Water treatment process for oilfield produced water Number:7,520,993 from the United States Patent and Trademark Office (PTO) owispatent The invention relates to a method and system for treating an aqueous liquid containing dissolved minerals and dissolved hydrocarbons. Method steps and apparatus for treating a waste water feed stream are disclosed which utilize a warm lime softening system in fluid communication with the waste water feed stream, wherein sludge from the warm lime softening system is recycled to improve lime utilization and enhance silica and boron removal without the addition of an external source of magnesium. In addition, a microfiltration system and/or an air stripper system may be used in fluid communication with at least one reverse osmosis system to produce a treatment water that meets state and federal guidelines for surface discharge.<H treatment, produced, Water, treatment, 7520993.html, Patent, pto, 7520993

Title: Water treatment process for oilfield produced water

Abstract: The invention relates to a method and system for treating an aqueous liquid containing dissolved minerals and dissolved hydrocarbons. Method steps and apparatus for treating a waste water feed stream are disclosed which utilize a warm lime softening system in fluid communication with the waste water feed stream, wherein sludge from the warm lime softening system is recycled to improve lime utilization and enhance silica and boron removal without the addition of an external source of magnesium. In addition, a microfiltration system and/or an air stripper system may be used in fluid communication with at least one reverse osmosis system to produce a treatment water that meets state and federal guidelines for surface discharge.

Patent Number: 7,520,993 Issued on 04/21/2009 to Laraway, et al.

Inventors: Laraway; James W. (West Jordan, UT), Weber; Richard E. (Zephyrhills, FL), Thomas; Donald J. (Tooele, UT)
Assignee: Water & Power Technologies, Inc. (Salt Lake City, UT)

Appl. No.: 11/999,582

Filed: December 6, 2007

Current U.S. Class: 210/652 ; 210/175; 210/195.2; 210/639; 210/650; 210/660; 210/749; 210/766; 210/767; 210/805; 96/234

Current International Class: B01D 61/00 (20060101); A61M 1/16 (20060101); C02F 1/44 (20060101)

Field of Search: 210/639,650,652,767,805,660,262,175,195.2,749,766 96/234 166/266

References Cited [Referenced By]

U.S. Patent Documents


2428418	October 1947	Goetz et al.
3639231	February 1972	Bresler
3715287	February 1973	Johnson
3721621	March 1973	Hough
3870033	March 1975	Faylor et al.
3953580	April 1976	Allen
3964999	June 1976	Chisdes
3985648	October 1976	Casolo
3992291	November 1976	Hirs
4008162	February 1977	Korenowski et al.
4035469	July 1977	Richmond et al.
4182676	January 1980	Casolo
4201758	May 1980	Allain et al.
4224148	September 1980	Lindman et al.
4235715	November 1980	Wiegert
4277344	July 1981	Cadotte
4311679	January 1982	Queneau et al.
4321145	March 1982	Carlson
4384889	May 1983	Wiewiorowski et al.
4402835	September 1983	Mattera et al.
4430226	February 1984	Hegde et al.
4434057	February 1984	Marquardt
4465597	August 1984	Herman et al.
4497781	February 1985	Spoors et al.
4532045	July 1985	Littmann
4532047	July 1985	Dubin
4548716	October 1985	Boeve
4571263	February 1986	Weir et al.
4574043	March 1986	Chester et al.
4574049	March 1986	Pittner
4619814	October 1986	Salter et al.
4670150	June 1987	Hsiung et al.
4698153	October 1987	Matsuzaki et al.
4755298	July 1988	Grinstead
4818410	April 1989	Bellos et al.
4820421	April 1989	Auerswald
4824574	April 1989	Cadotte et al.
4839054	June 1989	Ruebush et al.
4900450	February 1990	Schmidt
4917806	April 1990	Matsunaga et al.
4969520	November 1990	Jan et al.
4995983	February 1991	Eadie et al.
5028336	July 1991	Bartels et al.
5061374	October 1991	Lewis
5071477	December 1991	Thomas et al.
5073268	December 1991	Saito et al.
5076930	December 1991	Rubin
5076934	December 1991	Fenton
5128042	July 1992	Fenton
5174901	December 1992	Smith
5236590	August 1993	Sciamanna et al.
5236722	August 1993	Schroeder
5246586	September 1993	Ban et al.
5246589	September 1993	Nichols et al.
5250185	October 1993	Tao et al.
5266203	November 1993	Mukhopadhyay et al.
5292439	March 1994	Morita et al.
5338456	August 1994	Stivers
5352345	October 1994	Byszewski et al.
5358640	October 1994	Zeiher et al.
5385664	January 1995	Oinuma et al.
5401296	March 1995	Martenson et al.
5403495	April 1995	Kust et al.
5439592	August 1995	Bellos et al.
5476591	December 1995	Green
5489326	February 1996	Thomas et al.
5529689	June 1996	Korin
5536297	July 1996	Marchbank et al.
5571419	November 1996	Obata et al.
5573662	November 1996	Abe et al.
5573666	November 1996	Korin
5645727	July 1997	Bhave et al.
5670053	September 1997	Collentro et al.
5695643	December 1997	Brandt et al.
5766479	June 1998	Collentro et al.
5804078	September 1998	Morrow et al.
5814224	September 1998	Khamizov et al.
5855793	January 1999	Ikeda et al.
5879562	March 1999	Garbutt
5879563	March 1999	Garbutt
5925255	July 1999	Mukhopadhyay
6039789	March 2000	McMullen et al.
6054050	April 2000	Dyke
6071413	June 2000	Dyke
6207059	March 2001	Moore, III
6267891	July 2001	Tonelli et al.
6296773	October 2001	McMullen et al.
6461514	October 2002	Al-Samadi
6537456	March 2003	Mukhopadhyay
6695968	February 2004	Hart
6919031	July 2005	Blumenschein et al.
6964737	November 2005	Abu-Orf et al.
7097769	August 2006	Liberman et al.
7132052	November 2006	Rawson et al.
7150320	December 2006	Heins
7368058	May 2008	Nishikawa et al.
7442309	October 2008	Wilf et al.
2004/0035802	February 2004	Emery et al.
2005/0051488	March 2005	Nagghappan et al.
2005/0194323	September 2005	Ruth et al.
2005/0244313	November 2005	Petrik
2005/0279716	December 2005	Jackman
2007/0083398	April 2007	Ivey et al.
2008/0135478	June 2008	Zuback et al.

