JP2022152743A - Wastewater treatment equipment and wastewater treatment method - Google Patents

Abstract

A wastewater treatment apparatus using conventional microorganisms cannot efficiently treat wastewater containing nitrogen compounds. A wastewater treatment apparatus (100) includes a reaction vessel (51) for treating wastewater, and a gas supply (10) disposed submerged in the wastewater in the reaction vessel (51). The gas supplier (10) supplies oxygen-containing gas to the wastewater from the inside and carries nitrifying bacteria on the outer surface in contact with the wastewater. [Selection drawing] Fig. 4

Description

TECHNICAL FIELD The present disclosure relates to a wastewater treatment apparatus and a wastewater treatment method, in which wastewater containing nitrogen compounds is introduced into a reaction tank, oxygen is supplied to nitrifying bacteria, and the wastewater is treated.

Wastewater treatment using aerobic microorganisms is known. However, in wastewater treatment using microorganisms, the biodegradation reaction (nitrification reaction, denitrification reaction) of nitrogen compounds begins after removal of BOD substances (BOD causative substances), which are organic substances that inhibit the reaction. Therefore, there is a problem that it is difficult to simultaneously remove organic matter and remove nitrogen compounds.

In the wastewater treatment method described in Patent Document 1, oxygen is supplied from the inside of the membrane, so that aerobic nitrifying bacteria settle on the surface of the membrane and denitrifying bacteria settle on the outer layer (wastewater side) of the membrane, and nitrification and denitrification occur in the same tank. Nitrogen (nitrogen removal) is possible. However, nitrifying bacteria grow very slowly compared to other microorganisms and denitrifying bacteria, and when contaminants other than nitrogen compounds are present, bacteria other than nitrifying bacteria grow. Furthermore, in MABR, since the oxygen supply direction and the organic matter supply direction are opposite, peeling of the microbial film is suppressed. Therefore, in the aforementioned state, there is a problem that the nitrification reaction does not proceed sufficiently.

In the treatment methods described in Patent Documents 2 and 3, either nitrifying bacteria or denitrifying bacteria are carried on the hollow fiber surface to shorten the acclimatization period of microorganisms involved in nitrification or denitrification. . However, in the method using hollow fibers, oxygen is supplied only to the vicinity of the pores, and in order to maintain the effective surface area, it is necessary to aerate to peel off the biofilm, and it is necessary to maintain a high degree of anaerobicity for denitrification. Therefore, it is necessary to install the nitrification and denitrification tanks separately. Since the two-step decomposition process of nitrogen compounds, that is, the nitrification reaction and the denitrification reaction are carried out in separate tanks, there is a problem that the reaction tank installation space and cost increase.

JP 2019-104007 Japanese Patent No. 5039093 Japanese Patent No. 3474476

Conventional wastewater treatment equipment using microorganisms cannot efficiently treat wastewater containing nitrogen compounds.

A wastewater treatment apparatus according to a first aspect of the present disclosure supplies oxygen to nitrifying bacteria to treat wastewater containing nitrogen compounds,
a reactor for treating wastewater;
a gas feed disposed submerged in waste water in the reaction vessel;
The gas supplier supplies the oxygen-containing gas from the inside to the wastewater and supports the nitrifying bacteria on the outer surface that contacts the wastewater.

The wastewater treatment apparatus of the second aspect is the wastewater treatment apparatus of the first aspect, wherein the gas supply body has a waterproof air permeable membrane on its outer surface that contacts the wastewater.

The wastewater treatment apparatus of the third aspect is the wastewater treatment apparatus of the second aspect, wherein the waterproof air permeable membrane is adherent to microorganisms.

A wastewater treatment apparatus according to a fourth aspect is the wastewater treatment apparatus according to any one of the first to third aspects, wherein the gas supply bodies are plural.

The wastewater treatment method of the fifth aspect is a wastewater treatment method in which wastewater containing a nitrogen compound is introduced into a reaction tank in which a gas supply is installed to treat the wastewater,
supplying waste water and a microbial preparation containing nitrifying bacteria to the reaction tank, immersing the gas supplier in the waste water;
A gas containing oxygen is supplied to the inside of the gas feed immersed in the wastewater, and the gas is transferred to the outer surface of the gas feed and supplied to the nitrifying bacteria.

A wastewater treatment method according to a sixth aspect is the wastewater treatment method according to the fifth aspect, wherein the gas supplier has a waterproof gas-permeable membrane on its outer surface in contact with the wastewater.

The wastewater treatment method of the seventh aspect is the wastewater treatment method of the sixth aspect, wherein the waterproof air permeable membrane is adherent to microorganisms.

The wastewater treatment method of the eighth aspect is the wastewater treatment method of the fifth to seventh aspects, wherein the gas supply is plural.

The wastewater treatment method of the ninth aspect is the wastewater treatment method of the fifth to eighth aspects, wherein the nitrifying bacteria are supplied at the same time as the wastewater is initially supplied to the reaction tank.

The wastewater treatment method of the tenth aspect is the wastewater treatment method of the fifth to ninth aspects, wherein the nitrifying bacteria are supplied at the same time as the wastewater is initially supplied to the reaction tank.

In the wastewater treatment apparatus using the gas supplier of the present embodiment, nitrifying bacteria are introduced at the initial stage of acclimatization, so that both the nitrifying bacteria and the denitrifying bacteria are supported on the microbial support layer on the surface of the gas supplier, and in one tank. , nitrogen compounds can be efficiently removed, and tank installation space and costs can be reduced.

Furthermore, since the nonporous membrane can supply oxygen from the entire surface of the membrane, it is more advantageous in terms of oxygen supply than the effective membrane. In addition, hollow fibers aerate to detach biofilms to maintain effective surface area, whereas flat plates do not. Therefore, high denitrification performance can be expected because the anaerobic degree in the tank can be kept high in the area away from the sheet outside the biofilm.

