Electrolysis device for the purification of water, comprising a cathode, an anode and an ion exchange membrane, which is arranged between the cathode and the anode and is held at least circumferentially in the peripheral area, characterized in that (a) the electrolysis device is structurally designed in the form of individual cells and is substantially formed by two half-shells, (i) wherein the outermost border of the half-shells is formed as a circumferential flange, which is adjoined after a circumferential edge by a cell border which borders the rear wall of the cell, (ii) wherein the electrodes are attached from the inside to the respective cell rear wall by means of webs and, opposite the webs, on the electrode side facing the membrane, spacing elements are arranged for fixing the membrane and conducting the power, whereby the electrode and the anode and cathode chambers that form between the respective electrode and the membrane are subdivided into a number of parallel compartments, (iii) wherein the space between the cell rear wall and the electrode is filled to over 90% with an inert material, so that, during operation as intended, the water is directed into the space between the electrode and the membrane apart from small peripheral flows, and (b) a multiplicity of feed inlets and discharge outlets are arranged on the upper and lower peripheral regions of the electrolysis device. (a) the electrolysis device is structurally designed in the form of individual cells and is substantially formed by two half-shells, (i) wherein the outermost border of the half-shells is formed as a circumferential flange, which is adjoined after a circumferential edge by a cell border which borders the rear wall of the cell, (ii) wherein the electrodes are attached from the inside to the respective cell rear wall by means of webs and, opposite the webs, on the electrode side facing the membrane, spacing elements are arranged for fixing the membrane and conducting the power, whereby the electrode and the anode and cathode chambers that form between the respective electrode and the membrane are subdivided into a number of parallel compartments, (iii) wherein the space between the cell rear wall and the electrode is filled to over 90% with an inert material, so that, during operation as intended, the water is directed into the space between the electrode and the membrane apart from small peripheral flows, and (i) wherein the outermost border of the half-shells is formed as a circumferential flange, which is adjoined after a circumferential edge by a cell border which borders the rear wall of the cell, (ii) wherein the electrodes are attached from the inside to the respective cell rear wall by means of webs and, opposite the webs, on the electrode side facing the membrane, spacing elements are arranged for fixing the membrane and conducting the power, whereby the electrode and the anode and cathode chambers that form between the respective electrode and the membrane are subdivided into a number of parallel compartments, (iii) wherein the space between the cell rear wall and the electrode is filled to over 90% with an inert material, so that, during operation as intended, the water is directed into the space between the electrode and the membrane apart from small peripheral flows, and (b) a multiplicity of feed inlets and discharge outlets are arranged on the upper and lower peripheral regions of the electrolysis device.