Biodegradation Of Volatile Organic Compounds Research Articles

Biodegradation of n-eicosane and VOCs: Cometabolism in a marine consortium

Several batch scale assays were performed in order to establish a correlation between the microbial removals of neicosane, in presence of different concentrations of volatile organic compounds (VOCs) which showed a partial removing.The selected VOCs were toluene and benzene. Results with benzene showed that the removal of this aromatic compoundwas decreased in presence of n-eicosane and the lowest removal was obtained when VOC concentration was higher. Theremoval of hydrocarbon was increased when VOC concentration was increased. In the assays with toluene, n-eicosanereached a higher removal when VOC concentration was increased, but the aromatic compound showed a decrease in itselimination dynamics. Control assays performed with VOCs at 28 mg/L without hydrocarbon showed higher removaldynamics for benzene than toluene. Also control assays of n-eicosane at two different concentrations but without anyVOC showed that its removal dynamic decreased in the absence of the aromatic compounds for both assays. The kineticadjustrnent obtained for toluene (Hill kinetic model) showed that the removal rate of this compound increased while itsconcentration at water-phase was higher. Although, when it was used a concentration of 50 mg/L or higher, the removalrate became almost constant. For benzene, the higher removal rate was reached with 38 mg/L. With higher concentration,the kinetic model showed inhibition, so the adjustrnent analyses fitted for a Monod kinetic model. n-Eicosane showed abetter adjustrnent with the Haldane kinetic model with an initial concentration of 188 mg/L for the highest removal rate.

Dynamic modeling of biodegradation and volatilization of hazardous aromatic substances in aerobic bioreactor

The aerobic biological process is one of the best technologies available for removing hazardous organic substances from industrial wastewaters. But in the case of volatile organic compounds (benzene, toluene, ethylbenzene, p-xylene, naphthalene), volatilization can contribute significantly to their removal from the liquid phase. One major issue is to predict the competition between volatilization and biodegradation in biological process depending on the target molecule. The aim of this study was to develop an integrated dynamic model to evaluate the influence of operating conditions, kinetic parameters and physical properties of the molecule on the main pathways (biodegradation and volatilization) for the removal of Volatile Organic Compounds (VOC). After a comparison with experimental data, sensitivity studies were carried out in order to optimize the aerated biological process. Acclimatized biomass growth is limited by volatilization, which reduces the bioavailability of the substrate. Moreover, the amount of biodegraded substrate is directly proportional to the amount of active biomass stabilized in the process. Model outputs predict that biodegradation is enhanced at high SRT for molecules with low H and with a high growth rate population. Air flow rate should be optimized to meet the oxygen demand and to minimize VOC stripping. Finally, the feeding strategy was found to be the most influential operating parameter that should be adjusted in order to enhance VOC biodegradation and to limit their volatilization in sequencing batch reactors (SBR).

Biodegradation of Volatile Organic Compounds from Paint Industries

Methyl ethyl ketone (MEK) and methyl iso-butyl ketone (MIBK) constitute significant proportion of the total VOC emissions from manufacturing and application processes of surface coatings. Biodegradation of MEK and MIBK using an acclimatized mixed culture was evaluated, under aerobic condition. Biodegradation studies were carried out using MEK and MIBK as single substrates and in combination. Mixed-pollutant studies were conducted in MEK-dominated system, MIBK-dominated system, and MEK-MIBK equi-concentration systems to understand the concentration-dependent interaction of these compounds in a biosystem. Experimental data obtained from single-pollutant system was used to estimate the biokinetic parameters, viz. μ(max), K(s), K(i), and Y(T), for these compounds. Among the several bio-kinetic models tested, Monod inhibition model was best suited for predicting the biodegradation of these two VOCs. Four multiple-substrate models, viz. no-interaction, competitive, un-competitive, and non-competitive were used to study the nature of inhibition for different combinations of these compounds. The biodegradation of MEK and MIBK mixtures was found to be best described by competitive inhibition model. However, the predictions were not very good for systems where MEK concentration was higher than MIBK concentration.

