Browsing by Author "Tyrrel, Sean"
Now showing 1 - 20 of 66
Results Per Page
Sort Options
Item Open Access The absence or presence of a lytic coliphage affects the response of Escherichia coli to heat, chlorine, or UV exposure(Springer, 2018-03-15) Ameh, Ekwu M.; Tyrrel, Sean; Harris, Jim A.; Ignatiou, Athanasios; Orlova, Elena; Nocker, AndreasDisinfection aims at maximal inactivation of target organisms and the sustainable suppression of their regrowth. Whereas many disinfection efforts achieve efficient inactivation when the effect is measured directly after treatment, there are questions about the sustainability of this effect. One aspect is that the treated bacteria might recover and regain the ability to grow. In an environmental context, another question is how amenable surviving bacteria are to predation by omnipresent bacteriophages. Provisional data suggested that bacteria when subjected to sublethal heat stress might develop a phage-resistant phenotype. The result made us wonder about the susceptibility to phage-mediated lysis for bacteria exposed to a gradient of chlorine and UV-LED disinfection strengths. Whereas bacteria exposed to low sublethal chlorine doses still underwent phage-mediated lysis, the critical chlorine Ct of 0.5 mg min/L eliminated this susceptibility and induced phage resistance in the cells that survived treatment. In the case of UV, even the smallest tested dose of 2.8 mJ/cm2 abolished phage lysis leading to direct regrowth. Results suggest that bacteria surviving disinfection might have higher environmental survival chances directly after treatment compared to non-treated cells. A reason could possibly lie in their compromised metabolism that is essential for phage replication.Item Open Access Air quality and mental health: evidence, challenges and future directions(Cambridge University Press (CUP), 2023-07-05) Bhui, Kamaldeep; Newbury, Joanne B.; Latham, Rachel M.; Ucci, Marcella; Nasir, Zaheer A.; Turner, Briony; O'Leary, Catherine; Fisher, Helen L.; Marczylo, Emma; Douglas, Philippa; Stansfeld, Stephen; Jackson, Simon K.; Tyrrel, Sean; Rzhetsky, Andrey; Kinnersley, Rob; Kumar, Prashant; Duchaine, Caroline; Coulon, FredericBackground: Poor air quality is associated with poor health. Little attention is given to the complex array of environmental exposures and air pollutants that affect mental health during the life course. Aims: We gather interdisciplinary expertise and knowledge across the air pollution and mental health fields. We seek to propose future research priorities and how to address them. Method: Through a rapid narrative review, we summarise the key scientific findings, knowledge gaps and methodological challenges. Results: There is emerging evidence of associations between poor air quality, both indoors and outdoors, and poor mental health more generally, as well as specific mental disorders. Furthermore, pre-existing long-term conditions appear to deteriorate, requiring more healthcare. Evidence of critical periods for exposure among children and adolescents highlights the need for more longitudinal data as the basis of early preventive actions and policies. Particulate matter, including bioaerosols, are implicated, but form part of a complex exposome influenced by geography, deprivation, socioeconomic conditions and biological and individual vulnerabilities. Critical knowledge gaps need to be addressed to design interventions for mitigation and prevention, reflecting ever-changing sources of air pollution. The evidence base can inform and motivate multi-sector and interdisciplinary efforts of researchers, practitioners, policy makers, industry, community groups and campaigners to take informed action. Conclusions: There are knowledge gaps and a need for more research, for example, around bioaerosols exposure, indoor and outdoor pollution, urban design and impact on mental health over the life course.Item Open Access Anaerobic Digestion Foaming Causes(Cranfield University, 2008-10) Ganidi, Nafsika; Tyrrel, Sean; Cartmell, EliseAnaerobic digestion foaming has been encountered in several sewage treatment plants in the UK. Foaming has raised major concerns for the water utilities due to significant impacts on process efficiency and operational costs. Several foaming causes have been suggested over the past few years by researchers. However, the supporting experimental information is limited and in some cases site specific. The present report aimed to provide a better understanding of the anaerobic digestion foaming problem and to identify the underlying mechanisms of foaming. Field and laboratory investigation identified organic loading as a cause of foaming. Bench scale batch digestion studies in sludge showed that the critical organic loading for foaming was at 2.5 kg VS.m -3 while the 5 kg VS.m -3 resulted in persistent foaming. Moreover, full scale foaming digesters exhibited higher foaming potential in digested sludge under aeration in the laboratory than the full scale non- foaming digesters indicating that the concentration of surface active agents was higher. Further investigation of the effect of the surface active compounds, BSA and n-valeric acid on foaming showed that both compounds induced persistent foaming at all the examined