Increased public awareness, stricter legislation standards, and environmental and health effects associated with water pollution are driving the development of improved wastewater treatment techniques. In order to meet these challenges, a novel and cost effective process has been developed at the University of Manchester to treat water contaminated with dissolved organics by exploiting a combination of adsorption and electrochemical regeneration. Adsorption of organics takes place on the surface of a non-porous and highly electrically conductive graphite adsorbent, followed by anodic electrochemical regeneration leading to oxidation of the adsorbed organic contaminants. The mechanism of degradation of adsorbed organics during electrochemical regeneration is particularly important from the point of view of the breakdown products. Ideally, complete oxidation of the adsorbed organics to CO2 and H2O should occur, but it is also possible that intermediate by-products may be formed. These breakdown products could be released into the water, be released as gases during the regeneration process or may remain adsorbed on the surface of the adsorbent. Information about the breakdown products is an important requirement for the commercial application of the process. This PhD project focused on an investigation of the formation of intermediate oxidation products released into the water (liquid phase) and with the regeneration gases. Phenol was chosen as a model pollutant and a graphite intercalation compound (GIC) adsorbent, Nyex®1000 (Arvia® Technology Ltd) was used. The main oxidation products formed during both batch and continuous adsorption with electrochemical regeneration were 1,4-benzoquinone, maleic acid, oxalic acid, 4-chlorophenol and 2,4-dichlorphenol. These compounds were detected in small concentrations compared to the overall concentration of the phenol removed. Two mechanisms of organic oxidation during electrochemical regeneration of the GIC adsorbents were identified. The first was the complete oxidation of the adsorbed species on the surface of the adsorbent and the second involved the indirect electrochemical oxidation of organics in solution. Breakdown products were found to be formed due the indirect oxidation of organics in solution. The formation of (chlorinated and non-chlorinated) breakdown products was found to be dependant on current density, pH, initial concentration, chloride content and the electrolyte used in the cathode compartment. The concentrations of chlorinated breakdown products can be minimized by using low current density, low initial concentrations, a chloride-free environment and/or treating the water over a number of adsorptions and regeneration cycles. On the other hand, non-chlorinated breakdown products can be minimized by applying higher current density and treating the solution over several cycles of adsorption and regeneration. Therefore, selection of optimum conditions is important to reduce the formation of undesirable breakdown products. The formation of free chlorine during batch electrochemical regeneration was also investigated under a range of operating conditions including the initial concentration of chloride ions, current density and pH. The outcomes of this study have important implications in optimising the conditions for the formation of chlorinated breakdown products and in exploring the role of electrochlorination for water disinfection. Analysis of the regeneration gases has revealed that the main components of the gases generated during the electrochemical regeneration of GIC adsorbents were CO2 and H2O. A preliminary mass balance has suggested that about 60% of the adsorbed phenol was oxidised completely to CO2. However, further work is needed to determine the fate of the remaining phenol. The surface characterization of the GIC adsorbent during adsorption and electrochemical regeneration was carried out using surface techniques including Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, Energy dispersive X-ray spectroscopy (EDS) and Boehm titration. FTIR and Raman spectroscopy were found to be unsuitable for determining the concentration changes at the surface of the adsorbent during adsorption and regeneration. However, Boehm titration has shown that the GIC adsorbent has phenolic, carboxylic and lactonic groups. The concentrations of phenolic groups were found to be higher after phenol adsorption and to decrease during electrochemical regeneration. The results of EDS analysis gave results which were consistent with these observations. Another important aspect of this PhD project was to explore the potential application of adsorption and electrochemical regeneration using GIC adsorbents to water disinfection. A model microorganism E. coli was selected for adsorption and electrochemical regeneration studies under a range of experimental conditions. This study has provided evidence that the process of adsorption and electrochemical regeneration using GIC adsorbents can be used for disinfection of water. Disinfection of water was found to be a combination of two processes: the adsorption of microorganisms followed by their deactivation on the surface; and electrochemical disinfection in solution due to indirect oxidation. The possible disinfection mechanisms involved in these processes include electrochlorination, pH changes and deactivation by direct oxidation of microorganisms. Scanning electron microscopy was found to be a useful tool for investigating changes in surface morphology of microorganisms during adsorption and electrochemical regeneration. The disinfection of a variety of bacteria, fungi and yeasts was tested and evaluated. However, disinfection of protozoa including C. parvum was not demonstrated successfully. It was also demonstrated that the process of adsorption with electrochemical regeneration using GIC adsorbents can be used to simultaneously remove organics and to disinfect microorganisms.

