Advanced Controls Maximizes Energy Efficiency of A Large Effluent Pump Station

Orange County Utilities Department had an aging 40-mgd effluent pump station that needed pumping system replacements at the South Water Reclamation Facility. This included rehabilitating five existing 6,500-gpm vertical turbine pumps, installing a new 1,000 HP motor, replacing the existing variable frequency drives, and replacing the obsolete pump station control system. When this station was commissioned, it was realized that the specified replacement control scheme was too simplistic and advanced controls were required.A better strategy was developed which incorporated the use of a second PID controller to form a cascade control scheme. The equipment changes needed to implement this strategy were minimal because the control system was software based. Although the need to reduce energy consumption was not originally recognized, new advanced controls provided the flexibility to reduce the electrical costs of the station.