Surface Aeration Revisited

New technology of surface aerators may offer excellent oxygen transfer performance and much better process economics than membrane fine bubble diffusers.

Introduction
The intention of this paper is to have a critical review of the theory and practice of today's Waste Water Aeration Technology.

WWTP aeration processes are designed to promote growth of aerobic microorganisms, which, in turn, reduce the biological demand of the wastewater.

Aeration is the mean of dissolving of oxygen in waste water. This is done by creation of the largest possible contact area. The process economy is expressed by Standard Aeration Efficiency (SAE) as the amount of oxygen transferred per energy unit in lb of O2/Hp-h or kg of O2/kWh and is the driving for force for the new aeration technology development.

Efficiency of different types of aeration equipment is qualified based on SAE in clean water. In the Waste Water environment, due to the presence of surfactants, increased viscosity, solids load etc., aeration efficiency changes significantly. What is performing well in clean water may not be efficient and economical in wastewater.

Membrane fine bubble diffusers that dominate WWT technology for more than 20 years, are very efficient in clean water, but in waste water, loaded with solids and surfactants do not perform as well. After careful screening of many WWTP installations, we concluded that surface aerators may offer better performance and economics than membrane technology. The capital cost of surface aeration is also much lower than the membrane technology.