JP2001070999A - Method and apparatus for treating wastewater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To promote denitrification and dephosphorization, to reduce the consumption of methanol, and to hold useful microorganisms of a small propagation speed in a reactor in a high concentration by introducing a substance containing an organic fibrous material into a sludge concentration tank in the treatment of sewage, industrial wastewater, etc. SOLUTION: A substance 10 containing an organic fibrous material is introduced into a concentration apparatus 15 to be decomposed. Next, concentrated/ separated liquid 17 in the apparatus 15 is returned to an anaerobic tank 9, and introduced wastewater 1 is introduced into the tank 9 via precipitation basin 11. Part of sludge from a precipitation basin 7 is introduced as return sludge into the tank 9. The discharged liquid of the tank 9 is introduced with circulating liquid 3 which is part of discharged liquid from an aerobie tank 4 into an oxygen-free tank 2, and the discharged liquid of the tank 2 is introduced into the tank 4. Part of the discharged liquid of the tank 4 is circulated as the circulating liquid 3 in the tank 2, and the rest is introduced into the precipitation basin 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the treatment of sewage and industrial wastewater.

[0002]

2. Description of the Related Art Conventionally, a biological treatment method using microorganisms represented by an activated sludge method has been used for water treatment of sewage and industrial wastewater. In this biological treatment, when removing nitrogen components in wastewater, first, ammonia nitrogen is oxidized to NO ₂ -N or NO ₃ -N by the action of nitrifying bacteria, and then NO ₂ -N or NO ₃ -N Has generally been reduced to N ₂ gas. Further, the biological treatment method of phosphorus is a method of removing phosphorus in wastewater by ingesting phosphorus into microorganisms, and specifically, is performed by alternately exposing microorganisms to an anaerobic state and an aerobic state. In this case, the microorganisms exhale phosphorus using an organic substance in an anaerobic state, while the microorganisms excessively ingest phosphorus into the body using an organic substance in an aerobic state. Utilizing such properties of microorganisms, methods for biologically treating phosphorus have been developed.
In the biological treatment of phosphorus, the higher the organic matter / phosphorus ratio of the influent, the higher the phosphorus removal rate.

[0003] As described above, organic substances are useful as a reducing agent for causing a reduction reaction of a denitrification reaction, and for improving phosphorus removal efficiency. Organic substances and methanol contained in waste water have been used as such organic substances that act as reducing agents. In addition, a method has been proposed in which sludge is decomposed in an anaerobic state to generate an organic acid, and the organic acid is used as a reducing agent (hereinafter referred to as Conventional Technique 1).

[0004] In the activated sludge method, microorganisms (activated sludge) and treated water are separated in a final sedimentation basin, and a part of the settled and separated sludge is subjected to dehydration treatment after concentration. In recent years, sludge dewaterability tends to decrease due to changes in dietary habits, etc.However, as a method of improving sludge dewaterability and reducing the water content of dewatered cake, waste paper is added to sludge to be dewatered before dewatering To improve the dewatering property (Japanese Unexamined Patent Publication No. 9-2
No. 16000 (hereinafter referred to as Conventional Technique 2) has been proposed, and some are being put to practical use. Also, a method of charging a granular carrier such as waste paper or wood chips into a reaction tank (Japanese Patent Application Laid-Open No. 11-010182;
) Has also been proposed.

There has also been proposed a method of subjecting organic fibers such as cellulose to biological treatment in an anaerobic state to generate alcohol or methane (hereinafter referred to as prior art 4).

[0006]

As described above, in the conventional method for removing nitrogen from wastewater using microorganisms, when removing nitrogen components from wastewater, NO ₂ -N or NO ₃ -N is converted to N.
_This is a method of reducing to _two gases. Although a reducing agent is required to cause this reduction reaction, generally only organic substances contained in wastewater are insufficient as a reducing agent. On the other hand, when methanol is used (added) as a reducing agent, the cost of methanol is required, which causes a problem that the processing cost increases.

Further, in the technology for anaerobically decomposing sludge as shown in the prior art 1, ammonia nitrogen and phosphoric acid are generated simultaneously with the organic acid accompanying the decomposition of sludge. Since most of the organic matter generated by the biological reaction is used for treating the ammoniacal nitrogen generated, the merits of the organic matter with respect to nitrogen removal are offset, and there arises a problem that the generated phosphorus needs to be removed.

[0008] In the technique shown in the prior art 2, although the water content of the dewatered cake is reduced and the amount of the coagulant required for dewatering is also reduced, it is necessary to refine the used paper when adding the used paper. A waste paper dissolution tank must be provided. In addition, this method is a technique applied to a sludge treatment system and the like, and is effective in reducing the water content of the dewatered cake and the amount of the coagulant used for dewatering, but it is effective in removing nitrogen and phosphorus in wastewater treatment. Has no effect on

The technique shown in the prior art 3 has the advantages of improving the dewatering property and the sludge concentration in the reaction tank, but the carrier is anaerobic or anaerobic when brought into the final sedimentation tank. It becomes a state. Such a condition is undesirable for aerobic microorganisms,
Aerobic microorganisms attached to and immobilized on a carrier, such as nitrifying bacteria, are greatly damaged. Therefore, the method of the prior art 3 does not achieve the high advantage of using the carrier, that is, the high concentration of nitrifying bacteria. Further, in this method, the used waste paper and wood chips are drawn out as excess sludge and subjected to dehydration treatment, and at this time, useful microorganisms immobilized on the carrier also flow out of the reaction tank at the same time. .

