Bacterial sulphide production from sulphate‐enriched spent distillery liquor—II

Abstract

Summary. Accumulation of volatile acids produced during anaerobic fermentation of distillery-spent liquor decreased the activity of Desulphovibrio desulphuricans employed in previously communicated studies; this caused a decrease in the reduction of sulphates to sulphides. An enriched strain of Desulphovibrio rubentschikii made in a synthetic mineral medium (NH4C1, 1.0 g ; MgS04.7H20, 2.0 g ; NaCl, 10.0 g ; CaS04, 1.0 g; calcium acetate, 1.0 g ; K2HP04, 0.5 g; Mohrs' salt, trace in 1 1.) using calcium acetate as the substrate and carbon from the tap-water was gradually built up to a 3-1. volume. The amount of hydrogen sulphide in this medium was found to be 225 mg/l. The fermentation was next carried out in a synthetic medium containing volatile acids from distillery-spent liquor as the only substrate. A 3-1. fermentation set up with diluted distillery-spent liquor (300 ml of raw liquor in 3,000 ml of water), neutralized with NaOH to pH 7.2 and supplemented with calcium sulphate and 0.1 per cent urea, showed sulphide productions (calculated as milligrams of hydrogen sulphide per litre of raw distillery-spent liquid) of 2,000, 4,000 and 6,000 with 0.1, 1.0 and 2.0 per cent calcium sulphate in the charge respectively. The volatile acid content, expressed as acetic acid, was 18,564 mg/litre of raw distillery-spent liquor on an average throughout the study. The ratio of hydrogen sulphide produced per litre of raw distillery-spent liquor to the amount of volatile acids developed expressed in milliequivalents per litre of raw liquor during fermentation increased gradually from 0.1 367 to 0.5567 in the presence of 0.1 to 2-0 per cent of calcium sulphate in the charge. PrefaceIn a previous communication (Part I, in press), studies carried out with organisms of the type Desulp?wvibrio desulphuricans in the bacterial reduction of sulphates to sulphides using distillery -spent liquor as carbon and hydrogen donor were reported. It was pointed out that increased yields of sulphide might be obtained by employing in the microbial sulphate-reduction a volatile-acid-utilizing 181 182 S. K. BASU AND T. K. GHOSE bacteria of the type Desulphovibrio rubentschickii. Studies subsequently conducted on the enrichment, isolation and fermentation characteristics of a specific volatile-acid-utilizing strain of sulphate reducers isolated from Calcutta City Sewage are reported. A comparative study on the sulphide fermentation with the agency of both D . desulphuricans and D . rubentschickii using distillery-spent liquor as hydrogen-donor has also been made. The influence of volatile acids on the bacterial reduction of sulphates to sulphides is also reported here.

Biological sulphate reduction

“…The use of crude cultures of dissimilatory sulphate-reducing bacteria for treating distillery wastes has been reported by Basu and GHOSE (1961) and similar work has been done in Czechoslovakia for citric acid wastes on an industrial scale (BARTA 1962). A British project for the production of sulphide by bacterial fermentation of sewage sludge has been discontinued despite the fact that it was within reach of economic feasibility (BuTLIN, SELWXN, and WAKERLY 1960).…”

Recent advances in the study of the sulfate-reducing bacteria.

“…The use in India of crude cultures of sulfatereducing bacteria for the treatment of distillery wastes has been reported (17,64,65). Comparable work has continued in Czechoslovakia (15,16) where the bacteria were used to treat distillery and citric acid wastes.…”