1 is a vertical sectional view of a wastewater treatment device 100 of a first embodiment; FIG. 1 is a horizontal sectional view of a wastewater treatment device 100 of a first embodiment; FIG. 1 is a vertical sectional view of a wastewater treatment device 100 of a first embodiment; FIG. 2 shows a cross section orthogonal to FIG. 1; 2 is a vertical cross-sectional view of the gas supply body 10 of the first embodiment; FIG. 5 is a perspective view showing a gas delivery layer 12 that constitutes the gas supplier 10 of FIG. 4. FIG. Microorganism aggregates formed on the surface of the waterproof air permeable membrane 21 of the gas supplier 10 immersed in the wastewater in the wastewater treatment tank 51 of the wastewater treatment apparatus 100 of FIG. 1, and at least one organic substance or nitrogen by the microorganisms It is a schematic diagram explaining decomposition|disassembly of a source. FIG. 3 is an exploded perspective view showing the configuration of a gas delivery layer included in the gas supply body according to the present invention; 4 is a perspective view showing a gas delivery layer included in the gas supplier according to the present invention; FIG. FIG. 5 is a vertical cross-sectional view of a gas supply body 10a of a second embodiment; FIG. 8 is a vertical cross-sectional view of a gas supply body 10a of a modified example of the second embodiment; It is a schematic perspective view of the wastewater treatment apparatus 100b of 3rd Embodiment.

<First embodiment>
(Nitrogen compound-containing wastewater treatment device 100)
The nitrogen compound-containing wastewater treatment apparatus 100 of the present embodiment utilizes the action of microorganisms (nitrifying bacteria) to decompose at least one nitrogen compound component in the nitrogen compound-containing wastewater to purify the wastewater. As shown in FIG. 1 , the nitrogen compound-containing wastewater treatment apparatus 100 includes a nitrogen compound-containing wastewater treatment tank 51 and a system 50 .

(Nitrogen compound-containing wastewater treatment tank 51)
As shown in FIG. 1 or FIG. 2, the nitrogen compound-containing wastewater treatment tank 51 is a bottomed container in which nitrogen compound-containing wastewater W is stored, and has an inlet 51a and an outlet 51b on opposite sides. is provided. In this embodiment, the inlet 51a and the outlet 51b are always open. The nitrogen compound-containing wastewater W is continuously or intermittently supplied from the inflow port 51a toward the outflow port 51b disposed opposite the inflow port 51a (the dashed-dotted arrow in FIG. 3 indicates flow of nitrogen compound-containing wastewater W). The volume of the nitrogen compound-containing wastewater treatment tank 51 is not particularly limited, but may be, for example, a volume of 1 m ³ or more and 10,000 m ³ or less.

(System 50)
System 50 comprises a supply unit 52 and a gas supply 53 .

(Supplier unit 52)
As shown in FIG. 1, the supply unit 52 is a unitized gas supply unit 10 and is arranged inside the nitrogen compound-containing wastewater treatment tank 51 . In FIG. 1, the feeder unit 52 is made up of a plurality of gas feeders 10 arranged in parallel. The supply unit 52 is arranged such that the portions of the gas supply units 10 other than the upper end portions are immersed in the nitrogen compound-containing waste water W during use.

(Gas supplier 10)
The gas supplier 10 includes a gas delivery layer 12 and a waterproof permeable membrane 21, as shown in FIG. Each gas supplier 10 constituting the supplier unit 52 is immersed in the nitrogen compound-containing wastewater W of the nitrogen compound-containing wastewater treatment tank 51, and supplies the gas supplied from the opening 21b into the nitrogen compound-containing wastewater W. is a structure that feeds into The gas supplied to the nitrogen compound-containing wastewater W through the gas supplier 10 is preferably a gas containing oxygen in order to promote the activation of the aerobic microorganisms in the nitrogen compound-containing wastewater W. Specifically, it may be air or pure oxygen. In the illustrated example, the gas from the gas supply source 53 is supplied to the opening 21b, and an air supply device or the like can be used as the gas supply source 53. FIG. From the viewpoint of keeping the manufacturing cost low, air in the atmosphere may be taken into the gas supply body 10 as it is from the opening 21b without using the gas supply source 53 . As shown in FIG. 2, each gas supplier 10 is a plate-like member, and is arranged so that its surfaces are developed along the vertical direction (depth direction) and lateral direction (horizontal direction). there is Thereby, the contact area with the nitrogen compound-containing waste water W is efficiently secured. In addition, by arranging the gas supply bodies 10 so that the sides of the gas supply bodies 10 are parallel to the straight line connecting the inlet 51a and the outlet 51b, the nitrogen compound-containing wastewater can be discharged from the inlet 51a. The nitrogen compound-containing wastewater W supplied into the treatment tank 51 smoothly flows toward the outflow port 51b. It should be noted that the number of gas supply bodies 10 constituting the supply body unit 52 is not necessarily plural, and may be singular. When the interval between the gas supply bodies 10 is defined as "the interval between the outer surfaces of two adjacent gas supply bodies 10 excluding the thickness of the gas supply bodies 10", the interval between the gas supply bodies 10 is 5 mm or more and 200 mm or less. is preferably If the gap between the gas supply members 10 is less than 5 mm, there is a risk of clogging caused by microorganisms growing on the waterproof air permeable membrane 21 . If the interval between the gas supply bodies 10 exceeds 200 mm, the efficiency of contact with wastewater may be poor, making it difficult to improve the wastewater treatment performance. In order to reliably avoid the above problem, it is more preferable to set the distance between the gas supply bodies 10 to 15 mm or more and 50 mm or less. FIG. 4 is a vertical sectional view of the gas supplier 10. As shown in FIG. As shown in FIG. 4, the gas supplier 10 includes a gas delivery layer 12 and a waterproof air permeable membrane 21. The gas delivery layer 12 is placed in a bag formed by the waterproof air permeable membrane 21. be. The bag is made by superimposing two waterproof air permeable membranes 21, 21 and adhering three ends of these waterproof air permeable membranes 21, 21, and the upper end (the gas supply in the gas delivery layer 12). side end) has an opening 21b (see FIG. 4). By inserting the gas delivery layer 12 into the inside of the bag through the opening 21 b , the outer periphery of the gas delivery layer 12 is covered with the waterproof air permeable membrane 21 . The position or shape of the opening 21b is not limited, and for example, a part of each end (including the top side, bottom side, and horizontal side (vertical line) of the bag) may be the opening.

