PhD, EngD and MSc by research theses (SWEE)
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Item Embargo Biocontrol of ochratoxigenic fungi by endogenous lactic acid bacteria and yeasts from ivorian robusta coffee in the context of climate change(Cranfield University, 2023-09) Lopez Rodriguez, Claudia; Medina-Vaya, Angel; Schorr-Galindo, Sabine; Verheecke-Vaessen, Carol; Fontana, Angelique; Strub, CarolineThis doctoral research delves into the innovative domain of biocontrol strategies targeting mycotoxigenic fungi in the context of climate change. Focusing on Ivorian coffee, a vital economic and agricultural commodity, the study explores the potential of indigenous lactic acid bacteria (LAB) and yeasts as biocontrol agents. Mycotoxins, toxic secondary metabolites produced by fungi, pose significant health risks and economic losses. As climate change amplifies the proliferation of mycotoxigenic fungi, the demand for sustainable and eco-friendly interventions intensifies. The research encompasses comprehensive isolation, identification, and characterization of LAB and yeasts from Ivorian coffee, evaluating their antagonistic properties against mycotoxigenic fungi. Furthermore, the study elucidates the mechanisms underlying the biocontrol activity, shedding light on how these microorganisms mitigate mycotoxin contamination. This research is pivotal in the pursuit of climate-resilient strategies for mycotoxin management, contributing to both food safety and agricultural sustainability.Item Embargo Influencing factors and mechanisms of local government green development behaviour: evidence from China(Cranfield University, 2024-01) Zhu, Xiaowen; Unal, Enes; Longhurst, PhilipGreen development has become an important strategy for local governments to achieve greater sustainability, and adopting green development behaviours has significant implications for local governments in addressing the relationship between the environment and the economy. Previous research demonstrated that the unique characteristics of green development practices have received considerable attention from scholars. Most studies have highlighted green development practices in the private sector, although the adoption of green development practices in the public sector remains understudied. Current research on green development behaviour in the public sector primarily reflects, at the individual level, the green behaviour of employees and, at the organisational level, the green purchasing behaviour of a particular government department. The discussion of local government green development behaviour is not predominant. Therefore, this thesis proposes that a detailed understanding of the processes and specific practices of local government green development behaviours may be essential for local governments to improve the effectiveness of implementing sustainable practices. Although existing studies have addressed the influencing factors that lead to the adoption of sustainable development by local governments, there needs to be a more systematic theoretical analysis of the underlying mechanisms adopted by local governments to achieve green development behaviours. Accordingly, this thesis aims to explore the factors that influence the implementation of green development behaviours by local governments and the mechanisms of influence between the factors. This study draws on mixed methods to develop two studies. The first is a qualitative study that explores local government green development behaviour and its influencing factors. It applies various data collection methods, including semi-structured interviews and document analysis. Fifty-three officials from local government departments related to green development in China’s Jiangsu province were interviewed, and the data were analysed using a grounded theory method. The second is a quantitative study. Seven hundred twenty-two valid questionnaires were collected, and the model proposed in the first study with Structural Equation Modelling (SEM). The findings illustrate how the interactions between various factors shape the green development behaviour of local governments. The main findings show that: (1) local government green development behaviour is a kind of behavioural change, which can be divided into local government green development policy formulation and implementation. (2) The three main influences on local governments’ green development behaviours include internal driving factors, external environmental pressures, and the basis of regional green development. (3) Internal driving factors and external environmental pressure can influence local governments’ green development behaviours. (4) Internal driving factors mediate the relationship between external environmental pressure and green development behaviour. The basis of regional green development has a moderating effect on the relationship between internal driving factors and green development behaviours, as well as the relationship between external environmental pressures and green development behaviours. This thesis provides a framework that supports local government behaviour's decision-making process on the managerial implications. Paper I analyses the specific processes and practices of local government green development behaviour, Paper II constructs a theoretical model of local government green development behaviour, and Paper III examines the mechanisms by which various factors influence local green development behaviour. At a broader level, this thesis enriches and expands the research content of sustainable practices in the public sector. It also provides novel insights for local governments to formulate effective green development policies, which will help them develop green development directions and implement green development behaviours to promote more remarkable sustainable development in the region.Item Open Access Advancing biosensing techniques for detection of antimicrobial resistance genes and antibiotics in water(Cranfield University, 2024-09) Li, Wenliang; Yang, Zhugen; Coulon, FredericAntimicrobial resistance (AMR) poses a significant global public health threat requiring urgent attention for surveillance of antibiotic resistance genes (ARGs) and antibiotics in the environment. In this PhD study, a real-time fluorescent detection assay of antimicrobial resistance genes (ARGs) was developed to specifically target two key ARGs, tet(M) and tet(x3) to detect tetracycline and tigecycline resistance respectively in water samples. Additionally, crassphage gene was investigated for anthropogenic activities since they also play a vital role in the AMR transmission. The advanced ARG detection assay was based on multiplexing recombinase polymerase amplification (RPA) and subsequent