Endogenous Nitrous Oxide Emission for Denitrifiers Acclimated with Different Organic Carbons

Abstract

Nitrous oxide (N 2 O) emission occurs during denitrification, such as in biological wastewater treatments, but few studies have focused on N 2 O emission during denitrification under endogenous conditions. In the present study denitrifiers were acclimated with acetate or methanol as the electron donor, and endogenous denitrification kinetics including denitrification rates and N 2 O emission were examined in batch experiments for the acclimated denitrifiers. Oxidized nitrogen was denitrified slowly during endogenous respiration for denitrifiers acclimated with acetate or methanol, with the denitrification rate of lower than 2 mg/g VSS•h. When the nitrate was used as electron acceptor, a low N 2 O emission ratio (lower than 1%) was obtained, while a high emission ratio (above 10%) was observed with nitrite as electron acceptor for both organic carbon acclimated denitrifiers. More attention should be paid to N 2 O emission during denitrification under endogenous conditions (such as in the settlement tanks) especially for systems with short-cut biological nitrogen removal through nitrite or systems with a high nitrite accumulation.

Heterotrophs are key contributors to nitrous oxide production in activated sludge under low C‐to‐N ratios during nitrification—Batch experiments and modeling

“…C). These results are in agreement with literature where showed a larger impact on N 2 O production compared to under endogenous conditions (Wu et al, ). The net N 2 O produced after an (or followed by ) spike was approximately 0.9% of the nitrogen oxidized, while 1.9% of the nitrogen oxidized was converted to N 2 O when was spiked followed by .…”

“…Depending on the system, AOB or HB have been considered to be the main contributor to the total N 2 O production (Itokawa et al, ; Ni et al, ). ND and HD occur under similar DO and concentrations, thus, leading to possible interferences between autotrophic and heterotrophic N 2 O production (Shen et al, ; Wu et al, ). However, under certain operating conditions, the contribution of a pathway can be considered negligible, thus allowing for more accurate model calibrations.…”

The effect of pH on N2O production in intermittently-fed nitritation reactors

“…Two orders of magnitude higher heterotrophic N2O production rate has been observed in anoxic conditions than in oxic incubations (≥ 0.2 mg O2/L) in the nitritation-anammox biomass (Ma et al, 2017). However, previous studies could not elaborate on the individual contribution of heterotrophic denitrification solely with bulk N2O measurements due to the co-occurrence of both pathways under similar NO2and DO thus leading to possible interferences between autotrophic and heterotrophic N2O production in mixed culture biomass (Itokawa et al, 2001;Shen et al, 2015;Wu et al, 2014).…”