CA2948419C

CA2948419C - Treatment and recycle of landfill leachate into evaporators of an in situ hydrocarbon recovery operation

Info

Publication number: CA2948419C
Application number: CA2948419A
Authority: CA
Inventors: Andrew Crompton; Jun Park; Mark Smith
Original assignee: Suncor Energy Inc
Current assignee: Suncor Energy Inc
Priority date: 2016-11-10
Filing date: 2016-11-10
Publication date: 2019-01-08
Anticipated expiration: 2036-11-10
Also published as: CA2948419A1

Abstract

Techniques for reprocessing waste water streams derived from hydrocarbon production operations can include determining characteristics of the streams and units of a zero or reduced liquid discharge (ZLD/RLD) system, selecting streams and reprocessing units of the ZLD/RLD system, and recycling the streams into the ZLD/RLD system. The streams can include landfill leachate derived from ZLD/RLD sludge, and the units of the ZLD/RLD system can include an evaporator. Selected recycle streams can be recycled into an evaporator and a crystallizer based on silica content of the streams. Advantages such as facilitating operational enhancements in the ZLD/RLD system, reducing fresh water requirements, enhancing the use of the ZLD/RLD system, managing the risk of scale formation in reprocessing units, and reducing costs of alternative waste water disposal can be facilitated.

Description

TREATMENT AND RECYCLE OF LANDFILL LEACHATE INTO EVAPORATORS OF
AN IN SITU HYDROCARBON RECOVERY OPERATION
TECHNICAL FIELD
[0001] The technical field generally relates to in situ hydrocarbon recovery, and more particular to the treatment of aqueous waste streams derived from produced water.
BACKGROUND

[0002] In the context of in situ hydrocarbon recovery operations, production fluid that is recovered from a production well is separated into a hydrocarbon stream and a produced water stream. The produced water stream contains various contaminants, including organic compounds, dissolved salts, and suspended solids. The produced water can be subjected to water treatment in order to produce a treated water stream suitable for use as boiler feed water that can be supplied to a steam generator, such as a once-through steam generator (OTSG).

[0003] The water treatment units as well as the OTSG generate contaminant-enriched aqueous streams, such as blowdown streams. Blowdown streams can be further treated or supplied to a disposal site. In some situations, the blowdown streams are supplied to a zero liquid discharge (ZLD) system that recovers water and generates a solids-enriched sludge that is sent to a landfill. There are various challenges associated with the handling, treatment and disposal of aqueous waste streams derived from produced water.
SUMMARY

[0004] In some implementations, there is provided an in situ hydrocarbon production process, comprising: injecting a mobilizing fluid comprising steam into a hydrocarbon-containing formation; recovering a production fluid from the formation, the production fluid comprising hydrocarbons and water; separating the production fluid into a hydrocarbon stream and a produced water stream; subjecting the produced water stream to water treatment to produce a treated water; feeding the treated water into a steam generation unit comprising at least one once-through steam generator (OTSG), to produce steam and blowdown; supplying the steam as at least part of the mobilizing fluid for injection into the hydrocarbon-containing formation; supplying the blowdown to a zero or reduced liquid discharge (ZLD/RLD) system to produce recovered water and a solids-enriched sludge, the ZLD/RLD system comprising at least one evaporator;
supplying the solids-enriched sludge to a landfill for disposal; retrieving leachate produced from the landfill; pre-treating the leachate to produce a pre-treated leachate stream;
and recycling the pre-treated leachate stream as part of the feed stream supplied into the at least one evaporator of the ZLD/RLD system.

[0005] In some implementations, the pre-treating comprising adding a chemical agent to the leachate. In some implementations, the chemical agent comprises a chelating agent, an anionic dispersant for dispersing inorganic suspended solids, a scale inhibitor, a hydrocarbon dispersant, and/or an anti-foam agent.

[0006] In some implementations, the mobilizing fluid is dry steam. In some implementations, the mobilizing fluid is injected via an injection well and the production fluids are recovered from a production well. In some implementations, the injection well and the production well each has a vertical section and a horizontal section.
In some implementations, the injection well and the production well form a vertically spaced-apart well pair operable for steam-assisted gravity drainage (SAGD).

[0007] In some implementations, the process also includes supplying the blowdown to a first evaporator that produces a first condensate stream and a first evaporator blowdown stream; supplying the first evaporator blowdown stream to a second evaporator that produces a second condensate stream and a second evaporator blowdown stream; supplying the second evaporator blowdown stream to a crystallizer that produces a crystallizer slurry; and supplying the crystallizer slurry to a dryer that produces the solids-enriched sludge.

[0008] In some implementations, the ZLD/RLD system comprises the first evaporator, the second evaporator, the crystallizer, and the dryer. In some implementations, the at least one evaporator that receives the pre-treated leachate stream consists of the first evaporator. In some implementations, the at least one evaporator that receives the pre-treated leachate stream comprises the first evaporator.
In some implementations, the at least one evaporator that receives the pre-treated leachate stream further comprises the second evaporator.

[0009] The at least one evaporator that receives the pre-treated leachate stream comprises the second evaporator.

[0010] In some implementations, there process also includes supplying a first portion of the leachate to the at one evaporator; and supplying a second portion of the leachate to the crystallizer. In some implementations, all of the pre-treated leachate stream is supplied to a single evaporator. In some implementations, the single evaporator is the first evaporator. In some implementations, the single evaporator is the second evaporator.

[0011] In some implementations, the process also includes supplying the leachate from the landfill to a lagoon; supplying the leachate from the lagoon to a holding tank that is proximate to the evaporator; and supplying the leachate from the holding tank to the at least one evaporator.

[0012] In some implementations, the process also includes combining the pre-treated leachate stream with the blowdown to form the feed stream supplied into the at least one evaporator.

[0013] In some implementations, there is provided a process for treating landfill leachate derived from leaching from a solids-rich sludge by-product of an in situ hydrocarbon recovery operation, the process comprising recycling a waste water stream comprising the landfill leachate into an evaporator that is part of the in situ hydrocarbon recovery operation.

[0014] In some implementations, the evaporator is part of a zero or reduced liquid discharge (ZLD/RLD) system. In some implementations, the ZLD/RLD system comprises a first evaporator, a second evaporator, a crystallizer, and a dryer arranged in series;
and the waste water stream is recycled into the first evaporator and/or the second evaporator. In some implementations, the process also includes pre-treating the waste water stream prior to introduction into the evaporator. In some implementations, the pre-treating comprises adding a chemical agent to the leachate. In some implementations, the chemical agent comprises a chelating agent, an anionic dispersant for dispersing inorganic suspended solids, a scale inhibitor, a hydrocarbon dispersant, and/or an anti-foam agent.

[0015] In some implementations, there is provided a process for treating waste water derived from a by-product of a bitumen production operation, the process comprising:
retrieving a waste water stream from a disposal site comprising the by-product and the waste water; pre-treating the waste water stream to produce a pre-treated waste water stream; and recycling the pre-treated waste water stream into an evaporator that is part of an in situ hydrocarbon recovery operation.

