Effects of extremely low bulk liquid DO on autotrophic nitrogen removal performance and NOB suppression in side‐ and mainstream one‐stage PNA

Abstract

BACKGROUND Results in the literature are divergent regarding dissolved oxygen (DO) level to ensure nitrite‐oxidizing bacteria (NOB) suppression in mainstream conditions. In this study, a one‐stage granular partial‐nitritation (PNA) was operated controlling the oxygen transfer over ammonium loading rate (OTR/ALR). The effects of extremely low DO availability on autotrophic nitrogen removal (ANR) performance and NOB suppression were assessed. RESULTS The strategy applied in the sequencing batch reactor (SBR) in sidestream and mainstream conditions (temperature at 25 °C) allowed micromolar bulk liquid DO concentrations to be obtained. Nitrite production rate (NPR) by aerobic ammonium‐oxidizing bacteria (AOB) was sufficient to provide nitrite to anammox bacteria (AnAOB) and sustain nitrogen removal rates (NRR) of 0.34 ± 0.05 and 0.37 ± 0.07 kg N m−3 d−1 during sidestream and mainstream operation, respectively. Extremely low DO assisted by free ammonia (FA; ≤6.2 mg N L−1) in sidestream conditions resulted in complete nitratation suppression. In mainstream conditions, Nitrospira spp. growth led to limited nitratation rates. Decreasing the OTR/ALR resulted in lower oxygen consumption by AOB than by NOB, as well as reduced nitrite consumption by AnAOB, which is likely to be due to granule structure. CONCLUSIONS Low DO availability did not compromise ANR. Micromolar DO allowed complete NOB suppression only with FA assistance (sidestream) but was sufficient to keep nitratation limited in mainstream conditions. © 2018 Society of Chemical Industry

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“…The nitrite half-saturation coefficient (KS) of pure cultures of Nitrobacter was 0.69-7.6 mg-N l -1 , while pure cultures of Nitrospira showed lower values of 0.13-0.38 mg-N l -1 [31]. The oxygen half-saturation coefficient (KO) of mixed cultures of Nitrobacter was 0.43-5.31 mg l -1 [3,33,34] while the value of KO of Nitrospira was 0.33-0.54 mg l -1 [33,35]. The difference of KS and KO between Nitrobacter and Nitrospira allows them to be dominant in distinct environments.…”

“…The process can be promoted by providing environmental conditions that suppress the activity of nitrite-oxidizing bacteria (NOB) while allowing the activity of ammonia-oxidizing bacteria (AOB) to occur. Such conditions include maintaining high pH [1], high temperature (>35°C) [2], and/or low oxygen (0.3-0.5 mg l -1 ) [3,4].…”

Synergy between Comammox and Anammox Bacteria in Wastewater Ammonia Removal

“…6,7 Nitrospira spp. are usually the dominant NOB in domestic wastewater treatment by partial nitritation-anammox, 8 but recently it is known that they also include complete ammonia-oxidizing bacteria (CAOB). 9,10 In fact, the partial nitritation-anammox process can even be overtaken by CAOB, turning into a complete nitrification reactor.…”

“…In recent years, anammox-based wastewater nitrogen removal process that combines partial-nitritation with anammox in granular sludge reactors, biofilm reactors, and filters have been scaled up from lab-scale to pilot- and full-scale. − However, domestic wastewater treatment by partial nitritation-anammox is often challenged by the overgrowth of nitrite oxidizing bacteria (NOB). , Nitrospira spp. are usually the dominant NOB in domestic wastewater treatment by partial nitritation-anammox, but recently it is known that they also include complete ammonia-oxidizing bacteria (CAOB). , In fact, the partial nitritation-anammox process can even be overtaken by CAOB, turning into a complete nitrification reactor . However, roles of CAOB in the anammox-based wastewater nitrogen removal process remained unclear, and exploring the relationship between CAOB and AnAOB is of great importance for achieving efficient nitrogen removal.…”

Membrane aerated biofilm reactor integrated with mainstream anammox processes

“…Liu and Wang (2013) and Wett et al (2013) reported higher 𝐾 𝑂 2 value for AOB when reactors were kept at lower temperature for the long-term. Reports from Li et al (2019a), del Rio et al (2019 and Akaboci et al (2018b) suggested that low DO needed to be supplemented with other strategies to achieve better NOB suppression in mainstream condition. Floating oxygen availability control strategy relies on online monitoring of ammonium, nitrate, or pH to regulate aeration.…”