JP2008519674A - Method and apparatus for treating organic wastewater to reduce excess sludge generation - Google Patents

Abstract

The present invention provides a technique capable of reducing the amount of excess sludge discharged in a biological treatment method and apparatus for organic wastewater. One aspect of the present invention is a method for treating organic wastewater by a biological treatment system accompanied by generation of excess sludge, and a process for solubilizing sludge obtained by treating organic wastewater by a biological treatment system and returning it to the biological treatment tank. In this method, the extracted sludge is introduced into the acid fermentation tank, the sludge in the sludge storage tank is introduced into the ultrasonic treatment apparatus by a pump, is refined by the ultrasonic treatment apparatus, and is circulated to the acid fermentation tank. An organic wastewater treatment method is provided.

Description

  The present invention relates to a technology capable of reducing the amount of surplus sludge generated by biological treatment of organic wastewater such as sewage and organic industrial wastewater, and in particular, organic wastewater that can reduce energy consumption necessary for sludge liquefaction. The present invention relates to a processing method and apparatus.

  Sewage and organic industrial wastewater are treated by biological treatment using activated sludge. The biological treatment method of organic wastewater is an excellent treatment method, but a large amount of excess sludge is generated in the process, and the annual amount of the wastewater is over 10 million tons in Japan. Usually, surplus sludge is landfilled or incinerated after dehydration, but its treatment costs are increasing year by year, which is one of the causes of increasing the cost of wastewater treatment as a whole. Therefore, in recent years, a technique for reducing the amount of excess sludge generated has attracted attention. For example, in Japanese Examined Patent Publication No. 57-19719 “Excess Sludge Treatment Method”, by irradiating the sludge with ultrasonic waves, cell membranes of microorganisms in the sludge are destroyed and the contents of the sludge are changed to liquefied organic matter. It has been shown that mineralization of liquefied organic matter by biological treatment reduces excess sludge. In addition to ultrasonic treatment, for example, a method of physically refining activated sludge and a method of liquefying sludge by adding alkali or acid have been proposed. Furthermore, a technique for solubilizing (liquefying) sludge with thermophilic bacteria (JP-A-11-90493) and a technique for solubilizing sludge by the action of ozone (JP-A-6-206088) Various sludge liquefaction methods have been announced. The sludge liquefied by these various means is returned again to the biological treatment tank and is mineralized by the microorganisms in the biological treatment tank, thereby reducing the amount of excess sludge generated.

  However, in order to reduce sludge by sonication, etc., very large energy is required. By simply returning the sonicated sludge to the aerobic biological treatment tank, the quality of the treated water deteriorates and activated sludge I found outflow.

  Accordingly, an object of the present invention is to provide an organic wastewater treatment method and apparatus that reduce excess sludge without causing deterioration of the quality of the treated water. Another object of the present invention is to provide an organic wastewater treatment method and apparatus that can reduce energy required for sludge liquefaction.

  The present invention has solved the above problems by the following means.

1. A method for treating organic wastewater by a biological treatment system involving generation of surplus sludge, comprising treating organic wastewater by a biological treatment system and solubilizing and returning the obtained sludge to the biological treatment system,
The sludge extracted from the biological treatment system is introduced into the acid fermenter, the sludge from the acid fermenter is introduced into the ultrasonic treatment device by a pump, refined by the ultrasonic treatment device, and circulated to the acid fermenter. A method for treating organic wastewater, comprising:

2. A method for treating organic wastewater by a biological treatment system involving generation of surplus sludge, comprising treating organic wastewater by a biological treatment system and solubilizing and returning the obtained sludge to the biological treatment system,
The sludge extracted from the biological treatment system is introduced into the acid fermentation tank, the sludge from the acid fermentation tank is introduced into a flow-type ultrasonic treatment apparatus by a pump, and is refined by the ultrasonic treatment apparatus. The method for treating organic wastewater according to item 1, wherein the organic wastewater is circulated in a tank.

3. A method for treating organic wastewater by a biological treatment system involving generation of surplus sludge, comprising treating organic wastewater by a biological treatment system and solubilizing and returning the obtained sludge to the biological treatment system,
A method comprising introducing sludge flowing into an acid fermentation tank and sludge flowing out of the acid fermentation tank into a heat exchanger.

  The present invention also relates to the following means.

  B-1. A method for treating organic wastewater by a biological treatment system accompanied by generation of excess sludge, treating organic wastewater in a biological treatment tank, introducing the sludge extracted from the biological treatment tank into an acid fermentation tank, and The sludge in the tank is introduced into the ultrasonic treatment apparatus by a pump, refined by the ultrasonic treatment apparatus and circulated in the acid fermentation tank, and the sludge stored in the acid fermentation tank is returned to the biological treatment tank. A method for treating organic wastewater.

  B-2. A method for treating organic wastewater by a biological treatment system accompanied by generation of excess sludge, treating organic wastewater in a biological treatment tank, introducing the sludge extracted from the biological treatment tank into an acid fermentation tank, and The tank sludge is introduced into a flow-type ultrasonic treatment apparatus by a pump, refined by the ultrasonic treatment apparatus and circulated to the acid fermentation tank, and the sludge stored in the acid fermentation tank is supplied to the biological treatment tank. An organic wastewater treatment method characterized by returning it.

  B-3. A method for treating organic wastewater by a biological treatment system that involves generation of excess sludge, treating organic wastewater in a biological treatment tank, and introducing the sludge extracted from the biological treatment tank into an acid fermentation tank to solubilize it. The sludge solubilized in the acid fermentation tank is returned to the biological treatment tank, and the sludge flowing into the acid fermentation tank and the sludge flowing out of the acid fermentation tank are introduced into the heat exchanger. A method characterized by.

  Furthermore, the present invention relates to the following means.

  C-1. A method for treating organic wastewater by a biological treatment system accompanied by generation of surplus sludge, after treating the organic wastewater by the biological treatment system and after all or part of the sludge extracted from the biological treatment system is directly or concentrated Introducing into the sludge storage tank, introducing the sludge in the sludge storage tank into the sludge refiner, refining it with the sludge refiner, circulating it back to the sludge reservoir, and storing it in the sludge reservoir A method for treating organic wastewater, characterized in that the accumulated sludge is returned to the biological treatment system again.

  C-2. The said sludge storage tank is heated to 30-70 degreeC, and the residence time of the sludge in a sludge storage tank shall be 0.5-10 days, The processing method of the organic wastewater of the said C-1 characterized by the above-mentioned .

  C-3. Organic wastewater is treated in an aerobic biological treatment method in a biological treatment tank, and the effluent from the biological treatment tank is separated into treated water and separated sludge in a solid-liquid separation tank, and the separated sludge from the solid-liquid separation tank is separated. Introduce and stay in the sludge storage tank, introduce sludge from the sludge storage tank into the sludge refiner, circulate it back to the sludge storage tank, return the sludge in the sludge storage tank to the biological treatment tank An organic wastewater treatment method characterized in that the sludge storage tank is further kept warm so as to prevent release of heat and / or the sludge flowing into the sludge storage tank and the outflow from the sludge storage tank From the sludge and sludge refiner that heats the sludge flowing into the sludge storage tank with the heat of the sludge flowing out from the sludge storage tank and / or flows into the sludge storage tank The spilled sludge is introduced into the heat exchanger and flows from the sludge refiner. How in the sludge heat to the sludge heating the flowing into the sludge storage tank, characterized in that.

