Method and apparatus for recovering liquid and solid constituents of water solutions containing sparingly soluble solids

• US 4,176,057 A
• Filed: 06/24/1977
• Issued: 11/27/1979
• Est. Priority Date: 06/24/1977
• Status: Expired due to Term

• Current Assignee: El Paso Environmental Systems Incorporated
• Original Assignee: El Paso Environmental Systems Incorporated
• Inventors: Wheatley, Robert T., Kosarek, Louis J.
• Primary Examiner(s): Spear, Jr., Frank A.
• Application Number:
  US05/809,751
• Time in Patent Office: 886 Days
• Field of Search: 210/23 H, 210/23 F, 210/433 M, 210/71, 210/321 R, 210/48, 210/58, 210/73 R, 210/137, 210/170, 210/188, 210/259 M
• US Class Current: 210/637
• CPC Class Codes: B01D 2321/12 Use of permeate
• CPC Class Codes: B01D 2321/162 Use of acids
• CPC Class Codes: B01D 61/025 Reverse osmosis; Hyperfiltration
• CPC Class Codes: B01D 65/08 Prevention of membrane fouling or of concentration polarisation
• CPC Class Codes: C02F 1/5236 using inorganic agents
• CPC Class Codes: C02F 9/00 Multistage treatment of water, waste water or sewage
• CPC Class Codes: Y02W 10/37 using solar energy

Abstract

Water, such as the effluent from cooling towers, boilers, waste streams of industrial plants, hydrometallurgical processes or other sources of water solutions containing sparingly soluble solids is efficiently separated into its aqueous and solid constituents by reverse osmosis and chemical treatments effective to achieve a zero discharge of effluent and a minimum volume of sludge or a recovery of valuable solids.

Claims

1. In a method of recovering liquid and solid constituents of water solutions containing sparingly soluble solids using a reverse osmosis unit with a chemically treated, recycled brine stream, the improvements which comprise:

pre-treating the water solution with chemicals which increase the solubility of the sparingly soluble constituents thereof,

flowing the pre-treated water solution through a reverse osmosis unit,

controlling the rate of flow of the pre-treated water solution through the reverse osmosis unit just above a flow rate that would allow precipitation of solids inside of the reverse osmosis unit to discharge a supersaturated brine and purified water permeate,

reacting the supersaturated brine with a trivalent cation to precipitate the sparingly soluble solids,

flushing the reverse osmosis unit with permeate to prevent fouling of the membrane of the unit, and

recovering the permeate.

2. The method of recovering liquid and solid constituents of water solution containing sparingly soluble solids which comprises:

adjusting the temperature of the water solution within a temperature range of about 60°

to 95°

F.,

adjusting the pH of the solution within the range of about 7 to 8,

filtering the thus adjusted solution,

reducing the pH of the filtered solution within the range of about 5 to 5.5,

reacting the solution with a polyphosphonate to increase the solubility of the solids in the solution,

pumping the reacted solution through a reverse osmosis unit to separate the solution into a permeate and a brine containing the dissolved solids,

decarbonating the permeate from said unit to produce purified water,

adjusting the pH of the brine from said unit to about 7,

subjecting the adjusted brine to the following reactions;

space="preserve" listing-type="equation">1. X.sub.2 (Y).sub.3 +3Z(HCO.sub.3).sub.2 →

3ZY+2X(OH).sub.3 +6CO.sub.2

space="preserve" listing-type="equation">2. X(HCO.sub.3).sub.2 +Z(OH).sub.2 →

2ZCO.sub.3 +2H.sub.2 O

wherein;

X is a trivalent cation such as boron, aluminum, scansium, reduced titanium, chromium, manganese, oxidized iron, oxidized cobalt, oxidized nickel, gallium, arsenic, yttrium, reduced niobium, reduced molybdenum, rhodium, indium, reduced antimony, lanthanum, iridium, gold, oxidized thallium, reduced bismuth or the rare earths,

Y is a divalent anion such as sulfate, molybdate, phosphate, chromate, mangnate, arsenate, borate, fluorosilicate, germanate, nitrite, oxalate, sulfite, tellurite, thiosulfate, tungstate or uranate,

Z is a divalent cation such as beryllium, magnesium, calcium, reduced vanadium, reduced chromium, reduced manganese, reduced iron, reduced cobalt, reduced nickel, copper, zinc, strontium, palladium, cadmium, barium, reduced platinum, oxidized mercury, lead, polonium, or radium,

separating the liquid and solid products of said reactions, and recycling the separated liquid to the water solution for further recovery therewith.

3. The method of claim 2 wherein the brine is subjected to the following representative reaction:

space="preserve" listing-type="equation">2AlCl.sub.3 +3SO.sub.4 =+3Ca.sup.++ +6HCO.sub.3 →

3CaSO.sub.4 +2Al(OH).sub.3 +6CO.sub.2 +6Cl.sup.-.

4. The method of claim 2 wherein the solid products are collected as a flowable sludge which is settled to provide a further water constituent for recycling back to the water solution.

