Abstract
New Gold operates the Rainy River Mine in Ontario, which has multiple water treatment systems. One of these is an anaerobic gravel bed bioreactor (GBBR) called “BCR2”. The GBBR was piloted in 2018 and built in 2019. The system was brought from a technology readiness level (TRL) 6 through to 8 within under 2 years. The BCR2 was not used much from 2019 to 2021, except for some nitrate polishing. In 2022, the mine received a limited operational flexibility (LOF) permit to test the system for treatment of metalliferous drainage from a mine rock pond. The GBBR performed well with treatment of ~3 mg/L of dissolved zinc and >20 mg/L of nitrate.
In late 2022, optimization opportunities were identified that improve future performance. Renovations were carried out in winter 2022/2023 to implement these changes. In 2023, the GBBR received a second LOF to treat tailings water with nitrate (up to 10 mg/L), copper (sometimes >1 mg/L), and other metals. Throughout 2023, the GBBR treated either tailings water or mine rock drainage. Performance data suggests the system could treat 2-3x its current 20,000 m3/day capacity. The GBBR is a more efficient water treatment system than the LDS, capable of treating both metals and nitrate in a single step. It can also treat metals bound to cyanide complexes and has a lower carbon footprint than conventional lime treatment.