Method for starting anaerobic processing tank
The method accelerates anaerobic treatment tank startup by using a coagulant and sludge addition process with classification and mixing, ensuring rapid microbial adhesion and biofilm formation on carriers, thus improving efficiency and reducing costs.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- SUMITOMO HEAVY IND LTD
- Filing Date
- 2025-11-26
- Publication Date
- 2026-06-04
AI Technical Summary
Existing methods for starting up anaerobic treatment tanks filled with carriers take too long to achieve sufficient anaerobic treatment capacity due to the slow formation of biofilms and uniform microbial adhesion on carrier surfaces.
A method involving multiple stages of adding a coagulant and sludge to the carriers, utilizing a cationic polymer coagulant and dispersed sludge, and promoting classification through specific gravity differences to efficiently adhere microorganisms to the carrier surfaces, accompanied by a mixing step to enhance separation and adhesion.
This method significantly shortens the startup time of anaerobic treatment tanks by ensuring uniform microbial adhesion and biofilm formation on carriers, enhancing the efficiency and reducing operational costs by eliminating the need for temporary adjustment tanks and minimizing excess sludge/coagulant use.
Smart Images
Figure JP2025041071_04062026_PF_FP_ABST
Abstract
Description
Method for starting up an anaerobic treatment tank
[0001] The present invention relates to a method for starting up an anaerobic treatment tank. More specifically, the present invention relates to a method for starting up an anaerobic treatment tank filled with carriers.
[0002] Generally, as a method for treating wastewater containing organic substances, biological treatment using various microorganisms is known. In particular, biological treatment under an anaerobic environment (hereinafter referred to as "anaerobic treatment") has high merits in terms of introduction, such as no need for aeration power and almost no generation of excess sludge.
[0003] As such anaerobic treatment, an upflow anaerobic sludge bed method (UASB) using a treatment tank filled with sludge or granules is known. Further, in order to increase the concentration of anaerobic microorganisms in the treatment tank, it is also known to use a treatment tank filled with carriers.
[0004] When using a treatment tank filled with carriers, it is known that microorganisms adhere to the carriers and it takes time to exhibit sufficient anaerobic treatment capacity. In particular, at the time of starting up the device, studies have been conducted on how to shorten the time. For example, in Patent Document 1, in anaerobic treatment using a treatment tank that holds carriers, when starting up the device (treatment tank), organic wastewater is passed through while the carriers and methane bacteria granules are present in a predetermined ratio in the treatment tank, and then the passage of the organic wastewater is continued to disassemble and disperse a part of the methane bacteria granules.
[0005] Japanese Patent Application Laid-Open No. 2012-110821
[0006] As described in Patent Document 1, it is known to use a laminate of carriers and granules to shorten the time required for starting up a treatment tank for anaerobic treatment. However, with this method, it takes a period of months until a biofilm is formed on the carrier surface and the treatment becomes stable (in other words, until the microorganisms adhere uniformly to the carrier surface and the domestication is completed), so sufficient time shortening cannot be said to have been achieved.
[0007] The object of the present invention is to provide a method for setting up an anaerobic treatment tank that efficiently promotes microbial adhesion to the carrier surface and shortens the time required to set up the anaerobic treatment tank.
[0008] As a result of diligent research into the above-mentioned problems, the inventors of the present invention have discovered that, in a method for setting up an anaerobic treatment tank, by adding substances involved in microbial adhesion to a carrier filled in the anaerobic treatment tank in a predetermined order, and by repeating this process multiple times, it is possible to efficiently attach microorganisms to the carrier, and have completed the present invention. That is, the present invention is the following method for setting up an anaerobic treatment tank.
[0009] The present invention provides a method for setting up an anaerobic treatment tank to solve the above problems, comprising a carrier coating step which includes a coagulant input step of adding a coagulant to an anaerobic treatment tank filled with carriers, and a sludge input step of adding sludge to the anaerobic treatment tank after the coagulant input step, and is characterized by performing the carrier coating step multiple times. According to the present invention's method for setting up an anaerobic treatment tank, a coagulant is first added to the carriers filled in the anaerobic treatment tank, bringing the carriers and the coagulant into contact and forming a state in which the coagulant adheres to the surface of the carriers. By adding sludge thereto, a coagulation reaction between the coagulant and the sludge proceeds on the surface of the carriers, making it possible to form a state in which the surface of the carriers is uniformly covered with sludge (in other words, a state in which microorganisms adhere uniformly to the surface of the carriers). Furthermore, by dividing the addition of the coagulant and sludge into multiple stages, the anaerobic treatment tank will contain both sludge-coated and uncoated carriers. However, due to the difference in specific gravity, the sludge-coated and uncoated carriers will move within the tank and become separated (in other words, a phenomenon based on classification occurs). Therefore, when the coagulant and sludge are added next, it becomes easy to efficiently bring the coagulant and sludge into contact with the uncoated carriers. By repeating this process, it becomes possible to create a state where the entire anaerobic treatment tank is filled with sludge-coated carriers. In other words, during the startup of the anaerobic treatment tank, microbial adhesion to the carrier surface is efficiently promoted, and the time required for startup of the anaerobic treatment tank can be shortened.
[0010] Furthermore, one embodiment of the anaerobic treatment tank startup method of the present invention includes a mixing step for circulating the treated water of the anaerobic treatment tank, and the mixing step is performed during the carrier coating step. With this feature, after the coagulant and sludge are introduced into the anaerobic treatment tank, a circulating flow is formed within the anaerobic treatment tank, thereby shortening the time required for the sludge-coated carriers and uncoated carriers to move within the anaerobic treatment tank and become separated. In other words, it becomes possible to shorten the time required to start up the anaerobic treatment tank even more effectively.
