NICAboard

Aquaculture and Fisheries News => Aquaculture Tech => ข้อความที่เริ่มโดย: pramaiporn ที่ เมษายน 05, 2010, 09:50:33 AM



หัวข้อ: Performance of a closed recirculating system with foam separation, nitrification
เริ่มหัวข้อโดย: pramaiporn ที่ เมษายน 05, 2010, 09:50:33 AM
Performance of a closed recirculating system with foam separation, nitrification and denitrification units for intensive culture of eel: towards zero emission

Yoshihiro Suzukia, Toshiroh Maruyamaa, Hiroyuki Numataa, Hajime Satoa and Makio Asakawab

a Department of Civil and Environmental Engineering, Faculty of Engineering, Miyazaki University, Miyazaki 889-2192, Japan
b Laboratory of Food Science, Faculty of Education, Kumamoto University, Kumamoto 860-8555, Japan
Received 23 September 2002;  accepted 5 August 2003. ; Available online 20 October 2003.

Abstract
The development of a closed recirculating aquaculture system that does not discharge effluents would reduce a large amount of pollutant load on aquatic bodies. In this study, eel were reared in a closed recirculating system, which consisted of a rearing tank, a foam separation unit, a nitrification unit and a denitrification unit. The foam separation unit has an inhalation-type aerator and supplies air bubbles to the rearing water. The growth of eel, which were fed a commercial diet, was satisfactory, with gross weight increases of up three times in 3 months. The survival rate under the congested experimental conditions was 91%. The foam separation unit maintained oxygen saturation in the rearing water at about 80%. Furthermore, fine colloidal substances were absorbed on the stable foam formed from eel mucus and were removed from the rearing water by foam separation. Ammonia oxidation and the removal of suspended solids were accomplished rapidly and simultaneously in the nitrification unit. The ammonia concentration and turbidity were kept at less than 1.2 mg of N per litre and 2.5 units, respectively. When the denitrification process was operated, nitrate that accumulated in the rearing water (151 mg of N per litre) was reduced to 40 mg of N per litre. The sludge was easily recovered from the nitrification and denitrification tanks, and the components were found suitable as compost. Based on these results, the intensive aquaculture of freshwater fish such as eel can be achieved using a closed recirculating system without emission.

Author Keywords: Aquaculture system; Recirculating; Eel; Foam separation; Zero emission

Aquacultural Engineering
Volume 29, Issues 3-4, December 2003, Pages 165-182