A Microcosm Study On Anaerobic Bioremediation Of 1,2,4-TCD And Its Dechlorination Products In Groundwater

Chlorobenzene homologues are common pollutants in the soil and groundwater of industrial sites in China.Anaerobic microbial remediation is a cost-effective method for remediation of such pollution.Groundwater of an abandoned chemical plant in Nanjing is seriously polluted by 1,2,4-TCB.Previous studies have found that:(1)There are bacteria in the groundwater which can degrade 1,2,4-TCB anaerobically and make the Nanjing site natural attenuation;(2)If the o-nitro-pmethylphenol produced by this plant contaminates the groundwater,it will be reduced to o-aminop-methylphenol,while inhibit Anaerobic degradation of 1,2,4-TCB.Based on the previous work,this research further studies the changes of the microbial community structure,the degradation process under different substrate conditions and the differences of the microbial community in the above processes.This study will help to understand the natural attenuation process of 1,2,4-TCB in the Nanjing site more fully,and further reveal the degradation process of 1,2,4-TCB.It lays an important foundation for promoting the research and development of culture for anaerobic microbial remediation of chlorobenzene pollution in groundwater,which has practical significance and application value.The research contents of the thesis include:(1)the effect of o-nitro-p-methylphenol and oamino-p-methylphenol on the anaerobic degradation process of 1,2,4-TCB;(2)degradation process of the three dichlorobenzene and monochlorobenzene when they are used as the only substrate;(3)microbial community structure changes in the degradation processes in the above two studies.Research content 1 designed three sets of microcosm experiments,and research content 2 designed four sets of microcosm experiments.The experimental results show that:(1)In the experimental group with o-nitro-p-methylphenol and o-amino-p-methylphenol,the direct degradation products of 1,2,4-TCB are only 1,4-DCB.O-nitro-p-methylphenol inhibits the degradation of 1,2,4-TCB.Although o-amino-p-methylphenol does not affect the degradation process of 1,2,4-TCB,it does show inhibition on the degradation rate.(2)Under the condition of feeding three dichlorobenzenes individually,the maximum degradation rate is ranked as 1,2-DCB> 1,3-DCB> 1,4-DCB,which is different from the results of mixed feeding.The biodegradation process of 1,2,4-TCB conforms to the first-order kinetic model.(3)Azospira and Pseudomonas are related to the reduction of o-nitrop-methylphenol to o-amino-p-methylphenol under anaerobic conditions.(4)Dehalobacter and Dehalogenimonas are functional bacteria for 1,2,4-TCB dechlorination.In the experimental group fed only 1,4-DCB,the relative abundance of Dehalogenimonas increased by a factor of 25 within 15 days.However,to prove that Dehalogenimonas is 1,4-DCB dechlorination functional bacteria,additional data are needed.