JP7752986B2 - Water treatment system and water treatment method - Google Patents

Description

Embodiments of the present invention relate to a water treatment system and a water treatment method for treating organic wastewater.

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.

In an MBR system, 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.

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.

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 is discharged as excess sludge for disposal.

As such, MBR has the advantages of producing a cleaner separated liquid through solid-liquid separation using a separation membrane, facilitating operation and management, and being able to be implemented in a small space.

Japanese Patent Application Laid-Open No. 2003-144165 Japanese Patent Application Laid-Open No. 2018-153788

Physiological characteristics of biopolymer-degrading Bacillus sp., 55th Sewerage Research Conference, pp.218-220

However, as operation progresses, clogging known as fouling occurs in separation membranes. When fouling occurs in separation membranes, the separation efficiency of the separation membrane decreases, not only reducing the treatment capacity of the entire water treatment system but also potentially deteriorating the quality of the treated water.

For this reason, in MBRs that use separation membranes, various measures are taken to prevent fouling of the separation membranes. For example, bubbles generated by air supplied from a cleaning blower are caused to rise from below the separation membrane, and the shear force associated with these rising bubbles cleans the separation membrane surface.

This anti-fouling measure can be implemented while the separation membrane is in operation, but while this measure alone can mitigate the occurrence of fouling, it is not sufficiently effective. Even if it is implemented constantly during operation, membrane fouling will progress, and over time, membrane separation will eventually become impossible. Furthermore, 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 significant cost impact.

As such, even if the cleaning blower is operated, fouling cannot be sufficiently removed, so in order to restore the condition of the separation membrane, 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.

However, chemical cleaning requires the separation membrane to be shut down, resulting in a decrease in the availability of the water treatment system.

If a water treatment system has multiple systems that use separation membranes to separate solids and liquids, even if the separation membranes of one system are being chemically cleaned, the raw water can still be treated using the separation membranes of other systems, so there is no need to shut down the entire water treatment system. However, in this case, the system will be operating with fewer systems, resulting in a lower treatment volume. Also, 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 greater than usual, which may accelerate the occurrence of fouling and lead to deterioration of the treated water.

In addition, immediately after chemical cleaning is completed and operation of the separation membranes in the system that had been shut down is restarted, the chemicals that were 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.

As such, chemical cleaning is not desirable from the perspective of reducing treatment volume and deteriorating the quality of the treated water, and it is preferable to keep both the frequency and the amount of chemical used as low as possible.

As described above, in water treatment systems that use separation membranes, measures to prevent membrane fouling are implemented at considerable expense and effort, but these measures are not necessarily sufficient.

The problem that this invention aims to solve is to provide a water treatment system and water treatment method that incorporates anti-fouling measures that reduce operating costs, improve availability, and stabilize the quality of treated water.

The water treatment system of this 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 the activated sludge from treated water, which is produced by treating raw water with the activated sludge. The culture tank cultures an enzyme-secreting substance that secretes enzymes that decompose substances adhering to the separation membrane. The supply unit supplies the enzymes secreted from the enzyme-secreting substance cultured in the culture tank to the treatment tank.

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. FIG. 2 is a conceptual diagram for explaining the mechanism of production of the enzyme-secreting substance in the enzyme-secreting substance production section. FIG. 3 is a diagram illustrating the procedure for identifying the genetic information of an enzyme. 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. 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. 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. FIG. 6 is an input/output diagram for explaining the control of the discharge rate of the injection pump by the controller.

Below, a water treatment system to which the water treatment method of each embodiment of the present invention is applied will be described with reference to the drawings.

(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.

The water treatment system 10 is suitable for use, for example, in sewage treatment, and includes an enzyme-secreting substance production unit 20, an enzyme-secreting substance culture tank 30, and a treatment tank 40.

The treatment tank 40 stores activated sludge b inside and receives raw water a, which contains organic wastewater such as sewage. An air diffuser pipe 43 connected to an auxiliary air diffuser blower 42 is installed at the bottom of the treatment tank 40. Air sent from the auxiliary air diffuser blower 42 is converted into bubbles g by the air diffuser pipe 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.

A separation membrane 41 is also provided at the bottom of the treatment tank 40, downstream of the aeration pipe 43. The separation membrane 41 separates the treated water (c), which is produced by decomposing organic matter in the raw water (a), from the activated sludge (b).

As a result, the treatment tank 40 does not contain any activated sludge b, which is a solid component, and only discharges very good treated water c, in which organic matter has been decomposed.

Meanwhile, a portion of the solids 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 solids i are discharged outside the system as excess sludge and disposed of.

