Biological filters

Biotechnol Bioeng, 2004 Jan 5, 85(1), 68 - 77
Toluene removal from waste air using a flat composite membrane bioreactor; Jacobs P et al.; In this report, gaseous toluene biodegradation results in a flat composite membrane reactor inoculated with Pseudomonas putida TVA8 are presented . Preliminary abiotic experiments showed that transport of toluene through the membrane was linearly and negatively correlated with the gas residence time (tau) . During a 339-day biofiltration experiment, the influence of gas residence time (2-24 sec) and mass loading rate (B(v); 10-483 g x m(-3) h(-1)) on the toluene elimination capacity was investigated . A maximum elimination capacity (EC(max)) of 397 g x m(-3) h(-1) was achieved at tau = 24 sec and B(v) = 473 g x m(-3) h(-1) . Expressed per unit membrane area, the EC(m,max) was 0.793 g x m(-2) h(-1), which is five times higher than results obtained with other membrane bioreactor experiments in the same range of loading rates . At low gas residence times, reactor performance was limited by mass transfer . Toluene concentration profiles along the membrane were measured for several biotic and abiotic conditions . For inlet concentrations (C(in)) up to 1 g x m(-3), more than 90% was eliminated at 15 cm from the reactor inlet . For C(in) > 1.65 g x m(-3), longer membranes are necessary to obtain these high removal efficiencies .

J Nephrol, 2003 Jul-Aug, 16(4), 572 - 9
Cost analysis of blood purification in intensive care units: continuous versus intermittent hemodiafiltration; Vitale C et al.; BACKGROUND: We implemented a program for continuous renal replacement therapies (CRRT) in intensive care units (ICU) based on the cooperative work of dialysis and ICU personnel . Our aim was to report the main details of this program and compare its cost with that of intermittent hemodiafiltration (IHDF) . METHODS: The study referred to 181 ICU patients with renal failure . We considered the costs of both technical devices and assisting personnel . CRRT was performed as continuous veno-venous hemodiafiltration (CVVHDF) (24 hr daily); dialysis and ICU nurses shared surveillance . Only dialysis nurses performed IHDF (as acetate-free biofiltration, 4 hr daily) in the ICU . RESULTS: The daily cost of CRRT was Euro 276.70; of which 79% was for devices and 21% was for human resources . Nurse surveillance required 141 min per day, ICU nurses supplied 55% (77 min) and dialysis nurses 45% (64 min) . On average, CRRT surveillance required less than 1 min/nurse/hr for both dialysis and ICU nurses . The daily cost of 4-hr IHDF sessions of was Euro 247.83, of which 44% was for technical devices and 56% was for human resources . CONCLUSIONS: The cooperation between dialysis and ICUs improved the use of human resources and allowed us to supply CRRT to all critically ill patients with acute renal failure . The expenditure for CRRT was 12% higher than that for IHDF, due to the cost of technical devices.

Bioresour Technol, 2004 Apr, 92(2), 143 - 9
Aerobic degradation of the azo dye acid red 151 in a sequencing batch biofilter; Buitron G et al.; The azo dye acid red 151 (AR151) was aerobically biodegraded in a sequencing batch biofilter packed with a porous volcanic rock . AR151 was used as the sole source of carbon and energy for acclimated microorganisms . Acclimation was followed using the degradation time and the oxygen uptake rate . A maximal oxygen uptake rate of 0.5 mg O(2)/(lmin) was obtained . Mineralization studies showed that 73% (as carbon) of the initial azo dye was transformed to CO(2) by the consortia . A maximal substrate degradation rate of 247 mg AR151/(l(reactor)d) was obtained . Color removal was up to 99% using an initial concentration of 50 mg AR151/l . Anaerobic tests suggested that in the interior of the porous material, anaerobic biotransformations can occur, contributing from 14% to 16% of the decoloration of the azo dye.

Water Sci Technol, 2003, 48(8), 89 - 96
Biomass accumulation patterns for removing volatile organic compounds in rotating drum biofilters; Yang C et al.; A rotating drum biofilter (RDB) with multi-layered foam media was developed for the improvement of current biofiltration technology . The biofilter was used to investigate the effects of organic loadings and influent volatile organic compound (VOC) concentrations on VOC removal efficiency and biomass accumulation . These effects were evaluated using diethyl ether and toluene separately as model VOCs at an empty bed contact time (EBCT) of 30 s . When the toluene loading increased from 2.0 to 4.0 and 8.0 kgCOD m(-3) day(-1), toluene removal efficiency of the biofilter decreased from over 99% to 78% and 74%, respectively . The biomass distribution was found to be more even within the medium when removing toluene than when removing diethyl ether . Higher organic loading also resulted in the more even distribution of the biomass . The ratios of biomass accumulation rates in the medium of the outermost, middle and innermost layers ranged from 1:0.11:0.02 when removing diethyl ether at 2.0 kgCOD m(-3) day(-1) to 1:0.69:0.51 when removing toluene at 8.0 kgCOD m(-3) day(-1) . Review of these ratios revealed three biomass accumulation patterns: surface pattern, in-depth pattern and shallow pattern . Different patterns represent different removal mechanisms in the biofiltration process . Improved biofilter design and operation should be based on the biomass accumulation pattern.

Water Res, 2004 Jan, 38(2), 404 - 13
Hydrodynamic behaviour and comparison of technologies for the removal of excess biomass in gas-phase biofilters; Mendoza JA et al.; The hydrodynamic behaviour of a biofilter fed toluene and packed with an inert carrier was evaluated on start-up and after long-term operation, using both methane and styrene as tracers in Residence Time Distribution experiments . Results indicated some deviation from ideal plug flow behaviour after 2-year operation . It was also observed that the retention time of VOCs gradually increased with time and was significantly longer than the average residence time of the bulk gas phase . Non-ideal hydrodynamic behaviour in packed beds may be due to excess biomass accumulation and affects both reactor modeling and performance . Therefore, several methods were studied for the removal of biomass after long-term biofilter operation: filling with water and draining, backwashing, and air sparging . Several flow rates and temperatures (20-60 degrees C) were applied using either water or different chemicals (NaOH, NaOCl, HTAB) in aqueous solution . Usually, higher flow rates and higher temperatures allowed the removal of more biomass, but the efficiency of biomass removal was highly dependent on the pressure drop reached before the treatment . The filling/draining method was the least efficient for biomass removal, although the treatment did basically not generate any biological inhibition . The efficiency of backwashing and air sparging was relatively similar and was more effective when adding chemicals . However, treatments with chemicals resulted in a significant decrease of the biofilter's performance immediately after applying the treatment, needing periods of several days to recover the original performance . The effect of manually mixing the packing material was also evaluated in duplicate experiments . Quite large amounts of biomass were removed but disruption of the filter bed was observed . Batch assays were performed simultaneously in order to support and quantify the observed inhibitory effects of the different chemicals and temperatures used during the treatments.

Biodegradation, 2003 Dec, 14(6), 415 - 21
Addressing biofilter limitations: a two-phase partitioning bioreactor process for the treatment of benzene and toluene contaminated gas streams; Davidson CT et al.; A two-phase partitioning bioreactor (TPPB) achieved simultaneous and continuous removal and degradation of benzene and toluene from an air stream . The aqueous- organic system utilized n-hexadecane as the organic phase, and the organism Alcaligenes xylosoxidans Y234 in the aqueous phase to achieve the degradation of benzene and toluene . The system, which operates as a well-mixed dispersion and is therefore resistant to substrate surges, was first shown to be capable of utilizing toluene while operating at a loading capacity of 235 g m(-3) h(-1) with an elimination capacity of 233 g m(-3) h(-1) . It was also determined that to characterize TPPB performance in terms of elimination capacity the definition of elimination capacity must be extended to include the cell mass present, a readily controllable variable given the nature of the system . Based on this criterion, it was estimated that for a cell concentration of 1 g l(-1) present in the TPPB, the potential maximum toluene elimination capacity is 1290 g m(-3) h(-1) which is substantially higher than any toluene elimination capacity achieved by biofilters at a high removal efficiency . If no other factor were to limit the system, elimination capacities could be many times higher still, and are dependent on maintaining desired cell concentrations above 1 g l(-1) . The TPPB was then operated at nominal loading capacities of 63 g m(-3) h(-1) (benzene) and 51 g m(-3) h(-1) (toluene) at a removal efficiency greater than 99% to demonstrated the applicability of this system in dealing with two chemical species simultaneously . TPPB systems therefore have been shown to be effective at removing gaseous organic contaminants at high removal efficiencies while also possessing desirable operating features, such as providing and maintaining high cell concentrations throughout the reactor, and a capacity to effectively deal with high contaminant loadings.

Appl Microbiol Biotechnol, 2004 Jun, 64(6), 855 - 61 Epub 2003 Dec 10.
Mesophilic and thermophilic BTEX substrate interactions for a toluene-acclimatized biofilter; Strauss JM et al.; Benzene, toluene, ethylbenzene and xylene (BTEX) substrate interactions for a mesophilic (25 degrees C) and thermophilic (50 degrees C) toluene-acclimatized composted pine bark biofilter were investigated . Toluene, benzene, ethylbenzene, o-xylene, m-xylene and p-xylene removal efficiencies, both individually and in paired mixtures with toluene (1:1 ratio), were determined at a total loading rate of 18.1 g m(-3) h(-1) and retention time ranges of 0.5-3.0 min and 0.6-3.8 min for mesophilic and thermophilic biofilters, respectively . Overall, toluene degradation rates under mesophilic conditions were superior to degradation rates of individual BEX compounds . With the exception of p-xylene, higher removal efficiencies were achieved for individual BEX compounds compared to toluene under thermophilic conditions . Overall BEX compound degradation under mesophilic conditions was ranked as ethylbenzene >benzene > o-xylene > m-xylene > p-xylene . Under thermophilic conditions overall BEX compound degradation was ranked as benzene > o-xylene >ethylbenzene > m-xylene > p-xylene . With the exception of o-xylene, the presence of toluene in paired mixtures with BEX compounds resulted in enhanced removal efficiencies of BEX compounds, under both mesophilic and thermophilic conditions . A substrate interaction index was calculated to compare removal efficiencies at a retention time of 0.8 min (50 s) . A reduction in toluene removal efficiencies (negative interaction) in the presence of individual BEX compounds was observed under mesophilic conditions, while enhanced toluene removal efficiency was achieved in the presence of other BEX compounds, with the exception of p-xylene under thermophilic conditions.

Microbiol Mol Biol Rev, 2003 Dec, 67(4), 503 - 49
Recent advances in petroleum microbiology; Van Hamme JD et al.; Recent advances in molecular biology have extended our understanding of the metabolic processes related to microbial transformation of petroleum hydrocarbons . The physiological responses of microorganisms to the presence of hydrocarbons, including cell surface alterations and adaptive mechanisms for uptake and efflux of these substrates, have been characterized . New molecular techniques have enhanced our ability to investigate the dynamics of microbial communities in petroleum-impacted ecosystems . By establishing conditions which maximize rates and extents of microbial growth, hydrocarbon access, and transformation, highly accelerated and bioreactor-based petroleum waste degradation processes have been implemented . Biofilters capable of removing and biodegrading volatile petroleum contaminants in air streams with short substrate-microbe contact times (<60 s) are being used effectively . Microbes are being injected into partially spent petroleum reservoirs to enhance oil recovery . However, these microbial processes have not exhibited consistent and effective performance, primarily because of our inability to control conditions in the subsurface environment . Microbes may be exploited to break stable oilfield emulsions to produce pipeline quality oil . There is interest in replacing physical oil desulfurization processes with biodesulfurization methods through promotion of selective sulfur removal without degradation of associated carbon moieties . However, since microbes require an environment containing some water, a two-phase oil-water system must be established to optimize contact between the microbes and the hydrocarbon, and such an emulsion is not easily created with viscous crude oil . This challenge may be circumvented by application of the technology to more refined gasoline and diesel substrates, where aqueous-hydrocarbon emulsions are more easily generated . Molecular approaches are being used to broaden the substrate specificity and increase the rates and extents of desulfurization . Bacterial processes are being commercialized for removal of H(2)S and sulfoxides from petrochemical waste streams . Microbes also have potential for use in removal of nitrogen from crude oil leading to reduced nitric oxide emissions provided that technical problems similar to those experienced in biodesulfurization can be solved . Enzymes are being exploited to produce added-value products from petroleum substrates, and bacterial biosensors are being used to analyze petroleum-contaminated environments.

J Air Waste Manag Assoc, 2003 Nov, 53(11), 1373 - 83
Biofiltration of cyclic air emissions of alpha-pinene at low and high frequencies; Dirk-Faitakis C et al.; Biofiltration of periodically fluctuating concentrations of an alpha-pinene-laden waste gas was investigated to treat both high-frequency and low-frequency fluctuations . The effects of periodic concentration fluctuations on biofilter performance were measured . Controlled variables of periodic operation included cycle period and amplitude . The cycle period ranged from 10 min to 6 days, with the inlet alpha-pinene concentration fluctuating between 0 and 100 parts per million volume . At high-frequency concentration cycling (i.e., on the order of minutes), both cyclic and constant concentration biofilters maintained similar long-term performance with an average removal efficiency of 77% at an averaged loading rate of 29 g alpha-pinene/m3 bed/hr . A first approximation suggests kinetics that are time-independent, indicating that steady-state data can be used to predict transient behavior at this time scale . Cyclic biofilter operation with a cycle period of 24 hr (with equal on/off time) was achievable for biofilters without a significant loss in performance . At longer time scales, cyclic biofilter performance decreased at the restart of the ON cycle . The recovery time to previous levels of performance increased with increasing cycle period; the recovery time was less than 1 hr for a cycle period of 24 hr and between 6 and 8 hr for a cycle period of 6 days.

Water Sci Technol, 2003, 48(6), 311 - 8
Combined anaerobic-aerobic treatment of landfill leachates under mesophilic, submesophilic and psychrophilic conditions; Kalyuzhnyi S et al.; As a first step of treatment of landfill leachates (total COD--1,430-3,810 mg/l, total nitrogen 90-162 mg/l), a performance of laboratory UASB reactors has been investigated under mesophilic (30 degrees C), sub-mesophilic (20 degrees C) and psychrophilic (10 degrees C) conditions . Under hydraulic retention times (HRT) of around 7 h, when the average organic loading rates (OLR) were around 5 g COD/l/day, the total COD removal accounted for 81% (on the average) with the effluent concentrations close to anaerobic biodegradability limit (0.25 g COD/l) for mesophilic and sub-mesophilic regimes . The psychrophilic treatment conducted under the average HRT of 8 h and the average OLR of 4.22 g COD/l/day showed a total COD removal of 47% producing the effluents (0.75 g COD/l) more suitable for subsequent biological nitrogen removal . All three anaerobic regimes used for leachate treatment were quite efficient for elimination of heavy metals (Fe, Zn, Cu, Pb, Cd) by concomitant precipitation in the form of insoluble sulphides inside the sludge bed . The application of aerobic/anoxic biofilter as a sole polishing step for psychrophilic anaerobic effluents was acceptable for elimination of biodegradable COD and nitrogen approaching the current standards for direct discharge of treated wastewater.

Biotechnol Lett, 2003 Oct, 25(20), 1757 - 61
Development and operation of a trickling biofilter system for continuous treatment of gas-phase trichloroethylene; Lee EY et al.; A parallel trickling biofilter (TBF) system that consists of two TBFs units in parallel, one for biodegradation of trichloroethylene (TCE) and the other for reactivation of an inactivated biofilm, was developed and operated for continuous treatment of gas-phase TCE by Burkholderia cepacia G4 . For inlet loadings below 8.6 mg TCE l(-1) d(-1) complete removal of TCE was achieved . The maximal TCE elimination capacity was 17 mg l(-1) d(-1).

J Air Waste Manag Assoc, 2003 Oct, 53(10), 1248 - 55
Biofiltration of trichloroethylene-contaminated air: a pilot study; Lackey LW et al.; This project demonstrated the biofiltration of a trichloroethylene (TCE)-contaminated airstream generated by air stripping groundwater obtained from several wells located at the Anniston Army Depot, Anniston, AL . The effects of several critical process variables were investigated to evaluate technical and economic feasibility, define operating limits and preferred operating conditions, and develop design information for a full-scale biofilter system . Long-term operation of the demonstration biofilter system was conducted to evaluate the performance and reliability of the system under variable weather conditions . Propane was used as the primary substrate necessary to induce the production of a nonspecific oxygenase . Results indicated that the process scheme used to introduce propane into the biofiltration system had a significant impact on the observed TCE removal efficiency . TCE degradation rates were dependent on the inlet contaminant concentration as well as on the loading rate . No microbial inhibition was observed at inlet TCE concentrations as high as 87 parts per million on a volume basis.

Bioresour Technol, 2004 Jan, 91(2), 145 - 52
A dispersion modelling approach to determining the odour impact of intensive pig production units in Ireland; Sheridan BA et al.; It is becoming more common now to use atmospheric dispersion models to predict where odour nuisance is likely to occur near pig units . An odour threshold concentration of 1 OuE m(-3) is the level at which an odour is detectable by 50% of screened panellists . A new odour annoyance criterion (C(98,1-h) (98%-ile, 1-h average odour concentration) < or = 4.3 OuE m(-3)) was developed in this study and compared to the Environmental Protection Agency (EPA) (Ireland) recommendation (C(98,1-h)< or = 6 OuE m(-3)) using the ISCST3 model with data from three meteorological stations . Abatement techniques such as exhaust vent modification, feed manipulation, and biofiltration were assessed . Based on current limits (C(98,1-h)< or = 6 OuE m(-3)) for existing facilities, predicted setback distances can be up to 780 m for a 1000-sow unit, depending on which meteorological data set is used . However, if using the suggested odour impact criterion in this research (C(98,1-h)< or = 4.3 OuE m(-3)), setback distances could reach a maximum of 1000 m . Biofilters on second stage weaning and finishing pig buildings offer the greatest single reduction (up to 650 m) in odour impact . When combined with feed manipulation and increased exhaust air velocity, the figure can be as high as 920 m . Due to the critical requirement for local meteorological data, it is recommended that a meteorological station be installed on large pig units to facilitate more accurate predictions . Site measurements of odour emissions should be made in each case because emissions are influenced by a range of local factors including feed, manure management, building design and operation.

Water Environ Res, 2003 Sep-Oct, 75(5), 444 - 54
Odor and volatile organic compound removal from wastewater treatment plant headworks ventilation air using a biofilter; Converse BM et al.; Laboratory-scale experiments and field studies were performed to evaluate the feasibility of biofilters for sequential removal of hydrogen sulfide and volatile organic compounds (VOCs) from wastewater treatment plant waste air . The biofilter was designed for spatially separated removal of pollutants to mitigate the effects of acid production resulting from hydrogen sulfide oxidation . The inlet section of the upflow units was designated for hydrogen sulfide removal and the second section was designated for VOC removal . Complete removal of hydrogen sulfide (H2S) and methyl tert-butyl ether (MTBE) was accomplished at loading rates of 8.3 g H2S/(m3 x h) (15-second empty bed retention time {EBRT}) and 33 g MTBE/(m3 x h) (60-second EBRT), respectively . In field studies performed at the Hyperion Treatment Plant in Los Angeles, California, excellent removal of hydrogen sulfide, moderate removal of nonchlorinated VOCs such as toluene and benzene, and poor removal of chlorinated VOCs were observed in treating the headworks waste air . During spiking experiments on the headworks waste air, the percentage removals were similar to the unspiked removals when nonchlorinated VOCs were spiked; however, feeding high concentrations of chlorinated VOCs reduced the removal percentages for all VOCs . Thus, biofilters offer a distinct advantage over chemical scrubbers currently used at publicly owned treatment works in that they not only remove odor and hydrogen sulfide efficiently at low cost, but also reduce overall toxicity by partially removing VOCs and avoiding the use of hazardous chemicals.

Chemosphere, 2004 Jan, 54(3), 243 - 54
Evaluation of dispersion methods for enumeration of microorganisms from peat and activated carbon biofilters treating volatile organic compounds; Khammar N et al.; To enumerate microorganisms having colonized biofilters treating volatile organic compounds, it is necessary firstly to evaluate dispersion methods . Crushing, shaking and sonication were then tested for the removal of microflora from biofilters packing materials (peat and activated carbon) . Continuous or discontinuous procedures, and addition of glass beads had no effect on the number of microorganisms removed from peat particles . The duration of treatment also had no effect for shaking and crushing, but the number of microorganisms after 60 min of treatment with ultrasound was significantly higher than that obtained after 0.5 min . The comparison between these methods showed that crushing was the most efficient for the removal of microorganisms from both peat and activated carbon . The comparison between three chemical dispersion agents showed that 1% Na-pyrophosphate was less efficient, compared with 200 mM phosphate buffer or 1% Na-hexametaphosphate . To optimize the cultivation of microorganisms, three different agar media were compared . Tryptic soy agar tenfold diluted (TSA 1/10) was the most suitable medium for the culture of microflora from a peat biofilter . For the activated carbon biofilter, there was no significant difference between Luria Bertoni, TSA 1/10, and plate count agar . The optimized extraction and enumeration protocols were used to perform a quantitative characterization of microbial populations in an operating laboratory activated carbon biofilter and in two parallel peat biofilters.

J Environ Sci (China), 2003 Sep, 15(5), 691 - 6
Biodegradation of methanol vapor in a biofilter; Arulneyam D et al.; Volatile organic compounds (VOCs) are a new class of air pollutants posing threat to the environment . Newer technologies are being developed for their control among which biofiltration seem to be most attractive . Biofiltration of methanol vapor from air stream was evaluated in this study . Experimental investigations were conducted on a laboratory scale biofilter, containing mixture of compost and polystyrene inert particles as the filter materials . Mixed consortium of activated sludge was used as an inoculum . The continuous performance of biofilter for methanol removal was monitored for different concentrations and flow rates . The removal efficiencies decreased at higher concentrations and higher gas flow rates . A maximum elimination capacity of 85 g/(m3 x h) was achieved . The response of biofilter to upset loading operation showed that the biofilm in the biofilters was quite stable and quickly adapted to adverse operational conditions.

Water Sci Technol, 2003, 48(4), 209 - 12
Microbiological removal of hydrogen sulfide from biogas by means of a separate biofilter system: experience with technical operation; Schieder D et al.; The "BIO-Sulfex" biofilter of ATZ-EVUS removes hydrogen sulfide from biogas in a biological way . Hydrogen sulfide causes massive problems during power generation from biogas in a power plant, e.g . corrosion of engines and heat exchangers, and thus causes frequent and therefore expensive engine oil changes . The BIO-Sulfex module is placed between the digester and the power-plant and warrants a cost-effective, reliable and fully biological desulfurization . In the cleaned gas concentrations of less than 100 ppm can be achieved . Power-plant manufacturers usually demand less than 500 or less than 200 ppm . At present, several plants with biogas flow rates between 20 and 350 m3/h are in operation.

J Environ Sci Health A Tox Hazard Subst Environ Eng, 2003, 38(10), 2077 - 88
Pharmaceutical wastewater treatment using an anaerobic/aerobic sequencing batch biofilter; Buitron G et al.; The performance of a sequencing batch biofilter integrating anaerobic/aerobic conditions in one tank to treat a pharmaceutical wastewater effluent was studied . A pilot reactor, packed with a porous volcanic stone (puzzolane) was used in the study . The reactor operated as a sequencing batch biofilter, SBB, with reaction times varying for the anaerobic stage from 8 to 24 h and for the aerobic one from 4 to 12 h . The volume of exchange was from 16 to 88% . The pharmaceutical wastewater contained organic chemicals including phenols and o-nitroaniline, a concentration of organic matter that varied from 28,400 to 72,200 mg/L (as total COD), 280 to 605 mg N-NH4/L . and 430 to 650 mg SST/L . In order to acclimatize the microorganisms to the industrial wastewater, the organic load was increased stepwise from 1 to 7.7 kg COD/m3/d . The adequate time was obtained when the removal efficiency of COD reached 80%, or more . Maximal removal loads, associated to high removal efficiencies (95-97% as COD), varied from 4.6 to 5.7 kg COD/m3/d . Under these conditions color removal was 80% as Pt-Co units . Microtox analysis was performed to the wastewater and to the anaerobic and aerobic stages . It was observed that the aerobic stage was the responsible for wastewater detoxification . Results showed that the anaerobic/aerobic SBB was able to treat efficiently initial concentrations of the raw effluent up to 28,400 mg COD/L.