sequence-specific recognition by the trans-cleavage activity of Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas12a. The assay achieved limits of detection (LODs) of 1 copy µL⁻¹ for all three gene targets with an accuracy of 100% in spiked tap and surface water samples. Expanding the assay by including two additional end-point detection modalities, lateral flow assay (LFA) and voltametric detection, further demonstrate its versatility. LODs of 1 copy µL⁻¹ for tet(x3) and crassphage, and 10 copies µL⁻¹ for tet(M) (LFA) and 10 copies µL⁻¹ for all three targets (electrochemical) were reached. Validation against gold standard quantitative polymerase chain reaction (qPCR) using real water samples, including wastewater and drinking water samples, revealed a remarkable 100% accuracy rate. Antibiotics detection assay was conceptualised based on the amplification of hybridisation chain reaction (HCR) followed by CRISPR/Cas mediated cleavage within a DNA hydrogel matrix. This approach aimed to release electroactive methylene blue (MB) particles, detectable and quantifiable by square wave voltammetry (SWV). While unforeseen circumstances impeded full assay development, the preliminary data illustrated the viability of the proposed method, suggesting avenues for further research to develop rapid and onsite antibiotics detection methods.Item Open Access The epidemiology and management of cladosporium on raspberry(Cranfield University, 2024-01) Farwell, Lauren; Xu, Xiangming; Medina-Vaya, AngelCladosporium is a genus of fungi that causes dark mycelial lesions on raspberries, rendering fruit unmarketable. As Cladosporium is an opportunistic pathogen, its prevalence varies across years, and there is insufficient research on its epidemiology and management. This study aimed to investigate the epidemiology of Cladosporium on raspberries and to elucidate which management strategies could be effective. Isolates of Cladosporium were obtained from raspberries, with C. cladosporioides being the most predominant, and was therefore used in further experiments. The susceptibility of raspberry fruit development was determined, with ripening and ripe fruit found to be susceptible to skin lesions; this stage of development was subsequently targeted in management studies. The effects of ripening and fruit location (fruit location within a tunnel vs. across a farm) on the inoculum load on the surface of raspberries were investigated using metabarcoding studies. The fungal and bacterial microbiomes were also investigated to better elucidate the ecology of Cladosporium on the fruit surface. Cladosporium was more abundant on green fruit than ripening fruit; perhaps due to organisms such as Rouxiella present on the fruit’s surface. Fungal α diversity increased during ripening while bacterial diversity decreased. The Cladosporium inoculum load in the air was also investigated, with more spores trapped inside a raspberry polytunnel than an open field. The efficacy of commercial Biological Control Agents (BCAs) and resistant varieties to control Cladosporium skin lesions were tested across two years in field applications. The Trichoderma sp. was the most effective at reducing the incidence of Cladosporium on raspberry than compared to the other tested products. The variety resistance study was inconclusive, but results indicate further testing will reveal which varieties are more susceptible. This research will inform potential management strategies against Cladosporium on raspberries that will aid growers in reducing food waste sustainablyItem Embargo Investigating the hydraulic performance of fullscale treatment wetlands using electrical resistivity tomography(Cranfield University, 2024-01) Hassan, Syed Shuja Ul; Bajón-Fernández, Yadira; Lyu, TaoHorizontal subsurface flow constructed wetlands (HSFCWs) have been widely used for tertiary treatment of wastewater in the United Kingdom (UK). One of the main objectives for UK’s water industry is achieving a reduction in maintenance costs of HSFCWs by reducing frequency and cost of clogging remedial measures. However, inability of conventional clogging assessment methods to provide reliable subsurface visualisation of the HSFCWs limits understanding of clogging profiles across treatment units, hindering proactive maintenance and remedial interventions. Without trustworthy information about subsurface conditions of HSFCWs, clogging remedial measures cannot be optimised to provide targeted, proactive, and cost-effective maintenance. In this study, electric resistivity tomography (ERT) has been applied to identify its effectiveness to provide reliable visualisation of the subsurface conditions of HSFCWs. On this project, two HSFCWs with different clogging levels were tested using ERT. Anomalies in subsurface distribution of water and profiles of clog matter accumulation across the HSFCWs were identified by changes in electric resistance of the media. The output was in form of cross sections showing variation in resistance across the media with different colours. The visual representation of subsurface conditions covered the full depth as well as the length of HSFCWs. The subsurface conditions identified in ERT results were in line with those observed by conventional clogging measurement methods, including substrate permeability measurement and tracer test, which provides preliminary validation of the ERT methodology. A recently refurbished HSFCW was found to have negligible level of clogging and subsurface visualisation was depicted by consistent shades showing uniform electric resistivity values (between 20 to 300 ohm.m) across the HSFCW. Contrarily, a mature HSFCW with many years of operation and no recent remedial interventions resulted in significant colour variation across the sections, indicating uneven electric resistance across the HSFCW (between 20 to 4000 ohm.m) and the ability of the ERT methodology to infer clogging levels. Considerably higher resistivity values and their chaotic variations across the subsurface indicated the distribution of wastewater and clog matter. To Identify the effectiveness of ERT to visualise subsurface of wetland systems, two different ERT arrays (electrode configurations) were used: Dipole-Dipole characterised by better horizontal resolution and effective depth coverage at the ends of ERT line and Wenner Array characterised by better vertical resolution and less susceptibility to noise. Both arrays were successful in identifying variations in local clogging levels in the HSFCWs, with the Dipole-Dipole array results found to be more relatable with actual site conditions. This work has evidenced the potential of ERT to profile clogging in HSFCWs, providing a tool for implementing targeted asset maintenance and reduced operational