Which wastewater treatment stage is designed to remove special contaminants?

Tertiary treatment is the stage of wastewater treatment specifically designed to remove special contaminants that remain after the primary and secondary processes have been completed. This stage targets substances that are not effectively eliminated during earlier treatments, such as nutrients like nitrogen and phosphorus, as well as pathogens and specific chemical pollutants.

During tertiary treatment, advanced filtration, chemical treatment, and additional biological processes may be employed to ensure that the effluent meets stringent quality standards. This step is crucial for protecting the environment and public health, particularly when the treated water is intended for reuse or discharge into sensitive ecosystems.

In contrast, primary treatment primarily focuses on the removal of large solids and greases through physical processes, while secondary treatment employs biological processes to further reduce organic matter and suspended solids. Pre-treatment generally addresses the initial conditioning of wastewater before it undergoes further treatment stages but does not specifically target the removal of special contaminants like the tertiary stage does.