PILOT-SCALE NEUTRALIZATION OF UNDERGROUND MINE WATER

Traditionally acid mine water is neutralised with lime (Ca(OH)(2)). Li mestone (CaCO3) is a cheaper alternative for such applications. This p aper describes an investigation aimed at demonstrating that undergroun d mine water can be neutralised with limestone in a fluidised-bed. The contact time required between the limestone and the acid water, chemi cal composition of water before and after treatment, and economic feas ibility of the fluidised bed neutralisation process are determined. A pilot plant with a capacity of 10k1/h was operated continuously underg round in a gold mine. The underground water could be neutralised effec tively using the limestone process. The pH of the water was increased from less than 3 to more than 7, the alkalinity of the treated water w as greater than 120 mg/l (as CaCO3) and the contact time required betw een mine water and limestone was less than 10 min (the exact contact t ime depends on the limestone surface area). Chemical savings of 56.4% can be achieved compared to neutralisation with lime. Copyright (C) 19 96 IAWQ.