JP2014097478A - Effluent treatment method and effluent treatment apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide means of not only promptly booting but also stably perpetuating a treatment predicated on anaerobic ammonia oxidation bacteria performed during a nitrogen-containing effluent treatment.SOLUTION: A provided effluent treatment method includes: a nitrite-type oxidation step of oxidizing, in the presence of aerobic ammonia oxidation bacteria, a portion of ammonia-state nitrogen included within an effluent into nitrite-state nitrogen; a diluting water feeding step of feeding, into the oxidized effluent, diluting water for decreasing at least either of the nitrite-state nitrogen concentration and dissolved oxygen concentration within the effluent; and a denitrification step of converting, into a nitrogen gas in the presence of anaerobic ammonia oxidation bacteria, ammonia-state nitrogen and nitrite-state nitrogen included within the oxidized effluent.

Description

  The present invention relates to a wastewater treatment method and a wastewater treatment apparatus. Specifically, the present invention relates to a wastewater treatment method and a wastewater treatment apparatus for treating nitrogen-containing wastewater containing ammonia nitrogen by an anaerobic ammonia oxidation reaction.

  Wastewater discharged from general households and business establishments may contain inorganic nitrogen such as ammonia, ammonium compounds, nitrite compounds and nitrate compounds, and organic nitrogen such as amino acids and proteins. Since such nitrogen-containing wastewater containing nitrogen components causes eutrophication of the water environment and a decrease in dissolved oxygen, resulting in deterioration of water pollution, the discharge to public water bodies is regulated based on wastewater standards . Therefore, wastewater treatment for nitrogen-containing wastewater is being implemented mainly in large-scale business establishments and wastewater treatment facilities.

  Generally, chemical treatment such as a method of removing nitrate nitrogen using ion exchange or a method of oxidative decomposition using an oxidizing agent such as ozone is used as a treatment of low concentration nitrogen-containing wastewater. Many. On the other hand, biological treatment using microorganisms is performed for treatment of high concentration nitrogen-containing wastewater.

  In the conventional biological treatment of nitrogen-containing wastewater, since most of the nitrogen components in the wastewater are present in an ammonia state, a treatment combining a nitrification step and a denitrification step has become the mainstream. Nitrosomonas bacteria, Nitrobacter bacteria and other nitrifying bacteria can be used in the nitrification process under the aerobic conditions, through ammonia nitrogen and nitrite nitrogen. The process of conversion to nitrate nitrogen is performed, and the subsequent denitrification process uses the reducing action of denitrifying bacteria such as Pseudomonas bacteria to harm the nitrate nitrogen under anaerobic conditions. The conversion to nitrogen gas is performed.

In recent years, wastewater treatment using anaerobic ammonia oxidation (ANAMMOX) has been promoted as an alternative to the treatment combining such a nitrification step and a denitrification step.
Anaerobic ammonia oxidation is a method in which nitrite nitrogen is reduced with ammonia nitrogen and converted to nitrogen gas under the anaerobic condition by the action of a specific microorganism.
The reaction formula of this conversion is expressed as the following formula 1.
1.00NH ₄ ⁺ + 1.32NO ₂ + 0.066HCO ₃ + 0.13H ⁺
→ 1.02N ₂ + 0.26NO ₃ + 0.066CH ₂ O _0.5 N _0.15 + 2.03H ₂ O (Formula 1)
In the treatment by anaerobic ammonia oxidation, as shown in Formula 1, nitrite nitrogen is necessary as a substrate. Therefore, a nitrite type oxidation process for oxidizing a part of ammonia nitrogen in waste water to nitrite nitrogen and converting it is combined in the preceding stage.

Conventionally, it is difficult to improve the nitrogen treatment speed in the treatment that is generally performed by combining the nitrification step and the denitrification step, and a large-capacity treatment tank is required for treatment of high-concentration nitrogen-containing wastewater. In addition, since denitrifying bacteria used in the denitrification process are generally heterotrophic, it is necessary to supply a carbon source, and in the nitrification process, oxygen aeration is necessary. Is the method.
On the other hand, the treatment using anaerobic ammonia oxidation has the advantage that it does not require supply of carbon source and aeration of oxygen, and the amount of sludge generated can be reduced, and it is promising to enable high-load wastewater treatment. It is attracting attention as a wastewater treatment method.
However, anaerobic ammonia-oxidizing bacteria that carry out the anaerobic ammonia oxidation reaction (ANAMMOX reaction) represented by Formula 1 have the characteristic that the activity decreases when the concentration of nitrite nitrogen as a substrate becomes high. It is known that it is easily affected by environmental factors such as dissolved oxygen, pH, temperature, C / N ratio, and it is not easy to start up and maintain a wastewater treatment stably.
Therefore, as in Patent Document 1, it is possible to improve long-term operation stability in an anaerobic ammonia oxidation apparatus, and simple and steady operation at the start of operation from start-up, load fluctuation, deactivation and operation. As an operating method of the anaerobic ammonia oxidation apparatus that can be transferred to the anaerobic ammonia oxidation tank, the treated water treated in the anaerobic ammonia oxidation tank is circulated to the inlet of the anaerobic ammonia oxidation tank so that the flow velocity in the tank is constant. Improvement of the method has been promoted, for example, a technique for adjusting the circulation amount and / or the raw water amount of the raw water is proposed.

JP 2006-110511 A

Anaerobic ammonia-oxidizing bacteria used in wastewater treatment using anaerobic ammonia oxidation are the nitrite nitrogen produced by the nitrite-type oxidation combined with the anaerobic ammonia-oxidizing bacteria and the ammonia state contained in the wastewater. The activity is inhibited by the influence of nitrogen and dissolved oxygen, and stable wastewater treatment cannot be maintained. In particular, if the wastewater treatment apparatus is affected during start-up operation, there is a problem that the period required for start-up is prolonged.
Therefore, the subject of this invention is providing the means to start stably the process by anaerobic ammonia oxidation performed in a nitrogen-containing wastewater process, and to continue stably.

The present invention which has solved the above problems
A wastewater treatment method for treating nitrogen-containing wastewater by anaerobic ammonia oxidation reaction,
A nitrite oxidation process that oxidizes a part of ammonia nitrogen contained in wastewater to nitrite nitrogen in the presence of aerobic ammonia oxidizing bacteria;
A diluted water supply step of supplying diluted water for reducing the nitrite nitrogen concentration or ammonia nitrogen concentration or dissolved oxygen concentration in the waste water to the oxidized waste water;
A denitrification step of converting ammonia nitrogen and nitrite nitrogen contained in the oxidized wastewater into nitrogen gas in the presence of anaerobic ammonia oxidizing bacteria;
It is a wastewater treatment method characterized by including.

Also,
A wastewater treatment apparatus for treating nitrogen-containing wastewater by anaerobic ammonia oxidation reaction,
A nitrification tank that oxidizes part of ammonia nitrogen contained in wastewater to nitrite nitrogen in the presence of aerobic ammonia-oxidizing bacteria;
Dilution water supply means for supplying dilution water for reducing the nitrite nitrogen concentration, ammonia nitrogen concentration or dissolved oxygen concentration in the waste water to the waste water flowing out from the nitrification tank;
A denitrification tank for converting ammonia nitrogen and nitrite nitrogen contained in waste water flowing out of the nitrification tank into nitrogen gas in the presence of anaerobic ammonia oxidizing bacteria;
A wastewater treatment apparatus comprising:

ADVANTAGE OF THE INVENTION According to this invention, the process by the anaerobic ammonia oxidation performed in a nitrogen-containing wastewater process can be started rapidly, and can be maintained stably.
For example, even if wastewater treated with anaerobic ammonia oxidation contains high concentrations of nitrite nitrogen, high concentrations of ammonia nitrogen, or high concentrations of dissolved oxygen, these effects on anaerobic ammonia oxidation bacteria The time required for starting up the operation of the wastewater treatment apparatus can be shortened, and stable wastewater treatment can be maintained in the steady operation after the start-up.

It is a block diagram of the waste water treatment apparatus which concerns on embodiment. It is a block diagram of the 1st modification of the waste water treatment apparatus which concerns on embodiment. It is a block diagram of the 2nd modification of the waste water treatment apparatus which concerns on embodiment.

A wastewater treatment method according to an embodiment of the present invention is as follows.
A wastewater treatment method for treating nitrogen-containing wastewater by anaerobic ammonia oxidation reaction,
A nitrite oxidation process that oxidizes a part of ammonia nitrogen contained in wastewater to nitrite nitrogen in the presence of aerobic ammonia oxidizing bacteria;
A diluted water supply step of supplying diluted water for reducing the nitrite nitrogen concentration or ammonia nitrogen concentration or dissolved oxygen concentration in the waste water to the oxidized waste water;
A denitrification step of converting ammonia nitrogen and nitrite nitrogen contained in the oxidized wastewater into nitrogen gas in the presence of anaerobic ammonia oxidizing bacteria;
Is a wastewater treatment method including at least

The present embodiment is applied to nitrogen-containing wastewater containing ammonia nitrogen as a nitrogen component, and the nitrogen component in the wastewater is converted into nitrogen gas harmless to the environment by an anaerobic ammonia oxidation reaction. It is.
In the present embodiment, the treatment is applied to both waste water from a general household and waste water from a business establishment. Specifically, wastewater to be treated includes an aqueous phase generated by solid-liquid separation of sludge digested in sewage treatment, wastewater from scrubbers for ammonia treatment, wastewater from semiconductor factories such as RCA cleaning wastewater, metal Examples include wastewater from smelters and waste leachate.
Therefore, this embodiment is implemented in any of the wastewater treatment apparatus individually provided downstream of specific drainage lines of various business establishments and the wastewater treatment apparatus provided in large-scale wastewater collection facilities such as sewage treatment plants. The

  Hereinafter, a wastewater treatment method according to an embodiment of the present invention will be described more specifically with reference to the drawings as appropriate together with a wastewater treatment apparatus used for carrying out the method.

