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Energy, the Environment & Water 34 Focus on: Water & Waste Management | Plant &Works Engineering | Annual Buyers’ Guide 2019 Replacing unreliable belt drive systems with gear motors and variable speed drives has enhanced control and reduced breakdowns at a German sewage treatment plant. PWE reports. T he residents of Ensdorf in Western Germany probably give little thought to their local sewage treatment works. Many won’t even know where it is since the facility, opened in 1995, has been carefully designed to blend into the landscape. Yet Ensdorf sewage treatment plant plays a vital role in the social, economic and ecological fabric of the German municipality. Situated on the right bank of the River Saar, close the borders of France and Luxemburg, the sewage treatment plant processes the waste water generated by the region’s 50,000 or so inhabitants, together with effluent generated by several local industries. Like all modern sewage treatment facilities, the Ensdorf plant relies on a combination of, mechanical and biological processes to remove dissolved contaminants and solid materials from the incoming effluent. Its job is to ensure that water leaving the facility meets strict cleanliness rules, allowing it to be safely discharged into the Saar, and that the remaining solids are also transformed into a condition suitable for safe disposal, typically as agricultural soil enhancers. That’s a delicate balancing act. The inflow rate to the plant can vary significantly, from 26,000 m3 per day in dry weather to 57,888 m3 per day during periods of heavy rain. The volumes of contaminants and solid wastes processed by the facility similarly vary over time. To keep the plant’s processes running properly, the plant’s staff must adjust the operating speeds of equipment across the facility as demand rises and falls. Originally, speed control in some of the plant’s important equipment was achieved via mechanical means. As part of the sludge dewatering process, the pumps that supply sludge to the two centrifuges were powered Sewage works saves energy and improves reliability by 7.5 kW asynchronous geared motors with belt drive adjustment. Additional pumps used a similar system with 4 kW motors to transport the thickened sludge away from the centrifuges and on to the next process. While the belt drive approach did enable the necessary speed control, the system proved unreliable in operation. Adjusting the belts frequently was inconvenient for operators, and breakages were common, leading to downtime and disruption. In search of a better approach, the plant’s managers contacted drive technology specialists, Klebs + Hartmann GmbH, who proposed a solution that not only resolved the reliability issues, but also promised useful energy savings. Klebs + Hartmann is a Bauer Gear Motor Gear Centre which offers its customers engineered solutions for improved performance. In this case Matthias Klee, project engineer Drive Technology, and Peter Siepel, project engineer Inverter After successful testing in one of the centrifuges, Ensdorf has now installed Bauer motors in all four locations. The introduction of variable speed drives eliminated the need for belts and allowed the automation of speed control.