阅读说明：本技术 采出水的处理系统和用于从采出水回收有机化合物的方法 (Produced water treatment system and method for recovering organic compounds from produced water ) 是由 里吉斯·迪迪尔·阿兰·维拉吉内斯 纪尧姆·罗伯特·让·弗朗索瓦·雷内尔 于 2017-08-30 设计创作，主要内容包括：用于处理含有有机化合物的采出水的系统和方法包括处理容器(100)；过滤层(150),其包括过滤材料；和清洁系统,其在清洁循环期间向所述过滤材料提供洗涤溶液。所述过滤层(150)被配置成使得在所述处理系统的处理循环期间进入所述处理容器(100)的至少一部分采出水(160)在离开所述处理容器之前通过所述过滤层(150)。所述过滤材料(150)是基本上不可溶于水溶液的金属化合物,例如金属氢氧化物或金属氧代氢氧化物。所述洗涤溶液包括能够将所述金属化合物还原成可溶于水溶液的还原化合物而不分解所述有机化合物的试剂。在所述清洁循环之后,例如原油的所述有机化合物能够从所述过滤层材料中回收,并且所述过滤层(150)能够再生。(Systems and methods for treating produced water containing organic compounds include a treatment vessel (100); a filter layer (150) comprising a filter material; and a cleaning system that provides a wash solution to the filter material during a cleaning cycle. The filter layer (150) is configured such that at least a portion of produced water (160) entering the treatment vessel (100) during a treatment cycle of the treatment system passes through the filter layer (150) before exiting the treatment vessel. The filter material (150) is a metal compound that is substantially insoluble in aqueous solutions, such as a metal hydroxide or a metal oxohydroxide. The wash solution includes a reagent capable of reducing the metal compound to a reduced compound soluble in an aqueous solution without decomposing the organic compound. After the cleaning cycle, the organic compounds, such as crude oil, can be recovered from the filter layer material and the filter layer (150) can be regenerated.)

1. A treatment system for produced water containing organic compounds, the treatment system comprising:

a treatment vessel having a vessel inlet in fluid communication with a source of produced water and a first vessel outlet;

a filtration layer in the processing vessel between the vessel inlet and the first vessel outlet, the filtration layer comprising a filtration material; and

a cleaning system that provides a wash solution to the filter material during a cleaning cycle of the treatment system,

wherein:

the filtration layer is configured in the treatment vessel such that at least a portion of produced water from the produced water source entering the treatment vessel through the vessel inlet during a treatment cycle of the treatment system passes through the filtration layer and subsequently exits the treatment vessel through the first vessel outlet as filtered produced water;

said filter material is a metal compound that is substantially insoluble in aqueous solutions, said metal compound being selected from the group consisting of metal hydroxides, metal oxohydroxides, or combinations thereof;

the wash solution comprises a reducing agent; and is

The metal compound is capable of being reduced by the reducing agent during the cleaning cycle to form a reduced metal compound that is soluble in an aqueous solution.

2. The processing system of claim 1, wherein:

the metal hydroxide is selected from the group consisting of: iron (III) hydroxide, copper (II) hydroxide, manganese (III) hydroxide, chromium (III) hydroxide, and combinations thereof; and is

The metal oxohydroxide is selected from the group consisting of: iron (III) oxyhydroxide (ferrihydrite), manganese (III) oxyhydroxide, chromium (III) oxyhydroxide, and combinations thereof.

3. The treatment system of claim 1 or 2, wherein the metal compound comprises a metal hydroxide selected from the group consisting of: iron (III) hydroxide, copper (II) hydroxide, manganese (III) hydroxide, chromium (III) hydroxide, and combinations thereof.

4. The treatment system of any one of claims 1 to 3, wherein the metal compound comprises a metal oxohydroxide selected from the group consisting of: iron (III) oxohydroxide (ferrihydrite), manganese (III) oxohydroxide, chromium (III) oxohydroxide, and combinations thereof.

5. The treatment system of claim 1, wherein the metal compound is selected from the group consisting of: iron (III) hydroxide, ferrihydrite, and combinations thereof.

6. The treatment system of any one of the preceding claims, wherein the reducing agent is selected from hypophosphorous acid or a salt thereof, phosphorous acid or a salt thereof, oxalic acid or a salt thereof, formic acid or a salt thereof, ammonia water, ammonium salts, hydroxylamine, hydrogen under alkaline conditions, metal thiosulfate, metal sulfite or alkali metal sulfite, hydride, sodium borohydride, sodium bisulfite, disodium sulfite, aqueous sulfur dioxide, sulfurous acid or a salt thereof, or any combination thereof.

7. The treatment system of claim 6, wherein the reducing agent comprises aqueous sulfur dioxide, sulfurous acid, or a salt of sulfurous acid.

8. The treatment system of claim 7, wherein the reducing agent is selected from aqueous sulfur dioxide, sulfurous acid, sodium bisulfite, or disodium sulfite.

9. The treatment system according to any one of claims 6 to 8, wherein the metal compound is ferrihydrite.

10. The treatment system of any of the preceding claims, wherein the wash solution is the aqueous reducing agent solution.

11. The treatment system of claim 1, further comprising a ceramic membrane between the filtration layer and the first vessel outlet, wherein the filtration layer comprises a coating of the metal compound on a coated surface of the ceramic membrane.

12. The treatment system according to claim 11, wherein the ceramic membrane is selected from a titanium-zirconium oxide membrane, a silicon dioxide membrane, or an aluminum oxide membrane.

13. The processing system of claim 11 or 12, wherein:

the metal hydroxide is selected from the group consisting of: iron (III) hydroxide, copper (II) hydroxide, manganese (III) hydroxide, chromium (III) hydroxide, and combinations thereof; and is

The metal oxohydroxide is selected from the group consisting of: iron (III) oxohydroxide (ferrihydrite), manganese (III) oxohydroxide, chromium (III) oxohydroxide, and combinations thereof.

14. The treatment system of any one of claims 11 to 13, wherein the metal compound comprises a metal hydroxide selected from the group consisting of: iron (III) hydroxide, copper (II) hydroxide, manganese (III) hydroxide, chromium (III) hydroxide, and combinations thereof.

15. The treatment system of any one of claims 11 to 14, wherein the metal compound comprises a metal oxohydroxide selected from the group consisting of: iron (III) oxohydroxide (ferrihydrite), manganese (III) oxohydroxide, chromium (III) oxohydroxide, and combinations thereof.

16. The treatment system of any one of claims 11 or 12, wherein the metal compound is selected from the group consisting of: iron (III) hydroxide, ferrihydrite, and combinations thereof.

17. The treatment system of any one of claims 11 to 16, wherein the reducing agent is selected from hypophosphorous acid or a salt thereof, phosphorous acid or a salt thereof, oxalic acid or a salt thereof, formic acid or a salt thereof, ammonia water, an ammonium salt, hydroxylamine, hydrogen under alkaline conditions, a metal thiosulfate, a metal sulfite or an alkali metal sulfite, a hydride, sodium borohydride, sodium bisulfite, disodium sulfite, aqueous sulfur dioxide, sulfurous acid or a salt thereof, or any combination thereof.

18. The treatment system of claim 17, wherein the reducing agent comprises aqueous sulfur dioxide, sulfurous acid, or a salt of sulfurous acid.

19. The treatment system of claim 18, wherein the reducing agent is selected from aqueous sulfur dioxide, sulfurous acid, sodium bisulfite, or disodium sulfite.

20. The treatment system of any one of claims 17 to 19, wherein the metal compound is ferrihydrite.

21. The treatment system of any one of claims 11 to 20, wherein the wash solution is the aqueous reducing agent solution.

22. The treatment system of any one of claims 11 to 21, wherein the vessel inlet, the filter layer, the ceramic membrane and the vessel outlet are configured such that produced water from the produced water source entering the treatment vessel through the vessel inlet during a treatment cycle of the treatment system passes through the filter layer, then through the ceramic membrane, and then exits the treatment vessel through the first vessel outlet as filtered produced water.

23. The processing system of any of claims 11 to 22, further comprising a second vessel outlet, and wherein:

the ceramic membrane is a tubular membrane having an outer surface and longitudinal channels defined within the tubular membrane from an inlet end of the tubular membrane to an outlet end of the tubular membrane;

the outer surface of the tubular membrane is in fluid communication with the first container outlet;

the outlet end of the tubular membrane is in fluid communication with the second vessel outlet;

at least a portion of the produced water from the vessel inlet passes through the longitudinal passageway of the tubular membrane as a retentate stream to the second vessel outlet; and

at least a portion of produced water from the vessel inlet permeates through the filtration layer and the tubular membrane to the outer surface of the tubular membrane and exits the outer surface as the filtered produced water.

24. The processing system of claim 1, wherein:

the processing vessel is vertically configured in an upward configuration, wherein the vessel inlet is lower than the first vessel outlet, or in a downward configuration, wherein the vessel inlet is higher than the first vessel outlet;

the filtration layer comprises a bed of particles supported by a screen within the treatment vessel between the vessel inlet and the first vessel outlet, the bed of particles comprising the metal compound particles; and is

The screen has a mesh size and configuration that allows produced water to flow from the vessel inlet to the first vessel outlet and prevents the particles of the particle bed from passing down the screen.

25. The processing system of claim 24, wherein:

the metal hydroxide is selected from the group consisting of: iron (III) hydroxide, copper (II) hydroxide, manganese (III) hydroxide, chromium (III) hydroxide, and combinations thereof; and is

The metal oxohydroxide is selected from the group consisting of: iron (III) oxohydroxide (ferrihydrite), manganese (III) oxohydroxide, chromium (III) oxohydroxide, and combinations thereof.

26. The treatment system of claim 24 or 25, wherein the metal compound comprises a metal hydroxide selected from the group consisting of: iron (III) hydroxide, copper (II) hydroxide, manganese (III) hydroxide, chromium (III) hydroxide, and combinations thereof.

