Method for starting up anaerobic treatment tank
The method for starting up anaerobic treatment tanks using carriers in multiple stages with controlled sludge coverage and differential settling velocities addresses short-circuit flows, enhancing fluidity and efficiency by ensuring uniform microorganism distribution.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- SUMITOMO HEAVY IND LTD
- Filing Date
- 2025-12-16
- Publication Date
- 2026-06-25
Smart Images
Figure JP2025043867_25062026_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 using a carrier.
[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 advantages in terms of introduction, such as not requiring aeration power and hardly generating excess sludge.
[0003] As such anaerobic treatment, an upflow anaerobic sludge bed method (UASB) using a treatment tank holding 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 using a carrier (a treatment tank holding a carrier inside).
[0004] When using a treatment tank holding a carrier, it is known that it takes time for microorganisms to adhere to the carrier and exhibit sufficient anaerobic treatment ability. 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 holding a carrier, when starting up the device (treatment tank), organic wastewater is passed through while the carrier and methane bacteria granules are present in a predetermined ratio in the treatment tank, and then, by continuing the passage of the organic wastewater, a part of the methane bacteria granules is disintegrated and dispersed. It is described that this promotes the adhesion of microorganisms to the carrier and forms an active biofilm on the carrier surface at an early stage, significantly shortening the time required for starting up a treatment tank for performing anaerobic treatment.
[0005] Japanese Patent Application Laid-Open No. 2012-110821
[0006] According to Patent Document 1, using a treatment tank in which carriers and granules are stacked together shortens the startup time of the treatment tank that performs anaerobic treatment (hereinafter also referred to as the "anaerobic treatment tank"). On the other hand, as described in Patent Document 1, when the anaerobic treatment tank is started up by holding (stacking) carriers and granules together in the anaerobic treatment tank, adhesion may occur between carriers with biofilms formed on their surfaces until a biofilm is formed on the surface of the carrier and the treatment stabilizes (in other words, until microorganisms uniformly adhere to the surface of the carrier and acclimatization is completed). In this case, within the anaerobic treatment tank in which the carriers are held, the adhesion between carriers can create short-circuit channels where fluid can easily pass (areas through which fluid passes preferentially over others), and so-called short-circuit flow may occur in the fluid flow. This can lead to a decrease in fluidity within the anaerobic treatment tank, which in turn can cause a decrease in the contact efficiency between the carrier and the water to be treated (a decrease in treatment efficiency).
[0007] The object of the present invention is to provide a method for starting up an anaerobic treatment tank that can suppress the generation of short-circuit flow within the anaerobic treatment tank, ensure fluidity within the anaerobic treatment tank, and improve treatment efficiency after startup, when starting up an anaerobic treatment tank that utilizes a carrier.
[0008] As a result of diligent research into the above-mentioned problems, the inventors of the present invention have found that by introducing a carrier and a substance involved in microbial adhesion into the anaerobic treatment tank in a predetermined order, it is possible to suppress the generation of short-circuit flow within the anaerobic treatment tank, ensure fluidity within the anaerobic treatment tank, and improve treatment efficiency after startup, thereby completing the present invention. That is, the present invention is the following method for starting up an anaerobic treatment tank.
[0009] The present invention provides a method for starting up an anaerobic treatment tank to solve the above problems, comprising: a first carrier input step of introducing carriers into the anaerobic treatment tank; a sludge input step of introducing sludge into the anaerobic treatment tank after the first carrier input step; and a second carrier input step of introducing even more carriers into the anaerobic treatment tank after the sludge input step. Conventionally, when starting up an anaerobic treatment tank using carriers, it is common to introduce the entire amount of carriers and microorganisms (sludge such as granules) into the anaerobic treatment tank and wait for time to pass during the process of forming a state in which the surface of the carriers is uniformly covered with sludge (in other words, a state in which microorganisms are uniformly attached to the surface of the carriers) (acclimatization process). At this time, in the anaerobic treatment tank, short-circuit channels may be formed where fluid can easily pass through (areas through which fluid passes preferentially over others) due to the adhesion of carriers to each other, and so-called short-circuit flow may occur in terms of fluid flow. When a short-circuit flow occurs in an anaerobic treatment tank, the fluidity within the tank decreases, leading to a reduction in treatment efficiency due to decreased contact efficiency between the carrier (microorganisms on the carrier surface) and the water to be treated. On the other hand, the method for setting up an anaerobic treatment tank according to the present invention involves adding carriers to the anaerobic treatment tank in multiple stages, and adding sludge to the carriers that were added first, and then adding the remaining carriers. In this case, with respect to the carriers added first, during the acclimatization process that proceeds as sludge is added, adhesion occurs between carriers on which a biofilm has formed on their surface, and a short-circuit flow can be formed. However, by adding more carriers, the difference in settling velocity between carriers covered with sludge (carriers on which a biofilm has formed) and uncovered carriers causes each carrier to move and exchange positions within the anaerobic treatment tank. As the carriers move, uncovered carriers are inserted between carriers that are covered with sludge and adhered to each other (in other words, carriers that are in a state where a short-circuit flow can be formed), thus suppressing the formation of a short-circuit flow and, consequently, suppressing the generation of a short-circuit flow. This ensures fluidity within the anaerobic treatment tank and improves treatment efficiency after startup.
