JP2019010636A - Wastewater treatment method and wastewater treatment apparatus - Google Patents

Abstract

To provide a method for treating wastewater and an apparatus for treating wastewater which can efficiently remove organic nitrogen and ammonia nitrogen in the treatment of wastewater containing organic matter and containing at least one of organic nitrogen and ammonia nitrogen.SOLUTION: The method for treating wastewater according to the present invention comprises the steps of: performing acid generation treatment to produce an organic acid from the organic matter in the wastewater to obtain acid-produced treated water having an organic acid content of 200 mg/L or more; and treating the acid-formed treated water obtained by the treatment with activated sludge treatment using aerobic direct nitrogen gasification bacteria to obtain sludge-containing treated water containing biologically treated water and activated sludge.SELECTED DRAWING: None

Description

  The present invention relates to a wastewater treatment method and wastewater treatment apparatus that contains an organic substance and contains at least one of organic nitrogen and ammonia nitrogen.

Organic waste treatment and nitrogen treatment are performed as wastewater treatment for wastewater containing at least one of organic nitrogen and ammonia nitrogen, particularly wastewater containing high concentrations of ammonia and organic matter such as food and livestock wastewater.
One of the organic matter treatments is methane fermentation treatment. Methane fermentation treatment has the advantage that it produces less sludge and saves energy.

  The methane fermentation treatment includes three reactions: a hydrolysis reaction, an acid production reaction by acid producing bacteria, and a methane fermentation reaction by methanogenic bacteria. In the hydrolysis reaction, organic substances (polysaccharides, lipids, etc.) contained in the wastewater are hydrolyzed to produce low molecular weight organic substances (monosaccharides, glycerin, long chain fatty acids, etc.). In the acid generation reaction, the low-molecular organic substances are further decomposed to produce lower fatty acids (propionic acid, butyric acid, acetic acid, etc.), alcohols, aldehydes, and the like. In the methane fermentation reaction, lower fatty acids are further decomposed to produce methane and the like. The acid production reaction and the methane fermentation reaction are each caused by anaerobic microorganisms and are performed under anaerobic conditions.

  The methane fermentation apparatus used for the methane fermentation treatment includes a one-tank apparatus that performs all reactions in a single tank, and a two-tank apparatus that performs the reaction up to the acid generation reaction and the methane fermentation reaction in separate reaction tanks. is there. A suitable pH exists in each step, and the optimum pH for the acid production reaction is 5.5 to 6.5, and the optimum pH for the methane fermentation reaction is 7 to 8. Since it is possible to manage under each optimum operating condition, a two-tank device is the mainstream. In addition, it has been proposed to install a pH meter and an oxidation-reduction potential (ORP) meter in a two-tank apparatus and perform operation management of the two-tank anaerobic treatment apparatus using pH and ORP (Patent Document 1).

As for the nitrogen treatment, stripping treatment, treatment using a nitrifying liquid circulation method, and treatment using an endogenous denitrification method are generally used.
In the treatment using the nitrification liquid circulation method, first, ammonia nitrogen in raw water (waste water) is converted to nitrite nitrogen or nitrate nitrogen under aerobic conditions by nitrifying bacteria. Thereafter, nitrite nitrogen or nitrate nitrogen is reduced to nitrogen gas under oxygen-free conditions by using organic substances as reducing power by denitrifying bacteria.

Nitrifying bacteria are a general term for ammonia-oxidizing bacteria that oxidize ammonia nitrogen to nitrite and nitrite-oxidizing bacteria that oxidize nitrite nitrogen to nitrate nitrogen. Denitrifying bacteria reduce nitrite nitrogen or nitrate nitrogen to nitrogen gas by using nitrite nitrogen or nitrate nitrogen as an electron acceptor and organic matter as an electron donor under anoxic conditions. It is a microorganism.

In recent years, as a method for treating wastewater containing ammonia at a high concentration, such as livestock and food wastewater, Alkaline Genes faecalis No. 1 capable of denitrifying ammonia nitrogen by aerobically changing to nitrogen gas. A treatment method using four strains has been proposed (Patent Document 2).
Alkaligenes faecalis no. The four strains are one type of aerobic direct nitrogen gasifying bacteria, and can aerobically directly gasify ammonia into nitrogen gas while being heterotrophic bacteria. In addition, compared with the conventional nitrifying bacteria, there is an advantage that the ammonia removal rate is high and the growth rate is high.
The digestive fluid circulation system requires two tanks, an aerobic tank (nitrification tank) and an oxygen-free tank (denitrification tank) as treatment tanks. In the treatment using 4 strains, nitrogen removal is possible only by aerobic treatment, so that there is an advantage that treatment can be performed in one tank.

  In addition, as an equipment for treating food and livestock wastewater, an ammonia removal treatment tank that performs an ammonia removal treatment using aerobic direct nitrogen gasification bacteria is provided in the latter stage of the methane fermentation treatment tank, and is generated in this treatment tank. A processing apparatus has been proposed that includes a gas lead-out path for extracting gas from a processing tank and an ammonia gas separation unit that is provided in the path and separates ammonia gas in the gas (Patent Document 3). In this treatment apparatus, ammonia contained in a high concentration in waste water (digested liquid) after methane fermentation treatment is removed by treatment with aerobic direct nitrogen gasifying bacteria and stripping treatment. Treatment performance with actual wastewater has also been confirmed.

JP 2011-115721 A JP 2002-199875 A JP 2014-50767 A

  Aerobic direct nitrogen gasifying bacteria use only organic acids as substrates. As described in Patent Document 3, when the digestive juice produced by the methane fermentation treatment is treated with an aerobic direct nitrogen gasifying bacterium, the digestive juice contains a small amount of organic acid component as a substrate. The nitrogen gasification effect of ammonia nitrogen by the direct nitrogen gasification bacteria is not sufficient. If an organic acid is added to the digestive juice, the nitrogen gasification effect is improved, but the improvement effect is not sufficient. In addition, the cost increases.

  The present invention provides a wastewater treatment method and a wastewater treatment apparatus capable of efficiently removing organic nitrogen and ammonia nitrogen in the treatment of wastewater containing organic substances and containing at least one of organic nitrogen and ammonia nitrogen. For the purpose.

The inventors of the present invention performed an acid generation treatment on the wastewater in the previous stage of the treatment in the activated sludge tank using the aerobic direct nitrogen gasifying bacteria, and the acid generation treated water was not used as a digestion solution, but the latter stage. It was found that the direct nitrogen gasification reaction can proceed efficiently and nitrogen removal can be carried out by supplying the activated sludge tank to the activated sludge tank and completing the present invention.
Here, the acid generation process is a process including a hydrolysis reaction and an acid generation reaction in the methane fermentation process.

