Browsing by Author "Taha, M. P. M."
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Item Open Access Dispersion of bioaerosols from composting facilities.(2006-09-01T00:00:00Z) Drew, Gillian H.; Tamer Vestlund, Asli; Taha, M. P. M.; Smith, Richard; Longhurst, Philip J.; Kinnersley, R.; Pollard, Simon J. T.The promotion of composting as an option for sustainable waste management has raised concerns regarding public health impacts of exposures to potentially hazardous bioaerosols. Recent source term experiments show that bioaerosol emissions are episodic and that peak emissions are related to compost agitation. The Environment Agency requires risk assessments for facilities that have sensitive receptors within 250m of their boundary. In order to improve current risk assessment methodologies, improved predictions of bioaerosol dispersal are required. Dispersion modelling has been successfully used to determine dispersion of odours from waste management. In this paper, bioaerosol concentration data measured at a composting facility is analysed in an ongoing series of model experiments, using the ADMS air dispersion model. Initial modelling results reveal that the concentrations of bioaerosols decrease rapidly with distance from the site, although under certain circumstances, it is possible that higher concentrations may still be present at 200m from the site boundary. However, dispersion models are not yet able to take into account all the properties of bioaerosols, in particular, their viability and their ability to aggregate and form clumps, which will affect the rate of dispersal. A series of experiments were designed to examine how the options within dispersion model affect the dispersion of bioaerosols and under which circumstances high concentrations may disperse to sensitive receptors. The results will be compared with bioaerosol measurements taken downwind of a composting facility, to determine the accuracy of the model predictions. This is the first stage in an attempt to design a best practice method for modelling bioaerosols.Item Open Access Enumerating actinomycetes in compost bioaerosols at source—Use of soil compost agar to address plate ‘mask(2007-07-01T00:00:00Z) Taha, M. P. M.; Drew, Gillian H.; Tamer Vestlund, Asli; Aldred, David; Longhurst, Philip J.; Pollard, Simon J. T.Actinomycetes are the dominant bacteria isolated from bioaerosols sampled at composting facilities. Here, a novel method for the isolation of actinomycetes is reported, overcoming masking of conventional agar plates, as well as reducing analysis time and costs. Repeatable and reliable actinomycetes growth was best achieved using a soil compost media at an incubation temperature of 44 °C and 7 days’ incubation. The results are of particular value to waste management operators and their advisors undertaking regulatory risk assessments that support environmental approvals for compost facilitiItem Open Access Estimating fugitive bioaerosol releases from static compost windrows: feasibility of portable wind tunnel approach(Elsevier Science B.V., Amsterdam., 2005-01-01T00:00:00Z) Taha, M. P. M.; Pollard, Simon J. T.; Sarkar, Ujjaini; Longhurst, Philip J.An assessment of the fugitive release of bioaerosols from static compost piles was conducted at a green waste composting facility in South East England; this representing the initial stage of a programme of research into the influence of process parameters on bioaerosol emission flux. Wind tunnel experiments conducted on the surface of static windrows generated specific bioaerosol emission rates (SBER2s) at ground level of between 13 - 22 x10 3 cfu/m 2 /s for mesophilic actinomycetes and between 8 - 11 x10 3 cfu/m 2 /s for Aspergillus fumigatus. Air dispersion modelling of these emissions using the SCREEN3 air dispersion model in area source term mode was used to generate source depletion curves downwind of the facility for comparative purposes.Item Open Access Improving bioaerosol exposure assessments 1 - comparative modelling of 2 emissions from different compost ages and activities.(2007-07-01T00:00:00Z) Taha, M. P. M.; Drew, Gillian H.; Tamer Vestlund, Asli; Hewings, G.; Jordinson, G. M.; Longhurst, Philip J.; Pollard, Simon J. T.We present bioaerosol source term concentrations from passive and active composting sources and compare emissions from green waste compost aged 1, 2, 4, 6, 8, 12 and 16 weeks. Results reveal that the age of compost has little effect on the bioaerosol concentrations emitted for passive windrow sources. However emissions from turning compost during the early stages may be higher than during the later stages of the composting process. The bioaerosol emissions from passive sources were in the range of 103–104 cfu m−3, with releases from active sources typically 1-log higher. We propose improvements to current risk assessment methodologies by examining emission rates and the differences between two air dispersion models for the prediction of downwind bioaerosol concentrations at off-site points of exposure. The SCREEN3 model provides a more precautionary estimate of the source depletion curves of bioaerosol emissions in comparison to ADMS 3.3. The results from both models predict that bioaerosol concentrations decrease to below typical background concentrations before 250 m, the distance at which the regulator in England and Wales may require a risk assessment to be compleItem Open Access The influence of process variables on bioaerosol emission flux and exposure - estimating fugitive bioaerosol releases from static compost windrows(2004-01-01T00:00:00Z) Taha, M. P. M.; Pollard, Simon J. T.; Sarkar, Ujjaini; Longhurst, Philip J.An assessment of the fugitive release of bioaerosols from static compost piles was conducted at a green waste composting facility in South East England; this representing the initial stage of a programme of research into the influence of process parameters on bioaerosol emission flux. Wind tunnel experiments conducted on the surface of static windrows generated specific bioaerosol emission rates (SBER2s) at ground level of between 13 - 22 x10(3) cfu/m(2)/s for mesophilic actinomycetes and between 8 - 11 x10(3) cfu/m(2)/s for Aspergillus fumigatus. Air dispersion modelling of these emissions using the SCREEN3 air dispersion model in area source term mode was used to generate source depletion curves downwind of the facility for comparative purposes.Item Open Access Progress towards a best practice method for modelling dispersion of bioaerosols from composting facilities(2007-10-01T00:00:00Z) Drew, Gillian H.; Tamer Vestlund, Asli; Jordinson, G.; Taha, M. P. M.; Smith, Richard; Tyrrel, Sean F.; Longhurst, Philip J.; Pollard, Simon J. T.The promotion of composting in the UK as a sustainable waste management option has led to concerns regarding exposure of the public to potentially harmful emissions of airborne micro-organisms or bioaerosols. In response to public concerns, the Environment Agency in England and Wales requires a risk assessment for any licensed composting facility that has a sensitive receptor within 250m of the site boundary. An ongoing programme of studies in association with the Environment Agency has begun to explore methods to improve exposure assessments for bioaerosols. Our results have shown that is is possible to use air dispersion models for estimating downwind concentrations of bioaerosols, and the more advanced modelling options, such as the use of intermittent emission rates, result in lower downwind concentrations. Current risk assessments may be over-estimating the exposure of receptors to bioaerosols from composting, however further studies are needed to validate the results presented here. 1. INTRODUCTION The promotion of composting in the UK as a more sustainable waste management option has led to concerns regarding exposure of the public to potentially harmful emissions of airborne microorganisms or bioaerosols. The composting process is reliant on various micro-organisms, such as bacteria and fungi, to break down the organic matter. However, if as a result of composting operations these micro-organisms become airborne, may be breathed in, and due to their small size, can penetrate deep into the human respiratory system. Conditions such as farmer's lung disease and aspergillosis (Latgé, 1999) have been linked to high concentrations of bioaerosols, although dose-response relationships are not well defined. In response to public concerns, the Environment Agency in England and Wales requires a risk assessment for any licensed composting facility that has a sensitive receptor within 250m of the