Hydrogen sulfide dissolution solution generation system

Abstract

This invention provides a technology that can efficiently dissolve hydrogen sulfide, which is generated during the wastewater treatment process, into the treatment liquid. [Solution] The hydrogen sulfide solution generation system comprises a treatment tank, a pH adjuster, and a control device. The treatment tank is equipped with a carrier that supports sulfate-reducing bacteria. The treatment tank separates the target substance from the liquid to be treated, which contains at least sulfate ions and organic matter, and generates hydrogen sulfide from the sulfate ions and organic matter using the sulfate-reducing bacteria, thereby producing a hydrogen sulfide solution in which hydrogen sulfide is dissolved. The pH adjuster adjusts the pH of the liquid to be treated, and the control device controls the pH adjuster according to the pH of the liquid to be treated.

Description

Technical Field

[0001] The present disclosure relates to a hydrogen sulfide dissolution solution generation system.

Background Art

[0002] Conventionally, various systems for wastewater treatment (hereinafter also referred to as wastewater treatment systems) have been proposed. For example, an organic matter recovery device by solid-liquid separation using a filter medium has been proposed (see Patent Document 1). Note that the wastewater treatment system is also called a wastewater treatment system. In addition, it is known that hydrogen sulfide is generated depending on the properties of the wastewater. Since hydrogen sulfide is harmful to the human body and corrodes concrete and ducts, a wastewater treatment system equipped with a decomposition treatment tank for decomposing hydrogen sulfide has been proposed (see Patent Document 2).

[0003] On the other hand, in order to realize a decarbonized society, hydrogen has attracted attention as a next-generation energy to replace carbon, and as a method of decomposing hydrogen sulfide absorbed in an alkaline aqueous solution (amine aqueous solution) to recover hydrogen, a method using a photocatalyst has been proposed as an alternative to the Claus method (see Patent Document 3).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] In order to generate hydrogen that can be used as an energy source from wastewater, it is desired to efficiently dissolve hydrogen sulfide generated in the process of wastewater treatment in a treatment liquid. [Means for solving the problem]

[0006] One aspect of this disclosure is a hydrogen sulfide solution generation system comprising: a treatment tank on which a carrier for carrying sulfate-reducing bacteria is arranged, which separates a target substance from a liquid to be treated containing at least sulfate ions and organic matter, and generates a hydrogen sulfide solution containing dissolved hydrogen sulfide by generating hydrogen sulfide from the sulfate ions and organic matter using the sulfate-reducing bacteria; a pH adjusting device for adjusting the pH of the liquid to be treated; and a control device for controlling the pH adjusting device according to the pH of the liquid to be treated. [Effects of the Invention]

[0007] According to the technology disclosed herein, hydrogen sulfide generated during the wastewater treatment process can be efficiently dissolved in the treatment liquid. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram illustrating a wastewater treatment system 100 to which the hydrogen sulfide dissolution solution generation system 10 according to the first embodiment is applied. [Figure 2] Figure 2 is a schematic diagram illustrating the hydrogen sulfide dissolution solution generation system 10 according to the first embodiment. [Figure 3] Figure 3 is a diagram illustrating the hardware configuration of the control device 6 according to the first embodiment. [Figure 4] Figure 4 is a flowchart showing the pH adjustment process in the first embodiment. [Figure 5] Figure 5 is a flowchart showing the HRT adjustment process in the first embodiment. [Figure 6] Figure 6 is a flowchart showing the HRT adjustment process in a modified example of the first embodiment. [Figure 7] Figure 7 is a schematic diagram illustrating the hydrogen sulfide dissolution solution generation system 10 according to the second embodiment. [Figure 8]Figure 8 is a flowchart showing the temperature control process in the second embodiment. [Figure 9] Figure 9 is a graph showing the relationship between ORP and hydrogen sulfide concentration. [Figure 10] Figure 10 is a graph showing the relationship between HRT and hydrogen sulfide concentration. [Modes for carrying out the invention]

[0009] Embodiments of this disclosure will be described below with reference to the drawings. However, this description should not be interpreted as limiting, and will not limit the subject matter described in the claims. Furthermore, various changes, substitutions, and modifications can be made without departing from the spirit and scope of this disclosure. Different embodiments can also be combined as appropriate.

[0010] The liquid to be treated in this disclosure is a liquid containing at least sulfate ions and organic matter. The liquid to be treated is not particularly limited, but examples include wastewater, and more specifically, influent sewage from a sewage treatment plant, return water from sludge treatment, dewatered separated liquid, industrial wastewater, mining wastewater, etc. The following describes the case where the liquid to be treated is influent sewage from a sewage treatment plant.

[0011] <First Embodiment> [Wastewater treatment system] Figure 1 is a schematic diagram illustrating a wastewater treatment system 100 to which the hydrogen sulfide dissolution solution generation system 10 according to the first embodiment is applied. The wastewater treatment system 100 decomposes the hydrogen sulfide dissolved in the liquid to be treated during the wastewater treatment process and generates hydrogen.

[0012] As shown in FIG. 1, the wastewater treatment system 100 includes a hydrogen sulfide solution generation system 10, a hydrogen generation system 20, a hydrogen utilization facility 30, and a subsequent-stage facility 40. Note that the hydrogen generation system 20, the hydrogen utilization facility 30, and the subsequent-stage facility 40 may be outside the wastewater treatment system 100. Further, the wastewater treatment system 100 may be incorporated into the water treatment facility, for example, instead of the primary sedimentation tank, or the liquid to be treated may be introduced from the water treatment facility as a separate system from the normal water treatment facility. Further, the wastewater treatment system 100 may treat organic wastewater having a higher concentration than the wastewater treated in the water treatment facility.

[0013] The hydrogen sulfide solution generation system 10 separates (filters) a separation target (hereinafter also referred to as a suspension), which is a solid matter, from a liquid to be treated containing at least sulfate ions and an organic substance (for example, acetic acid), and dissolves hydrogen sulfide in the liquid to be treated, thereby generating a hydrogen sulfide solution (a liquid to be treated in which solid-liquid separation has been performed and which is mainly composed of dissolved components). Details of the hydrogen sulfide solution generation system 10 will be described later.

[0014] The hydrogen generation system 20 generates hydrogen from the hydrogen sulfide contained in the hydrogen sulfide solution generated by the hydrogen sulfide solution generation system 10. The hydrogen generation system 20 has, for example, a reaction tank (not shown) to which the hydrogen sulfide solution is supplied, a photocatalyst (not shown) accommodated in the reaction tank, and a light irradiation device (not shown) that irradiates the photocatalyst with light. The photocatalyst promotes a reaction for generating hydrogen from hydrogen sulfide by being activated by receiving light.