FIG. 1 is a configuration diagram of a wastewater treatment apparatus 1 that performs a wastewater treatment method according to an embodiment. As shown in FIG. 1, the wastewater treatment apparatus 1 is a wastewater treatment apparatus composed of two tanks, a nitrification tank 10 and a denitrification tank 20.
As shown by the arrow in FIG. 1, waste water containing ammonia nitrogen first flows into the nitrification tank 10, stays in the nitrification tank for a predetermined time, and undergoes biological treatment under aerobic conditions. Next, it flows out from the nitrification tank 10, flows into the denitrification tank 20 in the direction indicated by the arrow in FIG. 1, stays in the denitrification tank 20 for a predetermined time, and further biologically by anaerobic ammonia oxidation under anaerobic conditions. The nitrogen component is processed under the general treatment. Then, it flows out from the denitrification tank 20 and is drained as treated water to the outside of the wastewater treatment apparatus 1.

The upstream end (the left end in the figure) of the nitrification tank 10 that is the first treatment tank is connected to a pipe line that is drawn from a waste water supply source (not shown), and the waste water to be treated is supplied from the supply source. Is introduced into the wastewater treatment apparatus 1 through the pipe.
A water pump and a waste water flow meter (not shown) are installed on this pipeline, and the waste water introduced into the waste water treatment apparatus 1 from the supply source is flowed by the driving force of the water pump under the monitoring of the waste water flow meter. Being controlled. Or when the wastewater sent from a supply source is pressurized, flow volume may be controlled by the opening degree of a sluice, a valve, etc.
Examples of the wastewater supply source include a storage tank in which wastewater to be processed is stored and a processing tank in which pretreatment such as a first sedimentation basin is performed.
The waste water introduced into the waste water treatment apparatus 1 is preferably subjected to treatment such as filtration, sedimentation, and agglomeration to remove main suspended solids and solid matter, and sulfides that may impede the treatment. Is preferably removed.

Such wastewater may contain environmental factors that are not suitable for microorganisms used in wastewater treatment, such as excessively dissolved ammonia nitrogen and other organic and inorganic components. is there.
Therefore, when starting up the operation of the wastewater treatment apparatus, the start-up operation is usually performed over a predetermined period. By acclimatizing microorganisms in the start-up operation and growing them to a sufficient number of microorganisms, a better nitrogen component treatment ability can be obtained, and in the subsequent steady operation, the composition, temperature and pH conditions of the wastewater to be treated Even if such fluctuations occur, stable processing can be continued.

During steady operation, the concentration of ammonia nitrogen in the wastewater introduced into the wastewater treatment apparatus 1 is not particularly limited, but is preferably 10 to 2000 mg-N / L, and preferably 40 to 1000 mg-N / L. L is more preferable.
On the other hand, during start-up operation where acclimation of microorganisms is not performed, if the concentration of ammonia nitrogen is excessively high, there is a risk that the growth and treatment activity of microorganisms used for wastewater treatment may be inhibited. Waste water having a lower nitrogen concentration may be introduced into the waste water treatment apparatus 1. In this case, for example, the concentration of ammonia nitrogen is reduced by mixing tap water or the like with the waste water before being introduced into the waste water treatment apparatus 1. Then, with the progress of acclimatization of microorganisms, the concentration of ammonia nitrogen in the introduced wastewater is gradually adjusted to a high concentration to obtain the concentration during steady operation.
The concentration of ammonia nitrogen and the concentration of other nitrogen components in the waste water introduced into the waste water treatment apparatus 1 should be monitored by providing ammonia nitrogen measuring means and total nitrogen measuring means on the pipe drawn from the supply source. Can do.

  In the wastewater treatment apparatus 1, the microorganisms introduced into the biological treatment tank are acclimatized with the same wastewater as the wastewater to be treated at the time of steady operation being introduced. Therefore, the configuration of the wastewater treatment apparatus 1 and the operation after the start-up operation will be described below.

In the start-up operation of the wastewater treatment apparatus 1, the wastewater introduced into the wastewater treatment apparatus 1 first flows into the nitrification tank 10.
The nitrification tank 10 is a treatment tank in which a nitrite type oxidation process is performed in which a part of ammonia nitrogen contained in waste water is oxidized to nitrite nitrogen in the presence of aerobic ammonia oxidizing bacteria.
Usually, most of the nitrogen component contained in the wastewater is ammonia nitrogen, so that a part of this ammonia nitrogen is oxidized to nitrite nitrogen, which results in the anaerobic ammonia oxidation reaction shown in Formula 1. A substrate ratio is realized. Therefore, in this step, a nitrite-type oxidation reaction is performed in which at least a part of ammonia nitrogen is oxidized to nitrite nitrogen and oxidation from nitrite nitrogen to nitrate nitrogen is not performed. This nitrous acid type oxidation reaction is expressed by the following formula 2.
NH ₄ ⁺ + 3 / 2O ₂ → NO ₂ ⁻ + 2H ⁺ + H ₂ O (Formula 2)
As Equation 2 shows, the nitrite oxidation process is performed under aerobic conditions.

The nitrification tank 10 mainly includes an aeration unit, a dissolved oxygen measurement unit 81, a nitrogen component measurement unit 91, and an aeration control unit 70.
Moreover, other measuring means, such as a water temperature measuring means and a pH measuring means, can be provided.

The aeration unit is a unit that diffuses oxygen gas into the waste water in the nitrification tank 10 so that biological treatment in the nitrification tank 10 is performed under aerobic conditions.
As the aeration means, any of a blow-type device that diffuses in water, a device that mechanically stirs the water surface and mixes air, etc. may be used, but in this embodiment, as shown in FIG. A blower 60, a diffuser 61, and an air supply pipe 62 are included.
The blower 60 blows oxygen-containing gas supplied from an oxygen source (not shown) to the diffuser 61 through the air supply pipe 62. The oxygen source is not particularly limited as long as it is a gas containing oxygen gas at a certain concentration, such as oxygen sealed in air or a tank.
The diffuser 61 diffuses the blown oxygen-containing gas into the nitrification tank 10, thereby increasing the dissolved oxygen concentration in the wastewater and making the nitrification tank 10 an aerobic condition.
The diffuser 61 has a plurality of disk shapes in FIG. 1, but may have any shape such as a diffuser tube or a diffuser plate, and the diffuser port may be either a membrane type or a hole type. The diffuser 61 is preferably disposed at a high density and dispersed at the bottom of the nitrification tank 10 so that the inside of the tank is agitated by air diffusion and a uniform dissolved oxygen concentration is maintained.

The dissolved oxygen measuring means 81 measures the concentration of dissolved oxygen contained in the wastewater.
The dissolved oxygen measuring means 81 is provided near the outlet at the downstream end of the nitrification tank 10 so as to be able to measure the dissolved oxygen that is generated in the processing in the nitrification tank 10 and can flow out to the subsequent stage. 1 is connected to the aeration control unit 70 via a signal line.
The dissolved oxygen measuring means 81 may be either a diaphragm electrode type such as a galvanic cell type or a polarographic type, a fluorescent type, or the like.

The aeration control unit 70 is a control device that controls the amount of aeration in the nitrification tank 10.
The aeration control unit 70 is connected to the dissolved oxygen measuring means 81, the nitrogen component measuring means 91, and the blower 60 through signal lines as indicated by broken lines in FIG.
The aeration control unit 70 is configured to include a calculation unit, a signal input / output unit, an A / D and D / A conversion unit, an operation unit, and the like.
The calculation unit has a calculation circuit that calculates proportional control, integral control, and differential control for performing PI control or PID control. In addition, the dissolved oxygen concentration and the blower output are converted here.
The signal input / output unit has signal input means for receiving the output signal of the measuring means and signal output means for outputting the control signal of the blower.
The A / D and D / A converters have conversion circuits that perform digital conversion and analog conversion of input / output signals.
The operation unit has an input device for inputting a target value of the dissolved oxygen concentration.

The aeration control unit 70 calculates a control amount of feedback control for controlling the dissolved oxygen concentration in the nitrification tank 10 measured by the dissolved oxygen measuring means 81 to the target value of the dissolved oxygen concentration in the aerobic condition of the nitrification tank 10, The output control of the blower 60 is performed. When the output of the blower 60 is controlled, the aeration amount of the oxygen-containing gas into the nitrification tank 10 is adjusted, and the dissolved oxygen concentration in the nitrification tank 10 is maintained within the target value range.
Further, for example, a dissolved oxygen measuring means is provided on a pipeline drawn from the supply source to the waste water treatment apparatus 1, and this dissolved oxygen measuring means is connected to the aeration control unit 70, thereby the waste water introduced into the waste water treatment apparatus 1. Feedforward control and feedback control according to the dissolved oxygen concentration can be performed.

