Wastewater treatment method and treatment system, and use thereof

Abstract

To provide a method capable of performing anaerobic treatment, in waste water treatment 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 diluting the waste water so that total nitrogen concentration satisfies 10-800 mg / L and total sulfur concentration satisfies 3-500 mg / L, and an anaerobic treatment step (e) of treating diluted waste water diluted in the step (d) with a treatment tank containing anaerobic bacteria.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] PHA is a biomass plastic produced by microbial fermentation using 100% plant-derived resources, and is a biodegradable plastic that can be degraded in the ocean. Because the plants that make up PHA absorb CO2, a cause of global warming, through photosynthesis during their growth, it can also help reduce greenhouse gas emissions. Even if PHA is incinerated, the amount of CO2 emitted will be the same as the amount absorbed by the plants that made it, meaning it will not affect the increase or decrease of CO2 in the atmosphere, making it a carbon-neutral material.

[0003] In this PHA production process using microbial culture, wastewater containing a large amount of organic components derived from the culture solution, bacterial residue, etc. is generated from the cultivation step of culturing the microorganisms, the step of disrupting and / or solubilizing the microorganisms, the purification step of separating the bacterial residue from the PHA, etc. Patent Document 1, for example, discloses a production method including a step of treating this wastewater, which includes a production step of purifying or molding polyhydroxyalkanoic acid biosynthesized within the cells of the 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 residual rate of polyhydroxyalkanoic acid in the production step is 99% by weight or less, and the wastewater biologically treated in the nitrogen removal step contains polyhydroxyalkanoic acid in addition to the nitrogen-containing impurities. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2017 / 221755 Summary of the Invention [Problem to be solved by the invention]

[0005] However, there is room for improvement in wastewater treatment in the PHA production process using microbial culture, from the perspective of making the production process environmentally friendly.

[0006] Therefore, an object of the present invention is to provide a new wastewater treatment technology that enables anaerobic treatment in a PHA production process that utilizes microbial culture. [Means for solving the problem]

[0007] As a result of intensive research to solve the above-mentioned problems, the inventors have discovered that by mixing wastewater from a PHA production process using microbial culture with wastewater from cleaning various tanks, equipment, pipes, etc. and miscellaneous water, it is possible to perform anaerobic treatment on wastewater with very high concentrations of nitrogen and sulfur from the PHA production process, which has previously been difficult to treat anaerobically, and that as a result, it is possible to recover more methane gas that can be used as an energy source, which has led to the completion of the present invention.

[0008] 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 diluting the wastewater so that the total nitrogen concentration is 10 to 800 mg / L and the total sulfur concentration is 3 to 500 mg / L; and step (e) of anaerobic treatment of the diluted wastewater diluted in step (d) in a treatment tank containing anaerobic bacteria, wherein the wastewater is wastewater generated in 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 crushing and / or solubilizing the microorganisms containing the PHA; and step (c) of separating the PHA from the treatment liquid obtained in step (b).

[0009] Another aspect of the present invention is a wastewater treatment system (hereinafter referred to as "the present treatment system") for wastewater generated during the production of PHA from microorganisms, the system comprising: a dilution tank (D) for diluting the wastewater so that the total nitrogen concentration is 10 to 800 mg / L and the total sulfur concentration is 3 to 500 mg / L; and an anaerobic treatment tank (E) containing anaerobic bacteria for treating the diluted wastewater diluted in the dilution tank (D), 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 the PHA from the treatment liquid obtained in step (b). [Effects of the Invention]

[0010] According to the present invention, anaerobic treatment of wastewater with extremely high nitrogen and sulfur concentrations in a PHA production process using microbial culture can be performed, enabling the recovery of methane gas, which can be used as an energy source, from the waste, resulting in a production process with low environmental impact.Furthermore, by significantly reducing the volume of the aerobic treatment tank, a compact wastewater treatment process with low equipment costs can be realized. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram showing a process for producing PHA according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] 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.

[0013] 1. Overview of the Invention As mentioned above, PHA is a 100% plant-based plastic, and is a material that is expected to help eliminate reliance on 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.

[0014] 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.

[0015] However, in Europe, ahead of Japan, product regulations based on life cycle assessment (LCA) have been discussed, and there is a growing demand for technology that reduces the amount of fossil fuels used in product manufacturing processes as much as possible.

[0016] Furthermore, as described above, in the PHA production process using microbial culture, wastewater containing a large amount of organic components derived from the culture solution, bacterial residues, etc. is generated from the cultivation step of culturing the microorganisms (corresponding to step (a)), the step of disrupting and / or solubilizing the microorganisms (corresponding to step (b)), the purification step of separating the PHA from the bacterial residues (corresponding to step (c)), etc. This wastewater is generally treated by the activated sludge method, but in order to make the production process environmentally friendly, it is desirable to recover methane gas from the organic components by anaerobic treatment, as fuel for the energy required for production.

