Question

What are the types of chlorination?

Answer 1

We need to know that when dissolved in water, chlorine converts to an equilibrium mixture of chlorine, hypochlorous acid ($HOCl$), and hydrochloric acid ($HCl$) and $HOCl$, whereas in alkaline solution, effectively only $Cl{O^ - }$ (hypochlorite ion) is present.

Complete answer:
We need to know that it is the method of disinfection by which the microorganisms are killed if chlorine & its components are used. Chlorination serves not only for disinfection, but as an oxidant for other substances (iron, manganese, cyanide, etc) & for taste & odor control in water & wastewater. Other chemical disinfectants include chlorine dioxide, ozone, bromine, iodine. The last two chemicals are generally used for personal application, not for the public water supply. Chlorination is of three types: Plain chlorination, Pre chlorination and Post chlorination we will discuss each one by one:
Plain chlorination: In this type of chlorination, the water is chlorinated free from suspended particles without any chemical treatment.
Pre chlorination: The application of chlorine to raw water before any other treatment to improve the coagulation & to remove the taste, odor, & color
Post Chlorination: Application of chlorine to treated water after all the other treatment. Dosage chlorine ranges from $0.25 - 5.0mg/lit$ in order to obtain the combined residual chlorine in range of$0.1 - 0.2mg/lit$.

Note:
These are different types of chlorination: simple chlorination, super-chlorination followed by dechlorination, and shock chlorination. In simple chlorination, the residual should be measured at the faucet farthest from the chlorine source. In super chlorination, Super-chlorinated water has a strong chlorine smell and taste that is removed with an activated carbon filter following chlorine treatment.