JP2001070980A - Wastewater treatment method and treatment device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To promote the removal of nitrogen and phosphorus, reduce the amount of methanol used, improve the dewatering properties of excess sludge, improve the separation / condensability of sludge, and use a flocculant for dehydration. Provided is a treatment device for reducing waste amount and holding wastewater having a low growth rate at a high concentration in a reaction tank to treat wastewater. SOLUTION: The first settling basin is provided with means for introducing a substance containing organic fibrous material.

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 in wastewater, NO ₂ -N or NO ₃ -N is converted to N _2.
This is a method of reducing the gas. 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 decompose organic fibrous materials are generally anaerobic microorganisms having a low growth rate, but aerobic reactions having a large growth rate in an aerobic state in a system having an aerobic reaction tank. 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 an organic fiber into a sedimentation tank at first.

The present invention also provides an apparatus for treating wastewater, characterized in that a means for introducing a substance containing organic fibrous material is provided in the first settling basin.

Hereinafter, the present invention will be described in detail.

In the present invention, first, a substance containing an organic fiber is first introduced into a precipitation tank, and the organic fiber is physically and / or biologically degraded. The material containing organic fibrous material may first be introduced directly into the settling basin, or may first be introduced into the pipe leading to the settling basin. At first, organic fiber is physically and / or biologically decomposed in the sedimentation basin, whereby at least a part of cellulose, which is a main component of the organic fiber, is decomposed to obtain a low molecular weight organic substance. At the same time, fine organic fibers are generated. To physically break down organic fiber,
For example, a used paper shearing device can be used. The organic matter, which is the decomposition product, and a part of the finely divided organic fibrous material first reach the biological reaction system (biological wastewater treatment system) from the sedimentation basin, and are used to treat wastewater.

The decomposition product obtained by decomposing and reducing the molecular weight of organic fibers in the first settling tank and the decomposition product obtained by decomposing and reducing the molecular weight of organic fibers in the wastewater treatment system are as follows: Used for denitrification and dephosphorization reactions in wastewater treatment. By utilizing these, the effects of promoting nitrogen removal, improving the nitrogen removal rate, reducing methanol, and improving the phosphorus removal rate can be obtained. In addition, the main component of the organic fiber is cellulose. Since cellulose is a molecule composed of carbon, hydrogen, and oxygen, the decomposed substance contains almost no nitrogen or phosphorus, and is generated by decomposition of the organic fiber. 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 can also be solved.

Further, a part of the organic fiber (a part of cellulose, lignin, etc.) is passed through a biological treatment system, and the remaining part is directly withdrawn from a sedimentation basin first and is not decomposed. Since the dewatering is performed until then, the dehydration efficiency and stabilization, the effect of lowering the water content of the dewatered cake, and the effect of reducing the coagulant for dewatering are obtained.

The improvement in dewatering properties and the decrease in 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 costs.
In addition, in the case of performing incineration treatment in a later stage, there is a merit such as a reduction in auxiliary materials or an increase in energy recovery.

When the above-mentioned organic fiber is in the form of powder, it is preferable to disperse the organic fiber in a liquid in advance before introducing it into the precipitation tank. Depending on the type and condition of the organic fiber (dryness, whether or not it is charged with static electricity), when it is first introduced into the sedimentation basin, lumps 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. As the liquid in which the substance containing the powdery organic fiber is dispersed in advance, a part or all of the liquid substance generated in the wastewater treatment process, or tap water, factory water, miscellaneous water, well water, or the like may be used. it can. As the liquid substance generated in the wastewater treatment step, for example, inflow water, returned sludge, excess sludge, circulating water, concentrated sludge, concentrated sludge desorbed liquid,
Examples include a dewatering solution for a dehydration step, return water for a sludge registration step, and filtration and washing wastewater. 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, it is preferable to use a waste material mainly composed of the organic fiber, such as 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 addition, in the case where used paper is used, it is confirmed that even in the case where it is supplied in the form of a few centimeters in a granular form, the state in the reaction tank is so complicated that almost no prototype is left, so that the organic type is used. The input form of the fibrous material is not limited at all. However, from the viewpoint of the reaction rate, it is preferable to make the finer in advance. Whether or not to perform the miniaturization process may be appropriately determined by comprehensively judging the effect to be obtained and the cost for the miniaturization process.

