| IMPURITIES |
METHODS |
| Cations |
|
| 1. Calcium and magnesium |
a. Cold, warm, or hot lime-soda process: precipitation, settling, and filtration |
|
b. Ion exchange |
| 2. Sodium, potassium, and ammonium |
a. Hydrogen and cation exchange, if bicarbonate present exceeds total hardness |
|
b. Demineralization |
| 3. Iron and Manganese |
a. Oxidation (aeration) and precipitation, settling (if high amounts present), and filtration
(chlorine and alkali may be needed).
|
|
b. Filtration through manganese zeolite
|
| Anions |
|
| 4. Alkalinity |
a. Lime process as in 1a, but without soda ash. |
|
b. Hydrogen Cation exchange |
|
c. Chloride anion exchange salt-splitting (dealkalization) |
| 5. Sulfate, chloride, nitrate, and phosphate |
a. Demineralization. |
| 6. Silica |
a. Absorption by ferric hydroxide, precipitatted by adding ferric sulfate; Settling and filtration follow. |
|
b. Absorption by magnesium hydroxide, formed when lime or dolomitic lime is added; settling and filtration follow; adding activated magnesia with the lime in warm or hot process is helpful. |
|
c. Hydroxide anion exchange salt splitting(desilization). |
|
d. Demineralization |
| 7. Organic matter and color |
Treated by the same methods employed for ionic types of impurities. |