JPH0866696A - Removing device of nitrogen and phosphorus - Google Patents

Abstract

PURPOSE: To simultaneously remove a nitrogen and phosphorus in a waste water. CONSTITUTION: A raw water is subjected to solid-liquid separation in a precipitation tank 1, and supernatant liquor is passed through a biological membrane filter tank 2 to remove nitrogen and BOD component. An initial precipitate in the precipitation tank is mixed with biologically treated water, and an inorg. salt is added to the biologically treated water and introduced into a granulating and concentrating tank 3. In the tank 3, the granulating concentration is executed by using a polymer flocculant to flocculate and remove the phosphorus. In this way, the biological membrane filter device cannot remove the phosphorus but an efficient removing of the nitrogen is possible by a compact device. The granulating concentration device cannot remove the nitrogen but a solid-liq. separartion and modification of dehydrated sludge can be execute and phosphorus can be removed with a compact device. The compact device removing simultaneously the nitrogen and the phosphorus, and also dehydrating the sludge is provided by combining these devices.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for removing nitrogen and phosphorus, and more particularly, by combining a biofilm filtration device and a granulation concentrating device, nitrogen and phosphorus in wastewater can be simultaneously removed and sludge can be removed. The present invention relates to a device for removing nitrogen and phosphorus, which makes it possible to dehydrate water within a small site area.

[0002]

2. Description of the Related Art As a method for removing nitrogen in wastewater,
A biological nitrification / denitrification treatment method using microorganisms is effective because of its low running cost. The most common biological nitrification / denitrification treatment method is a floating method in which microorganisms are suspended in a tank and drained water is passed through.In this floating method, a sedimentation basin is used for solid-liquid separation of treated water. Since it is necessary, there is a drawback that the required site area is large.

On the other hand, in recent years, a biofilm filtration method has attracted attention as a method for efficiently removing nitrogen in a small site area. The biofilm filtration method is a method in which microorganisms are attached to the surface of a carrier (filter material), and wastewater is passed through a biofilm filtration tank on which a filter material layer of this microorganism-attached carrier is formed for treatment. Since the microorganisms can be maintained at a high concentration, the treatment capacity per volume of the biofilm filtration tank is high, and since it also has a filtration function, a sedimentation basin for solid-liquid separation of treated water is not required, and the equipment can be installed in a small site area. Has the advantage that it can be installed.

However, although the biofilm filtration method can efficiently remove nitrogen, it cannot simultaneously remove phosphorus.

On the other hand, as a method for removing phosphorus in wastewater,
Conventionally, a biological method of absorbing phosphorus by microorganisms and a physicochemical method of using a flocculant are common.

It is possible to simultaneously remove phosphorus and nitrogen by applying a conventional phosphorus removal treatment to the biofilm filtration method. However, each of them has the following problems, and thus phosphorus to the biofilm filtration method has the following problems. The removal process is difficult to apply.

That is, the method utilizing microorganisms is low in cost, but it is difficult to obtain stable treated water quality. In addition, the method using a flocculant is
It is sufficient to add a flocculant to the final settling basin, which can be easily performed. However, for biofilm filtration, flocculation flocs generated by the addition of a flocculant increase the SS load on the filter media layer, so stable treatment is possible. Can't continue. That is, when the coagulant is added to the wastewater and then the water is passed through the biofilm filtration tank, the increase in the differential pressure is accelerated due to the increase in the SS load due to the generated phosphorus coagulation flocs, and it is necessary to perform backwashing frequently.

By the way, in the field of sludge treatment, sludge can be dehydrated by adding metal salt to the wastewater to neutralize the charge and adding a polymer flocculant in the granulation tank to concentrate and solid-liquid separate the granules. A device for refining has been developed. Since this apparatus uses a metal salt as a coagulation aid, it has the advantages that the water content of the dehydrated cake is reduced and phosphorus can be removed. That is, the granulation concentrator is used for solid-liquid separation and conditioning of dehydrated sludge.
It is a device that can remove phosphorus all at once. However, nitrogen cannot be removed by the granulation concentrator.

