Water treatment system and water treatment method

Abstract

To provide a water treatment system equipped with a countermeasure against fouling that achieves reduction in operating cost, improvement in operating rate, and stabilization of a water quality of treated water.SOLUTION: According to an embodiment, a water treatment system includes a treatment tank, a separation membrane, a culture tank, and a feeder. The treatment tank treats raw water with activated sludge. The separation membrane is provided in the treatment tank and separates treated water from activated sludge, the treated water being obtained by treating raw water with activated sludge. The culture tank cultures an enzyme-secreting substance that secretes an enzyme that decomposes an adherent substance adhering to the separation membrane. The feeder supplies the enzyme secreted from the enzyme-secreting substance cultured in the culture tank to the treatment tank.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a water treatment system and a water treatment method for treating organic wastewater. [Background technology]

[0002] For example, some water treatment systems that treat organic wastewater discharged from urban sewage and food factories use the membrane bioreactor (MBR) method, which utilizes a collection of microorganisms called activated sludge.

[0003] In an MBR, raw water containing organic wastewater is treated with a collection of microorganisms called activated sludge, which breaks down the organic matter. The treated water, in which the organic matter has been broken down, is then separated from the activated sludge by a separation membrane and discharged as separated liquid.

[0004] The separated liquid does not contain activated sludge, which is a solid component, and since the organic matter has been decomposed, it is discharged as very good treated water.

[0005] The solids separated by the separation membrane are returned by a pump to the upstream stage of the MBR where they are reused as activated sludge, and a portion of them is discharged as excess sludge for disposal.

[0006] As such, MBR has the advantages of producing a cleaner separated liquid through solid-liquid separation using a separation membrane, of being easy to operate and manage, and of being able to be implemented in a small space. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-144165 [Patent Document 2] Japanese Patent Application Laid-Open No. 2018-153788 [Non-patent literature]

[0008] [Non-Patent Document 1] Physiological characteristics of biopolymer-degrading Bacillus sp., 55th Sewerage Research Conference, pp.218-220 Summary of the Invention [Problem to be solved by the invention]

[0009] However, clogging known as fouling occurs in separation membranes over time. When fouling occurs in a separation membrane, the separation efficiency of the separation membrane decreases, which not only reduces the treatment capacity of the entire water treatment system but also may lead to a deterioration in the quality of the treated water.

[0010] For this reason, various fouling countermeasures are taken for MBRs that use separation membranes. For example, bubbles generated by air supplied from a cleaning blower are raised from below the separation membrane, and the shear force caused by these rising bubbles cleans the separation membrane surface.

[0011] This anti-fouling measure can be implemented while the separation membrane is in operation, but although this measure alone can mitigate the occurrence of fouling, it cannot be said to be sufficiently effective, and even if it is implemented constantly during operation, the fouling of the separation membrane will progress, and over time, membrane separation will eventually become impossible.In addition, the cost of constantly operating the cleaning blower while the separation membrane is in operation accounts for most of the operating cost of the entire water treatment system, so it has a large cost impact.

[0012] As such, even if the cleaning blower is operated, fouling cannot be sufficiently removed. Therefore, in order to restore the condition of the separation membrane, the operation of the separation membrane is stopped approximately every two weeks to one month, and the separation membrane is cleaned with a chemical solution such as sodium hypochlorite.

[0013] However, chemical cleaning involves stopping the operation of the separation membrane, which reduces the availability of the water treatment system.

[0014] In a water treatment system equipped with multiple systems that separate solids and liquids using separation membranes, raw water can be treated using the separation membranes of other systems even while the separation membranes of one system are being chemically cleaned, so there is no need to shut down the entire water treatment system. However, in this case, the system will be operated with fewer systems, resulting in a lower treatment volume. Furthermore, by stopping the operation of the separation membranes of the system being chemically cleaned, the number of separation membranes in operation will be reduced, and the treatment load on the separation membranes of the operating systems will be higher than usual, which may accelerate the occurrence of fouling and lead to deterioration of the treated water.

[0015] In addition, immediately after chemical cleaning is completed and operation of the separation membranes in the system that had been shut down is resumed, the chemicals that had been used will be mixed into the treated water, so measures must be taken, such as returning the treated water to the upstream section of the treatment tank, and the treated water cannot be discharged outside the system until all the chemicals have been discharged.

