Processing Magazine

Injecting wastewater underground could increase mercury levels in groundwater

March 13, 2014


New research carried out by a scientist at non-profit marine research organization Woods Hole Oceanographic Institution (WHOI) suggests there are increased levels of mercury in Cape Cod's groundwater.

Biogeochemist Carl Lamborg claims that the naturally low concentration level of mercury in wastewater can increase during treatment processes that break down waste, due to microbial action that transforms it into a more toxic form of the chemical. His research, published in the Environmental Science and Technology journal, looked into the level of mercury and its forms in water and ground samples taken between 2010 and 2012 from the area around a wastewater treatment plant run by the Massachusetts Military Reservation. He noticed that mercury concentration in the groundwater was much higher than could be expected and when he investigated the reason he discovered that the key was in the plume of pollutants formed where wastewater had been discharged underground for nearly 60 years.

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Examining two different points of the plume, he found that upstream there were microbes breaking down iron in a process known as iron reduction, which also made mercury less likely to stick to sediment, allowing it to seep into groundwater. The sample taken downstream revealed a higher concentration of monomethylmercury, which could badly damage fish and human health if accumulated.

Although Lamborg claimed there is no immediate risk to people from the levels of mercury present in the groundwater, he stressed the fact that it would not have risen to such levels if water had not been disposed of underground.