This work presents a non-invasive and non-destructive electrochemical impedance spectroscopy (EIS) method for studying membrane fouling at a sub-stoichiometric TiO2 reactive electrochemical membrane (REM). An asymmetric, ceramic, ultrafiltration REM is studied through EIS simulations, that are based on a mathematical transmission line model (TLM). The TLM is developed to interpret EIS data and is shown to be sensitive to fouling at multiple interfaces of the REM (outer surface, active and support layers). Mathematical interpretation of penetration depth of the alternating voltage signal allows a determination of the characteristic frequencies associated with different layers of the membrane. The simulation results of membrane fouling mechanisms, such as monolayer adsorption and pore constriction at either active or support layer, and intermediate pore blockage at the outer surface produce distinguishable EIS spectra. Simulation results suggest that interpreting EIS spectra by the TLM is a useful technique for spatially characterizing membrane fouling and determining prevalent fouling mechanisms at a conductive membrane surface. (C) 2016 Elsevier B.V. All rights reserved.