Which of the following does NOT contribute to the treatment of sewage?

The correct answer highlights that pathogenic bacteria do not contribute to the treatment of sewage. During sewage treatment processes, the goal is to reduce harmful pathogens to acceptable levels while promoting the growth and activity of beneficial microorganisms that aid in the breakdown of organic matter. While pathogenic bacteria can be present in sewage, their presence is undesirable, as they can cause diseases and pose health risks.

In contrast, aerobic bacteria are essential for the treatment process, as they utilize oxygen to break down organic materials in wastewater. Submerged filtration is a method used to physically remove particles and contaminants from sewage, enhancing the purification process. Activated sludge refers to a process that employs aeration and microbial action to decompose organic pollutants in sewage, making it a critical component of wastewater treatment systems.

Thus, the correct answer indicates that pathogenic bacteria, which can be harmful, do not play a role in effectively treating sewage and are instead a target to be minimized during treatment processes.