Construction And Electrogenic Characteristics Of A Baffled Tubular Air-Cathode Microbial Fuel Cell

Nowadays, the contradiction of supply over demand in energy has become very obvious. Sustainable development is seriously hampered by resources, energy and environment. The power supply structure should be optimized based on structural adjustment. Development of techniques of energy from wastewater has become the main direction of energy restructuring.Based on the techniques of anaerobic baffled reactor, a baffled tubular air-cathode MFC (BTAMFC) configuration was designed (200810063876.5 and PCT/CN2009/070168). It was indicated that configuration of BTAMFC reserved excellent efficiency of ABR process in wastewater treatment. Modified parts (the graphite plate used as the guide plate and plastic tubes inserted in the reactor) did not affect removal efficiency of wastewater.Single-compartment BTAMFC (SBTAMFC) was developed. In order to establish a rational system, the construction of anode was selected. A three dimensional anode made from graphite granules was beneficial to both in COD removal and electricity generation. The internal resistance of MFC was decreased from 19.8? to 12.1?; the maximum power density was increased to 582.4 mW/m2. The COD removal rate was from 47% up to 88%. The charge-transfer resistance and diffusion resistance of the cell was affected by operational mode. In fed-batch mode, the internal resistance was increased 7.4?. Compared with that under continuous mode, the maximum power density was reduced to 407.1mW/m2; however the COD removal rate was kept in the same lever. Consequently continuous mode was more suitable for single-compartment BTAMFC.Dual- compartment BTAMFC (DBTAMFC) was set-up under continuous flow. With 1g/L glucose fed as substrate, an average voltage of 652 mV was obtained under the external resistance of 1000 ? (30 oC). The maximum power density was 15.2 W/m~3 with the chemical oxygen demand (COD) removal rate of 88%. The overall resistance was 13.7 ? while ohmic internal resistance was 10.8 ?. Average COD removal rate was 70% to 88%, when COD loading varied from 4.11 kg COD/ (m~3 NAC·d) to 16.0 kg COD/ (m~3 NAC·d). The maximum power density was 20.8 W/m~3 at HRT 2.5 h and COD loading 9.60 kg COD/ (m~3 NAC·d). The maximum coulombic efficiency of 48% was obtained when HRT was controlled at 3.5 h. Therefore, in DBTAMFC system, the optimized HRT could be regarded as 2.5 h to 3.5 h. DBTAMFC was operated for at least ten months. During this period, the HRT faceters were determined and a high volumetric loading was used in this system. And DBTAMFC was then running at the same condition as set-up. It was indicated that the cell was run well and kept a stable voltage and COD removal rate. The voltage output was decreased slightly, only 6%. Although decreased 48.4%, the maximum power density was still kept 7.9 W/m3. The COD removal rate was increased from 88% to 90%. It was documented that the DBTAMFC was stable and suitable for a long-term operation, and the life of the cell was at least ten months.The volume of BTAMFC was increased 4.5 times from two compartments to five compartments. During this process, the electrogenic performance of BTAMFC was enhanced. The voltage out-put was kept stably, and maximum power density was up to 54.7 W/m3. As a result, the COD removal rate was increased obviously. 5g/L glucose was used as the substrate, and the COD removal rate was kept higher than 85%. The internal resistance was stable between 12? and13?, indicating the internal resistance was not changed by the adding of BTAMFC conmpartments. It was afford to further increasing of compartments. The effluent of each compartment was 67%, 25%, 32%, 3.5% and 11% in sequence, which indicated that more than half of influent COD was removed in compartment 1. Without the reflux in five-compartment BTAMFC, the maximum power density in each compartment was reduced, leading to the total maximum power density was decreased 13.6 W/m3. However, the COD removal rate was increased from 86% to 94%. Although the power density was reduced 24.9%, the COD removal was enhanced, and economic effectiveness was recovered. BTAMFC was affected by the concentration of influent. The performance of power production in compartment 1 and 3 was declined following the increasing of glucose concentration. When FBTAMFC was fed with 10 g/L glucose, the maximum power density was decreased 33.9W/m3. Nevertheless the COD removal rate was kept at 94%, when the influent COD was up to 10600mg/L. It was apparently shown that BTAMFC had good capacity of resisting the shock loads. The wastewater from COFCO's corn stover cellulosic ethanol plant was directly treated by BTAMFC for the first time. The liquid from corn stover steam explosion process (COD=7160±50 mg/L) was treated by DBTAMFC, and the maximum power density was 10.7 W/m~3 with the average COD removal rate was 89.1%. The maximum power density was 10.7 W/m3, while the volumetric loading rate was as high as 29.5 kg COD/ (m~3 NAC·d). When FBTAMFC was used distillate wastewater as the substrate, the total maximum power density of 20.8 W/m~3 was obtained with the COD removal rate of 95%. Wastewater treatment process was designed and including CSTR ( hydrolysis-acidification reactor ), EGSB ( methanogenic reactor ), SBR (aerobic reactor ) and single-compartment BTAMFC. The effluent from SBR process was used as the substrate for the BTAMFC. The maximum power density was 2.7 W/m3. The COD removal rate was 72 %, and the COD for effluent of BTAMFC was below 100mg/L. The dark influent wastewater became light after treatment by BTAMFC, which also addressed the discoloring ability of the system. It was illustrated that BTAMFC preferred to high-concentration industrial wastewater treatment, which brought a good application prospect for this configuration. It was provided a new way of thinking in MFC technology for the application in the field of wastewater treatment.