Page 359 - Water and wastewater engineering

8-28 WATER AND WASTEWATER ENGINEERING

8-7. Repeat Problem 8-5 assuming a three-column system in series and operation of the
“lead” column until the bed is exhausted. Assume the total out-of-service time is
three hours.

8-8. Continuing the design of the ion exchange column for the Village of Calcite, provide
the following for the two-bed system that will operate in parallel with staggered
regeneration cycles:

3
2
a. Surface loading rate (m /d · m )
b. Height and diameter of the resin bed
c. Empty bed contact time (min)
3
3
d. Service flow rate (m /d · m )

e. Height and diameter of the column vessel
f. Pressure drop
3
Assume the density of the resin is 830 kg/m (moist), a resin height less than or equal
to 4.0 m, and that 50% expansion of the bed will be used during backwash. The pres-
sure drop across the bed should be less than 140 kPa.
8-9. Repeat Problem 8-8 using the three bed system designed in Problem 8-4 .

8 -10. Continuing the design of the ion exchange column for the Village of Dolomite, pro-
vide the following for the two-bed system that will operate in parallel with staggered
regeneration cycles:
2
3
a. Surface loading rate (m /d · m )
b. Height and diameter of the resin bed
c. EBCT
3
3

d. Service flow rate (m /d · m )
e. Height and diameter of the column vessel
f. Pressure drop
3
Assume the density of the resin is 850 kg/m (moist), a resin height less than or equal
to 4.0 m, and that 50% expansion of the bed will be used during backwash. The pres-
sure drop across the bed should be less than 140 kPa.

8-11. Repeat Problem 8-10 using the three-bed system designed in Problem 8-7 .

8-8 DISCUSSION QUESTION

8-1. Two pilot ion exchange columns treating the same raw water in a parallel opera-
tion yielded the breakthrough curves shown below. Assuming the resins are equally
priced, which resin would you choose? Explain your choice.