Hi Muhamad You need to know ...

Hi Muhamad

You need to know the final use of the treated water. Sometimes you need a residual concentration of disinfectant to ensure microbial inactivation. For example, if you need to supply  drinking water to a big city or you have a long time of storage for water, chlorine is an economic option for disinfection, because the residual concentration belongs in the time, the disvantage of chlorine is toxical subproducts and bad taste of water. Ozonation is a good option for disinfection and chemical oxidation treatment, the disvantage of ozone is the expensive cost and the short time of residual concentration, due to the ozone is an unestable molecule, the ozone needs to be produced in situ