The advantage of using a carrier to immobilize microorganisms is that useful microorganisms having a low growth rate are retained on the carrier, and this advantage is due to the residence time of microorganisms (or solids in a reaction tank). (Generally SR
T: Solid Retention Time). In the technique described in the prior art 3, as described above, the carrier and the suspended sludge reach the final sedimentation basin at substantially the same ratio and are drawn out at substantially the same ratio. Furthermore, in order to obtain the merit of reducing the content of the dehydrated cake as described in the prior art 3,
A relatively large amount of fiber must be introduced. Specifically, the SRT is shortened because fibrous material of about 10% or more of the generated sludge solid content when not charged is required. Therefore, the advantage obtained by using the carrier is negated in the case of the prior art 3.

A method has been proposed in which the sludge concentration (MLSS) in the reaction tank is set higher to increase the SRT. In fact, the method using the microorganism-immobilized carrier developed so far does not allow the carrier to flow out of the reaction tank,
SRT has been increased by using a carrier separation means such as a screen. However, in the prior art 3, since the carrier flows out to the final sedimentation basin and the solids load in the final sedimentation basin increases by that amount, the effect of extending the SRT by increasing the MLSS is little or negligible. In general sewage treatment, the SRT is set to about 2 to 5 days, depending on the water temperature, and is set to 3 days or more in order to retain nitrifying bacteria. In the prior art 3, the retention time of the carrier in the reaction tank is about 2 to 5 days or less, which is almost the same as suspended sludge, and the reaction time for the organic fiber to undergo the decomposition reaction is short. In addition, the organic fiber is taken out. Furthermore, the process is not such that a large amount of microorganisms having the ability to decompose organic fibers are retained. In other words, microorganisms having the ability to degrade organic fibrous materials are generally anaerobic microorganisms having a small growth rate, but have a large growth rate in an aerobic state in a system having an aerobic reaction tank. Aerobic bacteria grow in large quantities. Therefore, in an aerobic state having an aerobic reaction tank, a microorganism capable of decomposing organic fibers cannot be a priority species. For this reason, since organic fiber is hardly decomposed, no organic matter is generated, and the effect of promoting nitrogen removal and phosphorus removal and the effect of reducing methanol consumption cannot be obtained.

As described above, a method of treating wastewater that promotes nitrogen removal and phosphorus removal and reduces the amount of methanol used has not yet been obtained. Furthermore, the improvement of dehydration of excess sludge, improvement of sludge separation / condensation, and reduction of the amount of flocculant used for dehydration have not been sufficiently achieved, and useful microorganisms with a low growth rate are placed in the reaction tank. At present, maintaining at a high concentration has not yet been achieved.

[0013] Accordingly, the present invention promotes the removal of nitrogen and phosphorus, reduces the amount of methanol used, improves the dewatering properties of excess sludge, improves the separation and condensation properties of sludge, and uses a coagulant for dehydration. It is an object of the present invention to provide a method for treating wastewater capable of reducing the amount and maintaining useful microorganisms having a low growth rate at a high concentration in a reaction tank.

Further, the present invention promotes the removal of nitrogen and phosphorus, reduces the amount of methanol used, improves the dehydration of excess sludge, improves the separation and condensation of sludge, and uses a flocculant for dehydration. It is an object of the present invention to provide a treatment apparatus for reducing waste and treating wastewater by holding useful microorganisms having a low growth rate in a reaction tank at a high concentration.

[0015]

In order to solve the above-mentioned problems, the present invention provides a method for treating wastewater, which comprises introducing a substance containing organic fibers into a sludge thickening tank.

Further, the present invention provides a wastewater treatment apparatus comprising a sludge thickening tank having a means for introducing a substance containing an organic fiber.

Hereinafter, the present invention will be described in detail.

In the present invention, first, a substance containing an organic fiber is mixed in a sludge concentration tank with the organic fiber and a microorganism, and at least a part of the organic fiber is decomposed by the action of the microorganism. . The substance containing the organic fiber may be directly introduced into the sludge thickening tank, or may be introduced into a pipe leading to the sludge thickening tank. By treating the substance containing organic fibrous material in the sludge concentration tank, at least a part of cellulose, which is a main component of the organic fibrous material, is decomposed to obtain a low molecular weight organic substance. Is returned to the wastewater treatment system as a separation liquid in the concentration tank or a liquid removed from the dehydration step in the subsequent stage. In the present invention, wastewater is treated using the organic matter that is the decomposition product.

Decomposition products obtained by decomposing and reducing the molecular weight of organic fibers are used for denitrification and dephosphorization reactions in wastewater treatment to promote nitrogen removal, improve nitrogen removal rate,
The effect of reducing methanol and the effect of improving the phosphorus removal rate can be obtained. In addition, the main component of the organic fiber is cellulose, and since cellulose is a molecule composed of carbon, hydrogen, and oxygen, the decomposition material contains little nitrogen or phosphorus.
The problem of the prior art 1 in which the nitrogen load and the phosphorus load in the wastewater treatment increase due to the organic matter generated by the decomposition of the organic fiber can be solved.

Further, a part of the organic fiber (a part of cellulose, lignin, etc.) moves to the concentrated sludge side of the concentrated layer without being decomposed, and is further dewatered by the dehydrator. Efficiency, stabilization, the effect of reducing the water content of the dewatered cake, and the effect of reducing the coagulant for dewatering are obtained. In addition, since the dewatering property is improved and the water content of the dewatered cake is reduced, since the volume of the sewage sludge cake is reduced, there are merits in terms of handling such as transportation costs, and in the case of incineration treatment at a later stage. This also has the advantage of reducing auxiliary fuel or increasing energy recovery.