Part of the step of treating wastewater can be carried out in an aerobic reaction vessel. When the step of treating wastewater is carried out in an aerobic reaction vessel, this aerobic reaction vessel can be used. The 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. In this case, only the amount equivalent to the input of organic fiber (more precisely, of the organic matter initially introduced into the sedimentation basin, after being decomposed and reduced in molecular weight, introduced into the biological treatment system together with the influent water) And
The part that is re-synthesized by microorganisms and solidified, and the part that flows out of the biological treatment system without being decomposed), the amount of generated sludge solids increases, and the organic fiber is not fed into the first sedimentation basin SRT is slightly shortened as compared with. For this reason, there is a slight disadvantage in maintaining the nitrifying bacteria in the reaction tank at a high concentration. However, by accommodating the microorganism-immobilized carrier in the reaction tank, the nitrifying bacteria are maintained at a high concentration in the carrier, and thus 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 device 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 charged into the aerobic reaction vessel, the fine fiber is generated along with the decomposition of the organic fiber, and the fine fiber is used for the screen. It is desirable that the screen width be as large as possible because of the possibility of blockage. Practically, the mesh width of the screen is preferably 2 mm or more, more preferably 2.5 mm or more. However, if the mesh width of the screen is increased, the size of the carrier must be increased. 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, at least one of an organic fibrinolytic enzyme and a microorganism capable of degrading organic fibrous material may be introduced in the step of treating the substance containing organic fibrous material.

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.

Furthermore, a part of a liquid containing microorganisms involved in wastewater treatment may be introduced into the sedimentation basin at first, and such liquids include, for example, returned sludge, excess sludge, and sludge treatment system return water. . Since bacteria having a cellulose-decomposing ability are present in these liquids, it is possible to accelerate the decomposition of the organic fiber in the first settling tank.

[0029]

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 an organic fiber is first introduced into a sedimentation basin 11. In the first sedimentation basin 11, the substance 10 containing organic fibrous material is physically and / or biologically decomposed. In the present invention, as the organic fiber,
Waste materials such as waste paper mainly composed of organic fibers can be used.

An anaerobic tank 9, an anoxic tank 2, an aerobic tank 4, a sedimentation basin 7, a concentrator 15, and a dehydrator 18 are provided downstream of the first settling basin 11. Be composed. 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. At this time, the organic fiber which has been decomposed and reduced in molecular weight in the sedimentation basin and a part of the finely divided organic fiber are introduced into the anaerobic tank 9 together with the inflow water. A part of the sludge from the sedimentation basin 7 is returned to the sludge 13.
Is introduced into the anaerobic tank 9. Further, as shown in the figure, the concentrated separated liquid 17 from the concentrating device 15 and the dehydrating device desorbed liquid 20 from the dehydrating device 18 may be returned to the anaerobic tank 9, but these are not necessarily required.
In some cases, the concentrated separated liquid 17 and the desorbing liquid 20 are introduced into a dedicated treatment step, or may be initially 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 contains a microorganism-immobilized carrier 5, and a carrier outflow preventing (carrier separating) device 6 is installed 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 polymer-based 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 separation 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 can be used. For the reason already described, the screen width is practically 2 mm.
Or more, and 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.

First, the sludge 12 drawn from the sedimentation basin is:
It is introduced into the concentration device 15.

First, the concentrated sludge 12 and excess sludge 14 in the sedimentation basin
In the concentration device 15 into which the sludge is introduced, the sludge is concentrated and introduced into the dehydration device 18 as the concentrated sludge 16, and then subjected to dehydration treatment and discharged as the dewatered cake 19. Further, the desorbed liquid 20 generated in the dehydration step 18 is returned and processed to the anaerobic tank 9 together with the separated liquid 17 generated in the concentration step.

In the present invention, various types of concentrating equipment 15 and dehydrating equipment 18 can be used, such as a centrifugal concentrator, a filtration concentrator, a floating concentrator, a belt press dehydrator, A centrifugal dehydrator, a filter press dehydrator, a rotary press dehydrator, or the like may be used. In addition, depending on the treatment facility, there is a case where the sludge treatment facility is not possessed, and the sludge is condensed or treated by a mobile sludge treatment facility. .

