Scottish Water has said an innovative process to treat sewage sludge, while generating green energy, is to be introduced at Seafield Waste Water Treatment Works.

The company's PFI partner, Stirling Water, is investing in a thermal hydrolysis plant (THP) within the works, which treats waste water from Edinburgh and surrounding areas. The new facility will pasteurise the leftover solids from the waste water treatment before being processed further in the six existing anaerobic sludge digesters.

Heat breaks the sludge down, making it easier to digest by natural bacterial action. This helps to generate more biogas which, in turn, is used to generate renewable electricity on site.


The final processed sludge is also then suitable for onward use as a fertiliser.

As a result, around 30% less sludge will need to be transported from Seafield after treatment, meaning a reduction in traffic in and out of the site.

Bill Elliot, Scottish Water's Regional Community Manager for Edinburgh, said: "This is a safe and cost-effective way to dispose of leftover sludge from sewage treatment at Seafield. It produces sludge which is suitable for use as a fertiliser and means less solid matter is left over, resulting in fewer lorry movements in and out of the site.

"It has the added advantage of helping the Seafield site become increasingly energy self-sufficient, as we are able to use the biogas generated to help power the waste water treatment plant, helping to reduce the carbon footprint of the site.

"It is an environmentally-friendly process which will help lower the overall odour potential of the sludge processing stream."

(JP/CD)