concentrations. Filamentous bacteria contribution to foam initiation and stabilization was considered insignificant, apart from one occasion (FI:5), due to the abundance of filaments in foaming sludge (FI≤3) and their partitioning in foam (FI≤3). Part of the current work also assessed the cost implications of a foaming incident at the full scale. The antifoam cost was found to be of major concern for the water utilities costing between £1.30 and £13.00 per 1000 m 3 of digester volume per day. However, there was no information on biogas and energy loss whereas the information provided on cleaning, maintenance costs and manpower working hours was poor. Thus, the overall cost of a foaming incident at the full scale could not be estimated at this stage.Item Open Access Assessing consistency in the aerobic co-composting of faecal sludge and food waste in a municipality in Ghana(Springer, 2023-10-30) Nartey, Eric Gbenatey; Sakrabani, Ruben; Tyrrel, Sean; Cofie, OlufunkeBackground: A faecal sludge (FS) co-composting study assessed the extent of consistency in compost characteristics between and within batches. The study focused on the consistency of the co-composting process by measuring the variability of key parameters. Method: The set up consisted of 12 FS and food waste (FW) co-composting piles in three successive batches (1, 2 and 3). Consistency was assessed in the three successive batches of co-composted FS and food waste (FW). Within batches, consistency was assessed in each of them by dividing it into four separate replicate piles. Characteristics of interest were E. coli, as well as selected physico-chemical parameters (pH, EC, Mg, Ca, N, NH4-N, NO3-N, P, avail. P, and K) and heavy metals (Se, Fe, Cd, Cu, Hg, Ni, Pb and Cr). Data were subjected to analysis of variance (ANOVA) using SPSS. Result: Results show that, E. coli levels were not consistent between the successive batches during the entire co-composting process. While variations between batches were only observed for EC and nutrient parameters, variations were evident for several measured characteristics within batches. The measured coefficient of variations (CVs) within batches ranged between 0–125% and 3–111% for heavy metals and nutrients, respectively. Conclusion: In conclusion, there was less consistency in nutrients between successive batches and CV within batches was wide. Consistency levels for E. coli may not be an issue if pathogen inactivation is complete. Recommendation: It is recommended that a threshold value be created for determining what is an acceptable level of variation in FS co-composting.Item Open Access Bioaerosol emissions from open windrow composting facilities : emission characterisation and dispersion modelling improvements(Cranfield University, 2013-06) Douglas, Philippa; Drew, Gill H.; Tyrrel, SeanBioaerosol emissions from open windrow composting facilities are becoming of increasing concern due to the negative health effects associated with bioaerosols, and the fact that emissions from open windrow facilities are not contained. Current bioaerosol monitoring techniques provide only a snapshot of bioaerosol concentrations spatially and temporally, whereas dispersion models have the potential to offer a more continual overview of bioaerosol levels, alongside existing sampling methods. However, dispersion models have not been successful at accurately predicting bioaerosol concentrations from open windrow composting facilities, generally under predicting concentrations by at least one order of magnitude. This is predominantly due to a lack of knowledge and data surrounding the complex nature of bioaerosol release and transportation, particularly when the compost is agitated. This study aimed to improve the reliability in the outputs of the ADMS dispersion model, specifically in the open windrow composting scenario, by performing several model tests alongside selected input parameter quantification improvements. This involved completing a sensitivity analysis, and a model calibration and validation specific to this scenario for the first time. Results from the sensitivity analysis showed that the use of wet and dry deposition modules is significant, and the majority of model inputs associated with the representation of the source of the emission are sensitive. These findings helped select the model input parameters for quantification improvements. Novel preliminary measurements of bioaerosol temperature, velocity and concentration at the source of composting agitation activities were completed. These values provided more accurate model inputs. Collectively, these results allowed the model to be successfully calibrated, and consequently, validated for the first time for this specific scenario, resulting in model outputs corresponding to within one order of magnitude to measured data. This has helped to generate an initial set of modelling recommendations, allowing modellers to use the ADMS dispersion model in a reliable manner, when applied to the open windrow composting scenario. Eventually, these improved model outputs may be used to predict bioaerosol exposure levels at sensitive receptors, particularly in conditions where current monitoring methods are not feasible.Item Open Access Chemical fingerprint database of