[0016] In some implementations, the bitumen production operation is an oil sands extraction operation, and the disposal site is a tailings pond from which the waste water stream is retrieved. In some implementations, the waste water stream comprises leachate and the disposal site is a landfill. In some implementations, the bitumen production operation is the in situ hydrocarbon recovery operation. In some implementations, the in situ hydrocarbon recovery operation comprises steam assisted gravity drainage (SAGD).

[0017] In some implementations, the by-product comprises a solids-enriched sludge that is derived from a zero or reduced liquid discharge (ZLD/RLD) system of the in situ hydrocarbon recovery operation. In some implementations, the ZLD/RLD system comprises a first evaporator, a second evaporator, a crystallizer, and a dryer arranged in series; and the waste water stream is recycled into the first evaporator and/or the second evaporator.

[0018] In some implementations, the pre-treating comprises adding a chemical agent to the waste water stream. In some implementations, the chemical agent comprises a chelating agent, an anionic dispersant for dispersing inorganic suspended solids, a scale inhibitor, a hydrocarbon dispersant, and/or an anti-foam agent.

[0019] In some implementations, all of the pre-treated waste water stream is supplied to the first evaporator. In some implementations, all of the pre-treated waste water stream is supplied to the second evaporator.

[0020] In some implementations, there process also includes adding the pre-treated waste water stream to a blowdown stream to form an evaporator feed stream; and supplying the evaporator feed stream to the evaporator. In some implementations, the blowdown stream comprises blowdown from a once-through steam generator (OTSG) that is part of the in situ hydrocarbon recovery operation.

[0021] In some implementations, there is provided a method for selecting and treating waste water streams derived from a hydrocarbon production operation, comprising: determining compositional characteristics of each waste water stream;
determining production rates or volumes of each waste water stream;
determining disposal capacity characteristics of disposal sites at which respective waste water streams are held; determining operational feed quality characteristics and operational capacity characteristics of one or more units that are part of a zero or reduced liquid discharge (ZLD/RLD) system that is part of an in situ hydrocarbon recovery operation;
and based on the determined compositional characteristics, production rates or volumes, disposal capacity characteristics, operational feed quality characteristics, and operational capacity characteristics, performing the following steps:
selecting a waste water stream for recycling and reprocessing; selecting a unit of the ZLD/RLD
system to receive the selected waste water stream; blending the selected waste water stream with the feed of the selected unit to form a combined feed stream; and supplying the combined feed stream into the selected unit.

[0022] In some implementations, the selected waste water stream comprises landfill leachate and the selected unit comprises an evaporator. In some implementations, the selected unit comprises multiple evaporators. In some implementations, the units of the ZLD/RLD system comprise an evaporator, a crystallizer, and a dryer. In some implementations, determining capacity characteristics of the units comprises determining capacity of associated vapor coolers.

[0023] In some implementations, there method also includes determining pre-treatment requirements for the waste water streams based on at least one of the following: the determined compositional characteristics, the production rates or volumes, the feed quality characteristics of the units, and the capacity characteristics of the units;
and subjecting the selected waste water stream and/or the combined feed stream to a selected pre-treatment.

[0024] In some implementations, the units comprise a mechanical vapor recompression (MVR) evaporator, an MVR feed flash tank, a steam-driven evaporator, and a crystallizer.

[0025] It should be noted that variables/characteristics that are obtained or measured and used for selection, blending and recycling steps can be dynamic variables and can also include static variables such as specifications for units. It should also be noted that a select number of variables/characteristics can be used for selection, blending and recycling steps, and such selected variables/characteristics can be chosen based on their degree of impact on the given process implementation. For example, certain variables/characteristics can be used or prioritized if they have a high impact on the given process, whereas others that have little to no impact may be minimized or ignored.

[0026] In some implementations, there is provided a method for treating internal waste water streams generated by an in situ hydrocarbon recovery operation and external waste water streams obtained from a disposal site, comprising:
analyzing the internal and external waste water streams to determine compositional characteristics thereof; and distributing the internal and external waste water streams as multiple recycled waste water streams into an evaporative waste water treatment system that is part of the in situ hydrocarbon recovery operation.

[0027] In some implementations, the internal waste water streams comprise boiler blowdown. In some implementations, the boiler blowdown is obtained from a once-through steam generator (OTSG). In some implementations, the external waste water streams comprise landfill leachate.

[0028] In some implementations, the method includes subjecting external waste water streams to pre-treatment prior to introduction into the evaporative waste water treatment system. In some implementations, the pre-treatment comprises chemical addition.

[0029] In some implementations, the evaporative waste water treatment system comprises a zero or reduced liquid discharge (ZLD/RLD) system.

[0030] In some implementations, the evaporative waste water treatment system comprises an evaporator and a crystallizer. In some implementations, the evaporative waste water treatment system comprises multiple units and the distributing of the multiple recycled waste water streams comprises: supplying a first recycle stream into the evaporator; and supplying a second stream into the crystallizer. In some implementations, the first and second recycle stream are selected for recycling into the evaporator and the crystallizer, respectively, based on silica content. For example, a higher silica waste stream can be recycled to the crystallizer while a lower silica waste stream can be recycled to the evaporator.

[0031] The techniques described herein can facilitate various advantages, such as facilitating operational advantages in a ZLD/RLD system, reducing fresh water requirements, enhancing the use of available capacity of unit in a ZLD/RLD
system, reducing costs of alternative waste water disposal methods, and managing the risk of scale formation in reprocessing units.
BRIEF DESCRIPTION OF DRAWINGS

[0032] Fig 1 is a block diagram showing of a hydrocarbon recovery operation and a produced water treatment operation.

[0033] Fig 2 is a block diagram of units for treating waste water streams in an in situ hydrocarbon recovery operation.

[0034] Fig 3 is another block diagram of units for treating waste water streams in an in situ hydrocarbon recovery operation.

[0035] Fig 4 is another block diagram of units for treating aqueous streams in an in situ hydrocarbon recovery operation.

[0036] Fig 5 is a further block diagram of units for treating a waste water stream.

[0037] Fig 6 is a block diagram of an operation for treating waste water streams.
DETAILED DESCRIPTION

[0038] Waste water streams can be analyzed and recycled back into various units of an evaporative waste water treatment system, based on the composition of the waste water streams as well as the capacities and operating limits of the units. In some implementations, a waste water stream can be retrieved from a waste disposal site and recycled into an evaporator that is part of an in situ hydrocarbon recovery operation, thereby reducing capacity issues for the waste disposal site, recovering additional water from the waste water stream for reuse in the in situ hydrocarbon recovery operation, and r leveraging existing equipment (i.e., the evaporator). In some implementations, the waste water stream includes aqueous leachate that is recovered from a landfill or a lagoon, and is derived from the disposal of a solids-enriched sludge, which can be the end-product of a zero or reduced liquid discharge (ZLD/RLD) system. The ZLD/RLD
system can include at least one evaporator, a crystallizer and a dryer. The aqueous leachate can be recycled as part of the feed water supplied to the evaporator, which is part of the ZLD/RLD system. In some implementations, the aqueous leachate can be pre-treated using various pre-treatment methods, including the addition of chemical agents prior to introduction into the evaporator.

