Chlorine removal chemical is often used as pre-treatment to large RO systems for free chlorine removal and as a biostatic. Carbon filters are a common alternative for small systems, but Chlorine removal chemicals have the advantage for larger systems due to a lower risk of bacteria growth that can cause biological fouling. 

Chlorine levels in the RO/NF feed should be monitored continuously to prevent chlorine passing into the RO/NF system. Chlorine removal chemicals are commercially available as a solid or liquid and in various % purities, typically up to 99%.