Anaerobic Biodegradation Of Tetrachlorobisphenol-A(TCBPA) In River Sediment And The Microbial Community Changes

Tetrachlorobisphenol A(TCBPA) is a kind of reactive halogenated flame retardantswhich is widely used in building materials, paints, synthetic textiles, plastic products,electronic circuit boards, and other electronic equipment as a halogenated bisphenol Aderivative. TCBPA is a common endocrine disrupting chemical in electronic wastedismantling area and it does harm to the environment and human health seriously. In thisresearch, we studied the anaerobic degradation of TCBPA in river sediments of three samplingpoints and the effects of various enviromental factors on anaerobic degradation of TCBPA.Moreover, the change of microbial community during TCBPA biodegradation was studied.We compared biodegradation of TCBPA in3different sampling points,9%,18%, and65%of TCBPA was degraded in Xinzao Town, Qingyuan Town, and Guiyu Town,Guangdong Province, respectively. Using river sediment of Guiyu, we comparedbiodegradation of TCBPA under different reducing conditions. TCBPA was degraded morequickly under methanogenic condition than sulfate reducing condition. Degradation rateconstants and half-lives under methanogenic condition and sulfate-reducing condition are0.0844d-1,0.0694d-1;8.2d, and10.0d respectively. The degradation rate constant is0.0561d-1and the half-life is12.4d in Guiyu Town, which ise the most effective sediment in the testsampling points. Adding electron donors can increase the degradation rate constant of TCBPAby28.7%, while adding butyl phthalate can decrease he degradation rate constant of TCBPAby12.5%.The numbers of sulfate-reducing bacteria (SRB) increased during TCBPA degradation inthe group which extra Na2SO4and electron donors were added or extra electron donors wereadded. However, the number of sulfate-reducing bacteria was unchanged or even reduced inthe control group. Real time PCR experiment proved the positive role of SRB in the processof TCBPA degradation.Dominant populations of microorganisms are very similar in different sampling points.New dominant populations appeared in the sediments of Xinzao and Qingyuan, while noobvious change was observed in the sediments of Guiyu. Abundances of microbialpopulations are all at a high level in3sampling points. Dominant populations ofmicroorganisms didn’t change very much after the addition of different substances. However,several new dominant populations appeared and some original dominant populationsdisappeared when different subtances were added. The abundance of microbial populations was decreased only in the group with extrabutyl phthalate while it was inceased continuously under methanogenic condition. In thegroup with extra Na2SO4and electron donors and the group with extra electron donors only,the abundance of microbial populations increased at first, then it was decreased after a fewdays degradation. The abundance of microbial populations remains stable in the control group.High homologous bands appeared in the TCBPA degradation process.