Nitrous Oxide Emissions from Wastewater Treatment Plants. A Balancing Act (original) (raw)
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Nitrous oxide emission during wastewater treatment
Water Research, 2009
Nitrous oxide (N 2 O), a potent greenhouse gas, can be emitted during wastewater treatment, significantly contributing to the greenhouse gas footprint. Measurements at lab-scale and full-scale wastewater treatment plants (WWTPs) have demonstrated that N 2 O can be emitted in substantial amounts during nitrogen removal in WWTPs, however, a large variation in reported emission values exists. Analysis of literature data enabled the identification of the most important operational parameters leading to N 2 O emission in WWTPs: (i) low dissolved oxygen concentration in the nitrification and denitrification stages, (ii) increased nitrite concentrations in both nitrification and denitrification stages, and (iii) low COD/N ratio in the denitrification stage. From the literature it remains unclear whether nitrifying or denitrifying microorganisms are the main source of N 2 O emissions. Operational strategies to prevent N 2 O emission from WWTPs are discussed and areas in which further research is urgently required are identified.
Recent advances in nitrous oxide production and mitigation in wastewater treatment
Water Research, 2020
Nitrous oxide (N 2 O) emitted from wastewater treatment plants has caused widespread concern. Over the past decade, people have made tremendous effort s to discover the microorganisms responsible for N 2 O production, elucidate metabolic pathways, establish production models and formulate mitigation strategies. The ultimate goal of all these effort s is to shed new light on how N 2 O is produced and how to reduce it, and one of the best ways is to find key opportunities by integrating the information obtained. This review article critically evaluates the knowledge gained in the field within a decade, especially in N 2 O production microbiology, biochemistry, models and mitigation strategies, with a focus on denitrification. Previous research has greatly deepened the understanding of the N 2 O generation mechanism, but further efforts are still needed due to the lack of standardized methodology for establishing N 2 O mitigation strategies in full-scale systems. One of the challenges seems to be to convert the denitrification process from a net N 2 O source into an effective sink, which is recommended as a key opportunity to reduce N 2 O production in this review.
Nitrous Oxide Emissions and the Anthropogenic Nitrogen in Wastewater and Solid Waste
Journal of Environmental Engineering, 2002
In the 20th century, human interference in the nitrogen cycle has caused a doubling of the global nitrogen fixation rate ͑an element critical in the proteins of all organisms͒, thereby intensifying global nitrous oxide (N 2 O) production during microbial nitrification and denitrification. Nitrous oxide is a powerful greenhouse gas, important in climate change, and as well, is a stratospheric ozonedepleting substance. It is likely that much of the Earth's population now relies on anthropogenic nitrogen in its food supplies, resulting in anthropogenic nitrogen contained in wastes requiring management. Food production is considered as a source of global nitrous oxide emissions; however, the nitrogen in wastewater and solid wastes may be a significant fate of much anthropogenic nitrogen. This factor has largely escaped in-depth, critical analysis from the perspective of nitrous oxide emissions. This paper introduces nitrogen cycling and nitrous oxide production and reviews the research currently available on N 2 O emissions from wastewater treatment operations, landfilling, composting, and incineration; demonstrating that each process can emit large amounts of this important gas. This is followed by a discussion of the limited research. The relative importance of N 2 O in waste management is also estimated, indicating that wastewater treatment may be the most important operation for managing anthropogenic nitrogen in wastes.
Significance of Wastewater Treatment to Nitrous Oxide Emission
Civil and Environmental Engineering Reports, 2021
The sewage flowing into the wastewater treatment plant through the sewer system, as well as transported by the slurry fleet, are subjected to treatment processes. These processes, carried out under both aerobic and anaerobic conditions, contribute to the emission of greenhouse gases. On the basis of available reports and previous research, the emission of nitrous oxide (N2O) from wastewater was estimated at approx. 4-5% in relation to the global amount of this gas emission from anthropogenic sources. Data obtained from the operation of full-scale WWTPs show a wide range of values of the N2O emission factors from 0.0006 to 0.045 (kgN2O-N/kgN) [18]. The article describes possible sources of nitrous oxide emission from wastewater treatment plants and presents the basic principles of its balancing.
Journal of Environment Quality, 2011
Nitrous oxide (N 2 O) is a long-lived and potent greenhouse gas produced during microbial nitrifi cation and denitrifi cation. In developed countries, centralized water reclamation plants often use these processes for N removal before effl uent is used for irrigation or discharged to surface water, thus making this treatment a potentially large source of N 2 O in urban areas. In the arid but densely populated southwestern United States, water reclamation for irrigation is an important alternative to longdistance water importation. We measured N 2 O concentrations and fl uxes from several wastewater treatment processes in urban southern California. We found that N removal during water reclamation may lead to in situ N 2 O emission rates that are three or more times greater than traditional treatment processes (C oxidation only). In the water reclamation plants tested, N 2 O production was a greater percentage of total N removed (1.2%) than traditional treatment processes (C oxidation only) (0.4%). We also measured stable isotope ratios ( 15 N and 18 O) of emitted N 2 O and found distinct 15 N signatures of N 2 O from denitrifi cation (0.0 ± 4.0‰) and nitrifi cation reactors ( 24.5 ± 2.2‰), respectively. ese isotope data confi rm that both nitrifi cation and denitrifi cation contribute to N 2 O emissions within the same treatment plant. Our estimates indicate that N 2 O emissions from biological N removal for water reclamation may be several orders of magnitude greater than N 2 O emissions from agricultural activities in highly urbanized southern California. Our results suggest that wastewater treatment that includes biological nitrogen removal can signifi cantly increase urban N 2 O emissions.
