UFC 3-280-04
17 DEC 2003
Filtration
Influent
Effluent*
Backwash
Advantages and Disadvantages
Process
Granular media
>2 L/s (30
46 microns
23% of
Low head.
Gravity filter
design flow.
High removal.
gpm)
1.4 (L/s)/m2 (2
10.5 to 14
Larger footprint than pressure filter.
(L/s)/m2 (15 to
gpm)
Needs pump for backwash.
20 gpm/ft2).
< 50 mg/L TSS
Backwash disposal required.
Minimum
High capital cost.
once/day.
Medium operating and labor cost.
Not as susceptible to upsets.
Moderate complexity of control and
operation.
Granular media
>2 L/s (30
510
3 to 5% of
Low head.
Traveling
gpm)
No clear well and no mud well.
microns
design flow.
1.4 (L/s)/m2 (2
bridge filter
Small Footprint.
Controlled by
gpm) dosing.
Air scour available (requiring auxiliary
timer, max
3.5 (L/s)/m2 (5
air supply).
level.
gpm) peak flow
Cannot have high level of solids or oil
Minimum
30 mg/L TSS
and grease.
once/day.
17.5 (L/s)/m2
avg.
Not as high removal efficiency as
(25 gpm/ft2) for
(50 mg/L TSS
gravity up pressure filters.
90 s/cell.
peak)
Backwash disposal required.
High capital and operating cost.
Medium labor cost.
Susceptible to upset.
Complex control and maintenance.
Granular media
>2.5 L/s (40
1030
10 to 25% of
Continuous; no shutdown.
Continuous
gpm) design
microns
design flow.
Not as high removal.
backwash filter
(can operate at
Continuous.
Backwash disposal required.
lower flow)
Auxiliary air required.
30 mg/L TSS
High capital cost.
More susceptible to upset than
pressure filters.
Moderate controls and maintenance.
Cartridge
1 to 2 mg/L
< 1 micron
None with
High removal.
filter
TSS
Flow and
disposable
Not economical for high solids.
at <3 L/s (48
removal
filter elements.
Certain solids can qualify used
gpm).
rating varies
elements as a hazardous waste.
5 to 10 mg/L
per filter
Low capital, operating and labor cost
TSS
element.
for correct application.
at 0.3 to 0.6
Common
Not susceptible to upsets but may be
L/s (5 to 10
filter
easily blinded by high solids loading
gpm).
elements:
system.
10 to 15 mg/L
Woven wire
Is not complex and requires little
TSS
5 m.
maintenance other than element
at < 0.3 L/s (5
Woven fabric
change out.
gpm).
10 um.
Few controls and little auxiliary
Cartridge 1
equipment.
um.
4-2
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