[0010] Furthermore, one embodiment of the method for starting up an anaerobic treatment tank according to the present invention is characterized by having a coagulant input step between the first carrier input step and the sludge input step, in which a coagulant is added to the anaerobic treatment tank. According to this feature, by first adding the coagulant to the carrier that has been introduced and held in the anaerobic treatment tank, the carrier and the coagulant come into contact and form a state in which the coagulant adheres to the surface of the carrier. When sludge is then introduced, the coagulation reaction between the coagulant and the sludge proceeds on the surface of the carrier, and it becomes possible to quickly form a state in which the surface of the carrier is uniformly covered with sludge (in other words, a state in which microorganisms adhere uniformly to the surface of the carrier). As a result, when starting up the anaerobic treatment tank, it is possible to reduce the time required for start-up, in addition to suppressing the generation of short-circuit flow.
[0011] Furthermore, one embodiment of the method for starting up an anaerobic treatment tank according to the present invention is characterized in that a second carrier input step is started after a predetermined time has elapsed following the sludge input step. According to this characteristic, by setting a certain limit (lower limit) on the contact time between the carrier previously introduced and held in the anaerobic treatment tank and the sludge, the surface of the carrier is made to be covered with sludge in a substantially uniform state, and by introducing new carriers to this state, the difference in settling velocity between the previously introduced carriers and the newly introduced carriers becomes larger, enabling efficient movement. In addition, by setting a certain limit (upper limit) on the contact time between the carrier previously introduced and held in the anaerobic treatment tank and the sludge, it becomes possible to introduce new carriers before adhesion between the previously introduced and held carriers progresses and a short-circuit channel is firmly established. In other words, it becomes possible to effectively suppress the formation of a short-circuit channel. Furthermore, since the carriers that have been covered with sludge to a certain extent and the new carriers are efficiently mixed in the anaerobic treatment tank, it becomes possible to shorten the time required to complete the acclimatization of the entire carrier in the anaerobic treatment tank.
[0012] Furthermore, one embodiment of the method for starting up an anaerobic treatment tank according to the present invention is characterized by providing a pressure measurement step to measure the pressure inside the anaerobic treatment tank, and starting a second carrier input step according to the measurement results obtained from the pressure measurement step. Pressure changes inside the anaerobic treatment tank are caused by the adhesion state between carriers. More specifically, adhesion between carriers progresses inside the anaerobic treatment tank, and the formation of a short-circuit channel and the generation of a short-circuit flow cause a pressure difference between the upstream and downstream sides of the anaerobic treatment tank, resulting in so-called pressure loss. With this feature, by measuring the pressure inside the anaerobic treatment tank, the occurrence of pressure loss can be detected, the tendency related to the formation of a short-circuit channel (generation of a short-circuit flow) can be quickly detected, and by adding new carriers at this stage, it is possible to effectively suppress the formation of a short-circuit channel.
[0013] Furthermore, one embodiment of the method for setting up the anaerobic treatment tank of the present invention is characterized in that the carrier introduced 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 a large difference in specific gravity between the sludge-coated carrier and the uncoated carrier, resulting in a large difference in settling velocity. As a result, efficient movement is possible between the carrier introduced into the anaerobic treatment tank beforehand and the newly introduced carrier, and the effect of suppressing the generation of short-circuit flow is significantly exhibited.
[0014] Furthermore, one embodiment of the method for starting up an anaerobic treatment tank according to the present invention is characterized by using carriers with different settling velocities in the first carrier input step and the second carrier input step. This characteristic makes it possible to use carriers that have a large difference in settling velocity between carriers that have been previously introduced into the anaerobic treatment tank and are coated with sludge, and newly introduced uncoated carriers. As a result, efficient movement between carriers previously introduced into the anaerobic treatment tank and newly introduced carriers becomes possible, and the effect of suppressing the generation of short-circuit flows is significantly exhibited.
[0015] According to the present invention, it is possible to provide a method for starting up an anaerobic treatment tank that suppresses the generation of short-circuit flow within the anaerobic treatment tank, ensures fluidity within the anaerobic treatment tank, and improves the treatment efficiency after startup, when starting up an anaerobic treatment tank that utilizes a carrier.
[0016] 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 embodiment 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 a schematic diagram illustrating an anaerobic treatment tank and surrounding equipment to which the anaerobic treatment tank startup method according to the second embodiment 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 second embodiment of the present invention.
[0017] 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).
[0018] 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.
[0019] The method for starting up an anaerobic treatment tank according to this embodiment relates to the start-up of an anaerobic treatment tank that biologically treats wastewater (anaerobic treatment). More specifically, the method for starting up an anaerobic treatment tank according to this embodiment aims to suppress the generation of short-circuit flow within the anaerobic treatment tank, ensure fluidity within the anaerobic treatment tank, and improve treatment efficiency after start-up, during the start-up process of an anaerobic treatment tank that utilizes a carrier.
[0020] [First Embodiment] (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 in the first embodiment of the present invention is applied. As shown in Figure 1, the anaerobic treatment tank 10 in this embodiment has a carrier C inside, and by the anaerobic treatment tank startup method in this embodiment, microorganisms are attached to this carrier C and acclimatization is completed, thereby carrying out anaerobic treatment using these microorganisms, and 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, and the filled block arrows (surface arrows) indicate the introduction of sludge S.
[0021] 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.
[0022] 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.
[0023] 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.
[0024] 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.
[0025] 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.
[0026] Furthermore, the anaerobic treatment tank 10 of this embodiment may be provided with a structure for circulating treated water W1 within the anaerobic treatment tank 10, in consideration of improving the treatment efficiency of anaerobic treatment. For example, as shown in Figure 1, in addition to line L3, a line L4 may be provided for discharging treated water W1 and connected to the upstream side of the anaerobic treatment tank 10. In this case, line L4 may be connected to line L2, or it may be connected to the acid generation tank 20.