Key Role of Microbial Characteristics on the Performance of VOC Biodegradation in Two-Liquid Phase Bioreactors

Despite being studied for over 20 years, little is known about the mechanisms underlying the treatment of volatile organic compounds (VOCs) from industrial off-gases in two-liquid phase bioreactors (TLPBs). Recent reports have highlighted a significant mismatch between the high abiotic mass transfer capacity of TLPBs and the low VOC biodegradation rates sometimes recorded, which suggests that a process limitation might also be found in the microbiology of the process. Therefore, this study was conducted to assess the key role of microbial characteristics on the performance of VOC biodegradation in a TLPB using three different hexane degrading consortia. When silicone oil 200 cSt (SO200) was added to the systems, the steady state hexane elimination capacities (ECs) increased by a factor of 8.7 and 16.3 for Consortium A (hydrophilic microorganisms) and B (100% hydrophobic microorganisms), respectively. In the presence of SO200, Consortium C supported a first steady state with a 2-fold increase in ECs followed by a 16-fold EC increase after a hydrophobicity shift (to 100% hydrophobic microorganisms), compared to the system deprived of SO200. This work revealed that cell hydrophobicity can play a key role in the successful performance of TLPBs, and to the best of our knowledge, this is the first report on hydrophobic VOC treatment with exclusive VOC uptake within a nonbioavailable non aqueous phase. Finally, an independent set of experiments showed that metabolite accumulation can also severely inhibit TLPB performance despite the presence of SO200.

Potential of ionic liquids for VOC absorption and biodegradation in multiphase systems

This work aims to evaluate the feasibility of using imidazolium ionic liquids (ILs) in the design of multiphase bioreactors for the removal of volatile organic compounds (VOCs). The IL affinity for three model VOCs (dimethyl sulfide, dimethyl disulfide and toluene) was evaluated by means of the dimensionless partition coefficient ( K). It was observed that ILs showed K values comparable to typical liquid solvents used in multiphase bioreactors for VOC biodegradation ( K values ranged from 0.009 to 0.011, 0.0012 to 0.0013 and 0.00061 to 0.00096 for dimethyl sulfide, dimethyl disulfide and toluene, respectively). Toxicity tests showed that both ILs at concentrations of 5% and 10% (v/v) inhibited the glucose uptake of an activated sludge during approximately 24 h. After such lag period, the microorganisms were able to recover its metabolic activity. However, VOC biodegradation experiments showed that ILs at 5% (v/v) were toxic for the activated sludge and a toxic synergistic effect of the IL–VOC combination likely occurred. After acclimation to the target VOCs, only the toluene biodegradation capacity was significantly increased in the presence of ILs. These toxic effects represent a key drawback for the potential of IL-based multiphase systems devoted to VOC biodegradation. Therefore, this study suggests that microbial acclimation only to the VOCs is not enough to get an efficient biodegradation in multiphase systems including ILs as non-aqueous phases.

Integrated process for hydrophobic VOC treatment—solvent choice

AbstractA process coupling absorption of a gaseous pollutant in an organic phase and biodegradation was considered to treat hydrophobic volatile organic compounds (VOC). The purpose of this work was to choose the best solvent for the absorption of some VOC (dimethylsulfide, dimethyldisulfide, and toluene) and to examine solvent biodegradability as well as VOC biodegradation by activated sludge. Some experiments were carried out on some selected solvents leading to select di‐2‐ethylhexyl‐adipate (DEHA) and poly‐di‐methyl‐siloxane (PDMS) for their high absorption capacity. Biodegradation experiments showed that toluene and DMDS can be removed in solvent on water emulsions, while DMS removal by biodegradation remains to confirm owing to its high volatility. However, experiments showed DEHA biodegradation, contrarily to PDMS which was therefore selected for subsequent experiments.

