Mitigating N2O gas Emission via Enhancing Denitrification in a Biological Landfill Leachate Treatment using External Carbon from Fermented Sewage Sludge

Abstract

Biological landfill leachate treatment plants have been recognized as nitrous oxide (N2O) emission source, one of the main contributors to global warming with 310 times of global warming potential (GWP) that of CO2. In this study, effect of external carbon source (C-source) was achieved on phase 2 (OLR, 41.04 ± 4.22 gCOD/L·day; 1.5 days of SRT; thermophilic condition (55 °C)), obtaining 7.04 ± 1.20 gVFAs/L as COD equivalent, degrees of hydrolysis (15.65 ± 3.35%) and acidogenesis (5.69 ±2.36%). Microbial community analysis in anaerobic fermentation reactor on phase 2 implied that degradation of sewage sludge was potentially affected by proteolytic microorganisms that produces VFAs from proteinaceous materials. Supernatant of fermented sludge (SFS) was retrieved from anaerobic fermentation reactor and used as external C-source for denitrification test. SFS showed better denitrification performance compared to methanol, showing 10.70 mgNOx-N/gVSS·hr of specific denitrification rate (SDNR). In N2O emission test without adding external C-sources, 74.51 % of aqueous N2O was emitted as N2O gas while 43.56% of aqueous N2O was emitted. The addition of SFS to landfill leachate accelerated reduction of aqueous N2O, resulting in reduced N2O emission by 41.53%. The results in this study indicates that N2O emission from biological landfill leachate treatment can be attenuated via addition of external C-source retrieved from anaerobically fermented sewage sludge.