Foreign Patent Documents


1 792 304	Mar., 1972	DE
26 07 737	Sep., 1976	DE
196 03 494	Aug., 1997	DE
0044872	Feb., 1982	EP
50-075987	Jun., 1975	JP
50-088017	Jul., 1975	JP
53-004777	Jan., 1978	JP
53-046163	Apr., 1978	JP
54-069579	Jun., 1979	JP
54-083688	Jul., 1979	JP
55-012284	Jan., 1980	JP
56-139106	Oct., 1981	JP
57-071692	May., 1982	JP
58-118538	Jul., 1983	JP
58-122084	Jul., 1983	JP
59-112890	Jun., 1984	JP
59-166290	Sep., 1984	JP
61-204892	Sep., 1986	JP
62-110795	May., 1987	JP
62-204892	Sep., 1987	JP
62294484	Dec., 1987	JP
63-028486	Feb., 1988	JP
02-052088	Feb., 1990	JP
02-207888	Aug., 1990	JP
02-227185	Sep., 1990	JP
04-118004	Apr., 1992	JP
05-012040	Jan., 1993	JP
05-269463	Oct., 1993	JP
06-049191	Feb., 1994	JP
08-029315	Feb., 1996	JP
1560484	Apr., 1990	SU
WO 98/06483	Feb., 1998	WO
WO 99/50187	Oct., 1999	WO
WO 2007/051167	May., 2007	WO

