Submitted in fulfillment of the requirements of the Degree of Master of Technology: Chemistry, Durban University of Technology, 2014. / This project arose out the need for a simple method to analyse NOM on a routine basis. Water samples were obtained from the Vaal dam, which is one of the dams used by a hydroelectric power station. Analysis was preceded by separation of NOM into the humic and non-humic portions. The humic portion was separated into two fractions by employing a non-ionic resin (DAX-8) to separate humic acid from fulvic acid. High performance size exclusion chromatography (HPSEC), equipped with an Ultraviolet( UV) detector and an Evaporative Light Scattering (ELS) detector connected in series, was used to obtain molecular weight distribution information and the concentration levels of the two acids. Mixed standards of polyethylene oxide/glycol were employed to calibrate the selected column. Suwanee River humic acid standard was used as a certified reference material. The molecular weight distributions (MWDs) of the isolated fractions of humic and fulvic acids were determined with ELSD detection as weight-average (Mw), number-average (Mn) and polydispersity (ρ) of individual NOM fractions. The Mw/Mn ratio was found to be less than 1.5 in all the fractions, indicating that they have a low and narrow size fraction. An increase in Mn and Mw values, with increasing wavelength for all three humic substances (HS) examined was observed. The HS, isolated from the dam water, was found to be about the same molecular weight as the International Humic Acid Standard (IIHSS). For the fulvic acid standard, the molecular weight was estimated to be around 7500 Da. Characterization of NOM was done to assist in the identification of the species present in the water. FTIR-ATR was used to as a characterization tool to identify the functional groups in the structure of the humic and fulvic acid respectively present in the Vaal Dam. Analysis of the infrared (IR) spectra indicated that the humic acids of the Vaal dam have phenolic hydroxyl groups, hydroxyl groups, conjugated double bond of aromatic family (C=C), and free carboxyl groups. The isolation method has proved to be applicable and reliable for dam water samples and showed to successfully separate the humic substances from water and further separate the humic substances into its hydrophobic acids, namely, humic and fulvic acids. It can be concluded that the Eskom Vaal dam composes of humic substance which shows that the technique alone gives a very good indication of the characteristics of water. The HPSEC method used, equipped with UV and ELSD was able to identify the molecular weight range of NOM present in source water as it confirmed that the Eskom Vaal dam contains humic substances as humic acid and fulvic acid and these pose a health concern as they can form disinfectant byproducts in the course of water treatment with chemicals. FTIR characterization was successful as important functional groups were clearly assigned. Lastly, the use of the TOC and DOC values to calculate SUVA was also a good tool to indicate the organic content in water. It is recommended to use larger amounts of water must be processed to obtain useful quantities of the humic and fulvic acid fractions.

