Introduction Run-off from Johannesburg mine dumps is a source of environmental pollution and a public health concern. This study focussed on assessing and developing remediation strategies for Manuel Street Park (MSP) that has been affected by run-off from the Princess Mine dump. Study objectives were threefold: to use a survey involving residents living around MSP to determine community use and perception of rehabilitation of the Park; to determine the impact of the addition of a preparation known as “Effective Micro-organisms” (EM®) to polluted Park soil and; to prepare a remediation plan for this Park. Methodology A qualitative survey was conducted amongst users of the park as to their use and perceptions of rehabilitation of the park and their understanding of mine-related pollution and acid mine drainage. Controlled greenhouse trials were conducted to determine optimal germination and growth of Pennisetum clandestinum (Kikuyu grass) in Park soil, with and without EM® or compost. A landscaper was consulted to collate research results to facilitate park rehabilitation. Results Survey participants understood the risks of Acid Mine Drainage (AMD) and other mine pollution and gave valuable information which assisted in understanding local issues concerning the park. Tests with soil polluted with AMD showed that it promoted seed germination while treatment of park soil with fertiliser, compost and enhanced microorganisms improved plant development and growth. Practically, it was determined that the use of EM1 at the park would be difficult because of on-going flooding of the park with contaminated water. For this reason, an improved drainage plan was suggested, along with raised walkways. Conclusion A remediation plan can be implemented on site involving installation of French drains, raised walkways, and soil remediation involving EM® / Agriculture, Animal Health and Human Ecology / M. Sc. (Environmental Management Ornamental Horticulture)

M.Sc. (Aquatic Health) / Wetlands play an extremely important role in the hydrological cycle as well as biodiversity. Until recently, however, wetlands in South Africa have been neglected both in terms of research and monitoring. The lack of knowledge is even greater for the inward draining wetlands, which is better known as pans. Pans are isolated aquatic systems, which are quite shallow and do not have an outlet. Pans receive water from precipitation and surface runoff, and lose water mainly through evaporation. Some pans can be ephemeral (dry up often) and other perennial (dry up only during drought). The little ecological knowledge available is mainly focused on these ephemeral pans. In this present study conducted in the Western Free-State province, study was only focused on the perennial pans in this area. Due to the fact that this province are one of the biggest areas for gold mining in the country, the pans suffer under the impacts, and this results in the alteration of community structures in and around the pan, simplifying food chains which can lead to the collapse of an ecosystem. The aim of the study was to assess the water quality, bioaccumulation of toxicants (metals and pesticides) in sediment and aquatic invertebrate community of perennial pans in the Western Free State Province, mainly because of the lack of literature on pans in these areas. Seventeen pans were selected for the study of which eight were classified as saline eutrophic and nine as alkaline dystrophic. Various physico-chemical and sediment characteristics were assessed in addition to the characterization of the aquatic invertebrate communities. It became clear that there is great difference in the physical-chemical characteristics of the selected pans. The difference in the trophic state was the most clear, with differences in water colour, nutrient concentration and vegetation growth, classifying pans as either saline eutrophic or alkaline dystrophic. These trophic states influence the distribution and richness of aquatic invertebrates in certain pans. Mining activity, urbanization, agricultural activities and sewage runoff into the pan, all affects the pans negatively, there is sighs of water quality degradation as well as changes in the community structure of invertebrates when compared to the reference pans.

Submitted in partial fulfillment for the Degree of Master of Applied Sciences in Biotechnology, Durban University of Technology, Durban, South Africa, 2017. / The study aims to assess and compare the concentration of microbial contaminants, their sources and distribution in surface water and sediment, and to determine the impact of seasonal variations and corresponding risks of faecal contamination using conventional and molecular methods. Historical data analysis was conducted using E. coli values from the eThekwini Water and Sanitation (EWS) department for 66 months (2009-2014). E. coli and Enterococci were analysed in surface water and sediment samples using the mFC/ spread plate and Colilert-18 (IDEXX) methods. The impact of seasonal variations was assessed using E. coli and Enterococci data collected during rainfall and no rainfall events, using an auto-sampler and sediment trap in parallel. Conventional standard membrane filtration methods using mFC agar, Slanetz & Bartley/ Bile Esculin and Brilliance E. coli selective agar were compared to the enzymatic Colilert-18 and Enterolert (IDEXX) test methods along the Isipingo and Palmiet Rivers. In addition, comparison of the analytical performance of droplet digital PCR (ddPCR) and qPCR for the detection of Salmonella targeting ttr gene in river sediment samples collected from the four sites of the Palmiet River in Durban, South Africa was done. In order to assess the public health risk associated with exposure of men, women and children to microbial pathogens in polluted surface water during recreational activities, the QMRA tool was employed in relation to the risk exposure to pathogenic E. coli, Campylobacter, Salmonella and Shigella. Also, the risk associated with crop irrigation (on farmers) as well as the consumption of crops irrigated with surface water from the Isipingo river was determined. Analysis of the historical data gave a baseline of the two rivers of interest, thus helps understand the current situation of the rivers enabling researchers to pick up potential gaps. In this study after the analysis of the historical data it was evident that at the Palmiet river, microbial analysis must be conducted around the QRI settlements which is a major pollution source. Also, from this study it was found that sampling points situated close to wastewater treatment plants, pump stations or informal settlements were of major concern, thus were considered for the study. It was found that sediment exhibited higher microbial concentrations than surface water, which was observed in both rivers. Also, rainfall had a significant impact on microbial variability. Higher microbial concentrations (indicator organisms) were observed in surface water after a heavy rainfall as appose to when there was no rainfall. This was due to contamination that is washed off into the river and sediment resuspension. Methodology comparison revealed that Colilert-18 and Brilliance E. coli were more selective compared to mFC agar. Brilliance E. coli /Coliform agar was comparable with Colilert-18 IDEXX, which was also observed with Slanetz & Bartley and Enterolert IDEXX. However, when mFC agar was compared with Colilert-18 IDEXX, significant difference was observed. In comparison of two Molecular methods, ddPCR were found to be fully amenable for the quantification of Salmonella and offer robust, accurate, high-throughput, affordable and more sensitive quantitation than qPCR in complex environmental samples like sediments. Quantitative Microbial Risk Assessment (QMRA) relating to recreational and occupational exposure showed that children were at the highest risk of getting infected. Also, it was observed that the probability of infection upon exposure to surface water from the Isipingo and Palmiet rivers was significantly high, hence exceeded the WHO guidelines values. Risk assessment on crops revealed that pathogenic bacteria may pose a risk to the consumer, however, a 9-log reduction may be achieved according to the WHO multi-barrier approach which involves proper washing and proper cooking of the crop before ingestion. Overall the sampling points that had the highest pollution level and constantly exceeded the WHO and DWAF guidelines at the Isipingo river were the points situated and named “Next to the WWTP”, and “Downstream of QRI” at the Palmiet River. / M

M.Sc. / Please refer to full text to view abstract

Ph.D. (Zoology) / Please refer to full text to view abstract

M.Sc. / The water quality monitoring project undertaken on the Blyde River in Pilgrim's Rest and surrounding area, provided information on various parameters. These included the macro variables (pH, temperature, conductivity, dissolved oxygen concentration, oxygen saturation percentage and turbidity), micro variables (ionic and metal concentrations) and fauna (fish and invertebrates). Field and experimental data were integrated to form a realistic and representative picture of the general state of health of the Blyde River. The macro variables (pH, temperature, conductivity, dissolved oxygen concentration, oxygen saturation percentage and turbidity) were all within the guideline limits as provided by the Department of Water Affairs and Forestry. The ionic concentrations (calcium, magnesium, sodium, chloride and nitrate) were acceptable and conformed to guideline values. The aquatic macro-invertebrate and habitat quality survey indicated that most of the sampling sites could be described as good. Sampling site 2 (next to reduction works) was classified as poor. This is the result of mining activity at this specific site situated at the rock dump at Peach Tree Creek. The extensive disturbance of the habitat is the result of 130 years of mining activities. The metal concentrations in the Blyde River exceeded the guideline limits, except for manganese. Aluminium toxicity is pH dependent, and increases with a decrease in the pH. The alkaline pH in the Blyde River acts as a buffer against the aluminium toxicity. The lead concentration in the Blyde River exceeded the Department of Water Affairs and Forestry guideline limit. Lead is hazardous to most forms of life. Zinc is toxic to fish and aquatic organisms at relatively low concentrations. Although nickel is a natural element of the earth and water, mining activities cause nickel emissions and an increase in the nickel concentrations in water systems. Copper is regarded as a highly toxic metal if present in high concentrations. Iron is not easily absorbed by aquatic organisms and because of its limited toxicity and bioavailability, described as a noncritical element. Chromium is biologically inert. Despite of a lack of information on the concentrations of metals in the Blyde River before the onset of mining activities at Pilgrim's Rest, it is clear that the extensive disturbance of the habitat at Peach Tree Creek and Vaalhoek, and to a lesser extent at Delvers' Creek exists. Present and past mining activities in the Pilgrim's Rest area resulted in the deterioration of the water quality in the Blyde River. Rehabilitation of the area around the rock dump at Peach Tree Creek will have to be done to prevent seepage from the rock dump and disturbed area to the river. Measures, such as the construction of paddocks and berm walls to collect seepage before it reaches the river, will have to be implemented. The water will then have to be treated before releasing it into the river. The acute, sub-lethal toxicity tests with nickel and lead were conducted based on the concentrations as derived from water samples taken from the Blyde