That is, this invention has the following aspects.
[1] A method for treating wastewater containing an organic substance and containing at least one of organic nitrogen and ammonia nitrogen,
Performing an acid generation process for generating an organic acid from the organic matter in the wastewater, and obtaining an acid generation process water having an organic acid content of 200 mg / L or more (acid generation process step);
A step of performing activated sludge treatment using the aerobic direct nitrogen gasification bacteria on the acid-generated treated water obtained by the acid-generating treatment to obtain sludge-containing treated water containing biological treated water and activated sludge (activated sludge) Process)
Wastewater treatment method.
[2] The method for treating wastewater according to [1], wherein the pH of the acid-generated treated water is 5 or more and less than 8.
[3] The wastewater treatment method according to [2], wherein the pH of the wastewater is controlled to 5 or more and less than 8 during the acid generation treatment.
[4] The wastewater treatment method according to any one of [1] to [3], including a step (separation step) of performing solid-liquid separation treatment on the sludge-containing treated water using a separation unit.
[5] The wastewater treatment method according to [4], wherein the separation unit is a membrane separation unit.
[6] The wastewater treatment method according to [5], wherein the membrane separation means is provided in an activated sludge treatment tank that performs the activated sludge treatment.
[7] The wastewater treatment method according to [5], wherein the membrane separation means is provided at a subsequent stage of the activated sludge treatment tank that performs the activated sludge treatment.
[8] The wastewater treatment method according to [7], including a step (sludge return step) of returning a part of the activated sludge separated by the membrane separation unit from the membrane separation unit to the activated sludge treatment tank.
[9] Treatment of wastewater according to any one of [1] to [8], including a step (neutralization step) of neutralizing the acid generation treated water after the step of obtaining the acid generating treated water Method.
[10] The method for treating wastewater according to any one of [1] to [9], comprising a step of adding aerobic direct nitrogen gasifying bacteria to the acid generation treated water (bacterial cell addition step).
[11] The aerobic direct nitrogen gasifying bacterium is Alkalinegenes faecalis no. The wastewater treatment method according to any one of [1] to [10], which is 4 strains (FERM P-21814).
[12] An apparatus for treating wastewater containing organic matter and containing at least one of organic nitrogen and ammonia nitrogen,
An acid generation tank for performing an acid generation treatment for generating an organic acid from organic substances in the wastewater, and an acid generation treatment water having an organic acid content of 200 mg / L or more;
An activated sludge treatment tank that performs activated sludge treatment using aerobic direct nitrogen gasification bacteria on the acid produced treated water obtained by the acid producing treatment to produce biologically treated water and sludge-containing treated water containing activated sludge. When,
Including wastewater treatment equipment.
[13] The wastewater treatment apparatus according to [12], wherein the acid-generating treated water has a pH of 5 or more and less than 8.
[14] An in-tank pH measurement unit for measuring the pH of waste water in the acid generation tank, an acid addition unit for adding acid to the acid generation tank, and an alkali for adding alkali to the acid generation tank An addition unit is provided, and based on the pH measured by the in-bath pH measurement unit, an acid or an alkali is added into the acid generation tank so that the pH of the wastewater can be adjusted to 5 or more and less than 8. [13] The waste water treatment apparatus according to [13].
[15] The wastewater treatment apparatus according to any one of [12] to [14], including separation means for performing solid-liquid separation treatment on the sludge-containing treated water.
[16] The wastewater treatment apparatus according to [15], wherein the separation means is a membrane separation means.
[17] The wastewater treatment apparatus according to [16], wherein the membrane separation means is provided in the activated sludge treatment tank.
[18] The wastewater treatment apparatus according to [16], wherein the membrane separation means is provided at a subsequent stage of the activated sludge treatment tank.
[19] The wastewater treatment apparatus according to [18], including sludge return means for returning a part of the activated sludge separated by the membrane separation means from the membrane separation means to the activated sludge treatment tank.
[20] The wastewater treatment apparatus according to any one of [12] to [19], further including a neutralization tank that performs a neutralization process on the acid generation treated water after the acid generation tank.
[21] The wastewater treatment apparatus according to any one of [12] to [20], further comprising a cell addition means for adding an aerobic direct nitrogen gasification bacterium to the acid generation treated water.
[22] The aerobic direct nitrogen gasifying bacterium is alkaline genus faecalis no. The wastewater treatment apparatus according to any one of [12] to [21], which is 4 strains (FERM P-21814).

  According to the wastewater treatment method and the wastewater treatment apparatus of the present invention, organic nitrogen and ammonia nitrogen can be efficiently removed in the treatment of waste water containing organic matter and containing at least one of organic nitrogen and ammonia nitrogen. .

It is a schematic block diagram which shows the wastewater treatment apparatus of 1st embodiment of this invention. It is a schematic block diagram which shows the wastewater treatment apparatus of 2nd embodiment of this invention. It is a schematic block diagram which shows the wastewater treatment apparatus of 3rd embodiment of this invention.

Hereinafter, the present invention will be described in detail with reference to embodiments. However, the present invention is not construed as being limited to these embodiments.
In the present invention, the “organic substance” means an organic acid that becomes a substrate for an aerobic direct nitrogen gasification bacterium, and a substance (polysaccharide, lipid, etc.) that becomes an organic acid in the acid generation step. Specifically, they are polysaccharides, lipids, citric acid, and acetic acid. Among these, from the viewpoint of becoming a substrate for aerobic direct nitrogen gasifying bacteria, organic acids are preferable, and acetic acid and citric acid are more preferable.
“Organic nitrogen” means nitrogen contained in an organic component, and is generally a protein or amino acid. “Ammonia nitrogen” is an ammonium salt among nitrogen components, and includes those in which the protein and amino acid are produced by acid generation treatment.
“Aerobic direct nitrogen gasifying bacteria” are microorganisms that gasify ammonia nitrogen nitrogen heterotrophically under aerobic conditions. It is also a microorganism that converts (oxidizes) organic nitrogen to ammonia nitrogen.
In the present invention, waste water before activated sludge treatment is also referred to as `` raw water '', waste water after acid generation treatment is also referred to as `` acid generation treatment water '', waste water after methane fermentation treatment is also referred to as `` methane fermentation treatment water '', The acid-generated treated water after the activated sludge treatment is also referred to as “biologically treated water”, and the sludge-containing treated water after membrane treatment (specifically, the biologically treated water that has passed through the filtration membrane) is also referred to as “permeated water”.

"First embodiment"
<Wastewater treatment equipment>
The wastewater treatment apparatus of the present invention is an apparatus for treating wastewater containing an organic substance and containing at least one of organic nitrogen and ammonia nitrogen.
FIG. 1 is a schematic configuration diagram of a wastewater treatment apparatus 1 according to a first embodiment of the present invention. Note that the dimensional ratio in FIG. 1 is different from the actual one for convenience of explanation. The same applies to FIGS.
The wastewater treatment apparatus 1 according to this embodiment includes an acid generation tank 11, an activated sludge treatment tank 21, a fungus body addition means 30, an ammonia removal means 40, a membrane module 52 (membrane separation means), and a storage tank 61. With. The activated sludge treatment tank 21 is provided in the subsequent stage of the acid generation tank 11. The fungus body adding means 30 and the ammonia removing means 40 are respectively provided in the activated sludge treatment tank 21. The membrane module 52 is provided in the activated sludge treatment tank 21. The storage tank 61 is provided in the subsequent stage of the activated sludge treatment tank 21.

(Waste water)
The wastewater to be treated in the present invention is water to be treated discharged from factories, offices, etc., contains organic matter, and contains at least one of organic nitrogen and ammonia nitrogen. Examples of such waste water include the following.
(1) Waste water containing organic matter and organic nitrogen and not ammonia nitrogen.
(2) Waste water containing organic matter and ammonia nitrogen and not containing organic nitrogen.
(3) Waste water containing organic matter, organic nitrogen, and ammonia nitrogen.

(Acid generation tank)
The acid production tank 11 is filled with microorganisms for biological wastewater treatment (anaerobic treatment with acid producing bacteria). Specifically, the wastewater is subjected to an acid generation treatment that generates an organic acid from an organic substance, and biological wastewater treatment is performed as acid generation treatment water. The acid producing bacterium may be a known acid producing bacterium in methane fermentation.

An acid production process is a process which produces | generates an organic acid from the organic substance in wastewater, and is a process which typically performs the reaction to the front | former stage of the methane fermentation reaction in a methane fermentation process. In the acid generation treatment, a hydrolysis reaction and an acid generation reaction are performed, and an organic substance contained in the wastewater is decomposed into an organic acid (propionic acid, butyric acid, acetic acid, etc.). Therefore, the acid generation treated water contains this organic acid.
In the methane fermentation treatment, a methane fermentation reaction is further performed, and the organic acid is further decomposed. As the methane fermentation reaction proceeds, the content of organic acid decreases. Methane fermentation treated water contains no or little organic acid.
Therefore, it can be said that the acid generation treated water is obtained by acid generation treatment of waste water and contains an organic acid generated by the acid generation treatment with a content of a certain level or more.

