Rapid Start-Up and Stable Maintenance of Partial Nitrification Process Through Different Inhibitor Addition and Real-Time Aeration Control

Abstract

This study investigated the rapid start-up of partial nitrification through different inhibitor addition, including hydroxylamine (NH₂OH), potassium chlorate (KClO₃), and formic acid (HCOOH). Then, the performances of the three inhibitors on the rapid recovery of partial nitrification once increasing the influent ammonium sharply were also compared. Finally, real-time aeration control strategy was adopted to maintain partial nitrification during a period. In the present work, batch experiments were used to confirm the optimum dosage of each inhibitor in a similar adding range first. The results showed that nitrite-oxidizing bacteria (NOB) were more vulnerable to NH₂OH and KClO₃ than HCOOH. Second, the rapid start-up of partial nitrification in a sequencing batch reactor was evaluated. It finished in 22 days without any inhibitor. However, only 12 days were needed when adding 0.15 mM NH₂OH. It used 14 days when adding 0.5 mM KClO₃ and 17 days under 0.5 mM HCOOH addition, respectively. The partial nitrification, which was destroyed by the high influent ammonium, was easily and rapidly recovered using the inhibitors. The nitrite accumulation rate was still more than 80% using the real-time aeration control strategy when ceasing the inhibitor addition. Furthermore, high-throughput sequencing analysis revealed that the main genera of NOB, Nitrospira, was suppressed by the three inhibitors; however, a difference in bacterial community structure was found due to the different influence mechanisms. Overall, inhibitor addition and real-time aeration control is an excellent strategy for establishing, recovering, and maintaining effective partial nitrification.