Wastewater treatment method and treatment system, and use thereof

Abstract

To provide a new waste water treatment technique which can reduce a capacity of an active sludge treatment tank, in a PHA production process using microorganism culture.SOLUTION: A waste water treatment method is a treatment method of waste water generated when PHA is produced from microorganisms, and includes a step (d) of separating the waste water into high concentration waste water having a BOD of 7,000 mg / L or more and low concentration waste water having a BOD of 1,000 mg / L or less, a high concentration waste water treatment step (e) of treating the high concentration waste water, which is obtained through the separation in the step (d), and a low concentration waste water treatment step (f) of treating the low concentration waste water, which is obtained through the separation in the step (d), as a step different from the high concentration waste water treatment step.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method and system for treating wastewater generated during the production of polyhydroxyalkanoates (hereinafter also referred to as "PHA") from microorganisms, and to uses thereof. [Background technology]

[0002] Biodegradable plastics are completely biodegraded by microorganisms in soil or water and incorporated into the natural carbon cycle, making them an environmentally friendly plastic material with little adverse impact on ecosystems. Plant-derived biodegradable plastics such as PHA are attracting attention as representative biodegradable plastics. PHA is an aliphatic polyester (thermoplastic polyester) that is produced by microorganisms using natural plant-derived organic acids and oils as a carbon source and accumulates within the cells as an energy storage substance.

[0003] In the process of producing PHA using microbial culture, wastewater containing a large amount of organic components derived from bacterial cell residues is generated. For example, Patent Document 1 discloses a production method including a step of treating this wastewater, which includes a production step of purifying or molding PHA biosynthesized in the cells of microorganisms, a discharge step of discharging wastewater containing nitrogen-containing impurities from the production step, and a nitrogen removal step of biologically treating the wastewater to remove the nitrogen-containing impurities from the wastewater, in which the PHA residual rate in the production step is 99% by weight or less, and the wastewater biologically treated in the nitrogen removal step contains PHA in addition to the nitrogen-containing impurities.

[0004] Furthermore, Patent Document 2 discloses a technology for reusing wastewater in a manufacturing process by removing inorganic ions from wastewater treated by an activated sludge method using an NF membrane or an RO membrane. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2017 / 221755 [Patent Document 2] International Publication No. 2021 / 186872 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the PHA manufacturing process using microbial culture, reducing the amount of organic matter in the wastewater to a level that allows it to be discharged or reused through membrane separation treatment requires an activated sludge treatment tank with a very large volume, which poses the problem of requiring a large factory site and resulting in very high equipment costs.

[0007] Therefore, an object of the present invention is to provide a new wastewater treatment technology that can reduce the volume of the activated sludge treatment tank in a PHA production process that utilizes microbial culture. [Means for solving the problem]

[0008] As a result of intensive research aimed at solving the above-mentioned problems, the present inventors have found for the first time that the volume of the activated sludge treatment tank can be significantly reduced by separating (storing) wastewater from the PHA production process into (i) high-concentration wastewater with a high organic component content and low-concentration wastewater with a low organic component content, (ii) treating only the low-concentration wastewater by the activated sludge method, and (iii) treating the high-concentration wastewater in an evaporative concentration apparatus, a coagulation separation tank, an anaerobic treatment tank, an incineration apparatus, or the like, which require relatively inexpensive equipment, and have thereby completed the present invention.

[0009] Therefore, one aspect of the present invention is a method for treating wastewater generated during the production of PHA from microorganisms, comprising: step (d) of separating the wastewater into high-concentration wastewater with a BOD of 7000 mg / L or more and low-concentration wastewater with a BOD of 1000 mg / L or less; high-concentration wastewater treatment step (e) of treating the high-concentration wastewater separated in step (d); and low-concentration wastewater treatment step (f), which is a separate step from the high-concentration wastewater treatment step, of treating the low-concentration wastewater separated in step (d); the wastewater is wastewater generated in any one or more of the following steps (a) to (c) (hereinafter referred to as "the treatment method"): step (a) of culturing microorganisms that produce PHA; step (b) of performing a crushing and / or solubilization treatment of the microorganisms containing the PHA; and step (c) of separating PHA from the treatment liquid obtained in step (b).

[0010] Another aspect of the present invention is a wastewater treatment system for wastewater generated during the production of PHA from microorganisms, comprising: a wastewater separation section (D) that separates the wastewater into high-concentration wastewater with a BOD of 7000 mg / L or more and low-concentration wastewater with a BOD of 1000 mg / L or less; a high-concentration wastewater treatment section (E) that treats the high-concentration wastewater separated in the wastewater separation section (D); and a low-concentration wastewater treatment section (E) that treats the low-concentration wastewater separately from the high-concentration wastewater treatment section (E), wherein the wastewater is wastewater generated in one or more of the following steps (a) to (c): step (a) of culturing microorganisms that produce PHA; step (b) of crushing and / or solubilizing the microorganisms containing the PHA; and step (c) of separating PHA from the treated liquid obtained in step (b). [Effects of the Invention]

[0011] According to the present invention, a new wastewater treatment technology can be provided that can reduce the volume of the activated sludge treatment tank in a PHA production process that utilizes microbial culture. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic diagram showing each step in a wastewater treatment method according to one embodiment of the present invention. [Figure 2] 1 is a schematic diagram showing each step in a wastewater treatment method according to one embodiment of the present invention. [Figure 3] 1 is a schematic diagram showing each step in a wastewater treatment method according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] An embodiment of the present invention will be described in detail below. In this specification, unless otherwise specified, "A to B" representing a numerical range means "A or more and B or less." In addition, all documents described in this specification are incorporated herein by reference.

[0014] 1. Overview of the Invention PHA is a 100% plant-based plastic, and is a promising material for moving away from fossil fuels. In the production of PHA, it is desirable to build manufacturing facilities near consumption areas in order to reduce greenhouse gas emissions associated with transportation.

[0015] In recent years, growing awareness of environmental conservation has led to increased demand for biomass-based plastics in Europe, and PHA production in Europe is expected to increase in the future.

[0016] However, in Europe, some countries have strict restrictions on the amount of water intake and discharged, and as mentioned above, technologies have been developed to reuse wastewater in manufacturing processes by removing inorganic ions from wastewater treated by the activated sludge method using NF membranes or RO membranes (particularly, Patent Document 2).

[0017] In order to reuse wastewater using this method, it is necessary to sufficiently reduce the organic matter concentration using the activated sludge method so that the NF membrane or RO membrane does not clog. However, this requires an activated sludge treatment tank with a very large volume per PHA produced, which poses the problem that it is not possible to build manufacturing facilities with high PHA production capacity within the limited plant site area.

[0018] Therefore, the present inventors have conducted extensive research from the above perspectives, and have found for the first time that the volume of the activated sludge treatment tank can be significantly reduced by separating (storing) wastewater from the PHA production process into (i) high-concentration wastewater with a high organic component content and low-concentration wastewater with a low organic component content, (ii) treating only the low-concentration wastewater by the activated sludge method, and (iii) treating the high-concentration wastewater using an evaporation concentration apparatus, coagulation separation tank, anaerobic treatment tank, incineration apparatus, or the like, which require relatively inexpensive equipment.

[0019] According to the present invention, a new wastewater treatment technology can be provided that can reduce the volume of the activated sludge treatment tank in a PHA production process that utilizes microbial culture. That is, according to the present invention, treated water with a sufficiently reduced organic matter concentration can be obtained from wastewater in a PHA production process by treatment using an activated sludge treatment tank with a small volume.

[0020] Furthermore, according to the above-mentioned configuration, since energy can be recovered from waste in the form of combustible gas or heat, a manufacturing process using PHA with low environmental impact can be provided, which can contribute to the achievement of Sustainable Development Goals (SDGs) such as Goal 12 "Ensure sustainable consumption and production patterns" and Goal 14 "Conserve and sustainably use the oceans and marine resources for sustainable development." The present invention will be described in detail below.

[0021] [2. Wastewater treatment method] This treatment method includes the following steps (d) to (f): Step (d): A step of separating wastewater generated during the production of PHA from microorganisms into high-concentration wastewater with a BOD of 7000 mg / L or more and low-concentration wastewater with a BOD of 1000 mg / L or less. Step (e): A high-concentration wastewater treatment step for treating the high-concentration wastewater separated in step (d). Step (f): A low-concentration wastewater treatment step, separate from the high-concentration wastewater treatment step, for treating the low-concentration wastewater separated in step (d).

