JPH10137787A - Denitrifying method and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a device compact and to improve a denitrifying efficiency by executing a nitrifying stage with nitrifying bacteria carried on a plurality of carries and executing a denitrifying stage with a denitrifying granule. SOLUTION: A granule-accumulated part 6 formed by accumulating granule particles containing denitrifying bacteria at a bottom part in a denitrifying tank 1 is provided, and a raw water supplied from a raw water supply part 5 is brought into contact with the granule-accumulated part 6 by upward stream. Then the generated gaseous nitrogen is captured at a capturing part 12. The denitrified treated water is collected with a collection through 13 and sent to a nitrifying tank 2 from a discharge passage 9. Many carriers 15 to which aerobic nitrifying bacteria are stuck are packed in the nitrifying tank 2, and the nitrogen incorporated in a form of an ammonia nitrogen in the raw water is nitrified and converted to nitrogen oxide. The carrier 17 is formed in a cylindrical shape and a radial supporting plate is projectingly fitted in the radial direction on the inner surface side to increase a containing area of the water to be treated. In this way, the nitrifying bacteria are liable to stick. In this way, the device is made compact while maintaining a high treating ability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for denitrification for biologically denitrifying nitrogen from wastewater containing nitrogen to remove nitrogen.

[0002]

2. Description of the Related Art Hitherto, as a biological denitrification treatment method for removing nitrogen in wastewater using microorganisms, a method of denitrification by contacting wastewater containing nitrogen with denitrifying bacteria has been performed. Was. In this case, the denitrifying bacteria reduce nitrogen oxides (nitrate nitrogen or nitrite nitrogen) to nitrogen gas. For denitrification, the nitrogen component in the wastewater must be in the form of nitrogen oxides. It is not possible to denitrify, so if the wastewater contains ammonia nitrogen, nitrification of the ammonia nitrogen in the wastewater into nitric oxide by nitrifying bacteria and then denitrification by the above denitrifying bacteria. Was.

[0003] As this denitrification treatment method, a floating denitrification method in which denitrifying bacteria are floated in treated water as it is, or a fixed bed type in which denitrifying bacteria are adhered to a filler or the like and wastewater is brought into contact with the filler is used. Method was used.

[0004]

However, in the case of the floating type denitrification method, since the cells are floating in the denitrification tank as they are, they are easily washed away with the treated water, and the cells are high in the denitrification bacteria tank. It is difficult to maintain a sufficient concentration, and even in the case of a fixed bed type, in order to increase the denitrification efficiency, it is necessary to make the fixed bed large and increase the denitrifying bacteria attached to it. By increasing the size of the whole, a certain level of denitrification efficiency was maintained.

As the nitrification tank, a floating type in which nitrifying bacteria are normally suspended in treated water is used, but the nitrifying tank also holds nitrifying bacteria at a high concentration to maintain the nitrification efficiency at a certain level or more. Therefore, the nitrification tank had to be made large.

[0006] Therefore, the entire denitrification treatment apparatus becomes large and requires a large installation area, the installation place is limited, and the installation cost and the manufacturing cost of the apparatus increase, which is uneconomical. Was.

[0007] The present invention has been made to solve such problems, and an object of the present invention is to provide a compact denitrification treatment apparatus while maintaining high denitrification efficiency.

[0008]

The features of the denitrification method for solving the above-mentioned problems include a step of biologically nitrifying ammoniacal nitrogen in raw water into nitrogen oxides, and a step of nitrifying nitrogen in raw water. In a denitrification treatment method comprising a step of reducing substances and biologically denitrifying, the nitrification step is performed by nitrifying bacteria supported on a plurality of carriers, and the denitrifying step is performed by a denitrifying bacteria granule. To be done.

The denitrification treatment apparatus is characterized by a nitrification tank 2 filled with nitrifying bacteria for nitrifying ammoniacal nitrogen in raw water into nitrogen oxides, and a denitrification by reducing nitrogen oxides in raw water. In a denitrification treatment apparatus provided with a denitrification tank 1 filled with denitrifying bacteria, the nitrifying bacteria filled in the nitrification tank 2 are carried on a plurality of carriers 15, and the denitrification tank 1 is placed in the denitrification tank 1. That is, the granules are filled.

