<p> Fenton's Reagent Oxidation can significantly enhance the COD removal efficiency of landfill leachate. The results presented in this thesis show that the maximum amount of COD that could be removed by Fenton's Reagent Oxidation was about 80% of the initial value. Such a maximum removal was achieved using reagent dosage of 300 mg/L of H₂O₂, 55.84 mg/L of Fe²⁺, and a pH of 3 at 25&deg;C. </p><p> A mechanistic model was developed based on the kinetic reactions. A coefficient &alpha;, representing the proportional constant between organic matter and COD was firstly introduced to this model. This model fit the data well. The modeling coefficients of &alpha;, [&middot;OH] and <i>k</i>₇ are 0.013mol <i>mg</i>^-1, 1.65&times;10^-9 <i> M</i> and 1.55&times;10^-9 <i>M</i>^-1<i>s</i>^-1, respectively. Hydroxyl radical concentration was calculated and the results confirm the pseudo steady state assumption. Response surface design and analysis results predicted that COD remaining can achieve the lowest value of 48 mg/L with the treatment conditions of a reaction time of 3.8 hours, a pH of 2.3, and a mass ratio of H₂O₂ to Fe²⁺ of 38 at 60&deg;C.</p>

<p> In this dissertation, as a monitoring technology for cyanotoxins, a multiwalled carbon nanotube (MWCNT)-based electrochemical biosensor was developed to determine microcystin-LR (MC-LR), a potent cyanobacterial toxin, in sources of drinking water supplies. The performance of the MWCNT array biosensor is evaluated using micro-Raman spectroscopy, X-ray photoelectron spectroscopy, cyclic voltammetry, optical microscopy, and Faradaic electrochemical impedance spectroscopy. A linear dependence of the electron-transfer resistance on the MC-LR concentration is observed in the range of 0.05 to 20 &micro;g L^-1, which enables cyanotoxin monitoring well below the World Health Organization provisional concentration limit of 1 &micro;g L^-1 for MC-LR in drinking water. </p><p> In addition to the development of monitoring tools for cyanotoxins, visible light-activated (VLA) TiO₂ and monodisperse TiO₂ were developed and evaluated for treatment of water contaminants of emerging concern. These materials were synthesized using modified sol-gel methods (i.e., wet chemistry-based methods) such as self-assembly-based and ionic strength-assisted techniques. For this study, first, VLA-sulfur-doped TiO₂ (S-TiO₂) nanocrystalline films were synthesized by a self-assembly-based sol-gel method using nonionic surfactant to control nanostructure and an inorganic sulfur source for decomposing MC-LR under visible light illumination. Second, the effects of solvent on the synthesis of VLA-S-TiO₂ films were scrutinized. Four different polar, protic solvents, isopropanol, 1-butanol, ethanol, and methanol, were chosen as the solvent in four titania sol-gel preparations. Third, monodisperse anatase titania nanoparticles with controllable sizes (typically 10-300 nm) were synthesized using an efficient and straightforward protocol via fine tuning of the ionic strength in the devised sol-gel methodology. Finally, noble metal Ag-decorated, monodisperse TiO₂ (TiO₂-Ag) aggregates were successfully synthesized by an ionic strength-assisted, simple sol-gel method and were used for the photocatalytic degradation of the pharmaceutical oxytetracycline (OTC) under both UV and visible light irradiation. With a self-assembly-based sol-gel method, nanostructured anatase S-TiO₂ with high surface area (> 100 m² g^-1) and porosity (> 30 %) was synthesized and the sample calcined at 350 ^oC demonstrated the highest visible light absorption and visible light-induced photocatalytic activity in the decomposition of MC-LR. The structural and morphological properties of S-TiO₂ could be also tailor-designed using different solvents in the sol-gel synthesis, while inducing negligible effects on the sulfur doping and the visible light activation of TiO₂. Thus, it can be concluded that the enhancement of photocatalytic activity of S-TiO₂ films can be achieved by judicious choice of the main solvent for the sol-gel method. With an ionic strength-assisted sol-gel method, monodisperse spherical anatase TiO₂ (10-300 nm in diameter) as well as monodisperse TiO₂-Ag aggregates with 350 nm of diameter were synthesized. For TiO₂-Ag, its visible light absorption increased due to the presence of Ag on the surface of monodisperse TiO₂, which resulted in the enhancement of the photocatalytic degradation of OTC under both UV-visible light and visible light irradiation compared to pure TiO₂. There was an optimal Ag content to obtain the highest photocatalytic degradation of OTC. These newly developed materials demonstrated the efficient decomposition of water contaminants of emerging concern, especially MC-LR and OTC, under UV-visible light and visible light illumination.</p>