costs. Further improvement in the ERT methodology is recommended by testing the impact of smaller probe spacing, controlled water levels in HSFCWs, and increased observations of the same systems at different operation ages.Item Open Access Developing engineering systems with stakeholder engagement(Cranfield University, 2022-05) Chapman, Harris Spencer; Smith, Heather; Williams, LeonThe activities of the early stages of new product development (NPD) projects have a significant impact on its results. This is evident by the failures of outputs to meet expected levels of adoption being traced back to inadequate elicitation of requirements and validation of the need for the output itself. To address this, the development of consumer goods, software and large-scale construction projects have been shown to benefit from the early involvement of stakeholders in these outputs. However, few studies focus on how this early involvement of stakeholders might advance the development of engineering systems. Although studied in the context of complex products and systems (CoPS), which includes large-scale constructions, engineering systems differ significantly to these and other NPD project outputs. This is due to the absence of end-users, or the general public, being involved as such systems are often automated and hidden within other systems or infrastructure. Adhering to development frameworks prioritising technical maturation furthers this difference, although, like consumer products, a market needs to be addressed. To explore this phenomenon, a single case study of the beginning of a wastewater system NPD project is conducted and supported by studies that identify, engage and evaluate the extent stakeholders can affect its activities. The results support the need for a dedicated early stage for stakeholder engagement. This will help address the implications of findings evidencing problems engineering systems need to address so to achieve expected levels of adoption. Successfully incorporating this new stage whilst prototyping the engineering system itself requires further research. The contributions of this thesis challenge prioritising technical interests during early stages of development, demonstrate the extensive value of analysing qualitative data and support iterative and collaborative NPD approaches. Incorporating these findings will contribute to ensuring highly innovative engineering systems effectively address the needs of their salient stakeholders.Item Open Access Soil bioengineering for sustainable bioremediation of oil contaminated soils(Cranfield University, 2022-11) Atai, Emmanuel; Pawlett, Mark; Coulon, FredericContaminated soils arising from the petroleum industry remains a major problem globally, resulting in levels of petroleum hydrocarbons and metals that are dangerous to the environment. Modern remediation strategies focus on sustainability, thus maximizing environmental, social, and economic benefits. The use of materials derived from agricultural and industrial waste, for example biochar and spent mushroom compost (SMC), may provide a potential solution to sustainable remediation strategies. Biochar has numerous properties, e.g., high surface area and pore volume that may provide benefits to the remediation industry. SMC, a by-product of mushroom production, may contain diverse groups of microorganisms and extracellular enzymes important for the biotransformation of contaminants. Biochar and spent mushroom compost interactions in soil may induces diverse responses in microbial species leading to changes in soil enzyme activity, reshaping of microbial community structure and consequent enhancement of contaminants transformations. However, the mechanisms underlying these interactions are poorly understood, with unpredictable outcomes. There is a deficit of research designed to understand their collective response on soil fungi and the subsequent benefits to remediation success. Research needs to focus on the benefits of biochar towards affecting contaminant bioavailability of multiple rather than single contaminants. Combining biochar with SMC may facilitate the biodegradation of petroleum hydrocarbons in saline soils. The aim of the research was to develop a biotechnological approach for the best use of biochar and SMC to promote microbial remediation of soil contaminated with complex chemical mixture contaminants (hydrocarbons and heavy metals). It provides a mechanistic understanding of the physicochemical and biological parameters influencing the remediation approach. The study further sheds light into the influence of low carbon soil amendment on the behaviour and fate of heavy metal(loids) and petroleum hydrocarbons, and the underlying microbial community responses in a genuinely contaminated soil in a four-month microcosms study, and in crude oil and salt spiked soil in another four-month microcosms study.Item Open Access Developing the next generation of treatment flowsheets for rural wastewater(Cranfield University, 2022-12) Brown, Gareth; Jefferson, Bruce; MacAdam, Jitka; Dotro, GabrielaSeptic tank systems (STS) are one of the most common wastewater treatment systems in the world however these systems are becoming antiquated, struggling to meet tighter consent, needing frequent desludging and venting greenhouse gases to the environment. A flowsheet to tackle these issues was proposed consisting of an enhanced septic tank (EST) and a constructed wetland (CW). The proposed flowsheet was assessed by examining the underlying mechanisms, testing the flowsheet at pilot scale and assessing the cost and carbon implications of the flowsheet. A key aim of the thesis is to decrease the maintenance of the flowsheet to once every 5 to 7 years. The maintenance of septic tank is due to desludging, as the tank needs to be emptied when the sludge bed reaches a certain height. The desludging of a septic tank is dependent on the hydrolysis rate within the reactor. Batch studies into anaerobic digestion found that low operating temperatures in septic tanks impact the hydrolysis rate. However, temperature is not the dominant factor of hydrolysis and optimisation of mass transfer between hydrolytic microorganisms and degradable particulates can increase the hydrolysis rate by 200%. A pilot scale study investigated using baffles to promote hydraulic mixing within a septic tank. The presence of hydraulic mixing due to the baffles increased the hydrolysis rate constant of a septic tank from 0.0089 d⁻¹ to 0.035d⁻¹, extending the time between desludging from 4.9 to 6.7 years. The proposed flowsheet is a lower cost treatment system than a conventional package treatment system (e.g. submerged aerated filter) over a 30 year life time and leads to a significant reduction in lifetime carbon