JP2004249213A - Excess sludge treatment apparatus and activated sludge treatment system using the apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simple excess sludge treatment apparatus capable of reducing the production amount of excess sludge without doing damage to environment, and an activated sludge treatment system using it. <P>SOLUTION: The excess sludge treatment apparatus 8a for treating excess sludge produced in an activated sludge treatment apparatus has an excess sludge treatment tank 9 into which excess sludge is introduced, the grinding parts 12 and 13 provided in the excess sludge treatment tank 9 and grinding excess sludge to activate the same, a first circulation part 14 for extracting the excess sludge 10 in the excess sludge treatment tank 9 to send out the extracted sludge to the grinding parts 12 and 13 while mixing air with the sludge, a second circulation part 18 for extracting the excess sludge 10 activated in the excess sludge treatment tank 9 to send out the same to the activated sludge treatment apparatus, a temperature detecting part 17 for detecting the temperature of the excess sludge 10 activated in the excess sludge treatment tank 9 and a flow rate control part 6 for regulating the introducing amount of the excess sludge into the excess sludge treatment tank 9 on the basis of the detection signal of the temperature detecting part 17. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an apparatus for treating excess sludge generated by an activated sludge method.
[0002]
[Prior art]
In general, organic wastewater treatment methods include chemical treatment, physicochemical treatment such as electric treatment, and biological treatment. Biological treatment is now preferred because many environmental issues are taken up. For this biological treatment, there are aerobic treatment that requires oxygen such as activated sludge method, anaerobic treatment that does not require oxygen such as methane fermentation method, and a treatment method that uses both aerobic treatment and anaerobic treatment. is there. Among them, the activated sludge method, which is one of the aerobic treatments, is mainly used for sewage treatment. In this method, wastewater containing organic matter is brought into contact with activated sludge and subjected to aeration and stirring to convert the wastewater into activated sludge and treated water, and finally to water and carbon dioxide. In addition, the methane fermentation method, which is one of the anaerobic treatments, is suitable for decomposing high-concentration organic substances such as food wastewater, garbage, and livestock manure.In the absence of oxygen, wastewater containing organic substances is converted to anaerobic bacteria. That is, it is decomposed by being brought into contact with methanogens and converted into methane gas and carbon dioxide gas. The generated methane gas is reused as clean gas.
However, in both the aerobic treatment and the anaerobic treatment, microorganisms grow at the stage of purifying pollutants, so that excess sludge that is unnecessary to maintain the balance of the treatment process is generated. For this reason, excess sludge generated in the reactor is drawn out with a pump, concentrated and dehydrated, and then treated by incineration, landfilling, or use as compost (compost) or construction material. -A plurality of steps, such as concentration, dehydration, and incineration, must be performed, and there is a problem that the processing requires a lot of labor and cost.
In addition, there is a problem that harmful substances such as dioxin may be generated in the incineration treatment. In addition, there is a problem that a large landfill must be secured in the landfill process, and the landfill may have an adverse effect on the environment.
[0004] In order to address such problems, several inventions and ideas have been disclosed.
For example, Patent Literature 1 has a name of “method of reducing excess sludge generated by activated sludge method, excess sludge reduction apparatus and crusher for sludge pulverization”, and includes excess sludge generated by activated sludge treatment apparatus. The invention which discloses a method for reducing crushing and grinding by shearing and grinding and an apparatus used therefor is disclosed.
Hereinafter, the technique disclosed in Patent Document 1 will be described with reference to FIG.
The apparatus for reducing excess sludge disclosed in Patent Document 1 includes an activated sludge treatment apparatus 32 for reacting wastewater with activated sludge as shown in FIG. 6A, and an activated sludge treatment apparatus 32 connected thereto. An excess sludge storage tank 33 for storing the excess sludge generated in the above, a sludge tank 34 for receiving the sludge temporarily stored in the excess sludge storage tank 33, and a crushing method for shearing and grinding the sludge supplied from the sludge tank 34 And a hopper 35 and a pump 39 for feeding the sludge finely pulverized by the crusher 31 to the sludge tank 34 connected thereto, and the sludge pulverized provided between the hopper 35 and the sludge tank 34. It comprises a cooler 36 for cooling and a flow meter 37 for measuring the flow rate of sludge returned from the crusher 31 to the sludge tank 34.
