TM 5813-8
(5 pounds/cubic feet) (.93 pounds acid/
x
pound) (7 kilograins/pound)
= 2.44
50 Equivalent Weight CaCO3
49 Equivalent Weight H2S04
13.6 kilograins/cubic feet
or 250 percent stoichiometric
Cations Removed
380.5 gallons
488 parts per million - 61 parts per million
1 pound
x
x
kilogallon potable water
17.1 parts per million/grains/gallon
7000 grains
=
1.36 pounds as CaCO3
1000 gallons potable water
At 250 Percent Regeneration Efficiency:
Acid Required
49 equivalent weight acid
1pound H2SO4
1.36 pounds as CaCo 3 x
= 2.5
x
50 euqivalent weight CaCO3 .995 percent H2SO4
1 kilogallon potable water
pounds 99.5 percent H2SO4
= 3.35
1000 gallons potable water
Waste Acid
(2.5-1.0) x 1.34 = 2.01 pounds acid/1000 gallons potable water
Chemical Costs
Acid Cost = 3 cents/pound
99.5 percent H2SO4
NaOH Cost = 10 cents/pound
100 percent NaOH
1.34 pounds 99.5 percent H2SO4
Regeneration Acid=
1000 gallons potable water
If neutralization of the waste acid is required prior to disposal:
2.01pounds 99.5 percent H2SO4
Waste acid =
1000 gallons potable water
If we use 100 percent NaOH
40 equivalent weight NaOH
NaOH = 2.04 pounds of 100% acid as CaCO3 x
50 equivalent weight CaCO3
pounds of 100 percent NaOH
= 1.63
1000 gallons potable water
Summary of Cost per 1000 Gallons of Potable Water
Cation exchange acid usage
= 1.34 pounds x 3.0 cents = 4.02 cents
Waste acid
= 2.01 pounds x 3.0 cents = 6.0 cents
Neutralization NaOH
= 1.63 pounds x 10 cents = 16.3 cents
These chemical costs and water quantities can now be used for life cycle costing of the system.
The ion-exchange equipment size and cost will vary with the cation-exchange flow rate and loading.
The traded water quantities are:
Potable water requirement 450,000 gallons per day
With 5 pounds/cubic foot regeneration, 38 percent of the potable water is treated by ion exchange
= 171,000 gallons per day.
With 3 pounds/cubic foot regeneration, 40.9 percent of the potable water is treated by ion exchange
= 184,050 gallons per day.
Figures A-20 and A-21 show the plan view of two cation exchangers and a degasifier, respectively,
similar to the equipment that will be necessary for such an ion-exchange system.
A-30
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