Page 481 - Water and wastewater engineering
P. 481
11-54 WATER AND WASTEWATER ENGINEERING
Media analysis (continued)
Sand Anthracite
U.S. Standard mass percent coal mass percent
Sieve No. retained retained
16–18 4.22
18–20 10.60 2.96
20–25 41.50
25–30 31.10
30–35 9.70
35–40 4.7
40–45 2.4
0.5
NOTE: geometric mean diameter of successive sieves is d g ( d 1 d 2 ) .
The following is to be provided to complete this portion of the filter design:
Clean bed headloss
Backwash velocity
Depth of expanded bed
Number of filter beds
Area of an individual filter bed
Plan dimensions
Backwash trough layout
Maximum backwash water trough flow rate
Backwash trough dimensions
Backwash trough weir elevation above undisturbed bed
Gullet dimensions
Backwash water volume
Backwash tank volume
Maximum allowable filtration headloss
Depth of filter box
Backwash tank low water elevation
11-10 DISCUSSION QUESTIONS
11-1. Identify two design parameters that may be adjusted if the clean bed headloss in a
granular filter is too large.
11-2. Which of the following granular filtration systems should be chosen if the quality of
raw water is highly variable: (a) dual media, (b) monomedia?