River, during the monitoring phase of the project. The results of the blood physiological experimentation indicated that normal physiological functioning were disturbed when fish were exposed to sub-lethal concentrations of lead and nickel. Results indicated that stimulation of the immune system, osmotic stress and hypoxic conditions arise after lead and nickel exposure. Hypoxia arises because of a deficiency in the amount of oxygen reaching bodily tissues. Osmotic stress is a result of affected gill and kidney functioning. The metabolic variables indicated that the metabolism of trout was affected, because of stress associated with metal exposure. The nervous system functioning was also, affected, as derived from the enzymatic variables. Taking these factors into consideration, the normal functioning and survival of rainbow trout (Oncorhynchus mykiss) is hindered. The acute, lethal toxicity tests of nickel on rainbow trout (Oncorhynchus mykiss) and chubby head barb (Barbus anoplus) were performed using nickel concentrations as determined in the Blyde River. The 100% mortalities recorded, when exposing the fish to these concentrations, indicated that the Blyde River provides a buffer action against the toxic effect of nickel on the aquatic organisms. Should this buffer action be disturbed, for instance a sudden drop in water pH, the toxicity of nickel will increase and have detrimental effects on the aquatic organisms. Further deterioration of the water quality in the Blyde River should be avoided at all cost. Large scale yellow fish (Barbus marequensis) were only found at sites below sampling site no 8, which is alarming and a further confirmation of habitat degradation. To prevent further degradation of the water quality in the Blyde River annual biomonitoring in conjunction with experimental studies are suggested to obtain information, which enables effective managerial decision making. Measurements should be taken to reduce the impacts of mining and agricultural activities, if future studies indicate further water quality degradation. Objectives regarding the health of the aquatic environment should be set and actions taken to prevent the impactors from doing further harm. The Pilgrim's Rest area can be developed for Eco-tourism, and therefore the aim should be to create awareness of the river and its surroundings and involve people in the conservation thereof.

This thesis is based on a case study of the degraded Boksburg Lake social-ecological system and an environmental education initiative that aimed to support its transformation. This initiative aimed to involve local people in reclaiming the lake’s social and ecological value, through a process of collectively reimagining possibilities, shaping identities, gaining knowledge and developing local human agency. The focus was on social learning processes in schools and churches to explore opportunities for co-engaged reflexivity that might produce transformation. Schools and Christian churches, two institutions that reflect modern, western socialecological worldviews also have the potential to bring about change. Critical Realism was chosen as my philosophical framework as it provided the tools to explore deeper mechanisms beyond empirical reality, both influencing the degrading trajectory as well as providing possibilities for transformation. It also legitimised case study research as a means to understand more generalised processes characterising modern social-ecological systems. The choice of Critical Realism informed the scope of my primary research question: What generative mechanisms constrain and enable the development of social-ecological resilience for well-being, in the modern social-ecological system of Boksburg Lake? The following three goals were formulated to address this primary question. Goal 1: Based on a multitheoretical perspective of social-ecological literature, develop conceptual tools that have explanatory power to probe generative mechanisms operating in the Boksburg Lake social-ecological system. Goal 2: Identify generative mechanisms driving the current degradation of the Boksburg Lake social-ecological system. Goal 3: Identify learning mechanisms that support transformation for greater social-ecological resilience of the Boksburg Lake social-ecological system. By addressing the primary question and research goals I aimed to gain insights into modern global socialecological systems, the mechanisms that drive high social-ecological risk and the requirements for and possibilities of global systemic change. Drawing on a broad reading of social-ecological literature from different vantage points, tools with explanatory power were developed to probe for generative mechanisms in the Boksburg Lake social-ecological system (goal 1). The human capacity for symbolic representation is identified as an emergent property of coevolving human-ecological systems. These symbolic representations become expressed in culture and worldviews, and influence patterns of identifying, types of knowledge and forms of agency. The nature of these will determine the degree that cultural systems are embedded within ecological reality and the extent of cultural-ecological coupling. A cultural system closely coupled with ecological realities is likely to value ecological systems and manage them for their health, while less coupled cultural-ecological systems are likely to lead to the opposite. Because of their integrated nature, the extent of ecological health and value will affect the decline or sustainability of cultural-ecological systems. There are numerous examples of the learning that can take place when cultural-ecological systems are facing decline. This learning can enhance or reduce biophyllic instincts that become encoded in patterns of identifying, types of knowledge and forms of agency. This in turn affects the strength of cultural-ecological coupling and the extent that human