An extensive review and discussion relating to surface properties of solids in aqueous media, sedimentation and flocculation of suspensions are presented. Attention is given to the properties of polymeric flocculant solutions and to factors affecting the behaviour of flocculated suspensions. The effects of prolonged stirring on the viscosities of polymer flocculant solutions have been investigated. It is shown that a slight decrease in viscosity with prolonged stirring occurs even at moderate stirring rates. The viscosity decrease is attributed to molecular degradation which is strongly affected by the ionic nature of both flocculant and medium. The research was mainly devoted to the study of the properties of suspensions flocculated by different agitation methods. The methods employed included inverting and rotating cylinders, mechanical stirrers and agitation by plunger and cyclone. Experimental apparatus and technique are described by which settling rate, sediment volume, clarity of supernatant liquid and compressive strength of sediment may be conveniently measured. The following exponential relationship was found to exist between the compressive strength, a, and the solids volume fraction, c, of flocculated sediment: n(c-c z) o = a. e where the constants a, n and c were dependent on the type of agitation and flocculant dosage. The properties of flocculated suspensions are shown to be considerably affected by the type of agitation used. It appears that the suitability of an agitation method is dependent on the requirements of subsequent processes.

Complete mixed batch reactor (CMBR) and column type experiments successfully investigated the migration of single solute and complex solute mixtures of hydrophobic organic compounds (HOCs) in subsurface environmental conditions and the importance of sorption kinetics. CMBR experiments proved relatively rapid and inexpensive, but their application to environmentally relevant settings was limited. Therefore, a large proportion of this research is devoted to the design, construction and validation of a mesoscale contaminant hydrogeology column for improved emulation of subsurface conditions. On-line solid phase extraction (SPE) of the column effluent facilitated convenient collection of complex mixtures of HOCs present at extremely low concentrations (0.1 - 1 μg L-1). Column 'miscible displacement' experiments and CMBR experiments were conducted to investigate sorption characteristics of the polycyclic aromatic compounds (PAHs) phenanthrene and benzo[e]pyrene (b[e]p) to quartzitic sands. CMBR experiments for phenanthrene sorption to two quartzitic sands of low soil organic matter (SOM) content, SMA (foc=0.000362) and SMB (foc=0.00025), determined equilibrimn sorption isotherms to be linear over the entire range of phenanthrene's aqueous solubility. The results indicate that SOM was the predominant sorption domain. CMBR determined values of the organic carbon distribution coefficient, Koc, were 1844 mL g-l and 2997 mL g-l for SMA and 5MB respectively, and are significantly less than previously reported. An empirical two-site model that accounted for observed bi-phasic sorption kinetics fitted the rate of sorption data well. Key model parameters were the fraction of instantaneous sorption (SMAf=0.37, 5MB f=0.42) and the rate constant (SMA k2-=0.044 hr-1, 5MB k2=0.076hr-1). Two column miscible displacement experiments investigated phenanthrene migration through SMA at high pore water velocities (v=56 cm hr-1). Results were fitted using the one-dimensional advection-dispersion equation, modified to account for kinetically limited sorption. Fitted parameters for duplicate experiments were: Koc=1229 mL g-l and 1237 mL g-l; /= 0.491 and 0.537; k2= 0.678 h{l and 0.589 hr-l. Parameters/and Koc were comparable to CMBR results. A single miscible displacement experiment was conducted investigating b[e]p migration through SMA. Fitted parameters were Koc=44503 mL g-l,/= 0.068 and k2 = 0.03 hr-1, and were contrary to previously published literature. Two column leachate experiments were successfully conducted that highlight the suitability of the column to complex environmental systems. The first experiment investigated desorption characteristics of environmentally important P AHs from historically contaminated manufactured gas plant (MGP) soil over a 62 day period. P AH desorption rates were small and indicated that the significant quantities of PAHs sorbed to the MGP soil were essentially irreversibly bound. The second experiment was a novel application of the column in which an organic unresolved complex mixture (the aromatic fraction of Venezuelan Tia Juana Pesado (ATJP) crude oil) was partially fractionated. SPE extracts of the column effluent were significantly less complex than the original ATJP crude oil sample, with many compounds completely resolved. Subsequent GC-MS analysis of SPE extracts identified four classes of compound: phenols, acids, straight chained and branched alkanes and alkenes, and aromatics.