27. The treatment system of any one of claims 24 to 26, wherein the metal compound comprises a metal oxohydroxide selected from the group consisting of: iron (III) oxohydroxide (ferrihydrite), manganese (III) oxohydroxide, chromium (III) oxohydroxide, and combinations thereof.

28. The treatment system of any one of claims 24, wherein the metal compound is selected from the group consisting of: iron (III) hydroxide, ferrihydrite, and combinations thereof.

29. The treatment system of any one of claims 24 to 28, wherein the reducing agent is selected from hypophosphorous acid or a salt thereof, phosphorous acid or a salt thereof, oxalic acid or a salt thereof, formic acid or a salt thereof, ammonia water, an ammonium salt, hydroxylamine, hydrogen under alkaline conditions, a metal thiosulfate, a metal sulfite or alkali metal sulfite, a hydride, sodium borohydride, sodium bisulfite, disodium sulfite, aqueous sulfur dioxide, sulfurous acid or a salt thereof, or any combination thereof.

30. The treatment system of claim 29, wherein the reducing agent comprises aqueous sulfur dioxide, sulfurous acid, or a salt of sulfurous acid.

31. The treatment system of claim 30, wherein the reducing agent is selected from aqueous sulfur dioxide, sulfurous acid, sodium bisulfite, disodium sulfite, or sulfurous acid.

32. The treatment system according to any one of claims 29 to 31, wherein the metal compound is ferrihydrite.

33. The treatment system of any one of claims 24 to 33, wherein the wash solution is the aqueous reducing agent solution.

34. The treatment system of any one of claims 24 to 33, wherein the particle bed is configured as a fixed particle bed or a fluidized particle bed.

35. The processing system of claim 34, wherein:

the processing vessel further comprises a pellet inlet above the screen and a pellet outlet above the screen;

the particle inlet provides fresh particles of the metal compound to the particle bed during the treatment cycle; and is

During the treatment cycle, waste particles from the particle bed flow to the particle outlet.

36. The processing system of claim 35, further comprising a recovery vessel that receives the waste particles from the particle outlet.

37. A processing system for recovering crude oil from produced water, the processing system comprising:

a treatment vessel having a vessel inlet in fluid communication with a source of produced water and a first vessel outlet;

a ceramic membrane between the vessel inlet and the first vessel outlet;

a coating of a metal compound on the coated surface of the ceramic membrane facing the inlet of the vessel; and

a cleaning system that provides a wash solution to the filter material during a cleaning cycle of the treatment system,

wherein:

the metal compound is selected from the group consisting of: iron (III) hydroxide, copper (II) hydroxide, manganese (III) hydroxide, chromium (III) hydroxide, iron (III) oxohydroxide (ferrihydrite), manganese (III) oxohydroxide, chromium (III) oxohydroxide, and combinations thereof;

the ceramic membrane is configured such that at least a portion of produced water entering the treatment vessel during a treatment cycle of the treatment system passes through the coating, subsequently permeates the ceramic membrane and exits the treatment vessel through the first vessel outlet as filtered produced water; and is

The wash solution is an aqueous solution of a reducing agent selected from hypophosphorous acid or its salts, phosphorous acid or its salts, oxalic acid or its salts, formic acid or its salts, ammonia, ammonium salts, hydroxylamine, hydrogen under alkaline conditions, metal thiosulfate, metal sulfite or alkali metal sulfite, hydride, sodium borohydride, sodium bisulfite, disodium sulfite, aqueous sulfur dioxide, sulfurous acid or its salts, or any combination thereof.

38. The treatment system of claim 37, wherein the metal compound is selected from the group consisting of: iron (III) hydroxide, ferrihydrite, and combinations thereof.

39. The treatment system of claim 38, wherein the reducing agent comprises aqueous sulfur dioxide, sulfurous acid, or a salt of sulfurous acid.

40. The treatment system of claim 39, wherein the reducing agent is selected from aqueous sulfur dioxide, sulfurous acid, sodium bisulfite, or disodium sulfite.

41. The treatment system according to any one of claims 38 to 40, wherein the metal compound is ferrihydrite.

42. A method of recovering organic compounds from produced water, the method comprising:

providing produced water to a produced water source of a treatment system according to any one of claims 1 to 41;

starting a treatment cycle;

passing the produced water through the filtration layer during the treatment cycle until the organic compounds accumulate within the filtration layer;

initiating a cleaning cycle to provide the wash solution to the filter material of the filter layer, thereby reducing the metal compound to a reduced metal compound that is soluble in the wash solution;

removing the wash solution from the treatment vessel, the wash solution removed from the treatment vessel containing dissolved reduced metal compounds and the organic compound; and is

Separating the organic compound from the wash solution.

43. The method of claim 42, wherein the organic compound comprises crude oil.

44. The method of claim 42 or 43, further comprising recovering the reduced metal compound from the wash solution removed from the treatment vessel.

45. The method of claim 44, further comprising:

oxidizing the reduced metal compound recovered from the wash solution to reform the metal compound; and

transferring the reformed metal compound into the processing vessel.

46. The method of any one of claims 42 to 45, wherein:

the treatment system further comprises a ceramic membrane between the filtration layer and the outlet of the first vessel;

said filter layer comprising a coating of said metal compound on a coated surface of said ceramic membrane; and is

The coating of the metal compound dissolves from the ceramic membrane when the metal compound is reduced during the cleaning cycle.

47. The method of claim 46, further comprising:

coating the surface of the fresh ceramic membrane with the reducing metal compound;

oxidizing said reduced metal compound on said fresh ceramic membrane to form a regenerated coating of said metal compound on said surface of said fresh ceramic membrane; and

inserting the fresh ceramic membrane into the treatment vessel either before or after the reduced metal compound is oxidized.

48. The method of any one of claims 42 to 47, wherein:

the metal hydroxide is selected from the group consisting of: iron (III) hydroxide, copper (II) hydroxide, manganese (III) hydroxide, chromium (III) hydroxide, and combinations thereof; and is

The metal oxohydroxide is selected from the group consisting of: iron (III) oxohydroxide (ferrihydrite), manganese (III) oxohydroxide, chromium (III) oxohydroxide, and combinations thereof.

49. The method of any one of claims 42 to 48, wherein the metal compound comprises a metal hydroxide selected from the group consisting of: iron (III) hydroxide, copper (II) hydroxide, manganese (III) hydroxide, chromium (III) hydroxide, and combinations thereof.

50. The method of any one of claims 42 to 49, wherein the metal compound comprises a metal oxohydroxide selected from the group consisting of: iron (III) oxohydroxide (ferrihydrite), manganese (III) oxohydroxide, chromium (III) oxohydroxide, and combinations thereof.

51. The method of any one of claims 42 to 47, wherein the metal compound is selected from the group consisting of: iron (III) hydroxide, ferrihydrite, and combinations thereof.

52. The method of any one of claims 42 to 51, wherein the reducing agent is selected from hypophosphorous acid or a salt thereof, phosphorous acid or a salt thereof, oxalic acid or a salt thereof, formic acid or a salt thereof, ammonia, ammonium salts, hydroxylamine, hydrogen under alkaline conditions, metal thiosulfate, metal sulfite or alkali metal sulfite, hydride, sodium borohydride, sodium bisulfite, disodium sulfite, aqueous sulfur dioxide, sulfurous acid or a salt thereof, or any combination thereof.

53. The method of claim 52, wherein the reducing agent comprises aqueous sulfur dioxide, sulfurous acid, or a salt of sulfurous acid.

54. The method of claim 53, wherein the reducing agent is selected from aqueous sulfur dioxide, sulfurous acid, sodium bisulfite, or disodium sulfite.

55. The method of any one of claims 52 to 54, wherein the metal compound is ferrihydrite.

56. The method of any one of claims 42 to 55, wherein the wash solution is the aqueous reducing agent solution.

Technical Field

The present disclosure relates generally to the treatment of produced water, and more particularly, to a system for treating produced water and a method of recovering organic compounds from produced water.

Background

Large quantities of water are produced when exploiting hydrocarbon energy (currently, it is estimated that there are approximately 140 billion barrels per year [1 barrel: 42 gallons ] in the united states all over the year). Produced water includes water that has been trapped in subterranean formations for hundreds of years, often, and is brought to the surface during oil and gas exploration and production. In addition, produced water can be produced from power plant scrubbers, dehydration and uranium sources, carbon fixation, and development of unconventional energy. Produced water from any application typically contains large amounts of hydrocarbons, such as crude oil, which may prevent the produced water from being reused in other applications. Accordingly, there is a continuing need for apparatus and methods for treating large volumes of produced water, particularly for removing contaminants (e.g., hydrocarbons) from produced water.

Ceramic membranes have limited ability to treat water (e.g., produced water) because the membranes are likely to experience complete fouling and even mechanical failure when oil and other hydrocarbons, sand, salt, and other chemicals come into contact with or pass through the ceramic membrane. Thus, there is a continuing need for improved ceramic membranes that may be capable of continuously filtering produced water without becoming irreversibly disabled by complete scaling.

Fixed bed or fluidized bed filtration may also be used to adsorb organic contaminants in the produced water. In such processes, contaminants in the produced water may be trapped in or adsorbed onto the particulate layer. Eventually, the particles need to be cleaned or replaced. Cleaning or replacing the particles involves increased costs. Accordingly, there is a continuing need for filtration processes that can clean or recycle particles in an efficient manner.

Regardless of the filtration process used to treat the produced water, the hydrocarbons (e.g., crude oil) removed from the produced water are typically discarded as waste. These types of waste materials may have adverse environmental effects. Furthermore, the hydrocarbons themselves may have a real monetary value that cannot be realized when the hydrocarbons are simply discarded. Thus, there is a continuing need for systems that can minimize hydrocarbon waste from produced water treatment, as well as realize value from hydrocarbons recovered under processing conditions compatible with hydrocarbon production and its downstream operations.

