Bioaugmenting the poplar rhizosphere to enhance treatment of 1,4-dioxane

1,4-Dioxane is a highly mobile and persistent groundwater pollutant that often forms large dilute plumes. Because of this, utilizing aggressive pump-and-treat and ex-situ technologies such as advanced oxidation can be prohibitively expensive. In this study, we bioaugmented the poplar rhizosphere with dioxane-degrading bacteria Mycobacterium dioxanotrophicus PH-06 or Pseudonocardia dioxanivorans CB1190 to enhance treatment of 1,4-elioxane in bench-scale experiments. All treatments tested removed 10 mg/L dioxane to near health advisory levels (<4 mu g/L). However, PH-06-bioaugmented poplar significantly outperformed all other treatments, reaching <4 mu g/L in only 13 days. Growth curve experiments confirmed that PH-06 could not utilize root extract as an auxiliary carbon source for growth. Despite this limitation, our findings suggest that PH-06 is a strong bioaugmentalion candidate to enhance the treatment of dioxane by phytoremediation. In addition, we confirmed that CB1190 could utilize both 1.4-dioxane and root extract as substrates. Finally, we demonstrated the large-scale production of these two strains for use in the field. Overall, this study shows that combining phytoremediation and bioaugmentation is an attractive strategy to treat dioxane-contaminated groundwater to low risk-based concentrations (similar to 1 mu g/L). (C) 2020 Elsevier B.V. All rights reserved.