[0015] In the hydrogen generation system 20, when the photocatalyst activated by the light irradiated from the light irradiation device comes into contact with the hydrogen sulfide solution, the hydrogen sulfide contained in the hydrogen sulfide solution is decomposed into hydrogen and sulfur by the photonic energy conversion of the photocatalyst. Thereby, hydrogen is generated. The hydrogen generated from the hydrogen sulfide solution is discharged to the hydrogen utilization facility 30 in a gaseous state. The remaining liquid containing sulfur (sulfur-containing liquid) is discharged to the subsequent-stage facility 40. Note that sulfur exists stably in the liquid as a sulfur cluster called S2 2- and exists stably in the liquid as a sulfur cluster called S2.

[0016] The hydrogen utilization facility 30 is a facility that utilizes the hydrogen generated by the hydrogen generation system 20. For example, the hydrogen utilization facility 30 is a facility that uses hydrogen for power generation or stores hydrogen. Note that the stored hydrogen may be sold.

[0017] The subsequent stage facility 40 is a facility that performs a predetermined treatment on the sulfur-containing liquid supplied from the hydrogen generation system 20. The subsequent stage facility 40, for example, recovers sulfur from the sulfur-containing liquid. The recovered sulfur can be used for fertilizers and the like. Thereby, sulfur resources can be utilized. Further, the subsequent stage facility 40 may be a facility that performs organic matter removal or nitrification / nitrogen removal on the treatment liquid (sulfur-containing liquid) as a predetermined treatment according to the target water quality of the effluent water from the subsequent stage facility 40.

[0018] As described above, according to the wastewater treatment system 100, the hydrogen sulfide dissolution liquid generation system 10 can separate the suspended matter contained in the wastewater and the hydrogen generation system 20 can generate hydrogen from hydrogen sulfide. Therefore, hydrogen sulfide generated in the process of wastewater treatment can be decomposed and hydrogen as an energy source can be generated.

[0019] [Hydrogen Sulfide Dissolution Liquid Generation System 10] FIG. 2 is a diagram schematically illustrating the hydrogen sulfide dissolution liquid generation system 10 according to the first embodiment. Hereinafter, the details of the hydrogen sulfide dissolution liquid generation system 10 according to the first embodiment will be described with reference to FIG. 2. The hydrogen sulfide dissolution liquid generation system 10 is, for example, a continuous process type generation system that manufactures a hydrogen sulfide dissolution liquid by continuously treating a continuously supplied liquid to be treated. However, the manufacturing form may be a batch process type.

[0020] As shown in FIG. 2, the hydrogen sulfide dissolution liquid generation system 10 includes a carrier reaction tank 1 (an example of the "treatment tank" according to the present disclosure), a pH measurement device 2, a pH adjustment device 3, an ORP measurement device 4 (an example of the "concentration measurement device" according to the present disclosure), an HRT adjustment device 5, a control device 6, an inflow channel L1, an outflow channel L2, and a circulation channel L3.

[0021] [Flow path L1~L3] The inflow channel L1 is, for example, a channel for supplying the liquid to be treated to the carrier reaction tank 1, and connects the upstream equipment (not shown) of the hydrogen sulfide dissolution solution generation system 10 to the carrier reaction tank 1. The liquid to be treated supplied to the hydrogen sulfide dissolution solution generation system 10 flows through the inflow channel L1 and into the carrier reaction tank 1.

[0022] The outflow channel L2 is, for example, a channel for discharging the hydrogen sulfide solution from the carrier reaction tank 1, and connects the carrier reaction tank 1 and the hydrogen generation system 20. The hydrogen sulfide solution flowing out from the carrier reaction tank 1 flows through the outflow channel L2 and is discharged from the hydrogen sulfide solution generation system 10.

[0023] The circulation channel L3 is, for example, a channel for circulating the liquid to be treated in the HRT adjustment process described later. The circulation channel L3 bypasses (spans) the carrier reaction tank 1 and connects the inflow channel L1 and the outflow channel L2. In Figure 2, the symbol C1 indicates the connection point (confluence point) between the inflow channel L1 and the circulation channel L3, and the symbol C2 indicates the connection point (confluence point) between the outflow channel L2 and the circulation channel L3.

[0024] Hereafter, the inflow channel L1 will be defined as the first inflow channel L11 upstream of the connection C1, and the inflow channel L12 downstream of the connection C1. Similarly, the outflow channel L2 will be defined as the first outflow channel L21 upstream of the connection C2, and the outflow channel L22 downstream of the connection C2.

[0025] [Carrier reaction vessel 1] The carrier reaction tank 1, for example, has a tank body 11 and a carrier 12, and generates a hydrogen sulfide solution by passing the liquid to be treated through it. In addition, the carrier reaction tank 1 separates (filters) the substances to be separated from the liquid to be treated during the process of passing the liquid to it.

[0026] The tank body 11 is a container into which the liquid to be treated is supplied and in which the hydrogen sulfide solution is produced. The shape of the tank body 11 is not particularly limited; for example, it may be a cylindrical shape with a circular or elliptical horizontal cross-section, or a box shape with a rectangular horizontal cross-section. The tank body 11 has, for example, an inlet 111 for the liquid to be treated to flow into the inside of the tank body 11 and an outlet 112 for the hydrogen sulfide solution to flow out of the tank body 11. An inflow channel L1 is connected to the inlet 111, and an outflow channel L2 is connected to the outlet 112. As an example, the outlet 112 is located above the inlet 111.

[0027] The carrier 12 carries, for example, sulfate-reducing bacteria that produce hydrogen sulfide from sulfate ions and organic matter contained in the liquid to be treated. The carrier 12 is placed, for example, inside the tank body 11, between the inlet 111 and the outlet 112. The sulfate-reducing bacteria carried on the carrier 12 decompose organic matter such as acetic acid by reducing sulfate ions contained in the liquid to be treated in an anaerobic environment. This reduction of sulfate ions and decomposition of organic matter produces hydrogen sulfide, water, and carbon dioxide. In addition to sulfate-reducing bacteria, the carrier 12 can also carry various other bacteria to treat organic matter contained in the liquid to be treated through biological reactions. In the carrier reaction tank 1, an anaerobic environment is maintained to promote the biological reaction by sulfate-reducing bacteria.

[0028] Furthermore, the carrier 12 also functions as a filter material (solid-liquid separation function) that separates (filters) suspended matter, which is the substance to be separated, from the liquid being treated as it passes through the carrier 12. Specifically, for example, the separation of the substance to be separated occurs on the surface of the carrier 12. Note that the carrier 12 only needs to have the function of supporting sulfate-reducing bacteria, and for example, a filter material with a solid-liquid separation function may be placed in the tank body 11 separately from the carrier 12.

[0029] The internal space of the carrier reaction vessel 1 (vessel body 11) is divided, for example, by the carrier 12 into a first region 11a connected to the inlet 111, a filtration region 11b where the carrier 12 is arranged, and a second region 11c connected to the outlet 112. In other words, the first region 11a and the second region 11c are separated by the carrier 12, with the first region 11a formed below the filtration region 11b and the second region 11c formed above the filtration region 11b.

[0030] The principle by which hydrogen sulfide solution is generated by the carrier reaction vessel 1 is explained below. Various bacteria, such as sulfate-reducing bacteria, are growing on the carrier 12 in the filtration area 11b.

[0031] First, the liquid to be treated that flows into the tank body 11 from the inlet 111 remains in the first region 11a. The liquid to be treated remaining in the first region 11a moves upward due to the upward flow, passes through the filtration region 11b, and reaches the second region 11c.

[0032] As the liquid to be treated flows through the carrier reaction tank 1, the carrier 12, positioned in the filtration region 11b, filters out suspended matter (substances to be separated) from the liquid to be treated as it passes through the filtration region 11b. Hereinafter, the liquid from which the suspended matter has been separated by the carrier 12 will also be referred to as the "filtrate." Furthermore, organic matter is decomposed and hydrogen sulfide is produced by a biological reaction carried out by sulfate-reducing bacteria supported on the carrier 12. At this time, because the suspended matter has been filtered out by the carrier 12, the biological reaction by the sulfate-reducing bacteria is accelerated.

[0033] In this way, in the carrier reaction tank 1, organic matter contained in the liquid to be treated is decomposed, and suspended solids are filtered out, reducing turbidity. At least a portion of the hydrogen sulfide produced by sulfate-reducing bacteria dissolves in the filtrate, generating a hydrogen sulfide solution. The hydrogen sulfide solution is discharged through the outlet 112 to the outflow channel L2 and supplied to the hydrogen generation system 20. As described above, the carrier reaction tank 1 can generate a hydrogen sulfide solution in conjunction with wastewater treatment by solid-liquid separation.

[0034] In this embodiment, the carrier reaction tank 1 is configured to move the liquid to be treated by an upward flow, but this disclosure is not limited thereto. The carrier reaction tank 1 may also be configured to move the liquid to be treated by a downward flow, for example.

[0035] [pH measuring device 2] The pH measuring device 2 measures, for example, the pH of the liquid to be treated. The pH measuring device 2 is installed, for example, in the second inflow channel L12 and measures the pH of the liquid to be treated that flows into the carrier reaction tank 1. The pH measuring device 2 can be any known pH meter and is not particularly limited as long as it is capable of measuring the pH of the liquid to be treated.

[0036] [pH adjustment device 3] The pH adjustment device 3 adjusts the pH of the liquid to be treated, for example, by adding a pH adjusting agent to the liquid to be treated. The pH adjustment device 3 includes, for example, a chemical tank 31 in which the pH adjusting agent is stored, and a chemical injection pump 32 that pressurizes the pH adjusting agent from the chemical tank 31 to the inflow channel L1.

[0037] The pH adjustment device 3 adds the pH adjusting agent to the liquid to be treated flowing into the carrier reaction tank 1, for example, by supplying the pH adjusting agent to the inflow channel L1 in response to the control of the control device 6. This adjusts the pH of the liquid to be treated. The pH adjusting agent is supplied, for example, upstream of the pH measuring device 2 in the inflow channel L1, more specifically between the connection part C1 in the second inflow channel L12 and the pH measuring device 2. The pH adjusting agent is not particularly limited as long as it can adjust the pH of the liquid to be treated, and for example, an alkaline agent such as sodium hydroxide can be used. In the following embodiment, an example of using an alkaline agent as the pH adjusting agent will be given.

[0038] [ORP measuring device 4] ORP measuring device 4 uses, for example, a hydrogen sulfide solution. The oxidation-reduction potential (ORP) of the solution is measured. More specifically, the ORP measuring device 4 is installed, for example, upstream of the connection point C2 in the outflow channel L2, and measures the ORP of the hydrogen sulfide solution flowing out of the carrier reaction tank 1. The ORP measuring device 4 can be any known ORP meter, and is not particularly limited as long as it can measure the ORP of the liquid being treated.

[0039] As will be explained in more detail later, there is a relationship between ORP and hydrogen sulfide concentration, and it has been confirmed that hydrogen sulfide concentration tends to increase as ORP decreases. Therefore, it is possible to estimate hydrogen sulfide concentration by measuring ORP.

[0040] ORP measuring device 4 is an example of a "concentration measuring device" according to this disclosure. The concentration measuring device is not particularly limited as long as it is capable of measuring a value related to the hydrogen sulfide concentration in a liquid. The concentration measuring device may be, for example, a concentration meter capable of measuring the hydrogen sulfide concentration in the gas. In that case, for example, a portion of the hydrogen sulfide solution that flows out of the carrier reaction vessel 1 may be branched off, and the hydrogen sulfide may be vaporized by lowering the pH by adding an acid, and the hydrogen sulfide concentration in the gas may be measured to estimate the hydrogen sulfide concentration in the hydrogen sulfide solution. Alternatively, the concentration measuring device may be, for example, a pH measuring device. In that case, for example, the hydrogen sulfide concentration in the hydrogen sulfide solution may be estimated based on the pH of the hydrogen sulfide solution that flows out of the carrier reaction vessel 1.

[0041] [HRT adjustment device 5] The HRT adjustment device 5 adjusts, for example, the hydraulic retention time (HRT) of the liquid to be treated in the carrier reaction tank 1. The HRT adjustment device 5 includes, for example, an inlet pump 51, an inlet valve 52, a circulation valve 53, and a circulation pump 54.

[0042] The inflow pump 51 is located, for example, upstream of the connection point C1 with the circulation channel L3 in the first inflow channel L11, and pumps the liquid to be treated supplied to the hydrogen sulfide dissolution solution generation system 10 to the carrier reaction tank 1.

[0043] The inlet valve 52 is located, for example, upstream of the connection point C1 with the circulation channel L3 in the first inlet channel L11 and downstream of the inlet pump 51, and is switchable between open and closed. The "open state" of the inlet valve 52 includes, for example, a state in which the valve is completely open (fully open state). The "closed state" is, for example, a state in which the valve is completely closed (fully closed state). Furthermore, the inlet valve 52 can be adjusted, for example, by adjusting the degree of opening in the open state, thereby adjusting the flow rate of the liquid to be treated flowing into the carrier reaction tank 1.

[0044] The flow rate of the liquid to be treated flowing into the carrier reaction tank 1 may be adjusted by the inflow pump 51.

[0045] The circulation valve 53 is, for example, a three-way valve installed at the connection point C2 (junction) between the outflow passage L2 and the circulation passage L3, and can switch the destination of the first outflow passage L21 to the second outflow passage L22 and the circulation passage L3. In other words, the passage to which the hydrogen sulfide solution that has flowed through the first outflow passage L21 and reached the connection point C2 is supplied can be switched between the second outflow passage L22 and the circulation passage L3 by the circulation valve 53.

