JP2000070989A - Method and apparatus removing nitrogen in waste water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively and inexpensively prevent the deterioration of nitrogen removing performance while compensating the shortage of the organic material concentration in the waste water and effectively utilizing a generated organic material by crushing or grinding at least a part of deposits in a sedimentation basin for the waste water to be treated and supplying them to a denitrification vessel or an anaerobic vessel. SOLUTION: The waste water 1 is fed to the denitrification vessel 3 and a nitrification vessel 4 through solid-liquid separation in an initial sedimentation basin 2 and is separated into treated water 9 and activated sludge in a final sedimentation basin 7. The deposits 10 of sedimentation basin are crushed or ground by a crushing or grinding device 11 and sent to the denitrification vessel 3 directly or through a flow-out water passage or the like. In the nitrification vessel 4, nitrogen compounds in the waste water are oxidized and organic materials are oxidized and decomposed to be removed. In the denitrification vessel 3, nitrate nitrogen or the like contained in the waste water 1, nitrified circulating liquid 6 and the like is reduced into gaseous nitrogen and denitrified by utilizing the organic materials originating from the initial sedimentation basin 10. Thus, the method is effectively and rapidly utilized for the denitrification reaction by denitrifying bacteria.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally belongs to the field of sewage and wastewater treatment, and more particularly to a method and an apparatus for removing nitrogen from wastewater.

[0002]

2. Description of the Related Art An activated sludge process is one of the conventional typical treatment processes for removing organic substances from wastewater, and a biological nitrification denitrification process is a conventional method for simultaneously removing nitrogen compounds and organic substances. is there.

FIG. 6 shows an example of a wastewater treatment apparatus using a biological nitrification and denitrification method. A wastewater treatment apparatus based on the biological nitrification and denitrification method comprises a nitrification tank 4 for oxidizing (nitrifying) nitrogen compounds in a sedimentation basin 2 and wastewater to nitrate nitrogen or nitrite nitrogen.
And a denitrification tank 3 for reducing (nitrifying) nitrate nitrogen or nitrite nitrogen to nitrogen and a final sedimentation tank 7. After removing relatively large and heavy solids contained in the wastewater 1 in the first sedimentation basin 2, nitrogen is finally released into the atmosphere in the form of nitrogen gas through a nitrification step and a denitrification step. Is removed from the wastewater. Organic matter in the wastewater is removed in both the denitrification step and the nitrification step.

There are the following problems in removing nitrogen from wastewater using a wastewater treatment apparatus based on biological nitrification and denitrification. That is, when the concentration of organic matter in the wastewater is reduced due to inflow of rainwater or the like, the wastewater is diluted while being supplied with oxygen. Therefore, the organic matter in the wastewater is supplied to the denitrification step after being oxidized and diluted. As a result, the organic matter concentration supplied to the denitrification step is lower than the nitrogen concentration, so that the denitrification reaction rate in the denitrification step becomes lower, and the quality of the treated water deteriorates.

[0005] Further, since solid pollutants of wastewater are settled and separated in the first sedimentation basin, the wastewater supplied to the denitrification step via the first sedimentation basin is mainly composed of soluble pollutants. Therefore, even when the organic matter concentration / nitrogen concentration ratio of the soluble pollutants in the wastewater supplied to the denitrification step is low, the denitrification reaction rate in the denitrification step becomes low, and the quality of the treated water deteriorates.

In order to cope with such a problem, an organic chemical such as methanol is supplied to the denitrification step together with the wastewater to compensate for the shortage of the organic matter concentration in the wastewater, thereby preventing a reduction in the denitrification reaction rate. Is used.

[0007] In the prior art in which organic chemicals are flowed into the denitrification step, relatively inexpensive methanol has usually been used, but the fact that chemicals are still expensive is a major problem with operating costs. In addition, since methanol is a fourth-class hazardous substance, it must be handled in consideration of safety, and measures must be taken for storage facilities and facilities for receiving and supplying.

