In biological wastewater treatment plants, aeration accounts for one of the largest shares of the plant's total energy consumption. The air supplied to the aeration tank provides the oxygen required by bacteria to break down organic matter in the wastewater. Proper selection of the blower determines both treatment efficiency and operating costs.

1. Required air flow rate

Air demand is calculated based on the daily flow rate of the plant, the pollution load (BOD), and the oxygen transfer efficiency of the diffusers used. The air flow rate determined by the project engineer is the starting point for blower selection. If the plant is to expand over time, the future air demand must also be taken into account.

2. Discharge pressure

The pressure that the blower must overcome mainly consists of the following:

  • Water head above the diffusers (tank depth)
  • Pressure drop across the diffusers themselves
  • Losses in piping, valves, and elbows

For example, in a tank 5 meters deep, the water head alone creates a backpressure of approximately 500 mbar; other losses are added on top of this. Failing to calculate the pressure realistically leads to the blower drawing excessive power or remaining insufficient.

3. Variable demand and energy savings

Wastewater load varies throughout the day. Instead of running the blower continuously at full speed, adjusting its speed with a frequency inverter linked to dissolved oxygen measurements in the tank provides significant energy savings. In systems installed with multiple blowers, keeping one unit on standby prevents the treatment process from stopping during maintenance.

4. Installation and environment

Proper ventilation of the blower room, keeping the intake filter clean, and using an acoustic enclosure improve both efficiency and the working environment. The helical lobe ZNS series operates with lower vibration and noise compared to straight lobe designs.

Contact us with your plant's air flow rate and tank depth information, and let us jointly determine the appropriate blower model, motor power, and accessories.