Field Testing for Oxygen Transfer and Mixing in Static Mixer® Aeration Systems

Authors:

R. Gary Gilbert

Donald Libby

This technical report evaluates the field performance of Kenics static mixer aeration systems within the activated sludge process at three industrial wastewater treatment facilities. The study demonstrates that these systems achieve high oxygen transfer efficiencies, ranging from 3.1 to 3.6 pounds of oxygen per horsepower hour, while confirming that factory test results scale accurately to full-sized installations. Furthermore, tracer studies indicate that the aeration equipment provides nearly ideal backmixing and rapid dispersion of shock loads through effective vertical circulation.

Key Learnings

• Scalability of Data: Field testing confirmed that oxygen transfer data from factory test facilities scales one-to-one for full-sized aeration tanks when design conditions like air flow, water depth, and spacing are matched.
• Transfer Efficiency: The static mixer systems achieved high efficiency rates, ranging from 3.1 to 3.6 pounds of oxygen per line horsepower hour at a 20-foot water depth.
• System Effectiveness: Total air delivery system efficiency was measured between 67% and 73%, falling well within the expected design range for industrial wastewater applications.
• Mixing Characteristics: Tracer studies using lithium chloride demonstrated that the system creates a nearly ideal backmix environment, which prevents short-circuiting and channeling of wastewater.
• Rapid Dispersion: The aerators function as submerged air-lift pumps, providing enough circulation to disperse shock loads and achieve uniform tracer concentration within approximately 2% of the total tank detention time.