JP2018065081A - Waste water treatment method and waste water treatment equipment - Google Patents

Abstract

A wastewater treatment method capable of efficiently biologically treating wastewater containing a hardly decomposable organic substance. A wastewater treatment method according to the present embodiment includes a biological treatment step of biologically treating wastewater containing a hardly decomposable organic substance by an MBR tank and a treatment obtained in the biological treatment step by a separation membrane module. A membrane treatment step of membrane-treating water, and in the biological treatment step, a microorganism for decomposing the hardly decomposable organic substance cultured in the culture tank 12 is added to the waste water. [Selection] Figure 1

Description

  The present invention relates to a method for treating waste water containing a hardly decomposable organic substance and a technology of a treatment apparatus.

  In the field of wastewater treatment, biochemical water treatment is often used in which the pollutant in the wastewater is changed to a harmless substance using the physiological activity of microorganisms. The activated sludge method using a mixed microorganism system is the mainstream as a general biological treatment method. Since various kinds of microorganisms coexist in the activated sludge, there is an advantage that waste water mixed with various organic substances can be treated. However, when the wastewater to be treated contains a hardly decomposable organic substance, among the microorganisms contained in the wastewater, the growth rate of the microorganism that decomposes the easily decomposable organic substance is very fast and decomposes the hardly decomposable organic substance. Since the growth rate of microorganisms is slow, microorganisms that decompose the hardly decomposable organic substances do not appear in the activated sludge that is a mixed microorganism system, and the hardly decomposable organic substances may remain in the treated water.

  Therefore, as a conventional technique for treating wastewater containing persistent organic substances, after physicochemical oxidation treatment such as coagulation treatment method, ozone oxidation treatment method, ultraviolet oxidation treatment method, Fenton oxidation method, etc. The mainstream is a method for performing biological treatment (see, for example, Patent Document 1). However, the treatment methods using these physicochemical treatment methods have a problem in that the treatment cost increases because of the large input energy and the use of special chemicals.

  Here, the hard-to-decompose organic substance means an organic substance that is water-soluble, diffuses widely when released into the environment, has low degradability in the natural environment, and is difficult to remove from water. For example, it has acute toxicity and chronic toxicity, or has carcinogenicity. For example, since phenol has acute and chronic toxicity, a strict drainage standard of 5 mg / L is set for phenols. In addition, alkylphenols such as nonylphenol and butylphenol, which are a kind of phenols and having an alkyl group bonded to phenol, are widely used industrially as raw materials for surfactants and may be contained in industrial wastewater. In addition to having chronic toxicity, it is also an environmental hormone-like substance with suspected endocrine disrupting effects. In particular, nonylphenol was newly added to the environmental standards related to the preservation of aquatic organisms among the environmental standards related to the preservation of the living environment related to water pollution based on the Environmental Basic Law in 2012. In addition, 1,4-dioxane, which is a cyclic ether, is a substance that may be industrially used as a reaction solvent for organic synthesis or may be discharged from a factory as a by-product of resin production. In addition, since it is an acute and chronic toxic and carcinogenic substance, there is a strict regulation of a wastewater standard of 0.5 mg / L.

  Such a hardly decomposable organic substance is difficult to treat by a normal activated sludge method. However, there are bacteria (microorganisms) that can be propagated by using them as a carbon source or that can be partially decomposed although complete decomposition is difficult. For example, the Sphingobium fulriginis OMI strain shown in Non-Patent Document 1 and Non-Patent Document 2 is capable of decomposing and growing using 4-tert-butylphenol, which is a persistent organic substance, as a single carbon source. Moreover, it is also possible to decompose a wide range of hardly decomposable organic substances such as other alkylphenols such as nonylphenol and bisphenols. However, microorganisms (special bacteria) that degrade such persistent organic substances do not easily appear in complex microbial systems such as activated sludge, or even if they can appear, it takes a long time to acclimatize. There are problems such as.

