JP7813082B2 - Decarbonized septic tank - Google Patents

Description

The present invention relates to a purification treatment device, i.e., a decarbonized septic tank, that can be driven for purification treatment using driving energy that does not emit greenhouse gases like fossil fuels.

Traditionally, septic tanks that purify wastewater and other wastewater through biological filtration have a front-stage (upstream) section filled with relatively large filter media for anaerobic treatment, and a rear-stage (downstream) section filled with relatively small filter media for aerobic treatment, with air supplied from an external fan.

In addition, one type of septic tank known to this type is equipped with a cleaning device (hereinafter simply referred to as "cleaning device") that uses air supplied from a blower to instantly lower the water level in the treatment tank containing the filter media, thereby cleaning the filter media and other components in the aerobic treatment tank (see Patent Documents 1 to 4, etc.).

Such a cleaning device comprises an air supply pipe connected to a blower, an air reservoir chamber submerged in the treatment tank to store air sent from the air supply pipe, and an exhaust pipe inserted into the air reservoir chamber to discharge the stored air out of the treatment tank when a predetermined amount of air has accumulated in the air reservoir chamber.When the stored air in the air reservoir chamber is discharged from the exhaust pipe, the water in the treatment tank flows into the air reservoir chamber, instantly lowering the water level in the treatment tank and cleaning the filter carrier in the treatment tank.

Japanese Patent Application Publication No. 8-132082 JP 2010-184210 A JP 2010-207662 A Japanese Patent Application Laid-Open No. 2021-10876

For example, it is estimated that there are approximately 7.5 million septic tanks installed and in operation in Japan (as of 2019). The fans attached to each septic tank are powered by electricity provided by various power generation facilities. If we assume that each fan operates 24 hours a day with an average power output of 50W (0.05kW), this amounts to approximately 400,000kW of electricity, equivalent to the power consumed by one nuclear power plant, just by the septic tanks. Given the current situation in which efforts toward decarbonization have accelerated in recent years, there is a need for efforts (improvements) with a view to decarbonization, even for septic tanks, which involve such energy consumption.

Therefore, the problem to be solved by this invention is to provide a septic tank that can clean the filter carrier using new energy consumption instead of conventional electricity consumption, i.e., a decarbonized septic tank.

The above problems are solved by the decarbonizing septic tank of the present invention. In other words, this septic tank comprises a plurality of treatment tanks, including at least one anaerobic treatment tank in which a filter carrier is housed, and a cleaning device for cleaning the filter carrier in the anaerobic treatment tank. The cleaning device comprises a gas reservoir capable of storing gas, a gas collection unit connected to the gas reservoir and collecting gas generated in at least one of the plurality of treatment tanks at its upper portion, an outside air supply unit powered by electricity generated using renewable energy and supplying outside air as gas to the gas reservoir directly or indirectly, and an air lift pump powered by the gas stored in the gas reservoir and configured to return treated water from a downstream treatment tank of the plurality of treatment tanks to an upstream treatment tank. When the gas stored in the gas reservoir reaches a predetermined amount and the pressure balance between the stored gas and the treated water is disrupted, the air lift pump is activated to generate a flow of treated water in the anaerobic treatment tank as the water level rises in the gas reservoir, thereby cleaning the filter carrier.

As described above, the septic tank of the present invention includes a gas collection section that collects gas generated in each treatment tank and connects this gas collection section to the gas reservoir. It also includes an outside air supply device that is powered by electricity generated using renewable energy and supplies outside air as gas to the gas reservoir. This allows the air lift pump to operate using only natural energy, without using any electrical energy generated from fossil fuels, as is the case with conventional blowers. Furthermore, by providing both the gas collection section and the outside air supply device, it is possible to supply a sufficient amount of gas to the gas reservoir to operate the air lift pump over a consistent period, even when the amount of gas generated in each treatment tank is small. As described above, the present invention makes it possible to consistently provide excellent cleaning effects while contributing to the suppression of greenhouse gases such as carbon dioxide.

As described above, the decarbonized septic tank of the present invention allows the filter media to be cleaned using only natural energy instead of conventional electrical energy, thereby contributing to decarbonization while ensuring the purification capacity of the septic tank over the long term through stable cleaning of the filter media.

