Seafield Waste Water Treatment Works

Seafield Waste Water Treatment Works

Seafield Waste Water Treatment Works is Scotland’s largest waste water treatment facility, processing 265 million litres of waste water daily – that’s the equivalent of 120 Olympic-sized swimming pools.

Located on the Firth of Forth to the north of Edinburgh, the facility serves the equivalent of nearly 850,000 people in the capital and the wider Lothians.

Operation

Seafield plays a crucial role in maintaining public health and protecting the environment by treating waste water before it is safely released back into the water environment.

The facility has undergone significant investment in recent years - £34million since 2011 – and is one of the most modern and environmentally-friendly sites of its kind.

Seafield also uses biogas captured during the treatment process to generate green energy, up to 2300 kilowatts of sustainable electricity, enough to make the site self-sufficient, even exporting electricity back to the grid during peak performance.

Ownership

Seafield is financed, designed, built, owned, operated, and maintained by Stirling Water Ltd under the Almond Valley Seafield and Esk (AVSE) Private Finance Initiative (PFI).

Stirling Water subcontracts the operation and maintenance to Veolia Water Outsourcing Ltd (VWOL).

Scottish Water oversees the facility and collaborates with Veolia to ensure optimal performance and compliance with environmental standards at all times.

Update - October 2025

Seafield Sludge Investment Project (SSIP)

The £10 million investment announced in 2020 as part of our response to the Strategic Odour Review remains a key commitment to customers and is continuing to progress. 

Although it may not always be apparent, the outline and detailed design stages are crucial elements that involve a lot of planning and engineering to develop a scope that can go out to competitive tendering.

As advised through the Seafield Stakeholder Group forum, the Seafield Sludge Investment Project (SSIP) has been reviewed in response to market conditions to ensure it both meets the recommendation of the Strategic Odour Review to provide additional sludge storage capacity, and that it is deliverable.

There is some further work to do to procure the works before construction timelines can be confirmed. 

The project will meet the recommendations of the Strategic Odour Review, and any cost inflation will not affect this commitment. We will be posting a further update here before the end of the year.

Continued Operational Improvements Since 2020 

While the SSIP capital investment has taken longer than anticipated, a range of operational improvements have been implemented at Seafield WWTW to reduce odour risk and improve community confidence. These include: 

• Specialist chemical treatments designed to prevent and reduce odour emissions, deployed strategically during periods of elevated risk, which represent a significant ongoing investment in odour control
• Proactive and more efficient storm tank cleaning, scheduled during favorable weather conditions and supported by detailed odour risk assessments
• Improved maintenance planning, with high-risk tasks such as primary settlement tank cleaning and grit removal tank cleaning now scheduled outside the summer months wherever possible
• Reduction in odour incidents, supported by performance data showing improved compliance and fewer complaints relative to historical baselines
• Direct stakeholder communications, including regular updates to elected members and community representatives
• Annual Doors Open Day events, which provide local residents and environmental groups with access to the site and an opportunity to engage directly with operational staff

Long-Term Strategy for Seafield WWTW 

We anticipate Seafield WWTW will reach capacity in the 2030s and are planning for significant upgrades to meet future demand.

Investment proposals are being developed for submission to the Water Industry Commissioner for Scotland (WICS) as part of the Strategic Review of Charges (known as SR27) process.

A draft Business Plan has been submitted and feedback from WICS, the Scottish Government, and stakeholders will inform the final plan.

We expect WICS to issue its Final Determination in October 2026, confirming expected outcomes and customer charges for the 2027–2033 period.

The SR27 process aims to identify necessary investments to maintain service levels, including a strategic plan for Edinburgh and upgrades at Seafield to ensure sufficient wastewater treatment capacity.

Subject to the Final Determination, detailed planning for Edinburgh will begin, including system analysis, stakeholder engagement, and environmental assessments.

Future investments at Seafield will align with long-term service ambitions, regulatory expectations, and the evolving needs of Edinburgh and the Lothians.

We are committed to keeping stakeholders and customers informed and engaging meaningfully as options are developed and appraised during the SR27 investment period.

Odours

A multi-million-pound Odour Improvement Plan was completed in 2012, and the facility is now continually monitored for any potential odour issues.

To ensure any odour issues are logged, tracked, and responded to appropriately, we strongly encourage residents to report through our official channels:

• Scottish Water’s 24-hour Customer Helpline: 0800 0778 778, and
• The Scottish Water online reporting portal: Scottish Water Online Portal

Following this process will ensure that complaints are captured in real time and routed to the appropriate operational teams for investigation and resolution.