Microbial Sulphide Production From Sulphate‐enriched Sewage Sludge

SUMMARY A laboratory process for the microbial production of sulphide from sewage sludge enriched with sulphate has been further developed. Semicontinuous fermentations yielded 0·9–1·0% S 2‐ using a 10‐day replacement time (RT) and 0·8% S 2‐ with a 5‐day RT. Yields at 37° were slightly higher than at 30°; at 43° and above yields were much lower. A mixture of 70% N 2 and 30% CO 2 was successfully used as sweeping gas to remove H 2 S; other proportions of these gases were less efficient. Stripping H 2 S from the sludge in an external column was as efficient as passing the stripping gas through the bulk of the fermenting sludge.