Calcium and magnesium carbonate and bicarbonates are the main components that cause hardness in water. Sodium salts and its chloride compounds cause briskness in water. In case of surface water, along with above components, it contains suspended solids (dirt, sand, mud and clay) and microorganisms. The need of soft water is not only permitted to household utilisation but mainly for the industries. Boilers and coolers use a large amount of water in the operation. An ideal municipal treatment system or industrial water treatment system follow the standards step of cleaning water and remove hardness of water:
- Sedimentation (clarification, precipitation, settling)
- Filtration (ultra/membrane processes)
- coagulation and flocculation (removal of colloidal particles by lime-soda processes)
- Ion exchange (water softening process)
The ionic components effectively removed by ion exchange technology. Resins (synthetic organic polymeric) with strong cationic and anionic properties are suitable for removing the hardness causing substances from raw water.
Important properties considered for selection of resin:
- Regeneration capability of resins
- Stabilities and life of the operation
Refinery industries and thermal or nuclear power plants use ion-exchange columns, to handle the large quantity of water for softening and deionization. They mainly use it for boiler operation to produce steam. Ion exchange columns in practice designed to operate in combination with activated charcoal purification system.
With a simple diagram, the ion exchanger setup displaced here to show the flow of raw water stream, effluent and soft water streams. Pipeline connections displayed to the ion exchange tank to perform a cyclic process of softening and regeneration periodically. Backwash operation practised regenerating the resin using NaCl for cation ion exchanger, which we see in the diagram. Automatic control value performs the backwash, salt entry and rinsing operation with a sequential order by closing and opening the inlet and outlet value of the ion exchange unit.
Flow diagram of equipments arrangement based on ion exchange technology: