Abstract: A membrane separation device that treats water constructed such that at least two permeate streams of different electrical conductivity are generated therein, including at least two membrane modules arranged in a common pressure vessel such that they can be successively subjected to incoming flow of the water to be treated, wherein the pressure vessel is a tube in which the at least two membrane modules are arranged one behind the other in an axial direction and the at least two membrane modules are spirally wound modules.

Abstract: A membrane separation device that treats water constructed such that at least two permeate streams of different electrical conductivity are generated therein, including at least two membrane modules arranged in a common pressure vessel such that they can be successively subjected to incoming flow of the water to be treated, wherein the pressure vessel is a tube in which the at least two membrane modules are arranged one behind the other in an axial direction and the at least two membrane modules are spirally wound modules.

Abstract: A description is given of a multistage process for treating water, wherein a water stream is purified in a membrane separation stage and a downstream deionization unit having at least one concentrate chamber and at least one diluate chamber, wherein the water stream is separated in the membrane separation device into a concentrate stream and at least two permeate streams of different electrical conductivity, and wherein at least the permeate stream having the highest electrical conductivity is fed at least partially into the at least one concentrate chamber and at least the permeate stream having the lowest electrical conductivity is fed at least partially into the at least one diluate chamber of the downstream deionization unit.

Abstract: A description is given of a multistage process for treating water, wherein a water stream is purified in a membrane separation stage and a downstream deionization unit having at least one concentrate chamber and at least one diluate chamber, wherein the water stream is separated in the membrane separation device into a concentrate stream and at least two permeate streams of different electrical conductivity, and wherein at least the permeate stream having the highest electrical conductivity is fed at least partially into the at least one concentrate chamber and at least the permeate stream having the lowest electrical conductivity is fed at least partially into the at least one diluate chamber of the downstream deionization unit.

Abstract: A spiral wound module for the electrochemical desalination of aqueous salt-containing solutions, whose feeds for solution to be desalinated and whose discharge for desalinated water are mounted on side walls of the dilution chamber of the module, permits an axial instead of tangential flow in the dilution chamber.