A method for removing a fluorine-containing compound from discharge water, which includes bringing discharge water containing two or more fluorine-containing compounds represented by the following general formula (1) or (2) into contact with an adsorbent so as to adsorb the two or more fluorine-containing compounds:

(H—(CF.sub.2).sub.m—COO).sub.pM.sup.1  General Formula (1):

wherein m is 3 to 19, M.sup.1 is H, a metal atom, NR.sup.b.sub.4, where R.sup.b is the same or different and is H or an organic group having 1 to 10 carbon atoms, imidazolium optionally having a substituent, pyridinium optionally having a substituent, or phosphonium optionally having a substituent; and p is 1 or 2;

(H—(CF.sub.2).sub.n—SO.sub.3).sub.qM.sup.2  General Formula (2):

wherein n is 4 to 20; M.sup.2 is H, a metal atom, NR.sup.b.sub.4, where R.sup.b is the same as above, imidazolium optionally having a substituent, pyridinium optionally having a substituent, or phosphonium optionally having a substituent; and q is 1 or 2.

A method for removing a fluorine-containing compound from discharge water, which includes bringing discharge water containing two or more fluorine-containing compounds represented by the following general formula (1) or (2) into contact with an adsorbent so as to adsorb the two or more fluorine-containing compounds:

(H—(CF.sub.2).sub.m—COO).sub.pM.sup.1  General Formula (1):

wherein m is 3 to 19, M.sup.1 is H, a metal atom, NR.sup.b.sub.4, where R.sup.b is the same or different and is H or an organic group having 1 to 10 carbon atoms, imidazolium optionally having a substituent, pyridinium optionally having a substituent, or phosphonium optionally having a substituent; and p is 1 or 2;

(H—(CF.sub.2).sub.n—SO.sub.3).sub.qM.sup.2  General Formula (2):

wherein n is 4 to 20; M.sup.2 is H, a metal atom, NR.sup.b.sub.4, where R.sup.b is the same as above, imidazolium optionally having a substituent, pyridinium optionally having a substituent, or phosphonium optionally having a substituent; and q is 1 or 2.

Provided is a water softening device including a water softening tank that softens raw water using a weakly acidic cation exchange resin, a pH adjustment tank, an electrolytic cell that produces acidic electrolyzed water, a conductivity measurement unit S.sub.1 that measures conductivity of the raw water, a conductivity measurement unit S.sub.2 that measures conductivity of soft water, a water flow amount detecting unit, and a control unit, wherein the control unit calculates a regeneration time for the weakly acidic cation exchange resin based on an amount of the hardness component adsorbed to the weakly acidic cation exchange resin calculated from a difference between the conductivity of the raw water and the conductivity of the soft water and from the accumulated water flow amount of the raw water, and performs a regeneration treatment of the weakly acidic cation exchange resin during the regeneration time.

A sustainable system for removing and concentrating per- and polyfluoroalkyl substances (PFAS) from water. The system includes an anion exchange vessel having a selected anion exchange resin therein configured to remove PFAS from the water. A line coupled to the vessel introduces a flow of water contaminated with PFAS such that the PFAS bind to the selected anion exchange resin and are thereby removed from the water. A regenerant solution line is coupled to the anion exchange vessel to introduce an optimized regenerant solution to the anion exchange vessel to remove the PFAS from the anion exchange resin, thereby regenerating the anion exchange resin and generating a spent regenerant solution comprised of the removed PFAS and the optimized regenerant solution. A separation and recovery subsystem recovers the optimized regenerant solution for reuse and separates and concentrates the removed PFAS.

A sustainable system for removing and concentrating per- and polyfluoroalkyl substances (PFAS) from water. The system includes an anion exchange vessel having a selected anion exchange resin therein configured to remove PFAS from the water. A line coupled to the vessel introduces a flow of water contaminated with PFAS such that the PFAS bind to the selected anion exchange resin and are thereby removed from the water. A regenerant solution line is coupled to the anion exchange vessel to introduce an optimized regenerant solution to the anion exchange vessel to remove the PFAS from the anion exchange resin, thereby regenerating the anion exchange resin and generating a spent regenerant solution comprised of the removed PFAS and the optimized regenerant solution. A separation and recovery subsystem recovers the optimized regenerant solution for reuse and separates and concentrates the removed PFAS.

A method of producing treated ion exchange resin material includes exposing an enclosed vessel containing ion exchange resin and a pre-treatment solution to high energy radiation. The treated ion exchange resin material has reduced organic impurities or total organic carbon (TOC).

A method of producing treated ion exchange resin material includes exposing an enclosed vessel containing ion exchange resin and a pre-treatment solution to high energy radiation. The treated ion exchange resin material has reduced organic impurities or total organic carbon (TOC).

A method as described herein may include contacting a fluid with a single resin to cause the single resin to bond to nitrates and perchlorates contained in the fluid. The method may regenerate the single resin by a regeneration process comprising contacting the single resin with a salt solution, wherein regenerating removes a substantial portion of the nitrates contained within the single resin but does not remove a substantial portion of the perchlorates contained within the single resin, wherein the single resin comprises a nitrate-specific resin and does not comprise a perchlorate-specific resin.

A method as described herein may include contacting a fluid with a single resin to cause the single resin to bond to nitrates and perchlorates contained in the fluid. The method may regenerate the single resin by a regeneration process comprising contacting the single resin with a salt solution, wherein regenerating removes a substantial portion of the nitrates contained within the single resin but does not remove a substantial portion of the perchlorates contained within the single resin, wherein the single resin comprises a nitrate-specific resin and does not comprise a perchlorate-specific resin.

A method of removing boron from water to be treated includes subjecting the water to be treated to reverse osmosis membrane treatment, subjecting at least part of permeated water after the reverse osmosis membrane treatment to cation-removing treatment, and measuring a concentration of boron in the resulting permeated water after the cation-removing treatment, in which a measured value for the concentration of boron is used to regulate at least one of: (a) the recovery rate of water to be treated in the above reverse osmosis membrane treatment, (b) the temperature of the water to be treated, (c) the pH of the water to be treated, (d) the supply pressure of the water to be treated, which pressure is applied to the reverse osmosis membrane during the reverse osmosis membrane treatment, and (e) when the reverse osmosis membrane used for the reverse osmosis membrane treatment should be changed.