WO2016111652A1

WO2016111652A1 - System and method for treating sagd produced water or other fluids using hollow fiber dcmd modules

Info

Publication number: WO2016111652A1
Application number: PCT/TH2015/000001
Authority: WO
Inventors: Photchanathip PHOTONG; Supakorn ATCHARIYAWUT; Sakarin KHAISRI; Dayin Jearsiripongkul; Chanon THAICHAROEN; Duanghathai PANICHAKUL; Kanokros PHALAKORNKUL
Original assignee: Ptt Public Company Limited
Priority date: 2015-01-08
Filing date: 2015-01-08
Publication date: 2016-07-14

Abstract

A produced water treatment system includes a conduit configured for passing a heated produced water stream therethrough, the heated produced water stream including chemical contaminants comprising naphthenic acid at a concentration greater than approximately 50 ppm and acetone at a concentration greater than approximately 5 ppm; a permeate reservoir; a cooling unit fluidically coupled to the permeate reservoir and configured for receiving permeate therefrom; a pump fluidically coupled to the cooling unit and configured for outputting a permeate stream at a temperature lower than that of the heated produced water stream; a plurality of hollow fiber direct contact membrane distillation (DCMD) modules, each of which is fluidically coupled for receiving the heated produced water stream and the permeate stream in crossflow configuration; and an outlet for providing a treated water stream that contains essentially no naphthenic acid and less than approximately 1.5 ppm of acetone.

Description

SYSTEM AND METHOD FOR TREATING SAGD PRODUCED WATER OR OTHER FLUIDS USING HOLLOW FIBER DCMD MODULES

Technical Field

Aspects of this disclosure relate to systems and methods by which produced water generated as a result of oil production through steam assisted gravity drainage (SAGD) can be treated by way of direct contact membrane distillation (DCMD) using hollow fiber membrane modules, such as hollow fiber membrane modules based upon polyvinylidene fluoride (PVDF), polytetraflurouroethylene (PTFE), polypropylene (PP), and/or another polymer material.

Background

Produced water is referred to water in an underground geological formation that is brought to the surface together with oil and/or gas, which is a large volume by product or waste stream after separation of oil and gas therefrom. It was estimated that for 1999, an average of 210 million bbl of produced water was generated each day worldwide. The chemical and physical characteristics of produced water vary widely depending on geographic location and the type of geological formation under consideration. Apart from oil and gases which are separated, produced water contains various types of chemical contaminants, such as toxic organic and inorganic compounds that present a threat to the environment.

Several techniques for managing produced water have been discussed. A first option attempts to minimize the amount of produced water that reaches the surface, such as by way of mechanical devices. A second option involves recycling and reuse of produced water, and a third option is the disposal of produced water. In some situations, produced water can be put to other uses without treatment, particularly when the produced water is very clean or essentially pure. However, in most cases, the produced water must be treated before it can be reused. The cost of treatment (e.g., including equipment costs and energy costs) is an important factor in determining which produced water management option is selected.

The most common technique for reusing produced water is the reinjection thereof into the underground formation from which the produced water originated for the purpose of increasing oil and/or gas recovery. Most produced water (~71%) is reinjected for purpose of maintaining reservoir pressure and driving oil toward a producing well.

The injection of water into a formation that contains oil and/or gas is called water flooding. One type of water flooding is steam injection, which is an increasingly common technique for extracting heavy crude oil. There are two common steam injection technologies, namely, cyclic steam stimulation and steam flooding, both of which are widely used in the United States and Canada. A form of steam flooding that has been popular in the Alberta oil sands is steam assisted gravity drainage (SAGD). Briefly, in SAGD there are two horizontal wells, one a few meters above the other. Steam is injected into an upper horizontal steam injection well to reduce heavy oil viscosity such that, by gravity, the oil flows down to a lower horizontal producing well.

The treatment of produced water before injection is necessary to ensure compatibility with the formation water and to enhance oil recovery. Treated produced water can be a good source of boiler feed water for a SAGD process, and it is important that the quality of the treated produced water meets the standards of boiler feed water.

The reverse osmosis (RO) process is a well-known and widely used membrane process for clean water production, which can be applied for treating produced water because reverse osmosis membranes can retain both macromolecules and soluble solids, as small as salts. Thermally resistant RO membranes are required for handling high temperature produced water. Due to the high pressure required in RO, researchers have explored alternative membrane processes for desalination or clean water production, and the direct contact membrane distillation (DCMD) process has recently received much interest. DCMD is the simplest MD process, which applies a porous hydrophobic membrane as a phase barrier separating two aqueous streams. In DCMD, heated feed (at a temperature lower than its boiling point) flows on one side of the membrane, while cooler clean water (permeate) flows on the opposite side. The water in the feed evaporates, diffuses through the membrane pores, and condenses in the cooler permeate stream. A complete injection of non-volatile compounds in the feed can be achieved provided that there is no penetration of liquid feed into the membrane pores and there is no membrane wetting. The DCMD process has been shown to have good potential for clean water production. The operation of DCMD near atmospheric pressure makes the process versatile. It is also suitable for the treatment of high temperature feeds, such as produced water or dye rinsing water. Unfortunately, existing systems and techniques for treating produced water may not adequately reduce or remove one or more types of chemical contaminants that can be present in and can vary across different geological formations, and may operate at higher than desired temperatures, which adversely affects energy costs. A need exists for an improved system and method for treating produced water.

Summary

In accordance with an aspect of the present disclosure, a system for treating produced water includes a produced water passage, conduit, or channel configured for carrying, passing, or transferring a heated produced water stream therethrough, the heated produced water stream including chemical contaminants comprising naphthenic acid at a concentration greater than approximately 50 ppm and acetone at a concentration greater than approximately 5 ppm (e.g., approximately 10 ppm, or approximately 7.5 - 25 ppm, or higher); a permeate reservoir; a cooling unit fluidically coupled to the permeate reservoir and configured for receiving permeate therefrom; a pump fluidically coupled to the cooling unit and configured for outputting a permeate stream at a temperature lower than that of the heated produced water stream; \a plurality of hollow fiber direct contact membrane distillation (DCMD) modules, each of the plurality of hollow fiber DCMD modules fluidically coupled for receiving the heated produced water stream and the permeate stream in crossflow or countercurrent configuration; and an outlet for providing a treated water stream, wherein the treated water stream contains essentially no naphthenic acid and less than approximately 1.5 ppm of acetone. In a number of embodiments, the heated produced water stream is provided to (e.g., pumped into) the produced water conduit at a temperature of less than approximately 100 °C, for instance, less than approximately 80 °C (e.g., between approximately 40 - °80 C, such as about 60 - 80 °C), which can aid conservation of energy / reduction of energy costs. Depending upon embodiment details, the system can also include a heating unit fluidically coupled to a produced water inlet or source (e.g., corresponding to a SAGD production / extraction well produced water output / outlet), where the heating unit is configured for establishing / maintaining an intended produced water temperature; and/or a pump fluidically coupled to the heating unit and configured for generating and outputting heated produced water to the produced water conduit (e.g., at a given / selectable flow rate). In some embodiments, the heating unit can be configured for heating a produced water feed by way of waste heat recovered from another system or process.