Fouling occurs on the separation membrane 41 as operation progresses. Therefore, as a countermeasure against fouling, the water treatment system 10 installs an aeration pipe 45 connected to a membrane cleaning blower 44 below the separation membrane 41 in the treatment tank 40. While the separation membrane 41 is operating, air is sent from the membrane cleaning blower 44 to this aeration pipe 45. The air sent from the membrane cleaning blower 44 is transformed into bubbles G by the aeration pipe 45, which rise toward the separation membrane 41. The shear force generated by the rising bubbles G cleans the separation membrane 41, thereby reducing fouling of the separation membrane 41.

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 enzyme h, which decomposes the adhering substances d adhering to the separation membrane 41. To this end, an enzyme-secreting substance q, which 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. Within the treatment tank 40, the enzyme h decomposes the adhering substances d adhering to the separation membrane 41, thereby mitigating fouling. This anti-fouling measure can be applied in conjunction with the anti-fouling measure using cleaning with air bubbles G described above.

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

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

In the enzyme-secreting substance production unit 20, enzyme-secreting substance q is produced using genetic recombination technology as follows:

Figure 2 is a conceptual diagram illustrating the mechanism by which enzyme-secreting substance q is produced in the enzyme-secreting substance production unit 20.

In the enzyme-secreting substance production unit 20, genetic information k for enzyme h secreted from enzyme-secreting bacteria, such as Bacillus bacteria, which coexist with fouling-causing adhering substances d, is introduced into host microorganism m, thereby producing enzyme-secreting substance q.

Extracellular polymeric substances (EPS), extracellular metabolic products released by microorganisms, are thought to play a major role in the formation of adhesive substances d. EPS are known to be complexly composed of components such as polysaccharides, proteins, and nucleic acids. 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 the cell walls of microorganisms, is also effective in destroying the microorganisms that synthesize EPS, so it is also effective.

Figure 3 illustrates the procedure for identifying genetic information k of enzyme h.

First, as shown in Figure 3 (1), the attached substance d is obtained from the separation membrane 41, which has progressed fouling. The attached substance d can be obtained from the separation membrane 41 by scraping the surface of the separation membrane 41. Alternatively, the attached substance d can be extracted by immersing the separation membrane 41 in a chemical solution such as sodium hydroxide, oxalic acid, citric acid, or EDTA.

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

Sludge dominated by Bacillus genus j is known to contribute to fouling suppression (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.

As a result, the decomposition of the attached substance d by the enzyme h proceeds, as shown in Figure 3 (3). Then, once the decomposition has progressed to a certain extent, solid-liquid separation is performed, and a liquid w containing the enzyme h can be obtained, as shown in Figure 3 (4).

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 bacterium 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 bacterium j is identified.

The genetic information k shown in Figure 2 was identified in this way.

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 encoding the information for enzyme h into a specific organism, host microorganism m, it is possible to convert host microorganism m into an enzyme-secreting substance q that expresses enzyme h.

The enzyme-secreting substance production unit 20 then obtains a gene sequence fragment of enzyme h, for example by PCR or artificial synthesis, incorporates it into a secretory vector, and introduces this secretory vector into a host microorganism m to produce enzyme-secreting substance q.

The host microorganism m is one that grows faster than a predetermined rate and has a size (e.g., 0.4 μm or larger) that facilitates 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.

In addition, lactic acid bacteria such as Streptococcus faecalis, Leuconostoc mensenteroides, and Lactobacillus delbruckii, gram-positive bacteria of the Bacillus genus such as Bacillus subtilis and B. megaterium, gram-positive bacteria of the Clostridium genus such as Clostridium acetobutylicum and C. beijerinckii, gram-positive bacteria of the Arthrobacter genus 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 host microorganisms.

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.

The enzyme-secreting substance q thus produced in the enzyme-secreting substance production unit 20 is supplied to the enzyme-secreting substance culture tank 30.

As shown again in Figure 1, the enzyme-secreting substance culture tank 30 is also supplied with substrate r, which is a carbon source, nitrogen source, and inorganic salts, for culturing the enzyme-secreting substance q. The supplied substrate r is used in the enzyme-secreting substance culture tank 30 as culture medium f for the enzyme-secreting substance q.

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

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.

Examples of inorganic salts include magnesium phosphate, magnesium sulfate, sodium chloride, monopotassium phosphate, dipotassium phosphate, ferrous sulfate, manganese sulfate, copper sulfate, calcium carbonate, etc.

In addition, since the intended use of the water treatment system 10 does not require high purity of the enzyme h, as will be described later, organic waste from food factories, waste liquid discharged from food factories, or raw water a itself can also be used as substrate r instead of the above. This reduces the cost of substrate r. However, when waste liquid or raw water a is used as substrate r, it is sterilized before being supplied to the enzyme-secreting substance culture tank 30 to avoid contamination within the enzyme-secreting substance culture tank 30.

