Method for detecting sludge layer and sludge layer detection device

Abstract

To provide a method for detecting a sludge layer capable of easily and inexpensively detecting the height of the interface between a sludge layer formed on the bottom of a storage tank and water.SOLUTION: There is provided a method for detecting a first interface S1 by using a first float 3 with specific gravity adjusted so as to be positioned at the first interface S1 between a sludge layer L1 and a water layer L2 on the bottom part of a storage tank 100 in the storage tank 100 storing processing target water, the method including the steps of holding the first float 3 in water at a higher level than the first interface S1 and detecting the height of the first float 3 after the first float 3 has dropped to the first interface S1 and stopped by cancelling the holding of the first float 3.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for detecting a sludge layer. [Background technology]

[0002] Wastewater such as domestic wastewater is treated before being released into rivers, etc. Conventional treatment is carried out at designated regional wastewater treatment facilities, agricultural village wastewater treatment facilities, community plants, etc. However, as these facilities have become obsolete, conversion to septic tanks has recently been considered, and cases of installing small septic tanks in detached houses, apartment buildings, etc. are increasing.

[0003] When wastewater flows into a septic tank, the sludge settles in the separation tank and the scum rises to the surface, and after they are separated, they are transferred to the aeration tank. However, if the height of the sludge layer accumulated at the bottom of the separation tank exceeds a certain height, there is a risk that the sludge will flow into the aeration tank, so regular inspections of the septic tank by a septic tank manager are necessary. However, while the demand for septic tank managers is increasing with the shift from sewerage to septic tanks, there is an overwhelming shortage of such managers, and therefore reducing the workload of septic tank managers through measures such as remote monitoring has become an urgent issue.

[0004] Patent Document 1 discloses a device for monitoring the water level at the interface between two layers with different specific gravities, which includes a support shaft suspended within a fuel tank, a float that can move up and down along the support shaft, and a detector that detects the axial position of the float relative to the support shaft. This device sets the specific gravity of the float so that it is located at the interface between fuel and water in the fuel tank, and can grasp the water level at the interface through detection by the detector. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-1748 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when attempting to use the float-type detector disclosed in Patent Document 1 above to detect the sludge layer interface in a septic tank, there is a problem in that as the sludge flows in and increases, the sludge may adhere to and accumulate on the float floating on the interface, causing the float to become buried in the sludge layer without floating up, making it difficult to detect the sludge layer interface.

[0007] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a sludge layer detection method and device that can easily and inexpensively detect the interface height between the sludge layer formed at the bottom of a storage tank and water. [Means for solving the problem]

[0008] The above-mentioned object of the present invention is achieved by a method for detecting a first interface, which is the interface between a sludge layer formed at the bottom of a storage tank for storing water to be treated, using a first float whose specific gravity is adjusted to be positioned at the height of the first interface, which is the interface between the sludge layer and water, in a storage tank for storing water to be treated, the method comprising the steps of: holding the first float in water above the first interface; and detecting the height of the first float, which has fallen to the first interface and stopped there by releasing the holding of the first float.

[0009] In this sludge layer detection method, the specific gravity ρ1 of the first float is preferably set to satisfy the relationship 1.0<ρ1<1.1.

[0010] The primary float preferably has a tapered portion tapered upward.

[0011] The sludge layer detection method of the present invention can further include a step of holding a second float, the specific gravity of which is adjusted so that it is positioned at the height of a second interface, which is the interface between the water and a scum layer formed on the water surface side of the treated water stored in the storage tank, in water below the second interface, and a step of detecting the height of the second float, which has risen to the second interface and stopped there by releasing the holding of the second float.

[0012] Furthermore, the above-mentioned object of the present invention is achieved by a device for detecting a first interface, which is the interface between a sludge layer formed at the bottom of a storage tank for storing water to be treated, using a first float whose specific gravity is adjusted to be positioned at the height of the first interface, which is the interface between the sludge layer and water, and which is equipped with a first holding mechanism that holds the first float in water above the first interface in a manner that allows it to be released from the hold. [Effects of the Invention]

[0013] According to the sludge layer detection method and device of the present invention, the interface height between the sludge layer formed at the bottom of the storage tank and water can be detected easily and inexpensively. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a diagram for explaining the detection principle of a sludge layer detection method according to an embodiment of the present invention. FIG. [Figure 2] 1 is a perspective view showing a main part of a sludge layer detection device used in a sludge layer detection method according to one embodiment of the present invention. [Figure 3] 3 is a perspective view showing another main part of the sludge layer detection device shown in FIG. 2. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a diagram for explaining the detection principle of a sludge layer detection method according to one embodiment of the present invention. The sludge layer detection method of this embodiment detects the interfaces S1 and S2 of each layer of water to be treated that is supplied to a storage tank and separated into three layers L1, L2, and L3 based on differences in specific gravity.