emissions compared to a STS. The cost and carbon reduction of the flowsheet make the flowsheet a viable abatement technique.Item Open Access The impacts of airport de-icers on water quality and the growth of undesirable biofilms in rivers(Cranfield University, 2023-07) Exton, Benjamin Machael; Grabowski, Robert C.; Hassard, Francis; Medina Vaya, Angel; Natural Environmental Research (NERC)Undesirable river biofilms (URBs, formerly “sewage fungus”) are polymicrobial biofilms that grow in rivers as a response to organic pollution. Despite a continued widespread occurrence, limited research has been conducted in recent decades. Therefore, to reignite research into URBs, this thesis aims to investigate how the delivery of airport de-icer contaminated runoff to receiving waters impacts the growth and composition of URBs. The research conducted can be categorised into four themes: (i) a re-evaluation of “sewage fungus”; (ii) a field study to characterize the composition and drivers of URBs; (iii) microcosm growth experiments to determine how different airport de-icers contribute to URB growth; and (iv) pilot-scale mobilisation experiments to evaluate the mobilisation of airport de-icers in surface runoff. A bimonthly field study conducted over two winters revealed shifts in the bacterial composition of riverbed biofilms with suspected de-icer discharge. The community became dominated by the genera Rhodoferax (19.5 – 56.7% relative abundance) and Sphaerotilus (9.5 – 25.4%) prior to and during a visible URB incident. When aggregated at the family taxonomic level, Comamonadaceae (55.7 – 81.4%) emerged as the key indicator taxon of the significant shift in periphyton and has been proposed as a possible organic pollution biosentinel. The URB had a long-term influence on the periphyton, highlighting the importance of preventing their occurrence. Microcosm experiments of URB taxa growth using common freeze-point depressants as the sole carbon source confirmed de-icers can facilitate URB growth. Sphaerotilus natans growth was stimulated by all de-icers, except formate salts, in suspended culture (assessed by turbidimetric microcosms) and total growth was heavily dependent on carbon concentration. There were some significant differences in the growth kinetics between the active ingredients in de- icers (e.g., maximum growth rate). However, there were only negligible differences between pure active ingredients and their commercial products demonstrating that the additives used in commercial de-icers have negligible influence on microbial growth, despite their potential toxicity to aquatic fauna. Growth experiments with mixed cultures using S. natans and Zoogloea oleivorans were also tested to explore the interactions between URB taxa, including the novel application of timelapse microscopy in URB growth studies and provide a basis for further research. Mobilisation of commercial airport de-icers by rainfall was tested after exposure to various meteorological conditions (sun, wind, temperature) to explore the transport pathways of de-icers in runoff. Runoff was significantly affected by weather between de-icer application and a rainfall event. Sunlight and wind caused less de-icer mobilisation than decreases in temperature, attributed to drying effects. This research has considerable implications to inform surface water winter management plans by airport operators. This research highlights the continued prominence of URBs in rivers, even in countries with advanced wastewater treatment, and has added substantial contributions to knowledge about their composition and growth as a consequence of airport de-icing activities. Through a process-based understanding of de-icer transport and impact, airports can develop more effective and resilient solutions to minimise the ecological impacts in receiving water courses.Item Open Access Understanding and predicting flow behaviour of water and air in serpentine pipes using machine learning and CFD modelling(Cranfield University, 2023-09) Sekar, Rajesh; Verdin, Patrick; Lao, LiyunThe flow behaviour of two-phase fluid (water and air) in serpentine pipes is complex and poorly understood. This study aims to address this research problem by using machine learning concepts to gain a deeper understanding of the flow behaviour and optimize the geometry of serpentine pipes. Experimental data from the Cranfield process engineering laboratory was used in this work, for a fixed pipe diameter and varying water and gas velocities. Regression models were developed and trained. The study aimed to accurately predict the pressure drop, void fraction and liquid film thickness in serpentine pipes in a timely manner with high accuracy. In addition, Computational Fluid Dynamics (CFD) models were developed to predict the flow behaviour with two different geometries, and machine learning was applied to determine the best model for capturing the intermediate geometry flow behaviour. Results provide valuable insights into the behaviour of two-phase fluid in serpentine pipes. The use of machine learning in this research contributes to the field by offering a new approach for optimizing the geometry of serpentine pipes with improved accuracy and efficiency. The findings demonstrate the potential for machine learning to play a role in improving our understanding of two-phase fluid flow in serpentine pipes. This research is expected to have potential future applications in various sectors, including automotive, electronics cooling systems, and industrial and chemical processing systems.Item Open Access Dual model sensors for viral RNA and protein detection for SARS- CoV-2 in saliva(Cranfield University, 2023-10) Ma Xuanye; Yang, Zhugen; Chiarelli, IvaThe coronavirus disease 2019 (Covid-19) pandemic emerged as an infection by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) over the past 3 years, causing enormous threats to humans and economic loss. It was reported that currently, nearly 68% of the population shows a degree of immunity to the disease. Though vaccine has played a critical role to protect the population, people are at risk of second or third infections with fading antibody titers against the virus. The detection of the viral load was crucial for monitoring the spread of this disease, and the detection of the antibody concentration to the virus was significant as well to understand the neutralization activity and vaccine response. This thesis reports the development of a rapid paper-based platform, which provides nucleic acid detection and immunoassay to test both active infections and body immunity. The project focused on a non-invasive sample, human saliva, as an alternative to nasopharyngeal swabs for diagnosis. The nucleic acid test, employing reverse transcription