A Microcosm Study On Anaerobic Bioremediation Of 1,2,4-TCB In Groundwater

Site investigations were conducted at a former chemical plant,located in Nanjing,which manufactured fluorescent whitening agent PF.The results delineated the groundwater was contaminated with 1,2,4-trichlorobenzene(TCB),dichlorobenzene(DCB)isomers,mono-chlorobenzene(MCB),benzene and PF.The five-year groundwater monitoring results revealed that the chlorobenzenes were likely naturally attenuated to non-toxic compounds via benzene under anaerobic conditions.The biodegradation process of 1,2,4-TCB in anaerobic conditions was targeted as the research object.The soil and water samples collected at contamination site were acclimated to get the enriched anaerobic cultures.To explore the degradation mechanisms of chlorobenzenes and to confirm the effect of PF on dechlorination processes,a corresponding laboratory microcosm study was conducted.In addition,fluorescent whitening agent PF and its two composite products:2-Amino-4-methylphenol and 4-Methyl-2-nitrophenol was added to study their effect on 1,2,4-TCB reductive dechlorination process respectively.The experiment results revealed that:(1)1,2,4-TCB undergoes sequential reductive dechlorination to benzene via DCB isomers and MCB.(2)The molar proportions of 1,2-DCB,1,3-DCB and 1,4-DCB is about 10%/35%/55%,and the order of 1,2,4-TCB reductive dechlorination product is 1,4-DCB>1,3-DCB>1,2-DCB.(3)The addition of PF did not change the dechlorination processes of 1,2,4-TCB and DCB isomers,but inhibited the further dechlorination of MCB to benzene.(4)The addition of 4-Methyl-2-nitrophenol inhibited the dechlorination of 1,2,4-TCB,and 4-Methyl-2-nitrophenol was reduced to 2-Amino-4-methyl-phenol under anaerobic condition.(5)2-Amino-4-methylphenol is not degraded in the anaerobic condition,and it doesn’t inhibit the reductive dechlorination process of 1,2,4-TCB.