Partial nitrification adjusted by hydroxylamine in aerobic granules under high DO and ambient temperature and subsequent Anammox for low C/N wastewater treatment

Partial nitritation–Anammox process is regarded as a promising nitrogen removal method for nitrogen removal from low C/N wastewaters. In the present work, stable partial nitrification was successfully achieved by 10 mg/l hydroxylamine dosing in aerobic granules under experimental conditions of pH 7.8–8.2, dissolved oxygen (DO) above 5 mg/l and temperature around 25 °C. When the NH4–N and COD were fixed at 100 mg/l and 400 mg/l, the TN removal efficiency was 57% with a NO2–N/NOx–N (NO2 + NO3)–N ratio of 99.8% in the effluent. Meanwhile, 79% COD was removed by aerobic granules, which was regarded as beneficial to the following Anammox. Sequentially, a mixture of the SBR effluent and raw influent with an average NO2–N/NH4–N ratio of 1.67 was fed to an Anammox reactor. The COD and TN removal efficiencies reached 77% and 81%, respectively, through coupling of Anammox and denitrification. SEM detection showed that the main composition of aerobic granules was coccus and bacilli bacteria. FISH results demonstrated that ammonia-oxidizing bacteria (AOB) became the dominant bacteria of aerobic granules, which further proved the important effects of hydroxylamine on the achievement of partial nitrification by aerobic granules under conditions of high DO and ambient temperature.

► Nitritation/denitritation is achieved by hydroxylamine dosing in aerobic granules.
► Hydroxylamine can selectively inhibit NOB over AOB in aerobic granules.
► Hydroxylamine is the key parameter for development of AOB-based granules.
► Nitritation effluent with little nitrogen is treated by Anammox/denitrification.
► Anammox could be applied to treat low ammonia wastewaters.