Hardness fouling occurs when calcium sulfate (\(CaSO_{4}\)) precipitates in the resin bed of an ion exchange system.
This can cause the resin to become saturated with calcium ions, which can lead to high leakage and short runs.
Causes
Calcium and barium: When sulfuric acid is used to regenerate the resin, it reacts with calcium and barium from the resin to form calcium sulfate.
pH changes: Changes in pH can cause precipitation.
Salt concentration: Changes in the concentration of relatively insoluble salts can cause precipitation.
Signs
The system requires more rinsing
The system becomes more sensitive to temperature and flow rate variations
The effluent quality and operating capacity decrease more quickly than expected
Solutions
Step-wise acid addition: Start with a lower acid concentration and gradually increase it to achieve good regeneration without precipitation.
Regular cleaning: Regular cleaning treatments can reduce fouling and extend resin life.
Increase regeneration temperature: Increasing the regeneration temperature can reduce fouling.
Select the right regenerant: Use a regenerant that's suitable for the resin and the water being treated.
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