The main reactions in the above-described process are: first, physical fineness, decomposition, and low-molecularization reaction of organic fibers in the sedimentation basin 11; decomposition, low-molecular weight of organic fibers in the anaerobic tank 9. Chemical reaction, phosphorus exhalation reaction; decomposition and depolymerization reaction of organic fibers in anoxic tank 2; denitrification reaction; and organic substance decomposition reaction, nitrification reaction, phosphorus absorption reaction in aerobic tank 4 is there.

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 matter generated first in the sedimentation basin 11 and the anaerobic tank 9 and introduced into the anoxic tank 2 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, and then the microorganisms that exhale phosphorus mainly absorb more phosphorus in the body than the amount exhaled in the aerobic tank 4. Thus, the phosphorus in the wastewater is removed by absorbing the phosphorus in the wastewater into the body of the microorganism.

When a reaction occurs in the anaerobic tank 9 where microorganisms use the organic substance to exhale phosphorus in the body, the organic substance is required as an energy source. As the organic matter, an organic matter generated from organic fibers in the precipitation tank 11 and 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 sedimentation basin 11 and the anaerobic tank 9 at the beginning 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.

There are also organic fibrous materials which are extracted from the biological treatment system to the sludge treatment system without decomposition, but these improve the sedimentation and separability of the sludge. , The solids concentration becomes smaller and the quality of the treated water becomes even better.

Furthermore, undecomposed organic fibrous materials are first introduced into the dewatering facility via the sedimentation basin and the biological treatment system. There is also an advantage that the water content of the cake 19 is reduced, and the cost of auxiliary fuel for incinerating the dewatered cake can be greatly 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 decrease in 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 treatment in a later stage, there is a merit such as a reduction in auxiliary materials or an increase in energy recovery.

In the present invention, the organic fibrous material (raw material) 10 first introduced into the sedimentation basin 11 includes waste paper, wood chips (including construction waste materials), sawdust, rice hulls, kitchen garbage, and the like. The above mixture 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 concentration of organic fibers and the concentration of organic substances are high and the concentrations of nitrogen and phosphorus components are low, waste and wastewater generated from factories and offices can be used as raw materials. The shape is not particularly limited, and may be any of a granular shape, a powdery shape, a thread shape, and a paper piece shape. From the viewpoints of reaction efficiency and reaction rate, the finer the organic fiber, the more advantageous. However, even in the form of granules or pieces of paper, they are easily refined first in the sedimentation basin. In addition, in the case of inputting after performing the miniaturization process, cost, 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 organic fibrous materials include shredder waste generated in offices and the like, shredder waste compressed and formed, waste paper formed into granules, wood chips and rice husks, and the like. In the case of waste paper, if it is to be recycled as 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.

Further, by pre-treating the organic fibrous material before being decomposed and reduced in molecular weight in the first settling basin 11, 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 amount of the organic fiber 10 introduced into the first settling basin 11 varies depending on the quality of the influent 1, the required quality of the treated water 8, the residence time in the first settling basin and the fractional efficiency. Generally, when the desired nitrogen or phosphorus concentration of the treated water is low; the BOD / nitrogen ratio or BO
When the D / phosphorus ratio is small; when it is desired to reduce the water content of the dewatered cake; or when it is desired to increase 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 can be determined from the amount of the organic fiber 10 to be charged, the decomposition rate, and the average residence time.

When the organic fiber is first decomposed and depolymerized in the sedimentation basin 11 to mainly produce saccharides, organic acids, alcohols, etc., depending on the conditions, the organic fiber may be decomposed depending on the conditions. Methane gas may be generated due to excessive decomposition and low molecular weight. Under conditions where methane gas is generated and diffused in large quantities, saccharides and organic acids,
Alternatively, since alcohol and the like are wasted, it is required that the inside of the sedimentation basin 11 is initially set to a condition that does not cause a methane gas generation reaction. To do so, first settling basin 11
In this method, the retention time of the solid matter in step (1) is adjusted, specifically, shortened to prevent the methanogen from accumulating in the tank at a high concentration.

