This dissertation addresses the role of individual fouling mechanisms on productivity decline and solute mass transport in nanofiltration (NF) of surface waters. Fouling mechanisms as well as solute mass transport mechanisms and capabilities must be understood if NF of surface waters is to be successful. Nanofiltration of surface waters was evaluated at pilot-scale in conjunction with advanced pretreatment processes selected for minimization of nanofilter fouling, which constituted several integrated membrane systems (IMSs). Membrane fouling mechanisms of concern were precipitation, adsorption, particle plugging, and attached biological growth. Fouling was addressed by addition of acid and antiscalent for control of precipitation, addition of monochloramine for control of biological growth, microfiltration (MF) or coagulation-sedimentation-filtration (CSF) for control of particle plugging, and in-line coagulation-microfiltration (C/MF) or CSF for control of organic adsorption. Surface water solutes of concern included organic solutes, pathogens, and taste and odor compounds. Solute mass transport was addressed by evaluation of total organic carbon (TOC), Bacillus subtilis endospores, gesomin (G), 2-methlyisoborneol (MIB), and threshold odor number (TON). This evaluation included modeling to determine the role of diffusion in solute mass transport including assessment of the homogeneous solution diffusion equation. A cellulose acetate (CA) NF was less susceptible to fouling than two polyamide (PA) NFs. NF fouling was minimized by the addition of monochloramine, lower flux, lower recovery, and with the use of a coagulant-based pretreatment (C/MF or CSF). NF surface characterization showed that the low fouling CA film was less rough and less negatively charged than the PA films. Thus the theory that a more negatively charged surface would incur less adsorptive fouling, due to charge repulsion, was not observed for these tests. The rougher surface of the PA films may have increased the number of sites for adsorption and offset the charge repulsion benefits of the negatively charged surface. The addition of monochloramine significantly reduced biodegradation and integrity loss of the CA membrane. PA membranes are inherently not biologically degradable due to their chemical structure. Monochloramination reduced the rate of fouling of the PA membrane but resulted in a gradual increase in water mass transfer coefficient and a decrease in TDS rejection over time, which indicated damage and loss of integrity of the PA membrane. Based on surface characterization by X-ray Photoelectron Spectroscopy (XPS) and Fourier Transform Infrared Spectrometry (FTIR), the PA membrane degradation appeared to be chemically-based and initiated with chlorination of amide nitrogen and/or aromatic rings, which ultimately resulted in disruption of membrane chemical structures. The recommended Integrated Membrane System to control fouling of a surface water nanofiltration system is CSF monochloramine/acid/antiscalent„³monochloramine-tolerant NF. This IMS, at low flux and recovery, operated with no discernable fouling and is comparable to a groundwater nanofiltration plant with cleaning frequencies of once per six months or longer. A significant portion of the organic solutes including total organic carbon (TOC) passing through the membranes was diffusion controlled. Permeate concentration increased with increasing recovery and with decreasing flux for both PA and CA membranes. The influence was diminished for the PA membrane, due to its high rejection capabilities. Total rejection of spores used as pathogen surrogates was not achieved as spores were indigenous and high spore concentrations were used in all challenge studies; however, Integrated Membrane System spore rejection exceeded credited regulatory rejection of similar sized microorganisms by conventional treatment by several logs. Spore rejection varied by NF but only slightly by MF as size-exclusion controlled. There was no difference among spore rejection of IMS with and without in-line coagulation. Consequently, these results indicate membrane configuration (Hollow fiber>Spiral Wound) and membrane film (Composite Thin Film>CA) significantly affected spore rejection. Geosmin and methylisoborneol have molecular weights of 182 and 168 respectively, and are byproducts of algal blooms, which commonly increase taste and odor as measured by the threshold odor number (TON) in drinking water. Although these molecules are neutral and were thought to pass through NFs, challenge testing of IMS unit operations found that significant removal of TON, G and MIB was achieved by membrane processes, which was far superior to conventional processes. A CA NF consistently removed 35 to 50 percent of TON, MIB, and G, but did not achieve compliance with the TON standard of 3 units. A PA NF provided over 99 percent removal of MIB and G. Challenge tests using MIB and G indicated that size-exclusion controlled mass transfer of these compounds in NF membranes.

The expanding urbanisation, growing population, and industrial development are threatening global surface water quality. With increasing concern about surface-water quality, it is crucial to deeply understand the evolution of surface-water quality problems and comprehensively de-termine its fundamental driving forces. In this Dissertation, systematic work on the mechanisms of water pollution with trace elements has been carried out in three steps: i) to identify the sources contributing to surface water pollution by receptor-based models, ii) to determine the factors dominating the pollution risk transmission from sources to surface water by a source-based model, and iii) to capture the primary driving forces to the spatiotemporal variation in surface water pollution by Bayesian-based approaches. The following specific topics were ad-dressed based on five publications: a) The temporal trends of trace metal pollution in the surface water were characterised by the Mann-Kendall test and the Generalised Additive Model. b) The primary source contributors to the long-term trace metal pollution in a river system were determined by the Self-organised Map, Positive Matrix Factorization receptor model, and Bayesian multivariate receptor model. The distributions of the source contributions to trace metal pollution were estimated. c) The risk transmission of trace pollutants in the surface water was estimated by a source-based dynamic model. The sensitivities of the risk to human activities, characteristics of wastewater treatment plants, and river flow regimes were evaluated. d) The contributions of hydro-chemical factors, climate impact, and sampling methods to water pollution and data uncertainty were analysed by the Wavelet Analysis and Bayesian Net-work. Both the models’ accuracy and robustness were evaluated by statistical analysis. The methods and results provided herein could improve the standard of statistical rigour and support the authorities’ decision-making.

