solve problem 8-7

-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 is 7,000m3/d. The design final hardness is 120mg/L as CaCO3. 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: Ca2+=111.0mg/L as CaCO3 Mg2+=131.8mg/L as CaCO3 Operating temperature =5C Iron and turbidity concentrations are negligible Pilot scale column data: Column diameter =10.0cm Column height =150.0cm Resin density =0.80g/cm3 on a moist basis Moisture content =70% Flow rate through the column =0.25m3/h Pilot scale breakthronoh data for Dolomitn wn-.l- ter 3-7. 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