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Water Supplies Disinfection with Chlorination

Chlorine is a supplement and not a substitute to sand filtration
-It kills pathogenic bacteria
-But has no effect on spores and certain viruses (e.g. polio, viral hepatitis) except in high doses
In addition to being germicidal, it has other properties
-Oxidizes iron, manganese and hydrogen sulphide
-It destroys some taste and odour producing constituents
-It controls algae and slime organisms and aids coagulation
How does chlorine act as disinfectant?
When chlorine is added to water, it forms:
-Hydrochloric acid (HCl) and
-Hypochlorous acid (HOCl)
-HCL neutralizes the alkalinity of the water.
-The Hypochlorous acid ionizes to form hydrogen ions and hypochlorite ions (H^+, 〖OCl〗^-)
The disinfecting action is due to:
-hypochlorous acid and
-to some extent, due to hypochlorite ions
Chlorine disinfects best when the pH of water is around 7
-When the pH value exceeds 8.5, it is unreliable as a disinfectant (as 90% of the hypochlorous acid gets ionized to hypochlorite ions)
Fortunately, most waters have a pH value of 6 – 7.5

OT and OTA test:

Membrane processes in water purification:

Super Chlorination and Break Point Chlorination:

Slow sand filter:

Rapid sand filter:

Purification of water at a large scale:

Criteria for a Chemical to be Suitable as Water Disinfectant in Water Supplies:

Water Supplies Disinfection with Chlorination:

Principles of Chlorination:

Methods of Chlorination in Water Supplies:

Horrock's Apparatus:

Disinfection of well during emergency:

Double Pot method:

Disinfection of Wells:

OT and OTA test:

Domestic or Household Purification of Water: