More than £8m of improvements to a Southampton wastewater treatment works are helping to protect the River Itchen and its salmon population.
Work began last year on upgrades to Southern Water’s Portswood site, aimed at improving the quality of treated final effluent entering the neighbouring chalk stream.
On a dry day, the site treats over 15 million litres of wastewater from Southampton – but this total can more than quadruple when it rains and surface water runs into the sewers.
So far during the works, teams have added a new treatment process on site called ferric dosing, reducing odours and phosphates, and have been adding extra oxygen to watercourses to support the local environment.
And by summer 2025 Southern Water will have added a giant new storm tank capable of holding back increased flows during rainfall – stopping it from being released into the environment as storm overflows.
Southern Water expect this will play its part in reducing storm overflows from the site.
The River Itchen, and its neighbour the Test, are renowned across the world for their chalk stream habitats, and annually attract a population of Atlantic Salmon to their waters.
Southern Water said it has been working hard with a range of partner agencies, including the Environment Agency and other partners to protect and enhance water quality in the area.
Since the work began it has helped to reduce odour complaints from the local community, and Southern Water are closely monitoring the health of the Itchen.
John Penicud, Managing Director for Wastewater, said:
“We’re keen to play our part in improving the health of this much-loved chalk stream and its Atlantic Salmon population, and that is why we are investing in major upgrades to our Portswood site.
“We are one of numerous guardians of water quality in this area, led by the Environment Agency, and we support a shared aim of creating bathing waters or ‘blue spaces’ in the lower Itchen. Only by working together can we achieve the progress we all want to see.”
The storm tank is being built by GtB who are also supporting Southern Water on a number of other key projects to treatment sites across its region.
Stuart Whisby, Project Manager for GTb, said:
“This is a really exciting project and one of many in the Southampton area. We have a number of constraints that we’ve had to overcome and I’m proud that we have done so. These include dealing with existing buried structures and working close to the River.”
