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Science of Water : Concepts and Applications

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<strong>Water</strong> Treatment Calculations 363<br />

Step 6. Recheck R.<br />

Step 7. Repeat Step 5 with new R.<br />

Step 8. Recheck R.<br />

Step 9. Repeat Step 7.<br />

pud 0.809980.1920.001 R <br />

156<br />

<br />

0.00098<br />

C<br />

u<br />

D<br />

2<br />

24 3<br />

034 . 073<br />

.<br />

156 156<br />

49.8114020.001 159<br />

ms<br />

30.73998 0.809980.1590.001 R <br />

130<br />

0.00098<br />

CD<br />

24 3<br />

0.34 0.79<br />

130 130<br />

2 49.8114020.001 u <br />

30.79998 u 0.152 ms (b) The estimated velocity is approximately 0.15 m/s.<br />

OVERFLOW RATE (SEDIMENTATION)<br />

Overfl ow rate, along with detention time, horizontal velocity, <strong>and</strong> weir loading rate are the parameters<br />

typically used for sizing sedimentation basin. The Theoretical Detention Time (plug fl ow<br />

theory) is computed from the volume <strong>of</strong> the basin divided by average daily fl ow.<br />

where<br />

t = detention time, h<br />

24 = 24 h/day<br />

V = volume <strong>of</strong> basin, m 3 or million gallon (MG)<br />

Q = average daily fl ow, m 3 /d or Mgal/d (MGD)<br />

V<br />

t <br />

Q<br />

24 (10.65)<br />

The overfl ow rate is a st<strong>and</strong>ard design parameter that can be determined from discrete particle<br />

settling analysis. The overfl ow rate or surface loading rate is calculated by dividing the average<br />

daily fl ow by the total area <strong>of</strong> the sedimentation basin.<br />

u Q Q<br />

(10.66)<br />

A lw

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