Furthermore, since methane-producing bacteria are generally bacteria that are greatly damaged by the presence of oxygen, that is, obligate anaerobic bacteria, oxygen-containing gas is first blown into the sedimentation basin 11 or peroxide or ozone is introduced. By doing so, the growth and activity of methane bacteria can be suppressed. DO (dissolved oxygen concentration) or ORP (redox potential) can be used as an index of the anaerobic degree. In particular, control by the oxidation-reduction potential is effective, and it is effective to control the molecular weight of the organic fiber to be in the range of +50 mV to -250 mV, which is a range in which methanation hardly proceeds.

In addition, intermittently making the atmosphere aerobic for a short time is effective for preventing decomposition of organic substances by methane bacteria. This is because methane bacteria are absolutely anaerobic and are very susceptible to oxygen, whereas cellulolytic bacteria are anaerobic bacteria but more resistant to oxygen than methane bacteria. Therefore, by performing an operation to make the atmosphere aerobic intermittently for a short period of time, it becomes possible to seriously damage only the methane bacteria. This concept is the same as that of pickling bran miso once a day. In the case of bran miso, the growth of anaerobic germs is suppressed by feeding oxygen in this way. However, if the time for maintaining the aerobic state is too long, not only methane bacteria but also cellulolytic bacteria may be damaged. Furthermore, in this case, various aerobic heterotrophic bacteria appear, which further degrades the degradation products of cellulose. Therefore, there is a problem even if the aerobic state is too long, and it is desired to select appropriately.
The duration of aerobic conditions and the frequency of aerobic conditions depend on the operating conditions of the initial settling basin (eg, temperature, solids residence time,
Solids concentration, etc.), but generally 1
A time period in which the concentration of dissolved oxygen is 0.05 mg / L or more may be provided about once to eight times a day for one minute or more each time.

When blowing an oxygen-containing gas,
Since the solid-liquid separation performance, which is the original role of the sedimentation basin, temporarily decreases, such an operation is preferably performed during a time period such as early in the morning when the amount of inflow water is relatively small.

The organic fiber is decomposed by a microorganism or an enzyme (cellulase or the like) having an organic fiber decomposing ability.
It is preferable that these are first supplied to the precipitation tank or the reaction tank of the biological treatment system at the start of the reaction. As described above, if microorganisms having the ability to decompose organic fibers are included in the reaction tank from the beginning, it may not be particularly necessary to introduce enzymes and microorganisms into the reaction tank. 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 to always add the addition, not to add, or how much the amount to add 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, the addition of enzymes and microorganisms can be determined as appropriate in consideration of the stability of the reaction, the obtained reaction rate, and the like, and the economic efficiency.

Further, the anaerobic tank 9 may be charged with a carrier on which microorganisms, enzymes, and yeasts having organic fiber decomposing ability are immobilized. 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, phosphorus component) and trace elements necessary for the growth of microorganisms having organic fibrous decomposing ability to the anaerobic tank 9, a further improvement in efficiency is recognized. In some cases.

In the present invention, as described above, a part of a liquid containing microorganisms involved in wastewater treatment, such as returned sludge, excess sludge, and sludge treatment return water, may be first introduced into the sedimentation basin. This is because bacteria having the ability to degrade cellulose exist in such a liquid, which accelerates the degradation of organic fiber in the first settling basin.

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 nitrification denitrification method, an anaerobic-aerobic method, a Badenho method, a modified Badenho 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 decomposes the organic fibrous material first in the settling basin 11 and / or the anaerobic tank 9,
The decomposition products are used for biological reactions to promote nitrogen removal and phosphorus removal, and organic fibrous undecomposed substances are used to improve sludge separation, concentration and dewatering properties. Yes, all processing flows based on such a concept are included in the scope of the present invention. Regarding the treatment of the sludge 12 drawn from the first settling basin, it is not necessary to introduce the sludge into the concentrating device 15, and depending on the equipment, it is also possible to perform direct dehydration.

Further, the pipe introduced into each tank does not need to be directly introduced into each tank, and can be obtained by combining with the pipe introduced into the tank, mixing with the liquid, and then putting the mixture into the tank. The effect remains the same.