[0017] During the initial stages of the refining process, wastewater with particularly high concentrations of bacterial residues is discharged. Because this wastewater from the initial stage contains particularly large amounts of organic matter, it is possible to recover a large amount of methane gas by anaerobic treatment. However, because it also contains large amounts of nitrogen and sulfur components that inhibit anaerobic treatment, anaerobic treatment is not applicable. Therefore, the inventors conducted extensive research from the above perspectives and discovered for the first time that by mixing the wastewater generated in the PHA production process with wastewater from cleaning various tanks, equipment, and piping, as well as wastewater from other sources, and adjusting the concentrations of nitrogen and sulfur components, anaerobic treatment can be applied to wastewater with particularly high concentrations of bacterial residues generated during the initial stage of refining, thereby enabling the recovery of more methane gas from the wastewater. Furthermore, while the total nitrogen and sulfur concentrations can be adjusted by diluting the wastewater with industrial water, they discovered that adjusting the concentrations using wastewater from cleaning and wastewater enables wastewater treatment while achieving efficient use of water resources.

[0018] According to the present invention, in a PHA production process using microbial culture, wastewater containing a large amount of organic components can be adjusted to a total nitrogen concentration and total sulfur concentration suitable for anaerobic treatment, thereby making the organic components in the wastewater valuable as an energy source and achieving a production process with a low environmental impact. Furthermore, in PHA production processes using microbial culture, environmental factors such as temperature and water quality affect the growth of bacteria, which results in large fluctuations in the wastewater treatment load depending on the lot, making stable wastewater treatment difficult. However, according to the present invention, the dilution ratio can be adjusted in accordance with fluctuations in the wastewater treatment load, making it possible to stably treat wastewater so that it meets the discharge standards regardless of the lot.

[0019] Furthermore, according to the present invention, by generating methane gas, which can be used as an energy source, from waste discharged from the PHA production process, it is possible to reduce the amount of waste and the amount of fossil fuel used.Furthermore, by reducing 70 to 90% of the organic components in wastewater through anaerobic treatment, the load on the aerobic treatment step can be significantly reduced, and a compact wastewater treatment process with a small aerobic treatment tank volume and low equipment costs can be achieved.

[0020] Furthermore, according to the above-mentioned configuration, it is possible to provide a manufacturing process using PHA with a low environmental impact, which can contribute to the achievement of the Sustainable Development Goals (SDGs), such as Goal 12 "Ensure sustainable consumption and production patterns" and Goal 14 "Conserve and sustainably use the oceans, seas 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 (e): Step (d): A step of diluting wastewater generated during the production of PHA from microorganisms so that the total nitrogen concentration is 10 to 800 mg / L and the total sulfur concentration is 3 to 500 mg / L. Step (e): An anaerobic treatment step in which the diluted wastewater diluted in step (c) is treated in a treatment tank containing anaerobic bacteria.

[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 (f) to (i): Step (f): A step of recovering methane gas produced in the anaerobic treatment step (e). Step (g): an aerobic treatment step in which the wastewater generated in the anaerobic treatment step (e) is treated by the activated sludge method. Step (h): A desulfurization step for desulfurizing the methane gas produced in the anaerobic treatment step (e). Step (i): A step of utilizing the methane gas produced in the anaerobic treatment step (e) and / or the methane gas obtained in the desulfurization step (h) as an energy source. 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."

[0024] In one embodiment of the present invention, there is provided a method for producing PHA (hereinafter also referred to as "the present production method") that 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 a wastewater treatment method. The present production method utilizes wastewater generated in the PHA production process, and therefore can produce PHA while reducing the environmental burden.

[0025] One embodiment of the present invention will be described with reference to Fig. 1. However, the present invention is not limited to Fig. 1. Furthermore, unless otherwise specified, known vessels and devices and mechanisms can be suitably used.

