Importance of quality and quantity of organic carbon for bioremediation of acid mine drainage (ph ~ 2.2) lake water
A controlled and replicated experimental microcosm study evaluated bioremediation of acidic mine drainage contaminated water from a mine pit lake through bacterial sulphate reduction by addition of sewage sludge as carbon source. Sewage sludge was supplemented in acidic mine drainage water at two different concentrations and loading regime to stimulate bacterial sulphate reduction. The bioremediation processes were evaluated for increase in pH, decrease in Oxidation Reduction Potential, acidity removal and sulphate reduction. Sewage sludge was inefficient in providing sufficient carbon for growth of sulphate reducing bacteria. Though sewage sludge had high concentrations of total carbon, it failed to increase dissolved organic carbon levels. Microcosms amended with doubled doses of sewage sludge and even extended reaction time still failed to demonstrate any substantial improvement in water quality. In order to determine if low Labile Organic Carbon concentrations in sewage sludge were the cause of sulphate reduction failure, Labile Organic Carbon was then supplemented to all microcosm treatments. Labile Organic Carbon as a mixture of ethanol and lactic acid was supplemented at concentrations of 3,000, 6,000 and 9,000mg/L. After treatment microcosms were amended with Labile Organic Carbon, water quality improved considerably in the lowest carbon concentration treatment (3,000mg/L). This lowest carbon concentration was effective for removal of acidity, sulphate and heavy metals whereas 6,000 and 9,000mg/L Labile Organic Carbon concentrations did not alter mine water chemistry.
Dr Naresh Radhakrishnan
Dr Clint McCullough
Associate Professor Mark Lund