Despite being the subject of peer reviewed research since the mid-1980s, the conservative nature of the wastewater treatment industry means that the commercial application of membrane aerated biofilm reactors has not realized the potential that the published research demonstrates. The early research demonstrated the ability of membrane aerated biofilm reactors to achieve good levels of pollutant removal from various types of wastewater, but also exposed several weaknesses of the technology (i.e. cost of membranes, control of biofilm thickness) which have prevented the concept of MABfRs being developed in viable wastewater treatment technologies. However, as membrane technology has developed, the cost of suitable membranes has fallen, prompting the research community to revisit the concept. This later batch of research has identified several niche applications where membrane supported biofilms can be used for effective removal of pollutants from water. Using the MABfR for the treatment of secondary effluent as a polishing step is another niche application which has been identified and is examined in this work; leading to the development of a patented treatment technology – the BioSettler.

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The efficacy of pond treatment systems is dependent on the internal hydrodynamic and mixing interactions between aquatic vegetation and the adjacent flow. In attempting to improve pollution degradation and reduce the effects of hydraulic short circuiting, an understanding and quantification of these interactions was sought for seasonal changes in vegetation growth. Controlled laboratory studies were conducted using detailed Laser Induced Fluorometry (LIF) and Ultrasound Velocity Profiling (UVP) techniques to quantify mixing across vegetated shear layer, emergent Cattail reeds (Typha latifolia). An Optimised Finite Difference Model (OFDM) was developed to predict the best fit downstream concentration distributions given the input profiles of transverse mixing coefficient, Dy(y). The model provided strong fitting in artificial vegetation (R2 = 0.977 and 0.969 for high and low density rigid cylinders). A good fitting was also made for the winter reeds (R2 = 0.976); although the physical application of conventional shear layer theory failed to significantly improve predictions in the summer season reeds above those of a simple discontinuity functionality describing Dy(y). The form of the lateral variation in transverse mixing coefficient was confirmed in the artificial vegetation studies where peak mixing is enhanced by shear layer vortices. However, in real vegetated shear flows, the heterogeneities in stem morphology and distribution render the relative magnitude of shear layer mixing diminished when compared to other regions of the flow. It is shown that, while the OFDM provides good predictions of concentration distributions when using a physically justified profile of the transverse mixing coefficient, a discrete step formulation is sufficient for describing mixing in real vegetated shear flows. This study shows therefore, that, while shear layer mixing is dominant in artificial, uniform vegetation, transverse mixing in real vegetated flows is dominated by complex geometries, localised shear processes and bed roughness effects.

The Kufra region of south eastern Libya comprises an area about 850 km south to north, and some 500 km wide rising to 450 m above sea level. Rainfall is low and agriculture depends on irrigation. Most of the population of Kufra are private farmers who use flood irrigation from shallow wells (19-60 m), but there are co-operatives of farmers that have shared the cost of deeper wells (120 - 150 m) and sprinkler irrigation. The Kufra Agricultural Project (KAP) state farm is made up of 100 circles (farms) each having its own deep well (220 – 352 m) and rotary sprinkler. The experimental work was conducted in three phases. An initial study was made of soil profiles and irrigation water on 4 private and 4 state farms. An inter laboratory study compared results in the KAP and Glasgow University (GU) laboratories. The third phase was a survey of top soils, irrigation water, crop yield and questionnaires for a much larger number of farms. Chapter 3 describes the comparison between chemical analysis results of 33 soils in the KAP and GU laboratories. There was a good level of agreement between the two laboratories. The high correlation coefficients indicate a high level of precision in both laboratories. However there were systematic differences between the two laboratories, results for EC, Ca2+, Mg2+ and Cl- were 2% to 6% lower in the KAP laboratory. There were no significant differences in the results for Na+ and K+ between the laboratories. It is important that all analyses were carried out in one laboratory, so all subsequent samples were sent to the KAP laboratory. Chapter 4 evaluates the