[0016] Thus, chemical cleaning is not desirable from the viewpoint of reducing the amount of treatment and deteriorating the quality of the treated water, and it is preferable to keep the frequency and amount of chemical used as low as possible.

[0017] As described above, in water treatment systems that use separation membranes, countermeasures against fouling of the separation membranes are implemented at considerable expense and effort, but these measures are not necessarily sufficient.

[0018] The problem to be solved by the present invention is to provide a water treatment system and a water treatment method that are equipped with anti-fouling measures that reduce operating costs, improve availability, and stabilize the quality of treated water. [Means for solving the problem]

[0019] The water treatment system of the embodiment includes a treatment tank, a separation membrane, a culture tank, and a supply unit. The treatment tank treats raw water with activated sludge. The separation membrane is provided in the treatment tank and separates treated water, which is obtained by treating raw water with the activated sludge, from the activated sludge. The culture tank cultures an enzyme-secreting substance that secretes an enzyme that decomposes substances adhering to the separation membrane. The supply unit supplies the enzyme secreted from the enzyme-secreting substance cultured in the culture tank to the treatment tank. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a schematic diagram showing an example of the configuration of a water treatment system to which the water treatment method of the first embodiment is applied. [Figure 2] FIG. 2 is a conceptual diagram for explaining the mechanism of production of the enzyme-secreting substance in the enzyme-secreting substance production section. [Figure 3] FIG. 3 is a diagram illustrating the procedure for identifying the genetic information of an enzyme. [Figure 4A] FIG. 4A is a flowchart (1 / 2) showing an example of the operation of the water treatment system to which the water treatment method of the first embodiment is applied. [Figure 4B] FIG. 4B is a flowchart (2 / 2) showing an example of the operation of the water treatment system to which the water treatment method of the first embodiment is applied. [Figure 5] FIG. 5 is a schematic diagram showing an example of the configuration of a water treatment system to which the water treatment method of the second embodiment is applied. [Figure 6] FIG. 6 is an input / output diagram for explaining the control of the discharge rate of the injection pump by the controller. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, a water treatment system to which the water treatment method according to each embodiment of the present invention is applied will be described with reference to the drawings.

[0022] (First embodiment) FIG. 1 is a schematic diagram showing an example of the configuration of a water treatment system to which the water treatment method of the first embodiment is applied.

[0023] The water treatment system 10 is suitably used for, for example, sewage treatment, and includes an enzyme-secreting substance production section 20, an enzyme-secreting substance culture tank 30, and a treatment tank 40.

[0024] The treatment tank 40 stores activated sludge b inside and receives raw water a containing organic wastewater such as sewage. An air diffuser 43 connected to an auxiliary air diffuser blower 42 is provided at the bottom of the treatment tank 40, and air sent from the auxiliary air diffuser blower 42 is turned into air bubbles g by the air diffuser 43 and supplied to the activated sludge b. This maintains the activity of the activated sludge b and promotes the decomposition process of organic matter contained in the raw water a by the activated sludge b.

[0025] A separation membrane 41 is further provided at the bottom of the treatment tank 40 downstream of the aeration pipe 43, and the separation membrane 41 separates the treated water c, which is obtained by decomposing the organic matter in the raw water a, from the activated sludge b.

[0026] As a result, the treatment tank 40 discharges very good treated water c that does not contain activated sludge b, which is a solid content, and in which organic matter has been decomposed.

[0027] On the other hand, a portion of the solid content i separated by the separation membrane 41 is returned to the upstream stage of the treatment tank 40 by the return sludge pump 46 and reused as activated sludge b in the treatment tank 40, while the remaining solid content i is discharged outside the system as excess sludge and disposed of.

[0028] Fouling occurs in the separation membrane 41 as operation progresses. Therefore, as a countermeasure against fouling, the water treatment system 10 provides an air diffuser 45 connected to a membrane cleaning blower 44 below the separation membrane 41 in the treatment tank 40, and sends air from the membrane cleaning blower 44 to this air diffuser 45 while the separation membrane 41 is in operation. The air sent from the membrane cleaning blower 44 is turned into air bubbles G by the air diffuser 45 and rises toward the separation membrane 41. The shear force caused by the rising air bubbles G cleans the separation membrane 41, thereby mitigating fouling of the separation membrane 41.

