JP2003047990A - Biological denitrifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To steadily and efficiently perform biological denitrification by preventing steadily a hindrance of nitrite nitrogen flowing in a denitrification vessel to ANAMMOX microorganisms even when the nitrite nitrogen concentration in raw water fluctuates, when biological denitrification of the raw water containing ammoniacal nitrogen and nitrite nitrogen is carried out by the action of autotrophic denitrifying microorganisms with the ammonia nitrogen as an electron donor and nitrite nitrogen as an acceptor. SOLUTION: The amount of raw water flowing into a reaction vessel 1 or the amount of dilution water diluting the raw water is adjusted on the basis of a measured value by measuring the concentration of the nitrite ion in the vicinity of a raw water flowing-in port of the reaction vessel 1.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to the action of a denitrifying microorganism that uses raw water containing ammoniacal nitrogen and nitrite nitrogen as the electron donor for the ammoniacal nitrogen and the electron acceptor for the nitrite nitrogen. The present invention relates to a device for biological denitrification, and in particular, in this biological denitrification, a biological denitrification for preventing stable and efficient biological denitrification by preventing inhibition of denitrifying microorganisms by high concentration nitrite nitrogen in raw water. Regarding the device.

[0002]

2. Description of the Related Art Ammoniacal nitrogen contained in drainage is one of the causative substances of eutrophication in rivers, lakes and oceans, and it is necessary to remove it efficiently in the drainage treatment process. Generally, ammoniacal nitrogen in wastewater is a nitrification process in which ammoniacal nitrogen is oxidized to nitrite nitrogen by ammonia-oxidizing bacteria, and this nitrite nitrogen is further oxidized to nitrate nitrogen by nitrite-oxidizing bacteria. Nitrogen gas and nitrogen gas are transformed into nitrogen gas by a denitrification process in which organic substances are used as electron donors to decompose them into nitrogen gas by denitrifying bacteria, which are heterotrophic bacteria. Be disassembled.

However, in such a conventional nitrification denitrification method, a large amount of an organic substance such as methanol is required as an electron donor in the denitrification step, and a large amount of oxygen is required in the nitrification step, so that the running cost is high. There is a drawback that.

On the other hand, in recent years, ammoniacal nitrogen and nitrite nitrogen have been utilized by utilizing an autotrophic microorganism (autotrophic bacterium) having ammoniacal nitrogen as an electron donor and nitrite nitrogen as an electron acceptor. A method of denitrifying by reacting with was proposed. This method does not require addition of organic matter, and thus can reduce the cost as compared with the method using heterotrophic denitrifying bacteria. In addition, the yield of autotrophic microorganisms is low, and the amount of sludge generated is significantly smaller than that of heterotrophic microorganisms, so that the amount of excess sludge generated can be suppressed. Furthermore, N observed by the conventional nitrification denitrification method
_It also has the feature that it does not generate ₂ O and can reduce the load on the environment.

This autotrophic denitrifying microorganism (hereinafter referred to as "ANA
Sometimes referred to as "MMOX microorganism". ) Is used in Strous, M, et al., Appl. Microbio
l. Biotechnol., 50, p.589-596 (1998), it is believed that ammoniacal nitrogen and nitrite nitrogen react with each other in the following reaction to decompose into nitrogen gas. .

[0006]

[Chemical 1]

ANAM involved in the reaction in the above-mentioned biological denitrification method
MOX microorganisms are inhibited and become less active in the presence of high concentrations of nitrite nitrogen. When the inside of the denitrification tank is incompletely mixed (for example, plug flow type), the concentration of nitrite nitrogen near the raw water inlet may be locally high. Therefore, when the nitrite nitrogen concentration of the raw water flowing into the denitrification tank is high, the raw water is diluted by circulating treated water, etc., and the nitrite nitrogen concentration in the denitrification tank is lower than the above-mentioned inhibitory concentration. It is being held.

[0008]

If the concentration of nitrite nitrogen in the raw water is constant, circulation of a predetermined amount of treated water causes a high concentration of nitrite nitrogen to flow into the denitrification tank.
Although it is possible to prevent inhibition of MOX microorganisms, when the nitrite nitrogen concentration of the raw water fluctuates, the circulation of such treated water causes a high concentration of nitrite nitrogen in the ANAMMOX.
It cannot prevent the inhibition of microorganisms. That is, when raw water having a high nitrite nitrogen concentration flows into the denitrification tank, the nitrite nitrogen concentration near the raw water inlet of the denitrification tank rises, and the ANAMMOX microorganism in this part is inhibited. Then, the activity of the ANAMMOX microorganism near the inlet of the raw water of the denitrification tank is inhibited and the activity is reduced, so that the nitrite nitrogen concentration in the denitrification tank cannot be decomposed and remains in the denitrification tank. Is increased, and further, the ANAMMOX microorganism is inhibited by this high-concentration nitrite nitrogen, and the activity is further reduced. The lower limit of the nitrite nitrogen (NO ₂ —N) concentration at which the ANAMMOX microorganism is inhibited is about 1
It is said to be 00 mg-N / L.

