Comparison of combined and separate sewer networks for cities with hot and dry climates using AHP method

Abstract

Despite water regulations and standards that often favour separate sewer networks over combined ones, the substantial investments required-along with financial and economic limitations-make the selection of urban drainage systems particularly challenging for city managers, especially in developing countries. This study aims to identify the most suitable system for hot and dry regions by examining a real-world case in Ahvaz, Iran. Using Karizonai Sewer, an automated platform for designing and optimizing drainage systems, both combined and separate networks were planned with a focus on minimizing construction costs. Their performance under extreme loading conditions was then evaluated using SWMM software. Subsequently, a hierarchical framework of criteria and sub-criteria was established, and pairwise comparison matrices were developed based on modelling results and expert judgments. The final analysis reveals that the combined sewer network, is a better urban drainage solution for the given test case.