Turbidity characterises a cloudy condition in water caused by particles in suspension ( organic residues, clays, microscopic organisms, etc.. ).

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Problems for users caused by turbidity are related to acceptance.

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High turbidity allows micro-organisms to become fixed ( adsorption ) to particles in suspension: the bacteriological quality of turbid water is therefore suspect as strong turbidity can also protect micro-organisms fixed on particles from disinfection.

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Turbidity is a major constraint for chlorination, as pathogens associated with particles are protected from oxidation.

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Another concern is the formation of organochlorides that are toxic.

 

Sphere recommends turbidity below 5 NTU to enable effective chlorination.

 

Analysis to be done in situ ( recommended ) with a turbidity meter :

 

Units : 1 NTU ( Nephelometric Turbidity Unit ) = 1 JTU ( jackson TU ) = 1 FTU ( Formazin TU ).

 

WHO recommendation : < 5 NTU and < 0,1 NTU for effective disinfection.