(Waterproof air permeable membrane 21)
The waterproof air permeable membrane 21 is immersed in liquid (waste water) so that the outermost layer is in contact with the liquid (waste water), and oxygen supplied to the inside (gas delivery layer 12 side) permeates to the outside. Oxygen is supplied to the liquid (waste water) by The waterproof gas-permeable membrane 21 allows air to permeate from the inside (gas delivery layer 12) to the outside (wastewater W) in a state in which the gas supplier 10 is immersed in the nitrogen compound-containing wastewater treatment tank 51, and the outside ( It has the property of preventing permeation of wastewater from the nitrogen compound-containing wastewater W) to the inside (gas delivery layer 12). As a result, as shown in FIG. 6, the aerobic microorganisms in the nitrogen compound-containing wastewater W gather on the surface 21a of the waterproof permeable membrane 21 to which air (oxygen) is continuously supplied. Therefore, microorganisms adhere to the surface 21 a of the waterproof air permeable membrane 21 to form a biofilm 214 . Microorganisms dissolved or dispersed in water or nitrogen compounds are decomposed by the action of microorganisms contained in the nitrogen compound-containing wastewater W or retained on the surface 21a, and the wastewater is discharged. Purified. The waterproof gas permeable membrane 21 preferably includes a substrate 211 and a gas permeable non-porous layer 212 . In the illustrated example, the waterproof gas-permeable membrane 21 is laminated in the order of a base material 211, a gas-permeable non-porous layer 212, and a microorganism-supporting layer 213. As shown in FIG. Note that unlike the illustrated example, the waterproof air permeable membrane 21 may be one in which the gas permeable nonporous layer 212, the base material 211, and the microorganism supporting layer 213 are laminated in this order.

(Base material 211)
The base material 211 is a microporous membrane made of thermoplastic resin. The microporous membrane is a membrane having a large number of fine through holes. Materials for the substrate 211 include fluororesins including polyolefin, polystyrene, polysulfone, polyethersulfone, polyarylsulfone, polymethylpentene, polytetrafluoroethylene, and polyvinylidene fluoride, polybutadiene, and poly(dimethylsiloxane). including polymeric materials selected from silicone-based polymers, and copolymers of these materials; The method for manufacturing the base material 211, which is a microporous membrane, is not particularly limited, but for example, the base material can be manufactured by any one of a phase separation method, a stretching opening method, a dissolution recrystallization method, a powder sintering method, a foaming method, and a solvent extraction method. Material 211 can be manufactured. Substrate 211 may also be a self-assembled honeycomb microporous membrane. The thickness of the base material 211 is preferably 10 μm to 500 μm, more preferably 50 μm to 200 μm. The thickness of the base material 211 is a value measured by JIS1913:2010 general nonwoven fabric test method 6.1 thickness measurement method. The pore diameter of the substrate 211 is preferably 0.01 μm to 50 μm from the viewpoint of preventing defects in the gas permeable nonporous layer, and 0.1 μm to 30 μm from the viewpoint of maintaining high strength and gas permeability. is more preferable. The pore size is a pore size obtained by observing the surface with a scanning electron microscope (SEM) and obtaining the observed image by the following method. Observation can be performed at any magnification as long as the pore size of the object to be observed can be calculated appropriately.

(Method for obtaining pore diameter)
An image obtained by SEM observation is binarized, and the pore diameter is calculated by image analysis. In the calculation, the pore diameter is approximated to an ellipse, and the average value is evaluated using the length of the long axis of the ellipse as the pore diameter. Alternatively, the pore diameter of the base material 211 is defined as an average pore diameter obtained from pore diameter distribution measurement (perm porosimetry) by a capillary condensation method. In perm porosimetry, the relationship between the differential pressure between the atmospheric pressure and the measured pressure and the gas permeation flow rate is obtained from the gas permeation flow rate that is measured when the measurement pressure of the gas applied to the sample is gradually increased. To determine the pore size, a wet curve measured with a wet sample after immersing the sample in a wetting liquid with a known surface tension and a dry curve measured with a dried specimen are determined. By gradually increasing the pressure within a predetermined pressure range, it is possible to obtain information on the through-pore diameter in the sample. The average pore diameter is obtained by finding the point X where the wet curve and the half dry curve (half dry curve) intersect, and substituting this into the equation d=2860×γ/DP. In the above equation, d is the average pore diameter (mm), γ is the surface tension of the wetting liquid (dynes/cm), and DP is the pressure difference between atmospheric pressure and gas pressure at point X (Pa). For measurement, a perm porometer (CFP-1500-AEC) manufactured by Porous Materials can be used. As test conditions, for example, the test temperature is room temperature (20° C.±5° C.), the wetting liquid is Galwick (surface tension 15.7 dynes/cm), the pressurized gas is compressed air, the diameter of the sample used is 33 mm, and the maximum supply pressure is can be measured at 250 psi and the rate of differential pressure rise at 4 psi/min. When preparing a wet sample, the sample can be sufficiently wetted by putting the wetting liquid in which the sample is immersed into a desiccator and degassing it.

