1,4-dioxane (dioxane), a probable human carcinogen, is a persistent and highly mobile groundwater pollutant. Because of this, dioxane plumes are often large and diffuse, which pose a challenge for remediation. To make matters worse, dioxane is commonly found comingled with various chlorinated solvents. Many states have issued health-based cleanup guidelines for dioxane, ranging from 1 µg L-1 in California, to 0.35 µg L-1 in Colorado, and to 0.25 µg L-1 in New Hampshire. Reaching these low cleanup guidelines through remediation has proven to be particularly difficult and costly. Utilizing aggressive pump-and-treat and ex-situ technologies such as advanced oxidation on dilute dioxane plumes is prohibitively expensive. Alternatively, phytoremediation using poplar trees has been proposed as a cost-effective clean-up strategy. However, questions remain if this technology can alone remediate dioxane, especially from deep groundwater plumes. Bioaugmentation of deeper plumes with dioxane-degrading microbes is one possibility. Another promising solution is to pump the contaminated water onto plantations of trees and to bioaugment the poplar rhizosphere with dioxane degrading bacteria to speed degradation. In prior laboratory studies, Pseudonocardia dioxanivorans CB1190 has been utilized as a pure culture bacterium to speed the biodegradation rate of 1,4-dioxane by hybrid poplar (Populus deltoides x nigra, DN34) via bioaugmentation. However, CB1190 has been shown to be ineffective at low dioxane concentrations (&lt;500 µg L-1) commonly encountered in the field, which also violate health advisory guidelines. In addition, chlorinated solvents have been shown to inhibit dioxane degradation by CB1190. Due to these shortcomings, there is a need to isolate novel bacteria better suited for bioaugmentation of hybrid poplar. In this research, we report the degradation rates of dioxane in simulated groundwater by CB1190 as well as novel bioaugmentation candidates. Furthermore, we report the ability of these bacteria to utilize root exudates as an auxiliary substrate to determine the relative potential for these bacteria to be effectively applied to bioaugment hybrid poplar at various sites contaminated with dioxane.

Bioaugmentation and phytoremediation of dioxane in simulated groundwater

2019 Spring National Meeting

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