1 is a cross-sectional view of a decarbonization type septic tank according to one embodiment of the present invention. FIG. FIG. 2 is a plan view of the decarbonization type septic tank shown in FIG. 1. FIG. 2 is a diagram showing an example of use of the decarbonization type septic tank shown in FIG. 1, showing a state in which gas begins to accumulate in the gas accumulation portion. FIG. 2 is a diagram showing an example of use of the decarbonization type septic tank shown in FIG. 1, showing a state in which gas begins to flow into the air lift pump. FIG. 2 is a diagram showing an example of use of the decarbonization type septic tank shown in FIG. 1, showing a state in which gas has flowed into the air lift pump. FIG. 2 is a diagram showing an example of use of the decarbonization type septic tank shown in FIG. 1, illustrating the state when the balance between the gas pressure and the treated water pressure in the air lift pump is lost. FIG. 2 is a diagram showing an example of use of the decarbonization type septic tank shown in FIG. 1, and shows the state when treated water is lifted up by an air lift pump. FIG. 10 is a cross-sectional view of a decarbonization type septic tank according to another embodiment of the present invention. FIG. 10 is a cross-sectional view of a decarbonization type septic tank according to another embodiment of the present invention.

Below, the details of a decarbonizing septic tank according to one embodiment of the present invention will be explained based on the drawings.

Figure 1 shows a cross-sectional view of a decarbonization septic tank 1 according to one embodiment of the present invention. This septic tank 1 mainly comprises multiple treatment tanks 2-4 and a cleaning device 5.

The cleaning device 5 also includes a gas reservoir section 7, a gas collection section 8, an outside air supply device 9, a solar power generation device 10, and an air lift pump 11.

The multiple treatment tanks 2-4 include at least one anaerobic treatment tank. In this embodiment, all three treatment tanks 2-4 can function as anaerobic treatment tanks. The first treatment tank 2, located most upstream among the three treatment tanks 2-4, is partitioned by a partition wall 13 into a relatively upstream first chamber 2a and a relatively downstream second chamber 2b. In this case, an inlet 14 for the treated water W is provided at the top of the first chamber 2a. Multiple filter media 6a are housed in a predetermined area of the second chamber 2b, and the vertical movement of the filter media 6b is restricted within a predetermined range by upper and lower restricting members 15a, 15b. The restricting members 15a, 15b may be made of wire mesh, plastic mesh, or the like that does not allow the filter media 6b to pass through. Anaerobic microorganisms are attached to each filter media 6a, and the treated water W passing through the filter media 6a (second chamber 2b of the first treatment tank 2) is subjected to decomposition treatment utilizing the metabolic reactions of the anaerobic microorganisms.

The second treatment tank 3 is disposed downstream of the first treatment tank 2. The second treatment tank 3 is partitioned by a partition wall 16 into a first chamber 3a located relatively upstream and a second chamber 3b located relatively downstream. Multiple filter media 6a are housed in a predetermined area of the first chamber 3a, and the vertical movement of the filter media 6b is restricted within a predetermined range by upper and lower restriction members 15a, 15b. As with the first treatment tank 2, anaerobic microorganisms are attached to each filter media 6a in the second treatment tank 3, and the treated water W passing through the filter media 6a (first chamber 3a of the second treatment tank 3) is subjected to decomposition treatment utilizing the metabolic reactions of the anaerobic microorganisms.

A third treatment tank 4 is disposed downstream of the second treatment tank 3. Multiple filter media 6b are housed in a specified area of the third treatment tank 4, and the upper and lower regulating portions 16a, 16b restrict the vertical movement of the filter media 6b within a specified range. Here, relatively large filter media 6a are disposed in the upstream treatment tanks (first treatment tank 2 and second treatment tank 3), and relatively small filter media 6b are disposed in the downstream treatment tank (third treatment tank 4). The regulating portions 16a, 16b may be made of wire mesh, plastic mesh, or the like that does not allow the filter media 6b to pass through.

In this case, treated water W flowing from the inlet 14 into the first chamber 2a of the first treatment tank 2 flows from below the first chamber 2a into the second chamber 2b, passes from bottom to top through the storage area of the filter media 6a, and then flows from above the second chamber 2b into the second treatment tank 3. The treated water W flowing into the second treatment tank 3 passes from top to bottom through the storage area of the filter media 6a provided in the first chamber 3a, flows into the adjacent second chamber 3b, passes from bottom to top through the second chamber 3b, and flows into the third treatment tank 4 from above. The treated water W flowing into the third treatment tank 4 passes from top to bottom through the storage area of the filter media 6b provided in the third treatment tank 4, and then is released from the decarbonization type septic tank 1 through the outlet 17 provided further downstream.

