JP2006061743A - Method and apparatus for treating excess sludge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method which enables the efficient reduction of the volume of excess sludge generated by an activated sludge method with relatively simple equipment and a treatment apparatus therefor. <P>SOLUTION: In the method serving as a biological treatment method of the excess sludge generated in accompany with activated sludge treatment of raw water, the excess sludge is mixed with a part of the raw water to biologically treat the mixture water generated by the mixture at least aerobically by a contact material which carries a microbe. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a treatment method for treating surplus sludge generated when wastewater containing pollutants is biologically treated by an activated sludge method or the like, or a treatment apparatus therefor.

  The method of biologically treating raw water such as industrial wastewater containing pollutants using the activated sludge method is a widely used wastewater treatment method, but the treatment of a large amount of excess sludge generated at that time is a problem. It was. Excess sludge is an industrial waste with a high moisture content, and usually requires coagulation using a large amount of coagulant, mechanical dehydration, and incineration, and these treatments have a certain cost. Take it. For this reason, various treatment methods using organisms that can be more easily treated have been proposed.

  First, the surplus sludge is made into a BOD component by destroying the cell wall of the excess sludge by using a physicochemical method, eluting the cytoplasm and lysing it, and returning it to the activated sludge tank and aerobically decomposing it. A technique for reducing the volume of excess sludge has been proposed. An example of such an apparatus is shown in FIG. The raw water 1 is sent to the aeration tank 20 which is an activated sludge tank via the storage tank 10, where it is aerobically decomposed by the air and activated sludge supplied from the air diffuser 21. Subsequently, the sedimentation sludge and the treated water are solid-liquid separated in the sedimentation tank 30, and a part of the sedimentation sludge is returned to the activated sludge tank 20 as it is, but the other part is a solubilizer 110 using some method. Solubilized and returned to the activated sludge tank 20 as a BOD component. The remaining settled sludge is subjected to a normal flocculation process or the like as the excess sludge 112.

  Specifically, for example, Patent Document 1 or 2 discloses a method using ozone treatment as a physicochemical method for solubilizing excess sludge with the solubilizer 110. However, this method requires an ozone generation facility and a waste ozone facility, and the operation cost is high. Furthermore, it is necessary to increase the capacity of the aeration tank in order to cope with an increase in BOD load accompanying lysis. Also, denitrification tends to be insufficient in terms of water quality.

  Further, as a physicochemical method for solubilizing excess sludge, for example, Patent Document 3 discloses a method in which surplus sludge is heated to 50 ° C. and cell walls are destroyed with hydroxy radicals by the Fenton oxidation method. . However, in this method, iron oxide is generated by the Fenton oxidation method, and about 20% of the excess sludge remains and does not disappear completely. Furthermore, even in this method, it is necessary to increase the capacity of the aeration tank in response to an increase in the BOD load.

  Further, as a physicochemical method for solubilizing excess sludge, for example, Patent Document 4 discloses a method in which excess sludge is mechanically destroyed and lysed by a mill using ceramic beads having a diameter of several millimeters. It is disclosed. However, it is necessary to increase the capacity of the aeration tank as in the above method. In addition, surplus sludge that has been broken or lysed is likely to cause poor water quality due to decomposition residue in the aeration tank, and about 20% of the excess sludge is extracted from the settling tank and discharged out of the system. There must be.

  Further, Patent Document 5 discloses a method in which biological treatment is added to the physicochemical method as described above to lyse excess sludge and then aerobic treatment is performed. In this method, excess sludge is lysed by a high-temperature aerobic reaction at 60 to 70 ° C. About 20% of the excess sludge needs to be extracted from the sedimentation tank and subjected to conventional agglomeration, dehydration and incineration treatments.

In addition, instead of applying some treatment to the surplus sludge and returning it to the activated sludge device again, the surplus sludge is put into a separately prepared sludge treatment device and a number of contacts provided in the contact aeration tank of the sludge treatment device. Patent Document 6 discloses a method for continuously decomposing and digesting excess sludge using high-grade microorganisms on the material. However, in this method, the activity of high-grade microorganisms is low and the treatment efficiency of excess sludge is low. For example, in order to eliminate all the excess sludge generated in an activated sludge apparatus in one day with a sludge treatment apparatus of the same size, a biological reaction time over 11 days is required for calculation. In other words, if the generated sludge is to be treated within the same time, a sludge treatment device having a capacity 10 times or more that of the activated sludge device in which excess sludge is generated is required.
Japanese Patent Laid-Open No. 6-206088 Japanese Patent Laid-Open No. 7-232184 Japanese Patent Laid-Open No. 10-128376 JP-A-11-300393 JP-A-9-10791 JP 2002-143895 A

  An object of the present invention is to propose a sludge treatment method or a treatment apparatus therefor capable of efficiently reducing the volume of excess sludge generated by the activated sludge method with relatively simple equipment.

  A first aspect of the present invention is a biological treatment method for surplus sludge generated with the activated sludge treatment of raw water, wherein a part of the raw water is mixed with the surplus sludge, and the mixed water generated by the mixing is contacted. It is a biological treatment method for surplus sludge characterized in that it is at least aerobically biologically treated with microorganisms carried on the material.

  Here, it is preferable that the mixing ratio of the excess sludge and the raw water in the mixed water is within a range of 1: 9 to 7: 3. Moreover, it is preferable that the aerobic biological treatment uses a microanimal feeding mechanism composed of microorganisms, protozoa, and metazoans. Furthermore, it is preferable to include a denitrification treatment in a facultative anaerobic atmosphere. Moreover, it is preferable that the precipitate is separated after the biological treatment. Further, it is preferable that the separation treatment is performed by membrane separation. Furthermore, it is preferable that the supernatant water from which the precipitate has been separated is subjected to a dephosphorization treatment. Moreover, it is preferable that the said contact material consists of a helical core material and the loop-shaped fiber provided many in the said core material surface. The loop-like fiber is preferably made of vinylidene chloride.

  A second aspect of the invention is a biological treatment apparatus for surplus sludge generated by the activated sludge treatment of raw water, wherein a mixing means for mixing a part of the raw water with the surplus sludge to obtain mixed water and a microorganism are supported. A surplus sludge biological treatment apparatus comprising a contact member and a treatment means for biologically treating the mixed water at least aerobically.

  The excess sludge generated in the activated sludge device can be efficiently reduced with relatively simple and small equipment. The operating cost at that time is also low. Moreover, since it is not necessary to enlarge the capacity | capacitance of the existing activated sludge tank and conversely some raw water can be processed with a sludge processing apparatus, the processing amount in an activated sludge tank reduces. It is also possible to treat all excess sludge.

  Embodiments of the present invention will be described with reference to the drawings. First, FIG. 1 is a conceptual diagram of a configuration example in which a sludge treatment apparatus 60 according to the present invention is incorporated in an activated sludge apparatus that is almost the same as a conventional one so that the sludge treatment method of the present invention can be implemented. The activated sludge apparatus treats the raw water 1 in the aerobic atmosphere provided by the blower 22 and the air diffuser 21, which receives the raw water 1 such as factory effluent containing BOD components, nitrogen, phosphorus, etc. The activated sludge tank 20 that digests the BOD component to generate surplus sludge, the precipitation tank 30 that solid-liquid separates the precipitated sludge 31 from the treated water, and the precipitated sludge 31 that is extracted from the precipitation tank 30 through the line 40. And a line 41 for returning a part to the activated sludge tank 20.

  Raw water 1 subject to biological treatment is general sewage, agricultural village drainage, community drainage systems such as community plans, food factory effluents, kitchen effluents of hotels, fermented effluents of amino acid industries, chemical factories and water-soluble paints. There is no particular limitation as long as it is a wastewater that can be biologically treated, such as solvent wastewater from a factory. The raw water 1 is sent from the storage tank 10 to the activated sludge tank 20, and then sent to the sedimentation tank 30, and finally discharged as treated water 4 with a reduced BOD component.

  In the activated sludge tank 20, aerobic microorganisms exist in a floating state that does not particularly use a carrier, and proliferate by consuming oxygen supplied from the air diffuser using the BOD component in the raw water as a nutrient source. As a result, biological treatment of raw water is performed and surplus sludge is generated. These microorganisms are aerobic bacteria having a size of 0.5 μm to 1.0 μm, and secrete mucus substances themselves to form a population (floc). The microbial population is vigorously activated by being agitated and mixed by the air from the diffuser and supplied with oxygen (aeration), and consumes the BOD component in the raw water. The biota of activated sludge is mainly composed of these microorganisms, and protozoa higher than microorganisms may coexist, but the activity tends to be suppressed because there are many emissions from microorganisms. . That is, it can be said that activated sludge is almost uniformly a mass of this microorganism.

  When such activated sludge is sent to the sedimentation tank 30, the microorganisms are settled by being left in a stationary state to form a sedimentation sludge 31. The sedimentation sludge 31 is extracted from the sedimentation tank 30 as needed, and a part thereof is returned to the activated sludge tank 20 to be used for maintaining the activated sludge tank, but the rest is surplus sludge. This excess sludge is sent from the line 42 to the sludge treatment apparatus 60 for processing.

  In addition to the excess sludge, a part of the raw water 1 stored in the storage tank 10 is sent from the storage tank 10 through the line 51 to the sludge treatment apparatus 60. The raw water 1 and surplus sludge are combined and biologically treated by the sludge treatment apparatus 60, whereby treated water 7 is generated. That is, in the sludge treatment apparatus 60, the biological treatment of both the water treatment of digesting the BOD component of raw water and the decomposition treatment of surplus sludge is performed simultaneously. As a result, the surplus sludge treatment efficiency is significantly improved.

  The reason why the efficiency is improved is unknown, but it is assumed that the activation of the biota in the sludge treatment apparatus 60 is the cause. In general, in biological treatment, the species of the biota changes depending on the target to be decomposed. For example, surplus sludge has few BOD components, and the activity of microorganisms is inactive. Therefore, when only the excess sludge is decomposed, only protozoa and metazoans corresponding to this inactive microorganism appear. However, the actual situation is that active biological activities are not necessarily performed with this alone, and the decomposition efficiency of excess sludge remains low.

