The treatment of waste-air containing mixed solvent using a biofilter: 1. Transient behavior of biofilter to treat waste-air containing ethanol

Transient behavior of a biofilter packed with mixed media (of granular activated carbon and compost) inoculated with a pure culture ofPseudomonas putida was observed at the height of each sampling port to treat wasteair containing ethanol. In addition, flooding effects of an excess supply of buffer solution was observed at each sampling port of the biofilter until it recovered the status prior to the flooding. Unlike previous investigations, various process conditions were applied to successive biofilter runs in order to monitor the corresponding unsteady behavior of the biofilter in this work. In early stage of biofilter run the removal efficiency of ethanol maintained almost 100%. However, it began to decrease when inlet load surpassed 100 g/m³/h consistent with maximum elimination capacity. At the end of biofilter-run removal efficiency was decreased and maintained at 40%. The results of this work were compared to those of such biofiltration studies as the work of Christen et al. from the point of view that pure cultures of microorganism were used in both works. Except for the period of flooding effect of the 2nd stage, the inlet load and removal efficiency continued at 105.5 g/m³/h and 95%, respectively, while they were 93.7 g/m³/h and 95%, respectively, according to the result of Christine et al. Removal efficiency remained at 90% for the beginning period of 3 days of the 3rd stage, and it gradually decreased to 60% for remaining 5 days of the stage with an inlet load of 158.26 g/m³/h, which may be interpreted as better than the result of Christine et al. Their result was that the removal efficiency on the inlet load of 154 g/m³/h of ethanol was continued to be 60% for 6 days of a separate biofilter run and decreased to 40% later. Thus, with similar inlet loads of ethanol, removal efficiency of this work was equivalent to or higher than that of Christine et al.     

Transient behavior of biofilter inoculated with Thiobacillus sp. IW to treat waste-air containing hydrogen sulfide

Hydrogen sulfide is heavier than air and is colorless, toxic and flammable, the gas odor threshold of which is about 0.47 ppbv, which causes nuisance odor at concentrations as low as about 8ppbv and corrosion problems in sewer systems. The transient behavior of biofilter packed with mixed media (of granular activated carbon and compost) inoculated with a pure culture of Thiobacillus sp. IW was observed at a height of four sampling ports to treat wasteair containing hydrogen sulfide in this investigation, which shall be used as control to be compared with the performance of a biofilter-involved integrated system for the treatment of waste-air containing hydrogen sulfide in a subsequent investigation. Unlike the previous studies of the other investigators, various process conditions were applied to successive biofilter runs in order to monitor and correlate each corresponding unsteady behavior of the biofilter at the height of each sampling port. During 10 days (20 times) after start-up of a biofilter hydrogen sulfide was continuously adsorbed on the media and that the adsorption of hydrogen sulfide was under way since the inlet loads of 1st and 2nd stage operations were very low. Afterwards it was obvious that the breakthrough curves at the 1st, 2nd, 3rd and 4th (exit) sampling ports responded rapidly to the change of operating conditions of a biofilter so that the breakthrough curve at each sampling port responded rapidly to approach a new state of saturation, which suggests that the adsorption capacity of biofilter-media may be relatively small or its affinity to hydrogen sulfide may be relatively high, compared to such volatile organic compound as ethanol. Up to the 3rd stage of operation the removal efficiency continued to be nearly 100%. However it began to decrease as inlet load increased. At the end of last stage of the biofilterrun removal efficiency was decreased and maintained at 94%. The maximum elimination capacity was observed to be ca. 95 g/m³/h, which was higher than that of the biofiltration-work of any other previous investigator except for that of the biofiltration-work with use of each of two inorganic packing materials (porous ceramics, calcinated and formed obsidian).     

