Metals and Sulfate Removal in a Passive Bioreactor

Adit seepage from an abandoned copper mine has been successfully treated by Hydrometrics, Inc. through a pilot-scale passive bioreactor. Primary constituents of concern at this site are iron, zinc, manganese and sulfate. Within 45 days after reactor start-up, removal rates for total metals were 99 percent for both iron and zinc, and 78 percent for manganese. Initial concentrations were approximately 80 mg/L of iron, 25 mg/L of zinc and 90 mg/L of manganese. Sulfate removal was approximately 90 percent, to an effluent concentration of 250 mg/L. Treatment also increased the water pH by approximately 1 unit, to pH 6.7.

Flow to the pilot-scale reactor was 100 ml/min, which created a metals loading rate of approximately 0.3 moles per cubic meter per day. Higher loading rates are also being evaluated. It is now planned to begin design of a permanent, full-scale passive bioreactor at the mine, which would treat approximately 15 gallons per minute. Pilot testing was performed for less than $20,000.

For more information contact Dr. Mark Reinsel at 406-443-4150, mreinsel@hydrometrics.com.