Tennessee Wastewater Operator Practice Exam

When heterotrophic bacteria consume CBOD in the presence of oxygen, what are the byproducts?

1. Oxygen and nitrogen

2. Ammonia and methane

3. Carbon dioxide and water

4. Hydrogen and sulfur compounds

The correct answer is: Carbon dioxide and water

When heterotrophic bacteria decompose carbonaceous biochemical oxygen demand (CBOD) in the presence of oxygen, the primary byproducts of this metabolic process are carbon dioxide and water. This occurs through aerobic respiration, where bacteria utilize organic materials for energy. In this process, they convert organic compounds into energy-rich molecules while releasing carbon dioxide as a gaseous byproduct, which is an essential component of the carbon cycle, and water, which is a vital substance for all forms of life. The availability of oxygen is crucial in this context, as it allows for efficient energy extraction from the organic materials. The carbon dioxide produced can be released into the atmosphere or captured by other organisms, such as plants, during photosynthesis. The water produced is typically released as part of the metabolic processes, maintaining cellular functions and contributing to the overall hydration of the environment. While the other choices mention various substances, they do not accurately represent the primary metabolic products when heterotrophic bacteria consume CBOD under aerobic conditions.