In this invention, even if methane fermentation reaction advances after an acid production | generation reaction, as long as organic acid content is 200 mg / L or more, it treats as acid production process water.
The organic acid content in the acid generation treated water is typically the total amount of propionic acid, butyric acid and acetic acid. The organic acid content is preferably 2000 mg / L or more, more preferably 3000 mg / L or more, and particularly preferably 4000 mg / L or more.
The organic acid content in the acid generation treated water is preferably 15000 mg / L or less, particularly preferably 10,000 mg / L or less, from the viewpoint of reducing the residual organic acid in the discharged treated water (in the activated sludge treated water).
Therefore, the organic acid content in the acid generation treated water is preferably 200 to 15000 mg / L, more preferably 2000 to 15000 mg / L, further preferably 3000 to 15000 mg / L, particularly preferably 4000 to 15000 mg / L, and 4000 to 10,000 mg / L is most preferred.
Organic acids function as substrates for aerobic direct nitrogen gasifying bacteria. In particular, the organic acid produced by the acid generation treatment is useful as a substrate for aerobic direct nitrogen gasifying bacteria. When the content of the organic acid is not less than the lower limit, the nitrogen gasification effect of ammonia nitrogen by the aerobic direct nitrogen gasification bacteria is sufficiently exhibited.

Further, the acid generation treated water contains ammonia nitrogen. The ammonia nitrogen includes those originally contained in waste water and those produced by decomposition of nitrogen-containing organic substances (organic nitrogen) by acid generation treatment.
The content of ammonia nitrogen in the acid generation treated water is usually about 500 to 1000 mg / L.

One end of the first flow path 12 and one end of the second flow path 13 are connected to the acid generation tank 11. The other end of the second flow path 13 is connected to the activated sludge treatment tank 21.
The first flow path 12 is a flow path for allowing waste water discharged from a pig farm or the like to flow into the acid generation tank 11.
The second flow path 13 is a flow path for supplying the acid generation treated water generated in the acid generation tank 11 to the activated sludge treatment tank 21 at the subsequent stage. The second flow path 13 is provided with a pump 13a. When the pump 13a is operated, acid generation treated water is supplied from the acid generation tank 11 to the activated sludge treatment tank 21.

Further, the acid generation tank 11 is provided with an in-tank pH measurement unit 14, an acid addition unit 15, and an alkali addition unit 16. Further, the in-tank pH measurement unit 14, the acid addition unit 15, and the alkali addition unit 16 are each connected to a control unit 17.
The tank pH measurement unit 14, the acid addition unit 15, and the alkali addition unit 16 are means for monitoring and controlling the pH in the acid generation tank 11. The pH affects the ease of the acid production reaction and the difficulty of the methane fermentation reaction. By monitoring the pH in the acid generation tank 11 and controlling the pH so that the acid generation reaction is easy to proceed and the methane fermentation reaction is difficult to proceed, the methane fermentation reaction proceeds and the organic acid content decreases. This can be suppressed.

The in-tank pH measurement unit 14 measures the pH of the wastewater in the acid generation tank 11. Various pH measuring devices can be used as the in-tank pH measuring unit 14.
The acid addition unit 15 adds an acid to the acid generation tank 11. The acid addition unit 15 includes an acid storage tank 15a, an acid supply channel 15b, and a pump 15c provided in the acid supply channel 15b. By operating the pump 15 c, the acid (acid solution or the like) in the acid storage tank 15 a is added to the acid generation tank 11.
The alkali addition unit 16 adds an alkali to the acid generation tank 11. The alkali addition unit 16 includes an alkali storage tank 16a, an alkali supply channel 16b, and a pump 16c provided in the alkali supply channel 16b. By operating the pump 16c, the alkali (alkali solution or the like) in the alkali storage tank 16a is added to the acid generation tank 11.

The control unit 17 controls the acid addition unit 15 and the alkali addition unit 16 based on the pH measured by the in-tank pH measurement unit 14 so that the pH of the waste water in the acid generation tank 11 is within a range of 5 or more and less than 8. Configured to maintain.
The pH suitable for the acid production reaction is in the range of 5 or more and less than 8, particularly in the range of 5.5 or more and 6.5 or less. By maintaining the pH of the wastewater in the acid generation tank 11 within this range, the acid generation reaction proceeds well. When the pH of the wastewater in the acid generation tank 11 is maintained within the above range, the pH of the acid generation treated water to be generated is also within the above range.
The control unit 17 may include an arithmetic processing unit such as a CPU (Central Processing Unit).

The operation of the control unit 17 will be described.
When the pH (pH of waste water in the acid generation tank 11) input from the in-tank pH measurement unit 14 to the control unit 17 is higher than the upper limit of the preferable pH range set in advance, the control unit 17 controls the pump 15c. The operation is started, and the acid in the acid storage tank 15a is caused to flow into the acid generation tank 11 via the acid supply channel 15b. Thereafter, when the pH input from the in-tank pH measurement unit 14 to the control unit 17 falls within the preferable pH range, the operation of the pump 15c is stopped.
On the other hand, when the pH input from the in-bath pH measuring unit 14 to the control unit 17 is lower than the lower limit of the preferred pH range, the control unit 17 starts the operation of the pump 16c and the alkali in the alkali storage tank 16a. Is allowed to flow into the acid generation tank 11 via the alkali supply channel 16b. Thereafter, when the pH input from the in-tank pH measurement unit 14 to the control unit 17 falls within the preferable pH range, the operation of the pump 16c is stopped.
Note that the operation of the pumps 15c and 16c may be manually switched based on the pH measured by the in-tank pH measurement unit 14 without providing the control unit 17.

  The acid generation tank 11 is preferably provided with means for monitoring and controlling conditions such as the temperature in the acid generation tank 11 and the oxidation-reduction potential. Although these conditions have less influence than pH, they affect the ease of the acid generation reaction and the difficulty of the methane fermentation reaction, similarly to pH. By monitoring these conditions and controlling the conditions so that the acid generation reaction is easy to proceed and the methane fermentation reaction is difficult to proceed, the methane fermentation reaction can be prevented from proceeding and the organic acid content being reduced. .

(Activated sludge treatment tank)
The activated sludge treatment tank 21 is filled with microorganisms (activated sludge) in order to perform biological wastewater treatment (activated sludge treatment). Specifically, activated sludge treatment is performed on the acid generation treated water from the acid generation tank 11 using an aerobic direct nitrogen gasification bacterium to obtain a sludge-containing treated water containing biological treated water and activated sludge. It is.
As described above, the acid generation treated water contains an organic acid and ammonia nitrogen. In activated sludge treatment using aerobic direct nitrogen gasification bacteria, aerobic direct nitrogen gasification bacteria directly aerobically convert ammonia nitrogen into nitrogen gas using organic acid in acid generation treated water as a substrate, Denitrified acid production treated water (biologically treated water) is obtained. The aerobic direct nitrogen gasifying bacteria will be described in detail later.

The other end of the second flow path 13 is connected to the activated sludge treatment tank 21, and acid generation treated water is supplied from the acid generation tank 11 to the activated sludge treatment tank 21.
In addition, one end of a sludge extraction flow path 25 is connected to the activated sludge treatment tank 21. The sludge extraction flow path 25 is provided with a valve 25a.
The sludge extraction flow path 25 is a flow path for extracting activated sludge from the activated sludge treatment tank 21. Generally, it is assumed that the biological treatment performance is higher when the bacterial cell concentration in the activated sludge treatment tank 21 is higher. However, if the bacterial cell concentration is too high, the possibility of clogging the membrane module 52 is increased during the membrane treatment. Therefore, when the bacterial cell concentration increases too much, the bacterial cell concentration can be controlled by opening the valve 25a and discharging the activated sludge from the sludge extraction channel 25.

An air diffuser 22 is installed in the activated sludge treatment tank 21 and below the membrane module 52. The air diffuser 22 is used for maintaining the inside of the tank in an aerobic condition. In the present embodiment, the membrane module 52 is also used for cleaning.
The air diffuser 22 includes an air diffuser 22a that diffuses air into the activated sludge treatment tank 21, an introduction tube 22b that supplies air to the air diffuser 22a, and a blower 22c that supplies air.
The air diffuser 22a is not particularly limited as long as the air supplied from the blower 22c can be discharged upward, and examples thereof include a perforated single tube and a membrane type.