Environ Sci Technol, 2003 Sep 15, 37(18), 4299 - 303
Biofiltration at composting facilities: effectiveness for bioaerosol control; Sanchez-Monedero MA et al.; Biofiltration was evaluated as a method to control the airborne microorganisms released at composting facilities . Seven commercial composting plants were selected for this study because of their different operating conditions and biofilter designs . In all plants, the biofilters were originally designed for odor control . The concentrations of both Aspergillus fumigatus and mesophilic bacteria were measured in the air stream before and after passing through the biofilters and compared with the background concentrations in the surrounding area . Results showed that biofiltration achieved an average reduction greater than 90% and 39% in the concentrations of A . fumigatus and mesophilic bacteria, respectively . In all the plants, the airborne A . fumigatus concentration after the biofilter was lower than 1.2 x 10(3) cfu m(-3), independent of the inlet concentration, whereas the mesophilic bacteria concentration was dependent on the inlet concentration . The different behaviors of the two microorganism groups were thought to be due to the different aerodynamic characteristics of the particles that affected the capture by impact in the biofilter bed . The fungus, whose spores had a maximum of diameter size distribution between 2.1 and 3.3 microm, were more effectively captured in the biofilter than the bacteria, which had diameters mainly between 1.1 and 2.1 microm.

Environ Sci Technol, 2003 Sep 15, 37(18), 4228 - 34
Dimethyl sulfide removal from synthetic waste gas using a flat poly(dimethylsiloxane)-coated composite membrane bioreactor; De Bo I et al.; The reduction of volatile organic sulfur emissions should be completely as they cause odor nuisance, even when they are emitted in very small amounts . In general, biofilters are applied for odor reduction, but their operational control is limited . A new biotechnique for the treatment of complex emissions is the use of membranes integrated within bioreactors (MBRs) . In this study, the reactor performance of MBRs for removal of dimethyl sulfide (DMS) as a model compound is presented . Composite membranes with a poly(dimethylsiloxane) (PDMS)-coating layer were used . The MBRs were inoculated with the sulfur-degrading culture Hyphomicrobium VS or a suspension of Hyphomicrobium VS, ammonium-oxidizing bacteria (AOB), and nitrite-oxidizing bacteria (NOB) to colonize the PDMS-coating layer . Although inoculation with AOB and NOB might give rise to competition for space on the membrane, their presence in the MBRs appeared to be positive as they co-oxidize DMS . Dimethyl sulfide elimination depended on the inoculum type, DMS inlet concentration, gas residence time, and membrane polymer . For equal loading rates, the elimination capacity (EC) increased at larger gas residence times and inlet concentrations . The maximum EC obtained with the MBRs was 4.8 kg of DMS x m(-3) x d(-1) . This value is higher than any reported figure for biofilters and biotrickling filters.

Appl Biochem Biotechnol, 2003 Sep, 110(3), 125 - 36
Biofiltration of 1,1,1-trichloroethane by a trickle-bed air biofilter; Lu C et al.; The performance of a trickle-bed air biofilter (TBAB) in the removal of 1,1,1-trichloroethane (TCLE) was evaluated in concentrations varying from 0.025 to 0.049 g/m3 and at empty-bed residence time (EBRT) varying from 20 to 90 s . Nearly complete TCLE removal could be achieved for influent carbon loading between 0.98 and 5.88 g/m3 h . The TBAB appeared efficient for controlling TCLE emission under low-carbon-loading conditions . Carbon recoveries higher than 95% were achieved, demonstrating the accuracy of results . The carbon mass rate of the liquid effluent was approximately two orders of magnitude less than that of the effluent CO2, indicating that dissolved TCLE and its derivatives in leachate were present in negligible amounts in the TBAB.

J Biotechnol, 2003 Oct 9, 105(1-2), 83 - 94
Biofiltration of waste gases containing both ethyl acetate and toluene using different combinations of bacterial cultures; Hwang SC et al.; To investigate the microbial degradation of ethyl acetate and toluene mixtures in biofiltration, three strains were selected, identified and studied in a shake-flask culture, and finally inoculated into biofilters . These strains, namely AC6, TO3 and B5, can degrade different substrates at a different rate . The results showed that competitive inhibition from substrate and microbial community would affect the toluene degradation efficiency . Owing to substrate competition, the toluene degradation efficiency of strain B5 would decrease in the presence of high concentration of ethyl acetate . However, the addition of strain AC6 would alleviate such inhibition because it could remove ethyl acetate rapidly . Microbial community competition from strain AC6 or B5 would impede the toluene degradation efficiency of strain TO3 unless a large amount of strain TO3 was inoculated . In biofiltration, strain B5 would be a better choice for inoculation into biofilters than strains AC6 and TO3, as it would grow rapidly under a low concentration of ethyl acetate.

Water Res, 2003 Nov, 37(18), 4497 - 505
Nitrogen utilization in a vapor-phase biofilter; Song J et al.; The effect of media nitrogen levels on biofilter performance was investigated in a lab-scale biofilter treating toluene and p-xylene . Nitrogen utilization rates and the quantity of nitrogen recycled to meet microbial demand in the biofilm were estimated using a nitrogen balance approach . Experimental data imply that overall biofilter performance was a strong function of normalized nitrogen levels in the synthetic media . The biodegradation of p-xylene was found to be more sensitive to media nitrogen levels than was the degradation of toluene . However, increasing the nitrogen supply improved both toluene (>99%) and p-xylene removal efficiencies (>90%) . Nitrogen balance calculations indicate that substantial recycling of nitrogen occurred in the biofilm even under nitrogen-rich conditions . The fraction of nitrogen demand met by recycling nitrogen increased when the external supply of nitrogen was terminated, and the biofilm became nitrogen limited . However, to avoid severe nitrogen limitation conditions, an external nitrogen source must be provided to sustain high pollutant removals in the biofilter.

Bioprocess Biosyst Eng, 2002 Apr, 25(1), 61 - 7 Epub 2002 Mar 16.
Removal of acrylonitrile and styrene mixtures from waste gases by a trickle-bed air biofilter; Lu C et al.; The trickle-bed air biofilter (TBAB) performance for treating acrylonitrile (AN) and styrene (SR) mixtures was evaluated under different influent carbon loadings . In the pseudo steady state conditions, the elimination capacities of AN and SR increased but the removal efficiencies decreased with increased influent carbon loading . The removal efficiencies of AN were higher than those of SR, indicating that AN is a preferred substrate in the ANSR waste gas . More than 80% removal efficiencies were achieved with influent carbon loadings of AN and SR below 28 and 22 g/m(3)/h, respectively . The TBAB appears to be efficient for controlling ANSR emission with low to medium carbon loadings, and the effectiveness could be maintained over 175 days of laboratory operation . The elimination capacities of AN and SR for a pure volatile organic compound (VOC) feed were higher than those for a mixed VOC feed and the differences increased with increased influent VOC loading.

J Environ Sci (China), 2003 Jul, 15(4), 494 - 9
Phosphorus limitation in biofiltration for drinking water treatment; Yu X et al.; Bacterial growth potential (BGP) method and two parallel pilot-scale biofilters were used to investigate phosphorus limitation and its effect on the removal of organic matters in biofiltration for drinking water treatment . Addition of phosphorus can substantially increase the BGPs of the samples . Its effect was equivalent to that of addition of a mixture of various inorganic nutrients including phosphorus . The biofilter with phosphate added into its influent performed a higher biological stability of the effluent and a higher COD(Mn) removal than the control filter . These results suggested that phosphorus was the limiting nutrient in the biofiltration and the removal efficiency of organic matters could be improved by adding phosphate into the influent.

Waste Manag, 2003, 23(7), 609 - 19
Kinetics of microbial landfill methane oxidation in biofilters; Gebert J et al.; A methane oxidizing biofilter system fitted to the passive venting system of a harbor sludge landfill in Germany was characterized with respect to the the methanotrophic population, methane oxidizing capacity, and reaction kinetics . Methanotrophic cell counts stabilized on a high level with 1.3 x 10(8) to 7.1 x 10(9) cells g dw(-1) about one year after first biofilter operation, and a maximum of 1.2 x 10(11) cells g dw(-1) . Potential methane oxidizing activity varied between 5.3 and 10.7 microg h(-1) g dw(-1) . Cell numbers correlated well with methane oxidation activities . Extrapolation of potential activities gave methane removal rates between 35 and 109 g CH4 h(-1) m(-3), calculated for 30 degrees C . Optimum temperature was 38 degrees C for freshly sampled biofilter material and 22 degrees C for a methanotrophic enrichment culture grown at 10 degrees C incubation temperature . Substrate kinetics revealed the presence of a low-affinity methane oxidizing community with a high Vmax of 1.78 micromol CH4 h(-1) g ww(-1) and a high K(M) of 15.1 microM . K(MO2) for methane oxidation was 58 microM . No substantial methane oxidizing activity was detected below 1.7-2.6 vol.-% O2 in the gaseous phase . Methane deprivation led to a decrease in methane oxidation activity within 5-9 weeks but could still be detected after 25 weeks of substrate deprivation and was fully restored within 3 weeks of continuous methane supply . Very high salt loads are leached from the novel biofilter material, expanded clay, yielding electric conductivity values of up to 15 mS cm(-1) in the leachate . Values > 6 mS cm(-1) were shown to depress methane consumption . Water retention characteristics of the material proved to be favourable for methane oxidizing systems with a gas permeable volume of 78% of bulk volume at field capacity water content . Correspondingly, no influence of water content on methane oxidation activity could be detected at water contents between 2.5 and 20 vol.-%.

Waste Manag, 2003, 23(7), 573 - 80
Microbial oxidation of methane from old landfills in biofilters; Streese J et al.; Landfill gas emissions are among the largest sources of the greenhouse gas methane . For this reason, the possibilities of microbial methane degradation in biofilters were investigated . Different filter materials were tested in two experimental plants, a bench-scale plant (total filter volume 51 l) and a pilot plant (total filter volume 4 m3) . Three months after the beginning of the experiment, very high degradation rates of up to 63 g CH4/(m3h) were observed in the bench-scale plant at mean methane concentrations of 2.5% v/v and with fine-grained compost as biofilter material . However, the degradation rates of the compost biofilter decreased in the fifth month of the experiment, probably due to the accumulation of exopolymeric substances formed by the microorganisms . A mixture of compost, peat, and wood fibers showed stable and satisfactory degradation rates around 20 g/(m3h) at mean concentrations of 3% v/v over a period of one year . In this material, the wood fibers served as a structural material and prevented clogging of the biofilter . Extrapolation of the experimental data indicates that biofilters for methane oxidation have to be at least 100 times the volume of biofilters for odor control to obtain the same cleaning efficiency per unit volume flow of feed gas.

Arch Environ Contam Toxicol, 2003 Jul, 45(1), 1 - 10
Use of a coupled biological system to treat a chemically complex air stream; Manninen MR et al.; The use of biological systems to remove contaminants from waste streams has been well documented . However, when dealing with complex waste streams, the use of one biological treatment system may not be the best alternative . When treating a complex waste stream, the use of "treatment trains" or "coupled systems" may be advantageous compared with any single biological technology . This article demonstrated that a coupled system was effective in biodegrading a chemically complex mixture of volatile organic compounds (VOCs) . A bench-scale system consisting of a liquid bioreactor and a biofilter was used for the biodegradation of acetone, methanol, methyl ethyl ketone, naphthalene, alpha-pinene, and toluene . The bioreactor contained an inert solid support that immobilized a microbial population . The biofiltration portion of the system utilized the same microbial inoculum but employed Douglas fir bark as its solid support . Successful biodegradation of the complex VOC mixture was accomplished with this coupled system with an average VOC removal efficiency of 96% and VOC loading rates as high as 79 g/m3/h for inlet concentrations of > 8,000 ppmv . At elevated flow rates the liquid reactor demonstrated limited removal of some compounds, such as alpha-pinene and toluene, while maintaining excellent removal of other compounds, such as methanol and acetone . The biofilter portion of the system proved very successful in degrading the remaining toluene and alpha-pinene, thus complementing the removal from the bioreactor . This study demonstrates that coupled biological systems may be utilized for a chemically complex VOC-laden air stream that previously may not have been considered for biological treatment.

J Air Waste Manag Assoc, 2003 Aug, 53(8), 1011 - 21
Changes in physical properties of a compost biofilter treating hydrogen sulfide; Morgan-Sagastume JM et al.; A technique is presented that can be used to estimate the changes in physical structure in a natural biofilter packing medium, such as compost, over time . The technique applies information from tracer studies, grain size distribution, and pressure drop analysis to a model that estimates the number of channels, average channel diameter, number of particles, and specific surface area of the medium . Important operational factors, such as moisture content, pressure drop, and sulfate accumulation also were evaluated both in a conventionally operated biofilter and in one operated with periodic compost mixing . In the conventionally operated laboratory-scale compost biofilter, hydrogen sulfide (H2S) removal efficiency decreased from 100% to approximately 90% over 206 days of operation . In a similar system, operated with compost mixing, the H2S removal efficiency was maintained near 100% . Variations in media moisture conditions and specific surface area can explain the results observed in this study . Under conventional operation, drying near the inlet disintegrated the compost particles, producing a large number of particles and flow channels and increasing the specific surface area . At the top of the column, where moisture was added, particle size increased and specific surface area decreased . In the column with media mixing, moisture content, particle size, and specific surface area remained homogeneous.

Environ Technol, 2003 Jul, 24(7), 797 - 807
Pressure drop and gas distribution in compost based biofilters: medium mixing and composition effects; Morgan-Sagastume JM et al.; The pressure drop and gas distribution in four different filter media for compost biofilters were studied as a function of three superficial loading rates of moist air and by carrying out the filter medium homogenization by mixing . The filter media used were compost, compost with cane bagasse, lava rock and aerobic sludge previously dried to 60% of water content . The pressure drop increased when lava rock and cane bagasse were used as bulking agents . The same trend was observed when water was added to the filter medium . Pressure drop tended to decrease with time as flow channels were formed inthe filter media . Tracer studies were carried out to quantify the gas distribution and the effect of channel formation . For the biofilters submitted to an airflow of 10, 40 and 70 l min(-1), an average normalized time of 0.96, 0.89 and 0.82, respectively were obtained . The results showed that channel formation was increased as the superficial loading rate was also increased . An operational practice that this work proposes and evaluates to improve gas distribution and medium moisture control is to carry out intermittent medium mixing . The medium moisture and void volume achieved under mixing condition were around 50% and 0.40, respectively with an average constant pressure drop of 11, 45 and 78 cm of water m(-1) for air velocities of 75, 300 and 525 m h(-1).

Waste Manag, 2003, 23(5), 403 - 9
Assessment of the environmental impact of management measures for the biodegradable fraction of municipal solid waste in São Paulo City; Mendes MR et al.; There is increasing concern about landfilling of biodegradable wastes . Therefore, biological treatment processes such as composting and biogasification have been considered as alternative strategies for managing those wastes . In this work, life cycle assessment was employed to compare the environmental impacts of landfilling, composting, and biological treatment of municipal solid waste in Sao Paulo City, Brazil . Energy consumption, recovered resources, and emissions to air and water were quantified and analyzed in terms of their potential contribution to global warming, acidification, and nutrient enrichment impact . The results demonstrated that processes that require high levels of energy consumption, such as wastewater treatment, play an important role in the outcome of environmental impact potentials . It was found that the landfilling of all waste is generally the worst strategy from an environmental point of view . However, significant reductions in the resulting impacts can be accomplished through biogasification and composting of the biodegradable fraction . Regarding composting, the application of a biofilter for gas treatment reduced significantly the gaseous emissions.

Environ Technol, 2003 Jun, 24(6), 745 - 54
Greenhouse gas emissions from mechanical and biological waste treatment of municipal waste; Clemens J et al.; The mechanical and biological waste treatment (MBT) is an increasingly important technology for the treatment of municipal solid waste (MSW) before landfilling . This process includes composting of the material with intensive aeration in order to minimize the organic fraction that may induce methane and leachate emissions after landfilling . The exhaust air is treated by biofilters to remove odorous and volatile organic compounds . The emission of direct and indirect greenhouse gases, namely methane (CH4), carbon dioxide (CO2), ammonia (NH3), nitric (NO) and nitrous oxide (N2O) was studied in four existing treatment plants . All gases except NO were emitted from the composting material . The emission factors were 12 to 185 kg ton(-1) substrate for CO2, 6-12 x 10(3) g ton(-1) substrate for CH4, 1.44 to 378 g ton(-1) substrate for N2O and 18-1150 g ton(-1) for NH3 . In general, emission factors increased with increasing treatment time . The biofilters had no net effect on CH4, but removed 13-89% of the NH3 . For CO2 the biofilters were a small, for N2O a major and for NO the exclusive source . Approximately 26% of the NH3-N that was removed in the biofilter was transformed into N2O when NH3 was the exclusive nitrogen source . Assuming that all municipal waste was treated by MBT, the emissions would account for 0.3 to 5% of the N2O and for 0.1 to 3% of the CH4 emissions in Germany, respectively . Optimising aeration and removing NH3 before the exhaust gas enters the biofilter could lead to reduced greenhouse gas emissions.

Water Sci Technol, 2003, 47(10), 55 - 9
Anaerobic treatment of textile dyeing wastewater; Stern SR et al.; Aerobic treatment commonly applied to textile wastewater results in good or even excellent removal of organic load . This is not, however, accompanied by an equally good removal of colour . Traditional or advanced chemical methods of decolourisation are costly and not always reliable in justifying an interest in microbial decolourisation . Among several processes anaerobic methods seem most promising . In this paper, the results of a study conducted in two pilot-scale plants comprising anaerobic fixed bed biofilters of 15 L and 5 m3 operating as continuous reactors are presented, along with evaluation of the microbial kinetics . As is shown the process proved efficient in a long-term study with no stability problems of the biofilters . The six-month performance of the pilot plant confirmed also that the pre-treated wastewater could be applied in the operation of dyeing . For the majority of the colours applied in the factory no problems were encountered when the dyeing baths were prepared by substituting 90% of fresh water to the effluent treated by a sequence of activated sludge processes: anaerobic-aerobic.

Lett Appl Microbiol, 2003, 37(1), 7 - 11
Degradation of the main components of cellulose-paint thinner by the mould Scopulariopsis brevicaulis cultured on rice hulls; Alba J et al.; AIMS: Biodegradation of the main components of the cellulose-paint thinner (toluene, acetone, isopropanol and xylenes) by Scopulariopsis brevicaulis, isolated from a thinner biodegradation microbial consortium was investigated . METHODS AND RESULTS: Our results showed that 90% of S . brevicaulis conidia survived after 4 weeks in a cellulose-paint thinner saturated atmosphere . The mould was able to grow under these environmental conditions with a low development of conidia . The biodegradation potential of S . brevicaulis was established with and without support material (rice hulls) . Biodegradation without support was very limited, <10% for all the components quantified . There was notable thinner biodegradation when the fungus was grown on rice hulls . CONCLUSIONS: Our results suggest the potential use of fungi in biofiltration systems employed in biodegradation of the main components of the cellulose-paint thinner . SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report of volatile organic compounds biodegradation by this fungal species.

Environ Technol, 2003 May, 24(5), 605 - 14
Determination of the hydraulic residence time in a trickling biofilter filled with organic matter; Garzon-Zuniga MA et al.; Biofiltration process using peat as media has been shown to be efficient for the treatment of agroindustrial, chemical and municipal effluents . However, determining the hydraulic retention time of this process is difficult due to many factors . Generally tracer techniques are used, but they measure the molecular retention time instead of the hydraulic retention time; and depending on the case, the results can be wrong . In order to contribute to solving this problem, the objective of this research was to find a trustworthy and adequate technique to determine the hydraulic retention time for a process using a very adsorbent filter bed material (peat) . An overview of the hydraulic behaviour of a peat bed filter related to their particular structural composition is presented . Then, based on these characteristics, two different techniques to determine the hydraulic retention time were developed and tested . The first, an indirect modified tracing technique and, the second, a direct one which determines the volume of liquid in treatment into the filter bed through the establishment of a relation between the volume of porosity and the volume of empty spaces (or not occupied by liquid) into the filter bed . The results obtained showed that the proposed techniques gave similar results and proved adequate.

Environ Technol, 2003 May, 24(5), 531 - 44
Sequencing batch biofilter operation for treatment of methyl ethyl ketone (MEK) contaminated air; Li C et al.; Biofiltration is increasingly used as a method for decontaminating gas streams containing low concentrations of biodegradable volatile organic compounds . In typical biofilter installation control is quite passive and is often restricted to adjustment of the medium's moisture content or nutrient supply . Although inexpensive, such operation limits implementation of engineering decisions that could improve performance during normal operation orallow effective handling of the short-term variations in the waste stream typical of industrial operations . This paper describes how sequencing batch operation can be applied to biofilters designed and operated as controlled, unsteady-state, periodic processes for the destruction of gas-phase contaminants . In the studies described herein, the impact of sequencing batch operation was assessed in a methylethyl ketone degrading biofilter over a 130-day period . The biofilter was packed with a polyurethane foam medium that contained activated carbon . Methyl ethyl ketone and carbon dioxide concentrations were monitored during both normal steady loading conditions and short-term, unsteady-state transient loading conditions (i.e., shock loading) . A gas stream containing 106 ppm, methyl ethyl ketone was used for normal loading studies, and several model shock loads consisting of 530 ppm, methyl ethyl ketone for a duration of one hour were used to assess system response to transient loads . Data are presented which clearly demonstrate that sequencing batch operation can be successfully applied to biofilters treating methyl ethyl ketone contaminated air streams . Such operation can increase an operator's ability to minimize contaminant emission during transient periods of elevated contaminant loading.

Biodegradation, 2003, 14(1), 9 - 18
Biofiltration of isopropyl alcohol by a trickle-bed air biofilter; Chang K et al.; The performance of trickle-bed air biofilter (TBAB) for the removal of isopropyl alcohol (IPA) was evaluated in concentrations varying from 100 to 500 ppmv and at empty-bed residence time (EBRT) varying from 20 to 90 s . Nearly complete IPA removal could be achieved for influent carbon loading between 6 and 88 g/m3 x h . The TBAB appears efficient for controlling IPA emission under low-to-high carbon loading conditions . Carbon recoveries of 95-99% were achieved demonstrating the accuracy of results . Applicable operating conditions of TBAB for controlling IPA emission were suggested.

Biotechnol Bioeng, 2003 Aug 20, 83(4), 479 - 88
Biofiltration of a mixture of volatile organic compounds on granular activated carbon; Aizpuru A et al.; The performance of a biofilter packed with Active Carbon (AC) was evaluated . The effluent (alcohol, ketones, esters, aromatic and chlorinated compounds) treated was a representative mixture of most common industrial emissions . To achieve a better knowledge of multicomponent adsorption mechanisms, and to underline the interest of inoculating AC, a control abiotic humidified filter had been operated in the same conditions as the biofilter . For a load of 110 g VOC m(-3) AC h(-1), after 55 days of operation, the removal efficiency was higher in the biotic than in the abiotic filter (85% vs 55%, respectively) . Moreover, in the biofilter, at steady state, the elimination of all compounds was almost complete except for chlorinated compounds and p-xylene (removal efficiency of 25% and 64%, respectively) . The microbial colonization of AC involved a decrease of the adsorption sites accessibility and enhanced the treatment of VOCs (volatile organic compounds) having a lower affinity for activated carbon . Moreover, while aromatic compounds and MIBK were eliminated along the overall height of the biofilter, pollutants with reduced affinity for AC, such as methanol, acetone, and halogenated compounds were only treated on the second half of the reactor . Thus, the affinity for activated carbon was an important parameter controlling the biodegradation process . Nevertheless, the use of AC as packing material in biofilters treating complex mixtures of VOCs is limited . Actually, similar removal efficiency could be reached, in the same conditions, for a biofilter packed with granular peat . Furthermore, for the biofilter packed with AC, the column height necessary to remove biodegradable compounds, with reduced affinity for the support, was important .

