Water/Wastewater Laboratory Calculations - Basic Mathematics for Water and Wastewater Operators - page 252

Find pounds of bleach:
83.4 lb ÷ 0.10 = 834 lb
Find gallons of bleach:
834 lb ÷ 8.34 lb/gal = 100 gal
Find gallons per hour:
100 gal ÷ 18 hr = 5.5 gal/hr
■ Example 16.29
Problem: A 12-in. pipe is 1875 ft long and must be disinfected with 60 ppm of 65%
HTH. How many pounds of HTH are needed?
Solution: Find the volume of the pipe in gallons:
Volume = D 2 × 0.0408 × Length = (12 in.) 2 × 0.0408 × 1875 ft = 11,016 gal
Change gallons to MGD:
11,016 gal ÷ 1,000,000 = 0.011 MGD
Find pounds of chlorine:
Chlorine (lb) = 60 ppm × 0.011 MGD × 8.34 lb/gal = 5.5 lb
Change percent available to a decimal equivalent:
65% = 0.65
Find pounds of HTH:
5.5 lb chlorine ÷ 0.65 = 8.5 lb HTH
Liquid chemical dosages can be calculated to determine the gallons per day.
Chemical feed pumps are calibrated using milliliters per minute (mL/min). If you
take 3650 mL/gal and divide it by 1440 min/day, the conversion for gal/day can be
determined.
3650 mL/gal ÷ 1440 min/day = 2.5 mL/min/gal/day
■ Example 16.30
Problem : A 20% available fluoride solution is used to dose 2,000,000 gpd at 440 ppb
(parts per billion). How many milliliters per minute is the pump feeding?