(Gas permeable non-porous layer 212)
The gas-permeable non-porous layer 212 is a layer that has pores with a pore diameter smaller than that of the base material, or the pore diameter cannot be detected and is permeable to gas. The pore diameter of gas permeable non-porous layer 212 can be measured by the same method as the pore diameter of substrate 211 . Examples of the gas that permeates the gas permeable nonporous layer 212 include oxygen, carbon dioxide, nitrogen, hydrogen, alcohols such as methanol and ethanol, organic solvents, and mixed gases thereof. From the viewpoint of effectively growing and activating microorganisms, the gas is preferably oxygen or a mixed gas containing oxygen. Gas permeability can be measured by the method defined in JIS K7126. Gas permeable non-porous layer 212 may be a thermoplastic resin or a thermosetting resin. The thermosetting resin may be a thermosetting resin or a resin that is cured by irradiation with ultraviolet rays. It may also be a resin that cures by organic peroxide cross-linking, addition reaction cross-linking, or condensation cross-linking. Materials for gas permeable nonporous layer 212 may include thermosetting polymers selected from polyolefins, polystyrenes, polysulfones, polyethersulfones, polytetrafluoroethylenes, acrylic resins, polyurethane resins, and copolymers of these materials. Also, silicone-based silicone resins such as poly(dimethylsiloxane) having a siloxane skeleton of (Si--O--Si)n (n=integer) can be used. Among these, it is particularly preferable to use urethane resins and silicone resins. Examples of the above polyurethane resins include "Asaflex 825" (manufactured by Asahi Kasei Corporation), "Perethene 2363-80A", "Perethene 2363-80AE", "Perethene 2363-90A", "Perethene 2363-90AE",・Chemical Co., Ltd.) and “Heimlen Y-237NS” (manufactured by Dainichiseika Kogyo Co., Ltd.) can be used. There are no particular restrictions on the formulation or composition of the silicone-based resin, silicone polymer, or silicone-based resin composition for obtaining them. The monomer used in the silicone-based resin composition may be monofunctional, bifunctional, trifunctional, or tetrafunctional, and may be used alone or in combination of two or more. Halogenated alkylsilanes, unsaturated group-containing silanes, aminosilanes, mercaptosilanes, epoxysilanes, and the like may be used as monomers. Examples of monomers that can be used include monomers represented by the following chemical formulas. _HSiCl3 , _SiCl4 , _MeSiHCl2 , _Me3SiCl , MeSiCl3, _Me2SiCl2 , _Me2HSiCl , _PhSiCl3 , _Ph2SiCl2 , _MePhSiCl2 , _Ph2MeSiCl , _{CH2 = CHSiCl3 ,} Me _{( CH2 =} CH) _SiCl2 , Me2 _{( CH2 =} CH)SiCl _{, ( CF3CH2CH2} ) _{MeSiCl2 , ( CF3CH2CH2} ) _SiCl3 , _CH18H37SiCl3 (where "= " represents a double bond, "Me" represents a methyl group, and "Ph" represents a phenyl group). The monomers may be used alone or in combination of two or more. Other organic groups include alkyl groups such as propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, hexyl group, octyl group and decyl group; An aryl group; a cycloalkyl group such as a cyclopentyl group and a cyclohexyl group; an aralkyl group such as a benzyl group, a 2-phenylethyl group and a 3-phenylpropyl group, and the like may be used. Among these, a methyl group, a phenyl group, or a combination of both is preferred. This is because a component that is a methyl group, a phenyl group, or a combination of both is easy to synthesize and has good chemical stability. In addition, when a polyorganosiloxane having particularly good solvent resistance is to be used, a combination of a methyl group, a phenyl group, or a combination of both of them and a 3,3,3-trifluoropropyl group is preferred. preferable. Further, the silicone-based resin composition may contain an organoalkoxysilane. Organoalkoxysilanes include, for example, compounds represented by the following chemical formulas, which may be used singly or in combination of two or more. _Me3SiOCH3 , _{Me2Si (} OCH3) ₂ , MeSi(OCH3) _{3 ,} Si ₍ OCH3) _{4 ,} Me _{( C2H5} )Si ₍ OCH3) _{2 , C2H5Si (} OCH3 ) ₃ , C ₁₀ H ₂₁ Si(OCH ₃ ) ₃ , PhSi(OCH ₃ ) ₃ , Ph ₂ Si(OCH ₃ ) ₂ , MeSiOC ₂ H ₅ , Me ₂ Si(OC ₂ H ₅ ) ₂ , Si(OC _{2 H5} ) ₄ , _{C2H5Si ( OC2H5} ) ₃ , PhSi _{( OC2H5} ) _{3 , Ph2Si ( OC2H5} ) ₂ . Furthermore, the silicone-based resin composition may contain an organosilanol. Organosilanols include, for example, compounds represented by the following chemical formulas, which may be used singly or in combination of two or more. _Me3SiOH , Me2Si(OH) ₂ , MePhSi(OH) ₂ , ( _C2H5 ) _3SiOH , _{Ph2Si (} OH) _{2 , Ph3SiOH} . The reaction method for obtaining the silicone polymer used in the silicone-based resin may include, for example, hydrolysis of chlorosilane, ring-opening polymerization of cyclic dimethylsiloxane oligomer, and the like. Examples of polymers to be used include dimethyl-based polymers, methylvinyl-based polymers, methylphenylvinyl-based polymers, and methylfluoroalkyl-based polymers. The method of curing the silicone polymer, that is, the method of reacting (vulcanizing) to obtain the silicone resin is not particularly limited. Heat vulcanization or room temperature vulcanization may be used. Either the millable type silicone resin composition or the liquid rubber type silicone resin composition may be used as the state before the reaction. A polymer having a degree of polymerization of about 4,000 to 10,000 is preferably used for the millable type silicone resin composition. Moreover, it may be of a one-liquid type or a two-liquid type. Examples of reaction methods include dehydration condensation reaction between silanol groups (Si—OH), condensation reaction between silanol groups and hydrolyzable groups, methylsilyl groups (Si—CH ₃ ), vinylsilyl groups (Si—CH═CH ₂ ). reaction with an organic peroxide, addition reaction between a vinylsilyl group and a hydrosilyl group (Si--H), reaction with ultraviolet rays, reaction with electron beams, and the like may be used.

