Early produced water treatment technologies were developed before carbon dioxide emissions and hazardous waste discharge were recognised as operational priority. These technologies are deficient in the removal of dissolved hydrocarbons and dissolved heavy metal ions which have been identified as major contributors to the high environmental impact factor of produced water. The simultaneous removal of heavy metals and polycyclic aromatic hydrocarbon (PAH) from produced water via photoelectrochemical process was identified in this work as a produced water treatment alternative with the potential to virtually eliminate the cost for chemical reagents and high energy input. Several grades of simulated produced water were synthesised and used to understand different parameters necessary for developing a successful photoelectrochemical treatment. The process demonstrated in this work followed a simple two–electrode photoelectrochemical cell where heavy metals were recovered on a platinum electrode with simultaneous degradation of PAH (phenanthrene) on a photoanode, with the aid of sunlight (simulated) and an applied cell voltage of 1.0 V. Multiwall CNT-TiO2 synthesised via a modified sol-gel method served as the photoanode after it was immobilised at a loading of 2.5 mg/cm2 on a titanium plate. The results obtained from the photoelectrochemical treatment showed a recovery of 1.6 g/cm2 of lead, 0.2 g/cm2 of copper and 0.1 g/cm2 of nickel from produced water on a 0.1 cm diameter platinum electrode after 24 hours of irradiation with simulated sunlight at 1.0 V cell voltage and a simultaneous degradation of up to 16 % phenanthrene on the photoanode, which gives a potential of scaling up the process to a commercial throughput.

In order to address ground and industrial water pollution, the University of Manchester has developed a novel and economic water treatment technology called the Arvia® process. This technology is being commercialized through a spin-out company, Arvia Technology Ltd. This process consists of adsorption and electrochemical regeneration in a single unit and can be carried out in batch or continuous modes where both operations can run simultaneously. This process has been successfully demonstrated for the removal and destruction of a number of organic contaminants using a graphite based adsorbent known as Nyex®1000. Nyex®1000 is an intercalation compound prepared from Chinese natural large fake graphite. This adsorbent has been found to be capable of fast adsorption and quick electrochemical regeneration in minutes due to its non-porous surface and high electrical conductivity. However, Nyex®1000 has a small adsorptive capacity for a number of organic pollutants and there is thus a need to develop new adsorbents with the aim of achieving high adsorptive capacity with maintaining good electrical conductivity. In this context, three routes for the development of adsorbents were selected, adsorbents developed through electrochemical intercalation, adsorbent developed through thermal and mechanical treatment of GIC-bisulphate and adsorbents developed through the formulation of composite materials. In order to strengthen the contributing effect of surface treatment, all raw graphite materials and developed adsorbents were characterized using Boehm titration, X-ray EDS, zeta potential, powder XRD, SEM, BET surface area, pore volume, particle size and bulk density techniques. These adsorbents were tested for the removal of a number of different target organic pollutants such as acid violet 17, mercaptans, phenol and humic acid using the Arvia® process. The performance of the developed materials was compared with the current adsorbent used in the Arvia® process i.e. Nyex®1000. A range of graphite types (synthetic graphite, Chinese natural large fake gra- phite, Madagascan medium fake graphite, natural vein graphite and recycled Abstract 27 vein graphite) were tested for the removal of acid violet 17 before and after electrochemical treatment in order to investigate the selection of the graphite types for the Arvia® process. The electrochemical surface treatment improved the adsorptive capacity by a factor of two for most of the graphite types tested and changed the surface of the graphite from hydrophobic to hydrophilic. Results obtained through surface characterization using Boehm titration, X-ray (EDS) elemental analysis and zeta potential measurements revealed a significant increase in oxygen containing surface functional groups on the surface of CNLFG in consequence of electrochemical surface treatment. The second type of adsorbent was developed through thermal and mechanical treatment of GIC bisulphate. It was tested for the removal of acid violet 17, mercaptans (ethane thiol & methyl propane thiol), phenol and humic acid using the Arvia® process. This material had twice the electrical conductivity of Nyex® 1000 and improved the adsorptive capacity by a factor of three for acid violet 17, approximately seven to eight for ethane thiol and methyl propane thiol, seven for phenol and two for humic acid. Starting and developed adsorbent materials were characterized using above mentioned techniques. The third type of adsorbent materials, three composite adsorbents were developed using high shear (wet) and compaction (dry) granulation methods. The composite adsorbent made through high shear wet granulation was found to have poor mechanical strength. The second and third composite adsorbents were developed through dry compaction granulation using carbon black, synthetic graphite and exfoliated graphite as raw materials. These adsorbents delivered improved adsorptive capacity for acid violet 17 by a factor of 100 and 9 respectively. Electrochemical regeneration efficiencies of around 100 % were obtained for these adsorbent materials. However, electrochemical parameters required to achieve 100 % regeneration, such as current density and regeneration time were found to vary depending on the adsorptive capacity of each adsorbent material for a particular polluting agent.

