Patent ID: 7115201

Claim:
A method for inhibiting precipitation of calcium salt and metal oxide and/or metal hydroxide from hard mine drainage water comprising: (a) providing hard mine drainage water having a pH of from 4.5 to 10; calcium hardness greater than 100 mg/l of Ca +2 as calcium carbonate; alkalinity greater than 100 mg/l as calcium carbonate; and one or more metal ions or metal salts selected from the group consisting of iron, copper, zinc, lead, mercury, cadmium, arsenic, barium, selenium, silver, chromium, aluminum, manganese, nickel, cobalt, uranium, and antimony; and (b) adding a scale control agent to the mine drainage water, wherein the scale control agent is one or more selected from the group consisting of polymeric scale control agents, water-soluble polycarboxylates, phosphonates, organic phosphates, organic polyphosphates, and sulfonates, at a level sufficient to inhibit precipitation of calcium salt and metal oxide and/or metal hydroxide in said hard mine drainage water.