[0039] Falling film evaporators that are used for in situ hydrocarbon recovery operations are not typically designed or identified for recycling waste water streams obtained from disposal sites (e.g., landfills) that are external or remote to the in situ hydrocarbon recovery facility. The falling film heat exchange that occurs within such evaporators can have fouling issues when the feed stream has high levels of contaminants, which can lead to costly shutdowns. While certain units, such as crystallizers, are designed to handle solids formation and thus can handle higher contaminant levels in their feed streams, evaporators are not. Landfill leachate and other waste water streams retrieved from remote disposal sites can have high and variable contaminant levels.

[0040] Furthermore, waste water streams derived from hydrocarbon production operations can be selected based on various factors, including composition and disposal site capacity, and recycled into pre-selected units of a ZLD/RLD system based on unit capacity and feed quality requirements. By selecting and matching waste water streams with particular units of the ZLD/RLD system, additional water can be recovered for reuse and capacity issues for the waste water disposal can be overcome.

[0041] A "ZLD" system refers to a system that treats waste water from a facility and includes multiple units that leverage evaporative recovery of water for enabling recycle of virtually all of the recovered water back into the facility. ZLD systems include evaporation of the waste water until the dissolved solids and contaminants form crystals, which are removed and dewatered. Water vapor from evaporation can be condensed and returned into the facility. For the purposes of the present description, a ZLD system = CA 02948419 2016-11-10 can be defined as one that enables at least 90% of the water entering the ZLD
system to be recovered and recycled back into the facility.

[0042] An "RLD" system is similar to a ZLD system, but has a recycle percentage that is lower than 90% of the water entering the RLD system. RLD systems also rely on evaporative water recovery.

[0043] It should be noted that both ZLD and RLD systems can include units such as ultrafiltration (UF), ion exchange, reverse osmosis (RO), among others, depending on process design.

[0044] "Leachate" is a liquid that has passed through solid material and has extracted soluble and/or suspended components from the solid material.
Leachate is often collected from a lower level where the liquid has accumulated after draining through the solid material.

[0045] A "landfill" is a site for the disposal of waste materials. The waste material is typically dumped into a confined disposal area, compacted to reduce volume, and covered with layers of soil. Covering may be done daily or other frequencies.
Landfills can include leachate collection systems that capture leachate that has passed through the waste material.

[0046] "Blowdown" is a general term that includes waste water streams generated by equipment and unit operations, such as steam generators, evaporators, and other units. Blowdown from steam generators (e.g., OTSGs) is contaminated water intentionally wasted from the steam generator to avoid concentration of impurities during continuing evaporation of steam. Since boiler feed water includes some contaminants and the generated steam includes essentially no contaminants, the blowdown from steam generators typically includes much higher contaminant levels compared to the feed water. For example, OTSG-type steam generators typically generate blowdown that has contaminant levels that are four to five times higher than the feed water.
Blowdown is generated by OTSGs continuously during operation. Other types of units can generate blowdown periodically when the units are evacuated by pressure.

[0047] Referring to Fig 1, in the context of an in situ hydrocarbon recovery operation (e.g., SAGD), production fluid 10 is recovered via a production well 12 that is located in a hydrocarbon-containing formation 14. Many in situ hydrocarbon recovery operations use a mobilizing fluid, such as steam 16, that is injected via an injection well 18 into the formation in order to reduce the viscosity of the hydrocarbons. Mobilizing fluids can be particularly useful for mobilizing heavy hydrocarbons such as heavy oil or bitumen. It should be noted that other hydrocarbon mobilization mechanisms can be used, e.g., electromagnetic heating.

[0048] The production fluid 10 includes hydrocarbons and water as well as various other components, such as suspended mineral solids and dissolved salts. The water in the production fluid 10 can come from injected aqueous mobilizing fluids (e.g., steam or hot water) and/or from native water present in the formation itself.

[0049] Still referring to Fig 1, the production fluid 10 is supplied to a separator 19 which produces a hydrocarbon stream 20 and a hydrocarbon-depleted produced water stream 22. This separation step can be performed with the addition of a hydrocarbon diluent or without. The hydrocarbon stream 20 can be further processed to remove contaminants and produce a hydrocarbon product that can be stored and/or pipelined.
The hydrocarbon-depleted produced water stream 22 can be supplied to another oil-removal separator 24 which removes residual oil 26 and produces a produced water stream 28.

[0050] The produced water stream 28 can then be supplied to a water treatment operation, which may include a number of different water treatment units. Fig illustrates the scenario where the water treatment operation includes a warm lime softener (VVLS) 30 followed by a weak acid cation (WAC) exchange unit 32, which produces a treated water stream suitable for use as boiler feed water 34. It should be noted that other water treatment units can also be used (e.g., evaporators) instead of, in series with and/or in parallel with WLS and WAC exchange units.

[0051] The boiler feed water 34 can be supplied to a steam generator, such as an OTSG 36, which produces wet steam 38 and an OTSG blowdown stream 40. The wet steam 38 can be separated to produce dry steam which can be fed to the injection well 18 as part of, or all of, the mobilizing fluid 16.

[0052] Still referring to Fig 1, the OTSG blowdown stream 40 includes various contaminants, including organic compounds, dissolved salts, suspended solids, = CA 02948419 2016-11-10 hardness and silica. Part of the OTSG blowdown stream can be recycled back upstream into one or more of the water treatment units. However, continuously recycling all of the OTSG blowdown to such unit would lead to upcycling of contaminants in the system.
Thus, at least a portion of the OTSG blowdown stream 40 can be supplied to a waste water treatment system, which may be a ZLD system 42. The ZLD system 42 can include various units that recover water from the blowdown stream and produce waste streams that have increasing solids concentrations.

[0053] Fig 1 illustrates an example of a ZLD system 42 that can be used. The OTSG
blowdown stream 40 is supplied to a first evaporator 44 that produces a first condensate stream 46 and a first evaporator blowdown stream 48. It should be noted that multiple OSTG blowdown streams can be combined together and then supplied to the evaporator. The first evaporator blowdown stream 48 is then supplied to a second evaporator 50 that produces a second condensate stream 52 and a second evaporator blowdown stream 54. The first and second condensate streams can be recycled back into the system as boiler feed water or for other uses. The second evaporator blowdown stream 54 can then be fed to a crystallizer 56 which removes additional water 55 and facilitates crystal formation to produce a crystallizer slurry 58. The crystallizer slurry 58 can then be supplied to a dryer 60 that produces a solids-enriched sludge 62.

[0054] The solids-enriched sludge 62 can then be supplied to a landfill 64, which is located off-site compared to the ZLD system 42 and the overall in situ hydrocarbon recovery operation. The landfill 64 can receive various waste streams (e.g., sludge 62 from the dryer 60, a portion of the crystallizer slurry 58, etc.) in different proportions. The landfill 64 can generate leachate 66, which may be produced at higher levels depending on the quantity of precipitation 68.

