JP6941830B2 - Anaerobic membrane separation activated sludge device - Google Patents

Description

The present invention relates to an anaerobic membrane separation activated sludge apparatus using MBR (Membrane Bioreactor, membrane separation activated sludge method) under anaerobic conditions.

MBR (Membrane Separation Activated Sludge Method) is known as a method for treating wastewater containing organic substances. Specifically, in the food industry, wastewater treatment methods such as urine treatment, a method of immersing a filtration membrane in activated sludge and drawing out the treated water, and the filtration membrane is agitated and washed by bubbling air.

In the stainless steel manufacturing process of a steel mill, there is a process of pickling the surface of a stainless steel sheet. Since the flush wastewater contains ammonia nitrogen and nitrate nitrogen, the nitrogen is removed by the dedicated wastewater treatment facility in the facility, and after confirming that the water quality is below the agreed value, the treated water is discharged to the public sea area. There is. For nitrogen removal, a method using biological treatment utilizing the action of microorganisms is common.

In the conventional stainless steel washing wastewater treatment method, as shown in the biological treatment flow chart in FIG. 6, pretreatment is performed using a raw water tank, a reaction tank, a adjusting tank, a settling tank and a raw water tank. In the pretreatment, a pH adjuster, a coagulant, or the like is used to precipitate the precipitate in the raw water, and the precipitate is removed as much as possible, and the obtained raw supernatant raw water is obtained in the raw water tank.
The pretreated raw water passes through the nitrification tank, the denitrification tank, and the reaeration tank from the raw water tank, obtains the supernatant from the settling tank, and is discharged to the outside as treated water. The pretreated raw water is nitrified in a nitrification tank to obtain nitrogen nitrate (NO ₃ ^- N) or nitrogen nitrite (NO ₂ ^- N), and hydrogen such as methanol and organic substances are added in the denitrification tank to cause denitrification. Biological treatment is performed, and the denitrification step shown by the chemical formula in FIG. 2 is performed to obtain N ₂ gas. After the denitrification step, the treated water is obtained through a re-aeration tank and a settling tank that remove too much methanol.
Such conventional biological treatment has the following problems.
1) There is a risk that clear water quality cannot be obtained.
In order to retain the activated sludge in the biological treatment in the reaction tank, the activated sludge is settled and separated in a settling basin (sedimentation tank) and returned to the reaction tank. Therefore, if the sludge is not sufficiently precipitated, carryover (sludge outflow) may occur and the amount of suspended solids in the treated water may increase.
2) A vast installation area is required.
As described above, in biological treatment, it is common to install a settling basin (sediment tank) for sedimentation separation from activated sludge. Therefore, a certain installation area or more is required to obtain an appropriate settling time.
3) Difficult to maintain.
Since the number of facilities is large, there are many management items. Also, unlike simple coagulation sedimentation treatment, it is necessary to control the amount of biomass and sludge.

Patent Document 1 describes "a biological treatment method in which a biological treatment step of biologically treating water to be treated containing calcium phosphate with activated sludge is carried out, and water containing activated sludge is membrane-separated. A method for adjusting the pH to a specific range (claim 1) ”is described. The object to be treated is water containing inorganic particles, organic compounds, etc., and "By adjusting to a predetermined pH range, membrane separation can be performed in a state where inorganic particles such as calcium phosphate particles are dissolved (Patent Document 1). (See [0038]). " It is also described that a gas containing oxygen (for example, air) is supplied from the air diffuser 52 below the membrane separation device 51 (see Patent Document 1 [0022]).

Patent Document 2 describes a method of depleting oxygen in an aerobic gas, supplying it as an anaerobic gas, and circulating it in a processing apparatus in which aerobic treatment and anaerobic treatment are alternately or intermittently performed. A method of cleaning the separation membrane with a sex gas is described. This method cannot be applied to the method of performing anaerobic treatment without performing aerobic treatment.

On the other hand, it has been considered difficult to apply the MBR for the purpose of removing nitrogen. In the membrane separation device, it is essential to take measures to prevent clogging of the membrane by cleaning the membrane surface for a certain period of time or continuously. Generally, a means such as blowing air on the surface of the film or blowing air from the lower part is used. However, since it is necessary to have a low oxygen concentration state in order to maintain the anaerobic condition, it is difficult to carry out solid-liquid separation by a membrane while maintaining the anaerobic condition because it contradicts the act of blowing air. rice field. There are no known devices for biological treatment with activated sludge under anaerobic conditions and / or membrane separation between activated sludge and treated water under anaerobic conditions.