FIG. 6B is a schematic view showing the detailed structure of the crusher 31. The excess sludge stored in the sludge tank 34 is drawn out by the pump 38 and crushed from the sludge introduction part 40 above the outer jacket 46. The upper disk 42 is fed into the gap between the upper disk 42 and the lower disk 43 from the opening of the upper disk 42. The upper disk 42 is fixed and does not rotate, but the lower disk 43 is fixed to the driving force transmitting unit 44 connected to the high-speed rotation motor 45, so that high-speed rotation can be performed. Therefore, the excess sludge flowing into the gap between the upper disk 42 and the lower disk 43 is sheared and crushed by the high-speed rotation of the two disks, the upper disk 42 and the lower disk 43. Then, the surplus sludge that has been sheared and crushed is sent to the hopper 35 through the discharge unit 41, and is returned to the sludge tank 34 again by the pump 39. Since the excess sludge is pulverized by being subjected to shear crushing and grinding, the sludge mass is crushed and the surface area of the high-molecular organic matter composed of dead microorganisms increases. At the same time, the microorganisms in the sludge are also ground, so that the organic substance decomposing enzyme is extracted from the inside of the ground microorganisms. As a result, the organic decomposing enzyme and the high molecular organic substance come into contact with and react with each other with a large surface area, so that the low molecular weight of the high molecular organic substance, that is, the solubilization of excess sludge can be promoted. Further, the excess sludge stored in the sludge tank 34 is circulated in the order of the crusher 31, the hopper 35, the cooler 36, the flow meter 37, the sludge tank 34, and the crusher 31, and is repeatedly subjected to shear crushing and grinding. Since part of the excess sludge in the sludge tank 34 is returned to the activated sludge treatment tank 32, the amount of excess sludge generated can be reduced.
[0007] Further, Patent Document 2 discloses a method for treating excess sludge under the name of "method for treating activated organic wastewater" as an excess sludge treatment, in addition to the treatment by grinding, such as ozone and hydrogen peroxide. An invention relating to a method for treating excess sludge using an oxidizing gas, an alkali chemical such as sodium hydroxide, a mineral acid such as hydrochloric acid, an anaerobic treatment such as an acid fermentation, a heat treatment, a pulse discharge treatment, an ultrasonic treatment or the like is disclosed. .
The excess sludge generated in the activated sludge treatment is inferior in activity to the activated sludge. By applying energy such as ultrasonic waves to destroy and solubilize the cell walls of microorganisms in sludge, that is, high-molecular organic matter, decomposition is promoted, and the amount of excess sludge generated can be reduced.
[0008]
[Patent Document 1]
JP 2001-70993 A
[Patent Document 2]
JP 2001-96290 A
[0009]
[Problems to be solved by the invention]
However, in the above-described conventional technology, for example, in the invention disclosed in Patent Document 1, the excess sludge can be reduced by pulverizing the excess sludge to promote the decomposition of the high-molecular organic matter in the excess sludge. However, there is a problem that the processing rate of surplus sludge cannot catch up with the activated sludge processing rate because the biological decomposition rate is generally slow. In addition, a hopper and a cooler must be provided in addition to the crusher, and there is a problem that the entire sludge treatment system becomes a large-scale device.
[0010] In the invention disclosed in Patent Document 2, it is possible to improve the treatment capacity of excess sludge by using ozone treatment, chemical treatment, heat treatment, pulse discharge treatment, ultrasonic treatment or the like having high decomposition ability. Although it can be done, the problem of high cost in the ozone treatment, and the problem of taking time and effort in the treatment of chemicals after use in the chemical treatment, as well as the need to consider the environment and the corresponding equipment etc. There is a problem that even microorganisms in sludge may be killed, but there is a problem that the apparatus is increased in pulse discharge treatment and ultrasonic treatment.
SUMMARY OF THE INVENTION The present invention has been made in view of such a conventional situation, and has an excess sludge treatment apparatus which is simple and can reduce the amount of excess sludge generated without harming the environment. An object of the present invention is to provide an activated sludge treatment system.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, a surplus sludge treatment apparatus according to the first aspect of the present invention includes a surplus sludge treatment tank for introducing surplus sludge from an activated sludge treatment apparatus, and a surplus sludge provided in the surplus sludge treatment tank. A grinding unit that crushes and activates, a first circulation unit that extracts surplus sludge in the excess sludge treatment tank, mixes air, and sends the mixture to the grinding unit, and extracts excess sludge in the excess sludge treatment tank. A second circulating section for sending out to the activated sludge treatment apparatus, a temperature detecting section for detecting the temperature of the excess sludge in the excess sludge treatment tank, and introduction of the excess sludge into the excess sludge treatment tank based on a detection signal of the temperature detecting section. And a flow control unit for adjusting the amount.