In this thesis, the bioconversion of palladium and gold solutions and gold-bearing wastes into highly valuable mono- and bimetallic catalysts is described. This process relies on bioreduction; the ability of some bacteria to reduce Pd(II) and Au(III) ions at the expense of an exogenous electron donor with precipitation as zero valent metals. The resulting metallic nanoparticles (NPs) immobilised on the outer membrane and within the periplasm exhibit remarkable catalytic properties, sometimes surpassing commercially available catalyst formulations in terms of activity and/or selectivity. Previous studies in the field have mainly focused on the ability of Desulfovibrio spp. to reduce Pd(II) from both surrogate solutions and reprocessing wastes. The mechanism of Pd(II) reduction in this genus was previously shown to be enzymatic, involving hydrogenases, key enzymes of hydrogen metabolism. In this study, a detailed investigation into the mechanism of Pd(II) reduction by Escherichia coli using a genetic approach confirmed hydrogenase involvement and additionally showed that these enzymes are needed to initiate the formation of Pd(O) nuclei. Genetically engineered strains depleted of all functional hydrogenases lost their ability to produce Pd(O) NPs, which in turn greatly affected the catalytic activity of the resulting bioinorganic catalyst ("bioPd(O)"). Further studies suggested that the nature of the bacterial support also influenced the catalytic activity of bioPd(O) preparations. Seven bacterial strains, representing different Gramnegative and Gram-positive genera, were tested for Pd(II) reduction. Large differences in Pd(II) sorption and Pd(II) reduction ability were observed between strains; the combination of these factors affected the final size distribution of the cell-bound Pd(O) NPs and hence the catalytic activity of the resulting bioPd(O) preparations. Bioinorganic catalysts were shown to be active and/or selective in a wide variety of reactions, including Cr(VI) reduction, hydrogenolysis (reductive dehalogenation), Heck coupling and oxidations. The bioreductive approach was applied to demonstrate Au(III) reduction and recovery using cells of D. desulfuricans and E. coli and the first evidence of the catalytic activity of biogenic Au(O) NPs is presented. Au(III) reduction was slower than Pd(II) reduction and only partially involved hydrogenases which suggested the involvement of an additional different reduction route. However, introducing a bionanocatalyst consisting of lightly pre-palladized cells into the process greatly improved the speed of Au(III) reduction and resulted in the formation of highly ordered AulPd core/shell nanostructures which exhibited catalytic properties not seen with traditional chemical counterparts.

Surface water and groundwater systems are linked dynamically in reality as the one generally impacts directly on the other. Traditionally, however, these two water bodies have more often than not been treated as different entities by water managers and other professionals. The issue of the compartmentality of these two resources is the main focus of the study described herein. In this study, an existing 1D-2D hydro-environmental surface water model that includes a groundwater model (DIVAST-SG) has been extended to 2-D and refined through testing against three laboratory studies. A surface water-groundwater system model using foam to replicate groundwater material was created in the laboratory and the results of the hydrodynamic processes (i.e. water elevations and flowpaths) were compared with the numerical model predictions. On the whole the comparisons showed good agreement. However, dye studies for replicating pollutant transport did not show such good agreement and this discrepancy was thought to be due to a number of reasons. In the second series of studies, the groundwater material was then replaced with the more traditional sand embankment and again results for both hydrodynamic and solute transport processes (by way of dye studies) from the laboratory set up were compared with the numerical predictions which were in almost perfect agreement. In the same tidal basin, a Severn Estuary model was then designed and set up. Although there were differences from the prototype owing to space and scaling difficulties, the results showed good agreement for both tidal amplitudes and tidal currents with the predictions from the numerical model and particularly the tidal amplitudes were found to compare favourably with field studies. Tracer results from the physical model also showed consistency with simulations from previous researchers in the main estuary. Overall, the purpose of this study, which was to investigate the manner in which flow and solute (conservative tracer) fluxes interacted between surface and sub-surface flows, for simulated riverine and tidal conditions, has been achieved. These experiments and the corresponding datasets are thought to be unique.

