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.

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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.

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.

No description available.

This thesis is the result of five years research into road traffic emissions of air pollutants. It includes a review of traffic pollution studies and models, and a description of the PREDICT model suite and PREMIT emissions model. These models were used to evaluate environmentally sensitive traffic control strategies, some of which were based on the use of Advanced Transport Telematics (ATT). This research has improved our understanding of traffic emissions. It studied emissions of the following pollutants: carbon monoxide (CO), hydrocarbons (HC) and oxides of nitrogen (NOx). PREMIT modelled emissions from each driving mode (cruise, acceleration, deceleration and idling) and, consequently, predicted relatively complex emission characteristics for some scenarios. Results suggest that emission models should represent emissions by driving mode, instead of using urban driving cycles or average speeds. Emissions of NOx were more complex than those of CO and HC. The change in NOx, caused by a particular strategy, could be similar or opposite to changes in CO and HC. Similarly, for some scenarios, a reduction in stops and delay did not reduce emissions of NOx. It was also noted that the magnitude of changes in emissions of NOx were usually much less than the corresponding changes in CO and HC. In general, the traffic control strategies based on the adjustment of signal timings were not effective in reducing total network emissions. However, high emissions of pollutants on particular links could, potentially, be reduced by changing signal timings. For many links, mutually exclusive strategies existed for reducing emissions of CO and HC, and emissions of NOx. Hence, a decision maker may have to choose which pollutants are to be reduced, and which can be allowed to increase. The environmental area licensing strategy gave relatively large reductions in emissions of all pollutants. This strategy was superior to the traffic signal timing strategies because it had no detrimental impact on the efficiency of the traffic network and gave simultaneous reductions in emissions of CO, HC and NOx.