四氯乙烯在不同地下水环境的生物共代谢降解

Co-metabolism Biodegradation of Tetrachloroethylene under Different Groundwater Conditions

四氯乙烯是地下水中常见的污染物,采用生物方法进行处理的优点是可以实现无害化、无二次污染、处理成本低。四氯乙烯只能在厌氧条件下发生还原脱氯,目前对产甲烷环境下四氯乙烯的降解研究较多,而对较弱还原环境,如反硝化、铁锰还原和硫酸盐还原环境下四氯乙烯的脱氯行为研究甚少。本文采用批实验,研究了在不同地下水环境,包括反硝化、铁还原、硫酸盐还原、混合电子受体和天然地下水环境下四氯乙烯的脱氯性能。结果表明,铁还原环境的四氯乙烯脱氯效果最好,天然地下水环境次之,四氯乙烯的去除率分别达到91.34%和84.71%,四氯乙烯很快转化为三氯乙烯,并可以进一步转化为二氯乙烯,四氯乙烯的降解符合准一级反应动力学方程。在反硝化、硫酸盐还原、混合电子受体环境,四氯乙烯的去除以挥发为主,降解只占很小的比例,且最终的降解产物只有三氯乙烯。地下水中三价铁的存在,对于四氯乙烯脱氯起促进作用;而当地下水中硝酸盐和硫酸盐的浓度较高时,四氯乙烯脱氯受到抑制。

Tetrachloroethylene （PCE） is one of the most common contaminants in groundwater. The microorganism treatment method has the advantages of low cost and no secondary pollution. PCE can only be biodegraded under reducing conditions, and most research aimed at PCE biodegradation under methanogenic conditions and few under relatively weak reducing conditions, such as denitrifying, iron reducing, sulfate reducing. Trichloroethylene （TCE） biodegradation under different groundwater conditions, including denitrifying, iron reducing, sulfate reducing, mixing electron acceptors and natural groundwater condition, was studied with batch experiments and is described in this paper. The results show that the iron reducing condition is the best condition for PCE biodegradation, followed by natural groundwater condition with PCE removal efficiencies of 91.34% and 84.71% respectively. PCE is transformed to TCE quickly, and to dichlorethane （DCE） eventually. PCE biodegradation is in accordance with the first order kinetic equation. It is difficult to achieve PCE biodegradation in denitrifying, sulfate reducing and mixing electron acceptor conditions, and the degradation product is TCE only, where most PCE is removed by volatilization. PCE biodegradation is promoted by the existence of ferric iron, while it is inhibited by the high concentration of nitrate and sulfate.