The plurality of hollow fiber DCMD modules is arranged in one of a single stage configuration, a batch multi-stage configuration, a continuous multi-stage configuration, and a continuous multi-stage with retentate recycling configuration relative to each other. A given stage of each configuration can include a plurality of hollow fiber DCMD modules. Each of the plurality of hollow fiber DCMD modules includes a set of polymer membranes based on one of (i) polyvinylidene fluoride (PVDF), (ii) modified PVDF, (iii) polytetrafluoroethylene (PTFE), (iv) modified PTFE, (v) polypropylene (PP), (vi) modified PP, and (vii) a combination of (i) - (vi). Depending upon embodiment details, produced water chemical composition / contaminant profile (e.g., associated with a particular type of geological formation and/or geographic region / area under consideration), and/or intended produced water treatment performance characteristics, each of the plurality of hollow fiber DCMD modules can include or exclude membranes based on a particular type of polymer membrane technology (e.g., such as excluding unmodified PTFE membranes or another type of polymer membrane).

In accordance with an aspect of the present disclosure, the system can further include a primary treatment unit comprising at least the produced water conduit configured for carrying the heated produced water stream, the permeate reservoir, the cooling unit, the pump that is- fluidically coupled to the cooling unit and configured for outputting the permeate stream, and the plurality of hollow fiber DCMD modules, and an output configured for providing an intermediate feed; and a secondary treatment unit configured for receiving the intermediate feed and outputting the treated water stream, wherein the primary treatment unit is more effective for removing a first set of chemical contaminants from the produced water feed than the secondary treatment unit, and the secondary treatment unit is more effective for removing a second set of chemical contaminants from the intermediate feed than the primary treatment unit. For instance, the secondary treatment unit can be more or much more effective than the primary treatment unit with respect to removing organic contaminants such as acetone, such that the secondary treatment unit outputs a treated water stream that contains less than approximately 500 ppb of acetone. Depending upon embodiment detail, the primary treatment unit can also include a heating unit fluidically coupled to a produced water inlet or source; and a pump fluidically coupled to the heating unit and configured for generating and outputting heated produced water to the produced water conduit (e.g., at a given / selectable flow rate). The primary treatment unit can be configured for processing the permeate feed at a first temperature, and the secondary treatment unit can be configured for processing the intermediate feed at a second temperature lower or higher than the first temperature.

In certain embodiments, the secondary treatment unit can include or be a set of activated carbon aqueous phase adsorption modules or a membrane photocatalytic reactor.

In accordance with an aspect of the present disclosure, a process for treating produced water includes providing a produced water conduit configured for carrying a heated produced water stream including chemical contaminants comprising naphthenic acid at a concentration greater than approximately 50 ppm and acetone at a concentration greater than approximately 5 ppm; providing a permeate reservoir; providing a cooling unit fluidically coupled to the permeate reservoir and configured for receiving permeate therefrom; providing a pump fluidically coupled to the cooling unit and configured for outputting a permeate stream at a temperature lower than that of the heated produced water stream; providing a plurality of hollow fiber direct contact membrane distillation (DCMD) modules, each of the plurality of hollow fiber DCMD modules fluidically coupled for receiving the heated produced water stream and the permeate stream in crossflow configuration; providing an outlet for providing a treated water stream; passing the heated produced water stream through the produced water conduit; processing the heated produced water stream by way of the plurality of hollow fiber DCMD modules; and outputting a treated water stream that contains essentially no naphthenic acid and less than approximately 1.5 ppm of acetone. Passing the heating produced water stream through the produced water conduit can include providing a heated produced water feed a temperature of less than approximately 80 °C to the produced water conduit at a predetermined flow rate.

The process further includes arranging the plurality of hollow fiber DCMD modules in one of a single stage configuration, a batch multi-stage configuration, a continuous multi-stage configuration, and a continuous multi-stage with retentate recycling configuration relative to each other. A given stage of each configuration can include a plurality of hollow fiber DCMD modules. Each of the plurality of hollow fiber DCMD modules includes a set of polymer membranes based on one of (i) polyvinylidene fluoride (PVDF), (ii) modified PVDF, (iii) polytetrafluoroethylene (PTFE), (iv) modified PTFE, (v) polypropylene (PP), (vi) modified PP, and (vii) a combination of (i) - (vi). In certain embodiments, unmodified PTFE membranes can be excluded from the plurality of hollow fiber DCMD modules. In accordance with an aspect of the present disclosure, the process can include providing a primary treatment unit that includes the produced water conduit, the permeate reservoir, the cooling unit, the pump, the plurality of hollow fiber DCMD modules, and an output configured for providing an intermediate feed; and providing a secondary treatment unit configured for receiving the intermediate feed and outputting the treated water stream, where the primary treatment unit is more effective for removing a first set of chemical contaminants from the produced water feed than the secondary treatment unit, and the secondary treatment unit is more effective for removing a second set of chemical contaminants from the intermediate feed than the primary treatment unit. In some embodiments, the intermediate feed can be processed using the secondary treatment unit such that the treated water stream contains less than approximately 500 ppb of acetone. The heated produced water stream can be processed using the primary treatment unit at a first temperature, and the intermediate feed can be processed using the secondary treatment unit at a second temperature lower than the first temperature. Processing the intermediate feed using the secondary treatment unit can include at least partially removing the secondary set of contaminants using one of a set of activated carbon aqueous phase adsorption modules and a membrane photocatalytic reactor.

Brief Description of the Drawings

FIG. 1 is a schematic illustration of a reference feed treatment system in accordance with an embodiment of the present disclosure, corresponding to reference experiments performed using deionized (DI) water as a first reference feed and synthetic produced water (SPW) as a second reference feed. FIGs. 2A - 2C are graphs illustrating measured permeation fluxes of hollow fiber PVDF and PTFE membranes at different feed temperatures, different laminar reference feed flow rates at a reference feed temperature of 70 °C; and different turbulent reference feed flow rates at a reference feed temperature of 70 °C, respectively.

FIGs. 3 A - 3B are graphs illustrating measured permeation fluxes of hollow fiber PVDF and PTFE membranes, respectively, at different laminar reference feed flow rates for reference feed temperatures of 60 °C, 70 °C, and 80 °C. FIG. 4 is a graph illustrating representative expected long term performance of hollow fiber PVDF and PTFE membranes under conditions of a reference feed flow rate of 0.4 L/min and a reference feed temperature of 70 °C.

FIGs. 5A - 5B are graphs illustrating measured acetone and phenols concentrations, respectively, in permeate obtained at different reference feed flow rates using a reference feed temperature of 70 °C.

FIG. 6A - 6B are graphs illustrating measured acetone and phenols concentrations, respectively, in permeate obtained at different reference feed temperatures at a fixed feed flow rate of 0.4L/min.

FIG. 7 is a graph illustrating FTIR spectra of naphthenic acid concentrations in each of (a) an SPW feed solution containing 300 ppm naphthenic acid, (b) an SPW feed solution containing 50^' ppm naphthenic acid, and (c) permeate following treatment of the SPW feed solution containing 300 ppm naphthenic acid.

FIG. 8A illustrates portions of a representative single stage produced water treatment system 100 in accordance with an embodiment of the present disclosure, having multiple hollow fiber PVDF or PTFE DCMD modules arranged in a parallel configuration.

FIG. 8B illustrates an expected number of modeled or designed hollow fiber reference PVDF DCMD modules required for treating 20 m³ of S AGD produced water / day by way of operating the single stage produced water treatment system of FIG. 8A at approximately 60 °C or 80 °C when the system 100 utilizes reference PVDF DCMD modules.

FIG. 8C illustrates an expected number of modeled or designed hollow fiber reference PVDF or reference PTFE DCMD modules required for treating 20 m³ of SAGD produced water / day by way of the single stage produced water treatment system of FIG. 8 A with respect to different SAGD produced water feed flow rates using a produced water feed temperature of approximately 80 °C. FIG. 8D illustrates an expected percentage recovery of clean water achievable at different SAGD produced water feed flow rates for treating approximately 20 m of SAGD produced water / day by way of the single stage produced water treatment system of FIG. 8A utilizing modeled or designed hollow fiber reference PVDF or reference PTFE DCMD modules using a produced water feed temperature of approximately 80 °C.