Disclosure of Invention

According to some embodiments, a treatment system for produced water containing organic compounds comprises: a treatment vessel having a vessel inlet in fluid communication with a source of produced water and a first vessel outlet; a filter layer in the processing vessel between the vessel inlet and the first vessel outlet, the filter layer comprising a filter material; and a cleaning system that provides a wash solution to the filter material during a cleaning cycle of the treatment system. The filter layer is configured in the treatment vessel such that at least a portion of produced water from the produced water source entering the treatment vessel through the vessel inlet during a treatment cycle of the treatment system passes through the filter layer and is subsequently processedProduced water for filtration exits the treatment vessel through a first vessel outlet. The filter material is a metal compound that is substantially insoluble in aqueous solutions. In particular, the metal compound is selected from a metal hydroxide, a metal oxohydroxide, or a combination thereof. Examples of metal hydroxides include, but are not limited to, iron (III) hydroxide, copper (II) hydroxide, manganese (III) hydroxide, and chromium (III) hydroxide. Examples of the metal oxohydroxide include iron (III) oxohydroxide (ferrihydrite), manganese (III) oxohydroxide, and chromium (III) oxohydroxide. The wash solution includes a reducing agent. The metal compound may be reduced by a reducing agent during the cleaning cycle to form a reduced metal compound that is soluble in the aqueous solution. In particular, the reducing agent is a compound having a sufficiently large reducing ability to reduce the metal compound without decomposing the organic compound. In some embodiments, the reducing agent may be selected from hypophosphorous acid (H)₃PO₂) Phosphorous acid (H)₃PO₃) Oxalic acid, formic acid, and ammonia (NH)₃) Hydroxylamine (NH)₂OH), hydrogen under alkaline conditions, metal thiosulfate (S)₂O₃ ^2-) Metal sulfites, hydride sources (e.g., sodium borohydride), aqueous or soluble sulfur dioxide (SO)₂) Sodium bisulfite, disodium sulfite, sulfurous acid, or any combination of these. In some embodiments, the reducing agent may be selected from sulfurous acid, salts of sulfurous acid, or combinations thereof.

According to other embodiments, a processing system for recovering crude oil from produced water may include: a treatment vessel having a vessel inlet in fluid communication with a source of produced water and a first vessel outlet; a ceramic membrane between the vessel inlet and the first vessel outlet; a metal compound coating on the coated surface of the ceramic membrane facing the inlet of the vessel; and a cleaning system that provides a wash solution to the filter material during a cleaning cycle of the treatment system. In such embodiments, the metal compound is selected from the group consisting of: iron (III) hydroxide, copper (II) hydroxide, manganese (III) hydroxide, chromium (III) hydroxide, iron (III) oxohydroxide (ferrihydrite), manganese (III) oxohydroxide, chromium (III) oxohydroxide, and combinations thereof. The ceramic membrane is configured such that it is at a processing systemAt least a portion of the produced water entering the treatment vessel during the treatment cycle passes through the coating and then exits the treatment vessel through the first vessel outlet after permeating the ceramic membrane and as filtered produced water. The wash solution is an aqueous solution containing a reducing agent. In some embodiments, the reducing agent may be selected from hypophosphorous acid (H)₃PO₂) Phosphorous acid (H)₃PO₃) Oxalic acid, formic acid, and ammonia (NH)₃) Hydroxylamine (NH)₂OH), hydrogen under alkaline conditions, metal thiosulfate (S)₂O₃ ^2-) Metal sulfites, hydride sources (e.g., sodium borohydride), aqueous or soluble sulfur dioxide (SO)₂) Sodium bisulfite, disodium sulfite, sulfurous acid, or any combination of these. In some embodiments, the reducing agent may be selected from sulfurous acid, salts of sulfurous acid, or combinations thereof.

According to other embodiments, a method for recovering organic compounds from produced water may include providing produced water to a produced water source of a treatment system according to the previously described embodiments. A treatment cycle is initiated during which produced water is passed through filtration until organic compounds accumulate within the filtration layer. Subsequently, a cleaning cycle is initiated to provide a wash solution to the filter material of the filter layer, thereby reducing the metal compound to form a reduced metal compound that is soluble in the wash solution. The scrubbing solution is removed from the treatment vessel, and the scrubbing solution removed from the treatment vessel contains dissolved reduced metal compounds and organic compounds. The organic compound is separated from the wash solution. In some embodiments, the organic compound separated from the wash solution is subsequently recovered. The organic compounds recovered from produced water in this manner may include crude oil.

It is to be understood that both the foregoing general description and the following detailed description describe various embodiments, and are intended to provide an overview or framework for understanding the nature and character of the claimed subject matter. The accompanying drawings are included to provide a further understanding of the various embodiments and are incorporated in and constitute a part of this specification. The drawings illustrate various embodiments described in the present disclosure and together with the description serve to explain the principles and operations of the claimed subject matter.

Drawings

FIG. 1 is a schematic illustration of a treatment system for produced water containing organic compounds, according to an embodiment.

Fig. 2A is a schematic illustration of fluid flow through a ceramic membrane coated with a filtration layer at an initial stage of treatment according to an embodiment.

Fig. 2B is a schematic illustration of fluid flow through the ceramic membrane of fig. 2A with collection of organic matter from produced water within the protective filtration layer commencing.

Fig. 2C is a schematic illustration of fluid flow through the ceramic membrane of fig. 2A after additional treatment of the produced water as compared to the ceramic membrane of fig. 2B, with substantial collective collection of organic matter from the produced water within the protective filtration layer.

Fig. 3A is a schematic view of the start of a cleaning cycle on the plugging membrane of fig. 2C.

Fig. 3B is a schematic illustration of disrupting and fusing the filtration layer to unblock the membrane of fig. 3A during a cleaning cycle, thus regenerating a reused ceramic membrane.

Fig. 4 is a schematic illustration of an endless configuration of a treatment system for produced water according to an embodiment.

Fig. 5A is a side view of a tubular ceramic membrane internally coated with a filtration layer according to an embodiment.

Fig. 5B is a cross-section of the tubular ceramic membrane of fig. 5A.

FIG. 6 is a treatment vessel of a treatment system according to an embodiment including a tubular ceramic membrane for cross-flow treatment of produced water.

Fig. 7 is a schematic diagram of a treatment system for produced water including a parallel subsystem of tubular ceramic membranes according to an embodiment.

FIG. 8 is a treatment vessel of a treatment system according to an embodiment that includes a fixed or fluidized bed having filter material particles and configured in a downflow configuration.

FIG. 9 is a treatment vessel of a treatment system according to an embodiment that includes a fixed or fluidized bed having filter material particles and configured in an upflow configuration.

Fig. 10 is a treatment vessel of a treatment system according to an embodiment comprising a fluid bed for continuously regenerating filter material and configured in an upward or downward flow configuration.

Fig. 11 is a schematic diagram of a treatment system for produced water including a parallel subsystem of the treatment vessel of fig. 9 configured in an upflow configuration, according to an embodiment.

Fig. 12 is a schematic diagram of a treatment system for produced water including the treatment vessel of fig. 10 configured in a down-flow configuration, according to an embodiment.

FIG. 13 is a normalized throughput (J/J) of a coated ceramic membrane for a treatment system according to an embodiment₀) Normalized flux (J/J) to uncoated ceramic membranes of the prior art₀) A comparison is made of the graphs as a function of the produced water quantity treated.

Fig. 14 is a graph of time-varying specific flux data collected from a treatment system according to an embodiment in which the treatment vessel comprises a tubular ceramic membrane internally coated with a filter layer configured in a cross-flow configuration as in fig. 6.

Detailed Description

Specific embodiments of the present disclosure will now be described. It will be apparent to those skilled in the art that the present disclosure may be practiced with only those specific embodiments that are specifically described. Therefore, the disclosure of specific embodiments should not be construed as limiting the full scope of the disclosure. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the subject matter to those skilled in the art.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in this specification and the appended claims, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

Embodiments of the present disclosure relate generally to systems and methods for treating produced water. As used in this disclosure, "treatment" with respect to produced water may include any procedure that filters or removes impurities from produced water. In some embodiments of the present disclosure, the treatment of the produced water comprises passing the water through a ceramic membrane or through a fixed or fluidized particle bed. Systems and methods for treating produced water according to embodiments utilize a filtration layer or protective material that includes a metal compound having a water insoluble oxidation state and a water soluble oxidation state. Typically, the water-soluble oxidation state is a reduced form of the filter layer material formed by reacting the filter layer material with a reducing agent. The two oxidation states of the filter layer or protective material make the protective layer susceptible to dissolution and reformation, thereby promoting the efficiency of cleaning and processing operations. Typically, the metal compounds create a protective coating that prevents foreign matter in the produced water from completely plugging the treatment system, for example, by irreversibly contaminating a ceramic membrane that may be included in the treatment system in some embodiments.

As used in this disclosure, the term "produced water" refers to water that has undergone a process or procedure in which the water has been contaminated with organic compounds (e.g., crude oil). Produced water is typically sourced from natural gas and oil production plants, and water extracted from the surface under anaerobic conditions and contaminated with oil. Produced water may also be contaminated with particulate matter such as sand.

FIG. 1 is a schematic diagram conceptually illustrating a treatment system 100 for produced water containing organic compounds. Although the various processing system embodiments that will be described subsequently may differ in configuration and mechanical characteristics, it should be understood that each embodiment of the processing system generally includes components that perform in a manner similar to the processing system 100 of FIG. 1. Thus, it should be understood that features, components, or materials described as suitable for use in the treatment system 100 are equally suitable for use in similar features, components, or materials of embodiments of the treatment system 100 specifically described in this disclosure, including, but not limited to, an endless filtration system 200 (fig. 4) comprising a membrane or a bed of particles, a parallel cross-flow filtration system 400 (fig. 7) comprising tubular membranes, a filtration system 800 (fig. 11) comprising a parallel upward arrangement of a bed of particles, or a system 900 (fig. 12) comprising a downward arrangement of a bed of particles, unless otherwise specified.

