Abandoned manufactured gas plants (MGPs) are a serious environmental concern because they pose potential risks to human health and the environment. Many MGPs are located close to populated areas on lands that would be economically valuable if not for the presence of contaminants including polycyclic aromatic hydrocarbons (PAHs), xylenes (BTEX), and heavy metals. Battelle is working with the U.S. Environmental Protection Agency (EPA) and two utility companies on a multi-technology cleanup demonstration/evaluation project at an MGP site in Bedford, Indiana.

“Battelle can be justifiably proud of the expertise and professionalism they are bringing to this vitally important project.”

Mr. Richard Brenner, EPA Project Officer

The objective of the Bedford project is to compare the performance and cost of several remedial technologies to develop a technically viable and cost-effective approach for addressing PAH contamination. Battelle implemented a statistical experimental design for soil processing that includes nine replicates each of natural attenuation, phytoremediation, land treatment, and biopile/composting technologies. EPA has demonstrated these technologies to be effective for MGP soils at laboratory scale.

Natural attenuation relies on naturally occurring processes including biodegradation, chemical reaction, diffusion, and dispersion to lower contaminant concentrations to levels where the risk to sensitive receptors becomes acceptable. The technology involves no engineered intervention, but does require significant monitoring to prove contaminant reduction and risk mitigation. At Bedford, the natural attenuation results will serve as the baseline against which other technologies will be evaluated.

Phytoremediation uses different species of plants that have been found effective for enhancing the reduction of a wide variety of contaminant levels in soils and ground water. At Bedford, deep-rooted hybrid poplar trees are under evaluation for in situ treatment, while shallow-rooted fescue and rye grasses, and two types of clover are under evaluation for their ability to polish soils that have been treated by land treatment or biopile/composting.

Land treatment is a more mature technology that has been used for various types of biodegradable organic contaminants. For this demonstration, biosolids from a municipal wastewater treatment plant provide essential nutrients to the indigenous microorganisms in the site soil. The technology is an ex situ approach wherein soil is mixed with biosolids, placed in fixed bed systems, and then tilled regularly for aeration while maintaining soil moisture.

Biopile/composting combines aspects of the two technologies to effect more rapid treatment. Contaminated soil is combined with corncobs and nutrients, and then formed into a pile on top of a leachate collection and recirculation system. The pile is aerated, and the leachate circulation system is used to maintain the soil moisture.

At the end of this three-year study, the data will be tabulated and a statistical analysis will be performed to compare the cost and treatment effectiveness of the different technologies. For more information, please contact Dr. Bruce Alleman (614) 424-5715, allemanb@battelle.org.