Wastewater treatment device and wastewater treatment method

Abstract

To provide a waste water treatment apparatus which can efficiently remove and use a suspension property organic material that is separated by a filtration treatment.SOLUTION: A waste water treatment unit 30 includes treatment tanks 1a-1e, and the treatment tanks 1a-1e are filled with filtration materials 11a-11e and have air diffusers 7a-7e. The treatment tanks 1a-1e sequentially execute a filtration treatment and a methane fermentation treatment. The filtration treatment and the methane fermentation treatment are executed on the filter material that carries methanogen. Suspensible organic materials accumulated on the filtration material by the filtration treatment are decomposed by the methanogen by the methane fermentation treatment and are recovered as digestion gas. The treatment tanks 1a-1e are connected to a waste water inflow pipe 4, a filtration water outflow pipe 5, a digestion gas inflow pipe 6, a digestion gas outflow pipe 8, and a steam introduction pipe 9. The filtration treatment and the methane fermentation treatment are switched by opening / closing valves of these pipes. When the filtration treatment is executed in one of the treatment tanks 1a-1e, the methane fermentation treatment is executed in the other treatment tanks.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a wastewater treatment device and a wastewater treatment method. [Background technology]

[0002] Conventionally, when treating wastewater such as sewage containing impurities, organic matter, and water, water treatment involves removing bulky waste and large foreign matter from the wastewater using a screening system or the like, and then decomposing and removing the organic matter in the wastewater using activated sludge or the like. While the screening system can remove bulky waste and large foreign matter from the wastewater, the treated water still contains relatively large impurities such as hair and scum, as well as suspended organic matter. This places a heavy load on downstream water treatment equipment, causing problems such as scum accumulation in the water treatment equipment and clogging of measuring instruments.

[0003] Furthermore, in response to the recent aging society, it is expected that garbage disposals will become more widespread in the future. As garbage disposals become more widespread, food residues of sizes that cannot be removed with conventional screening equipment will increase in wastewater. In addition, it is expected that small-scale sewerage systems will be consolidated and abolished in the future due to the declining population, and the amount of wastewater treatment will increase. There are concerns that the increase in food residues in wastewater and the increase in the amount of treated water will further increase the load on water treatment equipment.

[0004] In response to this, a filtration device is known that separates suspended organic matter from wastewater using a filter medium such as a porous material (see, for example, Patent Document 1). The filter medium is packed into the filter device, and the packed filter medium forms a filtration layer. When wastewater supplied to the filter device passes through the filtration layer, the water contained in the wastewater permeates the filter medium, but the suspended organic matter is captured by the filter medium because it is larger than the pore size of the filter medium. This separates the suspended organic matter from the water in the wastewater. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-10888 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the case of a filtration device that separates suspended organic matter from wastewater using a filter medium, as the filtration process continues, suspended organic matter accumulates in the filter medium, reducing the filtration efficiency. Therefore, in order to remove the suspended organic matter accumulated in the filter layer, it is necessary to perform a complicated process such as chemical cleaning. Therefore, there is a problem that the suspended organic matter separated by the filtration process cannot be efficiently removed and utilized.

[0007] An object of the present invention is to provide a wastewater treatment device and a wastewater treatment method that can efficiently remove and utilize suspended organic matter separated by filtration. [Means for solving the problem]

[0008] In order to achieve the above object, the wastewater treatment device of the present invention is a wastewater treatment device that performs a filtration process in which wastewater containing suspended organic matter and water is filtered to separate the suspended organic matter from the water, and a decomposition process in which the suspended organic matter separated by the filtration process is anaerobically decomposed, and the separation of the suspended organic matter from the water is performed by a decomposition process. filter media And, filter media a decomposition means for anaerobic decomposition of the suspended organic matter separated by the The filter medium is a hollow cylindrical porous body having a specific gravity of 0.95 to 1.05 or a nonwoven fabric having a specific gravity of 0.95 to 1.05. It is characterized by:

[0009] In order to achieve the above object, the wastewater treatment unit of the present invention is a wastewater treatment unit that performs a filtration process of filtering wastewater containing suspended organic matter and water to separate the suspended organic matter from the water, and a decomposition process of anaerobically decomposing the suspended organic matter separated by the filtration process, and the unit that separates the suspended organic matter from the water is filter media And, filter mediaThe present invention is characterized in that it comprises a plurality of wastewater treatment devices each having a decomposition means for anaerobically decomposing suspended organic matter separated by a filtration process, and a switching means for switching between the filtration process and the decomposition process to be performed in the plurality of wastewater treatment devices.

[0010] In order to achieve the above object, the present invention provides a wastewater treatment method that performs a filtration process for filtering wastewater containing suspended organic matter and water to separate the suspended organic matter from the water, and a decomposition process for anaerobically decomposing the suspended organic matter separated by the filtration process, wherein the separation of the suspended organic matter from the water is performed using a decomposition apparatus. filter media And, filter media and a decomposition means for anaerobically decomposing suspended organic matter separated by a filtration step of filtering the wastewater to separate suspended organic matter from water, a decomposition step of anaerobically decomposing the separated suspended organic matter, and a switching step of switching between the filtration process and the decomposition process.