loop-mediated isothermal mediated amplification (RT-LAMP), was further integrated into a novel paper microfluidic platform, where the result could be reported within 30 mins. Under the optimized conditions, RT- LAMP assay correctly detects above 135 copies µL⁻¹ of synthetic SARS-CoV-2 sequence. Moreover, a paper-based immunoassay was devised and constructed, following meticulous refinement of detection parameters and comparative analysis against a conventional 96-well plate assay for the identification of immunoglobulin G (IgG) targeting the SARS-CoV-2 spike protein. For the paper- based immunoassay, the dynamic range of the IgG was 0.5 μg mL⁻¹ to 50 μg mL⁻¹ , which was sensitive enough compared to clinical values. It should be noted that only commercially available artificial saliva was utilized to test the analytical performance of the developed assay. In conclusion, these results demonstrated a rapid and easy-to-use paper microfluidics platform with the potential to be further implemented as a comprehensive detection tool for monitoring both pathogenetic infection and immune levels.Item Open Access Supersaturation control in membrane distillation crystallisation(Cranfield University, 2022-11) Jikazana, Aphiwe; McAdam, Ewan; Campo Moreno, PabloMembrane distillation crystallisation (MDC) has emerged as a potential alternative to conventional industrial crystallisers. MDC provides controlled hydrodynamics and uniform supersaturation conditions for crystallisation, thereby enhancing scalability, which is desperately lacking in conventional crystallisation systems. Unfortunately, crystallisation near the membrane surface is also associated with inorganic fouling (scaling), which can ultimately lead to process failure. As such, the viability of the technology is dependent on scale-free bulk crystallisation. To date however, scaling mitigation strategies have been based on empirical observations with contradictory postulations regarding the governing crystallisation mechanism(s). In this work, the distinct mechanisms of scaling and bulk crystallisation have been elucidated for the first time. The application of novel inline and online experimental techniques facilitated the development of a mechanistic framework which is able to predict the likelihood of scaling in addition to mediating bulk nucleation kinetics. As such, scale-free operation was achieved at temperatures and hydrodynamic conditions which were previously associated with scaling. This study has therefore broadened the perceived range of kinetic trajectories achievable with MDC and evidenced its applicability to multi- component systems, polymorph selection, and a variety of product specifications. Furthermore, the use of hydrodynamics to decouple nucleation and growth kinetics revealed the potential of MDC to minimise the usual trade-off between product quality and yield in crystallisation systems. While existing scaling mitigation strategies are largely hydrodynamic and thermodynamic in nature, this study has shown that the contribution of crystallisation kinetics (supersaturation rate) to scaling propensity cannot underestimated. Hence, application of the kinetic framework developed could provide more targeted strategies for scaling prevention in various applications such as heat exchangers and reverse osmosis/nanofiltration (RO/NF), where polarisation phenomena are prevalentItem Open Access Sustainable production of bioplastics from various lipid-rich oil wastes using selected pseudomonas strains(Cranfield University, 2023-02) Hano Jibril, Lawal; Wagland, Stuart; Soares, AnaBioplastics, also known as polyhydroxyalkanoates (PHAs), are produced by bacteria through aerobic processes using a variety of carbon sources, showing significant potential as a polymer. Despite efforts to produce cost-effective processes, the production of PHA remains expensive, posing challenges in its utilization as a cost-effective material for products. This study aims to demonstrate the potential of these microorganisms as a sustainable solution for producing bioplastics from renewable sources. The suitability of two selected Pseudomonas oleovorans (DSMZ1045 and ATCC29347) was investigated to accumulate bioplastic polyhydroxyalkanoates (PHAs) from lipid-rich wastes: Glycerol, fats, oils, and greases (FOGs), soybean oil (SO), and palm oil (PO) were used as carbon sources. Under the conditions of 180 rpm and temperature of 30℃ for 48 hours, using 2% (v/w) of each oil. The accumulated PHA was extracted using sodium hydroxide and enzyme-hydrogen peroxide-based methods. The polymers were qualitatively analysed using Fourier transforms infrared (FTIR) and Scanning electron microscopy (SEM). FTIR and SEM analyses revealed that the produced bioplastic polymers are MCL-PHAs types. However, the findings showed that these lipid-rich wastes are efficient carbon feedstocks used in producing MCL-PHAs by the selected Pseudomonas strains. The yield accumulated by P. oleovorans DSMZ1045 from these waste resources was 43wt%, 39%wt, 34%wt, and 32%wt of dry cell weight, while P. oleovorans ATCC29347 was 38%, 37%, 34%, and 33% of cell dry weight, respectively, suggesting the potential for an effective solution for producing bioplastics. The results indicated substantial improvements in PHA accumulation for both strains when pretreatment methods (lipase, microwave, and ultrasound-assisted) were employed. % PHA yield between pretreatment and non-pretreatment conditions with DSMZ1045 and ATCC29347 showing enhancement of 46.88%, 41.18%, 41.03%, and 23.26% of cell dry weight and 40.63%, 38.46%, 26.47%, and 18.60% of cell dry weight, respectively. Glycerol and FOG gave a higher PHA accumulation than the other carbon sources. More polymer yields were achieved using both oil samples from P. oleovorans DSMZ1045 compared to Pseudomonas oleovorans ATCC29347. This research underscores the viability of P. oleovorans DSMZ1045 in producing bioplastics from waste oils, especially those derived from fats, oils, and grease (FOG)Item Open Access Real-life resilience in international water utilities(Cranfield University, 2022-09) Giffoni, Eduarda; Smith, Heather; Jude, SimonResilience is a highly aspired capability for the water sector. Whilst the concept has been vastly utilised in technocentric and engineering objectives, few studies have investigated the human dimensions of resilience in the context of international water utilities. Specifically, little is known about how the organisational environment, organisational culture and engagement with water customers may contribute to the resilience of the water sector and the challenges and opportunities of building resilience capabilities in these domains. As the central context for this research, water utilities provide critical