In fulfilling the needs of the society, the introduction of new synthetic chemicals into the industry have created a new threat to the environment. Advanced Oxidation Processes (AOPs) are one of the treatment technologies currently being developed to deal with this problem. Fenton's Reagent (FR) can be considered as the oldest AOPs available today. In this thesis, study has been conducted to explore the effect of several reaction variables on FR and ultra-violet (UV) photo-Fenton processes. The aim of this study was to improve the process through manipulation of these variables which include mixing intensity, reagent dosing strategy (i.e. addition timing and position), initial dissolved oxygen content (IOOe) and UV light intensity. With consideration to the wastewater generated by textile dyeing industry, a reactive dyestuff, Reactive Black S (RBS) was used as the model pollutant. Within the range of the experimental conditions used in this study, the RBS was found to be easily decolourised by FR. RBS was observed to further increase the degradation of HZ02, which is expected to generate more hydroxyl radicals (HO·) for better RBS degradation. Mineralisation of the dyestuff, however, required higher reagents dosage and longer reaction time. Mixing intensity was found to have a significant effect on the process. The behaviour of the mixing effect appears to be a function of reagents dosing strategy applied. In general, increasing mixing intensity was found to improve the RBS mineralisation in the early stages. For a given dosing strategy, this effect was still observed later. A very high mixing rate, however, caused reduction in TOe removal. The requirement for mixing intensity could be reduced by adopting an appropriate dosing strategy, hence reducing the potential process operational cost. Initial dissolved oxygen content was also observed to have a significant influence on the FR process. Reducing the looe was found to enhance the process performance. However, the influence was trivial for the photo-Fenton process. The presence of UV light greatly enhances the FR process and the light intensity also has significant effect on the process. The significance of some of the factors was observed to change as the reaction progress. Several factors were also found to affect the process interactively and some of the effects as a function of the factors were non-linear.

The Economic Level of Leakage (ELL) is the leakage level which minimizes the total of the present value cost of leakage management and the present value cost of the water lost through leakage. Reducing the leakage below the ELL would cost a water utility more than the benefits of the leak reduction. The overall aim of this research is to contribute to the reduction of carbon emissions associated with management of water leakages in water distribution networks. This study adapted an IWA methodology for the determination of an Economic Level of Leakage that incorporates energy externalities associated with active leakage detection, for a water distribution zone in the city of Zaragoza, Spain, which has no history of active leakage management. The methodology used in this research divided the leakage into four components: Reported Burst Volumes, Estimated Background Leakage, Trunk Mains and Service Reservoir Leakage and Economic Unreported Real Losses. In the case of the Economic Unreported Real Losses, the calculation requires only three system-specific parameters: Cost of Intervention (CI), Variable Cost of Lost Water (CV), and Rate of Rise of Unreported Leakage (RR). Of these parameters, the most critical in the research was the RR due to the experimental nature. The Estimated Background Leakage was calculated using the Burst and Background Estimate (BABE) method which requires field data such as the number of bursts, the average zone night pressure, length of mains, trunk-main losses, and number of billed properties that might not be available but that can be obtained by the water utility with a reasonable level of investment. According to the experience with the Water Utility in Zaragoza, the lack of a centralized depository of information in the Water Utility made the data collection process complicated for some data. It was noted that the main problem is not the lack of standardization between databases, but the lack of awareness of the information collected or considered by other teams in the water utility. This awareness can be improved by sharing the access to information between teams. Implementing a centralized information management system can solve the problem. The utility in Zaragoza estimated non-revenue water (NRW) to the tune of 21 million m3 (i.e. 34% of system input volume) in 2008 when the fieldwork was carried out. Approximately half of the NRW (about 9-12 million m3) was estimated to be physical losses in the distribution network. The model developed as part of this study show that the estimated ELL was 1,638 m3x103/yr, based on only one approach for active leakage detection (using noise loggers). It can be seen that the physical losses are between 5.5-7.3 times bigger than the ELL. This shows that investment in Active Leakage Control would provide significant economic and financial benefits, and improve the performance of the water utility. This research found that inclusion of energy externalities raised the ELL value by 0.4%, which appears insignificant. However, quantifying the emissions will be useful in future scenarios when various national legislations will make it compulsory to report on the energy emissions. Therefore, the model developed in this research can be adapted by utilities with limited data to quantify the effect of energy externalities in the water distribution systems. This has future important implications for policy and practice.

