Treatment of groundwater contaminated with 1,4-dioxane (1,4-D) is an emerging requirement at many cleanup sites. Although numerous studies on aerobic cometabolic biodegradation (ACB) of 1,4-D have been published, most of them have been laboratory studies at high 1,4-D concentrations, not the low 1,4-D levels typically found at cleanup sites. To better evaluate the potential of ACB to treat 1,4-D and co-contaminants in a dilute plume, the project team has conducted laboratory tests using two gaseous substrates, propane and oxygen, to evaluate the ACB potential towards 1,4-D of numerous aerobic propane-oxidizing bacteria under low 1,4-D concentrations (below 200 mg/L). The laboratory pre-screening test results indicate that, out of the 5 commercially available strains, only one organism, Arthrobacter sp. has exhibited robust 1,4-D-transformation activity in our screening procedure. In contrast, all of the isolates obtained from previous MTBE and TBA degradation studies appear to have substantial 1,4-D transformation activities. One of the isolates, Isolate 1A, was found capable of degrading 1,4-D to trace levels (below 1 mg/L) . This isolate was chosen for bioaugmentation testing in the field. An in-situ pilot test is underway that examines the effectiveness of ACB of 1,4-D at a former air force base in Sacramento, California. Propane and oxygen is pulsed into a groundwater recirculation zone to stimulate indigenous propane-oxidizing bacteria in order to assess the background ACB activity towards 1,4-D, trichloroethene, and 1,2-dichloroethane. Following the biostimulation study, the need for bioaugmentation will be assessed and bioaugmentation will be performed if needed. The results of the laboratory tests and field testing available will be shown and discussed in our presentation.

Laboratory and field studies on aerobic cometabolic biodegradation of 1,4-dioxane and co-contaminants

251st National Meeting (2016)

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