Nitrous oxide and methane emissions from a plug-flow full-scale bioreactor and assessment of its carbon footprint

Abstract

Fugitive greenhouse gas (GHG) emissions in the form of nitrous oxide (N 2 O) and methane (CH 4 ) have been reported from many different wastewater treatment plants.However, the majority of the current literature only reports emissions during short periods of time and only focuses on one of the two GHGs. In this study, N 2 O and CH 4 emissions from the aerated parts of a plug-flow full-scale bioreactor treating municipal wastewater were studied over five months from November through March. A multiple gas hood collection system was used to simultaneously monitor the first three aerated compartments of the plug-flow bioreactor. Results show temporal variations in N 2 O emissions with N 2 O detected during November, no emissions during December and January, and a recovery of emissions from February onwards. In addition, different spatial emissions were found across the three aerated zones, with the highest N 2 O emissions detected in the second aerated zone. A daily N 2 O emission pattern was characterised by an N 2 O peak correlated with the ammonium that arrived in the monitored zone. However, CH 4 emissions occurred during the whole monitored period and showed a spatial variability inside the plug-flow bioreactor, presenting the highest emissions in the first aerated zone and then decreasing in the two subsequent zones. In addition, the dynamic carbon footprint (C-footprint

Methanotrophs: Discoveries, Environmental Relevance, and a Perspective on Current and Future Applications

“…et al, 2014). Effluents from WWTP, in particular from AD, carry a fraction of the methane dissolved which subsequently escapes to the atmosphere without control measures (Guisasola et al, 2008;Kampman et al, 2014;Schaum et al, 2016;Nguyen et al, 2019;Ribera-Guardia et al, 2019). Furthermore, in low-temperature waters, up to 60 per cent of methane can remain dissolved in the water and subsequently released into the atmosphere (Noyola et al, 2006;Souza et al, 2011).…”

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

“…The contribution of CH 4 emissions varied mostly from 4% to 19% of the overall carbon footprint (Table 6.2). In cases when N 2 O emissions are particularly low, the CH 4 emissions could be the dominant source (45-57%) of overall GHG emissions, as reported by Ribera-Guardia et al (2019). Overall, CH 4 emissions from WWTPs should be monitored, especially in facilities where anaerobic treatment is implemented.…”

“…WWTPs also emit CH 4 Ribera-Guardia et al, 2019). Emissions of CH 4 in WWTPs mainly originate from the influent, anaerobic wastewater treatment and anaerobic sludge handling processes and can present large variations from plant to plant.…”

“…The biological generation of CH 4 requires strict anaerobic conditions. Due to the short residence time, and periodical exposure to oxygen and nitrate or nitrite, it is often not believed that CH 4 can be produced from the headworks or from the aerobic/anoxic wastewater treatment processes (Ribera-Guardia et al, 2019). Instead, it is more likely to be generated in pressurized sewer mains (see next section).…”

Carbon footprint of constructed wetlands for winery wastewater treatment

“…CO2, CH4 and N2O) emissions generated in the septic tank (scenario W1), the constructed wetlands (scenario W2) and the activated sludge system (scenario W3) were measured by using a Gasmet DX4015 Fourier transform infrared (FTIR) gas analyser. The measurements of CO2, CH4 and N2O fluxes were done using the static chamber method for the constructed wetlands (scenario W2) (Chen et al, 1997;De la Varga et al, 2015;Uggetti et al, 2012) and the floating chamber method for the activated sludge treatment plant (scenario W3) (Czepiel et al, 1995;Hwang et al, 2016;Ribera-Guardia et al, 2019). Two campaigns were carried out during the vintage season (August/September 2018) and the rest of the year (February/March 2018).…”