JP2006239635A - Method and apparatus for treating waste water of organic waste water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a treatment method which enables the execution of a high sludge volume reduction by solving a problem related to a treatment of excess sludge and sludge volume reduction, and a treatment apparatus. <P>SOLUTION: The method for treating organic waste water comprises a process for biologically treating the organic waste water, a process for separating sludge from the treated organic waste water, a process for solubilizing the separated sludge by a high-speed agitator placed on the bottom part of a tank and a process for recirculating the solubilized treated liquid to a biological treatment process. The apparatus for treating the organic waste water includes biological treatment means for biologically treating the organic waste water, solid-liquid separation means for separating the sludge from the treated organic waste water, solubilization means for solubilizing the separated sludge by the high-speed agitator placed on the bottom part of the tank and recirculation means for recirculating the solubilized treated liquid to biological treatment means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method and apparatus for treating organic wastewater that solubilizes excess sludge generated when organic wastewater is biologically treated to reduce the volume of sludge.

  Conventionally, biological sludge treatment, fixed bed treatment, fluid carrier treatment, aerobic treatment such as membrane separation treatment, or anaerobic treatment are used to purify organic wastewater discharged from sewage and business establishments. ing. In any of these biological treatments, when microorganisms decompose organic matter in wastewater, the microorganisms grow and surplus sludge is generated. These surplus sludge is mainly dehydrated and then converted into industrial waste, which is landfilled or dried or incinerated. However, due to the high cost of landfill disposal and incineration, there is a need to reduce the amount of excess sludge.

  As a method for reducing the volume of excess sludge, there are biological aerobic digestion and anaerobic digestion. However, there are problems that the processing time is long, a period of 10 days or more and a large-scale facility are required, and the volume reduction rate is low. There is also a method using special bacteria. Other volume reduction treatment methods include chemical treatment using ozone (such as Patent Document 1) or alkali high temperature, and ultrasonic treatment (such as Patent Document 2), mechanical treatment by applying high pressure, or a bead mill. Mechanical processing. However, both have high equipment costs and complicated operation.

JP 2003-285090 A JP 2002-59200 A

  An object of the present invention is to solve the problems related to the disposal of excess sludge and sludge volume reduction, and to provide a treatment method and a treatment apparatus capable of achieving high sludge volume reduction.

  In order to solve the above-mentioned problems, sludge is efficiently stirred in a short time by using a high-speed stirrer having high impact force, shear force, and cavitation force, preferably having a special blade structure. It was found that solubilization is possible, and if this solubilized sludge is treated in a biological treatment tank, the generation of excess sludge can be greatly reduced.

  That is, the present invention is a step of biologically treating organic wastewater, a step of separating sludge from the treated organic wastewater, a step of solubilizing the separated sludge with a high-speed stirrer installed at the bottom of the solubilization tank, The present invention also relates to a method for treating organic wastewater comprising a step of returning a solubilized treatment liquid to a biological treatment step.

  In addition, the high-speed stirrer is installed at the bottom of the solubilization tank, and has a stator having a plurality of crushing blades in a circular shape on the upper surface opposite to the installation surface, and a plurality of stirring blades meshed with the crushing blades of the stator in the diameter direction A homogenizer comprising a rotor having an opening for taking in the pulverized material, the rotor being fixed to the stator by sandwiching the stator by a shaft, and stirring the liquid or liquid and powder by the rotation of the rotor, and the opening of the rotor A homogenizer equipped with a hood is preferable.

  Moreover, it is preferable that a screen is provided in the step of solubilizing the separated sludge with a high-speed stirrer.

  Further, the present invention is a biological treatment means for biologically treating organic wastewater, a solid-liquid separation means for separating sludge from the treated organic wastewater, and a high-speed stirrer in which the separated sludge is installed at the bottom of the solubilization tank. The present invention relates to a treatment apparatus for organic wastewater provided with a solubilizing means for solubilization and a returning means for returning the solubilized treatment liquid to the biological treatment means.

