Achieving stable nitritation for mainstream anammox by combining nitrite exposure inhibition with high DO reactivation

Abstract

This study achieved stable nitritation by eliminating both Nitrobacter and Nitrospira through combing nitrite exposure inhibition with high dissolved oxygen (DO) reactivation. After treated by nitrite exposure (5–30 mg·L−1), nitrite-oxidizing bacteria (NOB) of two nitrifying reactors (RL and RH) was suppressed seriously than ammonium-oxidizing bacteria (AOB) with faster activity decay rate (0.035 ± 0.003 d−1) and larger population reduction as well as slower functional gene transcription, wherein Nitrobacter was inhibited more significantly than Nitrospira. During reactivation period, the RH (high DO: 2.5–3.0 mg·L−1) achieved nitritation with high NAR of 97.9%, which was twice faster than RL (low DO: 0.1–0.6 mg·L−1). Though temperature declined to 16.6 °C, RH remained constant nitritation with ideal effluent NO2−-N:NH4+-N of 1:1 for anammox. Further analysis indicated that high DO reactivation accelerated AOB overcome NOB by promoting AOB growth but severely inhibited Nitrospira. The findings provided novel insights into suppressing NOB in targeted ways which facilitated mainstream deammonifcation.