OVERVIEW

Disinfection is a process designed for the deliberate reduction of the number of pathogenic microorganisms. While other water treatment processes, such as filtration or coagulation-flocculation-sedimentation, may achieve pathogen reduction, this is not generally their primary goal. A variety of chemical or physical agents may be used to carry out disinfection. The concept of disinfection preceded the recognition of bacteria as the causative agent of disease. Averill (1832), for example, proposed chlorine disinfection of human wastes as a prophylaxis against epidemics. Chemical addition during water treatment for disinfection became accepted only after litigation on its efficacy (Race, 1918). The prophylactic benefits of water disinfection soon became apparent, particularly with respect to the reduction of typhoid and cholera.

While significant progress is being made in controlling the classic waterborne diseases, newly recognized agents have added to the challenge. These include viruses (Melnick et al., 1978; Mosley, 1966), certain bacteria ( Campylobacter, Palmer et al., 1983; Yersinia, Brennhovd et al., 1992; Reasoner, 1991; or Mycobacteria, Geldreich, 1971; Iivanainen et al., 1993; Reasoner, 1991; for example), and protozoans ( Giardia, Brown et al., 1992; Le Chevallier et al., 1991; Miller et al., 1978; Reasoner, 1991; Renton et al., 1996; Rose et al., 1991; Cryptosporidium, Bridgman et al., 1995; Centers for Disease Control and Prevention, 1995; Gallaher et al., 1989; Goldstein et al., 1996; Hayes et al., 1989; Le Chevallier et al., 1991; Leland et al.,...