Which combination of processes is commonly used in wastewater treatment to simultaneously reduce odors and generate energy?

• A. Biofiltration followed by anaerobic digestion.
• B. Solar evaporation and chemical precipitation.
• C. Direct discharge without treatment.
• D. Granular activated carbon filtration only.

Answer: (A)

Odor control paired with energy recovery is best achieved by using biofiltration to scrub odorous air, followed by anaerobic digestion to recover energy from organics. Biofiltration uses a bed of media with microbes that oxidize volatile compounds like hydrogen sulfide and ammonia, turning them into odor-free end products and significantly reducing nuisance smells from wastewater air streams. After odors are reduced, the remaining organic matter in the wastewater or sludge can be treated in an anaerobic digester, where microbes work without oxygen to break down organics and produce biogas (mainly methane). That biogas can be captured and used for energy, making the process both odor-controlled and energy-generating. Other options don’t deliver both benefits: they may address odors or solids in different ways, but they don’t provide a pathway to generate usable energy while effectively reducing odors at the same time.