Solution processing apparatus and solution processing method

Abstract

To provide a solution treatment apparatus and a solution treatment method which achieve excellent suppression of odor generated in a solution treatment step and suppression of odor generated from dewatered sludge generated in the solution treatment step.SOLUTION: A solution as a processing object is treated by nitrification reaction and denitrification reaction by microorganisms in an environment where alkali-treated sludges and minerals coexist.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a solution processing apparatus and a solution processing method. [Background technology]

[0002] Components (e.g., ammonia) contained in various solutions (e.g., wastewater, sewage, human waste, septic tank sludge, sewage sludge) cause environmental pollution, and therefore it is necessary to remove these components from the solutions. Techniques for removing these components, for example, techniques using microorganisms, have been developed (see, for example, Patent Documents 1 to 4).

[0003] For example, Patent Document 1 discloses a technique for purifying wastewater by a nitrification-denitrification method using microorganisms. This technique employs an alkaline treatment using an alkaline agent. On the other hand, Patent Documents 2 to 4 disclose techniques for purifying wastewater using Bacillus bacteria. These techniques employ minerals. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5981096 [Patent Document 2] Patent No. 4759557 [Patent Document 3] Patent No. 4922214 [Patent Document 4] Japanese Patent Application Laid-Open No. 2005-295887 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the above-mentioned conventional techniques have room for improvement in terms of suppressing odors generated during the solution treatment process and suppressing odors generated from the dewatered sludge obtained during the solution treatment process.

[0006] One aspect of the present invention aims to provide a solution treatment device and a solution treatment method that are excellent at suppressing odors generated during the solution treatment process and at suppressing odors generated from dehydrated sludge obtained during the solution treatment process. [Means for solving the problem]

[0007] The present inventors have discovered that treating a solution to be treated by nitrification and denitrification reactions using microorganisms in an environment where alkali-treated sludge and minerals coexist can suppress odors generated during the solution treatment process and odors generated from the dewatered sludge obtained during the solution treatment process, and have completed the present invention. One aspect of the present invention includes the following.

[0008] <1> a nitrification / denitrification tank that accommodates a solution to be treated and treats the solution through nitrification and denitrification reactions using microorganisms to obtain a treated solution; an alkaline treatment tank for alkaline treating the sludge contained in the treatment liquid discharged from the nitrification / denitrification tank and then returning the sludge to the nitrification / denitrification tank; a mineral input section for inputting minerals into the nitrification / denitrification tank.

[0009] According to the above configuration, an environment is created in the nitrification / denitrification tank where alkali-treated sludge and minerals coexist. In this environment, a bacterial flora dominated by specific microorganisms is realized. As a result, the generation of odors can be suppressed. More specifically, for example, odors generated in various components of the solution treatment device (e.g., the nitrification / denitrification tank, the alkali treatment tank, and other tanks), odors from the water tank (e.g., the storage tank) and treatment equipment to which the solution treated by the solution treatment device is transferred, and odors generated from the dewatered sludge obtained after treatment can be suppressed.

[0010] <2> a microorganism detection unit for detecting at least one selected from the group consisting of alkaliphilic bacteria, sulfate-reducing bacteria, sulfur-oxidizing bacteria, ammonia-oxidizing bacteria, and nitrite-oxidizing bacteria contained in the microorganisms in the nitrification / denitrification tank; <1> The solution treatment device according to claim 1.

[0011] As can be seen from the examples, the generation of odors can be suppressed by a bacterial flora dominated by specific microorganisms. By detecting specific microorganisms in a single tank, such as a nitrification / denitrification tank, as in the above configuration, it is possible to easily determine whether the entire solution treatment apparatus is operating in a desired state, in other words, whether the various components of the solution treatment apparatus (e.g., the nitrification / denitrification tank, the alkaline treatment tank, and other tanks) are operating in a desired state. Furthermore, with the above configuration, the detection results of the microorganism detection unit can be used as an index for adjusting the operating conditions of the solution treatment apparatus.

[0012] <3> the alkaliphilic bacterium is at least one selected from the group consisting of bacteria of the genus Bacillus, bacteria of the genus Mycobacterium, bacteria of the genus Acetobacterium, bacteria of the genus Corynebacterium, and bacteria of the genus Clostridium; the sulfate-reducing bacteria are at least one selected from the group consisting of bacteria of the genus Desulfobulbus, bacteria of the genus Desulfomicrobium, bacteria of the genus Desulfovibrio, and bacteria of the genus Desulfomonile; the sulfur-oxidizing bacteria is at least one selected from the group consisting of bacteria of the genus Allochromatium, bacteria of the genus Paracoccus, and bacteria of the genus Thiobacillus; The ammonia-oxidizing bacteria is at least one selected from the group consisting of bacteria of the genus Nitrosomonas and bacteria of the genus Nitrosococcus, The nitrite-oxidizing bacteria is at least one selected from the group consisting of bacteria of the genus Nitrospira and bacteria of the genus Nitrobacter. <2> The solution treatment device according to claim 1.

[0013] As can be seen from the examples, the generation of odors can be suppressed by a bacterial flora dominated by specific microorganisms. By detecting specific microorganisms in a single tank, such as a nitrification / denitrification tank, as in the above configuration, it is possible to easily determine whether the entire solution treatment apparatus is operating in a desired state, in other words, whether the various components of the solution treatment apparatus (e.g., the nitrification / denitrification tank, the alkaline treatment tank, and other tanks) are operating in a desired state. Furthermore, with the above configuration, the detection results of the microorganism detection unit can be used as an index for adjusting the operating conditions of the solution treatment apparatus.

[0014] <4> The mineral input unit inputs the minerals into the sludge returned from the alkaline treatment tank to the nitrification / denitrification tank. <1> ~ <3> 10. The solution treatment device according to claim 9, wherein the solution treatment device is a solution treatment apparatus.

[0015] According to the above-described configuration, minerals can be easily introduced into the nitrification / denitrification tank, and a bacterial flora in which specific microorganisms are dominant can be easily realized in the nitrification / denitrification tank.

[0016] <5> A pre-alkali treatment tank is provided for alkali-treating the solution before it is transferred to the nitrification / denitrification tank. <1> ~ <4> 10. The solution treatment device according to claim 9, wherein the solution treatment device is a solution treatment apparatus.

[0017] According to the above-mentioned configuration, the pH in the nitrification / denitrification tank can be easily adjusted, and a bacterial flora in which specific microorganisms are dominant can be easily realized in the nitrification / denitrification tank.

