Which environmental issue is primarily associated with sewage in groundwater?

Sewage in groundwater is primarily associated with bacterial contamination, which can occur when untreated or poorly treated sewage infiltrates soil and aquifers. This contamination introduces harmful pathogens into the water supply, posing health risks to humans and wildlife. Bacteria from sewage can lead to serious diseases and infections, making it a critical concern in environmental health.

Although contaminated fish populations can be an outcome of sewage pollution, they are a secondary effect rather than the primary issue. Nitrogen saturation refers to the excessive presence of nitrogen compounds, often from fertilizers, which can be a concern but is not directly related to sewage. Oxygen depletion typically results from organic matter decomposition, where bacteria break down sewage and consume oxygen, but the immediate concern with sewage is the contamination it introduces to water sources, primarily through harmful bacteria.