A Snapshot of Coal Mine Drainage Discharge Limits for Conductivity, Sulfate, and Manganese across the Developed World

Coal mine drainage (CMD) negatively affects aquatic ecosystems around the world. This article presents the current state of regulatory guidelines and discharge limits established for selected parameters of concern in CMD: specific conductance (SC), SO 4 2− , and Mn. Though not exhaustive, this review provides a representative snapshot of the existing regulatory status in developed nations of North America, Australia, Asia, Europe, and Africa. It was found that most of the nations surveyed have a separate approach to regulating CMD apart from other water quality issues, varying from national or regional guidelines and standards to individual site licenses or permits. In addition, there is broad variability between nations and regions. The selected parameters have a range of required discharge concentrations and in the case of Mn, a variety of categories (i.e. dissolved, total, bioavailable). A few countries use toxicity testing to assist in determining discharge limits, while others take a watershed-based approach to determine mass loading of pollutants, considering the status of the receiving water body and dilution effects. Overall, the myriad approaches encountered underscores the complex and dynamic scientific, ecosystemic, and political landscape in which these regulatory systems have evolved.