[0029] As an additional anti-fouling measure that can be applied during operation of the separation tank 41, the water treatment system 10 supplies the treatment tank 40 with an enzyme h that decomposes the adhering substances d adhering to the separation membrane 41. To this end, an enzyme-secreting substance q that secretes this enzyme h is cultured in the enzyme-secreting substance culture tank 30. Then, a culture solution f containing the enzyme h secreted from the enzyme-secreting substance q is supplied from the enzyme-secreting substance culture tank 30 to the treatment tank 40. In this way, the enzyme h is supplied to the treatment tank 40. In the treatment tank 40, the enzyme h decomposes the adhering substances d adhering to the separation membrane 41, thereby alleviating fouling. This anti-fouling measure can be applied in combination with the anti-fouling measure using cleaning with bubbles G described above.

[0030] The culture medium f is supplied from the enzyme-secreting substance culture tank 30 to the treatment tank 40 by an injection pump 32 provided between the enzyme-secreting substance culture tank 30 and the treatment tank 40 .

[0031] The enzyme-secreting substance q to be cultured in the enzyme-secreting substance culture tank 30 is produced in the enzyme-secreting substance production section 20 and supplied to the enzyme-secreting substance culture tank 30 .

[0032] In the enzyme-secreting substance production section 20, the enzyme-secreting substance q is produced by genetic recombination technology as follows.

[0033] FIG. 2 is a conceptual diagram for explaining the mechanism of production of the enzyme-secreting substance q in the enzyme-secreting substance production unit 20. As shown in FIG.

[0034] In the enzyme-secreting substance production section 20, genetic information k of an enzyme h secreted from an enzyme-secreting bacterium, such as a Bacillus bacterium, which coexists with an attached substance d that causes fouling, is introduced into a host microorganism m, thereby producing an enzyme-secreting substance q.

[0035] Extracellular polymeric substances (EPS), extracellular metabolites released by microorganisms, are thought to play a major role in the formation of adhesive substances. EPS are known to be complexly composed of components such as polysaccharides, proteins, and nucleic acids. Effective enzymes that contribute to the degradation of EPS include proteases produced by Bacillus bacteria that break down proteins, nucleases that break down nucleic acids, and glucanases that break down polysaccharides, as well as enzymes such as amylase, cellulase, lyase, and xylanase. Lysozyme, which destroys microbial cell walls, is also effective in destroying EPS-synthesizing microorganisms.

[0036] FIG. 3 is a diagram illustrating the procedure for identifying genetic information k of enzyme h.

[0037] First, as shown in Fig. 3(1), the adhered substances d are collected from a separation membrane 41 in which fouling has progressed. The adhered substances d can be collected from the separation membrane 41 by scraping the surface of the separation membrane 41. Alternatively, the adhered substances d can be extracted by immersing the separation membrane 41 in a chemical solution such as sodium hydroxide, oxalic acid, citric acid, or EDTA.

[0038] Next, as shown in FIG. 3(2), the obtained adherent substance d is placed in a beaker (not shown) together with Bacillus bacteria j, which are enzyme-secreting bacteria, and cultured.

[0039] It is known that sludge dominated by Bacillus genus j contributes to the suppression of fouling (see Non-Patent Document 1). This is thought to be due to the enzymes released by Bacillus genus j. Therefore, as shown in Figure 3(2), in an environment where attached substance d and Bacillus genus j coexist, Bacillus genus j secretes enzymes such as protease, amylase, lipase, and cellulase. These are enzymes h that decompose attached substance d.

[0040] As a result, the decomposition of the attached substance d by the enzyme h proceeds as shown in Figure 3(3). Then, when the decomposition has progressed to a certain extent, solid-liquid separation is performed to obtain a solution w containing the enzyme h as shown in Figure 3(4).

[0041] Next, as shown in Figure 3(5), enzyme h is extracted from the containing solution w, and the sequence information of enzyme h is read, for example, by proteome analysis.Furthermore, as shown in Figure 3(6), the genetic information (DNA information) of Bacillus j is compared with the amino acid sequence information of enzyme h, and the genetic information (DNA information) k of enzyme h secreted from Bacillus j is identified.

[0042] The gene information k shown in FIG. 2 was identified in this way.

[0043] Generally, living organisms synthesize enzymes based on their genetic information (DNA information) k. Therefore, as shown in Figure 2, by artificially introducing (i.e., genetically modifying) genetic information k that encodes the information for enzyme h into a specific organism, host microorganism m, it is possible to turn host microorganism m into an enzyme-secreting substance q that expresses enzyme h.

[0044] Therefore, in the enzyme-secreting substance production unit 20, a gene sequence fragment of enzyme h is obtained, for example, by PCR or artificial synthesis, and inserted into a secretory vector. This secretory vector is then introduced into a host microorganism m to produce an enzyme-secreting substance q.

[0045] The host microorganism m used grows faster than a predetermined rate and has a size (e.g., 0.4 μm or larger) that allows for easy solid-liquid separation from the enzyme-secreting substance q. Therefore, for example, gram-negative bacteria of the genus Pseudomonas such as Pseudomonas alcaligenes, P. putida, and P. dacunhae, gram-negative bacteria of the genus Gluconobacter such as Gluconobacter melanogenes and G. oxydans, gram-negative bacteria of the genus Alcaligenes such as Alcaligenes eutrophus, acetic acid bacteria such as Acetobacter suboxydans, coliform bacteria such as Escherichia coli, E. freundii, and Enterobacter aerogenes, and other gram-negative bacteria such as Erwinia carotovora, Serratia marcescens, Protaminobacter rubrum, and Proteus mirabilis can be used as the host microorganism m.

[0046] In addition, lactic acid bacteria such as Streptococcus faecalis, Leuconostoc mensenteroides, and Lactobacillus delbruckii, gram-positive bacteria of the genus Bacillus such as Bacillus subtilis and B. megaterium, gram-positive bacteria of the genus Clostridium such as Clostridium acetobutylicum and C. beijerinckii, gram-positive bacteria of the genus Arthrobacter such as Arthrobacter simplex, and other gram-positive bacteria such as Corynebacterium glutamicum, Brevibacterium ammoniagenes, B. flavum, and Propionibacterium sp. can also be used as the host microorganism m.

[0047] Furthermore, actinomycetes such as Nocardia rhodocrous, Streptomyces phaeochromogenes, S. rimosus, S. roseochromogenes, S. tendae, and S. rimosus, yeasts such as Saccharomyces sp., Hansenula jadinii, Candida tropicalis, and Rhodotorula minuta, and filamentous fungi such as Rhizopus nigricans, R. stolonofer, Curvularia lunata, Aspergillus ochraceus, A. niger, and Penicillium chrysogenum can also be used as host microorganisms.

[0048] The enzyme-secreting substance q thus produced in the enzyme-secreting substance production section 20 is supplied to the enzyme-secreting substance culture tank 30.

[0049] 1 , a carbon source, a nitrogen source, and inorganic salts, which are substrates r for culturing the enzyme-secreting substance q, are also supplied to the enzyme-secreting substance culture tank 30. The supplied substrates r are used in the enzyme-secreting substance culture tank 30 as a culture medium f for the enzyme-secreting substance q.

[0050] Examples of carbon sources include sugars such as glucose, fructose, and sucrose, and carbohydrates such as starch or starch hydrolysates.

[0051] Examples of nitrogen sources include inorganic acids such as ammonia, ammonium chloride, ammonium sulfate, and ammonium acetate, or ammonium salts of organic acids, peptone, meat extract, yeast extract, corn stew liquor, casein hydrolysate, soybean meal, soybean meal hydrolysate, and various fermentation bacterial digests.

[0052] Examples of inorganic salts include magnesium phosphate, magnesium sulfate, sodium chloride, monopotassium phosphate, dipotassium phosphate, ferrous sulfate, manganese sulfate, copper sulfate, calcium carbonate, and the like.

[0053] In applications of the water treatment system 10, as will be described later, it is not necessary to increase the purity of the enzyme h, so instead of the above, organic waste from food factories, waste liquid discharged from food factories, or raw water a itself can also be used as the substrate r. This reduces the cost of the substrate r. However, when waste liquid or raw water a is used as the substrate r, it is necessary to sterilize it before supplying it to the enzyme-secreting substance culture tank 30 to avoid contamination within the enzyme-secreting substance culture tank 30.

[0054] The enzyme-secreting substance q supplied to the enzyme-secreting substance culture tank 30 is cultured and grows in a culture solution f containing a substrate r. As the enzyme-secreting substance q grows, an enzyme h is secreted from the enzyme-secreting substance q into the culture solution f.

