Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/4931
標題: 紫色不含硫光合作用細菌於連續流產氫之研究
Continuous photobiohydrogen production by purple nonsulfur bacterium
作者: 林瑤玓
Ti, Lin Yao
關鍵字: purple nonsulfur bacterium;紫色不含硫光合作用菌;CSTR reactor with recycle;CSTR reactor without recycle;hydrogen production rate;連續流迴流試程;連續流無迴流試程;產氫率
出版社: 環境工程學系
摘要: 
本研究的目的為利用不同之連續流操作條件以試驗出厭氧之光合作用細菌於連續流產氫之最佳操作條件。以前三年研究所篩選之菌株編號為WP3-5,具產氫能力之紫色不含硫光合作用細菌,植種於連續流之光合反應槽中,添加麩胺酸作為氮源,並以厭氧產氫程序放流水中主要之有機物成份作為模擬進流基質,分別進行無迴流式及迴流式之連續流光合產氫的試驗,最後並測試以實際經鹼篩處理之厭氧產氫程序放流水作為光合產氫可行性的研究。
開始連續流試程之前,先利用批次的方法分別研究以麩胺酸或氨氮為氮源時、光合菌所需之最佳產氫之基質條件,並針對乙醇及磷酸鹽等影響光合菌產氫之因子來進行測試。利用批次所得之最佳產氫之基質條件來進入連續流的試驗。
由批次研究的結果顯示,以麩胺酸為氮源時,由單一基質丁酸之產氫測試中獲得最佳產氫之碳氮比為6.7,而最佳產氫之丁酸濃在3000 mg/L。而於混合酸之測試結果為,複合基質條件於乙酸280mg/L,丙酸99 mg/L及丁酸1200 mg/L添加麩胺酸500 mg/L 時,其產氫效果最佳,培養60小時後約有75.6 mmole/L之產氫量。
在以氨氮為氮源配製合成廢水之批次研究中,額外添加麩胺酸及乙醇對產氫的影響均為負面。雖大部份的紫色不含硫光合細菌能夠利用乙醇作為碳源及電子供給者,但即使於最低乙醇濃度178 mg/L之條件下仍有抑制產氫的情形。於實驗中並發現,在有機酸濃度控制較低的條件下,乙酸140 mg/L,丙酸45 mg/L,及丁酸120 mg/L,氯化銨添加100 mg/L時,70小時後之氨氮剩餘濃度為20mg-NH4+/L,細胞濃度約在0.58 g/L,其氨氮利用速率較高產氫量也較大。
於連續流之無迴流試程中有三個試程,分別是水力停留時間15,20,及56.8小時。水力停留時間控制於15小時無法使反應槽中光合菌的細胞濃度維持衡定,而在水力停留間20小時的進流條件下有最佳的產氫量,平衡時有0.504 mmole/hr 的產氫率,主要是利用丙酸來產氫。
在水力停留時間控制為56.8小時,其產氫率為0.345 mmole/hr,MLSS為1.3 g/L,雖系統所能維持的MLSS雖較高,但由於光能利用率降低,以及所累積的氨氮濃度較高而使得產氫量沒有提升。而將試程之進流基質濃度降為原來的50 % 後,系統平衡時的產氫率為0.28 mmole/hr,細胞濃度約在0.6 g/L,並沒有較高的產氫率。此外,若系統中的氨氮濃度累積至25 mg-NH4+/L,氫氣濃度會降低至8 % 以下,且由有機酸的監測結果可知,光合菌能同時利用乙酸丙酸及丁酸作為電子供給者。
由迴流式連續流試程的測試結果顯示,迴流試程中所控制之細胞停留時間較無迴流試程要高,因此系統之產氫率均較無迴流試程要高。於水力停留時間30小時迴流比50 %的進流條件下,原來以丙酸、丁酸產氫時,其產氫率為0.710 mmole/hr,而在80小時後系統明顯改以乙酸產氫,其平衡時的產氫率即降為0.648 mmole/hr,其MLSS為0.96 g/L,SRT為2.25天。
而改變進流條件為40小時,100 %的迴流比時,系統產氫率提高為0.967 mmole/hr,MLSS控制在0.94 g/L,平均污泥停留時間有7.5天。於此操作條件下,因有較高的細胞停留時間,且MLSS控制較低,其光能利用率較高,加以系統中平均氨氮濃度較低,因此連續的氫氣生成量最佳。另外,於此試程的後續研究中,藉由提高系統控制之麩胺酸濃度250 mg/L,以改變系統操作之碳氮比,約50小時後再降回原系統所控制之碳氮比後,系統轉而只大量地利用丁酸為其電子供給者,由此可知,不同碳氮比的控制能轉換細胞能量代謝的途徑。
在實際以鹼篩處理之厭氧產氫程序放流水作為光合產氫基質之測試中,由於氨氮濃度太高,因此只能以間歇進流的方式獲得少量氫氣,系統操作中並沒有偵測到甲烷氣。
由本研究的試驗結果,光合菌能同時利用乙酸丙酸及丁酸作為電子供給者,將進流條件控制為40小時迴流比100 %的條件下有最佳的產氫率,為0.967 mmole/hr。在反應槽的控制方面,藉由改善污泥迴流效率以及適度增加迴流比以控制反應槽中的MLSS能得到更好的產氫結果。

Abstract
For the study of continuous flow hydrogen photobioproduction, CSTR reactors w/o recycle were operated with seeded purple nonsulfur bacterium. Artificial substrate with glutamate as the nitrogen source was prepared to simulate the main organic composition in the effluent of anaerobic hydrogen production process.
