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Doctor of Philosophy / Department of Diagnostic Medicine/Pathobiology / Deon van der Merwe / 1,4-Dioxane is a potentially carcinogenic solvent. It is a problematic groundwater contaminant because of its unique physical-chemical properties. It is found in a wide range of consumer products as a by-product contaminant. This research aimed to investigate contaminant properties and behavior of dioxane in the environment and also in the human body. The dioxane ability to decontamination by adsorption processes was evaluated with four adsorbents. The adsorption efficiencies of activated carbon (AC), metal oxide nanomaterials (TiO[subscript]2 and MgO), and diatomaceous earth (DE) were assessed in aqueous and vapor phases using infrared spectroscopy. AC showed the highest adsorptive capacity for dioxane at equilibrium in both phases. The rate and extent of dermal absorption are important in the analysis of risk from dermal exposure to dioxane. For this purpose, a new flow through diffusion system (FTDS) was developed by modifying a Bronaugh flow through diffusion cell with flow capacity in both the donor and receptor compartments and using attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) as the analytical technique. FTDS can provide ‘real time’ quantitative high-density permeation data over time and is characterized by the simplicity of its use and the low cost of test samples. The in vitro dermal absorption study of dioxane across human skin showed that the absorption parameters of dioxane were 1.16 ± 0.22 hr, 5.7 X 10[superscript]-4 ± (0.62) cm/hr, 0.286 ± 0.035 mg/cm2/hr, 4.8 X 10-5 (± 0.32) cm[superscript]2/hr, and 1.99 ± 0.086 mg for lag time, permeability, steady-state flux, diffusivity, and total amount absorbed over 8 hr, respectively. The study of the effect of the surfactant sodium lauryl sulphate and solvent systems water, ethanol, propylene glycol, and ethyl acetate on permeation profiles revealed that these solvents and surfactants increased the permeation of dioxane significantly. The FT-IR spectra of stratum corneum treated with solvents showed that there was broadening of the CH[subscript]2 asymmetric stretching vibration of the CH[subscript]2 peak near 2920 cm[superscript]-1 only in samples treated with ethanol. The lipid extract precipitates were detected and were mostly composed of the stratum corneum lipid part.

abstract: Widespread use of chlorinated solvents for commercial and industrial purposes makes co-occurring contamination by 1,1,1-trichloroethane (TCA), trichloroethene (TCE), and 1,4-dioxane (1,4-D) a serious problem for groundwater. TCE and TCA often are treated by reductive dechlorination, while 1,4-D resists reductive treatment. Aerobic bacteria are able to oxidize 1,4-D, but the biological oxidation of 1,4-D could be inhibited TCA, TCE, and their reductive transformation products. To overcome the challenges from co-occurring contamination, I propose a two-stage synergistic system. First, anaerobic reduction of the chlorinated hydrocarbons takes place in a H2-based hollow-fiber “X-film” (biofilm or catalyst-coated film) reactor (MXfR), where “X-film” can be a “bio-film” (MBfR) or an abiotic “palladium-film” (MPfR). Then, aerobic removal of 1,4-D and other organic compounds takes place in an O2-based MBfR. For the reductive part, I tested reductive bio-dechlorination of TCA and TCE simultaneously in an MBfR. I found that the community of anaerobic bacteria can rapidly reduce TCE to cis-dichloroethene (cis-DCE), but further reductions of cis-DCE to vinyl chloride (VC) and VC to ethene were inhibited by TCA. Also, it took months to grow a strong biofilm that could reduce TCA and TCE. Another problem with reductive dechlorination in the MBfR is that mono-chloroethane (MCA) was not reduced to ethane. In contrast, a film of palladium nano-particles (PdNPs), i.e., an MPfR, could the simultaneous reductions of TCA and TCE to mainly ethane, with only small amounts of intermediates: 1,1-dichloroethane (DCA) (~3% of total influent TCA and TCE) and MCA (~1%) in continuous operation. For aerobic oxidation, I enriched an ethanotrophic culture that could oxidize 1,4-D with ethane as the primary electron donor. An O2-based MBfR, inoculated with the enriched ethanotrophic culture, achieved over 99% 1,4-D removal with ethane as the primary electron donor in continuous operation. Finally, I evaluated two-stage treatment with a H2-based MPfR followed by an O2-MBfR. The two-stage system gave complete removal of TCA, TCE, and 1,4-D in continuous operation. / Dissertation/Thesis / Masters Thesis Civil, Environmental and Sustainable Engineering 2018