Other References

Abdel-Wahab, et al., "An Equilibrium Model for Chloride Removal from Recycled Cooling Water Using the Ultra-High Lime with Aluminum Process," Water Environment Research, vol. 77, No. 7, pp. 3059-3065, Nov./Dec. 2005. cited by other .
Abdel-Wahab and Batchelor, "Chloride Removal from Recycled Cooling Water Using Ultr-High Lime with Aluminum Process," Water Environment Research, vol. 74, No. 3, pp. 256-263, May/Jun. 2002. cited by other .
Abdel-Wahab and Batchelor, "Effects of pH, Temperature, and Water Quality on Chloride Removal with Ultra-High Lime with Aluminum Process," Water Environment Research, vol. 78, No. 9, pp. 930-937, Sep. 2006. cited by other .
Abdel-Wahab and Batchelor, "Interactions Between Chloride and Sulfate or Silica Removals Using an Advanced Lime-Aluminum Softening Process," Water Environment Research, vol. 78, No. 13, pp. 2474-2479, Dec. 2006. cited by other .
Abdel-Wahab and Batchelor, "Interactions Between Chloride and Sulfate or Silica Removals from Wastewater Using an Advanced Lime-Aluminum Softening Process: Equilibrium Modeling," Water Environment Research, vol. 79, No. 5, pp. 528-535, May 2007. cited by other .
Batchelor and McDevitt, "An innovative process for treating recycled cooling water," Journal WPCF, vol. 56, No. 10, pp. 1110-1117, Oct. 1984. cited by other .
Batchelor, et al., "Removal of Sulfate from Recycled Cooling Water by the Ultra-High Lime Process," Water Reuse Symposium III, 1985. cited by other .
Batchelor, et al., "Technical and economic feasibility of ultra-high lime treatment of recycled cooling water," Research Journal WPCF, vol. 63, No. 7, pp. 982-990, Nov./Dec. 1991. cited by other .
Okey and Coombs, "Enhanced Silica Removal in Solids Contact Systems," EIMCO Process Equipment Company, Salt Lake City, Utah, pp. 1-26, Jun. 1985. cited by other .
Alai, et al. "Evaporative evolution of a Na-Cl-NO.sub.3-K-Ca-SO.sub.4-Mg-Si brine at 95.degree. C: Experiments and modeling relevant to Yucca Mountain, Nevada." Geochemical Transactions, vol. 6, No. 2, pp. 31-45. Jun. 2005. cited by other .
Allegrezza, Jr. "Commercial Reverse Osmosis Membranes and Modules." Bipin S. Parekh (Ed.) Reverse Osmosis Technology--Applications for High-Purity-Water Production. Chapter 2, pp. 53-120. cited by other .
Bridle, Michael K. "Esso's Experience with Produced and Waste Water Recycle Systems." Esso Resources Canada Limited. Energy Processing/Canada, pp. 8, Sep.-Oct. 29-32, 1986. cited by other .
Cadotte, John E. "Evolution of Composite Reverse Osmosis Membranes." 1985 American Chemical Society. FilmTec Corporation, Minneapolis, MN 55435. cited by other .
DeSilva, Francis J. "Essentials of Ion Exchange." 25.sup.th Annual WQA Conference Mar. 17, 1999. cited by other .
Doran and Leong. "Developing a Cost Effective Environmental Solution for Produced Water and Creating a `New` Water Resource." ARCO Western Energy, 4550 California Ave., Bakersfield, CA 93302. Apr. 28, 1997. cited by other .
Doran. "Developing a Cost Effective Environmental Solution for Produced Water and Creating a `New` Water Resource." ARCO Western Energy, 4550 California Ave., Bakersfield, CA 93302. May 2000. cited by other .
Dorr-Oliver Eimco. "EIMCO.RTM. MAXR.TM. Treatment Process--Maximum Removal of Soluble Species Using Physical Chemical Treatment". GL&V EMC 3330, 2003. cited by other .
Dyke, et al. "Removal of Salt, Oil, and Boron from Oil Field Wastewater by High pH Reverse Osmosis Processing."Sep. 1992. cited by other .
Fritz and Tiwari. "An Economical New Zero Liquid Discharge Approach for Power Plants." Power-Gen International, Dec. 10-12, 2002. cited by other .
Goldberg and Glaubig. "Boron Adsorption on Aluminum and Iron Oxide Minerals." Soil Sci. Soc. Am. J., vol. 49, pp. 1374-1379, 1985. cited by other .
