Southern Water has optimised its Swalecliffe Wastewater Treatment Works to increase available storage, reducing storm overflows by 36%. The optimisation cost around 90% less than building a new storm tank and was much less carbon intensive.

The storm tanks at Swalecliffe Wastewater Treatment Works (WWTW) were not being used to full capacity, and as a result the site was using its long sea outfall around 100 times a year. The water company said that to prevent this it wanted to find a way to use the storage while staying within regulatory permits and guidelines.

Optimising the site to manage more stormwater

Southern Water worked with the Environment Agency to get new permits and design a complex engineering solution to completely overhaul the way the site worked. The comany installed new chambers and pipework which enabled it to redirect 450 litres of storm water per second during heavy rainfall and store it in the 1,800 cubic metres of extra storage capacity.

The installation of the new chambers and pipework cost a total of £750,000, as opposed to the millions that would be needed to build a new storm tank. This optimisation of existing assets means that building of new structures was avoided, saving time, cost, and carbon.

The work was completed in August 2023 and immediately started preventing storm overflow releases from the long sea outfall at Tankerton Beach.

Southern Water said it has seen a consistent 36% reduction in storm overflows as a result of the optimisation and will continue to monitor the results.

The utility is investing over £25 million on upgrades to the Swalecliffe Wastewater Treatment works, including the replacement of the storm overflow pipe.

Southern Water said that by using optimisation over building new structures, it was able to make the investment go much further.