[0011] Furthermore, in one embodiment of the anaerobic treatment tank startup method of the present invention, the coagulant input step is characterized by the input of a coagulant into the anaerobic treatment tank via an acid generation tank installed upstream of the anaerobic treatment tank, and the sludge input step is characterized by the input of sludge into the anaerobic treatment tank via an acid generation tank. When starting up an anaerobic treatment tank, it is necessary to bring in sludge from outside the system, and generally a temporary adjustment tank is prepared, in which the sludge is stored and then introduced into the anaerobic treatment tank. With this feature, when starting up the anaerobic treatment tank, it becomes possible to introduce the entire amount of sludge brought in from outside the system into the acid generation tank, eliminating the need for a temporary adjustment tank and thus reducing costs. In addition, by enabling the input of the coagulant via the same route as the sludge, it is possible to suppress the complexity and cumbersomeness of the operation as a carrier coating process.
[0012] Furthermore, one embodiment of the anaerobic treatment tank startup method of the present invention is characterized in that the total amount of sludge introduced in the sludge input step is limited to 3% of the weight of the carriers filled in the anaerobic treatment tank, and the total amount of coagulant introduced in the coagulant input step is limited to 1.1% of the total amount of sludge. According to this characteristic, by introducing a predetermined total amount of sludge according to the weight of the carriers filled in the anaerobic treatment tank, it is possible to suppress sludge outflow due to excessive sludge input. Also, if there is an excess of coagulant in the anaerobic treatment tank, the carriers covered with sludge will aggregate to form aggregates, and it will become difficult for the sludge-covered carriers and uncovered carriers to move within the anaerobic treatment tank due to the difference in specific gravity (making it difficult to exert the effect of classification). Therefore, by keeping the total amount of coagulant introduced below a predetermined value, it is possible to achieve both improved efficiency of carrier coating by sludge and suppression of obstruction of movement between sludge-covered and uncovered carriers within the anaerobic treatment tank (maintaining the effect of classification).
[0013] Furthermore, one embodiment of the method for setting up the anaerobic treatment tank of the present invention is characterized in that the carrier filled into the anaerobic treatment tank is activated carbon. This characteristic allows for the use of a carrier that excels in its function as a carrier for attaching and supporting sludge (microorganisms), and also allows for the use of a carrier that exhibits a significant difference in specific gravity between the sludge-coated carrier and the uncoated carrier, resulting in a remarkable effect due to the classification action.
[0014] Furthermore, one embodiment of the anaerobic treatment tank startup method of the present invention is characterized in that the coagulant is a cationic polymer coagulant. It is known that general activated carbon has a negative charge, and that sludge is also in a negatively charged state. Due to this characteristic, when the carrier is activated carbon, using a cationic polymer coagulant as the coagulant increases the adhesion efficiency of the coagulant itself to the carrier surface, suppresses the electrical repulsion between the activated carbon and the sludge which have the same charge, and, together with the improved coating efficiency of the carrier by the sludge, enables the formation and maintenance of a stable coating state.
[0015] Furthermore, one embodiment of the anaerobic treatment tank startup method of the present invention is characterized by the sludge being dispersed sludge. This characteristic improves the contact efficiency of the sludge with the carrier, enhances the adhesion of the sludge, and facilitates the formation and maintenance of a stable covering state.
[0016] Furthermore, one embodiment of the anaerobic treatment tank startup method of the present invention is characterized by determining the number of carrier coating steps based on the carrier filling height in the anaerobic treatment tank. According to this feature, when forming a state in which the entire anaerobic treatment tank is filled with sludge-coated carriers, it becomes possible to add an appropriate amount of coagulant and sludge relative to the carrier height (amount of carrier) filled in the anaerobic treatment tank. This makes it possible to shorten the startup time of the anaerobic treatment tank and suppress the occurrence of problems and cost increases due to excessive coagulant and sludge addition.
[0017] According to the present invention, it is possible to provide a method for setting up an anaerobic treatment tank that efficiently promotes microbial adhesion to the carrier surface and shortens the time required to set up the anaerobic treatment tank.
[0018] This is a schematic diagram illustrating an anaerobic treatment tank and surrounding equipment to which the anaerobic treatment tank startup method according to the first to third embodiments of the present invention is applied. This is an explanatory diagram showing the contents of each step in the anaerobic treatment tank startup method according to the first embodiment of the present invention. This is an explanatory diagram showing the overall process sequence for the anaerobic treatment tank startup method according to the first embodiment of the present invention. This is an explanatory diagram showing the contents of each step in the anaerobic treatment tank startup method according to the second embodiment of the present invention. This is an explanatory diagram showing the contents of each step in the anaerobic treatment tank startup method according to the third embodiment of the present invention. This is a schematic diagram illustrating an anaerobic treatment tank and surrounding equipment to which the anaerobic treatment tank startup method according to the fourth embodiment of the present invention is applied.
[0019] In the present invention, the wastewater to be treated by the anaerobic treatment tank contains organic matter and includes industrial wastewater discharged from various factories such as food processing plants, chemical plants, and pulp and paper mills, as well as domestic wastewater such as sewage. However, the wastewater is not limited to this; any wastewater containing organic matter that can be biologically treated under anaerobic conditions is subject to treatment in the present invention. Examples of such wastewater include organic wastewater containing livestock manure and sludge (excess sludge).
[0020] Hereinafter, embodiments of the anaerobic treatment tank startup method according to the present invention will be described in detail with reference to the drawings. Note that the anaerobic treatment tank startup method described in the embodiments is merely illustrative for illustrating the anaerobic treatment tank startup method according to the present invention and is not limited thereto.
