In situ microbial fuel cell-based biosensor for organic carbon

doi:10.1016/j.bioelechem.2011.02.002

Bioelectrochemistry

Volume 81, Issue 2, June 2011, Pages 99-103

https://doi.org/10.1016/j.bioelechem.2011.02.002 Get rights and content

Abstract

The biological oxygen demand (BOD) may be the most used test to assess the amount of pollutant organic matter in water; however, it is time and labor consuming, and is done ex-situ. A BOD biosensor based on the microbial fuel cell principle was tested for online and in situ monitoring of biodegradable organic content of domestic wastewater. A stable current density of 282 ± 23 mA/m² was obtained with domestic wastewater containing a BOD₅ of 317 ± 15 mg O₂/L at 22 ± 2 °C, 1.53 ± 0.04 mS/cm and pH 6.9 ± 0.1. The current density showed a linear relationship with BOD₅ concentration ranging from 17 ± 0.5 mg O₂/L to 78 ± 7.6 mg O₂/L. The current generation from the BOD biosensor was dependent on the measurement conditions such as temperature, conductivity, and pH. Thus, a correction factor should be applied to measurements done under different environmental conditions from the ones used in the calibration. These results provide useful information for the development of a biosensor for real-time in situ monitoring of wastewater quality.

Research highlights

► Electrochemically active biofilms transfer electrons to electrode surface. ► Carbon content of the wastewater as the electron donor to the microorganisms. ► Different concentrations of Biological Oxygen Demand of the wastewater traduced in different maximums of the current density in a MFC. ► Submersible Microbial Fuel Cell can act as a BOD biosensor.

Introduction

Domestic wastewater commonly contains organic matter that includes nitrogenous compounds, proteins and amino acids, and non-nitrogenous compounds, carbohydrates and lipids. A detailed characterization of the organic matter in domestic wastewater is time and labor consuming; therefore, bulk parameters like biological oxygen demand (BOD) and chemical oxygen demand (COD) are routinely used as a measure of the degree of water pollution by organic carbon. The BOD is a measure of the quantity of oxygen used by microorganisms (e.g., aerobic bacteria) to oxidize the organic matter in a sample of water during a period of 5 days (BOD₅), while the COD is used as a measure of the oxygen requirement of a sample that is susceptible to oxidation by a strong chemical oxidant (e.g., potassium dichromate). COD values are always higher than BOD values. COD measurements can be made in a few hours, while BOD measurements take five days, but they do not differentiate between biologically available and inert organic matter [1], [2], [3], [4], [5].

An online biosensor to quantify BOD was developed using the microbial fuel cell (MFC) principle [6]. In a MFC, microorganisms growing on the surface of an anode electrode transfer electrons from the oxidation of organic matter present in the wastewater through an electrical circuit to a cathode electrode, thus generating an electrical current [7]. A biosensor based on the MFC principle does not need a transducer to read the signal and converts it to an electrical signal because the measured signal is already an electrical current [8]. This type of biosensor is an example of the successful application of an electrochemical method in the evaluation of wastewater quality. Several configurations based on MFC have been tested and optimized to be used as a BOD biosensor. The usual configuration was a mediator-less MFC, with two chambers separated by a cation exchange membrane and continuous wastewater flow in the anode chamber [6], [9], [10], [11], [12], [13], [14]. The main drawback of this configuration is the complexity of the setup that is not suitable for in situ applications.

A very compact MFC configuration, known as submersible microbial fuel cell (SMFC), was developed by Min and Angelidaki [15]. This configuration uses an air-cathode which simplifies considerably the MFC configuration [16]. The aim of the present study was to adapt and test the SMFC configuration as an in situ BOD biosensor. The SMFC contained an anode electrode connected to a rectangular cathode chamber and was submerged in anaerobic wastewater. The cathode chamber was continuously flushed with air. A proton exchange membrane was assembled between anode and cathode. The membrane-electrodes assembly was pulled together to reduce the internal resistance of the cell and placed on one side of the cathode chamber. Several experiments were carried out with domestic wastewater containing a BOD₅ concentration in the range of 17 ± 0.5 mg O₂/L to 183 ± 4.6 mg O₂/L. The effect of temperature (11 ± 0.2 °C–33 ± 0.3 °C), wastewater conductivity (1.1 ± 0.012 mS/cm–13.4 ± 0.013 mS/cm) and pH (6.0 ± 0.1–8.5 ± 0.1) were investigated.

Section snippets

Wastewater collection and composition

Domestic wastewater was collected at the Lundtofte Wastewater Treatment Plant (Lyngby, Denmark), screened to remove coarse particles and, used as a source of organic matter and inoculum to start biofilm formation on the anode surface of the BOD biosensor. The composition of the wastewater was: 470 ± 79 mg O₂/L as COD, 317 ± 15 mg O₂/L as BOD₅, 61 ± 13 mg/L total nitrogen, 12 ± 2.6 mg/L total phosphorous, 6.93 ± 0.16 pH units and 1.53 ± 0.04 mS/cm conductivity. After collection, the wastewater was sparged with

Biofilm formation

When the BOD biosensor was immersed in domestic wastewater (317 ± 15 mg O₂/L BOD₅), current kept increasing over time and, after a period of 3 weeks, it stabilized at a maximum value of 0.27 mA, corresponding to a current density of 282 ± 23 mA/m². Once the maximum current was reached, it could be maintained as long as domestic wastewater was periodically changed. The profile of current generation of a single-batch operation was characterized by a steep increase of current after addition of domestic

Conclusions

A mediator-less submersible microbial fuel cell was tested as an in situ BOD biosensor. BOD₅ values of up to 78 ± 8 mg O₂/L could be measured based on a linear relation between organic carbon content of the wastewater and current density, and the biosensor response time was lower than 10 h. The current density measured with the biosensor was affected by changes in pH and temperature and the measured values need to be corrected.

The biosensor developed and tested in the present work has an

Acknowledgements

The authors are indebted and grateful to Uwe Wolter and Hector Garcia from the Technical University of Denmark (Environmental Engineering Department), for technical help and to Lundtofte Wastewater Treatment Plant (Lyngby, Denmark) for the samples and other wastewater composition parameters. The authors also acknowledge the Grant SFRH/BD/38331/2007 from the FCT/MCTES, Portugal, awarded to Luciana Peixoto and the FP7 EU project ModelProbe.

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¹: Present address: IBB — Institute for Biotechnology and Bioengineering, Centre of Biological Engineering, University of Minho, Campus de Gualtar, 4710–057 Braga, Portugal.

²: Present address: Department of Environmental Science and Engineering, Kyung Hee University, Yongin-Si, Gyeonggi-Do 446–701, Republic of Korea.

³: Present address: ARH Norte, R. Formosa, 254, 4049–030 Porto, Portugal.

View full text

In situ microbial fuel cell-based biosensor for organic carbon

Abstract

Research highlights

Introduction

Section snippets

Wastewater collection and composition

Biofilm formation

Conclusions

Acknowledgements

Anal. Chim. Acta

Bioelectrochemistry

Biosens. Bioelectron.

Biosens. Bioelectron.

Biosens. Bioelectron.

J. Power Sources

Bioelectrochemistry

Bioelectrochemistry

Microbial electrode BOD sensors

Biotechnol. Bioeng.

Yeast BOD sensor

Biotechnol. Bioeng.

A fast estimation of biochemical oxygen demand using microbial sensors

Appl. Microbiol. Biot.