[0046] The circulation pump 54 is installed, for example, near the connection point C2 between the circulation channel L3 and the outlet channel L2, and pumps the hydrogen sulfide solution that has flowed from the outlet channel L2 into the circulation channel L3 to the inflow channel L1.

[0047] The HRT adjustment device 5 can switch the flow path configuration of the hydrogen sulfide solution generation system 10 between "normal mode (discharge mode)" and "circulation mode" by, for example, switching the state of the inlet valve 52 and the circulation valve 53.

[0048] Specifically, for example, the normal mode is activated by driving the inflow pump 51, opening the inflow valve 52, connecting the first outflow channel L21 and the second outflow channel L22 with the circulation valve 53, and stopping the circulation pump 54. In normal mode, the inflow valve 52 is opened, allowing flow through the first inflow channel L11, and the liquid to be treated is supplied to the hydrogen sulfide dissolution system 10. Also in normal mode, a flow path is formed by, for example, the first inflow channel L11, the second inflow channel L12, the carrier reaction tank 1, the first outflow channel L21, and the second outflow channel L22. When the inflow pump 51 is driven, the liquid to be treated flows through the inflow channel L1 and is pressurized to the carrier reaction tank 1. The hydrogen sulfide dissolution generated in the carrier reaction tank 1 as the liquid to be treated flows flows through the outflow channel L2 and is discharged outside the hydrogen sulfide dissolution system 10 (for example, to the hydrogen generation system 20).

[0049] Furthermore, for example, by stopping the inflow pump 51, closing the inflow valve 52, connecting the first outflow channel L21 and the circulation channel L3 with the circulation valve 53, and driving the circulation pump 54, the system enters circulation mode. In circulation mode, the inflow valve 52 is closed, blocking the first inflow channel L11 and stopping the supply of the liquid to be treated to the hydrogen sulfide solution generation system 10. Also, in circulation mode, for example, a ring-shaped flow path is formed by the second inflow channel L12, the carrier reaction tank 1, the first outflow channel L21, and the circulation channel L3. The hydrogen sulfide solution generated in the carrier reaction tank 1 flows through the first outflow channel L21 and into the circulation channel L3. The hydrogen sulfide solution that has entered the circulation channel L3 is pumped to the inflow channel L1 by driving the circulation pump 54. The hydrogen sulfide solution that flows into the inflow channel L1 flows through the second inflow channel L12 and is returned to the carrier reaction tank 1 as the liquid to be treated (i.e., it flows back into the carrier reaction tank 1). In this way, in the circulation mode, the liquid to be treated circulates within the hydrogen sulfide solution generation system 10.

[0050] [Control device 6] The control device 6 operates the hydrogen sulfide solution generation system 10 by, for example, acquiring information from the pH measuring device 2 and the ORP measuring device 4, and controlling the pH adjustment device 3 and the HRT adjustment device 5.

[0051] The control device 6 controls the pH adjustment device 3 according to the pH of the liquid to be treated measured by the pH measuring device 2 (hereinafter also referred to as pH adjustment control). More specifically, the control device 6 controls the chemical injection pump 32, for example, and adds the alkaline agent stored in the chemical tank 31 to the liquid to be treated, thereby adjusting the pH of the liquid to be treated to be above a predetermined threshold.

[0052] Furthermore, the control device 6 controls the HRT adjustment device 5 (hereinafter also referred to as HRT adjustment control) according to a value related to the hydrogen sulfide concentration, in this example, according to the ORP of the hydrogen sulfide solution measured by the ORP measuring device 4. More specifically, the control device 6 controls, for example, the inflow pump 51, inflow valve 52, circulation valve 53, and circulation pump 54, and switches the flow path configuration between normal mode and circulation mode, thereby adjusting the HRT in the carrier reaction tank 1 of the treated liquid so that the ORP of the hydrogen sulfide solution is above a predetermined threshold. Alternatively, the control device 6 may adjust the HRT by, for example, controlling the inflow pump 51 or the inflow valve 52 to adjust the flow rate of the treated liquid flowing into the carrier reaction tank 1.

[0053] Figure 3 is a diagram illustrating the hardware configuration of the control device 6 according to the first embodiment. As shown in Figure 3, the control device 6 is, for example, an electronic device having an electronic circuit. More specifically, the control device 6 is a computer device having, for example, a CPU 601 which is a processor, a memory 602, a communication device 603, and a storage medium 604. Each part is connected to the others, for example, via a bus 605.

[0054] The storage medium 604 has, for example, a program storage area (not shown) for storing a program 610 for performing pH adjustment control and HRT adjustment control. The storage medium 604 also has, for example, an information storage area 620 for storing information used when performing pH adjustment control and HRT adjustment control. The storage medium 604 may be, for example, an HDD (Hard Disk Drive) or an SSD (Solid State Drive).

[0055] The CPU 601 performs control for the ozone generation process, for example, by executing a program 210 loaded into memory 602 from storage medium 604.

[0056] The communication device 603 accesses, for example, an operating terminal (not shown) where an operator inputs necessary information via a network (not shown), such as the Internet.

[0057] Furthermore, the electronic circuitry of the control device 6 may be, for example, an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit). The pH adjustment control and HRT adjustment control may also be performed, for example, by the FPGA or ASIC.

[0058] [pH adjustment control] Sulfate-reducing bacteria thrive in neutral to slightly alkaline environments. Therefore, in acidic environments with low pH, sulfate-reducing bacteria may not grow, potentially resulting in insufficient hydrogen sulfide production. Furthermore, in acidic environments, even if hydrogen sulfide is produced, it tends to volatilize (vaporize) rather than dissolve in the liquid. Since volatilized hydrogen sulfide can cause odors and deterioration of the tank, it is desirable to keep as much hydrogen sulfide dissolved in the liquid as possible. Accordingly, in order to produce and dissolve hydrogen sulfide in the liquid, it is important to maintain the pH of the liquid being treated at a relatively high level (for example, in the range of neutral to slightly alkaline).

[0059] In contrast, the hydrogen sulfide dissolution solution generation system 10 according to the first embodiment can, for example, adjust the pH of the liquid to be treated to a predetermined threshold or higher by pH adjustment control, thereby creating a suitable growth environment for sulfate-reducing bacteria supported on the carrier 12, and making it easier to generate hydrogen sulfide and dissolve it in the liquid. The pH adjustment control performed by the control device 6 in the first embodiment will be described below.

[0060] Figure 4 is a flowchart illustrating the pH adjustment control according to the first embodiment. In this embodiment, for example, pH measurement by the pH measuring device 2 and the addition of an alkaline agent by the chemical injection pump 32 are automatically performed under the control of the control device 6, but this disclosure is not limited to this. For example, pH measurement and the addition of an alkaline agent may be performed manually by an operator.