[0009]

As described above, in the conventional technique, nitrogen and phosphorus could be removed individually, but both could not be removed efficiently at the same time.

The present invention has been made in view of the above conventional circumstances, and it is an object of the present invention to provide a nitrogen and phosphorus removing apparatus capable of simultaneously removing nitrogen and phosphorus in waste water.

[0011]

A device for removing nitrogen and phosphorus according to the present invention comprises a solid-liquid separation device for separating SS in wastewater,
A biofilm filtration device for nitrifying and denitrifying the separated water discharged from the solid-liquid separation device, and a biologically treated water discharged from the biofilm filtration device and a solid content discharged from the solid-liquid separation device are mixed. Means, a means for adding an inorganic salt and a polymer flocculant to the biologically treated water in which solids are mixed, a rotary blade for generating a rotary flow inside, a draining means for discharging separated water, and a concentrated flocculation It is characterized by comprising a coagulating and concentrating device having a means for discharging sludge, and a means for introducing biologically treated water to which an inorganic salt and a polymer coagulant have been added into the coagulating and concentrating device.

[0012]

Although the biofilm filtration device cannot remove phosphorus, it can efficiently remove nitrogen with a compact device. On the other hand, the granulating and concentrating device cannot remove nitrogen, but a compact device can perform solid-liquid separation, conditioning of dehydrated sludge and removal of phosphorus. According to the present invention, by combining these devices, a compact device that can simultaneously remove nitrogen and phosphorus and also dehydrate sludge is provided.

[0013]

Embodiments of the nitrogen and phosphorus removing apparatus 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 nitrogen and phosphorus removing apparatus of the present invention.

In FIG. 1, 1 is a sedimentation tank, 2 is a biofilm filtration tank, 3 is a granulation concentration tank, 4 is a dehydrator, and 11 to 21.
Each symbol of indicates a pipe.

The biofilm filtration tank 2 is an upflow type organism filled with a floatable filter medium having a very small specific gravity as a carrier, which is formed by foaming polypropylene, urethane resin or the like into a spherical or irregular shape having a diameter of 3 to 10 mm. It is a membrane filtration tank, and diffuses air from an air pipe 5 provided in the middle of the filter medium layer to carry out nitrification on the upper side of the filter medium layer (nitrification section 2B).
It is configured to circulate in the lower part of the tank by 4 to perform denitrification on the lower side (denitrification section 2A).

In this embodiment, the raw water is first supplied from a pipe 11 to a settling tank (first settling tank) 1 as a solid-liquid separator.
Clear water (separated water) introduced into
Is introduced into the biofilm filtration tank 2 through the pipe 12. Settling tank 1
The separated sludge (solid content: first settled sludge) is extracted from the pipe 13 and mixed with the biologically treated water discharged from the biological membrane filtration tank 2 described later.

The supernatant water of the precipitation tank 1 introduced into the biofilm filtration tank 2 is nitrified and denitrified by microorganisms in the biofilm filtration tank 2, and decomposable organic substances are decomposed and removed. In the processing in this biofilm filtration tank 2,
Since the SS in the raw water has been removed in the settling tank 1 in advance, the SS load on the biofilm filtration tank 2 is small, so the biofilm filtration device can be operated stably for a long time without causing clogging of the filter medium layer. You can continue.

In the biofilm filtration tank 2, nitrogen and BOD
The biologically treated water from which is removed is extracted from the pipe 15,
After being mixed with the first settled sludge fed from the pipe 13, an inorganic salt is further added from the pipe 16 and introduced into the bottom of the granulation thickening tank 3. A polymer flocculant is introduced into the granulation concentration tank 3 through a pipe 17, and the sludge is slid as the liquid is swirled by the rotation of the agitator 3a equipped with a rotary blade in the granulation concentration tank 3. Is granulated to form a granulated product (pellet). The liquid that has not been pelletized in the granulation concentrating tank 3 passes through the filtering unit (water draining means) 3b and is used as treated water in the pipe 1
It is discharged to the outside of the system via 8. The granulated product is sent to the dehydrator 4 through a pipe 19 together with a small amount of liquid, and the dehydrated cake is a pipe 2
It is discharged from the system from 0.