[0008] The organic matter concentration of the wastewater supplied to the denitrification process /
If the nitrogen concentration ratio is low, it is difficult to cause a sufficient nitrogen removal reaction, particularly a denitrification reaction due to a shortage of organic substances.
The introduction of the organic matter contained in the wastewater flowing into the first sedimentation basin and removed in the first sedimentation basin, that is, the organic matter mainly composed of solid matter, into the denitrification step is effective for improving the nitrogen removal treatment performance. is there.

[0009] As a conventional facility operation method having such an effect, the number of first sedimentation ponds used in a wastewater treatment facility having a plurality of treatment systems is reduced, and the operation of increasing the water area load on the first sedimentation basin is performed. Sedimentation basin effluent SS
And increasing the amount of organic matter flowing into the denitrification step.

[0010]

However, it is difficult to accurately control the solid organic matter flowing into the denitrification step by digital control of changing the number of first settling ponds.

[0011] In order to solve such a problem, the present inventor has proposed a technique capable of performing a good nitrogen removal treatment by increasing the amount of organic substances supplied to a denitrification tank or an anaerobic tank. A method for removing nitrogen from wastewater, wherein at least a part of the material is flowed into a denitrification tank or an anaerobic tank, and a method wherein ultrasonic treatment is performed on the precipitate to flow into the denitrification tank or the anaerobic tank. A nitrogen removal method for wastewater (Japanese Patent Application No. 9-133,893) and a nitrogen removal method for wastewater characterized by subjecting the precipitate to ozone treatment and flowing into a denitrification tank or an anaerobic tank. No. 133988) has already been filed.
However, these methods have the following problems. When the sediment of the first sedimentation basin is directly introduced into a denitrification tank or an anaerobic tank, the solid particles contained in the settling sludge are relatively large and have a small surface area per unit weight. However, there is a problem that the speed of decomposition and treatment in the biological treatment reaction tank is relatively low. In addition, when the sediment in the sedimentation tank is first subjected to ultrasonic treatment and then introduced into a denitrification tank or an anaerobic tank, microorganisms or cellulose wrapped in relatively hard cell walls or cell membranes are contained in the solid matter as the sediment. Fibers and the like are contained and are not easily destroyed by the ultrasonic vibration treatment. Therefore, there is a problem that the particle diameter of the solid introduced into the denitrification tank or the anaerobic tank does not become sufficiently small.
Furthermore, when the sediment in the sedimentation basin is first subjected to ozone treatment and then introduced into a denitrification tank or an anaerobic tank, some of the organic matter contained in the sediment is oxidized and mineralized to reduce its effectiveness as an organic matter. And lose about 10 to ozone
There is a problem that a relatively large amount of power of 15 kWh / kgO ₃ is consumed, so that the operation cost is relatively large.

SUMMARY OF THE INVENTION The present invention has been made to solve the problem of deterioration of nitrogen removal performance of a biological nitrification and denitrification wastewater treatment apparatus caused by an insufficient concentration of organic substances in wastewater, particularly, a concentration of soluble organic substances. Organic substances generated in the wastewater treatment facility by supplying sludge containing solid organic substances generated in the sedimentation basin to the denitrification tank or anaerobic tank to compensate for the lack of organic matter concentration in the wastewater flowing into the denitrification tank or anaerobic tank Method to prevent deterioration of nitrogen removal performance while effectively utilizing
It is an object of the present invention to provide a method and apparatus that can be implemented more effectively and economically.

[0013]

SUMMARY OF THE INVENTION According to the present invention, at least the wastewater to be treated is treated at the time of removing nitrogen from the wastewater by using an apparatus consisting of a sedimentation basin, a denitrification tank or an anaerobic tank and a nitrification tank. The present invention relates to a method and an apparatus for removing nitrogen from wastewater, which comprises crushing or grinding at least a part of the sediment of a wastewater settling tank and supplying the crushed or crushed wastewater to a denitrification tank or an anaerobic tank.

