Constructed wetland treatment systems applied research program at The Electric Power Research Institute

Abstract

The Electric Power Research Institute's (EPRI) Environmental and Health Sciences Business Unit, within the Environment Group, has initiated a multi-disciplinary applied research program to develop constructed wetland treatment systems as a cost-effective technology for the treatment of metal-bearing electric utility aqueous discharges. EPRI's program involves the building of constructed wetland treatment systems, collection of field data from these systems, and conduct of controlled laboratory experiments to more fully understand their functions and the factors affecting these functions. Both data collected through this program and existing data will be used to develop and deliver design criteria for the effective use of this technology to reduce or eliminate the risk that electric utilities will not meet regulatory-imposed effluent discharge limits. Currently, EPRI along with one of its members, is funding the construction of a state-of-the-art constructed wetland treatment system to treat a discharge from a closed dry ash management facility in Pennsylvania. This constructed wetland treatment system, along with existing ones located in California and Tennessee, will be used to collect data on the cycling of trace metals. Controlled laboratory experiments are underway to develop trace element uptake curves for wetland plant species, to determine which plant species one should plant in a wetland in a particular geographic area to maximize trace element removal. Plants also will be identified that are high volatilizers for selenium, arsenic and lead. As part of this research, the best plant/microbe associations (i.e., best plant species with the best microbe species) will be identified for achieving the highest rates of trace metal removal. Once this work is completed, these plants will be introduced into the three constructed wetland treatment systems mentioned above and the wetlands will be monitored to determine if any improvement in trace metal uptake is occurring. Additionally, EPRI is coordinating its research program with the Tennessee Valley Authority's (TVA) program, where design criteria for manganese rock drains for the removal of manganese and successive alkalinity-producing constructed wetlands for the treatment of acidic aerobic discharges will be developed. TVA is also supporting the development of EPRI's Wetland Environmental and Management (WEM) Model and is conducting research on anoxic limestone drains.