bioaerosols(Cranfield University, 2017-04-21 11:08) Garcia Alcega, Sonia; Coulon, Frederic; Tyrrel, SeanThe impact of emissions from urban, agricultural and industrial scenarios on local air quality is of growing policy concern. Deleterious health effects can arise following exposure to infective microbes and the exposure risk to bioaerosols are difficult to quantify in real time. Current monitoring methods are labour intensive and a standardised protocol does not exist yet. Additionally, capturing sufficient amounts of material to generate distinguishable and reproducible patterns for bioaerosols identification and classification is still difficult. To overcome the inherent limitations of culturing, chemical fingerprint analysis of microbial biomarkers such as phospholipid fatty acids (PLFAs) and microbial volatile organic compounds (MVOCs) is proposed. Different air samples collection devices are currently being tested (Coriolis, Tenax® cartridges and polycarbonate filters) and each method will be evaluated depending on the complexity of the sampling, laboratory procedure, compounds identified and the limit of detection of the equipment.Item Open Access Competitive exclusion as a means to reduce Escherichia coli regrowth in digested sludge(Cranfield University, 2014-09) Williams, Tyson; Harris, Jim A.; Tyrrel, Sean; Ritz, K.In recent years, it has been reported that numbers of Escherichia coli increase significantly following centrifugation of sludge during the treatment process. E. coli is used as an indicator of the microbiological quality of sludge-derived products destined for agricultural recycling and of the efficacy of the sludge treatment processes. The re-growth phenomenon is of concern because of the potential for additional treatment requirement / higher disposal costs and loss of consumer confidence associated with a compliance failure. It is hypothesised that a competitive exclusion treatment could be the solution wherein the digestate be exposed to a ‘probiotic’ or defined mixture of micro-organisms, to effectively out compete or eliminate any resident E. coli remaining following treatment. The competitive exclusion principle as a treatment method has already seen application in various industrial sectors, the most well-known being the poultry industry. In experiments it was determined that an antimicrobial producing organism would be most likely to succeed. From the candidates screened, Lactobacillus reuteri proved the most promising. L. reuteri is a known producer of reuterin in the presence of glycerol and organic acids as a part of its normal metabolic activity. In sludge derived nutrient broth in the presence of glycerol and low pH, L. reuteri addition resulted in a reduction of E. coli to undetectable levels. In sludge cake under the same conditions, L. reuteri was less successful. However the addition of glycerol and L. reuteri to sludge cake restricted E. coli growth to a 2 log increase from the initial concentration of E. coli recorded following pasteurisation (an average of around 1x102 cfu/gDs), in comparison in the positive control a 4 log increase was recorded. From this result the sludge cake could be defined as conventionally treated. It can be concluded that competitive exclusion and L. reuteri show promise as a treatment for reducing E. coli re-growth in sludge cakeItem Open Access A conceptual framework for negotiating public involvement in municipal waste management decision-making in the UK(Elsevier, 2017-04-13) Garnett, Kenisha; Cooper, Tim; Longhurst, Philip J.; Jude, Simon; Tyrrel, SeanThe technical expertise that politicians relied on in the past to produce cost-effective and environmentally sound solutions no longer provides sufficient justification to approve waste facilities. Local authorities need to find more effective ways to involve stakeholders and communities in decision-making since public acceptance of municipal waste facilities is integral to delivering effective waste strategies. This paper presents findings from a research project that explored attitudes towards greater levels of public involvement in UK waste management decision-making. The study addressed questions of perception, interests, the decision context, the means of engagement and the necessary resources and capacity for adopting a participatory decision process. Adopting a mixed methods approach, the research produced an empirical framework for negotiating the mode and level of public involvement in waste management decision-making. The framework captures and builds on theories of public involvement and the experiences of practitioners, and offers guidance for integrating analysis and deliberation with public groups in different waste management decision contexts. Principles in the framework operate on the premise that the decision about ‘more’ and ‘better’ forms of public involvement can be negotiated, based on the nature of the waste problem and wider social context of decision-making. The collection of opinions from the wide range of stakeholders involved in the study has produced new insights for the design of public engagement processes that are context-dependent and ‘fit-for-purpose’; these suggest a need for greater inclusivity in the case of contentious technologies and high