Exp Appl Acarol, 2002, 27(4), 265 - 76
Mite growth on fungus under various environmental conditions and its potential application to biofilters; Woertz JR et al.; The effects of relative humidity, temperature, pH and vapor-phase toluene concentration on Tyrophagus putrescentiae growth on Cladophialophora sp . were tested in controlled environmental chambers . It was observed that the mites were able to reproduce readily at relative humidities between 90% and 97% as well as on porous perlite support material pre-soaked in nutrient media of pH 2.5, 4 and 7 . Also, the presence of toluene at gas-phase concentrations of 500 to 2000 mg m(-3) was found to be non-toxic to the mites . The mites, however, were unable to maintain a large population when the temperature was maintained at 14 degrees C, and overpopulation of the living space led to declines in mite population over time . Overall, it was found to be relatively simple to cultivate mites that may be used for fungal biomass control measures in biofilter applications.

Appl Biochem Biotechnol, 2003 Apr-Jun, 109(1-3), 181 - 95
Removal of chemical oxygen demand, nitrogen, and heavy metals using a sequenced anaerobic-aerobic treatment of landfill leachates at 10-30 degrees C; Kalyuzhnyi S et al.; As a first step of treatment of landfill leachates (total chemical oxygen demand {COD}: 1.43-3.81 g/L; total nitrogen: 90-162 mg/L), performance of laboratory upflow anaerobic sludge bed reactors was investigated under mesophilic (30 degrees C), submesophilic (20 degrees C), and psychrophilic (10 degrees C) conditions . Under hydraulic retention times (HRTs) of about 0.3 d, when the average organic loading rates (OLRs) were about 5 g of COD/(L.d), the total COD removal accounted for 81% (on average) with the effluent concentrations close to the anaerobic biodegradability limit (0.25 g of COD/L) for mesophilic and submesophilic regimes . The psychrophilic treatment conducted under an average HRT of 0.34 d and an average OLR of 4.22 g of COD/(L.d) showed a total COD removal of 47%, giving effluents (0.75 g of COD/L) more suitable for subsequent biologic nitrogen removal . All three anaerobic regimes used for leachate treatment were quite efficient for elimination of heavy metals (Fe, Zn, Cu, Pb, Cd) by concomitant precipitation in the form of insoluble sulfides inside the sludge bed . The application of aerobic/ anoxic biofilter as a sole polishing step for psychrophilic anaerobic effluents was acceptable for elimination of biodegradable COD and nitrogen approaching the current standards for direct discharge of treated wastewater.

Appl Biochem Biotechnol, 2003 Apr-Jun, 109(1-3), 77 - 94
Sustainable treatment and reuse of diluted pig manure streams in Russia: from laboratory trials to full-scale implementation; Kalyuzhnyi S et al.; This article summarizes the results obtained during the laboratory and pilot development of integrated biologic and physicochemical treatment and reuse of diluted pig manure streams . The application of a straw filter was an effective means to separate the solid and liquid fractions of raw wastewater and resulted in the removal of a significant part of the dry matter, total nitrogen, and phosphorus (65, 27, and 32%, respectively) . From the filtrate generated, 60-80% of the total chemical oxygen demand (COD) was removed in an upflow anaerobic sludge bed reactor operating at 15-30 degrees C . Ammonia was efficiently eliminated (>99%) from the anaerobic effluents using Ural laumantite as an ion exchanger . However, the nitrogen-content of the zeolite was too low to consider this method of ammonia removal economically feasible . The phosphate precipitation block, consisting of stripper of CO2 and fluidized-bed crystallizator, was able to decrease the concentration of soluble phosphate in the anaerobic effluents up to 7-15 mg of phosphate/L . The application of aerobic/anoxic biofilter as a sole polishing step was acceptable from an aesthetic point of view (the effluents were transparent and almost colorless and odorless) and elimination of biochemical oxygen demand (the resting COD was hardly biodegradable) . However, the effluent nutrient concentrations (especially nitrogen) were far from the current standards for direct discharge of treated wastewater . We discuss the approaches for further improvement of effluent quality . Finally, we provide an outline of a full-scale system that partially implements the laboratory- and pilotscale results obtained.

Nat Mater, 2003 Jun, 2(6), 386 - 90
Dextran templating for the synthesis of metallic and metal oxide sponges; Walsh D et al.; Silver or gold-containing porous frameworks have been used extensively in catalysis, electrochemistry, heat dissipation and biofiltration . These materials are often prepared by thermal reduction of metal-ion-impregnated porous insoluble supports (such as alumina and pumice), and have surface areas of about 1 m(2) g(-1), which is typically higher than that obtained for pure metal powders or foils prepared electrolytically or by infiltration and thermal decomposition of insoluble cellulose supports . Starch gels have been used in association with zeolite nanoparticles to produce porous inorganic materials with structural hierarchy, but the use of soft sacrificial templates in the synthesis of metallic sponges has not been investigated . Here we demonstrate that self-supporting macroporous frameworks of silver, gold and copper oxide, as well as composites of silver/copper oxide or silver/titania can be routinely prepared by heating metal-salt-containing pastes of the polysaccharide, dextran, to temperatures between 500 and 900 degrees C . Magnetic sponges were similarly prepared by replacing the metal salt precursor with preformed iron oxide (magnetite) nanoparticles . The use of dextran as a sacrificial template for the fabrication of metallic and metal oxide sponges should have significant benefits over existing technologies because the method is facile, inexpensive, environmentally benign, and amenable to scale-up and processing.

Biomed Environ Sci, 2003 Mar, 16(1), 29 - 39
Improving removal efficiency of organic matters by adding phosphorus in drinking water biofiltration treatment; Yu X et al.; OBJECTIVE: To investigate phosphorus limitation and its effect on the removal efficiency of organic matters in drinking water biological treatment . METHODS: Bacterial growth potential (BGP) method and a pair of parallel pilot-scale biofilters were used for the two objectives, respectively . RESULTS: The addition of phosphorus could substantially increase the BGPs of the water samples and the effect was stronger than that of the addition of carbon . When nothing was added into the influents, both CODMn removals of the parallel biofilters (BF1 and BF2) were about 15% . When phosphate was added into its influent, BF1 performed a CODMn removal, 6.02 percentage points higher than the control filter (BF2) and its effluent had a higher biological stability . When the addition dose was < 20 micrograms.L-1, no phosphorus pollution would occur and there was a good linear relationship between the microbial utilization of phosphorus and the removal efficiency of organic matters . CONCLUSIONS: Phosphorus was a limiting nutrient and its limitation was stronger than that of carbon . The addition of phosphate was a practical way to improve the removal efficiency of organic matters in drinking water biological treatment.

Appl Microbiol Biotechnol, 2003 May, 61(4), 366 - 73 Epub 2003 Feb 20.
Pseudomonas putida as the dominant toluene-degrading bacterial species during air decontamination by biofiltration; Roy S et al.; The microbial communities established in three laboratory-scale compost matrix biofilters fed with toluene were characterized . The biofilters were operated for 7 weeks at inlet concentrations of toluene ranging over 250-500 ppm with daily irrigation, using a nutrient solution containing variable concentrations of nitrogen, supplied as urea, and other inorganic salts . The indigenous microflora of the compost included toluene-degrading species, making inoculation unnecessary . The numerically predominant toluene-degrading strains were isolated from the most diluted positive wells of most-probable-number counts on mineral medium with toluene as sole carbon source and identified by rRNA 16S gene sequencing . On the basis of sequence similarity, all the isolated strains were assigned to the species Pseudomonas putida, although some variations were observed in their respective sequences . It is concluded that the mode of biofilter operation including a daily supply of non-carbon nutrients created an environment favoring the constant numerical predominance of this fast-growing toluene-degrading species.

Appl Microbiol Biotechnol, 2003 Aug, 62(2-3), 297 - 301 Epub 2003 May 13.
The treatment of gaseous benzene by two-phase partitioning bioreactors: a high performance alternative to the use of biofilters; Davidson CT et al.; A 2-l (1-l working volume) two-phase partitioning bioreactor (TPPB) was used as an integrated scrubber/bioreactor in which the removal and destruction of benzene from a gas stream was achieved by the reactor's organic/aqueous liquid contents . The organic solvent used to trap benzene was n-hexadecane, and degradation of benzene was achieved in the aqueous phase using the bacterium Alcaligenes xylosoxidans Y234 . A gas stream with a benzene concentration of 340 mg l(-1) at a flow rate of 0.414 l h(-1) was delivered to the system at a loading capacity of 140 g m(-3) h(-1), and an elimination capacity of 133 g m(-3 )h(-1) was achieved (the volume in this term is the total liquid volume of the TPPB) . This elimination capacity is between 3 and 13 times greater than any benzene elimination achieved by biofiltration, a competing biological air treatment strategy . It was also determined that the evaluation of TPPB performance in terms of elimination capacity should include the cell mass present in the system, as this is a readily controllable quantity . A specific benzene utilization rate of 0.57 g benzene (g cells)(-1) h(-1) was experimentally determined in a bioreactor with a cell concentration that varied dynamically between 0.2 and 1 g l(-1) . If it assumed that this specific benzene utilization rate (0.57 g g(-1) h(-1)) is independent of cell concentration, then a TPPB operated at high cell concentrations could potentially achieve elimination capacities several hundred times greater than those obtained with biofilters.

Biotechnol Bioeng, 2003 Jul 5, 83(1), 29 - 38
Macrokinetic and quantitative microbial investigation on a bench-scale biofilter treating styrene-polluted gaseous streams; Zilli M et al.; We performed a macrokinetic and quantitative microbial investigation of a continuously operating bench-scale biofilter treating styrene-polluted gases . The device was filled with a mixture of peat and glass beads as packing medium and inoculated with the styrene-oxidizing strain, Rhodococcus rhodochrous AL NCIMB 13259 . The experimental data of styrene and microbial concentrations, obtained at different biofilter heights, were used to evaluate the pollutant concentration profiles as well as the influence of styrene loading on biomass distribution along the packing medium . Styrene and biomass concentration profiles permitted detection of a linear relationship between the amount of biomass grown in a given section of the biofilter and that of pollutant removed, regardless of the operating conditions tested . Biomass development in the bed appeared to: depend linearly on pollutant concentration at an inlet styrene concentration of <0.10 g m(-3) in the gaseous stream; achieve a maximum value (7 . 10(7) colony forming units per gram of packing material) within a wide styrene concentration range (0.10 to 1.0 g m(-3)); and fall sharply beyond this inhibition threshold . The process followed zeroth-order macrokinetics with respect to styrene concentration, which is consistent with zeroth-order microkinetics with either fully active or not fully active biofilm . The maximal volumetric styrene removal rate was found to be 63 g m(packing material) (-3) h(-1) for an influent pollutant concentration of 0.80 g m(-3) and a superficial gas velocity of 245 m h(-1) .

Appl Environ Microbiol, 2003 May, 69(5), 2616 - 23
Naturally occurring bacteria similar to the methyl tert-butyl ether (MTBE)-degrading strain PM1 are present in MTBE-contaminated groundwater; Hristova K et al.; Methyl tert-butyl ether (MTBE) is a widespread groundwater contaminant that does not respond well to conventional treatment technologies . Growing evidence indicates that microbial communities indigenous to groundwater can degrade MTBE under aerobic and anaerobic conditions . Although pure cultures of microorganisms able to degrade or cometabolize MTBE have been reported, to date the specific organisms responsible for MTBE degradation in various field studies have not be identified . We report that DNA sequences almost identical (99% homology) to those of strain PM1, originally isolated from a biofilter in southern California, are naturally occurring in an MTBE-polluted aquifer in Vandenberg Air Force Base (VAFB), Lompoc, California . Cell densities of native PM1 (measured by TaqMan quantitative PCR) in VAFB groundwater samples ranged from below the detection limit (in anaerobic sites) to 10(3) to 10(4) cells/ml (in oxygen-amended sites) . In groundwater from anaerobic or aerobic sites incubated in microcosms spiked with 10 microg of MTBE/liter, densities of native PM1 increased to approximately 10(5) cells/ml . Native PM1 densities also increased during incubation of VAFB sediments during MTBE degradation . In controlled field plots amended with oxygen, artificially increasing the MTBE concentration was followed by an increase in the in situ native PM1 cell density . This is the first reported relationship between in situ MTBE biodegradation and densities of MTBE-degrading bacteria by quantitative molecular methods.

Chemosphere, 2003 Jul, 52(1), 161 - 73
In situ cadmium reclamation by freshwater bivalve Lamellidens marginalis from an industrial pollutant-fed river canal; Das S et al.; The biofilter potential of the freshwater bivalve, Lamellidens marginalis was examined in cage experiments conducted in a river canal (Ichhapore, 24-Parganas, West Bengal, India) receiving industrial effluents from steel and metal factories as well as from an ordinance factory . Cadmium is one of the major contaminants in this river canal . Lamellidens collected from pollution free natural ponds, were sorted into three size groups (large: 59+/-3.2 g, 10+/-2.3 cm; medium: 30+/-2 g, 6+/-1.7 cm and small: 13+/-1.5 g, 4+/-1.2 cm) were held in cages at three different sites along a cadmium concentration gradient . Concentrations of cadmium were measured from water, sediment and different tissues of Lamellidens at weekly intervals using atomic absorption spectrophotometric methods . Cadmium uptake by Lamellidens in all media were highly concentration dependent in both summer and winter months . For all three size groups, cadmium uptake was maximum in the gills at the beginning of experiment, and liver at the later phase . Cadmium uptake was maximum in the small bivalves and minimum in the large bivalves groups . Cadmium uptake was 11-67% higher during summer than during the monsoon season for all tissues and size groups . Estimation of concentration factor revealed that tissues were saturated with cadmium during the 13-14th week after Lamellidens introduction during summer, but remained unsaturated during the monsoon season . It is concluded that Lamellidens might be considered as an efficient biofilter for reclamation of aquatic environment having sub-lethal concentrations of cadmium.

J Ind Microbiol Biotechnol, 2003 Mar, 30(3), 168 - 74 Epub 2003 Feb 26.
Biofiltration eliminates nuisance chemical odors from industrial air streams; Shareefdeen Z et al.; This paper focuses on recent developments of biofiltration technology used in treating nuisance chemical odors from industrial and municipal air streams . In the biofiltration process, odorous chemical constituents in the air are first transported to biofilms by diffusion, solubilization and adsorption processes . Bacteria within the biofilms oxidize odor constituents into harmless and odorless products . Through successful laboratory and pilot research on biofiltration of odorous air-stream constituents, numerous commercial biofilters have been designed and installed across North America . In this paper, case studies related to biofiltration of air emissions from meat rendering plants, municipal wastewater treatment applications, and printed circuit board production are discussed to demonstrate the robustness of this technology in eliminating a wide variety of compounds.

Huan Jing Ke Xue, 2003 Jan, 24(1), 57 - 62
{Phosphorus as a limiting nutrient in drinking water biological treatment}; Yu X et al.; Bacterial Growth Potential (BGP) method was used to investigate the limiting effect of phosphorus in the biological process for drinking water treatment in a water plant in Huai River basin . BGP was increased by 54% when 50 micrograms.L-1 KH2PO4-P was added to the raw water, while addition of other inorganic nutrients had no significant difference from the addition of phosphorus . The effect of addition of 20 mg.L-1 C6H12O6 to raw water was not so strong as that of 50 micrograms.L-1 KH2PO4-P . The CODMn removal rate of the biological filter was 7.5 percentiles higher than the control one and carbon was the main limiting nutrient in its effluent when phosphorus was added to the raw water, while phosphorus was the main limiting nutrient in the effluent of the control filter . These results suggest that phosphorus was a limiting nutrient and had a stronger limiting effect than carbon on the biological process in this plant thus the removal efficiency of the organic matters could be increased by adding phosphorus to the influent.

Environ Technol, 2003 Mar, 24(3), 265 - 75
Effects of packing material on the biofiltration of benzene, toluene and xylene vapours; Ortiz I et al.; Biofiltration was used to eliminate volatile organic compounds from air streams in bench-scale reactors inoculated with an adapted consortium . Organic and inert supports were tested on 100 days of operation . The supports were: peat, vermiculite, a mixture of vermiculite and activated carbon, tree bark and, porous glass Rashig rings . A mixture of benzene, toluene and xylene vapors with a load of 200 gC m(-3) h(-1) was fed to the biofilters with an empty bed residence time of 60 s . Removal efficiencies higher than 95% were obtained with the mixture of vermiculite and activated carbon, 85% for peat and bark, 80% for vermiculite and 65% for the Rashig rings . In all cases, drying problems in beds were observed after several days of operation . Water addition with or without nutrients was required to maintain and increase the performance of biofilters . In steady state operation, experiments at loads ranging from 50 to 400 gC m(-3) h(-1) were carried out and a maximum elimination capacity of 260 gC m(-3) h(-1) was obtained for vermiculite-activated carbon support . The three xylene isomers were degraded . Observations of the supports surface by scanning electronic microscopy at the end of the biofiltration experiment showed abundant growth of fungi, which were not in the inoculum, had colonized the biofilter.

Tunis Med, 2002 Aug, 80(8), 473 - 84
{Clinical evaluation of acetate-free biofiltration at 84 0/00 in patients with chronic renal insufficiency}; Hmida J et al.; We report in this study the outcome of chronically hemodialysed patients with a new technique: Acetate free biofiltration 84@1000 . This study is divided into two steps: during the first period we studied the hemodynamic stability of the technique in patients hemodynamically unstable under bicarbonate hemodialysis . During the second period we compared the hemodynamic effects and the quality of dialysis in these patients with other patients under bicarbonate hemodialysis . We obtained less hypotensive episodes, a better correction of acidosis, a better tolerance of the technique and comfort of the patient with the new technique, the quality of dialysis was the same with both techniques . We recommend the use of acetate free biofiltration 84@1000 whenever the patients are hemodynamicallyunstable with bicarbonate hemodialysis.

Meded Rijksuniv Gent Fak Landbouwkd Toegep Biol Wet, 2002, 67(2), 117 - 28
Effects of addition of straw, chitin and manure to new or recycled biofilters on their pesticides retention and degradation properties; Genot P et al.; Pollution of surface and groundwater by pesticides is an increasing problem that needs to be addressed by the authorities as well as by the farmers themselves . Nowadays, some researchers are considering the numerous small spillages at the farm sites as a relevant entry route to be taken into account for predicting surface and groundwater pollution . In order to tackle this problem, several solutions exist for limiting the disposal of pesticide wastes into the environment . One such system is biopurification of farm wastes by biobed, biofilter or phytobac . In this study, the results of pesticides retention by biofilters under outdoor conditions are presented . The biofilters were filled with a mixture of a soil + peat constituent (25% by volume for each of them) and the rest (50%) with straw or with composted manure ot with chitin (in this later case at the rate of 5 g chitin per liter of substrate) . The soil + peat constituent was made either of a material already challenged by pesticides (= recycled biofilters) or of untreated material (new biofilters) . Selected pesticides (atrazine, carbofuran, chloridazon, chlortoluron, cyanazine, isoproturon and lenacil) were applied onto biofilters and the eluates were collected and analyzed . Two successive injections of pesticides into the biofilters were conducted . After the first pesticides application, the recycled biofilters made of soil + peat previously treated with pesticides had better retention and degradation rates than the new biofilters . Adding manure also improved these properties of biofilters . Columns made of unchallenged soil + peat and straw (new biofilters) were the least satisfactory: up to 25% of carbofuran were lost . Biofilters made of unchallenged soil + peat and chitin retained the least lenacil . Atrazine was the most retained by biofilters (either new or recycled) with added chitin . Cyanazine was almost absent in the percolates of all biofilters . After the second application of carbofuran and isoproturon, all biofilters improved to the point where (with the exception the new biofilters made of chitin) they retained the totality of the pesticides.

Bioresour Technol, 2003 Sep, 89(2), 199 - 205
Biofiltration of n-butyric acid for the control of odour; Sheridan BA et al.; Odour control from pig production facilities is a significant concern due to increased public awareness and the development of more stringent legislation to control production . Although many technologies exist, biofiltration is still the most attractive due to its low maintenance and operating costs . One of the key odour components, n-butyric acid, was selected for a laboratory scale biofilter study . It was examined as a sole carbon substrate in order to investigate the effectiveness of biofiltration in reducing n-butyric acid concentration under different operating conditions using a moist enriched woodchip medium . Three superficial gas velocities; 38.2, 76.4, and 114.6 m x h(-1) were tested for n-butyric acid concentrations ranging from 0.13 to 3.1 g {n-butyric acid} m(-3) {air} . For superficial gas velocities 38.2, 76.4, and 114.6 m x h(-1), maximum elimination capacities (100% removal) of 148, 113 and 34.4 g x m(3) x h(-1), respectively, were achieved . Upon investigation of effective bed height, true elimination capacities (100% removal) of 230, 233 and 103 g x m(-3) x h(-1), respectively, were achieved at these superficial gas velocities . Averaged pressure drops for superficial gas velocities 38.2, 76.4, and 114.6 m x h(-1) were 30, 78 and 120 Pa, respectively . It was concluded that biofiltration is a viable technology for the removal of n-butyric acid from waste exhaust air, but near 100% removal efficiency is required due to the low odour detection threshold for this gaseous compound.

Water Res, 2003 Feb, 37(3), 525 - 32
Biofouling reduction in recirculating cooling systems through biofiltration of process water; Meesters KP et al.; Biofouling is a serious problem in industrial recirculating cooling systems . It damages equipment, through biocorrosion, and causes clogging and increased energy consumption, through decreased heat transfer . In this research a fixed-bed biofilter was developed which removed assimilable organic carbon (AOC) from process water, thus limiting the major substrate for the growth of biofouling . The biofilter was tested in a laboratory model recirculating cooling water system, including a heat exchanger and a cooling tower . A second identical model system without a biofilter served as a reference . Both installations were challenged with organic carbon (sucrose and yeast extract) to provoke biofouling . The biofilter improved the quality of the recirculating cooling water by reducing the AOC content, the ATP concentration, bacterial numbers (30-40 fold) and the turbidity (OD660) . The process of biofouling in the heat exchangers, the process water pipelines and the cooling towers, was monitored by protein increase, heat transfer resistance, and chlorine demanded for maintenance . This revealed that biofouling was lower in the system with the biofilter compared to the reference installation . It was concluded that AOC removal through biofiltration provides an attractive, environmental-friendly means to reduce biofouling in industrial cooling systems.

Klin Lab Diagn, 2003 Feb, (2), 23 - 4, 33-7
{The functional role of arterial intima . Endogenous and exogenous pathogens and specificity of atheromatosis as an inflammation}; Titov VN; We believe that the intima is a biological filter accountable for arresting the endogenous and exogenous pathogens, which activate the biological function of inflammation, and for preventing the access of pathogens into the internal-space intercellular pool . The below described biological reactions occur in the arterial intima: trans-cytosis of pathogens by endothelial cells onto the intima surface; sorption of pathogens into the filter proteoglycan matrix; destruction of the matrix by macrophage metalloproteinases; desorption of pathogens with matrix elements by resident macrophages through squewenjer-receptor endocytosis; proteolysis of pathogens in lysosomes; retroendocytosis of non-hydrolyzed components of pathogens into the intercellular medium; and a recovery of the integrity of proteoglycan matrix by the smooth-muscle cells . Sorption and desorption of pathogens (i.e . modified low-density lipoproteins who carry the essential polyene fat acids to cells) by resident macrophages (from the filter) under the conditions of the blockade of apoB-100-receptoral endocytosis predetermine the specificity of atheromatosis as an inflammation.

J Ind Microbiol Biotechnol, 2003 May, 30(5), 260 - 70 Epub 2003 Apr 03.
Accelerated biodegradation of petroleum hydrocarbon waste; Ward O et al.; Conventional landfarming approaches to bioremediation of refinery and other petroleum sludges are not acceptable environmentally and are banned in most North American jurisdictions . While initial bioreactor-based systems for treatment of these sludges required batch-cycle process-times of 1-3 months, an accelerated process has now been developed which can be completed in 10-12 days . In this process, up to 99% of total petroleum hydrocarbons are degraded and the sludges are converted from hazardous to non-hazardous according to the United States EPA's toxicity characteristic leachate procedure criteria . Understanding and exploiting mechanisms to improve hydrocarbon accession to the degrading microorganisms was a key development component of the process . Contrasting physiological mechanisms were observed for different component organisms of the mixed culture with respect to their associations with the hydrocarbon substrate; and the beneficial effects of using surfactants were demonstrated . The mixed culture used in the process exhibited a capacity for high-rate degradation of volatile organic carbons and the potential use of the culture as a liquid biofilter was demonstrated . The culture was also effective as an inoculant for the bioaugmentation of total petroleum hydrocarbon-contaminated soil and as a de-emulsifier of oilfield emulsions and could transform some other environmental contaminants which are not predominant components of crude oil.

