This study explores the efficacy of two advanced oxidation processes for generation of hydroxyl radicals to promote degradation of emerging contaminants. Drought and water shortage have become pressing issues caused by our world’s changing climate. Water reclamation and reuse are increasingly important options for relieving this water stress. Water reuse runs the risk of reintroducing recalcitrant compounds that can accumulate in our bodies and environment. Advanced treatment methods that degrade these compounds are vital to protect our health and the health of the environment while providing necessary water resources. Advanced oxidation processes (AOPs) have shown great promise for removing recalcitrant compounds through the production of highly reactive hydroxyl radicals (·OH). This study investigated two AOPs for their production of ·OH as indicated by the probe compound pCBA. One of the AOPs examined was a proprietary device that utilizes ambient air and UV to generate singlet oxygen, which subsequently produces ·OH in water. The other is a more common method that combines UV and ozone (O3) to produce ·OH. The proprietary method was not found to produce notable hydroxyl radicals compared to the UV/O3 AOP. The UV dose of the UV/O3 AOP was also altered to analyze the impact on hydroxyl radical production and removal of a representative emerging contaminant, diclofenac (DCF). The sleeves made to alter the UV dose were not found to change the UV dose enough to show a consequential difference in degradation for the fluence indicator atrazine (ATZ) or the emerging contaminant DCF. Further testing with thicker sleeves would be important to determine the necessary amounts of UV and reasonably scale this technology for a water treatment facility.

No description available.

With increasing global population comes an increase in the need to safe and clean drinking water. Contaminants can arise in drinking water either naturally, or by the interaction of disinfection chemicals with naturally occurring materials, or simply due to by-products of the disinfection mechanism itself. Due to the oxidative nature of our disinfection treatments, these species are in highly oxidized states, and in some cases require chemical reduction to become less harmful. The present work demonstrates the capabilities of aqueous phase corona plasma in reductive treatment of oxidized contaminants found in drinking water. This study focuses on the treatment of the nitrate ion, bromate ion, chlorate ion and monobromoacetic acid, all of which can be found in typical drinking water systems. The second and third chapters within this thesis establish the optimal water matrix conditions for the treatment of bromate, chlorate and nitrate. These experiments investigate the influence of pH, temperature, presence and types of oxidative scavengers, dissolved gases and by-products that are made by this treatment process with these compounds. The main conclusion of these works is that aqueous phase corona discharge is capable of producing chemical compounds with sufficient energy to chemically reduce the nitrate, bromate and chlorate anions. Acidic conditions, under low dissolved oxygen scenarios facilitated the highest amount of reduction of the target contaminants, as well as having the presence of oxidative species scavengers. It was also observed that the anoxic environment could be obtained by introducing alcohols into the contaminated solution which generated sufficient cavitation and bubbling to strip the oxygen from solution. Through a comparison of various carbonaceous compounds as oxidative species scavengers, it was determined that the volatile alcohols provided a better performance than other soluble carbon sources, due to the decrease in dissolved oxygen. The fourth chapter considers different methods of introducing argon, oxygen and nitrogen into the test solution for the effect they would have on the treatment of solutions containing the bromate anion or monobromoacetic acid. The optimal pH for the treatment of monobromoacetic acid was also established, where again the acidic conditions prevailed. Tests were conducted to consider the effect of having the solution pre-saturated with the test gas, continually sparged, or with the gas passing through a hollow discharge electrode. The tests in which gas was blown through the discharge electrode greatly surpassed all other treatment regimes, where nitrogen provided the best removal for both contaminants under acidic conditions for bromate and under acidic and basic conditions for monobromoacetic acid. The fifth chapter provides conclusions for the overall thesis and recommendations for future work. / Thesis / Doctor of Philosophy (PhD)

The Department of Defense (DoD) has numerous sites that contain groundwater contaminated with 2,4,6-trinitrotoluene (TNT). The currently applied technologies for treating TNT contaminated waters are carbon adsorption and chemical oxidation. Carbon adsorption is a non-destructive technology, which could create future liability issues and is inefficient at relatively low TNT concentrations. On the other hand, application of chemical oxidation for the treatment of TNT contaminated water generates trinitrobenzene (TNB), a by-product of the incomplete oxidation of TNT. TNB is regulated as strictly as TNT. Additionally, over 70% of the reactor required treatment time for meeting target levels is due solely for TNB removal. This study evaluated the potential integration of zero-valent metallic species and advanced oxidation for the treatment of waters contaminated with TNT. The idea was to reduce treatment time, and thus, operational costs, when advanced oxidation is used as a stand-alone treatment technology by reducing TNT prior to oxidation. The use of zero-valent metals as the first treatment step transformed TNT into reduced organic compounds which were easily oxidized. The effectiveness of zinc, iron, nickel, copper, and tin as TNT reducing agents was evaluated. Zinc and iron were selected for further study based on their performance degrading TNT. Then, the reduction mechanism (pathway) and associated by-products of TNT reduction using zinc were examined using a zinc specimen manufactured by Sigma Corporation. Three amines were identified during reduction : 2-amino-4,6-dinitrotoluene, 4-amino-2,6-dinitrotoluene, and 2,4-diamino-toluene. Other intermediates were observed but not identified. Many of these reduction by-products adsorbed strongly onto the metal surface, significantly reducing the rate of TNT degradation during aging experiments. The aging of the metallic species was modeled using a power decay law parameter with the rate expression for TNT degradation. Corrosion promoters such as KCl addition, ozonation, and peroxone were evaluated as alternatives to reactivate zinc and iron to achieve steady TNT degradation. The addition of KCl performed significantly better than ozonation and peroxone. Furthermore, addition of KCl during the reduction step using iron or zinc generated organics that were successfully mineralized by ozonation or peroxone.

No description available.

No description available.

No description available.

No description available.

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

Heterogeneous photocatalysis is an advanced oxidation technology widely applied in environmental remediation processes. It is a relatively safe and affordable technology with a low impact on the environment and has found applications in a number of fields from chemical engineering, construction and microbiology to medicine. It is not catalysis in the real sense of the word as the photons which initiate the desired photocatalytic reaction are consumed in the process. The cost of these photons is by far the limiting economic factor in its application. From a technical standpoint, the inefficient use of the aforementioned photons during the photocatalytic reaction is responsible for the limited adoption of its application in industry. This inefficiency is characterised by low quantum yields or photonic efficiencies during its application. The mechanism of the technique of controlled periodic illumination which was previously proposed as a way of enhancing the low photonic efficiency of TiO2 photocatalysis has been investigated using a novel controlled experimental approach; the results showed no advantage of periodic illumination over continuous illumination at equivalent photon flux. When the technique of controlled periodic illumination is applied in a photocatalytic reaction where attraction between substrate molecules and catalyst surface is maximum and photo-oxidation by surface-trapped holes, {TiIVOH•}+ ads is predominant, photonic efficiency is significantly improved. For immobilized reactors which usually have a lower illuminated surface area per unit volume compared to suspended catalyst and mass transfer limitations, the photonic efficiency is even lower. A novel photocatalytic impeller reactor was designed to investigate photonic efficiency in gas–solid photocatalysis of aromatic volatile organic compounds. The results indicate photonic efficiency is a function of mass transfer and catalyst deactivation rate. The development of future reactors which can optimise the use of photons and maximize photonic efficiency is important for the widespread adoption of heterogeneous photocatalysis by industry.