On 27 April 2009, just months into Queensland's new fluoridation mandate, Seqwater's North Pine water treatment plant north of Brisbane shut down. The fluoride dosing did not.
What happened
- With no water flowing through the plant, fluoride kept being added, building up a highly concentrated slug of water.
- About 400 households in Joyner received water reported at around 13 times the maximum recommended level. Some reports put it at up to 20 times.
- On 29 April, a fluoride analyser gave an off-scale alarm. Staff assumed it was a false reading.
- A flow switch and a high-fluoride alarm, both designed to stop exactly this, had been disabled.
The inquiry
An independent inquiry led by Associate Professor Mark Pascoe of the International Water Centre found the plant's design was adequate, but it was not being operated in line with the Water Fluoridation Regulation. Secondary reports also said residents found out late, and that the public notice gave the wrong date.
Could it happen again?
Rules have tightened. NSW's Code of Practice, for example, requires:
- Fluoride to be dosed in a range of 0.9 to 1.5 mg/L, with consumers never receiving more than 1.5 mg/L.
- Utilities to notify NSW Health within 3 working days of any overdose above 1.5 mg/L.
- Day tanks to be refilled manually, which limits how much fluoride can ever be released at once.
But North Pine shows the weak point is not the chemistry. It's people and maintenance: disabled interlocks and ignored alarms. The same applies in reverse in Dubbo, where broken equipment meant years without fluoride.