Data for Pilot-scale biofiltration at a Materials Recovery Facility - Impact on Bioaerosol Control

Biofilters have long been considered as an effective technology for the abatement of odour and more recently, bioaerosols at enclosed waste management facilities. However, there is a lack of quantitative data on the influence of biofilter operating parameters on bioaerosol removal effectiveness. It is imperative to develop a better understanding of biofilter design and effective performance monitoring techniques especially if they are to continue to control all emissions and achieve their full potential. This study investigated the performance of pilot-scale biofilters for removal of bioaerosols from waste airstreams in a materials recovery facility based in Leeds, UK, with the objectives of assessing impact of gas phase residence time on bioaerosol control; evaluating net bioaerosol emitting potentials of biofilters and assessing the effect of inlet concentration on bioaerosol control; as well as assessing size distribution of bioaerosol particles in air exhausted from biofilters in order to relate these to the tidal volume inhaled by humans. A six-stage Andersen sampler was used to measure the concentrations of four groups of bioaerosols (Aspergillus fumigatus, total fungi, total mesophilic bacteria and Gram negative bacteria) in the airstream before and after passing through the biofilters over a period of 11 months. The biofilters achieved a removal efficiency up to 97% for A. fumigatus, 94% for total fungi, 86% for total mesophilic bacteria and 85% for Gram negative bacteria, provided that the inlet concentration was high (103 – 105 cfu m-3), which is the case for most waste treatment facilities. The performance was highly variable at low inlet concentration with some cases showing an increase in outlet concentrations, suggesting that biofilters had the potential to be net emitters of bioaerosols. The gas phase residence time did not appear to have any statistically significant impact on bioaerosol removal efficiency. Particle size distribution varied between the inlet and outlet air, with the outlet having a greater proportion of smaller sized particles that represent a greater human health risk as they can penetrate deep into the respiratory system where gaseous exchange occurs. However, the outlet concentrations were low and would further be diluted by wind in full scale applications. In conclusion, this study shows that biofilters designed and operated for odour degradation can also achieve significant bioaerosol control in waste gas.