System and method for treating high total dissolved solids wastewater

Abstract

The present application relates to systems and methods for treating high total dissolved solids wastewater. Systems and methods are provided that enable efficient biological treatment of high salt concentration fluid streams (e.g., spent caustic) to reduce the COD concentration in the fluid stream, the method comprising: a) subjecting the wastewater to wet air oxidation to remove an amount of COD from the wastewater and produce a first treated stream comprising a TDS concentration of at least about 10 g / L and a first reduced COD concentration; b) subjecting the first treated stream to a biological process in a bioreactor comprising an amount of biomass and powdered activated carbon therein, wherein the biological process produces a second treated stream comprising at least a second reduced COD concentration.

Description

[0001] This application is a divisional application of Chinese patent application No. 201780052554.8, filed on August 24, 2017, entitled "System and Method for Treating Wastewater with High Total Dissolved Solids".

[0002] Cross-references to related applications

[0003] This application claims priority and interest in U.S. Provisional Application No. 62 / 381,890, filed August 31, 2016, the entire contents of which are incorporated herein by reference. Technical Field

[0004] This invention relates to treatment systems and methods for treating waste streams, and more particularly to systems and methods that enable the efficient biological treatment of fluid streams with high total dissolved solids (TDS) concentrations (e.g., waste alkali) to reduce the chemical oxygen demand (COD) concentration in the fluid stream. Background Technology

[0005] In industries such as petroleum refining and ethylene production, caustic alkali washing is sometimes used to improve product quality and / or aid the refining process. Alkali washing is performed to remove, for example, sulfide components and / or acidic components from the relevant hydrocarbon streams. For instance, aqueous alkali waste streams from these treatments may contain high chemical oxygen demand (COD) and other contaminants such as sulfides, thiols, naphthenates, cresols, and emulsified hydrocarbons. Aqueous alkali waste typically has a high pH concentration, for example, around 13 or higher. Environmental and safety considerations require the treatment of alkali waste before it is released into the environment.

[0006] To reduce the COD concentration in waste alkali, biological treatment of wastewater is widely implemented. Wastewater is typically treated with activated sludge, allowing dissolved and suspended organic matter to be acted upon by bacteria, for example, during the sludge residence time within a bioreactor (e.g., an aeration tank). However, the odor and reactivity properties of waste alkali often preclude the use of biological treatment alone as a single treatment method—even in the case of diluting the waste alkali. For this reason, another treatment (e.g., wet air oxidation) is used in combination with biological treatment (e.g., upstream of it) to treat waste alkali.

[0007] Wet air oxidation (WAO) is a well-known technique for treating process streams and is widely used, for example, to remove oxidizable contaminants from wastewater (e.g., the aforementioned waste alkali stream). The method involves the aqueous-phase oxidation of undesirable components by an oxidant (typically molecular oxygen from an oxygen-containing gas) at elevated temperatures and pressures. For example, the method can convert organic contaminants into carbon dioxide, water, and biodegradable short-chain organic acids (e.g., acetic acid). Inorganic components, including sulfides, thiols, and cyanides, can also be oxidized. In the case of waste alkali, WAO detoxifies the waste alkali by oxidizing sulfides and thiols to sulfates and decomposing toxic cycloalkanes and cresols.

[0008] However, one problem with the biological treatment of waste alkali streams is that the total dissolved solids (TDS) concentration in the waste alkali is often incompatible with biological treatment, even after wet air oxidation. TDS mainly consists of salts and can also contain soluble organic matter. If the TDS / salt concentration is too high, the waste alkali can cause a decrease in biological treatment efficiency, which may result in high effluent concentrations of soluble COD and soluble nitrogen, as well as reduced biosolid settling. Furthermore, the TDS / salt concentration can cause a significant increase in osmotic pressure in the bioreactor, which may further lead to bioreactor shutdown. For these reasons, waste alkali streams are often added to very large biological treatment systems, resulting in significant dilution of the waste alkali. However, the dilution fluid used significantly increases the overall system's materials, cost, treatment, and volume.

[0009] Furthermore, if it is desired to reuse waste alkali (after treatment) for purposes such as boiler feedwater, salt removal is necessary. A common method for salt removal is reverse osmosis. However, the significant dilution of the caustic alkali stream used to allow for biological treatment, combined with reverse osmosis, significantly increases the stream volume, and thus the required size of the associated reverse osmosis unit and the volume of fluid to be treated. Reverse osmosis typically also requires a pretreatment step, which further increases the system footprint compared to systems treating waste alkali streams without dilution. Summary of the Invention

[0010] According to one aspect of the invention, the inventors have developed systems and methods that enable wet air oxidation and biological treatment of high-salinity wastewater (e.g., waste alkali) while significantly reducing floor space, material costs, and operating costs. In some embodiments, biological treatment can be carried out with dilution of the wastewater introduced into the bioreactor, but the dilution fluid used is generated primarily or entirely internally. In other embodiments, wet air oxidation and biological treatment of high-salinity wastewater can be accomplished without dilution of the wastewater at all, as described herein. In any case, the methods and systems described herein allow for the treatment of wastewater, such as waste alkali, streams separated from other streams in the treatment unit. In this way, problems that may arise from the merging of waste alkali with, for example, other streams (e.g., odor problems, foaming, toxicity) are reduced or eliminated.

[0011] More specifically, according to one aspect of the invention, the inventors have developed systems and methods for diluting wastewater (e.g., waste alkali) with an in-situ generated dilution fluid prior to biological treatment to allow for efficient biological treatment of the wastewater. For example, dilution is carried out without adding or significantly adding water to the relevant systems and processes, and allows for the recycling of water (already in the system) to provide the required dilution fluid prior to biological treatment. In other words, once operation begins, the systems and processes do not require repeated addition of dilution fluid to meet discharge requirements that typically require biological treatment. In another aspect, the methods and systems described herein allow for efficient reduction of COD and contaminants from waste alkali streams while also providing a concentrated, treated caustic alkali stream for discharge.

[0012] According to another aspect of the invention, the inventors have developed additional systems and methods that enable the biological treatment of high-salinity wastewater without diluting the initial stream. In one embodiment, this is carried out by first subjecting the high-salinity wastewater to a wet air oxidation process to reduce a first amount of COD from the wastewater, and then contacting the high-salinity effluent from the wet air oxidation (the first treated stream) with a mixture of biomass and powdered activated carbon in a bioreactor under conditions that effectively further reduce a second amount of COD from the wastewater, wherein the powdered activated carbon is considered to provide a substrate (e.g., waste carbon) for the attached growth of the wastewater.

[0013] According to one aspect of the invention, a method is provided for treating wastewater comprising a chemical oxygen demand (COD) concentration and a total dissolved solids (TDS) concentration of at least about 10 g / L, the method comprising:

[0014] a) subjecting wastewater to wet air oxidation to remove a certain amount of COD from the wastewater and producing a first treated stream including a first reduced COD concentration and a TDS concentration of at least about 10 g / L;

[0015] (b) subjecting the first treated stream to a biological process in a bioreactor comprising a certain amount of biomass and powdered activated carbon, wherein the biological process produces a second treated stream comprising at least a second reduced COD concentration.

[0016] According to another aspect, another processing system is provided, which includes:

[0017] (a) This includes sources of wastewater with a chemical oxygen demand (COD) concentration and a total dissolved solids (TDS) concentration of at least about 10 g / L;

[0018] (b) A wet air oxidation unit, the wet air oxidation unit being in communication with the source fluid and configured to remove a certain amount of COD from the wastewater and produce a first treated stream containing a first reduced COD concentration and a TDS concentration of at least about 10 g / L relative to the wastewater; and

[0019] (c) A bioreactor, said bioreactor being downstream of and in fluid communication with a humid air oxidation unit, said bioreactor comprising a quantity of biomass and powdered activated carbon, and said bioreactor being configured to further remove COD from a first treated stream and produce a second treated stream containing at least a second reduced COD concentration relative to the first treated stream.

[0020] According to another aspect, a method for treating wastewater including chemical oxygen demand (COD) concentration and total dissolved solids (TDS) concentration is provided, the method comprising:

[0021] (a) Wastewater is directed to a wet oxidation unit to oxidize oxidizable pollutants therein, thereby producing a first treated stream including a first reduction in COD concentration and TDS concentration;

[0022] (b) Diluting the first treated stream with a diluent produced by the brine concentration process, thereby producing a diluted first treated stream having a diluted TDS concentration; and

[0023] (c) The diluted first treated stream is directed to a biological treatment process, wherein the biological treatment process includes contacting the source fluid with a certain amount of biological material and activated carbon material, and wherein the biological treatment process produces a second treated stream including a second reduced COD concentration and a diluted TDS concentration.

[0024] According to another aspect, a treatment system for wastewater containing pollutants and salt concentrations is provided, the system comprising:

[0025] (a) The source of the wastewater;

[0026] (b) A humid air oxidation unit in communication with the source fluid;

[0027] (c) A bioreactor in fluid communication with a wet oxidation unit via a fluid pipeline, the bioreactor comprising biomass and powdered activated carbon; and

[0028] (d) A brine concentrator in fluid communication with a bioreactor and fluid pipeline. Attached Figure Description

[0029] The accompanying drawings illustrate the invention as described in the following description:

[0030] Figure 1 This is a schematic diagram of a system according to one aspect of the present invention.

[0031] Figure 2 This is a schematic diagram of another system according to one aspect of the present invention.

[0032] Figure 3 This is a schematic diagram of yet another system according to one aspect of the present invention.

[0033] Figure 4 This is a schematic diagram of yet another system according to one aspect of the present invention. Detailed Implementation

[0034] Now refer to the attached diagram, Figure 1 A first embodiment of a system according to one aspect of the invention is shown. As shown, a treatment system 10 is provided for treating wastewater 11 (e.g., waste alkali 12) comprising at least a COD concentration and a total dissolved solids (TDS) concentration. Hereinafter, wastewater 11 may be referred to as, for example, "waste alkali 12," however, it should be understood that the invention is not limited to waste alkali. It should be understood that wastewater 11 may also comprise any other aqueous fluid having a COD concentration and a TDS concentration. The system includes a source 14 of wastewater 11 (e.g., waste alkali 12) and a wet air oxidation (WAO) unit 16 in fluid communication with the source 14 via a fluid line 18. Furthermore, system 10 includes a bioreactor 20 in fluid communication with the WAO unit 16 via a fluid line 19, and a brine concentrator 22 in fluid communication with the bioreactor 20 (via a fluid line 21) and with the fluid line 19 (via a fluid line 23).

[0035] According to one aspect, the brine concentrator 22 is capable of generating a dilution fluid 28, which is used to dilute the wastewater 11 upstream of the bioreactor 20 (after humid air oxidation), so that the resulting diluted stream can be optimally and safely delivered to the biological treatment process in the bioreactor 20. In this way, the dilution water is repeatedly recycled within the system 10. Furthermore, the recycling of the dilution water eliminates the need for external addition of dilution water in the biological treatment of waste alkali with, for example, high TDS concentrations (e.g., >about 10 g / L). As used herein, the term "about" means a value ±1% of said value.

[0036] Source 14 may include any suitable container or system that provides a quantity of wastewater 11 (e.g., waste alkali 12) having at least a COD concentration and a high TDS concentration. "High TDS concentration" means that wastewater 11 includes at least 10 g / L TDS, and in some specific embodiments, about 10 g / L to 200 g / L TDS, and in other embodiments, about 100 g / L to 200 g / L TDS. When the wastewater contains waste alkali, waste alkali 12 may contain refinery waste alkali or sulfide waste alkali, each known in the art. In one embodiment, the term "refinery waste alkali" refers to waste alkali generated during the operation of equipment and processes, such as those found in refineries. Refinery waste alkali typically has high levels of chemical oxygen demand (COD), in some cases about 400,000 mg / L to 500,000 mg / L or higher. Refinery waste alkali may also contain naphthenic waste alkali or cresol waste alkali.

[0037] Naphthenic waste alkali can be generated from the washing of kerosene and jet fuel, and can contain high concentrations of organic compounds consisting of naphthenic acids, as well as phenolic compounds and reduced sulfur compounds. Naphthenic waste alkali can also contain high levels of chemical oxygen demand (COD), in some cases exceeding 100,000 mg / L. Naphthenic waste alkali can also contain thiosulfates and naphthenic acids, which can be decomposed during wet air oxidation at temperatures above about 220°C to about 280°C or higher. Cresol waste alkali can be generated from the washing of gasoline, and can contain high concentrations of phenolic compounds (cresolic acids), as well as reduced sulfur compounds.

[0038] In another embodiment, waste alkali 12 may comprise sulfide waste alkali. Sulfide waste alkali can be generated from hydrocarbon washing and may contain high concentrations of reduced sulfur compounds (e.g., sulfides and thiols) and organic compounds. In a particular embodiment, sulfide waste alkali comprises ethylene waste alkali. The term "ethylene waste alkali" refers to waste alkali generated during the operation of equipment and processes, such as those found at ethylene production units, for example, caustic alkali used in ethylene washing. For example, ethylene waste alkali may originate from the alkali washing of cracked gas from an ethylene cracking unit. This liquid can be generated by an alkali washing tower. Ethylene product gases may be contaminated with H2S(g) and CO2(g), and these contaminants can be removed by absorption in the alkali washing tower to produce NaHS(aq) and Na2CO3(aq). Sodium hydroxide may be consumed and the resulting wastewater (ethylene waste alkali) is contaminated with sulfides, carbonates, and a small fraction of organic compounds. Insoluble polymers generated during the condensation of olefins during washing may also be present. Other examples of waste alkali containing compounds that can be oxidized by wet oxidation as described herein are illustrated in U.S. Patent No. 9,630,867, the entire contents of which are incorporated herein by reference.

[0039] The total dissolved solids (TDS) concentration in wastewater 11 (e.g., waste alkali 12) comprises any number of salts and, in some cases, dissolved organic matter. Exemplary salts in wastewater 11 include, but are not limited to, salts such as carbonates, thiols, disulfide oils, phenolates, cresols, xylenols and naphthenates, alkali metal salts of sulfides, and any alkaline components (e.g., sodium hydroxide) added to the original alkali washing solution. In some embodiments, wastewater 11 may contain sodium sulfide, sodium disulfide, and sodium hydroxide. In one aspect, the TDS concentration is a concentration that reduces the efficiency of bioreactor 20 or has a detrimental effect (e.g., lifetime). In some aspects, wastewater 11 has a TDS concentration equal to or greater than 10 g / L. In a particular embodiment, the TDS concentration is from 100 g / L to 200 g / L. In some embodiments, the salt concentration comprises sodium hydroxide, and the sodium hydroxide in wastewater 11 ranges from about 1% by weight to about 20% by weight.

[0040] WAO unit 16 includes one or more dedicated reactor vessels in which the oxidation of oxidizable components in wastewater 11 (e.g., waste alkali 12) occurs at elevated temperature and pressure (relative to atmospheric conditions) and in the presence of oxygen. In one embodiment, the WAO process is carried out at a temperature of 150°C to 320°C (275°F to 608°F) and a pressure of 10 bar to 220 bar (150 psi to 3200 psi). Furthermore, in one embodiment, wastewater 11 may be mixed with an oxidant (e.g., pressurized oxygen-containing gas supplied by a compressor). The oxidant may be added to wastewater 11 before and / or after it flows through a heat exchanger (not shown). Within WAO unit 16, the materials therein are heated for a suitable time under suitable conditions to effectively oxidize the components in wastewater 11 and produce a first treated stream 24 comprising a first reduced COD concentration (relative to wastewater 11) and a TDS concentration. A gaseous component (exhaust gas) with an oxygen content may also be produced.

[0041] Bioreactor 20 may include one or more suitable containers, each containing a biomass mass suitable for further processing a certain amount of compounds / contaminants from materials within bioreactor 20. Figure 1 In one embodiment, the first treated stream 24 is diluted with dilution fluid 28 to produce a diluted stream 30 before being delivered to bioreactor 20. The diluted stream 30 is then delivered to bioreactor 20. In one embodiment, the contaminants treated within bioreactor 20 include carbonaceous compounds retained from oxidation by humid air and any other compounds that can be reduced or removed by biological treatment. In one embodiment, bioreactor 20 includes one or more treatment zones. As used herein, the phrase “treatment zone” is used to refer to a separate treatment area. A separate treatment zone may be housed in a single container having one or more compartments. Alternatively, a separate treatment zone may be housed in separate containers in which different treatments are performed. The size and shape of the treatment zone (e.g., container, tank, or compartment) can be determined based on the desired application and volume of the material to be treated to provide the desired retention time.

