Oxidation of hydrogen sulphide in sour gas by Chlorobium limicola

The aim of this work was to assess the potential for bacterial oxidation of hydrogen sulphide as a purification method of sour gas. Using a continuous culture of Chlorobium limicola, high efficiencies of oxidation of both soluble and gaseous sulphide were achieved, with efficiencies for the latter exceeding 95%. Sulphide added as aqueous sodium sulphide was converted to sulphur and sulphate with almost total removal of the initial 100 mg S l−1 within 24 h. Gaseous sulphide was oxidized at an efficiency of 95% (approximately 3 mmol S h−1 (unit biomass Abs)−1) over 1 h runs at a gas flow rate of 60 ml min−1. With a sulphur recovery system to prevent sulphur accumulation, an efficiency of 70% was maintained. Biological removal of sulphide represents a potentially important biotechnological process, with high potential for viable scale up.