Thesis (MTech (Chemistry))--Cape Peninsula University of Technology, 2018. / Trihalomethanes (THMs) are a group of four compounds that are formed, along with other disinfected by-products. This happens when chloride or other disinfectants are used to control microbial contamination in drinking water, which then reacts with natural organic or inorganic substances in water. Trihalomethanes are better known by their common names such as chloroform, bromodichloromethane, chlorodibromomethane and bromoform. These four compounds are known to be classified as cancer group B carcinogens (shown to cause cancer in laboratory animals). Trihalomethane levels tend to increase with pH, temperature, time and the level of “precursors" present. Precursors are known to be organic substances which react with chloride to form THMs. One significant way of reducing the amount of THMs in water is to eliminate or reduce chlorination before filtrations and reduce precursors. There are guideline limits for THMs in the SANS 241:2015 document, but they are not continuously monitored and their levels in natural water are not known. The aim of this study is to develop a rapid, fast and reliable liquid-liquid microextraction technique, to determine the presence of THMs in natural water sources. This study particularly focuses on different water sources e.g. river, underground, borehole and chlorinated water. Chlorinated water is the water that has been presumably treated for bacteria and fungus growth. The results that were obtained for chlorinated water are as follow, 10.120 μg/L − 11.654 μg/L for chloroform, 2.214 μg/L - 2.666 μg/L for bromodichloromethane, 0.819 μg/L − 0.895 μg/L chlorodibromomethane and 0.103 μg/L - 0.135 μg/L for bromoform from validation data. All these THMs concentrations have been found to be below the SANS 241:2015 limits. Natural water shows a very high affinity for chloroform. This is what is expected under normal conditions as chloroform is the most abundant THM of all THMs present in natural water. The liquid-liquid microextraction technique that was optimized and used for the determination of THMs in this study is a rapid, simple and inexpensive technique that provides low limits of detection (LOD) e.g. 0.1999 μg/L chlorodibromomethane and 0.2056 μg/L bromoform and wide dynamic range (LOQ) of 0.6664 μg/L chlorodibromomethane and 0.6854 μg/L bromoform for the determination of THMs.

Thesis (DTech (Environmental Health))--Cape Peninsula University of Technology, 2016. / Trihalomethanes are disinfection byproducts of chlorinated waters, and there is a growing interest to understand plant responses to organohalogens. This study investigates the effects of increasing trihalomethane dose on the physiology of tomato (Solanum lycopersicum) and determines whether the extent of physiological impacts of trihalomethane exposure on seedling radicle length, biomass accumulation, concentration levels of 12 key nutrients, oxidative stress, fatty acids and α-tocopherol content in membrane lipids of tomato correlated with either the number of bromine or chlorine atoms in the trihalomethane molecules. The 2 x 4 x 5 factorial experiment was laid out in CRD with four replications. Two cultivars of tomato were exposed to 4 levels of trihalomethanes (bromodichloromethane, bromoform, chloroform and dibromochloromethane) and 5 levels of concentration (0.0, 2.5, 5.0, 7.5, and 10.0 mg.L-1) in a green house. The decrease in seedling biomass and the inhibition of radicle growth increased with increasing trihalomethane concentrations in a dose dependent manner. Also, both these parameters decreased in response to an increase in the number of bromine atoms in the trihalomethane molecule. However, in growing plants the decrease in concentration levels of seven essential nutrients namely nitrogen (N), phosphorus (P), potassium (K), sulphur (S), copper (Cu), zinc (Zn) & boron (B) correlated to an increase in the number of chlorine atoms. Increase in trihalomethane dose also induced a decrease in all the above mentioned nutrients with the addition of manganese (Mn), although the decrease in P and S were not significant at P ≤ 0.05. The increase in trihalomethane dose induced an increase in oxidative stress parameters such as the total phenolic content, ferric reducing antioxidant power (FRAP), oxygen radical absorbance capacity (ORAC), ascorbate peroxidase (APX), guaiacol peroxidase (GPX) and lipid peroxidation. The increase in the above parameters correlated to an increase in the number of chlorine atoms, however, no such correlations were observed in superoxide dismutase (SOD) activity, general lipid peroxidation, α-tocopherol content and totalsoluble proteins. In plant membrane lipids, increase in the saturated fat hexadecanoic acid was observed in both tomato cultivars that correlated to the degree of chlorination in the trihalomethane molecule. The increase in α-linolenic acid stress signaling correlated with an increase in the degree of chlorination in only one tomato cultivar suggesting variable tolerance between cultivars to chemical action. Membrane lipids adjustments in tomato plants exposed to increasing trihalomethane dose were based on two factors; first the adjustments of membrane fluidity with the increase in plant sterols and fatty acids content and secondly, the increase in lipophyllic antioxidants such as phenols, quinones and α-tocopherol content. The phenolic lipophyllic antioxidant was tentatively identified to be 2,2’-methylenebis [6-(1,1-dimethylethyl)-4-methyl] phenol. In conclusion, the magnitude of plant responses to trihalomethanes is more dependent on the halogenation number of the molecule and less on its concentration.