(Operation) That is, as described above, in the present invention, since the denitrification step is performed in the denitrifying bacteria granules, the denitrifying bacteria in the denitrification tank can be maintained at a high concentration. Even if it is smaller than a fixed bed type denitrification tank, the denitrification efficiency can be kept high. At the same time, in the nitrification step, the nitrifying bacteria are carried on a plurality of carriers 15, so that the nitrifying bacteria concentration in the nitrifying tank can be maintained at a high concentration, and the nitrifying tank can be made compact without reducing the nitrification efficiency. Can be

Therefore, the installation area of the entire denitrification processing apparatus can be reduced by making the denitrification tank and the nitrification tank compact.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.

A denitrification tank 1 shown in FIG. 1 is provided at the bottom of the denitrification tank 1 with a raw water supply unit for introducing waste water discharged from a factory or the like as shown in FIG. 2 into raw water stored in a storage tank 1a. 5 are provided. At the bottom of the denitrification tank 1, a granule depositing section 6 in which granules containing denitrifying bacteria are deposited is formed, and raw water supplied from the raw water supply section 5 is mixed with the granule depositing section 6 on the top. They are contacted in countercurrent.

Inside the denitrification tank 1, there are provided a gas collection part 12 for collecting nitrogen gas generated by the granules and a denitrification treatment water discharge passage 9 for discharging the denitrification treatment water. A collecting trough 13 is formed. Further, the nitrogen gas collected by the gas collection unit 12 is discharged from the nitrogen gas discharge path 21.

Reference numeral 2 denotes a nitrification tank into which the treated water treated in the denitrification tank 1 is introduced. In the nitrification tank 2, nitrogen contained in the form of ammoniacal nitrogen in raw water is converted into nitrogen oxides by nitrification. Aerobic nitrifying bacteria that convert to (nitrate nitrogen or nitrite nitrogen) are packed in a state attached to a large number of synthetic resin carriers 15.

The carrier 15 is composed of a carrier body 17 suspended in treated water of a cylindrical body as shown in FIG.
A support plate 17a is radially formed on the inner surface of the support 17 and a projection 17b is formed on the outer surface thereof.

By forming the carrier main body 17 in a cylindrical shape and forming the support plate 17a and the projections 17b in this manner, the surface area in contact with the treated water is increased, and the nitrifying bacteria are more likely to adhere. Carrier body 17 when nitrifying bacteria adhere to
The inside and the like are clogged, and the contact area with the treated water is eventually reduced.

Therefore, the carrier body 17, the support plate 17a and the projection
The size and shape of 17b are preferably set so that nitrifying bacteria can easily adhere thereto, peel off appropriately by aeration or the like, always attach an appropriate amount of nitrifying bacteria, and secure a contact area with treated water. The material is polypropylene,
It can be arbitrarily selected from ordinary synthetic resins such as polyethylene.

Reference numeral 16 denotes aeration means provided at the bottom of the nitrification tank 2 for blowing air to aerate nitrifying bacteria. Further, a screen 24 is provided near the treated water outlet of the nitrification tank 2 so as to separate the treated water and the carrier 15 and hold the carrier 15 to which the nitrifying bacteria are attached in the nitrification tank 2.

Reference numeral 3 denotes a sludge separation tank in which the treated water treated in the nitrification tank 2 is introduced together with the sludge separated from the carrier 15 to separate the treated water and sludge by flotation and concentration. A treated water discharge passage 10 for discharging only the treated treated water, and a sludge discharge passage 18 provided with a pump 23 for transferring the separated sludge to the sludge dewatering facility 22 are provided.

Reference numeral 4 denotes a re-denitrification tank for denitrifying the treated water which has been treated in the nitrification tank 2 and separated from the sludge in the separation tank 3 again. Granule depositing section 8 on which granules of denitrifying bacteria granules are deposited
Are formed.

Reference numeral 11 denotes an aeration tank for aerating the treated water denitrified in the re-denitrification tank 4. The aeration tank 11 is provided downstream of the aeration tank 11.
Sedimentation tank for sedimentation of suspended solids in treated water aerated in
In the settling tank 19, supernatant water is discharged as purified water.

Reference numeral 20 denotes a return water discharge passage for returning a part of the treated water separated in the sludge separation tank 3 to the denitrification tank 1.

Next, a case where the denitrification of raw water is performed using the denitrification treatment apparatus 25 having the above-described configuration will be described.