[0055] Referring still to Fig 1, the leachate 66 can be pumped from the landfill or another intermediate holding area back to the ZLD system 42. In some implementations, the recycled leachate 66 is added to the blowdown stream 40 to form an evaporator feed stream 70 introduced into the first stage evaporator 44. In some scenarios, the leachate 66 can be combined with an additive stream 72, which can be a make-up water stream or a chemical addition stream, to form a pretreated leachate stream 74 that is combined with the blowdown stream 40. The combination of the leachate stream 66 with the additive stream 72 and/or the blowdown stream 40 can be done using various = CA 02948419 2016-11-10 pipeline joints (e.g., T or Y addition joints) or various mixers (e.g., static, in-line, stirred tank, etc.).

[0056] It should be noted that the leachate 66 or portions thereof can be recycled to other units that are part of the ZLD system or part of another unit operation.
As will be explained in further detail below, the leachate 66 can be recycled to one or more units of the ZLD system and there may be a recycle system that controls adaptive recycle strategies.

[0057] In some scenarios, the leachate 66 can be mixed with OTSG
blowdown and/or upstream evaporator blowdown (also called evaporator "purge" or evaporator "brine"), and the resulting mixture can be fed into the evaporator sump. The evaporator recovers water from the leachate, and thus acts as a pre-concentrator so that the downstream crystallizer can handle the fluid more efficiently.

[0058] Referring now to Fig 2, there may be multiple waste water streams VVWA, VWVB, VVVVC that are retrieved and recycled back into the ZLD system. One or more of the waste water streams can be leachate derived from the landfill. A recycle system 76 can be provided in order to manage and control the recycling of the waste water streams into the different ZLD units. The recycle system 76 can include piping and valves that are arranged to facilitate adding different waste water streams together, keeping different waste water streams separate, and feeding different waste water streams and flowrates into different ZLD units. The recycle system 76 can also include recycle lines that supply waste water to part of the water treatment system used for the produced water (e.g., WLS 30). The recycle system 76 can be configured and controlled to provide different waste water streams and pre-determined or continuously modulated flow rates into the evaporators 44, 50, the crystallizer 56, the dryer, and other units.
In some implementations, the only units that receive the waste water streams are the evaporators 44, 50 and the crystallizer 56. In some implementations, as illustrated in Fig 1, the only units that receive the waste water streams are the evaporators 44, 50. A
control unit 78 can be provided to control the recycle system 76 and its valves and other flow control apparatuses to provide the desired flows of waste water to the desired units.

[0059] Referring now to Fig 3, a pre-treatment unit 80 can be used to pre-treat the leachate and/or other waste water streams prior to introduction into the evaporator 44.

Multiple pre-treatment units (generally indicated as PT and/or 80) can be provided for pre-treating different waste water streams and/or for providing different pre-treatments.
In some implementations, pre-treatment can include the addition of one or more chemicals. For example, chemical additives can include a chelating agent, an anionic dispersant for dispersing inorganic suspended solids, a scale inhibitor, a hydrocarbon dispersant, and/or an anti-foam agent. There may therefore be at least one chemical addition line 82 for supplying one or more chemicals to the pre-treatment unit 80.
Chemical agents can be delivered as part of one or more aqueous solutions, and can be added simultaneously or sequentially to the leachate and/or to the evaporator feed stream (i.e., after combining the leachate with the blowdown). Various formulations of chemical agents can be provided depending on water chemistry, evaporator operation and other process parameters, in order to reduce or avoid fouling in the evaporator.

[0060] In addition, the pre-treatment unit 80 can be controlled to adapt the pre-treatment (e.g., chemical dosages) in accordance with measured contaminant levels.
Since landfill leachate and other waste water streams can vary in composition, a measurement unit can be provided to measure certain contaminants levels (e.g., suspended solids, organics, salts, hardness, silica, etc.) in order to adapt the pre-treatment to the measured values. For example, if high suspended solids content is detected, the pre-treatment can be modified to include a filtering step. If high organic content is detected, the chemical dosage of the hydrocarbon dispersant can be increased.

[0061] Still referring to Fig 3, each of the recycle lines for supplying a portion of recycled waste water can be equipped with its own pre-treatment unit 80a, 80b, 80c, which may be particularly useful when the recycled portions are respectively supplied to different units suited to handling different water chemistries. For instance, an upstream unit 84 may be designed and operated to facilitate handling of streams having high contaminant concentrations, and thus the pre-treatment unit 80a for that waste water stream may be able to reduce chemical addition and/or avoid adding certain chemicals altogether. Fig 4 illustrates a scenario where two different pre-treatment units 80x, 80y are respectively used for two different evaporators 44, 50.

[0062] In some scenarios, as illustrated in Fig 5, the pre-treatment unit 80 may include a tank that receives the leachate 66 from a lagoon 86, and is coupled to multiple chemical addition lines 80a, 80b for receiving the chemical compounds to pre-treat the leachate 66. Pumps 88 can be provided for transporting the leachate 66, and holding tanks 90 can be provided as well. Trucking 92 can also be used to remove leachate from the lagoon, but the leachate recycle system can reduce or even eliminate as recourse to expensive trucking.

[0063] Still referring to Fig 5, the treated leachate stream 74 can be added to an evaporator 100, which can be downstream from another evaporator 102 and upstream from a crystallizer 56. The upstream evaporator 102 can receive a feed stream 104 that includes blowdown derived from an OTSG and/or from other units used in an in situ hydrocarbon recovery operation. The upstream evaporator can be a Mechanical Vapor Recompression (MVR) evaporator, for example.

[0064] Recycling waste water streams, such as landfill leachate, to an evaporator can facilitate certain operational advantages in the ZLD system. For example, in some scenarios, processing recycled waste water streams into the crystallizer can be constrained by limited capacity of the crystallizer equipment, such as the capacity of the vapor cooling system and solids handling unit of the crystallizer. By recycling the waste water stream (all or in part) to the evaporator of the ZLD, additional crystallizer capacity can be obtained.

[0065] In some scenarios, the evaporator that is used to receive and treat the recycled waste water stream (e.g., leachate 66) is selected as an evaporator having excess capacity. In situ hydrocarbon recovery operations may include a multitude of evaporators having different designs, sizes, capacities and purposes. For example, some evaporators can be used to treat produced water in order to produce condensate for use as boiler feed water, whereas other evaporators can be used as part of a ZLD
system. Some in situ hydrocarbon recovery operations can have multiple trains as part of steam generation system, and some or all of the trains can include one or more evaporators in parallel (as a bank of evaporators) and/or in series. Depending on a variety of factors (e.g., process design, equipment sizing, operating parameters, etc.) a given evaporator may have excess capacity in terms of the flow rate of feed it can receive and/or in terms of the contaminant levels it can handle. Thus, an evaporator having excess capacity can be selected for receiving the leachate 66. In addition, when the evaporator has a certain excess capacity in terms of the contaminants it can handle, the pre-treatment of the leachate 66 can be provided and adapted so that the evaporator feed stream 70 comes close to but does not exceed contaminant limits for that evaporator.