The inorganic salt added to the mixed system of the biologically treated water and the first settling sludge neutralizes the negatively charged SS and agglomerates, and at the same time, immobilizes phosphorus. Then, in the granulation concentrate tank 3, such agglomerated flocs are coarsened and densified by the polymer coagulant while being stirred in the granulation concentrate tank, and thus granulated particles having excellent separability from water. Becomes

When granulating in the granulating concentrating tank, if only the biologically treated water is to be granulated without mixing the first settling sludge, SS will be insufficient and it will be difficult to granulate agglomerated flocs. Granulation can be carried out smoothly by mixing the first treated sludge with the biologically treated water to allow the SS content to exist.

In the granulating / concentrating tank 3, as described above, the filtering section 3
Since the flocculation reaction is carried out while draining the water in b, even if the concentration of the SS is dilute like biologically treated water, it is possible to granulate hard and large flocs by the small granulation concentrating tank.

The treated water withdrawn from the agglomeration reaction system of the granulation concentrating tank 3 is of extremely high quality, in which phosphorus is further removed from the biological treated water from which nitrogen and BOD components have been removed.

In the biofilm filtration tank 2, surplus microorganisms generated in the tank and S captured in the filter material layer in the tank are used.
Backwashing is regularly performed to remove S, and the backwash drainage is discharged. This backwashing wastewater is sent to the settling tank 1 through the pipe 21 for solid-liquid separation.

In the present embodiment, the initial precipitation separated in the precipitation tank 1 is fed to the granulation / concentration tank without biological treatment. Therefore, the soluble organic matter contained in this initial precipitation cannot be completely coagulated and removed even if an inorganic salt is added, but the mixing ratio of the initial precipitation to the biologically treated water from the biofilm filtration tank 2 is usually 1 Solubility in raw water B because it is less than wt%
If the OD is 100 mg / l or less, the concentration of the soluble BOD in the initial precipitation introduced into the granulation concentrating tank will be 1 mg / l or less when diluted with the biologically treated water, so this is not a problem. Similarly, the soluble nitrogen in the initial precipitation is also sufficiently diluted, so that the soluble nitrogen in the raw water is several 100 mg /
If it is about 1 or less, there is no particular problem.

The apparatus shown in FIG. 1 is an embodiment of the present invention, and the present invention is not limited to the illustrated apparatus as long as the gist thereof is not exceeded.

For example, as the solid-liquid separation device, a flotation tank, a membrane separation device or the like may be used in addition to the settling tank shown in FIG. Further, the type of the biofilm filtration device is also arbitrary, and as shown in FIG. 1, in addition to the upflow type biofilm filtration device using a floatable filter medium as a carrier, sedimentable filter media such as sand, activated carbon and synthetic resin are also available. It may be a downward flow type biofilm filtration device in which the treated water is used as the carrier and the treated water flows downward. In addition, as shown in FIG. 1, the biofilm filtration apparatus is of a one-column type in which denitrification and nitrification are performed in one filtration tank, and a multi-column type in which denitrification and nitrification are performed in different filtration tanks. You can also A BOD removal tower may be further provided at the latter stage or the former stage of this biofilm filtration device.

As for the means for mixing the solid content separated by the solid-liquid separation device (first settling from the settling tank in FIG. 1) with the biologically treated water, as shown in the figure, a pipeline mixing system is used in which the solid content is directly mixed with the piping. Alternatively, a separate mixing tank may be provided and mixing may be performed in the mixing tank.

Similarly, as for the means for adding the inorganic salt, in addition to the pipeline injection shown in the figure, a separate coagulation tank may be provided to add the solid content to the biologically treated water. Further, the polymer coagulant may be directly injected into the granulation concentrating tank as shown in the figure, or may be injected into the pipeline or may be added inside the coagulating tank. Alternatively, two types of polymer coagulants may be used, one of which is added in the coagulation tank and the other of which is directly injected into the granulation concentrating tank, so that they are added by different injection means.