It is preferable that the substance containing the organic fiber is retained in a part of the sludge concentration tank for a residence time longer than the residence time of the sludge. In general, since organic fibers such as cellulose have a low decomposition rate, they must be retained for a long time under conditions in which a reaction occurs in order to obtain a high conversion. For this purpose, the residence time of the substance containing the organic fiber in the concentration tank must be increased. For example, if organic fibrous material is charged in a granular form and a screen having a mesh width smaller than the particle size is used, relatively new particles containing a large amount of undecomposed components are maintained in the concentration tank, and undergo cracking to become ragged. The waste passes through the screen and moves to the concentrated sludge side. Most of the decomposition products are returned to a wastewater treatment system or the like as a separation liquid in a concentration tank. It is preferable to use an automatic cleaning type provided with a scraping device or the like, since there is a possibility that particles which have become smaller to some extent may get into the screen. The same effect can also be expected when a part of the concentration tank is processed and divided, and the organic fiber is charged here so as to be retained for a long time. For example, a metal mesh having an opening of about 0.5 mm to about 30 mm or a basket-shaped container made of punching metal or the like is put into a concentration tank, and an organic fiber having a diameter larger than the mesh width is introduced here. In addition, the residence time of the organic fiber in the container can be increased. Therefore, organic fibers are decomposed in such a container, and the decomposition products obtained by decomposition and depolymerization of the organic fibers are used for denitrification and dephosphorization reactions in wastewater treatment to remove nitrogen. Promotion, nitrogen removal rate,
The effect of reducing methanol and the effect of improving the phosphorus removal rate can be obtained. In addition, a part of the organic fiber (a part of cellulose, lignin, etc.) moves to the concentrated sludge side of the concentration tank without being decomposed, and is further dewatered by the dewatering device. The effect of stabilization, the effect of reducing the water content of the dewatered cake, and the effect of reducing the coagulant for dewatering are obtained. Here, too, there is a possibility that particles that have become smaller to some extent may be trapped in the basket-shaped container. Therefore, it is preferable to use an automatic cleaning type provided with a scraping device, etc. It is preferable that

Prior to treating the substance containing organic fibrous material in the sludge thickening tank, it is preferable to disperse the substance in a liquid in advance. Depending on the type and state of the organic fiber (dryness, whether or not it is charged with static electricity, etc.), when it is introduced into the sludge thickening tank, lumps having irregular particle sizes may be formed. Only the agglomerated surface comes into contact with microorganisms, enzymes and the like, and a good contact state between the introduced organic fiber and the microorganisms or enzymes cannot be obtained. Therefore, the reaction efficiency of the decomposition reaction of the organic fibrous material may decrease. Similarly, depending on the type and condition of the organic fiber to be introduced (dryness, whether or not it is charged with static electricity, etc.), it floats at the time of introduction into the concentration tank, and immediately returns to the return water side as a separation liquid of the concentration tank. And may flow out of the concentration tank. Further, as described above, the granulation of the organic fiber is advantageous in terms of increasing the residence time of the organic fiber in the concentration tank, but the organic fiber having a relatively high degradability is obtained. If added, the residence time does not need to be very long. Rather, if it is a powdery organic fiber, it may be better to maintain a large contact area in the powdery state. In such a case, it is effective to disperse the substance containing the organic fiber in a liquid in advance. As the liquid in which the substance containing the organic fiber is dispersed in advance, a part or all of the liquid substance generated in the wastewater treatment step, tap water, industrial water, miscellaneous water, well water, and the like can be used. The liquid substances generated in the wastewater treatment process include, for example, influent water, returned sludge, excess sludge, sludge withdrawn from the first settling basin, circulating water, concentrated sludge, concentrated sludge desorbent, dewatering process desorbent, and sludge treatment process return. Although there are running water, filtration washing wastewater, and the like, the organic fiber is introduced into the concentration tank, so that it is most convenient to use the inflow liquid of the concentration tank. Further, as a dispersing method, a usual mixer, disperser, stirrer, mixer or the like may be used. If necessary, a dispersant may be added, and the dispersing agent can be dispersed using ultrasonic waves or the like.

In the present invention, as the organic fiber (raw material), used paper, wood chips (including construction waste), sawdust, rice hulls, kitchen waste, and the like, and a mixture of two or more of these can be used. . However, kitchen garbage having a high concentration of nitrogen and phosphorus components is not preferable because the effects of the present invention are reduced. In addition, as long as the organic fiber concentration or the organic fiber concentration is high and the nitrogen and phosphorus component concentrations are low, waste and wastewater generated from factories and offices can be used as raw materials. is there. In particular, in the present invention, as the organic fiber, it is preferable to use a waste material containing the organic fiber as a main component, for example, waste paper. This has the effect of reducing the cost of treating waste materials, and is also effective in terms of the current social demands of recycling and zero emissions.

In the present invention, part of the step of treating wastewater can be carried out in an aerobic reaction vessel, and when the step of treating wastewater is carried out in an aerobic reaction vessel,
The aerobic reaction vessel preferably contains a microorganism-immobilized carrier. As a result, nitrifying bacteria having a low growth rate and difficult to maintain at a high concentration, such as ammonia-oxidizing bacteria and nitrite-oxidizing bacteria, can be maintained at a high concentration in the reaction vessel, so that the nitrogen component is further increased. Processing efficiency is achieved. That is, improvement of the nitrogen removal rate, stabilization of nitrogen removal, and downsizing of the reaction tank are achieved. When the present invention is applied, it is generated in a concentration tank,
The amount equivalent to the organic fiber returned to the wastewater treatment system and the organic fiber that has not been decomposed but returned to the wastewater treatment system (more precisely, is re-synthesized into microorganisms in the wastewater treatment system and solidified. SRT is slightly shorter than when no sludge solids are generated and decomposition products of substances containing organic fibers and undecomposed parts are not charged. Is done. For this reason, there is a slight disadvantage in maintaining the nitrifying bacteria in the reaction tank at a high concentration. However, since the nitrifying bacteria are kept at a high concentration in the carrier by charging the microorganism-immobilized carrier into the reaction tank, the efficiency of nitrogen removal as described above can be achieved.

