Cadmium, Copper & Ammonia Treatment; Rainy River Gold Mine Water Treatment Plant; Feasibility Phase

Hydrology and geochemical studies determined that Cd and Cu would be the main treatment challenges, in addition to the ever-present NH3 in gold mine tailings.

Ammonia is usually present due to use of the SO2/Air treatment process, wherein the cyanide used to leach out gold is oxidized to cyanate, which in turn hydrolyzes to ammonia. The process selected pumped water to a lime reactor for pH adjustment which in turn overflowed into a U-shaped Settling Pond for a 3-day settling period.

A pH adjustment step before flowing into a large pond where ammonia removal was achieved naturally by biological reactions before release.

This approach, when compared to using a clarifier, or one that accomplishes settling over the entire pond, was determined to have the lowest associated capital cost and the optimal sludge management and ammonia removal.

Location: Fort Frances, Ontario, Canada