Microbial transformations of substituted benzenes during infiltration of river water to groundwater: laboratory column studies

The microbial transformations of dimethyl- and dichlorobenzenes have been studied in laboratory aquifer columns simulating saturated-flow conditions typical for a river water/groundwater infiltration system. The behavior of all compounds in the laboratory was qualitatively the same as that observed at a field site. Both dimethyl- and dichlorobenzenes were biotransformed under aerobic conditions, the dimethylbenzenes faster than the chlorinated analogues. Evidence is presented that dimethylbenzenes are degraded by denitrifying bacteria under anaerobic conditions. Dichlorobenzenes were not transformed under these conditions. Significant differences in the rates of transformation between isomers were found. The dimethylbenzenes and p-dichlorobenzene appeared to be utilized by bacteria as sole carbon and energy sources. Transfer of rate constants determined in the laboratory at elevated substrate concentrations to the field was difficult.