Effect of inlet mass loading,water and total bacteria count on methanol elimination using upward flow and downward flow biofilters

An upward flow biofilter and a downward flow biofilter using compost for removing methanol from air were investigated to compare the biofilter performance and to realize the advantages of using downward flow biofilters for accessibility to water make‐up. Both the upward flow and downward flow columns showed similar performance in terms of elimination capacity (EC) versus inlet mass loading (IC). The maximum elimination capacity (EC) from these two biofilters was approximately 101 g m⁻³ h⁻¹ with an optimum methanol loading rate at inlet (IC) of 169 g m⁻³ h⁻¹ (7.5 g m⁻³ of methanol with superficial velocity of 7.6 m h⁻¹). The effect of water movement within the bed on elimination capacity was monitored. In addition, it was found that when the water content in the compost was below 35% by weight, microbial activity was impaired. Once the compost media had dried, it became hydrophobic and could be rewetted only with great difficulty. Total bacteria count was performed on compost samples during the entire operation. The relationship between elimination capacity and total bacteria count was reported. Similar trends were shown by the variations of elimination capacity and total bacteria count with methanol loading: both initially increase, go through a plateau, then decrease with loading. © 2000 Society of Chemical Industry     

Removal of Hydrogen Sulphide by Immobilized Thiobacillus sp. strain CH11 in a Biofilter

An autotropic Thiobacillus sp. CH11 was isolated from piggery wastewater containing hydrogen sulphide. The removal characteristics of hydrogen sulphide by Thiobacillus sp. CH11 were examined in the continuous system. The hydrogen sulphide removal capacity was elevated by the BDST (Bed Depth Service Time) method (physical adsorption) and an immobilized cell biofilter (biological conversion). The optimum pH to remove hydrogen sulphide ranged from 6 to 8. The average specific uptake rate of hydrogen sulphide was as 1·02×10⁻¹³ mol-S cell⁻¹ h⁻¹ in continuous systems. The maximum removal rate and saturation constant for hydrogen sulphide were calculated to be V_m = 30·1 mmol-S day⁻¹ (kg-dry bead)⁻¹ and K_s = 1·28 μmol dm⁻³, respectively. A criterion to design a scale-up biofilter was also studied. The maximum inlet loading in the linear region (95% removal) was 47 mmol-S day⁻¹ (kg-dry bead)⁻¹. Additionally, the biofilter exhibited high efficiency (>98·5%) in the removal of hydrogen sulphide at both low (<0·026 mg dm⁻³) and high (0·078 mg dm⁻³) concentrations. The results suggested that the Thiobacillus sp. CH11 immobilized with Ca-alginate is a potential method for the removal of hydrogen sulphide. © 1997 SCI.     

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     

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     

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     

Simultaneous treatment of methane and swine slurry by biofiltration

BACKGROUND: The piggery industry is important both worldwide and in Canada, but localized production of large quantities of swine slurry causes severe environmental problems such as aquatic pollution and greenhouse gas emissions. The main objective of this study was to determine whether it is possible to simultaneously treat methane (CH₄) and swine slurry using an inorganic biofilter. RESULTS: A novel biofilter was designed to overcome the inhibition of CH₄ biodegradation by swine slurry. The CH₄ elimination capacity increased with the inlet load and a maximum value of 18.8 ± 1.0 g m^?3 h^?1 was obtained at an inlet load of 46.7 ± 0.9 g m^?3 h^?1 and a CH₄ concentration of 3.3 g m^?3. Four pure strains of fungi were used in an attempt to improve the removal of CH₄, but no significant effect was observed. Between 0.35 and 3.4 g m^?3, the CH₄ concentration had no effect on swine slurry treatment with removal efficiencies of 67 ± 10% for organic carbon and 70 ± 7% for ammonium. The influence of the slurry supply was analyzed and the best results were obtained with a supply method of six doses of 50 mL per day. CONCLUSION: Even though the results were lower than those obtained for the biofiltration of CH₄ alone, this study demonstrated the feasibility of treating CH₄ and swine slurry with the same biofilter using a novel design. Copyright © 2012 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     

Comparison of packing materials in biofilter system for the biological removal of hydrogen sulfide: Polypropylene fibrils and volcanic stone

In order to develop a method for the removal of hydrogen sulfide via a biological process, two different packing materials were tested to assess their capabilities as biofilter bed materials under variable conditions of two parameters: inlet gas concentration and inlet gas flow rate. We detected a maximal elimination capacity (critical loading rate) of 515.1 (410.5) g-H₂S/m³·hr, and 415.5 (80.0) g-H₂S/m³·hr, respectively, when polypropylene fibrils and volcanic stone were employed as supporting materials. The results of this study show that the application of polypropylene fibrils might be a favorable choice as a packing material in biofilter for the biological removal of hydrogen sulfide.     