Due to the ever increasing concerns about pollutants and contaminants found in water, new treatment technologies have been developed. Ozonation is one of such technologies. It has been widely applied in the treatment of pollutants in water and wastewater treatment processes. Ozone has many applications such as oxidation of organic components, mineral matter, inactivation of viruses, cysts, bacteria, removal of trace pollutants like pesticides and solvents, and removal of tastes and odours. Ozone is the strongest conventional oxidant that can result in complete mineralisation of the organic pollutants to carbon dioxide and water. Because ozone is unstable, it is generally produced onsite in gas mixtures and is immediately introduced to water using gas/liquid type reactors (e.g. bubble columns). The ozone reactions are hence of the type gas liquid reactions, which are complex to model since they involve both chemical reactions, which occur in the liquid phase, and mass transfer from the gas to the liquid phase. This study focuses on two aspects: mass transfer and chemical reactions in multicomponent systems. The mass transfer parameters were determined by experiments under different conditions and the chemical reactions were studied using single component and multicomponent systems. Two models obtained from the literature were adapted to the systems used in this study. Mass transfer parameters in the semi-batch reactor were determined using oxygen and ozone at different flow rates in the presence and absence of t-butanol. t-Butanol is used as a radical scavenger in ozonation studies and it has been found to affect the gas-liquid mass transfer rates. An experimental study was carried out to investigate the effects of t-butanol concentrations on the physical properties of aqueous solutions, including surface tension and viscosity. It was found that t-butanol reduced both properties by 4% for surface tension and by a surprising 30% for viscosity. These reductions in the solution physical properties were correlated to enhancement in the mass transfer coefficient, kL. The mass transfer coefficient increased by about 60% for oxygen and by almost 50% for ozone. The hydrodynamic behaviour of the system used in this work was characterised by a homogeneous bubbling regime. It was also found that the gas holdup was significantly enhanced by the addition of t-butanol. Moreover, the addition of t-butanol was found to significantly reduce the size of gas bubbles, leading to enhancement in the volumetric mass transfer coefficient, kLa. The multicomponent ozonation was studied with two systems, slow reactions when alcohols were used and fast reactions when endocrine disrupting compounds were used. ii These experiments were simulated by mathematical models. The alcohols were selected depending on their volatilization at different initial concentrations and different gas flow rates. The degradation of n-propanol as a single compound was studied at the lowest flow rate of 200 mL/min. It was found that the degradation of n-propanol reached almost 60% within 4 hours. The degradation of the mixture was enhanced with an increase in the number of components in the mixture. It was found that the degradation of the mixture as three compounds reached almost 80% within four hours while the mixture as two compounds reached almost 70%. The effect of pH was studied and it was found that an increase in pH showed slight increase in the reaction. Fast reactions were also investigated by reacting endocrine disrupting chemicals with ozone. The ozone reactions with the endocrine disrupters were studied at different gas flow rates, initial concentrations, ozone concentrations and pH. The degradation of 17β-estradiol (E2) as a single compound was the fastest, reaching about 90% removal in almost 5 minutes. However estrone (E1) degradation was the lowest reaching about 70% removal at the same time. The degradation of mixtures of the endocrine disruptors was found to proceed to lower percentages than individual components under the same conditions. During the multicomponent ozonation of the endocrine disruptors, it was found that 17β-estradiol (E2) converted to estrone (E1) at the beginning of the reaction. A MATLAB code was developed to predict the ozone water reactions for single component and multicomponent systems. Two models were used to simulate the experimental results for single component and multicomponent systems. In the case of single component system, good simulation of both reactions (slow and fast) by model 1 was obtained. However, model 2 gave good agreement with experimental results only in the case of fast reactions. In addition, model 1 was applied for multicomponent reactions (both cases of slow and fast reaction). In the multicomponent reactions by model 1, good agreement with the experimental results was also obtained for both cases of slow and fast reactions.

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

M. Tech. (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology, 2016 / Natural organic matter if not removed from water used for electricity generation has dire consequences that affect the long term plant health. The main problem is that organic matter at higher temperature and pressure disintegrate into smaller organic acids and carbon dioxide. This causes the cycle water and steam to be acidic and this can result in corrosion of the plant. The raw water from the Komati (Arnot power station) and Usutu (Kriel power station) scheme were analysed to determine the organic profile and seasonal variation. There was a noticeable variation in the quality of the water with an increase in DOC during rainy season. The water was found to be containing hydrophobic as well as hydrophilic molecules that could be quantified with a liquid chromatography organic detector (LC-OCD). Current water treatment processes employed at the two stations, Arnot and Kriel, has demonstrated the capability of removing organics to just over 50 percent at the pre-treatment section. The water treatment plant includes demineralisation plant that was able to produce water that met Eskom’s target specifications of less than 250 ppb DOC values. Qualitative and quantitative analysis of the steam-condensate water was done by use of an ion chromatography method. The determined organic anions were found to be acetates, formats and lactates.

A study has been conducted for the qualitative and Quantitative analysis of chlorinated organic compounds in water. The study included the adaptation of Amberlite XAD macroreticular resin techniques for the concentration of municipal wastewater samples, followed by GC/MS analysis. A new analytical method was developed for the determination of volatile halogenated organics using liquid-liquid extraction and electron capture gas chromatography. And, a computer program was written which searches raw GC/MS computer files for halogen-containing organic compounds.

Graphitic carbon nitride (g-C3N4) heterojunction composites with the semiconducting metal oxides, CeO2, ZnO and TiO2 are prepared in situ by co-calcination of the precursor materials or by a solvothermal method. The structural, morphological and the optical properties of the prepared materials are studied using various microscopy and spectroscopy techniques. The synthesized composite materials, CeO2/g-C3N4, ZnO/g-C3N4 and TiO2/g-C3N4 are more efficient in the photocatalytic degradation of the water pollutants indigo carmine (IC) and atrazine than the pure metal oxide, g-C3N4, or their physical mixtures. The CeO2/g-C3N4 and ZnO/g-C3N4 composites also exhibit improved degradation efficiencies of atrazine as compared to the individual metal oxide or g-C3N4 materials. The improved photocatalytic activity of the composites are attributed to the effective electron-hole charge separation within composite heterojunction, resulting from the well matched energy levels of the metal oxide and g-C3N4. This strategy could be helpful for the synthesis of other metal oxide and g-C3N4 composites for photocatalytic applications.