No description available.

Nanofiltration (NF) membranes are used for a range of industrial applications one of which is for the removal of the sulphate constituent in seawater. This is a mature activity for the treatment of seawater that is to be injected into oil reservoirs in the offshore oil/gas industry. Such sulphate removals have also been the subject of much interest, as a pretreatment strategy, in seawater desalination plants that is either utilising thermal technology or reverse osmosis. Nevertheless, there is a need for robust criteria, such as the comparative permeate flux and sulphate rejection, of selecting the optimum NF membrane. There is a major difficulty in the assessment of the comparative filtration performance and the role of membrane structure because the data from manufacturers and also the information from the scientific literature emanates from different testing protocols. This can result in an enigmatical situation for obtaining the optimum NF membrane for a particular application. Against the above background this PhD project has focused on undertaking a fundamental study of different commercially available NF membranes in order to facilitate improved assessment of their filtration performance for sulphate rejection applications in relevant standardised testing conditions. Moreover, on the basis that those variations in membranes’ functioning are attributed to membrane structure and characteristics, a major segment of the research was focused on correlating filtration performance and membrane features. The research comprised two main phases; the first phase involved determining the comparative filtration performance of eight commercially available NF membranes supplied from four manufacturers. The second main phase was to undertake detailed characterisation studies on the NF membranes in order to obtain a clear understanding of their sulphate separation mechanism and permeate flux. The first phase involved assessments of the permeate flux and selectivity of the eight membranes. The experimental protocol in the second, characterisation part of the work was directed to the identification and evaluation of NF active surface layer characteristics:  Pore characterisation by porosity factor calculations,  Hydrophilicity/Hydrophobicity nature by contact angle measurements,  Surface Free Energy calculations,  Surface roughness measurements by AFM,  Membrane potential measurements and average charge density calculations. This approach is an acknowledged strategy for NF membrane scientific research assessment and, in the current work provided key data of membrane features that facilitated a systematic understanding of membrane functioning. These characterisation features were also linked successfully to the membrane performance parameters to yield a characterisation/performance envelope which represents a useful basis for NF membrane selection and utilisation to optimise membrane usage and consequent economic advantage. The general discussion includes a summary of the interface between the role of NF and the operational and economic features of the two main types of desalination processes. It includes an outline of a process scheme for the incorporation of NF pretreatment into an MSF plant from the conceptual design stage as opposed to the application employed hitherto where the emphasis has been on attaching NF pretreatment equipment on to an existing unit. As a result, it is expected that NF usage should increase performance ratio, reduce energy consumption, hence the running cost, and increase recovery.

