Determination of priority regions for rehabilitation in waste systems

In wastewater systems, the different types of failures such as collapse, reverse slope, clogging, incorrect building connection, lubrication, cracks and so on occur. These failures are caused by different factors such as physical, operational and environmental factors. Failures that occur constantly in older systems, cause continuous maintenance and repair work in the street. The frequency of these failures increases the operating cost of the system and disrupts normal operating conditions. For this reason, considering all factors at the same time in the wastewater systems, risky areas should be determined and a rehabilitation program should be established. In this study, it is aimed to determine priority areas for rehabilitation in wastewater systems by applying multi-criteria methods. The ENTROPI method is applied to determine the weight coefficients of the factors. According to the results of the ENTROPI method, the highest weight coefficient is for the reverse slope ratio with 0.121, while the lowest value is calculated for the pipe depth variation with 0.0007. Considering the weight coefficients and field data, priority areas in risky and rehabilitation were determined using the methods of ELECTRE, MAUT, TOPSIS and PROMETHEE. For this, in the field of application, 19 regions and 52 critical streets were determined and 28 parameters were considered. According to the calculations made using these four different methods, the regions are ordered from the region with the highest risk to the region with the lowest risk. According to the results of the risk prioritization of all four methods, it is generally determined that similar areas are risky. It is considered that the results obtained in the study will be used as a reference in terms of determining the priority of rehabilitation for wastewater systems for Water Authorities having wastewater systems which produce old and continuous failure.