Method for treatment of feedwaters by membrane separation under acidic conditions

Abstract

A process for treatment of acidic waters via membrane separation equipment. A feedwater is maintained or adjusted to a pH of 4.3 or lower, and fed to a membrane separation system. In this manner, species such as total organic carbon (TOC) become more ionized, and (a) their rejection by the membrane separation process is significantly increased, and (b) their solubility in the reject stream from the membrane process is significantly increased. Passage of total organic carbon (TOC) through the membrane is significantly reduced. A recovery ratio at or exceeding eighty percent (80%) is achievable with most feedwaters, while simultaneously achieving a substantial reduction in cleaning frequency of the membrane separation equipment. The method is particularly useful for the preparation of high purity water.

1 . A process for treatment of a feedwater stream using reverse osmosis membrane separation equipment, said reverse osmosis membrane separation equipment comprising at least one reverse osmosis membrane separator, to produce a low solute containing product stream and a high solute containing reject stream, said process comprising:
 (a) providing a feedwater stream containing solutes, said solutes comprising at least one constituent that can contribute to fouling of said reverse osmosis membrane separator in the absence of free mineral acidity;   (b) pretreating said feedwater stream by controlling the pH of said feedwater stream to about 4.3 or lower by the time said feedwater stream enters said reverse osmosis membrane separator, to assure at least some free mineral acidity in the pretreated feedwater;   (c) passing the resultant pretreated feedwater stream through said reverse osmosis membrane separation equipment, said reverse osmosis membrane separation equipment substantially resisting passage of at least some dissolved species therethrough, to concentrate said pretreated feedwater to said preselected concentration factor, to produce
 (i) a high solute containing reject stream, and 
 (ii) a low solute containing product stream; 
   (d) wherein feedwater stream comprises one or more total organic carbon (TOC) constituents, and wherein said one or more total organic carbon (TOC) constituents are substantially prevented from passing through said reverse osmosis membrane separator to said product stream; and   (e) wherein said one or more total organic carbon (TOC) constituents comprise one or more non-ionizable species, said one or more non-ionizable species comprising isopropyl alcohol, or acetone.   
     
     
         2 . The process as set forth in  claim 1 , wherein said total organic carbon (TOC) constituents in said product stream is approximately ten percent (10%) or less of the concentration of such total organic carbon (TOC) constituents in said feedwater stream. 
     
     
         3 . The process as set forth in  claim 1 , or in  claim 2 , wherein said feedwater stream comprises ammonium ions, and wherein said product stream contains approximately eight percent (8%) or less of the ammonium ion concentration present in said feedwater stream. 
     
     
         4 . The process as set forth in  claim 1 , or in  claim 2 , further comprising (i) adding either ferrous or ferric ions to said feedwater stream before entry of said feedwater stream to said reverse osmosis membrane separation equipment, as reactants to facilitate removal of total organic carbon (TOC) constituents, and (ii) adding hydrogen peroxide to said feedwater stream at any point before feed to said reverse osmosis membrane separation equipment. 
     
     
         5 . The process as set forth in  claim 1 , or in  claim 2 , further comprising ozonation of said feedwater stream with an ozone containing gas, and wherein said total organic carbon (TOC) constituents are effectively prevented from entering said product stream. 
     
     
         6 . The process as set forth in  claim 1 , or in  claim 2 , further comprising ozonation of said product water stream with an ozone containing gas, and wherein said total organic carbon (TOC) constituents are effectively eliminated from said product stream. 
     
     
         7 . The process as set forth in  claim 1 , or in  claim 2 , further comprising removal of oxidants from said feedwater stream, and wherein said pretreatment process of oxidant removal comprises the addition of sodium meta-bisulfite to said feedwater stream. 
     
     
         8 . The process as set forth in  claim 7 , further comprising one or more additional pretreatment processes, said additional pretreatment processes comprising (i) media filtration, (ii) cartridge filtration, (iii) ultrafiltration, (iv) nanofiltration, or (v) degasification. 
     
     
         9 . The process as set forth in  claim 1 , further comprising one or more additional pretreatment processes, said additional pretreatment processes comprising (i) media filtration, (ii) cartridge filtration, (iii) ultrafiltration, (iv) nanofiltration, (v) degasification, or (vi) oxygen removal. 
     
     
         10 . The process as set forth in  claim 1 , wherein said membrane separator comprises a loose reverse osmosis membrane. 
     
