Which stage in the sewage treatment process is primarily focused on the breakdown of organic material?

The stage in the sewage treatment process primarily focused on the breakdown of organic material is the aeration stage. During this phase, sewage is exposed to air, which promotes the growth of aerobic bacteria. These bacteria consume the organic matter in the wastewater, breaking it down into simpler substances. This process is crucial for reducing the biochemical oxygen demand (BOD) of the sewage, making it less harmful to the environment when it is eventually discharged.

Aeration significantly enhances the microbial activity, allowing for a more effective decomposition of organic pollutants. This is an essential step in the secondary treatment of sewage, which aims to reduce contaminants and improve the quality of the effluent before it moves on to further treatment stages.

The other stages mentioned, such as pretreatment, filtration, and disinfection, serve different functions. Pretreatment focuses on removing large solids and debris, filtration helps to separate remaining particles, and disinfection targets pathogens in the treated effluent to ensure it is safe for release into the environment. However, only the aeration stage is specifically designed for the effective breakdown of organic materials.