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Reliability of drinking water quality data used for compliance determinations
Author(s) -
Phillips Charles R.,
Chmelynski Harry J.,
Sensintaffar Edwin L.,
Darlow Kira E.
Publication year - 2012
Publication title -
journal ‐ american water works association
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.466
H-Index - 74
eISSN - 1551-8833
pISSN - 0003-150X
DOI - 10.5942/jawwa.2012.104.0141
Subject(s) - environmental science , reliability (semiconductor) , sample (material) , water quality , sampling (signal processing) , statistics , contamination , quality (philosophy) , computer science , mathematics , chemistry , biology , ecology , power (physics) , physics , philosophy , filter (signal processing) , chromatography , quantum mechanics , epistemology , computer vision
Public water systems are required by Safe Drinking Water Act regulations to collect and analyze samples of water for contaminants from each entry point within a system, generally on a quarterly basis. The averages of the quarterly sample results are used for compliance determinations and potential treatment decisions that may require costly actions by system operators. Analysis of data reported by the US Environmental Protection Agency in 2009 identifies a high degree of uncertainty in the average (mean) of four quarterly samples. Statistical analysis of 970 datasets for 10 analytes indicated wide variation in the sample data for more than one third of the cases. Moreover, when the means were at or near the maximum contaminant level for the contaminant measured, the variability was significantly more pronounced. Limited analysis indicated that the variability is not geographically dependent and increased sampling beyond quarterly is only practical for selected contaminants.