Assessing the impact of wastewater treatment plant effluent on the norovirus contamination of shellfisheries
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Norovirus (NoV) is the most common cause of viral gastroenteritis in the developed world. The discharge of Wastewater treatment plant (WWTP) effluent to the marine environment has implications for the virus quality of shellfish harvested that can accumulate NoV from contaminated water. This research project aimed to investigate NoV concentrations in WWTPs, the subsequent NoV contamination of oysters and the inactivation kinetics for NoV in the marine environment. Concentrations of NoV were determined in weekly samples of wastewater at different stages of treatment (influent, post primary and post secondary). NoV concentrations were also determined in weekly samples of oysters placed adjacent to the WWTP outfall. NoV was detected year-round and concentrations peaked during the winter months that were correlated with concentrations in oysters. In a second WWTP providing UV disinfection, the reduction of NoV was similar to FRNA bacteriophage GA using RT-qPCR. However, the reduction of infectious FRNA bacteriophage GA was significantly greater than that obtained using the RT-qPCR assay. A significantly higher percentage of infectious virus was present in combined sewer overflow effluent than in UV disinfected effluent. The inactivation kinetics of NoV and FRNA bacteriophage GA in was investigated in a lab setting. The reduction in detectable viruses was not significantly different between summer and winter for NoV GI and NoV GII. However, using FRNA bacteriophage GA the RT-qPCR assay significantly overestimated the survival of infectious virus. Overall, the findings from this thesis demonstrate that RT-qPCR is an unsuitable method to determine the reduction of infectious NoV that occurs during wastewater treatment and in the marine environment.