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This thesis comprises three papers that address the evaluation of potential climate impacts of solid waste management (SWM) systems and processes from a life cycle perspective for purpose of decision-support. Paper I presents a critical review of the carbon footprint quantification and communication practice of large UK-based waste management companies. Results indicated a lack of methodological consistency and transparency in current practice, emphasising the need for a robust, transparent, and standardised approach to corporate carbon footprint quantification and reporting. Paper I also describes the importance of greenhouse gas (GHG) emission factors (EF) in helping stakeholders better understand and address the potential climate impacts of their SWM activities. However, existing EFs were reviewed in Paper II and were found to lack transparency and breadth. Consequently, Paper II presents an original and fully transparent series of GHG EFs for the recycling of a wide range of source-segregated materials . Results showed that materials recycling generally leads to (often substantial) climate benefits, due to avoided primary material production. However, results also highlighted the dearth of available high quality materials recycling life cycle inventory data, which are essential to support effective SWM decision-making. Paper III presents a novel, practical framework for evaluating the potential climate impacts of complex SWM systems through the innovative use of publically-available waste flow data and a combined material flow analysis (MFA) and LCA approach. The performance of a complete, meso-level SWM system was evaluated and the potential effectiveness of real world waste policies was analysed. Results showed that landfilling was the greatest source of potential impacts for the existing system, whilst the increased diversion of food waste from landfill lead to the greatest reduction in potential impacts. Overall, this thesis presents an original, practical analytical framework and valuable information to support decision makers at multiple levels in evaluating the potential life cycle climate impacts of their SWM activities.

The uncontrolled release of landfill leachate poses a significant threat to the environment and is prevented in part by the landfill liner. The attenuation of contaminants by the liner material may be crucial in limiting environmental damage should the containment of the landfill fail. While the sorption of hydrophobic organic contaminants (HOCs) to clay materials is well documented in the literature in terms of the organic carbon content of the sorbent in a variety of solution phases, a knowledge gap exists in respect to the influence of landfill leachate dissolved organic carbon (DOC) on the attenuation of HOCs. A laboratory based batch sorption study was undertaken, using leachates with five differing DOC characters and origins, at various dilutions, to establish the influence that DOC present in landfill leachates had on the attenuation of the HOCs toluene and naphthalene by Oxford Clay. The aim of this work was to increase the understanding of attenuation of toluene and naphthalene to Oxford Clay in the presence of leachate DOC and to elucidate the role of DOC chemical composition and concentration in landfill leachates on the sorption of HOCs to the Oxford Clay. The objective of this work was to provide more reliable data for predicting the contribution of attenuation of HOCs by sorption in the risk assessment of landfills and recommending updates to the selection process of Kd values for landfill risk assessment models such as LandSim. The chemical character of the DOC was found to affect how the DOC interacted with the solid phase and humic substance-like (HSL) DOC was observed to preferentially sorb to the Oxford Clay. The sorption of DOC was reversible, indicating that DOC, and so DOC-HOC complexes, had the potential to desorb from the clay. The addition of DOC to the aqueous phase resulted in deviation from the sorption and desorption isotherms in a DOC free leachate in the case of both toluene and naphthalene. While DOC effects on toluene sorption and desorption behaviour were not clear cut, with both increases and decreases in sorption and desorption observed with the addition of DOC; a uniform decrease in sorption and an increase in desorption relative to the DOC free leachate was observed for naphthalene sorption and desorption behaviour. No desorption was observed for toluene in three of the leachates. In all other DOC containing leachates sorption was reversible and exhibited hysteresis. The alteration in sorption and desorption behaviour of HOCs due to DOC could not be explained solely by the maturity or the concentration of DOC in solution, and was attributed to a complex interaction of both factors. Increasing the hydrophobicity of the HOC resulted in increased sorption (naphthalene > toluene). Recommendations were made for the selection of a Kd value to model HOC attenuation on the basis of a ‘worst case’ scenario. Implications for the post closure monitoring and containment of the landfill and the relevance of commercially available humic acid as a leachate DOC surrogate are also presented.

