Comparing fixed-biofilm and suspended microbial fuel cells’ performances - electricity generation, growth rate of microalgae and COD removal efficiency

• Main Authors: Yan-chen Lin, 林彥臣
• Other Authors: Chun-sheng Wu
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/66438251444809926406

碩士 === 康寧大學 === 休閒資源暨綠色產業研究所 === 99 === Four kinds of microbial fuel cell (MFC) systems, fixed-film MFC (FMFC), suspended-growth MFC (SMFC), photosynthetic fixed-film MFC (PFMFC), and photosynthetic suspended-growth MFC (PSMFC) were conducted in this study. In the FMFC and SMFC, the buffer solution was added in cathode chambers. In the PFMFC and PSMFC system, two different growth stages of Nannochloropsis oculata was added in the cathode chambers: (1) from the lag phase to the stationary phase. (2) from the lag phase to the death phase. The MFC performance parameters , including power density, coulombic efficiency, COD (chemical oxygen demand) removal efficiency, and concentration of metabolic intermediates VFAs (volatile fatty acids), and also the growth rate of Nannochloropsis oculata population, were measured. Glucose was used as the feeding substrate. The results showed that: (1) The maximum power density (PDmax) 42.7 mW/m2 of the FMFC system was similar to that 49.2 mW/m2 of the SMFC system. The coulombic efficiency (CE) of two systems were also similar (0.59% and 0.72%).(2) When the growth phase of Nannochloropsis oculata was the stationary phase in cathode chamber, the maximum power density (PDmax) 159.7 mW/m2 of the PFMFC system was higher than that 66 mW/m2 of the PSMFC system. The coulombic efficiency (CE) of the former system was about two times of the latter system (2.35% and 1.13%). (3) When the growth phase of Nannochloropsis oculata was the death phase in cathode chamber, The average PDmax 91.2 ± 61.7 mW/m2 of the PFMFC system was also higher than that 27.1 ± 16.7 mW/m2 of the PSMFC system. The average CE value of the former system (1.14 ± 0.62 %) was also higher than the latter system (0.35 ± 1.10 %). The COD removal efficiency of the MFC system in this study has all reached more than 95%, but the VFAs concentrations of the FMFC system and the SMFC system (acetic acid: 6-7 mg/L, propionic acid: 4-5 mg/L) were lower than the PFMFC system and the PSMFC system (acetic acid: more than 15 mg/L, propionic acid: more than 8 mg/L), this results showed that maybe the metabolism of bacteria in the anode chamber of the MFC system have changed when add the microalgae in the cathode chamber of the MFC system. The growth rate of Nannochloropsis oculata groth in the PFMFC system and the PSMFC system ( 0.0413 hr-1 and 0.0539 hr-1 ) were both higher than Nannochloropsis oculata groth in the photobioreactor system. We speculate that the MFC system perform some kind of functions to increase the growth rate of the microalgae.