British Columbia Mine Reclamation Symposium

Biochemical reactor system at the Brule mine : a semi-passive approach to operational and post-closure selenium and nitrate reduction Miller, Trudy; Marshall, Michelle; Gilron, Guy


Long-term management of selenium and other parameters, specifically, innovative treatment technologies applied to final effluents, has been established at coal mining operations throughout North America. A holistic approach to site-wide selenium and nitrate management is being developed at Conuma Coal’s Brule Mine, in northeastern British Columbia, in the context of the post-closure phase of the mine life cycle. The purpose of this study is to improve upon the application of semi-passive treatment system comprising a biochemical reactor (BCR). Conuma Coal’s objective for the system is to reduce selenium, nitrate, and other parameters. The BCR will be used as a tool to aid in the on-going improvement of water quality leading to the goal of compliance with provincial permits and proposed national effluent limits. The basic design and initial construction of the BCR treatment system took place in 2015, with a recent upgrade in 2017. A sampling strategy for effluent monitoring has been established to evaluate the system. Based upon a year of accumulated operating data, parameter concentrations have trended downwards. To date, the BCR has demonstrated success: selenium has been removed in the range 50-90%, while nitrates have been removed in the range 65-99%. Several challenges have been encountered in implementing the system, yielding a number of lessons learned, including: sequencing and flow control are crucial to the proper functioning of the BCR system; sediment curtains help to reduce sediment load to the aerator; and, raised edges help to reduce surface water run-off entering BCR system. Future work relating to the dynamics of resident microbial communities is being planned.

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