接種量及進料pH對固定化微生物燃料電池效能之影響

Abstract

本研究係利用固定化菌種顆粒填充於空氣陰極式的微生物燃料電池，以探討菌種接種量與進流液酸鹼值對微生物燃料電池效能的影響。該燃料電池利用碳布做為陽極，白金鈦網做為陰極，養豬厭氧底泥經熱前處理當做菌種；而固定菌種的材料則是醋酸纖維，固定成片狀後切割為1 cm × 1 cm大小的顆粒，選取170個固定化顆粒均勻放置於陽極槽內，並利用人工廢水當做基質，實驗設計為兩種菌種接種量：10 g、20 g與30 g，五種進流液酸鹼值：pH 4, 5, 6, 7, 9。 實驗結果顯示，操作於中性環境(pH 7)時，接種量20 g有最大的開路電壓1.04 V，而接種量10 g與30 g的開路電壓皆為0.76 V 。在pH 4時，接種量30 g的最大功率密度與最大庫倫效率都較其他兩種接種量來的大，分別為6.33% 與14.97 mW/m2。而在pH 5時，菌種接種量20 g的最大功率密度與最大庫倫效率都較菌種接種量30 g與10 g來的大，分別為：14.19 mW/m2與4.15%。然而，在pH 6、7時，接種量20 g的系統卻比接種量30 g與10 g來的小，在進流液pH 9時，菌種接種量30 g的功率密度與庫倫效率分別為1.13 mW/m2 與0.23 %，其庫倫效率明顯小於接種量20 g (1.53%)與10 g (1.99%)，這樣的結果說明菌種非常容易受到進流液酸鹼值的影響。 此外，本研究尚針對菌種前處理進行探討，在相同的操作程序與接種量(30 g)下分別製造兩批不同菌種來源的固定化顆粒，一為有經過100 oC連續沸騰15分鐘的熱前處理，另一則無。經試驗發現，菌種前處理並沒有明顯效果，前處理後的菌種與未處理的菌種相比，最大功率密度分別為3.17 mW/m2與2.43 mW/m2，平均的COD去除率分別為43.43±14.788%及34.81±3.947%。此結果說明本實驗所使用的前處理方式或是菌種來源並不適合製造出胞外產電菌，建議使用別種前處理方式以降低處理成本。

In this study, the performance of microbial fuel cells (MFCs) was investigated by applying immobilized cells entrapped treated anaerobic sludge with cellulose acetate at three different inoculum sizes (10 g, 20 g and 30 g) and five feeding pHs (4, 5, 6, 7, 9) , respectively. A mediatorless single air-cathode MFC was constructed where Carbon paper was used as anode electrode, Pt-Ti net as cathode and synthetic wastewater was the substrate. When the feeding was pH 4, the optimum performance of power output and coulombic efficiency (CE) at inoculum sizes of 30 g were the highest at 14.97 mW/m2 and 6.33 %. But in the feeding of pH 5, they were 14.19 mW/m2 and 4.15 % when inoculum sizes was 20 g. In pH 6, there were no apparently differences between these three systems. However in feeding pH 7, the highest power output was observed in inoculum sizes of 10 g at 8.18 mW/m2. The power output and CE in inoculum sizes 30 g were the lowest in pH 9, they were 1.13 mW/m2 and 0.23 %, respectively. These results showed the performance of MFCs would be strongly affected by the feeding pH. Besides, this study focused on the investigation of the pre-treatment of sludge. Two groups of immobilized cells with different sludge supplier but the same inoculum sizes of 30 g were made. One was produced by heat pre-treatment which means the sludge was boiled at 100oC for 15 min, and the other was no heat pre-treatment. The results showed the maximum power output in pre-treatment and un-treatment system were 3.17 mW/m2 and 2.43 mW/m2. The average COD removal efficiencies were 43.43±14.788 % and 34.81±3.947 %. According to these observations, we found heating pre-treatment was no apparently effects on the performance of MFCs. It is better to use another pre-treatment method or select different kinds of sludge to decrease the cost of MFC in real application.