Japanese Patent No. 4612078 Japanese Unexamined Patent Publication No. 2000-117278

An object of the present invention is to operate MBR under anaerobic conditions, which has been used under aerobic conditions including some anaerobic conditions, for treating organic matter-containing wastewater such as urine and food factories, and to use anaerobic bacteria. An attempt is made to provide an anaerobic membrane separation activated sludge apparatus.

The problems of the present invention can be solved by the following devices and methods.
(1) Membrane-treated water by separating a reaction tank that performs biological treatment with activated sludge containing anaerobic microorganisms, an air diffuser that stirs the activated sludge inside the reaction tank with an inert gas, and treated water after biological treatment. An anaerobic membrane separation activated sludge device that treats wastewater containing nitrate nitrogen with a membrane separation tank.
(2) The anaerobic membrane separation activated sludge apparatus according to (1), further comprising a membrane cleaning means for cleaning the membrane surface with an inert gas.
(3) Further, it has a raw water inlet, a reaction tank, a membrane separation tank, and a membrane-treated water outlet, and supplies the inert gas from the inert gas supply means to the reaction tank and the membrane separation tank via an air diffuser. The anaerobic membrane separation active sludge device according to (1) or (2), which has an inert gas discharge pipe for maintaining the inside of the device anaerobically and discharging the supplied inert gas.
(4) The anaerobic membrane separation activated sludge apparatus according to any one of (1) to (3), wherein the inert gas is nitrogen.
(5) The anaerobic microorganisms present in the active sludge are nitrate-reducing bacteria belonging to the genus Dokdonella of the family Xanthomonadaceae, and Methyloversatilis of the family Rhodocyclaceae. ) Nitrate-reducing bacteria belonging to the genus, Nitrate-reducing bacteria belonging to the genus Methylophilus of the family Methylophilaceae, the genus Azohydromonas and the genus Caldimonas of the order Burkholderiales. Any of (1) to (4), which is at least one nitrate-reducing bacterium selected from the group consisting of nitrate-reducing bacteria belonging to the genus Fluviicola belonging to the genus Fluviicola of the Flavobacteriia family. The anaerobic membrane separation active sludge apparatus according to 1.
(6) When the type and amount of anaerobic microorganisms in the activated sludge were determined by microbial community flora analysis, Dokdonella immobilis and Methyloversatilis universalis, which have been reported to have nitrate reducing ability, were reported. , Methylophilus sp., Azohydromonas lata, Fluviicola taffensis, Dyella sp., And Caldimonas hydrothermale, at least selected from the group. The anaerobic membrane-separating activated sludge apparatus according to any one of (1) to (5), wherein one nitrate-reducing bacterium significantly increases during the operating period of the treatment apparatus.

(7) A step of biologically treating water to be treated containing nitrate nitrogen while stirring activated sludge containing anaerobic microorganisms with an inert gas, and a membrane treatment by separating the treated water after biological treatment into a membrane. An anaerobic membrane separation activated sludge method comprising a step of obtaining water.
(8) The anaerobic membrane separation activated sludge method according to (7), wherein the inert gas further cleans the membrane surface.
(9) The anaerobic membrane separation activated sludge method according to (7) or (8), wherein the water to be treated containing nitrate nitrogen is stainless steel pickled wastewater.
(10) The anaerobic membrane separation activated sludge method according to any one of (7) to (9), wherein the inert gas is nitrogen gas which is a by-product of an oxygen plant obtained in the steel manufacturing process.
(11) The method or apparatus of the present invention is preferably a substantially sealed device, and is a high-purity nitrogen gas described later {the oxygen concentration in the gas is preferably less than 10,000 ppm (1 vol%), more preferably 1,000. It is preferable to introduce ppm (less than 0.1 vol%)} from the outside of the device and release it to the outside after cleaning the membrane. As the inert gas that separates the biotreated water into a membrane and cleans the membrane surface, it is preferable to introduce the above-mentioned high-purity nitrogen gas from the outside.

