Greenhouse gases from wastewater treatment plant: towards a new protocol for field measurements

Greenhouse gases (GHGs) emission from wastewater treatment plants (WWTPs) represents anincreasing interest in the water industry at the present moment. The biological processes neededfor treating wastewater have been found responsible for the unintentional generation of GHGs,such as carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). The quality and quantityof a GHG emitted from a WWTP can significantly vary with the wastewater treated, the processconfiguration, and the strategies employed in process control. In the recent past, efforts formonitoring and accounting for GHGs emissions from WWTPs have considerably increased, andclassifications of emission type were proposed to facilitate reporting. However, knowledge gaps(e.g., N2O production dynamics) and data availability mar the quantification of a WWTP carbonfootprint. Moreover, too often the acquired information is insufficient to understand the dynamicsresponsible for GHG production. Further, it is not even comparable with measurements fromdifferent plants due to the heterogeneity of materials, methods, and instrumentation used. For thesereasons, in order to produce useful and comparable information for assessing the carbon footprintof WWTPs, there is a crescent need for a generally accepted methodology for GHGsmeasurement. This paper proposes a comprehensive protocol for monitoring and accounting fordirect and internal indirect GHG emissions related to the aerated compartments of biologicalWWTPs. The proposed protocol also provides important guidelines for quantifying thecontribution of anaerobic processes to the carbon footprint of the plant.