High purity water production using ion exchange

A method of producing high purity water using dealkalization and reverse osmosis membrane systems having enhanced membrane life, the method comprising:

• (a) providing a body feedwater to be purified;
• (b) adding a body of coagulent to said feedwater to provide flocs for adsorbing contaminants therefrom;
• (c) removing a portion of said body through a submerged semi-permeable membrane to provide purified feedwater;
• (d) treating said feedwater with a weak acid cation exchange for purposes of dealkalization to remove at least one of the ions from the group consisting of bicarbonate, carbonate, sulfate and nitrate ions to provide a substantially completely dealkalized water having a pH in the range of 4 to 6;
• (e) removing carbon dioxide from said dealkalized water to provide dealkalized, decarbonated water substantially free of carbon dioxide;
• (f) maintaining said decarbonated water at a pH in the range of 6.7 to 7.7 and having a conductivity in the range of 100 to 500 micro-Siemens;
• (g) providing a first membrane module having a high pressure side and a low pressure side separated by a first membrane;
• (h) introducing said dealkalized, decarbonated water to the high pressure side of said first membrane and producing a first permeate in said low pressure side having a pH in the range of about 6.5 to 7.5;
• (i) providing a second membrane module having a high pressure side and a low pressure side separated by a second membrane;
• and
• (j) introducing said first permeate to the high pressure side of said second membrane module and passing water through said second membrane producing said high purity water having a resistivity greater than 0.8 microhm-cm in the low pressure side of said second membrane.

A method of producing high purity water using dealkalization and reverse osmosis membrane systems having enhanced membrane life, the method comprising:

• (a) providing a body of feedwater to be purified;
• (b) adding a coagulent to said body to form flocs in said body in a concentration range of 2 to 6 gms/l and in a size range of 0.2 to 10 μm for purposes of adsorbing contaminants thereon;
• (c) removing a portion of said body through a submerged hollow fiber membrane to provide a purified feedwater;
• (d) treating said purified feedwater with an ion exchange for purposes of dealkalization to remove a material from the group consisting of bicarbonate, carbonate, sulfate and nitrate ions to provide a substantially completely dealkalized water having a pH in the range of 4 to 6;
• (e) removing carbon dioxide from said dealkalized water to provide dealkalized, decarbonated water substantially free of carbon dioxide;
• (f) maintaining said decarbonated water at a pH in the range of 6.7 to 7.7 and having a conductivity in the range of 100 to 500 micro-Siemens;
• (g) providing a first membrane module having a high pressure side and a low pressure side separated by a first membrane;
• (h) introducing said dealkalized, decarbonated water to the high pressure side of said first membrane and producing a first permeate in said low pressure side to proved a permeate having a pH in the range of about 6.5 to 7.5;
• (i) providing a second membrane module having a high pressure side and a low pressure side separated by a second membrane;
• and
• (j) introducing said first permeate to the high pressure side of said second membrane module and passing water through said second membrane producing said high purity water having a resistivity greater than 0.8 microhm-cm in the low pressure side of said second membrane.

A method of producing high purity water using dealkalization and reverse osmosis membrane systems having enhanced membrane life, the method comprising:

• (a) providing a feedwater to be purified;
• (b) treating said feedwater with a weak acid cation exchange for purposes of dealkalization to remove ions including bicarbonate, carbonate, sulfate and nitrate ions to provide a substantially completely dealkalized water;
• (c) removing carbon dioxide from said dealkalized water to provide dealkalized, decarbonated water substantially free of carbon dioxide;
• (d) maintaining said decarbonated water at a pH in the range of 6 to 9.5;
• (e) providing a first membrane module having a high pressure side and a low pressure side separated by a first membrane;
• (f) introducing said dealkalized, decarbonated water to the high pressure side of said first membrane and producing a first permeate in said low pressure side having a pH in the range of about 6.5 to 7.5;
• (g) providing a second membrane module having a high pressure side and a low pressure side separated by a second membrane;
• (h) introducing said first permeate to the high pressure side of said second membrane module and passing water through said second membrane producing said high purity water having a resistivity greater than 0.8 microhm-cm in the low pressure side of said second membrane;
• (i) measuring the resistivity of said high purity water produced at said second low pressure side of said second membrane module to provide a resistivity measurement;
• (j) relaying said resistivity measurement to a programmable logic controller;
• (k) in said programmable logic controller, comparing said resistivity measurement with a previous resistivity measurement to provide a comparison;
• and
• (l) in response to said comparison, maintaining or changing the pH of said dealkalized, decarbonated water upwardly or downwardly to produce said high purity water having said desired resistivity.

A method of producing high purity water using dealkalization and reverse osmosis membrane systems having enhanced membrane life, the method comprising:

• (a) providing a body of feedwater to be purified;
• (b) adding a coagulant to said body to form flocs in said body in a concentration range of 2 to 6 gms/l and in a size range of 0.2 to 10 μm for purposes of adsorbing contaminants thereon;
• (c) removing a portion of said body through a submerged hollow fiber membrane to provide a purified feedwater;
• (d) treating said purified feedwater with a weak acid cation exchange for purposes of dealkalization to remove ions including at least one of the ions selected from the group consisting of bicarbonate, carbonate, sulfate and nitrate ions to provide a substantially completely dealkalized water ions and having a pH in the range of 4 to 6;
• (e) removing carbon dioxide from said dealkalized water to provide dealkalized, decarbonated water substantially free of carbon dioxide;
• (f) maintaining said decarbonated water at a pH in the range of 6.7 to 7.7 and having a conductivity in the range of 100 to 750 micro-Siemens;
• (g) providing a first membrane module having a high pressure side and a low pressure side separated by a first membrane;
• (h) introducing said dealkalized, decarbonated water to the high pressure side of said first membrane and producing a first permeate in said low pressure side having a pH in the range of about 6.5 to 7.5;
• (i) providing a second membrane module having a high pressure side and a low pressure side separated by a second membrane;
• (j) introducing said first permeate to the high pressure side of said second membrane module and passing water through said second membrane producing said high purity water in the low pressure side of said second membrane.
• (k) measuring the resistivity of said high purity water produced at said low pressure side of said second membrane module to provide a resistivity measurement;
• (l) relaying said resistivity measurement to a programmable logic controller;
• (m) in said programmable logic controller, comparing said resistivity measurement with a previous resistivity measurement to provide a comparison;
• and
• (n) in response to said comparison, maintaining or changing the pH of said dealkalized, decarbonated water upwardly or downwardly to produce said high purity water having said desired resistivity.