When wastewater remains in the collection system too long, it tends to become septic resulting in a decrease in pH as well as which of the following?

When wastewater is held in the collection system for an extended period, it can undergo anaerobic decomposition. This process occurs in the absence of oxygen, leading to the breakdown of organic matter by microorganisms that thrive in low-oxygen environments. During anaerobic decomposition, various byproducts are created, including gases like methane and hydrogen sulfide, which contribute to the septic conditions of the wastewater.

As a result of this prolonged retention time, not only does the pH decrease due to the production of acids from the breakdown of organic materials, but the overall quality of the water deteriorates. Anaerobic decomposition is characterized by the predominance of these specific bacteria, which are distinct from aerobic bacteria that require oxygen for decomposition.

This microbiological process can lead to odors, corrosion in the collection system, and potential health hazards, emphasizing the importance of timely removal of wastewater from the collection system to prevent it from becoming septic. The other choices, such as aerobic decomposition and oxidation, typically do not occur optimally under these stagnant conditions and thus are not reflective of the situation described in the question.