Nitrous oxide emissions from high rate algal ponds treating domestic wastewater
Bioresource Technology, 2015
h i g h l i g h t s Under normal operation, HRAP treating wastewater released <2 nmol N 2 O/g TSS h. These N 2 O emissions (60.0047% N input) generated a low carbon footprint. External supply of nitrite significantly boosted N 2 O production in darkness. Ammonium overloading was associated with N 2 O emissions up to 11 nmol/g TSS h. C. vulgaris was the most likely significant N 2 O producer in the HRAP microcosms.
Factors Affecting Nitrous Oxide Emissions from Activated Sludge Wastewater Treatment Plants—A Review
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Nitrous oxide (N2O) is a greenhouse gas contributing to ozone layer depletion and climate change. Wastewater treatment plants (WWTPs) contribute significantly to the global anthropogenic N2O emissions. The main factors affecting N2O emissions are the dissolved oxygen concentration (DO), the nitrite accumulation, the rapidly changing process conditions, the substrate composition and COD/N ratio, the pH, and the temperature. Low DO in the nitrification process results in higher N2O emissions, whereas high aeration rate in the nitration/anammox process results in higher N2O production. High DO in the denitrification inhibits the N2O reductase synthesis/activity, leading to N2O accumulation. High nitrite accumulation in both the nitrification and denitrification processes leads to high N2O emissions. Transient DO changes and rapid shifts in pH result in high N2O production. Ammonia shock loads leads to incomplete nitrification, resulting in NO2− accumulation and N2O formation. Limiting ...
The Mechanism and Affecting Factors of Nitrous Oxide Emission in Wastewater Treatment
Nitrous oxide (N 2 O) can be produced and directly emitted from wastewater treaatment plants (WWTPs). N 2 O not only is a greenhouse gas, with an approximately 300-fold warming effects compared to carbon dioxide, also reacts with ozone in the stratosphere leading to ozone layer depletion. The concentration of N 2 O the atmosphere increasing at a rate of 0.2-0.3% per year. Watewater treatment is a potential antropogenic source of N 2 O to the atmosphere. In this review, the mechanisms of N 2 O production and factors leading to N 2 O emission in wastewater treatment are discussed.
Environmental Science & Technology, 2011
The increasing regulatory demands to achieve greater nutrient removal from wastewater treatment plant effluents, while minimizing infrastructure investments and operating costs, has resulted in the development of several innovative biological nitrogen removal (BNR) processes. Partial nitrification based processes such as the single reactor system for high ammonium removal over nitrite (SHARON 1 ) and its variants are attractive for treating high-strength nitrogen waste streams such as anaerobic digestion reject water or centrate, owing to their reduced consumption of energy (for aeration) and organic carbon (for denitrification). Indeed, separate treatment of centrate via partial nitrification is one of the options for limiting nitrogen discharges to Jamaica Bay in New York City 2 and is part of PlaNYC, a sustainability plan for New York City targeted for 2030.
Nitrous oxide emissions from the oxidation tank of a pilot activated sludge plant
Water Research, 2012
This study discusses the results of the continuous monitoring of nitrous oxide emissions from the oxidation tank of a pilot conventional wastewater treatment plant. Nitrous oxide emissions from biological processes for nitrogen removal in wastewater treatment plants have drawn great attention over the last years, due to the high greenhouse effect. However, even if several studies have been carried out to quantify nitrous oxide emission rates from different types of treatment, quite wide ranges have been reported. Only grab samples or continuous measurements over limited periods were considered in previous studies, which can account for the wide variability of the obtained results. Through continuous monitoring over several months, our work tries to fill this gap of knowledge and get a deeper insight into nitrous oxide daily and weekly emission dynamics. Moreover, the influence of some operating conditions (sludge age, dissolved oxygen concentration in the oxidation tank, nitrogen load) was studied to determine good practices for wastewater treatment plant operation aiming at the reduction of nitrous oxide emissions. The dissolved oxygen set-point is shown to play a major role in nitrous oxide emissions. Low sludge ages and high nitrogen loads are responsible for higher emissions as well. An interesting pattern has been observed, with quite negligible emissions during most of the day and a peak with a bell-like shape in the morning in the hours of maximum nitrogen load in the plant, correlated to the ammonia and nitrite peaks in the tank.