The nitrogen component measuring means 91 measures the concentration of the nitrogen component contained in the wastewater.
The nitrogen component measuring means 91 includes a total nitrogen meter and at least one of an ammonia nitrogen meter and a nitrite nitrogen meter.
The nitrogen component measuring means 91 is installed in the vicinity of the outlet at the downstream end of the nitrification tank 10, so that the concentration of all nitrogen components present in the nitrification tank 10 and ammonia nitrogen partially consumed in the nitrite type nitrification reaction It is provided so that at least one of the concentration or the concentration of nitrite nitrogen produced by the nitrite type oxidation reaction can be measured.
Examples of the total nitrogen meter include a total nitrogen meter that measures absorbance based on potassium peroxodisulfate decomposition and catalytic pyrolysis. As an ammonia nitrogen meter and a nitrite nitrogen meter, an ion electrode type and an absorptiometric type are available. Examples include measuring instruments.

The total nitrogen component concentration (C ₀ ), the ammonia nitrogen concentration (C ₁ ), or the nitrite nitrogen concentration (C ₂ ) in the wastewater, which is measured by the nitrogen component measuring means 91, is nitrified by the following equation (3). The nitrification rate (R _N ) in the tank 10 is calculated.
R _N (%) = (1−C ₁ / C ₀ ) × 100 = C ₂ / C ₀ × 100 (Equation 3)

As shown in Formula 1, in the anaerobic ammonia oxidation reaction, the ratio of ammonia nitrogen and nitrite nitrogen reacts at 1: 1.32, so the value of this nitrification rate (R _N ) is 56 to 57%. The nitrite-type oxidation reaction needs to be controlled so as to reach a degree.
As a method for controlling the nitrite type oxidation reaction, the waste water flowing into the nitrification tank 10 and the waste water bypassing the nitrification tank 10 are distributed at a predetermined ratio upstream of the nitrification tank 10, and the nitrite type oxidation is performed in the nitrification tank 10. There is a method of allowing the reaction to proceed completely and remixing it so that the ratio is achieved downstream of the bypassed wastewater and nitrification tank 10.
Further, there is a method for controlling the progress of the nitrite type oxidation reaction so that the nitrification rate is achieved based on the measured values of the concentrations of ammonia nitrogen and nitrite nitrogen during the nitrite type oxidation reaction.

The progress of the nitrite oxidation reaction can be controlled by adjusting the amount of aeration, supply of carbon source, ammonia nitrogen concentration, amount of carrier, pH, water temperature and the like.
For example, since alkalinity is consumed by nitrification, an alkaline carbon source such as sodium carbonate or sodium hydrogen carbonate is supplied as necessary, but the amount can be adjusted according to the amount.
In the present embodiment, a method of controlling the progress of the nitrite type oxidation reaction in the nitrification tank 10 is adopted, and the nitrification rate is mainly controlled by adjusting the amount of aeration by the aeration means.

The aeration control unit 70 can be operated by inputting the target value of the dissolved oxygen concentration determined from the nitrogen component concentration measured by the nitrogen component measuring unit 91 and the dissolved oxygen concentration measured by the dissolved oxygen measuring unit 81. By being connected to the nitrogen component measuring means 91 via a signal line, control based on the nitrogen component concentration can also be performed.
For example, by providing the aeration control unit 70 with a calculating unit that calculates the nitrification rate from the total nitrogen component concentration measured by the nitrogen component measuring unit 91 and the ammonia nitrogen concentration or nitrite nitrogen concentration according to the equation 3, the nitrification tank The blower output can be controlled so that the nitrification rate at 10 achieves the target value.

The operation in the nitrification tank 10 is performed as follows.
In the start-up operation of the wastewater treatment apparatus 1, when wastewater flows into the nitrification tank 10, the aeration means is first driven.
When the operation of the blower 60 constituting the aeration means is started, an oxygen-containing gas, for example, air supplied from an oxygen source (not shown) is blown to the diffuser 61 through the air supply pipe 62, and from the diffuser port of the diffuser 61. The waste water stored in the nitrification tank 10 is diffused.
At this time, the dissolved oxygen concentration means 81 monitors the dissolved oxygen concentration of the wastewater in the nitrification tank 10.
The measurement signal output from the dissolved oxygen measuring means 81 is input to the aeration control unit 70, and the aeration control unit 70 samples the input measurement signal at a predetermined sampling period.
As an aerobic condition in the nitrite type oxidation reaction performed in the nitrification tank 10, a dissolved oxygen concentration of about 1 to 5 mg / L is necessary.
Therefore, the aeration control unit calculates feedback control based on the sampled dissolved oxygen concentration. As the target value at this time, a predetermined concentration within a range of about 1 to 4 mg / L is set via the operation unit or the nitrification rate calculation unit.
The control amount calculated by the dissolved oxygen concentration control unit is output as a control signal to the blower 60, and when the blower 60 receives the control signal, the blower output is adjusted, so that the dissolved oxygen concentration of the wastewater in the nitrification tank 10 is predetermined. An amount of oxygen-containing gas that is maintained at the value is diffused.

  When the aeration of the wastewater due to the diffusion of the oxygen-containing gas is performed until the dissolved oxygen concentration of the wastewater is stabilized at a predetermined concentration within the range of about 1 to 5 mg / L, then the nitrification tank 10 is favored. Tempered ammonia-oxidizing bacteria are introduced.

The aerobic ammonia bacterium is a bacterium that undergoes a nitrite-type oxidation reaction using ammonia nitrogen in wastewater as a substrate and converts it into nitrite nitrogen.
It is preferable that the aerobic ammonia bacterium is immobilized and used so as not to flow out of the tank. As a method of immobilizing the aerobic ammonia oxidizing bacterium in the nitrification tank 10, a method of immobilizing it on a carrier or a fixed bed is used. A method of immobilization is used.

The carrier is not particularly limited, and examples thereof include gels such as polyvinyl alcohol, alginic acid, polyethylene glycol, agarose, acrylamide, and plastics such as cellulose, polyester, polypropylene, vinyl chloride, and polyurethane.
As a method for immobilization on a carrier, either a method of entrapping and immobilizing bacterial cells inside the carrier or a method of adhering and immobilizing on a carrier surface may be used.
The shape of the carrier is not particularly limited, but is preferably a porous or sponge-like one molded into a spherical shape, a cylindrical shape, a cubic shape or a rectangular parallelepiped shape.
The size of the carrier is preferably 1 to 10 mm, and the filling rate of the carrier is preferably 5 to 50% by volume with respect to the waste water volume.

Although it does not restrict | limit especially as a fixed bed, Plastics, such as polyethylene, polyester, a polypropylene, vinyl chloride, activated carbon fiber, etc. are mentioned.
The shape of the fixed floor is not particularly limited, and a flat or corrugated plate, a fiber shape, a chrysanthemum shape, a honeycomb shape, a gravel shape, or the like is used.
The porosity of the fixed bed is preferably 80% or more, and the filling rate of the fixed bed is preferably 30 to 80% and more preferably 40 to 80% as the apparent volume of the fixed bed filled in the tank.

As the aerobic ammonia oxidizing bacterium, a bacterium that performs a nitrite type nitrification reaction using ammonia as a substrate under an aerobic condition is used.
Examples of such bacteria include bacteria of the genus Nitrosomonas, bacteria of the genus Nitrosococcus, bacteria of the genus Nitrosospira, bacteria of the genus Nitrosovibrio, bacteria of the genus Nitrosolobus, and the like.

The aerobic ammonia-oxidizing bacteria can be obtained as isolated or separated as bacterial flora from, for example, soil, rivers, lakes, oceans, groundwater, sludge in drainage, and the like.
In addition, as aerobic ammonia-oxidizing bacteria, conventionally used nitrifying bacteria can be used. If the bacterial flora contains nitrite-oxidizing bacteria that oxidize nitrite, aerobic ammonia-oxidizing bacteria And is used after a treatment for selectively eliminating nitrite-oxidizing bacteria.
As a method for eliminating nitrite-oxidizing bacteria, for example, there is a method using a difference in behavior due to the presence of ammonia nitrogen between an aerobic ammonia-oxidizing bacterium and a nitrite-oxidizing bacterium, or a difference in growth temperature range.
Specifically, after entrapping and immobilizing complex microbial sludge containing aerobic ammonia-oxidizing bacteria and nitrite-oxidizing bacteria, nitrite oxidation is performed by heating at 50 to 90 ° C., preferably 60 to 80 ° C. for about 2 hours. A treatment for selectively killing bacteria or a treatment for selectively killing nitrite-oxidizing bacteria by immersing the bacterial flora in acid or alkali can be used. Examples of the acid treatment include a treatment of immersing in an acid having a pH of 6 or less for 15 minutes or more. Examples of the alkali treatment include a treatment of immersing in an alkali having a pH of 9 or more for 20 minutes or more.

