Study On Enrichment Of 2,4,6-trichlorophenol Anaerobic Dechlorination Bacteria And Enhancement Efficiency Of Composite Functional Biological Carrier

2,4,6-trichlorophenol is widely used in industrial and agricultural production.However,due to improper disposal,a large amount of 2,4,6-trichlorophenol is released into the environment,and its special physical and chemical properties lead to slow degradation in nature,posing a threat to the environment and human health.For this reason,more and more Organiohalide-Respiring Bacteria(ORB)are isolated in the environment for enhancing bioremediation of halogenated organic pollutants.However,ORB are difficult to survive in natue and have poor competitiveness to electron donors,so the degradation efficiency is low.Herein,the mixed-bacteria with stable reductive dechlorination of 2,4,6-trichlorophenol under anaerobic conditions were acclimatized and enriched,and the community structure of mixed-bacteria and potential 2,4,6-trichlorophenol degrading bacteria were identified.Furthermore,the dechlorination efficiency of 2,4,6-trichlorophenol under different carbon sources and the degradation ability of mixed-bacteria to other halogenated organic compounds were investigated.Finally,the composite functional biological carrier was prepared and its enhancement efficiency for biodegradation of 2,4,6-trichlorophenol was revealed.In this study,2,4,6-trichlorophenol degrading mixed-bacteria with reductive dechlorination were acclimatized and enriched from the polluted sediment in China.When adding 20 m M sodium lactate as carbon source and electron donor,2,4,6-trichlorophenol with initial concentration of 200 ?M could be completely dechlorinated by mixed-bacteria within 4 days.The intermediate and final products of dechlorination were 2,4-dichlorophenol and 4-chlorophenol,respectively.The 16 S r RNA sequencing showed the Pseudomonas sp.was the 2,4,6-trichlorophenol degrading bacteria in the mixed-bacteria.It was found that the mixed-bacteria can dechlorinate 2,4,6-trichlorophenol when sodium lactate,sodium formate and hydrogen,sodium acetate and hydrogen,sodium propionate and hydrogen were used as carbon sources,and the dechlorination rate was sodium formate > sodium acetate ? sodium lactate > sodium propionate.In the dechlorination process,small-molecular organic acids played the role of a co-carbon sources,while hydrogen served as an electron donor(It's difficult for the mixed-bacteria to use substances other than hydrogen as electron donors.).Because of its high and stable degradation efficiency of 2,4,6-trichlorophenol,simple structure and less side reactions,sodium acetate was selected as the optimal carbon source.When glucose,methanol and sodium acetate(without hydrogen)were used as carbon sources,it is difficult for the mixed-bacteria to dechlorinate 2,4,6-trichlorophenol.The dechlorination efficiency of 2,4,6-trichlorophenol with polylactic acid,polycaprolactone and starch-based plastics as slow-release carbon sources was discussed.It was found that only starch-based plastics could be used as a slow-release carbon source for the biological dechlorination of 2,4,6-trichlorophenol.When the concentration of starch-based plastics was 50 g/L,the degradation rate of 2,4,6-trichlorophenol with an initial concentration of 80 ?M was 20.5% during a 24-day incubation period.The dehalogenation of 2,4,6-tribromophenol,tetrabromobisphenol A,pentachlorophenol and triclosan by mixed-bacteria were investigated.It was found that the mixed-bacteria had a good debromination degradation effect on 2,4,6-tribromophenol,and the degradation rate of 2,4,6-tribromophenol with an initial concentration of 10.67 mg/L could reach 100% after 8 days.However,the mixed-bacteria could not dehalogenate tetrabromobisphenol A,pentachlorophenol and triclosan.Tourmaline composite functional biological carrier and iron-carbon microelectrode composite functional biological carrier were prepared.Both kinds of composite functional biological carriers can be used as electron donors for anaerobic biological dechlorination of 2,4,6-trichlorophenol.Under the condition that sodium acetate was added without hydrogen,2,4,6-trichlorophenol with an initial concentration of 80 ?M was completely removed at the 8 d with tourmaline and 6 d with iron-carbon microelectrode.It is speculated that the mixed-bacteria can directly obtain electrons from spontaneous microelectrode of tourmaline.While iron-carbon microelectrode composite functional biological carrier was used as electron donor due to the generation of a large amount of hydrogen(9.34 mg/L).The two kinds of composite functional biological carriers have good strengthening effect on the anaerobic biological dechlorination process of 2,4,6-trichlorophenol.Through the strengthening of tourmaline and iron-carbon microelectrode composite functional biological carriers,the dechlorination rate of bacteria on 2,4,6-trichlorophenol can be increased to 1.2-fold and 1.5-fold respectively.Based on the above results,an application mode of composite functional biological carrier for in-situ remediation of 2,4,6-trichlorophenol contaminated groundwater was proposed.The composite functional biological carrier immobilized with mixed-bacteria was filled into the permeable reactive barrier.With the polluted groundwater flowing through the permeable reactive barrier,the 2,4,6-trichlorophenol can be removed and hindered effectively.The analysis showed that the application mode had less impact on the environment and lower cost,which was expected to solve the electronic shortage problem commonly existing in in-situ bioremediation technology,and had certain research significance and application potential.