<p> Nitrate (NO₃^-) loadings from stormwater runoff promote eutrophication in surface waters. Low Impact Development (LID) is a type of best management practice aimed at restoring the hydrologic function of watersheds and removing contaminants before they are discharged into ground and surface waters. Also known as rain gardens, a bioretention system is a LID technology that is capable of increasing infliltration, reducing runoff rates and removing pollutants. They can be planted with visually appealing vegetation, which plays a role in nutrient uptake. A modified bioretention system incorporates a submerged internal water storage zone (IWSZ) that includes an electron donor to support denitrification. Modified (or denitrifying) bioretention systems have been shown to be capable of converting NO₃^- in stormwater runoff to nitrogen gas through denitrification; however, design guidelines are lacking for these systems, particularly under Florida-specific hydrologic conditions. </p><p> The experimental portion of this research investigated the performance of denitrifying bioretention systems with varying IWSZ medium types, IWSZ depths, hydraulic loading rates and antecedent dry conditions (ADCs). Microcosm studies were performed to compare denitrification rates using wood chips, gravel, sand, and mixtures of wood chips with sand or gravel media. The microcosm study revealed that carbon-containing media, acclimated media and lower initial dissolved oxygen concentrations will enhance NO₃^- removal rates. The gravel-wood medium was observed to have high NO₃^- removal rates and low final dissolved organic carbon concentrations compared to the other media types. The gravel-wood medium was selected for subsequent storm event and tracer studies, which incorporated three completely submerged columns with varying depths. Even though the columns were operated under equivalent detention times, greater NO₃^- removal efficiencies were observed in the taller compared to the shorter columns. Tracer studies revealed this phenomenon was attributed to the improved hydraulic performance in the taller compared to shorter columns. In addition, greater NO₃^- removal efficiencies were observed with an increase in ADCs, where ADCs were positively correlated with dissolved organic carbon concentrations. </p><p> Data from the experimental portion of this study, additional hydraulic modeling development for the unsaturated layer and unsaturated layer data from other studies were combined to create nitrogen loading model for modified bioretention systems. The processes incorporated into the IWSZ model include denitrification, dispersion, organic media hydrolysis, oxygen inhibition, bio-available organic carbon limitation and Total Kjeldahl Nitrogen (TKN) leaching. For the hydraulic component, a unifying equation was developed to approximate unsaturated and saturated flow rates. The hydraulic modeling results indicate that during ADCs, greater storage capacities are available in taller compared to shorter IWSZs Data from another study was used to develop a pseudo-nitrification model for the unsaturated layer. A hypothetical case study was then conducted with SWMM-5 software to evaluate nitrogen loadings from various modified bioretention system designs that have equal IWSZ volumes. The results indicate that bioretention systems with taller IWSZs remove greater NO₃^- loadings, which was likely due to the greater hydraulic performance in the taller compared to shorter IWSZ designs. However, the systems with the shorter IWSZs removed greater TKN and total nitrogen loadings due to the larger unsaturated layer volumes in the shorter IWSZ designs.</p>