  However, if the surplus sludge is mixed with a BOD component such as that contained in the raw water, the surplus sludge microorganisms will start active, and as a result, the sludge treatment apparatus 60 is composed of microorganisms, protozoa, and metazoans. The biota is activated, and the micro-animal predation mechanism between them becomes active. As a result, despite the increase in the number of biodegradable objects, it is surprising that the decomposition efficiency of surplus sludge may be significantly improved.

  FIG. 2 is a conceptual diagram showing a configuration example of a sludge treatment apparatus 60 capable of growing such a biota. The process of this apparatus is a circulating two-stage denitrification method, and is configured to perform both aerobic treatment and facultative anaerobic treatment. As a result, not only hydrocarbons but also nitrogen compounds are targeted for decomposition. In particular, in the facultative anaerobic treatment, a denitrification treatment for nitrogen is performed.

  Here, aerobic refers to a state where the oxygen concentration (DO) in water is 0.3 ppm or more, and facultative anaerobic refers to a state where DO is less than 0.3 ppm but not zero. Furthermore, the state where DO is zero is called obligate anaerobic. The DO of zero means that the dissolved oxygen available to the organism is substantially zero. If the obligate anaerobic region is partially generated for some reason, the planned biota is destroyed, and colonies composed of microorganisms and protozoa are peeled off from the contact material. Moreover, when the part is blackened and taken out into the air, a peculiar rot odor is felt.

As can be seen from the fact that the biomass organic matter is represented by the general formula (C ₅ H ₇ NO ₂ ) _n, it is desirable that the excess sludge is decomposed into carbon dioxide gas, water and nitrogen gas. In particular, it is desirable that the nitrogen atom of the nitrogen compound in the microorganism not only decomposes from NH ₃ to NO ₃ but also decomposes into nitrogen gas. This is because, especially when treated water is discharged into closed waters and seas, all nitrogen such as NH ₃ and NO ₃ becomes a causative substance that generates red tides. Because it is made. That is, eliminating excess sludge usually means decomposing the excess sludge into carbon dioxide, water, and nitrogen gas. In addition, when the denitrification process is not particularly necessary, only the aerobic process can be performed.

  In the aerobic treatment in the sludge treatment apparatus 60, the treatment is performed using not only microorganisms but also a protozoan that is a higher organism on the food chain than microorganisms and a microanimal predation mechanism that is composed of higher-grade metazoans. The Therefore, it is necessary to prevent the activities of protozoa and metazoans from being suppressed by microbial emissions. Therefore, it is preferable that the number of aeration tanks to be subjected to aerobic treatment is two to four tanks so that the species that live in each can be segregated. In this way, microorganisms are activated by decomposing organic substances (BOD components) in the preceding tank, and in the latter stage, higher-order protozoa and metazoans are sacrificed and efficiently consumed by the former stage microorganisms. become able to.

Moreover, in the denitrification process in the sludge treatment apparatus 60, NH ₃ produced by decomposing proteins constituting microorganisms is oxidized by nitrifying bacteria using oxygen several times the amount of nitrogen in an aeration tank, and NO ₂ or Converted to NO _X such as NO ₃ In addition, since the power of nitrifying bacteria is weak in activated sludge, a large aeration tank (that is, a large residence time) is required. Usually, MLSS of excess sludge is in the range of from about a few thousand 20,000, produced NO _X concentration is high. To remain in the degradation of 80% level in the denitrification one step, in order to reduce the NO _X to 10ppm level, to carry out the two-stage denitrification of circulation such as described in FIG desirable. These NO _X are reduced by denitrifying bacteria and decomposed into N ₂ gas. This completes the denitrification.

  Here, the structure of the example of the sludge treatment apparatus of FIG. 2 is demonstrated concretely. The sludge treatment apparatus 60 includes a mixing tank 70, a biological treatment tank 80, and a sedimentation tank 100. The mixing tank 70 receives and stores the raw water 1 containing the BOD component and the excess sludge at a constant ratio and stirs and mixes them with the stirrer 71. The mixed treated water (hereinafter referred to as mixed water) is sent to the biological treatment tank 80 that continues from the overflow water line 5. In addition, instead of the mixing tank 10, the storage tank 10 may be used, and the raw water and excess sludge may be mixed by the stirrer 90 in the subsequent first anaerobic tank 81.

  The mixing ratio of surplus sludge and raw water is preferably in the range of 1: 9 to 7: 3. Within this range, the biota is activated moderately, and excess sludge can be treated efficiently. That is, the capacity of the biological treatment tank of the sludge treatment apparatus required when a certain amount of excess sludge is treated can be reduced. Preferably it is in the range of 2 to 8 to 6 to 4, more preferably in the range of 3 to 7 to 5 to 5.

  For example, in the case of the raw water 9 with respect to the excess sludge 1, the size of the biological reaction tank necessary for eliminating a certain amount of excess sludge is (1 + 9) / 1 = 10 times the amount of excess sludge. Moreover, when raw water is 5 with respect to the excess sludge 5, it becomes (5 + 5) / 5 = 2 times, and the magnitude | size of the biological reaction tank about twice the amount of excess sludge is needed. That is, the larger the ratio of surplus sludge in the mixed water, the smaller the capacity of the biological reaction tank necessary for treating a certain amount of surplus sludge, and the facility cost and tank installation area are significantly reduced. On the other hand, the activity of the microorganism group is reduced, and the time required for decomposing a certain amount of excess sludge is increased. In short, if only surplus sludge is used (that is, raw water is 0 with respect to surplus sludge 10), the biological reaction tank needs a capacity of about 10 times the amount of surplus sludge discharged per day.

