The following observations were made on 2% dilution of wastewater:
Dissolved oxygen of aerated water used for dilution = 0 mg/l
Dissolved oxygen of diluted sample after 5 days = 0.6 mg/l
Dissolved oxygen of original sample = 2.0 mg/l
The BOD of 5 days of the sample is:
1
80 mg/l
2
60 mg/l
3
100 mg/l
4
50 mg/l
5
70 mg/l