Details of the cleaning device 5 are described below.

The gas reservoir 7 is, for example, approximately box-shaped and opens downward, allowing it to store a specified gas. In this embodiment, the gas reservoir 7 is disposed inside the third treatment tank 4 and is located lower than the water surface of the treated water W in the third treatment tank 4. Therefore, when no gases Ga and Gb (described below) are stored in the gas reservoir 7, the entire gas reservoir 7 is submerged in the treated water W (see Figure 1).

The gas collection unit 8 is configured to collect gas Ga generated in at least one of the treatment tanks 2-4 at its upper portion and is connected to the gas reservoir 7 via a flow pipe 18. This allows the gas Ga collected by the gas collection unit 8 to be sent to the gas reservoir 7 and stored there. In this embodiment, the gas collection unit 8 is open downward, and has a shape in which the opening area increases as it extends downward. The gas collection unit 8 configured as described above is disposed above the storage area for the filter carrier 6a in the first chamber 3a of the second treatment tank 3. This makes it possible to collect gas Ga, an organic gas generated during the microbial decomposition of organic wastewater in the storage area for the filter carrier 6a or in sediments S such as sludge accumulated at the bottom of each treatment tank 2-4.

The outside air supply device 9 is capable of supplying outside air Gb as gas to the gas reservoir 7 and is powered by electricity generated by the solar power generation device 10. Any gas supply device can be used as the outside air supply device 9, and a blower is preferably used, for example. In this embodiment, an outside air supply pipe 24 is connected to the outside air supply device 9, and the tip opening of the outside air supply pipe 24 is positioned below the gas reservoir 7, so that the outside air Gb pressurized by the outside air supply device 9 is supplied directly to the gas reservoir 7 through the outside air supply pipe 24.

The outside air Gb may be supplied directly or indirectly to the gas reservoir 7 as described above. That is, when the gas reservoir 7 is connected to the gas collection unit 8 via the connecting pipe 18 as in this embodiment, the outside air supply device 9 and the outside air supply pipe 24 may be configured so that the outside air Gb is supplied to the gas collection unit 8 or the inside of the connecting pipe 18.

The air lift pump 11 integrally comprises a first flow pipe 19, which allows the inflow of gases Ga and Gb, a second flow pipe 20, and a connecting pipe 21, which connects the lower end of the first flow pipe 19 with the lower end of the second flow pipe 20. In this case, the first flow pipe 19 and the second flow pipe 20 extend vertically, and the connecting pipe 21 is connected to each other while extending horizontally. Note that "extending vertically" does not necessarily mean extending only vertically; some inclination relative to the horizontal is acceptable. Similarly, "extending horizontally" does not necessarily mean extending only horizontally; some inclination relative to the horizontal is acceptable. In the illustrated example, both flow pipes 19 and 20 extend linearly, but this does not mean that curved shapes are completely excluded.

An opening 19a is provided in the first flow pipe 19 above the connection position with the communicating pipe 21, and this opening 19a is located within the gas reservoir 7. In this embodiment, the opening 19a is the upward-facing connection port of the three connection ports of the tee (T-shaped joint) 19b connected to the first flow pipe 19. The first flow pipe 19 is connected to the side-facing connection port of the tee 19b. A return pipe 22 is connected to the end (upper end) of the second flow pipe 20 opposite the communicating pipe 21. The return pipe 22 extends to a treatment tank (here, the first treatment tank 2) located upstream of the treatment tank (here, the third treatment tank 4) in which the air lift pump 11 is installed.

An inlet pipe 23 for treated water W is also connected to the first circulation pipe 19. In this embodiment, the inlet pipe 23 is connected to a connection port facing downward of the cheese 19b. In this case, the inlet pipe 23 extends in the vertical direction, and can draw in treated water W near the bottom of the third treatment tank 4 by the action of the air lift pump 11 described below.

Next, an example of how to use the decarbonization septic tank 1 configured as described above will be explained mainly based on Figures 3 to 7.