[0011] In order to achieve the above object, the wastewater treatment method of the present invention is a wastewater treatment unit that performs a filtration process of filtering wastewater containing suspended organic matter and water to separate the suspended organic matter from the water, and a decomposition process of anaerobically decomposing the suspended organic matter separated by the filtration process, wherein the separation of the suspended organic matter from the water is performed by a decomposition unit. filter media And, filter media a decomposition means for anaerobically decomposing suspended organic matter separated by a filtration process; and a switching means for switching between filtration and decomposition processes to be performed in the plurality of wastewater treatment devices. The method for wastewater treatment using a wastewater treatment unit is characterized by comprising: a filtration and decomposition step in which filtration is performed in one of the plurality of wastewater treatment devices and decomposition processes are performed in another of the plurality of wastewater treatment devices; and a switching step in which the switching means switches one device that has performed the filtration process from filtration to decomposition, and switches another device from decomposition to filtration. [Effects of the Invention]

[0012] According to the present invention, suspended organic matter separated by filtration can be efficiently removed and utilized. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a diagram schematically illustrating a wastewater treatment device according to an embodiment of the present invention. [Figure 2] 2 is a flowchart showing the procedure of wastewater treatment carried out by the wastewater treatment device of FIG. [Figure 3] FIG. 2 is a diagram schematically showing a wastewater treatment unit provided with a plurality of the wastewater treatment devices of FIG. [Figure 4] 4 is a flowchart showing the procedure of wastewater treatment carried out by the wastewater treatment unit of FIG. 3. [Figure 5] FIG. 4 is a diagram showing a large-scale sewage treatment flow using the wastewater treatment unit of FIG. 3. [Figure 6] FIG. 4 is a diagram showing a small-scale sewage treatment flow using the wastewater treatment unit of FIG. 3. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0015] FIG. 1 is a diagram schematically illustrating a wastewater treatment device 10 according to an embodiment of the present invention.

[0016] (Wastewater treatment device 10) The wastewater treatment device 10 in FIG. 1 includes a filtration and methane fermentation treatment tank 1 (hereinafter referred to as "treatment tank 1"), a gas holder 2, a heating device 3, a blower B, and a pump P. The treatment tank 1 is filled with a filter medium 11 (separation means) and has an aeration device 7 (agitation device). A wastewater storage tank (not shown) stores wastewater after treatment in a primary sedimentation tank or screen. The treatment tank 1 is connected to a wastewater inlet pipe 4, which has a pump P and valves V1, V2, and V3. The flow of wastewater from the wastewater storage tank (not shown) into the treatment tank 1 is controlled by opening and closing valves V1 and V3 while keeping valve V2 closed. The treatment tank 1 is also connected to a filtrate outlet pipe 5, which has a valve V5. The flow of filtered water out of the treatment tank 1 is controlled by opening and closing valve V5 of the filtrate outlet pipe 5.

[0017] The gas holder 2 stores digester gas, which is primarily composed of methane, and the treatment tank 1 and gas holder 2 are connected via a digester gas inlet pipe 6 and a digester gas outlet pipe 8. The digester gas inlet pipe 6 has a blower B and a valve V6, and the digester gas supplied from the gas holder 2 to the treatment tank 1 is controlled by opening and closing the valve V6. The digester gas supplied to the treatment tank 1 is diffused into the treatment tank 1 by an aeration device 7 (agitation device). The digester gas outlet pipe 8 has a valve V8, and the digester gas flowing out of the treatment tank 1 is controlled by opening and closing the valve V8.

[0018] The treatment tank 1 and the heating equipment 3 are connected via a steam inlet pipe 9, and digested sludge is supplied to the treatment tank 1 through a digested sludge supply pipe 12. Digested sludge is the sludge that remains after the organic matter in the sludge is broken down (hereinafter also referred to as digestion) by the action of methanogens, generating digester gas containing methane gas and carbon dioxide, and contains methanogens that carry out methane fermentation.

[0019] (Treatment tank 1) The treatment tank 1 is a rectangular, corrosion-resistant tank with external insulation, in which filtration and methane fermentation are carried out sequentially. The filter media 11 packed inside the treatment tank 1 also serves as a carrier for the microorganisms (decomposition means) used in the methane fermentation process, which will be described later. Two perforated plates (supports) made of punched metal or the like with holes slightly smaller than the outer diameter of the filter media 11 are installed inside the treatment tank 1, and the filter media 11 is packed into the area between these two perforated plates to form a filtration layer.

[0020] The filter medium 11 is made of a porous material or nonwoven fabric. As the porous material, for example, a hollow cylindrical foam made of foamed polypropylene, having an uneven surface and a large number of pores inside, can be used. The outer diameter and length of the hollow cylindrical foam are 5 mm to 20 mm, and the specific surface area is 500 to 1500 m. 2 / m 3 As the nonwoven fabric, for example, a ball-shaped nonwoven fabric having many voids extending to the interior and a large amount of SS (suspended solids) can be used. The outer diameter of the filter material is usually 5 to 30 mm, preferably 10 to 20 mm, and the pore size of the foam filter material and the gaps in the nonwoven fabric are usually 10 μm to 1 mm. By using such a filter material, the amount of SS retained can be increased and microorganisms can be easily retained. Furthermore, by using a filter material with a specific gravity of 0.95 to 1.05, appropriate shaking or moving mixing, as described below, can be achieved without uneven distribution within the treatment tank 1. To enable shaking or moving mixing, as described below, the filter material is preferably packed in the region between the two perforated plates so that 10 to 30 volume % of the volume of the filter material is left empty above. Note that a portion of the perforated plate installed above the filter material may be substituted with a water collection nozzle with a shape that is less likely to clog.

[0021] Filtration is performed by bringing wastewater containing suspended organic matter and moisture that has flowed into treatment tank 1 into contact with filter media 11. When the wastewater passes through the filtration layer, the moisture contained in the wastewater permeates filter media 11, but the suspended organic matter is captured by filter media 11, specifically on the surface and inside of filter media 11. Therefore, suspended organic matter accumulates in filter media 11 as the filtration process continues.

