23 JULY 2003
d. A sludge transfer system will be used to pump the sludge from the sludge
storage tank to the conditioning tank. If required, the sludge will be passed through an
in-line grinder before it reaches the sludge transfer pumping system. This in-line grinder
will improve sludge mixing and flow characteristics and protect downstream pumping
and dewatering equipment.
e. The conditioning system will consist of a conditioning tank to which the
sludge and conditioning chemicals are added and are assumed to be completely mixed.
The conditioned sludge will then be pumped to the filter press units.
f. The feed pumps will have the capacity to deliver the sludge to the filter
press at the design pressure of 345 kPa (50 psig) for 20 minutes (1200 seconds). After
completion of the feed cycle, the compression cycle will proceed by pumping water at
1550 kPa (225 psig) for 15 minutes (900 seconds) behind the filter press diaphragms for
5-18.104.22.168 Compute the Size of Sludge Storage Required. Assume that the sludge
must be stored for 4 days (GLUMRB 1990).
Volume of sludge to be stored = 80,000 L/d x 4 day = 320,000 L (84,400 gallons)
Therefore, a storage tank or tanks should be selected with a capacity of
320,000 L or 320 m3 (85,000 gallons) from manufacturers' catalogs.
5-22.214.171.124 Compute the Size of Lime Storage Facility Required. Provide 30 days or 1
month storage and assume 4.33 weeks/month and the use of hydrated lime at 90%
Lime required per 8 h day = 280 kg/d (620 lb/d)
Lime required per month = 280 kg/d x 5 d/wk x 4.33 wk/mo = 6100 kg/mo (13,430 lb/mo)
For 30 day storage quantity of hydrated lime required = [(6100 kg/mo)/0.9] x [74 (MW of
Ca(OH)2)/56 (MW of CaO)] = 8960 kg/mo (19,740 lb/mo)
Number of bags of hydrated lime needed per month = (8960 kg/mo)/(45 kg/bag) = 199 bags/mo
Therefore, storage should be provided for 200 bags. The capacity of the hydrated lime
feed hopper should be large enough to contain one day's supply of lime.
Number of bags needed per day = [199 bags/mo] / [(5 d/wk) x (4.33 wk/mo) = 10 bags/day
Based on the bulk density of hydrated lime of 480 kg/m3 (30 lb/ft3) and allow-
ing provision for two hoppers to hold 5 bags of hydrated lime each,
Volume required for each hopper = [(5 bags) x (45 kg/bag)] / [480 kg/m3] = 0.47 m3 (17 ft3)