Corporate Responsibility

Sustainable sewage treatment.

Last reviewed:
We transport and treat 4.4 billion litres of sewage per day for 15 million customers. We need a healthy natural environment to manage treated wastewater, and we’re continuing to work hard to make sure our sewerage network and treatment sites are as sustainable as possible.

Aeration lanes at Beckton sewage treatment works.

Maintaining compliance.

Once wastewater has been safely treated, the water is discharged from our sewage treatment works into local watercourse. This means it’s really important for us to get our treatment processes right, to make sure the watercourses stay healthy.

The Environment Agency is responsible for setting quality standards for discharges from our 351 sewage treatment works. We must pass every discharge quality test to meet our sewage treatment works compliance commitment of 100 per cent, but in 2017/18 only 99.43 per cent of our sewage treatment works achieved their discharge compliance target. Some of the problems were the result of extreme wet weather, unconsented discharge of effluent into our sewers by customers and human error.

To make sure we meet our compliance commitments in the future, we’ve continued to invest in our assets - for example, by installing new inlet screens to reduce the likelihood of problems during the treatment process, and upgrading our site monitoring technology so we can respond quickly when problems do occur.

London Tideway improvements.

We’re working to improve the water and sewer networks across London to make sure they can cope with current and future demands. One of the biggest projects to improve and future-proof our network is the Thames Tideway Tunnel (also known as the “super sewer”). We’re working with Tideway (Bazalgette Tunnel Limited) to deliver the Thames Tideway Tunnel.

When it’s complete, together with the Lee Tunnel, it will prevent millions of tonnes of sewage from overflowing into the tidal Thames every year from the capital’s overloaded Victorian sewer system. The new tunnel will pipe sewage to our Beckton treatment works where we’ll return treated and safe water to the environment and use the sewage waste (sludge) to generate more renewable energy. Find out more about the tunnel and its progress at

London 2100.

The water industry, through WaterUK, has developed an approach for strategic long-term drainage and wastewater management planning (DWMP) and we are applying this methodology to London. This strategy will tackle a range of challenges including population growth, climate change, land locking of our sites, ageing assets and striving to meet tighter environmental standards.

The scale of these challenges means we need to think differently about the future, and look far beyond the conventional five-year price review cycles of the water sector. London’s wastewater system is immense and complex, and significant changes will take time to achieve.

A much longer-term approach is needed to manage risks and embrace opportunities for innovation, which is why we’re now considering time horizons of 25 and 80 years in a way that reflects water resource planning. We call this new approach London 2100. Click on the case study below to find out more: