Settling Velocity?

[Pump2005]

I was calculating out my surface loading rate for my solids contact basin to see if we actually fell within the state regulation on SLR. We did under NJ rule running at 700gpm/1962ft2 = 0.356 gpm/ft2. I decided to go a step further and find out what the settling velocity was but using the equation I have does not bring me anywhere close to what range it should be, 1 to 3 cm/min. I don't think the equation I'm following is written correctly. If someone could clarify this it would be appreciated.

gpd/ft2 x 3785 cm3/gal x 1ft2/929 x 1 day/1440 min = cm/min

 

[bimr]

1 gpm = 63.09 cm3/sec

1 sq ft = 929 cm2

1 gpm/ft2 = 63.09/929 = 0.47 m/sec = 0.68 mm/sec = 0.068 cm/sec = 4.08 cm/min

"In practice, the overflow rates at maximum flow are often 0.34 to 0.68 mm / s."

http://web.deu.edu.tr/atiksu/ana52/wdesign03.html

.356 gpm/ft2 x 3785 cm3/gal x 1ft2/929 x = 1.45 cm/min

 

[Pump2005]

Thanks bimr. After playing around with the equation I see its not a straight forward multiplication problem even though it's written that way. I see it can be calculated two ways. I'm still learning all the conversions but see a lot of equations written as straight multiplication when unless you know the conversion you'll always get the wrong answer.

GPM/FT2 x 4.0746 = CM/MIN

Or

GPD/FT2 x 3785 / 1440 / 929 = CM/MIN