The diversity and abundance of ammonia oxidizing bacteria (AOB) and Archaea (AOA) were investigated in five oil refinery wastewater treatment plants in the UK using culture-independent molecular techniques. The AOB found in the plants were phylogenetically associated with the Nitrosomonas oligotropha and Nitrosomonas marina lineages and clones related to the Nitrosomonas oligotropha lineage may represent novel AOB species. Putative AOA were found in a trickling filter system and in two activated sludge systems and were phylogenetically placed within marine group 1.1a and terrestrial group 1.1b, Crenarchaeota. Evidence suggests that these are most closely related to AOA from other wastewater treatment systems. Only three of the refinery wastewater treatment plants were nitrifying. AOB numbers quantified through real-time PCR of amoA ranged from 1.54 x 105 cells/mL to 9.49 x 105 cells/mL in the trickling filter system. In contrast, AOB numbers in one of the activated sludge systems ranged from 1.24 x 104 cells/mL to 1.68 x 106 cells/mL, while in the other, AOB numbers ranged from 7.14 x 103 cells/mL to 9.56 x 104 cells/mL, despite showing good nitrification. Conversely, AOA were detected in the trickling filter system at 1.54 x 107 cells/mL. In the activated sludge systems AOA were more abundant than AOB. In the activated sludge system with the higher AOB numbers, AOA abundance ranged from 4.32 x 106 cells/mL to 1.77 x 108 cells/mL, and in the activated sludge system with the lower AOB numbers, AOA abundance ranged from 6.15 x 106 cells/mL to 2.69 x 108 cells/mL. The high abundance of AOA in the nitrifying refinery wastewater treatment systems suggested that AOA may play an important role in nitrification in these reactors. However microautoradiography coupled with CARD-FISH (conducted by Dr Marc Muβmann, University of Vienna) indicated that the AOA were not chemoautotrophic ammonia-oxidizers. Assessment of AOA and AOB abundance in relation to ammonia removal in the treatment plants indicated that ammonia removal was consistent with the AOB numbers detected and thus, AOB are probably responsible for most of the nitrification observed and the overall contribution of putative AOA to nitrification in these wastewater treatment plants appears to be relatively minor. Keywords: Ammonia oxidizing bacteria (AOB), ammonia oxidizing archaea (AOA), nitrite oxidizing bacteria (NOB), diversity, phylogeny, abundance, real-time PCR, CSAOR (cell specific ammonia oxidizing rate or rates), fluorescence in situ hybridization (FISH), oil refinery wastewater treatment plants.

This thesis aims to investigate for the first time the chemical mechanism and efficiency of the process of unmixed steam reforming (also known as chemical looping reforming in a packed bed reactor) in producing hydrogen when utilising liquids of waste biomass origin as the feedstocks, in particular waste cooking oil. Moreover, the optimisation of unmixed steam reforming is investigated by incorporating a natural CO2 sorbent, calcined dolomite, in the reactor bed material, resulting in the process called Sorption Enhanced Unmixed Steam Reforming, which operates by shifting the reactions toward more favourable thermodynamics. The characteristic properties of three liquids of waste biomass origin (waste cooking oil, and fast pyrolysis oils from EFB -palm empty fruit bunches- and pinewood), are examined, including their decomposition kinetics by numerical modelling for the first time. The sorbent's efficiency, as expressed by its extent of C02 intake and release is examined at both 'micro'- and 'macro'-scales (i.e, from few mg to few g samples) through the kinetics of the carbonation and calcination reactions in conditions simulating sorption enhanced unmixed steam reforming, in addition to its durability in both set ups. These are compared to the sorbent's performance during the sorption enhanced unmixed steam reforming of the waste cooking oil throughout several chemical loops or cycles. The chemical looping (cyclic operation) of both processes is assessed using the Ni-NiO and CaO-CaC03 'loops', and compared against the equivalent process in thermodynamic equilibrium. The production from waste cooking oil of a nearly pure H2 stream (>96% vol), with a hydrogen yield enhancement of between 29 and 120%, with long periods of autothermality per cycle, at lower molar steam to carbon ratios (2.5 and 4) and lower temperatures (by 200°C) than the literature to date on steam reforming of equivalent virgin vegetable oils is shown. This investigation thus demonstrates the success in producing H2 from waste cooking oil using these advanced steam reforming processes, auguring promising results for similarly challenging organic waste liquid fuels.

