Page 358 - Water and wastewater engineering

ION EXCHANGE 8-27

8-3. Repeat Problem 8-2 assuming column leakage is 5.0 mg/L as CaCO 3 .
8-4. Repeat Problem 8-2 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 two hours.
8-5. A pilot scale ion exchange column was used to develop design data for a softening
system for the Village of Dolomite. The data are shown below. The design flow rate
3
is 7,000 m /d. The design final hardness is 120 mg/L as CaCO 3 . Regeneration is to be
once per day. The manufacturer’s operating capacity to breakthrough is 50%.
Assume a two-column system and that there is no leakage before breakthrough. Use
the mass balance technique to determine the mass of resin that will be required.
Raw water data:
2
Ca 111.0 mg/L as CaCO 3
2
Mg 131.8 mg/L as CaCO 3
Operating temperature 5 C
Iron and turbidity concentrations are negligible
Pilot scale column data:
Column diameter 10.0 cm
Column height 150.0 cm.
3
Resin density 0.80 g/cm on a moist basis
Moisture content 70%
3
Flow rate through the column 0.25 m /h

Pilot scale breakthrough data for Dolomite raw water
3
Volume, m Effluent concentration,
meq/L
0.0 0.0
0.1 0.0
0.25 0.0
0.50 0.0
1.0 0.0
2.0 0.0
2.25 0.0
2.5 0.0
3.0 0.1
3.3 0.6
3.4 1.05
3.5 1.58
3.6 2.37
3.7 3.09
3.8 3.49
4.0 4.33

8-6. Repeat Problem 8-5 assuming column leakage is 10.0 mg/L as CaCO 3 .