In the method and apparatus for removing biological nitrogen from wastewater according to the present invention, at least a part of the sediment of the first sedimentation basin rich in solid organic matter, that is, at least a part of the solid organic matter is subjected to a denitrification step or It is to flow into the anaerobic process to secure the concentration of organic substances required for the denitrification reaction in the denitrification step, but to enable the microorganisms to use the solid organic substance effectively and quickly for the denitrification reaction Then, by subjecting at least a part of the sediment in the first sedimentation basin to a crushing or grinding treatment, solid organic substances contained in the sediment in the first sedimentation basin are made into fine particles or solubilized. Further, when the organic matter concentration of the wastewater is low and the organic matter concentration required for performing the denitrification reaction in the denitrification step cannot be secured, the oxidation-reduction potential (ORP) in the denitrification step becomes 0 mV or more. ORP in the denitrification step was measured according to the findings based on the experiments of the present inventors, and when ORP was a value of 0 mV or more, that is, when the organic matter concentration required for performing the denitrification reaction in the denitrification step was not ensured. Only the first sedimentation basin, which has been subjected to crushing or grinding treatment, flows into a denitrification tank or an anaerobic tank, and replenishes organic matter derived from solids. To secure.

[0015]

FIG. 1 shows an example of a biological nitrogen removal treatment apparatus according to the present invention. The present invention will be described in detail with reference to FIG.

As shown in FIG. 1, the biological nitrogen removal treatment apparatus according to the present invention mainly comprises a first sedimentation tank 2, a denitrification tank 3, a nitrification tank 4, and a final sedimentation tank 7. In the denitrification tank 3, only stirring is performed, and in the nitrification tank 4, oxygen is supplied by the diffuser 5, and stirring is performed by a water flow generated by the diffusion.

In the biological nitrogen removal treatment apparatus according to the present invention shown in FIG. 1, wastewater 1 is first passed through a sedimentation basin 2 through a solid-liquid separation to a denitrification tank 3 and a nitrification tank 4 sequentially. The effluent flowing out of the nitrification tank 4 and flowing into the final sedimentation basin 7 is separated into treated water 9 and activated sludge in the final sedimentation basin 7, and at least a part of the activated sludge separated and concentrated in the final sedimentation basin 7 is returned. It is sent to the denitrification tank 3 as sludge 8. A part of the effluent flowing out of the nitrification tank 4 is sent to the denitrification tank 3 as a nitrification circulating liquid 6.

The first sedimentation basin sediment 10 is subjected to crushing or grinding treatment by a crushing treatment device or attrition treatment device 11, and then directly to the denitrification tank 3 as a crushed or crushed material 12 of the first sedimentation basin sediment. It is sent to the denitrification tank 3 via the outflow channel of the first sedimentation basin 2, or the portion of the first sedimentation basin 2 excluding the portion that re-sediments in the first sedimentation basin 2 via the inflow channel of the first sedimentation basin 2. It is sent to the denitrification tank 3 via the outflow channel 2.

In the nitrification tank 4, the nitrogen compounds in the wastewater are oxidized to nitrate nitrogen or nitrite nitrogen (= nitrification reaction) by the action of activated sludge, and the organic substances are oxidatively decomposed and removed. In the denitrification tank 3, the activated sludge is made up of the wastewater 1 and the return sludge 8 by utilizing the organic matter mainly composed of the soluble component in the wastewater 1 and the organic matter derived from the first sedimentation tank sediment 10.
And nitrate nitrogen or nitrite nitrogen contained in the nitrification circulating fluid 6 is reduced to nitrogen gas (= denitrification reaction) and denitrification treatment is performed.

The solid organic matter contained in the first sedimentation tank sediment 10 is treated by a crushing device or a grinding device 11 so that at least a part thereof becomes fine particles and at least a part thereof becomes a soluble component. That is, when the particle diameter of the solid is reduced by the crushing or grinding treatment, the surface area of the solid having the same weight increases. The first sedimentation basin sediment 10 contains microorganisms, animals and plants, and the like, and these organisms are composed of cells wrapped in cell membranes or cell walls, and these membrane-like structures are crushed. Cell liquid is released outside the cell when destroyed by processing or grinding,
First sedimentation tank sediment 12 after crushing or grinding
As a result, the concentration of the soluble organic matter in the wastewater charged into the wastewater is increased.