societies co-evolve with ecological systems. / Normalising ideologies is a concept coined in the thesis to refer to symbolic representations of reality that have become integral to a social fabric and determine meaning, while maintaining the domination of the powerful. These ideologies determine patterns of identifying, knowledge and agency and are recognised as having a fundamental influence on the resilience of social-ecological systems. Four normalising ideologies are identified that promote apparent human progress at the expense of ecological integrity and social equality and thus alienation with each other and the ecological world. These are human-ecological dualism, anthropocentrism, nature is mechanised and nature is to be controlled. There are also a number of ideologies promoting connectedness with the ecological world that, if they became normalised, would support greater social-ecological resilience for well-being. Generative mechanisms driving the current degradation of the Boksburg Lake socialecological system were identified (goal 2). Drawing on critical methodology, the main method adopted was document analysis of the Boksburg Advertiser archives, Boksburg’s local newspaper. Four generative mechanisms are recognised as most influential. Two of these have been named hegemonic symbolic systems. The primary symbolic system consists of the four normalising ideologies, mentioned above, that promote human progress at the expense of ecological health. The secondary, more explicit symbolic system, built on this, consists of the following normative ideologies: economic growth is imperative, unrestrained development is promoted, competition is the necessary means and consumerism is the good life. These two symbolic systems have had causal influence on the systematic erosion of ecological processes and biological diversity that has occurred in Boksburg, with the consequent undermining of social-ecological resilience for well-being. The third mechanism that constrains resilience is the power dynamics that have shaped Boksburg’s economic history and social-ecological system. This has resulted in a society built on inequality and injustice with all its associated social and environmental ills, expressed as externalities. The fourth mechanism resides in Boksburg’s political and municipal dynamics. These structures are not designed to tackle complex social-ecological problems and they hold considerable agential power, yet seem dysfunctional at present. Learning mechanisms that support transformation for greater social-ecological resilience of the Boksburg Lake social-ecological system were identified (goal 3). By adopting the role of a reflexive practitioner, supported by action research, case study and interpretivist methodologies, data on the empirical manifestations of the environmental educational initiative were collected. Methods included semistructured interviews, focus groups, document analysis and participant observation. Findings indicate that schools and churches are important institutions that can positively influence patterns of identifying, knowledge about and agency for Boksburg Lake and can thus play a role in transforming hegemonic normalising ideologies. Important learning mechanisms identified included: Learning reflexively together within communities of practice that provide opportunities for active rather than passive learning; involving the youth as they are a group of people with notable enthusiasm, vision, energy and motivation; learning through information acquisition, investigation, action and deliberation; learning about abstract concepts and theoretical knowledge but embedding this in local realities; and learning that provides reference markers for how things can be different.

M.Sc. / The evaluation of population exposure to air pollution is a fundamental reason for management and control of regional air quality. The purpose of this study was to determine the exposure of the local population to PM-10 emissions from sources within the Vaal Triangle using a Geographic Information System (GIS). The emission inventory compiled by van Nierop for the calendar year of 1992 (van Nierop, 1994) was used as input data for these calculations. The Industrial Source Complex Short Term Model (ISCST) was applied for dispersion calculations of annual PM-10 emissions. The ReGIS package was applied to determine the applicability of GIS as a management tool. Annual average PM-10 concentration contours were calculated for the different air pollution source groups within the Vaal Triangle. The combined source group resulted in the highest population exposure from annual average PM-10 concentrations. Population exposure from high- (> 200 m), medium- (10 to 200 m) and low- (< 10 m) elevation air pollution source groups were determined. The medium-elevation source group resulted in high population exposure followed by the low-elevation source group. The high-elevation source group had very low population exposure as a result. The population exposures from all the industrial sources within the Vaal Triangle were calculated and found to be very high. Annual average PM-10 concentrations from domestic fuel combustion sources were surprisingly low, resulting in low population exposure. ReGIS was found to be inadequate for the task and is not recommended for further use. Despite this, GIS was found to be a powerful decision-making tool and other GIS software packages should be explored for future research.

MPH / Department of Public Health