  C-4. The above-mentioned items C-1 to C-3, wherein the sludge refining device uses at least one of an ultrasonic treatment device, a homogenizer, a cutter mill, a ball mill, a stone mill type pulverizer, and an explosion device. The processing method of the organic waste water of any one of these.

  C-5. The sludge refining device is an ultrasonic treatment device, wherein the sludge in the sludge storage tank is introduced into a sludge crusher to refine coarse particles and then introduced into the ultrasonic treatment device. The processing method of the organic wastewater of the item -4.

  C-6. An organic wastewater treatment apparatus using a biological treatment system having an aerobic biological treatment tank and a solid-liquid separation apparatus, wherein the sludge extracted from the solid-liquid separation apparatus is introduced and retained, and the sludge storage tank And a sludge refiner connected by a circulation path, and a pipe for returning sludge from the sludge storage tank to the biological treatment tank.

  C-7. A biological treatment tank for treating organic wastewater by an aerobic biological treatment method; a solid-liquid separation tank for separating outflow water from the biological treatment tank into treated water and separated sludge; and A sludge storage tank in which the extracted sludge is introduced and retained, a sludge refiner connected to the sludge storage tank by a circulation path, a sludge storage tank heat retaining means for preventing heat release from the sludge storage tank, and / or Or, a heat exchanger that introduces sludge flowing into the sludge storage tank and sludge flowing out of the sludge storage tank, and heats the sludge flowing into the sludge storage tank using the heat of the sludge flowing out of the sludge storage tank, and / Or sludge flowing into the sludge storage tank and sludge flowing out from the sludge refining device are introduced, and a heat exchanger is provided to heat the sludge flowing into the sludge storage tank with the heat of sludge flowing out from the sludge refining device Organic wastewater treatment characterized by Apparatus.

  C-8. The sludge refiner is an ultrasonic treatment device, a sludge crusher is placed between the sludge storage tank and the sludge refiner, and the sludge refiner after crushing the sludge from the sludge reservoir with the sludge crusher The apparatus according to the above section C-6 or C-7, characterized in that the apparatus is configured to process in the above.

  According to one aspect of the present invention, the sludge flowing into the sludge storage tank and the sludge flowing out of the sludge storage tank are introduced into the heat exchanger, and the heat of the sludge flowing out of the sludge storage tank is used in the sludge storage tank. Heating the sludge flowing in and / or introducing the sludge flowing into the sludge storage tank and the sludge flowing out from the sludge refiner into the heat exchanger and utilizing the heat of the sludge flowing out from the sludge refiner By heating the sludge flowing into the sludge storage tank, the amount of excess sludge generated can be reduced, and the energy consumption required for sludge liquefaction can be reduced. In addition, the water quality of the treated water was particularly effective in removing nitrogen, and a good water quality could be obtained.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment for carrying out the present invention will be described in detail with reference to the drawings. In the following drawings, constituent elements having the same function will be described with appropriate reference numerals.
FIG. 5 (biological treatment apparatus used in Example 2) shows a biological treatment tank of organic waste water (denitrification tank 7 and nitrification tank 8 in FIG. 5), effluent from the biological treatment tank (“activated sludge mixed solution”). A biological treatment according to an embodiment of the present invention comprising a solid-liquid separation device 9 for separating water into treated water 2 and separated sludge 4, a heat exchanger 12, a sludge storage tank 10, an ultrasonic treatment device 11 (sludge refinement device), and the like. It is the schematic which shows a liquefaction process flow of an apparatus and sludge.

  Organic wastewater (raw water 1) is supplied to the biological treatment tank. In the biological treatment tank, the organic matter in the raw water 1 is mineralized by activated sludge. As the biological treatment tank used here, all biological treatment tanks having an aerobic part such as standard activated sludge method, anaerobic aerobic method, anaerobic anaerobic aerobic method, nitrification denitrification method, and biofilm method can be applied.

  The activated sludge mixed liquid 3 from the biological treatment tank is supplied to the solid-liquid separator 9 and separated into the treated water 2 and the separated sludge 4. Part or b of the separated sludge 4 is supplied to the heat exchanger 12. Part or all of the separated sludge heated by the heat exchanger is sent to the sludge storage tank 10, refined and liquefied by the ultrasonic treatment device 11, and returned to the sludge storage tank 10. The liquefied sludge 5 treated in the sludge storage tank 10 passes through the heat exchanger 12, heats the separated sludge 4, and is then returned to the biological treatment tank. When only a part 4b of the separated sludge 4 is sent to the heat exchanger 12, the remaining 4a of the separated sludge 4 is directly returned to the biological treatment tank.

  Next, features of the biological treatment method for organic wastewater according to the present invention will be described with reference to FIG.

  All or part of the sludge 13 drawn out from the biological treatment system is stored as it is or after being concentrated in the sludge storage tank 10 having a circulation path including the sludge refiner 14. Part or all of the stored sludge in the sludge storage tank 10 is refined by the sludge refiner 14 and then returned to the sludge reservoir 10 again as the refined sludge 15. The stored sludge in the sludge storage tank 10 is returned to the biological treatment system again as the liquefied sludge 5.

  According to this configuration, the sludge 13 extracted from the biological treatment system is once stored in the sludge storage tank 10. In the sludge storage tank (acid fermentation tank) 10, the action of microorganisms contained in the stored sludge causes the production of organic acids and the decomposition of proteins by acid fermentation and the like, and the sludge is converted into easily decomposable organic matter. Hereinafter, this change may be referred to as “liquefaction (solubilization)”. Some sludge is decomposed to carbon dioxide and mineralized (digested). This reduces the volume of sludge. The liquefied sludge 5 liquefied in the sludge storage tank 10 is returned to the biological treatment system, and easily decomposable organic substances are mineralized together with organic substances contained in the organic wastewater in the biological treatment tank.

  When the sludge 13 of a general activated sludge method is supplied to the sludge storage tank 10, the concentration is often 2% or less, and the liquefaction of the sludge proceeds even if it is as it is, but it is liquefied by concentrating the sludge 13 and storing it. The amount can be increased. Moreover, since the sludge storage tank 10 can be reduced in size by this, it can also be expected to reduce the size of the entire sludge treatment facility.

  Part or all of the stored sludge in the sludge storage tank is refined and liquefied by the sludge refiner 14. Here, as the sludge refiner 14, an apparatus that physically refines and liquefies sludge, such as an ultrasonic treatment device or a ball mill, can be applied. In the sludge refiner 14, the flocs and impurities contained in the sludge are refined and, in some cases, liquefied. In the sludge refiner 14, the sludge is refined, but since this is a physical action, the energy added to the sludge is finally converted into heat. For this reason, the sludge processed by the sludge refiner 14 is heated, and the sludge in the sludge storage tank 10 is also heated by returning the heated refined sludge 15 to the sludge storage tank 10. It will be. In the sludge storage tank 10, solubilization of sludge is significantly promoted by simply heating the sludge rather than simply storing it.

  Since the sludge in the sludge storage tank 10 is heated and has a reduced viscosity, the energy consumed by the pump when the sludge is sent to the sludge refiner (ultrasonic treatment device) 14 can be reduced. Moreover, since the viscosity of sludge has fallen, the pressure loss at the time of sludge passing through the sludge refinement | miniaturization apparatus 14 falls, and the reduction of the energy consumption of a pump and stabilization of an operation | movement can be aimed at.

