Energy Assessment :: Case Study
Eastside Utility District, Chattanooga, Tennessee
An energy assessment was conducted at the Eastside Utility District facility in Chattanooga in December 2005. The treatment plant was once operated by the Department of Defense, producing over 30 million gallons per day (MGD). Eastside Utility currently produces around 8 to 12 MGD using much of the original equipment and piping. This assessment identified potential energy savings of over $30,000 per year when the entire system is optimized.
Much of the savings at the Eastside facility identified in PSAT analyses can be achieved by equipment upgrades and operational changes that reduce power consumption. Significant savings through reduced demand charges due to coincidental operation of finished water pumps were identified. The results of PSAT analyses of two 350 hp and two 150 hp raw water pumps at the Eastside plant also identified potential energy savings. Adjustment of the lift settings on the two smaller pumps significantly improved their performance and reduced vibration.
In addition to the PSAT analyses, data were collected in the field to verify SCADA flow and pressure readings at various flow rates for raw and finished water pumps. Performance curves were developed and compared to pump curves provided by the manufacturer to determine if pumps were operating at their BEP. The large finished water pumps were operating at high flow rates at the end of their pump curves, constraining them to an operating efficiency 15 to 20 percent below the BEP . Installing variable frequency drives for two of the finished water pumps would provide a broad range in flow at significantly reduced energy costs. Costs for the drives can be recovered in less than three years from energy savings.
