Risk assessment of municipal wastewater chlorination unit equipment using traditional and fuzzy FMEA: a case study

FMEA is one of the experienced and very useful methods for identifying, classifying, analyzing faults, and assessing the risks arising from them. This study aims to identify, evaluate, prioritize, and analyze the risks associated with the equipment of Sahand municipal wastewater disinfection unit using traditional and fuzzy FMEA method. The present study is a cross-sectional analytical study that was conducted in a period of about 6 months. First, a team of 5 experts was formed and the traditional FMEA worksheet was completed. Then the fuzzy functions were determined by the MATLAB program according to the opinions of experts and the severity, probability of occurrence, and probability of detection and risk priority number (RPN) became fuzzy. According to the fuzzy logic outputs, the risks were prioritized and corrective measures were proposed according to the type of risk. In this study, a total of 28 faults were identified for chlorination unit equipment. The traditional FMEA results showed that a total of 28 faults (100%) identified for the equipment of the Sahand municipal wastewater chlorination unit is in the low-risk range. While according to the results of fuzzy FMEA, one fault (3.6%) is in the low-risk range, 24 faults (85.7%) are in the medium-risk range and 3 faults (10.7%) are in the high-risk range. The results of the risk assessment of the chlorination unit of Sahand municipal wastewater treatment plant using fuzzy FMEA are more accurate and better compared to traditional FMEA. Using experts’ opinions in risk assessment using fuzzy FMEA leads to more realistic results as well as better and clearer prioritization of corrective actions.