<p> Nitrogen and phosphorus are known to cause eutrophic conditions in lakes and rivers, resulting ultimately in deteriorating water quality in these natural systems. Nitrate poses a threat to the ecosystem and aquatic life, and also has an adverse impact on human health when present in water in large concentrations. Regulatory bodies such as the Federal EPA and state agencies are imposing increasingly stringent effluent standards on point sources to protect and preserve natural water bodies. Technologies using biological nutrient removal processes are being incorporated into the waste treatment scheme at most wastewater treatment plants in an attempt to limit nutrient discharge. The use of completely-submerged anoxic rotating biological contactors (RBCs) to remove NO₃-N is a relatively new concept, although RBCs have been used for removal of ammonia and biochemical oxygen demand (BOD) for some time. In this study, HDPE disks (10&rdquo; x 9&rdquo;) obtained from the Greater Peoria Sanitary District (GPSD) were used as RBC media and mounted on a shaft rotating at 1 rpm in two 20-liter enclosed reactors. At a flowrate of 45 liters per day, synthetic wastewater containing sodium citrate as the carbon source and nitrate as the electron acceptor was used as influent. The duration of each experiment was about 30 days, during which, overall nitrate removal and denitrification rate constants were estimated under different experimental conditions. Factors affecting startup growth were also identified. </p>

<p> Disinfection by-products (DBPs) form as Natural Organic Matter reacts with disinfectants used in water treatment. Several of the DBPs formed are known carcinogens and regulated by the EPA for drinking water. Arctic utility design requires piped systems to recirculate water to avoid excessive heat loss and subsequent freezing. Recirculating systems have the potential to retain water in the system for extended periods of time and in turn allow longer reaction times for chlorine decay and the formation of DBPs. The purpose of this study was to appropriately model the effect of chlorine decay and DBP formation for these unique cold regions' distribution systems based on water age and total organic carbon concentration. The model resulted in the average retention time being double for a continuously circulating system than for a standard system of equal size. The extended retention time correlated to lower chlorine residuals and a DBP formation up to 2.5 times the regulatory limit.</p>

<p> The world population of the 21st century is facing an increasingly challenging energy landscape and declining water quality and availability, further compounded by a rapidly expanding global population against the backdrop of climate change. To meet the challenges of the water-energy nexus in a sustainable manner, existing methods need to be advanced and new technologies developed. Osmotically-driven and ion-exchange membrane processes are two classes of emerging technologies that can offer cost-effective and environmentally sensible solutions to alleviate the pressure on our water and energy demands. The objective of this thesis is to advance forward osmosis (FO), pressure retarded osmosis (PRO), and reverse electrodialysis (RED) for the sustainable production of water and energy.</p><p> A main hindrance restricting the progress of osmotically-driven membrane processes, FO and PRO, is the absence of adequate membranes. This work demonstrates the fabrication of thin-film composite polyamide FO membranes that can attain high water flux and PRO membranes capable of achieving power density of 10 W/m², twice the benchmark of 5 W/m² for PRO with natural salinity gradients to be cost-effective. A membrane fabrication platform based on mechanistic understanding of the influence of membrane transport and structural parameters on process performance was developed. The morphology and microstructure of the porous support layer, and hydraulic permeability and salt selectivity of the polyamide active layer were specifically tailored by thoughtful control of the fabrication and modification conditions.</p><p> The Gibbs free energy from the mixing of river water with seawater can potentially be harnessed for clean and renewable energy production. This work analyzed the thermodynamics of PRO power generation and determined that energy efficiencies of up to &sim;91% can theoretically be attained. The intrinsic limitations and practical constraints in PRO were identified and discussed. Using a tenth of the annual global river water discharge of 37,000 km³ for PRO could potentially produce electricity for over half a billion people, ascertaining natural salinity gradients to be a sizeable renewable source that can contribute to diversifying our energy portfolio.</p><p> However, fouling of the membrane support layer can diminish the PRO productivity by detrimentally increasing the hydraulic resistance. Analysis of the water flux behavior and methodical characterization of the membrane properties shed light on the fouling mechanism and revealed the active-support layer interface to play a crucial role during fouling. A brief osmotic backwash was shown to be effective in cleaning the membrane and achieving substantial performance recovery.</p><p> Reverse electrodialysis (RED) is an ion-exchange membrane process that can also extract useful work from salinity gradients. This dissertation research examined the energy efficiency and power density of RED and identified a tradeoff relation between the two performance parameters. Energy efficiency of &sim;33-44% can be obtained with technologically-available membranes, but the low power densities of &lt; 1 W/m² is likely to be impede the realization of the process. To further advance RED as a salinity energy conversion method, ion-exchange membrane technology and stack design need to be advanced beyond their current limitations.</p><p> When analyzed with simulated existing state-of-the-art membranes, PRO exhibited greater energy efficiencies (54-56%) and significantly higher power densities (2.4-38 W/m²) than RED (18-38% and 0.77-1.2 W/m²). The drawback of RED is especially pronounced at large salinity gradients, where the high solution concentrations overwhelm the Donnan exclusion effect and detrimentally diminish the ion exchange membrane permselectivity. Additionally, the inherent different in driving force utilization (osmotic pressure difference for PRO and Nernst potential for RED) restricts RED from exploiting larger salinity gradients to enhance performance. Overall, PRO is found to be the more favorable membrane-based technology for accessing salinity energy.</p><p> This work presents pioneering advances for forward osmosis and pressure retarded osmosis membrane development. The fundamental studies of the osmotically-driven membrane processes and ion-exchange membrane processes yielded significant findings that enhanced our mechanistic and thermodynamic understanding of the technologies. The important insights can serve to inform the realization of the emerging membrane-based technologies for the sustainable production of water and energy. The implications of the thesis are potentially far-reaching and are anticipated to shape the discussion on FO, PRO, and RED.</p>