The presence of emerging contaminants (ECs) in water and wastewater systems has become a subject of significant concern worldwide. These emerging contaminants are complex organic molecules which potentially affect human health and environment. Conventional wastewater treatment plants are unable to completely remove these contaminants from water and therefore can discharge them into environment. The need to develop effective methods for ECs removal is essential. This study assess the potential of ozone based advanced oxidation processes (AOP) to oxidize number of emerging contaminants. Different combinations of ozone with hydrogen peroxide and sodium persulfate were tested. For this study 1-4, dioxane, perfluorinated compounds (PFCs), N,N-Diethyl-metatoluamide, and three pharmaceuticals sulfamethoxazole, trimethoprim and carbamazepine have been selected. The effect of different process parameters such as chemical dosages, ozone weight percent, ozone flow rates, etc. on destruction of ECs were examined. It was observed that 1, 4-dioxane were persistent to direct ozone reaction, however were easily oxidized by hydroxyl radical. However, ozonation was solely very effective (> 99 %) in removing pharmaceuticals such as sulfamethoxaole, trimethoprim and carbamazepine. It was not very efficient for the removal of perfluorinated compound and N,N-Diethylmeta-toluamide. The operational conditions were optimized for maximum removal of every compound and their influence on the degradation process is discussed. / Civil Engineering

Clean water is essential to life. Growth in world population, changing diets, and a warming climate are driving an increase in the demand for water. Better management of water resources will help prevent scarcity, but in order to fully meet the future demand for safe, clean drinking water, new water treatment technologies are needed. This dissertation investigates a technology which is not well understood; the combination of ozone and ultrasound as potentially an efficient technology. Since nearly all previously published studies of combined ozone/ultrasound utilized batch reactors, a continuous flow reactor was constructed for this research. 1,4-Dioxane, henceforth referred to as dioxane, was chosen to evaluate the effectiveness of the combined ozone/ultrasound process. Dioxane is commonly detected in surface and groundwater and is a suspected human carcinogen. A recalcitrant contaminant, it resists direct oxidation by chlorine, oxygen, ozone, and biological treatment. It is miscible in water and doesn't sorb readily to organic matter, so it spreads rapidly in groundwater contamination plumes. It also resists air stripping and filtration, including reverse osmosis. For these reasons, dioxane makes an excellent candidate to measure the effectiveness of advanced oxidation processes, such as combined ozone/ultrasound. The treatment of dioxane by advanced oxidation processes has been studied extensively in the past. However, only one study has been published using combined ozone/ultrasound, and it was done in a batch reactor operating at a high ultrasonic frequency. The reactor built for this study also permitted reactor pressurization effects to be studied in a manner that has not been reported before for the combined ozone/ultrasound process. In this study, the combination of ozone and ultrasound was found to cause synergistic removal of dioxane from drinking water; the removal achieved by the combination significantly exceeded the sum of the removal achieved by ozone and ultrasound separately. In fact, the combination of ozone and ultrasound was found to remove more than double the dioxane that would be removed by doing both treatment processes separately. Ultrasound (20 kHz) was ineffective in removing dioxane alone, achieving less than 20% removal. At 16 mg/L, ozone alone was found to achieve removal of up to 86% after a 16 minute treatment time, but appears sensitive to matrix effects, especially pH. When ultrasound was combined with just 1.2 mg/L of aqueous ozone, over 90% removal occurred after a 16 minute treatment. Removal of dioxane was found to be driven not by ozone itself, but by radicals, suggesting that the decomposition of ozone is responsible for the generation of radical species and subsequent removal of dioxane. Ultrasound was found to increase the decomposition of ozone and appeared to be driving increased mass transfer of ozone into the aqueous phase. Modest reactor pressure appears to aid dioxane removal, but further increases in pressure did not appear to further enhance removal. An empirical model was constructed using a form similar to