[0027] (Carrier) The carrier C introduced and maintained in the anaerobic treatment tank 10 can be any carrier to which anaerobic microorganisms (sludge S) involved in anaerobic treatment adhere, and there are no particular limitations on its structure or material, but suitable examples of carrier C in this embodiment include carbonaceous carriers, ion exchange resins, and silica. In this embodiment, the carrier C is coated with sludge S (microorganisms) after sludge S (microorganisms) has adhered to its surface. Here, since the specific gravity of sludge S is generally lower than the specific gravity of the carrier C itself, the carrier coated with sludge S (carrier C2, described later) has a lower specific gravity than the uncoated carrier (carrier C1, described later). In other words, there is a difference in settling velocity between the sludge-coated carrier and the uncoated carrier.
[0028] In this embodiment, one example of a carrier C is a carbonaceous carrier made of an inorganic material whose main component is carbon. Specifically, examples include carbon black, graphite, coke, and activated carbon. Carbonaceous carriers are easy to mold as carriers and generally have a higher specific gravity than resin carriers, which has the advantage of suppressing outflow to the outside of the anaerobic treatment tank 10 when it is held and flowed within the tank. Furthermore, by using a carbonaceous carrier with a relatively high specific gravity as carrier C, in the process of setting up the anaerobic treatment tank in this embodiment, the difference in specific gravity between the carrier that is initially introduced into the anaerobic treatment tank 10 and coated with sludge S (microorganisms) and the newly introduced, uncoated carrier becomes larger, further increasing the difference in settling velocity. This makes it possible to efficiently move the sludge-coated carrier and the uncoated carrier so as to exchange positions within the anaerobic treatment tank 10. In other words, by using a carbonaceous carrier as carrier C, the effect of suppressing short-circuit flow generation is 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, in addition to being able to adsorb components that inhibit anaerobic treatment by anaerobic microorganisms (anaerobic treatment inhibitors), and specifically, it is particularly preferable to use activated carbon.
[0029] Furthermore, as will be described later, the carrier C in this embodiment is added to the anaerobic treatment tank 10 in multiple stages in the method for starting up the anaerobic treatment tank of this embodiment, which comprises a first carrier addition step and a second carrier addition step. At this time, the carrier C used in the carrier addition steps may have the same physical and chemical properties and the same shape in each carrier addition step, but is not limited to this, and for example, carriers with different physical and chemical properties or different shapes may be used in the first carrier addition step and the second carrier addition step, respectively.
[0030] In this case, a particularly suitable example is to use carriers with different settling velocities in the first carrier input step and the second carrier input step. This makes it possible to use carriers that have an even greater difference in settling velocity between the carriers that have been previously introduced into the anaerobic treatment tank and are coated with sludge, and the newly introduced uncoated carriers. This enables efficient movement between the carriers previously introduced into the anaerobic treatment tank 10 and the newly introduced carriers, thereby significantly enhancing the effect of suppressing short-circuit flow generation. Here, "carriers with different settling velocities" refers to a combination of carriers that have different settling velocities due to differences in physical properties (specific gravity) or particle size. Specifically, examples include using activated carbon with different degrees of activation as carriers of the same material but different specific gravities, or selecting two or more from the group consisting of carbonaceous carriers (activated carbon), ion exchange resins, and silica, and using a combination of carriers made of different materials.
[0031] The means by which the carrier C of this embodiment is introduced into the anaerobic treatment tank 10 are not particularly limited. For example, the carrier C can be introduced from the top of the anaerobic treatment tank 10, or from the bottom of the anaerobic treatment tank 10. In this case, considering the ease of operation related to the introduction of the carrier itself and the ease of operation related to the uniform retention of the carrier within the anaerobic treatment tank 10 (ease of operation to ensure uniformity in the horizontal spread of the carrier in the anaerobic treatment tank 10), it is more preferable to introduce the carrier C from the top of the anaerobic treatment tank 10.
[0032] (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.
[0033] 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.
[0034] 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 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 sludge S to be introduced. Alternatively, line L5 may be directly connected to the anaerobic treatment tank 10 without going through line L2, and the sludge S may be introduced from there. Furthermore, if an acid generation tank 20 is provided upstream of the anaerobic treatment tank 10, the sludge S may be introduced into the anaerobic treatment tank 10 via the acid generation tank 20.
[0035] 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.
[0036] (Steps related to the startup of the anaerobic treatment tank) Figure 2 is a schematic diagram illustrating the contents of each step related to the method for starting up the anaerobic treatment tank in the first embodiment of the present invention. Note that in Figure 2, 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.
[0037] The following describes each step involved in setting up the anaerobic treatment tank in this embodiment, based on Figure 2. The steps involved in setting up the anaerobic treatment tank in this embodiment include a first carrier input step (Figure 2A) in which carrier C is introduced into an empty anaerobic treatment tank 10, a sludge input step (Figure 2B) in which sludge S is introduced into the anaerobic treatment tank 10 after the first carrier input step, and a second carrier input step (Figure 2C) in which carrier C is introduced into the anaerobic treatment tank 10 after the sludge input step.
[0038] First, as the first carrier input step, as shown in Figure 2A, carrier C is added to an empty anaerobic treatment tank 10. At this time, there will be uncoated carrier C1 in the anaerobic treatment tank 10 that remains unchanged in state from the time it was added to and held in the anaerobic treatment tank 10. In the first carrier input step, the amount of carrier C added is less than or equal to the amount required to carry out the anaerobic treatment in the anaerobic treatment tank 10. At this time, as mentioned above, the means of adding carrier C to the anaerobic treatment tank 10 are not particularly limited, but in this embodiment, as shown in Figure 2A, it is preferable to add carrier C from the top of the anaerobic treatment tank 10.
