2019 Changes to Drinking Water Testing
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2019 Changes to Drinking Water Testing

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Changes to Drinking Water Testing

The New Zealand Drinking Water Standards currently allows for E. coli samples to be analysed by a presence/absence technique in order to meet compliance. Under these standards, any positive sample can only be reported as either present or not-present and must be followed-up by the collection of new samples. The retests are analysed for E. coli by MPN which is a technique that provides an actual E. coli Most Probable Number count.

On 1 March 2019 the way that laboratories process drinking water samples will change. From this date forward all drinking water samples used for compliance will need to be analysed for E. coli AND Total Coliforms by an MPN technique. This change will affect many of our existing customers as the minimum testing requirement of E.coli by presence/absence has shifted to include total coliforms by MPN. MPN costs more to process due to increased consumable costs. However, the technique provides customers a quicker response time in the event of a positive, by not needing to take an extra day to enumerate follow-up samples.

By the time this newsletter is delivered, our routine council customers will have been contacted to organise changes to the testing programme. This will include a review of the method that is currently being used as well as the tests that we analyse to you. All data will continue to be available as both pdf and excel spreadsheet and everything will be uploaded into the Drinking Water Online database on a quarterly basis. Each quarter sees us uploading over 22,000 results into this database, including onsite results such as pH and FAC as well as laboratory chemistry tests.

For further information please contact Sunita Raju