by MARISSA CALLIGEROS
January 4, 2010 - 10:57AM

South-East Queensland's water authority has admitted it faced difficulties integrating new fluoride dosing systems with ageing water treatment plants, resulting in underdosing.

But a spokesman for the authority said the problems were not unexpected.

At least one water treatment and fluoride plant required replacement piping and flow meters, resulting in underdosing in the three months to June last year, while another plant remained out of action following an overdose.

While water supplies should be fluoridated between 0.7 milligrams per litre and 0.9 mg/L, water from the treatment plants at Mt Crosby 0.44 mg/L and Mudgeeraba 0.54 mg/L in the second quarter.

However the Molendinar plant on the Gold Coast was the only operational plant in the most recent quarter to fall shy of the target with an average of 0.68mg/L added to supplies.

SEQWater conceded the fluoride plants had not been operating as they should, but attributed the underdosing to teething problems in the fluoride system during the first 12 months of operation.

"We can't get away from the fact that the plants aren't performing as they should," SEQWater spokesman Mike Foster said.

"[The underdosing] was part and parcel of bedding down the system. It's the nature of those plants. The added complication was that we were introducing these fluoride plants to existing water treatment plants and many of those plants are quite aged."

While the underdosing was a technical breach of health regulations, Mr Foster said Queensland Health had fully supported the authority's decision to gradually add fluoride to water supplies.

"There was a deliberate approach taken by the organisation that we would introduce levels gradually. Our target in the first six to 12 months was to at least ensure we were delivering 0.4 mg/L and above," he said.

"Certainly 0.4 mg/L and above delivers a health benefit."

The North Pine treatment plant was shut down in May, when it was discovered Brisbane residents received 20 times the allowable limit, and was not back online until October.

"North Pine will now take two to three months to build back up again," Mr Foster said.

Further complications arose at the Mt Crosby plant in the three months to September 30 where extended piping needed to be installed and faulty equipment, including flow meters, needed to be replaced.

But Mr Foster said adequate fluoride levels should finally be added to water supplies in the new year as SEQWater eased its conservative approach.