The excess sludge treatment apparatus having the above-described structure is configured to finely pulverize a mixture of air and excess sludge in the grinding section, thereby reducing the amount of excess sludge and increasing the contact area between the excess sludge and the microorganisms. It has the effect of improving the activity of surplus sludge by supplying air to the microorganisms. Further, the first circulating section has an effect of activating the excess sludge by circulating the excess sludge to the grinding section in the excess sludge treatment tank. Further, by controlling the amount of surplus sludge introduced from the activated sludge treatment device to the surplus sludge treatment tank by the flow rate control unit, the temperature of the surplus sludge treatment device is controlled to rise.
[0013] The surplus sludge treatment apparatus according to the second aspect of the present invention includes a surplus sludge treatment tank for introducing surplus sludge from the activated sludge treatment apparatus, and a surplus sludge provided in the surplus sludge treatment tank for grinding excess sludge. A crushing unit for activating the excess sludge, a first circulating unit for extracting excess sludge in the excess sludge treatment tank and sending it to the grinding unit, an air supply unit for supplying air to the grinding unit, and an excess sludge treatment. A second circulating section for sending the excess sludge in the tank to the activated sludge treatment apparatus, a temperature detection section for detecting the temperature of the excess sludge in the excess sludge treatment tank, and a detection signal from the temperature detection section to the excess sludge treatment apparatus. And a flow control unit for adjusting the amount of surplus sludge introduced.
In the surplus sludge treatment apparatus having the above structure, in addition to the operation of the invention described in claim 1, air is mixed with the surplus sludge into the grinding section separately without mixing, so that air is mixed in the first circulation section. Has the effect of preventing a decrease in the circulation speed of excess sludge, and has the effect that air supply control can be performed independently of the excess sludge to be circulated.
Finally, an activated sludge treatment system according to a third aspect of the present invention comprises an activated sludge tank for reacting wastewater with activated sludge while aerating, and a product in the activated sludge tank connected to the activated sludge tank. Activated sludge treatment apparatus having an excess sludge storage tank that separates activated sludge into treated water and activated sludge and accumulates excess activated sludge as excess sludge, and sends some activated sludge in the excess sludge storage tank to the activated sludge tank It has a circulation part and an excess sludge treatment device according to claim 1 or 2 which is connected to the activated sludge treatment device and treats excess sludge.
In the activated sludge treatment system having the above configuration, the excess sludge is treated by using the excess sludge treatment device according to claim 1 or 2, and is circulated again to the activated sludge treatment device, thereby causing the excess sludge generated by the activated sludge treatment. Has the effect of lowering the amount of phenol.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of a surplus sludge treatment apparatus and an activated sludge treatment system using the same according to the present invention will be described below with reference to FIGS.
First, an embodiment of a surplus sludge treatment apparatus and an activated sludge treatment system using the same according to the present invention will be described with reference to FIGS. (Corresponding to claims 1 to 3)
FIG. 1 (a) is a conceptual diagram of a surplus sludge treatment apparatus and an activated sludge treatment system including the same according to a first embodiment of the present invention. An activated sludge treatment apparatus including a sludge tank 1, an excess sludge storage tank 3 for separating and accumulating products in the activated sludge tank into a treated water 4 and an activated sludge 5, and an unnecessary activated sludge generated by the activated sludge treatment That is, it is composed of a surplus sludge treatment device 8a for treating surplus sludge. Then, while further processing the excess sludge that is hardly decomposed by microorganisms, the activated sludge treatment system is repeatedly circulated and treated in the activated sludge tank 1, the excess sludge storage tank 3, the excess sludge treatment device 8a, and the activated sludge tank 1 in this order. The final conversion into carbon dioxide and water reduces excess sludge generation.
Here, a sewage treatment method using an activated sludge treatment system will be described with reference to FIG.