[0042] The biomass community can include any suitable bacterial microbiome that effectively digests biodegradable materials, including bacterial microbiomes that do so under conditions of reduced solids production. Exemplary wastewater treatment for reduced solids production is described in U.S. Patent Nos. 6,660,163, 5,824,222, 5,658,458, and 5,636,755, each of which is incorporated herein by reference in its entirety. The bacteria can include any bacteria or combination of bacteria adapted to reproduce under anoxic and / or aerobic conditions. Representative aerobic genera include bacteria such as Acinetobacter, Pseudomonas, Zoogloea, Achromobacter, Flavobacterium, Norcardia, Bdellovibrio, Mycobacterium, Shpaerotilus, Baggiatoa, Thiothrix, Lecicothrix, and Geotrichum; nitrifying bacteria such as Nitrosomonas and Nitrobacter; and protozoa such as Ciliata, Vorticella, Opercularia, and Epistylis. Representative anoxic genera include denitrifying bacteria, Achromobacter, Aerobacter, Alcaligenes, Bacillus, Brevibacterium, Flavobacterium, Lactobacillus, Micrococcus, Proteus, Pserudomonas, and Spirillum. Exemplary anaerobic organisms include Clostridium spp., Peptococcus anaerobus, Bifidobacterium spp., Desulfovibrio spp., Corynebacterium spp., Lactobacillus, Actinomyces, Staphylococcus, and Escherichia coli.

[0043] In some embodiments, bioreactor 20 may also include a quantity of activated carbon material. The presence of activated carbon is thought to help adsorb compounds that may be toxic to the biomass, thereby protecting it. When present, activated carbon can be provided in an amount that effectively adsorbs or otherwise removes a quantity of organic material from the diluted stream 30. In one particular embodiment, the activated carbon comprises powdered activated carbon. In some aspects, activated carbon can effectively remove a quantity of refractory organic matter from the fluid (diluted stream 30) delivered to bioreactor 20. As used herein, refractory organic matter is defined as a class of organic matter that may be slowly or poorly biodegraded relative to the majority of organic matter in the diluted stream 30. For example, refractory organic matter includes synthetic organic chemicals. Other refractory organic matter includes polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), polychlorinated diphenylene oxides (PCBs), and para-diphenyl ethers. Anthracenes and polychlorinated dibenzofurans. Endocrine disrupting compounds are also a class of stubborn organic compounds that can affect the hormone systems of organisms and are found in the environment.

[0044] In one embodiment, activated carbon can be added to bioreactor 20 and contacted with the diluted stream 30 for a sufficient time to adsorb material from the diluted stream 30. It should be understood that activated carbon can be introduced into system 10 at any location within system 10, as long as it is present in bioreactor 20. Typically, activated carbon is added directly to bioreactor 20. Alternatively, activated carbon can be added upstream of bioreactor 20.

[0045] In addition to activated carbon, in some embodiments, bioreactor 20 may include membrane bioreactors known in the art, comprising one or more porous or semi-permeable membranes for reducing a certain amount of TDS from the diluted stream 30. In some embodiments, the membranes are disposed within the shell of bioreactor 20. In other embodiments, the membranes are disposed within a different shell from bioreactor 20, which may be referred to as a “membrane unit.” In one embodiment, one or more membranes (hereinafter referred to as “membrane” for ease of reference) may include microfiltration or ultrafiltration membranes as known in the art. Furthermore, the membranes may have any construction suitable for their intended application, such as sheets or hollow fibers.

[0046] Furthermore, the membrane can be formed from any suitable material having the desired porosity and / or permeability for its intended application. In one embodiment, the membrane can be formed from polymer hollow fibers. In other embodiments, the membrane may comprise a ceramic material, such as a ceramic plate. Furthermore, the membrane can have any suitable shape and cross-sectional area, such as square, rectangular, or cylindrical. In one embodiment, the membrane has a rectangular shape. Additionally, in one embodiment, one or more membranes may be arranged, for example, vertically, such that they are completely submerged by the treated flow, the biomaterial, and activated carbon (if present).

[0047] In its setup, bioreactor 20 or discrete membrane unit may include blowers connected thereto for supplying fluids (e.g., gases) to flush the membranes and prevent solids from accumulating on the membrane surfaces. In one embodiment, additional blowers may be provided (if desired) to supply oxygen-containing gas to the biomass in bioreactor 20. Each blower may generate fine bubbles, coarse bubbles, jets of gas, jets of gas and fluid, and combinations thereof. The gas may include nitrogen, air, fuel gas, or any other suitable gas. Furthermore, the blowers may supply gas along the length of one or more membranes. Pumps may also typically be provided to generate suitable suction to draw the desired material through each membrane.

[0048] A second treated stream 26, with a further reduced COD content (relative to the first treated stream 24), can be delivered from the bioreactor 20 or the membrane unit (if present) to the brine concentrator 22. As detailed below, when the brine concentrator 22 is present, its purpose is to generate a dilution fluid 28, such as an aqueous stream with a relatively low salt concentration (e.g., less than 50 g / L TDS), which can be used to repeatedly dilute the first treated stream 24 from the WAO unit 16 and generate a diluted stream 30 (at each dilution) before being delivered to the bioreactor 20. The diluted stream 30 is then delivered to the bioreactor 20 for treatment.

[0049] The brine concentrator 22 may include any suitable means employing a process to remove TDS from the fluid and produce a diluted fluid 28 with a reduced TDS concentration relative to the fluid introduced into the brine separator 22. In one aspect, the brine concentrator 22 may be configured to perform suitable processes such as high-pressure reverse osmosis, membrane filtration, evaporation, forward osmosis, etc. It should be understood that the selected technology and its operation may be based on the amount of dilution water that needs to be recirculated and delivered to the first treated stream 24 for its dilution. In one embodiment, the brine concentrator 22 includes a reverse osmosis unit as known in the art, which produces a TDS concentrate and permeate (which can be used to dilute the first treated stream 24).