The microorganism-immobilized carrier accommodated in the aerobic reaction vessel is preferably in the form of a hollow cylinder, and the aerobic reaction vessel has an opening of 2.0 mm or more for preventing the microorganism-immobilized carrier from flowing out. It is preferable to provide a carrier outflow prevention means such as a screen on the outflow side. Since the surface area per unit volume of the microorganism-immobilized carrier can be increased by using the hollow cylindrical microorganism-immobilized carrier, a large amount of nitrifying bacteria can be held on the carrier surface, and the shape of the carrier can be improved. The coefficient is small and the fluidity is high. Here, when the organic fiber is put into the concentration tank, fine fiber is generated along with the decomposition of the organic fiber, and a part of the fine fiber is returned to the wastewater treatment system. Since the formed fiber may cause blockage of the screen, it is desirable that the mesh width of the screen be as large as possible. Practically, the mesh width of the screen is 2 mm or more, and moreover, 2.
Although it is preferable to set it to 5 mm or more, if the mesh width of the screen is made large, the size of the carrier must also be made large. In this case, since the specific surface area of the carrier also decreases, it is desired to employ a hollow-shaped carrier capable of increasing the specific surface area.

Alternatively, in the step of treating the substance containing organic fibers, ie, the step of treating the sludge concentration tank and / or the wastewater, a microorganism having an organic fibrinolytic enzyme and an organic fibrous degrading ability can be used. May be introduced.

In order to decompose substances containing organic fibers, microorganisms and enzymes capable of decomposing organic fibers are required, and it is preferable that these are supplied at the start of the reaction. If the wastewater treatment apparatus already contains a microorganism capable of decomposing organic fibers, it may not be necessary to introduce the above-mentioned enzymes and microorganisms. However, these additions at the start of the reaction are effective for promptly starting the reaction. Whether to add only at the start of the reaction, to continue the addition, or the amount of addition depends on the regional characteristics, the presence or absence of inflow of factory wastewater, etc. as described above. It should be decided in consideration of economic efficiency from the above.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic diagram showing the configuration of an example of the wastewater treatment apparatus of the present invention. In the illustrated wastewater treatment apparatus, first, a substance 10 containing organic fibrous material
5 is introduced. For this introduction, the sludge may be initially dispersed in the sedimentation basin drawn sludge 12 or the surplus sludge 14. Further, in the concentrating device 15, a cage-like container is accommodated so that the residence time of the organic fiber can be extended for a long time, or the organic fiber is introduced in a granular form, and a screen having a mesh width smaller than the particle diameter is accommodated. You may. In the concentrating device 15, the substance 10 containing organic fiber is decomposed. In the present invention, as the organic fibrous material, a waste material mainly composed of an organic fibrous material such as waste paper can be used. In the illustrated example, the concentrated separated liquid 17 from the concentrating device 15 is returned to the anaerobic tank 9, but the concentrated separated tank 17 may be first returned to the sedimentation basin 11.

On the downstream side of the anaerobic tank 9, the oxygen-free tank 2, the aerobic tank 4, the sedimentation basin 7, the concentrator 15 and the dehydrator 18 are provided, and these constitute a wastewater treatment process. The order of the arrangement of the tanks and the like is not limited to the illustrated example.

The inflow wastewater 1 is first introduced into the anaerobic tank 9 via the sedimentation basin 11. A part of the sludge from the sedimentation basin 7 is introduced as returned sludge 13. Further, as shown in the figure, the dehydrating solution 20 from the dehydrating device 18 may also be returned to the anaerobic tank 9 or the first settling basin 11,
These returns are not necessary. In some cases, the dehydration liquid 20 is introduced into a dedicated treatment step, or is first introduced into a sedimentation basin or a sand basin.

The reaction proceeds in the anaerobic tank 9 under anaerobic conditions, and the effluent of the anaerobic tank 9 is introduced into the oxygen-free tank 2 together with the circulating liquid 3 which is a part of the effluent from the aerobic tank 4. . The reaction proceeds in the oxygen-free tank 2 under oxygen-free conditions, and the effluent from the oxygen-free tank 2 is introduced into the aerobic tank 4.

The aerobic tank 4 accommodates a microorganism-immobilized carrier 5, and a carrier outflow prevention (carrier separation) device 6 is provided at the outflow side of this tank. Is always retained. A part of the effluent of the aerobic tank 4 is used as the circulating liquid 3 as described above.
And the remainder is introduced into the sedimentation basin 7. The shape of the microorganism-immobilized carrier 5 housed in the aerobic tank 4 is as follows.
Although a hollow cylindrical shape is preferable, effects can be obtained with other shapes. By using a hollow cylindrical carrier, there are advantages that the surface area per unit volume of the microorganism-immobilized carrier can be increased, and that the carrier has a small shape factor and high fluidity.

As the material of the carrier, any of a high molecular weight material and an inorganic material can be used. Examples of the polymer system include polyvinyl alcohol, polyethylene glycol, polypropylene glycol, polyacrylamide, polyvinyl fermal, polypropylene, polyethylene, vinylidene chloride, nylon, polyvinyl chloride, and mixtures thereof. System, sand, activated carbon, and minerals such as anthracite and zeolite. Further, wood chips or the like may be used.

On such a carrier, not only microorganisms but also enzymes may be immobilized. At that time, polyvinyl alcohol,
Polyethylene glycol, polypropylene glycol,
And an enzyme can be immobilized inside a gel such as polyacrylamide.

A screen is generally used as the carrier separating device 6, but the system is not particularly limited as long as it can separate the carrier and the effluent of the aerobic tank 4, and any device may be used. Can be. For the reasons as described above, the screen width is practically 2 mm or more, preferably 2.5 mm or more.

