JP2005137969A - Organic wastewater treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic wastewater treatment apparatus which achieves a higher reduction of surplus sludge. <P>SOLUTION: The organic wastewater treatment apparatus comprises an aeration tank which passes organic wastewater to bring the wastewater in contact with floating microbial sludge to biologically treating the wastewater; a submerged filter bed tank which has a packed bed consisting of a filler the surface of which has deposits of activated sludge and passes the treated water of the aeration tank through the packed bed to biologically treat it, a sludge separator which separates sludge from the treated water of the submerged filter bed tank and from back washing water generated when a submerged filter bed is back washed, a sludge solubilization device which solubilizes the sludge separated by the sludge separator; and a means for returning sludge-solubilized liquid after the solubilization treatment to the aeration tank. The organic wastewater treatment apparatus comprises the aeration tank which passes the organic wastewater to bring the wastewater in contact with the floating microbial sludge to biologically treat the wastewater, a fluidized bed tank which contains the filler the surface of which has deposits of the activated sludge and passes the treated water of the aeration tank to aerate the treated water together with the filling material while mixing them, the sludge separator which separates sludge from the treated water of the fluidized bed tank, the sludge solubilization device which solubilizes the sludge separated by the sludge separator, and the means for returning the sludge-solubilized liquid after the solubilization treatment to the aeration tank. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an organic wastewater treatment apparatus for reducing the amount of excess sludge generated when biologically treating organic wastewater.

  As biological wastewater treatment of organic wastewater, the activated sludge method, the submerged filter bed method and the fluidized bed method are mainly used. In the activated sludge method, treated water and microbial sludge are mixed and aerated in an aeration tank, and a sludge mixed solution from the aeration tank is separated in a sludge separation tank to obtain treated water. On the other hand, in the submerged filter bed method, water to be treated is passed through a submerged filter bed in which a filler having activated sludge deposited on the surface is immersed and biologically treated to obtain treated water. In the fluidized bed method, treated water is passed through a tank containing the filler and biologically treated to obtain treated water. In the activated sludge method, the biggest problem is that there is a lot of excess sludge.

  On the other hand, a submerged filter bed generally contains a mixture of microorganisms that decompose organic matter in organic wastewater, protozoa that supplement the microorganisms, and metazoans that supplement the protozoa, forming a higher-order food chain. Therefore, the amount of sludge generated is reduced. However, in the submerged filter bed, rapid oxygen consumption occurs and the filter bed is clogged due to rapid bacterial growth, resulting in a decrease in gas-liquid contact efficiency in the filter bed tank. There is a problem of deteriorating water quality. Moreover, the reverse washing operation for removing the activated sludge accumulated on the filter bed is required at a high frequency.

  Then, the processing method (refer patent document 1) which combined these activated sludge methods and the immersion filter bed method is proposed. Specifically, two tanks, an immersion filter bed tank and an aeration tank, are arranged in series in this order as biological treatment tanks. First, biological wastewater is biologically treated in the immersion filter bed tank, and then the obtained filter bed is obtained. The treated water is passed through the aeration tank for further biological treatment. The treatment method can reduce the amount of generated sludge as compared with a simple activated sludge method.

  However, in the submerged filter bed method, the microorganisms that have grown on the filler are non-floating, and such non-floating microorganisms are less organic than the floating microorganisms, so organic matter is first decomposed. In the above treatment method in which the effluent is brought into contact with non-floating microorganisms, a considerable amount of excess sludge is still generated.

  On the other hand, as a method of reducing the generation of surplus sludge, a solubilization means for solubilizing a part or all of the surplus sludge is provided in the organic wastewater treatment process, and the solubilization is treated with an alkaline agent by using a homogenizer, a mixer or the like. A method of performing processing in combination (see Patent Document 2) is known.

JP 2000-229297 A JP 2002-113487 A

  Therefore, an object of this invention is to provide the organic waste water treatment equipment which can reduce a higher surplus sludge.