Dissolved organic carbon (DOC) has received increased prominence in drinking water research, as concentrations in surface waters have increased in many parts of northern Europe and North America in recent decades. This presents a problem, since DOC gives colour, taste and odour to drinking water and can form potentially harmful by-products on disinfection. This research explored these issues through a series of experiments focussing on DOC flux from peat soils and the litter layer under different climate conditions. The aim of the work was to assess the likely impact of changes in temperature, precipitation and drought frequency and severity as well as changes to vegetation species diversity on DOC production and drinking water treatment. This will determine whether common treatment processes (coagulation/flocculation) are able to cope with potential changes in DOC quality, and therefore whether new treatment processes may be required as an adaptation to climate change. Through assessment of the impact of changes in species diversity and the effect of drought, this work also aims to build the evidence base for current catchment management schemes which have sought to support Sphagnum dominance and raise peatland water-tables. The experimental work included the optimisation of coagulation/flocculation for DOC removal from common peatland sources as well as grassland species which are currently encroaching on the uplands. The role of temperature, rainfall and drought in controlling DOC production from litter and soils was considered, as well as the abiotic role of temperature in DOC solubilisation. The findings were also tested in the field using a litterbag study across an altitudinal gradient which provided a natural range of temperature and rainfall. The environmental persistence of DOC from different sources was also examined. The research indicates that the type of vegetation is significant in controlling the amount, treatability and environmental persistence of the DOC produced. Temperature and rainfall influence DOC quantity and quality, however the effect of these climatic variables is much smaller than for the source of the DOC. The decomposition of litter and resulting DOC production are controlled primarily by biotic factors such as the litter’s ratio of carbon to nitrogen, which indicates nutrient availability to the decomposer community. Common peatland species such as Sphagnum and Calluna vulgaris are adapted to nutrient poor environments and therefore have high C:N ratios and produce low amounts of DOC per unit weight when compared to grassland species. The invasive grassland species, such as Molinia caerulea and Juncus effusus, produce high amounts of DOC per unit weight and large amounts of above-ground biomass which decays readily due to its low C:N ratio. A new conceptual model of carbon cycling in peatlands is proposed which shows that climate change may decrease the overall size of the litter carbon pool by facilitating the encroachment of grassland species which decompose rapidly. These species will increase the seasonality of DOC flux due to their cycles of growth and produce DOC which is more persistent and harder to treat than common peatland species. Drought has been highlighted as major problem for drinking water treatment in peatland catchments as it causes large increases in DOC production from peat soils whilst also decreasing its treatability. Taken together these results suggest the secondary effects of climate change, namely vegetative change, may be more important for DOC production that changes in temperature and rainfall. Catchment management schemes which support Sphagnum and increase resilience to drought are justified as Sphagnum produces DOC readily removed by coagulation/flocculation and drought can cause an increase in the amount of DOC from peat soils and produce DOC which is also harder to remove by standard treatment processes.

IIn recent decades the application of UV disinfection technology in water treatment has rapidly increased on a global scale, however important uncertainties remain regarding; the methods to achieve consistent and accurate measurement of polychromatic UV output, the fluence-response of microorganisms to UV wavelengths over the entire polychromatic lamp output range, and the optimal lamp conditions and compositions to optimise polychromatic UV disinfection performance. This research aimed to address each of these areas of uncertainty. First, limitations in the existing methods that are used for lamp output measurement were identified and quantified in terms of their potential to cause significant errors in polychromatic UV fluence calculation; solutions are proposed to overcome these limitations in future polychromatic fluence measurements. Next, a novel experimental apparatus was constructed, achieving the necessary spectral requirements to produce a high resolution action spectra for waterborne microorganisms over the 200-300 nm wavelength range. Application of this experimental setup to the comparison of the fluence-response of T1 and T1UV phage, common organisms used in UV reactor validation, identified important differences in UV sensitivity dependent on host selection, and high resolution action spectra were then produced for T1UV with two hosts over the full polychromatic UV range for the first time. Also, new viral surrogates were identified using a theoretical genomic model to predict their UV sensitivities, two of which were identified as having the potential to extend the upper UV fluence validation test limits. Finally, the production of a novel high pressure plasma discharge polychromatic lamp was achieved without the use of mercury, showing considerable potential for future applications.

