The model generates odour contours which depict likely odour concentrations, expressed as odour units (OUs), which can be mapped spatially.
In this example provided, the 5 OU contour represents a point at which it can be expected that odours of weak concentration will not be noticeable for 99.9 % of the time. Depending on the input parameters, the location and shape of the odour contours can vary significantly.
Local meteorological patterns are determined through data obtained from nearby weather stations, located at airports, agricultural research stations, industrial sites. If these sources are not available then a weather station is established on site and data is captured over an extended period.
A key output from the weather data is a wind rose - it visually identifies the predominant wind direction, speed and frequency over time. This helps to assess the rate at which odour will disperse. The direction of light winds is also important, as these disperse odour at a slower rate and pose a greater risk of impacting residents’ amenity.
Odour buffers are a useful tool to support the planning and management of wastewater treatment plants and their surrounding areas. Defining the extent of buffers is dependent on the results of odour modelling and many factors which can vary over time.
Many treatment plants are dynamic, adapting to service an increasing population and deliver new products and services, such as recycled water, nutrients, biosolids, biogas. This means buffer lines also need to be dynamic. Odour modelling and buffers are a tool which should be used to support, not replace, best practice land use planning and urban design.
Strategic resource areas