[0061] pH adjustment control is performed repeatedly, for example, while the hydrogen sulfide generation process is being carried out in the hydrogen sulfide dissolution solution generation system 10, that is, while the liquid to be treated is flowing through the carrier reaction tank 1. pH adjustment control may be performed, for example, when the flow path configuration of the hydrogen sulfide dissolution solution generation system 10 is in normal mode or when it is in circulation mode.

[0062] The control device 6 waits, for example, until it is time to perform pH adjustment control (hereinafter also referred to as pH adjustment control execution time). The pH adjustment control execution time may occur periodically, for example, at predetermined intervals.

[0063] Then, for example, when the time for pH adjustment control execution arrives, the control device 6 acquires the pH measured by the pH measuring device 2 (the pH of the liquid to be treated flowing into the carrier reaction tank 1) (step S11 in Figure 4).

[0064] Next, the control device 6 determines, for example, whether the pH obtained in step S11 is above a predetermined threshold (step S12 in Figure 4).

[0065] The pH threshold is not particularly limited, but for example, it can be set to a value that allows hydrogen sulfide to be generated and easily dissolve in the treated liquid without volatilizing.

[0066] In step S12, if the pH is above the threshold (step S12: YES), that is, above the target pH, then the process does not proceed to step S13, for example, but returns to step S11.

[0067] In step S12, if the pH is not above the threshold (step S12:NO), that is, if it is below the target pH, the control device 6 adds an alkaline agent to the liquid to be treated by controlling, for example, the pH adjustment device 3 (step S13 in Figure 4). This raises the pH of the liquid to be treated. Once step S13 is completed, the process returns to step S11. The addition of the alkaline agent is repeated until the pH is above the threshold.

[0068] As described above, the control device 6 controls the pH adjustment device 3 to adjust the pH of the liquid to be treated that flows into the carrier reaction tank 1 (the pH of the liquid to be treated before being supplied to the carrier reaction tank 1) to be above a predetermined threshold. This makes it easier to generate hydrogen sulfide and dissolve it in the liquid, and as a result, the efficiency of generating the hydrogen sulfide solution can be increased.

[0069] From the viewpoint of creating a suitable growth environment for sulfate-reducing bacteria, it is preferable to adjust the pH of the treated solution to be neutral to weakly alkaline, for example, to a pH of 6 to 9. Furthermore, from the viewpoint of making the generated hydrogen sulfide easily soluble in the solution, it is preferable to adjust the pH of the treated solution to be alkaline, for example, to a pH of 8 or higher. Based on the above, it is most preferable to adjust the pH of the treated solution to be weakly alkaline, for example, to a pH of 8 to 9. However, this disclosure is not limited to the above.

[0070] [HRT adjustment control] To obtain the target hydrogen sulfide concentration, it is necessary to ensure a HRT (Heat Recovery Time) of the treated liquid in the carrier reaction tank 1 for a predetermined period of time or longer. For example, by increasing the HRT, the biological reaction by sulfate-reducing bacteria is carried out sufficiently per unit volume of the treated liquid, and the amount of hydrogen sulfide dissolved in the liquid increases. As a result, the hydrogen sulfide concentration increases. Furthermore, a relationship exists between HRT and hydrogen sulfide concentration, and it has been confirmed that the hydrogen sulfide concentration increases linearly as the HRT increases.

[0071] In contrast, the hydrogen sulfide dissolution solution generation system 10 according to the first embodiment can increase the hydrogen sulfide concentration of the hydrogen sulfide dissolution solution by adjusting the HRT of the liquid to be treated in the carrier reaction tank 1, for example, through HRT adjustment control. The HRT adjustment control performed by the control device 6 in the first embodiment will be described below.

[0072] Figure 5 is a flowchart illustrating HRT adjustment control by circulating operation according to the first embodiment. In this embodiment, for example, ORP measurement by the ORP measuring device 4 and HRT adjustment by the HRT adjustment device 5 are automatically performed by the control device 6, but this disclosure is not limited to this. For example, ORP measurement and HRT adjustment may be performed by manual operation by an operator.

[0073] HRT adjustment control is performed repeatedly, for example, while the hydrogen sulfide generation process is being carried out in the hydrogen sulfide dissolution solution generation system 10, that is, while the liquid to be treated is flowing through the carrier reaction tank 1. HRT adjustment control may be performed in parallel with the pH adjustment control described above, or at different timings. Furthermore, the following example illustrates the case in which HRT adjustment control is started when the hydrogen sulfide dissolution solution generation system 10 is operating in a normal mode flow path configuration (hereinafter also referred to as normal operation), but HRT adjustment control may also be started when the hydrogen sulfide dissolution solution generation system 10 is operating in a circulation mode flow path configuration (hereinafter also referred to as circulation operation). In that case, HRT adjustment control starts, for example, from step S24 in Figure 5.

[0074] The control device 6 waits, for example, until it is time to perform HRT adjustment control (hereinafter also referred to as HRT adjustment control execution time). HRT adjustment control execution time may occur periodically, for example, at predetermined intervals.

[0075] Then, for example, when the HRT adjustment control execution time is reached during normal operation, the control device 6 acquires the ORP measured by the ORP measuring device 4 (ORP of the hydrogen sulfide solution discharged from the carrier reaction vessel 1) (step S21 in Figure 5).

[0076] Next, the control device 6 determines, for example, whether the ORP obtained in step S21 is below a predetermined threshold (step S22 in Figure 5).

[0077] The ORP threshold is not particularly limited, but can be set based on the target hydrogen sulfide concentration. For example, the ORP threshold may be set so that the hydrogen sulfide concentration is 30 mg / L or higher.

[0078] In step S22, if the ORP is below the threshold (step S22: YES), that is, if the estimated hydrogen sulfide concentration is above the target value, the process does not proceed to step S23, for example, but returns to step S21.

[0079] In step S22, if the ORP is not below the threshold (step S22:NO), that is, if the estimated hydrogen sulfide concentration falls below the target value, the control device 6 switches the hydrogen sulfide solution generation system 10 to circulation operation by, for example, controlling the HRT adjustment device 5 (step S23 in Figure 5). Specifically, in step S23, for example, the flow path configuration is switched to circulation mode by the HRT adjustment device 5. As a result, the supply of new liquid to be treated to the carrier reaction tank 1 is stopped, while the hydrogen sulfide solution generated in the carrier reaction tank 1 flows through the circulation flow path L3 and is returned to the carrier reaction tank 1 as the liquid to be treated. As the liquid to be treated is repeatedly returned to the carrier reaction tank 1 by the circulation operation, the HRT of the liquid to be treated in the carrier reaction tank 1 increases. As a result, the hydrogen sulfide concentration of the liquid to be treated (hydrogen sulfide solution) increases. Also, as the hydrogen sulfide concentration increases, the ORP decreases. During circulating operation, the supply of the liquid to be treated into the hydrogen sulfide dissolution solution generation system 10 and the discharge of the hydrogen sulfide dissolution solution outside the hydrogen sulfide dissolution solution generation system 10 are stopped.

