Variable frequency drives optimize energy savings on the effluent pump motors at the DSRSD wastewater treatment plant.Click here to enlarge imageDSRSD staff evaluated two different types of ultraviolet (UV) lamps for the purpose of disinfecting recycled water. The UV lamp system selected was 50 percent more costly and required more space, but it was 64 percent more efficient than the alternative. This increase in energy efficiency was too compelling to decline. Finally, staff at the DSRSD decided to install premium efficiency pump motors with variable speed drives (VSD) on the recycled water effluent pumps. While the alternative, fixed-speed pumps, were less costly and capable of managing fluctuations in flow rates, the greater energy efficiency of the premium efficiency VSD units enabled the DSRSD to meet their goal of maximum energy efficiency.
Project successes and lessons
DSRSD increased the capacity of their wastewater treatment plant and improved the energy efficiency of the overall plant. They are now able to treat 48 percent more wastewater for the residents of Dublin and San Ramon. The plant’s annual energy use savings were estimated to be 2,232,000 kWh and the annual energy cost savings were estimated to be US$ 290,000. This enabled the DSRSD to earn a total of $67,000 in incentives from PG&E. The new plant cost an additional $2,209,000 more than a less efficient one, yielding a simple payback of 6.6 years.
Author’s Note
Robert Bruce Lung is a senior associate of Resource Dynamics, based in Vienna, Virginia, USA.
Plant description
Wastewater Treatment plants use large amounts of electricity to drive pumping and aeration systems, as well as other crosscutting technologies essential to the treatment process. When a wastewater treatment plant is built or upgraded, proper design and configuration of these systems is essential for optimal performance and energy efficiency.
Variable frequency drives optimize energy savings on the effluent pump motors at the DSRSD wastewater treatment plant.