Anaerobic decomposers are utilized in the breakdown of sewage sludge treatment of stormwater final chlorination process, after which water is dinkable primary wastewater treatment process

I think the correct answer would be the first option. Anaerobic decomposers are utilized in the breakdown of sewage. Anaerobic microorganisms do not need the presence of oxygen to work or metabolize their food. They are usually found in trenches and in places where there is no air. A sewage is a possible location.