Understand how odour buffers are defined, why they may need to change over time and how they are used to support planning and management processes.

Odour buffers ensure residential and other sensitive land uses are not located close to wastewater treatment plants or wastewater pump stations, where people may be exposed to unpleasant odours.

Odour buffers help to:

  • Minimise the impact of odour on surrounding areas, which can lead to land use conflict
  • Protect the community's investment in wastewater treatment plants and wastewater pump stations
  • Provide certainty for planning and future investment
  • Plan for compatible and beneficial land use around wastewater treatment plants – such as agriculture, industry, recreation areas or urban forests – to make the most of the investment by reusing outputs
  • Reduce operational costs to the community

Odour buffers are also used to support:

  • Planning infrastructure upgrades to existing plants
  • Planning the location of new plants
  • Providing input into state and local government planning processes, such as planning strategies and schemes, structure planning, subdivision and development
  • Providing a spatial focus for beneficial and compatible land uses, including waste recycling and renewable energy uses
  • Environmental impact assessment, licensing and compliance

We have defined buffer zones for all our wastewater treatment plants across WA, using 2 basic methods:

  • Generic buffer – involves drawing a line with a consistent radius (usually 500 metres) around the operational area of the treatment plant. This method is used for most plants in WA, especially those plants servicing smaller urban settlements.
  • Modelled buffer – uses scientific modelling software combined with wind data and other site specific and local data to define odour contours. This method is relatively expensive and time consuming. It is often used to define buffers for large plants in the Perth-Peel region and in major regional centres.

The modelled buffer zone size is determined by factors such as:

  • Existing and planned wastewater treatment plant capacity
  • Type of treatment processes and odour emission rates
  • Wastewater treatment plant load
  • Local topography and vegetation
  • Local meteorological patterns

The model generates odour contours which depict likely odour concentrations, expressed as odour units (OUs), which can be mapped spatially.

Image - Diagram showing odour contours

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.

Diagram showing the wind direction in Manjimup

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.  Read more about strategic resource areas.