quality of irrigation water from 86 wells in the Kufra region in line with FAO and USDA standards for irrigated agriculture. pH, EC, Ca2+, Mg2+, Na+ and SAR were not significantly affected in state farms by well depth or age, but were significantly affected in the private farms by well depth, where the values were higher in shallow wells and significantly related to well age. There are two responses to well age related to well depth shown by two distinct lines. The shallow wells (<30 m) show a significant (p< 0.001) increase in EC, Ca2+ and Na+ and significant (p< 0.01) increase in Mg2+ as well age decreases. The deeper wells (>30 m) exhibits no significant effect of well age (p> 0.05). USDA classification indicates that the water of all the wells of private farms is unsuitable for irrigation purposes. The FAO criteria showed that all private wells had limitations on use due to salinity and SAR. (EC: 78% severe, 22% slight/moderate ; SAR: 35% severe, 65% slight/moderate) Chapter 5 describes a survey of soil profiles from state and private farms. Irrigation lowered the salinity of the virgin soil profiles, with a clear distinction observed between the virgin and irrigated profiles for EC and water soluble Ca2+, Mg2+, Na+, K+, Cl- and SO42- in state farms, and for EC and water soluble Na+, Cl- and SO42- in private farms. In the virgin soil profiles, these parameters showed a clear decrease with depth, while in the irrigated soil profiles they were much lower in concentration and more uniform with depth. There was no clear trend with depth in irrigated soil profiles for pH, HCO3-, CaCO3%, exchangeable cations, and ESP % in the state farms and for pH, water soluble Ca2+, Mg2+and K+, CaCO3%, exchangeable cations, and ESP% in the private farms. The profile averages for pH, EC, ESP%, water soluble Na+, Cl-, HCO3- and SO42- and exchangeable sodium were significantly greater (t-test, p≤0.05) in the irrigated profiles of private farms than in KAP farms. The irrigated topsoils (0–25 cm) showed similar results except that bicarbonate and sulphate were not significantly different. The second part of chapter 5 describes a larger survey of irrigated topsoils. This showed that the pH, EC, ESP% and exchangeable Na+ were much higher in the private farms compared to state farms soils. According to the USDA classification all state farm soils were classed as normal, while 70% of private farm soils were classed as saline alkaline, 15% normal, 10% saline and 5% alkaline. There was no significant effect of crop type on any soil parameter for state or private farms. There was no significant correlation in the combined data for state and private farms between irrigation water and soil for pH, Ca2+ and Mg2+ but there is for EC, Na+ and SAR. In all the graphs there are 2 clusters of points separating the state and private farms which masks the correlation relationship. Chapter 6 compares the yields of alfalfa and potatoes in the state and private farms. The mean values for dry yield of alfalfa from state (6.32 t/ha) and private (3.06 t/ha) farms were significantly different (p<0.001, pooled t-test). The age of the alfalfa crop had a significant (p<0.001) positive effect on yield in the state farms, but a significant (p<0.001) negative effect in private farms. Crops on the private farms were 2 to 8 years old compared with under 2 years on the state farms. Although there were low yields at high values of water and soil parameters (private farms) and high yields at low values of water and soil parameters (state farms) plotting yield against these parameters shows 2 clusters. Looking at the private farms alone there was no significant correlation between alfalfa yield and any of the quality parameters for soil or water. No potatoes were grown on state farms when the samples were collected, so historical data was used (average yield 40 t/ha). The mean yield of potatoes from private farms was significantly lower (p<0.001) 23.16 t/ha. None of the correlation relationships between crop yield with soil and water quality parameters for private farms was significant. Despite the large differences in soil and irrigation water chemistry between state and private farms, there was no evidence that poor irrigation water quality or soil salinity currently limits production on private farms. Chapter 7 describes the survey of private farmers and shows that 81% of respondents did not consider farming as a professional activity they could rely on, but rather an activity to fill their free time. The study also examined other aspects including the farmers’ education level, the farms’ age, irrigation and the impact of water salinity, types and sources of fertilisers. The study concluded that traditional agricultural systems in this region are not built on a scientific basis, or an adequate knowledge of economic feasibility. Consequently, the production rates of agricultural crops are very low.

