The complex systems behind the water coming out of your tap
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Turning on the tap to get a cold, refreshing drink of clean water is so simple and commonplace it's almost impossible not to take it for granted. Catherine Groenestein reports on water's long journey to your tap.
Livia Peters was just two years old when a drink of water nearly killed her.
In March the Taranaki girl, her mother Amelia and a 15-year-old cousin, all drunk water from a rainwater tank at their home.
Before long they all became seriously ill with what they later learned to be VTEC, a serious vomiting and diarrhoea infection.
Both women needed hospital treatment and Livia was rushed to Starship hospital in Auckland with renal failure and spent 10 days on dialysis.
Even though their water looked and smelt clean, tests revealed it was highly contaminated with E-coli, a bacteria that can cause serious intestinal illness.
"The results said one part per 100 was safe for drinking water and ours was 23," said Livia's father Roy Peters.
The source of the bacteria remains a mystery but the family now have a high-tech UV water filtering system to keep them safe.
While the Peters have been able to ensure their water is safe relatively simply, the process for public supplies is far more complicated.
When it does go wrong, the effects are devastating. In August 5200 residents in Havelock North got sick after drinking from the town's contaminated water. Residents wondered how such a thing could happen in New Zealand, a country not usually associated with third world problems.
But perhaps the more pertinent question is why it doesn't happen more often.
Water New Zealand president Brent Manning, who is also the South Taranaki District Council's engineering manager, says most people have no idea of the science and effort that goes into treating the water that flows from taps throughout the country.
Councils tread a line between providing safe water that complies with government standards, and doing so at a price the community is able to pay, he says.
Manning welcomes a recently-announced Government inquiry into the Havelock North issue as a chance for a public discussion on what level of health risk the community will tolerate, instead of leaving it to water suppliers to decide.
"There is a huge opportunity to educate New Zealanders better about the quality of their water and how they get their water because in my view we have taken it for granted for far too long."
At the moment most councils do a good job of doing the best with what they've got, he says.
"You can put a whole lot of risk mitigation measures in place to stop what happened in Havelock North occurring elsewhere but it comes at a cost. It's a matter of how much you need to spend.
"On the whole, councils and engineers in New Zealand have done it very well. It works, you generally turn on the tap and there's water."
South Taranaki District Council's engineers run 10 water supply schemes in the district and also oversee three in central Taranaki for the Stratford District Council.
Stratford's new water treatment plant, and those at Opunake and Kapuni, use micro-filtration membranes, a process Manning says is the best technology currently available to remove micro-organisms.
Behind the scenes is a complicated network of electrical and instrumentation and computerised systems for monitoring and control of all the equipment at the plants scattered around the province.
That engineering is shared between Taranaki's three district councils.
"The New Plymouth District Council team helps Stratford and South Taranaki out with their electrical and instrumentation technicians. They service the three councils across the region for water and waste water systems and in my view they do a damn good job," says Manning.
Taranaki is 'a bit of an exemplar' in terms of regional standardisation and regional operation, he says.
Not all water is treated equally as the work needed to make it safe for drinking depends on the source.
Water from a river, such as that supplied to New Plymouth, Opunake and Stratford residents, requires more filtration to remove debris and disinfection with chlorine.
Water from a deep aquifer, such as that supplied to Patea, where the water is so old and so deep does not harbour bacteria.
Here's where the science gets interesting.
Water flowing from taps in Patea and Waverley older than anyone who is drinking it. It began its "life" between 158 and 179 years ago, meaning it was already in the ground around the time the British government was deciding to establish a colony in New Zealand in 1837, and when the New Zealand wars began in 1860.
One way scientists figure out the "age" of water involves looking for traces of radioactive tritium, because tiny amounts can be found in water that is younger than 50-years-old due to above ground nuclear testing in the 1960s and 70s.
However, no matter how pure the water, on its journey from the treatment plant to the customer's tap, it can be contaminated with pathogens, and that's why most councils chlorinate water despite the impact on it taste.
Chlorine is the best way to provides residual protection that travels with the water, Manning says.
In New Plymouth treating the water is just one of the issues they face. Taranaki's most populous already has the highest per capita water use in the province of 336 litres per person per day and overall demand is only increasing.
If not controlled, this demand, combined with the city's expected growth to 88,000 people by 2045 means the council will soon have to find a new water source, council infrastructure manager David Langford says.
"Even if we manage our demand, at some point in the future we will have to find an additional water source because we will outstrip what we can take from the Waiwakaiho River."
He believes a combination of the region's high rainfall and historically low cost to ratepayers for getting that water, means people in the district don't value it as much as other district's populations might.
"It doesn't cost a lot, it's easy to use lots of it, you just turn the tap on. We just generally take it for granted.
"We are in the top third [of users] for New Zealand.
"The Australian average is only 195 litres per person per day and if you look at some European countries, the Netherlands are down to 119 litres. We use a lot of water," Langford says.
The council is introducing new charging regimes, including voluntary water meters for some residential users, and educating residents to use less water.
Because even in summer, when water supply is tight, water use remains high.
Using a hand-held hoses instead or sprinklers, washing cars using a bucket and sponge rather than with a hose were two simple ways to use less water Langford says.
Problem is, these basic conservation methods just haven't caught on in New Plymouth.
"We've seen some people washing their driveways down with a hose when they could be using a broom. When you've got 70,000 people in the district, if we all save a litre each, it will soon add up."
He's often asked why the council charges for something that falls from the sky for free.
"What we do charge for is the process of treating it so its safe and drinkable and the process of transporting it from the water treatment plant to your home."
Another conversation that needs to be had is balancing the opposing requirements of health versus flavour, he says.
It's a touchy subject. New Plymouth's water is renowned for its dirty taste and though residents are largely oblivious to it after years of exposure , its taste is often one of the things visitors stick their tongue out in disgust at.
"People want the water to taste nice but have the protection of having chlorine." Langford says. "But if you want to have protection you have to compromise on taste."
We wanted to find Taranaki's best tasting water, so we filled bottles from taps around the province and a panel of six rated them from 1 (yuck) to 5 (I'd pay for that).
A noticeable chlorine smell marred many of the samples from the larger supplies. The terroir of more than 100 years underground showed in Patea's water. It also split the panel, with one person declaring "I'd pay for this, " while others noted a "strange metallic taste".
Oakura's water and some from a rainwater tank were the preferred tipples overall. Oakura's water comes from an underground aquifer and contains more minerals than the water in other places that is from surface sources.surface sources,
Oakura: Fresh, pure, "I'd move there". 5
Filtered rainwater: Fresh, pure. 5
Okato: Nice natural taste. 4
Eltham: Most liked of Southern waters. Slight chlorine smell. 4
Stratford: Can smell chlorine, flavour good. 4
Hawera: Flavour good, initial chlorine odour. 3.5
Opunake: Tastes a bit silty, 3.5
Inglewood: Chlorine smell, taste ok. 3
Waitara: Bit of an odd taste. 3
Patea: Slight metallic taste, panel opinion very polarised. Some loved it, others loathed it. 3
New Plymouth: Noticeable chlorine aroma, slight undertones of dirt. 2.5