REDUCTION OF LEACHABILITY OF HEAVY-METALS IN ACID-MINE DRAINAGE

The leaching characteristics of sludges from the treatment of acid min e drainage(AMD) from Iron Mountain Mine near Redding, California were compared using two different processes: caustic soda treatment and a m odified lime/sulfide treatment process. The modified lime/sulfide proc ess produced a sludge with better dewaterability characteristics than sludge from the caustic soda process. The results of the Cal WET indic ated that the modified lime/sulfide process sludge had less leachabili ty than that of sludge from the caustic soda process. Both processes c ould achieve a substantial reduction of heavy metals in leachate to le vels below the federal regulatory limits(TCLP). For cadmium and zinc, however, neither process produced a sludge that met the requirements o f the Cal WET procedure.