Descripción

Disclosed is a water punfication method, especially for obtaining fresh water from salt water by means of mem- o brane distillation. Investment costs and operating expenses are substantially reduced compared with previously known methods by e a combination of the following measures: - the water that is to be purified is retained in a feeding chamber, the wall of which is formed at least in part by a hydrophobic steam-permeable membrane; - a hydrophilic membrane that has a greater thickness and lower heat conductivity per unit area than the hydrophobic membrane extends parallel to the hydrophobic membrane; - a difference in steam pressure is created between the water that ir to be punfied and the fresh water by means of a pumping action such that membrane distillation is driven by the difference in steam pressure created by the pump action, the water condensing in the pores of the hydrophilic membrane.