Balancing the risks of communicable disease transmission spready by waterborne pathogenic microorganisms against the risks of toxicity associated with disinfectants and disinfection by-products (DBPs) has become a major concern for water uality control. Additionally, it is becoming evident that the use of conventional indicator organisms may be inappropriate for detection of nonbacterial pathogens (e.g,, viruses). In an effort to elucidate these issues, research has been performed in which the antimicrobial efficiacies of several alternative disinfectants (free chlorine, combined chlorine, UV radiation, and 2, 2-dibromo-3-nitriloproprionamicde (DBNPA)) were examined against seven potential pathogenic cindicators, including four bacteria (Escherichia colis, Pseudomonas aeruginosa, Streptococcus faecalis, and Staphylococcus aureus), and three viruses (Polovirus, Rotavirus, and Bacteriophage MS-2). Dose-response behavior for each disinfectant-indicator organism pair was examind using batch reactors. Results showed that free chlorine and UV radiation are effective against all indicator microorganisms, while chloramine and DBNPA are effective against bacteria but not against viruses. In addion, the resistance of indicator organsisms to all disinfectants follows the general order: gram-negative bacteria < gram-positive bacteris < animal Viruses < bacterial phages.
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