JPH10277599A - Sludge concentrating method and apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sludge concentrating method capable of efficiently concentrating sludge, easy in maintenance control and capable of always making the quality of discharged water good, and provide further an apparatus therefor. SOLUTION: Raw water containing sludge generated in a waste water treatment process is supplied to a separation and concn. tank 1 having a membrane separator 2 equipped with a separation membrane and the permeated water filtered by the membrane separator 2 is discharged to the outside of the separation and concn. tank 1 to concentrate sludge in raw water and, after the concn. of sludge in raw water within the separation and concn. tank 1 reaches a predetermined value, a part or the whole of conc. sludge is discharged to the outside of the separation and concn. tank 1. Hollow yarn type separation membranes are used in the membrane separator 2. For example, a cellulosic or polyolefinic material is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for concentrating and reducing sludge generated in a wastewater treatment process for biologically treating wastewater such as human waste and sewage.

[0002]

2. Description of the Related Art Conventionally, urban wastewater such as night soil and sewage,
Organic industrial wastewater from factories and the like is discharged to rivers and the like after being subjected to a treatment for removing various suspended substances (SS) and soluble organic substances contained therein. The treatment of the municipal wastewater and the organic industrial wastewater is performed, for example, as follows using a system as shown in FIG. First, in the raw wastewater to be treated, a relatively large suspended substance is settled and separated in the initial settling tank. Next, the water-soluble organic components in the raw water are decomposed by the activated sludge in the aeration tank.
Subsequently, the sludge is settled and separated in the final sedimentation tank and then discharged into rivers and the like.

[0003] Excess sludge generated by the treatment using the above system is withdrawn from the system and finally incinerated.
Although treatments such as landfill and composting are performed, in order to facilitate such final treatment, it is preferable that the excess sludge is concentrated to some extent before drawing to reduce the water content to reduce the amount. The concentration of sludge in the wastewater treatment method using the above system is performed by gravity sedimentation of the sludge in the final sedimentation tank and the sludge concentration tank.
In this sludge concentration method, a long time is required for thickening the sludge, so that a large-capacity final sedimentation tank must be used, and there is a problem that a vast site is required for installation of the equipment. In addition, the concentration ratio of the obtained concentrated sludge was insufficient and the water content was high, resulting in an increase in the cost required for the final treatment.

[0004] Furthermore, especially when the wastewater is sewage, the quality of the wastewater, the amount of water, the temperature of the water, and the like vary greatly, and the amount of generated sludge may vary greatly due to these variations. In the above method, since it takes a long time to concentrate the sludge, if the amount of sludge increases significantly, the sludge concentration treatment by the final sedimentation tank may not be in time.If such a capacity of the final sedimentation tank is exceeded, Then, a measure is taken to stop the extraction of excess sludge from the final sedimentation tank and temporarily store the excess sludge in the aeration tank or the final sedimentation tank. However, when such excess sludge is accumulated, there is a possibility that the treatment conditions of the entire system are disrupted, sludge flows out of the final sedimentation tank, and the quality of the discharged water is deteriorated. To cope with this problem, it is conceivable to provide a spare tank that temporarily stores the sludge to be concentrated when the amount of sludge becomes excessive.However, a separate tank that is not used for actual wastewater treatment should be provided. Is extremely uneconomical, and has the disadvantage of requiring a larger area for the installation of the spare tank. In addition, sludge concentration methods using separation membranes are also being studied, but there is a problem that the permeation flux decreases in a short period of time,
There is a problem that a great deal of labor is required for maintenance and management, and the processing cost increases.

[0005]

DISCLOSURE OF THE INVENTION In view of the above points, the present invention can efficiently concentrate sludge, and can always improve the quality of discharged water, and can maintain and manage the discharged water. An object of the present invention is to provide a sludge concentration method and an apparatus that are easy and can reduce the processing cost.