Design and performance of biofilters for the removal of alkylbenzene vapors

Three identical biofilters, run under the same conditions but inoculated with different mixed cultures, were fed a mixture of toluene, ethylbenzene, and o-xylene (TEX) gases. Inert porous perlite was used as support material, in contrast to the more conventional biofiltration systems where natural supports are used. Biodegradation started in all three biofilters a few hours after inoculation, without previous adaptation of the inocula to the toxic mixture. Despite acidification of the systems to pH values below 4·5, the elimination capacities reached were fully satisfactory. The best performing biofilter, in which bacteria were dominant, showed an elimination capacity of 70 g TEX m⁻³ h⁻¹ with a near complete removal of the mixture up to an influent concentration of 1200 mg TEX m⁻³ at a gas residence time of 57 s. Most of the ingoing carbon was recovered as carbon dioxide in the outgoing gas. In the other biofilters fungi dominated and performance was slightly worse. With single substrates, the elimination capacity was higher for toluene and ethylbenzene than for the TEX mixture, whereas o-xylene removal was slowest in all cases. Also when feeding the mixture to the biofilters, o-xylene was removed most slowly.     

Biofiltration of toluene in the absence and the presence of ethyl acetate under continuous and intermittent loading

BACKGROUND: Two peat biofilters were used for the removal of toluene from air for one year. One biofilter was fed with pure toluene and the other received 1:1 (by weight) ethyl acetate:toluene mixture. RESULTS: The biofilters were operated under continuous loading: the toluene inlet load (IL) at which 80% removal occurred was 116 g m^?3 h^?1 at 57 s gas residence time. Maximum elimination capacity of 360 g m^?3 h^?1 was obtained at an IL of 745 g m^?3 h^?1. The elimination of toluene was inhibited by the presence of ethyl acetate. Intermittent loading, with pollutants supplied for 16 h/day, 5 days/week, did not significantly affect the removal efficiency (RE). Biomass was fully activated in 2 h after night closures, but 6 h were required to recover RE after weekend closures. Live cell density remained relatively constant over the operational period, while the dead cell fraction increased. Finally, a 15 day starvation period was applied and operation then re‐started. Performance was restored with similar re‐acclimatization period to that after weekend closures, and a reduction in dead cell fraction was observed. CONCLUSION: This study demonstrates the capacity of the system to handle intermittent loading conditions that are common in industrial practices, including long‐term starvation. Copyright © 2008 Society of Chemical Industry     

Removal of monochlorobenzene from air in a trickling biofilter at high loading rates

BACKGROUND: In this study, the biofiltration of air streams laden with monochlorobenzene (MCB) vapours was investigated using a trickling biofilter operated co‐currently. The device was filled with ceramic material and inoculated with an acclimated microbial culture. A neutralization process was carried out in a separate unit using crushed oyster shells. Long‐term biofilter performance was evaluated over a 10‐month period of continuous experiments under different influent pollutant concentrations from 0.10 to 1.75 g m^?3, sequentially stepped up through three different apparent air residence times of 60, 30, and 15 s. RESULTS: Pollutant removal was shown to be complete at influent concentrations up to 1.25, 0.75 and 0.20 g m^?3, and apparent air residence times of 60, 30, and 15 s, respectively. The maximum elimination capacity was found to be 95.0 g m_PM^?3 h^?1 for an influent concentration of 1.0 g m^?3 and an apparent air residence time of 30 s, corresponding to a loading rate of 120.0 g m_PM^?3 h^?1. Monochlorobenzene and biomass concentration profiles along the biofilter evidenced the dependence of microbial concentration distribution on the pollutant loading rate and the existence of a linear relationship between biomass concentration and specific pollutant removal rate, regardless of the operating conditions applied. A macrokinetic analysis shows that the MCB removal rate is zeroth order for low values of MCB concentration. A critical value of MCB concentration exists at all superficial air velocity at which the biomass growth is inhibited. A simple kinetic model is developed which is able to describe the inhibition behaviour under any operating conditions. CONCLUSION: The experimental results indicated that the system was effective and stable under various working conditions and over a long operating period, provided that the loading conditions corresponding to substrate inhibition of microbial growth are not exceeded. Copyright © 2012 Society of Chemical Industry     