[0022] Methane fermentation is a process that uses a reaction (hereinafter also referred to as "digestion") in which microorganisms (anaerobic bacteria) decompose organic matter to produce digestive gas and digestive fluid, which are mainly composed of methane. Specifically, the anaerobic bacteria first hydrolyze the organic matter to produce soluble amino acids, etc. The produced amino acids, etc. are then taken into the cells of the anaerobic bacteria and metabolically decomposed to produce acetic acid, hydrogen, carbon dioxide, etc. After that, methane is produced as biogas from the acetic acid, hydrogen, and carbon dioxide.

[0023] In this embodiment, microorganisms (decomposition means) are supported on the filter medium 11 (separation means), and suspended organic matter captured by the filter medium 11 during filtration is brought into contact with the microorganisms on the filter medium, thereby enabling efficient methane fermentation treatment. The microorganisms are anaerobic bacteria, primarily methane bacteria, and are contained in the digested sludge supplied to the treatment tank 1 from the digested sludge supply pipe 12. In order to support the microorganisms on the filter medium, it is sufficient to mix the digested sludge supplied to the treatment tank 1 with the filter medium 11. By mixing the digested sludge with the filter medium 11, the microorganisms quickly penetrate into the interior of the filter medium 11 and are supported on the filter medium 11. The microorganisms supported on the filter medium 11 are not destroyed by the general agitation performed inside the treatment tank 1, and the state of being supported on the filter medium 11 is maintained.

[0024] The aeration device 7 (agitation device) diffuses the digester gas supplied from the gas holder 2 into the treatment tank 1 as coarse bubbles. The coarse bubbles diffused by the aeration device 7 rise throughout the entire interior of the treatment tank 1, agitating the interior of the treatment tank 1 and shaking or moving and mixing the filter media 11. This agitation by the digester gas promotes contact between the suspended organic matter captured by the filter media 11 and microorganisms during methane fermentation, thereby accelerating methane fermentation. Uniform agitation within the treatment tank 1 also prevents the formation of scum within the treatment tank 1 and the separation of the sludge and liquid layers. Furthermore, it accelerates the heat transfer of the wastewater within the treatment tank 1 during methane fermentation, thereby enabling uniform temperature control within the treatment tank 1. Agitation can be performed continuously or intermittently, for example, once every 1 to 3 hours for 10 to 30 minutes. Methods of stirring the inside of the treatment tank 1 include gas stirring by diffusing digester gas from the aeration device 7, mechanical stirring by installing paddles, and stirring by controlling the amount of steam injected.

[0025] FIG. 2 is a flowchart showing the procedure of wastewater treatment carried out by the wastewater treatment device of FIG. Hereinafter, the wastewater treatment method performed by the wastewater treatment device of FIG. 1, that is, the filtration treatment, the switching from the filtration treatment to the methane fermentation treatment, and the methane fermentation treatment, will be described with reference to FIGS.

[0026] (filtration process) In the wastewater treatment device 10, first, valve V2 is closed to block the outflow of wastewater to the methane fermentation facility, and V6 and V8 are closed to block the circulation of digester gas between the treatment tank 1 and the gas holder 2. Next, valves V1, V3, and V5 are opened and pump P is driven, so that wastewater is supplied from a wastewater storage tank (not shown) to the treatment tank 1 via the wastewater inlet pipe 4 (S201).

[0027] Wastewater flowing into the treatment tank 1 rises within the treatment tank 1 as an upward flow, passes through the filtration layer, and comes into contact with the filter media 11. At this time, the water contained in the wastewater permeates the filter media 11, but because the outer diameter of the suspended organic matter is larger than the pore size of the filter media 11, the suspended organic matter is captured by the filter media 11 and remains (S202: filtration step). Therefore, as the filtration process continues, suspended organic matter accumulates in the filter media 11, reducing the filtration efficiency. Generally, in filtration devices filled with filter media, the filter media is periodically cleaned to remove the captured matter. However, in this embodiment, the suspended organic matter captured by the filter media 11 is decomposed by a methane fermentation process, as described below, so there is no need to clean the filter media. The filtered water that has permeated the filter media 11 is transported via the filtrate outlet pipe 5 to the water treatment facility for the next process.

[0028] (Switching from filtration to methane fermentation) Next, the environment inside the treatment tank 1 is switched to one in which methane fermentation (decomposition) can be performed in order to remove suspended organic matter accumulated in the filter medium 11 by filtration through methane fermentation, which anaerobically decomposes the suspended organic matter. When the filtration efficiency of the filtration process decreases, the operation of the pump P of the wastewater treatment device 10 is stopped and the valves V1, V3, and V5 are closed to stop the inflow of wastewater into the treatment tank 1 and the outflow of filtered water from the treatment tank 1, thereby terminating the filtration process (S203).

[0029] Next, while keeping valve V8 of digester gas outlet pipe 8 closed, valve V6 of digester gas inlet pipe 6 is opened and blower B is driven to supply digester gas from gas holder 2 into treatment tank 1 (S204). The digester gas supplied into treatment tank 1 is diffused into treatment tank 1 by air diffuser 7 (agitation device) installed below the filter media filling area. At this time, coarse bubbles of digester gas rise from air diffuser 7 and agitate the entire interior of treatment tank 1, causing filter media 11 to oscillate or move and mix. As a result, the wastewater present around the filter media 11 leaves the filter media 11 and moves to the bottom of treatment tank 1. Because treatment tank 1 is sealed except for the part connected to digester gas inlet pipe 6, the pressure of the digester gas causes the wastewater present at the bottom of treatment tank 1 to flow out into wastewater inlet pipe 4. After that, valves V2 and V3 are opened and the wastewater is transferred to a methane fermentation tank for primary sludge and screen residue (S204: switching step). After the wastewater is discharged, valve V3 is closed to shut off the flow of wastewater through treatment tank 1.

