"Tris-2-chlorethyl phosphate (TCEP) is a flame retardant and plasticizer that has been detected in drinking water sources and wastewater effluents in many countries. TCEP has been proven to be a recalcitrant compound that is also toxic and carcinogenic. The incomplete removal of TCEP in water and wastewater treatment plants necessitates that treatment processes be identified or developed that will completely remove TCEP from waters. Ozonation has been successfully used as an oxidant to degrade many problematic contaminants in water and wastewater. This research examined the effectiveness of ozone and ozone/hydrogen peroxide oxidation for removing TCEP from water. In laboratory experiments, batch reactions of TCEP solutions were conducted in purified water at different pH conditions and O3:H2O2:TCEP doses. The samples were tested at O3:TCEP molar ratios of 6:1, 15:1, and 30:1 and with O3:H2O2:TCEP molar ratios of 6:4.2:1, 15:10.5:1and to 30:21:1 respectively. Solution pHs of 4, 7, and 9 were investigated to cover the typical water and wastewater pH range. The Indigo Method was used to measure the starting ozone concentrations in sample water. TCEP concentrations were quantified by liquid-liquid extraction followed by gas chromatography (GC). Greater than 90% reduction of TCEP was achieved at equilibrium conditions with an O3:H2O2:TCEP molar ratio of 30:21:1 at all pH levels examined. Greater than 80% TCEP removal in diluted wastewater was observed at purified water to wastewater dilution of 4:1. The kinetics of oxidation of TCEP with ozone and ozone/hydrogen peroxide were explored in this research. It was found that the reaction rate constants of TCEP are lower than those of other contaminants typically found in water and wastewater. "

Organic wastes like sewage sludge and dairy manure were subjected to microwave enhanced advanced oxidation process ( MW/H₂0₂-AOP). The MW/H₂O₂-AOP was developed to release nutrients like phosphorus and nitrogen in the soluble form from the organic waste; these nutrients could be further recovered and reused. In the past, this process has been successfully applied to a series of organic waste for the purpose of solubilizing nutrients. The objectives of this research were to: (1) improve the MW/H₂0₂-AOP in terms of nutrient release by determining the different factors that influence the treatment, (2) define the factors affecting the process in their order of significance and (3) check the efficacy of the process on various waste. In the MW/H₂0₂-AOP, the role of mixing was verified, using municipal sewage sludge (aerobic and anaerobic). It was speculated that mixing the samples during the process would facilitate uniform heating and thus promote more nutrient release. At a microwave temperature of 80 °C, heating time of 5 minutes and hydrogen peroxide dosage of 1 mL per 1% of total solids, the results showed that mixed samples gave a higher nutrient solubilization compared to the unmixed. Subsequently, mixing and solids concentration were incorporated in a screening design with the other proven important factors viz., microwave temperature and hydrogen peroxide dosage. The results showed that microwave temperature and hydrogen peroxide dosage were the most significant factors for the release of orthophosphate, ammonia and soluble chemical oxygen demand. Preliminary experiments treating anaerobic sludge using MW/H₂O₂-AOP showed a decrease in orthophosphate concentration below the initial untreated value while for ammonia and volatile fatty acids the concentrations remained same as the initial. In this case, the set microwave temperature was 80 °C with 5 minutes heating and hydrogen peroxide dosage of 1 mL per 1% total solids at pH 7. To investigate this behavior, anaerobic sludge was treated at two pH conditions (7.8 and 4) at microwave temperatures ranging from 80 to 160 °C with hydrogen peroxide dosage of lmL per 1% total solids for 5 minutes. The results showed that acid addition helped in the destruction of sludge solids and release of nutrients. TheMW/H₂0₂-AOP was used to treat separated solid dairy manure. Solid dairy manure with total solids 1.6% was subjected to microwave temperature of 120 °C for 10 minutes with a hydrogen peroxide dosage of 2 mL per 1% total solids at three pH conditions (3.5, 7.3 and 12). Only at pH 3.5, substantial quantity of orthophosphate, ammonia, soluble chemical oxygen demands and volatile fatty acids could be released. Further, a screening experiment was designed including microwave temperature, hydrogen peroxide dosage and heating time, to determine the factors most affecting nutrient solubilization from solid dairy manure. Hydrogen peroxide dosage and temperature were important factors in orthophosphate release while microwave temperature and heating time were important in the release of ammonia and volatile fatty acids. The results clearly define the efficacy of the MW/H₂0₂-AOP on various organic waste as well as the conditions under which the treatment can be optimized.