FIG. 9A illustrates a modeled number of enhanced or better optimized hollow fiber DCMD modules required for treating approximately 20 m of produced water / day at a produced water feed temperature of approximately 80 °C and a Reynolds number of approximately 1940 by way of the single stage produced water treatment system of FIG. 8A in accordance with an embodiment of the present disclosure.

FIG. 9B illustrates a modeled percentage recovery of clean water attainable by the single stage produced water treatment system of FIG. 8A using enhanced or better optimized hollow fiber DCMD modules at a produced water feed temperature of approximately 80 °C and a Reynolds number of approximately 1940.

FIGs. 10A - IOC are schematic illustrations showing portions of a representative multistage produced water treatment system in accordance with an embodiment of the present disclosure, which are configured for batch produced water treatment, continuous produced water treatment, and continuous produced water treatment with retentate recycling capabilities, respectively. FIG. 1 1 is a schematic illustration of a produced water treatment system including a primary treatment unit and a secondary treatment unit in accordance with an embodiment of the present disclosure. Detailed Description

In the present disclosure, the depiction of a given structural or functional element or consideration or use of a particular corresponding number in a FIG. or a reference thereto in corresponding descriptive material can encompass the same, an equivalent, or an analogous element or element number identified in another FIG. or descriptive material associated therewith. Herein, the use of "/" in text or an associated FIG. is understood to mean "and/or" unless otherwise indicated. The recitation of a particular numerical value or value range herein is understood to include or be a recitation of an approximate numerical value or value range, such as to within +/- 20%, +/- 10%, or +/- 5% of the recited value or value range. In an analogous manner, the terms "approximately" and "about" refer to approximate values or value ranges, such as to within +/- 20%, +/- 10%», +/- 5%, +/- 2%>, +/- 1%, or +/- 0.5%) of a recited value or value range. Herein, the mention of or a reference to "an embodiment in accordance with the present disclosure" can correspond or apply to multiple embodiments in accordance with the present disclosure, and/or vice versa. Hence, the mention of or a reference to "an embodiment in accordance with the present disclosure" can mean "at least one embodiment in accordance with the present disclosure."

As used herein, the term "set" corresponds to or is defined as a non-empty finite organization of elements that mathematically exhibits a cardinality of at least 1 (i.e., a set as defined herein can correspond to a unit, singlet, or single element set, or a multiple element set), in accordance with known mathematical definitions (for instance, in a manner corresponding to that described in An Introduction to Mathematical Reasoning: Numbers, Sets, and Functions, "Chapter 1 1 : Properties of Finite Sets" (e.g., as indicated on p. 140), by Peter J. Eccles, Cambridge University Press (1998)). The term "subset" as used herein correspondingly refers to a particular portion (e.g., a fractional portion) of a set having two or more elements. In general, an element of a set or subset can include or be a compound, a composition, an ingredient, a constituent, a portion of a process, a physical parameter, or a value depending upon the type of set or subset under consideration.

Overview

Various embodiments in accordance with the present disclosure are directed to systems, apparatuses, units, devices, and processes that utilize hollow fiber direct contact membrane distillation (DCMD) modules in a crossflow configuration for treating / purifying produced water that has been generated in association with an oil production steam stimulation process, such as steam assisted gravity drainage (SAGD). Produced water that has been treated / purified in accordance with several embodiments of the present disclosure can be suitable for use (e.g., directly used, without further treatment / purification) as recycled water for the production of steam that is reinjected into a SAGD well, or otherwise utilized in association with a SAGD oil production process or facility. At least some embodiments in accordance with the present disclosure are additionally or alternatively directed to systems, apparatuses, devices, and processes that utilize hollow fiber DCMD - modules in a crossflow configuration for treating / purifying additional or other types of fluids or liquids, for instance, waste liquid or wastewater containing one or more types of dye compounds (e.g., textile industry dye rinsing wastewater). A waste liquid or wastewater that has been treated / purified in accordance with a number of embodiments of the present disclosure can be suitable for use (e.g., directly used) as recycled liquid or water that can be fed back into a process by which the waste liquid or wastewater was generated, respectively, or for other purposes. For purpose of brevity and to aid understanding, in the description hereafter the term "produced water" can refer to produced water or waste liquid or wastewater, and the term "produced water feed" can correspondingly refer to a produced water feed or a waste liquid or wastewater feed.

A produced water treatment system in accordance with an embodiment of the present disclosure, such as a SAGD produced water treatment system, includes (a) a primary treatment unit having a set of primary treatment stages, where each primary treatment stage includes a number of hollow fiber DCMD modules configured for crossflow DCMD; and optionally (b) a secondary treatment unit having a set of secondary treatment stages, where a given secondary stage can be based upon or utilize a set of DCMD modules (e.g., which can be identical to or different from the DCMD module(s) of the primary treatment stage(s)) and/or another type of separation / decomposition / filtration technology, as further detailed below. As also detailed below, a system in accordance with an embodiment of the present disclosure can be configured for batch treatment or continuous treatment of produced water.

The primary treatment unit can be directed to or mainly configured for separating or removing a primary, first, or initial set of chemical compounds from a produced water feed, and the secondary treatment unit can be directed to or mainly configured for separating or removing a secondary, second, or additional set of chemical compounds from an intermediate feed obtained from an output or outlet of the primary treatment unit. The primary treatment unit can operate such that a produced water feed provided thereto exhibits a temperature within a primary treatment temperature range or at a primary treatment temperature, and the secondary treatment unit can operate such that the intermediate feed provided thereto from the output or outlet of the primary treatment unit exhibits a secondary treatment temperature range or at a secondary treatment temperature, which can be approximately identical to or different from (e.g., lower or higher than) the primary treatment temperature range or temperature depending upon embodiment details and/or an actual or expected chemical composition profile of a produced water feed under consideration. For instance, the primary treatment temperature range or temperature can fall within a temperature span of approximately 40 - 100 °C (e.g., less than approximately 80 °C, or between about 60 - 80 °C), and the secondary treatment temperature range or temperature can fall within a temperature span of approximately 20 - 80 °C, or approximately ambient temperature - 80 °C (e.g., 40 - 70 °C). Multiple embodiments in accordance with the present disclosure include or utilize hollow fiber DCMD modules in which module membranes are based upon or formed using / formed of one or more particular types of polymers, such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polypropylene (PP), another type of polymer, and/or one or more combinations thereof. In at least some embodiments, one or more polymers on which the hollow fiber DCMD modules are based or of which the hollow fiber DCMD modules are formed can include specific types of intentionally introduced materials or particles (e.g., natural polymer materials, such as chitosan; and/or micro- or nano-materials / structures / particles / fillers). Reference Experiments Using Deionized Water and Synthetic Produced Water

A number of reference experiments were conducted for purpose of estimating, generally predicting, or establishing performance characteristics and/or chemical separation / removal capabilities of particular types of hollow fiber DCMD modules, namely, hollow fiber DCMD modules based on unmodified PVDF membranes and hollow fiber DCMD modules based on unmodified PTFE membranes. The reference experiments intentionally utilized PVDF and PTFE DCMD modules corresponding to technologically primitive / non-optimal / outdated membrane technology as well as non-optimal or old / outdated system equipment (e.g., piping, insulation, and pumps) in order to estimate, establish, or define (a) conservative reference or benchmark (e.g., highly conservative or minimum) DCMD module performance characteristics for the treatment of two types of reference feeds, namely (i) deionized (DI) water, and (ii) a synthesized or synthetic SAGD produced water feed, which is hereafter simply referred to as a synthetic produced water (SPW) feed or an SPW feed solution; and (b) reference or benchmark DCMD module chemical compound separation / removal capabilities, characteristics, and/or trends corresponding to the treatment the SPW feed solution using such DCMD modules.

