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To assess the state of knowledge regarding the effectivenessof distribution system disinfectant residualsduring accidental microbial intrusions, the authorsreviewed laboratory-, pilot-, and full-scale experimentalstudies. The persistence of microorganisms in thebiofilms of simulated mains at the laboratory scale wasmuch longer than in pilot-scale settings, under the typicaldisinfectant residual concentrations used in distributionsystems. Most of the studies reviewed used culture-basedmethods for the enumeration of microorganisms,which are known to underestimate the number anddiversity of microorganisms.Because the distribution system is the last barrierbetween the treatment plant and the consumer, intrusionis of concern to utility managers. Conditions experiencedduring some repairs, zero- or low-flow conditionsand/or delay in reinstatement of disinfection, arelikely to be critical for the persistence of intrudedmicroorganisms in the biofilm, a fact that underscoresthe importance of adequate chlorination and flushingprocedures. For the research community, this reviewhighlights the need for additional studies using methods(e.g., molecular tools) that allow the detection of viablebut nonculturable microorganisms. Includes 62 references, tables.

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Edition: Vol. 100 - No. 10 Published: 10/01/2008 Number of Pages: 15 File Size: 1 file , 400 KB