Basic Wastewater Operator Practice Exam

What is the standard volume for a BOD sample bottle?

1. 150 mL

2. 200 mL

3. 300 mL

4. 500 mL

The correct answer is: 300 mL

The standard volume for a BOD (Biochemical Oxygen Demand) sample bottle is typically 300 mL. This volume is utilized in biochemical testing to ensure that the sample can accurately reflect the oxygen demand of the water sample during incubation. A 300 mL bottle allows for sufficient headspace to accommodate the potential changes in gas concentrations that occur during the incubation period, while also providing enough volume to conduct reliable measurements after five days. Using a proper volume is important in maintaining the validity of the test results because smaller volumes might not capture the totality of the organic matter present, while larger bottles might inadvertently introduce errors due to the different surface area to volume ratios affecting gas exchange. Thus, the 300 mL standard is widely accepted in laboratory practices when measuring BOD to ensure consistency and reliability in the results.