Tennessee Wastewater Operator Practice Exam

In aerobic digestion, what is the main byproduct of organic matter breakdown?

1. Heat

2. Solid sludge

3. Methane

4. Carbon dioxide

The correct answer is: Carbon dioxide

In aerobic digestion, organic matter is broken down by microorganisms in the presence of oxygen. During this process, the primary byproduct formed is carbon dioxide, which results from the respiration of bacteria as they metabolize organic material. These microorganisms consume organic compounds and convert them into energy, releasing carbon dioxide and water as byproducts. This process is essential in the treatment of wastewater as it helps to reduce the volume of organic matter and improve water quality. While heat is generated during this process as a byproduct of microbial activity, it is not the primary byproduct in terms of chemical composition. Similarly, solid sludge may be produced as a more residual product, but it primarily consists of microbial biomass and un-decomposed materials rather than being a direct byproduct of aerobic digestion. Methane, on the other hand, is primarily associated with anaerobic digestion processes, where organic materials are broken down without oxygen. Therefore, in the context of aerobic digestion, carbon dioxide is the correct and most significant byproduct of the breakdown of organic matter.