The present invention solves the above-mentioned conventional problems, and reliably prevents the inhibition of the ANAMMOX microorganisms by the nitrite nitrogen flowing into the denitrification tank when the concentration of nitrite nitrogen in the raw water fluctuates and stabilizes. It is an object of the present invention to provide a biological denitrification device for performing efficient biological denitrification.

[0010]

The biological denitrification apparatus according to claim 1 has an inlet for raw water containing ammoniacal nitrogen and nitrite nitrogen and an outlet for the treatment liquid, and A denitrifying tank that performs biological denitrification by the action of a denitrifying microorganism that uses an electron donor and nitrite nitrogen as an electron acceptor, and a nitrite nitrogen concentration in the liquid near the raw water inlet in the denitrifying tank is measured. It is characterized by comprising a nitrate nitrogen concentration measuring means and means for adjusting a flow rate of raw water flowing into the denitrification tank based on an output signal of the nitrite nitrogen concentration measuring means.

The biological denitrification apparatus of claim 2 has an inlet for raw water containing ammoniacal nitrogen and nitrite nitrogen, and an outlet for the treatment liquid, wherein the ammoniacal nitrogen is used as an electron donor. A denitrification tank for biological denitrification by the action of denitrifying microorganisms using nitrate nitrogen as an electron acceptor, a diluting water supply means for supplying diluting water for diluting raw water, and a raw water inlet near the denitrification tank. Nitrite nitrogen concentration measuring means for measuring the nitrite nitrogen concentration of the liquid, and means for adjusting the amount of dilution water supplied by the dilution water supply means based on the output signal of the nitrite nitrogen concentration measuring means And is provided.

Based on the concentration of nitrite nitrogen in the liquid near the inlet of raw water in the denitrification tank, when the concentration of nitrite nitrogen exceeds a preset upper limit value, the inflow amount of nitrite nitrogen is reduced. If the amount of nitrite nitrogen is below the preset lower limit, the inflow of high-concentration nitrite nitrogen is increased to increase the concentration of nitrite nitrogen.
It is possible to reliably prevent the inhibition of X microorganisms and perform stable and efficient biological denitrification.

In the biological denitrification apparatus of claim 1, the amount of nitrite nitrogen flowing into the denitrification tank is controlled by controlling the amount of raw water flowing into the denitrification tank based on the measured nitrite nitrogen concentration. Adjust.

In the biological denitrification apparatus of claim 2, the amount of dilution water for diluting the raw water is adjusted based on the measured concentration of nitrite nitrogen to adjust the concentration of nitrite nitrogen in the inflow water of the denitrification tank. It controls the amount of nitrite nitrogen flowing into the denitrification tank.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the biological denitrification device of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a system diagram showing an embodiment of the biological denitrification apparatus of the present invention.

The biological denitrification apparatus shown in FIG. 1 has a USB (Upflow Sludge Bed) reaction tank 1 having a granulated sludge bed of ANAMMOX microorganisms formed therein as a denitrification tank. A raw water inflow pipe 2 is connected to the bottom of the reaction tank 1. A gas-liquid solid separation device 3 is provided above the reaction tank 1, and a treated water discharge pipe 4 is drawn out from the gas-liquid solid separation device 3. A circulation pipe 5 is provided which branches into the treated water discharge pipe 4 and returns a part of the treated water to the raw water inflow pipe 2 as circulating water. P ₁ is a raw water pump and P ₂ is a circulation pump.

In this biological denitrification apparatus, the raw water is introduced from the pipe 2 to the bottom of the USB reaction tank 1 together with the circulating water from the pipe 5. The raw water introduced into the USB reaction tank 1 is A
While the NAMMOX microorganism granulated sludge bed is rising in the upward flow, the biological water is denitrified by the ANAMMOX microorganisms, and the treated water is discharged from the pipe 4 to the outside of the system. A part of the treated water is circulated from the pipe 5 to the raw water introduction pipe 2.