The activated sludge treatment tank 21 may be provided with various measuring devices (all not shown) that measure the pH, oxidation-reduction potential, water temperature, ammonia concentration, and the like of the acid generation treated water in the tank.
In particular, pH control is important in biological reactions. When the pH of the acid-generating water in the tank is acidified or alkalized, a device for adding alkali or acid is further installed to adjust the pH in the tank. Accordingly, it is preferable to add an alkali or an acid to the activated sludge treatment tank 21. As such an apparatus, the apparatus similar to the pH measurement part 14, the acid addition part 15, and the alkali addition part 16 in a tank is mentioned, for example.

(Bacteria addition means)
The cell addition means 30 adds aerobic direct nitrogen gasification bacteria to the acid generation treated water.
The microbial cell addition means 30 of this embodiment adds aerobic direct nitrogen gasification bacteria to the acid production treated water in the activated sludge treatment tank 21.
The cell addition means 30 includes a cell storage tank 31 and a cell supply channel 32.
The microbial cell storage tank 31 stores aerobic direct nitrogen gasification bacteria.
One end of the fungus body supply channel 32 is connected to the fungus body storage tank 31, and the other end is connected to the activated sludge treatment tank 21. The fungus body supply flow path 32 is provided with a pump 32a. By operating the pump 32a, the aerobic direct nitrogen gasification bacteria in the fungus body storage tank 31 are supplied into the activated sludge treatment tank 21.
The cell storage tank 31 is preferably provided with a heating or cooling mechanism (not shown) so that the temperature inside the cell storage tank 31 can be maintained at an appropriate temperature. The temperature in the tank is preferably 0 to 15 ° C. In the cell storage tank 31, means capable of culturing aerobic direct nitrogen gasification bacteria in the cell storage tank 31 (stirring means, aeration means, medium addition means, etc., all not shown). Is preferably provided.

Examples of the aerobic direct nitrogen gasifying bacterium include Alkaligenes faecalis No. 4 strains (Alcaligenes faecalis No. 4) (FERM P-21814), Alkaligenes faecalis OKK17 strain (Alcaligenes faecalis OKK17), etc .; Examples include bacteria. In addition to the above, as aerobic direct nitrogen gasifying bacteria, Rhodocox sp. CPZ24. (Rhodococcus sp. CPZ24.), Agrobacterium sp. LAD9 (Agrobacterium sp.LAD9), Pseudomonas stutzeri YZN-001 (Pseudomonas stutzeri YZN-001), Providencia retzgeri YL (Providencia rettgeri YL), etc. can be used. Any one of these aerobic direct nitrogen gasifying bacteria may be used alone, or two or more thereof may be used in combination.
As an aerobic direct nitrogen gasifying bacterium, Alkaligenes faecalis No. 1 is used in terms of culture efficiency, growth rate and denitrification efficiency. Four strains are preferred.

(Ammonia removal means)
The ammonia removing unit 40 includes a third flow path 41 and an ammonia removing device 42. One end of the third channel 41 is connected to the activated sludge treatment tank 21 and the other end is open to the atmosphere. The ammonia removing device 42 is provided on the third flow path 41.
The ammonia removing means 40 is for removing ammonia scattered from the acid generation treated water in the activated sludge treatment tank 21.
The acid generation treated water in the activated sludge treatment tank 21 contains ammonia nitrogen at a high concentration as described above. Ammonia nitrogen is converted to nitrogen gas by aerobic direct nitrogen gasification bacteria, but a part of the ammonia nitrogen is scattered from the acid generation treated water as gaseous ammonia by the stripping effect. The ammonia removing means 40 removes the scattered ammonia.
The gas containing ammonia scattered from the acid generation treated water passes through the third flow path 41, is introduced into the ammonia removing device 42, and is removed into the atmosphere after the ammonia is removed.
The ammonia removal device 42 is not particularly limited, and examples thereof include an ammonia oxidative decomposition device using a catalyst or the like, an ammonia absorption device using an absorption tower, an ammonia combustion device, and the like.

(Membrane module)
The membrane module 52 performs a solid-liquid separation process on the sludge-containing treated water containing the biologically treated water and the activated sludge generated in the activated sludge treatment tank 21.
The membrane module 52 includes a filtration membrane, and the sludge-containing treated water is solid-liquid separated (membrane treatment) into biologically treated water and activated sludge. Moreover, since the membrane module 52 is installed in the activated sludge treatment tank 21 in the present embodiment, an improvement in biodegradation treatment performance due to the concentration of cells in the activated sludge treatment tank 21 can be expected.
In addition, one end of a fourth flow path 53 is connected to the membrane module 52. The other end of the fourth channel 53 is connected to the storage tank 61. The fourth flow path 53 is provided with a pump 53a. By operating the pump 53 a, permeated water (biologically treated water) that has passed through the filtration membrane of the membrane module 52 is discharged from the membrane module 52 and supplied to the storage tank 61.

The filtration membrane is not particularly limited as long as it has filtration ability, and examples thereof include a hollow fiber membrane, a flat membrane, a tubular membrane, and a monolith membrane. Among these, a hollow fiber membrane is preferable because of its high volume filling rate.
When a hollow fiber membrane is used as the filtration membrane, examples of the material include cellulose, polyolefin, polysulfone, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and the like. Among these, as the material for the hollow fiber membrane, PVDF and PTFE are preferable from the viewpoint of chemical resistance and resistance to pH change. When a monolithic membrane is used as the filtration membrane, it is preferable to use a ceramic membrane.
The average pore size of the micropores formed in the filtration membrane is generally about 0.001 to 0.1 μm for a membrane called an ultrafiltration membrane, and about 0.1 to 1 μm for a membrane commonly called a microfiltration membrane. . In the present invention, it is preferable to use a filtration membrane having an average pore diameter within the above range (about 0.001 to 1 μm).

(Reservoir)
The storage tank 61 stores biologically treated water (permeated water) separated from activated sludge by solid-liquid separation processing.

<Wastewater treatment method>
In the wastewater treatment method using the wastewater treatment apparatus 1 shown in FIG. 1, first, wastewater discharged from a pig farm or the like is caused to flow into the acid generation tank 11 through the first flow path 12. In the acid production tank 11, acid producing bacteria are held in advance. Next, the inside of the acid generation tank 11 is maintained under anaerobic conditions, acid generating bacteria are prioritized, and acid generation processing is performed on the wastewater to obtain acid generation processing water (acid generation processing step).

  Next, the acid generation treatment water is caused to flow from the acid generation tank 11 to the activated sludge treatment tank 21 through the second flow path 13. Next, the aerobic direct nitrogen gasification bacteria are added to the acid generation treated water in the activated sludge treatment tank 21 by the fungus body addition means 30 (bacterial cell addition step). Moreover, the air diffuser 22 in the activated sludge treatment tank 21 is operated, the inside of the tank is maintained in an aerobic condition, the activated sludge treatment is performed on the acid generation treated water, and the sludge containing treated water is obtained (activated sludge treatment). Process).

  In the activated sludge treatment process, the ammonia nitrogen in the acid generation treated water is converted to nitrogen gas by aerobic direct nitrogen gasification bacteria, and nitrogen is removed from the acid generation treated water. At this time, the organic acid in the acid generation treated water is consumed by the aerobic direct nitrogen gasifying bacteria. Moreover, a part of ammonia nitrogen is scattered from acid generation treated water as gaseous ammonia by the stripping effect. Therefore, the gas containing the scattered ammonia is introduced from the activated sludge treatment tank 21 to the ammonia removing device 42 through the third channel 41, and the ammonia is removed by the ammonia removing device 42 (sprayed ammonia removing step). The gas from which the ammonia has been removed is then released into the atmosphere.