Environ Sci Technol, 2003 Mar 1, 37(5), 985 - 92
Effect of drying on biofilter performance: modeling and experimental approach; Morales M et al.; The moisture content of biofilter media is a key parameter for its adequate performance . Control of moisture requires a better understanding of the drying of the support due to changes in inlet air temperature and relative humidity and from metabolic heat production by pollutant oxidation . A dynamic one-dimensional model was developed to describe drying and its effect on biofilter performance . Mass and energy balances were established on an elementary representative volume . The biological reaction term incorporated temperature, water content, and pollutant concentration effects . The model describes the variations in pollutant concentration, air relative humidity, temperature, and water content of the media . It predicts (1) water evaporation from the packing material as a consequence of metabolic heat generation and variations of the relative humidity of the inlet air stream, and (2) the resulting decrease in biofilter performance . The model was validated with biofiltration experiments treating gaseous toluene using peat as support . Various ranges of inlet air relative humidity, temperature, air velocity, and inlet pollutant concentration were assayed.

Appl Biochem Biotechnol, 2003 Mar, 104(3), 199 - 214
Mass transfer and benzene removal from air using latex rubber tubing and a hollow-fiber membrane module; Fitch M et al.; A dense-phase latex rubber tube and a polyporous propylene hollow-fiber membrane module (HFMM) were investigated for control of benzene-contaminated gas streams . The abiotic mass flux observed through the latex tube was 3.9 13 mg/(min.m(2)) for 150 ppm of benzene at various gas and liquid flow rates, while a 100-fold lower mass flux was observed in the HFMM . After seeding with an aromatic-degrading culture enriched from activated sludge, the observed removal was 80% of 150 ppm, corresponding to a mass flux of 45 mg/(min.m(2)) . The observed mass flux through the HFMM during biofiltration also rose, to 0.4 mg/(min.m(2)) . Because the HFMM had a 50-fold higher surface area than the latex tube, the observed benzene removal was 99.8% . Compared to conventional biofilters, the two reactors had modest elimination capacities, 2.5 18 g/(m(3).h) in the latex tube membrane bioreactor and 4.8 58 g/(m(3).h) in the HFMM . Although the HFMM had a higher elimination capacity, the gas-phase pressure drop was much greater.

Braz J Biol, 2002 Nov, 62(4A), 713 - 23 Epub 2003 Feb 11.
Utilization of macrophyte biofilter in effluent from aquaculture: I . Floating plant; Sipauba-Tavares LH et al.; The objective of this work was to manufacture a low-cost biofilter, made of floating macrophyte (Eichhornia crassipes) . Limnological studies were conducted 7 days after the macrophytes were placed in the biofilter, and continued over a period of 30 consecutive days . During rainy and dry seasons, and high production period, samples were taken three times a week . The lowest levels of nitrogen compounds were observed in the July/August period, which corresponded to lower fish production and low supply rattion in the culture ponds . During the experimental period, pH values ranged from acid to alkaline and did not oscillate with higher average values during April/May . Alkalinity and bicarbonate dominance in the medium were directly affected by pH . With respect to associated micro-fauna, among phyto-plankton Chlorophyta was the dominant group and among zooplankton, Rotifera . It is recommended that during production peaks, the aquatic plants should be replaced by small buds every 10 days.

Water Sci Technol, 2003, 47(3), 147 - 50
Inactivation of Salmonella spp . from secondary and tertiary effluents by UV irradiation; Keller R et al.; The aim of this study was to verify the efficiency of UV irradiation in the inactivation of Salmonella spp . in treated wastewater with different levels of turbidity and exposed to increasing doses of UV irradiation . Experiments were carried out in a batch reactor and in a real scale reactor . Salmonellae obtained from clinical samples were seeded into autoclaved wastewater collected from a wastewater treatment plant (WWTP) comprising an association of a UASB reactor followed by three submerged aerated biofilters (BAF) and one tertiary filter . The results showed that salmonellae were not inactivated in effluents from the UASB reactor indicating that the presence of suspended solids was an important obstacle to UV penetration in bacteria . However, UV irradiation was efficient in inactivating Salmonella of effluents from aerated secondary and tertiary biofilm reactors.

Bioresour Technol, 2003 Jul, 88(3), 259 - 63
Characterization of five agricultural by-products as potential biofilter carriers; Ramirez-Lopez E et al.; Biofiltration is the most commonly used biological gas treatment technology and is extensively used for the treatment of polluted air with gas flow rates of up to 2 x 10(5) m(3)/h . It involves a filter bed of organic matter serving both as carrier for microorganisms and as nutrient supplier . Polluted gas passes through the filter bed and is cleaned by biological activity . Biofiltration is not being developed in Latin America as in the USA, Canada or Europe; the main reason probably being the absence of specific technology and of potential organic carriers locally available . Five different agriculture by-products available in Latin America: peanut shells, rice husk, coconut shells, cane bagasse and maize stubble, were chemically, physically and structurally characterized for their potential use as biofilter carrier . It was found that peanut shells could be used as biofilter carrier and therefore would have potential biological application.

J Environ Sci Health B, 2003 Jan, 38(1), 89 - 101
Bench-scale biofilter for removing ammonia from poultry house exhaust; Shah SB et al.; A bench-scale biofilter was evaluated for removing ammonia (NH3) from poultry house exhaust . The biofilter system was equipped with a compost filter to remove NH3 and calcium oxide (CaO) filter to remove carbon dioxide (CO2) . Removal of NH3 and CO2 from poultry house exhaust could allow treated air with residual heat to be recirculated back into the poultry house to conserve energy during winter months . Apart from its use as a plant nutrient, NH3 removal from poultry house exhaust could lessen the adverse environmental impacts of NH3 emissions . Ammonia and CO2 were measured daily with gas detector tubes while temperatures in the poultry pen and compost filter were monitored to evaluate the thermal impact of the biofilter on treated air . During the first 37 days of the 54-day study, exhaust air from 33 birds housed in a pen was treated in the biofilter; for the final 17 days, NH3-laden exhaust, obtained by applying urea to the empty pen was treated in the biofilter . The biofilter system provided near-complete attenuation of a maximum short-term NH3 concentration of 73 ppm . During the last 17 days, with a mean influent NH3 concentration of 26 ppm, the biofilter provided 97% attenuation . The CaO filter was effective in attenuating CO2 . Compared with a biofilter sized only for NH3 removal, an oversized biofilter would be required to provide supplemental heat to the treated air through exothermic biochemical reactions in the compost . The biofilter could conserve energy in poultry production and capture NH3 for use as plant nutrient . Based on this study, a house for 27,000 broilers would require a compost filter with a volume of approximately 34 m3.

Environ Microbiol, 2003 Mar, 5(3), 183 - 201
Microbial community and physicochemical analysis of an industrial waste gas biofilter and design of 16S rRNA-targeting oligonucleotide probes; Friedrich U et al.; A study was conducted to investigate the microbial community structure, the physicochemical properties, and the relationships between these parameters of a full-scale industrial biofilter used for waste gas abatement in an animal-rendering plant . Fluorescence in situ hybridization (FISH) was successfully combined with digital image analysis to study the composition of the microbial community . Several new nucleic acid probes were designed and established based on published 16S rDNA sequences and on ones retrieved from the biomass of the biofilter under investigation . Bacterial detection rates varied greatly over time and filterbed depth between 27.2% and 88.1% relative to DAPI counts . Overall, members of the Betaproteobacteria followed by Actinobacteria, Alphaproteobacteria, Cytophaga-Flavobacteria, Firmicutes and Gammaproteobacteria were the most abundant groups . Among the groups below phylum level, members of the Alcaligenes/Bordetella lineage were on average the most abundant group accounting for up to 8.5% of DAPI-stained cells . Whereas the community composition generally showed no vertical gradient, the lower 50 cm of the biofilter proved to be the most active part for the degradation of aldehydes such as 2- and 3-methylbutanal, 2-methylpropanal, and hexanal . This zone of the filterbed being operated in up-flow direction degraded about 80% of these compounds . Dimethyldisulphide was the most common reduced sulphur compound . Statistical analysis of microbial versus waste gas parameters generally revealed only weak or non-significant correlations between the two . Possible explanations for this finding are discussed.

Adv Space Res, 2003, 31(1), 201 - 10
The "C.E.B.A.S . MINI-MODULE": a self-sustaining closed aquatic ecosystem for spaceflight experimentation; Blum V et al.; The C.E.B.A.S . MINI-MODULE is the miniaturized space flight version of the Closed Equilibrated Biological Aquatic System (C.E.B.A.S.) . It fits into a large middeck locker tray and is scheduled to be flown in the STS 85 and in the NEUROLAB missions . Its volume is about 9 liters and it consists of two animal tanks, a plant cultivator, and a bacteria filter in a monolithic design . An external sensor unit is connected to a data acquisition/control unit . The system integrates its own biological life support . The CO2 exhaled by the consumers (fishes, snails, microorganisms) is assimilated by water plants (Ceratophyllum demersum) which provide them with oxygen . The products of biomass degradation and excretion (mainly ammonia ions) are converted by bacteria into nitrite and nitrate . The latter is taken up by the plants as a nitrogen source together with other ions like phosphate . The plants convert light energy into chemical energy and their illumination is regulated via the oxygen concentration in the water by the control unit . In ground laboratory tests the system exhibited biological stability up to three month . The buffer capacity of the biological filter system is high enough to eliminate the degradation products of about one half of the dead animal biomass as shown in a "crash test" . A test series using the laboratory model of the flight hardware demonstrated the biological stability and technical reliability with mission-identical loading and test duration . A comprehensive biological research program is established for the C.E.B.A.S . MINI-MODULE in which five German and three U.S.-American universities as well as the Russian Academy of Sciences are involved . c2002 Published by Elsevier Science Ltd on behalf of COSPAR.

J Air Waste Manag Assoc, 2003 Jan, 53(1), 92 - 101
Removal of ammonia by biofilters: a study with flow-modified system and kinetics; Choi JH et al.; The characteristics of ammonia removal by two types of biofilter (a standard biofilter with vertical gas flow and a modified biofilter with horizontal gas flow) were investigated . A mixture of organic materials such as compost, bark, and peat was used as the biofilter media based on the small-scale column test for media selection . Complete removal capacity, defined as the maximum inlet load of ammonia that was completely removed, was obtained . The modified biofilter showed complete removal up to 1.0 g N/kg dry material/day . However, the removal capacity of the standard biofilter started to deviate from complete removal around 0.4 g N/kg dry material/day, indicating that the modified biofilter system has higher removal efficiency than the standard upflow one . In kinetic analysis of the biological removal of ammonia in each biofilter system, the maximum removal rate, Vm, was 0.93 g N/kg dry material/day and the saturation constant, Ks, was 32.55 ppm in the standard biofilter . On the other hand, the values of Vm and Ks were 1.66 g N/kg dry material/day and 74.25 ppm, respectively, in the modified biofilter system.

Huan Jing Ke Xue, 2002 Sep, 23(5), 13 - 8
{Use of biological activated carbon to degrade benzene and toluene in a biofilter}; Li G et al.; The biodegradation of toluene and benzene in a biofilter using cylindrical activated carbon as the filler materials was studied . For total mass loading lower than 350 g/(h.m3), retention time ranging from 15 s to 90 s the biofilter proved to be highly efficient in biodegradation of toluene and benzene, their removal capacity were 120 and 150 g/(h.m3) respectively and toluene was more easily degraded than benzene . The CO2 produced increased with the degradation of benzene and toluene, but the experimental value was lower than the theoretical value . The observation of biotic community demonstrated that the microbes consisted of bacillus, spore bacillus and fungi, of them spore bacillus was dominant . According to basic theories of mass-transfer, adsorption and biodegradation process, mathematical model of removal of VOCs by biofiltration was established and verified.

Water Sci Technol, 2002, 46(11-12), 51 - 6
Biological treatment characteristics of benzene and toluene in a biofilter packed with cylindrical activated carbon; Li GW et al.; The biodegradation of toluene and benzene in a biofilter using cylindrical activated carbon as the filler materials was studied . Three gas low rates, i.e . 0.25, 0.50 and 0.75 m3/h, corresponding to empty bed gas residence of 75, 37.5 and 25 s, respectively, and total organic load lower than 400 g/m3 x h were tested . The biofilter proved to be highly efficient in biodegradation of toluene and benzene, and toluene was more easily degraded than benzene . When each inlet load was lower than 150 g/m3 x h, removal rate increased with inlet load and reached a maximum, which was 150 and 120 g/m(-3) x h for toluene and benzene, respectively . For inlet load higher than the maximum removal capacity conditions, the removal rate decreased with inlet load . Carbon dioxide concentration profile through the biofilter revealed that the mass ratios of carbon dioxide produced to the toluene and benzene removed were 2.15 g(CO2)/g(toluene) and 1.67 g(CO2)/g(benzene), which furthermore, confirmed the biodegradation performance in biofilter . The observation of biotic community demonstrated that the microbes consisted of bacillus, spore bacillus and fungi, of which the spore bacillus was dominant.

Environ Pollut, 2003, 121(2), 181 - 7
Biofiltration of gasoline vapor by compost media; Namkoong W et al.; Gasoline vapor was treated using a compost biofilter operated in upflow mode over 4 months . The gas velocity was 6 m/h, yielding an empty bed retention time (EBRT) of 10 min . Benzene, toluene, ethylbenzene and xylene (BTEX) and total petroleum hydrocarbon (TPH) removal efficiencies remained fairly stable approximately 15 days after biofilter start-up . The average removal efficiencies of TPH and BTEX were 80 and 85%, respectively, during 4 months of stable operation . Biodegradation portions of the treated TPH and BTEX were 60 and 64%, respectively . When the influent concentration of TPH was less than 7800 mg TPH/m3, approximately 50% of TPH in the gas stream was removed in the lower half of the biofilter . When the influent concentration of BTEX was less than 720 mg BTEX/m3, over 75% of BTEX in the gas stream was removed in the lower half of the biofilter . Benzene removal efficiency was the lowest among BTEX . A pressure drop could not be detected over a 1-m bed height at a gas velocity of 6 m/h after approximately 4 months of operation . Results demonstrated that BTEX in gasoline vapor could be treated effectively using a compost biofilter.

Waste Manag Res, 2002 Oct, 20(5), 434 - 44
The effect of various environmental and design parameters on methane oxidation in a model biofilter; Park S et al.; Methane from landfills built with RCRA (Resource Conservation and Recovery Act) covers is frequently vented directly to the atmosphere . Alternatively, landfill gasses could be vented through a layer of soil that could serve as a biofilter to oxidize CH4 to carbon dioxide and water . Properly designed soil biofilters may reduce atmospheric CH4 emissions from landfills and help reduce the accumulation of greenhouse gasses in the atmosphere . This study was conducted to investigate the performance of a lab-scale model biofilter system using soil as the filterbed medium in packed columns to measure the effect of a variety of environmental and design factors on the CH4 oxidation capacity of a soil biofilter . Biofilter performance was tested under a variety of environmental and design conditions . The optimum soil moisture content for CH4 oxidation in a loamy sand was 13% by weight . Addition of NO3-N did not affect the CH4 oxidation rate . Soil depths of 30 cm and 60 cm were equally efficient in CH4 oxidation . When the CH4 loading rate was decreased, the percentage of CH4 oxidized increased . The maximum CH4 oxidation rate was 27.2 mol m(-2) d(-1) under optimum conditions.

J Environ Qual, 2002 Nov-Dec, 31(6), 1782 - 8
Hydrogen sulfide effects on ammonia removal by a biofilter seeded with earthworm casts; Lee EY et al.; Ammonia (NH3) removal efficencies were evaluated when hydrogen sulfide (H2S) and NH3 in binary mixture gases were supplied to a ceramic biofilter seeded with earthworm (Lumbricus terrestris) casts . The effect of inlet H2S concentration and space velocity (SV) on the removal of NH3 was investigated after the acclimation of the biofilter with NH3 gas . When NH3 was singly supplied to the biofilter, NH3 removal was maintained at almost 100% until inlet NH3 concentration was increased up to 600 microL L(-1) and SV up to 330 h(-1), at which the elimination capacity of NH3 was 148 g N m(-3) h(-1) . When H2S was supplied simultaneously, however, the accumulation of toxic sulfide ions showed dual effects on NH3 removal efficiencies . First, no effects were observed at inlet H2S loading below 60 g S m(-3) h(-1); however, inhibition by H2S at higher loading was observed above 60 g S m(-3) h(-1) . The point at which loading achieved a maximum of more than 99% NH3 removal efficiency was 139 g N m(-3) h(-1), when inlet H2S concentration was held under 100 microL L(-1), but it dropped to 76 and 30 g N m(-3) h(-1) when the inlet H2S concentration increased to 220 and 460 microL L(-1), respectively . The critical points of inlet H2S loading that guaranteed over 99% NH3 removal were determined as 100, 100, 60, and 40 g S m(-3) h(-1) at inlet NH3 concentrations of 100, 200, 400, and 600 microL L(-1), respectively . Inlet NH3 loading had synergic effects of increasing the inhibition of inlet H2S loading on the NH3 removability of the biofilter.

J Air Waste Manag Assoc, 2002 Nov, 52(11), 1288 - 97
1-Butanol removal from a contaminated airstream under continuous and diurnal loading conditions; Fitch MW et al.; A polysulfone microporous membrane module was investigated for control of 1-butanol-contaminated gas streams . A diurnal loading condition, using two different butanol concentrations, was used to simulate start-up and stop conditions associated with shift work . The membrane module was also used to remove 1-butanol from air under continuous loading conditions in a bioreactor . The reactors were seeded with a mixed bacterial consortium capable of butanol biodegradation . Biokinetic parameters for butanol utilization were determined for the culture to be a maximum specific utilization rate (k) equal to 4.3 d(-1) and a half saturation constant (Ks) equal to 8.9 mg L(-1) . A biofilter running only with diurnal loading conditions giving a "40-hr work-week" had an average 1-butanol removal rate of 29% (111 ppm, 74 gm(-3) hr(-1)) from a 350-ppm influent at the end of an 8-hr operational day . End-of-day removal varied between 4 and 67% during the operational period . With continuous steady-state operation followed by placement on a diurnal loading schedule and influent butanol concentrations increased to 700 ppm, butanol removal averaged 38% (269 ppm, 145 gm-3 hr(-1)) . Under continuous loading, steady-state conditions, 1-butanol removal from the airstream was greater than 99% (200 ppm, 73 gm-3 hr(-1)) . These results suggest that the bioreactor can be operated on a diurnal schedule or 40-hr week operational schedule without any decline in performance.

Water Res, 2003 Jan, 37(1), 206 - 14
The sensitivity of fixed-bed biological perchlorate removal to changes in operating conditions and water quality characteristics; Brown JC et al.; Flow rate, electron donor addition, and biomass control were evaluated in order to optimize perchlorate (ClO4-) removal from drinking water using biologically active carbon (BAC) filtration . Influent dissolved oxygen (DO) was lowered from ambient conditions to approximately 2.5 mg/L for all experiments using a nitrogen sparge . When influent nitrate concentration was 0-2.0 mg/L, 1.6-2.8 mg/L as carbon of acetate or ethanol was required to achieve and sustain the complete removal of 50 microg/L perchlorate in a BAC filter . Most or all of the exogenous acetate and ethanol was removed during biofiltration . When a 72-h electron donor feed failure was simulated, a maximum perchlorate breakthrough of 18 microg/L was observed and, once electron donor was reapplied, 9 days were required to reestablish complete perchlorate removal . During a 24-h electron donor feed failure simulation, the maximum effluent perchlorate concentration detected was 6.7 microg/L . Within 24 h of reactivating the electron donor, the filter regained its capacity to consistently remove 50 microg/L perchlorate to below detection . Although biomass growth diminished the filter's ability to consistently remove perchlorate, a cleaning procedure immediately restored stable, complete perchlorate removal . This cleaning procedure was required approximately every 50 days (4800 bed volumes) when influent DO concentration was 2.5 mg/L . Empty-bed contact time (EBCT) experiments showed that 80% perchlorate removal was achieved using a 5-min EBCT, and complete perchlorate removal was observed for an EBCT of 9 min . It was also demonstrated that BAC filtration consistently removed perchlorate to below detection for influent perchlorate concentrations ranging from 10 to 300 microg/L, influent sulfate concentrations between 0 and 220 mg/L, influent pH values of 6.5-9.0, and operating temperatures of 5-22 degrees C.

Environ Microbiol, 2002 Nov, 4(11), 721 - 34
High bacterial diversity of a waste gas-degrading community in an industrial biofilter as shown by a 16S rDNA clone library; Friedrich U et al.; The bacterial diversity of an industrial biofilter used for waste gas abatement in an animal-rendering plant was investigated . A 16S rDNA clone library was generated and 444 clones were screened using computer-aided amplified ribosomal DNA restriction analysis (ARDRA) . Of the screened clones, 60.8% showed unique ARDRA patterns and the remaining 174 clones were clustered into 65 groups . Almost full-length 16S rDNA sequences of 106 clones were determined and 90.5% of the clones were affiliated with the two phyla Proteobacteria and Bacteroidetes . Alpha-, Beta-, and Gammaproteobacteria accounted for 22.1, 17.6 and 18.6% respectively . Minor portions were affiliated with the Actinobacteria (2.0%), Firmicutes and Verrucomicrobia (both 1.0%), and the Deltaproteobacteria and Thermomicrobia (each 0.5%) . Only six out of the 106 16S rDNA sequences exhibited similarities of more than 97% to classified bacterial species indicating that a substantial fraction of the clone sequences were derived from unknown taxa . It was also evaluated whether a database containing 281 computer-simulated bacterial rDNA fragment patterns generated from published reference sequences can be used for identification purposes . The data analysis demonstrated that this was possible only for a small number of clones, which were closely related to described bacterial strains . Rarefaction analysis of ARDRA clusters demonstrated that the 444 clones screened are insufficient to describe the entire diversity of the clone library.

J Hazard Mater, 2002 Nov 11, 95(1-2), 199 - 213
Simultaneous removal of ethyl acetate and toluene in air streams using compost-based biofilters; Liu Y et al.; Biofitration was successfully applied to treat air streams containing a mixture of ethyl acetate and toluene . The experiment was performed by two identical bench-scale biofilters, which were acclimated by ethyl acetate and toluene, respectively . During a 3 month steady-state performance, the two biofilters showed equivalent elimination capacity (EC) for toluene (50 g/m(3) bed/h of pure toluene) . However, the biofilter acclimated with ethyl acetate showed a much higher EC for ethyl acetate (400 g/m(3) bed/h of pure ethyl acetate) than that acclimated with toluene (250 g/m(3) bed/h) . The concurrent biofiltration of toluene was inhibited by the presence of ethyl acetate . The results also showed that more nitrogen and phosphorus were consumed in the process of the biofiltration of toluene compared with the treatment of ethyl acetate . After the 3 month experiment, the pH of the media treating ethyl acetate dropped from 6.71 to 5.50, whereas the pH of the media treating toluene increased from 6.71 to 7.08.

Prikl Biokhim Mikrobiol, 2002 Sep-Oct, 38(5), 523 - 8
{Stability of microbial association in the process of industrial biofiltration cleaning of gaseous discharges}; Vinarov AIu et al.; Results of industrial exploitation of a biofiltration plant tailored for purifying gaseous discharges of hazardous organic components such as toluene, cyclohexane, and xylene, are examined . Both numerical and compositional variations were monitored for a long-term (more than 1.5 years) utilization process in an association of microorganisms decomposing organic pollutants . A population of microbial association composed by one yeast and two bacterial strains in the biofilm on the surface of filtering sheets was abundant (10(8)-10(9) yeast cells/cm2 and 10(10)-10(11) bacterial cells/cm2) and stable during the whole period of monitoring . A microbial association in the culture medium averaging 10(6) yeast cells/l and 10(8) bacterial cells/l is more susceptible to technogenic impacts and seasonal fluctuations . Overall, the biofilter as an open and autonomic system maintained its microbial association, thereby providing a high-degree (93-98%) purification of industrial gaseous discharges from organic pollutants.

