Metal working fluids, process waters, bilge waters, ballast waters, lubricants, paper pulp, detergents, fuels, crude oil and sea water can all contain sulphur in varying forms such as sulphate, sulphite, sulphonate, sulphurised oil and mercaptans. These can all be converted to sulphide by consortia of micro-organisms containing both aerobic and anaerobic bacteria. The anaerobic bacteria in the consortia are usually referred to as Sulphate Reducing Bacteria (SRB).
Biochemical reduction of these sulphur compounds often leads to hydrogen sulphide gas being produced by SRB as an end product. Hydrogen sulphide gas is not only an unpleasant smelling gas and skin irritant but it is more toxic than hydrogen cyanide and can kill.
Hydrogen sulphide stains and corrodes ferrous and non-ferrous metals, stone and concrete and it discolours cutting fluids and fuel tank water bottoms. Sulphide generating bacteria cause rapid pitting corrosion of steel in contact with process water, ships’ bilge water, sludges, crude oil and fuel tank water bottoms, detergent washes, and various chemical solutions and slurries. Pitting corrosion of steel piling is often due to SRB activity. Sulphide production from emulsifying components (eg petroleum sulphonates) leads to emulsion instability.