As shown in FIG. 1, in the present embodiment, such aerobic ammonia oxidizing bacteria are fixed in a cuboid-shaped entrapping immobilization support 110 in the nitrification tank 10.
When the aerobic ammonia-oxidizing bacteria are introduced into the nitrification tank 10 during the start-up operation of the wastewater treatment apparatus 1, the aerobic ammonia-oxidizing bacteria are acclimatized in the presence of ammonia nitrogen.
At this time, the pH of the waste water in the nitrification tank 10 is adjusted to about pH 6.0 to 8.5, and the temperature of the waste water is about 10 to 35 ° C. Moreover, an alkali, a carbon source, etc. are supplied as needed.

During this time, the nitrogen component measuring means 91 measures the total nitrogen component concentration (C ₀ ), the ammonia nitrogen concentration (C ₁ ), or the nitrite nitrogen concentration (C ₂ ) in the waste water. nitrification rate calculated _{(R N)} is, start-up operation to stabilize is performed at 56 to 57%.
Specifically, the control of the nitrification rate is set so that the target value of the nitrification rate is 56 to 57%. When the nitrification rate is below the set range, the dissolved oxygen concentration is 5 mg / L, In this case, the dissolved oxygen concentration can be set to 2 mg / L, and when the concentration is higher than the set range, the dissolved oxygen concentration can be set to 1 mg / L, and the aeration amount can be adjusted.

Nitrification rate _{(R N)} is, after stabilized at 56 to 57%, as a steady operation is continued operation in continuing the same conditions.
Waste water that flows into the nitrification tank 10 and stays in the nitrification tank 10 for a predetermined time from the start of the start-up operation to the steady operation passes through a screen 64 installed at the downstream end of the nitrification tank 10. After the solid matter is separated and removed, it flows out from the nitrification tank 10.

The waste water flowing out from the nitrification tank 10 then flows into the denitrification tank 20.
The denitrification tank 20 converts ammonia nitrogen contained in the waste water and nitrite nitrogen produced by oxidizing a part of the ammonia nitrogen in the nitrification tank 10 into nitrogen gas in the presence of anaerobic ammonia oxidizing bacteria. It is the processing tank in which the denitrification process to be performed is performed.
In this step, an anaerobic ammonia oxidation reaction represented by Formula 1 is performed under anaerobic conditions.

The denitrification tank 20 mainly includes dilution water supply means (40, 50), stirring means 65, dissolved oxygen measurement means 82, and nitrogen component measurement means 92.
Moreover, other measuring means, such as a water temperature measuring means and a pH measuring means, can be provided.

The dilution water supply means supplies dilution water that lowers the concentration of nitrite nitrogen, ammonia nitrogen, or dissolved oxygen in the waste water to the waste water.
In the present embodiment, as shown in FIG. 1, the dilution water adjustment tank 40 and the dilution water supply pump 50 are configured. However, the present invention is not necessarily limited to such a configuration. The pipe line which connects between tanks is provided, and what is necessary is just to be able to supply dilution water to waste water.

The dilution water is supplied to the wastewater in order to mitigate the high concentration of nitrogen components and dissolved oxygen that may be contained in the wastewater to be treated from inhibiting the activity of the bacteria that perform the wastewater treatment. For example, for anaerobic ammonia oxidizing bacteria used in the denitrification tank 20, high concentrations of nitrous acid, ammonia and dissolved oxygen flowing from the nitrification tank 10 are harmful and hinder the growth of the number of bacteria and stable wastewater treatment. . By supplying dilution water that reduces the concentration of these substances to the wastewater, the anaerobic ammonia bacteria introduced into the denitrification tank 20 can be appropriately propagated when the wastewater treatment apparatus is started up. During steady operation, stable wastewater treatment can be maintained.
The dilution water is not particularly limited as long as it is a liquid having a composition that lowers the nitrite nitrogen concentration or ammonia nitrogen concentration or dissolved oxygen concentration in the waste water, such as tap water, industrial water, and industrial wastewater. A liquid substantially free of nitrite nitrogen and ammonia nitrogen, or a liquid from which dissolved oxygen gas has been degassed is preferred.
As such dilution water, it is preferable to use tap water or industrial water which can be easily obtained with little influence on the wastewater treatment tank.

The dilution water adjustment tank 40 is a tank or container that stores dilution water supplied from a dilution water supply source (not shown) and adjusts components, water temperature, pH, and the like as necessary.
Examples of the dilution water supply source include water supply and industrial water supply.
As the adjustment of components, removal of harmful substances such as removal of nitrogen components and dissolved oxygen, and addition of useful substances such as hydrogen donors such as methanol, organic nutrients, and inorganic nutrients may be performed. In order to remove the nitrogen component or dissolved oxygen, an ion exchange membrane, a deaeration means, or the like is used. Moreover, it can comprise so that dissolved oxygen may be removed before mixing dilution water with waste water by providing the deaeration means to mention later in the dilution water adjustment tank 40. FIG.

The dilution water supply pump 50 is a pump for supplying dilution water, and is provided on a pipe line connecting the treatment tank and the dilution water adjusting tank 40 or on a pipe line directly connecting the treatment tank and the dilution water supply source.
As the dilution water supply pump 50, it is preferable to use a metering pump whose discharge amount is controlled.
When such a dilution water supply pump 50 is driven, the dilution water stored in the adjustment tank 40 is supplied into the treatment tank, and the waste water in the treatment tank is mixed with the dilution water and diluted.

The agitation means 65 agitates the waste water in the denitrification tank 20 to make the components, water temperature, pH and the like uniform.
The agitation means 65 is shown on the surface of FIG. 1 but may be installed on the tank bottom or tank wall.
If the wastewater is locally retained in the tank, it may be reduced in efficiency due to inhibition by nitrous acid, etc., and anaerobic ammonia-oxidizing bacteria may be reduced. preferable.

The dissolved oxygen measuring means 82 measures the concentration of dissolved oxygen contained in the wastewater, and is the same as that provided in the nitrification tank 10.
The denitrification process performed in the denitrification tank 20 is performed under anaerobic conditions. Therefore, the dissolved oxygen concentration in the denitrification tank 20 is monitored by the dissolved oxygen measuring means 82.

The nitrogen component measuring means 92 measures the concentration of the nitrogen component contained in the wastewater, and is the same as that provided in the nitrification tank 10.
The nitrogen component measuring means 92 is installed in the vicinity of the outlet at the downstream end of the denitrification tank 20, so that the concentration of all nitrogen components present in the denitrification tank 20 and the ammonia nitrogen partially consumed by the nitrite type nitrification reaction It is provided so that at least one of the concentration or the concentration of nitrite nitrogen produced by the nitrite type oxidation reaction can be measured.
The nitrogen removal rate, which is the ratio of the nitrogen component that has been converted to nitrogen gas in the denitrification tank 20 by the nitrogen component measuring means 92, and the ammonia nitrogen or suboxide that can remain untreated in the wastewater and flow out as treated water. The concentration of nitrate nitrogen is monitored.

The operation in the denitrification tank 20 is performed as follows.
As the start-up operation of the wastewater treatment apparatus 1, when wastewater flows into the denitrification tank 20, the stirring means 65 is first driven, and the wastewater in the denitrification tank 20 starts to convect in the tank.
The dilution water is stored in advance in the dilution water adjustment tank 40 that constitutes the dilution water supply means.

Next, the dilution water supply pump 50 is driven, and supply of dilution water to the waste water in the denitrification tank 20 is started.
When the dilution water pressurized by the dilution water supply pump 50 is sent to the denitrification tank 20, the waste water and the dilution water are stirred in the denitrification tank 20 by the operation of the stirring means 65, and the waste water is diluted.

The concentration of nitrite nitrogen in wastewater to be treated during steady operation in the wastewater treatment apparatus 1 of the present embodiment is relatively such that the volume load is 0.1 to 5.0 kg-N / m ³ / day. High concentrations are planned. Therefore, the concentration of ammonia nitrogen introduced into the nitrification tank 10 in the start-up operation is relatively high, and thereafter the concentration of nitrite nitrogen that is oxidized by nitrite and flows into the denitrification tank 20 from the nitrification tank 10 is The concentration is not suitable for unfamiliar anaerobic ammonia-oxidizing bacteria. Therefore, in the start-up of the denitrification tank 20, the diluted water in an amount that keeps the concentration of nitrite nitrogen in the wastewater in the denitrification tank 20 low until the adaptation of the anaerobic ammonia oxidizing bacteria used in the denitrification tank 20 is finished. Is supplied. For example, the operation is stopped after the dilution water supply pump 50 is operated until the measured value of nitrite nitrogen by the nitrogen component measuring unit 92 is stabilized at about 70 mg-N / L.

Further, the dissolved oxygen concentration and the nitrogen component concentration in the denitrification tank 20 at this time can be adjusted not only by the dilution water supply means but also by the inflow amount from the nitrification tank 10 to the denitrification tank 20.
When the dissolved oxygen concentration in the denitrification tank 20 measured by the dissolved oxygen measuring means 82 and the nitrite nitrogen concentration in the denitrification tank 20 measured by the nitrogen component measuring means 92 are high, the amount of aeration in the nitrification tank 10 By reducing the above, dissolved oxygen and nitrite nitrogen flowing into the denitrification tank 20 can be suppressed to a low concentration, and the supply amount of dilution water can be reduced as necessary.