  In addition, the high-speed stirrer is installed at the bottom of the solubilization tank, and a stator having a plurality of crushing blades in a circular shape on the upper surface opposite to the installation surface, and a plurality of stirring blades and a sheath that mesh with the crushing blades of the stator in the diameter direction A homogenizer comprising a rotor having an opening for taking in the pulverized material, the rotor being fixed to the stator by sandwiching the stator by a shaft, and stirring the liquid or liquid and powder by the rotation of the rotor, and the opening of the rotor A homogenizer equipped with a hood is preferable.

  According to the present invention, in a method for treating organic waste liquid, by adding a solubilizer equipped with a high-speed stirrer to a biological treatment facility, a high sludge volume reduction effect can be obtained, as well as facility cost and running The cost is low, and the surplus sludge treatment cost can be reduced compared to the disposal cost after dehydration and the liquid disposal cost. Moreover, since a high-speed stirrer is installed in the bottom part of a tank, even if it is a small amount of sludge, it can process, and there exists an effect that the sludge in the bottom part of a tank is fully solubilized.

  The present invention includes a step of biologically treating organic wastewater (hereinafter referred to as a biological treatment step), a step of separating sludge from the treated organic wastewater (hereinafter referred to as a separation step), and the separated sludge in a solubilization tank. Treatment of organic wastewater comprising a step of solubilization with a high-speed stirrer installed at the bottom (hereinafter referred to as a solubilization step) and a step of returning the solubilized processing liquid to a biological treatment step (hereinafter referred to as a return step) Regarding the method.

  The equipment targeted by the treatment method of the present invention is not particularly limited as long as it is equipment that biologically treats organic wastewater. Biological treatment such as sewage treatment, agricultural settlement wastewater treatment, and other establishments. It is a facility and the volume of excess sludge generated from these facilities can be reduced.

  The processing method of the present invention will be described with reference to the drawings. FIG. 1 is a schematic flow showing an example of the processing method of the present invention.

  First, the organic waste water W is supplied to the biological treatment tank 1. In the biological treatment tank 1, the organic wastewater W is biologically treated by microorganisms decomposing organic matter in the organic wastewater W. The treated organic waste water is guided to the solid-liquid separation tank 2. In the solid-liquid separation tank 2, the organically treated organic waste water is separated into the treated water T and sludge. The separated sludge is returned to the biological treatment tank 1 as return sludge. In order to operate the biological treatment tank 1 at a constant sludge concentration, the sludge corresponding to the excess sludge in the biological treatment tank 1 is appropriately transferred to the sludge tank 3 (sludge concentration tank or sludge storage tank) and disposed outside the system. The sludge to be solubilized is extracted from the return sludge, the sludge tank 3 or the biological treatment tank 1 and transferred to the solubilizer 4. The solubilizer 4 is a solubilization tank 6 composed of a tank and a high-speed stirrer installed at the bottom of the tank after removing impurities by a pretreatment section 5 provided with a screen, and is solubilized by a high-speed stirrer. . The solubilized treatment liquid is returned to the biological treatment tank 1 because microorganisms can be decomposed. The returned solubilized processing solution can be biologically treated again to reduce the volume of sludge.

  In the biological treatment process, for example, organic wastewater is biologically treated in the biological treatment tank 1 by an aerobic treatment such as an activated sludge method, a fixed bed treatment, a fluidized carrier treatment and a membrane separation treatment, an anaerobic treatment, and a combination thereof. It is processed.

  In the separation step, sludge is separated from the organic wastewater in the solid-liquid separation tank 2 by, for example, a method of providing a precipitation tank or a method of using a solid-liquid separation membrane.

  The solubilization step is performed in the solubilization tank 6. The solubilization tank 6 includes a tank and a high-speed stirrer installed at the bottom of the tank.

  The solubilization tank 6 may be provided with a heating means for directly or indirectly heating the tank, and the heating means is not particularly limited, such as steam, an electric heater, a microwave, and hot water. Among these, steam is preferable from the viewpoint of running cost and shortening of processing time. By the heating means, the treatment temperature is 25 to 80 ° C., and particularly 60 to 80 ° C. is preferable in that the solubilization efficiency can be increased. If it is lower than 25 ° C., the solubilization efficiency tends to be extremely poor. Above 80 ° C, solubilization efficiency tends to slow down. The tank to be heated may be the solubilization tank 6 or a tank (temperature raising tank) provided separately.

  By the high-speed stirrer, the sludge that has passed through the gap between the teeth that have a narrow flow path and rotate at high speed and the teeth that have a narrow flow path and are fixed has a strong impact force (cutting force), shear force, and cavitation force. Solubilized.

  1-3, although it does not specifically limit as a high-speed stirrer installed in the bottom part of the solubilization tank 6, A stirrer with a turbine and a disper blade is mention | raise | lifted, Especially, a homogenizer is preferable. The homogenizer includes a stator 11 having a plurality of grinding blades 14 circumferentially on the upper surface opposite to the installation surface, a plurality of stirring blades 15 that mesh with the grinding blades 14 of the stator 11 in the radial direction (that is, radially), and an object to be ground. The rotor 10 has a plurality of openings 12 for taking The rotor 10 is fixed to the stator 11 by sandwiching the rotor 10 and the stator 11 by the shaft 8, and the liquid or the liquid and the powder are agitated by the rotation of the rotor 10. A hood 13 is provided in the opening 12 of the rotor 10. Such a homogenizer is preferable in terms of solubilization efficiency. Moreover, it is preferable that the high-speed stirrer is installed at the bottom of the solubilization tank in that it can be processed even with a small amount of sludge and the sludge at the bottom of the tank is sufficiently solubilized. .

  An example of the homogenizer will be described with reference to FIGS.

  FIG. 2 is an explanatory diagram showing an example of a state in which a homogenizer that can be used in the present invention is installed at the bottom of the solubilization tank 6. A stirring portion 9 is provided at the uppermost portion of the shaft 8 via a shaft 8 coaxially connected to the shaft 7, and the stirring portion 9 includes a rotor 10 and a stator 11. A plurality of holes 20 are formed in the stator 11, and the stator 11 is screwed to the bottom portion 6 b of the solubilization tank 6 by a plurality of bolts 21 through the holes 20. A rotational force is transmitted to the shaft 7 via a belt B from a rotational shaft A of a rotational driving device M such as a motor. Therefore, the shaft 7 rotates with the rotation of the belt B, and the stirring unit 9 rotates through the shaft 8.

  As shown in FIG. 3, the homogenizer stirring unit 9 that can be used in the present invention has a plurality of grinding blades 14 attached to the upper surface of a stator 11 in a circumferential shape. Although the said grinding | pulverization blade | wing 14 may have 2 or more rows like FIG. 3, it is not specifically limited. Having two or more layers of pulverization blades 14 is preferable in that a high shear force can be applied to the sludge. The shape of the pulverization blade 14 may be a rectangle, a square, a trapezoid, a triangle, or the like, but is not particularly limited. Among these, a rectangle or a square is preferable in terms of an area where shear is applied and a discharge amount of the processing liquid.

  As described above, the rotor 10 is fixed to the upper surface of the stator 11 by sandwiching the stator 11 with the shaft 8. Furthermore, as shown in FIG. 2, when an O-ring G is interposed between the rotor 10 and the stator 11 and a labyrinth-like protrusion P is provided on the joint surface of the rotor 10 with the stator 11, The sludge water in 6 can be prevented from entering between the rotor 10 and the stator 11.

  A plurality of stirring blades 15 are circumferentially attached to one surface of the rotor 10. The stirring blade 15 meshes with the grinding blade 14 of the stator 11 and the radial direction of the stator 11 (that is, radially), and is inserted between the grinding blade 14 on the outer peripheral side and the grinding blade 14 on the inside thereof. Unioned. When the rotor 10 rotates counterclockwise, a high shearing force is applied when the sludge passes through the pulverization blade 14 and the stirring blade 15.

