Solution-:
In hot lime soda method at higher temperature.
The reactions are fast.
Precipitation is more complete.
Settling rate and filtration rates are increased. As a result the precipitate and sludge formed settle rapidly and coagulants and also chemicals needed are in smaller quantities than that of cold L-S process.
Dissolved gases are eliminated from water to a certain extent.
The softened water recovered has hardness of about 15 to 30 ppm
Advantages-:
It is very economical process.
Less amount of coagulants are required.
Certain quantity of minerals is reduced from water.
The level of carbon dioxide can also be reduced using hot L-S Process.
Fe and Mn are also removed from the water.
The process increases the PH value of the treated water thereby corrosion of the distribution pipes is reduced.
Disdvantages-:
Sludge disposal is problem.
This can remove hardness only up to 15 ppm, which is not good for boilers.
Careful operations and skilled supervision are required for economical and efficient softening.