Microbes target toxic metals

Anglo American, one of the world’s largest mining companies, has installed new technology to remove nitrate and selenium from the wastewater discharge at its Peace River Coal Trend Mine in Tumbler Ridge, BC, located about 700 km northeast of Vancouver.

The coal mine, operating since 2006, is an open cut operation using trucks and shovels. It produces up to 1.5 million tonnes of hard coking coal per year from reserves of 15 million tons of coal.

New regulations prompted Anglo American, which is based in Brisbane, Australia, to build a new wastewater treatment plant to remove nitrate and selenium in the wastewater. Currently under construction, the new facility is turnkey, providing a flexible solution for heavy metal removal.

The mine selected GE’s Advanced Biological Metals Removal Process (ABMet) technology to remove nitrate and selenium from the wastewater. The project will represent the first installation of ABMet in Canada. By using this technology, Anglo American will meet British Columbia’s stringent standards for selenium and nutrient discharge limits.

ABMet is a patented biological water treatment system that uses naturally occurring microbes to reduce the amounts of selenium and other metals that can escape in discharge waters from coal mines and power plants. The ABMet process from GE Power and Water, Trevose, PA, involves running wastewater through a biologically active filter, which is seeded with naturally occurring microbes that target selenium and other potentially toxic metals. While selenium is typically difficult to remove from wastewater, ABMet enables the metal to be captured and removed from the wastewater stream.

“Before selecting GE’s ABMet technology for our new wastewater treatment plant, we commissioned a pilot study and competitive tender with multiple vendors. Ultimately, GE presented a turnkey water treatment solution, allowing us to achieve compliance with nitrate and selenium discharge limits,” said Brendan Crisp, specialist project engineer at Anglo American’s Peace River operations. “It also will be used as a demonstration plant to assess performance and develop the criteria for additional wastewater treatment plants at our operations.”

The new wastewater treatment plant has been designed to treat 24 l/s (380 gpm) of flow and to meet nitrate and selenium effluent targets. The targets will reduce nitrates from 85 mg/l to 3 mg/l and selenium from 130 µg/l to 5 µg/l. The system is designed to achieve these limits at water temperatures of 4.4°C (39.9°F) and warmer without the need for any post-treatment.

“We are committed to creating solutions for mine water discharge applications where the removal of key contaminants, such as selenium, nitrate, sulphate and heavy metals, is necessary to meet environmental regulations. Our ABMet technology is ideal for tough-to-treat water and is a perfect fit for Anglo American’s Peace River coal mine,” said Yuvbir Singh, general manager, engineered systems, water and process technologies, for GE Power & Water.

GE worked in cooperation with Lockerbie Stanley Inc. (AECON) of Edmonton, and Stantec Inc., which has offices across Canada and the US, for construction and engineering on the project. The wastewater treatment plant is expected to enter commercial operation in the summer of 2014.

ABMet is a way to remove elevated levels of selenium, nitrate and metals found in wastewater streams in many industrial, mining and utility applications, such as at coal-fired power plants. The simple, low-energy system can achieve up to 99% removal of selenium and can discharge treated effluent containing five parts-per-billion or less of selenium, depending on the wastewater makeup.