Selenium and Nitrate Removal From Coal-Mining Seepage Waters

Overview

Elevated nitrate and selenium concentrations are problematic and ubiquitous in coal mining environments. Weathering of coal mine waste rock releases minerals and associated trace elements like selenium. Nitrogen species are also commonly found in association with coal-mining drainages, leaching from the residual blasting compounds.

On-site pilot-scale Electro-Biochemical Reactor (EBR) systems were used to treat five British Columbia coal mine drainage waters. Influent selenium concentrations, averaging 35 μg/L to 531 μg/L, were removed to less than 1.5 μg/L. Varied levels of nitrate-N (11 mg/L – 170 mg/L) were removed to less than 2 mg/L. The test data demonstrated that the EBR technology is an effective treatment option for coal-mining waters.

Highlights

WesTech's Electro-Biochemical Reactor
Low chemical dosage
Low power requirements, suitable for remote drainage ponds
Selenium precipitated in a stable elemental form
Nitrate converted into harmless nitrogen gas
Consistent contaminant removal to below the discharge targets
No concentrated waste brine produced

Results

Water Test Group	Parameter	Average Influent	Average Effluent
Drainage Water A	NO₃-N (mg/L) Se (μg/L)	170 186	<0.1 1.2
Drainage Water B	NO₃-N (mg/L) Se (μg/L)	16.4 35	<0.1 1.4
Drainage Water C	NO₃-N (mg/L) Se (μg/L)	37 531	1.0 1.4
Drainage Water D	NO₃-N (mg/L) Se (μg/L)	11 355	<0.1 1.2
Drainage Water E	NO₃-N (mg/L) Se (μg/L)	50 105	2.0 0.5