Risk assessment methodology for iron stability under water quality factors based on fuzzy comprehensive evaluation

Changing water quality was prevalent in the current water supply. The fluctuation of iron stability due to changing water quality followed four characteristics: objectivity, relativity, predictability, and controllability. Therefore, it was necessary to study the stability of iron in the pipe network by integrating different water quality factors. The iron stability risk evaluation system was established according to the different water quality factors in the drinking water distribution systems (DWDSs). Meanwhile, an improved fuzzy comprehensive evaluation method was established to evaluate the risk of iron. Chloride, sulfate, dissolved organic matter (DOM) and pH were selected as the risk assessment index. The divisions of different evaluation levels were carried out through the values of water quality factor. On the basis of expert scoring, the weight and membership degree of water quality factors were analyzed by structural entropy method. In addition, risk analysis was established by using the optimized risk assessment system. According to the results of the comprehensive evaluation, DOM and pH were identified as two of the most important factors in the evaluation of the iron stability. In addition, compared with the traditional fuzzy comprehensive evaluation method, the optimized method had a higher degree of fit which could more clearly prove the relationship between the risk value and the iron concentration. The uncertainty between the factors was eliminated by establishment of the fuzzy evaluation method combined with the different effects of water factors on iron stability. The method could be used as a comprehensive evaluation and be beneficial to the analysis of iron risk in water supply network.