水資源缺乏引起的一系列問題在世界上已建得到廣泛關注，因此，確保提供潔淨衛生的水在保護人類健康和環境方面起著重要作用。近來，光催化作為頗有前景的替代方法被廣泛應用殺菌除污。二氧化鈦是目前研究最多應用最廣的光催化劑。基於紫外光譜照射，催化劑表面產生活性氧化物種，這些物種具有強氧化性能殺滅細胞。 / 本文首次研究了母體菌種大腸桿菌BW25113和它的同源單基因缺陷變異體對光催化殺菌的靈敏度差異。母體菌種和變異菌種表現出不同的耐受性。基於此，能幫助發掘出重要的變種。通過生物化學方法，可以檢測出不同菌種的生理性特徵。結合其他方法，可以進一步揭示光催化殺菌的生理性機理。 / 首先，我們篩選出了兩種重要的變異體。一種是大腸桿菌JW1081，即脂肪酸變異體，該菌種缺乏脂肪酸合成調節的關鍵基因。一種是大腸桿菌JW3942，即乙酰輔酶A變異體，該菌種缺乏乙酰輔酶A合成調控得到關鍵激酶。我們發現脂肪酸變異體對光催化處理的耐受性稍低，而乙酰輔酶A變異體則耐受性較高。 同時發現，溫度可以調節細胞膜的不飽和酸和飽和酸的比例。因此，我們提出脂肪酸和乙酰輔酶A是光催化殺菌中的重要影響因子。 / 更進一步研究發掘了細胞內酶和光催化產生的活性氧物種間的關係。大腸桿菌JW3914，即過氧化氫酶變異體，是發現的另一個重要的變異體。通過對母體和變異體的淬滅劑實驗，主要的殺菌活性氧物種是光催化產生的雙氧水，而不是羥基自由基。細胞體內的過氧化氫酶誘導在母體菌體內發現，而未在變異體內檢測到。 / 本課題採用母體/單基因變異體的研究方法，為全面深刻理解光催化殺菌的深層機理提供一種全新的研究思路。 / Many problems associated with the lack of clean, fresh water worldwide are well known. Developing countries will particularly be affected by water availability problems and there will be further pressure on water demand resulting from economic development and population growth. Therefore, the provision of safe and clean water plays a key role in protecting human health and the environment. Recently, photocatalytic oxidation (PCO) has been widely accepted as a promising alternative method of water disinfection. Titanium dioxide (TiO₂) has been investigated extensively and is the most widely used photocatalyst. Upon the irradiation of UVA lamp, reactive charged and oxidative species are generated on TiO₂ surface and can inactive the bacterial cells. / In this study, the photocatalytic performances of a parental strain (E.coli BW25113) and its isogenic single-gene deletion mutant strains have been investigated for the first time. These bacterial strains exhibited different sensitivies towards photocalytic inactivation. Based on this, it can help reveal some important mechanism from the mutations. Biotic factors were confirmed by physiological biochemical measurement. / Firstly, we screened out the potential mutation fabF⁻ mutant (E. coli JW1081, carrying the mutation of fabF759(del)::kan) and coaA⁻ mutant (E. coli JW3942, carrying the mutation of coaA755(del)::kan). The isogenic fabF⁻ mutant is slightly more susceptible, and coaA⁻ mutant is less susceptible to photocatalytic inactivation. Through conditioning temperature, it adjusts the ratio of unsaturated to saturated fatty acid (FA) of cell membrane. We propose that FA profile and coenzyme A level significantly affect photocatalytic inactivation of bacteria. Moreover, we show photogenerated electrons (e⁻) can directly inactivate the cells of E. coli. / Furthermore, we report the relationship between the bacterial intracellular enzyme and the reactive charged and oxidative species (ROSs) generated during photocataltic inactivation. The katG⁻ mutant, E. coli JW3914, carrying the mutation of katG729(del)::kan is another important mutation. The parental and katG⁻ mutant strains reveal that photogenerated H₂O₂ but not OH[subscript free] is another important reactive oxygen species to inactivate bacteria. The inducible catalase (CAT) corresponding to H₂O₂can be detected in parental strain but not in katG⁻ mutant. / The research methodology using parental/single-gene deletion mutant strains is expected to shed light on fully understanding of the fundamental mechanism of photocatalytic inactivation of E. coli. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Gao, Minghui. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 130-177). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Acknowledgements --- p.i / Abstract --- p.v / Table of contents --- p.ix / List of Figures --- p.xiii / List of Plates --- p.xvii / List of Tables --- p.xviii / List of Equations --- p.xix / Abbreviations --- p.xxi / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Water crisis --- p.1 / Chapter 1.2 --- Traditional disinfection methods --- p.3 / Chapter 1.2.1 --- Chlorination --- p.4 / Chapter 1.2.2 --- Ozonation --- p.6 / Chapter 1.2.3 --- Ultraviolet irradiation --- p.8 / Chapter 1.2.4 --- Multiple disinfectants --- p.10 / Chapter 1.3 --- Advanced oxidation process (AOPs) --- p.10 / Chapter 1.3.1 --- Hydrogen Peroxide/Ozone (H₂O₂/O₃) --- p.11 / Chapter 1.3.2 --- Ozone/Ultraviolet Irradiation (O₃/UV) --- p.12 / Chapter 1.3.3 --- Hydrogen Peroxide/ Ultraviolet Irradiation (H₂O₂/UV) --- p.12 / Chapter 1.3.4 --- Fenton's --- p.Reaction / Chapter 1.4 --- Solar photocatalytic disinfection (SPC-DIS) --- p.14 / Chapter 1.4.1 --- Photocatalyst-TiO₂ --- p.31 / Chapter 1.4.2 --- Irradiation sources --- p.35 / Chapter 1.4.3 --- TiO₂ photocatalytic process --- p.35 / Chapter 1.4.4 --- The role of photogenerated reactive charged and oxidative species (ROSs) --- p.38 / Chapter 1.5 --- Bacteria --- p.40 / Chapter 1.5.1 --- E. coli BW25113 --- p.40 / Chapter 1.5.2 --- E. coli Keio Collection --- p.41 / Chapter 1.5.3 --- Bacterial defense mechanism towards oxidative stresses --- p.44 / Chapter 1.6 --- Photocalytic applications --- p.53 / Chapter 1.7 --- Significance of the project --- p.55 / Chapter 2. --- Objectives --- p.58 / Chapter 3. --- Genetic studies of the roles of fatty acid and coenzyme A in photocatalytic inactivation of Escherichia coli --- p.61 / Chapter 3.1 --- Introduction --- p.61 / Chapter 3.2 --- Materials and methods --- p.65 / Chapter 3.2.1 --- Photocatalyst --- p.65 / Chapter 3.2.2 --- Bacterial nutrient --- p.66 / Chapter 3.2.3 --- Bacterial strains --- p.67 / Chapter 3.2.4 --- Photocatalytic inactivation --- p.69 / Chapter 3.2.5 --- Fatty acid profile --- p.72 / Chapter 3.2.6 --- Fluorescent measurement of bacterial coenzyme A content --- p.74 / Chapter 3.2.7 --- The role of photogenerated electrons (e⁻) to bacterial inactivation --- p.74 / Chapter 3.2.8 --- Transmission Electron Microscopic (TEM) --- p.75 / Chapter 3.2.9 --- Photoelectrochemical measurement --- p.77 / Chapter 3.3 --- Results --- p.77 / Chapter 3.3.1 --- Photocatalytic inactivation --- p.77 / Chapter 3.3.2 --- Effects of pre-incubation at different temperatures --- p.80 / Chapter 3.3.3 --- Fatty acid profile --- p.83 / Chapter 3.3.4 --- Fluorescent measurement of bacterial coenzyme A content --- p.84 / Chapter 3.3.5 --- The role of electron (e⁻) in photocataytic inactivation --- p.84 / Chapter 3.3.6 --- Transmission electron microscopy (TEM) --- p.89 / Chapter 3.3.7 --- Photocurrent measurement --- p.90 / Chapter 3.4 --- Discussion --- p.90 / Chapter 3.5 --- Conclusions --- p.96 / Chapter 4 --- Genetic and physiological studies of the role of Catalase and H₂O₂ in photocatalytic inactivation of E. coli --- p.98 / Chapter 4.1 --- Introduction --- p.98 / Chapter 4.2 --- Materials and methods --- p.101 / Chapter 4.2.1 --- Bacterial strains --- p.101 / Chapter 4.2.2 --- Photocatalytic performance --- p.102 / Chapter 4.2.3 --- Scavenger studies --- p.103 / Chapter 4.2.4 --- Effects of different pHs on photocatalytic inactivation --- p.104 / Chapter 4.2.5 --- Measurement of bacterial catalase activity and H₂O₂ --- p.104 / Chapter 4.2.6 --- Transmission electron microscopy (TEM) --- p.105 / Chapter 4.2.7 --- Atomic absorption spectrophotometer (AAS) --- p.105 / Chapter 4.3 --- Results and discussion --- p.106 / Chapter 4.3.1 --- Photocatalytic performance --- p.106 / Chapter 4.3.2 --- Scavenger studies --- p.108 / Chapter 4.3.3 --- Contribution of hydrogen peroxide (H₂O₂) --- p.111 / Chapter 4.3.4 --- Effects of different pHs on photocatalytic inactivation --- p.114 / Chapter 4.3.5 --- Bacterial catalase (CAT) activity --- p.116 / Chapter 4.3.6 --- Destruction model of bacterial cells --- p.118 / Chapter 4.4 --- Conclusions --- p.120 / Chapter 5. --- General conclusions --- p.122 / Chapter 6. --- Prospectives --- p.125 / Chapter 7. --- Appendix --- p.127 / Chapter 8. --- References --- p.130

No description available.

Bibliography: leaves 263-270.