Before the experiment of continuous flow, batch tests was performed for finding the optimum substrate concentrations for hydrogen production. Factors concerning hydrogen photobioproduction, such as alcohol and phosphate, was included in the batch tests. Optimum conditions obtained from batch study was then put in use for the continuous flow study.
The results from single substrate of batch tests indicated that the best C/N ratio was around 6.7 while butyrate was used as the only electron donor, glutamate as the nitrogen source. Highest hydrogen production was obtained when butyrate concentration was around 3000 mg/L. When applying complex substrate, acetate 280 mg/L, propionate 99 mg/L, butyrate 1200 mg/L and glutamate 500mg/L were resulted highest hydrogen production. The hydrogen production achieved 75.6 mmole/L after 60 hours cultivation under these conditions.
When ammonia was used as the nitrogen source, hydrogen productions were limited regardless the additions of glutamate or alcohol.
Under continuous flow experimentation, the results showed that CSTR reactor without recycle had a maximum hydrogen production rate of 0.504 mmole/hr when operated with a 20 hours hydraulic retention time (HRT). Propionate was identified to be the major electron donor. While operated under a 56.8 hours hydraulic retention time, acetate, propionate, and butyrate were found to serve as electron donor at the same time and the hydrogen production rate was around 0.35 mmole/hr.
The highest hydrogen production rate for operating under CSTR with recycle (HRT = 40hr, 100% recycle, MLSS=0.94 g/L and SRT = 7.5 days) was 0.967 mmole/hr. Hydrogen production rate went down to 0.648 mmole/hr when operated under HRT=30 hr, 50% recycle, MLSS 0.96 g/L and SRT=2.25 days. In the later condition, the system turned into using acetate as electron donor and the hydrogen concentration in the collected gas was down from 50% to 28%.
Sludge recycle improved hydrogen production in the continuos flow experiment.When feeding real effluent solution from anaerobic hydrogen production process as the influent for the same CSTR reactor used in this study, the resulted hydrogen production was unsatisfied. Methane gas was not detected in the collected gas. It was concluded that this hydrogen production was inhibited by the high ammonia concentration.
Maximum hydrogen production rate was 0.967 mmole/hr(HRT=40 hr, 100% recycle, MLSS=0.94 g/L, and SRT=7.5 days). In the biohydrogen production of applying real wastewaters, the manipulation of ammonia concentration could still be the limitation.
URI: http://hdl.handle.net/11455/4931
Appears in Collections:環境工程學系所

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