Single chamber air-cathode microbial fuel cells as biosensors for determination of biodegradable organics

Abstract

Objectives Single chamber air cathode microbial fuel cells (MFCs) were investigated with sodiumacetate and peptone as test substrates to assess the potential for application as biosensor to determine the concentration of biodegradable organics in water/ wastewater samples. Results MFCs provided well-reproducible performance at high ([2000 mg COD l-1-Chemical Oxygen Demand) acetate concentration values. Current in the cells proved to be steady from 25 to 35 °C, significant decrease was, however, revealed in the current below 20 °C. Direct calculation of nontoxic biodegradable substrate concentration in water/ wastewater from the current in MFCs is possible only in the non-saturated substrate concentration range due to the Monod-like dependence of the current. This range was determined by a fitted and verified Monodbased kinetic model. Half saturation constant (KS) values were calculated at 30 °C applying different external resistance values (100 X, 600 X and 1000 X, respectively). In each case KS remained below 10 mg COD l-1. Conclusions Biosensors with this particular MFC design and operation are potentially applicable for detecting as low as 5 mg COD l-1 readily biodegradable substrates, and measuring the concentration of these substances up to * 50-70 mg COD l-1.