The chemical constituents or species and the approximate concentrations thereof provided in the SPW feed solution were intended to represent or model the approximate concentrations of contaminants commonly found in produced water, and exceed a lowest or expected lowest typical concentration of such contaminants that can be encountered in produced water (e.g., a NaCl concentration greater than approximately 0.5%, a CaC0₃ concentration greater than approximately 100 ppm, a phenols concentration greater than approximately 10 ppm, an acetone concentration greater than approximately 5 ppm, and a naphthenic acid concentration greater than approximately 50 ppm (e.g., at least approximately 100 - 1000 ppm, or approximately 200 - 500 ppm). For the reference experiments, the chemical constituents or species and the approximate concentrations thereof provided in the SPW are given in Table 1 (relative to a 100% SPW feed solution total that includes water as will be readily understood by an individual having ordinary skill in the relevant art), as follows: Compositions Concentration

NaCl 1%

CaCC-3 300 ppm

Phenols 30 ppm

Acetone 10 ppm

Naphthenic acid 300 ppm

Table 1: Chemical species and their concentrations in SPW feed solution

FIG. 1 is a schematic illustration of a reference feed treatment system, apparatus, or unit 10 having a hollow fiber DCMD module 12 in accordance with an embodiment of the present disclosure, where "FI" corresponds to a flow indicator, sensor, or meter; "Ή" corresponds to a temperature indicator, sensor, or meter (e.g., a thermometer); and "P" corresponds to a pump (e.g., a peristaltic pump). For the reference experiments, the reference feed was heated to a predetermined temperature by a heating unit, and pumped through a produced water conduit 11 (e.g., a fluidic pathway, passage, or channel, such as provided by piping or tubing) to a lumen side of a given type of hollow fiber DCMD membrane module 12 under consideration. Prior to its entry into the hollow fiber DCMD membrane module 12, the flow rate and temperature of the reference feed were measured by a flow indicator and a temperature indicator, respectively. After the reference feed passed through the hollow fiber DCMD membrane module 12 and extited a retentate output thereof, the temperature of the retentate was measured, to facilitate monitoring of temperature changes over the hollow fiber DCMD module 12 length. In the reference experiments, the reference feed temperatures were established as approximately 60 °C, 70 °C, or 80 °C, and reference feed velocities were established for two ranges of operation, namely: 0.1 - 1.0 L/min (Reynolds number 385-2100) for laminar flow, and 1.72 - 2.74 L/min (Reynolds number 4950-6200) for turbulent flow.

With respect to a permeate stream in the reference experiments, permeate water was fixed at a temperature of 10 °C by a water bath, and then pumped to a shell side of the hollow fiber DCMD module 12, counter-current to the reference feed, at a constant or approximately constant flow rate of 0.4 L/min. Permeation flux was measured by collecting an overflow sample of the permeate stream in a sample collector. The results of each reference experiment run were averaged across three such sample collections.

The specifications of the hollow fiber DCMD modules 12 and their corresponding membrane characteristics considered in the reference experiments are given by Table 2, as follows:

Descriptions PVDF*' ** PTFE* PTFE*

Pore diameter (μπι) 0.20 0.1657 0.1657

Porosity (ε) 72.95 50 50

Fiber inner diameter (mm) 0.80 1.60 1.60

Fiber outer diameter (mm) 1.30 2.0 2.00

Module inner diameter (mm) 10.00 15.50 15.50

Number of fibers 24 25 25

Effective area (m²) 0.015 0.0416 0.0083

* Modules for laminar flow experiments

**Module for turbulent flow experiments

Table 2: DCMD module specifications and corresponding membrane characteristics

The techniques by which the concentrations of chemical contaminants or constituents in the permeate were measured following treatment of the SPW feed are given in Table 3, as follows:

Compositions Analysis techniques

NaCl Conductivity measurement using pH meter, conductivity mode

CaC0₃ Titration with EDTA

Phenols Gas Chromatography (GC)

Acetone Gas Chromatography (GC)

Naphthenic acid Fourier Transform Infrared Spectroscopy (FTIR)

Table 3: Permeate composition analysis techniques Reference Experiment Results

DI Water as Reference Feed

FIG. 2A is a graph illustrating measured permeation fluxes corresponding to hollow fiber PVDF and PTFE membranes at different reference feed temperatures, namely, approximately 60 °C, 70 °C, and 80 °C. As indicated in FIG. 2A, permeation flux significantly increases with reference feed temperature. An individual having ordinary skill in the relevant art will recognize that increasing temperature directly enhances the vapor pressure of water in accordance with Antoine's equation. Furthermore, the permeation flux for the PVDF membranes considered across the temperatures considered was larger than for the PTFE membranes considered. FIG. 2B is a graph illustrating measured permeation fluxes of hollow fiber PVDF and PTFE membranes at different laminar reference feed flow rates (relative to Reynolds numbers), for a reference feed temperature of approximately70 °C. The permeation fluxes obtained for the hollow fiber DCMD modules 12 under consideration can be ranked as PVDF > PTFE. More particularly, in following equation:

J = C(P_! - P₂) (1) J is the water flux (kg/m²h), C is the membrane distillation coefficient (kg/m-h-Pa), and V_\ and P₂ are the partial pressures of water at the membrane surfaces on the feed side and the permeate side, respectively. The value of C depends on membrane characteristics such as pore size, porosity, and tortuosity. From Table 2, the pore size of the PVDF membrane is larger than that of the PTFE membrane. Thus, the value of C is higher for the PVDF membrane than the PTFE membrane.

FIG. 2C is a graph illustrating measured permeation fluxes of hollow fiber PVDF and PTFE membranes at different turbulent reference feed flow rates (relative to Reynolds numbers), for a reference feed temperature of approximately 70 °C. As indicated in FIG. 2C, the permeation flux values obtained under turbulent flow conditions were moderately higher than those under laminar flow conditions. SPW Solution as Reference Feed

FIG. 3A is a graph illustrating measured permeation fluxes of hollow fiber PVDF membranes at different laminar reference feed flow rates (relative to Reynolds numbers), for reference feed temperatures of approximately 60 °C, 70 °C, and 80 °C. FIG. 3B is a graph illustrating measured permeation fluxes of hollow fiber PTFE membranes at different laminar reference feed flow rates (relative to Reynolds numbers), for reference feed temperatures of approximately 60 °C, 70 °C, and 80 °C. The results shown in FIGs. 3 A and 3B indicate that permeation flux increases with increasing feed temperature and flow rate. The permeation fluxes for the SPW feed solution were slightly lower than for DI water at the same operating condition, because the chemical compounds or constituents of the SPW feed solution reduced the vapor pressure of water, and hence the driving force for mass transfer was reduced.

