Resource-Oriented Treatment Technologies for Rural Domestic Sewage in China Amidst Population Shrinkage: A Case Study of Heyang County in Guanzhong Region, Shaanxi Province

The rural population shrinkage caused by China’s imbalanced regional development poses challenges to infrastructure configuration and operation. Traditional centralized sewage treatment models face issues in cost-effectiveness, facility utilization rates, and sustainable maintenance, necessitating the exploration of adaptive governance technologies under new demographic conditions. The utilization-driven governance approach is recognized as an emerging method for rural domestic sewage management. This study selects Heyang County, a representative agricultural area in Guanzhong Plain, as a case study. Through mixed-methods research integrating qualitative and quantitative approaches, we analyze the correlation between the Population Shrinkage Index (PSI) and facility operational efficiency, investigate the impact of resident population dynamics on rural sewage treatment patterns, and establish a theoretical “Source–Transmission–Sink” framework. Synthesizing local traditional governance practices with modern technological solutions, we propose a resource-oriented treatment system adapted to population shrinkage trends, comprising three technical components: source process reduction, transmission process interception, and sink process attenuation. This research emphasizes adjusting green water infrastructure (GWI) spatial configurations according to village characteristics in production–living–ecological spaces, forming a hierarchical attenuation mechanism through circular transmission pathways. This facilitates the transition from gray-infrastructure-dependent models to holistic pollution control systems with resource recovery capabilities. The findings provide theoretical foundations for policymaking and infrastructure planning in rural sewage management, offering significant references for sustainable rural water resource governance.