Denitrification is the process by which bacteria convert nitrates into nitrogen gas, anoxic process.

• A. The oxidation of ammonia to nitrate
• B. The removal of dissolved solids by filtration
• C. Process by which bacteria convert nitrates into nitrogen gas, anoxic process
• D. The settling of solids in a clarifier

Answer: (C)

Denitrification is the biological reduction of nitrate to nitrogen gas under anaerobic (anoxic) conditions. In wastewater treatment, this happens when oxygen is limited and nitrate serves as the electron acceptor for bacteria, typically with a carbon source available. The main outcome is nitrogen gas released to the atmosphere, removing nitrogen from the water. This differs from nitrification, which is the aerobic oxidation of ammonia to nitrate and requires oxygen. Filtration and settling remove solids, not nitrates or nitrogen gas, so they don’t describe denitrification.