English

Abstract

In late 2008, a passive treatment system was completed to treat mine drainage in the Tar Creek watershed, located in the Tri State Lead-Zinc Mining District of the Central United States. Untreated mine drainage at this site was characterized by elevated levels of Fe, Zn, Pb, Cd, As and sulfate. Mine water quality improvement at this and many other passive treatment sites has been well-documented, but these systems may have additional water quality impacts on the surrounding environment that were not considered in the design phase and are not typically monitored. An example is the potential production of nuisance constituents (i.e., potentially harmful concentrations of non-target contaminants). This research focused on export of two potential nuisance constituents: sulfide and nutrients. Research objectives were to determine nuisance constituent inputs and outputs for each unit of the ten-cell passive treatment system. The passive treatment system was sampled for typical mine drainage and potential nuisance constituents from Fall 2010 through Summer 2011. Phosphorus and N were found in the mine water at levels in excess of U.S. Environmental Protection Agency recommended ambient criteria for lakes or streams for Nutrient Ecoregion IX. Phosphorus and N were removed in the iron oxidation ponds and surface flow wetlands. Sulfide and nutrients were exported from the vertical flow bioreactors. All nuisance constituents were exported from the system at least seasonally. Although re-aeration decreased sulfide levels, it was still exported from the system at levels that exceeded aquatic toxicity and nuisance odor levels. Export of P, sulfide, and possibly N is expected to decrease as the system ages and readily digestible compounds in the vertical flow bioreactor compost layer are consumed.