In addition, there is enough room on the site of the treatment plant,
When a large aerobic tank is provided and nitrifying bacteria can be maintained at a high concentration, it is not always necessary to use the carrier 5 in the aerobic tank 4.

In the sedimentation basin 7, the effluent introduced from the aerobic tank 4 is settled and separated to obtain sludge.
The sludge is introduced into the concentration device 15 as surplus sludge 14, and the remaining portion of the sludge is introduced into the anaerobic tank 9 as returned sludge 13. On the other hand, the supernatant liquid subjected to solid-liquid separation in the sedimentation basin 7 is discharged as treated water 8. The sedimentation basin 7 is for separating the sludge from the treated water. If the sludge can be separated from the treated water, other methods (floating separation, membrane separation, filtration, centrifugation, etc.) can be used. May be used.

In the concentration device 15, the sludge is concentrated and introduced into the dehydration device 18 as the concentrated sludge 16, and then subjected to a dehydration treatment and discharged as a dewatered cake 19.

As the concentrating equipment 15 and the dewatering equipment 18, various types can be used. For example, a sedimentation concentrator, a centrifugal concentrator, a filtration concentrator, a floating concentrator, a belt concentrator and a belt press type Dehydrator, centrifugal dehydrator,
A filter press dehydrator, a rotary press dehydrator, or the like may be used. Also, depending on the processing facility,
In some cases, sludge concentration processing or treatment by mobile sludge treatment equipment is performed without holding sludge treatment equipment, but in such a case, the effect of the present invention is maintained without any change.

The main reactions in the above-mentioned processes are the decomposition and depolymerization of organic fibers in the concentrator 15; the discharge of phosphorus in the anaerobic tank 9;
Decomposition and depolymerization of organic fibrous material, denitrification reaction
And organic substance decomposition reaction, nitrification reaction in aerobic tank 4,
This is a phosphorus absorption reaction.

The nitrogen components in the wastewater are converted into ammonia nitrogen and organic nitrogen into NO ₂ -N and NO ₃ -N by the action of nitrifying bacteria in the aerobic tank 4. Here, the nitrifying bacteria refer to both those that are suspended and those that are immobilized on the carrier 5. Thereafter, a part of the effluent from the aerobic tank 4 is circulated as circulating water 3 to the oxygen-free tank 2, where NO ₂ -N and NO ₃ -N are reduced to N ₂ gas in the oxygen-free tank 2. . The N ₂ gas thus obtained is released to the atmosphere, whereby nitrogen components in the wastewater are removed.

As a reducing agent in this reduction reaction, an organic substance contained in the inflow water 1 is used. Further, the organic fibrous decomposed substance generated by the concentrator 15 also acts as a reducing agent. Phosphorus in wastewater is removed by the following actions of microorganisms. First, microorganisms use organic matter in the anaerobic tank 9 to exhale phosphorus in the body.
Microorganisms that have excreted phosphorus mainly absorb more phosphorus in the body than the amount exhaled in the aerobic tank 4. In this way, phosphorus in wastewater is absorbed into the body of microorganisms,
The phosphorus in the wastewater is removed.

When the microorganisms use the organic matter in the anaerobic tank 9 to cause a reaction in which the microorganisms exhale phosphorus, the organic matter is required as an energy source. As this organic substance, an organic substance generated from organic fibers in the anaerobic tank 9 is used.

Also, when the microorganisms that have discharged phosphorus absorb the phosphorus in the aerobic tank 4, the organic matter is required as an energy source. The organic matter generated from the organic fiber in the anaerobic tank 9 is also used as this energy source.

In the present invention, nitrogen in wastewater is removed by the above-described redox reaction, and phosphorus in wastewater is removed by excessive intake of phosphorus. Furthermore, in the present invention, organisms proliferate with a biological reaction utilizing a substance produced by the decomposition of organic fibrous materials. At this time, the microorganisms ingest the phosphorus compounds and nitrogen compounds in the water. Thus, the phosphorus concentration and the nitrogen concentration in the treated water are further reduced.

Although some undecomposed organic fibers are returned from the concentrator 15 to the wastewater treatment system, the undecomposed organic fibers improve the sedimentation and separation of sludge. The concentration of the solids in the treated water 8 obtained from the above becomes smaller, and the treated water quality becomes more excellent.

Further, the undecomposed organic fiber which is not decomposed in the condensing tank 15 and moves to the concentrated sludge side and the undecomposed organic fiber contained in the excess sludge reach the dewatering device 18 where the sludge is removed. Since the dewatering property is improved, the water content of the dewatered cake 19 from the dewatering device 18 is reduced, and there is also an advantage that the cost of auxiliary fuel for incinerating the dewatered cake can be significantly reduced. In addition, there is a merit that the amount of the coagulant for dehydration can be reduced as the dehydration property is improved.

Further, the improvement of the dewatering property and the reduction of the water content of the dewatered cake reduce the volume of the sewage sludge cake, which is advantageous in terms of handling such as transportation cost.
In addition, in the case of performing incineration at a later stage, there is an advantage that the amount of auxiliary fuel or energy recovered is increased.

In the present invention, the shape of the organic fibrous material 10 introduced into the concentration tank 15 is not particularly limited, and may be any of granular, powdery, thread-like, and paper-like shapes. From the viewpoint of the reaction rate, the finer the organic fiber is, the more advantageous it is. However, in the case of fine particles, they float up as described above and are returned as a separation liquid in the concentration tank, and it is difficult to take a sufficient reaction time in the concentration tank. It is good to disperse in a liquid or the like. When an organic substance rich in dispersibility is introduced, various substances can be used, but when an organic fiber having a large percentage of a hardly decomposable substance is used, it is present as a granular form in the anaerobic tank for a long time. It is preferable to increase the contact efficiency and the reaction efficiency by miniaturization. In addition, when introducing the semiconductor device after the microfabrication process, costs, maintenance and the like for the process are required. Therefore, the input form of the organic fiber may be appropriately determined in consideration of the necessity and effect.