Next, the pump 53a is operated to depressurize the inside of the membrane module 52, thereby performing a solid-liquid separation process on the sludge-containing treated water in the activated sludge treatment tank 21 (separation process). In the present embodiment, the separation step is performed in the activated sludge treatment tank 21.
At the time of solid-liquid separation, air is introduced from the air diffuser 22 into the membrane module 52, and the activated sludge and the biologically treated water are efficiently solid-liquid while washing the surface of the membrane of the membrane module 52 by air scrubbing. Can be separated.
The biologically treated water (permeated water) that has permeated through the filtration membrane of the membrane module 52 is supplied from the membrane module 52 to the storage tank 61 via the fourth channel 53 and stored.

It is preferable to perform an acid production | generation process process on the conditions on which an acid production | generation reaction advances easily and methane fermentation reaction does not advance easily. In the methane fermentation reaction, the organic acid generated in the acid generation reaction is further decomposed, and the content of the organic acid that becomes a substrate for the aerobic direct nitrogen gasification bacteria is reduced.
Examples of conditions that affect the ease of the acid production reaction and the difficulty of the methane fermentation reaction include pH and temperature. The influence of pH is particularly great.

As described above, the pH in the acid generation reaction is preferably in the range of 5 or more and less than 8, and is preferably in the range of 5.5 or more and 6.5 or less. If the pH is less than 8, the methane fermentation reaction is difficult to proceed. If pH is 5 or more, acid-producing bacteria are not easily damaged.
Therefore, in the acid generation treatment step, it is preferable to maintain the pH of the wastewater in the acid generation tank 11 within the range of 5 or more and less than 8, particularly within the range of 5.5 or more and 6.5 or less.
In order to set the pH within the above range, in the acid generation treatment step, for example, the pH of the wastewater in the acid generation tank 11 is constantly measured by the in-tank pH measurement unit 14, and an acid or alkali is added as necessary. .

  The temperature in the acid generation reaction (the temperature in the acid generation tank 11) is typically 20 ° C. or higher and lower than 40 ° C., and preferably 25 to 37 ° C. If the temperature is lower than 20 ° C, the activity may be lost, and if it is 40 ° C or higher, the bacteria may be killed.

  In the cell addition process, the amount of aerobic direct nitrogen gasification bacteria added is determined by the amount of dried aerobic direct nitrogen gasification bacteria per volume of acid-producing water from the viewpoint of nitrogen removal performance and cell sedimentation separation. The amount by which the mass concentration is 2,000 to 20,000 mg / L is preferred.

In the activated sludge treatment step, the bacterial cell concentration in the activated sludge treatment tank 21 is preferably 2000 to 20000 mg / L, more preferably 5000 to 10000 mg / L, as MLSS (Mixed Liquor Suspended Solid) concentration.
The pH in the activated sludge treatment tank 21 is preferably 7-9.
The temperature in the activated sludge treatment tank 21 is preferably 20 to 35 ° C.

<Effect>
In the wastewater treatment apparatus and wastewater treatment method of the first embodiment of the present invention described above, acid generation treatment is performed on the wastewater, and aerobic direct nitrogen is obtained for the obtained acid generation treatment water. Activated sludge treatment using gasified bacteria. Compared to methane fermentation treated water, the acid-generated treated water has a higher content of organic acids that are good substrates for aerobic direct nitrogen gasifying bacteria. Therefore, in the activated sludge treatment, aerobic direct nitrogen gasification bacteria can be efficiently acted without additional organic acid addition, and nitrogen can be efficiently removed.
Therefore, the biologically treated water obtained by the solid-liquid separation treatment with respect to the sludge-containing treated water generated by the activated sludge treatment has a sufficiently low nitrogen content.

In particular, in the present embodiment, since the separation means used for the solid-liquid separation treatment is the membrane module 52 (membrane separation means) provided in the activated sludge treatment tank 21, the aerobic direct from the activated sludge treatment tank 21. Nitrogen gasifying bacteria do not easily flow out, and the amount of cells in the activated sludge treatment tank can be sufficiently maintained. Therefore, the aerobic direct nitrogen gasification bacteria can be made to act more efficiently, and the efficiency of nitrogen removal is more excellent.
In the present embodiment, the ammonia removal means 40 removes the ammonia scattered from the acid generation treated water. Therefore, it is possible to suppress the scattered ammonia from re-dissolving in the acid generation treated water and increasing the concentration of ammonia nitrogen, and the nitrogen removal efficiency is further improved.

"Second embodiment"
<Wastewater treatment equipment>
FIG. 2 is a schematic configuration diagram of the wastewater treatment apparatus 2 according to the second embodiment of the present invention. In the embodiment described below, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
The wastewater treatment apparatus 2 of the present embodiment includes an acid generation tank 11, an activated sludge treatment tank 21, a fungus body addition means 30, an ammonia removal means 40, a membrane separation means 50, a sludge return means 55, and a storage. A tank 61. The activated sludge treatment tank 21 is provided in the subsequent stage of the acid generation tank 11. The fungus body adding means 30 and the ammonia removing means 40 are respectively provided in the activated sludge treatment tank 21. The membrane separation means 50 is provided in the subsequent stage of the activated sludge treatment tank 21. The sludge return means 55 communicates between the membrane separation means 50 and the activated sludge treatment tank 21. The storage tank 61 is provided in the subsequent stage of the membrane separation means 50.
The membrane separation means 50 includes a membrane separation tank 51, a membrane module 52 installed in the membrane separation tank 51, and a membrane cleaning air diffuser 54 installed below the membrane module 52.

(Acid generation tank)
The acid generation tank 11 of the present embodiment is the same as the acid generation tank 11 of the first embodiment.

(Activated sludge treatment tank)
The activated sludge treatment tank 21 of the present embodiment is that the membrane module 52 is not provided in the tank, one end of the fifth flow path 27 is connected, and the sludge return flow path 55a of the sludge return means 55. The activated sludge treatment tank 21 of the first embodiment is the same as that of the first embodiment except that one end thereof is connected. The other end of the fifth flow path 27 is connected to the membrane separation tank 51 of the membrane separation means 50.
The fifth flow path 27 is a flow path for allowing the activated sludge-containing water in the activated sludge treatment tank 21 to flow into the membrane separation tank 51.

(Bacteria addition means)
The microbial cell addition means 30 of this embodiment is the same as the microbial cell addition means 30 of the first embodiment.

(Ammonia removal means)
The ammonia removal means 40 of this embodiment is the same as the ammonia removal means 40 of the first embodiment.

(Membrane separation means)
The membrane separation tank 51 stores sludge-containing treated water containing activated sludge and biological treated water sent from the activated sludge treatment tank 21.
The membrane module 52 of the present embodiment is the same as the membrane module 52 of the first embodiment.
The air diffuser 54 includes an air diffuser tube 54a that diffuses air into the membrane separation tank 51, an introduction tube 54b that supplies air to the air diffuser tube 54a, and a blower 54c that supplies air. As the diffuser tube 54a, the same one as the diffuser tube 22a of the diffuser 22 of the first embodiment can be used.

(Sludge return means)
The sludge return means 55 returns a part of the activated sludge separated by the membrane separation means 50 from the membrane separation means 50 to the activated sludge treatment tank 21.
The sludge return means 55 includes a sludge return flow path 55a and a pump 55b provided in the sludge return flow path 55a. The sludge return flow path 55 a is a flow path for discharging a part of the sludge-containing treated water in the membrane separation tank 51 from the membrane separation tank 51 and allowing it to flow into (be supplied to) the activated sludge treatment tank 21. By operating the pump 55b, a part of the sludge-containing treated water in the membrane separation tank 51 can be returned from the membrane separation tank 51 to the activated sludge treatment tank 21.

(Reservoir)
The storage tank 61 of this embodiment is the same as the storage tank 61 of the first embodiment.

