Microbial metabolism of chlorophenolic compounds in ground water aquifers

The metabolism of phenol and various chlorophenols was studied in groundwater aquifer microcosms. Flow-through column microcosms containing pristine aquifer material were used to assess aerobic biodegradation processes. Reductive metabolism of the substrates was studied in serum bottles filled with aquifer material contaminated by municipal landfill leachate. We found that microorganisms present in an actively methanogenic aquifer were able to metabolize chlorophenols by replacing the halogen substituents with hydrogen atoms. The identity of the dehalogenated intermediates was confirmed by mass spectrometry for a model substrate and by cochromatography for others. Complete removal of the aryl halides was necessary before the phenol intermediate could be mineralized to methane and carbon dioxide. However, the chlorophenols tended to persist in anoxic microcosms containing material from the same aquifer but from a non-methanogenic site. Metabolism and acclimation of chlorophenols and phenol was noted in aerobic microcosm studies, but the degradation pathway(s) were not established.