5-2.3.3.2 **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).

5-2.3.3.3 **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.

5-2.3.3.4 **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

lb/gal).

5-7

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