[0050] The brine concentrator 22 can be located at different points in the system. The following description details the operation of two different systems in which the brine concentrator 22 has different locations. However, it should be understood that the invention is not limited to the disclosed embodiments. Figures 1 to 2 In the embodiment shown, brine concentrator 22 provides a fluid (dilution fluid 30) that can be used to dilute the wastewater between wastewater source 14 and brine concentrator 22. In other embodiments, other systems and methods for treating wastewater without prior dilution of the wastewater are disclosed, as will be described below.

[0051] Refer again Figure 1 A certain amount of wastewater 11 (e.g., waste alkali 12), including COD and TDS concentrations (e.g., 10 g / L to 200 g / L), is delivered from wastewater source 14 to WAO unit 16. In WAO unit 16, wastewater 11 is subjected to wet air oxidation to treat oxidizable pollutants therein and produce a first treated stream 24 including a first reduced COD concentration (relative to stream 12) and a TDS concentration. The TDS concentration is generally not altered or substantially unaffected by the wet air oxidation process (e.g., reduced by less than 10%). In one embodiment, when dilution is provided, the first treated material 24 is diluted with dilution fluid 28 before delivery to bioreactor 20 or within bioreactor 20. In one embodiment, the first treated material 24 is mixed / combined with dilution fluid 28 delivered via fluid line 23 (which establishes a flow path between WAO 16 and bioreactor 20). The resulting diluted stream 30 thus has a diluted TDS / salt concentration, making it more suitable for treatment in bioreactor 20. In some embodiments, the TDS concentration of the diluted stream 30 is less than about 50 g / L.

[0052] In this configuration, the dilution fluid 28 is supplied by the brine concentrator 22, eliminating the need for an external dilution fluid source and reducing material, processing, and operating costs. In the illustrated embodiment, the brine concentrator 22 may include a reverse osmosis unit 32 as known in the art, and the dilution fluid 28 may contain permeate 34 from the reverse osmosis unit 32. Alternatively, the dilution fluid 28 may contain a fluid with a reduced TDS concentration due to different treatment at the brine concentrator 22. In addition to the dilution fluid 34, the brine concentrator 22 will provide a TDS (salt) concentrate 36. In one embodiment, the salt concentration of the TDS concentrate 36 may be, for example, from 50 g / L to 200 g / L, which may be comparable to the original wastewater 11. The TDS concentrate 36 may be directed to any suitable location, such as for storage, transport, or further treatment.

[0053] In one embodiment, the brine concentrator 22 receives feed directly from the bioreactor 20. However, it should be understood that the invention is not limited thereto. Figure 2 Another embodiment is shown, illustrating another implementation of a system 100 for treating wastewater 11 (e.g., waste alkali 12). In this embodiment, the system 100 is alternatively configured such that the treated stream exits the bioreactor 20 and is combined with TDS concentrate exiting the brine concentrator 22 to provide a combined reconcentrated stream, which is then delivered to the inlet of the brine concentrator 22. In this way, the method includes reconcentrating a second treated stream 26 from the biological treatment at the bioreactor 20 with a certain amount of TDS concentrate 36 from the brine concentration treatment at the brine concentrator 22. The method also includes directing the reconcentrated (combined) stream to a brine concentration process at the brine concentrator 22 to regenerate the dilute fluid 28 and the brine concentrate 36.

[0054] To illustrate and as Figure 2 As shown, a system 100 with the same components as system 10 but with additional components added is illustrated. In system 100, wastewater 11 (e.g., waste alkali 12) is delivered from its source 14 to a WAO unit 16 via a fluid line 18. From the WAO unit 16, a first treated stream 24 exits the WAO unit 16 and is directed to the bioreactor 20 via a fluid line 19. However, in this embodiment, the brine concentrator 22 does not directly receive the fluid from the bioreactor 20, but still produces a diluted fluid 28 to be combined with the first treated stream 24. In one embodiment, the brine concentrator 22 includes a reverse osmosis unit.

[0055] In operation, brine concentrator 22 produces dilution fluid 28 and TDS concentrate 36, as previously described. However, in this embodiment, brine concentrator 22 alternatively delivers TDS concentrate 36 via fluid line 101 to be combined with a second treated stream 26 exiting bioreactor 20. To accommodate both streams 26 and 36, system 100 also includes container 102 in which TDS concentrate 36 and the second treated stream 26 can be combined and optionally mixed together. Streams 26 and 36 can be introduced into container 102 separately, or alternatively, concentrate 36 from line 101 can be combined with the second treated stream 26 in fluid line 103 (which defines a flow path between bioreactor 20 and container 102). The resulting combined (reconcentrated) TDS (salt) stream 104 can be delivered from container 102 back to brine concentrator 22 via fluid line 105 to provide dilution fluid 28 again via fluid line 106 to dilute the first treated stream 24 before entering bioreactor 20. The TDS concentration of the combined stream 104 is at least about 10 g / L, and in one embodiment is about 10 g / L to 200 g / L, and in some specific embodiments is about 100 g / L to 200 g / L.

[0056] According to another aspect, the inventors unexpectedly discovered that dilution is not necessary when treating wastewater 11 (e.g., waste alkali 12) in a bioreactor comprising an effective amount of biomass and powdered activated carbon. As used herein, the term "effective amount" refers to the amount required to achieve the desired results. Not wishing to be bound by theory, it is considered that the powdered activated carbon particles themselves act as a substrate on which biomass can be retained and grown, thereby providing attached-growth biological treatment. Furthermore, the powdered activated carbon itself can also assist in COD reduction (via adsorption, etc.), thereby removing target compounds from materials in contact with it, compared to artificial structures (e.g., discs and filters) that do not possess such adsorption or removal properties themselves, typically used in other "attached-growth" systems for biological growth therein.

