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

Su, Qingxian; Domingo-Félez, Carlos; Zhang, Zhen; Blum, J.M.; Jensen, Marlene Mark; Smets, Barth F.

doi:10.1016/j.watres.2019.03.015

Cited by 42 publications

(11 citation statements)

References 48 publications

(72 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In a separate study we quantified N 2 O emissions from a nitritation reactor from pH 6.5 to 8.5 and observed that the specific net N 2 O production rates and the fractional N 2 O yield increased 7-fold from pH 6.5 to 8, and decreased slightly with further pH increase to 8.5 (p < 0.05). 42 The results were consistent with previous studies: Law et al (2011) showed that the specific N 2 O production rate increased with pH to the maximum at pH 8 in the investigated pH range of 6.0−8.5, 43 while Rathnayake et al (2015) reported highest N 2 O emission at pH 7.5 in a PN reactor (pH 6.5−8.5). 44 Abiotic r N2O in the reactor was estimated from NH 2 OH oxidation by HNO 2 because its r N2O was 1−3 orders of magnitude higher compared to other abiotic reactions.…”

Section: Environmental Science and Technologysupporting

confidence: 92%

Abiotic Nitrous Oxide (N₂O) Production Is Strongly pH Dependent, but Contributes Little to Overall N₂O Emissions in Biological Nitrogen Removal Systems

Domingo-Félez

Jensen

et al. 2019

Environ. Sci. Technol.

Self Cite

View full text Add to dashboard Cite

Hydroxylamine (NH2OH) and nitrite (NO2 –), intermediates during the nitritation process, can engage in chemical (abiotic) reactions that lead to nitrous oxide (N2O) generation. Here, we quantify the kinetics and stoichiometry of the relevant abiotic reactions in a series of batch tests under different and relevant conditions, including pH, absence/presence of oxygen, and reactant concentrations. The highest N2O production rates were measured from NH2OH reaction with HNO2, followed by HNO2 reduction by Fe2+, NH2OH oxidation by Fe3+, and finally NH2OH disproportionation plus oxidation by O2. Compared to other examined factors, pH had the strongest effect on N2O formation rates. Acidic pH enhanced N2O production from the reaction of NH2OH with HNO2 indicating that HNO2 instead of NO2 – was the reactant. In departure from previous studies, we estimate that abiotic N2O production contributes little (< 3% of total N2O production) to total N2O emissions in typical nitritation reactor systems between pH 6.5 and 8. Abiotic contributions would only become important at acidic pH (≤ 5). In consideration of pH effects on both abiotic and biotic N2O production pathways, circumneutral pH set-points are suggested to minimize overall N2O emissions from nitritation systems.

show abstract

Section: Environmental Science and Technologysupporting

confidence: 92%

Abiotic Nitrous Oxide (N₂O) Production Is Strongly pH Dependent, but Contributes Little to Overall N₂O Emissions in Biological Nitrogen Removal Systems

Domingo-Félez

Jensen

et al. 2019

Environ. Sci. Technol.

Self Cite

View full text Add to dashboard Cite

show abstract

“…Different operational and environmental conditions are applied for nitrification and denitrification processes in WWTPs, including dissolved oxygen (DO), pH, temperature, and so on. These parameters are found to have a close relationship with N 2 O emissions (Adouani et al, 2015;Li et al, 2015;Su et al, 2019b;Tumendelger et al, 2014). Also, the substrates or intermediates in the nitrogen removal process are reported to influence N 2 O production, such as the nitrogen loading (Frison et al, 2015;Seuntjens et al, 2018), NO 2 − , NH 2 OH, NO (Domingo-Félez & Smets, 2019) and organic carbon (Zhu & Chen, 2011).…”

Section: Introductionmentioning

confidence: 91%

Full-scale source, mechanisms and factors affecting nitrous oxide emissions

Pijuan

Zhao

2022

Quantification and Modelling of Fugitive Greenhouse Gas Emissions From Urban Water Systems

View full text Add to dashboard Cite

Biological wastewater treatment is conducted by a wide range of microbes with multiple metabolic pathways that are normally affected by the operational conditions applied. Nitrous oxide (N 2 O) can be generated during wastewater treatment either as a by-product or an obligatory intermediate. As an environmentally detrimental greenhouse gas, N 2 O generated from wastewater treatment systems has attracted a lot of attention due to its important contribution to the overall carbon footprint. When aiming at its mitigation, it is imperative to understand the mechanisms that trigger its formation. Sources and pathways for N 2 O production have been categorized into four types based on previous studies: (i) hydroxylamine (NH 2 OH) oxidation during ammonia (NH 3 ) conversion to nitrite (NO 2 − ); (ii) NO 2 − reduction by ammonia oxidizing bacteria (AOB), which is called nitrifier denitrification; (iii) heterotrophic denitrification by denitrifiers; and (iv) hybrid abiotic/biotic N 2 O production. Despite extensive investigations, the mechanisms for N 2 O production await further clarification because of the complexity of wastewater treatment systems. N 2 O generation is influenced by a diversity of interrelated conditions: the different species of microbes with specialized functions, the interactions among these microbes in a mixed system, and the responses of microbes to the different environmental factors and operational conditions. This chapter provides an overview of the N 2 O production pathways and mechanisms during the biological nitrogen removal (BNR) process and describes the different factors that have been reported to have an effect on N 2 O production.