Organic wastes like sewage sludge and dairy manure were subjected to microwave enhanced advanced oxidation process ( MW/H₂0₂-AOP). The MW/H₂O₂-AOP was developed to release nutrients like phosphorus and nitrogen in the soluble form from the organic waste; these nutrients could be further recovered and reused. In the past, this process has been successfully applied to a series of organic waste for the purpose of solubilizing nutrients. The objectives of this research were to: (1) improve the MW/H₂0₂-AOP in terms of nutrient release by determining the different factors that influence the treatment, (2) define the factors affecting the process in their order of significance and (3) check the efficacy of the process on various waste. In the MW/H₂0₂-AOP, the role of mixing was verified, using municipal sewage sludge (aerobic and anaerobic). It was speculated that mixing the samples during the process would facilitate uniform heating and thus promote more nutrient release. At a microwave temperature of 80 °C, heating time of 5 minutes and hydrogen peroxide dosage of 1 mL per 1% of total solids, the results showed that mixed samples gave a higher nutrient solubilization compared to the unmixed. Subsequently, mixing and solids concentration were incorporated in a screening design with the other proven important factors viz., microwave temperature and hydrogen peroxide dosage. The results showed that microwave temperature and hydrogen peroxide dosage were the most significant factors for the release of orthophosphate, ammonia and soluble chemical oxygen demand. Preliminary experiments treating anaerobic sludge using MW/H₂O₂-AOP showed a decrease in orthophosphate concentration below the initial untreated value while for ammonia and volatile fatty acids the concentrations remained same as the initial. In this case, the set microwave temperature was 80 °C with 5 minutes heating and hydrogen peroxide dosage of 1 mL per 1% total solids at pH 7. To investigate this behavior, anaerobic sludge was treated at two pH conditions (7.8 and 4) at microwave temperatures ranging from 80 to 160 °C with hydrogen peroxide dosage of lmL per 1% total solids for 5 minutes. The results showed that acid addition helped in the destruction of sludge solids and release of nutrients. TheMW/H₂0₂-AOP was used to treat separated solid dairy manure. Solid dairy manure with total solids 1.6% was subjected to microwave temperature of 120 °C for 10 minutes with a hydrogen peroxide dosage of 2 mL per 1% total solids at three pH conditions (3.5, 7.3 and 12). Only at pH 3.5, substantial quantity of orthophosphate, ammonia, soluble chemical oxygen demands and volatile fatty acids could be released. Further, a screening experiment was designed including microwave temperature, hydrogen peroxide dosage and heating time, to determine the factors most affecting nutrient solubilization from solid dairy manure. Hydrogen peroxide dosage and temperature were important factors in orthophosphate release while microwave temperature and heating time were important in the release of ammonia and volatile fatty acids. The results clearly define the efficacy of the MW/H₂0₂-AOP on various organic waste as well as the conditions under which the treatment can be optimized.

Hazardous and recalcitrant pollutants in the environments have led to a great many environmental issues these days. Many researchers have focused on the approaches to treatment of these pollutants which contaminate environments such as soil, surface and groundwater. As an advanced oxidation processes (AOPs), sonolysis which is the oxidation technology involving the use of ultrasonic irradiation, has proven to be successful for the treatment and remediation of contaminated environments. In this thesis, hydrogen peroxide formation and formic acid degradation by ultrasonic irradiation of well-characterised solutions are described under various conditions in order to determinate reaction mechanism by which peroxide degradation and contaminant degradation occur. The effect of gas properties and frequency on hydrogen peroxide and formic acid degradation are examined. Experimental results obtained are analyzed in light of the reactions occurring. Successful mathematical modeling of the result s obtained confirms that, for the most part, hydrogen peroxide and formic degradation occur by free radical generation within bubbles with subsequent transfer of these radicals to the bubble-water interface where the majority of the degradation occurs. The effect of Fe(II) addition which can lead to Fenton reactions in the bulk solution are also investigated. Experimental and model results show that the heterogeneous reactions can enhance the degradation of formic acid in the presence of Fe(II). Oxidation of phenol by ultrasonic irradiation under a variety of initial conditions and solution environments is also described and validated by a simple kinetic model. The model developed will be useful for improving our understanding of free radicals behaviour and the interplay between free radical generation and contaminant degradation.

