The engineering firm CDM has come up with a more sustainable way to neutralize highly polluted soil. Instead of digging it up and trucking it to landfills, CDM is using a bioremediation process that relies on the cleaning power of bacteria that grow naturally in groundwater on the site, helped along with a boost from potassium lactate.
Potassium lactate is a cousin of lactic acid or “milk acid,” so called because it is a fermented product of milk sugar (lactose). Lactic acid is produced in muscles and can be used as energy by muscle cells. By adding potassium lactate to the bacteria’s diet, CDM found that bioremediation can work quickly and effectively on soil that is heavily contaminated with the solvent methylene chloride and other volatile organic compounds.
The Shrinking Carbon Footprint of Green Remediation
The U.S. EPA has adopted bioremediation, among other “green remediation” techniques, as a lower-carbon alternative to the old dig-and-dump method of site clean-up. In green remediation, the soil remains on site and the toxic chemicals are broken down by natural processes involving bacteria or pollution-sucking plants such as cattails or even sugar beets. In contrast, dig-and-dump simply shifts contaminants from one place to another, involving significant carbon emissions related to excavating, transporting, and landfilling or incinerating tons of soil.
Lactate, Bacteria, and Bioremediation
CDM is carrying out the bioremediation process on a nine-acre site in Florida owned by Rockwell Automation. Before Rockwell purchased the site, a previous operation had contaminated it with chlorinated solvents used to manufacture circuit boards. CDM recommended bioremediation using the bacteria Dehaloccoides spp., and potassium lactate was added to the groundwater to make the bacteria thrive more vigorously. The bacteria “breathe” with the solvent, breaking it down into harmless substances. To speed things along, CDM installed a system of recirculating wells and a treatment plant. The operation yielded an overall 90% reduction in contamination across the site within just the first six months. That included the total remediation of one particular area that had the highest concentration of methylene chloride, a carcinogenic solvent that affects the heart, central nervous system and liver.
Greener Green Remediation
CDM’s recirculating system was designed to be energy efficient, and the U.S. EPA is pushing for ways to make on-site remediation even greener. One way to do that is by making pumps, fans, and other equipment run on solar energy and other renewable sources.
Image: Milk by Marcin Chylinski on flickr.com.