Assignment 7 Math Worksheet
Each question is worth 20 points. Partial credit may be awarded.
- Determine the chlorinator setting (lb/day) required to treat a flow of 5.25 MGD with a chlorine dose of 6.5 mg/L.
Feed Rate = Chlorine (mg/L) x Flow (MGD) x 8.34 lb/gal
Feed Rate =
Feed Rate =
- A pipeline that is 10 inches in diameter and 1250 ft long is to be treated with a chlorine dose of 32 mg/L. How many lb of chlorine will this require?
First, determine the gallon volume in the pipeline:
Volume (gal) = 0.785 x D^{2}
x length x 7.48 gal/cu ft
Volume (gal) =
Volume (gal) =
Next, calculate the amount of chlorine required:
Feed Rate = Chlorine (mg/L) x Flow (MGD) x 8.34 lb/gal
Feed Rate =
Feed Rate =
- The chlorine dosage for water is 3.2 mg/L. If the chlorine residual after a 30-minute contact time is found to be 0.9 mg/L, what is the chlorine demand (in mg/L)?
Chlorine Demand = Chlorine Dose - Chlorine Residual
Chlorine Demand =
Chlorine Demand =
- What should the chlorinator setting be (lb/day) to treat a flow of 2.42 MGD if the chlorine demand is 3.8 mg/L and a chlorine residual of 0.7 mg/L is desired?
First, determine the chlorine dosage (in mg/L):
Chlorine Dose = Chlorine Demand + Chlorine Residual
Chlorine Dose =
Chlorine Dose =
Next, calculate the chlorine feed rate in lb/day:
Feed Rate = Chlorine (mg/L) x Flow (MGD) x 8.34 lb/gal
Feed Rate =
Feed Rate =
- A chlorinator setting is increased by 12 lb/day. The chlorine residual before the increased dosage was 0.8 mg/L. After the increased chlorine dose, the chlorine residual was 1.2 mg/L. The average flow rate being chlorinated is 1.45 MGD. Is the water being chlorinated beyond the breakpoint?
First, calculate the expected increase in chlorine residual:
Feed Rate = Chlorine (mg/L) x Flow (MGD) x 8.34 lb/gal
________________ = x mg/L x _________________ x ____________________
x mg/L = _____________________ / (________________ x ___________________)
x mg/L =
Actual increase in residual is:
________________________ - _________________________ = __________________________