specializing in

water restoration


The use of limestone to treat severely polluted mine water is limited by the low maximum alkalinity concentrations that can be produced. Alkalinity concentrations are controlled by calcite solubility which is highly dependent on natural dissolved CO2 concentrations in mine water. In this project, we combine conventional water carbonation technologies with conventional limestone mine water treatment technologies to increase alkalinity concentrations. This work was initially funded by an EPA SBIR Phase I grant and ongoing work is funded by an EPA SBIR Phase II grant.
Phase I work involved construction of two, 500 ft3 pilot scale mine water limestone systems outfitted with multiple carbonation technologies. This allowed for experiments varying the method of carbonation the amount of CO2 injected. We demonstrated that not only was the alkalinity concentrations leaving the systems increased with carbonation, but the kinetics of alkalinity generation were accelerated.

The EPA SBIR Phase I work also involved the carbonation of a 300-ton, full-scale passive anoxic limestone bed. Due to the high concentration of Fe and Mn, the limestone bed produced a net-acidic discharge (e.g. insufficient alkalinity to neutralize the acidity produced from Fe and Mn precipitation). The limestone bed was carbonated to generate a net alkaline discharge for the first time in 30 years.

Phase I of the project was completed in 2020. . A project summary is available here.