[0006]

According to the present invention, raw water containing sludge generated in the process of wastewater treatment is supplied to a separation / concentration tank having a membrane separation device provided with a separation membrane, and filtered by the membrane separation device. In discharging the permeated water out of the separation and concentration tank to concentrate the sludge in the raw water, after the sludge concentration in the raw water in the separation and concentration tank reaches a predetermined value, part or all of the concentrated sludge is separated and concentrated. A sludge concentration method characterized in that the sludge is discharged to the outside of the tank is a means for solving the above-mentioned problem. Also, when performing the sludge concentration treatment by the membrane separation device, the sludge concentration treatment is stopped before the raw water level in the separation / concentration tank drops to the upper end of the membrane separation device, and the concentrated sludge is discharged out of the separation / concentration tank. May do it. Also, when performing the sludge concentration treatment by the membrane separation device, the raw water level in the separation / concentration tank is kept almost constant by newly supplying the same amount of raw water as the discharged permeate to the separation / concentration tank successively. You may. Further, when the sludge concentration treatment is performed by the membrane separation device, it is preferable to gradually decrease the permeate flow rate in accordance with the increase in the sludge concentration in the raw water in the separation / concentration tank. In addition, the raw water sludge concentration in the separation / concentration tank is equal to 1. the raw water sludge concentration before the concentration treatment.
After reaching 5 to 30 times, part or all of the concentrated sludge may be discharged out of the separation and concentration tank. A hollow fiber membrane may be used as the separation membrane of the membrane separation device. As the membrane separation device, a device provided with a flat hollow fiber membrane module may be used. In addition, when performing the sludge concentration treatment by the membrane separation device, it is preferable to wash the separation membrane by appropriately performing air scrubbing treatment on the separation membrane. Further, it is preferable to add a flocculant into the separation / concentration tank when the sludge is concentrated by the membrane separation device. Further, the sludge concentration device of the present invention is provided with a membrane separation device and an aeration tube arranged below the membrane separation device in the separation / concentration tank, and in the separation / concentration tank, the sludge that has been subjected to the concentration treatment is out of the tank. Discharge means for discharging is connected.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings, but the present invention is not limited to only the following embodiments.

FIG. 1 shows an embodiment of a sludge concentration apparatus according to the present invention. The sludge concentrating device shown here is provided with a membrane separating device 2 and an aeration tube 3 disposed below the membrane separating device 2 in the separating and concentrating tank 1. A sludge discharge line 1b serving as a discharge means for discharging sludge to the outside of the tank is connected. The separation and concentration tank 1 is provided with a raw water supply line 1a for supplying raw water containing sludge to be concentrated into the tank. The sludge discharge line 1b is preferably connected near the bottom of the separation and concentration tank 1.

As the membrane separation device 2, for example, a flat hollow fiber membrane module having a hollow fiber type separation membrane shown in FIG. 2 can be used. This is roughly composed of a separation membrane 7 composed of a hollow fiber membrane composed of a plurality of hollow fibers and tubular supports 8 provided at both ends of the separation membrane 7. Various porous materials can be used for the hollow fiber of the separation membrane 7, and for example, those made of various materials such as cellulose, polyolefin, polyvinyl alcohol, PMMA, and polysulfone may be used. Among them, materials having high elongation such as polyethylene and polypropylene are preferable.
Further, although not particularly limited, the outer diameter of the hollow fiber is 20 to 2000 μm and the pore diameter is. It is preferable that the thickness is 0.01 to 1 μm, the porosity is 20 to 90%, and the thickness of the hollow fiber membrane is 5 to 300 μm.

The separation membrane 7 is desirably a so-called permanent hydrophilization membrane having a hydrophilic group on the surface. This is because, when the surface of the separation membrane 7 is hydrophobic, a hydrophobic interaction between the organic matter in the water to be treated and the surface of the separation membrane works, and organic matter is adsorbed on the membrane surface, which leads to blockage of the membrane pores. This is because the filtration life of the separation membrane 7 is likely to be short, and it is difficult to recover the decrease in filtration performance due to clogging due to such adsorption by washing. On the other hand, a permanent hydrophilizing membrane is preferable because the hydrophobic interaction between the organic substance and the surface of the separation membrane can be suppressed, and the adsorption of the organic substance on the membrane surface can be suppressed. Further, in the case of a hydrophobic membrane, when the air scrubbing treatment described later is performed, the membrane surface may be in a dry state due to bubbles, which further enhances hydrophobicity and may cause a decrease in permeation flux. On the other hand, a permanent hydrophilized membrane is unlikely to be hydrophobic even when dried, and the permeation flux is hardly reduced.