Gunnarsson, et al. "Magnesium-silicate scales in geothermal utilization. An experimental study." Science Institute University of Iceland RH-06-02. Apr. 2002. cited by other .
Idelovitch, et al. "The Role of Groundwater Recharge in Wastewater Reuse: Israel's Dan Region Project." American Water Works Association. Research and Technology Jounral AWWA, pp. 391-400, Jul. 1980. cited by other .
Infilco Degremont. "Borate Rejection by B-9 Permeators." Dec. 19, 1990. cited by other .
Jun, et al. "Semiconductors--High-Purity Water System Upgrade in Singapore Using High-Efficiency RO." UltraPure Water.RTM. May/Jun. 2004, pp. 27-30. cited by other .
Kawamura. "Specific Water Treatment Processes." Integrated Design of Water Treatment Facilities. Chapter 7, pp. 488-499. cited by other .
Koch Membrane Systems. "Fluid Systens.RTM. TFC.RTM. --XR8" Elements--Extra High Rejection RO Elements for Brackish Water. 2005. cited by other .
Lurie, et al. "Applying Reverse Osmosis in Dilute Fluoride-waste Treatment." Solid State Technology Mar. 2005 Online. www.solid-state.com. Tower Semiconductor Ltd., Migdal Haemek, Isreal. cited by other .
LNSP Nagghappan. "Desalination of Produced Water Using OPUS Technology" SPE Thermal and Facilities Study Group Luncheon, Jan. 9, 2007, Bakersfield, CA, Petroleum Club, International Water Conference 2006. cited by other .
McBride, Sr., and Mukhopadhyay. "Semiconductors--High Water Recovery and Solute Rejection Through a New RO Process." UltraPure Water.RTM. May/Jun. 1997, pp. 24-27. cited by other .
National Drinking Water Clearinghouse. "Membrane Filtration." Tech Brief 10, Mar. 1999. cited by other .
Nebgen, et al. "The Alumina-Lime-Soda Water Treatment Process." Research and Development Progress Report No. 820. United States Department of the Interior. Jan. 1973. cited by other .
Parks and Edwards. "Boron in the Environment." Critical Reviews in Environmental Science and Technology, 35:81-114, 2005. Taylor & Francis, Inc. cited by other .
Parks and Edwards. "Boron Removal via Formation of Magnesium Silicate Solids during Precipitative Softening." Journal of Environmental Engineering, Feb. 2007, pp. 149-156. cited by other .
Parks and Edwards. "Precipitative Removal of As, Ba, B, Cr, Sr, and V Using Sodium Carbonate." Journal of Environmental Engineering pp. 489-496, May 2006. cited by other .
Recepoglu and Beker. "A Preliminary Study on Boron Removal from Kizildere/Turkey Geothermal Waste Water." Geothermics, vol. 20, No. 1/2, pp. 83-89, 1991. Pergamon Press plc. cited by other .
Rigdon, Lester. "Defluoridation Study for Boise Geothermal Water."Lawrence Livermore Laboratory. Jun. 3, 1980. cited by other .
Sauer, et al. "Semiconductors--Boron Removal Experiences at AMD." UltraPure Water.RTM. May/Jun. 2000, pp. 62-68. cited by other .
Scott, et al. "Fluoride in Ohio Water Supplies--Its Effect, Occurrence and Reduction." J.A.W.W.A. vol. 29, No. 1, pp. 9-25. cited by other .
Stoessell, R. K. "25.degree. C. and 1 atm Dissolution Experiments of Sepiolite and Kerolite." Geochimica et Cosmochimica Acta vol. 52, pp. 365-374. Pergamon Journals Ltd. 1988. cited by other .
Tao, et al. "Conversion of Oilfield Produced Water Into an Irrigation/Drinking Quality Water." Society of Petroleum Engineers (SPE) 26003, pp. 571-579, Mar. 1993. cited by other .
Toray Membrane America, Inc. "TORAY Seawater RO Elements TM800." 12520 High Bluff Drive, Suite 120, San Diego, CA 92130. Feb. 2004. cited by other .
USFilter Corporation. "Auto-Shell.TM. Filter: Walnut Shell Filtration". www.zimpro.usfilter.com. 2005. cited by other .
VandeVenter, et al. "Innovative Processes Provide Cogeneration Power Plant with the Ability to Utilize Oil Field Water." With Prepared Discussion by R. Gregory Balmer. 50.sup.th Annual Meeting of the International Water Conference, Pittsburgh, PE, Oct. 23-25, 1989. cited by other .
