What is the primary process during secondary treatment of sewage?

The primary process during secondary treatment of sewage is biological degradation of organic matter. This stage focuses on removing dissolved and suspended organic matter from sewage through biological processes. Microorganisms, such as bacteria, play a crucial role in this stage by breaking down organic pollutants into simpler substances. This process not only reduces the biochemical oxygen demand (BOD) of the sewage but also helps in eliminating pathogens, thereby improving the overall quality of treated wastewater.

Biological treatment methods, such as activated sludge systems, trickling filters, or anaerobic digesters, are commonly employed to facilitate this degradation. The effectiveness of secondary treatment largely depends on factors like the design of the treatment system, the type of microorganisms utilized, and the operational conditions maintained throughout the process. This method is essential for ensuring that the resulting effluent is safe for discharge or further treatment, making it a central focus of modern sewage treatment practices.