The treatment system 100 includes a treatment vessel 110 having a vessel inlet 120 in fluid communication with a produced water source 160 and a first vessel outlet 130 leading to or in fluid communication with a collection vessel 170. The treatment vessel 110 may be any kind of enclosure or device in which water may be treated. The produced water source 160 may be any produced water source, such as a pipe or hose, a reservoir, a connection to a refinery system from which produced water is emitted, or a connection to a drilling system for a wellbore. The vessel inlet 120 is the fluid path into the treatment vessel 110 and may include conventional fittings or valves (not shown) to control the flow of produced water from the produced water source 160. Likewise, the first vessel outlet 130 is the fluid path out of the processing vessel 110 and may include conventional fittings or valves (not shown) required for implementation of the processing system 100.

The processing system 100 further includes a filter layer 150 in the processing vessel 110 between the vessel inlet 120 and the first vessel outlet 130. Filter layer 150 includes at least one filter material. The filtration layer may be supported by, against, or on porous support 140, which prevents filtration layer 150 from moving downstream within processing vessel 110. Filtration layer 150 is configured in treatment vessel 110 such that at least a portion of produced water from produced water source 160 that enters treatment vessel 110 through vessel inlet 120 during a treatment cycle of the treatment system passes through filtration layer 150 and subsequently exits treatment vessel 110 through first vessel outlet 130 as filtered produced water. In some embodiments, all of the produced water from the produced water source 160 that enters the treatment vessel 110 during a treatment cycle of the treatment system from the vessel inlet 120 passes through both the filtration layer 150 and the porous support 140 and then exits the treatment vessel 110 through the first vessel outlet 130 as filtered produced water. In some embodiments, a portion of the produced water from produced water source 160 that passes through filtration layer 150 then passes through porous support 140. In some embodiments, which will be described in more detail subsequently, the treatment vessel 110 includes a second vessel outlet (not shown in fig. 1) through which any portion of the produced water that does not exit the treatment vessel 110 as filtered produced water through the first vessel outlet 130 exits the treatment vessel 110 as an unfiltered retentate stream.

In some embodiments, the porous support 140 may be a ceramic membrane. In such embodiments, as will be described in detail below, the filter layer 150 may include a coating of filter material on the surface of the ceramic membrane. In other embodiments, the porous support 140 can be, for example, a mesh, screen, or mesh. In such embodiments, as will be described in detail below, the filter layer 150 may include a particulate bed of filter material particles. Regardless of the type of porous support 140 in the treatment system 100, the filtration layer 150 provides a filtration material selected to avoid clogging or fouling of the treatment system 100.

The filter material of filter layer 150 is a metal compound that is substantially insoluble in aqueous solutions. The metal compounds are substantially insoluble or completely insoluble in the produced water being treated by the treatment system 100. Thus, filter layer 150 may remain intact during processing cycles of processing system 100. The metal compound may be a transition metal compound in which the metal atom of the metal compound has at least two possible oxidation states, and in which the metal atom is in the greater of the two possible oxidation states, such that the metal compound can be reduced to a reduced metal compound by reaction with a reducing agent in which the metal atom is in the lesser of the two possible oxidation states. For example, an iron (III) metal compound that is insoluble in aqueous solution at a given pH, e.g., at a pH greater than 2.8, can be reduced to an iron (II) reducing metal compound that is soluble in aqueous solution.

In this regard, suitable filter materials include, but are not limited to, metal hydroxides, metal oxohydroxides, and combinations of metal hydroxides and metal oxohydroxides. Examples of metal hydroxides include, but are not limited to, iron (III) hydroxide, copper (II) hydroxide, manganese (III) hydroxide, chromium (III) hydroxide, and combinations thereof. Examples of metal oxohydroxides include, but are not limited to, iron (III) oxohydroxide (ferrihydrite), manganese (III) oxohydroxide, chromium (III) oxohydroxide, and combinations thereof. In example embodiments, the metal compound may include iron (III) hydroxide, ferrihydrite, or a combination thereof. In some embodiments, the metal compound comprises, consists essentially of, or consists of ferrihydrite.

The metal compound of filter layer 150 may be in the form of particles, beads, flakes, or may be a coating material on particles, beads, or flakes. Alternatively, the metal compound of the filter layer may be included in a coating layer on the porous support 140. To form a coating on a porous support 140, such as a ceramic membrane, a precursor compound (e.g., a metal nitrate) may be oxidized in an air or oxygen atmosphere under mild heating conditions, such as 25 ℃ to 200 ℃, to form a metal hydroxide or metal oxyhydroxide. For example, ferrihydrite may be formed by oxidizing one or more iron (II) salts, such as iron (II) chloride, iron (II) sulfate, iron (II) sulfite, or iron (II) nitrate, in air or oxygen. When the normally water-soluble iron (II) salt is oxidized, it forms water-insoluble iron (III) hydroxide or iron (III) oxyhydroxide which is present in the form of a precipitate in aqueous solution with a particle size significantly larger than the pore size of the ceramic membrane. An aqueous solution containing the iron (III) hydroxide or iron (III) oxyhydroxide precipitate is then poured onto the ceramic membrane such that water of the aqueous solution permeates through the pores of the ceramic membrane and a coating of the iron (III) hydroxide or iron (III) oxyhydroxide remains on the surface of the ceramic membrane onto which the aqueous solution is poured. The ceramic membrane may then be subjected to a heating or drying step to fix the particles on the surface of the ceramic membrane.

Treatment system 100 further includes a cleaning system 190 that provides a wash solution to the filter material of filter layer 150 during a cleaning cycle of treatment system 100. The wash solution includes a reducing agent. The reducing agent is selected such that the metal compound is reducible by the reducing agent during the cleaning cycle to form a reduced metal compound soluble in the aqueous solution. The wash solution provided to filter layer 150 during the cleaning cycle may be an aqueous solution of a reducing agent at a concentration sufficient to reduce the filter material, particularly metal compounds, in an industrially practical amount of time.

In some embodiments, the reducing agent is selected to have a reducing capacity large enough to reduce the metal compounds while also being sufficiently limited to avoid decomposing or otherwise deactivating organic compounds present in the produced water. For example, organic compounds may include crude oil or other hydrocarbons that are sought to be recovered or added value. Thus, in some embodiments, the reducing agent is selected such that it is capable of reducing the metal compounds of filter layer 150, while not decomposing or otherwise compromising the potential value of the crude oil or other hydrocarbons.

With regard to the ability to reduce the metal compound, the electrochemical potentials of the metal ions of the metal compound and the components of the reducing agent may be considered. Suitable reducing agents for the metal compound may include, but are not limited to, hypophosphorous acid (H)₃PO₂) Or a salt thereof, phosphorous acid (H)₃PO₃) Or a salt thereof, oxalic acid or a salt thereof, formic acid or a salt thereof, and ammonia (NH)₃) Ammonium salts, hydroxylamines (NH)₂OH), hydrogen under alkaline conditions, metal thiosulfate (S)₂O₃ ^2-) Metal or alkali metal sulfites, hydride sources (e.g. sodium borohydride), aqueous or soluble sulfur dioxide (SO)₂) Sodium bisulfite, disodium sulfite, sulfurous acid or salts thereof, or any combination thereof. In some embodiments, the reducing agent may be selected from aqueous sulfur dioxide, sulfurous acid, salts of sulfurous acid, or combinations thereof.

In an example embodiment, the metal compound may be an iron (III) compound, such as iron (III) hydroxide, ferric oxide trihydrate, or a combination thereof, and the reducing agent may be sulfurous acid or a sulfite, such as an alkali metal sulfite, sodium bisulfite, or disodium sulfite. For example, when the metal compound is water-insoluble iron (III) oxyhydroxide and the reducing agent is sulfurous acid, the reducing metal compound may be a water-soluble iron (II) compound, such as iron (II) bisulfate (ironhydrogen sulfate), also known as iron (II) bisulfate (ironbissulfate). In some embodiments, the reduced metal compound may be reused as a precursor after a cleaning cycle to reform the filtration layer 150 on the porous support 140 or ceramic membrane.

According to some embodiments, the treatment system 100 may include a ceramic membrane as the porous support 140 between the filter layer 150 and the first vessel outlet 130. In such embodiments, the filter layer 150 may be or may include a coating of a metal compound on the coated surface of the ceramic membrane.

The function of the ceramic membrane as a porous support 140 for a filter layer 150, which is a coating of a metal compound, is illustrated in fig. 2A-2C and fig. 3A-3B. Referring to fig. 2A, the ceramic membrane 10 is coated with a filtration layer 50, such as a water insoluble layer of iron (III) hydroxide or ferrihydrite. The vertical arrows through the holes 15 of the ceramic membrane 10 indicate the flow of produced water through the ceramic membrane 10, and in particular through the holes 15 of the ceramic membrane. The produced water may contain contaminants such as oil droplets 20 or particulate matter 40.

Referring to fig. 2B, as more produced water continues to be processed through the ceramic membrane 10, oil droplets may form oil deposits 25 on the filter layer 50, and particulate matter 40 may also adhere to the filter layer 50. Even so, the filter layer 50 prevents oil droplets and particulate matter from entering the pores 15 where they may stick to the walls of the pores 15, potentially clogging them. The proliferation of plugged pores in the ceramic membrane 10 is commonly referred to as fouling, and if fouling is extensive, this may be irreversible, such that the ceramic membrane 10 cannot be cleaned or reused.

Referring to fig. 2C, at some point during the treatment of the produced water, the size and extent of oil deposits 25 and particulate matter 40 on the filter layer may become so large that little or no additional produced water may pass through the apertures 15. Although for ceramic membranes lacking any kind of filter layer, such extensive fouling may result in the need to dispose of the ceramic membrane, in a treatment system according to embodiments, the filter layer 50 may be regenerated by a cleaning cycle. The function of the cleaning cycle is shown in fig. 3A and 3B.

