Field-Scale Demonstration of the Potential for Sewage to Remediate Acidic Mine Waters
Computing, Health and Science
Natural Sciences, Centre for Ecosystem Management
Pit lake waters are often contaminated by acid mine drainage (AMD) from weathering of pyritic materials exposed by mining operations, leading to low pH, and high solute and heavy metal concentrations. Few cost-effective engineering solutions exist for large-scale environmental remediation of AMD-contaminated pit lakes. However, various studies have demonstrated that biological remediation strategies for remediating AMD-contaminated waters, including microbially-mediated sulphate reduction, show promise at the laboratory-scale. The addition of acidic mine water to raw sewage and workshop wastewaters in an vaporation pond provided an opportunity for a field-scale experiment as essentially a reversal of suggested in-situ treatment of acidic pit lakes by addition of organic carbon. The hyper-eutrophic evaporation pond initially contained high concentrations of nutrients, a pH[8, high levels of sulphate (500 mg L-1), and had regular algal blooms. Soon after the addition of the AMD pit water, the evaporation pond pH fell to 2.4, and electrical conductivity (EC) and most metal concentrations were elevated by one to two orders of magnitude. Over the following 18 months, the pH of the pond increased and the EC and metal concentrations decreased. After only 18 months of addition of AMD, pond water quality had returned to a level similar to that before AMD addition. These observations suggest that addition of low-grade organic materials shows promise for remediation of acid mine waters at field scale and warrants experimental investigation.