QUALITY STANDARDS FOR DRINKING WATER

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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

 

WATER BORNE DISEASES

Water borne diseases are those which spread primarily through contaminated water.

(1) Disease caused by bacterial infections

1. Typhoid fever and paratyphoid fever – caused by salmonella typhi bacteria
2. Cholera – caused by vibrio-cholera bacteria
3. Bacillary dysentery – caused by shiga bacillus or Flexner bacillus

(2) Disease caused by viral infections

1. Infectious hepatitis or infectious jaundice – caused by hepatitis virus
2. Poliomyelitis – caused by polio virus
3. Gastroenteritis

(3) Disease caused by protozoal infections

Amoebic dysentery – caused by entamoeba histolytic germ