[0022] Here, the wastewater is wastewater generated in one or more of the following steps (a) to (c). Step (a): Cultivating a PHA-producing microorganism Step (b): A step of crushing and / or solubilizing the microorganisms containing PHA. Step (c): A step of separating PHA from the treated liquid obtained in step (b).

[0023] In one embodiment of the present invention, the present treatment method preferably further comprises the following steps (g) to (h): Step (g): A step of utilizing the heat and / or methane gas generated in step (e) as an energy source. Step (h): A step of treating intermediate-concentration wastewater other than the high-concentration wastewater and the low-concentration wastewater separated in step (d) from the wastewater generated in one or more of steps (a) to (c).

[0024] In this treatment method, the order and composition of the above steps can be appropriately changed depending on the purpose. In this specification, an aqueous suspension containing at least PHA may be abbreviated as "PHA aqueous suspension."

[0025] In one embodiment of the present invention, a method for producing PHA (hereinafter also referred to as "the present production method") is provided, which includes the present treatment method. The present production method may include the present treatment method as one of its steps, and may, for example, include at least one or more of steps (a) to (c), which are steps preceding the wastewater treatment method. In other words, a method for producing PHA that includes the present treatment method as one of its steps is also within the scope of the present invention. In addition to the present treatment method (e.g., steps (d) to (h)) and steps (a) to (c) above, the present production method may also include, for example, a step of producing a dry powder of PHA from the PHA obtained by separation in step (c), and known techniques can be suitably used for such a step. The present production method utilizes wastewater generated in the PHA production process, thereby enabling PHA to be produced while reducing the environmental impact. The present production method will be described mainly with reference to steps (a) to (c), which are primarily related to the present treatment method.

[0026] One embodiment of the present invention will be described with reference to Figures 1 to 3. Note that the present invention is not limited to Figures 1 to 3. Furthermore, well-known vessels, devices, mechanisms, etc. can be suitably used in each step unless otherwise specified.

[0027] [Embodiment 1] The first embodiment will be described with reference to the flowchart shown in FIG. 1. First, PHA-producing microorganisms are cultured in an appropriate medium (step (a)). Next, the microorganisms that have PHA stored therein are subjected to a disruption and / or solubilization treatment in a disruption and / or solubilization treatment step (step (b)). Next, PHA is separated from the resulting treated solution (step (c)). Using one or more of the wastewaters generated in steps (a) to (c), the wastewater is separated into at least a high-concentration wastewater having a specific concentration and a low-concentration wastewater having a specific concentration (step (d)). The wastewater used in this treatment method may be all of steps (a) to (c), or may be the wastewater generated in any one or two of steps (a) to (c). In a typical PHA production process, wastewater is generated only from step (c). In steps (a) and / or (b), if the desired PHA cannot be obtained due to a failure in medium preparation or contamination with other microbial species that inhibit the growth of the microorganisms, and the culture solution or treatment solution is treated as wastewater without separating the PHA, step (d) can be performed using the wastewater produced in steps (a) and / or (b) without undergoing the PHA separation step (c). In this specification, the term "culture solution" refers to a solution containing at least the medium components, and includes not only the culture solution itself that does not contain the target microorganisms, but also the culture broth containing the microorganisms, the culture broth containing PHA-containing microorganisms, and the culture broth containing PHA-free microorganisms due to failed culture. Separation in step (d) is preferably performed in three stages, including the intermediate-concentration wastewater. The high-concentration and intermediate-concentration wastewater are then sent to an evaporation concentration step for treatment (steps (e) and (h)). Meanwhile, the low-concentration wastewater is sent to an activated sludge treatment step for treatment (step (f)). The medium-concentration wastewater may be sent to an activated sludge treatment process together with low-concentration wastewater for treatment (step (h)). In addition to low-concentration wastewater and medium-concentration wastewater, the activated sludge treatment process may also be sent and treated with wash water discharged from the manufacturing process, rainwater that flows into the manufacturing process, miscellaneous wastewater, cooling water after use, steam condensate, etc. The concentrated liquid obtained in the evaporation concentration process is sent to an incineration process and used as a heat source for boilers, etc. (step (g)). The condensed water obtained in the evaporation concentration process is discharged if it meets the discharge standards.If the discharge standards are not met, the wastewater is treated by ammonia stripping until the water quality meets the standards, and then discharged. In another embodiment, the condensed water obtained in the evaporation and concentration process may be subjected to an activated sludge treatment process and then discharged. Because the carbon and nitrogen contents of the condensed water obtained in the evaporation and concentration process are sufficiently low, the volume of the activated sludge treatment tank does not increase significantly even if it is treated in the activated sludge treatment process. The low-concentration wastewater sent to the activated sludge treatment process (as well as medium-concentration wastewater, wash water discharged from the manufacturing process, rainwater flowing into the manufacturing process, miscellaneous wastewater, cooling water after use, steam condensate, etc.) is treated with activated sludge and then discharged.

[0028] [Embodiment 2] The second embodiment will be described using the flowchart shown in Figure 2. The process up to the separation of wastewater is the same as that of the first embodiment. Next, high-concentration wastewater and medium-concentration wastewater are sent to a coagulation / separation process for treatment (steps (e) and (h)). Meanwhile, low-concentration wastewater is sent to an activated sludge treatment process for treatment (step (f)). Medium-concentration wastewater may be sent to the activated sludge treatment process together with low-concentration wastewater for treatment (step (h)). In addition to low-concentration wastewater and medium-concentration wastewater, washing water discharged from the manufacturing process, rainwater flowing into the manufacturing process, miscellaneous wastewater, cooling water after use, steam condensate, etc. may also be sent to the activated sludge treatment process for treatment. The coagulates obtained in the coagulation / separation process are sent to an incineration process and used as a heat source for a boiler or the like (step (g)). If the treated water obtained in the coagulation / separation process meets the discharge standards, it is discharged. If it does not meet the discharge standards, it is subjected to an activated sludge treatment process and then discharged. Low-concentration wastewater (as well as medium-concentration wastewater, wash water discharged from manufacturing processes, rainwater that flows into manufacturing processes, miscellaneous wastewater, cooling water after use, steam condensate, etc.) sent to the activated sludge treatment process is discharged after being treated with activated sludge.

[0029] [Embodiment 3] The third embodiment will be described using the flowchart shown in Figure 3. The process up to the coagulation and separation step is the same as the second embodiment. The coagulation obtained in the coagulation and separation step is sent to the anaerobic treatment step. Next, the methane gas produced in the anaerobic treatment step is desulfurized in the desulfurization step. The desulfurization step may be composed of, for example, a biological desulfurization step and a dry desulfurization step. The methane gas desulfurized in the desulfurization step is stored in a methane gas holder and used as fuel in an energy recovery step such as a boiler (step (g)).

[0030] (Step (a)) In step (a), a microorganism that produces PHA is cultured.

[0031] <pha> As used herein, "PHA" is a general term for polymers containing hydroxyalkanoates (hydroxyalkanoic acids) as monomer units. Hydroxyalkanoic acids constituting PHAs are not particularly limited, but examples include 3-hydroxybutanoic acid, 4-hydroxybutanoic acid, 3-hydroxypropionic acid, 3-hydroxypentanoic acid, 3-hydroxyhexanoic acid, 3-hydroxyheptanoic acid, and 3-hydroxyoctanoic acid. These polymers may be homopolymers or copolymers containing two or more types of monomer units.

[0032] More specifically, examples of PHAs include poly(3-hydroxybutyrate) (P3HB), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P3HB3HH), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P3HB3HV), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate) (P3HB3HO), poly(3-hydroxybutyrate-co-3-hydroxyoctadecanoate) (P3HB3HOD), poly(3-hydroxybutyrate-co-3-hydroxydecanoate) (P3HB3HD), and poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate) (P3HB3HV3HH). Among these, P3HB, P3HB3HH, P3HB3HV, and P3HB4HB are preferred because they are easy to produce industrially.

