Water Resources Engineering (WRE) connects engineering hydrology and hydraulics with global, economic, environmental, and societal issues. Our student, Karyn Ehmann, makes the connection here…

The news article titled “The Microbes That Clean Up Contaminated Mine Sites” was reported by the Pacific Standard on December 2nd, 2015. The article relates to the WRE domain of hydrology and the issue of mine wastewater treatment and the movement of contaminants through the hydrologic cycle. In summary, the article is a basic overview of Dr. Amelie Janin, a scientist with the Yukon Research Center,  and her work with small scale bioreactors (Figure 1) to design a more efficient and cost effective method for removing heavy metals from mine tailing ponds in the Yukon Territory, Canada. Currently, the mines use a chemical treatment process in order to remove heavy metals from the wastewater before the tailing ponds are drained into nearby rivers. This is costly, energy intensive, and inefficient. Dr. Janin’s bioreactors, when scaled up to treat the mine tailing wastewater, will recreate the natural processes occurring in the Yukon Territory’s soil in order to efficiently remove heavy metals. The bioreactors use native sediment, gravel, and a carbon source, either woodchips or biochar, as a medium for heavy metal precipitation. The microorganisms naturally present in the native sediment facilitate reactions that are able to precipitate dissolved heavy metals out of water. Amazingly efficient, the bioreactors have shown the capability to removing more than 99% of copper, more than 99% of zinc, and 94 to 95% of arsenic from the contaminated water. Even more unique is that the reactors have shown no reduction in efficiency at lower temperatures. Native microorganisms are likely psychrotolerant; adapted to survive in the cold temperatures of northern Canada. In effect, the bioreactor is a small scale treatment wetland.

In 1978 the Army Corps of Engineers wrote a technical report on the uptake of heavy metals by wetland plant species grown in contaminated soil. Results of the report were inconclusive as most plants showed very little heavy metal contamination, whereas some species of plants showed a heavy metal concentration an order of magnitude greater than the others. (Lee et. al, 1978) Since then, community concern over heavy metals entering the food chain through plant uptake has led to skepticism over the reports that state plants do not significantly uptake the heavy metals. (O’Sullivan et. al, 1999) Dr. Janin states that 99% of heavy metals are maintained in the soil of a treatment wetland.

In a broad context, water resources engineering influences global, economic, environmental, and societal issues. Mines occur all over the world and significant impacts on health of humans and environment have been connected to mine tailings. Regulations have been implemented in several areas, forcing mine operators to comply with health and safety policies regarding their waste. Operating a wastewater treatment facility causes mining to become even more costly, thus reducing the profits of the mining industry. Metals and other materials are potentially forced into a supply deficit, driving up the price of the raw material and all products that contain the raw material. However, in developed nations the increased cost of a product is acceptable if it means increased protection of land and water resources. Social issues become important in mine waste decontamination when the environment and human health are impacted. In the article, the Yukon Territory is of focus. Many of the communities in the Yukon are Native. If contamination from the mine’s wastewater impacts the health of the water, soil, or air used by the community members, a social injustice occurs. The rapid growth of the mining industry in the Yukon Territory has increased wages for local workers, but decreased morale, time available for hunting and home life. Overall, the Native communities lost some of their basic beliefs, such as collective responsibility and reciprocity between community members and the land. (Gibson and Klinck) Unfortunately, the people affected by the social injustice, particularly regarding Native communities, do not have a strong enough voice in government or business to protect their land sufficiently.

 

Figure 1. Small scale bioreactors. (Janin et. al, 2015)

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URL: http://www.psmag.com/nature-and-technology/the-microbes-that-clean-up-contaminated-mine-sites

 

References:

Gibson G, Klinck J., “Canada’s Resilient North: The Impact of Mining on Aboriginal Communities” A Journal of Aboriginal and Indigenous Community Health 3(1). Available from: http://caid.ca/JAICH2005v3n1p115.pdf

Lee CR, Smart RM, Sturgis TC, Gordon RN, Landin MC., “Prediction of Heavy Metal Uptake by Marsh Plants Based on Chemical Extraction of Heavy Metals From Dredged Material” Dredged Material Research Program: Technical Report D-78-6. February 1978. Available from: http://el.erdc.usace.army.mil/elpubs/pdf/trd78-6.pdf

O’Sullivan AD, McCabe OM, Murray DA, Otte ML., “Wetlands for Rehabilitation of Metal Mine Wastes” Biology and Environment: Proceedings of the Royal Irish Academy, Vol 99B, No 1, The Ecology of Old Mine Sites (Sept 1999) pp. 11-17. Available from: http://www.jstor.org/stable/pdf/20500041.pdf?acceptTC=true

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