First, organic wastewater discharged from a home, a factory, or the like is fed into the activated sludge tank 1 from a pipe 19. Activated sludge 2 is contained in the activated sludge tank 1 in advance, and the organic matter in the sewage is decomposed into carbon dioxide, treated water 4 and activated sludge 5 by reacting the sewage with the activated sludge 2 while aerating. Then, the sludge is sent to the surplus sludge storage tank 3 through the pipe 21 and separated into the treated water 4 and the activated sludge 5. The air for aeration is sent in from the pipe 20. Further, the separated treated water 4 is drained to the outside from the pipe 22 as it is, but a part of the activated sludge 5 is returned to the activated sludge tank 1 through the pipe 23b to be reused as activated sludge, and the remaining Is extracted as excess sludge by the pump 6 to the excess sludge treatment device 8a via the pipe 23a, further processed, and returned to the activated sludge tank 1 again.
Next, an excess sludge treatment apparatus in the activated sludge treatment system will be described.
In FIG. 1A, the excess sludge drawn from the excess sludge storage tank 3 by the pump 6 is sent out to the excess sludge treatment tank 9 and stored in the lower part of the excess sludge treatment tank 9.
A lower disk 13 is fixed to the upper part of the excess sludge treatment tank 9, and the upper disk 12 is rotated at a high speed by the rotary motor 11 while forming a small gap with the lower disk 13.
The excess sludge 10 stored in the lower part of the excess sludge treatment tank 9 is extracted by the pump 14 through the pipe 24a, and is mixed with the air sent from the pipe 26 while forming a gap formed by the upper disk 12 and the lower disk 13. Supplied to. Excess sludge 10 sent into this gap is ground and refined by an upper disk 12 and a lower disk 13. In addition, the mixed air is also fined together with the excess sludge 10 and water by the centrifugal force between the upper disk 12 and the lower disk 13.
As described above, the excess sludge which has been solidified at the bottom of the excess sludge storage tank 3 and whose activity as the activated sludge has been reduced is ground to fine particles to remove microorganisms present in the excess sludge 10. The contact area with the organic matter in the excess sludge can be increased. Moreover, by mixing with air and grinding to make the air finer, the contact area between the excess sludge and the air can be enlarged and abundant oxygen can be supplied. That is, it is possible to increase the dissolution rate of oxygen and always maintain the dissolved oxygen concentration in the excess sludge in a saturated state. Therefore, the oxidative decomposition by microorganisms can be activated to activate the excess sludge 10 more.
FIG. 1B is a cross-sectional view taken along the line AA in FIG. 1A. The excess sludge 10 activated by grinding the upper disk 12 and the lower disk 13 is removed from the lower disk 13 and the excess sludge treatment. The excess sludge is stored in the excess sludge treatment tank 9 again by flowing through an inner wall surface of the excess sludge treatment tank 9 through a gap provided between the tank 9 and the excess sludge treatment tank 9.
Further, a part of the activated excess sludge 10 stored in the excess sludge treatment tank 9 is guided to a gap between the upper disk 12 and the lower disk 13 and circulates between the excess sludge treatment tank 9.
The circulation flow rate of the excess sludge 10 and the mixing ratio of the excess sludge 10 to the air can be adjusted by valves 15 and 16, respectively, and the oxygen required for microorganisms in the excess sludge 10 always activated by the above-described circulation. That is, BOD (biochemical oxygen demand) can be provided to the excess sludge 10. Thereby, in the excess sludge treatment tank 9, the aerobic microorganisms contained in the excess sludge 10 are supplied with dissolved oxygen and actively activated to promote oxidative decomposition to carbon dioxide and water. It is possible to promote the reduction of excess sludge more than when crushed. Further, a part of the activated excess sludge 10 is returned to the activated sludge tank 1 through the pipe 24b, and is used again for the activated sludge treatment. Therefore, as a whole system, the excess sludge generated by the activated sludge treatment is circulated in the activated sludge treatment system while being repeatedly milled while mixing air with the activated sludge, thereby activating the deactivated excess sludge. Weight loss can be further promoted.
