Full length ArticleRisk-based evaluation of wastewater treatment projects: A case study in Niasar city, Iran
Introduction
Due to the industrial revolution and changing lifestyles, total water use has grown considerably throughout the world in the last three centuries. Wastewater reuse is a promising approach for improving water resources management all over the world (Gómez-López et al., 2009). It is especially significant in arid and semi-arid regions that are facing both quantitative and qualitative water challenges.
Nowadays, proper management of wastewaters in modern industrialized societies is not an option, but a necessity (Belanche et al., 1999). The dependence of many communities on economic activities using water and change in consumption pattern of water implies that water and wastewater planning and management can directly and indirectly affect economic prosperity, social wellbeing and community cohesion. Hence, any decisions regarding wastewater management may have economic, social, environmental and political consequences. Therefore, a decision maker (DM) needs to know how to deal with the socio-political and environmental issues (Bloemhof-Ruwaard et al., 1995). It is clear that, although wastewater decision making plans may be designed and ratified without considering the socio-political and environmental criteria, the sustainable development and its long-term aims cannot be achieved without it.
The planning of regional wastewater treatment systems is a classic multi-attribute problem. The goals of such problems may generally be formulated as follows (De Melo and Câmara, 1994):
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To define the characteristics of the treatment and transport system in a region or water basin;
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to minimize economic cost;
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to minimize environmental impact;
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to maximize system reliability;
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to maximize system flexibility under uncertain conditions;
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to assure equity among users of the system;
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to maximize benefits of the reuse of treated effluent.
Therefore, using multi-attribute decision-making (MADM) methods is essential to consider the qualitative and quantitative attributes involved in decision making process.
The utilization of MADM methods does not have a long history in wastewater management projects. Nevertheless, there are some empirical studies using MADM methods for wastewater management. Kim and Chung (2014) developed an index-based robust decision making framework for watershed management, which deals with water quantity and quality issues under climate change. Kim et al. (2013) proposed a new framework to prioritize the best sites among 10 sites in a South Korean urban watershed for treated wastewater (TWW) instream use, employing fuzzy TOPSIS technique. Bottero et al. (2011) applied the Analytic Hierarchy Process (AHP) and Analytic Network Process (ANP) methods to make comparative assessments of alternative projects in relation to three factories located in the Italian-Swiss Alps region. Aulinas et al. (2011) developed a knowledge-based approach to support decision making in urban wastewater systems. An integrated approach using the hydrological simulation program in FORTRAN (HSPF), Storm Water Management Model (SWMM) with the use of an alternative evaluation index (AEI), and MADM methods was developed by Chung et al. (2011) and Chung and Lee (2009) in order to determine the priorities of a range of alternatives in watershed quality and quantity management. Anagnostopoulos et al. (2009) employed the AHP method with GIS in order to locate natural systems of wastewater treatment. Gómez-López et al. (2009) used the TOPSIS method in Cartagena city, Spain, to select the most appropriate method among six available options for disinfection before reusing filtered wastewater. A multi-function software decision support tool was developed by Hidalgo et al. (2007) for the promotion of the safe reuse of treated urban wastewater. In addition, Karamouz et al. (2003) utilized the Simple Additive Weighting (SAW) and AHP methods in order to develope a master plan for water resources pollution control in Isfahan Province, Iran. Using ELECTRE method, Ganoulis (2003) studied recycling and reuse of wastewater in the Mediterranean area. Al-Rashdan et al. (1999) employed the PROMETHEE method to prioritize wastewater projects in Jordan.
A limitation of many of the earlier works on MADM models in wastewater management is that they do not consider one factor that affects the ranking of alternatives: the DMs’ risk attitude, or degree of optimism/pessimism. In decision making process, DMs may have different optimism/pessimism degrees concerning the suggested plans, scenarios, and alternatives with respect to their experiences, knowledge, interests, and backgrounds. When faced with uncertainty, optimistic DMs focus more on the potential desirable attributes of options, whereas pessimistic DMs focus on the potential negative attributes (Mianabadi et al., 2014). In other words, whereas optimistic DMs are willing to take risks in order to get positive outcomes, pessimistic DMs are risk averse and prefer conservative options. In this study, the term of risk is used in a special meaning. Environmental management problems face uncertainty and therefore the decision making problem is under risk. If the DM strongly avoids the risk of making wrong decisions, he/she will consider more criteria in the decision process or take into consideration more undesirable conditions rather than desirable ones. However, it will result in conservative outcomes which are different than the results for a neutral or optimistic DM. In fact, environmental managers have varying optimism/pessimism opinions based on the nature of the problem especially with different stakeholders. The optimism degree of the DM is a measure defined to vary from very risk-averse DM up to very risk-prone DM (Zarghami and Szidarovszky, 2009).
What makes this research different from other studies regarding wastewater management is the consideration of the risk attitudes of the DMs using six risk-based MADM (RB-MADM) methods. Moreover, we apply these methods to a real case study in Niasar city, Iran. In the next section, the necessity of using MADM methods in IWWM problems is investigated. In the methodology section, we will briefly explain the MADM process and introduce some MADM methods. In the fourth section, the case study of Niasar city in central Iran will be presented. Furthermore, the influence of the different decision-making methods is surveyed by using different Fuzzy Risk-based MADM methods. To understand how the DMs’ risk attitudes might affect the final outcome, risk-based ranking of the options is made. Finally, the last section summarizes the research outcomes and the concluding remarks are presented.
Section snippets
Sustainable wastewater management
The concept of sustainable development was first introduced in the 1980s and has been used in a variety of ways over the years (Madurga et al., 2008). Rogers (2006) presents 50 widely used definitions. What is common in most definitions is that sustainable development can be achieved by proper use of current resources and preservation of the environment for future generations according to economic, environmental and socio-political criteria. According to the standard definition of the Project
Multi attribute decision-making
MADM is concerned with selecting, ranking and/or classifying alternatives among a set of available options. MADM problems are formulated as a decision-making matrix which is composed of m predetermined alternatives and n attributes. The MADM process includes four main steps (Mianabadi and Afshar, 2008):
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Identification and assessment
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Weighting of attributes
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Selection of the most preferred alternative using an MADM method
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Sensitivity analysis and final decision making.
Of these steps, selection of the
Case study
In the Iranian administrative structure, urban water and wastewater management is generally planned at two levels (Abrishamchi et al., 2005): by the national government and within the water and wastewater companies of the provinces. The national government is responsible for policy-making at the national level for urban water and wastewater management for all provinces, whereas the provincial companies have responsibility for water and wastewater management in their provinces (Abrishamchi et
Results and discussion
In this section, the Niasar's wastewater project is analyzed using the methods described in Section 3. Eqs. (1), (2), (3), (4), (5), (6), (7), (8), (9), (10), (11), (12) are used to calculate the ranking order of each option. To do so, the decision matrix (Table 5) should first be normalized in the dimensionless range of 0 to 1 using the following functions (Triantaphyllou et al., 1998):
Conclusion
Decision makers in wastewater management problems have different degrees of optimism. The risk-based MADM methods are able to consider the risk level and DMs’ degree of optimism in decision making process. In this study, the new concept of integrated wastewater management (IWWM) was developed and the importance of using risk-based MADM methods in wastewater management problems was investigated. Given the highlighted importance of taking into consideration DMs’ optimism/pessimism degree in
Acknowledgments
The authors gratefully acknowledge Dr. Susan Steele Dunne for her helpful comments and suggestions. The authors would like to thank the two anonymous reviewers for their valuable comments.
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