Abstract: A porous electrically conducting filter, e.g. a membrane for filtration equipment, is cleaned by setting up an electrochemical cell comprising the membrane as a first electrode (usually the cathode), a second electrode, and an electrolyte capable of being electrolyzed to a gaseous product at the first electrode. When a potential is applied across the cell, the gaseous product of electrolysis (e.g. in the form of microbubbles) cleans the surfaces of the membrane by forcing foulant material therefrom.The electrolyte is constituted by the liquid being filtered (with the possible addition of a salt to increase electrical conductivity, if necessary) thus enabling filter cleaning to be carried out in situ while the liquid being filtered continues to be passed through the filter.