Technology, Low Pressure Blowers

Wastewater Treatment: Rotary Lobe Blowers vs. Rotary Screw Blowers


Have you ever wondered what happens to wastewater after it’s disposed? It doesn’t immediately empty into landfills or run off into large bodies of water. In fact, it first enters the sewer system and then goes on to be treated at a wastewater treatment plant. These facilities operate 24/7 to clean wastewater for discharge or reuse.

Upon entering the treatment facility, the wastewater is introduced to millions of bacteria in the aeration tank. The bacteria feed on the organic waste and break down the wastewater into harmless byproducts of carbon dioxide, nitrogen and water. Because the bacteria need oxygen to survive, large quantities of compressed air are blown into the aeration tanks to speed up the activated sludge process. 

Two types of positive displacement blowers

Positive displacement blowers operate with flow and pressure as independent variables. When working at a constant speed, if pressure increases, the flow rate remains largely unaffected. 

  1. Roots, Lobe-Style Blower – The conventional blower uses two or three lobed rotors that rotate within an oval-shaped casing to draw air into the chamber and force it out the opposite side. When the rotor lobes uncover the exit port, it allows some air flow to move back into the casing, resulting in pressure pulsations. 
  1. Oil-Free Rotary Screw Blower – The rotary screw blower pairs male and female rotors that rotate and decrease the available volume between them, causing the air to compress. At the beginning of the compression cycle, the inlet air fills the flute space and becomes trapped. The air is then continually compressed as the male and female rotors mesh with each revolution until the air is pushed through the discharged outlet.

What’s the better blower option for wastewater treatment?

Laboratory testing was conducted to compare the two blower technologies in the same environment, under equal operating conditions. The energy consumed by each machine was measured at the power source along with flow levels at each machine’s respective outlet.

The result was a better ROI for rotary screw blowers. The rotary screw blowers were able to reduce the energy usage of aeration blower systems and decrease overall energy costs, making them more efficient than rotary lobe blowers.

If you’re interested in learning more about the use of positive displacement blowers in wastewater treatment plants, make sure to subscribe to our blog and leave us a comment below.