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

为了解决流域水资源短缺的问题，水的回用和循环利用往往被用于水利用系统。本研究的目的是建立水资源利用中病原体感染风险的评价模型。研究结果如下：1)减少水资源短缺危害的污水回收病原菌风险评价。在不同情景下，对Abukuma流域污水回收过程中脊髓灰质炎病毒的感染风险进行了评价。为了对流域缺水进行预测评价，用连续2天流量同时概率矩阵表示饮用水取水点河水流量的波动。用流速与总大肠菌群和总SS之间的关系式测定水质。当消毒灭活脊髓灰质炎病毒的效率高于99.9%时，污水回用可降低缺水危害，且不增加感染风险。在塔失活效率下，随着缺水危害的减小，感染风险呈指数级增加。2)病原病毒在河流水体中的行为研究通过对1型脊髓灰质炎病毒的实验分析病原病毒对悬浮物（SS）的吸附和对河流水体中灭活（不吸附）病毒的吸附。观察到吸附在SS上的病毒比例随SS浓度的增加而增加。河水中的游离病毒在头两天急剧失活。两天后的病毒浓度是初始浓度的十分之一。从第2天开始，5种病毒的灭活率逐渐降低，大约用了23天，90%的病毒灭活了。上述结果将有助于建立水利用系统，最大限度地降低流域的感染风险。

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.