[0030] (Methane fermentation treatment) Next, steam is supplied from the heating equipment 3 through the steam introduction pipe 9 into the treatment tank 1, and the temperature inside the treatment tank 1 is controlled to be maintained at a predetermined temperature at which methane fermentation progresses (S205). In the case of mesophilic methane fermentation, the temperature is maintained at 35 to 38°C, and in the case of thermophilic methane fermentation, the temperature is controlled to be maintained at 53 to 57°C. The temperature inside the treatment tank 1 may be controlled by installing a hot water pipe. Next, digested sludge is supplied into the treatment tank 1 through the digested sludge supply pipe 12 (S205). The digested sludge supplied to the treatment tank 1 comes into contact with and mixes with the filter medium 11, causing the methane bacteria in the digested sludge to penetrate into the filter medium 11 and be supported on the filter medium.

[0031] After that, the valve V8 of the digester gas outlet pipe 8 is opened, forming a circulation flow of digester gas between the treatment tank 1 and the gas holder 2. The digester gas supplied from the gas holder 2 to the treatment tank 1 is diffused into the treatment tank 1 as coarse bubbles by the aeration device 7 (agitation device). The coarse bubbles of the diffused digester gas rise throughout the entire interior of the treatment tank 1, agitating the interior of the treatment tank 1 (S205). This causes the filter medium 11 carrying methane bacteria to oscillate or move and mix. This gas agitation promotes contact between the suspended organic matter remaining in the filter medium 11 and the methane bacteria, thereby carrying out methane fermentation (S206: decomposition step). In this embodiment, the suspended organic matter and the methane bacteria are fixed in close proximity to each other on the filter medium 11. Therefore, methane fermentation proceeds more efficiently than in conventional methane fermentation processes in which wastewater containing suspended organic matter is supplied to a reaction tank containing methane bacteria and the two are brought into contact. Furthermore, gas agitation by the bubbles uniformly controls the temperature and conditions inside the treatment tank 1, preventing the generation of scum and the separation of the sludge layer and liquid layer. By using a filter medium 11 with a specific gravity of 0.95 to 1.05, the filter medium 11 can be appropriately shaken or moved and mixed inside the treatment tank 1 without uneven distribution when the digester gas is diffused from the air diffuser 7.

[0032] When methane fermentation is carried out, organic matter is decomposed to produce digester gas and digester liquid. The produced digester gas, together with the digester gas supplied from gas holder 2 to treatment tank 1, is circulated and stored in gas holder 2 via digester gas outflow pipe 8. Part of the digester gas stored in gas holder 2 is recovered as energy, and part is supplied again to treatment tank 1 by blower B.

[0033] Thereafter, when the suspended organic matter is decomposed and the production of digester gas by methane fermentation ceases, the methane fermentation process is terminated (S207). The methane fermentation process can be terminated by stopping the steam supply from the heating equipment 3 and closing valve V8 of the digester gas outlet pipe 8 to stop the outflow of digester gas from the treatment tank 1. Digestion gas is supplied to the treatment tank 1 from the gas holder 2 by blower B. Therefore, by opening valves V3 and V2 of the wastewater inlet pipe 4, the digester liquid inside the treatment tank 1 flows out of the system of the wastewater treatment device 10 from the bottom of the treatment tank 1 due to blower pressure. The outflowing digester liquid can be effectively used as fertilizer, for example, or further treated before being discharged. Thereafter, this process is terminated.

[0034] As described above, by performing the filtration process, switching from the filtration process to the methane fermentation process, and then performing the methane fermentation process, the suspended organic matter accumulated in the filter medium 11 by the filtration process can be efficiently removed by the methane fermentation process without performing a separate, complicated cleaning process, thereby reducing the load on the water treatment device to be performed in the next process.In addition, because the suspended organic matter can be converted into digester gas by methane fermentation, energy can be recovered, thereby achieving energy savings.

[0035] By sequentially repeating the above-described filtration process, switching from filtration process to methane fermentation process, and methane fermentation process, filtration process and methane fermentation process can be carried out continuously in the treatment tank 1.

[0036] FIG. 3 is a diagram schematically illustrating a wastewater treatment unit 30 including a plurality of the wastewater treatment devices of FIG.

[0037] The wastewater treatment unit 30 in Figure 3 includes five filtration and methane fermentation treatment tanks 1a-1e (hereinafter referred to as "treatment tanks 1a-1e"), a gas holder 2, a heating system 3, a blower B, and a pump P. The treatment tanks 1a-1e are filled with filter media 11a-11e (separation means), respectively, and have air diffusers 7a-7e (agitation devices). A wastewater storage tank (not shown) stores wastewater that has been treated in a primary sedimentation tank and screen. The treatment tanks 1a-1e have the same configuration and function as the treatment tank 1 described above.