[0018] <6> a nitrification / denitrification reaction step in which a solution to be treated is placed in a nitrification / denitrification tank and treated by microbial nitrification and denitrification to obtain a treated solution; an alkali treatment step in which sludge contained in the treatment liquid discharged from the nitrification / denitrification tank is alkali-treated in an alkali treatment tank, and then the sludge is returned to the nitrification / denitrification tank; a mineral introduction step of introducing minerals into the nitrification / denitrification tank.

[0019] According to the above configuration, an environment is created in the nitrification / denitrification tank where alkali-treated sludge and minerals coexist. In this environment, a bacterial flora dominated by specific microorganisms is realized. As a result, the generation of odors can be suppressed. More specifically, for example, odors generated in various components of the solution treatment device (e.g., the nitrification / denitrification tank, the alkali treatment tank, and other tanks), odors from the water tank (e.g., the storage tank) and treatment equipment to which the solution treated by the solution treatment device is transferred, and odors generated from the dewatered sludge obtained after treatment can be suppressed.

[0020] <7> a microorganism detection step of detecting at least one selected from the group consisting of alkaliphilic bacteria, sulfate-reducing bacteria, sulfur-oxidizing bacteria, ammonia-oxidizing bacteria, and nitrite-oxidizing bacteria contained in the microorganisms in the nitrification / denitrification tank; <6> The solution processing method according to claim 1.

[0021] As can be seen from the examples, the generation of odors can be suppressed by a bacterial flora dominated by specific microorganisms. By detecting specific microorganisms in a single tank, such as a nitrification / denitrification tank, as in the above configuration, it is possible to easily determine whether the entire solution treatment apparatus is operating in a desired state, in other words, whether the various components of the solution treatment apparatus (e.g., the nitrification / denitrification tank, the alkaline treatment tank, and other tanks) are operating in a desired state. Furthermore, with the above configuration, the detection results of the microorganism detection unit can be used as an index for adjusting the operating conditions of the solution treatment apparatus.

[0022] <8> the alkaliphilic bacterium is at least one selected from the group consisting of bacteria of the genus Bacillus, bacteria of the genus Mycobacterium, bacteria of the genus Acetobacterium, bacteria of the genus Corynebacterium, and bacteria of the genus Clostridium; the sulfate-reducing bacteria are at least one selected from the group consisting of bacteria of the genus Desulfobulbus, bacteria of the genus Desulfomicrobium, bacteria of the genus Desulfovibrio, and bacteria of the genus Desulfomonile; the sulfur-oxidizing bacteria is at least one selected from the group consisting of bacteria of the genus Allochromatium, bacteria of the genus Paracoccus, and bacteria of the genus Thiobacillus; The ammonia-oxidizing bacteria is at least one selected from the group consisting of bacteria of the genus Nitrosomonas and bacteria of the genus Nitrosococcus, The nitrite-oxidizing bacteria is at least one selected from the group consisting of bacteria of the genus Nitrospira and bacteria of the genus Nitrobacter. <7> The solution processing method according to claim 1.

[0023] As can be seen from the examples, the generation of odors can be suppressed by a bacterial flora dominated by specific microorganisms. By detecting specific microorganisms in a single tank, such as a nitrification / denitrification tank, as in the above configuration, it is possible to easily determine whether the entire solution treatment apparatus is operating in a desired state, in other words, whether the various components of the solution treatment apparatus (e.g., the nitrification / denitrification tank, the alkaline treatment tank, and other tanks) are operating in a desired state. Furthermore, with the above configuration, the detection results of the microorganism detection unit can be used as an index for adjusting the operating conditions of the solution treatment apparatus.

[0024] <9> The mineral addition step is a step of adding the minerals to the sludge returned from the alkaline treatment tank to the nitrification / denitrification tank. <6> ~ <8> The solution treatment according to any one of method.

[0025] According to the above-described configuration, minerals can be easily introduced into the nitrification / denitrification tank, and a bacterial flora in which specific microorganisms are dominant can be easily realized in the nitrification / denitrification tank.

[0026] <10> A pre-alkali treatment step of alkali-treating the solution before it is transferred to the nitrification / denitrification tank, <6> ~ <9> 10. The solution processing method according to claim 9, wherein the solution processing method comprises:

[0027] According to the above-mentioned configuration, the pH in the nitrification / denitrification tank can be easily adjusted, and a bacterial flora in which specific microorganisms are dominant can be easily realized in the nitrification / denitrification tank. [Effects of the Invention]

[0028] According to one aspect of the present invention, it is possible to realize a solution treatment device and a solution treatment method that are excellent at suppressing odors generated during the solution treatment process and at suppressing odors generated from dehydrated sludge obtained during the solution treatment process. [Brief explanation of the drawings]

[0029] [Figure 1] 1 is a diagram showing an outline of the configuration of a solution processing apparatus according to one embodiment of the present invention; [Figure 2] 1 is a flowchart showing the procedure of a solution processing method according to one embodiment of the present invention. [Figure 3] 10 is a graph showing the amount of odor in the human waste receiving tank of the solution treatment device according to the embodiment of the present invention. [Figure 4] 1 is a graph showing the amount of odor in a septic tank sludge receiving tank of a solution treatment apparatus according to an embodiment of the present invention. [Figure 5] 10 is a graph showing the amount of odor in the alkaline treatment tank of the solution treatment device according to the example of the present invention. [Figure 6] 10 is a graph showing the amount of odor in the retention tank of the solution treatment device according to the example of the present invention. [Figure 7] 1 is a graph showing the amount of odor in the alkaline-treated sludge input tank of the solution treatment device according to the example of the present invention. [Figure 8] 10 is a graph showing the amount of odor in the entire facility where the solution treatment apparatus according to the embodiment of the present invention is installed. [Figure 9] 10 is a graph showing the amount of odor generated from dewatered sludge obtained in a solution treatment device according to a comparative example of the present invention. [Figure 10] 1 is a graph showing the amount of odor generated from dewatered sludge obtained in a solution treatment device according to an example of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0030] An embodiment of the present invention is described below, but the present invention is not limited thereto. The present invention is not limited to the configurations described below, and various modifications are possible within the scope of the claims. Embodiments and examples obtained by appropriately combining the technical means disclosed in different embodiments and examples are also included in the technical scope of the present invention. Furthermore, all documents described in this specification are incorporated herein by reference. In this specification, when a numerical range is described as "A to B," this means "greater than or equal to A and less than or equal to B."

[0031] [1. Solution Treatment Equipment] A solution processing apparatus according to one embodiment of the present invention will be described with reference to FIG.

