Dm & Mb Plant

The filtered raw water, when passed through a two bed DM plant, cation resins exchange all cations in water and the salts are converted to respective acids. This acidic water is passed through the anion resins, which exchanges the anions and the pure water is achieved.
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The reaction of the units can be shown as under :

CaSO4 + R ( H ) = R ( Ca ) + H2SO4 --- Cation service cycle
H2SO4 + R ( OH ) = R ( SO4 ) + H2O --- Anion service cycle
R ( Ca ) + Hcl = R ( H ) + Cacl2 --- Cation regeneration
R ( SO4 ) + NaOH = R ( OH ) + Na2SO4 --- Anion regeneration

The water coming out of anion unit generally has following treated water quality :

Hardness: Nil
Conductivity: Less than 40 microsiemens
pH: 7.5 to 9.0
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The two bed DM plant generally consists of two pressure vessels for accommodating cation and anion resins, nest of valves or multiport valve, piping, chemical tanks, testing kit and conductivity meter.
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If the alkalinity in raw water is more, then the degasser tower is used to mechanically remove the alkalinity. This is done by passing the water after cation unit into the tower filled with media and the air is passed by using the blower, so that the water is scrubbed by air and the free carbon dioxide is removed through the vent resulting into alkalinity reduction at the outlet. This considerably reduces the ionic load on the DM plant. However, the cost of tower, sump and SS pump gets added into the system consuming more space & capital cost.