In general, when microorganisms proliferate by decomposing and utilizing organic substances, it takes a longer time to complete the decomposition and utilization of a substance having a large molecular weight, and a substance having a small molecular weight is easy to use and has a high reaction rate. It is. When organic matter is divided into solid organic matter and soluble organic matter, solid organic matter is generally harder to use for microorganisms because solid organic matter generally has a higher molecular weight. This is because when a microorganism takes in an organic substance into a microorganism via a cell membrane or a cell wall, the organic substance needs to have a sufficiently small molecular weight. It is considered that it takes a long time to decompose and use organic compounds, because a reaction of first decomposing organic substances having a large molecular weight into organic substances having a small molecular weight is required. In organisms, the reaction of decomposing high molecular weight organic substances into small molecular weight organic substances is mainly performed by enzymatic reactions.In such reactions, the more surfaces on which the enzyme acts, that is, the same weight of solid organic substances When the particle size is smaller, the reaction proceeds faster.
That is, in the method of the present invention, the crushing treatment or the grinding treatment of the sedimentation basin sediment 10 first to reduce the particle diameter of the solid substance is achieved by enzymatic reaction for decomposing and utilizing solid organic substances by microorganisms. It contributes to speeding up the progress of decomposition and utilization of solid organic matter, and is effective for terminating the microbial reaction with a limited reactor volume. Further, when the soluble organic matter generated by subjecting the sedimentation basin sediment 10 to crushing or grinding treatment is also introduced into the denitrification tank 3, it is effective for denitrification by denitrification bacteria. In this regard, the operation of subjecting the sedimentation basin sediment 10 to crushing or grinding treatment firstly requires the organic matter contained in the solid matter in the inflow wastewater 1 to be removed from the reaction tank. This contributes to increasing the rate of decomposition and utilization by microorganisms in the above, and is effective for terminating the microbial reaction with a limited reactor volume.

Crushed or ground material of the first sedimentation tank sediment 1
When the crushed material or the crushed material 12 flows into the denitrification tank 3 directly, the crushed material or the crushed material 12 can be directly flown into the denitrification tank 3. It is also possible to make the wastewater flow into any point of the flow path of the wastewater reaching the denitrification tank 3. When such a method is used, all of the crushed or crushed material 12 can flow into the denitrification tank 3. Further, since the capacity of the water channel from the supply point of the crushed material or the crushed material 12 to the denitrification tank 3 is relatively small and the residence time is relatively short, the supply amount of the crushed material or the crushed material 12 is changed. The reaction in the denitrification tank 3 can be affected in a relatively short time.
When the crushed material or the crushed material 12 flows into the denitrification tank 3, the crushed material or the crushed material 12 is allowed to flow directly into the denitrification tank 3, or the crushed material or the crushed material 12 is first discharged from the overflow weir of the sedimentation basin 2. Whether to flow into any point of the flow path of the wastewater to the denitrification tank 3 depends on the distance or the water head difference between the installation position of the crushing device or the grinding device 11 and the supply position of the crushed material or the crushed material 12. It can be determined in consideration of such factors.

The crushed material or the crushed material 12 is caused to flow into any point of the inflow channel of the first sedimentation basin 2 to separate and remove solids precipitated in the first sedimentation basin 2 again. It is also possible to allow the non-settling component of the crushed material 12 to flow into the denitrification tank 3 together with the overflow water of the first settling tank 2. When such a method is used, all of the crushed material or the crushed material 12 cannot flow into the denitrification tank 3, but the denitrification tank 3 is supplied from the supply point of the crushed or crushed material 12.
Because the capacity of the waterway leading to is large and the residence time is long,
The crushed material or the crushed material 1 having a relatively stable concentration
The components derived from 2 and excluding solids that easily settle can flow into the denitrification tank 3.

The removal of the sediment 10 from the first sedimentation basin 2 can be performed by opening a discharge port provided at a lower portion or a bottom portion of the first sedimentation basin 2. This may be done by natural drainage or by using a liquid feed pump depending on the position of the first sedimentation basin 2.

