Membrane Bioreactor for Control of Volatile Organic Compound Air Emissions

9530592 Ergas生物过滤是控制化工和加工行业可生物降解挥发性有机化合物(VOC)排放的低成本和有效方法。然而，这些系统的研究和现场应用仅限于入口VOC浓度低于1,000 ppmv。当进口浓度较高时，微生物生长会堵塞生物滤池介质的孔隙空间。此外，在降解导致形成酸性代谢物或必须添加共底物以诱导共代谢所需的酶的情况下，这些系统的使用有限。为了克服上述限制，必须开发用于控制VOC的生物处理系统：1)包括VOCs在具有高比表面积和低扩散长度的介质中的传质，2)包括高生物量浓度以保持高的生物降解率，3)提供一种浪费生物量的方法以防止堵塞，以及4)提供一种添加pH缓冲剂、营养物质和/或共基质的方法来支持微生物种群并中和酸性代谢物。一种特殊设计的生物反应器正在研究中，它有可能满足这些要求，并在较小的反应器体积内实现高VOC去除效率。该反应器采用疏水微孔中空纤维膜进行传质。含有VOCs的气体通过中空纤维膜。气相中的可溶化合物通过膜转移到周围的液体营养介质中。然后，液体中的化合物可用于生物降解。该项目将进一步研究微孔疏水中空纤维膜系统在气相VOCs生物处理中的应用。具体目标包括：调查控制传质和生物降解的因素；调查用于模型氯化挥发性有机化合物和三氯乙烯共代谢的条件；改进和测试传质和生物降解的数学模型。

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.