Regional Carbon Footprint of urban wastewater treatment service: experimental study about VIVERACQUA in Veneto

Greenhouse gas emissions are major contributors to climate change, with wastewater treatment plants (WWTPs) being significant sources of these emissions. In Europe, the water cycle accounts for 1-3% of the total electric energy consumption (Longo et al., 2016) and 3-10% of the global warming potential (Samuelsson et al., 2018). The emissions of CO2 , CH4 , and N2 O constitute the largest part of CF of WWTPs (Caniani et al., 2019; Huang et al., 2020). The goal of this study is to evaluate the carbon footprint (CF) of water services for companies in the VIVERACQUA consortium, in collaboration with Marche Polytechnic University and in line with the new European directive on urban wastewater treatment. The directive aims for energy neutrality in treatment plants, and mitigation scenarios, including self-production, have been assessed. The study found that the total carbon footprint of the water service for one consortium company is 24,485 tons CO2eq/year, with the majority (16,320 tons CO2eq/year) stemming from the treatment plants. Within the carbon footprint of the treatment service, 28% of emissions are from direct process-related emissions, 31% from indirect emissions on the receiving water body, and 23% from indirect emissions related to energy consumption and production. Energy self-production scenarios using renewable sources were explored. Field measurements were also conducted to collect data on direct emissions through continuous monitoring with the MIR9000 analyzer and a floating hood, as well as discontinuous monitoring with gas bags. Indirect emissions on the receiving water body were assessed through laboratory analysis, through typical laboratory analyses for pollutant and photoacoustic spectroscopy for the determination of dissolved GHGs concentrations in order to determine the actual emission levels of the plants.