Hello wastewater experts!,

Has anyone ever heard anything about the influence of the temperature of the air feed to the 'aeration water' and then especially looking at the oxygen uptake from the water?

Since we are treating water of +/- 40degrees celcius and we are adding blower air into the aeration of 85degrees celcius, could this by any means influence the oxygen uptake or the dissolvability of oxygen in the water?

Kind regards

I think the equilibrium concentration of DO depends on the temperature of the water rather than the temperature of the air. More significant factors include the bubble size and the pressure at the bubble.

grrun

Thanks all for the information, i agree that there are other big effects like the hot air adding up to the water temperature, and microbe effieciency, and the DO maximum depended on the water temp.

I guess if there are even effects of the air temperature its most likely going to influence the density of the air/bubble and stuff. Guess its very minor or even close to zero.

to DS: the watertreatment plant is running better then ever before, got high COD removal and all.

Thanks i know enough!

Luci,

air temperature increases due to the compression

Then, of course, air temperature DECREASES when the compression is removed, such as when a bubble is formed and rises, lowering the pressure.  Physical laws (even the aforementioned "gas laws") dictate this.  It's been the basis of artificial refrigeration for over 100 years.  

I find it ironic that many people understand how compressing a gas increases its latent heat per unit volume, but cannot grasp the opposite end of the same equation.  Those who have studied the phenomenon in detail can predict the level of heating of the liquid, which almost invariably results in a very low number.  The result is usually relative to the inefficiency of the blower equipment and the mechanical heat generated by the equipment, and not the compressive heating of the gas.  Of course, the ambient temperature of the intake air will transfer to the liquid in some measure, but if the ambient air is only 40° and the liquid is 40° there will likely be very little heat transfer.