Electrokinetic remediation is an in-situ technique in which a direct current is applied across a water-saturated contaminated soil. As a result, metal ions are transported through the soil from the anode toward the cathode by electromigration, electroosmosis and diffusion. Electrokinetic remediation experiments were performed with Bentonite clay contaminated with Pb and/or Zn under a constant current. The clay bed was cylindrical with a diameter of 5 cm and a length of 15 cm. / The electroosmotic flowrate decreased with time due to a significant increase in the concentration of H+ ions in the bed. Without cathode rinsing the clay bed cracked and the voltage increased. Rinsing the cathode prevented cracking and decreased the voltage applied across the bed. The acid front generated at the anode advanced across the clay bed at a speed of approximately 1.4 mm/hr. When there was no rinsing, most of the metals precipitated in the cathode region. With rinsing, the metals which reached the cathode compartment were removed by the effluent at constant rates over four days. For clay contaminated with Zn, the rate of removal was 15 mg/hr; for clay contaminated with Pb, the rate of removal was 54 mg/hr. For clays with single contaminants and cathode rinsing, the energy consumption was approximately 1.3 x 106 kJ/m3 of clean soil for zinc removal and 1.8 x 106 kJ/m3 for lead removal. For clays contaminated with both metals, the rates of removal were 11 mg/hr for Zn and 26 mg/hr for Pb. After four days, 23% of Pb and 67% of Zn was removed. The efficiency of current utilization was 32% for removal of Zn alone and 40% for removal of Pb alone. For removal of mixed contaminants the efficiency was 40%. (Abstract shortened by UMI.)

In recent years the disposal and the treatment of mine waste has been increasingly causing concern to the mining industry. One of the biggest challenges today is acid mine drainage (AMD), which is associated in particular with sulfide bearing tailings. As a consequence of AMD, heavy metals and sulfates are released into the environment. / This project has studied the effect of lime-based treatments in the stabilization of two sulfide tailings, one waste predominately containing pyrite minerals and the second containing pyrrhotite minerals. Different proportions of pozzolans (fly ash and slag) were also added to the lime-tailings mixtures. The physical properties of the mixtures have been evaluated, using several tests such as strength (unconfined compressive strength), permeability and durability. The mineralogical changes in the treated wastes were also examined. The stabilization process and the treatment validity would not be complete without a chemical analysis of the treated waste; therefore a quantitative analysis was performed, including leaching and extraction tests for some elements (Zn, Mg, Ca, and Fe), and also sulfate measurement. The samples were tested after 1 and 28 days of curing time. (Abstract shortened by UMI.)