[0066] In some implementations, an existing evaporator that is part of an existing facility is identified and used for the recycle strategies disclosed herein.
Alternatively, a new facility can be designed where at least one evaporator is overdesigned purposefully for the possibility of adding a recycle stream from an off-site source of waste water, such as landfill leachate. In such a case, the evaporator can be overdesigned relative to the anticipated design requirements for handling blowdown, thus leaving excess capacity for landfill leachate or another waste water stream. The evaporator can be overdesigned based on a maximum potential flow rate of landfill leachate that can be determined based on the maximum expected leachate production rates (e.g., according to variables including precipitation, lagoon holding capacity, sludge disposal rates, etc.).

[0067] It should be noted that various waste water streams from outside the hydrocarbon recovery facility can be retrieved and recycled into the evaporator. For example, landfill leachate can be retrieved by collecting the leachate from the landfill, supplying the leachate to a holding vessel or lagoon, and then pumping the leachate back to the facility as part of the evaporator feed stream. Landfill leachate that is derived from waste materials generated by in situ hydrocarbon recovery operations and/or oil sands mining operations could be used. In another example, tailings pond water may be used as a source of off-site waste water, where the tailings water could be pre-treated by filtering and treated to reduce or eliminate emulsifying behaviour (i.e., reduce surfactant content). Thus, in general, the waste water can thus be retrieved from a disposal site used to dispose of by-products that come from a bitumen production operation.
The disposal site is typically located remotely from the evaporator to which the waste water stream is recycled. A retrieval system including pumps, pipelines and holding tanks can thus be provided.

[0068] The pre-treatments (e.g., chemical addition) can be done at the remote disposal site and/or at the in situ hydrocarbon recovery facility. For example, depending on the mixing requirements and reactivity of the chemical additives, certain chemicals can be added near the disposal site prior to pumping of the waste water stream to the in situ hydrocarbon recovery facility, particularly where pipeline mixing can be beneficial to the chemical addition. Alternatively, chemical addition after pipeline transportation and thus proximate to the in situ hydrocarbon recovery facility may be used for chemicals that have rapid mixing or reaction.

[0069] In operation, overall volumes of recycled and reprocessed leachate can be balanced by storing excess fluid in the lagoon during the high volume season and reprocess it during low volume season. For example, excess volumes of leachate can be stored in the lagoon during times of high precipitation and leachate production (e.g., spring), and then accumulated leachate can be accessed from the lagoon during times of low leachate production (e.g., winter). In some implementations, the flow rate of the leachate that is recycled back into the evaporator can vary depending on various factors.
For example, during the winter, little to no leachate is produced by the landfill due to freezing, whereas in the spring time and times of high precipitation a greater amount of leachate may be produced. Managing variable flow rates of leachate or other waste water streams can be facilitated by recycling such streams back into the evaporator and, optionally, into other units in the facility (e.g., crystallizer).

[0070] In some implementations, the waste water stream to be recycled and processed in the evaporator can be identified and classified from a number of different potential waste water streams. In the context of in situ hydrocarbon recovery operations and bitumen mining and extraction operations, many different waste water streams can be generated, stored, treated, and disposed of as part of waste management.
Waste waters can be classified based on certain characteristics (e.g., salinity, hardness, free oil, silicate, solids content, etc.). Then, based on the feed stream quality and capacity limits of one or more units of the ZLD system or a Reduced Liquid Discharge (RLD) system, a blending ratio can be determined for blending the input stream of one more units with one or more waste water streams. High cost waste water streams, such as landfill leachate, can be prioritized for recycling and reprocessing. In addition, the pre-treatment can be determined for each waste stream and/or each blend, as necessary.

[0071] In some implementations, the waste water selection and treatment method can include the following steps:
(I) determine compositional characteristics of each waste water stream;
(ii) determine production rates of each waste water stream;

(iii) determine capacity characteristics of the disposal site at which each waste water stream is held;
(iv) determine alternative treatment options for the waste water streams (e.g., trucking excess leachate from lagoon) and the cost and challenges thereof;
(v) determine operational feed quality characteristics of the streams being fed into one or more units that are part of the ZLD or RLD system (e.g., evaporators, crystallizers, dryers, etc.), which may include determining compositional or physicochemical properties of the feed streams entering such units;
(vi) determine operational capacity characteristics of one or more of the operating units (e.g., evaporators, crystallizers, dryers, and associated equipment such as vapor coolers, etc.), which may include assessing available capacity of such units based on operational parameters, inlet and outlet flow rates, and vessel size information; and (vii) based on (i) to (vi) and, optionally, additional information such as pre-determined or known information that may include:
(1) feed quality limits of one or more units that are part of the ZLD or RLD system (e.g., evaporators, crystallizers, dryers, etc.); and (2) capacity limits of one or more units that are part of the ZLD or RLD
system (e.g., evaporators, crystallizers, dryers, and associated equipment such as vapor coolers);
perform the following steps:
(a) recycle one or more of the waste water streams into the ZLD system and/or RLD system;
(b) blend the recycled waste water streams with one or more of the feed fluids of the units to form corresponding feed streams; and (c) feed the combined streams into the respective units, thereby reprocessing the waste water streams.

[0072] It should be noted that certain variables including those of (i) to (vi) mentioned above can be considered dynamic in that they can change over time due to various factors. For example, the compositional characteristics of each waste water stream (i) can change due to the source of waste water streams, the precipitation levels, the upstream process variations that produced the waste from which the streams were derived, and so on. The production rates of each waste water stream (ii) can also vary due to factors such as time of year (e.g., high rates in spring when high amount of precipitation versus low rates in winter), the rate of waste production, the composition of the waste from which the streams were derived, and so on. Similarly, the capacity characteristics of the disposal site(s) (iii) can vary due to the rate at which waste has been disposed, the rate at which waste streams are being removed, and precipitation.
The alternative treatment options for the waste water streams (iv) can also be determined based on costs, equipment availability, and other factors. The operational feed quality characteristics (v) can change over time due to the upstream process, e.g., impurity levels of the produced water that relate to the properties of the formation, operation of the units upstream of the OTSGs (e.g., upsets), and so on. While the feed quality for each unit may be kept within a known operating envelope, there may be notable changes to the composition of the feeds over time (e.g., concentrations of the different impurities can change over time). The operational capacity characteristics (vi) of the units of the ZLD or RLD system can change due to upstream or downstream operation. For example, a unit may operate with decreasing excess capacity as the feed rate increases, which may be due to ramping up the process or taking a similar parallel unit offline for maintenance or repair. In addition, a unit's capacity may be considered to decrease due to internal fouling that can reduce the throughput of material that the unit can effectively handle. Such dynamic characteristics can be monitored and analyzed over time in order to perform steps (a) to (c) mentioned above.

[0073] It should also be noted that certain variables including those of (1) and (2) mentioned above can be considered static in that they can be pre-determined or are generally known. For example, certain units may have feed quality limits (1) that are recommended by manufacturers or pre-determined by the process operator. The feed quality limits can include maximum levels of impurities that can be effectively handled at certain operating conditions, for example. In addition, certain units may have capacity limits (2) that are recommended by manufacturers or pre-determined by the process operator. The capacity limits can be based on unit size, vessel wall thickness, pressure and temperature tolerances, piping, instrumentation or other construction parameters.
Such static characteristics can also be used in combination with various dynamic characteristics to perform steps (a) to (c) mentioned above.