First, in the initial stage after the treated water W is introduced, as shown in Figure 1, the entire gas reservoir section 7 and gas collection section 8 are both submerged in the treated water W in each treatment tank 3, 4. In this case, the first circulation pipe 19, second circulation pipe 20, and connecting pipe 21 that make up the air lift pump 11 are also filled with the treated water W.

When treated water W flows into the first treatment tank 2 through the inlet 14, the inflowing treated water W undergoes the purification process (here, anaerobic treatment) described above in each of the treatment tanks 2-4. Referring to FIG. 3, gas Ga generated in the first chamber 3a of the second treatment tank 3 is collected by the gas collection section 8 located above the filter carrier 6a and sent to the gas reservoir 7 through the connecting pipe 18. As a result, at least the gas Ga generated in the second treatment tank 3 is stored in the gas reservoir 7. Furthermore, when the weather conditions allow the solar power generation device 10 to operate, the outside air supply device 9 is driven by the electricity generated by the solar power generation device 10, thereby supplying outside air Gb as gas to the gas reservoir 7 through the outside air supply pipe 24 (see FIG. 3).

As gas accumulates in the gas reservoir 7 as described above, the position of the gas-liquid interface (the surface of the treated water W) in the gas reservoir 7 is gradually pushed down. The treated water W is then pushed down to the opening 19a of the first flow pipe 19, which serves as the gas inlet for the air lift pump 11, causing gases Ga and Gb to flow into the first flow pipe 19 and pushing down the gas-liquid interface within the first flow pipe 19 (see Figures 4 and 5).

Then, as the supply of gases Ga and Gb to the gas reservoir 7 continues, when the amount of gases Ga and Gb stored in the gas reservoir 7 reaches a predetermined amount—in other words, when the balance between the pressure of gases Ga and Gb in the air lift pump 11 and the pressure of the treated water W is lost (for example, as shown in Figure 6 )—the gases Ga and Gb in the air lift pump 11 are discharged out of the air lift pump 11 through the return pipe 22. This discharge causes the treated water W located below the gas reservoir 7 in the third treatment tank 4 to rise instantaneously, while the treated water W directly below the storage area of the filter media 6b connected to the bottom of the gas reservoir 7 is instantly drawn downward (see Figure 7 for both). This results in the cleaning process of the filter media 6b in the third treatment tank 4.

Furthermore, as the gases Ga and Gb described above flow, the gas Ga in the gas collection section 8, which is connected to the gas reservoir section 7, is discharged to the outside of the air lift pump 11 via the communication pipe 18, the gas reservoir section 7, and the return pipe 22. This discharge phenomenon causes the treated water W located directly below the gas collection section 8 to instantly rise. This causes the filter carrier 6a in the second treatment tank 3 to be cleaned.

In addition, in this embodiment, the lower opening of the inlet pipe 23 for the treated water W is positioned near the bottom of the third treatment tank 4. As a result, due to the flow action of the gases Ga and Gb described above, the treated water W near the bottom of the third treatment tank 4 is pulled up through the lower opening of the inlet pipe 23, and the sediment S that has accumulated at the bottom is also pulled up and returned to the first treatment tank 2 together with the treated water W. This reduces the amount of sediment S downstream. The amount of sediment S is also reduced by the sediment S returned to the upstream treatment tank (here, the first treatment tank 2) being subjected to purification treatment in each of the treatment tanks 2 to 4 together with the treated water W.

As described above, the decarbonization septic tank 1 according to this embodiment includes a gas collection unit 8 that collects gas Ga generated in the second treatment tank 3 and connects this gas collection unit 8 to the gas reservoir 7. It also includes an outside air supply device 9 that is driven by a solar power generation device 10 and supplies outside air Gb as gas to the gas reservoir 7. This allows the air lift pump 11 to be operated using only natural energy, without using any electrical energy generated using fossil fuels, as is the case with conventional blowers. Furthermore, by providing both the gas collection unit 8 and the outside air supply device 9, it is possible to supply a sufficient amount of gas Gb to the gas reservoir 7 to operate the air lift pump 11 over a constant period, even when the amount of gas Ga generated in the second treatment tank 3 is small. As described above, the decarbonization septic tank 1 according to this embodiment can consistently provide excellent cleaning effects while contributing to the suppression of greenhouse gases such as carbon dioxide.