  In Non-Patent Document 3, in an activated sludge method using a sedimentation basin, a genetically modified bacterium introduced with a phenol degrading gene is added to the activated sludge, and the behavior of the recombinant bacterium remaining in the activated sludge is verified. According to this document, although a certain amount of the added recombinant bacteria remains in the activated sludge, a rapid decrease of the recombinant bacteria is observed immediately after the addition of the recombinant bacteria. The rate of reduction of the recombinant bacteria exceeds the rate of reduction caused by the extraction of excess sludge. That is, it can be said that it is difficult for the special bacteria added from the outside to remain in the activated sludge method using a sedimentation basin.

Japanese Patent Laid-Open No. 10-165991

Ogata et al. (2013), Occurrence of 4-tert-butylphenol (4-t-BP) . Ogata et al. (2013), The 4-tert-butylphenol-utilizing bacterium Sphingomonas fuligenis OMI candegraded biphenols via 10 phenocyclic hydration and metabolism. Ike Michihiko (1993), Basic research on the use of genetically modified organisms for activated sludge process, Osaka University doctoral dissertation.

  Therefore, an object of the present invention is to provide a wastewater treatment method and a wastewater treatment apparatus capable of efficiently biologically treating wastewater containing a hardly decomposable organic substance.

  A wastewater treatment method according to the present embodiment includes a biological treatment process for biologically treating wastewater containing a hardly decomposable organic substance, and a membrane treatment process for membrane treating treated water obtained in the biological treatment process, In the biological treatment process, a microorganism that decomposes the hardly decomposable organic substance is added to the waste water.

  The waste water treatment method preferably includes a culture step of culturing a microorganism that degrades the hardly decomposable organic substance.

  In the wastewater treatment method, it is preferable that a part of the wastewater is supplied to the culturing step, and the wastewater is used as a nutrient source for microorganisms that decompose the hardly decomposable organic substance.

  The wastewater treatment method preferably includes a pretreatment step of membrane-treating the wastewater supplied to the culture step.

  In the wastewater treatment method, the hardly decomposable organic substance preferably contains at least one of alkylphenols and bisphenols.

  The wastewater treatment apparatus according to the present embodiment includes a biological treatment tank that biologically treats wastewater containing a hardly decomposable organic substance, and a membrane treatment means that membrane-treats treated water obtained in the biological treatment tank, In the biological treatment, a microorganism that decomposes the hardly decomposable organic substance is added to the waste water.

  The waste water treatment apparatus preferably includes a culture tank for culturing microorganisms that decompose the hardly decomposable organic substance.

  In the wastewater treatment apparatus, it is preferable that a part of the wastewater is supplied to the culture tank and the wastewater is used as a nutrient source for microorganisms that decompose the hardly decomposable organic substance.

  In the wastewater treatment apparatus, it is preferable that the wastewater treatment apparatus includes pretreatment means for membrane-treating the wastewater supplied to the culture tank.

  In the wastewater treatment apparatus, it is preferable that the hardly decomposable organic substance includes at least one of alkylphenols and bisphenols.

  According to the present invention, wastewater containing a hardly decomposable organic substance can be efficiently biologically treated.

It is a schematic diagram which shows an example of a structure of the waste water treatment apparatus which concerns on this embodiment. It is a schematic diagram which shows another example of a structure of the waste water treatment apparatus which concerns on this embodiment. It is a figure which shows the daily change of the 4-tert- butylphenol density | concentration in the treated water of an Example and a comparative example.

  Embodiments of the present invention will be described below. This embodiment is an example for carrying out the present invention, and the present invention is not limited to this embodiment.

  FIG. 1 is a schematic diagram illustrating an example of a configuration of a wastewater treatment apparatus according to the present embodiment. A wastewater treatment apparatus 1 shown in FIG. 1 includes an MBR system 10 and a culture tank 12. The MBR system 10 includes an MBR tank 14 and a separation membrane module 16 including a separation membrane. The separation membrane module 16 is installed in the MBR tank 14.

  In the wastewater treatment apparatus 1 shown in FIG. 1, the drainage inflow line 18 a is connected to the drainage inlet of the MBR tank 14, and the drainage inflow line 18 b branched from the drainage inflow line 18 a is connected to the drainage inlet of the culture tank 12. One end of the culture solution supply line 20 is connected to the culture solution outlet of the culture vessel 12, and the other end is connected to the culture solution inlet of the MBR vessel 14. Further, the treated water discharge line 22 is connected to the treated water outlet of the separation membrane module 16. A pump 24 is installed in the treated water discharge line 22.