Waggott, A. "An Investigation of the Potential Problem of Increasing Boron Concentrations in Rivers and Water Courses." Water Research, vol. 3, pp. 749-765. Pergamon Press 1969. cited by other .
Zalewski, et al. "Produced Water Recycling at BP Resources--Petro Canada's Wolf Lake Plant." Mar. 14, 1991. cited by other .
Aronovitch and Ford. "Weakly Acidic Cation Performance Treating Water Containing High Iron." Utrapure Water. vol. 12, No. 4, pp. 60, 62-64. May/Jun. 1995. cited by other .
Auerswald. "Optimizing the Performance of Reverse Osmosis/Continuous Electrodeionization System." Ultrapure Water, pp. 34-52, May/Jun. 1996. cited by other .
Crabbe. "A Double Pass Reverse Osmosis System." Industrial Water Engineering, vol. 13, No. 6, Dec. 1976/Jan. 1977. (Adapted from a paper delivered at the "Second Annual Conference on New Advances in Separation Technology" Cherry Hill, NJ, Sep. 24, 1976). cited by other .
Hydranautics. "Membrane Element 4040-LST-CPA2." 1994. cited by other .
FilmTec Corporation. "4'' Brackish Water Element Specifications." Technical Bulletin, Jan. 1984. cited by other .
FilmTec Corporation. "4'' Brackish Water RO Element Specifications." Technical Bulletin, Dec. 1982. cited by other .
FilmTec Corporation. "8'' Brackish Water RO Element Specifications." Technical Bulletin, Dec. 1982. cited by other .
FilmTec Corporation (The Dow Chemical Company). "FilmTec Membranes, Membrane System Design Guidelines," Product Information, Mar. 1996. cited by other .
FilmTec Corporation (The Dow Chemical Company). "FilmTec Membranes, FT-30 Membrane Description," Technical Bulletin, Dec. 1992. cited by other .
FilmTec Corporation. "FilmTec Membrane Elements: System Design, Introduction to Reverse Osmosis, Water Chemistry and Pretreatment." Technical Manual, pp. 1, 9, 11, 13-14, Apr. 1995. cited by other .
Handbook of Membrane Technology, Jul. 15, 1985, pp. 184-198. cited by other .
Idelovitch and Wachs. "Magnesium Recycling by Carbonation and Centrifugation of High-lime Wastewater Sludge." Journal WPCF (Water Pollution Control Federation), vol. 55, No. 2, pp. 136-144 (XP-002092114). cited by other .
Miyaharo, et al. "Practical Ion Exchange," Jan. 1, 1972, published by Kagaku Kogyo Ltd., pp. 99-102. cited by other .
Okay, et al. "Boron Pollution in the Simav River, Turkey and Various Methods of Boron Removal." Water Research vol. 19, No. 7, p. 857-562, 1985. cited by other .
Parks and Abrams. "Fundamentals of Ion Exchange in Water Treatment." Presented at the 7.sup.th Annual Liberty Bell Corrosion Conference, 1969. Heating, Piping and Air Conditioning (HPAC Engineering), vol. 42, No. 8, pp. 98-102, Aug. 1970. cited by other .
Petersen, et al. "Development of the FT-30 Thin-Film Composite Membrane for Desalting Applications." National Water Supply Improvement Association, 8.sup.th Annual Conference and International Trade Fair, San Francisco, California, Jul. 6-10, 1980. cited by other .
Shikoku Electric Power Co., Ltd., "Annual Research Report No. 42," Sep. 1983. cited by other .
Turek. "The Influence of Magnesium Hydroxide Precipitation Conditions on the Boron Content." Polish Journal of Applied Chemistry, pp. 211-213, 1995 (XP-002092123). cited by other .
U.S. Filter Corporation. "FlexRO.RTM. Reverse Osmosis Systems." 1995. cited by other .
Wong. "Boron Control in Power Plant Reclaimed Water for Potable Reuse." Environment Progress, vol. 3, No. 1, pp. 5-11, Feb. 1984. cited by other .
Zosui Gijutsu (Water Producing Technology) vol. 10, No. 2, pp. 13-22, 1984. cited by other .
Rautenbach, "Membranverfahren" 1997, Springer-Verlag, Berlin, XP002508147, pp. 152-154. cited by other.