published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

Thesis (MSc Food Sc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Fresh produce irrigation water from Western Cape Rivers carries faecal coliforms (FC) (Escherichia coli) at concentrations which often exceed the suggested limit of 1 000 FC per 100 mL and presents a health risk to consumers. On-farm ultraviolet (UV) irradiation presents several advantages for water disinfection but is an uncommon practice in South Africa. The aim of this study was to investigate the use of UV irradiation for river water disinfection prior to irrigation. Escherichia coli (E. coli) strains were exposed to low-pressure (LP) UV (4 mJ.cm-2) and UV/Hydrogen peroxide (H2O2) (4 mJ.cm-2/20 mg.L-1) treatments in Sterile Saline Solution (SSS). Strain variation in reductions was observed and ranged from 1.58 to 3.68 and 1.34 to 3.60 log for the UV and UV/H2O2 treatments, respectively. The UV/H2O2 treatment (4 mJ.cm-2/20 mg.L-1) was more effective, compared to UV singly, against some of the E. coli strains. Selected strains showed increased sensitivity at higher UV doses (8, 10 and 13 mJ.cm-2) and H2O2 concentrations (100 and 200 mg.L-1 with 4 mJ.cm-2) but a 3 log target reduction was not always reached. For all UV and UV/H2O2 treatments maximum resistance was shown by an environmental strain. Reference strains should, therefore, not be used for the optimisation of UV based disinfection parameters. At 10 mJ.cm-2 an American Type Culture Collection (ATCC) reference strain and an environmental strain (ATCC 25922 and F11.2) were both significantly less inactivated in sterilised river water compared to SSS. Enhanced water quality allowed for improved inactivation of the ATCC strain. Also, the efficiency of LP UV (5, 7 and 10 mJ.cm-2) and medium-pressure (MP) UV (13, 17 and 24 mJ.cm-2) radiation was investigated using water from the Plankenburg River. Water was sampled and treated on three respective days (Trials 1 to 3). Physico-chemical and microbiological water quality was always poor. The FC concentration reached a maximum of 6.41 log cfu.100 mL-1 while UV transmission was always below 38%. For LP and MP UV irradiation increased doses resulted in increased disinfection but a 3 log reduction of FC was only attained when MP UV light was used in Trial 1. Disinfection efficiency was dependent on water quality and on the characteristics of the microbial population in the water. Since FC were never reduced to below 3 log cfu.100 mL-1, the water did not adhere to guidelines for produce irrigation. Photo-repair following irradiation was investigated in river water using MP UV doses of 13 and 24 mJ.cm-2 and 3.5 kLux reactivating light, initially. Ultraviolet transmission was close to 50% and total coliform (TC) reduction exceeded 3 log, even at 13 mJ.cm-2. However, TC were reactivated from below 1 000 cfu.100.mL-1 to 3.93 and 4.41 log cfu.100 mL-1 for the 13 and 24 mJ.cm-2 treatments, respectively. A higher MP dose (40 mJ.cm-2) and a different treatment regime (2 x 20 mJ.cm-2) inhibited photo-repair (compared to 13 and 24 mJ.cm-2) but TC were always recovered to a final concentration surpassing 3 log cfu.100 mL-1, even under lower light intensities (1.0 to 2.0 kLux). In the current study UV irradiation did not produce water of acceptable standards for produce irrigation, mainly as a result of extremely poor water quality. However, on farm-scale, UV efficiency could be enhanced by improving water quality before irradiation. Also, stronger lamps that deliver higher UV doses may result in adequate disinfection, irrespective of water quality. Higher UV doses and the use of combination treatments (such as UV/Chlorine and UV/Peracetic acid) should be further investigated also to determine its disinfection efficiency and possible capability to inhibit post-disinfection repair. / AFRIKAANSE OPSOMMING: Varsproduk besproeiingswater