levels of uncertainty regarding decision outcomes.Item Open Access Control of E.coli in biosolids(Cranfield University, 2016-11) Fane, Sarah Elizabeth; Tyrrel, SeanAchieving microbial compliance levels in biosolids storage is complicated by the unpredictable increase of Escherichia coli (E. coli), which serves as an important indicator for pathogen presence risk. Meeting required microbial specifications validates sludge treatment processes and ensures that a safe product is applied to agricultural land. Controlled indicator monitoring provides confidence for farmers, retailers and the food industry, safeguarding the sludge-to-land application route. Following mechanical dewatering biosolids products are stored before microbial compliance testing permits agricultural application. During storage, concentrations of E. coli bacteria can become elevated and prevent the product from meeting the conventional or enhanced levels of treatment outlined in The Safe Sludge Matrix guidelines. Literature research identified innate characteristics of sludge and ambient environmental parameters of storage which are factors likely to influence E. coli behaviour in stored biosolids. The research hypothesis tested whether E. coli growth and death in dewatered sewage sludge can be controlled by the modification of physical-chemical factors in the cake storage environment. Parameters including nutrient availability, temperature, moisture content and atmospheric influences were investigated through a series of laboratory-scale experiments. Controlled dewatering and the assessment of modified storage environments using traditional microbial plating and novel flow cytometry analysis have been performed. At an operational scale, pilot trials and up-scaled monitoring of the sludge storage environment have been conducted enabling verification of laboratory results. Understanding the dynamics of cell health within the sludge matrix in relation to nutrient availability has provided a valuable understanding of the mechanisms that may be affecting bacterial growth post-dewatering. The importance of elevated storage temperatures on E. coli death rates and results showing the benefits of a controlled atmosphere storage environment provide important considerations for utilities.Item Open Access A controlled study on the characterisation of bioaerosols emissions from compost(2018-09-28) Nasir, Zaheer A.; Rolph, Catherine A.; Collins, Samuel; Stevenson, David; Gladding, Toni L.; Hayes, Enda; Williams, Ben; Khera, Shagun; Jackson, Simon; Bennett, Allan; Parks, Simon; Kinnersley, Robert P.; Walsh, Kerry; Pollard, Simon J. T.; Drew, Gillian; Garcia Alcega, Sonia; Coulon, Frederic; Tyrrel, SeanBioaerosol emissions arising from biowaste treatment are an issue of public concern. To better characterise the bioaerosols, and to assess a range of measurement methods, we aerosolised green waste compost under controlled conditions. Viable and non-viable Andersen samplers, cyclone samplers and a real time bioaerosol detection system (Spectral Intensity Bioaerosol Sensor (SIBS)) were deployed simultaneously. The number-weighted fraction of fluorescent particles was in the range 22–26% of all particles for low and high emission scenarios. Overall fluorescence spectral profiles seen by the SIBS exhibited several peaks across the 16 wavelength bands from 298 to 735 nm. The size-fractionated endotoxin profile showed most endotoxin resided in the 2.1–9 μm aerodynamic diameter fraction, though up to 27% was found in a finer size fraction. A range of microorganisms were detected through culture, Matrix Assisted Laser Desorption and Ionisation Time of Flight Mass Spectrometry (MALDI-TOF) and quantitative polymerase chain reaction (qPCR), including Legionella pneumophila serogroup 1. These findings contribute to our knowledge of the physico-chemical and biological characteristics of bioaerosols from composting sites, as well as informing future monitoring approaches and data interpretation for bioaerosol measurement.Item Open Access Data accompanying A randomised controlled feasibility trial of a BabyWASH household playspace: The CAMPI study(Cranfield University, 2021-06-30 10:29) Parker, Alison; Tyrrel, SeanWater, sanitation and hygiene (WASH) interventions should support infant growth but trial results are inconsistent. Frequently, interventions do not consider behaviours or transmission pathways specific to age. A household playspace (HPS) is one intervention component which may block faecal-oral transmission. This study was a two-armed, parallel-group, randomised, controlled feasibility trial of a HPS in rural Ethiopia. It aimed to recommend proceeding to a definitive trial. Secondary outcomes included effects on infant health, injury prevention and women’s time. Methods. November 2019−January 2020 106 households were identified and assessed for eligibility. Recruited households (N=100) were randomised (blinded prior to the trial start) to intervention or control (both n=50). Outcomes included recruitment, attrition, adherence, and acceptability. Data were collected at baseline, two and four weeks. Findings. Recruitment met a priori criteria (≥80%). There was no loss to follow-up, and no non-use, meeting adherence criteria (both ≤10%). Further, 48.0% (95% CI 