Sulphate-rich industrial effluents present a serious environmental pollution problem. A biological sulphate removal process has been developed for the treatment of such effluents. In this process, sulphate is converted to hydrogen sulphide in the anaerobic stage when an energy source, such as molasses, sugar or producer gas is added. The hydrogen sulphide is stripped off in a stripping stage, with a carrier gas such as nitrogen. The gas is recycled through a ferric solution where it is oxidized to elemental sulphur. In a subsequent aerobic stage, degradation of organic carbon residuals and calcium carbonate crystallization are achieved simultaneously. In this study the anaerobic stage of the process was evaluated on pilot scale. After the inoculation period, sulphate was removed continuously for a period of 100 days from 2200 mg/l to below 200 mg/l. For the first part of the study acetic acid served as energy source as the sugar content of molasses was allowed to ferment. Thereafter fresh molasses was supplied as energy source and the bacterial culture had to adapt to utilize sugar in molasses as energy source. A volatile suspended solids (VSS) concentration of 27 g/l was present in the packing material of the anaerobic reactor. With this VSS-value, a hydraulic retention time of 12 hours was needed for sulphate removal.