Organic wastes like sewage sludge and dairy manure were subjected to microwave enhanced advanced oxidation process ( MW/H₂0₂-AOP). The MW/H₂O₂-AOP was developed to release nutrients like phosphorus and nitrogen in the soluble form from the organic waste; these nutrients could be further recovered and reused. In the past, this process has been successfully applied to a series of organic waste for the purpose of solubilizing nutrients. The objectives of this research were to: (1) improve the MW/H₂0₂-AOP in terms of nutrient release by determining the different factors that influence the treatment, (2) define the factors affecting the process in their order of significance and (3) check the efficacy of the process on various waste. In the MW/H₂0₂-AOP, the role of mixing was verified, using municipal sewage sludge (aerobic and anaerobic). It was speculated that mixing the samples during the process would facilitate uniform heating and thus promote more nutrient release. At a microwave temperature of 80 °C, heating time of 5 minutes and hydrogen peroxide dosage of 1 mL per 1% of total solids, the results showed that mixed samples gave a higher nutrient solubilization compared to the unmixed. Subsequently, mixing and solids concentration were incorporated in a screening design with the other proven important factors viz., microwave temperature and hydrogen peroxide dosage. The results showed that microwave temperature and hydrogen peroxide dosage were the most significant factors for the release of orthophosphate, ammonia and soluble chemical oxygen demand. Preliminary experiments treating anaerobic sludge using MW/H₂O₂-AOP showed a decrease in orthophosphate concentration below the initial untreated value while for ammonia and volatile fatty acids the concentrations remained same as the initial. In this case, the set microwave temperature was 80 °C with 5 minutes heating and hydrogen peroxide dosage of 1 mL per 1% total solids at pH 7. To investigate this behavior, anaerobic sludge was treated at two pH conditions (7.8 and 4) at microwave temperatures ranging from 80 to 160 °C with hydrogen peroxide dosage of lmL per 1% total solids for 5 minutes. The results showed that acid addition helped in the destruction of sludge solids and release of nutrients. TheMW/H₂0₂-AOP was used to treat separated solid dairy manure. Solid dairy manure with total solids 1.6% was subjected to microwave temperature of 120 °C for 10 minutes with a hydrogen peroxide dosage of 2 mL per 1% total solids at three pH conditions (3.5, 7.3 and 12). Only at pH 3.5, substantial quantity of orthophosphate, ammonia, soluble chemical oxygen demands and volatile fatty acids could be released. Further, a screening experiment was designed including microwave temperature, hydrogen peroxide dosage and heating time, to determine the factors most affecting nutrient solubilization from solid dairy manure. Hydrogen peroxide dosage and temperature were important factors in orthophosphate release while microwave temperature and heating time were important in the release of ammonia and volatile fatty acids. The results clearly define the efficacy of the MW/H₂0₂-AOP on various organic waste as well as the conditions under which the treatment can be optimized. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

Titanium dioxide (TiO2) is an established photocatalyst utilized for the photo-oxidation of organics in wastewater. Aqueous suspensions of TiO2 require separation and re-suspension steps to be used on an industrial scale. A method of immobilizing TiO2 within the mesoporous structure of silica has been developed at the University of Alabama. The objective of this thesis was to design and evaluate a bench-scale, continuous, photocatalytic reactor utilizing these films. This was accomplished in two phases of work: (1) batch reactions and (2) continuous reactions. The batch reactor was a one-liter standard photochemical reactor from Ace Glass. The continuous photocatalytic reactor designed for this study consisted of nine 12-inch long, 6-mm ID quartz tubes aligned around the medium-pressure, ultra-violet lamp (UV) used in the batch reactor. The tubes were coated on the inside with a thin film of mesoporous silica impregnated with TiO2 and connected in series with 6-inch pieces of Masterflex tubing. Experimental conditions were as follows: 190 ppm solutions of 2,4-dichlorophenol (2,4-DCP), UV lamp, TiO2 in either 0.05 wt% suspensions (slurry) or thin films of mesoporous silica (film); and/or 750 ppm hydrogen peroxide (H2O2). In batch and continuous experiments the UV/H2O2 and the UV/TiO2 (slurry)/H2O2 systems were the most successful with respect to the oxidation of 2,4 ? DCP. The loss of 2,4 ? DCP in continuous UV/TiO2 (film) systems was not significantly different from continuous UV only systems. However, the continuous UV/TiO2 (film)/H2O2 system degraded more 2,4 ? DCP than the systems utilizing UV light alone. The continuous reactor developed in this study showed enhanced by-product degradation using UV/TiO2 (film)/H2O2 over the UV/H2O2 system.