the Chick & Watson model for disinfection. Given inputs of initial aqueous ozone concentration, initial dioxane concentration, treatment time, and ultrasonic power, the model is able to predict effluent concentrations of dioxane with a relative root mean squared error of less than 5%. Additionally, RCT and mass balance analyses were performed, and both analysis techniques suggested that the removal of dioxane is dependent on the consumption of aqueous ozone. Spiked drinking water is representative of water that has undergone conventional treatment but requires a polishing step, and the combined ozone/ultrasound has shown promise as a polishing technology. Owing to its recalcitrance, prevalence, and mobility, dioxane represents a real and challenging groundwater contaminant, and combined ozone/ultrasound has shown promise as a groundwater treatment option. Additionally, the process is capable of dioxane removal in a pH range of 4-10. This pH independence, coupled with its ability to degrade recalcitrant contaminants, suggests that combined ozone/ultrasound holds promise as an industrial wastewater treatment option, too. The removal achieved by both ozone and combined ozone/ultrasound was an order of magnitude greater than what has been reported in previously published reports. However, a comparison of cost effectiveness relative to other advanced oxidation processes remains an area for future study. Finally, the combined ozone/ultrasound process holds promise as a drinking water treatment option in remote areas, since it requires only electricity. As a promising technology for polishing water for reuse, treating contaminated groundwater, treating industrial wastewater, and potentially improving access to safe drinking water in remote areas, combined ozone/ultrasound could aid in meeting global water demand in the future. / Civil Engineering

Indirect potable reuse has been practiced with the potential to enhance sustainability of water resources if planned accordingly. Depending on the pretreatment implemented for potable reuse, emerging contaminants; such as pharmaceuticals, personal care products, industrial solvents, bacterial/viral pathogens, and disinfection byproducts, might be present in source water and difficult to remove via various water treatment technologies. Low molecular weight organic compounds are especially challenging to remove and may require treatment optimization. The overarching purpose of this study was to demonstrate the feasibility of a carbon-based advanced treatment train; including ozonation, biological activated carbon (BAC) filtration and granular activated carbon (GAC) adsorption to achieve water quality suitable for potable reuse and assess the impact of a range of operating conditions for emerging contaminant removal at pilot-scale. The results from this study showed that carbon-based treatment train is equally effective as more commonly used, and more costly, membrane-based treatment trains in terms of pathogen and disinfection byproduct removal. A multiple-barrier approach was implemented, with each treatment stage capable of removing total organic carbon (TOC). GAC was responsible for removal of most of the TOC and emerging contaminants and this removal depended on the number of bed volumes of water processed by GAC. Empty bed contact time was another factor that dictated the extent of TOC removal in the BAC and GAC units as the carbon media was exhausted. Among the emerging contaminants detected, sucralose, iohexol and acesulfame-k were present in the highest concentrations in the influent and were detected consistently in the GAC effluent, thus making them good indicators of treatment performance. Apart from organics removal, BAC played an important role in removal of nutrients, such as ammonia via nitrification. N-Nitrosodimethlyamine (NDMA) was formed in the treatment process by ozone, but was shown to be effectively removed by BAC. EBCT, temperature, ozone dose and presence of pre-oxidants, such as monochloramine, played an important role in determining the amount of NDMA removed. These factors can be further optimized to improve NDMA removal. Sodium bisulfite was used for dechlorinating monochloramine residual post ozone. Nitrification in the BAC was shown to be inhibited by excess of sodium bisulfite dose. Thus monochloramine residual needs to be dechlorinated with sodium bisulfite to help with NDMA degradation but at the same time the sodium bisulfite dose needs to be monitored to allow complete nitrification in the BAC. 1,4-dioxane, another contaminant of emerging concern, was monitored in the treatment process. Biodegradation of 1,4-dioxane was