Department of Ecology and Resource Management / PhDENV / Groundwater has traditionally been perceived to be low in chemical species toxicity and microbiologically 'pure'. However, depending on the geological chemistry, formations and anthropogenic activities creating the frequent occurrence of microbiological contamination and excess toxic chemical constituents, the high quality of groundwater as a drinking water source can easily be compromised rendering it unsafe, thus, leading to severe waterborne epidemics. The rapid increase in fluoride and microbial contamination of groundwater have become a global problem to human health. Fluoride in its acceptable concentration in drinking water (< 1.5 mg/L); is known to be beneficial for human growth and development but becomes detrimental at higher concentrations (> 1.5 mg/L) leading to the prevalence of dental and crippling skeletal fluorosis. On the other hand, consumption of microbiologically contaminated water has led to many types of diseases including diarrhea, cholera, typhoid, dysentery and other serious illnesses often leading to millions of deaths annually worldwide. South Africa had experienced water-borne diseases epidemic in the recent past due to failing water treatment facilities in many parts of the country including rural areas. Fluorosis, diarrhea, and cholera are among the chronic health hazards affecting a large population in South Africa. Continuous outbreaks of water-related diseases have been at an unimaginable high level with a reported increase in death rate. The inefficiency of conventional water treatment plants to remove fluoride and disinfect these pathogens from the contaminated domestic and rural community has led to the development of many techniques. These include membrane filtration, ion-exchange, coagulation-precipitation, adsorption among others of which adsorption process proves to be a more significant technology for fluoride removal. Equally, the emergence of nanomaterials has also proved to be the natural answer to solve problems associated with microbes in water since these are absolute barriers to pathogens whose size exceeds most sorbent pore sizes. Also, materials from natural biopolymers or biomass can be utilized at an affordable cost as effective sorbent material for toxic chemical ions and pathogens removal from contaminated water. Consequently, extensive research works have been channeled into the development of more advanced low cost sustainable functionalized sorbent materials and technologies with multifunctional properties for effective water purification. The present study focused on the development of a functionalized chitosan-cellulose hybrid nanocomposite decorated with metal-metal oxides nanoparticles for simultaneous fluoride and microbial removal from groundwater. This was to increase the selectivity and disruption of such pollutants for effective groundwater purification technology. The thesis is presented in nine chapters: (1) General introduction, problem statement, and motivation, research objectives, hypothesis and delimitations of the research are briefly discussed, (2) This chapter gives the literature review of occurrence and sources of fluoride, various fluoride removal techniques; sources, control measures and prevention of microbial pollution in groundwater; the importance of biosynthesis of nanomaterials as emerging novel water treatment adsorbents, the strength of Point-Of-Use as a means of water treatment, water treatment adsorbents synthesis and types of adsorbents with emphasis on hydroxyapatites and biopolymeric based sorbent materials, (3) Optimization of microwave-assisted synthesis of silver nanoparticle by Citrus paradisi peel extracts and its application against pathogenic water strain, (4) Biosynthesis of ultrasonically modified Ag-MgO nanocomposite and Its potential for antimicrobial activity, (5) Green synthesis of Ag/MgO nanoparticle modified nanohydroxyapatite and its potential for defluoridation and pathogen removal in groundwater (6) Green Synthesis of AgMgOnHaP nanoparticles supported on Chitosan matrix: defluoridation and antibacterial effects in groundwater, (7) Biosynthesis of nanofibrous cellulose decorated Ag-MgO-nanohydoxyapatite composite for fluoride and bacterial removal in groundwater, (8) Defluoridation and removal of pathogens from groundwater by hybrid vi cross-linked biopolymeric matrix impregnated Ag-MgOnHaP nanocomposite (9) Conclusions and Recommendations. It is important to point out that Chapters 3 to 8 contains a collection of the research deliverables produced in forms of paper publications and manuscripts and are summarized in a systemic order of experimental protocol. This first output (Chapter 3) of this study evaluated the optimization of a time-dependent microwave-assisted biosynthesis of silver nanoparticles using aqueous peel extracts of Citrus paradisi (Grapefruit red) as a reducing, stabilizing and capping agent with emphasis on its antibacterial property. Optical, structural and morphological properties of the synthesized Citrus paradisi peel extract silver nanoparticle (CPAgNp) were characterized using UV-visible spectrophotometer, transmission electron microscope (TEM), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), Brunauer–Emmett–Teller (BET) and X-ray diffractometer (XRD). The antimicrobial activity was evaluated using the well- and disc-diffusion as well as microdilution methods. Characteristic surface plasmon resonance (SPR) wavelength in the range of 420-440 nm at an optimized intensity growth rate typical of silver nanoparticles was obtained. Microwave irradiation accelerates the reaction medium within seconds of nucleation compared to conventional heating methods of synthesis. The influence of the reaction mixtures affected the SPR patterns on the different nucleation, stability and nanoparticle growth. The mixing ratio of 2:3 (C. paradisi peel extracts: 1 mM AgNO3) was chosen as the optimum reaction mixing ratio relative to the bio-reduction intensity of SPR process contributing to the particle size growth of CPAgNps. The presence, interaction and shifting of the functional groups in the FT-IR spectra of biosynthesized CPAgNps indicated that bioactive compounds present in C. paradisi peel extract were responsible for the bio-reduction of the silver ion to silver