[0074] Certain variables that can be considered dynamic may not vary sufficiently over the time period of interest to warrant continued monitoring and analysis in determining the blending and recycle strategy into the ZLD/RLD system. For example, for relatively stable process operations, one may observe relatively constant feed quality characteristics (v) and operational capacity characteristics (vi) of the units. In such instances, one may consider such variables as being relatively static and they can therefore be determined based on pre-determined or known information.

[0075] The method can also include determining pre-treatment requirements for the waste water streams in light of one or more characteristics determined in (i) ¨ (vi). For example, taking the two potential waste water streams of tailings pond water and landfill leachate, one can determine that landfill leachate is suitable to be recycled back into a ZLD/RLD evaporator having excess capacity. It is also noted that this waste water selection and treatment method can be implemented in part by the recycle system 76 (as shown in Fig 2) where one or more different waste water streams (WVVA, VWVB, VVWC) can be blended with one or more feed streams to different units of the ZLD/RLD
system. The controller 78 can be configured to receive input information regarding the various determined characteristics in order to adjust the blend ratios, as needed. The recycle system can be adjusted on a continuous basis based on continuous input of information, or can be implemented in a relatively consistent manner based on previously-determined information.

[0076] Referring now to Fig 6, some implementations of the waste water selection and treatment method will be described in greater detail. The ZLD/RLD system 42 can be leveraged to treat multiple waste water streams, which may include internal waste water streams 106a, 106b, 106c as well as external waste water streams 108a, 108b, 108c, 108d. The internal waste water streams are produced by the in situ hydrocarbon recovery and steam generation facility 107, and may include blowdown streams obtained from OTSGs or other units, such as WLS units, evaporator units used to treat the produced water, as well as other units used in the system. The internal waste water streams 106a, 106b, 106c can be fed into one or more of the units of the ZLD/RLD
system 42 as individual streams, or they can be combined together and fed as a single feed stream into the ZLD/RLD system 42. The internal waste water streams 106a, 106b, 106c can have different compositions including different concentrations of organic compounds, dissolved salts, suspended solids, hardness, and silica. The internal waste water streams 106a, 106b, 106c or the combined feed stream can be monitored and/or analyzed to determine compositional features (e.g., one or more of the above-mentioned components) prior to entering the ZLD/RLD system 42.

[0077] The external waste water streams 108a, 108b, 108c, 108d are derived from unit, facilities or disposal sites that are outside of the in situ hydrocarbon recovery and steam generation facility 107. One example of an external waste water source 110 is a landfill 64a, 64b, which may receive sludge 62 and/or other solid waste derived from the in situ hydrocarbon recovery and steam generation facility 107 and/or the ZLD/RLD
system 42. The external waste water sources 110 can include other disposal sites, such as ponds, lagoons, and the like. The external waste water streams 108a, 108b, 108c, 108d can include leachate, tailings cap water, and other types of waste water that has come into contact with the environment. Each of the external waste water streams 108a, 108b, 108c, 108d can be fed into one or more of the units of the ZLD/RLD
system 42 as individual streams, or they can be combined together and fed as one or more combined feed streams into the ZLD/RLD system 42. For example, two leachate streams (108a, 108b) can be combined together and fed into the ZLD/RLD system 42 as a single feed stream supplied to a single unit (e.g., an evaporator) or the combined stream can be split into distinct streams that are fed into different units of the ZLD/RLD system 42.

[0078] In some implementations, waste water streams (e.g., external and internal) are first analyzed for compositional features, such as organic compounds, dissolved salts, suspended solids, hardness, and/or silica. Then, one or more waste water streams are selected for introduction into the ZLD/RLD system 42, based on the compositional features. The analyses can be done online, at line and/or in the laboratory setting. In addition, in some scenarios, certain waste water streams can be combined together to form a combined waste water stream for introduction into a certain unit of the ZLD/RLD
system 42. For example, waste water streams that are high in silica can be combined together to form a silica-rich waste water stream which is introduced into a unit that can handle high silica contents, such as the crystallizer; while waste water streams that are lower in silica can be combined together to form a silica-poor waste water stream which is introduced into a unit that may be more sensitive to silica, such as an evaporator. One challenge to waste water recycling is the prevention of silica fouling inside steam-driven and mechanical-driven evaporators. If these evaporator units become fouled, they will first limit production and can lead to plant outages for equipment cleaning and maintenance is required. Silica scales are not only difficult to remove, but are also costly to do so. Consequently, the recycle points into the plant can advantageously be provided in the context of managing the risk of scale formation, chemical interaction for scale mitigation, water recovery, and solids formation for land fill disposal.

[0079] In some implementations, waste water streams can be combined in order to bring the concentration of a given component below a pre-determined or desired threshold for the unit into which the combined waste water stream will be recycled. For example, a high silica waste water stream can be combined with a low silica waste water stream in a proportion such that the silica content of the combined stream is below the silica limit for operation of a mechanical- or steam-driven evaporator. Thus, the high silica waste water stream can be recycled and treated in the evaporator despite its high silica levels. In addition, in some implementations multiple waste water streams can be combined together to reduce chemical requirements for a given unit.

[0080] In another example, a waste water stream with high total suspended solids (TSS) can be selected for recycling into the crystallizer, which is designed for high solids streams. Other waste water streams that have lower TSS can be selected for recycling into the evaporators.

[0081] In yet another example, waste water streams can be blended based on their compositions in order to obtain a desired blended composition having chemical requirements below a pre-determined or desired level. For instance, a chemical treatment formula can be determined in which maximum qualities of various chemical additives (e.g., chelating agent, dispersant, anti-foam) are established based on various parameters (e.g., cost, impact on process, equipment availability, etc.).
Certain waste water streams may have chemical treatment requirements that exceed the maximum qualities of certain chemical additives. In such cases, the waste water streams can be combined with another waste water stream that has lower chemical treatment requirements (e.g., for a given chemical additive or for several chemical additives) such that the combined waste water stream falls within the chemical treatment requirements and therefore can be recycled.

[0082] In some implementations, both internal waste water streams and external waste water streams can be stored in a common containment structure, such as a lagoon. Alternatively, external waste streams can be stored in such structures while internal streams are held in tanks or supplied directly into ZLD/RLD equipment via pipeline.

[0083] The monitoring/analysis of various waste water streams can facilitate enhanced blending and treatment of those streams by tailored introduction into the ZLD/RLD system. This not only increased utilization of ZLD/RLD equipment capacity but also reduces offsite disposal or storage of waste streams.

[0084] In some scenarios, the waste water streams can be selected and recycled such that the ZLD/RLD system operates at a recycle percentage of 100%, instead of around 90% for ZLD or lower recycle rates for RLD. In some scenarios, more than 100%
recycle can be achieved if precipitation is taken into consideration, since leachate can include precipitation that was not part of the water used at the in situ hydrocarbon recovery facility. Achieving 100% or more water recycle can reduce fresh water requirements, which is another advantage of the methods described herein.

[0085] The methods described herein can be applied to existing ZLD/RLD
systems through retrofitting (e.g., addicting a recycle system that includes piping, valves, monitoring, etc.) or to new ZLD/RLD systems. The methods can also be applied to other evaporative water treatment technologies that may not necessarily go by ZLD or RLD.

