Biological removal of arsenic in a multi-stage engineered wetlands : treating a suite of heavy metals Mattes, Al; Duncan, William F. A. (William Frederick Alexander); Gould, W. Douglas
A biological engineered wetlands treatment system designed to treat high concentrations of heavy metals built for Teck Cominco in Trail, BC has treated leachate since 1998. Leachate is collected from an historical landfill (now capped) and arsenic storage areas. Metal loadings have averaged more than 350 ppm Zn, 85 ppm As and 5 ppm Cd with peaks of 790 ppm Zn, 355 ppm As and 25 ppm Cd. Total volume of water treated is more than 11 million liters. The system has consistently removed As, reducing the initially high concentrations to 0.5 ppm or lower year round. During periods of extensive changes and reconstruction the operating characteristics of the system changes and As removal efficiency drops demonstrating the importance of maintaining a consistent environment for the bacteria responsible for As removal. A pilot-scale arsenic research project has been constructed in Trail. As well as the field program a multifaceted research project has been developed to examine the removal process under controlled laboratory conditions at the Royal Military College in Kingston, Ontario (As speciation) and at CANMET research facilities in Ottawa, Ontario (microbiological studies). Preliminary results from this research program are presented.
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