Membrane Bioreactor for Control of Volatile Organic Compound Air Emissions

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9530592 Ergas Biofiltration is a low cost and effective method for controlling emissions of biodegradable volatile organic compounds (VOC's) from chemical and process industries. Studies and field applications of these systems, however, have been limited to inlet VOC concentrations of less than 1,000 ppmv. At high inlet concentrations, microbial growth results in plugging of biofilter media pore spaces. In addition, these systems are of limited use where degradation results in the formation of acidic metabolites or where cosubstrates must be added to induce enzymes required for cometabolism. To overcome the limitations described above, biological treatment systems for VOC control must be developed which: 1) incorporate mass transfer of VOCs across a media with high specific surface area and low diffusion length, 2) incorporate high biomass concentrations to maintain high biodegradation rates, 3) provide a method for wasting biomass to prevent clogging, and 4) provide a method for addition of pH buffers, nutrients, and/or co- substrates to support the microbial population and neutralize acidic metabolites. A specially designed bioreactor is under investigation which has the potential to meet these requirements and achieve high VOC removal efficiencies in small reactor volumes. The reactor utilizes hydrophobic microporous hollow fiber membranes for mass transfer. Gases containing VOCs are passed through bundles of hollow fiber membranes. Soluble compounds in the gas phase are transferred through the membranes to the surrounding liquid nutrient media. Compounds in the liquid phase are then available for biodegradation. The proposed project will further investigate the use of microporous hydrophobic hollow fiber membrane systems for biological treatment of gas phase VOCS. Specific objectives include: investigation of factors controlling mass transfer and biodegradation; investigation of conditions for use in cometabolism of the model chlorinated VOC, tr ichloroethene; refinement and testing of mathematical models of mass transfer and biodegradation.