Hassan Taghipour
1 
, Seyedeh Maryam Seyed Mousavi
2* 1 Department of Environmental Health Engineering, School of Public Health, Tabriz University of Medical Sciences, Tabriz, Iran
2 Health and Environment Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
Abstract
Background. In most developing countries, concern about leachate pollution is serious. This study aimed to determine the best alternative for leachate management and disposal using the Analytic Hierarchy Process (AHP) method.
Methods. In this descriptive-applied research, the criteria and alternatives for leachate management and disposal were selected, including evaporation pond (natural with sunlight), recirculation/evaporation, and treatment (physical and chemical, biological/advanced). Then, three criteria and 11 sub-criteria were selected. The criteria and sub-criteria were weighted, using the Expert Choice 11 software and compared two by two to determine the relative importance of each. Then, each of the alternatives was compared and prioritized two by two in relation to the criteria and sub-criteria.
Results. The results of the study showed that the evaporation pond (natural with sunlight) was the most preferable alternative with an importance coefficient of 0.569. The alternative of recycling/evaporation and treatment (physical and chemical, biological/advanced) with an importance factor equal to 0.216 was placed in the next priority. The consistency ratio (CR) of all the paired matrices of the alternatives was equal and less than 0.1.
Conclusion. By considering the economic, technical, operating, health, and environmental criteria, the evaporation pond method (natural with sunlight) was chosen as the best method for managing and disposing landfill leachate in Iran. Therefore, it is recommended to consider the alternative of leachate management in landfills, especially considering the climatic conditions of the country (90% dry and semi-arid climate).
Extended Abstract
Background
The generation of Municipal Solid Waste (MSW) is directly related to the development of human activities in the world. Methods of recycling, composting, sanitary landfilling, and incineration are known to be used in integrated waste management, depending on the type of waste and location. Due to economic and feasibility considerations, sanitary landfilling is one of the most common methods for most countries, especially in developing countries. The production of leachate and its management is among the most important environmental concerns related to landfilling. Comprehensive evaluation to decide on the best management method and disposal of leachate is relatively difficult. In some studies, Analytic Hierarchy Process (AHP) method was used for this purpose. Given that one of the most common methods of urban waste disposal in Iran is landfilling, this study aimed to provide an optimal alternative for the management and disposal of leachate produced from landfill sites using the AHP method.
Methods
Using the AHP method, this descriptive applied study aimed to determine the best method for managing and disposing leachate produced from landfills in Iran in 2021. In this method, we selected the alternatives of evaporation pond (natural with sunlight), recirculation/evaporation and treatment (physical and chemical, biological/advanced) and three economic criteria (including two sub-criteria), technical and operational (including six sub-criteria), health and environment (including three sub-criteria). After determining the criteria and sub-criteria of each department and ensuring the correct selection, the criteria and sub-criteria of each department were carried out through designing a validation and scoring table by an expert team that included eight university professors with expertise in environmental health engineering and executive experts in the field of waste management. Then, calculation was done using the Excel software. Next, the questionnaire of paired comparisons of the criteria was compiled and provided to the expert team to weight the criteria using paired comparisons. To prioritize different methods of management and disposal of production leachate from landfill sites, a questionnaire was prepared. In this questionnaire, different methods of management and disposal of leachate produced from landfill sites in three main criteria and 11 sub-criteria including I) evaporation pond, the natural evaporation with sunlight; II) recirculation/evaporation; and III) treatment (physical and chemical, biological/advanced) were compared. The data obtained from the analysis of the questionnaires filled by the expert team (pairwise comparison matrices) were imported into the Expert Choice 11 software to determine the weight of criteria and sub-criteria. To check consistency and inconsistency, Saati's judgment (1990) was used, which suggested the use of consistency index (CI) and consistency ratio (CR).
Results
We used the AHP to make an effective decision regarding the selection of the best alternative for leachate management and disposal. After creating a hierarchical structure, to calculate the relative weight of the criteria and sub-criteria using the AHP method, pairwise comparisons of each group were made, and the opinions of experts (including university professors and expert executive experts) were obtained through the questionnaire. The degree of inconsistency of the hierarchical matrix was equal to and less than 0.1, which was acceptable. So, there was no need to revise the judgments. The results of the Expert Choice 11 software showed that based on the summation of the opinions of the expert team, the relative weight of the health and environmental, technical and operational, and economic criteria was equal to 0.493, 0.311, and 0.196, respectively. Therefore, the health and environmental factors had the greatest impact in choosing the optimal method for managing and disposing the produced leachate from landfill sites. In the health and environmental criteria and its sub-criteria, water pollution had the greatest impact with a relative weight of 0.527. In terms of technical and operational factors, the sub-criterion of the locality of technology and required equipment with a relative weight of 0.308 had the greatest impact and the required manpower with a relative weight of 0.086 had the least impact. Regarding economic factors, the sub-criterion of cost investment (equipment and construction) with a relative weight of 0.667 had the greatest impact. Then, we calculated and prioritized each of the alternatives. Considering the weight and effect of all criteria (economic, technical and operation, health and environmental) and the relevant sub-criteria, we witnessed that the evaporation pond alternative (natural with sunlight) with a relative weight of 0.569 had the highest final score while recycling/evaporation and treatment alternative (physical and chemical, biological/advanced) was in the next place with a score of 0.216. Sensitivity analysis was performed to determine the importance of each alternative compared to other alternatives in terms of effective criteria in achieving the overall goal of the study. The results of the sensitivity analysis showed that the evaporation pond process (natural with sunlight) had the most sensitivity to economic, technical and operational, as well as health and environmental criteria.
Conclusion
The results of the study showed that the evaporation pond option (natural with sunlight) was the most preferable alternative with an importance coefficient of 0.569. The alternatives of recycling/evaporation and treatment (physical and chemical, biological/advanced) with an importance coefficient equal to 0.216 was placed in the next priority. Among the influential criteria in choosing the best alternative, health and environmental criteria were the most important ones. Considering the climatic conditions of Iran, which is mostly considered dry and semi-arid, this method can be considered effective in leachate management and disposal.