First, raw water containing nitrogen discharged from a factory or the like is introduced into the denitrification tank 1 through the raw water supply unit 5. The raw water comes into contact with the granule depositing section 6 formed at the bottom of the denitrification tank 1 in an upward flow, and nitrogen oxides (nitrate nitrogen and nitrite nitrogen) in the raw water are denitrified by the denitrifying bacteria in the granule. Reduced to nitrogen gas.

After the generated nitrogen gas is collected by the gas collection unit 12, the nitrogen gas passes through the nitrogen gas discharge path 21 and is supplied to the denitrification tank 1.
Is discharged from

Since the denitrification tank 1 is filled with denitrification bacteria as granules, the concentration of the denitrification bacteria in the denitrification tank 1 is maintained at a high concentration, and is higher than that of the conventional floating denitrification tank. Even if the volume is small, the denitrification treatment can be efficiently performed. Therefore, the installation area of the denitrification tank can be reduced to about 1/5 of the conventional floating type denitrification tank.

The denitrifying bacteria in the denitrification tank 1 can reduce nitrogen oxides (nitrate nitrogen and nitrite nitrogen) contained in the raw water into nitrogen gas. Nitrogen cannot be reduced.

For this reason, the treated water from which nitrogen oxides have been denitrified to some extent in the denitrification tank 1 is then introduced into the nitrification tank 2 through the above-mentioned denitrification treatment water discharge passage 9.

Here, the nitrogen contained in the raw water in the form of ammonia nitrogen is converted into nitrate nitrogen and nitrite nitrogen by nitrifying bacteria attached to the carrier 15 in the nitrification tank 2. Is done.

Since the nitrifying bacterium is an aerobic bacterium, the ammonia nitrogen in the raw water is nitrified into nitrogen oxides while supplying air by aeration by the aeration means 16. At this time, the nitrifying bacteria are suspended in the treated water in a state of being attached to the projections 17b on the outer surface of the carrier main body 17 or the cylindrical interior of the carrier main body 17 in a large amount. Can be maintained at a high concentration, and the required amount of nitrifying bacteria can be secured even if the volume of the tank body 2a is reduced. Therefore, the installation area of the tank main body 2a is about 1 compared with the conventional floating type nitrification tank.
/ 2 to ３.

Further, the treated water nitrified in the nitrification tank 2 is sent to the sludge separation tank 3 together with the sludge separated from the carrier 15 after being separated from the carrier 15 by the screen 24, and treated with the sludge by the floating concentration method. Separated by water.
In this separation step, the nitrifying bacteria are transferred to the nitrification tank 2 as described above.
Since it is supported by the carrier 15 inside, the generation of excess sludge is smaller than that of the conventional floating nitrifying bacteria. In addition, since the screen 24 is provided near the treated water outlet of the nitrification tank 2, the treated water and the carrier 15 can be separated and the outflow of nitrifying bacteria can be prevented. However, even if an outflow preventing means other than the screen is provided. good.

Then, the excess sludge is sent to a sludge dewatering facility 22 by a pump 23 via a sludge discharge passage 18, and the treated water is sent to the bottom of the re-denitrification tank 4 by a treated water discharge passage 10.
As described above, since the amount of excess sludge generated in the nitrification tank 2 is small, only a small amount of withdrawn sludge is required, and equipment such as a pump can be formed in a small size, and management is easy.

Further, a part of the treated water is returned to the return water discharge passage.
The water is returned to the denitrification tank 1 as return water through 20. Since the organic matter contained in the return water serves as a hydrogen donor required at the time of denitrification, alcohol such as alcohol as a hydrogen donor is separately supplied to the denitrification tank 1. There is no need to supply organic matter.

Then, the treated water transferred to the re-denitrification tank 4 is again supplied to the denitrification bacterium granule depositing section 8 similar to the denitrification tank 1.
Is contacted in upward flow. In the re-desorption tank 4, nitrogen oxides generated by converting ammoniacal nitrogen contained in the raw water in the nitrification tank 2 are reduced by denitrifying bacteria and discharged as nitrogen gas.

In this way, the nitrogen is removed, and the treated water is discharged outside the apparatus as purified water after the suspended components and the like are removed through the aeration tank 11 and the sedimentation tank 19. The sedimentation tank and the aeration tank may not be provided, but if provided, it is more preferable because the quality of purified water can be improved.

