Fuzzy risk-based decision-making approach for selection of drinking water disinfectants

The potential effects of disinfection by-products (DBP) on human health have become a serious concern over the last three decades. In addition to the chronic cancer risk, several acute effects such as cardiac anomalies, stillbirths, miscarriages, low birth weights and pre-term deliveries have also been reported as a result of exposure to the DBP. Although several disinfectants including chlorine, ozone, ultraviolet ray (UV) radiation, chloramine and chlorine dioxide are available to supply safe drinking water, comparative evaluations of these disinfectants and their application approaches for a particular source of water is rare. This may be due to the variability associated with predicting DBP formation, health effects from DBP exposure, cost and disinfection performance of various disinfectants used in public water supply systems; and/or the knowledge gap in the assessment and comparison of risks associated with specific disinfection strategies. In this study, a framework for comparative evaluation of disinfectants and their application approaches has been developed through incorporation of human health risk from DBP exposure, cost of disinfection process, technical feasibility and disinfection performance. A fuzzy synthetic evaluation technique has been incorporated where fuzzy triangular membership functions were developed to capture uncertainties of the basic attributes. This paper compared three disinfection approaches: chlorination, chloramination and granular activated carbon with post chlorination through a multi-stage hierarchy risk model in which the analytical hierarchy process has been used to determine the relative importance of various attributes at different hierarchy levels. Then the best disinfection approach has been outlined. This evaluation was found to be sensitive to the assignment of relative importance.