Man-made wetlands remove toxins from water supply

Researchers in the US are constructing a wetland near a mine and smelter plant that will help remove lead and other toxins from the water supply.

Researchers at the University of Missouri-Rolla in the US are involved in the construction of a wetland near a mine and smelter plant in southeastern Missouri to help remove lead and other toxins from the water supply.

Wetlands are an effective way to trap and remove lead and other toxins from water because of the chemical reaction that occurs among the natural materials that make up a wetland, said Dr. Mark Fitch, associate professor of civil, architectural and environmental engineering at UMR.

The wetland forms something of a filter, letting the water seep through and leaving the lead, zinc and other toxins behind. A wetland constructed correctly may be effective for more than 30 years, said Fitch.

Over the past six years the US Environmental Protection Agency has contributed about $200,000 to the project. The University of Missouri Research Board has contributed about $32,000, and the Doe Run Company, headquartered in St. Louis, has contributed about $10,000 and has allowed UMR to use its Doe Run Buick Resource Recycling facility in Boss, Missouri, as a test site for the project.

Based on UMR’s research, the Doe Run Buick Resource Recycling facility has designed a wetland the size of a football pitch. The recycling facility is a prime location for the man-made wetland because it will keep the chemicals released during the recycling process from getting into the water supply, said Fitch.

‘This is a very inexpensive way of removing toxic components of wastewater, particularly mine water,’ Fitch said. ‘This is also very important because Missouri is one of the largest lead mining areas in the United States.’

Fitch said the constructed wetland consists of 50 percent chip bark, 20 percent gravel, 15 percent sand, and a miscellaneous amount of straw, peat moss, sewage sludge and aged manure.

‘The sewage and manure, however, does not cause the wetland to stink,’ said Fitch. ‘It provides the bacteria needed to make the whole process work.’

The wetland at the Buick Recycling facility may become so effective that the company could make money from the process. ‘We may be able to deposit so much lead and zinc into the wetlands that rather than become waste, it becomes a feed for the smelters, developing into a low-grade ore,’ said Fitch. ‘The company would be able to take the waste and actually extract lead from it.’

Once the wetland construction is completed at the Doe Run Buick Recycling facility, Fitch and his team of researchers will put in sampling ports to monitor its effectiveness.