Membrane Bioreactor for Control of Volatile Organic Compound Air Emissions

Ergas生物过滤是一种低成本和有效的控制化学和加工工业中可生物降解的挥发性有机化合物（VOC）排放的方法。然而，这些系统的研究和现场应用仅限于进口VOC浓度低于1,000 ppmv。在高进口浓度下，微生物生长导致生物过滤器介质孔空间堵塞。此外，当降解导致酸性代谢物的形成或必须添加共底物以诱导共代谢所需的酶时，这些系统的用途有限。为克服上述限制，必须发展控制挥发性有机化合物的生物处理系统：1)在具有高比表面积和低扩散长度的介质中加入挥发性有机化合物的传质，2)加入高生物量浓度以保持高生物降解率，3)提供一种浪费生物质以防止堵塞的方法，4)提供一种添加pH缓冲液、营养物质和/或共底物以支持微生物种群和中和酸性代谢物的方法。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，并在小反应器体积内实现高VOC去除效率。反应器利用疏水微孔中空纤维膜进行传质。含有挥发性有机化合物的气体通过中空纤维膜束。气相中的可溶性化合物通过膜转移到周围的液体营养介质中。然后，液相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：研究控制传质和生物降解的因素；模型氯化挥发性有机化合物（VOC）、三氯乙烯共代谢使用条件研究质量传递和生物降解数学模型的改进和测试。

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.