During ferrochrome (FeCr) production, three types of generic chromium (Cr) containing wastes are generated, i.e. slag, bag filter dust (BFD) and venturi sludge. The loss of these Cr units contributes significantly to the loss in revenue for FeCr producers. In this study, the liberation of Cr units was investigated utilising two case study waste materials, i.e. BFD from a semi-closed submerged arc furnace (SAF) operating on acid slag and the ultrafine fraction of slag (UFS) originating from a smelter operating with both open and closed SAFs on acid slag. A detailed material characterisation was conducted for both case study materials, which included particle size distribution, chemical composition, chemical surface composition and crystalline content. Cr liberation was achieved utilising two methods, i.e. aqueous ozonation and the advanced oxidation method. Various advanced oxidation processes could be applied. However, the advanced oxidation processes considered in this study was the use of gaseous ozone (O3) in combination with hydrogen peroxide (H2O2). Controlling parameters such as the influence of pH, ozonation contact time, waste material solid loading, gaseous O3 concentration and temperature on Cr liberation were investigated for the aqueous ozonation process. The influence of pH, volume H2O2 added and the method of H2O2 addition were considered for the advanced oxidation process. Results indicated that with aqueous ozonation, limited Cr liberation could be achieved. The maximum Cr liberation achieved was only 4.2% for BFD by varying the process controlling parameters. The Cr liberation for UFS was significantly lower than that of the BFD. The difference in the results for the two waste materials was attributed to the difference in characteristics of the materials. The Cr content in BFD was mostly related to chromite and/or altered chromite particles, while the Cr content of the UFS was mostly related to FeCr particles. It is possible that the Cr(III) present in the chromite and/or partially altered chromite might be more susceptible to oxidation to Cr(VI) than the metallic Cr(0) present in the FeCr. During ozonation, aqueous O3 spontaneously decomposes to form hydroxyl (OH•) radicals, which are very strong oxidants in water. The above-mentioned Cr liberation observed was related to the formation of the OH• radicals during the spontaneous decomposition of aqueous O3. This was indicated especially by enhanced Cr liberation at higher pH values, which was attributed to the acceleration of the spontaneous decomposition to OH• radicals at higher pH levels. The advanced oxidation method gave significantly higher Cr liberation results for both case study materials considered, achieving Cr liberations of more than 21%. The advance oxidation processes improve normal oxidation methods. In this study, the H2O2 used in combination with O3 enhanced the formation of the OH• radicals that are responsible for the oxidation of Cr. The Cr liberation levels achieved are possibly not high enough to be feasible for industrial purposes. However, a further investigation of the advanced oxidation process could optimise the process to yield even higher Cr liberation. / MSc (Chemistry), North-West University, Potchefstroom Campus, 2014

During ferrochrome (FeCr) production, three types of generic chromium (Cr) containing wastes are generated, i.e. slag, bag filter dust (BFD) and venturi sludge. The loss of these Cr units contributes significantly to the loss in revenue for FeCr producers. In this study, the liberation of Cr units was investigated utilising two case study waste materials, i.e. BFD from a semi-closed submerged arc furnace (SAF) operating on acid slag and the ultrafine fraction of slag (UFS) originating from a smelter operating with both open and closed SAFs on acid slag. A detailed material characterisation was conducted for both case study materials, which included particle size distribution, chemical composition, chemical surface composition and crystalline content. Cr liberation was achieved utilising two methods, i.e. aqueous ozonation and the advanced oxidation method. Various advanced oxidation processes could be applied. However, the advanced oxidation processes considered in this study was the use of gaseous ozone (O3) in combination with hydrogen peroxide (H2O2). Controlling parameters such as the influence of pH, ozonation contact time, waste material solid loading, gaseous O3 concentration and temperature on Cr liberation were investigated for the aqueous ozonation process. The influence of pH, volume H2O2 added and the method of H2O2 addition were considered for the advanced oxidation process. Results indicated that with aqueous ozonation, limited Cr liberation could be achieved. The maximum Cr liberation achieved was only 4.2% for BFD by varying the process controlling parameters. The Cr liberation for UFS was significantly lower than that of the BFD. The difference in the results for the two waste materials was attributed to the difference in characteristics of the materials. The Cr content in BFD was mostly related to chromite and/or altered chromite particles, while the Cr content of the UFS was mostly related to FeCr particles. It is possible that the Cr(III) present in the chromite and/or partially altered chromite might be more susceptible to oxidation to Cr(VI) than the metallic Cr(0) present in the FeCr. During ozonation, aqueous O3 spontaneously decomposes to form hydroxyl (OH•) radicals, which are very strong oxidants in water. The above-mentioned Cr liberation observed was related to the formation of the OH• radicals during the spontaneous decomposition of aqueous O3. This was indicated especially by enhanced Cr liberation at higher pH values, which was attributed to the acceleration of the spontaneous decomposition to OH• radicals at higher pH levels. The advanced oxidation method gave significantly higher Cr liberation results for both case study materials considered, achieving Cr liberations of more than 21%. The advance oxidation processes improve normal oxidation methods. In this study, the H2O2 used in combination with O3 enhanced the formation of the OH• radicals that are responsible for the oxidation of Cr. The Cr liberation levels achieved are possibly not high enough to be feasible for industrial purposes. However, a further investigation of the advanced oxidation process could optimise the process to yield even higher Cr liberation. / MSc (Chemistry), North-West University, Potchefstroom Campus, 2014

