Biological sulphate removal from industrial effluent in an upflow packed bed reactor

A biological process for the removal of sulphate, using molasses as organic carbon source, is described. Sulphate is converted to sulphur via sulphide, and molasses to bicarbonate. Sulphate reducing bacteria are responsible for the reduction of sulphate to sulphide, while photosynthetic sulphur bacteria oxidize sulphide to elemental sulphur. It has been shown that these bacteria can live symbiotically in an upflow anaerobic packed bed reactor. The process is accompanied by the precipitation of calcium carbonate and heavy metal sulphides. Sulphate reduction follows zero order kinetics with respect to both reactants and products. The reduction of 1 g sulphate consumes 1.2 ml molasses and requires 6 h for completion. The optimum temperature for sulphate reduction was found to be 31°C.