What major byproduct is produced during anaerobic treatment?

During anaerobic treatment processes in wastewater treatment, microorganisms break down organic matter in the absence of oxygen. This digestion process primarily generates biogas, which is a mixture mainly composed of methane and carbon dioxide, along with small amounts of other gases. The production of biogas is a crucial aspect of anaerobic treatment as it serves as a renewable energy source that can be utilized for heating, electricity generation, or further processing into natural gas.

In contrast, chlorine gas, ozone, and hydrogen peroxide are chemical agents typically used in disinfection processes or as oxidants rather than byproducts of biological treatment methods. These substances do not result from the microbial activity that characterizes anaerobic digestion, highlighting why biogas is recognized as the appropriate answer to the question.