Since the anaerobic membrane separation activated sludge apparatus of the present invention can use the membrane separation activated sludge method for removing nitrogen, at least one of the following effects can be obtained.
1) The treated water is obtained in a completely solid-liquid separated state.
Since membrane separation is used, activated sludge can be completely removed from the treated water. Therefore, the removal performance of pollutants is improved as compared with the conventional sedimentation treatment method, and extremely clear treated water containing no suspension can be obtained. Alternatively, advanced removal of pollutants such as nitrogen, phosphorus and organic substances contained in suspended solids can be expected.
2) The installation area of the facility can be reduced.
Since the treatment process such as the final settling basin, which is required in the conventional activated sludge method, can be omitted, the installation space can be significantly reduced. It can also contribute to the reduction of construction costs.
3) Easy operation management Since there is no final sedimentation basin, there is no need to pay attention to bulking (a phenomenon in which sludge is difficult to settle and clear water is difficult to obtain) and the sludge interface, and the burden of sludge management is eliminated. In addition, since the main operation management items are the amount of permeated water and the membrane differential pressure by automatic measurement, it is easy to incorporate automatic control operation and operation management is easy.
4) Reduction of generated sludge amount, high concentration treatment, shortening of treatment time Since there is no final settling basin, sludge carryover does not occur. Therefore, since the amount of biomass can be maintained high and the sludge retention time is long, it is expected that the amount of sludge generated by the autolysis of sludge will be reduced. In addition, since the biomass is high, it is possible to deal with high-concentration waste liquid.

It is a schematic diagram explaining the experimental apparatus of the anaerobic membrane separation activated sludge apparatus of this invention used in an Example. It is a schematic diagram which shows the outline of the denitrification process. It is a graph which shows the transition of the TN (nitrate total nitrogen) amount and the total organic carbon amount during the experiment period of an Example. It is a graph which shows the relationship between the transition (relative increase amount) of 2 species out of 9 species which increased among the bacterial dominant species during the experimental period of the example, and the transition of the TN (nitrate total nitrogen) amount. FIG. 5 is a graph showing the transition of the TN (nitrate total nitrogen) amount shown in FIG. 4 by enlarging the scale of the relative abundance of 7 types of bacteria of de novo25716 or less among the 9 types of bacteria increased in the examples. be. The scale of the amount of TN (total nitrate nitrogen) is the same as in FIG. It is a flow chart which shows the conventional biological treatment.

The apparatus of the present invention will be described below with reference to FIG. 1, but the drawings are an example, and the apparatus of the present invention is not limited to the structure described in the drawings.

The apparatus of the present invention includes a reaction tank 3 for biological treatment with activated sludge 2 containing anaerobic microorganisms, an air diffuser pipe 6 for stirring the activated sludge 2 inside the reaction tank 3 with an inert gas from a bubbling pipe 5, and biological treatment. An anaerobic membrane separation activated sludge device 10 for treating wastewater containing nitrate nitrogen, which has a membrane separation tank 8 for separating the treated water afterwards with a membrane module 9 to obtain a membrane treated water 25. The inert gas that agitates the activated sludge 2 keeps the inside of the apparatus in an anaerobic state. The inert gas is not particularly limited as long as it is a gas that does not contain oxygen and does not harm bacteria, but nitrogen, argon, helium and the like can be exemplified, and a mixture thereof may be used. Among the inert gases, high-purity nitrogen gas is preferable, and the oxygen concentration at that time is preferably less than 10,000 ppm (1 vol%), preferably less than 1,000 ppm (0.1 vol%). Such high-purity nitrogen gas can be obtained from air by a deep cold separation method, a PSA separation method, a membrane separation method, or the like. In particular, the deep cold separation method is suitable because it can generate a large amount of high-purity nitrogen of 100 ppm (0.01 vol%) or less. Further, the gas production device by the deep cold separation method is preferably used in a factory such as a steel mill that requires a large amount of oxygen gas for refining, and a large amount of high-purity nitrogen is generated as a by-product at that time, which is suitable. Is.
Further, the apparatus of the present invention preferably has the membrane cleaning means 7 for cleaning the membrane surface with an inert gas. The membrane cleaning means 7 cleans the membrane surface to keep the membrane surface clear, and keeps the inside of the membrane module 9 and the membrane separation tank 8 more anaerobic.
The apparatus of the present invention further has an inlet 21 for raw water, a reaction tank 3, a membrane separation tank 8, and an outlet 22 for the membrane-treated water 25, and the inert gas is diffused from the inert gas supply means 4 into the air diffuser 6. An anaerobic membrane separation having an inert gas discharge pipe 14 that supplies the device to the reaction tank 3 and the membrane separation tank 8 via the above, maintains the inside of the apparatus anaerobically, and preferably discharges the supplied inert gas. The active sludge device 10.
It is preferable that the apparatus of the present invention is entirely covered because air contamination can be avoided and wastewater can be easily treated under anaerobic conditions. The reaction tank 3 may further include a second reaction tank 13, and may further include two or more reaction tanks and membrane separation tanks.
The inflow port 21 may also serve as an inflow port for methanol (substrate), or may be separately provided with a methanol inflow port 12.
The activated sludge from which the membrane-treated water 25 has been drawn out by the membrane module 9 is returned to the reaction tank 3 from the inflow port 21 via the return pipe 15 as return sludge. A part of the returned sludge in the return pipe 15 may be preferably sent to a sludge storage tank (not shown) to discard the portion where the microorganisms are killed, or additional activated sludge may be added.
The reaction tanks and the membrane separation tanks are communicated with each other by communication pipes 17 and 17 having necessary structures, respectively.

