ANAEROBIC TRANSFORMATION OF AROMATIC HYDROCARBON POLLUTANTS UNDER FERMENTATIVE METHANOGENIC CONDITIONS

This article is a review of the experimental work on anaerobic (methan ogenic) degradation of aromatic hydrocarbon pollutants that has been p erformed in the Environmental Engineering and Science laboratories of the Civil Engineering Department, Stanford University, in the last sev en years. Three groups of compounds have been examined: homocyclic mon oaromatic and polyaromatic hydrocarbons, nitrogen heterocycles, and su lfur heterocycles. The microbial inocula were derived from anaerobic s ludge, and from the methanogenic zone of a ground water aquifer contam inated by creosote. It has been shown that the initial transformation reaction involves an oxidation with the water-derived oxygen, and that the aromatic compounds are subsequently completely degraded to carbon dioxide and methane. Molecular oxygen is not needed for this type of degradation of aromatic hydrocarbons. The microbial catalysts involved are complex fermentative/methanogenic microbial communities. Parallel studies of the transformation of aromatics in laboratory microcosms a nd in situ in the contaminated aquifer have shown similar results, ind icating the usefulness of the microcosms as models for understanding a nd predicting the fate of the pollutants in the environment. Anaerobic degradation of aromatic pollutants has a great application potential in remediation of subsurface and soil, and especially ground water aqu ifers, where the reaeration is insufficient to support the aerobic mic robial processes.