33.7−62.6; n=24) of households appropriately used and 56.0% (41.3−70.0; n=28) cleaned the HPS over four weeks, partly meeting adherence criteria (≥50%). For acceptability, 41.0% (31.3−51.3; n=41) of infants were in the HPS during random visits, failing criteria (≥50%). Further, the proportion of HPS use decreased during some activities, failing criteria (no decrease in use). A modified Barrier Analysis described good acceptability and multiple secondary benefits, including on women’s time burden and infant injury prevention. Interpretation. Despite failing some a priori criteria, the trial demonstrated mixed adherence and good acceptability among intervention households. A definitive trial to determine efficacy is warranted if recommended adjustments are made. Includes data, protocols and ethical approval documents.Item Open Access Data: Storage duration and temperature affect pathogen load, heavy metals, and nutrient levels in faecal derived fertiliser(Cranfield University, 2024-02-08 15:33) Gbenatey Nartey, Eric; Sakrabani, Ruben; Tyrrel, Sean; Cofie, OlufunkeThis dataset describes the changes in nutrient characteristics and pathogen in two types of stored faecal derived fertiliser over a period of time.Item Open Access Desalination technologies for developing countries: what solutions?(Cranfield University, 2009-09) Groult, Lucille; Tyrrel, SeanDesalination is a water treatment option known by people at large for its large scale use in rich countries such as in the Middle East. Nevertheless, this is not an option for some developing countries such as Kenya, as, due to the water scarcity existing in such places, saline water is the only source for drinking purposes. Numerous technologies exist for desalinating water, from the very simple process of solar desalination already in use in the antiquity, to the most complicated membrane or electronic technologies. Appropriate solutions adapted to development or emergency situations have to be taken depending on the context in place in developing countries. Through discussions with private companies and research laboratories, some of the most up to date systems currently usable have been reviewed in order to assess their suitability for an implementation by the charity Oxfam GB in a near future in several locations in West African and South Asian countries. Criteria have been defined according to the needs observed by the charity in targeted places, better targeting possible appropriate technologies. The study focused on technological details as well as long term management issues for optimising ownership of the local communities. After comparison of the reviewed technologies and confrontation with the defined criteria, it resulted that interesting options available for development are membrane-based or distillation. The use of clean energy sources such as brute strength (mechanical systems using animal or human strength) simplify operation and maintenance, and lower operation cost at the same time for a sustainable implementation in remote villages. Automated electronic-based systems are also an opportunity for emergency situations. However, most of those solutions have not been in use in a developing country yet. Consequently, innovative experimentation is needed for the good of all.Item Open Access Design and commissioning of a multi-mode prototype for thermochemical conversion of human faeces(Elsevier, 2018-03-23) Jurado Pontes, Nelia; Somorin, Tosin; Kolios, Athanasios J.; Wagland, Stuart; Patchigolla, Kumar; Fidalgo, Beatriz; Parker, Alison; McAdam, Ewan; Williams, Leon; Tyrrel, SeanThis article describes the design and commissioning of a micro-combustor for energy recovery from human faeces, which can operate both in updraft and downdraft modes. Energy recovery from faecal matter via thermochemical conversion has recently been identified as a feasible solution for sanitation problems in low income countries and locations of high income countries where access to sewage infrastructures is difficult or not possible. This technology can be applied to waterless toilets with the additional outcome of generating heat and power that can be used to pre-treat the faeces before their combustion and to ensure that the entire system is self-sustaining. The work presented here is framed within the Nano Membrane Toilet (NMT) project that is being carried out at Cranfield University, as part of the Reinvent the Toilet Challenge of the Bill and Melinda Gates Foundation. For this study, preliminary trials using simulant faeces pellets were first carried out to find out the optimum values for the main operating variables at the scale required by the process, i.e. a fuel flowrate between 0.4 and 1.2 g/min of dry faeces. Parameters such as ignition temperature, residence time, and maximum temperature reached, were determined and used for the final design of the bench-scale combustor prototype. The prototype was successfully commissioned and the first experimental results, using real human faeces, are discussed in the paper.Item Open Access Development and evaluation of a rapid enzymatic hydrolysis test method to assess the biodegradability of organic waste(Cranfield University, 2008-11) Wagland, Stuart Thomas; Tyrrel, Sean; Godley, Andrew R.The amount of