  An example of operation | movement of the waste water treatment equipment 1 of this embodiment is demonstrated.

  The waste water containing the hardly decomposable organic substance is introduced into the MBR tank 14 from the waste water inflow line 18a and is introduced into the culture tank 12 from the waste water inflow line 18b. In the culture tank 12, a microorganism (hereinafter referred to as a special bacterium) that decomposes a hardly decomposable organic substance is initially charged as an inoculum, and the special bacterium initially charged in the culture tank 12 is, for example, under aerobic conditions. Then, it is cultured using the persistent organic substance in the wastewater as a nutrient source. The culture solution containing the special bacteria cultured for a predetermined time in the culture tank 12 is discharged from the culture tank 12 and supplied to the MBR tank 14 through the culture liquid supply line 20. In the MBR tank 14, the hardly decomposable organic substance in the wastewater is decomposed by special bacteria or the like supplied from the culture tank 12 under aerobic conditions (biological treatment process). In addition, it is desirable to put normal activated sludge in the MBR tank 14 in advance.

  By operating the pump 24, the treated water biologically treated in the MBR tank 14 is passed through the separation membrane module 16, and the sludge in the treated water is removed (membrane treatment step). The treated water that has passed through the separation membrane of the separation membrane module 16 (filtered water from which sludge has been removed) is discharged out of the system from the treated water discharge line 22.

  According to this embodiment, since many special bacteria supplied from the culture tank 12 remain in the MBR tank 14, wastewater containing a hardly decomposable organic substance can be efficiently treated. The reason why the special bacteria remain in the MBR tank 14 is that the treated water is obtained by membrane filtration, and therefore it is difficult for the special bacteria to be discharged together with the treated water as compared with the activated sludge method using a sedimentation pond. It is thought that. Moreover, in the MBR system 10, it is possible to operate by increasing the sludge concentration in the system, that is, the sludge residence time (SRT) in the MBR tank 14 is longer than that in the activated sludge method using a sedimentation basin. One of the factors is that it can be set. The microflora in the sludge operated with a long SRT has a higher diversity than the microflora in the sludge operated with a short SRT, and is likely to change depending on environmental conditions. And in the sludge in which the microflora is highly diverse and the microflora is likely to change depending on the environmental conditions, the special bacteria with a slow growth rate supplied from the outside are difficult to be defeated by indigenous microorganisms. It is considered that various microorganisms and special bacteria can coexist.

  Below, the process conditions of the waste water treatment equipment 1 of this embodiment are explained in full detail.

  Examples of the hardly decomposable organic substances contained in the wastewater to be treated according to this embodiment include cyclic ethers, dioxins, phenols, polycyclic aromatic hydrocarbons, phthalates, and organic halogen compounds. It is done.

  Examples of the cyclic ethers include 1,4-dioxane, 1,3-dioxane, tetrahydrofuran, tetrahydropyran and the like.

  Examples of the dioxins include halogenated dibenzodioxins such as tetrachlorodibenzodioxin, halogenated dibenzofurans such as tetrachlorodibenzofuran, PCBs such as tetrachlorobiphenyl, and the like.

  Examples of phenols include alkylphenols such as 4-tert-butylphenol, nonylphenol and octylphenol, halogenated phenols such as tetrachlorophenol and pentachlorophenol, 2,2-bis (4-hydroxyphenyl) propane (bisphenol A), and the like. And bisphenols such as 1-bis (4-hydroxyphenyl) cyclohexane.

  Examples of the polycyclic aromatic hydrocarbon include benzopyrene, chrysene, benzoanthracene, benzofluoranthene, and picene.

  Examples of the phthalic acid ester include dibutyl phthalate, butyl benzyl phthalate, and di-2-ethylhexyl phthalate.

  Examples of the organic halogen compound include dichloropropane, trichloroethane, trichloroethylene, tetrachloroethylene, dichloroethylene, and the like.

  The sludge concentration in the MBR tank 14 is preferably adjusted to be, for example, 15,000 mg / L or less, and more preferably adjusted to be in the range of 5,000 to 12,000 mg / L. . When the sludge concentration exceeds 15,000 mg / L, the differential pressure of the separation membrane rises rapidly, the separation membrane is frequently washed, and stable operation may be difficult.

