The efficiency of compressed air generators in aeration systems is assessed not only at the compressor level but across the entire chain of air delivery and oxygen transfer.
At the machine level, the key parameters are operating-point airflow and electrical power consumption. Common performance indicators include specific power input or specific energy consumption, expressed for example as kW per Nm³/min of air.
From a process perspective, the critical factor is the amount of oxygen actually transferred into the water per unit of energy consumed. Standardized performance indicators such as Standard Oxygen Transfer Rate (SOTR), oxygen utilization efficiency, and Standard Aeration Efficiency (SAE) are commonly used. SAE is expressed as the mass of oxygen transferred per unit of electrical energy supplied.
In practice, additional factors such as pressure losses in filters, pipelines, and diffusers, part-load performance, and differences between clean-water and wastewater conditions must also be considered.
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