JP2006326438A - Apparatus and method for treating sludge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for treating sludge, the running cost of which is reduced by improving the throughput capacity when waste sludge is digested biologically and dispensing with large-scale equipment and to provide a method for treating sludge. <P>SOLUTION: The apparatus for treating sludge is used for biologically digesting the sludge generated at a waste water treatment step of cleaning organic waste water by biological treatment. A pretreatment unit 2 for pretreating a sludge-mixed liquid containing the sludge to assist the biological digestion of the sludge by a microbe is arranged on the preceding stage of a digestion tank 7 for housing the sludge-mixed liquid containing the sludge and digesting the housed sludge biologically by the microbe. A magnetic separation unit 8 for throwing a magnetic material in the sludge-mixed liquid so that the sludge-mixed liquid is separated into magnetized sludge and treated liquid by solid-liquid separation is arranged incidentally to the digestion tank 7. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sludge treatment apparatus and a sludge treatment method for biologically digesting sludge generated in a wastewater treatment process for purifying organic wastewater such as sewage, industrial wastewater, and domestic wastewater by biological treatment.

  In general, a biological treatment method represented by a standard activated sludge method is widely used for the treatment of organic waste water. In this activated sludge method, organic matter contained in organic wastewater is oxidatively decomposed by microorganisms in a biological treatment tank such as an aeration tank. In the treatment process, microorganisms grow and a large amount of excess sludge is generated. The excess sludge is generally concentrated, then dehydrated, and then incinerated, discarded or recycled. Moreover, depending on the case, the biological weight reduction process is made | formed by the anaerobic or aerobic digestion before the dehydration process after concentration.

In this treatment of organic wastewater, for example, sludge is further reduced by using magnetic separation. This magnetic separation is performed as follows. First, by introducing a magnetic material into the sludge mixed liquid, the magnetic material is attached to the sludge to generate magnetized sludge. In the magnetic separation device described above, a magnetized roller is rotated, only the magnetized sludge is magnetically adsorbed by the roller, and the scraped plate is scraped off from the roller to separate the sludge mixed liquid into magnetized sludge and treatment liquid, By increasing the concentration of sludge in the biological treatment tank, self-digestion is promoted and weight reduction is achieved (for example, see Patent Documents 1 and 2).
Japanese Patent Laid-Open No. 57-135091 JP-A-8-52487

  By the way, in order to incinerate surplus sludge generated in a large amount in the above-mentioned organic wastewater treatment process, a large amount of heat energy is required and the generation of harmful substances is regarded as a problem. Also, surplus sludge is discarded. In recent years, the disposal of surplus sludge has become a major issue, such as securing landfill sites.

  In addition, when the dewatering process is performed after the excess sludge is concentrated, the amount of sludge provided to the dehydrator is larger than that after the reduction process, and the cost required for the operation of the dehydrator is inevitably large. . For this reason, it is preferable to perform biological weight reduction treatment by anaerobic or aerobic digestion before the dehydration treatment after the excess sludge is concentrated, but even in this case, there are the following problems.

  First, energy recovery is possible in the treatment by anaerobic digestion, but there is a problem that the scale of the facility becomes large, and in the treatment by aerobic digestion, aeration is necessary, and the running cost for that is large. There was a problem. Moreover, although sludge reduction has been realized by magnetic separation, there has been a problem of further drastic reduction of sludge.

  Therefore, the present invention has been proposed in view of the above-mentioned problems, and its purpose is to improve the processing capacity in biological digestion of surplus sludge, without requiring large-scale equipment and running. An object is to provide a sludge treatment apparatus and a sludge treatment method capable of easily reducing the cost.