Carbon Dioxide Fixation by Algal Cultivation Using Wastewater Nutrients

Chlorella vulgaris was cultivated in wastewater discharged from a steel-making plant with the aim of developing an economically feasible system to remove ammonia from wastewater and CO₂ from flue gas simultaneously. Since no phosphorus compounds existed in wastewater, external phosphate (15·3–46·0 g m⁻³) was added to the wastewater. After adaptation to 5% (v/v) CO₂, the growth of C. vulgaris was significantly improved at a typical concentration of CO₂ in flue gas of 15% (v/v). Growth of C. vulgaris in raw wastewater was better than that in wastewater buffered with HEPES at 15% (v/v) CO₂. CO₂ fixation and ammonia removal rates were estimated as 26·0 g CO₂ m⁻³ h⁻¹ and 0·92 g NH₃ m⁻³ h⁻¹, respectively, when the alga was cultivated in wastewater supplemented with 46·0 g PO₄³ m⁻³ without pH control at 15% (v/v) CO₂. © 1997 SCI.     

Experimental and neural model analysis of styrene removal from polluted air in a biofilter

BACKGROUND: Biofilters are efficient systems for treating malodorous emissions. The mechanism involved during pollutant transfer and subsequent biotransformation within a biofilm is a complex process. The use of artificial neural networks to model the performance of biofilters using easily measurable state variables appears to be an effective alternative to conventional phenomenological modelling. RESULTS: An artificial neural network model was used to predict the extent of styrene removal in a perlite‐biofilter inoculated with a mixed microbial culture. After a 43 day biofilter acclimation period, styrene removal experiments were carried out by subjecting the bioreactor to different flow rates (0.15–0.9 m³ h^?1) and concentrations (0.5–17.2 g m^?3), that correspond to inlet loading rates up to 1390 g m^?3 h^?1. During the different phases of continuous biofilter operation, greater than 92% styrene removal was achievable for loading rates up to 250 g m^?3 h^?1. A back propagation neural network algorithm was applied to model and predict the removal efficiency (%) of this process using inlet concentration (g m^?3) and unit flow (h^?1) as input variables. The data points were divided into training (115 × 3) and testing set (42 × 3). The most reliable condition for the network was selected by a trial and error approach and by estimating the determination coefficient (R²) value (0.98) achieved during prediction of the testing set. CONCLUSION: The results showed that a simple neural network based model with a topology of 2–4–1 was able to efficiently predict the styrene removal performance in the biofilter. Through sensitivity analysis, the most influential input parameter affecting styrene removal was ascertained to be the flow rate. Copyright © 2009 Society of Chemical Industry     

Biotrickling filtration of air contaminated with ethanol

A biotrickling filter (BTF) for treating high ethanol loads was operated for one year and the effect of operating conditions was studied. The BTF was operated in a range of ethanol inlet concentrations of 0.2–15.0 g m^?3 and at three different residence times (30, 65 and 130 s). The experiments show that removal efficiency decreased with increasing ethanol inlet concentration and decreasing air residence time. Removal efficiency varied in the range of 60–100%. A maximum elimination capacity of 970 g m^?3 h^?1 was obtained for an inlet load of 1610 g m^?3 h^?1. At a constant residence time, the carbon dioxide (CO₂) production rate varied with ethanol inlet concentration. BTF presented the maximum CO₂ production rate in the range of inlet concentration of 3.0–7.0 g m^?3. Two strategies for controlling biomass accumulation were applied: one consisted in periodical washing; the other combined periodical washing with nutrient starvation by consuming less water and energy. Both strategies led to maintaining the BTF stable, with high adaptability and reproducibility. Copyright © 2007 Society of Chemical Industry     

Characterization of an organic filter medium for the biofiltration treatment of air contaminated with 1,2‐dichlorobenzene

Laboratory experiments were conducted to determine the potential for removing 1,2‐dichlorobenzene (1,2‐DCB) in gaseous phase by biofiltration. Experiments were carried out over 8 months in a steel tank (0.45 m³) using an organic filter medium composed of peat, maple wood chips, chicken manure and 1,2‐DCB‐contaminated soil. During the first 6 months, the biofilter was operated without injecting 1,2‐DCB in order to characterize the physicochemical, mechanical and microbiological properties of the filter bed. The results revealed that it is an excellent medium for both microbial development (up to 10⁹ cells for heterotrophic bacteria) and long‐term stability with a limited drop of pressure (30 cm of water) and no clogging. Over the final 2 months, the biofilter treated air laden with 1,2‐DCB (0.30 and 0.75 g m^?3) and the maximum elimination capacity reached was 9 g m^?3 h^?1 (inlet load of 13 g m^?3 h^?1), which represented 69% efficiency. Elimination performance was strongly dependent upon inlet concentration, sorption/desorption and biodegradation phenomena occurring in the filter medium. Sorption/desorption and biodegradation mechanisms during the start‐up period were characterized using the elimination efficiency (%). At the beginning of the 1,2‐DCB injection, the microorganisms were strongly impacted and sorption/desorption phenomena prevailed. With the decrease of the inlet concentration, biodegradation progressively increased to become the most important mechanism. It was concluded that biofiltration possesses an excellent potential for treating volatile chlorinated benzene, known to be recalcitrant to biodegradation. Copyright © 2003 Society of Chemical Industry     

