PROCEDURES OF CHOOSING WASTEWATER RECLAMATION METHODS TO ASSURE SAFETY AGAINST VIRUS INFECTION

This study attempted to quantify the risk of enteric virus infection in case of wastewater reuse, and to clarify appropriate reclamation methods for safety. To assess the potential risk associated with the use of reclaimed wastewater in various applications, some exposure scenarios were assumed, and enteric virus concentrations in secondary effluents were monitored at ten wastewater treatment plants for 2 years.The virus concentrations in secondary effluents were distributed according to a lognormal distribution, and annual infection risks (r) corresponding to the scenarios were calculated using the Monte Carlo method. Assuming some virus removal efficiencies (x), annual infection risks (r) were calculated and the relationship between virus removal efficiencies and annual infection risks (r=f (x)) was obtained for each scenario. The necessary virus removal efficiency (x0), satisfying the assumed acceptable annual risk (r0) under the scenario, was calculated using the equation r=f (x). A virus removal method satisfying the virus removal efficiency (x0) was chosen using the existing data of enteric virus removal efficiencies of several reclamation methods.