en Environmental Health, Sciences, and Engineering Environmental Health, Sciences, and Engineering پژوهشي Original Article <div style="text-align: justify;"><span style="font-size:14px;"><span style="font-family:times new roman;"><strong>Background:</strong> Population growth and industrial and agricultural activities have increased the consumption of water, leading to clean water scarcity. Wastewater treatment is an important concern as determining proper sites for wastewater treatment plants (WWTP) largely influences proper operation. The present study aimed to determine an optimized site for WWTP in the rural complexes of Zanjanrood catchment in Zanjan province, Iran.<br> <strong>Methods:</strong> The site priority map was generated using the geographical information system (GIS) and analytical hierarchy process (AHP). Locating of the plants was based on various parameters. After map preparation, the weight of each parameter was determined using the AHP approach, and the conversion of the layers was performed using the GIS. The site priority map for each sub-catchment was determined and optimized.<br> <strong>Results:</strong> In the criteria pairwise comparison matrix, the distance from the city had the highest value (16%), while the distance from the oil and gas transmission pipelines had the lowest value (1%). The site was located at the lowest elevation compared to the villages in each complex.<br> <strong>Conclusion:</strong> According to the results, the AHP followed by the optimization method could pinpoint the optimal sites for the environmental protection of treatment plant construction in rural areas.</span></span></div> Site selection,Wastewater treatment plant,Optimization,AHP,GIS 137 144 http://jhehp.zums.ac.ir/browse.php?a_code=A-10-72-2&slc_lang=en&sid=1 Samaneh Taghilou samanetaghilou@yahoo.com 10031947532846009751 10031947532846009751 No Department of Environmental Health Engineering, School of Public Health, Zanjan University of Medical Sciences, Zanjan, Iran. Mazyar Peyda Mazyarpeyda@yahoo.com 10031947532846009752 10031947532846009752 Yes Department of Environmental Health Engineering, School of Public Health, Zanjan University of Medical Sciences, Zanjan, Iran. Younes Khosravi khosravi@znu.ac.ir 10031947532846009753 10031947532846009753 No Department of Environmental Science, School of Science, University of Zanjan, Iran. Mohammad Reza Mehrasbi zmehr@zums.ac.ir 10031947532846009754 10031947532846009754 No Department of Environmental Health Engineering, School of Public Health, Zanjan University of Medical Sciences, Zanjan, Iran.