The orientation in basic water chemistry presented here has included an overview of some of the major impurities present in water and has suggested the nature of the problems they cause.
Table briefly summarizes the most common problems arising from the presence of such major impurities as hardness, iron, and microorganisms. Referring to these same impurities, Table focuses on some of the processes and chemicals most generally used to control them for avoidance of problems of water use both in industry and by municipalities.
|
Substances in water |
Process used for removal |
Chemical used |
|
Hardness |
Precipitation Ion exchange |
Lime, soda ash, caustic, phosphate, Salt, acid |
|
Alkalinity |
Precipitation Ion exchange Neutralization |
Lime, gypsum Acid, salt Acid |
|
Carbon dioxide |
Precipitation Ion exchange Neutralization Degasification |
Lime Caustic Lime, caustic None |
|
Dissolved solids |
Reverse osmosis |
None |
|
|
Reduction by removal of separate components adding to dissolved solids |
|
|
Suspended solids |
Coagulation, flocculation, sedimentation |
Alum, aluminate, coagulant aids |
|
Iron and manganese |
Oxidation and nitration Precipitation Ion exchange |
Chlorine, lime Lime, chlorine, air Salt, acid |
|
Silica |
Precipitation Ion exchange |
Iron, salts, magnesia Caustic |
|
Organic matter |
Clarification Oxidation |
Alum, aluminate Chlorine |
|
|
Adsorption |
Activated carbon |
|
Oxygen |
Degasification Reduction |
None Sulfite, hydrazine |
|
Microrganisms |
Clarification Sterilization |
Various, coagulants, coagulant aids Chlorine, sterilants, |
|
|
|
heat |
|
|
|
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