Primary Examiner: Fortuna; Ana M
Attorney, Agent or Firm: Morriss O'Bryant Compagni

Claims

What is claimed is:

1. A method of treating an aqueous liquid containing dissolved minerals and dissolved hydrocarbons, the method comprising: passing an aqueous liquid containing dissolved minerals and dissolved hydrocarbons through a warm lime softener, with a pH of liquid in the warm lime softener raised to a pH of about 11; adjusting the pH of an effluent from the warm lime softener to a pH of between about 9 and about 9.6 by adding a mineral acid; and passing the effluent from the warm lime softener through a microfilter and an ion exchange based softener in fluid communication with the microfilter prior to contacting a reverse osmosis system; and passing an effluent from the reverse osmosis system through an air stripper.

2. The method according to claim 1, further comprising recycling at least a part of a precipitate sludge produced by the warm lime softener back into the warm lime softener.

3. The method according to claim 1, wherein the aqueous liquid in the warm lime softener is at a temperature of between about 140.degree. F. and about 210.degree. F.

4. The method according to claim 1, further comprising raising the pH of an effluent from the microfilter to about a pH of 11 and adding an antiscalant/dispersant for silica scale prevention before contacting the reverse osmosis system.

5. The method according to claim 4, further comprising passing the effluent from the warm lime water softener through a granular filter media or an ion exchange softener prior to passing through the microfilter.

6. The method according to claim 5, wherein the granular filter media comprises walnut shells.

7. The method according to claim 4, further comprising passing an effluent from the air stripper through a second reverse osmosis system and passing the effluent from the ion exchange based softener in fluid communication with the microfilter through an air cooled heat exchanger and evaporative cooler prior to contacting the first reverse osmosis system.

8. The method according to claim 7, further comprising neutralizing the pH of the effluent from the air stripper system to a pH of about 7.

9. The method according to claim 8, further comprising producing a discharge water meeting California irrigation water regulations.

10. A waste water treatment system comprising: a waste water feed stream; a warm lime softening system in fluid communication with the waste water feed stream, wherein the warm lime softening system comprises a lime silo, a sodium carbonate silo and a caustic storage tank in fluid communication with a lime and soda precipitation softener vessel; a sludge storage tank in fluid communication with the lime and soda precipitation softener vessel, wherein contacting the waste water feed stream with lime and sodium carbonate in the lime and soda precipitation softener vessel produces a particulate suspension that settles to produce a sludge that is recycled back to the lime and soda precipitation softener vessel; a microfiltration system in fluid communication with the lime and soda precipitation softener vessel; a first pass reverse osmosis system in fluid communication with the microfiltration system; an air stripper system in fluid communication with the first pass reverse osmosis system; and a second pass reverse osmosis system in fluid communication with the air stripper system.

11. The system of claim 10, further comprising an ion exchange softener in fluid communication with the microfiltration system.

12. The system of claim 11, wherein the guard softener comprises a sodium cycle ion exchange softener.

13. The system of claim 10, wherein the caustic storage tank is configured to raise the pH of the waste water feed stream in the lime and soda precipitation softener vessel to a pH of about 11.

14. The system of claim 13, wherein the caustic storage tank is further configured to raise the pH of a waste water stream in the microfiltration system to about a pH of 11 before contacting the first pass reverse osmosis system.

15. The system of claim 14, further comprising an acid tank in fluid communication with the effluent from the air stripper system configured to adjust the pH of the effluent to about 7.

16. The system of claim 10, further comprising an inlet alkalization tank and a high energy mixer in fluid communication with the lime and soda precipitation softener vessel, wherein the inlet alkalization tank and high energy mixer are configured to contact the waste water with fresh lime and recycled sludge.

17. The system of claim 10, wherein the microfilter comprises an outside-in, near dead end, hollow fiber microfilter.

18. The system of claim 10, further comprising a granular activated carbon system in fluid communication with an effluent from a reverse osmosis system.

19. The system of claim 10, further comprising an additional treatment system selected from the group consisting of a cooling system in fluid communication with the lime and soda ash precipitation softener vessel comprising an air cooled heat exchanger and/or an evaporative cooler; an ion exchange resin softener system in fluid communication with the microfiltration system; a caustic storage tank configured to raise the pH of the waste water feed stream in the lime and soda precipitation softener vessel to a pH of about 11; an acid tank in fluid communication with an effluent from the air stripper system configured to adjust the pH of the effluent to about 7; a degasification system in fluid communication with the warm lime softening system; an inorganic coagulant system in fluid communication with the warm lime softening system; and combinations thereof.

Description

TECHNICAL FIELD

The invention relates to the removal of solutes from an aqueous solvent, more particularly, to the removal of solutes present in oil field produced water to a level sufficient to meet state and/or federal requirements for discharge of the treated water.

BACKGROUND

As oil supplies diminish the need for improved recovery methods continually increases. One of the predominant methods used to improve viscous or heavy crude oil recovery involves injecting steam into the oil well, see U.S. Pat. No. 5,080,172. Injecting steam into a well results in recovery of an oil/water mixture, where the water is typically removed from the oil and then contaminated produced water is lightly treated and recycled as poor quality steam back into the formation. This eventually results in an increase of the injection pressures over time as the recycled water builds up in the formation and eventually blocks the movement and recovery of known oil reserves in the formation. As a result, the produced water eventually has to be disposed of to decrease the volume of water in the formation and in turn improve production. However, disposal of this produced water is problematic due to the presence of a large number of solutes, including minerals and organic compounds, which requires that the produced water be injected underground at a remote site or treated for surface discharge.