In this biological denitrification device, the liquid inside the tank is drawn out from the raw water inflow portion at the bottom of the USB reaction tank 1, the nitrite nitrogen concentration of this liquid is measured, and then the pipes 6A and 6B are returned to the USB reaction tank 1. And a nitrite ion sensor installation unit 6 is provided. That is, from the raw water inflow part of the reaction tank 1 to the pipe 6A
After measuring the nitrite ion concentration of the extracted liquid in the tank with the nitrite ion sensor installation part 6, the liquid after measurement is piped 6
It is configured to return from B to the reaction tank 1 again.

As the nitrite ion sensor, a commercially available product,
For example, a nitrite ion electrode manufactured by Electrochemical Instruments Co., Ltd. or the like can be used.

In the biological denitrification apparatus of FIG. 1, the operation of the raw water pump P ₁ is controlled based on the nitrite ion concentration measured by such a nitrite ion sensor.

That is, an upper limit value (hereinafter sometimes referred to as "set upper limit value") and a lower limit value (hereinafter sometimes referred to as "set lower limit value") of the nitrite ion concentration of the liquid in the tank are set in advance. If the concentration of nitrite ion in the tank liquid exceeds the upper limit value, the raw water inflow amount is reduced, and if the concentration is lower than the lower limit value, the raw water inflow amount is increased.

As mentioned above, the ANAMMOX microorganism is NO
200 m after being inhibited at _2- N concentration of 100 mg / L or more
Almost no activity is lost at g / L or more. Therefore, the set upper limit value needs to be set to a value lower than 200 mg-N / L. On the other hand, the microorganisms in the tank are present in the form of flocs or biofilms, and in order to sufficiently permeate the substrate into the flocs or biofilms and effectively utilize the microbes inside,
Higher substrate concentration in the bulk is preferred. The set upper limit varies depending on the target processing efficiency and other conditions, but is generally 50 to 200 mg-N in NO ₂ -N concentration.
/ L, preferably 75 to 150 mg / L. On the other hand, if the set lower limit value is excessively low, it is possible to reliably prevent the inhibition of the activity of the ANAMMOX microorganisms, but since the treatment efficiency deteriorates, the set lower limit value varies depending on the target treatment efficiency and other conditions. , Generally N
O ₂ -N concentration is about 5 to 70 mg-N / L, especially 20 to
It is preferably 50 mg / L.

In the present invention, for example, the raw water inflow amount can be adjusted as follows.

When the reference value of the raw water inflow is set in advance and the NO ₂ —N concentration in the tank liquid exceeds the set upper limit value, the raw water inflow is slightly higher than the reference value, for example, 5 to 50.
%, And when the NO ₂ —N concentration in the tank liquid falls below the lower limit value, the raw water inflow rate is returned to the standard value.

When the NO ₂ —N concentration in the tank liquid exceeds the set upper limit value, the raw water inflow amount is slightly reduced from the current value, for example, by 5 to 50%, and the NO ₂ —N concentration in the tank liquid is reduced. When it is below the set lower limit value, the raw water inflow amount is slightly increased from the current value, for example, 5 to 50%.

In the above, NO _{2 of the} liquid in the tank
The amount of reduction or increase of the raw water inflow is changed depending on the magnitude of the difference between the N concentration and the set upper limit value or the set lower limit value. That is,
For example, when the NO ₂ -N concentration in the tank liquid is significantly higher than the set upper limit value, the raw water inflow amount is significantly reduced, and the NO ₂ -N concentration in the tank liquid is slightly higher than the set upper limit value. In some cases, the raw water inflow is reduced slightly.

In the biological denitrification apparatus of FIG. 1, the operation of the raw water pump P ₁ is controlled based on the nitrite ion concentration measured by such a nitrite ion sensor, but the circulation pump P ₂
The amount of circulating water for diluting the raw water may be adjusted by controlling the operation of.

In this case, when the concentration of nitrite ions in the liquid in the tank exceeds the set upper limit value, the circulating water amount is increased, and conversely, when the concentration is lower than the set value, the circulating water amount is reduced.

For example, the amount of circulating water can be adjusted as follows.

A reference value of the circulating water amount is set in advance,
When the NO 2 _-N concentration in the bath within liquid exceeds the set upper limit value is slightly circulating water than the reference value, for example, it is increased 5-50%, the NO 2 _-N concentration in the bath within the fluid set lower limit If it falls below the range, return the circulating water amount to the standard value.

