Project 3: Metal Removal by Constructed Wetlands

Principal Investigators: Mark Fitch and Joel Burken (University of Missouri at Rolla)

Collaborators: Doe Run Mining Company, Sterns and Wheeler, and Cominco Ltd.

Lab-scale constructed wetlands have proven able to treat mine drainage, negating toxicity and removing metals from the site. There remains, however, a need to establish the wetlands' ability to remove metals in the long term, including knowledge of the fate of metals in the wetlands. More fundamentally, effective and proven design criteria do not exist for constructed wetlands for metals removal. The goal of this research is to evaluate the capacity for constructed wetlands to treat lead mine drainage, including determination of metal geochemistry in the wetland substrate, and to propose and validate design criteria for such wetlands. Lead mines are of significant interest in Missouri, the nation's leading lead producer. Not only does the state have issues with existing production; more than 100 square miles of the state are listed on the EPA National Priorities List due to historical lead mining. Lead mine drainage differs from acid mine drainage in pH (the effluent is neutral), but this allows it to act as an excellent case study for examining the fate of metals removed from wastewater by constructed wetlands and for the application of this technology to specific industrial effluents. The research will focus both on lab-scale and two existing field-scale wetlands, one treating lead mine effluent and the other treating lead contaminated machining wastewater. Based on the rates of removal and wetland hydraulics, design equations will be proposed. These design equations will be validated by application at the lab scale and at the field scale, if possible.