Basic Wastewater Operator Practice Exam

Calculate the BOD using the given information: Initial DO: 8.3, Final DO: 5.9, Milliliters of sample used: 2

1. 360 mg/L

2. 210 mg/L

3. 856 mg/L

4. 36 mg/L

The correct answer is: 360 mg/L

To calculate the Biochemical Oxygen Demand (BOD), you can use the formula: BOD = (DO_Initial - DO_Final) x ( dilution factor ) x 1000 / volume of sample in milliliters From the information provided: - Initial Dissolved Oxygen (DO) is 8.3 mg/L. - Final Dissolved Oxygen (DO) is 5.9 mg/L. - The volume of the sample used is 2 mL. First, calculate the difference in DO, which indicates how much oxygen was consumed by microorganisms during the test: DO_Initial - DO_Final = 8.3 - 5.9 = 2.4 mg/L. Next, determine the dilution factor. Since 2 mL of the sample was used and diluted in a total volume, it's typically assumed to be in a larger volume for the calculation. However, if we consider the dilution factor as being based on a common standard practice, let's assume it represents the total volume for an example of 1 L (1000 mL). Therefore, the dilution factor would be: Dilution factor = 1000 mL / 2 mL = 500. Now, substitute these values into the BOD