  In light of such circumstances, the present inventors have made extensive studies on an organic wastewater treatment apparatus that can efficiently reduce excess sludge. As a result, an aeration tank and a submerged filter bed tank or a biological treatment tank for a wastewater treatment apparatus It was found that surplus sludge can be stably reduced by installing two fluidized bed tanks in this order and bringing organic wastewater into contact with floating microorganisms with high organic matter decomposing ability first. It was.

  That is, the present invention has an aeration tank in which organic wastewater is passed through and brought into contact with floating microbial sludge for biological treatment, a packed bed made of a filler on which activated sludge is deposited, and the aeration Sludge from the submerged filter bed for biological treatment by passing the treated water of the tank through the packed bed, the treated water of the submerged filter bed and the backwash water generated when the submerged filter bed is backwashed Sludge separation device for separating the sludge, sludge solubilization device for solubilizing the sludge separated by the sludge separation device, and organic waste water provided with means for returning the sludge solubilized liquid after the solubilization treatment to the aeration tank A processing device is provided.

  The present invention also includes an aeration tank in which organic wastewater is passed through and brought into contact with floating microbial sludge for biological treatment, and a filler on which activated sludge is deposited, and the treated water in the aeration tank is passed through. A fluidized bed tank that is mixed and aerated with the filler, a sludge separator that separates sludge from the treated water of the fluidized bed tank, a sludge solubilizer that solubilizes sludge separated by the sludge separator, And an organic wastewater treatment apparatus comprising means for returning the solubilized sludge solubilized liquid to the aeration tank.

  According to the present invention, it is possible to reduce the amount of excess sludge generated without deteriorating the quality of treated water. Moreover, the generation | occurrence | production of excess sludge can further be reduced by performing the solubilization process of the sludge which combined the process by a homogenizer etc. with the process by an alkaline agent. Furthermore, in the wastewater treatment apparatus of the present invention using a fluidized bed tank, the backwashing operation is unnecessary, so that the wastewater treatment becomes simple.

  The organic wastewater treatment apparatus of the present invention can be applied to biological treatment of various organic wastewaters that generate excess sludge. 1st Embodiment of the organic waste water treatment apparatus of this invention is shown in FIG.

  Organic wastewater is passed from the drainage line 1 to the aeration tank 14 and aerated in the aeration tank 14 to undergo aerobic biological treatment. The microbial sludge in the aeration tank 14 has few protozoa and is predominantly populated with floating microorganisms.

  The treated water in the aeration tank flows into the immersion filter bed tank 15 via the line 2. The inside of the submerged filter bed tank 15 is filled with a filler on which microorganisms are deposited, and a packed bed is formed. As the filler, various materials and shapes can be used, and examples thereof include a cylindrical mesh filler. For example, the filler of the cylindrical nonwoven fabric is formed by molding a nonwoven fabric of propylene fiber into a hollow cylindrical shape, and the packed layer is formed by stacking in a grid pattern so that the direction of the filler cylinder is perpendicular to each other. . That is, in one layer, the cylinders are arranged in the same direction, and in the upper layer, the cylinders are arranged in a direction perpendicular to the cylinder.

  A diffuser pipe is installed at the bottom of the packed bed, and air is supplied from the line 13 into the tank, whereby the inside of the submerged filter bed 15 is aerated. Bubbles supplied from the air diffuser rise in the packed bed. For this reason, the rising speed of the bubbles is lower than that of the empty tower, and the oxygen dissolution efficiency is increased. In particular, when the filler is a cylindrical mesh, the filler can subdivide the bubbles, increase the gas-liquid contact area, and remarkably increase the oxygen dissolution efficiency. Inflow water flows in from the bottom of the packed bed, ascends the packed bed, and treated water is discharged from the top. The immersion filter bed treated water treated in the immersion filter tank 15 flows into the sludge separation tank 17 via the line 3.

