Part of the function of a water and sewerage undertaker is to collect and treat wastewater and return it to the environment. Without treatment the wastewater from domestic and residential premises, industrial wastewater discharges to sewers and rainwater contaminated with metals, oils and other pollutants from run-off in urban areas draining to sewers, would have significant adverse impacts on the water environment. Effective treatment also means treated wastewater can be returned to the environment to maintain river flows for conservation, fisheries and recreational interests.
Like all water and wastewater companies, our investment programme and operational practices are required to adhere to strict regulatory controls, as set out by the Environment Agency. To safeguard river, shellfish and bathing water quality we aim to ensure the wastewater we return to the environment is treated to the required standards. All our discharges are permitted by the Environment Agency and it is these permits that set out the required standards and levels of treatment required to protect the environment.
South West Water is the regulator for industrial wastewater discharges to the public sewer. The company conducts careful checks before permitting any release into the sewer, and monitors compliance with those consents. This is designed to protect both our processes and the environment from harm by ensuring levels discharged to the sewer are safe, treatable and do not harm the integrity of the sewer.
Objectives and Targets
Our objectives and targets for effluent management are driven by environmental compliance to ensure the treated wastewater returned to the environment (discharge) meets the environmental standards agreed with our regulator.
Our target remains 100% compliance with environmental permit conditions, with performance reported annually through South West Water’s Annual Performance Report. In 2025/26, numeric compliance was 98.1%.
Reducing storm overflows and pollution incidents remains one of our key strategic priorities for the 2025–2030 period. During 2025/26, we delivered measurable improvements, including a 17% reduction in storm overflow spills, a 25% reduction in spill duration, and an estimated 6,000 spills avoided, with over 8,300 spills prevented through targeted interventions.
We also achieved a 34% reduction in pollution incidents (absolute) and 53% reduction (normalised), alongside a 60% reduction in repeat pollution incidents.
These improvements are being delivered through a combination of targeted infrastructure investment and enhanced operational practices, including:
- Storm overflow improvements, with a 50% reduction in spills at the highest spilling sites
- Installation of additional storm storage capacity and optimisation of treatment works
- Sewer network upgrades and maintenance, including cleansing of over 114 km of sewers and a 33% reduction in sewer collapses
- Reduction of surface water and non-sewage flows entering the network
- Enhanced monitoring, with 100% of overflows fitted with Event Duration Monitoring (EDM) and 96.7% operability
Alongside these interventions, we continue to expand the use of catchment management and nature-based approaches, including management of 5,138 hectares of land, 254 hectares of peatland restoration, and 31,893 trees planted during the year.
Together, this integrated approach is delivering sustained improvements in water quality, reducing pollution risk and strengthening resilience to climate change.