[0055] As described above, the culture solution f containing the enzyme h is supplied from the enzyme-secreting substance culture tank 30 to the treatment tank 40 by the injection pump 32. However, in the enzyme-secreting substance culture tank 30, the culture solution f also contains the enzyme-secreting substance q. Because the enzyme-secreting substance q is used repeatedly to produce the enzyme h and because, as described above, genetic engineering technology is applied to it, it is undesirable for it to be discharged outside the water treatment system 10, it needs to be retained in the enzyme-secreting substance culture tank 30 without being supplied to the treatment tank 40.

[0056] For this reason, the enzyme-secreting substance culturing tank 30 is provided with a separation membrane 31 that separates the enzyme-secreting substance q from the culture solution f so that the enzyme-secreting substance q is not supplied to the treatment tank 40 by the injection pump 32.

[0057] As shown in Figure 2, enzyme-secreting substance q is obtained by introducing genetic information k of enzyme h into host microorganism m. Therefore, the size of enzyme-secreting substance q and host microorganism m is the same. Since the size of host microorganism m is 0.4 μm or more, the size of enzyme-secreting substance q is also 0.4 μm or more.

[0058] Separation membrane 31 prevents the passage of substances with a size of 0.4 μm or more. Therefore, enzyme-secreting substance q cannot pass through separation membrane 31. Therefore, injection pump 32 can supply culture solution f, from which enzyme-secreting substance q has been removed, to treatment tank 40.

[0059] Since the enzyme-secreting substance culture tank 30 contains the culture solution f containing the enzyme h, fouling hardly occurs in the separation membrane 31. Therefore, blower equipment for preventing fouling, such as the membrane cleaning blower 44 and the air diffuser 45 provided for the separation membrane 41, is not required for the separation tank 31.

[0060] When the culture solution f is supplied to the treatment tank 40, the enzyme h contained in the culture solution f decomposes the adhering substance d adhering to the separation membrane 41 in the treatment tank 40. This enhances the fouling suppression effect, reducing the load on the membrane cleaning blower 44 used in combination, and the operating cost of the membrane cleaning blower 44 can be reduced to about one-third of that when the enzyme h is not supplied to the treatment tank 40.

[0061] In addition, the water treatment system 10 can also perform chemical cleaning as described in the prior art, but since the supply of enzyme h already suppresses the generation of fouling during operation, not only the frequency of chemical cleaning but also the amount of chemical used can be reduced compared to when enzyme h is not supplied to the treatment tank 40.

[0062] Next, an example of the operation of the water treatment system to which the water treatment method of the first embodiment configured as above is applied will be described.

[0063] 4A and 4B are flowcharts showing an example of the operation of the water treatment system to which the water treatment method of the first embodiment is applied.

[0064] In the water treatment system 10, an enzyme-secreting substance q is produced by genetic recombination technology in the enzyme-secreting substance production unit 20. To this end, as shown in FIG. 3(1), an adhering substance d is obtained from a separation membrane 41 in which fouling has progressed (S1).

[0065] Next, as shown in FIG. 3(2), the obtained adhered substance d is placed in a beaker (not shown) together with Bacillus bacteria j, which are enzyme-secreting bacteria, and cultured in the beaker (S2).

[0066] As a result, the decomposition of the attached substance d by the enzyme h proceeds as shown in Fig. 3(3). Then, when the decomposition has progressed to a certain extent, solid-liquid separation is performed to obtain a solution w containing the enzyme h as shown in Fig. 3(4) (S3).

[0067] Next, as shown in FIG. 3(5), the enzyme h is extracted from the containing solution w, and its sequence information is read by, for example, proteome analysis (S4).

[0068] 3(6), the genetic information (DNA information) of Bacillus bacterium j is compared with the amino acid sequence information of enzyme h to identify the genetic information (DNA information) k of enzyme h secreted from Bacillus bacterium j (S5). Then, in enzyme-secreting substance production unit 20, a gene sequence fragment of enzyme h is obtained by PCR or artificial synthesis, and inserted into a secretory vector. This secretory vector is then introduced into host microorganism m to produce enzyme-secreting substance q (S6).

[0069] The produced enzyme-secreting substance q is supplied from the enzyme-secreting substance production unit 20 to the enzyme-secreting substance culture tank 30, where it is cultured and grows in the enzyme-secreting substance culture tank 30 containing the substrate r (S7). As the enzyme-secreting substance q grows, an enzyme h is secreted from the enzyme-secreting substance q into the culture solution f (S8).

[0070] The enzyme-secreting substance culture tank 30 is provided with a separation membrane 31 that prevents the passage of substances having a size of 0.4 μm or more. Therefore, the enzyme-secreting substance q having a size of 0.4 μm or more is separated by the separation membrane 31 (S9).

