| 摘要 |
PROBLEM TO BE SOLVED: To provide a device for treating water, capable of largely reducing periodic water exchange operations carried out for decreasing the concentration of nitrate-based nitrogen in a fish fry-producing field, an aquarium, etc., enabling the reutilization of culture water, not necessitating a work for inversely washing a filtration device, capable of reducing the amount of used raw water, and capable of improving the quality of the water. SOLUTION: A contact type trickling filter 12 and a hypochlorite-injecting device 16 are disposed in a route for purifying water circulated in plural water tanks 10. The water is used for producing or breeding fish fries. The water used for producing or breeding the fish fries is circulated in the trickling filter 12 to contact-treat contaminants, and then treated with chlorine in the hypochlorite-injecting device 16. Nitrate-based nitrogen is reduced into nitrogen gas by the oxidation power of the hypochlorite, and the concentration of the nitrate-based nitrogen is maintained at a low level near to that of fresh sea water.
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