Hard water can cause scaling problems in water heaters and soap does not lather well in hard water. Therefore, some water utilities often water to improve its quality for domestic use. Lime softening is best suited to groundwater sources, which have relatively stable water quality. The combination of variable source water quality and the complexity of the chemistry of lime softening may make lime softening too complex for small systems that use surface water sources.
The water to be softened by flowing a resin filling in a pressure tank (bottle softening). The hardnessforming calcium and magnesium ions are absorbed by the resin and "soft" sodium ions are released into the water. Therefore, we speak of an ion exchange process. The previously hard water by replacing the hardness components to soft water. If the exchange capacity is exhausted, the resin with concentrated sodium chloride solution must be regenerated. During the regeneration, the resin takes sodium ions and releases the previously accumulated calcium and magnesium ions to the rinsing water. This rinse water is correspondingly hard and is usually discarded.
Softened water has high causticity and scale-formation potential; hence, recarbonation is employed to reduce pH and mitigate scaling of downstream processes and pipelines. Onsite combustion generation of carbon dioxide (CO2) or liquid CO2 is the most common source of carbon dioxide for recarbonation.