[0032] A solution treatment apparatus 10 according to one embodiment of the present invention includes a nitrification / denitrification tank 1 that accommodates a solution to be treated and treats the solution through microbial nitrification and denitrification reactions to obtain a treated solution; an alkali treatment tank 2 that alkali-treats sludge contained in the treated solution discharged from the nitrification / denitrification tank 1 and then returns the sludge to the nitrification / denitrification tank 1; and a mineral input section 3 that inputs minerals into the nitrification / denitrification tank 1.

[0033] The solution treatment device 10 according to one embodiment of the present invention may further include (i) a pre-alkali treatment tank 4 for alkaline treatment of the solution before it is placed in the nitrification / denitrification tank 1, and / or (ii) a microorganism detection unit 5 for detecting at least one selected from the group consisting of alkaliphilic bacteria, sulfate-reducing bacteria, sulfur-oxidizing bacteria, ammonia-oxidizing bacteria, and nitrite-oxidizing bacteria contained in the microorganisms in the nitrification / denitrification tank 1.

[0034] The solution to be treated is not limited, and examples thereof include wastewater, sewage, human waste, septic tank sludge, and sewage sludge.

[0035] The nitrification / denitrification tank 1 is configured to treat the solution contained therein through nitrification and denitrification reactions by microorganisms, thereby obtaining a treated solution. An outline of the nitrification and denitrification reactions is shown below.

[0036] [ka]

[0037] Nitrification is a reaction that occurs in aerobic environments with microorganisms, converting NH4 to NO2 and NO3, while denitrification is a reaction that occurs in anaerobic environments with microorganisms, converting NO3 back to N2.

[0038] There are no limitations on the specific configuration of the nitrification / denitrification tank 1. The nitrification / denitrification tank 1 may be configured to perform both the nitrification reaction and the denitrification reaction in one tank, or may be configured to perform the nitrification reaction and the denitrification reaction in separate tanks.

[0039] When the nitrification / denitrification tank 1 is configured to perform both the nitrification reaction and the denitrification reaction in a single tank, for example, a vent for supplying air into the nitrification / denitrification tank 1 can be provided, and by supplying air into the nitrification / denitrification tank 1, the nitrification reaction can be caused to occur in an aerobic environment, and by stopping the supply of air into the nitrification / denitrification tank 1, the denitrification reaction can be caused to occur in an anaerobic environment.

[0040] When the nitrification / denitrification tank 1 is configured so that the nitrification reaction and the denitrification reaction are carried out in separate tanks, the nitrification / denitrification tank 1 can be configured, for example, with at least one nitrification tank provided with a fumarole for supplying air into the tank (nitrification tank) and at least one denitrification tank not provided with a fumarole for supplying air into the tank (denitrification tank). By supplying air into the nitrification tank, the nitrification reaction can be caused to occur in an aerobic environment in the nitrification tank, and by not supplying air into the denitrification tank, the denitrification reaction can be caused to occur in an anaerobic environment in the denitrification tank.

[0041] Upstream of the nitrification / denitrification tank 1, there may be provided a receiving port for receiving the solution to be treated before it is stored in the nitrification / denitrification tank 1, a grit tank for settling and separating sand and stones contained in the received solution, a receiving tank for the solution to be treated (also called a night soil receiving tank if the solution to be treated is night soil) for temporarily storing the solution from which the sand and stones have been separated by settling, pretreatment equipment for removing screen residue contained in the solution in the receiving tank, and / or a storage tank for storing the solution after the screen residue has been removed. The solution to be treated can be temporarily stored in the receiving tank for the solution to be treated and then introduced to the next process.

[0042] Downstream of the nitrification / denitrification tank 1, there may be provided (i) a settling tank for receiving the treated liquid discharged from the nitrification / denitrification tank 1 and performing solid-liquid separation, or a membrane separation raw water tank in which a membrane separation device for solid-liquid separation is immersed, and / or (ii) a return sludge tank for storing sludge separated from the treated liquid in the membrane separation raw water tank.

[0043] In the solution treatment apparatus 10 according to one embodiment of the present invention, the sludge treated in the nitrification / denitrification tank 1 can be returned from the nitrification / denitrification tank 1 or from at least one of the settling tank, membrane separation raw water tank, and return sludge tank (in other words, from the downstream structure of the nitrification / denitrification tank 1) to the receiving port, receiving tank, and / or storage tank for the solution to be treated. This configuration can suppress the generation of odor in the receiving tank for the solution to be treated.

[0044] Upstream of the nitrification / denitrification tank 1, there may be provided a receiving port for receiving sludge (for example, septic tank sludge) generated in other facilities, a grit tank for settling and separating sand and stones contained in the received solution, a sludge receiving tank (also called a septic tank sludge receiving tank if the sludge is septic tank sludge) for temporarily storing the solution from which the sand and stones have been separated, pretreatment equipment for removing screen residue from the solution in the receiving tank, and / or a storage tank for storing the solution after screen residue has been removed. The solution in the storage tank is introduced into the nitrification / denitrification tank 1 and treated.

[0045] In the solution treatment apparatus 10 according to one embodiment of the present invention, the sludge treated in the nitrification / denitrification tank 1 can be returned from the nitrification / denitrification tank 1 or from at least one of the settling tank, membrane separation raw water tank, and return sludge tank to the septic tank sludge receiving port, septic tank sludge receiving tank, and septic tank sludge storage tank. This configuration can suppress the generation of odors in the sludge receiving tank.

[0046] The alkaline treatment tank 2 is configured to transfer sludge contained in the treatment liquid discharged from the nitrification / denitrification tank 1 from the nitrification / denitrification tank 1 or from at least one of the settling tank, membrane separation raw water tank, and return sludge tank (in other words, from the downstream structure of the nitrification / denitrification tank 1), perform alkaline treatment on the sludge, and then return the sludge to the nitrification / denitrification tank 1.

[0047] In the alkaline treatment tank 2, (i) the sludge contained in the treated liquid discharged from the nitrification / denitrification tank 1 may be alkaline-treated by adding an alkaline agent to the treated liquid to adjust the pH of the treated liquid to alkaline, or (ii) the sludge contained in the treated liquid discharged from the nitrification / denitrification tank 1 may be separated, and an alkaline agent may be added to the sludge to adjust the pH of the sludge to alkaline, to thereby alkaline-treat the sludge contained in the treated liquid.

[0048] The alkaline agent is not particularly limited, and examples thereof include at least one selected from the group consisting of NaOH, KOH, Na2CO3, KCO3, Ca(OH)2, CaO, and NaOCl. Of these alkaline agents, NaOH, KOH, and NaOCl are preferred because they are inexpensive, have high alkaline strength, are available in highly concentrated aqueous solutions, and are easy to store and transport.

[0049] The pH during the alkaline treatment is not particularly limited, and is preferably 9.4 to 13.6, more preferably 10.5 to 12.5, and even more preferably 11.6 to 12.5. With the above configuration, odors generated during the solution treatment step and odors generated from the dewatered sludge obtained in the solution treatment step can be more effectively suppressed.

[0050] The amount of the alkaline agent used is not particularly limited and can be appropriately set based on the type of alkaline agent and / or the pH at which the alkaline treatment is carried out.

[0051] A retention tank may be provided downstream of the alkaline treatment tank 2 to temporarily retain the alkaline-treated liquid in the alkaline treatment tank 2. In the retention tank, the alkaline-treated sludge can be stored for a certain period of time, and organic matter eluted from the sludge can be broken down into smaller molecules. Furthermore, this configuration can suppress the generation of odors in the retention tank.

[0052] An alkali-treated sludge input tank may be provided downstream of the retention tank to temporarily store the sludge accumulated in the retention tank and then return the sludge to the nitrification / denitrification tank 1. This configuration makes it possible to adjust the amount of alkali-treated sludge returned to the nitrification / denitrification tank 1. This configuration also makes it possible to suppress the generation of odor in the alkali-treated sludge input tank.

[0053] The route for returning sludge from the alkaline treatment tank 2 to the nitrification / denitrification tank 1 is not particularly limited as long as it is a route that can return sludge to the nitrification / denitrification tank 1. For example, the sludge may be returned to any configuration (e.g., any tank, any flow path) located upstream of the nitrification / denitrification tank 1, or the sludge may be returned to a flow path for supplying a solution to the nitrification / denitrification tank 1, or the sludge may be returned to the pre-alkaline treatment tank 4, or the sludge may be returned to a flow path for supplying a solution from the pre-alkaline treatment tank 4 to the nitrification / denitrification tank 1, or the sludge may be returned to a flow path for supplying a solution to the pre-alkaline treatment tank 4, or the sludge may be returned directly to the nitrification / denitrification tank 1 (see, for example, FIG. 1).

[0054] The mineral feeding section 3 is configured to feed minerals into the nitrification / denitrification tank 1.

[0055] The mineral is not particularly limited, and examples thereof include at least one selected from the group consisting of magnesium, silica, calcium, iron, manganese, and aluminum. Among these minerals, magnesium and silica are preferred because they are necessary for the growth of microorganisms such as Bacillus bacteria and their addition has the advantage of making these microorganisms more likely to dominate.

[0056] There are no limitations on the amount of minerals fed into the nitrification / denitrification tank 1. For example, the amount may be 0.01 kg to 10 kg, 0.01 kg to 5 kg, or 0.1 kg to 1 kg per 100 kg of BOD (Biochemical Oxygen Demand) in the nitrification / denitrification tank 1. With the above configuration, odors generated during the solution treatment process and odors generated from the dewatered sludge obtained during the solution treatment process can be more effectively suppressed.

[0057] The path for introducing minerals from the mineral introduction unit 3 into the nitrification / denitrification tank 1 is not particularly limited as long as it is a path that can introduce minerals into the nitrification / denitrification tank 1. For example, minerals may be introduced into any configuration (e.g., any tank or any flow path) located upstream of the nitrification / denitrification tank 1, or into a flow path for supplying a solution to the nitrification / denitrification tank 1, or into the pre-alkali treatment tank 4, or into a flow path for supplying a solution from the pre-alkali treatment tank 4 to the nitrification / denitrification tank 1, or into a flow path for supplying a solution to the pre-alkali treatment tank 4, or directly into the nitrification / denitrification tank 1, or into a flow path for supplying a treatment liquid (or sludge contained in the treatment liquid) from the nitrification / denitrification tank 1 to the alkaline treatment tank 2, or into a flow path for returning alkaline-treated sludge from the alkaline treatment tank 2 to the nitrification / denitrification tank 1 (see, for example, FIG. 1 ).

[0058] The mineral feeding section 3 preferably feeds the minerals to the sludge returned from the alkaline treatment tank 2 to the nitrification / denitrification tank 1. With the above-described configuration, minerals can be easily fed to the nitrification / denitrification tank 1, and a bacterial flora dominated by specific microorganisms can be easily achieved in the nitrification / denitrification tank 1.

[0059] The microorganism detection unit 5 is configured to detect at least one (e.g., one, two, three, four, or five) selected from the group consisting of alkaliphilic bacteria, sulfate-reducing bacteria, sulfur-oxidizing bacteria, ammonia-oxidizing bacteria, and nitrite-oxidizing bacteria contained in the microorganisms in the nitrification / denitrification tank 1.

[0060] The alkaliphilic bacterium is preferably at least one (e.g., one, two, three, four, or five) selected from the group consisting of bacteria of the genus Bacillus, bacteria of the genus Mycobacterium, bacteria of the genus Acetobacterium, bacteria of the genus Corynebacterium, and bacteria of the genus Clostridium.

[0061] The sulfate-reducing bacteria are preferably at least one (e.g., one, two, three, or four) selected from the group consisting of bacteria of the genus Desulfobulbus, bacteria of the genus Desulfomicrobium, bacteria of the genus Desulfovibrio, and bacteria of the genus Desulfomonile.

[0062] The sulfur-oxidizing bacteria are preferably at least one (e.g., one, two, or three) selected from the group consisting of bacteria of the genus Allochromatium, bacteria of the genus Paracoccus, and bacteria of the genus Thiobacillus.

[0063] The ammonia-oxidizing bacteria are preferably at least one (for example, one or two) selected from the group consisting of bacteria of the genus Nitrosomonas and bacteria of the genus Nitrosococcus.

[0064] The nitrite-oxidizing bacteria are preferably at least one (for example, one or two) selected from the group consisting of bacteria of the genus Nitrospira and bacteria of the genus Nitrobacter.

[0065] The microorganisms detected by the microorganism detection unit 5 may be microorganisms other than the above-mentioned microorganisms, but may also have the same ability as the above-mentioned microorganisms (for example, the ability to suppress odors).

[0066] There are no particular limitations on the specific configuration of the microorganism detection unit 5. For example, the microorganism detection unit 5 may include only (a) a sampling unit for sampling microorganisms in the nitrification / denitrification tank 1 or a solution in the nitrification / denitrification tank 1 containing the microorganisms, or (b) both a sampling unit for sampling microorganisms in the nitrification / denitrification tank 1 or a solution in the nitrification / denitrification tank 1 containing the microorganisms, and a detection unit for detecting the microorganisms.

