AOTR to SOTR

[jartgo]

In the fourth edition of M&E, the explanation of finding SOTR makes an accounting for the depth of diffusers and a fouling factor.

Admittedly, I'm relatively new to wastewater treatment, but I have seen and worked with this equation on pieces of other projects, but never have seen a coefficient to account for depth of diffusers or a fouling factor.

Can you all confirm that the Ot factor (percent oxygen concentration leaving the tank) should be used as whole numbers in this equation?
That is, if the concentration is 20 percent, it should be entered as 20 and NOT 0.20.

Also, that Pd should be entered as (pressure due to water depth + the atmospheric pressure), such that Pd should always be greater than Patm.

Thanks!

 

[bimr]

The SOTR is the standard oxygen transfer rate under test conditions of 20 Deg C and zero DO.

There is an equation to modify the SOTR to the actual field conditions or the OTR. This equation has a Beta to account for the effect of wastewater characterisics and a c factor to account for oxygen transfer at the reactor bottom.

The apparent alpha should be replaced by the equivalent term alphaF where F is the fouling factor. The UE EPA came up with the F factor which varies between 0.5 and 1.0 to account for fouling. The f parameter attempts to account for impairment in diffuser performance caused by fouling or material deterioration. Needless to say, the alpha parameter is somewhat controversial.

0 PSIG (gauge) = 14.7 PISA (Atmosheric)

The pressure at the bottom of a 15 foot deep water tank will be 6.5 PSIG or 21.2 PSIA.

 

[jartgo]

Thanks bimr, by playing with the equations for a few evenings I figured it out.

And in case anyone else stumbles across this post, the equations referenced in this post are on page 429 of the fourth edition of M&E.

The Ot factor should be entered as a whole number, such that if the concentration is 20 percent, you should enter 20 in the equation and not 0.20.

The Pd factor should absolute and as pointed out by bimr, should include both pressure due to depth and atmospheric pressure, such that Pd should always be greater than Patm.

Thanks.