Comparison and selection of rural domestic sewage treatment processes based on carbon footprint accounting

As a vital part of the wastewater treatment industry, rural domestic wastewater treatment holds substantial potential for emission reduction. However, there has been little research on carbon footprint accounting in rural domestic wastewater treatment processes. Therefore, accounting for the carbon footprint of these processes is crucial. An emission inventory based on life cycle assessment (LCA) was compiled, and carbon footprint accounting for four typical rural domestic wastewater treatment technologies was conducted based on this inventory. The results indicated that the carbon footprint of the Anaerobic-oxic process (AO) was 1.635 kg/m³ (in terms of CO₂-eq, applies throughout the text), the membrane bio-reactor process (MBR) was 2.140 kg/m³, the biological aerated filter (BAF) + constructed wetland (CW) process was 0.814 kg/m³, and the Oxygenating tank (OT) + CW process was 1.060 kg/m³. The factors influencing the carbon footprint ranked by impact were electricity consumption (45.70%-64.61%), direct greenhouse gas emissions (20.02%-29.73%), chemical/material consumption (6.93%-16.70%), sludge treatment and disposal (5.53%-9.99%), and effluent discharge (2.01%-5.98%). Under the "dual carbon" strategy, BAF+CW process emerged as a relatively ideal rural domestic wastewater treatment process. The results of carbon emissions per unit of pollutant and sensitivity analysis showed that reducing electricity consumption was identified as the primary approach to lowering the carbon footprint. This study could provide a theoretical basis for selecting rural domestic wastewater treatment processes under the "dual carbon" strategy.