An electrochemical cell (710, 720) for wastewater treatment comprising: a. a solid polymer electrolyte membrane; b. an anode catalyst layer adjacent to a first side of the solid polymer electrolyte membrane and a cathode catalyst layer adjacent to a second side of the solid polymer electrolyte membrane, opposite to the first side; c. a first open pore mesh adjacent to the anode catalyst layer and a second open pore mesh adjacent to the cathode catalyst layer, the first and second open pore meshes being made of conductive metals or ceramics and having a thickness of between 10 to 5000 microns and a porosity between 30 and 95%; d. a first compression frame made of a conductive metal or ceramics, adjacent to the first open pore mesh and a second compression frame made of a conductive metal or ceramics, adjacent to the second open pore mesh, each of the compression frames having a thickness of 0.5 to 5 mm, wherein each of the compression frames has compression arms spread within the area delimited by the perimeter of the frame, the compression arms being connected to each other at connection sites; e. fasteners made of a non-conductive material which protrude through holes provided in the compression arms of the first and second compression frames at the connection sites, through holes provided in the first and second open pore meshes and through the solid polymer electrolyte membrane and the anode and cathode catalyst layers; and f. leads provided on the first and second compression frame (112, 114) to make electrical connections with a power supply, wherein a cover (760A,760B, 760) is attached to the first compression frame or to the second compression frame, wherein the cover (760A, 760B, 760) is made of a non-conductive material and forms, together with the first or second compression frame (112, 114) to which the cover (760A, 760B, 760) is attached, an enclosure (790A, 790B) for isolating the anode or the cathode catalyst layer from a solution in a reactor tank (302; 430; 530; 630) where the electrochemical cell is placed, wherein the cover (760A, 760B, 760) has an inlet pipe for feeding wastewater, a cathode solution or an anode solution into the enclosure formed by the cover (760A, 760B, 760), one side provided with an opening for allowing access of the wastewater, anode solution or cathode solution to the anode or cathode catalyst layer of the electrochemical cell, an outlet pipe for removing reaction products that are formed at the anode catalyst or at the cathode catalyst from the enclosure formed by the cover (760A, 760B, 760) and a vent pipe for removing gases from the enclosure formed by the cover (760A, 760B, 760), and further comprising a seal between the side of the cover (760A, 760B, 760) provided with the opening and the compression frame next to that side. a. a solid polymer electrolyte membrane; b. an anode catalyst layer adjacent to a first side of the solid polymer electrolyte membrane and a cathode catalyst layer adjacent to a second side of the solid polymer electrolyte membrane, opposite to the first side; c. a first open pore mesh adjacent to the anode catalyst layer and a second open pore mesh adjacent to the cathode catalyst layer, the first and second open pore meshes being made of conductive metals or ceramics and having a thickness of between 10 to 5000 microns and a porosity between 30 and 95%; d. a first compression frame made of a conductive metal or ceramics, adjacent to the first open pore mesh and a second compression frame made of a conductive metal or ceramics, adjacent to the second open pore mesh, each of the compression frames having a thickness of 0.5 to 5 mm, wherein each of the compression frames has compression arms spread within the area delimited by the perimeter of the frame, the compression arms being connected to each other at connection sites; e. fasteners made of a non-conductive material which protrude through holes provided in the compression arms of the first and second compression frames at the connection sites, through holes provided in the first and second open pore meshes and through the solid polymer electrolyte membrane and the anode and cathode catalyst layers; and f. leads provided on the first and second compression frame (112, 114) to make electrical connections with a power supply, wherein a cover (760A,760B, 760) is attached to the first compression frame or to the second compression frame, wherein the cover (760A, 760B, 760) is made of a non-conductive material and forms, together with the first or second compression frame (112, 114) to which the cover (760A, 760B, 760) is attached, an enclosure (790A, 790B) for isolating the anode or the cathode catalyst layer from a solution in a reactor tank (302; 430; 530; 630) where the electrochemical cell is placed, wherein the cover (760A, 760B, 760) has an inlet pipe for feeding wastewater, a cathode solution or an anode solution into the enclosure formed by the cover (760A, 760B, 760), one side provided with an opening for allowing access of the wastewater, anode solution or cathode solution to the anode or cathode catalyst layer of the electrochemical cell, an outlet pipe for removing reaction products that are formed at the anode catalyst or at the cathode catalyst from the enclosure formed by the cover (760A, 760B, 760) and a vent pipe for removing gases from the enclosure formed by the cover (760A, 760B, 760), and further comprising a seal between the side of the cover (760A, 760B, 760) provided with the opening and the compression frame next to that side.