Page 272 - Water Engineering Hydraulics, Distribution and Treatment

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Chapter 8
Pumping, Storage, and Dual Water Systems
demands. The recommended standards for sizing a water
2. The minimum storage capacity (or equivalent capac-
ity) for systems not providing fire protection shall be
storage tank or reservoir as stated in the Recommended Stan-
equal to the average daily consumption. This require-
dards for Water Works, 2007 Edition (Health Research, 2007;
often referred to as the Ten-States Standards), are as follows:
ment may be reduced when the source and treatment
facilities have sufficient capacity with standby power
to supplement peak demands of the system.
1. Fire flow requirements established by the appropri-
3. Excessive storage capacity should be avoided to pre-
ate state insurance services office should be satisfied
vent potential water quality deterioration problems.
where fire protection is provided.
EXAMPLE 8.6 TOTAL WATER STORAGE VOLUME
3
For a steady gravity supply equal to the maximum daily demand, a 4-h fire supply at 8,000 gpm (0.505 m ∕s = 505 L∕s), and no
3
particular hazard to the supply works, find the storage to be provided for a city using an average of 7.5MGD (0.328 m ∕s = 328 L∕s)
of water.
Solution 1 (US Customary System):
The equalizing storage is 15% of average daily consumption:
0.15 × 7.5MG = 1.13 MG.
The fire reserve is 8,000 gpm for 4 h:
6
(8,000 gal∕min × 4h × 60 min∕h)∕10 = 1.92 MG.
The resulting subtotal is 1.13 + 1.92 = 3.05 MG.
Because the emergency reserve is one-fourth of the total storage, the subtotal is three-fourths (0.75) of the total storage.
Therefore,
Total storage = 3.05∕0.75 = 4.1MG.
Solution 2 (SI System):
3 3 3
0.328 m ∕s = 0.328 × 24 × 60 × 60 m ∕d = 28,387 m ∕d.
The equalizing storage is 15% of average daily consumption:
3 3
0.15 × 28, 387 m = 4,258 m .
3
The fire reserve is 0.505 m /s for 4 h:
3 3
(0.505 m ∕s)(4 × 60 × 60 s) = 7,269 m .
3
The resulting subtotal is 4,258 + 7,269 = 11,527 m .
Because the emergency reserve is one-fourth of the total storage, the subtotal is three-fourths (0.75) of the total storage.
Therefore,
3
Total storage = 11,527∕0.75 = 15,369 m .
EXAMPLE 8.7 TOTAL WATER STORAGE VOLUME USING THE TEN-STATES STANDARDS
3
For a steady gravity supply equal to the maximum daily demand, a 4-h fire supply at 8,000 gpm (0.505 m ∕s = 505 L∕s), and no
3
particular hazard to the supply works, find the storage to be provided for a city using an average of 7.5MGD (0.328 m ∕s = 328 L∕s)
of water using the Ten-States Standards.
(Note: This example uses the same parameters as Example 8.6.)
Solution 1 (US Customary System):
Storage volume for domestic consumption = average daily consumption (Ten-States Standards):
= 7.5MGD

= 7.5MGdaily.