[0067] When the microorganism detection unit 5 has the above-described configuration (a), microorganisms may be detected by a configuration that is external to the solution treatment device 10. In this case, the microorganism detection unit 5 may include an input unit for inputting the detection result of the microorganisms to the microorganism detection unit 5.

[0068] The configuration of the sampling unit is not limited, and any known configuration can be used that can aspirate and sample microorganisms or a solution containing the microorganisms in the nitrification / denitrification tank 1. The configuration of the detection unit is not limited, and for example, a commercially available analyzer for analyzing bacterial flora (e.g., MiSeq (registered trademark) system) can be used. The configuration of the input unit is not limited, and any commercially available configuration can be used as appropriate.

[0069] The collection unit, detection unit, and input unit may comprise a computer that executes instructions of a software program that realizes each function. The computer may, for example, comprise at least one processor (controller) and at least one computer-readable recording medium storing the program. In the computer, the processor reads the program from the recording medium and executes it, thereby achieving the object of the present invention. The processor may, for example, be a CPU (Central Processing Unit). The recording medium may be a "non-transitory tangible medium," such as a ROM (Read Only Memory), a tape, a disk, a card, a semiconductor memory, or a programmable logic circuit. The computer may also further comprise a RAM (Random Access Memory) for expanding the program. The program may also be supplied to the computer via any transmission medium capable of transmitting the program (such as a communication network or broadcast waves). Note that one aspect of the present invention may also be realized in the form of a data signal embedded in a carrier wave, in which the program is embodied by electronic transmission.

[0070] The detection results of microorganisms can be used as indicators for adjusting the operating conditions of the solution treatment device 10. For example, the detection results of microorganisms can be sent from the microorganism detection unit 5 to the alkaline treatment tank 2 and / or the mineral input unit 3 (see FIG. 1).

[0071] In the alkaline treatment tank 2, the operating conditions of the solution treatment device 10 may be adjusted based on the detection results of the microorganisms, for example, by adjusting the type of alkaline agent, the amount of alkaline agent used, and / or the pH during alkaline treatment. This configuration makes it easier to achieve a bacterial flora dominated by specific microorganisms.

[0072] In the mineral input unit, the operating conditions of the solution treatment device 10 may be adjusted, for example, by adjusting the type of mineral and / or the amount of mineral used based on the detection results of the microorganisms. With this configuration, it is possible to more easily achieve a flora dominated by specific microorganisms.

[0073] Based on the results of the detection of microorganisms, the amount of solution to be placed in the nitrification / denitrification tank 1, the amount of oxygen to be supplied, the amount of sludge to be extracted, and / or the pH may be adjusted. This configuration makes it easier to achieve a bacterial flora dominated by specific microorganisms.

[0074] By adjusting the operating conditions of the solution treatment device 10 based on the results of microbial detection as described above, it is possible to better suppress odors generated during the solution treatment process and odors generated from the dehydrated sludge obtained during the solution treatment process.

[0075] The pre-alkali treatment tank 4 is configured to subject the solution to alkaline treatment before it is transferred to the nitrification / denitrification tank 1. The pre-alkali treatment tank may be configured to subject the entire solution before it is transferred to the nitrification / denitrification tank 1, or to subject a portion of the solution before it is transferred to the nitrification / denitrification tank 1 to alkaline treatment.

[0076] In the pre-alkali treatment tank 4, the solution before being transferred to the nitrification / denitrification tank 1 may be subjected to an alkaline treatment by adding an alkaline agent to the solution before being transferred to the nitrification / denitrification tank 1 to adjust the pH of the solution to alkaline.

[0077] The alkaline agent, the pH during the alkaline treatment, and the amount of the alkaline agent used are not particularly limited, and the alkaline agent, the pH during the alkaline treatment, and the amount of the alkaline agent used in the alkaline treatment tank 2 can also be used in the pre-alkaline treatment tank 4.

[0078] 2. Solution Processing Method A solution processing method according to one embodiment of the present invention will be described with reference to FIGS.

[0079] A solution treatment method according to one embodiment of the present invention includes a nitrification / denitrification reaction step S1 in which a solution to be treated is placed in a nitrification / denitrification tank 1 and treated by microbial nitrification and denitrification to obtain a treated solution; an alkali treatment step S2 in which sludge contained in the treated solution discharged from the nitrification / denitrification tank 1 is alkali-treated in an alkali treatment tank 2 and then the sludge is returned to the nitrification / denitrification tank 1; and a mineral introduction step S3 in which minerals are introduced into the nitrification / denitrification tank 1.

[0080] The mineral addition step S3 may be a step of adding minerals to the sludge returned from the alkaline treatment tank 2 to the nitrification / denitrification tank 1.

[0081] The solution treatment method according to one embodiment of the present invention may further include (i) a pre-alkali treatment step S4 in which the solution is subjected to an alkali treatment before being placed in the nitrification / denitrification tank 1, and / or (ii) a microbial detection step S5 in which at least one selected from the group consisting of alkaliphilic bacteria, sulfate-reducing bacteria, sulfur-oxidizing bacteria, ammonia-oxidizing bacteria, and nitrite-oxidizing bacteria contained in the microorganisms in the nitrification / denitrification tank 1 is detected.

[0082] The nitrification-denitrification reaction process S1, the alkaline treatment process S2, the mineral addition process S3, the pre-alkali treatment process S4, and the microbial detection process S5 can be carried out by the above-mentioned nitrification-denitrification tank 1, the alkaline treatment tank 2, the mineral addition section 3, the pre-alkali treatment tank 4, and the microbial detection section 5, respectively.

[0083] Regarding each component of the solution processing method according to one embodiment of the present invention, the items already explained in the above section [1. Solution Processing Apparatus] will not be explained here.

[0084] In the microorganism detection step S5, at least one (e.g., one, two, three, four, or five) selected from the group consisting of alkaliphilic bacteria, sulfate-reducing bacteria, sulfur-oxidizing bacteria, ammonia-oxidizing bacteria, and nitrite-oxidizing bacteria contained in the above microorganisms in the nitrification / denitrification tank 1 is detected.

[0085] The alkaliphilic bacterium is preferably at least one (e.g., one, two, three, four, or five) selected from the group consisting of bacteria of the genus Bacillus, bacteria of the genus Mycobacterium, bacteria of the genus Acetobacterium, bacteria of the genus Corynebacterium, and bacteria of the genus Clostridium.

[0086] The sulfate-reducing bacteria are preferably at least one (e.g., one, two, three, or four) selected from the group consisting of bacteria of the genus Desulfobulbus, bacteria of the genus Desulfomicrobium, bacteria of the genus Desulfovibrio, and bacteria of the genus Desulfomonile.