[0038] Each of the five treatment tanks 1a-1e is connected to a wastewater inlet pipe 4 and a filtered water outlet pipe 5. The wastewater inlet pipes 4 connected to the treatment tanks 1a-1e are interconnected, and each pipe has a pump P and valves V1, V2, and V3a-V3e. The wastewater flowing into the treatment tanks 1a-1e from a wastewater storage tank (not shown) is controlled by opening and closing the valves V1, V2, and V3a-V3e. The filtered water outlet pipes 5 connected to the treatment tanks 1a-1e are interconnected, and each pipe has valves V5a-V5e. The filtered water flowing out of the treatment tanks 1a-1e is controlled by opening and closing the valves V5a-V5e. The treatment tanks 1a-1e are connected to the gas holder 2 via a digester gas inlet pipe 6 and a digester gas outlet pipe 8. The digester gas inlet pipe 6 has a blower B and valves V6a-V6e, and the digester gas outlet pipe 8 has valves V8a-V8e. The treatment tanks 1a to 1e are connected to the heating equipment 3 via a steam introduction pipe 9. As with the treatment tank 1 described above, the treatment tanks 1a to 1e each sequentially perform a filtration process and a methane fermentation process, and the performed filtration process and decomposition process can be switched by opening and closing the above-mentioned valves V1, V2, V3a to V3e, V4a to V4e, V5a to 5e, and V6a to 6e (switching means).

[0039] Table 1 below shows an example of an operation cycle for wastewater treatment using the wastewater treatment unit of FIG.

[0040] [Table 1]

[0041] In the operation cycle of Table 1, the filtration treatment lasts for two days, and the treatment tanks are switched from filtration to methane fermentation (digestion) treatment in a merry-go-round fashion once every two days, in the order of treatment tanks 1a to 1e, with filtration treatment being carried out in all treatment tanks over a period of 10 days. Also, when filtration treatment is carried out in one of the treatment tanks 1a to 1e, methane fermentation treatment (digestion) is carried out in the other treatment tanks.

[0042] (Performs filtration and methane fermentation processes) The method in which the treatment tank 1a performs the filtration treatment and the other treatment tanks 1b to 1e perform the methane fermentation treatment on the first and second days in Table 1 will be described below. When performing the first day of treatment using the wastewater treatment unit 30, it is assumed that filtration has already been performed in the treatment tanks 1b to 1e, since the methane fermentation treatment is a process for decomposing suspended organic matter that has accumulated in the filter media due to the filtration process.

[0043] First, in the wastewater treatment unit 30 shown in Figure 3, valve V2 is closed to block the flow of wastewater to the methane fermentation equipment. Next, valves V1, V3a, and V4a are opened to allow the inflow and outflow of wastewater to treatment tank 1a, and valves V3b-V3e and V4a-V4e are closed to block the inflow and outflow of wastewater to treatment tanks 1b-1e. Steam is supplied from heating equipment 3 to treatment tanks 1b-1e to control the temperature suitable for methane fermentation, and digested sludge is supplied to the treatment tanks 1b-1e, causing the methane bacteria in the digested sludge to be supported on filter media 11b-11e. After that, valves V6a and V8a are closed to block the circulation of digestion gas between treatment tank 1a and gas holder 2, and valves V6b-6e and V8b-8e are opened to circulate the digestion gas between treatment tanks 1b-1e and gas holder 2. By setting each valve (switching means) as described above, in treatment tank 1a, the inflowing wastewater comes into contact with filter medium 11a and filtrate flows out, and in treatment tanks 1b to 1e, a methane fermentation process is carried out to decompose the suspended organic matter accumulated in filter media 11b to 11e. Note that even if filtration is carried out in one treatment tank other than treatment tank 1a and methane fermentation is carried out in the other treatment tanks on days 3 to 10, these processes can be carried out by appropriately opening and closing each valve according to the above valve settings.

[0044] (Switching between filtration and methane fermentation processes) Next, a method for switching the treatment tank 1a from filtration treatment to methane fermentation treatment and the treatment tank 1b from methane fermentation treatment to filtration treatment to decomposition treatment will be described below. (1) First, the filtration process in the treatment tank 1a is stopped by closing the valves V1 and V5a (end of the filtration process in the treatment tank 1a). (2) Next, valve V2 is opened to allow the wastewater to flow into the methane fermentation facility.

[0045] (3) Next, valve V6a is opened to transfer the digestion gas from the gas holder 2 to the aeration device 7 of the treatment tank 1a, and the digestion gas is diffused from the aeration device 7 to agitate the inside of the treatment tank 1a. This causes the filter medium 11a to oscillate or move and mix, and the sludge present around the filter medium 11a moves downward, so that air pressure based on the digestion gas causes wastewater with a high sludge concentration, for example, wastewater with an SS (suspended solids) concentration of approximately 5% by weight, to flow out from the bottom of the treatment tank 1a. The wastewater flowing out from the bottom of the treatment tank 1a is transferred to a methane fermentation facility (not shown) for treating sludge from a primary sedimentation tank or the like (wastewater flowing out due to aeration by the device 1a). In addition, when sludge is to be left in the treatment tank 1a, by introducing digester gas from a digester gas inlet pipe (not shown) installed at the top of the treatment tank 1a rather than from the aeration device 7, it is possible to discharge wastewater with a low sludge concentration, for example, wastewater with an SS (suspended solids) concentration of approximately 1% by weight, without stirring the filter material 11a (wastewater outflow from the treatment tank 1a).

[0046] (4) Then, the supply of steam from the heating equipment 3 to the treatment tank 1b is stopped, and the valve V8b of the digester gas outlet pipe 8 is closed to stop the outflow of digester gas from the treatment tank 1b, thereby terminating the methane fermentation process in the treatment tank 1b (completion of the methane fermentation process in the treatment tank 1b).

