratory-scale biofilters indicate that anaerobic biofiltration of CT may be a feasible full-scale process.

Biodegradation, 1999 Jun, 10(3), 169 - 76
Biofilter performance and characterization of a biocatalyst degrading alkylbenzene gases; Veiga MC et al.; A biofilter treating alkylbenzene vapors was characterized for its optimal running conditions and kinetic parameters . Kinetics of the continuous biofilter were compared to batch kinetic data obtained with biofilm samples as well as with defined microbial consortia and with pure culture isolates from the biofilter . Both bacteria and fungi were present in the bioreactor . Five strains were isolated . Two bacteria, Bacillus and Pseudomonas, were shown to be dominant, as well as a Trichosporon strain which could, however, hardly grow on alkylbenzenes in pure culture . The remaining two strains were most often overgrown by the other three organisms in liquid phase batch cultures . mu max, KS, KI values and biodegradation rates were calculated and compared for the different mixed and pure cultures . Since filter bed acidification was observed during biofiltration studies reaching a pH of about 4, experiments were also undertaken to study the influence of pH on performance of the different cultures . Biodegradation and growth were possible in all cases, over the pH range 3.5-7.0 at appreciable rates, both with mixed cultures and with pure bacterial cultures . Under certain conditions, microbial activity was even observed in the presence of alkylbenzenes down to pH 2.5 with mixed cultures, which is quite unusual and explains the ability of the present biocatalyst to remove alkylbenzenes with high efficiency in biofilters under acidic conditions.

J Air Waste Manag Assoc, 1999 Aug, 49(8), 973 - 9
Biofiltration of high loads of ethyl acetate in the presence of toluene; Deshusses M et al.; To date, biofilters have been used primarily to control dilute, usually odorous, off-gases with relatively low volatile organic compound (VOC) concentrations (< 1 g m-3) and VOC loads (< 50 g m-3 hr-1) . Recently, however, U.S . industry has shown an interest in applying biofilters to higher concentrations of VOCs and hazardous air pollutants (HAPs) . In this study, the behavior of biofilters under high loads of binary VOC mixtures was studied . Two bench-scale biofilters were operated using a commercially available medium and a mixture of wood chips and compost . Both were exposed to varying mixtures of ethyl acetate and toluene . Concentration profiles and the corresponding removal efficiencies as a function of VOC loading were determined through frequent grab-sampling and GC analysis . Biofilter response to two frequently encountered operating problems--media dry-out and operating temperatures exceeding 40 degrees C--was also evaluated under controlled conditions . Microbial populations were also monitored to confirm the presence of organisms capable of degrading both major off-gas constituents . The results demonstrated several characteristics of biofilters operating under high VOC load conditions . Maximum elimination capacities for ethyl acetate were typically in the range of 200 g m-3 hr-1 . Despite the presence of toluene degraders, the removal of toluene was inhibited by high loads of ethyl acetate . Several byproducts, particularly ethanol, were formed . Short-term dry-out and temperature excursions resulted in reduced performance.

J Air Waste Manag Assoc, 1999 Jul, 49(7), 784 - 93
Characterization of compost biofiltration media; Cardenas-Gonzalez B et al.; The effect of compost quality on performance of biofiltration media was investigated . Three types of compost media were characterized in terms of their key properties, including pH, total organic carbon (TOC) and nitrogen, moisture content, oxygen uptake rates and heterotrophic and fungal plate counts . Laboratory-scale biofilter columns were each filled with a different compost medium mixed with buffer and a bulking agent . The columns were operated with a volatile organic compound (VOC) mixture consisting of ethyl alcohol, butyraldehyde, ethyl acetate, and 1,1-diethoxybutane and subjected to various operating conditions . After 13 months, the columns were sampled and post-characterization of the media was performed . A mixture of biosolids/horse manure compost, which had a high initial microbial activity, had the shortest acclimation period . Best overall performance, however, was observed with yard waste compost, which was the most stable medium . Media hydrophobicity was a key factor in long-term performance . Significant changes in compost structure, moisture content, pH, volatile solids, oxygen uptake rates, and microbial population densities were observed over the course of the study . Analyses of organic nitrogen content showed that significant amounts of nitrogen were not depleted from the media.

Appl Environ Microbiol, 1999 Aug, 65(8), 3547 - 54
Community analysis of biofilters using fluorescence in situ hybridization including a new probe for the Xanthomonas branch of the class Proteobacteria; Friedrich U et al.; Domain-, class-, and subclass-specific rRNA-targeted probes were applied to investigate the microbial communities of three industrial and three laboratory-scale biofilters . The set of probes also included a new probe (named XAN818) specific for the Xanthomonas branch of the class Proteobacteria; this probe is described in this study . The members of the Xanthomonas branch do not hybridize with previously developed rRNA-targeted oligonucleotide probes for the alpha-, beta-, and gamma-Proteobacteria . Bacteria of the Xanthomonas branch accounted for up to 4.5% of total direct counts obtained with 4',6-diamidino-2-phenylindole . In biofilter samples, the relative abundance of these bacteria was similar to that of the gamma-Proteobacteria . Actinobacteria (gram-positive bacteria with a high G+C DNA content) and alpha-Proteobacteria were the most dominant groups . Detection rates obtained with probe EUB338 varied between about 40 and 70% . For samples with high contents of gram-positive bacteria, these percentages were substantially improved when the calculations were corrected for the reduced permeability of gram-positive bacteria when formaldehyde was used as a fixative . The set of applied bacterial class- and subclass-specific probes yielded, on average, 58.5% (+/- a standard deviation of 23.0%) of the corrected eubacterial detection rates, thus indicating the necessity of additional probes for studies of biofilter communities . The Xanthomonas-specific probe presented here may serve as an efficient tool for identifying potential phytopathogens . In situ hybridization proved to be a practical tool for microbiological studies of biofiltration systems.

Arch Environ Contam Toxicol, 1999 Aug, 37(2), 151 - 7
Characterization of alpha-pinene-degrading microorganisms and application to a bench-scale biofiltration system for VOC degradation
Kleinheinz GT, Bagley ST, St John WP, Rughani JR, McGinnis GD.
A study was conducted to isolate and characterize monoterpene-degrading microorganisms and apply them to a biofiltration unit for use in degrading high levels of alpha-pinene . Soil from a monoterpene-contaminated site was used with enrichment culture techniques to recover a consortium of bacteria able to utilize alpha-pinene as the sole source of carbon and energy . The Biolog system was utilized to identify the bacteria as Pseudomonas fluorescens and Alcaligenes xylosoxidans . Aerobic growth and biodegradation studies confirmed that rapid growth and biodegradation were being achieved with alpha-pinene . Complete degradation of alpha-pinene was achieved in 36 h with a maximum rate of degradation of 3.9 mg/L/h . The microorganisms were placed in a biofiltration column and demonstrated good removal of alpha-pinene from an air stream at concentrations averaging 295 ppmv . A nitrogen test was performed and confirmed that the removal of alpha-pinene was due to biological activity . Given the ability of these microorganisms to utilize high levels of alpha-pinene, they will be used in a coupled treatment system using a physical/chemical adsorption/desorption unit coupled to a biofiltration column . Often, biofiltration studies are performed using much lower levels of analyte in the influent air stream . However, the ability of these microorganisms to utilize higher levels of compounds expands the capabilities for future coupled biofiltration systems . During future studies, high flow rates with low levels of analyte will be concentrated so that a higher analyte concentration and lower flow rate can be utilized with the biofilter.com/link/service/journals/00244/bibs/37n2p151.html

Clin Nephrol, 1999 May, 51(5), 304 - 9
Improved cardiovascular variables during acetate free biofiltration; Schrander-vd Meer AM et al.; BACKGROUND AND AIM: Acetate free biofiltration (AFB) provides a well-tolerated and efficient renal replacement therapy . Replacement of most of the acetate by bicarbonate in standard hemodialysis has resulted in a decrease in intradialytic hypotensive episodes . This has been attributed to a decrease in the acetate-induced impairment of myocardial contractility . The aim of the present study was to investigate whether the total absence of acetate in AFB would further enhance dialysis stability and improve cardiovascular status . PATIENTS AND METHODS: In a long-term, randomized trial we included 11 patients on AFB and 9 patients on bicarbonate hemodialysis (HD) for one year . Patients were matched for age, sex and urea reduction rate, but not for the presence of hypertension or cardiovascular history . During each dialysis session blood pressure was measured automatically and the presence of significant hypotension was recorded . Antihypertensive medication was registered every three months . Before and at the end of the study M-mode echocardiography was performed and left ventricular mass index (LVMi) was calculated . Every six months serum lipids were measured . RESULTS: At baseline, mean arterial pressure (MAP) before and after dialysis, the percentage of hypotensive dialyses, LVMi and serum lipids did not differ between AFB and HD . Pre-dialysis MAP decreased in AFB (from 112.5 to 107 mmHg) and increased in HD (from 101.7 to 105.3 mmHg; p = 0.01, HD versus AFB) . Postdialysis MAP remained stable in both groups (AFB 91.6 mmHg at 0 months and 90.6 mmHg at 12 months, for HD respectively 83.9 and 86.5 mmHg, NS) . The percentage of hypotensive dialyses did not differ significantly between the groups during the study . LVMi decreased in AFB from 195.4 to 162.1 gr/m2 and increased in HD patients from 153.8 to 182.5 gr/m2 (p = 0.03 HD versus AFB) . The number of antihypertensive medications per patient did not differ between groups . Serum lipids remained unchanged during the trial . CONCLUSION: In conclusion, AFB provided better control of pre-dialysis MAP compared to HD, and stable postdialysis MAP . The percentage of dialysis sessions with hypotension did not differ . LVMi decreased significantly in AFB, but rose in HD.

ASAIO J, 1999 May-Jun, 45(3), 151 - 6
Duocart biofiltration: a new method of hemodialysis; Mercadal L et al.; DuoCart biofiltration (DCB) is a new hemodialysis method using a dialysate with only sodium chloride and bicarbonate obtained from two separate powder cartridges (BiCart and SelectCart, Gambro, Sweden) . The ionic complement is directly reinfused in postdilution mode, using one 2 L bag of a specially designed sterile solution . The adaptation of the quantity of these infused substances to their removal through the dialysis membrane is made possible by repeated measurements of ionic dialysance (D), which are automatically performed every 30 min by the Diascan module, systematically available on the Integra dialysis monitor (Hospal, Italy), and by subsequent modification of the infusion rate (Q(R)) . An appropriate kinetic model was used to determine the composition of the reinfusion solution (mM: 57 K, 47 Ca, 14.5 Mg, 180 Cl), the conductivity dialysate (set at 14.8 mS/cm) and the ratio Q(R)/D (set at 1/28) . This ratio is kept constant by updating Q(R) after each measurement of D . The implementation of this technique requires an Integra dialysis monitor equipped with a two-powder-cartridge dialysate generation system . Fifteen dialysis sessions were performed (duration: 213+/-38 min; blood flow: 238+/-26 ml/min; ultrafiltration rate: 16+/-6 ml/min) . The per-dialytic changes of ion plasma concentrations were monitored and found to be within the predicted range . The results substantiate the feasibility of this new hemodialysis method that presents several advantages: dialysate concentrates are in powder form, an alkaline and acetate-free dialysate is used with superior dialysate biocompatibility, no precipitation of Ca and Mg carbonate occurs in the dialysate circuit, the supply of calcium and potassium is easily adapted to individual patients' needs by change in the composition of the reinfusion solution, and a calcium-free dialysate that facilitates citrate anticoagulation is used.

J Air Waste Manag Assoc, 1999 May, 49(5), 544 - 53
VOC elimination in a compost biofilter using a previously acclimated bacterial inoculum; Quinlan C et al.; A comparison of biodegradation efficiencies was done for volatile benzene, toluene, ethylbenzene, m-xylene, p-xylene, and o-xylene elimination in a compost biofilter . The column was first exposed to a synthetic mixture and then a free phase product mixture containing these compounds at increasing pollutant loads . The optimal moisture content of the system was determined, and this was used in the biodegradation experiments . An acclimated culture was used as an inoculum for the biofilter, the matrix of which consisted of composted forestry products, composted sewage sludge, lime, and perlite . Inlet and outlet concentrations were measured, and pollutant loads, elimination capacities, and removal efficiencies were determined for each of the compounds . Optimal moisture content for this system was found to be 40%, and the short lag times (one to five days) in acclimating to the compounds was ascribed to the presence of the well-acclimated inoculum . The compounds in the synthetic mixture had higher removal efficiencies (80-99%) even at the higher pollutant loads experienced, with the exception of o-xylene . Dynamic removal efficiencies and acclimation periods were seen in the free phase product mixture, with a removal efficiency range from 70 to 95% . This was attributed to the presence of chlorinated aliphatics in the free phase product.

Appl Microbiol Biotechnol, 1999 Apr, 51(4), 536 - 40
Effects of nitrogen limitation on biofilm formation in a hydrocarbon-degrading trickle-bed filter; Holubar P et al.; The effect of nitrogen limitation on young and mature steady-state biofilm in a trickle-bed filter was studied . Toluene and n-heptane were the sole carbon source . Biomass concentration, respiration, substrate-induced respiration, metabolic quotient, and total hydrocarbon degradation efficiency were measured . The aim of the experiment was to control excess biomass production in the trickle-bed filter by limiting the mineral nutrients and to achieve increased mineralization of the carbon source . Biofilm growth responded strongly to the amount of available nitrogen, whereas hydrocarbon degradation efficiency reached a maximum of 60% and could not be increased even by further addition of nitrogen . The experiments showed that 95% of the adsorbed carbon was mineralized completely and only 5% was used for biofilm formation . This complete mineralization can also be concluded from the metabolic quotient . The value of the latter was about 6-10 mg CO2-C g-1 Cmic h-1, indicating an expanded energy demand due to stress effects in the presence of nutrient deficiency . It was postulated that determination of the metabolic quotient could be an simple instrument to measure the rate of mineralization of carbon sources and also the rate of biomass formation in trickle-bed filters or biofilters.

Biotechnol Bioeng, 1999 Apr 20, 63(2), 175 - 84
Microbiological and kinetic aspects of a biofilter for the removal of toluene from waste gases
Acuna ME, Perez F, Auria R, Revah S.
Microbiological and kinetic aspects of a biofilter inoculated with a consortium of five bacteria and two yeast adapted to remove toluene vapors were investigated . Initially the toluene sorption isotherm on peat and the effect of different environmental conditions on the toluene consumption rates of this consortium were measured . The fast start-up of the biofilter and the decay in the elimination capacity (EC) were reproduced using microcosm assays with toluene successive additions . Nutrient limitation and a large degree of heterogeneity were also detected . EC values, extrapolated from microcosms, were higher than biofilter EC when it was operating close to 100% efficiency but tended to relate better as the biofilter EC diminished . In studies on the microbial evolution in the biofilter, an increase in the cell count and variation in the ecology of the consortium were noted . Bacterial counts up to 10 x 10(11) cfu/gdry peat were found in 88 days, which corresponds to about a 10(4) increase from inoculum . Observations with SEM showed a nonuniform biofilm development on the support and the presence of an extracellular material . The results obtained in this work demonstrated that activity measurement in microcosms concomitant to the biofilter operation could be an important tool for understanding, predicting and improving the biofiltration performance .

Biotechnol Bioeng, 1998 Nov 20, 60(4), 483 - 91
Start-up and the effect of gaseous ammonia additions on a biofilter for the elimination of toluene vapors; Morales M et al.; Biotechnological techniques, including biofilters and biotrickling filters are increasingly used to treat air polluted with VOCs (Volatile Organic Compounds) . In this work, the start-up, the effect of the gaseous ammonia addition on the toluene removal rate, and the problems of the heat accumulation on the performance of a laboratory scale biofilter were studied . The packing material was sterilized peat enriched with a mineral medium and inoculated with an adapted consortium (two yeast and five bacteria) . Start-up showed a short adaptation period and an increased toluene elimination capacity (EC) up to a maximum of 190 g/m3/h . This was related to increased CO2 outlet concentration and temperature gradients between the packed bed and the inlet (Tm-Tin) . These events were associated with the growth of the microbial population . The biofilter EC decreased thereafter, to attain a steady state of 8 g/m3/h . At this point, gaseous ammonia was added . EC increased up to 80 g/m3/h, with simultaneous increases on the CO2 concentration and (Tm-Tin) . Two weeks after the ammonia addition, the new steady state was 30 g/m3/h . In a second ammonia addition, the maximum EC attained was 40 g/m3/h, and the biofilter was in steady state at 25 g/m3/h . Carbon, heat, and water balances were made through 88 d of biofilter operation . Emitted CO2 was about 44.5% of the theoretical value relative to the total toluene oxidation, but accumulated carbon was found as biomass, easily biodegradable material, and carbonates . Heat and water balances showed strong variations depending on EC . For 88 d the total metabolic heat was -181.2 x 10(3) Kcal/m3, and water evaporation was found to be 56.5 kg/m3 . Evidence of nitrogen limitation, drying, and heterogeneities were found in this study .

Biotechnol Bioeng, 1998 Oct 5, 60(1), 97 - 104
Biomass growth monitoring using pressure drop in a cocurrent biofilter
Deront M, Samb FM, Adler N, Peringer P.
The possibility of following the biomass growth by pressure drop measurement was investigated in an aerated cocurrent upflow fixed-bed bioreactor continuously fed with wastewater containing industrial organic pollutants . The experiments were carried out in a biological filtration oxygenated reactor (Biofor) pilot plant packed with expanded clay balls (Biolite) of 2.7-mm diameter, which served as biomass carriers . The column was equipped for on-line pressure drop measurements . Correlation between pressure drop measurements and Reynolds numbers of air and water were determined in experiments carried out without biomass . Under operating conditions with biomass, it was demonstrated that column clogging and the operating time between washing cycles can be predicted depending on the volumetric organic load for a given total organic carbon inlet concentration . The biological activity of the fixed biomass was estimated from the oxygen consumption rate per unit time and carrier area . The oxygen consumption rate measurements demonstrated that the biological activity depends on the inlet substrate concentration, and that the Biofor column was most efficient between 75 and 100 g m-3 of total organic carbon inlet concentration . In the course of the wastewater treatment, using pressure drop measurements, the equivalent diameter of the Biolite particles, the reduced column macroporosity, and the biofilm thickness were calculated . An expression correlating biofilm density and biofilm thickness, as determined from the pressure drop measurements, was proposed . Good agreement was found between the fixed biomass in the reactor, determined as volatile suspended solids, and the biologically active biomass, estimated by respirometry .

Biotechnol Bioeng, 1998 Jul 5, 59(1), 40 - 51
Modeling trichloroethylene degradation by a recombinant pseudomonad expressing toluene ortho-monooxygenase in a fixed-film bioreactor
Sun AK, Hong J, Wood TK.
Burkholderia cepacia PR123(TOM23C), expressing constitutively the TCE-degrading enzyme toluene ortho-monooxygenase (Tom), was immobilized on SIRANtrade mark glass beads in a biofilter for the degradation and mineralization of gas-phase trichloroethylene (TCE) . To interpret the experimental results, a mathematical model has been developed which includes axial dispersion, convection, film mass-transfer, and biodegradation coupled with deactivation of the TCE-degrading enzyme . Parameters used for numerical simulation were determined from either independent experiments or values reported in the literature . The model was compared with the experimental data, and there was good agreement between the predicted and measured TCE breakthrough curves . The simulations indicated that TCE degradation in the biofilter was not limited by mass transfer of TCE or oxygen from the gas phase to the liquid/biofilm phase (biodegradation limits), and predicts that improving the specific TCE degradation rates of bacteria will not significantly enhance long-term biofilter performance . The most important factors for prolonging the performance of biofilter are increasing the amount of active biomass and the transformation capacity (enhancing resistance to TCE metabolism) .

J Anim Sci, 1999 Feb, 77(2), 430 - 9
Potential for reduction of odorous compounds in swine manure through diet modification; Sutton AL et al.; Recent public concern about air pollution from pork production units has prompted more research to develop methods to reduce and control odors . Masking agents, enzymes and bacterial preparations, feed additives, chemicals, oxidation processes, air scrubbers, biofilters, and new ventilation systems have been studied . Research relating the effects of the swine diet on manure odors has been scarce . Introducing feed additives to bind ammonia, change digesta pH, affect specific enzyme activity, and mask odors has been either costly or not consistently successful . Recent research emphasis has focused on manipulating the diet 1) to increase the nutrient utilization of the diet to reduce excretion products, 2) to enhance microbial metabolism in the lower digestive tract to reduce excretion of odor-causing compounds, and 3) to change the physical characteristics of urine and feces to reduce odor emissions . Primary odor-causing compounds evolve from excess degradable proteins and lack of specific fermentable carbohydrates during microbial fermentation . Reductions in ammonia emissions by 28 to 79% through diet modifications have been reported . Limited research on reduction of other odorous volatile organic compounds through diet modifications is promising . Use of synthetic amino acids with reduced intact protein levels in diets significantly reduces nitrogen excretions and odor production . Addition of nonstarch polysaccharides and specific oligosaccharides further alters the pathway of nitrogen excretion and reduces odor emission . Continued nutritional and microbial research to incorporate protein degradation products, especially sulfur-containing organics, with fermentable carbohydrates in the lower gastrointestinal tract of pigs will further control odors from manure.

Biodegradation, 1998, 9(3-4), 273 - 84
Abatement of volatile organic sulfur compounds in odorous emissions from the bio-industry; Smet E et al.; Compounds of interest in this work are methanethiol (MeSH), dimethyl sulfide (Me2S), dimethyl polysulfides (Me2Sx) and carbon disulfide (CS2) since these volatiles have been identified as predominant odorants in the emission of a wide range of activities in the bio-industry (e.g . aerobic waste water treatment plants, composting plants, rendering plants) . In these processes, the occurrence of volatile organic sulfur compounds is mainly related to the presence of anaerobic microsites with consecutive fermentation of sulfur containing organic material and/or to the breakdown of the latter due to thermal heating . Due to the chemical complexity of these low-concentrated waste gas streams and the high flow rates to be handled, mainly biotechnological techniques and scrubbers can be used to control the odour emission . When using biofilters or trickling filters, inoculation with specific microorganisms and pH-control strategies should be implemented to optimise the removal of volatile organic sulfur compounds . In scrubbers, chemical oxidation of the volatile organic sulfur compounds can be obtained by dosing hypochlorite, ozone or hydrogen peroxide to the scrubbing liquid . However, optimal operational conditions for each of these abatement techniques requires a further research in order to guarantee a long-term and efficient overall odour abatement.