  When the stator 11 has two rows in the diametrical direction as shown in FIG. 3, it is preferable that the stirring blades 15 have three rows. It is not limited. Especially, having two or more rows is preferable in that a high shearing force can be applied to the sludge. The clearance between the stirring blades 15 (that is, between the blade rows) can also be adjusted as appropriate according to the thickness of the grinding blades 14 in the diameter direction. The clearance between the outer stirring blade 15 and the inner grinding blade 14 (that is, between the blade rows) is preferably 0.3 to 0.8 mm.

  Further, the shape of the stirring blade 15 may be a rectangle, a square, a trapezoid, a triangle, or the like, but is not particularly limited. Among these, a rectangle or a square is preferable in terms of an area where shearing is applied to the sludge and a discharge amount of the treatment liquid.

  The rotor 10 preferably has two or more openings 12 for sucking sludge. When only one opening 12 is provided, the sludge is not sufficiently sucked and the stirring efficiency tends to be insufficient.

  Referring to FIG. 3, the rotor 10 is provided with four hoods 13 on the surface opposite to the surface having the stirring blades 15 so as to cover the opening 12 at equal intervals. Although four hoods 13 are provided in the figure, the number of hoods 13 is not limited to four, and for example, three or five hoods 13 are possible. From the viewpoint of ease of processing and sludge suction efficiency. 3 are most preferable. Although the hood 13 is provided in at least one opening 12, it is preferable that the hood 13 is provided in all the openings 12 in order to make it easy to take in sludge into the opening 12. The hood 13 is provided in order to make it easy to take in sludge into the opening 12 as described above, and is open toward the rotation direction of the rotor 10. Since the sludge can be reliably taken into the opening portion 12 by the hood 13, sufficient shearing can be applied to the sludge.

  The shape of the hood 13 is not particularly limited as long as sludge can be taken into the opening 12. Specifically, as shown in FIG. 3, a conical shape inclined in the rotation direction of the rotor 10, a triangular or quadrangular pyramid shape, and the like can be given. Especially, sludge is taken in into the opening part 12 reasonably, and it is preferable to incline in the rotation direction of the rotor 10 as shown in FIG.

  The shape of the solubilization tank 6 in which the high-speed stirrer is installed is not particularly limited, and examples thereof include a square flat bottom, an inverted pyramid flat bottom type, and a circular end plate bottom type, but a circular end plate bottom type is preferable from the viewpoint of stirring efficiency. Moreover, the size of the solubilization tank 6 is determined by the processing amount.

  The size of the stirrer of the high-speed stirrer may be appropriately determined according to the size of the solubilization tank 6, but is a size that provides a blade diameter of 15 to 20% with respect to the diameter of the solubilization tank 6. It is preferable. If it is 20% or more, the power tends to increase and the cost tends to increase, and if it is 15% or less, the solubilization efficiency tends to decrease. The installation place of the high-speed stirrer is not particularly limited.

  The number of revolutions of the high-speed stirrer varies depending on the size of the tank, the processing amount, the sludge concentration, the solubilization efficiency, and the processing time, but is preferably 1,000 to 20,000 rpm. If the treatment amount, the sludge concentration, and the treatment time are the same, the higher the rotation speed, the higher the solubilization rate. The treatment time is usually preferably 5 to 20 minutes, more preferably 5 to 10 minutes. If it is 20 minutes or longer, the power consumption will only increase and the solubilization effect will not be improved so much.

  In the solubilization step, it is preferable that a screen (or a strainer) is provided as a pretreatment unit in terms of preventing a reduction in performance of the high-speed stirrer. This screen removes sand and large solids that are clogged in the gaps between the blades of the high-speed stirrer or that damage the high-speed stirrer. The shape of the screen is not particularly limited, and examples thereof include a mesh shape and a slit shape. Of these, the slit shape is preferable in terms of maintenance. In addition, the opening is preferably about 0.5 to 1 mm. If it is smaller than 0.5 mm, clogging tends to become severe, and if it exceeds 1 mm, it tends to cause clogging or failure of the blades of the high-speed stirrer.

  Since the sludge solubilized in the solubilization step is improved in biodegradability, the treatment liquid can be returned to the biological treatment step and reprocessed, and the amount of excess sludge generated can be reduced. .

