Tennessee Wastewater Operator Practice Exam

What is the difference between the BOD test and the CBOD test?

1. A nitrification inhibitor is added

2. Different incubation times

3. Varied temperature conditions

4. Distinct sample dilution methods

The correct answer is: A nitrification inhibitor is added

The BOD test, or Biochemical Oxygen Demand test, measures the amount of oxygen that microorganisms will consume while decomposing organic matter in water. In standard BOD testing, the process includes the oxidation of nitrogenous compounds, which can lead to measurement of oxygen demand from both carbon and nitrogen sources. The CBOD test, or Carbonaceous Biochemical Oxygen Demand test, specifically measures oxygen demand due only to the degradation of carbonaceous material. It requires the addition of a nitrification inhibitor to the sample to suppress the activity of nitrifying bacteria. This ensures that the test primarily measures the carbonaceous component of oxygen demand without interference from nitrogenous compounds. The main difference between these two tests lies in the presence of this nitrification inhibitor in the CBOD test. By adding this inhibitor, it isolates the carbon component, allowing for a more accurate reading of the biodegradable organic matter without the complicating effects of nitrogen consumption. This distinction is essential for wastewater treatment facilities to assess the organic load accurately and optimize treatment processes.