January 2022

35 www.drivesncontrols.com January 2022 VARIABLE-SPEED DRIVES n Drive upgrade cuts energy and costs at water purifying plant A n oxygenation process introduced at a water purification plant near Milan, Italy, pumps oxygen into the waste sludge, encouraging the activation and growth of bacteria. These consume the organic matter, allowing clean water to be released into a nearby river. The amount of oxygen has to be varied to suit changing environmental conditions, as well as the amount of sludge being processed. The water technology, design and management company So.T.Eco, which was appointed to upgrade and renovate the Robecco sul Naviglio plant, turned to VSDs to improve the efficiency of the process and to cut energy and maintenance costs. “In biological purification plants it is important to regulate the supply of oxygen adequately as insufficient oxygenation impairs the result of purification while excessive oxygenation results in considerable energy costs for pumps or other ventilation devices,” explains Roberto Giordano, the company’s technical manager. “It can also create excessive wear on the components used, which can cause maintenance costs and expensive downtime.” Using VSDs means that the pump speed can be controlled accurately to suit the conditions, and to ensure an even spread throughout the activated sludge process. “To obtain a good regulation and keep the oxygen concentration as close as possible to optimal levels, it is necessary to avoid switching the pumps on and off,” Giordano continues. “Instead, a variable-flow device was needed and we opted for the Optidrive P2 from Invertek Drives due to its accurate control functions, ease of set-up and use, and, importantly, its durability. By doing this the oxygenation process can be altered precisely depending on the various factors.” So.T.Eco worked with Invertek Drives Italia and SP Electric to identify the right drive for the process. It had to be capable of a high torque start-up as well as being easy to set up. They chose eight 3PH Optidrive P2 for the application, with ratings from 4kW (380V, 9.5A) to 37kW (380V, 72A). Vincenzo di Giuseppe, Invertek Drives Italia’s area manager, says that these drives are ideal for demanding environments such as water purification. They can handle 150% overloads for 60 seconds as standard, he points out, which makes them“perfect for heavy-duty applications”. n Significant energy and cost savings are being made at a water purification plant in Italy following the introduction of VSDs. The drives cabinet at the water purification facility