QUALITY STANDARDS FOR DRINKING WATER

S.No.

Type of characteristics

Type of impurity

Permissible limit

Absolute maximum limit

Remarks

1

Physical

Turbidity

5

25

On silica scale

Colour

5

50

Colour number on cobalt scale

Taste and odour

1

3

Threshold odour number

2

Chemical

pH value

7 – 8.5

6.5 – 9.2

Hardness

75 mg/l

110 mg/l

Hardness expressed as CaCO₃

Total solids

500 mg/l

1500 mg/l

As per WHO standards

Magnesium and sodium

500 mg/l

1000 mg/l

As per WHO standards

Chlorides

200 mg/l

600 mg/l

As per WHO standards

Sulphates

200 mg/l

400 mg/l

As per WHO standards

Calcium

75 mg/l

200 mg/l

As per WHO standards

Zinc

5 mg/l

15 mg/l

As per WHO standards

Copper

1 mg/l

1.5 mg/l

As per WHO standards

Iron

0.3 mg/l

1.0 mg/l

As per WHO standards

Manganese

0.1 mg/l

0.2 mg/l

As per WHO standards

Arsenic

Nil

0.2 mg/l

As per WHO standards

Lead

Nil

0.1 mg/l

As per WHO standards

Selenium

Nil

0.05 mg/l

As per WHO standards

Chromium

Nil

0.05 mg/l

As per WHO standards

Phenolic compounds as phenol

0.001 mg/l

0.002 mg/l

As per WHO standards

Cynide

Nil

0.01 mg/l

As per WHO standards

Fluoride

0.5 mg/l

1.5 mg/l

As per WHO standards

Cadmium

-         

0.05 mg/l

As per WHO standards

3

Biological and micro-organic

Coliform bacteria

Nil coliform per 100 ml or MPN of B coli 1 per 100 ml

1 coliform

4

Radiological

 -emitters

Nil

1 /l

WHO standard

-emitters

Nil

10 /l

WHO standard