Inactivation of Health-Related Microorganisms in Water by Disinfection Processes

Abstract

The recent literature on disinfection of health-related microorganisms in water and wastewater is reviewed. There is now considerable evidence that traditional microbial indicators of water and wastewater quality, such as total and fecal coliform bacteria, are inadequate to predict the presence or disinfection responses of several important, newly recognized bacterial, viral and protozoan pathogens. This review emphasizes the response to disinfection of waterborne microbial pathogens and potential indicators of recent recognition and public health concern. These organisms include heterotrophic plate count (HPC) bacteria, frank and opportunistic bacterial pathogens, such as Campylobacter jejuni, Yersinia enterocolytica, non-tubercular mycobacteria, Legionella spp. and pseudomonads; coliphage indicators and enteric viral pathogens, such as hepatitis A virus, rotaviruses and Norwalk virus; and protozoan pathogens, such as Giardia lamblia, Cryptosporidium, and the free-living amoeba (e.g., Acanthamoeba spp. and Negleria spp.). The responses of these organisms to widely used, traditional disinfectants, such as free and combined chlorine, and to disinfectants of more recent interest, such as ozone, chlorine dioxide and ultraviolet light, are reviewed. This review also attempts to identify the variety of factors influencing disinfection efficiency, especially those that interfere with disinfection. It is apparent that traditional microbial indicators, such as total and fecal coliforms, are more sensitive to disinfection than such pathogens of recent concern as mycobacteria, enteric viruses and protozoan cysts. Therefore, efforts must be continued to find more reliable indicators of disinfection efficiency and microbial water quality and improved methods for water and wastewater disinfection.