Case Study: South San Francisco / San Bruno Water Quality Control Plant (WQCP)

Replacing existing multi-stage centrifugal with APG-Neuros’ Turbo Blower results in an efficiency gain of 22.7%

The Water Quality Control Plant (WQCP) replaced one of its centrifugal blowers with a new APG-Neuros turbo blower. The new turbo blower supplies the majority of aeration for one of the trains in the two parallel trains of activated sludge treatment process. With the use of a single high-speed centrifugal impeller, the new blower technology offers significant energy savings and a wider flow turndown.

Project Background
The WQCP uses primarily settling treatment followed by an aerated-activated sludge process for removal of organics and other constituents from the wastewater. The activated sludge process has two parallel trains of activated sludge treatment. Each train has multiple aeration tanks and multiple air blowers to furnish air for the treatment process. As wastewater flow rate and strength vary throughout each day, an average of 8.6 million gallons, the aeration air to the basins varied to meet process demands. Each day, the air flow varies from as little as 35 percent to 100 perfect of the maximum flow measured during testing. The activated sludge process is the single largest consumer of electrical power energy in the treatment plant. Newer technologies such as the APG-Neuros high-speed turbo blowers, have since been commercialized and are significantly more energy efficient than the existing blowers.

Project Development
The WQCP facility audit examined the plant electrical energy consumption to find ideas to reduce plant energy use while meeting the process demand. Based on discussions with plant staff and a brief review of the process, it was decided to focus the effort on reducing the electrical energy required to provide aeration air to the secondary activated sludge process. The aeration air blowers were the largest consumers of electrical power in the plant and the existing blowers were significantly less efficient than blowers that have come to the marketplace in the last five years. The project replaced one 300 HP blower with the APG-Neuros NX300M-C070 for Aeration Basins 5 to 7. The WQCP will add another 300 HP blower to replace existing blowers in Aeration Basins 8 and 9. To achieve the largest power reduction required, the new APG-Neuros NX300M-C070 blower operates in a permanent lead position.

The California Wastewater Process Optimization Program (CalPOP) and the WQCP confirmed that the replacement of first blower with the APG-Neuros NX300M-C070 saved the city $55,673 reducing power consumption by 448,525 kilowatt-hours (kWh) per year. The project implementation cost is $302,343 with the CalPOP incentive rebate for the upgrade totaling $45,487 the net cost is $256,856 representing four (4) years payback. The City of South Francisco and WQCP is now looking to replace an existing blower with a new second high speed turbo blower.