Case Study: City of Orange Cove WWTP, California

Retrofit upgrade project confirms energy savings at wastewater treatment plant

The City of Orange Cove is an agricultural community in Fresno County that is located along the eastern foothills of the Sierra Nevada Mountains. Through value engineering and the assistance of incentive money from their utility provider, the WWTP pursued various upgrades; including the addition of one NX75 (75HP) blower to replace their aging and inefficient multistage centrifugal blower. The post installation report administered through the CalPOP program, verified that the aeration system upgrades had an annual savings of approximately $ 53,557.

Project Background
Like many other WWTP’s across the region, the department of Public Works sought to improve their wastewater treatment process, increase reliability with newer equipment, and reduce their monthly energy consumption. The City utilized the assistance of a local and experienced engineering firm to assist with value engineering and the design of the plant upgrades required, which included the retrofit of their existing blowers, upgrading diffusers, and adding dissolved oxygen control. In an effort to reduce capital costs, the City considered retrofitting their existing blowers with VFDs to provide better turndown. However, following a detailed comparison between this option and retrofitting with a high speed turbo blower, the latter proved to be the better investment as it not only optimized energy savings, but also significantly reduced associated maintenance costs.

The City of Orange Cove decided to move forward with the project but had to resolve major challenges. The existing blowers were not able to satisfy the low turndown requirement during the agricultural off season, therefore the new blower had to provide as low as 50% turndown on max flow. Moreover, the location reaches annual temperatures of 105F throughout the summer months, hence having the ability to operate in high temperatures was absolutely critical. Additionally, the turbo blower had to meet strict “Buy American” requirements, as the City had qualified for ARRA grant funding. Lastly, in order to receive the total qualified incentives, they had to have the blower on site within 8 weeks. They solicited for quotes from 3 different vendors but APG-Neuros was the only manufacturer who could meet the deadline, without sacrificing quality of construction and testing before shipment.

Positive Results
Prior to any upgrades, the baseline kWh per month from January 2010-November 2011, was averaged to be 81,876 kWh. The potential electricity savings after the upgrades were promising, and the City was able to secure additional funds through the CalPOP program. Post installation measurement from December 2011-November 2013, demonstrated an average monthly usage at 39,689 kWh. According to the CalPOP report, the APG-Neuros NX75-C050 turbo blower, along with the supplied diffusers, contributed to an annual savings of $ 53,557 a year.
Of all the upgrades implemented, the turbo blower and diffuser retrofit were estimated to have the quickest payback on investment at 6.5 years, as well as highest incentive payout from the utility. The APG-Neuros NX Series turbo blower was approximately 1/3 the aeration project costs, which significantly cuts the payback to approximately 2 years if evaluating the turbo blower alone.
To date, the NX75 blower has operated flawlessly and saved the city over $ 100,000 in electricity costs.
Source: CalPOP Verification Report. City of Orange Cove WWTP.