Bioclogging can be defined as the reduction of hydraulic conductivity and porosity of a saturated porous medium due to microbial growth. Wastewater disposals, artificial groundwater recharge, in-situ bioremediation of contaminated aquifers, construction of water reservoirs, or secondary oil recovery are all affected by this process. The potential for soil and groundwater contamination may increase by the rapid movement of the solutes through soil due to the presence of preferential flow which resulted in increasing bypassing of soil matrix and increasing pore water velocities. On the other hand the presence of preferential flow could affect the clean-up process of the contaminated land by extending the remedial time. The reason behind that is the relatively quick contaminant clean-up in the high permeable zones compared to the slow contaminant clean-up in the low permeable layers. Therefore, this study aims to investigate the bioclogging process in porous media and the factors that can affect this process, also to understand how all aspects of flow are affected by the clogging process, and finally to investigate the potential of biological growth to control direction and location of subsurface hydraulic flow to overcome the problems of preferential flow. The bioclogging process was investigated through a series of sand column experiments in homogeneous and heterogeneous porous media. Six sand fractions ranging from 63-1180 μm were selected as a porous media. Two bacterial strains (P. putida mt-2 and B. indica) were used in this study. Different analytical methods such as loss on ignition and the total number of cells were used to analyse the soil samples. iv The outcomes of this study showed that the growth of bacteria in porous media can reduce the heterogeneity of the porous media, thereby reducing the impact of the preferential flow which could affect the clean-up process of the contaminated land. Pore throat model with the incorporation of different bioclogging models such as the biofilm or plugs (Vandevivere et al., 1995), micro-colony (Okubo and Matsumoto, 1979), and macroscopic (Clement et al., 1996) models were applied to evaluate the results of the experimental work in heterogeneous porous media. The changes in hydraulic conductivity and the porosity of porous media were modelled by assuming that the bioclogging occurs in the small pores which connect the large pores of the porous media. Generally amongst the three bioclogging models, the current study showed that the measured values of the hydraulic conductivity relatively coincide with the predicted values obtained by using Vandevivere et al. (1995) model. Nevertheless, the predicted values of the hydraulic conductivity coincided to some extent with the measured values of the hydraulic conductivity for the large sand fractions. This corresponds with the findings of several previous studies which also confirmed that bioclogging models can only predict the change of the hydraulic conductivity for the large sand fractions. The failure of these models could be related to the assumptions made by each model, which could be less appropriate in fine-textured materials than they are in coarse textured ones. The second possible reason for the disparities between observations and model predictions is related to the assumption made in some of these models that the microorganisms which are responsible for clogging form biofilms of constant thickness which uniformly coated the surface of soil particles.

Stiffness identification of an impacted constraint is the main issue discussed in this thesis. Primarily, a change of stability (bifurcation) is used to determine the dynamical stiffness of an impacted beam for a piecewise-linear impact oscillator. Detailed one- and two-parameter bifurcation analyses of this impacting system are carried out by means of experiments and numerical methods. Particularly, the two-parameter numerical continuation of the obtained codimension-one bifurcation (period-doubling bifurcation, or fold bifurcation) indicates a strong monotonic correlation between the stiffness of the impacted beam and the frequency at which this bifurcation appears. In addition to the bifurcation techniques, another method for stiffness identification is analysis of impact duration. To accurately detect impact durations from numerical or experimental signals, nonlinear time series methods are utilised. Two impacting systems, including the piecewise-linear impact oscillator and a drillbit-rock vibro-impact system, are studied to demonstrate this proposed method. For either system, the impact duration is relatively constant when the response of oscillator is a period-one one-impact motion, and it is approximated as a half of the natural period of the oscillator-constraint system. When the mass of oscillator is constant, for an impacted constraint with a certain stiffness, the higher the stiffness, the lower the impact duration. This monotonic correlation provides another mechanism to estimate the stiffness of the impacted constraint. Based on the developed two dynamical methods for stiffness identification, a control algorithm for parameter adjustment of the axial vibration for rotary-percussive drilling applications is designed. This control algorithm aims to maintain the optimal drilling state under the varying formations. By this way, the efficiency of rotary-percussive drilling is expected to be promoted.