This thesis investigates the effectiveness of a passive treatment technology for Fe removal from low pH metal mine water. In addition, the use of electrocoagulation (EC) in removing Zn from circumneutral mine water and acid mine drainage AMD) was studied. Using an advanced oxidation process (AOP) followed by EC converted Fe(II) from coal mine drainage to a stable magnetic form of Fe. Research also studied the use of Cu electrodes in removing high concentrations of metals and sulphate from AMD. A 1 m³ field pilot scale vertical flow reactor (VFR) for passively treating an average flow of 0.6 L/min was deployed for 414 days. The system was gravity fed and removed an average of 65% of the Fe from pH 3 AMD. Potential removal mechanisms are a combination of bacterially mediated Fe(II) oxidation by Ferrovum myxofaciens and filtration of Fe nanoparticles. The build-up of the ochre bed did not compromise the permeability of the VFR. Mineralogical and microbiological studies combined with PHREEQC modelling show that the main mineral precipitated in the VFR is schwertmannite. Using EC, it was shown that the addition of Fe from neutral mine water by electrical dissolution of an Fe electrode resulted in Zn to be removed at a near neutral pH through a combination of co-precipitation and adsorption reactions. An inert Pt electrode rapidly removed 70 mg/L of Fe(II) from coal mine water by AOP applying 5 A during 4 min treatment. A second stage treatment adding Fe by electrical dissolution of Fe electrodes generated the required Fe(II):Fe(III) ratio and Eh-pH conditions to form magnetic Fe (magnetite). Further investigations into EC proved that the removal of sulphate and metals from AMD was highly effective when adding Cu from a copper electrode at 40 min at 5 A with aeration. Sulphate was reduced from 1324 mg/L to 112 mg/L without leaving Cu in solution. ESEM images and mineralogical studies of the precipitates showed that the mineral cuprite is formed. This has future potential implications for metal recycling/recovery from AMD.

The development of nanostructured materials for environmental applications has received considerable attention in recent years. The properties of nanoparticles or nanostructured materials, such as large surface areas or high aspect ratios, translate into large improvements in the performance of existing devices and in the discovery of novel applications. On the other hand, photocatalysis is an attractive technology for the elimination of organic pollutants in water due to its simplicity, ease of implementation and reasonable cost compared to other advanced oxidation processes. A key disadvantage of many photocatalysts is their use in powder form which makes their recovery from treated water costly. In addition, incomplete removal can lead to accumulation over time with adverse effects to the environment. As a result significant effort has been placed in immobilizing photocatalytic materials on different substrates. The immobilization of photocatalyst results in a decrease in photocatalytic performance mainly due to reduction of surface area; therefore, research is now focusing on developing nanostructured materials which combine the attributes of nanotechnology and photocatalysis. In the present thesis, a systematic study of the relationship between properties of supported ZnO nanostructures and their photocatalytic activity was performed. Analysis was carried out by producing ZnO nanostructured films via anodization. The effects of voltage, temperature, reaction time and type of electrolyte on the morphology of ZnO nanostructures was studied. Results show that the type of electrolyte and its concentration determine the morphology and size of the nanostructures. Voltage, time and temperature affect the distribution and density of the nanostructures along the surface and affect the crystal size of the ZnO. The band gaps of the films were in the range of 3.27 and 3.50 eV. Although ZnO is a hydrophilic material, some of the films displayed hydrophobic and super-hydrophobic behaviour. The results obtained in this study and some data already published in the literature were correlated to the synthesis parameters, and were used to devise design guidelines to obtain ZnO films with specific nanostructures and macroscopic properties by controlling the anodization parameters. The photocatalytic activity of the ZnO nanostructured films (ZnO-NFs) were studied using three different photocatalytic reactors, (i) a thermo-stated batch reactor, (ii) a recirculating flat plate reactor, and (iii) a recirculating tubular annular reactor. Phenol and methyl orange (MO) were used as a model compounds. It was found that crystal size does not affect the photocatalytic performance of the films while morphology has an important impact on the degradation of phenol. The stability of the ZnO nanostructures was tested under different levels of oxygen, degradation of phenol occurred even at anoxic conditions following the Mars-van Krevelen mechanism. The formation of new nanostructures produced during the photocatalytic reaction was studied and a mechanism of formation was proposed. The study of the photocatalytic performance in the flat plate reactor showed that there was a mass transfer limitation in the process. ZnO nanostructures showed higher photocatalytic activity and morphology stability in the tubular annular reactor. Degradation of MO and phenol was produced in darkness by the nanostructures supported in Zn foil. It was also demonstrated that oxygen plasma post-treatment enhances the photocatalytic activity of the ZnO-NF by 36% while making the photocatalyst more stable for the photocatalytic degradation of phenol compared to those treated with heat. An electrical current was applied to the photocatalyst in the tubular annular reactor, which improved the degradation of phenol and participated in the formation of nanostructures in the Zn wire surface.