[0021] The method for setting up an anaerobic treatment tank according to this embodiment relates to setting up an anaerobic treatment tank for biological treatment (anaerobic treatment) of wastewater. More specifically, the method for setting up an anaerobic treatment tank according to this embodiment aims to quickly create a state in which microorganisms involved in biological treatment (anaerobic treatment) are attached to an anaerobic treatment tank filled with a carrier without any prior preparation of the carrier, thereby shortening the time required to enable stable biological treatment (anaerobic treatment) of wastewater.
[0022] (Anaerobic Treatment Tank) Figure 1 is a schematic diagram showing an anaerobic treatment tank and its surrounding equipment to which the anaerobic treatment tank startup method described later in the first to third embodiments (hereinafter referred to as "this embodiment") is applied. As shown in Figure 1, the anaerobic treatment tank 10 in this embodiment is filled with a carrier C inside, and by attaching microorganisms to this carrier C using the anaerobic treatment tank startup method in this embodiment, anaerobic treatment using these microorganisms is carried out and the wastewater W0 is discharged outside the system as treated water W1. In Figure 1, the linear arrows indicate the flow of wastewater W0 and treated water W1, the white block arrows (surface arrows) indicate the introduction of the coagulant F, and the filled block arrows indicate the introduction of sludge S.
[0023] The anaerobic treatment tank 10 in this embodiment is not particularly limited, as long as it has a structure for performing anaerobic treatment on wastewater W0. Examples of anaerobic treatments performed in the anaerobic treatment tank 10 include methane fermentation by acid-producing bacteria and methane-producing bacteria, denitrification treatment in which nitrate and nitrite are reduced by denitrifying bacteria, and sulfate reduction treatment in which sulfuric acid is reduced by sulfate-reducing bacteria.
[0024] Furthermore, the anaerobic treatment tank 10 in this embodiment may be equipped with various additional facilities. For example, the anaerobic treatment tank 10 may be equipped with means for adjusting the internal water temperature, means for adding pH adjusters, and means for adding metals such as nitrogen, phosphorus, cobalt, and nickel, which are nutrients required by microorganisms. In particular, when methane fermentation by acid-producing bacteria and methane-producing bacteria is performed as anaerobic treatment, it is preferable to provide the anaerobic treatment tank 10 with facilities for recovering, purifying, and storing methane gas.
[0025] Furthermore, another reaction tank may be provided upstream of the anaerobic treatment tank 10 in this embodiment. In particular, when methane fermentation using acid-producing bacteria and methane-producing bacteria is performed as anaerobic treatment, it is known that the optimal conditions for the treatment process using acid-producing bacteria, which is a treatment process that reduces organic matter in wastewater W0 to low molecular weight (hereinafter referred to as the "acid production process"), and the treatment process using methane-producing bacteria, which decomposes the reduced molecular weight organic matter to produce methane gas (hereinafter referred to as the "methane production process"), are different. Therefore, as shown in Figure 1, it is preferable to provide an acid production tank 20 upstream of the anaerobic treatment tank 10 and to carry out the acid production process and the methane production process in separate tanks. The acid production tank 20 should function as a tank for carrying out the acid production process, in which wastewater W0 is introduced upstream of the anaerobic treatment tank 10, and in an anaerobic atmosphere without dissolved oxygen, the acid-producing bacteria (one of the facultative anaerobic bacteria) contained inside promote the reduction of organic matter in wastewater W0 (decomposition of organic matter) to produce organic acids. Furthermore, it is desirable that the acid generation tank 20 be a sealed system and that an anaerobic environment be maintained.
[0026] In this embodiment, the description will mainly focus on a configuration in which an acid generation tank 20 is provided upstream of the anaerobic treatment tank 10, but the invention is not limited to this configuration. For example, the acid generation tank 20 may be omitted, and the wastewater W0 may be directly introduced into the anaerobic treatment tank 10. Alternatively, a raw water adjustment tank or raw water storage tank may be provided further upstream of the acid generation tank 20.
[0027] In this embodiment, the anaerobic treatment tank 10 and the acid production tank 20 are arranged as shown in Figure 1, with the acid production tank 20 positioned upstream of the anaerobic treatment tank 10, and the acid production tank 20 being provided with a line L1 for introducing wastewater W0 and a line L2 for connecting to the anaerobic treatment tank 10, while the anaerobic treatment tank 10 is provided with a line L3 for indirectly introducing wastewater W0 via line L2 and for discharging treated water W1 after anaerobic treatment.
[0028] Furthermore, in this embodiment, the anaerobic treatment tank 10 is provided with a line L4 in addition to line L3, which discharges the treated water W1 and is connected to the upstream side of the anaerobic treatment tank 10, in order to circulate the treated water W1 within the anaerobic treatment tank 10 in a step related to the startup of the anaerobic treatment tank 10. At this time, line L4 may be connected to line L2, or it may be connected to the acid generation tank 20.
[0029] (Carrier) The carrier C to be filled into the anaerobic treatment tank 10 can be any material to which anaerobic microorganisms (sludge S) involved in anaerobic treatment adhere, and there are no particular limitations on its structure or material, but in this embodiment, it is preferable to use a carbonaceous carrier as the carrier C. A carbonaceous carrier refers to an inorganic material whose main component is carbon, and specifically, examples include carbon black, graphite, coke, and activated carbon. In addition to being easy to mold as a carrier, carbonaceous carriers generally have a higher specific gravity than resin carriers, and have the advantage of suppressing outflow to the outside of the tank when filled into the anaerobic treatment tank 10 and allowed to flow. Furthermore, by using a carbonaceous carrier as the carrier C, in the process related to the start-up of the anaerobic treatment tank in this embodiment, when sludge S (microorganisms) is applied to the surface of the carrier, the difference in specific gravity between the carrier covered with sludge S and the uncovered carrier can be made large. As a result, the difference in specific gravity causes the sludge-covered carrier and the uncovered carrier to move within the anaerobic treatment tank 10, and the time required to reach a separated state can be shortened. In other words, by using a carbonaceous carrier as carrier C, the effects of classification are significantly exhibited in the process of setting up the anaerobic treatment tank in this embodiment. Furthermore, while the carbonaceous carrier in this embodiment is not particularly limited in terms of whether or not it has pores, it is preferable that it has pores from the viewpoint of being able to adsorb components that inhibit anaerobic treatment by anaerobic microorganisms (anaerobic treatment inhibitors) in addition to retaining anaerobic microorganisms, and specifically, it is particularly preferable to use activated carbon.