[0016] As shown in FIG. 1(a), the storage tank of this embodiment is a separation tank 100 provided in a small septic tank installed in a detached house or the like, and sewage S, such as domestic wastewater, is supplied as the water to be treated. When the sewage S is supplied to the separation tank 100, the solids contained in the sewage S settle, forming a sludge layer L1 at the bottom of the separation tank 100. Furthermore, some of the sludge forming the sludge layer L1 floats due to the adhesion of putrefactive gases, etc., and a scum layer L3 forms on the liquid surface side within the separation tank 100. In this way, a water layer L2 consisting of the remaining water is formed between the sludge layer L1 and the scum layer L3. The water forming the water layer L2 is discharged via a discharge port 101 toward an aeration tank (not shown).

[0017] The height H1 of the discharge section 101 in the separation tank 100 is set to match the height of the water layer L2 so that the water in the water layer L2 can be supplied to the aeration tank, but if the amount of sludge accumulation increases and the height of the sludge layer L1 becomes too high, there is a risk that the sludge will be mixed into the water supplied to the aeration tank, and therefore it becomes necessary to discharge the sludge from the separation tank 100. The sludge layer detection method of this embodiment periodically detects the height of the sludge layer L1 using the sludge layer detection device 1, thereby reducing the inspection burden on the manager and suppressing the outflow of sludge into the aeration tank.

[0018] The sludge layer detection device 1 includes a first float 3 and a second float 4 that are guided in the vertical direction by a guide tube 2 that stands upright from the bottom of the separation tank 100 .

[0019] The first float 3 is disposed below the second float 4, and its specific gravity is adjusted so that it is located at the height of the first interface S1, which is the interface between the sludge layer L1 and the water layer L2. The specific gravity ρ1 of the first float 3 is preferably set to be smaller than that of the sludge near the first interface S1 of the sludge layer L1 and larger than the specific gravity of the water in the water layer L2, and more specifically, is preferably set to be 1.0<ρ1<1.1.

[0020] The specific gravity of the second float 4 is adjusted so that it is located at the height of the second interface S2, which is the interface between the water layer L2 and the scum layer S3. The specific gravity ρ2 of the second float 4 is preferably set so that it is greater than the specific gravity of the scum near the second interface S2 of the scum layer L3 and less than the specific gravity of the water in the water layer L2, specifically, so that 0.9<ρ2<1.0 is satisfied.

[0021] The sludge layer detection method of this embodiment includes the steps of: (a) holding a first float 3 in water above the first interface S1 when not performing measurement; and (b) detecting the height of the first float 3, which has dropped to the first interface S1 and stopped there, by releasing the first float 3 during measurement, as shown in FIG. 1(b). The holding height H2 of the first float 3 (the height from the bottom of the separation tank 100 to the underside of the first float 3) need only be higher than the maximum height H3 of the first interface S1, which may vary. In this way, the first float 3 is held at a height H2 at which sludge does not adhere or accumulate during normal times when no measurement event is taking place, and then the first float 3 is released from its holding position and allowed to drop through the water layer L2 during measurement. This ensures that the first float 3 stops at the first interface S1, and therefore the height H3 of the first interface S1 can be easily and reliably detected by detecting the height of the first float 3. Furthermore, by always keeping the first float 3 in the less polluted water layer L2, it is possible to expect an effect of extending the maintenance cycle.

[0022] When a scum layer L3 is formed above the water layer L2, the retention height H2 of the first float 3 is preferably set below the second interface S2, thereby preventing not only sludge but also scum from adhering to and accumulating on the first float 3.

[0023] The shape of the first float 3 is not necessarily limited, but by providing the first float 3 with a tapered portion tapered upward, it is possible to more reliably prevent the adhesion and accumulation of solid matter such as sludge on the first float 3. In this embodiment, the tapered portion is formed in a truncated cone shape, but it may also be conical, pyramidal, truncated pyramidal, or the like. The second float 4 also has a shape similar to that of the first float 3, tapering downward.

[0024] The sludge layer detection method of this embodiment can further include the steps of holding the second float 4 in water below the second interface S2 as shown in Figure 1(a), and detecting the height of the second float 4 that has risen (floated) to the second interface S2 and stopped there by releasing the holding of the second float 4 as shown in Figure 1(b). This makes it possible to easily and reliably detect not only the height H3 of the first interface S1 but also the height H4 of the second interface S2. The holding height H5 of the second float 4 (the height from the bottom of the separation tank 100 to the upper surface of the second float 4) need only be lower than the lowest height H4 of the second interface S2, which may vary.

