Viricidal Efficiency of Disinfectants in Water

RECALLING the recent outbreak of water- borne infectious hepatitis in New Delhi, India (1), and the discovery in the past decade of more than 70 new human enteric viruses, it seems appropriate to review the information available regarding the viricidal efficiency of disinfectants in water.The term "enteric viruses" as used here includes infectious hepa¬ titis virus, Coxsackie groups A and B, polio¬ virus, adenovirus, and the ECHO viruses.All of these are excreted in feces and can be found in urban sewage, especially in the late summer and early fall.Proved waterborne epidemics have occurred only with the virus of infectious hepatitis; however, outbreaks of poliomyelitis suspected of being waterborne have been reported (2,3).No waterborne diseases caused by Coxsackie and ECHO viruses have been re¬ corded.No adenovirus infections have been attributed to drinking water, but three out¬ breaks of one of the clinical diseases caused by adenoviruses have been associated with swim¬ ming pools (Ir-6). ChlorineBecause chlorine reacts with organic matter and forms combined chlorine compounds, re¬ liable data on virus destruction depend on the chemical definition of the test water and deter¬ mination of the types of titrable chlorine pres¬ ent, which are markedly influenced by the pH of the substrate.The rate of kill under fixed test conditions is proportional to the concen¬ tration of the kind of chlorine available.Sufficient demand-free virus material should be present to allow for accurate determination of the inactivation rate.Since many of the earlier studies on the destruction of viruses by chlorine did not meet these criteria, the resulting data are not included in this review.The reports before 1946 did not differentiate between free and combined chlorine, and many of the reports also showed such a high chlorine demand of the test system that the data on the viricidal effi¬ ciency of chlorine cannot be accurately interpreted.Free Chlorine Information on the viricidal efficiency of free chlorine in water is presented in the table.