[0047] (5) Furthermore, by increasing the amount of digestion gas supplied from the gas holder 2 to the aeration device 7 of the treatment tank 1b and diffused from the aeration device 7, the inside of the treatment tank 1b is agitated more strongly than during methane fermentation treatment, thereby separating the digested sludge adhering to the filter 11b from the filter material (sludge separation by aeration in the device 1b). The agitation time by the digestion gas is 10 to 30 minutes. By using a filter material 11b with a specific gravity of 0.95 to 1.05, the filter material 11b is properly shaken or moved and mixed without being unevenly distributed inside the treatment tank 1b, separating the digested sludge from the filter material.

[0048] Next, by closing valve V2 and opening valves V3b and V8a, the digested sludge exfoliated by the air pressure generated by the digestion gas diffused from the aeration device 7b flows out from the bottom of treatment tank 1b and is transferred to treatment tank 1a as seed sludge for methane fermentation treatment. By transferring the digested sludge from treatment tank 1b, for which methane fermentation treatment has been completed, to treatment tank 1a in this manner, the methane fermentation treatment in treatment tank 1a can be rapidly advanced (transfer of digested sludge from treatment tank 1b to treatment tank 1a).

[0049] (6) Thereafter, valve V3a is closed, and steam is supplied from heating equipment 3 to treatment tank 1a to control the temperature, while a circulating flow of digester gas is formed between treatment tank 1a and gas holder 2. As a result, on the third and fourth days, treatment tank 1a performs methane fermentation treatment, and treatment tanks 1c to 1e continue methane fermentation treatment. Also, valve V6b of digester gas inlet pipe 6 is closed to block the inflow of digester gas from gas holder 2 to treatment tank 1b, and valves V1 and V5b are opened to allow the inflow and outflow of wastewater to treatment tank 1b, thereby causing treatment tank 1b to perform filtration treatment on the third and fourth days. The above switching operations can be performed in 15 minutes to 1 hour.

[0050] Methane bacteria are microorganisms that are extremely sensitive to temperature changes and oxygen. However, by performing the above-described switching operation, the activity of the methane bacteria in the digested sludge can be maintained while the digested sludge used in the methane fermentation process can be transferred to a treatment tank where filtration has been completed as seed sludge for the next methane fermentation process, thereby shortening the processing time of the methane fermentation process itself.

[0051] Fig. 4 is a flowchart showing the procedure of wastewater treatment performed by the wastewater treatment unit of Fig. 3 in the operation cycle of Table 1. In the wastewater treatment of Fig. 4, a CPU (control means) of an information processing device (not shown) alternates between filtration treatment and decomposition treatment in each of the treatment tanks 1a to 1e. The wastewater treatment procedure according to the operation cycle of Table 1 will be explained below with reference to Figs.

[0052] First, on the first and second days, the treatment tank 1a performs a filtration process, and the other treatment tanks 1b to 1e perform a methane fermentation process (S401). Next, the switching means switches the treatment tank 1a from a filtration process to a decomposition process, and the treatment tank 1b from a decomposition process to a filtration process (S402). Subsequently, on the third and fourth days, the treatment tank 1b performs the filtration process, and the other treatment tanks 1a, 1c to 1e perform the decomposition process (S403). Next, the switching means switches the treatment tank 1b from the filtration process to the decomposition process, and the treatment tank 1c from the decomposition process to the filtration process (S404). Thereafter, on the fifth and sixth days, the treatment tank 1c performs the filtration process, and the other treatment tanks 1a, 1b, 1d, and 1e perform the decomposition process (S405). Next, the switching means switches the treatment tank 1c from the filtration process to the decomposition process, and the treatment tank 1d from the decomposition process to the filtration process (S404). Furthermore, on the 7th to 8th days, the treatment tank 1d performs a filtration process, and the other treatment tanks 1a to 1c and 1e perform a decomposition process (S405). Next, the switching means switches the treatment tank 1d from a filtration process to a decomposition process, and the treatment tank 1e from a decomposition process to a filtration process (S404). Subsequently, on the ninth and tenth days, the treatment tank 1e performs a filtration process, and the other treatment tanks 1a to 1d perform a decomposition process (S405). Through the above operation, filtration processes are performed in all treatment tanks over a period of 10 days (S406). Thereafter, this process is terminated.

[0053] After performing the filtration process in all treatment tanks over 10 days using the above operation, treatment tank 1e is switched from filtration to decomposition, and treatment tank 1a is switched from decomposition to filtration. By repeating the above processes and switching, wastewater treatment can be carried out continuously using the wastewater treatment unit 30. As a result, suspended organic matter separated by filtration can be efficiently removed and recovered as digester gas, reducing the load on the water treatment device and enabling energy-saving wastewater treatment.

[0054] FIG. 5 is a diagram showing a large-scale sewage treatment flow using the wastewater treatment unit of FIG.

[0055] In Figure 5, sewage discharged from homes, factories, etc. is transported to equipment 51, which consists of a grit basin and a primary sedimentation basin, or a grit basin and a screening facility, where coarse solids in the sewage are removed. The sediment, screen residue, and primary sludge removed in equipment 51 are either disposed of or effectively utilized, or crushed using a crusher and transported to a conventional methane fermentation facility 52 for methane fermentation treatment. A flocculant is added to the treated water from equipment 51, and then the water is transported to the wastewater treatment unit (filtration and methane fermentation treatment unit) 30 (Figure 3) of this embodiment. Various types of flocculants can be used, but iron-based compounds and organic polymers can be used to reduce digestion inhibition. Adding such a flocculant to the treated water from equipment 51 can improve the removal rate of the filtration process in the wastewater treatment unit 30. The wastewater treatment unit 30 is equipped with five treatment tanks 1a to 1e (FIGS. 1 and 3), each of which performs a filtration process and a methane fermentation process, with switching between the filtration process and the methane fermentation process performed in a merry-go-round fashion.