The study used continuously monitored, high resolution turbidity, ammonia, rainfall and flow data from EA UK. Urban storm events were not systematically characterised previously leading to gaps in process understanding; previous studies used short time periods and with most of them formed on single gauges. Aimed at improving understanding with novel contributions, the objectives were characterising the events, finding their seasonal influence and the spatial scale effect on turbidity patterns. Universally adaptable quantified events characterisation and classification were developed yielding single, double and multiple events. Double and multiple events together was more than single events for both smaller and larger catchments. Thus, analysing only single events could miss key dynamics of multiple events which showed significant increases in turbidity. More anticlockwise events than clockwise were found. Anticlockwise events decreased and clockwise increased from single to multiple events. Events with more number of turbidity than discharge peaks were found. Seasonally, most attributes as well as high urban extent and effluent spillage showed significant effects on turbidity mostly in summer and autumn. All seasons but spring with more anticlockwise than clockwise events had more low flows. Winter had the highest anticlockwise events, possibly because of its wider areal rain event extent, high number of low flows as well as more distal runoff sources. In the spatial scale studies, more single events in the smaller and more multiple events in the larger catchments as well as more anticlockwise events in the smaller and more clockwise events in the larger catchment were found.

This dissertation focusses on some advancements in methodology for measuring and analysing dissolved organic carbon (DOC): analysing data from a high resolution sensor generating DOC concentrations, [DOC] and secondly the use of Raman spectroscopy to analyse the composition of DOC. Recent advances in sensor technology have enabled the collection of DOC data with greater frequency over extended time periods than was previously possible through manually collecting water samples. In this research a time series of 30 minute [DOC] data for 2.5 years from Drumtee water, a peaty catchment in Scotland, was generated and analysed using a Spectro::lyserTM from S::CanTM, with a customised algorithm for calculating [DOC]. The time series revealed details of events and strong seasonal variation in the [DOC], with a range of 8.0 mg/l to 55.7 mg/l. During the same time period measurements made using manual sampling of river water were very similar, ranging from 10.2 mg/l to 81.1 mg/l (with the second largest value at 64.1 mg/l). Similar DOC export budgets were calculated from Spectro::lyserTM measurements and from the laboratory-analysed samples for both the hydrological year 2012/13 (HY 2012/13) and hydrological year 2013/14 (HY 2013/14). For the HY 2012/13 year the DOC budgets using the field collected data and the laboratory collected data were 16.6 gCm2.yr-1 and 19.8 gCm2.yr-1 respectively. For the HY 2013/14 year the DOC budgets using the field collected data and the laboratory collected data were 18.1 gCm2.yr-1 and 19.5 gCm2.yr-1 respectively. The similarity between the budgets calculated using the high-resolution [DOC] sensor and the budget calculated using laboratory measured [DOC] samples indicated that seasonal variation had a greater influence on export budgets than short term events had. GAMs were used to model the high resolution [DOC] data, and the model generated an R2 value of 0.75 and a p-value of < 2.2 x 10-16. It was also identified statistically that there were regular [DOC] dilutions during events and that these dilutions tended to coincide with the time period when discharge was increasing most rapidly. To identify relationships and periodicities in the high resolution [DOC] time series that would otherwise be challenging to identify three forms of wavelet analysis were used. These were continuous wavelet transforms (CWTs), maximal overlap discrete wavelet transforms (MODWTs) and wavelet coherence transforms (WTCs). Using the WTCs, it was determined that there were short term correlations between the [DOC] and pH between 25 June 2013 and 17 July 2013, between [DOC] and SC during 7 August 2013 and 7 October 2013 and between [DOC] and water temperature during 19 June 2013 and 30 June 2013. Although the although the relationship between [DOC] and temperature is strong over a full year it was over these shorter time periods the weakest of the three relationships established. Identifying this coherence was not possible using bivariate analysis and the long periods of no coherence obscured these responses when analysing the data on scatter plots. Although wavelet analysis has been used in other applications this is one of the first instances in which this technique has been applied to [DOC] time series. Raman spectroscopy, conducted using a 785 nm laser, was explored as an analytical tool that could enable a better understanding of DOC composition, as an alternative to the use of fluorescence spectroscopy. Tests were conducted using both Stokes and anti-Stokes Raman spectroscopy measurements with the best results obtained