  As described above, there is a local minimum value when the surplus sludge mixing ratio is changed in the capacity of the biological reaction tank necessary for treating a certain excess sludge. In other words, the mixing ratio and the capacity of the biological reaction tank with the highest decomposition efficiency of surplus sludge exist. The optimization of the mixing ratio also affects the degree of biodegradability of the substrate contained in the raw water. The biodegradable substrate has a higher activity of the microorganism group in the biological reaction tank, and the reaction tank can be made smaller.

  The biological treatment tank 80 is divided into six tanks from a tank 81 to a tank 86 by a plurality of partition walls 96. When both BOD treatment and denitrification treatment are performed in biological treatment, it is preferable that the biological treatment tank has 4 to 6 stages. Although the partition 96 is simplified in FIG. 2, it communicates with an adjacent tank at the top of the partition. All of the six tanks from the tank 81 to the tank 86 are sequentially communicated by the same partition. The partition wall 96 has a combination of a partition wall connected to the upper part and a partition wall connected to the lower part in order from the left side to the right side of the drawing, and overflow water flows from the upper part of the first partition wall. It is desirable to be guided and flow into the tank from the lower part of the adjacent tank. Thereby, a process is made more uniform.

The 1st tank of the biological treatment tank 80 is the 1st anaerobic tank 81, and the contact material module which is not illustrated is installed in the inside. In this tank, denitrification is performed using the BOD component in the mixed water while the liquid inside is stirred by the stirrer 90. As a result, the nitrate compound is decomposed into nitrogen gas and water. Here, about 80% of the NO ₃ component is denitrified.

In the subsequent aerobic aeration tanks 82 to 84, contact material modules 92 to 94 are installed inside, and air is supplied from the air diffuser 91 to the inside of each tank. Here, decomposition of BOD components derived from raw water, and protozoa and metazoans that live more in the aeration tanks 82 to 84, particularly the tank 83 and the tank 84, consume ammonia nitrogen (NH ₃ ) discharged by eating excess sludge. Nitrification is performed.

  Here, an amount of about 200% to 400% of the inflow amount is taken out from the third aeration tank 84 through the line 97 and circulated in the first anaerobic tank 81. This is because the nitric acid compound generated in the aeration tanks 82 to 84 is sent to the first anaerobic tank 81 to increase the denitrification efficiency. Ammonia nitrogen is also nitrified while being circulated through this line.

  By doing so, the biota inside the aerobic tank is activated due to the BOD component derived from raw water. In particular, in the aeration tank 82, microorganisms derived from the mixed water are also activated, and accordingly, biological activities are also activated in the tanks inhabiting the protozoa and metazoans in the aeration tank 83 and 84, and surplus sludge is actively eaten. Result.

The remaining treated water in the third aeration tank 84 moves to the second anaerobic tank 85 which is the next tank. In order to decompose 20% NO ₃ remaining in the tank, a hydrogen donor such as methanol is supplied from the outside as a BOD component through a line 99, and the remaining nitrate compound is denitrified using this. . Subsequently, at the end of the biological treatment tank, overflow water flows into the aerobic tank 86 also provided with the contact material module 95 and the air diffuser 91, and the remaining BOD component is decomposed.

  Subsequently, the overflow water 6 moves to the sedimentation tank 100, and MLSS suspended in the water settles to form the sedimentation sludge 101. The activated sludge suspended matter (MLSS) from the first tank to the sixth tank has substantially the same concentration. The MLSS as the sedimentation sludge 101 whose concentration is increased by 20% to 40% as this sedimentation sludge is mixed with 100% to 150% of the mixed water using an air lift pump (not shown) included in the line 98. It returns to the 1st anaerobic tank 81 which comes as a circulating fluid. This is the same for both the aerobic process and the process using the anaerobic process and the aerobic process shown in FIG.

  In the supernatant of the sedimentation tank 100, hydrocarbons and nitrogen compounds are treated to a certain standard or less, but it is desirable to strictly treat phosphorus following nitrogen in order to prevent the occurrence of plankton abnormalities. This is because phosphorus is contained in raw water as well as microbial degradation products. For this purpose, it is desirable to perform dephosphorization by adding a flocculant (PAC or the like) to the supernatant water of the sedimentation tank 100 and causing the phosphorus compound to chemically react with insoluble aluminum phosphate or the like to precipitate and remove. Rather than using a flocculant, phosphorus removal may be performed using a zirconia-based anion adsorption exchanger. By doing in this way, the treated water of the preferable discharge | emission water quality is obtained.

  By the way, the decomposition | disassembly of the excess sludge originating in mixed water is performed by the predation mechanism of the microorganisms by the protozoa and metazoans which live in the aeration tank 82-84. Therefore, a contact material is required as a carrier that supports these protozoa and metazoans and can reproduce them in large quantities. A normal contact material may be used as the biological contact oxidation material, but a large number of loop-shaped protrusions are formed on the surface of a flexible core material such as a single-wire copper wire that has been coated to prevent corrosion. However, it is preferable to use one that protrudes 1.0 cm to 1.5 cm in length from the core surface and expands into a petal shape because the processing efficiency of excess sludge increases. A cross-sectional view of such a contact material is shown in FIG. It can be seen that a covering 75 and a base cloth 76 are wound around the core material 74, and a protrusion 73 made of loop-like fibers protrudes around the core material 74 so as to form a petal shape.