[0033] Furthermore, by changing the composition ratio of the repeating units, it is possible to change the melting point and degree of crystallinity, and as a result, physical properties such as Young's modulus and heat resistance can be changed. It is also possible to impart physical properties between those of polypropylene and polyethylene. Furthermore, as described above, from the viewpoint of being an easily produced industrially and physically useful plastic, P3HB3HH, which is a copolymer of 3-hydroxybutyric acid and 3-hydroxyhexanoic acid, is more preferred.

[0034] In one embodiment of the present invention, from the viewpoint of a balance between flexibility and strength, the composition ratio of the repeating units of P3HB3HH is preferably 80 / 20 to 99.9 / 0.1 (mol / mol), and more preferably 85 / 15 to 97 / 3 (mol / mol). When the composition ratio of 3-hydroxybutyrate units to 3-hydroxyhexanoate units is 99.9 / 0.01 (mol / mol) or less, sufficient flexibility is obtained, and when it is 80 / 20 (mol / mol) or more, sufficient hardness is obtained.

[0035] For PHA to be put to practical use, processed products must exhibit usable physical properties, and the weight-average molecular weight of the PHA, measured by gel chromatography using polystyrene as the molecular weight standard, is preferably 10,000 or more. It is more preferably 50,000 or more, more preferably 100,000 or more, even more preferably 200,000 or more, particularly preferably 200,000 to 2,000,000, extremely preferably 200,000 to 1,500,000, and most preferably 200,000 to 1,000,000. If the molecular weight exceeds 2,000,000, the fluidity decreases when the PHA is melted and processed, which can make handling difficult.

[0036] <Microorganisms (microbial cells)> The microorganism used in step (a) is not particularly limited, so long as it is a microorganism that produces (generates) PHA intracellularly. For example, microorganisms isolated from nature or deposited in a depository institution for strains (e.g., IFO, ATCC, etc.), or mutants or transformants prepared from such microorganisms, can be used. Examples include bacteria of the genera Cupriavidus, Alcaligenes, Ralstonia, Pseudomonas, Bacillus, Azotobacter, Nocardia, and Aeromonas. Strains such as Alcaligenes lipolytica, Alcaligenes latus, Aeromonas caviae, Aeromonas hydrophila, and C. necator are particularly preferred. Furthermore, when a microorganism does not inherently have the ability to produce PHA or produces only a low amount of PHA, a transformant can be obtained by introducing the desired PHA synthase gene and / or its mutant into the microorganism. The PHA synthase gene used to generate such a transformant is not particularly limited, but a PHA synthase gene derived from Aeromonas caviae is preferred. By culturing these microorganisms under appropriate conditions, microbial cells that have accumulated PHA within the cells can be obtained. The culture method is not particularly limited, but methods described in, for example, JP 05-93049 A and WO 08 / 010296 can be used.

[0037] When recovering PHA from microorganisms, it is natural that a higher PHA content in the microorganisms (microorganisms containing PHA) after cultivation is preferable. For industrial applications, the PHA content in the dried cells is preferably 50% by weight or more. Taking into consideration the subsequent separation procedures and the purity of the separated polymer, the PHA content is preferably 60% by weight or more, and more preferably 70% by weight or more.

[0038] In one embodiment of the present invention, step (a) is carried out in a culture tank (A) in a PHA production system described below.

[0039] (Step (b)) In step (b), the microorganisms containing PHA are disrupted and / or solubilized, and the PHA accumulated within the microbial cells is extracted from the microbial cells.

[0040] <Crushing and solubilization treatment> The PHA produced by the microorganism is recovered by subjecting the microorganism to disruption and / or solubilization treatment.

[0041] In step (b), either the disruption treatment or the solubilization treatment may be performed, or both may be performed. When both the disruption treatment and the solubilization treatment are performed, the order in which they are performed is not particularly limited.

[0042] In step (b), an aqueous suspension of PHA-containing microorganisms is preferably used as the target for disruption and / or solubilization. The culture broth containing the PHA-containing microorganisms after completion of the culture can be used as the aqueous suspension, or an aqueous suspension of PHA-containing microorganisms prepared by adding water to the microorganisms recovered from the culture broth can be used. Methods well known to those skilled in the art, such as centrifugation and membrane separation, can be used to recover the microorganisms from the culture broth. Furthermore, the microorganisms may be killed by heating or the like when they are recovered. Here, the heating temperature is preferably 50°C to 80°C. It is preferable to kill the microorganisms during disruption and / or solubilization.

[0043] The disruption and / or solubilization treatment preferably includes at least one treatment selected from the group consisting of chemical treatment and physical disruption treatment, and more preferably includes both chemical treatment and physical disruption treatment.

[0044] Solubilization treatments for microorganisms containing PHA include chemical treatments such as enzyme treatment, alkali treatment, and surfactant treatment. These solubilization treatments may be performed alone or in combination of two or more. When two or more of these solubilization treatments are performed, the order in which they are performed is not particularly limited. Among these, it is preferable to perform two or more selected from the group consisting of enzyme treatment, alkali treatment, and surfactant treatment (particularly alkali treatment and surfactant treatment), and it is preferable to perform all three.

[0045] The enzyme treatment can be carried out according to a conventionally known method, and is not particularly limited thereto. For example, the method described in JP 2012-115145 A (a method in which a PHA-containing microorganism is enzymatically treated to decompose the cell wall and obtain a higher purity) can be used. The enzyme is not particularly limited as long as it can be used in industrial products, but protease and cell wall-decomposing enzymes are preferred. The amount of enzyme added can be selected appropriately. During the enzyme treatment, if the pH of the solution is outside the optimal pH range for the enzyme, it is preferable to add an acidic or alkaline compound to adjust the pH to within the optimal range. The acidic compound is not particularly limited, and examples include inorganic acids such as nitric acid, sulfuric acid, hydrochloric acid, and phosphoric acid, and organic acids such as acetic acid, formic acid, citric acid, and oxalic acid. The alkaline compound is not particularly limited, and examples thereof include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, and lithium hydroxide; alkali metal carbonates such as sodium carbonate and potassium carbonate; alkali metal bicarbonates such as sodium bicarbonate and potassium bicarbonate; alkali metal salts of organic acids such as sodium acetate and potassium acetate; alkali metal borates such as borax; alkali metal phosphates such as trisodium phosphate, disodium hydrogen phosphate, tripotassium phosphate, and dipotassium hydrogen phosphate; alkaline earth metal hydroxides such as barium hydroxide; and ammonia water.

[0046] The alkali treatment can be carried out, for example, by adding an alkali to an aqueous suspension of PHA-containing microorganisms. Conventional alkalis can be used as the alkali, but there is no particular limitation as long as they are capable of destroying the cell walls of PHA-containing microorganisms and releasing the PHA from the cells. Examples of alkalis include alkali metal hydroxides, such as sodium hydroxide, potassium hydroxide, and lithium hydroxide; alkali metal carbonates, such as sodium carbonate and potassium carbonate; alkali metal bicarbonates, such as sodium bicarbonate and potassium bicarbonate; alkali metal salts of organic acids, such as sodium acetate and potassium acetate; alkali metal borates, such as borax; alkali metal phosphates, such as trisodium phosphate, disodium hydrogen phosphate, tripotassium phosphate, and dipotassium hydrogen phosphate; alkaline earth metal hydroxides, such as barium hydroxide; and aqueous ammonia. The pH of the aqueous suspension used in the alkali treatment is not particularly limited, but is preferably adjusted to a range of 8.0 to 12.0.

[0047] The surfactant treatment can be carried out according to a conventionally known method, and is not particularly limited thereto. For example, the method described in JP 2012-115145 A (a method of adding a surfactant to an aqueous suspension of PHA-containing microorganisms) can be used. Conventionally known surfactants can be used, but the surfactant is not particularly limited as long as it can destroy the cell walls of PHA-containing microorganisms and release the PHA from the cells. Examples of surfactants include anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants. From the viewpoint of cleaning performance, anionic surfactants and / or nonionic surfactants are preferred. For the purpose of cleaning and removing proteins, etc., anionic surfactants are preferred, while for the purpose of cleaning and removing fatty acids and oils, nonionic surfactants are preferred. Both anionic and nonionic surfactants may be used. Anionic surfactants such as sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, sodium cholate, sodium deoxycholate, and sodium oleate, and nonionic surfactants such as polyoxyethylene alkyl ethers and polyoxyalkylene alkyl ethers are preferred, and two or more of these may be used in combination. Among these, sodium dodecyl sulfate (SDS) is preferred from the standpoints of cost, amount used, and additive effect. The surfactant treatment is preferably carried out under alkaline conditions, i.e., it is preferably carried out together with alkaline treatment.

