Fate of Viruses in Water Systems

Abstract

This paper reviews the state of knowledge regarding human viruses in water systems from an environmental engineer's perspective. The authors describe (1) viruses of concern and potential human diseases; (2) waterborne outbreaks related to viruses; (3) the sources, reservoirs, and fate of viruses in the environment; (4) the use of viruses as microbial source tracking tools; (5) virus survival and virus transport; (6) virus concentration and detection methods; (7) the fate of viruses in water treatment; (8) the removal of viruses in full-scale, bench, and pilot-scale conventional and membrane bioreactor (MBR) wastewater systems; and (9) other issues related to viruses in water systems such as the role of bacterial viruses (phages) and viral risk assessment. Occurrence of human pathogenic viruses in environmental waters (i.e., surface waters, groundwater, drinking water, recreational water, and wastewater) raises concerns regarding the possibility of human exposure and waterborne infections. Commonly observed waterborne viruses include adenoviruses, enteroviruses, noroviruses, and rotaviruses. Viruses are the smallest of all microorganisms, and their size facilitates transport in environmental media. In addition, viruses have very low die-off rates and low infectivity doses, increasing concern over outbreaks of disease related to waterborne or sludge-related virus exposures. Overall, virus presence in water and wastewater is a difficult problem for environmental engineers because of prevalence, infectivity, and resistance of viruses to disinfection. Environmental engineers should be aware that even state-of-the-art wastewater treatment plants may not be able to eliminate viruses from wastewater, and viruses potentially escaping from drinking water treatment plants because of technical and management deficiencies may lead to human exposure and disease. The knowledge and tools summarized in this paper provide basic information needed to make decisions for efficient water and wastewater management and reduction of risk of human exposure.