[0030] (Coagulant) The coagulant F is one of the substances involved in the attachment of microorganisms to the carrier C in the method for setting up the anaerobic treatment tank in this embodiment. The coagulant F in this embodiment can be any substance that comes into contact with the carrier C, adheres to the surface of the carrier C, and then promotes a coagulation reaction with the sludge S that is introduced, so that the surface of the carrier C is covered with sludge S. For example, it can be selected from substances known as inorganic coagulants or polymer coagulants according to the type of carrier C (material, surface charge, etc.).
[0031] Here, considering the formation and maintenance of adhesion to the carrier C and the efficiency of the flocculation reaction with the sludge S, it is preferable to use a polymer flocculant as the flocculant F. In particular, when a carbonaceous carrier (activated carbon) is used as the carrier C in this embodiment, as described above, it is preferable to use a cationic polymer flocculant as the flocculant F. General activated carbon has a negative charge, and it is known that sludge S is also in a negatively charged state. Therefore, when the carrier C is activated carbon, using a cationic polymer flocculant as the flocculant F increases the adhesion efficiency of the flocculant F itself to the carrier C, suppresses the electrical repulsion between the activated carbon and the sludge S which have the same charge, and, together with the improved coating efficiency of the carrier C by the sludge S, enables the formation and maintenance of a stable coating state.
[0032] Regarding specific examples of the flocculant F in this embodiment, the cationic polymer flocculant can be any flocculant that contains at least one cationic monomer as an essential component, such as a homopolymer or copolymer of cationic monomers. More specifically, examples include polyethyleneimine, ethylenediamine epichlorohydrin polycondensate, polyalkylene polyamine, polymers whose constituent monomers are diallyldimethylammonium chloride or quaternary ammonium salts of dimethylaminoethyl (meth)acrylate (DAM).
[0033] Other cationic polymer flocculants include those consisting of copolymers of cationic monomers and nonionic monomers that exhibit cationic properties. Examples of cationic monomer components include dimethylaminoethyl acrylate, dimethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, and their quaternary derivatives. A specific example of this quaternary derivative is dimethylaminoethyl acrylate methyl chloride quaternary derivative (DAA). Alternatively, dimethylaminopropyl acrylamide (DAPAAm) hydrochloride salt may be used as another component of the cationic monomer. On the other hand, examples of nonionic monomer components include acrylamide (AAm), methacrylamide, and N,N-dimethyl(meth)acrylamide.
[0034] In this embodiment, among these cationic polymer flocculants, those having particularly low ionic (low cationic) properties are preferred as the flocculant F. This improves the efficiency of sludge S coating on the surface of the carrier C, while suppressing the formation of strongly aggregated bodies of carriers C, thereby maintaining the fluidity of the carrier C in the anaerobic treatment tank 10.
[0035] The means for introducing the coagulant F into the anaerobic treatment tank 10 in this embodiment are not particularly limited. For example, as shown in Figure 1, the coagulant F can be introduced via a line L5 connected to a line L2 that introduces wastewater W0 into the anaerobic treatment tank 10. In this case, it is preferable to provide a mechanism on line L5 for adjusting the amount and timing of the coagulant F to be introduced. Alternatively, line L5 may be connected directly to the anaerobic treatment tank 10 without going through line L2, and the coagulant F may be introduced from there.
[0036] (Sludge) Sludge S is one of the substances involved in the attachment of microorganisms to carrier C in the method of setting up the anaerobic treatment tank in this embodiment. In this embodiment, the sludge S used is one that functions as so-called seed sludge. More specifically, activated sludge (digested sludge) collected from anaerobic treatment equipment other than the anaerobic treatment tank 10 to be set up, or granulated microorganisms with a diameter of about 0.3 to 3 mm called granules can be used. Granules are microbial masses that utilize self-immobilization and can maintain a high concentration of microbial cells, so they are a preferred example of sludge S in this embodiment.
[0037] Furthermore, it is preferable that the sludge S in this embodiment be dispersed sludge. Here, dispersed sludge in this embodiment refers to sludge having a diameter smaller than the diameter of the carrier C, and more specifically, examples include crushed sludge (crushed granules) obtained by crushing microbial masses such as granules. By using dispersed sludge as sludge S, the contact efficiency of the sludge S with respect to the carrier C is increased, improving the adhesion of the sludge S, and making it easier to form and maintain a stable covering state.
[0038] The means for introducing the sludge S into the anaerobic treatment tank 10 in this embodiment are not particularly limited. For example, as shown in Figure 1, the sludge S can be introduced into the anaerobic treatment tank 10 via a line L6 connected to a line L2 that introduces wastewater W0. In this case, it is preferable to provide a mechanism on line L6 for adjusting the amount and timing of the sludge S to be introduced. Alternatively, line L6 may be connected directly to the anaerobic treatment tank 10 without going through line L2, and the sludge S may be introduced from there.
[0039] The steps related to the startup method of the anaerobic treatment tank 10 in this embodiment, which are applied to the anaerobic treatment tank 10 described above, will be explained in detail below.
