What is a likely consequence of prolonged wastewater detention in collection systems?

Prolonged detention of wastewater in collection systems often leads to septic conditions. This occurs because the lack of adequate oxygen over an extended period allows anaerobic bacteria to thrive. These bacteria are responsible for breaking down organic matter in an oxygen-depleted environment, resulting in the production of foul odors, and potentially harmful gases like hydrogen sulfide. Septic conditions can also lead to the generation of other undesirable chemicals, contributing to the deterioration of water quality.

While increased nutrient levels and algal blooms may be concerns in specific contexts, they are not direct consequences of prolonged detention in the way that septic conditions are. Increased oxygen levels would only occur in well-aerated systems, which is contrary to what happens in stagnant conditions. Therefore, the establishment of septic conditions is the most accurate consequence associated with long detention times in wastewater collection systems.