FIG. 4 is a graph illustrating representative expected long term performance of hollow fiber PVDF and PTFE membranes under conditions of a reference feed flow rate of approximately 0.4 L/min and a reference feed temperature of approximately 70 °C. As indicated in FIG. 4, small decreases in permeation fluxes over time occurred during a time interval of approximately 10 hours. More particularly, the PVDF membranes exhibited a permeation flux decrease of approximately 4.9%, and the PTFE membranes exhibited a permeation flux decrease of approximately 0.25%. Overall, the generally constant permeation fluxes observed across such a time period indicated that the membranes were not wetted over the time period, and thus the membranes can be expected to have stable or very stable performance characteristics on a long term basis. FIG. 5A is a graph illustrating measured acetone concentration in the permeate obtained at different reference feed flow rates (relative to Reynolds numbers) using a reference feed temperature of approximately 70 °C. FIG. 5B is a graph illustrating measured phenols concentration in the permeate obtained at different reference feed flow rates (relative to Reynolds numbers) using a reference feed temperature of approximately 70 °C. Acetone and phenols can transfer through the membrane pores to the permeate because of their high vapor pressure and low boiling point. The concentration of acetone and phenols decreased in the permeate with increasing reference feed flow rate (possibly due to reduced contact time). The amount of acetone transferred to the permeate was higher than the amount of phenols transferred to the permeate due to the higher vapor pressure of acetone compared to phenols. However, only trace amounts of these species (e.g., approximately 1.1 ppm) were detected in the permeate. It was found that the PVDF membranes showed lower acetone and phenols rejection performance than the PTFE membranes due to higher porosity.

FIG. 6A is a graph illustrating measured acetone concentrations in the permeate obtained at different reference feed temperatures at a fixed feed flow rate of approximately 0.4L/min. FIG. 6B is a graph illustrating measured phenols concentrations in the permeate obtained at different reference feed temperatures at a fixed feed flow rate of approximately 0.4L/min. These results indicate that the acetone and phenols concentrations in the permeate noticeably increased with increasing reference feed temperature, due to vapor pressure enhancement at higher temperatures. FIG. 7 is a graph illustrating FTIR spectra of naphthenic acid concentrations in each of (a) the SPW feed solution containing approximately 300 ppm naphthenic acid, (b) an SPW feed solution containing approximately 50 ppm naphthenic acid, and (c) the permeate following treatment of the SPW feed solution containing approximately 300 ppm naphthenic acid. For the SPW feed solution containing approximately 300 ppm naphthenic acid, FTIR peaks were observed at wave numbers of approximately 1210 - 1320 cm^"1 (C-.O stretching), approximately 910 - 950 cm^"1 and approximately 1395 - 1440 cm^"1 (O-H bending), approximately 1690 - 1760 cm^"1 (C=0 stretching), and approximately 2500 - 3300 cm^"1 (O-H stretching). For the SPW feed solution containing approximately 50 ppm naphthenic acid, peaks corresponding to such wave numbers were also observed, but such peaks were lower due to the lower naphthenic acid concentration. For the permeate samples obtained during the reference experiments, no peaks representing naphthenic acid in the permeate were detected, demonstrating that naphthenic acid could not transfer to the permeate. Table 4 shows approximate measured concentrations of permeate contaminants with respect to different reference feed flow rates (relative to Reynolds numbers) for hollow fiber PVDF membranes under turbulent and laminar flow conditions, as follows: Concentration (ppm)

Reynolds number

NaCl CaC0₃ acetone phenols Naphthenic acid

Turbulent

- 3.65 12.38

4000

5500 3.41 12.34

6000 2.45 10.55

Laminar

- 0.9-1.1 0.19-0.72

1070-2140

Table 4: approximate measured concentrations of permeate contaminants at

different reference feed flow rates for PVDF membranes. As indicated in Table 4, it was found that NaCl and CaC0₃ were not detected on the permeate side under all conditions considered in the reference experiments. These two components cannot vaporize under such conditions, and they would only be able to transfer through the membrane to the permeate in the event that the membrane pores are wetted. Thus^ this further confirms that the PVDF and PTFE membranes were not wetted under the reference experiment conditions. As additionally indicated in Table 4, the concentrations of acetone and phenols in the permeate samples was significantly higher under turbulent flow conditions than laminar flow conditions.

Representative Single Stage System and Performance based on Modeled Reference Modules

FIG. 8A illustrates portions of a representative single stage produced water treatment system 100 in accordance with an embodiment of the present disclosure, which utilizes multiple hollow fiber DCMD modules 120 arranged in a parallel configuration. In the representative single stage produced water treatment system 100, the treatment of produced water is continuous. Heated produced water passes through a produced water conduit 110 in a manner essentially identical or analogous to that described above, and is fed into the lumen side of each hollow fiber DCMD module 120 at an identical or approximately identical feed velocity and temperature. Depending upon embodiment details, the single stage produced water treatment system 100 can include a heating unit and/or a pump, in a manner essentially identical or analogous to that set forth above. In the single stage produced water treatment system 100, the permeate streams are fed into the shell sides of the hollow fiber DCMD modules 120, counter current to the produced water feed streams. Some outlet permeate is recirculated to a permeate reservoir in order to keep the flow rate of the permeate side constant or essentially constant, while the remainder is drawn out as treated or clean water.

In a representative model of the performance of the single stage produced water treatment system 100, hollow fiber DCMD modules 120 can respectively be modeled or designed based upon the hollow fiber PVDF or PTFE DCMD modules used in the above reference experiments, and can correspondingly have modeled or designed hollow fiber reference PVDF or reference PTFE DCMD module specifications as indicated in Table 5 hereafter:

Description PVDF PTFE

Pore size (μηι) 0.2 0.166

Inner diameter (mm) 0.80 1.60

Outer diameter (mm) 1.30 2.00

Shell diameter (cm) 7.22 7.22

Effective length (m) 1.5 1.5

Number of fiber 1327 664

Mass transfer area (m²) 5.0 5.0

Table 5: Representative modeled or designed hollow fiber reference PVDF and reference PTFE DCMD module specifications

For each of the modeled or designed hollow fiber reference DCMD modules, the shell diameter and effective length is 7.22 cm and 1.5 m, respectively. The number of fibers was varied to obtain mass transfer area of 5 m (based on hollow fiber inner diameter).

FIG. 8B illustrates an expected number of modeled or designed hollow fiber reference PVDF DCMD modules 120 required for treating 20 m³ of SAGD produced water / day by way of continuously operating the single stage produced water treatment system 100 of FIG. 8 A at approximately 60 °C or 80 °C when the system 100 utilizes reference PVDF DCMD modules 120 corresponding to Table 5. FIG. 8B shows that the number of such modules 120 required directly corresponds to the required mass transfer area, and decreases with increasing feed velocity and temperature because of increasing permeation flux. Hence, produced water treatment process performance directly relates to the permeation flux. At a permeate feed temperature of 80 °C, the number of modeled or designed hollow fiber reference PVDF DCMD modules 120 required are 93 and 56 for Reynolds numbers 725 and 1940, respectively.

FIG. 8C illustrates an expected number of modeled or designed hollow fiber reference PVDF or reference PTFE DCMD modules 120 corresponding to Table 5 that would be required for treating 20 m of SAGD produced water / day by way of the single stage produced water treatment system 100 of FIG. 8 A with respect to different SAGD produced water feed flow rates (relative to Reynolds numbers) at a produced water feed temperature of approximately 80 °C. The number of modeled or designed hollow fiber reference PTFE DCMD modules 120 is greater than that for modeled or designed hollow fiber reference PVDF DCMD modules 120 because the PTFE membrane exhibits lower permeation flux. At a Reynolds number of approximately 1940, the number of modeled or designed hollow fiber reference PVDF DCMD modules 120 and reference PTFE DCMD modules 120 equals 56 and 132, respectively. FIG. 8D illustrates an expected percentage recovery of clean water achievable at different SAGD produced water feed flow rates (relative to Reynolds numbers) for treating approximately 20 m³ of SAGD produced water / day by way of the single stage produced water treatment system 100 of FIG. 8 A utilizing the modeled or designed hollow fiber reference PVDF or reference PTFE DCMD modules 120 corresponding to Table 5, and a produced water feed temperature of approximately 80 °C. The percent recovery is determined in accordance with the following equation:

% Recovery = (Q_C / QF) * 100 (2) where QF is the total flow rate of produced water fed into the process, and Qc is the total flow rate of clean water provided, output, generated, or produced.

