A specific amperometric assay involving the nitrocefin substrate and disposable carbon sensors. The rapid (<5h30) and quantitative detection of extended-spectrum β-lactamase (ESBL) activity in wastewaters. Calibration of the method with sterilized wastewater samples spiked with ESBL-producing E. coli. Good correlation between the electrochemical detection and the culture-based enumeration for wastewater monitoring.