Monday, December 26, 2011

No. 392: A closed cycle system for low cost aquafarming (December 27, 2011)

A branch laboratory of Fisheries ResearchAgency developed a closed cycle system for low cost aquafarming. The system is complete with a biofiltration unit and a unit to remove impurities using bubbles. It can also be used as effluent treatment equipment because it provides such features as energy-saving and pest prevention. It consists of two devices of biofiltration and foam separation. The filtration device removes residual baits and fece and urine of fish using the principle of siphon, making the water level inside the lauter tub rises and falls automatically. The foam separation device creates microbubbles and makes them adsorb impurities in water to remove them. The water temperature hardly fluctuates because water is continuously circulated. Accordingly heating by a boiler to keep the water temperature stable is not necessary.  

Residual baits and fece and urine of fish produced in the ocean aquafarming accumulate on the seabed and invite fish disease and red tide. More than 50% of discharged organic substance is eluted as ammonia. Because ammonia is highly toxic, a mechanism to remove ammonia from the farming water is necessary for the aquafarming in a tank. The system with a 50-ton tank will be available for 2,000,000 yen. With this system, the cost to farm fries will be reduced from 12 yen to 7 yen a fry. The laboratory plans to commercialize it in collaboration with local companies as the next-generation aquafarming equipment.    

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