The tubular support 8 is a tubular one having an internal passage 9 formed therein. The tubular support 8 shown in FIG. 2 has a cylindrical shape, but is not limited to this. For example, the tubular support may have a square pillar shape. A slit 11 is formed in a side wall 10 of the tubular support 8 along a length direction thereof. The end of the separation membrane 7 is inserted into the slit 11, the gap between the slit and the separation membrane is closed with a sealing material, and the separation membrane 7 is firmly supported and fixed. That is, in the membrane separation device 2, both ends of the separation membrane 7 are supported by the two tubular supports 8, respectively.
In this case, the ends of the separation membrane 7 are both ends in the fiber direction of the hollow fiber, and both ends of each hollow fiber are located in the internal passage 9 of the tubular support 8. The width of the slit 11 is preferably 30 mm or less, and more preferably 10 mm or less. This is because, by reducing the width of the slit 11, the hollow fibers constituting the separation membrane 7 can be more easily arranged in one line. If the hollow fibers are not aligned and the hollow fiber membrane is disturbed and formed, a plurality of hollow fibers are bundled and adhered and integrated due to the adhesion of sludge and the like, and the surface area of the separation membrane cannot be used effectively.
Separation performance decreases. The length of the slit 11 is not particularly limited, but if it is too short, the membrane area of the separation membrane cannot be increased, and the separation performance cannot be improved. If the length is too long, the production becomes difficult. 100
２０００2000 mm is appropriate.

The above-mentioned sealing material converges and fixes each hollow fiber of the separation membrane 7 to the slit 11 while keeping the open state of the end thereof, and makes the internal passage 9 of the tubular support 8 liquid-tight from the outside. The slit 11 is formed by filling an epoxy resin, an unsaturated polyester resin, a polyurethane, or the like in a liquid state into the liquid and curing the liquid. Also,
Inserting and fixing the separation membrane in two or more rows for one slit, or forming two or more slits for one tubular support, inserting and fixing the separation membrane in each slit, It is possible to form a plurality of separation membranes 7 in one membrane separation device. It is preferable that the number of the separation membranes 7 is large because the overall membrane area can be increased and the processing performance can be enhanced. However, if three or more separation membranes are provided, the washing effect of the separation membrane located on the inside cannot be enhanced at the time of washing the separation membrane described later. Therefore, two separation membranes are appropriate.

A plurality of the membrane separation devices 2 having such a configuration can be arranged in one separation / concentration tank 1. By arranging a plurality of membrane separation devices 2, the overall membrane area can be increased, and the processing performance can be improved. Further, in consideration of making the separation / concentration tank compact, it is preferable that the interval between the adjacent membrane separation devices 2 is small. For this reason, it is necessary to select the interval between the membrane separation devices in consideration of the size of the membrane area of the separation membrane occupying the membrane separation device, the number of membrane separation devices, and the thickness of the tubular support,
The interval is preferably in the range of 5 to 100 mm, and
The range of mm is more preferable. A permeated water discharge pipe 6 having a suction pump 5 is connected to each tubular support 8, and the permeated water permeated through the separation membrane 7 can be discharged out of the separation / concentration tank 1 through the internal path 9 and the pipe 6. It has become.

The height position of the membrane separation device 2 in the separation / concentration tank 1 is preferably determined as follows. Membrane separation device 2
The amount of raw water in the tank 1 is reduced and the water level is lowered with the filtration by the filter. However, when the water level is lower than the upper end of the membrane separation device 2, the separation membrane 7 comes into contact with the outside air and the separation membrane 7 is made hydrophobic. Therefore, it is not preferable to lower the raw water level further. For this reason, in order to concentrate raw water sludge at a high magnification without lowering the permeation flux of the separation membrane 7, the ratio of the height of the tank 1 to the height from the bottom of the tank 1 to the upper end of the membrane separation device must be adjusted. Larger,
It is preferable to arrange the membrane separation device 2 as low as possible in the separation / concentration tank 1. This ratio is appropriately set in consideration of the sludge concentration in the raw water to be treated.
It is preferably from 30 to 30.

The air diffuser 3 is formed as a hollow body having a large number of pores, and is connected to a blower 4 for feeding air into the air diffuser 3. A gas such as air can be sent into the tank 1 as bubbles. By using the air diffuser 3, an air scrubbing process is performed on the separation membrane 7, that is, the separation membrane 7 is swung by bubbles diverging and rising from the air diffuser 3 and a water flow generated by the air scrubbing, thereby forming a hollow constituting the separation membrane 7. A treatment for removing sludge attached to the membrane surface by rubbing of yarns or relative flow of water can be performed.

