JP2004041953A - Method and equipment for treating organic waste water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and equipment for organic waste water treatment capable of reducing the load on an aerobic biological treatment equipment capable of increasing the concentration of the sludge to be supplied to a solubilization treating step to a desirable concentration and supplying such sludge, capable of making facilities compact, and capable of making the discharge amount of the excess sludge lower or zero. <P>SOLUTION: The method of treating the organic waste water is characterized by being provided with an aerobic biological treating step for the organic waste water, a first solid-liquid separating step and second solid-liquid separating step of performing the solid-liquid separation of the sludge in the liquid mixture of the aerobic biological treating step, a sludge returning step of returning the sludge separated in the first solid-liquid separating step to the biological treating step, a sludge thickening step of the sludge separated in the second solid-liquid separating step, a solubilization treating step of the thickened sludge, and a solubilizing liquid returning step of returning the solubilizing liquid subjected to the solubilization treatment to the biological treating step. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a wastewater treatment method and apparatus for biologically treating organic wastewater, and more particularly, to an organic wastewater capable of reducing or eliminating the amount of excess sludge generated in the step of aerobically treating organic wastewater. The present invention relates to a method and an apparatus for treating wastewater.
[0002]
[Prior art]
Conventionally, as an apparatus for treating organic wastewater such as sewage, food wastewater, kitchen wastewater or septic tank sludge, an activated sludge treatment apparatus, a fixed-bed biological treatment apparatus, a fluidized-bed treatment apparatus, and the like have been used.
[0003]
In the activated sludge treatment apparatus, an organic wastewater (hereinafter simply referred to as wastewater) is supplied into an aerobic aerobic biological treatment tank in which sludge, which is an aerobic microorganism, floats, and is aerated with air to produce suspended sludge. It is a device that oxidatively decomposes organic matter in wastewater by the biological action of microorganisms that constitutes, and in a fixed-bed type biological treatment device, a fixed bed of biological carriers is provided in a treatment tank, and air is applied. Microorganisms adhere to and grow on the surface of the carrier by aeration and oxidatively decompose organic matter in the wastewater by the biological action of the adhered microorganisms. By filling the liquid inside the cell with the biological carrier so that it can flow, supplying wastewater and aerating with air, the organic matter in the wastewater is oxidized by the biological action of microorganisms attached and grown on the surface of the biological carrier to be fluidized. It is a device that disassembles .
[0004]
In any of the above-mentioned aerobic biological treatment apparatuses, a large amount of microorganisms that have proliferated are generated as sludge as biological substances are biologically decomposed. The generated sludge is separated and concentrated in a sedimentation tank, etc., and part of the sludge is circulated to the biological treatment process, but the remainder is discharged outside the system as surplus sludge. The sludge is reduced by anaerobic digestion in combination with an anaerobic digester. It is said that the amount of excess sludge generated in the aerobic biological treatment apparatus is 20 to 50% of the amount of organic matter (BOD) in the wastewater introduced into the biological treatment step.
[0005]
Further, as a method of reducing the volume of generated sludge as much as possible, Japanese Patent Application Laid-Open No. 6-509986 discloses that a medium-temperature biological treatment tank and a thermophilic biological treatment tank are combined and generated from a medium-temperature biological treatment tank such as an activated sludge treatment tank. Sludge to be treated by thermophilic microorganisms by the biological action of thermophilic microorganisms in a thermophilic biological treatment tank, and then returned to a medium-temperature biological treatment tank to treat the thermophilic aerobic biologically treated sludge together with wastewater. A method for reducing the volume is disclosed, and Japanese Patent No. 3048889 discloses solid-liquid separation of a biological treatment liquid biologically treated in an aerobic biological treatment tank in a sedimentation tank, and separation of the settled sludge into a thermophilic microorganism. Discloses a method for reducing the volume of sludge in which a solubilization treatment is carried out by the biological action of the present invention, and the solubilized liquid is returned to the aerobic biological treatment tank for treatment. Further, Japanese Patent No. 2973761 discloses a method for reducing the volume of sludge which is obtained by extracting sludge from an aerobic biological treatment tank, subjecting the sludge to oxidative decomposition treatment by ozone treatment, and then returning the sludge to the aerobic biological treatment tank for treatment. I have.
