Removing and stabilizing as in acid mine water

Arsenic is often present in a variety of forms in sulfide mineral deposits and can become a soluble constituent of mine drainage due to oxidation reactions taking place in mine workings and waste deposits. Its removal from solution must be carried out to meet water-quality discharge criteria, and it must be fixed in a solid form that is environmentally stable. The preferred form of arsenic for disposal is as a basic ferric arsenate, FeAsO4. xFe(OH)(y) which can be readily produced by coprecipitation with iron in a high-density sludge process. High-density sludge plants are simple to operate and can be designed to meet stringent water-quality specifications and produce stable sludges over long periods of continuous operation.