Theme: 14. Emerging Contaminants

Topic Area: 14b2. Advances in Biological Treatment of Mixed Contaminant Plumes

Formatted Title:

Degradation of 1,4-Dioxane and CVOC Mixtures by CAT 100 in Bench Tests

Background/Objectives:

CVOC sites impacted by 1,4-dioxane are notoriously problematic, and the best approaches presently employ multiple remedies, which exacerbate costs. During a 1,4-dioxane adsorption study supporting work at a CDOT site, BOS 100 outperformed the granular activated carbon (GAC) from which it is manufactured. The difference in performance was significant and indicated that the 1,4-dioxane was not simply being adsorbed. Subsequent to the CDOT study, synergy between bio (ERD) and BOS 100 was investigated. First, an independent analysis of the Trap & Treat® CAT 100 microbial consortia was commissioned to determine its capacity to degrade 1,4-dioxane. The study found that five bacteria could independently degrade 1,4-dioxane, while the other seven degraded 1,4-dioxane co-metabolically. The bacteria are from such as Rhodococcus, Pseudomonas, and Gordonia. Expanding upon these findings, we present multiple lines of evidence that CAT 100 offers a single step solution to sites impacted by 1,4-dioxane and CVOCs.

Approach/Activities:

The CAT 100 consortia were grown on non-nutrient agar (NNA) petri dishes having 1,4-dioxane vapor as the sole energy source. Iron-impregnated activated carbon and nutrients were bench-tested over various concentrations to find the combination most effective in degrading mixtures of 1,4-dioxane and CVOCs. The protocol evaluates the degradation of 1,4-dioxane and concentrations 1,1,1-trichloroethane and 1,1-dichloroethene mixtures. Chemical analysis of the aqueous concentrations and the compounds adsorbed to the carbon allows mass balance calculations that include degradation byproducts from both 1,4-dioxane and CVOCs. A field study has commenced.

Results/Lessons Learned:

This technology may offer a one-step solution to what has required multiple reagents implemented over an extended time. The generation of degradation byproducts, chloride, lightweight hydrocarbon gases, and carbon dioxide support the degradation of a mixture of 1,4-dioxane and CVOCs. 1,4-dioxane in the carbon only control settled to about 160 ppb, while that in the BOS 100 control was about 60 ppb: verifying the interaction of 1,4-dioxane with the metallic iron. In the CAT 100 tests, the 1,4-dioxane concentration had fallen below detection limit (5 ppb). The absorption of 1,4-dioxane and its interaction with the embedded metallic iron in CAT100, combined with CAT’s microbial consortium and electron donor, supports stable and aggressive degradation of 1,4 dioxane in bench tests. Data suggest reaching MCLs for CVOCs and 1,4-dioxane is achievable.

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Jason Ritenour