UFC 3-280-03
23 JULY 2003
Therefore, each hopper should have a minimum capacity of 0.5 m3 (17 ft3)
and will feed lime into a mixing tank where, a 10% lime slurry by weight will be prepared
prior to being metered into the sludge conditioning tank.
5-3.2.3.4 Compute the Size of the Polymer Storage Facility Required. Provide 30
days or 1 month storage.
Polymer required per 8-h day = 112 kg/d (250 lb/d)
Polymer required per month = 112 kg/d x 5 d/wk x 4.33 wk/mo = 2425 kg/mo (5420 lb/mo)
Number of bags of polymer needed per month = (2425 kg/mo) / (22 kg/bag) = 110 bags/mo
Therefore, storage should be provided for 110 bags. The capacity of the polymer feed
hopper should be large enough to contain 1 day's supply of polymer.
Number of bags needed per day = (112 kg/d) / (22 kg/bag) = 5 bags
The bulk density of the polymer is assumed to be 320 kg/m3 (20 lb/ft3) and the
daily supply will be stored in two hoppers.
Volume required for each hopper = [112 kg/d)] / [2 x 320 kg/m3] = 0.2 m3 (7 ft3)
Therefore, each hopper should have a minimum capacity of 0.2 m3 (7 ft3) and
will feed polymer to a mixing tank for preparation of the 5% solution prior to being
metered into the sludge conditioning tank.
5-3.2.3.5 Compute Size of the sludge Pump Used Before the Conditioning Tank.
Assume the conditioning tank is connected to all of the filter processes, and all the
operating filters are fed at one time.
Total sludge pumped per operating day = (80,000 L/d x 7 d/wk) / (5 d/wk operating) = 112,000 L/d
Pumping rate per cycle (filling time 20 min [1200 s]) = [112,000 L/d] / [(8 cycle/day) x (1200
s/cycle)] = 12 L/s (185 gpm)
Therefore, the total minimum required pumping capacity is 12 L/s (185 gpm).
For this application, at least two pumps should be provided, one operating pump and
one standby pump. To size these pumps, the system hydraulic (static and dynamic)
head requirements would need to be determined, as would an additional safety factor of
10 to 25%, as described in Subparagraph 2-7.2.2.1, to overcome any effects from the
sludge such as its thixotropic properties. Using the pump capacity and head, the
designer should obtained manufacturers' catalogs and select the appropriate pump.
5-3.2.3.6 Compute the Size of the Conditioning Tank. Assume use of an in-line
conditioning tank with a 10-minute (600-second) retention and mixing time.
Volume required for conditioning tank = 12 L/s x 600 s = 7200 L (1900 gallons)
5-17
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