Inside the screw pump lifting station, pumps lift the wastewater by 5.5 m from sewer level to plant level so it can flow through the downstream mechanical cleaning stages and the first biological cleaning stage only by gravity. Six screw pumps are in operation to transport 18,000 litres of wastewater per second during stormwater events. If less wastewater flows in, the number of operating screw pumps can be reduced. Up to 680,000 m³ of wastewater are transported by the pumps within 24 hours during low flow. In case of heavy rainfalls, this volume may rise up to 1,500,000 m³ daily.