     
         11 . A process for treatment of a feedwater stream using reverse osmosis membrane separation equipment, said reverse osmosis membrane separation equipment comprising at least one reverse osmosis membrane separator, to produce a low solute containing product stream and a high solute containing reject stream, said process comprising:
 (a) providing a feedwater stream containing solutes, said solutes comprising at least one constituent that can contribute to fouling of said reverse osmosis membrane separator in the absence of free mineral acidity;   (b) pretreating said feedwater stream to reduce the pH of said feedwater stream to about 4.3 or lower by the time said feedwater stream enters said reverse osmosis membrane separator, to assure at least some free mineral acidity in the pretreated feedwater;   (c) passing the resultant pretreated feedwater stream through said reverse osmosis membrane separation equipment, said reverse osmosis membrane separation equipment substantially resisting passage of at least some dissolved species therethrough, to concentrate said pretreated feedwater to said preselected concentration factor, to produce
 (i) a high solute containing reject stream, and 
 (ii) a low solute containing product stream; 
   (d) wherein feedwater stream comprises one or more total organic carbon (TOC) constituents, and wherein said one or more total organic carbon (TOC) constituents are substantially prevented from passing through said reverse osmosis membrane separator to said product stream; and   (e) wherein the ratio of the quantity of said product stream produced to the quantity of said feedwater stream provided is about eighty percent (80%) or more.   
     
     
         12 . The process as set forth in  claim 11 , wherein the ratio of the quantity of said product stream produced to the quantity of said feedwater stream provided is about eighty-five percent (85%) or more. 
     
     
         13 . The process as set forth in  claim 11 , wherein the ratio of the quantity of said product stream produced to the quantity of said feedwater stream provided is about ninety percent (90%) or more. 
     
     
         14 . The process as set forth in  claim 11 , or in  claim 12 , or in  claim 13 , wherein said total organic carbon (TOC) constituents in said product stream is approximately ten percent (10%) or less of the concentration of such total organic carbon (TOC) constituents in said feedwater stream. 
     
     
         15 . The process as set forth in  claim 14 , wherein said feedwater stream comprises ammonium ions, and wherein said product stream contains approximately eight percent (8%) or less of the ammonium ion concentration present in said feedwater stream. 
     
     
         16 . The process as set forth in  claim 11 , or in  claim 12 , or in  claim 13 , wherein said feedwater stream comprises ammonium ions, and wherein said product stream contains approximately eight percent (8%) or less of the ammonium ion concentration present in said feedwater stream. 
     
     
         17 . The process as set forth in  claim 14 , further comprising (i) adding either ferrous or ferric ions to said feedwater stream before entry of said feedwater stream to said reverse osmosis membrane separation equipment, as reactants to facilitate removal of total organic carbon (TOC) constituents, and (ii) adding hydrogen peroxide to said feedwater stream at any point before feed to said reverse osmosis membrane separation equipment. 
     
     
         18 . The process as set forth in  claim 11 , further comprising ozonation of said feedwater stream with an ozone containing gas, and wherein said total organic carbon (TOC) constituents are effectively prevented from entering said product stream. 
     
     
         19 . The process as set forth in  claim 11 , further comprising ozonation of said product water stream with an ozone containing gas, and wherein said total organic carbon (TOC) constituents are effectively eliminated from said product stream. 
     
     
         20 . The process as set forth in  claim 11 , further comprising pretreatment for removal of oxidants from said feedwater stream, and wherein said pretreatment process of oxidant removal comprises the addition of sodium meta-bisulfite to said feedwater stream. 
     
     
         21 . The process as set forth in  claim 20 , further comprising one or more additional pretreatment processes, said additional pretreatment processes comprising (i) media filtration, (ii) cartridge filtration, (iii) ultrafiltration, (iv) nanofiltration, or (v) degasification. 
     
     
         22 . The process as set forth in  claim 11 , further comprising one or more additional pretreatment processes, said additional pretreatment processes comprising (i) media filtration, (ii) cartridge filtration, (iii) ultrafiltration, (iv) nanofiltration, (v) degasification, or (vi) oxygen removal. 
     
     
         23 . The process as set forth in  claim 11 , wherein said membrane separator comprises a loose reverse osmosis membrane. 
     
     
         24 . A process for treatment of a feedwater stream using membrane separation equipment, said membrane separation equipment comprising at least one membrane separator, to produce a low solute containing product stream and a high solute containing reject stream, said process comprising:
 (a) providing an acidic feedwater stream containing solutes, said acidic feedwater stream having a pH that assures the presence of free mineral acidity therein;   (b) pretreating said acidic feedwater stream, if necessary, to maintain the acidity of said feedwater stream to a pH of between about 4.3 and about 2.0 at the time said feedwater stream enters said membrane separator, to assure at least some free mineral acidity remains in the pretreated feedwater;   (c) passing the resultant pretreated feedwater stream through said reverse osmosis membrane separation equipment, said membrane separation equipment substantially resisting passage of at least some dissolved species therethrough, to concentrate said pretreated feedwater to said preselected concentration factor, to produce
 (i) a high solute containing reject stream, and 
 (ii) a low solute containing product stream; 
   
     
     
         25 . The process as set forth in  claim 24 , wherein said membrane separator comprises a reverse osmosis membrane separator. 
     