Examples of the particulate matter include shredder waste generated in offices and the like, shredder waste compressed and formed, waste paper formed into granules, wood chips (including construction waste materials), rice hulls, and garbage. Etc., and mixtures of two or more of these. However, kitchen garbage having a high concentration of nitrogen and phosphorus components is not preferable because the effects of the present invention are reduced. In addition, the concentration of organic fiber or organic fiber is high, and nitrogen,
As long as the phosphorus component concentration is low, waste and wastewater generated from factories and offices can be used as raw materials.

In the case of used paper, if it is to be recycled as paper (recycled paper), it is usually necessary to separate it in advance. On the other hand, in the present invention, separation is not particularly necessary, and so-called mixed waste paper, which is currently the most difficult to separate and is difficult to reuse as paper, and is a major problem, can be used. The portion of the high-quality paper in the mixed waste paper contains a large amount of cellulose, which is decomposed and degraded to low molecular weight and used for removing nitrogen and phosphorus. On the other hand, the low-quality paper portion in the mixed waste paper contains a large amount of hardly decomposable components such as lignin, but the undecomposed portion contributes to the improvement of the sedimentation property, concentration property, or dewatering property of sludge.

In addition, by pre-treating the organic fiber before it is decomposed and depolymerized in the concentration tank 15, the reaction efficiency and the reaction speed can be improved. As the pretreatment, for example, acid treatment, alkali treatment,
Examples include ozone treatment, peroxide treatment, temperature treatment, ultrasonic treatment, and combinations thereof. Whether or not to perform these processes can be appropriately determined by comprehensively judging the processing costs, the necessity of maintenance and management for the processes, the effects, and the like.

The organic fiber 10 introduced into the concentration tank 15
Varies depending on the water quality of the inflow water 1, the required water quality of the treated water 8, and the required water content of the dewatered cake. Generally, when the desired nitrogen concentration or phosphorus concentration of the treated water is low; when the BOD / nitrogen ratio or BOD / phosphorus ratio of the influent is small; when it is desired to reduce the water content of the dewatered cake;
Alternatively, when it is desired to enhance the solid-liquid separation property in the sedimentation basin, it is necessary to increase the amount of the organic fiber 10 to be introduced. When treating general sewage, the input amount is about 10 g to 500 g per 1 m ³ of inflow sewage. The volume of the organic fiber 10 to be charged is the same as that of the organic fiber 1 to be charged.
It can be determined from the amount of zero, the degradation rate, and the average residence time.

In addition, microorganisms or enzymes (cellulase, etc.) capable of decomposing organic fibers can be used to decompose organic fibers.
Is preferably present, and it is desired to supply them to the concentration tank 15 at the start of the reaction. As described above, if microorganisms capable of decomposing organic fibers are included in the concentration tank 15 from the beginning, it may not be particularly necessary to introduce enzymes or microorganisms into the concentration tank 15. However, it is effective to add these at the start of the reaction in order to quickly start the reaction.
Whether to add only at the start of the reaction,
Whether or not the addition is performed or the amount of the addition depends on the regional characteristics, the presence or absence of inflow into the factory wastewater, and the like, as described above. In addition, the conditions for adding enzymes and microorganisms vary depending on the required degree of molecular weight reduction of organic substances and the water content of the dehydrated cake. Therefore, taking into account the stability of the reaction, the obtained reaction rate, etc. and economics,
The addition of enzymes and microorganisms can be determined appropriately.

Also, a carrier in which microorganisms, enzymes, and yeasts having organic fiber decomposing ability are immobilized is charged into the concentration tank 15, and an outflow prevention device is provided so that the carrier is maintained in the concentration tank. It may be. As a result, the effect of shortening the startup period of the system, the effect of stabilizing the reaction of the system, and the effect of reducing the size of the reaction tank can be obtained.

Further, by adding nutrients (nitrogen component and phosphorus component) and trace elements necessary for the growth of microorganisms having an organic fiber decomposing ability to the concentration tank 15 and the wastewater treatment system, the efficiency can be further improved. In some cases, some improvement may be observed.

Note that the flow of FIG. 1 shows an example of the wastewater treatment apparatus of the present invention, and the present invention is not limited to this flow. The anaerobic tank 9, the anaerobic tank 2, the aerobic tank 4, the aerobic tank circulating liquid 3, the sedimentation basin 7, and the returned sludge 13 in FIG. 1 constitute a water treatment process. It is a typical sewage advanced treatment flow called the method. Even if the water treatment step is replaced with a treatment method other than the anaerobic anoxic aerobic method, the effects of the present invention can be obtained with almost no change. For example, when the flow of the water treatment step is the standard activated sludge method, the standard activated sludge method itself does not assume the flow of nitrogen removal or phosphorus removal due to excessive intake of phosphorus. The effect of the promotion effect is weakened. However, even in this case, a biological reaction utilizing substances produced by the decomposition of the organic fibrous material occurs, and the organism grows accordingly. At this time, the microorganisms ingest the phosphorus compounds and nitrogen compounds in the water into the living body. I do. Thus, the phosphorus concentration and the nitrogen concentration of the treated water are reduced. further,
All effects such as improvement of the dewatering property of excess sludge, reduction of the amount of coagulant used for dewatering, and improvement of sludge separation / concentration property are maintained without any change.