Treatment of mixed solvent vapors with hybrid system composed of biofilter and photo-catalytic reactor

The transient behavior of a hybrid system composed of biofilter and photo-catalytic reactor was observed at the height of each sampling port to treat waste-air containing ethanol. The biofilter packed with mixed media (of granular activated carbon and compost) was inoculated with a pure culture ofBurkholderia cepacia G4 andPseudomonas putida, while a photo-catalytic reactor was composed of 15W UV-A lamps and annular pyrex tubes packed with glass beads coated with sol type of TiO₂ before calcination. The maximum elimination capacities of toluene and ethanol turned out to be 130 g/m³/h and 230 g/m³/h, respectively, which were greater by 40 g/m³/h and 130 g/m³/h, respectively, than those from the experiments performed with a biofilter only. Thus, the maximum elimination capacities for toluene and ethanol increased by 44% and 130%, respectively, by use of a hybrid system. The photo-catalytic process contributed to the maximum elimination capacities of hybrid system on toluene and ethanol by 30.8% and 56.5%, respectively, which contributions for the elimination capacities on toluene and ethanol were allocated indirectly by 25.4% and 44.3% as well as directly by 5.4% and 12.2%, respectively. Direct contributions of photo-catalytic process were 17.5% and 21.5% to the increments of the elimination capacities on toluene and ethanol, respectively, while its indirect contributions were 82.5% and 78.5% to those on toluene and ethanol, respectively.     

Effect of temperature on the performance of a biofilter inoculated withPseudomonas putida to treat waste-air containing ethanol

The microbes ofPseudomonas putida (KCTC1768) were fixed on the biofilter-packing media comprising an equivolume mixture of granular activated carbon (GAC) and compost, by recycling the liquid medium containing incubatedPseudomonas putida (KCTC1768). A biofilter experiment was performed to observe its transient behavior under the operating condition of 2,180 ppmv of ethanol-inlet concentration and 158 g/m³/h of ethanol-inlet load for the five consecutive temperature-stages of operation ranging from 25 °C to 40 °C. For the five temperaturestages of operation their removal efficiencies were measured and were compared with each other. The optimum operating temperature of the biofilter turned out to beca. 30 °C, which was consistent with the previous experimental result of Lim and Park. However, the optimum incubation-temperatures ofPseudomonas putida (KCTC1768) and the equivalent (i.e., NCIMB8858) were announced to be of 26 °C and 25 °C by Korea Collection for Type Cultures (KCTC) and National Collections of Industrial, Food and Marine Bacteria (NCIMB), respectively. It was also confirmed by the experiment in which the microbes were incubated in the same liquid medium as in the previous work of Lim and Park at temperature ranging from 20 °C to 40 °C and their growth rates were subsequently measured. Thus, the optimum operating temperature of a biofilter inoculated withPseudomonas putida (KCTC 1768) was proved to be 30 °C, which was higher than its optimum incubation-temperature byca. 5 °C     

Comparison of biological reactors (biofilter,biotrickling filter and modified RBC) for treating dichloromethane vapors

BACKGROUND: Bioreactors used for waste gas and odor treatment have gained acceptance in recent years to treat volatile organic compounds (VOCs). Different types of bioreactors (biofilter, biotrickling filter and rotating biological reactor) have been used for waste gas treatment. Most studies reported in the literature have used one of these systems to treat several types of inorganic and organic gases either individually or in mixtures. Each of these reactors has some advantages and some limitations. Though biodegradation is the main process for the removal of pollutants, the mechanisms of removal and the microbial communities may differ among these bioreactors. Consequently their performance or removal efficiency may also be different. RESULTS: At low loading rate (<35 g m^?3 h^?1), all three bioreactors showed comparable removal efficiencies and elimination capacity, but at higher loading rates, rotating biological contactors (RBC) showed a better performance with higher removal efficiency (40–50%) than both the biofilter and biotrickling filter (20–40%). The biofilter showed a sharp drop in removal efficiency and elimination capacity at high loading rates. CONCLUSIONS: The modified RBC had no clogging problems and no increase in pressure drop when compared with the other bioreactors. It can thus handle pollutant load for a longer period of time. This is the first study attempting to compare the performance of three different bioreactors for removal of the same VOC under different conditions. Copyright © 2010 Society of Chemical Industry     