[0039] Next, as a sludge input step, as shown in Figure 2B, sludge S is introduced into the anaerobic treatment tank 10 where carrier C1 is located via lines L5 and L2. As a result, inside the anaerobic treatment tank 10, carrier C2 exists with sludge S adhering to carrier C1 and covered with sludge S. At this time, the position of line L2 (or line L5) is preferably at the lower side or bottom of the anaerobic treatment tank 10. In the sludge input step, sludge S is attached to the carrier (carrier C1) located in the lower part of the anaerobic treatment tank 10 after the first carrier input step. Therefore, by introducing 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 carrier C1.
[0040] The first carrier input process and the sludge input process initiate a process (acclimatization process) in which the carrier surface is uniformly covered with sludge (in other words, a state in which microorganisms uniformly adhere to the carrier surface). At this time, within the anaerobic treatment tank 10, short-circuit channels may be formed where fluid can easily pass through (areas through which fluid passes preferentially over others) due to the adhesion between carriers (especially between carriers C2). When short-circuit channels are formed, a so-called short-circuit flow occurs in the fluid flow within the anaerobic treatment tank 10. In this case, a decrease in fluidity occurs within the anaerobic treatment tank 10, which in turn leads to a decrease in the contact efficiency between the carrier and the treated water (a decrease in treatment efficiency).
[0041] Therefore, the method for starting up the anaerobic treatment tank in this embodiment includes a step to suppress the formation of short-circuit channels caused by the adhesion state of the carriers C2 within the anaerobic treatment tank 10. In other words, the method for starting up the anaerobic treatment tank in this embodiment includes a step to ensure the fluidity of the carriers C (carriers C2) introduced and held in the anaerobic treatment tank 10 during the acclimatization process. Specifically, the method for starting up the anaerobic treatment tank in this embodiment includes a second carrier introduction step in which carriers C are introduced into the anaerobic treatment tank 10 after the first carrier introduction step and the sludge introduction step.
[0042] In the second carrier input step, after the sludge input step, carrier C (carrier C1) is introduced into the anaerobic treatment tank 10 where carrier C2 is present. At this time, within the anaerobic treatment tank 10, the difference in settling velocity between carrier C2, which is covered with sludge, and carrier C1, which is not covered, causes each carrier to move and exchange positions within the anaerobic treatment tank 10. As this carrier movement occurs, the uncovered carrier C1 will be inserted between carriers C2 that are covered with sludge and are adhering to each other (in other words, in a state where a short-circuit channel can be formed), thereby suppressing the formation of a short-circuit channel and, consequently, suppressing the generation of a short-circuit flow.
[0043] At this time, regarding the means of introducing the carrier C (carrier C1) into the anaerobic treatment tank 10 as the second carrier introduction step, it is considered in view of the magnitude relationship between the sedimentation rate of the carrier C2 already present in the anaerobic treatment tank 10 and the sedimentation rate of the newly introduced carrier C1. Specifically, for example, when the sedimentation rate of the carrier C1 is greater than the sedimentation rate of the carrier C2, as shown in FIG. 2C, the carrier C (carrier C1) is introduced from the upper part of the anaerobic treatment tank 10. Thereby, the carrier C1 introduced above the carrier C2 moves to the carrier C2 side (lower part of the anaerobic treatment tank 10) due to the difference in sedimentation rate, while the carrier C2 moves to the upper part of the anaerobic treatment tank 10. As a result, regarding the short-circuit flow path that may be formed by the adhesion of the carriers C2, it becomes possible to suppress the formation of the short-circuit flow path itself and to collapse the formed short-circuit flow path. On the other hand, when the sedimentation rate of the carrier C1 is smaller than the sedimentation rate of the carrier C2, by introducing the carrier C (carrier C1) from the lower part of the anaerobic treatment tank 10, the carriers move so as to exchange positions between the carrier C2 and the carrier C1, and it becomes possible to suppress the formation of the short-circuit flow path.
[0044] Also, even when the same carrier C is used in the first carrier introduction step and the second carrier introduction step, a difference in sedimentation rate occurs between the carrier C1 and the carrier C2. More specifically, when a carrier having a specific gravity greater than that of the sludge S such as activated carbon is used as the carrier C, the carrier C2 coated with the sludge S (on which a biofilm is formed) is lighter in specific gravity than the uncoated carrier (carrier C1). And in this case, regarding the carrier introduction step of the carrier C, as a preferable example, in both the first carrier introduction step and the second carrier introduction step, the carrier C is introduced from the upper part of the anaerobic treatment tank 10 as shown in FIGS. 2A and 2C.
[0045] Furthermore, as described above, even when carriers with different settling velocities are used in the first carrier input step and the second carrier input step, the means for introducing carrier C (carrier C1) into the anaerobic treatment tank 10 as the second carrier input step should take into account the relationship between the settling velocity of the carrier introduced in the first carrier input step and the settling velocity of the carrier newly introduced in the second carrier input step. Specifically, for example, when a carrier with a settling velocity v1 is used as the carrier introduced in the first carrier input step and a carrier with a settling velocity v2 (v2 > v1) is used as the carrier introduced in the second carrier input step, as shown in Figures 2A and 2C, carrier C is introduced from the top of the anaerobic treatment tank 10 in both the first and second carrier input steps. This makes it possible to increase the difference in settling velocity between the carriers that have been previously introduced into the anaerobic treatment tank 10 and are coated with sludge, and the newly introduced uncoated carriers. This enables efficient movement between the previously introduced carriers and the newly introduced carriers in the anaerobic treatment tank 10, and significantly enhances the effect of suppressing the generation of short-circuit flows.
