(644f) Novel Microbial Fuel Cell Based Biosensor for Continuous Measurement of BOD (Biochemical Oxygen Demand) In Wastewater

Shailesh Kharkwal^{a, b}, Min Lu^a, How Yong Ng^b

and Sam Fong Yau Li^a

^a Department of Chemistry, Faculty of Science, National University of Singapore, 3 Science Drive 3, Singapore 117543;

^bCentre for Water Research, Department of Civil and Environmental Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117576;

In recent years microbial biosensors have demonstrated great potential as an alternative to the conventional analytical method for BOD measurement in wastewater. These biosensors have certain advantages over the conventional 5-day BOD analytical method, such as rapid response, portability of sensing device, high accuracy, and are less rigorous and time consuming. Various BOD sensors have been reported in literature. They can be generally classified as respirometer type and bioluminescence based biosensors. Respirometer type biosensors, mainly made by immobilizing yeast, Bascillus subtilis, and Serratia marcescens cells, take advantages of the high reaction rates of microorganisms interfaced to electrodes to measure the dissolved oxygen (DO) consumption. While, the luminous bacteria, such as Photobacterium phosphoreum, isolated from marine sources, emits light at a constant rate in proportion to the amount of assimilable organic compounds in wastewater. However, the major disadvantage of respirometer and bioluminescence based biosensors is that they are unable to utilize a broad range of organic substrates. This may result in some unconsumed compounds in wastewater which subsequently may interfere with the performance of the sensor. In this regard, microbial fuel cell (MFC) based BOD sensors have been designed and tested. MFC-type BOD sensors have the various advantages over the other kinds of biosensors such as broad substrate versatility, long operational stability, high result reproducibility, etc.

This work aims to develop an efficient and stable MFC-type BOD sensor system with much reduced cost of operation. Keeping the economics in mind, low cost manganese dioxide materials, i.e., α-MnO₂, β-MnO₂ and γ-MnO₂, were tested as alternative cathode catalysts for oxygen reduction reaction (ORR) in air-cathode MFC. Three MnO₂ species were further used as cathode catalysts in air-cathode cubic MFCs, in which mixed culture was inoculated as biocatalysts and domestic wastewater was used as the substrate in the anode chamber. It was found that β-MnO₂ yielded the best performance with power density of 97.8 mW·m^-2 that is comparable to that of Pt. This study demonstrated that using β-MnO₂ on CNT support instead of Pt could potentially improve the feasibility of scaling up MFC designs for practical applications such as BOD sensing device by lowering the cost. The performance of β-MnO₂ based MFC is further investigated as BOD sensor using artificial wastewater. The performance of the BOD sensor is evaluated in terms of response time, reproducibility, and operational solubility to a wide range of COD. The sensor output, generated current or voltage, have a linear relationship with BOD of up to 400 ppm, and a stability of more than 5 months.

References:

Gil, G.C., Chang, I.S., Kim, B.H., Kim, M., Jang, J.K., Park, H.S., Kim,H.J., 2003. Operational parameters affecting the performance of a mediator-less microbial fuel. Biosens. Bioelectron. 18, 327–334.

Chang, I.S., Jang, J.K., Gil, G.C., Kim, M., Kim, H.J., Cho, B.W., Kim, B.H., 2004. Continuous determination of biochemical oxygen demand using microbial fuel cell type biosensor. Biosensors & Bioelectronics 19, 607–613.

Di Lorenzo, M., Curtis, T. P., Head, I. M., Scott, K., 2009. A single-chamber microbial fuel cell as a biosensor for wastewaters. Water Research 43, 3145-3154.

Riedel, K., Renneberg, R., Kuhn, M., Scheller, F., 1988. A fast estimation of biochemical oxygen demand using microbial sensors. Appl Environ Microbiol 28, 316–318.