The percent recovery results show that percent recovery decreases with increasing feed velocity. This is because even though the permeation flux increases with velocity, the rate of permeation flux increase is lower than the amount of produced water fed into the process.

Performance Enhancement via More Advanced Hollow Fiber Membrane Technologies The above reference experiments and hence the modeled or designed hollow fiber reference PVDF and reference PTFE DCMD modules 120 corresponding to Table 5 are intentionally based upon primitive / non-optimized / outdated DCMD module technology (e.g., utilizing non-modified membranes based only upon a single polymer technology, where the hollow fiber reference PVDF and reference PTFE DCMD modules were approximately 1 decade old) and non-optimized / outdated system equipment (e.g., piping, insulation, and pumps) in order to estimate, define, establish conservative reference or benchmark (e.g., highly conservative or effectively a minimum) performance characteristics of a representative reference or benchmark produced water treatment system or a primary treatment unit thereof. If more technologically advanced or better optimized membrane technology, as well as better optimized / modern system equipment (e.g., piping, insulation, and pumps) are employed in a produced water treatment system in accordance with an embodiment of the present disclosure instead of the hollow fiber reference PVDF or hollow fiber reference PTFE DCMD modules and outdated system equipment, significantly or greatly improved hollow fiber DCMD module configuration requirements (e.g., total module count requirements) and enhanced produced water treatment performance will result. For instance, the number of modules required for treating an intended volume of produced water can be reduced by approximately 40% - more than approximately 90%, and produced water treatment process performance (e.g., as measured by percent recovery) can be improved by more than an order of magnitude, including under operating conditions (e.g., temperature and flow rate conditions) that are approximately equivalent or analogous to those described above for the reference experiments. More particularly, hollow fiber membrane performance data reported in publications by various groups can be utilized to model or design enhanced or better optimized hollow fiber DCMD modules, for instance, in a manner elaborated upon hereafter, and corresponding enhanced or better optimized hollow fiber DCMD modules that are based upon such model(s) / design(s) can be employed in a produced water treatment system that utilizes better optimized / modern equipment (e.g., piping, insulation, and pumps) in accordance with essentially any embodiment of the present disclosure to thereby provide enhanced or better optimized (e.g., greatly enhanced or dramatically optimized) produced water treatment system configurations and/or produced water treatment performance. Table 6A provides expected approximate performance characteristics of enhanced or better optimized hollow fiber membranes based upon data reported in particular publications describing more technologically advanced membrane technologies, as follows:

Feed Permeate

Reference Flux (kg/m²h)

T (°C) v (m/s) T (°C) v (m/s)

Teoh et al. [1] 75 0.86 20 0.05 5.8

Gryta [2] 90 0.96 20 0.29 34

Teoh et al. [3] 80 1.9 17.5 0.9 46.1

Yang et al. [4] 70 1.86 25 0.18 51

Bonyadi et al. [5] 90 1.6 16.5 0.8 55.2

Table 6A: Expected approximate performance characteristics of enhanced or better optimized hollow fiber membranes based upon published data.

The hollow fiber membrane technology of publication [1], Teoh et al, is based on PP; the hollow fiber membrane technology of publication [2], Gryta, is based on PP; the hollow fiber membrane technology of publication [3], Teoh et al., is based on PTFE-PTFEPVDF- PTFE; the hollow fiber membrane technology of publication [4], Yang et al., is based on modified PVDF; and the hollow fiber membrane technology of publication [5], Bonyadi et al., is based on modified PVDF. The bibliographic citation corresponding to each of publications [1] - [5] is provided at the end of this detailed description.

Table 6B provides approximate enhanced or better optimized hollow fiber DCMD module specifications corresponding to the enhanced or better optimized hollow fiber membrane performance characteristics of Table 6 A, as follows: Reference: [1] [2] [3] [4] [5]

DCMD Module Specs

Inner diameter (μηι) 260 1800 680 1 195 520

Outer diameter (μιη) 370 2600 980 1470 1200

Shell diameter (cm) 7.22 7.22 7.22 7.22 7.22

Effective length (m) 1.5 1.5 1.5 1.5 1.5

Number of fibers 4080 590 1560 889 2040

Mass transfer area (m²) 5 5 5 5 5

Table 6B; Enhanced or better optimized hollow fiber DCMD module specifications

Use of enhanced or better optimized hollow fiber DCMD modules having the hollow fiber DCMD module specifications given in Table 6B in a produced water treatment system in accordance with embodiments of the present disclosure, such as the single stage produced water treatment system 100 of FIG. 8 A, would result in a significantly or greatly enhanced single stage produced water treatment system compared to the use of the modeled or designed hollow fiber reference PVDF or reference PTFE DCMD modules 120 described above. For instance, FIG. 9A illustrates a modeled number of enhanced or better optimized hollow fiber DCMD modules required for treating approximately 20 m of produced water / day using the single stage produced water treatment system 100 of FIG. 8A at a produced water feed temperature of approximately 80 °C and a Reynolds number of approximately 1940, compared to the fifty-six modeled or designed hollow fiber reference PVDF DCMD modules required under corresponding conditions as indicated in FIG. 8B. More particularly, based on the membrane technology of publication [1], fewer than thirty enhanced or better optimized hollow fiber DCMD modules would be required; and based on the membrane technology of each of publications [2] - [5], six or fewer enhanced or better optimized hollow fiber DCMD modules would be required. With respect to publication [5], only three enhanced or better optimized hollow fiber DCMD modules would be required.

FIG. 9B illustrates a modeled percentage recovery of clean water attainable by the single stage produced water treatment system of FIG. 8A using enhanced or better optimized hollow fiber DCMD modules corresponding to Table 6B, compared to the modeled or designed hollow fiber reference PVDF DCMD module of FIG. 8C at a produced water feed temperature of approximately 80 °C and a Reynolds number of approximately 1940. As shown in FIG. 9B, use of the enhanced or better optimized hollow fiber DCMD modules that are modeled or designed based upon data in publications [2] - [4] gives a percentage recovery of between approximately 3 - 6%, which is several times greater than the result for the modeled or designed hollow fiber reference PVDF DCMD module indicated in FIG. 8C. Use of the enhanced or better optimized hollow fiber DCMD module that is modeled or designed based upon data in publication [5] gives a percentage recovery of approximately 11%, which is dramatically higher than that for the modeled or designed hollow fiber reference PVDF DCMD module indicated in FIG. 8C.

An individual having ordinary skill in the relevant art will recognize that enhanced or better optimized hollow fiber DCMD modules can be designed based upon reported results associated with or corresponding to essentially any type of hollow fiber membrane material(s) or technology / technologies, such as PVDF, PTFE, PP, modifications or modified versions (e.g., surface modified versions) thereof, and/or combinations of these. In a number of embodiments, enhanced or better optimized hollow fiber DCMD modules are based upon polymer membranes other than or which exclude unmodified PTFE membranes.

