23 JULY 2003
5-220.127.116.11 Compute the Size of Sludge Storage Required. Assume sludge must be
stored for 4 days (GLUMRB 1990).
Volume of sludge to be stored = 37,850 L/d x 4 days = 151,400 L (40,000 gallons)
Therefore, a storage tank or tanks should be selected with a capacity of
152,000 L or 152 m3 (40,000 gallons) from manufacturers' catalogs (40,000 gallons is
the largest size tank that can be shipped from factories).
5-18.104.22.168 Compute the Size of Lime Storage Facility Required. Provide 30 days or 1
month of storage. Assume approximately 4.33 weeks/month.
Lime required per 8-h day = 106 kg/d
Lime required per month = 106 kg/d x 5 d/wk x 4.33 wk/mo = 2300 kg/mo (5070 lb/mo)
a. Assume use of hydrated lime at 96% purity.
For 30 day storage quantity of hydrated lime required = [(2300 kg/mo)/0.96] x [74(MW of
Ca(OH)2)/56(MW of CaO)] = 3170 kg/mo (7160 lb/mo)
Number of bags of hydrated lime needed per month= (3170 kg/mo)/(45 kg/bag) = 71 bags/mo
Therefore, storage should be provided for 80 bags.
b. The capacity of the hydrated lime feed hopper should be large enough to
contain 1 day's supply of lime.
Bags needed per day = [71 bags/mo] / [(5 d/wk) x (4.33 wk/mo)]= 4 bags/day
Based of the bulk density of hydrated lime of 480 kg/m3 (30 lb/ft3) and allowing provi-
sions for two hoppers to hold two bags of hydrated lime each.
Volume required for each hopper = [(2 bags) x (45 kg/bag)] / [480 kg/m3] = 0.2 m3 (7 ft3)
Therefore, each hopper should have a minimum capacity of 0.2 m3 (7 ft3) and will feed
lime into a mixing tank where a 10% by weight lime slurry will be prepared prior to being
metered into the sludge conditioning tank.
5-22.214.171.124 Compute the Size of the Ferric Chloride Storage Facility Required. Pro-
vide 30 days or 1 month of storage at operating condition.
Ferric chloride required per 8-h day = 53 kg/d
Ferric chloride required per month = 53 kg/d x 5 d/wk x 4.33 wk/mo = 1150 kg/mo (2530 lb/mo)
Assume use of ferric chloride at 40% purity with a density of 1.45 kg/L (12