Study on the Relationship between Different Wastewater Treatment Technologies and Effluent Standards in Jilin Liaohe River Basin Based on the Coupled Model of AHP and Fuzzy TOPSIS Method

Abstract

Wastewater treatment plants play a critical role in reducing point source pollution in watersheds; however, in taking on the task of reducing pollutants such as COD and NH3-N, they also consume energy intensively, which can result in additional greenhouse gas (GHG) emissions and operating (OAM) costs. Therefore, appropriate effluent targets should be implemented to achieve a balance between pollution load reduction, greenhouse gas emissions and operating costs, depending on the field conditions of the wastewater plant. In this study, four different wastewater treatment technologies, namely, A2/O, CASS, MBR and A/O-MBR, which are mainly operated in the Liaohe River Basin of Jilin Province, were selected using the coupled AHP and fuzzy TOPSIS models, and the appropriate effluent standards were preferred according to the characteristics of these technologies. Firstly, the AHP model is used to determine the criteria layer (environmental, economic and social benefits) of the four treatment technologies and the weights of each indicator, and then the fuzzy TOPSIS model is used to determine the indicator values of the different alternatives (effluent standards) of the four treatment technologies, and finally the optimal value of the effluent standard is determined, in terms of COD, 30 mg/L for A2/O and CASS process and 50 mg/L for MBR and A/O-MBR.