The BOD volume load of the MBR tank 14 is preferably adjusted to be, for example, 1.5 kgBOD / m ³ / day or less, and adjusted to be in the range of 0.2 to 1.0 kg BOD / m ³ / day. More preferably. If the BOD volumetric load exceeds 1.5 kg BOD / m ³ / day, there is a concern that the decomposition of organic matter will be insufficient and the quality of the treated water will be deteriorated, and the differential pressure of the separation membrane is likely to increase, so that the separation membrane can be washed. It becomes frequent and stable operation may be difficult.

  It is preferable that the sludge load (BOD-MLSS load) of the MBR tank 14 is adjusted to be in the range of 0.005 to 0.15 kgBOD / kgMLSS / day, for example. When the sludge load exceeds 0.15 kg BOD / kg MLSS / day, there is a concern that the decomposition of organic matter will be insufficient and the quality of the treated water will be deteriorated, and the differential pressure of the separation membrane is likely to rise, and the separation membrane is frequently washed. , Stable operation may be difficult. In addition, when the sludge load is less than 0.005 kg BOD / kg MLSS / day, the sludge floc is dismantled and the differential pressure of the separation membrane is likely to rise, resulting in frequent cleaning of the separation membrane, which makes stable operation difficult. There is.

  It is preferable to remove excess sludge from the MBR tank 14 so that the sludge concentration and load of the MBR tank 14 satisfy the above ranges, and the SRT (sludge retention time) for that purpose depends on the volume load, for example, 5 It is preferably set in a range of ˜50 days, and more preferably set in a range of 20 days to 40 days. When the SRT is longer than 50 days, the microorganisms in the sludge are auto-oxidized, and a polymer substance that does not permeate the separation membrane accumulates in the MBR tank 14 and the membrane may be clogged. If it is shorter than 5 days, sludge becomes dispersed and clogging of the separation membrane may occur.

  The pH in the MBR tank 14 is preferably adjusted to be in the range of 6.0 to 8.5, for example, and more preferably adjusted to be in the range of 6.5 to 7.5. . If the pH is less than 6.0 or exceeds 8.5, the decomposition of organic matter may be insufficient, the quality of treated water may deteriorate, the differential pressure of the separation membrane tends to increase, and the separation membrane is frequently washed. Thus, stable operation may be difficult.

  The DO (dissolved oxygen) concentration in the MBR tank 14 is preferably 1 mg / L or more, for example, and preferably in the range of 2 to 5 mg / L. If the DO (dissolved oxygen) concentration is less than 1 mg / L, the decomposition of the organic matter becomes insufficient, and there is a concern that the quality of the treated water will deteriorate, the membrane differential pressure tends to increase, and the separation membrane is frequently washed. Stable operation may be difficult. In addition, according to the measured value of dissolved oxygen concentration, you may adjust the air volume of the aeration blower for aerating the inside of the MBR tank 14 with an inverter etc.

  A carrier may be put into the MBR tank 14. The carrier is not particularly limited, and examples thereof include those made of a resin such as plastic and polyurethane. By using the carrier, the special bacteria supplied from the culture tank 12 are easily indwelled in the MBR tank 14.

  The separation membrane module 16 of the present embodiment exemplifies an immersion type separation membrane module installed in the MBR tank 14, but is not limited thereto, and is an outside tank type separation membrane module installed outside the MBR tank 14. It may be. Among these, it is desirable to employ an immersion type separation membrane module from the viewpoint of the installation area of the apparatus and the driving power.

  Examples of the shape of the separation membrane installed in the separation membrane module 16 include a flat membrane type, a hollow fiber type, a tubular type, and a spiral type. Examples of the material of the immersion film include polyethylene (PE), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), polyethersulfone (PES), and cellulose acetate (CA). Examples thereof include organic films and ceramic inorganic films. For example, the pore size of the separation membrane is preferably 1.0 μm or less, and is preferably a microfiltration membrane or an ultrafiltration membrane having a pore size of 0.1 μm or less. The permeation flow rate of the separation membrane is preferably operated in the range of about 0.1 to 0.8 m / day, and more preferably in the range of 0.2 to 0.6 m / day. There is no problem in operation even if the permeation flow rate of the separation membrane is less than 0.1 m / day, but the required membrane area may become very large, and if it exceeds 0.8 m / day, the differential pressure of the separation membrane increases. , The separation membrane is frequently washed, and stable operation may be difficult.

