폐쇄식 양식 시스템 AIRRAS와 AIRBFT 간의 어류 사육 실험과 경제효율성 연구

Abstract

The system is specially designed for the function of the system by only air force, negating any use of water pumps. The primary function is supplying oxygen and expelling carbon dioxide, so-called by gas exchange. In addition, flowing of ample amount of water throughout the all parts of the system is realized using very low head water flowing mechanism specially designed for this system. Stripping of fine suspended solid matter and dissolved organic matter is very effectively realized as the primary function of this system. One special feature in this system is very low water lifting head, normally 30 mm between levels before and after the airlift chamber. To cope with this very low lift head high dimensional water channels are employed for the ample amount of water circulation. It may be called as river-flow system. Pipe plumbing is used only for air flow. This system is first developed for recirculating aquaculture systems (RAS) and the principles are also applied for biofloc technology (AIRBFT). Both systems are patented. The AIRRAS module consists of rearing tanks, solid settling tanks, biological filter tanks, airlift pumping section and water channels for the water to flow through all parts. The rearing tanks are octagonal that is square tanks with corners cut off. The diameter of the tanks used for this presentation was 6 m. The rearing tank is sloped down toward the center, depth being 1.0 m at the periphery and 1.2 m at the center, respectively. The circulating water in the tank collects waste solids at the center of the tank bottom, and the solids are drained to settling tanks through pipe plumbing installed under the bottom of the tank. Wastes are moved with very small amount of water to small settling tank where solids are settled down on the bottom of the tank. Supplementary air lift devices are installed in rearing tanks to further strengthen the gas exchange ability. Settling tanks: The size of the settling tank is about 1 m2 in diameter. Because the amount of water flowing through is very small, solids are effectively settled down on the bottom of the tank. Scanted clear water joins the main water flow. The air lift pumping section is equipped with a number of air lift pipes to allow a large capacity of water flowing. Biological filter section is divided into 9 tanks and each tank is 4 m × 3.3 m in size. It is designed for suspended solids to effectively settle on the surfaces of surfaces of fixed filter material, corrugated PVC sheets. The rearing results of tilapia weight gain in the AIRRAS was higher than that of the AIRBFT system by about 69 g(AIRRAS: 469 g, AIRBFT: 100 g). Feed conversion efficiency difference (FCR) between the AIRBFT and the AIRRAS systems was large. The AIRBFT system is more advantageous than the AIRRAS system in terms of feed efficiency. Tilapia survival rate was 100% both in AIRRAS and AIRBFT, the two eco-friendly aquaculture systems, AIRBFT system regulates ammonia nitrogen concentration faster than in AIRRAS. The pH remained in the range of 4.27 to 5.30 in both systems.

The results of the economic evaluation in AIRRAS and AIRBFT systems showed that although total investment cost of the AIRRAS system about 2.8 and 1.4 times higher than the AIRBFT system, the fish production is more than 79% higher than the AIRRAS system. The net profits were also high. In other words, the ROI that measures return on investment is 32.43% for AIRRAS system and 10.23% for AIRBFT system. The results of the economic evaluation between AIRRAS and AIRBFT system show that although the total cost of the AIRRAS system and the investment cost of the facility are about 2.8 and 1.4 times higher than the AIRBFT system, the fish production is more than 79% higher than the AIRRAS system. The net profits were also high. In other words, the ROI that measures return on investment is 32.43% for AIRRAS system and 10.23% for AIRBFT system. The AIRRAS system is about 3.2 times higher than AIRBFT system, so AIRRAS system for eco-friendly closed aquaculture system for improving fish productivity and economic efficiency. It has been evaluated to be more efficient than the AIRBFT system.