Theme: 14. Emerging Contaminants

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

Formatted Title:

Assessment of Metabolic and Cometabolic 1,4-Dioxane Biodegradation in Groundwater with Complex Hydrocarbon Contamination

Background/Objectives:

1,4-Dioxane is a synthetic industrial chemical commonly detected in groundwater due to its widespread use as a solvent and solvent stabilizer. Its prevalence, physical and chemical properties including high solubility, low volatility, and low sorptive capacity pose significant challenges for its characterization and treatment.

Pseudonocardia dioxanivorans and other aerobic microbes have been identified and utilize 1,4-dioxane as a carbon and energy source as well as participating in cometabolism. It has also been established that other common groundwater co-contaminants can inhibit biodegradation of 1,4-dioxane.

Approach/Activities:

Bench-scale treatability studies were conducted to evaluate the biodegradation of 1,4-dioxane in a complex water stream containing 2,4-dimethylmorpholin (DMM), chlorinated anilines, chlorinated benzenes and petroleum hydrocarbons in order to understand if 1,4-dioxane could be biodegraded in their presence. The study design included preliminary and secondary batch microcosms to evaluate different amendments including oxygen addition, and bioaugmentation with a culture capable of promoting cometabolic and metabolic biodegradation of 1,4-dioxane. The secondary batch biotreatability study microcosms were then constructed to evaluate both metabolic and cometabolic 1,4-dioxane degradation in more detail. Following the secondary batch microcosm study, flow through columns may be constructed to further evaluate the best performing batch microcosm treatment option.

Results/Lessons Learned:

Preliminary bench-scale testing indicated that aerobic cometabolism with bioaugmentation was successful in the presence of these compounds.

The results from the ongoing secondary microcosm study have indicated that the onset of 1,4-dioxane degradation occurred after degradation of other constituents. Continued analysis will look to identify the sequence of degradation for the complex contaminant mixture and calculate half-lives. These data will be used to evaluate on-site treatment options to promote 1,4-dioxane degradation at this challenging site.

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Alfredo Perez-de-Mora