Insight into how high dissolved oxygen favors the startup of nitritation with aerobic granules

Successful mainstream nitritation through NOB inactivation

“…The plug flow feed in SBRs can enhance the formation of granules, which have shown great potential for the suppression of NOB. However, to achieve sludge granulation most studies have used synthetic wastewater, or have added additional chemical oxygen demand (COD), especially in the form of acetate, to their influent (Kent et al, 2019;Reino et al, 2016;Wang et al, 2021), which does not represent realistic conditions. Additional potential advantages of a bottom-fed (SBR) lie in the relatively high ammonium concentrations at the beginning of the reaction phase, which allow for a high DO while still maintaining a low DO/TAN ratio.…”

Effects of dissolved oxygen on water quality and biofilms in the raw water distribution pipeline for a reserved water source

“…The startup of nitritation with aerobic granular sludge was proved to be faster under high DO concentrations in previous study. 39…”

“…The startup of nitritation with aerobic granular sludge was proved to be faster under high DO concentrations in previous study. 39 As the intermediate product the conversion of NH 4 -N to NO 3 -N, the effluent concentration of NO 2 -N also increased slightly with an increase in the initial DO concentration, and there was an accumulation phenomenon to some extent. This is because nitrobacteria are more sensitive to the concentration of DO than AOB, and their DO demand is also higher.…”

How to Provide Nitrite Robustly for Anaerobic Ammonium Oxidation in Mainstream Nitrogen Removal

“…In a lab-scale mainstream PN system (influent 35.8 ± 4.4 mg NH 4 + -N/L), NOB genus ( Nitrospira ) was washed out during the startup period with increasing DO from 0.5 to 5.5 mg/L, and a stable nitrite accumulation was maintained even after the DO was low at 0.5–1.0 mg/L . It should be noted, high DO conditions (3.0–7.0 mg/L) can be adopted more conveniently in granular sludge and biofilm systems, by which a faster growth of AOB can be maintained, ensuring a competitive advantage of AOB in competing for habitable space (i.e., granule and biofilm surface) with NOB. , Indeed, in a lab-scale granular-based PN system, the specific AOR was increased by 2.3 times along with the DO concentration increasing from 0.7 mg/L to 2.7 mg/L, ultimately developing a, AOB dominant shell on the granular surface . With DO concentration at 3.5–7.0 mg/L, a biofilm reactor packed with carriers achieved an excellent nitrite accumulation (NAR > 90%) when treating domestic wastewater (60–90 mg NH 4 + -N/L) .…”

“…There are three reasons for this phenomenon: (i) the lower oxygen consumption for biomass yield (10.5 g O 2 /g COD) of NOB; (ii) the smaller colony size (1–8 μm) of NOB than of AOB (16.1 g O 2 /g COD and 2–16 μm) and (iii) the variation of the dominant NOB genus. Indeed, Nitrospira , which is considered as k -strategist with a low oxygen affinity constant (0.10–0.56 μmol/L), could predominate and outcompete other NOB genera (e.g., Nitrobacter and Ca . Nitrotoga (0.17–165.63 μmol/L)) with low DO conditions (<1.0 mg/L). , NOB could also shift from Nitrospira to Ca .…”