vanuit Wes-Kaapse riviere bevat fekale kolivorme (FK) (Escherichia coli) in konsentrasies wat dikwels die voorgestelde limiet van 1 000 FK per 100 mL oorskry en hou `n gesondheidsrisiko vir verbruikers in. Plaasvlak ultraviolet (UV) bestraling bied verskeie voordele met verwysing na water dekontaminering, maar word selde aangewend in Suid-Afrika. Die doel van hierdie studie was om die gebruik van UV bestraling vir die dekontaminering van rivierwater, voor besproeiing, te ondersoek. Escherichia coli (E. coli) isolate is blootgestel aan lae-druk (LD) UV (4 mJ.cm-2) en UV/Waterstofperoksied (H2O2) (4 mJ.cm-2/20 mg.L-1) behandelings in Steriele Sout Oplossing (SSO). Isolaat variasie in reduksies is waargeneem en het gewissel tussen 1.58 tot 3.68 en 1.34 tot 3.60 log vir die UV en UV/H2O2 behandelings, onderskeidelik. In vergelyking met UV bestraling alleen was die UV/H2O2 behandeling (4 mJ.cm-2/20 mg.L-1) meer effektief teen sommige E. coli isolate. Geselekteerde isolate was meer sensitief tot hoër UV dosisse (8, 10 en 13 mJ.cm-2) en H2O2 konsentrasies (100 en 200 mg.L-1 met 4 mJ.cm-2), maar `n 3 log teikenreduksie was nie altyd haalbaar nie. Vir alle UV en UV/H2O2 behandlinge was die meeste weerstand deur `n omgewingsisolaat gebied. Verwysingsisolate behoort daarom nie aangewend te word vir die optimisering van UV-gebaseerde behandelingsparameters nie. By 10 mJ.cm-2 was beide `n ATCC verwysingsisolaat en `n omgewingsisolaat (ATCC 25922 en F11.2) betekenisvol minder gedeaktiveer in rivierwater as in SSO. Verbeterde waterkwaliteit het verhoogde inaktivering van die ATCC isolaat toegelaat. Die doeltreffendheid van LD UV (5, 7 en 10 mJ.cm-2) en medium-druk (MD) UV (13, 17 en 24 mJ.cm-2) bestraling is ook ondersoek deur watermonsters vanuit die Plankenburg Rivier te gebruik. Watermonsters was getrek en behandel op drie verskillende dae (Proewe 1 tot 3). Fisies-chemiese en mikrobiologiese kwaliteit van die water was deurentyd swak. Die FK konsentrasie het `n maksimum van 6.41 log kve.100 mL-1 bereik terwyl UV transmissie altyd laer as 38% was. Vir beide LD en MD UV bestraling het verhoogde dosisse gelei tot verbeterde dekontaminering, maar `n 3 log reduksie is slegs bereik toe MD UV lig gebruik is in Proef 1. Die effektiwiteit van die behandelings was afhanklik van waterkwaliteit en die eienskappe van die mikrobiese populasie in die water. Aangesien FK nooit tot onder 3 log kve.100 mL-1 verminder is nie het die water nie voldoen aan riglyne vir varsproduk-besproeiing nie. Fotoherstel na bestraling was ondersoek in rivierwater deur aanvanklik gebruik te maak van MD UV dosisse van 13 en 24 mJ.cm-2 en 3.5 kLux heraktiverende lig. Ultraviolettransmissie het byna 50% bereik en reduksie van totale kolivorme (TK) het 3 log oorskry, selfs by 13 mJ.cm-2. Totale kolivorme was egter geheraktiveer van onder 1 000 kve.100.mL-1 tot 3.93 en 4.41 log kve.100 mL-1 vir die 13 en 24 mJ.cm-2 behandelings, onderskeidelik. In vergelyking met 13 en 24 mJ.cm-2 het `n hoër MD dosis (40 mJ.cm-2) en `n veranderde bestralingstegniek (2 x 20 mJ.cm-2) fotoherstel onderdruk, maar TK was in elke geval geheraktiveer tot `n finale konsentrasie hoër as 3 log kve.100 mL-1, selfs onder laer intensiteit lig (1.0 tot 2.0 kLux). In hierdie ondersoek het UV bestraling nie water van aanvaarbare standaarde vir varsproduk besproeiing gelewer nie, hoofsaaklik as gevolg van swak waterkwaliteit. Nietemin, op plaasvlak mag die effektiwiteit van UV bestraling verhoog word deur waterkwaliteit voor bestraling te verbeter. Die gebruik van sterker lampe, om hoër UV dosisse te produseer, mag verder bydra tot voldoende dekontaminasie, ongeag van waterkwaliteit. Hoër UV dosisse en die gebruik van kombinasie behandelinge (soos UV/Chloor en UV/Perasynsuur) moet ook verder ondersoek word om die dekontaminasie effektiwiteit, en vermoë daarvan om heraktivering na dekontaminering te onderdruk, vas te stel.