[0057] Reference Figure 3An exemplary system 200 is shown for treating wastewater 11 (e.g., waste alkali) with high salt concentrations (e.g., 10 g / L to 200 g / L TDS) without dilution. As shown, wastewater 11 is delivered from its source 14 to a wet air oxidation (WAO) unit 16. As previously described herein, when wastewater 11 contains waste alkali 12, waste alkali 12 may contain refinery waste alkali, sulfide waste alkali, or a mixture thereof. Wastewater 11 includes a COD concentration and a TDS (salt) concentration of at least 10 g / L, and in one particular embodiment, the TDS (salt) concentration is from about 10 g / L to about 200 g / L. Within the WAO unit 16, wastewater 11 is subjected to a wet air oxidation process under time, temperature, pressure, and oxygen-enriched conditions that effectively produce a first treated stream 24 with a reduced COD concentration (relative to wastewater 11) and the same or substantially the same TDS concentration as wastewater 11. In some embodiments, at least 90% by weight of the TDS concentration is transported from wastewater 11 to a first treated stream 24 (after humid air oxidation).

[0058] exist Figure 3 In one embodiment, the waste alkali treated by WAO (first treated stream 24) can be delivered directly from the wet air oxidation unit 16 to the bioreactor 20 without diluting stream 24. To achieve this, the bioreactor 20 includes a certain amount of biomass and a certain amount of powdered activated carbon to effectively further reduce the COD in the first treated stream 24 and produce a second treated stream 26 with a COD concentration below a predetermined level. In one embodiment, the predetermined level is about 50 mg / L. The biomass and powdered activated carbon can be arranged in the bioreactor 20 in a suitable ratio to effectively reduce the desired amount of COD therein. In one embodiment, the weight ratio of powdered activated carbon to biomass in the bioreactor 20 is about 1:1 to about 5:1, and in a particular embodiment it is about 3:1 to 5:1. Again, the combination of biomass and powdered activated carbon is considered to allow for the attached growth of biological treatment of the waste alkali treated by WAO (stream 24) (even at its high salt concentration). In this way, system 200 eliminates the need to dilute the waste alkali 24 treated by WAO and also allows for the separate (without merging with other aqueous streams) treatment of wastewater 11 (e.g., waste alkali 12), which saves on equipment costs, material costs, space and operating costs, and prevents the possible odor, toxicity and foaming problems mentioned above.

[0059] The second treated stream 26, with a further reduced COD concentration, can be separated from the biomass / activated carbon using any suitable processing and structure, and can be recovered from the bioreactor 20. In one embodiment, as... Figure 3As shown, effluent 202 from bioreactor 20 (comprising treated stream 26, powdered activated carbon, and biomass) is delivered from bioreactor 20 to solid / liquid separator 204. Solid / liquid separator 204 is configured to separate solid biomass / activated carbon from the liquid portion to provide a second treated stream 26. Solid / liquid separator 204 may include membrane units (e.g., reverse osmosis units), hydrocyclones, belt filter presses, centrifuges, clarifiers, combinations thereof, or any other suitable device. In any case, the resulting second treated stream 26 may include a COD concentration less than a predetermined threshold for disposal, discharge, delivery, or transport. In some embodiments, the threshold is 50 mg / L. In one embodiment, the second treated stream 26 still has a high TDS (containing salt) concentration from the original wastewater 11. In one embodiment, the TDS concentration of the second treated stream 26 is from about 10 mg / L to 200 mg / L (comparable to the original wastewater 11).

[0060] In some embodiments, it may be desirable to reduce TDS from the second treated stream 26 before reuse, disposal, discharge, transport, or storage. In one embodiment, for example, the solid / liquid separator 204 may include a membrane unit comprising a plurality of membranes within a housing as previously described herein, which will retain TDS (including salts) as permeate and allow permeate to pass through the membrane unit with a reduced TDS concentration. Alternatively, any other suitable means for removing TDS from the stream introduced therein may be used. In some embodiments, the solid / liquid separator 20 (e.g., a membrane unit) may be as follows: Figure 3 The discrete units from bioreactor 20 are shown.

[0061] In other embodiments, the bioreactor 20 itself may be equipped with a solid / liquid separator 204, which enables the removal of TDS from the liquid in the bioreactor (first treated stream 24) and produces an effluent (second treated stream 26) with a reduced TDS concentration. In one embodiment, as... Figure 4As shown, a system 300 with the same components as system 200 is illustrated, except that bioreactor 20 includes membrane bioreactor 212. Wastewater 11 (e.g., alkali 12) is subjected to wet air oxidation in WAO unit 16 to provide a first treated stream 24, which is then delivered to membrane bioreactor 212. In this case, membrane bioreactor 212 may include a quantity of biomass, powdered activated carbon, and one or more membranes 206 for separating solids / TDS from the liquid portion of the bioreactor and producing a second treated stream 26. In this case, the second treated stream 26 includes a reduced COD concentration and also includes a reduced TDS concentration relative to the first treated stream 24. Membranes 206 may have any suitable structure as described above. In some embodiments, membranes 206 are housed in different membrane housings (units) within bioreactor 20. The combination of biological treatment, activated carbon treatment, and membrane filtration in a single unit can be commercially available, for example, from the PACT® MBR system from Siemens Energy, Inc. For example, this compact system typically occupies 50% less space compared to conventional treatment systems that use separate activated sludge, ultrafiltration, and activated carbon stages, and also significantly reduces equipment and operating costs.

[0062] In any of the implementations described herein, and as Figure 4 As shown, it may be desirable to regenerate the spent activated carbon from bioreactor 20. In this case, a certain amount of spent carbon 208 can be delivered from the outlet of bioreactor 20 back to WAO unit 16 via line 209 to regenerate the spent carbon material and oxidize biosolids (if present) and oxidizable materials (e.g., organic matter). “Waste” means that the carbon material’s ability to further remove target components in bioreactor 20 is at least reduced. In some embodiments, the spent carbon is regenerated in wet air oxidation unit 16 while treating the wastewater 11 introduced therein. Once regenerated to the desired extent, effluent 210, containing at least spent carbon and optionally also containing the first treated stream 26, can be returned to bioreactor 20 via line 211 for use / treatment therein.