The anaerobic membrane separation activated sludge method of the present invention will be described below. The method of the present invention may use the above-mentioned wastewater treatment apparatus of the present invention, but is not limited thereto.
The method of the present invention comprises a step of biologically treating the water to be treated containing nitrate nitrogen with the activated sludge containing anaerobic microorganisms while stirring the activated sludge with an inert gas, and the treated water after the biological treatment. This is an anaerobic membrane separation activated sludge method, which comprises a step of membrane separation to obtain membrane treated water.
The water to be treated of the present invention preferably contains an organic substance from the viewpoint of removing nitrogen.
By using the apparatus of the present invention, a small amount of organic matter such as methanol is added to remove nitrogen as nitrogen gas from the water to be treated containing nitrate nitrogen even in industrial wastewater having a low TOC (total organic carbon concentration) content. be able to.
The apparatus of the present invention using an inert gas can increase denitrifying bacteria even in industrial wastewater having a low TOC (total organic carbon concentration) content, as will be described later in Examples. For example, water to be treated having a TOC (total organic carbon concentration) content of 500 mmg / L or less, more preferably 100 mmg / L or less can be effectively treated.
The inert gas used in the method of the present invention preferably further cleans the membrane surface.
As the water to be treated containing nitrate nitrogen, stainless steel pickled wastewater may be used. When the raw water to be treated has other nitrogen instead of nitrate nitrogen, the pretreatment for obtaining the treated water having known nitrate nitrogen may be performed before the anaerobic membrane separation activated sludge method of the present invention. , Nitrification may be performed using a nitrification tank.
Examples of the inert gas to be used include nitrogen, argon, helium and the like, and a mixture thereof may be used. If nitrogen gas, which is a by-product of the oxygen plant obtained in the steel manufacturing process, is used, it is not necessary to use high-purity nitrogen gas, and wastewater can be treated at low cost while maintaining anaerobic conditions. The amount of the inert gas blown is, for example, 5 to 10 L / min with respect to the capacity of the reaction vessel of 10 L. Can be blown at the ratio of.

In the method of the present invention, the activated sludge apparatus of the present invention that supplies an inert gas to the reaction tank and the membrane separation tank through an air diffuser may be used. It is preferable to use nitrogen as the inert gas. The processing apparatus illustrated in FIG. 1 is composed of three tanks: a reaction tank 3, a second reaction tank 13, and a membrane separation tank for solid-liquid separation. Wastewater to be treated and methanol as a hydrogen donor are supplied to the reaction tank 3, and denitrification treatment with activated sludge is carried out in the reaction tank 3 and the second reaction tank 13. The membrane module 9 which is a solid-liquid separation device is immersed in the membrane separation tank, and the treated water after the membrane separation and the activated sludge are separated in the membrane separation tank.

Nitrogen gas is supplied through an air diffuser to stir the activated sludge in the reaction vessel and preferably to perform membrane cleaning of the membrane module. In the reaction tank 3, an air diffuser that aerates (bubbling) from the lower part of the reaction tank in the range of 5 to 10 L / min with respect to 10 L of activated sludge is preferably used. The inert gas for cleaning the membrane is preferably injected parallel to the membrane surface, and nitrogen gas is preferably supplied at 10 L / min or more for ^{an effective membrane area of 0.012 m 2.} The membrane cleaning process is an intermittent operation, for example, 9 min. The treated water was withdrawn, and then 1 min. Can be exemplified by intermittent treatment in which the withdrawal of treated water is stopped and the washing time is set.

