In a wastewater treatment plant, which organisms are primarily responsible for breaking down dissolved organic chemical wastes (biological degradation) during secondary treatment?

• A. Multicellular fungi that perform most breakdown in municipal aeration tanks
• B. Aerobic bacteria (prokaryotic decomposers) in activated sludge biofilms
• C. Viruses that lyse waste particles into smaller molecules
• D. Protozoa that photosynthesize and release oxygen for decomposition

Answer: (B)

Verified step by step guidance

1. Understand the context of secondary treatment in wastewater treatment plants, which focuses on biological degradation of dissolved organic chemical wastes.
2. Identify the types of organisms involved in this process: multicellular fungi, aerobic bacteria, viruses, and protozoa.
3. Recall that aerobic bacteria are prokaryotic decomposers that thrive in oxygen-rich environments such as activated sludge biofilms in aeration tanks.
4. Recognize that these aerobic bacteria metabolize and break down organic pollutants effectively, making them the primary agents of biological degradation during secondary treatment.
5. Note that multicellular fungi, viruses, and protozoa do not play the main role in this specific stage of wastewater treatment.