纳米铁为脱氯菌供电降解三氯乙烯实验研究

Microbial Reductive Dechlorination of TCE with Nano Iron Serving as Electron Donor

采用一种从氯乙烯污染场址土壤中提取的脱氯菌种(Dehalococcoidesspp.)进行三氯乙烯(TCE)降解实验,研究纳米铁厌氧腐蚀产氢为该脱氯菌种提供电子的可能性.结果表明,在甲醇做电子供体时,稀释25倍的菌液[(2.0±0.44)×105cell/mL)]可以在96 h内将20 mg/L TCE完全降解,并在190 h时有2.706μmol乙烯产生.而在无甲醇做电子供体时,96 h内只有部分TCE转化为顺二氯乙烯(cis-DCE),且190 h时几乎无乙烯产生(0.159μmol),因此无电子供体时菌液脱氯活动不能维持.但在4 g/L纳米铁腐蚀产氢的情况下,脱氯菌可以利用纳米铁产生的阴极氢维持脱氯活动,在131 h内将20 mg/L TCE完全降解,并且其耦合的脱氯速率高于纳米铁单独降解时的速率.从乙烯的产量分析中可以看出,纳米铁供电时190 h后由脱氯菌产生的乙烯量为1.187μmol,明显低于甲醇做电子供体时乙烯的产量2.706μmol,表明纳米铁可能对微生物存在一定的毒性效应.同时反应190 h后乙炔的产量为0.109μmol,相对低于与纳米铁单独降解TCE时的产量0.161μmol,说明微生物在无电子供体的情况下,竞争利用了纳米铁与水反应产生的电子导致乙炔的生成量降低.上述结果表明,4 g/L的纳米铁与水反应生成的活性氢可以为脱氯菌提供电子,并维持其脱氯活动,这对纳米铁和脱氯菌耦合应用于地下水的有机氯修复具有重要的实际意义.

A trichloroethylene （TCE） dechlorinatlng enrichment （Dehalococcoides spp. ）, which was isolated from soil of chlorinated ethene contaminated site, was used to investigate whether nano-scale zero valent iron （NZVI） could serve as electron donor for this consortium via cathodic H2 production during anaerobic corrosion. The results show that in the presence of methanol serving as electron donor, deehlorinating culture of 25 fold dilution E （2.0±0.44）×10^5 cell/mL] degraded 20 mg/L rICE completely in 96 h, which was accompanied by the production of 2.706 μmol ethene in 190 h. Methanol-free control caused partial degradation of TCE to primarily c/s-DCE in 96 h, with only 0.159μmol ethene produced in 190 h. This indicates bacteria cannot reduce ＇ICE to ethene without electron donor. But when 4 g/L NZVI was added as sole electron donor, this deehlorinating culture degraded 20 mg/L TCE into ethene and vinyl chloride （VC） in 131 h at a speed higher than that by NZVI alone. Compared to 2.706μmol ethene produced by Dehalococcoides spp. with methanol added as the electron donor, there was only 1.187 μmol ethene produced by bacteria with NZVI serving as the electron donor, which means NZVI has a potential toxicity on Dehalococcoides spp.. At the meantime, 0. 109μmol acetylene was produced in 190 h, which was relatively lower than 0.161 μmol produced by NZVI alone, indicating bacteria competed with NZVI under electron deficient condition. In conclusion, NZVI could serve as electron donor and support deehlorination activity for Dehalococcoides spp. which could enhance the application of NZVI and usage of dechlorinating culture as a polishing strategy in future ground water remediation.