On the Removal of Chlorinated Solvents from Groundwater Aquifers
Just when we thought we had it all down pat…
Chlorinated solvents present enormous threat to groundwater aquifers. Chlorinated solvents have properties that make them useful for degreasing fats, oils, waxes, and resins. Historically they have been used widely in dry cleaning and industrial degreasing operations and manufactured in large quantities. Some chlorinated solvents are dichloromethane, tetrachloroethene, trichloroethane, and tricholoroethene. The U.S. production of these compounds in 1980 was 255,000, 347,000, 314,000, and 121,000 metric tons, respectively.
Chlorinated solvents are harmful to human and ecological health. They can cause or are suspected of causing cancer, and are toxic or harmful to aquatic organisms.
Spills and leaks of chlorinated solvents have caused widespread subsurface contamination in the environment. Because the density of these substances is greater than water, they sink in groundwater systems (aquifers) in complex dispersal and plume patterns, resulting in long-term sources in the subsurface, and difficult cleanup. Commonly these contaminants are present in the subsurface in the form of bulk chemical product also known as dense non-aqueous phase liquids (DNAPL), as dissolved contaminants in ground water, in contact (adsorption) to aquifer sediments, and as vapors in the unsaturated zone.
The traditional method used to clean up chlorinated solvents in ground water has been through pump and treat that is highly ineffective. For soils cleanup, excavation and disposal at a special landfill has been used which is very expensive and shifts the problem from one site to another. As these solvents are volatile, a technology known as “soil-vapor extraction” has been used to clean up soils that are permeable like various rock formations; however, this technology does not work well in tight soils like various combinations of clay and silt. Attenuation through natural anaerobic microbial processes has been problematic insofar as it is very slow and the daughter products created through the process, dichloroethene and Vinyl Chloride, are more toxic than the original contaminates.
However, there is a new kid on the block……
Professor Alan Harker, PhD in microbiology from Brigham Young University, has created a variant of a naturally occurring aerobic bacterium by inserting an additional enzyme in it. It completely degrades chlorinated solvents and leaves nothing but CO2, salt and water behind.
To utilize Dr. Harker’s special bug, we use a delivery system known as Subsurface Metabolic Enhancement (SME), created by Mark Ellis of Lehi, Utah, US patent #6,464,005. A grid work of pipes is developed into the contaminated soil(s) and water. Air is then injected at a very low pressure so as to saturate the substrate. What this does is turn the environment from anaerobic to aerobic. Aerobic bacterial action is 15 to 20 times faster than anaerobic. The bacteria and nutrients are also delivered through the grid work. To keep the bugs healthy, we clean up after them by extracting their CO2 waste product.
It is completely green, safe and fast. When coupled with the SME delivery system created and patented by Mark Ellis, we achieve an optimal solution to the most widespread groundwater contamination problem in the world. Ami Adini & Associates, Inc., is licensed to use SMEcl.
For a brief overview of SME®, click here. For detailed information on the science and application of SME® and the bacterium, Ralstonia Eutropha variant, click here. For case study data, click here
For further information on the application of SME or SMEcl please contact