The necessity of cost effective, environmentally friendly technology has become increasingly important to remediate persistent organic pollutants in the environment. The emerging greener ultrasound technology has the potential to serve the remediation industry. In this study, the use of low power, high frequency (HF) ultrasound (1.6 MHz, 145 W/L) has been shown to effectively remediate DDT (90% of 8 mg/L) in water and sand slurries. Addition of iron powder accelerated DDT degradation in the sand slurry under ultrasonication. The potential of HF ultrasound (1.6 MHz, 160 W/L) in degradation of the non-volatile, polar model compound methylene blue (MB) was studied in MB spiked demineralised water and wastewater. A 70 % of 0.4 mg/L of MB was degraded in demineralised water whereas only 54% of MB degraded in MB spiked wastewater. There was a decrease in MB degradation rate with an increase in MB concentration. High power, low frequency (LF) ultrasound (20 kHz, 932 W/L) was used to desorb 400 mg/L of DDT added to three different natural soil slurries at 5, 10, 15 and 20 wt. % each. Each soil slurry was prepared in 0.1% v/v SDS surfactant solution, soaked for 30 min. and heated for another 30 min. at 40 oC before sonication. For the neutral pH soil slurry with higher dissolved organic carbon, the desorption efficiency achieved was over 80% in 30 s sonication. Alkaline soil with higher surface area than neutral soil indicated 60% desorption efficiency while the acidic soil, with the highest surface area and a higher amount of non-soluble organic matter, yielded 30% desorption efficiency under similar desorption conditions. Coconut fibre, used to biosorb the desorbed DDT in the decanted solution, was found to have over 25 g/kg of biosorption capacity for DDT. The surfactant SDS and associated DDT were completely separated from decanted liquid of the desorbed slurry with alum using adsorptive micellar flocculation in 60 min. settling. Acidic pH and molar concentration ratio of Al3+/SDS = 0.5 was used to completely remove the DDT. Using 20 kHz, 1125 W/L of sonication in an 80 mL reactor with air saturated 50 mg/L DDT at 20oC, the DDT removal efficiency achieved was 80% in 20 min. With zero valent iron addition, DDT removal efficiency in 15 min. is 100% with 15 and 22 mg/L of initial DDT concentrations. The settled DDT slurrywas remediated using 20 kHz at 240 W/L achieving DDT removal efficiency of 87% in 15 min. Also LF ultrasound was found to be effective in remediating chloroform (8 mg/L in 60 min) from spiked demineralised water and contaminated groundwater in both batch (120 W/L) and flow cell (6000 W/L) modes. Modeling and simulation of the ultrasonic reactor under 20 kHz ultrasonication was performed for various shape reactors using commercially available software. For almost all reactors, the highest ultrasonic intensity was observed near the transducer???s vibrating area. It was found that the highest acoustic pressure distribution, which is critical to the performance of the reactor, occurred in the conical reactor and flow cell configuration. / Thesis (PhD)--University of South Australia, 2010

