気泡サイズの異なる泡沫分離装置を用いた閉鎖循環式ヒラメ飼育水の処理

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Effects of bubble size in foam fractionation on the removal of organic carbon, protein, and trace elements (Fe, Co, Cu, Zn, and Sr) from the closed recirculating culture of Japanese flounder were investigated. Twenty juvenile fish of 5 g body weight were stocked in a glass culture tank of 57 L water volume equipped with a submerged bio-filter, a foam fractionator, a blower and diffusers, and were fed commercial pellet diet twice daily 6 days a week for 116 days at 20°C. Two bubble sizes (0.55 mm in diameter, SB; 1.50 mm, LB) were prepared with different pore size of ceramic air stones as experimental groups in duplicates. Foam fractionator was not operated for the control group. Air was supplied to foam fractionator by 0.4 mL/min flow rate for 8 hours a day 5 days a week from the 79th day of the experiment. Total volume of foam condensate obtained during 79th to 116th day in SB group was 8.6±1.4 L, and was significantly higher than that in LB group of 1.0±0.3 L (P<0.05). Concentration of organic carbon and protein in the foam condensate were 1.4 to 9.1 times higher than those in the rearing water. Seventy % of total organic carbon and protein in the foam condensate were particulate form in SB group, while, dissolved form occupied 60% for LB group. Trace elements in the foam condensate were higher than those in the rearing water, and the concentration rates (foam/ rearing water) depended on the trace elements.