Browsing by Author "Erbay, Barbaros"

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Citation Count: 21
Evaluation Of Water Supply Alternatives For Istanbul Using Forecasting And Multi-Criteria Decision Making Methods
(Elsevier Ltd, 2020) Hekimoğlu, Mustafa; Erbay, Barbaros; Hekimoğlu, Mustafa; Burak, Selmin
Water scarcity is one of the most serious problems of the future due to increasing urbanization and water demand. Urban water planners need to balance increasing water demand with water resources that are under increasing pressure due to climate change and water pollution. Decision makers are forced to select the most appropriate water management alternative with respect to multiple, conflicting criteria based on short and long term projections of water demand in the future. In this paper, we consider water management in Istanbul, a megacity with a population of 15 million. Purpose: The purpose of this paper is to develop a method combining demand forecasting with multi-criteria decision making (MCDM) methods to evaluate five different water supply alternatives with respect to seven criteria using opinions of experts and stakeholders from different sectors. Methodology: To combine forecasting with MCDM, we design a data collection method in which we share our demand forecasts with our experts. For demand forecasting, we compare Holt-Winters, Seasonal Autoregressive Integrated Moving Average (S-ARIMA), and feedforward Artificial Neural Network (ANN) models and select S-ARIMA as the best forecasting model for monthly water consumption data. Generated demand projections are shared with experts from different sectors and collected data is evaluated with Fuzzy Theory using two distinct MCDM models: Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) and Preference Ranking Organization Method for Enrichment Evaluations (PROMETHEE). Also our analyses are complemented with two sensitivity analyses. Findings: Our results indicate that greywater reuse is the best alternative to satisfy the growing water demand of the city whereas all experts find desalination and inter-basin water transfer as the least attractive solutions. In addition, we adopt the PROMETHEE GDSS procedure to obtain a GAIA plane indicating consensus among experts. Furthermore, we find that our results are moderately sensitive to the number of experts and they are insensitive to changes in experts’ evaluations. Novelty: To the best of our knowledge, our study is the first one incorporating water demand and supply management concepts into the evaluation of alternatives. From a methodological perspective, water demand projections have never been used in an MCDM study in the literature. Also, this paper contributes to the literature with a mathematical construction of consensus and Monte Carlo simulations for the sufficiency of experts consulted in a study.
Citation Count: 0
Multi-Criteria Decision-Making Analysis for the Selection of Desalination Technologies
(2022) Hekimoğlu, Mustafa; Savun-hekimoğlu, Başak; Erbay, Barbaros; Gazioğlu, Cem
Accessible fresh water resources for drinking and usage are very limited in our world. Furthermore, these limited fresh water resources are gradually decreasing due to climate change, industrialization, and population growth. Despite the ever-increasing need for water, the inadequacies in our resources have made it critical to develop alternative drinking and utility water production methods. Desalination, one of the most important alternatives for fresh water supply, is on the rise on a global scale. Desalination facilities use various thermal and membrane techniques to separate water and salt. Concentrated brine, which contains desalination chemicals and significant amounts of salt, and is formed in high volumes from desalination processes, is also a concern. This article compares various desalination techniques using a multi-criteria decision-making method. The findings show that the Reverse Osmosis & Membrane Crystallization process is the most preferred technology due to its cost advantages as well as operational efficiency. Similarly, Multistage flash &Electrodialysis, the least preferred alternative, has been criticized for its low cost-effectiveness. These results suggest that cost and operational efficiency will continue to be the main drivers in the evaluation of desalination technologies in the near future.