The Closed Recycling System for Combined Aquatic Animal and Plant Production. Water Management for Aquatic Animal and Nutrient Characteristics of the Waste Water.:Water Management for Aquatic Animal and Nutrient Characteristics of the Waste Water

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Combined Aquatic Animal and vegetable production system is developed and investigated. It is anticipated that the waste water from fish culture could be put into better use through recycling system to save water and nutrient. Basic data required to develop a combined fish and plant production system were determined from an experimental system consisting of a fish tank, hydroponic bed and water management section (nitrification) in a greenhouse. Fish tank and biofilter water temperatures could be maintained at a suitable range within the whole year, but the air temperature in the vegetable section at times was more than 35°C and necessary control was required. Nitrification (the oxidation of NH4+ to NO2- and NO3-) is required for fish and it took 45 days to breed microorganism which facilitates this process. After this period, the recycle was confirmed to be working satisfactorily since only NO3- could be detected. Hence, for the water management, linear regression equations could be given in terms of the elements in water and the number of days. Using the equations, the expected nutrient characteristics of waste water after 85 days were determined and it was found that the resulting nutrient balance was almost the same as that in hydroponic solution when KOH was added to maintain pH level, however the resulting concentration of nutrient was quite low for plant production.
農業施設学会の論文