Water Softening


Methods of Removing of Temporary Hardness

  1. Boiling Ca(HCO_{3}){2} + Heat \longrightarrow CaCO{3} \downarrow + CO_{2} \uparrow + H_{2}O
  2. Addition of Lime MgCO_{3} + Ca(OH)_2 \longrightarrow Mg(O_2) \downarrow + CaCO_3 \downarrow  Mg(HCO_3)_2 + Ca(OH)_2 \longrightarrow Ca(HCO_3)_2 + Mg(OH)_2\downarrow  Ca(HCO_3)_2 + Ca(OH)_2 \longrightarrow 2CaCO_3 \downarrow + 2H_2O

Method of Removing Permanents Hardness

(i) Lime – soda process  (a) \:Ca(HCO_3)_2 + Ca(OH)_2 \longrightarrow 2CaCO_3 \downarrow + 2H_2O

 (b)\: (i) \:Mg(HCO_3)_2 + Ca(OH)_2 \longrightarrow CCa(HCO_3)_2 + Mg(OH)_2\downarrow  (ii) \:MgCO_3 + Ca(OH)_2 \longrightarrow Mg(OH)_2 + CaCO_3 \downarrow

 (C) \:MgCl_2 + Ca(OH)_2 \longrightarrow Mg(OH)_2 \downarrow +\: CaCl_2

 (d)\: MgSO_4 + Ca(OH)_2 \longrightarrow Mg(OH)_2 \downarrow +\: CaSO_4

 (e)\: CO_2 + Ca(OH)_2 \longrightarrow CaCO_3 \downarrow +\: H_2O

 (f)\: CaCl_2 + Na_2CO_3 \longrightarrow CaCO_3 \downarrow +\: 2NaCl

 (g)\: CaSO_4 + Na_2CO_3 \longrightarrow CaCO_3 +\: Na_2SO_4

  • Lime removes the entire carbonate hardness
  • The lime reacts with a non-carbonate hardness of magnesium to convert the non-carbonate hardness of calcium
  • Non Carbonate hardness of Calcium is further removed by Soda Ash
  • Dry Sluge produced in mg/l= Ca removed+0.58 Mg removed + Lime added

(ii) Zeolite or Base Exchange or Cation

 Na_2Z\: + CaMg \begin{cases} (HCO_3)_2 \SO_4 \Cl_2 \end {cases} \longrightarrow Na_2 \begin{cases} (HCO_3)_2 \SO_4 \Cl_2 \end {cases} + \: CaMg [Z

 CaMg ]Z + 2NaCl \longrightarrow Na_2Z +\: CaMg] Cl_2

  • This process is very effective and can produce zero hardness
  • No sludge is formed
  • Zeolite is a natural or synthetic cation o base exchange hydrated silicates of sodium and aluminum. Also called Green Sand.


When water consists of an extensive amount of calcium and magnesium, it’s far known as hard water. Hard water is understood to clog pipes and to complicate cleaning soap and detergent dissolving in water. Water softening is a method that serves the elimination of the ions that purpose the water to be hard, in maximum calcium and magnesium ions. Iron ions can also be eliminated at some point of softening. The fine manner to meltwater is to apply a water softener unit and join it immediately to the water supply. A water softener is a unit this is used to meltwater, by eliminating the minerals that reason the water to be tough. Water softening is a vital process, due to the fact the hardness of the water in families and businesses has decreased at some point in this process. When water is tough, it may clog pipes, and cleaning soap will dissolve in it much less easily. Water softening can save youth terrible consequences. Hard water reasons a better hazard of limescale deposits in family water systems. Due to this limescale build-up, pipes are blocked and the performance of warm boilers and tanks is decreased. This will increase the price of home water heating by approximately fifteen to 20 percent. Another terrible impact of limescale is that it has detrimental consequences on family machinery, inclusive of laundry machines. Water softening approach increasing the lifestyles span of the family machine, inclusive of laundry machines, and the lifestyles span of pipelines. It additionally contributes to the progressed working, and longer lifespan of solar heating systems, air-con devices, and plenty of different water-primarily based totally applications.

Water softeners are precise ion exchangers that are designed to eliminate ions, which can be undoubtedly charged. Softeners particularly eliminate calcium (Ca2+) and magnesium (Mg2+) ions. Calcium and magnesium are frequently stated as ‘hardness minerals’.Softeners are every now and then even carried out to eliminate iron. The softening gadgets are capable of eliminating as much as 5 milligrams in step with a liter (five mg/L) of dissolved iron. Softeners can function automatic, semi-automatic, or manual. Each kind is rated on the quantity of hardness it may eliminate earlier than regeneration is necessary. A water softener collects hardness minerals inside its conditioning tank and every now and then flushes them away to drain. Ion exchangers are frequently used for water softening. When an ion exchanger is carried out for water softening, it’ll update the calcium and magnesium ions withinside the water with different ions, for instance, sodium or potassium. The exchanger ions are brought to the ion exchanger reservoir as sodium and potassium salts (NaCl and KCl).

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