Which stage of wastewater treatment involves biological treatment processes?

The stage of wastewater treatment that involves biological treatment processes is secondary treatment. This stage is designed to further reduce the organic matter in wastewater that remains after the primary treatment. In secondary treatment, microorganisms such as bacteria play a crucial role in breaking down organic pollutants.

During this process, the activated sludge method or other biological treatments are employed, where microorganisms consume the dissolved and suspended organic matter. This process not only reduces the biochemical oxygen demand (BOD) in the wastewater but also helps to stabilize the waste, ensuring that harmful pathogens and organic materials are effectively treated before the water moves on to final stages of treatment or discharge.

Understanding the role of secondary treatment is vital, as it significantly improves the quality of the effluent and is a critical component of removing nutrients, particularly nitrogen and phosphorus, from the wastewater stream. This treatment is essential to meet regulatory standards before the water is released back into the environment or reused for various applications.