Optimization Layout and Comprehensive Benefit Analysis of Urban Sewage Treatment Plants Based on Decentralized Reuse

The centralized approach to sewage treatment limits the feasibility of nearby reuse of recycled water, whereas decentralized wastewater treatment emphasizes the integration of resource utilization, environmental protection, and social benefits. To comprehensively evaluate the performance of different spatial configurations of sewage treatment plants, a cost–benefit evaluation index system was established, comprising 12 indicators across four dimensions: cost input, economic benefits, social benefits, and ecological benefits. A mixed-integer linear programming (MILP) model was developed using ArcGIS and Python to optimize the spatial layout of treatment facilities. Within a decentralized decision-making framework, which focuses on the number, scale, and location of facilities, the model simultaneously determines the optimal deployment of plants based on local service demands and economies of scale in service zones. The optimal allocation of wastewater among these service zones and the selected treatment plants is then analyzed. The comprehensive evaluation demonstrated favorable results, indicating a high return on investment with an overall benefit-to-cost ratio of 1.54:1.