Risk assessment and modeling of chlorine leakage consequences using fuzzy HAZOP technique and PHAST software

Document Type : Original Article


1 Assistant Professor of Occupational Health Engineering, Department of Occupational Health, School of Health, Kashan University of Medical Sciences, Kashan, Iran

2 Associate Professor of Biostatistics, Department of Epidemiology and Biostatistics, School of Health, Kashan University of Medical Sciences, Kashan, Iran

3 Master Student of Health, Safety and Environmental Management, School of Health, Kashan University of Medical Sciences, Kashan, Iran

4 PhD Student in Occupational Health, School of Health, Hamadan University of Medical Sciences, Hamadan, Iran


Objectives: This study aims to develop strategies for risk management and accurately model the potential outcomes in hazardous zones.
Methods: The initial step of this study involved conducting HAZOP studies to identify all process nodes and deviations in an urban water-treatment plant located in Markazi province. Subsequently, all risks associated with the identified deviations were evaluated using a qualitative risk matrix. To enhance the scientific accuracy of the risk assessment results, the fuzzy HAZOP methodology was employed. Finally, the assessed risks were prioritized with precision, and PHAST software was utilized to visualize critical scenarios and determine the zones of catastrophic consequences.
Results: The initial findings from the HAZOP investigations conducted in the chlorination unit of the treatment facility reveal a total of 41 deviations out of 55 identified risks. Out of these risks, 47 (85%) were classified as high risk (HR), while 8 (15%) were categorized as medium risk (MR). The results of the risk assessment clearly demonstrate that the risks are of significant concern, despite the presence of existing controls. Ultimately, eight scenarios were identified and extracted from the analysis.
Conclusion: Based on the research results, it is imperative that all chlorination facilities undergo redesigning to prevent corrosion, erosion, leakage, and rupture and to conduct risk-based inspections (RBI). Furthermore, regular chlorine leakage drills should be included to enhance emergency response and preparedness.


Main Subjects

  1. Thompso T, Fawell J, Kunikane S, Jackson D, Appleyard S, Callan P, et al. Chemical safety of drinking water: assessing priorities for risk management: World Health Organization; 2007.
  2. Anthony ET, Ojemaye MO, Okoh OO, Okoh AI. A critical review on the occurrence of resistomes in the environment and their removal from wastewater using apposite treatment technologies: Limitations, successes and future improvement. Environmental Pollution. 2020;263:113791.American Water World Association. Standard Methods for the Examination of Water and Wastewater, 19th Edition; 1995.
    doi:10.1016/j.envpol.2019.113791 PMid:32224385
  3. Noble RT, Weisberg SB, Leecaster MK, McGee CD, Ritter K, Walker KO, et al. Comparison of beach bacterial water quality indicator measurement methods. Environ Monit Assess. 2003;81 (1-3):301-12. doi:10.1007/978-94-017-0299-7_25 PMID: 12620023
  4. World Health Organization. Guidelines for drinking-water quality. World Health Organization; 2004 Aug 31.
  5. Ruj B, Chatterjee PK. Toxic release of chlorine and off-site emergency scenario-A case study. J Loss Prev Process Ind. 2012; 25(3):650-3. doi:10.1016/j.jlp.2012.01.002
  6. Salehi AJ, Shamizadeh H, Alinejadeh SR, Arjamnd M. Risk of emission of chlorine gas in water refinery. 2012; 3(9):39-50.
  7. Adl J, Mohammadfam I, Nezamodin M. Evaluation of chorine leakage hazards in chlorination stations of Tehran water purification system by FTA technique. Sci Med J. 2010;6(4).
  8. Li J. Leakage consequence simulation and quantitative risk assessment on gas offtake station. Oil & Gas Storage and Transportation. 2009.
  9. Lees F. Lees' Loss prevention in the process industries: Hazard identification, assessment and control: Butterworth-Heinemann, Fourth Edition; 2012.
  10. Pula R, Khan F, Veitch B, Amyotte P. A grid based approach for fire and explosion consequence analysis. Process Saf Environ Prot. 2006;84(2):79-91 doi:10.1205/psep.05063
  11. Beheshti MH, Dehghan SF, Hajizadeh R, Jafari SM, Koohpaei A. Modelling the consequences of explosion, fire and gas leakage in domestic cylinders containing LPG. Ann Med Health Sci Res. 2018; 8(83-88).
  12. Tseng J, Su T, Kuo C. Consequence evaluation of toxic chemical releases by ALOHA. Procedia Eng. 2012;45:384-389.
  13. Malviya RK, Rushaid M. Consequence analysis of LPG storage tank. Materials Today: Proceedings. 2018;5(2):4359-67.
  14. Wang W, SUN B, Guo K. Quantitative risk analysis for LNG station accidents. J Saf Sci Technol. 2011.
  15. Miranzadeh MB, Mesdaghinia AR, Heidari M, Younesian M, Nadafi K, Mahvi AH. Investigating the chemical quality and chlorination status of drinking water in Kashan's villages. J Health Syst Res. 2011;6(5):0-.
  16. Hosseini SH. Assessment and modeling of chlorine release in urban region: A case study in water supply of Eyvan city, Iran. J Bas Res Med Sci 2016; 3(3):7-14 doi:10.18869/acadpub.jbrms.3.3.7
  17. Parvini M, Gharagouzlou E. Consequence modeling for chlorine release of a storage tank with the field experiment data. J Model Eng. 2014;12(38):15-25.
  18. Setareshenas N, Khalilipour MM, Shahraki F, Mansouri M. Consequence modeling of chlorine release from water treatment plant. Am Chem Sci J. 2014;4(1):97-104 doi:10.9734/ACSJ/2014/5961
  19. Haghnazarloo H, Parvini M, Lotfollahi MN. Consequence modeling of a real rupture of toluene storage tank. J Loss Prev Process Ind. 2015;37:11-8 doi:10.1016/j.jlp.2015.06.007
  20. Shamizadeh H, Alinejad Shahabi R, Arjmand M. Modeling the Chlorine Gas Dispersion in the Water Treatment Plant. J Chem Health Risks. 2018;8(2).
  21. Mortazavi S, Parsarad M, Mahabadi HA, Khavanin A. Evaluation of chlorine dispersion from storage unit in a petrochemical complex to providing an emergency response program. Iran Occup Health. 2011;8(3).
  22. Ahn J, Chang D. Fuzzy-based HAZOP study for process industry. J Hazard Mater. 2016;317:303-311 doi:10.1016/j.jhazmat.2016.05.096 PMid:27318726
  23. Rahimi H, Khodabakhshi Sh, Rahimi H, Jamshidi Farz. HAZOP Risk Assessment Technique of Operations and Risk Study Technique: A Case Study in a Water Treatment Plant in 2017. 11th New Health Sciences Student Conference. 2018.
  24. Ebrahimian Dehaghani M, Khademi Mal Amiri Ma. Assessing and prioritizing the risk of the industrial consumption unit of Ahwaz Water Treatment Plant using the comparative multi-criteria decision making method and HAZOP with TOPSIS model and providing control and improvement solutions. Fifth National Conference on Iranian Environmental Crises and Strategies for Improving Them. 2011.
  25. Hadad Iraninejad F, Pardakhti A. Assessing the risk of exposure to chemicals in wastewater treatment plants using multivariate decision making methods, 10th National Conference on Environment, Energy and Sustainable Natural Resources.2020.
  26. Paul R, Mondal A, Choudhury M, editors. Dispersion modeling of accidental release of chlorine gas. Proceedings of the International Conference on Chemical Engineering. 2014.