Environ Technol, 2002 Sep, 23(9), 981 - 8
Effect of mineral salts addition on the behaviour of an ethanol biofilter; Teran Perez W et al.; Ethanol biofiltration was studied in a 0.1651 packed bed reactor filled with sugar cane bagasse complemented with mineral medium and inoculated with Candida utilis . The main objective was to improve the elimination capacity of the system by adding salts to the solid medium . The biofilter was operated for one month, varying both the inlet ethanol concentration (7.6-16.5 g m(-3) and the airflow rate (1.61-2.50 x 10(-3) m3 h(-1)) . Removal efficiency (RE) of 100% was attained at ethanol loads ranging from 74.2 to 250 g h(-1) m(-3) . When the RE decreased, acetaldehyde and ethyl acetate appeared in the outlet stream; adding mineral salts restored a 100% RE . Both ammonium sulfate and ammonia were assimilated by the yeast (conversion yield of nitrogen from the N-source to biomass of 75%), but only ammonia restored the pH of the medium to a value adequate for efficient biofiltration (7.7) . Fifty seven percent of the carbon from ethanol was converted into CO2, and 8.7% into biomass . Final yeast population was 7 x 10(9) cells g(-1) dry matter, corresponding to 56 mg protein g(-1) dry matter, which offers potential to also use the protein enriched bagasse as feed.

Water Sci Technol, 2002, 46(4-5), 7 - 12
Influence of the nutrient balance on biofilm composition in a fixed film process; Hendrickx TL et al.; An attached fungal growth has appeared in a fixed biofilm process at the waste water treatment plant of the City of Oulu, Finland . Due to the filamentous morphology of the fungi, biofilm support material is easily washed out . The appearance is believed to be the result of the unbalanced availability of nutrients, where phosphorus has been identified as the key component . Experimental work concentrated on the influence of phosphorus on the fungal growth . Bench scale experiments showed that a higher uptake of phosphorus for the removal of organic material is possible, which also resulted in a suppression of the fungal growth by bacterial biomass . The results were confirmed by experimentation in a full-scale biofilter . Addition of extra phosphoric acid to the biofilter influent resulted in a biofilm where the fungal growth is less pronounced . The fungal growth is believed to be competitive with the desired bacterial growth . It is possible to keep the fungal growth within limits by changing the conditions in favour of the bacterial growth, thus avoiding the operational problems connected with the filamentous fungi.

J Chromatogr A, 2002 Sep 13, 970(1-2), 259 - 73
Gas chromatography-mass spectrometry as a tool for estimating odour concentrations of biofilter effluents at aerobic composting and rendering plants; Defoer N et al.; The relationship between chemical concentrations (gas chromatography-mass spectrometry analysis) and odour concentrations (olfactometry) was studied for biofilter emissions from four aerobic vegetable, fruit and garden waste (VFG) composting plants and one animal rendering plant . For the VFG composting plants, the study revealed a good linear relationship of the odour concentration with the total volatile organic compounds (VOC) concentration (R2=0.97, n=16) as well as with the concentration of esters and ketones (R2=0.9, n=19) . For biofilter emissions of the animal rendering plant, the total VOC concentration was a poor estimator for odour concentration . However, for this type of odour, concentrations of organic sulphur containing compounds correlated well with odour concentrations (R2=0.94, n=8) . The results of the study also showed that the relationship between chemical and odour concentrations is specific for each type of odour and cannot be generalized.

Am J Kidney Dis, 2002 Oct, 40(4), 783 - 93
Effect of acetate-free biofiltration and bicarbonate hemodialysis on neutrophil activation; Todeschini M et al.; BACKGROUND: Activation of polymorphonuclear neutrophils (PMNs) and monocytes has been described during hemodialysis (HD), which results in the release of reactive oxygen species and cytokines . Acetate-free biofiltration (AFB) has been shown to cause less monocyte activation and cytokine release than bicarbonate HD (BHD) . No data are available to date on the effect of AFB on PMN activation . METHODS: We studied ex vivo superoxide anion release by PMNs isolated from nine patients treated in random order with AFB or BHD (three sessions each) . Plasma interleukin-1beta (IL-1beta) levels and the nitric oxide (NO) synthetic pathway also were evaluated . A polyacrylonitrile (AN69; Hospal, Bologna, Italy) dialyzer was used for both treatments . Fourteen healthy volunteers were used as controls . Blood samples were drawn predialysis and 5 and 15 minutes after starting dialysis to obtain plasma and PMNs . RESULTS: Neither ex vivo superoxide anion release nor blood PMN count was affected by AFB . Conversely, a peak in superoxide anion production associated with a decrease in PMN count was observed at 5 minutes during BHD . Results of superoxide anion production by control PMNs exposed in vitro to AFB or bicarbonate dialysis bath or Hank's balanced salt solution supplemented with bicarbonate or acetate indicated that BHD-induced PMN activation could be attributed to the amount of bicarbonate present in the dialysis bath . IL-1beta plasma levels did not change during dialysis with AFB and were numerically higher at 5 and 15 minutes with respect to predialysis values during BHD . Uremic plasma obtained during either AFB or BHD induced greater NO synthesis by human umbilical vein endothelial cells than control plasma . CONCLUSION: AFB, unlike BHD, does not cause PMN and monocyte activation, which could have a positive impact on dialysis-associated cardiovascular disease of dialyzed patients .

Water Res, 2001 Nov, 35(16), 3817 - 24
Comparative measurements of microbial activity in drinking water biofilters; Fonseca AC et al.; Tetrazolium reduction assays, phospholipid analysis, and 16S rRNA (rDNA) sequence analysis were applied to assess the distribution, composition and activity of microbial communities developing in biofilters treating non-ozonated and ozonated drinking water . The response of media-attached biomass to both operating temperature (3 degrees C vs . > 12 degrees C) and ozone application point was assessed . As judged by 2-(p-iodo-phenyl)-3-(p-nitrophenyl)-s-phenyl tetrazolium chloride (INT) reduction, the dehydrogenase activity in biofilter systems that were operated with non-ozonated water was 55% lower than in identical filters operating with ozonated water . There was no significant difference between the microbiological activity measured in a biofilter series treating ozonated water and an identical series where ozonated water was introduced at an intermediate point . The biomass levels in biofilter systems that were operated with ozonated water were 47% higher on average than identical systems operated with non-ozonated water . Operating temperature had no significant impact on total biomass levels; however, specific dehydrogenase activity was 70% higher in systems operated at ambient temperatures (> 12 degrees C) than in systems held at 3 degrees C . Phospholipid and rDNA analysis suggests that there was a community structure response to ozone application and operating temperature, but no response to different ozone application points.

Water Sci Technol, 2002, 45(12), 79 - 87
Combined biological and physico-chemical treatment of filtered pig manure wastewater: pilot investigations; Kalyuzhnyi S et al.; Combined biological and physico-chemical treatment of filtered pig manure wastewater has been investigated on the pilot installation operated under ambient temperatures (15-20 degrees C) and included: i) UASB-reactor for elimination of major part of COD from the filtrate; (ii) stripper of CO2 + fluidised bed crystallisator for phosphate (and partially ammonia) removal from the anaerobic effluents in the form of insoluble minerals-struvite (MgNH4PO4) and hydroxyapatite (Ca5(PO4)3OH); (iii) aerobic-anoxic biofilter for polishing the final effluent (elimination of remaining BOD and nutrients) . Under overall hydraulic retention time (HRT) for the system of 7.8 days, the total COD, inorganic nitrogen and total phosphorous removals were 88, 65 and 74%, respectively . A decrease of the overall HRT to 4.25 days led to 91, 37 and 82% removals for total COD, inorganic nitrogen and total phosphorus removals, respectively . The approaches for further improvement of effluent quality are discussed.

Water Sci Technol, 2002, 45(10), 299 - 304
Using a UASB reactor for thickening and digestion of discharged sludge from submerged aerated biofilters; Franci Goncalves R et al.; Results from one year of experimental monitoring the wastewater treatment plant of UFES (Federal University of Espirito Santo) treating a residential urban area of city of Vitoria ES, Brazil, have shown a good performance by a UASB reactor as a part of domestic sewage treatment and also performing aerobic sludge thickening and digestion . The total solids concentration around 6% was obtained in main sludge blanket at bottom of reactor despite a high daily aerobic sludge load discharged from four aerobic submerged biofilters containing 0.4% TS and 80% of VS/TS . Similar values were found in another experimental period when the reactor was fed only with raw domestic sewage . The average removal efficiency of organic matter and suspended solids observed for domestic sewage treatment are around 63% of SS and 64% COD . These results were obtained in the UASB reactor working with or without aerobic sludge recycling, with constant or variable load and hydraulic detention time (HDT) less than 6 hours . A proposed mass balance allows a theoretical assessment of aerobic sludge digestion and accumulation into UASB reactor.

Water Res, 2002 Jul, 36(13), 3387 - 97
Treatment of a colored groundwater by ozone-biofiltration: pilot studies and modeling interpretation; Rittmann BE et al.; Pilot studies investigated the fates of color, dissolved organic carbon (DOC), and biodegradable organic matter (BOM) by the tandem of ozone plus biofiltration for treating a source water having significant color (50 cu) and DOC (3.2 mg/l) . Transferred ozone doses were from 1.0 to 1.8 g O3/g C . Rapid biofilters used sand, anthracite, or granular activated carbon as media with empty-bed contact time (EBCT) up to 9 min . The pilot studies demonstrated that ozonation plus biofiltration removed most color and substantial DOC, and increasing the transferred ozone dose enhanced the removals . For the highest ozone dose, removals were as high as 90% for color and 38% for DOC . While most of the color removal took place during ozonation, most DOC removal occurred in the biofilters, particularly when the ozone dose was high . Compared to sand and anthracite biofilters, the GAC biofilter gave the best performance for color and DOC removal, but some of this enhanced performance was caused by adsorption, since the GAC was virgin at the beginning of the pilot studies . Backwashing events had no noticeable impact of the performance of the biofilters . The Transient-State, Multiple-Species Biofilm Model (TSMSBM) was used to interpret the experimental results . Model simulations show that soluble microbial products, which comprised a significant part of the effluent BOM, offset the removal of original BOM, a factor that kept the removal of DOC relatively constant over the range of EBCTs of 3.5-9 min . Although improved biofilm retention, represented by a small detachment rate, allowed more total biofilm accumulation and greater removal of original BOM, it also caused more release of soluble microbial products and the build up of inert biomass in the biofilm . Backwashing had little impact on biofilter performance, because it did not remove more than 25% of the biofilm under any condition simulated.

Appl Microbiol Biotechnol, 2002 Aug, 59(4-5), 567 - 73 Epub 2002 Jun 19.
Optimization of nutrient supply in a downflow gas-phase biofilter packed with an inert carrier; Prado OJ et al.; Several methodologies were tested to supply nutrients to a downflow biofilter packed with perlite and used to treat toluene-polluted air . Despite the presence of an inorganic carrier, elimination capacities of up to around 60 g/m(3) per hour could be maintained when a basal medium, containing nitrogen, phosphorus and potassium, was supplied once every fortnight or even once a month rather than once a week . Experimental results also indicated that the addition of vitamins or trace minerals to the basal aqueous medium hardly improved biofilter performance . Furthermore, the nutrient supply could be combined with a biomass control strategy, using air sparging, without any adverse effect on biofilter performance compared to supplying nutrients alone, and limiting the accumulation of excess biomass on the packing material . The performance of the biofilter was not significantly affected by temperature fluctuations between 25 and 33 degrees C.

Bioresour Technol, 2002 Sep, 84(2), 129 - 43
Assessment of the influence of media particle size on the biofiltration of odorous exhaust ventilation air from a piggery facility; Sheridan BA et al.; Two pilot scale biofiltration systems were constructed and installed at the University College Dublin Research Farm, Lyons Estate . Experimental units consisting of two pens in a 12 pen pig house were sealed off from other pens . Air from each pen was extracted and treated separately in two biofiltration systems . Wood chips larger than 20 mm were selected as the medium for biofiltration system 1, whereas chips of between 10 and 16 mm were used in biofiltration system 2 . The moisture content of the media was maintained at 69+/-4% (w.w.b.) using a load cell method . The volumetric loading rates ranged from 769 to 1847 m3 {gas} m(-1) {medium} h(-1) over a 63-day experimental period . Both biofilters reduced odour between 88% and 95% . Ammonia removal efficiencies ranged from 64% to 92% and 69% to 93%, for biofiltration systems 1 and 2, respectively . Sulphur-containing compounds were reduced between 9-66%, and -147-51% across biofiltration systems 1 and 2 . The pH of the biofilters' leachate remained between 6 and 8 . Pressure drop for biofilter 2 was 16 Pa greater than that of biofilter I at the maximum volumetric loading rate of 1847 m3 {gas} m(-3) {medium} h(-1) . It is recommended that a wood chip media particle size greater than 20 mm be used for large scale operation of a biofiltration system on intensive pig production facilities to reduce the development of anaerobic zones and to minimize pressure drop on the system fans.

J Biotechnol, 2002 Sep 11, 98(1), 113 - 23
Environmental biotechnology: the ongoing quest; Grommen R et al.; Environmental biotechnology, until now, has primarily focused on the development of technologies to treat aqueous, solid and gaseous wastes . At present, the basic knowledge on how biotechnology can handle these wastes has been acquired and the focus is now on the implementation of these processes as 'best available technology not entailing excessive costs' (BATNEEC) in the framework of strict and transparent environmental legislation . New environmental challenges continue to evolve, as it becomes clear that waste streams should be tackled in an overall holistic way . New technologies to reach this goal are currently under development . Novel aspects with respect to the domain of water treatment are, for example, the biomembrane reactor technology and the newly discovered processes to remove nitrogen by means of anaerobic ammonium oxidation . Also, most challenging is the continuing strive for re-use of treated wastewater . Indeed, water shortage is emerging in an increasing number of countries all over the world and necessitates the short cycling of water . Finally, biotechnology has a key role to play in the novel approaches to design wastewater treatment based on decentralised sanitation and reuse (DESAR) . Solid waste is a major challenge worldwide . The implementation of anaerobic digestion to treat biowastes has become a grown-up technology . New approaches in which biotechnological processes are linked to physical processes, such as plasma technology, certainly deserve special attention for the coming decades . Soil and sediment clean up by means of biostimulation/remediation/augmentation is now well established . Certainly, a number of prospects need to be further explored, such as the use of special energy sources to stimulate in situ the microbial community and the seeding of knowledge to the in situ community by means of horizontal gene transfer mechanisms . A number of waste gases can be handled by biofilter systems . Biological treatment of wastegases is also evolving, inasmuch as that besides conventional chemical pollutants, now also highly problematic chemicals (even dioxins) can be dealt with through proper biotechnological approaches . A remarkable new potential is the use of well designed probiotics to upgrade aquaculture and together with conventional biological water treatment processes, to guarantee the overall water quality of this domain of food production.

Mem Inst Oswaldo Cruz, 2002 Jun, 97(4), 531 - 4
Predation potential of the water bugs Sphaerodema rusticum on the sewage snails Physa acuta; Aditya G et al.; The sewage snail Physa acuta is a serious threat to certain economic plants and to the purification plant of sewage works by rendering the biofilters ineffective . Various attempts are being made to control it . The efficacy of the predacious water bugs Sphaerodema rusticum was judged experimentally, in the laboratory in the potential control of P . acuta . It is revealed that, when supplied separately, the first, second and third instar and the adult S . rusticum did not attack P . acuta belonging to 3.1-8 mm, 5.1-8 mm, 7.1-8 mm and </= 3 mm size classes respectively . In the remaining trials predation rate varied from zero to eight (average 2.3) individuals per predator per day . In experiments with P . acuta belonging to all the size classes supplied together, none, except the first instar S . rusticum, attacked the prey individuals belonging to the lowest (</= 3 mm) size class . The first and second instar S . rusticum, in both trials did not attack P . acuta larger than 4 mm and 5 mm in shell length respectively . The water bugs belonging to the third, fourth, fifth instar and adult stages though preyed upon P . acuta with 3.1-8 mm shell length . The average rate of predation by a single S . rusticum varied from 0.14-3.08 individuals per day depending upon the size of P . acuta and the stage of S . rusticum . A single S . rusticum, irrespective of instar and adult stages, destroyed on average 4.16 P . acuta daily irrespective of sizes . It is estimated that one S . rusticum could destroy 1,360 P . acuta in its life time . The results clearly indicate that the water bug S . rusticum may be used to control the snails P . acuta.

Water Res, 2002 May, 36(9), 2342 - 56
The transient-state, multiple-species biofilm model for biofiltration processes; Rittmann BE et al.; We describe the transient-state, multiple-species biofilm model (TSMSBM), which is a novel synthesis of key modeling features needed to describe multiple-species biofilms that experience time-varying conditions, particularly including periodic detachment by backwashing . The TSMSBM includes six features that are essential for describing multiple-species biofilms that undergo changes over time: (1) four biomass types: heterotrophs, ammonia oxidizers, nitrite oxidizers, and inert biomass; (2) seven chemical species: input biodegradable organic material (BOM), NH4(+)-N, NO2(-)-N, NO3(-)-N, utilization-associated products, biomass-associated products, and dissolved oxygen; (3) eight reactions that describe the rates of consumption or production of the different species, as well as the stoichiometric linkages among the rates; (4) reaction with diffusion of all the soluble species in the biofilm; (5) growth, decay, detachment, and flux of each biomass type by location in the biofilm; and (6) constant or periodic detachment of biofilm, both of which allow for protection of biomass deep inside the biofilm . The last two features of the TSMSBM provide novel additions to biofilm modeling, and the synthesis of all features is a unique advancement . A series of examples illustrates insights that the TSMSBM can provide about the transient development of multiple-species biofilms; the roles of soluble microbial products and detachment in controlling the distribution of biomass types and process performance; and how backwashing affects the biofilm in drinking-water biofiltration.

Environ Technol, 2002 Apr, 23(4), 467 - 77
Use of biological activated carbon to treat mixed gas of toluene and benzene in biofilter; Li GW et al.; The biodegradation of toluene and benzene in a biofilter filled with cylindrical activated carbon was studied . Three various gaseous flow rates, i.e . 0.25, 0.50 and 0.75 m3 h(-1), corresponding to empty bed gas residences of 75, 37.5 and 25 s, respectively, and total organic load lower than 400 g m(-1) h(-1) were tested . The biofilter proved to be highly efficient in biodegradations of toluene and benzene, and toluene was more easily degraded than benzene . When each inlet load of toluene and benzenewas lower than 150 g m(-3) h(-1), removal rate increased with inlet loads and reached maximum values of 150 and 120 g m(-3) h(-1) for toluene and benzene, respectively . For inlet load higher than the maximum removal capacity conditions, the removal rate decreased with inlet load . The carbon dioxide concentration profile through the biofilter revealed that the mass ratios of carbon dioxide produced to the toluene and benzene removed were 2.15 g CO2 g(-1) toluene and 1.67 g CO2 g(-1) benzene . Model predictions for toluene, benzene and carbon dioxide concentration gradient profiles were in agreement with experimental data for the tested conditions . The observation of biotic community demonstrated that the microbes consisted of bacillus, spore bacillus and fungi, of them spore baxillus was dominant.

Environ Technol, 2002 Apr, 23(4), 437 - 44
Biodegradation of gaseous benzene with microbial consortium in a biofilter; Kim JO et al.; The objective of this study was to investigate the biodegradation of gaseous benzene in a biofilter inoculated with benzene-oxidizing microorganisms . The biofilter performance was monitored in terms of benzene removal efficiency and carbon dioxide production . The biofilter was capable of achieving as much as 96% benzene removal efficiency at a residence time of 2 min and an inlet concentration of 220 ppm . During operation with an inlet benzene of 220 ppm, the maximum elimination capacity of the biofilter was 483 g of C6H6 m(-3) day(-1) . Under the same conditions, carbon dioxide with a concentration of up to 726 ppm was produced . It was found that carbon dioxide wasproduced at a rate of 608 mg day(-1), which corresponded to a volume of 0.35 l day(-1) . Observable features of the microorganisms, meaning microbial activity occurrence in the biofilter, were investigated with the microscopy analysis.

Int J Food Microbiol, 2002 Jul 25, 77(1-2), 125 - 33
Depuration dynamics of viruses in shellfish; Muniain-Mujika I et al.; The consumption of shellfish has been associated with viral infections even in cases where shellfish complied with the current regulation, which is based on bacterial analysis . In this study, depuration rates of potential indicators and human viruses have been analysed in order to study the use of complementary parameters for evaluating the microbiological quality of depurated shellfish . Depuration of naturally highly polluted mussels has been evaluated and analyses for Escherichia coli, Clostridium perfringens, somatic coliphages, F-RNA phages and bacteriophages infecting Bacteroides fragilis RYC2056 and HSP40, human adenovirus, enterovirus have been done . Seawater of the depuration tank was disinfected by UV irradiation, ozone and passed through a skimmer and a biological filter . The correct functioning of the depuration tank was monitored by the quantification of total organic carbon (TOC), NH4+ and total aerobic bacteria in the seawater . To study the relation between the bacteriophages and the human viruses analysed, a logistic regression model was applied . F-RNA phages are significantly related to human adenoviruses and enteroviruses . Thus, they can be used as a complementary parameter for evaluating the efficiency of the depuration treatment . Somatic coliphages are also significantly associated with enteroviruses . Bacteriophages infecting B . fragilis HSP40 were analysed by the double-agar-layer (DAL) method, which quantifies infectious viruses, and by nested PCR, which detects the presence of the genome of these phages . The highest sensitivity of the molecular techniques was demonstrated and the results obtained are an indicator of a close relation between positive results by PCR and the presence of infectious viral particles in shellfish . All shellfish samples were negative for human viruses by PCR after 5 days of depuration treatment and the results obtained applying a regression model also showed negative results or nearly for F-RNA phages and bacteriophages infecting B . fragilis RYC2056 . Thus, in this specific depuration treatment, 5 days may be necessary to assess the sanitary quality of shellfish.

Bioresour Technol, 2002 Jun, 83(2), 153 - 7
Sugarcane bagasse as alternative packing material for biofiltration of benzene polluted gaseous streams: a preliminary study; Sene L et al.; Removal of benzene vapor from gaseous streams was studied in two identically sized lab-scale biofiltration columns: one filled with a mixture of raw sugarcane bagasse and glass beads, and the other one packed with a mixture of ground sugarcane bagasse and glass beads, in the same volume ratio, as filter materials . Separate series of continuous tests were performed, in parallel, under the same operating conditions (inlet benzene concentration of 10.0, 20.0 or 50.0 mg m(-3), and superficial gas velocity of 30.6, 61.2 or 122.4 m h(-1)) in order to evaluate and compare the influence of the packing material characteristics upon the biofilter effectiveness . The maximum elimination capacities obtained, at an inlet load of 6.12 g m(-3) h(-1), were 3.50 and 3.80 g m(-3)packibng material h(-1) with raw and ground sugarcane bagasse, respectively . This was a preliminary study and the results obtained suggest only a limited application with more work needed.