[0048] The amount of surfactant added in the surfactant treatment is not particularly limited, but is preferably 0.001 to 10 parts by weight per 100 parts by weight of PHA, and more preferably 5 parts by weight or less from the viewpoint of cost.

[0049] The physical disruption treatment can be carried out by applying a conventionally known method, and is not limited as long as it is a physical treatment that can detach and pulverize cells other than PHA in the cells. Examples of devices used for physical disruption treatment include high-pressure homogenizers, ultrasonic disrupters, emulsifying dispersers, and bead mills.

[0050] In one embodiment of the present invention, step (b) is carried out in a treatment tank (B) in a PHA production system described below.

[0051] (Process (c)) In step (c), PHA is separated from the treatment liquid obtained in step (b) (also referred to as "disruption treatment liquid"). Step (c) can also be described as a step of recovering PHA from the treatment liquid obtained in step (b).

[0052] Methods for separating PHA from the disruption treatment solution include conventionally known methods such as centrifugation and membrane separation. Among these, centrifugation is preferred because it allows for industrially large-scale processing and continuous use. Among centrifuges, centrifugal settlers with a perforated rotating container are preferred, and examples include separator plate type, cylindrical type, and decanter type. Because PHA particles have a small specific gravity difference from water, separator plate type (intermittent discharge type, nozzle discharge type) is preferred, as it has a large separation and settling area and can achieve high acceleration. Furthermore, nozzle discharge type is particularly preferred when the PHA concentration in the disruption treatment solution is high. Furthermore, decanter type is generally unsuitable for low acceleration and small differences in solid-liquid specific gravity, but decanter type can also be used by changing the particle size of the PHA. Some decanter type models have separator plates and a large separation and settling area, and such models may be usable without changing the particle size.

[0053] In step (c), after separating and recovering PHA from the disruption solution using the separation method described above, the PHA can be washed with water, for example, by suspending the PHA in water and then separating the PHA again to remove cellular material other than PHA. The pH during this washing is preferably 8.0 to 12.5 (i.e., the washing is with alkaline water). In this washing, wash water with a high BOD is generated in the first wash, but the BOD of the wash water decreases with each wash.

[0054] In one embodiment of the present invention, step (c) is carried out by a separation device (C) in a PHA production system described below.

[0055] (Step (d)) In step (d), wastewater generated during the production of PHA from microorganisms is separated into high-concentration wastewater with a BOD of 7000 mg / L or more and low-concentration wastewater with a BOD of 1000 mg / L or less. By separating the high-concentration wastewater from the low-concentration wastewater in step (d), it is possible to reduce the volume and make the low-concentration wastewater treatment unit (e.g., activated sludge treatment tank) used in step (f) more compact.

[0056] In one embodiment of the present invention, the wastewater generated during the production of PHA from the microorganism is wastewater generated in any one or more of the steps (a) to (c).

[0057] In this specification, "BOD" stands for biochemical oxygen demand, and is a numerical value indicating the amount of oxygen (mg) required per liter of water over 5 days when aerobic bacteria decompose organic substances in water at 20°C. BOD can be measured by conventionally known methods, for example, by the method specified in JIS K 0102.

[0058] As used herein, "high-concentration wastewater" refers to wastewater with a BOD concentration of 7000 mg / L or more. High-concentration wastewater can be obtained, for example, from wastewater initially produced when a PHA-containing suspension is centrifuged in step (c) (e.g., wastewater produced after the first or second centrifugation). Furthermore, when the desired PHA is not obtained in steps (a) and / or (b), and the culture broth or treatment solution is treated as wastewater without going through step (c), a culture broth with a BOD of 7000 mg / L or more is treated as high-concentration wastewater.

[0059] As used herein, "low-concentration wastewater" refers to wastewater with a BOD concentration of 1000 mg / L or less. Low-concentration wastewater can be obtained, for example, from wastewater generated later when centrifuging a suspension containing PHA in step (c) (e.g., wastewater generated after the third to sixth centrifugation). Furthermore, for example, when the desired PHA is not obtained in steps (a) and / or (b), and the culture broth or treatment solution is treated as wastewater without going through step (c), the culture broth with a BOD of 1000 mg / L or less is treated as low-concentration wastewater.

[0060] In one embodiment of the present invention, in addition to wastewater generated during the production of PHA from microorganisms (for example, wastewater generated from all of steps (a) to (c) or wastewater generated from any one or two of steps (a) to (c)), the treatment method can also use wash water discharged from the production steps, rainwater flowing into the production steps, miscellaneous water, etc. These wash water discharged from the production steps, rainwater flowing into the production steps, miscellaneous water, etc. have sufficiently low BOD, so they can be treated in step (f) in the same way as low-concentration wastewater.

[0061] As used herein, "wash water discharged from the PHA production process and / or wastewater treatment process" refers to wastewater generated by cleaning various tanks, equipment, piping, etc. used in the present treatment method and / or PHA production method. For example, "wash water discharged from the production process" includes wastewater generated by cleaning the culture tank used in step (a), the treatment tank used in step (b), the separation equipment used in step (c), etc. Furthermore, if a process includes a step of drying the PHA obtained in step (c), wastewater generated by cleaning the tanks and equipment used in those steps is also included in "wash water discharged from the production process." "Wash water discharged from the production process" is not limited to wash water used to wash the inside of tanks and equipment; for example, wastewater discharged when cleaning the inside of a dike in which equipment for the process is installed is also included in "wash water discharged from the PHA production process and / or wastewater treatment process."

[0062] In this specification, "rainwater that has flowed into the PHA production process and / or wastewater treatment process" refers to rainwater that has been mixed in during any step of the present treatment method and / or PHA production process. Furthermore, "greywater" refers to wastewater generated during any step of the present treatment method and / or PHA production process, other than "wash water discharged from the PHA production process and / or wastewater treatment process" and "rainwater that has flowed into the PHA production process and / or wastewater treatment process."

[0063] In the step (d), the method, apparatus, etc. for separating the high-concentration wastewater and the low-concentration wastewater are not particularly limited, and any method, apparatus, etc. used in the technical field can be employed.

[0064] In one embodiment of the present invention, step (d) is carried out by wastewater separation section (D) in the treatment system.

[0065] (Step (e)) In step (e), the high-concentration wastewater separated in step (d) is treated.

[0066] In one embodiment of the present invention, the step (e) preferably includes, as treatment of the high-concentration wastewater, at least one selected from the group consisting of an evaporation concentration step, a flocculation separation step, an anaerobic treatment step, and an incineration step.

[0067] The evaporation concentration step is a step of evaporating water from the high-concentration wastewater separated in the step (d) and concentrating the solid content in the wastewater.

[0068] The specific method, apparatus, etc. for the evaporation and concentration step are not particularly limited, and any method, apparatus, etc. used in the relevant technical field can be used. For example, an apparatus can be used that heats and / or reduces the pressure of an aqueous solution or aqueous suspension to vaporize the water, and then cools the generated water vapor and separates it as condensed water to concentrate it. Furthermore, if severe foaming occurs during the evaporation and concentration step, it is preferable to add an antifoaming agent to the wastewater to suppress foaming. The type of antifoaming agent is not particularly limited, and any known or commonly used antifoaming agent in the relevant technical field can be used.

[0069] In the evaporation concentration step, concentration is preferably carried out so that the solid concentration becomes 5% to 80%, more preferably 15% to 50%, and even more preferably 25% to 40%.

[0070] In one embodiment of the present invention, the evaporation step is performed by an evaporation device in the present processing system.

[0071] In one embodiment of the present invention, as shown in Figure 1, the concentrated liquid obtained in the evaporation and concentration step is sent to an incineration step and can be used as a heat source for a boiler, etc. Furthermore, in one embodiment of the present invention, the condensed water obtained in the evaporation and concentration step may be discharged as is if it satisfies the discharge standards, or it may be treated by ammonia stripping or activated sludge treatment if it does not meet the discharge standards.