The sediment to be treated by the crushing device or the attrition treatment device is in the form of a suspension or slurry in wastewater, and has a concentration of about 3000 to 12000 mg / l, usually about 5 mg / l.
It is about 000 to 10000 mg / l.

The time of addition of the crushed material or the crushed material can be known, for example, by measuring the oxidation-reduction potential of the denitrification tank, and the addition is performed when it becomes 0 mV or more.
In addition, when the ratio of the organic matter concentration / nitrogen concentration of the soluble pollutants in the wastewater 1 is almost always low, it is practical to always add the crushed material or the crushed material.

The pump used for pulling out the sediment 9 in the first sedimentation basin is usually a slurry pump in which clogging does not easily occur, and thus has little effect of crushing or grinding the sediment. Therefore, in order to crush or grind the precipitate, it is necessary to provide a crushing device or a grinding device. As the crushing device or the grinding device 10, various types such as a gear type and a multi-shaft disk type can be used. To control the degree of crushing or grinding,
It is effective to select the screen width of the screen to be passed after crushing or grinding, but if the screen width is too small, it is easy to clog, and if it is too large, solids with a large particle size tend to come out, The screen width of the screen is preferably about 1 to 5 mm. In addition, the crushing treatment device or the grinding treatment device 11 can be installed in-line or in an open channel, but in consideration of the fact that the sedimentation basin sediment 10 first becomes a source of offensive odor, the in-line installation is preferable. preferable. Since it is possible to apply a commercially available general-purpose product as the crushing device or the grinding device 11, the equipment cost is relatively low, and the operating cost mainly including the power cost of the motor is relatively low. The effect of reducing the particle size of the solid is relatively large.

The amount of the crushed material or the crushed material is about 0.1 to 1.5% with respect to the volume of the wastewater 1, usually 0.5 to 1.0%.
% Is appropriate. The addition may be continuous or intermittent.

When the addition is completed, the oxidation-reduction potential is -50 to -1.
It is appropriate to reach about 50 mV, and as a result,
It is also effective to continue the addition at all times.

FIG. 2 shows another example of the biological nitrogen removal treatment apparatus according to the present invention. According to the biological nitrogen removal treatment apparatus based on the prior art shown in FIG. 6, according to the experimental findings of the inventor, the concentration of the soluble organic matter in the wastewater 1 is high, and the organic matter necessary for the denitrification reaction in the denitrification tank 3. When the concentration is obtained, the ORP in the denitrification tank 3 becomes 0 mV or less, the organic matter concentration of the wastewater 1 is low, and the organic matter of the concentration required for the denitrification reaction in the denitrification tank 3 is not supplied. The ORP in the denitrification tank 3 becomes 0 mV or more. Based on these findings, in the biological nitrogen removal treatment apparatus according to the present invention in FIG. 2, the measured value of the ORP meter 13 installed in the denitrification tank 3 is 0 m.
In the case of V or less, an operation such as stopping the flow of the crushed material or the crushed material 12 of the sedimentation tank sediment into the denitrification tank 3 or stopping the operation of the crushing device or the crushing device 11 is performed first. When the measured value is 0 mV or more, the operation of the apparatus is controlled so that the crushed or crushed material 12 flows into the denitrification tank 3. These controls are performed by the control device 14.

In addition to a wastewater treatment apparatus comprising a denitrification step and a nitrification step, a nitrogen removal method according to the present invention is also applied to a wastewater treatment apparatus comprising an anaerobic step, a denitrification step (anoxic step) and a nitrification step (aerobic step). Can be applied.

FIG. 3 shows another example of the biological nitrogen removal treatment apparatus according to the present invention. The biological nitrogen removal treatment apparatus according to the present invention shown in FIG. 3 is obtained by adding a new anaerobic tank 15 to the biological nitrogen removal treatment apparatus according to the present invention shown in FIG. Pond 2, Anaerobic tank 1
5, a denitrification tank 3, a nitrification tank 4, and a final sedimentation basin 7.

