Please use this identifier to cite or link to this item:
Performances of anaerobic digestion system treating poultry mortalities
|關鍵字:||poultry mortalities;家禽死屍;anaerobic digestion;Leachbed;upflow anaerobic sludge blanket;厭氧醱酵;滲漏床;上流式厭氧污泥床||出版社:||農業機械工程學系||摘要:||
本研究的目的在探討以中溫 (35 ℃) 兩相循序批次厭氧醱酵的方式處理家禽死屍 (雞屍) 的操作特性。即探討甲烷化槽與水解/酸化槽間的容積比 (VR) 及甲烷化槽本身的高度/直徑比 (H/D) 對整體消化效率的影響。
臺灣地區畜產事業發達，雞隻年飼養頭數約 1 億 1054 萬隻（民國 85 年）。每年需處理的死雞達到 1105.4 萬隻，相當於每天產生雞屍 43.0 公噸。如果不妥善處理，對環境品質有相當大的影響。以厭氧醱酵的方式處理禽畜死屍，可改善傳統處理方式（如掩埋、焚燒、精鍊、餵飼魚類及製成堆肥等）之缺點，應是一值得深入研究的替代方案。
本研究採用滲漏床 (Leachbed) 與上流式厭氧污泥床 (UASB) 組合而成的系統，類似兩相厭氧醱酵系統 (Tow phase anaerobic digestion process)。死屍分解的水解液由蠕動泵打入 UASB 底端，經 UASB 處理過之出流液則溢流回滲漏床中，達到循環分解的功能。UASB 出流液體將菌種與酵素植種入滲漏床，待滲漏床的環境適宜甲烷化作用時，滲漏床即成為一個單相的反應槽。在此將這個系統稱為批次循序系統。
UASB 對於衝擊負荷與餵飼中斷有很好的恢復力，加上控制容易、穩定性佳，極適合處理原料來源不穩定的雞屍等廢棄物。在 35 ℃ 中溫環境下，UASB 厭氧污泥在處理本實驗的高濃度廢水時，最高可承受 5.5 g.COD/L/day 的負荷（loading rate）而仍可保持 80 % 以上的去除率。就雞屍而言，實驗前後重量減少百分比都在 82 % 以上，因此本實驗中厭氧菌的能力已充分發揮，可有效處理雞屍等生物固體廢棄物。
比較加水量對系統的影響，加入中等水量（10 L）的組別表現最佳，不論是甲烷化槽的 COD 分解能力或是水解/酸化槽進入單相厭氧化的時間快慢，都顯示如此結果。因此可判斷在水解/酸化槽中必然存在一最佳固體（雞屍）/液體（水）的比例，而非加水量越大者表現越好。在實驗中得到的較佳比例為固狀物 7.5 %。在實廠應用上，硬體的建設、維護成本與效能（包括處理時間與甲烷產率）之間必須找到最理想的設計。
在甲烷化槽的比較上，因為 H/D 比值大的反應槽有較高的污泥床厚度，也就是基質有接觸更多污泥的機會，液體與污泥顆粒間質傳作用更佳，UASB 的效率越高。尤其在處理含 LCFA 物質時，足夠的混合與接觸是絕對需要的。在本實驗結果探討中，也可以見到此一趨勢。
The main purpose of this research is aimed at exploring the operational characteristics, based on the method of two-phase anaerobic digestion process, in dealing with disposal of poultry mortalities(chicken corps) at 35 ℃(mesophilic). Namely, it is designated to probe the entire digestion efficiency influenced by the volume ratio(VR)between methanogenic reactor and hydrolysis/acidification reactor and efficiency influenced by methanogenic reactor's ratio of height against diameter(H/D).
Due to the rampant development of livestock industry in Taiwan, the total quantity of chickens amounted to 110.54 millions in the year of 1996. The total quantity of dead chickens handled came up with the figure of 11.054 millions, which is equivalent to 43 tons produced daily. If not properly dealing with, it will definitely lead to tremendous impact upon quality of environment. By means of anaerobic digestion process to deal with dead poultry, the drawback of traditional way of handling can be improved, such as burial, burning, refinery, feeding fish or making compost, etc. Indeed, it is a very feasible substitute deserving to be further explored.
This system consists of a leachbed(LB)and a upflow anaerobic sludge blanket(UASB), which is similar to two-phase anaerobic digestion process. The fermentation liquid was pumped into the bottom of UASB. The liquid tackled by UASB is to be flowing back to leachbed, achieving the result of circulated digestion. The liquid of UASB overflowed will inoculate the anaerobic bacteria and enzyme into the leachbed. As the environment of leachbed turns out to be ideal for methanogenesis, the leachbed has become a single methanogenic reactor. The system can be defined as batch subsequent system.
Since UASB can very well recovery ability when dealing with shock loading and stop of feeding, added with easy control and steadiness, it is very suited to handling those residuals of poultry mortalities which come unsteadily. In the mesophilic environment of 35℃, while dealing with the high COD concentration wastewater in this experiment, it can tolerate the loading rate up to the maximum of 5.5 g.COD/L/day and still the COD reduction rate can be kept at 80 %. As far as the poultry mortalities is concerned, the weight reduction ratio between prior to and after the experiment is always above at least 82 %. Hence, the ability of anaerobic bacteria has been fully achieved in this experiment, which can effectively tackled the disposal of poultry mortalities.
When comparing the influence upon the system caused by the water volume filled, the LB loaded with medium volume of water(10 L)can result in better performance. It has been shown that both the COD reduction rate of UASB and the time of the LB spent to be a single methanogenic reactor. We thus can come to the conclusion that there must be the best ratio of solid(poultry mortalities)/ liquid(water)existing inside LB - more water not necessarily mean better performance. In the experiment, 7.5 % of solid material can give rise to better result. As to the application to factory operation, the best design must be made considering construction of hardware, cost of maintenance and effectiveness, including the digestion time and methane production rate.
In comparing UASBs, the reactor with bigger ratio of H/D will possess thicker sludge bed, which means that substrates will have more access to sludge, transmission effect between liquid and granulated sludge is even better ; and the effectiveness of UASB is higher. In particular, while dealing with the material consisting of LCFA, sufficient mixture and approach are absolutely needed. We can see this trend in the experiment result.
|Appears in Collections:||生物產業機電工程學系|
Show full item record
TAIR Related Article
Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.