A decision framework for rural domestic sewage treatment models and process: Evidence from Inner Mongolia Autonomous Region, China.

Rural domestic sewage treatment is critical for environmental protection. This study defines the spatial pattern of villages from the perspective of rural sewage treatment and develops an integrated decision-making system to propose a sewage treatment mode and scheme suitable for local conditions. By considering the village spatial layout and terrain factors, a decision tree model of residential density and terrain type was constructed with accuracies of 76.47 % and 96.00 %, respectively. Combined with binary classification probability unit regression, an appropriate sewage treatment mode for the village was determined with 87.00 % accuracy. The Analytic Hierarchy Process (AHP), combined with the Technique for Order Preference (TOPSIS) by Similarity to an Ideal Solution model, formed the basis for optimal treatment process selection under different emission standards. Verification was conducted in 542 villages across three counties of the Inner Mongolia Autonomous Region, focusing on the standard effluent effect (0.3773), low investment cost (0.3196), and high standard effluent effect (0.5115) to determine the best treatment process for the same emission standard under different needs. The annual environmental and carbon emission benefits of sewage treatment in these villages were estimated. This model matches village density, geographic feature, and social development level, and provides scientific support and a theoretical basis for rural sewage treatment decision-making.