[0046] Then, after the second carrier input step shown in Figure 2C, the newly introduced carrier C1 moves within the anaerobic treatment tank 10 while in contact with carrier C2, which is covered with sludge S. As time passes, sludge S adheres to carrier C1 as well, making it possible to create a state in which the entire anaerobic treatment tank 10 is filled with carriers (carriers C2) covered with sludge S. In other words, in the anaerobic treatment tank startup method of this embodiment, the acclimatization process within the anaerobic treatment tank 10 can be carried out without adding any additional sludge S after the second carrier input step. Here, when starting up the anaerobic treatment tank 10, it is necessary to bring in sludge S as seed sludge from outside the system, so excessive use or outflow of sludge S leads to increased costs. On the other hand, in the anaerobic treatment tank startup method of this embodiment, excessive sludge S is not added to the anaerobic treatment tank 10, and it is also possible to suppress the outflow of sludge S during the acclimatization process.
[0047] In this embodiment, a preferred timing for starting the second carrier input process is the point at which efficient movement occurs between the carriers previously introduced in the first carrier input process and the carriers newly introduced in the second carrier input process, or the point at which the formation of short-circuit channels can be effectively suppressed.
[0048] More specifically, in the method for starting up the anaerobic treatment tank in this embodiment, for example, the second carrier input process is started after a predetermined time has elapsed following the sludge input process. The "predetermined time" at this time refers to the contact time between the carrier C1, which was previously introduced and held in the anaerobic treatment tank 10 by the first carrier input process and the sludge input process, and the sludge S, and refers to a time for which a certain degree of limitation (lower or upper limit) is set. For example, in setting a certain degree of limitation (lower limit) on the contact time between the carrier C1, which was previously introduced and held in the anaerobic treatment tank, and the sludge S, the "predetermined time (lower limit)" in this embodiment is set to the point in time when the carrier C2, whose surface is substantially uniformly covered with sludge S, replaces the carrier C1 in the anaerobic treatment tank 10, so that it is predominantly replaced. At this point, by introducing new carrier C1 into the anaerobic treatment tank 10 through the second carrier introduction step, the difference in settling velocity between the previously introduced carrier (mainly carrier C2) and the newly introduced carrier (C1) increases, enabling efficient movement. Furthermore, regarding setting a certain limit (upper limit) on the contact time between the carrier C1 previously introduced and held in the anaerobic treatment tank 10 and the sludge S, one example of setting the "predetermined time (upper limit)" in this embodiment is the point at which the previously introduced and held carriers C2 in the anaerobic treatment tank 10 adhere to each other and a short-circuit channel is firmly constructed. By introducing new carrier C1 through the second carrier introduction step before this point, it becomes possible to effectively suppress the formation of the short-circuit channel. Furthermore, by setting the predetermined time described above and starting the second carrier input process, the carrier (carrier C2) that has been covered with sludge S to a certain extent and the new carrier (C1) are efficiently mixed in the anaerobic treatment tank 10. This makes it possible to shorten the time required to complete the acclimatization of the entire carrier in the anaerobic treatment tank 10.
[0049] Also, as another example, for instance, in the method of starting up the anaerobic treatment tank in this embodiment, a pressure measurement step of measuring the pressure inside the anaerobic treatment tank 10 is provided, and according to the measurement result obtained in the pressure measurement step, the second carrier input step is started. The pressure change inside the anaerobic treatment tank 10 is caused by the adhesion state of the carriers to each other. More specifically, the adhesion of the carriers to each other (especially the carriers C2 to each other) progresses inside the anaerobic treatment tank 10, and due to the formation of a short-circuit flow path and the generation of a short-circuit flow, a pressure difference occurs between the upstream side and the downstream side inside the anaerobic treatment tank 10, more specifically, between the upstream side and the downstream side of the carrier layer (the layer of the carrier C2), and a so-called pressure loss occurs. Therefore, by measuring the pressure inside the anaerobic treatment tank 10, the occurrence of the pressure loss can be detected, the tendency related to the formation of the short-circuit flow path (the generation of the short-circuit flow) in the layer of the carrier C2 can be promptly detected, and at this stage, by further inputting a new carrier (the carrier C1) by the second carrier input step, it becomes possible to effectively suppress the formation of the short-circuit flow path. Note that the specific means for measuring the pressure inside the anaerobic treatment tank 10 is not particularly limited, but it is preferable to enable the detection related to the occurrence of the pressure loss. Specifically, pressure gauges are provided on the upstream side and the downstream side of the carrier layer (the layer of the carrier C2), and detection related to the occurrence of the pressure loss is performed from the difference therebetween.
[0050] Furthermore, as another example, in the method for starting up the anaerobic treatment tank in this embodiment, after the first carrier input step and the sludge input step, a carrier property assessment step is provided to confirm and understand the properties of the carrier (shape, color, etc.), and the second carrier input step is started according to the information obtained in the carrier property assessment step. More specifically, the carrier property assessment step is provided with means to confirm and understand the properties of the carrier C in the anaerobic treatment tank 10 and means to determine the properties of the carrier C (especially whether or not it is covered with sludge S), and the second carrier input step is started when it is determined that the surface of the carrier C (carrier C1) introduced in the first carrier input step has been covered with sludge S (biofilm has been attached). Means for confirming and understanding the properties of the carrier C in the anaerobic treatment tank 10, and means for determining the properties of the carrier C, include those based on the judgment of workers, such as visual inspection from a window provided in the side wall of the anaerobic treatment tank 10 or visual inspection of a sample taken from the anaerobic treatment tank 10, as well as acquiring information about the carrier C in the anaerobic treatment tank 10 using imaging means such as a camera, and basing this information on image analysis.
