When a wastewater treatment plant near Florence, Italy, needed to replace a set of mixers, it consulted Xylem’s experts to find the optimal mixing solution. The Publiacqua treatment plant selected the new low-speed, high-efficiency Flygt 4530 mixers, which can reduce energy consumption by up to 50%.
The Publiacqua water treatment plant, located in San Colombano, handles wastewater for more than 600,000 people. Serving the city of Florence and eight regional municipalities, the plant plays a crucial role in removing pollutants from wastewater and ensuring effluent concentrations remain within defined limits.
The plant, which treats more than 65 million cubic meters of wastewater every year, has three lots of 24 sludge tanks. Each tank requires a submersible mixer to keep activated sludge in suspension. The mixers are crucial in reducing deposits that slowly diminish process efficiency, and in reducing the number of times the tanks need to be cleaned.
When Publiacqua identified that one lot of tanks required new mixers, they compared and tested different brands and models in the sludge tanks, including the Flygt 4530 mixer from Xylem.
Efficient mixing with a lower speed and larger propeller
Xylem’s approach to mixer projects is to assist customers in evaluating their tank geometry, liquid characteristics, installation restrictions and mixing duty in order to find the correct mixer for the application.
“The technical support and relationship with Xylem have been very good,” says Simone Caffaz, Process Engineer and Wastewater Treatment Plant Manager at San Colombano. “Publiacqua is also interested in all new technologies, such as the Flygt 4530 mixer.”
The Flygt 4530 was the clear winner in operational efficiency in all 24 tanks tested, thanks to its larger propeller and lower speed of rotation. The mixer is a recent addition to the Flygt range of innovative mixers and agitators. It is designed to operate in small and medium-sized tanks in activated sludge processes, and in sludge holding tanks and digesters where there is adequate depth for a larger propeller.
