Which is the most cheapest, efficient and medically safe method of industrial portable drinking water production you know? (Give reasons)

Chlorination Method

Its the most efficient method of making free chlorine available to raw water,therefore inhibiting bacterial attack

Techniques include heat , filtration, chemical disinfection e.g. chlorine, iodine, ozone. ultraviolet purification , distillation.

with the modern laboratoire . but i don't know what exactly do for it