What is a primary environmental concern regarding the use of reclaimed water?

The primary environmental concern regarding the use of reclaimed water is excess nutrient loading. When reclaimed water is used for irrigation and other purposes, it often contains higher levels of nutrients such as nitrogen and phosphorus. These nutrients can lead to unintended consequences if they are released into the environment in excess. For instance, when these nutrients enter rivers, lakes, or oceans, they can stimulate algal blooms, which can deplete oxygen levels in water bodies, harming aquatic life and disrupting ecosystems. This process, known as eutrophication, often leads to ecological imbalance, fish kills, and can affect water quality, making it hazardous for both wildlife and human activities.

While increased costs of treatment, reduced agricultural yields, and high energy consumption are relevant factors in the broader discussion about the use of reclaimed water, they do not directly capture the significant environmental impact that excess nutrient loading can have on ecosystems. Thus, the concern regarding nutrient loading stands out as a critical issue associated with reclaimed water use.