[0006]
[Problems to be solved by the invention]
In the conventional method of disposing of excess sludge, in the method of concentrating and dewatering sludge and then incinerating or landfilling the sludge, even after concentration and dewatering of sludge, the water content is as high as 70 to 80% by weight, so that the bulk is large. In the case of requesting a waste disposal company to dispose of the wastewater, the cost of picking up the wastewater becomes high, and at present, the wastewater treatment accounts for much of the cost. In the landfill disposal, the remaining years of the industrial waste landfill are decreasing, and the collection cost is increasing year by year. In addition, incineration disposal requires high fuel consumption due to high water content, increases fuel cost, and requires disposal of exhaust gas and incineration ash.In recent years, incineration itself has become difficult due to dioxin problems. It is a situation that is becoming more common.
[0007]
In the method of reducing the volume by the anaerobic digestion method, sludge is supplied into a treatment tank in which anaerobic microorganisms such as methane bacteria are suspended, and the organic matter in the sludge is supplied by the biological action of the anaerobic microorganism. Is a method of decomposing methane gas into methane gas or carbon dioxide gas, which has the advantage that methane gas can be effectively used as fuel, but because of the time it takes to process, equipment such as digestion tanks becomes excessively large, Since the amount of sludge is large and must be disposed of, the problems in incineration and landfill disposal cannot be solved.
[0008]
Further, in the method disclosed in Japanese Patent No. 2973761, the equipment cost of the ozone production apparatus is expensive, and the oxygen in the ozone-containing gas is not effectively used, so that the equipment cost and the operating cost increase. However, the sludge volume reduction method disclosed in Japanese Patent Application Laid-Open No. 6-509986 has a problem that the process is complicated and requires a long processing time because the process is performed by a plurality of cycle operations.
[0009]
Furthermore, in the sludge volume reduction method disclosed in Japanese Patent Publication No. 6-509986 and Japanese Patent No. 3048889, etc., the biologically treated liquid is subjected to solid-liquid separation in a sedimentation tank, and the sludge separated and settled. At least a portion is solubilized, and the solubilized liquid is returned to the aerobic biological treatment tank for processing.However, the amount of excess sludge generated is larger than the amount of wastewater treated, for example, in food drainage facilities, The amount of sludge to be solid-liquid separated in the sedimentation tank is increased by 1.5 to 2 times or more, which may cause problems such as insufficient sludge separation ability and reduced concentration due to short settling time. In addition, when a trouble such as bulking occurs in the biological treatment tank, there is a problem that it is difficult to settle and separate sludge in the sedimentation tank.
[0010]
The present invention has been made in view of the problems in the conventional organic wastewater treatment method and volume reduction treatment method, and can reduce the load on the aerobic biological treatment apparatus, The concentration of sludge to be supplied to the solubilization process can be increased to a preferable concentration, and the equipment such as a settling tank, a sludge concentrator, and a solubilization device can be made compact, and excess sludge can be discharged. The purpose of the present invention is to provide an organic wastewater treatment method and apparatus capable of reducing or eliminating the amount.
[0011]
[Means for Solving the Problems]
The gist of the present invention for achieving the above object is that, in the invention described in claim 1, an aerobic biological treatment step for aerobic biological treatment of organic wastewater, and a biological treatment in the aerobic biological treatment step. A first solid-liquid separation step and a second solid-liquid separation step of solid-liquid separation of the sludge in the mixed liquid, and returning the sludge separated in the first solid-liquid separation step to the aerobic biological treatment step as return sludge. A sludge returning step, a sludge concentration step of concentrating the sludge separated in the second solid-liquid separation step, a solubilization treatment step of solubilizing the sludge concentrated in the sludge concentration step, and a solubilization step. An organic wastewater treatment method, comprising a solubilized solution returning step of returning a solubilized solution that has been solubilized in a treatment step to the aerobic biological treatment step.
[0012]
Further, in the invention described in claim 2, an aerobic biological treatment device for aerobic biological treatment of organic wastewater, and solid-liquid separation of sludge in a mixed solution biologically treated by the aerobic biological treatment device. A first solid-liquid separator and a second solid-liquid separator, a sludge return path for returning the sludge separated by the first solid-liquid separator to the aerobic biological treatment device as return sludge, and the second solid-liquid. A sludge concentrator for concentrating the sludge separated by the separation device, a solubilization device for solubilizing the sludge concentrated by the sludge concentrator, and a solubilizing solution solubilized by the solubilization device An organic wastewater treatment apparatus, wherein a solubilized liquid return path for returning the solubilized liquid to the aerobic biological treatment apparatus is provided.
[0013]
According to the configuration of claim 1 or 2, since the concentrated sludge to be supplied to the solubilization treatment step is obtained in a separate system from the sludge returned to the aerobic biological treatment step, the sludge is supplied to the aerobic biological treatment apparatus. Load, and the concentration of sludge to be supplied to the solubilization process can be increased to a preferable concentration, so that the equipment such as a sedimentation tank, a sludge concentration device, and a solubilization device can be provided. Can be made compact. Therefore, it is possible to reduce equipment costs and operating costs of equipment capable of reducing or eliminating the amount of surplus sludge discharged.