  Anaerobic ammonia-oxidizing bacteria are introduced into the denitrification tank 20 along with the dilution of the wastewater by such dilution water supply means. The input of the anaerobic ammonia-oxidizing bacteria is not necessarily limited to after the dilution of the wastewater, and may be in the process of supplying the dilution water before starting the supply of the dilution water.

The anaerobic ammonia bacterium is a bacterium that performs an anaerobic ammonia oxidation reaction using ammonia nitrogen and nitrite nitrogen in wastewater flowing out of the nitrification tank 10 as substrates and converts it into nitrogen gas. The reaction is performed mainly using ammonia nitrogen remaining in the nitrification tank 10 without being nitrite-type oxidized and nitrite nitrogen generated by the nitrite-type oxidation reaction in the nitrification tank 10 as substrates.
It is preferable that the anaerobic ammonia bacterium is immobilized and used so as not to flow out of the tank. As a method of immobilizing the anaerobic ammonia oxidizing bacterium in the denitrification tank 20, a method of immobilizing it on a carrier, a fixed bed, etc. For example, a method of immobilizing on a granule or a method using granules formed by self-granulation of bacteria is used.

The carrier is not particularly limited, and examples thereof include gels such as polyvinyl alcohol, alginic acid, polyethylene glycol, agarose, acrylamide, and plastics such as cellulose, polyester, polypropylene, vinyl chloride, and polyurethane.
As a method for immobilization on a carrier, either a method of entrapping and immobilizing bacterial cells inside the carrier or a method of adhering and immobilizing on a carrier surface may be used.
The shape of the carrier is not particularly limited, but is preferably a porous or sponge-like one molded into a spherical shape, a cylindrical shape, a cubic shape or a rectangular parallelepiped shape.
The size of the carrier is preferably 1 to 10 mm, and the filling rate of the carrier is preferably 5 to 50% by volume with respect to the waste water volume.

Although it does not restrict | limit especially as a fixed bed, Plastics, such as polyethylene, polyester, a polypropylene, vinyl chloride, activated carbon fiber, etc. are mentioned.
The shape of the fixed floor is not particularly limited, and a flat or corrugated plate, a fiber shape, a chrysanthemum shape, a honeycomb shape, a gravel shape, or the like is used.
The porosity of the fixed bed is preferably 80% or more, and the filling rate of the fixed bed is preferably 30 to 80% and more preferably 40 to 80% as the apparent volume of the fixed bed filled in the tank.

In the method using granule, it is preferable to convect the wastewater so that the granulating sediment rises and circulates in the tank.
For example, the flow path of the waste water flowing from the nitrification tank 10 to the denitrification tank 20 is connected to the tank bottom of the denitrification tank 20, so that the granules are raised from the tank bottom by the inflowing waste water.

As anaerobic ammonia oxidizing bacteria, anaerobic ammonia oxidizing bacteria (ANAMMOX bacteria), which are autotrophic facultative anaerobic bacteria using ammonia as a hydrogen donor in a denitrification reaction, are used.
Examples of such bacteria include bacteria belonging to the genus Brocadia, Scalindua, Kuenenia, and the like, which have a ladderane lipid in the cell membrane.
Anaerobic ammonia-oxidizing bacteria, for example, using wastewater treatment sludge, etc., and accumulating with ammonia nitrogen and nitrite nitrogen as substrates under anaerobic conditions at a temperature of about 37 ° C. and a pH of about 6.5 to 8.0. It can be obtained by culturing.

As shown in FIG. 1, in the present embodiment, such anaerobic ammonia-oxidizing bacteria are immobilized on a cubic shaped immobilization carrier 120 and charged.
When the anaerobic ammonia oxidizing bacteria are introduced into the denitrification tank 20 during the start-up operation of the wastewater treatment apparatus 1, the anaerobic ammonia oxidizing bacteria are acclimatized in the diluted waste water.
The pH of the waste water in the denitrification tank 20 at this time is adjusted to about pH 6.0 to 8.5, and the temperature of the waste water in the denitrification tank 20 is about 10 to 35 ° C. Moreover, since acidity is consumed by denitrification, acids, such as hydrochloric acid and a sulfuric acid, are supplied as needed.

During this time, the nitrogen component measuring means 92 monitors the fluctuation of the concentration of the nitrogen component, and the progress of the anaerobic ammonia oxidation reaction is managed. For example, the nitrite nitrogen concentration (C ₂ ) of the wastewater in the denitrification tank 20 is measured.
When it is confirmed that the nitrite nitrogen concentration in the denitrification tank 20 shows a predetermined decrease, the nitrite nitrogen concentration in the denitrification tank 20 is stepwise in order to promote the adaptation of the anaerobic ammonia oxidizing bacteria. Be raised.
For example, when it is confirmed that the nitrite nitrogen concentration in the diluted wastewater at the start of the habituation is reduced to about 25 to 50%, the nitrite nitrogen concentration in the denitrification tank 20 is set to 100 mg-N / L to Pulling up in the range of about 1000 mg-N / L, shifting the acclimatization of anaerobic ammonia oxidizing bacteria to a higher concentration stage. Thereafter, when it is confirmed that the nitrite nitrogen concentration raised again decreases by a predetermined concentration, the nitrite nitrogen concentration in the denitrification tank 20 is raised again.
The increase of the nitrite nitrogen concentration here is performed mainly by controlling the progress of nitrite oxidation in the nitrification tank 10 and controlling the supply amount of dilution water.
By repeating such a process, anaerobic ammonia oxidizing bacteria are acclimatized, and the nitrogen removal speed in the denitrification tank 20 is increased to the speed required during steady operation.

Thereafter, in the denitrification tank 20, steady operation is continued with a predetermined volume load and a predetermined residence time.
In addition, even during steady operation, if there are signs that the nitrite nitrogen concentration, ammonia nitrogen concentration or dissolved oxygen concentration fluctuates to a high concentration, by supplying dilution water to the wastewater, Nitrite nitrogen concentration, ammonia nitrogen concentration or dissolved oxygen concentration can be reduced. For example, a dilution water supply control unit that controls the amount of dilution water to be supplied is installed so as to be connected to the dilution water supply unit, and the measurement value of the nitrogen component measurement unit 92 is input to the dilution water supply control unit. The configuration. Then, the dilution water supply control unit calculates feedback control of the nitrite nitrogen concentration or the ammonia nitrogen concentration in the denitrification tank 20, and controls the output of the dilution water supply pump 50 provided in the dilution water supply means. Moreover, it is set as the structure by which the measured value of the nitrogen component measurement means 91 with which the nitrification tank 10 is equipped is input into a dilution water supply control part, By the dilution water supply control part and dilution water supply means which were installed in the denitrification tank 20, Feed-forward control based on fluctuations in nitrite nitrogen concentration or ammonia nitrogen concentration in the nitrification tank 10 is performed.

  The waste water staying in the denitrification tank 20 for a predetermined time flows out of the denitrification tank 20 after passing through a screen 64 installed at the downstream end of the denitrification tank 20 to separate and remove solids. At the downstream end of the denitrification tank 20 (the right end in the figure), a drainage pipe connected to the outside of the wastewater treatment apparatus 1 is formed, and the wastewater from which the nitrogen component has been removed is disposed of through the pipe. It is drained out of the processing apparatus 1 as treated water.

According to the wastewater treatment apparatus 1 provided with such dilution water supply means, since the concentration of nitrite nitrogen and ammonia nitrogen in the denitrification tank 20 can be managed, the denitrification treatment is stably continued. be able to.
In addition, anaerobic ammonia-oxidizing bacteria are less susceptible to the effects of nitrite nitrogen and ammonia nitrogen in wastewater, so the time required for acclimatization of anaerobic ammonia-oxidizing bacteria is shortened and the time required for start-up operation is prolonged. Can be suppressed.
In addition, since the concentration of nitrite nitrogen and ammonia nitrogen in wastewater that contacts anaerobic ammonia-oxidizing bacteria placed in the treatment tank can be adjusted freely by operating the dilution water supply means, special habituation means and habituation The waste water treatment apparatus can be started up without using waste water by using the same apparatus configuration and nitrogen-containing waste water as those in the steady operation.

[Modification 1]
Next, a first modification of the embodiment of the present invention will be described.

FIG. 2 is a configuration diagram of a first modification of the wastewater treatment apparatus according to the embodiment. As shown in FIG. 2, the wastewater treatment apparatus 2 is a wastewater treatment apparatus configured by three tanks in which a degassing tank 30 is further provided between the nitrification tank 10 and the denitrification tank 20.
As shown by the arrow in FIG. 2, waste water containing ammonia nitrogen first flows into the nitrification tank 10, stays in the nitrification tank for a predetermined time, and undergoes biological treatment under aerobic conditions. Next, it flows out from the nitrification tank 10 and flows into the deaeration tank 30 in the direction indicated by the arrow in FIG. 2 and stays in the deaeration tank 30 for a predetermined time to degas dissolved oxygen. Next, it flows into the denitrification tank 20, stays in the denitrification tank 20 for a predetermined time, and further undergoes a biological treatment by anaerobic ammonia oxidation under anaerobic conditions to treat nitrogen components. Then, it flows out from the denitrification tank 20 and is drained as treated water to the outside of the wastewater treatment apparatus 2.

