UFC 3-280-04
17 DEC 2003
backwash filters are proprietary. The size and number of units is to be determined with
Vendors A, B and C (data presented in this example) and evaluated against criteria and
specifications.
For rough sizing in this example, use 4.0 L/m2 s (5.9 gpm/ ft2) and select the
next larger stock diameter.
C-2.5
Filters. Size and number of units is to be determined. Each manufacturer can
provide further guidance on acceptable hydraulic loading rates for an influent stream
with a given total suspended solids concentration and solids size and density. Allowable
hydraulic loading is inversely related to solids loading. Using the plant flow and the hy-
draulic loading, the filter area is determined as:
Filter area [m2 (ft2)] = plant flow [L/s (gpm)] / hydraulic loading [L/m2s (gpm/ft2)]
Determine a preliminary filter diameter for the sustained pumping rate, using 4.0 L/m2s
(5.88 gpm/ft2) for the surface loading.
C-2.5.1 Consider a single filter at Q = 12 L/s (190 gpm), determine df = filter diameter,
A = filter surface area, and Q/A = hydraulic loading rate.
=
Q/A
Q/A
4.0 L/m2 s
=
12 L/s / A
12 L/s / 4 L/m2s
=
A
3.00 m2
=
A
=
1.954 m (6 ft, 5 in.)
d
C-2.5.2
Consider two units in parallel at 6 L/s (95.1 gpm) each, with af = area of each
filter.
=
A/number
af
3.00 m2 / 2
=
af
1.50 m2
=
af
=
1.38 m (4 ft, 7 in.)
df
C-2.5.3
Consider three units in parallel at 5 L/s (79.3 gpm) each.
=
A/number
af
3.00 m2 / 2
=
af
1.50 m2
=
af
=
1.38 m (4 ft, 7 in.)
df
C-2.5.4
Consider three units in parallel at 5 L/s (79.3 gpm) each.
=
A/number
af
3.00 m2 / 3
=
af
1.00 m2
=
af
=
1.13 m (3 ft, 8 in.)
df
C-9
Previous Page