The ceramic membrane 10 of fig. 3A includes oil deposits 25 and particulate matter on the filter layer 50 at the beginning of the cleaning cycle, such as on the ceramic membrane 10 of fig. 2C. During the cleaning cycle, the cleaning solution containing the reducing agent is backwashed through the ceramic membrane 10 as shown in fig. 3A with the vertical arrows pointing upwards through the pores 15 of the ceramic membrane 10. The effect of backwashing was simulated in fig. 3B. That is, as the cleaning solution permeates through the pores 15, the metal compound forming the filter layer 50 is reduced to a water-soluble reduced metal compound. Thus, the cleaning solution effectively dissolves and disrupts the filter layer to dissolve particles 55 that may eventually dissolve completely. The oil that has now been deposited on the filter layer (fig. 3A) is present in the cleaning solution as oil droplets 20 along with the particulate matter 40. The cleaning solution containing the solvated reduced metal compounds, oil droplets 20, and particulate matter may then be phase separated to recover the oil that has been captured on the filtration layer 50. Once the oil is recovered, dissolved metal compounds in the aqueous phase of the cleaning solution may be deposited back onto the ceramic membrane 10, helping it to subsequently be oxidized to reform the filter layer 50 for further processing cycles.

Referring to fig. 4, in one embodiment, the treatment system 100 may be configured as an endless filtration system 200. In the endless filtration system 200, produced water from the produced water source 160 may be directed into the processing vessel 110 by the inlet pump 167. An inert gas, such as nitrogen, may be added to the produced water at the produced water source 160 that is, for example, non-reactive to organic compounds or crude oil in the produced water to provide a non-reactive gas layer in the filtered produced water collected in the collection vessel 170. Produced water from inlet pump 167 enters treatment vessel 110 through vessel inlet 120, where it passes through filtration layer 150 and porous support 140 to exit as filtered produced water through first vessel outlet 130 in treatment vessel 110. In some embodiments, porous support 140 of endless filtration system 200 may be a ceramic membrane, and filter layer 150 may be a metal compound coating on the face or surface of the ceramic membrane facing vessel inlet 120. The filtered produced water may be collected at collection vessel 170.

A flow control device, such as a three- way valve 230, 235 or a pressure monitor 240, may also be included in the endless filtration system 200. The endless filter system 200 also includes a cleaning system 190. The cleaning system 190 is configured relative to the three- way valves 230, 235 such that the three- way valves 230, 235 can be actuated to switch the endless filtration system 200 from a treatment cycle to a cleaning cycle. During the treatment cycle, produced water flows from the produced water source 160 to the collection vessel 170 when the cleaning system 190 is in a dormant state. During the cleaning cycle, the washing solution containing the reducing agent flows from the washing solution container 191 to the treatment container 110 by means of the washing solution pump 192 in a return flow direction opposite to the flow direction during the treatment cycle. The wash solution is collected in a solution collection vessel, such as separation vessel 196. At the solution collection or separation vessel 196, the wash solution may contain a reducing agent, solvated reduced metal compounds, and organic compounds, such as crude oil. The wash solution may then be phase separated or further processed to recycle the reducing agent, reduce the metal compounds, or both, and recover the organic compounds, including any crude oil that may be present.

In the embodiment of the treatment system 100 (fig. 1) that includes the endless filtration system 200 (fig. 4) and other embodiments to be described subsequently, for the treatment system, the porous support 140 is a ceramic membrane, which may be any type of ceramic membrane commonly used for filtering water or produced water. Suitable ceramic films include, for example, a titania-zirconia film, a silica film, or an alumina film. The ceramic membrane may be a flat membrane, such as a disk, square or rectangle; an elongate solid or tubular membrane having a long longitudinal bore or channel.

In some embodiments, treatment system 100 may include a ceramic membrane as porous support 140 between filter layer 150 and first vessel outlet 130, and filter layer 150 is a metal compound coating on the coated surface of the ceramic membrane. In such embodiments, the metal compound may be selected from iron (III) hydroxide, copper (II) hydroxide, manganese (III) hydroxide, chromium (III) hydroxide, iron (III) oxohydroxide (ferrihydrite), manganese (III) oxohydroxide, chromium (III) oxohydroxide, and combinations thereof. Further, in such embodiments, the wash solution is an aqueous solution of a reducing agent, and the reducing agent may be selected as previously described, including, for example, sodium bisulfite, disodium sulfite, or sulfurous acid.

In some embodiments where the treatment system 100 includes a ceramic membrane as the porous support 140, produced water from the produced water source 160 that enters the treatment vessel 110 through the vessel inlet 120 during a treatment cycle of the treatment system 100 passes through the filter layer 150, then through the ceramic membrane (porous support 140), and then exits the treatment vessel 110 through the first vessel outlet 130 as filtered produced water.

Referring to fig. 5A and 5B, in other embodiments where the treatment system 100 includes a ceramic membrane as the porous support 140, the ceramic membrane may be a tubular membrane 180 having an inner surface 185 and an outer surface 187. As shown in fig. 5A and 5B, the tubular membrane 180 may be a cylindrical membrane having a circular cross-section, or may have any geometric cross-section, such as oval, square, triangular, hexagonal, or the like. The tubular membrane 180 may itself be the processing vessel 110 (fig. 1) of the processing system, or may be enclosed within the processing vessel 110, for example as part of a tubular membrane vessel 300 (fig. 6). The tubular membrane has an internal passageway defined longitudinally through the tubular membrane 180 from a first end 182 (which may serve as the vessel inlet 120) to a second end 183 opposite the first end 182.

The inner surface 185 of the tubular membrane 180 may be coated or covered by a filtration layer 150 of a metal compound, as generally described previously with respect to the treatment system 100. Filter layer 150 may be applied to inner surface 185 of tubular membrane 180 using the chemistry previously described for applying metal compounds in combination with known techniques for coating the inner surface of tubular membrane. When incorporated into a treatment system for treating produced water containing organic compounds, the produced water may enter tubular membrane 180 through first end 182. A portion of the produced water permeates through the filtration layer and the walls of tubular membrane 180 to exit outer surface 187 as filtered produced water that may collect. The remaining produced water that does not permeate tubular membrane 180 may pass longitudinally through tubular membrane 180 to second end 183 as an unfiltered retentate stream.

Referring to fig. 6, a tubular film container 300 that may be incorporated into a processing system according to embodiments is shown in cross-section. Tubular membrane vessel 300 includes tubular membrane 180 coated with filtration layer 150. The tubular membrane 180 is inserted into an inlet support 310 and an outlet support 315 that provide a seal around the longitudinal ends of the tubular membrane 180. The tubular membrane 180, the inlet support 310 and the outlet support 315 are enclosed within the processing vessel 110. A fluid connection is established between the tubular membrane 180 and the vessel inlet 120 by means of the inlet support 310. During a treatment cycle, as shown by the arrows in fig. 6, a portion of the produced water entering tubular membrane 180 through vessel inlet 120 permeates through the wall of tubular membrane 180 and enters intermediate space 320 of treatment vessel 110 between outer surface 187 of tubular membrane 180 and inner wall 112 of treatment vessel 110. The permeated produced water, which is filtered produced water, may be removed from the treatment vessel 110 through the first vessel outlet 130. The treatment vessel 110 of the tubular membrane vessel 300 further comprises a second vessel outlet 135 through which second vessel outlet 135a retentate stream of the unfiltered produced water exits the treatment vessel 110. A fluid connection is established between the tubular membrane 180 and the second container outlet 135 via the outlet support 315. The treatment vessel 110 of the tubular membrane vessel 300 further comprises a backwash inlet 194 through which backwash inlet 194 wash solution may be added to the tubular membrane vessel 300 during the cleaning cycle.

Thus, referring to fig. 1 and 6, a treatment system 100 according to embodiments may include a ceramic membrane, particularly a tubular membrane 180, as the porous support 140, and further include a second vessel outlet 135. In such embodiments, the tubular membrane 180 has an outer surface 187 and an internal passage defined within the tubular membrane 180 from a first end 182 (e.g., inlet end) of the tubular membrane 180 to a second end 183 (outlet end) of the tubular membrane 180. The outer surface 187 of the tubular membrane 180 is in fluid communication with the first container outlet 130. The second end 183 (outlet end) of the tubular membrane 180 is in fluid communication with the second container outlet 135. At least a portion of the produced water from vessel inlet 120 passes through the interior of tubular membrane 180 as a retentate stream to second vessel outlet 135. At least a portion of the produced water from vessel inlet 120 permeates through tubular membrane 180 to outer surface 187 of tubular membrane 180 and exits from outer surface 187 as filtered produced water.

In certain embodiments of the processing system 100 (fig. 1), the processing system 100 may include one tubular film container 300 or more than one tubular film container 300. An example of such an embodiment includes the parallel cross-flow filtration system 400 of fig. 7. In parallel crossflow filtration system 400, two processing systems are combined, both of which have similar components, the component numbers of which end in either a lower case "a" or a lower case "b". In particular, the parallel cross-flow filtration system 400 comprises two tubular membrane vessels 300a, 300b and is configured in a first state such that the first tubular membrane vessel 300a can operate in a process cycle while the second tubular membrane vessel 300b operates in a cleaning cycle. For the first tubular film container 300a in a processing cycle, valves 410a, 136a and 420a are open and valves 193a and 195a to the first cleaning system 190a are closed. For the second tubular film container 300b in the cleaning cycle, valves 410b, 136b and 420b are closed and valves 193b and 195b to the second cleaning system 190b are open.

