What is the primary performance metric for a surface aerator?

The Standard Oxygen Transfer Rate (SOTR) in kg O₂/h and the aeration efficiency in kg O₂/kWh, as defined in Clause 4.

What are the standard conditions for reporting aerator performance?

Clean water at 20°C, with zero initial dissolved oxygen, and under one standard atmosphere of pressure (Clause 3.12).

What is the main test procedure described in this standard?

The non-steady state reaeration test (Clause 5.3), where water is first deoxygenated and then the rate of dissolved oxygen increase is measured over time as the aerator runs.

How is power consumption measured?

The input power to the motor is measured using a power analyzer/wattmeter under the same conditions as the oxygen transfer test (Clause 5.4).

IS 13166

: 1992

mechanical surface aerators-guidelines for evaluation and testing

CurrentSpecializedGuidelinesEnvironmental · Public Health Engineering

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This standard provides guidelines for evaluating the performance and conducting tests on mechanical surface aerators used in wastewater treatment. It outlines the methodology for determining the Standard Oxygen Transfer Rate (SOTR) and aeration efficiency (kg O₂/kWh) under defined test conditions. The code specifies the test facility requirements, measurement procedures, and calculations for converting field data to standard, comparable performance metrics.

mechanical surface aerators-guidelines for evaluation and testing

Quick Reference Values

Standard temperature for SOTR20 °C

Standard initial dissolved oxygen for testing0 mg/l

Standard atmospheric pressure for SOTR1 atmosphere

Theta (θ) factor for temperature correction1.024

Minimum test tank volume to power ratio0.6 m³/W

Key Formulas

SOTR = Ns * (Cs_sat,20 / (β * Cs_sat,T - C)) * θ^(20-T) * α — Formula to correct field oxygen transfer rate to standard conditions (SOTR)

Practical Notes

Accurate DO measurement is critical; calibrate DO probes frequently against the Winkler method (Annex C) before and during the non-steady state reaeration test.

The performance (SOTR/kW) is highly sensitive to the aerator's immersion depth; this must be precisely controlled and reported.

Ensure the test tank volume is sufficiently large as per Clause 5.2.1 to avoid boundary effects on mixing and to allow for a reasonable test duration.