Three inclined tubular digesters of 13-15.3L volume were operated successfully at 20-35 C with hydraulic retention times (HRT) of 10-50 days on pig slurry of 10, 5, 2.5 and 1% Total Solids content. Tube inclination of 16-20 overcame the scumming problems encountered with horizontal tubular digesters. Performance compared favourably with completely mixed digesters, gas yields showing similar variations with operational parameters and reaching 0.46L gas gVS added ~ . Tracer studies show that soluble components of slurry mix throughout the digester (which contains minimal dead space) in 25% of the HRT or less. Solids move in well dispersed plug flow and are retained longer than in completely mixed digesters with a consequent improvement in gas yields. Solids retention is affected by the size of the digester exit and is greater with slurry of low solids content. There appears to be a link between the movement of solids and gas along and out of the digesters which can lead to unstable 'oscillating' gas production. Gas production is most rapid in the central section of the digester tubes and relatively slow at the lower (influent) end where sediment accumulates. Acetoclastic methanogens are not closely associated with slurry solids. Gas production from acetate is restricted both by the population of acetoclastic methanogens and by the acetate concentration, to differing 'extents in different parts of the digesters. Extractable exocellular endoglucanase activity against carboxymethyl cellulose decreases and cell associated activity increases as slurry enters and passes along the digesters. Detectable activity is associated with particulate solids and does not disperse widely. Electron microscopy showed that digester bacteria degrading cellophane are predominantly rods with activity localised to within 0.5 ym of the cells.

Due to the extensive use of xenobiotic azo dyes in the colour industry and their proven mutagenic and cytotoxic nature, their treatment prior to discharge is essential and is legally enforced. However, currently used wastewater treatment technologies such as activated sludge systems, anaerobic digestion, electrochemical destruction, adsorption and membrane filtration are ineffective in removing azo dyes due to reasons such as inefficient dye degradation, slow degradation kinetics, toxic metabolite formation, inhibitory costs and generation of secondary waste streams. Therefore, in this study, microbial fuel cells (MFCs) were studied as possible systems that could effectively degrade azo dyes with an additional benefit of concomitant biogenic electricity generation. The co-metabolic degradation of the model azo dye Acid Orange-7 (AO-7) using Shewanella oneidensis and mixed anaerobic cultures in MFC was carried out with particular emphasis on AO-7 degradation kinetics in the initial study. The effect of using various carbon sources including cheaper complex ones such as molasses and corn steep liquor as electron donors for azo dye degradation in MFCs was also investigated. The outcomes of this study demonstrated that fast AO-7 reductive degradation kinetics using cheap, sustainable co-substrate types can be achieved with concomitant bioelectricity generation in two-chamber MFCs. Power densities up-to 37 mWm-2 were observed in the two-chamber MFC system during AO-7 decolourisation. Co-metabolic reductive degradation of azo dye mixtures using dye acclimated mixed microbial populations under industrially relevant conditions (high temperatures and salinities) and changes in microbial community structure in the MFCs in presence of complex azo dye mixtures in two-chamber MFCs was investigated. The outcomes of this work demonstrated that efficient colour and organic content removal can be achieved under high temperatures and moderate salinities using azo dye adapted mixed microbial populations in two-chamber MFCs. Microbial community analysis of the original anaerobic consortium and the azo dye adapted microbial culture following MFC operation indicated that both cultures were dominated by bacteria belonging to the phylum Firmicutes. However, bacteria belonging to phyla Proteobacteria and Bacteroidetes also became selected following MFC operation. Peak power densities up-to 27 mWm-2 were observed in this study during decolourisation of complex azo dye mixtures. The complete degradation of the azo dye AO-7 using a sequential reductive – oxidative bioprocess in a combined MFC-aerobic bioreactor system operating at ambient temperature in continuous mode was studied. The outcomes of this study demonstrated that the azo dye AO-7 can be fully decolourised and degraded into non-toxic and simpler metabolites. Maximum power densities up-to 52 mWm-2 were observed during azo dye degradation. A modular scale-up version (with a volumetric scale-up factor of 6) of the two stage integrated bioreactor system demonstrated the capability to efficiently treat two types of real wastewater originating from colour industry without any apparent deterioration of reactor performance in terms of dye decolourisation and COD removal. The use of applied external resistance (Rext) and redox mediators as tools for enhancing azo dye degradation kinetics in dual chamber MFCs was studied. The outcomes of this work suggest that azo dye reductive degradation kinetics in MFC anodes can be influenced by varying Rext. Furthermore, AO-7 reductive degradation kinetics was improved in a concentration-dependent manner by exogenous addition of two electron shuttling compounds anthraquinone-2,6-disulfonic acid and anthraquinone-2-sulfonic acid in MFC anodes. The overall outcomes of this study implies that MFCs could be successfully applied for achieving enhanced azo dye reductive biodegradation kinetics in MFC anodes coupled with concomitant bioelectricity generation. It further demonstrated that MFC systems can be successfully integrated with existing wastewater treatment technologies such as activated sludge systems for complete degradation and toxicity removal of azo dyes and their biotransformation metabolites.

