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 measureme