Further, the water treatment process in the apparatus shown in FIG. 1 includes a circulation type nitrification denitrification method, an anaerobic-aerobic method, a Badenho method, a modified Badenjo method, a step-flow type nitrification denitrification method, a nitrification-endogenous denitrification method, Almost all biological treatment flows such as the anaerobic-nitrification-endogenous denitrification method and the like can be replaced by the flow of the carrier charging method. In any case, the effect of the present invention is almost maintained.

The present invention basically promotes the removal of nitrogen and phosphorus by decomposing the organic fiber in the concentration tank 15 and utilizing the decomposition product in a biological reaction. The purpose of the present invention is to improve the separation, concentration and dehydration properties of sludge by utilizing undecomposed substances, and all processing flows based on such a concept are included in the scope of the present invention. When the organic fiber is charged, the fiber may be dispersed in a liquid in advance.

[0061]

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

First, in the flow shown in FIG. 1, an apparatus for introducing the organic fibrous material 10 into the concentration tank 15 was configured, and the waste water was treated using the apparatus. In addition,
In the first embodiment, the specific gravity of the aerobic tank 4 is 1.0.
1. A hollow cylindrical carrier 5 made of expanded polypropylene having a length of 5 mm, an outer diameter of 4 mm, and an inner diameter of 3 mm is accommodated at 7% based on the true volume, and a wedge wire screen having a mesh width of 2.5 mm is used as a carrier outflow prevention device 6 in an aerobic tank. 4 at the exit.

Further, an apparatus similar to that of the above-described embodiment 1 is configured except that the microorganism-immobilized carrier 5 is removed from the aerobic tank 4, and the wastewater is treated using the same apparatus. And

Further, in order to promote the removal of nitrogen and phosphorus and to compare the sludge separation, concentration and dehydration properties, Comparative Example 1 was used.
The wastewater treatment was performed by the following method as No. 4 to No. 4.

The wastewater is treated by the anaerobic anoxic aerobic method,
Comparative Example 1 was used. This method corresponds to a case where the organic fiber is not introduced in the processing apparatus shown in the second embodiment.

In the anaerobic oxygen-free anaerobic method, waste water was treated by a method of mixing finely-used waste paper before dehydration to obtain Comparative Example 2. This method corresponds to a flow in which Conventional Technique 2 is further applied to the method of Comparative Example 1 which is an anaerobic anoxic aerobic method.

First, a mixed sludge of the first settling tank sludge and the excess sludge was subjected to acid fermentation, and then the wastewater was treated by a method of throwing the mixed sludge into an anaerobic tank. The aerobic tank 4 does not contain a carrier. This method is a flow in which Conventional Technique 1 is applied to an anaerobic anoxic aerobic method. Here, the volume of the acid fermentation tank was 300 liters.

Comparative Example 4 was obtained by treating wastewater by a method employing an anaerobic oxygen-free aerobic method in the reaction tank according to the third prior art in which granular waste paper was charged into the reaction tank. The aerobic tank 4 does not contain a carrier.

The raw water used in Examples 1 and 2 and Comparative Examples 1 to 4 was the effluent of the first sedimentation basin of the domestic wastewater treatment plant, and the measured values shown below were measured 10 times in 10 months. It is the average of the measurements. Items common to each treatment include inflow water quality, water temperature, inflow water flow rate (100 L / hr),
Oxygen-free tank 2 volume (300 L), aerobic tank 4 volume (200 L), final sedimentation tank water area load (100 m /
Days), ratio of circulating water (200%), ratio of returned sludge (50
%), The concentration tank has an average residence time of solids of 12 hours. Also, the amount of sludge withdrawn was set so that only the comparative example 4 had a sludge concentration of the aerobic tank 4 of 3000 mg / L,
In other cases (Examples 1, 2 and Comparative Examples 1 to 3),
It implemented so that the sludge density | concentration of the aerobic tank 4 might be set to 2000 mg / L.

Recycled paper is used as the organic fibrous material 10. Specifically, shredder dust from office offices is compressed and
A molded product cut into a 10 mm square was used. In Examples 1 and 2 and Comparative Example 4, 3.6 g / hr of waste paper was added to the concentration tank 15, and in Comparative Example 2, 1.8 g / hr.
g / hr of waste paper was added before dewatering.

In the prior art 3, the introduced particulate organic material acts as a carrier and is withdrawn from the water treatment system to the sludge treatment system as a carrier. A 2 mm square shredder dust from a business office would quickly fall apart and not serve as a carrier. For this reason,
In Comparative Example 4, a shredder dust of a business office was cut into 2 mm square and compression molded into a 3 mm square shape, and the carrier was pulled out before the shape of the carrier was broken.

In each example and comparative example, the total length was 2
A rectangular stirring blade having a height of 8 cm and a height of 8 cm is installed from the top so as to have a clearance of 5 cm from the bottom of the concentrator 15, and 35 rpm at which the inside of the concentrator is almost uniformly stirred.
And stirred.

After treating wastewater according to Examples 1 and 2 and Comparative Examples 1 to 4, the quality of the treated water, the sedimentation / separation of sludge, and the water content of the dewatered cake were examined. The results obtained are shown in Table 1 below. Put together.

The sedimentation and concentration of the sludge were examined by measuring the sedimentation curve of the sludge with a 1-liter graduated cylinder, and the SVI and concentrated sludge concentration were determined based on the input sludge concentration and the sludge interface after 30 minutes of sedimentation. Was evaluated by measuring.

The dewatering property of the sludge is determined by determining the appropriate amount of the polymer flocculant to be added by a jar test, and then transferring the sludge after flocculation and gravity dewatering between filter cloths of a belt press dehydrator using a pressure tester. After dehydration under pressure at 1.5 kg / cm ² for 1 minute, the moisture content of the dehydrated cake was measured and evaluated.