Further, the excess sludge treatment device 8a is provided with a thermometer 17 for detecting the temperature of the excess sludge 10 in the excess sludge treatment tank 9, and the thermometer 17 is provided with the excess sludge in the excess sludge treatment tank 9. It is connected to a valve 7 for adjusting the amount of sludge introduced and a valve 18 for adjusting the amount of activated excess sludge 10 in the excess sludge treatment tank 9 to be returned to the activated sludge tank 1. Therefore, even if the temperature of the excess sludge 10 rises due to frictional heat generated in the grinding treatment, the excess sludge is introduced into the excess sludge treatment tank 9 by the valve 7 to cool the excess sludge 10 and to cool the excess sludge. Since the temperature rise of the excess sludge 10 can be suppressed, the temperature of the excess sludge 10 can be maintained at a temperature at which the microorganisms do not die or a temperature at which the microorganisms are actively activated, and the microorganisms are oxidatively decomposed by the microorganisms in the excess sludge treatment tank 9. That is, it is possible to further promote the reduction of excess sludge, and it is not necessary to provide a cooling device in addition to the grinding device as in the related art, so that the entire system can be made compact. Also, since the discharge amount of the excess sludge 10 activated by the valve 18 can be adjusted, even when the amount of the excess sludge introduced is increased by opening the valve 7 for temperature control, the excess sludge treatment tank 9 can be used. It can be adjusted so that the amount of surplus sludge 10 in the inside does not increase too much.
In the activated sludge treatment system shown in FIG. 1A, air is introduced as an aeration unit and an oxygen supply source of the first circulation unit, but oxygen may be introduced directly.
A method for treating excess sludge using the apparatus for treating excess sludge according to the second embodiment of the present invention will be described with reference to FIG.
FIG. 2 is a conceptual diagram of an excess sludge treatment apparatus according to a second embodiment of the present invention. In the excess sludge treatment apparatus 8a shown in FIG. The excess sludge is treated by mixing and circulating and grinding the air. However, in the excess sludge treatment apparatus 8b shown in FIG. 2, the excess sludge 10 and the air are separately supplied to the gap between the upper disk 12 and the lower disk 13, respectively. Surplus sludge is treated by grinding and circulating excess sludge. 2, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and the description of the configuration will be omitted.
As shown in FIG. 2, the excess sludge 10 ground and activated by the upper disk 12 and the lower disk 13 is drawn out by the pump 28 without mixing air, and is passed through the pipe 24a. The air and oxygen necessary for the oxidative decomposition of the microorganisms in the activated excess sludge 10 while being ground by the lower disk 13 are sent directly between the upper disk 12 and the lower disk 13 through the pipe 29. In the excess sludge treatment apparatus 8a shown in FIG. 1A, the excess sludge 10 and the air are separated into a two-phase flow in a pipe 25 for circulating the activated excess sludge 10 and the air together, and a pipe 24a for the excess sludge 10 is formed. , 25, there is a possibility that the excess sludge treatment capacity will be reduced, but the excess sludge treatment device 8b separates the excess sludge 10 and air separately from the upper disk 12 and the lower disk 13 between the upper disk 12 and the lower disk 13. , The circulation speed of the excess sludge 10 can be increased, and at the same time, the processing capacity of the excess sludge can be further improved. The flow rate of the excess sludge 10 can be adjusted by a valve 27, and the air and oxygen supplied by the pipe 29 can be independently adjusted by a valve or the like, though not shown.
In this embodiment or the first embodiment, air or oxygen is locally supplied by a pipe or the like. For example, the excess sludge treatment tank 9 may be set to an oxygen atmosphere or the like. However, it is preferable to directly mix the excess sludge with the excess sludge from the viewpoint of efficiently supplying air or oxygen to the excess sludge.
Finally, in the surplus sludge treatment apparatus and the activated sludge treatment system using the same, an experiment was conducted to examine the treatment capacity when air was introduced and when air was not introduced, and the results are described. .
First, in aerobic treatment such as activated sludge treatment, oxygen is essential for microorganisms to oxidatively decompose organic substances as contaminants, and the treatment capacity of microorganisms is related to the amount of dissolved oxygen in the solution. It was considered that the amount of dissolved oxygen was different between the case where air was introduced into the excess sludge 10 and the case where air was not introduced.
