Wastewater New York State Practice Exam

What are the main byproducts produced by acid-forming bacteria during the initial digestion phase?

1. Methane and water

2. Carbon dioxide and organic acids

3. Nitrogen and hydrogen

4. Sulfides and ammonia

The correct answer is: Carbon dioxide and organic acids

During the initial digestion phase in wastewater treatment, acid-forming bacteria play a crucial role in breaking down organic material. These bacteria primarily convert complex organic substrates into simpler compounds. As they metabolize these organic materials, the main byproducts produced are carbon dioxide and organic acids. Carbon dioxide is released as a result of the fermentation process, which involves the breakdown of sugars and other organic compounds. This gas is generally produced in significant amounts during initial stages of anaerobic digestion. Alongside carbon dioxide, organic acids, such as acetic acid, propionic acid, and butyric acid, are also generated. These organic acids can serve as substrates for other microorganisms in subsequent stages of digestion, particularly in the production of methane during later phases. In contrast, the other options represent byproducts that are typically associated with different biological processes. Methane and water are primarily produced in the later stages of anaerobic digestion by methanogenic bacteria, while nitrogen and hydrogen can be produced through different metabolic pathways not directly related to the acid-forming stage. Sulfides and ammonia could result from other processes or conditions that involve sulfur-reducing or nitrogen-reducing bacteria but are not the primary outputs of the initial digestion phase. Therefore, the focus on carbon dioxide