[0014]
In the invention described in claim 3, the first solid-liquid separation device and the second solid-liquid separation device described in claim 2 are organic wastewater treatment devices that are sedimentation tanks that settle and separate sludge.
With the configuration according to the third aspect, the operation management of the equipment is facilitated and the equipment cost can be reduced.
[0015]
Further, in the invention described in claim 4, the first solid-liquid separation device according to claim 2 is a settling tank for settling and separating sludge, and the second solid-liquid separation device is a immersion separation membrane for separating sludge by membrane. It is an organic wastewater treatment device.
According to the configuration of the fourth aspect, the operation management of the facility becomes easy and the concentration of the sludge can be easily adjusted.
[0016]
Further, in the invention described in claim 5, the solubilization treatment apparatus according to claim 2, 3, or 4 blows an oxygen-containing gas into the separated sludge to form an aerobic atmosphere, and a temperature of 45 to 100 ° C. This is an organic wastewater treatment device that is a high-temperature aerobic digestion tank that performs a thermophilic aerobic biological treatment by the biological action of a thermophilic microorganism under high temperature conditions.
According to the configuration of the fifth aspect, the microorganisms that form sludge by the biological action of the aerobic and thermophilic microorganisms are efficiently killed and decomposed into low molecular organic substances, and are solubilized. As a result, operating costs and equipment costs can be reduced.
[0017]
In each of the above claims, the aerobic biological treatment apparatus in the aerobic biological treatment step may have a configuration in which a plurality of tanks are connected in series, and a fixed-bed treatment tank or a biological carrier in which a biological carrier is fixed and filled can be made to flow. A filled fluidized bed biological treatment tank or the like may be used. Further, the sludge concentration device in the sludge concentration step is preferably a centrifugal concentration device, but may be a membrane separation device or a filtration device.
[0018]
Further, the solubilization treatment apparatus in the solubilization treatment step is preferably a high-temperature aerobic digestion tank, but an ozone solubilization treatment tank that oxidizes and decomposes sludge with an ozone and an alkali solubilization that alkali-decomposes sludge under alkaline conditions of pH 9 to 11. An appropriate solubilizing apparatus such as a processing tank or a processing apparatus using them together with heating or ultrasonic waves can be used. The high-temperature aerobic digestion tank is preferably heated by a heating device such as steam, and may be provided with a heat exchanger for exchanging heat between the concentrated sludge and the solubilized liquid. The gas phase part and the liquid phase part of all the divided tanks are provided so as to communicate with each other, and all the tanks are partially provided with a diffuser for blowing an oxygen-containing gas and / or a gas circulation unit for circulating a gaseous gas. It is good also as a structure provided with the air diffuser. Further, the gas circulation path for circulating the gaseous phase gas in the liquid phase may be provided inside or outside the high-temperature aerobic digestion tank, and provided with a suitable stirring means such as a screw-type stirrer or a paddle-type stirrer. Is also good. The operating temperature is 45 to 100 ° C, preferably 55 to 75 ° C.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a system diagram of a wastewater treatment device according to one embodiment of the present invention, and FIG. 2 is a system diagram of a wastewater treatment device according to another embodiment of the present invention.
[0020]
In the figure, reference numeral 1 denotes an organic substance in raw water by aerating a raw water such as sewage, food wastewater, kitchen wastewater or septic tank sludge with an oxygen-containing gas such as air in which a diffuser 1a is provided in a bottom portion. The aerobic biological treatment tank for activated sludge treatment, which is an aerobic biological treatment step for aerobic biological treatment, is a first solid-liquid separation step for solid-liquid separation of sludge in the biologically treated mixture. 2a in 1 is a 1st settling tank, 2b in FIG. 2 is a settling tank. 3 is a second solid-liquid separation step for solid-liquid separation of sludge in the mixed liquid biologically treated similarly to the first solid-liquid separation step, 3a in FIG. 1 is a second sedimentation tank, and 3b in FIG. It is an immersion separation membrane device.
[0021]
Reference numeral 4 denotes a centrifugal concentrator in the sludge concentration step for concentrating the sludge separated in the second solid-liquid separation step 3, and reference numeral 5 denotes a solubilization treatment in which a diffuser 5a is provided at the bottom to solubilize the concentrated sludge. It is a high-temperature aerobic digestion tank that performs an aerobic atmosphere by blowing an oxygen-containing gas into the concentrated sludge, which is a process, and performs a thermophilic aerobic biological treatment by a biological action of a thermophilic microorganism at a high temperature of 45 to 100 ° C. .
