Following the pioneering installation of an Aero-Fac treatment system at Errol five years ago, Scottish Water Solutions has ordered a similar 2,500 pe plant for Tobermory on the Isle of Mull.

Following the pioneering installation of an Aero-Fac treatment system at Errol five years ago, Scottish Water Solutions has reaffirmed its faith in the process by ordering a similar 2,500 pe plant to be constructed at Tobermory on the Isle of Mull. The Aero-Fac process is a low energy, low maintenance wastewater treatment system that removes the requirement for sludge handling and disposal. A recent report (Ref1), independently produced by the University of Leeds, and shortly to be published in the CIWEM journal, confirmed that, over a 12 month monitoring period at Errol, 99.99% of the solids entering the system were successfully destroyed by the process.

At Errol, not one sludge tanker has passed through the gates of the plant in the 5 years since its construction, nor is it anticipated one will be needed over the remaining lifetime of the plant.

At Tobermory, Scottish Water Solutions are taking further advantage of this feature to process not just sewage from the local communities, but also septic tank sludge collected from outlying areas.

Up until now, a tanker has had to make frequent trips by ferry to collect septic tank sludge for export back to the mainland, highlighting the unsustainable nature of this means of disposal.

Once the Aero-Fac plant is commissioned, septic tank sludge will be deposited at a collection centre incorporated into the new facility, from where it will be steadily pulsed into the primary treatment cell.

Here the sludge will be digested in an odour-free manner; just as will any solids entering the plant via the main sewer.

Many Water Companies estimate that sludge disposal now accounts for up to 50% of the operating cost of a WwTP, so remove this requirement and add the savings to those of low energy consumption through the use of wind power, couple that with minimal operational complexity and it's not difficult to see why theAero-Fac process is attracting increasing attention.