nanoparticles. The electron micrographs of the synthesized CPAgNps showed a face-centered cubic (FCC) unit phase structure, spherically-shaped nanoparticles size of 14.84 ± 5 nm with a BET pore diameter of 14.31 nm. The use of biological material allowed the control of the size and stability of the nanoparticle but was obtained in low quantity. The Citrus paradisi peel extract mediated AgNp were found to possess a broad-spectrum antimicrobial activity against water-borne pathogenic microbes in the order: Escherichia coli > Staphylococcus aureus > Klebsiella pneumonia. In Chapter 4, a synergistic bi-layered Ag-MgO nanocomposite from Ag and MgO precursor salts using a natural source from the waste product (citrus fruits outer cover) as a reducing and capping agent was successfully synthesized by a simple rapid, integrated bio-mediated microwave and ultrasonic methods. This was carried out to investigate the interfacial interaction and the encapsulated growth rate behind their combination in obtaining an enhanced antibacterial activity against common water fecal pathogen (Escherichia coli). The growth sequence, structural and morphology interface as well as the composition of the nanocomposite were examined and evaluated by the different characterization techniques. The respective potential application as an antimicrobial agent was evaluated and compared against Escherichia coli. The bio-mediated core-shell Ag-MgO nanocomposite showed characteristic synergetic UV-visible absorption bands at 290 nm for MgO nanoparticle and at around 440 nm for Ag nanoparticle, which moved to a lower wavelength of 380 nm in the composite. The shifting to a lower wavelength confirmed the reduction in the particle size as influenced by the growth rate optical property of biomolecular capped Ag-MgO nanocomposite from the phytochemical constituents in the peel extract of the Citrus paradisi. FTIR analysis further elaborated the role of the organic moieties in the Citrus paradisi extracts acting as the capping and stabilizing agent in the formation of the core-shell Ag-MgO nanocomposite. SEM analysis revealed an agglomeration of layered clustered particles, which was poly-dispersed while XRD showed the cubical crystal lattice network phase structure of the Ag-MgO nanocomposite. The TEM micrograph vii showed a structurally uniform and spherical biosynthesized Ag-MgO nanocomposite with a diameter of about 20–100 nm with an average particle size of 11.92 nm. The bi-layered Ag-MgO nanocomposite exhibited a higher level broad-spectrum of antibacterial potential on E. coli with 22 mm zone of inhibition and MIC of 20 (μg/mL) in comparison with the Ag (9 mm; 40 μg/mL) and MgO (9 mm; 80 μg/mL) nanoparticles. The leaching and toxicity level of the time-dependent releases of metal ions indicates that the effluents contain a lower concentration of Ag and Mg ions as compared to World Health Organization permissible limit of < 100 ppb (Ag). The biosynthesized Ag-MgO nanocomposite exhibited an enhanced antibacterial activity synergistic effect against E. coli than Ag and MgO nanoparticles, thus, proving to be a potential disinfect material against common pathogens in water treatment. Chapter 5 presented the biosynthesis, characterization, and assessment of simultaneous fluoride and pathogen removal potential in aqueous solutions of a multi-layered Ag-MgO/nanohydroxyapatite (Ag-MgOnHaP) composite. The successful incorporation of Ag-MgO into nanohydroxyapatite (Ag-MgOnHaP) sorbent via an in-situ solution-gelation (sol-gel) method was ascertained from UV-visible absorption spectrum bands at 290 and 440-378 nm typical of MgO and Ag nanoparticles combination in Ag-MgOnHaP composite. FTIR analysis showed the main surface functional groups involved to be –OH, C=N, carbonate and phosphate species on the backbone of Mg-O-Mg vibrational mode. The hydroxyl and amine groups indicated the interaction of a variety of metabolites components present in citrus peel extract as bio-reductive compounds associated with the Ag-MgO and also in fluoride ion exchange. SEM, TEM images and XRD analysis showed a well-dispersed discretely embedded layered-spherical Ag-MgOnHaP nanocomposite without any form of agglomeration after ultrasound exposure ranging in size from 20 to 100 nm with an average mean particle size diameter of 16.44 nm. The high purity of the synthesized Ag-MgOnHaP nanocomposite was confirmed by the presence Ag, Mg and O impregnated on the nanohydroxyapatite template from EDS spectrum analysis. Batch sorption studies using the nanocomposite under different experimental parameters were conducted and optimized. Equilibrium fluoride adsorption capacity of 2.146 mg/g at 298 K was recorded with more than 90% fluoride removal at optimized conditions of 60 min, 10 mg/L initial F- concentration, 0.3 g/L dosage, and pH 6 at 250 rpm. pHpzc of Ag-MgOnHaP nanocomposite was established to be 8. The equilibrium data were best fitted to the Freundlich isotherm model and followed the pseudo-second-order kinetics model at room temperature. The presence of competing anions such as Cl−, NO3−, does not have an impact on percentage fluoride uptake efficiency, but SO42− and CO32− reduce the F- removal efficiency. Moreover, as the concentration of the co-anions increased, fluoride adsorption uptake decreases. The biosynthesized nanohydroxyapatite incorporated Ag/MgO nanoparticle adsorbent (Ag-MgOnHaP) showed strong antibacterial activity against Escherichia coli and Klebsiella pneumonia when compared to hydroxyapatite alone. The presence and interaction between the Ag, MgO nanoparticles with the respective bacterial genomes was suggested to have accounted for this bioactivity. The synthesized Ag-MgOnHaP sorbent was found to portray a better sorption capacity compared to other adsorbents of similar composition in the literature and could be successfully regenerated with 0.01 M NaOH with fluoride removal of 74.24% at the 4th