[0080] Next, the control device 6 acquires the ORP measured by the ORP measuring device 4 when, for example, the HRT adjustment control execution time is reached during cyclic operation (step S24 in Figure 5).

[0081] Next, the control device 6 determines, for example, whether the ORP obtained in step S24 is below a predetermined threshold (step S25 in Figure 5).

[0082] In step S25, if the ORP is not below the threshold (step S25:NO), that is, if the estimated hydrogen sulfide concentration has not yet reached the target value, the process does not proceed to step S26, for example, but returns to step S24. In other words, the circulating operation continues until the ORP falls below the threshold and the estimated hydrogen sulfide concentration reaches the target value.

[0083] In step S25, if the ORP is below the threshold (step S25: YES), that is, if the estimated hydrogen sulfide concentration reaches the target value, the control device 6 switches the hydrogen sulfide dissolution solution generation system 10 to normal operation by, for example, controlling the HRT adjustment device 5 (step S26 in Figure 5). Specifically, in step S26, for example, the flow path configuration is switched to normal mode by the HRT adjustment device 5. As a result, the supply of a new liquid to be treated from outside the hydrogen sulfide dissolution solution generation system 10 to the carrier reaction tank 1 begins, and the hydrogen sulfide dissolution solution generated in the carrier reaction tank 1 is discharged outside the hydrogen sulfide dissolution solution generation system 10 without refluxing to the carrier reaction tank 1 (for example, supplied to the hydrogen generation system 20). Once step S26 is completed, the process returns to step S21.

[0084] As described above, the control device 6 controls the HRT adjustment device 5 to adjust the HRT of the liquid to be treated in the carrier reaction tank 1 so that the ORP of the hydrogen sulfide solution is below a predetermined threshold. This makes it possible to increase the hydrogen sulfide concentration of the hydrogen sulfide solution.

[0085] The ORP threshold is not particularly limited, but it is preferable to adjust the HRT so that, for example, the measured value when measuring ORP using an ORP electrode on a portable pH meter LAQUAact D-72 (manufactured by HORIBA) is -300 [mV] or less, more preferably -350 [mV] or less.

[0086] [Modified example of HRT adjustment control] The control device 6 may adjust the HRT, for example, by adjusting the flow rate of the liquid to be treated flowing through the carrier reaction tank 1. The following describes HRT adjustment control by flow rate adjustment.

[0087] Figure 6 is a flowchart illustrating HRT adjustment control by flow rate adjustment according to the first embodiment. HRT adjustment control by flow rate adjustment is performed, for example, during normal operation.

[0088] For example, when the HRT adjustment control execution time is reached, the control device 6 acquires the ORP measured by the ORP measuring device 4 (ORP of the hydrogen sulfide solution discharged from the carrier reaction vessel 1) (step S31 in Figure 6).

[0089] Next, the control device 6 determines, for example, whether the ORP obtained in step S31 is below a predetermined threshold (step S32 in Figure 6).

[0090] In step S32, if ORP is below the threshold (step S32: YES), the process does not proceed to step S33, for example, but returns to step S31.

[0091] In step S32, if the ORP is not below the threshold (step S22: NO), the control device 6 reduces the flow rate of the liquid to be treated into the carrier reaction tank 1 by, for example, controlling the HRT adjustment device 5 (step S33 in Figure 6). This increases the HRT of the liquid to be treated in the carrier reaction tank 1. As a result, the hydrogen sulfide concentration in the liquid to be treated (hydrogen sulfide solution) increases. In addition, the ORP decreases as the hydrogen sulfide concentration increases. Once step S33 is completed, the process returns to step S31. The reduction in flow rate is repeated until the ORP falls below the threshold.

[0092] Since HRT adjustment control by flow rate adjustment can basically be achieved by controlling the inlet pump 51 or the inlet valve 52, the flow path design can be simplified and power consumption can be reduced.

[0093] Furthermore, HRT adjustment control by circulating operation and HRT adjustment control by flow rate adjustment may be performed simultaneously. For example, while performing the circulating operation described above, the flow rate of the liquid to be treated may be reduced by controlling the circulation valve 53 or the circulation pump 54.

[0094] Furthermore, the control device 6 may adjust the HRT by switching the generation of the hydrogen sulfide solution to a kind of batch process. Specifically, for example, the HRT may be extended by stopping the inflow and outflow of the liquid to be treated to the carrier reaction vessel 1 by controlling a valve or pump.

[0095] [Effects / Effects] As described above, the hydrogen sulfide solution generation system 10 according to this embodiment includes a carrier reaction tank 1 on which a carrier 12 supporting sulfate-reducing bacteria is arranged. The carrier reaction tank 1 separates the target substance from the liquid to be treated, which contains at least sulfate ions and organic matter, and generates hydrogen sulfide from the sulfate ions and organic matter using sulfate-reducing bacteria, thereby producing a hydrogen sulfide solution in which hydrogen sulfide is dissolved. The hydrogen sulfide solution generation system 10 also includes a pH adjustment device 3 for adjusting the pH of the liquid to be treated, and a control device 6 for controlling the pH adjustment device 3 according to the pH of the liquid to be treated.

[0096] According to the hydrogen sulfide dissolution solution generation system 10 configured as described above, hydrogen sulfide can be generated and easily dissolved in the liquid by adjusting the pH of the liquid to be treated. As a result, the efficiency of hydrogen sulfide dissolution solution generation can be increased. In other words, hydrogen sulfide in a dissolved state in the liquid can be obtained efficiently.

[0097] Furthermore, the hydrogen sulfide dissolution solution generation system 10 is further equipped with an HRT adjustment device 5 that adjusts the HRT in the carrier reaction tank 1 of the liquid to be treated, and the control device 6 controls the HRT adjustment device 5 according to ORP, which is a value related to the hydrogen sulfide concentration. As a result, the hydrogen sulfide concentration of the hydrogen sulfide dissolution solution can be increased by adjusting the HRT of the liquid to be treated.

[0098] Furthermore, the carrier reaction tank 1, for example, generates a hydrogen sulfide solution by passing the liquid to be treated through it. The HRT adjustment device 5 can either recirculate the hydrogen sulfide solution generated by the carrier reaction tank 1 back to the carrier reaction tank 1 as the liquid to be treated, or adjust the flow rate of the liquid to be treated flowing through the carrier reaction tank 1. This allows for adjustment of the HRT of the liquid to be treated in the treatment tank.

