Removal of Permanent Hardness, Softening Of Water:

Water softening treatment is to be given to water for the removal of permanent hardness. Removes calcium & magnesium salts, the precipitate from water & collect on the piping in the boiler. Softening methods are –

(I) Lime Soda Process:

Zeolite is manmade plastic resin that chemically form a loose bond with chloring & has an infinity to calcium & magnesium. Zeolite releases its chlorine & sodium & attracts calcium & magnesium to complete the chemical reaction.


It release water in the form of steam sodium ions from the Zeolite replace the calcium & magnesium in hot water salt is replaced with soft water salt containing very low amount of sodium chlorite or table salt & resulting safe water does not taste salty when the Zeolite has absorbed all the hard water, salts it can hold & softening stops.

The system must be re-charged with chlorine when sodium present in Zeolite is exhausted (Solution of salt is passed through Zeolite). The latest type of ball-valve is designed to prevent any possible contamination of the water supply in the cistern.

The ball-valve should be adjusted to make it close at the required water level in the cistern and should be fixed securely to the cistern.

The ball-valve should undergo regular maintenance because, like taps, it will be in constant use. The washer or diaphragm may require replacement. The float should be checked for buoyancy and the point at which it closes should correspond with the water level in the cistern.



(i) Sludge is not formed (ii) Unit is compact

(iii) Process is automatic (iv) It removes hardness completely.

Demineralization/Deionization/Ion Exchange Process:


The hard water is passed first through Caution exchange column then. It is passed through an ion exchange column. Water is freed of the dissolved salts Dematerialized water does not contain any ion.

Advantage – The process can be used to soft highly acidic or alkalens water.

It produces water of 2 ppm hardness

Disadvantage –


(i) -The equipment is costly

(ii) More expensive chemicals are need for this method. If water contains turbidity then the output is reduced.

(II) Zeolite:

Is compound of aluminum, sili & soda? It has got excellent property of inter changeable. It is used to remove calcium & magnesium salts.


Sodium chloride is mixed with water & passed through the Zeolite bed & chemical reaction is reversed driving off the loosely held calcium & magnesium salts & replacing with the chlorine again. Waste water is discharged to the drainage system. The Zeolite process carried out in pressure type fitters with a layer of Zeolites change Zeolite are of two types:-

(1) Natural Zeolite nonporous Natrolite durable green

(2) Synthetic Zeolite Porous gel structure.

Soft Water:


Ca (HC03) 2 + Na2 Ze- CaZe + 2 Na H C03 CaS04 + Na2 Ze-^CaZe + Na2 S04 Mg Cl2 + Na2Ze – MgZe + 2NaCl Mg (N03)2 + Ze -» MgZe + 2 NaNO,


CaZe + 2NaCl-» Na2 Ze + Ca Cl2 Mg Ze +2 Na CI Na,Ze + Mg CI Advantages –

(a) Sludge is not formed.

(b) Unit is compact.

(c) Process is automatic

(d) It removes hardness completely.

(e) It is quite clean.

(f) It requires less time

(g) It requires fewer skills.

Disadvantages –

(a) It cannot be used for highly turbid water

(b) It is unsuitable for water containing iron & manganese.

(c) Treated water contains more sodium salt.

(d) It leaves acidic ions.

(e) It cannot be cured for water containing mineral acids: