Ozonation of drinking waters, particularly as a preoxidant, is becoming a widespread practice. Ozone is a powerful oxidant and reacts with many of the natural constituents present in water. The presence of bromide ion in water can lead to the formation of brominated disinfection by-products upon ozonation. The existence of brominated by-products in a public water supply could be of public health concern since some of them have been shown to be mutagenic. Production of both organic and inorganic by-products upon ozonation of waters containing bromide ion was investigated. Organic by-products identified include bromoform, dibromoacetonitrile (DBAN), and 1,1(DBAA); inorganic by-products identified include bromate, hypobromous acid and hypobromite ion. Formation of by-products is a function of bromide ion concentration, the source and concentration of humic substances, pH, ozone dose, temperature, alkalinity and reaction time. Bromoform concentration ranged from 5 to 60 $\mu$g/L and total organic bromine (TOBr) concentration varied from 15 to 150 $\mu$g/L for a bromide concentration ranging from 0.5 to 1.5 mg/L. TOBr concentrations were much higher than bromoform indicating that bromoform constitutes only a fraction of the pool of brominated DBP material. Bromate threshold levels were shown to vary according to precursor source and pH level. At pH 7.5 bromide threshold concentrations for bromate were higher than at pH 8.5; the exact opposite case was observed for bromoform. Ionic strength had no significant effect on the formation of by-products whereas an increase in alkalinity resulted in decreased amounts of by-products. Temperature effects are manifested in two different ways: (i) the water temperature at which ozonation was carried out versus (ii) the subsequent incubation temperature. While enhanced precursor oxidation was observed at higher ozonation temperatures, the partial oxidation by-products varied in their reactivity in forming brominated by-products upon incubation. An increase in incubation temperature from 20 to 30$\sp\circ$C produced about a 30% increase in bromoform where as an increase in ozonation temperature resulted in a 20% increase in bromoform. Results of this research indicate that control of by-products can be effected by using PEROXONE (hydrogen peroxide plus ozone) or ammonia. PEROXONE produced 55% less organic by-products at the cost of a 25% increase in bromate. Ammonia addition resulted in a 30% decrease of both organic and inorganic by-products.

Since their discovery in 1973, rotaviruses have been reported to be responsible for waterborne outbreaks of gastroenteritis. The simian rotavirus (SA11) was used as a model for the human strains during the development of the method for concentration of rotaviruses from drinking and naturally occurring waters. The microporous filter method developed was capable of recovering an average of 49% of the input virus from 20 liters of tap water and an average of 31% from 378 liters. Of the various eluents evaluated, a mixture of 10% tryptose phosphate broth and 3% beef extract (pH 10.0) was found to give the greatest efficiency of elution. The 1MDS filters were found to be superior to the 50S for the concentration of SA11. The method developed was successfully used to concentrate viruses from environmental waters. Indigenous viruses were isolated from waters in Bolivia and Colombia. Several treatment plants as well as raw surface and groundwaters were sampled for the presence of entero— and rotaviruses. Rotaviruses were isolated from one sample which had undergone complete treatment and met all current standards for potability. This study indicated that enteric viruses can be found in drinking waters considered safe due to the absence of indicator bacteria. Prior to this study there were no reports of the occurrence of enteric viruses in water in Colombia or Bolivia. The results of this study also indicate the need for some type of virus monitoring of waters which are contaminated with sewage in order to evaluate the impact of these viruses on the population.

