Behavior Analysis and Risk Evaluation of Paftogens for the Water Utilization System in the Watershed

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In order to solve the water shortage in the watershed, water reuse and recycling often have been employed in the water utilization system. The purpose of this study was to develop the evaluation model for infectious risks by pathogens in the water utilization.The following results were obtained:1) Risk evaluation of pathogens in wastewater reclamation for reducing the damage of water shortageInfectious risks by poliovirus through wastewater reclamation in the Abukuma watershed were evaluated under various scenarios. For predictive evaluation of water shortage in the watershed, fluctuation of river flow rate at the intake point of drinking water were represented with the matrix of simultaneous probability of flow rates in consecutive two days. Water qualities (total coliforms and SS) were also determined with matrices between flow rate and them. When the inactivation efficiency of poliovirus by disinfection was higher than 99,9%, the damage of water shortage could be reduced by wastewater reclamation without any increase of infectious risk. In case of tower inactivation efficiency, infectious risks would exponentially increase with reduction of damage of water shortage.2) Studies on the behaviors of pathogenic viruses in river waterThe adsorption of pathogenic vims to suspended solids (SS) and the inactivation office (not adsorbing) virus in river water wete analyzed through some experiments using poliovirus type 1. It was observed that the ratio of viruses adsorbing to SS was increased in proportion to the SS concentration. Free viruses in river water woe drastically inactivated in first two days. The viral concentration after two days was onetenth of initial concentration. Since the second day, the inactivation rate of fiee viruses became smaller and it took about 23 days that ninety peicents of vims weie inactivated.Above results witt be able to contribute to establishment of the water utilization system minimizing infectious risks in the watershed.