<Wastewater treatment method>
In the wastewater treatment method using the wastewater treatment apparatus 2 shown in FIG. 2, first, wastewater discharged from a pig farm or the like is caused to flow into the acid generation tank 11 via the first flow path 12. In the acid production tank 11, acid producing bacteria are held in advance. Next, the inside of the acid generation tank 11 is maintained under anaerobic conditions, and acid generation treatment is performed on the wastewater to obtain acid generation treatment water (acid generation treatment step).

  Next, the acid generation treatment water is caused to flow from the acid generation tank 11 to the activated sludge treatment tank 21 through the second flow path 13. Next, the aerobic direct nitrogen gasification bacteria are added to the acid generation treated water in the activated sludge treatment tank 21 by the fungus body addition means 30 (bacterial cell addition step). Moreover, the air diffuser 22 in the activated sludge treatment tank 21 is operated, the inside of the tank is maintained in an aerobic condition, the activated sludge treatment is performed on the acid generation treated water, and the sludge containing treated water is obtained (activated sludge treatment). Process).

  In the activated sludge treatment process, as described above, a part of the ammonia nitrogen is scattered from the acid generation treated water as gaseous ammonia by the stripping effect. Therefore, the gas containing the scattered ammonia is introduced from the activated sludge treatment tank 21 to the ammonia removing device 42 through the third channel 41, and the ammonia is removed by the ammonia removing device 42 (sprayed ammonia removing step). The gas from which the ammonia has been removed is then released into the atmosphere.

Next, the activated sludge-treated acid generation treated water (biologically treated water) is allowed to flow into the membrane separation tank 51 through the fifth channel 27 as activated sludge-containing treated water. A solid-liquid separation process is performed on the sludge-containing treated water in the membrane separation tank 51 by operating the pump 53a and reducing the pressure in the membrane module 52 (separation process).
When solid-liquid separation is performed, air is introduced into the membrane module 52 from the air diffuser 54, so that the solid-liquid separation can be efficiently performed while the surface of the filtration membrane of the membrane module 52 is washed by air scrubbing.
Further, part of the activated sludge-containing water in the membrane separation tank 51 is returned to the activated sludge treatment tank 21 by the sludge return means 55 (sludge return step).
The biologically treated water (permeated water) that has permeated through the filtration membrane of the membrane module 52 is supplied from the membrane module 52 to the storage tank 61 via the fourth channel 53 and stored.

Preferred conditions in each of the acid generation treatment step, the fungus body addition step, and the activated sludge treatment step are the same as the wastewater treatment method of the first embodiment.
In the sludge return step, the amount of returned sludge from the membrane separation means 50 to the activated sludge treatment tank 21 is generally preferably 1 to 5 times the amount of treated water.

<Effect>
In the wastewater treatment apparatus and wastewater treatment method of the second embodiment of the present invention described above, acid generation treatment is performed on the wastewater, and aerobic direct nitrogen is obtained with respect to the acid generation treatment water obtained. In order to perform activated sludge treatment using gasified bacteria, the aerobic direct nitrogen gasifying bacteria can be efficiently removed without adding additional organic acid during the activated sludge treatment as in the first embodiment. Therefore, nitrogen can be removed efficiently.

Moreover, in this embodiment, since the solid-liquid separation process is performed in the membrane separation tank 51 subsequent to the activated sludge treatment tank 21, compared with the case where the solid-liquid separation process is performed in the activated sludge treatment tank 21. There are advantages that the maintenance of the amount of cells and the stabilization of the treated water are easy.
In particular, in this embodiment, since the sludge returning means for returning a part of the activated sludge in the membrane separation tank 51 to the activated sludge treatment tank 21 is provided, the amount of cells in the activated sludge treatment tank 21 can be sufficiently maintained. Therefore, the aerobic direct nitrogen gasification bacteria can be made to act more efficiently, and the efficiency of nitrogen removal is more excellent.
In the present embodiment, the ammonia removal means 40 removes the ammonia scattered from the acid generation treated water. Therefore, it is possible to suppress the scattered ammonia from re-dissolving in the acid generation treated water and increasing the concentration of ammonia nitrogen, and the nitrogen removal efficiency is further improved.

"Third embodiment"
<Wastewater treatment equipment>
FIG. 3 is a schematic configuration diagram of the wastewater treatment apparatus 3 according to the third embodiment of the present invention.
The wastewater treatment apparatus 3 of the present embodiment includes an acid generation tank 11, a neutralization tank 71, an activated sludge treatment tank 21, a fungus body addition means 30, an ammonia removal means 40, a membrane module 52 (membrane separation means). ) And a storage tank 61. The neutralization tank 71 is provided in the subsequent stage of the acid generation tank 11. The activated sludge treatment tank 21 is provided in the subsequent stage of the neutralization tank 71. The fungus body adding means 30 and the ammonia removing means 40 are respectively provided in the activated sludge treatment tank 21. The membrane module 52 is provided in the activated sludge treatment tank 21. The storage tank 61 is provided in the subsequent stage of the activated sludge treatment tank 21.

(Acid generation tank)
The acid generation tank 11 of the present embodiment is the same as the acid generation tank 11 of the first embodiment.

(Neutralization tank)
The neutralization tank 71 neutralizes the acid generation treated water from the acid generation tank 11.
A suitable pH in the acid generation treatment is 5 or more and less than 8 as described above. On the other hand, the preferred pH in activated sludge treatment using aerobic direct nitrogen gasifying bacteria is 7-9, and if this pH is too low, nitrogen gasification of ammonia nitrogen by aerobic direct nitrogen gasifying bacteria The effect is not enough. Therefore, when the pH of the acid generation treated water is too low with respect to a suitable pH in the activated sludge treatment, the acid generation treated water is neutralized in the neutralization tank 71, and the pH is adjusted to the activated sludge treatment. The pH is adjusted within a suitable range.

The other end of the second flow path 13 and one end of the sixth flow path 72 are connected to the neutralization tank 71. The other end of the sixth channel 72 is connected to the activated sludge treatment tank 21.
In the present embodiment, the second flow path 13 is a flow path for supplying acid generation treated water generated in the acid generation tank 11 to the subsequent neutralization tank 71.
The sixth flow path 72 is a flow path for allowing the acid generation treated water neutralized in the neutralization tank 71 as necessary to flow into the activated sludge treatment tank 21 at the subsequent stage.

Further, the neutralization tank 71 is provided with an in-tank pH measurement unit 74, an acid addition unit 75, and an alkali addition unit 76. The in-tank pH measurement unit 74, the acid addition unit 75, and the alkali addition unit 76 are connected to the control unit 77, respectively.
The tank pH measurement unit 74, the acid addition unit 75, and the alkali addition unit 76 are means for monitoring and controlling the pH in the neutralization tank 71.

The in-tank pH measurement unit 74 measures the pH of the acid generation treated water in the neutralization tank 71. Various pH measuring devices can be used as the in-tank pH measuring unit 74.
The acid addition unit 75 adds acid to the neutralization tank 71. The acid addition unit 75 includes an acid storage tank 75a, an acid supply channel 75b, and a pump 75c provided in the acid supply channel 75b. By operating the pump 75c, the acid (acid solution or the like) in the acid storage tank 75a is added to the neutralization tank 71.
The alkali addition unit 76 adds alkali to the neutralization tank 71. The alkali addition unit 76 includes an alkali storage tank 76a, an alkali supply channel 76b, and a pump 76c provided in the alkali supply channel 76b. By operating the pump 76 c, the alkali (alkali solution or the like) in the alkali storage tank 76 a is added to the neutralization tank 71.

The control unit 77 controls the acid addition unit 75 and the alkali addition unit 76 based on the pH measured by the in-tank pH measurement unit 74, and the pH of the acid generation treated water in the neutralization tank 71 is in the range of 6-9. Among them, it is preferably configured to be maintained within the range of 7-9.
The control unit 77 may include an arithmetic processing device such as a CPU, for example.
The operation of the control unit 77 is the same as the operation of the control unit 17 except that the pH range is different.
The operation of the pumps 75c and 76c may be manually switched based on the pH measured by the in-tank pH measurement unit 74 without providing the control unit 77.

