Adventus Americas Inc.

Metals in Groundwater Immobilized Using Multiple-Mechanism In Situ Approach


Courtesy of Adventus Americas Inc.

Until a way is invented to destroy elemental metals in groundwater, environmental practitioners have just a few ways of dealing with them. Water can be extracted for treatment, or the metals can be immobilized in place. The problem with pumping the groundwater is that such systems are usually operated for many years, if not decades, with minimal improvement in groundwater quality unless the source of the metals is removed. This can lead to very high O&M costs as machinery must be maintained over long periods of time. Generally, the more cost-effective solution is to prevent the metals from moving past a given area in the subsurface.

EHC-M™ bioremediation technology immobilizes metals in groundwater. It comprises a combination of three main components: controlled release foodgrade solid organic carbon, zero valent iron and sulphate. The combination of
these reactive materials results in multiple mechanisms through which metals are removed from the water phase. Native microorganisms already present in the water will, over time, consume the organic carbon, creating reducing conditions (an excess of free electrons) helpful for metals precipitation. The presence of sulphate, combined with the strong reducing conditions, will lead to the formation of a significant amount of metal sulphides, such as arsenic, zinc, and lead
sulphides. Iron will slowly corrode, which reinforces the reducing conditions and further promotes formation of metal sulphides. These corrosion by-products, in particular iron oxides and iron oxyhydroxides, provide surfaces to which metals such as mercury will strongly adsorb.

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