Nephrol Dial Transplant, 1998, 13 Suppl 8, 30 - 4
Short-term outcome of diabetic patients in renal replacement therapy; Romagnoli GF et al.; BACKGROUND: Diabetic nephropathy or diabetes-related nephropathies represents one of the most relevant causes of renal failure in recent years . This complex pathological picture becomes particularly severe as time elapses and after starting renal replacement therapy (RRT) . METHODS: In an attempt to investigate the evolution of the major clinical features, a retrospective study was carried out on a cohort of 76 diabetic patients on RRT . Sixty-five have been treated by haemodialysis (HD) and 11 by peritoneal dialysis (CAPD), for at least 1 year . In these patients change in modality of treatment, metabolic control, cardiovascular, and ophthalmological complications, peripheral neuropathy, state of vascular access, and intradialytic complications were surveyed at initiation and after 1 year of treatment . A modified Karnofski's score was utilized, to evaluate the degree of rehabilitation . The comparison of prevalence was evaluated, using Student's t-test for paired samples . RESULTS: After 1 year, 11 patients on CAPD remained on the same type of treatment . Out of 65 patients on standard bicarbonate HD, 11 were moved to acetate free biofiltration, two to paired filtration dialysis and one to haemofiltration . A worsening in arrhythmias was recorded with an increased prevalence from 25.0 to 35.0% (n.s.), and one more patient (15 vs 16 and 19 vs 20 respectively) experienced ischaemic cardiomyopathy and cerebrovascular insufficiency . Hypertension showed a significant improvement (72 vs 42, P<0.01) . Nausea and vomiting, hypotensive episodes, and muscular cramps were more frequently observed . A worsening in patient's welfare was also recorded but without statistical significance . CONCLUSIONS: This clinical evaluation even if retrospective and lasting 1 year, may suggest that RRT does not per se represent a cause of the development and progression of the major complications related to diabetic disease.

J Appl Microbiol, 1998 Oct, 85(4), 635 - 42
Effects of hydrocarbon enrichment on trichloroethylene biodegradation and microbial populations in finished compost; Sukesan S et al.; This study focused on the capacity of finished compost, often used as packing material in biofiltration units, to support microbial biodegradation of trichloroethylene (TCE) . Finished compost was enriched with methane or propane (10% head space) to stimulate cometabolic biodegradation of gaseous TCE . Successful hydrocarbon enrichment, as indicated by rapid depletion of hydrocarbon gas and measurable growth of hydrocarbon-utilizing micro-organisms, occurred within a week . Within batch reactor flasks, approximately 75% of head space TCE (1-40 ppmv) was rapidly sorbed onto compost material . Up to 99% of the remaining head space TCE was removed via biodegradation in compost enriched with either hydrocarbon . Hydrocarbon enrichment with methane or propane corresponded to 10-fold increases in methanotrophic or propanotrophic populations, respectively . Based on growth assessment under different nutritional regimes, there appeared to be complex metabolic interactions within the microbial community in enriched compost . Five separate bacterial cultures were derived from the hydrocarbon-enriched compost and assayed for the ability to degrade TCE.

ASAIO J, 1998 Sep-Oct, 44(5), M423 - 32
Dialysis kinetics of homocysteine and reactive oxygen species; Biasioli S et al.; In patients with chronic renal failure who undergo hemodialysis (HD), the antioxidant system is inadequate to correct the imbalance between the generation and scavenging of reactive oxygen species . To clarify the role of six different membranes on oxidative stress, the authors measured plasma lipid peroxidation and erythrocyte (E) concentrations of several antioxidant enzymes in 30 HD patients: 20 on bicarbonate HD, 4 on paired filtration dialysis, 3 on acetate free biofiltration, and 3 on hemodiafiltration . Before, during, and after the first session of the week (at times 0, 30, 60, and 120 min, end, and 30 min after end of HD), several blood samples were drawn . Plasma (P) homocysteine (HCY), cysteine (CYS), malondialdehyde (MDA), E-glutathione (GSH), glucose-6-phosphodehydrogenase, glutathione reductase (GR), glutathione peroxidase (GP), catalase (CAT), and superoxide dismutase (SOD) were determined . All six membranes (Hemophan {HEMO}; cellulose diacetate {DIAC}; acrylonitrile-69 {AN69}; polymethylmethacrylate {PMMA}; cuprammonium rayon {CURAY}; polysulfone plus hemophan {PS + HEMO}) induced a significant decrease in plasma lipid peroxidation (p < 0.001) and an increase in E-GSH, GR, GR + flavinadenine dinucleotide, GP, and SOD (p < 0.001) . Some membranes, however, showed some peculiar effects on reactive oxygen species: HEMO is better than DIAC, as far as P-MDA and P-HCY are concerned; PMMA induces higher changes in E-GR and P-CYS than does HEMO; and patients chronically using PMMA and PS + HEMO membranes show the lowest P-HCY levels both before and after dialytic sessions . Based on these changes, implications as to the effects on vascular disorders could be derived.

Appl Environ Microbiol, 1998 Nov, 64(11), 4168 - 73
Ethylene removal by a biofilter with immobilized bacteria
Elsgaard L.
A biofilter which eliminated ethylene (C2H4) from the high parts-per-million range to levels near the limit for plant hormonal activity (0.01 to 0.1 ppm) was developed . Isolated ethylene-oxidizing bacteria were immobilized on peat-soil in a biofilter (687 cm3) and subjected to an atmospheric gas flow (73.3 ml min-1) with 2 or 117 ppm of C2H4 . Ethylene was eliminated to a minimum level of 0.017 ppm after operation with 2.05 ppm of C2H4 for 16 days . Also, the inlet C2H4 concentration of 117 ppm was reduced to <0.04 ppm . During operation with 2 and 117 ppm of C2H4, an increase in the C2H4 removal rate was observed, which was attributed to proliferation of the immobilized bacteria, notably in the first 0- to 5-cm segment of the biofilter . The maximal C2H4 elimination capacity of the biofilter was 21 g of C2H4 m-3 day-1 during operation with 117 ppm of C2H4 in the inlet gas . However, for the first 0- to 5-cm segment of the biofilter, an elimination capacity of 146 g of C2H4 m-3 day-1 was calculated . Transition of the biofilter temperature from 21 to 10 degreesC caused a 1.6-fold reduction in the C2H4 removal rate, which was reversed during operation for 18 days . Batch experiments with inoculated peat-soil demonstrated that C2H4 removal still occurred after storage at 2, 8, and 20 degreesC for 2, 3, and 4 weeks . However, the C2H4 removal rate decreased with increasing storage time and was reduced by ca . 50% after storage for 2 weeks at all three temperatures . The biofilter could be a suitable tool for C2H4 removal in, e.g., horticultural storage facilities, since it (i) removed C2H4 to 0.017 ppm, (ii) had a good operational stability, and (iii) operated efficiently at 10 degreesC.

Int J Syst Bacteriol, 1998 Apr, 48 Pt 2, 529 - 36
Identification of bacterial isolates from biofilters as Paracoccus alkenifer sp . nov . and Paracoccus solventivorans with emended description of Paracoccus solventivorans; Lipski A et al.; Two groups of strains isolated from biofilters for the treatment of waste gases were assigned to the genus Paracoccus by phylogenetic and chemotaxonomic methods . All type strains of the genus Paracoccus were compared with these groups using 16S rDNA sequence analysis, fatty acid patterns and physiological reaction profiles . For both groups, the nearest related reference species was Paracoccus solventivorans based on 16S rDNA sequence similarity . However, whereas one group of isolates was identified as a member of this species by fatty acid analysis and DNA-DNA hybridization, the other group was proposed as a new species, Paracoccus alkenifer sp . nov . Fatty acid analysis showed the unusual fatty acid 20:1cis13 instead of 19:0 cyclo11-12 for P . alkenifer and P . solventivorans, and 14:1cis7 instead of 12:1cis5 for P . alkenifer and Paracoccus kocurii . By means of a GC-MS method, diaminopimelic acid was detected for P . solventivorans . Based on these results we propose an emended description for the species P . solventivorans.

Int J Syst Bacteriol, 1998 Apr, 48 Pt 2, 441 - 9
Pseudonocardia asaccharolytica sp . nov . and Pseudonocardia sulfidoxydans sp . nov., two new dimethyl disulfide-degrading actinomycetes and emended description of the genus Pseudonocardia; Reichert K et al.; Seven bacterial strains capable of oxidizing methyl sulfides were isolated from experimental biofilters filled with tree-bark compost . The isolates could be divided into two groups according to their method of methyl sulfide degradation . Four isolates could use only dimethyl disulfide as the sole source of energy and three strains were able to use dimethyl sulfide and dimethyl disulfide . Oxidation of the methyl sulfides by both groups led to the stoichiometric formation of sulfate . Chemotaxonomic, morphological, physiological and phylogenetic properties identified all isolates as members of the genus Pseudonocardia . The absence of phosphatidylcholine from the polar lipid pattern, as well as results of 16S rDNA analyses, led to the proposal of two new species, Pseudonocardia asaccharolytica sp . nov . and Pseudonocardia sulfidoxydans sp . nov . The type strains are P . asaccharolytica DSM 44247T and P . sulfidoxydans DSM 44248T . With respect to the characteristic polar lipid pattern and the ability to oxidize sulfides, an emended description of the genus Pseudonocardia is proposed.

Med Tekh, 1998 May-Jun, (3), 33 - 4
{A scheme for performing simultaneous acetate-free biofiltration for 2 patients}; Kotov MV et al.; The advantages of an original regimen of acetate-free biofiltration as an alternative to hemodialysis, which has been modified and used in the treatment of patients on programmed hemodialysis, are shown . The method has been first used in Russia and may be used with the routine artificial kidney apparatus.

Clin Nephrol, 1998 Jul, 50(1), 28 - 37
Acetate free biofiltration (AFB): from theory to clinical results; Galli G et al.; Acetate free biofiltration (AFB) is a hemodiafiltration technique based on a buffer-free dialysate and bicarbonate infusion in the postdilution mode . The performance of AFB requires a dialysis machine equipped with an automatic control system to balance the infusion rate to that of ultrafiltration . The filters employed are usually polyacrylonitrile hollow-fiber hemodialyzers . A 145 mEq/l sodium bicarbonate solution is generally used and the infusion rate is regulated at about 8-10 liters per session to ensure optimal convective removal of toxins as well as to compensate for the bicarbonate lost in the dialysate . During AFB bicarbonate transfer results from the balance between diffusive and convective bicarbonate losses in the dialyzer and the amount of bicarbonate infused in the venous return . Thus bicarbonate supply can increase along with the rise in plasma bicarbonate concentration until a steady state is reached when the rate of infused bicarbonate equals bicarbonate losses into the dialyzer . A mild alkalosis may sometimes occur which can be avoided by slightly reducing bicarbonate concentration and/or infusion rate during the session . In spite of the large amount of sodium infused and the unusual high chloride concentration in the dialysate, no difference in the postdialysis plasma sodium levels nor in chloremia has been observed between AFB and bicarbonate dialysis . This is essentially due to the very large removal of these anions by convection (chloride and sodium) and by diffusion (sodium) into the dialyzer . Similarly the significant convective losses of calcium suggest a high dialysate calcium concentration to avoid negative intradialytic calcium balance . Polyacrylonitrile membranes, regularly employed in AFB, allow the passage of endotoxin fragments to the blood circuit in a lesser extent than other membranes . Coupled with the fact that a buffer-free dialysate and a sterile bicarbonate infusion are used AFB can be considered a highly biocompatible dialysis technique . As compared to conventional dialysis AFB allows adequate removal of small molecules and better removal of larger molecules such as beta2-microglobulin . In the short run AFB is characterized by an increase in cardiovascular stability: it improves dialysis symptoms and the subjective well-being of patients . A better acid-base correction is regularly reported together with a rise in some nutritional indices like serum albumin levels . The reasons for these favorable results are not well defined yet . A number of multicenter studies on the effects of AFB have been published with quite similar results, but most of them are non-randomized, and use historical controls . Only one prospective, cross-over study comparing bicarbonate dialysis with AFB in diabetic dialysis patients is available . It concludes that in a six-month observation period with AFB it is possible to better control some metabolic aspects and to improve both treatment tolerance and patients' life quality . However, it is not known whether these positive effects may entail better long-term prognosis; moreover, comparisons between AFB and conventional dialysis were never designed to ascertain the role of the dialysis membrane from that of the other components of AFB on clinical results . Therefore, large prospective trials with long observation periods are necessary to clarify the mechanisms through which AFB might be superior to conventional dialysis as well as the impact of these techniques on long-term prognosis . In such studies other relevant factors such as rehabilitation and life quality of the patients, which have been generally neglected in previous surveys, must also be included to evaluate cost-effectiveness of this therapy.

Clin Chim Acta, 1998 Jul 6, 275(1), 19 - 26
Investigation of fluoride elimination during a dialysis session; Nicolay A et al.; We have conducted a study of the elimination kinetics of fluoride ions by a log linear regression analysis of plasma levels obtained during a bicarbonate hemodialysis session, with a dialyzer in polymercaprin for six patients with chronic renal failure . Using plasma fluoride levels of 35 patients studied for 20 months, we have validated these kinetics for hemodialysis with sodium bicarbonate, acetate-free biofiltration, hemodiafiltration with low flow rate and other dialyzers . Our results show that the decrease in plasma fluoride levels is statistically significant only after the first hour, and the fall reaches approximately 30% after a 4 h dialysis session . We propose that post-dialysis measurements of plasma fluoride are now not necessary if levels before dialysis are known.

J Air Waste Manag Assoc, 1998 Jul, 48(7), 627 - 36
Evaluation of trickle bed air biofilter performance as a function of inlet VOC concentration and loading, and biomass control; Smith FL et al.; The 1990 Amendments to the Clear Air Act have stimulated strong interest in the use of biofiltration for the economical, engineered control of volatile organic compounds (VOCs) in effluent air streams . Trickle bed air biofilters (TBABs) are especially applicable for treating VOCs at high loadings . For long-term stable operation of highly loaded TBABs, removal of excess accumulated biomass is essential . Our previous research demonstrated that suitable biomass control for TBABs was achievable by periodic backwashing of the biofilter medium . Backwashing was performed by fluidizing the pelletized biological attachment medium with warm water to about a 40% bed expansion . This paper presents an evaluation of the impact of backwashing on the performance of four such TBABs highly loaded with toluene . The inlet VOC concentrations studied were 250 and 500 ppmv toluene, and the loadings were 4.1 and 6.2 kg COD/m3 day (55 and 83 g toluene/m3 hr) . Loading is defined as kg of chemical oxygen demand per cubic meter of medium per day . Performance deterioration at the higher loading was apparently due to a reduction of the specific surface of the attached biofilm resulting from the accumulation of excess biomass . For a toluene loading of 4.1 kg COD/m3 day, it was demonstrated that the long-term performance of biofilters with either inlet concentration could be maintained at over 99.9% VOC removal by employing a backwashing strategy consisting of a frequency of every other day and a duration of 1 hr.

Artif Organs, 1998 Jul, 22(7), 601 - 7
Estimation of mass transfer through a hemodialyzer: theoretical approach and clinical applications; Petitclerc T; The estimation of the solute mass transfer through a dialyzer is generally based on the solute dialysance, but the concept of dialysance has been precisely defined only in the case of a merely diffusive transfer . In actuality the mass transfer of a solute is also influenced by the ultrafiltration responsible for a convective transfer and, if the solute is an ionic substance, by the transmembrane gradient of electrical potential due to the Gibbs-Donnan effect . The aim of this paper is to generalize the concept of dialysance when the diffusive, convective, and electric components of the transfer are simultaneously active . There are at least 3 modes to generalize the concept of dialysance for it to be identical, when the amount of ultrafiltration and the Gibbs-Donnan effect are negligible, to the usual dialysance defined in the case of a merely diffusive transfer . The dialysance can be defined so that it can be equal to the clearance for a solute absent from the dialysate again, so that it still represents the rate at which the plasma concentration of a given solute is reaching its equilibrium value, or so that it represents the merely diffusive component (independent of the ultrafiltration rate) of the mass transfer . This generalized concept of dialysance can be useful to provide a real-time estimation of the effective dialysis dose actually delivered to the patient; to automatically optimize, by a biofeedback process, the sodium balance during a hemodialysis session; and to adapt dialysate concentrations for new hemodialysis techniques with convective transfer (acetate-free biofiltration).

Am J Kidney Dis, 1998 Jul, 32(1), 115 - 24
Effect of acetate, bicarbonate dialysis, and acetate-free biofiltration on nitric oxide synthesis: implications for dialysis hypotension; Noris M et al.; The effect of acetate dialysis (AD), bicarbonate dialysis (BD), and acetate-free biofiltration (AFB) on nitric oxide (NO) synthesis and the implications for dialysis hypotension was studied . The finding that uremic plasma is a potent inducer of NO synthesis by endothelial cells in vitro suggested that the cardiovascular instability of dialysis patients might result from excessive NO formation . Cardiovascular instability is more frequent in patients undergoing AD than BD . To see whether these differences were attributable to NO, we studied the NO synthetic pathway ex vivo in patients undergoing different dialysis procedures . Five patients were treated, in a random order, with AD, BD, and AFB, a technique using a buffer-free dialysate and postdilution of a sterile bicarbonate solution . Each type of dialysis was used for 1 week, comprising three dialysis sessions . A polyacrylonitrile dialyzer was used for all three methods . Before and after the third dialysis, plasma was collected, added to {3H}L-arginine, and incubated with human umbilical vein endothelial cells (HUVECs) for 24 hours . NO synthesis was evaluated as {3H}L-citrulline formation . Plasma concentrations of interleukin-1beta (IL-1beta), a potent inducer of inducible NO synthase (iNOS) in endothelial cells, were also measured . Plasma collected from patients after AD stimulated endothelial NO synthesis more than plasma from the same patients before the dialysis session (pre-AD, 0.173+/-0.028 nmol/10(5) cells v post-AD, 0.280+/-0.093 nmol/10(5) cells; P < 0.05) . A slight, although not significant, increase was also observed when HUVECs were incubated with plasma drawn after BD (pre-BD, 0.151+/-0.014 nmol/10(5) cells; post-BD, 0.230+/-0.055 nmol/10(5) cells) . AFB did not aggravate the stimulatory effect of uremic plasma on endothelial NO synthesis (pre-AFB, 0.184+/-0.038 nmol/10(5) cells; post-AFB, 0.189+/-0.040 nmol/10(5) cells) . Plasma IL-1beta was greater (P < 0.01) after AD than after BD and AFB (post-AD, 0.234+/-0.028 pg/mL; post-BD, 0.124+/-0.019 pg/mL; post-AFB, 0.120+/-0.013 pg/mL) . With AD, there was a greater intradialytic decrease in systolic blood pressure than with BD or AFB . Weight and blood volume loss and sodium balance were similar in AD, BD, and AFB . These data were consistent with the possibility that NO and cytokines, released in excessive amounts during AD, may contribute to hemodynamic instability.

Nippon Jinzo Gakkai Shi, 1998 May, 40(4), 258 - 62
{The influence of correction of acidosis on plasma level of branched-chain amino acids in chronic hemodialysis patients}; Kikuchi F et al.; Seven patients undergoing chronic hemodialysis three times a week and whose plasma bicarbonate concentration on predialysis was consistently under 18 mmol/l due to bicarbonate dialysis (BCD), were treated with BCD for 2 weeks, then switched to acetate-free biofiltration (AFB) for 8 weeks . In both periods, the same high flux dialyzer (AN69HF) was used . The treatment time, dialysate flow rate and blood flow rate were kept constant in each patient during both periods . Plasma bicarbonate concentration (HCO3-), serum urea nitrogen (SUN), serum creatinine (Cr) and plasma amino acids concentrations (AA) were measured before dialysis and KT/V was calculated on the 2nd days of the last week in both periods . HCO3- on AFB was significantly higher than that on BCD (16.4 +/- 0.9 vs 19.9 +/- 1.8 mmol/l; p < 0.05) . SUN on AFB was significantly lower than that on BCD even though the dialysis schedule and dietary content were not changed (84.7 +/- 3.7 vs 76.6 +/- 3.8 mg/dl; p < 0.05) . TP, Cr and KT/V were not significantly different . Plasma total amino acid concentration (TAA) and plasma essential amino acid concentration (EAA) were not significantly different in both periods . In contrast, plasma branched-chain amino acid concentrations (BCAA) on AFB were significantly higher than that on BCD (313.5 +/- 44.3 vs 390.3 +/- 50.7 mumol/l; p < 0.05) . Plasma BCAA concentrations, valine (VAL), leucine (LEU) and isoleucine (ILE), were significantly higher on AFB than that on BCD, respectively (p < 0.05) . These findings suggest that optimal correction of the metabolic acidosis in chronic hemodialysis patients by AFB leads to a significant increase in plasma BCAA concentration.

Appl Environ Microbiol, 1998 Jul, 64(7), 2755 - 9
Microbial characterization of biological filters used for drinking water treatment; Moll DM et al.; The impact of preozonation and filter contact time (depth) on microbial communities was examined in drinking water biofilters treating Ohio River water which had undergone conventional treatment (coagulation, flocculation, sedimentation) or solutions of natural organic matter isolated from groundwater (both ozonated and nonozonated) . With respect to filter depth, compared to filters treating nonozonated waters, preozonation of treated water led to greater differences in community phospholipid fatty acid (PLFA) profiles, utilization of sole carbon sources (Biolog), and arbitrarily primed PCR fingerprints . PLFA profiles indicated that there was a shift toward anaerobic bacteria in the communities found in the filter treating ozonated water compared to the communities found in the filter treating nonozonated settled water, which had a greater abundance of eukaryotic markers.

Ren Fail, 1998 May, 20(3), 493 - 503
Acetate-free biofiltration for acute renal failure; Bret M et al.; The characteristics of acetate-free biofiltration (AFB) are now well documented in patients with chronic renal failure: hemodynamic tolerance, correction of acid-base imbalance, buffer-free dialysate (without acetate) and absence of backfiltration . This hemodialysis technique can be beneficial to patients with acute renal failure (ARF) . In our intensive care unit, we prospectively studied 29 patients with isolated ARF or ARF associated with failure of other organs . All eligible patients were randomly assigned to undergo dialysis with bicarbonate hemodialysis (BH) or with (AFB) . All used the same high flux biocompatible dialysis membranes . Effectiveness and hemodynamic tolerance of hemodialysis sessions and evolution of patients were analyzed . Correction of metabolic disorders, although better in the AFB group was not statistically different from that in the BH group . Re-equilibration of acid-base balance was also similar, with or without mechanical ventilation . Heparin consumption was significantly higher in the AFB group, with no effect on haemorrhagic complications . Analysis of hypo- and hypertensive episodes, defined as arterial pressure (AP) variations 20% greater than initial pressure, showed no difference in terms of number or degree of AP variation . However, weight loss and the rate of ultrafiltration led to a higher hypotensive risk in the BH group (p < 0.05) . Finally, the clinical course and prognosis was similar in both groups . In summary, AFB may be considered as effective a hemodialysis technique as BH in patients with ARF . Weight loss was better tolerated in the AFB group and can be a favorable factor considering the deleterious effect of overhydration in patients admitted to an intensive care unit . This study invites a comparison of longer dialysis session of AFB therapy and continuous hemodiafiltration.