Hydrous aluminum oxide colloids of 0.5 Am diameter were used to study the coagulation of submicron particles under water-treatment conditions. The research was aimed at understanding the effects of pH and ligands (organic and inorganic) on precipitation of the added coagulant and their influences on incorporation of the colloids into larger flocs. The reduction in the concentration of submicron particles as a result of alum coagulation was monitored by conventional jar-test experiments. Scanning electron microscopy was used for submicron particle counting. Up to three orders of magnitude reduction in submicron particle concentrations were observed in jar-test experiments. Higher pH (i.e., 7.5) and alum dose (i.e., 1.0 mg L⁻¹) favored homogeneous precipitation of aluminum hydroxide, whereas heterogeneous precipitation occurred at lower pH (i.e., 6.5) and alum dose (i.e., 0.5 mg L⁻¹). Homogeneous precipitation, involving formation of Al(OH)₃(s) from aqueous species, formed large masses of light-weight flocs that can effectively remove submicron particles by subsequent coagulation. Heterogeneous precipitation, which involves precipitation on the surfaces of the seed particles, resulted in destabilized particles that can efficiently coagulate with each other. The presence of ligands, inorganic (e.g., HCO₃⁻) and organic (e.g., functional groups of humic substances) inhibited the coagulation process, reducing particle removal up-to 250 fold. While these ligands inhibit coagulation by modifying particle surfaces, they may enhance the precipitation reactions of aluminum hydroxide. The presence SO₄²⁻ enhanced precipitation relative to NO₃⁻. Electrophoretic mobility values were used to derive equilibrium constants for aluminum speciation and precipitation reactions, both on the surface of particles and in solution. The adsorption of ligands lowered the pHiep, by almost 2 pH units in the presence of HCO₃⁻, and to a pH of less than 3 in the presence of organics. Aluminum species elevated the pHiep by 1 pH unit. Stoichiometric ratios of aluminum hydroxide precipitation were determined using a pH stat. This ratio (1.9 to 3.7) is a function of pH, and concentrations of particles and organics. These results were modeled as spherical precipitates (OH/A1 =3) with adsorbed aluminum species (OH/A1 = 1 to 4). The results of this research suggest that the aluminum precipitation pathway dictates the removal of submicron particles. Submicron particles provide most of the surfaces from particulate matter, thus suggesting the importance of surface precipitation for their removal. Samples from water treatment plants indicated 1.5 to 2.0 log removal of submicron particles. These plants were operating at higher pH values (above 7.5) relative to that of maximum removal experiments in laboratory. Plant operations can be optimized by careful control parameters affecting supersaturation ratio, thus improving removal of submicron particles.Such optimization should include efficient rapid mixing to achieve uniform upersaturation ratios, proper coagulant dose, and possibly better pH control.

Dissolved organics in wastewater samples were separated into three size fractions (0-1,000 amu, 1,000-10,000 amu, and 10,000 amu-0.22 m) using ultrafiltration (UF) membranes. The mass distribution within each fraction was adjusted by using a new permeation coefficient model to account for membrane rejection. Dissolved organic and soluble BOD (sBOD) removals in a trickling filter were studied for the different size fractions. The Logan trickling filter model was recalibrated and used to generate predicted removals by size fraction of sBOD, dissolved organic carbon (DOC), and biodegradable DOC (bDOC) for a given influent. Although there was moderate agreement between observed and predicted removals, more investigation is needed to explain shifts in material between different size fractions. Of the three parameters, bDOC may offer a better parameter for modelling trickling filter performance than sBOD.

The area of research for this thesis concerns the role played by microorganisms in the process of organic breakdown of waste effluent. Although considerable research has been done since the early 1950's, little consideration has been given to the role of the microorganisms in this type of waste water purification.

