Theme: 1. Remediation Technology Innovations

Topic Area: 1d2. Combined Remedies and Treatment Train Technologies for Chlorinated Contamination

Formatted Title:

Treatment of a Combined CVOC and 1,4-Dioxane Plume in Urban Geology with Combined Remedy Approach

Background/Objectives:

Various remedial strategies have been employed at a former dry cleaner in New Jersey to mitigate a combined CVOC and 1,4-dioxane plume migrating from overburden to bedrock aquifers. The contamination plume extended for 30 acres through residential neighborhoods. Remedial activities have included removal of contaminated soils, and installation of a sub-slab depressurization system to mitigate vapor intrusion concerns. In 2017 an injection of sodium persulfate for a “hot spot” area treatment of the CVOCs was conducted with limited success; around this time 1,4-dioxane was detected on the Site due to lower NJDEP standards. In 2020 a set of permeable reactive barriers was installed combining electron donor (3-D Microemulsion) and sulfidated micro zero-valent iron and bioaugmentation culture (BDI Plus). In 2022 after the levels of CVOC were reduced, a situ bioremediation program was conducted to treat the 1,4-dioxane plume.

Approach/Activities:

In 2017, 40,000 lb of PersulfOx was injected into a section of groundwater plume containing the highest levels (source material) of CVOCs. This injection was met with limited success and was followed up with a multi-tiered injection program in 2020 which included the treatment of the shallow aquifer utilizing direct push injection of 5,000 gallons of remediation chemicals, a combination of 3-D microemulsion and sulfidated micro zero-valent iron and bioaugmentation culture (BDI Plus). The deep aquifer (bedrock) was treated by injecting 4,000 gallons of remediation chemicals into 12 injection wells. To treat the 1,4-dioxane plume an in situ bioremediation program was conducted in 2022. A bacterial culture was injected to induce metabolic biodegradation of 1,4-dioxane. The addition of oxygen and propane induced the cometabolic biodegradation of 1,4-dioxane.

The project was successfully completed on time and within project budget even though significant design modifications were required to achieve desired objectives.

Results/Lessons Learned:

The 2017 PersulfOx injections yielded CVOC reductions between 33 and 42%. However, PCE and TCE concentrations rebounded over a 2 year period, indicating low permeability soils stored contamination, which was equilibrating with the aqueous phase through matrix back diffusion.

Due to changes in remediation standards it was discovered that an 1,4-dioxane plume was present on the Site which was not previously known to exist. The 1,4-dioxane plume altered the proposed remediation strategy.

The application of the 3-D microemulsion and sulfidated micro zero-valent iron and bioaugmentation culture (BDI Plus) in 2020 has led to a 99% reduction in CVOCs.

The 1,4-dioxane in situ bioremediation program conducted in 2022 has led to a 98% reduction in 1,4-dioxane.

Menu

Joseph Chiappetta

Biography