[0087] The sulfur-oxidizing bacteria are preferably at least one (e.g., one, two, or three) selected from the group consisting of bacteria of the genus Allochromatium, bacteria of the genus Paracoccus, and bacteria of the genus Thiobacillus.

[0088] The ammonia-oxidizing bacteria are preferably at least one (for example, one or two) selected from the group consisting of bacteria of the genus Nitrosomonas and bacteria of the genus Nitrosococcus.

[0089] The nitrite-oxidizing bacteria are preferably at least one (for example, one or two) selected from the group consisting of bacteria of the genus Nitrospira and bacteria of the genus Nitrobacter.

[0090] The microorganisms detected in the microorganism detection step S5 may be microorganisms other than the above-mentioned microorganisms, but may have the same ability as the above-mentioned microorganisms (for example, the ability to suppress odors).

[0091] The detection results of the microorganisms can be used as an indicator for adjusting the operating conditions of the solution treatment device 10 (solution treatment device operating condition adjustment step). For example, the detection results of the microorganisms can be sent from the microorganism detection unit 5 to the alkaline treatment tank 2 and / or the mineral input unit 3 (see FIG. 1).

[0092] In the alkaline treatment tank 2, the operating conditions of the solution treatment device 10 may be adjusted based on the results of the detection of microorganisms, for example, by adjusting the type of alkaline agent, the amount of alkaline agent used, and / or the pH during alkaline treatment (alkaline treatment tank operating condition adjustment process).

[0093] In the mineral input section, the operating conditions of the solution treatment device 10 may be adjusted, for example, by adjusting the type of mineral and / or the amount of mineral used based on the results of the detection of microorganisms (mineral input section operating condition adjustment process).

[0094] Based on the results of the detection of microorganisms, the amount of solution placed in the nitrification / denitrification tank 1, the amount of oxygen supplied, the amount of sludge withdrawn, and / or the pH may be adjusted.

[0095] By adjusting the operating conditions of the solution treatment device 10 based on the results of microbial detection as described above, it is possible to better suppress odors generated during the solution treatment process and odors generated from the dehydrated sludge obtained during the solution treatment process.

[0096] As explained in the section [1. Solution Treatment Apparatus] above, upstream of the nitrification / denitrification tank 1 may be provided a receiving port for receiving the solution to be treated before it is stored in the nitrification / denitrification tank 1, a grit tank for settling and separating sand and stones contained in the received solution, a receiving tank for the solution to be treated (a night soil receiving tank if the solution to be treated is night soil) for temporarily retaining the solution from which the sand and stones have been separated, pretreatment equipment for removing screen residue contained in the solution in the receiving tank, and / or a storage tank for storing the solution after the screen residue has been removed. Furthermore, in the solution treatment apparatus 10 according to one embodiment of the present invention, sludge treated in the nitrification / denitrification tank 1 can be returned to the receiving port, receiving tank, and / or storage tank for the solution to be treated.

[0097] Based on this configuration, the solution treatment method according to one embodiment of the present invention may include a return process A in which the sludge treated in the nitrification / denitrification tank 1 is returned to the receiving port for the solution to be treated, the receiving tank, and / or the storage tank.

[0098] As explained in the section [1. Solution Treatment Apparatus] above, upstream of the nitrification / denitrification tank 1 may be provided a receiving port for receiving sludge (e.g., septic tank sludge) generated in other facilities, a grit tank for settling and separating sand and stones contained in the received solution, a sludge receiving tank for temporarily storing the solution from which the sand and stones have been separated (a septic tank sludge receiving tank if the sludge is septic tank sludge), pretreatment equipment for removing screen residue from the solution in the receiving tank, and / or a storage tank for storing the solution after screen residue has been removed. Furthermore, in the solution treatment apparatus 10 according to one embodiment of the present invention, the sludge treated in the nitrification / denitrification tank 1 can be returned from the nitrification / denitrification tank 1 or from at least one of the settling tank, membrane separation raw water tank, and return sludge tank (in other words, from the configuration subsequent to the nitrification / denitrification tank 1) to the septic tank sludge receiving port, septic tank sludge receiving tank, or septic tank sludge storage tank.

[0099] Based on this configuration, the solution treatment method according to one embodiment of the present invention may include a return process B in which sludge treated in the nitrification / denitrification tank 1 is returned from the nitrification / denitrification tank 1 or from at least one of the settling tank, membrane separation raw water tank, and return sludge tank (in other words, from the configuration downstream of the nitrification / denitrification tank 1) to a septic tank sludge receiving port, a septic tank sludge receiving tank, or a septic tank sludge storage tank.

[0100] As explained in the section [1. Solution Treatment Apparatus] above, a retention tank may be provided downstream of the alkaline treatment tank 2 to temporarily retain the alkaline-treated solution in the alkaline treatment tank 2. In the retention tank, the alkaline-treated sludge is stored for a certain period of time, and organic matter eluted from the sludge can be broken down into smaller molecules.

[0101] Based on this configuration, the solution treatment method according to one embodiment of the present invention may include a separation step of separating the alkali-treated sludge (e.g., separating the alkali-treated sludge from the solution / liquid).

[0102] As explained in the section [1. Solution Treatment Apparatus] above, an alkali-treated sludge input tank may be provided downstream of the retention tank to temporarily store the sludge accumulated in the retention tank and then return the sludge to the nitrification / denitrification tank 1. With this configuration, the amount of alkali-treated sludge returned to the nitrification / denitrification tank 1 can be adjusted.

[0103] Based on this configuration, the solution treatment method according to one embodiment of the present invention may have a return amount adjustment step of adjusting the amount of alkali-treated sludge returned to nitrification / denitrification tank 1.

[0104] The solution treatment apparatus and solution treatment method according to one embodiment of the present invention can suppress odors generated during the solution treatment process and odors generated from dewatered sludge obtained during the solution treatment process. Therefore, the solution treatment apparatus and solution treatment method according to one embodiment of the present invention can also contribute to the achievement of the Sustainable Development Goals (SDGs) advocated by the United Nations, including Goal 3 "Good health and well-being," Goal 6 "Ensure availability and sustainable management of water and sanitation for all," and Goal 11 "Sustainable cities and communities." [Example]

[0105] <1. Solution treatment equipment design and operating conditions> In this example, a solution treatment device 10 was used, which was equipped with the nitrification / denitrification tank 1, alkaline treatment tank 2, and mineral input section 3 shown in Figure 1, and further equipped with the treatment target solution receiving tank (sewage receiving tank, septic tank sludge receiving tank), retention tank, alkaline treatment sludge input tank, membrane separation raw water tank, and return sludge tank described above in [1. Solution treatment device].