M.Sc. / The removal of organic pollutants from industrial and municipal water is a great challenge to water providers worldwide. Some of these pollutants are very toxic and pose serious health risks to both humans and animals. Additionally, the presence of organic pollutants in the water often leads to the corrosion of turbines used for power generation at power stations. This obviously makes the power generation process less efficient and thus has cost implications, especially for the end user. Besides the corrosion of turbines, organic water pollutants impact on the cost of generating clean water. To this end, municipalities and industries sourcing water from Rand Water’s treatment plants and Eskom’s power stations (coal-fired power station) may be plagued by high water costs. Geosmin and 2-MIB are detectable by the human nose at concentration levels as low as 10 ng/L. These common water pollutants and are renowned for causing bad taste and odour in drinking water. Although geosmin and 2-MIB do not pose any serious health risks to humans, they impact on the aesthetic and consumer acceptability of drinking water. Currently available technologies such as activated carbon are unable to remove these pollutants to low levels (i.e. ppb levels). In our laboratories, we have found cyclodextrin-based polyurethanes to be effective in the removal of a range of organic pollutants from water to the desired ppb levels. However, these investigations were confined to water samples deliberately spiked with specific pollutants and have not been proven with "real" water samples. We sought to integrate data accumulated in the laboratory by testing and applying these polymers on a larger scale and on real systems. Cyclodextrin (CD) polymers were employed in the removal of 2-MIB, geosmin and other organic pollutants from water. The water was sampled from a coal-fired power station and Zuikerbosch Water Treatment Plant (Rand Water). After using Solid Phase Microextraction (SPME) for the extraction of organic pollutants from the water samples the organic pollutants were identified and quantified using Gas chromatography-mass spectrometry (GC-MS). The new cyclodextrin polymer technology was compared with treatment methods currently applied at both the power station and treatment plant. To determine the environmental friendliness of this technology, polymer degradation studies were also carried out. These entailed performing soil burial tests prior to the characterization of the polymers. Thermogravimetric analysis (TGA), Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM) and Braunner Emmet Tellet (BET) analysis were used for the characterization of the polymers. The techniques were also used to determine if any degradation modifications occurred on the polymeric material. The findings of the study are summarized below: • SPME extraction and GC-MS analyses of geosmin, 2-MIB and other pollutants were successfully accomplished. • The cyclodextrin polymers were effective in the removal of geosmin and 2-MIB (up to 90%) from water sampled at Zuikerbosch water treatment plant. The polymers remained effective (90%) in the absorption of geosmin and 2-MIB even when the water samples were spiked with a competing pollutant (i.e. humic acid). Activated carbon has been noted to have reduced adsorption capacity when humic acid is present in water. • The polymers demonstrated the ability to remove as much as 90% of organic pollutants from raw water compared to the 50% removed by the polyelectrolyte and optimum minimal polyaluminium chloride employed at the coal-fired power station. Analyses of the samples using TOC before and after treatment were accomplished. Reduction in the TOC was noted at the different sampling points after Eskom’s water treatment regime. • Results from the study indicated that the β-CD TDI polymers underwent a greater weight-loss during soil burial when first digested in sulphuric acid (ca. 50% maximum mass loss). On the other hand, β-CD HMDI polymers appeared to be unaffected by predigestion and experienced the same amount mass loss for the digested and undigested polymers (ca. 30% maximum mass loss). SEM studies revealed changes in the surface morphology of the polymers. Moreover, thermogravimetric analysis (TGA) gave an indication of polymer degradation under all soil burial conditions the polymer was subjected to.

