The assumed site data are summarized below:
1-Available ground water is a consideration.
2-Ion exchange will be considered for the potable water treatment.
3-Pond evaporation of regenerate wastes would be approximately 0.7, multiplied by net pan evaporation (87
inches per year), which equals 508 inches per year.
Laboratory analyses are available, and the following water quality data are shown in figure A-13.
Ion-Exchange Resin Selection
On the physical and chemical analysis of water report (fig. A-13), the following data were extracted:
Total dissolved solids 800 milligrams per liter
77 milligrams per liter
107 milligrams per liter
9 milligrams per liter
0.01 milligrams per liter
0.01 milligrams per liter
2.0 milligrams per liter
In comparing the extracted data with the potable water maximum contaminant levels found in Army Medical Corps
documents, total dissolved solids is the only limit exceeded.
The choice of the proper ion-exchange method depends on the composition of the raw water and its intended use. A
strongly acidic cation exchange resin replaces the cations in the raw water with hydrogen, and the effluent from the
exchanger unit is both softened and acidic. Since sodium is the most predominant cationic ion in the well water, a
reduction of sodium and associated alkalinity will reduce the total dissolved solids to within the potable water limits.
Therefore, a strongly acidic cation exchange resin system is indicated. No specific pretreatment process is necessary.
A strongly acidic cation exchange system converts carbonate and bicarbonate alkalinity to carbonic acid, which breaks
down to carbon dioxide and water. Then, the carbon dioxide may be removed by air stripping in a degasification tower.
After degasification, a percentage of the raw well water containing alkalinity may be blended to obtain the desired 500
milligrams per liter of total dissolved solids.
Ion-Exchange Engineering Data
Since total dissolved solids only need to be reduced approximately 40 percent, consider low acid regeneration levels.
Regeneration levels of 5 and 3 pounds per cubic foot will be considered. Leakage can be estimated from vendor data
such as figure A-14.
With a 5-pound H2S04 (66 degrees Be)/cubic foot regeneration level, the average sodium leakage equals 60.5 parts
per million as CaCO3. The capacity of the ion-exchange resin can be found in figure A-15.
With a 5-pound H2S04 (66 degrees Be)/cubic foot regeneration level, the book capacity = 15.1 kilograins/cubic foot.
The alkalinity correction factor can be found in figure A-16.
At 56 percent, the alkalinity correction factor is 1.125
The corrected capacity = 17.0 kilograins/cubic foot.
Use equipment factor = 0.8
. . Design Capacity = 13.6 kilograins/cubic foot.
With a 3-pound H2SO4 (66 degrees Be)/cubic foot regeneration level, the average sodium leakage = 104.5 parts
per million as CaCO3. Leakage can be estimated from vendor data such as figure A-17.
With a 3-pound H2S04 (66 degrees Be)/cubic foot regeneration level, the book capacity = 11.0 kilograins/cubic
foot. The capacity of the ion-exchange resin can be found in figure A-18.