Advanced Waterworks Mathematics, 2019a

9. Ferric chloride is used as the coagulant of choice at a 5.75 MGD rated capacity
treatment plant. If the plant operated at the rated capacity for 75% of the year and
operated at 60% of rated capacity for 25% of the year, how many pounds of the
coagulant was needed to maintain a dosage of 45 mg/L?
10. A water softening treatment process uses 25% NaOH during 20% of the year and 50%
NaOH for 80% of the year. Assuming a constant flow rate of 1,100 gpm and a dosage of
70 mg/L, what is the annual budget if the 25% NaOH (SG = 1.18) costs $0.95 per gallon
and the 50% NaOH (SG = 1.53) costs $1.70 per gallon?
114 | A dvanced Waterworks Mathematics