Representative Multi-Stage System Designs

As an alternative to a single stage system design, embodiments in accordance with the present disclosure can exhibit a multi-stage design for treating produced water. Such multi-stage designs can significantly or greatly enhance produced water treatment process performance, and can be directed to batch treatment or continuous treatment of produced water, as further detailed below. A multi-stage produced water treatment system in accordance with an embodiment of the present disclosure (e.g., corresponding to or analogous to any one of embodiments shown in FIGs. 10A - IOC) includes at least one conduit through which heated produced water travels and is subsequently provided or distributed to a plurality of hollow fiber DCMD modules, in a manner essentially identical or analogous to that described above. Depending upon embodiment details, a given multistage produced water treatment system in accordance with an embodiment of the present disclosure can include a set of heating units configured for heating a produced water feed, and/or a set of pumps, in a manner essentially identical or analogous to that set forth above.

FIG. 10A is a schematic illustration showing portions of a representative multi-stage produced water treatment system 200 in accordance with an embodiment of the present disclosure, which is configured for batch produced water treatment. In a batch produced water treatment process, the percent recovery attainable can theoretically approach 100%, and high permeation flux can be achieved by increasing recirculation rate. However, process performance drops over time due to increasing solution contaminant concentrations.

FIG. 10B is a schematic illustration showing portions of another representative multi-stage produced water treatment system 300 in accordance with an embodiment of the present disclosure, which is configured for continuous produced water treatment. Continuous produced water treatment processes exhibit low energy requirements, and constant permeation flux over their periods of operation. However, percent recovery is lower compared to other produced water treatment processes, and permeation flux cannot be improved. FIG. IOC is a schematic illustration showing portions of yet another representative multistage produced water treatment system 350 in accordance with an embodiment of the present disclosure, which is configured for continuous produced water treatment with retentate recycling capabilities. Continuous produced water treatment with recycling capabilities can achieve high permeation flux by increasing the recycling rate. However, energy requirements are high(er) due to the system's high flow rate.

Systems Including: Primary and Secondary Produced Water Treatment Units

As indicated above, some embodiments of produced water treatment systems or processes include (a) a primary treatment unit having one or more primary treatment stages therein, where each primary treatment stage includes a number of hollow fiber DCMD modules configured for crossflow DCMD; and optionally (b) a secondary treatment unit having one or more secondary treatment stages therein, where a given secondary stage can be based upon or utilize a set of DCMD modules (e.g., which can be identical to or different from the DCMD module(s) of the primary treatment unit) and/or another type of separation / decomposition / filtration technology.

FIG. 11 is a schematic illustration of a produced water treatment system 400 including a primary treatment unit 500 fluidically coupled to a secondary treatment unit 600 in accordance with an embodiment of the present disclosure, where the secondary treatment unit 600 is configured for outputting a treated or clean water stream. The primary treatment unit 500 can be based on, correspond to, include, or be any of the foregoing types of produced water treatment systems 10 / 100 / 200 / 300 / 350 described above with reference to FIGs. 1, 8 A, and 10A - IOC, depending upon embodiment details. Thus, the primary treatment unit 500 includes at least one produced water conduit 1 10 through which heated produced water flows, and is subsequently provided to a set of hollow fiber DCMD modules. Depending upon embodiment details, the primary treatment unit 500 can also include a set of heating units configured for heating a produced water feed, and/or one or more pumps for providing the heated produced water feed to the produced water conduit(s) 110 at a given (e.g., predetermined / selectable / adjustable) flow rate.

The primary treatment unit 500 can be directed to or mainly configured for separating or removing a primary, first, or initial set of chemical compounds or contaminants such as naphthenic acid and other compounds (e.g., NaCl and CaC0₃) from a produced water feed, and the secondary treatment unit 600 can be directed to or mainly configured for separating or removing a secondary, second, or additional set of chemical compounds or contaminants^' such as acetone, phenols, and/or particular volatile organic compounds (VOCs) from an intermediate feed corresponding to partially treated produced water obtained from an output or outlet of the primary treatment unit 500. Thus, the primary treatment unit 500 can be more or much more effective for removing the primary set of chemical compounds than the secondary treatment unit 600, and the secondary treatment unit 600 can be more or much more effective for removing the secondary set of chemical compounds than the primary treatment unit 500, where the first and second sets of chemical compounds are distinguishable from each other. By way of the combination of the primary treatment unit 500 and the secondary treatment unit 600, the treated or clean water can be free or essentially free of each of the primary and secondary sets of chemical contaminants, (for instance, chemical contaminants within each of the primary and secondary sets of chemical contaminants can be present in the treated / clean water at concentrations of less than approximately 500 ppb, e.g., less than approximately 100 - 300 ppb). The primary treatment unit 500 can operate such that a produced water feed provided thereto exhibits a temperature within a primary treatment temperature range or at a primary treatment temperature, and the secondary treatment unit 600 can operate such that the intermediate feed provided thereto from the output or outlet of the primary treatment unit 500 exhibits a secondary treatment temperature range or at a secondary treatment temperature, which can be approximately identical to or different from (e.g., lower or higher than) the primary treatment temperature range or temperature depending upon embodiment details and/or an actual or expected chemical composition profile of a produced water feed under consideration. For instance, the primary treatment temperature range or temperature can fall within a temperature span of approximately 20 - 100 °C (e.g., about 40 - 80 °C, or about 60 - 80 °C), and the secondary treatment temperature range or temperature can fall within a temperature span of approximately 20 - 200 °C, for instance, a temperature between approximately ambient temperature - 80 °C (e.g., about 20 - 80 °C, or about 40 - 70 °C). The use of a secondary treatment unit that is configured for processing the intermediate feed at a lower temperature than that at which the primary treatment unit processes the permeate feed can aid the management or reduction of energy costs associated with producing treated or clean water.

The type, characteristics, specifications, and/or operating conditions of the secondary treatment unit 600 can depend upon the particular chemical species or contaminants that are or which are expected to be present in produced water associated with a particular source thereof, such as a particular geological formation into which steam is injected and from which produced water is extracted or withdrawn. An individual having ordinary skill in the relevant art will understand that the specific chemical contaminants present in produced water extracted from one geographical region or area can differ or significantly differ from the chemical contaminants present in produced water extracted from another geographical region or area. Thus, a produced water treatment system 400 that includes an appropriate type of secondary treatment unit 600 can enhance or significantly enhance the cleanliness or purity of water output by the produced water treatment system 400. In certain embodiments, the secondary treatment unit 600 includes a set of activated carbon aqueous phase adsorption modules or filters, which in at least some embodiments can utilize or be treated with an oxidizing agent for purpose of enhancing acetone removal. Such activated carbon adsorption modules / filters can periodically undergo or be subjected to a steam regeneration process to facilitate their reuse, in a manner understood by an individual having ordinary skill in the relevant art. Additionally or alternatively, the secondary treatment unit 600 can include a different type of chemical filtration or decomposition / degradation technology, for instance a membrane photocatalytic reactor (MPR) such as a submerged MPR (sMPR) that utilizes polymer - titanium dioxide membranes (e.g., PVDF - Ti02 membranes) under UV irradiation conditions (e.g., at approximately 254 nm or shorter optical wavelengths) to decompose / degrade organic compounds. In embodiments such as the foregoing, when the intermediate feed contains acetone, the secondary treatment unit 600 can remove or decompose / degrade essentially all of the acetone in the intermediate feed such that treated or clean water output from the secondary treatment unit 600 contains essentially no or no acetone and phenols (for instance, the concentration of acetone in the treated / clean water would be less than approximately 500 ppb, e.g., less than approximately 100 - 300 ppb). An individual having ordinary skill in the relevant art will additionally recognize that the secondary treatment unit 600 can include or be fiuidically coupled to a set of pumps, and can include or be thermally coupled to a set of heat exchangers in accordance with a type of secondary treatment unit 600 under consideration. Aspects of particular embodiments of the present disclosure address at least one aspect, problem, limitation, and/or disadvantage associated with exiting systems and processes for treating produced water, such as SAGD produced water. While features, aspects, and/or advantages associated with certain embodiments have been described in the disclosure, other embodiments may also exhibit such features, aspects, and/or advantages, and not all embodiments need necessarily exhibit each of such features, aspects, and/or advantages to fall within the scope of the disclosure. It will be appreciated by a person of ordinary skill in the art that several of the above-disclosed systems, apparatuses, components, processes, or alternatives thereof, may be desirably combined into other different systems, apparatuses, components, processes, and/or applications. In addition, various modifications, alterations, and/or improvements that fall within the scope of the present disclosure may be made to various embodiments by an individual having ordinary skill in the relevant art.

