Trickle-bed Air Biofilter Research Articles

A comparative study in treating two VOC mixtures in trickle bed air biofilters

Two independent parallel trickling bed air biofilters (TBABs) ("A" and "B") with two different typical VOC mixtures were investigated. Toluene, styrene, methyl ethyl ketone (MEK), and methyl isobutyl ketone (MIBK) were the target VOCs in the mixtures. Biofilter "A" was fed equal molar ratio of the VOCs and biofilter "B" was fed a mixture based on EPA 2003 emission report. Backwashing and substrate starvation operation were conducted as biomass control. Biofilter "A" and "B" maintained 99% overall removal efficiency for influent concentration up to 500 and 300 ppmv under backwashing operating condition, respectively. The starvation study indicated that it can be an effective biomass control for influent concentrations up to 250 ppmv for biofilter "A" and 300 ppmv for "B". Re-acclimation of biofilter performance was delayed with increase of influent concentration for both biofilters. Starvation operation helped the biofilter to recover at low concentrations and delayed re-acclimation at high concentrations. Furthermore, re-acclamation for biofilter "B" was delayed due to its high toluene content as compared to biofilter "A". The pseudo first-order removal rate constant decreased with increase of volumetric loading rate for both biofilters. MEK and MIBK were completely removed in the upper 3/8 media depth. While biofilter depth utilization for the removal of styrene and toluene increased with increase of influent concentrations for both biofilters. However, toluene removal utilized more biofilter depth for biofilter "B" as compared to biofilter "A".

Role of biological activity and biomass distribution in air biofilter performance

The effects of temporal and spatial changes in biological activity and biomass amount on biofilter performance were investigated in a lab-scale trickle-bed air biofilter at a toluene loading of 46.9 g m −3 h −1 under two different experimental strategies, namely, periodic backwashing at a rate of 1 h once a week and 2 d starvation. Analysis of the overall reaction for toluene metabolism revealed that cell synthesis was relatively favored over toluene oxidation in the inlet section of the biofilter, but over time its oxidation became favored throughout the biofilter bed. Periodic in situ backwashing with media fluidization effectively made even spatial distribution of biomass along the bed media, by which consistent high removal performance in the biofilter has been attained. After 2 d starvation, the ratio of the biofilm EPS to the total biomass increased along the media bed depth, while the total biomass in the media bed subsequently decreased. The presence of sufficient biomass and microbial activity favorably influenced biofilter reacclimation after restart-up following starvation.

Performance of Trickle-Bed Air Biofilter: A Comparative Study of a Hydrophilic and a Hydrophobic Voc

Two lab-scale trickle-bed air biofilters were operated for investigating the difference in performance between a hydrophilic and a hydrophobic volatile organic compound (VOC). Methyl isobutyl ketone (MIBK) and styrene were selected as a model hydrophilic and hydrophobic VOCs, respectively. Effects of loading rates, biofilter re-acclimation, removal profile along biofilter depth, nitrogen consumption, and CO2 production were compared under three operating conditions, namely, backwashing and two non-use periods (starvation and stagnant).

Kinetics of the removal of mono-chlorobenzene vapour from waste gases using a trickle bed air biofilter

The performance of a trickle bed air biofilter (TBAB) in the removal of mono-chlorobenzene (MCB) was evaluated in concentrations varying from 0.133 to 7.187 g m −3 and at empty bed residence time (EBRT) varying from 37.7 to 188.52 s. More than 90% removal efficiency in the trickle bed air biofilter was achieved for the inlet MCB concentration up to 1.069 g m −3 and EBRT less than 94.26 s. The trickle bed air biofilter was constructed with coal packing material, inoculated with a mixed consortium of activated sludge obtained from sewage treatment plant. The continuous performance of the removal of MCB in the trickle bed air biofilter was monitored for various gas concentrations, gas flow rates, and empty bed residence time. The experiment was conducted for a period of 75 days. The trickle bed air biofilter degrading MCB with an average elimination capacity of 80 g m −3 h −1 was obtained. The effect of starvation was also studied. After starvation period of 8 days, the degradation was low but recovered within a short period of time. Using macrokinetic determination method, the Michaelis–Menten kinetic constant K m and maximum reaction rate, r max evaluated as 0.121 g m −3 s −1 and 7.45 g m −3, respectively.