This thesis investigates the phenomenon of environmental annoyance from waste management, specifically landfill odours. The research study identifies the scope and significance of parameters that influence the extent of impact and includes these in a framework that can be used to influence the design and development of a population response model for odours. The research design considers the physiological, lifestyle and location factors that influence exposure and response to landfill odour and addresses three research objectives: • To produce a framework within which a community based population response model could be developed. • Determine and demonstrate the variability of response within a popUlation exposed to landfill odour. • To determine and demonstrate how spatial and temporal factors also contribute to the differential exposure and response of individuals to odour pollution. The research activity involved the design and implementation of an odour monitoring panel. Volunteers were recruited in the vicinity of two landfill sites where they monitored daily for odours for three months. This programme provided information on their routine activities and exposure to odour at the time. The thesis concludes by noting the following: • Location and climatic factors may generate more variability (at this scale of sample) than interpersonal differences. • The results from laboratory experiments examining hedonic properties were not repeated in the external environment. • The response levels between males and females were inconsistent with current knowledge and research assessing gender differences in the ability to detect odours. Additionally, the research demonstrates how data on the detection of odour in communities could be included in research activity that links olfactometry and the experience of odour in the environment.

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Treatment of liquid effluents is a serious challenge owing to the high stability and colloidal nature of the particles. In many applications, microbubbles (< 150 µm) are employed for separation purposes due to their buoyancy and increased surface area to volume ratio. This property has been exploited in the water treatment industry for separation in a process known as dissolved air flotation (DAF). Though practically efficient, the process is energy intensive operating at >5 bars and consequently consuming ~90% of the total energy required in water purification plants. Other approaches in generating microbubbles for separation are not without challenges. One example is dispersed air flotation, which generates bubbles several orders of magnitude larger than the bubble exit pore and consequently unsuitable for flotation of these colloidal particles. These two concerns have been addressed in this research with the designing and development of a microbubble diffuser driven by a fluidic oscillator to facilitate microbubble generation suitable for flotation as well as investigating its performance for flotation applications. This fluidic oscillator converts continuous air supply into oscillatory flow with a regular frequency to generate bubbles of the scale of the exit pore. Bubble characterisation results showed that average bubble size generated under oscillatory air flow state from a 50 µm pore membrane was 86 µm, ~ twice the size of the diffuser pore size of 38 µm. In contrast, continuous airflow at the same rate through the same diffusers yielded an average bubble size of 1059 µm, 28 times larger than the pore size. In the first application, fluidic oscillator generated microbubbles were investigated for the separation of emulsified oil using Aluminium sulphate as the coagulant. The effect of surfactant concentration on oil droplet size was investigated. It was found that oil droplet size varied inversely proportional to surfactant concentration. In addition, it was found that the oil removal efficiency also depends on the surfactant concentration. The maximum oil removal efficiency by Microflotation was found to be 91% under lowest surfactant concentration tested (0.3 wt%) whilst at highest surfactant concentration used (10 wt%); lowest recovery efficiency (19.4%) was recorded. In the second application, the separation of algal cells under fluidic oscillator generated microbubbles was investigated by varying metallic coagulant types, concentration and pH. Best performances were recorded at the highest coagulant dose (150 mg/L) applied under acidic conditions (pH 5). Amongst the three metallic coagulants studied, ferric chloride yielded the overall best result of 99.2% under the optimum conditions followed closely by ferric sulphate (98.1%) and aluminium sulphate with 95.2%. The third application investigated the performance of Microflotation for the recovery of yeast cells from their growth medium at different pH levels, flocculant dose and varying bubble sizes. In this study, the food-grade-constituent- Chitosan was used as the flocculant. Results reaching 99% cell recovery were obtained under various conditions examined. Bubble size profiling showed an increase in average bubble size with diffuser pore size. Also, cell recovery efficiency was a function of both bubble size and particle size (cell size). For smaller particles (<50 μm), relatively smaller bubbles (<80 μm) were found to be more effective for recovery, otherwise, relatively larger bubbles (80-150 μm) proved to be efficient in recovering larger particles (particle size: ~250 μm). Acidic and neutral pHs were effective in separation as hydrophobic particles were formed. As pH tends towards alkalinity, flocs become more hydrophilic, leading to low recovery from the aqueous solution. In addition, separation efficiency was dependent on flocculant dose as increase in concentration improved flocculation and consequently, yeast recovery. However, above a critical concentration, overdosing occurred and inadvertently, recovery efficiency decreased. The results compare well with conventional dissolved air flotation (DAF) benchmarks, but has a highly turbulent flow, whereas Microflotation is laminar with several orders of magnitude lower energy density.

