Question

5. Discuss some of the most common methods of Water Disinfection with their merits, and demerits.

Answer 1

The most common methods of Water Disinfection are -

1) Chlorination => Chlorination is defined as the process of mixing chlorine in the water to disinfect it and kill the microorganisms. Chlorine is generally available as compressed gas, solid calcium hypochlorite (Ca(OCl)2 or sodium hypochlorite solution (NaOCl) . Chlorine kills microorganisms by breaking the chemical bonds in their molecules. Disinfectants that are used for this purpose consist of chlorine compounds which could exchange atoms with other compounds, like enzymes in bacteria and different cells. When enzymes come in contact with chlorine, more than one of hydrogen atoms in the molecule replaced by chlorine. This leads to the killing of microorganisms.

Merits of chlorination -

=> Economical to use .

=> Effective in killing microorganisms.

=> Residual to kill the later infection in water.

=> Easy to use .

Demerits of chlorination -

=> Less effective in turbid water .

=> Effects the taste and odour of water .

=> Less effective in case of protozoa.

2) U. V method ( ultraviolet radiation method)

=> In this method the ultraviolet radiation deactivates the microorganisms through physical process . When the microorganisms are exposed to the germicidal wavelength of U.V lught , they makes the pathogens inactive.

Merits -

=> Not toxic to the water .

=> No taste and odour problem.

=> Effective in killing microorganisms.

Demerits -

=> It requires skilled labour handling.

=> No disinfectant residual.

=> Difficulty in determining dosage .

3) Ozonation -

Ozonation is a method of oxidising the microorganisms , that leds to the destruction of pathogens . The ozone is said to be a very good oxidant . When it is exposed to microorganisms the nascent oxygen works as the oxidising agent.

Merits -

=> Effective in killing microorganisms.

=> No odour and taste problem.

Demerits -

=> No residual.

=> Costly process .