Observations of atmospheric corrosion on aluminium alloy AA2024-T3 were made within droplets of NaCl solution and simulated ASTM ocean water. High speed in-situ synchrotron X-ray tomography has been used to observe the initiation and propagation of corrosion sites. Tomographic scans had a temporal resolution of 300s per full tomographic scan, providing a non-destructive visualisation of corrosion. Sites initiate at numerous surface morphologies, including at intermetallic inclusions, under surface deposits and salt crystals, and also at sites with no obvious micron-scale microstructural features. It was observed that corrosion sites grow discontinuously and inhomogeneously when conditions are constant, consistent with bursts of dissolution followed by some repassivation. The nature of corrosion products was investigated with Raman spectroscopy and EDX. The dominant corrosion product was Dawsonite for both droplet solutions, however the distribution of corrosion products differed between the two types of droplet. NaCl droplets spread more, resulting in fewer, larger corrosion sites. ASTM ocean water droplets showed multiple small corrosion sites within the droplet owing to the presence of Hydrotalcite around the droplet perimeter. Corrosion development under wet-dry cycling conditions was different for NaCl and ASTM ocean water droplets. Under NaCl droplets, no growth or initiation was observed during “dry” phases. However, ASTM ocean water remains partially wet in “dry” periods as some of the salt constituents in ASTM ocean water remain hydrated. As a consequence, corrosion site growth is able to continue.

The key product from anaerobic digestion (AD) is biogas, which is used to generate heat and/or electricity. Anaerobic digestion involves degradation and stabilisation of the feedstock by microorganisms, leading to the formation of biogas and a digestate residue, which is used as a fertiliser. Contaminants entering the system in the feedstock may limit biogas yield if functioning of the methanogenic archaea is disrupted. Digestate quality may also be compromised. Approximately 40% of the current UK biogas plants are farm-based, using manures and slurry as the main feedstock. Veterinary medicines are excreted in dung of treated animals and if used prophylactically, concentrations in the faeces or urine may be significant. Contaminated animal waste is therefore likely to be used as a feedstock in AD. Since digestates are commonly used as fertilisers, contaminant loading and fate must be understood to prevent transfer into crops, reductions in soil microbial activity, increased antibiotic resistance and detrimental effects to livestock if digestates are applied to fodder crops or pasture. It is unlikely that the use of veterinary pharmaceuticals will be reduced whilst livestock farming is intensifying and the current demand for meat is growing, therefore understanding the operational processes of AD that influence the persistence of commonly used veterinary medicines and subsequent toxicity are crucial to minimising potentially detrimental effects. Research was undertaken using laboratory-scale digestion vessels to quantify the effect of the commonly used veterinary antibiotics, oxytetracycline and tylosin, when added to naïve (organic) cattle dung or to slurry from a conventional dairy farm. Anaerobic digestion units were spiked with either oxytetracycline or tylosin at low (environmentally realistic) and artificially high concentrations, either at start-up (day 0) or once the system was producing gas (day 15). Biogas production was measured and gas collected every 5 days to quantify the temporal effect of the antibiotics on methane production. Oxytetracycline and tylosin significantly reduced both biogas quality and quantity, with the extent of the effect differing with each feedstock. In organic cow dung, the low (4.33 mg L-1) and artificially high (86.63 mg L-1) concentration of oxytetracycline added on day 15 to organic cow dung caused an overall drop in biogas production of 12% and 25% respectively, whilst the same concentrations incorporated at start-up caused a drop of only 4% and 18% respectively. Both the low and artificially high concentrations of tylosin added on day 15 caused a 33% drop in biogas production, whilst the same concentrations incorporated on day 0 caused a drop of 15% and 42% respectively. In conventional dairy slurry, low (4.33 mg L-1) and artificially high (86.63 mg L-1) concentrations of oxytetracycline caused an overall 3% and 10% drop in biogas production respectively, with tylosin amendment causing a decrease in total biogas production of 7% and 22% respectively. Feedstock origin affected biogas production and quality when the system was challenged by antibiotic inputs. These data highlight the complex interactions that can occur between feedstock and exposure to veterinary pharmaceuticals.

Within the last decades the importance of sustainable treatment technologies, such as constructed wetlands (CWs) and vegetated ponds, has raised due legislation (e.g. WFD), directing toward green infrastructure to mitigate water pollution. The efficiency of pond and CW treatment systems depends on the internal hydrodynamics and mixing interactions between water and aquatic vegetation. In order to contribute to the current knowledge of how emergent real vegetation affects solute mixing, and physical flow characteristics in full-scale aqueous systems, an understanding and quantification of those processes and interactions was sought under the: i) natural seasonal vegetation and flow rate variation in two CWs, and ii) physical flow characteristics in overall six different full-size treatment units. To address these issues, outdoor tracer field studies were undertaken in each treatment unit. Regarding the seasonal plant variation, an intelligent automated tracer injection system was developed to achieve autonomous remote measurements in two CWs, vegetated by Phragmites australis, in different seasons and flow rates. Experiments involved measurements of longitudinal mixing, physical flow characteristics and vegetation characteristics in different plant ages and various discharges. It was shown that seasonal vegetation variation influences the longitudinal mixing coefficient by up to four times, and the physical flow characteristics by increasing the flow resistance and creating stagnant backwaters at the end of plant cycle, achieving reduction of the peak concentration by three times. Longitudinal mixing decreased with discharge in all plant ages. Furthermore, it was shown that internal design (i.e. bed topography or vegetation distribution) overwhelm the seasonal plant variation effects on mixing and flow characteristics. Moreover, relative comparison of outlet configuration, inflow conditions, and internal features, between the six different treatment units demonstrated an increase in residence time by up to three times. Results underlined the importance of investigating hydrodynamics and physics of flow in full-size units to enhance treatment efficiency and predictions of water quality models.

Due to high regeneration energy demands for amine absorption processes for post-combustion CO2 capture, alternative technologies such as adsorption processes using solid adsorbents have been considered. Other practical issues such as corrosion of equipment and loss of solvent can be avoided with adsorption processes. Fixed bed adsorption processes, in which CO2 adsorption and adsorbent regeneration are performed successively in a vessel packed with adsorbent, are the most common adsorption processes. However, in fixed bed temperature swing adsorption (TSA) processes, large columns and long heating and cooling times would be needed. Fixed bed pressure swing adsorption (PSA) processes use electrical energy, which is more expensive than thermal energy in a power plant. Therefore, the feasibility of moving bed adsorption processes including fluidised-bed, co-current and counter-current systems is investigated. In these systems, the adsorbent continuously circulates from a CO2 adsorber to a regenerator. The adsorbents considered are a supported amine adsorbent, activated carbon and zeolite 13X. Numerical simulations of moving bed TSA cycles for CO2 capture have been carried out. The effects of influential parameters in the process have been assessed via sensitivity analyses. It was found that counter-current beds with supported amine adsorbent give the best overall performance. Compared to an amine absorption process, it was found that a moving bed TSA process without heat integration requires the same heat consumption per unit mass of CO2 captured. There is a potential for a lower heat consumption in moving bed TSA processes if, similarly to amine absorption processes, heat integration is carried out or if the CO2 working capacity of the adsorbent can be increased.

An aerosol chemical ageing (ACA) system has been developed for artificially processing atmospheric particles. An aerosol flow tube coupled to a scanning mobility particle sizer (SMPS) and an aerosol time-of-flight mass spectrometer (ATOFMS) have been proposed to study the heterogeneous reaction (HR) between two oxidants, ozone (O\(_3\)) and hydroxyl radical (OH), and three different single organic aerosol proxies: oleic acid (OL), maleic acid (MA) and bis(2-ethylhexyl) sebacate (BES). The ACA system operates under conditions equivalent to ambient processing times of 1 and 20 days with respect to ozone and OH ambient levels, respectively. The study provides evidence for the ageing process of organic aerosol. The physical characterisation of aged particles suggests the formation of volatile products resulting in appreciable decrease in particles size and mass. The chemical study, however, shows that the properties of the aged particles are sensitive to the oxidant and organic material identities, the particle size and the oxidation environment. The applicability of the developed ageing technique has been tested on real atmospheric particles, however, it is concluded that extrapolating laboratory procedures to ambient atmosphere may be challenging due to the complexity of the real atmosphere, particularly, the urban atmosphere.