using anti-Stokes Raman spectroscopy. Solid phase measurements were made of glucose, fructose, sucrose, glycine, tyrosine, tryptophan and phenylalanine, but only the glucose produced a measurable spectrum of these substances. Measurements (powders and solutions) were made of humic and fulvic acids and these produced spectra that were measurably different from the background signals. The limit of detection was measured to be approximately 500 mg/l for both the humic acid and fulvic acid. It was identified that comparing the sections of the measured spectra between wavenumbers -1100 cm-1 to -1400 cm-1 to -1800 cm-1 to -2000 cm-1 could be used to differentiate between humic and fulvic acids. In summary, this research has focussed on the use of use high resolution sensor technology to generate and then analyse a long time series in a fluvial system with a particularly high [DOC], and made advances in being able to model the [DOC] using a GAM model, despite the complex relationship measured between discharge and [DOC]. Additionally, wavelet analysis has been applied to a [DOC] data set to identify trends in the [DOC] time series that would otherwise be hard to identify. Wavelet analysis has been applied to other geophysical time series such as those found in atmospheric research, but this appears to be the first time it has been applied to [DOC]. Additionally, the use of the anti-Stokes region of the Raman spectra has allowed identification of humic and fulvic acids, and established a limit of detection. Furthermore, an absorbance ratio was identified that can be used to determine whether a solution of humic substances is dominated primarily by humic acid or fulvic acid. This research appears to be the first study to explore this.

Clean water is a vital resource, which climate change and population growth conspire to make increasingly scarce. Thus it is imperative that we maintain the quality of our watercourses and recycle polluted waters. Biological treatment of wastewater is at the forefront of current strategies employed to treat domestic wastewater. The transformation of wastewater into less harmful products is performed by complex naturally forming microbial communities. Waste treatment processes are essentially a product of the ecology of these communities and yet we have a poor understanding of some of the most basic ecological processes. In particular, the coming together, or assembly of the community. Thus when failure occurs it can be baffling. In the last decade, there has been growing evidence that stochastic processes are an important component of microbial community assembly. In open biological communities, if species are functionally equivalent and it is only stochasticity that shapes the community then the dynamics are said to be neutral. It is then important to ascertain the relative importance of stochasticity in engineered systems and on that basis formulate theories to guide the successful design and operation of wastewater treatment plants. Neutral community assembly theory has been in the limelight for more than a decade because of its ability to predict species area relationship and species abundance distribution. Its underlying assumption of equivalent specific growth rates is controversial and has led to much debate, which is muddied by sampling issues, parameter estimation techniques and lack of data. In this thesis, I attempt to address these confounding factors and properly parameterize the stochastic model originally postulated by Hubbell (Hubbell, 2001) and subsequently modified by Sloan (Sloan et al., 2006) to suit microbes. This is done by conducting detailed experiments in parallel chemostats to give time series of the abundance of organisms that have been engineered to have highly tunable kinetics. Calibration using time series data affords the first opportunity to validate neutral (and near neutral) dynamics. Previous studies only use stationary abundance distributions that could have emerged from a variety of alternative mechanisms. The organisms with tunable kinetics were engineered by a genetic recombination technique, which generated two strains of E.coli with different antibiotic resistance genes placed at the same location in otherwise identical genomes. When no antibiotics are present these stains have identical growth characteristics and hence are neutral with respect to one another. In the presence of low concentrations of antibiotics the strain with the appropriate resistance gene has an advantage. Time series abundance of the two strains were obtained under three different experimental setups that were devised to give differing weight to neutral and selective processes. A model that incorporates selective and neutral effects could be calibrated in all cases, but the match between experimental and theoretical parameters could only be achieved if an ‘effective community size’ that is smaller than the real community size is used. Evidence is given for this being a phenomenon associated with spatial correlation in the demographics of the community. The consequences of this are profound. It means that even in very large microbial populations random drift will affect community composition and identically engineered systems will yield differing population dynamics.