(Activated sludge treatment tank)
The activated sludge treatment tank 21 of the present embodiment is the same as the activated sludge treatment tank 21 of the first embodiment except that one end of the sixth flow path 72 is connected instead of the second flow path 13. is there.

(Bacteria addition means)
The microbial cell addition means 30 of this embodiment is the same as the microbial cell addition means 30 of the first embodiment.

(Ammonia removal means)
The ammonia removal means 40 of this embodiment is the same as the ammonia removal means 40 of the first embodiment.

(Membrane module)
The membrane module 52 of the present embodiment is the same as the membrane module 52 of the first embodiment.

(Reservoir)
The storage tank 61 of this embodiment is the same as the storage tank 61 of the first embodiment.

<Wastewater treatment method>
In the wastewater treatment method using the wastewater treatment apparatus 3 shown in FIG. 3, first, wastewater discharged from a pig farm or the like is caused to flow into the acid generation tank 11 through the first flow path 12. In the acid production tank 11, acid producing bacteria are held in advance. Next, the inside of the acid generation tank 11 is maintained under anaerobic conditions, and acid generation treatment is performed on the wastewater to obtain acid generation treatment water (acid generation treatment step).
Next, the acid generation treatment water is caused to flow from the acid generation tank 11 to the neutralization tank 71 via the second flow path 13. Next, neutralization treatment is performed on the acid generation treated water (neutralization step).

  Subsequently, the neutralized acid generation treated water is caused to flow from the neutralization tank 71 to the activated sludge treatment tank 21 through the sixth flow path 72. Next, the aerobic direct nitrogen gasification bacteria are added to the acid generation treated water in the activated sludge treatment tank 21 by the fungus body addition means 30 (bacterial cell addition step). Moreover, the air diffuser 22 in the activated sludge treatment tank 21 is operated, the inside of the tank is maintained in an aerobic condition, the activated sludge treatment is performed on the acid generation treated water, and the sludge containing treated water is obtained (activated sludge treatment). Process).

  In the activated sludge treatment process, as described above, a part of the ammonia nitrogen is scattered from the acid generation treated water as gaseous ammonia by the stripping effect, and thus the gas containing the scattered ammonia is used as the activated sludge treatment tank 21. To the ammonia removing device 42 through the third flow path 41, and ammonia is removed by the ammonia removing device 42 (scattered ammonia removing step). The gas from which the ammonia has been removed is then released into the atmosphere.

Next, the pump 53a is operated to depressurize the inside of the membrane module 52, thereby performing a solid-liquid separation process on the sludge-containing treated water in the activated sludge treatment tank 21 (separation process). In the present embodiment, the separation step is performed in the activated sludge treatment tank 21.
At the time of solid-liquid separation, air is introduced from the air diffuser 22 into the membrane module 52, and the activated sludge and the biologically treated water are efficiently solid-liquid while washing the surface of the membrane of the membrane module 52 by air scrubbing. Can be separated.
The biologically treated water (permeated water) that has permeated through the filtration membrane of the membrane module 52 is supplied from the membrane module 52 to the storage tank 61 via the fourth channel 53 and stored.

  Preferred conditions in each of the acid generation treatment step, the fungus body addition step, and the activated sludge treatment step are the same as the wastewater treatment method of the first embodiment.

<Effect>
In the wastewater treatment apparatus and wastewater treatment method of the third embodiment of the present invention described above, acid generation treatment is performed on the wastewater, and aerobic direct nitrogen is obtained with respect to the acid generation treatment water obtained. In order to perform activated sludge treatment using gasified bacteria, the aerobic direct nitrogen gasifying bacteria can be efficiently removed without adding additional organic acid during the activated sludge treatment as in the first embodiment. Therefore, nitrogen can be removed efficiently.

In particular, in this embodiment, since neutralization treatment is performed on the acid generation treated water before the activated sludge treatment, the activated sludge treatment can be performed at a suitable pH, and the nitrogen removal efficiency is more excellent.
Moreover, in this embodiment, since the separation means used for the solid-liquid separation treatment is the membrane module 52 (membrane separation means) provided in the activated sludge treatment tank 21, the aerobic direct from the activated sludge treatment tank 21. Nitrogen gasifying bacteria do not easily flow out, and the amount of cells in the activated sludge treatment tank can be sufficiently maintained. Therefore, the aerobic direct nitrogen gasification bacteria can be made to act more efficiently, and the efficiency of nitrogen removal is more excellent.
In the present embodiment, the ammonia removal means 40 removes the ammonia scattered from the acid generation treated water. Therefore, it is possible to suppress the scattered ammonia from re-dissolving in the acid generation treated water and increasing the concentration of ammonia nitrogen, and the nitrogen removal efficiency is further improved.

"Other embodiments"
The wastewater treatment apparatus and wastewater treatment method of the present invention are not limited to the above-described embodiments.
For example, in the first embodiment to the third embodiment, the aerobic direct nitrogen gasifying bacteria may be added to the wastewater flowing through the first flow path 12. In the third embodiment, the aerobic direct nitrogen gasifying bacteria may be added to the acid generation treated water in the neutralization tank 71 or the acid generation treated water flowing through the sixth flow path 72.
An organic acid such as acetic acid may be added to the acid generation treated water. The organic acid may be in an acid form or a salt form (sodium salt or the like). However, in the present invention, the nitrogen gasification effect of ammonia nitrogen by aerobic direct nitrogen gasification bacteria can be sufficiently exhibited without adding an organic acid.

The separation means used for the solid-liquid separation process is not limited to the membrane separation means, and may be a separation means other than the membrane separation means. For example, a sedimentation tank may be used instead of the membrane separation means 50 in the second embodiment. Membrane separation means is preferable in terms of maintaining the concentration of aerobic direct nitrogen gasifying bacteria.
In the first embodiment to the third embodiment, a raw water storage tank may be provided upstream of the acid generation tank 11 and the wastewater may be temporarily stored before the acid generation treatment. By storing the wastewater before the acid generation treatment, fluctuations in the amount of raw water or the quality of the raw water can be made uniform.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these.

"Examples 1-4, Comparative Examples 1-2"
Using anaerobic treated water (two types of acid producing treated water and methane fermented treated water with different organic acid contents) generated by anaerobic treatment (acid production treatment or methane fermentation treatment) of enzyme production wastewater, the following Study was carried out.
A test for evaluating nitrogen removal performance by aerobic direct nitrogen gasifying bacteria was performed under the test conditions shown in Table 1 by the following test method.
Each test condition changes the kind of anaerobic treated water to be evaluated and whether or not sodium acetate (organic acid) is added to the anaerobic treated water.
The organic acid content (total amount of propionic acid, butyric acid and acetic acid) and ammonia nitrogen content in the anaerobic treated water used were as follows.
Acid production treated water A: organic acid content 3800 mg / L, ammonia nitrogen content 1000 mg / L.
Acid production treated water B: organic acid content 400 mg / L, ammonia nitrogen content 1000 mg / L.
Methane fermentation treated water: organic acid content 0 mg / L, ammonia nitrogen content 1000 mg / L.

(Test method)
350 mL of anaerobic treated water was collected in a 1 L Erlenmeyer flask, and aerobic direct nitrogen gasifying bacteria were added. Depending on the test conditions, sodium acetate was added. When sodium acetate was added (when organic acid was added afterwards), the amount added was 2000 mg / L.
Next, the flask was shaken under the conditions of a shaking time of 48 hours, a temperature of 25 ° C., and a shaking speed of 120 rpm. As an aerobic direct nitrogen gasifying bacterium, Alkaligenes faecalis No. cultivated as described in JP-A-2002-199875. Four strains (FERM P-21814) were added.
After shaking for 48 hours, the liquid (biologically treated water) in the flask was sampled, and the total nitrogen concentration was measured by the following measurement method. From the measurement results, the total nitrogen (TN) removal rate was calculated by the following formula.
TN removal rate (%) = (total nitrogen concentration of anaerobic treated water-total nitrogen concentration of biological treated water)

(Measurement method of total nitrogen concentration)
The total nitrogen concentration is a nitrogen detector (“ND-210 type” manufactured by Mitsubishi Chemical Analytech Co., Ltd.) connected to the rear stage of the total organic carbon analyzer (“TOC-300V” manufactured by Mitsubishi Chemical Analytech Co., Ltd.). ). The measuring method of this apparatus was an oxidative decomposition-chemiluminescence method (decompression method).