[0106] NaOH was used as the alkaline agent. In alkaline treatment tank 2, the sludge contained in the treatment liquid was alkaline treated for 2.5 hours under conditions of approximately pH 11.5. The alkaline-treated sludge was sent to a retention tank / alkaline-treated sludge input tank located downstream of alkaline treatment tank 2.

[0107] The mineral used was a mineral agent (Blue Mineral BM-B manufactured by Chuo Batyl World) whose main components were magnesium and silica. Approximately 1 kg of this mineral was added per 100 kg of BOD to the alkaline-treated sludge input tank.

[0108] The sludge in the alkali-treated sludge input tank was returned to the nitrification / denitrification tank 1 and also returned to the solution receiving tank to be treated (night soil receiving tank).

[0109] <2. Test results regarding odor generation in each configuration of solution treatment equipment> The solution treatment device 10 was operated to treat the human waste, and the amount of odor (specifically, H2S, NH3, and mercaptans) was measured in each component of the solution treatment device 10 (specifically, the human waste receiving tank, the septic tank sludge receiving tank, the alkaline treatment tank 2, the retention tank, the alkaline-treated sludge input tank, and the entire facility where the solution treatment device 10 was installed). The amount of odor was measured using a commercially available measuring device.

[0110] The amount of odor in the night soil receiving tank is shown in Figure 3. In Figure 3, "Before modification" indicates the test results before the return of sludge to the night soil receiving tank began, "After modification" indicates the test results after the return of sludge to the night soil receiving tank began, and "After acclimation" indicates the test results after the return of sludge to the night soil receiving tank began and after sufficient time had passed for the quality of the returned sludge to stabilize.

[0111] As is clear from Figure 3, the generation of odors (especially H2S and NH3) could be suppressed in the night soil receiving tank by returning sludge.

[0112] The amount of odor in the septic tank sludge receiving tank is shown in Figure 4. In Figure 4, "Before modification" indicates the test results before the return of sludge to the septic tank sludge receiving tank began, "After modification" indicates the test results after the return of sludge to the night soil receiving tank began, and "After acclimation" indicates the test results after the return of sludge to the night soil receiving tank began and after sufficient time had passed for the quality of the returned sludge to stabilize.

[0113] As is clear from Figure 4, the septic tank sludge receiving tank does not return sludge, so it is not possible to suppress the generation of odors like in the sewage receiving tank.

[0114] Figure 5 shows the amount of odor in alkaline treatment tank 2. In Figure 5, "Before modification" indicates the test results before the return of sludge to nitrification / denitrification tank 1 began, "After modification" indicates the test results after the return of sludge to nitrification / denitrification tank 1 began, and "After acclimation" indicates the test results after the return of sludge to nitrification / denitrification tank 1 began and after a sufficient amount of time had passed until the quality of the returned sludge had stabilized.

[0115] As is clear from FIG. 5, in the alkaline treatment tank 2, the generation of odors (especially NH3) could be suppressed by returning the sludge.

[0116] The amount of odor in the retention tank is shown in Figure 6. In Figure 6, "Before modification" indicates the test results before the return of sludge to nitrification / denitrification tank 1 began, "After modification" indicates the test results after the return of sludge to nitrification / denitrification tank 1 began, and "After acclimation" indicates the test results after the return of sludge to nitrification / denitrification tank 1 began and after sufficient time had passed until the quality of the returned sludge had stabilized.

[0117] As is clear from Figure 6, the generation of odors (especially NH3) could be suppressed in the retention tank by returning the sludge.

[0118] The amount of odor in the alkali-treated sludge input tank is shown in Figure 7. In Figure 7, "Before modification" indicates the test results before the return of sludge to nitrification / denitrification tank 1 began, "After modification" indicates the test results after the return of sludge to nitrification / denitrification tank 1 began, and "After acclimation" indicates the test results after the return of sludge to nitrification / denitrification tank 1 began and after a sufficient amount of time had passed until the quality of the returned sludge had stabilized.

[0119] As is clear from FIG. 7, in the alkali-treated sludge input tank, the generation of odors (especially H2S and NH3) could be suppressed by returning the sludge.

[0120] Figure 8 shows the amount of odor in the entire facility where solution treatment device 10 is installed. In Figure 8, "Before modification" shows the test results before the start of returning sludge to nitrification / denitrification tank 1, "After modification" shows the test results after the start of returning sludge to nitrification / denitrification tank 1, and "After acclimation" shows the test results after the start of returning sludge to nitrification / denitrification tank 1 and after a sufficient amount of time has passed until the quality of the returned sludge has stabilized.

[0121] As is clear from FIG. 8, in the entire facility where the solution treatment device 10 is installed, the generation of odors (particularly H2S and NH3) could be suppressed by returning sludge.

[0122] <3. Test results regarding odor generation from dewatered sludge> The amount of odor (specifically, H2S, NH3, mercaptans) in the dewatered sludge obtained by removing liquid from the solution in the sludge storage tank, which stores the coagulated sludge precipitated and separated in the coagulation and sedimentation tank from the excess sludge extracted from the return sludge tank and the membrane separated liquid separated in the membrane separation equipment, was measured. The amount of odor was measured using a commercially available measuring device.

[0123] Figure 9 shows the test results of dewatered sludge obtained before the return of sludge to the nitrification / denitrification tank 1 began, and Figure 10 shows the test results of dewatered sludge obtained after the return of sludge to the nitrification / denitrification tank 1 began and after sufficient time had passed for the quality of the returned sludge to stabilize.

[0124] 9 and 10, it is clear that the odor of the dewatered sludge obtained by the solution treatment apparatus according to the embodiment of the present invention is suppressed even after a long period of time has passed. This indicates that the dewatered sludge can be stored and transported for a long period of time without a special deodorizing device.

[0125] <4. Analysis results of bacterial flora> The solution treatment device 10 of this example was operated for a long period of time until the conditions in the nitrification / denitrification tank 1 stabilized, while returning the sludge in the alkali-treated sludge input tank to the nitrification / denitrification tank 1 and also to the treatment target solution receiving tank (night soil receiving tank).

[0126] Thereafter, the treated liquid in the nitrification / denitrification tank 1 was sampled, and the microbial flora contained in the treated liquid was subjected to amplicon sequencing analysis using a MiSeq device manufactured by Illumina.

[0127] The test results revealed that the treated liquid in the nitrification / denitrification tank 1 contained a large number of alkaliphilic bacteria, sulfate-reducing bacteria, sulfur-oxidizing bacteria, ammonia-oxidizing bacteria, and nitrite-oxidizing bacteria.

