Study On Anaerobic Microbial Degradation Of Typical Organic Pollutants In Xihe Mud In Shenyang Sewage Irrigation District

Shenyang Xihe River sewage irrigation area has been affected by sewage irrigation for a long time,and accumulated a large amount of organic pollutants.Among them,phthalic acid esters and organic chlorides are more polluted and are typical organic pollutants,which not only destroy soil quality and production functions,but also enter the food chain for enrichment,which has a negative impact on human health.The aerobic microbial degradation process,pathways and influencing factors of these two types of pollutants are clear.But there are few research results under anaerobic conditions.Based on this,sediment samples were collected from the Xihe River,micro-ecological systems were established in the laboratory,phthalate esters and organic chlorides were studied for anaerobic microbial degradation,and chemical strengthening effects were analyzed.Surfactant-enhanced bioremediation is one of the most promising techniques for the repair of hydrophobic organic pollutants.Previous studies have shown that surfactants can promote microbial degradation of organic pollutants under aerobic conditions.The effect of surfactants on microbial degradation of pollutants under anaerobic conditions is now analyzed.The paper has achieved the following main results:(1)A stable anaerobic microbial ecosystem was constructed,and the optimal pH of the phthalic acid degradation of phthalic acid under anaerobic conditions was 7,and the optimum temperature was 30°C.The benzene was reacted under the action of 10 mM nitrate.The degradation rate of dicarboxylic acid reached 100%on the 23rd day,and when the nitrate concentration was reduced by half,the removal rate of phthalic acid was reduced by 33.3%.(2)After the optimal culture condition was transferred to the third-generation sediment community structure stability,PCE disappeared completely on the 7th day,and the PCE completely degraded from PCE to non-toxic ETH in 30 days.It inhibited by the action of the biosurfactant rhamnolipid and the chemical surfactant Tween80.The rhamnolipid had the strongest inhibition on the degradation of PCE by sediments,and the degradation of DCE to VC no longer occurred.The concentration of rhamnolipid at 5 mg/L showed complete inhibition of TCE degradation by single bacteria 195.The degradation rate of TCE was 0%.When rhamnolipid concentration was 1 mg/L,the efficiency of Bavl degradation of DCE was 0%.In contrast,the chemical surfactant Tween 80 has less inhibition.Tween80 can degrade PCE into ETH in sediments,but the inhibition effect on the degradation of single bacteria 195 and Bavl is still very significant when the concentration is higher than 5 mg/L.The results of 16SrDNA sequencing showed that the dechlorination system was driven by a combination of Geobacter and Dehalococcoides;the species diversity and abundance of bacteria in different concentrations of surfactant rhamnolipid,Tween80 and control group.There are significant differences.Under the action of the surfactant Tween80,Geobacter and Dehalococcoides play a more significant role than the action of rhamnolipid.Pure culture found that the concentration of rhamnolipid 5 mg/L showed complete inhibition of TCE degradation by dechlorination 195.TCE TCE degradation rate was 0%,when rhamnolipid concentration was 1 mg/The L-mode dechlorination Bavl degraded DCE with an efficiency of 0%.When the rhamnolipid concentration was 1 mg/L,the efficiency of the dechlorinated Bavl degrading DCE was 0%.In contrast,the chemical surfactant Tween80 has less inhibition.Tween80 can degrade PCE into ETH in sediments,but the inhibition effect on the degradation of single bacteria 195 and Bavl is still very significant when the concentration is higher than 5 mg/L.Preliminary results indicate that surfactants with enhanced microbial degradation of organic pollutants under aerobic conditions can not promote the anaerobic dechlorination of microorganisms,but inhibit the dechlorination process and final products,mainly due to the different dechlorination bacteria on surfactants.Sensitivity is different,especially obligate organochlorine respiratory dechlorococcus is the least resistant to surfactants.