Strategies for mitigating nitrous oxide production and decreasing the carbon footprint of a full-scale combined nitrogen and phosphorus removal activated sludge system

Optimization of the Aeration Strategies in a Deammonification Sequencing Batch Reactor for Efficient Nitrogen Removal and Mitigation of N2O Production

“…The rate r N 2 O [mg N/(L·d)] consists of two components related to aerated and non-aerated conditions. The details of r N 2 O calculations can be found elsewhere …”

“…A conceptual model of the biochemical transformations in the studied SBR is shown in Figure . The N 2 O production/consumption mechanisms (along with the gas–liquid transfer) were adopted from Zaborowska et al, including NH 2 OH oxidation (NN) and autotrophic denitrification (ND) mediated by AOB and three-step heterotrophic denitrification (HD) with NO 2 – -N and N 2 O as intermediates. For modeling, the only source of electron donors for autotrophic denitrification was NH 4 + -N .…”

“…Typical examples of the predicted and measured DO concentrations are shown in Figure S1. The N 2 O emission during the aerated phase (air-stripping) was influenced by the K L a coefficient and estimated airflow rate . The initial active biomass composition in each modeling phase (CAL, REC, and VAL) was assumed based on the results of the metagenomics analysis (Table S5).…”

Activated sludge and other aerobic suspended culture processes

“…Nelson et al (2019) proposed that the hydraulic retention time in ASM1, which varied as either the recycle ratio or the composition of the influent stream, was a critical value predicting the viable heterotrophic biomass and autotrophic biomass. Zaborowska et al (2019) extended the Activated Sludge Model 2d (ASM2d) with N 2 O liquid-gas transfers and N 2 O production pathways to evaluate nitrogen (N) and phosphorus (P) removal and the total carbon footprint for the operational strategy of wastewater treatment plants (WWTPs). It found that heterotrophic denitrification played a leading role in N 2 O production under either anoxic or aerobic conditions, on account of the abundance of heterotrophic denitrifying bacteria over nitrifying bacteria.…”

“…Zaborowska et al (2019) extended the Activated Sludge Model 2d (ASM2d) with N 2 O liquid–gas transfers and N 2 O production pathways to evaluate nitrogen (N) and phosphorus (P) removal and the total carbon footprint for the operational strategy of wastewater treatment plants (WWTPs). It found that heterotrophic denitrification played a leading role in N 2 O production under either anoxic or aerobic conditions, on account of the abundance of heterotrophic denitrifying bacteria over nitrifying bacteria.…”