Carbon Footprint and Sensitive Design Parameters of Residential and Industrial (Whey) Wastewater Treatment Plants: A Comparative Life Cycle Assessment (LCA)

This study calculates the carbon footprint of chemical coagulants and operational energy for residential and industrial (whey digestion) wastewater treatment using ReCiPe 2016 methodology within a clearly defined system boundary from cradle to gate. Data from water treatment facilities have been analyzed to quantify environmental impacts and identify sensitive design parameters. The estimated emission of treating 1 m3 of wastewater from whey digestion (7.1195 kg CO2 eq) is over 50 times higher than that of a residential one (0.1349 kg CO2 eq). Life cycle impact assessment (LCIA) reveals that iron (III) chloride (40% in H2O) and operational electricity consumption have higher impact categories compared to other design components. The uncertainty analysis indicates that electricity consumption (r = 0.4) is the dominant contributor to emissions, with a mean value of 4.22 kg CO2-eq per m3 of wastewater treated. In contrast, iron (III) chloride emerges as the most sensitive parameter (r = 0.88) with small variations in dosing causing a disproportionately large impact on overall emissions. Therefore, the optimized use of an iron-based coagulant, the adoption of membrane electrolysis, and the integration of renewable electricity into the process supply chains have been identified as effective strategies for reducing emissions.