  It is desirable to provide an air diffuser directly below the separation membrane module 16 to supply aeration air to the separation membrane. The aeration air causes an air lift upward flow, a shearing force is applied on the membrane surface, and sludge accumulation on the membrane surface is suppressed. The membrane aeration is preferably performed with a predetermined air volume during filtration, for example. Alternatively, the separation membrane may be backwashed to remove the sludge deposited on the membrane surface.

  The special bacteria supplied to the MBR tank 14 is not particularly limited as long as it is a microorganism having the ability to decompose the hardly decomposable organic substance contained in the waste water, and is special according to the kind of the hardly decomposable organic substance. Although bacteria can be selected, for example, bacteria belonging to the genus Sphingobium and the like can be mentioned.

  Specific examples of the bacterium belonging to the genus Sphingobium include the Sphingobium fulginis OMI strain isolated by the present inventors. The Sphingobium fulriginis OMI was deposited by the present inventors at the Patent Microorganism Depositary Center of the National Institute of Technology and Evaluation on “Receipt Number: AP-02367” and “Receipt Date: September 29, 2016”. Sphingobium fulriginis OMI is mainly useful for degrading alkylphenols such as 4-tert-butylphenol and bisphenols, which are environmental hormone-like substances, but can also decompose other persistent organic substances.

  The culture method of the special bacteria in the culture tank 12 is not particularly limited, and examples thereof include a batch aerobic culture method and a continuous aerobic culture method. In the case of a batch culture method, for example, at a timing when a culture solution containing a special bacterium is supplied to the MBR tank 14, a predetermined amount of the special bacterium is added as an inoculum to the culture tank 12, and wastewater containing a hardly decomposable organic substance is added. A part is supplied to the culture tank 12, and special bacteria are aerobically cultured. Although the entire amount of the culture solution in the culture tank 12 may be supplied to the MBR tank 14, the culture solution is concentrated by sedimentation separation or the like due to concerns that the flow rate load on the MBR tank 14 temporarily increases. It is preferable that the concentrated culture solution is supplied to the MBR tank 14 and the treated water is discharged out of the system. In the case of a continuous culture method, for example, while continuously adding the above-mentioned special bacteria as seeds to the culture tank 12, waste water containing a hardly decomposable organic substance is supplied and the special bacteria are aerobically cultured. At the same time, a culture solution of the same amount as the supplied waste water is supplied from the culture tank 12 to the MBR tank 14.

  Although this embodiment illustrated the form which supplies the waste_water | drain containing a hardly degradable organic substance to the culture tank 12, and utilizes the said waste_water | drain as a nutrient source of a special microbe, it is not restrict | limited to this. For example, a chemical containing a hardly decomposable organic substance may be supplied to the culture tank 12 without introducing waste water containing the hardly decomposable organic substance into the culture tank 12. In this case, it is possible to selectively and cultivate a specific special bacterium in a high concentration with a hardly decomposed organic substance. However, in consideration of economy and practicality, it is preferable to culture special bacteria by supplying wastewater containing a hardly decomposable organic substance to the culture tank 12.

  The culture tank 12 may be supplied with a nitrogen source such as ammonium chloride and urea, a phosphorus source such as potassium phosphate, and other nutrient sources such as inorganic substances such as calcium, magnesium and iron.

  The pH in the culture tank 12 is preferably adjusted to be in the range of 6.0 to 8.5, for example, in terms of growth of special bacteria, and is preferably in the range of 6.5 to 7.5. It is more preferable to adjust to. Moreover, it is preferable that the temperature in the culture tank 12 is the range of 20-35 degreeC, for example at the point of proliferation of a special microbe. For the determination of the culture conditions as described above, it is more preferable to investigate the physiological characteristics of the special bacteria in advance and apply the obtained fastest growing conditions.