  As a technical means for achieving the above-mentioned object, the sludge treatment apparatus according to the present invention is a sludge treatment apparatus for biologically digesting sludge generated in a wastewater treatment process for purifying organic wastewater by biological treatment. In addition, a pre-treatment device for pre-treatment for assisting biological digestion of sludge by microorganisms is disposed in the previous stage of the digestion tank that contains the sludge mixed liquid containing the sludge and biologically digests the sludge by microorganisms. In addition, a magnetic separation device for solid-liquid separating the sludge mixed liquid into magnetized sludge and treatment liquid by introducing a magnetic material into the sludge mixed liquid is provided in the digestion tank. The sludge treatment method according to the present invention is a sludge treatment method for biologically digesting sludge generated in a wastewater treatment process for purifying organic wastewater by biological treatment, wherein the sludge is biologically digested by microorganisms. Pretreatment for assisting biological digestion of sludge by microorganisms in the first stage of the digesting tank, and then introducing a magnetic substance into the sludge mixed liquid in the digestive tank, thereby making the sludge mixed liquid and magnetized sludge It is characterized by magnetic separation into a treatment liquid. The biological digestion in the digestion tank described above can be applied to either aerobic digestion or anaerobic digestion.

  In the present invention, in a sludge treatment process for biologically digesting sludge generated in a wastewater treatment process for purifying organic wastewater by biological treatment, a magnetic separator is attached to the digestion tank, and sludge mixing in the digestion tank is performed. By introducing a magnetic material into the liquid, the sludge can be concentrated to a high concentration by solid-liquid separation of the sludge mixed liquid into magnetized sludge and treatment liquid by magnetic separation. For this reason, decomposition | disassembly of a hardly decomposable substance is accelerated | stimulated and self-digestion is also accelerated | stimulated and the processing capacity in the biological digestion of sludge can be improved.

  Further, in the present invention, in the above-described sludge treatment step, a pretreatment device is disposed in the front stage of the digestion tank, and a pretreatment for assisting biological digestion of sludge by microorganisms is performed, so that biological digestion in the latter stage is performed. Can be promoted. As the pretreatment, for example, there is a treatment in which sludge is solubilized with an alkaline solution and the solubilized sludge is digested with an alkalophilic microorganism. This digestion treatment may be performed in an aerobic atmosphere or an anaerobic atmosphere. In some cases, the digested sludge may be neutralized after digesting the solubilized sludge with an alkalophilic microorganism. When neutralizing digested sludge, it is preferable to use acid fermentation of anaerobic microorganisms, but it is also possible to use neutralizing agents such as sulfuric acid and hydrochloric acid.

  When a series of alkaline treatments consisting of alkali solubilization, aerobic digestion by alkaline microorganisms, and neutralization by acid fermentation of anaerobic microorganisms are carried out as pretreatment, pH adjustment of the sludge mixture is not necessary. There is no need to use Japanese medicines. As the pretreatment, in addition to the alkali treatment, heating, ultrasonic waves, physical crushing, acid treatment, enzyme treatment, biological treatment, or a combination treatment thereof can be performed.

  According to the present invention, in a sludge treatment process for biologically digesting sludge generated in a wastewater treatment process for purifying organic wastewater by biological treatment, a magnetic separation device is attached to the digestion tank, By introducing a magnetic substance into the sludge mixture, the sludge can be concentrated at a high concentration by solid-liquid separation of the sludge mixture into magnetized sludge and treatment liquid. Is promoted and self-digestion is also promoted, so that the treatment capacity in biological digestion of sludge can be improved. As a result, it is possible to easily reduce the amount of sludge, compared to only biological digestion by microorganisms that are not concentrated at high concentration without introducing magnetic material, reducing the equipment size and running costs. Easy to plan.

  Further, for example, a pretreatment device that solubilizes sludge by alkali treatment, aerobically digests the solubilized sludge with an aerobic microorganism, and neutralizes the digested sludge by acid fermentation of anaerobic microorganisms. When provided in the previous stage, it is not necessary to adjust the pH of the sludge mixture by carrying out a series of pretreatments consisting of alkali solubilization, aerobic digestion by alkaliphilic microorganisms, and neutralization by acid fermentation of anaerobic microorganisms. Therefore, the processing cost can be simplified, and since the neutralizing agent is not used, the running cost of the agent can be greatly reduced.

  1 and 2 show an embodiment of a sludge treatment apparatus according to the present invention, which is a sludge treatment for biologically digesting sludge generated in a wastewater treatment process for purifying organic wastewater by biological treatment. Installed in the process. Here, the above-mentioned “sludge” means a solid matter mainly composed of organic matter such as excess sludge, raw sludge or mixed sludge.

