Havelock North water chlorination: Brent Manning responds to MP Stuart Nash

You may have seen the opinion piece published in the Hawkes Bay Today http://www.nzherald.co.nz/hawkes-bay-today/opinion/news/article.cfm?c_id=1503459&objectid=11700023

on Thursday 25 August by Napier MP Stuart Nash.

Mr Nash wrongly attributed a recent Radio NZ interview http://www.radionz.co.nz/audio/player?audio_id=201812605

to me rather than Chief Executive John Pfahlert who gave the interview, however as President of Water New Zealand I have been happy to respond to Mr Nash.

I do agree with Mr Nash on a number of points he made: we do undervalue our water in this country and take its provision and supply for granted; secondly, it is important to “ensure the infrastructure delivering the water is up to standard” - this in fact one of the strategic priorities encapsulated in the National Infrastructure Plan 2015 and strongly supported by Water New Zealand and our members nationwide. Lastly the events and effect of the water contamination and ensuing gastric outbreak in Havelock North is a travesty, but it is one which could possibly have happened in a number of other towns or cities in New Zealand.

We know Councils and public water supply engineers and treatment technicians work hard to deliver good quality safe drinking water - New Zealand mandated a suite of comprehensive Drinking Water Standards in 2008 - and a timeframe for compliance which many public water supplies now meet, thanks in part to investment by councils aided in some cases by government subsidy. The Drinking Water Standards are entirely about mitigating the risk to public health through supplied water (including tankered delivery), however compliance won't guarantee mitigation against every risk.

Without chlorination, once a waterborne pathogen (disease causing microorganism) becomes prevalent in a water network there needs to be a means of disinfecting the water mains and killing the bugs. Although there are alternatives, chlorine has for decades been used as a very effective disinfectant because it provides for residual disinfecting, all the way to our homes and businesses.

There can be downsides - chlorine added to water high in organics can give rise to disinfection by products, some of which are claimed to be carcinogenic. And chlorine won’t remove protozoa (single-celled microorganisms such as cryptosporidiosis and giardia) if they find their way into the water network. Micro-filtration of the water to less than 1 micron will, however, and this treatment is fairly commonplace in New Zealand now. Properly treated, the water quality can be controlled through successive treatment 'barriers’ and the risks managed – primarily though the level of treatment required is determined by the quality of the source water – a secure groundwater offers some protection but even for the purest water or highly treated water, once it is in the water network and pipes in the streets, if there is no residual disinfectant then there is no remaining protection if a bug does enter the pipes.

It is time for a more public discussion about what level of public health risk the community is prepared to tolerate (or not) and not simply leave it to the water suppliers - a point I'm pretty sure Mr Nash would agree with.

Brent Manning,
President, Water New Zealand