What is the primary function of the aeration basin in wastewater treatment?

The primary function of the aeration basin in wastewater treatment is to provide an oxygen-rich environment for microorganisms. This is crucial because the microorganisms, such as bacteria, thrive in oxygenated conditions and play a significant role in breaking down organic matter present in the wastewater. Through the process of aerobic digestion, these microorganisms metabolize the organic pollutants, thereby reducing the overall biochemical oxygen demand (BOD) of the wastewater.

Oxygen supply is essential for these biological processes to efficiently convert waste into carbon dioxide and biomass, which can either be further treated or settled out. The aeration basin thus facilitates the growth of these organisms and ensures that they can function effectively to purify the water.

In contrast, the other options pertain to different processes or stages in wastewater treatment that do not primarily involve the aeration basin. Reducing the volume of sludge or removing heavy metals are separate objectives that involve different treatment systems or processes, while filtering out solid debris is typically handled by preliminary or secondary treatment methods rather than in the aeration basin itself.