Which of the following substances is typically NOT removed by wastewater treatment facilities?

Pharmaceuticals are typically not fully removed by wastewater treatment facilities due to their complex chemical structures and the limitations of conventional treatment processes. While these facilities are designed to reduce the levels of various contaminants, many pharmaceuticals can pass through treatment systems because they may not be effectively broken down by biological processes or removed through standard physical and chemical treatments.

In contrast, heavy metals, nutrients like nitrogen and phosphorus, and organic matter are usually targeted for removal during wastewater treatment. Heavy metals can be precipitated or adsorbed, while nutrients are often biologically processed or removed through methods like chemical precipitation. Organic matter is typically reduced through aerobic and anaerobic digestion processes, effectively diminishing the biochemical oxygen demand in effluent.

The challenge with pharmaceuticals lies in the need for advanced treatment technologies, such as advanced oxidation processes or membrane bioreactors, which are not always available or economically feasible at all wastewater treatment facilities. As a result, significant quantities of these substances can remain in treated effluent and contribute to environmental and health concerns.