  In order to supply the sludge from the sludge storage tank 10 to the sludge refiner 14 at a constant flow rate using a pump and return it to the sludge reservoir 10 again, the sludge flow rate in the sludge refiner 14 can be adjusted regardless of the sludge treatment amount. You can control. If the pump that supplies the sludge to the sludge refiner 14 is configured so that the pump flow rate can be adjusted by an inverter or the like, the sludge refiner 14 according to changes in the concentration and properties of sludge due to seasonal fluctuations and changes in sedimentation properties. It is desirable because the processing conditions can be controlled. Moreover, if the flow rate in the sludge refiner 14 is increased, adhesion of sludge to the sludge refiner 14 is suppressed, and the frequency of maintenance such as cleaning can be reduced.

In addition, when using an ultrasonic treatment apparatus for the sludge refinement | miniaturization apparatus 14, another sludge crusher, such as a cutter mill, can be provided in the front | former stage of an ultrasonic treatment apparatus. The ultrasonic treatment apparatus can refine relatively small particles, but coarse particles such as hair and toilet paper are difficult to refine. Further, when these coarse particles are supplied to the ultrasonic processing apparatus, the coarse particles adhere to the ultrasonic oscillator, which causes a reduction in processing capability. By crushing coarse particles in advance, adhesion of sludge to the ultrasonic oscillator can be suppressed and stable operation can be expected.
In addition, when using the flow which removes nitrogen, such as a nitrification denitrification method, as a biological treatment method of organic wastewater, if the liquefaction sludge 5 is supplied to the tank or part which performs denitrification, the easily degradable contained in the liquefaction sludge 5 Since the organic substance can be used as a hydrogen donor for the denitrification reaction, effects such as promotion and stabilization of the denitrification reaction and reduction of the organic substance load in the aerobic part can be expected.

  The operating conditions of the sludge storage tank 10 in the present invention are that the sludge storage tank 10 is heated to 30 to 70 ° C., preferably 40 to 50 ° C., and the sludge retention time is set to a range of 0.5 to 10 days. preferable.

  When the temperature of the sludge storage tank 10 is lower than 30 ° C., liquefaction by microorganisms is difficult to proceed, and when it is higher than 70 ° C., acid fermentation is difficult to proceed, and ammonia generated during the liquefaction process diffuses as a gas and requires treatment. Since problems arise, the range of 30-70 ° C is good. Although the sludge residence time in the sludge storage tank 10 depends on the temperature, it may be in the range of 0.5 to 10 days. If the temperature of the sludge storage tank 10 is low, the storage time can be lengthened, and if the temperature is high, it can be adjusted by shortening the storage time. The reaction time may be determined by determining the degree of sludge liquefaction, for example, by measuring the concentration of soluble organic matter. In the experiment conducted by the inventor, the preferable temperature range was 40 to 60 ° C., and the storage time was 0.5 to 3 days.

  In addition, when sludge is heated, less energy is required as the sludge volume is smaller. Therefore, concentrating the excess sludge 13 is an effective means in terms of heating.

  Next, the sludge 13 liquefaction process according to the organic wastewater treatment method and apparatus of the present invention will be described in more detail.

In the organic wastewater treatment apparatus according to the present invention, the sludge storage tank 10 and the sludge refiner 14 are provided, and more preferably, the path for circulating the sludge reservoir 10 and the sludge refiner 14 and the sludge reservoir. 10 is provided with a heat retaining means for preventing the release of heat in 10, and a means for heating the sludge storage tank 10 with heat generated by the sludge refiner 14.
Specifically, as shown in FIG. 1, the sludge 13 that flows into the sludge storage tank 10 and the liquefied sludge 5 that flows out of the sludge storage tank 10 are introduced into the heat exchanger 12 and flows out of the sludge storage tank 10. The heat of the liquefied sludge 5 can heat the sludge 13 flowing into the sludge storage tank. Alternatively, as shown in FIG. 2, the sludge 13 flowing into the sludge storage tank 10 and the refined sludge 15 flowing out from the sludge refiner 14 are introduced into the heat exchanger 12, and the fine flowing out from the sludge refiner 14. The sludge 13 flowing into the sludge storage tank 10 can be heated by the heat of the activated sludge 15.

  In the organic wastewater treatment apparatus according to the present invention, as already described, heating the sludge storage tank 10 is an effective means for promoting liquefaction, but in order to save energy required for heating. It is preferable to perform heat insulation. In order to suppress the release of heat from the sludge storage tank 10, it is preferable to heat the sludge flowing into the sludge storage tank with the sludge flowing out from the sludge storage tank 10. Moreover, in the process by the sludge refinement apparatus 14, since the sludge after a process has heat, using this heat for heating the sludge storage tank 10 without releasing it is an effective means that can suppress the amount of energy used. It becomes. In addition, when waste heat can be utilized in a factory etc., the energy required for heating can be saved by using this for the heating of the sludge storage tank 10. FIG.

  In the organic wastewater biological treatment method of the present invention, the sludge refinement using the sludge refiner 14 is at least an ultrasonic treatment device, a homogenizer, a cutter mill, a ball mill, a stone mill, a blasting device, or the like. Although one means can be used, it is preferable to use an ultrasonic processing apparatus provided with an ultrasonic oscillator.

The ultrasonic oscillator is characterized by a simple structure and easy integration because the apparatus is compact. Also, in the treatment with an ultrasonic oscillator, when the input energy amount is constant, the sludge liquefaction rate is constant regardless of the sludge concentration when the sludge concentration is 5% or less. The amount of sludge liquefaction can be increased with the same energy. The input energy when an ultrasonic oscillator is used is optimally 25 to 200 kJ / liter with respect to the volume of the sludge 13 supplied to the sludge storage tank 10, and the energy consumption per ultrasonic horn cross-sectional area is 30 W / cm. It is desirable that it is ² or more. Although there is no direct relationship with sludge volume reduction, ultrasonic treatment can inactivate filamentous fungi that cause bulking, so it can also be expected to suppress bulking, which is a major problem during activated sludge treatment operation. .

  In addition, when using the ultrasonic processing apparatus using an ultrasonic oscillator for refinement | miniaturization of sludge, since the vibrator | oscillator becomes dirty by processing sludge, there exists a problem that an output falls. In addition, since the sludge becomes dirty, it becomes difficult for the sludge to flow, so that the pressure of the mud pump increases and stable operation becomes difficult. Further, when the pressure of the mud pump increases, the output of the ultrasonic oscillator increases and a load is applied, which may cause a failure of the oscillator. In order to prevent these problems, it is desirable to periodically clean the ultrasonic oscillator. As a specific method, for example, as shown in FIG. 18, motor-operated valves are attached to the ultrasonic oscillator 311 in advance on the upstream side and the downstream side. A pressure gauge is attached to the ultrasonic oscillator 311 to monitor the pressure. When the pressure becomes higher than a predetermined value, the ultrasonic oscillator 311 is stopped, and the upstream valve a and the downstream valve b are closed. In addition, the pressure which stops an ultrasonic oscillator can be determined according to the pressure | voltage resistant performance of an ultrasonic oscillator or a mud pump. Instead of measuring the pressure, the power consumption of the ultrasonic oscillator 311 is measured, and the ultrasonic oscillator 311 is provided with a power meter for measuring the output, and when the power consumption becomes higher than a predetermined power A method of stopping the ultrasonic oscillator 311 can also be used. Next, the valve c and the valve f are opened, and cleaning water 316 is supplied. After flushing water for a certain time, the valves c and f are closed. Next, valves d and e are opened, and cleaning water is passed in a direction opposite to the normal sludge flow for a certain period of time. After passing water, valves d and e are closed, valves a and b are opened, sludge treatment is restarted, and ultrasonic treatment sludge 305 is obtained. In addition, it is desirable to operate the ultrasonic oscillator while passing the cleaning water because the sludge adhering to the oscillator is easily removed.

  That is, another aspect of the present invention is as follows.

4). A method of refining sludge with a flow-type ultrasonic treatment device equipped with an ultrasonic oscillator,
Detect the output of the ultrasonic oscillator, stop the ultrasonic oscillator when it falls below the specified output, and wash the inside of the ultrasonic treatment device by flowing cleaning water through the ultrasonic oscillator. Feature method.

5. A method of refining sludge with a flow-type ultrasonic treatment device equipped with an ultrasonic oscillator,
By detecting the pressure in the ultrasonic oscillator and stopping the ultrasonic oscillator when the detected pressure is higher than the specified pressure, flush water is passed through the ultrasonic oscillator to A method characterized by washing.

  The present invention also provides the following means.

  C-9. A method of refining sludge by treating sludge using an ultrasonic treatment device equipped with an ultrasonic oscillator, detecting the output of the ultrasonic oscillator, and the detected pressure is lower than a predetermined output In this case, the ultrasonic oscillator is stopped, and the inside of the ultrasonic oscillator is cleaned by alternately flowing cleaning water in the sludge flow direction and in the opposite direction.

  C-10. An ultrasonic treatment apparatus that has a sludge supply port and a treated sludge discharge port and is equipped with an ultrasonic oscillator and that refines sludge using ultrasonic waves, and an output detector of the ultrasonic oscillator And a controller that has the function of detecting that the output has dropped below a predetermined level and stopping the ultrasonic oscillator, and a structure that can inject cleaning water from the sludge supply port and sludge discharge port of the ultrasonic processing device. A device characterized by comprising:

  The above method and apparatus can be employed as a sludge refinement method and apparatus in the organic wastewater treatment method and apparatus according to one aspect of the present invention described above.

  The present invention also relates to a method for determining the amount of sludge liquefied in sludge liquefaction, a method for controlling the amount of sludge reduction, and a control device usable therefor. More specifically, the present invention measures the amount of ammonia nitrogen produced in the filtrate obtained by filtering the sludge mixed solution after the liquefaction treatment process, in particular, the sludge mixed solution after the liquefaction treatment step, as an index of sludge lowering. And the method of determining the amount of sludge liquefaction based on this measured value is also provided.

In the method for reducing the volume of sludge by sludge refinement treatment (liquefaction treatment) as described above, Kjeldahl nitrogen (Kj-N) in the filtrate obtained by filtering the sludge mixed solution after the liquefaction treatment step. ) And COD _Cr production, and it has been proposed to use as an indicator of the amount of liquefaction (Ebara Time Report No. 192 (2001-7), Kiyoshi Arakawa et al., Sludge reduction in activated sludge process using ozone. Basic research on tolerance))).

  However, in the sludge liquefaction treatment, the sludge liquefaction amount and the actual sludge reduction amount are not necessarily correlated, and it has been difficult to estimate the sludge reduction amount from the sludge liquefaction amount. In particular, in sludge liquefaction treatment that can cause digestion reaction such as heating treatment, it is difficult to estimate the sludge reduction amount from the sludge liquefaction amount.

In addition, when trying to control the amount of sludge reduction in sludge volume reduction processing, the measurement of Kj-N and COD _Cr relies on manual analysis and is a simple method for using dangerous reagents and the like. However, a better method for determining the amount of sludge liquefaction is desired.

  In view of the above technical requirements and background art thereof, the present invention aims to establish a more accurate method for determining the amount of sludge liquefaction in the sludge liquefaction method, and further, the determined amount of sludge liquefaction. The present invention provides a method and apparatus for easily predicting sludge reduction from the above, a control method for sludge reduction, and a control device usable for the method.

The present inventors paid attention to ammonia nitrogen in the filtrate obtained by filtering the sludge liquid obtained by liquefying sludge in the sludge liquefaction treatment. Then, by measuring the NH ₄ -N concentration of the filtrate was filtered sludge solution obtained by liquefaction sludge (sludge filtrate) was found to be determined sludge liquefaction amount efficiently. Furthermore, the present inventors also found that the amount of sludge liquefaction can be efficiently determined not only by the filtrate obtained by filtering sludge liquid obtained by liquefying sludge but also by measuring the NH ₄ -N concentration of the sludge liquid obtained by liquefying sludge. .

  That is, the other aspect of this invention is as follows.

6). A method for treating organic wastewater by a biological treatment system involving generation of excess sludge, comprising solubilizing sludge obtained by treating organic wastewater by a biological treatment system and returning the sludge to the biological treatment system,
A method characterized by predicting a sludge reduction amount by measuring a sludge liquefaction amount and determining a sludge amount to be sent to a liquefaction (solubilization) treatment step based on the predicted sludge reduction amount.

  The present invention also provides the following means.

  B-6. A method for treating organic wastewater by a biological treatment system with generation of excess sludge, treating organic wastewater in a biological treatment tank, solubilizing sludge extracted from the biological treatment tank, and returning it to the biological treatment tank Furthermore, the sludge reduction amount is predicted by measuring the sludge liquefaction amount in the solubilization treatment, and the sludge amount to be sent to the solubilization treatment process is determined based on the predicted sludge reduction amount. how to.

  Furthermore, the present invention also provides the following means.

  C-11. A method for liquefying sludge, wherein the amount of sludge liquefied is determined using the amount of ammonia nitrogen produced as an index.

  C-12. The method according to C-11 above, wherein the amount of ammonia nitrogen produced in the filtrate obtained by filtering the liquefied sludge is measured.

  C-13. The method according to item C-12, wherein the sludge liquefaction treatment step includes a step of heating the sludge.

  C-14. In the sludge liquefaction method, the sludge reduction amount is predicted by determining the sludge liquefaction amount, and the sludge reduction amount is controlled by determining the sludge amount to be sent to the liquefaction treatment process based on the predicted sludge reduction amount. A method characterized by.

  C-15. The sludge liquefaction treatment step includes a step of heating the sludge or a step of refining the sludge. The method for controlling the amount of sludge reduction according to the above C-14.

  C-16. A heating treatment tank for storing sludge in a heated state, an ammoniacal nitrogen concentration measuring device for measuring the ammonia nitrogen concentration in the sludge liquid in the heating treatment tank, and sending the sludge to the heating treatment tank A sludge treatment apparatus comprising: a mud pump; and a controller that predicts a sludge reduction amount from the measured ammonia nitrogen concentration and instructs the sludge pump to send the sludge to the heating treatment tank. .

  C-17. An organic wastewater treatment apparatus comprising the sludge treatment apparatus according to item C-16.

As described in detail below, since the NH ₄ -N concentration in the sludge filtrate before liquefaction is extremely low, there is no problem even if this is ignored, and the NH ₄ -N in the sludge filtrate after liquefaction is not caused. If the concentration is measured, the amount of sludge liquefaction can be determined. The sludge liquefaction amount ΔLNH ₄ -N (g / d) using the ammoniacal nitrogen concentration as an index is close to the relationship of ΔX / ΔL = 1 with the sludge reduction amount ΔX, and ΔLNH ₄ -N And ΔX are in a proportional relationship (see FIG. 8), the amount of sludge liquefaction can be determined based on the NH ₄ —N concentration of the sludge filtrate. That is, the concentration of ammonia nitrogen in the sludge liquid (in other words, the amount produced) is extremely useful as a determinant of the sludge liquefaction amount and a predictor of sludge reduction.

