Farming sustainably can often be expensive, but Queensland researchers have found a way for aquaculture to profit from being eco-friendly, by growing worms in waste water.

Marine biologists at the Bribie Island Aquaculture Research Centre, north of Brisbane, have developed a system that recycles aquaculture waste water through sand filtration.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Listen Duration: 4 minutes 14 seconds 4 m 14 s Marty McCarthy reports on an innovative aquaculture research program underway at Queensland's Bribie Island Research Centre ( Marty McCarthy ) Download 1.9 MB

The dirty waste water is pumped into large sand pits. The sand then filters the water, and the algae left behind is fed on by the marine worms ( Marty McCarthy )

In the treatment process the water is also used to grow marine worms, which until now have been difficult to grow on a commercial scale. Farmers can then feed the worms to their prawns or sell them for a high price.

Research centre senior biologist Paul Palmer said the project had been running for seven years and the findings were a "world first".

"The significant achievement we've made in this project is we've been able to recycle the water through the sand worm beds, and re-use that on the prawn farm," Dr Palmer said.

"We eliminated the need for regular contact with the waters [in oceans and rivers] adjacent to the farms."

The discovery means prawn and fish farms who implement the system won't need to draw as much water from the natural environment to fill their ponds, and won't need to release treated water either.

The second aspect of the innovation is called bio-remediation, which involves using animals, in this case worms, to assist in the water purification process.

"Marine prawns need a very balanced range of essential fatty omega 3 and 6 acids. Because the worms are growing up on algae produced in the water they hold a very good group of fatty acids," Dr Palmer said.

"We're compacting that into the worms, and then the worms are fed to the prawn brood stock.

"Most prawn hatcheries around the world need a certain percentage of the diet they feed to brood stock to be marine worms, because the worms hold the essential vitamins that make them reproduce successfully.

"What it means is prawn farmers can produce food on their own farms to supply to their own hatcheries and have control over the quality."

Findings used around the world and could develop new industry

There are only about 30 prawn farms in Australia, but Dr Palmer said the waste water recycling findings would have global significance.

"This has world-wide application... overseas there's lots of diseases affecting prawn farming so they will be interested in this because they can protect themselves from disease out there," Dr Palmer said.

"From an Australian point-of-view, we're very interested in keeping the nutrients that come from these systems under control, because if you're not releasing water from the system you're not losing any nutrients."

In addition to the recycling innovation, Dr Palmer said the ability to grow marine worms in the treatment process was also significant, as until now researchers have struggled to produce them in captivity on a large scale.

"This potentially could create large volumes of marine worms which could be used in a whole range of ways. Worm farming is taking off around the world and several countries are investigating it," he said.

"The worms are worth quite a lot on a per kilogram basis. Marine worms in Australia at the moment are very expensive, as fishermen will attest to.

"If this project leads to industrialisation it may make the marine worm industry even more valuable by making them more available.

"I do think it's an industry in its own right and it's very interesting that it can fit so nicely into prawn farming."

Dr Palmer said in some Asian nations the worms are eaten as a delicacy and used to flavour soups, while in some Pacific Island nations they're "used as a special treat for the higher dignitaries in their societies".