What is a likely consequence of biological activity in long, sluggish-flow, flat grade sewer lines?

Biological activity in long, sluggish-flow, flat grade sewer lines can lead to the production of gases as microorganisms break down organic material. This decomposition process can generate odors, which are often perceived as unpleasant smells in the surrounding environment. In stagnant or slow-flowing sewage, the reduced movement allows for these gases to accumulate, further exacerbating the issue.

While other consequences, such as blockages, may occur due to the buildup of solids and debris, the primary and most immediate consequence of biological activity is the generation of odors. Over time, if left unaddressed, these odors can become more pronounced and potentially lead to complaints from residents or businesses near the sewer lines. Thus, focusing on controlling biological activity and ensuring adequate flow can help mitigate these odor problems.