QUALITY REQUIREMENTS OF DRINKING WATER

Quality Requirements of Drinking Water

Parameter Requirements (Desirable Limits) Undesirable effect when outside permissible limit Permissible limit in the absence of alternate source

ESSENTIAL CHARACTERISTIC

pH 6.5 – 8.5 Beyond this range the water will affect the mucous membrane and/or water supply system No relaxation
Colour (Hazen units), maximum 6.5 – 8.5 Above 5, consumer acceptance decreases 25
Odour Unobjectionable    
Taste Agreeable    
Turbidity, NTU, Max 5 Above 5, consumer acceptance decreases 10
Total hardness (as CaCO3), Max 300 mg/L Encrustation in water supply structure and adverse effects on domestic use 600 mg/L
Iron (as Fe), Max 0.30 mg/L Beyond this limit taste/appearance are affected, has adverse effect on domestic uses and water supply structures, and promotes iron bacteria 1.0 mg/L
Chlorides as Cl, Max 250 mg/L Beyond this limit taste, corrosion and palatability are effected 1000 mg/L
Residual free chlorine, Min 0.20 mg/L    

DESIRABLE CHARACTERISTICS

Dissolved solids, Max 500 mg/l Beyond this, palatability decreases and may cause gastro intenstinal irritation 2000 mg/l
Calcium (as Ca), Max 75 mg/l Encrustation in water supply structure and adverse effects on domestic use 200 mg/l
Magnesium (as Mg), Max 30 mg/l   100 mg/l
Copper (as Cu), Max 0.05 mg/l Astringent taste,

discoloration and

corrosion of pipes,

fitting and utensils

will be caused

beyond this

1.5 mg/l
Manganese (as

Mn), Max

0.1 mg/l Beyond this limit

taste/appearance

are affected, has

adverse effect on

domestic uses and

water supply

structures

0.3 mg/l
Sulphate (as

SO4), Max

200 mg/l Beyond this causes

gastro intenstinal

irritation when

magnesium o

400 mg/l
Nitrates as NO3 45 mg/l Beyond this methane-moglobinemia takes place 100 mg/l
Fluoride, Max 1.0 mg/l Fluoride may be kept as low as possible. High fluoride may cause fluorosis 1.5 mg/l
Alkalinity, Max 200 mg/l Beyond this limit taste becomes unpleasant 600 mg/l

 

Reference

IS: 10500 – 1992 – DRINKING WATER [SPECIFICATION]

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