Three-compartment septic tanks are a prominently advocated environmentally sustainable sanitation facility in rural China. However, the comprehensive elimination efficacy and underlying mechanisms of pathogenic bacteria within septic tanks remain incompletely understood. In particular, the operational performance in low-temperature conditions has received limited attention in the existing literature. In this work, a simulation of the three-compartment septic tank treatment system was conducted under low-temperature conditions (15 °C). The operational results exemplify the synergistic interplay of volatile fatty acids (VFAs), NH₃-N, and bacterial communities, culminating in a partial reduction in Enterococcus faecalis, Escherichia coli, Staphylococcus aureus, and Salmonella enteritidis, within the three-compartment septic tank. Their respective population abundances were decreased by magnitudes of 2.2, 1.3, 0.03, and 1.46 logarithmic units (copies/mL), respectively. Through the utilization of qPCR and physicochemical indicators, it was observed that the bactericidal effect of VFA primarily occurred during the initial 0–21-day period, while NH₃-N consistently proved to be the most vital sterilizing agent throughout the operation of the three-compartment septic tank. Predominant bacterial communities within the septic tank, such as Christensenellaceae_R-7_group, Brevundimonas, Acinetobacter, and Saccharimonadales, exerted substantial inhibitory impacts on Enterococcus faecalis, Escherichia coli, and Salmonella enteritidis through niche competition and suppression. In essence, this study elucidated the actual efficiency of elimination and the underlying mechanisms of typical pathogenic bacteria within three-compartment septic tanks in low-temperature conditions, thereby providing compelling evidence supporting the viability of environmentally sound treatment using such septic tanks. Concurrently, it also shed light on several limitations associated with this treatment approach, aiming to contribute valuable insights for the assessment of ecological risks and health hazards associated with the environmentally benign treatment of rural toilet waste.

Improving the rural living environment is of great significance in enhancing the life quality of rural residents and promoting rural sustainable development. The Chinese government initiated a nationwide three-year action in 2018, followed by a five-year campaign starting in 2021, to improve the rural living environment. Despite these efforts, comprehensive assessment covering multiple facets of the rural living environment at the national level remained scarce. A novel evaluation method was proposed in this study that included seven aspects and nineteen indicators, applied AHP for weighting, and PLS-SEM to analyze the relationships between variables. Then, the completion of key tasks of rural living environment improvement in 37 counties, which were incentivized by the State Council on account of its excellent governance results, was comprehensively investigated and evaluated. The assessment of key tasks in the 37 incentivized counties revealed high completion in rural household solid waste disposal, domestic sewage treatment, and toilet improvement. However, the level of the rural living environment was uneven among different regions, and the progress varied in different key tasks. The funds input had a greater impact on the comprehensive level of rural living environment than social and economic factors. Accordingly, the government should provide more targeted financial and policy support to underdeveloped areas. And priority should be given to the sewage treatment and sanitation, especially in rural and remote areas. Furthermore, local governments should diversify funding sources to ensure the sustainability of rural living environment development. These findings provide a theoretical basis for developing policies and specific plans to address the challenges of financial investment and rural living environment management in China and other developing countries and regions worldwide.