由於潔淨用水日漸短缺，科學家著力研究各種水淨化方法，其中以光催化技術作水淨化處理為可行的方法之一。光催化是以半導體光催化劑在光照射下所產生的活性物種（reactive oxidative species）進行消毒，其中的失活原理、各活性物種的作用和活性物種對細菌的攻擊方位，雖然已有廣範的研究，但當中仍有不清之處，比如說過氧化氫(H₂O₂)在光催化失活的作用便是其中之一，在光催化系統中所產生的H₂O₂濃度一般較低，因此其對細菌失活的效能仍然存有爭議。 / 本研究設計一種新的反應器去研究H₂O₂在連續供應模式中的失活動力學。在 8 mM 的H₂O₂下，10⁵的大腸桿菌(Escherichia coli)在8小時內完全失活。而在 2 mM 的H₂O₂ 下，並無出現顯著失活，由於該濃度遠遠高於一般光催化系統所產生的濃度（<50 μM），因此可以推斷，即使一般光催化系統所產生的H₂O₂是連續供應，也不會使細菌失活。然而在光照的情況下，其失活動力學大為不同，在強光照射(200 mW cm⁻²)下，H₂O₂的失活效率顯著增強，證明光照和過氧化氫之間存有協同效應。這現象亦出現於光預處理過(light pretreated)的大腸桿菌，進一步證實了光照改變細菌的生理機能，從而使其易於被H₂O₂失活。 / 其後我們使用RNA測序(RNA sequencing)去檢測的大腸桿菌的基因表達水平在光照下的變化，以便研究光照和H₂O₂之間的協同作用的機理。大多數涉及抵抗氧化的基因，包括過氧化氫酶(catalase, CAT)和超氧化物歧化酶(superoxide dismutase,SOD)的表達、DNA修復及細菌內的鐵含調控等等，其mRNA 水平沒有顯著的增加或減少，只有dps、fes和sodB有明顯的變化。此外，還有幾種調控細胞內的銅合量（cutA和cueR）和細胞膜組成（ompA、ompC、resx和gnsB）的基因在光照下產生顯著變化。 經RNA測序後，我們選定了10個目標基因，並選擇相對的大腸桿菌變異體(mutants)，對比他們和母體(E. coli BW25113)經過光預處理後被H₂O₂的失活效能。雖然這次研究並未找到相關基因，但研究結果表示，光照和H₂O₂的協同效應，應該是光照增加細胞膜的通透性和提高細菌內Fenton劑含量，使細菌內的羥基自由基(·OH)的濃度增加，因此加強對細菌DNA的損傷。 / 最後，我們亦比較了AgBr/Ag/Bi₂WO₆在不同的光源的照射下的對大腸桿菌的光催化失活效率。雖然發光二極管(light emitting diode)和熒光管都常用於室內照明，但AgBr/Ag/Bi₂WO₆的細菌失活效率在兩者的光照下表現出顯著的差異，而不同的發射波長下的細菌失活效率和AgBr/Ag/Bi₂WO₆光學吸收表現出良好的相關性。此外，相對其他顏色的發光二極管，綠色發光二極管照射下在犧牲劑研究(scavenger study)的結果大為不同，進一步表明了光照的發射波長(emissionwavelength)對光催化失活機制的影響。 / 本研究揭示了H₂O₂和光照在光催化失活中的重要性，並演示了H₂O₂和光照射之間的協同作用，也闡明了光照的屬性如何影響光催化下各活性物種的產生。本研究不僅提供了一個新的角度去探討的光照、H₂O₂和細菌的生理狀態在光催化失活中的重要性，也提供了新的方向和方法去研究光催化失活機制的。 / Due to the increasing concern for the need of clean drinking water, different methods for water purification have been developed. Photocatalysis, which makes use of semiconductor photocatalyst for the generation of reactive charged and oxidative species (ROSs) under light irradiation, is one of the most promising methods for water disinfection. The mechanisms of the photocatalytic inactivation have been extensively investigated. Different factors, including the roles of ROSs and the ROSs target site(s) of bacterial cell, were elaborated by different studies. However, there are still controversial issues on the role of H₂O₂ in photocatalytic inactivation. The effectiveness of the low concentration of H₂O₂ in the bacterial inactivation process is still under question. / This study designs a new reactor to study the kinetic of H₂O₂ inactivation in continuous supply mode. Complete inactivation of 5-log Escherichia coli within 8 h is achieved when 8 mM of H₂O₂ is applied. No significant inactivation was observed when 2 mM H₂O₂ is applied, this concentration of H₂O₂ is much higher than that detected in common photocatalytic system (< 50 μM). The results show that H₂O₂ produced by common photocatalytic system is not harmful to bacterial cell, even they are produced continuously. However, when light irradiation of 200 mW cm⁻² , using Xenon lamp as lighting source, was applied to the system, the inactivation efficiency of H₂O₂ was significantly enhanced, which demonstrate the synergistic effect between the light irradiation and H₂O₂. The enhancement of inactivation by H₂O₂ can also be observed with light pretreated E. coli K-12, further confirms that light irradiation alter the physiology of the bacterial cell which increases their sensitivity to H₂O₂. / In order to find out the mechanism(s) of the synergism