By measuring the NH ₄ -N concentration of the liquefied sludge liquid, and more preferably, by measuring the ammonia nitrogen concentration in the filtrate obtained by filtering the liquefied sludge liquid, the amount of sludge liquefaction can be efficiently increased. Can be determined. Moreover, the sludge reduction amount can be predicted from the sludge liquefaction amount determined in this way, and the sludge reduction amount can be controlled efficiently. When measuring the NH ₄ -N concentration of the liquid, measuring in the filtrate obtained by filtering the liquefied sludge liquid has an effect on the measuring instrument rather than measuring directly with the liquefied sludge liquid. A small and highly accurate measurement value can be obtained.

  Hereinafter, the above-described embodiment will be described in detail with reference to the drawings.

FIG. 8 shows the relationship between the sludge liquefaction amount and the sludge reduction amount. Sludge liquefaction amount using ammonia nitrogen as an index (referred to as “ammonia nitrogen-based sludge liquefaction amount”; ΔLNH ₄ -N) is close to the relationship between sludge reduction amount ΔX and ΔX / ΔL = 1, ΔLNH ₄ -N and ΔX are in a proportional relationship. On the other hand, with sludge liquefaction using Kjeldahl nitrogen as an indicator (referred to as “Kjeldahl nitrogen-based sludge liquefaction”; ΔLKj-N), sludge reduction ΔX hardly increases at sludge liquefaction of 400 g / d or more. It is difficult to estimate the sludge reduction amount from the sludge liquefaction amount. Actually, since the NH ₄ -N concentration of the sludge filtrate before liquefaction is extremely low, the amount of sludge reduction can be controlled by measuring the NH ₄ -N concentration of the sludge filtrate after liquefaction. . In particular, in a treatment with a large amount of ammonia elution, such as a warming treatment, it is advantageous to use the ammonia nitrogen-based sludge liquefaction amount as an index.

In addition, regarding the sludge liquefaction amount using CODCr as an index (referred to as “CODCr-based sludge liquefaction amount”; ΔLCODCr), in the flow as shown in FIG. The numerical value becomes lower than the ammonia nitrogen-based sludge liquefaction amount and the Kjeldahl nitrogen-based sludge liquefaction amount, which is not preferable as an index.
The calculation method of the ammoniacal nitrogen-based sludge liquefaction amount is shown below. As a reference, a conventional method for calculating the Kjeldahl nitrogen-based sludge liquefaction amount and the CODCr-based sludge liquefaction amount is also shown. The sludge filtrate was prepared using filter paper having an average pore diameter of 1.0 μm, but is not limited thereto.

  FIG. 9 shows a flow of a biological treatment process of organic wastewater including a sludge volume reduction treatment process. The raw water 1 is flowed into the denitrification tank 7 and subjected to aerobic treatment in the next nitrification tank 8. After the activated sludge mixed liquid 3 is solid-liquid separated by the solid-liquid separator 9, a part of the concentrated sludge 4 is returned to the denitrification tank 7 as a return sludge 4a. Further, a part of the separated sludge 4 is introduced into the sludge storage tank 10 as a liquefaction process inflow sludge 4b and heated. The temperature of the sludge storage tank 10 is preferably in the range of 30 to 70 ° C. If it is lower than 30 ° C, liquefaction by microorganisms is difficult to proceed, and if it is higher than 70 ° C, acid fermentation is difficult to proceed. The sludge retention time in the sludge storage tank 10 may be 0.5 to 10 days, although it depends on the temperature. In experiments conducted by the present inventors, a preferable temperature range was 40 to 60 ° C., and a storage time was 0.5 to 3 days. The sludge that has been heated in the sludge storage tank 10 is introduced into the ultrasonic treatment device 11 and subjected to ultrasonic treatment. The ultrasonically treated sludge is returned to the sludge storage tank 10 and circulated. The liquefied sludge 5 obtained in the liquefaction process is returned to the denitrification tank 7.

  FIG. 7 shows an example of a sludge reduction amount control device. FIG. 21 shows an example of a specific flow of the sludge reduction amount control method. First, set the target sludge reduction amount. The sludge is heated in the sludge storage tank 10 while stirring the sludge with the stirring device 116. Heating is performed by the heater 117. The ammonia nitrogen concentration measuring device 113 is immersed in the heated sludge 112 and the ammonia nitrogen concentration in the sludge liquid is measured. The controller 115 calculates the ammonia nitrogen-based sludge liquefaction amount based on the measured ammonia nitrogen concentration, and then predicts the sludge reduction amount based on the relationship between the sludge liquefaction amount and the sludge reduction amount shown in FIG. If the predicted sludge reduction amount is smaller than the set sludge reduction amount, the controller 115 instructs the mud pump 114 to send the sludge to the sludge storage tank 10. On the other hand, when the predicted sludge reduction amount is larger than the set sludge reduction amount, the controller 115 gives an instruction to continue the operation as it is. In the experiments by the present inventors, the knowledge that the amount of sludge liquefaction increases as the sludge concentration increases is obtained. When the ammoniacal nitrogen concentration measuring device 113 is immersed in the filtrate obtained by filtering the liquefied sludge mixed solution, the measurement accuracy becomes higher.

  According to the above-mentioned aspect, the amount of sludge reduction is efficiently controlled by measuring the ammonia nitrogen concentration in the liquefied sludge liquid or the filtrate obtained by filtering the liquefied sludge liquid ("sludge filtrate"). Therefore, it is useful for sewage treatment in which surplus sludge is generated in large quantities, particularly for sewage and organic industrial wastewater.

  The method and apparatus according to the above-described aspect can be employed as sludge liquefaction treatment means, sludge reduction amount control means, and apparatus in the organic wastewater treatment method and apparatus of the present invention.

  In still another aspect of the present invention, there is provided a waste treatment apparatus for solubilizing an organic waste slurry such as sludge obtained by aerobic biological treatment of organic sewage.

  According to this aspect, a processing apparatus for solubilizing an organic waste slurry, a reactor storing a slurry to be processed, a solubilizing apparatus including an ultrasonic processing apparatus, and the reactor and the solubilizing apparatus A circulation line through which the slurry to be treated can circulate, and the reactor has a storage part for retaining the residual heat given to the slurry to be treated in the solubilizer in the reactor, and discharges from the reactor There is provided an organic waste slurry processing apparatus characterized by comprising a heat exchanging portion for applying heat of the processing slurry to the slurry to be processed supplied to the reactor.

  In the above apparatus, it is preferable that the ultrasonic processing apparatus is of a distribution type. The apparatus may further include a line for supplying the slurry to be treated to the reactor, and a concentrating device for concentrating the solid content contained in the slurry to be treated supplied to the line. Further, the apparatus includes a temperature sensor that detects a temperature in the reactor installed in the reactor, and a means for operating, stopping, or controlling the output of the solubilizer according to the measured temperature in the reactor. Furthermore, it can comprise.

  With the above configuration, it is possible to efficiently reduce the amount of excess sludge generated with a small amount of electric power.

  According to the above aspect, the sludge generated from the aerobic biological treatment facility is temporarily stored in the reactor, and the sludge stored in the reactor is supplied to the solubilizer using ultrasonic waves, solubilized, and obtained. The treatment liquid is returned to the reactor again, and sludge solubilization is promoted by effectively utilizing the heat discharged by the ultrasonic treatment. Examples of the organic waste slurry to which the embodiment of the present invention can be applied include not only sludge generated from an aerobic biological treatment facility but also sludge generated from an anaerobic treatment facility, food residue, livestock manure, etc. It can be applied to all things.