[0076]

[Table 1]

As shown in Table 1, in Examples 1 and 2, the treated water quality was clearly excellent in both TN and TP, and SS and SVI, which are indicators of the sedimentation and separation of sludge, were also excellent. And the moisture content of the dehydrated cake is also a low value.
These effects are as follows: introduction of organic substances accelerated denitrification and dephosphorization reactions, added only organic substances and did not add nitrogen component phosphorus components, and undecomposed organic substances were able to settle and separate sludge and dehydrate. Of the present invention, such as having a positive effect on

In particular, the microorganism-immobilized carrier 5 is
In this case, NH ₄ —N was completely removed as shown in the results of Example 1 containing NH ₄ -N
NO _x -N generated by the oxidation of
This is because nitrification bacteria were maintained at a high concentration by the introduction of the microorganism-immobilized carrier 5, and the denitrification reaction was promoted by the addition of organic substances generated by the decomposition of organic fibrous materials.

In Example 2, although the removal of NH ₄ —N was not complete, the removal reaction (removal of NO _x —N) generated due to the addition of the organic matter generated by the decomposition of the organic fibrous material was carried out. Nitrogen reaction) is promoted. For this reason, NO _x -N in the treated water becomes a small value, and as a result, TN
Is a small value following the first embodiment.

On the other hand, in each of Comparative Examples 1 to 4,
The effect as in the present invention has not been obtained. In Comparative Example 1,
Both TN and TP in the treated water are high, and the water content of the dehydrated cake is also high. In Comparative Example 2, although the water content of the dewatered cake is slightly improved, the quality of the treated water is not much different from Comparative Example 1.

In Comparative Example 3, the effect of the addition of the organic matter is apparent in that there is almost no NO ₃ -N in the treated water, but the values of TN and TP are not necessarily low. This is because the nitrogen component and the phosphorus component generated by the decomposition of sludge flow into the treatment system together with the organic matter.

In Comparative Example 4, only a slight effect was obtained in reducing the water content of the dehydrated cake, and the quality of the treated water was almost the same as in Comparative Example 1, and there was no significant change. This is because, under the conditions of Comparative Example 4, that is, under the condition that the carrier shape is maintained and the carrier is pulled out and the residence time cannot be sufficiently ensured, the generation of low molecular weight organic substances due to the decomposition of the organic fibers constituting the carrier Because there is almost no.

[0083]

As described above, according to the present invention, nitrogen removal and phosphorus removal are promoted, the amount of methanol used is reduced, and excess sludge is dewatered, sludge is separated and condensed. The present invention provides a method for treating wastewater capable of reducing the amount of a flocculant used for dehydration and dehydration and maintaining useful microorganisms having a low growth rate at a high concentration in a reaction tank. Further, according to the present invention, it is possible to promote the removal of nitrogen and phosphorus and reduce the amount of methanol used, and also to improve the dehydration of surplus sludge, to improve the separation and condensation of sludge, and to use a flocculant for dehydration. Provided is a treatment apparatus for reducing the amount and holding a useful microorganism having a low growth rate at a high concentration in a reaction tank to treat wastewater.

In the present invention, a part of organic fibers such as waste paper containing little components such as nitrogen and phosphorus is decomposed, and the generated decomposition products are used for removing nitrogen and phosphorus in wastewater treatment. Since it can be used, advanced treatment of wastewater (nitrogen and phosphorus removal) is achieved, and undecomposed organic fibers improve the separation, concentration and dewatering properties of sludge. Also,
As compared with the method of adding methanol, there is obtained an advantage that the processing cost can be reduced. Further, when the microorganism-immobilized carrier is accommodated in the aerobic tank, the treatment efficiency of the advanced treatment is improved (the removal rate is improved and the volume of the reaction tank is reduced), and the treatment is stabilized. In addition, the use of waste paper, which is waste, is effective in terms of effective use of resources and waste disposal, and its industrial value is great.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration of an example of a wastewater treatment apparatus according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Inflow water 2 ... Oxygen-free tank 3 ... Aerobic tank circulating liquid 4 ... Aerobic tank 5 ... Carrier 6 ... Carrier outflow prevention device 7 ... Sedimentation tank 8 ... Treated water 9 ... Anaerobic tank 10 ... Input organic fiber 11 ... First sedimentation basin 12 ... First sedimentation basin influent 13 ... Returned sludge 14 ... Excess sludge 15 ... Concentrator 16 ... Concentrated sludge 17 ... Concentrator desorbed liquid 18 ... Dewatering device 19 ... Dewatering cake 20 ... Dewatering device separated liquid 21 ... screen

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kenichiro Mizuno 1-1-2 Marunouchi, Chiyoda-ku, Tokyo F-term in Nihon Kokan Co., Ltd. 4D059 AA05 BA01 BA11 BA26 BA27 BA31 BA34 BE01 BE16 BE38 BE41 BE53 CA22 CA28 CB27 DB32 DB34

Claims (6)

[Claims] 1. A method for treating wastewater, comprising introducing a substance containing organic fiber into a sludge thickening tank. 2. A method for treating wastewater, comprising dispersing a substance containing an organic fibrous material into a liquid and introducing the substance into a sludge concentration tank. 3. The wastewater treatment method according to claim 1, wherein the substance containing the organic fiber is waste paper. 4. The method according to claim 1, wherein at least one of organic fibrinolytic enzymes and microorganisms capable of decomposing organic fibrous substances is introduced into the sludge thickening tank. Wastewater treatment method as described. 5. An apparatus for treating wastewater, comprising a sludge thickening tank having means for introducing a substance containing organic fiber. 6. The wastewater treatment apparatus according to claim 5, wherein the sludge thickening tank is provided with a unit for preventing a substance containing an organic fiber from flowing out.