[0072] The flocculation and separation step is a step of flocculating and separating solids from the high-concentration wastewater separated in the step (d).

[0073] The specific method, apparatus, etc. for the aggregation and separation step are not particularly limited, and any method, apparatus, etc. used in the relevant technical field can be adopted.

[0074] In one embodiment of the present invention, the flocculation and separation step is carried out by a flocculation and separation tank in the present treatment system.

[0075] The chemicals added in the coagulation and separation step are not particularly limited as long as they can effectively remove organic components from the wastewater, and known coagulants can be used. Examples of the coagulant include inorganic coagulants such as aluminum sulfate, polyaluminum chloride, polyferric sulfate, ferric chloride, ferrous sulfate, and calcium hydroxide, and polymer coagulants such as polyacrylamide, sodium polyacrylate, polyethyleneimine, polyethylene oxide, polypropylene oxide, and copolymers thereof.

[0076] The flocculants produced in the flocculation and separation process are separated from the treated water in a separation process using a settling tank, decanter, filter press, belt press, screw press, pressure flotation device, or the like.

[0077] In the coagulation and separation step, a coagulant is added to the high-concentration wastewater so as to reduce the BOD in the treated water by preferably 40 to 99%, more preferably 55 to 95%, and even more preferably 70 to 90%.

[0078] In one embodiment of the present invention, as shown in Figure 2, the flocculants obtained in the flocculation and separation step can be sent to an incineration step and used as a heat source for a boiler, etc. Also, in one embodiment of the present invention, the treated water obtained in the flocculation and separation step can be subjected to an activated sludge treatment step described below and then discharged.

[0079] In another embodiment of the present invention, as shown in Figure 3, the flocculants obtained in the flocculation and separation step are sent to an anaerobic treatment step, and then the methane gas and the like obtained in the anaerobic treatment step are sent to an incineration step and can be used as a heat source for a boiler, etc. In another embodiment of the present invention, the treated water obtained in the flocculation and separation step can be subjected to an activated sludge treatment step described below and then discharged.

[0080] The anaerobic treatment step is a step in which the flocculants obtained in the flocculation and separation step are anaerobically treated in a treatment tank containing anaerobic bacteria. By including the anaerobic treatment step in step (e), a portion of the organic matter contained in the flocculants can be extracted as methane gas, thereby generating energy from wastewater treatment. Anaerobic treatment also has the advantages of being able to recover energy (methane), requiring no aeration power, producing very little excess sludge, requiring a small installation space, reducing foaming in surfactant-containing wastewater, and being more tolerant to starvation conditions than aerobic treatment.

[0081] The anaerobic bacteria used in the anaerobic treatment step are not particularly limited as long as they are anaerobic bacteria (i.e., methanogens) that can produce methane from wastewater. Examples of anaerobic bacteria include those of the genera Methanococcus, Methanobacterium, Methanothermobacter, Methanobrevibacter, Methanosarcina, Methanosaeta, Methanothrix, and Methanocorpusculum, and those of the class Methanomicrobia.

[0082] The pH of the aggregates in the anaerobic treatment step is not particularly limited as long as it allows methane production by anaerobic bacteria, but is preferably, for example, 6.5 to 8.2. When the pH of the aggregates in the anaerobic treatment step is 6.5 to 8.2, the anaerobic bacteria are not affected by a decrease in pH due to the accumulation of organic acids, and suppression of methane fermentation associated with an increase in pH due to excess alkali can be avoided. If the pH is outside this range, it is preferable to adjust the pH to within the range of 6.5 to 8.2 by adding an acidic or alkaline compound. The acidic compound is not particularly limited, and examples include inorganic acids such as nitric acid, sulfuric acid, hydrochloric acid, and phosphoric acid, and organic acids such as acetic acid, formic acid, citric acid, and oxalic acid. The alkaline compound is not particularly limited, and examples thereof include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, and lithium hydroxide; alkali metal carbonates such as sodium carbonate and potassium carbonate; alkali metal bicarbonates such as sodium bicarbonate and potassium bicarbonate; alkali metal salts of organic acids such as sodium acetate and potassium acetate; alkali metal borates such as borax; alkali metal phosphates such as trisodium phosphate, disodium hydrogen phosphate, tripotassium phosphate, and dipotassium hydrogen phosphate; alkaline earth metal hydroxides such as barium hydroxide; and ammonia water.

[0083] The temperature of the aggregates in the anaerobic treatment step is not particularly limited as long as it is a temperature at which methane can be produced by anaerobic bacteria, but is, for example, 15 to 65°C, and preferably 25 to 55°C.

[0084] The anaerobic treatment conditions in the anaerobic treatment step can be appropriately set by those skilled in the art depending on the purpose, etc.

[0085] The anaerobic treatment method used in the anaerobic treatment step is not particularly limited, but suitable methods include the flotation method, UASB method, EGSB method, IC method, wet methane fermentation method, and dry methane fermentation method. Two or more of these methods may be combined, or multiple anaerobic treatment tanks may be connected in series and / or parallel. These methods may also be combined with an acid production tank in which high-molecular-weight carbohydrates and lipids are decomposed into organic acids and lower alcohols by the action of acid-producing bacteria.

[0086] In one embodiment of the present invention, the anaerobic treatment step is carried out in an anaerobic treatment tank in the treatment system.

[0087] The incineration step is a step of incinerating the aggregates after flocculation and separation and the evaporated concentrated liquid obtained as residues from the treatment of high-concentration wastewater in the high-concentration wastewater treatment step (e). By including the incineration step in step (e), heat is generated, and the heat can be used as an energy source.

[0088] The specific method, apparatus, etc. for the incineration step are not particularly limited, and any method, apparatus, etc. used in the relevant technical field can be used, for example, a fluidized bed incinerator, a submerged combustion apparatus, a kiln furnace, a stoker furnace, or a biomass boiler.

[0089] In one embodiment of the present invention, the incineration step is performed by an incinerator in the treatment system.

[0090] (Step (f)) In step (f), the low-concentration wastewater separated in step (d) is treated as a separate step from the high-concentration wastewater treatment step.

[0091] In one embodiment of the present invention, step (f) preferably includes an activated sludge treatment step, which allows treatment of the BOD, nitrogen components, and the like in the low-concentration wastewater separated in step (d).

[0092] In the activated sludge treatment process, for example, a tank consisting of a denitrification tank (activated sludge treatment tank) and an aeration tank (activated sludge treatment tank) is used to decompose organic matter in wastewater through the action of aerobic bacteria. The aerobic treatment tank may be composed of, for example, a first denitrification tank, an aeration tank, a second denitrification tank, and a reaeration tank. Alternatively, a membrane bioreactor may be used, in which case, for example, a membrane bioreactor (MBR) using a UF membrane or MF membrane may be installed in the aeration tank and / or reaeration tank.

[0093] The aerobic bacteria used in the aeration tank of the activated sludge treatment step are not particularly limited as long as they are aerobic bacteria that can treat the BOD, nitrogen components, etc. in the low-concentration wastewater separated in step (d). Examples of such aerobic bacteria include nitrifying bacteria such as bacteria of the genus Nitrosomonas, Nitrosococcus, Nitrococcus, Nitrobacter, Nitrospira, Nitrosospira, and Nitrosovibrio.

[0094] The bacteria used in the denitrification tank of the activated sludge treatment step are not particularly limited as long as they are capable of metabolizing nitrite nitrogen and / or nitrate nitrogen contained in wastewater to generate nitrogen gas, and examples of such bacteria include bacteria of the genera Paracoccus, Micrococcus, Pseudomonas, Bacillus, and Alcaligenes.

[0095] The pH of the low-concentration wastewater in the activated sludge treatment step is not particularly limited as long as it is a pH at which aerobic treatment by the activated sludge method can be carried out, but is preferably 6.0 to 9.2, and more preferably 6.5 to 8.0. When the pH of the low-concentration wastewater in the activated sludge treatment step is 6.0 to 9.2, aerobic treatment by the activated sludge method can be carried out appropriately, for example.

