natural activation 4 stage UF water purifier(water purifier,UF water purifier,water softener) natural activationThey are 4 stages.Stage 1: Sediment filter removes suspended impurities from inlet water. Stage 2: Metallic ion exchange filterThis patented high precision ion exchange can effectively remove chlorine and heavy metals as lead, mercury, arsenic,cadmium, zinc, manganese, selenium, iron, ...