The city of Benicia, California is running its wastewater treatment plant more efficiently – and using almost half the energy it used to – by upgrading their compressor/blower system with help from PG&E and Ecos Air.
Wastewater treatment facilities commonly use low-pressure compressors in aeration tanks to mix and promote the biological oxidation of wastewater. However, the multistage compressors that provide the air required for the process are inefficient, require a great deal of maintenance, and offer poor control, requiring independent cooling.
The wastewater treatment plant was able to upgrade their system significantly by replacing their multistage compressors with centrifugal high-volume, low-pressure compressors. This new system can achieve the required pressure and flow more efficiently than the previous system, while reducing the need for additional cooling.
“Essentially, this project used old technology and re-engineered it to use in a new way,” said Rupert Dallas, Utility Solutions manager. “Its proving ground was this wastewater project, but we see it being used in other applications as well.”
With the new technology, the plant is saving 625,100 kWh and more than 71 kW annually, essentially cutting the energy use of its aeration system in half. The savings work out to roughly $54,000 annually, equivalent to removing 45 cars from Benicia’s roads and 33 residential homes from the city’s electrical grid.
Although the new compressors were substantially more expensive than replacing the multi-stage compressor, the city received an incentive from PG&E to help pay for the system, and with the gains in efficiency, the system will repay its cost in three years, while maintaining energy savings for 10 to 15 years.
