Virus contamination, removal characteristics and quantitative risk assessment from drinking water source to secondary water supply system

Abstract

The drinking water (DW) supply system is the last line of defense against virus infections for people's DW health. This study systematically evaluated the virus pollution characteristics and human health risks in the entire DW supply systems. The detection frequency range of the virus in DW was 5.30% to 71.21%, and the concentration range at not detected (n.d.) -1.45×105 copies/L. DNA virus like adenovirus was more persistent than RNA viruses like norovirus and enterovirus in the DW system. Drinking water treatment plants (DWTPs) play a crucial role in reducing the target virus with degradation rates ranging from 47.09% to 100% when compared with the removal rates in DW source and secondary water supply (SWS). It was found the persistence and accumulation of the virus in the treated water from DWTPs to the downstream water transmission network. Principal component analysis showed that the virus contamination was positive correlation with water quality indexes like total phosphorus (TP), total nitrogen (TN), dissolved oxygen (DO) but negative correlation with temperature and the dose of free chlorine. Quantitative microbial risk assessment (QMRA) of adenovirus in the SWS showed that the DALYs/person/year of gastroenteritis ranged from 8.11×10-6 to 2.68×10-4 DALYs/person/year. Uncertainty analysis of different distributions of model inputs like virus concentrations showed the risk caused by adenovirus was changed appreciably for different person by using 100,000 Monte Carlo simulations. It is necessary to efficiently remove the virus in the DW systems to ensure human health for the direct ingestion of secondary water supply water.