Performance and Microbial Diversity of a Trickle-Bed Air Biofilter under Interchanging Contaminants

A trickle-bed air biofilter (TBAB) was evaluated under conditions of interchanging the feed volatile organic compounds (VOCs) in the sequence methyl ethyl ketone (MEK), toluene, methyl isobutyl ketone (MIBK), styrene, and then back to MEK. The obtained performance results revealed that the biofilter provided high removal efficiency within the critical loading of each VOC, which was previously defined in the non-interchanging VOC fed biofilter. The biofilter easily acclimated to the oxygenated compounds (MEK and MIBK), but re-acclimation was delayed for the aromatic compounds (toluene and styrene). Ratios of the molar mass of CO2 produced per molar mass of VOC removed were investigated. It has been found that the ratios for the aromatic compounds closely resembled the theoretical complete chemical oxidation based ratios while larger differences were encountered with the oxygenated compounds. Denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA genes was used to assess the impact of interchanging VOCs on the bacterial community structure in the biofilter. The results from denaturing gradient gel electrophoresis (DGGE) showed that the structure of the microbial community in the biofilter was different after each interchange of VOCs.

Removal of Methyl Isobutyl Ketone From Contaminated Air by Trickle-Bed Air Biofilter

A laboratory-scale trickle-bed air biofilter was evaluated for the removal of methyl isobutyl ketone (MIBK) from a waste gas stream. Six-millimeter (6 mm) Celite pellets (R-635) were used as the biological attachment medium. Effects of MIBK volumetric loading rates on removal efficiency, biofilter reacclimation, biomass growth, and removal kinetics were studied under three different operating conditions, namely, backwashing and two intermittent periods (off chemical—no MIBK input; and off flow-no flow input). Backwashing of the biofilter once a week with full-medium fluidization removed the excess biomass and attained stable long-term performance with over 99% removal efficiency for loading rates less than 3.26 kg chemical oxygen demand (COD) ∕ m3 day . The two intermittent periods could also sustain high removal efficiency for loading rates up to 1.09 kg COD∕ m3 day without any backwashing. The recovery time increased with an increase in loading rates. Furthermore, the intermittent operations required a ...

Behavior of trickle‐bed air biofilter for toluene removal: Effect of non‐use periods

AbstractA laboratory‐scale trickle bed air biofilter (TBAB) packed with synthetic, inorganic media for microbial attachment was used for toluene removal from an air stream. Three experimental strategies—including backwashing as the active biomass control and two non‐use periods (starvation, which represents a period without toluene loading, and stagnant, which reflects no flow)—were considered in this study. The non‐use periods can be considered as another means of biomass control for low VOC loadings (0.70 and 1.41 kg COD/m3·day), whereas at high VOC loading (>3.52 kg COD/m3·day) backwashing is deemed essential to remove the excess biomass accumulation in the biofilter. As the toluene loading rate was increased, a considerably longer reacclimation period was unavoidable for biofilter performance to reach the 99% removal for all experimental strategies (backwashing, starvation, and stagnant). Because the biofilter response was strongly dependent on the active biomass in the system, biofilter response after the non‐use periods was significantly different from that after backwashing. © 2005 American Institute of Chemical Engineers Environ Prog, 2005