[0056] The wastewater discharged from the wastewater treatment unit 30 when switching between filtration and methane fermentation is transferred to a methane fermentation facility 52 for methane fermentation. The digester gas discharged from the wastewater treatment unit 30 is transferred to an energy recovery facility 53 for effective utilization, along with the digester gas discharged from the methane fermentation facility 52. ​​The treated filtered water from the wastewater treatment unit 30 is transferred to a water treatment facility 54 together with the digested sludge discharged from the methane fermentation facility 52. ​​In large-scale sewage treatment, the water treatment facility 54 may employ, for example, a conventional activated sludge process or a membrane separation activated sludge process, in which soluble organic matter in the wastewater is oxidized and decomposed by the activated sludge. A portion of the activated sludge used for wastewater treatment in the water treatment facility 54 is subjected to conditioning treatment, and then transferred as excess sludge to a dehydration facility 55 for dehydration. The dehydrated filtrate discharged from the dehydration facility 55 is transferred to a grit-containing facility 51, and the dehydrated cake is then disposed of or effectively utilized. Furthermore, the treated water from the water treatment facility 54 is either discharged or put to effective use.

[0057] As described above, in large-scale sewage treatment, by using the wastewater treatment unit 30 of this embodiment as a pre-process of the water treatment facility 54, suspended organic matter and the like in the wastewater can be efficiently removed without performing a complicated cleaning process, and the digester gas can be effectively utilized. This significantly reduces the load on the water treatment facility 54 and increases the amount of energy recovered, enabling energy-saving wastewater treatment.

[0058] FIG. 6 is a diagram showing a small-scale sewage treatment flow using the wastewater treatment unit of FIG.

[0059] In FIG. 6, sewage discharged from homes, factories, etc. is transferred to equipment 61, which is composed of a grit chamber and a fine mesh screen, where coarse solids are removed. The fine mesh screen equipment has a screen with a mesh size of 0.5 to 10 mm, preferably 1 to 5 mm. Examples of suitable equipment include a drum-type separator / dehydrator (such as the new Mae Sepa Press manufactured by Maezawa Industries, Inc.) capable of separating and dehydrating impurities, and a screen with rotating perforated panels (such as the MMS (Multi-Mesh Screen) manufactured by Maezawa Industries, Inc.). The treated water from equipment 61 is added with a coagulant similar to that used in the large-scale sewage treatment flow shown in FIG. 5, and then transferred to the wastewater treatment unit (filtration and methane fermentation treatment unit) 30 of this embodiment. Adding such a coagulant to the treated water from equipment 61 improves the removal rate of the filtration process in the wastewater treatment unit 30.

[0060] Since the fine screen equipment can reliably remove relatively large impurities such as hair and scum, installing it as a pre-processing step for the wastewater treatment unit 30 can prevent problems such as the generation of scum and clogging of measuring instruments in the treatment tank of the wastewater treatment unit 30. Furthermore, by reliably removing relatively large impurities using the fine screen equipment, it is possible to select a filter material effective for methane fermentation treatment as the filter material to be filled into the treatment tank of the wastewater treatment unit 30. The sediment, screen residue, and primary sludge removed in equipment 61 are either disposed of or effectively utilized, or crushed in a crusher and then transferred to the wastewater treatment unit (filtration and methane fermentation treatment unit) 30 together with the treated water from equipment 61. The screen residue removed by the fine screen equipment can be dehydrated and disposed of, or it can be crushed in a crusher and then subjected to methane fermentation treatment.

[0061] The wastewater treatment unit 30 is equipped with five treatment tanks 1a to 1e (FIGS. 1 and 3)), each of which performs a filtration process and a methane fermentation process, with switching between the filtration process and the methane fermentation process performed in a merry-go-round fashion.

[0062] The digester gas flowing out of the wastewater treatment unit 30 is transported to an energy recovery facility 53 for effective use. In addition, filtered water, which is treated water from the wastewater treatment unit 30, is transported to a water treatment facility 54. The maximum wastewater volume is 5,000 m 3 For small-scale sewage treatment of less than 1000 m3 / day, for example, an oxidation ditch (hereinafter referred to as OD) system is used as the water treatment system 54. In an OD system, an endless channel is used as a ditch (reaction tank) to carry out activated sludge treatment of soluble organic matter. A portion of the activated sludge used for wastewater treatment in the water treatment system 54 is subjected to conditioning treatment and then transferred as excess sludge to a dehydration system 55 for dehydration. The dehydrated filtrate discharged from the dehydration system 55 is transferred to a system 61 equipped with a fine screen, and the dehydrated cake is then disposed of or, to reduce the burden on the environment, is effectively utilized as gardening soil, cement raw material, etc. The treated water from the water treatment system 54 is either discharged or effectively utilized.

[0063] As described above, in small-scale sewage treatment, by using the wastewater treatment unit 30 of this embodiment as a pre-process of the water treatment facility 54, suspended organic matter and the like in the wastewater can be efficiently removed without performing a complicated cleaning process, while the digester gas can be effectively utilized. This allows for a significant reduction in the load on the water treatment facility 54, an increase in the amount of energy recovered, and energy-saving wastewater treatment. As a result, it is possible to provide a wastewater treatment device that can adequately cope with the expected increases in food residue in wastewater and increases in the amount of water to be treated in the future.