[0071] As a result, the enzyme-secreting substance q is confined within the enzyme-secreting substance culture tank 30 without being supplied to the treatment tank 40 by the injection pump 32. In this way, the enzyme-secreting substance q, which is a genetically modified substance, is prevented from being discharged outside the system, and does not adversely affect the water environment where it is released.

[0072] Meanwhile, the culture fluid f containing the enzyme h that has passed through the separation membrane 31 is supplied to the treatment tank 40 by the injection pump 32. In this way, the enzyme h is supplied to the treatment tank 40 (S10).

[0073] Raw water a containing organic wastewater such as sewage is continuously introduced into the treatment tank 40. Activated sludge b is stored in the treatment tank 40, and the organic matter contained in the raw water a is decomposed by this activated sludge b, and treated water c is obtained.

[0074] A separation membrane 41 is provided in the treatment tank 40, and the separation membrane 41 separates treated water c from activated sludge b. Fouling occurs on the separation membrane 41 as operation progresses. To mitigate this fouling, air is sent from a membrane cleaning blower 44 to an aeration pipe 45, and the separation membrane 41 is cleaned by the shear force caused by the rising air bubbles G generated in the aeration pipe 45.

[0075] In addition, enzyme h is supplied to the treatment tank 40. As a result, the adhering substances d adhering to the separation membrane 41 are decomposed by the enzyme h, further reducing fouling (S11). This fouling reduction effect can reduce the load on the membrane cleaning blower 44 to about one-third of that when enzyme h is not supplied.

[0076] Thereafter, the treatment of the raw water a in the treatment tank 40 can be continued (S13) until the amount of adhering substances d adhering to the separation membrane 41 reaches a predetermined amount (S12: Nos).

[0077] On the other hand, if the amount of the attached substance d attached to the separation membrane 41 reaches a predetermined amount (S12: Yes), the process returns to step S10, and the enzyme h is supplied to the treatment tank 40. The amount of attached substance d can be estimated from information from a differential pressure gauge, using the relationship that the transmembrane pressure difference increases as the amount of attached substance increases. Alternatively, the enzyme h may be supplied at all times regardless of the amount of attached substance d.

[0078] In this way, fouling of the separation membrane 41 can be efficiently alleviated, and therefore the raw water a can be treated continuously in the treatment tank 40 for a longer period of time.

[0079] As described above, in the water treatment system 10 to which the water treatment method of the first embodiment is applied, the enzyme-secreting substance q that secretes the enzyme h that decomposes the adhering substance d that causes fouling of the separation membrane 41 is cultured in the enzyme-secreting substance culture tank 30. Then, the enzyme h secreted by the enzyme-secreting substance q is supplied from the enzyme-secreting substance culture tank 30 to the treatment tank 40. This can enhance the effect of suppressing fouling in the separation membrane 41.

[0080] In addition, by culturing the enzyme h for suppressing fouling in the treatment tank 40 in the enzyme-secreting substance culture tank 30 and then supplying it to the treatment tank 40 rather than producing it in the treatment tank 40, the following effects can be obtained.

[0081] That is, in order to produce the enzyme h in the treatment tank 40, it is necessary to selectively and stably make the treatment tank 40 predominantly dominated by an enzyme-secreting substance q, such as Bacillus bacteria. However, since raw water a is introduced into the treatment tank 40, a wide variety of microorganisms exist, and the properties of the raw water a change constantly, especially in sewage treatment. For this reason, it is not easy to selectively and stably make the treatment tank 40 predominantly dominated by a specific enzyme-secreting substance q, such as Bacillus bacteria. Therefore, it is extremely difficult to produce a sufficient amount of enzyme h in the treatment tank 40.

[0082] Therefore, in the water treatment system 10 to which the water treatment method of the first embodiment is applied, enzyme h can be stably produced in the enzyme-secreting substance culture tank 30 without being affected by environmental changes in the treatment tank 40, and supplied to the treatment tank 40.

