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Nanobubble Oxygenation of Recirculating Aquaculture Systems to Increase Fish Production

 


Funded by: 2019 NOAA Sea Grant National Aquaculture Initiative 

BACKGROUND:

Dissolved oxygen (DO) is the most critical factor in determining the stocking density and production yield in Recirculating Aquaculture Systems (RAS). Poor DO levels can exert negative influences on feeding, feed conversion, growth and fish health. Traditional aeration (diffused) is limited by temperature, salinity, and altitude on oxygen solubility and can support about 40 kg/m3 (0.3 lbs/gal) of fish. Various devices have been employed to raise DO further such as U-tubes, packed columns, low-head oxygenators, and speece cones to name a few. By using pure oxygen and gas transfer devices, stocking densities can be greatly increased. While these methods have increased production levels, they still have a limit to how high they can go. 

Oxygen stone in salmon tank.jpg

NANOBUBBLE TECHNOLOGY:

Nanobubbles are miniature gas bubbles with <200 nm in diameter that have been shown to have unique physiological benefits for fish. Nanobubbles can also more efficiently catalyze reactions of chemicals, thereby improving the efficiency of recirculating water treatment. Nanobubbles may also enhance activities of microbes and improve biofiltration in RAS. They are an environmentally friendly technique that could possibly reduce the size of the filtration systems resulting in significant potential for design and operational cost reduction.

The presence of stable nanobubbles in water has been experimentally confirmed yet little applied research on the mechanisms of physical and biological effects of nanobubbles has been completed. Additionally, even with a limited amount of work that has focused on the effect of nanobubbles on fish growth rate and health, the role of increased DO due to the use of nanobubbles has not been separated from the physiological effect of the nanobubble itself.

PROJECT:

This project will seek to study the revolutionary potential of nanobubbles in RAS by:

1. Comparing three types of oxygen delivery systems supplying pure oxygen in RAS.

2. Determining a cost-benefit analysis model for the use of nanobubbles in RAS.

3. Documenting the differences in amounts of oxygen required and the overall power required for maintaining the same DO levels in the tanks using the identified delivery systems.

4. Documenting and characterizing nanobubbles to better understand their chemistry in an RAS and their effects on the growth of fish, fish health, and water quality in cold and warm-water RAS.

5. Through a well-established aquaculture outreach program share results (deliverables) with stakeholders interested in applying this innovative technology.


PARTNERS:

University of Wisconsin-Sea Grant Institute

UW-Stevens Point Northern Aquaculture Demonstration Facility

UW-Extension

Wisconsin Aquaculture Association 

Praxair, Inc.

Gaia Water, Inc.



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