利用CO2为碳源的新型氢基质生物膜技术去除水中氧化性污染物

The treatment of drinking water or groundwater contaminated with oxidized contaminants has been extensively concerned. The H2-based membrane biofilm reactor (MBfR) delivers H2 gas as a clean and inexpensive inorganic electron donor to autotrophic bacteria, and reduces oxidized contaminants as electron acceptors. MBfR process has been studied for many years in our group. Nitrate (NO3-), sulfate(SO42-) chromate (Cr(VI)) and chlorophenol (2-CP) removal characteristic in MBfR were tested and good results were obtained. In all these processes, NaHCO3 was used as inorganic carbon resource and pH adjuster combined with phosphate buffer solution. Here in our new MBfR, double membrane aeration technique will be used to deliver H2 and CO2 simultaneously, H2 gas is the electron donor to the autotrophic bacteria, while, CO2 is inorganic carbon resource and pH adjuster. Due to the hollow-fiber membranes aeration technique can improve the solutions of H2 and CO2 in water in a "bubbleless" way and increase the utilization of the two gases, so the mutual gains function of oxidized contaminants removal and CO2 emission reduction will be gained in the new process. Vanadium (V), selenium (Se) and arsenic (As) are the potential target contaminants in this project. We will focus on the bioreduction of V, Se and As in the double membrane aeration MBfR which uses CO2 as carbon source. Microbial ecology will be investigated to identification the microbial community structure during the bioreduction process. H2 and CO2 permeability of different membrane materials (PVC, PVDF) will be determined by different mathematics models. A steady-state, multispecies biofilm model for simultaneous reductions in MBfR will be developed to simulate the MBfR performance, the effects of different factors, and biofilm characteristics during the bioreduction process. This project will develop a new bioreduction process for vanadium, selenium, arsenic, and other similar oxidized contaminants.

水中氧化性污染物严重威胁着生态和人类健康，氢基质膜生物膜反应器(MBfR)去除该类污染物是以H2为电子供体、以氧化性污染物为电子受体，无二次污染。课题组已研究MBfR技术多年，对几种典型氧化性污染物进行了研究并取得成果，过程是采用NaHCO3为无机碳源并与磷酸盐缓冲液结合调节系统的pH值。 本项目采用双膜曝气技术同时通入H2和CO2，前者提供电子供体，后者为贫营养地下水提供碳源并稳定pH值。气体利用率因膜曝气得到提高，在去除污染物的同时实现CO2减排。拟以高价钒、硒和砷为目标污染物，考察以CO2为碳源的双膜曝气MBfR去除污染物的效果；鉴定微生物群落结构，解析微生物与去除效果的内在联系；研究不同气体通过不同膜材料的渗透性能，建立扩散模型；结合研究数据建立多种污染物共存体系的数学模型，预测主要成分变化趋势，分析不同因素的影响和生物膜特征参数变化，为该类污染物的治理提供高效、清洁途径。

水中氧化性污染物严重威胁着自然生态和人类健康，对其去除是国内外研究的热点。氢基质膜生物技术(MBfR)去除该类污染物是以H2为电子供体、以氧化性污染物为电子受体，无二次污染。本项目在传统MBfR的基础上进行改进，采用双膜曝气技术同时通入H2和CO2，前者提供电子供体，后者为贫营养地下水提供碳源并稳定pH值。.为了精确提供CO2以维持反应器内pH稳定，通过费克第一定律和连续曝气稳态实验，求出在25℃气温下，CO2在PVC膜丝中的扩散系数为3.8375×10−7 m2/d。根据求得的扩散系数设计反应器的膜丝面积，进行硝酸盐去除试验。试验结果表明：通过膜曝气提供的CO2在18d-58d的反应过程中可以有效中和反硝化过程中产生的碱基，维持反应器内的pH在7.3-7.5之间，同时提供的CO2满足微生物新陈代谢需要的碳源，反应器的总氮去除效率可以稳定在98%以上。这也验证了之前求得的CO2扩散系数的准确性。.通过构建了一种H2/CO2双膜曝气型H2-MBfR，并测算实验所用的PVDF中空纤维超滤膜H2和CO2的扩散系数分别为：0.005 m2/d·bar和3.8×10-7 m2/d，以此为基础计算并调节PH2和PCO2使反应器能够在稳定的pH条件下长期运行。在提供足量的PH2条件下，NO3--N表面负荷和去除率可以达到0.137 g N/m2·d和99.6%，ClO4-表面负荷最高可达0.068 g/m2·d。.本基金研发了新型的双膜曝气式MBfR，并对其进行了系统的研究。基于双膜曝气式MBfR运行过程中CO2分压控制的必要性建立了数学模型预测CO2分压对双膜曝气式MBfR出水pH，LSI的影响，对实际工况运行中CO2分压的设定具有指导意义。本研究对双膜曝气MBfR长期运行的稳定性进行了考察。当反应器在适宜CO2分压下运行时，反应器内的pH值控制良好，出水效果稳定。双膜曝气式MBfR同步去除多种污染物共存的实际地下水时运行稳定，对各污染物去除效果良好，分子生物学研究结果发现通H2和通CO2的膜丝表面微生物群落结构有差异，但是在两束生物膜上均检测到氢自养反硝化功能菌。