Nephrol Dial Transplant, 1998 Apr, 13(4), 955 - 61
Acetate-free biofiltration versus bicarbonate haemodialysis in the treatment of patients with diabetic nephropathy: a cross-over multicentric study; Verzetti G et al.; BACKGROUND: Morbidity and mortality rates in diabetic patients on regular dialysis treatment (RDT) are higher than in non-diabetic-subjects on RDT . Moreover, diabetic patients experience an intradialitic morbidity unacceptably higher than in patients with other causes of terminal renal failure . The aim of the present investigation was to compare standard bicarbonate haemodialysis (BHD) with acetate-free biofiltration (AFB) in a group of 41 diabetic patients stable on dialysis treatment for 25 +/- 22 months . METHODS: Twenty-four type II and 17 type I diabetic patients, all requiring insulin therapy, were included and were followed for 1 year in a 6-month cross-over randomized study for both methods . The analysis was carried out on dialysis symptoms, interdialysis symptoms, and nutritional status, and the multivariate analysis of variance for repeated measures on the same subjects in the two techniques was used . RESULTS: AFB significantly reduced dialytic and extradialytic symptoms (P=0.003 and 0.001 respectively) . Cardiovascular collapses decreased by 43%, and other dialysis symptoms showed a similar trend (-35%) . The interdialysis symptoms decreased by 28% and were accompanied by an increase in subjective wellbeing (39%) when patients were switched from traditional haemodialysis to AFB . Acid base control was better with AFB (P=0.01), both at the beginning and during the session . Slightly significant differences were also obtained for Kt/V (AFB 1.48 +/- 0.29 vs BHD 1.38 +/- 0.30), while no significant difference was noted with respect to sodium mass balance, nutritional status, calorie-protein intake, nPCR, blood glucose profile, and insulin requirements . The number of hospital admissions and the mortality rate, which were much lower during the AFB than the BHD period, were not analysed statistically . CONCLUSIONS: AFB allows better control of some metabolic aspects, reduces intra- and extradialysis symptoms, and improves patient quality of life . Whether the long-term prognosis can be improved by AFB remains to be established with further studies.

Nephron, 1998, 78(3), 274 - 7
Accidental aluminum intoxication in patients undergoing acetate-free biofiltration; Hdez-Jaras J et al.; Eight patients undergoing acetate-free biofiltration (AFB) suffered aluminum intoxication . The source of this outbreak was parenteral exposition to high concentrations of aluminum in sodium bicarbonate solutions . The manufacturer of bicarbonate solutions used in AFB was substituted in May 1994 and the solutions were stored in glass containers . At the peak of intoxication (July 1994) serum aluminum determination revealed an average value of 147.3 +/- 21 microg/l . Aluminum levels in bicarbonate solutions were 400 microg/l . Serum ferritin rose from 307.4 +/- 161 to 735.6 +/- 206 ng/ml, whereas MCV decreased significantly from 98.4 +/- 9 to 90.1 +/- 10 fl . No significant changes were found in hemoglobin, neither in plasma iron, nor in iron transferrin saturation . The doses of recombinant human erythropoietin showed a considerable increase . The replacement solutions were changed and a new solution, stored in plastic containers and with aluminum levels lower than 10 microg/l, was used . The biochemical parameters were normalized . This outbreak demonstrates the need for a stringent control of aluminum-containing replacement fluids.

Nephrol Dial Transplant, 1998 Feb, 13(2), 370 - 4
Dialysis efficacy during acetate-free biofiltration; Schrander-vd Meer AM et al.; BACKGROUND: Acetate-free biofiltration (AFB) is a haemodiafiltration technique based on continuous post-dilution infusion of a sterile isotonic bicarbonate solution . We performed a long-term randomized prospective trial to compare dialysis efficacy and metabolic control of AFB versus bicarbonate haemodialysis (HD) . METHODS: The AFB group consisted of 11 and the HD group of nine patients, matched for age, sex and urea reduction rate . Biochemical parameters were obtained every 3 months for 1 year (haemoglobin, calcium, phosphate, urea, pre- and post-dialysis bicarbonate, and parathormone (PTH)) and medication was updated . Efficacy of dialysis calculated by KT/V using the dialysate sampling method was determined every 3 months . In AFB patients, the infusion rate of bicarbonate solution was adjusted individually to obtain bicarbonate values of > or = 22 mmol/l before dialysis and < or = 32 mmol/l after dialysis . In the HD group, bicarbonate was added as oral medication to match these bicarbonate concentrations . Statistical analysis was performed using ANOVA for repeated measurements . RESULTS: Pre-dialysis serum bicarbonate levels had risen to the same extent in both groups at the end of the study period (AFB from 21.8 to 26.1 mmol/l, P < 0.001, and HD from 20.8 to 24.9 mmol/l, P < 0.001) . Post-dialysis bicarbonate level was higher in the AFB than in the HD group (P < 0.01) . Calcium and phosphate levels remained stable in both groups . PTH increased in both groups (AFB from 10.6 to 23.7 pmol/l, and HD from 24.6 to 32.8 pmol/l), with a significant rise only in the AFB patients (P < 0.04) . In AFB patients, KT/V increased from 2.73 to 3.17 per week (P < 0.04) . In HD patients KT/V did not change (P < 0.38); the difference between the groups was significant at the end of the trial (P < 0.013) . Finally, haemoglobin levels and erythropoietin dosage did not change in either group . No significant differences between the two groups were observed . CONCLUSIONS: Acidosis was better corrected in AFB without the need for oral supplementation of bicarbonate . However, neither serum calcium nor phosphate levels changed . The observed increase in PTH in the AFB group remains to be clarified . Dialysis efficacy, measured as KT/V, improved during AFB.

Appl Microbiol Biotechnol, 1997 Dec, 48(6), 738 - 44
Bacterial degradation of styrene in waste gases using a peat filter; Arnold M et al.; A biofiltration process was developed for styrene-containing off-gases using peat as filter material . The average styrene reduction ratio after 190 days of operation was 70% (max . 98%) and the mean styrene elimination capacity was 12 g m-3 h-1 (max . 30 g m-3 h-1) . Efficient styrene degradation required addition of nutrients to the peat, adjustment of the pH to a neutral level and efficient control of the humidity . Maintenance of the water balance was easier in a down-flow than in an up-flow process, the former consequently resulting in much better filtration efficiency . The optimum operation temperature was around 23 degrees C, but the styrene removal was still satisfactory at 12 degrees C . Seven different bacterial isolates belonging to the genera Tsukamurella, Pseudomonas, Sphingomonas, Xanthomonas and an unidentified genus in the gamma group of the Proteobacteria isolated from the microflora of active peat filter material were capable of styrene degradation . The isolates differed in their capacity to decompose styrene to carbon dioxide and assimilate it to biomass . No toxic intermediate degradation products of styrene were detected in the filter outlet gas or in growing cultures of isolated bacteria . The use of these isolates in industrial biofilters is beneficial at low styrene concentrations and is safe from both the environmental and public health points of view.

Biotechnol Prog, 1997 Nov-Dec, 13(6), 814 - 21
Microbial removal of alkanes from dilute gaseous waste streams: kinetics and mass transfer considerations; Barton JW et al.; Treatment of dilute gaseous hydrocarbon waste streams remains a current need for many industries, particularly as increasingly stringent environmental regulations and oversight force emission reduction . Biofiltration systems hold promise for providing low-cost alternatives to more traditional, energy-intensive treatment methods such as incineration and adsorption . Elucidation of engineering principles governing the behavior of such systems, including mass transfer limitations, will broaden their applicability . Our processes exploit a microbial consortium to treat a mixture of 0.5% n-pentane and 0.5% isobutane in air . Since hydrocarbon gases are sparingly soluble in water, good mixing and high surface area between the gas and liquid phases are essential for biodegradation to be effective . One liquid-continuous columnar bioreactor was operated for more than 30 months with continued degradation of n-pentane and isobutane as sole carbon and energy sources . The maximum degradation rate observed in this gas-recycle system was 2 g of volatile organic compounds (VOC)/(m3.h) . A trickle-bed bioreactor was operated continuously for over 24 months to provide a higher surface area (using a structured packing) with increased rates . Degradation rates consistently achieved were approximately 50 g of VOC/(m3.h) via single pass in this gas-continuous columnar system . Effective mass transfer coefficients comparable to literature values were also measured for this reactor; these values were substantially higher than those found in the gas-recycle reactor . Control of biomass levels was implemented by limiting the level of available nitrogen in the recirculating aqueous media, enabling long-term stability of reactor performance.

Biodegradation, 1997, 8(3), 135 - 41
Active compost biofiltration of toluene; Matteau Y et al.; Composting of leaves and alfalfa (i.e . active compost) was used for the biofiltration of toluene-contaminated air in a 6-L biofilter (initial bed height: 180 mm) . During the thermophilic phase (45 to 55 degrees C), toluene biodegradation rates reached 110 g toluene.m-3.h-1 at an inlet concentration of about 5 g.m-3 and a gas residence time of 90 seconds . The highest rates were obtained in the thermophilic phase suggesting a microbial adaptation was occurring . Biodegradation rates decreased rapidly (50% in 48 h) in the cooling stage . Under mesophilic conditions, the maximum biodegradation rates that could be obtained by increasing the inlet toluene concentration were near 89 g toluene.m-3.h-1 which is similar to that reported in the literature for mature compost biofilters . No volatile by-product was detected by gas chromatherapy . Mineralization of 14C-toluene and benzene showed that they were completely degraded into CO2 and H2O under both thermophilic and mesophilic conditions . Bacteria isolated from late mesophilic stage had the capacity to degrade all BTEX compounds but were not able to transform chlorinated compounds . No organisms were isolated which could use toluene as their sole source of carbon and energy at 50 degrees C . Active compost biofiltration should be an excellent process for the treatment of gaseous BTEX by biofiltration . This is the first report of thermophilic biofiltration of toluene.

Am J Nephrol, 1997, 17(5), 428 - 34
Chronic effects of long-term acetate-free biofiltration on the production of interleukin-1beta and interleukin-1 receptor antagonist by peripheral blood mononuclear cells; Higuchi T et al.; The production of interleukin-1beta (IL-1beta) and interleukin-1 receptor antagonist (IL-1Ra) by peripheral blood mononuclear cells (PBMC) was examined in patients on long-term acetate-free biofiltration (AFB) . Five stable patients on AFB were switched to bicarbonate hemodialysis (BCD) for a 2-week period using the same AN69 membrane dialyzer . IL-1beta and IL-1Ra production was measured by ELISA before and after dialysis in the last session of both treatments . Cytokine production by unstimulated PBMC did not differ significantly before and after both AFB and BCD . However, the spontaneous IL-1Ra/IL-1beta production ratio in AFB was significantly higher than that in BCD . These findings indicate that AFB may have more beneficial effects on cytokine production by PBMC compared to BCD.

J Immunol Methods, 1997 Aug 7, 206(1-2), 171 - 82
Hierarchical affinity maturation of a phage library derived antibody for the selective removal of cytomegalovirus from plasma; Pini A et al.; Recombinant antibody fragments can be produced in large quantities using bacterial expression systems and could potentially be useful for the generation of biofilters for the selective removal of viral particles from fluids . A human single chain-Fv antibody library, derived from synthetic repertoires of germ line VH-gene segments rearranged in vitro and paired to a single light chain (Nissim et al., 1994, EMBO J., 13, 692-698), has recently been used to isolate hundreds of different binding specificities by panning with antigen . Antibodies from this library typically have affinities in the 10(6)-10(7) M-1 range . Occasionally, better binders are isolated but at other times the affinities recovered are poor . In the latter situation binding cannot be detected with soluble antibodies, but only by high-avidity display of multiple copies of antibodies on phage . By panning with human cytomegalovirus (HCMV)-coated immunotubes, we have isolated a number of antibody clones from this library that bound to the antigen only if displayed on the filamentous phage, but not in soluble form . One of these clones was selected for an affinity maturation procedure, achieved by combinatorial mutagenesis of the complementarity determining region 3 (CDR3) of the antibody light chain, followed by selection of the resulting library for HCMV binding . By this means, we were able to isolate a number of binders, some of which exhibited specific HCMV binding in soluble form . The clone that gave the strongest ELISA signal was expressed in bacteria, purified in solution, characterised using a novel capture methodology with surface plasmon resonance detection on a BIAcore instrument and used for the production of an immunofilter for the removal of HCMV form human serum . The filter removed more than 99% of applied HCMV in 10 min circulation time, while the amount of HCMV retained non-specifically in a cartridge derivatised with a non-specific antibody was less than 10% under similar conditions.

Curr Opin Biotechnol, 1997 Jun, 8(3), 335 - 9
Biological waste air treatment in biofilters; Deshusses MA; Recent studies in the area of biological waste air treatment in biofilters have addressed fundamental key issues such as microbial dynamics, microscopical characterization of the process culture and oxygen and nutrient limitations . The results from these studies have provided a deeper insight into the overall biofiltration process . In the coming years, such advances should allow for the design of better reactor controls and the improvement of pollutant removal in gas-phase bioreactors.

J Air Waste Manag Assoc, 1997 Jun, 47(6), 674 - 81
Screening of biofiltering material for VOC treatment; Chou MS et al.; Screening of biofiltering material for treatment of volatile organic compounds was performed by using a gas stream containing methyl ethyl ketone (MEK) as a target pollutant . Filtering media (FM) for screening were prepared by blending compost (such as pig and cow manure) and filling material (such as fern chips, wheat bran, and bagasse) . Results show that a blend of pig manure/fern chips = 9:1 (wt basis) was superior with respect to the stability of the pH and the water-holding capacity of the FM and in the capacity for treating the target compound . Complete removal of the target compound was obtained at an organic loading of 100 g per cubic meter of filtering media per hour . By using the screened FM for treating MEK and toluene, long-term stability (> 1,200 hours) and complete removal can be obtained at an organic loading of 50 g per cubic meter of FM per hour for either compound.

J Ind Microbiol Biotechnol, 1997 Feb-Mar, 18(2-3), 189 - 97
A bioengineering system for in situ bioremediation of contaminated groundwater; Knapp RB et al.; Much of the past and current focus of bioremediation has been on laboratory studies of microbial processes . By necessity, early studies have ignored important field properties, parameters, and processes that control the ultimate success of in situ bioremediation of contaminated groundwater . This paper presents a bioengineering systems approach that examines the impact of some of these field variables on common bioremediation practices . Using simple systems, the niche of biostimulation is shown to be aquifers with high contaminant sorption . A novel gas-phase biostimulation filter and a novel resting-state bioaugmentation/biofilter approach which show promise for effective field implementation are discussed.

Environ Health Perspect, 1997 Feb, 105 Suppl 1, 5 - 20
Healthy environments for healthy people: bioremediation today and tomorrow; Bonaventura C et al.; Increases in environmental contamination lead to a progressive deterioration of environmental quality . This condition challenges our global society to find effective measures of remediation to reverse the negative conditions that severely threaten human and environmental health . We discuss the progress being made toward this goal through application of bioremediation techniques . Bioremediation generally utilizes microbes (bacteria, fungi, yeast, and algae), although higher plants are used in some applications . New bioremediation approaches are emerging based on advances in molecular biology and process engineering . Bioremediation continues to be the favored approach for processing biological wastes and avoiding microbial pathogenesis . Bioremediation may also play an increasing role in concentrating metals and radioactive materials to avoid toxicity or to recover metals for reuse . Microbes can biodegrade organic chemicals; purposeful enhancement of this natural process can aid in pollutant degradation and waste-site cleanup operations . Recently developed rapid-screening assays can identify organisms capable of degrading specific wastes and new gene-probe methods can ascertain their abundance at specific sites . New tools and techniques for use of bioremediation in situ, in biofilters, and in bioreactors are contributing to the rapid growth of this field . Bioremediation has already proven itself to be a cost-effective and beneficial addition to chemical and physical methods of managing wastes and environmental pollutants . We anticipate that it will play an increasingly important role as a result of new and emerging techniques and processes.

Appl Environ Microbiol, 1996 Dec, 62(12), 4632 - 40
Activity and three-dimensional distribution of toluene-degrading Pseudomonas putida in a multispecies biofilm assessed by quantitative in situ hybridization and scanning confocal laser microscopy; Moller S et al.; As a representative member of the toluene-degrading population in a biofilter for waste gas treatment, Pseudomonas putida was investigated with a 16S rRNA targeting probe . The three-dimensional distribution of P . putida was visualized in the biofilm matrix by scanning confocal laser microscopy, demonstrating that P . putida was present throughout the biofilm . Acridine orange staining revealed a very heterogeneous structure of the fully hydrated biofilm, with cell-free channels extending from the surface into the biofilm . This indicated that toluene may penetrate to deeper layers of the biofilm, and consequently P . putida may be actively degrading toluene in all regions of the biofilm . Furthermore, measurements of growth rate-related parameters for P . putida showed reduced rRNA content and cell size (relative to that in a batch culture), indicating that the P . putida population was not degrading toluene at a maximal rate in the biofilm environment . Assuming that the rRNA content reflected the cellular activity, a lower toluene degradation rate for P . putida present in the biofilm could be estimated . This calculation indicated that P . putida was responsible for a significant part (65%) of the toluene degraded by the entire community.

Biotechnol Prog, 1996 Nov-Dec, 12(6), 773 - 8
Biodegradation of hydrogen sulfide by a laboratory-scale immobilized Pseudomonas putida CH11 biofilter; Chung YC et al.; A heterotrophic Pseudomonas putida CH11 was isolated from livestock farming wastewater and applied for the treatment of H2S-containing gas . Extensive tests including removal characteristics, metabolic products, and removal efficiencies of H2S by P . putida CH11 were examined in batch and continuous systems . The optimum pH required to remove hydrogen sulfide was found in the range of 6-8 . The maximum removal rate and the saturation constant were calculated to be Vm = 1.36 g S/day.kg dry bead and Ks = 45.9 ppm, respectively . The main metabolic product of H2S oxidation was determined to be elemental sulfur . When P . putida CH11 was immobilized within Ca alginate, the cells exhibited high H2S removal efficiency, in excess of 96%, at concentration of hydrogen sulfide from 10 to 150 ppm (flow rates of 36 and 72 L/h) . These results suggest that P . putida CH11 immobilized within Ca alginate has the potential to be used as a H2S removal agent.

Int J Syst Bacteriol, 1996 Oct, 46(4), 876 - 80
Gordona hirsuta sp . nov; Klatte S et al.; Bacterial strain K718aT (T = type strain), which was isolated from the packing material of a biofilter used for deodorization of animal-rendering plant emissions, was subjected to a polyphasic taxonomic study in which physiological, chemotaxonomic, and genomic methods were used . On the basis of the chemotaxonomic and physiological properties found and the results of 16S ribosomal DNA sequence comparisons, it was evident that strain K718aT belongs to a new species in the genus Gordona . We propose that strain K718a should be the type strain of the new species Gordona hirsuta.

Cas Lek Cesk, 1996 Aug 21, 135(16), 525 - 9
{The effect of acetate-free biofiltration on anemia and use of erythropoietin}; Eiselt J et al.; BACKGROUND: Chronic renal failure is associated with anaemia and a large percentage of patients is indicated for erythropoietin (rHuEPO) treatment . The degree of anaemia depends also on the quality of substitution of renal function . The objective of the present study was to assess whether transfer of patients from haemodialysis (HD) to acetate-free biofiltration (AFB) will influence the anaemia and rHuEPO consumption . METHODS AND RESULTS: Anaemia and rHuEPO consumption were investigated in 10 patients in a stabilized condition with regular dialyzation treatment . The patients suffered from corrected anaemia on a maintenance dose of rHuEPO . During AFB (follow-up period one year) the rHuEPO consumption declined as compared with the condition during HD, while the target haemoglobin level (95-110 g/l) was maintained . The easier control of anaemia during AFB was not due to a change of iron saturation, the aluminium level or a change of the residual blood volume in the dialyzer . During AFB metabolic acidosis was controlled more effectively, the elimination of urea and beta-2-microglobulin increased . CONCLUSIONS: During AFB, as compared with HD, the rHuEPO consumption declines sufficiently to correct anaemia . The authors conclude that one of the reasons may be the more effective control of metabolic acidosis and elimination of uraemic toxins with a low or medium molecular weight . The authors discuss also other factors which affect anaemia during treatment of renal failure by extracorporcal clearing methods.

Microbiol Rev, 1996 Jun, 60(2), 439 - 71
Methanotrophic bacteria; Hanson RS et al.; Methane-utilizing bacteria (methanotrophs) are a diverse group of gram-negative bacteria that are related to other members of the Proteobacteria . These bacteria are classified into three groups based on the pathways used for assimilation of formaldehyde, the major source of cell carbon, and other physiological and morphological features . The type I and type X methanotrophs are found within the gamma subdivision of the Proteobacteria and employ the ribulose monophosphate pathway for formaldehyde assimilation, whereas type II methanotrophs, which employ the serine pathway for formaldehyde assimilation, form a coherent cluster within the beta subdivision of the Proteobacteria . Methanotrophic bacteria are ubiquitous . The growth of type II bacteria appears to be favored in environments that contain relatively high levels of methane, low levels of dissolved oxygen, and limiting concentrations of combined nitrogen and/or copper . Type I methanotrophs appear to be dominant in environments in which methane is limiting and combined nitrogen and copper levels are relatively high . These bacteria serve as biofilters for the oxidation of methane produced in anaerobic environments, and when oxygen is present in soils, atmospheric methane is oxidized . Their activities in nature are greatly influenced by agricultural practices and other human activities . Recent evidence indicates that naturally occurring, uncultured methanotrophs represent new genera . Methanotrophs that are capable of oxidizing methane at atmospheric levels exhibit methane oxidation kinetics different from those of methanotrophs available in pure cultures . A limited number of methanotrophs have the genetic capacity to synthesize a soluble methane monooxygenase which catalyzes the rapid oxidation of environmental pollutants including trichloroethylene.

