Risk Assessment of Wastewater Collection Performance Using the Fuzzy Decision-making Approach

Document Type : Research Paper


1 PhD Student of Water Civil Eng., University of Tehran, Tehran

2 Prof., Center of Excellence for Engineering and Management of Civil Infrastructures, School of Civil Engineering, College of Engineering, University of Tehran, Tehran

3 Assist. Prof. of Water Eng., College of Aburaihan, University of Tehran, Tehran


Wastewater collection network simulation in normal conditions dose not provide performance assessment in unusual circumstances. In this paper, a model has been developed for risk assessment of wastewater collection systems to manage their performance under natural or man-made critical conditions. In this model, certain criteria were defined, fuzzy MADM techniques were exploited, and a questionnaire was employed to measure such risk parameters as the probability of threats, the severity of their impacts, and the vulnerability of the network components. Based on the calculated magnitude of the risks, the threats and hazards were classified into groups ranging from low-risk to high-risk threats. The approaches adopted to combat the risks were also classified into the following three categories: "to deal with the risk", "risk shifting", and "risk taking". This process was implemented for the wastewater collection system in Shahrak-Gharb District in Tehran as a case study. ‘Introduction of chemical pollutants into the sewers’ and ‘drastic changes in wastewater quality’ were identified as the most threatening crises for the district and the ‘risk reduction strategy’ was proposed for combating the critical conditions in this district.


Main Subjects

  1. FEMA 452. (2005). A how to guide to mitigate potential terrorist attacks against buildings, Risk Management Series, Published by Federal Emergency Management Agency, USA.
  2. Garvey, P.R. (2009). Analytical methods for risk management: A system engineering perspective, ISBN.
    1-5848-8637-4, Taylor and Francis Group, Boca Rotan, FL.
  3. Torres, J.M., Brumbelow, K., and Guikema, S.D. (2009). “Risk classification and uncertainty propagation for virtual water distribution systems.” J. of Reliability Engineering and System Safety, 94(8), 1259-1273.
  4. Roozbahani, A., Zahraie, B., and Tabesh, M. (2013). “Integrated risk assessment of urban water supply systems from source to tap.” Stochastic Environmental Research and Risk Assessment, 27,
  5. Demotier, S., Schon, W., Denoeux, T., and Odeh, K. (2003). “A new approach to assess risk in water treatment using the belief function framework.” IEEE International Conference on Systems, Man and Cybernetics, 2, 1792-1797.
  6. RAMCAP. (2006). Risk analysis and management for critical asset protection, ASME Innovative Technologies Institute, LLC, Version 2.0.
  7. Tecle, A. (1988). “Choiceof multi-criteria decision making techniques for watershed management.”
    PhD Dissertation, University of Arizona, USA.
  8. Triantaphyllou, E. (2000). Multi-criteria decision making: A comparative study, Kluwer Academic Publisher, Netherlands.
  9. Zanakis, S.H., Solomon, A., Wishart, N., and Dublish, S. (1998). “Multi-attribute decision making:
    A simulation comparision of selected methods.” European J. of Operational Research, 107(3), 507-529.

10. Chang, D.Y. (1996). “Application of the extent analysis method on fuzzy AHP.” European J. of Operation Research, 95(3), 649-665.

11. Deng, H. (1999). “Multi-criteria analysis with fuzzy pair wise comparison.” Proceedings of IEEE International Fuzzy Systems Conference, Seoul, Korea, 726-731.

12. Aczel, J., and Saaty, T.L. (1983), “Procedure for synthesizing ratio judgements.” J. of Mathematical Psychology, 27(1), 93-102.

13. Chi, H.K., Huery, R.Y., and Liao, L.H. (2008). “Applying fuzzy analytic hierarchy process to explore the university organizational preformance in Taiwan.” J. of Human Resource and Adult Learning, 4(1),

14. Asgharpour, M.J. (2008). Multi-criteria decision making, 15th Ed., Tehran University Press, Tehran.
(In Persian)

15. Yager, R.R. (1980). “On a general class of fuzzy connectives.” J. of Fuzzy Sets and Systems, 4(3),

16. Sylves, R., and Cumming, W.R. (2000). “FEMA’s path to homeland security: 1979-2003.” J. of Homeland Security and Emergency Management, 1(2), doi: 10.2202/1547-7355.1029.

17. Azimi, A.S., Taklifi, A., Riazati, E., and Mesr Zadeh, A. (1390). “Increasing the capacity of existing municipal wastewater treatment plant using a MBBR (case study: Shahrak-Gharb wastewater treatment network).” 15th National Conference and Exhibition of Environmental Engineering, Tehran. (In Persian)

18. Saaty, T.L. (2008). “Decision making with the analytic hierarchy process.” Int. J. of Services Sciences, 1(1), 83-98.