FIG. 3 is a graph showing the dissolved oxygen concentration in the excess sludge 10 at an arbitrary temperature when air is introduced from the valve 16 and when air is not introduced. It is natural that the lower the liquid temperature, the more dissolved oxygen is dissolved in the solution. However, when air is introduced, the dissolved oxygen is increased by about 1 mg / L at each temperature as compared with the case where air is not introduced. It can be seen from FIG. 3 that the activated excess sludge is dissolved in the activated excess sludge 10. This is because the dissolved oxygen concentration is almost saturated when air is introduced, whereas the dissolved oxygen concentration in the activated excess sludge 10 is saturated when air is not introduced. It is shown that it is in an unsaturated state. In other words, when air is introduced, oxygen necessary for microbial decomposition is sufficiently provided and the processing capacity of microorganisms is extracted to the maximum. It can be said that sufficient oxygen is not given to the microorganisms, and that the processing ability of microorganisms is reduced. Therefore, it is considered that the microorganisms can exhibit higher treatment capacity when air is introduced than when air is introduced.
Next, the dissolved oxygen concentration, BOD and MLSS (active sludge suspended matter) amount in the excess sludge treatment apparatus 8a were measured when air was introduced into the excess sludge 10 and when air was not introduced. And the sludge treatment capacity was compared.
In the experiment, after adding 5 liters of excess sludge to the excess sludge treatment tank 9, the excess sludge is activated by grinding with the upper disk 12 and the lower disk 13, and the air is mixed with or without air. The operation of circulating the excess sludge 10 with the pump 14 and grinding it with the upper disk 12 and the lower disk 13 is repeated, and the concentration of dissolved oxygen, BOD, MLSS and temperature in the excess sludge treatment tank 9 for a certain period of time are measured. Was. At this time, the rotation speed of the upper disk 12 was 1600 rpm, the circulation amount of the pump 14, that is, the flow rate of the excess sludge 10 was 24 L / min, and the air introduction amount from the valve 16 was 20 cc / min.
The measurement result of the dissolved oxygen concentration in the excess sludge treatment tank 9 will be described with reference to FIG. As shown in FIG. 3, it is known that the concentration of dissolved oxygen is higher when air is introduced than when air is introduced, and the dissolved oxygen concentration after 1 hour from the measurement is also shown in FIG. 4 (a). It can be confirmed that the oxygen concentration is higher by about 1 mg / L when air is introduced. Further, from FIG. 4A, the dissolved oxygen concentration sharply decreases for 1 to 3 hours after the start of the measurement regardless of the introduction of air. This is probably because surplus sludge activated by grinding consumes oxygen rapidly. Although the dissolved oxygen concentration increases again after 4 hours, the dissolved oxygen concentration after 4 hours increases to almost the same concentration as that after 1 hour when air is introduced. It can be seen that when the introduction was not performed, the concentration did not reach the concentration one hour after the measurement. From this, assuming that each dissolved oxygen concentration one hour after the measurement is the dissolved oxygen concentration in a saturated state, when air is introduced, a constant amount of oxygen is always supplied to the excess sludge 10 to reduce the saturated state. While oxygen is not supplied, the dissolved oxygen concentration in the excess sludge 10 is in an unsaturated state.
FIG. 4B is a graph showing the measurement results of the BOD in the excess sludge treatment tank 9, and this BOD indicates the amount of oxygen required by the microorganisms in the excess sludge 10 for decomposition. At the same time, it corresponds to the ability to decompose microorganisms in surplus sludge 10. As described above, one hour after the measurement, the excess sludge 10 activated by the grinding requires a large amount of oxygen, so that the BOD is rapidly increased both when oxygen is introduced and when oxygen is not introduced. . After that, when no air was introduced, the BOD rapidly decreased and then gradually decreased to approach the initial value. However, when air was introduced, the BOD hardly decreased even after 64 hours. You can see that. Thus, when air is introduced, the amount of oxygen consumed by the microorganisms in the activated excess sludge 10 can be sufficiently supplied, so that the ability to decompose the microorganisms in the excess sludge 10 is maximized. It is considered that microorganisms are always decomposing a certain amount of excess sludge. In addition, when air is not introduced, the excess sludge cannot be constantly treated because the amount of oxygen consumed by the microorganisms in the activated excess sludge cannot be sufficiently supplied. It can be seen that the ability of microorganisms to degrade gradually decreases.