[0064] In this embodiment, the wastewater treatment unit 30 (Figure 3) has been described as having five treatment tanks 1a to 1e as an example, but the effects of the present invention can also be achieved when using, for example, 2 to 20 treatment tanks, preferably 3 to 15 treatment tanks.

[0065] In this embodiment, the treatment tanks 1a to 1e have a filtration area of ​​4 m 2 If the filter is of this size, it can be manufactured in a factory and transported in an assembled state. If the filtration rate is 200 m / day, 2One treatment tank with a filtration area of ​​800m 3 One unit is made up of five treatment tanks as shown in Figure 3, and can filter wastewater up to 800 m per day. 3 / day, and can treat 5,000m 3 In order to perform filtration treatment at a rate of 1000 / day, 6 to 7 units can be used. As described above, according to this embodiment, the size of each treatment tank can be made small, and small treatment tanks can be manufactured in the wastewater treatment plant, so that treatment tanks with good performance can be manufactured at low cost and in a short delivery time and used for wastewater treatment.

[0066] Although the present invention has been described above using the above-mentioned embodiment, the present invention is not limited to the above-mentioned embodiment. [Explanation of symbols]

[0067] 1. Filtration and methane fermentation treatment tank 2 Gas holder 3 Heating equipment 7 Air diffuser 10 Wastewater treatment equipment 11 Filter media (microorganism carrier) 30 Wastewater treatment unit V1, V2, V3, V4, V5, V6 valves

Claims

1. A wastewater treatment device that performs a filtration process in which wastewater containing suspended organic matter and moisture is filtered to separate the suspended organic matter from the moisture, and a decomposition process in which the suspended organic matter separated by the filtration process is anaerobically decomposed, The apparatus comprises a filter medium for separating the suspended organic matter from the water, and a decomposition means for anaerobically decomposing the suspended organic matter separated by the filter medium, The wastewater treatment device is characterized in that the filter material is a hollow cylindrical porous body having a specific gravity of 0.95 to 1.05, or a nonwoven fabric having a specific gravity of 0.95 to 1.

05.

2. 2. The wastewater treatment device according to claim 1, wherein the decomposition means is a microorganism, and the microorganism is supported on the filter medium.

3. 3. The wastewater treatment device according to claim 1, further comprising an agitator.

4. 4. The wastewater treatment device according to claim 1, further comprising a wastewater inlet pipe, a filtered water outlet pipe, a digester gas outlet pipe, and a heating device.

5. A wastewater treatment unit that performs a filtration process of filtering wastewater containing suspended organic matter and water to separate the suspended organic matter from the water, and a decomposition process of anaerobically decomposing the suspended organic matter separated by the filtration process, a plurality of wastewater treatment devices each having a filter medium for separating the suspended organic matter from water and a decomposition means for anaerobically decomposing the suspended organic matter separated by the filter medium; a switching means for switching between the filtration treatment and the decomposition treatment to be performed in the plurality of wastewater treatment devices.

6. The wastewater treatment unit according to claim 5, characterized in that it has a control means for controlling the other wastewater treatment devices to perform decomposition treatment when filtration treatment is performed in one of the plurality of wastewater treatment devices, and the one device performing filtration treatment is sequentially changed by the switching means.

7. 7. The wastewater treatment unit according to claim 5, wherein the switching means includes means for transferring digested sludge from a wastewater treatment device after completion of decomposition treatment to another wastewater treatment device after completion of filtration treatment.

8. A wastewater treatment method using a wastewater treatment device that performs a filtration process in which wastewater containing suspended organic matter and water is filtered to separate the suspended organic matter from the water, and a decomposition process in which the suspended organic matter separated by the filtration process is anaerobically decomposed, the method comprising: a filter medium that separates the suspended organic matter from the water; and a decomposition means that anaerobically decomposes the suspended organic matter separated by the filter medium, a filtration step of filtering the wastewater to separate suspended organic matter and water; a decomposition step of anaerobic decomposition of the separated suspended organic matter; and a switching step of switching between the filtration treatment and the decomposition treatment.

9. 9. The wastewater treatment method according to claim 8, wherein the filtering step, the switching step, and the decomposition step are repeatedly performed in this order.

10. A wastewater treatment method using a wastewater treatment unit that performs a filtration process of filtering wastewater containing suspended organic matter and water to separate the suspended organic matter from the water, and a decomposition process of anaerobically decomposing the suspended organic matter separated by the filtration process, the wastewater treatment unit comprising a plurality of wastewater treatment devices each having a filter medium that separates the suspended organic matter from the water and a decomposition means that anaerobically decomposes the suspended organic matter separated by the filter medium, and a switching means that switches between the filtration process and the decomposition process that are performed in the plurality of wastewater treatment devices, a filtration and decomposition step of performing a filtration treatment in one of the plurality of wastewater treatment devices and performing a decomposition treatment in another of the plurality of wastewater treatment devices; a switching step in which the switching means switches one device that has been performing the filtration treatment from filtration treatment to decomposition treatment, and switches another device from decomposition treatment to filtration treatment.

11. The wastewater treatment method according to claim 10, wherein the filtering and decomposition step and the switching step are repeatedly performed, so that the plurality of wastewater treatment devices sequentially perform the filtering treatment.

12. 12. The wastewater treatment method according to claim 10, wherein the switching step includes a step of transferring digested sludge from the wastewater treatment device after completion of decomposition treatment to another wastewater treatment device after completion of filtration treatment.

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