  The sludge to be solubilized may be any of returned sludge, concentrated sludge, or sludge in the biological treatment process that is returned to the biological treatment process after the solid-liquid separation process. The higher the sludge concentration, the better the solubilization efficiency, and the same solubilization rate can be obtained with a small amount of treatment as compared with the case where the concentration is low. Therefore, the solubilizing apparatus can be reduced in size and the processing time can be shortened, which is preferable in that the operating cost can be reduced. The sludge concentration is preferably 0.5 to 5% by weight, more preferably 1 to 3% by weight. When the sludge concentration is low, it is desirable to concentrate using a concentrator. The sludge concentrating device is not limited, and examples thereof include membrane concentration and centrifugal concentrators. Here, the sludge concentration refers to the mass of suspended matter in the sludge to be solubilized (MLSS: Mix Liquor Suspended Solids).

  The amount of treatment in the solubilization process is determined from the amount of excess sludge generated (this excess sludge amount includes the amount of excess sludge generated when the solubilized sludge is reprocessed in the biological treatment process) and the sludge concentration. Set as appropriate.

  In the returning process, the solubilized processing liquid is obtained by, for example, a method using a device such as a centrifugal pump or a positive displacement pump, a method using a solubilizer installed on the top of the biological treatment layer, and utilizing a drop of the biological treatment step. Will be returned.

  The present invention also provides biological treatment means for biologically treating organic wastewater, solid-liquid separation means for separating sludge from the treated organic wastewater, and a high-speed stirrer installed at the bottom of the solubilization tank for the separated sludge It is related with the processing apparatus of organic wastewater provided with the solubilization means which solubilizes by this, and the return means which returns the solubilized process liquid to a biological treatment means.

  Examples of biological treatment means for biologically treating organic wastewater include an aerobic treatment such as an activated sludge method, a fixed bed treatment, a fluid carrier treatment and a membrane separation treatment, an anaerobic treatment, and a combination thereof.

  Examples of the solid-liquid separation means for separating sludge from the treated organic wastewater include means such as a method of providing a sedimentation tank and a method of using a solid-liquid separation membrane.

  The solubilizing means for solubilizing the separated sludge with a high-speed stirrer is a high-speed stirrer installed at the bottom of the solubilization tank. Although it does not specifically limit as a solubilization tank and a high-speed stirrer, It is preferable at the point of solubilization efficiency to use the solubilization tank and homogenizer mentioned above.

  The number of rotations of the high-speed stirrer varies depending on the size of the tank, the processing amount, the sludge concentration, the solubilization efficiency and the processing time, but is preferably 1,000 to 20,000 r / min. If the treatment amount, the sludge concentration, and the treatment time are the same, the higher the rotation speed, the higher the solubilization rate. The treatment time is usually preferably 5 to 20 minutes, more preferably 5 to 10 minutes. If it is 20 minutes or longer, the power consumption will only increase and the solubilization effect will not be improved so much.

  Moreover, it is preferable to remove sand and a large solid content by the screen as a pretreatment before performing the solubilizing means in terms of preventing the performance deterioration of the high-speed stirrer.

As a return means for returning the solubilized treatment liquid to the biological treatment means, for example, a device such as a centrifugal pump or a positive displacement pump is used, or a solubilization device is installed at the upper part of the biological treatment tank and the head is used. Can be given.

  Next, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

Example 1
The Example in a food processing factory is shown. Factory wastewater is treated in a biological treatment tank 80m ³ and solid-liquid separation tank 25m ³ , and the treated water is discharged into the river. The proliferating sludge is separated into a sludge tank 3m ³ and then disposed of as industrial waste by reducing the water with a dehydrator.

  Factory waste water (raw water W) had an average water volume of 20 m 3 / d and an average BOD of 2,200 mg / L. The treated water T separated into solid and liquid is discharged at an average BOD of 20 mg / L. The sludge concentration in the biological treatment tank during the experiment period was kept at 5 g / L, and the growth was appropriately extracted and managed in the sludge tank. The water temperature of the biological treatment tank was 30 to 32 ° C., and the concentration of dissolved oxygen was 2 to 4 mg / L.

