The central sewage treatment plant in Kulmbach Germany upgraded its inlet lifting pump station for enhanced energy efficiency and optimal operation. Replacing the older variable speed drive (VSD) with an ABB ACQ580 water and wastewater drive, paired with an ABB IE5 synchronous reluctance (SynRM) motor, promises significant energy savings.
Located in the heart of upper Franconia, the town of Kulmbach operates a municipal wastewater utility servicing 8,000 households. Back in 2022, the total volume of wastewater amounted to around 11.6 million cubic meters. The city's central sewage treatment plant has the capacity to handle wastewater for a population of 270,000 persons. The inlet lift pump station at the Kulmbach central sewage treatment plant is the end station of the local sewer network. It is also the first station of the sewage treatment plant. Here, the incoming wastewater is elevated up to around six meters with the aid of two alternately operating Archimedes screws. The wastewater then passes through all treatment stages using gravity.
New IE5 SynRM motor
In the event of a high inflow of mixed water after e.g. a heavy rainfall, a maximum of 1,400 liters of wastewater per second can be pumped using both Archimedes screw pumps. Since the fall o2022, one of the two pumps has been driven by an ABB IE5 Ultra-premium energy efficient SynRM motor. Enrico Porzelt, who is the responsible electrician for the wastewater disposal division at Stadtwerke Kulmbach, explains how the replacement in the utility came about: "The old variable speed drive from another manufacturer that controlled the pump motor, had been tripping sporadically at full load. We decided to replace the entire drivetrain.”
Energy efficiency and cost-effectiveness of ABB IE5 SynRM motors were decisive factors. According to Enrico Porzelt " With energy costs on the rise and resources growing scarcer, it's crucial to safeguard the public and municipal interests in wastewater disposal. For Stadtwerke Kulmbach, energy efficiency and cost-effectiveness are of essential importance. Whether it's designing new buildings or renovating systems, our priority always concern sustainable and energy-efficient solutions".
Good experience with ABB
Another factor that led Enrico Porzelt to choose ABB was their advanced drive technology. During the recent pandemic, ABB’s industry manager and ABB channel partner Max Lamb were able to support Porzelt in a timely manner concerning an incident at a sewage pumping station. Two of the variable speed drives from a third-party manufacturer broke down within a week for dry-installed wastewater pumps. While the third-party manufacturer had a delivery time of over six months, ABB was able to deliver and commission two ACQ580 variable speed drives in a very short time.
The ACQ580 drive has embedded functions for water and wastewater applications, which together with the intuitive control panel, simplify commissioning, set-up and motor control. It replaced the pump's old variable speed drive, which was still equipped with a passive filter. The 90-kilowatt IE5 SynRM motor replaced the old, less efficient asynchronous motor. In addition to high energy efficiency, this motor is characterized by its higher reliability and lower maintenance requirements. "The fact that we now get the variable speed drive and motor from a single supplier makes it easier for us to design the system that simplifies project planning," explains Enrico Porzelt.
The ACQ580 water and wastewater drive regulates the speed of the motor within a speed range of 15 to 50 Hertz. This corresponds to a pump capacity of zero to 100 percent. The amount of wastewater to be pumped depends on the level of wastewater in the upstream basin of the screw pumps. If the water level in the feed shaft rises, the speed increases. If the water level drops, the speed is reduced. If the maximum speed is reached and the level continues to rise, the second Archimedes screw is switched on.
Continuous operation offers savings potential
The Archimedes screw pumps are switched on during alternating weeks so that the load and operating hours are roughly the same. "The Archimedes screw pumps run around the clock and are only switched off for maintenance. With the ABB motor-drive package, we expect an energy saving potential that results in lower energy consumption," says Enrico Porzelt.
Significant energy savings are expected
"As the energy measurement of the inlet screws and the inlet pumps are carried out on the same line, the real energy savings from the new ABB motor-drive solution cannot yet be conclusively determined. However, we expect energy savings to be around from 7 to 10 percent," says Enrico Porzelt. The information is attained from the assessment of evaluated operating data and the engine data provided by the ACQ580.
The motor monitoring function in the drive is utilized to surveil the temperature of the windings. Additionally, the availability of a second control circuit for on-site manual operation, allowing for zero to 100 percent setpoint specification via a potentiometer, is appreciated. Another advantage is the straightforward operation of the ACQ580 water and wastewater drive that is easy to use.
The motor-drive train for the second Archimedes pump is scheduled for an upgrade during 2024. An ABB package consisting of an IE5 SynRM motor and an ACQ580 drive for water and wastewater is already waiting to be installed at the central sewage treatment plant in Kulmbach.