The wastewater treatment apparatus 2 includes a nitrification tank 10 having a configuration similar to that in the wastewater treatment system 1 and a denitrification tank 20.
Further, a pipe line drawn from a waste water supply source (not shown) is connected to the upstream end (left end in the figure) of the nitrification tank 10, and the waste water treatment device is connected to the downstream end (right end in the figure) of the denitrification tank 20. 2 is connected to the outside of the pipe for drainage.

  Hereinafter, the configuration of the waste water treatment apparatus 2 and the operation after the start-up operation will be described.

When the start-up operation of the wastewater treatment apparatus 2 is started, wastewater containing ammonia nitrogen fed from the supply source first flows into the nitrification tank 10 as in the wastewater treatment apparatus 1.
In the nitrification tank 10, as in the wastewater treatment apparatus 1, a nitrite type oxidation process is performed so that the nitrification rate is 56 to 57%, and the wastewater staying in the nitrification tank 10 for a predetermined time is nitrified. It flows out of the tank 10.

Subsequently, in the wastewater treatment apparatus 2, the wastewater that has flowed out of the nitrification tank 10 flows into the deaeration tank 30.
The deaeration tank 30 is a treatment tank in which a deaeration process for deaerating dissolved oxygen in the wastewater is performed.
Oxygen supplied to the wastewater in the nitrite-type nitrification process performed under favorable conditions becomes a factor that inhibits the reaction in the anaerobic ammonia oxidation reaction performed in the absence of oxygen.
For this reason, in this step, the dissolved oxygen that has become a high concentration by aeration in the nitrification tank 10 is degassed, and wastewater suitable for anaerobic conditions for performing anaerobic ammonia oxidation is introduced into the denitrification tank 20. .

The deaeration tank 30 mainly includes a deaeration unit and a dissolved oxygen measurement unit 83.
In addition, other measurement means such as a deaeration control unit, a nitrogen component measurement means, a water temperature measurement means, and a pH measurement means (not shown) may be provided.

The deaeration means is a means for deaerating oxygen gas dissolved in the wastewater flowing into the deaeration tank 30.
As a degassing means, a degassing membrane type device that provides a gas-permeable membrane at the gas-liquid interface, a blow-in type device that diffuses oxygen-free gas in water, a device that adsorbs and removes oxygen, an oxygen scavenger is added However, an apparatus using an oxygen-free gas diffuser is preferable in that the re-dissolution of oxygen in the air is small.
In the present embodiment, the deaeration means includes a blower 63, a diffuser 61, and an air supply pipe 62 as shown in FIG.
The blower 63 blows oxygen-free gas supplied from an oxygen-free gas source (not shown) to the diffuser 61 through the air supply pipe 62. The oxygen-free gas is not particularly limited as long as it is a gas that does not substantially contain oxygen gas such as nitrogen gas, carbon dioxide gas, or rare gas and has a relatively low solubility in wastewater.
The diffuser 61 diffuses the blown oxygen-free gas into the deaeration tank 30, thereby reducing the solubility of oxygen in the wastewater and degassing the oxygen gas.
The diffuser 61 has a plurality of disk shapes in FIG. 2, but may have any shape such as a diffuser tube or a diffuser plate, and the diffuser port may be either a membrane type or a hole type. It is preferable that the diffuser openings of the diffuser 61 are arranged at a high density and dispersed at the bottom of the deaeration tank 30 so that the inside of the tank is uniformly deaerated.

The dissolved oxygen measuring means 83 measures the concentration of dissolved oxygen contained in the wastewater, and is the same as that provided in the nitrification tank 10.
The dissolved oxygen measuring means 83 is provided near the outlet at the downstream end of the deaeration tank 30 so that dissolved oxygen that can flow out to the subsequent stage can be measured.

The operation in the deaeration tank 30 is performed as follows.
When the wastewater flows into the deaeration tank 30, an oxygen-free gas, for example, carbon dioxide gas supplied from an oxygen-free gas source (not shown) is operated via the air supply pipe 62 by the operation of the blower 63 constituting the deaeration means. Then, the air is diffused from the diffuser port of the diffuser 61 to the waste water stored in the deaeration tank 30.
Usually, the dissolved oxygen concentration in the anaerobic condition of the denitrification tank 20 is controlled to be 0.5 mg / L or less, preferably 0.2 mg / L or less at a water temperature of 25 to 30 ° C.
Therefore, under the monitoring of the dissolved oxygen concentration by the dissolved oxygen measuring means 83, the oxygen-free gas is diffused to such an extent that the dissolved oxygen in the deaeration tank 30 is completely removed.
Aeration of oxygen-free gas can be performed constantly on the inflowing wastewater, or intermittently according to fluctuations in the measured value of dissolved oxygen concentration in the wastewater, or by adjusting the amount of aeration Can do.
For example, by providing a degassing control unit (not shown) connected to the blower 63 and the dissolved oxygen measuring means 83 via a signal line, the amount of diffused air can be controlled based on the measured dissolved oxygen concentration. .
The deaeration control unit is configured to include a calculation unit, a signal input / output unit, an A / D and D / A conversion unit, an operation unit, and the like, and the dissolved oxygen in the deaeration tank 30 measured by the dissolved oxygen measuring unit 83. The control amount of feedback control for controlling the concentration to the target value of the dissolved oxygen concentration in the anaerobic condition of the denitrification tank 20 is calculated, and the output control of the blower 63 is performed. When the output of the blower 63 is controlled, the amount of oxygen-free gas diffused into the denitrification tank 30 is adjusted, and the dissolved oxygen concentration in the degassing tank 30 is maintained within the target value range.
However, at the time of start-up, it is preferable to deaerate a predetermined amount or more until the acclimatization of the anaerobic ammonia bacteria proceeds. As anaerobic ammonia oxidation progresses in the denitrification process, the concentration of nitrogen gas increases, and the effect of dissolved oxygen in the wastewater is mitigated. Good.

The wastewater that stays in the degassing tank 30 for a predetermined time and from which the dissolved oxygen has been degassed then flows out from the degassing tank 30 and flows into the denitrification tank 20.
In the denitrification tank 20, as in the wastewater treatment apparatus 1, a denitrification step by anaerobic ammonia oxidation is performed.
First, acclimatization of anaerobic ammonia-oxidizing bacteria is performed under a nitrite nitrogen concentration that is adjusted in stages by the operation of the dilution water supply means, and then nitrogen removal is performed on wastewater with the raised nitrite nitrogen concentration. It is performed as a steady operation.
The waste water staying in the denitrification tank 20 for a predetermined time flows out of the denitrification tank 20 and is drained as treated water to the outside of the waste water treatment apparatus 2 through a drainage pipe connected to the outside of the waste water treatment apparatus 2. .

According to the wastewater treatment apparatus 2 provided with such a degassing tank 30, the dissolved oxygen in the wastewater having a high concentration in the nitrous acid type oxidation step is surely removed before being subjected to the anaerobic ammonia oxidation reaction. Therefore, the denitrification process can be continued stably.
In addition, anaerobic ammonia-oxidizing bacteria are less susceptible to dissolved oxygen in the wastewater, so the time required to adapt to anaerobic ammonia-oxidizing bacteria can be shortened and the time required for start-up operation can be prevented from being prolonged. .
In addition, stable denitrification treatment can be continued in the treatment with increased aeration amount, such as when treating high-concentration nitrogen-containing wastewater.

[Modification 2]
Next, a second modification of the embodiment of the present invention will be described.

FIG. 3 is a configuration diagram of a second modification of the wastewater treatment apparatus according to the embodiment. As shown in FIG. 3, this wastewater treatment apparatus 3 is a wastewater treatment apparatus composed of three tanks each having a degassing tank 30 between the nitrification tank 10 and the denitrification tank 20, as with the wastewater treatment apparatus 2. It has become.
The waste water treatment device 3 is different from the waste water treatment device 2 in that the dilution water supply means is connected to the deaeration tank 30.
As shown by the arrow in FIG. 3, waste water containing ammonia nitrogen first flows into the nitrification tank 10, stays in the nitrification tank for a predetermined time, and undergoes biological treatment under aerobic conditions. Next, it flows out from the nitrification tank 10 and flows into the deaeration tank 30 in the direction indicated by the arrow in FIG. 3 and stays in the deaeration tank 30 for a predetermined time to degas dissolved oxygen. Next, it flows into the denitrification tank 20, stays in the denitrification tank 20 for a predetermined time, and further undergoes a biological treatment by anaerobic ammonia oxidation under anaerobic conditions to treat nitrogen components. Then, it flows out from the denitrification tank 20 and is drained as treated water to the outside of the wastewater treatment apparatus 2.

The wastewater treatment apparatus 3 includes a nitrification tank 10, a denitrification tank 20, and a deaeration tank 30 having the same configuration as in the wastewater treatment system 2.
However, in the wastewater treatment system 2, the dilution water supply means provided in the denitrification tank 20 is provided in the deaeration tank 30 in the wastewater treatment apparatus 3. Further, the deaeration tank 30 is provided with a nitrogen component measuring means 93.
Further, a pipe line drawn from a waste water supply source (not shown) is connected to the upstream end (left end in the figure) of the nitrification tank 10, and the waste water treatment device is connected to the downstream end (right end in the figure) of the denitrification tank 20. 3 is connected to the outside of the pipe 3 for drainage.

