Optimal Design of Urban Sewer Networks Underlining the Execution Aspects (Case Study: Sewer Network of Urmia City)

In this paper a genetic algorithm method is applied for the optimal design of sewer networks. By studying the list price and the records and reports of contractors of sewer network construction, a cost function is derived. The variables in this function are the pipe diameter and the pipe slope. The results showed the capability of the presented model for the optimal design of sewer networks. Optimization of Urmia sewer network using the proposed model led to 13 percent decrease in construction cost. Among the advantages of the proposed model are considering the execution aspects and avoiding drop at pipe joints. Proposing a method for calculating rainwater, the impact of rainwater on design of sewer networks was also examined. According to the results for the case study of Urmia city, considerable discharge of rainwater (up to 10 times of sanitary sewer discharge) enters into the sewer network which is not consistent with the primary design criteria of the separate network. Considering the rainwater in design of sewer networks would lead to considerable increases in pipe sizes and network costs.