biodegradable municipal waste (BMW) that can be disposed of in a landfill must be reduced, in accordance with the landfill allowance trading scheme (LATS) in England and Scotland (LAS in Wales). Biodegradability test methods are used to monitor the quantities of BMW diverted by waste treatment processes. This research has outlined the requirements for timescale improvements on the currently used methods. The rapid (<24 h) enzymatic hydrolysis test (EHT) has been developed and the relationship of this with the long-term BM100 test has been compared with that of the established DR4 method. A range of untreated and treated organic waste materials taken from a number of treatment processes, and samples taken over a period of 9 months from a single treatment facility were analysed using each test method. The EHT is completed within 1 day, compared with 4 days for the current DR4 method, and was shown to possess a stronger correlation with the long- term BM100 test. This finding indicated the suitability of the EHT as an alternative short-term test method. A humic substance extraction step was added to the EHT procedure, which was expected to provide a more accurate estimation of sample biodegradability. This technique was, however, found to be unsuitable for use in a short-term test method based on the results presented, although further understanding of the processes involved in the EHT has been discussed. This thesis presents a new biodegradability test method, which has been developed, applied and evaluated. The processes of the EHT have been investigated, understood and discussed. Further developments are suggested based on the findings and observations throughout the thesis.Item Open Access Disruption of cells in biosolids affects E. coli dynamics in storage(IWA Publishing, 2019-05-22) Fane, Sarah Elizabeth; Madureira, D.; Nocker, A.; Vale, P.; Rivas Casado, Monica; Wilson, A.; Bajón Fernández, Yadira; Harris, Jim A.; Cartmell, Elise; Tyrrel, SeanAchieving microbial compliance during biosolids storage can be complicated by the unpredictable increase of Escherichia coli. Thermal treatment during anaerobic digestion (AD) and the effects of dewatering may be a significant factor contributing to indicator survival. Shear forces present during dewatering may promote cell damage, releasing nutrient for E. coli growth. The effect of cell damage on E. coli survival was assessed in laboratory-scale thermal and physical disruption experiments. E. coli growth curves for disrupted treatments were compared with control conditions and quantified using flow cytometry and membrane filtration techniques. A significant difference (p < 0.05) in the level of damaged cells between control and disrupted conditions was observed. For thermal and physical disruption treatments, the peak of E. coli concentration increased significantly by 1.8 Log and 2.4 Log (CFU (colony forming units) g−1 DS), respectively, compared with control treatments. Research findings contribute to the understanding of bacterial growth and death dynamics in biosolidsItem Open Access Do domestic animals contribute to bacterial contamination of infant transmission pathways? Formative evidence from Ethiopia(IWA Publishing, 2019-08-26) Budge, Sophie; Hutchings, Paul; Parker, Alison; Tyrrel, Sean; Tulu, Tizita; Gizaw, Mesfin; Garbutt, CamilaChild stunting is associated with poor water, sanitation and hygiene (WASH), partly due to the effect of infection on intestinal nutrient absorption. WASH interventions however show little effect on growth. A hypothesis is that bacterial contamination of hands and floors from domestic animals and their faeces, and subsequent ingestion via infant hand-to-mouth behaviours, may explain this. This formative study used microbial testing and survey and observational data from twenty households in Ethiopia to characterise principle bacterial transmission pathways to infants, considering WASH facilities and practices, infant behaviours and animal exposure. Microbial swabbing showed contamination of hands and floor surfaces from thermotolerant coliform (TTC) bacteria. Animal husbandry practices, such as keeping animals inside, contributed significantly (all p<0.005). There was no evidence that latrine facilities mitigated contamination across infant (p=0.76) or maternal (p=0.86) hands or floor surfaces (p=0.36). This small study contributes to the evidence that animal faeces are an important source of domestic bacterial contamination. The results imply that interventions aiming to reduce pathogen transmission to infants should think beyond improving WASH and also consider the need to separate infants and animals in the home. Intervention studies will be required to determine whether this reduces infant infection and improves linear growth.Item Open Access Do domestic animals contribute to bacterial contamination of infant transmission pathways? Formative evidence from Ethiopia(IWA Publishing, 2019-08-26) Budge, Sophie; Hutchings, Paul; Parker, Alison; Tyrrel, Sean; Tulu, Tizita; Gizaw, Mesfin; Garbutt, CamilaChild stunting is associated with poor water, sanitation and hygiene (WASH), partly due to the effect of infection on intestinal nutrient absorption. WASH interventions, however, show little effect on growth. A hypothesis