[0026] Specifically, first, PHA-producing microorganisms are cultured in an appropriate medium (step (a)), and then the microorganisms that have stored PHA therein are crushed and / or solubilized in a treatment tank 1 (step (b)). The treated liquid after the treatment is sent to a separation device 2, where PHA is separated from the treated liquid (step (c)). The wastewater produced in any one or more of the steps (a) to (c) is diluted in a dilution tank 3 so that the total nitrogen concentration and total sulfur concentration of the wastewater reach specific concentrations. The wastewater used in this treatment method may be the wastewater produced in all of the steps (a) to (c), or may be the wastewater produced in any one or two of the steps (a) to (c). If the desired PHA is not obtained in steps (a) and (b), the culture liquid obtained from steps (a) and / or (b) may be sent as wastewater to step (d) without undergoing the PHA separation step of step (c). The wastewater diluted in the dilution tank 3 is passed through an acid generation tank 4 and then treated in an anaerobic treatment tank 5 containing anaerobic bacteria. In addition, the dilution tank 3 may be used to treat wash water discharged from a production process, which does not have high total nitrogen and total sulfur concentrations. It is preferable to dilute the wastewater with rainwater (process wash water, rainwater) that flows into the production process. In FIG. 1, wastewater A and wastewater B refer to wastewater with different total nitrogen and total sulfur concentrations from any one or more of the wastewaters generated in steps (a) to (c). The wastewaters with different concentrations can be generated, for example, by centrifugation in separation device 2. In this case, for example, wastewater A and wastewater B in FIG. 1 can be wastewater (wastewater A) generated when PHA is first separated from the crushing treatment liquid, and wastewater (wastewater B) generated by repeated redispersion and separation in water thereafter. While FIG. 1 shows a case where two types of wastewater with different total nitrogen and total sulfur concentrations are generated, the types of wastewater generated from steps (a) to (c) do not necessarily have to be two; three or more types may be used, or even one type.

[0027] In one embodiment of the present invention, the methane gas produced in the anaerobic treatment tank 5 is desulfurized in the desulfurization tank 50. The desulfurization tank 50 is composed of, for example, a biological desulfurization tank 6 and a dry desulfurization tank 7.

[0028] In one embodiment of the present invention, the methane gas produced in the anaerobic treatment tank 5 and desulfurized in the desulfurization tank 50 is collected and stored in a storage tank (methane gas holder) 8. The collected and stored methane gas is used as fuel in a boiler 9.

[0029] Furthermore, in one embodiment of the present invention, the wastewater generated in the anaerobic treatment tank 5 is treated by the activated sludge process in the aerobic treatment tank 100. The aerobic treatment tank 100 is composed of, for example, a first denitrification tank 10, an aeration tank 11, a second denitrification tank 12, and a reaeration tank 13. The excess sludge generated in the aerobic treatment tank 100 is stored in a sludge storage tank 14, then subjected to a sludge dehydrator 15 and disposed of as industrial waste. Alternatively, the treated water from the aerobic treatment tank 100 is discharged after components that do not meet the discharge standards, such as carbon, nitrogen, sulfur, and phosphorus, are removed in a flocculation reaction tank 16 and a settling tank 17. The flocs that settle in the settling tank 17 are also subjected to a sludge dehydrator 15 and disposed of as industrial waste.

[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 solution pH 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 thereof 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 the method is not particularly limited. 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. The surfactant is not particularly limited as long as it can disrupt 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., it is preferable to use an anionic surfactant, and for the purpose of cleaning and removing fatty acids and oils, it is preferable to use a nonionic surfactant. 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 PHA is separated and recovered from the disruption solution by the above-mentioned separation method, it 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, the first washing produces wash water with high concentrations of total nitrogen and total sulfur, but the concentrations of total nitrogen and total sulfur in the wash water decrease with each washing.

[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 diluted to a total nitrogen concentration of 10 to 800 mg / L and a total sulfur concentration of 3 to 500 mg / L. The wastewater primarily contains proteins and sugars derived from the microorganisms, and may also contain medium components used to culture the microorganisms, enzymes used in step (b), surfactants, and inorganic salts (phosphates, sodium salts, sulfates, etc.). Because this wastewater contains a large amount of organic components, a large amount of methane gas can be recovered by anaerobic treatment. However, because it also contains large amounts of nitrogen and sulfur components that inhibit anaerobic treatment, anaerobic treatment cannot be performed as is. Therefore, by diluting the wastewater in step (d) so that the total nitrogen and sulfur concentrations in the wastewater fall within the above-mentioned ranges, anaerobic treatment in the anaerobic treatment step (e) becomes possible.

[0056] In one embodiment of the present invention, the wastewater generated during the production of PHA from the microorganism is wastewater generated in one or more of the steps (a) to (c). That is, the wastewater may be wastewater generated from all of the steps (a) to (c), or from any one or two of the steps. In a typical PHA production process, wastewater is generated only from step (c). In steps (a) and (b), if the desired PHA cannot be obtained due to a failure in medium preparation or contamination with another microbial species that inhibits the growth of the microorganism, and the culture solution is treated as wastewater without separating PHA, step (d) can be performed using the wastewater generated in steps (a) and / or (b) without undergoing the PHA separation step of step (c). In this specification, the term "culture solution" refers to a solution containing at least medium components, and includes not only the culture solution itself that does not contain the target microorganism, but also a culture broth containing the microorganism, a culture broth containing PHA-containing microorganisms, and a culture broth containing PHA-free microorganisms due to culture failure.