(Microorganism support layer 213)
Microorganism support layer 213 is a layer that retains microorganisms on its surface or inside. Materials for the microorganism support layer 213 include, for example, meshes, woven fabrics, non-woven fabrics, foams, and porous sheets such as microporous membranes. Porous sheet materials include polyolefin resin, polystyrene resin, polyester resin, polyvinyl chloride resin, acrylic resin, urethane resin, epoxy resin, polyamide resin, methyl cellulose resin, ethyl cellulose resin, polyvinyl alcohol resin, vinyl acetate resin, phenol resin, Fluorine resins, polyvinyl butyral resins, polyimides, polyphenylene sulfides, para- and meta-aramids, polyarylates, carbon fibers, glass fibers, aluminum fibers, steel fibers, ceramics, and the like. Polyolefin resins, polyester resins, polyamide resins, acrylic resins, polyurethane resins, and carbon fibers are preferred in consideration of microbial adhesion and workability. The basis weight of the microorganism supporting layer 213 is preferably 2 g/m ² or more and 500 g/m ² or less, more preferably 10 g/m ² or more and 200 g/m ² or less. The basis weight of the microorganism supporting layer 213 is a value measured by mass per unit area according to JIS 1913:2010 general nonwoven fabric test method 6.2. When the basis weight of the microorganism-supporting layer 213 is 2 g/m ² or more, unevenness is generated on the surface of the microorganism-supporting layer 213, so that the microorganism-supporting layer 213 can easily retain microorganisms. In addition, when the basis weight of the microorganism supporting layer 213 is 500 g/m ² or less, a space in which the microorganisms can grow is generated inside the microorganism supporting layer 213, so that the microorganisms are easily retained, and the space allows oxygen to be transferred to the microorganisms. The effect of facilitating supply can be obtained. The thickness of the microorganism support layer 213 is preferably 5 μm or more and 2000 μm or less, more preferably 20 μm or more and 500 μm or less. The thickness of the microorganism-supporting layer 213 is a value measured by JIS1913:2010 general nonwoven fabric test method 6.1 thickness measurement method.

The waterproof air permeable membrane 21 has a gas permeable nonporous layer 212 and is characterized by having a liquid permeability of 1 or less as measured by a liquid permeability measurement test.

(Liquid permeability measurement test)
(1) A 50 mm square polyethylene terephthalate resin nonwoven fabric (basis weight: 220 to 300 g/mm2) is laminated on the surface of the 50 mm square waterproof air permeable membrane 21 opposite to the surface in contact with the treated water to form a test piece. , 10 test pieces are prepared. (2) Each of 10 test pieces is placed on a glass plate so that the surface of the nonwoven fabric side is in contact with the glass plate, and the four corners of the test piece are fixed to the glass plate with tape having a width of 10 mm. (3) 0.7% by mass of perfluoroalkyl group-containing carboxylate and Allura Red (CAS No.: 25956-17-6) are added to ion-exchanged water on the side of each test piece that contacts the treated water. 10 mL of a test solution in which 0.3% by mass of is dissolved is dropped at once with a pipette so as not to protrude from the test piece. (4) Each test piece is allowed to stand for 18 hours under conditions of a temperature of 25±5° C. and a humidity of 50±10%. (5) Transmittance is the number of test pieces that can be confirmed from the glass plate side that the test liquid has passed through the test piece. As a method of laminating the waterproof air permeable membrane 21 and the nonwoven fabric in the step (1), it is sufficient to simply stack them. More specifically, the method of fixing the test piece in step (2) includes a method of fixing the four corners corresponding to the vertices of the test piece with a 10 mm square tape. In the above step (3), if the amount of the test liquid is so large that it cannot be avoided that it overflows the test piece when dripped, it is preferable to reduce the amount of the test liquid by half and conduct the test.

(Gas delivery layer 12)
FIG. 5 is a perspective view showing the gas delivery layer 12. As shown in FIG. The gas delivery layer 12 is a hollow plate-like member made of paper, resin, or metal. The gas delivery layer 12 is a structure having a gas flow path S for delivering gas supplied from the first end along the first direction. Gas from the gas supply source 53 (FIG. 1) is supplied to the lower end portion of the gas delivery layer 12 via the gas delivery portion 31a. The gas delivery layer 12 has a gas flow path S that delivers the supplied gas in the first direction (see the dashed line in FIG. 5), and releases the gas from the gas passage holes 13 on the side surface. More specifically, as shown in FIG. 5, the gas delivery layer 12 has a plurality of cores 12a, a front liner 12b and a back liner 12c. The front and back surfaces of the gas delivery layer 12 are composed of a front liner 12b and a back liner 12c, which are plate-shaped members. The plurality of core members 12a each extend in the first direction and are arranged at predetermined intervals in a direction orthogonal to the first direction. By sandwiching the plurality of core members 12a between the front liner 12b and the back liner 12c, a plurality of gas flow paths S partitioned by the core members 12a are formed in the space between the front liner 12b and the back liner 12c. is formed. Further, each core member 12a functions as a supporting portion that supports the space between the front liner 12b and the back liner 12c so that the space between the front liner 12b and the back liner 12c does not shrink when pressed from the front liner 12b and back liner 12c sides. As shown in FIG. 1 or 2, when the gas supplier 10 is immersed in the waste water W, the core material 12a is arranged between the front liner 12b and the back liner so that the cross-sectional area of the gas flow path S does not shrink due to water pressure. 12c. Thereby, a sufficient amount of gas delivery can be ensured in the gas delivery layer 12 (gas flow path S). A plurality of gas passage holes 13 are formed in each of the front liner 12b and the back liner 12c. The gas passage holes 13 are through holes formed in the front liner 12b and the back liner 12c. The flowing gas is supplied into the liquid through the waterproof gas permeable membrane 21 . For example, the gas passage holes 13 are formed when the gas delivery layer 12 is molded. Alternatively, the gas passage holes 13 may be formed by processing the front liner 12 b and the back liner 12 c after molding the gas delivery layer 12 . A porous sheet may be used for the front liner and the back liner. A porous sheet may be used for the gas delivery layer as long as sufficient gas supply performance is obtained. Materials for each member constituting the gas delivery layer 12 include paper, ceramic, aluminum, iron, plastic (polyolefin resin, polystyrene resin, polyester resin, polyvinyl chloride resin, acrylic resin, urethane resin, epoxy resin, polyamide resin, methyl cellulose resin, ethyl cellulose resin, polyvinyl alcohol resin, vinyl acetate resin, phenol resin, fluororesin and polyvinyl butyral resin) and the like. The material of the gas delivery layer 12 is preferably paper, aluminum, iron, polyolefin resin, polystyrene resin, vinyl chloride resin, or polyester resin because of their superior strength. From the viewpoint of keeping material costs low, it is preferable to use paper, resins such as polyolefin, polystyrene, vinyl chloride and polyester, and metals such as aluminum as materials for the gas delivery layer 12, for example. Also, the material cost of the gas delivery layer 12 can be kept low by using corrugated cardboard formed so that the gas flow path S extends in the first direction (see FIGS. 4 and 5) as the gas delivery layer 12. . The shape of the holes forming the gas permeable holes of the gas delivery layer 12 can be of various shapes such as a circular shape and a polygonal shape (including a honeycomb structure). Although the shape of the hole is not particularly limited, it is preferably polygonal, and specifically rectangular or square.