  The amount of special bacteria supplied from the culture tank 12 to the MBR tank 14 is, for example, equivalent to the dry weight with respect to the activated sludge (MLSS) in the MBR tank 14, preferably 0.5% or more, more preferably 1% or more and 10% or less. Considering the extraction of excess sludge from the MBR tank 14, if it is lower than 0.5%, there is a concern that a sufficient amount of special bacteria will not exist in the MBR tank 14. Moreover, it is preferable that the amount of special bacteria added is large, but if an amount of bacteria exceeding 10% is to be supplied to the MBR tank 14, a large culture tank 12 may be required.

  The frequency of adding the culture solution from the culture tank 12 is preferably at least once between 15 days and 50 days, and more preferably at least once between 30 days and 40 days. Although there is no particular problem in setting the frequency to less than 15 days, it is preferable to carry out at intervals of 15 days or more from the viewpoint of economy and workability. In consideration of the extraction of excess sludge in the MBR tank 14, it is preferable to add the culture solution at intervals of 50 days or less.

  The wastewater treatment apparatus 1 of the present embodiment includes the culture tank 12, but is not necessarily limited thereto, and a culture solution in which special bacteria are cultured is prepared in advance, and the culture solution is stored in the MBR tank. 14 may be supplied.

  FIG. 2 is a schematic diagram illustrating another example of the configuration of the waste water treatment apparatus according to the present embodiment. In the waste water treatment apparatus 2 shown in FIG. 2, the same components as those in the waste water treatment apparatus 1 shown in FIG. The wastewater treatment apparatus 2 shown in FIG. 2 includes a separation membrane module 26 that includes a separation membrane in the previous stage of the culture tank 12. The separation membrane is the same as that described above.

  Suspended substances such as bacteria contained in the waste water containing the hardly decomposable organic substance are removed by the separation membrane module 26, and the filtered water discharged from the separation membrane module 26 is supplied to the culture tank 12. Since the growth rate of miscellaneous bacteria is faster than that of special bacteria, the amount of miscellaneous bacteria mixed in the culture tank is reduced by membrane treatment of the wastewater supplied to the culture tank 12 as in the wastewater treatment apparatus 2 of FIG. Thus, since the special bacteria in the culture tank 12 are easy to prey using the organic matter in the wastewater as a nutrient source, the special bacteria can be efficiently propagated. The concentrated liquid after the membrane separation of the waste water is preferably returned to the waste water inflow line 18 a or supplied to the MBR tank 14.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail more concretely, this invention is not limited to a following example.

<Example>
Biological treatment of simulated wastewater containing 4-tert-butylphenol, which is a kind of alkylphenols, was performed using a treatment apparatus in which a separation membrane module was installed in the MBR tank. The conditions for biological treatment are as follows.

(Simulated drainage)
Wastewater in which 4-tert-butylphenol, which is a kind of alkylphenols, was added to a composite substrate wastewater mixed with fish meat extract and peptone so as to be 15 to 25 mg / L was used.

(MBR tank and separation membrane module)
Effective volume of MBR tank: 24L
Separation membrane: Flat membrane with a pore size of 0.4 μm Hydraulic retention time in MBR tank: 12 hours MLSS in MBR tank: 8000 to 10000 mg / L
(The MBR tank was loaded with activated sludge collected at a sewage treatment plant that mainly treats domestic wastewater to start up biological treatment.)
Sludge residence time in MBR tank: 24-48 days

(Microorganisms that decompose persistent organic substances (special bacteria))
Along with the activated sludge introduced at the start of the biological treatment, the following special bacteria previously cultured in the LB medium were introduced into the MBR tank. The input amount of the special bacteria was 1% by dry weight with respect to MLSS in the MBR tank.
Special fungus: Sphingobium fuligenis OMI isolated from duckweed rhizosphere

<Comparative example>
Biological treatment of simulated waste water was carried out in the same manner as in Example, except that the special bacteria were not introduced into the MBR tank.

  In Examples and Comparative Examples, the 4-tert-butylphenol concentration and the dissolved organic carbon concentration (DOC) in the treated water were measured. In addition, the OMI strain in the sludge in the MBR tank was quantified by a real-time PCR method targeting the catechol 2,3-dioxygenase (C23O) gene involved in phenol degradation.