[0063] In the systems and processes described herein, it should be understood that any of the components, containers, systems, and processes described herein may include one or more inlets, channels, mixers, filters, outlets, pumps, valves, coolers, energy sources, flow sensors, or controllers (including microprocessors and memories), etc., to facilitate the introduction, inflow, output, timing, volume collection, selection, and guidance of the flow of any of the materials therein. Additionally, instructions stored on a computer-readable medium may be provided to assist in automating any of the functions described herein. Furthermore, those skilled in the art should understand or be able to modify the concentration, volume, flow rate, and other parameters necessary to achieve the desired results.

[0064] The functionality and advantages of these and other embodiments of the invention will be more fully understood from the following examples. These examples are intended to be illustrative in nature and should not be considered as limiting the scope of the invention.

[0065] Example

[0066] Example 1: Simulated treatment of waste alkali without dilution

[0067] First, experimental data determined that conventional activated sludge treatment, without dilution of the feed stream, could not meet the 50 mg / L dissolved organic carbon (DOC) requirement at salt concentrations as low as 30 g / L. For comparison, ethylene waste alkaline wet air oxidation (WAO) effluent was simulated via the PACT® MBR process described above. The effluent from this test was filtered and the dissolved components were analyzed. Table 1 shows the results of the final stage of the test, where an additional 5% (50 g / L) of TDS in the form of sodium sulfate (Na₂SO₄) was added to the WAO effluent to achieve 10% by weight or 100 g / L. The data in Table 1 clearly demonstrate that, with the aid of powdered activated carbon (PAC), a TDS concentration of <10% (<100 g / L) meets the 50 mg / L effluent DOC requirement without any dilution.

[0068] Table 1

[0069]

[0070] Example 2: Waste carbon regeneration using WAO

[0071] A method for regenerating carbon used in the treatment of waste alkali, as described herein, was tested. A certain amount of waste carbon, equal to the daily carbon dose required to achieve effluent quality, was delivered to a wet air oxidation (WAO) unit and simultaneously regenerated with 1% to 20% by weight (10 g / L to 200 g / L) TDS ethylene waste alkali. The regenerated carbon was then returned to the attached growth biological treatment process along with the treated caustic alkali stream.

[0072] Data shows that waste carbon from biological treatment can be satisfactorily regenerated (even when combined with waste alkali). In fact, the data shown in Table 3 below illustrates significant regeneration of waste alkali, up to 20%.

[0073] Table 3

[0074]

[0075] While various embodiments of the invention have been shown and described herein, it is apparent that these embodiments are provided by way of example only. Many changes, modifications, and substitutions can be made without departing from the invention described herein. Therefore, the invention is intended to be limited only by the spirit and scope of the appended claims.

Claims

1. A method for treating wastewater (11), said wastewater (11) comprising a total dissolved solids (TDS) concentration of at least about 10 g / L and a chemical oxygen demand (COD) concentration, said method comprising: a) subject the wastewater (11) to wet air oxidation to remove a certain amount of COD from the wastewater (11) and produce a first treated stream (24) having a TDS concentration of at least about 10 g / L and a first reduced COD concentration. b) subjecting the first treated stream (24) to a biological process in a bioreactor (20) comprising a certain amount of biomass and powdered activated carbon, wherein the biological process produces a second treated stream (26) comprising at least a second reduced COD concentration.

2. The processing method according to claim 1, wherein the TDS concentration in the first treated stream (24) is from 10 g / L to 200 g / L.

3. The processing method according to claim 2, wherein the TDS concentration in the first treated stream (24) is 100 g / L to 200 g / L.

4. The treatment method according to claim 1, wherein at least 90% by weight of the TDS in the wastewater (11) is conveyed to the second treated stream (26).

5. The processing method according to claim 1, wherein the second reduced COD concentration in the second treated stream (26) is 50 mg / L or less.

6. The processing method according to claim 1 further includes: A certain amount of waste carbon (208) from the bioreactor (20) is delivered to the wet air oxidation unit (16) to regenerate the waste carbon (11) via wet air oxidation; and The recycled carbon (210) is returned to the bioreactor (20) for further use in the biological process.

7. The processing method according to claim 1 further includes subjecting the second treated stream (26) to a separation process to further reduce the TDS concentration in the second treated stream (26).

8. The processing method according to claim 1, wherein the separation process includes at least one of membrane filtration and reverse osmosis.

9. The processing method according to claim 1, wherein the bioreactor (20) further comprises a plurality of membranes (206), wherein the method further comprises removing at least a portion of the TDS concentration in the first treated stream (26) in the bioreactor (20) by passing the first treated stream (24) through the plurality of membranes (206).

10. The processing method according to claim 1, further comprising: Waste carbon (208) from the bioreactor (20) is regenerated by humid air oxidation; as well as The recycled carbon (210) is recycled back to the bioreactor (210).

11. The treatment method according to claim 1, wherein the wastewater (11) comprises waste alkali (12).

12. The treatment method according to claim 12, wherein the waste alkali (12) comprises refinery waste alkali or sulfide waste alkali.

13. The treatment method according to claim 14, wherein the sulfide waste alkali comprises ethylene waste alkali.

14. A processing system (10, 100, 200, 300), comprising: This includes sources (14) of wastewater (11) with a total dissolved solids (TDS) concentration and a chemical oxygen demand (COD) concentration of at least 10 g / L. A wet air oxidation unit (16), which is in fluid communication with the source (14) and configured to remove a certain amount of COD from the wastewater (11) and generate a first treated stream (24), the first treated stream (24) containing a TDS concentration of at least 10 g / L and a first reduced COD concentration relative to the wastewater (11); and A bioreactor (20) is located downstream of and in fluid communication with the humid air oxidation unit (16), wherein the bioreactor (20) comprises a quantity of biomass and powdered activated carbon, wherein the bioreactor (20) is configured to further remove COD from the first treated stream (24) and produce a second treated stream (26), the second treated stream (26) containing at least a second reduced COD concentration relative to the first treated stream (24).

