The Water Softening process is primarily designed to remove calcium ions from the water. The calcium in the water causes scale in water heaters and plumbing, develops soap scum and creates unwanted precipitates. The resin that is used for this process will also remove magnesium, ferrous (clear) iron, and traces of metals such as copper, aluminum, zinc and radium. During the removal process these metal ions are replaced or exchanged for potassium if potassium chloride is used as a regenerating chemical or sodium if sodium chloride is used. By their nature, neither potassium nor sodium will cause scale, interfere with soap or normally create precipitates.
When a water softener regenerates it goes through four steps: backwash, brine draw, slow rinse and rapid rinse. The backwash discharge is the same as the incoming water, the brine draw and slow rinse waters contain the ions removed during the process, plus some sodium or potassium, and are high in chlorides. The rapid rinse water is softened water.
One should know the chemistry of the water to be softened as well as the application (laundry, boiler feed, process water, etc..) in able to fine tune the design to lower salt use, reduce pressure drop, regenerate using the least amount of water and lower system cost. |
