Performance evaluation of a biotrickling filter treating a mixture of oxygenated VOCs during intermittent loading

Laboratory scale-studies on the biodegradation of a 1:1:1 weight mixture of three oxygenated volatile organic compounds (VOCs), ethanol, ethyl acetate, and methyl-ethyl ketone (MEK) in a biotrickling filter (BTF) were carried out using two identically sized columns, filled with different polypropylene rings. The performance of the BTFs was examined for a period of 10 months applying several operational strategies. Similar performance was obtained for both supports. Intermittent flow rate of trickling liquid was shown beneficial to improve the removal efficiency (RE). Continuous feeding of VOC resulted in an excessive accumulation of biomass so high pressure drop was developed in less than 2…

Biofiltration of ethyl acetate under continuous and intermittent loading

A laboratory-scale peat biofilter was used for ethyl acetate removal from an air stream over a period lasting 1 yr. In a first stage, the biofilter was operated under continuous mode: a maximum elimination capacity of 400 g m−3 h−1 was obtained, and ethyl acetate was efficiently degraded with empty bed residence time (EBRT) as short as 22 s. The estimated yield coefficient, determined from the carbon dioxide production, resulted in 0.42 g dry biomass produced per gram of ethyl acetate consumed. The living and the dead cell concentrations were also monitored. The dead cell percentages varied between 18 and 85%, progressive increases in the dead cell percentages were achieved as EBRT decrease…

Modelling Cd(II) removal from aqueous solutions by adsorption on a highly mineralized peat. Batch and fixed-bed column experiments

This paper evaluates the potential use of a locally available organic soil amendment as a low-cost adsorbent. The removal of cadmium from aqueous solutions was studied by means of kinetic, batch and fixed-bed experiments. Batch experiments were conducted to evaluate the process kinetics and the removal equilibrium over a broad pH range. Pseudo-second-order kinetics and Freundlich equilibrium parameters were obtained. Six column experiments were carried out at different flow-rates and feed concentrations. Breakthrough curves showed higher metal retention than expected from the batch adsorption isotherms. Column modelling assuming rate-controlled pore diffusion was successfully performed. The…

A Tool for Predicting the Dynamic Response of Biotrickling Filters for VOC Removal

This article presents the development of a MATLAB® computer program to simulate the performance of biotrickling filters. Since these filters behave differently during spraying and nonspraying cycles, the presented simulation tool is built on top of a mathematical description of each situation. The resulting variable-structure model is then used as the basis for simulation experiments. The model presented herein represents the first attempt to take into account the variable spraying pattern usually found in industrial installations. Overall, the software is flexible and easy to use, allowing the user to specify the emission concentration pattern, the gas concentration pattern, as well as the…

Investigating bacterial populations in styrene-degrading biofilters by 16S rDNA tag pyrosequencing

Microbial biofilms are essential components in the elimination of pollutants within biofilters, yet still little is known regarding the complex relationships between microbial community structure and biodegradation function within these engineered ecosystems. To further explore this relationship, 16S rDNA tag pyrosequencing was applied to samples taken at four time points from a styrene-degrading biofilter undergoing variable operating conditions. Changes in microbial structure were observed between different stages of biofilter operation, and the level of styrene concentration was revealed to be a critical factor affecting these changes. Bacterial genera Azoarcus and Pseudomonas were among…

Modelling mass transfer properties in a biotrickling filter for the removal of isopropanol

Abstract A study was carried out to model mass transfer properties in biotrickling filters, treating isopropanol as the target pollutant. This study was extended to the mass transfer of oxygen related to the fact that the treatment of hydrophilic compounds by biotrickling filtration is often limited by oxygen. A simple method for each compound was developed based on their physical properties. The influence of temperature on Henry’s law constant of isopropanol was determined. An increase of 1.8 per 10 °C for the dimensionless Henry’s law constant was obtained. The determination of the overall mass transfer coefficients of isopropanol (KGa) was carried out, obtaining values between 500 and 18…

Mathematical modeling of the biofiltration of ethyl acetate and toluene and their mixture

Abstract A dynamic model for ethyl acetate and toluene removal by biofiltration is presented. Haldane-type kinetic expressions that include the oxygen limitation, the inhibition effect due to high concentration of substrate, and the cross-inhibition between substrates have been considered. A decrease in the biomass density with the bed height was proposed to represent the performance of peat biofilters over a broad range of operating conditions. Experimental yield coefficients have been derived from the experimental CO 2 production data. The unknown kinetic parameters of the model along with the coefficient for axial biomass density distribution were calibrated using experimental data from …

Removal of ethyl acetate, n-hexane and toluene from waste air in a membrane bioreactor under continuous and intermittent feeding conditions

BACKGROUND: European Union environmental policy has focused on abatement of volatile organic compounds (VOCs) from industrial emissions, and new European VOC emission limits have been established. This study analyzes the performance of a composite membrane bioreactor treating air stream contaminated with ethyl acetate, n-hexane and toluene under continuous and intermittent feeding conditions. RESULTS: The system was operated under continuous feeding conditions: removal efficiencies (REs) higher than 99% were obtained for inlet loads up to 200 g m−3 h−1 and empty bed residence times (EBRTs) as short as 15 s for ethyl acetate. A maximum elimination capacity of 75 g m−3 h−1 (RE ∼66%) at an EBR…

Removal of TEX vapours from air in a peat biofilter: influence of inlet concentration and inlet load

This paper presents the results of the study of the removal of toluene, ethylbenzene, and o-xylene (TEX) by biofiltration using a commercial peat as filter-bed material. Runs with a single organic compound in air, and with the mixture of TEX in air, were carried out for at least 55 days in laboratory-scale reactors inoculated with a conditioned culture. The influence of organic compound inlet load and of gas flow rate on the biofilter's performance was studied, including relatively high values of pollutant inlet concentration (up to 4.3 gC m−3 for ethylbenzene, 3.2 gC m−3 for toluene, and 2.7 gC m−3 for o-xylene). Results obtained show maximum elimination capacities of 65 gC m−3 h−1 for o-x…

Long-term performance of peat biofilters treating ethyl acetate, toluene, and its mixture in air.

