Stimulation of Sulfate‐Reducing Bacteria in Lake Water from a Former Open‐Pit Mine Through Addition of Organic Wastes

A method to improve water quality in a lake occupying a former open‐pit mine was evaluated in a laboratory‐scale study. Untreated pit lake water contained high levels of sulfate, iron, and arsenic (1 200, 100, and 5 mg/L, respectively) and was mildly acidic (∼pH 6). Varying amounts of two locally available organic waste products (waste from a potato‐processing plant and composted steer manure) were added to pit water and maintained in microcosms under anoxic conditions. In selected microcosms, populations of sulfate‐reducing bacteria increased with time; sulfide was generated by sulfate reduction; sulfate, iron, and arsenic concentrations approached zero; and pH approached neutrality. Best results were obtained with intermediate amounts of waste potato skin.