  Such a contact material core 74 keeps the shape of the contact material in a predetermined shape, and the contact materials are brought closer than necessary due to the influence of gravity and liquid flow, or the shape of the contact material is lost. And it plays the role which prevents that a liquid flow is bad and DO falls and an obligate anaerobic region arises. It is preferable to use a flexible metal wire for the core material because it is easy to process and has strength against gravity even after being supported by microorganisms. The metal wire may be a stranded wire obtained by bringing together a plurality of fine wires, but in order to have both strength and flexibility, it is preferable to use a single wire made of a single metal wire. As the material of the metal wire, a material having relatively large flexibility such as soft iron, aluminum, copper, etc. can be used without particular limitation, but copper is preferable from the viewpoint of corrosion resistance in water.

  Since the metal wire is used for a long time in water, it is preferable to provide a coating 75 for preventing corrosion. The coating may be a waterproof coating or the like, but it is preferable to provide a coating such as vinyl chloride, polyethylene or polypropylene from the viewpoint of handling and followability of the coating against deformation. Although the diameter of a metal wire changes with materials, it is preferable that they are 1 mm or more and 7 mm or less. More preferably, it is 2 mm or more and 6 mm or less. More preferably, it is 3 mm or more and 5 mm or less.

  In addition to the above coating, a base fabric 76 is preferably wound around the core material. By previously weaving loop-like fibers 73 for supporting microorganisms on this base fabric, microorganisms can be stably supported and a contact material that can withstand long-term use can be obtained. The material of the base fabric is polyamide fiber, polyester fiber, polyurethane fiber, polyvinyl chloride fiber, polyvinylidene chloride fiber, polyacrylic because it maintains strength in water and has dimensional stability, and is difficult to be decomposed by microorganisms. It is preferably made of a synthetic fiber such as a base fiber. The diameter of the core material including the base fabric is preferably 3 mm or more and 8 mm or less. By setting it as such a diameter, it becomes possible to earn the area of the base fabric which implants a loop-like fiber.

  On the surface of the core material, a large number of protruding loop-like fibers 73 are provided for supporting microorganisms, metazoans and the like. The loop-like fibers are fixed to the surface of the core material only at both ends of the fiber material having a certain length, and other than the both ends of the fiber material protrude from the surface of the core material. By making the contact material fibrous, the surface area per unit volume of the contact material can be remarkably increased to increase the density of microorganisms and the like, and the treatment capacity per unit volume of the water treatment device can be increased. . Here, the thickness of the fiber is preferably 50 dtex or more and 150 dtex or less. Above 50 dtex, the grown microorganisms and the like are less likely to fall off from the contact material due to gravity and swirling flow, and at 150 dtex or less, the surface area per unit volume of the contact material increases. Further, the fiber is fixed to the core material as a loop shape. The loop shape makes it difficult for the microorganisms and giant microorganisms that have adhered to the fiber surface and proliferated to fall out of the fiber due to the swirling flow for gravity and oxygen supply.

  Length of loop-like fiber (refers to the length from one end fixed to the core material surface to the other end fixed to the core material surface by measuring the length along the loop) Is preferably 10 mm or more and 50 mm or less. The length of the loop-like fiber is 50 mm or less, and the vicinity of the base of the loop is less likely to be an anaerobic region. In the aerobic region, it is difficult to cause a situation in which the activity of microorganisms or the like is reduced or the microorganisms themselves are killed. Preferably they are 20 mm or more and 45 mm or less, More preferably, they are 30 mm or more and 45 mm or less, More preferably, they are 30 mm or more and 40 mm or less. The contact material is configured by implanting loop-like fibers in a ribbon-like base cloth so as to have such a length, and winding this base cloth on the surface of the core material in a spiral shape.

  The loop-like fiber is preferably a fiber bundle obtained by bundling 3 to 20 fibers, and the fiber bundle is preferably provided on the core surface as a unit. In the shape of an independent loop where each loop-like fiber is separated, the loop becomes weak, it is difficult to resist the weight of microorganisms attached to the fiber, and the swing of the loop due to swirl tends to become intense. is there. However, in the shape of the fiber bundle, the loop easily maintains its original shape against the weight of microorganisms and the swirling flow, so that it is easy to secure a liquid flow and an anaerobic region is unlikely to occur. It is also easy to supplement microorganisms. Preferably they are 5 or more and 15 or less, More preferably, they are 7 or more and 12 or less.

The density at which the fiber bundles are provided on the core material surface is preferably 25 to 81 bundles per cm ^{2 of} the core surface. When the number of bundles is 81 or less, an obligate anaerobic region is hardly generated, and when the number is 25 or more bundles, sludge can be firmly captured against agitation caused by aeration and the resulting swirling sulfur. In addition, since protozoa and constituent animals are also difficult to drop out, they are liable to occur and proliferate. More preferably, it is 36 bundles or more and 64 bundles or less.

