System design expertise leads to breakthrough in treatment of recalcitrant chlorinated solvent compounds
An industrial giant steps to the plate
While working with a major industrial client on the management of their legacy remediation project portfolio, the team at Haley & Aldrich became aware of its persistent problem with 1,4-dioxane and knew that it could help. Widely used in the past in aerospace and other industries as a stabilizer for the degreasing agent 1,1,1-trichloroethane (TCA), 1,4-dioxane is classified by the EPA as a probable human carcinogen.
Within a relatively short timeframe, the team developed and installed a test system at one of the client’s sites in Massachusetts, where an existing air stripping system could not treat 1,4-dioxane from the influent groundwater. The new system pioneered the use of a synthetic resin as the treatment medium.
The influent contained high levels of both 1,4-dioxane and chlorinated volatile organic compounds (VOCs). Yet the treated effluent from the synthetic media system showed no trace of the contaminants. Adsorption was based on the micro pore structure of the media rather than any chemical reaction, with the media serving as a highly effective adsorbent of 1,4-dioxane and VOCs. The synthetic media has five to 10 times the treatment capacity of granular activated carbon, largely due to its highly-engineered pore structure and extreme hydrophobicity. Treatment media that is fully saturated with the contaminants is fully regenerated by exposure to steam, with no loss of capacity; tests showed that the media could endure thousands of regenerations without need for replacement.
The pilot system was replaced by a full-scale system at the facility, and has proven over three years of service to be straightforward and reliable, providing consistent results over a range of treatment conditions.
A second challenge: treating thermal byproducts
Haley & Aldrich worked with the client to install a second full-scale synthetic media system at a site in Florida to treat 1,4-dioxane and other miscible contaminants in groundwater generated by an in situ thermal remediation system. The water matrix was complex, containing elevated levels of 1,4-dioxane comingled with high levels of acetone, alcohols and phenols formed by multiple mechanisms including decomposition of VOCs during soil/groundwater heating.
Influent 1,4-dioxane concentrations were high, ranging from 2,000 to 40,000 μg/L. Using the synthetic media system, the effluent concentrations were reduced by many orders of magnitude, to consistently well below the 3.2 μg/L regulatory limit, while the other miscible compounds and VOCs were similarly reduced from very high concentrations to non-detectable levels.
The groundwater produced during thermal remediation of a source area contained highly concentrated, variable and challenging contaminant matrix. The synthetic media proved to be a dynamic, scalable and effective technology even for these extreme conditions.
The power of innovation
Previously an intractable problem, the remediation of 1,4-dioxane in groundwater was met with an elegant solution by innovations from Haley & Aldrich and ECT scientists and system engineers. The synthetic media technology developed provides a reliable and economic solution for clients seeking to meet their environmental obligations, while also avoiding the need to upgrade or replace the technology if regulatory limits are stricter in the future.
More information about the treatment system is available at ect2.com, the website for Emerging Compounds Treatment Technologies, a Haley & Aldrich subsidiary.
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