Every year, new trace chemicals are detected in natural waters as well as treated wastewater effluents all over the world. Public health and environmental concerns have driven the development of new technologies to treat water and eliminate chemicals that may pose risk to humans and wildlife. This work presents a detailed statistical analysis on the removal of some of the most widely occurring chemicals of emerging concern in wastewater based on information available in the literature. Results show that existing water treatment processes only partially eliminate most of these contaminants. Advanced oxidation processes (AOPs) are some of the technologies that have shown the most promising results for the removal of recalcitrant organics in water. Hydrogen peroxide photolysis (UV/H₂O₂) and Fenton’s reaction are some examples of AOPs that use hydroxyl radicals to oxidize organics. The kinetics of UV/H₂O₂ and Fenton’s reaction were studied from the experimental and mathematical points of view. Comprehensive models with no adjustable parameters successfully accounted for radical initiation via photolysis of H₂O₂ or radical initiation via Fenton’s mechanism; reaction of organic targets such as p-cresol and nonylphenol with hydroxyl radicals; and recombination mechanisms, as well as changes in solution pH due to evolution of carbon dioxide because of target mineralization. The presence of radical scavengers was successfully handled by the models, suggesting that they can be generalized to the treatment of complex matrices. The UV/H₂O₂ model was also extended to solar catalyzed applications. Using an atmospheric solar irradiation model (SMART) and data from the Giovanni-NASA online database, ground-level solar spectral irradiance were obtained and used as model inputs. The kinetic model provided an excellent fit to experimental results obtained with p-cresol and fluorescein targets using no fitted parameters. The UV/H₂O₂ process was also studied in commercial flow-through UV reactors with monochromatic and polychromatic light sources. Organic targets of interest such as pcresol can be degraded effectively in these reactors at relatively low peroxide concentrations. Results with wastewater effluents suggest that these commercial reactors can be used for AOP tertiary treatment as a way to reduce dissolved organic matter and eliminate potential harmful chemicals present in the water.

Polyfluorinated compounds (PFCs) are a class of anthropogenic chemicals that have been found in groundwater and wastewater around the world. Perfluoroctane sulfonate (PFOS) and perfluoroctanoic acid (PFOA) are primarily used for industrial surfactants, and aqueous film forming foams (AFFFs). These PFCs and many of their constituents have been found to be carcinogenic to humans and other animals. A simple method for defluorination of these compounds is needed. Advanced oxidation of PFOS, PFHxS, and PFBS-k was carried out using activated sodium persulfate through ultrasonic irradiation with the following condition; [PFC] = 20 millimolar (mM), [Na2S2O8] = 25 mM, pH = 7, and 25°C. Fluoride concentrations were quantified by ion chromatography (IC). In laboratory experiments, batch reactions of PFBS solutions were conducted in purified water at different pH conditions and N2S¬2O8: PFBS molar ratios of 1:1, 2:1, 10:1, and 100:1 respectively. Solution pH was maintained at 7 using HNO3. Of the three compounds, PFHxS had the greatest defluorination (11%) after 120 minutes reaction time. However, PFBS-K had the greatest increase in defluorination (115%) between the control ultrasound (US) experiment and the combination experiment. When Na2S2O8 was increased, the defluorination ratio of PFBS decreased. This decrease was partly attributed to scavenging reactions between SO4¯• and S2O8²¯. These results show a synergism between ultrasonic irradiation and activated sodium persulfate as a form of advanced oxidation. Recommendations for further research into defluorination of PFOS and its constituents by ultrasonic degradation include: the use of high performance liquid chromatograph with accompanying mass spectrometry (HPLC/MS), the use of an ultrasonic probe with alternate frequencies, and the effects of surface tension on defluorination.