Effect of pre‐treatments based on UV photocatalysis and photo‐oxidation on toluene biofiltration performance

BACKGROUND: The integration of UV photocatalysis and biofiltration seems to be a promising combination of technologies for the removal of hydrophobic and poorly biodegradable air pollutants. The influence of pre‐treatments based on UV_{254 nm} photocatalysis and photo‐oxidation on the biofiltration of toluene as a target compound was evaluated in a controlled long‐term experimental study using different system configurations: a standalone biofilter, a combined UV photocatalytic reactor‐biofilter, and a combined UV photo‐oxidation reactor (without catalyst)‐biofilter. RESULTS: Under the operational conditions used (residence time of 2.7 s and toluene concentrations 600–1200 mg C m^?3), relatively low removal efficiencies (6–3%) were reached in the photocatalytic reactor and no degradation of toluene was found when the photo‐oxidation reactor was operated without catalyst. A noticeable improvement in the performance of the biofilter combined with a photocatalytic reactor was observed, and the elimination capacity of the biological process increased by more than 12 g C h^?1 m^?3 at the inlet loads studied of 50–100 g C h^?1 m^?3. No positive effect on toluene removal was observed for the combination of UV photoreactor and biofilter. CONCLUSIONS: Biofilter pre‐treatment based on UV_{254 nm} photocatalysis showed promising results for the removal of hydrophobic and recalcitrant air pollutants, providing synergistic improvement in the removal of toluene. Copyright © 2011 Society of Chemical Industry     

Application of a pore network model to a biofilter treating ethanol vapor

Pore volume clogging due to biomass growth from the biodegradation of volatile organic compounds and other pollutants has significant implications for biofilter operation. As the larger pores in the biofilter narrow and the smaller pores fill, airflow through the biofilter is restricted, and headloss increases. The biomass surface area available for contaminant biodegradation is reduced, resulting in diminished removal efficiencies. As biomass clogging increases, flow channeling may occur, further reducing treatment efficiency. Biofilter designers try to overcome the effect of biomass clogging by making beds larger to reduce loading, which is costly. Better insight into the phenomena that occur during biofilter clogging is, therefore, clearly needed. In this paper the effect of biomass accumulation on the removal efficiency and pressure drop of a bench-scale biofilter treating an air stream containing ethanol vapor was investigated using a pore network model. In the model, the biofilter pore structure is described by a cubic lattice of cylindrical pores of uniform length and varying diameters following an experimentally determined pore size distribution. The model assumes that at the pore level biomass growth depends on the oxygen diffusion in the biofilm and on oxygen-limited Monod-type kinetics. Unlike prior biofilter models, this model accounts in detail for phenomena that occur at the pore level, and for the impact of the pore network structure on biofilter behavior. It accounts for the biomass growth in the biofilter and its interaction with the airflow distribution, and explains its influence on the headloss and the ethanol removal efficiency.     

Comparison of chemical wet scrubbers and biofiltration for control of volatile organic compounds using GC/MS techniques and kinetic analysis

Increasing public concerns and EPA air regulations in non‐attainment zones necessitate the remediation of volatile organic compounds (VOCs) generated in the poultry‐rendering industry. Wet scrubbers using chlorine dioxide (ClO₂) have low overall removal efficiencies due to lack of reactivity with aldehydes. Contrary to wet scrubbers, a biofilter system successfully treated the aldehyde fraction, based on GC/MS analysis of inlet and outlet streams. Total VOC removal efficiencies ranged from 40 to 100% for the biofilter, kinetic analysis indicated that the overall removal capacity approached 25 g m⁻³ h⁻¹, and aldehyde removal efficiency was significantly higher compared with chemical wet scrubbers. Process temperatures monitored in critical unit operations upstream from the biofilter varied significantly during operation, rising as much as 30 °C within a few minutes. However, the outlet air temperature of a high intensity scrubber remained relatively constant at 40 °C, although the inlet air temperature fluctuated from 50 to 65 °C during monitoring. These data suggest a hybrid process combining a wet scrubber and biofilter in series could be used to improve overall VOC removal efficiencies and process stability. Copyright © 2005 Society of Chemical Industry     

