Introduction: Decentralized wastewater treatment facilities are an expensive approach for developing countries. Decentralized wastewater treatment plants (DWWTPs) are a flexible technology. They have low construction and operational costs. Site selection is the most significant stage in the implementation of a DWWTP_S. Therefore, the present study aimed to perform a site selection among the proposed locations for a DWWTP_S in Qom.
Materials and Methods: In this experimental study, the criteria of DWWTP_S site selection were determined, judged by interview experts, and analyzed by the analytic hierarchy process (AHP) using the Expert Choice 11 software. Finally,  according to the performed judgments, the proposed locations (sites) were ranked in order of preference.
Results: The slope of the land held maximum importance, while the density of the population had minimum importance in the site selection process. The southern and north-eastern regions of Qom had appropriate sites.
Conclusion: The AHP is a decision analysis method that considers both the qualitative and quantitative information applicable for the various subjects, especially site selection. In this study, according to the expert’s notices, the AHP technique could determine an appropriate site among the proposed locations for the construction of DWWTP_S.