socio-economic utility to society. Disruptions felt by water utilities can negatively impact multiple communities, regional prosperity, and national security. However, water utilities monopoly nature may insulate them from the new and evolving demands derived from the free market, thus delaying the organic development of adaptive and agile capabilities. In addition, given that the infrastructure of water utilities tends to be ‘locked-in’ to a fail- safe stance, this bleeds through the organisation’s norms and beliefs, thus further perpetuating previous paths and hindering experimentation and transformative change. This is problematic because water utilities are more sensitive to local shocks and stresses as they are bound to local catchments and providing services to local communities, as opposed to energy utilities that may source energy from a wide range of geographical locations. All these factors make water utilities an interesting population of research from the lenses of Organisational Resilience. Therefore, this thesis aims to understand the current stance and context within international water utilities in relation adaptability and Organisational Resilience – ii spanning the organisational environment, culture, and interactions with customers. This work seeks to critically evaluate how the organisational and human capabilities may be shaped to enhance water sector resilience and the challenges and opportunities of doing so. Through semi-structured interviews and an iterative survey with international water utilities this qualitative research captures perceptions from water managers on embedding Organisational Resilience properties. This research provides several contributions to the current body of knowledge. Primarily, the findings empirically identified novel challenges utilities face - spanning the cognitive frame, behaviour of individuals, and the context of the organisational environment - which flagged some key developmental areas to establish an organisational setting conducive of resilience. For instance, chapter 2 delves deep into the organisational environment in water utilities. and identifies a need to broaden the cognitive frame of utilities to account for flexible concepts for enhanced sense-making and proposes novel categories of organisational silos and a set of cultural attributes that contribute to organisational resilience. Moreover, chapter 3 explores the contextual property of organisational resilience, based on external relationships, to examine how customers may influence the resilience of water utilities. Although it was recognised a role of customers as passive beneficiaries of resilience, positive roles were also identified, such as: facilitators of more targeted initiatives, contributors to higher tolerance levels and positive behaviour-change, and resilience advocates. An additional contribution of this research is the creation of a framework of an organisational culture of organisational resilience for the water sector in chapter 4. A iii novel set of cultural attributes that were validated as conducive to the Organisational Resilience of water utilities were appraised from relevant literature. Derived based on the perspectives of utility managers, the set of cultural attributes clarifies Organisational Resilience beliefs and values that should shape individuals’ behaviour and the organisational environment. Thematic analysis identified an over-emphasis on standards and procedures that may hinder positive changes towards a culture of organisational resilience. In addition, addressing organisational barriers perceived as a pre-requisite to cultural changes, which may lead to inaction. However, the water sector’s impetus for talent recruitment and staff retention translated as an appetite to foment deeper relational ties with personnel. Finally, this study highlights a real need for transforming the beliefs, values, and behaviour in water utilities to implement and sustain efforts in the human and organisational dimensions that are conducive of Organisational Resilience. Such resilience transformation will entail efforts in the cognitive, behavioural, and contextual aspects within utilities to address current challenges and leverage identified opportunities.Item Embargo Reliability as a metric for structural health monitoring systems performance: application on fixed jacket offshore structures(Cranfield University, 2023-10) Etebu, Ebitimitula Tari-Inei; Sanson, Chris; Simms, Nigel; Shafiee, MahmoodThis research work addresses the need for reliability performance metrics for Structural Health Monitoring (SMH) systems on a fixed offshore jacket platform. The most common metric used to quantify SHM performance is the probability of detection (POD), it only quantifies the probability of detecting damage of a specific size. While POD is of high importance, it does not fully quantify the total performance of SHM systems. SHM systems can produce outcomes on the detection of damage, its predicted location of damage on the monitored structure and severity of damage detected at the predicted location. These outcomes are of interest for maintenance of the monitored structure. It is paramount to quantify the quality of information attained from all three SHM outcomes. This work proposes the use of Reliability as a metric to quantify outcomes from SHM systems. Furthermore, it also proposes the use of conditional reliability to quantity the interdependence of the predicted damage severity, given damage was localized, and damage was detected. The dependency of the Monitored structured reliability on the reliability of the SHM system was also proposed a metric of overall SHM performance. Probability performance metrics were also proposed in this work to extend the widely used POD, to other outcomes of SHM systems. The Probability of accurate localization and probability of accurate assessment were presented. Additionally, conditional probabilities were also proposed to address the interdependencies between SHM outcomes. Methods used in this work to estimate reliability include the First order reliability method (FORM), and Monte Carlo simulation. Finite element models of Fixed offshore platform were created, the modal response under specific loading conditions, and simulated damage events were used as inputs for Vibration based SHM methods. Hit/Miss techniques were implemented to calculate the probability-based parameters for each SHM outcome. A framework was developed to capture the uncertainties associated with the SHM process, with a limit state function generated for each SHM outcome. Fatigue reliability was implemented using Paris Law to estimate the reliability of structure members in the Fixed offshore platform. Bayes method was implemented to