Enhancing Nitrogen Removal from Low C/N Municipal Wastewater via Redistributing Hydraulic Retention Time in a Pilot-Scale Anaerobic/Aerobic/Anoxic Process.

Redistributing hydraulic retention time in a pilot-scale AOA process increased nitrogen removal efficiency from 63% to 78.6% in low C/N municipal wastewater.

• Why it matters: Effective nitrogen removal in low-carbon wastewater is limited by insufficient organic carbon for denitrification, posing challenges for sustainable treatment systems.
• What they did: A 57.6 m3/d AOA reactor operated for 175 days with adjusted anoxic durations, maintaining a constant HRT of 14 hours, to enhance internal carbon-supported denitrification.
• The result: Effluent TN decreased significantly, with 75.3% of net nitrogen removal occurring in the anoxic zone, and microbial analysis showed increased GAOs and nitrifiers, demonstrating a practical upgrade strategy.