[0057] The wastewater is preferably diluted in step (d) using wash water discharged from the PHA production process and / or wastewater treatment process, rainwater flowing into the PHA production process and / or wastewater treatment process, miscellaneous wastewater, cooling water after use, or condensed water from steam, which all have a low treatment load. This reduces the amount of industrial water used and allows for efficient use of water resources. The medium used for the dilution may be one type or a combination of two or more types.

[0058] In this specification, the "total nitrogen concentration" refers to the concentration of nitrogen atoms in water excluding nitrogen dissolved as nitrogen gas, and is the sum of ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, and organic nitrogen. The total nitrogen concentration can be measured by a conventionally known method, for example, the method specified in JIS K 0102.

[0059] In this specification, the "total sulfur concentration" refers to the concentration of sulfur atoms in water, and can be measured by a conventional method, such as ICP analysis, X-ray fluorescence analysis, or combustion product gas analysis. Alternatively, the total sulfur concentration may be measured using a chemical reaction that produces a color upon reaction with a sulfur-containing compound, or a reaction that produces a precipitate upon reaction with a sulfur-containing compound.

[0060] 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, in FIG. 1, wastewater generated by cleaning one or more of the culture tank 20, treatment tank 1, and separation device 2 is included in "wash water discharged from the production process." Furthermore, if a process such as drying the PHA obtained in step (c) is included, wastewater generated by cleaning the tanks and equipment used in those processes is also included in "wash water discharged from the production process." Furthermore, "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 process equipment is installed is also included in "wash water discharged from the production process."

[0061] 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."

[0062] Each medium used for the dilution (e.g., wash water, rainwater, or miscellaneous wastewater) preferably has a total nitrogen concentration of 50 mg / L or less and a total sulfur concentration of 30 mg / L or less. This allows the wastewater in step (d) to be efficiently diluted to a total nitrogen concentration of 10 to 800 mg / L and a total sulfur concentration of 3 to 500 mg / L. The total nitrogen concentration of each medium is preferably 50 mg / L or less, more preferably 20 mg / L or less, and even more preferably 10 mg / L or less. The lower limit of the total nitrogen concentration of each medium is not particularly limited, but is preferably, for example, 0.001 mg / L or more. The total sulfur concentration of each medium is preferably 30 mg / L or less, more preferably 10 mg / L or less, and even more preferably 3 mg / L or less. The lower limit of the total sulfur concentration of each medium is not particularly limited, but is preferably, for example, 0.001 mg / L or more.

[0063] In one embodiment of the present invention, in the step (d), the wastewater is diluted with wash water discharged from the production process and / or rainwater flowing into the production process, both of which have a total nitrogen concentration of 50 mg / L or less and a total sulfur concentration of 30 mg / L or less. The wash water discharged from the production process and / or rainwater flowing into the production process that has not been used for dilution may be sent directly to the step (g) and treated by the activated sludge method, since the load of aerobic treatment is not particularly high.

[0064] The concentrations of the wastewater after dilution in step (d) may be a total nitrogen concentration of 10 to 800 mg / L and a total sulfur concentration of 3 to 500 mg / L. When the concentrations of the wastewater after dilution satisfy the above, anaerobic treatment in the anaerobic treatment step (e) becomes possible. The total nitrogen concentration of the wastewater after dilution is 10 to 800 mg / L, preferably 50 to 600 mg / L, and more preferably 100 to 400 mg / L. Furthermore, the total sulfur concentration of the wastewater after dilution is 3 to 500 mg / L, preferably 10 to 300 mg / L, and more preferably 30 to 150 mg / L.

[0065] To ensure stable operation of the anaerobic treatment process, it is preferable to measure the physical quantities and / or chemical concentrations of one or more of the wastewater generated in any one or more of steps (a) to (c), the diluted wastewater, the wash water used for dilution, or rainwater, and adjust the dilution ratio based on the measurement results to control the total nitrogen and total sulfur concentrations of the diluted wastewater so that they always fall within a predetermined range. The physical quantities and / or chemical concentrations to be measured in this case are not necessarily limited to direct measurements of the total nitrogen and / or total sulfur concentrations, and are not particularly limited as long as they are the physical quantities and / or chemical concentrations necessary to calculate an appropriate dilution ratio. Therefore, it is also possible to measure the concentrations of other physical quantities and / or chemical substances correlated with the total nitrogen and / or total sulfur concentrations and calculate an appropriate dilution ratio. The physical quantities and / or chemical substance concentrations to be measured are not particularly limited, but examples include total nitrogen concentration, ammonia nitrogen concentration, organic nitrogen concentration, total sulfur concentration, total organic carbon concentration, chemical oxygen demand, biochemical oxygen demand, total phosphorus concentration, suspended solids, pH, electrical conductivity, turbidity, absorbance, flow rate, temperature, etc.