When the NO ₂ —N concentration in the tank liquid exceeds the set upper limit value, the circulating water amount is slightly increased from the current value, for example, 5 to 50%, and the NO ₂ —N concentration in the tank liquid is set. When the value is below the lower limit, the amount of circulating water is slightly reduced from the current value, for example, 5 to 50%.

In the above, NO _{2 of the} liquid in the tank
-The reduction amount or increase amount of circulating water is changed according to the magnitude of the difference between the N concentration and the set upper limit value or the set lower limit value. That is, for example, when the NO ₂ —N concentration in the tank liquid is significantly higher than the set upper limit value, the circulating water amount is significantly increased to increase the N 2 in the tank liquid.
Slightly increase the circulating amount of water when O 2 _-N concentration is slightly higher than the set upper limit value.

By adjusting the amount of circulating water in this way, the concentration of nitrite nitrogen in the inflow water of the reaction tank 1 is adjusted,
The concentration of nitrite nitrogen in the raw water inflow portion of the reaction tank 1 can be maintained within a suitable concentration range.

It is also possible to provide a diluting water supply means different from the circulating water and control the operation of the diluting water supply pump. Further, both the amount of dilution water (circulation water) and the amount of raw water may be controlled together. In this case, it is possible to increase the amount of raw water and reduce the amount of dilution water, or to reduce the amount of raw water and increase the amount of dilution water so that the amount of inflow water flowing into the reaction tank can be made constant, which is preferable.

The measurement with the nitrite ion sensor may be continuous measurement or intermittent measurement. When performing intermittent measurement, there is no particular limitation on the measurement frequency, and it is appropriately measured based on the possibility of fluctuation of the nitrite ion concentration in the tank liquid due to fluctuations of raw water quality and other treatment conditions. Generally, it is preferable to measure once every 0.1 to 24 hours.

In the biological denitrification apparatus shown in FIG. 1, a nitrite ion sensor installation unit is provided outside the reaction tank 1, and the in-tank liquid is drawn from the reaction tank 1 to measure the nitrite nitrogen concentration. However, a nitrite ion sensor installation portion may be provided at the raw water inlet of the reaction tank 1 to directly measure the nitrite nitrogen concentration of the solution in the reaction tank 1.

Further, the biological denitrification apparatus shown in FIG. 1 uses a USB reaction tank for holding granulated sludge of ANAMMOX microorganisms as a denitrification tank, but in the present invention, the type of denitrification tank is not particularly limited. Alternatively, any type such as a sludge suspension method, a fixed bed, a fluidized bed, and a carrier addition method may be used.

For example, when a sludge suspension type denitrification tank is used as the biological denitrification device, a solid-liquid separation means such as a sedimentation tank is provided in the subsequent stage of the denitrification tank, and the separated sludge is returned to the denitrification tank. However, in such a case, the nitrite ion sensor may be provided near the inflow port of the raw water of the denitrification tank.

In the biological denitrification method of the present invention, the raw water to be treated is water containing ammoniacal nitrogen and nitrite nitrogen, and may contain organic matter and organic nitrogen. Prior to the denitrification treatment, it is preferable to decompose it to the extent that it becomes ammoniacal nitrogen, and if the dissolved oxygen concentration is high, it is preferable to remove the dissolved oxygen as necessary. Raw water may contain an inorganic substance. Further, the raw water may be a mixture of a liquid containing ammoniacal nitrogen and a liquid containing nitrite nitrogen. For example, wastewater containing ammoniacal nitrogen can be subjected to aerobic treatment in the presence of ammonia-oxidizing microorganisms, and a part of the ammoniacal nitrogen, preferably one-half of which can be partially oxidized to nitrous acid, can be used as raw water. . Furthermore, a part of the wastewater containing ammoniacal nitrogen is subjected to aerobic treatment in the presence of ammonia-oxidizing microorganisms to oxidize the ammoniacal nitrogen to nitrous acid,
The raw water may be a mixture with the rest of the wastewater containing ammoniacal nitrogen.

In general, wastewater containing ammonia nitrogen, organic nitrogen, and organic matter such as sewage, night soil, anaerobic nitrifying and desorbing liquid, etc. is often treated, but in this case, these are aerobic or It is preferable to use anaerobic treatment to decompose organic substances, decompose organic nitrogen into ammonia nitrogen, and further perform partial nitrite oxidation or partial nitrite oxidation as raw water.

