Nitrate-reducing bacteria in Kuwait domestic sewage.

Domestic sewage in Kuwait is mainly treated by an activated-sludge process, where different effluents and sludges are separated. Nitrate reduction in the raw sewage, effluent-1 and effluent-2 were studied. Various enrichments of these sewage samples were effected using 0.2 mg/ml of nitrogen as potassium nitrate and/or 0.5% carbon as glucose. Addition of 0.2 mg/ml nitrate-nitrogen enhanced more ammonia production (117.6 micrograms/ml) in comparison with other enrichments to sewage samples. Nitrate-reducing bacteria were also at a maximum with nitrate enriched sewage samples, especially with effluent-1 (109 X 10(6)/ml). Escherichia coli and Klebsiella pneumoniae were the only two nitrate-reducing bacteria found in all sewage samples tested. Nitrite was unstable during the 7 days incubation period under anaerobic conditions which suggests that nitrates are reduced to ammonia.