In the present invention, as the inorganic salt,
Sulfate band, ferric chloride, aluminum chloride, polyaluminum chloride, polyiron sulfate and the like can be used, but polyaluminum chloride is particularly preferable.

These inorganic salts are usually added so that the pH of the system after addition is 4.5 to 7. If necessary, an acid such as hydrochloric acid or sulfuric acid may be added to adjust the pH.

On the other hand, as the polymer flocculant, an amphoteric polymer having a cation constitutional unit and an anion constitutional unit in the molecule is preferable, and the molar ratio of the cation constitutional unit and the anion constitutional unit is more than 1, particularly , 2 to 5 amphoteric polymer flocculants are desirable.

Examples of the amphoteric polymer flocculant include a copolymer of an anionic monomer component and a cationic monomer component, and a copolymer of an anionic monomer component, a cationic monomer component and a nonionic monomer component. Examples thereof include a Mannich modified product or a Hoffmann degradation product of a polymer or a copolymer of an anionic monomer component and a nonionic monomer component.

Examples of the anionic monomer component include acrylic acid (AA), sodium acrylate (NaA), methacrylic acid and sodium methacrylate. As the cationic monomer component, for example, dimethylaminoethyl acrylate (DA
A), dimethylaminoethyl methacrylate (DA
M), dimethylaminopropyl acrylate, dimethylaminopropyl methacrylate, dimethylaminopropyl acrylamide (DAPAAm), dimethylaminopropyl methacrylate and their quaternized products. Examples of the quaternary compound include dimethylaminoethyl acrylate methyl chloride quaternary compound. Also, a carbonate of dimethylaminopropyl acrylamide or the like can be used. Examples of the nonionic monomer component include acrylamide (AAm), methacrylamide, N, N-dimethylacrylamide, and N, N-dimethylmethacrylamide. Specific examples of the copolymer of these compounds include a DAA quaternized product / AA / AAm copolymer, a DAM quaternized product / AA / AAm copolymer, and DAPA.
Examples thereof include Am / AA / AAm copolymers, DAA quaternized products / AA copolymers, and Mannich modified products of NaA / AAm copolymers.

The amount of these amphoteric polymer flocculants added is usually preferably in the range of 0.5 to 2.5% by weight based on the SS content.

In the present invention, the coagulating and concentrating device is not particularly limited and may be of any type.

Next, a granulating and concentrating tank (aggregating and concentrating device) suitable for the present invention will be described in detail with reference to FIGS. In FIGS. 2 and 3, 31 is a cylindrical tank, and the agitator 3 a is provided at the center of the cylindrical tank 31.
The stirrer 3a includes a rotating shaft 32 that is driven to rotate by a motor and a transmission, and a rotary shaft 32 that is arranged in two stages above and below the rotating shaft 32.
Stirring blades 33, 34 radially provided with a phase of 80 °
It has. The filtration part 3b is a bottomed filtration cylinder 37, which is a little smaller than a semicircle and is installed along the inner circumference of the cylindrical tank 31 along an arcuate portion of the same curvature, and a bottom 37 'of the filtration cylinder 37.
And a plurality of arcuate slits 38 concentrically provided with the cylindrical layer 31.

A hook 35 is provided on the filter cylinder 37, and the filter cylinder 37 is fixed by engaging the hook 35 with the upper edge of the cylindrical tank 31.

The upper end of the filter cylinder 37 and the upper end of the cylindrical tank 31 are at the same level. The bottom 37 ′ of the filter cylinder 37 is separated from the upper edge of the upper stirring blade 33 by only about 1 to 10 mm and is close to it. If necessary, a rubber plate is attached to the upper edge of the stirring blade 33, and this rubber plate is used to rotate the filter cylinder 37 during rotation.
Alternatively, the bottom 37 'may be stroked. The width of the slit 38 is 5 mm or less, preferably about 1 to 2 mm, the interval between adjacent slits in the cylindrical direction is about 2 mm, and the interval between the inner and outer slits in the radial direction is about 5 mm.

