During which stage of wastewater treatment is biogas typically produced?

• A. Primary treatment
• B. Aeration phase
• C. Anaerobic digestion
• D. Disinfection stage

Answer: (C)

Biogas is typically produced during the anaerobic digestion stage of wastewater treatment. In this process, organic matter is broken down by microorganisms in an oxygen-free environment. As bacteria decompose the organic materials, they generate biogas, which primarily consists of methane and carbon dioxide. This biogas can be harnessed as a renewable energy source, making anaerobic digestion a valuable step in the treatment process.

In contrast, primary treatment involves the physical removal of large solids from wastewater and does not produce biogas. The aeration phase focuses on adding air to promote aerobic microbial activity, which is beneficial for breaking down organic matter but does not result in biogas production. The disinfection stage aims to kill pathogenic organisms and remove harmful microbes, and it does not contribute to biogas generation either. Thus, the anaerobic digestion stage stands out as the specific phase in which significant biogas is produced during wastewater treatment.