Synthesis of a new type poly(vinyl alcohol)/peat/bamboo charcoal/KNO3 composite bead used as biofilter material

A new type poly(vinyl alcohol) (PVA)/peat/bamboo charcoal (BC)/KNO₃ composite bead was prepared, which has a diameter of 2.4–6.0 mm and a density of 1.133 g/cm³ and is a porous spherical particle. The biochemical kinetic behaviors of n‐butyl acetate in PVA/peat/BC/KNO₃ spherical composite bead biofilter (BC biofilter) and PVA/peat/granular activated carbon (GAC)/KNO₃ spherical composite bead biofilter (GAC biofilter) were investigated. The values of half‐saturation constant K_s for BC biofilter and GAC biofilter were 27.89 and 27.95 ppm, respectively. The values of maximum reaction rate V_m for BC biofilter and GAC biofilter were 13.49 and 13.65 ppm/s, respectively. Zero‐order kinetic with the diffusion limitation was regarded as the most adequate biochemical reaction model for the two biofilters. The microbial growth rate and biochemical reaction rate for two biofilters were inhibited at higher inlet concentration, and the degree of inhibitive effect was more pronounced in the inlet concentration range of 100–800 ppm. The biochemical kinetic behaviors of the two biofilters were similar. The maximum elimination capacity of BC biofilter and GAC biofilter were 111.65 and 122.67 g C/h m³ bed volume, respectively. The PVA/peat/BC/KNO₃ composite bead was suitable as a biofilter material. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

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.     

Control of H2S waste gas emissions with a biological activated carbon filter

The removal of high concentrations of H₂S from waste gases containing mixtures of H₂S and NH₃ was studied using the pilot‐scale biofilter. Granular activated carbon (GAC), selected as support material in this study, demonstrated its high adsorption capacity for H₂S and good gas distribution. Extensive tests to determine removal characteristics, removal efficiency, and removal capacity of high H₂S levels and coexisting NH₃ in the system were performed. In seeking the appropriate operating conditions, the response surface methodology (RSM) was employed. H₂S removal capacities were evaluated by the inoculated bacteria (biological conversion) and BDST (Bed Depth Service Time) methods (physical adsorption). An average 98% removal efficiency for 0.083–0.167 mg dm^?3 of H₂S and 0.004–0.021 mg dm^?3 of NH₃ gases was achieved during the operational period because of rapid physical adsorption by GAC and subsequently an effective biological regeneration of GAC by inoculated Pseudomonas putida CH11 and Arthrobacter oxydans CH8. The results showed that H₂S removal efficiency for the system was not affected by inlet NH₃ concentrations. In addition, no acidification was observed in the BAC biofilter. High buffer capacity and low moisture demand were also advantages of this system. The maximal inlet loading and critical loading for the system were 18.9 and 7.7 g‐H₂S m^?3 h^?1, respectively. The results of this study could be used as a guide for the further design and operation of industrial‐scale systems. Copyright © 2004 Society of Chemical Industry     

Degradation of benzene and toluene by a fluidized bed bioreactor including microbial consortium

A fluidized bed bioreactor including microbial consortium was used to remove benzene and toluene simultaneously. The microbial consortium was obtained from sewage treatment plant, and showed maximum benzene degradation rate of 45.2 mg/l·h·mg cell in 30 °C and pH 7.0, and maximum toluene degradation rate of 44.4 mg/l·h·mg cell in 30 °C and pH 8.0. The optimum operating condition of the fluidized bed bioreactor was 30 °C, pH 7.0 and 150 cm of liquid bed height. The average removal efficiency of benzene was 94% for inlet concentration of 53(±5) ppm benzene and that of toluene was 96% for an inlet concentration 48(±5) ppm toluene at 600 l/h of gas volumetric flow rate. The maximum removal capacity in the experimental condition was 22.3 g/m³·h for benzene and 16.3 g/ m³·h for toluene. This paper is dedicated to Professor Dong Sup Doh on the occasion of his retirement from Korea University.