The movement and distribution of elephants can be influenced by environmental factors over time (Foley, 2002). Examining how features in the landscape such as vegetation productivity, water sources and anthropogenic activities drive the movement of elephants can help in understanding patterns of movement. It can also help to inform the establishment and alignment of protected areas, wildlife corridors and identification of tourism hotspots as well as policy interventions to manage Human-Elephant Conflict (HEC). The Okavango Panhandle in Botswana is a HEC hotspot and the focus of My study. A number of strategies to address HEC are underway in the area, however one longer term strategy that has been proposed in this area involves provision of artificial water sources to influence elephant movements and keep animals away from fields during the cropping season. However, an improved understanding of how elephants utilize their habitats in relation to natural ephemeral surface water and other factors that influence their movements from dryland habitats to the Okavango Delta resources is needed to inform such management decisions. My study seeks to establish the role of ephemeral surface water on elephant distribution in the eastern Okavango Panhandle, Botswana as well as assess the movement distribution of elephants in relation to the seasonality, proximity and spatial extent of water presence represented by ephemeral surface water. Time series analysis of water extent on ephemeral surface water of the eastern Okavango panhandle will be developed and overlaid with elephant movement datasets. Elephant collar data from 15 elephants (5 males and 10 females) in the eastern Okavango Panhandle, Botswana have been analysed and Home Range (HR) sizes estimated using Kernel Density Estimation (KDE). The relative importance/probability of environmental variables in determining elephants' movement based on the Utilization Distribution (UD) were computed using Generalized Linear Mixed Models (GLMMs). I utilized a remote sensing spectral index, namely the Automated Water Extraction Index (AWEI) to delineate ephemeral surface water in dryland (excluding permanent waters) of the study area. The results reveal that during the wet season, elephants were evenly spread out all over the study area until the early dry season (April-June) when the ephemeral waterholes dried up. Elephants moved southwards towards the permanent waters of the Okavango River, where there are many human settlements and farms. Male HR sizes were found to be bigger than those of female elephants. Wet season (early and late) home range sizes were also bigger when compared to dry season (early and late) HR size. Mean daily distances were computed to investigate the effect of season on elephant daily distances and the distances ranged between 5km and 6.8km in the late wet and in the early wet and late dry season respectively. The Resource Selection Function (RSF) analysis shows that water adjacent sites are preferred over distant ones and both sexes prefer areas with high NDVI, with this preference being more pronounced in males. The seasonal variation of water use is notable in that it affirms the importance of proximity to water for elephants and has implications for their management and HEC. For example, I found that ephemeral surface water has a significant role in influencing elephant spatial use in the area, particularly during the early and late wet season. As ephemeral pans dried and NDVI (vegetation greenness) decreased, elephants started to move closer to the Okavango Delta and consequently human settlements and fields. However, further investigations into the timing of movements away from ephemeral waterholes and the influence of other environmental factors on elephant movements in the area would be needed before any recommendations can be made regarding artificial water provision in this area.

Chemical disinfection is the cornerstone of safe drinking water. However, the use of chemical disinfection results in the unintentional formation of disinfection by-products (DBPs), an outcome of reactions between the disinfectant and natural organic matter (NOM) present in the native (raw) water. DBPs are suspected carcinogens, and as such, have been regulated by the U.S. Environmental Protection Agency (USEPA) under the Safe Drinking Water Act (SDWA). This document reports the results of a study that investigated the use of chlorine dioxide pre-oxidation for the reduction of DBP precursors, and subsequently, DBP formation potential (FP). To determine the effectiveness of the chlorine dioxide pre-oxidation process, two surface waters were studied: raw water from Lake Claire (Orlando, FL) and raw water from the East Maui Watershed (Makawao, HI). Lake Claire water contains approximately 11-12 mg/L of NOM and 35 mg/L as CaCO3 of alkalinity, while the Maui source water typically ranges between 7-8 mg/L of NOM with 2-10 mg/L as CaCO3 of alkalinity. Two chlorine dioxide doses were investigated (0.75 mg/L and 1.5 mg/L) and compared to a control to quantify the effectiveness of this advanced pre-treatment oxidation process. Water collected at each site was subject to the following treatment process: oxidation, coagulation, flocculation, sedimentation, ultrafiltration, and disinfection with free chlorine. Disinfection by-product formation potential (DBPFP) analysis showed that ClO2 pre-oxidation, in general, increased the 7-day DBPFP of the East Maui water, and decreased the 7-day DBPFP of the Lake Claire source water. For the Lake Claire water at the higher ClO2 dose, total trihalomethanes (TTHM) were decreased by 37 percent and the five regulated haloacetic acids (HAA5) by 23 percent. For the East Maui source water at the higher ClO2 dose, TTHM’s were increased by 53 percent and HAA5’s by 60 percent. Future research should determine the effect of alkalinity on DBPFP, which could be the reason why chlorine dioxide pre-oxidation caused one water source’s DBPFP to decrease and the other to increase.

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