Page 141 - Water and wastewater engineering

3-38 WATER AND WASTEWATER ENGINEERING

Length of pipe from intake structure to wet well 2,500 m
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Maximum demand at design life 26,000 m /d
Concrete pipe
Assume the lake bottom is as shown in Figure P-3-4

Low water surface elevation = 153.5 m

Intake
106.6 m Conduit

FIGURE P-3-4
Specify the following:
Wet well drawdown elevation
Minimum slope of energy grade line required to carry the maximum demand
Diameter of the conduit
Velocity in the conduit
Depth of soil cover at the intake structure and at the wet well

Provide a sketch showing the following:
Low water surface elevation
Surface elevation of water in the wet well at maximum fl ow rate
Pipe profi le from the intake structure to the low-lift pump station
Elevation of bottom of conduit at the intake structure and at the wet well
Note: Because both the slope of the energy grade line and the diameter are unknown,
a trial and error solution is required. A spreadsheet solution for the trial and error cal-
culation is recommended.

3-5. Show by calculation that losses for valves, fittings, and velocity head are negligible
compared to the static head at the maximum flow rate for Example 3-5.
3-6. Develop the system head curves for the low-lift pump station to the water treatment plant
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pumping system shown in Figure P-3-6 . The minimum flow rate is 9,500 m /d. The av-
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erage flow rate is 19,000 m /d. The maximum flow rate is 38,000 m /d. You may ignore
losses from valves, fittings, and velocity head.
3-7. Develop the system head curves for the low-lift pump station to the water treatment
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plant pumping system shown in Figure P-3-7 . The minimum flow rate is 4,500 m /d.
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The average flow rate is 9,000 m /d. The maximum flow rate is 18,000 m /d. You
may ignore losses from valves, fittings, and velocity head.