BIOTRANSFORMATION AND BIODEGRADATION OF N-SUBSTITUTED AROMATICS IN METHANOGENIC GRANULAR SLUDGE

N-Substituted aromatic compounds are environmental contaminants associ ated with the production and use of dyes, explosives, pesticides and p harmaceuticals. In this article, we examine the potential of anaerobic granular sludge from anaerobic treatment systems towards the detoxifi cation, transformation, and mineralization of nitroaromatic and azo co mpounds. Nitroaromatics and azo dyes with strong electron withdrawing are highly inhibitory to acetoclastic methanogenic bacteria. However, nitro and azo substituted aromatics are readily reductively detoxified in methanogenic consortia to their respective aromatic amines, which are several orders of magnitude less toxic. This reductive detoxificat ion has allowed the successful operation of anaerobic reactors for the treatment of highly toxic aromatic compounds. In the course of the ex periments it was discovered that some aromatic amines were mineralized . These results indicate that some N-substituted aromatic compounds ca n be completely mineralized and serve as a carbon and energy source fo r anaerobic bacteria.