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Should the effluent limits for manganese be modified?
Kleinman RLP; Watzlar GR
Mine Drainage and Surface Mine Reclamation. Volume II: Mine Reclamation, Abandoned Mine Lands and Policy Issues. Pittsburgh, PA: U.S. Bureau of Mines, 1988 Apr; :305-310
As a result of the 1912 and 1911 Clean Water Acts, effluent mine water is limited to a 30-day average concentration of 2 mg/L manganese and a single-day maximum of 4 mg/L. These limits were selected by EPA after a survey of mine water treatment facilities indicated that these values could be achieved consistently, and that in the process of removing manganese, other trace metals were also controlled. There are, however, several reasonable arguments against such low limits. Current mining operations often face much higher levels of manganese than were considered by EPA when they established the limits. As a result, many operators must raise the pH of mine water to 10 or above, increasing their chemical treatment costs by as much as 100 pct. Precipitation of manganese then lowers the pH somewhat, but an effluent pH of 9 or even higher is common. Can the limits be safely eased? Based on recent studies, it appears that manganese is only toxic to fish at low concentrations when the stream water is exceptionally soft and pure. Except in such rare instances, manganese can be considered to be about as toxic as potassium. Our work also indicates that the other, trace metals of concern are removed at a pH below 9. It is therefore suggested that the manganese effluent limits should be reexamined in light of this information.
Miners; Mining-industry; Manganese-compounds; Waste-treatment; Water-analysis; Water-purification; Water-sampling
IH; Conference/Symposia Proceedings
Mine Drainage and Surface Mine Reclamation. Volume II: Mine Reclamation, Abandoned Mine Lands and Policy Issues
Page last reviewed: June 15, 2021
Content source: National Institute for Occupational Safety and Health Education and Information Division