15. The system (10, 100, 200, 300) according to claim 14, wherein the TDS concentration in the wastewater (11) is from 10 g / L to 200 g / L.

16. The system (10, 100, 200, 300) according to claim 14, wherein the TDS concentration in the wastewater (11) is 100 g / L to 200 g / L.

17. The system (10, 100, 200, 300) according to claim 14, wherein the COD concentration in the second treated stream (206) is 50 mg / L or less.

18. The system (10, 100, 200, 300) according to claim 14, further comprising: A first recirculation line (209) extends between the outlet of the bioreactor (20) and the inlet of the wet air oxidation unit (16) and is configured to deliver a certain amount of waste carbon (208) from the bioreactor (20) to the wet air oxidation unit (16). A second pipeline (211) extends from the outlet of the wet air oxidation unit (16) to the inlet of the bioreactor (20) to return the regenerated carbon (210) from the wet air oxidation unit (16) to the bioreactor (20).

19. The system (10, 100, 200, 300) according to claim 14 further includes a solid / liquid separator (204) downstream of the bioreactor (20), the solid / liquid separator (204) being configured to further separate solids from the liquid in the second treated stream (26) and reduce the amount of TDS concentration in the second treated stream (26).

20. The system (10, 100, 200, 300) according to claim 14, wherein the solid / liquid separator (204) comprises at least one of a membrane filtration unit, a reverse osmosis unit, a hydrocyclone separator, a belt filter press, a centrifuge, and a clarifier.

21. The system (10, 100, 200, 300) according to claim 14, wherein the bioreactor (20) further comprises a plurality of membranes (206).

22. The system (10, 100, 200, 300) according to claim 14, wherein the wastewater (11) comprises waste alkali (12).

23. The system (10, 100, 200, 300) according to claim 14, wherein the waste alkali (12) comprises refinery waste alkali or sulfide waste alkali.

24. The system (10, 100, 200, 300) according to claim 14, wherein the sulfide waste alkali comprises ethylene waste alkali.

25. A method for treating wastewater (11), said wastewater (11) comprising a chemical oxygen demand (COD) concentration and a total dissolved solids (TDS) concentration, said method comprising: (a) The wastewater (11) is directed to a wet oxidation unit (16) to oxidize oxidizable pollutants therein, thereby producing a first treated stream (24) including a first reduced COD concentration and the total dissolved solids concentration. (b) The first treated stream (24) is diluted with a dilution fluid (28) produced by the brine concentration process, thereby producing a diluted first treated stream (30) having a diluted total dissolved solids concentration relative to the wastewater (11); and (c) The diluted first treated stream (30) is directed to a biological treatment process, wherein the biological treatment process includes contacting the wastewater (11) with a certain amount of biological material and activated carbon material, and wherein the biological treatment process produces a second treated stream having the diluted total dissolved solids concentration and including a second reduced COD concentration.

26. The method according to claim 25, wherein the total dissolved solids concentration in the wastewater (11) is from 10 g / L to 200 g / L.

27. The method of claim 25, wherein the total dissolved solids concentration of the first treated stream (24) is less than 50 g / L.

28. The method of claim 25, wherein the biological treatment process further comprises contacting the wastewater (11) with one or more membranes (206).

29. The method of claim 25, wherein the brine concentration process includes a reverse osmosis process.

30. The method of claim 25, wherein the dilution fluid (28) is provided via: The second treated stream (26) from the biological treatment is directed to the brine concentration process; and The second processed stream (26) is separated into TDS concentrate (36) and the diluted fluid (28).

31. The method of claim 30, further comprising: The second treated stream (26) from the biological treatment process is combined with a certain amount of TDS concentrate (36) from the brine concentration process; as well as The combined stream (104) is directed to the brine concentration process to regenerate the dilution fluid (28) and the TDS concentrate (36).

32. A treatment system (10, 100, 200, 300) for wastewater (11), said wastewater (11) comprising a chemical oxygen demand (COD) concentration and a total dissolved solids (TDS) concentration, said system (10, 100, 200, 300) comprising: The source of the wastewater (11) is (14). A humid air oxidation unit (16) in fluid communication with the source (14). A bioreactor (20) in fluid communication with the humid air oxidation unit (16) via a fluid line (19), the bioreactor (20) comprising biomass and powdered activated carbon; and A brine concentrator (22) in fluid communication with the bioreactor (20) and the fluid line (19).

33. The system (10, 100, 200, 300) according to claim 34, wherein the brine concentrator (22) is configured to deliver a diluted fluid (28) produced by the brine concentrator (22) to the fluid line (19) between the wet air oxidation unit (16) and the bioreactor (20) to produce a diluted first treated stream (30).

34. The system (10, 100, 200, 300) according to claim 34, wherein the total dissolved solids concentration in the wastewater (11) is from 10 g / L to 200 g / L.

35. The system (10, 100, 200, 300) according to claim 36, wherein the bioreactor further comprises one or more membranes.

36. The system (10, 100, 200, 300) according to claim 36 further includes: Container (102), the container (102) is configured to receive a second treated stream (26) from the bioreactor (20) and to receive TDS concentrate (36) from the brine concentrator (22) to produce a combined fluid (104). The container (12) is in fluid communication with the brine concentrator (22) for delivering the combined fluid (104) to the brine concentrator (22) to produce the diluted fluid and TDS concentrate (36) from the combined fluid (104).

Images