1. Seasonality of nitrous oxide emissions at six full-scale wastewater treatment plants.
- Author
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Sieranen M, Hilander H, Haimi H, Larsson T, Kuokkanen A, and Mikola A
- Subjects
- Carbon Footprint, Cold Temperature, Sewage, Water, Nitrous Oxide, Greenhouse Gases
- Abstract
Nitrous oxide (N
2 O) is an ozone-depleting greenhouse gas that contributes significantly to the carbon footprint of a wastewater treatment plant (WWTP). Plant-specific measurement campaigns are required to reliably quantify the emission level that has been found to significantly vary between WWTPs. In this study, the N2 O emissions were quantified from five full-scale WWTPs during 4-19-day measurement campaigns conducted under both cold period conditions (water temperature below 12 °C) and warm period conditions (water temperature from 12 to 20 °C). The measurement data were studied alongside long-term monitoring data from a sixth WWTP. The calculated emission factors (EFs) varied from near 0 to 1.8% relative to the influent total nitrogen load. The results confirmed a significant seasonality of N2 O emissions as well as a notable variation between WWTPs in the emission level, which a single fixed EF cannot represent. Wastewater temperature was one explanatory factor for the emission seasonality. Both low and high emissions were measured from denitrifying-nitrifying activated sludge (AS) processes, while the emissions from only nitrifying AS processes were consistently high. Nitrite (NO2 - ) at the end of the aerobic zones of the AS process was linked to the variability in N2 O emissions during the cold period.- Published
- 2024
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