This thesis is an exploration into the modelling of anaerobic digestion (AD) with a focus on its integration into a microgrid for rural electrification. The work investigated the improvement of Anaerobic Digestion Model No 1 (ADM1) in order to better describe the kinetics of biogas production in an AD system with particular focus on substrate characterisation, codigestion and the mechanisms of inhibition. The resulting model was used to investigate the possible role of AD in microgrid systems. A novel biochemical and kinetic fractionation method was developed in order to fully characterise any substrate and produce the required input parameters into the a modified version of ADM1. The method uses a combination of analytical and digestion batch tests and was applied to food waste, green waste, pig manure and oat processing residues. The fractionation method was validated using measurements from semi-continuous laboratory scale digesters, operated with varying substrate combinations and loading rates. The model was able to suitably predict the methane production rate and the typical off-line measurements in AD systems, except during periods of high organic loading rate where biochemical inhibition became an important phenomenon. Possible inhibiting mechanisms were investigated by model based analysis of the experimental data characterised by inhibition, and a possible inhibition mechanism was proposed and integrated in the ADM1 model. Microgrid modelling software HOMER was used alongside the updated version of ADM1 in order to perform a benchmark of various operational and control strategies for the demand-driven operation of an AD system integrated in a microgrid. Different biogas demand profiles were considered. In the case of a biogas demand profile with low variability it was found that simple operational strategies could be used, with limited required biogas storage buffer and without causing process instabilities. With more variable demand profiles, an expert control system was needed in order to reduce the biogas storage requirements and guarantee process stability.

Many continuous granulation plants operate below their design capacity, suffering from high recycle rates and instabilities. Thus, there is an immediate economic incentive for effective operation and control of granulation units. The overall granulation process is integrated and interacting, with limited manipulated variables available (e. g. binder addition, nozzle locations and mixing rate). Hence. the complex process dynamics and operational challenges presented warrant a fundamental model-based strategy for design, operation, control and scale-up that is well supported by experimental analyses. A realistic model of the granulation process has to account for the granule size, the binder content, and the porosity (or related parameter bulk density), thereby necessitating a three-dimensional population balance model to yield a good representation of the process. While this multidimensional population balance model is warranted by the physics of the problem. it is a bigger challenge to derive kernels (rate laws) for the key granulation mechanisms. Most kernels in the literature are empirical and/or semi-empirical and provide little insight into the intricacies of the granulation mechanisms. This effectively results in an inability to make the necessary engineering decisions to improve control of the granulation process. Hence, this thesis is concerned with a more systems-centric approach to enhance the design, control and scale-up of granulation processes. Experimental studies on a lab-scale batch drum granulator for a Calcite/PVOH-H20 system were performed to assess granulation kinetics and model development of the granulation process. Effects of process /material properties and liquid binder distribution on granule properties, illustrating the non-homogeneity of key particle attributes and which justify the need for multi-dimensional population balances, were studied. Process sensitivities, manipulations and potential disturbances were identified, formulating a comprehensive control configuration for granulation processes, with application seen in a continuous drum granulation of limestone. While carrying out experiments, multiple granule attributes were characterised and this presents a challenge, which this research addresses accordingly. A population balance model incorporating nucleation, aggregation, breakage and consolidation was developed in this research. Novel aspects are the mechanistic formulations of the nucleation, aggregation and breakage kernels which are derived from first-principles. Such mechanistic descriptions of the rate processes lend themselves to a more in-depth understanding of the granulation process, contributing fundamental knowledge to the design, control and scale-up of these processes. A sensitivity analysis of the model was then performed to ascertain the influence of model parameters on the particle density distribution. Continuing from this, a compartmentalised version of the combined population balance model was developed, for the purpose of controllability analysis. Results obtained were used to identify suitable control-loop pairings to facilitate enhanced control-loop performance. Experimental validation of the population balance model is an integral part of this research. The model was quantitatively validated using lab-scale experimental data for granule size, binder content and porosity. The tuned model was then able to predict evolutions and distributions of granule attributes for different operating conditions and formulations. The model was also validated for different granulation systems. This illustrates the robustness and flexibility of the model and these results are promising toward the longer-term step of a first-principles based predictive model for the granulation process that can help alleviate the need for large number of experiments. As an alternative to deriving the above-mentioned mechanistic kernels, a discrete element modelling (DEM) approach was also undertaken in this thesis. Based on a Volume of Fluid (VOF) method, the analysis carried out provided useful information to help understand the effect of primary particle morphology on granulation kinetics making it possible to establish relationships between material and process/design properties and granulation process behaviour