Please tell me the reason of decreasing the pH of water. First day it will stable around 6-7 and next day suddenly pH will decrease to 4.
And also tell me how to control it.

During regeneration of DM water plant HCL used in large volume in comparison with NaOH.

pH will change time to time you can not control it because acid and base are contineuously used in treatment of water.

When CO2 dissolves in water it produces H2CO3 (carbonic acid) that is the main cause of the decrease in pH of water. You can store the water in a closed container to prevent this formation.

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Hello sir.
When the plant is continuous even then the same issue in pH is observed. In a continuous process what is the possibility of inclusion of CO2 into the stream of water??

Regeneration of Cation Filter as per your monograph. Before regeneration you have to backwash the cation filter for 15 min. after that rinse for 5 min then after starts the regeneration process as per your procedure. after completion of regeneration only rinse up-to coming of pH 4. Routinely only rinse the cation filter for 5 min never backwash. and same procedure for anion filter , rinse the after regeneration of anion fltre after reaching pH-7…

Executive Production
Karnataka Antibiotics and Pharmaceuticals Limited

During regeneration process of softer by using HCL then not sufficient Rinse of water then water come out to softer belong <5 pH

Softner Regeneration always done by NaCl rather than HCl.

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The reason is that DM water dissolves carbon dioxide from the air. It dissolves carbon dioxide until it is in dynamic equilibrium with the atmosphere. That means that the amount being dissolved balances the amount coming out of solution. The total amount in the water is determined by the concentration in the atmosphere. The dissolved carbon dioxide reacts with the water and finally forms carbonic acid.
2 H2O + CO2 --> H2O + H2CO3 (carbonic acid) --> (H30+) (charged acidified water) + (HCO3-) (charged bicarbonate ion)
Only recently been produced DM water has a PH value of approximately 7, but affected by the presence of carbon dioxide it will reach a slightly acidic pH-value within a couple of hours.|

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In order to prevent this, you must prevent the water from coming in contact with the air by using a nitrogen blanket or some other means.

sir i think we can use degasser to remove the CO2