  The material of the loop-like fiber is made of synthetic resin because it is resistant to dissolved oxygen, can maintain strength and dimensional stability in water, is hardly decomposed by microorganisms, and can be easily molded into a fiber. Is preferred. Especially, it is preferable to use a thermoplastic resin from the ease of manufacture of a fiber. Examples of the thermoplastic resin include polyethylene, polypropylene, polyester, nylon, polyvinyl chloride, polyvinylidene chloride, and polyvinylidene fluoride. It is preferable to use polyvinylidene chloride because the specific gravity is large and the fiber can maintain a certain degree of rigidity and can easily maintain the shape of the loop. The method for producing the loop-shaped fiber is not particularly limited as long as it is spun according to a conventional method within the range where the effects of the invention are exhibited.

  The zeta potential on the surface of the loop-like fiber is desirably positive within the range of pH 5 to 9, and more desirably stable within this range. The magnitude of the positive zeta potential is 1 mV or more and 30 mV or less. Within this range, not only microorganisms but also protozoa and metazoans can be prevented from falling off, and as a result, an excellent effect of greatly reducing excess sludge in water treatment is exhibited. More preferably, it is 1 mV or more and 24 mV or less, More preferably, it is 1 mV or more and 20 mV or less, Furthermore, 2 mV or more and 10 mV or less are preferable. Such a zeta potential can be measured by a normal streaming potential method or the like.

  Such a contact material 72 is preferably shaped into a spiral shape as shown in FIG. 4 in order to increase the contact efficiency between microorganisms and dissolved oxygen in the biological treatment tank. FIG. 4B is a conceptual diagram when the contact material 72 is viewed from the direction perpendicular to the central axis 78 of the helical rotation, and FIG. 4A is a contact from the parallel direction to the same central axis 78. It is a conceptual diagram at the time of seeing the material 72. FIG. By setting it as such a shape, the biological density can be maintained high and the stirring effect accompanying aeration can be acquired. The outer diameter r of the rotating circle viewed from the direction of the helical center axis 78 is preferably 60 mm or more and 90 mm or less. In addition, the spiral pitch d, which is the distance traveled in the direction of the rotation axis as it goes around the rotation circle, is preferably 5 cm or more and 20 cm or less. In this range, it is possible to make it difficult for the obligate anaerobic region to occur while maintaining high utilization efficiency of the water treatment tank space. More preferably, it is 7 cm or more and 13 cm or less.

  Such a contact material is fixed to a metal frame so that a large number of the contact materials are arranged in parallel in the vertical direction to constitute a contact material module. The upper and lower ends of each contact material are fixed to a metal frame or mount. The distance between the outer peripheries of the contact materials is preferably as small as possible from the viewpoint of the utilization efficiency of the tank volume. On the other hand, if the distance is too small, stirring between the outer peripheries of the contact materials becomes insufficient, and sludge is easily clogged between the outer peripheries. . If sludge is clogged, an obligate anaerobic zone will occur. In order to prevent this, it is preferable to arrange the contact materials so that the distance between the outer circumferences of the contact materials is 15 mm or more. The same applies to the distance between the inner wall or frame of the tank and the outer periphery of the contact material.

  Incidentally, membrane filtration can be used instead of the sedimentation tank 100 of FIG. Although the settling tank requires a relatively large installation area, the membrane filtration can save more space. Further, in the sedimentation tank, sludge may not be sufficiently settled or bubbles may carry over due to fluctuations in the biological reaction, but there is no such fear in the case of membrane filtration. Furthermore, when a membrane separation apparatus is used, not only MLSS but also microorganisms, SS substances and colloid substances in the treated water are separated and removed, so that there is an advantage that good recovered water can be obtained.

  The membrane type that can be used in the membrane separator is a UF membrane or an MF membrane. As the shape of the membrane, any of a hollow fiber membrane, a flat membrane and a tubular membrane can be used. The membrane filtration device can be an MBR method (membrane separation activated sludge method) in which the membrane module is immersed in the biological treatment tank at the final stage and filtered by making the inside of the membrane module have a negative pressure. Or it is good also as a method of pumping up activated sludge liquid from the biological treatment tank of the last stage, carrying out pressurized liquid feeding to a membrane separator, and filtering. Either method is applicable. When the MLSS concentration in the biological treatment tank is high, the immersion type is advantageous from the viewpoint of energy efficiency.

  The concentrated liquid separated from the membrane separation device is returned to the top treatment tank of the preceding biological treatment tank. Further, the water filtered by the membrane separator is SS = 0, and is recovered and reused or discharged as described above. When more purified treated water is required for reuse, for example, when used for water for production processes in factories, etc., RO membrane is further used after membrane separation equipment using UF or MF. It is preferable to connect the existing membrane separator. The treated water thus treated can be pure water having an electric resistance of 1 MΩ or more, and can be reused without any particular problem. Hereinafter, the present invention will be specifically described with reference to examples.