Several mitigation procedures have been proposed to limit the transfer of Hg and MeHg to aquatic organisms but most cannot be applied to large reservoirs such as those of northern Quebec for practical, economical, and environmental reasons. A better understanding of the diagenetic behaviour of Hg and methylmercury in aquatic environments has lead us to consider methods of enhancing natural processes which would either limit the mobility of Hg in flooded soils or its methylation. Different concentrations of iron oxide, iron shavings and ferrous ammonium sulphate were added to soil slurries in the presence or absence of calcite and gypsum. Mercury released to the supenatent solutions and methylmercury adsorbed to the slurry solids were monitored with time to determine the trapping efficiency of the different chemical additives under both reducing and oxygenated conditions. Whereas all three reagents limited the release of Hg(2+) to the supernatent solution when reducing conditions were allowed to develop in the slurries, ferrous ammonium sulphate appeared to be the most effective at limiting Hg methylation. (Abstract shortened by UMI.)

<p> Population pressures, land-use conversion and its resulting pollution consequences appear to be the major diffuse pollution problems of today. Research also indicates that the increase in imperviousness of land due to urbanization increases the volume, rate of stormwater runoff causing increased channel erosion and flooding downstream, water quality contamination, aquatic biota, and drinking water supplies. In the past, negative impacts were never seriously considered as urbanization increased, but the attitude of citizens and governments are changing and people now want to retain, restore or rehabilitate existing waterways, and manage future urban and rural development in order to improve environmental conditions. </p><p> Water quality management in the contributing watersheds is vital to the management of water quality in the main stem rivers. Hence, policy makers should decide which places should be considered for restoration projects based on priority analyses. To carry out these evaluations in Korea, mathematical models are needed to forecast the environmental results after applying watershed restoration measures. However, the scope of sophisticated watershed modeling is very complicated, expensive and time consuming, and not really required for planning level decision making. Therefore, simpler evaluation methods should be applied, that can adequately discern for planning purposes the changes in aquatic environmental quality that can be expected in different watersheds after adapting restoration or protective measures. </p><p> Thus, this research proposed to create a simple equation specifically for watershed planning. To create such a simple equation, three main tasks were undertaken. The tasks are as follows: (1) the creation of a selection program for available watershed models, (2) establish simple equations to be used instead of watershed models, and (3) verify the simple equations by comparing them with a physically based model (HSPF). </p><p> In regards to the first task mentioned above, this dissertation presents a review of thirty three watershed models available for watershed planning and shows that these watershed models can not easily be applied to large-scale planning projects that are being undertaken by South Korea like the Four River Restoration Project. One of the main reasons for their inapplicability is that they require vast amounts of data and significant application effort to be used in a prioritization project involving many watersheds (Roesner, personal commutation). In addition, it is vital to select an appropriate watershed model that are realistically models a watershed's conditions and more specifically, to match users' needs. However a selection program has not yet developed, as well. Therefore, eight factors were selected for task 1 to examine the specific characteristics of each of the 33 watershed models in great detail. </p><p> Based on the results of the 8 factors proposed, the selection program was developed to screen which will be most useful to a project. Based on these literature reviews of the 33 available watershed models but unrealistically complex models, it was determined that a simpler model utilizing accessible base data, such as land use type, is needed to evaluate and prioritize watersheds in the feasibility stage of a spatially large projectstudies for national based projects (i.e. National level). A correlation study between land use types and water quality parameters has been published (Tu, 2011, Mehaffey et al., 2005, Schoonover et al., 2005, etc.), however, the research examined the correlation between land usage and water quality in great detail, but did not address any correlations to implement real-based watersheds. </p><p> Therefore, Task 2 is the development of simple equstions, for this task, two important sub-tasks were undertaken 1) Hydrology (rainfall), geology (slope), and land usage data were analyzed to verify their relationships with the water quality (BOD, COD, T-N, T-P) in the watershed, and 2) Simple Equations were constructed based on Statistical Methods (Excel Solver, Statistical Analysis Systems) and Data Mining (Model Tree, Artificial Neural Network, and Radial Based Function) in order to prove their accuracy. Thus, if the equations are accurate, they can be used to prioritize basins within a watershed with respect to their impact on water quality in the mainstem river. </p><p> For the final task, task 3, Simple Equations were verified by comparing them with a physically based model, HSPF, based upon the real-based watersheds which are located in South Korea in order to prove the Simple Equations are capable of being a reliable alternative to physically based models. These simple equations could be used to allow management to identify and prioritize restoration and rehabilitation areas in a watershed even though sufficient data had yet been collected to satisfy the requirements of a physically based model. </p>