Which statement best describes aerobic digestion?

• A. Takes place without oxygen (anaerobic) and stores sludge.
• B. Is a thermal process used for sterilizing sludge.
• C. Treats sludge before dewatering and disposal; stores sludge.
• D. Increases the smell of the sludge.

Answer: (C)

Aerobic digestion is a biological process that uses oxygen to stabilize and reduce organic material in sludge. Microorganisms consume the organic matter as they digest it, producing a more stable, less odorous sludge. This step is typically done in aerated digesters and is placed before dewatering and disposal because the sludge becomes easier to handle and transfer. The digested sludge can be stored in the aerated digester or in storage tanks for continued stabilization. It is not an anaerobic process (which would occur without oxygen), not a thermal sterilization, and it generally lowers odors rather than increases them.