[0083] When the enzyme h is supplied from the enzyme-secreting substance culture tank 30 to the treatment tank 40, it is supplied in a state contained in the culture solution f. Therefore, when the culture solution f is supplied from the enzyme-secreting substance culture tank 30 to the treatment tank 40, impurities other than the enzyme h contained in the culture solution f are also supplied. However, the impurities in the culture solution f are decomposed by the action of the activated sludge b in the treatment tank 40. For this reason, there is no problem even if the culture solution f contains impurities, and fouling can be suppressed even if the purity is low as long as a predetermined amount of enzyme h is supplied to the treatment tank 40. Therefore, when the culture solution f is supplied from the enzyme-secreting substance culture tank 30 to the treatment tank 40, there is no need to provide equipment for additional treatment, such as a purification process to increase the purity of the enzyme h.

[0084] The water treatment system 10 to which the water treatment method of the first embodiment is applied can thus enhance the effect of suppressing fouling, and therefore can reduce the load on the membrane cleaning blower 44 used in combination.

[0085] In conventional water treatment systems, the operating costs of the membrane cleaning blower 44 accounted for more than half of the operating costs of the entire water treatment system. According to the water treatment system 10 of this embodiment, the fouling suppression effect of the enzyme h can reduce the load on the membrane cleaning blower 44, and compared to when the enzyme h is not supplied to the treatment tank 40, the operating costs of the membrane cleaning blower 44 can be reduced to about one-third of the conventional costs, thereby making it possible to significantly reduce the operating costs of the water treatment system 10.

[0086] In addition, the water treatment system 10 can reduce the frequency of chemical cleaning and the amount of chemical used, which makes it possible to improve the overall operating rate of the water treatment system 10 and avoid deterioration in the quality of the treated water c when operation is resumed.

[0087] Furthermore, according to the water treatment system 10, the enzyme-secreting substance q produced by genetic engineering technology is confined within the enzyme-secreting substance culture tank 30 and is not discharged into the treatment tank 40, so there is no adverse effect on the water environment where it is discharged.

[0088] As described above, according to the water treatment system to which the water treatment method of the first embodiment is applied, fouling of the separation membrane 41 can be efficiently suppressed by supplying the enzyme h to the treatment tank 40. Such an excellent anti-fouling measure makes it possible to reduce the operating cost by reducing the load on the membrane cleaning blower 44, improve the availability rate by reducing the frequency of chemical cleaning, and stabilize the water quality by reducing the amount of chemical used during chemical cleaning.

[0089] (Second embodiment) FIG. 5 is a schematic diagram showing an example of the configuration of a water treatment system to which the water treatment method of the second embodiment is applied.

[0090] In Fig. 5, the same parts as those in Fig. 1 are denoted by the same reference numerals, and redundant explanations of these same parts will be avoided in this embodiment.

[0091] The water treatment system 11 shown in FIG. 5 has a configuration in which a differential pressure gauge 51 and a controller 52 are added to the water treatment system 10 shown in FIG.

[0092] The differential pressure gauge 51 measures the transmembrane pressure difference of the separation membrane 41 and outputs the measurement result, that is, the transmembrane pressure difference, to the controller 52 .

[0093] The controller 52 controls the discharge rate of the injection pump 32 based on the transmembrane pressure output from the differential pressure gauge 51, for example, by applying PID control as follows.

[0094] FIG. 6 is an input / output diagram for explaining the control of the discharge rate of injection pump 32 by controller 52.

[0095] The controller 52 receives the transmembrane pressure p dif is entered.

[0096] The controller 52 also includes a transmembrane pressure target value or a transmembrane pressure increase rate target value p target is pre-entered.

[0097] Using these parameters, controller 52 performs a typical PID calculation, such as that shown in the following equation (1), and determines the discharge rate of injection pump 32 according to the resulting operation signal MV.

[0098] MV=Kp(e+1 / TI·∫edt)···Formula (1) e: deviation (here, p dif :Transmembrane pressure -p target : Transmembrane pressure target value or transmembrane pressure increase rate) MV: Operation signal (here, corresponds to the discharge volume of the injection pump 32) Kp: Proportional gain TI: Integral time According to the PID calculation shown in equation (1), the transmembrane pressure p dif When the transmembrane pressure p increases, the value of the operation signal MV increases, so the controller 52 controls the injection pump 32 to increase the discharge rate. dif When the value of the operation signal MV decreases, the discharge rate of the injection pump 32 decreases.

[0099] The amount of enzyme h supplied from the enzyme-secreting substance culture tank 30 to the treatment tank 40 also increases or decreases depending on the increase or decrease in the discharge rate of the injection pump 32. dif The injection pump 32 can be controlled so that the amount of enzyme h supplied from the enzyme-secreting substance culture tank 30 to the treatment tank 40 also increases or decreases according to the increase or decrease in the amount of enzyme h.

