Oil-free screw blowers increase sewage plant efficiency

Two Atlas Copco ZS 55+ oil-free screw blowers with variable speed drive (VSD) are supplying energy-efficient compressed air to process sewage at a treatment plant in Versmold, Germany. As a result, the plant has achieved energy savings of 10%, which means lower sewage fees for customers.

The plant cleans around 3 million m³ of sewage water every year, 60% of which is industrial sewage water. The plant has a high proportion of industrial customers from the meat processing industry, which generates varying rates of high polluting loads and above-average quantities of phosphate. The cleaning technology, measuring technology, process control system and compressed air technology must be able to quickly detect the pollution level of the sewage water and respond accordingly.

Nitrification and denitrification take place simultaneously in two aeration tanks, each of which is supplied with oxygen via blowers. The control function is taken over in each case by an Atlas Copco ZS 55+ VSD oil-free screw blower with VSD. The two machines, working together with two blowers from another manufacturer, supply compressed air between 1500 and 3500 m³/h with a target excess pressure of 500-600 mbar. The volume flow is automatically adjusted to the exact air demand by the VSD.

“The blowers from Atlas Copco are compact and it is not necessary to make many modifications,” said plant manager Khosrow Ghobadi. “The machine is simply linked to the process control system, which we did easily without any problems.”

Initially, said Ghobadi, only one of the two tanks was equipped with a ZS+ blower in order to test the increased efficiency. He noted, “At the end of the test run, we were actually able to determine that the blower from Atlas Copco was 10% more efficient than our other machines.”

In light of this, the second screw blower was purchased. Ghobadi said, “The two machines have run smoothly for the past two years. The only thing that we need to do is routine maintenance work.”