Christchurch water's chlorine levels to be reduced
The Christchurch City Council will lower the amount of chlorine in the water hoping it will reduce smell and taste issues.
The Christchurch City Council will lower the amount of chlorine it is adding to the city's water after public outcry over the taste and smell.
Council city services general manager David Adamson said the chlorine doses at 27 of the 53 pump stations being treated would be reduced from 1 part per million to 0.5 parts per million. The change was expected to take two weeks.
"We are hoping reducing the dose will help with the taste and smell issues that some people have been experiencing, but until we roll this out we cannot make promises," he said.
"That being said, both our expert and the Drinking Water Assessor believe the potential benefits outweigh that risk and it is worth shifting to a lower dose where we can."
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Adamson said there was a chance it would not make a significant difference.
Since the chlorination rollout began in March, complaints ranged from the smell and taste of the water to skin irritations such as eczema and eye problems.
Christchurch Mayor Lianne Dalziel says staff have been working since last week when she asked them if they could reduce the chlorine levels in the supply because of the widespread dissatisfaction.
Christchurch Mayor Lianne Dalziel said staff had been working since last week when she asked them if they could reduce the chlorine levels in the supply because of the widespread dissatisfaction.
"They've been working with the chlorination expert, the Drinking Water Assessor, they've got them to agree at this stage on 27 of the pump stations where they can reduce it."
It is not known which stations will have lower chlorine doses.
When asked why the 27 pumps could not have been dosed at lower levels in the first place, Adamson said it was "really complex" and staff only found out it was an option after analysis.
When asked how it was possible 10 per cent of the council samples had the same amount of chlorine as a swimming pool – above the level of 1 part per million – Adamson said it was because the water flowed in different directions at different times of the day.
Adamson said the council was advertising, until this Wednesday, for expressions of interest for UV treatment supplies.
Canterbury medical officer of health Alistair Humphrey at a media briefing announcing the Christchurch City Council's water chlorination scheme in January.
UV, a substitute for chlorination, was originally ruled out as being too expensive, but he said it might now be "cheaper and quicker" at certain pump sites.
The 27 pump stations were selected because they were in areas where the water travelled down the pipes for at least two minutes before reaching people's homes. That lag was important because it allowed the chlorine to be effective at a lower dose, Adamson said.
At the other pump stations the chemical had only a minute's contact time with the water so the dose needed to remain at current levels.
The changes would be rolled out over the coming weeks, Adamson said.
"We are prioritising our well head improvement work on those pump stations where we are most likely to get approval to stop chlorinating."
The roll-out of water chlorination started in the city on March 26.
- Stuff
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