Pilot Study of Oxic–Anoxic Process under Low Dissolved Oxygen for Nitrogen Removal from Low COD/N Tropical Wastewater

Conventionally, nitrification in biological nitrogen removal (BNR) requires high dissolved oxygen (DO) concentrations (>2 mg L−1), making the process energy intensive. Recent studies have shown that efficient ammonium and reduction can be realized by operating at low DO (<1 L−1). In this study, low-DO oxic anoxic (low-DO OA) was operated a pilot-scale sequencing batch reactor (SBR) over 218 days to evaluate feasibility of from chemical demand-to-nitrogen ratio (COD/N) tropical municipal wastewater. The results revealed OA attained efficiency for (97%) total (TN) (80%) under an average concentration 0.6 L−1. effective TN is attributed occurrence simultaneous nitrification–denitrification (SND) conditions. Further tests slowly biodegradable COD (sbCOD) wastewater support denitrification post-anoxic phase, resulting rate. Compared with (2 conditions achieved 10% higher efficiency, similar efficiency. This study crucial promoting sustainability treatment plants treating COD/N