15 March 2000

Following is an article in the Coonabarabran Times on 24 February 2000 regarding Coonabarabran Council's experience over the last four months in destratifying the water body in Timor Dam. Timor Dam is the primary water supply for Coonabarabran.
There is a long history of Blue Green Algae blooms in this dam however there have been none since installation of a destratification unit in November 1999.

MIXING OF TIMOR DAM WATER PROVIDES BETTER QUALITY WATER
Council's efforts to improve the water quality in Timor Dam are providing positive results for water quality. Council in conjunction with the company Water Engineering and Research Solutions Pty Ltd installed a mixer with the aim of eliminating stagnant conditions in the dam. Known as destratification, the aim of the mixer is to eliminate different temperature and oxygen layers within the dam.

The mixer was installed on 2 November 1999 and following tests on 14 February 2000 there were no temperature or dissolved oxygen layers down to a depth of 10m. It is known that stagnant conditions favour Blue Green Algae (BGA) blooms and that mixing may eliminate or reduce blooms. Council is very encouraged by the results, as there has not been a BGA bloom since the mixer was installed.

The mixer is simply a 2.5m diameter impeller powered by a 1.1kW electric motor. The impeller is mounted on pontoon and is anchored in the middle of the dam. Council invested $70,000 in the technology, which includes the extension of power to the dam. Because there have been no BGA blooms there has been no requirement for the use of activated carbon at the water treatment plant resulting in savings to date of around $25,000.

The destratification project is just one of a number of recommendations from an ecological study that was commissioned by Council. Known as the Gamtron report, the study also recommended better land management practices in the catchment area, creation of a wetlands at the inlet to the dam and removing sediments and sludge from the bottom of the dam. Council is investigating the implementation of each of these recommendations.

While the installation of the mixer appears to have been successful in the reducing the occurrence of BGA blooms there are still many questions to be answered. Council will be working with WEARS and Griffith University in monitoring water quality and the operation of mixer as season's change.

Coonabarabran Council's experience may be useful for other water authorities that are experiencing Blue Green Algae blooms. Further Council would be pleased to receive comment from members on the project and results obtained to date.

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