Biodegradation of 1,4-dioxane has been successfully established in the laboratory; however, it is not often observed in contaminated environments. In addition to limitations caused by inadequate microbial communities, dissolved oxygen, and aquifer biogeochemistry, the inhibitory effects of co-contaminants might be responsible for hindering in situ 1,4-dioxane biodegradation. Equally importantly, many sites with 1,4-dioxane are currently or were previously treated for chlorinated compounds, thus resulting in the implementation of remedies that do not remove 1,4-dioxane, or may hinder 1,4-dioxane biodegradation. The objective of this project is to evaluate suspected limiting effects of co-contaminants and remedial technologies on 1,4-dioxane biodegradation.

1,4-Dioxane biodegradation will be investigated in the presence of chlorinated solvents or metals, which are known to co-exist with 1,4-dioxane at many contaminated Department of Defense sites. Differences in degradation kinetics (rates and affinity constants) will provide insights into potentially synergistic or competitive interactions between chlorinated solvents, metal ions, and 1,4-dioxane. The rates of metabolic and cometabolic 1,4-dioxane biodegradation in flow-through columns will be established and compared to those measured for planktonic cultures. Subsequently, 1,4-dioxane biodegradation will be determined under natural subsurface flow environments where various solvents, metals, dissolved natural organic matter, and minerals usually co-exist. Column studies will be expanded to evaluate the impact of co-contaminants and enhanced reductive dechlorination (ERD) treatment on 1,4-dioxane biodegradation in environmental samples. A subset of the column samples will be analyzed for changes in 1,4-dioxane biodegradation potential using biomarkers for the 16S rRNA, metal resistant genes (cop and chr), and genes related to 1,4-dioxane biodegradation (THFMO and sMMO). Changes in gene abundance and expression determined using quantitative polymerase chain reaction (qPCR) would indicate mechanisms of toxicity, inhibition, or regulation associated with exposure to the co-contaminants. In addition, a functional gene array (GeoChip 3.0) will be used to elucidate changes in microbial community structure and functional activity associated with exposures to chlorinated solvents and metals.

These results will help determine whether 1,4-dioxane biodegradation should be integrated into a remedial solution concurrently with or after ERD for chlorinated solvents, or as separate biobarriers for plume migration control. The identification of microbial cultures as well as biogeochemistry, which generate desirable enzymatic activity for 1,4-dioxane biodegradation in multiple organic compound-contaminated, metal-stressed environments, will be valuable for engineering professionals and researchers in designing appropriate strategies for successful bioremediation at 1,4-dioxane-contaminated sites. (Anticipated Project Completion - 2018)

Gedalanga, P.B., A. Madison, Y. Miao, T. Richards, R. Illes, J. Hatton, W.H. Diguiseppi, J. Wilson, and S. Mahendra. 2016. A Multiple Lines of Evidence Framework to Evaluate Intrinsic Biodegradation of 1,4-Dioxane. Remediation, 27(1):93-114.

Johnson, N. W., P. B. Gedalanga, L. Zhao, B. Gu, S. Mahendra. 2020. Cometabolic Biotransformation of 1,4-Dioxane in Mixtures with Hexavalent Chromium Using Attached and Planktonic Bacteria. Science of the Total Environment, 706:135734.

Liu, Y., N. W. Johnson, C. Liu, R. Chen, M. Zhong, Y. Dong, and S. Mahendra. 2019. Mechanisms of 1,4-Dioxane Biodegradation and Adsorption by Bio-zeolite in the Presence of Chlorinated Solvents: Experimental and Molecular Dynamics Simulation Studies. Environmental Science & Technology, 53(24):14538-14547. 

Miao, Y., N.W. Johnson, P.B. Gedalanga, D.T. Adamson, C.J. Newell, and S. Mahendra. 2019. Response and Recovery of Microbial Communities Subjected to Oxidative and Biological Treatments of 1,4-Dioxane and Co-contaminants. Water Research, 149(2):74-85.

Miao, Y., N. W. Johnson, T. Phan, K. N. Heck, P. B. Gedalanga, X. Zheng, D. T. Adamson, C. J. Newell, M. S. Wong, and S. Mahendra. 2020. Monitoring, Assessment, and Prediction of Microbial Shifts in Coupled Catalysis and Biodegradation of 1,4-Dioxane and Co-contaminants. Water Research, 173:115540.

Myers, M., N.W. Johnson, E. Zerecero-Marin, P. Pornwongthong, Y. Liu, P.B. Gedalanga, and S. Mahendra. 2018. Abiotic and Bioaugmented Granular Activated Carbon for the Treatment of 1,4-Dioxane-Contaminated Water. Environmental Pollution, 240(9):916-924. 

Pornwongthong, P., A. Mulchandani, P.B. Gedalanga, and S. Mahendra. 2014. Transition Metals and Organic Ligands Influence Biodegradation of 1,4-Dioxane. Applied Biochemistry and Biotechnology, 173(1):291-306.

Zhang, S., P.B. Gedalanga, and S. Mahendra. 2016. Biodegradation Kinetics of 1, 4-Dioxane in Chlorinated Solvent Mixtures. Environmental Science & Technology, 50(17):9599-9607.

Zhang, S., P.B. Gedalanga, and S. Mahendra. 2017. Advances in Bioremediation of 1,4-Dioxane-Contaminated Waters. Journal of Environmental Management, 204(2):765-774.

Zhao, L., X. Lu, A. Polasko, N.W. Johnson, Y. Miao, Z. Yang, S. Mahendra, and B. Gu. 2018. Co-contaminant Effects on 1,4-Dioxane Biodegradation in Packed Soil Column Flow-through Systems. Environmental Pollution, 243(A):573-581. 

Theses and Dissertations

Miao, Y. 2019. Microbial Ecology Insights into Natural and Engineered Biodegradation Processes for 1,4-Dioxane (PhD Thesis). University of California-Los Angeles.

Myers, M. 2016. 1,4-Dioxane Biodegradation using Bioaugmented Granular Activated Carbon (Master’s Thesis). University of California-Los Angeles.

Polasko, A.L. 2017. Sequential Anaerobic-Aerobic Biodegradation of Trichloroethylene and 1,4-Dioxane (Master’s Thesis). University of California-Los Angeles.

Pornwongthong, P. 2014. Stable Isotopic and Molecular Biological Tools to Validate Biodegradation of 1,4-Dioxane (PhD Thesis). University of California-Los Angeles.

Zhang, S. 2017. Biodegradation of 1,4-Dioxane in Co-contaminant Mixtures (PhD Thesis). University of California-Los Angeles.