J Environ Sci Health A Tox Hazard Subst Environ Eng, 2002, 37(5), 863 - 73
Enhanced nutrient removals using conventional anoxic biomechanic aerobic system for on-site wastewater treatment; Kwun SK et al.; A bench-scale absorbent biofilter system combined with a conventional anoxic process was investigated in regard to its feasibility for removing organic as well as nutrient materials from small community wastewater in Korea . A polyurethane biofilter medium with high porosity and a large surface area were used for the aerobic system . Part of treated wastewater was recirculated into the anoxic process to promote removal rate of nutrients . At three different ratios of recirculation, the BOD and SS of treated wastewater satisfied standard regulations for a small wastewater treatment facility (10 mg/l) during the overall experimental period . The system reduced the concentration of BOD from approximately 130 mg/l to 6.1 (removal rate of 95.2%) and 1.7 mg/l (removal rate of 98.7%) . These results correspond to recirculation ratios of 1 and 2, respectively . A further increase of the recirculation ratio did not significantly improve the removal rate or further reduce effluent BOD concentration . Nutrients such as nitrogen and phosphorus also were removed effectively, with maximum removal rates of 65.3 and 84.1% for nitrogen and phosphorus, respectively . The recirculation ratio for optimum nitrogen removal was 2, while the removal of phosphorus continued to increase across the entire range of recirculation ratios tested . With a recirculation ratio of 2, the total phosphorous removal rate increased dramatically as initial ammonium concentration increased, while nitrogen removal was not affected in this manner . During the experimental period of 2 years, the system was quite stable, requiring the minimum amount of maintenance and a relatively low cost compared to other utility expenses . Based on the experimental data, the proposed anoxic-biofilter aerobic recirculation system might be used as a new alternative technology for wastewater treatment in small communities in Korea.

J Air Waste Manag Assoc, 2002 May, 52(5), 511 - 20
Water transformation in the media of biofilters controlled by Rhodococcus fascians in treating an ethyl acetate-contaminated airstream; Hwang SC et al.; Biofilters do not provide much water for bacteria to grow . To use them efficiently and properly, it is essential to understand the kinetics of water transformation and to control moisture levels . This study aims to clarify whether the metabolism of microorganisms will improve the water-holding capacity of media or will intensify drying . This experiment was conducted in duplicate, that is, both with and without bacterial inoculation . Both the constant water content mode and the declining water content mode show that microbial growth in a log phase will enhance drying . In contrast, the bacteria growing in a logarithmic decline phase will improve water-holding capacity . Basically, water evaporation can result from the latent heat obtained from microbial respiration or from the physical temperature difference between the unsaturated air and the wet media . Two ways that biofilters can gain water are from water incorporated into bacteria cells and from water obtained from the oxidation of volatile organic compounds (VOCs).

Bioresour Technol, 2002 Apr, 82(2), 103 - 7
Use of wastewater as a nutrient solution in a closed gravel hydroponic culture of giant reed (Arundo donax); Mavrogianopoulos G et al.; The objective of this experimental work was to examine the efficiency of giant reed (Arundo donax L.), as a source of biomass production and as a biofiltering device for sewage effluents . Two giant reed populations were cultivated in a closed gravel hydroponic system, where pig's waste was used as a nutrient solution . The results showed that stem biomass production varied from 12 to 23 kg DM m(-2) yr(-1), more than the ordinary production in the soil . According to stem analysis, for the first two years, there was an average infiltration rate of 31 g m(-2) yr(-1) total N, 7.5 g m(-2) yr(-1) total P, 18.8 g m(-2) yr(-1) K, 2.1 g m(-2) yr(-1) Ca, 2.1 g m(-2) yr(-1) Mg, 0.27 g m(-2) yr(-1) Fe, 0.02 g m(-2) yr(-1) Mn, 0.14 g m(-2) yr(-1) Zn and 0.08 g m(-2) yr(-1) Cu . During the third year, when a nutrient solution with added P was used, the average infiltration rate for most elements increased by 46% and for P by 169%.

J Air Waste Manag Assoc, 2002 Apr, 52(4), 400 - 6
Degradation characteristics of toluene, benzene, ethylbenzene, and xylene by Stenotrophomonas maltophilia T3-c; Lee EY et al.; Stenotrophomonas maltophilia T3-c, isolated from a biofilter for the removal of benzene, toluene, ethylbenzene, and xylene (BTEX), could grow in a mineral salt medium containing toluene, benzene, or ethylbenzene as the sole source of carbon . The effect of environmental factors such as initial toluene mass, medium pH, and temperature on the degradation rate of toluene was investigated . The cosubstrate interactions in the BTEX mixture by the isolate were also studied . Within the range of initial toluene mass (from 23 to 70 pmol), an increased substrate concentration increased the specific degradation of toluene by S . maltophilia T3-c . The toluene degradation activity of S . maltophilia T3-c could be maintained at a broad pH range from 5 to 8 . The rates at 20 and 40 degrees C were 43 and 83%, respectively, of the rate at 30 degrees C . The specific degradation rates of toluene, benzene, and ethylbenzene by strain T3-c were 2.38, 4.25, and 2.06 micromol/g-DCW/hr . While xylene could not be utilized as a growth substrate by S . maltophilia T3-c, the presence of toluene resulted in the cometabolic degradation of xylene . The specific degradation rate of toluene was increased by the presence of benzene, ethylbenzene, or xylene in binary mixtures . The presence of toluene or xylene in binary mixtures with benzene increased the specific degradation rate of benzene . The presence of ethylbenzene in binary mixtures with benzene inhibited benzene degradation . The presence of more than three kinds of substrates inhibited the specific degradation rate of benzene . All BTEX mixtures, except tri-mixtures of benzene, ethylbenzene, and xylene or mixtures of all four substrates, had little effect on the degradation of ethylbenzene by S . maltophilia T3-c . The utilization preference of the substrates by S . maltophilia T3-c was as follows: ethylbenzene was degraded fastest, followed by toluene and benzene . However, the specific degradation rates of substrates, in order, were benzene, toluene, and ethylbenzene.

Environ Technol, 2002 Mar, 23(3), 309 - 18
Biodegradation of toluene by a lab-scale biofilter inoculated with Pseudomonas putida DK-1; Park DW et al.; The biodegradation of toluene by biofiltration inoculated with Pseudomonas putida DK-1 was investigated with variation of the several environmental parameters, such as temperature, bed length, gas flow rate and optimal humidity zone . The optimal temperature range to treat toluene gas was found to be 32-35 degrees C . Increasing the gas flow rate showed an inverse effect on the elimination capacity and the removal efficiency . The optimal gas flow rate was obtained at 65 ml min(-1) from the relation between the removal efficiency and the elimination capacity . The biodegradation rate of the toluene with respect to the bed lengths (3, 6, 9, 12 and 15 cm) increased up to 80 h but was then independent of the bed lengths after 80 h except for the 3 cm bed length . The elimination capacity was improved by about 70% compared with that reported in other literature and was also in agreement with theoretical models.

Environ Technol, 2002 Mar, 23(3), 243 - 52
Removal of acetone and methylacetate mixtures from waste gases by a trickle-bed air biofilter; Lu C et al.; The biofilter process is a relatively new technology that has been proven more cost-effective than traditional technologies for treating low-strength and some high-strength volatile organic compounds (VOCs) from waste gases . Acetone (AT) and methylacetate (MA) mixtures are commonly encountered from the manufacture of artificial rubber or polyurethane resin . This research attempts to employ a trickle-bed air biofilter (TBAB) for treating AT and MA mixtures under different influent carbon loadings . In the pseudo-steady-states, the elimination capacities of AT and MA increased but the removal efficiencies decreased with increased influent carbon loading . The removal efficiencies of MA were higher than those of AT showing that MA is a preferred substrate in the ATMA waste gas and the differences were enhanced at a high carbon loading . Greater than 95% AT removal and nearly complete MA removal were achieved with influent carbon loadings of AT and MA below 20 and 27 g m(-1) h(-1), respectively . The TBAB appears very efficient for treating ATMA emission with low to medium carbon loadings.

Water Environ Res, 2002 Jan-Feb, 74(1), 17 - 27
Optimization of biofiltration for odor control: model calibration, validation, and applications; Martin RW Jr et al.; A dynamic model that describes the biofiltration process for hydrogen sulfide removal from wastewater treatment plant air emissions was calibrated and validated using pilot- and full-scale biofilter data obtained from the Cedar Rapids (Iowa) Water Pollution Control Facilities . After calibration, the model was found to predict the dynamic effluent concentrations of the pilot- and full-scale biofilters well, with the measured data falling within 58 to 80% of the model output values . In addition, the model predicted the trend of the field data, even under field conditions of changing input concentration and at effluent concentrations below 1 ppm by volume . The model demonstrated that increasing gas residence time and temperature and decreasing influent concentration decreases effluent concentration . In addition, model simulations showed that a longer residence time is required to treat dynamic loading increases, indicating that biofilter design should account for the maximum influent concentration . These results can be used to help design and operate biofilters for controlling odorous and hazardous air emissions.

Water Environ Res, 2002 Jan-Feb, 74(1), 5 - 16
Optimization of biofiltration for odor control: model development and parameter sensitivity; Li H et al.; A dynamic model that describes the mass transport and attenuation of odor-causing air emissions (i.e., hydrogen sulfide and other reduced sulfur compounds) in a biofiltration unit was developed and incorporated into a software package called Biofilter . Mechanisms included advective flow, mass transfer from the bulk phase to the biofilm, biofilm internal diffusion, and biological reaction in the biofilm . A dimensionless analysis revealed that the mass transport and attenuation of target compounds can be characterized by several dimensionless groups . Model equations were converted to ordinary differential equations using orthogonal collocation and the resulting ordinary differential equations were solved using the DGEAR algorithm . Numerical solutions were verified by comparing model simulations to analytical solutions . The model simulations showed that the existence of a water layer surrounding the biofilm in a biofiltration unit lowers the removal efficiency of hydrogen sulfide . A sensitivity analysis of model parameters (including the film transfer coefficient, biofilm diffusivity, biofilm thickness, maximum specific biomass growth rate, yield coefficient, half-saturation coefficient, and initial active biomass concentration) using data from two biofilters located at the Cedar Rapids (Iowa) Water Pollution Control Facilities, showed that biofilm internal diffusion and biofilm kinetics have a significant effect on hydrogen sulfide removal, while external mass transfer has little effect.

J AOAC Int, 2002 Mar-Apr, 85(2), 341 - 8
Determination of oxytetracycline residues in matrixes from a freshwater recirculating aquaculture system; Carson MC et al.; This paper describes related procedures to determine the amount of oxytetracycline (OTC) present in trout tissue (muscle with skin attached), biofilter sand, sediment, and tank water from a recirculating aquaculture system . OTC was extracted from the matrixes by different techniques, depending on complexity of the matrix and desired OTC detection level in that matrix . Listed in order of increasing complexity, OTC was extracted from tank water by dilution with acidic buffer containing ethylenediaminetetraacetic acid (EDTA); from biofilter sand by shaking with 0.1 N HCl; from sediment by homogenization and shaking with buffer/EDTA; and from ground trout by homogenization and shaking with buffer/EDTA (twice), with further cleanup and concentration of the extract on a polymeric solid-phase extraction cartridge . The 4 procedures all used the same reversed-phase gradient chromatography on a polymeric column with UV detection at 350 nm . The lower limit of detection (estimated) and upper limit of validation for each of these 4 matrixes were 0.04-4.0 microg/g (ppm; trout), 0.03-20 ppm (biofilter sand), 1-6000 ppm (sediment), and 0.003-10 ppm (water) . Recoveries ranged from 82 to 108%, with relative standard deviation <20% over the applicable concentration ranges . These procedures were used to monitor OTC residues resulting from medicated feed administered to rainbow trout in a recirculating aquaculture system.

Rev Neurol, 2002 Jan 16-31, 34(2), 121 - 30
{The thalamus: a dynamic door to perception}; Cudeiro-Mazaira FJ et al.; y dependent on the activity of our senses for our relationship with the outside world, we may consider the thalamus to be a key part of perception . DEVELOPMENT . Far from behaving as a simple relay station, the thalamic circuits represent the framework on which to build a truly dynamic biological filter which can select the messages to reach the cortex according to their relevance and the behavioural state of the person . Such filtering implies the participation of many neurotransmitters which represent as many different systems . Outstanding amongst these are the groups formed by acetylcholine and nitric oxide axons arising from the brainstem, and corticofugal fibers which are sent back from the cortex to the thalamus . CONCLUSIONS . In this paper we review the functional aspects of the thalamic control of information, particularly of the visual system, with reference to alterations derived from its malfunction.

J Ind Microbiol Biotechnol, 2002 May, 28(5), 245 - 51
Comparison of microporous and nonporous membrane bioreactor systems for the treatment of BTEX in vapor streams; Attaway H et al.; Increased regulatory constraints on industrial releases of atmospheric volatile organic compounds (VOCs) have resulted in an interest in using biofilters, bioscrubbers and air/liquid membranes for treatment of vapor phase waste streams . In this report, we describe the comparison of the use of two fundamentally different types of membrane module systems that allow the rapid diffusion of vapor phase aromatics and oxygen to an active biofilm for subsequent biodegradation . One system used a commercial membrane module containing microporous polypropylene fibers while the other used a nonporous silicone tubing membrane module for the delivery of substrate (a mixture of benzene, ethylbenzene, toluene, and xylenes {BTEX}) and electron acceptor (O(2)) . Tests of the systems under similar conditions with BTEX in the vapor feed stream showed significant performance advantages for the silicone membrane system . The average surface-area-based BTEX removal rate for the microporous membrane system over 500 h of operation was 7.88 microg h(-1) cm(-2) while the rate for the silicone membrane system was 23.87 microg h(-1) cm(-2) . The percentages of BTEX removal were also consistently better in the silicone membrane system versus the microporous system . Part of the performance problem associated with the microporous membrane system appeared to be internal water condensation and possible plugging of the pores with biomass over time that could not be resolved with vapor phase backflushing.

J Agric Food Chem, 2002 May 8, 50(10), 2846 - 55
Recovery and characterization of the metal polymeric organic fraction (polymerin) from olive oil mill wastewaters; Capasso R et al.; A dark and complex metal polymeric organic mixture, named polymerin, was recovered from olive oil mill wastewaters (OMWW) and characterized by chemical analysis, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and atomic absorption spectrometry (AAS) . Polymerin proved to be composed of carbohydrates (52.40 mg 100(-1), w/w), melanin (26.14 mg 100(-1)), and proteins (10.40 mg 100(-1)), and the respective composition of monosaccharides, phenols, and amino acids was determined . It also contained metals (11.06 mg 100(-1)), mainly K(+) and, to a lesser extent, Na(+), Ca(2+), Mg(2+), Zn(2+), Fe(3+), and Cu(2+), which were naturally bound and chelated through carboxylate anions and other characteristic nucleophilic functional groups naturally occurring in polymerin . The distribution of polymerin relative molecular size was assessed to be approximately between 500.0 and 2.0 kDa by calibrated molecular weight gel filtration chromatography, indicating also that a fraction consisted of protein, melanin, and polysaccharide, strongly aggregated to each other in a supramolecular status by a combination of covalent and hydrogen bonds and CH/Pi interactions, and another fraction of only free polysaccharide . Polymerin was transformed into a potassium salt deglycosylated derivative, named KSDpolymerin, which was also characterized by chemical analysis, DRIFTS, and AAS . KSDpolymerin consisted of carbohydrates (6.00 mg 100(-1)), melanin (52.49 mg 100(-1)), and proteins (35.40 mg 100(-1)), and the composition of monosaccharides, phenols, and amino acids was determined . It also contained metals (6.11 mg 100(-1)), mainly K(+) and to a lesser extent Na(+), Ca(2+), Mg(2+), Zn(2+) and Fe(3+), bound as in polymerin . All the organic components were strongly linked in a supramolecular aggregate status and the relative average molecular size proved to be 6.3 kDa . Finally, we briefly discuss the possible use of such polymerins in agriculture as bioamendments and macro- and microelement biointegrators and as a biofilter for toxic metal removal, in light of their similarity with humic acids.

Appl Microbiol Biotechnol, 2002 Apr, 58(5), 684 - 9 Epub 2002 Feb 21.
Biodegradation of volatile organic compounds by five fungal species; Qi B et al.; Five fungal species, Cladosporium resinae (ATCC 34066), Cladosporium sphaerospermum (ATCC 200384), Exophiala lecanii-corni (CBS 102400), Mucor rouxii (ATCC 44260), and Phanerochaete chrysosporium (ATCC 24725), were tested for their ability to degrade nine compounds commonly found in industrial off-gas emissions . Fungal cultures inoculated on ceramic support media were provided with volatile organic compounds (VOCs) via the vapor phase as their sole carbon and energy sources . Compounds tested included aromatic hydrocarbons (benzene, ethylbenzene, toluene, and styrene), ketones (methyl ethyl ketone, methyl isobutyl ketone, and methyl propyl ketone), and organic acids ( n-butyl acetate, ethyl 3-ethoxypropionate) . Experiments were conducted using three pH values ranging from 3.5 to 6.5 . Fungal ability to degrade each VOC was determined by observing the presence or absence of visible growth on the ceramic support medium during a 30-day test period . Results indicate that E . lecanii-corni and C . sphaerospermum can readily utilize each of the nine VOCs as a sole carbon and energy source . P . chrysosporium was able to degrade all VOCs tested except for styrene under the conditions imposed . C . resinae was able to degrade both organic acids, all of the ketones, and some of the aromatic compounds (ethylbenzene and toluene); however, it was not able to grow utilizing benzene or styrene under the conditions tested . With the VOCs tested, M . rouxiiproduced visible growth only when supplied with n-butyl acetate or ethyl 3-ethoxypropionate . Maximum growth for most fungi was observed at a pH of approximately 5.0 . The experimental protocol utilized in these studies is a useful tool for assessing the ability of different fungal species to degrade gas-phase VOCs under conditions expected in a biofilter application.

J Air Waste Manag Assoc, 2002 Mar, 52(3), 279 - 86
Effects of nitrogen and oxygen on biofilter performance; Yang H et al.; Three laboratory-scale biofilters packed with inert material were used to study the nitrogen and oxygen requirements for biofiltration of methanol . Mixtures of methanol with inorganic nitrogen (NH3 or NO3) at nitrogen-to-carbon (N:C) ratios ranging from 0.015 to 0.4 were employed to reveal nitrogen effects on biofiltration . In the oxygen study, mixtures of air and oxygen at different oxygen contents were used . At low nitrogen levels, the removal rate increased with increasing N:C ratio for both NH3 and NO3 . However, at high concentrations, NH3 had an inhibitory effect on biodegradation while the removal rate reached a plateau at high NO3 concentrations . Biofiltration with 63% oxygen in the inlet gas stream increased the maximum removal rate from 120 to 145 g/m3/hr after 3 days in comparison with biofiltration with air . However, a further increase in oxygen content up to 80% did not lead to a further improvement in biofilter performance, suggesting that both oxygen and biofilm thickness can be the relevant factors limiting biofilter performance and creating the plateau in removal rates at high loadings.

Artif Organs, 2002 Feb, 26(2), 169 - 80
Online hemodiafiltration versus acetate-free biofiltration: a prospective crossover study; Ding F et al.; Online hemodiafiltration (online HDF) and acetate-free biofiltration (AFB) are 2 innovative renal replacement therapies . Convincing evidence has shown that both techniques are superior to conventional hemodialysis in many aspects . The aim of the present investigation was to compare online HDF and AFB in 12 stable maintenance hemodialysis patients in a prospective, randomized crossover trial . Twelve stable dialysis patients, age 49.7 +/- 11.3 years and on dialysis for 83.5 +/- 76.7 months, were treated prospectively and randomly by either AFB, predilution HDF (pre-HDF), or postdilution HDF (post-HDF) for a total of 36 weeks using exclusively F60S high-flux dialyzers . Routine blood biochemical tests, bone metabolism parameters, and clearance for both small and larger molecular weight substances were measured at defined intervals . During the trial period inter- and intradialysis symptoms, e.g., hypotensive episodes and intradialysis arterial blood gas analyses, were recorded . Both online HDF and AFB were well accepted by the overwhelming majority of patients and also by the dialysis staff . Pretreatment sodium, total and ionized calcium, chloride, bicarbonate, and urea did not differ within or between the 3 treatment groups . Potassium increased slightly in HDF patients while phosphate and beta2-microglobulin (beta2-M) decreased in all groups . After dialysis, AFB patients exhibited a significantly higher bicarbonate concentration and lower potassium level when identical potassium concentrations in dialysate were used . Patients receiving AFB manifested less intradialysis partial pressure of oxygen drop and partial pressure of carbon dioxide rise than those on HDF treatments . HDF treatments could afford higher single-pool and double-pool Kt/V, higher effective urea and beta2M clearance, and lower total interdialysis symptom scores than the AFB treatment method . While bone metabolism parameters did not differ between the 3 dialysis modalities, some parameters such as deoxypyridinoline in HDF and osteocalcin, pyridinoline, and deoxypyridinoline in AFB deteriorated at the end of the crossover study . Aluminum concentration decreased progressively to about one-third of prestudy values at the end of the study with all 3 treatments . AFB was associated with a lower predialysis mean arterial pressure (MAP), a smaller drop in MAP during treatment, and similar hypotension episodes compared with the 2 HDF treatments . Albumin concentration showed a trend to decrease during the first 2 months of the trial period followed by a slight increase thereafter but still significantly lower than initial value at the end of crossover . Both online HDF and AFB share most of the features of optimal renal replacement therapy . Online HDF is superior to AFB in such aspects as increased delivered dialysis dose both for small and larger molecular weight toxins and less interdialysis symptoms . On the other hand, AFB is associated with a smaller effect on arterial blood gas values and improved intradialysis hemodynamic tolerance . Some dialysis-related symptoms and complications in the case of our AFB practice could be attributable, at least in part, to low dialysate calcium level.

Water Environ Res, 2001 Nov-Dec, 73(6), 673 - 83
Aerated biofiltration for simultaneous removal of iron and polycyclic aromatic hydrocarbons from groundwater; Richard DE et al.; Filters incorporating the principles of biological accumulation have been used in Europe to remove iron from drinking water for many years . The authors of this study hypothesized that a modified biological iron-removing filter could simultaneously degrade polycyclic aromatic hydrocarbons (PAHs) in groundwater impacted by former manufactured gas plant (MGP) operations . The MGP-impacted groundwater obtained for this study had an average total iron concentration of 3.8 mg/L and an average total dissolved PAH concentration of 3.0 mg/L . Naphthalene was the primary PAH, with an average concentration of 2.8 mg/L . The groundwater was passed intermittently through duplicate gravel-media columns at 15 to 30 cm/d for 2 months while filtered air was delivered countercurrently at 4 mL/min . The columns remained partially saturated throughout the study . Flooding, which would have indicated plugging of the columns, was not observed, and the pressure needed to aerate the columns remained constant . Total iron in the effluent was below the detection limit of 0.1 mg/L (97% removal) for 40 days of operation . Removal of total PAHs, primarily two- and three-ring compounds, averaged 99% . This single-stage treatment process represents an economical alternative to biological treatment systems currently available for MGP-impacted groundwater that require pretreatment to remove iron.

Environ Sci Technol, 2002 Jan 15, 36(2), 247 - 53
Biofiltration of methyl tert-butyl ether vapors by cometabolism with pentane: modeling and experimental approach; Dupasquier D et al.; Degradation of methyl tert-butyl ether (MTBE) vapors by cometabolism with pentane using a culture of pentane-oxidizing bacteria (Pseudomonas aeruginosa) was studied in a 2.4-L biofilter packed with vermiculite, an inert mineral support . Experimental pentane elimination capacity (EC) of approximately 12 g m(-3) h(-1) was obtained for an empty bed residence time (EBRT) of 1.1 h and inlet concentration of 18.6 g m(-3) . For these experimental conditions, EC of MTBE between 0.3 and 1.8 g m(-3) h(-1) were measured with inlet MTBE concentration ranging from 1.1 to 12.3 g m(-3) . The process was modeled with general mass balance equations that consider a kinetic model describing cross-competitive inhibition between MTBE (cosubstrate) and pentane (substrate) . The experimental data of pentane and MTBE removal efficiencies were compared to the theoretical predictions of the model . The predicted pentane and MTBE concentration profiles agreed with the experimental data for steady-state operation . Inhibition by MTBE of the pentane EC was demonstrated . Increasing the inlet pentane concentration improved the EC of MTBE but did not significantly change the EC of pentane . MTBE degradation rates obtained in this study were much lower than those using consortia or pure strains that can mineralize MTBE . Nevertheless, the system can be improved by increasing the active biomass.

