Pilot scale assessment of the continuous biological sulphate removal from coal acid mine effluent using grass cutting as carbon and energy sources

This paper considers the evaluation of the performance of the biological sulphate reduction in continuous mode using grass cutting. Initially the reactor was operated in batch mode for 26 days, followed by a change to a continuous feeding mode at a Hydraulic Retention Time (HRT) varying from 8 to 2 days. At the start of the experimental period the bioreactor was filled with 89 kg of ceramic rings as support medium for Sulphate Reducing Bacteria (SRB) and 50 L SRB (COD = 852 mg/L and SO42 = 600 mg/L) obtained from an existing biological sulphate reducing bioreactor. Rumen fluid was collected from a slaughterhouse and added to the bioreactor. Grass cuttings (10 kg) were added to the bioreactor as a carbon and energy source. The results showed that from day 59–106 the bioreactor was operated in continuous mode and the percentage SO42− reduction efficiencies were 73%, 85% and 71%, corresponding to the HRT of 8, 6 and 4 days respectively.