By analyzing the microorganisms in the activated sludge at an appropriate time when the activated sludge apparatus of the present invention or the activated sludge method of the present invention is carried out, anaerobic microorganisms, particularly nitrate-reducing bacteria, sufficiently act to remove nitrogen from the treated water. Can be confirmed to be valid. The analysis of microorganisms is not particularly limited, but it is preferable to use a high-performance sequencer called a "next-generation sequencer". In the next-generation sequencer, by registering the nucleotide sequences shown in SEQ ID NOs: 1 to 9 in the sequence listing, it is possible to identify microorganisms and search for their homology in large quantities at one time, and further, it can be performed in a short time. can. Such a next-generation sequencer is not particularly limited, but for example, MiSeq manufactured by Illumina can be used, and its detection can be carried out according to the attached manual. However, it is preferable to use a PC and analysis software to acquire more accurate and detailed phylogenetic information. As the analysis software, for example, various software described later in the examples can be used.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples.

Using the anaerobic membrane separation activated sludge device 10 of the present invention shown in FIG. 1, an experiment was carried out for the purpose of removing nitrogen from water to be treated containing nitrate nitrogen. As the water to be treated, cleaning wastewater obtained by acid-cleaning the surface of a stainless steel sheet was used in the stainless steel manufacturing process of a steel mill. Nitrogen gas was used as the inert gas.
Amount of activated sludge: 28L
Return sludge amount: 28 L / day Water supply amount to be treated: 1.25 L / day Hydraulic residence time: 6 days Aeration amount is 5 L / min in reaction tank 3 and 5 L / min in reaction tank 13. , Membrane separation tank 10 L / min. It was carried out in.
The operation pattern is as follows: treated water withdrawal time 9 min, treated water stop time 1 min. It was an intermittent operation. The amount of methanol added was: 17 μL / min. , 34 μL / min. And said.

As shown in FIG. 4, May 27 was set as the 0th day, the experiment was started on the 28th, and the transition of bacterial species on June 23 (until the 27th day) was evaluated. As shown in FIG. 3, the first amount of methanol was continuously added from the 6th day, and the amount was increased on the 22nd day and each was continuously added. The DO (dissolved oxygen amount) in the treatment device during the experiment period was 0.5 mg / L or less in all of the reaction tank 3, the second reaction tank 13, and the membrane separation tank 8, and the anaerobic state in the treatment device due to nitrogen aeration. Was able to be maintained. The MLSS (Mixed Liquor Suspended Solids amount), which is an index of activated sludge, was maintained within 3000 to 4500 mg / L.
The aeration in the reaction tank was also used to circulate the activated sludge, and even in the nitrogen aeration of the present invention, the activated sludge did not settle in the lower part of the treatment apparatus, and the same aeration performance as the air aeration could be confirmed. In addition, the same membrane cleaning performance as air aeration was confirmed on the membrane surface of the membrane separation tank.

FIG. 3 shows the transition of nitrate nitrogen (TN) and total organic carbon (TOC) concentrations in the treatment liquid solid-liquid separated in the membrane separation tank. From the 6th day after the start of the experiment, the supply of methanol was started to remove nitrogen from the wastewater. Immediately after the addition of methanol, no change in nitrate nitrogen could be confirmed, and the TOC increased because methanol remained in the treatment equipment. In FIG. 4, the amount of nitrate nitrogen (TN) after the addition of methanol is indicated by ●. After the addition of methanol, the TN value reached near the peak on June 15. After that, nitrate nitrogen decreased sharply as the TOC decreased. After that, aiming at further removal of nitrate nitrogen, the amount of methanol input was 34 μl / min. Increased to. It was found that nitrate nitrogen could be completely removed 4 days after the change in the amount of methanol input, and nitrogen removal by anaerobic MBR was possible. As shown in FIG. 3, total organic carbon was almost 0 until 1 or 2 days after the addition of methanol, and rapidly increased due to the addition of methanol, reached a peak on the 15th day, and decreased sharply from the 20th day, so that on the 22nd day. The amount of methanol added was increased. Since TOC decreases with the decrease of nitrate nitrogen, it is considered that the consumption by living organisms is stable. The addition of methanol was 17 μL / min. In the first half, the addition was continued, and in the second half, the amount was increased to 34 μL / min and continued during the experimental period.