In the biological nitrogen removal treatment apparatus according to the present invention shown in FIG. 3, the anaerobic tank 15 is a tank in which only stirring is performed, and the waste water 1 and the returned sludge 8 are sent to this tank. In the anaerobic tank 15, the activated sludge reduces the nitrate nitrogen or the nitrite nitrogen contained in the wastewater 1 and the return sludge 8 to nitrogen gas by using an organic matter mainly composed of a soluble component in the wastewater 1. A denitrification reaction) and a denitrification treatment are performed, and activated sludge releases phosphate ions accumulated in cells into wastewater (= biological phosphorus release reaction). In addition, denitrification tank 3
Is performed, nitrate nitrogen or nitrite nitrogen contained in the nitrification circulating liquid and the sludge mixture flowing from the anaerobic tank 15 is reduced to nitrogen gas (= denitrification reaction) and denitrification treatment is performed. Further, in the denitrification tank 3 and the nitrification tank 4, the activated sludge takes up phosphate ions in the wastewater into cells (biological phosphorus uptake reaction). Then, in the nitrification tank 4, organic nitrogen or ammonia nitrogen is oxidized to nitrate nitrogen or nitrite nitrogen (= nitrification reaction). The organic matter is consumed and processed in each of the anaerobic tank 15, the denitrification tank 3, and the nitrification tank 4.

In the biological nitrogen removal treatment apparatus shown in FIG. 3 according to the present invention, the flow is such that the crushed or ground material 12 of the sedimentation tank sediment first flows into the anaerobic tank 15. Alternatively, part or all of the crushed material or the crushed material 12 may flow into the denitrification tank 3.

[0035]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the method for removing biological nitrogen according to the present invention will be described below. FIG. 4 shows an experimental apparatus. In the present embodiment, a mixture of returned sludge, nitrification circulating liquid, wastewater and first settling tank sediment collected from the wastewater treatment apparatus having the flow shown in FIG. 6 was put into the apparatus shown in FIG. The characteristics of denitrification reaction of activated sludge under were investigated.
Table 1 shows the composition of the sample. The BOD concentration of the wastewater collected from the wastewater treatment apparatus having the flow shown in FIG.
L, and the MLSS concentrations of the returned sludge and the nitrification circulating fluid were 4300 mg / L and 1800 mg / L, respectively.
Met. In order to check whether the flow shown in FIG. 1 works effectively, the MLSS concentration of 3400 mg collected from the first sedimentation basin of the wastewater treatment apparatus consisting of the flow shown in FIG.
An experimental study was conducted to determine whether a 1 / L primary sedimentation tank sediment was ground for 3 minutes with a potter-type glass homogenizer having a capacity of 10 ml as an organic matter source.

[0036]

[Table 1]

FIG. 5 shows the change over time in the concentration of nitrate nitrogen in the sample wastewater. From these results, it was found that the sample A obtained when the denitrification treatment was performed under the condition that the sedimentation tank sediment subjected to the grinding treatment was added.
Compared with Sample B when denitrification treatment was performed under the condition that the first sedimentation basin sediment subjected to the grinding treatment was not added, the first sedimentation basin sediment was subjected to the grinding treatment. When the denitrification treatment was performed by adding the wastewater, the rate of reduction of nitrate nitrogen in the wastewater was large. That is, the first settling tank sediment is subjected to a grinding treatment to reduce the particle size of the solid,
It was found that the rate of denitrification in the denitrification step was increased by adding some organic substances to the sample wastewater after solubilization.

The crushing treatment is also similar to the crushing treatment, and is considered to be effective in reducing the particle diameter of solids in the sedimentation tank sediment and solubilizing some organic substances.

[0039]

According to the present invention, the first sedimentation basin after crushing or grinding to the denitrification step or anaerobic step of the biological nitrogen removal apparatus having a denitrification step and an anaerobic step and a nitrification step as the case may be. The structure was such that the sediment flowed in and the concentration of organic substances required for the denitrification reaction in the denitrification step was ensured.