  In the sludge treatment apparatus in each embodiment, as shown in FIGS. 1 and 2, the sludge is biologically digested by microorganisms as sludge predatory fungi in a digestion tank 7 containing a sludge mixed solution containing sludge. A magnetic separation device 8 is attached to the digestion tank 7. The magnetic separation device 8 exhibits a function of solid-liquid separating the magnetized sludge mixed liquid generated by introducing a magnetic material into the sludge mixed liquid into magnetized sludge and a processing liquid.

  The digestion process in the digestion tank 7 includes aerobic digestion in which aeration is performed and anaerobic digestion in which aeration is not performed. In the case of aerobic digestion, the treatment liquid separated by the magnetic separation device 8 is precipitated in the latter stage. It is further settled and separated in the tank 12 and discharged as clear treated water. The digested sludge settled and separated in the settling tank 12 is returned to the aerobic digester 7 as return digested sludge, and a part thereof is withdrawn from the settling tank 12 as excess digested sludge. In the case of anaerobic digestion, the concentrated sludge mixed solution is introduced into the dehydrator 13 and dehydrated.

  In this sludge treatment apparatus, the magnetic separation device 8 is attached to the digestion tank 7, so that the sludge is concentrated to a high concentration by solid-liquid separation of the magnetized sludge mixed liquid into the magnetized sludge and the treatment liquid. Thus, since sludge is concentrated in high concentration, decomposition | disassembly of a hardly decomposable substance is accelerated | stimulated and self-digestion is also accelerated | stimulated, and the processing capability in biological digestion of sludge can be improved.

  In the case of the aerobic digestion method in this embodiment, since the sludge concentration is maintained high, the digester tank 7 becomes more compact than the conventional aerobic digestion method. Furthermore, the concentration of the sludge discharged from the digestion tank 7 can be kept low, and since the magnetic sludge contains a magnetic material, the specific gravity increases and the settling speed is improved, so that the subsequent settling tank 12 is also dramatically compact. become.

  Further, in the case of the anaerobic digestion method in this embodiment, the concentration of solids in the processing liquid after being concentrated and separated is lowered, so that the transparency of the processing liquid is increased and even if some processing process is required in the subsequent stage. , The solids load on the process can be reduced.

  In this sludge treatment process, the sludge is solubilized by alkali treatment, and the solubilized sludge is aerobically digested by an aerobic microorganism and then the digested sludge is neutralized by acid fermentation of anaerobic microorganisms. 2 is provided in the front stage of the digestion tank 7. Thus, by carrying out a series of pretreatments consisting of alkali solubilization, aerobic digestion by alkaliphilic microorganisms, and neutralization by acid fermentation of anaerobic microorganisms, pH adjustment of the sludge mixed liquid becomes unnecessary, and There is no need to use Japanese medicines.

  FIG. 1 illustrates a sludge treatment apparatus that performs pretreatment by alkaline treatment and aerobic digestion. In the wastewater treatment process, the raw wastewater is supplied to the biological treatment tank 1 and the wastewater treated in the biological treatment tank 1 is discharged as wastewater treated water. The sludge generated from the biological treatment tank 1 along with the purification of the wastewater in the wastewater treatment process is supplied to a sludge treatment apparatus installed in the sludge treatment process for biologically digesting the sludge generated in the wastewater treatment process.

  In the sludge treatment process, the sludge generated from the biological treatment tank 1 in the wastewater treatment process is supplied to the pretreatment device 2. The pretreatment device 2 includes a solubilization tank 3, a digestion tank 4, a precipitation tank 5, and a neutralization tank 6. In this pretreatment device 2, first, in the solubilization tank 3, the sludge generated from the biological treatment tank 1 is solubilized by introducing an alkaline solution such as sodium hydroxide, and the solubilized sludge is digested in the digestion tank 4. Aerobic digestion by alkaliphilic microorganisms. Then, the digested sludge is precipitated in the sedimentation tank 5, and a part of the digested sludge is returned to the digestion tank 4 and the excess sludge is discharged. The remainder of the digested sludge is neutralized in the neutralization tank 6 by acid fermentation with anaerobic microorganisms.