Hydrodynamic characterization of a trickle bed air biofilter

This paper reports the effect of superficial liquid mass flow rate and bed void fraction on the pressure drop, dynamic liquid hold-up, mean liquid residence time and biofilm wetting, in a co-current down-flow xylene-removing trickle bed air biofilter (TBAB). The gas–liquid pressure drop increased with liquid mass flow rate and it also increased with diminishing bed void fraction, the effect being larger at bed void fraction of 0.41. Dynamic liquid hold-up was higher with increasing liquid mass flow rate, and showed a maximum when the bed void fraction was 0.69. The same pattern was observed for the mean liquid residence time and the wetting efficiency. Liquid residence time distribution curves indicate stagnant regions, channeling, and recirculation within the TBAB, whose effects were larger at a bed void fraction of 0.41. A maximum elimination capacity of 30 g/m 3 h, with 78% removal efficiency, was reached when the bed void fraction was 0.8 and the liquid mass rate 14.1 kg/m 2 s. An average minimum elimination capacity of 6 g/m 3 h was observed at a bed void fraction of 0.41. Xylene isomers were preferentially removed in the order of o > m > p. © 2005 Elsevier B.V. All rights reserved.

Impact of interchanging VOCs on the performance of trickle bed air biofilter

Abstract Trickle bed air biofilters (TBABs) were evaluated under conditions of an interchange of the feed volatile organic compounds (VOCs). Two aromatic compounds (toluene and styrene) and two oxygenated compounds (methyl ethyl ketone and methyl isobutyl ketone) were interchanged as single solutes. The results obtained revealed that the biofilter provided high removal efficiency within the critical loading, which was previously defined in the non-interchanging VOC-fed biofilters. The biofilter recovered easily to the 99% removal after interchanging to oxygenated compounds, regardless of the immediately preceding compound fed to each biofilter, but for aromatic compounds, a longer reacclimation period was required. The biofilter response after interchange of feed VOCs depended on the physicochemical property of feed VOCs as well as the biomass retained in the biofilter prior to interchanging VOC. Using high EBRT at the critical loading (which corresponds to high inlet concentration), problems related to oxygen limitation within the biofilm may have appeared. It was noticed that a smaller ratio of COD/N and a larger ratio of CO 2 /COD were encountered after an interchange of the feed VOCs.

Evaluation of Trickle-Bed Air Biofilter Performance under Periodic Stressed Operating Conditions as a Function of Styrene Loading

Trickle-bed air biofilters (TBABs) are suitable for treating volatile organic compounds (VOCs) at a significantly high practical loading because of their controlled environmental conditions. The application of TBAB for treating styrene-contaminated air under periodic backwashing and cyclical nonuse periods at a styrene loading of 0.64–3.17 kg chemical oxygen demand (COD)/m3·day was the main focus of this study. Consistent long-term efficient performance of TBAB strongly depended on biomass control. A periodic in situ upflow with nutrient solution under media fluidization, that is, backwashing, was approached in this study. Two different nonuse periods were employed to simulate a shutdown for equipment repair or during weekends and holidays. The first is a starvation period without styrene loading, and the second is a stagnant period, which reflects no flow passing through the biofilter. For styrene loadings up to 1.9 kg COD/m3·day, removal efficiencies consistently above 99% were achieved by conducting a coordinated biomass control strategy, that is, backwashing for 1 hr once per week. Under cyclical nonuse periods for styrene loadings up to 1.27 kg COD/m3·day, stable long-term performance of the biofilter was maintained at more than 99% removal without employing back-washing. No substantial impact of nonuse periods on the biofilter performance was revealed. However, a coordinated biomass control by backwashing subsequently was unavoidable for attaining consistently high removal efficiency at a styrene loading of 3.17 kg COD/m3·day. As styrene loading was increased, reacclimation of the biofilter to reach the 99% removal efficiency following back-washing or the nonuse periods was delayed. After the nonuse periods, the response of the biofilter was a strong function of the biomass in the bed. No significant difference between the effects of the two different nonuse periods on TBAB performance was observed during the study period.

