The use of passive treatment alternatives for the mitigation of acidic drainage at the Williams Brother mine, California: Bench-scale study

• Published in: Applied geochemistry 2010-07, Vol.25 (7), p.958-971
• Main Authors: Clyde, Erin J., Champagne, Pascale, Jamieson, Heather E.
• Format: Article
• Language: English
• Subjects: Bioreactors; Copper; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; Geochemistry; Iron; Mathematical analysis; Nickel; Pollution, environment geology; Water quality; Zinc
• ISSN: 0883-2927; 1872-9134
• DOI: 10.1016/j.apgeochem.2010.04.004

The aim of the study was to evaluate passive treatment system alternatives to mitigate acid mine drainage (AMD) characterized by low SO 4 2 - and metal concentrations associated with adit drainage at the Williams Brothers Mine located in the Sierra National Forest, California. Surface water from the site drains into the San Joaquin River Basin and a goal of this study was to mitigate AMD to meet water quality objectives for the San Joaquin River Basin. Effluent sampling from the opening of the lowermost adit identified (AMD) characterized by a pH of 3.90, average SO 4 2 - concentration of 101 mg/L and relatively low average metal concentrations of 4.60, 0.074, 0.047 and 0.133 mg/L for Fe, Cu, Ni and Zn, respectively. The bench-scale study involved the testing of three passive treatment systems: (1) a peat biofilter followed by an anoxic limestone drain (ALD); (2) a SO 4 2 - -reducing bacteria (SRB) bioreactor followed by an ALD; and (3) a single SRB bioreactor. Synthetic AMD was produced to represent the AMD characteristics observed at the site. The peat–ALD system efficiently increased the pH of the effluent to an average of 6.95. Metals were reduced to average concentrations of 0.06, 0.008, 0.013 and 0.057 mg/L, respectively, for Fe, Cu, Ni and Zn. The SRB–ALD system increased the effluent pH to an average of 6.47, decreased SO 4 2 - concentrations to an average of 11.6 mg/L and decreased the concentrations of Fe, Cu, Ni and Zn to averages of 1.04, 0.004, 0.016 and 0.025 mg/L, respectively. The SRB system efficiently increased the pH to an average of 6.56 and decreased SO 4 2 - concentrations to an average of 18.8 mg/L. Metal concentrations for Fe, Cu, Ni and Zn were reduced to 0.63, 0.006, 0.010 and 0.027 mg/L, respectively. The peat–ALD and SRB systems were capable of increasing the pH of the AMD to 6.5 to meet water quality objectives. The peat–ALD system was capable of removing Fe and Cu to below water quality objectives, however, removal of other metals was insufficient. The SRB containing systems were incapable of removing Fe to water quality objectives, while sufficient removal of Cu, Ni and Zn was attained. From these results, the most effective treatment system would incorporate a peat biofilter, for Fe and Cu removal and a SRB bioreactor for Cu, Ni and Zn removal. The results of this study demonstrate that passive treatment mitigation of AMD can best be accomplished via the use of a combined treatment system that incorporates a peat biofilter,