How to Choose a Roots Blower for Your Application (Wastewater & Aeration Guide)

However, selecting the right Roots blower is not just about choosing a machine—it is about matching the blower precisely to your system requirements. An incorrect selection may lead to high energy consumption, insufficient aeration, or equipment damage.

In this guide, we will explain how to properly select a Roots blower in a practical and easy-to-understand way.

1. Understanding the Core Principle of a Roots Blower

A Roots blower is a positive displacement machine. It works by using two synchronized rotors that rotate in opposite directions. Air is trapped between the rotors and the casing, then pushed from the inlet side to the outlet side.

Key characteristics:

· Constant air volume output

· Stable performance regardless of pressure changes

· Simple structure and easy maintenance

· Suitable for continuous 24/7 operation

Because of these advantages, Roots blowers are widely used in wastewater treatment aeration systems, where stable oxygen supply is critical for biological processes.

2. The Two Most Important Selection Parameters

In most real-world wastewater applications, especially aeration systems, blower selection mainly depends on two key parameters:

1) Airflow (Capacity)

Airflow is the amount of air the blower must deliver, usually measured in:

· m³/min or m³/h (Metric)

· CFM (Imperial)

In wastewater treatment, airflow is determined by:

· Biological oxygen demand (BOD/COD load)

· Tank size

· Aeration efficiency requirements

· Number and type of diffusers 

2) Pressure (Water Depth + System Resistance)

Pressure is often misunderstood but is equally important as airflow.

For aeration systems, total pressure is mainly composed of:

· Water depth (submergence level)

· Pipe friction losses

· Valve resistance

· Diffuser backpressure

· Safety margin (10–20%)

A simple rule:

Every 1 meter of water depth ≈ 9.8 kPa pressure requirement

For example:

· 4 meters depth → ~40 kPa base pressure

· Plus system resistance → final required blower pressure may reach 50–60 kPa

If pressure is underestimated, the blower may:

· Fail to deliver enough oxygen

· Overheat during operation

· Experience reduced lifespan

3. How to Select a Roots Blower Step-by-Step

Step 1: Confirm Application Type

Different applications require different designs:

· Wastewater aeration (most common)

· Aquaculture oxygenation

· Pneumatic conveying

· Backwashing systems

Each has different airflow stability and pressure requirements.

Step 2: Calculate Required Airflow

This is usually provided by process engineers or can be estimated based on:

· Tank volume

· Oxygen demand (kg O₂/day)

· Treatment process type (SBR, MBBR, oxidation ditch)

Step 3: Calculate Total Pressure

Use this formula:

Total Pressure = Water Depth Pressure + Pipe Loss + Diffuser Resistance + Safety Margin

This is the most critical step in blower selection mistakes.

Step 4: Select Motor Power

Once airflow and pressure are confirmed, motor power is selected based on blower performance curves.

Oversizing should be avoided because:

· It increases energy consumption

· Causes unstable operation at low load

· Reduces system efficiency

Step 5: Consider Energy Efficiency Options

Modern systems often include:

· VFD (Variable Frequency Drive)

· Soundproof enclosure

· High-efficiency rotor design

These can significantly reduce operating costs, especially in 24/7 wastewater plants.

4. Common Mistakes in Blower Selection

Many system failures come from incorrect selection rather than equipment quality.

Mistake 1: Only considering airflow

Ignoring pressure leads to underperforming systems.

Mistake 2: Oversizing “for safety”

Too large = energy waste + unstable DO control.

Mistake 3: Ignoring future expansion

A good design includes 10–20% margin for future load increase.

Mistake 4: Ignoring operating conditions

Temperature, humidity, and gas composition all affect performance.

4. Why Proper Selection Matters in Wastewater Treatment

In wastewater treatment plants, aeration can account for 50–70% of total energy consumption. That means blower selection directly affects:

· Electricity cost

· Treatment efficiency

· System stability

· Maintenance frequency

A correctly sized Roots blower ensures:

· Stable dissolved oxygen (DO)

· Lower energy consumption

· Longer equipment lifespan

· Reduced downtime

5. Why Work with an Experienced Manufacturer

Choosing a reliable manufacturer is just as important as choosing the right specifications.

A professional Roots blower supplier should provide:

· Engineering selection support

· Performance curve data

· Custom voltage/frequency options

· After-sales maintenance support

· Application-based recommendations

For example, Zhan’er Machinery (Shandong, China) 

focuses on Roots blowers, rotary blowers, and air suspension blowers for wastewater treatment and industrial applications. As a source manufacturer, we support OEM customization and provide solutions based on real operating conditions rather than just catalog parameters.

https://www.zhanerblower.com/

7. Conclusion

Selecting a Roots blower is not complicated if you focus on the two core parameters: airflow and pressure. However, real engineering success comes from correctly understanding system conditions such as water depth, resistance losses, and operating environment.

A properly selected blower will not only improve aeration efficiency but also significantly reduce long-term operating costs.

If you are designing or upgrading a wastewater treatment system, always work with an experienced blower manufacturer to ensure accurate sizing and reliable performance.