  Hereinafter, the configuration of the waste water treatment apparatus 3 and the operation after the start-up operation will be described.

When the start-up operation of the wastewater treatment apparatus 3 is started, the wastewater containing ammonia nitrogen fed from the supply source flows into the nitrification tank 10 as in the wastewater treatment apparatus 2.
In the nitrification tank 10, as in the wastewater treatment apparatus 2, a nitrite-type oxidation process is performed so that the nitrification rate is 56 to 57%, and the wastewater staying in the nitrification tank 10 for a predetermined time is nitrified. It flows out of the tank 10.

Next, the waste water flowing out from the nitrification tank 10 flows into the deaeration tank 30.
At this time, the dilution water is stored in advance in the dilution water adjustment tank 40 constituting the dilution water supply means connected to the deaeration tank 30.

  In the deaeration tank 30, as in the wastewater treatment apparatus 2, a deaeration process for degassing dissolved oxygen in the wastewater is performed. In addition, the dilution water supply process is started substantially simultaneously with the degassing of the dissolved oxygen.

  In the deaeration, the dissolved oxygen concentration is measured so that the dissolved oxygen concentration under anaerobic conditions flowing into the denitrification tank 20 is 0.5 mg / L or less, preferably 0.2 mg / L or less at a water temperature of 25 to 30 ° C. Deaeration is performed under the supervision of means 83.

Further, the dilution water in the deaeration tank 30 is supplied in the same manner as in the wastewater treatment apparatus 2.
The concentration of nitrite nitrogen in the wastewater flowing into the denitrification tank 20 from the nitrification tank 10 during steady operation in the wastewater treatment apparatus 3 is 0.1 to 5.0 kg-N as in the wastewater treatment apparatus 1. A relatively high concentration is expected to be / m ³ / day. Therefore, the concentration of ammonia nitrogen introduced into the nitrification tank 10 in the start-up operation is relatively high. Thereafter, the nitrous acid is oxidized and flows into the denitrification tank 20 from the nitrification tank 10 through the deaeration tank 30. The concentration of nitrate nitrogen is not suitable for unfamiliar anaerobic ammonia-oxidizing bacteria. Accordingly, the deaeration tank 30 is supplied with an amount of dilution water that keeps the concentration of nitrite nitrogen in the wastewater flowing into the denitrification tank 20 low until the adaptation of the anaerobic ammonia oxidizing bacteria used in the denitrification tank 20 is completed. Is done. For example, after the dilution water supply pump 50 is operated until the measured value of nitrite nitrogen by the nitrogen component measuring means 93 is stabilized at about 70 mg-N / L, the operation is stopped.

When the dilution water pressurized by the dilution water supply pump 50 is sent to the deaeration tank 30, the waste water and the dilution water are stirred in the deaeration tank 30. Stirring is usually performed by aeration with a deaeration means.
The waste water that has been retained in the deaeration tank 30 for a predetermined time, diluted and degassed dissolved oxygen flows out of the deaeration tank 30 and flows into the denitrification tank 20.

In the denitrification tank 20, a denitrification process by anaerobic ammonia oxidation is performed as in the wastewater treatment apparatus 2.
First, anaerobic ammonia-oxidizing bacteria are acclimatized in the wastewater diluted in the deaeration tank 30.
When it is confirmed that the concentration of nitrite nitrogen in the denitrification tank 20 shows a predetermined decrease, the concentration of nitrite nitrogen flowing into the denitrification tank 20 is stepwise in order to promote the adaptation of the anaerobic ammonia oxidizing bacteria. To be raised.
For example, when it is confirmed that the nitrite nitrogen concentration in the diluted wastewater at the start of the habituation is reduced to about 25 to 50%, the nitrite nitrogen concentration in the denitrification tank 20 is set to 100 mg-N / L to Pulling up in the range of about 1000 mg-N / L, shifting the acclimatization of anaerobic ammonia oxidizing bacteria to a higher concentration stage. Thereafter, when it is confirmed that the nitrite nitrogen concentration raised again decreases by a predetermined concentration, the nitrite nitrogen concentration in the denitrification tank 20 is raised again.
The raising of the nitrite nitrogen concentration here is mainly performed by controlling the supply amount of dilution water in the deaeration tank 30 and controlling the progress of nitrite oxidation in the nitrification tank 10.
By repeating such a process, the nitrogen removal speed in the denitrification tank 20 is increased to a speed required during steady operation.

Thereafter, in the denitrification tank 20, steady operation is continued with a predetermined volume load and a predetermined residence time.
In addition, even during steady operation, when signs of nitrite nitrogen concentration or ammonia nitrogen concentration or dissolved oxygen concentration changing to a high concentration are observed, by supplying dilution water to waste water in the deaeration tank 30, The nitrite nitrogen concentration, ammonia nitrogen concentration or dissolved oxygen concentration in the denitrification tank 20 can be reduced. For example, in the deaeration tank 30, a dilution water supply control unit that controls the amount of dilution water to be supplied is installed so as to be connected to the dilution water supply unit, and the measurement value of the nitrogen component measurement unit 93 is set in the dilution water supply control unit. Is configured to be input. In the dilution water supply control unit, the feedback control of the nitrite nitrogen concentration or the ammonia nitrogen concentration in the deaeration tank 30 is performed to control the output of the dilution water supply pump 50 provided in the dilution water supply means. Moreover, it is set as the structure by which the measured value of the nitrogen component measurement means 91 with which the nitrification tank 10 is equipped is input into a dilution water supply control part, and by the dilution water supply control part and dilution water supply means which were installed in the deaeration tank 30 Then, feedforward control based on fluctuations in the nitrite nitrogen concentration or ammonia nitrogen concentration in the nitrification tank 10 is performed.

  The waste water staying in the denitrification tank 20 for a predetermined time flows out from the denitrification tank 20 and is drained out of the waste water treatment apparatus 3 through a drainage pipe connected to the outside of the waste water treatment apparatus 3.

According to the wastewater treatment apparatus 3 provided with such a degassing tank 30, the dissolved oxygen in the wastewater having a high concentration in the nitrous acid type oxidation step is surely removed before being subjected to the anaerobic ammonia oxidation reaction. Therefore, the denitrification process can be continued stably.
In addition, anaerobic ammonia-oxidizing bacteria are less susceptible to dissolved oxygen in the wastewater, so the time required to adapt to anaerobic ammonia-oxidizing bacteria can be shortened and the time required for start-up operation can be prevented from being prolonged. .
In addition, stable denitrification treatment can be continued in the treatment with increased aeration amount, such as when treating high-concentration nitrogen-containing wastewater.
Further, since the dilution water supply means is connected to the deaeration tank 30, the dilution water can be degassed in the deaeration tank 30, and the dissolved oxygen of the diluted wastewater flowing into the denitrification tank 20 can be reduced. Can be a concentration.

  Next, an example of the present invention will be shown and described in detail.

[Example 1]
As Example 1, the wastewater treatment test of the nitrogen-containing wastewater which assumed the time of start-up operation was done using the wastewater treatment apparatus 1 which concerns on embodiment.
As the raw water to be treated, synthetic waste water imitating waste water containing ammonia nitrogen was used.
The ammonia nitrogen concentration of this synthetic wastewater was increased stepwise from 150 mg-N / L to 1000 mg-N / L.

(Nitrite-type oxidation process)
First, as a nitrite type oxidation step, approximately half of ammonia nitrogen in raw water was oxidized to nitrite nitrogen in the presence of aerobic ammonia oxidizing bacteria.
As the aerobic ammonia-oxidizing bacteria, sludge containing aerobic ammonia-oxidizing bacteria was used as a entrapping immobilization support, and was introduced into the nitrification tank so that the volume ratio was 20%.
Moreover, the water temperature of the nitrification tank was 30 degreeC, pH was adjusted to pH7.6 using the sodium hydrogencarbonate aqueous solution, and Mg, K, Na, and the phosphate were added as an inorganic nutrient.
The volume load of the nitrification tank was operated at 1.0 to 3.0 kg-N / m ³ / day.
The nitrification rate in the nitrification tank was calculated according to Equation 3 by measuring the total nitrogen (C ₀ ) and ammonia nitrogen concentration (C ₁ ) by installing a total nitrogen meter and an ammonium ion electrode.
In this example, the target value of the nitrification rate in the nitrite oxidation process was 56 to 57%, and the dissolved oxygen concentration was adjusted by controlling the amount of aeration to adjust the nitrification rate. Specifically, when the measured nitrification rate is below the target value range, the dissolved oxygen concentration is controlled to be 5 mg / L, and when it is within the target value range, the dissolved oxygen concentration is 2 mg / L. When the target value range was exceeded, the dissolved oxygen concentration was controlled to 1 mg / L.

(Denitrification process)
Next, as a denitrification step, ammonia nitrogen and nitrite nitrogen in raw water were converted to nitrogen gas by anaerobic ammonia oxidation in the presence of anaerobic ammonia oxidizing bacteria.
As the anaerobic ammonia oxidizing bacteria, a sludge containing anaerobic ammonia oxidizing bacteria was used as a entrapping immobilization support, and was introduced into a denitrification tank so that the volume ratio was 20%.
The water temperature of the denitrification tank was 30 ° C., and the pH was adjusted to pH 7.6 using an aqueous sodium hydrogen carbonate solution.
The denitrification tank was operated at a volume load of 0.1 to 5.0 kg-N / m ³ / day.

