A water expert has told the Government inquiry into New Zealand's drinking water that
councils should be prosecuted for contaminations.

The outbreak last year made some 5500 of the Village's 14000 residents ill with campylobacteriosis, while putting 45 in hospital and has been linked to three deaths.

At Stage 2 of the Havelock North water inquiry yesterday International drinking water expert Dr Colin Fricker said there must be penalties if suppliers don't have a functioning water safety plan.

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Dr Fricker said if councils don't have that, then it's people's lives at risk.

"Prosecution occurs quite widely in some areas - in the US and UK where there are water treatment failures utilities are prosecuted as well as individuals, board members and operators.

"Prosecution gives the sort of incentive for people to abide by the rules."

Other matters considered this week were aimed at preventing any recurrence of contamination.

Introducing the proceedings inquiry panel chairman Lyn Stevens QC said water was life giving and precious.

"We should all pause to remember those who died, those who became sick and those whose businesses were disrupted," he said.

"This is important not only to the people of Havelock North but all New Zealanders."

Appearing at the inquiry was a panel of national and international experts comprising Dr Fricker, Dr Dan Deere, Iain Rabbitts, Dr Chris Nokes and James Graham, who were asked their views on drinking water safety and treatment.

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This panel generally agreed the universal principals for drinking water safety were to protect the water source, to have multi-barrier protection against potential contamination, and to have the ability to respond quickly and effectively in the event of any sudden or extreme change in water quality, flow or environmental conditions.

As had been seen with overseas outbreaks, it was noted there was a level of complacency among public water suppliers, due to the fact systems worked well 99 per cent of the time, and a tendency for suppliers to have static water safety plans that were not set up well to respond to sudden changes.

Other principles for water safety included managing risks, the responsibility for which extended to not only the water supply operators but also council senior managers and elected representatives.

The treatment of reticulated public water supplies was also discussed with four of the five panel experts agreeing some form of treatment was required.

Environmental scientist James Graham had a slightly different view, noting internationally outbreaks had occurred even in treated supplies, and he said that in exceptional circumstances it may be appropriate not to treat water.

"It would need to be a deep groundwater source, with online real-time monitoring and the supplier would need to demonstrate to a highly expert regulator that they could manage it effectively."

Water quality scientist Dan Deere noted that the international outbreaks Mr Graham referred to were a result of the treatment failing.

He said that although in theory non-treatment could be acceptable in some situations, it could be more practical and cost-effective to have treatment, rather than spending a lot of money trying to identify if treatment was needed.

"Chlorine is the only reliable barrier - it's easy to measure and control and is reliable."

Water treatment specialist Dr Iain Rabbitts said people needed to think about reticulation all the way to the tap, which could not be controlled in an extensive network that was always going to be prone to leaks and backflow issues.

"If you have no residual disinfectant you are in a dangerous place."

The panel was then asked whether they thought the public should be able to oppose chlorination as a treatment for reasons such as unpleasant taste or odour.

Mr Graham said that if a community was prepared to pay the higher costs of not having treatment, that should be explored.

"Communities have a right to have an input -in the end decisions about water safety must be made by the water supplier, but they must take into account the views of the community."

Dr Rabbitts said taste and odour issues were important, and that they tended to occur in places which were non-chlorinated, but then were over-chlorinated.

"If it's done properly there should not be taste and odour issues ... and we should not be listening to the vocal minority about this."