Environ Technol, 2001 Sep, 22(9), 1091 - 103
Gas characteristics before and after biofiltration treating odorous emissions from animal rendering processes; Luo J et al.; Studies of odour-control biofilters at two animal rendering plants were conducted . Biofilter influent and effluent gases were characterized using a gas chromatograph-mass spectrometer (GC-MS) and a GC fitted with an odour sniffing port . Overall odour-removal performance of the biofilters was evaluated using forced-choice dynamic-dilution olfactometers . GC-MS analysis revealed that the biofilter influent gases at each plant contained about 300 compounds . About 20% of these compounds were identified, and included hydrocarbons, ketones, heterocyclics, aldehydes, aromatics, carobxylic acids, esters, sulphur compounds, nitriles, an amine and an amide . About 20 identified compounds were present in both biofilter influent gases . The influent gas at Plant 1 contained more straight chain hydrocarbons, while the influent gas at Plant 2 contained more sulphur compounds and esters . Sensory evaluation of the gas samples using the GC-odour port technique indicated that about 45 compounds in the biofilter influent gases were odorous at Plant 1, and about 30 were odorous at Plant 2 . A variety of odour characters was observed in the two biofilter influent gases . The biofilters reduced the concentration of most of the odorous compounds to levels that were not detectable by the GC-odour port analysis . The rendering process gases had odour concentrations of between 59,000 and 1,000,000 OU m(-1) . The biofilters reduced the odour concentration by 82-99% and also reduced the "offensiveness" of the odour . Uneven gas distribution affected biofilter odour-removal performance.

Appl Occup Environ Hyg, 2002 Jan, 17(1), 10 - 4
Evaluation of bioaerosol exposures during conditioning of biofilter organic media beds; Barth E et al.; Biological media air filters (biofilters) are currently being used for the treatment of inorganic and organic gases from sewage treatment plants, industrial processes, and remediation systems . The media may be organic material such as compost, wood chips, or synthetic plastic media, each with a large surface area for microorganism growth and activity . An occupational health and safety graduate student team (OHS team) evaluated potential particulate and bioaerosol exposure from a biofilter unit process used to treat hydrogen sulfide (H2S) gas generated from a primary sludge settling unit process . The OHS team included an industrial hygiene/environmental health engineering specialist, an occupational safety specialist, an occupational health physician, and an occupational health nurse . Concerns were raised regarding the possibility of adverse health effects to maintenance workers during "conditioning" of the biofilter compost-like media beds . Conditioning activities may include in-situ rearrangement of the existing media, removal from the tank/surface, drying/reinsertion of the existing media, or complete removal of the media, and replacement with new . Neither the design engineering firm nor the manufacturer had specific written recommendations or precautions regarding exposure during the conditioning of the compost beds . No personal protection equipment has been used for this activity . The expected agents for adverse health effects associated with this unit process are respirable particulate dust and bioaerosols, which may contain viable bacteria and fungi, as well as endotoxin . Safety procedures are already in place for H2S . Mixed dust from the compost media bed may cause irritation of pre-existing health conditions such as asthma, chronic lung disease, and some skin conditions, and may also lead to new health problems such as inhalation fever, occupational asthma, hypersensitivity pneumonitis, skin rashes and/or skin infections, and upper or lower respiratory infections . Air samples were taken immediately before (background samples) and during a simulation of the conditioning procedure of one of the two compost beds . Airborne samples collected during the simulated procedure yielded more bacteria per volume of collected air than the background samples . These findings suggest an increased risk for bacterial infection during the conditioning procedure . The airborne samples cultured for fungi during the simulation were less than the background sample . Stachybotrys chartarum was not detected in a sample of the filter media . As with the fungi data, endotoxin air sampling yielded less endotoxin during the simulated conditioning procedure than in the background . Two inches of rain had fallen in the 24 hours preceding the sampling, soaking the upper layers of the compost media . Sampling during an actual conditioning procedure on a warm, dry day may yield additional evidence relevant to potential health risks from dust and microorganisms . Although the data is not representative of an actual conditioning procedure, the following common sense precautions are recommended: (1) Dust minimization during dry conditions can be achieved by thoroughly wetting the compost bed prior to removing the compost, and wetting the compost again before returning it to the bed . (2) Based on scientific literature rather than this project's sampling results, the use of an appropriate respirator should be proactively considered . In addition, consideration must be given to the worker's cardiopulmonary effects associated with respirator use, decreased work performance effects, and OSHA administrative requirements of a respirator protection program . (3) Workers with immunocompromised status, asthma, allergic rhinitis/conjunctivitis, or allergic conditions of the skin, eyes, or lungs should be excluded from this particular job, unless it can be shown that their personal protective equipment is effective . (4) Protective outer wear, goggles, and gloves should be worn to minimize health risks associated with clothing garments contaminated by microorganisms.

Protoplasma, 2001, 218(3-4), 117 - 24
Heavy metal localisation in mycorrhizas of Epipactis atrorubens (Hoffm.) Besser (Orchidaceae) from zinc mine tailings; Jurkiewicz A et al.; The metal distribution within mycorrhizal and nonmycorrhizal roots of Epipactis atrorubens collected from zinc mine tailings and an area rich in heavy metal ores (both located in southern Poland) was investigated . The tailings, consisting of post-flotation material, were characterised by high levels of toxic elements such as Zn, Pb, and Cd, while soil outside the tailings was also strongly enriched in heavy metals . Atomic absorption spectrometry and proton-induced X-ray emission analysis revealed that heavy metals were mostly accumulated within orchid roots . Elemental maps from proton-induced X-ray emission showed that plant root epidermis and fungal coils which had developed within cortical cells of roots collected from the zinc mine tailings were the main places of Zn and Pb accumulation, associated with increased concentrations of Fe, Cd, Ti, Mn, Si, Ca, and S . The mean content of Pb and Zn in the coils was 4 to 5 times higher than in the root epidermis . In mycorrhizal roots from the tailings a statistically significant decrease in Pb and Zn content towards the inside of the root was observed . The mean content of Pb in coils from roots of plants growing outside the tailings was about 1% of the concentration in root coils from the tailings . Coils selected from orchid roots originating from a site outside the tailings contained comparatively high concentrations of Zn, Cd, and Cu, which was probably due to the high content of these elements in the soil . The results presented suggest a biofiltering effect against heavy metals by orchid mycorrhizal fungi.

Water Res, 2001 Dec, 35(18), 4405 - 9
Removal of cadmium and manganese by a non-toxic strain of the freshwater cyanobacterium Gloeothece magna; Mohamed ZA; The ability of both living and dry cells of Gloeothece magna, a non-toxic freshwater cyanobacterium, to adsorb cadmium and manganese is demonstrated in this study . Chlorophyll a content of living cells was not influenced by either cadmium or manganese concentrations, indicating that adsorption of both Cd2+ and Mn2+ by living cells of G . magna, was independent of the metabolic state of the organism . Moreover, the adsorption of both Cd2+ and Mn2+ to living cells and dry cells, was dependent on the metal concentrations, and fitted the Freundlich adsorption isotherm . However, dry cells had larger binding capacity for both Cd2+ (Kf = 912.6) and Mn2+ (Kf = 2,398) than living cells (Kf = 151.4 & 63, respectively) . The role of the capsular polysaccharides, the main constituents of the cyanobacterial envelope, in binding these two metals was also studied . Polysaccharide extracts of this organism adsorbed high amounts of both Cd2+ (I15-425 microgmg(-1)) and Mn2+ (473-906 microgmg(-1)) . This study suggests that G . magna would probably be cultured in water bodies contaminated by heavy metals to ameliorate their toxicity . Also dry material of this cyanobacterium being a non-toxic species, could be used as a safe biofilter to remove toxic metals from drinking water.

Water Sci Technol, 2001, 44(9), 327 - 33
Removal of hydrogen sulfide and methyl mercaptan by a packed tower with immobilized micro-organism beads; Pinjing H et al.; To develop a more effective process for removing H2S and methyl mercaptan (MeSH), which are the important odorous components emitted from wastewater treatment facilities, a packed bed filled with immobilized micro-organism beads was studied . This study encompassed bacteria enrichment, evaluation of bacteria immobilization methods, determination of optimum operation parameters, such as environmental conditions for bacteria growth, removal rate of the packed bed etc . The experimental results are shown as follows: (1) the cultures able to metabolize H2S and MeSH can be enriched from activated sludge and the enrichment periods are 1-2 days and 7-10 days for H2S and MeSH, respectively; (2) the key environmental parameter influencing the cultures is pH value, the suitable ranges are 2-3 and 6-8 for H2S and MeSH, respectively; (3) the maximum removal rate for H2S and MeSH are 6500 g/m3 bed d and 4 g/m3 bed d, respectively; (4) the superficial M-M kinetics parameters are Vm: 11.2 g S/kg dry beads h and Ks: 95.8 mg/m3 for H2S, and Vm: 0.052 g S/kg dry beads and Ks: 2.1 mg/m3 for MeSH; (5) a two-stage biofilter operated in series under different pH values is recommended, which can remove the H2S and MeSH effectively.

Water Sci Technol, 2001, 44(9), 301 - 8
Removal of odor emitted from composting facilities using a porous ceramic biofilter; Park SJ et al.; A field experiment was conducted using a full-scale ceramic biofilter (approximately 150 m3/min) in order to determine the potential for biofiltration to remove malodorous gases from composting facilities . The main compounds found in malodorous gases were NH3 and H2S . These compounds were analyzed by a UV-spectrophotometer and gas chromatograph . The microbial carrier was a porous ceramic consisting of diatomite and fly ash . About 12 m3 of ceramic media inoculated with waste activated sludge were filled in the biofilter . The experimental conditions were space velocity of 500 hr(-1), empty bed residence time of 7.2 s, and linear velocity of 0.2 m/s . About 90 L/d of water were sprayed for the operation . The NH3 concentration in inlet gases ranged from 8 to 90 ppmv . The concentration of H2S ranged from 3.2-5.5 ppmv . The acclimation of the biofilter was slow, but more than 95% of removal efficiency was achieved after one month of operation . No nutrients were supplied to the biofilter . The pressure drop in the biofilter varied from 20-40 mmAq during the operation . The energy consumption of this biofilter was about 200 kW/d . It was estimated that the deodorization using this ceramic biofilter was successfully carried out to remove the odor emitted from composting facilities.

Water Sci Technol, 2001, 44(9), 287 - 93
Biofiltration of dichlorobenzenes; Roberge F et al.; The use of air biofiltration for the degradation of dichlorobenzenes (1,2-DCB and 1,4-DCB) was studied at a refinery site . At this plant, 93 m3/h of contaminated groundwater, used in a cooling system and containing a maximum of 2 ppm of dichlorobenzenes, had to be treated . Stripping of the DCBs followed by biofiltration was selected as the most suitable technology to avoid volatilization in ambient air as expected with a wastewater aerobic treatment system . A stripper of 15 m height and 1.27 m diameter was designed as a first step treatment to volatilize DCBs with 3400 m3/h of air . Two f ull-scale biofilters of 70 m3 each were built and filled with 45 m3 of filtering media for the adsorption and biodegradation of the DCBs in the gas-phase . Filtering media was composed mainly of peat moss, with animal manure, wood chips and DCBs contaminated soil . Air to be treated was also contaminated with naphthalene . Laboratory tests showed an effective microbial activity in the contaminated soil and in the filtering media for DCBs degradation . Degradation of naphthalene induced slower degradation of DCBs . Full-scale operation was studied during four months . Water flow and DCBs content in the water entering the stripper were lower than expected with only 57 m3/h and a maximum concentration of only 240 ppb . Effective desorption was obtained in the stripper in the full-scale operation (more than 99% removal) . Full-scale biofilters maintained a DCB concentration of less than 1 ppmv in the air outlet, but removal efficiency varied between 0 and 79% because of the low DCB inlet concentrations, load variations and sporadic naphthalene presence.

Water Sci Technol, 2001, 44(9), 277 - 85
A pilot-scale study on biofilters for controlling animal rendering process odours; Luo J; Heating of animal tissue during the process of rendering liberates a variety of odorous compounds . The performance of biofiltration in removing these odours was investigated using pilot-scale biofilters containing different media (sand, finely and coarsely crushed wood bark, and bark/soil mixture) . Odour-removal performance of the biofilters was determined using olfactometry . Biofilter odour removal efficiencies of between 29.7% and 99.9% were measured at influent odour concentrations of between 143,100 and 890,000 odour units m(-3), and various air loading rates (0.074-0.592 m(-3) air m(-3) medium min(-1)) . Biofilters with bark or bark/soil media and low air loading rates gave the best odour removal . The bark and sand biofilters generally maintained good odour reduction for about three years at an air loading rate of 0.148 m(-3) air m(-3) medium min(-1) . Drainage from the biofilters contained significant concentrations of nitrogenous and organic compounds, suggesting that controlled leaching has the potential to remove accumulated substances in biofilter media from rendering gas emissions and increase the longevity of a biofilter system . High pressure drop across biofilter media can adversely affect the odour removal performance . Sand and fine bark, due to their small particle size, caused high pressure drops . Coarse bark showed negligible pressure drop at several examined air loading rates . Pressure drop also increased with moisture content, particularly in sand and fine bark biofilters . Overall pressure drop characteristics of the biofilters described in this paper were maintained without significant change over the three year operation.

Water Sci Technol, 2001, 44(9), 261 - 7
Biofilter media mixture ratio of wood chips and compost treating swine odors; Nicolai RE et al.; Biofilter media mixtures were compared in 18 pilot-scale biofilters treating pit gases from a swine facility . The compost and wood chips mixtures ranged from 100% wood chips to a 50-50 blend in 10% increments . The effect of three media moisture contents (low, medium, and high) on biofilter performance was also evaluated . Odor and hydrogen sulfide reduction did not change significantly for mixtures with greater than 20% compost . For efficient odor, hydrogen sulfide, and ammonia reduction media moisture must be greater than 40% wb . Media moisture content influenced odor, hydrogen sulfide, and ammonia reduction more than the ratio of compost and wood chips . The count of heterotrophic or sulfur-oxidizing bacteria did not change in a discernable pattern with respect to media mixture or moisture content . As the amount of compost increased in the media mixtures, the pressure drop also increased . Based on this experiment, the recommended mixing ratio of compost to wood chips for biofilters on swine facilities is minimum 30% compost and 70% wood chips by weight.

Water Sci Technol, 2001, 44(9), 253 - 60
Biofilters--the influence of different filter materials and different operating conditions on the reduction efficiency; Hartung E et al.; A series of biofilter materials were tested for performance efficiency in treating ventilation air from pig sheds . Two different phases were conducted . In phase A five different biofilter materials were tested with the aim of selecting the best material regarding the odor reduction and over all efficiency . In conclusion of phase A, biochips, a new filter material, was selected due to its high average odor reduction (81%) in combination with a very low flow resistance (less than 30 Pa for filter volume loads of 600 m3 h(-1) m(-3)) . In phase B, biochips and coconut fiber peat were tested under different operating conditions . Biofilters number 3 and 4 each with down-flow air supply could realize a higher average odor reduction than biofilter 5 with up-flow air supply . All three filter materials had the same moisture, however the two biofilters with down-flow air supply showed a more homogenous moisture distribution but they also used approximately three times more water than biofilter 5 . Like in phase A the specific odor cleaning efficiency was mainly influenced by the specific odor loading rate and showed only slight differences between the five biofilters differing in bulk layer height (0.5 m and 1.0 m) and air supply mode . All in all the investigation showed that the efficiency of biofilters can be optimized by using an new filter material and a appropiate operating mode.

Water Sci Technol, 2001, 44(9), 227 - 32
Biofilters based on the action of fungi; van Groenestijn JW et al.; Traditional biofilters for waste gas treatment are mainly based on the degradation activity of bacteria . The application of fungi in biofilters has several advantages: fungi are more resistant to acidification and drying out, and the aerial mycelia of fungi form a larger surface area in the gas phase than bacterial biofilms, which may facilitate the uptake of hydrophobic volatile compounds . The research described here identifies important conditions for the operation of fungal-based biofilters . Biofilters with perlite packing were operated at different pHs and relative inlet gas humidities . Toluene was used as a model pollutant . It was shown that a low pH is a prerequisite for fungal growth in biofilters . Also, the fungal biofilters were more resistant to drying out and more active than the bacterial biofilters . Fungal biofilters eliminated 80-125 g toluene/m3 filterbed/h . Several measures that could limit the clogging of fungal biofilters with fungal biomass were investigated . The introduction of mites helped to control excessive fungal growth and pressure drop . The pressure drop of a perlite/fungi/mites filter of 1 m height, loaded with 200 m3 gas/m3 filter/h stabilised around 130 Pa . Biofilters based on the action of fungi are cost-effective for the treatment of waste gases containing aromatic compounds, alkenes and other hydrophobic compounds.

Water Sci Technol, 2001, 44(9), 219 - 26
Biotreatments of odours: control and performances of a biofilter and a bioscrubber; Le Cloirec P et al.; Biotechnology has been applied to find systems to decrease the level of pollution . The main biological systems used in the deodorisation of waste gases are biofilters, biotrickling filters and bioscrubbers . These technologies work at normal operating conditions of temperature and pressure, and therefore they are relatively cheap with high efficiencies when the waste gas is characterised by high flow and low concentrations of odorous compounds . The aim of this work was to study the influence of different parameters (residence time of the gas phase, pollutant loads) of a biofilter and a bioscrubber on removal efficiencies . Ethanol was used as pollutant compound, because it is representative of both volatile organic compounds and odorous molecules . The performances of the two biological systems are presented and discussed . The use of pressure drop monitoring as a tool to control the operation of a biofilter and to obtain optimal conditions in a bioscrubber is proposed.

Biotechnol Bioeng, 2001 Dec 5, 75(5), 550 - 8
Removal of toluene in a vapor-phase bioreactor containing a strain of the dimorphic black yeast Exophiala lecanii-corni; Woertz JR et al.; Stricter regulations on volatile organic compounds and hazardous air pollutants have increased the demand for abatement technologies . Biofiltration, a process in which contaminated air is passed through a biologically active bed, can be used to remove these pollutants from air streams . In this study, a fungal vapor-phase bioreactor containing a strain of the dimorphic black yeast, Exophiala lecanii-corni, was used to treat a gas stream contaminated with toluene . The maximum toluene elimination capacity in short-term tests was 270 g m(-3) h(-1), which is 2 to 7 times greater than the toluene elimination capacities typically reported for bacterial systems . The fungal bioreactor also maintained toluene removal efficiencies of greater than 95% throughout the 175-day study . Harsh operating conditions such as low moisture content, acidic biofilms, and nitrogen limitation did not adversely affect performance . The fungal bioreactor also rapidly reestablished high toluene removal efficiencies after an 8-day shutdown period . These results indicate that fungal bioreactors may be an effective alternative to conventional abatement technologies for treating high concentrations of pollutants in waste gas streams .

J Hazard Mater, 2002 Jan 28, 89(2-3), 253 - 65
Biofiltration of volatile ethanol using sugar cane bagasse inoculated with Candida utilis; Christen P et al.; Candida utilis (C . utilis) growing on sugar cane bagasse complemented with a mineral salt solution was studied for gaseous ethanol removal in a biofilter . Ethanol loads from 93.7 to 511.9 g/h m(3) were used, by varying both inlet ethanol concentration (9.72 to 52.4 g/m(3)) and air flow rate (1.59 x 10(-3) to 2.86 x 10(-3) m(3)/h) . At a loading rate of 93.7 g/h m(3), a steady-state was maintained for 300 h . Ethanol removal was complete, and 76.3% of the carbon consumed was found in carbon dioxide . At an higher aeration rate (ethanol load=153.8 g/h m(3)), the biofilter displayed an average removal efficiency (RE) of 70%, and an elimination capacity (EC) of 107.7 g/h m(3) . Only 64.4% of the carbon consumed was used for CO(2) production . Acetaldehyde and ethyl acetate in the outlet gas attained 7.86 and 20.4% in terms of carbon balance, respectively . In both cases, the transient phase was less than one day . At a high inlet ethanol concentration (52.4 g/m(3)), no steady-state was observed and the process stopped during the third day . In the three cases, final biomass was poor, ranging from 10.5 to 14.8 mg/g dm . Final pH 4.0-4.6, indicated that acidifying non-volatile metabolites, such as acetate, accumulated in the reactor.

Environ Sci Technol, 2001 Nov 1, 35(21), 4347 - 52
Treatment of volatile organic compounds in a biotrickling filter under thermophilic conditions; Kong Z et al.; The objectives of this research were to investigate the potential to biologically treat volatile organic compounds emitted by the forest products industry at thermophilic conditions and to examine the microbial community developed at high temperatures . Three biotrickling filters were run in parallel at temperatures ranging from 40 degrees C (mesophilic control) to 70 degrees C . The first phase involved treatment of methanol, for a 3-month run, and the second phase involved a 260-day run on the treatment of alpha-pinene . Methanol removal rates over 100 g m(-3) h(-1) where achieved at temperatures up to 70 degrees C . Alpha-pinene removal was achieved at temperatures up to 60 degrees C with optimal treatment occurring at 55 degrees C at rates up to 60 g m(-3) h(-1) . The time for acclimation increased with increasing temperature and was longer for pinene than for methanol . Filter performance was also able to quickly recover from a shutdown period of up to 2 weeks due to the robustness of the microbial communities as determined by DNA fingerprinting analysis . The high-temperature communities treating methanol or pinene were more similar to each other than the mesophilic communities (i.e., 40 degrees C) . The mesophilic methanol community had a high degree of functional redundancy, while the mesophilic pinene community was more unique and very distinct from the others . These results show that biofiltration at high temperatures is achievable and opens up a range of possibilities for applying biofiltration to hot gas streams.

Folia Microbiol (Praha), 2001, 46(3), 211 - 6
The start-up period of styrene degrading biofilters; Weigner P et al.; Styrene vapors from contaminated air were eliminated using long-term adapted mixed microbial culture inoculated on four perlite packed biofilters (serial arrangement, up-flow configuration) . During start-up the inlet concentration of styrene rose from 175 to 1300 mg/m3 of total carbon . The total actual residence time in the four biofilters was 24 s . Styrene was successfully degraded by the microbial population in the biofilter . An average of 66% of eliminated styrene was transformed to CO2 . The removal efficiency of the pollutant was, after 18 d of start-up, nearly 85% at an organic load of 170 g/m3 per h . The concentration profiles along the bed height were linear for various pollutant inlet concentrations . The total amount of microorganisms in analyzed biomass from the biofilters was about 10(9) per gram of dry packing mass . The moisture content was around 80% in all biofilters.

Folia Microbiol (Praha), 2001, 46(3), 205 - 9
Effect of pH and loading manner on the start-up period of peat biofilter degrading xylene and toluene mixture; Marek J et al.; Laboratory-scale biofilters packed with a mixture of peat, bark and wood were used for xylene and toluene removal from waste air . Two kinds of peat, which differed in the resulting pH of the leachate, were chosen for degradation of the pollutants by a mixed culture . Using peat with the lower pH value, the feasibility of single and multiple pollutant loading during the start-up period and augmentation with Pseudomonas putida strains were characterized . The lower pH value of the bed resulted in higher efficiency of toluene degradation from the mixture of pollutants . At higher pH values better degradation of both pollutants was achieved . Regarding the manner of loading during the start-up period, the best results were obtained using toluene as a single pollutant in the initial phase of operation . Pseudomonas strains demonstrated a high ability to degrade both pollutants; more efficient degradation for xylene than for toluene was observed at high loading rates.

Biodegradation, 2000, 11(6), 423 - 7
Application of biofiltration to the degradation of hydrogen sulfide in gas effluents; Elias A et al.; A laboratory scale bioreactor has been designed and set up in order to degrade hydrogen sulfide from an air stream . The reactor is a vertical column of 7 litre capacity and 1 meter in height . It is divided into three modules and each module is filled with pellets of agricultural residues as packing bed material . The gas stream fed into the reactor through the upper inlet consists of a mixture of hydrogen sulfide and humidified air . The hydrogen sulfide content in the inlet gas stream was increased in stages until the degradation efficiency was below 90% . The parameters to be controlled in order to reach continuous and stable operation were temperature, moisture content and the percentage of the compound to be degraded at the inlet and outlet gas streams (removal or elimination efficiency) . When the H2S mass loading rate was between 10 and 40 g m(-3) h(-1), the removal efficiency was greater than 90% . The support material had a good physical performance throughout operation time, which is evidence that this material is suitable for biofiltration purposes.