  In addition, in the submerged filter bed tank, in order to prevent clogging of the filler and deterioration of gas-liquid contact efficiency due to the growth of microorganisms, a reverse cleaning operation is periodically performed to remove the activated sludge accumulated on the surface of the filler. Is called. Specifically, the washing water or air rapidly flows from the bottom of the filler from the line 4 and overflows from the upper part of the submerged filter bed, and then is collected in the backwash water storage tank 16 through the line 5. In this specification, the “activated sludge” that has grown or accumulated on the surface of the filler includes non-floating microorganisms, protozoa that inhabit the submerged filter bed that supplements this, and metazoites that supplement the protozoa. Includes animals.

  The backwash water after recovery contains a large amount of excess sludge, joins the line 3 at a constant flow rate from the line 6 and flows into the sludge separation tank 17, where it is separated into excess sludge and treated water. The treated water is discharged via line 7. Examples of the sludge separation tank 17 include a sedimentation separation tank, a pressurized flotation separation tank, and a membrane separation apparatus that are frequently used for sludge separation, and a sedimentation separation tank or a pressurized flotation separation tank is preferable.

  A flocculant is added to the treated water containing SS (substance suspended in water) in line 3 and the backwash water containing excess sludge in line 6 as necessary. As a result, the SS component is agglomerated and the surplus sludge flocs become larger. As a result, the surplus sludge naturally settles in the sludge separation layer 17. The precipitated sludge is usually obtained at a solid concentration of about 0.5 to 2.5%.

  And a part or all of the surplus sludge which passed the line 8 flows in into a sludge solubilizer through the line 9, and is sludge solubilized. Although this solubilization treatment step is essential, it is sufficient that the entire amount or a part of the sludge is treated. Further, a part of the excess sludge that has passed through the line 8 may be discharged as excess sludge 19 from the line 11 after being further concentrated by a dehydrator or the like without passing through the line 9. Furthermore, it is desirable that surplus sludge passing through the line 9 is concentrated in the middle of the line 9 by a known sludge concentrator, for example, a sludge settling tank, a dehydrator or the like, so that the solids concentration of the surplus sludge is increased. The solids concentration of the concentrated sludge is usually about 2%.

  The sludge solubilization treatment may be performed by one or more treatments selected from treatment with an alkali agent, treatment with a homogenizer, treatment with a mixer, treatment with a mill, treatment with high pressure and instantaneous decompression, and treatment with an oxidizing agent. preferable. That is, the cells of the microorganisms constituting the sludge are chemically destroyed by the treatment with the alkaline agent, and the cells of the microorganisms constituting the sludge are also physically destroyed by the treatment with the homogenizer. The amount of the alkali agent used can be reduced by combining the treatment with the alkali agent with a treatment having a strong grinding force such as a mill or a mixer. In order to promote solubilization, it may be heated to 50 to 100 ° C.

  Examples of the alkali agent used for the treatment with the alkali agent include sodium hydroxide, sodium carbonate, sodium hydrogen carbonate, calcium hydroxide, calcium carbonate, calcium oxide and the like, and sodium hydroxide or calcium oxide is preferable. The addition amount of the alkaline agent is preferably 0.005 to 0.1N, particularly preferably 0.01 to 0.05N, with respect to the excess sludge to be solubilized.

  The processing by a homogenizer, a mixer, and a mill is performed, for example, by processing excess sludge to which an alkaline agent has been added using a homogenizer or the like. As a homogenizer or the like, any known one can be used as long as it can apply mechanical shear stress or grinding force to the cells of the microorganisms constituting the sludge and can destroy the cell membrane and cell wall of the cells. . Specifically, let the excess sludge added with alkaline agent pass through a pipe with a baffle plate at high speed, or sharp edge like a food mixer at high speed in excess sludge added with alkaline agent. One that rotates or passes through a narrow space between two disks that rotate at high speed, such as a mill that turns food into powder.

  The treatment time of the solubilization treatment combining treatment with an alkaline agent and treatment with a homogenizer or the like is generally 1 minute to 5 hours, preferably 1 minute to 3 hours, particularly preferably 2 minutes to 2 hours. The solubilization time can be significantly shortened as compared with the solubilization treatment only with the treatment with the alkali agent.