FIG. 4 (c) is a graph showing the measurement results of MLSS in the excess sludge treatment tank 9, where MLSS is the amount of organic matter in the excess sludge treatment tank 9, that is, This indicates the amount of excess sludge that has not been processed. Therefore, it is considered that when the excess sludge is decomposed and reduced, the MLSS also decreases accordingly. In addition, when air was introduced, the amount of MLSS gradually and slowly decreased from 9600 mg / L after 1 hour to 8000 mg / L after 64 hours, indicating that excess sludge was decomposed. Understand. On the other hand, when air was not introduced, although it decreased steadily until 40 hours later, it can be seen that the MLSS amount increased again and decreased again. This is probably because the MLSS in the excess sludge treatment tank 9 has become uneven due to the circulation.
FIG. 4D is a graph showing the measurement results of the temperature in the excess sludge treatment tank 9 during the reaction. The excess sludge was removed in both cases where air was introduced and when air was not introduced. It can be seen that the temperature in the excess sludge treatment tank 9 increases one hour and two hours after the start of grinding by friction, but thereafter gradually decreases. This is considered to be because the large sludge in the excess sludge was crushed in the first two hours, the particles in the excess sludge were made uniform, and the frictional heat due to the grinding was hardly generated.
Finally, an experiment similar to that shown in FIG. 4 (when air was introduced) was carried out by changing the unit of time from hours to days, and the MLSS, BOD, COD (chemical oxygen demand) in the excess sludge treatment tank 9 were measured. ) And dissolved oxygen concentration were measured for comparison.
FIG. 5A is a graph showing the measurement results of the MLSS in the excess sludge treatment tank 9, and similarly to the measurement results of FIG. 4C, the MLSS amount decreases until about the second day, ie, Although the surplus sludge has decreased only slightly, a remarkable phenomenon can be seen after 2.5 days. From this, it can be seen that although the grinding process takes time, the excess sludge is surely reduced.
FIG. 5B shows the measurement results of BOD and COD in the excess sludge treatment tank 9. Although the shape of the graph is slightly different from that of FIG. 4B for BOD, it is considered that the behavior is similar in that BOD once increases and then decreases and shows a constant value. As described above, the excess sludge activated by attrition requires a large amount of oxygen, so that the BOD rapidly increases immediately after the reaction and then gradually decreases. Further, in the excess sludge 10, COD shows the same behavior as BOD, and it is understood that not only biochemical decomposition but also chemical decomposition, that is, oxidation using an oxidizing agent, is performed.
FIG. 5 (c) shows the measurement results of the dissolved oxygen in the excess sludge treatment tank 9. Although not shown on the graph within 12 hours of the measurement, FIG. It is considered that after the decrease, the behavior of rapidly rising again is exhibited. Also, it can be seen that, after that, as in FIG.
The temperature during the experiment was in the range of 16 to 48 ° C.
[0036]
【The invention's effect】
As described above, in the excess sludge treatment apparatus according to claim 1 or 2 of the present invention, by introducing air or oxygen into the grinding treatment, the amount of excess sludge can be reduced as compared with the case of only the grinding treatment. Can be promoted. In addition, by controlling the temperature in the excess sludge treatment tank according to the detection signal of the temperature detection unit, it is possible to maintain a temperature at which the microorganisms in the excess sludge can be actively activated, and the decomposition ability of the microorganisms, that is, the processing capacity of the excess sludge Can be improved.
In particular, in the excess sludge treatment apparatus according to the second aspect, the excess sludge and the air are separately supplied to increase the circulation rate of the excess sludge, thereby improving the treatment capacity of the excess sludge. Can be.
In the activated sludge treatment system according to the third aspect of the present invention, the excess sludge is repeatedly circulated while the excess sludge is being treated by the excess sludge treatment apparatus according to the first or second aspect, thereby generating excess sludge in the entire system. The amount can be reduced. Further, by providing the temperature detection unit and the flow rate control unit in the excess sludge treatment apparatus, the necessity of a cooler can be eliminated, and the whole system can be made compact.
[Brief description of the drawings]
FIG. 1A is a conceptual diagram of an activated sludge treatment system including a surplus sludge treatment apparatus according to a first embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along line AA in FIG. FIG.
FIG. 2 is a conceptual diagram of a surplus sludge treatment device according to a second embodiment of the present invention.
FIG. 3 is a graph showing a change in dissolved oxygen concentration with respect to a change in liquid temperature (temperature of grinding excess sludge) in the excess sludge treatment apparatus according to the first embodiment of the present invention.
