Page 422 - Water and Wastewater Engineering Design Principles and Practice

SEDIMENTATION 10-39

• Use lower mixer speed (80 to 85 percent of maximum) and postion the blades a full diam-
eter from the floor.
• Use large sand grain sizes: 130–150 m instead of 80 or 100–120 m diameter.

Visit the text website at www.mhprofessional.com/wwe for supplementary materials
and a gallery of additional photos.

10-6 CHAPTER REVIEW

When you have completed studying this chapter, you should be able to do the following without
the aid of your textbooks or notes:

1. Describe the difference between Type I, II, III, and IV settling and give an example of
where they are applied in water or wastewater treatment.

2. Show by derivation why overflow rate “controls” the efficiency of settling in both the
upflow clarifier and the horizontal flow clarifier.
3. Calculate the percent removal of a discretely settling particle in a vertical or horizontal
flow sedimentation basin.
4. Explain why a settling column study is probably not appropriate for design of a new
water treatment plant.
5. Identify four potential causes that you would investigate to explain the poor perfor-
mance of a settling tank.

6. Describe, for a client, the three types of sedimentation systems described in this text
and the reasons you would recommend one over another.

7. Explain the reason for calculating the Reynolds number and Froude number in check-
ing a horizontal-flow rectangular settling basin.
8. Given the dimensions of a horizontal-flow rectangular settling basin or high-rate set-
tler, recommend a mechanical collector.
With the use of this text, you should be able to do the following:

9. Calculate the settling velocity of a discrete particle given its density, diameter, and the
water temperature.

10. Analyze settling column data to determine an overflow rate and detention time to
achieve a specified percent removal.
11. Calculate the settling time and particle travel time in a high-rate settler.

12. Design a rectangular horizontal-flow sedimentation basin.
13. Design a high-rate settler including the horizontal flow tank.