Durante la última década se han publicado un gran número de estudios de investigación sobre la ubicuidad de diferentes contaminantes orgánicos en todo tipo de matrices ambientales, principalmente en agua. Entre éstos, la presencia medioambiental de fármacos y en concreto de antibióticos ha sido investigada con especial interés, debido a sus altas tasas de consumo y elevada actividad biológica (promoción de resistencia bacteriana). A este deterioro de la calidad de los recursos hídricos se une además el problema de su escasez, sobre todo en las cuencas mediterráneas, de modo que la reutilización del agua se hace imprescindible. Sin embargo, la falta de eficacia de los sistemas convencionales de tratamiento de aguas residuales para eliminar estos contaminantes orgánicos pone de manifiesto su entrada continuada en las aguas superficiales receptoras mediante los efluentes de las depuradoras, y el riesgo que supondría esta reutilización. Así pues, queda patente la necesidad de disponer de información nueva y valiosa sobre la presencia medioambiental de las sulfamidas, familia de antibióticos de alto consumo y cuya presencia medioambiental tiene origen en un uso principalmente veterinario y agrícola, (sulfametazina, sulfadimetoxina), pero también humano (sulfametoxazol, sulfapiridina). Para ello, es necesario el desarrollo de diversas herramientas analíticas avanzadas que nos permitieran la determinación de esta familia de antibióticos en diferentes matrices de agua ambiental, así como en fango de depuradora y suelo agrícola. Con las diferentes metodologías analíticas se pretende evaluar la presencia y persistencia de estos antibióticos y de sus metabolitos mayoritarios en los diferentes ecosistemas acuáticos, evaluando la eficacia de las técnicas de tratamiento de aguas residuales convencionales aplicadas en la actualidad en diferentes EDARs, y también de varias alternativas como los bioreactores de membrana o los bioreactores de lecho fijo (MBR o FBBR, respectivamente). Asimismo, estudiando su biodegradabilidad y persistencia medioambiental, es posible conocer en mayor profundidad la naturaleza y comportamiento de estos compuestos. Considerando todo lo anterior, durante el desarrollo de esta Tesis nos hemos marcado como principal objetivo el desarrollo y aplicación de nuevas metodologías analíticas basadas en la cromatografía de líquidos acoplada a la espectrometría de masas para la determinación de sulfamidas y sus metabolitos acetilados en aguas (residuales, superficiales, subterráneas) y matrices sólidas (fangos de depuradora y suelos agrícolas). Durante el análisis de aguas residuales, se evaluó también la eliminación de estos compuestos durante el tratamiento en las diferentes depuradoras, comparando la eficacia de diferentes tipos de tratamiento y su impacto en las zonas de vertido, comprendiendo así el destino de estos antibióticos en todo el ciclo del agua. Posteriormente, estudiamos la biodegradabilidad de diferentes sulfamidas mediante el tratamiento con hongos en medio líquido y sólido, y se llevó a cabo la identificación de los productos de transformación derivados mediante cromatografía de líquidos de ultra-alta resolución-espectrometría de masas en tándem con un sistema híbrido cuadrupolo tiempo de vuelo (UHPLC-QqTOF-MS/MS). También realizamos un estudio de destino de las sulfamidas, evaluando la fotodegradación de algunas de ellas y sus metabolitos acetilados en diferentes matrices acuosas, considerando también la aparición e identificación de los productos de fototransformación que se generan durante su fotólisis mediante UHPLC-QqTOF-MS/MS. Por último, mencionar que con los datos de presencia medioambiental obtenidos se llevó a cabo la evaluación del impacto medioambiental de las sulfamidas detectadas en los diferentes tipos de agua estudiados, estimando los coeficientes de riesgo asociados siguiendo las directrices marcadas por la Agencia Europea del Medicamento (EMEA). / Sulfonamides (SAs) are one of the most widely used antibiotics in human and especially in animal husbandry. So far, concern regarding the environmental presence of sulfonamides and other species of antibiotics has focused mainly on the potential spread of antimicrobial resistance. However, their biological activity and high resistance to biodegradation may lead to long residence times in both water and soil matrices. Long-term ecological risks and unpredicted effects can result from unintentional exposure of different organisms and even human health could be negatively affected. In this context, this PhD thesis aimed to study the environmental occurrence of the most relevant sulfonamides in all types of waters, sewage sludge and agricultural soils. In order to fully understand the fate and effects of this family of antimicrobials in the environment, further research on their resiliance and biodegradability has been carried out. The need of developing new advanced analytical methodologies, fast, robust and with high sensitivity for the analysis of sulfonamides and their acetylated metabolites at environmental levels was the first and one of the main objectives of this PhD Thesis. These analytical methodologies were succesfully applied for the analysis of real samples in different monitoring studies in wastewater treatment plants, rivers and aquifers. Sulfonamides and their acetylated metabolites were ubiquitous in all the water samples studied, with levels ranging from the low pg L-1 to μg L-1 (mainly in wastewater influents, but also in some surface water samples from the Llobregat River). Maximum levels detected in sewage sludge were up to 139.2 ng g-1 (sulfamethazine). The last part of the PhD focused on the biodegradability and behaviour of the sulfonamides in the environment. The efficiency of conventional wastewater treatments, usually based on activated sludge (CAS), was evaluated and removal rates were estimated for the different sulfonamides studied. The ability of white rot fungi Trametes versicolor to degrade sulfamethazine was also studied, as well as the photodegration kynetics of sulfapyridine, sulfamethazine and their respective acetylated metabolites in wastewater effluents and HPLC water under simulated irradiation.