The upper stage 33 of the stirring blade is preferably a flat plate having a constant vertical width over the entire length from the base fixed to the rotary shaft 32 to the tip as shown.

The cylindrical tank 31 is also provided with a drainage pipe 18 for penetrating the tank wall and discharging filtered water from the inside of the filter cylinder 37.

While the sludge and the polymer coagulant respectively supplied from the pipes 16 and 17 to the center of the bottom of the tank are stagnant in the tank by the stirring action of the stirring blades 33 and 34 attached to the rotary shaft 32. And mix evenly to react. Water (separated liquid) injected into the filter cylinder 37 through the slit 38 at the bottom of the filter cylinder 37 is discharged from the pipe 18 to the outside of the tank. As a result, the sludge continuously supplied is sufficiently concentrated and becomes a granulated product having high strength. This granulated product is discharged from the pipe 19.

Immediately below the bottom 37 'of the filter cylinder 37, the stirring blade 33 swirls to cause a horizontal swirling flow a.
Occurs. The slit 38 provided on the bottom 37 ′ of the filter cylinder has a concentric arc shape along the horizontal swirling flow a. Therefore, the flocs and fibrous substances in the liquid flow under the bottom 37 ′ in the same direction as the slit 38 extends. As a result, the flocs and the like do not get caught in the slits 38, and the agglomerated flocs roll under the bottom 37 'to become a denser and stronger granule.

In the lower stirring blade 34, the vertical width of the base portion 40 on the side attached to the rotary shaft 32, which is about half the total length, is narrow, and the remaining free end portion 41 is wide in the vertical direction. A battledore shape is preferred. In this way, under the horizontal swirling flow a generated by the upper stirring blade 33, the lower battledore stirring blade 34 pushes water outward at the wide free end portion 41, and the flow swirls to the inner circumference of the tank. In the vicinity, it is divided into an upflow b and a downflow b ', and the upflow b comes into contact with the horizontal swirl flow a by the upper plate type stirring blade 33 and descends toward the center part, and the downflow b'is the bottom surface of the tank. Along the center of the tank, thus creating a vertical circulating flow that swirls between the center and bottom of the tank, and sludge and coagulant supplied to the center of the bottom of the tank ride on these flows b, b '. And efficiently agglomerates with the flocs that have already formed, and agglomerates well. Then, as shown in the drawing, when the wide free end portion 41 is bent at an angle (for example, 45 °) so as to recede with respect to the turning direction of the blade, the free end portion pushes water toward the inner circumference of the tank. As a result, the swirling circulation flows b and b ′ are strengthened and stronger, so that the mixing and contact efficiencies are further improved. Furthermore, the lower end of the inner circumference of the cylindrical tank 31, the upper stirring blade 33 and the lower stirring blade 3
When the guide plates 42, 43 which are located in the intermediate portion of 4 and extend in the swirling direction of the stirring blades and gradually deviate from the inner circumference toward the tip end or curved as shown in the drawing, the circulating flow b
Can flow downwards in the horizontal swirl flow a and then downward in the central part, and downward circulation flow b'can also assist downwards in the central part and then upward in the central part. The contact efficiency can be improved.