With increasing water quality standards, surface discharge of the produced water has become even more problematic and has produced a need for methods to treat the produced water prior to discharge. In addition, the loss of drinking and/or irrigation water in arid regions presents a motivation to reclaim the produced water to a purity level allowing above ground disposal.

Unfortunately, the solutes present in produced water vary depending upon its origin and the particular characteristics of the oil well site. This has made the standardization of water treatment facilities difficult, if not impossible. California has imposed standards for irrigation water that require removal of certain elements or compounds to levels below those of the initial source water, see U.S. Pat. No. 5,250,185. In light of these difficulties, there is a need in the art for a water treatment method that removes the various solutes to levels that are acceptable for surface discharge under various state and/or federal regulations, particularly the California regulations.

SUMMARY OF THE INVENTION

The present invention comprises a method and system for treating an aqueous liquid containing dissolved minerals and dissolved hydrocarbons. In an exemplary embodiment, the method comprises passing an aqueous liquid containing dissolved minerals and dissolved hydrocarbons through a warm lime softener at a pH of about 11, wherein the effluent from the warm lime softener may have the pH adjusted to about 9 with an acid to minimize the continued precipitation of insoluble compounds before passing the effluent through a microfiltration system prior to contacting a reverse osmosis system.

In another exemplary embodiment, the method further includes one or more of the following: an ion exchange resin based softener in fluid communication with a microfiltration system; recycling at least a part of a precipitate sludge produced by the warm lime softener back into the warm lime softener; maintaining the temperature of the aqueous liquid in the warm lime softener between about 170.degree. F. and about 210.degree. F. (or about 180.degree. F.) (e.g., by installing insulation around the warm lime softener); passing an effluent from the reverse osmosis system through an air stripper; raising the pH of an effluent from a microfiltration system to a pH of about 11 before contacting the reverse osmosis system; passing the effluent from a warm lime water softener through a media filter comprising anthracite, walnut shells, garnet or similar media and combinations thereof; a second reverse osmosis system following the air stripper; neutralizing the pH of the effluent from the air stripper system to a pH of about 7; producing a discharge water meeting California irrigation water regulations; and combinations and permutations thereof.

In an exemplary embodiment, the system for treating an aqueous liquid containing dissolved minerals and dissolved hydrocarbons comprises passing the aqueous liquid, or a waste water feed stream, through a warm lime softener, wherein the warm lime softener or warm lime softening system comprises a lime silo, a sodium carbonate silo and a caustic storage tank in fluid communication with a lime and soda precipitation softener vessel, which is in fluid communication with a sludge storage tank, wherein contacting the waste water feed stream with lime and sodium carbonate in the lime and soda precipitation softener vessel produces a particulate suspension that settles to produce a sludge part of which may be recycled back to the lime and soda precipitation softener vessel. The system may also further include at least one of: a cooling system in fluid communication with the lime and soda ash precipitation softener vessel comprising an air cooled heat exchanger and/or an evaporative cooler; a microfiltration system in fluid communication with the cooling system; an ion exchange resin softener system in fluid communication with the microfiltration system; a first pass reverse osmosis system in fluid communication with the ion exchange resin softener system; an air stripper in fluid communication with the first pass reverse osmosis system; a second pass reverse osmosis system in fluid communication with the air stripper system; a caustic storage tank configured to raise the pH of the waste water feed stream in the lime and soda precipitation softener vessel and/or the membrane filtration system to a pH of about 11; an acid tank in fluid communication with the effluent of the air stripper system to adjust the pH of the effluent to about 7; and combinations thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings illustrate exemplary embodiments for carrying out the invention. Like reference numerals refer to like parts in different views or embodiments of the present invention in the drawings.

FIG. 1 is a flow chart of a method of water treatment according to an exemplary embodiment of the invention.

FIG. 2 is a flow chart illustrating a method of operating a warm lime softening system according to an exemplary embodiment of the invention.

FIG. 3 is a flow chart illustrating a method of operating a warm lime softening system according to an exemplary embodiment of the invention.

FIG. 4 is a flow chart illustrating a membrane filtration system according to an exemplary embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to systems and methods for treating waste water. It will be appreciated by those skilled in the art that the embodiments herein described, while illustrating certain embodiments, are not intended to so limit the invention or the scope of the appended claims. Those skilled in the art will also understand that various combinations or modifications of the embodiments presented herein can be made without departing from the scope of the invention. All such alternate embodiments are within the scope of the present invention. Similarly, while the drawings depict illustrative embodiments of devices and components in accordance with the present invention and illustrate the principles upon which the system is based, they are only illustrative and any modification of the invented features presented herein are to be considered within the scope of this invention.

