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Non-achievement of the Drinking-water Standards for New Zealand: E. coli transgressions

Please note: As of 1 July 2025, the New Zealand Institute for Public Health and Forensic Science (PHF Science) is the new name for the Institute of Environmental Science and Research (ESR). Research and reports published prior to this date may reference the organisation’s former name.

Summary

This report was undertaken for the Ministry of Health to review data from the annual survey of drinking water quality to see if there was evidence that maintaining a chlorine residual could overcome occasional E. coli transgressions, and evidence of the cause of these transgressions.

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