[0099] Furthermore, by controlling the pH, hydrogen sulfide is less likely to volatilize into the air. For example, if the hydrogen sulfide dissolution solution generation system 10 is applied to the primary sedimentation tank, corrosion of the primary sedimentation tank structure can be prevented. The alkaline agent added for pH adjustment can be used, for example, for nitrification in a subsequent reaction tank.

[0100] <Second Embodiment> Figure 7 is a schematic diagram illustrating the hydrogen sulfide dissolution solution generation system 10A according to the second embodiment. The details of the hydrogen sulfide dissolution solution generation system 10A according to the second embodiment will be described below with reference to Figure 7. Note that components similar to those in the first embodiment are denoted by the same reference numerals, and detailed explanations are omitted.

[0101] As shown in Figure 7, the hydrogen sulfide dissolution solution generation system 10A differs from the hydrogen sulfide dissolution solution generation system 10 shown in Figure 2 in that it further includes a temperature measuring device 7 and a temperature control device 8.

[0102] The temperature measuring device 7 is provided, for example, downstream of the connection point C1 with the circulation channel L3 in the second inflow channel L12, and measures the temperature of the liquid to be treated flowing into the carrier reaction tank 1. The temperature measuring device 7 can be any known thermometer, and is not particularly limited as long as it can measure the temperature of the liquid to be treated. The temperature measuring device 7 may also be provided, for example, in the carrier reaction tank 1, and may measure the temperature of the liquid to be treated inside the carrier reaction tank 1. Furthermore, the temperature measuring device 7 may be configured integrally with, for example, the pH measuring device 2. For example, the hydrogen sulfide dissolution solution generation system 10A may be equipped with a pH meter with a temperature measuring function as both the pH measuring device 2 and the temperature measuring device 7. This reduces the workload for maintenance and management.

[0103] The temperature control device 8 is installed, for example, in the circulation channel L3 and adjusts the temperature of the liquid to be treated (the liquid to be treated before it is supplied to the carrier reaction tank 1) that flows into the carrier reaction tank 1. The temperature control device 8 is not particularly limited, but for example, it is a heat exchanger that heats the liquid to be treated with a fluid (e.g., hot water) supplied from an external heat source (not shown).

[0104] Furthermore, when a heat exchanger is used as the temperature control device 8, the heat source for heating the fluid supplied to the heat exchanger may be, for example, a heat exchanger that heats the fluid using waste heat from exhaust gas generated in an incinerator (not shown) that incinerates digested sludge discharged from a digester tank (not shown) of a sewage treatment facility. Alternatively, the heat source may be, for example, a heat exchanger that heats the fluid using waste heat generated by power generation using digester gas discharged from a digester tank. Alternatively, the heat source may be, for example, a water heater that heats the fluid using digester gas discharged from a digester tank.

[0105] The control device 6 controls the temperature adjustment device 8 according to the temperature of the liquid being processed measured by the temperature measuring device 7 (hereinafter also referred to as temperature adjustment control).

[0106] [Temperature control] To promote the growth of sulfate-reducing bacteria, it is preferable to maintain the growth environment (specifically, the water temperature) above a predetermined temperature. The hydrogen sulfide dissolution solution generation system 10A according to the second embodiment can suitably promote the growth of sulfate-reducing bacteria by adjusting the temperature of the liquid to be treated, for example, through temperature control. The temperature control performed by the control device 6 in the second embodiment will be described below.

[0107] Figure 8 is a flowchart illustrating temperature control by circulation operation according to the second embodiment. Temperature control is repeatedly performed, for example, while the hydrogen sulfide generation process is being carried out in the hydrogen sulfide dissolution solution generation system 10A, that is, while the liquid to be treated is flowing through the carrier reaction tank 1. Temperature control may be performed in parallel with, for example, the pH adjustment control or HRT adjustment control described above, or at different timings. Furthermore, as an example, the case in which temperature control is performed during circulation operation is illustrated below, but temperature control may also be performed during normal operation. In that case, the temperature control device 8 may be provided, for example, in the inflow channel L1.

[0108] The control device 6 waits, for example, until it is time to perform temperature control (hereinafter also referred to as temperature control execution time). The temperature control execution time may occur periodically, for example, at predetermined intervals.

[0109] Then, for example, when it is time to execute temperature control, the control device 6 acquires the temperature of the liquid to be treated (the temperature of the liquid to be treated before it is supplied to the carrier reaction tank 1) measured by the temperature measuring device 7 (step S41 in Figure 8).

[0110] Next, the control device 6 determines, for example, whether the temperature obtained in step S41 is above a predetermined threshold (step S42 in Figure 8).

[0111] In step S42, if the temperature is above the threshold (step S42: YES), the process does not proceed to step S43, for example, but returns to step S41.

[0112] In step S42, if the temperature is not above the threshold (step S22: NO), the control device 6 heats the liquid to be treated flowing into the carrier reaction vessel 1, for example, using the temperature control device 8 (step S43 in Figure 8). This raises the temperature of the liquid to be treated flowing into the carrier reaction vessel 1. Once step S43 is completed, the process returns to step S41. Heating of the liquid to be treated is repeated until the temperature reaches or exceeds the threshold.

[0113] As described above, the control device 6 controls the temperature control device 8 to adjust the temperature of the liquid to be treated flowing into the carrier reaction tank 1 to be above a predetermined threshold. This promotes the growth of sulfate-reducing bacteria.

[0114] Furthermore, the control device 6 may, for example, control the inflow pump 51 or the inflow valve 52 to reduce the flow rate of the newly supplied liquid to be treated, thereby suppressing the temperature drop of the liquid to be treated that has been heated by the temperature control device 8.

[0115] [Relationship between ORP and hydrogen sulfide concentration] The relationship between ORP and hydrogen sulfide concentration was confirmed through tests using a filtration system (ORP-hydrogen sulfide concentration confirmation test). In the ORP-hydrogen sulfide concentration confirmation test, two small filtration systems were prepared. The filtration system consisted of a carrier on which sulfate-reducing bacteria were placed inside the tank, and the liquid to be treated was circulated by an upward flow. Hereafter, the two filtration systems will be referred to as filtration system A and filtration system B, respectively. The liquid to be treated was wastewater obtained from the inflow aeration channel of a sewage treatment plant and stored in a raw water tank.

[0116] In Experimental System 1, the liquid to be treated was introduced from the raw water tank at a flow rate of 5.5 [L / min] into filtration device A, and the ORP and hydrogen sulfide concentration of the filtered liquid to be treated (hereinafter referred to as filtrate A1) were measured.

[0117] In Experimental System 2, the above-mentioned filtrate A1 was further introduced into a water-spraying carrier filter bed at a flow rate of 2 [L / min], and the flow rate of the treated liquid was reduced to 0.5 to 1.5 [L / min], and it was combined with the liquid to be treated supplied from the raw water tank at a flow rate of 5.5 [L / min]. The combined liquid to be treated was introduced into filtration device B, and the ORP and hydrogen sulfide concentration of the filtered liquid to be treated (hereinafter referred to as filtrate B1) were measured.

