What is the difference between primary and secondary treatment?

The correct distinction acknowledges that primary treatment focuses on the removal of solids from wastewater, typically through physical processes like screening and sedimentation. This stage deals with the larger particulate matter and works to separate the solid waste materials from the liquid.

In contrast, secondary treatment is primarily aimed at removing dissolved and suspended organic matter from the wastewater. This phase often utilizes biological processes, such as aeration and biological filtration, wherein microorganisms break down organic compounds, leading to significant reduction in pollutants. This treatment stage is crucial for improving the overall water quality before any potential discharge or further treatment steps.

Understanding this differentiation is key for wastewater treatment operators as it underlines the sequence and purpose of each treatment stage in the overall wastewater management process.