In wastewater treatment, what does the term “eutrophication” refer to?

Eutrophication refers to the process in which a water body becomes overly enriched with nutrients, primarily nitrogen and phosphorus, often due to runoff from land activities, such as agriculture and urban areas. This excessive nutrient input leads to a rapid increase in the growth of algae, known as algal blooms. These blooms can deplete oxygen in the water when they die and decompose, resulting in hypoxic conditions that can harm aquatic life. Eutrophication not only disrupts the ecological balance of water bodies but can also lead to the production of toxins by certain algal species, further threatening aquatic ecosystems and human health.

The other options do not accurately describe eutrophication. Urban development impacts water bodies but does not directly relate to nutrient enrichment. An increase in fish populations may occur as a result of better management, but it is not the essence of eutrophication. Lastly, the filtration of solids pertains to physical processes in wastewater treatment, which is unrelated to the nutrient-driven changes described in eutrophication. Thus, option B correctly captures the essence of this environmental phenomenon.