Breakpoint chlorination/Disinfection method in drinking water treatment

It describes the breakpoint chlorination in water treatment using the graph. It lists the disinfection methods. It explains the free residual chlorine, combined chlorine and total residual chlorine. It speaks about chlorine shock in pools. The graph of break point chlorination is explained.
Break point chlorination/Disinfection in Drinking water treatment
You will be able to
enumerate the various disinfection methods
explain combined and free residual chlorine
define the break point chlorination.
Rivers, ponds, dams, reservoirs, flood and storm run-offs
Should be free from odour, colour and taste
Should be free from dissolved objectionable gases
Should be slightly alkaline (pH about 8.0)
TDS should be less than 500ppm.
Should be free from toxic impurities.
Should not be turbid.
Should be free from pathogens such as bacteria, virus, protozoa etc.
Floating matter –paper, cloth, twigs, logs, leaves, fish, plastic waste etc.
Suspended particles –sand, silt etc.
Colloidal particles –fine particles, clay etc.
Microorganisms –bacteria, virus, protozoa etc.
Destroys the pathogens (disease causing microorganisms)
Methods of disinfection
Chlorination – bleaching powder, chloramines or liquid/gas chlorine

Ozone treatment –
Ultraviolet (UV) light – 254 nm UV light damages the RNA and DNA of the microorganisms. Destroys chemical contaminants also.
Breakpoint chlorination : It is a point where all the impurities present in the water such as reducing compounds,organic compounds and ammonia are oxidised by chlorine and the chlorine added further acts as a disinfectant to kill the pathogens.
upto A : chlorine reacts with reducing compounds – no residual chlorine
A to B : chlorine reacts with organic impurities and nitrogen compound like ammonia to form chlororganics and chloramines. (Combined chlorine residuals)
B to C : Partial destruction of chloro-organics and chloramines
C : Breakpoint chlorination – All the reducing substances, organic impurities and ammonia are oxidised and further residual chlorine acts as a disinfectant to destroy the pathogens.
Beyond C: Total residual chlorine (free and combined chlorine) – acts as a disinfectant.