     
         26 . The process as set forth in  claim 24 , wherein said membrane separator comprises a loose reverse osmosis separator. 
     
     
         27 . The process as set forth in  claim 24 , wherein said membrane separator comprises a nanofiltration separator. 
     
     
         28 . The process as set forth in  claim 24 , wherein in the pH of said acidic feedwater stream is adjusted to a pH of about 2.6 or lower. 
     
     
         29 . The process as set forth in  claim 24 , wherein said acidic feedwater stream comprises total organic carbon (TOC) constituents, and wherein said total organic carbon (TOC) constituents are substantially prevented from entering said product stream. 
     
     
         30 . The process as set forth in  claim 29 , wherein said total organic carbon (TOC) constituents in said product stream are approximately ten percent (10%) or less of the concentration of such constituents in said acidic feedwater stream. 
     
     
         31 . The process as set forth in  claim 24 , wherein said acidic feedwater stream comprises sodium ions, and wherein said product stream contains approximately two percent (2%) or less of the sodium ion concentration present in said feedwater stream. 
     
     
         32 . The process as set forth in  claim 24 , wherein said acidic feedwater stream comprises ammonium ions, and wherein said product stream contains approximately eight percent (8%) or less of the ammonium ion concentration present in said acidic feedwater stream. 
     
     
         33 . The process as set forth in  claim 24 , wherein said acidic feedwater stream comprises chloride ions, and wherein said product stream contains approximately twenty five percent (25%) or less of the chloride ion concentration present in said acidic feedwater stream. 
     
     
         34 . The process as set forth in  claim 1 , or in  claim 11 , or in  claim 24 , further comprising treating said product stream in an anion exchange system, said anion exchange system removing free mineral acidity from said product stream. 
     
     
         35 . The process as set forth in  claim 34 , wherein said anion exchange system is selected as one or more system from the group consisting of (a) a weak base anion exchange system, (b) an intermediate base anion exchange system, and (c) a strong base anion exchange system. 
     
     
         36 . The process as set forth in  claim 34 , wherein said anion exchange system effectively removes all anions contained in said product stream. 
     
     
         37 . The process as set forth in  claim 24 , wherein said pretreatment comprises adding ferric or ferrous ions to said acidic feedwater stream. 
     
     
         38 . The process as set forth in  claim 37 , further comprising adding hydrogen peroxide to said acidic feedwater stream. 
     
     
         39 . The process as set forth in  claim 24 , wherein said pretreatment comprises use of cation exchange. 
     
     
         40 . The process as set forth in  claim 39 , wherein said pretreatment using cation exchange comprises use of weak acid cation exchange. 
     
     
         41 . The process as set forth in  claim 39 , wherein said pretreatment using cation exchange comprises use of strong acid cation exchange. 
     
     
         42 . The process as set forth in  claim 27 , wherein said pretreatment comprises irradiation of said acidic feedwater stream with a UV light source, and wherein said total organic carbon constituents are effectively eliminated from said product stream. 
     
     
         43 . The process as set forth in  claim 29 , further comprising irradiation of said product stream with a UV light source, and wherein said total organic carbon constituents are effectively eliminated from said product stream. 
     
     
         44 . The process as set forth in  claim 24 , wherein said pretreatment process comprises oxidant removal, said oxidant removal comprising the addition of sodium meta-bisulfite to said feedwater stream. 
     
     
         45 . The process as set forth in  claim 24 , further comprising one or more additional pretreatment processes, said additional pretreatment processes comprising (i) media filtration, (ii) cartridge filtration, (iii) ultrafiltration, (iv) nanofiltration, or (v) degasification. 
     
     
         46 . The process as set forth in  claim 24 , further comprising one or more additional pretreatment processes, said additional pretreatment processes comprising (i) media filtration, (ii) cartridge filtration, (iii) ultrafiltration, (iv) nanofiltration, (v) degasification, or (vi) oxygen removal. 
     
     
         47 . The process as set forth in  claim 24 , wherein said acidic feedwater stream comprises hydrogen peroxide, and wherein said process further comprises treatment of said acidic feedwater stream in an activated carbon system, so as to effective remove hydrogen peroxide from said acidic feedwater stream. 
     
     
         48 . The process as set forth in  claim 24 , further comprising ozonation of said feedwater stream with an ozone containing gas, and wherein said total organic carbon (TOC) constituents are effectively prevented from entering said product stream. 
     
     
         49 . The process as set forth in  claim 24 , further comprising ozonation of said product water stream with an ozone containing gas, and wherein said total organic carbon (TOC) constituents are effectively eliminated from said product stream.