5. The method of claim 2 wherein the solution is pumped into the reverse osmosis unit at pressures of from 400 to 800 p.s.i..

6. The method of separating water containing sparingly soluble solids into its water and solids constituents which comprises:

reacting the water with a chemical increasing the solubility of the sparingly soluble solids in the water,

pumping the water solution through a reverse osmosis unit to separate the reacted solution into purified water and a supersaturated brine containing the dissolved solids,

reacting the supersaturated brine with trivalent cations to precipitate dissolved solids from the brine,

separating the solids from the liquid portion of the thus reacted brine, and

feeding the clarified liquid portion of the reacted brine to the water solution being fed to the reverse osmosis unit.

7. The method of claim 6 including the step of adjusting the pH of the water solution to 5 to 5.5 before pumping the solution into the unit.

8. The method of purifying waste waters containing dissolved sparingly soluble solids and suspended solids which comprise:

feeding the waste water to a settling pond,

decanting water from the pond to a mixing control vessel,

introducing chemicals into the vessel for admixture with the water to adjust the pH value of the water,

adding anti-scalent to the water in the mixing vessel to increase the solubility of the sparingly soluble solids in the water and scaling of subsequent treating apparatus,

pumping the chemically treated water through a reverse osmosis unit to separate the water into a supersaturated brine and a water permeate,

decarbonating the permeate to provide purified water,

chemically treating the supersaturated brine to precipitate solids therefrom, and recycling the liquid portion of the chemically treated supersaturated brine back to the settling pond.

9. The method of claim 8 including the step of collecting the precipitated solids in flowable sludge form and collecting the sludge in a solid evaporation pond.

10. In a reverse osmosis method of separating a water solution of solids into its water and solids constituents, the improvements which comprise:

reacting the solution with a polyphosphonate to increase the solubility of the sparingly soluble solid in the solution,

controlling the rate of flow of the reacted solution through osmosis membranes just above a rate allowing precipitation of solids forming a supersaturated brine,

chemically treating the thus formed supersaturated brine to precipitate solids therefrom, and

recycling the liquid portion of the precipitated brine back to the water solution.

11. Apparatus for separating water solutions into constituent solid and purified water portions which comprises:

a settling pond for receiving the water solution,

a feed pump for decanting water from said pond,

heating and cooling means adjusting the temperature of the water input to said pump within the range of 65°

to 95°

F.,

a mixing vessel receiving the water from said pump,

apparatus for introducing chemicals into said mixing vessel for adjusting the pH value of the water therein and for adding anti-scalent to the water,

a filter receiving water from said mixing vessel,

apparatus for introducing a polyphosphonate to the water after filtration to increase the solubility of the solids in the water solution,

a reverse osmosis unit receiving water under pressure from said feed pump,

membranes in said unit separating the water into a permeate and a brine,

means controlling the flow rate through the unit just above a rate allowing precipitation of the solids and thereby form a supersaturated brine,

a decarbonator receiving the permeate,

a pump for pumping the decarbonated permeate to storage,

a reactor receiving the supersaturated brine from the reverse osmosis unit,

means for introducing chemicals into said reactor to precipitate solids from the supersaturated brine,

a tank receiving the chemically treated supersaturated brine from the reactor having a bottom outlet for settled solids and a decanting top outlet for clarified brine liquid,

a decant pit receiving the settled out solids from said tank,

a polishing precipitator receiving the clarified brine from said tank, and

a recycling pump feeding the clarified brine back to the mixing vessel for admixture with the water solution from the feed pump

whereby dissolved chemicals in the clarified brine effectively decrease the amount of chemicals needed for adjusting the pH value and the anti-scalent capacity of the water fed to the filter.

12. The apparatus of claim 11 including an inline mixer receiving filtered solution from said filter, and a chemical injector feeding chemicals to the filtered solution entering the mixer for reducing the pH of the solution to about 5 to 5.5.

13. A closed loop apparatus for recycling waste water containing sparingly soluble solids from an industrial plant which comprises:

a settling pond receiving the waste water,

a mixing vessel,

means decanting water from pond to said vessel,

means introducing chemicals to said vessel to adjust the pH of the solution within the range of 7 to 8,

means filtering the chemically treated solution,

means for introducing chemicals into the filtered solution to reduce the pH thereof within the range of 5 to 5.5,

means for introducing chemicals into the reduced solution to increase the solubility of the sparingly soluble solids in the water,

a reverse osmosis unit,

a high pressure pump feeding the reduced pH solution to said unit for separating the solution into a water permeate and a supersaturated brine containing the solids,

means controlling the flow rate through said unit just above a rate allowing precipitation of the solids,

means feeding the permeate for reuse in the plant,

means adding chemicals to the supersaturated brine effective to precipitate solids therefrom,

means separating a solid sludge and a clarified brine from the chemically treated supersaturated brine,

a decant pit receiving the sludge,

means feeding decant water from the pit to the pond, and

means feeding the clarified brine to the mixing vessel.