(Matters that can be changed in the first embodiment)
In the first embodiment, an example using the planar gas supply member 10 has been described. However, the present invention is not limited to this. For example, the gas supply body 10 may be wound, or a cylinder-shaped gas supply body may be used.

In the first embodiment, an example in which the gas delivery layer 12 is inserted from the opening 21b of the bag made of the sheet laminate to form the gas supply body 10 has been described. However, the present invention is not limited to this. For example, a sheet laminate may be laminated and adhered to the surface of the gas delivery layer. As for the portion to be bonded, only the outer peripheral portion of the sheet stack may be bonded, or if the gas can be supplied to the sheet stack, the sheet stack and the gas delivery layer may be bonded over the entire surface. may

The member constituting the gas delivery layer is not limited to the hollow plate-shaped member shown in the first embodiment, and may be modified as shown in FIG. In the gas delivery layer 311 shown in FIG. 7, a first structure 312 having a honeycomb structure and cells (gas passage holes 313a) different in size from the cells (gas passage holes 312a) of the first structure 312 are arranged. and a second structural body 313 having a honeycomb structure.

In the first embodiment, an example using the gas delivery layer 12 including the core material 12a, the front liner 12b, and the back liner 12c has been described. However, the present invention is not limited to this. For example, as shown in FIG. 8, between a front liner 412b and a back liner 412c, which are arranged along the gas flow path S and have a corrugated core material 412a in a cross-sectional view, and in which a plurality of gas passage holes 413 are formed. The arranged hollow plate member 412 may be used as a gas delivery layer.

(biological denitrification method)
Biological denitrification is known as a method for treating nitrogen compound-containing wastewater. This treatment method consists of a nitrification process in which ammonium nitrogen is treated with microorganisms under aerobic conditions and oxidized to nitrite or nitrate nitrogen, and a denitrification process in which nitrites and nitrate nitrogen are reduced and removed as nitrogen gas under anaerobic conditions. consists of processes. Microorganisms involved in the nitrification process are nitrifying bacteria, and these are aerobic bacteria that require the presence of sufficient dissolved oxygen in the reaction tank. Nitrifying bacteria are autotrophic bacteria that acquire energy by oxidizing ammonia and nitrite nitrogen, and grow by assimilating inorganic carbon compounds. The nitrifying bacteria adhering to the gas supplier 10 can be selected from bacteria having enzymes involved in nitrification reaction. Examples of such nitrifying bacteria include ammonia-oxidizing bacteria (genus Nitrosomonas and Nitrospira), nitrite-oxidizing bacteria (genus Nitrobacter), and the like. Representatives of the genus Nitrosomonas include Nitrosomonas and europa, and representatives of the genus Nitrobacter include Nitrobacter agilis. At least one of the nitrifying bacteria is selected and attached to the gas supplier 10 . Microorganisms involved in denitrification are heterotrophic microorganisms that use the carbon source of organic matter as an energy source. Under aerobic conditions, they respire oxygen. It is often a facultative anaerobic bacterium that performs

(Supply method of nitrifying bacteria)
When the nitrifying bacteria are immobilized on the carrier, the contact amount of the nitrifying bacteria per surface area of the gas supplier 10 may be appropriately selected depending on the material and shape of the surface of the gas supplier 10. For example, nitrogen compound-containing wastewater treatment. When the ratio of the surface area of the gas supplier 10 to the effective volume of the tank 51 is 50 m ² /m ³ , the nitrifying bacteria culture solution (SS measurement amount of 20000 mg / L or more) is added to the effective volume of the nitrogen compound-containing wastewater treatment tank 51. On the other hand, it may be added at a rate of 1 mL/L or more, preferably 10 mL/L or more, more preferably 100 mL/L or more. The culture solution may be supplied continuously or intermittently to the nitrogen compound-containing wastewater W supply. Preferably, it should be continuously supplied in order to keep the concentration of the culture medium in the wastewater treatment tank 51 constant.

(Nitrogen compounds to be treated)
Nitrogen compounds to be treated include ammonia, ammonium compounds, nitrite compounds, and nitrate compounds.

<Second embodiment>
As shown in FIG. 9, the gas supplier 10a of the second embodiment has the same features as those of the first embodiment, except that the gas permeable non-porous layer 212a differs from the gas permeable non-porous layer 212 of the first embodiment. is the same as the gas supplier 10 of . The wastewater treatment apparatus 100a of the second embodiment is the same as the wastewater treatment apparatus 100 of the first embodiment, except that the gas supplier 10a is different from the gas supplier 10 of the first embodiment.

