Biological Removal Characteristics Of Dichlorophenol And Cr(â…¥)in Water And Community Analysis

Chlorophenol compounds and heavy metal Cr(VI) are often detected in groundwater and surface water. Based on this, in this paper,2,5-dichlorophenol(2,5-DCP) and Cr(VI) were selected as targeted pollutants, anaerobic removal of the two pollutants by the enriched communities and the effect of various redox mediators were investigated. Moreover, bacterial communities in reaction systems were studied using molecular technique.Sodium pyruvate was the optimal electron donor. Its amendment resulted in the removal of62.8%2,5-DCP in56days. In the presence of lactate and sodium acetate, the degradation efficiencies of2,5-DCP reached62.56%and47.69%, respectively. Meanwhile, it was found that2,5-DCP could be degraded by the enriched bacterial community without electron donors. Moreover, the degradation efficiency reached61.94%. Further studies showed that riboflavin(VB2) amendment could accelerate the degradation of2,5-DCP with34.8%increase.When sodium pyruvate was used as an electron donor, pH was7.0and temperature was35℃,10mg/L Cr(VI) could be completely reduced in24hour. With the increase of Cr(VI) concentration, Cr(VI) reduction rate decreased. Redox mediator amendments could greatly increase the reduction rate of Cr(VI). The optimal redox mediator was2-hydroxy-1,4-naphthoquinone(lawsone), followed by anthraquinone-2,6-sodium(AQDS), riboflavin and vitamin B12CVB12).In the presence of both2,5-DCP and Cr(VI), the removal rates of2,5-DCP and Cr(VI) were higher than that of them alone, respectively, when sodium pyruvate was used as an electron donor. Especially, the removal rate of Cr(VI) increased7.15%. Additional riboflavin could accelerate their removal. In the absence of sodium pyruvate,2,5-DCP and Cr(VI) could be used as an electron donor and acceptor, respectively. Their removal rates were higher than that of them alone, respectively. Additional riboflavin could greatly enhance the reduction of Cr(VI). However, little effect on the degradation of2,5-DCP was observed.DGGE analysis showed that the main microorganisms in bacterial community were Clostridium sp., Eubacterium limosum KIST612, Streptomyces sp. and Escherichia coli JJ1886. In this community, Clostridium sp., Streptomyces sp. and Eubacterium limosum have the capability of dechlorination and the E.coli played a key role in Cr(VI) reduction. In the absence of electron donors, the rate of Cr(VI) reduction decreased perhaps due to less abundance of E.coli in the bacterial community.