Three laboratory-scale peat biofilters were operated at 90 s empty bed residence time (EBRT) for over a year. Biodegradation of ethyl acetate, toluene, or a 1:1 mixture were investigated. In first stage, inlet concentration was progressively increased from 0.4 to 4.5 g/m3. The maximum elimination capacity (EC) found for ethyl acetate was 190 gC/m3·h, and it was not affected by toluene. The maximum EC found for toluene as a sole contaminant was 150 gC/m3·h, but the presence of ethyl acetate decreased the toluene maximum EC to 80 gC/m3·h. From respirometry monitoring, values of 3.19 g CO2/gC and 3.06 g CO2/gC for pure ethyl acetate and pure toluene, respectively, were found, with overall yiel…

Ethylbenzene removal under mesophilic conditions in a biofilter withMacadamia ternifolianutshells as a carrier material

BACKGROUND Biofilters are suitable to treat industrial emissions polluted with volatile organic compounds (VOCs), responsible for photochemical smog and depletion of the ozone layer. This study analyzes the performance of a biofilter with Macadamia ternifolia nutshells as a carrier material treating air streams contaminated with ethylbenzene under mesophilic conditions with continuous feeding. RESULTS The biofilter was operated continuously for 5 months applying several inlet loads (IL), empty bed residence times (EBRT) and temperatures. At a temperature of 303 ± 1 K removal efficiencies (RE) higher than 90% were obtained for ILs lower than 85.6 g m−3 h−1 and 70.6 g m−3 h−1 at an EBRT of 15…

Biotrickling filter modeling for styrene abatement. Part 2: Simulating a two-phase partitioning bioreactor.

Abstract A dynamic model describing styrene abatement was developed for a two-phase partitioning bioreactor operated as a biotrickling filter (TPPB-BTF). The model was built as a coupled set of two different systems of partial differential equations depending on whether an irrigation or a non-irrigation period was simulated. The maximum growth rate was previously calibrated from a conventional BTF treating styrene (Part 1). The model was extended to simulate the TPPB-BTF based on the hypothesis that the main change associated with the non-aqueous phase is the modification of the pollutant properties in the liquid phase. The three phases considered were gas, a water–silicone liquid mixture, …

Biological nitrate removal from wastewater of a metal-finishing industry

An upflow packed bed reactor at laboratory scale has been operated for a continuous period of 5 months to investigate the technical feasibility of biological nitrate removal applied to the effluent of the coagulation-sedimentation wastewater of a metal-finishing industry. The reactor was fed with industrial wastewater in a five-fold dilution to reproduce the global spill in the factory (20/80, industrial wastewater/domestic wastewater) with a concentration of nitrate between 141 and 210 gNO(3)-N/m(3). Methanol was added as a carbon source for denitrification. Inlet flow rate was progressively increased from 9 to 40 L/day (nitrogen input load from 45 to 250 gNO(3)-N/(m(3)h)). The highest obs…

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 a…

Biotrickling Filters for Removal of Volatile Organic Compounds from Air in the Coating Sector

Performance of a pilot-scale biotrickling filter in controlling the volatile organic compound emissions in a furniture manufacturing facility.

A 0.75-m3 pilot-scale biotrickling filter was run for over 1 yr in a Spanish furniture company to evaluate its performance in the removal of volatile organic compounds (VOCs) contained in the emission of two different paint spray booths. The first one was an open front booth used to manually paint furniture, and the second focus was an automatically operated closed booth operated to paint pieces of furniture. In both cases, the VOC emissions were very irregular, with rapid and extreme fluctuations. The pilot plant was operated at an empty bed residence time (EBRT) ranging from 10 to 40 sec, and good removal efficiencies of VOCs were usually obtained. When a buffering activated carbon prefil…

Fully aerobic bioscrubber for the desulfurization of H2S-rich biogas

Abstract A fully aerobic bioscrubber for the desulfurization of H2S-rich biogas was developed in the present study by coupling an absorption column and a bubble column bioreactor. The bioscrubber treated H2S loading rates of 37, 59, and 100 g S mliquid−3 h−1 at gas residence times of 6.6, 4.1 and 2.4 min in the absorption column, respectively. Stable H2S removal efficiencies above 80% were recorded at all the conditions tested. The bioscrubber was robust towards short- and long-term operation shutdowns (5 and 18 days), the H2S removal performance being recovered after few hours. The aerated bubble column bioreactor was operated at slightly alkaline conditions (pH 8 ± 0.5), which prevented H…

Dynamic Mathematical Modelling of the Removal of Hydrophilic VOCs by Biotrickling Filters

A mathematical model for the simulation of the removal of hydrophilic compounds using biotrickling filtration was developed. The model takes into account that biotrickling filters operate by using an intermittent spraying pattern. During spraying periods, a mobile liquid phase was considered, while during non-spraying periods, a stagnant liquid phase was considered. The model was calibrated and validated with data from laboratory- and industrial-scale biotrickling filters. The laboratory experiments exhibited peaks of pollutants in the outlet of the biotrickling filter during spraying periods, while during non-spraying periods, near complete removal of the pollutant was achieved. The gaseou…