An outbreak of cryptosporidiosis in a drinking water system with no apparent treatment deficiencies or breakdowns suggests that waterborne outbreaks are a potential threat in other US cities. When Las Vegas, Nev., experienced an outbreak of cryptosporidiosis in the AIDS population early in 1994, the Clark County Health District requested that the Centers for Disease Control and Prevention (CDC) assist in determining the cause of the outbreak. Results of CDC's epidemiological study indicated that AIDS patients drinking tap water in Las Vegas are at greater risk of contracting cryptosporidiosis than if they consume bottled or filtered water. An AWWA Research Foundation peer review panel concurred with the CDC that the epidemiologic evidence pointed to tap water as the only risk factor in the outbreak. The paradox of this outbreak is that the influent water quality at the treatment plant did not change, no treatment breakdowns or deficiencies were identified, and the outbreak ended as suddenly as it began, with no changes in water treatment.
In the development of a 1500‐ML/day treatment plant, consideration was given to alternative means of disinfection to reduce the formation of total trihalomethanes. Chlorine dioxide (CIO2) was examined on a plant scale of 760 ML/day. This article relates the design considerations and problems encountered in the production of CIO2 free of chlorine (Cl2). The chief problem, which remains unresolved, is the development of an analytical technique that can routinely identify CIO2, CI2, chlorates, and chlorites in the same solution.
Despite recent advances in water-utility technology, operators are still receiving consumer complaints of funny-tasting water. Presented here is a new technique to rid treated water of polysulfide taste by sulfonating and by monitoring the process with Threshold-Odor-Number (TON) determination.Objections to sulfide in potable water are, of course, well known rotten-egg odor appeals to no one. Because of this singularly rank odor, it is understandable that solutions to the problem were forthcoming early in the history of water treat ment. Use of the TON method' possibly can enable waterutility personnel to discern such odors.'Positions at the time of presentation were J. T. Monscvitz., operalions-maint. supt., and L. D. Ainsworth, treat, supt.,
A flexible system for treating water with consistently low turbidities but greatly varying odor levels is described in this article. Pretreatment, filtration, and odor‐control procedures are discussed, among other aspects of the system.
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