The raw water is pumped from above to a sand filter. Solids are captured and retained as raw water flows through the filter bed. The filtered water emerges from the lower end of the sand filter and then flows through two ion exchangers (cation and anion exchangers). In the process, unwanted ions are exchanged for hydrogen and hydroxide ions. The raw water is softened and desalinated. The sand filter and the two ion exchangers can be used in combination or separately. Solids deposited in the sand filter result in increased pressure loss. Backwashing cleans the filter bed and reduces pressure loss. Ion exchangers can be regenerated with acid or caustic.

Code: CE 582