Next, taking the case where the above-mentioned device is used as an example,
A first embodiment of the sludge concentration method of the present invention will be described.
First, raw wastewater containing sludge to be concentrated is supplied into the separation / concentration tank 1 through the raw water supply line 1a. Next, the suction pump 5 is operated, and the raw water in the tank 1 is filtered by the membrane separation device 2. The permeated water filtered by the separation membrane 7 of the membrane separation device 2 is discharged out of the separation / concentration tank 1 through the pipe 6 and discharged as it is. On the other hand, the concentration of the sludge in the raw water in the separation and concentration tank 1 increases as the filtration proceeds, and the sludge is concentrated, and the water level in the raw water in the tank 1 decreases. The filtration process is performed until the sludge concentration in the raw water in the separation / concentration tank 1 reaches a predetermined value.

The sludge concentration is 1.5 to 6% by weight.
It is preferably about 2 to 4.5% by weight. At this time, if the separation membrane 7 is exposed to the outside air, the membrane becomes hydrophobic and the flux decreases. Therefore, it is preferable to stop the filtration process before the raw water level falls to the upper end of the membrane separation device 2. Further, the concentration of the concentrated sludge may be determined according to the concentration ratio of the sludge, and the concentration ratio is determined in consideration of the concentration of the sludge in the raw water before concentration. The concentration is preferably 1.5 to 30 times the sludge concentration.

When the above-mentioned sludge concentration treatment is performed until the raw water level in the separation / concentration tank 1 reaches the upper end of the membrane separation device 2, the sludge concentration ratio is determined from the bottom of the separation / concentration tank 1 It is determined according to the ratio of the tank height to the distance to the upper end. For example, when the ratio is 2, the sludge is concentrated twice, and when the ratio is 3, the sludge is concentrated three times.

Further, as the concentration of the sludge in the raw water in the separation / concentration tank 1 increases with the above-mentioned filtration operation, the pores of the separation membrane 7 are inevitably clogged and the filterability deteriorates. Generally, membrane pore blockage is more likely to occur as the permeation flux of the membrane increases. For this reason, it is preferable to restrict the operation of the suction pump 5 continuously or stepwise and to gradually reduce the permeate flux, that is, the permeate flow rate, in order to stably perform the filtration as the sludge concentration increases. At this time, the rate of decrease in the flow rate is determined in consideration of the properties of sludge and the sludge concentration in raw water, but usually, the flow rate is reduced by 5 to 70% every time the sludge concentration doubles. Preferably, 10
More preferably, it is reduced by 50%. When the rate of decrease in the flow rate is set to be less than 5% every time the sludge concentration is doubled, the effect of preventing membrane pore blockage and preventing a decrease in flux is insufficient, and is set to exceed 70%. Then, the flow rate of permeated water becomes low, and the time required for sludge treatment becomes too long, which is not preferable.

In the process of performing the above-mentioned sludge concentration treatment, the blower 4 is operated as required, and air is sent into the separation / concentration tank 1 in the form of bubbles through the diffuser pipe 3, and the air is brought into contact with the separation membrane 7. By performing the air scrubbing treatment on the separation membrane 7, sludge adhering to the membrane surface is removed, the flux is prevented from decreasing due to membrane pore blockage, and stable operation can be performed for a long period of time.

In addition, in the above-mentioned sludge concentration treatment, if a coagulant is added to the separation and concentration tank 1, the interaction between the sludge and the membrane is weakened, and the sludge can be prevented from adhering to the separation membrane 7. Therefore, it is preferable. When the flocculant is added, the sludge of the fine flocs also collects to form larger and higher-strength flocs, which are less likely to adhere to the separation membrane 7.

The flocculants that can be used in the present invention are:
There is no particular limitation as long as the fine flocs of the sludge are coarsened into flocs of an appropriate size. Examples include cationic, anionic, nonionic or amphoteric polymeric flocculants. Among them, a cationic synthetic polymer flocculant is particularly suitable. When only the polymer flocculant is added, the amount of the polymer flocculant to be used is preferably 0.1 to 5 parts by weight based on 100 parts by weight of the suspended solid (SS), depending on the properties of the sludge. , 0.1 to 1 part by weight is particularly preferred. If the amount is less than 0.1 part by weight, the formation of flocs becomes insufficient. On the other hand, if the amount is more than 5 parts by weight, the floc may be re-dispersed or the adhesion of the floc to the separation membrane may increase, which is not preferable. The flocculant may be added in a pipe for transferring raw water to the separation / concentration tank 1, or may be added directly to the separation / concentration tank 1. An existing method such as dropping or in-line mixing may be used as appropriate.

Further, in the method of the present invention, a metal-based floc modifier such as an iron-based or aluminum-based modifier may be used. It is preferable to adopt a method of adding an amphoteric polymer flocculant. As the metal-based floc modifier, a sulfate band, ferric chloride, ferrous sulfate, polyiron sulfate and the like are used, and among them, an iron-based inorganic coagulant is preferable.

The amphoteric polymer flocculant is a polymer flocculant having both a cationic group and an anionic group in one molecule. Examples of the cationic group include a tertiary amine, a neutralized salt thereof, and a quaternary salt. Examples of the anionic group include a carboxyl group, a sulfone group, and salts thereof. Further, a nonionic component may be contained in addition to these ionic components. More specifically, examples of the anionic monomer unit include acrylic acid, methacrylic acid, and alkali metal salts thereof. Examples of the cationic monomer unit include dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylamide, diethylaminopropyl (meth) acrylamide, allyldimethylamine, and neutralized salts thereof.
Grade salts and the like. Examples of the nonionic monomer unit include (meth) acrylamide, N, N-dimethyl (meth) acrylamide, and N, N-diethyl (meth) acrylamide.

As a method of adding the flocculant after the addition of the metal floc modifier, a metal floc modifier is added in a pipe for transferring raw water to the separation / concentration tank 1, and the coagulant is added to the separation / concentration tank. May be employed.

In such a method of adding a metal-based floc modifier and a flocculant, first, by adding a metal-based floc modifier, the mucous substance layer and dissolved components in the sludge are reduced to a metal-based floc. By reacting with the modifier, charge neutralization is performed, and the hydrocolloid is hydrophobized. Thereby, the sludge is modified so as to form a strong nucleus having a small particle size but a small stickiness. Thereafter, when the amphoteric polymer flocculant is added, the amphoteric polymer flocculant ion dissociates in the liquid phase and has both positive and negative charges, and the flocculants are cross-linked directly or via a metal ion. Then, the cross-linked flocculant combines with the core of the sludge particles to generate coarse flocs. Further, when the raw water in the tank is mixed by stirring or the like, the above-mentioned floc generation reaction proceeds efficiently, and the generated floc becomes more hydrophobic and contracted and strong. Furthermore, almost no metal ions or polymers remain in the liquid phase, and the sludge has no viscous filterability,
A good state of peelability is obtained. Therefore, even if the sludge in the raw water is hardly dewaterable, it is satisfactorily coagulated, and the sludge can be efficiently concentrated.

The sludge concentrated in the separation / concentration tank 1 as described above is partially or wholly discharged.
b and is discharged out of the separation / concentration tank 1. Subsequently, raw water is newly supplied into the separation / concentration tank 1, and the above-mentioned concentration treatment operation is performed again, and thereafter, this operation is repeated. The concentrated sludge taken out of the tank 1 through the sludge discharge line 1b is further dehydrated using a belt press or the like, and then subjected to final treatment such as incineration, landfill, composting, and the like.
The concentrated sludge is already concentrated at a high magnification in the separation / concentration tank 1 and the water content is reduced and the volume is reduced, so that the dehydration treatment is facilitated. Also, the water content of the sludge after dehydration can be reduced, and the cost required for the final treatment can be reduced.

In the above-mentioned sludge concentration method, raw water containing sludge is supplied into the separation / concentration tank 1 and the sludge is concentrated using the membrane separation device 2, so that the sludge is concentrated in a short time and at a high magnification. In addition, sludge having a low water content can be efficiently obtained, and the sludge treatment cost can be reduced. Further, the quality of the discharged water can always be improved. In addition, since the amount of excess sludge withdrawn can be adjusted freely, even if the amount of excess sludge increases due to load fluctuations, etc., it is possible to flexibly cope with it, prevent deterioration of discharged water quality, and facilitate maintenance and management. it can. Also, sludge which is difficult to concentrate to a high concentration by sedimentation and separation, for example, sludge containing a large amount of filamentous microorganisms, can be efficiently concentrated to obtain sludge having a low water content. Further, it is not necessary to use a large tank such as a final sedimentation tank, and a spare tank is not required, so that equipment cost and equipment installation area can be reduced.

Further, by gradually decreasing the flow rate of the permeated water in accordance with the increase in the concentration of the sludge in the raw water in the separation / concentration tank 1, the increase in pressure loss in the filtration by the membrane separation device 2 is suppressed, and the filtration conditions with a small pressure loss , And the permeation flux can be kept high. Therefore, stable processing can be performed, and maintenance and management can be facilitated and processing costs can be reduced. Further, the load on the separation membrane to be used can be reduced, the life of the separation membrane can be prolonged, the membrane area can be reduced, and the processing cost can be further reduced.

Further, by using the flocculant, it is possible to make the sludge harder to adhere to the separation membrane 7 as coarser flocs, maintain a high permeation flux, and enable a stable treatment. Further, the life of the separation membrane can be further extended, the membrane area can be reduced, and the processing cost can be further reduced.

Further, in the above-mentioned sludge concentrator, sludge having a low water content can be efficiently obtained, and the sludge treatment cost can be reduced. In addition, the quality of the effluent water can always be improved. Further, it is not necessary to use a large tank such as a final sedimentation tank, and a spare tank is not required, so that equipment cost and equipment installation area can be reduced. Also,
Troubles such as sludge outflow into the effluent water due to overload can be prevented beforehand, maintenance can be facilitated, and labor and cost required for maintenance can be reduced.

Next, a second embodiment of the sludge enrichment method of the present invention will be described by taking as an example the case of using the sludge enrichment apparatus shown in FIG. The difference between the method of the present embodiment and the method of the first embodiment is that the sludge concentration method according to the first embodiment differs from the method of the first embodiment in that the raw water level in the separation / concentration tank 1 ′ due to the filtration by the membrane separation device 2 decreases. Separates raw water into concentrated water tank 1 '
The point is that sludge is concentrated while the raw water level in the tank is kept almost constant by supplying the water into the tank. At this time, fresh raw water may be supplied by a pump or the like in accordance with the raw water level in the separation / concentration tank 1 ′, or may be continuously pumped or water headed in accordance with the filtration speed of the separation membrane 7. You may supply by difference etc. When the concentration of the sludge in the separation / concentration tank 1 'reaches a predetermined concentration, part or all of the concentrated sludge is passed through the sludge discharge line 1b.
Discharge more.

In the method of the present embodiment, similarly to the method of the first embodiment, sludge having a low water content can be obtained efficiently, and the sludge treatment cost can be reduced. In addition, the quality of the effluent water can always be improved. In the method of the first embodiment, the ratio of the total height to the distance from the bottom of the tank to the upper end of the membrane separation device 2 according to the target concentrated sludge concentration is used as the separation and concentration tank 1 ′. However, in the case of this example, it is possible to use a separation / concentration tank of any shape regardless of the target concentration of the concentrated sludge, and the equipment cost and the installation area of the separation / concentration tank 1 ' Can be further reduced. In addition, even if the properties and concentration of the sludge in the raw water to be concentrated fluctuate, the final concentrated sludge concentration can be easily reset according to the fluctuation. Therefore, the above-mentioned sludge concentration treatment is always performed under optimum conditions, the permeation flux of the membrane separation device 2 is kept high, and stable treatment can be performed.

In each of the above examples, a hollow fiber type separation membrane is used as the separation membrane used in the membrane separation apparatus 2.
In the present invention, the shape is not limited to this, and any shape such as a flat membrane type, a tubular type, and a bag type may be used. As the material of the separation membrane, cellulose-based, polyolefin-based, polysulfone-based, polyvinylidene fluoride (PVDF) -based, polytetrafluoroethylene (PTF)
E) type, ceramic type and the like may be used. The pore size of the separation membrane can be arbitrarily set as long as solid-liquid separation is not hindered. For example, if it is intended to completely separate even bacteria in sludge from permeated water, the pore size may be set to 0. 2μ
m or less.