[0066]

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 first into the settling basin 11 was constructed, and the waste water was treated using the apparatus.
In Example 1, the aerobic tank 4 was loaded with a hollow cylindrical carrier 5 made of expanded polypropylene having a specific gravity of 1.01, a length of 5 mm, an outer diameter of 4 mm, and an inner diameter of 3 mm by 7% based on the true volume.
A wedge wire screen having a mesh width of 2.5 mm was installed at the outlet of the aerobic tank 4 as the carrier outflow prevention device 6.

Further, an apparatus similar to that of the above-described Example 1 was constructed except that the microorganism-immobilized carrier 5 was removed from the aerobic tank 4, and the wastewater was 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, 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 an 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 anoxic aerobic method, waste water was treated by a method of mixing waste paper that had been made fine 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 initial settling tank sludge and the excess sludge was subjected to acid fermentation, and then the wastewater was treated by a method of introducing the sludge into an anaerobic tank to obtain Comparative Example 3. 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.

In Comparative Example 4, waste water was treated by a method employing an anaerobic oxygen-free aerobic method in the reaction tank according to the prior art 3 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 Comparative Examples 1 to 4 was the effluent of the first sedimentation basin of the domestic wastewater treatment plant, and in Examples 1 and 2, the same water area load as that of the first sedimentation basin of the domestic wastewater treatment plant was used. The first settling basin for the experiment was set up so that waste paper was introduced there. The measurements shown below are 10 months
It is the average of the measurements. Items common to each treatment include inflow water quality, water temperature, and inflow water flow rate (100 L / h
r), the volume of the anoxic tank 2 (300 L), the volume of the aerobic tank 4 (200 L), and the final sedimentation tank water area load (100
m / day), circulating water ratio (200%), returned sludge ratio (50
%). The amount of sludge withdrawn was set so that the aerobic tank 4 had a sludge concentration of 3000 mg / L only in Comparative Example 4, and in other cases (Examples 1, 2 and Comparative Examples 1 to 3) 4. Sludge concentration of 2000mg / L
It was carried out so that

Waste paper is used as the organic fibrous material 10. Specifically, shredder dust in an office is 2 mm.
Those cut into corners were used. In Examples 1 and 2 and Comparative Example 4, 3.6 g / hr of waste paper was added to the organic fibrous reaction tank 11, and in Comparative Example 2, 1.8 g / h.
r equivalent 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 of 8 cm and height of 8 cm was first set in the sedimentation basin 11.
It is installed from the top so that there is a clearance of 5 cm from the bottom, and the inside of the sedimentation basin is almost uniformly stirred at 35r.
Stirred at pm.

After treating wastewater according to Examples 1 and 2 and Comparative Examples 1 to 4, the quality of the treated water, the sedimentation and 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 from the input sludge concentration and the sludge interface after 30 minutes of sedimentation. Was evaluated by measuring.

The dewatering property of the sludge was determined by determining the appropriate amount of the polymer flocculant to be added by a jar test. The sludge after the flocculation and gravity dehydration was passed 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.

[0081]

[Table 1]

As shown in Table 1, in Examples 1 and 2, first, the BOD of the inflow water became higher than that of the comparative example due to biological decomposition and physical decomposition of the introduced organic fiber in the first settling tank. And SS is also slightly higher. The treated water quality is clearly excellent in both TN and TP, SS and SVI, which are indicators of the sedimentation and separation of sludge, are also excellent values, and the water content of the dewatered 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 fiber was added. 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 that the treated water has almost no NO ₃ -N, 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 dewatered 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.

[0088]

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 almost no 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 drawn sludge 13 ... Returned sludge 14 ... Excess sludge 15 ... Concentrator 16 ... Concentrated sludge 17 ... Concentrator desorbed liquid 18 ... Dewatering device 19 ... Dewatered cake 20 ... Dewatered device separated liquid

Claims (5)

[Claims] 1. A method for treating wastewater, comprising first introducing a substance containing organic fiber into a settling basin. 2. A method for treating wastewater, comprising dispersing a substance containing an organic fibrous material into a liquid and introducing the dispersed substance into a settling tank first. 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 an organic fibrinolytic enzyme and a microorganism capable of decomposing organic fibrous substances is introduced into the first sedimentation basin. Wastewater treatment method as described. 5. An apparatus for treating wastewater, wherein a means for introducing a substance containing organic fibrous material is provided in the first settling basin.