Errol Scotland WWTP

For the Errol project, siting the project did not require consideration of access roads for sludge lorries due to the uniqueness of the Aero-Fac® system.

Client: Scottish Water
Date: Tuesday, 14 August 2001
Info: Remote mostly automated WWTP for small village

Errol city

Visitors to the Errol plant are typically amazed by the lack of odour. Many remark that it is hard to believe that they are at a sewage treatment plant.

The Aero-Fac® treatment system incorporates a number of highly unique features, not least of which is the self digesting sludge process that requires no pre-screening, sedimentation tanks or clarifiers, no sludge removal, dewatering or conditioning, and best of all, no routine sludge disposal and the associated lorry traffic in and out of the works. All sludge is continuously self-digested within the initial treatment stage.

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North of Scotland Water (NoSWA), the Scottish water agency at the time of construction, had implemented a fast, innovative and economic solution for treating the wastewater from the community of Errol on the scenic Tay estuary near Dundee, Scotland. The innovative Aero-Fac® approach provided cost and environmental benefits that came to have implications for wide application across the rest of the UK. 

An analysis of various options demonstrated a remarkable cost advantage for the Aero-Fac® option in both immediate CAPEX as well as ongoing OPEX.

Following construction and commissioning of the new wwtp, the effluent from Errol routinely met rigid European requirements. Most importantly, it did so without the production of sludges requiring costly handling and highly-regulated disposal.

By adopting a highly sustainable system with a completely biological process, very little in the way of mechanical equipment, operational manpower or energy  has been needed for routine operation of the plant, thereby meeting the then needs of NoSWA in providing affordable public services. The well-proven technology provided reliable process control to achieve quality of effluent with low capital and exceptional flexibility.

An independant long term study of the Aero-Fac® plant at Errol commissioned by Scottish Water and carried out by the University of Leeds, confirmed the performance of the system. In the final report, particular mention was given to the plant's class-leading disinfection performance together with its ability to destroy 99.99% of the solids entering the system.

Errol is a good example of just how good a neighbour an Aero-Fac® plant can be! No odours. No sludge lorries. No noisy mechanical equipment. The Errol wwtp routinely processes the community's wastewater with little operator attention and is an attractive facility that fits within its sensitive environment.


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Errol filled  Errol difuser construct


UPDATE: Errol Celebrates 20th Anniversary

20-years is often referred to as the expected lifetime of a mechanical WwTP, yet after 20 years the Errol Aero-Fac® wastewater treatment plant continues to perform with incredibly low ongoing OPEX, no sludge, no odours and little in manpower and energy.

In 2001, Gurney Environmental along with project partners Montgomery-Watson (now Stantech) and then North of Scotland Water christened the very first Aero-Fac® WwTP in the UK (Click Here to see full Case Study). The idea? Provide consistent effluent quality for the sensitive Tayside estuary area, eliminate bothersome sludge lorry movements, accommodate both long-term growth and peak load/flow swings spanning 20+ years, whilst requiring minimal manpower and energy. Plus install a treatment works that would not create any odour issues for the area.

Errol, Scotland Aero-Fac® WwTP in 2021

2021 celebrates 20 years of successful operation for the Errol facility. According to Robert Dey of Scottish Water, "The [Aero-Fac®] system offered high process performance, but with low OPEX costs compared to a traditional plant, both in terms of operator attendance, maintenance and power usage, and in the fact the plant only needed sludge removal at intervals of several decades.

"In the 20 years since the plant was brought into service, it has indeed had both low maintenance costs, and low operator input. At the last testing it has been found to have very low sludge build up and at this anniversary of its commissioning, there has had to be no consideration of emptying to remove sludge build-up. We have never had any odour complaints at Errol.

"In tandem, it has given consistent performance with a 100% record in terms of compliance with consent conditions. Another important element of the Aero-Fac® system was low energy costs and with the wind-driven SERIES 3 aerators augmenting the mains-powered blowers, it has reduced the potential energy costs. Although it was not such a high consideration 20 years ago, Errol also supports Scottish Water’s moves to becoming carbon neutral."

Dey went on to say, "The Aero-Fac® system also uses much less concrete than traditional forms of construction, with much of the material dug out to form the two ponds being re-used to form their wall structure. The aforementioned reduction in OPEX costs and the renewable energy element means that in both CAPEX and OPEX terms, the Aero-Fac® system accords with Scottish Water’s carbon-neutral vision.

"Gurney-Environmental have since installed two further Aero-Fac® systems for Scottish Water and are currently in discussions re a number of projects at design stage."



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news Kruger Park sat

Scottish Water Recognizes Errol Aero-Fac® For 20 Years of Performance

Scottish Water recently featured the Errol WwTP project on their website, recognising two decades of low carbon operation.

CLICK HERE to learn about our various low-energy wastewater treatment systems and options.