[0035]

As described above, according to the sludge concentration method of the present invention, sludge concentration is performed in a short time and at a high magnification.
Sludge having a low water content can be obtained, and the sludge treatment cost can be reduced. In addition, even if the amount of sludge increases, it is possible to flexibly cope with it, to facilitate the maintenance and management, and to always make the discharged water quality good. Further, the size of the equipment can be reduced, and the equipment cost and the installation area of the equipment can be reduced. In addition, by gradually decreasing the permeated water flow rate according to the increase in the concentration of raw water sludge in the separation and concentration tank,
It is possible to suppress an increase in pressure loss during filtration by the membrane separation device, perform filtration under a filtration condition with small pressure loss, and keep the permeation flux high. Therefore, stable processing can be performed, maintenance and management can be facilitated, the life of the separation membrane can be prolonged, the membrane area can be reduced, and the processing cost can be further reduced.

In the sludge concentrator of the present invention,
Sludge having a low water content can be obtained efficiently, and sludge treatment costs can be reduced. In addition, the quality of the effluent water can always be improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of a sludge concentrator according to the present invention.

FIG. 2 is a perspective view showing a membrane separation device of the sludge concentration device shown in FIG.

FIG. 3 is a schematic configuration diagram showing a second embodiment of a sludge concentrator according to the present invention.

FIG. 4 is a flowchart showing a conventional wastewater treatment system.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Separation concentration tank, 1b ... Sludge discharge line (discharge means), 2 ... Membrane separation device, 3 ... Aeration tube, 7 ... Separation membrane

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Satoshi Miyashita 4-160 Sunadabashi, Higashi-ku, Nagoya-shi, Aichi Prefecture Mitsubishi Rayon Co., Ltd. Product Development Laboratory (72) Inventor Masumi Kobayashi 4-1-1 Sunadabashi, Higashi-ku, Nagoya-shi, Aichi Prefecture No. 60 Mitsubishi Rayon Co., Ltd. Product Development Laboratory (72) Inventor Shinya Sueyoshi 4-160 Sunadabashi, Higashi-ku, Nagoya-shi, Aichi Japan

Claims (10)

[Claims] 1. Raw water containing sludge generated in the process of wastewater treatment is supplied to a separation / concentration tank having a membrane separation device provided with a separation membrane, and permeated water filtered by the membrane separation device is discharged outside the separation / concentration tank. In discharging and concentrating the sludge in the raw water, after the sludge concentration in the raw water in the separation and concentration tank reaches a predetermined value, a part or all of the concentrated sludge is discharged out of the separation and concentration tank. Sludge concentration method. 2. When the sludge concentration treatment is performed by the membrane separation device, the sludge concentration treatment is stopped before the raw water level in the separation / concentration tank falls to the upper end of the membrane separation device, and the concentrated sludge is separated from the separation / concentration tank. The sludge concentration method according to claim 1, wherein the sludge is discharged outside. 3. When the sludge concentration treatment is performed by the membrane separation device, raw water having substantially the same amount as the permeated water discharged is newly supplied to the separation / concentration tank successively to make the raw water level in the separation / concentration tank substantially constant. The sludge concentration method according to claim 1, wherein the sludge concentration is maintained. 4. When sludge concentration treatment is performed by a membrane separation device, the sludge concentration in raw water in the separation and concentration tank increases.
2. The method according to claim 1, wherein the flow rate of the permeated water is gradually reduced.
4. The method for concentrating sludge according to any one of items 1 to 3. 5. After the sludge concentration in the raw water in the separation and concentration tank reaches 1.5 to 30 times the sludge concentration in the raw water before the concentration treatment,
The sludge concentration method according to any one of claims 1 to 4, wherein a part or all of the concentrated sludge is discharged out of the separation and concentration tank. 6. The method for concentrating sludge according to claim 1, wherein a hollow fiber membrane is used as a separation membrane of the membrane separation device. 7. The method for concentrating sludge according to claim 1, wherein a device provided with a flat hollow fiber membrane module is used as the membrane separation device. 8. The method for concentrating sludge according to claim 1, wherein the separation membrane is washed by air scrubbing when the sludge concentration treatment is performed by the membrane separation device. 9. The method for concentrating sludge according to claim 1, wherein a coagulant is added into the separation and concentration tank when the sludge is concentrated by the membrane separation device. 10. A sludge concentrator for concentrating sludge generated in a wastewater treatment process, comprising: a separation / concentration tank provided with a membrane separation device and an air diffuser disposed below the membrane separation device. A sludge concentrator, wherein a discharge means for discharging the sludge subjected to the concentration treatment to the outside of the tank is connected to the separation / concentration tank.