Effects of DO on N₂O emission during biological nitrogen removal using aerobic granular sludge via shortcut simultaneous nitrification and denitrification

Abstract

Dissolved oxygen (DO) is an important factor influencing biological nitrogen removal. This study investigated the effects of different DO concentrations (4, 2, 1 mg/L) on nitrous oxide (NO) production and nitrogen removal via shortcut simultaneous nitrification and denitrification by aerobic granular sludge (SND) using a sequencing bath reactor. The results showed that NO production was highest (127.6 mg/m) at a DO concentration of 2 mg/L; this was 24.17 and 2.90 times the production at DO concentrations of 4 and 12 mg/L, respectively. The removal efficiency of total nitrogen also was the highest (61.68%) when the DO concentration was 2 mg/L, compared to 35.22% and 50.65% at DO concentrations of 4 and 1 mg/L, respectively. The efficiency of the SND process reached 53.86% at a DO concentration of 2 mg/L, which was 1.33 and 1.67 times the efficiencies at DO concentrations of 4 and 1 mg/L, respectively. Therefore, reducing the DO concentration benefited the SND process, but increased the emission of NO.

Identification of critical effect factors for prediction of spatial and intra-annual variability of shallow groundwater nitrate in agricultural areas

“…Denitrification still exists when the DO concentration of groundwater is 2~6 mg L -1 , but the rate is reduced with higher DO (Peng et al, 2020). The average monthly DO concentration in the study area from May 2017 to April 2019 was 11.78 mg L -1 , and there was no record of below 2 mg L -1 values in any of the samples.…”

“…In this study, DO usually ranged from 4 to 20 mg L -1 . It is generally believed that the appropriate DO concentration for denitrification is 2 mg L -1 (Peng et al, 2020).…”

Smaller Aerobic Granules Significantly Reduce N2O Production by Ammonia-Oxidizing Bacteria: Evidences from Biochemical and Isotopic Analyses

“…Elevated DO levels increased AOR (Figure 3C) while decreased N 2 O emission factors (Figure 1C) and specific production rates (Figure 2C), in agreement with previous findings. 10,20 However, Peng et al 50 found that with DO increasing from 1 to 4 mg-O 2 /L, both N 2 O production and emission were first elevated and subsequently decreased in the shortcut simultaneous nitrification-denitrification AGS system. Such different profiles were likely related to the contribution of heterotrophic bacteria with higher activity within granules to N 2 O production and consumption.…”

Response of simultaneous nitrification-denitrification to DO increments in continuously aerated biofilm reactors for aquaculture wastewater treatment

“…Since the raw influent contained both NO 3 À -N and TAN (Table 1), NO 3 À -N removal during SND did not all derive from ammonium oxidation. This differed from those cases dealing only with ammonium (He et al 2009;Chai et al 2019;Xia et al 2019;Peng et al 2020). Therefore, the SND rate was only used in this study for impact analysis, without comparison to other cases.…”

“…Wang et al (2020) and Cao et al (2017) state that maximum TN/TIN removal was achieved in a moving-bed, sequencing batch reactor (SBR) at a DO of 2.5 mg/L when treating synthetic ammonium wastewater. Peng et al (2020) reported that the SND rate in an anaerobic granular SBR reached the maximum of 53.86% at a DO of 2 mg/L. Zhang et al (2020b) reported that the SND rate achieved a maximum of 92.3% in an aerobic biofilm system at a DO of 2 mg/L, when treating real industrial/domestic wastewater.…”