calculate conditional reliabilities. The outcomes from the proposed approach presented in this thesis, present a pathway to quantify SHM system performance beyond damage assessment. iii Presented in this work is a comparison between two SHM systems, where their performance outcomes are quantified for damage detection, localization, and severity assessment. The contribution of the overall SHM systems reliability on the predicted monitored structure members predicted fatigue reliability was presented. Furthermore, a comparison between different vibration based SHM systems at all levels of SHM performance was also presented. In addition, the fusion of multiple SHM systems and their potential contribution to the improvement in predictions of the monitored structure’s reliability was also described. This methodology can stand as a generic approach that can be applied to non-vibration based SHM systems or structures that are not fixed offshore platforms.Item Open Access Solid-phase denitrification for tertiary nitrate removal from municipal wastewater(Cranfield University, 2023-03) Affo Souleymane, Ayisha; Pidou, Marc; Alibardi, LucaElevated levels of nitrate in surface water and groundwater can lead to eutrophication, algal blooms, and depletion of dissolved oxygen, causing harm to aquatic ecosystems. Solid-phase denitrification (SPD) offers a promising approach for removing nitrate from wastewater sources using carbon-based materials to promote the activity of microorganisms that convert nitrate into nitrogen gas. This study evaluated the suitability of six common cheap and readily available materials as external carbon sources for denitrification in SPD systems. The materials tested were woodchips, barley straw, spruce wood bark, beech sawdust, and polycaprolactone (PCL). The study focused on the leaching rates of organic compounds and their impact on denitrification efficiency, with particular attention to the potential for secondary pollution. Results indicated that woodchips and wood bark exhibited a good balance between carbon content and secondary pollution risk, while barley straw posed the highest risk for secondary pollution and potential for the rapid depletion of organic compounds. PCL showed promise as a carbon source for nitrate removal and released minimal nitrate or ammonium-nitrogen. The low concentrations of metals found in the media suggest that they would not inhibit denitrification or pose significant health risks. The method was transferred to a pilot scale to evaluate the potential of woodchips in removing nitrate from wastewater sources and the performance of four columns for solid-phase denitrification using woodchip media, based on the results of the first part of the study, was studied for a period of 168 days. The nitrate removal efficiency was observed to be between 62-75% with the best performance seen in the hardwood seeded with sludge column. The addition of sludge from a wastewater treatment plant helped to speed up the start-up process. The results suggest that higher removal rates can be expected with higher influent nitrate concentrations. Over time, significant variability in the performance was observed. However, the variability in the results could not be clearly explained. In conclusion, all tested media have the potential to be used as supporting carbon sources for SPD, but their efficacy and potential for secondary pollution must be evaluated on a case-by-case basis.Item Embargo Examination of prolonged dry cold storage and hydration lengths during the process stage on cut roses vase life(Cranfield University, 2024-03) Hosseini, Sara; Girkin, Nick; Alamar, MariCarmen; Veheecke-Vaessen, CarolCut flowers have found an important role in human life, so market demand and cultivation are increasing. As cut flowers are highly perishable, it is important to extend their vase life to address sustainability challenges, avoid waste of natural resources, reduce carbon footprint and gain customer satisfaction. In the UK approximately 90% of cut flowers are imported (ca. 30% represent cut roses) and kept under dry cold conditions. During periods of high consumer demand, flowers may experience prolonged dry storage time compared to the rest of the year; this can affect vase life negatively. There are few studies mimicking real supply chain scenarios and, therefore, we simulate it for cut roses in the UK to examine the impacts of prolonged dry cold storage and hydration lengths on rose vase life in two separate experiments. The first study investigated drying lengths (24, 48, 72, and 96 hours at 5ºC) on vase life of two varieties: ‘Revival Sweet’ and ‘Golden Smile’. Interaction between drying (96 and 168 hours) and hydration solution usage time (0, 12, 24 and 48 hours) on ‘Revival Sweet’ was examined in the second experiment. In general, shorter drying times resulted in the longest vase life with fewer signs of physical damage (bent neck and damaged flower). In colour examination, no clear relationship between L*, C* h°, drying and hydration lengths was seen which may be because of the pink colour of ‘Revival Sweet’. Expanding hydration length improved solution uptake, reduced the pH, eliminated bacterial growth in vase water, preserved the sugar source and postponed senescence. When flowers were kept dry for 168 hours, hydration for 48 hours helped them show less than 50% damaged flowers and just approximately 30% bent necks after 18 days. In conclusion, during peak period, hydration for more than 24 hours is suggested to eliminate the negative impacts of prolonged dry storage.Item Embargo Development of bimetallic catalysts for (sorption-enhanced) steam methane reforming(Cranfield University, 2023-12) Wang, Siqi; Clough, Peter T.; Nabavi, Seyed AliHydrogen has gained increasing attention in recent years as one of the most promising solutions to decarbonize the energy sector, as it emits zero carbon when combusted. The demand for clean hydrogen continues to rise as government, industry, and academia endeavour to meet the net zero goal by the year 2050. Steam methane reforming is currently the predominant hydrogen production pathway and is predicted to remain so for the years to come. Many techniques exist for the optimization and decarbonization of the steam methane reforming process. Two of the most widely employed methods include using more efficient and stable catalysts and adding in an in-situ carbon capture step using solid CO₂ sorbents. The overall aim of this PhD study is to develop and evaluate the performance of novel bimetallic catalysts for the (sorption-enhanced) steam methane reforming process. Starting from a comprehensive literature review, recent advances in the field of bimetallic SMR catalysts were summarized and reviewed, based on their