enhanced via addition of tetrahydrofuran as a growth substrate. Biodegradation of 1,4-dioxane can help reduce energy and capital costs associated with advanced oxidation processes that are currently used for 1,4-dioxane removal. Further, relying on biodegradation for the removal of 1,4-dioxane can help avoid the formation of disinfection byproducts associated with advanced oxidation processes such as ozone with peroxide or ultraviolet disinfection with peroxide. The results from this project can be useful for designing potable reuse treatment trains and provide a baseline for removal of organic carbon and emerging contaminants. The conventionally used reverse osmosis and ultrafiltration approach is useful for organics removal in areas where the rationale behind potable reuse is water scarcity. Operational difficulties encountered during this study can prove to be important as this treatment process is scaled up to treat a total of 120 MGD of water for managed aquifer recharge. Overall the lessons learnt from this study can give a better understanding of a carbon-based treatment and further the advancement of reuse projects that have drivers other than water scarcity. / Doctor of Philosophy / The increased growth in urban areas has been accompanied by an increase in potable water demand, leading to depletion of surface and groundwater. Further, the discharge of nutrients such as nitrogen and phosphorus into some of these water bodies can lead to algal blooms. Water reuse involves treating used water and discharging into either a surface or groundwater body. Water reuse has been sought after as a solution to prevent these nutrients being discharged into surface water and to provide a sustainable solution for depletion of water sources. Direct or indirect potable reuse can include a combination of advanced treatment methods such as membrane filtration using ultrafiltration and reverse osmosis, biological filtration, granular or powdered activated carbon adsorption and disinfection methods such as ozonation and ultraviolet disinfection. This study focused on Hampton Roads Sanitation District's managed aquifer recharge project 'sustainable water initiative for tomorrow' (SWIFT), two different advanced water treatment strategies, namely carbon-based and membrane-based were implemented on a pilot-scale (20,000 L/day). The driver for indirect potable reuse in this study was not related to water shortage but aimed at reducing the nutrients discharged into the Chesapeake Bay. Other reasons for implementing reuse included recharging the depleting groundwater levels, land subsidence, and preventing flooding and seawater intrusion near the coastal areas. Membrane-based treatments, such as reverse osmosis, have been well established and studied for potable reuse. The less frequently used carbon-based treatment, that includes used of activated carbon for adsorption and biodegradation of organics (not involving any membrane barrier), was shown to be cost-effective and provided equal protection as that of the membrane-based system in terms of removal of pathogens. Further, since there is no membrane involved in the carbon-based treatment the energy requirements are less than that of the membrane-based treatment and concentrated brine solution is not produced, which makes it favorable for potable reuse where water scarcity is not an issue. This carbon-based treatment which included ozonation and activated carbon filtration and adsorption was further monitored and optimized for removal of organic contaminants and disinfection byproducts. Emerging contaminants such as pharmaceuticals, industrial solvents and personal care products can be harmful to human health and water ecology even at low concentrations. These contaminants are often present in wastewater effluent and can enter drinking water sources if untreated. These emerging contaminants were shown to be effectively removed by ozonation and granular activated carbon adsorption. The formation of disinfection byproducts such as N-nitrosodimethylamine in the treatment process and its removal in the biological activated carbon filtration was also monitored. The impact of temperature, presence of pre-oxidants and design factors such as ozone dose and empty bed contact time affected the removal of all these contaminants. This study provided an understanding of implementing carbon-based treatment for managed aquifer recharge for optimizing removal of bulk organic carbon and emerging contaminants. The results from this study can be utilized for designing advanced water treatment systems and can prove to be a guideline for monitoring and removing emerging contaminants.