[0128] Further detailed analysis revealed that (1) alkaliphilic bacteria were predominantly Bacillus, Mycobacterium, Acetobacterium, Corynebacterium, and Clostridium, and (2) sulfate-reducing bacteria were predominantly Desulfobulbus, Desulfomicrobium, Desulfovibrio, and Desulfomonil. (3) sulfur-oxidizing bacteria were abundant in the genera Allochromatium, Paracoccus, and Thiobacillus; (4) ammonia-oxidizing bacteria were abundant in the genera Nitrosomonas and Nitrosococcus; and (5) nitrite-oxidizing bacteria were abundant in the genera Nitrospira and Nitrobacter.

[0129] In other words, it has been revealed that in an environment where the above-mentioned microorganisms are present in large numbers, the odor generated during the solution treatment process and the odor generated from the dewatered sludge obtained during the solution treatment process can be suppressed. [Industrial Applicability]

[0130] The present invention can be used to treat solutions (for example, wastewater, sewage, human waste, septic tank sludge, and sewage sludge). [Explanation of symbols]

[0131] 1 Nitrification and denitrification tank 2. Alkaline treatment tank 3 Mineral injection section 4 Pre-alkali treatment tank 5 Microbial detection unit 10 Solution treatment device S1 Nitrification and denitrification reaction process S2 Alkaline treatment process S3 Mineral addition process S4 Pre-alkali treatment process S5 Microbial detection process

Claims

1. a nitrification / denitrification tank that accommodates a solution to be treated and treats the solution through nitrification and denitrification reactions using microorganisms to obtain a treated solution; an alkaline treatment tank for alkaline treating the sludge contained in the treatment liquid discharged from the nitrification / denitrification tank and then returning the sludge to the nitrification / denitrification tank; a mineral input unit that inputs minerals into the nitrification / denitrification tank; a treatment target solution receiving tank for retaining the treatment target solution before it is received in the nitrification / denitrification tank; a path for returning the sludge treated in the nitrification-denitrification tank or the sludge treated with alkali in the alkali treatment tank to the receiving tank for the solution to be treated.

2. 2. The solution treatment device according to claim 1, further comprising a microorganism detection unit that detects at least one selected from the group consisting of alkaliphilic bacteria, sulfate-reducing bacteria, sulfur-oxidizing bacteria, ammonia-oxidizing bacteria, and nitrite-oxidizing bacteria contained in the microorganisms in the nitrification / denitrification tank.

3. the alkaliphilic bacterium is at least one selected from the group consisting of bacteria of the genus Bacillus, bacteria of the genus Mycobacterium, bacteria of the genus Acetobacterium, bacteria of the genus Corynebacterium, and bacteria of the genus Clostridium; the sulfate-reducing bacteria are at least one selected from the group consisting of bacteria of the genus Desulfobulbus, bacteria of the genus Desulfomicrobium, bacteria of the genus Desulfovibrio, and bacteria of the genus Desulfomonile; the sulfur-oxidizing bacteria is at least one selected from the group consisting of bacteria of the genus Allochromatium, bacteria of the genus Paracoccus, and bacteria of the genus Thiobacillus; The ammonia-oxidizing bacteria is at least one selected from the group consisting of bacteria of the genus Nitrosomonas and bacteria of the genus Nitrosococcus, 3. The solution treatment device according to claim 2, wherein the nitrite oxidizing bacteria is at least one selected from the group consisting of bacteria of the genus Nitrospira and bacteria of the genus Nitrobacter.

4. 2. The solution treatment apparatus according to claim 1, wherein the mineral input section inputs the minerals into the sludge returned from the alkaline treatment tank to the nitrification / denitrification tank.

5. 2. The solution treatment apparatus according to claim 1, further comprising a pre-alkali treatment tank for alkali-treating the solution before it is transferred to the nitrification / denitrification tank.

6. A solution treatment device as described in claim 1, wherein the mineral is at least one selected from the group consisting of magnesium, silica, calcium, iron, manganese, and aluminum.

7. a nitrification / denitrification reaction step in which a solution to be treated is placed in a nitrification / denitrification tank and treated by microbial nitrification and denitrification to obtain a treated solution; an alkali treatment step in which sludge contained in the treatment liquid discharged from the nitrification / denitrification tank is alkali-treated in an alkali treatment tank, and then the sludge is returned to the nitrification / denitrification tank; a mineral addition step of adding minerals to the nitrification / denitrification tank; a step of retaining the solution to be treated in a tank for receiving the solution to be treated before being stored in the nitrification / denitrification tank; and returning the sludge treated in the nitrification-denitrification tank or the sludge treated with alkali in the alkali treatment tank to the tank for receiving the solution to be treated.

8. 8. The solution treatment method according to claim 7, further comprising a microorganism detection step of detecting at least one selected from the group consisting of alkaliphilic bacteria, sulfate-reducing bacteria, sulfur-oxidizing bacteria, ammonia-oxidizing bacteria, and nitrite-oxidizing bacteria contained in the microorganisms in the nitrification / denitrification tank.

9. The alkaliphilic bacterium is at least one selected from the group consisting of bacteria of the genus Bacillus, bacteria of the genus Mycobacterium, bacteria of the genus Acetobacterium, bacteria of the genus Corynebacterium, and bacteria of the genus Clostridium; the sulfate-reducing bacteria are at least one selected from the group consisting of bacteria of the genus Desulfobulbus, bacteria of the genus Desulfomicrobium, bacteria of the genus Desulfovibrio, and bacteria of the genus Desulfomonile; the sulfur-oxidizing bacteria is at least one selected from the group consisting of bacteria of the genus Allochromatium, bacteria of the genus Paracoccus, and bacteria of the genus Thiobacillus; The ammonia-oxidizing bacteria is at least one selected from the group consisting of bacteria of the genus Nitrosomonas and bacteria of the genus Nitrosococcus, 9. The solution treatment method according to claim 8, wherein the nitrite-oxidizing bacteria is at least one selected from the group consisting of bacteria of the genus Nitrospira and bacteria of the genus Nitrobacter.

10. 8. The solution treatment method according to claim 7, wherein the mineral adding step is a step of adding the minerals to the sludge returned from the alkaline treatment tank to the nitrification / denitrification tank.

11. 8. The solution treatment method according to claim 7, further comprising a pre-alkali treatment step of alkali-treating the solution before it is transferred to the nitrification / denitrification tank.

12. A solution treatment method as described in claim 7, wherein the mineral is at least one selected from the group consisting of magnesium, silica, calcium, iron, manganese, and aluminum.

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