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

AbstractBACKGROUND: 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

Numerical simulation for volatile organic compound removal in rotating drum biofilter

Rotating drum biofilters (RDBs) could effectively remove volatile organic compounds (VOCs) from waste gas streams. A mathematical model was developed on the basis of mass transport and mass balance equations in an RDB, the two-film theory, and the Monod kinetics. This model took account of mass transfer and biodegradation of VOC in the gas-water-biofilm three-phase system in the biofilter, and could simulate variations of VOC removal efficiency with a changing specific surface area and porosity of the media due to the increasing of biofilm thickness in the biofilter. Toluene was used as a model VOC. This model was further simplified by introducing a coefficient of the gas velocity and neglecting the water phase due to the complexity of operating conditions. The equations for the biofilm phase, gas phase, and biofilm accumulation in this model were solved using colloction method, analytic method, and the Runge-Kutta method separately. A computer program was written down as MATLAB to solve this model. Results of numerical solutions showed that toluene removal efficiency in the RDB increased and reached the maximum values of 97% on day 4 after the startup, and then decreased the remained at 90% after 5 more days of operation. Toluene concentration was high at the outermost layer where more than 70% toluene was removed, and was low at the innermost layer where less than 10% toluene was removed. The dynamic removal efficiencies from this model correlated reasonably well with experimental results for toluene removal in a multi-layered RDB.

Design of a large-scale surface-aerated bioreactor for biomass production using a VOC substrate

The design of a large-scale bioreactor for the production of bacterial biomass adapted to the biodegradation of volatile organic compounds was carried out. The bioreactor model used integrated the microbial kinetics and fluid dynamics described by the compartment model approach. The process conditions and kinetic parameters were adopted from the laboratory experimental study of (León, E., Seignez, C., Adler, N., Péringer, P., 1999. Growth inhibition of biomass adapted to the degradation of toluene and xylenes in mixture in a batch reactor with substrates supplied by pulses. Biodegradation 10, 245–250). The performance of the pulsed-batch stirred bioreactor under surface aeration conditions was simulated for different mixing configurations and conditions such as the impeller diameter, number of impellers, stirring speed, and oxygen pressure. The simulations were used for the cost analysis which resulted in the optimal design of the bioreactor.

Volatilization and Biodegradation of VOCs in Membrane Bioreactors (MBR)

Volatilization and biodegradation are major competitive volatile organic compound (VOC) removal mechanisms in biological wastewater treatment process, which depend on compound specific properties and system design/operational parameters. In this study, a mathematical model was used to determine major removal pathways at various organic loading rates (OLR), solids residence time (SRT) and dissolved oxygen (DO) concentrations in a biological process for vinyl acetate. Model results showed that biological treatment process should be designed with long SRT, high OLR and low DO concentrations to maximize biodegradation and minimize volatilization of VOCs. Unless a VOC is toxic to microorganisms under the given conditions, low VOC emission rates are an inherent advantage of MBRs, which operate at higher OLR and longer SRT compared to conventional activated sludge process. A lab scale membrane bioreactor (MBR) was operated at varying OLR to investigate the relative volatilization and biodegradation rates for acetaldehyde, butyraldehyde and vinyl acetate. Synthetic wastewater containing three VOCs was introduced to the MBR. The DO concentration and SRT was maintained at 2.0 mg L− 1 and 100 days, respectively. The overall VOC removal rate was more than 99.7% for three VOCs at all the OLR. For vinyl acetate, the biodegradation rate increased from 93.87 to 99.40% and the volatilization removal rate decreased from 6.09 to 0.59% as OLR was increased from 1.1 to 2.0 kg COD m− 3 d− 1. It was confirmed that a MBR can be a promising solution to reduce VOC emissions from wastewater.

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.

Biodegradation of volatile organic compounds by five fungal species.

