Confidential Site with 1,4-Dioxane

Treatment of low concentrations of 1,4-Dioxane at a chlorinated solvent site

Site Summary:

Contamination from chlorinated solvents and 1,4-Dioxane was detected in the ground water at a confidential site. CL Solutions participated in a pilot study to verify that CL-Out aerobic bioaugmentation could successfully degrade not only the chlorinated solvents, but also the 1,4-Dioxane. The effectiveness of CL-Out bioremediation on chlorinated solvents has been demonstrated at numerous sites, but CL-Out has not been used to specifically target 1,4-Dioxane. The data below shows that CL-Out significantly reduced the 1,4-Dioxane concentrations in less than four weeks.

Application

Two units of CL-Out microbes (110 gallons) were added to two direct-push points in the pilot study area, which extended 90 feet below grade. Before and after the CL-Out injections, ground water samples were collected from four wells within the pilot study area. These wells were located upgradient, downgradient, and near the injection points. The upgradient well, PT07, was 10 feet away and monitoring well, PT08, was located near the injection points. The downgradient wells, PT09 and PT10, are located 10 and 30 feet downgradient of the injection points, respectively. Please note that the highest initial 1,4-Dioxane concentration was reported to be 25 micrograms per liter (µg/L) at PT09. The table below summarizes the concentration results before and after the injection.

1,4-Dioxane Concentrations

	Pre-treatment	Post-treatment (2 weeks)	Post-treatment (4 weeks)
PT07 (10 feet upgradient)	9.7	11	7.9
PT08 (near injection points)	6.9	<1.9	<1.9
PT09 (10 feet downgradient)	25	6.7	<1.9
PT10 (30 feet downgradient)	5.5	2.8	<1.9

Concentrations are in µg/L

The monitoring well near the injection points show almost a complete removal of the 1,4-Dioxane in less than 2 weeks, but this may be partially caused by dilution from the injections. At 10 feet downgradient, the 1,4-Dioxane concentration decreased by more than 25% in 2 weeks and more than 90% in 4 weeks. At 30 feet downgradient, the 1,4-Dioxane concentrations also decreased to below the detection limits within 4 weeks.

Conclusion:

The pilot study confirmed that under these site specific conditions, CL-Out bioremediation can effectively degrade 1,4-Dioxane rapidly.