How much biodegradable organic matter is typically removed during primary wastewater treatment in terms of BOD?

In primary wastewater treatment, the focus is primarily on the removal of solids through physical processes such as sedimentation and flotation. The biological oxygen demand (BOD) is a measure of the amount of biodegradable organic matter in the wastewater, and it is typically reduced during this treatment stage.

Approximately 30% of the biodegradable organic matter, reflected as BOD, is removed during primary treatment. This is achieved through the gravitational settling of solids, which removes some of the larger suspended particles and a fraction of the dissolved organic materials present in the wastewater. While some BOD is eliminated, a significant portion remains for further reduction in secondary treatment stages, where biological processes are utilized to degrade the remaining organic matter.

This percentage may vary depending on the characteristics of the wastewater and the effectiveness of the treatment process, but 30% accurately reflects the typical performance of primary treatment systems in reducing BOD.