Influence of nitrogen on the degradation of toluene in a compost‐based biofilter

Two identical laboratory‐scale bioreactors were operated simultaneously, each treating an input air flow rate of 1 m³ h^?1. The biofilters consisted of multi‐stage columns, each stage packed with a compost‐based filtering material, which was not previously inoculated. The toluene inlet concentration was fixed at 1.5 g m^?3 of air. Apart from the necessary carbon, the elements nitrogen, phosphorus, sulfur, potassium and other micro‐elements are also essential for microbial metabolism. These were distributed throughout the filter bed material by periodic ‘irrigations’ with various test nutrient solutions. The performance of each biofilter was quantified by determining its toluene removal efficiency, and elimination capacity. Nutrient solution nitrogen levels were varied from 0 to 6.0 g dm^?3, which led to elimination capacities of up to 50 g m^?3 h^?1 being obtained for a toluene inlet load of 80 g m^?3 h^?1. A theoretical analysis also confirmed that the optimum nitrogen solution concentration lays in the range 4.0–6.0 g dm^?3. Validation of the irrigation mode was achieved by watering each biofilter stage individually. Vertical stage‐by‐stage stratification of the biofilter performance was not detected, ie each filter bed section removed the same amount of pollutant, the elimination capacity per stage being about 16 g m^?3 h^?1 per section of column. © 2001 Society of Chemical Industry     

Biodegradation of aromatic hydrocarbons in a compost biofilter

Two laboratory‐scale biofilters filled with the same type of packing material were operated at different gas flow rates and influent concentrations of toluene and xylene in order to investigate their performance in treating waste gas streams. The columns contained a mixture of municipal compost as a base material and wood chips as a bulking agent in an 80:20 ratio; the porosity was 54%. Microbial acclimation was achieved by addition of nutrient‐enriched solution along with pollutants for a week by daily mixing and natural aeration. During the start‐up of the systems with inlet concentrations of 20 and 70 ppm for toluene and xylene, respectively, high biomass growth resulted in pressure drops in excess of 2000 Pam^?1. Under steady state conditions, the response of each biofilter to variations in contaminant mass loading was studied by either changing the influent concentration or flow rate of the inlet waste stream. The results show that organic loading rates of up to 110 and 150 gm^?3h^?1 can be handled without any indication of the elimination capacity being saturated. However, maintaining the pressure drop below 1000 Pam^?1 to avoid operational problems, optimal organic loading rates for toluene and xylene of 78 ± 8 and 80 ± 14 gm^?3h^?1 respectively are suggested for an HRT value of 60 s. Under these conditions, elimination capacities of 73 ± 4 and 73 ± 14 gm^?3h^?1 and removal efficiencies of 94 ± 6% and 91 ± 8% were achieved for toluene and xylene, respectively. Copyright © 2003 Society of Chemical Industry     

Styrene degradation along the bed height of perlite biofilter

The whole bed height of a biofilter was divided into four individual reactor stages in series. This configuration permits a measurement of the leachate pH of each stage individually and minimizes interstage mixing of the immobilized culture. The extent to which the residence time of pollutant in the filter bed influenced biodegradation characteristics and the composition of immobilized culture under conditions of a constant loading rate was studied using a perlite biofilter having an internal diameter of 50 mm and the bed height of each stage being 27 cm. The residence time of pollutant in the bed had no influence on the removal efficiency and the elimination capacity of the whole biofilter although some changes of these parameters in the individual stages were observed. The biofilter achieved an elimination capacity of 140 gm^?3 h^?1 at removal efficiencies greater than 90%. Degradation activity decreased the pH value of the leachate to 3.5–3.0. Microbial analyses showed that styrene was degraded by eukaryotic cells at low pH values. At pH values above 4.0 prokaryotes were also present in the mixed culture. © 2001 Society of Chemical Industry     