By manipulating the valves 410a, 410b, 136a, 136b, 420a, 420b, 193a, 193b, 195a, 195b, the parallel cross-flow filtration system 400 can be switched to a second state in which the first tubular membrane vessel 300a is operating in a cleaning cycle and the second tubular membrane vessel 300b is operating in a treatment cycle, as opposed to the function of the first state. In particular, the parallel cross-flow filtration system 400 can be switched to the second state by opening valves 193a, 195a, 410b, 136b, and 420b (shown closed in fig. 7) and closing valves 410a, 136a, 420a, 193b, and 195b (shown open in fig. 7). It is apparent that the parallel cross-flow filtration system 400 in the second state can be restored to the first state (as shown in fig. 7) by again closing the valves 193a, 195a, 410b, 136b, and 420b and opening the valves 410a, 136a, 420a, 193b, and 195 b.

As shown in fig. 7, in a treatment cycle, produced water from the produced water source 160 is pumped into the vessel inlet 120a of the treatment vessel 110a by the inlet pump 167a into the internal passage of the tubular membrane 180a, relative to the first tubular membrane vessel 300 a. A portion of the produced water permeates into intermediate space 320a of treatment vessel 110a through filtration layer 150a and tubular membrane 180a and exits treatment vessel 110a through first vessel outlet 130a as filtered produced water. The filtered produced water may then collect in the permeate collection vessel 137 a. The remaining portion of the produced water that does not permeate tubular membrane 180a exits treatment vessel 110a through second vessel outlet 135a as an unfiltered produced water or retentate stream. When recirculation valve 430 is open (as shown), unfiltered produced water may be fed back through first tubular membrane vessel 300a for filtration and treatment again. When the retentate valve 440 is open (not shown), unfiltered produced water or retentate stream may exit the parallel cross-flow filtration system 400 to the retentate collection vessel 175. During a treatment cycle involving the first tubular membrane vessel 300a, components of the first cleaning system 190a are isolated from system components involved in the treatment of produced water and shut down. The isolated components include a wash solution vessel 191a, a wash solution pump 192a, a valve 193a, a backwash inlet 194a, a valve 195a, a separation vessel 196a, an organic collection vessel 197a, and a separator gas source 198 a.

As shown in fig. 7, in the cleaning cycle, the wash solution containing the reducing agent in the wash solution vessel 191b is delivered to the backwash inlet 194b through valve 193b with the aid of wash solution pump 192b relative to the second tubular membrane vessel 300 b. The washing solution enters the intermediate space 320b of the treatment vessel 110b and permeates into the inner passage of the tubular membrane 180b through the outer surface of the tubular membrane 180 b. Upon reaching the internal passage of the tubular membrane 180b, the washing solution reduces the metallic compounds of the filtering layer (which is intended to be missing in fig. 7), dissolves the filtering layer and carries with it the dissolved reduced metallic compounds and any organic compounds, such as crude oil that have adhered to the filtering layer during the previous treatment cycle, and therefore a cleaning cycle has to be carried out. The wash solution and its solvated and unsolvated components flow out of the process vessel 110b through the vessel inlet 120b and are returned to the cleaning system 190b through the valve 195 b.

The wash solution proceeds to a separation vessel 196 b. In the separation vessel 196b, the wash solution may be phase separated into, for example, an aqueous phase and an organic phase floating on the aqueous phase. For example, a blanket of an inert gas (e.g., nitrogen) may be injected into the separation vessel 196b from the separator gas source 198b to protect the organic compounds in the organic phase from decomposition or reaction within the separation vessel 196 b. The organic phase may contain organic compounds, such as crude oil, originally present in the produced water exiting the produced water source 160. The organic compounds may be extracted from the separation vessel 196b to an organic recovery vessel 197b for further use, purification, or value-addition. The aqueous phase may contain solvated reduced metal compounds and unreacted reducing agent. Once the organic phase is extracted from separation vessel 196b, the aqueous phase may be further processed to recover reduced metal compounds for subsequent reoxidation and applied as a filter layer to a fresh tubular membrane. Alternatively, or after any desired recovery, the aqueous phase may be recycled back to the wash solution container 191 b. If the concentration of the reducing agent in the circulating water phase is too low for the wash solution to continue to dissolve the filter layer on tubular membrane 180b, additional reducing agent may be added to the wash solution at wash solution reservoir 191 b. During a cleaning cycle involving the second tubular membrane vessel 300b, the assembly comprising the first vessel outlet 130b, valve 136b, valve 410b, valve 420b, inlet pump 167b, permeate collection vessel 137b, and second vessel outlet 135b is isolated and closed from system components involved in the cleaning cycle.

Referring to fig. 4 and 7, generally in an illustrative embodiment of a treatment system, a treatment system for recovering crude oil from produced water may include a treatment vessel 110a, 300a having a vessel inlet 120a and a first vessel outlet 130a in fluid communication with a produced water source 160. The treatment system may include a flat ceramic or tubular membrane 180a between the vessel inlet 120a and the first vessel outlet 130 a. The treatment system may include a metal compound coating (e.g., filter layer 150) on the coating surface 185 (e.g., fig. 5B) of the ceramic membrane facing the vessel inlet 120 a. The treatment system may include a cleaning system 190a that provides a wash solution to the filter material during a cleaning cycle of the treatment system. In such embodiments, the metal compound may include iron (III) hydroxide, copper (II) hydroxide, manganese (III) hydroxide, chromium (III) hydroxide, iron (III) oxyhydroxide (ferrihydrite), manganese (III) oxyhydroxide, chromium (III) oxyhydroxide, or a combination thereof. Further, in such embodiments, the ceramic membrane may be configured such that at least a portion of the produced water entering the treatment vessel 110a during a treatment cycle of the treatment system passes through the coating, subsequently permeates the ceramic membrane and exits the treatment vessel 110a through the first vessel outlet 130a as filtered produced water. Further, in such embodiments, the wash solution may be an aqueous solution containing a reducing agent selected from sulfurous acid, a salt of sulfurous acid, or a combination thereof. In alternative embodiments, the metal compound may be selected from iron (III) hydroxide, ferrihydrite, and combinations thereof. In other alternative embodiments, the metal compound may include, consist essentially of, or consist of ferrihydrite.

Embodiments of the treatment system 100 of fig. 1 have been previously described for which the porous support 140 comprises a ceramic membrane and the filter layer 150 is a metal compound coating on the ceramic membrane. Other embodiments of the treatment system 100 that will now be described with reference to fig. 8-12 include embodiments in which the filtration layer 150 is a particle bed 155 of metal compound particles and the porous support 140 is a screen 157 or mesh that prevents removal of the particle bed from the treatment vessel 110, for example by gravity, to hold the particle bed in place.

Referring to fig. 8, in some embodiments, the processing system 100 may include a processing receptacle 110 configured as a downwardly disposed receptacle 500. In the downwardly disposed vessel 500, the processing vessel 110 is vertically arranged such that the vessel inlet 120 is higher than the first vessel outlet 130. The filter layer of the down-set vessel 500 comprises a particle bed 155 of metal compound particles. The particle bed 155 is supported by a porous support, such as a screen 157 or other suitable mesh, having a pore or mesh size that is substantially smaller than the particle size of the metal compounds in the particle bed 155. A porous support or screen 157 is placed between the vessel inlet 120 and the first vessel outlet 130, particularly between the particle bed 155 and the first vessel outlet 130. The mesh size and configuration of the screen 157 allows produced water to flow from the vessel inlet 120 to the first vessel outlet 130 and prevents particles of the particle bed 155 from passing down through the screen 157 to the first vessel outlet 130.

Referring to fig. 9, in some embodiments, the processing system 100 may include a processing receptacle 110 configured as an upwardly disposed receptacle 600. In the upwardly arranged container 600, the processing container 110 is vertically arranged such that the container inlet 120 is lower than the first container outlet 130. As in the downwardly disposed vessel 500 (fig. 8), the filter layer of the upwardly disposed vessel 600 includes a particle bed 155 of metal compound particles. The particle bed 155 is supported by a porous support, such as a screen 157 or other suitable mesh, having a pore or mesh size that is substantially smaller than the particle size of the metal compounds in the particle bed 155. A porous support or screen 157 is placed between the vessel inlet 120 and the first vessel outlet 130, particularly between the particle bed 155 and the vessel inlet 120. The mesh size and configuration of the screen 157 allows produced water to flow from the vessel inlet 120 to the first vessel outlet 130 and prevents particles of the particle bed 155 from passing down through the screen 157 to the first vessel outlet 120.

In embodiments of the processing system configured as a downwardly disposed vessel 500 (fig. 8) or an upwardly disposed vessel 600 (fig. 9), the metal compound may be selected from metal hydroxides, such as iron (III) hydroxide, copper (II) hydroxide, manganese (III) hydroxide, chromium (III) hydroxide, and combinations thereof; or selected from metal oxohydroxides, such as iron (III) oxohydroxide (ferrihydrite), manganese (III) oxohydroxide, chromium (III) oxohydroxide, combinations thereof, and combinations thereof; or a combination of a metal hydroxide and a metal oxohydroxide. For example, the metal compound may be selected from iron (III) hydroxide, ferrihydrite, and combinations thereof. As another example, the metal compound can include, consist essentially of, or consist of ferrihydrite.

Also in embodiments of the treatment system configured as the downwardly disposed vessel 500 (fig. 8) or the upwardly disposed vessel 600 (fig. 9), the reducing agent may be selected from the previously described reducing agents, including but not limited to hypophosphorous acid (H)₃PO₂) Or a salt thereof, phosphorous acid (H)₃PO₃) Or a salt thereof, oxalic acid or a salt thereof, formic acid or a salt thereof, and ammonia (NH)₃) Hydroxylamine (NH)₂OH), hydrogen under alkaline conditions, metal thiosulfate (S)₂O₃ ^2-) Metal sulfites, hydride sources (e.g., sodium borohydride), aqueous or soluble sulfur dioxide (SO)₂) Sodium bisulfite, disodium sulfite or sulfurous acid. The wash solution may be an aqueous solution of a reducing agent.

