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When a mine closes, mining companies must face the challenge of handling contaminated water and returning the surrounding environment to its natural state.
One way that some mining companies are handling mine wastewater is through the use of man-made wetlands. While that might seem novel, the use of constructed wetlands is anything but new.
The US Environmental Protection Agency notes that about 5,000 wetlands have been built in Europe, with about 1,000 in operation in the US — and that was in 2004. In addition to being used to treat wastewater from mines, constructed wetlands can be used to filter wastewater from other industries and to improve water quality in general. The process works by mimicking the complex filtration processes of natural wetlands, involving soils and vegetation as well as bacteria and other microorganisms.
Now, researchers are taking a look at using man-made wetlands to treat mine wastewater in Canada’s north. According to an article from Yukon News, scientists at the Yukon Research Center at Yukon College have been looking at the potential of man-made wetlands by running water containing copper, selenium, cadmium and zinc through eight Rubbermaid containers containing sand, gravel and wetland plants.
The process has been shown to remove up to 99 percent of heavy metals from the water. Furthermore, the metals being tested stayed in the soil, rather than moving into the roots or leaves of wetland plants. That’s because bacteria, rather than the plants themselves, are responsible for actually removing heavy metals from the water.
Of course, temperatures fall well below freezing in the Yukon for much of the year, and there has been little research into how constructed wetlands work in cold temperatures. However, Andre Sobolewski, who’s been building constructed wetlands for over 20 years, told Yukon News that bacteria adapted to cold climates in wetlands could continue to work on wastewater through the winter.
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