FIG. 4A is a graph showing a temporal change of a dissolved oxygen concentration in the excess sludge treatment apparatus according to the first embodiment of the present invention, and FIG. 4B is a graph showing the change over time in the first embodiment of the present invention. It is a graph which shows the temporal change of the BOD in the excess sludge processing apparatus which concerns on embodiment, and (c) is a graph which shows the temporal change of the MLSS amount in the excess sludge processing apparatus which concerns on 1st Embodiment of this invention. (D) is a graph showing a temporal change of the liquid temperature in the excess sludge treatment apparatus according to the first embodiment of the present invention.
FIG. 5A is a graph showing a time change of the MLSS in the excess sludge treatment apparatus according to the first embodiment of the present invention, and FIG. 5B is a graph showing the change over time in the first embodiment of the present invention. It is a graph which shows the temporal change of BOD and COD in such an excess sludge processing apparatus, and (c) is a graph which shows the temporal change of the dissolved oxygen in the excess sludge processing apparatus according to the first embodiment of the present invention. It is.
FIG. 6 (a) is a schematic diagram of a device for reducing excess sludge according to the related art, and FIG. 6 (b) is a schematic diagram of a crusher for sludge differential crushing.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Activated sludge tank 2 ... Activated sludge 3 ... Excess sludge storage tank 4 ... Treatment water 5 ... Activated sludge 6 ... Pump 7 ... Valve 8 ... Excess sludge treatment tank 9a, 9b ... Excess sludge treatment apparatus 10 ... Excess sludge 11 ... Rotation Motor 12 ... Upper disk 13 ... Lower disk 14 ... Pump 15 ... Valve 16 ... Valve 17 ... Thermometer 18 ... Valve 19 ... Piping 20 ... Piping 21 ... Piping 22 ... Piping 23a, 23b ... Piping 24a, 24b ... Piping 25 ... Piping 26 ... Piping 27 ... Valve 28 ... Pump 29 ... Piping 30 ... Reducer 31 ... Crusher 32 ... Activated sludge treatment apparatus 33 ... Excess sludge storage tank 34 ... Sludge tank 35 ... Hopper 36 ... Cooler 37 ... Flow meter 38 ... Pump 39 ... Pump 40 ... Sludge introduction part 41 ... Discharge part 42 ... Upper disk 43 ... Lower disk 44 ... Driving force transmission part 45 ... High speed Rolling motor 46 ... mantle

Claims (3)

In an excess sludge treatment device for treating excess sludge generated in the activated sludge treatment device, a surplus sludge treatment tank for introducing excess sludge from the activated sludge treatment device, and polishing the excess sludge provided in the surplus sludge treatment tank. A grinding unit that crushes and activates, a first circulation unit that extracts the surplus sludge in the surplus sludge treatment tank, mixes air therein, and sends the mixed air to the grinding unit; A second circulation unit that extracts the excess sludge and sends it to the activated sludge treatment device, a temperature detection unit that detects the temperature of the excess sludge in the excess sludge treatment tank, and a detection signal from the temperature detection unit. A surplus sludge treatment apparatus, comprising: a flow control unit for adjusting an amount of the surplus sludge introduced into the surplus sludge treatment tank. In an excess sludge treatment device for treating excess sludge generated in the activated sludge treatment device, a surplus sludge treatment tank for introducing excess sludge from the activated sludge treatment device, and polishing the excess sludge provided in the surplus sludge treatment tank. A grinding unit for crushing and activating, a first circulation unit for extracting the excess sludge in the excess sludge treatment tank and sending it to the grinding unit, and an air supply unit for supplying air to the grinding unit A second circulation unit that sends the excess sludge in the excess sludge treatment tank to the activated sludge treatment device, a temperature detection unit that detects the temperature of the excess sludge in the excess sludge treatment tank, and the temperature A surplus sludge treatment device, comprising: a flow control unit for adjusting an amount of the surplus sludge introduced into the surplus sludge treatment device according to a detection signal of a detection unit. An activated sludge tank for reacting wastewater with activated sludge while aerating, and connected to the activated sludge tank to separate products in the activated sludge tank into treated water and activated sludge and accumulate excess activated sludge as excess sludge An activated sludge treatment device having a surplus sludge storage tank, a circulating unit for sending a part of the activated sludge in the surplus sludge storage tank to the activated sludge tank, and a treatment unit connected to the activated sludge treatment device for treating the excess sludge An activated sludge treatment system comprising the excess sludge treatment device according to claim 1 or 2.

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