The quality of the raw water was pH 7, total nitrate nitrogen (TN) 6300 mg / L, and total organic carbon (TOC) 23 mg / L.

From this result, in order to consider the state of biological treatment during the experiment, microbial community flora analysis was performed during the experiment period.
[Microbial group analysis]
Here, the microbiota analysis with the next-generation sequencer was performed according to the following procedure.
First, a bead beater (Zirconia / Silica Beads) having an average particle size of 0.1 mm was added to a sludge sample (centrifugal precipitate) of activated sludge obtained by centrifugation. It is subjected to Shake Master, manufactured by Biomedical Science Co., Ltd., and the cells of the microorganism contained in the sludge sample are crushed.
Next, chromosomal DNA is extracted and purified from the obtained cell disruption solution by a phenol-chloroform extraction method.
Then, based on the universal primer targeting 16S rRNA of the chromosomal DNA, the primer described in Reference 1 below to which the barcode sequence for MiSeq manufactured by Illumina was added was used by the PCR (Polymerase Chain Reaction) method. The 16S rRNA gene was amplified.
Reference 1: J Gregory Caporaso et al., The ISME Journal (2012) 6, (1621-1624)

The obtained PCR augmentation by-product was removed using AM Pure magnetic beads (Beackmann coulter, A63881) and a purification magnet stand (Beackmann coulter, A32782) to remove unreacted primers and primer dimers, and then obtained. The purified product was fractionated by agarose gel electrophoresis, and only the PCR-enhancing by-product having the desired fragment length was purified using a spin column (Wizard SV Gel and PCR Clean-up System manufactured by Promega).
Next, the DNA concentration in the DNA sample was quantified using the Quant-iT PicoGreen dsDNA Assay Kit (manufactured by Thermo scientific, P11496) and the tendency spectrometer for trace amounts (manufactured by Thermo scientific, NanoDrop 3300), and required. The amount was subjected to MiSeq Reagent Kits v2 (manufactured by Illumina, MS-102-2001), and DNA sequence analysis was performed using the next-generation sequencer.
As a result, sequence data of about 50,000 to 100,000 reads were obtained from each of the DNA samples.
For the acquired sequence data, the gene sequence information is linked using the software ea-utils-1.1.2-301 (free software available on the Internet), and further, the software Mothur version 1.31.2 is used. After removing the chimeric sequence, the gene sequence was systematically analyzed by software QIIME version 1.6.0, and the relationship between the increase / decrease in the relative abundance of each microbial species and the physicochemical parameters was considered. For details of software Mothur version 1.31.2, refer to Reference 2 below, and for details of software QIIME version 1.6.0, refer to Reference 3 below.
Reference 2: Schloss PD et al., Appl.Environ.Microbiol (2009) 75,7537-7541
Reference 3: Caporaso HG et al., Nat.methods (2012) 7,335-336.

The results are shown in FIGS. 4 and 5 together with the total nitrogen content. It was found that nitrate-reducing bacteria exist as resident anaerobic microorganisms in activated sludge. Furthermore, among the 20 most dominant microorganisms at the end of the experiment (June 23), the nitrate reducing ability of those closely related species during the period from the 19th to the 27th day from the start of the experiment in which nitrate decreases. Two species closely related to Dokdonella immobilis, one species closely related to Methyloversatilis universalis and one closely related to it, one closely related to Methylophilus sp. Species, one closely related to Azohydromonas lata, one closely related to Fluviicola taffensis, one closely related to Dyella sp., And Caldimonas hydrothermale. It was found that the amount of one type of microorganism closely related to (hydrothermale) was significantly increased (increase rate: 1.7 to 48.3 times). The nucleotide sequences used to identify these nine types are shown in SEQ ID NOs: 1 to 9 in the sequence listing. Each array depends on the database. That is, it is suggested that these nitrate-reducing bacteria are involved in the oxidative decomposition of methanol accumulated and the reduced decomposition of nitrate coupled to it, and contribute to the removal of nitrate nitrogen from the activated sludge. rice field.
Table 1 below shows the relative abundance (%) of the dominant bacterial species and its hold change as of June 23.

