SIMULTANEOUS REMOVAL OF SULPHATE AND SULPHIDE USING SUGAR AS ENERGY SOURCE

A novel biological process is described in which sulphate and sulphide are removed simultaneously. In this process sulphate is reduced to sulphide in a completely-mixed reactor through addition of sucrose or ethanol as carbon and energy source. Sulphide is oxidised by allowing oxygen to enter the system in a controlled way. The experimental investigation of the process showed that sulphate and sulphide can be removed simultaneously due to coexistence of sulphate reducing bacteria and sulphur oxidising bacteria. The volumetric sulphate reduction rate in a completely-mixed reactor, with sucrose as organic carbon and energy source, amounts to 12.4 g SO4/(l.d). The rate of biological sulphate removal was found to be directly related to the square root of sulphate, COD and VSS concentrations respectively, and inversely proportional to sulphide concentration. The practical value of simultaneous sulphate and sulphide removal is that only one stage is required for removal of both sulphate and sulphide; a conventional completely-mixed reactor can be used, and sulphate can be removed in a consistent way to below 200 mg/l (as SO4) due to the stability of the process.