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

Mass transfer coefficients of decane to emulsions in a bubble column reactor

The absorption of n-decane in water–silicone oil emulsions was studied in a laboratory-scale bubble column at different gas flow rates for the whole range of emulsion compositions. The volumetric mass transfer coefficients to the emulsions were estimated assuming that the gas phase contacts preferentially the non-aqueous phase. This assumption was supported by the experimental results. The Flory–Higgins equation was used for calculating the vapor pressure of n-decane dissolved in silicone oil. It was established that the volumetric mass transfer coefficient based on the emulsion volume is independent of the emulsion composition. These results indicate that a small fraction of silicone oil may be enough to provide a strong enhancement of volatile organic compounds and oxygen absorption, improving the economic aspects of the use of emulsions for biodegradation of volatile organic compounds.

Sorption and Biodegradation of Vapor-Phase Organic Compounds with Wastewater Sludge and Food Waste Compost

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

Parameter Estimation in Biofilter Systems

The purpose of this research is to estimate the unknown parameters of a mathematical model of the biodegradation of volatile organic compounds (VOCs) in a gas phase trickle-bed biofilter, using experimental results from a two-reactor pilot-scale system treating the VOC diethyl ether. The model considers a dynamic three-phase system, (biofilm, water, and gas), nonuniform bacterial population, and one limiting substrate. The nonlinear parameter estimation was done in two stages: estimates of the steady-state model parameters were obtained first, and then, these values were used in the estimation of the remaining parameters. Experimentally obtained biofilter performance curves and batch tests were used for the estimation of the steady-state parameters: maximum rate of substrate utilization (μmXf/Y), Monod constant (Ks), and biofilm/water diffusivity ratio for ether, rd. Dynamic biofilter performance data were used to obtain the estimates of the six remaining parameters: yield coefficient (Y). maximum grow...

Mathematical model for the biodegradation of VOCs in trickle bed biofilters

The objective of this work is to develop a fundamental mathematical model that describes the biodegradation of volatile organic compounds (VOCs) in gas phase trickle-bed biofilters, and to estimate the unknown model parameters. The mathematical model considers a three-phase system (biofilm, water, and gas phase), non-uniform bacterial population, and one limiting substrate. Two pilot-scale trickle-bed biofilters were operated to remove the VOC diethyl ether from a waste gas stream. Experimental results from this system were used to estimate the unknown parameters of the steady-state model: the maximum rate of substrate utilization μmXf/Y, the Monod constant, Ks, and the ether biofilm/water diffusivity ratio, rd. While the value of μmXf/Y was uniquely determined, the values of Ks and rd were highly correlated. High values of the Monod constant and the ether diffusivity in the biofilm gave similar predictions to those corresponding to low values of both parameters. Batch studies were used to estimate the value of Ks without mass transfer limitations showing that Ks < 1 mg/L=2.6 mg COD/L. Using this information and biofilter operating data the true values of Ks and rd were determined.

Mathematical model for the biodegradation of VOCs in trickle bed biofilterss

The objective of this work is to develop a fundamental mathematcal model that describes the biodegradation of volatile organic compounds (VOCs) in gas phase trickle-bed biofilters, and to estimate the unknown model parameters. The mathematical model considers a three-phase system (biofilm, water, and gas phase), non-uniform bacterial population, and one limuting substrate. Two pilot-scale trickle-bed biofilters were operated to remove the VOC diethyl ether from a waste gas stream. Experimental results from this system were used to estmate the unknown parameters of the steady-state model: the maximum rate of substrate utilization µmXf / Y, If. the Monod constant, Ks and the ether biofilm/water dlffusivity ratio. rd While the value of µmXf / Y was uniquely determined, the values of Ks, and rd, were highly correlated. High values of the Monod constant and the ether diffusivity in the biofilm gave similar predictions to those corresponding to low values of both parameters. Batch studies were used to estimate the value of Ks, without mass transfer limitations showing that Ks, < 1 mg/L=2.6 mg CODIL. Using this information and biofilter operating data the true values of Ks, and rd were determined.

