Topic Area: 3f. Impacts of Mixed Contaminants on Biodegradation

Formatted Title:

In Situ Bioremediation of 1,4-Dioxane in Mixed Plume with Cycled Anaerobic and Aerobic Metabolic Bioaugmentation and Cometabolism

Background/Objectives:

1,4-Dioxane is widely associated with chlorinated solvent source-zones/plumes and presents a significant remediation challenge due to high mobility and persistence. Geochemical conditions that are suitable for chlorinated solvent degradation (e.g., strongly negative ORP reducing conditions) are generally incompatible with aerobic 1,4-dioxane degradation. Biodegradation of 1,4-dioxane can occur through two types of processes, both of which require aerobic conditions. Direct metabolism of 1,4-dioxane may be feasible, but requires a specific bacteria that are often not naturally occurring. Alternatively, cometabolism of 1,4-dioxane has also been demonstrated, but field-scale implementation has been limited to a handful of sites. Aerobic bioremediation of 1,4-dioxane may cause perturbations of natural attenuation of chlorinated solvents.

This presentation will focus on an industrial site in Puerto Rico. The source area is impacted with mixed constituents including chlorinated solvents, hydrocarbons, and 1,4-dioxane (and others). Under ambient conditions there is a robust microbial community with both aerobic and anaerobic biomarkers. While natural attenuation appears to be occurring, engineered methods are being evaluated to expedite treatment.

Approach/Activities:

A side-by-side aerobic bioremediation pilot test was started in the summer of 2022 to investigate direct metabolism and cometabolism. Both sides are treated by a single biosparge system that delivers air at moderate flow rates and pressures to establish aerobic conditions. Bioaugmentation was performed to support direct metabolism. SiREM’s DXO-88^TM bioaugmentation culture was injected into sparge wells and pushed into the formation with the biosparge system. Cometabolism is being implemented by propane sparging.

The initial phases of aerobic bioremediation indicated that 1,4-dioxane concentrations were reduced by 50% to 90%. However, concentrations of chlorinated compounds increased. To mitigate chlorinated compounds, anaerobic bioremediation using a fast-acting, locally-available carbon source (corn syrup) was implemented in spring 2024.

Ana Hopper

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In Situ Bioremediation of 1,4-Dioxane in Mixed Plume with Cycled Anaerobic and Aerobic Metabolic Bioaugmentation and Cometabolism