As described above, the denitrification tank 1 is a denitrification tank 1 using granules, and the nitrification tank 2 is filled with nitrifying bacteria carried on a floating carrier. It is possible to reduce the volume compared to conventional ones, that is, a floating type or fixed-bed type denitrification tank or nitrification tank in which the cells are directly suspended while maintaining a high processing capacity. as a result,
The installation area of the entire denitrification system is about 1 /
It is about 5 compact, and a denitrification treatment device can be installed in a narrow place.

In the above-described embodiment, the carrier for supporting nitrifying bacteria is a synthetic resin tubular carrier having a support plate and projections formed thereon. However, the shape of the carrier is not limited to this. For example, as shown in FIG. 4 (a), the inside may be a prismatic carrier having a hollow inside, or a support plate or a polygonal cylindrical body as shown in FIG. 4 (b) may be used. What provided the projection may be sufficient. In addition, the material is not limited to the synthetic resin, but any material may be used as long as the carrier is made of a material capable of appropriately adhering nitrifying bacteria and maintaining the concentration as high as possible. However, when formed from a synthetic resin, molding is easy, and the carrier can be economically manufactured.
Particularly preferred.

In the above embodiment, the nitrification tank 2 is provided on the downstream side of the denitrification tank 1 and the re-denitration tank 4 is further provided on the downstream side, but the nitrification tank 2 is provided on the upstream side of the denitrification tank 1. It may be provided.

In such a case, it is not necessary to particularly provide a re-denitrification tank. However, by repeatedly performing the denitrification step, the nitrogen that could not be completely denitrified at once can be reliably reduced to perform the denitrification. And the quality of purified water can be further improved.

In the above embodiment, part of the treated water after nitrification is returned to the denitrification tank as a hydrogen donor. However, it is not a condition that part of such treated water is returned to the denitrification tank. .

Further, in the above embodiment, the storage tank for storing the wastewater is provided. However, in this storage tank, the raw water may be agitated and homogenized, or the pH of the raw water may be adjusted. It is not a condition to provide such a storage tank.

Further, in the above embodiment, the separation of the sludge and the treated water in the sludge separation step was performed by flotation and concentration. However, the separation method is not limited to this, and the method of sedimentation separation, centrifugation, A separation method such as membrane separation may be used. However, when the flotation concentration method is adopted as described above, the enrichment degree is high and the concentration time is short in comparison with the sedimentation separation, etc., and the installation area of the sludge separation tank is small. In addition, there is an advantage that operation management is easy.

[0044]

As described above, according to the present invention, since the apparatus can be formed compact while maintaining high denitrification efficiency and nitrification efficiency, the effect that the installation area is small and economical is obtained. In addition, since the nitrifying bacteria are carried on the floating carrier, the separation of the sludge after the nitrification step becomes easy, and the operation of the apparatus can be easily managed.

[Brief description of the drawings]

FIG. 1 is a flowchart of a denitrification treatment method as one embodiment.

FIG. 2 is a schematic view of a main part of a denitrification treatment apparatus according to the present invention.

FIG. 3 is an enlarged sectional view of the carrier according to the present invention.

FIG. 4A is a cross-sectional view showing a carrier according to another embodiment,
(B) is a sectional view showing a carrier according to another embodiment.

[Explanation of symbols]

 1 Denitrification tank 2 Nitrification tank 15 Carrier

Claims (2)

[Claims] 1. A denitrification treatment method comprising the steps of biologically nitrifying ammoniacal nitrogen in raw water into nitrogen oxides and reducing and biologically denitrifying nitrogen oxides in raw water. A denitrification treatment method, wherein the nitrification step is performed by nitrifying bacteria supported on a plurality of carriers, and the denitrification step is performed by denitrifying bacteria granules. 2. A nitrification tank (2) filled with nitrifying bacteria for nitrifying ammoniacal nitrogen in raw water into nitrogen oxides, and a denitrifying bacterium for reducing nitrogen oxides in raw water and denitrifying the same. In a denitrification treatment apparatus provided with a denitrification tank (1), the nitrification tank
(2) A denitrification treatment apparatus characterized in that the nitrifying bacteria filled therein are supported on a plurality of carriers (15), and the denitrification tank (1) is filled with denitrification bacteria granules. .