In the treatment by high pressure and instantaneous decompression expansion, the excess sludge to which the alkali agent is added is pressurized to a high pressure of, for example, 70 to 180 kg / cm ² , and the pressure is reduced instantaneously from the high pressure. This is done by instantaneously expanding the sludge and destroying the cells of the microorganisms that make up the sludge. This treatment may be performed, for example, by inserting excess sludge to which an alkali agent is added into a pipe containing a baffle plate at a high pressure, and then discharging the sludge from the pressurized pipe to a normal pressure tank. it can. The treatment time of the solubilization treatment combining treatment with an alkaline agent, treatment with high pressure and instantaneous decompression expansion is generally 1 to 60 minutes, preferably 5 to 30 minutes. The solubilization time can be significantly shortened as compared with the solubilization treatment only with the treatment with the alkali agent.

  As the oxidizing agent used for the treatment with the oxidizing agent, hydrogen peroxide, sodium peroxide, sodium percarbonate, etc., which have strong oxidizing power and change itself to be harmless to activated sludge after decomposition, are preferable. The treatment with the oxidizing agent is performed by adding an oxidizing agent together with the alkaline agent to the excess sludge. At this time, the pH of the excess sludge is preferably 11 or more, more preferably 11 to 12.5. If the pH of the excess sludge is less than 11, solubilization of the sludge is insufficient, which is not preferable. The addition amount of the oxidizing agent is generally 10 to 10000 ppm, preferably 100 to 1000 ppm, based on the amount of dry sludge in the excess sludge. The treatment time of the solubilization treatment that combines treatment with an alkaline agent and treatment with an oxidizing agent is generally 1 to 6 hours, preferably 1 to 4 hours. Generally, the solubilization time can be shortened as compared with the solubilization treatment only with the treatment with the alkali agent.

  Other solubilization methods include thermophilic bacteria methods, bead mill methods, methods of adding chemicals such as hypochlorite, ozone oxidation methods, ultrasonic methods, UV irradiation treatments, Processing by combination is mentioned.

  The sludge solubilizing solution after the solubilization treatment (hereinafter referred to as “solubilizing solution”) may be subjected to neutralization treatment or decolorization treatment with an oxidizing agent as necessary. By performing the decolorization treatment, it is possible to reduce the adverse effect on the color of the solubilized treatment product generated when the volume of excess sludge is reduced and the hue of the treated water resulting therefrom. Although the decoloring treatment and the neutralization treatment can be used in combination, it is preferable to perform the decoloring treatment before the neutralization treatment. For the neutralization treatment, a mineral acid such as sulfuric acid, a spent waste acid or the like can be used. As the oxidizing agent, hydrogen peroxide, sodium peroxide, sodium percarbonate, etc., which have strong oxidizing power and change itself to be harmless to activated sludge after decomposition, are preferable, and hydrogen peroxide is particularly preferable.

  The solubilized liquid is returned to the aeration tank 14 through the line 10. The returned solubilized liquid is diluted by the organic wastewater flowing from the drainage line 1 and further decomposed in the aeration tank 14 by microorganisms living in the tank and bacteria remaining in the solubilized liquid.

  In the aeration tank 14, the BOD (biochemical oxygen demand) load increases due to the return of the solubilized liquid. In the aeration tank 14, air is supplied from the diffuser pipe at the bottom of the aeration tank 14 through the line 12. High gas-liquid contact efficiency can be obtained, and organic substances in organic waste water and organic substances in solubilized liquid can be decomposed at high speed. The microorganisms grown in the aeration tank 14 become SS together with the treated water and flow into the submerged filter tank 15 via the line 2. In the submerged filter bed 15, organic substances slightly remaining in the treated water flowing in from the line 2 are decomposed, and microorganisms that flowed in mainly as SS are supplemented by protozoa, and sludge generation is suppressed. . Thus, the clogging of the filler in the submerged filter bed 15 and the reduction of the gas-liquid contact efficiency are suppressed by separating the decomposition process of the organic matter in the organic waste water and the supplementing process of the grown microorganisms. Is done.

