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Bubbling On: De-gas Project Boosts Land-based Potential

Technology & equipment

Land based aquaculture using water recirculation within fish tanks will become increasingly important. However, maintaining water quality and hence fish performance, can be difficult. TheFishSite talks to Sheila Kvindesland, International Projects Developer at the National Institute of Technology, Stavanger, Norway, who is part of a collaborative venture developing a degassing system that improves water quality and benefits productivity.

Land based aquaculture is of increasing interest, yet the supply of fresh, unpolluted water is becoming scarce in many areas of the world, due to human usage and climate change. This will put increasing pressure on aquaculture businesses to develop recirculation systems.

The degasser unit in a land-based recirculation fish farm.

In addition to culturing local species, land-based fish production also makes it possible to bring non-local or more exotic aquaculture species closer to the market, thus providing fresher products and more variety.

"Providing high quality water supplies in land-based farms is of paramount importance for both optimal growth and welfare. The fish in the tanks consume oxygen, so reducing quality, while food in the water and fish waste, such as faecal deposits, create other gases and pollutants. If these contaminants are not managed optimally, then growth, performance and fish survival rate will be significantly compromised," explains Ms Kvindesland.

There are many devices for supplying and monitoring oxygen within fish tanks, but few devices exist that can 'de-gas' fish tanks and improve the tank environment.

The AquaDeGas project, currently underway at Norway's Stavanger University, is aiming to develop a cost effective, reliable, robust and efficient method for degassing land-based aquaculture systems.

The system, say its developers, must meet the needs of aquaculture production yet be practical and economically viable. The system will remove over saturated harmful gases, such as carbon dioxide, nitrogen and argon, that accumulate in the water. The method under development uses an ejector and nozzle technique to form micro-bubbles. These tiny bubbles promote effective gas exchange in water and when integrated with sensor and control technology, can prove effective at 'degassing' water tanks.

The degasser unit consisting of ejectors and reaction chambers.
The two-year project began in January 2007, and initial results are very promising. Further reports on the development of the system, trial results and commercial experience will be available throughout this year and will be reported on TheFishSite.

Development Phase

A number of key parameters must be evaluated. These include the water quality requirements for different species of fish, the gas exchange rate/potential in fresh and salt water and the production and maintenance of the micro-bubbles in water.

A degasser unit is under development. The prototype uses two potential ejectors and a reaction chamber. These elements will be integrated into a prototype and tested at AqWa facilities at the University of Swansea. The sensor and control technology will be developed next and finally the whole system will be integrated together and tested industrially at a Villa Salmon fish farm.

The commercial partners involved the project comprise a number of leading the technology companies:

  • Norwegian Artec Aqua AS - supplies products and services for water control quality and management in land based fish farming

  • Danish OxyMat AS - supplies oxygenation and sensors to the aquaculture and fishing industry

  • British Transvac Ltd - designs and manufactures Venturi and fluid jet equipment

  • Estonian Aswega Ltd - manufactures hydrometers and water flow monitoring equipment.

The research and technological development work is being provided by the National Institute of Technology in Norway, PERA in United Kingdom and by Aquaculture Wales (AqWa) based at the University of Swansea.

Water quality data and the final testing facilities for the developed degasser will take place at BFF, a turbot farming enterprise using advanced recirculation tanks; Selonda Aquaculture, a leading producer of warm water species and at Villa Salmon one of Norway's leading salmon producers.

For details on this project go to www.aquadegas

January 2007