<p>The low electrical energy generated by the integrated system of constructed wetlands and microbial fuel cells (CW-MFCs) during water remediation processes is frequently underestimated. Herein, the correlation between the electrical signals and pollutant concentrations was investigated to explore its potential for organic matter and Cu²⁺ monitoring. The results demonstrated that both peak current (R² = 0.957) and cumulative charge (R² = 0.958) exhibited strong correlations with COD concentrations within the COD range of 25 to 200 mg/L. However, the external resistance was found to restrict electron flux under elevated substrate concentrations, which diminished the correlation coefficient between electrical signals and COD levels. Then, the prediction accuracy under high-COD conditions (200–1000 mg/L) was improved by reducing the external resistance to 500 Ω and 100 Ω. To predict COD concentrations over a wider range, a piecewise fitting strategy was developed to optimize the correlation between electrical signal intensity and substrate concentrations. The cumulative charge displayed higher accuracy and sensitivity to COD variations, while peak current exhibited a shorter detection time. After that, the correlation between the electrical signals and Cu²⁺ concentrations was investigated. Cumulative charge demonstrated superior accuracy for Cu²⁺ monitoring under low-concentration conditions, whereas the peak current only exhibited responsiveness to Cu²⁺ concentration variations when a concentration threshold was reached. The results revealed a significant correlation between the electrical signal and pollutant concentration levels, and highlighted the potential applicability of CW-MFCs as biosensors.</p> Graphical Abstract <p></p>