[0040] [First Embodiment] Figures 2 and 3 are schematic diagrams illustrating the steps related to the method for setting up an anaerobic treatment tank in the first embodiment of the present invention. Figure 2 shows the contents of each step related to the method for setting up an anaerobic treatment tank in the first embodiment of the present invention, and Figure 3 shows the overall sequence of steps related to the method for setting up an anaerobic treatment tank in the first embodiment of the present invention. Note that in Figures 2 and 3, components other than the anaerobic treatment tank 10 and the parts related to the input of the coagulant F and sludge S into the anaerobic treatment tank 10 are not shown.
[0041] The following describes each step involved in setting up the anaerobic treatment tank based on Figure 2. The steps involved in setting up the anaerobic treatment tank in this embodiment include a carrier coating step which includes a coagulant input step (Figure 2A) in which a coagulant F is added to the anaerobic treatment tank 10 filled with carrier C, and a sludge input step (Figure 2B) in which sludge S is added to the anaerobic treatment tank 10 after the coagulant input step, and this carrier coating step is performed multiple times.
[0042] First, as part of the coagulant input process, as shown in Figure 2A, the coagulant F is introduced into the anaerobic treatment tank 10, which is filled with carrier C, via lines L5 and L2. As a result, inside the anaerobic treatment tank 10, there are carrier C1 to which the coagulant F is attached, and uncoated carrier C2 that remains unchanged from the time of filling. At this time, it is preferable that the position of line L2 (or line L5) into which the coagulant F is introduced into the anaerobic treatment tank 10 is at the lower side or bottom of the anaerobic treatment tank 10. This makes it easy to efficiently bring the coagulant F into contact with the uncoated carrier C2 that moves to the lower part of the anaerobic treatment tank 10 due to the classification process described later.
[0043] Next, as a sludge input step, as shown in FIG. 2B, sludge S is input into the anaerobic treatment tank 10 in which the carriers C1 and C2 are present via line L6 and line L2. As a result, inside the anaerobic treatment tank 10, sludge S adheres to the carrier C1 to which the flocculant F has adhered, and there is a carrier C3 covered with sludge S and an uncovered carrier C2 whose state remains unchanged from the time of filling. At this time, the position of line L2 (or line L6) is preferably at the lower side or bottom of the anaerobic treatment tank 10, similar to when the flocculant F is input as described above. As described above, in the flocculant input step, the flocculant F adheres to the carrier (carrier C2) present in the lower part of the anaerobic treatment tank 10. Therefore, by inputting the sludge S from the lower part of the anaerobic treatment tank 10, it becomes easy to efficiently bring the sludge S into contact with the carrier C1 to which the flocculant F has adhered.
[0044] The carrier C3 formed through the carrier coating step including the flocculant input step and the sludge input step has a smaller specific gravity than the original carrier (carrier C2). Therefore, as shown in FIG. 2C, a classification action works in the anaerobic treatment tank 10, and the carrier C2 at the upper part of the anaerobic treatment tank 10 moves downward, and the carrier C3 at the lower part of the anaerobic treatment tank 10 moves upward. That is, in the anaerobic treatment tank 10, the carrier (carrier C3) covered with sludge S and the uncovered carrier (carrier C2) move in the anaerobic treatment tank due to the difference in their specific gravities and are in a separated state. For this state, by performing the carrier coating step of inputting the flocculant F and the sludge S again, it becomes easy to efficiently bring the flocculant F and the sludge S into contact with the uncovered carrier (carrier C2).
[0045] Also, as shown in FIG. 3, by repeating the steps based on FIGS. 2A to 2C, it becomes possible to create a state in which the anaerobic treatment tank 10 is entirely filled with the carrier (carrier C3) covered with the sludge S.
[0046] More specifically, as shown in the upper part of FIG. 3, first, a carrier C1 is formed at the lower part of the anaerobic treatment tank 10 by the first flocculant injection step, and then the first sludge injection step is performed to make the carrier C1 into a carrier C3. When the carrier C3 is formed, the classification function works in the anaerobic treatment tank 10, and the position exchange between the carrier C2 and the carrier C3 occurs. Here, since the carrier C2 will exist in the lower part of the anaerobic treatment tank 10 due to the position exchange by the classification function, by performing the second flocculant injection step through the line L2 (or line L5) provided at the lower part of the anaerobic treatment tank 10, the flocculant F can be efficiently brought into contact with the carrier C2, and it becomes possible to form the carrier C1 at the lower part of the anaerobic treatment tank 10. Next, as shown in the lower part of FIG. 3, by performing the second sludge injection step, the sludge S comes into contact with the carrier C1 to form the carrier C3. Then, the newly formed carrier C3 moves to the upper part of the anaerobic treatment tank 10 by the classification function, and the carrier C2 remaining in the anaerobic treatment tank 10 moves to the lower part. By repeating this, finally, a state in which the anaerobic treatment tank 10 is entirely filled with the carrier (carrier C3) coated with the sludge S is created.
[0047] In the method for starting up the anaerobic treatment tank 10 of the present embodiment based on FIGS. 2 and 3, each step for forming a state in which the entire anaerobic treatment tank 10 is filled with the carrier C3 can be made to proceed in a very short time compared with the conventional acclimation operation, and the time required for starting up the anaerobic treatment tank can be shortened.
[0048] Regarding the amounts of the flocculant and sludge to be injected in the flocculant injection step and the sludge injection step, it is preferable to set an upper limit based on a predetermined value. More specifically, the total amount of sludge injected by the sludge injection step is preferably limited to 3% of the total weight of the carrier C filled in the anaerobic treatment tank 10, and the total amount of flocculant injected by the flocculant injection step is preferably limited to 1.1% of the total amount of sludge. And based on this upper limit value, it is preferable to set the injection amount in each carrier coating step per time.
