Development of an Integrated Recirculation System for Aquaculture
Date Issued
2012
Date
2012
Author(s)
Yu, Zih-Huei
Abstract
Recirculation system is one of the most important technologies for aquaculture nowadays. However, due to the multiple internal parts, complex pipelines, and expensive operation costs, it has many restrictions on practical application. The bead filter, a filter used in recirculation system that can do both mechanical and biological filtration, which function would decrease by intensively growing biofilm and those suspended solid captured between beads when the feeding rate is high, needs backwash regularly in order to maintain its function, but, by doing this, the bead filter would lose some biological filtration effect.
This research devised a new bead filter by reforming the structure, piping system and backwashing function based on the present bead filter. This new bead filter, which changes those beads from top to bottom by turns, extents the time for the biofilm to do nitrification and removes solid with the two-layer pipe set at the bottom. It uses LDPE as filtration material, and this research explored its biological filtration function and the method of operation by giving different feeding rates such as 20 ppm, 40 ppm and 80 ppm daily. This research also tried different total-changed time of beads for both 24-hours and 48-hours. The result showed that in the condition of 48-hours total-changed time, beads would be caked after a period of time. The new bead filter was operating in following conditions : water temperature about 26~30℃, pH 7.2~8.5, HRT about 15 minutes, dissolved oxygen in the calture tank not less than 6 ppm and the total-changed time is 24 hours. This bead filter has the best ability of daily TAN removing (55.72 g) under the feeding rate of 80 ppm. Focus on TAN and NO2-N concentration in culture tank, daily feeding rate of 60 ppm showed the lowest value ( TAN = 0.39 ppm, NO2-N = 0.04 ppm ). In this case, the areal conversion rate of TAN is 617.92 mg m-2 day-1.
This new bead filter can also use small pieces of PE tube as filtering material. In the same conditions as before words, using PE tube can bring better culture tank environment ( TAN=0.32 ppm, NO2-N = 0.02 ppm ) compared with using LDPE under 40 ppm daily feeding rate, and the areal conversion rate of TAN in this case is 343.00 mg m-2 day-1.
Subjects
recirculation system
bead filter
nitrification
biological filtration
Type
thesis
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