[0096] The temperature of the low-concentration wastewater in the activated sludge treatment step is not particularly limited as long as it is a temperature at which aerobic treatment can be carried out by the activated sludge method, but is preferably 10 to 40°C, and more preferably 20 to 30°C.

[0097] The aerobic treatment conditions in the activated sludge treatment step can be appropriately set by those skilled in the art depending on the purpose, etc.

[0098] If it is difficult to achieve discharge standards using activated sludge treatment alone, the low-concentration wastewater treatment step (f) may further include a coagulation reaction step. In this coagulation reaction step, a coagulant is added and the purified coagulates are separated to remove organic components, nitrogen components, sulfur components, phosphorus components, and other components so as to meet the discharge standards. The chemicals added in the coagulation reaction step are not particularly limited as long as they can effectively remove components that do not meet the discharge standards, and known coagulants can be used. Examples of such coagulants include inorganic coagulants such as aluminum sulfate, polyaluminum chloride, polyferric sulfate, ferric chloride, ferrous sulfate, and calcium hydroxide, and polymer coagulants such as polyacrylamide, sodium polyacrylate, polyethyleneimine, polyethylene oxide, polypropylene oxide, and copolymers thereof. Activated carbon, which can adsorb and remove components that do not meet the discharge standards, may also be added.

[0099] The flocculants produced in the flocculation reaction step can be separated from the treated water in a separation step using a settling tank, decanter, filter press, belt press, screw press, pressure flotation device, or the like.

[0100] In one embodiment of the present invention, step (f) is carried out by a low-concentration wastewater treatment unit (F) (for example, an activated sludge treatment tank) in the treatment system.

[0101] (Process (g)) In step (g), the heat and / or methane gas generated in step (e) is utilized as an energy source. In step (e), methane gas, heat, etc. are generated. By utilizing this heat and / or methane gas as an energy source in step (g), it is possible to achieve a reduction in the amount of waste and the amount of fossil fuel used, etc.

[0102] The manner of use of the energy source in step (g) is not particularly limited, and it may be converted into electricity and used, or may be used in its thermal state for heating, drying, etc. Examples include boilers, generators, gas turbines, gas engines, fuel cells, heat exchangers, dryers, etc. That is, the heat and / or methane gas generated in step (e) can be used to operate the boilers, gas turbines, gas engines, fuel cells, heat exchangers, dryers, etc.

[0103] In one embodiment of the present invention, step (g) is performed by a mechanism (G) in the processing system.

[0104] (Process (h)) In step (h), intermediate-concentration wastewater other than the high-concentration wastewater and the low-concentration wastewater separated in step (d) is treated from among the wastewater generated in one or more of steps (a) to (c).

[0105] In this specification, the term "medium-concentration wastewater" refers to wastewater generated in one or more of the steps (a) to (c) other than the high-concentration wastewater and the low-concentration wastewater separated in the step (d).

[0106] In step (d), the intermediate-concentration wastewater may be separated into three types of wastewater: high-concentration, intermediate-concentration, and low-concentration wastewater. Alternatively, the intermediate-concentration wastewater may be separated into high-concentration wastewater or low-concentration wastewater according to one embodiment of the present invention described below, and the method and system configuration may be set appropriately.

[0107] In one embodiment of the present invention, when step (e) includes an evaporation concentration step, the treatment of the intermediate-concentration wastewater in step (h) is preferably carried out by the low-concentration wastewater treatment step. Furthermore, in one embodiment of the present invention, the low-concentration wastewater treatment step preferably includes an activated sludge treatment step. Because intermediate-concentration wastewater has a lower solids concentration than high-concentration wastewater, concentrating intermediate-concentration wastewater to a solids concentration suitable for incineration requires a large-scale evaporation concentration facility. Furthermore, because the majority of organic components, which impose a high wastewater treatment load on the wastewater discharged from step (c), are contained in the high-concentration wastewater, the volume of the activated sludge treatment tank is sufficiently small even if the intermediate-concentration wastewater is treated in the activated sludge treatment step. Therefore, by treating only the high-concentration wastewater in the evaporation concentration step and treating the intermediate-concentration wastewater and low-concentration wastewater in a process including the activated sludge treatment step, the overall wastewater treatment facility cost can be minimized. It is also possible to treat intermediate-concentration wastewater in the high-concentration wastewater treatment step.

[0108] In one embodiment of the present invention, when the step (e) includes a coagulation / separation step, the treatment of the medium-concentration wastewater in the step (h) is preferably carried out by the high-concentration wastewater treatment step. Furthermore, in one embodiment of the present invention, the low-concentration wastewater treatment step preferably includes an activated sludge treatment step. Since high-concentration wastewater contains a large amount of surfactants that inhibit coagulation, the amount of flocculant used can be significantly reduced by mixing the high-concentration wastewater with the medium-concentration wastewater to reduce the surfactant concentration before subjecting the mixture to the coagulation / separation step.

[0109] In one embodiment of the present invention, it is not necessary to treat the entire amount of intermediate-concentration wastewater generated from step (c) in either the high-concentration wastewater treatment step or the low-concentration wastewater treatment step. The intermediate-concentration wastewater may be divided into two groups, with a portion treated in the high-concentration wastewater treatment step and the remaining portion treated in the low-concentration wastewater treatment step. To effectively reduce the capacity of the activated sludge treatment tank, it is preferable to select a treatment method for intermediate-concentration wastewater in the high-concentration wastewater treatment step so as to treat 60 to 99% of the total BOD load generated from step (c), more preferably 70 to 95% of the BOD load, and even more preferably 80 to 90% of the BOD load. In this specification, the term "BOD load" refers to a value expressed by BOD [mg / L] × wastewater volume [L / day].

[0110] In one embodiment of the present invention, step (h) is performed by mechanism (H) in the processing system.

[0111] (Other processes) In one embodiment of the present invention, the present treatment method may include a step of desulfurizing the methane gas produced in the anaerobic treatment step.

[0112] The methane gas produced in the anaerobic treatment step generally contains hydrogen sulfide and the like in addition to methane and carbon dioxide. Hydrogen sulfide corrodes equipment such as boilers, so it is preferable to remove it from the methane gas.

[0113] The method for desulfurizing methane gas is not particularly limited, and any method used in the art can be used. Desulfurization of methane gas can be carried out, for example, using a biological desulfurization tank or a dry desulfurization tank. Preferably, a combination of these methods is used.

[0114] As one embodiment of the present invention, the above description mainly describes a method for discharging treated wastewater, but the treated water discharged from the high-concentration wastewater treatment process and / or the low-concentration wastewater treatment process may be reused in the process by further treating it by a method such as membrane separation. As a treatment method for reuse in the process, a conventionally known method can be applied and is not particularly limited. For example, the method described in WO 2021 / 186872 can be used.

[0115] [3. Wastewater Treatment System] The processing system includes the following components (D) to (F): (D): A wastewater separation unit that separates wastewater generated during the production of PHA from microorganisms into high-concentration wastewater with a BOD of 7000 mg / L or more and low-concentration wastewater with a BOD of 1000 mg / L or less. (E): A high-concentration wastewater treatment unit that treats the high-concentration wastewater separated in the wastewater separation unit (D). (F): A low-concentration wastewater treatment unit that treats the low-concentration wastewater separately from the high-concentration wastewater treatment unit (E). Here, the wastewater is wastewater generated in one or more of the following steps (a) to (c). Step (a): Cultivating a PHA-producing microorganism Step (b): A step of crushing and / or solubilizing the microorganisms containing PHA. Step (c): A step of separating PHA from the treated liquid obtained in step (b).

[0116] In one embodiment of the present invention, the processing system preferably further comprises the following steps (G) to (H): (G): A mechanism for utilizing the heat and / or methane gas generated in the high-concentration wastewater treatment unit (E) as an energy source. (H): A mechanism for treating intermediate-concentration wastewater other than the high-concentration wastewater and the low-concentration wastewater separated in the wastewater separation section (C) from the wastewater generated in one or more of the steps (a) to (c).

[0117] In one embodiment of the present invention, there is provided a PHA production system (hereinafter also referred to as "the present production system") that includes the present treatment system. The present production system may include the present treatment system as one of its components, and may include, for example, at least one of the following (A) to (C) that serve as a supply source of wastewater used in the present drainage system: (A): A culture tank for culturing PHA-producing microorganisms (B): A treatment tank for crushing and / or solubilizing microorganisms containing PHA. (C): A separation device for separating PHA from the treatment liquid obtained in the treatment tank (B). This manufacturing system utilizes wastewater generated during the PHA manufacturing process, allowing PHA to be manufactured while reducing the environmental impact.