A Model for the Biofiltration of Butyl Acetate and Xylene Mixtures by a Trickle-Bed Air Biofilter

A mathematical model that incorporates the rates of the mass transfer process and the biofilm reaction is presented to predict the performance of a trickle-bed air biofilter (TBAB) for treating butyl acetate and xylene mixtures. A thorough understanding of the factors that influence these rates is necessary before the practical application of a TBAB for treating many kinds of pure and mixed volatile organic compounds (VOC) in the air stream. The model presented consists of a set of mass balance equations for butyl acetate, xylene and oxygen in the bulk gas phase and within the biofilm. The butyl acetate and xylene concentration profiles of the gas phase predicted by the model were in good agreement with the measured data documented in a previous study. The most relevant parameters were evaluated in a sensitivity analysis to determine their respective effects on the model performance. Four parameters were identified to strongly influence the model performance, the surface area of the biofilm per volume unit of the packing material (AS), the empty-bed residence time (EBRT), the maximum specific growth rate of the microorganism (μm), and the microbial yield coefficient (Y). The practical application of the model to derive the performance equation is also presented and discussed. This equation makes it possible to simultaneously obtain a relatively high VOC removal efficiency and to minimize the capital cost.

Evaluation of trickle-bed air biofilter performance for MEK removal

A lab-scale trickle-bed air biofilter (TBAB) was operated to evaluate the removal of methyl ethyl ketone (MEK) from waste gas. Three biomass control strategies were investigated, namely, backwashing and two non-use periods (starvation and stagnant). Five volumetric loading rates from 0.70 to 7.04 kg COD/m 3 day were employed. Backwashing once a week removed the excess biomass and obtained long-term, stable performance over 99% removal efficiency for loading rates less than 5.63 kg COD/m 3 day. The two non-use periods could also sustain 99% removal efficiency and could be employed as another means of biomass control for loading rates up to 3.52 kg COD/m 3 day. The non-use periods did not delay the recovery when the loading rate did not exceed 3.52 kg COD/m 3 day. The pseudo-first-order removal rate constant decreased with increase in volumetric loading rate. The effect of non-use periods on removal rate showed apparent transition from positive to negative with the increase in loading rate.

Biofiltration of Butyl Acetate and Xylene Mixtures Using a Trickle‐Bed Air Biofilter

AbstractButyl acetate and xylene mixtures are commonly encountered from the manufacture of semi‐conductor or opto‐electronic apparatuses. The release of these substances into the ambient air may have a negative effect on the air quality. This study attempts to employ a trickle‐bed air biofilter for treating butyl acetate and xylene mixtures under different gas flow rates and influent concentrations. Almost complete VOC removal could be attained with influent carbon loadings of BA (butyl acetate) and X (xylene) below 40 and 15 g/m3h, respectively. As the influent carbon loadings of BA and X were increased up to 150 and 110 g/m3h, removal efficiencies higher than 80 % were achieved. Therefore, the trickle‐bed air biofilter (TBAB) appeared efficient in the control of emissions containing mixtures of butyl acetate and xylene with low to medium carbon loadings. The removal efficiencies of butyl acetate were higher than those of xylene, indicating that butyl acetate was the substrate preferred in the utilization of butyl acetate and xylene mixtures by the microorganisms. Carbon recoveries of 98–101 % were achieved, demonstrating the accuracy of results. The carbon mass rate of the liquid effluent was approximately two to three orders of magnitude less than that of the CO2 effluent, indicating that the dissolved VOCs and their derivatives in the leachate were present in a negligible amount in the reactor. Applicable operating conditions of the TBAB unit for treating BA and X mixtures were suggested.

A model for treating toluene and acetone mixtures by a trickle-bed air biofilter

A mathematical model that incorporates mass transfer process and biofilm reactions is presented to predict the performance of a trickle-bed air biofilter (TBAB) for treating toluene (T) and acetone (ACE) mixtures. The model consists of a set of mass balance equations for T, ACE and oxygen in the bulk gas phase and within the biofilm. The gas phase T and ACE concentrations predicted by the model were in good agreement with the measured data available in a previous study. The important parameters were evaluated in the sensitivity analysis to determine their respective effects on the model performance. Four parameters were identified as strongly influencing the model performance, the surface area of the biofilm per unit volume of packing material (A S), the empty-bed residence time (EBRT), the maximum specific growth rate of microorganism (μ m), and the microbial yield coefficient (Y). A practical application of the model to derive the performance equation of TBAB is also given.