[0086] In some implementations, the method can include alternating or modifying the recycle between two different units. For example, a waste water stream can be recycled into a ZLD/RLD evaporator and then the recycle can be partly or fully switched to the ZLD/RLD crystallizer. The switch can be due to various factors, such as an increase in contaminants in the waste water stream or an increase in blowdown flow rate into the evaporator requiring additional capacity, for example.

[0087] It is also noted that the external waste water streams can be partly recycled back into the in situ hydrocarbon recovery and steam generation facility 107, via a recycle line 112. This recycled waste water can be fed to one or more units of the facility, some of which are described in relation to Fig 1, for example. In some implementations, portions of the waste water can be recycled into different units of the in situ hydrocarbon recovery operation, notably units that are part of the produced water treatment system and the steam generators. For instance, portions of the waste water can be fed directly into OTSGs which can handle higher contaminant content compared to other types of boilers, particularly where the boiler feed water stream 34 has a composition that can accommodate an increase in contaminants. This recycle approach can have the benefit of debottlenecking or increasing the capacity of the water treatment units.

[0088] In some implementations, the recycle control unit 78 (illustrated in Fig 2) can be configured and operated to analyze and control the recycling of multiple waste water streams, having the same or different compositions, into both the in situ hydrocarbon recovery facility 107 and the ZLD/RLD system 42. The control unit 78 can receive information regarding the composition and flow rate of the waste water streams, the composition and flow rate of the input streams into each of the units, and the operational parameters of the units. The control unit 78 can also be configured with information regarding upper threshold limits of the units in terms of the contaminant levels that can be handled. The control unit 78 can then be configured to distribute the waste water streams to appropriate units of the in situ hydrocarbon recovery facility 107 and the ZLD/RLD system 42, thus allowing feedforward process control of the waste water recycling. The control unit 78 can also receive information regarding the output streams of the units, in order to monitor the performance of the units and potentially enable feedback process control.

[0089] Furthermore, the waste water pre-treatment strategy can be managed in order to provide different pre-treatments for different streams. For example, in some scenarios, a filtration unit can be provided for filtering only waste water streams that have certain solids content characteristics (e.g., solids concentration, solids particle size distribution, etc.), and the streams having such solids content characteristics can be treated separately or as a blended stream fed to the filtration unit. In another example, chemical additives can be provided via separate chemical addition assemblies such that the dosing of each chemical additive can be done based on a particular waste water . CA 02948419 2016-11-10 stream to be recycled. For instance, for a waste water stream having high silica and low organics, the chemical addition can be managed by providing a higher dose of a silica scale prevention chemical (e.g., polyvalent metal hydroxides) and a lower dose of a hydrocarbon dispersant. By pre-treating the waste water streams individually, overall chemical dosage requirements can be reduced.

[0090] In addition, in some scenarios, the feed stream into which the recycled waste water stream is to be introduced may include residual chemicals from upstream unit operations which can be leveraged for the waste water stream. For example, if the feed stream already has high levels of hydrocarbon dispersants that would be able to disperse the organics contained in the waste water stream to be added to the feed stream, then chemical pre-treatment can be adapted by reducing or avoiding further addition of hydrocarbon dispersant. The feed streams can thus be analyzed for such properties and the chemical pre-treatment can be adjusted accordingly (e.g., via the control unit 78).

[0091] It should be noted that various steps or features described herein can be combined with other steps, features, implementations, methods and processes described herein. In addition, in some cases, process steps can be conducted in various orders that may not be explicitly be described herein. Waste streams can be obtained from various sources that can be derived from in situ hydrocarbon recovery operations, oil sands mining and extraction operations, steam generation operations, and/or other mining or industrial process operations. The processes and methods described herein can also be used with various in situ hydrocarbon recovery operations besides SAGD, including cyclic steam stimulation (CSS), steam drive, in situ combustion, solvent-assisted processes, hybrid processes, and so on, including combinations thereof. The processes and methods described herein can also be used during various stages of the operational life of the in situ hydrocarbon recovery operation, including start-up, ramp up, steady state, and wind down.

Claims

1. An in situ hydrocarbon production process, comprising:
injecting a mobilizing fluid comprising steam into a hydrocarbon-containing formation;
recovering a production fluid from the formation, the production fluid comprising hydrocarbons and water;
separating the production fluid into a hydrocarbon stream and a produced water stream;
subjecting the produced water stream to water treatment to produce a treated water;
feeding the treated water into a steam generation unit comprising at least one once-through steam generator (OTSG), to produce steam and blowdown;
supplying the steam as at least part of the mobilizing fluid for injection into the hydrocarbon-containing formation;
supplying the blowdown to a zero or reduced liquid discharge (ZLD/RLD) system to produce recovered water and a solids-enriched sludge, the ZLD/RLD system comprising at least one evaporator;
supplying the solids-enriched sludge to a landfill for disposal;
retrieving leachate produced from the landfill;
pre-treating the leachate to produce a pre-treated leachate stream; and recycling the pre-treated leachate stream as part of a feed stream supplied into the at least one evaporator of the ZLD/RLD system.

2. The process of claim 1, wherein the pre-treating comprising adding a chemical agent to the leachate.

3. The process of claim 2, wherein the chemical agent comprises a chelating agent, an anionic dispersant for dispersing inorganic suspended solids, a scale inhibitor, a hydrocarbon dispersant, or an anti-foam agent, or a combination thereof.

4. The process of any one of claims 1 to 3, wherein the mobilizing fluid is dry steam.

5. The process of any one of claims 1 to 4, wherein the mobilizing fluid is injected via an injection well and the production fluids are recovered from a production well.

6. The process of claim 5, wherein the injection well and the production well each has a vertical section and a horizontal section.

7. The process of claim 6, wherein the injection well and the production well form a vertically spaced-apart well pair operable for steam-assisted gravity drainage (SAGD).

8. The process of any one of claims 1 to 7, further comprising:
supplying the blowdown to a first evaporator that produces a first condensate stream and a first evaporator blowdown stream;
supplying the first evaporator blowdown stream to a second evaporator that produces a second condensate stream and a second evaporator blowdown stream;
supplying the second evaporator blowdown stream to a crystallizer that produces a crystallizer slurry; and supplying the crystallizer slurry to a dryer that produces the solids-enriched sludge.

9. The process of claim 8, wherein the ZLD/RLD system comprises the first evaporator, the second evaporator, the crystallizer, and the dryer.

10. The process of claim 8 or 9, wherein the at least one evaporator that receives the pre-treated leachate stream consists of the first evaporator.

11. The process of claim 8 or 9, wherein the at least one evaporator that receives the pre-treated leachate stream comprises the first evaporator.

12. The process of claim 11, wherein the at least one evaporator that receives the pre-treated leachate stream further comprises the second evaporator.

13. The process of claim 8 or 9, wherein the at least one evaporator that receives the pre-treated leachate stream comprises the second evaporator.

14. The process of any one of claims 8 to 13, further comprising:
supplying a first portion of the leachate to the at least one evaporator; and supplying a second portion of the leachate to the crystallizer.

