Enumeration, isolation and identification of sulphate-reducing bacteria of anaerobic digestion

Abstract

A method was developed for the enumeration and isolation of the sulphate-reducing bacteria in the anaerobic digestion of raw sewage sludge. This method differed from conventional methods used for the enumeration and isolation of sulphate-reducing bacteria in that anaerobiosis was achieved by the use of media with a low redox potential in stoppered bottles containing oxygen-free gas atmospheres. Carbon dioxide—bicarbonate buffer systems were employed in the media. Sulphate-reducing bacteria occurred in numbers of 3–5 × 10 4/ml in a raw sewage sludge digester. Seven pure cultures of sulphate-reducing bacteria were isolated from digesters and all proved to be Desulfovibrio desulfuricans. No evidence for the presence of Desulfotomaculum ssp. was found. The role of sulphate-reducing bacteria in the anaerobic digestion of raw sewage sludge is discussed.