Phytoremediation is an emerging green technology for the restoration of contaminated sites with various organic and inorganic contaminants. However, phytoremediation efficiency is limited by factors such as contaminant concentration, toxicity and bioavailability, plant choice and stress tolerance, and competence of indigenous microorganisms. A number of possible solutions have been proposed to overcome these limitations. The use of tolerant plant candidates, mixed plant communities and bioaugmentation with microbes and/or plant growth promoting bacteria (PGPB) have been proposed to suppress plant growth inhibition/phytotoxicity and enhance contaminant degradation through the rhizosphere effect but there is need for more research to understand their impact. This research assessed the impact of contaminant stress (diesel fuel, PAH; phenanthrene, fluoranthene and benzo[a]pyrene, and heavy metal) on selected plant species and microbial community structure, contribution of abiotic processes and rhizoremediation to PAH dissipation, and the impact of PGPB on plant growth and PAH dissipation. These objectives were achieved through greenhouse experiments with M. sativa, F. arundinacea and L. perenne on diesel fuel- and PAH-spiked soils. Diesel-fuel treatments had a negative impact on plant biomass yields while the single and mixed PAH treatments had stimulatory and inhibitory effects on plant biomass yields relative to the control.

<p>In this work, different aspects on the re-use of wood based fibres have been studied, focusing on ink detachment of flexographic ink from model cellulose surfaces and changes in porous structure of kraft fibres following different treatments. New model systems for evaluation of ink detachment and ink-cellulose interactions were used. Ink detachment was studied using Impinging jet cell equipment, taking into consideration the influence of storage conditions, surface roughness and surface energy of the cellulose substrate. A micro adhesion measurement apparatus (MAMA) was used to directly study ink-cellulose interactions, from which the adhesive properties between ink and cellulose, having various surface energies, could be derived. UV-light, elevated temperatures, longer storage time, decreased surface energy, i.e. making the cellulose surface more hydrophobic, and high surface roughness all negatively affected ink detachment. Attenuated total reflectance - fourier transform infra red (ATR-FTIR) and atomic force microscopy (AFM) was used to evaluate structural and chemical changes of ink and cellulose upon storage at elevated temperature or under UV-light. After storage at elevated temperatures, ATR-FTIR spectra indicated that a hydrolysis or an oxidative reaction took place as a peak at 1710 cm-1 appeared. AFM revealed that storage at elevated temperatures caused the latex particles present in the ink to form a film, most likely due to annealing. Less ink detached from hydrophobic cellulose surfaces. Ink detachment decreased for rougher cellulose substrates due to an increased molecular contact area.</p><p>Fibre pore structure and water retaining ability influenced fibre/fibre joint strength and different paper strength properties. Investigations took into account the effect of pulp yield, counter-ion types, pH, salt, hornification and strength enhancing additives. Nuclear magnetic resonance relaxation (NMR), inverse size exclusion chromatography (ISEC) and water retention value (WRV) measured the changes that occur in the fibre wall upon varying the conditions. Each different measuring technique contained unique information such that a combination of the techniques was necessary to give as complete a picture as possible over the changes that occurred in the fibre wall upon varying the conditions for the fibre. A correlation between fibre pore radius and sheet strength properties was found, suggesting that fibres with larger pores allow for a larger molecular contact area between fibres to be formed during drying and consolidation of the paper. Fibre/fibre joint strength, fibre flexibility, and the number of efficient fibre/fibre contacts also controlled sheet strength. The effect of different strength enhancing additives on fibre pore structure and paper strength was investigated. Larger pores in the fibres allowed for additives to penetrate into the fibre wall. Additives with low molecular mass (Mw) penetrated into the fibre wall to a larger extent than additives with a high Mw, causing an embrittlement of the fibre. However, low Mw additives gave higher sheet tensile strength despite a leveling out in strength at high additions, indicating that the fibre wall can only adsorb a limited amount of chemical. Polyallylamine hydrochloride (PAH) and polyelectrolyte complexes (PEC) of PAH and polyacrylic acid (PAA) were added separately to the pulp. PEC significantly improved both tensile strength and Z-strength, whereas PAH alone did not increase the strength properties to the same extent unless the sheets were heated to 150°C for 10 minutes. The results suggested that the effect of PEC was dominated by an improvement in fibre/fibre joint strength, whereas the effect of PAH was significantly affected by an improvement of the intra-fibre bond strength</p>

