Correct Answer - Option 1 :
Nil
Concept:
The biochemical oxygen demand of safe drinking water is zero.
BOD represents the amount of biodegradable organic matter present in water. It also indicates the amount of treatment required for purifying. If the BOD is high the extent of treatment required will be high.
Hence, there should not be any BOD in safe drinking water.
The permissible limits of various compounds are as follows:
|
Parameters
|
Permissible
Limit
|
Cause for
rejection
|
|
Total suspended solids
|
500
|
2000
|
|
Turbidity (NTU)
|
1
|
10
|
|
Colour (TCU)
|
5
|
25
|
|
Taste & odour (TON)
|
1
|
3
|
|
Total dissolved solids (mg)
|
500
|
2000
|
|
Alkalinity
|
200
|
600
|
|
pH
|
7 - 8.5
|
<6.5 & > 9.2
|
|
Hardness (mg/L)
|
200
|
600
|
|
Chloride content (mg/L)
|
250
|
1000
|
|
Free ammonia (mg/L)
|
0.15
|
0.15
|
|
Organic ammonia (mg/L)
|
0.3
|
0.3
|
|
Nitrite (mg/L)
|
0
|
0
|
|
Nitrate (mg/L)
|
45
|
45
|
|
Fluoride content (mg/L)
|
1
|
1.5
|
|
Iron as Fe (mg/L)
|
0.1
|
1.0
|
|
Sulphate (mg/L)
|
200
|
400
|
|
Calcium (mg/L)
|
75
|
200
|