Water supply systems are usually designed, constructed, operated, and managed in an open environment, thus they are inevitably exposed to varied uncertain threats and conditions. In order to evaluate the reliability of water supply systems under threatened conditions, risk assessment has been recognised as a useful tool to identify threats, analyse vulnerabilities and risks, and select proper mitigation measures. However, due to the complexity and uncertainty of water supply systems and risks, consistent and effective assessments are hard to accomplish by using available risk techniques. With respect to this, the current study develops a new method to assess the risks in complex water supply systems by reconsidering the organisation of risk information and risk mechanism based on the concepts of object-oriented approach. Then hierarchical assessments are conducted to evaluate the risks of components and the water supply system. The current study firstly adopts object-oriented approach, a natural and straightforward mechanism of organising information of the real world systems, to represent the water supply system at both component and system levels. At the component level, components of a water supply system are viewed as different and functional objects. Associated with each object, there are states transition diagrams that explicitly describe the risk relationships between hazards/threats, possible failure states, and negative consequences. At the system level, the water supply system is viewed as a network composed of interconnected objects. Objectoriented structures of the system represent the whole/part relationships and interconnections between components. Then based on the object states transition diagrams and object-oriented structures, this study develops two types of frameworks for risk assessment, i.e., framework of aggregative risk assessment and framework of fault tree analysis. Aggregative risk assessment is to evaluate the risk levels of components, subsystems, and the overall water supply system. While fault trees are to represent the cause-effect relationships for a specific risk in the system. Assessments of these two frameworks can help decision makers to prioritise their maintenance and management strategies in water supply systems. In order to quantitatively evaluate the framework of aggregative risk, this thesis uses a fuzzy evidential reasoning method to determine the risk levels associated with components, subsystems, and the overall water supply system. Fuzzy sets theory is used to evaluate the likelihood, severity, and risk levels associated with each hazard. Dempster-Shafer theory, a typical evidential reasoning method, is adopted to aggregate the risk levels of multiple hazards along the hierarchy of aggregative risk assessment to generate risk levels of components, subsystems, and the overall water supply system. Although fuzzy sets theory and Dempster-Shafer theory have been extensively applied to various problems, their potential of conducting aggregative risk assessments is originally explored in this thesis. Finally, in order to quantitatively evaluate the cause-effect relationships in a water supply system, fuzzy fault tree analysis is adopted in this study. Results of this analysis are likelihood of the occurrence for a specific event and importance measures of the possible contributing events. These results can help risk analysts to plan their mitigation measures to effectively control risks in the water supply system.

This Thesis is concerned with the quality of surface waters in rural catchments across northern England and the mitigation of Diffuse Water Pollution from Agriculture (DWPA). Runoff Attenuation Features (RAFs) are a range of soft--‐engineered DWPA transport management options, which target hydrological flow pathways for the purpose of slowing, storing and filtering water. This study demonstrates the potential of RAFs to significantly reduce losses of suspended sediment (SS), phosphorus (P) and nitrate (NO3) in agricultural runoff. To implement RAFs effectively it is vital to understand how, where and when to best target mitigation efforts. This relies on knowledge of the sediment and nutrient regime and hydrological functioning of a catchment. In response to this a stratified, synchronous grab sampling programme was implemented over two consecutive years in the upper Eden catchment (334 km2), Cumbria, covering thirteen sub--‐catchments of multiple scales. No relationship was found between sedimentutrient yield and catchment area but it was recognised that certain lowland sub--‐catchments deliver a disproportionate amount of the pollutant load, particularly SS and P, due to increased agricultural activity, and that there were large variations in flux affected by season and hydrological conditions. One particular sub--‐catchment dominated by improved grassland, Blind Beck (9 km2), exhibited both higher nutrient and SS concentrations per unit runoff and higher yields compared with any other sub--‐catchment. The Blind Beck sub--‐catchment was selected in which to implement a more detailed investigation of SS and nutrient delivery, which included event sampling. High flows (accounting for 10% of flow duration) contributed 84% of the annual SS load, 76% of the total P and 68% of the soluble reactive P, but just 32% of the NO3 load. This highlights the acute nature of the SS and P diffuse pollution problem and demonstrates the need to target storm events for effective mitigation. A number of RAFs were constructed in two established research catchments in Northumberland with a similar mixed land use to the Eden: Belford (15 ha) and Netherton (80 ha). Synchronous inlet and outlet water samples were collected during storm events. Results demonstrate that relatively small RAFs, principally sediment traps, constructed in farm ditches (<1 km2 catchment area) can reduce mean SS, TP, SRP and NO3 loads during storm events by 30--‐49%, 23--‐37%, 12--‐27% and 8--‐14%, respectively. The potential of RAFs designed to reduce DWPA in key locations and at certain scales will be proposed based on the findings of the PhD study.

