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Drinking-water Standards revision concerns


The Ministry of Health has released an updated drinking-water standard, DWSNZ 2005 (Revised 2018) which will come into effect on 1 March this year. Water New Zealand supports some of the changes but has concerns about others. This has prompted Jim Graham, Principal Water Quality Advisor for Water New Zealand to write to the Director General of Health, raising a number of these concerns and asking that implementation of the new standard be delayed until adequate consultation with the industry can be undertaken.

While we agree with the introduction of total coliform testing and enumeration of E. coli tests, we are concerned that the protozoa treatment level is being reduced to a default of 3-log. We understand that the Ministry of Health has made this decision based on Cryptosporidium sampling undertaken by water suppliers over the last 10 years which indicate that average Cryptosporidium levels are low. Our concern is supported by expert evidence provided to the Havelock North Inquiry which indicated that Cryptosporidium sampling should be targeted to rainfall events and that peak levels were significant rather than average levels. It seems that the approach taken by New Zealand over the last 10 years is not consistent with international best practice.

We are also concerned that this is a significant change to the standards and has been made without industry consultation. The Health Act (S69P) requires consultation if the changes are not minor.

The implications of requiring total coliform testing do not appear to have been fully considered. A total coliform result can be determined from the defined substrate E .coli test. One test produces two results. But the referee methods for E. coli and total coliform testing are different. This would seem to mean that for the total coliform test to be valid, it would have to be repeated using the MPN total coliform referee method.

Additionally it seems unreasonable to make these non-urgent changes part way through a compliance period, affecting how compliance monitoring is assessed and reported. The changes also are not aligned with Local Authority budget setting processes.

It is our view that had consultation drawn on the expertise within our industry, the above and a number of other smaller issues would not have arisen. We have requested that the date of implementation for the revised standards be delayed so that further consultation with the industry can be undertaken. We have asked for an opportunity to discuss these matters with the Director General and will keep you informed of the outcome.

Contact Jim Graham, Environmental Scientist, Principal Advisor Water Quality.