Which treatment stage is primarily focused on reducing organic matter?

The stage primarily focused on reducing organic matter is secondary treatment. During this phase of wastewater treatment, biological processes are employed to break down organic pollutants present in the water. This typically involves the use of microorganisms that consume organic matter as their food source, leading to its conversion into more stable forms or biomass.

Secondary treatment techniques include methods like activated sludge processes, trickling filters, and biofilm reactors. In these methods, microorganisms are allowed to flourish and metabolize organic materials, effectively reducing the biochemical oxygen demand (BOD) of the wastewater. The significant reduction of organic matter not only improves water quality but also prepares the treated water for further stages of purification if necessary.

In contrast, while primary treatment is concerned with solid matter removal through physical processes like sedimentation, tertiary treatment focuses on further purification and removal of remaining contaminants, including nutrients and pathogens. Pre-treatment, on the other hand, addresses the initial screening and removal of larger debris before the primary treatment stage. Each treatment stage has its own specific focus, but secondary treatment is key for effectively reducing organic matter.