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IS 13166:1992 is the Indian Standard (BIS) for mechanical surface aerators-guidelines for evaluation and testing. 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
! 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.
Consolidated list per BIS. For the text of each amendment, refer to the BIS portal link above.
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International Equivalents
Similar International Standards
ASCE/EWRI 2-17American Society of Civil Engineers (ASCE), USA
HighCurrent
Measurement of Oxygen Transfer in Clean Water
Specifies the non-steady state clean water test procedure for determining oxygen transfer, which is the core of IS 13166.
EN 12255-15:2003European Committee for Standardization (CEN), Europe
HighCurrent
Wastewater treatment plants - Part 15: Measurement of the oxygen transfer in clean water in aeration tanks of activated sludge plants
Provides the European standard for the same clean water oxygen transfer test methodology for aeration equipment.
DWA-M 209E (2018)German Association for Water, Wastewater and Waste (DWA), Germany
MediumCurrent
Measurement of the Oxygen Transfer in Activated Sludge Aeration Tanks in Clean Water
Covers the same fundamental clean water testing principles, though often with a focus on diffused aeration systems.
Key Differences
≠IS 13166 primarily describes the logarithmic deficit method for calculating the oxygen transfer coefficient (KLa), whereas modern standards like ASCE/EWRI 2-17 strongly recommend or require non-linear regression analysis for greater accuracy.
≠The ASCE and EN standards provide more stringent and detailed requirements for power measurement, including calibration, accounting for gearbox/motor losses, and defining wire-to-water efficiency, which is less detailed in IS 13166.
≠International standards specify more rigorous criteria for the number and placement of dissolved oxygen (DO) probes based on tank volume and geometry to ensure a spatially representative measurement, while IS 13166 gives a more general guideline (minimum of 2).
≠ASCE/EWRI 2-17 includes detailed procedures for uncertainty analysis and statistical validation of test results, a requirement not explicitly detailed in the IS 13166 guideline.
Key Similarities
≈All standards are based on the same fundamental non-steady state re-aeration test method in clean water to evaluate aerator performance.
≈The primary performance metrics to be determined are the Standard Oxygen Transfer Rate (SOTR) and Standard Aeration Efficiency (SAE), which are common across all listed standards.
≈All standards specify the correction of test data to standard conditions: 20°C, 1 atmosphere pressure, and zero initial dissolved oxygen concentration, using similar physical principles and formulas.
≈The deoxygenation process is similar, typically using sodium sulphite catalyzed by a cobalt salt to chemically remove dissolved oxygen from the test water before starting aeration.
Parameter Comparison
Parameter
IS Value
International
Source
Standard Temperature for SOTR
20°C
20°C
ASCE/EWRI 2-17, EN 12255-15
Temperature Correction Factor (θ)
Recommends 1.024 for surface aerators.
1.024 is commonly used, but standards emphasize it should be experimentally determined if high accuracy is needed.
ASCE/EWRI 2-17
KLa Calculation Method
Logarithmic deficit method
Non-linear regression (NLR) is the preferred method.
ASCE/EWRI 2-17
Test Termination Point
When DO reaches 90% of saturation value (Cs).
Data collection until at least 90% Cs AND for a duration of at least 3/KLa, whichever is longer.
ASCE/EWRI 2-17
Minimum DO Probes (Small Tank)
Minimum of 2 probes.
Minimum of 4 probes for tanks up to 100 m³.
ASCE/EWRI 2-17
Deoxygenation Catalyst
Cobalt chloride at 0.05 to 0.1 mg/L as Co.
Cobalt chloride at ~0.05 mg/L as Co, with discussion on avoiding excess.
ASCE/EWRI 2-17
DO Probe Response Time
Not explicitly defined with a quantitative limit.
Response time (T90) should be less than 5% of the aeration process time constant (1/KLa).
ASCE/EWRI 2-17
⚠ Verify details from original standards before use
Key Values5
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)
Tables & Referenced Sections
Key Tables
Annex A - Proforma for Collection of Data
Annex B - Details of Test Facility
Annex C - Methods for Determination of Dissolved Oxygen
Key Clauses
Clause 3.12 - Standard Conditions
Clause 4 - Evaluation of Performance
Clause 5 - Procedure for Evaluation of Performance
Clause 5.3 - Determination of Oxygen Transfer Rate
Clause 5.4 - Determination of Power Consumption
Frequently Asked Questions4
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).