The Environment Agency has told South West Water (SWW) that its plan to install a long-sea outfall serving parts of the Isles of Scilly would not provide the level of wastewater treatment required to protect the marine environment.
Regulator demands appropriate treatment rather than screening alone
SWW had proposed discharging screened effluent through a new outfall, removing larger and smaller solids before release. In its assessment the Environment Agency concluded that this approach would be unlikely to meet permitting requirements and has asked the company to develop an alternative that includes more substantive treatment prior to any coastal discharge.
“We recognise South West Water must improve wastewater infrastructure on the Isles of Scilly; a community where the economy relies on the quality of the environment and with logistical challenges for engineering works. Our position reflects government policy that any coastal discharges serving communities with over 2,000 people needs secondary treatment.”
The agency highlighted both environmental protections and national policy as factors in its decision. It said it will review the outfall and screening application if submitted but that the onus is on SWW to demonstrate why a different solution would be acceptable.
What South West Water says and the practical challenges
SWW acknowledged the difficulty of delivering wastewater infrastructure on the islands and has said it has revisited its plans to include secondary treatment. The company warned that there are substantial practical issues to resolve before such treatment can be introduced.
“There are no straightforward solutions,”
SWW added that additional technical assessment is required to consider the challenges of operating on the islands, particularly how any resulting sludge would be transported and disposed of off-island. The firm is also progressing plans to upgrade Bishop and Wolf pumping stations and to install a new rising main to transfer wastewater to a new treatment facility.
Local concerns and next steps
Conservation groups have already expressed alarm. The Isles of Scilly Wildlife Trust described the idea of discharging effluent into a designated Marine Conservation Zone as unacceptable and has called for clear justification if regulators and industry conclude that treatment and shipping sludge off the islands would cause greater environmental harm than sea disposal.
A public consultation is expected within 30 working days of any permit application being lodged, giving residents and stakeholders an opportunity to comment on the proposals. The Environment Agency has said it will continue to work with SWW while seeking a solution that both safeguards the marine environment and delivers essential wastewater services to island communities.
- Current proposal: long-sea outfall with screening
- Regulator’s position: screening-only approach unlikely to meet permit standards
- Company response: reviewing proposals to include secondary treatment, further technical work planned
- Next step: public consultation within 30 working days of application
| Feature | Planned/Proposed work |
|---|---|
| Outfall | New long-sea outfall proposed to discharge screened effluent |
| Pumping stations | Upgrades to Bishop and Wolf pumping stations under consideration |
| Rising main | New rising main to transfer wastewater to a new treatment plant |
For island residents and businesses, the outcome will be important for both environmental quality and the local economy, which relies heavily on clean seas and a healthy marine setting. The regulator’s insistence on appropriate treatment before any coastal discharge sets a clear direction for future planning and means SWW must now show how it will meet those standards amid the logistical constraints of working on the Isles of Scilly.
