Abstract: A process for purifying water by removing dissolved materials therefrom, the process capable of producing purified water having a resistivity in the range of 2 to 10 megohm-cm. The process comprises providing a water feed stream to be purified and adjusting the pH of the water feed stream to a basic water solution to drive the equilibrium of a first weakly ionized material to become ionized in the basic solution. The basic water solution is introduced to a high pressure side of a first reverse osmosis membrane module and water is passed through the first reverse osmosis membrane to provide a first retentate having ions therein from the first weakly ionized material concentrated therein and a first permeate depleted in ions from the first weakly ionized material. The pH of the first permeate is adjusted to an acidic water solution to drive the equilibrium of a second weakly ionized material to become ionized in an acidic solution.

Abstract: A process for purifying water including removing cations, anions and carbon dioxide and/or ammonia from water feed stream to produce high purity water having a resistivity of greater than 1 megohm-era comprising the steps of providing a water feed stream to be purified, the stream containing cations, anions and carbon dioxide and/or ammonia; introducing the water feed stream to a high pressure side of a first reverse osmosis membrane module; passing water through the first reverse osmosis membrane to provide a first retentate having cations and anions concentrated therein and a first permeate depleted in cations and anions and containing carbon dioxide and/or ammonia; adding the first permeate to a high pressure side, of a gas permeable hydrophobic membrane module; passing carbon dioxide and/or ammonia through the gas-permeable membrane from the first permeate in the high pressure side of the gas-permeable hydrophobic membrane to provide a carbon dioxide and/or ammonia permeate on a low pressure side of the h