[0051] In this embodiment, the method for starting up the anaerobic treatment tank is shown in Figure 2, in the order of a first carrier input step (Figure 2A), a sludge input step (Figure 2B), and a second carrier input step (Figure 2C). However, in addition to these steps, a carrier input step and a sludge input step may also be performed. In other words, in order to input and maintain the total amount of carrier C necessary for carrying out anaerobic treatment in the anaerobic treatment tank 10, not only the first and second carrier input steps may be used, but carrier C may also be input in multiple stages, along with the input of sludge S. More specifically, after the second carrier input step shown in Figure 2C, a second sludge input step may be provided to input sludge S (in this case, the sludge input step based on Figure 2B becomes the first sludge input step), and then a third carrier input step may be provided to input carrier C1. As a result, within the anaerobic treatment tank 10, carrier C2 generated by the second carrier input step and the second sludge input step and carrier C1 introduced by the third carrier input step will move to exchange positions, thereby suppressing the formation of short-circuit channels. There are no particular limitations on the number of operations for the carrier input step and the sludge input step, but the operation of the entire anaerobic treatment tank startup method shall be completed with the carrier input step. This makes it possible to proceed with the acclimatization process in the anaerobic treatment tank 10 while suppressing the outflow of the introduced sludge S, and suppressing the formation of short-circuit channels by carrier movement involving the exchange of positions between carrier C2 and carrier C1.
[0052] As described above, the method for starting up an anaerobic treatment tank in this embodiment relates in particular to the start-up of an anaerobic treatment tank that utilizes a carrier. In the start-up of an anaerobic treatment tank that utilizes a carrier, it has been common practice to introduce the entire amount of carrier and microorganisms (sludge such as granules) into the anaerobic treatment tank and wait for time to pass during the process of forming a state in which the carrier surface is uniformly covered with sludge (in other words, a state in which microorganisms are uniformly attached to the carrier surface) (acclimatization process). At this time, a short-circuit channel is formed in the anaerobic treatment tank due to the adhesion of the carriers to each other, resulting in a so-called short-circuit flow. When a short-circuit flow occurs in the anaerobic treatment tank, the fluidity in the anaerobic treatment tank decreases, leading to a decrease in treatment efficiency due to a decrease in the contact efficiency between the carrier (microorganisms on the carrier surface) and the water to be treated. On the other hand, the method for starting up an anaerobic treatment tank in this embodiment involves introducing the carrier into the anaerobic treatment tank in multiple stages, and introducing sludge to the carrier that was introduced first, and then introducing the remaining carrier. At this time, with respect to the carriers introduced earlier, during the acclimatization process that proceeds as sludge is introduced, adhesion occurs between carriers with biofilms formed on their surfaces, potentially creating a short-circuit channel. However, by introducing more carriers, the difference in settling velocity between carriers covered with sludge (carriers with biofilms formed) and uncovered carriers causes each carrier to move and exchange positions within the anaerobic treatment tank. As the carriers move, uncovered carriers intersect between carriers that are covered with sludge and adhered to each other (in other words, carriers that are in a state where a short-circuit channel could be formed), thereby suppressing the formation of a short-circuit channel and, consequently, the generation of a short-circuit flow. This ensures fluidity within the anaerobic treatment tank and improves treatment efficiency after startup, allowing the operation related to the startup of the anaerobic treatment tank to proceed. In other words, the anaerobic treatment tank startup method of this embodiment makes it possible to proceed with the operation related to the startup of the anaerobic treatment tank without causing a decrease in the contact efficiency between the carriers (microorganisms on the carrier surface) and the water to be treated.
[0053] [Second Embodiment] Figure 3 is a schematic diagram illustrating an anaerobic treatment tank and surrounding equipment to which the anaerobic treatment tank startup method according to the second embodiment of the present invention is applied. Figure 4 is a schematic diagram illustrating the steps related to the anaerobic treatment tank startup method in the second embodiment of the present invention. The anaerobic treatment tank startup method according to this embodiment further includes a coagulant input step of adding a coagulant to the anaerobic treatment tank between the first carrier input step and the sludge input step in the anaerobic treatment tank startup method of the first embodiment. 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.
[0054] The method for starting up the anaerobic treatment tank 10 in this embodiment involves a step to promote the formation of carrier C2 (adhesion of sludge S to carrier C1) when replacing carrier C2, which is covered with sludge S, with carrier C1, which is introduced into the anaerobic treatment tank 10 by the first carrier introduction step, by the sludge introduction step. More specifically, after introducing carrier C (carrier C1) into an empty anaerobic treatment tank 10 by the first carrier introduction step, a coagulant F is introduced by the coagulant introduction step, and then sludge S is introduced by the sludge introduction step, thereby shortening the time required to form carrier C2 covered with sludge S from uncovered carrier (carrier C1).
[0055] (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 (carrier C1) and adheres to its surface, and then promotes a coagulation reaction with the sludge S that is introduced, so that the surface of the carrier C (carrier C1) 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.).
[0056] 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.
[0057] 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).
[0058] 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.
[0059] 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.
[0060] 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 3, the coagulant F can be introduced via a line L6 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 L6 for adjusting the amount and timing of the coagulant F to be introduced. Alternatively, line L6 may be directly connected to the anaerobic treatment tank 10 without going through line L2, and the coagulant F may be introduced from there. Furthermore, if an acid generation tank 20 is provided upstream of the anaerobic treatment tank 10, the coagulant F may be introduced into the anaerobic treatment tank 10 via the acid generation tank 20.