Measurements and modeling of heat generation in a trickling biofilter for biodegradation of a low concentration volatile organic compound (VOC)

The experimental and theoretical heat generation behavior of a trickling biofilter treating toluene is discussed. The experimental results show that the temperature of the packed bed has a significant effect on the purification performance of the trickling biofilter and that an optimal operation temperature exists between 30 and 40 °C. During the gas–liquid co-current flow, the temperature in the packed bed gradually rises along the direction of the gas and liquid flow due to the exothermic biodegradation of toluene. The temperature rise between the inlet and outlet of the trickling biofilter increases with an increase in the gas flow rate and inlet toluene concentration. In addition, a larger liquid flow rate leads to a smaller temperature rise. The heat generation process occurring in the trickling biofilter is modeled by representing the packed bed as an equivalent set of parallel capillary tubes covered by the biofilm. The temperature profile in the packed bed during the liquid–gas co-current flow is analyzed by simultaneously solving the problem of gas–liquid two-phase flow and heat and mass transfer through the liquid film and biofilm. It is shown that the model agrees well with the experimental data, predicting the variations of the temperature rise between the inlet and outlet of trickling biofilter with the increasing gas and liquid flow rates.     

Biological purification of exhaust air containing toluene vapor in a filter-bed reactor

Experiments during a period of 93 days are reported on the treatment of waste air containing toluene vapor using a laboratory scale biofilter system packed with peat inoculated with specific florae (Pseudomonas type) and intermittently humidified with a nutrient solution necessary for the survival of the micro-organisms. Design and operation parameters were regularly measured in order to check the performance of the biodegradation process. Under pseudo-steady state conditions, a maximum elimination capacity of 70 g/m³.h was obtained for an inlet load of 190 g/m³.h. Elimination capacity data obtained agreed well with the predictions of two recognized zero order kinetic models. Also, the biofilm thickness as predicted from the Ottengraf and van den Oever model (1983) was around lmm.     

Modeling of a bacterial and fungal biofilter applied to toluene abatement: Kinetic parameters estimation and model validation

Biofiltration has been established as a promising alternative to conventional air pollution control technologies. However, gas biofilters modeling has been less developed than experimental research due to the complexity of describing the fundamental processes and the lack of globally accepted physical, chemical and biological parameters. In addition, biofiltration modeling based on degradation activity of fungi has been rarely considered. For this reason, in this work, a dynamic model describing toluene abatement by a bacterial and fungal biofilter is developed, calibrated and validated. The mathematical model is based on detailed mass balances which include the main processes involved in the system: convection, absorption, diffusion and biodegradation. The model was calibrated and validated using experimental data obtained from two equal lab-scale biofilters packed with coconut fiber and pine leaves, respectively. Both reactors were operated under similar conditions during 100 days at an empty bed residence time of 60 s and an average inlet load of 77 g toluene m⁻³ h⁻¹. Biofilters were initially inoculated with a bacterial consortium, even though reactors were mostly colonized by fungi after 60 days of operation according to microscopic observation and reactors pH. Removal efficiency increased notably from 20% for the bacterial period to 80% for the fully developed fungal biofilters. Since kinetic parameters are strongly dependent on the biological population, semi-saturation constants for toluene and maximum growth rates were determined for bacterial and fungal operation periods. Kinetic parameters were fitted by means of an optimization routine using either outlet concentrations or removal efficiency data from the coconut fiber biofilter. A novel procedure in gas biofilters modeling was considered for checking the model calibration, by the assessment of the parameters confidence interval based on the Fisher Information Matrix (FIM). Kinetic parameters estimated in the coconut fiber reactor were validated in the pine leaves biofilter for bacterial and fungal operation. Adequate model fitting to the experimental outlet gas concentration for both bacterial and fungal operation periods was verified by using a standard statistical test.     