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

As described above, the culture solution f containing 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 enzyme h and, as described above, genetic engineering technology is used, it is undesirable for it to be discharged outside the water treatment system 10, and therefore it must be retained in the enzyme-secreting substance culture tank 30 without being supplied to the treatment tank 40.

For this reason, the enzyme-secreting substance culture tank 30 is provided with a separation membrane 31 that separates the enzyme-secreting substance q from the culture solution f to prevent the enzyme-secreting substance q from being supplied to the treatment tank 40 by the injection pump 32.

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

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

In addition, since the enzyme-secreting substance culture tank 30 contains culture solution f containing enzyme h, there is almost no fouling of the separation membrane 31. For this reason, blower equipment for preventing fouling, such as the membrane cleaning blower 44 and air diffuser 45 provided for the separation membrane 41, is not required for the separation tank 31.

When culture solution f is supplied to the treatment tank 40, enzyme h contained in the culture solution f decomposes the adhering substances d adhering to the separation membrane 41 within the treatment tank 40. This increases the fouling suppression effect, reducing the load on the membrane cleaning blower 44 used in conjunction with the treatment tank 40 and reducing the operating costs of the membrane cleaning blower 44 to about one-third of what they would be if enzyme h were not supplied to the treatment tank 40.

In addition, the water treatment system 10 can also perform chemical cleaning as described in the prior art, but because the supply of enzyme h already suppresses the formation 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.

Next, we will explain an example of the operation of a water treatment system to which the water treatment method of the first embodiment configured as described above is applied.

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

In the water treatment system 10, the enzyme-secreting substance production unit 20 produces the enzyme-secreting substance q using genetic engineering. To this end, as shown in Figure 3 (1), adhered substance d is obtained from the separation membrane 41, which has advanced fouling (S1).

Next, as shown in Figure 3 (2), the obtained adherent substance d is placed in a beaker (not shown) together with enzyme-secreting Bacillus bacteria j, and cultured in the beaker (S2).

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

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

Furthermore, as shown in Figure 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 the enzyme-secreting substance production unit 20, a gene sequence fragment of enzyme h is obtained by PCR or artificial synthesis and incorporated into a secretory vector. This secretory vector is then introduced into host microorganism m to produce enzyme-secreting substance q (S6).

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, enzyme h is secreted from the enzyme-secreting substance q into the culture solution f (S8).

The enzyme-secreting substance culture tank 30 is equipped with a separation membrane 31 that prevents the passage of substances with a size of 0.4 μm or larger. Therefore, enzyme-secreting substances q with a size of 0.4 μm or larger are separated by the separation membrane 31 (S9).

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.

Meanwhile, the culture solution 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. This supplies the enzyme h to the treatment tank 40 (S10).

Raw water a, which contains organic wastewater such as sewage, is continuously introduced into the treatment tank 40. Activated sludge b is stored in the treatment tank 40, and this activated sludge b decomposes the organic matter contained in the raw water a, producing treated water c.

A separation membrane 41 is installed 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 over the course of operation. To mitigate this fouling, air is sent from the membrane cleaning blower 44 to the air diffuser 45, and the shear force caused by the rising air bubbles G generated in the air diffuser 45 cleans the separation membrane 41.

In addition, enzyme h is supplied to the treatment tank 40. As a result, the substances d adhering to the separation membrane 41 are decomposed by the enzyme h, further reducing fouling (S11). This fouling reduction effect reduces the load on the membrane cleaning blower 44 to approximately one-third of what it would be if enzyme h were not supplied.

After that, treatment of the raw water a in the treatment tank 40 can continue (S13) until the amount of adhering substances d adhering to the separation membrane 41 reaches a predetermined amount (S12: Nos).

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

In this way, fouling of the separation membrane 41 can be efficiently mitigated, making it possible to treat raw water a in the treatment tank 40 continuously for a longer period of time.

As described above, in the water treatment system 10 to which the water treatment method of the first embodiment is applied, an enzyme-secreting substance q that secretes an 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. The enzyme h secreted by the enzyme-secreting substance q is then supplied from the enzyme-secreting substance culture tank 30 to the treatment tank 40. This enhances the effect of suppressing fouling in the separation membrane 41.

Furthermore, by cultivating the enzyme h used to suppress 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 achieved.

In other words, in order to produce enzyme h in the treatment tank 40, it is necessary to selectively and stably make the treatment tank 40 dominated by an enzyme-secreting substance q, such as Bacillus bacteria. However, because raw water a is introduced into the treatment tank 40, a wide variety of microorganisms are present, and the properties of the raw water a change constantly, particularly in sewage treatment. For this reason, it is not easy to selectively and stably make the treatment tank 40 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.

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 and supplied to the treatment tank 40 without being affected by environmental changes within the treatment tank 40.

