We know that odour is the key concern for local residents living near Deephams Sewage Works.
We want to significantly reduce the odour from the works, at a reasonable cost to all of our waste customers.
The causes of odour
Sewage can give off odour when it is treated, or moved around during the treatment process. Although it is mainly water, sewage contains polluting materials that produce gases when they are treated or turn septic.
If the treatment process takes place in tanks that are open to the air, these gases can be released into the air and cause odour.
The amount of odour from a sewage treatment works depends on a range of issues including what is in the sewage, how long it takes to arrive at the sewage works, how it is treated, the direction and strength of the wind and how warm the weather is (sewage can smell more on hot days). We have no control over many of these issues.
What we will do about the smell
We have carried out a number of improvements since 2010 to reduce the smell from the works and local residents have told us that they have noticed the smell starting to reduce.
We want to do more. So achieving a much more significant reduction in odour is a priority in our plans to upgrade the sewage works. We plan to spend around £24m on measures to control the odour produced by the smelliest parts of the works. This will involve covering equipment and tanks and installing equipment to capture and clean odorous air. Our plans include covering the following parts of the site to capture odorous air:
- The inlet works – the part of the works where the raw sewage first enters the site
- The primary settlement tanks – used at the first stage of the treatment process
- The first part of the aeration tanks – used at the second stage of the treatment process
- The secondary sludge digesters – used to treat the solid waste left over from the treatment process
Why we can’t get rid of the smell entirely
We will never be able to guarantee that any sewage treatment works will be completely free from odour.
We want to reduce odour as much as we can, by focusing our improvements on the smelliest parts of the works, at a reasonable cost to all of our wastewater customers.
What the smell will be like in the future
The amount of odour produced by the sewage works will be significantly reduced. Once the upgrade work is finished, the number of properties in the area most affected by odour from the sewage works will be reduced by 99 per cent.
Our neighbours and local residents will be able to smell the works far less often, and when odour is produced, the smell will not be as strong as it is now.
The maps below show the area that can currently be affected by odour from the sewage works, and the area that may be affected after the upgrade work has been completed.
Before the upgrade
After the upgrade