When Rockwell Automation acquired a former industrial property, shallow groundwater at the 9-acre parcel of land in Orlando, Florida was severely impacted. Chlorinated solvents—previously used in printed circuit board production—had leached into the groundwater and high levels of volatile organic compound (VOC) contaminants were prevalent on the site.
Despite exhaustive efforts over several years, Rockwell was unable to find an appropriate remediation solution until partnering with CDM. After partnering, the firm discovered contamination beyond initial reports and explored various cleanup options. The then emerging technology of enhanced anaerobic bioremediation (EAB) was selected for its ability to leverage the power of naturally occurring bacteria, Dehalococcoides spp., boosted by simple lactate, to cleanse the groundwater in place.
In addition, CDM designed and implemented a complex and innovative groundwater circulation system that creates the optimal conditions for effective treatment:
- Horizontal extraction wells draw water from the aquifer to an onsite treatment plant for lactate addition. Lactate-enhanced water is then re-injected into groundwater target zones through vertical injection wells. Lactate expedites the dechlorination process, aiding the bacteria in breaking down chlorinated solvents into harmless byproducts.
- The innovative horizontal well system—installed using unique one-pass trenching technology—controls water flow in multiple aquifer zones and continually recirculates groundwater to ensure that lactate, bacteria, and contaminants are in constant contact, creating an unparalleled environment for decontamination.
- A sophisticated control system allows groundwater to be redistributed or shut down for optimal conditions—reducing energy use and operating costs. Continued monitoring facilitates optimal reductive dechlorination.
Within the first 6 months of full-scale operation, VOC mass was reduced by more than 90 percent. At startup, the highest concentration area had more than 2,000,000 ppb of methylene chloride. After 6 months, the methylene chloride in this target area had been completely remediated and has not been observed since. In addition, destroying the contaminants in the ground mitigates risks such as accidental release to the environment or worker exposure.