The ratio of the ammoniacal nitrogen to the nitrite nitrogen in the raw water is preferably 0.5 to 2 and more preferably 1 to 1.5, in molar ratio, to 1 ammoniacal nitrogen. The concentrations of ammoniacal nitrogen and nitrite nitrogen in the raw water are preferably 5 to 1000 mg / L and 5 to 200 mg / L, respectively, but not limited to this if the treated water is circulated and diluted.

The biological denitrification conditions of the raw water include, for example, the temperature of the liquid in the reaction tank is 10 to 40 ° C., especially 20 to 35 ° C., and the pH.
5-9, especially 6-8, dissolved oxygen concentration 0-2.5 mg
/ L, especially 0-0.2 mg / L, BOD concentration 0-50
mg / L, especially 0-20 mg / L, nitrogen load 0.1-
10 kg-N / m ³ · day, especially 0.2 to 5 kg-N
It is preferably in the range of / m ³ · day.

As shown in FIG. 1, when the granule sludge is formed in the UASB reaction tank 1, it takes a long time to form the granules only with the microorganisms. Therefore, a substance to be the core is added, and the ANAMMOX microorganism is added around the nucleus. It is desirable to form a biofilm. In this case, examples of the nucleus include microbial granules and abiotic simple substances.

Examples of the microbial granules used as nuclei include anaerobic microbes such as methane bacterium granules and heterotrophic denitrifying bacterium granules. As the methane bacteria granule, those used in a methane fermentation tank in which methane fermentation is performed by the UASB method or the EGSB method can be applied. As the heterotrophic denitrification granule, those used in a normal denitrification tank such as UASB or EGSB can be applied. These granules can be used as they are or as a crushed product. The autotrophic denitrifying microorganisms are likely to attach to such microbial granules, shortening the time required for granule formation. It is also more economical than using abiotic materials as the core.

As the abiotic material used as the core, for example, activated carbon, zeolite, silica sand, diatomaceous earth, calcined ceramics, ion exchange resin, etc., preferably activated carbon, zeolite, etc., having a particle size of 50 to 200 μm,
It is preferably 50 to 100 μm, and the average specific gravity is 1.01 to 1.01.
2.5, preferably 1.1 to 2.0 carriers can be mentioned.

ANAMMOX formed in this way
The microbial granule sludge has an average particle size of 0.25 to 3
mm, preferably 0.25 to 2 mm, more preferably about 0.25 to 1.5 mm and having an average specific gravity of 1.01 to 2.
It is desirable that it is 5, preferably 1.1 to 2.0.
Since the smaller the particle size of the granule, the larger the specific surface area, it is preferable from the viewpoint of maintaining a high sludge concentration and efficiently performing the denitrification treatment.

[0048]

As described above in detail, according to the biological denitrification apparatus of the present invention, in the biological denitrification treatment by the ANAMMOX microorganism, even if the nitrite nitrogen concentration of the raw water changes, the denitrification tank can be used. ANAM due to inflowing nitrite nitrogen
Stable and efficient biological denitrification can be performed by reliably preventing the inhibition of MOX microorganisms.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of a biological denitrification device of the present invention.

[Explanation of symbols]

1 USB reaction tank 3 Gas-liquid separation device 6 Nitrite ion sensor installation section

Claims (2)

[Claims] 1. An inlet for raw water containing ammoniacal nitrogen and nitrite nitrogen, and an outlet for a treatment solution, wherein the ammoniacal nitrogen serves as an electron donor and the nitrite nitrogen serves as an electron acceptor. A denitrification tank for biological denitrification by the action of denitrifying microorganisms, a nitrite nitrogen concentration measuring means for measuring the concentration of nitrite nitrogen in the liquid near the inlet of raw water in the denitrification tank, and the nitrite nitrogen concentration Means for adjusting the flow rate of raw water flowing into the denitrification tank based on the output signal of the measuring means. 2. An inlet for raw water containing ammonia nitrogen and nitrite nitrogen, and an outlet for a treatment liquid, wherein ammonia nitrogen serves as an electron donor and nitrite nitrogen serves as an electron acceptor. The denitrification tank for biological denitrification by the action of the denitrifying microorganisms, the dilution water supply means for supplying the dilution water for diluting the raw water, and the nitrite nitrogen concentration of the liquid near the raw water inlet in the denitrification tank. It is characterized by comprising: nitrite nitrogen concentration measuring means for measuring; and means for adjusting the amount of dilution water supplied by the dilution water supplying means based on the output signal of the nitrite nitrogen concentration measuring means. Biological denitrification equipment.