Calculate the BOD for a sample volume of 15 mL with an initial DO of 8.0 mg/L and a DO of 4.0 mg/L after 5 days incubation.

To calculate the Biochemical Oxygen Demand (BOD), you need to determine the amount of dissolved oxygen (DO) consumed by microorganisms over the incubation period. The formula to calculate BOD is:

BOD = (DO initial - DO final) × dilution factor.

In this case, the initial DO is 8.0 mg/L and the final DO after 5 days is 4.0 mg/L. The difference in DO is:

8.0 mg/L - 4.0 mg/L = 4.0 mg/L.

Since the volume of the sample is 15 mL, to find the dilution factor, you typically express the sample in terms of a standard volume, usually in liters. Since the sample volume is 15 mL, the dilution factor is:

Dilution Factor = (total volume of the diluted BOD sample)/(volume of the sample).

If the sample is analyzed without further dilution and we consider the analysis performed on the 15 mL sample, the dilution factor in a standard calculation (for a 300 mL bottle) would lead to the assumption that all 15 mL was used in a larger volume (300 mL for example), but without further information, we simply calculate based on the