Table 1 shows that among the 20 dominant species, the relative abundance was significant (P <0.05) as the total nitrate nitrogen (TN) decreased (on June 23 compared to the amount on June 15). The measurement results of 9 bacterial species increased in. FIG. 4 shows the transition of 2 out of 9 species that increased among the bacterial dominant species during the experimental period of the example. FIG. 5 shows an enlarged graph of the relative abundance of seven of them. Table 1 shows the abundance on June 23 with respect to the abundance on June 15 for 9 species in the column of increase rate, and shows that the increase rate was 1.7 times to 48.3 times.

Conventionally, it has been considered difficult to apply the MBR for the purpose of removing nitrogen. The reason is that it is necessary to have a low oxygen concentration state in order to maintain anaerobic conditions, which contradicts the act of blowing air to stir activated sludge and clean the membrane, so the membrane is maintained anaerobic. It was difficult to carry out solid-liquid separation by.
The present invention solves this problem for the first time, and can provide an anaerobic membrane separation activated sludge device that can be applied to MBR in wastewater treatment while maintaining anaerobic conditions, and is expected to be useful in future industrial development. Is high. The anaerobic membrane separation activated sludge method of the present invention can treat wastewater using the membrane separation method under anaerobic conditions, so that a vast settling tank facility is not required, and denitrification treatment of factory wastewater can be effectively performed by MBR. Highly useful above.

2 ... Activated sludge, 3 ... Reaction tank, 4 ... Inert gas supply means, 5 ... Bubbling pipe 6 ... Air diffuser pipe, 7 ... Membrane cleaning means, 8 ... Membrane separation tank, 9 ... Membrane module,
10 ... Anaerobic membrane separation activated sludge device 11 ... Raw water, 12 ... Methanol 13 ... Second reaction tank, 14 ... Inert gas discharge pipe, 15 ... Return pipe,
17 ... communication pipe, 21 ... inlet, 22 ... outlet, 25 ... treated water

Claims (5)

A reaction tank that performs biological treatment with activated sludge containing anaerobic microorganisms, an air diffuser that stirs the activated sludge inside the reaction tank with an inert gas, and a membrane that separates the treated water after biological treatment into a membrane to obtain membrane-treated water. An anaerobic membrane separation activated sludge device that has a separation tank and does not blow air into the treated water after biological treatment, and treats waste water containing nitrate nitrogen .
Further, it has a raw water inlet, a reaction tank, a membrane separation tank, and a membrane-treated water outlet, and the inert gas is supplied from the inert gas supply means to the reaction tank and the membrane separation tank via the diffuser pipe, and inside the apparatus. Has an inert gas discharge pipe that maintains the anaerobic condition and discharges the supplied inert gas.
The raw water inlet is provided in only one reaction vessel.
An anaerobic membrane separation activated sludge device in which the reaction vessel is covered . The anaerobic membrane separation activated sludge apparatus according to claim 1, further comprising a membrane cleaning means for cleaning the membrane surface in the membrane separation tank with an inert gas. The anaerobic membrane separation activated sludge apparatus according to claim 1 or 2 , wherein the inert gas is nitrogen. The anaerobic microorganisms present in the active sludge belong to the genus Methyloversatilis of the family Rhodocyclaceae, a nitrate-reducing bacterium belonging to the genus Dokdonella of the family Xanthomonadaceae. Nitrate-reducing bacteria belonging to, Nitrate-reducing bacteria belonging to the genus Methylophilus of the family Methylophilaceae, Nitrate reduction belonging to the genus Azohydromonas and the genus Caldimonas of the order Burkholderiales. The method according to any one of claims 1 to 3 , wherein the bacterium is at least one nitrate-reducing bacterium selected from the group consisting of a bacterium and a nitrate-reducing bacterium belonging to the Fluviicola genus of the Flavobacteriia family. Anaerobic membrane separation active sludge device. Dokdonella immobilis, Methyloversatilis universalis, and Methylophilus, whose nitrate reducing ability has been reported when the type and amount of anaerobic microorganisms in the activated sludge were determined by microbial community flora analysis. At least one selected from the group consisting of sp. (Methylophilus sp.), Azohydromonas lata, Fluviicola taffensis, Dyella sp. (Dyella sp.), And Caldimonas hydrothermale. The anaerobic membrane-separating activated sludge apparatus according to any one of claims 1 to 4 , wherein bacterial microorganisms increase at an increase rate of 1.7 times or more during the operating period of the treatment apparatus.

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