Theme: 14. Emerging Contaminants

Topic Area: 14a. 1,4-Dioxane Remediation Challenges

Formatted Title:

Laboratory Testing of Metal Activated Oxidants for Treatment of 1,4-Dioxane

Background/Objectives:

The United States Environmental Protection Agency (USEPA) has determined that 1,4-dioxane is a probable human carcinogen that has been detected in drinking water supplies, soil, and groundwater. Typically, 1,4-dioxane has been used as a stabilizer for chlorinated solvents in addition to a solvent in paints, personal care products, and in the processing of crude petroleum and refining. Due to its physical and chemical properties, this synthetic industrial compound is highly miscible in water and rapidly migrates in soil. The current regulatory landscape for drinking water and groundwater widely varies for Federal and State promulgated standards and advisory levels between 0.3 micrograms per liter (µg/L) and 200 µg/L.

Many conventional treatment processes such as traditional pump and treat systems utilizing separation and/or adsorption by granular activated carbon have limited effectiveness for 1,4-dioxane treatment. Therefore, advanced oxidation processes (AOPs) have emerged that provide strong oxidizing agents capable of mineralizing 1,4-dioxane. Persulfate is a strong oxidant that has been extensively studied for its highly reactive species. Reaction kinetics can be increased by using activators to promote the formation of free radical species such as sulfate radical, hydroxyl radical, and superoxide radical that can be generated because of the breakdown of persulfate in the aqueous phase.

The objective of the laboratory study to be presented was to evaluate the effectiveness of AOPs capable of reducing 1,4-dioxane concentrations in impacted water samples.

Approach/Activities:

Laboratory experiments were conducted with oxidant activation employing sodium persulfate, catalyzed hydrogen peroxide, sodium percarbonate, sodium perborate, and potassium permanganate towards the degradation of 1,4-dioxane in spiked (5 milligrams per liter [mg/L]) water samples. Screening of a variety of treatment combinations were evaluated at ambient temperature within 1-liter (L) HDPE containers at various time intervals over 24 hours while monitoring 1,4-dioxane concentration utilizing SW-846 Test Method 8260. Oxidant concentrations were 4 mM (millimolar) while catalyst concentrations were 0.9 mM.

Results/Lessons Learned:

The preliminary results of this study show that metal activated oxidants are capable of reducing 1,4-dioxane concentrations. Treatments that performed best included metal activated persulfate and hydrogen peroxide with greater than 99-percent reduction in 1,4-dioxane. Other treatments resulted in less percent reductions such as 29-percent reduction without using metal-catalyzed persulfate activation. Follow-up experiments are currently underway that include technology demonstration on site water evaluating the impact of oxidant and metal activator concentrations.

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Ryan Thomas