California Wastewater Treatment Operator Practice Exam

What is one of the requirements for a BOD test?

1. The BOD bottle should be completely filled to the top

2. The BOD sample should be diluted with tap water

3. The BOD test should be conducted in direct sunlight

4. The BOD bottle should be left partially filled for accurate results

The correct answer is: The BOD bottle should be completely filled to the top

The requirement for a BOD test to be effective is that the BOD bottle should be completely filled to the top. This practice is essential because it prevents any air from being trapped in the bottle, which could lead to inaccurate measurements of the biochemical oxygen demand. An air gap can introduce variability and negatively impact the results, as oxygen in the air can be taken up by microorganisms in the sample, thereby skewing the data. In contrast, diluting the BOD sample with tap water is not appropriate because it can alter the concentration of organic material present in the sample, thus affecting the test results. Conducting the BOD test in direct sunlight is also unsuitable, as it can increase temperature and influence microbial activity, leading to inconsistent results. Leaving the BOD bottle partially filled would similarly compromise the test, since trapped air can again affect the oxygen levels and lead to inaccurate readings. These considerations highlight why a fully filled BOD bottle is crucial for accurate and reliable BOD test results.