Constructed Wetland Treatment System (CWTS)

Mount Polley On-site Pilot Scale CWTS 2020

Project Highlights

  • Off-site and on-site pilot-scale trials have demonstrated treatment of constituents of potential concern (COPC) to below discharge criteria
  • Selenium and nitrate removal was achieved at pilot scale (on-site and off-site)
  • Demonstrated 95-99% removal of copper in off-site trials with starting concentrations of ~0.2 mg/L
  • Constructed wetlands are a feasible passive treatment option for this remote cold climate mine at closure

The Challenge

The Mount Polley Mine is an open pit and underground copper/gold mine owned and operated by the Mount Polley Mining Corporation (MPMC), a subsidiary of Imperial Metals. Mine operations were suspended in May 2019 and the mine is on care and maintenance status, with remediation efforts continuing through this time. Ensero was retained in 2016 conduct a detailed assessment and independent evaluation of Constructed Wetland Treatment Systems (CWTS) as part of a long-term passive or semi-passive water management strategy for the mine. Long-term passive technologies are a low cost and low maintenance option for effective mine water management at closure.

Constituents of potential concern include copper, selenium, nitrate, and potentially sulphate at closure.

The Ensero Solution

Both off-site and on-site pilot-scale trials demonstrated COPC removal and provided proof-of-concept for CWTS. Through this work, several important design and commissioning considerations were identified for implementation of CWTS, including vegetation and site materials selection, removal rates, evapotranspiration rates, and commissioning requirements. On-site pilot-scale trials provided valuable information about the buildability of a full-scale system. Future work includes revisiting locations for implementing CWTS at the mine using site-specific removal rates and construction of larger-scale systems.  

Mount Polley CWTS Offsite Pilots 2019

For more information about this project please view and download the project summary.