As used herein and in the appended claims, the singular forms, for example, "a", "an", and "the," include the plural, unless the context clearly dictates otherwise. For example, reference to "a reverse osmosis membrane" includes a plurality of such membranes and equivalents thereof.

As used herein, "comprising," "including," "containing," "characterized by," and grammatical equivalents thereof are inclusive or open-ended terms that do not exclude additional, unrecited elements or method steps, but also includes the more restrictive terms "consisting of" and "consisting essentially of."

As used herein, "about 180.degree. F." means a temperature range of about 140.degree. F. to about 200.degree. F.

As used herein, "about 90.degree. F." means a temperature range of about 85.degree. F. to about 95.degree. F.

As used herein, "about 60.degree. F." means a temperature range of about 60.degree. F. to about 85.degree. F.

As used herein, "a microfiltration system" means a membrane based filtration system and is used merely to facilitate discussion of the system, no lower pore size limit is intended, thus the phrase includes microfiltration, ultrafiltration, and nanofiltration systems.

Referring to FIG. 1, feed water 2, or produced water is subject to oil separation and, optionally, passage through media filters 40. From the media filters 40 the oil separated feed water 4 enters a warm lime softener 60, which includes a clearing well 62, where hardness (e.g., calcium and magnesium), boron, and silica concentrations are reduced by precipitation to produce a softened feed water 6. From the warm lime softener 60, the softened feed water 6 is passed through a walnut shell filter 80 and an ion exchange resin water softener system 100 (e.g., such as a strong acid cation (SAC) exchange softener), which may include a soft water storage tank 102. The resulting softened and filtered feed water 14, 16 is next passed through a cooling unit 120 to drop the temperature of the softened and filtered feed water 14, 16 from about 180.degree. F. to about 90.degree. F. The cooled feed water 18 is then passed through a microfiltration system 140, which may include guard softeners 160 and/or reverse osmosis (RO) pretreatment cartridge filters 180, before contacting the first pass reverse osmosis (RO) system 200 (see FIG. 4). The first pass permeate 24 is then sent to an air stripper system 220 and then to a second pass RO system 240. The second pass RO permeate 28 is suitable surface discharge, although it may require some mineral or chemical addition and/or temperature change in order to comply with particular aspects of state and/or federal regulations, such as the California regulations concerning irrigation water.

In an exemplary embodiment, after an oil/water separation phase, which includes processes such as Induced Air Flotation (IAF) and other processes known in the art, the normal oil level in the produced water or oil separated feed water 4 is less than or equal to about 1 ppm, with occasional excursions to a maximum concentration of about 20 ppm. After the existing oil water separation process the treatment method may feed conditioning chemicals, such as a dispersant, to keep any remaining oil and grease dispersed or dissolved in the oil separated feed water 4. Media filtration 40 may optionally be used in a guard role ahead of the warm lime softener system 60. Such media filters may be operated for many weeks without any increase in differential pressure or decrease in flow. Optionally, sacrificial cartridge filters may be installed downstream of the oil/water separation phase and ahead of the warm lime softener system 60 to trap residual free oil carryover from the oil water separation process steps.

In another exemplary embodiment, a degasification system (e.g., a vacuum degasification system) may be used between an oil/water separation phase and the warm lime softener system 60. For example, carbon dioxide and hydrochloric acid may be used to condition (i.e., decrease the pH to an acidic condition, below a pH of about 7 or below about a pH of 4) feed water applied to the degasification system, thereby allowing the degasification system to remove or reduce the concentration of carbon dioxide or alkalinity, hydrogen sulfide, methane, and other volatile organics from the feed water (see U.S. Pat. Nos. 4,839,054 and 5,804,078). The degasification system may be a two stage system or a single stage system.

A vacuum degasification system may be operated at a vacuum level just a few millimeters of mercury above the vapor pressure of the water at the temperature of the water being treated. The flash to vapor may be controlled by bleeding the exhaust gases from the discharge of the vacuum pumps back into the vacuum draw lines used to evacuate the degasifier tower.

In another exemplary embodiment, an inorganic coagulant system, such as a ferric or aluminum coagulant system, may be used between an oil/water separation phase and the warm lime softener system 60, optionally the inorganic coagulant system my be combined with a degasification system (see, Enhanced Coagulation and Enhanced Precipitative Softening Guidance Manual, U.S. Environmental Protection Agency, 1999). For example, there may be an oil/water se