Treatment of Acid Mine Drainage (AMD) by Ultra-Low-Pressure Reverse Osmosis and Nanofiltration

Secondary treatment of acid mine drainage (AMD) from a copper mine in China which has very low-concentration heavy metal ions and high conductivity (2,800 μs/cm), was attributed to the high concentration of dissolved monovalent and divalent ions. Commercially available polyamide ultra-low pressure reverse osmosis (ULPRO) and nanofiltration (NF) membranes were used to remove heavy metal ions and reclaim AMD. Effects of operation pressure, pH, temperature, water recovery efficiency, and operation time on ULPRO and NF performance were investigated. Experimental results show that the rejection increased with an increase of feed pressure and decreased with an increase of feed temperature, and it is dependent on feed pH. Generally, the rejections of heavy metal and total conductivity were greater than 97 and 96% for the ULPROM tested, respectively, which suggested the suitability of such membrane for AMD for the recovery of heavy metal and reclaiming wastewater. However, NF process was capable of removing about 90% of the heavy metals in the AMD and decreased 48% of the total conductivity.