Operational Improvement of Main Pumps for Energy-Saving in Wastewater Treatment Plants

Efforts towards energy independence in wastewater treatment plants (WWTPs) constitute important policy in Japan. Energy-saving strategies consist of operational improvements and the installation of energy-saving devices. The energy consumed by the main pumps is equal to approximately 14% of the energy consumed by WWTPs in average in Japan. The main pumps, which are simple machines, do not have the innovative, energy-saving devices associated with other equipment used in WWTPs; therefore, realizing energy savings through operational improvement is extremely important. In recent years, variable frequency drives (VFDs) have increasingly been used to control the rotation speed of main pumps in order to save energy. However, there are many cases where power consumption increases due to the excessive rotation speed control ignoring pump characteristics. In this study, improvement of the operating method based on the power consumption analysis is examined for A WWTP. Differences in characteristics between water pumps and wastewater pumps are discussed, and simulation results without rotational speed control show a reduction in power consumption of 10%. Daily operational report data of the WWTP are used for the power consumption analysis, and additional data acquisition is not necessary. Thus, the power consumption analysis method used in this study can be easily applied to other WWTPs.