Industrial Water Softening plants

There are so many water treatment methods to remove the hardness of water. The popularly adopted water  treatment is the ion-exchange method.                              
Water treatment through ion-exchange is a simple and effective method and any layman can be trained to run the plant. The mechanical operation of this water treatment plant is just closing and opening of the various valves of the unit.
The temporary hardness is due to the presence of
And permanent hardness is due to
 The above salts get precipitated in alkaline medium and a turbidity will be formed. If these Calcium and Magnesium salts are converted to water soluble Sodium salts, then the precipitation will not be there. The process of changing the basic radicals viz., Ca++ and Mg++ in to Na+ is taking place in the ion–exchange type water softening plants.

Ion Exchange Water Softening Plant:
The Ion-exchange resin contains a macro molecular organic polymer called cat-ion exchange resin. Let this be RNa where R- is the resin part and Na+ is sodium radical. When hard water is passed through this resin, the Na ion replaces Ca++/Mg++ ion in water and thus the water becomes soft.

2  Ca(HCO3)2   + RNa  = NaHCO3 + RCa   (Not Balanced)
  Mg(HCO3)2  + RNa  = NaHCO3 + RMg  (Not Balanced)
  CaSO4              + RNa   = Na2SO4   + RCa   (Not Balanced)
  MgSO4            + RNa   = Na2SO4   + RMg  (Not Balanced)
When continuously water is passed through this resin, the Ca++ and Mg++ and other heavy earth metals will replace all the Na+ radical in the resin and thus the resin will become fully exhausted of Na+ ions.





Hard water does cause soap scum, clog pipes and clog boilers.
Soap scum is formed when the calcium ion binds with the soap. This causes an insoluble compound that precipitates to form the scum you see. Soap actually softens hard water by removing the Ca2+ ions from the water.
When hard water is heated, CaCO3 precipitates out, which then clogs pipes and industrial boilers. This leads to malfunction or damage and is expensive to remove.

The exhausted resin can be regenerated using a concentrated solution of common salt. During this process all the unwanted Mg++ and Ca++ ions are replaced by Na+ ions and thus the resin becomes ready for next cycle of operation.       

Standard Water Quality for dyeing -
Standard for Textile Dye House Water Supply The following lists the minimum standards which a textile dye house water supply should meet. To achieve these levels it may be necessary to pre-treat the water before it is used for wet processing or dyeing.

Standard Water Quality

Water Hardness: Total Max.

5 dH - German
6.25 U.K.
5.2 USA 
8.95 French

Suspended Solids

< 1 .0 mg/liter

Organic Load (KMNO4, absorption)

< 20 mg/liter

Solid Residues 

< 40 mg/liter

Iron (Fe)

< 0.1 mg/liter

Managanese (Mn) 

< 0.05 mg/liter

Copper (Cu) 

< 0.01 mg/liter


< 50 mg/liter

pH should be in the range    

7 - 8   (pH values should be checked using calibrated pH meters)

The water should be both odourless and colorless.


The water should be free from carbonic acid (CO2), as its presence can lead to long term machine corrosion.


Inorganic salts 

< 0.5 gram/liter

You should daily check the level of Sodium bicarbonate (NaOH3)So proper water treatment is very much essential to get rid of the unwanted salts, solids and metals to attain the above standard water quality level.

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