[0049] During the startup of the anaerobic treatment tank 10, it is necessary to bring in seed sludge S from outside the system, so excessive use or outflow of sludge S leads to increased costs. Therefore, in the sludge input process, by inputting a predetermined total amount of sludge according to the total weight of carrier C filled into the anaerobic treatment tank 10, it is possible to suppress sludge outflow due to excessive sludge input. Furthermore, if there is an excess of coagulant F in the anaerobic treatment tank 10, the carriers (carriers C3) covered with sludge S will aggregate to form aggregates, making it difficult for the sludge-covered carriers (carriers C3) and uncovered carriers (carriers C2) to move within the anaerobic treatment tank 10 due to the difference in specific gravity. Therefore, by keeping the total amount of coagulant added in the coagulant input process below a predetermined value, it is possible to improve the efficiency of carrier C coating by sludge S and suppress the inhibition of movement between sludge-covered carriers (carriers C3) and uncovered carriers (C2) within the anaerobic treatment tank 10 (maintaining the effect of classification).
[0050] Furthermore, in the method for starting up the anaerobic treatment tank 10 in this embodiment, the number of carrier coating steps may be determined based on the carrier filling height in the anaerobic treatment tank 10. In this case, if the amount of coagulant F and sludge S added in each carrier coating step is kept constant (fixed value), it becomes possible to add an appropriate amount of coagulant F and sludge S relative to the height of carrier C filled in the anaerobic treatment tank 10 in order to form a state in which the entire anaerobic treatment tank 10 is filled with sludge-coated carriers (carriers C3). That is, if the amount of coagulant F and sludge S added is kept constant (fixed value), the height to which carrier C3 is formed in one carrier coating step is determined, so by dividing the value of the carrier filling height by the value of this height, it is possible to derive the appropriate number of carrier coating steps to form carrier C3 in the anaerobic treatment tank 10 without excess or deficiency. This makes it possible to shorten the start-up time of the anaerobic treatment tank 10 and suppress the occurrence of problems and cost increases due to excessive coagulant and sludge addition.
[0051] As described above, the method for setting up the anaerobic treatment tank in this embodiment involves adding a coagulant and then sludge to the carrier filled in the anaerobic treatment tank, first bringing the carrier and coagulant into contact and creating a state where the coagulant adheres to the carrier surface. By then adding sludge, the coagulation reaction between the coagulant and sludge proceeds on the carrier surface, making it possible to create a state where the carrier surface is uniformly covered with sludge (in other words, a state where microorganisms are uniformly attached to the carrier surface). Furthermore, by dividing the addition of the coagulant and sludge into multiple steps, both sludge-covered and uncovered carriers are present in the anaerobic treatment tank, and these carriers move (exchange positions) due to a classification action based on their specific gravity difference. Therefore, when adding the coagulant and sludge next, it becomes easy to efficiently bring the coagulant and sludge into contact with the uncovered carriers, and by repeating this, it becomes possible to quickly create a state where the entire anaerobic treatment tank is filled with sludge-covered carriers. In other words, during the startup of an anaerobic treatment tank, microbial adhesion to the carrier surface can be efficiently promoted, making it possible to shorten the time required to start up the anaerobic treatment tank.
[0052] [Second Embodiment] Figure 4 is a schematic diagram illustrating the steps related to the method for starting up an anaerobic treatment tank in the second embodiment of the present invention. The method for starting up an anaerobic treatment tank in this embodiment includes, in addition to the method for starting up an anaerobic treatment tank in the first embodiment, a mixing step for circulating the treated water W1 of the anaerobic treatment tank 10, and this mixing step is performed during the carrier coating step. Note that the explanation of the method for starting up an anaerobic treatment tank in this embodiment that is the same as in the first embodiment will be omitted.
[0053] The method for starting up the anaerobic treatment tank 10 in this embodiment involves a mixing step (Figure 4C) in which the treated water W1 of the anaerobic treatment tank 10 is circulated after the carrier coating step shown in Figures 4A and 4B, in order to further promote the movement of carriers due to classification (exchange of positions between carriers C2 and C3). More specifically, after introducing the coagulant F and sludge S into the anaerobic treatment tank 10, a circulating flow is formed within the anaerobic treatment tank 10 to shorten the time required for the carriers covered with sludge S (carrier C3) and uncovered carriers (carrier C2) to move and be separated within the anaerobic treatment tank 10. In this embodiment, treated water W1 refers to the solution present in the anaerobic treatment tank 10 and ultimately discharged outside the system, and is not limited to treated water produced as a result of biological treatment by introducing wastewater W0 into the anaerobic treatment tank 10, but also includes fluids not subject to treatment (dispersed solvents such as water) introduced when adding the coagulant F and sludge S.
[0054] The mixing step in the startup method of the anaerobic treatment tank 10 in this embodiment can be any step that can form a circulating flow within the anaerobic treatment tank 10. For example, as shown in Figure 4C, after the coagulant input step and the sludge input step, a portion of the treated water W1 generated in the anaerobic treatment tank 10 is returned to the anaerobic treatment tank 10 via line L4 for circulation. At this time, as described above, line L4 may be connected to line L2 to directly return the treated water W1 to the anaerobic treatment tank 10, or the treated water W1 may be returned to the anaerobic treatment tank 10 via the acid generation tank 20.
[0055] Furthermore, another aspect of the mixing process may involve stopping or reducing the amount of coagulant F and / or sludge S added from the coagulant addition process and the sludge addition process. In this case, a circulating flow is formed in the anaerobic treatment tank 10, promoting the movement related to the exchange of positions between carriers C2 and C3, while simultaneously allowing the formation of carrier C1 by coagulant addition and the formation of carrier C3 by sludge addition to proceed in parallel.