[0061] The following describes each step involved in setting up the anaerobic treatment tank in this embodiment, based on Figure 4. The steps involved in setting up the anaerobic treatment tank in this embodiment include a first carrier input step of introducing carrier C into an empty anaerobic treatment tank 10, a coagulant input step (Figure 4A) of introducing coagulant F into the anaerobic treatment tank 10 after the first carrier input step, a sludge input step (Figure 4B) of introducing sludge S into the anaerobic treatment tank 10 after the coagulant input step, and a second carrier input step (Figure 4C) of introducing carrier C into the anaerobic treatment tank 10 after the sludge input step.
[0062] First, as shown in Figure 4A, the first carrier input step involves adding carrier C to an empty anaerobic treatment tank 10. At this time, uncoated carrier C1 remains in the anaerobic treatment tank 10, unchanged in state from the time it was added to and held in the anaerobic treatment tank 10. This first carrier input step can be the same as described in the first embodiment above, and details will be omitted.
[0063] Then, after the first carrier input step, as a coagulant input step, as shown in Figure 4A, the coagulant F is introduced into the anaerobic treatment tank 10 holding the carrier C via lines L6 and L2. As a result, carrier C3 with the coagulant F attached is present inside the anaerobic treatment tank 10. At this time, it is preferable that the position of line L2 (or line L6) for introducing the coagulant F 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 carrier (carrier C1) located in the lower part of the anaerobic treatment tank 10 after the first carrier input step.
[0064] Next, as a sludge input step, as shown in Figure 4B, sludge S is introduced into the anaerobic treatment tank 10 where carrier C3 is located via lines L5 and L2. As a result, inside the anaerobic treatment tank 10, carrier C2 exists covered with sludge S, with the sludge S adhering to carrier C3 to which the coagulant F is attached. At this time, the position of line L2 (or line L5) is preferably at the lower side or bottom of the anaerobic treatment tank 10, similar to when the coagulant F is introduced as described above. As described above, in the coagulant input step, the coagulant F is attached to the carrier (carrier C1) located in the lower part of the anaerobic treatment tank 10. For this reason, by introducing 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 carrier C3 to which the coagulant F is attached.
[0065] In the method for setting up the anaerobic treatment tank in this embodiment, a coagulant F is first added to the carrier C (carrier C1) that has been introduced and held in the anaerobic treatment tank 10, thereby bringing the carrier C1 and the coagulant F into contact and creating a state in which the coagulant F adheres to the surface of the carrier. By then introducing sludge S, the coagulation reaction between the coagulant F and the sludge S proceeds on the surface of the carrier, making it possible to quickly create a state in which the surface of the carrier is uniformly covered with sludge (in other words, a state in which microorganisms are uniformly attached to the surface of the carrier).
[0066] Furthermore, as a second carrier input step, as shown in Figure 4C, carrier C (carrier C1) is introduced into the anaerobic treatment tank 10, which contains carrier C2 that has been covered with sludge S via carrier C3. At this time, as explained in the first embodiment above, within the anaerobic treatment tank 10, the difference in settling velocity between carrier C2 and carrier C1 causes each carrier to move so as to exchange positions within the anaerobic treatment tank 10. As this carrier movement occurs, the uncovered carrier C1 will be inserted between the carriers C2 that are covered with sludge and are adhering to each other (in other words, in a state where a short-circuit channel can be formed), thereby suppressing the formation of a short-circuit channel and, consequently, suppressing the generation of a short-circuit flow.
[0067] The second carrier input step can be the same as described in the first embodiment above, and details will be omitted. In this embodiment, the method for starting up the anaerobic treatment tank shortens the time required for carrier C2, in which the carrier surface is substantially uniformly covered with sludge S, to replace carrier C1 in the anaerobic treatment tank 10. Therefore, it becomes possible to reduce the set value (especially the lower limit) related to the predetermined time elapsed after the sludge input step when starting the second carrier input step, thereby shortening the time required to start up the anaerobic treatment tank, in addition to suppressing the generation of short-circuit flows.
[0068] Then, after the second carrier input step shown in Figure 4C, the newly introduced carrier C1 moves within the anaerobic treatment tank 10 while in contact with carrier C2, which is covered with sludge S. As time passes, sludge S adheres to carrier C1 as well, making it possible to create a state in which the entire anaerobic treatment tank 10 is filled with carriers (carrier C2) covered with sludge S.
[0069] Furthermore, after the second carrier input step, when carrier C1 is located on the lower side of the anaerobic treatment tank 10 due to the movement of carriers C1 and C2, the coagulant F may be added again in the coagulant input step. This promotes the adhesion of sludge S by changing carrier C1, which is located on the lower side of the anaerobic treatment tank 10, to the state of carrier C3, and makes it possible to create a state in which the entire anaerobic treatment tank 10 is covered with sludge S and contains carriers (carrier C2) even more quickly.
[0070] Furthermore, in the method for setting up the anaerobic treatment tank in this embodiment, similar to the first embodiment described above, in order to input and maintain the total amount of carrier C necessary for carrying out anaerobic treatment in the anaerobic treatment tank 10, the carrier C may be input in multiple stages, not just in the first and second carrier input stages, and the sludge S and coagulant F may also be input at the same time. At this time, there is no particular limit to the number of operations for the carrier input stage, the sludge input stage, and the coagulant input stage, but similar to the first embodiment described above, the operation of the overall method for setting up the anaerobic treatment tank shall end with the carrier input stage. This makes it possible to proceed with the acclimatization process in the anaerobic treatment tank 10 while suppressing the outflow of the input sludge S, while suppressing the formation of a short-circuit channel by moving the carriers, which involves the exchange of positions between carrier C2 and carrier C1.