  Each of 2- (2′-hydroxy-3′-t-butyl-5′-methylphenyl) -5-chlorobenzotriazole, SF green, and citric acid was added in an amount of 0.3 wt% with respect to the polyvinylidene chloride resin. It was kneaded after being mixed with polyvinylidene chloride resin so as to be 0.5 wt% and 0.5 wt%, and then spun to obtain a fiber having a thickness of 105 dtex. Subsequently, the surface of the fiber was treated with a saturated calcium chloride aqueous solution and then washed with water. The zeta potentials of the fibers at pH 9, 7, and 5 were +2.1 mV, +2.5 mV, and +2.6 mV, respectively.

Using a long polyester woven ribbon with a width of 5 mm as a base fabric, a pile fabric was prepared in which the fibers obtained above were woven so as to form a loop on one side of the base fabric. At that time, in one ribbon, a bundle of 10 fibers is bundled, and a bundle of loop-shaped fibers whose length is adjusted to be 35 mm is 72 bundles per 1 cm ^2. A pile woven fabric was woven into the base fabric.

  Next, with the copper wire, which is a flexible single wire, coated with polyvinyl chloride, a metal wire with a predetermined length of 4.3 mm in diameter is placed on the outside so that the loop-like fibers come out to the outside, and the above ribbon is not spaced A fiber contact material was manufactured by winding and fixing the ribbon so that the ribbon could not be unwound at both ends of the metal wire. Thereby, the contact material provided with the loop-like fiber was obtained in both the length direction and the circumferential direction of the contact material. This fiber-type contact material was processed into a spiral shape in which the outer diameter of the outer peripheral portion was about 85 mm and the inner diameter was about 21 mm, and the pitch accompanying one rotation around the helical rotation axis was about 11 cm.

  A plurality of the contact materials were passed up and down on a stainless steel frame having a height of 2.3 m, a length of 0.5 m, and a width of 1.6 m to fix the upper end and the lower end, and a module was manufactured. At that time, the arrangement of the helical fiber contact materials was arranged so that the distance between the tips of the loop-shaped fibers was 30 mm. A gantry frame having a height of 0.3 m was attached to the lower part of the module. Three more similar modules were made.

Next, a sludge treatment apparatus similar to that shown in FIG. 2 was prepared. The sludge treatment apparatus is a circulating two-stage denitrification system with a biological treatment tank with a total capacity of 12 m ³ and a sedimentation tank of 3 m ³ , mixing tank → first anaerobic tank → first aeration tank → second aeration tank → second 2 Anaerobic tank → 3rd aeration tank → Precipitation tank. In addition, four times the amount of inflow from the second aeration tank is returned to the first anaerobic tank, and the sedimentation sludge in the settling tank is returned to the first anaerobic tank for 1 to 2 times the amount of inflow.

  The contact material module obtained above was installed in the first, second, and third aeration tanks. In the first aeration tank, the two modules manufactured above are submerged in parallel with the water flow. In the second aeration tank and the third aeration tank, one of the above modules is submerged. Yes.

  Next, the wastewater of the soybean food factory whose BOD component density | concentration is 1500 ppm on average was prepared. The wastewater is biologically treated in a standard activated sludge tank as shown in FIG. 1 provided in the factory, and surplus sludge having an MLSS concentration of 11000 ppm to 15000 ppm is generated.

  First, without introducing excess sludge, only the above-mentioned factory wastewater was introduced into the mixing tank of the sludge treatment apparatus prepared above, and the operation was started. After about one month of acclimatization operation, MLSS was stabilized at approximately 7000 ppm to 1000 ppm 0, and stable operation was achieved. The water quality after 5 months was BOD 10 ppm or less, total nitrogen (TN) 10 ppm or less, and SS 15 ppm or less. Further, no excess sludge was generated, and no sedimentation sludge was drawn from the sedimentation tank. In this state, when the biological contact material in the third aeration tank was pulled up and observed, many yarn earthworms were found to be attached, and in part, the contact material appeared red.

Subsequently, both were introduced into the mixing tank so that the factory wastewater was 10 m ³ / day and surplus sludge was 2 m ³ / day (surplus sludge / raw water = 2/10), and then overflowed into the biological treatment tank. I let you. Operation was performed in this state, and MLSS and sludge amount in the third aeration tank were measured as needed. The quality of the treated water was evaluated by measuring the supernatant water of the sedimentation tank. The residence time (HRT) of factory raw water and excess sludge is 24 hours.

The MLSS of the third aeration tank after 5 days, 10 days, 1 month and 2 months after the start of operation was 13600 ppm, 11000 ppm, 10000 ppm, 8000 ppm and 8500 ppm, respectively. Despite surplus sludge flowing in daily at 2 m ³ / day, MLSS was stable at a value of 8000 to 9000 ppm. Moreover, sedimentation sludge in the sedimentation tank of the sludge treatment apparatus did not increase. That is, although the excess sludge was newly mixed, they disappeared and the sedimentation sludge did not increase. 1440 kg of MLSS was loaded in 2 months, but the MLSS in the third aeration tank at that stage was 8500 ppm, and when the amount of BOD component in the factory raw water was added, about 2000 kg of sludge disappeared. become.

  The water quality of the treated water was BOD 15 ppm, TN 18 ppm, and SS 18 ppm, which were values that could be discharged.

