Page 468 - Water and wastewater engineering

GRANULAR FILTRATION 11-41

TABLE 11-8
Design criteria for single-medium filters
Reported GLUMRB
Parameter range recommendation Recommended

Sand only
Effective size 0.35– 0.7 mm 0.45–0.55 mm
Uniformity coefficient 1.3–1.8 1.65
Shape factor (f) 0.7– 0.95
Porosity 0.4– 0.47
Specific gravity 2.65
Depth of medium 0.6– 0.75 m 0.6 m and .76 m
Filtration rate 5–12 m/h 7.5 m/h
Backwash rate 30–60 m/h 37 m/h
Backwash duration a 10–20 min 15 min
Surface wash rate
Revolving arms 1.2–1.8 m/h 1.2m/h
Fixed arms 4.9–10 m/h 4.9 m/h
Air scour Staged or special baffle
Anthracite coal only
Effective size 0.70– 0.75 mm 0.45–0.55 mm
Uniformity coefficient 1.3–1.8 1.65
Shape factor (f) 0.46–0.73
Specific gravity 1.45–1.75
Porosity 0.53–0.60
Depth of medium 0.6–0.75 m
Filtration rate 5–12 m/h 7.5 m/h
Backwash rate 37– 45 m/h 24 m/h
Backwash duration a 10–20 min 15 min
Surface wash rate
Revolving arms 1.2–1.8 m/h 1.2 m/h
Fixed arms 4.9–10 m/h 4.9 m/h
Underdrain
Pipe lateral Yes
Block Yes
Air scour No
Air scour Staged or special baffle
a
Actual off-line time will be 30 min because of the time required to drain the filter and gradually come up to the
full backwash rate. An additional 30–40 minutes off-line is required for “filter-to-waste” to clear the bed of wash
water and dislodged turbidity.
Sources: Castro et al., 2005; Cleasby and Logsdon, 1999; GLUMRB, 2003; Kawamura, 2000; MWH, 2005;
Reynolds and Richardson, 1996.