Although the case where the filter tank is provided inside the cylindrical tank has been described above, the filter tank may be provided outside the cylindrical tank. In that case, the filtration tank is provided outside the upper outer periphery of the tank wall of the cylindrical tank, and the slit for filtering the liquid in the cylindrical tank into the upper part of the tank wall of the cylindrical tank surrounded by the filtration tank and putting it into the filtration tank. Is provided horizontally, and the outer edge of the stirring blade may be brought close to the inner circumference of the upper part of the tank wall of the cylindrical tank at an interval of 1 to 10 mm. If necessary, a rubber plate may be attached to the outer edge of the stirring blade, and the inner periphery of the tank wall of the cylindrical tank provided with slits may be rubbed during rotation by the rubber plate. Even in the granulating and concentrating tank having such a structure, the sludge and the coagulant supplied from the bottom of the cylindrical tank are agitated and react in the tank, while the water entering the filtration tank through the slit of the tank wall is pumped. Since the sludge is drained to the outside of the tank, the sludge that is continuously supplied is sufficiently concentrated, grows into high-strength floc, is discharged from the sludge pipe, and is guided to the dehydrator. The flocks generated in the cylindrical tank are pushed by the stirring blades that horizontally swirl close to the inner circumference of the upper part of the cylindrical tank provided with the slits and roll along the slit along the inner circumference of the tank wall. It does not get caught in the clogs and is not clogged, and by rolling along the inner circumference of the tank wall along the slit, it becomes dense and strong.

As the treatment conditions in the granulation concentrating tank, it is preferable to adopt a concentration in the tank of 0.5 to 3% by weight / volume and a peripheral speed of the stirring blade of 5 to 20 m / min.

The granulated product thus produced in the granulation concentrating tank is supplied to a dehydrator as it is or after removing the separated liquid, and dehydrated. A belt press is usually used as this dehydrator, but a screw press, a filter press, or the like can also be used.

The present invention will be described in more detail with reference to specific examples.

Example 1 A pilot plant shown in FIG. 1 was installed and treated. The processing conditions were as shown in Table 1. As the inorganic salt, 200 mg / l was added so that the pH after addition of polyaluminum chloride would be 6.8, and as the polymer flocculant, an amphoteric polymer (trade name “Crybest P702” manufactured by Kurita Water Industries Ltd.) was used. 1.5 wt% was added to SS.

[0050]

[Table 1]

FIGS. 4 and 5 show changes in TN concentration and changes in TP concentration of raw water and treated water during the period. Table 2 shows the average water quality of raw water and the average water quality of treated water.

From Table 2 and FIGS. 4 and 5, according to the nitrogen and phosphorus removing apparatus of the present invention, nitrogen and phosphorus can be simultaneously and stably removed over a long period of time to obtain high-quality treated water. I understand.

[0053]

[Table 2]

[0054]

As described in detail above, according to the nitrogen and phosphorus removing apparatus of the present invention, nitrogen and phosphorus in the waste water can be removed at the same time. The biological treatment tank is made compact and management is easy. Sludge thickening tank and final settling tank are unnecessary, and it can be installed in a small site area. Sludge treatment process is simplified and management is easy. With such an effect, a compact and easy-to-manage device can efficiently treat nitrogen and phosphorus in wastewater to obtain high-quality treated water.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of a nitrogen and phosphorus removing apparatus of the present invention.

FIG. 2 is a partial cross-sectional perspective view showing an example of a granulation concentrating tank suitable for the present invention.

FIG. 3 is a plan view of the granulation thickening tank shown in FIG.

FIG. 4 is a graph showing the results of nitrogen treatment in Example 1.

FIG. 5 is a graph showing results of phosphorus treatment in Example 1.

[Explanation of symbols]

 1 Precipitation tank 2 Biofilm filtration tank 3 Granulation concentration tank 4 Dehydrator 31 Cylindrical tank 32 Rotating shaft 33, 34 Stirring blade 37 Filtration cylinder

Claims (1)

[Claims] 1. A solid-liquid separation device for separating SS in waste water, a biofilm filtration device for nitrifying and denitrifying the separated water discharged from the solid-liquid separation device, and a biofilm filtration device for discharging the separated water. A means for mixing the biologically treated water with the solid content discharged from the solid-liquid separation device, a means for adding an inorganic salt and a polymer coagulant to the biologically treated water mixed with the solid content, and a rotary flow inside. A coagulation / concentration device having rotary blades for generating water, a drainage means for discharging separated water, and a means for discharging concentrated coagulation sludge, and biological treatment water to which an inorganic salt and a polymer coagulant are added A device for removing nitrogen and phosphorus, which comprises a means for introducing the same.