Arsenic contamination of drinking water is problematic across the globe, with a serious effect on human health. The WHO guideline of 10 μg L-1 maximum concentration for arsenic in drinking water is regularly exceeded in developing countries in South East Asia, and many other countries across the world including the USA and Japan. Aqueous arsenic is commonly found in two oxidation states, AsV (arsenate) or AsIII (arsenite). Arsenate exists in water as a tetrahedral oxyanion, analogous to phosphate. Recently there has been great interest in developing new materials than can remove arsenate from drinking water. Specifically, chelating resins loaded with transition metal cations have shown potential for use in arsenate remediation. This Thesis describes the synthesis of two series of metal complexes that were evaluated as arsenate receptors and subsequent development of one of these receptors into a novel arsenate adsorbent. Firstly, a range of bridging di-metallic complexes was synthesised. The aqueous phase oxyanion binding properties of these receptors were investigated by indicator displacement assays, isothermal titration calorimetry and in the solid phase by X-ray crystallography. Metallo-receptors containing boronic acid binding sites were also synthesised and arsenate binding was studied by isothermal titration calorimetry, UV-vis spectroscopy and NMR spectroscopy. An arsenate sorbent was prepared by immobilising a phenolate di-zinc(II) complex onto a polystyrene resin. The novel material thus obtained was studied as an arsenate adsorbent in a range of batch adsorption experiments. The effects of solution pH and presence of competing ions on arsenate uptake were investigated and the Langmuir adsorption capacity was obtained. These results were compared with those of a commercially used arsenic adsorbent, Bayoxide E33. Finally the novel adsorbent was packed into a glass column and its ability to adsorb arsenate in flow through experiments was studied.

The composition of water can be influenced by the input of elemental constituents from natural and anthropogenic sources. Elevated levels of vanadium, arsenic, fluoride and other trace elements in water (ground, surface and tap) from various provinces in Argentina (including La Pampa, south east Buenos Aires, Río Negro and Neuquén), were analysed by inductively coupled plasma mass spectrometry (ICP-MS) and ion selective electrode (for fluoride). Vanadium species were determined in water by a newly developed solid phase extraction method (SPE). Vanadate (VV) was found to be the predominant species in water samples. The correlation between vanadium and arsenic species, and total elemental levels are presented. Vanadate (VV) correlates strongly with total arsenic, vanadium, fluoride and also the inorganic arsenic species compared to the vanadyl ion (VIV). However, vanadyl (VIV) had stronger Spearman correlations with the organosenical species. The levels of vanadium, arsenic and other trace elements were analysed in hair and nail samples and in water to evaluate exposure levels. The elemental exposure via drinking water increased in the following order: La Pampa (General San Martin-GSM and Eduardo Castex-EC) > Buenos Aires (Moron-MO) > Río Negro (General Roca-GR). In La Pampa (GSM and EC) and Buenos Aires (South east-SE) many sites showed vanadium, arsenic and fluoride levels exceeded the international regulatory limits for drinking water. La Pampa residents had the widest distribution of vanadium and arsenic in hair, fingernails and toenails compared to other populations in this study. A significant Spearman correlation (P < 0.0001) exists between the levels of vanadium and arsenic in groundwater from La Pampa and hair or nail values. The rural farms in La Pampa have no access to treated water. An electrocoagulation method using aluminium and iron electrodes showed a high level of efficiency in removing vanadium, arsenic and fluoride from groundwater. This may offer clean, and safe drinking water for farmers living in these areas of Argentina.