[0025] Preferably, the sludge layer detection device 1 automatically holds the first and second floats 3 and 4 at a predetermined height and detects the heights of the first and second floats 3 and 4 after the hold is released. Remote monitoring via a communication line allows efficient detection of the sludge layer. Figures 2 and 3 are perspective views showing an example of such a sludge layer detection device 1. Holding the first and second floats 3 and 4 at a predetermined height can also be performed manually, and the heights of the first and second floats 3 and 4 after the hold is released can also be read visually.

[0026] As shown in Figure 2, the sludge layer detection device 1 has a guide tube 2 that extends vertically upward from a base 10 placed on the bottom of the separation tank and is inserted into the hollow portions of the first float 3 and the second float 4. The top of the first float 3 and the bottom of the second float 4 each have a tapered portion in the shape of a truncated cone.

[0027] This sludge layer detection device 1 has a configuration similar to that of a magnetic float type level gauge such as the liquid level detector disclosed in Patent Document 1, and has magnets built into the first float 3 and the second float 4, and can output the respective heights of the first float 3 and the second float 4 as electrical signals through the operation of a plurality of reed switches provided at regular intervals inside the guide tube 2. The sludge layer detection device 1 is not limited to a magnetic float type configuration, and can also adopt other float type level gauge configurations, such as a spring balance type, counterweight type, or arm float type.

[0028] The sludge layer detection device 1 further includes a first holding mechanism 20 that releasably holds the first float 3 in the water above the first interface S1 (see Figure 1), and a second holding mechanism 30 that releasably holds the second float 4 in the water below the second interface S2 (see Figure 1).

[0029] The first holding mechanism 20 includes a linear body 21 and a tension pulley 22 that is supported by the base 10 and maintains the tension of the linear body 21. The first float 3 and the second float 4 are formed with a plurality of through-holes 3a, 4a that penetrate vertically and through which the linear body 21 is inserted so as to be movable relative to one another. The linear body 21 is made of, for example, a high-strength, non-stretchable thread or wire, and is inserted from above into the through-holes 4a, 3a of the second float 4 and the first float 3 in this order, then folded back at the tension pulley 22 via a guide portion 23, and then inserted from below into the other through-holes 3a, 4a of the first float 3 and the second float 4 in this order via a guide portion 24. A locking portion 25 having a larger diameter than the through hole 3a is fixed to the portion of the linear body 21 located between the first float 3 and the guide portion 24, and by pulling up one end side 21a of the linear body 21 and pulling down the other end side 21b, the locking portion 25 rises and engages with the lower peripheral portion of the through hole 3a.

[0030] The first holding mechanism 20 having the above-described configuration can raise and hold the first float 3 together with the locking portion 25 to a predetermined height in the water layer L2 (see FIG. 1) by lifting up one end side 21a of the linear body 21. During measurement, the other end side 21b of the linear body 21 is lifted up to pull the locking portion 25 below the first interface S1 (see FIG. 1), releasing the hold on the first float 3, and the first float 3 is dropped to the first interface S1, thereby detecting the height of the first float 3 located at the first interface S1.

[0031] Similar to the first holding mechanism 20, the second holding mechanism 30 includes a linear body 31 and a tension pulley 32. The linear body 31 is inserted from above through the through holes 4a, 3a of the second float 4 and the first float 3, in that order, then bent back by the tension pulley 32 via a guide portion 33, and then inserted from below through the other through holes 3a, 4a of the first float 3 and the second float 4, in that order, via a guide portion 34. A locking portion 35 having a larger diameter than the through hole 4a is fixed to the other end 31b of the linear body 31 located above the second float 4. By pulling up the one end 31a of the linear body 31 and pulling down the other end 31b, the locking portion 35 descends and engages with the upper peripheral portion of the through hole 4a of the second float 4, and the second float 4 can be pulled down together with the locking portion 35.

[0032] As with the first holding mechanism 20, the second holding mechanism 30 can also hold the second float 4 together with the locking portion 35 at a predetermined height in the water layer L2 (see FIG. 1) by lifting up one end 31a of the linear body 31. During measurement, the other end 31b of the linear body 31 is lifted up to raise the locking portion 35 above the second interface S2 (see FIG. 1), releasing the hold on the second float 4, and the second float 4 is raised up to the second interface S2, thereby detecting the height of the second float 4 located at the second interface S2.

[0033] The operation of lifting each of linear bodies 21, 31 can be performed by drive device 40 shown in Fig. 3. As shown in Fig. 3, drive device 40 is configured such that motor 42, reduction gear 43, worm gear 44, and winding drum 45 are supported on base 41, and the driving force of motor 42 is transmitted to winding drum 45 via reduction gear 43 and worm gear 44 through gear meshing, thereby driving winding drum 45 to rotate in both forward and reverse directions around rotating shaft 46.

