Dustin is a Project Manager for AECOM in Connecticut. He has over 13 years experience designing, implementing, managing and technical peer-reviewing complex remedial technologies. Dustin has a Bachelors of Science from the University of Connecticut and is a Registered Professional Engineer.
Full Scale Remediation of a 1,4-Dioxane Plume with Activated Potassium Persulfate
Background 1,4-Dioxane is present in a substantial number of water supply sources and has entered groundwater aquifers. 1,4-dioxine is mostly commonly associated with its role as a stabilizer for chlorinated solvents such as 1,1,1-trichloroethane. Currently, it is commonly found at sites co-mingled with the chlorinated solvents it was used to stabilize and their daughter products. This co-mingling of 1,4-dioxane with chlorinated solvents can make treatment of the entire contaminated suite more complex as 1,4-dioxane is typically treated using an oxidative radical pathway and several of the chlorinated solvents are best treated with a reductive pathway. In several instances this has led to sites where the chlorinated solvents were treated only to expose the untreated 1,4-dioxane. In addition, 1,4-dioxane has relatively unique characteristics including a low organic partitioning coefficient and relatively higher solubility that result separate subsurface behavior compared to its comingled contaminants. These characteristics were displaced at a former industrial site in the Northeastern United States. The plume includes 1,4-dioxane as several 1,1,1-TCA daughter products including 1,1-DCE and DCAs. This plume migrated from the industrial area into remote wetlands. Approach The specific characteristics of 1,4-dioxane in a contaminant plume make it more amendable to treatment using a permeable reactive barrier type of approach. Alkaline activated persulfate has been shown to have a complex chemistry capable of both oxidative and reductive reactions. The potential application of alkaline activated potassium persulfate in a PRB strategy was evaluated in a stepwise process that included bench scale assessment of treating the comingled contaminants using a series of column studies, a field pilot test and eventually, a full-scale application. Access had to be created to the wetlands in a manner that resulted in three separate permeable reactive barriers spaced at approximately 1 year of groundwater travel time apart. Hydrated lime was used to create alkaline activated conditions for a solid slurry mixture of both potassium and sodium persulfate. The potassium persulfate was dosed with an anticipation of one year or longer persistence while the sodium was used for initial rapid treatment and reactivity with non-target demand associated with site soils. Results The column studies confirmed the longevity of hydrated lime and potassium persulfate necessary to behave as a permeable reactive barrier and demonstrated remediation of all the comingled contaminants of concern to non-detect. The 6-month long field pilot study again confirmed the longevity and technical efficacy of the permeable reactive barrier strategy with hydrated lime and potassium persulfate. This included reducing 1,4-dioxane to below the detection limit at the monitoring well at the PRB and combined comingled contaminants by greater than 99.8 percent. The PRB was designed to persist for 6 months was still active at the last monitoring event 8 months after installation. The full-scale application of potassium persulfate and hydrated lime was implemented in the Fall of 2018. This presentation will include subsequent monitoring data that is demonstrating the contraction of the comingled 1,4-dioxane plume at the site.