Air sparging affecting liquid SG in tank

[ICLL]

Anybody have any idea how much the SG in an atmospheric tank (and therefore the level as detected by a DP measurement device) would be affected by air sparging in the tank?

The application is a sanitary waste water equalisation tank on the inlet of a waste water treatment plant. Air blowers are used to maintain the fluid in an aerobic state. The HAZOP asked the question: "is do the air bubbles affect the water SG and cause the level instrument to read wrong?"

I'm guessing not, since the industry routinely uses DP measurement on this type of tank (often cable-suspended pressure transmitter types). Any thoughts on the physics of the question?

 

[Compositepro]

In almost any practical case there will be no measurable effect on your level reading. If you experience severe foaming there may be an effect.

 

[Jobst]

Your level might increase due to gas holdup, but the dP cell will read the same as all it cares about is density*gravity*height. You have reduced density but increased height.

You usually need a lot of gas flow to increase holdup significantly (unless you have very skinny tanks, but then people generally start using words like column).