  The sludge concentrated by the above-mentioned pretreatment device 2 is supplied to a digestion tank 7 that performs aerobic digestion. Since aerobic digestion is performed in this digestion tank 7, an aeration blower 10 and an air diffuser 11 are provided. A magnetic material is supplied from the magnetic material supply device 9 to the sludge mixed solution in the digestion tank 7, and a part of the magnetic material adheres to the sludge and becomes magnetized sludge. In this digestion tank 7, the magnetic sludge is concentrated to a high concentration by solid-liquid separation of the magnetized sludge mixed liquid into magnetized sludge and treatment liquid by the magnetic separation device 8.

  Thus, since sludge is concentrated in high concentration, decomposition | disassembly of a hardly decomposable substance is accelerated | stimulated and autolysis is also accelerated | stimulated, and the processing capacity in biological digestion of sludge improves. The magnetic separation device 8 rotates a magnetized roller, magnetically adsorbs only the magnetized sludge with the roller, and scrapes it off the roller with a scraping plate to separate it from the magnetized sludge mixed liquid. The treatment liquid separated from the magnetized sludge mixed liquid by the magnetic separation device 8 is supplied to the precipitation tank 12. In the sedimentation tank 12, the treatment liquid is further settled and separated, the clear treated water is discharged, the digested sludge separated and separated is returned to the digestion tank 7, and a part of the digested sludge is extracted as surplus sludge.

  The following table shows a comparison of treatment performance with and without magnetic separation in aerobic digestion. In this comparison of treatment performance, sludge generated by aerobic biological treatment of food factory wastewater (chemical oxygen demand COD = 12000 [mg / L], solid matter concentration SS = 12000 [mg / L], treatment Flow rate = 12 [L / day], solid load = 144 [g / day]), pretreatment [solubilized with NaOH at pH = 12 (HRT = 3 [h], 40 ° C), alkaliphilicity For aerobic digestion by microorganisms (hydraulic residence time HRT = 24 [h], 35 ° C. and neutralization by acid fermentation of anaerobic microorganisms (HRT = 50 [h], 35 ° C.)] Aerobic digestion with magnetic separation (SS concentration MLSS = 20000 [mg / L], HRT = 12 [h]) was performed.

  As is apparent from the above table, when magnetic separation is not performed, the amount of generated sludge was 48 [g / day], whereas when magnetically separated, the amount of generated sludge was 25 [g / day]. Significantly reduced, sludge reduction has been realized.

  FIG. 2 illustrates a sludge treatment apparatus that performs pretreatment by alkaline treatment and anaerobic digestion. As described in the above-described sludge treatment apparatus (see FIG. 1) for performing the aerobic digestion, the wastewater raw water is supplied to the biological treatment tank 1, and the wastewater treated in the biological treatment tank 1 is discharged as wastewater treated water. In the wastewater treatment process, the sludge generated from the biological treatment tank 1 is supplied to a sludge treatment apparatus installed in the sludge treatment process for biologically digesting the sludge produced in the wastewater treatment process.

  In the sludge treatment process, the sludge generated from the biological treatment tank 1 in the wastewater treatment process is supplied to the pretreatment device 2. Since the pretreatment device 2 and the magnetic separation device 8 are the same as those described in the sludge treatment device (see FIG. 1) that performs the aerobic digestion described above, duplicate description is omitted.

  The sludge concentrated by the pretreatment device 2 described above is supplied to a digestion tank 7 that performs anaerobic digestion. A magnetic material is supplied from the magnetic material supply device 9 to the sludge mixed solution in the digestion tank 7, and a part of the magnetic material adheres to the sludge and becomes magnetized sludge. In this digestion tank 7, the magnetic sludge is concentrated to a high concentration by solid-liquid separation of the magnetized sludge mixed liquid into magnetized sludge and treatment liquid by the magnetic separation device 8. Thus, since sludge is concentrated in high concentration, decomposition | disassembly of a hardly decomposable substance is accelerated | stimulated and autolysis is also accelerated | stimulated, and the processing capacity in biological digestion of sludge improves. The treatment liquid separated from the magnetized sludge mixed liquid by the magnetic separation device 8 is discharged, the concentrated sludge mixed liquid is supplied to the dehydrator 13, and the dehydrated magnetized sludge and the processed liquid are discharged respectively.

