A comparison of conventional theoretical analysis, oxygen uptake analysis under steady-state conditions and off-gas analysis for the determination of aeration system capacity

Document Type



Master of Science (MS)


Environmental Engineering

First Advisor's Name

Jeffrey H. Greenfield

First Advisor's Committee Title

Committee Chair

Second Advisor's Name

Jose T. Villate

Third Advisor's Name

Gerald W. Foess


wastewater treatment, aeration, diffused aeration, oxygen transfer efficiency, off-gas analysis, steady-state analysis, capacity

Date of Defense



This study compared aeration system capacity as determined by conventional theoretical analysis with aeration system capacity determined by two field methods: OUA under steadystate conditions and off-gas analysis.

Two methods of theoretical analysis were used to estimate the capacity of the aeration systems. The first method was based on a design criteria of 1.0 pound of oxygen per pound of BOD5 and an oxygen transfer efficiency (OTE) of 20%. The second method was based on a criterion of 1500 cubic feet of air per pound of BOD5. A total of seven field tests were run at three different wastewater treatment plants.

The capacities calculated from the results of the two field test methods correlated very closely, within 6% for four of the five tests performed. The capacities calculated using the theoretical factor of lbs O2/lb BOD5 showed good correlation with the field test results for 3 of the 7 field tests. The capacities calculated from the results of the field tests were 8% to 42% of the capacities determined by the theoretical factor using 1500 ft3 air/ lb BOD5. When the field test was run at design conditions for wastewater flow and airflow, the capacity was approximately twice the capacity determined under non-design conditions.

A sensitivity analysis was performed to estimate the theoretical precision of off-gas analysis and OUA under steady-state conditions. The results of the sensitivity analysis indicated that off-gas analysis provides a more precise oxygen transfer efficiency (+ 23%) than OUA under steady-state conditions ( + 88%).

The results of this study provide useful information on the use of theoretical factors for determining aeration system capacity, the reliability of the field test methods used, the need to test at design conditions when assessing capacity, the variability of OTE among treatment plants, and change in OTE within plug flow basins as opposed to complete mix basins.



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