Chemical oxygen demand (COD) is one of the major targets to remove in constructed wetlands (CWs) system. Traditional method for COD measurement is a complex, time-consuming and highly toxic reagents participated procedure. In this study, microbial fuel cell (MFC) was successfully integrated into CW for indicating COD concentration. Results showed that there are two linear correlations between bioelectrical signals (output voltage from MFC) and COD concentration (acetate), which are COD from 0 to 500 mg/L (101.99 +/- 7.42 to 631.74 +/- 7.41 mV, R-2 = 0.9710) and then from 500 to 1000 mg/L (631.74 +/- 7.41 to 668.46 +/- 0.01 mV, R-2 = 0.9245). Furthermore, results also revealed the specificity of the system in terms of different types of carbon source. Overall, this work presented the feasibility of using CW-MFC for insitu sensing COD during the wastewater treatment process, which will be a promising technique for water quality monitoring within CWs. (C) 2017 Elsevier Ltd. All rights reserved.