The test consists in taking the given sample in suitable concentrations in dilute water in B.O.D. bottles. Two bottles are taken for each concentration and three concentrations are used for each sample. One set of bottles is incubated in a B.O.D. incubator for 5 days at 20°C; the dissolved oxygen (initial) content (D1) in the other set of bottles will be determined immediately. At the end of 5 days, the dissolved oxygen content (D2) in the incubated set of bottles is determined.
P = decimal fraction of sample used.
D1 = dissolved oxygen of diluted sample (mg/L), immediately after preparation.
D2 = dissolved oxygen of diluted sample (mg/L), at the end of 5 days incubation.
Among the three values of B.O.D. obtained for a sample select that dilution showing the residual dissolved oxygen of at least 1 mg/L and a depletion of at least 2 mg/L. If two or more dilutions are showing the same condition then select the B.O.D. value obtained by that dilution in which the maximum dissolved oxygen depletion is obtained.
D1 = Initial Dissolved Oxygen = ...... mg/L
D2 = Dissolved Oxygen at the end of 5 days = ...... mg/L
P = Decimal fraction of sample used = ......
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