Multi-level advanced monitoring and quantification of fugitive methane emissions in a full-scale water resource...

Accurate monitoring and quantification of methane (CH₄) emissions from water resource recovery facilities (WRRFs) are essential for regulatory compliance, process optimization, and the development of effective greenhouse gas (GHG) mitigation strategies. A few previous studies applied individual CH₄ sensing methods (e.g., ground sensors or satellite imaging) to quantify CH₄ emissions from wastewater treatment and biogas facilities. However, the complementary benefits of integrating multiple approaches for WRRF emissions monitoring have not been evaluated. In the current study, sixteen ground sensors were strategically distributed and installed in a Canadian WRRF to capture the spatial and temporal variabilities of CH₄ concentrations emitted from various treatment processes within the plant. In addition, a one-week on-site campaign was conducted using a handheld optical gas imaging (OGI) camera and drone-based sensors to isolate CH₄ emissions from different treatment processes. The average CH₄ emissions from the WRRF were determined to be 4.0 ± 2.5 g-CH₄/m³ of treated wastewater, representing 3.2 - 3.5% of the influent COD load to the facility. Interestingly, the on-site campaigns revealed that approximately 63% of the plant's total CH₄ emissions originated from aeration basins and primary tanks. Moreover, it was found that OGI and drone-based measurements are complementary. Drone-based measurements were effective in covering large areas and detecting dispersed emissions while the OGI camera was valuable for detecting localized emissions in areas with stagnant airflow. This study demonstrates the value of integrating multiple sensing approaches for comprehensive CH₄ monitoring and reveals valuable insights into emission hotspots, enabling more targeted and effective mitigation strategies.