Page 277 - Water and wastewater engineering

6-54 WATER AND WASTEWATER ENGINEERING

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4. Velocity gradient 750 s
5. Impeller type: turbine, 6 flat blades, N p 3.6

6. Available impeller diameters: 0.25, 0.50, and 1.0 m
7. Assume B (1/3) H

Design the rapid-mix system by providing the following:
1. Water power input in kW
2. Tank dimensions in m

3. Diameter of the impeller in m
4. Rotational speed of impeller in rpm

6-16. Rework Example 6-8 to find the orifice diameter using a headloss if one of the floc-
culation basins is out of service when the design flow rate occurs.
6-17. Determine the number of orifices for a baffle wall with the following design parameters:
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Design flow rate 0.11 m /s
Orifice coefficient 0.75
Orifice diameter 150 mm
6-18. Using a spreadsheet program you have written, rework Example 6-8 for the follow-
ing cases:

a. Given velocities of 0.55, 0.45, and 0.35 m/s, find the corresponding diameters in cm
and headlosses for 60 orifices.
b. Given headlosses of 3, 6 and 9 mm, find the corresponding diameters and veloci-
ties for 60 orifices.
6-19. Continuing the preparation of the proposal for the Eau Gaullie treatment plant
( Problem 6-14 ), design the flocculation tank by providing the following for the first
two compartments only:
1. Water power input in kW
2. Tank dimensions in m
3. Diameter of the impeller in m
4. Rotational speed of impeller in rpm

Use the following assumptions:
1. Number of tanks 2
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2. Tapered G in three compartments: 90, 60, and 30 s
3. Gt 120,000