Massive energy saving at wastewater treatment plant

Water technology company Xylem Inc. claims has reduced the energy consumption of a wastewater treatment plant in Italy by 65%.

According to a comparison study conducted by Comopedur which operates the plant, Xylem’s Flygt 4530 submersible mixers have saved €50,000 in annual operational costs at the facility.

Located in the scenic Lake Como region of northern Italy, the plant treats 16 million metres3 of wastewater annually, serving a population of approximately 200,000. Treated water from the plant is expelled back into Lake Como. This, in addition to the fact that the plant is located in a heavily populated area of the city that is challenging to access with heavy machinery.

Comodepur commissioned Xylem to ascertain if operation costs could be reduced at the plant. Five mixers had been in operation for ten years in the pre-denitrification tank which, due to the particular shape of the 5,800 cubic metres tank, required a high level of energy to operate. This relatively large number of mixers was necessary due to the particular shape of the tank; ‘dead spots’, as well as the tank depth and irregular slopes made consistent mixing very challenging. The five mixers had delivered consistent and reliable mixing at the plant throughout the past decade.

However, having examined the operation using simulation software, Xylem advised that the existing mixers be replaced with the new, mid-size energy efficient Flygt 4530 model. A submersible mixer featuring a propeller of 1.2 m in diameter, the Flygt 4530 is specifically designed for biological wastewater treatment applications.

According to Luigi Cece, Director of the Comodepur plant, “The new Flygt mixers have reduced annual operation costs at the plant by €50,000 and they paid for themselves within just 13 months.”

The new mixers consume 175,000 kWh of energy annually, a 65% reduction on the 500,000 kWh the old mixers required to operate.

Due to the very positive energy and cost savings Comodepur has ordered an additional three Flygt 4530 mixers to replace mixers in another equalisation tank that they operate.