  In FIG. 3, the daily change of the 4-tert- butylphenol density | concentration in the treated water of an Example and a comparative example is shown. At the time when the water flow was started (1st day), the concentration of 4-tert-butylphenol in the treated water was 5 mg / L or less in both Examples and Comparative Examples. This is probably because 4-tert-butylphenol was adsorbed by the activated sludge in the MBR tank. On the second to fifth days, the 4-tert-butylphenol concentration in the treated water gradually increased in both Examples and Comparative Examples. However, in the examples, the 4-tert-butylphenol concentration decreased significantly from the 6th day, and was maintained below the detection limit (<1 mg / L) after the 7th day. On the other hand, in the comparative example, the 4-tert-butylphenol concentration in the treated water is maintained at 7 mg / L or more after the 6th day, and the 4-tert-butylphenol concentration in the treated water tends to further increase after the 21st day. Met.

  The treated water DOC of Examples and Comparative Examples was lower than the DOC in the simulated waste water, and the organic components in the simulated waste water were treated. And when DOC in the treated water of an Example and a comparative example was compared, although the difference was not seen in both from the start of water flow to the 6th day, 4-tert- butylphenol was detected in the Example. On and after the seventh day, the DOC in the treated water of the comparative example showed a value about 5 to 10 mg / L higher than the DOC in the treated water of the example. From these facts, it can be said that in both the examples and the comparative examples, the readily decomposable organic substances in the simulated waste water are decomposed, but in the comparative examples, 4-tert-butylphenol is not decomposed and remains in the treated water.

  In addition, regarding the measurement of C23O gene in sludge, in the examples, the above gene was detected two orders higher than the comparative example throughout the test period of one month, so that the OMI strain was culled in the MBR tank. It can be said that it is indigenous in the sludge.

  From the above, it can be said that it is possible to quickly and efficiently treat the hardly decomposable organic matter in the waste water by adding a special bacterium that decomposes the hardly degradable organic matter to the MBR tank.

  1, 2 Wastewater treatment equipment, 10 MBR system, 12 culture tank, 14 MBR tank, 16 separation membrane module, 18a, 18b Wastewater inflow line, 20 culture solution supply line, 22 treated water discharge line, 24 pump, 26 separation membrane module .

Claims (10)

A biological treatment process for biologically treating wastewater containing persistent organic substances;
A membrane treatment step for membrane treatment of treated water obtained in the biological treatment step,
In the biological treatment step, a microorganism for decomposing the hardly decomposable organic substance is added to the wastewater.   The wastewater treatment method according to claim 1, further comprising a culture step of culturing a microorganism that decomposes the hardly decomposable organic substance.   The wastewater treatment method according to claim 1 or 2, wherein a part of the wastewater is supplied to the culturing step, and the wastewater is used as a nutrient source for microorganisms that decompose the hardly decomposable organic substance.   The wastewater treatment method according to any one of claims 1 to 3, further comprising a pretreatment step of membrane-treating the wastewater supplied to the culture step.   The waste water treatment method according to any one of claims 1 to 4, wherein the hardly decomposable organic substance contains at least one of alkylphenols and bisphenols. A biological treatment tank for biological treatment of wastewater containing persistent organic substances,
A membrane treatment means for membrane-treating treated water obtained in the biological treatment tank,
In the biological treatment, the waste water treatment apparatus is characterized in that a microorganism that decomposes the hardly decomposable organic substance is added to the waste water.   The waste water treatment apparatus according to claim 6, further comprising a culture tank for culturing a microorganism that decomposes the hardly decomposable organic substance.   The wastewater treatment apparatus according to claim 6 or 7, wherein a part of the wastewater is supplied to the culture tank, and the wastewater is used as a nutrient source for microorganisms that decompose the persistent organic substance.   The wastewater treatment apparatus according to any one of claims 6 to 8, further comprising pretreatment means for membrane-treating the wastewater supplied to the culture tank.   The waste water treatment apparatus according to any one of claims 6 to 9, wherein the hardly decomposable organic substance includes at least one of alkylphenols and bisphenols.

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