Enhanced simultaneous nitrogen and phosphorus removal from low COD/TIN domestic wastewater through nitritation-denitritation coupling improved anammox process with an optimal Anaerobic/Oxic/Anoxic strategy

Advanced nitrogen and phosphorus removal in a single-stage suspending-sludge system was achieved by employing a novel Anaerobic/Oxic/Anoxic (AOA) strategy over 200 days. Satisfactory total inorganic nitrogen (TIN) removal efficiency of 90.4% was achieved and effluent phosphorus was below 0.5 mg/L when treating domestic wastewater with the chemical oxygen demand (COD)/TIN as low as 2.98 +/- 1.26. Stable nitritation was maintained with the ammonia residual and low dissolved oxygen of 0.2-0.5 mg/L at aerobic stage following by a post anoxic stage. The much higher activity of ammonia oxidation bacteria (12.99 mgN/gVSS/h) was achieved than the nitrite oxidation bacteria (0.09 mgN/gVSS/h). Notably, improved anammox performance was obtained without initial inoculation, contributing 47.4% to TIN removal. The abundance of Nitrosomonas increased from 0.12% to 0.95% (P < 0.001) and self-enrichment of anammox bacteria Ca. Brocadia was confirmed. It provided new insight into the advanced nutrient removal with comprehensible regulation and less aeration requirement.

Automated summary

Advanced nitrogen and phosphorus removal was achieved in a single-stage suspending-sludge system using a novel Anaerobic/Oxic/Anoxic (AOA) strategy for over 200 days. The system showed stable nitritation with high activity of ammonia oxidation bacteria and improved anammox performance without initial inoculation. The study provided new insights into advanced nutrient removal with comprehensible regulation and reduced aeration requirement.