Advanced acid mine remediation

Abstract

Acid mine water remediation can be a significant challenge for active, closing, or abandoned mines. The usual objective is to sufficiently treat this water so that it can be safely released to the environment. Of the several technologies employed, passive treatment and lime precipitation are the most common. Passive treatment is usually the least costly but frequently not feasible. Lime precipitation effectively removes heavy metals but has the disadvantage of creating large amounts of sludge that is 95% lime and 5% metal for which disposal may be difficult. Additional steps of pH adjustment may also be necessary. Electrocoagulation as an alternative technology has proven effective since before 1900. However, high power cost, unreliable reactors and maintenance difficulties have severely limited its past application. Recent developments have solved its most significant problems of anode passivation, internal sludge buildup, and system maintenance. Sludge generation, which is only about 10% of lime treatment may provide the largest advantage. This sludge is over 50% metal, and its refinement may offset the cost of operation. This paper compares electrocoagulation and lime precipitation for effectiveness and cost.