  2nd Embodiment of the organic waste water treatment apparatus of this invention is shown in FIG. Organic waste water is supplied from the line 1 to the aeration tank 14 and aerated in the aeration tank 14 to undergo biological treatment. The treated water in the aeration tank flows into the fluidized bed tank 20 via the line 2. In the fluidized bed tank 20, the filler on which the activated sludge described in the first embodiment is deposited floats. The filler on which the activated sludge is deposited is sufficiently mixed in the fluidized bed tank 20 together with the treated water of the aeration tank by the air supplied from the bottom of the tank. The material and shape of the filler are the same as those described in the first embodiment. A diffuser pipe is installed at the bottom of the fluidized bed tank 20, and air is supplied from the line 13 into the fluidized bed tank 20 and aerated in the fluidized bed tank 20.

  The treated water treated in the fluidized bed tank 20 flows into the sludge separation tank 17 via the line 3. The processes after the sludge separation are the same as in the first embodiment. Also in the second embodiment, it is preferable to carry out solubilization treatment of excess sludge, and this solubilization treatment includes treatment with an alkaline agent, treatment with a homogenizer, treatment with a mixer, treatment with a mill, high pressure and instantaneous. It is preferable to carry out the treatment by one or more treatments selected from the treatment by the expansion under reduced pressure and the treatment with the oxidizing agent.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention in more detail, this invention is not limited to these Examples.

Example 1
A wastewater treatment apparatus of this example is shown in FIG. After supplying factory wastewater (BOD1000-1100mg / L) to the aeration tank 24L with aeration time 8hr and activated sludge MLSS 3000-3500mg / L, the treated water flowing out from the aeration tank is further processed in a 15L submerged filter bed tank, 20L The activated sludge was settled and separated in a sedimentation tank to obtain a precipitated sludge having a solid concentration of 0.5 to 1%. In addition, the backwashing tank is periodically backwashed to recover the backwash water in the backwash water storage tank, and a large amount of excess sludge contained in the backwash water is allowed to flow into the sludge separator. It was. The factory wastewater treatment amount was 0.072 m ³ / day, and 2400 ml / day (dry-base 18 g / day) of the settled sludge was supplied to the sludge concentration step using a centrifugal separator, and the remaining precipitated sludge was returned to the aeration tank. When the precipitated sludge was concentrated by a centrifugal separator, a concentrated sludge having a solid concentration of about 2% was obtained. Next, this concentrated sludge is led to a sludge solubilizer having a batch type sludge solubilization tank with a residence time of 30 minutes, and NaOH is 0.05N concentration (pH about 12.5) with respect to the internal liquid of the tank. The sludge was solubilized while stirring at high speed (12000 rpm) with a homogenizer. The solubilized sludge (SS6000-9000 mg / L, supernatant TOC6000-8000 mg / L, pH 11) is neutralized to pH 8 by adding 2N sulfuric acid, and then returned to the aeration tank for aerobic biological treatment. It was. As a result of continuing the operation according to the above conditions for about one month, the water quality of the settling basin effluent was BOD 9-12. The total amount of excess sludge during that period was about 270 g-ss.

Example 2
Factory waste water was treated in the same manner as in Example 1 except that the amount of sludge to be solubilized was changed to 7200 ml / day (dry-base 54 g / day) of settled sludge. The solubilized sludge was SS6000-9000 mg / L, supernatant TOC6000-8000 mg / L, pH 11. Subsequently, biological treatment after neutralization was performed in the same manner as in Example 1 (FIG. 1). As a result of continuing the operation according to the conditions for about one month, the water quality of the settling basin effluent was BOD 11-15. The total amount of excess sludge during that period was about 50 g-ss.

Comparative Example 1
The factory waste water was treated in the same manner as in Example 1 except that the solubilization treatment was not performed (FIG. 3). As a result of continuing the operation according to the conditions for about one month, the water quality of the settling basin effluent was BOD 9-12. Moreover, the total surplus sludge amount in the meantime was about 600 g-ss.

