1. What is the chlorinator setting, in pounds per day, to treat a flow of 5,500,000 gpd if the chlorine dosage is 5 mg/L?
2. If the flow rate in the problem above is increased to 6,300,000 gpd, how many more pounds per day would be needed (assuming the same dosage rate).
3. If a treatment plant discharges 750,000 gpd with a chlorine residual of 0.1 mg/L, how many pounds per day of chlorine would the receiving waters receive?
4. What would be the chemical feed rate, in milligrams per liter, if the chemical feed rate was 65 pounds per day and the flow was 650,000 gpd?
5. A 150 gpm pump is discharging a chemical at a rate of 9 pounds per day to the wastewater. What is the dosage in mg/L?
Answers:
1. 229.35 lbs/day
This is a (Davidson Pie Chart or) Loading formula – Flow, MGD X Conc, mg/L X 8.34 lbs/gal
Convert flow from gpd to mgd (shuffle or) (5,500,000) / (1,000,000) = 5.5 mgd
Now work problem, 5.5 mgd X 5 mg/L X 8.34 lbs/gal =
2. 33.36 lbs/day
(Davidson Pie Chart or) Loading formula – Flow, MGD X Conc, mg/L X 8.34 lbs/gal
Convert flow from gpd to mgd (shuffle or) (6,300,000) / (1,000,000) = 6.3 mgd
Work problem, 6.3 mgd X 5 mg/L X 8.34 lbs/gal = 262.71 lbs/day
Find difference = (262.71 lbs/day – 229.35 lbs/day) =
3. 0.63 lbs/day
(Davidson Pie Chart or) Loading formula – Flow, MGD X Conc, mg/L X 8.34 lbs/gal
Convert flow from gpd to mgd (shuffle or) (750,000 gal) / (1,000,000) = 0.75 mgd
Work formula, 0.75 mgd X 0.1 mg/L X 8.34 lbs/gal =
4. 11.99 mg/L
(Davidson Pie Chart or) rearranged Loading formula – (lbs/day) / (Flow, mgd X 8.34 lbs/gal)
Convert flow from gpd to mgd = 650,000 gpd = 0.65 MGD
Work bottom part of formula = 0.65 mgd X 8.34 lbs/gal = 5.421 lbs/day
Work formula, (65 lbs/day) / (5.41 lbs/day) =
5. 5 mg/L
(Davidson Pie Chart or) rearrange Loading Formula – (lbs/day) / (Flow, mgd X 8.34 lbs/gal)
Convert flow from 150 gpm to gpd, 150 gpm X 1440 gal/day = 216,000 gpd
NOTE: Instead of 1440 you could have (150 gpm X 60 min/hr X 24 hrs/day) – 60 X 24 = 1440
Convert flow from gpd to mgd (shuffle or) (216,000 gpd) / (1,000,000) = 0.216
Work bottom portion, 2.16 mgd X 8.34 lbs/gal = 1.8 lbs/day
Work problem, (9 lbs/day) / (1.8 lbs/) =