Improving nutrients removal of Anaerobic-Anoxic-Oxic process via inhibiting partial anaerobic mixture with nitrite in side-stream tanks: Role of nitric oxide

A side-stream tank which was in parallel with the anoxic tank was used to improve the performance of an Anaerobic-Anoxic-Oxic process. The partial mixtures from the anaerobic tank were injected into the side-stream tank with the initial nitrite nitrogen (NO2 --N) concentrations of 10 mg/L and 20 mg/L. When the initial NO2 --N concentration in the tank was 20 mg/L, total nitrogen and total phosphorus removal efficiencies of the A2/O process increased from 72% and 48% to 90% and 89%, respectively. 2.23 mg/L of nitric oxide (NO) were observed in the side-stream tank. The abundance of Nitrosomonas sp. and Nitrospira sp. were varied from 0.98% and 6.13% to 2.04% and 1.13%, respectively. The abundances of Pseudomonas sp. and Acinetobacter sp. were increased from 0.81% and 0.74% to 6.69% and 5.48%, respectively. NO plays an important role for improving the nutrients removal of the A2/O process in the side-stream nitrite-enhanced strategy.

Automated summary

A side-stream tank was used to improve the performance of the Anaerobic-Anoxic-Oxic process. The injection of partial mixtures from the anaerobic tank into the side-stream tank with nitrite nitrogen concentrations increased total nitrogen and total phosphorus removal efficiencies. Nitric oxide (NO) was observed in the side-stream tank. The abundances of certain bacteria species varied and NO played a crucial role in improving nutrient removal in the side-stream nitrite-enhanced strategy.