Improving water quality in Chichester Harbour

What are we doing? 

We’re improving our network around Chichester Harbour to support future development and population growth — while protecting local shellfish waters and the ecosystems that rely on them.

At Thornham Wastewater Treatment Works, we’re installing a new UV disinfection system to enhance how we treat wastewater and improve the quality of water returned to the environment. This upgrade will also increase the site’s capacity, helping us manage more wastewater at once, reduce spills, and support the needs of a growing community.

This is part of a wider environmental investment around Chichester Harbour. Over the next five years, we’re:

•    looking into nature-based solutions such as wetlands and sustainable drainage systems to support our Storm Overflow Reduction Plan.
•    sealing sewers to prevent groundwater getting in and putting pressure on the system  
•    increasing treatment capacity at our sites by 60%, reducing overflow spills
•    determining levels of nutrients and chemicals and their sources for better treatment

We’ve also started a two-year investigation to better understand water quality in the Three Harbours - Langstone, Chichester, and Pagham. By working closely with our partners and collecting long-term data, we’ll be able to track changes over time and identify what’s affecting the health of these important coastal areas. 

Useful information for residents and visitors

We’re still in the early stages of this project, so there’s currently no impact on the local community. As things progress, we’ll keep you informed every step of the way — making sure you have all the details you need.