Phosphorus is a nutrient from fertilizers and wastewater that causes algal blooms in water bodies. It harms water quality and aquatic ecosystems through eutrophication.

Phosphorus, a naturally occurring element, enters water sources primarily through agricultural runoff, sewage discharge, and detergents. While essential for life, excess phosphorus in water bodies leads to eutrophication—a process that stimulates excessive algae growth, depleting oxygen levels and harming aquatic ecosystems. Water quality experts measure phosphorus concentrations in parts per million (ppm). Although not directly harmful to human health in drinking water, managing phosphorus levels is crucial for maintaining healthy aquatic environments and preventing ecological imbalances.