BIOLOGICAL PROCESS FOR SULFATE AND METALS ABATEMENT FROM MINE EFFLUENTS

A biological process was developed, aimed at treating water containing 1-2 g/L sulfate, typical of effluents in diverse mining operations. T he original inocula was adapted from sanitary fill culture, to reduce sulphate, utilizing hydrogen gas as energy source and carbon dioxide a s sole carbon source. Cost analysis, when compared to a lactate proces s, indicated the superiority of the hydrogen process. Experiences with an experimental 1 L reactor led to reaction rates ranging from 32 to 83 mg/L per h. Degradation rates could be accelerated by increasing th e feed sulphate concentration; however, this strategy is not feasible, because concentrating sulphate is a fairly expensive process. The sus pended solids in the effluent had good sedimentation and flotation pro perties, giving a process with few postreactor separation processes, p revious to environmental discharge. Process economic analyses for a ty pical mine operation indicate that sulphate, and consequently metals, can be removed from the effluent to an environmentally acceptable leve l by increasing the production cost of a pound of copper by a fraction oi a USA$ cent. The most sensitive parameter was not the cost of hydr ogen gas at the plant site but a source of acid (H+). A process flow d iagram was developed and the transport phenomena is currently being mo deled to optimize gas transfer processes, postulated as the controllin g step of the process. (C) 1997 by John Wiley & Sons, Inc.