Detailed Odour Assessment for Waste Transfer Station

Hertfordshire County Council appointed us to provide an Air Quality and Odour Assessment for a new waste transfer station in Ware.

Challenge

We used a dispersion model to predict the increases in local traffic-related pollutants. When considered in the context of existing concentrations, we found that the impact was not significant. The risk of dust and bio-aerosol impacts was also found to be negligible as most of the waste would be handled and processed within the main building.

An air handling system would provide odour control, maintaining a slight negative pressure within the main building, to avoid release of odorous air when the doors are opened. Odour control would be provided using activated carbon filters. The filtered air would be exhausted through a stack, located to the north of the main building and another stack located to the north-east of the additional building. The key challenge was to determine the best combination of stack height and odour emission concentration, from the filtration system, to minimise the risk of odour impacts in the local community.

Solution

We used an atmospheric dispersion model to predict odour concentrations across a 3km by 3km grid of receptors for a pre-determined odour emission concentration over a range of stack heights. The predictions were plotted on a graph against the stack heights. The graph showed that there was no obvious stack height at which benefits would be gained by increasing the stack height. 

We then assumed the stack ended 3m above the height of the main building. We then predicted the odour concentration at the nearest properties surrounding the site for a range of odour emission concentrations achieved by the filtration system. This allowed us to identify the odour emission concentration that the abatement needed to achieve to avoid impacts.

The results of the modelling helped the council to design the odour control system with an understanding of the optimum stack height and the odour emission concentration that needs to be achieved by the abatement selected.