When 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 culture solution f is supplied from the enzyme-secreting substance culture tank 30 to the treatment tank 40, impurities other than 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 activated sludge b in the treatment tank 40. For this reason, there is no problem even if culture solution f containing impurities is supplied to the treatment tank 40, 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 culture solution f is supplied from the enzyme-secreting substance culture tank 30 to the treatment tank 40, there is no need to install additional facilities for additional processing, such as a purification process to increase the purity of enzyme h.

The water treatment system 10 to which the water treatment method of the first embodiment is applied can thus enhance the fouling suppression effect, thereby reducing the load on the membrane cleaning blower 44 used in conjunction with it.

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 enzyme h reduces the load on the membrane cleaning blower 44, and compared to when 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 significantly reducing the operating costs of the water treatment system 10.

In addition, the water treatment system 10 can reduce the frequency of chemical cleaning and the amount of chemical used, thereby improving the overall operating rate of the water treatment system 10 and preventing deterioration in the quality of the treated water c when operation is restarted.

Furthermore, with the water treatment system 10, the enzyme-secreting substance q produced by genetic recombination 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.

As described above, with a water treatment system that applies the water treatment method of the first embodiment, fouling of the separation membrane 41 can be efficiently suppressed by supplying enzyme h to the treatment tank 40. Such excellent fouling countermeasures can reduce operating costs by reducing the load on the membrane cleaning blower 44, improve availability by reducing the frequency of chemical cleaning, and stabilize water quality by reducing the amount of chemical used during chemical cleaning.

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.

In Figure 5, the same parts as in Figure 1 are indicated using the same reference numerals. Duplicate explanations of these same parts will be avoided in this embodiment.

The water treatment system 11 shown in Figure 5 is configured by adding a differential pressure gauge 51 and a controller 52 to the water treatment system 10 shown in Figure 1.

The differential pressure gauge 51 measures the transmembrane pressure difference of the separation membrane 41 and outputs the measured transmembrane pressure difference to the controller 52.

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:

Figure 6 is an input/output diagram illustrating the control of the discharge rate of the injection pump 32 by the controller 52.

The transmembrane pressure difference p _dif is input to the controller 52 from the differential pressure gauge 51 .

Furthermore, a transmembrane pressure target value or a transmembrane pressure increase rate target value p _target is input to the controller 52 in advance.

The controller 52 uses these parameters to perform a typical PID calculation, such as that shown in equation (1) below, and determines the discharge volume of the injection pump 32 according to the resulting operation signal MV.

MV=Kp(e+1/TI・∫edt)...Formula (1)
e: deviation (here, p _dif : transmembrane pressure difference−p _target : transmembrane pressure target value or transmembrane pressure increase rate)
MV: operation signal (here, corresponding to the discharge volume of the injection pump 32)
Kp: proportional gain TI: integral time According to the PID calculation shown in equation (1), when the transmembrane pressure difference p _dif increases, the value of the operation signal MV increases, and the controller 52 increases the discharge rate of the injection pump 32. Conversely, when the transmembrane pressure difference p _dif decreases, the value of the operation signal MV decreases, and the controller 52 decreases the discharge rate of the injection pump 32.

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, so the controller 52 can control the injection _pump 32 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 depending on the increase or decrease in the transmembrane pressure difference p dif.

The calculation formula applied by the controller 52 is not limited to formula (1), and any calculation formula that increases or decreases the value of the operation signal MV in response to an increase or decrease in the transmembrane pressure p _dif can be applied.

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.

That is, the water treatment system 11 to which the water treatment method of the second embodiment is applied can control the injection pump 32 to increase the supply amount of enzyme h from the enzyme-secreting substance culture tank 30 to the _treatment tank 40 when the transmembrane pressure difference p _dif of the separation membrane 41 is high, and conversely, to decrease the supply amount of enzyme h when the transmembrane pressure difference p dif is low. This makes it possible to optimize the supply amount of enzyme h and to carry out the decomposition of the attached substance d on the separation membrane 41 in a finely tuned manner.

While 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 may be embodied in a variety of other forms, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. These embodiments and their variations are within the scope of the invention and its equivalents as defined in the claims, as well as the scope and spirit of the invention.

For example, while the above example shows the use of an enzyme to decompose the attached substance d, other substances such as cyclodextrin, acylase, and lactonase may also be used, and these may inhibit biofilm growth by inhibiting communication between microorganisms via acylated homoserine lactone.

10, 11... Water treatment system, 20... Enzyme secretion substance production unit, 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: attached material, f: culture liquid, G, g: bubbles, h: enzyme, i: solid content, j: Bacillus bacteria, k: genetic information, m: host microorganism, q: enzyme-secreted material, r: substrate, w: containing liquid

Claims (7)

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