Waste Water Treatment Plant Saves 31 % Energy with new Blower

The Danish waste water industry have been set a savings goal of 25% to reduce costs. This has meant optimisation in all areas is of the highest importance. Skanderborg, Denmark's waste water treatment plant is no different and has recently replaced their 75 kW lobe blowers with new 55 kW Atlas Copco ZS screw blower resulting in an energy reduction of 31%.

70% of energy consumption in a waste water treatment plant (WWTP) can come from low pressure aeration of the waste water making the aeration highly important. Atlas Copco’s ZS screw blowers are on average 30 % more energy efficient than lobe blowers. This has been proven by independent tests by TÜV and by WWTP’s in Scandinavia.

“Skanderborg WWTP had problems with their aeration using lobe blowers so we suggested that they should try the Atlas Copco ZS blow¬ers”, says Flemming Broksø, Sales Engineer at Atlas Copco Compressor Technique Scandinavia.

“We chose Atlas Copco as supplier of our new blower as they showed us possible energy savings of 30 % compared to our old lobe blower.” says Ivan Andersen at Skanderborg WWTP.

In August every year Denmark celebrates their traditional summer festival; Skanderborg. During this festival WWTP's workload is at its highest. It was during this festival a test was carried out to compare the energy consumption of two identical process lines. Both lines were equipped with two blowers each – one variable speed drive and one fixed speed. The operations are set up so that the variable speed drive blowers function as the primary blowers and the fixed speed blowers come in when the demand for low pressure air increases.

Line 1: 1 x 75 kW lobe blower, variable speed drive, 1 x 75/62 kW (dual speed) lobe blower, fixed speed
Line 2: 1 x Atlas Copco ZS55VSD-700 screw blower, variable speed drive, 1 x 75/62 kW (dual speed) lobe blower, fixed speed

The result:
Line 1: Total energy consumption: 19 989 kWh.
Line 2: Total energy consumption: 14 492 kWh
The figures show a total saving of energy for Line 2 – including the Atlas Copco ZS screw blower – at 31 %.

“The Atlas Copco ZS screw blower is working really well, better than expected. It runs smooth and has, besides replacing a bigger lobe blower, lowered the amount of time that the fixed speed lobe blower has to support the VSD blower in its aeration process line”, Ivan Andersen says.

“This has given us big energy sav¬ings and we are calculating a pay¬back time of the ZS blower as low as only 16 months. We also made it through the Skanderborg Summer Festival without any downtime, and it runs much more silent than the old lobe blower”, he concludes