[0100] The calculation formula applied by the controller 52 is not limited to formula (1), and the transmembrane pressure p dif Any arithmetic expression can be applied that increases or decreases the value of the operation signal MV in accordance with the increase or decrease of .

[0101] As described above, the water treatment system 11 to which the water treatment method of the second embodiment is applied can achieve the following effects in addition to the effects achieved by the water treatment system 10 to which the water treatment method of the first embodiment is applied.

[0102] That is, in the water treatment system 11 to which the water treatment method of the second embodiment is applied, the transmembrane pressure difference p dif When the transmembrane pressure difference p dif When the concentration is low, the injection pump 32 can be controlled to reduce the supply amount of the enzyme h, thereby optimizing the supply amount of the enzyme h and enabling the decomposition of the adhered substance d on the separation membrane 41 to be carried out in a detailed manner.

[0103] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention described in the claims and their equivalents.

[0104] For example, although the above example shows the use of an enzyme to decompose the attached substance d, the substance is not limited to enzymes, and may be a substance such as cyclodextrin, acylase, or lactonase, which inhibits communication between microorganisms via acylated homoserine lactone, thereby inhibiting biofilm growth. [Explanation of symbols]

[0105] 10, 11... Water treatment system, 20... Enzyme secretion substance production section, 30... Enzyme secretion substance culture tank, 31... Separation membrane, 32... Injection pump, 40... Treatment tank, 41... Separation membrane, 42... Auxiliary aeration blower, 43... Aeration pipe, 44... Membrane cleaning blower, 45... Aeration pipe, 46... Return sludge pump, 51... Differential pressure gauge, 52... Controller, a·· Raw water, b·· Activated sludge, c·· Treated water, d·· Adherent material, f·· Culture medium, G, g·· Air bubbles, h·· Enzyme, i·· Solid content, j·· Bacillus bacteria, k·· Genetic information, m·· Host microorganism, q·· Enzyme-secreting material, r·· Substrate, w·· Containing liquid

Claims

1. a treatment tank for treating raw water with activated sludge; a first separation membrane provided in the treatment tank for separating treated water obtained by treating the raw water with the activated sludge from the activated sludge; a culture tank for culturing an enzyme-secreting substance that secretes an enzyme that decomposes the adhering substance adhering to the first separation membrane; A supply unit that supplies the enzyme secreted from the enzyme-secreting substance cultured in the culture tank to the treatment tank; A water treatment system comprising a production unit that produces the enzyme-secreting substance to be provided to the culture tank by introducing genetic information of an enzyme secreted from an enzyme-secreting bacterium coexisting with the attached substance into a predetermined host microorganism.

2. The water treatment system according to claim 1 , wherein the enzyme-secreting bacteria are bacteria of the genus Bacillus.

3. 3. The water treatment system according to claim 1, further comprising a second separation membrane provided in the culture tank to separate the enzyme-secreting substance from the enzyme secreted from the enzyme-secreting substance so that the enzyme-secreting substance is not supplied to the treatment tank by the supply unit.

4. 4. The water treatment system according to claim 3, wherein the enzyme-secreting substance has a size of 0.4 μm or more, and the second separation membrane prevents passage of substances having a size of 0.4 μm or more.

5. 5. The water treatment system according to claim 1, wherein a portion of the raw water is used as a substrate for culturing the enzyme-secreting substance.

6. a differential pressure sensor that measures a transmembrane pressure difference of the first separation membrane; The water treatment system according to claim 1 , further comprising a controller that controls the amount of the enzyme supplied by the supply unit based on the transmembrane pressure measured by the differential pressure sensor.

7. treating the raw water with activated sludge in a treatment tank; separating the activated sludge from treated water obtained by treating the raw water with the activated sludge in the treatment tank using a separation membrane provided in the treatment tank; In a culture tank, an enzyme-secreting substance that secretes an enzyme that decomposes the adhering substance adhering to the separation membrane is cultured; Supplying the enzyme secreted from the enzyme-secreting substance cultured in the culture tank to the treatment tank; A water treatment method comprising: introducing genetic information of an enzyme secreted from an enzyme-secreting bacterium coexisting with the attached substance into a predetermined host microorganism, thereby producing the enzyme-secreting substance to be provided to the culture tank.

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