[0118] The culture tank (A) is a tank for carrying out step (a). The treatment tank (B) is a tank for carrying out step (b). The separation device (C) is a device for carrying out step (c). The wastewater separation section (D) is a section for carrying out step (d). The high-concentration wastewater treatment section (E) is a section for carrying out step (e). The low-concentration wastewater treatment section (F) is a section for carrying out step (f). The mechanism (G) is a mechanism for carrying out step (g). The mechanism (H) is a mechanism for carrying out step (h).

[0119] In one embodiment of the present invention, the low-concentration wastewater treatment unit (F) preferably includes an activated sludge treatment tank, and the high-concentration wastewater treatment unit (E) preferably includes at least one selected from the group consisting of an evaporation concentration unit, a flocculation separation unit, an anaerobic treatment unit, and an incineration unit.

[0120] In one embodiment of the present invention, when the high-concentration wastewater treatment unit (E) is equipped with an evaporation concentration apparatus, the treatment of the intermediate-concentration wastewater of the mechanism (H) is preferably carried out by the low-concentration wastewater treatment unit (F). Also, in one embodiment of the present invention, the low-concentration wastewater treatment unit (F) preferably includes an activated sludge treatment tank.

[0121] In one embodiment of the present invention, when the high-concentration wastewater treatment unit (E) comprises a coagulation and separation tank, the treatment of the medium-concentration wastewater of the mechanism (H) is preferably carried out by the high-concentration wastewater treatment unit (E). Also, in one embodiment of the present invention, the high-concentration wastewater treatment unit (E) preferably comprises at least one selected from the group consisting of an evaporation concentration unit, a coagulation and separation tank, an anaerobic treatment tank, and an incineration unit.

[0122] In one embodiment of the present invention, it is preferable to supply medium-concentration wastewater to either or both of the high-concentration wastewater treatment unit (E) and the low-concentration wastewater treatment unit (F) so that the high-concentration wastewater treatment unit (E) treats 60 to 99% of the BOD load of the wastewater.

[0123] By providing the above-described configurations, the present treatment system and / or the present production method can reduce the volume of the activated sludge treatment tank in the PHA production process.

[0124] In one embodiment of the present invention, the present processing system and / or the present production method may further include, in addition to the above-described components, various devices, tanks, etc. used in the relevant technical field. For example, the present processing system may further include various components used in each step shown in Figures 1 to 3.

[0125] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0126] That is, one embodiment of the present invention is as follows. <1> A method for treating wastewater generated during the production of PHA from microorganisms, comprising: (d) separating the wastewater into high-concentration wastewater having a BOD of 7000 mg / L or more and low-concentration wastewater having a BOD of 1000 mg / L or less; A high-concentration wastewater treatment step (e) for treating the high-concentration wastewater separated in the step (d); A low-concentration wastewater treatment step (f) for treating the low-concentration wastewater separated in the step (d) as a step separate from the high-concentration wastewater treatment step; Including, The method for treating wastewater, wherein the wastewater is wastewater generated in any one or more of the following steps (a) to (c): (a) a step of culturing a microorganism that produces PHA; (b) performing a disruption and / or solubilization treatment of the microorganisms containing the PHA; Step (c) of separating PHA from the treated liquid obtained in step (b). <2> The step (f) includes an activated sludge treatment step. <1> The method for treating wastewater according to claim 1. <3> The step (e) includes at least one selected from the group consisting of an evaporation concentration step, a flocculation separation step, an anaerobic treatment step, and an incineration step. <1> or <2> The method for treating wastewater according to claim 1. <4> Further comprising a step (g) of utilizing the heat and / or methane gas generated in the step (e) as an energy source; <1> ~ <3> The method for treating wastewater according to any one of the above. <5> The method includes a step (h) of treating intermediate-concentration wastewater other than the high-concentration wastewater and the low-concentration wastewater separated in the step (d) from the wastewater generated in any one or more of the steps (a) to (c), <1> ~ <4> The method for treating wastewater according to any one of the above. <6> The step (e) includes an evaporation concentration step, The treatment of the medium-concentration wastewater in the step (h) is carried out by the low-concentration wastewater treatment step. <5> The method for treating wastewater according to claim 1. <7> The step (e) includes a flocculation and separation step, The treatment of the medium-concentration wastewater in the step (h) is carried out by the high-concentration wastewater treatment step. <5> The method for treating wastewater according to claim 1. <8> The treatment of the medium-concentration wastewater in the step (h) is carried out by either or both of the high-concentration wastewater treatment step and the low-concentration wastewater treatment step, The medium-concentration wastewater is distributed and supplied to either or both of the high-concentration wastewater treatment step and the low-concentration wastewater treatment step so that 65 to 90% of the BOD load of the wastewater is treated in the high-concentration wastewater treatment step. <5> ~ <7> The method for treating wastewater according to any one of the above. <9> <1> ~ <8> 2. A method for producing PHA, comprising the method for treating wastewater according to any one of the above. <10> A system for treating wastewater generated during the production of PHA from microorganisms, A wastewater separation unit (D) that separates the wastewater into high-concentration wastewater having a BOD of 7000 mg / L or more and low-concentration wastewater having a BOD of 1000 mg / L or less; a high-concentration wastewater treatment unit (E) for treating the high-concentration wastewater separated in the wastewater separation unit (D); A low-concentration wastewater treatment unit (E) that treats the low-concentration wastewater separately from the high-concentration wastewater treatment unit (E); Equipped with A wastewater treatment system, wherein the wastewater is wastewater generated in any one or more of the following steps (a) to (c): (a) a step of culturing a microorganism that produces PHA; (b) performing a disruption and / or solubilization treatment of the microorganisms containing the PHA; Step (c) of separating PHA from the treated liquid obtained in step (b). <11> The low-concentration wastewater treatment unit (F) is equipped with an activated sludge treatment tank. <10> A wastewater treatment system according to claim 1. <12> The high-concentration wastewater treatment unit (E) comprises at least one selected from the group consisting of an evaporation concentration unit, a coagulation separation tank, an anaerobic treatment tank, and an incineration unit. <10> or <11> A wastewater treatment system according to claim 1. <13> Further provided is a mechanism (G) that utilizes the heat and / or methane gas generated in the high-concentration wastewater treatment unit (E) as an energy source. <10> ~ <12> The wastewater treatment system according to any one of the above. <14> A mechanism (H) for treating intermediate-concentration wastewater other than the high-concentration wastewater and the low-concentration wastewater separated in the wastewater separation unit (D) from the wastewater generated in any one or more of the steps (a) to (c), <10> ~ <13> The wastewater treatment system according to any one of the above. <15> The high-concentration wastewater treatment unit (E) is equipped with an evaporation concentration device, The treatment of the medium-concentration wastewater of the mechanism (H) is performed by the low-concentration wastewater treatment unit (F), <14> A wastewater treatment system according to claim 1. <16> The high-concentration wastewater treatment unit (E) is provided with a coagulation separation tank, The treatment of the medium-concentration wastewater by the mechanism (H) is performed by the high-concentration wastewater treatment unit (E), <14> A wastewater treatment system according to claim 1. <17> The treatment of the intermediate-concentration wastewater by the mechanism (H) is carried out by either or both of the high-concentration wastewater treatment unit (E) and the low-concentration wastewater treatment unit (F), The medium-concentration wastewater is distributed and supplied to either or both of the high-concentration wastewater treatment unit (E) and the low-concentration wastewater treatment unit (F) so that the high-concentration wastewater treatment unit (E) treats 65 to 90% of the BOD load of the wastewater. <14> ~ <16> The wastewater treatment system according to any one of the above. [Example]

[0127] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0128] Example 1 Ralstonia eutropha, described in International Publication No. 2019 / 142717, was cultured by the method described in paragraphs

[0041] to

[0048] of the same document to obtain a fungal culture solution containing fungal cells (microorganisms) containing PHA. Ralstonia eutropha is currently classified as Capriavidus necator.