Removal of pentane and styrene mixtures from waste gases by a trickle‐bed air biofilter

The biofilter process is a relatively new technology that has been proven to be more cost‐effective than traditional technologies for treating many kinds of volatile organic compounds (VOCs) from waste gases. Pentane and styrene mixtures are commonly encountered in the manufacture of polymers such as polystyrene. This research attempts to employ a trickle‐bed air biofilter (TBAB) for treating such mixtures under different influent carbon loadings. In the pseudo‐steady‐state conditions, the elimination capacities of pentane and styrene increased but the removal efficiencies decreased with increased influent carbon loading. The removal efficiencies of styrene were higher than those of pentane, indicating that styrene is a preferred substrate and the differences were enhanced at a high carbon loading. Removal efficiencies of more than 80% were achieved with influent carbon loadings of pentane and styrene below 25 and 68 gm^?3 h^?1, respectively. The TBAB appears to be efficient for controlling VOC emissions with low pentane and medium styrene loadings, and the effectiveness could be maintained over 140 days of laboratory operation. © 2001 Society of Chemical Industry     

Kinetics of toluene and sulfur compounds removal by means of an integrated process involving the coupling of absorption and biodegradation

BACKGROUND: Scrubbing using an organic solution instead of an aqueous solution could be a useful way to improve the removal of hydrophobic compounds. Absorption of toluene, dimethyldisulfide (DMDS) and dimethylsulfide (DMS) in an organic solution (di‐2‐ethylhexyladipate—DEHA), followed by biodegradation by activated sludge was considered, with particular attention to kinetic aspects. DEHA was selected for its relevance in terms of absorption capacity and absorption velocity of the selected volatile organic compounds (VOCs). After the biodegradation step and owing to its cost, recycling of the VOC‐free solvent should be considered. RESULTS: Enhancement of VOC mass transfer from the organic to the aqueous phase due to bacterial activity was highlighted and the main driving force was found to be biosurfactant production rather than biodegradation reaction. However, the mass transfer rate between the two phases was shown to be lower than VOC biodegradation rate; hence, significant biodegradation of DMDS and toluene was recorded in a few days during batch experiments, 0.10 and 0.09 mmol respectively. Toluene showed higher biodegradation rates (about 0.05 and 0.10 mg h^?1 for DMDS and toluene), leading to higher growth rates. Contrarily, owing to its high volatility, important DMS losses were observed. CONCLUSION: The relevance of the proposed integrated process was shown for hydrophobic VOC removal, at least for toluene and DMDS. Unfortunately, the absorbent phase was also degraded, proved by detection of by‐products during analyses of the aqueous phase headspace. The comparison of DEHA with other solvents or solid polymers available for multiphase bioreactor applications may be a reliable option to continue this work. Copyright © 2010 Society of Chemical Industry     

Treatment of air polluted with high concentrations of toluene and xylene in a pilot-scale biofilter