Although one embodiment of the present invention has been described above, the decarbonization type septic tank according to the present invention can also have configurations other than those described above as long as they do not deviate from the spirit of the invention.
In the above embodiment, a solar power generation device 10 is exemplified, but the present invention is not limited to solar power generation as long as the device generates electricity using renewable energy, and may be, for example, a power generation device that uses other renewable energy that does not generate carbon dioxide, such as wind power, geothermal power, hydropower, biomass, etc.

For example, in the above embodiment, the opening 19a of the first flow pipe 19, which serves as the gas inlet for the air lift pump 11, is positioned within the gas reservoir 7, but this is of course not limited to this. For example, although not shown, the opening 19a of the first flow pipe 19 may be directly connected to the connecting pipe 18, allowing the gas Ga collected in the gas collection unit 8 to flow into the first flow pipe 19. In this case, the gas reservoir 7 is composed of the first flow pipe 19 and the connecting pipe 18. Furthermore, although not shown, an outside air supply pipe 24 may be connected to the connecting pipe 18 or the first flow pipe 19, allowing outside air Gb to be sent directly into the first flow pipe 19. In any case, the air lift pump 11 and the gas reservoir 7 can be configured as desired, as long as they can be cleaned by operating the air lift pump 11 when the gas Ga, Gb stored in the gas reservoir 7 reaches a predetermined amount and the pressure balance between the stored gas Ga, Gb and the treated water W is disrupted, thereby generating a flow of treated water W in the anaerobic treatment tank as the water level in the gas reservoir 7 rises.

In addition, while the above embodiment illustrates a case in which the gas collection unit 8 is disposed only above the filter carrier 6a in the second treatment tank 3, other configurations are of course possible. For example, although not shown, the gas collection unit 8 may be disposed above the filter carriers 6a and 6b housed inside two or more of the treatment tanks 2 to 4, and the gas Ga generated in the filter carrier 6a and 6b housing area of each treatment tank 2 to 4 may be collected and sent to the gas reservoir 7.

Of course, even if the treatment tank is not an anaerobic treatment tank, if sediment S accumulates at the bottom due to various purification processes, gas Ga may be generated from the accumulated sediment S, so the gas collection section 8 may be installed in a treatment tank other than an anaerobic treatment tank.

In addition, while the above explanation illustrates an example in which three treatment tanks 2-4 are provided in the decarbonization septic tank 1, two or four or more treatment tanks may of course be provided. Furthermore, one or more of these treatment tanks may be treatment tanks other than anaerobic treatment tanks. Furthermore, the direction in which treated water flows in each of these multiple treatment tanks may be configured to be different from that shown in the illustrated example.

Furthermore, the air lift pump 11 is not limited to the above embodiment. For example, an inlet pipe 23 can be connected to the second flow pipe 20 as shown in Figure 8, or the inlet pipe 23 can be formed by extending the lower part of the second flow pipe 20 as shown in Figure 9.

1 Decarbonization type septic tank 2 First treatment tank 3 Second treatment tank 4 Third treatment tank 5 Cleaning device 6a, 6b Filter carrier 7 Gas accumulation section 8 Gas collection section 9 Outside air supply device 10 Solar power generation device 11 Air lift pump 13, 16 Partition wall 14 Inlet 15a, 15b, 16a, 16b Regulating section 17 Discharge port 18 Connecting pipe 19 First circulation pipe 19a Opening 20 Second circulation pipe 21 Connecting pipe 22 Return pipe 23 Intake pipe 24 Outside air supply pipe Ga Gas Gb Outside air S Sediment W Treated water

Claims (1)

a plurality of treatment tanks including at least one anaerobic treatment tank in which a filter carrier is housed;
a cleaning device that cleans the filter carrier in the anaerobic treatment tank,
The cleaning device is
a gas reservoir capable of storing gas;
a gas collecting section connected to the gas reservoir section and configured to collect, at an upper portion thereof, gas generated in at least one of the plurality of treatment tanks;
an outside air supply device that is driven by electricity generated using renewable energy and supplies outside air as gas to the gas reservoir;
and an air lift pump that is driven by the gas stored in the gas reservoir and is configured to return the treated water inside a treatment tank located downstream of the plurality of treatment tanks to a treatment tank located upstream, wherein when the gas stored in the gas reservoir reaches a predetermined amount and the pressure balance between the stored gas and the treated water is disrupted, the air lift pump is activated to generate a flow of the treated water in the anaerobic treatment tank as the water level rises in the gas reservoir, thereby making it possible to clean the filter carrier.