between the light irradiation and H₂O₂, RNA sequencing (RNA-Seq) was used to reveal the change of gene expression level of the E. coli under light irradiation. The mRNA level of most of the genes involve in catalase (CAT) and superoxide dismutase (SOD) expression, DNA repairing and intracellular iron regulation did not have significant increase or decrease. Only dps, fes and sodB showed significantly changes. Moreover, some genes that related to regulation of intracellular copper (cutA and cueR) and membrane composition (ompA, ompC, resX and gnsB) also showed significantly changes under light irradiation. After the RNA-Seq, ten genes were chosen as the possible target genes that related to the mechanism(s). Then the inactivation of E. coli BW25113 (parental strain) and the isogenic deleted mutants by H₂O₂ with light pretreatment were conducted and compared. Although the gene(s) that directly involved in the mechanisms of the synergy between H₂O₂ and light irradiation are not identified in the study, the results show that genes that are important to bacterial defense of oxidative damages, such those responsible for CAT and SOD expression and DNA repairing, are not involved in the mechanism(s). Increase of cell permeability and intracellular Fenton’s reagent content should be the main causes for the enhancement of H₂O₂ under light irradiation. / Finally, the inactivation efficiency of E. coli K-12 using AgBr/Ag/Bi₂WO₆ under different lighting sources is compared. The results show that inactivation efficiency under different emission wavelength are highly correlated with the optical absorption of the AgBr/Ag/Bi₂WO₆. Photocatalytic inactivation under two indoor lighting sources, LED lamps and Fluorescence tubes, also showed significant difference. The result of scavenger study under green LED lamps is completely different from those under other colour of LED lamps, indicates that emission wavelength also has great influence in photocatalytic inactivation mechanisms. / This study reveals the roles of H₂O₂ and light irradiation in photocatalytic inactivation and demonstrates the synergism between the H₂O₂ and light irradiation. The influence of the properties of light irradiation, including the light intensity and major emission wavelength, on the ROSs production by photocatalyst is also reported as well. This study not only provides a new perspective to the importance of light irradiation, H₂O₂ and the physiology of bacteria in photocatalytic inactivation, but a new approach in the investigation of photocatalytic inactivation mechanisms as well. / 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. / Ng Tsz Wai. / Thesis (Ph.D.) Chinese University of Hong Kong, 2014. / Includes bibliographical references (leaves 111-131). / Abstracts also in Chinese.

by Fong Wai-lan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves 138-152). / Text in English; abstracts in English and Chinese. / by Fong Wai-lan. / Acknowledgements --- p.i / Abstracts --- p.ii / Contents --- p.vi / List of figures --- p.xii / List of Plates --- p.xviii / List of tables --- p.xix / Abbreviations --- p.xxi / Chemical equations --- p.xxiii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Pentachlorophenol --- p.1 / Chapter 1.1.1 --- Characteristics of pentachlorophenol --- p.1 / Chapter 1.1.2 --- Use of pentachlorophenol --- p.4 / Chapter 1.1.3 --- Annual consumption and regulations for the use of pentachlorophenol --- p.4 / Chapter 1.1.4 --- Pentachlorophenol in the environment --- p.4 / Chapter 1.1.5 --- Toxicity of pentachlorophenol --- p.5 / Chapter I. --- Mechanism --- p.5 / Chapter II. --- Toxicity towards plant and animals --- p.7 / Chapter III. --- Toxicity towards human --- p.7 / Chapter 1.2 --- Treatments of pollutant --- p.9 / Chapter 1.2.1 --- Physical treatment --- p.9 / Chapter 