  In the experiment, the sludge (average concentration 16 g / L) in the sludge tank was transferred to a solubilizer, and the sludge was solubilized using a high-speed stirrer (ultra mixer) installed at the bottom of the tank. A solubilization tank can process 400L per time. The amount of treatment in the solubilizer was transferred to a sludge tank for treatment of sludge corresponding to 3 times the amount of excess sludge solids generated when the solubilizer was not used (Comparative Example 1 described later). The treatment amount was 3.2 m 3 / d (the number of treatments was 8 times / d).

  The treatment conditions were a temperature of 80 ° C., a high-speed stirrer rotation speed of 2,900 rpm, and a residence time of 10 minutes. The obtained solubilized processing liquid was returned to the biological treatment tank and reprocessed. The nitrogen and phosphorus contents in the treated water increased slightly, but the BOD, COD, and pH of the treated water did not change.

Comparative Example 1
The treatment was performed in the same manner as in Example 1 except that the system does not include a solubilizer. The factory waste water W was supplied in the same manner as in Example 1. There was no change in the BOD, COD and pH of the treated water.

  As a result of treating these treatments continuously for 65 days, the cumulative dry matter amount of excess sludge was 1,120 kg in Comparative Example 1, whereas it was reduced to 143 kg in Example 1 (reduction rate 87%). Was confirmed. As a result, it was found that the amount of surplus sludge to be discharged out of the system is greatly reduced if the solubilization treatment is performed on the sludge subjected to biological treatment by temperature and stirring.

It is a schematic flowchart which shows an example of the processing method of this invention. It is a figure which shows an example of the state which installed the homogenizer used by this invention in the solubilization tank bottom part. It is a figure which shows an example of the stirring part of the homogenizer used by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Biological treatment tank 2 Solid-liquid separation tank 3 Sludge tank 4 Solubilization apparatus 5 Pretreatment part 6 Solubilization tank 6b Bottom part 7 Axis 8 Shaft 9 Stirring part 10 Rotor 11 Stator 12 Opening part 13 Hood 14 Crushing blade 15 Stirring blade 20 Hole 21 Bolt A Rotating shaft B Belt G O-ring M Rotation drive P Projection

Claims (5)

A process for biologically treating organic wastewater, a process for separating sludge from the treated organic wastewater, a process for solubilizing the separated sludge with a high-speed stirrer installed at the bottom of the solubilization tank, and a solubilized treatment liquid A method for treating organic wastewater comprising a step of returning to a biological treatment step. The high-speed stirrer is installed at the bottom of the solubilization tank, the stator having a plurality of grinding blades in a circular shape on the upper surface opposite to the installation surface, and the plurality of stirring blades and the object to be ground that mesh with the grinding blades of the stator in the diameter direction A homogenizer comprising a rotor having an opening for taking in liquid and being fixed to the stator by sandwiching the stator by a shaft, and agitating liquid or liquid and powder by rotation of the rotor, and a hood at the rotor opening The method for treating organic wastewater according to claim 1, wherein the organic wastewater is a homogenizer. The method for treating organic wastewater according to claim 1 or 2, wherein a screen is provided in the step of solubilizing the separated sludge with a high-speed stirrer. Biological treatment means for biological treatment of organic wastewater, solid-liquid separation means for separating sludge from the treated organic wastewater, solubilization means for solubilizing the separated sludge with a high-speed stirrer installed at the bottom of the solubilization tank And an organic wastewater treatment apparatus comprising a return means for returning the solubilized treatment liquid to the biological treatment means. The high-speed stirrer is installed at the bottom of the solubilization tank, the stator having a plurality of grinding blades in a circular shape on the upper surface opposite to the installation surface, and the plurality of stirring blades and the object to be ground that mesh with the grinding blades of the stator in the diameter direction A homogenizer comprising a rotor having an opening for taking in liquid and being fixed to the stator by sandwiching the stator by a shaft, and agitating liquid or liquid and powder by rotation of the rotor, and a hood at the rotor opening The organic wastewater treatment apparatus according to claim 4, which is a homogenizer comprising:

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