Dynamic Mathematical Model for the Biodegradation of VOCs in a Biofilter: Biomass Accumulation Study

Although biofiltration is a firmly established technology for the control of emissions of volatile organic compound (VOCs), more fundamental research is still needed. This work uses a mathematical model describing the dynamic physical and biological processes occurring in a packed trickle-bed air biofilter to analyze the relationship between biofilter performance, biomass accumulation in the reactor, and mathematical description of the packed bed porous media. In this study a biofilter packed with pelletized support media was used to treat toluene achieving removal efficiencies over 99% and 97% for 4.1 and 6.2 kg COD/m{sup 3} day toluene loading, respectively. Experimental results showed that as biomass accumulates in the reactor, the available area for the contaminant to diffuse into the biofilm decreases causing a drop in removal efficiency. This effect is specially important for biofilters where there is a high degree of biomass accumulation that significantly affects biofilter performance. In response to these observations, a new approach for the calculation of the biofilm specific surface area of the reactor as a function of biomass growth was developed. Three models of the reactor porous medium were analyzed. The medium was represented as a bed of equivalent spheres in the first model, as an equivalentmore » set of parallel pipes in the second model, and as an equivalent set of flat parallel plates in the third model. The first two models, spheres and pipes, were proven superior in their ability to explain the system performance. The effect of contaminant solubility on biofilter performance was also analyzed.« less

Comparison of methods for determining biodegradation kinetics of volatile organic compounds

Regulations, such as the Synthetic Organic Manufacturing Industry Hazardous Organic National Emission Standards for Hazardous Air Pollutants (SOCMI‐HON) rule of the recently promulgated Clean Air Act Amendments, target the reduction of emissions of volatile organic compounds (VOCs) from industrial sources including process vents, tanks, equipment leaks, and wastewater. As required by the regulation, Method 304 was used to measure the VOC biodegradation kinetics, which were then used to determine the degree of biodegradation versus air stripping. In addition to Method 304, batch tests that use oxygen addition (BOX tests) and serum bottle (SB) tests were use dto determine the biodegradation kinetics of ethylene oxide (EO) andacetaldehyde (AA) in a chemical plant. The Method 304 first‐order rate constant was measured to be 0.99 L/g · h and 0.24 L/g · h for EO and AA, respectively. Linearized first‐order rate constants from the BOX and SB tests were greater than the Method 304 rate constants by at least an order of magnitude. Also, the BOX tests and SB test kinetics correctly predicted full‐scale bioreactor emissions, whereas the Method 304 kinetics did not.

Transient Behavior of Biofilters: Start-Up, Carbon Balances, and Interactions between Pollutants

The work describes the aerobic biodegradation of volatile organic compound (VOC) mixtures from effluent air streams in laboratory-scale compost based biofilters. A rapid start-up of the system (3–5 d) was observed and 82% of the carbon in the influent pollutant (methyl ethyl ketone) was recovered as carbon dioxide in the exhaust air after this period. Biofilter performance and carbon dioxide production were also investigated during and after 0.5–1-h step inputs of 2–10 g m−3 of hexane, acetone, 1-propanol, and/or methyl isobutyl ketone (MIBK) during steady methyl ethyl ketone (MEK) treatment. Carbon dioxide patterns suggest that pulsed pollutants were first sorbed onto the packing material and subsequently degraded within 2–5 h. Hexane was not sorbed, and thus not degraded to a significant extent. Little effect was observed of the step inputs on the overall MEK removal process, mainly because the reactors were operated well below MEK breakthrough loading. However, the analysis of MEK profiles within the biofilter bed showed that significant inhibition did indeed occur. An even more important inhibition was observed between 1-propanol, MIBK, and acetone, when such a mixture was injected into the reactor. Practical design of biofilters should consider the possibility of reduced performances due to the presence of multiple VOCs in the waste air stream.