The gas supplier 10a of this embodiment includes a gas delivery layer 12 and a waterproof air permeable membrane 210 . The waterproof air permeable membrane 210 includes a substrate 211 , a gas permeable non-porous layer 212 a and a microorganism supporting layer 213 . The gas-permeable non-porous layer 212 a of this embodiment also has the effect of promoting the adhesion of microorganisms to the microorganism-supporting layer 213 .

The gas permeable non-porous layer 212a is formed by modifying a resin layer. Since the surface roughness and membrane potential of the resin layer can be increased by modifying the surface of the resin layer, the adhesion of microorganisms to the surface of the waterproof air permeable membrane 210 is improved. For example, as the above surface modification treatment, graft polymerization of glycidyl methacrylate and further reaction with diethylamine or sodium sulfite can be performed. Alternatively, as the above surface modification treatment, after graft polymerization of glycidyl methacrylate, reaction with ammonia or ethylamine may be performed. Other surface modification treatments, such as plasma treatment, corona treatment, chlorine dioxide treatment, etc., can improve adhesion of microorganisms by introducing functional groups to the surface. In addition, the microorganism support layer 213 may be substituted by imparting adhesiveness to the gas permeable non-porous layer 212 . In other words, the microorganism support layer 213 may not be formed (shown in FIG. 10 as a modification of the second embodiment). By doing so, the adhesiveness described above improves the adhesion of microorganisms. As a method for imparting tackiness, it is possible to employ a wide range of known tacky resins, and there is no particular limitation. Among them, it is preferable to use a resin having a function as an adhesive in order to improve the adhesiveness of the film. Specific examples of such resins include resins that are rubber-like substances, acrylic resins having acrylic monomers as an essential component, urethane resins, polycarbonate resins, polyester resins, polyolefin resins, and acrylic urethane. It is also preferable to use a base resin, a vinyl base resin, a silicone base resin, or a pressure-sensitive adhesive grade resin composition thereof. Specific examples of the rubber-like substance include polybutadiene rubber, styrene-butadiene copolymer rubber, ethylene-propylene rubber, butadiene-acrylonitrile copolymer rubber, butyl rubber, acrylic rubber, and styrene-isobutylene-butadiene copolymer. Examples include rubber, isoprene-acrylic acid ester copolymer rubber, and the like. As the polyolefin resin, more specifically, a resin with high oxygen permeability such as polymethylpentene may be used. These resins may be used alone, or may be used as a copolymer in which multiple types are used together. Moreover, a solvent such as toluene or xylene may be mixed in the application. In addition to the above resin component, a resin having adhesiveness (hereinafter also referred to as "adhesive") may be added in order to increase adhesiveness. Moreover, it is also preferable to employ|adopt the adhesive itself as said resin component. The amount of adhesive is preferably 10 to 99% by mass in 100% by mass of the resin composition for forming the A layer in order to improve compatibility with the catalyst and solvent and facilitate viscosity adjustment, and 20 to It is more preferable to make it 80% by mass. Examples of the adhesive contained in the A-layer-forming resin composition include rubber-based adhesives, acrylic-based adhesives, silicone-based adhesives, polyester-based adhesives, and urethane-based adhesives. The type of pressure-sensitive adhesive is selected in consideration of oxygen permeability and compatibility, and is preferably made of a silicone-based pressure-sensitive adhesive composition.

(Silicone adhesive)
As an adhesive for imparting adhesiveness to the silicone resin, it is preferable to use, for example, a silicone adhesive. The silicone pressure-sensitive adhesive comprises, for example, silicone gum and MQ resin, an organic solvent, a hydrosilyl group (SiH group)-containing cross-linking agent, and a curing catalyst used as necessary. Also, MQ resin, for example, is preferably used as a silicone polymer that imparts adhesiveness. MQ resin is a polymer having a three-dimensional structure synthesized from monofunctional monomers (M units) and tetrafunctional monomers (Q units). The molecular weight of the polymer having the three-dimensional structure is preferably 10-100,000, more preferably 100-10,000. As the organic group of the monomer of each functional group, it is preferable to use a methyl group, but in the case of an addition reaction type silicone resin, it is preferable to use an alkenyl group. From the viewpoint of achieving both the strength and adhesiveness of the silicone resin, the content of the silicone adhesive in the silicone resin is 10 to 99% by mass in terms of the solid content of the silicone adhesive in 100% by mass of the A layer. It is preferably 20 to 80% by mass, and even more preferably 30 to 80% by mass. In the present invention, a bifunctional monomer (D unit) or a trifunctional monomer (T unit) may be added as appropriate when obtaining a silicone polymer that imparts adhesiveness, and other functional groups may be added. You may add the monomer and oligomer which have. The MQ resin preferably has a structure in which the ends of a condensate of Q units are blocked with M units. The molar ratio of M units to Q units is preferably 0.4 to 1.2, more preferably 0.6 to 0.9, from the viewpoint of achieving both adhesiveness and strength of the silicone resin.

(stickiness)
In this specification, having stickiness means that the film feels sticky when touched with a finger. More specifically, in the inclined ball tack test method of the sheet test method using JIS Z0237-14 adhesive tape, the ball number is preferably 1 or more, more preferably 2 or more at an inclination angle of 30 degrees. The upper limit of the ball number obtained by the inclined ball tack test method is not particularly limited, and is preferably 32 or less, more preferably 10 or less. When the membrane of the present invention has adhesiveness within this range, the biofilm on the membrane is less likely to peel off, and the wastewater treatment performance is improved or stabilized.

