Wednesday, February 28, 2018, 9:00AM - 10:00AM
Bridget A. Ulrich
Swiss Federal Institute of Aquatic Science and Technology (Eawag)
Delineating underlying removal processes for polar organic contaminants in aquatic systems: Case studies on stormwater and groundwater
Urbanization and water scarcity have caused growing concern for impaired water quality and exposure to organic contaminants, yet the fate of these contaminants in treatment systems and the environment remains poorly understood. In particular, organic compounds that contain polar functional groups (such as pesticides, flame retardants, and munitions compounds) are more water-soluble, making them more mobile in aquatic environments and difficult to treat. Two research efforts were undertaken to address this overarching problem, evaluating (1) the fate and transport of trace organic contaminants in stormwater biofilters, and (2) the isotope fractionation of energetic munitions compounds (i.e., explosives) that are relevant to groundwater remediation.
The objective of the first study was to develop an effective and affordable infiltration system for removal of polar organic contaminants from stormwater. It was hypothesized that contaminant attenuation could be improved by amending infiltration systems with (i) biochar (a highly porous and carbonaceous substance produced by thermal decomposition of biomass) to enhance sorption, and (ii) biodegradable organic carbon sources (e.g., compost and straw) to enhance biodegradation. Laboratory batch and column experiments indicated that biochar-enhanced contaminant retention could be predicted with a sorption-retarded transport model that accounts for intraparticle diffusion limitations. Further microcosm and column experiments evaluating the effects of biological activity revealed that co-amendment with compost enhanced contaminant attenuation by stimulating and sustaining microbial activity. The study concluded with vegetated column tests to assess performance under long-term, realistic operating conditions, revealing significantly improved contaminant removal in biofilters containing biochar.
The objective of the second study was to determine if the attenuation of 2,4-dinitroanisole (DNAN, a novel shock-insensitive alternative munitions compound to 2,4,6-trinitrotoluene, TNT) in contaminated groundwater could be assessed using compound specific stable isotope analysis (CSIA). It was hypothesized that CSIA could be used to delineate DNAN attenuation processes via characteristic isotope fractionation patterns (i.e., changes in elemental isotope ratios). Three of the most likely environmental DNAN degradation pathways were assessed in batch experiments: abiotic reduction, aerobic biodegradation, and alkaline hydrolysis. The results of this study revealed unique carbon and nitrogen isotope fractionation patterns among the three pathways, suggesting that CSIA could provide an important tool for future efforts to monitor and remediate DNAN-contaminated groundwater.
Dr. Bridget Ulrich joined the Department of Environmental Chemistry at Eawag (the Swiss Federal Institute of Aquatic Science and Technology) as a Postdoctoral Researcher in 2017, where her research is focused on developing and applying analytical methods for compound-specific isotope analysis of munitions compounds in groundwater. She obtained her PhD in Civil and Environmental Engineering from the Colorado School of Mines in 2016, where she completed her dissertation titled “Biochar-amended Biofilters for Removal of Trace Organic Contaminants from Stormwater.” Prior to her dissertation work she obtained Bachelor’s degrees in Chemical Engineering and Chemistry from the University of Minnesota Twin Cities (2010), and a Master’s degree in Chemical and Bioengineering from the Swiss Federal Institute of Technology Zurich (2012).
Free and open to the public.