Managing odour

The sewage treatment process can sometimes produce odours. This was not a problem in the past as sewage works were located away from residential areas.

Options to reduce odour from our sewage works can be costly as it involves covering parts of them to treat their air emissions. Retrofitting is usually difficult, as our sewage treatment works were not originally designed to collect air emissions. New sewage treatment developments can be designed to more readily meet the high performance standards required by local authorities.

A good example of this is our Reading Sewage Treatment Works, which opened in 2005. It is one of the most technically advanced plants of its kind in the UK, costing around £80 million to build, with the majority of the works enclosed to reduce odour.

We are developing a risk framework to help us identify priority sites where odour needs to be tackled. For these sites, we will then develop odour management plans and introduce odour control as appropriate to each site. The framework will also identify cost-beneficial levels of odour reduction at sites that need enhanced measures to reduce odour. Such measures will be completed at our Mogden Sewage Treatment Works in west London in 2008.

Our response

In the medium-term (2010-2015), we will:

Continue to operate a risk management framework that identifies and prioritises sites that are causing significant odour problems and sites that present a future risk of odour issues.

We will seek to reduce odour at these sites by: 

• Identifying main sources of odour
• Reviewing existing operations and maintenance practices to identify opportunities for improvement
• Introducing baseline measures to reduce sources of odour
• Implementing enhanced odour reduction measures (e.g. covering plant) if odour persists and where cost-beneficial
• Considering measures that go beyond an economic business case in exceptional circumstances (for example, regeneration projects)
• Design new works to meet industry best practice, typically five 'odour units' at the site boundary 
• Design upgrades to existing sewage works to avoid increasing odour
• Keep local communities better informed about the potential odour impacts of planned maintenance at existing sewage treatment sites
• Work with local authorities, Environmental Health Officers and developers to achieve the most sustainable use of land around sewage works

In the long-term (2015-2035), we will:

• Adopt a more proactive approach to odour management whereby potential odour issues are tackled at sites before they become a problem. Current projections indicate odour reduction will be needed at over 100 sites.
• Mitigate odour where cost-beneficial for customers at all risk sites. Seek to implement further mitigation in exceptional cases
• Monitor trends in customer acceptability of odour in the context of economic development and climate change
• Seek to reduce customer complaints to a minimum level