Chemical compounds are ubiquitous in the aquatic environment, causing numerous negative impacts and raising concern over human health and the environment. The principal elimination process is microbial degradation, the prediction of which plays an important role in risk assessment. Current biodegradation tests are notoriously variable and not effective at characterising chemical persistence. Enhancements to existing biodegradation tests have been proposed to enable a more effective prioritisation on persistence. Several of the proposed enhancements are examined in this study, including increasing total cell numbers within tests and extending test duration. Activated sludge (AS) and marine inocula were incorporated in OCED 301B type studies with different inocula concentrations, test volumes and over extended study duration. Evolved ¹⁴CO² was captured as a measure of degradation, subsequently converted to a probability of degradation and used in the calculation of degradation descriptors. Culture-independent methods were employed to study the diversity within batch systems (PCR-DGGE and 454 sequencing). AS inocula exhibited faster rates of degradation and shorter lag phases when operated at higher cell concentrations, although the greatest impact of increased cell concentration was observed in decreased inter-replicate variation (P < 0.01). Test volume had less effect than concentration, with inter-replicate variation again the main beneficiary of the enhancement. Typically, band richness, used as a measure of diversity, increased with increasing biomass concentration. DGGE analysis also suggested greater similarity between higher cell concentration replicates. The ideal system proposed is 300 mg SS L-¹ at 0.5-1.0 L. Marine systems did not show a significant concentration or volume effect (P>0.05). A number of systems exhibited rapid degradation rates following lengthy lag phases suggesting the importance of increasing test duration in order to accurately predict environmental behaviour and fate. A major concern for a novel screening test would be to underestimate persistency and approve chemicals which could pose a significant threat to the environment. Chemical validation studies using a set of recognised reference compounds of varying persistence showed no false positives in the enhanced screening test.

Pharmaceutical and personal care products (PPCPs) are emerging pollutants because they might cause adverse effects in aquatic ecosystems and humans since they are polar, refractory and persistent chemicals. PPCPs are detected in aquatic environment at low concentration after secondary wastewater treatment processes (WWTPs), indicating that the conventional WWTPs are ineffective in removing PPCPs. Therefore an innovative treatment technology is required for effective treatment. Titanium dioxide (TiO2) is one of the most appropriate treatments to remove PPCPs. However the low adsorption and initial efficiency of TiO2 limit the removal rate of PPCPs. Moreover, TiO2 treatment required additional separation process for powdery TiO2 photocatalyst and recycling process of the treated water. In order to overcome identified limitations, TiO2 has been synthesized with various types of absorbents. Coconut shell powder which can act as a support of TiO2 was used as absorbent precursor in this thesis. This thesis begins with a methodology for preparing novel TiO2 with CocoNut Shell Powder (TCNSP) composite by the semi-AMPL process to produce granulation. The proposed methodology provides novel TCNSP composite with great crush strength and produces a sufficient mass quantity for commercialization. Crystallinity, morphology, crush strength and BET specific surface area of the novel TCNSP composite are controlled by the mixing ratio of TiO2 sol and coconut shell powder loading amount. It also presents the study of removal efficiency on three selected PPCP using TCNSP composite. The kinetic parameters for each target compounds-TCNSP composite pair were determined using the fixed bed reactor coupled with circulative flow mode approach based on the Langmuir-Hinshelwood model. Kinetic parameters were used as input for modeling using Response Surface Method (RSM) design called Central Composite design (CCD). Finally the performances of TCNSP composite for mineralization, comparison, and recycling test were evaluated with four different types of media. Results showed that TCNSP composite had around 99% of removal efficiency, whereas, commercial TiO2 beads, pure TiO2 pellets and CNSP pellets showed around Results showed that TCNSP composite had around 99% of removal efficiency, whereas, commercial TiO2 beads, pure TiO2 pellets and CNSP pellets showed around 30% of removal efficiency of carbamazepine at 60min reaction time. For industrial practice, electrical energy consumption was also calculated. The novel TCNSP composite can be valuable for the treatment of PPCPs wastewater and the reuse of treated water.

Conventional water purification and disinfection generally involve potential hazardous substances, some of which known to be carcinogenic in nature. Titanium dioxide photocatalytic processes provide an effective route to destroy hazardous organic contaminants and bacteria, being operational in the UV domain with a potential application in the use of solar radiation. This work explores the possibility of the removal of organic pollutants and microbial contaminant by the application of TiO2 based photocatalysts. The production of series of metal ions doped or undoped TiO2 were carried out by sol gel method and wet impregnation method. Photoreactivity tests were carried out in a solar box with two UVA lamps. The photodegration of phenol and photodisinfection of E. coli in aquatic solution were selected as probe as a measure of photoreactivity. It is found that none of the doped TiO2 show any improvement compared with undoped TiO2 towards phenol degradation. In contrast, Cu doped TiO2 exhibits enhanced results from E. coli photodisinfection. The material properties of prepared photocatalysts were characterized in an attempt to understand the relation among preparation parameters (calcination temperature, the variations of dopant and the level of doping, etc.), material properties and the final photoactvity. The structural characterization includes Brunauer, Emmett and Teller (BET) method, X-ray diffraction (XRD), Scanning Electron Microscope (SEM) and X-ray Photoelectron Spectroscopy (XPS). Some field simulation experiments are also included in this research. The results of which proved TiO2 based photocatalytic process to be a promising alternative in the future application in water disinfection and degradation, especially in those tropical developing countries with abundant of solar irradiation and insufficient water sanitation. In the last part of this PhD work, a continuous flow photoreactor was designed. The effectiveness of the system was tested and fitted to mathematical models to describe the bacterial disinfection rate.

