Methods of Removing Impurites From Water


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.

2007 Arizona Board of Regents for The University of Arizona

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