Biofiltration of butyl acetate by a trickle-bed air biofilter

The performance of a trickle-bed air biofilter (TBAB) for treating butyl acetate (BA) vapour was evaluated under different influent concentrations and gas flow rates. Almost complete BA removal could be achieved for influent carbon loading between 12 and 177 g m −3 h −1 . The TBAB appeared to be efficient for controlling BA emission under these carbon loading conditions. The applicable conditions of TBAB were thus suggested. A mathematical model that incorporates mass transfer process and biofilm reactions was presented to predict the performance of TBAB for BA removal. The effluent gas phase BA concentrations predicted by the model were in good agreement with the measured data. In a sensitivity analysis, three parameters were identified to strongly influence the model performance, the surface area of the biofilm per unit volume of packing material ( A S ), the empty-bed residence time (EBRT), and the microbial yield coefficient on BA ( Y B ). A practical application of the model to derive the performance equation of TBAB is also given.

A model for treating isopropyl alcohol and acetone mixtures in a trickle-bed air biofilter

A mathematical model that incorporates mass transfer process and biofilm reactions is presented to predict the performance of a trickle-bed air biofilter (TBAB) for treating isopropyl alcohol (IPA) and acetone (ACE) mixtures. The model consists of a set of mass balance equations for IPA, ACE and oxygen in the bulk gas phase and within the biofilm. The effluent gas phase IPA and ACE concentrations predicted by the present model were in good agreement with the measured data available in a previous study. The important parameters were evaluated by sensitivity analysis to determine their respective effects on model performance. Four parameters were identified that strongly influenced model performance: surface area of the biofilm per unit volume of packing material ( A S), empty-bed residence time (EBRT), maximum specific growth rate of microorganism ( μ m), and microbial yield coefficient ( Y). Practical applications of the model to derive the performance equation of TBAB for treating different inlet IPA and ACE concentrations were also demonstrated.

Biofiltration of isopropyl alcohol and acetone mixtures by a trickle-bed air biofilter

The performance of a trickle-bed air biofilter (TBAB) treating isopropyl alcohol (IPA) and acetone (ACE) mixtures was investigated under different gas flow rates and influent concentrations. In pseudo-steady-state conditions, the elimination capacities of IPA and ACE increased but the removal efficiencies decreased with increased influent carbon loading. The removal efficiencies of IPA were higher than those of ACE, indicating that IPA is a preferred substrate in the IPA and ACE mixtures. More than 90% removal efficiencies were achieved with influent carbon loadings of IPA and ACE below 80 and 53 g/m 3·h, respectively. The TBAB appears efficient for controlling mixed IPA and ACE emission with low to medium carbon loadings. Applicable operating conditions of TBAB for treating mixed IPA and ACE emission were suggested.

Biofiltration of isopropyl alcohol by a trickle-bed air biofilter.

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.

Biofiltration of toluene and acetone mixtures by a trickle-bed air biofilter

Toluene and acetone mixtures are commonly encountered from the manufacture of semi-conductor or opto-electronic apparatus. This study attempts to employ a trickle-bed air biofilter (TBAB) for treating toluene and acetone mixtures under different gas flow rates and influent concentrations. In the pseudo-steady-states, the elimination capacities of toluene and acetone increased but the removal efficiencies decreased with the increase of influent carbon loading. The removal efficiencies of toluene were higher than those of acetone, indicating that toluene is a preferred substrate in the mixtures. Greater than 90% removal efficiencies were achieved with influent carbon loadings of toluene and acetone below 125 and 15 g/m3 h, respectively. The TBAB appears efficient for controlling toluene and acetone mixture with medium toluene and low acetone loadings. Applicable operating conditions of TBAB for treating mixed toluene and acetone emission are suggested.

Biofiltration of 1,1,1-trichloroethane by a trickle-bed air biofilter.

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.