15. The process of claim 8 or 9, wherein all of the pre-treated leachate stream is supplied to a single evaporator.

16. The process of claim 15, wherein the single evaporator is the first evaporator.

17. The process of claim 15, wherein the single evaporator is the second evaporator.

18. The process of any one of claims 1 to 17, further comprising:
supplying the leachate from the landfill to a lagoon;
supplying the leachate from the lagoon to a holding tank that is proximate to the evaporator; and supplying the leachate from the holding tank to the at least one evaporator.

19. The process of any one of claims 1 to 18, further comprising:
combining the pre-treated leachate stream with the blowdown to form the feed stream supplied into the at least one evaporator.

20. A process for treating landfill leachate derived from leaching from a solids-rich sludge by-product of an in situ hydrocarbon recovery operation, the process comprising recycling a waste water stream comprising the landfill leachate into an evaporator that is part of the in situ hydrocarbon recovery operation.

21. The process of claim 20, wherein the evaporator is part of a zero or reduced liquid discharge (ZLD/RLD) system.

22. The process of claim 21, wherein the ZLD/RLD system comprises a first evaporator, a second evaporator, a crystallizer, and a dryer arranged in series;
and the waste water stream is recycled into the first evaporator and/or the second evaporator.

23. The process of claim 22, further comprising:
pre-treating the waste water stream prior to introduction into the evaporator.

24. The process of claim 23, wherein the pre-treating comprises adding a chemical agent to the leachate.

25. The process of claim 24, wherein the chemical agent comprises a chelating agent, an anionic dispersant for dispersing inorganic suspended solids, a scale inhibitor, a hydrocarbon dispersant, or an anti-foam agent, or a combination thereof.

26. A process for treating waste water derived from a by-product of a bitumen production operation, the process comprising:
retrieving a waste water stream from a disposal site comprising the by-product and the waste water;
pre-treating the waste water stream to produce a pre-treated waste water stream;
recycling the pre-treated waste water stream into an evaporator that is part of an in situ hydrocarbon recovery operation.

27. The process of claim 26, wherein the bitumen production operation is an oil sands extraction operation, and the disposal site is a tailings pond from which the waste water stream is retrieved.

28. The process of claim 26, wherein the waste water stream comprises leachate and the disposal site is a landfill.

29. The process of claim 28, wherein the bitumen production operation is the in situ hydrocarbon recovery operation.

30. The process of claim 29, wherein the in situ hydrocarbon recovery operation comprise steam assisted gravity drainage (SAGD).

31. The process of claim 29 or 30, wherein the by-product comprises a solids-enriched sludge that is derived from a zero or reduced liquid discharge (ZLD/RLD) system of the in situ hydrocarbon recovery operation.

32. The process of claim 31, wherein the ZLD/RLD system comprises a first evaporator, a second evaporator, a crystallizer, and a dryer arranged in series;
and the waste water stream is recycled into the first evaporator and/or the second evaporator.

33. The process of claim 31, wherein the pre-treating comprises adding a chemical agent to the waste water stream.

34. The process of claim 33, wherein the chemical agent comprises a chelating agent, an anionic dispersant for dispersing inorganic suspended solids, a scale inhibitor, a hydrocarbon dispersant, or an anti-foam agent, or a combination thereof.

35. The process of claim 32, wherein all of the pre-treated waste water stream is supplied to the first evaporator.

36. The process of claim 32, wherein all of the pre-treated waste water stream is supplied to the second evaporator.

37. The process of any one of claims 26 to 36, further comprising:
adding the pre-treated waste water stream to a blowdown stream to form an evaporator feed stream; and supplying the evaporator feed stream to the evaporator.

38. The process of claim 37, wherein the blowdown stream comprises blowdown from a once-through steam generator (OTSG) that is part of the in situ hydrocarbon recovery operation.

39. A method for selecting and treating waste water streams derived from a hydrocarbon production operation, comprising:
determining compositional characteristics of each waste water stream;
determining production rates or volumes of each waste water stream;
determining disposal capacity characteristics of disposal sites at which respective waste water streams are held;
determining operational feed quality characteristics and operational capacity characteristics of one or more units that are part of a zero or reduced liquid discharge (ZLD/RLD) system that is part of an in situ hydrocarbon recovery operation;
based on the determined compositional characteristics, production rates or volumes, disposal capacity characteristics, operational feed quality characteristics, and operational capacity characteristics:
selecting a waste water stream for recycling and reprocessing;
selecting a unit of the ZLD/RLD system to receive the selected waste water stream;
blending the selected waste water stream with the feed of the selected unit to form a combined feed stream; and supplying the combined feed stream into the selected unit.

40. The method of claim 39, wherein the selected waste water stream comprises landfill leachate and the selected unit comprises an evaporator.

41. The method of claim 39, wherein the selected unit comprises multiple evaporators.

42. The method of claim 39, wherein the units of the ZLD/RLD system comprise an evaporator, a crystallizer, and a dryer.

43. The method of any one of claims 39 to 42, wherein determining capacity characteristics of the units comprises determining capacity of associated vapor coolers.

44. The method of any one of claims 39 to 43, further comprising:
determining pre-treatment requirements for the waste water streams based on at least one of the following: the determined compositional characteristics, the production rates or volumes, the feed quality characteristics of the units, and the capacity characteristics of the units;
and subjecting the selected waste water stream and/or the combined feed stream to a selected pre-treatment.

45. The method of any one of claims 39 to 44, wherein the units comprise a mechanical vapor recompression (MVR) evaporator, an MVR feed flash tank, a steam-driven evaporator, and a crystallizer.

46. A method for treating internal waste water streams generated by an in situ hydrocarbon recovery operation and external waste water streams obtained from a disposal site, comprising:
analyzing the internal and external waste water streams to determine compositional characteristics thereof; and distributing the internal and external waste water streams as multiple recycled waste water streams into an evaporative waste water treatment system that is part of the in situ hydrocarbon recovery operation.

47. The method of claim 46, wherein the internal waste water streams comprise boiler blowdown.

48. The method of claim 47, wherein the boiler blowdown is obtained from a once-through steam generator (OTSG).

49. The method of any one of claims 46 to 48, wherein the external waste water streams comprise landfill leachate.

50. The method of any one of claims 46 to 48, further comprising:
subjecting external waste water streams to pre-treatment prior to introduction into the evaporative waste water treatment system.

51. The method of claim 50, wherein the pre-treatment comprises chemical addition.

52. The method of any one of claims 46 to 51, wherein the evaporative waste water treatment system comprises a zero or reduced liquid discharge (ZLD/RLD) system.

53. The method of any one of claims 46 to 52, wherein the evaporative waste water treatment system comprises an evaporator and a crystallizer.

54. The method of claim 53, wherein the evaporative waste water treatment system comprises multiple units and the distributing of the multiple recycled waste water streams comprises:
supplying a first recycle stream into the evaporator; and supplying a second recycle stream into the crystallizer.

55. The method of claim 54, wherein the first and second recycle streams are selected for recycling into the evaporator and the crystallizer, respectively, based on silica content.