Do you need a water filter?
Photo:
Watercare
Poking through a pile of housewarming presents are two water filter jugs.
The fear is real.
"Tap water tastes disgusting," one gifter said.
"Tap water makes your hair fall," another one claimed.
The prevalence of this perception drove a household debate - do we need to filter our tap water, if it's already been through a complex process to make it safe to drink?
On a sunny April morning at Watercare's Ardmore Treatment Plant nestled in the foothills of Auckland's Hunua Ranges, production manager Tom Wallace explained how rain water gets from the dams through the filters and into our pipes.
"It's always like an optical illusion. The water is under gravity, so it's coming from the two big tunnels through the hillside and it comes in through the plant. And what's typically happening in the clarifiers is that the water goes in the bottom of the clarifiers. And as water rises up, the solids have been settled out through manipulation of the chemistry by dosing some chemicals upfront.
"You'll see the troughs running along the top, it collects the clean water and the water flows into the next part of the process, which is the sand filters. There's 30 sand filters and 83 clarifiers. So the clarifiers clarify the water first, they clean it up a little bit, and the filters do the removal of the remaining bits of solid before it goes for disinfection."
After the clarification, the water is already crystal clear. But Wallace said looking clean does not mean it's safe to drink.
A photo shows the comparison between dirty and clarified water.
Photo:
Ke-Xin Li
There are still harmful bacteria, which will be killed through either chlorine or chlorine combined with UV light.
While chlorine gas used at Ardmore is effective at killing harmful bacteria, Watercare's head of water Sharon Danks said it's not to everyone's taste.
"Some people are quite sensitive to the taste of chlorine, and so sometimes you can taste it, the chlorine, in the tap water. It doesn't make the water less safe."
Chlorine gas is used to disinfect water at Ardmore Water Treatment Plant.
Photo:
Ke-Xin Li
Wallace said lime is added at the final stage to make sure the water heading out to the network "isn't corrosive to the pipes".
It takes four hours for water from the reservoirs to pass through the Ardmore Water Treatment plant, before it goes to household taps as clean drinking water.
Wallace explained what should and should not be in the water by the time it reaches the tap.
"So there is no bacteria within that water that is in any way harmful to public health. We're regulated on that by the Ministry of Health. This plant in particular is sampled every single day for coliforms, E. coli. In terms of mineral content, we typically have what we get from the raw reservoir, we change it a little bit through the process by adding some lime, but we're not adding huge amounts."
Ardmore Water Treatment Plant has 30 sand filters and 83 clarifiers.
Photo:
Ke-Xin Li
Danks said the water flows by gravity and when the water leaves the Ardmore plant, it can make it all the way to Forrest Hill on the North Shore, or more than 50kilometres, before it need to be pumped.
"The forefathers of Watercare, so to speak, or the engineers that designed the system did very well for us to allow the water to move by gravity for such a long way. It's part of the reason why water is so affordable in Auckland as well."
The chlorine level decreased as water travelled through the network, which is why some people may taste stronger chlorine than others, said Danks.
On average, 1.2 milligrams of chlorine per litre is added at the Ardmore plant, which results in levels from 0.6 to 0.8 mg/l by the time it reaches Forrest Hill.
Chemical dosing at Watercare is done through a control room with computer screens, instead of labs.
Photo:
Ke-Xin Li
Every year the Water Industry Operations Group holds the National Water Taste Test competition. Last year, Rotorua was crowned for the best tasting tap water.
Professor Naresh Singhal is the director of the Water Research Centre at the University of Auckland.
He said most water filters on the market are like little water-treatment plants.
Activated carbon can filter out organic containments, but does not kill bacteria.
"Some may also remove chlorine a little bit, but again, I'm not 100 percent sure if they do that effectively. They can remove heavy metals. So if there's a concern that you have PFAs, heavy metals such as lead, then they could be useful in that sense. But generally in New Zealand, my understanding would be that you should not have these issues with drinking water."
Singhal said using a water filter at home is more about personal taste than necessity.
"People are used to a certain taste. And if the taste changes compared to what they've been used here, it may come across as being unpleasant. It may also come across as being unsafe, and then they will obviously be tempted to take some action."
But for those who like their water filtered at home, Singhal suggests actively maintaining and replacing the filters on time, otherwise you might be contaminating what comes through the tap.
Back at the Ardmore Treatment Plant, Wallace gives me a glass of freshly treated water from the kitchen. I asked him if they have an in-sink water filter, and the answer is positive, especially for guests who are not used to the stronger chlorine.
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