Passive Treatment of Metal and Sulphate-Rich Acid Mine Drainage (AMD) Using Mixed Limestone, Spent Mushroom Compost and Activated Sludge

Abstract

Acid mine drainage (AMD) is a major environmental problem as it involves the release of acidic, sulphateand metal-containing water into the environment. It usually has low pH which is acidic and contains toxic and nonbiodegradable pollutants such as heavy metals, e.g. lead (Pb), aluminium (Al), copper (Cu), iron (Fe) and zinc (Zn). Passive treatment has been regarded as a reliable means for treating AMD and was assessed in this study using multiple substrates. This study aims to provide an evaluation of passive treatment of metaland sulphate-rich AMD incorporating limestone, spent mushroom compost and activated sludge (mixed substrates). Batch experiment was conducted using different mixture of treatment media over 120 hours. Synthetic mine water was used in the batch experiment. Samples were analysed for pH and alkalinity increase, sulphate reduction and heavy metal removals. Spent mushroom compost was found to be effective in producing the highest increase in pH and alkalinity as well as the greatest sulphate removal among other single media. The mixed substrates (40% limestone, 30% spent mushroom compost, 20% activated sludge, and 10% woodchips) were effective for the removal of most heavy metals studied.