The formulation of synthetic domestic wastewater sludge medium to study anaerobic biological treatment of acid mine drainage in the laboratory

Abstract

Requirements for successful biological treatment of acid mine drainage (AMD) rely on the reduction of sulphates by microorganisms using a suitable organic carbon source. Various carbon sources, such as domestic wastewater sludge, have previously been used in the semi-passive biological treatment of AMD. Domestic wastewater sludge is however highly variable in its composition, making laboratory experimentation difficult. Synthetic medium was therefore formulated based on the chemical oxygen demand (COD) and the biological degradable organic matter (BOD) of domestic wastewater sludge. Four synthetic media compositions were formulated consisting of different ratios of meat extract, vegetable extract, sodium chloride, potassium phosphate, urea, ammonium chloride, iron sulphate, magnesium sulphate and glucose. The media composition with BOD and COD measurements closest to that of anaerobic domestic wastewater sludge was selected for further studies. The combination of AMD to synthetic wastewater sludge in 3 ratios was determined for COD and sulphate reduction in bioreactors over a period of 90 d. The highest reduction of 86.76% in COD and 99.22% in sulphate content were obtained in a 1:1 AMD: synthetic domestic wastewater sludge (SDWWS) ratio that calculated to a COD/sulphate ratio of 3.