Water/Wastewater Laboratory Calculations - Basic Mathematics for Water and Wastewater Operators - page 251

■ Example 16.26
Problem: A wastewater flow of 840,000 gpd requires a chlorine dose of 20 mg/L.
If sodium hypochlorite (15% available chlorine) is to be used, how many pounds
per day of sodium hypochlorite are required? How many gallons per day of sodium
hypochlorite is this?

Solution: Calculate the pounds per day chlorine required:

Chlorine (lb/day) = Chlorine (mg/L) × Flow (MGD) × 8.34 lb/gal

Chlorine (lb/day) = 20 mg/L × 0.84 MGD × 8.34 lb/gal = 140 lb/day

Calculate the pounds per day sodium hypochlorite:

140 lb/day chlorine
15% availablechlorine

×100 = 933 lb/day

Calculate the gallons per day sodium hypochlorite:

933 lb/day ÷ 8.34 lb/gal = 112 gal/day

■ Example 16.27
Problem: How many pounds of chlorine gas are necessary to treat 5,000,000 gal of
wastewater at a dosage of 2 mg/L?

Solution:

6

(5 × 10 gal) × 2mg/L × 8.34 lb/gal = 83 lb chlori ne

■ Example 16.28
Problem: A chlorine pump is feeding 10% bleach at a dosage of 5 mg/L. If 2,000,000
gal are treated in 18 hr, how many gallons per hour is the pump feeding?

Solution: Change gallons to million gallons:

2,000,000 gal = 2.0 MG

Find the pounds of chlorine:

5 mg/L × 2.0 MG × 8.34 lb/gal = 83.4 lb

Change percent available to a decimal equivalent:

10% = 0.10