cycle of re-use. The impregnation of metal-metal oxide nanoparticles on sustainable natural biopolymers from waste products was presented in Chapters 6, 7 and 8. The use of these sustainable natural biopolymers (chitosan and cellulose) was targeted with more emphasis on surface functionalization, improved structural diversity and improved specific surface area with the sole aim of increasing the adsorptive capacity of fluoride ions as well as antimicrobial properties. The selected polymers were chosen because of their biodegradability, viii non-toxicity, renewability, selectivity and abundance in nature, which makes them promising starting materials for the purpose of sustainable water treatment. Chapter 6 presents the successful sol-gel biosynthesis, characterization, potential application for fluoride and pathogens removal from aqueous solution using Ag-MgOnHaP embedded on a chitosan polymer backbone (AgMgOnHaP@CSn) sorbent material. The overall formation of the AgMgOnHaP@CSn nanocomposite from different surface functionalization precursors and phases were supported by the various characterization methods such as UV–vis spectroscopy, SEM-EDS, FTIR, TEM, and Brunauer–Emmett–Teller (BET) techniques. Batch fluoride sorption experiments were conducted to assess fluoride uptake efficiency through optimization of several operational parameters such as contact time, adsorbent dosage, initial pH and co-competing anions. The antimicrobial activity of the synthesized AgMgOnHaP@CSn nanocomposites was also determined. The presence and bio-reduction processes of both Ag and MgO chemical species due to the interaction and coordination of bonds within the bioactive functional species of the polymer matrix was confirmed by the emergence of a sharp peak appearing at around 290 nm to a broad plateau plasmon absorbance above 440 nm on the AgMgOnHaP@CSn nanocomposite. FTIR analysis further supported the presence of the main bioactive functional species to be –OH, –NH2 CO32−, PO43-, Mg–O-Mg amongst other groups on the material surface. SEM and TEM displayed homogeneously dispersed particles within the aggregated biopolymeric composite with a diameter ranging between 5-30 μm. Pore sizes were observed to be in the micro-mesoporous range with an average size of about 35.36 nm and a pore diameter of 33.67 nm. The optimized conditions were as follows: 30 mins contact time, a dose of 0.25 g/50 mL, adsorbate concentration of 10 mg/L F-, initial pH 7 while adsorption capacity decreases with increase in temperature. AgMgOnHaP@CSn composite has a pHpzc value of ≈ 10.6 and the maximum sorption capacity was established to be 6.86 mg/g for 100 mg/L F- concentration at 303 K. The effect of co-existing anions was observed to be of the following order: Cl- < NO3- < SO42- << CO32-. The fluoride sorption experimental data was well described by Langmuir adsorption isotherm while the sorption reaction mechanisms were diffusion-controlled and followed the pseudo-second-order sorption model. F- sorption process could best be described as a combination of ligand exchange, electrostatic attraction, and improved structural surface modification. The antimicrobial susceptibility analysis through the zone of inhibition (mean and standard deviation) showed the potency to pathogens of the following order: Staphylococcus aureus > Escherichia coli. Chapter 7 gives an insight into the development of cellulose nanofibrous matrix (isolated from saw-dust) decorated with Ag-MgO-nanohydroxyapatite (CNF-AgMgOnHaP) and its application in fluoride and pathogen removal from contaminated water. The synthesized CNF-AgMgOnHaP, unlike the cellulose nanofiber, showed characteristic absorption bands in UV–vis spectroscopy between 270-290 nm typical of MgO together with a broad band around 420 nm associated with the characteristic of silver nanoparticles. FTIR spectrometry suggested the presence of nanohydroxyapatite (nHaP) and MgO species impregnation within the CNF matrix. SEM, TEM, XRD, and EDS analysis showed a well-established structural and morphological modifications between cellulose nanofiber alone, biosynthesized CNF-AgMgOnHaP and fluoride sorbed CNF-AgMgOnHaP nanocomposite. A granulated aggregation of micro-mesoporous particles with an improved BET surface area of 160.17 m²/g was developed. Optimum fluoride sorption capacity was 8.71 mg/g for 100 mg/L F- solution at 303 K. F- sorption capacities decreased as the operating temperatures increases. Optimum F- removal of 93 % was achieved at optimum conditions established: pH 5, solid/liquid ratio of 0.25 g/ 50 mL, 10 mg/L F-, contact time 10 min, temperature 25 ± 3 °C and shaking speed of 250 rpm. Percent F- removal decreased with increasing initial adsorbate concentration. The pHpzc value of the CNF-AgMgOnHaP occurred at ≈ 4.7. Co-existing ions were observed to have an effect on the adsorption of F- in the following order: NO3- < Cl- < SO42- <<CO32-. Equilibrium fluoride sorption onto the CNF-AgMgOnHaP was best described by non-linear Freundlich isotherm model across all the operating temperatures. The linear Dubinin-Radushkevvich (D-R) model for F- sorption energies were in the 3.54 – 4.08 kJ/mol across all operating temperature. This suggested the physical adsorption mechanism processes were involved in the F- uptake by the CNF-AgMgOnHaP sorbent. The overall kinetic results indicated that the mechanisms not only depend on the pseudo-second-order process but were also governed by mass transfer of the adsorbate molecules across the CNF-AgMgOnHaP surface. The thermodynamic parameters revealed that the sorption process of F- onto CNF-AgMgOnHaP was endothermic and spontaneous at the sorbent/solution interface. The regeneration-reuse study showed that the synthesized adsorbent can be reused for a maximum of 5 adsorption-desorption cycles using Na2CO3 and NaOH as regenerants. Overall surface chemistry by XPS, FTIR, EDS as well as sorption isotherm and kinetic