WPL has developed the SAF, which can cut energy use by 40% and be retrofitted into full-scale sewage works. By altering the specific gravity, using a higher surface area biomedia and undertaking a hydraulic redesign of the SAF, engineers have ensured that the media now moves slowly, removing the need for scouring. This also enables a reduction in process air as oxygen transfer is improved.
This is one of the first steps of a three-year programme to reduce power consumption. The company has been looking at the way the media works inside the tank and the way this can be made more efficient.
Due to the hydraulic redesign and alteration of the specific gravity of the media when coated with biomass, the media sinks to the bottom of the SAF tank, where the process air is introduced. The air cleans off the biomass enabling the media to rise again, carrying sloughed off sludge with it. Trials at Cranfield University suggest that application of the new media, combined with the hydraulic design of the SA, removes the need for regular scouring by preventing sludge build-up in the tank.
