Suitability evaluation of rural domestic sewage treatment processes in cold areas of Northeast China: Regional differences analysis and engineering application

Rural domestic sewage (RDS) has been identified as one of the major factors hindering rural revitalization. The results of field research show that the cold areas of Northeast China have the characteristics such as scattered rural distribution and long duration of low temperature in winter, which makes it difficult to choose the most effective domestic sewage treatment processes. As a multi-objective decision-making issue based on specific scenarios, this study combines Analytic Hierarchy Process (AHP) with Fuzzy Comprehensive Evaluation (FCE) to establish a new suitability evaluation model for RDS in those areas. The model consists of sixteen evaluation factors covering aspect of technical performance, treatment effect, construction and operation, and economic benefits. Three treatment processes are presented and evaluated. The results of weighting calculation demonstrate that economic benefits is the primary factor in the selection of RDS treatment processes in cold areas, with a weighting value of 0.3118. The comprehensive scores of AHP-FCE for those three processes are 92.5070, 87.9390 and 85.7870, respectively, A/O or multi-stage A/O process is recommended as the optimal solution for RDS treatment in cold areas. Electrochemical technology is highly consistent with the development prospect of RDS treatment in cold areas due to its advantages such as freedom from temperature constraints and cost-saving. In order to further verify the general application of the evaluation results, the multi-stage A/O process is combined with electrochemical technology and applied to the practical engineering. The operation results show that the effluent concentration of COD, SS, NH4+-N and TP can meet the emission standards with lowest operation cost. The evaluation model proposed in this study can be a useful tool for government agencies, design firms and other related stakeholders to scientifically plan RDS treatment projects.