Rapid start-up and stable maintenance of domestic wastewater nitritation through short-term hydroxylamine addition

This study investigated the nitritation of domestic wastewater through the short-term addition of hydroxylamine (NH₂OH). Sequencing batch reactor (SBR) was used and the NH₂OH solution with an initial concentration of 5.0 mg/L was injected at each cycle. With NH₂OH addition, the nitritation was quickly established in 5 d with nitrite accumulation ratio above 95%. Further, stable nitritation could be maintained without NH₂OH addition in the following 53 days, even under unfavorable conditions (DO = 3 mg/L). According to qPCR results, NH₂OH significantly reduced and continuously suppressed nitrite oxidizing bacteria (NOB), while the abundance of ammonia oxidizing bacteria was stable, induced the start-up and maintenance of nitritation. Among NOB, NH₂OH significantly suppressed Nitrospira, while did not affect Nitrobactor. Nitrobactor gradually increased during the operation, which could induce the final deterioration of nitritation. Overall, this research provided the fundamental knowledge required to optimize the NH₂OH addition strategy for operating a stable nitritation in domestic wastewater.