[0071] As described above, the method for starting up the anaerobic treatment tank in this embodiment includes a coagulant input step between the first carrier input step and the sludge input step, in which a coagulant is added to the anaerobic treatment tank. This allows the coagulation reaction between the coagulant and sludge to proceed on the surface of the carrier, and quickly creates a state in which the surface of the carrier is uniformly covered with sludge (in other words, a state in which microorganisms are uniformly attached to the surface of the carrier). This makes it possible to reduce the time required for starting up the anaerobic treatment tank, in addition to suppressing the generation of short-circuit flow.
[0072] 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.
[0073] For example, in an alternative configuration of the anaerobic treatment tank startup method according to this embodiment, the sludge input step (or sludge input step and coagulant input step) in the anaerobic treatment tank startup method shown in the first and second embodiments may be replaced with a sludge input step (or sludge input step and coagulant input step) via an acid generation tank 20 located upstream of the anaerobic treatment tank 10. When starting up an 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, in an alternative configuration of the anaerobic treatment tank startup method of the present invention, by performing the sludge input step (or sludge input step and coagulant input step) via the acid generation tank 20, it becomes 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 allowing the coagulant F to be introduced via the same route as the sludge S, it is possible to suppress the complexity and cumbersome nature of the operations involved in setting up the anaerobic treatment tank.
[0074] In this case, a specific example of carrying out the sludge input process (or the sludge input process and the coagulant input process) via the acid generation tank 20 is to directly connect the line L6 for the coagulant input process and the line L5 for the sludge input process to the acid generation tank 20. Furthermore, the operations for inputting the coagulant F via line L6 and the sludge S via line L5 proceed in the same manner as in the first or second embodiment described above.
[0075] Regarding lines L5 and L6, which are directly connected to the acid generation tank 20, it is sufficient that they are capable of supplying sludge S and coagulant F to the acid generation tank 20, respectively. In particular, for line L5, 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 L6, the lid on top of the acid generation tank 20 may be opened, and coagulant F may be introduced.
[0076] Furthermore, the arrangement of lines L5 and L6 is not limited to direct connection to the acid generation tank 20, as long as the sludge input process (or the sludge input process and the coagulant input process) proceeds via the acid generation tank 20. For example, in another embodiment, lines L5 and / or line L6 may be connected to line L1 or line L4 which leads to the acid generation tank 20, and the coagulant F and sludge S may be introduced into the anaerobic treatment tank 10 via the acid generation tank 20.
[0077] Furthermore, regarding the method for setting up the anaerobic treatment tank according to this embodiment, a further alternative embodiment is to include, for example, an organic matter input step in which organic matter is added before the formation of the carrier C2 by the sludge input step, in the method for setting up the anaerobic treatment tank shown in the first and second embodiments. This allows organic matter to adhere to the carrier C1, and then by adding the sludge S, a state is formed in which the organic matter attached to the carrier C1, together with the sludge S, covers the carrier C (carrier C2), and this organic matter becomes available as a nutrient source for microorganisms in the sludge S on carrier C2.
[0078] Here, as a specific example of the organic matter input process, for example, wastewater W0 containing organic matter to be treated in the anaerobic treatment tank 10 may be introduced into the anaerobic treatment tank 10 via line L2. Alternatively, a solution containing organic matter other than wastewater W0 may be prepared, or other wastewater brought in from outside the system may be introduced 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 process.
[0079] In this embodiment, the method for setting up an anaerobic treatment tank, which includes an organic matter input step, allows for the inclusion of organic matter that serves as a nutrient source for microorganisms in the sludge when coating the carrier with sludge. Combined with microbial adhesion to the carrier, this makes it possible to shorten the time required for microbial growth and maintain 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.
[0080] 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 utilizes a carrier.
[0081] 10 Anaerobic treatment tank, 20 Acid generation tank, L1-L6 lines, C Carrier, C1 Uncoated carrier, C2 Carrier coated with sludge, C3 Carrier with flocculant attached, F Flocculant, S Sludge, W0 Wastewater, W1 Treated water
Claims
1. A method for starting up an anaerobic treatment tank, comprising: a first carrier input step of introducing a carrier into the anaerobic treatment tank; a sludge input step of introducing sludge into the anaerobic treatment tank after the first carrier input step; and a second carrier input step of introducing further carriers into the anaerobic treatment tank after the sludge input step.
2. The method for starting up an anaerobic treatment tank according to claim 1, characterized in that a coagulant input step of introducing a coagulant into the anaerobic treatment tank is provided between the first carrier input step and the sludge input step.
3. The method for starting up an anaerobic treatment tank according to claim 1, characterized in that the second carrier input step is started after a predetermined time has elapsed after the sludge input step.
4. A method for starting up an anaerobic treatment tank according to claim 1, characterized in that a pressure measurement step is provided for measuring the pressure inside the anaerobic treatment tank, and the second carrier input step is started according to the measurement result obtained by the pressure measurement step.
5. The method for starting up an anaerobic treatment tank according to any one of claims 1 to 4, characterized in that the carrier introduced into the anaerobic treatment tank is activated carbon.
6. A method for starting up an anaerobic treatment tank according to any one of claims 1 to 4, characterized in that carriers with different settling velocities are used in the first carrier input step and the second carrier input step, respectively.