The Suwannee River natural organic matter (SRNOM) was fractionated by preparative size-exclusion chromatography (SEC) into seven molecular weight (MW) fractions. The SRNOM and its MW fractions were subsequently analyzed for their concentrations of acidic functional groups by direct titrations, average MWs and MW distributions by semi-analytical SEC, and charge-to-MW distributions by capillary electrophoresis. Carboxyl concentrations in the MW fractions were inversely proportional to their average MWs. Conversely, the phenolic concentrations, though smaller than the carboxyl concentrations, were proportional to average MWs. Hysteresisthe non-overlap between sequential forward and reverse titrationswas observed for the SRNOM and its MW fractions, where the reverse titrations predicted a greater concentration of carboxylic acid groups than the forward titration. Because hysteresis is thought to be caused by the base-catalyzed hydrolysis of esters, this suggests that ester groups in the SRNOM are distributed over all MWs. Data for direct titrations, MW distributions, and capillary electrophoresis were evaluated by a computational scheme that solves for the most probable distribution of acidic functional groups and charges on solutes in the SRNOM and the MW fractions as a function of pH. Depending on the MW ranges of the samples, solutes in the SRNOM and the MW fractions are predicted to have from one to a maximum of 25 carboxyl groups per solute. Most phenolic groups are predicted to be on solutes that have a minimum of two carboxyl groups. At low pH, all samples have high relative abundances of solutes with the lowest charges. The charges of solutes are predicted to increase with increasing pH due to the sequential ionization of acidic functional groups. Depending on the MW ranges of the samples, the maximum probable charges of solutes in the SRNOM and the fractions at high pH are -12 to -30. By knowing the most probable distribution of charge and abundances of acidic functional groups, researchers will make better estimates of thermodynamic parameters and models that describe equilibria between metals and natural organic matter in the environment.

Water pollution is a major concern in vast countries such as India and other developing nations. Several methods of water purification have been practiced since many decades, Semiconductor photocatalysis is a promising technique, for photodegradation of various hazardous chemicals that are encountered in waste waters. The great significance of this technique is that, it can degrade (detoxify) various complex organic chemicals, which has not been addressed by several other methods of purification. This unique advantage made this field of research to attract many investigators particularly in latter eighties and after. This thesis incorporates the studies on the various semiconductor photocatalysts that have been employed for the detoxification purposes. The fundamental principles involved in the photoelectrochemistry, reactions at the interface (solid - liquid or solid - gas) and photocatalytic reactions on fine particles are briefed. General nature and size quantization in semiconductor particles, photocatalytically active semiconductors, TiCh and ABO3 systems, chemical systems and modifications for solar energy conversions are brought out in the introduction chapter besides giving brief description about photocatalytic mineralization of water pollutants with mechanism involved, formation of reactive species and the factors influencing photomineralization reactions. Scope of the present work is given at the end of the first chapter. Second chapter deals with the materials used for the preparation of photocatalyst, preparative techniques, methods of analysis, instruments employed for the photodegradation experiments and a brief description of material characterization methods such as X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, differential thermal analysis, optical absorption spectro photometry, Electron paramagnetic resonance (EPR), and gas chromatograph - mass spectroscopy (GC - MS). Various preparative routes such as wet chemical and hydrothermal methods for obtaining TiO2 (both rutile and anatase forms), BaTiOs and SrTiO3 fine particles and the chemical analysis of their constituents have been described in brief. Third chapter presents the results of materials characterization. T1O2 (rutile and anatase), BaTiO3 and SrTiO3 have been characterized separately using various techniques. Different routes of obtaining the photocatalyst fine particles, heat treatment at various temperature ranges, experimental procedures and the results of characterization are brought out in this chapter. Fourth and fifth chapters present the details of degradation studies carried out on the photomineralization of chlorophenol, trichloroethylene and formaldehyde. Studies include photodegradation of the pollutants with different catalysts varying experimental conditions to check the effects of change in concentration of pollutants, oxidizer, pH, surface hydroxylation, etc. The most favorable conditions for the complete mineralization of the pollutants have been studied. In case of TiO2, anatase form has shown greater photoactivity when compared to rutile and complete mineralization of chlorophenols has been achieved at low pollutant concentrations, neutral pH, with H2O2 and UV illumination. Retarding effects of surface hydroxylation and the formation of peroxotitanium species during photodegradation have been presented. TCE and HCHO degradation with BaTiO3/SrTiO3 has been studied. Photocatalyst heat-treated at 1100°G-1300°C is found to be highly active in combination with H2O2 as electron scavenger. HCHO is not getting degraded to its completeness in aqueous conditions owing to the strong competition in surface adsorption posed by H2O molecules. Vapour-solid phase reaction however gave good results in the detoxification of HCHO via disproportionation. Summary and conclusions are given at the end of the thesis.