Project Summary
The project addresses a common challenge in the remediation of groundwater contaminated with
chlorinated volatile organic compounds (CVOCs) and 1,4-dioxane. CVOCs include chlorinated solvents, such
as trichloroethylene (TCE) and 1,1,1-trichloroethane (1,1,1-TCA), and their degradation products. Many CVOCs
and 1,4-dioxane are known or potential human carcinogens and on the Substance Priority List (SPL) for
Superfund sites. CVOCs bioremediation under anaerobic conditions (i.e. reductive dechlorination) is well
established. However, bioremediation of mixtures of CVOCs and 1,4-dioxane is not yet feasible due to at least
the following three obstacles: 1) low biodegradability of 1,4-dioxane at environmentally relevant concentrations,
2) requirement for aerobic conditions for 1,4-dioxane metabolism but anaerobic conditions for most CVOCs
metabolism, and 3) inhibition of 1,4-dioxane biodegradation by CVOCs. This project proposes the following
combined remediation approach to address these challenges: first, an innovative macrocyclic material approach
to selectively adsorb CVOCs and promote the growth of dechlorinating biofilm on the material surface to
anaerobically biodegrade CVOCs. After the CVOCs treatment, another type of innovative macrocyclic material
as an effective and selective sorbent for 1,4-dioxane sustains biofilms consisting of a highly efficient culture to
aerobically metabolize 1,4-dioxane. The macrocyclic molecules, which comprise repeating cyclic oligomers with
unique geometry and internal chemistry, form specific host-guest complexes with only selected guest molecules
(i.e., 1,4-dioxane or CVOCs). A highly efficient 1,4-dioxane-metabolizing culture (previously established) is much
more effective at low, environmentally relevant concentrations compared to all others reported in literature. To
understand the mechanisms of how the novel sorbents enhance bioremediation and to demonstrate the
feasibility of the proposed remediation approach, the researchers will conduct the following work: 1)
Computational study, synthesis, and characterization of novel macrocyclic materials. Two sorbents, one that
selectively and reversibly adsorbs CVOCs and another that selectively adsorbs 1,4-dioxane will be optimized for
use in the bioremediation studies. 2) Mechanistic study of the highly efficient 1,4-dioxane-metabolizing culture.
Key microorganisms responsible for the high affinity to 1,4-dioxane in the mixed culture will be isolated and
investigated for their degradation intermediates, pathways, and kinetics. 3) Elucidation of interactions among
contaminants, microbial cultures, and the novel sorbents. To achieve this, completely mixed flow experiments
will be performed, and they will be coupled with mathematical modeling that incorporates phenomena of both
sorption and biodegradation in biofilms. 4) Proof-of-concept column studies for bioremediation of CVOCs and
1,4-dioxane mixtures. Two long-term column studies will be performed: ex situ treatment of 1,4-dioxane and in
situ bioremediation of CVOCs and 1,4-dioxane mixture in series. Performance objectives will be Maximum
Contaminant Levels for CVOCs and the Health Advisory Level for 1,4-dioxane (0.35 µg/L).