Publications mentioned above corresponding to enhanced or better optimized hollow fiber DCMD modules of FIGs. 9A - and 9B are as follows:

[1] M.M. Teoh, S. Bonyadi, T.-S. Chung, Investigation of different hollow fiber module designs for flux enhancement in the membrane distillation process, Journal of Membrane Science, 311 (2008) 371-379.

[2] M. Gryta, Influence of polypropylene membrane surface porosity on the performance of membrane distillation process, Journal of Membrane Science, 287 (2007) 67-78. [3] M.M. Teoh, T.-S. Chung, Membrane distillation with hydrophobic macrovoid-free PVDF-PTFE hollow fiber membranes, Separation and Purification Technology, 66 (2009) 229-236.

[3] X. Yang, R. Wang, L. Shi, A.G. Fane, M. Debowski, Performance improvement of PVDF hollow fiber-based membrane distillation process, Journal of Membrane Science, 369 (201 1) 437-447.

[5] S. Bonyadi, T.S. Chung, Flux enhancement in membrane distillation by fabrication of dual layer hydrophilic-hydrophobic hollow fiber membranes, Journal of Membrane Science, 306 (2007) 134-146.

Claims

1. A system for treating produced water, comprising:

a produced water conduit configured for passing a heated produced water stream therethrough, the heated produced water stream including chemical contaminants comprising naphthenic acid at a concentration greater than approximately 50 ppm and acetone at a concentration greater than approximately 5 ppm;

a permeate reservoir;

a cooling unit fluidically coupled to the permeate reservoir and configured for receiving permeate therefrom;

a pump fluidically coupled to the cooling unit and configured for outputting a permeate stream at a temperature lower than that of the heated produced water stream;

a plurality of hollow fiber direct contact membrane distillation (DCMD) modules, each of the plurality of hollow fiber DCMD modules fluidically coupled for receiving the heated produced water stream and the permeate stream in crossflow configuration; and

an outlet for providing a treated water stream,

wherein the treated water stream contains essentially no naphthenic acid and less than approximately 1.5 ppm of acetone.

2. The system of claim 1, wherein the plurality of hollow fiber DCMD modules is arranged in one of a single stage configuration, a batch multi-stage configuration, a continuous multi-stage configuration, and a continuous multi-stage with retentate recycling configuration relative to each other.

3. The system of claim 2, wherein a given stage of each configuration comprises a plurality of hollow fiber DCMD modules.

4. The system of claim 2, wherein each of the plurality of hollow fiber DCMD modules comprises a set of polymer membranes based on one of (i) polyvinylidene fluoride (PVDF), (ii) .modified PVDF, (iii) polytetrafluoroethylene (PTFE), (iv) modified PTFE, (v) polypropylene (PP), (vi) modified PP, and (vii) a combination of (i) - (vi).

5. The system of claim 2, wherein each of the plurality of hollow fiber DCMD modules comprises a set of polymer membranes that excludes unmodified PTFE membranes.

6. The system of claim 1, wherein the heated produced water stream is provided to the produced water conduit at a temperature of less than approximately 80 °C.

7. The system of claim 1 , further comprising:

a primary treatment unit comprising the produced water conduit, the permeate reservoir, the cooling unit, the pump, and the plurality of hollow fiber DCMD modules, and an output configured for providing an intermediate feed; and a secondary treatment unit configured for receiving the intermediate feed and outputting the treated water stream,

wherein the primary treatment unit is more effective for removing a first set of chemical contaminants from the produced water feed than the secondary treatment unit, and the secondary treatment unit is more effective for removing a second set of chemical contaminants from the intermediate feed than the primary treatment unit.

8. The system of claim 7, wherein the treated water stream contains less than approximately 500 ppb of acetone.

9. The system of claim 7, wherein the primary treatment unit is configured for processing the heated produced water stream at a first temperature, and the secondary treatment unit is configured for processing the intermediate feed at a second temperature lower than the first temperature.

10. The system of claim 7, wherein the secondary treatment unit comprises one of a set of activated carbon aqueous phase adsorption modules and a membrane photocatalytic reactor.

11. A method for treating produced water, comprising:

providing, a produced water conduit configured for carrying a heated produced water stream including chemical contaminants comprising naphthenic acid at a concentration greater than approximately 50 ppm and acetone at a concentration greater than approximately 6 ppm;

providing a permeate reservoir;

providing a cooling unit fluidically coupled to the permeate reservoir and configured for receiving permeate therefrom;

providing a pump fluidically coupled to the cooling unit and configured for outputting a permeate stream at a temperature lower than that of the heated produced water stream;

providing a plurality of hollow fiber direct contact membrane distillation (DCMD) modules, each of the plurality of hollow fiber DCMD modules fluidically coupled for receiving the heated produced water stream and the permeate stream in crossflow configuration;

providing an outlet for providing a treated water stream;

passing the heated produced water stream through the produced water conduit;

processing the heated produced water stream by way of the plurality of hollow fiber

DCMD modules; and

outputting a treated water stream that contains essentially no naphthenic acid and less than approximately 1.5 ppm of acetone.

12. The method of claim 1 1 , further comprising arranging the plurality of hollow fiber DCMD modules in one of a single stage configuration, a batch multi-stage configuration, a continuous multi-stage configuration, and a continuous multi-stage with retentate recycling configuration relative to each other.

13. The system of claim 12, wherein a given stage of each configuration comprises a plurality of hollow fiber DCMD modules.

14. The method of claim 12, wherein each of the plurality of hollow fiber DCMD modules comprises a set of polymer membranes based on one of (i) polyvinylidene fluoride (PVDF), (ii) modified PVDF, (iii) polytetrafluoroethylene (PTFE), (iv) modified PTFE, (v) polypropylene (PP), (vi) modified PP, and (vii) a combination of (i) - (vi).

15. The method of claim 12, further comprising excluding unmodified PTFE membranes from the plurality of hollow fiber DCMD modules.

16. The method of claim 11, wherein passing the heating produced water stream through the produced water conduit comprises providing a produced water feed heated to a temperature of less than approximately 80 °C to the produced water conduit at a predetermined flow rate.

17. The method of claim 11, further comprising:

providing a primary treatment unit that includes the produced water conduit, the permeate reservoir, the cooling unit, the pump, the plurality of hollow fiber DCMD modules, and an output configured for providing an intermediate feed; and providing- a secondary treatment unit configured for receiving the intermediate feed and outputting the treated water stream,

18. The method of claim 17, further comprising processing the intermediate feed using the secondary treatment unit such that the treated water stream contains less than approximately 500 ppb of acetone.

19. The method of claim 17, further comprising processing the heated produced water stream using the primary treatment unit at a first temperature, and processing the intermediate feed at a second temperature lower than the first temperature using the secondary treatment unit.

20. The method of claim 17, wherein processing the intermediate feed using the secondary treatment unit comprises at least partially removing the secondary set of contaminants using one of a set of activated carbon aqueous phase adsorption modules and a membrane photocatalytic reactor.