show abstract

“…NO is usually detected at very low concentrations in BNR reactors. Liquid NO concentrations of 0.11 ± 0.065 mg N/L were measured in lab-scale high nitritation reactors 93 , while off-gas NO concentrations of 50 ± 10 ppm and 50−90 ppm were measured in full-scale two-stage nitritation and anammox reactors, respectively 96 . In lab-scale denitrifying reactors, less than 0.3 ppm NO in the off-gas was detected 97 .…”

Section: Nomentioning

confidence: 99%

“…NH 2 OH is highly reactive and potentially toxic with a high turnover and is typically detected at low concentrations (e.g., 0.003–0.031 mg N/L in AOB pure cultures , and 0.03–0.11 mg N/L in lab-scale partial nitritation reactors − ). As a nucleophilic reducing agent, NH 2 OH can undergo decomposition (2NH 2 OH → NH 3 + HNO + H 2 O) or oxidation by O 2 (2NH 2 OH + 1.5O 2 → 2NO + 3H 2 O) to form highly reactive oxidizing intermediates, such as HNO or NO that can chemically transform OMPs .…”

Section: Direct Versus Indirect Enzymatic Omp Transformation Mechanismsmentioning

confidence: 99%

Role of Ammonia Oxidation in Organic Micropollutant Transformation during Wastewater Treatment: Insights from Molecular, Cellular, and Community Level Observations

Schittich

Jensen

et al. 2021

Environ. Sci. Technol.

Self Cite

View full text Add to dashboard Cite

Organic micropollutants (OMPs) are a threat to aquatic environments, and wastewater treatment plants may act as a source or a barrier of OMPs entering the environment. Understanding the fate of OMPs in wastewater treatment processes is needed to establish efficient OMP removal strategies.Enhanced OMP biotransformation has been documented during biological nitrogen removal and has been attributed to the cometabolic activity of ammonia oxidizing bacteria (AOB) and, specifically, to the ammonia monooxygenase (AMO) enzyme. Yet, the exact mechanisms of OMP biotransformation are often unknown. This review aims to fundamentally and quantitatively evaluate the role of ammonia oxidation in OMP biotransformation during wastewater treatment processes. OMPs can be transformed by AOB via direct and indirect enzymatic reactions: AMO directly transforms OMPs primarily via hydroxylation, while biologically produced reactive nitrogen species (hydroxylamine (NH2OH), nitrite (NO2 − ) and nitric oxide (NO)) can chemically transform OMPs through nitration, hydroxylation and deamination and can contribute significantly to the observed OMP transformations. OMPs containing alkyl-, aliphatic hydroxyl-, ether-, and sulfide functional groups as well as substituted aromatic rings and aromatic primary amines can be biotransformed by AMO, while OMPs containing alkyl groups, phenols, secondary amines and aromatic primary amines can undergo abiotic transformations mediated by reactive nitrogen species.Higher OMP biotransformation efficiencies and rates are obtained in AOB-dominant microbial communities, especially in autotrophic reactors performing nitrification or nitritation, than in non-AOB-dominant microbial communities. The biotransformations of OMPs in wastewater treatment systems can often be linked to ammonium (NH4 + ) removal following two central lines of evidence:(i) similar transformation products (i.e. hydroxylated, nitrated and desaminated TP) are detected in wastewater treatment systems as in AOB pure cultures; (ii) consistency in OMP biotransformation (rbio, µmol/g VSS/d) to NH4 + removal (rNH4+, mol/g VSS/d) rate ratios (rbio/rNH4+) are observed for 3 individual OMPs across different systems with similar rNH4+ and AOB abundances. In this review, we conclude that AOB are the main driver of OMP biotransformation during wastewater treatment processes. The importance of biologically driven abiotic OMP transformation is quantitatively assessed and functional groups susceptible to transformations by AMO and reactive nitrogen species are systematically classified. This review will improve the prediction of OMP transformation and facilitate the design of efficient OMP removal strategies during wastewater treatment.

show abstract

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

Cited by 42 publications

References 48 publications

Abiotic Nitrous Oxide (N₂O) Production Is Strongly pH Dependent, but Contributes Little to Overall N₂O Emissions in Biological Nitrogen Removal Systems

Abiotic Nitrous Oxide (N₂O) Production Is Strongly pH Dependent, but Contributes Little to Overall N₂O Emissions in Biological Nitrogen Removal Systems

Full-scale source, mechanisms and factors affecting nitrous oxide emissions

Role of Ammonia Oxidation in Organic Micropollutant Transformation during Wastewater Treatment: Insights from Molecular, Cellular, and Community Level Observations

Contact Info

Product

Resources

About

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

Cited by 42 publications

References 48 publications

Abiotic Nitrous Oxide (N2O) Production Is Strongly pH Dependent, but Contributes Little to Overall N2O Emissions in Biological Nitrogen Removal Systems

Abiotic Nitrous Oxide (N2O) Production Is Strongly pH Dependent, but Contributes Little to Overall N2O Emissions in Biological Nitrogen Removal Systems

Full-scale source, mechanisms and factors affecting nitrous oxide emissions

Role of Ammonia Oxidation in Organic Micropollutant Transformation during Wastewater Treatment: Insights from Molecular, Cellular, and Community Level Observations

Contact Info

Product

Resources

About

Abiotic Nitrous Oxide (N₂O) Production Is Strongly pH Dependent, but Contributes Little to Overall N₂O Emissions in Biological Nitrogen Removal Systems

Abiotic Nitrous Oxide (N₂O) Production Is Strongly pH Dependent, but Contributes Little to Overall N₂O Emissions in Biological Nitrogen Removal Systems