Table 10: Potable water quality standards as recommended by the WHO (in mg/litre)
|
Parameter
|
Class A: maximum permissible
limit
|
Class B: maximum allowable
limit
|
Indian Standards: 10500
(1991)
|
|
Physical parameters
Colour (hazen) |
5.0
|
25.0
|
5.0
|
|
Turbidity (NTU)
|
5.0
|
25.0
|
5.0
|
|
pH
|
7.0-8.5
|
6.5-9.2
|
6.5-8.5
|
|
Temperature (°C)
|
--
|
--
|
--
|
|
Conductivity (µ/cm)
|
--
|
--
|
--
|
|
Total dissolved
solids
|
--
|
--
|
--
|
|
Total suspended
solids
|
--
|
--
|
--
|
|
Total solids
|
500.00
|
1500.0
|
500.0
|
|
Chemical parameters
Total hardness |
--
|
--
|
300.0
|
|
Calcium as calcium
carbonate
|
175.0
|
500.0
|
75.0
|
|
Magnesium as calcium
carbonate
|
215.0
|
650.0
|
30.0
|
|
Acidity
|
--
|
--
|
--
|
|
Alkalinity as
calcium carbonate
|
--
|
--
|
200.0
|
|
Bicarbonate as
calcium carbonate
|
--
|
--
|
--
|
|
Carbonate as calcium
carbonate
|
--
|
--
|
--
|
|
Hydroxide as calcium
carbonate
|
--
|
--
|
--
|
|
Chlorides as chlorine
|
--
|
--
|
250.0
|
|
Total residual
chlorine
|
--
|
--
|
--
|
|
Sulphates
|
200.0
|
400.0
|
200.0
|
|
Fluorides
|
0.5
|
1.0-1.5
|
1.0
|
|
Phenol
|
0
|
0
|
0
|
|
Manganese
|
0.1
|
0.5
|
0.1
|
| Silica |
--
|
--
|
--
|
| Sodium |
--
|
--
|
--
|
| Potassium |
--
|
--
|
--
|
| Organic and nutrient parameters |
--
|
--
|
--
|
| Dissolved oxygen |
--
|
--
|
--
|
| Biological oxygen demand |
--
|
--
|
--
|
| Chemical oxygen demand |
--
|
--
|
--
|
| Phosphates |
--
|
--
|
--
|
| Mercury |
--
|
--
|
--
|
| Oil and grease |
--
|
--
|
--
|
| Ammoniacal nitrogen |
--
|
--
|
--
|
| Nitrates |
--
|
50.0-100.0
|
45.0
|
| Nitrites |
--
|
--
|
--
|
| Heavy
metals Iron |
0.3 |
1.0 |
0.3 |
| Chromium |
--
|
0.1
|
0.1
|
| Boron |
--
|
--
|
1.0
|
| Zinc |
--
|
--
|
5.0
|
| Copper |
1.0
|
1.5
|
1.5
|
| Lead |
--
|
0.1
|
0.1
|
Source: 1. WHO 1986. WHO Handbook. Geneva:
World Health Organisation 2. ISI 1991. Indian Standards (IS:10500). New Delhi:
Indian Standards Institute.