Although not shown, the high-temperature aerobic digestion tank 5 is provided with a steam heating device for heating sludge in the digestion tank.
[0022]
Further, in the above-described embodiment, a normal activated sludge treatment tank is disposed in the aerobic biological treatment step, but a fixed-bed treatment tank in which a biological holding carrier such as synthetic resin or fibrous material is fixed and filled. Or a fluidized bed biological treatment tank filled with a biological holding carrier so as to be able to flow, and usually, an adjustment tank for adjusting the wastewater supply amount and pH value of raw water is provided at the previous stage of the aerobic biological treatment step. .
[0023]
Further, the centrifugal concentrator is disposed in the sludge concentrating step, but may be a membrane separation device or a filtration device. Furthermore, although a high-temperature aerobic digestion tank is disposed in the solubilization treatment step, an ozone solubilization treatment tank that oxidizes and decomposes sludge with ozone, and an alkali solubilization treatment tank that performs alkaline decomposition of sludge under alkaline conditions of pH 9 to 11, Alternatively, a solubilization treatment device using heating and ultrasonic waves in combination with them can also be used.
[0024]
Next, a treatment method for treating organic wastewater (hereinafter referred to as raw water) by the wastewater treatment apparatus will be described in detail below.
If necessary, raw water whose pH and supply amount are adjusted by an adjusting tank (not shown) is supplied from the raw water supply path 10 to the aerobic biological treatment tank 1 for activated sludge treatment, and air supplied from the air diffuser 1a. By aeration with an oxygen-containing gas such as the above, organic matter in raw water is efficiently oxidatively decomposed by the biological action of sludge, which is a floating aerobic microorganism. Usually, in the aerobic biological treatment tank 1, the treatment is performed at a temperature of 10 to 45 ° C.
[0025]
In the aerobic biological treatment tank 1, the mixed liquid mixed with the sludge multiplied by the aerobic biological treatment step is supplied to the first settling tank 2 a or FIG. The sludge is spontaneously settled and separated by standing still in the sedimentation tank 2b, and the clarified treated water is discharged from the treated water discharge path 12 to the outside of the system. The sludge settled and separated in the first solid-liquid separation step 2 is extracted from the sludge extraction path 13 and returned as returned sludge for maintaining a predetermined sludge concentration in the aerobic biological treatment tank 1.
[0026]
Separately from the above, the mixed liquid mixed with the sludge multiplied by the aerobic biological treatment step in the aerobic biological treatment tank 1 passes from the mixed liquid discharge path 14 to the second solid-liquid separation step 3 in FIG. The sludge introduced into the two-sedimentation tank 3a or the immersion separation membrane device 3b in FIG. 2 is separated by natural sedimentation or permeation and concentration, and the clarified treated water is discharged from the treated water discharge path 15 to the outside of the system. Further, the sludge separated in the second solid-liquid separation step 2 is extracted from the sludge extraction path 16 and supplied to the centrifugal concentrator 4 in the sludge concentration step.
[0027]
The separated sludge supplied to the centrifugal concentrator 4 in the sludge concentrating step is separated into a concentrated sludge and a separated liquid by the action of centrifugal force. When the clarity is high, the separated liquid is directly discharged from the separated liquid discharge path 18a to the outside of the system. However, if there is a large amount of residual sludge, the sludge is returned to the second solid-liquid separation step 3 from the separation liquid circulation path 18b to recover sludge. In the sludge concentration step, it is possible to add a flocculant to coagulate the sludge. In this case, it is preferable to use an organic polymer flocculant. The sludge concentration condition in the sludge concentration step is a water content of 99% by weight or less, preferably 98 to 90% by weight.
[0028]
The concentrated sludge concentrated by the centrifugal concentrator 4 is supplied from the concentrated sludge supply path 17 to the high-temperature aerobic digestion tank 5 in the solubilization process, and the supplied concentrated sludge has a temperature of 45 to 100 ° C, preferably 55 to 100 ° C. By aeration at 75 ° C. for a residence time of 10 to 100 hours, preferably 10 to 50 hours, with an oxygen-containing gas such as air supplied from the air diffuser 5 a, biological aerobic and thermophilic microorganisms are used. Microorganisms that form sludge by the action are efficiently killed and decomposed to low molecular organic matter and solubilized.
