The 672 outbreaks of waterborne disease that were reported in the United States between 1946 and 1980 affected more than 150 000 persons. An analysis of the data from these outbreaks provides information on how often and where outbreaks occurred, as well as on what caused them.
A drinking-water treatment plant with high concentrations of trihalomethanes in its finished water and large numbers of viruses in its source water was located. This plant was used to study the effect of an alteration in the point of chlorination from the first to last step of water treatment on the biological and chemical qualities of its finished water. This alteration caused some reduction in trihalomethane production, but trihalomethane concentrations still exceeded the prescribed limit of 100 micrograms/liter. No viruses or bacterial indicators were ever isolated from the finished water of the modified plant. Total virus removal by the treatment steps before chlorination (coagulation, sedimentation, and sand filtration) averaged ca. 90%, whereas removal of bacterial indicators by these processes averaged between 88 and 98%. Recoveries of viruses and bacterial indicators in the source water were generally negatively correlated.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.