Can Zero-to-Low Energy windpowered aerators maintain high DO levels for maximum processing rates and positive odour control?
Accomplishing maximum BOD removal processing rates in a facultative biological treatment system is dependent on maintaining positive DO at all times. With positive DO conditions, the aerobic bacteria will perform at their maximum for a given water temperature. Additionally, odours can be 100% buffered/stripped by an oxygen-rich water column.
Gurney Environmental completed the installation of the primarily wind-powered Accel-o-Fac® wastewater treatment system upgrade for South Gippsland Water in Toora, Victoria, Australia in mid 2015. The Accel-o-Fac upgrade was designed to reduce the high operating costs from traditional surface aeration used at the wwtp. After a year of operation, managers of the wwtp have provided the results of typical DO profiles now being accomplished with dramatically reduced energy, and the results are impressive. The high residual DO levels being maintained by the Accel-o-Fac system now allow the original electric aeration to be shut off for much of the time through the use of a DO controller.
If a facultative primary treatment cell has a minimum of 1-2 ppm of residual DO, the aerobic bacteria perform waste removal at maximum rates (based on water temperature), as well as 100% odour removal/buffering. Systems are designed to maintain a typical minimum average of 2 ppm. The Toora Accel-o-Fac® mostly wind-powered system has maintained an average of 12 ppm with zero-to-low energy cost. This surplus DO profile would allow the cell to be loaded at an even higher surface rate without affecting performance.
Since the major provider of DO in a lagoon is photosynthesis, the maximum DO deficit in a facultative primary treatment cell occurs at about dawn. A large amount of DO is consumed overnight but is supplemented by the atmospheric absorption and redistribution provided by the wind-powered aeration units. The Toora Accel-o-Fac® system has been maintaining an average of 4 ppm at dawn with zero-to-low energy cost. This surplus DO profile underscores that the cell could be loaded at an even higher surface rate without affecting performance.
The Customer Is Pleased
According to Brett Vurlow of South Gippsland Water,
"Adding the Accel-o-Fac® system to South Gippsland Water treatment cells where traditional surface aeration was previously used allowed the corporation to significantly reduce energy use. The savings in kWh are excellent with one application saving 72% in energy compared to the previous year."