Recycling CIP process water to bacterial oxidation circuits via a thiocyanate degrading bioreactor

摘要

Significant concentrations of thiocyanate are generated in effluent from the CIP/CIL gold extraction process. As thiocyanate is toxic to iron- and sulphide-oxidising bacteria, the effluent cannot be returned directly to a bacterial oxidation plant. To overcome this problem, a rotating cage laboratory-scale bioreactor was inoculated with two strains of known thiocyanate-degrading bacteria. The reactor, which had a 20 L solution volume and surface area of 20 m~2 available for biomass support, degraded thiocyanate from a concentration of 2000 to <1 mg L~(-1) (flow rate 30 mL min~(-1); residence time 11 h). The efficiency of the thiocyanate-degrading bioreactor to detoxify process water was evaluated in bacterial oxidation tests using Fe~(2+) and arsenopyrite as energy sources. The experimental results indicated that water detoxified using the thiocyanate-degrading bioreactor could be recycled to a biological oxidation plant.