1.2.2 --- Chemical treatment --- p.9 / Chapter 1.2.3 --- Biological treatment --- p.12 / Chapter 1.2.4 --- Advanced Oxidation Processes (AOPs) --- p.14 / Chapter Chapter 2 --- Objectives --- p.28 / Chapter 3 --- Materials and methods --- p.29 / Chapter 3.1 --- Chemical reagents --- p.29 / Chapter 3.2 --- Photocatalytic reactor --- p.29 / Chapter 3.3 --- Determination of pentachlorophenol concentration --- p.31 / Chapter 3.4 --- Optimization of reaction conditions for UV-PCO --- p.34 / Chapter 3.4.1 --- Batch system --- p.34 / Chapter 3.4.1.1 --- Effect of initial hydrogen peroxide concentration --- p.34 / Chapter 3.4.1.2 --- "Effect of initial titanium dioxide concentration, light intensity and initial pH" --- p.34 / Chapter 3.4.1.3 --- Effect of initial pentachlorophenol concentration and irradiation time & determination of total organic carbon (TOC) removal during UV-PCO --- p.36 / Chapter 3.4.2 --- Continuous system --- p.36 / Chapter 3.5 --- Optimization of reaction conditions for VL-PCO --- p.38 / Chapter 3.5.1 --- "Effect of VL source, initial hydrogen peroxide, titanium dioxide concentration，light intensity, pH and reaction volume" --- p.38 / Chapter 3.5.2 --- Effect of initial pentachlorophenol concentration and irradiation time & determination of total organic carbon (TOC) removal during VL-PCO --- p.39 / Chapter 3.6 --- Optimization of reaction conditions for S-PCO --- p.39 / Chapter 3.6.1 --- "Effect of initial hydrogen peroxide, titanium dioxide concentration，light intensity and pH" --- p.39 / Chapter 3.6.2 --- Effect of irradiation time & determination of total organic carbon (TOC) removal during S-PCO --- p.41 / Chapter 3.7 --- Modification of photocatalytic oxidation --- p.41 / Chapter 3.7.1 --- Buffering system --- p.41 / Chapter 3.7.2 --- Immobilized titanium dioxide system --- p.41 / Chapter 3.7.2.1 --- Preparation of titanium dioxide coated spiral column --- p.41 / Chapter 3.7.2.2 --- Effect of flow rate for the UV-PCO (continuos- buffering/immobilized titanium dioxide) system --- p.43 / Chapter 3.8 --- Estimation of pentachlorophenol degradation pathway by photocatalytic oxidation --- p.43 / Chapter 3.9 --- Evaluation for the toxicity change of pentachlorophenol during the degradation process --- p.43 / Chapter 3.9.1 --- Microtox® test --- p.43 / Chapter 3.9.2 --- Amphipod survival test --- p.45 / Chapter Chapter 4 --- Results --- p.47 / Chapter 4.1 --- Determination of pentachlorophenol concentration --- p.47 / Chapter 4.2 --- Optimization of reaction conditions for UV-PCO --- p.47 / Chapter 4.2.1 --- Batch system --- p.47 / Chapter 4.2.1.1 --- Effect of initial hydrogen peroxide concentration --- p.47 / Chapter 4.2.1.2 --- Effect of initial titanium dioxide concentration --- p.54 / Chapter 4.2.1.3 --- Effect of light intensity --- p.54 / Chapter 4.2.1.4 --- Effect of initial pH --- p.54 / Chapter 4.2.1.5 --- Effect of initial pentachlorophenol concentration and irradiation time & determination of total organic carbon (TOC) removal during UV-PCO --- p.61 / Chapter 4.2.2 --- Continuous system --- p.61 / Chapter 4.3 --- Optimization of reaction conditions for VL-PCO --- p.69 / Chapter 4.3.1 --- Effect of VL source --- p.69 / Chapter 4.3.2 --- Effect of initial hydrogen peroxide concentration --- p.69 / Chapter 4.3.3 --- Effect of initial titanium dioxide concentration --- p.69 / Chapter 4.3.4 --- Effect of light intensity --- p.76 / Chapter 4.3.5 --- Effect of initial pH --- p.76 / Chapter 4.3.6 --- Effect of reaction volume --- p.76 / Chapter 4.3.7 --- Effect of initial pentachlorophenol concentration and irradiation time & determination of total organic carbon (TOC) removal during VL-PCO --- p.83 / Chapter 4.4 --- Optimization of reaction conditions for S-PCO --- p.83 / Chapter 4.4.1 --- Effect of initial hydrogen peroxide concentration --- p.83 / Chapter 4.4.2 --- Effect of initial titanium dioxide concentration --- p.90 / Chapter 4.4.3 --- Effect of initial pH --- p.90 / Chapter 4.4.4 --- Effect of irradiation time & determination of total organic carbon (TOC) removal during S-PCO --- p.90 / Chapter 4.5 --- Modification of photocatalytic oxidation --- p.96 / Chapter 4.5.1 --- Buffering system --- p.96 / Chapter 4.5.2 --- Immobilized titanium dioxide system --- p.104 / Chapter 4.6 --- Estimation of pentachlorophenol degradation pathway by photocatalytic oxidation --- p.104 / Chapter 4.7 --- Evaluation of the toxicity change of pentachlorophenol during photocatalytic oxidation --- p.104 / Chapter 4.7.1 --- Microtox® test --- p.104 / Chapter 4.7.2 --- Amphipod survival test --- p.112 / Chapter Chapter 5 --- Discussion --- p.116 / Chapter 5.1 --- Determination of pentachlorophenol concentration --- p.116 / Chapter 5.2 --- Optimization of reaction conditions for UV-PCO --- p.116 / Chapter 5.2.1 --- Batch system --- p.116 / Chapter 5.2.1.1 --- Effect of initial hydrogen peroxide concentration --- p.116 / Chapter 5.2.1.2 --- Effect of initial titanium dioxide concentration --- p.117 / Chapter 5.2.1.3 --- Effect of light intensity --- p.119 / Chapter 5.2.1.4 --- Effect of initial pH --- p.119 / Chapter 5.2.1.5 --- Effect of initial pentachlorophenol concentration and irradiation time & determination of total organic carbon (TOC) removal during UV-PCO --- p.120 / Chapter 5.2.2 --- Continuous system --- p.120 / Chapter 5.3 --- Optimization of reaction conditions for VL-PCO --- p.121 / Chapter 5.3.1 --- Effect of visible light (VL) source --- p.121 / Chapter 5.3.2 --- Effect of initial hydrogen peroxide concentration --- p.121 / Chapter 5.3.3 --- Effect of initial titanium dioxide concentration --- p.122 / Chapter 5.3.4 --- Effect of light intensity --- p.123 / Chapter 5.3.5 --- Effect of initial pH --- p.124 / Chapter 5.3.6 --- Effect of reaction volume --- p.124 / Chapter 5.3.7 --- Effect of initial pentachlorophenol concentration and irradiation time & determination of total organic carbon (TOC) removal during VL-PCO --- p.124 / Chapter 5.4 --- Optimization of reaction conditions for S-PCO --- p.125 / Chapter 5.4.1 --- Effect of initial hydrogen peroxide concentration --- p.125 / Chapter 5.4.2 --- Effect of initial titanium dioxide concentration --- p.126 / Chapter 5.4.3 --- Effect of initial pH --- p.127 / Chapter 5.4.4 --- Effect of irradiation time & determination of total organic carbon (TOC) removal during S-PCO --- p.127 / Chapter 5.5 --- Modification of photocatalytic oxidation --- p.128 / Chapter 5.5.1 --- Buffering system --- p.128 / Chapter 5.5.2 --- Effect of flow rate on removal efficiency for the UV-PCO (continuos-buffering/immobilized titanium dioxide) system --- p.129 / Chapter 5.6 --- Estimation of pentachlorophenol degradation pathway by photocatalytic oxidation --- p.130 / Chapter 5.7 --- Evaluation for the toxicity change of pentachlorophenol during photocatalytic oxidation --- p.132 / Chapter 5.7.1 --- Microtox® test --- p.132 / Chapter 5.7.2 --- Amphipod survival test --- p.133 / Chapter Chapter 6 --- Conclusions --- p.135 / Chapter Chapter 7 --- References --- p.138 / Appendix i --- p.153 / Appendix ii --- p.154 / Appendix iii --- p.154

