Abstract
The Rainy River Mine, owned by New Gold Inc., is a gold mine located in the Rainy River District of northwest Ontario. The ore processing is carried out using whole ore cyanidation for gold recovery and cyanide destruction carried out at the mill. Water used in processing must be treated and discharged to the Pinewood River to manage the site water balance. The primary constituents driving water treatment design include ammonia, thiocyanate, nitrate, copper, arsenic, selenium, cyanide, and TSS. New Gold and AEG developed an integrated water treatment train that uses both active and semi-passive biological treatment to accomplish water treatment goals of 20,000 m3/day.
The water treatment plant (WTP) first removes total suspended solids including suspended tailings and natural clay particulates, metals and metalloids from the process water by the addition of lime, flocculant, and ferric sulfate. The treated effluent has added soda ash for alkalinity and monopotassium phosphate as a nutrient, and this amended effluent is directed to the biological portion of the water treatment system. The biological treatment train was designed and implemented to remove N-compounds and additional metals/metalloids not removed in the lime WTP circuit. The biological treatment train consists of nitrification cells for the treatment of ammonia, a biochemical reactor (BCR) for treatment of nitrate, and a second BCR for selenium removal, polishing of metals and metalloids, and sulphate removal by FeS formation. The WTP, nitrification, and first BCR steps of the treatment train have been constructed and were operational in 2019, while the second BCR was constructed in June 2020.
This presentation will provide an overview of the integrated water treatment approach, commissioning and operational management, and future opportunities.