Assessing the Impact of Odour Mitigation Work by Thames Water

Thames Water aimed to secure funding from the economic regulator Ofwat for upgrade work at several of its Sewage Treatment Works. To support this process, Thames Water commissioned us to conduct research to understand customers’ willingness to pay for reducing odour. The study also included contextual questions about residents’ experiences with odour. In the following years, upgrade work was carried out at the Beckton and Long Reach Sewage Treatment Works to reduce odour emissions, and similar work was planned for the Deephams Sewage Treatment Works.

To meet the quality assurance requirements of Ofwat, Thames Water needed to demonstrate reduced nuisance from odour, with a reduction in odour complaints being considered crucial evidence. Since the communities around the treatment works rarely complained about odour emissions, Thames Water did not see community surveys as a reliable measure to gauge the impact of odour mitigation investment on customer experiences.

Research Aims:
Thames Water commissioned MEL to undertake independent research with the following objectives:

• Understand customers’ views on whether odour mitigation work at the Beckton and Long Reach sites had reduced the strength and frequency of odour and its effect on their lives.
• Compare customer views with the results from previous surveys.
• Establish a baseline of customers’ views on odour strength and frequency around the Deephams site before the planned odour mitigation work.

Approach

The research adopted a qualitative approach to gain deeper insights into customers’ perceptions, attitudes, and behaviors regarding odour impact. Face-to-face, in-depth interviews were chosen as the preferred method. These interviews, led by trained researchers, were conducted with single participants or adult partners in households. A pre-agreed topic guide was used to steer the discussions, allowing interviewees to share information at their own pace and in their own words. The qualitative interviews aimed to understand how changes over time impacted the household or family unit.

Sampling and Fieldwork:
A screener questionnaire was designed to identify households that had previously experienced local odour issues related to a treatment works. Residents who had not lived in their homes for 12 months or more were excluded. We conducted 24 in-home interviews.

Outcomes

The research findings indicated the following conclusions:

• Customers experienced a reduction in both the frequency and strength of odour from the Beckton and Long Reach sewage treatment works.
• The research was qualitative and not representative of the wider customer base. Nevertheless, it suggested that the odour reduction works at the two sewage treatment works were relatively effective for a majority of those interviewed.
• The qualitative research provided valuable insights for developing a structured questionnaire. Larger scale quantitative surveys were planned to build on the initial research and offer a more robust measurement of the impact of Thames Water’s odour mitigation work.