by Wong Kin-hang. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 99-127). / Text in English; abstracts in English and Chinese. / by Wong Kin-hang. / Acknowledgements --- p.i / Abstracts --- p.ii / Contents --- p.vi / List of Figures --- p.ix / List of Tables --- p.x / Abbreviations --- p.xi / Chemical Equations --- p.xii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Poly chlorinated biphenyls --- p.1 / Chapter 1.1.1 --- Characteristics of polychlorinated biphenyls (PCBs) --- p.1 / Chapter 1.1.2 --- Use of polychlorinated biphenyls --- p.3 / Chapter 1.1.3 --- World-wide production of polychlorinated biphenyls --- p.7 / Chapter 1.1.4 --- Polychlorinated biphenyls in the environment --- p.8 / Chapter 1.1.5 --- Toxicity of polychlorinated biphenyls --- p.12 / Chapter I. --- Mechanism --- p.12 / Chapter II. --- Toxicity towards plant and animals --- p.13 / Chapter III. --- Toxicity towards human --- p.14 / Chapter IV. --- Enzymatic induction by PCBs --- p.14 / Chapter V. --- Carcinogenicity of PCBs --- p.18 / Chapter 1.2 --- Treatments of pollutant --- p.19 / Chapter 1.2.1 --- Physical treatment --- p.19 / Chapter 1.2.2 --- Chemical treatment --- p.20 / Chapter 1.2.3 --- Biological treatment --- p.22 / Chapter 1.2.4 --- Photocatalytic oxidation (PCO) --- p.25 / Chapter Chapter 2 --- Objectives --- p.35 / Chapter Chapter 3 --- Materials and methods --- p.36 / Chapter 3.1 --- Chemical reagents --- p.36 / Chapter 3.2 --- Photocatalytic oxidation reactor --- p.36 / Chapter 3.3 --- Separation and determination of eight PCB congeners --- p.39 / Chapter 3.4 --- Determination of tetra-CB concentration --- p.40 / Chapter 3.5 --- Determination of PCO intermediates and products --- p.41 / Chapter 3.6 --- Optimisation of reaction conditions for UV-PCO in batch system --- p.44 / Chapter 3.6.1 --- Control experiments and effect of initial titanium dioxide concentration --- p.44 / Chapter 3.6.2 --- Effect of initial hydrogen dioxide concentration and UV intensity --- p.44 / Chapter 3.6.3 --- Effect of initial titanium dioxide concentration and initial pH --- p.45 / Chapter 3.7 --- Estimation of tetra-CB degradation pathway by photocatalytic oxidation --- p.45 / Chapter 3.8 --- Evaluation for the toxicity of hydrogen peroxide and toxicity change of tetra-CB during PCO by Microtox® test --- p.45 / Chapter 3.9 --- Determination of H202 concentration after PCO --- p.47 / Chapter Chapter 4 --- Results --- p.50 / Chapter 4.1 --- Separation and determination of eight PCB congeners --- p.50 / Chapter 4.2 --- Photocatalytic oxidation of mono-CB --- p.50 / Chapter 4.3 --- Determination of tetra-CB --- p.55 / Chapter 4.4 --- Optimisation of reaction conditions for UV-PCO in batch system --- p.56 / Chapter 4.4.1 --- Control experiments and effects of initial titanium dioxide concentration --- p.56 / Chapter 4.4.2 --- Effect of initial hydrogen peroxide concentration and UV intensity --- p.56 / Chapter 4.4.3 --- Effect of initial titanium dioxide concentration and initial pH --- p.60 / Chapter 4.5 --- Estimation of tetra-CB degradation pathway by photocatalytic oxidation --- p.71 / Chapter 4.6 --- Evaluation for the toxicity of hydrogen peroxide and toxicity change of tetra-CB by Microtox® test --- p.72 / Chapter 4.7 --- Determination of H202 concentration after PCO --- p.72 / Chapter Chapter 5 --- Discussion --- p.89 / Chapter 5.1 --- Separation and determination of eight PCB congeners --- p.89 / Chapter 5.2 --- Photocatalytic oxidation of mono-CB --- p.89 / Chapter 5.3 --- Determination of tetra-CB --- p.90 / Chapter 5.4 --- Optimisation of reaction conditions for UV-PCO in batch system --- p.90 / Chapter 5.4.1 --- Control experiments and effects of initial titanium dioxide concentration --- p.91 / Chapter 5.4.2 --- Effect of initial hydrogen peroxide concentration and UV intensity --- p.91 / Chapter 5.4.3 --- Effect of initial titanium dioxide concentration and initial pH --- p.93 / Chapter 5.5 --- Estimation of tetra-CB degradation pathway by photocatalytic oxidation --- p.95 / Chapter 5.6 --- Evaluation for the toxicity of hydrogen peroxide and toxicity change of tetra-CB by Microtox® test --- p.96 / Chapter 5.7 --- Determination of H202 concentration after PCO --- p.97 / Chapter Chapter 6 --- Conclusions --- p.98 / Chapter Chapter 7 --- References --- p.99

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