  Table 1 shows the test results.

From the comparison of Examples 1-2 and Comparative Example 1 in which no post-addition of an organic acid was performed, in Examples 1-2 where the treatment with aerobic direct nitrogen gasifying bacteria was performed on the acid-generated treated water, Compared with Comparative Example 1 in which methane fermentation treated water was treated with aerobic direct nitrogen gasifying bacteria, it has superior nitrogen removal performance (nitrogen gasification effect of ammonia nitrogen by aerobic direct nitrogen gasifying bacteria ) Is obtained.
The same tendency was observed in the comparison of Examples 3 to 4 and Comparative Example 2 in which the organic acid was added afterwards.

  As described above, in the case of wastewater treatment in which an anaerobic treatment is performed in the former stage and an activated sludge treatment using an aerobic direct nitrogen gasifying bacterium is carried out in the latter stage, as described in JP-A-2014-50767 Instead of allowing the reaction to proceed to the methane fermentation reaction, the reaction to the acid generation reaction that decomposes the organic acid into an organic acid is carried out, so that the organic acid that becomes the substrate for the aerobic direct nitrogen gasification bacteria becomes the activated sludge in the subsequent stage. It will be supplied to a processing tank, and it becomes possible to make aerobic direct nitrogen gasification bacteria efficient work efficiently.

  Therefore, according to the present invention, compared to the method described in Japanese Patent Application Laid-Open No. 2014-50767, aerobic direct nitrogen gasification bacteria can be effectively acted, and the biological reaction efficiency can be improved. . Furthermore, the anaerobic treatment using a two-phase treatment apparatus of an acid generation tank and a methane fermentation tank, which is the mainstream in conventional methane fermentation, can be processed by a single-phase treatment apparatus only for the acid generation tank, thereby Expected to reduce running costs by reducing the amount of organic acid added to improve the activity of compact and aerobic direct nitrogen gasification bacteria.

DESCRIPTION OF SYMBOLS 1 Waste water processing apparatus, 2 Waste water processing apparatus, 3 Waste water processing apparatus, 11 Acid production tank, 12 1st flow path, 13 2nd flow path, 13a pump, 14 pH measuring part in a tank, 15 Acid addition 15a acid storage tank, 15b acid supply channel, 15c pump, 16 alkali addition unit, 16a alkali storage tank, 16b alkali supply channel, 16c pump, 17 control unit, 21 activated sludge treatment tank, 22 air diffuser, 22a Air diffuser, 22b Inlet pipe, 22c Blower, 25 Sludge extraction flow path, 25a Valve, 27 Fifth flow path, 30 Cell addition means, 31 Cell storage tank, 32 Cell supply channel, 32a pump, 40 Ammonia removal means, 41 3rd flow path, 42 Ammonia removal apparatus, 50 Membrane separation means, 51 Membrane separation tank, 52 Membrane module, 53 4th flow path, 53a , 54 diffuser, 54a diffuser pipe, 54b inlet pipe, 54c blower, 55 sludge return means, 55a sludge return flow path, 55b pump, 61 storage tank, 71 neutralization tank, 72 sixth flow path, 74 tank Internal pH measurement section, 75 acid addition section, 75a acid storage tank, 75b acid supply flow path, 75c pump, 76 alkali addition section, 76a alkali storage tank, 76b alkali supply flow path, 76c pump, 77 control section

Claims (22)

A method for treating wastewater containing organic matter and containing at least one of organic nitrogen and ammonia nitrogen,
Performing an acid generation treatment for generating an organic acid from the organic matter in the wastewater to obtain an acid generation treatment water having an organic acid content of 200 mg / L or more;
A process of performing activated sludge treatment using an aerobic direct nitrogen gasification bacterium on the acid generation treated water obtained by the acid generation treatment to obtain a sludge-containing treated water containing biological treated water and activated sludge;
Wastewater treatment method.   The wastewater treatment method according to claim 1, wherein the acid-generating treated water has a pH of 5 or more and less than 8.   The wastewater treatment method according to claim 2, wherein the pH of the wastewater is controlled to be 5 or more and less than 8 during the acid generation treatment.   The processing method of the wastewater as described in any one of Claims 1-3 including the process of performing a solid-liquid separation process with respect to the said sludge containing treated water using a separation means.   The method for treating wastewater according to claim 4, wherein the separation means is a membrane separation means.   The wastewater treatment method according to claim 5, wherein the membrane separation means is provided in an activated sludge treatment tank that performs the activated sludge treatment.   The wastewater treatment method according to claim 5, wherein the membrane separation means is provided at a subsequent stage of the activated sludge treatment tank that performs the activated sludge treatment.   The wastewater treatment method according to claim 7, comprising a step of returning a part of the activated sludge separated by the membrane separation means from the membrane separation means to the activated sludge treatment tank.   The processing method of the wastewater as described in any one of Claims 1-8 including the process of performing the neutralization process with respect to the said acid production | generation treated water after the process of obtaining the said acid production | generation treated water.   The wastewater treatment method according to any one of claims 1 to 9, comprising a step of adding an aerobic direct nitrogen gasification bacterium to the acid generation treated water.   The aerobic direct nitrogen gasifying bacterium is Alkaligenes faecalis no. The wastewater treatment method according to any one of claims 1 to 10, which is 4 strains (FERM P-21814). An apparatus for treating wastewater containing organic matter and containing at least one of organic nitrogen and ammonia nitrogen,
An acid generation tank for performing an acid generation treatment for generating an organic acid from organic substances in the wastewater, and an acid generation treatment water having an organic acid content of 200 mg / L or more;
An activated sludge treatment tank that performs activated sludge treatment using aerobic direct nitrogen gasification bacteria on the acid produced treated water obtained by the acid producing treatment to produce biologically treated water and sludge-containing treated water containing activated sludge. When,
Including wastewater treatment equipment.   The treatment apparatus of the wastewater of Claim 12 whose pH of the said acid production treated water is 5 or more and less than 8.   In the acid generation tank, an in-tank pH measurement unit for measuring pH of waste water in the acid generation tank, an acid addition unit for adding acid to the acid generation tank, and an alkali addition unit for adding alkali to the acid generation tank It is provided, and based on the pH measured by the pH measurement unit in the tank, an acid or an alkali is added to the acid generation tank, and the pH of the wastewater can be adjusted to 5 or more and less than 8. The wastewater treatment apparatus according to claim 13.   The wastewater treatment apparatus according to any one of claims 12 to 14, further comprising a separation unit that performs a solid-liquid separation process on the sludge-containing treated water.   The wastewater treatment apparatus according to claim 15, wherein the separation means is a membrane separation means.   The wastewater treatment apparatus according to claim 16, wherein the membrane separation means is provided in the activated sludge treatment tank.   The wastewater treatment apparatus according to claim 16, wherein the membrane separation means is provided at a subsequent stage of the activated sludge treatment tank.   The wastewater treatment apparatus according to claim 18, further comprising a sludge return means for returning a part of the activated sludge separated by the membrane separation means from the membrane separation means to the activated sludge treatment tank.   The wastewater treatment apparatus according to any one of claims 12 to 19, further comprising a neutralization tank that performs a neutralization process on the acid generation treated water at a subsequent stage of the acid generation tank.   The wastewater treatment apparatus according to any one of claims 12 to 20, further comprising a cell addition means for adding aerobic direct nitrogen gasification bacteria to the acid generation treated water.   The aerobic direct nitrogen gasifying bacterium is Alkaligenes faecalis no. The wastewater treatment apparatus according to any one of claims 12 to 21, which is 4 strains (FERM P-21814).

Images