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Wastewater and landfill leachate treatment processes have the potential to generate nitrous oxide (N 2 O) and methane (CH 4), both significant greenhouse gases (GHG). However, little is known about these emissions when a combined treatment approach (wastewater with leachate) is utilized. This study aimed to assess the emissions of these gases and nutrient removal in an anaerobic/aerobic/anoxic sequencing batch reactor (SBR) employed for treating wastewater with landfill leachate (1% v/v). Leachate contributes significantly to the removal of organic matter and nutrients, primarily phosphorus. The production and emission of N 2 O occurred during the aerobic phase, whereas CH 4 was produced in the anaerobic and anoxic phases. This gas was emitted at the beginning of the aerobic phase and in the end of anoxic phase. The emission factors obtained in this work were 0.0108 and 0.0119 kg N 2 O-N per kg TN influent and 0.000225 and 0.000253 kg CH 4 -C per kg COD influent with and without landfill leachate, respectively. Regarding CO 2 -equivalent, the N 2 O was the major contributor, accounting for 99% of the emitted GHG by the process. Further studies are required; however, the main findings of this study suggest that this system may be appropriate when lower GHG emissions are required. [Display omitted] • The performance of anaerobic/aerobic/anoxic SBR was not impacted by adding of 1% leachate into wastewater. • The introduction of leachate increased significantly the N 2 O production and emissions. • CH 4 production and emission were similar in two experiments (processes with and without leachate). • N 2 O was the major contributor to CO 2 -equivalent emissions (90%) in two experiments. • Emission factors from these two systems were lower than those cited by the IPCC protocols. [ABSTRACT FROM AUTHOR]

Total nitrogen (TN) removal by sewage treatment required the development of nitrifying and denitrifying activities; however, these metabolite activities can produce and emit nitrous oxide (N 2 O), one of the greenhouse gases (GHG). With the expansion of sewage treatment in the world, compact systems such as moving bed biofilm reactor (MBBR) may be promising, mainly in more populated cities. However, little is known about N 2 O emission by the MBBR. This work investigated the N-NH x and TN removal, N 2 O production and emission and nitrogen mass balance in a MBBR under organic load and airflow variation. The highest TN removal (47%) was observed under higher load and higher aeration rate. Meanwhile, the MBBR under lower load and lower airflow had the lowest efficiency of TN and N-NH x removal probably due to a lower nitrifying activity. The N 2 O emission factors were lower than 1.6% (value estimated by the IPCC for sewage aerobic treatment systems). In addition, in the essay with higher load and lower airflow, half of removed TN was released by settled sludge and there is little research about this subject. Therefore, the MBBR showed to be a promising process for nitrogen removal with little emission of N 2 O even under different operational conditions that normally can occur in sanitary sewage system in cities around the world. • Importance of dissolved oxygen to N-NHx removal and nitrification activity in MBBR. • Low N 2 O emission factor in MBBR even under high aeration rate condition. • High removal of nitrogen in MBBR by settling sludge under low airflow condition. • High removal of nitrogen in MBBR by atmospheric air (as N 2) under high airflow condition. [ABSTRACT FROM AUTHOR]