The health risk of organic micro pollutants in water is yet to be comprehensively established. However, the persistence of these pollutants in the environment as a result of continuous discharge even at trace concentrations is considered to pose major environmental concerns. Advance treatment methods such as membrane-assisted processes (MAPs) are potential technologies capable of removing a wide range of these organic micropollutants (OMPs) detected in water. In this study, investigation of surface-coated ultrafiltration (UF) poly(vinylidene fluoride) (PVDF) hollow fibre membrane for the removal of organic micropollutants (OMPs) in water was performed. Coating of PVDF membranes with poly(1-phenylethene-1,2-diyl)/polystyrene and pluronics F68 solutions through physical adsorption was carried out in two modes: “dipping” and “spraying”. Surface characterization of coated membranes showed that the coating layer potentially influenced the surface properties suitable for improved solute-membrane interaction. Characterization of the pore size and distribution through Scanning electron microscopy (SEM) images analysis showed that polystyrene coating in sprayed and dipped coating procedure, exhibited more reduction in pore size (19−31%) and closer pore size distribution than the pluronics F68 dip coating (6%). The average roughness (Ra) and maximum peak-to-valley distance (Rmax) measured using the Atomic Force microscopy (AFM) recorded more roughness and irregularity in surface topography in the polystyrene coated membranes compared to the pluronics F68 coating with the dipped polystyrene coating method attaining more roughness (Ra – 0.393 µm). Contact Angle (CA) measurements showed that the dipped Polystyrene coated membrane achieved the highest increase in hydrophobicity (29%) while the dipped pluronics F68 coating achieved a 10% increase. Correlation between the changes in surface roughness and hydrophobicity was evident in the study. Generally, the polystyrene material impacted the membrane surface the most, and the dipped coating procedure recorded the highest surface modification impacts. The performances of the coated membranes in the rejection of the model organic micropollutants, caffeine (hydrophilic) and carbamazepine (hydrophobic) spiked (as single and mixed components) in various water matrices i.e. deionized water, surface water and synthetic wastewater (at concentration range of 300 -1000 μg/L) correlated with the coating materials and methods used. The dip-coated membranes using polystyrene material, achieved better removal of recalcitrant hydrophobic carbamazepine compared to the spray-coated membrane in deionised water, but not in other water matrices. Whereas for both methods of coating, removal of caffeine was relatively insignificant in deionised water but reasonably higher in surface water and synthetic wastewater. From these results, it is inferred that hydrophobic interactions and size exclusion might be the major removal mechanisms involved in rejection by the coated membranes and the colloidal and particulate matter in surface water and fouling in membrane bioreactor system facilitated sorption removal mechanism. The membrane coating enhanced reduction of the pore size, decreasing the membrane permeability and providing more sites for possible solute-membrane interactions. it is demonstrated that physical adsorption of functional polymers is a simple and efficient way to modify the surface properties of polymeric membranes for water filtration application.

The drinking-water environment is prone to chemical and biological pollution, and it remains a challenge to achieve contamination-free water for the consumer. Biological contaminants (microorganisms and their genetic traits) can become more difficult to treat, as compared to chemical, as they can escape treatment processes (including disinfection) and replicate. Their presence in the drinking water environment has become considered to be a hotspot for the dissemination of antimicrobial resistance genes (ARG). Moreover, the treatment process may create conditions that may exacerbate the development and dissemination of ARG. The inter-relationship between disinfectant exposure, a common water-treatment process and the development of antibiotic resistance was investigated in this study. Potential human and animal pathogens from municipal drinking water, representing twenty-two genera, were characterized for antibiotic and disinfectant resistances. The co-existence of antibiotic resistant and transferable genes was found in bacteria, and significant but weak correlations were detected between disinfectant and antibiotic resistance (against sulfamethoxazole, tetracycline and amoxicillin).The applicability of a minimum-selectable-concentration model (MSC) for the selection of resistant population was evaluated for the first time in this study MSCs were found to be lower than minimum inhibitory concentrations (MIC) causing the enrichment of resistant populations at sub-inhibitory concentrations. Both MIC and MSC metrics should be considered when planning treatment against resistant organisms. Finally, the potential roles of dispersal and gene enrichment in a model distribution system were explored. Different pipe surfaces, especially PVC, became colonized with bacteria and enriched the abundances of resistant populations in the presence of free chlorine. Additionally, resistant bacteria were enriched more in biofilm than water. This thesis highlights how water-distribution ecosystems contribute to the emergence of resistance. The water-supply system must be considered for the control of resistant bacteria. Further, we must prevent the presence of microorganisms post-treatment as exposure to sub-inhibitory disinfectant levels causes the greatest risk.