微米铁复合生物碳源对地下水中1,2-二氯乙烷的高效去除

1,2-二氯乙烷(1,2-DCA)是一类地下水中常见的难降解饱和氯代烃,为探究厌氧条件下零价铁(ZVI)协同生物作用对其降解规律,采集北京市某氯代烃污染场地地下水及含水层土壤,利用微宇宙实验体系,通过添加由微米级零价铁(mZVI)、生物碳源及营养组成的复合药剂,考察不同条件下1,2-DCA的去除效果,并对地下水理化参数的变化进行长期监测.结果表明:复合药剂添加量为3%时,恒温、避光、匀速振荡的反应条件下,15 d内地下水中的1,2-DCA即可降至低于检出限.中性pH及SO_4~(2-)的存在更有利于1,2-DCA的脱氯降解. 30 d后仅检测到体系中明显的乙烯产生,推测双脱氯消除为1,2-DCA在该体系内的主要降解途径.此外,复合药剂加入后,地下水可长时间维持较低的氧化还原电位(-100～-300 m V)、溶解氧(0. 5 mg·L~(-1))以及适宜的pH值(6. 5～7. 5),利于厌氧微生物活性的维持及脱氯反应的进行.

High Efficiency Removal of 1,2-Dichloroethane from Groundwater by Microscale Zero-valent Iron Combined with Biological Carbon Source

In order to explore the degradation mechanism of 1,2-dichloroethane (1,2-DCA), which is one of the refractory saturated chlorinated hydrocarbons, the groundwater and aquifer soil from a chlorinated hydrocarbon contaminated site in Beijing were collected to carry out microcosm experiments under anaerobic conditions using zero-valent iron (ZVI) coupled with biological action. The removal rate of 1,2-DCA under different conditions was investigated by adding a composite agent consisting of micron zero-valent iron (mZVI), a biological carbon source, and a few nutrients. Changes of the groundwater physical and chemical parameters were monitored. The results showed that, when the dosage of the composite agent reached 3%, the concentration of 1,2-dichloroethane could be reduced to below the detection limit within 15 days. Neutral pH and the presence of SO₄^2- were more conducive to the dechlorination of 1,2-DCA. After 30 days, an obvious increase in the ethene concentration was detected (0.17-0.52 mg·L^-1) and no significant vinyl chloride, chloroethane, or ethane was observed in the microcosms, illustrating that the dihaloelimination was the main degradation pathway of 1,2-DCA in the system. In addition, the groundwater could maintain a low oxidation-reduction potential (-100 to -300 mV), dissolved oxygen (<0.5 mg·L^-1), and a suitable pH value (6.5-7.5) for a long time under the synergy of mZVI and a biological carbon source. This was beneficial to the activity of anaerobic microorganisms and to the dechlorination reaction.