The Lea Navigation in the north-east of London, a canalised reach of the River Lea, is affected by episodes of very low levels of dissolved oxygen. The problem was detected by the Environment Agency in the stretch from the confluence with Pymmes Brook (which receives the final effluent of Deephams sewage treatment works) to the Olympic area (Marshgate Lane, Stratford). In this project, possible causes and sources of the poor water quality in the Lea Navigation have been investigated using a multi-parameter approach. A study of physico-chemical parameters, obtained from Environment Agency automated monitoring stations, gave a clear picture of the poor river water quality at three sites in this reach. River water ecotoxicity to the freshwater alga Pseudokirchneriella subcapitata was determined by algal growth inhibition tests, following the OECD guidelines. Moreover, a novel protocol was developed which involved the use of E. coli biosensors (CellSense) operating at a lower potential than the standard protocol and using pre-concentrated river water samples. This protocol is promising and it has the potential to be a useful tool to determine the toxicity of contaminants at environmental concentrations. Furthermore, the developed protocol is a rapid, easy to perform bioassay, with potential application in achieving the aims of the Water Framework Directive (WFD). In addition to the data from the Environment Agency automatic monitoring stations and the laboratory-based tests, two in situ monitoring approaches were performed: 1) a detailed spatial seasonal monitoring of physico-chemical parameters of river water at twenty-three sites, and 2) algal growth inhibition tests, with algae entrapped in alginate beads, at seven monitoring stations. Results showed chronic pollution, and identified polar compounds in the river water and high bacterial concentrations as possible causes of low dissolved oxygen levels. This study confirmed the negative impact of Deephams STW (throughout Pymmes Brook) on the water quality of the Lea Navigation. However, there was evidence of other sources of pollution, in particular Stonebridge Brook was identified as uncontrolled source of pollution and untreated wastewater. Other possible sources include Old Moselle Brook, diffuse pollution from surface runoff, boat discharges and other undetected misconnections. Finally, in the light of the WFD, this project provides a case study on the investigation of river water quality, providing evidence that the multiparameter approach is reliable, and low cost approach for the monitoring of freshwater bodies.

Today the water industry faces a huge challenge in supplying a sustainable, energy efficient and safe supply of drinking water to an increasing world population. Slow sand filters (SSFs) have been used for hundreds of years to provide a safe and reliable source of potable drinking water, with minimal energy requirements. However, a lack of knowledge pertaining to the treatment mechanisms, particularly the biological processes, underpinning SSF operation, has meant SSFs are still operated as “black boxes”. This lack of knowledge pertaining to the underlying ecology and ecophysiology limits the design and optimisation of SSFs. This thesis represents the most comprehensive microbial community survey of full-scale SSFs to-date. Using traditional microbiological methods alongside up-to-date molecular techniques and extensive water quality analyses, specific taxa and community metrics are linked to changes in water quality production. Furthermore, it has been verified that laboratory scale SSFs can mimic the microbial community and water quality production of full-scale filters. This allowed rigorous experiments pertaining to operational differences, pathogen and novel contaminant removal to be performed. This has revealed, for the first time, that multiple trophic interactions within SSFs are integral to optimal performance. This thesis has shown that SSFs are phylogenetically and metabolically diverse systems capable of producing high quality water, with the ability to adapt to remove novel contaminants. Using the information gathered, improvements to filter maintenance and operation can be achieved. Future work will apply the microbial and macrobial community dynamics and impact of novel contaminants on filter performance discovered in this thesis into predictive models for water quality.

Oil pipelines play a significant role in crude oil transportation and bring danger close to communities along their paths. Pipeline accidents happen every now and then due to factors ranging from operational cause to third party damage. In the Niger Delta pipeline system, interdiction is common; therefore, every length and breadth of land covered by a pipeline is vulnerable to oil pollution, which can pose a threat to land use. Weak enforcement of rights of way led to encroachment by farmers and human dwellings, thereby bringing people in close proximity to pipelines. Considering the impact exposure can have on human health, a method was developed for identifying vulnerable communities within a designated potential pipeline impact radius, and generic assessment criteria developed for assessing land use exposure. The GIS based model combines four weighted criteria layers, i.e. land cover, population, river and pipeline buffers in a multi-criteria decision making with analytical hierarchy process to develop an automated mapping tool designed to perform three distinct operations: firstly, to delineate pipeline hazard areas; secondly, establish potential pipeline impact radius; and thirdly, identify vulnerable communities in high consequence areas. The model was tested for sensitivity and found to be sensitive to river criterion; transferability on the other hand is limited to similar criteria variables. To understand spatial distribution of oil spills, 443 oil spill incidents were examined and found to tend towards cluster distribution. Meanwhile, the main causes of spills include production error (34.8%) and interdiction (31.6%); interdiction alone discharged about 61.4% of crude oil. This brings to light the significance of oil pipeline spills and the tendency to increase the risk of exposure. The generic assessment criteria were developed for three land uses using CLEA v 1.06 for aromatic (EC5-EC44) and aliphatic (EC5-EC44) fractions. The use of the model and screening criteria are embedded in a framework designed to stimulate public participation in pipeline management and pipeline hazard mitigation, which policy makers and regulators in the oil industry can find useful in pipeline hazard management and exposure mitigation.