Current/Recent Projects
Reactive membrane barriers for contaminant treatment and containment
Contamination of coastal/estuarine sediments with polychlorinated biphenyls (PCBs) is a pervasive problem. These contaminants often dominate the risk associated with polluted sediments and their persistence drives clean up goals. Because of their hydrophobic nature, PCBs strongly sorb to organic-rich sediments, making in situ remediation difficult because cleanup times are often dictated by the rate of contaminant release (i.e. bioavailabilty) rather than the maximum rate of transformation achievable. There is a need for an in situ technology that is capable of destroying sediment-associated PCBs while simultaneously protecting the overlying water column from  contaminant “leakage” and remobilization of contaminated-sediment. This collaborative research (with W. Arnold) is focused on developing a reactive biological/abiotic capping system that enriches and protects specific bacteria able to degrade sediment contaminants and prevents contaminant release to the overlying water. The innovation of the proposed system is that it is a combination of two techniques, bioremediation and containment. The outcome of the research is expected to be an in situ technology that will serve to both sequester and degrade PCBs in sediments.
This work is a joint effort with Prof. Edward Cussler (Chemical Engineering and Materials Science) and Prof. Bill Arnold (Civil Engineering).
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A natural niche for dehalorespirers
Given the extremely high cost associated with contaminated sediments in the United States, both in terms of human and ecological health and in terms of dollars, research on low-cost methods for sediment remediation is of critical importance. Although in situ bioremediation is promising, one major challenge that remains is how to effectively stimulate indigenous dehalorespirers (bacteria that physiologically respire halogenated compounds) in the presence of sorbed contaminants of limited bioavailability. The addition of alternative electron acceptors to contaminated sediment is able to successfully stimulate the growth of these organisms, encouraging the desorption and degradation of weathered contaminants. Nevertheless, the alternative electron acceptors used to date have also been toxic and/or bioaccumulative, precluding their use in the environment. Given the  recent evidence that large quantities of natural organochlorines exist in nature, it is plausible that a natural niche, and a natural non-toxic alternative electron acceptor exists for these dehalorespirers. This research is focused on testing the hypothesis that dehalorespirers are a natural component of uncontaminated ecosystems where their niche is the respiration of natural chlorinated organic compounds derived from humifying plant material. This research could facilitate the development of new remediation techniques designed to stimulate dehalorespirers with natural non-toxic alternative electron acceptors and will also provide important information regarding the global chlorine cycle.
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The treatment of estrogens and estrogen mimics in wastewater
Estrogen mimics are compounds that bind to receptor sites in humans or animals that would normally only bind natural hormones, such as estrogen. By doing so, they can have serious biological effects, especially in reproductive function and development. These compounds have been found in wastewater discharges throughout the world and in bleached Kraft pulp mill effluent; they are also present naturally in many vegetables, including corn and soybeans (so-called phytoestrogens). This collaborative (with M. Semmens and D. Swackhamer) and single-PI research is focused on determining how estrogens and estrogen mimics present in wastewater attenuate through various treatment processes and also whether these compounds are present in the effluents from plant- and animal-processing industries. Given the recent push in the United States towards increased production and use of biofuels, including soybean-derived biodiesel, this issue is particularly interesting and timely. This research should better prepare treatment plants to comply with possible future regulations and facilitate thoughtful wastewater treatment designs for new industrial facilities, such as biodiesel and bioethanol plants. Furthermore, this work should inform future toxicology studies regarding the actual ecological and human health impacts of industrial estrogen mimics by outlining expected environmental exposures.
This work is a joint effort with Prof. Deborah Swackhamer (Environmental Health Sciences and The Institute on the Environment) and Prof. Mike Semmens (Civil Engineering).
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PCB dechlorination
Polychlorinated biphenyls (PCBs) have been linked to developmental and  nervous system disorders and the induction of some cancers. These compounds also bioaccumulate and are biomagnified in the food chain, resulting in fish consumption advisories, restrictions on commercial fisheries, and ecological damage to affected areas. Our research has focused on identifying and characterizing the organsisms that dechlorinate PCBs so that appropriate sediment remediation technologies can be developed and implemented. These organisms have been found to be dehalorespirers and also seem to have rather specific dechlorination abilities. Current research is focused on isolating and further characterizing a PCB dechlorinator, investigating bioaugmentation with robust dechlorinating cultures, and exploring the complete anaerobic dechlorination of PCBs, which has previously been thought not to occur in nature.
Portions of this work are collaborative with Prof. Tim LaPara (Civil Engineering) and Prof. Mike Sadowsky (Soil Water and Climate and Microbiology).
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