[0129] The bacterial culture solution obtained above was sterilized by heating and stirring at an internal temperature of 60 to 80°C for 30 minutes.

[0130] The slurry containing the residue of crushed and solubilized microorganisms after the sterilization treatment and the fine particles of PHA was diluted with industrial water and centrifuged six times to obtain purified PHA from which the microbial residues had been removed. The amount of water in the mixed solution of the wastewater from the first and second centrifugations was 100 ml. 3 / day, BOD was 28,000 ppm, and the volume of the mixed liquor from the third and fourth centrifuged wastewater was 110 m 3 / day, BOD was 3300 ppm, and the volume of the mixed liquor from the fifth and sixth centrifuged wastewater was 110 m 3 The wastewater from the third to sixth centrifugal separations was treated by the activated sludge process, resulting in a volume of 320 m 3 The activated sludge treatment tank was able to treat the BOD down to 60 ppm. The first and second centrifuged wastewater was concentrated 15 times by evaporation and then incinerated in a fluidized bed incinerator. The heat generated by the fluidized bed incinerator was used to generate steam in a boiler, which was used as the heat medium for the evaporation and concentration.

[0131] Example 2 The slurry containing the residue of crushed and solubilized microorganisms after the sterilization treatment and the fine particles of PHA was diluted with industrial water and centrifuged six times to obtain purified PHA from which the microbial residues had been removed. The amount of water in the mixed solution of the wastewater from the first and second centrifugations was 100 ml. 3 / day, BOD was 28,000 ppm, and the volume of the mixed liquor from the third and fourth centrifuged wastewater was 110 m 3 / day, BOD was 3300 ppm, and the volume of the mixed liquor from the fifth and sixth centrifuged wastewater was 110 m 3 / day, and the BOD was 400 ppm. For the wastewater from the first to fourth centrifugal separations, a flocculant was added to reduce the BOD to 4,500 ppm. The treated liquid after this flocculation separation, as well as the wastewater from the fifth and sixth centrifugal separations, was treated by the activated sludge process, resulting in a 700 m3 volume. 3 The activated sludge treatment tank was able to treat the BOD down to 75 ppm. Methane gas was recovered from the flocs obtained by adding a flocculant through anaerobic treatment, and this methane gas was used as fuel for the boiler.

[0132] Comparative Example 1 The slurry containing the residue of crushed and solubilized microorganisms after the sterilization treatment and the fine particles of PHA was diluted with industrial water and centrifuged six times to obtain purified PHA from which the microbial residues had been removed. The amount of water in the mixed solution of the wastewater from the first and second centrifugations was 100 ml. 3 / day, BOD was 28,000 ppm, and the volume of the mixed liquor from the third and fourth centrifuged wastewater was 110 m 3 / day, BOD was 3300 ppm, and the volume of the mixed liquor from the fifth and sixth centrifuged wastewater was 110 m 3 / day and BOD was 400 ppm. If all of this wastewater is treated by the activated sludge process and the BOD is reduced to 75 ppm, the volume of the activated sludge treatment tank will be 2,300 m 3 was necessary. [Industrial Applicability]

[0133] The present invention can be suitably used in the field of wastewater treatment and other fields.< / pha>

Claims

1. A method for treating wastewater generated during the production of polyhydroxyalkanoate from microorganisms, comprising: (d) separating the wastewater into high-concentration wastewater having a BOD of 7000 mg / L or more and low-concentration wastewater having a BOD of 1000 mg / L or less; a high-concentration wastewater treatment step (e) for treating the high-concentration wastewater separated in the step (d); A low-concentration wastewater treatment step (f) for treating the low-concentration wastewater separated in the step (d) as a step separate from the high-concentration wastewater treatment step; Including, The wastewater is wastewater generated in any one or more of the following steps (a) to (c): (a) a step of culturing a microorganism that produces polyhydroxyalkanoate; Step (b) of crushing and / or solubilizing the microorganisms containing the polyhydroxyalkanoate; a step (c) of separating polyhydroxyalkanoate from the treatment liquid obtained in the step (b); the step (e) includes at least one selected from the group consisting of an evaporation concentration step, a flocculation separation step, an anaerobic treatment step, and an incineration step; The method for treating wastewater, wherein the step (f) comprises an activated sludge treatment step.

2. 2. The method for treating wastewater according to claim 1, further comprising a step (g) of utilizing the heat and / or methane gas produced in the step (e) as an energy source.

3. 3. The method for treating wastewater according to claim 1, further comprising a step (h) of treating intermediate-concentration wastewater other than the high-concentration wastewater and the low-concentration wastewater separated in the step (d) from among the wastewater generated in any one or more of the steps (a) to (c).

4. The step (e) includes an evaporation and concentration step, The method for treating wastewater according to claim 3, wherein the treatment of the medium-concentration wastewater in the step (h) is carried out in the low-concentration wastewater treatment step.

5. The step (e) includes a flocculation and separation step, The method for treating wastewater according to claim 3, wherein the treatment of the medium-concentration wastewater in the step (h) is carried out in the high-concentration wastewater treatment step.

6. The treatment of the medium-concentration wastewater in the step (h) is carried out by either or both of the high-concentration wastewater treatment step and the low-concentration wastewater treatment step, The method for treating wastewater according to any one of claims 3 to 5, wherein in the high-concentration wastewater treatment step, intermediate-concentration wastewater is distributed and supplied to either or both of the high-concentration wastewater treatment step and the low-concentration wastewater treatment step so as to treat 65 to 90% of the BOD load of the wastewater.

7. A method for producing a polyhydroxyalkanoate, comprising the method for treating wastewater according to any one of claims 1 to 6.

8. A system for treating wastewater generated during the production of polyhydroxyalkanoate from microorganisms, comprising: a wastewater separation unit (D) that separates the wastewater into high-concentration wastewater having a BOD of 7000 mg / L or more and low-concentration wastewater having a BOD of 1000 mg / L or less; a high-concentration wastewater treatment unit (E) for treating the high-concentration wastewater separated in the wastewater separation unit (D); A low-concentration wastewater treatment unit (F) for treating the low-concentration wastewater separately from the high-concentration wastewater treatment unit (E); Equipped with The wastewater is wastewater generated in any one or more of the following steps (a) to (c): (a) a step of culturing a microorganism that produces polyhydroxyalkanoate; Step (b) of crushing and / or solubilizing the microorganisms containing the polyhydroxyalkanoate; a step (c) of separating polyhydroxyalkanoate from the treatment liquid obtained in the step (b); the high-concentration wastewater treatment unit (E) comprises at least one selected from the group consisting of an evaporation concentration unit, a coagulation separation tank, an anaerobic treatment tank, and an incineration unit; A wastewater treatment system, wherein the low-concentration wastewater treatment unit (F) comprises an activated sludge treatment tank.

9. 9. The wastewater treatment system according to claim 8, further comprising a mechanism (G) for utilizing heat and / or methane gas generated in the high-concentration wastewater treatment unit (E) as an energy source.

10. The wastewater treatment system according to claim 8 or 9, further comprising a mechanism (H) for treating intermediate-concentration wastewater other than the high-concentration wastewater and the low-concentration wastewater separated in the wastewater separation section (D) from the wastewater generated in any one or more of the steps (a) to (c).

11. The high-concentration wastewater treatment unit (E) is equipped with an evaporation concentration device, The wastewater treatment system according to claim 10, wherein the treatment of the medium-concentration wastewater of the mechanism (H) is carried out by the low-concentration wastewater treatment unit (F).

12. The high-concentration wastewater treatment unit (E) is provided with a coagulation separation tank, The wastewater treatment system according to claim 10, wherein the treatment of the medium-concentration wastewater of the mechanism (H) is carried out by the high-concentration wastewater treatment unit (E).

13. The treatment of the medium-concentration wastewater by the mechanism (H) is carried out by either or both of the high-concentration wastewater treatment unit (E) and the low-concentration wastewater treatment unit (F), The wastewater treatment system according to any one of claims 10 to 12, wherein intermediate-concentration wastewater is distributed and supplied to either or both of the high-concentration wastewater treatment unit (E) and the low-concentration wastewater treatment unit (F) so that the high-concentration wastewater treatment unit (E) treats 65 to 90% of the BOD load of the wastewater.

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