ELECTRICITY GENERATION CHARACTERISTICS OF AN ANAEROBIC FLUIDIZED BED MICROBIAL FUEL CELL

Anaerobic fluidized bed microbial fuel cell (AFBMFC) was developed to investigate the effect of fluidization behaviors on the electrogenesis capacity. Waste water and active carbon were used as liquid and solid phase, respectively. The fuel cell was started up successfully using anaerobic activated sludge as inoculums. The power density is increased with increasing circular liquid velocity up to 450 mW·m. High COD remove rate reached 93% after five days operation. Meanwhile, the effects of cathode area on the electrogenesis capacity of AFB MFC were also investigated. INTRODUCTION Microbial fuel cell (MFC) is a device that can convert chemical energy from organic matter to electricity (1, 2, 3). The MFC for wastewater treatment is characterized by clean, safe, quiet performance, low emissions, high efficiency, and direct electricity recovery. Accordingly, MFC have great potential as a wastewater treatment approach (3, 4). Extensive studies have demonstrated that electrode materials (5) solution chemistry (7), reactor configuration (1, 2, 3), and some other aspects influence MFC performance. Recently, several types of membrane-less air cathode MFCs have been developed to operate in either batch or continuous mode. You et al. (8) developed a graphite-granule anode, tubular air-cathode MFC (GTMFC) to increase the power generation. Hu (9) developed a baffle-chamber reactor to improve the CE. He et al (3) used upflow microbial fuel cell (UMFC) to treat artificial wastewater of high COD 1 Guo et al.: ELECTRICITY GENERATION CHARACTERISTICS OF AN ANAEROBIC FLUIDIZED Published by ECI Digital Archives, 2010 2 concentration by combining the advantage of the UASB system. The fluidized bed reactor technique has been applied in many fields of biotechnology, especially in the biological treatment of wastewaters, where particles with attached microbial growth are fluidized by an uprising flux of the liquid to be treated (10). Ken et al. (11) compared the fluidized bed with packed bed bioreactors to produce biohydrogen and bioethanol, indicating that hydrogen and ethanol production rate in fluidized bed reactors exceeded packed bed reactors. Wen et al. studied (12) the treatment effect of nitrate-nitrogen from wastewater in gas-liquid-solid three phase fluidized bed bioreactor and the average removal ratios of COD and NOx are higher than 92% and 96%. We have developed a continuously fed MFC configuration, the anaerobic fluidized bed, featured by combing the fluidized bed system with single-chamber air cathode MFC. In this reactor, the wastewater was pumped into the fluidized bed and active carbon particles were fluidized with high mass transfer being achieved. In addition, the anaerobic fluidized bed MFC was more convenient to scale up than other single chamber MFCs. The purpose of the present study was to investigate continuous power generation in the anaerobic fluidized bed. Furthermore, the influence of fluidization behavior, the position, and area of cathode position in fluidized bed on electricity generation were examined. EXPERIMENTAL Reactor description Schematic diagram of the membrane-less fluidized-bed microbial fuel cell (MLFMFC) used in this study is shown in figure1. The membrane-less fluidized-bed MFC was made by a 1L glass effective volume with a diameter of 40 mm and a height of 600 mm. The distributor was a porous glass plate with a thickness of 2 mm, a pore size of 2 mm, and a fractional perforated area of 20%. A graphite rod was placed as the anode. 100 g fresh active carbon particles with an average of 0.2-0.9 mm, bulk density 566 kg·m, true density of 1150 kg·m, porosity of 0.45 were fed in fluidized bed which were used as the carrier media for biofilm. To investigate effects of the cathode area and the cathode position on electricity generation of anaerobic fluidized bed MFC, two carbon cloth cathode (3.14 cm, 0.35 mg·cm Pt; 30%wet–proofing, E-TEK, USA) coated with four diffusion layers were fixed onto one side of the chamber wall (cathodes 1 and 2 are at 150 mm and 300 mm above the distributor). The mixture of 150 mL anaerobic sludge and particle of active carbon were mixed to feed into the reactor. Wastewater was used as the fluidization liquid supplied with a peristaltic pump. During the experiments, the electricity signal generated was recorded by the personal 2 The 13th International Conference on Fluidization New Paradigm in Fluidization Engineering, Art. 43 [2010] http://dc.engconfintl. org/fluidization_xiii/43