The key question this thesis aims to address is to what extent can micro-generation sources contribute to the carbon emission reduction targets set by the UK government. The operational emissions of micro-CHP capable micro-generators were examined against the UK grid electricity and gas boiler heat. Fossil and biomass fuels were considered. The life-cycle emissions associated with the manufacturing, transport and disposal of micro-generators were calculated. Case studies were constructed, based on the literature. It was found that emissions associated with domestic electrical and thermal demand would be reduced significantly. A Virtual Power Plant (VPP) was defined for aggregating micro-generators, using micro-generation penetration projections for the year 2030 from the literature. An optimisation problem was described, where the goal was to minimise the VPP carbon emissions. The results show the amount of emissions that would potentially be reduced by managing an existing micro-generation portfolio in a VPP. An Environmental Virtual Power Plant (EVPP) was defined, for controlling micro-generator carbon emissions. A multi-agent system was designed. The principle of operation resembles an Emissions Trading Scheme. Emission allowances are traded by the micro-generators, in order to meet their emissions needs. Three EVPP control policies were identified. Fuzzy logic was utilised for the decision making processes. Simulations were performed to test the EVPP operation. The main benefit for the micro-generators is the ability to participate in markets from which they would normally be excluded due to their small size. The multi-agent system was verified experimentally using micro-generation sources installed in two laboratories, in Athens, Greece. Two days of experiments were performed. Results show that system emissions have been successfully controlled, since only small deviations between desired and actual emissions output were observed. It was found that Environmental Virtual Power Plant controllability increases significantly by increasing the number of participating micro-generators.

This thesis reports on work carried out in the development of ultraviolet fibre-optic based absorption sensor systems, including those with the newly available ultraviolet improved silica fibres having low attenuation in the 200 nm to 250 nm wavelength region. Several approaches to optimize the optical design of such sensor systems, their sensitivity and stability are discussed. These fibre-optic sensor systems may be used for remote on-line and real-time analysis of process and water quality, enabling a separation of monitoring equipment from the sensor cell, which thus may be situated in a potentially hazardous environment. The effect of temperature variations on wavelength stability and dark output of inexpensive spectrometer modules, potentially useful for field applications, and the subsequent effect on the accuracy of absorption measurements, as well as the sensitivity of such spectrometer modules at wavelength below 250 nm, is investigated. Further, the performance of a remote fibre-optic sensor system, based on a reflectance cell with an optical pathlength of 1 cm, to measure nitrate concentrations in the wavelength region between 200 nm and 250 nm, is reported. Finally, to improve the sensitivity of such ultraviolet sensor systems, the performance of two fibre-coupled sensor cells with increased optical pathlengths has been investigated. The first sensor cell, based on an aluminium coated fused silica capillary cell, having an optical pathlength of 43 em, is demonstrated in the construction of a residual chlorine sensor. The second sensor cell, a capillary cell with an inner coating of Teflon AF, uses the low refractive index and the high transparency of Teflon AF in the ultraviolet to form a liquid-core waveguide (LeW). This sensor cell has an optical pathlength of 203 mm, extending the use of long pathlength cells to the 200 nm to 250 nm wavelength region. Its performance is illustrated when applied to monitoring low concentrations of nitrates, chlorine and acetylsalicylic acid.

The integration of offshore wind farms through Multi Terminal DC (MTDC) networks into the GB network was investigated. The ability of Voltage Source Converter (VSC) High Voltage Direct Current (HVDC) to damp Subsynchronous Resonance (SSR) and ride through onshore AC faults was studied. Due to increased levels of wind generation in Scotland, substantial onshore and offshore reinforcements to the GB transmission network are proposed. Possible inland reinforcements include the use of series compensation through fixed capacitors. This potentially can lead to SSR. Offshore reinforcements are proposed by two HVDC links. In addition to its primary functions of bulk power transmission, a HVDC link can be used to provide damping against SSR, and this function has been modelled. Simulation studies have been carried out in PSCAD. In addition, a real-time hardware-in-the-loop HVDC test rig has been used to implement and validate the proposed damping scheme on an experimental platform. When faults occur within AC onshore networks, offshore MTDC networks are vulnerable to DC overvoltages, potentially damaging the DC plant and cables. Power reduction and power dissipation control systems were investigated to ride through onshore AC faults. These methods do not require dedicated fast communication systems. Simulations and laboratory experiments are carried out to evaluate the control systems, with the results from the two platforms compared.