[0056] In the method for setting up the anaerobic treatment tank 10 in this embodiment, by repeating the steps shown in Figures 4A to 4C, a state is created in which the entire inside of the anaerobic treatment tank 10 is filled with a carrier (carrier C3) covered with sludge S, similar to the method for setting up the anaerobic treatment tank in the first embodiment described above.
[0057] The method for starting up the anaerobic treatment tank in this embodiment makes it possible to shorten the time required for the sludge-coated carriers and uncoated carriers to move within the anaerobic treatment tank and become separated. In other words, it becomes possible to shorten the time required to start up the anaerobic treatment tank even more effectively.
[0058] [Third Embodiment] Figure 5 is a schematic diagram illustrating the steps related to the anaerobic treatment tank startup method in the third embodiment of the present invention. The anaerobic treatment tank startup method according to this embodiment is characterized in that, in the anaerobic treatment tank startup method of the first embodiment, an organic matter input step is added before the sludge input step. Note that the explanation of the anaerobic treatment tank startup method in this embodiment that is the same as in the first embodiment will be omitted.
[0059] The method for starting up the anaerobic treatment tank 10 in this embodiment includes an organic matter input step as one of the carrier coating steps, in which organic matter is added before the formation of carrier C3 by the sludge input step. This causes organic matter to adhere to carrier C1 or carrier C2, and then, when sludge S is added, a state is formed in which the organic matter attached to carrier C1 or carrier C2, together with the sludge S, coats carrier C, and this organic matter becomes available as a nutrient source for microorganisms in the sludge S on carrier C3.
[0060] In this embodiment, the organic matter input step may be performed between the coagulant input step and the sludge input step, as shown in Figure 5, or it may be performed before the coagulant input step. Furthermore, specific examples of the organic matter input step include, for example, as shown in Figure 5B, introducing wastewater W0 containing organic matter to be treated in the anaerobic treatment tank 10 into the anaerobic treatment tank 10 via line L2, or introducing a prepared organic matter-containing solution other than wastewater W0, or other wastewater brought in from outside the system, into the anaerobic treatment tank 10. In consideration of ease of operation and cost, it is preferable to introduce wastewater W0 to be treated in the anaerobic treatment tank 10 as the organic matter input step.
[0061] In the method for starting up the anaerobic treatment tank 10 in this embodiment, by repeating the steps shown in Figures 5A to 5C, a state is created in which the entire inside of the anaerobic treatment tank 10 is filled with a carrier (carrier C3) covered with sludge S, similar to the method for starting up the anaerobic treatment tank in the first embodiment described above. Furthermore, the method for starting up the anaerobic treatment tank 10 in this embodiment may include the mixing step shown in the second embodiment. In this case, similar to the second embodiment, by performing the mixing step between the carrier coating steps shown in Figures 5A to 5C, the movement of the carrier based on the classification action is promoted, and it becomes possible to further reduce the time required for starting up the anaerobic treatment tank.
[0062] In this embodiment, the method for setting up the anaerobic treatment tank involves coating the carrier with sludge, incorporating organic matter that serves as a nutrient source for microorganisms in the sludge. This, along with microbial adhesion, shortens the time required for microbial growth and maintains microbial activity. As a result, it is possible to shorten the time required to set up the anaerobic treatment tank and improve the efficiency of anaerobic treatment.
[0063] [Fourth Embodiment] Figure 6 is a schematic diagram illustrating an anaerobic treatment tank and surrounding equipment to which the anaerobic treatment tank startup method according to the fourth embodiment of the present invention is applied. In this embodiment, the anaerobic treatment tank startup method replaces the coagulant input step and sludge input step in the anaerobic treatment tank startup methods of the first to third embodiments shown in Figure 1 with respect to the anaerobic treatment tank 10, by performing the coagulant input step and sludge input step via an acid generation tank 20 provided in front of the anaerobic treatment tank 10. Note that the explanation of the anaerobic treatment tank startup method in this embodiment that is the same as in the first to third embodiments will be omitted.
[0064] In this embodiment, the method for starting up the anaerobic treatment tank 10 involves a coagulant input step in which a coagulant F is introduced into the anaerobic treatment tank 10 via an acid generation tank 20 installed upstream of the anaerobic treatment tank 10, and a sludge input step in which sludge S is introduced into the anaerobic treatment tank 10 via the acid generation tank 20. When starting up the anaerobic treatment tank, it is necessary to bring in sludge S from outside the system, and generally a temporary adjustment tank is prepared, in which the sludge S is stored and then introduced into the anaerobic treatment tank 10. On the other hand, with the method for starting up the anaerobic treatment tank 10 in this embodiment, it is possible to introduce the entire amount of sludge S brought in from outside the system into the acid generation tank 20, eliminating the need for a temporary adjustment tank and thus reducing costs. Furthermore, by enabling the introduction of the coagulant F via the same route as the sludge S, it is possible to suppress the complexity and cumbersome nature of the carrier coating process.