Am J Vet Res, 1996 May, 57(5), 624 - 7
Blood biochemical reference intervals for sunshine bass (Morone chrysops x Morone saxatilis) in three culture systems; Hrubec TC et al.; OBJECTIVE--To determine and compare biochemical reference intervals for sunshine bass (hybrid striped bass) from 3 culture systems . DESIGN--Observational comparison study . ANIMALS--Clinically normal sunshine bass (reciprocal hybrid striped bass, female Morone chrysops x male M saxatilis raised in high-density recirculating systems (80 g/L), low-density tanks (5 g/L) with biofilters, and cages (70 g/L) in a fresh water pond . PROCEDURE--Biochemical reference intervals were determined for fish from the different production systems following the National Committee for Clinical Laboratory Standards guidelines . Reference intervals from the 3 groups were compared . RESULTS--Reference intervals were significantly different between sunshine bass in the various culture systems . Though most of the differences in reference intervals were minor, fish in the high-density recirculating system had higher concentrations of total protein, albumin, globulin, creatinine, and phosphorus, and lower chloride values . There were no significant differences in glucose concentrations among the 3 groups of fish, and no differences in cortisol concentrations between fish in tanks and cages . CONCLUSIONS--Separate reference intervals should be developed for hybrid striped bass in different culture systems . CLINICAL RELEVANCE--Determining biochemical reference intervals for hybrid striped bass provides a tool to assess the health status of these fish.

Am J Vet Res, 1996 May, 57(5), 618 - 23
Comparison of hematologic reference intervals between culture system and type of hybrid striped bass; Hrubec TC et al.; OBJECTIVE--To determine and compare hematologic reference intervals for hybrid striped bass from different culture systems and for 2 types of hybrid . DESIGN--Observational comparison study . ANIMALS--Clinically normal sunshine bass (reciprocal hybrid striped bass, female Morone chrysops X male M saxatilis) raised in high-density recirculating systems, sunshine bass raised in tanks with biofilters, and palmetto bass (original hybrid striped bass, female M saxatilis X male M chrysops) raised in tanks with biofilters . PROCEDURES--Hematologic reference intervals were determined for fish from the different production systems, following the National Committee for Clinical Laboratory Standards guidelines . Reference intervals from the 3 groups were compared . RESULTS--Reference intervals were significantly different between sunshine bass in the 2 culture systems and between sunshine and palmetto bass . Many of the differences were slight, but notable differences were observed . Sunshine bass in recirculating systems had higher total leukocyte, lymphocyte, neutrophil, and monocyte counts than did either hybrid in tanks . Palmetto bass had a greater number of neutrophils than monocytes, whereas sunshine bass had more monocytes than neutrophils . Additionally, palmetto bass had a lower PCV and hemoglobin value than did either group of sunshine bass . CONCLUSIONS--Separate reference intervals should be developed for hybrid striped bass in different culture systems and for different types of hybrids . CLINICAL RELEVANCE--Determining reference intervals for hybrid striped bass provides a tool to assess the health status of these fish.

Am J Kidney Dis, 1996 Apr, 27(4), 541 - 7
A prospective comparison of bicarbonate dialysis, hemodiafiltration, and acetate-free biofiltration in the elderly; Movilli E et al.; Hemodiafiltration (HDF) and more recently acetate-free biofiltration (AFB) have shown good blood purification and cardiovascular stability in young and middle-aged hemodialysis patients . It is not clear if this is also valid for elderly patients . Twelve patients aged more than 70 years (mean age +/- SD, 76 +/- 4 years) on regular dialysis for at least 5 months were treated with bicarbonate dialysis (BD), HDF, or AFB in a randomized sequence and prospectively followed for 6 months (72 dialysis sessions/patient) for each procedure . The dialysis solution (containing bicarbonate), blood flow rate, and dialysate flow rate were the same with all the methods . During HDF and AFB solutions containing bicarbonate at a concentration of 27 to 30 mEq/L and 145 mEq/L, respectively, were infused postdilution at a rate of 66 +/- 7 mL/min and 2.81 +/- 0.12 L/hr, respectively . During the period of observation we evaluated the number of intradialytic hypotensions, the episodes of nausea, vomiting, headache (dialysis intolerance), body weight, the interdialysis weight gain, the duration of the dialysis session, the number of hospitalizations/patient, and the length of hospitalization/patient . At the end of each observation period we determined: Kt/V, protein catabolic rate, acid base balance, serum creatinine, serum calcium, serum phosphorus, alkaline phosphatases, and serum intact parathyroid hormone . After the switch from BD to either HDF or AFB, the results have shown a significant reduction of dialysis hypotension episodes (18 percent on BD, 14 percent on HDF, and 13 percent on AFB; BD v HDF, P = 0.001; BD v AFB, P = 0.0001; and HDF v AFB, P = NS) and of dialysis intolerance (3.3 percent on BD, 1.3 percent on HDF, and 1.1 percent on AFB; BD v HDF, P = 0.021; BD v AFB, P = 0.019; and HDF v AFB, P = NS) . Kt/V improved significantly after the switch from BD to either HDF or AFB (1.17 +/- 0.06 on BD, 1.32 +/- 0.12 on HDF, and 1.32 +/- 0.13 on AFB; BD v HDF, P = 0.021; BD v AFB, P = 0.003; HDF v AFB, P = NS) . Protein catabolic rate also improved in HDF and AFB compared with BD (0.90 +/- 0.12 on BD, 1.03 +/- 0.15 on HDF, and 1.04 +/- 0.14 on AFB; BD v HDF, P = 0.001; BD v AFB, P = 0.009; and HDF v AFB, P = NS) . AFB showed a better correction of acidosis compared either with BD or HDF (serum bicarbonate, 20.3 +/- 1.1 mEq/L on BD, 20.8 +/- 2.2 mEqL on HDF, and 22.2 +/- 2.4 mEq/L on AFB; BD v HDF, P = NS; BD v AFB, P = 0.01; and HDF v AFB, P = 0.030) . The other parameters observed did not differ . In conclusion HDF and AFB show a better dialysis efficiency and a better hemodynamic tolerance compared with BD . This fact is associated with an improvement in protein intake as assessed by kinetic criteria . Acetate-free biofiltration has the further advantage of a better control of the acid-base balance compared with BD and HDF . HDF and AFB are useful dialytic options to traditional BD hemodialysis even in patients older than 70 years.

Nephrol Dial Transplant, 1996, 11 Suppl 2, 11 - 5
Preventing haemodynamic instability in patients at risk for intra-dialytic hypotension; Leunissen KM et al.; Although as yet no major breakthroughs have occurred to improve long-term survival of haemodialysis patients with impaired cardiovascular function, it is possible to reduce morbidity by intra-dialytic hypotension in these patients by the use of relatively simple manoeuvres . In our experience, this can be achieved using the following approach (Table 1) . First, the decline in plasma volume can be reduced by adequate estimation of the optimal dry weight by objective methods, such as echography of the inferior caval vein or bioimpedance measurements . Furthermore, the ultrafiltration rate during haemodialysis should be moderate and should be limited to a maximum value, which has to be defined empirically for each individual patient . Especially in patients with excess inter-dialytic weight gain, isolated ultrafiltration should be used when the required amount of fluid cannot be removed during haemodialysis . The use of low-sodium dialysate should be avoided . Probably it is best to use a physiological sodium concentration of the dialysate because a greater sodium concentration may result in increased thirst and intra-dialytic weight gain . Sodium profiling should be based on further studies concerning plasma volume changes during haemodialysis in different patient groups . Because of the deleterious impact of acetate on vascular reactivity, it should never be used in patients prone to hypotensive periods . Vascular reactivity can also be impaired by the use of vasoactive medication prior to haemodialysis treatment . Therefore, in patients prone to hypotensive periods, vasoactive medication should be withheld the morning before haemodialysis, if possible . Also, one should be very cautious with the use of low-calcium dialysate in patients with frequent hypotensive periods, and ideally it should be avoided . If the use of these manoeuvres fails to control intra-dialytic hypotension, one should consider the use of cold dialysate . Switching to haemofiltration or to continuous treatment modes such as CAPD are other options . Future studies should address haemodynamics during other treatment modes, such as haemodiafiltration or acetate-free biofiltration.

Blood Purif, 1996, 14(3), 242 - 8
Blood purification procedures for acute renal failure: convenient strategy related to clinical conditions; Meloni C et al.; The choice in the renal replacement therapy of acute renal failure (ARF) should match the patients' individual needs and the characteristics of available therapies . 141 ARF patients, 65 with "isolated' ARF (group I) and 76 with ARF in multiorgan failure (group II), have been treated . In 33 patients of group I standard bicarbonate hemodialysis was used, while acetate-free biofiltration was used for the others . In group II, 42 patients have been treated by continuous arteriovenous hemofiltration and 34 patients by daily recycled bicarbonate hemodialysis . Our data show that acetate-free biofiltration and bicarbonate dialysis were both highly dependable, but acetate-free biofiltration was better tolerated . Continuous arteriovenous hemofiltration is the method of choice in high-risk patients; daily bicarbonate hemodialysis is preferable only in patients with hemorrhagic diathesis . The average survival time is 55.2% with a statistically significant difference between groups I and II, while no difference has been observed within the same group according to the procedure.

Bratisl Lek Listy, 1995 Dec, 96(12), 637 - 41
{Functional morphology of the spleen}; Jakubovsky J et al.; The spleen was till the first half of the twentieth century considered to represent an organ of no special significance . Nowadays its clearance function and position in the immunity system is thoroughly investigated . Informations on its cellular composition and compartments are sufficient . The problems coinciding with circulation in the spleen are solved . The study of interactions of T and B lymphocytes regarding the development of humoral immunity do not provide clear results . Unclear remain also the relations of extracellular and cellular structures . The localisation of the spleen in blood circulation and large amount of migrating lymphocytes justify its significant position in the protection of host against infections spreading haematogenously . It is not inevitable for survival, but its removal increases the risk of unmanageable infections carried by bacteria with polysaccharide capsules . The microenvironment in the spleen enables intercellular relations and determines the development of immune reactions . Microcirculation enables it to function as a biological filter without the necessity of specialized filtrating structures being present . In consequence of blood filtration everything leaks into the extravasal space . Subsequently all components normally constituting the blood return back into the blood within vessels . That is why no special structures are formed in order to filter individual components from the blood . All components that should not be present in the blood are excluded extravasally . The substances which are not let through the wall of sinuses into the blood, remain in the marginal zone and in the red pulp . The macrophages of the marginal zone and red pulp destroy and degrade the unrequired substances . (Ref . 26).

Int J Artif Organs, 1995 Nov, 18(11), 722 - 5
Prescription and surveillance of the acetate-free biofiltration sessions: the bicarbonate cycle; Pacitti A et al.; A computerized system, structured by 4 different models concerning urea depuration, and bicarbonate and sodium handling in acetate-free hemodiafiltration has been conceived for integrated use covering each step of the therapeutic cycle, from a) the prescription of the session to b) its delivery, up to c) the dose-response analysis: the system, now fully developed for the bicarbonate cycle, covers both working areas; the medical one, with a program implemented on a Personal Computer, called Skipper which deals with steps a) and c), and the nursing area, with a program built into the dialytic equipment software . The Skipper program supports the prescription step (a) testing the session schedule by bicarbonate, sodium and urea kinetics . The dialytic equipment, (step(b)) using a different program, on the basis of the scheduled parameters memorizes the end-session plasma bicarbonate level and reacts to any modifications of the parameters regarding blood flow and fluid reinfusion flow suggesting opposite changes in order to reach the scheduled results . Finally (step (c)), the Skipper system statistically evaluates the observed end session bicarbonate plasma level with an expected value with upper and lower confidence bounds obtained by a multiple regression analysis performed on a large population of patients.

Nephrol Dial Transplant, 1995 Nov, 10(11), 2110 - 3
Plasma advanced glycosylation end-products in maintenance haemodialysis patients; Odetti P et al.; BACKGROUND . Pentosidine is a useful marker of advanced glycation end-products (AGE) which form cross-links between proteins and have been found elevated in plasma and tissues of uraemic and haemodialysed subjects . The origin and fate of these molecules are not clearly understood, but they might play a role in the cardiovascular complications of end stage renal failure . The aim of this study was to evaluate the effect of different types of substitutive therapy on the removal of pentosidine . METHODS . Pentosidine was measured by a two-step HPLC methodology . Its concentration was evaluated in plasma before and after dialysis session, in 24-h urine, and in dialysate of subjects treated with three types of chronic substitutive therapy: bicarbonate haemodialysis, acetate-free biofiltration, and haemofiltration . Pentosidine levels were compared among the three therapy modalities and correlated with clinical and biochemical parameters . RESULTS . Plasma pentosidine level was extremely high (23.7 +/- 2.0 pmol/mg protein) in the patients treated with the different dialysis modalities . The dialysis session had no significant effect on its plasma concentration, but haemofiltration seemed to be the most efficient method (300-2000 nmol of pentosidine removed per session versus 250-700 nmol per session with the two other approaches) . An interesting correlation was found between pentosidine and blood urea nitrogen (r = 0.58, P < 0.01) and pentosidine with uric acid (r = 0.48, P < 0.05) . CONCLUSIONS . These results suggest that none of the methodology showed a good removal of pentosidine, but among them haemofiltration has the best efficiency . The statistical relationships between pentosidine and urea and uric acid respectively might provide insight into the origin of pentosidine . The accumulation of reactive AGE in uraemic patients may be implicated in the organ and tissue damage observed in uraemia.

Appl Environ Microbiol, 1995 Oct, 61(10), 3562 - 6
Growth of the fungus Cladosporium sphaerospermum with toluene as the sole carbon and energy source; Weber FJ et al.; The fungus Cladosporium sphaerospermum was isolated from a biofilter used for the removal of toluene from waste gases . This is the first report describing growth of a eukaryotic organism with toluene as the sole source of carbon and energy . The oxygen consumption rates, as well as the measured enzyme activities, of toluene-grown C . sphaerospermum indicate that toluene is degraded by an initial attack on the methyl group.

Cas Lek Cesk, 1995 Jul 12, 134(14), 445 - 9
{Acetate-free biofiltration: a possible method of renal replacement therapy}; Eiselt J; BACKGROUND . Acetate-free biofiltration (AFB) is a haemodiafiltration method which is used nowadays in the treatment of chronic renal failure . In AFB a dialyzation solution without a buffer is used, in the haemofilter some 2 1/hour are filtred . Simultaneously a sodium bicarbonate infusion in a postdilution mode is administered . The AFB investigation was conceived with the aim to introduce the method into clinical practice and to record the effect of AFB on the patient . METHODS AND RESULTS . Using the apparatus Monitral SC 30 of Hospal Co . the author made 120 AFB in 23 patients on long-term bicarbonate haemodialysis . In the investigation capillary haemofilters with an AN 69 membrane (Filtral 10 and 12) were used . The blood flow rate was 260 +/- 23 ml/min, the infusion rate of the substitution solution (NaHCO3 with a concentration of 167 mmol/l) was 1.7 +/- 0.1 l/h, the AFB period of 3.64 +/- 0.25 h . Before and after AFB values of the acid-base balance were investigated as well as the ion concentration, nitrogen catabolites, beta-2-microglobulin and cardiovascular stability of the patients . Optimal adjustment of metabolic acidosis was proved, the pH value before vs . after AFB was 7.359 +/- 0.053 vs . 7.444 +/- 0.048, p < 0.001, standard HCO3 20.2 +/- 2.6 vs . 26.0 +/- 2.1 l mmol/l, p < 0.001, adjustment of the ion balance, nitrogen catabolites were effectively eliminated, the Kt/V value was 1.03 +/- 0.22, beta-2-microglobulin declined after AFB from 36.3 +/- 10.0 to 23.8 +/- 8.2 mg/l, p < 0.001 . Cardiovascular stability of patients in the course of AFB was very good, symptomatic hypotension was recorded in one patient (0.83%) . CONCLUSIONS . AFB is considered by the authors, based on the results of their study and according to data in the literature, an effective and perspective form of substitution of renal function . AFB is particularly suitable for patients with circulatory instability and for those with a limited perspective of renal transplantation who are thus threatened by complications of long-term dialyzation treatment.

Pediatr Nephrol, 1995 Jun, 9(3), 357 - 8
Paediatric experience with acetate-free biofiltration; Espino Hernandez M et al.; We describe our preliminary experience with five children who received acetate-free biofiltration, a modification of haemodiafiltration without buffer in the dialysate and simultaneous infusion of bicarbonate through a venous port . Adequacy of haemodialysis (HD) was achieved with 3 h treatments three times per week (mean Kt/v 1.35 +/- 0.29, mean protein catabolic rate (PCR) 1.4 +/- 0.3 mg/dl) . During the session, pH increased from 7.4 pre HD to 7.5 post HD . The mean bicarbonate infused as a 0.166 M solution averaged 235 +/- 35 mEq/h . Hypertension did not occur . There were no cramps, hypotension or vomiting . Bicarbonate requirements correlated significantly with dialyser surface area and body weight (r = 0.76, P < 0.001).

J Chem Technol Biotechnol, 1995 May, 63(1), 85 - 91
Phospholipid coatings for the prevention of membrane fouling; Reuben BG et al.; The aim of the present work was the development of phosphorylcholine-based treatments for biofiltration membranes and the demonstration that such treatments prevent or inhibit protein fouling . Microfiltration membranes of cellulose triacetate, polyether sulphone and polyvinylidene fluoride were etched with oxygen in a plasma chamber to generate surface hydroxyl groups and were then treated with the monomer 2-methacryloyloxyethyl phosphorylcholine . These membranes were evaluated with water, buffer, bovine serum albumin (BSA), yeast fermentation broth, beer and orange juice . The treatment of cellulose triacetate membranes reduced both the initial flux and the extent of water fouling . In terms of the integrated flux, these factors tended to cancel each other out . For protein, the membranes gave similar or higher fluxes but worse fouling . The cellular feed (yeast) reacted more favourably to the coating than the BSA . The polyether sulphone was scarcely affected by the coating; fouling remaining high with most 'real' feeds . There was lower initial flux but less flux decline with water and beer . Washing with water and cleaning with Tergazyme did not restore the initial flux . Polyvinylidene fluoride membranes gave the most positive results . In most cases, the coating both increased initial flux and decreased the rate of fouling . The coating was particularly effective for BSA and for beer and orange juice, where fouling is probably caused by a polysaccharide rather than by a protein . Electron microscopy showed, nonetheless, that fouling by proteins was accompanied by protein adsorption primarily on the upper surface of the membrane and that coated membranes showed less deposition and in different places than did untreated membranes.

Vnitr Lek, 1995 Apr, 41(4), 235 - 9
{Lipid peroxidation and the antioxidant system in bicarbonate hemodialysis and acetate-free biofiltration}; Eiselt J et al.; Acetate-free biofiltration (AFB) is a modern haemodiafiltration method used at present as a variant in treatment of chronic renal failure . In AFB and standard bicarbonate haemodialysis (BHD), performed under equal conditions in 20 patients with chronic renal failure the authors investigated the degree of lipid peroxidation and the antioxidant defence system . As a marker of lipid peroxidation they used malondialdehyde (MDA); as to antioxidant factors they investigated the activity of superoxide dismutase (SOD) and glutathione peroxidase (GSHP) in red blood cells and the selenium (Se) concentration in blood . The MDA values were elevated in both dialyzation methods, as compared with 30 healthy controls (p < 0.001) . The SOD value before AFB did not differ from controls, before BHD it was higher than in controls (p < 0.01) . In the course of AFB or BHD the SOD values did not change . The GSHPx activity at the end of AFB rose significantly as compared with the initial value (p < 0.05) and the value during the 30th minute of AFB (p < 0.02) . In BHD the GSHPx activity was lower than in controls and did not change during the procedure (p < 0.01) . The selenium blood levels were before both AFB and comparative BHD lower than in controls (p < 0.001) . The authors found a positive correlation between the GSHPx activity and the Se level . The rise of GSHPx activity at the end of AFB may imply improved antioxidant defence during AFB and contribute to reduced tissue damage by free radicals.

Hepatology, 1995 Mar, 21(3), 863 - 74
Lipoproteins and the liver sieve: the role of the fenestrated sinusoidal endothelium in lipoprotein metabolism, atherosclerosis, and cirrhosis; Fraser R et al.; The liver sieve, formed by the fenestrated hepatic sinusoidal endothelium, is a dynamic biofilter separating the hepatic blood from the plasma within the space of Disse . It filters macromolecules of differing sizes, especially lipoproteins . More specifically, it acts as a barrier to the large triglyceride-rich parent chylomicrons, while permitting the smaller triglyceride-depleted but cholesterol- and retinol-rich remnants to enter the space of Disse . There the remnants contact specific receptor sites on the hepatocyte microvilli . Thus, the liver sieve is the first site of hepatic selection and consequent metabolism of dietary cholesterol and fat-soluble vitamins, as well as rejection of dietary triglycerides . Therefore, perturbations of the porosity of the sieve, whether from changes in size, number of fenestrae, or composition of the underlying extracellular matrix within the space of Disse, will have a profound influence on the metabolism of lipoproteins . This disturbance of the homeostasis of lipids, including fat-soluble vitamins and cholesterol, as well as other macromolecules, may tilt the balance between health and disease in a variety of organs and tissues, such as the liver, kidney and arteries.

Nephrol Dial Transplant, 1995, 10(8), 1405 - 10
Creatinine kinetic modelling: a simple and reliable tool for the assessment of protein nutritional status in haemodialysis patients; Canaud B et al.; While the mathematical modelling of urea kinetics is in wide use for evaluating treatment adequacy and protein nutrition in dialysis patients, the kinetics of creatinine generation in dialysis patients has been relatively unexplored . In this study creatinine kinetic modelling as a clinical tool was investigated in a group of 90 patients treated by haemodialysis (n = 20), haemodiafiltration (60), haemofiltration (7), or biofiltration (3) over a 6-36-month period . A single pool model of creatinine kinetics was employed to obtain monthly values of creatinine distribution space and creatinine appearance rate . Extrarenal creatinine degradation rate, estimated using a clearance of 0.038 l/kg/24 h as suggested by Mitch and co-workers, was added to creatinine appearance rate in urine and dialysate to calculate a corrected creatinine index (CI) . Extrarenal degradation accounted for 12 +/- 2% of CI . CI was higher in males (22.4 +/- 4.5 mg/kg/24 h) than females (19.8 +/- 4.8) and decreased with age, falling off more sharply for the female group (CI = 29.9-0.185.age, R = 0.72) than the males (CI = 24.1-0.030.age, R = 0.31) . CI was found to correlate strongly with protein catabolic rate determined by urea kinetic modelling (CI = 8.84 +/- 10.91.PCR) . Low or reduced CI was associated in this study group with severe malnutrition status and high mortality rate . CI is suggested as a strong predictor of patient morbidity and mortality.

