Wastewater treatment plants are of significant importance in facilitating China’s urbanization process. The fundamental purpose of wastewater treatment plants is to control water pollution and protect the environment. It is therefore essential that they are operated in a safe manner in order to achieve this goal. In order to guarantee a systematic and objective assessment of the operational safety risks inherent to wastewater treatment plants, the Wuli–Shili–Renli (WSR) theory has been introduced. Accordingly, a three-dimensional evaluation index system was developed for the assessment of these risks. A combination of subjective and objective methods utilizing game theory was employed to determine comprehensive risk factor weights. Subsequently, the material–element extension theory model was implemented in a wastewater treatment plant situated in the northern region of the Changchun Development Zone. The assessment classified the plant as Level 1 (safe), although it was determined that improvements in accident prevention are necessary. This study presents a robust framework for operational safety assessment that contributes to enhanced risk management and the long-term reliability of wastewater treatment operations. The results of the sensitivity analyses provide substantial evidence of the reliability and validity of the model.

With the rapid development of urbanization and industrialization, water resources are in increasingly short supply, and the construction of sewage treatment plants can ensure the sustainable development of water resources. To eliminate the potential safety hazards of municipal sewage treatment plants and prevent safety accidents from the source, this paper takes a municipal sewage treatment plant in Changchun as the research object, puts forward the evaluation method of the “improved Best-Worst Method (BWM)—fuzzy comprehensive evaluation method”, and carries out safety evaluation research on the research object. Firstly, combined with the technological process of sewage treatment plants, the evaluation index system is constructed from four factors: human factors, material factors, environmental factors, and management factors. Secondly, the improved BWM is used to calculate the weights. Finally, the fuzzy comprehensive evaluation method is used for safety evaluation, and the evaluation of safety status is obtained: the safety level.