Thus, as in the case of inflow of rainwater,
Also, when the concentration of organic substances supplied to the denitrification step falls below the level at which the nitrogen concentration decreases, the rate of the denitrification reaction in the denitrification step decreases, and the quality of the treated water deteriorates. The ratio of organic matter / nitrogen concentration of the soluble pollutants in the wastewater that flows into the denitrification process after undergoing solid-liquid separation treatment at a low rate reduces the denitrification reaction rate in the denitrification process and deteriorates the quality of treated water. Even in this case, the supply of organic substances necessary for performing the denitrification reaction is ensured, so that it is possible to prevent the rate of the denitrification reaction in the denitrification step from being lowered.

The ORP in the denitrification step was measured, and the ORP was measured.
Is only 0 mV or more, by flowing at least part of the sedimentation basin sediment after crushing or grinding into the denitrification step or anaerobic step, the organic matter concentration in the wastewater is reduced, Organic substances can be replenished only when the concentration of the organic substances required for performing the denitrification reaction in the nitriding step is not ensured. By such control, the power cost required to perform the crushing or grinding treatment on the first sedimentation tank sediment and the first sedimentation tank sediment after the crushing treatment or the grinding treatment are transferred to the denitrification process or the anaerobic process. To minimize the power costs required to
Further, the load of organic substances on the denitrification step, anaerobic step and nitrification step can be minimized.

The sedimentation basin sediment is subjected to crushing or grinding treatment to reduce the particle size of the organic solids contained in the sedimentation basin sediment and to partially solubilize it. By being introduced into a denitrification step such as a nitrification tank or an anaerobic tank, it can be used quickly and effectively in a microbial reaction mainly comprising a nitrogen reaction.

Also, since a general-purpose product can be used as an apparatus used for the crushing or grinding treatment, the equipment cost is economical, and the operation cost of the apparatus mainly including the power cost of the motor is relatively economical. The effect of breaking large solids is also great.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a biological nitrogen removal treatment apparatus according to one embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a biological nitrogen removal treatment apparatus according to another embodiment of the present invention.

FIG. 3 is a view showing a configuration of a biological nitrogen removal treatment apparatus according to still another embodiment of the present invention.

FIG. 4 is a side view of a denitrification reaction experiment apparatus used in one embodiment of the present invention.

FIG. 5 is a graph showing the change over time in the nitrate nitrogen concentration with and without the addition of the ground material of the sediment in the first sedimentation basin using the apparatus of FIG.

FIG. 6 is a diagram showing a configuration of a conventional biological nitrogen removal treatment apparatus.

[Explanation of symbols]

 1. Wastewater 2. First sedimentation basin 3. Denitrification tank 4. Nitrification tank 5. Air diffuser 6. 6. Nitrifying circulating fluid Final settling basin 8. Return sludge 9. Treated water 10. First sedimentation tank sediment 11. 11. Crushing device or grinding device 12. Crushed or ground material of first sedimentation tank sediment ORP meter 14. Control device 15. Anaerobic tank 16. Stirrer 17. Beaker 18. sample

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Jun Miyata 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan Inside the Kokan Kogyo Co., Ltd. (72) Inventor Kei Kei Bamba 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Sun (72) Inventor: Toshishi Sawada 1-1-2, Marunouchi, Chiyoda-ku, Tokyo Japan Nippon Steel Pipe Co., Ltd. (72) Satoru Udagawa 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan Inside (72) Inventor Shinichi Endo 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan Tube Co., Ltd. F-term (reference) 4D040 BB02 BB52 BB91 BB92 BB93 DD01 DD14

Claims (2)

[Claims] When removing nitrogen from wastewater using a device consisting of a sedimentation basin, a denitrification tank or an anaerobic tank and a nitrification tank for at least the wastewater to be treated, at least the sediment of the sedimentation basin of the wastewater to be treated is removed. A method for removing nitrogen from wastewater, which comprises crushing or grinding a part of the wastewater and feeding it to a denitrification tank or an anaerobic tank. 2. An apparatus comprising at least a sedimentation basin, a denitrification tank or an anaerobic tank for wastewater to be treated, a line for extracting sediment from the sedimentation basin, and an apparatus for crushing or grinding the extracted sediment. And a line for supplying the crushed or crushed material to a denitrification tank or an anaerobic tank.