  This aspect will be described in detail with reference to the drawings.

  FIG. 10 is a flow configuration diagram illustrating an example of an embodiment of an organic waste slurry processing apparatus according to an aspect of the present invention. In FIG. 10, surplus sludge supplied from an aerobic biological treatment process for treating organic wastewater is supplied to a reactor 202 through a mud supply pipe 211. The solubilization effect of sonication depends on the volume rather than the solids concentration of the slurry to be treated, so preferably before the excess sludge is fed to the reactor 202, gravity concentration, centrifugal concentration, pressurized flotation, atmospheric pressure It may be concentrated by a concentrator 230 such as flotation, coagulation sedimentation, or membrane concentration. The excess sludge stored in the reactor 202 is supplied to the solubilizer 201 by the circulation pump 203 and solubilized, and then returned to the reactor 202 through the circulating water pipe 212. As the solubilizer 201, it is necessary to eliminate the short circuit of the circulating sludge so that the total amount of the circulating sludge can be irradiated with ultrasonic waves. Therefore, a circulation type ultrasonic treatment apparatus is used rather than a water tank installation type. Is appropriate.

  Here, the flow-type ultrasonic device is an ultrasonic transducer disposed inside the solubilizing device 201 in which the object to be processed flows in a certain direction, and the influence range of cavitation generated by the ultrasonic wave is over the entire cross section of the flow path. 1 illustrates a sonicator with a wide range of shapes.

  The storage portion 222 of the reactor 202 is kept warm by covering the outside with a heat insulating material, and the heat of the solubilized sludge warmed by the heat discharged by the solubilizer 201 is held in the storage portion 222. Further, the reactor 202 makes the sludge to be discharged through the sludge pipe 213 and the sludge supplied through the mud supply pipe 211 face each other at a heat exchange part 221 partitioned by a partition wall 224 made of a heat insulating material. Thus, the heat exchange structure is provided, and the temperature of the sludge storage portion 222 can be kept high even if the ultrasonic output of the solubilizer 201 is low. In the heat exchanging portion 221, a method of submerging a serpentine tube or a plate-shaped heat exchanger in sludge is also effective. If the temperature of the storage part 222 is excessively high, the protein contained in the sludge is solidified and the biodegradability is deteriorated. Therefore, the temperature of the storage part 222 is 40 ° C to 60 ° C, preferably 50 ° C to 55 ° C. It is desirable to keep it. When the temperature of the storage part rises more than necessary, the temperature sensor 226 detects the temperature of the storage part 222 and includes a solubilizer 201, a circulation pump 203, and a crusher according to the measured temperature. If so, the temperature in the storage part 222 of the reactor 202 can be controlled by automatically stopping the crusher or automatically suppressing the output of the solubilizer 201.

  When the property of the sludge supplied to the solubilizer 201 changes, the solubilization performance of the solubilizer 201 is affected. Therefore, it is desirable to keep the sludge residence time in the storage portion 222 long. However, if the sludge residence time is excessively long, fermentation proceeds in the reactor 202, which may generate flammable gases such as methane. Therefore, the sludge residence time in the storage portion 222 should be maintained for about 1 to 4 days, preferably about 2 days. Furthermore, a portion 223 capable of gravity-precipating sludge is provided in the sludge outflow portion from the storage portion 222 to prevent a short-circuit flow and hold a sludge particle having a large particle size in the storage portion 222 so as to solubilize the sludge. In 201, sludge having a small particle diameter that has been reliably decomposed and solubilized can be discharged to the outside.

With the above configuration, in addition to the direct solubilization of sludge by ultrasonic waves, a combination of the self-decomposition effect by storing sludge and the self-decomposition promoting effect by keeping sludge in a heated state. The effect makes it possible to solubilize excess sludge efficiently with a small amount of electric power.
11 is a partial configuration diagram illustrating an example in which a plate heat exchanger 225 is used in the heat exchange portion 221 of the apparatus illustrated in FIG. 10, and FIG. 12 is a partial configuration diagram illustrating an example in which a serpentine tube 227 is used. .

Moreover, when the extra sludge contains impurities such as residue and fibers, the solubilizer 1 may be blocked. In this case, as shown in FIG. 13, a coarse crusher 205 can be installed in the previous stage of the solubilizer 201 to coarsely crush the contaminants to around 10 mm in advance.
Similarly, in the case where extra sludge contains impurities such as residue and fibers, the extra sludge supplied by the mud supply pipe 211 is preliminarily removed by the screen 206 as shown in FIG. As a result, blockage of the solubilizing device 201 can be prevented.

  The said aspect is as follows.

  C-18. A treatment device for solubilizing organic waste slurry, a reactor for storing the treatment slurry, a solubilization device including an ultrasonic treatment device, and the treatment slurry between the reactor and the solubilization device The reactor has a heat storage part that retains the residual heat given to the slurry to be treated in the solubilizer in the reactor, and the treatment slurry discharged from the reactor. An apparatus for treating an organic waste slurry, comprising: a heat exchanging portion for imparting heat to the slurry to be treated supplied to the reactor.

  C-19. The apparatus according to item C-18, wherein the ultrasonic treatment apparatus is a flow-through type.

  C-20. C-18 or C-19 above, further comprising a line for supplying the slurry to be treated to the reactor and a concentrating device for concentrating solids contained in the slurry to be treated to be supplied to the line. The device described in 1.

C-21. The apparatus further comprises a temperature sensor for detecting the temperature in the reactor installed in the reactor, and means for operating, stopping or controlling the output of the solubilizer according to the measured temperature in the reactor. The apparatus according to C-18, C-19 or C-20.
In the present invention, an appropriate organic wastewater treatment system or sludge treatment system can be constructed by appropriately combining the various embodiments described above.

Hereinafter, various embodiments of the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited by these examples.
[Example 1]
Sludge was liquefied by combining the sludge storage tank 10 described in FIG. 1 and an ultrasonic treatment device as the sludge refiner 14. The results are shown in FIGS.
In this test, as shown in FIG. 1, sludge having a sludge concentration of 3.7% is stored in the sludge storage tank 10, and the sludge in the storage tank is circulated and supplied to the ultrasonic processing device 14. Liquefaction treatment was performed, and changes in the sludge liquefaction rate with the passage of storage time were investigated. FIG. 3 shows the progress of the sludge liquefaction rate (rate of untreated sludge liquefied) when stored at an ultrasonic intensity of 100 kJ / liter and a storage temperature of 50 ° C. The liquefaction rate becomes higher as the storage time is longer, but since it hardly increases in the range of 2 to 3 days, it was found that a storage time of 1 to 3 days is sufficient at a storage temperature of 50 ° C.

Next, the sludge concentration was 0.7%, 2.0% and 3.6%, and the relationship between the sludge concentration and the liquefaction rate was examined. The experimental results are shown in FIG. Even when the sludge concentration was changed to 0.7%, 2.0% and 3.6%, the liquefaction rate was 25% or more. It was also found that the higher the sludge concentration, the larger the sludge liquefaction amount determined by the liquefaction rate and the sludge treatment amount.
[Example 2]
In this embodiment, processing is performed according to the processing flow shown in FIG. In Example 2, a circulation type nitrification denitrification tank divided into a denitrification tank 7 and a nitrification tank 8 was provided as a biological treatment tank. Inflow of raw water 1 (using sewage); 4 m ³ / d, volume of denitrification tank (anaerobic tank) 7; 1 m ³ , volume of aerobic tank 8; 2 m ³ . The sludge concentration in the biological treatment tank was 3000 mg-SS / liter, and the sludge concentration in the return sludge 4 was about 10,000 mg-SS / liter.