Membrane technologies are considered a promising solution for water scarcity in arid regions. However, fouling is a major challenge facing the application of membrane technologies. Fouling limits the economic viability and reduces the overall efficiency of membrane processes. Therefore, fouling mitigation is a crucial factor in spreading the use of membrane technologies for new applications. The first step in fouling mitigation is to predict the propensity of fouling. Unfortunately, there are immense limitations in current industrial practises for fouling propensity prediction. These limitations come from using outdated and inapplicable approaches, in which crucial assumptions are made. For example, in the case of crystallisation fouling or “scaling” one of the major simplifications is the use of pure scaling salt data to predict the propensity of scaling when, in reality, co-precipitation is present. This research work aims to introduce a new approach to systematic assessment of the fouling problem under real and complex conditions and to enhance understanding of the importance of including interactive effects and co-precipitation in the prediction of scaling propensity. In this research work a novel procedure accounting for the local variation of thermodynamic properties along a long membrane channel is proposed. A new approach considering ion interaction and process hydrodynamics for the prediction of the scaling propensity is then introduced. This new approach provides for the first time a completely theoretical assessment for pure salt scaling propensity along a full scale filtration channel without the use of any empirical constants. A new procedure for including the effect of co-precipitation on scaling propensity prediction is developed. The effect of process pressure on solubility products is included theoretically for the first time to enhance the accuracy of scaling propensity prediction during the full scale RO process. This research work helps to produce more reliable and accurate prediction of the onset of scaling which will help strategies to mitigate scaling and increase the overall efficiency of RO/NF processes. The new approach can be applied in practical situations and could be developed to a user-friendly programme able to give an accurate prediction of the fouling propensity in full scale processes allowing the optimisation of membrane processes accordingly. Moreover, comprehensive experimental work has been carried out during this PhD research work to enhance understanding of crystallisation fouling and coprecipitation. The effect of salinity and dissolved organics (DO) in CaSO4 and SrSO4 precipitation and co-precipitation are studied and discussed. Quantitative and qualitative thermodynamic and kinetic analyses combined with structural analyses of deposits are carried out to investigate the effect of salinity, DO presence and coprecipitation on SrSO4 and CaSO4 precipitation. The observations in this experimental study are very important for a deeper understanding of the effect of scaling salts’ coexistence, salinity and DO presence on the behaviour of the scaling salts. This is crucial to reaching a reliable prediction of the scaling propensity within RO/NF processes. Finally, the new developed approaches in this thesis have been validated using set of hydrodynamic tests. This set of tests has been carried out using a newly installed laboratory membrane rig. Moreover, a new technique to simulate full scale membrane processes is proposed using a laboratory membrane rig combined with the programs previously developed in this thesis. This new technique can be used to study the effect of process hydrodynamics on scaling and process performance of full scale membrane processes using a laboratory membrane rig. The outcomes of this research work can be used to investigate the optimal operating conditions and to guide design criteria for different RO/NF practical scenarios.