For the production of WPU, one must always start with potable water according to WHO, the purification of the water to obtain potable water depends on the source of raw feed water for the system (or local regulations). The feed water available for the production of pharmaceutical waters usually contains different concentrations of solids in suspension and contaminants which must be removed before feeding the various items of equipment for pure water production. These contaminants or compounds are usually oxides of iron and manganese, calcium, magnesium, solids in suspension of various sizes, soluble salts, organic compounds, and so forth.
The retention devices commonly used in pre-treatment are:
- Multimedia filters
- Duplex softeners
- Particulate filters
- Dosing of chlorine, NaOH, metabisulphite.