[0065] In this embodiment, the method for starting up the anaerobic treatment tank 10 is as shown in Figure 6, by connecting line L5 for the coagulant input process and line L6 for the sludge input process to the acid generation tank 20, and the operations for inputting the coagulant F via line L5 and the sludge S via line L6 proceed in the same manner as in the first to third embodiments described above. Specifically, first, as the coagulant input process, the coagulant F is introduced into the anaerobic treatment tank 10, which is filled with carrier C, via lines L5 and L2 connected to the acid generation tank 20. As a result, inside the anaerobic treatment tank 10, there is carrier C1 to which the coagulant F has adhered and uncoated carrier C2 that remains unchanged from the time of filling. Next, as the sludge input process, sludge S is introduced into the anaerobic treatment tank 10, which contains carriers C1 and C2, via lines L6 and L2 connected to the acid generation tank 20. As a result, inside the anaerobic treatment tank 10, carrier C3, which is covered with sludge S by the attachment of sludge S to carrier C1 to which the coagulant F has adhered, and uncovered carrier C2, which remains unchanged from the time of filling, exist. Then, carrier C3, formed through the carrier coating process including the coagulant input process and the sludge input process, has a lower specific gravity than the original carrier (carrier C2), so a classification effect occurs inside the anaerobic treatment tank 10, causing carrier C2, which was in the upper part of the anaerobic treatment tank 10, to move downwards, and carrier C3, which was in the lower part of the anaerobic treatment tank 10, to move upwards. By repeating this, a state is eventually created in which the entire anaerobic treatment tank 10 is filled with carriers (carrier C3) covered with sludge S. At this time, the mixing process shown in the second embodiment and the organic matter input process shown in the third embodiment may also be included.
[0066] Regarding lines L5 and L6 connected to the acid generation tank 20, any line that can supply the coagulant F and sludge S to the acid generation tank 20 is acceptable. In particular, for line L6, the lid on top of the acid generation tank 20 may be opened, and sludge S brought in from outside the system may be directly introduced. More specifically, a transport vehicle such as a tank truck may be used to directly introduce sludge S brought in from outside the system into the acid generation tank 20 from the transport vehicle. This makes it possible to introduce sludge S without setting up a temporary adjustment tank. Similarly, for line L5, the lid on top of the acid generation tank 20 may be opened, and the coagulant F may be introduced.
[0067] Furthermore, it is preferable to input the entire amount of sludge S (or a total amount of sludge S) equivalent to a predetermined number of transport vehicles that bring in the sludge S from outside the system as one sludge input process. This makes it easy to manage the transported sludge S (storage is unnecessary, or the transport vehicles can be used as temporary storage locations), and it also makes it easy to grasp the amount of sludge S that is input to the acid generation tank 20 (indirectly the anaerobic treatment tank 10) (the amount of sludge S in one sludge input process). In this case, when repeating the carrier coating process, the other processes (coagulant input process, mixing process, organic matter input process) are carried out after the entire amount of sludge that was input to the acid generation tank 20 in one sludge input process has been transferred to the anaerobic treatment tank 10. The timing for the transfer of the entire amount of sludge introduced into the acid generation tank 20 to the anaerobic treatment tank 10 and the transition to the next process may be defined as after a predetermined time has elapsed, or it may be determined using the amount of sludge introduced into the acid generation tank 20 in one go and the flow rate from the acid generation tank 20 to the anaerobic treatment tank 10.
[0068] Furthermore, in the method for starting up the anaerobic treatment tank 10 in this embodiment, the coagulant input process and the sludge input process can proceed via the acid generation tank 20, and the arrangement of lines L5 and L6 is not limited to that shown in Figure 6. For example, in another embodiment, lines L5 and / or line L6 can be connected to line L1 or line L4 leading to the acid generation tank 20, and the coagulant F and sludge S can be introduced into the anaerobic treatment tank 10 via the acid generation tank 20.
[0069] The above-described embodiment is merely one example of a method for setting up an anaerobic treatment tank. The method for setting up an anaerobic treatment tank according to the present invention is not limited to the above-described embodiment, and the method for setting up an anaerobic treatment tank according to the above-described embodiment may be modified without changing the gist of the claims.
[0070] The method for starting up an anaerobic treatment tank according to the present invention is used when starting up a new anaerobic treatment tank to perform anaerobic treatment of wastewater containing organic matter, and is particularly suitable for use when starting up an anaerobic treatment tank that has been filled with a carrier.
[0071] 10 Anaerobic treatment tank, 20 Acid generation tank, L1-L6 lines, C Carrier, C1 Carrier with coagulant attached, C2 Uncoated carrier, C3 Carrier covered with sludge, F Coagulant, S Sludge, W0 Wastewater, W1 Treated water
Claims
1. A method for starting up an anaerobic treatment tank, comprising a carrier coating step which includes a coagulant input step of introducing a coagulant into an anaerobic treatment tank filled with a carrier, and a sludge input step of introducing sludge into the anaerobic treatment tank after the coagulant input step, wherein the carrier coating step is performed multiple times.
2. The method for starting up an anaerobic treatment tank according to claim 1, comprising a mixing step of circulating the treated water of the anaerobic treatment tank, wherein the mixing step is performed between the carrier coating steps.
3. The method for starting up an anaerobic treatment tank according to claim 1, characterized in that the coagulant input step involves inputting a coagulant into the anaerobic treatment tank via an acid generation tank installed upstream of the anaerobic treatment tank, and the sludge input step involves inputting sludge into the anaerobic treatment tank via the acid generation tank.
4. The method for starting up an anaerobic treatment tank according to claim 1, characterized in that the total amount of sludge introduced in the sludge introduction step is limited to 3% of the weight of the carrier filled in the anaerobic treatment tank, and the total amount of coagulant introduced in the coagulant introduction step is limited to 1.1% of the total amount of sludge.
5. The method for starting up an anaerobic treatment tank according to claim 1, characterized in that the carrier filled in the anaerobic treatment tank is activated carbon.
6. The method for starting up an anaerobic treatment tank according to claim 5, characterized in that the flocculant is a cationic polymer flocculant.
7. The method for setting up an anaerobic treatment tank according to claim 1, characterized in that the sludge is dispersed sludge.
8. The method for starting up an anaerobic treatment tank according to claim 1, characterized in that the number of times the carrier coating process is performed is determined based on the carrier filling height in the anaerobic treatment tank.