In the sludge liquefaction process, a sludge storage tank 10 and an ultrasonic treatment device 11 were provided. Part 4b of the separated sludge was supplied to the sludge storage tank 10. The sludge residence time in the sludge storage tank 10 was about 2 days, and the sludge in the sludge storage tank was heated to about 50 ° C. by the heat from the heater and the ultrasonic treatment device 11. The sludge in the sludge storage tank 10 was supplied to the ultrasonic processing apparatus 11, and returned to the sludge storage tank 10 again after the ultrasonic treatment. The ultrasonic intensity in the ultrasonic treatment is set to 70 kJ / liter with respect to the liquefied sludge 5, but about 50 to 200 kJ / liter is suitable. The liquefied sludge 5 was returned to the denitrification tank 7. The results of the sludge treatment of Example 2 are shown in Table 1 and FIG. 6 together with the results of treatment in Comparative Examples 1 and 2.
[Comparative Example 1]
In order to compare the amount of sludge generated, a control system was compared under the same conditions as in Example 2 using an apparatus in which the liquefaction process (sludge tank 10 and ultrasonic treatment apparatus 11) was omitted from the biological treatment process of FIG. 1 was driven simultaneously. That is, the entire amount of the separated sludge 4 was returned to the derooming tank 7.
[Comparative Example 2]
In order to confirm the effect of the sonication, the device in which the sonication device 11 is omitted from the liquefaction process of the biological treatment device of FIG. The amount of sludge generated as a system was compared. The accumulated sludge generation amount (kg) is shown in FIG.

  When the results of the sludge treatment of Example 2 and Comparative Examples 1 and 2 are compared, as shown in FIG. 6, the amount of excess sludge generated in Example 2 is larger than that in Comparative Examples 1 and 2 as shown in FIG. It was possible to reduce 60% or more. Moreover, the difference in the amount of excess sludge generation was not seen by the comparative example 2 and the comparative example 1, and it has confirmed that it was necessary to use an ultrasonic wave and heating together in order to reduce the volume of sludge. From these results, it can be seen that the present invention can greatly fulfill the purpose of reducing the amount of excess sludge generation.

  In addition, among the results of the sludge treatment of Example 2 and Comparative Example 1, as shown in Table 1, the chemical oxygen demand, which is an indicator of organic matter, was 10.1 mg / liter in Example 2 for water quality. Although it was slightly worse than 8.8 mg / liter of Comparative Example 1, a good water quality comparable to the biological oxygen demand was obtained. Further, when the total amount of nitrogen was compared, it was shown that the removal of nitrogen was more advanced in Example 2, with 8.2 mg / liter in Example 2 and 11.9 mg / liter in Comparative Example 1.

[Example 3]
The ultrasonic oscillator 311 was cleaned using the apparatus shown in FIG. Sludge with a sludge concentration of about 4.5% was supplied to an ultrasonic oscillator with a maximum output of 4 kW and subjected to ultrasonic treatment. The ultrasonic oscillator was operated at an output of about 2 kW immediately after the sludge was supplied, but decreased to an output of 1.5 kW in about 2 days. When the output of the ultrasonic oscillator 11 became 1.5 kW or less, the ultrasonic oscillator was cleaned. The cleaning operation was performed by automatic operation. First, the ultrasonic oscillator 311 was stopped, and the valves a and b were closed. Next, valves c and f were opened, washing water 16 was passed for 4 minutes, and then c and d were closed. Next, the valves d and e were opened, and the washing water 16 was allowed to flow for 4 minutes in the reverse direction of the normal sludge treatment flow to perform the back washing. After completion of the cleaning, valves d and e were closed, a and b were opened, and sludge supply and operation of the ultrasonic oscillator were resumed. By this operation, the output of the ultrasonic oscillator recovered to 2 kW or more, and it was confirmed that the sludge adhered to the vibrator inside the ultrasonic oscillator 311 could be removed. By performing this cleaning, it was not necessary to disassemble and maintain the ultrasonic oscillator for about 6 months, and a stable operation could be carried out.

When cleaning is performed by supplying the cleaning water 16 to the ultrasonic oscillator 311, if the ultrasonic oscillator 311 is operated in conjunction with the supply of the cleaning water 16, sludge adhering to the vibration of the vibrator is easily removed. This is effective because the cleaning effect is further enhanced.
[Example 4]
Biological treatment of organic wastewater was performed using the apparatus shown in FIG. An oxidation ditch type biological treatment tank was provided as the biological treatment tank 319. The inflow amount of the raw water 1 was 450 m ³ / d, the volume of the biological treatment tank 319 was 660 m ³ . The sludge concentration in the biological treatment tank 319 was 3000 mg / L, and the sludge concentration in the return sludge 4 was about 6000 mg / L.

  As the liquefaction process 20, the sludge storage tank 10, the ultrasonic treatment apparatus 11, the centrifugal concentrator 318, and the sludge crusher 321 were provided. A part 4b of the returned sludge was supplied to the centrifugal concentrator 318 to obtain a concentrated sludge 320 having a sludge concentration of about 4.5%. The concentrated sludge 320 was supplied to the sludge storage tank 10 via the heat exchanger 12. The sludge residence time in the sludge storage tank 10 was set to about 1.5 days. Although no special heater or the like was provided in the sludge storage tank 10, the temperature of the sludge in the tank rose to about 50 ° C. due to heat from the ultrasonic treatment device 11 and the sludge crusher 321. The sludge in the sludge storage tank 10 is supplied to the sludge crusher 321 and coarse particles (hair, toilet paper, etc.) in the sludge are pulverized, and further supplied to the ultrasonic treatment device 11 for ultrasonic treatment. Then, it returned to the sludge storage tank 10 again. The sludge flow rate supplied to the ultrasonic treatment apparatus 11 was adjusted to 3.0 to 10.8 times that of the concentrated sludge 320 supplied to the sludge storage tank 10. The ultrasonic intensity in the ultrasonic treatment was 110 kJ / L with respect to the sludge capacity. The liquefied sludge 5 was returned to the biological treatment tank 319 after recovering heat with the heat exchange group 12.

In this example, in order to compare the amount of sludge generated, a control experiment in which the liquefaction process was omitted was simultaneously operated. That is, in the control experiment, the entire amount of the separated sludge 4 was returned to the biological treatment tank 319.
As a result of such operation, as shown in Table 2, the treated water of Example 4 was able to obtain a water quality comparable to that of the control experiment. Moreover, the time-dependent change of the accumulated sludge generation amount in a system is shown in FIG. As can be seen from FIG. 20, in Example 4, the amount of excess sludge generation was reduced by about 40% compared to the control experiment.

[Example 5]
The sludge treatment apparatus shown in FIG. 10 was added to a domestic wastewater treatment facility to conduct a wastewater treatment experiment. The results are shown in Table 3. In this example, the case where the sludge treatment apparatus shown in FIG. 10 incorporating the flow-type ultrasonic treatment apparatus 201 with a rated output of 1 kW is installed for the activated sludge treatment facility having a tank volume of 3 m ³ for treating domestic wastewater; Comparison was made with the case where no sludge treatment equipment was installed. The entire amount of the treatment liquid 213 of the sludge treatment apparatus was returned to the upstream of the activated sludge treatment facility. In the ultrasonic treatment 201, sludge was subjected to an ultrasonic irradiation treatment of 44 kW · s / L. By installing the sludge treatment apparatus shown in FIG. 10, it was possible to reduce the amount of excess sludge solids generated by 78%. The heat balance in the sludge treatment apparatus was as shown in FIG. 17, and even if the ultrasonic irradiation output was kept low by heat exchange, a good effect could be obtained.

