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  • Title: Sequential anaerobic and aerobic bioaugmentation for commingled groundwater contamination of trichloroethene and 1,4-dioxane.
    Author: Li F, Deng D, Zeng L, Abrams S, Li M.
    Journal: Sci Total Environ; 2021 Jun 20; 774():145118. PubMed ID: 33610989.
    Abstract:
    Chlorinated solvents, notably trichloroethene (TCE), and the cyclic ether stabilizer, 1,4-dioxane (dioxane), have been frequently detected commingling in contaminated aquifers. Here we developed a sequential anaerobic and aerobic treatment strategy effective to mitigate the co-contamination of TCE and dioxane, particularly when dioxane is present at ppb levels relevant to many impacted sites. After the primary anaerobic treatment by a halorespiring consortium SDC-9, TCE was effectively removed, though lingering less-chlorinated metabolites, vinyl chloride (VC) and cis-dichloroethene (cDCE). Subsequent aerobic bioaugmentation with Azoarcus sp. DD4, a cometabolic dioxane degrader, demonstrated the ability of DD4 to degrade dioxane at an initial concentration of 20 μg/L to below 0.4 μg/L and its dominance (~7%) in microcosms fed with propane. Even better, DD4 can also transform VC and cDCE in tandem, though cDCE and VC at relatively high concentrations (e.g., 1 mg/L) posed inhibition to propane assimilation and cell growth of DD4. Mutagenesis of DD4 revealed group-2 toluene monooxygenase and group-5 propane monooxygenase are responsible for cDCE and VC co-oxidation, respectively. Overall, we demonstrated the feasibility of a treatment train combining reductive dehalogenation and aerobic co-oxidation processes in tandem to not only effectively clean up prevalent co-contamination of TCE and dioxane at trace levels but also mitigate persistent products (e.g., cDCE and VC) when complete reductive dehalogenation of less-chlorinated ethenes occurs slowly in the field.
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