一體化養殖循環水處理系統之研發

Abstract

循環水養殖系統為現行養殖漁業極為重要之一項技術，極具發展潛力。然因其所屬元件眾多、管路複雜及營運成本高昂，應用上有諸多限制。粒子式過濾器為一合併機械過濾及生物過濾兩種過濾功能之循環水過濾裝置，其在高餵食量負擔下，會因生物過濾旺盛而使粒子間因生物膜密集生長及機械過濾攔截之懸浮物過多而結塊，必須透過定期清洗以維持其正常運作，但清洗機制同時又會降低生物過濾效果。本研究即以現行之粒子式過濾器為基礎，並改良外觀、管路結構及內部清洗機制，以分批置換粒子之模式取代整體攪拌，延長粒子層內生物膜有效進行硝化反應之時間，並可利用底部雙層套管之外層於過濾器運作中排除沉澱之髒汙。此新式粒子式過濾器採取LDPE粒為填充濾材，研究透過20 ppm、40 ppm、60 ppm及80 ppm等不同餵食濃度測試系統生物過濾效果及相關操作條件，並分別以24小時及48小時兩種不同粒子全置換周期觀察過濾器運作，後者將使過濾器粒子層在一段運作時間後結塊。該過濾器在26~30℃、pH 7.2~8.5、HRT等於15分鐘、養殖槽內水體溶氧6 ppm以上、粒子全置換周期為24小時之條件下，過濾器在餵食濃度80 ppm時單日可移除最多之TAN量(55.72 g)；以養殖槽內水體TAN、NO2-N殘留濃度為指標則以每日60 ppm之餵食濃度為最佳，可穩定維持TAN、NO2-N濃度停留在0.39 ppm、0.04 ppm，TAN單位面積日去除效率617.92 mg/m^2。如更換PE空壓管粒作為過濾器填充材料，在相同操作條件、餵食濃度40 ppm操作下可獲得較同樣餵食濃度且填充LDPE粒更理想之循環水過濾效果，TAN濃度維持在0.32 ppm、NO2-N濃度維持在0.02 ppm，TAN單位面積日去除效率343.00 mg/m^2。

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.