豬場廢水厭氧消化與沼氣生成之研究

Abstract

本研究目的為建立豬場廢水厭氧消化產沼氣的最佳化模式，因此使用批次式搖瓶試驗進行初步測試，並使用體積20公升 (實場 100,000 倍縮小)之柱流式厭氧消化反應器，進行為期30天之連續流厭氧消化試程。 批次搖瓶實驗測試不同pH值 6、7、8與7.3 (original)，以及不同溫度25、30、35與40 ℃之影響，以工作體積400 毫升，固定負荷20 gCODl-1d-1，為期5天的厭氧消化時間，監測了沼氣組成與水質變化，結果發現在pH 8、35℃為批次式厭氧搖瓶試驗的最佳產氣條件，累積甲烷氣產量為943.2毫升，TCOD去除率43%。實驗室連續流實驗則改變不同之水力停留時間、溫度與有機負荷量，同時監測甲烷、二氧化碳與有機酸等指標，發現當進流平均濃度為12,000 mgL-1，水力停留時間在8天的情況，甲烷氣體產量高出了其它水力停留時間28~38%，溫度的部份在28 ℃與35 ℃同甲烷氣產量為4.7與4.69 Ld-1，並無顯著差異，值得注意是55 ℃之總有機酸產量為28 ℃與35 ℃的9.3與6.5倍。有機負荷量不同也顯示出了產甲烷氣能力之差異，1.2、1.6與2.5 gCODl-1d-1的甲烷氣產量分別為3.9、4.7與5.3 Ld-1，代表厭氧反應器內有機物增加會增加產甲烷氣之效率。厭氧污泥之DGGE菌相分析結果顯示出條件變化會導致菌相改變，主要菌屬為Proteobacteria與 Firmicutes等所組成，其中以Clostridium sp.為主要菌屬，太古生物之主要菌屬為Methanothrix 與 Methanosphaerula等。本研究結果所得之最佳化操作參數，有助於實場規模反應器改善及應用，以提高整體厭氧消化效率並縮短污水處理時間，達到最有效的運作方式。

In this research, we aimed to establish an effective anaerobic digestion process condition which have ability to treat swine wastewater and produce renewable energy. Increases in methane (CH4) production were quantified when swine waste anaerobic digest with different condition. The anaerobic digestion experiments were conducted on flask (400 ml) in batch mode and lab-scale anaerobic digester (20 L) in continuous mode. In flask experiments was to treating swine waste under different pH adjustment and temperature by organic loading rate 20 gCODl-1d-1. The pH 8 and 35 ℃ showed the greatest methane production (186 mLd-1), a 58% increase from the control. In lab-scale anaerobic digester experiments, hydraulic retention times (HRT), temperatures and organic loading rates (OLR) were adjusted. Result showed that when inlet TCOD concentration about 12,000 mgl-1, it could methane production capacity achieved 4.6 Ld-1 (CH4 = 65.8%) at HRT 8 days. Temperatures and organic loading rates were also found feasible up to 36% of methane production. Polymerase chain reaction analysis of sludge in combination with denaturing gradient gel electrophoresis (DGGE) was used to determine changes in the composition of the bacterial and archaeal community during waste water treatment. Phylogenetic analysis showed that the sequences of DGGE were close to sequences of the Proteobacteria, Firmicutes, Methanothrix and Methanosphaerula. etc. The specific occurrence of these bacterial and archaeal species varied mainly with different condition. The investigation proved optimal operation parameters for anaerobic digestion, and it could application in full-scale reactors in agriculture field for clean energy.