Nitrogen removal and nitrous oxide emissions from woodchip bioreactors treating agricultural drainage waters

Abstract Nitrous oxide emissions can contribute significantly to the carbon footprint of municipal wastewater treatment plants even though emissions from conventional nitrogen removal processes are assumed to be moderate. An increased risk for high emissions can occur in connection with process disturbances and nitrite (NO2−) accumulation. This work describes the findings at a large municipal wastewater treatment plant where the levels of NO2− in the activated sludge process effluent were spontaneously and strongly increased on several activated sludge lines which was suspected to be due to shortcut nitrogen removal that stabilized for several months. The high NO2− levels were linked to a dramatic increase in nitrous oxide (N2O) emissions. As much as over 20% of the daily influent nitrogen load was emitted as N2O. These observations indicate that highly increased NO2− levels can occur in conventional activated sludge processes and result in high nitrous oxide emissions. They also raise questions concerning the risk of increased greenhouse gas (GHG) emissions of the nitritation-denitritation processes – although the uncontrolled nature of the event described here must be taken into consideration – and underline the importance of continuous monitoring and control of N2O emissions.

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Evaluation of two start-up strategies to obtain nitrogen removal via nitrite and examination of the nitrous oxide emissions for different nitritation levels during the treatment of slaughterhouse wastewater

Journal of Chemical Technology & Biotechnology ◽

10.1002/jctb.5403 ◽

2017 ◽

Vol 93 (2) ◽

pp. 569-576 ◽

Cited By ~ 4

Author(s):

Thomas Dobbeleers ◽

Michel Caluwé ◽

Dominque Daens ◽

Luc Geuens ◽

Jan Dries

Keyword(s):

Nitrous Oxide ◽

Nitrogen Removal ◽

Nitrous Oxide Emissions ◽

Slaughterhouse Wastewater ◽

Start Up

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Nitrogen removal and nitrous oxide emissions in woodchips biofilters treating agricultural drainage waters

10.5194/egusphere-egu2020-3318 ◽

2020 ◽

Author(s):

Joachim Audet ◽

Dominik Zak ◽

Carl Christian Hoffmann

Keyword(s):

Gas Chromatography ◽

Nitrous Oxide ◽

Nitrogen Removal ◽

Drainage Water ◽

Agricultural Landscapes ◽

Nitrous Oxide Emissions ◽

Temperate Climate ◽

Closed Chamber ◽

Total N ◽

N Removal

Eutrophication of aquatic ecosystems provoked by excess nitrogen (N) concentration is still a major concern worldwide with severe consequences such as hypoxia, biodiversity loss, and degradation of drinking water quality. To face these challenges, a novel N mitigation measure has emerged in the last decades consisting of biofilters made of woodchips. Drainage water from agricultural areas infiltrate through a layer of woodchips before it discharges to an aquatic recipient such as a ditch or a stream. The goal with this technique is to provide optimal conditions for denitrification i.e. an easy degradable carbon source (the woodchips) and an anaerobic environment. There is, however, some concerns regarding the emissions of the greenhouse gas nitrous oxide (N2O) which can be a by-product of denitrification.Here, we present results on N removal and N2O emissions from 9 biofilters differing in age (1&#8211;8 years) and representing a total of 18 years of monitoring. The biofilters were all located in agricultural catchments in Denmark (temperate climate conditions). Nitrogen removal in the biofilters was estimated using a mass balance approach measuring N species dissolved in the water (total N, nitrate, nitrite, ammonium) using time proportional automated samplers placed at inlet and outlet of the biofilters. Nitrous oxide emissions were measured every third week both as gaseous form at the surface of the biofilters (closed chamber technique and gas chromatography) and in dissolved form in the water phase at inlet and outlet of the biofilters (headspace technique and gas chromatography). We take advantage of this unique dataset to identify the factors enabling to maximize N removal while minimizing N2O emissions. Furthermore, we make a first assessment of the potential impact of the increasing number of biofilters on N2O emissions in agricultural landscapes.

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Nitrous oxide emission from agricultural drainage waters

Global Change Biology ◽

10.1046/j.1365-2486.2003.00584.x ◽

2003 ◽

Vol 9 (2) ◽

pp. 195-203 ◽

Cited By ~ 90

Author(s):

David S. Reay ◽

Keith A. Smith ◽

Anthony C. Edwards

Keyword(s):

Nitrous Oxide ◽

Nitrous Oxide Emission ◽

Agricultural Drainage ◽

Drainage Waters

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Nitrite build-up effect on nitrous oxide emissions in a laboratory-scale anaerobic/aerobic/anoxic/aerobic sequencing batch reactor

Ambiente e Agua - An Interdisciplinary Journal of Applied Science ◽

10.4136/ambi-agua.2634 ◽

2021 ◽

Vol 16 (2) ◽

pp. 1

Author(s):

Larissa Coelho Auto Gomes ◽

Barbara Costa Pereira ◽

Renato Pereira Ribeiro ◽

Jaime Lopes da Mota Oliveira

Keyword(s):

Nitrous Oxide ◽

Nitrogen Removal ◽

Sequencing Batch Reactor ◽

Batch Reactor ◽

Mitigation Strategies ◽

Nitrous Oxide Emissions ◽

Biological Nitrogen Removal ◽

N2o Emissions ◽

N2o Production ◽

Biological Nitrogen

Biological wastewater treatment processes with biological nitrogen removal are potential sources of nitrous oxide (N2O) emissions. It is important to expand knowledge on the controlling factors associated with N2O production, in order to propose emission mitigation strategies. This study therefore sought to identify the parameters that favor nitrite (NO2-) accumulation and its influence on N2O production and emission in an anaerobic/aerobic/anoxic/aerobic sequencing batch reactor with biological nitrogen removal. Even with controlled dissolved oxygen concentrations and oxidation reduction potential, the first aerobic phase promoted only partial nitrification, resulting in NO2- build-up (ranging from 29 to 57%) and consequent N2O generation. The NO2- was not fully consumed in the subsequent anoxic phase, leading to even greater N2O production through partial denitrification. A direct relationship was observed between NO2- accumulation in these phases and N2O production. In the first aerobic phase, the N2O/NO2- ratio varied between 0.5 to 8.5%, while in the anoxic one values ranged between 8.3 and 22.7%. Higher N2O production was therefore noted during the anoxic phase compared to the first aerobic phase. As a result, the highest N2O fluxes occurred in the second aerobic phase, ranging from 706 to 2416 mg N m-2 h-1, as soon as aeration was triggered. Complete nitrification and denitrification promotion in this system was proven to be the key factor to avoid NO2- build-up and, consequently, N2O emissions.

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