The feasibility of sulphate removal from sulphate-rich wastewater using an anaerobic fixed-bed reactor was investigated. The bioreactor was installed at a chemical industry producing organic peroxides, which generate wastewater with sulphate concentrations ranging from 12,000 to 35,000 mg SO42- 1(-1). A pilot-scale anaerobic fixed-bed reactor with a 94.2-1 volume was tested to treat part of the wastewater. The reactor was filled with 1-cm(3) polyurethane foam cubes and operated. initially, in discontinuous regime. Five batch tests were performed with diluted industrial wastewater. The sulphate reduction efficiency and the chemical oxygen demand (COD) removal efficiency were evaluated as a function of the COD to [SO42-] ratio in each batch test. The effect of the addition of supplementary ethanol on the sulphate-reducing bacteria growth was also evaluated. The reactor was then fed in a semi-continuous regime with raw industrial wastewater with high sulphate concentration. The addition of ethanol stimulated the sulphate-reducing bacteria, which predominated over the methane-producing organisms even at a high COD to [SO42-] ratio. A maximum sulphate removal efficiency of 97% was reached during discontinuous and semi-continuous operations. (C) 2002 Elsevier Science Ltd. All rights reserved.