Process and apparatus for blending product liquid from different TFC membranes

摘要

A process for membrane separation of a supply of potable tap water for obtaining a drinking water product, characterized by: feeding said tap water to at least one nanofiltration primary membrane, said at least one primary membrane separating said water into a primary membrane retentate retained by said at least one primary membrane, and a primary membrane permeate; feeding said primary membrane retentate directly to at least one reverse osmosis secondary membrane, said at least one secondary membrane separating said primary membrane retentate into a secondary membrane retentate retained by said at least one secondary membrane, and a secondary membrane permeate; and blending said primary membrane permeate and said secondary membrane permeate to form a product drinking water by directly passing said primary membrane permeate to a permeate blending point; wherein a solute concentration of said primary membrane permeate is greater than a solute concentration of said secondary membrane permeate, and said blending of permeates having distinct concentrations creates a drinking water product without adding supplemental minerals or untreated water post treatment.