  The table below shows a comparison of treatment performance with and without magnetic separation in anaerobic digestion. In this comparison of treatment performance, sludge generated by aerobic biological treatment of food factory wastewater (COD = 12000 [mg / L], SS = 12000 [mg / L], treatment flow rate = 12 [L / day] , Solid load = 144 [g / day]), pretreatment [NaOH, pH = 12, alkali solubilization (HRT = 3 [h], 40 ° C.), aerobic digestion (HRT = 24 [h], 35 ° C.) and neutralization by acid fermentation of anaerobic microorganisms (HRT = 50 [h], 35 ° C.)] anaerobic digestion with magnetic separation (MLSS = 30000 [mg / L], HRT = 30 [h]).

  As is clear from the above table, the amount of generated sludge was 210 [g / day] without magnetic separation, whereas the amount of generated sludge was 105 [g / day] when magnetically separated. Significantly reduced, sludge reduction has been realized.

It is a block diagram which shows the schematic structural example at the time of performing aerobic digestion in embodiment of the sludge processing apparatus which concerns on this invention. It is a block diagram which shows the schematic structural example at the time of performing anaerobic digestion in other embodiment of this invention.

Explanation of symbols

2 Pretreatment equipment 7 Digestion tank 8 Magnetic separation equipment

Claims (10)

  In a sludge treatment apparatus for biologically digesting sludge generated in a wastewater treatment process for purifying organic wastewater by biological treatment, the sludge mixed liquid containing the sludge is accommodated and the sludge is biologically treated by microorganisms. A pretreatment device that performs pretreatment to assist biological digestion of sludge by microorganisms is arranged in the front stage of the digester to be digested, and the sludge mixture is magnetized by introducing a magnetic substance into the sludge mixture. A sludge treatment apparatus characterized in that a magnetic separation device for solid-liquid separation into sludge and treatment liquid is attached to the digestion tank.   The sludge treatment apparatus according to claim 1, wherein the pretreatment apparatus solubilizes sludge with an alkaline solution and digests the solubilized sludge with an alkalophilic microorganism.   The sludge treatment apparatus according to claim 2, wherein the pretreatment apparatus neutralizes the solubilized sludge after digesting the solubilized sludge with an alkalophilic microorganism.   The sludge treatment apparatus according to claim 3, wherein the pretreatment device neutralizes the digested sludge by acid fermentation of anaerobic microorganisms.   The sludge treatment apparatus according to any one of claims 1 to 4, wherein the biological digestion in the digestion tank is either aerobic digestion or anaerobic digestion.   In a sludge treatment method for biologically digesting sludge generated in a wastewater treatment process for purifying organic wastewater by biological treatment, the sludge produced by microorganisms is disposed at a stage preceding a digestion tank for biologically digesting the sludge by microorganisms. A pretreatment for assisting biological digestion is performed, and then the sludge mixed solution is magnetically separated into a magnetized sludge and a processing solution by introducing a magnetic substance into the sludge mixed solution in the digestion tank. Sludge treatment method.   The sludge treatment method according to claim 6, wherein in the pretreatment, the sludge is solubilized with an alkaline solution, and the solubilized sludge is digested with an alkalophilic microorganism.   The said pretreatment is the sludge treatment method of Claim 7 which neutralizes the digested sludge after digesting the solubilized sludge with an alkalophilic microorganism.   The sludge treatment method according to claim 8, wherein the pretreatment neutralizes the digested sludge by acid fermentation of anaerobic microorganisms.   The sludge treatment method according to any one of claims 6 to 9, wherein the biological digestion in the digester is either aerobic digestion or anaerobic digestion.

Images