ASAIO J, 2001 Sep-Oct, 47(5), 516 - 21
Do different dialytic techniques have different atherosclerotic and antioxidant activities?
Biasioli S, Schiavon R, Petrosino L, Cavallini L, De Fanti E, Zambello A, Borin D, Targa L.
To compare the chronic effect of several dialytic techniques (bicarbonate dialysis, BHD; acetate free biofiltration, AFB; hemodiafiltration, HDF; paired filtration dialysis, PFD) on atherosclerosis and antioxidant activity, three different indices were created . The first (atherosclerotic index = AI) is formed using the sum of three plasma substances: MDA, Hcy, and Cys (malondialdehyde, homocysteine, cysteine) . The second (antioxidant activity index = AOAI) is the sum of five erythrocyte (E) parameters: E-GSH, GPx, CAT, SOD, GR (E-glutathione, E-glutathione peroxidase, E-catalase, E-superoxide dismutase, E-glutathione reductase) . The third (defense index = DI) is derived from the previous two: (AOAI - AI) . The indices were so expressed as AI in mmol/L, AOAI in U/g hemoglobin (Hb), and DI in arbitrary units . These indices were calculated in 20 controls and 51 chronic HD patients (26 female, 25 male) before, during, and after the first session of the week . HD patients were divided according to their dialytic technique: BHD, n = 35; AFB, n = 5 patients; HDF, n = 7 patients; or PFD = 4 patients . All patients had been treated with a given technique for at least 12 months, before entering the study . As expected, HD patients had AI values higher than controls, both before and after the session, with a mean value of 541 (before) and 331 (after), whereas controls had a mean value of 205 . The AOAI was lower than controls, both before and after the session, the mean value being 1,122 (before) and 1,582 (after), that of controls being 2,424 . In all cases, PFD gave the best "acute" results; at the end of a PFD session, near normal values of AI, AOAI, and DI (defensive index = AOAI - AI) were obtained.

Water Sci Technol, 2001, 44(4), 159 - 66
Biodegradation of disperse blue 79 using sequenced anaerobic/aerobic biofilters; Cruz A et al.; A sequential anaerobic/aerobic treatment process was used to biodegrade the azo dye disperse blue 79 (DB79) . The integrated process was successfully tested and operated for the mineralization of the DB79 dye until a concentration of 120 mg/l in 96 h . In the first stage, the anaerobic biofilter biotransformed the DB79 to amines with efficiencies of decolorization higher than 95% in 72 h . The amines produced in the first stage were degraded in the aerobic biofilter with efficiencies of 65% in 24 h . It was observed that the use of a co-substrate on the anaerobic biofilter influenced the performance of the bioreactor only when the concentration of the DB79 was higher than 48 mg/l . It was found that the residual dye in the effluent of the anaerobic stage inhibits the performance of the aerobic microorganisms.

Water Sci Technol, 2001, 44(4), 151 - 7
Degradation of p-nitrophenol in a batch biofilter under sequential anaerobic/aerobic environments; Melgoza RM et al.; A combined process anaerobic/aerobic in a single reactor was studied, P-nitrophenol (PNP) was used as the model compound . During the anaerobic stage the target compound is modified in such a way that the intermediate product is more readily biodegradable by the aerobic phase . A pilot biofilter was used for the experiment . The biofilter was packed with a volcanic stone (puzolane) to serve as support to the microorganisms and it was inoculated with activated sludge . The microorganisms were acclimated with an initial concentration of 25 mg PNP/l during 75 days (25 cycles) . After 230 days of operation, the reaction time of the cycles was reduced to 11.5 h (8 h for the anaerobic phase and 3.5 h for the aerobic one) . The PNP was transformed to p-aminophenol (PAP) in the anaerobic phase, with efficiencies near to 100% . A mineralization of 100% of the PAP was found in the oxidative stage . Global efficiencies of PNP mineralization of 98% were obtained . The reaction rates were 16 mg PNP/l-h (PNP uptake), 14 mg PAP/l-h (PAP formation) and 20 mg/l-h (PAP mineralization).

Appl Environ Microbiol, 2001 Oct, 67(10), 4796 - 804
Stable-isotope-based labeling of styrene-degrading microorganisms in biofilters; Alexandrino M et al.; Deuterated styrene ({(2)H(8)}styrene) was used as a tracer in combination with phospholipid fatty acid (PLFA) analysis for characterization of styrene-degrading microbial populations of biofilters used for treatment of waste gases . Deuterated fatty acids were detected and quantified by gas chromatography-mass spectrometry . The method was evaluated with pure cultures of styrene-degrading bacteria and defined mixed cultures of styrene degraders and non-styrene-degrading organisms . Incubation of styrene degraders for 3 days with {(2)H(8)}styrene led to fatty acids consisting of up to 90% deuterated molecules . Mixed-culture experiments showed that specific labeling of styrene-degrading strains and only weak labeling of fatty acids of non-styrene-degrading organisms occurred after incubation with {(2)H(8)}styrene for up to 7 days . Analysis of actively degrading filter material from an experimental biofilter and a full-scale biofilter by this method showed that there were differences in the patterns of labeled fatty acids . For the experimental biofilter the fatty acids with largest amounts of labeled molecules were palmitic acid (16:0), 9,10-methylenehexadecanoic acid (17:0 cyclo9-10), and vaccenic acid (18:1 cis11) . These lipid markers indicated that styrene was degraded by organisms with a Pseudomonas-like fatty acid profile . In contrast, the most intensively labeled fatty acids of the full-scale biofilter sample were palmitic acid and cis-11-hexadecenoic acid (16:1 cis11), indicating that an unknown styrene-degrading taxon was present . Iso-, anteiso-, and 10-methyl-branched fatty acids showed no or weak labeling . Therefore, we found no indication that styrene was degraded by organisms with methyl-branched fatty fatty acids, such as Xanthomonas, Bacillus, Streptomyces, or Gordonia spp.

Appl Environ Microbiol, 2001 Oct, 67(10), 4678 - 84
Generation of metal-binding staphylococci through surface display of combinatorially engineered cellulose-binding domains; Wernerus H et al.; Ni(2+)-binding staphylococci were generated through surface display of combinatorially engineered variants of a fungal cellulose-binding domain (CBD) from Trichoderma reesei cellulase Cel7A . Novel CBD variants were generated by combinatorial protein engineering through the randomization of 11 amino acid positions, and eight potentially Ni(2+)-binding CBDs were selected by phage display technology . These new variants were subsequently genetically introduced into chimeric surface proteins for surface display on Staphylococcus carnosus cells . The expressed chimeric proteins were shown to be properly targeted to the cell wall of S . carnosus cells, since full-length proteins could be extracted and affinity purified . Surface accessibility for the chimeric proteins was demonstrated, and furthermore, the engineered CBDs, now devoid of cellulose-binding capacity, were shown to be functional with regard to metal binding, since the recombinant staphylococci had gained Ni(2+)-binding capacity . Potential environmental applications for such tailor-made metal-binding bacteria as bioadsorbents in biofilters or biosensors are discussed.

Environ Technol, 2001 Aug, 22(8), 927 - 40
Biofiltration of air contaminated with toluene; Elmrini H et al.; In industrial activities, operation of air biofilters may be interrupted for a long period of time . In order to examine the effect of shut-down on the performance of biofilters, a pilot scale biofiltration unit was restarted up after a non-use duration of eight months . After a reacclimation period of eight days, the biofilter reached an elimination capacity of 35 g x m(-3) x h(-1) compared to 38 g x m(-3) x h(-1) before shut-down, for the same operating conditions . The results obtained indicate that the microorganism activity was completely restored and this was confirmed by the microbial count tests performed on filter bed material samples . The impact of varying the inlet concentration of toluene on biofilter performance was also investigated . A maximum elimination capacity of 120 g x m(-3) x h(-1) was achieved, compared to 135 g x m(-3) x h(-1) before shut-down . The biofilter removal efficiency exceeded 96% for inlet concentrations up to 1.8 g x m(-3) . Temperature measurements revealed that the filter bed temperature depends strongly on the intensity of microbial activity and the biofilter effectiveness in eliminating toluene . Experimental data were compared with the calculations of a mathematical model . Comparison showed that the theoretical model was successful in predicting the performance of the biofiltration unit.

Appl Microbiol Biotechnol, 2001 Aug, 56(3-4), 339 - 49
Microbial degradation and fate in the environment of methyl tert-butyl ether and related fuel oxygenates; Fayolle F et al.; Oxygenates, mainly methyl tert-butyl ether (MTBE), are commonly added to gasoline to enhance octane index and improve combustion efficiency . Other oxygenates used as gasoline additives are ethers such as ethyl tert-butyl ether (ETBE), tert-amyl methyl ether (TAME), and alcohols such as tert-butyl alcohol (TBA) . As a result of its wide use, MTBE has been detected, mainly in the USA, in groundwater and surface waters, and is a cause of concern because of its possible health effects and other undesirable consequences . MTBE is a water-soluble and mobile compound that generates long pollution plumes in aquifers impacted by gasoline releases from leaking tanks . Field observations concur in estimating that, because of recalcitrance to biodegradation, natural attenuation is slow (half-life of at least 2 years) . However, quite significant advances have been made in recent years concerning the microbiology of the degradation of MTBE and other oxygenated gasoline additives . The recalcitrance of these compounds results from the presence in their structure of an ether bond and of a tertiary carbon structure . For the most part, only aerobic microbial degradation systems have been reported so far . Consortia capable of mineralizing MTBE have been selected . Multiple instances of the cometabolism of MTBE with pure strains or with microflorae, growing on n-alkanes, isoalkanes, cyclohexane or ethers (diethyl ether, ETBE), have been described . MTBE was converted into TBA in all cases and was sometimes further degraded, but it was not used as a carbon source by the pure strains . However, mineralization of MTBE and TBA by several pure bacterial strains using these compounds as sole carbon and energy source has recently been reported . The pathways of metabolism of MTBE involve the initial attack by a monooxygenase . In several cases, the enzyme was characterized as a cytochrome P-450 . After oxygenation, the release of a C -unit as formaldehyde or formate leads to the production of TBA, which can be converted to 2-hydroxyisobutyric acid and further metabolized . Developments in microbiology make biological treatment of water contaminated with MTBE and other oxygenates an attractive possibility . Work concerning ex situ treatment in biofilters by consortia and by pure strains, and involving or not cometabolism, is under way . Furthermore, the development of in situ treatment processes is a promisinggoal.

Water Sci Technol, 2001, 44(2-3), 243 - 9
Odour removal with a trickling filter at a small WWTP strongly influenced by the tourism season; Patria L et al.; Etaples-Le Touquet's wastewater treatment plant (WWTP) is based on a coastal area of the Artois-Picardie region . The pollution load can vary from 20,000 p.e . to 60,000 p.e . over a weekend or in summer . The Collectivity and the Water Agency decided to cover and ventilate the main odour source points of the plant . The foul air was directed to a 2,500 m3/h inorganic bed biofilter (Alizair) for odour control . An odour monitoring took place during the first year of operation taking into account cold and warm seasons, high and low tourism seasons . The Alizair biofilter appeared an appropriate odour control process for small sized wastewater treatment plants, easy to operate and efficient even in areas where tourism seasons have a great impact on the pollution load arriving at the plant . The neighbourhood did not complain about odours any more and the operator was very confident with such a simple and effective system . The local Authorities and the Water Agency agreed to recommend Alizair biofilters with an autotrophic biomass adapted in the case of an old WWTP that cannot be up graded any more or for large pumping stations and wastewater storage prior treatment.

Life Support Biosph Sci, 1998, 5(1), 63 - 9
The use of biofilters to improve indoor air quality: the removal of toluene, TCE, and formaldehyde; Darlington A et al.; A biofilter composed of a scrubber, a hydroponic planting system, and an aquatic system with green plants as a base maintained air quality within part of a modern office building . The scrubber was composed of five parallel fiberglass modules with external faces of porous lava rock . The face, largely covered with mosses, was wetted by recirculating water . Air was drawn through the scrubber and the immediately adjacent hydroponic region by a dedicated air handling system . The system was challenged for 4 weeks with three common indoor organic pollutants and removed significant amounts of all compounds . A single pass through the scrubber removed 10% of the trichloroethylene and 50% of the toluene . A single pass lowered formaldehyde air concentrations to 13 micrograms m-3 irrespective of influent levels (ranging between 30 and 90 micrograms m-3) . The aquatic system accumulated trichloroethylene but neither toluene nor formaldehyde, suggesting the rapid breakdown of these materials . The botanical components removed some pollutants.

Life Support Biosph Sci, 1998, 5(1), 107 - 16
An ecological life support system for fish for 100-day experiments; Taub FB et al.; An aquatic habitat of 1.7 L was designed to support three adult fish (medaka, Oryzias latipes) for 100 days with minimal exchange of water . The Aquatic Habitat consisted of a specimen chamber (800 ml), biofilter chamber and associated tubing (250 ml), and a microbial control chamber (650 ml), filled with water . Fish were fed daily . The water was oxygenated via a hollow fiber oxygenator . The liquid flow rate was 30 ml/min and the air flow as 100 ml/min . Six units were established . Fish mortalities, when they occurred, were often associated with failures of the water flow system and lack of oxygen being supplied from the oxygenator . The bacterial community, from three "Bio-Chem Stars" inoculated from a medaka aquarium, transformed ammonia and prevented toxic conditions from occurring . The bacteria were grazed by protozoa, rotifers, nematodes, oligochaetes, and ostracods in all habitats . In three of six habitats, Daphnia and amphipods had been purposely introduced; their survival was variable . Biofilm and settled particulates accumulated during the experiment and eventually exceeded the weight of the fish . Of six units, two supported the initial fish through the whole experiment, another experienced fish mortalities, but replacement fish survived, and three units did not support fish survival for the 100 days . Our results demonstrated the feasibility of the system, but many improvements are needed such as improved water flow and oxygen monitoring to assure prompt corrective action.

Nephrol Dial Transplant, 2001 Sep, 16(9), 1914 - 9
Effect of acetate-free biofiltration on the anaemia of haemodialysis patients: a prospective cross-over study; Basile C et al.; BACKGROUND: The discussion about the pathogenesis of renal anaemia, whether it is primarily due to relative erythropoietin (Epo) deficiency or to uraemic inhibition of erythropoiesis, is still open . Although it has so far not been possible to identify or isolate a substance retained in uraemia with a suppressive action directed specifically against red-cell production, dialysis therapy can improve the effect of both residual endogenous Epo and exogenous rHuEpo . To what extent the mode and/or the dose of dialysis influence Epo efficacy is as yet poorly understood . METHODS: This study was performed as a single-centre trial . The protocol included a run-in period of 4 months followed by a prospective cross-over study including 6 months each of acetate-free biofiltration (AFB) with a high-flux biocompatible membrane and standard bicarbonate dialysis (BD) with a low-flux cellulosic membrane in a random sequence . AFB is a haemodiafiltration technique based on a continuous post-dilution infusion of a sterile isotonic bicarbonate solution . At the start of the run-in period (and for the entire length of the study), rHuEpo administration was withdrawn; patients whose haemoglobin (Hb) levels dropped at a level <8.0 g/dl at one single monthly check, had to be withdrawn from the study . A blood sample was collected every month for the blood gas analysis and for the determination of blood urea nitrogen, serum creatinine, sodium, potassium, calcium, phosphorus, Hb, erythrocyte, reticulocyte, leukocyte and thrombocyte cell counts, mean globular volume and haematocrit . An equilibrated single pool Kt/V(urea)>1.2 was mandatory in both treatment modalities . Serum iron, total iron-binding capacity, and ferritin were checked every 3 months . RESULTS: Twenty-three of 137 haemodialysis patients were considered eligible for the trial on the basis of the entry criteria . Of these, 15 volunteered and only 10 completed the study . No significant differences in the haematological indices, in the biochemical parameters assessing body iron stores, or in i.v . iron dosage was observed when comparing AFB with BD treatments . The equilibrated single pool Kt/V(urea) was always >1.2 and in no case was a significant difference observed when comparing AFB with BD treatments . Treatment time was significantly different between the two treatments (262+/-2 min in BD and 249+/-1 in AFB, P<0.0001) . Neither pre- nor post-dialysis systolic and diastolic blood pressures, pre-dialysis serum bicarbonate and pH, pre-dialysis serum sodium, potassium, calcium, or phosphorus were significantly different when comparing the two treatment modalities . All 10 patients completed the 1-year follow-up without any major side-effects . CONCLUSIONS: Our study did not show any improvement of anaemia when treating a highly selected patient group, in the absence of any Epo therapy, with AFB compared with standard BD . Even though these conclusions cannot be extended in toto to the entire dialysis population, in which there is a large proportion of Epo-treated patients with Hb levels around 11 g/dl, we may nevertheless conclude that when patients are well selected, adequately dialysed, and not iron- and/or vitamin-depleted, the effect of a haemodiafiltration technique with a high-flux biocompatible membrane is less than might be expected from the results of uncontrolled studies.

J Air Waste Manag Assoc, 2001 Aug, 51(8), 1237 - 44
Sorption and biodegradation of vapor-phase organic compounds with wastewater sludge and food waste compost; Kim HJ et al.; To test the possible use of composted food waste and wastewater sludge as biofilters to treat gas-phase volatile organic compounds (VOCs), batch experiments were conducted with an isolated strain that could degrade aromatic compounds under aerobic conditions . A benzene and trichloroethylene (TCE) mixture was used as the gas-phase pollutant in experiments with composted food waste, sludge, and soil . Under aerobic conditions, benzene was degraded as a primary substrate and TCE was degraded cometabolically, with water contents varying from 6 to 60% (volume of water added/volume of solid) . Optimal water content for VOC removal was 12% for the soil, 36% for the composted food waste, and 48% for the sludge . The extent of VOC sorption and biodegradation at the optimal water content was different for each material . With the same initial VOC concentration, more VOCs were removed by sorption onto the composted food waste and the sludge, while less VOCs were biodegraded in comparison with the results using soil . The reason the biodegradation in the soil was greater may be partly attributed to the fact that, due to less sorption, the aqueous-phase concentration of VOCs, which microorganisms could utilize as a carbon source or cometabolize, was higher . We also speculate that the distribution of microorganisms in each medium affects the rate of biodegradation . A large number of microorganisms were attached to the composted food waste and sludge . Mass transfer of VOCs and oxygen to these microorganisms, which appear to have been heterogeneously distributed in clusters, may have been limited, resulting in hindered biodegradation.

Water Sci Technol, 2001, 44(1), 57 - 65
The characteristics of phosphorus removal in an anaerobic/aerobic sequential batch biofilter reactor; Chiou RJ et al.; Previous research has shown that alternated anaerobic/aerobic conditions are effective in removing phosphorus from wastewater using a biofilter system . However, few studies have been conducted on the features of polyphosphate (poly-P) accumulating organisms (PAOs) in biofilm on phosphorus removal . This study investigated the characteristics of the phosphorus removal mechanism in various hydraulic loads and anaerobic/aerobic time ratios using a sequential batch biofilter reactor . The storage and release of intracellular inclusions, especially polyhydroxyalkanoates (PHAs) and poly-P, would be an important factor for phosphorus removal . Under different operating conditions, total phosphorus removal was always determined by accumulation of PHAs and phosphorus release under the anaerobic phase . The PHA accumulation under the anaerobic phase was always in proportion to the biofilm phosphorus content under aerobic conditions . The result shows PAOs activity was closely related to PHA accumulation . However, the PHA accumulation under the anaerobic phase would be dependent on the hydrolysis of the complex carbon source into short chain fatty acids (SCFA) . The result would be demonstrated by the simple carbon source effect . The effect of the An/Ox time ratio on TP removal was significant . Shorter anaerobic time would result in insufficient phosphorus release and greater time would result in inactive PAOs . The appropriate An/Ox time ratio was suggested as 1/2 . Comparisons of the phosphorus removal characteristics between biofilm and suspended growth under the same growth conditions are discussed in detail.

An Med Interna, 2001 Apr, 18(4), 175 - 80
{Pre-occupying increase in diabetes as cause for terminal kidney failure . Evaluation of treatment strategies}; Perez Garcia R et al.; OBJECTIVE: To study the incidence, prevalence, treatment modalities and prognosis of diabetic patients on renal replacement therapy . MATERIAL: We studied all end-stage renal failure (ESRF) diabetic patients on renal replacement therapy in "Area Sanitaria 1" in Madrid from 1978 to 1998 . RESULTS: Diabetes mellitus has become the leading cause of ESRF in our health area of Madrid, 30% of all causes of ESRF . Incidence of diabetics beginning RRT was 33.3 per million population (pmp) in 1998, while in 1993-94 diabetes was 15% and 21 pmp, respectively, table 1 . The proportion of diabetics on RRT has increased from 7.4% 1986 to 12.7% 1998 . The prevalence of diabetics on RRT in 1998 was 135 pmp, with an overall prevalence of 1054 pmp . At the mean time, the proportion between incident diabetics type 2/diabetics on RRT has increased from 15% in 1987-88, to 54% in 1993-94 and to 81% in 1997-98, consequently, mean age of diabetic patients at beginning RRT has increased from 47 years before 1988, 58 in 1989-90, 61 in 1993-94, 62 in 1995-96 and 63 in 1997-98 (Table I) . We studied 182 diabetics admitted for renal replacement therapy, 106 males and 76 females, 105 were diabetics type 1 and 77 type 2 . Their mean age at RRT beginning was 57.12 years (SD) . Hemodialysis (HD) was the first modality of treatment for 128 (70%) diabetics and CAPD for 54 . Seventy out of 128 patients on HD were dialyzed in the Hospital Unit, 40% on AFB (acetate free biofiltration) and 58 in two Satellite Units, that means a higher proportion of diabetics on CAPD and on HD in Hospital Unit . Diabetics allocated to CAPD were 5 years, as mean, younger than patients allocated to HD (p < 0.01) and the proportion of diabetes type 1 was higher in CAPD (72%) than in HD (51%), p 0.05 . During the mean follow-up period (51.45 months) 79 patients changed their treatment modality and 45 of them received a kidney allogral . Relative risk of drop-out was higher in CAPD technique when compared to HD . Clinical complications were frequently observed: ocular (77%), cardiovascular (Myocardial infarction 1.7%), acute cerebrovascular disease (21%) and distal angiopathy (35%), 10% amputee . At December of 1998, 89 patients were dead . Cardiovascular and cerebrovascular diseases (29%) and Infections (27%) were the two most frequent causes of death . Unknown-origin deaths represent 19% of all deaths . The overall survival (Kaplan Meier) was 92%, 80%, 72%, 61% and 54% at 1, 2, 3, 4 and 5 years, respectively (57 patients completed last period) . Survival was better on HD than on CAPD, but without statistical significance, although the significant difference in age and in proportion of diabetes type 2 between both groups . Data analysis estimated by Cox proportional hazards regression shows that younger age and ki,r transplantation had a positive independent effect on survival, whik clinical distal angiopathy had important negative effect on survival . CONCLUSIONS: Diabetes mellitus has become the leading case of ESRF in our health area of Madrid . Young age and kidney transplantation had a positive independent effect on survival, while clinical distal angiopathy had important negative effect.

J Ind Microbiol Biotechnol, 2001 May, 26(5), 316 - 25
Biodegradation of BTEX vapors in a silicone membrane bioreactor system; Attaway H et al.; The biotreatment of complex mixtures of volatile organic compounds (VOCs) such as benzene, toluene, ethylbenzene, and xylene isomers (BTEX) has been investigated by many workers . However, the majority of the work has dealt with the treatment of aqueous or soil phase contamination . The biological treatment of gas and vapor phase sources of VOC wastes has recently received attention with increased usage of biofilters and bioscrubbers . Although these systems are relatively inexpensive, performance problems associated with biomass plugging, gas channeling, and support media acidification have limited their adoption . In this report we describe the development and evaluation of an alternative biotreatment system that allows rapid diffusion of both BTEX and oxygen through a silicone membrane to an active biofilm . The bioreactor system has a rapid liquid recycle, which facilitates nutrient medium mixing over the biofilm and allows for removal of sloughing cell mass . The system removed BTEX at rates up to 30 microg h(-1) cm(-2) of membrane area . BTEX removal efficiencies ranged from 75% to 99% depending on the BTEX concentration and vapor flowrate . Consequently, the system can be used for continuous removal and destruction of BTEX and other potential target VOCs in vapor phase streams.

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