M.Sc. / Natural Organic Matter (NOM) is a complex of organic material present in a natural surface water. Odour, taste and acidity are some of the problems associated with NOM in water systems. Futhermore, it causes the yellow or brown colour of water, whic is aesthetically unpleasant to consumers. NOM is also the energy source of bacterial re-growth and aids in the transportation of metal ions in the distribution system.Moreover, NOM in water can react with disinfectants, e.g. chlorine, to form disinfection by products (DBPs) such as trihalomethanes (THMs) and habacetic acids (HAAs). DBPs have recently been found to have adverse effects in humans. This study was undertaken in order to assess the effectiveness of some of the water treatment techniques employed by selected water supplying companies in dealing with NOM. To achive this, the water treatment processes used by these companies to reduce NOM and metal ions were coagulation, sand filtration, the use of granular activated carbon, ozonation and chlorination. In addition, β-cyclodextrin (β-CD) polyurethanes synthesized in our laboratories were used to remove the DBPs present in the water samples.

Thesis (MTech (Chemistry))--Cape Peninsula University of Technology, 2016. / The release of wastewater to the aquatic environment is most likely to introduce some trace levels of organic contaminants, some of which may be toxic, carcinogenic, or endocrine disruptors, as well as, persistent in the environment. Additionally, increasing contamination of surface waters by wastewater effluents has made water treatment processes more challenging and expensive. The presence of these pollutants in the receiving water body may have negative effects on aquatic species and often pose potential human health risks through the reuse of treated wastewater for drinking purposes and other household use. In countries like South Africa, Namibia, USA, Singapore and Australia, water agencies are intensifying wastewater reclamation/wastewater reuse as part of their water resource agenda: in order to meet the demands of the growing populations. Nowadays, water reuse is generally considered as a viable method of water supply management. This study focused on the identification of the occurrence, quantification of emerging contaminants and evaluation of removal efficiency in wastewater treatment processes of three classes of emerging contaminants (ECs) in wastewater: 1) six types of perfluorinated compounds (PFCs), namely; perfluorooctanoic acid (PFOA), Perfluorooctane sulphonate (PFOS), perfluoroheptanoic acid (PFHpA), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), and perfluoroundecanoic acid (PFUDA); 2) bisphenol A (BPA); and 3) Acetaminophen (ACP). These contaminants were identified and quantified in four wastewater treatment plants in the Western Cape. These treatment plants include three WWTPs in Cape Town, namely: Bellville WWTP, Scottsdene WWTP and Zandvliet WWTP and one WWTP in the central Karoo (Beaufort West wastewater reclamation plant).

