Process Hazards Risk Assessment and Common Accidents Analysis of an Urban Water Treatment Plant Chlorination Unit Using Fuzzy HAZOP and PHAST (Case Study: One of Markazi province Water Treatment Plan)

Background and GoalThe leakage of chlorine gas in an urban water-treatment plant is one of the factors threatening the health of preoccupied people and residents in that place at all times, so the current research was defined so as to assess risks and model the consequences of leakage of chlorine gas.Materials and MethodsIn this research, by conducting HAZOP studies at first, all the processing deviations and risks in one of the urban water-treatment plants in Markazi province were identified and risk assessment was then carried out. Moreover, a novel dependent-HAZOP technique named Fuzzy HAZOP was used to promote the precision in risk assessment results, and all risks were ranked. PHAST software was utilized in order to model critical scenarios to predict the expansion of possible consequences.FindingsThe initial results of HAZOP studies in the chlorination unit of the urban water-treatment showed that the deviations like the increase of pressure, gas flow rate, and reactivity in some parts such as chlorine injection cylinder, regulators, copper interface pipe, flow regulating valves, ejectors, and chlorinators are of the utmost importance. It should be noted that ۴۱ deviations were detected. Out of ۵۵ risks, ۴۷ risks (۸۵%) and ۸ risks (۱۵%) were located in high risk (HR) and medium risk (MR), respectively. The risk assessment results plainly indicated that risks are in an important state of affairs in keeping with the available controls, and it is required to take precautionary and responsive procedures to the subsequent deviations and their consequences. Besides, ۸ scenarios were extracted, including liquid chlorine release from a cylinder, leakage from regulators, copper related-pipes, pipelines, and chlorinator facilities.ConclusionOn the word of the findings, it is critical for all chlorination facilities to be redesigned in order to avoid corrosion, leakage, and release, as well as to execute risk-based checkups. Furthermore, in emergency conditions, reaction systems need to develop operational methods and instructions.