Dispersion of bioaerosols from composting facilities.

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.