Also in embodiments of the processing system configured as a downwardly disposed vessel 500 (fig. 8) or an upwardly disposed vessel 600 (fig. 9), the particle bed 155 can be configured as a fixed particle bed or a fluidized particle bed. Typically, the fixed particle bed is comprised of large particles of metal compounds that remain fixed in place as the produced water flows through the treatment vessel 110. The size of the particles of the fixed particle bed may be in the range of 0.01mm to 3.0 mm. This particle size is defined as the square root of the projected area of the particle. In contrast, a fluidized particle bed consists of larger particles than a fixed bed. The particles of the fluidized particle bed are small enough that they can be washed away with the turbulence in the produced water as it flows through the treatment vessel 110. The particles of the fluidized particle bed are also large enough and heavy enough that they are not washed away from the first vessel outlet 130, particularly in the upwardly disposed vessel 600, where there may be no screen between the particle bed 155 and the first vessel outlet 130. The particle size of the fluidised particle bed may be in the range 1mm to 10mm and the elongation is less than 3. This particle size is defined as the square root of the projected area of the particle. Elongation is defined as the square root of the ratio of the maximum projected area to the minimum projected area of the particle.

Referring to fig. 10, in some embodiments of a treatment system for produced water, the treatment vessel 110 may be configured as a continuous particle recovery vessel 700 in addition to a particle bed comprising metal compound particles. The continuous particle recovery vessel 700 may operate in a downward configuration, as shown, with the vessel inlet 120 above the first vessel outlet 130, or may operate in an upward configuration similar to the upwardly configured vessel 600 (fig. 9), with the vessel inlet 120 below the first vessel outlet 130. In addition, the continuous particle recovery vessel 700 includes a particle inlet 715 above the screen 157 and a particle outlet 725 also above the screen 157. During a treatment cycle, the particle inlet 715 provides fresh metal compound particles from the particle source 710 to the particle bed 155.

In a treatment cycle of the continuous particle recovery vessel 700, waste particles from the particle bed 155 flow to the particle outlet 725 as the produced water flows through the treatment vessel 110. The waste particles exiting the processing vessel 110 through the particle outlet 725 may flow into a particle reclamation vessel 720, which receives the waste particles from the particle outlet 725. As previously described, in the particle reclamation vessel 720, the spent particles may be cleaned or reduced and dissolved with a wash solution that may contain a reducing agent. Furthermore, the wash solution used to clean or dissolve the waste particles may be phase separated into an organic phase and an aqueous phase. For example, organic compounds, such as crude oil, can be extracted and recovered from the organic phase. The washed particles of metal compound or solvated reduced metal compound may be recovered from the aqueous phase and may be regenerated or recycled back to the particle source 710 for reintroduction into the treatment vessel 110 of the continuous particle recycle vessel 700.

Particular embodiments of a treatment system for produced water including one or more beds of metal compound particles include the parallel upward configuration system 800 of fig. 11 and the downward configuration system 900 of fig. 12.

Referring to the system 800 of FIG. 11, laid out in parallel, up, two systems are combined, both of which have similar components, with part numbers ending in the lower case "a" or lower case "b". Specifically, the parallel-up arrangement system 800 includes two upwardly arranged containers 600a, 600b and is configured in a first state such that a first arrangement of containers 600a is operable in a processing cycle and a second upwardly arranged container 600b is operable in a cleaning cycle. For the first upwardly disposed container 600a in a processing cycle, valves 610a and 620a are open, while valves 193a and 195a to the first cleaning system 190a are closed. For the second upwardly disposed container 600b in the cleaning cycle, valves 610b and 620b are closed and valves 193b and 195b of the second cleaning system 190b are open.

By manipulating the valves 610a, 610b, 620a, 620b, 193a, 193b, 195a, 195b, the parallel-up arrangement of the system 800 can be switched to a second state in which the first up-arranged container 600a operates in a cleaning cycle and the second up-arranged container 600b operates in a processing cycle, in a functional reverse of the first state. In particular, the system 800 in the parallel-up layout can be switched to the second state by opening valves 193a, 195a, 610b, and 620b (shown closed in fig. 11) and closing valves 193b, 195b, 610a, and 620a (shown closed in fig. 11). It will be apparent that the system 800 in the second state in the parallel-up configuration can be restored to the first state (as shown in fig. 11) by again closing the valves 193a, 195a, 610b, and 620b and opening the valves 193b, 195b, 610a, and 620 a.

As shown in fig. 11, in a treatment cycle, produced water from the produced water source 160 is pumped into the vessel inlet 120a through the inlet pump 167a into the treatment vessel 110a, relative to the first upwardly disposed vessel 600 a. Produced water flows upward through screen 157a and particle bed 155, and then exits treatment vessel 110a through first vessel outlet 130a as filtered produced water. When the valve 640 is open (as shown), the filtered produced water may exit the system 800 in a parallel upward arrangement to the water collection reservoir 176. When the recirculation valve 630 is open (not shown), produced water may be fed back through the first upwardly disposed vessel 600a for re-filtration and treatment. During a treatment cycle involving the first upwardly disposed vessel 600a, components of the first cleaning system 190a are isolated and closed from system components involved in the treatment of produced water. The isolated components include a wash solution container 191a, a wash solution pump 192a, a valve 193a, a valve 195a, a separation container 196a, an organic collection container 197a, and a separator gas source 198 a.

As shown in fig. 11, in the cleaning cycle, with respect to the second upwardly arranged container 600b, the washing solution containing the reducing agent in the washing solution container 191b is conveyed by the aid of the washing solution pump 192b via the valve 193b to the container inlet 120 b. In contrast to the parallel cross-flow filtration system 400 described with respect to fig. 7, the scrubbing solution in the parallel upward configuration system 800 flows during the cleaning cycle as the produced water flows during the treatment cycle due to the support of the particle bed 155 by the screen 157 in the treatment vessel 110b of the upward configuration vessel 600b due to gravity. The wash solution enters the treatment vessel 110b and rises through the screen 157. After passing through the screen 157, the washing solution reduces the metallic compounds of the particle bed which during the treatment cycle act as a filtering layer (which is intended to be missing in fig. 11), dissolves the filtering layer and carries the dissolved reduced metallic compounds and any organic compounds, such as crude oil which had adhered to the filtering layer in the previous treatment cycle, so that a cleaning cycle has to be carried out. The wash solution and its solvated and unsolvated components flow out of the process vessel 110b through the first vessel outlet 130b and are returned to the cleaning system 190b through valve 195 b.

The wash solution proceeds to a separation vessel 196 b. In the separation vessel 196b, the wash solution may be phase separated into, for example, an aqueous phase and an organic phase floating on the aqueous phase. For example, a blanket of an inert gas (e.g., nitrogen) may be injected into the separation vessel 196b from the separator gas source 198b to protect the organic compounds in the organic phase from decomposition or reaction within the separation vessel 196 b. The organic phase may contain organic compounds, such as crude oil, originally present in the produced water exiting the produced water source 160. The organic compounds may be extracted from the separation vessel 196b to an organic recovery vessel 197b for further use, purification, or value-addition. The aqueous phase may contain solvated reduced metal compounds and unreacted reducing agent. Once the organic phase is extracted from separation vessel 196b, the aqueous phase may be further processed to recover reduced metal compounds for subsequent reoxidation and replaced as a filter layer with upwardly disposed vessel 600 b. Alternatively, or after any desired recovery, the aqueous phase may be recycled back to the wash solution container 191 b. If the concentration of the reducing agent in the circulating water phase is too low for the wash solution to continue to dissolve the filter layer of particles, such as the particle bed 155, then additional reducing agent may be added to the wash solution at the wash solution reservoir 191 b. During a cleaning cycle involving the second upwardly disposed container 600b, the assembly comprising the valve 610b, the valve 620b, and the inlet pump 167b is isolated and closed from the system components involved in the cleaning cycle.

Referring to fig. 12, a downward layout system 900 is depicted that is similar to the parallel upward layout system 800 of fig. 11, including only one downward layout container 500. It should be understood that a system comprising a downwardly disposed container may also be configured with a plurality of downwardly disposed containers. Depicted is the system 900 of the downward layout of fig. 12 having valves 410, 420, and 640 in the open position and valves 193 and 195 in the closed position, thus being a group of processing cycles. Switching of the reversing valves 410, 420, and 640 to the closed position and the valves 193 and 195 to the open position switches the system 900 of the down configuration of fig. 12 to a cleaning cycle. It should be readily understood that all components of the system 900 in the downward layout of fig. 12 operate in the same manner as their counterparts on both sides of the system 800 in the parallel upward layout of fig. 11. The main operational differences of the system 900 in the downward layout of FIG. 12 compared to the system 800 in the parallel upward layout of FIG. 11 are: produced water flows from the top of the treatment vessel 110 through the vessel inlet 120 to the bottom of the treatment vessel 110 through the first vessel outlet 130 during the treatment cycle of the downwardly disposed system 900, while produced water in the parallel upwardly disposed system 800 flows from the bottom of the treatment vessels 110a, 110b to the top of the treatment vessels 110a, 110 b. Thus, in the downwardly disposed system 900, the cleaning solution during the cleaning cycle flows in a direction opposite to the flow direction of the produced water during the treatment cycle, unlike the parallel upwardly disposed system 800, in which the cleaning solution during the cleaning cycle flows in the same direction as the produced water flowing in the treatment cycle in the parallel upwardly disposed system 800.

Various embodiments of treatment systems consistent with the general schematic of fig. 1 have been described, including treatment systems having a ceramic membrane as porous support 140 for the metal compound coating as filtration layer 150 and treatment systems having a screen as porous support 140 for the particle bed of metal compound particles as filtration layer 150. Embodiments of methods for treating produced water and, in particular, recovering organic compounds from produced water will now be described with reference to example systems 100, 200, 400, 800, and 900, fig. 1, 4, 7, 11, and 12, respectively, as previously described.