Comparative Example 2
The factory waste water was treated in the same manner as in Example 1 except that the treatment channel was changed so that the aeration tank was provided after the immersion filter bed (FIG. 4). Further, the solubilized liquid after neutralizing the solubilized sludge with 2N sulfuric acid was returned to the submerged filter bed. As a result of continuing the operation according to the conditions for about one month, the water quality of the settling basin effluent was BOD 20-40. Moreover, the total surplus sludge amount in the meantime was about 300 g-ss.

Example 3
A wastewater treatment apparatus of this example is shown in FIG. After supplying industrial wastewater (BOD1000-1100mg / L) to aeration tank 24L with aeration time 8hr and activated sludge MLSS 3000-3500mg / L, the treated water flowing out from the aeration tank is further processed in a 15L fluidized bed tank, and 20L The activated sludge was settled and separated in a sedimentation tank to obtain a precipitated sludge having a solid concentration of 0.5 to 1%. The factory wastewater treatment amount was 0.072 m ³ / day, and 2400 ml / day (dry-base 18 g / day) of the settled sludge was supplied to the sludge concentration step using a centrifugal separator, and the remaining precipitated sludge was returned to the aeration tank. After concentrating the precipitated sludge using a centrifuge, the same operation as in Example 1 was performed. As a result of continuing the operation according to the conditions for about 1 month, the water quality of the settling basin effluent was BOD 9-11. The total amount of excess sludge during that period was about 280 g-ss.

Comparative Example 3
Factory wastewater was treated in the same manner as in Example 3 except that the solubilization treatment was not performed (FIG. 5). As a result of continuing the operation according to the conditions for about one month, the water quality of the settling basin effluent was BOD 9-12. In addition, the total surplus amount during that period was about 560 g-ss.

  From the above, in Examples 1, 2 and 3, it was possible to reduce the amount of excess sludge generated while keeping the BOD value of the treated water low. On the other hand, in Comparative Examples 1 and 3, since solubilization was not performed, a large amount of excess sludge was generated. Moreover, in the comparative example 2, since the process by the immersion filter bed tank was implemented initially and the solubilization liquid was added, the BOD value of the treated water rose.

It is a figure which shows the one aspect | mode of the typical organic waste water treatment equipment of this invention. It is a figure which shows the one aspect | mode of the typical organic waste water treatment equipment of this invention. It is a figure which shows the organic waste water treatment apparatus of the comparative example 1. FIG. It is a figure which shows the organic waste water treatment apparatus of the comparative example 2. FIG. It is a figure which shows the organic waste water treatment apparatus of the comparative example 3. FIG.

Explanation of symbols

1 drainage line 2 line 3 line 4 backwash water line 5 line 6 line 7 treated water line 8 line 9 line 10 line 11 line 12 line 13 line 14 aeration tank 15 immersion filter bed tank 16 backwash water storage tank 17 sludge separation tank 18 Sludge solubilizer 19 Excess sludge 20 Fluidized bed tank

Claims (3)

  An aeration tank in which organic wastewater is passed through and brought into contact with floating microbial sludge for biological treatment, and has a packed bed consisting of a filler with activated sludge deposited on the surface. Submerged filter bed for biological treatment by passing through a packed bed, treated water of the submerged filter bed, and sludge separator for separating sludge from backwash water generated when the submerged filter bed is backwashed An organic wastewater treatment apparatus comprising a sludge solubilizer for solubilizing sludge separated by the sludge separator, and means for returning the solubilized sludge solubilized liquid to the aeration tank.   An aeration tank in which organic wastewater is passed through and brought into contact with floating microbial sludge for biological treatment, including a filler on which activated sludge has formed on the surface. Fluidized bed tank to be mixed and aerated with the material, sludge separator to separate sludge from the treated water of the fluidized bed tank, sludge solubilizer to solubilize sludge separated by the sludge separator, and after solubilization An organic wastewater treatment apparatus comprising means for returning the sludge solubilizing solution to the aeration tank. The solubilization treatment is a treatment with an alkali agent and one or more treatments selected from a treatment with a homogenizer, a treatment with a mixer, a treatment with a mill, a treatment with high pressure and instantaneous decompression expansion, and a treatment with an oxidizing agent. The organic waste water treatment apparatus of Claim 1 or 2.

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