is that bacterial contamination of hands and floors from domestic animals and their faeces, and subsequent ingestion via infant hand-to-mouth behaviours, may explain this. This formative study used microbial testing and survey and observational data from 20 households in Ethiopia to characterise principle bacterial transmission pathways to infants, considering WASH facilities and practices, infant behaviours and animal exposure. Microbial swabbing showed the contamination of hands and floor surfaces from thermotolerant coliform bacteria. Animal husbandry practices, such as keeping animals inside, contributed significantly (all p < 0.005). There was no evidence that latrine facilities mitigated contamination across infant (p = 0.76) or maternal (p = 0.86) hands or floor surfaces (p = 0.36). This small study contributes to the evidence that animal faeces are an important source of domestic bacterial contamination. The results imply that interventions aiming to reduce pathogen transmission to infants should think beyond improving WASH and also consider the need to separate infants and animals in the home. Intervention studies will be required to determine whether this reduces infant infection and improves linear growth.Item Open Access The Effect of Green Waste Composting on the Concentration and Composition of Ambient Bioaerosols(Cranfield University, 2010-01) Pankhurst, Louise J.; Tyrrel, Sean; Drew, Gill H.The emission and dispersal of bioaerosols from commercial composting facilities has become an issue of increasing concern over the past decade, as historical evidence links bioaerosol exposure to negative human health impacts. As a result, recommended concentrations and risk assessment limits were imposed in 2001. However, more recent research has suggested that these limits may be exceeded under certain circumstances. For example, underestimation of bioaerosol concentrations may occur through „snapshot‟ sampling, and the use of methods that may reduce culturability of bioaerosols. This study aimed to address several gaps in knowledge, including quantification of bioaerosol concentrations downwind from sites, analysis of the effect that operational and environmental influences have on emission and downwind concentrations, and investigation of methods for the enumeration of non-culturable bioaerosols. The concentrations of bioaerosols upwind, on-site and downwind from two open-air green waste windrow composting facilities were enumerated in extensive detail, producing the first detailed and validated database of bioaerosol concentrations at green-waste composting facilities. The effects of composting processing activities, season, and meteorological conditions on concentrations were also investigated utilising this dataset. Results from these studies suggested that bioaerosols are able to disperse in elevated concentrations to distances beyond the 250 m risk assessment limit. Downwind peaks in concentration were directly linked to compost processing activities on-site, with the risk of sensitive receptor exposure to bioaerosols during non-operational hours minimal. Further, it was found that patterns in downwind concentrations of bioaerosols are likely to be governed by buoyancy effects, as a second peak in concentrations was found at 100-150m downwind. This finding was further supported through the use of a novel direct counting method. Finally, molecular methods allowed the composition of bioaerosols emitted from composting to be determined and showed that composting significantly alters the aerobiotic community at distances downwind. The methods investigated provide the potential for detailed, continuous measurements of bioaerosols, alongside identification of potentially pathogenic microorganisms, and could ultimately lead to source apportionment of bioaerosols.Item Open Access Effect of various organic fertilisers on phosphorus mineralisation, use efficiency and maize yield(MDPI, 2022-09-28) Mnthambala, Frank; Tilley, Elizabeth; Tyrrel, Sean; Sakrabani, RubenWhen soils are phosphorus (P) deficient, external sources in the form of fertilisers have to be applied to increase crop yields. The world depends on mined sources for P fertilisers, and recent reports indicate that an increase in the human population has led to rising demand for P fertilisers, making its future supply uncertain. A low supply of chemical P fertilisers may lead to food insecurity. Although the efficacy of organic sources of P is unclear, organic waste materials containing P can potentially replace inorganic P sources. Previously, organic fertilisers have been used to supply N and even P, but the application rates were mostly N based, resulting in inconsistent and comparable results. This research was conducted to understand P mineralisation and the availability of the P-based organic fertilisers. The results showed that available P in the soil at 3 weeks accounted for 50%, 6 weeks accounted for 49%, and 9 weeks counted for 46% of the maize yield. The organic P sources maintained soil available P above the threshold available P value in Malawi. The P sources did not affect the maize P use efficiency (PUE). The results indicate that organic P sources could be used as an alternative fertiliser for maize production in Malawi.