[0066] The concentrations of these physical quantities and / or chemical substances are not particularly limited and can be measured according to conventionally known or commonly used methods. The measurement method in this case may involve an operator periodically sampling and measuring one or more of the separated wastewater, the diluted wastewater, the wash water used for dilution, and rainwater during the process. However, in order to operate the process stably, it is preferable to install sensors capable of measuring the concentrations of the physical quantities and / or chemical substances to be obtained in one or more of the steps (a), (b), (c), (d), and (e), and the pipes and tanks connecting these steps, and to monitor them constantly.

[0067] In one embodiment of the present invention, step (d) is carried out by a dilution tank (D) in the treatment system.

[0068] (Step (e)) In step (e), the diluted wastewater from step (d) is anaerobically treated in a treatment tank containing anaerobic bacteria, where the organic matter in the wastewater is decomposed into methane gas and carbon dioxide. Using anaerobic bacteria in step (e) allows for the extraction of some of the organic matter contained in the wastewater as methane gas, thereby generating energy from the wastewater treatment. Furthermore, anaerobic treatment in step (d) offers several advantages, including the ability to recover energy (methane), no aeration power required, minimal excess sludge volume, small installation space, reduced foaming in surfactant-containing wastewater, and greater tolerance to starvation conditions than aerobic treatment. Furthermore, step (e) can reduce the BOD (biochemical oxygen demand) of the wastewater by approximately 70-90%, thereby reducing the volume of the aerobic treatment tank in step (g).

[0069] The anaerobic bacteria used in step (e) 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.

[0070] The pH of the wastewater in step (e) 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 wastewater in step (e) 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.

[0071] The temperature of the wastewater in step (e) 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 40°C.

[0072] The anaerobic treatment conditions in step (e) can be appropriately set by those skilled in the art depending on the purpose and the like.

[0073] The anaerobic treatment method in step (e) is not particularly limited, but suitable methods include the flotation method, UASB method, EGSB method, and IC 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-producing tank in which high-molecular-weight carbohydrates and lipids are decomposed into organic acids and lower alcohols by the action of acid-producing bacteria.

[0074] In one embodiment of the present invention, step (e) is carried out in the anaerobic treatment tank (E) in the treatment system. (Step (f)) In step (f), the methane gas produced in the anaerobic treatment step (e) is recovered. The recovered methane gas can be used as fuel for boilers, etc.

[0075] The method for recovering methane gas is not particularly limited, and any method used in the art can be employed.

[0076] In one embodiment of the present invention, the process of recovering methane gas in step (f) preferably includes a step of desulfurizing the generated methane gas (e.g., step (h)). By including a step of desulfurizing the generated methane gas in the process of recovering methane gas in step (f), methane gas suitable for use as fuel for boilers, etc. can be prepared.

[0077] (Process (g)) In step (g), the treated water after the anaerobic treatment step (e) is aerobically treated by the activated sludge method, which can treat the BOD, nitrogen components, etc. remaining in the anaerobic treatment step (e).

[0078] In step (g), for example, a tank composed of a denitrification tank (activated sludge treatment tank) and an aeration tank (activated sludge treatment tank) can be used to decompose organic matter that was not decomposed by anaerobic treatment by 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) with a UF membrane or MF membrane may be installed in the aeration tank and / or reaeration tank.

[0079] The aerobic bacteria used in the aeration tank in step (g) are not particularly limited as long as they are aerobic bacteria that can treat the treated water after the anaerobic treatment step (e) by the activated sludge method. Examples of such aerobic bacteria include nitrifying bacteria such as bacteria of the genera Nitrosomonas, Nitrosococcus, Nitrococcus, Nitrobacter, Nitrospira, Nitrosospira, and Nitrosovibrio.

[0080] The bacteria used in the denitrification tank in step (g) are not particularly limited as long as they are capable of metabolizing nitrite nitrogen and / or nitrate nitrogen contained in the wastewater to generate nitrogen gas, and examples of such bacteria include bacteria of the genera Paracoccus, Micrococcus, Pseudomonas, Bacillus, and Alcaligenes.

[0081] The pH of the wastewater in step (g) is not particularly limited as long as it allows aerobic treatment by the activated sludge method, but is preferably 6.0 to 9.2, and more preferably 6.5 to 8.0. When the pH of the wastewater in step (f) is 6.0 to 9.2, aerobic treatment by the activated sludge method can be carried out appropriately.

[0082] The temperature of the wastewater in step (g) is not particularly limited as long as it is a temperature at which aerobic treatment by the activated sludge method can be carried out, but is preferably 10 to 40°C, and more preferably 20 to 30°C, for example.

[0083] The aerobic treatment conditions in step (g) can be appropriately set by those skilled in the art depending on the purpose, etc.

