• Quality of water is determined by its physical, chemical and biological parameters.

I. Physical parameters of water quality

1. Color: The guideline value (maximum acceptable level) for color of drinking water is 15 TCU (True color unit).
2. Turbidity: Drinking water should have turbidity less than 5 NTU (Naphthalometric turbidity unit)
3. Taste and odor: Pure water is always tasteless and odorless. Therefore if any types of taste and odor is present, it indicates water pollution.
4. Temperature: There is no guideline value for temperature for drinking water.
5. Foam
6. Conductivity
7. Total dissolved solid (TDS): TDS should not exceeds 300mg/ltr

II. Chemical parameters of water quality

1. Chloride ion: Maximum permissible limit of chloride ion in drinking water is 200mg/ ltr.
2. Ammonia: Concentration of NH3 in ground water system is usually 3mg/ltr. If its concentration is greater than 50mg/ltr, it gives characteristic taste and odor.
3. Nitrite: Level of nitrite in drinking water should not exceed 3mg/ltr.
4. Nitrate: It is most stable oxidized form of nitrogen. Like nitrite Nitrate should not exceed 3mg/ltr in drinking water.
5. Phosphate
6. Hardness: Water is classified as 9on the basis of concentration of calcium carbonate)
   • Soft water:<5omg/ltr
   • Moderately hard water: 50-150 mg/ltr
   • Hard water: 150-300 mg/ltr
   • Very hard water:>300 mg/dl

7. Biological oxygen demand (BOD)
8. Chemical oxygen demand (COD)
9. Dissolved oxygen (DO)
10. pH: pH of drinking water; 6.5-8.5

III. Biological parameters of water quality

1. Bacteriological aspects of water pollution
2. Viral aspects of water pollution
3. Parasitological aspects of water pollution
4. Algae

Water quality criteria/ Parameter of water quality

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