Nephrol Dial Transplant, 1995, 10(6), 821 - 4
Correction of chronic metabolic acidosis in haemodialysed patients by acetate-free biofiltration does not influence parathyroid function; de Precigout V et al.; In eight patients remaining acidotic after more than 1 year of bicarbonate haemodialysis, we studied the effect of correcting the chronic metabolic acidosis using acetate-free biofiltration for 4 months on the course of secondary hyperparathyroidism . An AN69 capillary membrane was employed with a bicarbonate infusion rate initially set at 1.8 l/h in all patients and then adjusted in each one to obtain a predialysis bicarbonate of > or = 23 mmol/l . Standard blood chemistry parameters were determined every 2 weeks . Measurements of PTH, calcifediol and calcitriol, as well as calcium-PTH curves were determined at the beginning and end of the study . While acetate-free biofiltration appears to be an adequate technique for the correction of chronic metabolic acidosis when bicarbonate dialysis fails, this study indicates that it does not influence secondary hyperparathyroidism in haemodialysed patients . The level of intact PTH did not vary significantly and the calcium-PTH curves at 0 and 4 months were superimposable with no significant differences in the set point and the slope of the curves.

Am Ind Hyg Assoc J, 1994 Nov, 55(11), 1055 - 60
Workers' exposure to airborne bacteria and endotoxins at industrial wastewater treatment plants; Laitinen S et al.; A study of sewage workers' exposure to airborne culturable bacteria and inhaled endotoxins was performed at nine waste-water treatment plants that treat mainly industrial effluents . Airborne endotoxins were collected on glass fiber filters and analyzed using a chromogenic limulus assay . Endotoxin concentrations measured in the immediate vicinity of the waste-water treatment process varied from 0.1 to 350 ng/m3 . The eight-hour time weighted average concentrations of endotoxin to which workers were exposed exceeded the suggested exposure limit (30 ng/m3 endotoxin) at four of the plants . Air samples of culturable bacteria concentrations varied between 10 and 10(5) colony-forming units/m3 . Of the particles carrying culturable bacteria, 88% had an aerodynamic diameter of less than 4.7 microns . The most common genera of airborne gram-negative bacteria were acinetobacter, citrobacter, enterobacter, klebsiella, and pseudomonas . High levels of exposure to bacteria and bacterial endotoxin usually were related to certain phases of the treatment process . The microbiological contamination of air was highest near the inlets where incoming wastewater entered the basins, in the sludge treatment area, and inside the biofilter tower . In these spaces it is necessary to control and reduce exposure to airborne bacteria and endotoxin at wastewater plants.

Med Tekh, 1994 Nov-Dec, (6), 7 - 8
{Scheme of acetate-free biofiltration with programmed hemodialysis}; Shumakov VI et al.; The paper shows the advantages and original scheme for acetate-free biofiltration (a method alternative to hemodialysis) applied to the treatment of patients on programmed hemodialysis . The method has been first used in Russia and can be applied by means of a routine artificial kidney apparatus.

ASAIO J, 1994 Oct-Dec, 40(4), 968 - 71
The plasma glutathione peroxidase enzyme in hemodialyzed subjects; Schiavon R et al.; The kidney is probably the major site of production of the plasma enzyme glutathione peroxidase (GSHPx-P) . For this study, GSHPx-P activity was determined in 40 healthy people, in 34 patients with differing degrees of renal impairment, and in hemodialysis patients from whom blood samples were withdrawn either before or after each session (18 patients) or throughout the dialysis session (27 patients) . Hemodialysis patients were treated by means of different techniques (bicarbonate hemodialysis, hemodiafiltration, and acetate free biofiltration), and different membranes (cuprophane, polyacrylonitrite, and polymethylmethacrylate) . The following results were obtained: 1) GSHPx-P activity was significantly decreased in renal impairment patients; 2) GSHPx-P activity negatively correlated with serum creatinine values in renal impairment patients (r = -0.55; p < 0.001); and 3) the enzyme activity slightly increased after the session in hemodialysis patients . The following conclusions can be drawn: GSHPx-P activity could be new index of renal function, because it was decreased in patients with renal failure; the decrease in GSHPx-P activity paralleled the severity of renal impairment, and was maximal in hemodialysis patients; GSHPx-P activity was slightly raised at the end of the hemodialysis session, concomitant with other enzyme activities (aspartate transaminase, alanine transaminase, and alkaline phosphatase) and total protein concentration . This seems to be attributable to the process of water loss rather than other hypothetical mechanisms, such as A) enzyme activation by either peroxide generation during blood-membrane contact, or by the removal of a hypothetical inhibitor; and B) de novo synthesis in the residual renal mass or in other sites of production.

Appl Environ Microbiol, 1994 Aug, 60(8), 2717 - 22
Design and performance of a trickling air biofilter for chlorobenzene and o-dichlorobenzene vapors; Oh YS et al.; From contaminated industrial sludge, two stable multistrain microbial enrichments (consortia) that were capable of rapidly utilizing chlorobenzene and o-dichlorobenzene, respectively, were obtained . These consortia were characterized as to their species composition, tolerance range, and activity maxima in order to establish and maintain the required operational parameters during their use in biofilters for the removal of chlorobenzene contaminants from air . The consortia were immobilized on a porous perlite support packed into filter columns . Metered airstreams containing the contaminant vapors were partially humidified and passed through these columns . The vapor concentrations prior to and after biofiltration were measured by gas chromatography . Liquid was circulated concurrently with the air, and the device was operated in the trickling air biofilter mode . The experimental arrangement allowed the independent variation of liquid flow, airflow, and solvent vapor concentrations . Bench-scale trickling air biofilters removed monochlorobenzene, o-dichlorobenzene, and their mixtures at rates of up to 300 g of solvent vapor h(-1) m(-3) filter volume . High liquid recirculation rates and automated pH control were critical for stable filtration performance . When the accumulating NaCl was periodically diluted, the trickling air biofilters continued to remove chlorobenzenes for several months with no loss of activity . The demonstrated high performance and stability of the described trickling air biofilters favor their use in industrial-scale air pollution control.

Biodegradation, 1994 Jun, 5(2), 105 - 12
Isolation of a dimethylsulfide-utilizing Hyphomicrobium species and its application in biofiltration of polluted air; Pol A et al.; The methylotrophic bacterium Hyphomicrobium VS was enriched and isolated, using activated sewage sludge as inoculum in mineral medium containing dimethylsulfide (DMS) at a low concentration to prevent toxicity . DMS concentrations above 1 mM proved to be growth inhibiting . Hyphomicrobium VS could use DMS, dimethylsulfoxide (DMSO), methanol, formaldehyde, formate, and methylated amines as carbon and energy source . Carbon was assimilated via the serine pathway . DMS-grown cells respired sulfide, thiosulfate, methanethiol, dimethyldisulfide and dimethyltrisulfide . To test Hyphomicrobium VS for application in biofiltration of air polluted with volatile sulfur compounds two laboratory scale trickling biofilters with polyurethane and lava stone as carrier material were started up by inoculation with this bacterium . Both methanol- and DMS-grown cells could be used . Only a short adaptation period was needed . Short term experiments showed that high concentrations of DMS (1-2 mumol l-1) were removed very efficiently by the biofilters at space velocities up to 100 h-1.

Blood Purif, 1994, 12(2), 85 - 94
Calcium mass balance and behavior of intact immunoreactive parathyroid hormone in acetate-free biofiltration: acute and one-year evaluation; de Vincenzi A et al.; The present study evaluated calcium mass balance (MB) during acetate-free biofiltration (AFB) with a dialysate calcium concentration of 2 mmol/l and different ultrafiltration rates (UF; 42.5 ml/min in schedule 1 and 48.5 ml/min in schedule 3), and with a calcium concentration of 1.75 mmol/l but an UF of 43 ml/min (schedule 2) . We also examined the effects of these schedules on the behavior of intact parathyroid hormone (I-PTH) . AFB according to schedule 1 and 3 achieve a positive calcium MB (8.49 +/- 1.56 and 5.59 +/- 1.06 mmol, respectively), while in schedule 2 calcium MB merely balanced (0.07 +/- 2.29 mmol/l) . A significant acute intradialytic I-PTH decrease was observed with all schedules; after 1 month, however, predialytic PTH values were unchanged in schedules 1 and 3, but worsening was noted in schedule 2 . Subsequently, AFB was performed for 12 months employing a dialytic schedule (No . 1) involving a positive calcium balance . A year later I-PTH was significantly lower, thus proving that AFB may play an additional part in controlling secondary hyperparathyroidism.

Nephrol Dial Transplant, 1994, 9(9), 1305 - 9
High- and low-flux acetate-free biofiltration: experimental assessment of calcium mass balance and intact parathyroid hormone behaviour; de Vincenzi A et al.; We studied total calcium mass balance and plasma intact parathyroid hormone behaviour in 10 uraemic patients who underwent acetate-free biofiltration carried out in accordance with six different dialytic schedules, where either a polyacrylonitrile or a polysulphone membrane was used . Schedules 1 and 2 involved a reinfusion flow rate of 33.3 ml/min with a dialysate calcium concentration (DCa) of 1.75 and 2 mmol/l respectively; in schedule 3, 4, 5 and 6 reinfusion flow rate amounted to 50 ml/min and DCa was respectively of 1.75, 2, 2.25 and 2.5 mmol/l . Dehydration remained unchanged in all schedules: 700 g/h . Finally high- and low-flux acetate-free biofiltration are able to induce different Ca mass balance which may suit different therapeutic contexts . Ca mass balance was either positive or negative depending on reinfusion flow rate and DCa . With a reinfusion flow rate of 33.3 ml/min a DCa of at least 2 mmol/l was necessary to obtain a positive mass balance, while with a reinfusion flow rate of 50 ml/min DCa had to equal 2.25 mmol/l . In high-flux acetate-free biofiltration, the estimation of predialytic Ca2+ and DCa values, using a simple formula, allows prediction of the mass balance that will be attained . At the end of acetate-free biofiltration, intact parathyroid hormone always decreased when a polyacrylonitrile membrane was employed while it increased, in the presence of negative Ca mass balance with a polysulphone membrane.

Artif Organs, 1993 Aug, 17(8), 687 - 90
Chronic biofiltration therapy; Djordjevic V et al.; Long-term follow-up evaluation of biofiltration treatment in 7 patients is presented . These patients experienced frequent episodes of hypotension during acetate hemodialysis . A 3-year biofiltration treatment reduced by 43% episodes of symptomatic hypotension and produced a significant increase in the pretreatment pH and plasma bicarbonate levels . The beta 2-microglobulin level was significantly reduced during biofiltration therapy . The mean systolic and diastolic blood pressures slightly increased during biofiltration . Uremic polyneuropathy, as demonstrated by an increase in motor nerve conduction velocity, slightly improved . The patients reported increased comfort during biofiltration therapy.

Kidney Int Suppl, 1993 Jun, 41, S60 - 6
Effects of dialysate composition during hemodialysis on left ventricular function; Sztajzel J et al.; To determine the effects of dialysate composition during hemodialysis on left ventricular systolic and diastolic function, 12 patients treated by chronic hemodialysis (mean age 40.8 +/- 2.7 years), without overt heart disease, were studied by Doppler-echocardiography successively before and after acetate hemodialysis (AHD), bicarbonate hemodialysis (BHD), and acetate-free biofiltration (AFB) . The three types of hemodialysis resulted in a comparable decrease of the body weight . Mean arterial blood pressure decreased by 5 mm Hg (NS), 8 mm Hg (NS) and 10 mm Hg (P < 0.05) during AHD, BHD and AFB, respectively . There was a significant increase of the heart rate and the shortening fraction of the left ventricular diameter after AHD, but not after BHD and AFB . Mean total systemic resistance increased by 20% after AHD, 18% after BHD and by 7% after AFB (all changes NS) . During each type of hemodialysis there was a significant reduction of the peak velocity of the early diastolic rapid filling wave (peak E) without change of the peak filling velocity during atrial contraction (peak A) . During AHD and BHD the pressure half-time of the early filling phase (TP/2) increased, and the velocity-integral of the early diastolic filling phase (E-area) decreased . However, TP/2 and E-area did not change significantly after AFB.(ABSTRACT TRUNCATED AT 250 WORDS)

Kidney Int Suppl, 1993 Jun, 41, S221 - 5
C5b-9 generation and cytokine production in hemodialyzed patients; Pertosa G et al.; The role of the complement system in the induction of cytokine release is controversial . Plasma terminal C complex C5b-9 along with Bb and C4d fragments were evaluated in 22 patients during routine acetate or bicarbonate hemodialysis using cuprophane membranes and hemodiafiltration (HDF) or acetate-free-biofiltration (AFB) using polyacrylonitrile (PAN) membranes . In a subgroup of six uremic patients we also evaluated the release of tumor necrosis factor (TNF alpha) and interleukin-6 (IL-6) from monocytes before and after six subsequent sessions with bicarbonate-cuprophane, HDF and AFB-PAN . At beginning of the dialysis increased plasma C5b-9 levels were found in patients treated by acetate or bicarbonate-cuprophane . Moreover, a rapid significant (P < 0.001) increase of C5b-9 levels occurred in both groups 15 minutes after the onset of the hemodialysis procedure with a plateau at 180 minutes . In contrast, only a slight increase in the plasma C5b-9 levels was observed in patients dialysed with HDF or AFB using PAN membranes . This increase was more pronounced with HDF at 0 minutes compared with controls . A positive linear correlation was found in all patients between C5b-9 generation and plasma Bb levels at different times in the dialysis session . The production of C4d fragment remained unchanged in all groups, indicating that C5b-9 complex generation is due to the prevalent alternative complement pathway activation . The pattern of cytokine production strictly resembled the complement system activation and C5b-9 generation.(ABSTRACT TRUNCATED AT 250 WORDS)

Kidney Int Suppl, 1993 Jun, 41, S188 - 94
Efficacy and tolerance of acetate free biofiltration: a central Italian multicenter trial; Albertazzi A et al.; One hundred and thirteen patients from 51 dialysis units have been treated for 12 months on AFB using a high flux AN69 dialyzer (Filtral 12 or 16-Hospal), a buffer free dialysate (Na+ 139, K+ 2, Ca++ 2 mmol/liter, glucose 1 g/liter) and a reinfusate solution containing 145 mmol/liter HCO3Na . All of them had previously been stabilized on acetate dialysis (30 patients) or bicarbonate dialysis (46 patients) or different dialysis procedures (37 patients) . AFB sessions were performed for 3.71 +/- 0.28 hrs, three times a week, at an average blood flow of 308 +/- 8.5 ml/min so as to ensure a stable Kt/V value > 1 (1.16 +/- 0.08) . Blood samples were drawn monthly pre- and post-dialysis, for blood electrolytes, calcium, phosphate, chloride, urea, creatinine and uric acid, proteins and lipid profiles, hemochrome . Body weights, blood pressures and adverse side effects were recorded at each session . Using a mean infusion volume of 7.96 +/- 0.61 liter/session, post-dialytic bicarbonate values consistently > 25 mmol/liter (26.33 +/- 2.71) were achieved . Intradialytic occurrence of symptoms was very low at an average rate < 1.5 episodes patient/month . After 12 months of Tx an adequate control of uremia, of electrolytes, of Ca-PO4 balance and of BP was obtained . AFB gets a very high intradialytic tolerance and an excellent depurative capacity which contributes to the well being of the patients.

Kidney Int Suppl, 1993 Jun, 41, S184 - 7
Analysis of the factors influencing bicarbonate balance during acetate-free biofiltration; Santoro A et al.; In acetate-free biofiltration (AFB), the physical separation between the base losses and the gains could facilitate the modeling of intradialytic bicarbonate (HCO3) balance . In order to verify this hypothesis, we analyzed in a multicenter study, 126 AFB sessions in which differing parameters were evaluated (dialysis time, blood flow, ultrafiltration, infused HCO3, pre- and post-dialytic HCO3, hematocrit and body wt) . Statistical analysis performed with multiple linear regression showed that the post-dialysis HCO3 was significantly dependent (F = 21.68, d.f . 5.95, P < 0.001) directly on the amount of infused HCO3, the level of pre-dialysis HCO3 and the final body weight, and inversely on the dialysis time and the blood flow . HCO3 values predicted by the statistical model correlated well with the observed ones (r = 0.788, P < 0.0001) with a mean absolute difference of 2.138 mEq/liter . This modeling approach allowed us to predict, with a computer-aided procedure, the quantities of HCO3 to be infused to obtain a desired and personalized acidosis correction.

Artif Organs, 1993 Mar, 17(3), 188 - 90
Acetate-free biofiltration in acute renal failure; Meloni C et al.; Hemodialysis treatment for acute renal failure is associated with a high incidence of adverse reactions . Hemodynamic stability and adequate correction of acid-base and hydroelectrolyte imbalance are the main goals of dialytic strategy in acute renal failure . However, the variety of etiology and the diversity of clinical conditions suggest that individualized treatment may be advisable . To this purpose, in 26 patients suffering from "isolated" acute renal failure of different etiologies, we have used acetate-free biofiltration . We have performed 411 dialyses with an extremely low incidence of symptomatic treatments and remarkable cardiovascular stability . Correction of fluid, electrolyte, and acid-base imbalance proved excellent . Dialytic efficacy proved adequate . Our data show that acetate-free biofiltration is an easy technique suitable for individualized treatment and adaptable to changing needs during hemodialysis in patients with isolated acute renal failure.

Artif Organs, 1992 Dec, 16(6), 625 - 9
Plasma lipids and fatty acid levels in chronically uremic patients undergoing blood purification with different methods; Marangoni R et al.; Levels of plasma lipids and the fatty acid composition of major plasma lipid classes have been determined in chronically uremic patients before and after treatments with hemofiltration, high efficiency paired filtration dialysis, or acetate-free biofiltration . The major findings are a decrease of triglycerides and an increase of total free fatty acids (FFAs) at the end of the dialytic session--already reported in the literature--that do not appear to be strictly dependent on heparin administration . The changes in the plasma concentrations of selected saturated and polyunsaturated fatty acids, which may contribute to alteration of functional parameters in the cardiovascular system in dialyzed patients, are different in the various types of techniques.

Nippon Jinzo Gakkai Shi, 1992 Nov, 34(11), 1167 - 76
{Clinical effects of six-month short time biofiltration}; Ando R et al.; The clinical effects of six-month short time biofiltration (SBF) were evaluated using a B-A-B' study (B, B': conventional bicarbonate hemodialysis; CBHD, A:SBF) in ten patients maintained on CBHD three times a week . An F80 hemodiafilter (1.9 m2, polysulfone, Fresenius) was used . In addition to routine clinical parameters for a patient on regular dialysis treatment, plasma von Willebrand factor antigen (vWF) (an index of stimulation of vascular endothelium), and the methylguanidine/creatinine ratio (MG/Cr) and malondialdehide (MDA) (indices of the levels of oxygen radicals), were evaluated . Nine patients completed the study, one patient dropping out at the 12th week of A because of muscle cramps during SBF . The treatment time was 2 hours in six cases and 2.5 hours in three cases . The mean blood flow rate was 280 +/- 42 (SD) minutes . Using the urea kinetics model, the mean KT/V was 1.26 +/- 0.28, and the mean protein catabolic rate was 1.22 +/- 0.18 g/kg body weight/day at the end of A . No change in ultrafiltration, blood pressure, cardiac function (assessed by echocardiography), CTR, human atrial natriuretic peptide, total protein, albumin, uric acid, serum creatinine, sodium, calcium, inorganic phosphorus, vWF, or MDA was found between each period . Blood urea nitrogen, c-PTH, and MG/Cr increased during the A period . Serum magnesium and beta-2 microglobulin decreased during the A period . Blood gas results, on the whole, did not change . In a patients, however, acidosis gradually developed . An increase in substitution fluid from 5 L/session to 7.5 L/session improved the acid-base balance in that patient . In conclusion, SBF is as effective as CBHD in removing small molecules and maintaining cardiocirculatory status, and is superior to CBHD in removing beta 2-microglobulin and is less stimulative to the endothelium than CBHD.

Int J Syst Bacteriol, 1992 Jul, 42(3), 474 - 86
Chemotaxonomic differentiation of coryneform bacteria isolated from biofilters; Bendinger B et al.; Coryneform bacteria that were isolated from biofilters which are used for waste gas treatment of animal-rendering plant emissions were differentiated and partially identified by using chemotaxonomic methods . On the basis of the results of a numerical analysis of whole-cell fatty acid profiles, 79 isolates were divided into two major groups; the members of the first group contained saturated and monounsaturated fatty acids, whereas the members of the second group were characterized by iso- and anteiso-branched fatty acids . Division into subclusters was based mainly on quantitative differences in fatty acid composition and was confirmed by the results obtained for additional chemical markers (e.g., respiratory quinones, mycolic acids, polar lipids, cell wall amino acids, and whole-cell sugar patterns) . By combining the results obtained for chemotaxonomic analyses that were performed for strains containing saturated and monounsaturated fatty acids, we were able to identify the genus Corynebacterium (two Corynebacterium species were differentiated on the basis of the occurrence of tuberculostearic acid), the genus Gordona, and the genus Mycobacterium . Among the strains that produced iso-anteiso fatty acid patterns, one subgroup was affiliated with the "nicotianae" group of the genus Arthrobacter; however, some strains contained a new combination of chemical markers . Peptidoglycan type A4 alpha, L-Lys-Gly-L-Glu was combined with menaquinones MK-7 and MK-8, whereas peptidoglycan type A4 alpha, L-Lys-L-Glu occurred together with MK-8 and MK-9 . The second subgroup was characterized by a new type B peptidoglycan and MK-11, as well as small amounts of MK-12 . Differentiation that was based first on chemotaxonomy and second on physiology gave reliable results . Thus, coryneform strains with new characteristics were isolated from biofilters.

Mikrobiol Zh, 1992 Jul-Aug, 54(4), 89 - 99
{Bacteria of the genus Aeromonas and their role in aquaculture}; Kompanets EV et al.; Bacteria of genus Aeromonas are constant components of microbiota of fresh reservoirs where they, together with other microorganisms, play the part of natural biofilter and promote water self-purification . They are necessarily present in normal microflora of hydrobionts inhabiting fresh reservoirs . The greatest attention is paid by the researchers to Aeromonas and biotrophs in connection with epizootics in aquaculture which have become more frequent, in particular, under fish breeding . That is why the review is, to more extent, concerned in the works of this trend made by the foreign and home researchers for the last decade.

Minerva Urol Nefrol, 1992 Apr-Jun, 44(2), 161 - 4
{Clinical evaluation of 12 months of biofiltration in an elderly group}; Melappioni M et al.; Biofiltration (BF) was performed on 8 elderly uraemic patients (mean age 73.75 +/- 8.72 years; dialytic age 75.00 +/- 38.42 months) to improve cardiovascular stability and to reduce the dialytic session time . Small molecules (nitrogen, creatinine, uric acid, phosphorus) depuration, heamogasanalysis and PA monitoring, were compared against previous datum obtained by the same group that had undergoing acetate dialysis (AC . HD) for a year . Small molecules showed no significant differences; in BF the incidence of symptomatic hypotensions and the dialytic session time were reduced (30% and 30 min . respectively), with a better metabolic acidosis correction versus AC.HD . Our results showed that BF is better than AC.HD in elderly uraemic patients.

Zentralbl Hyg Umweltmed, 1992 Feb, 192(5), 389 - 418
{Emission and control of gases and odorous substances from animal housing and manure depots}; Hartung J; Agricultural animal production in increasingly regarded as a source of gases which are both aggravating and ecologically harmful . An overview of the origin, number and quantity of trace gases emitted from animal housing and from manure stores is presented and possible means of preventing or reducing them are discussed . Of the 136 trace gases in the air of animal houses, odorous substances, ammonia and methane are most relevant to the environment . The role played by the remaining gases is largely unknown . Quantitative information is available for 23 gases . The gases are emitted principally from freshly deposited and stored faeces, from animal feed and from the animals themselves . Future work should determine sources and quantities of the gases emitted from animal housing more precisely and should aim to investigate the potential of these gases to cause damage in man, animals and environment . Odorous substances have an effect on the area immediately surrounding the animal housing . They can lead to considerable aggravation in humans . For years, VDI1 guidelines (3471/72), which prescribe distances between residential buildings and animal housing, have been valuable in preventing odour problems of this kind . Coverings are suitable for outside stores . The intensity of the odour from animal housing waste air increases from cattle through to hens and pigs; it is also further affected by the type of housing, the age of the animals and the purpose for which they are being kept . Methods of cleaning waste air (scrubbers/biofilters) are available for problematic cases . The need for guidelines to limit emissions from individual outside manure stores (lagoons) is recognised . Total ammonia emissions from animal production in the Federal Republic of Germany (up to 1989) are estimated at approximately 300,000 to 600,000 t/year . There is a shortage of satisfactory and precise research on the extent of emissions, in particular on those from naturally ventilated housing . It is calculated that between 12 and 21 kg/ha of nitrogen a year enter the soil via the air, the average of which is higher than the average "critical loads" for most natural habitats . Ammonia has a direct effect on the trees in the area surrounding animal housing and is transported long distances through the air causing eutrophication and acidification of water and vegetation . This frequently results in changes in plant sociology . Reduction measures must begin with the housing and manure removal systems and with feeding and management.(ABSTRACT TRUNCATED AT 400 WORDS)

Nephron, 1992, 62(2), 155 - 60
Phosphate dialytic removal: enhancement of phosphate cellular clearance by biofiltration (with acetate-free buffer dialysate); Fischbach M et al.; Phosphate dialytic removal (PDR) depends in part on the type (acetate or bicarbonate) and the concentration of the buffer dialysate . Plasma phosphate reduction or PDR during a dialysis treatment is the algebraic sum, of phosphate cellular flux (removal or captation) and of phosphate tissular precipitation . High bicarbonate levels induce an intracellular shift of phosphate, thus not available for dialytic removal . On the contrary, acidosis prevents P shifting into the intracellular space, thus more P is available for dialytic removal . In order to evaluate cellular phosphate sequestration (CPS) we tested PDR in a crossover study . Three children were dialyzed (18 sessions) successively using either biofiltration with free buffer dialysate and a constant bicarbonate fluid infusion rate (BF) or using sequential biofiltration (SBF) with an initial controlled acidosis period realized by bicarbonate reinjection fluid rate modelling . PDR was higher in SBF (32 +/- 4 mmol/session) than in BF (24 +/- 6 mmol/session) . SBF seemed to be efficient against CPS; it clearly demonstrates that bicarbonate modelling is a promising dialytic approach to enhance PDR . The real clinical relevance of these biological results needs clinical long-term evaluation.

Appl Biochem Biotechnol, 1992 Jan-Mar, 32, 135 - 48
Biological deodorization of dimethyl sulfide using different fabrics as the carriers of microorganisms; Tiwaree RS et al.; Biological deodorization of dimethyl sulfide (DMS) was studied using nine unwoven fabrics as the carriers of microorganisms in a laboratory-scale deodorizing system . The activated carbon fabric FN-200CF-15 was the best packing material compared with other packing materials used, on the basis of removal rate . The maximum removal rate (Vm), evaluated by using Michaelis-Menten equation, was 2.28 g-S.kg-dry fab.-1.day-1 in this fabric biofilter . The critical load of DMS in this fabric biofilter was dependent on space velocity (SV), determined as 0.78 and 0.66 g-S.kg-dry fab.-1 at SV 100 and 150 h-1, respectively . Strain IM1 isolated from the carbon fabric FN-200CF-15 biofilter in modified Waksman (MW) medium successfully degraded DMS as well as hydrogen sulfide (H2S), methanethiol (MT), and dimethyl disulfide (DMDS) in batch test . The DMS removal rates (g-S.cell-1.h-1) by this strain measured in batch culture and calculated in FN-200CF-15 biofilter by the cell numbers appeared in MW medium were found almost equal, indicating that strain IM1 may be the dominant microorganism in this biofilter.

ASAIO J, 1992 Jan-Mar, 38(1), 52 - 4
Acetate free biofiltration . Effects on peripheral blood monocyte activation and cytokine release; Carozzi S et al.; Acetate free biofiltration (AFB), a new hemodiafiltration (HDF) technique characterized by a buffer free dialysate and postdilution infusion of a sterile HCO3 solution, was recently proposed as an alternative to HDF performed with acetate or bicarbonate dialysate . To evaluate the effects of dialysate buffer on immune cell activation, release of interleukin-1 (IL-1), tumor necrosis factor (TNF), prostaglandin E2 (PGE2), and leukotriene B4 (LTB4) from peripheral blood monocytes was studied in 12 uremic patients before and after HDF with polyacrylonitrile membranes (Filtral 12, Hospal Laboratories, Bologna, Italy) and consecutive dialysis with acetate, bicarbonate, and AFB . Data were correlated with the monocyte cytoplasmic concentration of Ca++, an index of early cell activation . Levels of bacterial endotoxins in the acetate, bicarbonate, buffer free dialysate, and infusate for AFB were also determined . Results showed that release of IL-1, PGE2, and LTB4, was greater after HDF with acetate than with bicarbonate; after bicarbonate dialysis, however, TNF production was significantly higher . On the other hand, after AFB, minimal production of these cytokines was seen and TNF, in particular, was undetectable . There was a direct correlation between release of cytokines in the monocytes and cytoplasmic Ca++ content . In the bicarbonate dialysate, detectable levels of bacterial endotoxins were found, whereas the acetate, buffer free dialysate, and infusate were endotoxin free . It was concluded that acetate dialysis directly activates peripheral blood monocytes to produce IL-1, PGE2, and LTB4, whereas bicarbonate induced TNF activation occurs through endotoxins . In AFB, which uses a buffer free dialysate and sterile bicarbonate infusion, monocyte activation is negligible.

Schriftenr Ver Wasser Boden Lufthyg, 1992, 89, 247 - 54
{Use of bioreactors for continuous water monitoring}; Blessing B et al.; A commercially available bacterial toxicity monitor ("Toxiguard", BTG Anlagentechnik, Bochum, Germany) was tested for continuous river monitoring . Operating with biofilms, this system shall detect toxic substances in the water . River water passes through two bioreactors forming a biofilm of characteristic river bacteria . The indicating parameter of the biomonitor is the respiration rate of this bacterial biofilter . The remaining oxygen content in the effluent from the biofilter is measured continuously by an oxygen electrode . This value is related to the dissolved oxygen (DO) of the river water measured in a by-pass . In presence of inhibitory substances the DO content in the biofilter increases because of the reduced respiration activity of the bacteria . The addition of nutrients may lead to an increase of biomass and of respiration activity . This results in an increasing oxygen difference between DO contents in the biofilter influent and effluent . Therefore, the degree of poisoning is better perceptible . Moreover each nutrient causes a distinct biofilm with a specific sensitivity against chemicals . This effect will be shown for Sodium-Pentachlorophenolate (Na-PCP).

Kidney Int, 1991 Sep, 40(3), 525 - 32
Sodium modeling in hemodiafiltration; Pedrini LA et al.; A computer model was developed to simulate sodium and water kinetics during hemodiafiltration (HDF), acetate-free biofiltration (AFB) and hemodialysis (HD) . Multiple regression analysis of the results of 3,240 simulated applications of the model (1,620 HDF, 1,080 AFB, 540 HD) showed that, during HDF and AFB, there is a close correlation (R2 = 0.92 and 0.91) between plasma water sodium concentration {( Na+P}) and a set of three variables: 1) the sodium gradient between plasma water and dialysate, 2) the sodium concentration of the substitution fluid and 3) ultrafiltration (UF) rate . With HD, a close correlation (R2 = 0.94) was found between changes in {Na+P} and combined changes in sodium gradient and the UF rate . On this basis, a regression equation was formulated for each procedure which allowed a reliable prediction of final {Na+P} to be made on the basis of knowledge of the imposed Na gradient, the programmed infusion (during HDF and AFB), and the UF rate . Clinical validation of the model was obtained in 12 patients: predicted final {Na+P} agreed well with the values measured by means of direct potentiometry (141.9 vs . 142.1 mEq/liter; P = NS), with a mean difference (-0.16 mEq/liter) and limits of agreement (+0.8 to -1.03 mEq/liter) fully acceptable for clinical purposes.(ABSTRACT TRUNCATED AT 250 WORDS)

J Air Waste Manage Assoc, 1991 Aug, 41(8), 1045 - 54
Biofiltration: an innovative air pollution control technology for VOC emissions; Leson G et al.; Biofiltration is a relatively recent air pollution control (APC) technology in which off-gases containing biodegradable volatile organic compounds (VOC) or inorganic air toxics are vented through a biologically active material . This technology has been successfully applied in Germany and The Netherlands in many full-scale applications to control odors, VOC and air toxic emissions from a wide range of industrial and public sector sources . Control efficiencies of more than 90 percent have been achieved for many common air pollutants . Due to lower operating costs, biofiltration can provide significant economic advantages over other APC technologies if applied to off-gases that contain readily biodegradable pollutants in low concentrations . Environmental benefits include low energy requirements and the avoidance of cross media transfer of pollutants . This paper reviews the history and current status of biofiltration, outlines its underlying scientific and engineering principles, and discusses the applicability of biofilters for a wide range of specific emission sources.

Nippon Jinzo Gakkai Shi, 1991 Jun, 33(6), 605 - 13
{Comparison of two hours' biofiltration and four hours' bicarbonate hemodialysis by multiple clinical parameters}; Nakagawa S et al.; Ten uremic patients maintained stable on regular dialysis treatment participated in a comparison study of 2 hours' biofiltration and 4 hours' bicarbonate hemodialysis with informed consents . In biofiltration, ultrafiltrate was replaced by a solution consisting of Na 145 mEq/l, HCO3- 100 and Cl 45 at the infusion rate 2.51/hour . Dialysate composition was Na 130-149 mEq/l, K 1.0, Cl 119, Ca 2.5, Mg 0.5, CH3COO- 15 and glucose 200 mg/dl . Hemodiafilter was F80, polysulphone, 1.9 m2, manufactured by Fresenius Co . Ltd . Blood flow rate was 5 ml/min/kg.body.weight to keep urea index (Kt/V) over 1.0 . B-A-B' comparison was designed in which B and B' stand for 4 hours' bicarbonate hemodialysis while A for 2 hours' biofiltration, 3 times per week for 2 months, respectively . It was intended to find out if there are aggravations of clinical parameters in A after B and/or improvements in B' after A in view of evaluation of optimum for 2 hours' biofiltration . One patient was withdrawn from biofiltration at 15th treatment in A because of frequent muscular twitchings . Others finished the whole program, thus making drop-out rate 10% . No significant differences were observed in the following parameters between B and A and between A and B': cardiothoratic ratio, pre-treatment blood pressure, human atrial natriuretic hormone, cardiovascular dynamics, total protein, BUN, serum creatinine, uric acid, beta 2 microglobulin, blood counts, blood gas analysis, electrolytes, alkaline-phosphatase, PTH-C, protein catabolic rate (PCR), lipids and liver functions.(ABSTRACT TRUNCATED AT 250 WORDS)

Nippon Jinzo Gakkai Shi, 1991 Jan, 33(1), 53 - 7
Phosphate kinetics in acetate-free biofiltration; Kuno T et al.; The phosphate kinetics during bicarbonate dialysis (BCD) and Acetate-free Biofiltration (AFB) were determined in 3 stable regular dialysis patients . These patients were switched to a 6-month period of AFB after a 12-month period of BCD . The plasma levels of phosphate, urea, and bicarbonate, and mass removal of phosphate and urea were measured every hour, during 3 consecutive dialysis sessions on BCD and AFB . The plasma phosphate behavior revealed a peculiar form with two main components, which differed from that of urea . The plasma phosphate level fell sharply during the first 2 hours of treatment, and then remained at a plateau towards to the end of the session . The plasma bicarbonate levels during the treatment sessions in the case of AFB were significantly higher than that in BCD . The actual mass removal in AFB was similar to that BCD, despite a significantly lower value of pre-plasma phosphate . A high ultrafiltration rate and better control of acidosis might be the reason for the better performance of phosphate mass removal in AFB . Better control of phosphatemia due to AFB can lead to a reduction in the amount of phosphate binders which have several untoward side effects.

Blood Purif, 1991, 9(3), 123 - 8
Forecasting correct sodium balance in hemodiafiltration procedures involving infusions; Redaelli B et al.; Four patients, stable on acetate hemodialysis (AHD), were switched to acetate-free biofiltration (AFB) which differs from AHD and bicarbonate hemodialysis (BHD) in that the dialysate contains no buffer, which is given intravenously as a hypertonic (1/6 M) Na bicarbonate solution . Within the 1st month the patients developed thirst and hypertension attributed to a positive Na balance . The aim of this investigation was to check this (1) by a study based on the predictable changes induced in the body compartments of 13 patients by the infusion and ultrafiltration (UF) of a hypertonic solution and (2) by direct determination and calculation of 28 Na mass balances in BHD and AFB . The theoretical model indicated that infusion of 4.87 liters of a 166.7 mEq/l Na bicarbonate solution and UF of the same amount caused a positive balance of 233 mosm of Na . The Na mass balances showed a relationship between Na transmembrane gradient and loss or gain of Na in both methods (p less than 0.0001) . The slopes of the regression lines were not significantly different but there was a highly significant difference between the y axis intercepts (p less than 0.0001), which indicates that the same Na transmembrane gradient that gives no net change of Na in BHD, induces a net gain of 240 mosm (120 mEq of Na) in AFB and that to obtain the same Na balance dialysate Na should be reduced by about 8 mEq/l in AFB . These data are the same as the theoretical forecast which could be extended to all hemodiafiltration methods in which solutions of any tonicity have to be infused, in order to correctly predict the Na balance.

Nippon Jinzo Gakkai Shi, 1990 Jul, 32(7), 809 - 16
{The clinical value of correction of acidosis by acetate-free biofiltration in patients on regular dialysis treatment}; Kuno T et al.; Effects of metabolic acidosis were compared between bicarbonate dialysis (BCD) and acetate-free biofiltration (AFB) . Three stable dialysis patients (1M, 2F, mean age 30 yrs) were selected for the study because their bicarbonate (BC) pre-dialysis plasma concentration were always under 16 mmol/l while they were on 33 mmol/l-BCD thrice weekly for 12 months . They were switched to a 6 months period of AFB . Pre- and post-dialysis BC plasma concentration, other blood chemical parameters and mass removal (total collection of used dialysate) of urea (U), creatinine (Cr), uric acid (UA), and phosphate (P) were measured during the last week of each period, including 3 dialysis sessions . Mean calorie and protein intake were 29.4 KCal/kg.d and 1.5 g/Kg.d (BCD period) and 38.2 Kcal/Kg.d and 1.5 g/Kg.d (AFB period) respectively . BC plasma concentration (Mean +/- SE, mmol/l) at the pre and post-dialysis in AFB were significantly higher than those in BCD (16.6 +/- 0.7 vs 20.8 +/- 0.6; p less than 0.001, 22.7 +/- 0.8 vs 25.8 +/- 0.8; P less than 0.02) . Pre- and post-dialysis U plasma concentration (Mean +/- SE, mmol/l) in AFB were significantly lower than those in BCD (34.3 +/- 2.51 vs 20.8 +/- 0.59, 10.5 +/- 1.32 vs 7.5 +/- 0.92; P less than 0.001) . Pre-dialysis P plasma concentration (Mean +/- SE, mmol/l) in AFB was significantly lower than that in BCD (1.85 +/- 0.09 vs 1.50 +/- 0.15; P less than 0.01) . Cr, UA and P mass removal in BCD and AFB were not significantly different . However, U mass removal in AFB was significantly lower than that in BCD.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Purif, 1990, 8(1), 14 - 22
Acetate-free biofiltration: hemodiafiltration with base-free dialysate; Zucchelli P et al.; Bicarbonate dialysis has several clinical advantages compared to conventional acetate hemodialysis . However, the use of bicarbonate in the dialysate requires complicated hardware with considerable maintenance and servicing . We have developed a new dialysis technique, a modification of hemodiafiltration, called acetate-free biofiltration (AFBF), with no base replacement agents in the dialysate and with the infusion of bicarbonate solution in postdilution fluid . This study consisted of two parts, an acute phase (8 dialysis patients) and a chronic phase (4 patients) lasting up to 12 months . In the first phase we evaluated the effects of different amounts of infused bicarbonate (from 751 to 1,002 mEq per session) on acid-base balance . The best correction of uremic acidosis was obtained with the infusion of 900-1,000 HCO3 mEq during a 3-hour AFBF . There was a significant (p less than 0.0001) positive correlation between infused and gained bicarbonate . In the chronic part, 880-910 HCO3 mEq was infused per session and there was an increase in mean pretreatment plasma bicarbonate from 18.1 +/- 2.2 upon starting to 22.8 +/- 0.4 mEq/l by the end of the 12-month period . A very low incidence of intradialytic hypotension and stable serum chemistries were achieved with this technique as compared with standard hemodialysis despite a reduction of 3 h in weekly treatment time . AFBF is an easy-to-use, safe alternative to bicarbonate dialysis thanks to the absence of pyrogen reactions and comparatively low-cost maintenance.

Minerva Urol Nefrol, 1990 Jan-Mar, 42(1), 43 - 6
{Biofiltration without buffering substances in the dialysate}; Quarello F et al.; A new hemodiafiltration technique, acetate free biofiltration (AFB), has been recently introduced in the treatment of chronic uremia . It is performed with a buffer free dialysate and a simultaneous infusion in post-dilution mode of a sodium bicarbonate solution (concentration 145-166 mEq/l; infusion rate 1.2-2 l/h) . A polyacrylonitrile hollow fiber AN69 HF 1.2 sqm dialyzer is employed . In acute studies pCO2 remains stable throughout the treatment, as well as pCO2 . We have found a significant inverse correlation between delta{HCO3-} pre and post treatment and basal {HCO3-} (r = -0.88; p less than 0.001), with an excellent correction of uremic acidosis, avoiding post dialytic alkalosis . Our long term experience on 6 patients followed up to 31 months, allows us to consider AFB as a feasible and safe treatment, offering a good correction of uremic acidosis and an excellent hemodynamic tolerance . We propose AFB as a competitive technique with respect to bicarbonate hemodialysis, hemodiafiltration and standard biofiltration.

Patol Pol, 1990, 41(3), 129 - 33
{The use of millipore technique in cytodiagnostic studies of urine}; Faryna J; The author describes the principles of studying the urine by using millipore technique searching for neoplastic cells . The technique consists in passing the urine sample through a biological filter containing pores of specific diameter (millipore) allowing to condense the cellular and amorphous elements of the urine in a small surface and to obtain preparations of a good quality . This technique is recommended especially in case of transparent urine remaining within the limits of norm on gross examination.

Prikl Biokhim Mikrobiol, 1989 Nov-Dec, 25(6), 723 - 33
{Biological methods of air purification (review of the literature)}; Utkin IB et al.; Biological methods of air purification are reviewed, which can be applied to deep air purification of complex multicomponent mixtures from harmful, toxic and odorous substances at room temperature and atmospheric pressure . Microbiological and technological aspects of the problem are discussed . Operation characteristics of biofilters, bioscrubbers and trickle bed bioreactors are compared . Prospects of air biopurification are considered.

Artif Organs, 1989 Oct, 13(5), 476 - 9
Acetate-free biofiltration: a viable alternative to bicarbonate dialysis; Santoro A et al.; Eight patients were studied during four sessions of acetate-free biofiltration (AFBF) . AFBF is a new dialysis technique with no base replacement agents in the dialysate and with the addition in postdilution mode of bicarbonate (HCO3) solution directly into the extracorporeal blood circuit . In this study the effects on acid-base balance of different infusions of sodium bicarbonate (NaHCO3) ranging from 751 to 1,002 mEq per session was evaluated . There were significant positive correlations between the HCO3 infused and net HCO3 gained (r = 0.776, p less than 0.0001) and between HCO3 infused and plasma intratreatment HCO3 changes (n = 0.562, p less than 0.001) . Stepwise multiple linear regression analysis demonstrated that HCO3 infused and plasma predialysis HCO3 values played the major role in HCO3 balance in AFBF . The best correction of metabolic acidosis was obtained with the infusion of 900-1,000 mEq of HCO3 . The use of substitution fluid with 145 mEq/L of Na concentration avoids the risk of a positive intratreatment Na balance.

ASAIO Trans, 1989 Jan-Mar, 35(1), 8 - 13
Renal biofiltration; Man NK et al.; Biofiltration is a hemodiafiltration technique performed with a base-free dialysate and simultaneous infusion in postdilution mode of isotonic bicarbonate solution . This technique has the advantages without the inconveniences of bicarbonate dialysis that result from complicated hardware and the need of frequent trouble shooting . In biofiltration, 1) the sodium dialysate concentration should be monitored according to the patient's body weight gain and to the sodium concentration of infusion fluid to obtain adequate sodium mass balance and 2) plasma bicarbonate is easily controlled because the final plasma bicarbonate concentration depends upon the bicarbonate infusion flow rate . Long-term follow-up evaluation (6-24 months) of 76 patients on a dialysis strategy of 3 hr three times a week from 17 European dialysis centers has shown that biofiltration is a simple and safe alternative to bicarbonate dialysis . It could be the way to fulfill the requirements of short time/high quality dialysis, which seems to be the developing trend of dialysis in the future . These advantages are, however, balanced by the extra cost of high flux dialyzers and infusion fluid.