models analysis suggested that both physical and chemical adsorption processes were involved in the fluoride uptake by CNF-AgMgOnHaP nanocomposite. The observed zone of inhibition demonstrated that CNF-AgMgOnHaP adsorbent possesses antibacterial activity against all the bacterial strains in the following order: E. Coli > S. aureus > K. pneumonia. The antibacterial potency increased with increasing sorbent concentration. In chapter 8, Defluoridation and antimicrobial activity of synthesized cross-linked cellulose-chitosan impregnated with the developed nanomaterial (AgMgOnHap) are presented. The before and after fluoride sorption by the synthesized CECS@nHapAgMgO nanocomposites were characterized using several physical and chemical techniques which include, BET, SEM-EDS, TEM, XPS, XRD, and FTIR. The overall batch fluoride sorption processes and adsorption capacity through optimization of different experimental sorption parameters, sorption isotherms, and kinetic mechanisms as well as antibacterial potency were studied and reported. SEM and TEM analysis showed densely irregular multiple-layered structures, homogeneous deposition of the AgMgOnHaP on the polymeric matrices. Equilibrium fluoride sorption capacity on CECS@nHapAgMgO sorbents showed an increased affinity of 26.11 mg/g for 150 mg/L F- solution at 313 K.at optimized conditions of 40 min contact time, dosage of 0.3 g and pH of 5. The pH point of zero charge was found to be 7.27. The reaction pathway model sequence of fitness follows the order Pseudo first order < Elovich < Pseudo-second order kinetic model while intra-particle diffusion model and mass transfer of fluoride molecules from the external surface onto the improved pores of the adsorbent were found to be involved in the rate-controlling step. Although both non-linear Langmuir and Freundlich isotherms showed appropriate trends in the F- sorption process, the adsorption isotherm data were better fitted to the non-linear Freundlich isotherms models, suggesting stronger heterogeneous adsorption onto the active binding sites of the CECS@nHapAgMgO surface. The fluoride sorption was observed to be a favorable process across the operating temperatures. Temkin heat of sorption (BT) and the mean free adsorption energy (E) of the D-R isotherm model was within the range of 0.68-3.39 J/mol and 1.58 -7.45 kJ/mol respectively. The fluoride sorption process was observed to be temperature-dependent; while adsorption capacities (Qm) and Temkin heat of sorption (BT) increased with increasing temperature, D-R Mean free sorption energy (E) decreased at higher temperatures. The thermodynamic analysis demonstrated that fluoride sorption on the CECS@nHapAgMgO surface was exothermic, feasible and spontaneously inclined with a decrease in the degree of randomness at the sorbate-sorbent interface. The influence of co-existing anions on fluoride removal exhibited the following trend Cl−< NO3− <SO42- << CO32- <<HCO3−. The practical and economic viability, potential for regeneration showed its reusability up to 3 cycles with water and Na2CO3 as regenerants. The potential ability of CECS@nHapAgMgO to disinfect both gram- positive and gram-negative water bacterial was confirmed by the zone of inhibition and Minimum Inhibitory Concentration (MIC) measurements. The observed values showed the inhibitory efficiency in the following order: S. aureus > E. Coli > K. pneumonia where the MIC values of 20 μg/mL were recorded for S. aureus and E. Coli respectively and 10 μg/mL for K. pneumonia. Lastly, the applicability of the sorbents was tested with a field water sample collected from a high fluoride borehole water from a local village (Lephalale Municipality of Limpopo province, South Africa). The before and after analysis showed the excellent potential of CECS@nHapAgMgO sorbent in removing fluoride. In conclusion, the successful surface functionalization synthesis of these improved surface area hybrid nano-sorbents supported by the different morphological techniques was found to be effective in creating more surface-active binding sites for fluoride adsorption and disinfection of waterborne pathogens from aqueous solution. The originality of this developed sorbent lies firstly, in the ability to simultaneously remove both chemical and biological water pollutants; secondly, the use of biodegradable, eco-friendly and non-toxic abundance wastes raw materials to develop a water purification material and in solving waste management issues was a key factor towards environmental sustainability. Above all the developed materials were established to possess superior fluoride adsorption capacity when compared to other reported sorbent materials. Lastly, the project findings /innovation will contribute to Sustainable Development Goals (SDG) 3 and 6, aimed at improving clean water supply and health of the communities and the world at large. However, the following recommendations were made following the findings from this study: 1) In order to increase the surface area to volume ratio, greater selectivity, porosity, and mechanical stability of the polymers as well as size-exclusion mechanism without a large energy penalty of the microbes and fluoride ion for effective water treatment, a more effective and an enhanced multifunctional, multi-layer nanofibrous hybrid sorbent through electrospinning techniques should be considered for future work, 2) More studies on the mode of actions and morphological changes in the pathogens leading to the cell death through the influence of the nanocomposites should be further explored, 3) Application of this advanced technology vis-à-vis other biomaterials to generate filter membrane towards efficient microbial removal and deflouridation is a great challenge worth looking at, 4) Lastly, materials developed in the present study should be modeled, tested and fabricated at the point of use for fluoride and pathogen removal at household level. / NRF