[0029]
The solubilized solution that has been solubilized in the high-temperature aerobic digestion tank 5 in the solubilization step is returned from the solubilized solution return path 19 to the aerobic biological treatment tank 1 in the aerobic biological treatment step, and is subjected to the thermophilic aerobic organism. Since the organic matter and thermophilic microorganisms solubilized by the treatment are biologically oxidatively decomposed together with the organic matter in the wastewater, the amount of excess sludge generated can be reduced to zero or at least reduced.
[0030]
【Example】
Organic wastewater discharged from food factories is treated with activated sludge in an aerobic biological treatment tank, and the sludge in the biologically treated mixture is separated into solid and liquid in a sedimentation tank, and part of the separated sludge is returned as sludge. It is returned to the aerobic biological treatment tank, the remaining sludge is subjected to the thermophilic aerobic biological treatment by the biological action of the thermophilic microorganisms in the solubilization tank, and the solubilized lysate is returned to the aerobic biological treatment tank. In the conventional treatment method (Comparative Example), the sludge concentration in the aerobic biological treatment tank is obtained in a separate system from the sludge that returns the concentrated sludge to be solubilized to the aerobic biological treatment (implementation). Example), the amount of sludge returned from the sedimentation tank is reduced to 95 to 75% by weight, and the amount of sludge returned from the sedimentation tank is increased to 1.3 to 1.7 times. As a whole, sludge 1.5 to 2.0 times that of the example was drawn from the sedimentation tank. Ku was necessary.
[0031]
【The invention's effect】
The present invention obtains the concentrated sludge to be supplied to the solubilization treatment step in a separate system from the sludge returned to the aerobic biological treatment step, so that the load on the aerobic biological treatment apparatus can be reduced, Since the concentration of the sludge supplied to the solubilization treatment step can be increased to a preferable concentration, the equipment such as the sedimentation tank, the sludge concentration device, and the solubilization treatment device can be downsized. Therefore, there are provided a sludge treatment apparatus and a sludge treatment method capable of reducing equipment costs and operation costs of equipment capable of reducing or eliminating the amount of surplus sludge discharged.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a wastewater treatment apparatus according to one embodiment of the present invention. FIG. 2 is a schematic diagram of a wastewater treatment apparatus according to another embodiment of the present invention.
1: Aerobic biological treatment tank (aerobic biological treatment step)
2: First solid-liquid separation step 2a: First settling tank (first solid-liquid separation step)
2b: sedimentation tank (first solid-liquid separation step)
3: Second solid-liquid separation step 3a: Second precipitation tank (second solid-liquid separation step)
3b: Immersion separation membrane device (second solid-liquid separation step)
4: Centrifugal concentrator (sludge concentration process)
5: High temperature aerobic digestion tank (solubilization process)

Claims (5)

An aerobic biological treatment step for aerobic biological treatment of an organic wastewater, a first solid-liquid separation step and a second solid-liquid separation step for solid-liquid separation of sludge in the mixed liquid biologically treated in the aerobic biological treatment step A sludge return step of returning the sludge separated in the first solid-liquid separation step to the aerobic biological treatment step as return sludge; and a sludge for concentrating the sludge separated in the second solid-liquid separation step. A concentration step; a solubilization treatment step of solubilizing the sludge concentrated in the sludge concentration step; and a solubilization method of returning the solubilized solution solubilized in the solubilization treatment step to the aerobic biological treatment step. An organic wastewater treatment method comprising a liquid returning step. An aerobic biological treatment device for aerobic biological treatment of organic wastewater, a first solid-liquid separation device and a second solid-liquid separation device for solid-liquid separation of sludge in a mixed solution biologically treated by the aerobic biological treatment device An apparatus, a sludge return path for returning the sludge separated by the first solid-liquid separator to the aerobic biological treatment apparatus as return sludge, and a sludge for concentrating the sludge separated by the second solid-liquid separator. A concentrating device, a solubilizing device for solubilizing the sludge concentrated by the sludge concentrating device, and a solubilizing device for returning the solubilized solution solubilized by the solubilizing device to the aerobic biological treatment device. An organic wastewater treatment device comprising a liquid return path. The organic wastewater treatment device according to claim 2, wherein the first solid-liquid separation device and the second solid-liquid separation device are sedimentation tanks that settle and separate sludge. The organic wastewater treatment apparatus according to claim 2, wherein the first solid-liquid separation device is a settling tank for settling and separating sludge, and the second solid-liquid separation device is a submerged separation membrane device for separating sludge by membrane. A solubilization treatment device injects oxygen-containing gas into the separated sludge to form an aerobic atmosphere. The organic wastewater treatment apparatus according to claim 2, 3, or 4.

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