In an activated-sludge wastewater treatment plant, which type of organism is primarily responsible for breaking down organic chemical wastes?

• A. Helminths that mechanically shred solid waste
• B. Protozoa that photosynthesize and produce oxygen
• C. Aerobic heterotrophic bacteria
• D. Viruses that lyse cells to release digestive enzymes into the water

Answer: (C)

Verified step by step guidance

1. Understand the role of different organisms in an activated-sludge wastewater treatment plant. The main goal is to break down organic chemical wastes effectively.
2. Recall that aerobic heterotrophic bacteria consume organic compounds as their energy and carbon source, using oxygen to metabolize these wastes.
3. Recognize that helminths primarily act as mechanical shredders of solid waste, not chemical decomposers.
4. Note that protozoa in this context do not photosynthesize; photosynthetic organisms like algae produce oxygen but do not primarily break down organic wastes.
5. Understand that viruses lyse cells but do not directly break down organic chemical wastes; their role is more related to controlling microbial populations.