Membrane fouling results in increased operating costs for reverse osmosis plants due to increased pressure requirements, cleaning chemicals and downtime. In practice it is difficult to detect fouling by Flux decline. Hence methods which can detect flux decline online are of great practical interest.

Electrical Impedance Spectroscopy has previously been demonstrated to be able to detect the build-up of layers of model foulants on laboratory reverse osmosis membranes. In this work we continue our development of Electrical Impedance Spectroscopy for measuring fouling in situ. Electrical Impedance Spectroscopy measurements were made of fouled industrial membranes from the water industry. After these membranes were cleaned physically and chemically the impedance was found to decrease and the conductance increase, consistent with the results of our previous work with laboratory membranes.