Why are nitrogen and phosphorus significant to the receiving stream?

Nitrogen and phosphorus are critical nutrients that play a significant role in aquatic ecosystems, particularly in promoting the growth of aquatic plants and algae. When these nutrients are present in elevated concentrations in a receiving stream, they can lead to a process known as eutrophication. This process encourages rapid growth of aquatic plants and algae, which can initially seem beneficial as it supports biological productivity.

However, excessive plant growth can lead to a variety of ecological issues, such as oxygen depletion when the plants die and decompose, which can harm fish and other aquatic organisms. This emphasizes the importance of managing nitrogen and phosphorus levels in wastewater discharges to maintain healthy aquatic ecosystems and prevent negative impacts on water quality. Thus, the correct answer highlights the critical role these nutrients play in shaping the biological dynamics of receiving waters.