Seafield Waste Water Treatment Works

Seafield WwTW

Update 6th July

The cleaning of the Primary Settlement Tank 8 was successfully completed by Saturday 4th July.

Update 1st July:

This is a further update to the recent communication issued regarding the draining and cleaning of Primary Settlement Tank 8 (PST8).  A review of weather conditions was undertaken today and the conditions are forecast as favourable from Thursday evening through to Saturday 4 July. Therefore, Veolia will start to drain the tank on Thursday morning and cleaning will take place on Thursday evening when there is an offshore wind. The work is expected to be completed on Saturday evening.  

Veolia had planned to carry out the draining of the tank from Wednesday evening, however, they have moved this back to Thursday morning to recognise the changing wind conditions and reduce the potential odour impacts on the community during this phase.  As further mitigation, chemical treatment and odour neutralisers will be used as required for the duration of the task. 

It is vital that this planned maintenance work is completed to ensure that the remaining contents in PST8 are removed as soon as possible. 

Both SEPA and the City of Edinburgh Council have been made aware. 

We will issue a further update once Veolia has completed the work.


Update 25th June:

As part of planned maintenance, Seafield WWTW operators Veolia began cleaning primary Settlement Tank 8 (PST8), on Monday 22/06/2020. This tank was already out of service. This is standard procedure during the summer months to minimise the risk of odour, as PST8 is the closest tank to the boundary with the community. Cleaning had been planned for this week due to the favourable weather conditions forecast and to avoid the tank contents turning more odorous. 
However, Veolia is aware that the wind direction became variable on Wednesday 24/06/2020, which caused odour in the community and would like to apologise for the annoyance and inconvenience caused.

As the wind today remains onshore, a decision has been taken to pause this tank clean until weather conditions are more favourable, with work likely to commence on Monday 29/08/2020, as the forecast currently suggests offshore winds all week. In order to mitigate the odour risk, PST8 is currently being filled with treated effluent to cover the remaining contents in the tank. 

Scottish Water will work with Veolia to review the task planning processes in order to prevent a recurrence with this type of maintenance work. 

Seafield is Scotland’s largest waste water treatment works (WWTW) which processes 300 million litres of waste water every day – enough to fill 121 Olympic-sized swimming pools.

The site is a hugely important part of Scotland’s infrastructure and is critical to keeping the cycle flowing in Edinburgh and the wider Lothians serving almost one million people.

Since 2011 Scottish Water and Veolia have invested £34 million into Seafield, installing new equipment to improve odour as well as a thermal hydrolysis plant which treats and pasteurises the raw sewage, generating biogas energy which provides 85% of Seafield’s electricity.

The sewage is then turned into sludge cake and sold to farmers as organic fertiliser. This process makes it one of the greenest waste water treatment plants in the UK.

The site is one of the most modern and environmentally-friendly of its kind using a Combined Heat and Power plant and Thermal Hydrolysis to generate electricity and treat the waste for agricultural use. Over the last four decades it has been transformed from a much smaller site - which treated and separated waste water from untreated sewage disposed of in the Forth via the MV Gardyloo ship.

The plant is capable of producing up to 2300 kilowatts of sustainable electricity - enough to power up to 600 homes. This is produced by gas powered generators which use the gas produced in the 6 digesters on site to generate this ‘green’ power.

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

The works has a strict monitoring regime overseen by a number of environmental regulators. Local community groups and politicians attend regular stakeholder meetings with staff from Scottish Water and Veolia where they are updated on developments at the site. 

Click here for all stakeholder updates and related documents

Seafield Green Energy Video

Watch this video to see how we are making Seafield waste water treatment works in Edinburgh greener and more self-sufficient.