catalytic activity, stability, and physical-chemical properties. Based on the review, three bimetallic catalysts (Ni₃M ₁ /Al₂ O₃, M = Cu, Fe, and Ge) were synthesized, characterized using different techniques, and tested in a laboratory-scale fixed bed reactor under typical steam methane reforming conditions. CaO particles were then added to the system and the performance of the catalysts under sorption-enhanced steam methane reforming conditions was evaluated. A study on the influence of Cu loading on the bimetallic Ni-Cu catalysts was also carried out. The experimental studies were also accompanied by Density Functional Theory calculations of the carbon and oxygen adsorption energies on the bimetallic surfaces, and microkinetic modelling of the SMR reaction based on previous literature on its reaction mechanism. Finally, machine learning models were developed for the prediction of atomic adsorption energies using readily available elemental properties. Together with the previously developed microkinetic model, a fast high throughput screening of bimetallic alloys was carried out and catalysts with high sulphur resistance were successfully identified. Overall, the addition of Cu was found to be highly beneficial for promoting the catalytic activity of the conventional Ni catalysts, and the addition of Ge promotes the activity and can potentially improve the sulphur resistance of the catalysts. The wide application of these cost-effective and highly active bimetallic catalysts will contribute significantly to the decarbonisation of the energy sector by enabling the efficient production of hydrogen.Item Embargo Enhancement of radio frequency energy harvesting using embroidery conductive thread and improved power management circuit design(Cranfield University, 2023-07) Nwalike, Exekiel Darlington; Luo, Jerry; Luk, Patrick Chi-KwongThe global demand for remotely powering electronic devices without batteries, particularly for low-power electronics, through ambient RF (Radio Frequency) energy harvesting is increasing. However, several challenges must be addressed for Radio Frequency energy harvesting to achieve its full potential in wearable technology. These challenges include: 1. Maintaining continuous and steady conductivity of the antenna patch in RF energy harvesting (RFEH) devices. 2. Enhancing the efficiency of current rectification and power management circuits at extremely low power levels. This PhD project aims to overcome these obstacles by employing innovative embroidery conductive thread technology, which offers more uniform conductivity compared to traditional ink-based fabrication techniques. Additionally, the project focuses on designing an improved rectifier for the power management circuit. The proposed rectenna patch antenna is based on a 50-ohm impedance matching network. The design, simulation, optimization, and efficiency results of the rectenna patch antenna were recorded. The fabrication involved creating an efficient patch on both a textile substrate using conductive threads and a plastic substrate using liquid metal alloys. An embroidery machine was used for the textile design, while an inkjet printer was utilized for the plastic substrate. The harvested energy results were documented, demonstrating an improvement in the current wearable RF power harvesting system. This study provides valuable insights into materials, antenna design, and power management systems, advancing the state-of-the-art in RF energy harvesting and paving the way for further research and development.Item Embargo Exploring metal extraction potential from historical metallurgical sites and waste deposits using solvometallurgical and hydrometallurgical processes.(Cranfield University, 2023-12) Huntington, Victoria Estelle; Wagland, Stuart; Coulon, FredericMetalliferous waste from past metallurgical sites present significant environmental risks yet provide opportunities for metal extraction and recovery to supplement global demands in the shift towards renewable technologies. Characterising site conditions, metal specificity of green solvents and chelators, and an initial assessment of operating condition are required to develop these approaches into a commercial setting. This study evaluates the efficacy of solvo- and hydro-metallurgical approaches in extracting metals from real-world metalliferous waste. Specifically, it examines the performance of green deep eutectic solvents (DES) and chelating agents (CA) on blast oxide slag dust (BOS-D) and goethite, by-products of iron smelting and zinc refinery processes, respectively. Through batch tests and column studies, the impact of varying operational conditions, including molar ratio for DES and pH for CA were assessed. The results were used to inform sequential bioleaching to solvo- or hydroleaching tests to investigate the potential of hybrid extraction processes. The extraction efficiencies across batch, column and the sequential study from BOS-D were compared against a commercial chelating agent ethylenediaminetetraacetic acid (EDTA). DES extracted 60% more of the total metal load compared to CA and EDTA from BOS-D in batch tests. When applied to goethite, CA extracted 70% more of the total metal load than DES in batch tests. There was a 1% difference in metal extraction between DES and CA from BOS-D and 2 % from goethite in the column study. EDTA extracted the same or up to 15% more of the total metal load than DES and up to 18% than CA in the column study. The sequential study demonstrated that DES and CA have minimal influence in metal extraction under the operational conditions used in earlier batch tests, when applied to the residue after bioleaching extraction using Acidithiobacillus ferrooxidans. The extraction of the total metal load was improved by 4% using CA. The findings of this study demonstrate that CA and DES can extract a robust suite of metals from real metalliferous wastes. In BOS-D batch and column tests, analysis of metal group selectivity showed that DES had greater extraction than EDTA across all metal groups except rare earth lanthanides. In BOS-D batch studies, EDTA had greater extraction than CA across all metal groups except alkaline metals, but column studies showed that CA had greater extraction than EDTA across all metal groups except alkaline metals. This provides evidence for a robust metal extraction process and could improve the suite of extractable metals, providing sustainable alternatives in metal supply chains. The understanding of these extraction processes will be improved through, optimisation of more physical controls e.g., temperature, agitation, and further optimisation of the initial chemical conditions to improve metal extraction efficiencies, metal selection and potential revenue generation.