Diluted water was supplied to the denitrified raw water to dilute the nitrite nitrogen concentration to about 70 mg-N / L.
As the dilution water, industrial wastewater having a dissolved oxygen concentration of about 7 mg / L was used.
When anaerobic ammonia oxidation proceeds in the denitrification tank and the nitrite concentration is reduced to 20 mg-N / L, the nitrite nitrogen concentration after dilution is 200 mg, such as 200 mg-N / L, 400 mg-N / L. The ammonia nitrogen concentration of the synthetic wastewater was increased so as to gradually increase at intervals of about -N / L.

(result)
As a result, the nitrogen component removal rate after 120 days from the start of the start-up operation was 1.0 kg-N / m ³ / day.

[Example 2]
As Example 2, a wastewater treatment test for nitrogen-containing wastewater assuming a start-up operation was performed using the wastewater treatment apparatus 2 according to the first modification.
As the raw water to be treated, synthetic waste water imitating waste water containing ammonia nitrogen was used.
The concentration of ammonia nitrogen in the synthetic wastewater was increased stepwise from 150 mg-N / L to 1000 mg-N / L.

(Nitrite-type oxidation process)
First, the nitrite oxidation process was performed in the same manner as in Example 1.

(Deaeration process)
Next, as a degassing step, oxygen in the raw water that had undergone the nitrite type oxidation step was degassed and removed.
Deaeration was performed by aerating carbon dioxide gas into the raw water with a membrane diffuser provided at the bottom of the deaeration tank.
The water temperature in the deaeration tank was 30 ° C., the residence time was 30 minutes, and deaeration was performed so that the dissolved oxygen concentration in the raw water after the deaeration process was 0.5 mg / L or less.

(Denitrification process)
Subsequently, the denitrification step was performed in the same manner as in Example 1.

(result)
As a result, it was confirmed that the dissolved oxygen concentration of the raw water flowing into the denitrification tank was reduced to about 0.5 mg / L by passing through the deaeration tank.
After 92 days from the start of the start-up operation, the nitrogen component removal rate reached 4.0 kg-N / m ³ / day, and the diluted water having a relatively high dissolved oxygen concentration was supplied without degassing. Compared to the results in Example 1, it was observed that high rates of nitrogen removal were achieved in a shorter period of time. This result shows that anaerobic ammonia oxidizing bacteria are easily affected by dissolved oxygen during start-up operation, suggesting that removal of dissolved oxygen in raw water flowing into the denitrification tank is effective. .

[Reference Example 1]
As Reference Example 1, a wastewater treatment test for nitrogen-containing wastewater assuming a steady operation was performed using the wastewater treatment apparatus 1 according to the embodiment without supplying dilution water.
As the raw water to be treated, synthetic waste water imitating waste water containing ammonia nitrogen was used.
The ammonia nitrogen concentration of the synthetic wastewater was 1000 mg-N / L.

(Nitrite-type oxidation process)
First, the nitrite oxidation process was performed in the same manner as in Example 1. However, the entrapping immobilization support containing aerobic ammonia oxidizing bacteria was used after acclimatization in a separate tank in advance.

(Denitrification process)
Next, the denitrification step was performed in the same manner as in Example 1. However, the entrapping immobilization support containing anaerobic ammonia oxidizing bacteria was used after acclimatization in a separate tank in advance.

(result)
In this test, since the nitrification tank and the denitrification tank were loaded with a carrier that had been conditioned in a separate tank in advance, the activities of the nitrite oxidation reaction and the anaerobic ammonia oxidation reaction were obtained immediately after the loading of each carrier. . Therefore, it was operated by controlling the dissolved oxygen concentration in the nitrification tank using aeration means so as to be in the range of 2 to 5 mg / L.
On the other hand, the measured value of the dissolved oxygen concentration in the nitrification tank is measured to vary within the range of 1 to 6 mg / L, and the dissolved oxygen concentration in the nitrification tank shows a relatively high numerical value exceeding the control target value. It was recognized that there was a case.
As a result of operating under these conditions, the nitrogen removal rate after the denitrification step was 70 to 84%, which was a relatively low value compared to the planned nitrogen removal rate.
This result was thought to be due to the fact that dissolved oxygen in the nitrification tank flowed into the denitrification tank and the activity of anaerobic ammonia oxidizing bacteria was locally inhibited by dissolved oxygen.

[Reference Example 2]
As Reference Example 2, a wastewater treatment test for nitrogen-containing wastewater assuming a steady operation was performed using the wastewater treatment apparatus 2 according to the first modification without supplying dilution water.
As the raw water to be treated, synthetic waste water imitating waste water containing ammonia nitrogen was used.
The ammonia nitrogen concentration of the synthetic wastewater was 1000 mg-N / L.

(Nitrite-type oxidation process)
First, the nitrite oxidation process was performed in the same manner as in Example 1. However, the entrapping immobilization support containing aerobic ammonia oxidizing bacteria was used after acclimatization in a separate tank in advance.

(Deaeration process)
Next, the deaeration process was performed in the same manner as in Example 2.

(Denitrification process)
Subsequently, the denitrification step was performed in the same manner as in Example 1. However, the entrapping immobilization support containing anaerobic ammonia oxidizing bacteria was used after acclimatization in a separate tank in advance.

(result)
In this test, as in Reference Example 2, since the nitrification tank and the denitrification tank were loaded with a carrier that was previously conditioned in another tank, the dissolved oxygen concentration in the nitrification tank was in the range of 2 to 5 mg / L. As described above, it was controlled and operated using aeration means.
As a result of operation under these conditions, stable operation was possible within a range of 80 to 86% of the nitrogen removal rate after the denitrification step by passing through a degassing tank.
As a result, even if the dissolved oxygen concentration in the raw water in the nitrification tank may fluctuate to the high concentration side, the dissolved oxygen concentration in the raw water flowing into the denitrification tank decreases by passing through the degassing step, This was thought to be because the inhibition of the activity of anaerobic ammonia-oxidizing bacteria was reduced.

DESCRIPTION OF SYMBOLS 1 Waste water treatment system 2 Waste water treatment system 3 Waste water treatment system 10 Nitrification tank 20 Denitrification tank 30 Deaeration tank 40 Dilution water adjustment tank 50 Dilution water supply pump 60 Blower 61 Diffuser 62 Air supply pipe 63 Blower 64 Screen 65 Agitation means 70 Aeration control part 81, 82, 83 Dissolved oxygen measuring means 91, 92, 93 Nitrogen component measuring means 110 Aerobic ammonia oxidizing bacteria inclusion immobilization support 120 Anaerobic ammonia oxidation bacteria inclusion immobilization support

Claims (8)

A wastewater treatment method for treating nitrogen-containing wastewater by anaerobic ammonia oxidation reaction,
A nitrite oxidation process that oxidizes a part of ammonia nitrogen contained in wastewater to nitrite nitrogen in the presence of aerobic ammonia oxidizing bacteria;
A diluted water supply step of supplying diluted water for reducing the nitrite nitrogen concentration or ammonia nitrogen concentration or dissolved oxygen concentration in the waste water to the oxidized waste water;
A denitrification step of converting ammonia nitrogen and nitrite nitrogen contained in the oxidized wastewater into nitrogen gas in the presence of anaerobic ammonia oxidizing bacteria;
A wastewater treatment method comprising: further,
The wastewater treatment method according to claim 1, further comprising a degassing step of degassing the dissolved oxygen in the oxidized wastewater between the nitrous acid type oxidation step and the denitrification step.   The waste water treatment method according to claim 2, wherein the deaeration step is performed in combination with the dilution water supply step.   The wastewater treatment method according to any one of claims 1 to 3, wherein the wastewater treatment method is performed during start-up operation of a wastewater treatment apparatus that treats nitrogen-containing wastewater by an anaerobic ammonia oxidation reaction. A wastewater treatment apparatus for treating nitrogen-containing wastewater by anaerobic ammonia oxidation reaction,
A nitrification tank that oxidizes part of ammonia nitrogen contained in wastewater to nitrite nitrogen in the presence of aerobic ammonia-oxidizing bacteria;
Dilution water supply means for supplying dilution water for reducing the nitrite nitrogen concentration, ammonia nitrogen concentration or dissolved oxygen concentration in the waste water to the waste water flowing out from the nitrification tank;
A denitrification tank for converting ammonia nitrogen and nitrite nitrogen contained in the waste water flowing out of the nitrification tank into nitrogen gas in the presence of anaerobic ammonia oxidizing bacteria;
A wastewater treatment apparatus comprising:   The wastewater treatment apparatus according to claim 5, further comprising a deaeration tank that is provided between the nitrification tank and the denitrification tank and degassed dissolved oxygen in the wastewater flowing out of the nitrification tank.   The waste water treatment apparatus according to claim 6, wherein the dilution water supply means is connected to at least one of the deaeration tank and the denitrification tank.   The wastewater treatment apparatus according to any one of claims 5 to 7, wherein the dilution water supply unit is operated during start-up operation of the wastewater treatment apparatus.

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