[Example 6]
FIG. 15 shows the CODcr-based solubilization rate when factory wastewater-treated sludge is concentrated in several stages until the solids concentration reaches 4.1% at maximum and irradiated with ultrasonic waves. FIG. 15 shows that the solubilization rate of sludge does not depend on the solid concentration of sludge, but only on the ultrasonic output. Therefore, it can be seen that by concentrating the sludge before the sludge solubilization treatment and reducing the amount of sludge liquid, the time for the solubilization treatment can be reduced and the amount of electric power can be saved.

For example, when treating sludge with an ultrasonic irradiation output of 50 kW · s / L, the sludge with a solid concentration of 1% is concentrated to 4% with a concentrator to reduce the required power per 1 m ³ to 13.9 kW · h. To 3.5 kW · h.
[Example 7]
FIG. 16 shows the effect when the sludge treatment apparatus shown in FIG. 10 is operated by installing a cutter mill as the rough crusher 205 shown in FIG. When the rough crusher 205 was not used, fiber-like impurities were caught in the flow path of the ultrasonic processing apparatus, and the output of the ultrasonic oscillator increased only to around 1 kW, and the value was not stable. On the other hand, when the rough crusher 205 was used, the output of about 1.8 kW was stably output. The particle size of the fiber in the sludge at the outlet of the coarse crusher 205 was 10 mm or less. Table 4 shows the particle size distribution of the solid material.

  The present invention is used for biological treatment of organic wastewater discharged from wastewater treatment processes such as wastewater treatment facilities such as wastewater treatment plants, wastewater treatment plants, etc. And the amount of excess sludge generated can be reduced.

  In addition, according to another aspect of the present invention, sludge reduction can be achieved by measuring ammonia nitrogen concentration in liquefied sludge liquid or filtrate obtained by filtering liquefied sludge liquid ("sludge filtrate"). Since the amount can be controlled efficiently, it is useful for sewage treatment in which excess sludge is produced in large quantities, particularly for sewage and organic industrial wastewater.

It is a flow of the sludge liquefaction (solubilization) treatment process of this invention, Comprising: The flow which heats the sludge which flows in into a sludge storage tank with the sludge which flows out from a sludge storage tank is shown. It is a flow of the sludge liquefaction process of this invention, Comprising: The flow which heats the sludge which flows in into a sludge storage tank using the sludge which flowed out from the sludge refinement | miniaturization apparatus is shown. In Example 1, it is a figure showing the change of the sludge liquefaction rate and storage time when storing at 50 degreeC in the case where it liquefies combining sludge storage tank and ultrasonic treatment. In Example 1, it is a figure showing the relationship between the sludge liquefaction rate and sludge density | concentration when storing at 50 degreeC in the case where liquefaction processing is carried out combining a sludge storage tank and ultrasonic treatment. It is a figure which shows the processing flow of the organic waste water of Example 2. FIG. It is a figure which shows progress of Example 2 and the accumulation sludge generation amount of Comparative Examples 1-2, a horizontal axis represents the operation days (d), and a vertical axis | shaft represents accumulation sludge generation amount (kg). It is a figure which shows an example of the control apparatus of the sludge reduction amount which concerns on the other aspect of this invention. It is a graph which shows the relationship between sludge liquefaction amount and sludge reduction amount. It is a figure which shows the flow of the processing process of the organic waste water including a sludge volume reduction processing process. It is a flow block diagram which shows an example of the sludge processing apparatus which concerns on the other aspect of this invention. It is a partial block diagram which shows another example of the heat exchange part of the sludge processing apparatus shown in FIG. It is a partial block diagram which shows the other example of the heat exchange part of the sludge processing apparatus shown in FIG. In the sludge processing apparatus shown in FIG. 10, it is a partial block diagram which shows the example which installed the rough crusher in the front | former stage of the solubilization apparatus. It is a partial block diagram which shows the example which installed the screen in the sludge supply pipe | tube in the sludge processing apparatus shown in FIG. It is a graph which shows the relationship between an ultrasonic irradiation amount and a COD liquefaction rate. It is a graph which shows the change of the ultrasonic oscillator output by the presence or absence of an ultrasonic crusher. It is the schematic which shows the heat balance in the sludge processing apparatus in Example 5. FIG. It is a figure which shows the concept of the washing | cleaning means of an ultrasonic oscillator. It is a figure which shows the flow of the organic wastewater treatment process used in Example 4. FIG. It is a graph which shows a time-dependent change of the accumulated sludge generation amount in the system in Example 4. It is a figure which shows the flow of an example of the control method of sludge reduction amount.

Explanation of sign

1 Raw water 2 Treated water 3 Activated sludge mixed solution 4 Separated sludge 4a Return sludge 4b Part (or all) of separated sludge
5 Liquefaction sludge 6 Circulating fluid 7 Denitrification tank (anaerobic part)
8 Nitrification tank (aerobic part)
9 Solid-liquid separator 10 Sludge storage tank (acid fermentation tank)
DESCRIPTION OF SYMBOLS 11 Ultrasonic processor 12 Heat exchanger 13 Sludge 14 Sludge refiner 15 Refined sludge 20 Liquefaction process 112 Storage sludge 113 Ammonia nitrogen concentration measuring device 114 Mud pump 115 Controller 116 Stirrer 117 Heater 201 Solubilizer 202 Reactor 203 Circulation pump 204 Stirrer 205 Rough crusher 206 Screen 211 Mud pipe 212 Circulating water pipe 213 Waste mud pipe 214 Concentrated separation liquid 221 Heat exchange part 222 Storage part 223 Gravity precipitation part 224 Partition wall 225 Plate type heat exchanger 226 Temperature sensor 227 Conduit 230 Concentrator 305 Ultrasonic treatment sludge 311 Ultrasonic oscillator 316 Washing water 317 Centrifugal concentrator supernatant 318 Centrifugal concentrator 319 Biological treatment tank 320 Concentrated sludge 321 Sludge crusher

Claims (3)

A method of refining sludge with a flow-type ultrasonic treatment device equipped with an ultrasonic oscillator,
By detecting the output of the ultrasonic oscillator and stopping the ultrasonic oscillator when the detected output is lower than the predetermined output, flushing the ultrasonic oscillator with the washing water, the inside of the ultrasonic oscillator A method characterized by washing. A method of refining sludge with a flow-type ultrasonic treatment device equipped with an ultrasonic oscillator,
The pressure of the ultrasonic oscillator is detected, and when the detected pressure becomes higher than a predetermined pressure, the ultrasonic oscillator is stopped, and washing water is supplied to the ultrasonic oscillator to A method characterized by cleaning the interior. A method for treating organic wastewater by a biological treatment system involving generation of excess sludge, comprising treating organic wastewater by a biological treatment system, solubilizing the obtained sludge and returning it to the biological treatment system,
A method further comprising: predicting a sludge reduction amount by detecting a sludge liquefaction amount; and determining a sludge amount to be sent to a liquefaction treatment step based on the predicted sludge reduction amount.

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