Blood Purif, 1989, 7(6), 324 - 31
Comparison of clinical and neurological status in elderly patients treated with two different hemodialysis techniques; Briganti M et al.; Five patients with a mean age of 63.4 years (range 62-67) who had frequent episodes of intradialytic intolerance during acetate hemodialysis (HDA) received biofiltration (BF) . For each period of study (6 months on HDA and 6 months on BF), the patients underwent a complete clinical assessment, with evaluation of the electroencephalographic (EEG) pattern and acid-base status . During BF, we observed a reduction of hypotensive episodes (10% on BF vs . 26% on HDA) and EEG disturbances (18% on BF vs . 70% on HDA), with a more physiological correction of uremic acidosis . We conclude that BF improves clinical status and neurological tolerance with a better compensation of acidosis in the elderly.

Artif Organs, 1988 Dec, 12(6), 476 - 81
Continuous computerized monitoring of hemodynamic parameters during acetate dialysis, bicarbonate dialysis, and acetate-free biofiltration; Spongano M et al.; The effects of continuous, computerized, non-invasive hemodynamic monitoring on the appearance of intradialytic symptoms, aided by preventive therapeutic maneuvers, were evaluated in 30 critically ill patients undergoing regular acetate dialysis . The hemodynamic behavior was assessed by a system that interfaces a personal computer with a blood pressure monitor and to a transthoracic electrical impedance-measuring instrument . Monitoring allowed us to reduce significantly the frequency of some important intradialytic symptoms such as nausea, vomiting, and hypotension . The same monitoring system was used acutely to characterize differing hemodynamic behaviors during acetate dialysis (AD), bicarbonate dialysis (BD), and acetate-free biofiltration (AFBF) . AD showed a prevalent vasodilation effect with a compensatory increase in heart rate and higher cardiac output values, which were not sufficient to maintain blood pressure stability . BD and AFBF were characterized by a more efficient vasoconstrictor effect and good hemodynamic stability . AFBF, despite a 1 h reduction in session length compared to BD, did not present significant differences in hemodynamic response resulting from session shortness or other technical changes.

Int J Artif Organs, 1988 May, 11(3), 169 - 74
Comparison of four different short dialysis techniques; Ronco C et al.; The goal of shortening dialysis treatment time has stimulated the development of new, highly efficient dialytic strategies . In this study the Authors compared four different short dialysis treatments in terms of efficiency, clinical tolerance, technological investment and costs: 1) Rapid bicarbonate dialysis with 1.5 sq.m . cuprophane membrane; 2) High flux biofiltration with 1.2 sq.m . AN69S hollow fiber membrane; 3) Hemodiafiltration with 1.2-1.9 . sq.m . polysulphonic hollow fiber hemodiafilters, and 4) High flux hemodiafiltration with two serial hemodiafilters with AN69s membrane (total 2.4 sq.m.) . Hydraulic properties and solute clearances at different blood flows (300-500 ml/min) were tested for each technique . Once the optimal operative level was established three patients were treated with each technique for at least six months . Since BUN clearance averaged 310 ml/min, the treatment duration varied from 120 to 180 min/session with KT/V always higher than 1 . The average protein catabolic rate was 0.9 g/kg/24h . Clinical tolerance was generally good, slightly better in treatments with a high convective component . Despite the greater efficiency of treatment No . 4, the technological requirements and costs are such that the others are currently more feasible and acceptable in clinical routine . The study demonstrates that reduction of dialysis treatment time is possible in all centres in a selected population with adequate blood access . Treatment No . 1 can even be performed with standard equipment and cuprophan membranes, while bicarbonate in the dialysate is mandatory . The real limit to shortening treatment time seems to be related to the maximal rate of ultrafiltration achievable in the patient during dialysis.

Int J Artif Organs, 1987 May, 10(3), 173 - 8
Inorganic phosphate removal during different dialytic procedures; Zucchelli P et al.; In order to clarify the influence of membrane surface, membrane composition, dialysate buffer and convective transfer on the dialytic removal of inorganic phosphate (Pi), 11 uremic patients were studied . Each patient underwent 7 different dialysis techniques: conventional hemodialysis with acetate buffer and different surface or composition of the membrane, bicarbonate dialysis and a "soft" hemodiafiltration, also termed biofiltration, with post-dilution infusion of 4 liters . The treatment time was fixed at 4 hours . Our study showed that the dialyzer surface area and the ultrafiltration rate were the major factors in dialytic inorganic phosphorus (Pi) removal . The dialysate buffer does not modify dialytic Pi removal but may influence the rebound phenomenon.

Invest Ophthalmol Vis Sci, 1987 Mar, 28(3), 451 - 8
Fluorescence-labeled lectins, glycoconjugates, and the development of the mouse AOP; Vanden Hoek TL et al.; The development of the aqueous outflow pathway (AOP) in early postnatal mouse eyes was examined for the presence of a variety of lectin receptors using fluorescein isothiocyanate (FITC) conjugated lectins, 1 micron araldite plastic sections, and computer-aided fluorescence photography . The trabecular meshwork anlage (days 1-4) was characterized by the presence of loosely arranged cells and an extracellular matrix that exhibited intense areas of Con A- and RCA-lectin staining, and absence of WGA- and LPA-lectin staining . By day 6, trabecular meshwork LPA- and WGA-positive materials were observed as focal areas of staining . By day 10, LPA- and WGA-positive materials were present as diffuse areas of staining, as the AOP differentiated into an organized and functional biological filter . The age-dependent pattern of LPA- and WGA-positive materials indicated that there were time-dependent points in the synthesis of glycoconjugates in the developing AOP . The results suggest: The composition and/or conformation of the glycoconjugates on cells and extracellular matrix changed as the AOP differentiated into a functional tissue . The use of FITC lectins as biological markers for studies of the AOP provided information on the potential role of glycoconjugates in the development of the normal AOP . Modification in the type, amount, and distribution of glycoconjugates may provide a basis for understanding the cellular mechanisms of abnormal development of the AOP, eg, congenital glaucoma.

Vet Med Nauki, 1987, 24(8), 87 - 90
{Survival of pathogenic microorganisms in the Black Sea mussel with an experimental infection}; Matev I et al.; The survival rate was followed up of S . typhimurium, S . enteritidis, S . aureus, and E . coli in the organs of M . galloprovincialis L . in experimental conditions . A vat was used with 30 mussels in 10 l of sea water contaminated with 10 cm3 broth culture in conc . of 2.10(4) bacterial cells per cub . cm . The water was changed at 24-hour intervals . Microbiologic studies were carried out of the gills, liver, and meat of the mussels and of the sampled sea water . Lowest survival rate showed S . aureus--up to the second day, S . typhimurium and S . orientalis--up to the 4th days (in the gills only), and E . coli--up to the sixth day (in the gills and liver) . None of the experimental strains to the sixth day (in the gills and liver) . None of the experimental strains was isolated from the meat . With regard to the periods of investigation cited M . galloprovincialis L . could play the role of a carrier, resp . vector of the infection and could bring about a disease after consumption . Stated is the important part played by mussels as biofilter, and, at the same time, as source of pathogenic bacterial microflora.

Acta Microbiol Pol, 1987, 36(1-2), 109 - 18
A note on the forest soil as a biological filter in the sanitary purification of municipal waste water evaluated on the basis of Escherichia coli titre; Kermen J et al.; The paper presents the results of a 10-year study on waste water purification in forest soil, under conditions of lysimeters and in the field, using pine-, larch- and osier cultures . The investigation has shown that, under test conditions, treatment with waste water does not endanger the sanitary state of the soil and ground water . In weakly podzolised sandy soil of loose texture, at the soil profile depth of at least 150 cm, the watering dose of 25 mm, i.e . 25 l/m2, was found to be safe, when applied 4 times monthly during the vegetation season, from May to September, for the first 4 years of the experiment (annual dose of 500 mm) . Initially the waste water had pH equal to 6.8-7.2, BOD5 of about 220 mg O2/l and an Escherichia coli cells number mostly 10(5) per ml, but after filtering through the soil, the E . coli cells number was 10 or less per 1 ml . After a lapse of 4 years the single waste water dose could be increased up to 50 mm (annual dose 1000 mm) without any detriment to the degree of sanitary purification of waste water.

Int J Artif Organs, 1986 Dec, 9 Suppl 3, 9 - 14
Biofiltration with buffer-free dialysate; Buoncristiani U et al.; The presence of acetate in the dialysate appears to be superfluous in the new depurative technique indicated as biofiltration, which consists in a standard hemodialysis with high ultrafiltration combined with the reinfusion of 3-4 1/2 liters of solution containing bicarbonate . The presence of acetate could in fact be contraindicated by a number of potential side effects, metabolic, cardiovascular and biological . Hence, starting from the consideration that in standard biofiltration a buffer is already infused directly as bicarbonate, we tried to overcome the potential hazards of the acetate-containing bath simply by using a dialysate without acetate and by increasing the concentration of bicarbonate in the reinfusate . A cumulative clinical experience of 20 months in 4 patients proved the feasibility and safety of the technique and suggests further advantages over standard biofiltration (better control of acid-base equilibrium, better cardiovascular stability.

Int J Artif Organs, 1986 Dec, 9 Suppl 3, 85 - 8
L-ascorbatemia during biofiltration; Giordano R et al.; In a study of the intradialytic behaviour of l-ascorbatemia during acetate and bicarbonate dialysis we noted the paradoxical increase in l-ascorbatemia during the first hour of acetate dialysis . During biofiltration, the intradialytic curve of l-ascorbatemia is similar to that in bicarbonate dialysis, even though an acetate dialysis bath is used . Thus the paradoxical rise of l-ascorbatemia during acetate dialysis may be due to the relative acidosis of the first hour.

Int J Artif Organs, 1986 Dec, 9 Suppl 3, 79 - 80
Results of six months' biofiltration in six selected cases; Carcheri GP et al.; Results of six months' biofiltration in six selected cases . Biofiltration is a method by which haemodialytic treatment can be completed within three hours and acidosis is corrected in a shorter time than with bicarbonate dialysis . In six selected patients with different syndromes not one patient showed a symptom of insufficient dialysis . In one patient serious hypertension was resolved satisfactorily.

Int J Artif Organs, 1986 Dec, 9 Suppl 3, 75 - 7
Use of the AN69-S (Biospal) in conventional hemodialysis (HD) and in biofiltration (BF); Pisani E et al.; The authors report the results of a comparative study between biofiltration and conventional hemodialysis with cuprophan and AN69-S hemodialyzers . Using AN69-S in conventional hemodialysis and in biofiltration, there was an almost total absence of cramps, headache, nausea, vomiting and symptomatic hypotension even though map and DBW were reduced.

Int J Artif Organs, 1986 Dec, 9 Suppl 3, 73 - 4
Oxalate depuration during biofiltration with AN69 and in conventional hemodialysis in chronic renal failure (CRF) patients; Chimienti S et al.; Oxalate (Ox), an end product of amino acid metabolism, accumulates in CRF patients as calcium crystal deposits in many soft tissues such as myocardium, kidney interstitium, etc . Since BF employs AN69, a high efficiency membrane, we tested its depurative efficacy for Ox against a hollow-fiber cuprophan dialyzer . Five CRF patients previously in HD and after six months of BF were studied . End-dialysis and pre-dialysis Ox values and dialyzer clearance were obtained . Predialysis Ox values were: 0.44 +/- 0.15 mg/dl in HD and 0.42 +/- 0.09 mg/dl in BF (NS) . End-dialysis Ox values were: 0.30 +/- 0.09 mg/dl in HD and 0.22 +/- 0.04 mg/dl in BF (p less than 0.001) . Pre and post dialysis values differed by 31% in HD and 47% in BF (p less than 0.001) . Ox clearance was 98.8 +/- 10.3 ml/min in HD and 143 +/- 20.5 ml/min in BF . There was a rebound in Ox values at 48 hours (0.41 +/- 0.08 mg/dl in HD and 0.32 +/- 0.12 mg/dl in BF, (NS) . These results indicate that Ox is depurated better during BF than during HD.

Int J Artif Organs, 1986 Dec, 9 Suppl 3, 71 - 2
Efficacy of biofiltration for intradialytic hypotension; Manno C et al.; Biofiltration, a simplified variant of hemodiafiltration, relieved intradialytic hypotension and acidosis in three patients previously on conventional hemodialysis.

Int J Artif Organs, 1986 Dec, 9 Suppl 3, 67 - 70
Hemorheology in biofiltration and acetate dialysis (preliminary results); Borgatti PP et al.; Hemorheological measurements were made in 8 stable chronic haemodialysis patients observed in conventional acetate dialysis (AD) with Cuprophan membrane and then in biofiltration (BF) with PAN AN69S membrane . Blood viscosity diminished at the beginning, both during BF and AD, reaching pre-dialytic values again at the end of treatment . Blood and erythrocyte filtration increased after 20 min in AD and throughout the session in BF . Preliminary results suggest an improvement of hemorheological parameters during dialytic treatment, more notable in BF than in AD.

Int J Artif Organs, 1986 Dec, 9 Suppl 3, 63 - 5
The new AN69 membrane in biofiltration (BF): 18 month's follow-up; Bova C et al.; BF is a dialytic procedure employing the new AN69 polyacrylonitrile membrane, which is more permeable to both water and solutes than the traditional AN69 . A postdilutional bicarbonate infusion is necessary in BF . The treatment time is 3 hours . Six patients, previously on regular acetate (HD) or bicarbonate dialysis (BHD) with AN69 were treated for 18 months with BF . Biochemical and hematological parameters (BUN, creatinine, uric acid, CA, P, K, Na, blood pH, HCO3, hematocrit) and clinical signs were evaluated in BF, and compared to those of HD and BHD . An improvement in biochemical and hematological parameters accompanied by better clinical signs was seen in BF as compared to HD and BHD . In our opinion this is due both to better removal of small and middle molecules and the bicarbonate infusion, and to the shorter dialytic session.

Int J Artif Organs, 1986 Dec, 9 Suppl 3, 57 - 62
The acid-base balance and the electroencephalographic pattern in patients on biofiltration treatment; Briganti M et al.; Electroencephalogram (EEG) monitoring and arterial blood gases was performed during biofiltration (BF) treatment and during conventional acetate hemodialysis (HDA) . Biofiltration is an ultrashort hemodiafiltration with 3 liters of substitution fluid (Na+ 145 mEq/l, HCO-3 100 mEq/l) . Our data show a better correction of acid-base balance during BF than during HDA . Moreover, we observe a lower incidence of EEG disturbancies on BF, that suggests a better neurological tolerance of this treatment.

Int J Artif Organs, 1986 Dec, 9 Suppl 3, 51 - 4
Biofiltration and calcium-phosphate metabolism; Bianchi ML et al.; We evaluated the effect of one session of biofiltration on calcium-phosphate metabolism in four uremic patients and compared the results with those of a previous traditional hemodialysis (Cuprophane membrane) session, on the same subjects . The most noteworthy results were: both total and ionized plasma calcium rose less in biofiltration; phosphate clearance and parathyroid hormone clearance were higher in biofiltration; plasma 25-OH D did not change in either dialysis technique.

Int J Artif Organs, 1986 Dec, 9 Suppl 3, 39 - 42
Clinical evaluation of biofiltration in uremic patients undergoing chronic hemodialysis; Meloni C et al.; The clinical efficiency of biofiltration (BF) was evaluated in six hemodialysis patients with poor clinical tolerance for standard hemodialysis . Three were adults (mean age 34 years, mean body weight 67 kg) and three adolescents (mean age 17 years, mean body weight 38 kg) . Mean maintenance hemodialysis time was 90.5 months (range 49-132) . BF treatments lasted three hours in all cases, for a total of nine hours weekly, with AN69 S membranes and infusion of 3 liters of HCO3 solution (100 mEq/l for the adults, 80 mEq/l for the adolescents) . We recorded intra- and inter-dialytic symptoms daily, hematological values and acid-base status monthly . Multimodality evoked potentials were recorded after 3 and 9 months . Biochemical values reached a steady state 9 months from the beginning of the study, metabolic acidosis was corrected more efficiently in both groups at the end of dialysis, but only in the adult patients, were pre-dialysis plasma bicarbonates within normal limits . A clear drop in the number of episodes of intradialytic hypotension was noticed in both groups, but the adolescent patients' tolerance for dialysis did not improve . In conclusion our data show that in adult patients with poor tolerance BF offers a dependable alternative to standard hemodialysis, and the length of treatment can be reduced.

Int J Artif Organs, 1986 Dec, 9 Suppl 3, 35 - 8
Removal of phosphate (Pi) by either bicarbonate dialysis or biofiltration in uremics; Bazzato G et al.; The kinetics of extra and intracellular red blood cell (RBC) Pi and its removal by different therapeutic modalities were evaluated in 30 uremic patients over a 6 mo . period . Acetate hemodialysis alone, combined with hemoperfusion, or associated once a week with plasma-perfusion sessions using an activated bauxite cartridge, bicarbonate dialysis either in single pass or in recirculating system (40 L) and biofiltration, were the depurative treatments employed . The treatments with acetate buffer showed a temporary intracellular shift of Pi at the end of the sessions with post-dialytic plasma Pi rebound . This was not evident with bicarbonate buffer and biofiltration where acidosis was corrected better, and similarly during plasma perfusion treatment because blood pH remained unchanged . These findings may explain the better plasma Pi level at the end of our study with these later therapeutic models compared to acetate dialysis alone or combined with hemoperfusion . In these conditions Pi removal is limited by the correction of acidosis which implies acetate metabolism with ATP activation leading to a transient Pi intracellular influx and a subsequent efflux into the extracellular compartment.

Int J Artif Organs, 1986 Dec, 9 Suppl 3, 31 - 4
Is 3000 S Hospal a suitable dialyzer to shorten dialysis time schedule? A cooperative study on biofiltration; Fuiano G et al.; The Biofilter 3000 S Hospal may combine higher convective clearance rates (Cc) with usual diffusive clearance rates (Cd) (i.e . similar to Cuprophan dialyzers), giving a higher total clearance rate (Ct) of small and middle molecules . Use of the Biofilter has been suggested to shorten dialysis time schedules . This study was carried out in 8 patients on RDT 3 times weekly, by cuprophan filter and acetate dialysis . The patients were shifted to dialysis with 3000 S guided by two principles: to shorten dialysis time by 1 hour per session, and to reinfuse 6 liters of bicarbonate-saline solution (40 mEq/l) per single dialysis . Besides the usual clinical and laboratory controls, in three patients clearance studies were carried out during four different dialysis sessions: Ct, Cc and Cd of urea K+, creatinine, uric acid and phosphate were measured . No change was observed in the main clinical and laboratory parameters after 3-5 months (average 3.9) of treatment with Biofilter 3000 S; in addition, serum alkaline phosphatase concentration decreased progressively . Clearance results, however, indicate that the expected high values of Ct do not occur, because Cd decreases as Cc is increased . A primary goal of research in hemodialysis is to reduce the average time of treatment while ensuring simultaneously "physiological" dialysis . A possible approach to this problem is to use dialyzers with highly permeable and biocompatible membranes such as the "biofilter" 3000 S Hospal.(ABSTRACT TRUNCATED AT 250 WORDS)

Int J Artif Organs, 1986 Dec, 9 Suppl 3, 25 - 6
Puglia cooperative study on biofiltration; Mastrangelo F et al.; Biofiltration (BF) was performed on 60 patients from 12 dialytic centers in Puglia . The protocol was 9-10.5 hours a week with 1.2 m2 PAN dialyzers . A dialysate with 140 Na+, 2-2.5 K+, 3.5-4 Ca++, 38 mEq/l acetate was used in 49 patients; the acetate was replaced by bicarbonate (35-40 mEq/l) in 11 patients . The same patients were treated for 1 year with standard acetate dialysis (49 patients) and standard bicarbonate dialysis (11 patients) . The two protocols were compared on the basis of the clinical state, BUN and serum creatinine, acid-base balance, PTH, anemia, and nerve conduction velocity (NCV) . Favourable effects were achieved in 55 patients . Four patients left the program because of progressive hyperhydration . BUN and serum creatinine levels showed a moderate, but insignificant increase . PTH, anemia and NCV did not worsen . BF gave better correction of metabolic acidosis in the patients undergoing acetate dialysis.

Int J Artif Organs, 1986 Dec, 9 Suppl 3, 21 - 4
Effects of biofiltration versus hemofiltration in the treatment of chronic uremia; Cappelli G et al.; Biofiltration (BF), a new depurative hemo-diafiltration employing a high efficiency membrane (acrylonitrile and metallylsulphonate of sodium) and reinfusion of 8-9 liters of fluid was tested as an alternative method to hemofiltration (HF) . Sixteen uremic patients who showed circulatory instabilities during traditional hemodialysis (HD) were treated with HF (27 liters infused in postdilution), or BF (210 min/session) for 12 months . Low and middle molecular weight metabolites weekly clearances, calcium, phosphorus and bicarbonate serum levels in BF and HF showed no significant differences: in BF the incidence of symptomatic hypotension events and orthostatic changes of mean blood pressure were lower than in HD, but a little higher than in HF . Our results show that BF achieves satisfactory depuration of low and middle molecular weight metabolites in a shorter time than HF and an improvement of autonomic nervous system abnormalities is observed.

Int J Artif Organs, 1986 Dec, 9 Suppl 3, 149 - 52
Ionized calcium/total calcium ratio during biofiltration; Procaccini DA et al.; The transmembrane transfer of calcium during hemodialysis is related to many factors (calcium gradient, plasma volume flow, plasma concentration of phosphate) . During biofiltration the high ultrafiltration rate reduces the net transfer of calcium from dialysate to patient . Prolonged metabolic alkalosis occurs during biofiltration, lowering the ionized calcium/total calcium ratio . These two factors may stimulate PTH secretion, with negative long-term effects in dialysis bone disease.

Int J Artif Organs, 1986 Dec, 9 Suppl 3, 147 - 8
The clinical evaluation of biofiltration; Drinovec J et al.; The clinical evaluation of biofiltration . The authors have studied the effectiveness of biofiltration (BF) in patients with terminal renal failure . They did not find any reduction in the number of hypotensive episodes during BF . The reduced length of the dialysis procedure made possible by BF is suitable for some patients . Subjective feeling during the interdialysis period was better under treatment with BF than under conventional hemodialysis.

