Study On Microbial Fuel Cell-based BOD Biosensor

With rapid development of industry and economy, environment pollution becomes more and more prominent, especially, water pollution with organic matters in China. Biochemical oxygen demand (BOD) is an important indicator which reflects organic pollutants in water. The standard method to detect BOD,5-d diluted culture method, is time-consuming and shows poor result reproducibility. Microbial fuel cell (MFC) is a device which can convert chemical energy of organics into electrical energy. Using MFC as BOD sensor is a new way to detect BOD, which has the advantages of short detection time and good reproducibility.A double chamber MFC was designed and constructed with graphite felt (thickness of3mm, porosity of7%) as electrodes and titanium wire (diameter of1mm) for electron transportation. Two chambers were separated by Nation117proton exchange membrane. The results with different inocula and different configurations indicated that the cuboid MFC reactor inoculated with activated sludge in the anaerobic phase of A/O wastewater treatment process showed the best startup. After two-week startup, the current gereneted became stable, therefore, subsequent experiments were based on this MFC reactor.Some parameters containing external resistor, pH of the anode chamber, method to maintain anaerobic condition in anode chamber, method to supply oxygen as the cathode electron acceptor and different cathode electron acceptors were tested to investigate the performance of MFC. The optimal operating conditions of MFC were as follows:external resistor of500Ω, adding phosphate buffer solution with a pH of7.0in artificial waste water, L-cysteine as the oxygen uptake reagent, water with rich oxygen as cathode electron acceptor in cathode chamber. Electrolyte solutions as cathode electron acceptor can improve the performance of MFC.The MFC was used to detect BOD of the artificial wastewater. When O2was used as cathode electron acceptor, the MFC eccellently detected BOD of the water samples under50mg/L from the maximum current within5h and detected BOD of the water samples under100mg/L from electric charge within8-10h. When FeCl3was used as cathode electron acceptor, the upper detection limit of BOD wes broadened to250mg/L, but the electrodes might be corroded and the membrane minght be fouled. When KMnO4were used as electron acceptor, the upper detection limit increased with the increase of KMnO4concentration. With a KMnO4concentratio of10mmol/L, the upper detection limit of BOD reached500mg/L, and the detection time was under10h, meanwhile the data repeatability was excellent. KMnO4as electron acceptor might slightly foul the membrane.