MBBR Retrofit Provides An Increase In Capacity Without Interupting Mining Operations

Agnico-Eagle Mines (AEM) produces approximately 245,800 ounces of gold with a by-product production of 156 tons of silver, 7,300 tons of copper, and 82,000 tons of zinc annually.

The LaRonde Mine, AEM’s flagship mine, is one of the largest gold mining operations in North America, specializing in bio-mining of gold from low-grade ore deposits. Located in Cadillac, Quebec the mine includes underground mining operations, a mill complex, a wastewater treatment plant, a secondary crusher building, and related facilities. The mine uses a 2,250 meter Penna Shaft, the deepest single shaft in the Western Hemisphere, to hoist LaRonde’s ore production of approximately 7,300 tons per day.

A two-stage multi-train submerged biological contactor (“SBC”) process was employed for the degradation of thiocyanate and had operated successfully for many years until the SBC units experienced mechanical failures due to the excessive weight of the rotating biological contactors. The SBC units were attached-growth biofilm contactors that ineffectively sloughed off excess biomass, resulting in accumulated mass that exceeded the design limitations of the SBC mechanical shafts and bearing journals. This resulted in the eventual catastrophic mechanical breakdown of the biological treatment process.