Air biofiltration is now under active consideration for the removal of the volatile organic compounds from air polluted streams. In order to investigate the performance of this newly developed technology, a biofiltration pilot unit was operated for a continuous period of 8 months. The biofilter column was packed with commercially conditioned peat. At start-up, the filter bed was inoculated with four species of microorganisms. The resulting biofilter was fed with air contaminated with toluene, xylene or a mixture of toluene and xylene. The maximum elimination capacities attained were 165 g m⁻³ h⁻¹ for toluene, 66 g m⁻³ h⁻¹ for xylene and 115 g m⁻³ h⁻¹ for the mixture of toluene and xylene. These specific performances exceed the values published in the technical and commercial literature for similar processes. Xylene isomers were degraded in decreasing order of reactivity, m-xylene, p-xylene, o-xylene. In the case of air polluted with a toluene and xylene mixture, it was noticed that the metabolism of toluene biodegradation was inhibited by the presence of xylene. Characterization of the biofilm microbial populations after several weeks of operation showed that the dominant strains among the isolated culturable strains from the biofilm, even if different from the initially inoculated strains, had at least one physiological property favoring degradation of aromatic organic rings. The performance of the biofilter was found to be dependent on the temperature of the filter media and the pressure drop through the bed. Finally, a steady state mathematical model was tested in order to theoretically describe the experimental results. This model is used to illustrate the operating diffusion and reaction regimes at steady state for the case of each pollutant. © 1998 Society of Chemical Industry     

Elimination of chlorobenzene vapors from air in a compost‐based biofilter

In this work, the removal of monochlorobenzene (CB) vapors from air was studied, for the first time, in a non‐inoculated, laboratory‐scale, aerobic biofilter. The influence of three parameters on the bioprocess has been evaluated: the rate of nitrogen supplied to the bed, the inlet concentration of CB, and the flow rate. The CB inlet concentration was varied between 0.3 and 3.2 g m^?3, at a constant flow rate of 1.0 m³ h^?1. Removal rates of greater than 90% were achieved for CB inlet concentrations of up to 1.2 g m^?3. Then the flow rate was varied from 0.5 to 3.0 m³ h^?1 with a constant inlet concentration (1.2 g m^?3). Maximum elimination capacities (70 g m^?3 h^?1) were reached for contact times of greater than 60 s. The study of varying flow rates also permitted evaluation of a first order macrokinetic constant (1.1 × 10^?2 s^?1) for the CB biodegradation. Finally, the optimum nitrogen input value was found to lie between 0.3 and 0.4 g N h^?1 and gave rise to elimination capacities as high as 70 g m^?3 h^?1 for an inlet load of near 80 g m^?3 h^?1. Copyright © 2003 Society of Chemical Industry     

Biodegradation of toluene and dimethyl sulfide in a cocultured biofilter

Biofiltration was performed for 50 days in a perlite-packed biofilter (8 cm I.D.x 105 cm height) for the simultaneous removal of toluene and dimethyl sulfide (DMS). Two strains,Rhodococcus pyridinovorans PYJ-1 andGordonia sihwaniensis PKL-1, were cocultured in the biofilter. Removal efficiencies of toluene and DMS at an empty bed residence time (EBRT) of 3 min were 80–85% and 40–45%, respectively, for an input concentration of 2.5–3.0 mg/L of toluene and 1.5–2.0 mg/L of DMS. The pH of the perlite column was maintained at 7.0–7.2, and the moisture content varied from 61% at the bottom to 51% at the top. Starting from the same initial cell concentration (2.4 x 10₆ CFU/g of wet packing) the number ofR. pyridinovorans PYJ-1 was 2.5 times higher compared with that of G.sihwaniensis PKL-1 after 50 days of operation.     

生物膜滴滤床内温度及其分布特性对废气净化性能的影响

对不同温度下,陶瓷球填料生物膜滴滤塔净化低浓度有机废气的降解性能以及填料床内温度分布进行了实验研究,实验结果表明：填料床内微生物生长环境温度对微生物酶活性影响很大,从而造成温度对滴滤塔净化性能的显著影响.微生物酶活性最高时的温度为30℃,最高滴滤塔净化性能所对应的温度在30～40℃.在滴滤塔顺流操作条件下,滴滤床内温度沿气液流动方向升高;在进口碳源浓度一定时,滴滤床内沿气液流动方向的温升随着液体流量的减小和气体流量的增大而升高;废气进口浓度及系统操作方式对滴滤床温度分布也有显著影响.