In some embodiments, a method for recovering organic compounds from produced water may include providing produced water to the produced water source 160 of any of the treatment systems previously described according to embodiments of the present disclosure. In the case where produced water is provided to the treatment system, the treatment cycle may be initiated by opening all valves that allow the produced water to flow to the treatment vessel 110 while closing the flow of wash solution from the cleaning system 190 of the treatment system. The produced water is then passed through filtration layer 150 during the treatment cycle until organic compounds from the produced water accumulate within filtration layer 150.

The method of recovering organic compounds from produced water further includes initiating a cleaning cycle of the treatment system to provide a wash solution to the filter material of the filter layer 150 to reduce the metal compounds to form reduced metal compounds that are soluble in the wash solution. The wash solution may then be removed from the process vessel 110. The scrubbing solution removed from the treatment vessel may contain dissolved reduced metal compounds and organic compounds to be recovered. The organic compound may be separated from the wash solution, for example, in a separation vessel. The separated organic compound may then optionally be further cleaned or purified and then recovered in a state such that the organic compound may be further used or added value. In some embodiments of the method of recovering organic compounds from produced water, the organic compounds may include crude oil.

In some embodiments, a method for recovering organic compounds from produced water may include recovering reduced metal compounds from a wash solution removed from a treatment vessel, such as by separating an aqueous phase from the wash solution in a separator vessel. The method may further comprise oxidizing the reduced metal compounds recovered from the wash solution to reform the metal compounds, and then transferring the reformed metal compounds to the treatment vessel 110 to serve as a filter layer 150 on a ceramic membrane that itself serves as the porous support 140, or as a coating of metal compound particles in a particle bed 155, the particle bed 155 serving as the filter layer 150.

In some embodiments, the method for recovering organic compounds from produced water may include a treatment system having a ceramic membrane between the filter layer 150 and the first vessel outlet 130. Filter layer 150 may include a metal compound coating on the coated surface of the ceramic membrane. During the method according to such embodiments, the metal compound coating dissolves away from the ceramic membrane when the metal compound is reduced during the cleaning cycle.

In some embodiments, a method for recovering organic compounds from produced water may include coating the surface of a fresh ceramic membrane with a reduced metal compound recovered after a cleaning cycle. The method may further comprise oxidizing the reduced metal compounds on the fresh ceramic membrane to form a regenerated coating of the metal compounds on the surface of the fresh ceramic membrane. Fresh ceramic membranes may be inserted into the process vessel 110 before or after the reducing metal compounds are oxidized.

In some embodiments, a method for recovering organic compounds from produced water may include a treatment system in which the metal compound is selected from a metal hydroxide, a metal oxohydroxide, or a combination thereof. In an example embodiment, the metal hydroxide may be selected from the group consisting of: iron (III) hydroxide, copper (II) hydroxide, manganese (III) hydroxide, chromium (III) hydroxide, and combinations thereof. In an example embodiment, the metal oxohydroxide may be selected from the group consisting of iron (III) oxohydroxide (ferrihydrite), manganese (III) oxohydroxide, chromium (III) oxohydroxide, and combinations thereof. In further exemplary embodiments, the metal compound may be selected from iron (III) hydroxide, ferrihydrite, or a combination thereof. In further example embodiments, the metal compound may include, consist essentially of, or consist of ferrihydrite. In an example embodiment, the reducing agent of the wash solution may include a compound that reduces a metal compound without decomposing or reducing organic compounds in the produced water, particularly any crude oil that may be present in the produced water. In a non-limiting illustrative example, the reducing agent can include hypophosphorous acid (H)₃PO₂) Or a salt thereof, phosphorous acid (H)₃PO₃) Or a salt thereof, oxalic acid or a salt thereof, formic acid or a salt thereof, and ammonia (NH)₃) Hydroxylamine (NH)₂OH), hydrogen under alkaline conditions, metal thiosulfate (S)₂O₃ ^2-) Metal sulfites, hydride sources (e.g., sodium borohydride), aqueous or soluble sulfur dioxide (SO)₂) Sodium bisulfite, disodium sulfite or sulfurous acid. In some embodiments, the reducing agent may include aqueous sulfur dioxide, sulfurous acid, or a salt of sulfurous acid, such as sodium bisulfite, disodium sulfite, or a combination thereof. The wash solution may be an aqueous solution of a reducing agent.

Thus, embodiments of a treatment system for produced water, and methods of recovering organic compounds (e.g., crude oil) from produced water using the treatment system, have been described. Treatment systems and associated methods according to embodiments of the present disclosure may provide valuable solutions to problems associated with the filtration of oilfield produced water, such as plugging or fouling of ceramic membranes, and the inability to treat large quantities of produced water in granular bed applications. The fouling mitigation solution provided by the treatment system according to embodiments may improve the operating efficiency of ceramic filtration technologies and make such technologies competitive with other practiced water de-oiling technologies (e.g., walnut shell filtration or induced air flotation). By providing an economically efficient cleaning process for membrane-based and bed-based water treatment processes, the treatment system according to embodiments may be used to treat large quantities of produced water under anaerobic conditions, such as produced water produced daily by industrial processes, particularly in the oil and gas industry. Furthermore, the ability to avoid waste products in a treatment system by dewatering produced water and recycling of wash solutions used to clean filtration layers (e.g., ceramic membranes) according to embodiments increases the cost benefits and environmental benefits of methods for recovering organic compounds from produced water described in this disclosure.

Examples of the invention

The embodiments described in this disclosure will be further clarified by the following examples, which should not be construed as limiting the scope of the disclosure or the appended claims.

A laboratory scale endless filtration system was configured as depicted in fig. 4. A produced water sample containing 0.5% to 2.0% by volume crude oil was filtered through a ceramic membrane with a protective layer of ferrihydrite and, as a basis for comparison, through an unprotected ceramic membrane in 200mL increments. After each 200mL increase, a backwash cycle was performed using a saturated solution of sodium bisulfite. In both cases, the ceramic membrane was a flat zirconia-titania ceramic disk with a pore size of 140 nm. Specific flux (J) is measured in liters per square meter, hour, bar, as the total volume of produced water (mL) passing through the ceramic membrane. By dividing the specific flux J for a given volume by the initial flux J determined at the first flux measurement after the start of the system₀After the coming operation is processedNormalized flux (J/J) per flux measurement for a given volume of produced water₀). Thus, the normalized flux value indicates the fraction of the original flux as a function of the amount of produced water being treated by the system. The results of these experiments are summarized in fig. 13.

For the unprotected ceramic membranes, normalized flux (J/J) after treatment of about 325mL of produced water, as shown in FIG. 13₀) To about 0, which indicates that complete scaling has occurred and that the produced water is no longer able to permeate through the unprotected ceramic membrane. On the other hand, the ability of the coated membrane to maintain a stable normalized flux after at least two cleaning cycles. No sign of irreversible complete fouling of the coated membranes was observed over the time range and volume of the experiment, and the normalized flux immediately before each cleaning cycle was always about 0.05. This value indicates that the specific flux of the coated ceramic membrane immediately prior to the cleaning cycle is about 5% of the specific flux of the fresh coated ceramic membrane.

Further experiments were conducted to evaluate the ability to recover crude oil from produced water filtered through ferrihydrite coated ceramic membranes. Three 400mL samples of produced water containing 0.5, 1.0, and 2.0 vol% crude oil were processed through the endless filtration system of fig. 4 in increments of around 200 mL. After processing 200mL and 400mL of each produced water sample, a cleaning cycle was performed. During the cleaning cycle, a reducing solution of saturated sodium bisulfite is passed through the coated ceramic membrane to strip the crude oil from the surface and dissolve the ferrihydrite coating. The spent reducing solution was collected. The modified membrane was then immersed in a saturated sodium bisulfite solution for about one hour. Once the reducing solution dissolves the metal coating, the reducing solution is added to the reducing solution used in the backwash procedure. The reducing solution was transferred to a gravimetric separation tank where the crude oil was separated from the reducing solution by centrifugation. The data are summarized in table 1.

TABLE 1

A typical industrial facility that treats produced water may operate at a treatment rate of 5,000 barrels per day to 40,000 barrels per day (barrels per day) of produced water, with one barrel being 42 gallons (about 160 liters). Based on the data of table 1, it is believed that for typical recoverable crude oil content in the produced water so treated is about 0.45% to 1.7% by volume, a treatment system according to the examples can achieve about 20 barrels per day, at least 680 barrels per day of crude oil of determinable value, available for further use or refining.

In additional experiments, a cross-flow filtration pilot plant was configured as depicted in fig. 7 using a 150kDa titania-zirconia membrane with pore sizes less than 140nm, coated inside with ferro-ferrihydrite and the same produced water used for experiments on endless filtration systems. Trans-transmembrane pressure was 0.435 bar and the steady permeation flux was set at 60 ℃ to 325 liters/(m.multidot.h.bar). The Total Organic Composition (TOC) data of the retentate stream measured at 24 hours and 96 hours at the start of the experiment showed that only 30% of the crude oil was deposited on the tubular ceramic membranes even after 4 days without cleaning cycles. The data from this experiment are summarized in table 2.

TABLE 2

As provided in fig. 14, the specific flux of produced water through tubular membranes was plotted as a function of time. During more than 90 hours, the specific flow of the system is relatively constant even without a cleaning cycle. FIG. 14 is a graph showing consistent normalized flux (J/J) of greater than or equal to 0.92 over the experimental time range₀). It is believed that cross-flow filtration systems can retain a greater normalized flux because filtration in tubular membranes is through the membrane wall, while the unfiltered retentate material can still pass through the other end of the membrane without the need to permeate the membrane itself.

Unless otherwise indicated, the disclosure of any range in this specification and claims should be understood to include the range itself and also include any matter contained therein as well as the endpoints.

It will be apparent to those skilled in the art that modifications and variations can be made to the embodiments described herein without departing from the spirit and scope of the claimed subject matter. Thus, it is intended that the present specification cover the modifications and variations of the various embodiments described herein provided such modifications and variations fall within the scope of the appended claims and their equivalents.