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Department of Civil and Environmental Engineering

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https://hdl.handle.net/10217/100369
These digital collections include theses, dissertations, Civil Engineering Reports and other publications, materials relating to conferences including "Hydrology Days," other faculty and student publications, and datasets from the Department of Civil and Environmental Engineering. Due to departmental name changes, materials from the following historical departments are also included here: Civil Engineering; Irrigation Engineering.

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Browsing Department of Civil and Environmental Engineering by Subject "1,4-dioxane"

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    Reactor design for electrochemical oxidation of the persistent organic pollutant 1,4-dioxane in groundwater
    (Colorado State University. Libraries, 2018) Cottrell, P. Maxine, author; Blotevogel, Jens, advisor; Sale, Tom C., advisor; Dandy, David, committee member
    The common industrial solvent stabilizer and wetting agent 1,4-dioxane (DX) is one of the most widely occurring organic groundwater contaminants in the United States today. It is a probable human carcinogen, highly mobile in groundwater, and resistant to anaerobic biodegradation. The ineffectiveness of conventional treatment approaches such as stripping and sorption to activated carbon results in a critical need of advanced technologies for the treatment of DX in groundwater. Previous studies have shown that electrochemical oxidation is able to fully mineralize 1,4-dioxane, but testing has thus far been limited to proof-of-principle bench-scale experiments. Consequently, this study addresses the design of a configurable mobile pilot-scale reactor that can be used to test electrochemical degradation performance under site-specific conditions and with different dimensionally stable electrode materials. The goal of this reactor design is to accommodate straightforward scale-up for field applications, and low cost of production so that ultimately multiple modular units can be deployed to operate in series or in parallel. Assessment of critical design parameters in a bench-scale reactor showed that DX degradation rates almost doubled when no inter-electrode solid media were used. No significant differences were observed between operating the reactor in continuous versus batch mode. An additional 57% degradation rate improvement was achieved when the batch reactor was operated with 30-minute polarity reversals as compared with constant polarity. Bench-scale reactor and initial pilot reactor tests with Ti/IrO2-Ta2O5 electrodes were run using a synthetic groundwater solution containing DX in NaCl electrolyte, revealing substantial effects of scale, while DX degradation kinetics were similar. Groundwater from a contaminated industrial site was then treated in the pilot reactor with an apparent anode surface area per order of magnitude DX removal (ASAAO) of 305 h*m2/m3 at an electric energy consumption per order of magnitude DX removal (EEO) of 152 kWh/m3, with relatively minor production of undesirable by-products. The contaminated site groundwater was also treated in a commercial bench-scale reactor with a Magnéli-phase titanium oxide anode, resulting in an ASAAO of 28 h*m2/m3 at an EEO of 176 kWh/m3, but with a high yield of carbon tetrachloride (CCl4) and chlorate (ClO3-), and minor formation of perchlorate (ClO4-). In comparison of the surface-area normalized rates of removal, the commercial reactor was faster than the pilot reactor, but it consumed more energy per order reduction and generated more undesirable reaction by-products, commonly referred to as disinfection by-products (DBPs). Future testing at contaminated field sites will reveal the efficacy of our newly designed reactor, and thus electrochemical treatment, for the remediation of groundwater contaminated with DX and other persistent organic pollutants.