Analytic Methods And Removal Of Waterborne Viruses In Water Treatment Processes

Waterborne viral infection is one of the most important causes of human morbidity and mortality, and epidemics associated with waterborne viruses are well documented worldwide. Therefore, it’s urgent to develop rapid and sensitive detection methods in order to determine the concentration profiles of waterborne viruses in the environments, and to evaluate the efficiency of viral removal and inactivation during wastewater treatment processes.Quantitative PCR (qPCR) for rapid detection of rotaviruses (RV) and adenoviruses (RV) were established, the detection limits are approximately 102 copies /reaction, and the quantitative ranges are from 10~2 to 108 copies /reaction; An integrated cell culture and qPCR (ICC-RT-qPCR) was developed to detect infectious RV, which can detect as few as 0.2 PFU/mL, a linear correlation was obtained by plotting RV copies detected by ICC-RT-qPCR versus the logarithm of initial RV inoculated at concentrations ranging from 0.2 to 200 PFU/mL. In addition, a fluorescence-activated cells sorting (FACS) was established to rapidly and sensitively determine and quantify infectious Ad, with a detection limit of 1 PFU/mL and a linear correlation obtained by plotting the percentages of hexon-positive cells versus the logarithm of initial Ads inoculated ranging from 1 to 104 PFU/mL. Both the ICC-RT-qPCR and FACS assays reduced the detection time of infectious virus from 7-14 day by conventional plaque assay to 2-3 days with better sensitivities.The newly developed ICC-RT-qPCR method was applied to investigate the inactivation and resistance of RV to UV and free chlorine disinfection, and to compare the results with those obtained by conventional assays. The results showed that RV evaluated by ICC-RT-qPCR was more resistant to UV and free chlorine disinfection than that evaluated by plaque assay. Infectious RV and gene segments were detectable at UV dose of 360 mJ/cm2 and chlorine dose of 1200 mg·min/L. To achieve the same removal efficiency evaluated by plaque assay, the required UV dose and chlorine dose evaluated by ICC-RT-qPCR increased from 42 to 117 mJ/cm2 (4 log10) and from 60 to 300 mg·min/L (1.7 log10), respectively. The key target of RV during chlorine disinfection varies with different initial free chlorine concentrations. The damage of outside protein is pivotal target at low concentration, while the damage of nucleic acid is crucial at high concentration, and both the damages of protein and nucleic acid result in the inactivation of rotavirus at moderate concentration of free chlorine.The contaminations of waterborne viruses may be impacted by the epidemics, urban runoff and the waterbody quality. A one-year monthly monitoring of RV in raw and treated wastewater from three typical municipal wastewater treatment plants (WWTPs) in Beijing of China was conducted. Results showed that RVs were abundant in autumn and winter but rare in summer. During autumn and winter seasons, the average removal efficiencies of infectious RV in primary and secondary treated wastewater were 288-689 and 0.6-2.9 PFU/L, respectively. Among the different types of secondary and tertiary treatment processes, the anaerobic-anoxic-oxic (A2/O) process had higher removal efficiency than conventional activated sludge process, and the reverse osmosis (RO) was more efficient to remove infectious RV than membrane ultrafiltration and conventional flocculation-sedimentation and sand filtration process. The viral quantity of seawater intaked into the desalination plant at West Basin Desalination Plant at El Segundo, Los Angeles of USA, were evaluated during periods of coastal storms, which are used for drinking water production by reverse osmosis (RO). The results indicated that the adenoviral contamination in the seawater intake was not significantly impacted by the storm or urban runoff.