[0084] In one embodiment of the present invention, step (g) is carried out in the aerobic treatment tank (G) in the treatment system.

[0085] If the treated water discharged from the aerobic treatment process does not meet the discharge standards, it may be further treated in a coagulation reaction process to remove organic components, nitrogen components, sulfur components, phosphorus components, etc. so that the discharge standards are met. The chemicals added in the coagulation reaction process 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.

[0086] The flocculants produced in the flocculation reaction step are separated from the treated water in the separation step. The separation method used in the separation step is not particularly limited, and a conventionally known method can be used, for example, a settling tank, a decanter, a filter press, a belt press, a screw press, a pressure flotation device, etc. In the separation step, one of these devices may be used alone, or two or more types may be used in combination.

[0087] (Process (h)) In the step (h), the methane gas produced in the anaerobic treatment step (e) is desulfurized.

[0088] The methane gas produced in the anaerobic treatment step (e) 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.

[0089] 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. A combination of these methods is preferably used. Furthermore, multiple desulfurization tanks may be connected in series and / or in parallel.

[0090] In one embodiment of the present invention, step (h) is carried out by a desulfurization vessel (H) in the treatment system.

[0091] (Step (i)) In step (i), the methane gas produced in the anaerobic treatment step (e) and / or the methane gas obtained in the desulfurization step (h) is used as an energy source. By using the methane gas as an energy source in step (i), it is possible to achieve a reduction in the amount of waste and the amount of fossil fuel used.

[0092] The manner in which the energy source in step (i) is used is not particularly limited, and examples thereof include a boiler, a generator, a gas turbine, a gas engine, a fuel cell, etc. That is, the methane gas produced in the anaerobic treatment step (e) and / or the methane gas obtained in the desulfurization step (h) can be used to operate the boiler, gas turbine, gas engine, fuel cell, etc. For example, when a boiler is used, an example of the use is to generate steam using the methane gas as fuel.

[0093] The methane gas used as an energy source in step (i) may be the methane gas produced in the anaerobic treatment step (e) or may be the methane gas desulfurized in step (h). From the viewpoint of avoiding corrosion of boilers, etc., the methane gas desulfurized in step (h) is more preferable.

[0094] In one embodiment of the present invention, step (i) is carried out by mechanism (I) in the present production system.

[0095] [3. Wastewater Treatment System] The processing system includes the following components (D) to (E): (D): A dilution tank for diluting wastewater generated during the production of PHA from microorganisms to a total nitrogen concentration of 10 to 800 mg / L and a total sulfur concentration of 3 to 500 mg / L. (E): An anaerobic treatment tank containing anaerobic bacteria for treating the diluted wastewater diluted in the dilution tank (D). 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).

[0096] In one embodiment of the present invention, the processing system preferably further comprises the following steps (F) to (I): (F): A storage tank for collecting and storing the methane gas generated in the treatment tank (E). (G): An aerobic treatment tank that treats the wastewater generated in the anaerobic treatment tank (E) by the activated sludge method. (H): A desulfurization tank for desulfurizing the methane gas produced in the anaerobic treatment tank (E). (I): A mechanism for utilizing the methane gas generated in the anaerobic treatment tank (E) and / or the methane gas obtained in the desulfurization tank (H) as an energy source. 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 microorganisms that produce PHA (B): A treatment tank for crushing and / or solubilizing microorganisms containing PHA. (C): A separation device for separating PHA from the treated 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.

[0097] The culture tank (A) is a tank for carrying out step (a) and corresponds to culture tank 20 in FIG. 1. The treatment tank (B) is a tank for carrying out step (b) and corresponds to treatment tank 1 in FIG. 1. The separation device (C) is a device for carrying out step (c) and corresponds to separation device 2 in FIG. 1. The dilution tank (D) is a tank for carrying out step (d) and corresponds to dilution tank 3 in FIG. 1. The anaerobic treatment tank (E) is a tank for carrying out step (e) and corresponds to anaerobic treatment tank 5 in FIG. 1. The storage tank (F) is a tank for storing methane gas recovered in step (f) and corresponds to storage tank (methane gas holder) 8 in FIG. 1. The aerobic treatment tank (G) is a tank for carrying out step (g) and corresponds to first denitrification tank 10, aeration tank 11, second denitrification tank 12, and reaeration tank 13 in FIG. 1. The desulfurization tank (G) is a tank for carrying out the step (h), and in FIG. 1 corresponds to the biological desulfurization tank 6 and the dry desulfurization tank 7. The mechanism (I) is an apparatus for carrying out the step (i), and in FIG. 1 corresponds to the boiler 9.

