Development Of A Portable Microbial Fuel Cell Type On-Line BOD Sensor

This paper described a single-chamber mediator-less microbial fuel cell (MFC)-type BOD sensor as an alternative method to BOD5. In such MFC, MnO2 was used as the cathode catalyst instead of Pt and the expensive proton exchange membrane was replaced with the cation exchange membrane. The factors including the external resistance, pH of anolyte, the reaction time and rinse time on BOD sensor were explored, and the results were compared with the values determined by BOD5. On this basis, this paper constructed an air-cathode microbial fuel cell (MFC)-typebiotoxicity detector for the purpose of on-site and on-line monitoring. The principle of the detector is based on the effect of microbial toxicity of water sample on the electricity generation in MFC. The perfomance of the MFC-type biotoxicity detector was evaluated with the synthetic water containing the heavy metals of Cd2+and Cu2+.The experimental results showed that:1 the optimal conditions are:the external resistance of 12 kO, pH of 7.0, and the reaction period of 2 h and the rinse time of 2-10 min. The low detection limit is 0.2 mg/L and the precision is 0.33%;2 This study indicates that MFC-type sensor can be used as a reliable method to determine BOD in wastewater, supported by the good linear correlation between BOD concentration and coulombs generation (regression coefficient, R2=0.9992) and the small relative error of 4% between MFC-type sensor and BOD5;3 Such device provides a low-cost, easy-operated, fast-response, sensitive and reliable method to measure BOD in wastewater, and also is suitable for on-line measurements;4 Relative to the converntional methods, the MFC-type detector is easy to operate, and suitable for on-line measurements with high sensitivity;5 It only requires 4 h to compelte measurements, and can get ready for next measurement within 4 h;6 There is a significant linear correlation between the concentration of toxic metal(s) and inhibition ratios in Coulombic yields of MFC. As the IC20 (concentration causing 20% inhibiton) of Cd2+, Cu2+and mixed metals (Cd2+ and Cu2+) were 0.6,0.8 and 0.2 mg/L, the retression coefficients were shown to be 0.9960,0.9744 and 0.9907.