[0034] Winding drum 45 is provided with winding sections 47, 48 on both longitudinal sides of rotating shaft 46, around which linear bodies 21, 31 are wound, and winding force acts in a balanced manner on rotating shaft 46, thereby enabling a compact configuration and reliable operation of linear bodies 21, 31. One winding section 47 is provided with two storage sections 47a, 47b that respectively wind one end 21a and the other end 21b of linear body 21, and when rotating shaft 46 rotates in the direction indicated by the arrow, one end 21a of linear body 21 is wound into storage section 47a, and the other end 21b of linear body 21 is unwound from storage section 47b. When rotating shaft 46 rotates in the opposite direction to the direction indicated by the arrow, one end 21a of linear body 21 is unwound from storage section 47a, and the other end 21b of linear body 21 is wound into storage section 47b.

[0035] The other winding section 48 has two storage sections 48a, 48b, similar to the one winding section 47, and when the rotating shaft 46 rotates in the direction indicated by the arrow, one end side 31a of the linear body 31 is wound into storage section 48a, and the other end side 31b of the linear body 31 is paid out from storage section 48b. When the rotating shaft 46 rotates in the direction opposite to the direction indicated by the arrow, one end side 31a of the linear body 31 is paid out from storage section 48a, and the other end side 31b of the linear body 31 is wound into storage section 48b.

[0036] The first holding mechanism 20 is not necessarily limited to the configuration of this embodiment, as long as it can releasably hold the first float 3 in the water above the first interface S1. For example, the first holding mechanism 20 may be configured so that a gripping portion that detachably holds the first float 3 can be moved up and down by a linear actuator. The second holding mechanism 30 may also have another configuration as long as it can releasably hold the second float 4 in the water below the second interface S2.

[0037] The sludge layer detection device of this embodiment is equipped with a first holding mechanism 20 and a second holding mechanism 30, and is therefore capable of detecting both the sludge layer L1 and the scum layer L3, but if only the sludge layer L1 is to be detected, the device may be configured to be equipped with only the first holding mechanism 20.

[0038] As described above, the sludge layer detection method and device of the present invention can be suitably used in the separation tank of a septic tank, but can also be used in other tanks in the septic tank where sludge may accumulate. For example, by using the method and device in a settling tank that settles fine sludge particles contained in secondary effluent after aeration treatment (secondary treatment) of wastewater from a separation tank, it is possible to prevent sludge from leaking from the settling tank into a disinfection chamber. Alternatively, by using the method and device in a sludge thickening tank that thickens sludge transferred from the bottom of the settling tank or separation tank by gravity, it is possible to determine the time to remove sludge from the sludge thickening tank.

[0039] In addition, the sludge layer detection method and device of the present invention can be used in places other than septic tanks, and can be applied to various applications such as detecting the interface between the sludge layer and water formed at the bottom of a storage tank that stores water to be treated, such as a dam storage tank or a heat treatment tank. [Explanation of symbols]

[0040] 1. Sludge layer detection device 2 Guide tube 3. First Float 4. Second Float 20 First retention mechanism 30 Second retention mechanism 100 Separation tank (storage tank) L1 sludge layer L2 water layer L3 scum layer S1 1st interface S2 2nd interface

Claims

1. A method for detecting a first interface, which is an interface between a sludge layer formed at the bottom of a storage tank that stores water to be treated, using a first float whose specific gravity is adjusted to be located at the height of the first interface, which is an interface between the water and the sludge layer formed at the bottom of the storage tank, maintaining the first float in the water above the first interface; and detecting the height of the first float which has fallen to the first interface and stopped there by releasing the hold on the first float.

2. 2. The sludge layer detecting method according to claim 1, wherein the specific gravity ρ1 of the first float is set to satisfy the relationship 1.0<ρ1<1.

1.

3. The sludge layer detection method according to claim 1 , wherein the first float has a tapered portion that tapers upward.

4. The sludge layer detection method described in claim 1 further comprises the steps of: holding a second float, the specific gravity of which is adjusted so that it is positioned at the height of a second interface, which is the interface between the water and a scum layer formed on the water surface side of the treated water stored in the storage tank, in water below the second interface; and detecting the height of the second float, which has risen to the second interface and stopped there by releasing the holding of the second float.

5. A device for detecting a first interface, which is an interface between a sludge layer formed at the bottom of a storage tank that stores water to be treated, using a first float whose specific gravity is adjusted to be located at the height of the first interface, which is an interface between the water and the sludge layer formed at the bottom of the storage tank, A sludge layer detection device including a first holding mechanism that releasably holds the first float in water above the first interface.

Images