Arrangement for electrochemical purification or treatment of a liquid, utilizing an electrochemical cell (20), where two electrodes (20B,20C) are provided with ion exchange membranes (C,A) arranged between them to delimit a plurality of channels (CE,CC,CP). According to the invention, at least a few channels (CE,CC,CP) have respective second electrodes ( + ,- ) associated to them for obtaining a cleaning substance or solution, the latter being apt to dissolve and/or remove likely residuals and/or scaling deposited inside the cell (20).