How does sewage lead to eutrophication?

Sewage contains high levels of nutrients, particularly nitrogen and phosphorus, which are essential for plant growth. When sewage is discharged into water bodies, these nutrients promote excessive algal blooms, a process known as eutrophication. As algae proliferate and eventually die, their decomposition depletes oxygen in the water, leading to hypoxic conditions that can harm aquatic life. This cycle disrupts ecosystems and can result in dead zones where few organisms can survive.