Italy’s Robecco sul Naviglio Water Purification Plant, close to Milan, recently upgraded and renovated its existing facility. As part of the upgrades, it had introduced a new oxygenation process to its sludge processing.
The process pumps oxygen evenly into the waste sludge, which encourages the activation and growth of bacteria. These in turn consume the organic matter during the water purification process before clean water is released back into a river.
However, the amount of oxygen must be varied to suit changing environmental conditions as well as the amount of sludge being processed. This is where variable-frequency drive (VFD) technology improves the efficiency of the process and reduces 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,” said Roberto Giordano, Technical Manager at So.T.Eco SpA, the water technology company appointed for the installation. “It can also create excessive wear on the components used which can cause maintenance costs and expensive downtime.”
“In order to obtain a good regulation and always keep the oxygen concentration as close as possible to optimal levels, it is necessary to avoid switching the pumps on and off,” Giordano said. “By doing this the oxygenation process can be altered precisely depending on the various factors.”
The company worked with Invertek Drives Italia / SP Electric to identify the right drive for the process. It was necessary to have a drive capable of a high torque start-up as well as being easy to set up.
Vincenzo di Giuseppe, Area Manager at Invertek Drives Italia, said: “The Optidrive P2 is perfect for a demanding environment like water purification. It’s a high-performance drive and is more than capable of dealing with a high starting torque. It can handle a 150 percent overload for 60 seconds as standard which makes it perfect for heavy duty applications.”
Eight 3PH Optidrive P2 VFDs were used in the application. They included two 380V, Size 5, 37kW, 72A; two Size 3, 480V, 5.5Kw, 14A; two Size 2, 380V, 4kW, 9.5A; and two Size 3, 380V, 18A, 7.5kW.
The product is available in ingress protection ratings IP20, IP55 and IP66 / NEMA 4X enclosures. A new Size 8 has also been introduced capable of controlling electric motors up to 480A with a power rating up to 250kW / 400HP.
The new range also adds DNV marine certification, in addition to a built-in EMC filter to meet Category C3 with a factory fit option to upgrade to a high-performance EMC filter that meets Category C2. They also come with high-definition thin film transistor (TFT) displays as standard.