[0118] The ORP and hydrogen sulfide concentrations of filtrates A1 and B1 were measured multiple times at intervals of several days. For ORP measurement, a portable pH meter LAQUAact D-72 (manufactured by HORIBA) was used as the measuring device. For hydrogen sulfide concentration measurement, the collected filtrate was shaken multiple times to release hydrogen sulfide into the air, which was then measured using a detector tube. Based on these measurements, the hydrogen sulfide concentration in the liquid was calculated. The measurement results were plotted on a graph showing the hydrogen sulfide concentration against ORP for each measurement.

[0119] Figure 9 is a graph showing the relationship between ORP and hydrogen sulfide concentration in the ORP-hydrogen sulfide concentration confirmation test. As shown in Figure 9, it was possible to confirm that the hydrogen sulfide concentration tends to increase as the ORP decreases.

[0120] [Relationship between HRT and hydrogen sulfide concentration] The relationship between HRT and hydrogen sulfide concentration was confirmed through tests using a filtration system (HRT-hydrogen sulfide concentration confirmation test). In the HRT confirmation test, one filtration system similar to that used in the ORP-hydrogen sulfide concentration test was prepared. The treated liquid was wastewater, as in the ORP-hydrogen sulfide concentration test.

[0121] In the test, the liquid to be treated was introduced from the raw water tank into the filtration device, and the ORP and hydrogen sulfide concentration of the filtered liquid (filtrate) were measured. By gradually changing the flow rate of the liquid to be treated into the filtration device, the HRT in the carrier (filter media) was varied in stages from 1.9 [min] to 18.8 [min]. The measurement of ORP and hydrogen sulfide concentration was carried out in the same manner as in the ORP-hydrogen sulfide concentration test.

[0122] The flow rates of the liquid to be treated were 1 [L / min], 2 [L / min], 5.5 [L / min], 7 [L / min], and 10 [L / min], and the HRT for each flow rate was calculated using the following formula (1). HRT[min]=V[L]÷F[L / min]...Equation (1) Here, in equation (1), V [L] represents the volume of water in the region filled with the carrier (filter material) in the filtration device, and F [L / min] represents the flow rate. The measurement results were plotted on a graph showing the hydrogen sulfide concentration relative to HRT.

[0123] Figure 10 is a graph showing the relationship between HRT and hydrogen sulfide concentration in the HRT-hydrogen sulfide concentration test. As shown in Figure 10, it was possible to confirm that the hydrogen sulfide concentration tends to increase as the HRT lengthens.

[0124] (Note) This disclosure includes the following aspects: [Aspect 1] A treatment tank comprising a carrier for supporting sulfate-reducing bacteria, wherein the treatment tank separates a target substance from a liquid to be treated containing at least sulfate ions and organic matter, and generates hydrogen sulfide from the sulfate ions and organic matter by the sulfate-reducing bacteria, thereby producing a hydrogen sulfide solution containing dissolved hydrogen sulfide, A pH adjustment device for adjusting the pH of the liquid to be treated, The system includes a control device that controls the pH adjustment device according to the pH of the liquid to be treated, Hydrogen sulfide dissolution solution generation system. [Aspect 2] The system further includes an HRT adjustment device for adjusting the hydraulic residence time of the liquid to be treated in the treatment tank, The control device controls the HRT adjustment device according to a value relating to the hydrogen sulfide concentration of the hydrogen sulfide solution. A hydrogen sulfide dissolving solution generation system according to Embodiment 1. [Aspect 3] The treatment tank generates the hydrogen sulfide solution by circulating the liquid to be treated through the treatment tank. The HRT adjustment device adjusts the hydraulic residence time of the treated liquid in the treatment tank by returning the hydrogen sulfide solution generated by the treatment tank to the treatment tank as the treated liquid. A hydrogen sulfide dissolving solution generation system according to embodiment 2. [Aspect 4] The treatment tank generates the hydrogen sulfide solution by circulating the liquid to be treated through the treatment tank. The HRT adjustment device adjusts the hydrological residence time of the liquid to be treated in the treatment tank by adjusting the flow rate of the liquid to be treated flowing through the treatment tank. A hydrogen sulfide dissolving solution generation system according to embodiment 2. [Aspect 5] The device further includes a temperature control device for adjusting the temperature of the liquid to be treated, The control device controls the temperature adjustment device according to the temperature of the liquid to be processed. A hydrogen sulfide dissolving solution generation system according to any one of embodiments 1 to 4.

[0125] The technology relating to this disclosure may also be a method for producing a hydrogen sulfide solution that includes at least one of the above-described pH adjustment control, HRT adjustment control, and temperature adjustment control. [Explanation of Symbols]

[0126] 1: Carrier reactor 2:pH measuring device 3:pH adjustment device 4: Concentration measuring device 5:HRT adjustment device 6: Control device 7:Temperature measuring device 8: Temperature adjustment device 10: Hydrogen sulfide dissolving solution production system 100: Wastewater treatment system

Claims

1. A treatment tank comprising a carrier for supporting sulfate-reducing bacteria, wherein the treatment tank separates a target substance from a liquid to be treated containing at least sulfate ions and organic matter, and generates hydrogen sulfide from the sulfate ions and organic matter by the sulfate-reducing bacteria, thereby producing a hydrogen sulfide solution containing dissolved hydrogen sulfide, A pH adjustment device for adjusting the pH of the liquid to be treated, The system includes a control device that controls the pH adjustment device according to the pH of the liquid to be treated, Hydrogen sulfide solution generation system.

2. The system further includes an HRT adjustment device for adjusting the hydraulic residence time of the liquid to be treated in the treatment tank, The control device controls the HRT adjustment device according to a value relating to the hydrogen sulfide concentration of the hydrogen sulfide solution. A hydrogen sulfide dissolution solution generation system according to claim 1.

3. The treatment tank generates the hydrogen sulfide solution by circulating the liquid to be treated through the treatment tank. The HRT adjustment device adjusts the hydraulic residence time of the liquid to be treated in the treatment tank by returning the hydrogen sulfide solution generated by the treatment tank to the treatment tank as the liquid to be treated. A hydrogen sulfide dissolution solution generation system according to claim 2.

4. The treatment tank generates the hydrogen sulfide solution by circulating the liquid to be treated through the treatment tank. The HRT adjustment device adjusts the hydrological residence time of the liquid to be treated in the treatment tank by adjusting the flow rate of the liquid to be treated flowing through the treatment tank. A hydrogen sulfide dissolution solution generation system according to claim 2.

5. The device further includes a temperature control device for adjusting the temperature of the liquid to be treated, The control device controls the temperature adjustment device according to the temperature of the liquid to be processed. A hydrogen sulfide dissolution solution generation system according to claim 1.

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