Sustainable Urban Drainage Systems (SUDS) is a generic term that refers to various measures aimed at minimising surface runoff (and consequent flooding and pollution problems) from urban catchments. SUDS technologies include local infiltration, storage and storm-water re-use devices. Although there is considerable international evidence of the successful incorporation of SUDS technologies in new developments, there is very little indication of the extent to which they represent a viable rehabilitation option for retrofit applications to problem urban catchments in the UK. It is believed that uncertainties about the design, hydraulic performance and cost of retrofit SUDS schemes, as well as some regulatory issues, have prevented UK engineers from exploiting the full potential of this approach. This thesis presents two case studies in which retrofit SUDS have been evaluated against 'conventional' (i. e. in-sewer) drainage rehabilitation schemes. The case studies relate to the City of Leeds in Northern England, UK. In both cases it was found that SUDS technologies were viable, both in terms of hydraulic performance criteria (number and volume of CSO spills or flooding events) and in terms of comparative construction costs. Novel procedures were developed for evaluating hydraulic performance and SUDS scheme costings. The identification of the most cost-effective from all feasible SUDS technologies for a given location is not straightforward. This thesis, therefore, proposes a design methodology for retrofit SUDS. The methodology comprises a decision making model (flow chart) that indicates whether SUDS-based approaches are likely to be viable, and cost-effective for a particular application. The flow charts make reference to SUDS design criteria (such as land-take, slope and infiltration capacity) and regulatory constraints (such as Building Regulations and local groundwater protection policies). Fundamental to the flow charts arc hierarchies that characterise urban surface type, the treatment train concept, the disposal mechanism, and cost.

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In sewerage asset management, there has been a concerted move away from primarily assessing system capacity, to focus on 'serviceability' as a key performance indicator. In the UK, water regulators have imposed an expectation on water companies to significantly lower the risk posed to customer serviceability from the sewerage industry. Proactive maintenance is the main vehicle by which asset managers aim to achieve this outcome. This thesis outlines the development of a methodology which ranks network pipes in order of risk to serviceability. The tool is base on the Failure Mode, Effect and Criticality Analysis (FMECA) principle that risk is a function of failure consequence and likelihood and in exception to other recently developed tools, this method focuses the analysis towards data which is readily available within the industry and aims to avoid data where reliability is in doubt, such as records of past events. The tool consists of an initial screening process to eliminate those pipes which are at a significantly reduced likelihood of flooding before each remaining pipe is scored according to various factors which affect consequence and likelihood of flooding. Final risk scores, and therefore rankings are then achieved through the combination of consequence and likelihood scores. Appropriate scores and weightings have been achieved through customer research, discussion with industry representatives and the completion of an additional study into trends in failure likelihood. The methodology is a decision support tool developed to aid sewerage asset managers in their role in balancing risk to customer serviceability against cost of intervention, by providing a measure of risk which is not dependent on poor quality data.

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Further materials have been introduced to the study to test their properties against that of the fly ash and their performance as a cement replacement. It was found that applying the STi process to the fly ash produced results comparable to those of the GGBS controls at 33%. This was bettered when the fly ash was subject to a classification process however, the waste element of the fly ash increases. No further benefits were to be had from the inter-grinding of the fly ash when used in concrete.

A Hydrodynamic Vortex Separator (HDVS) is a form of Combined Sewer Overflow (CSO) used for solid-liquid separation. HDVSs are also used at sewage treatment works for the separation of grits that are transported through the sewer network. The residence time of the fluid that passes through these devices is increased by the rotational nature of the flow and hence, the time that gravity has to act on particulates is also increased. This feature of the fluid dynamics means that a HDVS may also be used as a contact vessel for disinfection of wastewater during a CSO event. To date the physics of these systems is not completely understood in terms of particulate separation. To achieve a greater understanding of the HDVS an initial sensitivity study using Computational Fluid Dynamics (CFD) was carried out looking at factors that may influence the efficiency and to gain an insight into variables that should be accounted for during experimentation and test rig design. Following this sensitivity study a 0.75m diameter HDVS was studied under laboratory conditions where it was found that a parameter described as the particle surface load controls the efficiency of the HDVS and not the particle settling velocity as previously thought. A model was developed to describe the retention efficiency and was also applied to scaling. However, more work is required to achieve a greater understanding of the application of the retention efficiency model to larger separators. Experimental trials on a 3.4m diameter HDVS were undertaken and from this it was found that the most suitable residence time distribution model for a HDVS is the axial dispersion model. Attempts to use CFD to model the separation efficiency of such systems have to date failed. However, validations of the residence time characteristics are reasonable. This has allowed CFD to be used to study the application of residence time to disinfection where it has been shown that an existing disinfection model may be developed to describe the disinfection performance of a HDVS. Scaling laws have also been developed using CFD for the residence time and CFD has consequently given an insight into the fluid dynamics within the HDVS.