Developing a Technical, Environmental and Economical Evaluation Model Based on GIS and ANP to Assess Municipal Solid Waste Management Scenarios (Case Study: Tehran, Iran)

Selecting Municipal Solid Waste (MSW) management alternatives, adaptable to local conditions as well as environmental, technical, and economical concerns, would be a time consuming and complicated task without carrying out modern methods of site selection and decision making. The horizontal development of settlement areas which in turn may enforce high costs of waste collection and transportation, beside the lack of unconstructed fields in the vicinity of large cities, enacting rigorous legislation contributing to the minimum distances of waste processing facilities by dwelling areas, and finally, the social objections, are the most noticeable challenges facing solid waste management practices. The main objective of the present research is to develop a computerized model facilitating MSW disposal site selection task, in addition to the determination of best applicable management scenarios capable with environmental, technical, and economical concerns. Tehran city was chosen as a case study to implement the model and to interpret its sensitivity to the factors affecting the overall decision making process. At the first stage of the current research, data layers, such as protected regions, military areas, historical and cultural areas, topography, rivers and lakes, faults, geology and land use information, was provided about the study area. By the means of a GIS based software, and superimposing the above-mentioned layers, acceptable areas were determined in the second stage. Finally, several scenarios including Material Recovery Facilities (MRF), compost production systems, incineration units, Waste-Derived Fuel (RDF) facilities, and landfilling sites were allocated to any acceptable area, according to the quality and quantity of wastes generated in the city of Tehran. These scenarios were evaluated using developed ANP model in this paper. Results showed the superiority of the first scenario (with normal weight of 0.3079), while the normal priority of other scenarios were as 0.2441, 0.2393 and 0.2087 for the second, fourth and third alternative, respectively. As the priority values of the second and forth scenarios were approximately the same, sensitivity analysis based on selective changes in the weight of main clusters were performed. Due to the fact that the fourth scenario, in which the bulk of collected wastes would be landfilled, might impose the greatest environmental risks among other scenarios, by any amplification in the weight of environmental criteria, the preference of this option would decrease. However, increasing the weight of technical criteria, might prefer the forth scenario because of its simplest technology used. Other scenarios have shown to be less sensitive to changes in the weights of the main criteria, so that the first scenario was usually dominant to the second one and the second scenario had always the top priority comparing to the third scenario.