<Third Embodiment>
The nitrogen compound-containing wastewater treatment apparatus 100b of the present embodiment is a batch-type wastewater treatment apparatus that utilizes the action of nitrifying bacteria to decompose at least one nitrogen compound component in the nitrogen compound-containing wastewater to purify the wastewater. is. As shown in FIG. 11, the nitrogen compound-containing wastewater treatment apparatus 100b includes a nitrogen compound-containing wastewater treatment tank 510 and a gas supply body 10b. , a bottomed container in which nitrogen compound-containing wastewater W is stored, provided with a hole 511 for exchanging treated water, and sealed with a lid provided with a gas supply member 10b. A hole 511 for replacing treated water is sealed with a plug 512 . Stopper 512 may include a bag for internal venting. The nitrogen compound-containing wastewater W is appropriately replaced after treatment. The volume of the nitrogen compound-containing wastewater treatment tank 510 is not particularly limited, but may be, for example, a volume of 100 mL or more and 1 L or less.

The gas supplier 10b of the third embodiment is the same as the gas supplier 10a of the second embodiment, except that it does not have a gas delivery layer 12, as shown in FIG.

(Example)
The invention is illustrated, but not limited, by the following examples.

(Example 1)
A wastewater treatment apparatus 100b having the configuration of the third embodiment was produced. The nitrogen compound-containing wastewater batch treatment apparatus has a nitrogen compound-containing wastewater treatment tank 510 with a volume of 0.3675 L, a gas supply body 10b having a surface area of 0.0049 m ² at the part immersed in the treatment tank 510, and one sheet installed at the bottom. It is composed of a supply section. Artificial sewage shown in Tables 1 to 5 was used as wastewater. Wastewater was fed such that the TN volume loading was about 77 g/m ³ /3day. Oosan Aid No. 1 manufactured by Nagao Co., Ltd. was used as a microbial preparation for nitrification reaction containing nitrifying bacteria. Oosan Aid No. 1 was seeded so as to be 50 wt% of the initial seeding activated sludge. In Example 1, the gas supplier 10b is composed of a microorganism-supporting layer 213, a gas-permeable non-porous layer 212, and a substrate 211 in this order from the outermost layer in contact with wastewater. As the base material 211, a microporous membrane sheet included in Cellpore NW07H manufactured by Sumika Sekisui Film Co., Ltd. was used. A gas permeable non-porous layer 212 was formed on the substrate 211 . The gas-permeable nonporous layer 212 is formed by applying a mixture of a methylvinyl-based silicone resin, a cross-linking agent, a platinum-based catalyst, etc. using a bar coater, and then leaving it to stand in an atmosphere of 70° C. for 1 hour. Thus, it was formed. The methylvinyl-based silicone resin contains an adhesive resin. The laminate of the gas permeable non-porous layer 212 on the base material 211 was measured by the inclined ball tack test method of the sheet test method using JIS Z0237-14 adhesive tape. The measurement result was a ball number of 1 or more at an inclination angle of 30 degrees. Microbial support layer 213 was placed on the outside of gas permeable non-porous layer 212 . The microorganism support layer 213 is a laminate of non-woven fabrics (weight per unit area: 10 g/m ² , thickness: 25 μm). A gas supply is placed in contact with air from which oxygen is supplied.

(Comparative example 1)
It is the same as Example 1 except that only activated sludge was seeded as the initial seeding sludge.
(Comparative example 2)
The procedure was the same as in Example 1, except that only Fish Aid No. 1 (nitrifying bacteria) was seeded as the initial seeding sludge.

(Nitrogen compound measurement method)
Each nitrogen compound was measured according to each nitrogen compound test method described in the sewage test method of the Japan Sewage Works Association.

(result)
As shown in Table 6, comparing Example 1, Comparative Example 1, and Comparative Example 2 with the same STN volume load of about 77 g/m ³ /3day, the STN removal rate was 61. % and 36% higher results were obtained.

以上、本開示の実施形態を説明したが、特許請求の範囲に記載された本開示の趣旨及び範囲から逸脱することなく、形態や詳細の多様な変更が可能なことが理解されるであろう。

Although embodiments of the present disclosure have been described above, it will be appreciated that various changes in form and detail may be made without departing from the spirit and scope of the present disclosure as set forth in the appended claims. .

100, 100a, 100b waste water treatment apparatus 10, 10a, 10b gas supply 12 gas delivery layer 21, 210 waterproof gas permeable membrane 211 substrate 212, 212a gas permeable nonporous layer 213 microorganism supporting layer 51, 510 nitrogen compound-containing waste water Treatment tank, reaction tank

Claims (10)

A wastewater treatment apparatus for treating wastewater containing nitrogen compounds by supplying oxygen to nitrifying bacteria,
a reactor for treating wastewater;
a gas feed disposed submerged in waste water in the reaction vessel;
The gas supply body supplies the gas containing oxygen to the wastewater from the inside, and supports the nitrifying bacteria on the outer surface in contact with the wastewater.
Wastewater treatment equipment. The gas supplier has a waterproof gas permeable membrane on the outer surface in contact with the waste water.
A wastewater treatment apparatus according to claim 1. The waterproof air permeable membrane is microbial adhesive,
A waste water treatment apparatus according to claim 2. wherein the gas supplier is plural;
A wastewater treatment apparatus according to any one of claims 1 to 3. A wastewater treatment method comprising introducing wastewater containing a nitrogen compound into a reaction tank in which a gas supplier is installed and treating the wastewater,
supplying waste water and a microbial preparation containing nitrifying bacteria to the reaction tank, immersing the gas supplier in the waste water;
supplying a gas containing oxygen to the inside of the gas feed immersed in wastewater, allowing the gas to migrate to the outer surface of the gas feed and feed the nitrifying bacteria;
Wastewater treatment method. The gas supply has a waterproof gas permeable membrane on the outer surface in contact with the waste water.
The wastewater treatment method according to claim 5. The waterproof air permeable membrane is microbial adhesive,
The wastewater treatment method according to claim 6. wherein the gas supplier is plural;
The wastewater treatment method according to any one of claims 5-7. When initially supplying waste water to the reaction tank, the nitrifying bacteria are supplied at the same time.
The wastewater treatment method according to any one of claims 5-8. Supplying 50 wt% of the nitrifying bacteria with respect to the amount of activated sludge at the time of initial acclimatization,
The wastewater treatment method according to any one of claims 5-9.

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