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Lower Hutt has the best drinking water

The Ministry of Health (MoH) has just confirmed what the locals of Lower Hutt have always known – Lower Hutt has the best drinking water in the country. It’s 100% poo-free and chemically compliant (it isn’t contaminated with a range of chemicals that New Zealand water is tested for) and comes from a naturally filtered fresh-water aquifer.

Annual report on New Zealand’s drinking water

The results are part of the Ministry of Health (MoH) annual report on New Zealand’s drinking water quality released in November 2009. The survey, compiled by the Institute of Environmental Science and Research (ESR), spans the period July 2007 to June 2008.

The survey covers water supplies from over 2,000 distribution zones and over 2,000 water treatment plants that feed water to approximately 91% of the population. Testing by various laboratories throughout the country included testing for a range of microbiological organisms such as Escherichia coli and Cryptosporidium and a range of chemical contaminants such as lead, arsenic, cadmium, copper and nickel.

The presence of E. coli in water indicates that the supply is contaminated with faeces (poo) and that water treatment is not adequate enough to prevent people who drink the water from being exposed to the risk of waterborne diseases.

The good news is that 83% of the New Zealand population is served by reticulated drinking-water supplies that comply with E. coli safety standards. The bad news is that many smaller communities were supplied with microbiologically contaminated drinking water.

E. coli in drinking water

Approximately 712,000 (17%) of New Zealanders were supplied with drinking water that either failed to comply bacteriologically with the criteria or for which there is no data because they were self-supplied. (This doesn’t mean their water was contaminated – it just means that no data was supplied for the survey.)

The MoH report says that, in reality, apart from groundwater from a confined aquifer (such as Lower Hutt), all source waters are faecally contaminated and so will contain the faecal indicator bacterium E. coli unless the water is adequately treated.

Some water suppliers in New Zealand are so keen to avoid scrutiny that, against MoH requirements, 78 suppliers ceased monitoring. The MoH lists these suppliers in its report.

The report also expressed concerns about the number of people served by supplies in which E. coli transgressions occurred and that were not appropriately followed up by immediate corrective action. The report says that this had “increased markedly between 2006/7 and 2007/8” and that it was “of concern because failure to remedy the cause of a transgression subjects the population to prolonged exposure to faecally contaminated drinking water and imposes an unacceptable risk of waterborne disease on the community”.

Details of the 38 local authority supplies that failed to take appropriate corrective action in 2007/8 are also listed in the report. Of these 38 local authority supplies, eight were also reported for the same practice in the previous review. Singled out were Marlborough, Hurunui, Selwyn and Waitaki District Councils, which were urged to “urgently review and improve their corrective action procedures following bacteriological transgressions”.

“Failure to reduce this risk by increased disinfection or by taking appropriate steps to reduce the hazard (i.e. closing or changing the supply) or exposure (i.e. recommending that people do not drink unboiled water) increases the likelihood of waterborne disease… Numerous waterborne disease outbreaks have occurred in New Zealand in recent years. During 2007/8, 15 waterborne outbreaks involving 205 cases were recorded, of which untreated or contaminated supplies were identified as a contributing factor in most of them. It is unlikely that this situation will change appreciably while so many drinking-water supplies, particularly those serving small communities, do not employ adequate risk management practices including treatment.”

Despite reported case numbers, it is likely that thousands of people a year are affected by waterborne diseases, with most going unreported.

Drinking water in rural schools

Drinking water in many rural schools, in particular, failed to meet standards, with some recording high levels of faecal contamination. Of the 590 schools with their own water supplies, only 17% managed to comply bacteriologically. The rest were either inadequately monitored or were contaminated with E. coli. Of the 590 schools, none was treated to a high enough level for protozoal compliance to protect children from diseases such as giardia and cryptosporidium. (This doesn’t mean that the water was infected with these things – it just means that the water was not treated enough to remove these contaminants if they were present.)

For example, in the Waikato District, of the 20 schools monitored, only 2 complied with bacteriological standards, 5 had unacceptable levels of E. coli, and the rest (13) had either inadequate sampling or failed to provide any data at all. The Waikato District is by no means the worst. Of the 40 schools listed in the Rodney District, only 3 complied, 8 had E. coli, and the rest were either not testing for E. coli or failed to take adequate samples. The story is similar across many other districts.

In terms of chemical contaminants in water supplies, approximately 3,468,000 people or 82% of the population were supplied with drinking water that is compliant with acceptable values. For the remainder of the water suppliers, inadequate or no monitoring continues to be a major reason for distribution zones not complying with the chemical criteria. However, there were also some 201,900 people who were supplied with chemically contaminated water during the year (either heavy metals or disinfection byproducts that exceeded maximum acceptable values). Worse still, of these cases, the MoH report considered that the corrective actions taken in just over half (56%) of the occurrences were inadequate.

Activity idea

In relation to this news article, your students may like to make an aquifer model.
Walking on water

To help them to do this, they could watch a video showing how the model is built.
Building an aquifer model

They may also like to watch a video of ESR scientist Dr Wendy Williamson explaining how she is developing a method for detecting viruses in water.
Detecting viruses in drinking water

In another video, ESR scientist Dr Brent Gilpin explains a method of identifying species-specific markers in poo so that he can tell if the poo contaminating our water came from ducks, cows or humans.
Sources of poo

Useful links

For details about the drinking water in your area, the complete report can be viewed on the Ministry of Health website.
www.moh.govt.nz/.../annual-review-drinking-water-quality-nz-2007-08external link

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