Trialling small-scale passive systems for treatment of acidmine drainage: A case study from Bellvue Mine, WestCoast, New Zealand.

Bellvue Mine is an abandoned coal mine on the West Coast of the South Island which discharges severe acid mine drainage (AMD) into the nearby Cannel Creek. This site is unique in that iron is in a ferrous or reduced form at the mouth of the mine, but due to the slope of the site, the AMD becomes aerated and subsequently the iron oxidises into ferric form as it moves downstream. Research was conducted to examine the geochemistry of the AMD at the site and investigate the performance of selected passive treatment systems at this site, with a view to informing decisions for passive treatment at other comparable mines on the West Coast. A range of small-scale trial passive remediation systems were installed, including an anoxic limestone drain (ALD), a bioreactor, and two mussel shell reactors. Results from the trials showed that the mussel shell reactor treating oxidised water was the most effective at reducing the concentration of dissolved metals in the AMD. A range of factors including hydraulic residence time, geochemistry of the Bellvue Mine discharge, and unexpected equipment issues all contributed to the results of the trials, and are important factors that need to be taken into consideration when designing a full-scale system for this site and others