Exploration of sustainable driving path of rural domestic wastewater treatment-from the perspective of life cycle assessment

Most rural wastewater treatment facilities require electricity to maintain operation. Traditional fossil energy consumption increases the environmental load and greenhouse gas emissions. Wind-solar power generation is widely recognized as a renewable energy technology. However, conventional wind-solar power systems need batteries to store energy, which can lead to secondary pollution. Additionally, the alternating aerobic and anaerobic process were crucial for nitrogen and phosphorus removal, and some distributed wastewater treatment systems do not require continuity operation. Therefore, this study reports on a wind–solar power generation mode without batteries (Mode-II) to control and drive a bioecological rural domestic wastewater treatment system with a scale of 0.5 m³/day. By logic control, the inspired combination of power generation capacity and treatment process requirements was realized. The effluent COD_cr, NH₄⁺-N, and TN concentrations were 14.63 ± 7.02, 1.39 ± 1.63, and 8.65 ± 4.02 mg/L, with removal rates of 89.01 ± 4.15%, 88.58 ± 2.28%, 75.47 ± 8.84%, respectively. From the perspective of environmental load and carbon emissions, based on life cycle assessment theory, this novel approach was compared with the traditional wind–solar power generation driven mode with battery storage (Mode-I) and mains power driven mode (Mode-III). The environmental load and carbon emissions of Mode-II were 1.08 kPt and 2836 kg CO₂ eq by end-of-life (25 years), the lowest of the three modes. Compared with the mains power drive mode, the environmental load and carbon emissions of Mode-II can be repayment until years 6 and 2. The supercapacitors and solar panels were the main source of environmental load and carbon emissions for Mode-II. Overall, Mode-II was found to be the most environmentally friendly mode all over the China, which is expected to be promoted in the field of rural wastewater treatment.