Resolving the facility-specific increase of local greenhouse gas concentrations by an industrial wastewater treatment plant

Wastewater treatment plants (WWTPs) have been the fourth largest sector for global methane emissions and fifth for nitrous oxide, generating 2.2% of the annual anthropogenic greenhouse gas (GHG) emissions. However, few studies have systematically examined the impact of an individual WWTP on the atmospheric GHG levels in surrounding areas, and in particular, the comprehensive analysis of facility-specific contribution is lacking. To address the research gap, this work performed AERMOD simulation with a 12-month GHG monitoring campaign at a full-scale industrial WWTP, covering all the 18 emission units in it. For the five populated towns in a 20 × 20 km area nearby, the increase of GHG concentration ranged from 13.0 to 83.2 ppb CO2-eq yr -1 , which was 1.45% of the global growth rate on average. A more detailed evaluation was conducted on Duct 1-5 and Ox A/B. It was found that these seven facilities produced 95.4% of the total GHG emissions, but caused only 86.9% of the concentration changes. Regardless of the type of GHGs, the ratios of concentration to emission were consistently lower than one for points sources, while higher than one for area sources. The model reliability was further validated through two additional months of continuous monitoring. These findings underscored the importance of incorporating facility-specific contributions on local GHG concentrations into the development of mitigation strategies for WWTP in future. • GHG emissions of all 18 units in an industrial WWTP were monitored for 12 months. • Contribution of WWTP on local GHG distribution was evaluated by AERMOD simulation. • CH 4 and N 2 O increases at nearby towns were 56 to 378.8 and 3.1 to 24 ppt yr -1 . • C/E ratios were constantly below 1 for point sources, and above 1 for area ones.