Natural organic matter, or NOM presents a treatment challenge to the conventional water treatment process and has been associated with the formation of disinfection by-products (DBP’s) such as Tri-halomethanes (THM’s) if not removed prior to the disinfection stage. Poor removal of NOM is also thought to lead to filter performance problems such as turbidity or particle count breakthrough, which represents an increased risk of passage of Cryptosporidium into the treated water. Understanding the complex nature of NOM floc and how its physico-chemical properties relate to the coagulation matrix within the water treatment process is therefore key to optimising NOM removal. This forms the basis of the study which was carried out entirely using a natural raw moorland source water, which is preferable over synthetic kaolin based systems. The experimental programme encompassed both bench-scale and pilot-scale tests, and investigated the effect of changes to a number of variables such as coagulant type, coagulation pH and Fe:DOC ratio on floc physico-chemical properties. The approach taken in this work, of monitoring NOM removal alongside floc properties obtained from the optical flocculation monitor revealed some key trends. Firstly under equivalent shear conditions the coagulant dose almost always correlated with the steady-state maximum floc size, and influenced the flocculation rate. Generally the ferric based systems with the largest and fastest forming floc correlated with the best NOM removal, but when the applied Fe:DOC range was narrow and within an optimal range it was difficult to pin-point the best dose. The organic coagulants polyDADMAC and Zetag 64 formed larger, amd more reversible floc than the ferric based systems but with poor NOM removal. Secondly under equivalent shear conditions the larger flocs exhibited the least resistance to breakage, regardless of the coagulant system. Finally with regard to floc physico-chemical properties and filter performance, some key trends were revealed. Zeta potential influenced both NOM removal and the filtered water quality with considerable improvement noted as the charge tended towards 0 mV, and poor performance in the form of breakthrough as the charge decreased to <-10 mV or >4 mV. Flocculant dosing prior to filtration increased floc reformation and prevented breakthrough when charge destabilisation was sub-optimal, and could prove a useful strategy to employ when experiencing challenging winter conditions.

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Continuously increasing water demand in various sectors is intensifying the water scarcity problem particularly in arid and semi-arid regions like Oman. In many areas of the Sultanate, demand for water far exceeds its current availability. This presents logistical challenges in overcoming this situation or at least keeping the water deficit as low as possible. In Oman, most of the readily accessible fresh groundwater resources have already been extensively developed in order to attempt to meet the increasing demand for water, and any further intensification of groundwater abstraction is therefore not sustainable. Attention has therefore turned to desalination of sea water to supplement the available groundwater resources. Desalination is expensive and energy intensive; hence it cannot realistically be the sole source of drinking water in Oman. Rather, a conjunctive use of groundwater and desalination optimally operated to meet water demands while ensuring the sustainability of the groundwater resources is the best option. Thus, a numerical simulation model of Ash Sharqiyah Sands Aquifer was developed in this study and used to assess the long-term impacts on piezometric heads of supplying the eight Wilayats of Ash Sharqiyah Region with water from the 29 operational wells located in two regional groundwater fields- the Jaalan and the Al Kamil. The simulation results showed that the existing provision from the two wellfields will be inadequate by the 1st of September 2025 to meet domestic water supply needs without creating excessive drawdown and the cessation of flow in some of the existing operational Aflaj, which are artificial, surface channels that tap and convey by gravity groundwater for diversion into various uses along its route. Supplementing the abstraction from the wellfields with the more costly desalinated water of the Sur Desalination Plant offers the prospect for combating the problem; consequently, a constrained optimization problem was formulated to find the least cost blending of groundwater and desalinated water to meet demands while satisfying various constraints including the need to maintain Aflaj flow. The optimisation revealed increasing contribution of desalination to future total water supply for the Region, as desalination water replaces pumping from wells that affect Aflaj flow, with implications for the project cost. However, significant reduction in the long-term total production cost was achieved by increasing up to 50% the existing pump capacity at the Jaalan, made possible because its associated Aflaj are located upstream of the wellfield and are hence only minimally affected by the current abstractions.