Distribution of Enteric Pathogens in Wastewater Secondary Effluent and Safety Analysis for Urban Water Reuse

Through a 1-year monitoring of enteroviruses and pathogenic bacteria in the secondary effluent using real-time polymerase chain reaction (real-time PCR), the pathogen removal requirement was evaluated for safeguarding the reclaimed water quality for urban reuse. The distribution of each pathogen in the secondary effluent was found to follow a log-normal relationship, although 50% cumulative concentrations differed much from each other (1.4 GEC/L of infectious enteroviruses, 3.1 x 10(2) CFU/L of Salmonella typhi, 1.0 x 10(3) CFU/L of Shigella, and 3.3 x 10(5) CFU/L of Escherichia coli). By exposure analysis regarding two reuse scenarios (golf course irrigation and recreational impoundment), risks were analyzed for pathogens in reused water based on monitoring data and dose-response relation. For enteroviruses and pathogenic bacteria, there were obvious differences in the relationship between the reliability and removal efficiency. Under an acceptable annual risk level (10(-4)/a), the pathogen removal requirement depends on the manner of water reuse. In the golf course irrigation, the removal efficiency of enteroviruses, Salmonella typhi, Shigella, and Escherichia coli reach to 3.8 approximate to 4.0-log, 1.4-log, 3.3-log, and 2.0-log, respectively, in order to ensure 95% reliability. However, if wastewater is reused for recreational impoundment, only a further increase around 1.5-log removal efficiency of pathogens can meet the requirement for the same reliability.