Science of Water : Concepts and Applications

338 The Science of Water: Concepts and Applications
collision. Through experience, we see that effective mixing reduces the required amount of chemicals
and greatly improves the sedimentation process, which results in longer fi lter runs and higher-
quality fi nished water.
The goal of fl occulation is to form a uniform, feather-like material similar to snowfl akes—
a dense, tenacious fl oc that entraps the fi ne, suspended, and colloidal particles and carries them
down rapidly in the settling basin.
Polymers are often added to increase the speed of fl oc formation and the strength and weight
of the fl oc.
COAGULATION AND FLOCCULATION GENERAL CALCULATIONS
In the proper operation of the coagulation and fl occulation unit processes, calculations are performed
to determine chamber or basin volume, chemical feed calibration, chemical feeder settings,
and detention time.
Chamber and Basin Volume Calculations
To determine the volume of a square or rectangular chamber or basin, use Equation 10.22
or 10.23:
3
Volume, ft (length, ft)(width, ft)(depth, ft)
(10.22)
Volume, gal (length, ft)(width, ft)(depth, ft)(7.48 gal ft 3
) (10.23)
Example 10.23
Problem:
A fl ash mix chamber is 4 ft2 with water to a depth of 3 ft. What is the volume of water (in gallons) in
the chamber?
Solution:
3
Volume, gal (length, ft)(width, ft)(depth, ft) ( 7.48 galft) (
359 gal
3
4 ft)(4 ft)(3 ft)(7.48 gal ft )
Example 10.24
Problem:
A fl occulation basin is 40 ft long, 12 ft wide, with water to a depth of 9 ft. What is the volume of water
(in gallons) in the basin?
Solution:
Volume, gal length, ft)(width, ft)(depth, ft)(7.48 gal ft 3
( )
3
( 40 ft)(12 ft)(9 ft)(7.48 galft) 32,314 gal