Comparative Example 1

In Example 1, in a state where the sludge treatment apparatus has reached a stable operation from the acclimatization operation after the start of operation, only surplus sludge 12m ³ generated from the activated sludge tank of the factory is biologically treated from the mixing tank without mixing raw water. The test was conducted in the same manner as in Example 1 except that the operation was continued without introducing surplus sludge and factory wastewater. The MLSS of excess sludge from the factory activated sludge tank was 12,500 ppm. The MLSS was measured by sampling appropriately from the third aeration tank, and the degree of extinction of excess sludge was observed.

  Two days after the introduction of excess sludge, the MLSS was 10300 ppm. Continued operation while managing DO. The MLSS after 5 days from the introduction was reduced to 5500 ppm. When the aeration tank was observed from the top on the 10th day after the introduction, MLSS was reduced and the immersed biological contact material was visible. At this stage, when sampling from the third aeration tank and measuring MLSS, the excess sludge was reduced to 100 ppm or less, so it took 10 days for the excess sludge to almost disappear. Excess sludge disappeared about 10% per day.

  The ratio of surplus sludge to factory effluent (excess sludge / factory effluent) was adjusted to the values shown in Table 1 below and input to the mixing tank, and the time (HRT) that the factory sewage stays in the sludge treatment equipment is shown. 1 except that it was set to be the value described in 1 and did not take a habituation period between the tests with different ratios, and the operation was performed for 60 days at each ratio by sequentially switching the ratios. The treatment operation was performed in the same manner as in Example 1. In each operation, MLSS was measured by sampling from the third aeration tank. Table 2 shows the measurement results of each MLSS and treated water quality on the 60th day. In any ratio, it can be seen that there is no outflow of MLSS to the treated water, and that the excess sludge is decomposed and extinguished. It shows the water quality until the treated water can be discharged sufficiently.

Table 3 shows the results of conversion of the size of the biological treatment tank for treating 10 m ³ / day of the raw water to be treated at each ratio, including the above results and Example 1 and Comparative Example 1. When surplus sludge is to be eliminated under the conditions of mixing surplus sludge at 10 m ³ / day with soybean food factory wastewater with an average BOD of 1500 ppm, the surplus sludge and wastewater are mixed and treated in a 1: 1 combination. The biological treatment tank was 30 m ³ , and the minimum result was obtained.

It is the schematic diagram which showed the state by which the sludge processing apparatus was integrated in the activated sludge apparatus. It is the schematic diagram which showed schematic structure of the sludge processing apparatus. It is the schematic diagram which showed the outline of the contact material cross section seen from the direction parallel to the core material direction of a contact material. It is a schematic diagram of a part of the contact material processed into a spiral shape. It is the schematic diagram which showed the example of the conventional volume reduction apparatus of activated sludge.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Raw water 2, 3 Treated water line 4 Treated water 5 Mixed water line 6 Overflow line 7 Treated water 10 Storage tank 20 Activated sludge tank 21 Aeration pipe 22 Blower 30 Settling tank 31 Precipitated sludge 40 Precipitated sludge extraction line 41 Sludge return line 42 Excess sludge transfer line 51 Raw water line 60 Sludge treatment device 70 Mixing tank 71 Stirrer 72 Contact material 73 Loop fiber 74 Core material 75 Cover 76 Base cloth 78 Center shaft 80 Biological treatment tank 81 First anaerobic tank 82-84 Aeration tank 85 First 2 Anaerobic tank 86 Aeration tank 90 Stirrer 91 Aeration pipe 92-95 Contact material module 96 Bulkhead 97 Circulation line 98 Return line 99 Methanol addition line 100 Sedimentation tank 101 Sedimentation sludge 110 Solubilizer 111 Return line 112 Discharge excess sludge

Claims (10)

  A method for biological treatment of surplus sludge produced by activated sludge treatment of raw water, wherein a part of the raw water is mixed with the surplus sludge, and the mixed water generated by the mixing is produced by microorganisms supported on a contact material. A surplus sludge biological treatment method, wherein the biological treatment is performed at least aerobically.   The surplus sludge biological treatment method according to claim 1, wherein a mixing ratio of the excess sludge and the raw water in the mixed water is within a range of 1: 9 to 7: 3.   2. The surplus sludge biological treatment method according to claim 1, wherein the aerobic biological treatment uses a micro-animal predation mechanism comprising microorganisms, protozoa, and metazoans.   Furthermore, the processing method of the excess pollution of Claim 1 including the denitrification process in facultative anaerobic atmosphere.   The method for treating excess pollution according to claim 1 or 4, wherein a precipitate is separated after the biological treatment.   6. The method for treating excess pollution according to claim 5, wherein the separation treatment is performed by membrane separation.   6. The method for treating excess pollution according to claim 5, wherein the supernatant water from which the precipitate has been separated is subjected to a dephosphorization treatment.   The method for treating excess sludge according to claim 1, wherein the contact material comprises a spiral core material and a plurality of loop-shaped fibers provided on the surface of the core material.   The method for treating excess sludge according to claim 8, wherein the loop-shaped fibers are made of vinylidene chloride. A biological treatment apparatus for surplus sludge generated by the activated sludge treatment of raw water, comprising a mixing means for mixing a part of the raw water with the surplus sludge to form mixed water, and a contact material supporting microorganisms, A surplus sludge biological treatment apparatus comprising a treatment means for biologically treating the mixed water at least aerobically.

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