[0098] By being equipped with the above-mentioned components, this processing system and / or this manufacturing system can produce methane gas, which can be used as an energy source, from waste discharged from the PHA manufacturing process, thereby achieving a reduction in the amount of waste and the use of fossil fuels.

[0099] In one embodiment of the present invention, the present processing system and / or the present manufacturing system may further include various devices, tanks, etc. used in the relevant technical field in addition to the above-described components. For example, the present processing system and / or the present manufacturing system may further include the various components shown in FIG.

[0100] 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.

[0101] 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) diluting the wastewater so that the total nitrogen concentration is 10 to 800 mg / L and the total sulfur concentration is 3 to 500 mg / L; An anaerobic treatment step (e) in which the diluted wastewater diluted in the step (d) is treated in a treatment tank containing anaerobic bacteria; 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 method further comprises a step (f) of recovering methane gas produced in the anaerobic treatment step (e), <1> The method for treating wastewater according to claim 1. <3> The step (d) includes a step of diluting the wastewater with wash water discharged from the production process and / or rainwater flowing into the production process, each having a total nitrogen concentration of 50 mg / L or less and a total sulfur concentration of 30 mg / L or less. <1> or <2> The method for treating wastewater according to claim 1. <4> measuring physical quantities and / or concentrations of chemical substances contained therein required for calculating the dilution ratio in step (d) for one or more of the wastewater, the diluted wastewater, the wash water, and the rainwater, and adjusting the dilution ratio in step (d) based on the measurement results; <1> ~ <3> The method for treating wastewater according to any one of the above. <5> The method further includes an aerobic treatment step (g) of treating the wastewater produced in the anaerobic treatment step (e) by an activated sludge method. <1> ~ <4> The method for treating wastewater according to any one of the above. <6> Further comprising a desulfurization step (h) of desulfurizing the methane gas produced in the anaerobic treatment step (e), <1> ~ <5> The method for treating wastewater according to any one of the above. <7> The method further comprises a step (i) of utilizing the methane gas produced in the anaerobic treatment step (e) and / or the methane gas obtained in the desulfurization step (h) as an energy source. <1> ~ <6> The method for treating wastewater according to any one of the above. <8> <1> ~ <7> 2. A method for producing PHA, comprising the method for treating wastewater according to any one of the above. <9> A system for treating wastewater generated during the production of PHA from microorganisms, a dilution tank (D) for diluting the wastewater so that the total nitrogen concentration is 10 to 800 mg / L and the total sulfur concentration is 3 to 500 mg / L; an anaerobic treatment tank (E) containing anaerobic bacteria for treating the diluted wastewater diluted in the dilution tank (D); 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). <10> Further provided is a storage tank (F) for recovering and storing the methane gas produced in the treatment tank (E). <9> A wastewater treatment system according to claim 1. <11> The dilution tank (D) dilutes the wastewater with wash water discharged from the production process and / or rainwater flowing into the production process, each having a total nitrogen concentration of 50 mg / L or less and a total sulfur concentration of 30 mg / L or less. <10> A wastewater treatment system according to claim 1. <12> measuring physical quantities and / or concentrations of chemical substances contained therein required for calculating the dilution ratio in the dilution tank (D) for one or more of the wastewater, the diluted wastewater, the cleaning water, and the rainwater, and adjusting the dilution ratio in the dilution tank (D) based on the measurement results; <10> or <11> A wastewater treatment system according to claim 1. <13> The system further includes an aerobic treatment tank (G) for treating the wastewater generated in the anaerobic treatment tank (E) by an activated sludge method. <10> ~ <12> The wastewater treatment system according to any one of the above. <14> The system further includes a desulfurization tank (H) for desulfurizing the methane gas produced in the anaerobic treatment tank (E). <10> ~ <13> The wastewater treatment system according to any one of the above. <15> The system further includes a mechanism (I) for utilizing the methane gas produced in the anaerobic treatment tank (E) and / or the methane gas obtained in the desulfurization tank (H) as an energy source. <10> ~ <14> The wastewater treatment system according to any one of the above. [Example]

[0102] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0103] 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.

[0104] The bacterial culture solution obtained above was sterilized by heating and stirring at an internal temperature of 60 to 80°C for 30 minutes.

[0105] 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 total nitrogen concentration of the wastewater generated after the six centrifugations was 1200 mg / L and the total sulfur concentration was 600 mg / L, making anaerobic treatment inapplicable.