Int J Artif Organs, 1986 Dec, 9 Suppl 3, 143 - 6
Biofiltration vs . bicarbonate dialysis: influence on plasma volume changes and extravascular fluid mobilization; Perin N et al.; The present study compares the effects of bicarbonate hemodialysis (Bic . HD) and biofiltration (BF), a new hemodiafiltration technique, on plasma volume (PV) changes and extravascular fluid mobilization (Vfm) . Ten uremic patients underwent one experimental session of Bic . HD and, one week later, one of BF, both on the second dialysis of the week . Net ultrafiltration rate was limited to 700 ml/min . At the start of each session, whole blood volume (WBV), PV and red cell volume (RCV) were determined using 5 mu Ci of radioiodinated serum albumin (RISA) . PV and Vfm were calculated at hourly intervals using a serial hematocrit method . On Bic . HD, PV increased at 60 min . then decreased at 120 and 180 min., with efficient Vfm only during the first hour . On BF, PV increased throughout treatment, with greater Vfm . It would appear that PV is better preserved in BF, on account of more efficient Vfm.

Int J Artif Organs, 1986 Dec, 9 Suppl 3, 141 - 2
Acid-base balance during biofiltration (BF); Cappelli G et al.; Acid base balance during biofiltration (BF): Six patients on standard acetate hemodialysis (HD) were switched to BF with 1 m2 AN69-S membrane, 12 hours weekly (BF-4h) and, later on, to a stage with 1.2 m2 AN69-S, 9 hours weekly (BF-3h) . During BF, in order not to exceed 25 mEq/l in intradialytic arterial HCO3, arterial acid-base was examined hourly and a mean of 178 and 199 mEq of HCO3 respectively were infused in BF-4h and BF-3h . We obtained a better control of acidosis with a reduction of the intradialytic pCO2 decrease and hypoxemia . The amount of HCO3 infused was related to the patients deficit in HCO3 total pool and therefore it can be predicted, to avoid postdialytic alkalosis.

Int J Artif Organs, 1986 Dec, 9 Suppl 3, 137 - 40
Clinical status and acid-base balance during biofiltration in patients with acetate dialysis intolerance; Panzetta G et al.; Nine patients intolerant to acetate hemodialysis were treated with biofiltration . This consisted in a 4-h acetate hemodialysis during which an additional 2 liters of ultrafiltrate were replaced by a bicarbonate solution (100 mEq/l) . Hypotensive episodes disappeared and six out of nine patients were symptom-free during the session . Compared to standard hemodialysis, arterial blood bicarbonate and pO2 did not drop during biofiltration . The anion gap did not change during standard hemodialysis, but was significantly reduced during biofiltration (24.5 +/- 2.9 vs 19.9 +/- 1.4 mEq/l) . In our conditions clinical results were positive with biofiltration . On the basis of anion gap changes and preliminary results of plasma acetate determinations, it is suggested that a better cellular metabolism of acetate may be induced by bicarbonate infusion.

Int J Artif Organs, 1986 Dec, 9 Suppl 3, 133 - 6
Biofiltration: an effective and simple method to reduce dialysis time; Mingardi G et al.; Biofiltration: an effective and simple method to reduce dialysis time . Six stable anuric patients, on maintenance hemodialysis, were treated for 10 weeks with a parallel flow 1 m2 cuprophan filter, for 20 weeks with a parallel flow 1.2 m2 polyacrylonitrile filter using the biofiltration (BF) technique and again 10 weeks with the cuprophan filter . Usual monitors were used, without automatic control of ultrafiltration . Biochemical and hematological profile, urea kinetic parameters, incidence of hypotensive episodes, body weight and blood pressure did not change throughout the study . We conclude that three hours of BF, at least for 20 weeks, are as effective and well tolerated as four hours standard hemodialysis and could be of value in reducing dialysis time, to permit better utilization of dialysis beds.

Int J Artif Organs, 1986 Dec, 9 Suppl 3, 123 - 8
Biofiltration in elderly uremic patients; Grimaldi C et al.; We treated five elderly patients with conventional hemodialysis (CH) or biofiltration (BF) to establish whether their dialytic tolerance was better . For three patients treatment time was reduced from twelve to nine hours a week; for the other two, treatment time remained unchanged (10.5-12 h/week) because of their high interdialytic weight gain . At the beginning and end of the study, clinical status, biochemical data, nutritional status and acid-base balance (ABB) were checked . Plasma levels of small molecules, potassium and phosphate were unchanged for all patients . All had a lower number of episodes or less severe hypotension and good control of ABB . No patients had metabolic alkalosis or worsened nutritional status . For all patients BF was an efficacious choice compared to CH, giving them good health.

Int J Artif Organs, 1986 Dec, 9 Suppl 3, 121 - 2
Clearances and solutes extraction in biofiltration and hemodialysis with the AN 69 S; Bertoli S et al.; Clearances and solutes extraction were assessed in biofiltration (BF) and in hemodialysis (HD) with the new polyacrylonitrile AN 69 S membrane . Three patients treated for three months by acetate dialysis (4 hours X 3) and subsequently by BF (3 hours X 3) were studied after achievement of steady state . Total intradepurative clearances (diffusive and convective) and solutes extraction of urea, creatinine, uric acid and phosphate were determined . Clearance of small molecular weight solutes was better in BF than in HD especially for uric acid and phosphate . This confirms the high depurative efficiency of the AN 69 S . BF gave better total clearances than HD, but the extraction of lower molecular weight solutes (due to the one-hour reduction of dialysis time) suggests that adequate treatment time is needed with this technique.

Int J Artif Organs, 1986 Dec, 9 Suppl 3, 117 - 20
Correction of uremic acid-base imbalance in biofiltration: standardization of the amount of bicarbonate infused; Morosetti M et al.; Beneficial effects of biofiltration on acid-base balance have been described, especially in patients showing poor tolerance to standard hemodialysis . This study was designed to standardize the amounts of bicarbonate to be infused for optimal control of the acid-base balance, without the adverse reactions of symptomatic metabolic alkalosis . In three adult patients (body weight greater than 55 kg) a 300 mEq . bicarbonate infusion achieved normal pre- and post-dialysis plasma levels of bicarbonate and normal pre- dialysis pH . Conversely, in three adolescent patients (body weight less than 40 kg) pre- dialysis plasma bicarbonate levels and pre- dialysis pH could not be adequately corrected in spite of increasingly high doses of bicarbonate infused up to a maximum of 240 mEq per treatment . Larger amounts brought on symptoms of metabolic alkalosis.

Int J Artif Organs, 1986 Dec, 9 Suppl 3, 115 - 6
The optimal use of PAN membrane in RDT; Gonella M et al.; In order to compare the efficiency of PAN (Biospal 3000S) for small molecules, Cr, BUN, UA and Pi clearances were determined during hemodiafiltration with both pre and postdilution fluid (PreHDF, PostHDF) and during biofiltration in 3 regular dialysis treatment patients . The highest clearances were obtained during PostHDF . Therefore, since the small molecules are still considered the most important toxins in chronic renal failure, these findings indicate that optimal use of PAN is with PostHDF, in which high diffusion and convection are combined, in order to obtain best dialytic efficiency.

Int J Artif Organs, 1986 Dec, 9 Suppl 3, 111 - 4
Biofiltration, a new method of short hemodiafiltration: preliminary report; Bigazzi R et al.; Four patients previously treated by traditional dialysis (HD, 240 min) were switched to biofiltration (BF, 180-210 min) and followed for twelve months . Before and at the end of this period, clinical and biochemical data were assessed for each patient . Patients treated for 180 min by BF presented no increase in BUN but a significant increase of predialytic phosphorus . The 210 min BF schedule achieved the same pattern of depuration as HD . Acidosis was corrected better in all patients during BF . No hypoxemia and no change of WBC count were observed during BF . Cardiac function, assessed by echocardiography, improved similarly with each session of both methods . BF is a useful alternative treatment procedure for patients with endstage renal failure.

Int J Artif Organs, 1986 Dec, 9 Suppl 3, 103 - 6
Biofiltration in chronic uremia: evaluation of long-term efficiency and hemodynamic tolerance with Swan-Ganz catheter; Cavatorta F et al.; Biochemical data and clinical tolerance were evaluated in eight uremic patients treated by Biofiltration (BF) for 5-20 months . In four patients hemodynamic parameters were monitored with a Swan-Ganz catheter during a session of BF . BF provides long-term biochemical safety and improved tolerance to fluid removal.

Int J Artif Organs, 1986 Dec, 9 Suppl 3, 17 - 20
Effects of chronic biofiltration with PAN membranes on acid-base status: polycentric study; Tarchini R et al.; Effects of chronic biofiltration (BF) with PAN membranes on acid-base status (ABS): polycentric study . From the 39 cases in a polycentric study we selected 13 patients with metabolic acidosis (pH 7.23 +/- 0.03), marked reduction of plasma bicarbonate (15.4 +/- 2.2 mEq/l) and hyperkalemia (6.2 +/- 0.6 mEq/l) . BF was performed with a continuous post-dilutional supply of HCO3 (85 mmol/h), and attained rapid normalisation of blood bicarbonates and serum potassium during the treatment . After 6 months of BF treatment the pre-dialytic ABS showed remarkable improvement, and values were normal after one year . The remaining 26 patients in the polycentric study, treated by chronic BF without severe acidosis, showed good dialytic tolerance . In 15 of them the supply of bicarbonate was too high (because of moderate post-BF alkalosis) and we had to reduce the buffer inflow to about 50 mmol/h.

Int J Artif Organs, 1986 Dec, 9 Suppl 3, 15 - 6
Polycentric 384-month study of biofiltration (BF) with AN69s; Mioli V et al.; Polycentric 384-month study of biofiltration (BF) with AN69s . Since January 1984, 39 uremic dialyzed patients have been included in a randomized prospective study, to evaluate the clinical utility of BF . The trial lasted 9.85 months/pt (384.15 months of total observations) and patients admitted had some not well controlled clinical signs: major acidosis, intradialytic cardiovascular instability, intolerance to acetate dialysis, hypercatabolism, neuropathy, etc . We obtained some positive effects: the incidence of intradialytic hypotension decreased 26.6%; interdialytic body weight gain fell from 3.1 to 2.7 kg (p less than 0.05) and the dialytic time per week was reduced from 12.3 to 10.0 hours (p less than 0.01) . At the same time dry body weight increased from 62.4 to 64.6 kg with worthwhile improvement of the acid-base status (ABS) in all patients . This controlled trial showed that BF is particularly useful for patients suffering from severe acidosis and/or cardiovascular instability.

Int J Artif Organs, 1986 Dec, 9 Suppl 3, 27 - 30
Treatment of uremic patients with biofiltration: efficacy, biocompatibility and medium-term results; Stefoni S et al.; The present report deals with a medium-term programme using biofiltration on a group of 10 patients, who underwent a regular reduced-time schedule (3 procedures per week, 3 hours duration each) lasting up to 12 months . A polyacrylonitrile AN 69 S membrane was used together with a substitution fluid containing Na and bicarbonate . Hematochemical and nutritional parameters were regularly checked to evaluate the efficacy of treatment . Biocompatibility of materials was evaluated by humoral and cellular immunological tests.

Int J Artif Organs, 1986 Dec, 9 Suppl 3, 93 - 6
Acid-base balance during biofiltration; Agazia B et al.; Five patients were shifted from acetate dialysis (AD) to biofiltration (BF); their pre-dialytic acid-base balance (ABB) was re-examined for six months before the start of BF . Samples for ABB were drawn at 0', 30', 60', 120' and 180' during three AD and 1, 2 and 3 hours after them (period A) . The same procedure was then repeated two months (period B) and 12 months (period C) after the start of BF . From analysis of the data it is concluded that the correction of AD-acidosis is very rapid during the early two months of BF, but the post-BF ABB may be too alkalotic, with risks if respiratory alkalosis is superimposed . After one year of BF, there were fewer pCO2 falls and pH variations; no more post-BF alkalotic rebounds were observed.

Int J Artif Organs, 1986 Dec, 9 Suppl 3, 43 - 8
Acid-base balance and respiratory response during biofiltration with polyacrylonitrile membrane; Salvadeo A et al.; To further elucidate the mechanisms responsible for the hypoxemia we studied ventilation, pulmonary gas exchanges, blood gas pressures and exchanges of CO2-T, CO2-D and HCO-3 in six patients during AD and BD on 1 m2 cuprophan filter and during BF on 1.2 m2 polyacrylonitrile filter . Blood passing through the dialyzer lost 172.8 mM/h of CO2-T in AD, 149.2 mM/h in BF and gained 25.6 mM/h in BD . In AD VE, VA and PaO2 decreased significantly after 30 and 60 min., in BF for the whole duration of dialysis . PoO2 showed a significant decrease both in AD and BF after 60 min . In AD PaCO2 was significantly reduced after 120 and 180 min . All the above parameters remained unchanged in BD . VCO2 remained unchanged in all . VCO2 and R decreased both in AD and BF . However, when VCO2 was corrected for CO2 loss across the dialyzer, overall CO2 loss (ventilated plus filtered) and R returned to basal values . In AD, HCO-3 and pH fell in the first 120 min., while in BD and BF they increased from the beginning of dialysis . In AD hypoventilation, hypoxemia and inadequate correction of acid-base balance were due to the loss of HCO-3 across the filter . In BF also hypoventilation and hypoxemia were due to the loss of HCO-3 across the filter but the acid-base balance was adequately corrected by HCO-3 reinfusion . In BD, there was HCO-3 gain across the filter which induced a gradual correction of acid-base balance without impairment of ventilation.

Int J Artif Organs, 1986 Dec, 9 Suppl 3, 1 - 4
Buffer kinetics in biofiltration; Feriani M et al.; A condition of metabolic alkalosis has been generally observed in patients undergoing regular biofiltration (BF) . The aim of this study was to assess buffer kinetics during a dialysis session in five patients regularly treated by BF for 10 months (dialyzer Biospal 3000S, Qb 301; Qd 545; UF 36.76 ml/min; dialysate CH3 COO 38 mEq/L; replacement fluid 1000 ml/h with HCO3 100 mEq/L solution) . As usually happens using dialyzers with high surface area and permeability, large HCO3 losses (756 +/- 112 mEq) and CH3COO uptakes (677 +/- 152 mEq) were observed . Acetate plasma levels rose to 10.4 mEq/L, a value potentially dangerous to the cardiovascular system . The dialytic buffer gain (acetate uptake + HCO3 administered - HCO3 loss) was high (230 +/- 137 mEq/dialysis) and excessive for patients' needs . It is therefore very important to reduce either the acetate concentration in dialysate or the amount of reinfused bicarbonate . In view of the plasma acetate levels it is preferable to use a dialysis solution containing less acetate.

Int J Artif Organs, 1986 Dec, 9 Suppl 3, 55 - 6
Biofiltration with bicarbonate as dialysate buffer; Rizzelli S et al.; The biofiltration with bicarbonate as dialysate buffer (BiBF) was used in 10 patients on RDT: the patients were treated for 10 months on standard BF and for 10 months on BiBF . The amount of fluid infused varied between 3 and 5 liters and Na-bicarbonate (100 mEq/h) was infused during BF . The dialytic protocol was 3 hours every other day . Cardiovascular stability, waste molecules and acid-base balance were investigated . No differences in vascular stability and no significant changes in the waste-molecules concentrations were found . Both protocols correct the metabolic acidosis; however, in standard BF 50% of patients showed acute hypocapnia at the end of dialysis.

Int J Artif Organs, 1986 Dec, 9 Suppl 3, 129 - 32
Effect of biofiltration on cardiac arrhythmias; Timio M et al.; The effect of biofiltration-PAN system and acetate-cuprophan hemodialysis on ventricular arrhythmias detected by long-term ECG monitoring was assessed in 12 patients with end-stage renal failure, studied according to a randomized cross-over design . Low and high risk ventricular ectopic beats were significantly (p less than 0.001) more frequent both during acetate dialysis and in the post-dialytic period than with biofiltration at any time . A significant inverse correlation was found in regression analysis (r = 0.40, p less than 0.001) between total ventricular ectopic beats and pH values in the pre-dialytic, intra-dialytic, early post-dialytic and total post-dialytic periods . The lower frequency of ectopic ventricular beats in biofiltration dialysis makes this technique more suitable for patients with dangerous and disabling arrhythmias.

Gen Physiol Biophys, 1986 Oct, 5(5), 517 - 28
Selection in regulated autocatalytic systems; Krempasky J et al.; The paper deals with problems involved in the formation of stable structures in a system, in which processes typical of bimolecular autocatalytical reactions occur when the respective components are directly influenced from the outside . Such systems can arise in biochemical, biological and ecological sphere (see, e.g . Glansdorff and Prigogine 1971; Nicolis and Prigogine 1977; Haken 1977; 1980) . It has been shown that a regions of so-called subcritical and supercritical regulation exist, manifested by the fact that the given system component would either persist or disappear . The selection of processes consists in the fact that generally only one solution can be realized from N alternatives as a stable state having the nature of a stable node, or a stable focus . When one of the components is supplied to the system from the exterior in a supercritical amount, the system can be "forced" to produce only that single substance . Thus, the system studied can be considered as a model of a biological filter . The results can also be applied in ecology and biotechnology.

Clin Nephrol, 1986 Jul, 26(1), 33 - 6
Biofiltration in the treatment of patients with acetate dialysis intolerance; Panzetta G et al.; Nine patients with intolerance to acetate hemodialysis were treated with biofiltration . It consisted of a 4 hour acetate hemodialysis during which an additional 2 liters of ultrafiltrate was replaced by a bicarbonate solution (100 mEq/l) . Hypotensive episodes disappeared and six out of nine patients were symptomless during the session . Compared to standard hemodialysis, arterial blood bicarbonate and pO2 did not drop during biofiltration . Serum acetate levels, which were abnormally high in patients during standard hemodialysis, were reduced during biofiltration to the levels of a control group of acetate tolerant patients . Our data show that positive clinical results are obtained with biofiltration and suggest that they can be due to a better cellular metabolism of acetate induced by the bicarbonate infusion.

Soz Praventivmed, 1986, 31(4-5), 242 - 4
{Measurement and evaluation of environmental odors}; Hangartner M; The odor problem in the vicinity of a sludge drying plant was solved by installation of a biofilter . The success of this measure was examined by olfactometric measurements such as dilution to threshold determination and scaling of hedonic tone . The odor emissions were evaluated by questioning of the population in the neighbourhood of the plant . The question of acceptability was answered by a simple empiric model based on the percentage of highly annoyed people in the afflicted areas.

Antonie Van Leeuwenhoek, 1985, 51(1), 71 - 8
The survival of anaerobes during sewage treatment employing biological filter beds; Thirkell D et al.; During the passage of sewage through a typical treatment plant employing biological filter beds and operating under dry weather flow conditions, about 7% of the input of anaerobic organisms survive to be released in the effluent . The greatest fall in numbers occurs in the first of two primary settling tanks operating in series and during passage through the filter beds . The predominant organisms were Bacteroides species, gram-positive cocci and clostridial species . There is no significant difference in the rate of survival of any of the genera through the different stages of treatment.

Br J Haematol, 1982 Oct, 52(2), 233 - 40
The influence of the 'collection injury' on the survival and distribution of indium-111-labeled canine platelets; Badenhorst PN et al.; The extent of the 'collection injury' sustained by platelets during labelling with In-111-oxine was investigated in three matched pairs of beagle dogs . The influence of the procedure on the survival, kinetics, in vivo distribution and fate of the labelled platelets was determined by serial blood sampling and quantitative computerized scintillation camera studies . Injured labelled platelets were removed in the matched dog acting as a biological filter . The survival, distribution and fate of the 'filtered' and 'unfiltered' platelets were compared . The mean platelet lifespan of the 'filtered' and 'unfiltered' platelets did not differ significantly, but the shape of the survival curve of the filtered platelets fitted a linear function more closely than that of the unfiltered platelets . Radioactivity in the different organs and regions was serially quantitated and expressed as a percentage of whole body radioactivity . Splenic and hepatic radioactivity of filtered and unfiltered platelets did not differ significantly at equilibrium or at the end of platelet lifespan . It is concluded that the currently employed isolation and labelling techniques for platelets are suitable for quantitative in vivo studies with a computerized scintillation camera system . The shape of platelet survival curves should, however, be interpreted with some caution as it may be influenced by these procedures.

J Immunol, 1977 Jul, 119(1), 256 - 62
Immunologic tolerance to heterologous immunoglobulin: its relation to in vitro filtration by macrophages; Cowing C et al.; The cellular and molecular basis for the difference in ability of BCG to induce tolerance in BALB/c and DBA/2 mice has been examined by in vitro biofiltration . It was found that incubation with the adherent cells from BALB/c but not DBA/2 spleens could remove the material from BGG which inhibited tolerance induction in BALB/c mice . This material was shown to represent only a trace component in BGG, was present in only certain commercial batches of BGG, and was apparently unrelated to the presence of aggregates or endotoxin.

Immunology, 1977 May, 32(5), 783 - 91
Cellular mechanisms of the resistance to the induction of immunological tolerance; Fujiwara M; Tolerance inducibility was examined in various strains of mice by injecting aggregate-free HGG, followed by challenge with aggregated HGG plus LPS and by assessing spleen PFC numbers . Marked differences were shown between C57BL/6 and DDD mice . The antibody response to HGG was totally suppressed in C57BL/6 mice injected with 0-1 to 1 mg of aggregate-free HGG whereas little suppresssion was observed in DDD mice . Cellular mechanisms of the resistance to tolerance induction in DDD mice were explored . On the injection of 1 mg of aggregate-free HGG, spleen cells were only partially tolerized (at minimum, 21 per cent of control level on 5th day) and thymus cells were suppressed to 40 per cent of the normal responsiveness . No suppression was observed in bone marrow cells . Macrophages do not seem to play a decisive role in the resistance to tolerance induction in DDD mice as the injection of biofiltered HGG or the pretreatment with carrageenan did not ease the resistance . From these data, it was suspected that the resistance to tolerance induction to HGG in DDD mice might be due to the raised threshold of T cells for tolerance.

Scand J Immunol, 1977, 6(8), 827 - 30
Antibody-dependent cell-mediated cytotoxicity in various orders of vertebrates; Imir T et al.; By using chicken antibodies and chicken lymphoid cells, we could demonstrate antibody-dependent cytotoxicity (ADCC) against haptenated chicken erythrocytes . ADCC could be demonstrated either by treating the target cells with antibody (sensitization) or by treating the effector cells (arming) . Approximately ten times higher antibody concentrations were required for arming than for sensitization . Chicken lymphoid cells did not co-operate with mammalian antibodies in either type of ADCC, and thus the situation was reciprocal to that observed earlier with mammalian lymphoid cells . In a further attempt to characterize the arming phenomenon we used biofiltered (aggregate-free) mouse antibodies for the arming of rat spleen cells . They were as efficient as nonfiltered antibodies, and this confirms that individual antibody molecules are efficient in arming.

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