Mitigating CH4 and N2O emissions from domestic and industrial wastewater

Methane (CH₄) and nitrous oxide (N₂O) emissions from wastewater treatment systems significantly contribute to global greenhouse gas levels, presenting challenges to climate change mitigation efforts. CH₄ emissions primarily arise from anaerobic conditions in wastewater treatment processes, such as lagoons and open sewers, which are common in both developing and developed regions. Constructed wetlands, designed to use natural processes for pollutant removal, can also generate CH₄ and N₂O under specific conditions. The variability in wastewater treatment methods, ranging from centralized anaerobic plants and lagoons to on-site septic systems, significantly affects emissions. For instance, lagoons deeper than 2–3 m typically create anaerobic conditions conducive to CH₄ production, especially in warmer climates where temperatures exceed 15 °C. The treatment of domestic and industrial wastewater using constructed wetlands shows promising pollutant removal efficiencies, often exceeding 50 %, but also presents challenges due to potential CH₄ and N₂O emissions. Emission estimation methods include using default values (Tier 1), country-specific data (Tier 2), or advanced country-specific methodologies (Tier 3). Mitigation of CH₄ involves recovery and flaring techniques, while N₂O emissions are linked to nitrogen degradation processes in wastewater. Thus, comprehending the specific treatment processes, organic load, and environmental conditions is essential for accurate emission assessments and developing strategies to minimize the climate impact of wastewater management. © 2024 Elsevier Ltd