[0106] Therefore, the wastewater was diluted two-fold using washwater discharged from the PHA manufacturing process and rainwater that flowed into the manufacturing process, resulting in a total nitrogen concentration of 600 mg / L and a total sulfur concentration of 300 mg / L. The diluted wastewater was then subjected to anaerobic treatment. The wastewater after anaerobic treatment was decomposed and removed using the activated sludge method, after which the remaining organic matter and phosphates were separated using a coagulation and separation process and then discharged for further treatment. Furthermore, the methane gas generated from the anaerobic treatment was collected, desulfurized, and used as boiler fuel. [Industrial Applicability]

[0107] The present invention can be suitably used in the field of wastewater treatment and other fields. [Explanation of symbols]

[0108] 1 Treatment tank 2 Separation device 3 Dilution tank 4 Acid generation tank 5. Anaerobic treatment tank 6 Biological desulfurization tank 7 Dry desulfurization tank 8 Storage tank (methane gas holder) 9. Boiler 10 First denitrification tank 11 Aeration tank 12 Second denitrification tank 13 Reaeration tank 14 Sludge storage tank 15 Sludge dewatering machine 16 Coagulation reactor 17 Sedimentation tank 20 Culture tank 50 Desulfurization tank 100 Aerobic treatment tank< / pha>

Claims

1. A method for treating wastewater generated during the production of polyhydroxyalkanoate from microorganisms, comprising: (d) diluting the wastewater so that the total nitrogen concentration is 10 to 800 mg / L and the total sulfur concentration is 3 to 500 mg / L; An anaerobic treatment step (e) in which the diluted wastewater diluted in the step (d) is treated in a treatment tank containing anaerobic bacteria; 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 polyhydroxyalkanoate; Step (b) of crushing and / or solubilizing the microorganisms containing the polyhydroxyalkanoate; A step (c) of separating polyhydroxyalkanoate from the treated liquid obtained in the step (b).

2. 2. The method for treating wastewater according to claim 1, further comprising a step (f) of recovering methane gas produced in the anaerobic treatment step (e).

3. 3. The method for treating wastewater according to claim 1 or 2, wherein the step (d) comprises a step of diluting the wastewater with wash water discharged from a production process and / or rainwater flowing into the production process, each having a total nitrogen concentration of 50 mg / L or less and a total sulfur concentration of 30 mg / L or less.

4. The method for treating wastewater according to any one of claims 1 to 3, wherein physical quantities and / or concentrations of chemical substances contained therein required for calculating a dilution ratio in the step (d) are measured for one or more of the wastewater and the diluted wastewater, and the dilution ratio in the step (d) is adjusted based on the measurement results.

5. The method for treating wastewater according to any one of claims 1 to 4, further comprising an aerobic treatment step (g) of treating the wastewater produced in the anaerobic treatment step (e) by an activated sludge method.

6. The method for treating wastewater according to any one of claims 1 to 5, further comprising a desulfurization step (h) of desulfurizing methane gas produced in the anaerobic treatment step (e).

7. 7. The method for treating wastewater according to claim 6, further comprising a step (i) of utilizing, as an energy source, the methane gas produced in the anaerobic treatment step (e) and / or the methane gas obtained in the desulfurization step (h).

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

9. A system for treating wastewater generated during the production of polyhydroxyalkanoate from microorganisms, comprising: A dilution tank (D) for diluting the wastewater so that the total nitrogen concentration is 10 to 800 mg / L and the total sulfur concentration is 3 to 500 mg / L; an anaerobic treatment tank (E) containing anaerobic bacteria for treating the diluted wastewater diluted in the dilution tank (D); 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 polyhydroxyalkanoate; Step (b) of crushing and / or solubilizing the microorganisms containing the polyhydroxyalkanoate; A step (c) of separating polyhydroxyalkanoate from the treated liquid obtained in the step (b).

10. 10. The wastewater treatment system according to claim 9, further comprising a storage tank (F) for recovering and storing methane gas produced in the treatment tank (E).

11. 11. The wastewater treatment system according to claim 10, wherein the dilution tank (D) dilutes the wastewater using wash water discharged from a production process and / or rainwater flowing into the production process, each having a total nitrogen concentration of 50 mg / L or less and a total sulfur concentration of 30 mg / L or less.

12. 12. The wastewater treatment system according to claim 10, wherein physical quantities and / or concentrations of chemical substances contained therein required for calculating a dilution ratio in the dilution tank (D) are measured for one or more of the wastewater and the diluted wastewater, and the dilution ratio in the dilution tank (D) is adjusted based on the measurement results.

13. The wastewater treatment system according to any one of claims 10 to 12, further comprising an aerobic treatment tank (G) for treating the wastewater produced in the anaerobic treatment tank (E) by an activated sludge method.

14. The wastewater treatment system according to any one of claims 10 to 13, further comprising a desulfurization tank (H) for desulfurizing methane gas produced in the anaerobic treatment tank (E).

15. 15. The wastewater treatment system according to claim 14, further comprising a mechanism (I) that utilizes, as an energy source, the methane gas produced in the anaerobic treatment tank (E) and / or the methane gas obtained in the desulfurization tank (H).

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