Nitrite‐shunt and biological phosphorus removal at low dissolved oxygen in a full‐scale high‐rate system at warm temperatures

) removal. Despite the low DO operation, very good bioP performance is achieved. Full-scale performance data and detailed bench-scale testing were conducted to assess the nitrogen and phosphorus removal at low DO conditions. Full-scale results showed that the plant achieves effluent total inorganic nitrogen (TIN) and total phosphorus (TP) concentrations of approximately 2.0 mgN/L and 0.5 mgP/L, respectively, at an average influent C:N ratio of 7:1 mgCOD:mgN. PRACTITIONER POINTS: Simple anaerobic-aerobic (A/O) process demonstrated combined N and P removal Ammonia oxidation was not hampered by low DO (<0.5 mg/L) operation Low DO (<0.5 mg/L) operation sustained SND via nitrite pathway in a high-rate process (HRT < 6 hr) P uptake was demonstrated at low DO which counters to the widely held understanding that high DO (>1.5 mg/L) is necessary Heterotrophic consumption of nitrite at low DO was the key to the out-selection of nitrite-oxidizing bacteria.