Characterization of Sulfate Reduction under Low Metal and Anaerobic Conditions by Sulfate-Reducing Bacteria in a Treatment Wetland System Treating a High Sulfate Concentrated Creek in an Urban Environment

Abstract

With an increase in urbanization, many ephemeral water ways are becoming perennial as a result of excess water runoff from impervious surfaces. The Cities of Reno and Sparks in Nevada have monitored watersheds draining to the Truckee River, a river with established total maximum daily loads (TMDLs), and identified one such water way (Chalk Creek) as a source of elevated total dissolved solids (TDS), total nitrogen, and total phosphorous to the Truckee River. The Nevada Division of Environmental Protection's (NDEP) 2006 303d list of impaired water bodies has listed Chalk Creek for sulfate, orthophosphate, TDS, and selenium. Chalk Creek by itself is not a major contributor of TDS to the Truckee River, but control of TDS in the creek and elsewhere would have positive implications throughout the watershed. A watershed characterization study by JBR Environmental Consulting, Inc. determined that sulfate was the major component of the TDS in Chalk Creek. A treatment wetland was constructed to reduce the levels of sulfate in the water and thereby reduce the levels of TDS. Sulfate levels and other water quality parameters were analyzed over a 49 week period. The purpose of this study was to analyze the reduction of sulfate in the wetland. At the time of this study, most literature involved sulfate reduction and subsequent sulfide removal by metal chelation in mining operations. Since the project area is low in metals, sulfide precipitation was not expected. The results of this study showed no significant change in sulfate levels or TDS levels over the study period.