Irradiation with ultraviolet (UV) light is used for the disinfection of bacterial contaminants in the production of potable water, and in the treatment of selected wastewaters. However, efficacy of UV disinfection is limited by the combined effect of suspended solids concentration and UV absorbance. Limited published UV disinfection data are available that account for the combined effects of UV dose, suspended solids concentration and UV absorbance. This present lack of a rigorous quantitative understanding of the kinetics of UV disinfection limits process optimisation and wider application of UV treatment. The development and validation of an adequate model to describe UV disinfection kinetics presented in this thesis can therefore be justified by an increased confidence of reliability of design for UV disinfection. Using the published data of Nguyen (1999), four established model forms were assessed to account for the combined effect of suspended solids and/or soluble UV absorbing compounds, and UV dose on the efficacy of disinfection. The four model forms were: a log-linear form, Davey Linear-Arrhenius (DL-A), Square-Root (or Ratkowsky- Belehradek) and a general nth order Polynomial (nOP) form that was limited to a third order. Criteria for assessment of an adequate predictive model were established including: accuracy of predicted against observed values, percent variance accounted for (%V), and; appraisal of residuals. The DL-A model was shown to best fit the data for UV disinfection of Escherichia coli (ATCC 25922); followed by the nOP, log-linear and Square-Root forms. However, the DL-A form must be used in conjunction with a first-order chemical reaction equation, and was shown to predict poorly at high experimental values of UV dose (> 40,000 μWs cm-2). The DL-A model was not amenable to extrapolation beyond the observed UV dose range. To overcome the shortcomings of the Davey Linear-Arrhenius model synthesis of two new, non-linear model forms was undertaken. The two models were a modified exponentially damped polynomial (EDPm) and a form based on the Weibull probability distribution. The EDPm model has three terms: a rate coefficient (k), a damping coefficient (λ), and; a breakpoint dose ([dose]B). The rate coefficient governs the initial rate of disinfection prior to the onset of tailing, whilst the breakpoint is the UV dose that indicates the onset of tailing. The damping coefficient controls curvature in the survivor curve. The Weibull model has just two terms: a dimensionless scale parameter (β0), and; a shape parameter (β1). The scale parameter represents the level of disinfection in the tail of the survivor curve (as log10 N/N0), whilst the shape parameter governs the degree of curvature of the survivor data. Each model was assessed against the independent and published UV disinfection data of Nelson (2000) for treatment of faecal coliforms in a range of waste stabilisation pond effluents. Both models were found to be well suited to account for tailing in these UV disinfection data. Overall, the EDPm model gave a better fit to the data than the Weibull model form. To rigorously validate the suitability of the new EDPm and Weibull models a series of experimental trials were designed and carried out in a small-scale pilot UV disinfection unit. These trials included data determined specifically at low values of UV dose (<10,000 μWs cm-2) to fill the gap in the experimental data of Nguyen (1999). The experimental trials were carried out using a commercially available, UV disinfection unit (LC5TM from Ultraviolet Technology of Australasia Pty Ltd). Purified water contaminated with Escherichia coli (ATCC 25922) with a range of feed water flow rates (1 to 4 L min-1) was used. E. coli was selected because it is found in sewage, or water contaminated with faecal material, and is used as an indicator for the presence of enteric pathogens. E. coli should not be present in potable water. The hydrodynamics of water flow within the disinfection unit were established using digital video photography of dye trace studies with Methylene Blue. Nominal UV dose (2,700 to 44,200 μWs cm-2) was controlled by manipulating the flow rate of feed water through the UV disinfection unit (i.e. residence time), or by varying the exposed length of the control volume of the disinfection unit. The transmittance of the feed water (at 254 nm) was adjusted by the addition of either a soluble UV absorbing agent (International RoastTM instant coffee powder; 0.001 to 0.07 g L-1), or by addition of suspended matter as diatomaceous earth (Celite 503TM; 0.1 to 0.7 g L-1, with a median particle size of 23 μm). The absorbing agent (instant coffee), when in a comparable concentration, was found to produce a greater reduction in water transmission than the suspended material (Celite 503TM). It therefore contributed to a greater reduction in the initial rate of disinfection. Neither agent was found to produce a systematic reduction in the observed efficacy of disinfection however. Experimental results highlight that in the absence of soluble absorbing agents, or suspended solids, the initial rate of disinfection is higher when fewer viable bacteria are initially present. Both the new EDPm and Weibull forms gave a good fit to the experimental data. The EDPm better fitted the data on the basis of residual sum-of-squares (0.03 to 2.13 for EDPm cf. 0.16 to 4.37 for the Weibull form). These models are both of a form suitable for practical use in modelling UV disinfection data. Results of this research highlight the impact of water quality, as influenced by the combined effect of UV dose, suspended solids concentration and UV absorbance, on small-scale UV disinfection for potable water production. Importantly, results show that the concentration of soluble UV absorbing agents and suspended solids are not in themselves sufficient criteria on which to base assessment of efficacy of UV disinfection / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1342403 / Thesis (M.Eng.Sc.) - University of Adelaide, School of Chemical Engineering, 2008