Theme: 14. Emerging Contaminants

Topic Area: 14b. Advances in 1,4-Dioxane Biological Treatment Technologies

Formatted Title:

Bioelectrochemical Biodegradation of 1,4-Dioxane in Groundwater under Anaerobic Conditions

Background/Objectives:

Background/Objectives. A landfill located in the Denver metropolitan area (Colorado) has groundwater impacted by a wide range of contaminants, with 1,4-dioxane (1,4-D) as one of the recalcitrant constituents of concern (COCs). Several microbial strains are known to degrade 1,4-D either metabolically or cometabolically, such as Pseudonocardia dioxanivorans CB1190, under aerobic or facultative conditions; however, the subsurface matrix that 1,4-D exists is commonly anaerobic, restricting the biodegradation activity. A bioelectrochemical remediation technology has been applied on scores of field sites to revive, facilitate and enhance biodegradation of a variety of organic contaminants in the subsurface deleted of electron acceptors and showing a stagnant biodegradation. Many sites and presumably the Lowry Landfill site are under such conditions. A feasibility study was conducted to evaluate the degradation efficiency of 1,4-D by the bioelectrochemical technology. A bioelectrochemical device trademarked as E-Redox-O was installed in a reactor packed with intact samples collected from the subsurface in the landfill.

Approach/Activities:

Approach/Activities. Two test reactors were constructed. One reactor served as the “control” (mimicking onsite condition without any E-Redox-O set up) and the other reactor was the “treatment” reactor with a bioelectrochemical device installed. Groundwater and soil samples from the landfill site were transported on ice and loaded into the reactors under anaerobic conditions. The reactors were operated and adjusted during the testing period as described below. Voltage produced from the bioelectrochemical system was monitored at least weekly, and samples were collected from the reactors (14 sampling events) and analyzed for 1,4-D, total organic carbon, nutrients, and heterotrophic bacteria.

Results/Lessons Learned:

Results/Lessons Learned. Up to 35 days after E-Redox-O startup, 1,4-D concentrations remained stable in both the control and treatment reactors. Photo-enhancement of the bioelectrochemical system was implemented on day 36. Microbial activities were determined to be lacking in the samples and was confirmed by the non-detection of bacterial in a bioassay. A known 1,4-D degrading bacterial culture was inoculated into the reactors. Within 3 weeks, approximately 90% decrease of 1,4-D (from 30 μg/L to 2.8 μg/L) was observed in the treatment reactor while no substantial reduction was observed in the control reactor (staying around 30 to 31 μg/L). Supplemental parameters such as TOC supported that there was robust microbial growth/metabolism in the treatment reactor versus no substantial microbial activities in the control. In summary, data to date have indicated that bioelectrochemical technology can achieve effective biodegradation of 1,4-D in the landfill material with the presence of capable microbes but depletion of oxygen as the terminal electron acceptor (anaerobic condition), which will otherwise restrict aerobic and facultative biodegradation of 1,4-D.

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Manuela Seewald