Method for treating asbestos-contaminated water

Abstract

To provide a method for efficiently treating turbid asbestos-contaminated water.SOLUTION: There is provided a method for treating asbestos-contaminated water by separating asbestos-contaminated water W1 containing asbestos peeled from a structure into dischargeable water and sludge, the method including a process in which asbestos-contaminated water W1 generated in a process of removing asbestos from a structure is sent to a reaction tank 4 in a unit amount for reaction treatment, and is left in the reaction tank 4 for a predetermined treatment time to allow solids in the asbestos-contaminated water to coagulate and settle, then, an entire amount of supernatant liquid W2 in the reaction tank 4 is sent to a relay tank 5 having a larger capacity than the reaction tank 4, and each time the transfer of the supernatant liquid to the relay tank 5 is completed, a precipitate SL in the reaction tank 4 is sent to a sludge recovery container 9, and the supernatant liquid W2 stored in the relay tank 5 is pressure-fed to a dehydrator 6, where a primary filtrate W3 is squeezed out.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for treating turbid asbestos-contaminated water. [Background technology]

[0002] In the past, to prevent asbestos from scattering during the demolition of structures containing asbestos, wet treatment was carried out by using ultra-high water pressure to remove the asbestos from the structure and recovering the treated water containing asbestos. This wet treatment produces a large amount of turbid asbestos-containing water. However, asbestos must be strictly controlled, so asbestos-containing water generated during demolition work must be separated into dischargeable water and sludge, and the sludge must be disposed of as industrial waste. In addition, in order to separate the water that can be discharged from the turbid asbestos water, the turbid asbestos water was filtered using a filtration device equipped with a filter with fine mesh of 1 μm or less (hereinafter referred to as a "fine filter"). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-209324 [Patent Document 2] Patent No. 6542940 Summary of the Invention [Problem to be solved by the invention]

[0004] When filtering turbid asbestos-contaminated water, the fine filters quickly become clogged, which means the filtration equipment must be replaced frequently, resulting in time-consuming and costly filtering operations. Furthermore, if the system continued to be used with a clogged fine filter, there was a risk that the fine filter would not be able to process the asbestos-containing water and the overflowing water would be discharged as is. An object of the present invention is to provide a method for treating turbid asbestos-contaminated water which is easy to work with and reliable. [Means for solving the problem]

[0005] The first invention is a method for treating asbestos-contaminated water, which contains asbestos stripped from a structure and is separated into dischargeable water and sludge. The method comprises the steps of: sending the asbestos-contaminated water generated in the process of stripping asbestos from the structure to a reaction tank in a unit amount for reaction treatment; leaving the water in the reaction tank for a predetermined treatment time to allow solids in the asbestos-contaminated water to coagulate and settle; and then sending the entire supernatant liquid from the reaction tank to a relay tank having a larger capacity than the reaction tank; and sending the sediment in the reaction tank to a sludge collection container each time the supernatant liquid is transported to the relay tank is completed; and pressurizing the supernatant liquid stored in the relay tank to a dehydrator, which squeezes out a primary filtrate.

[0006] The second invention comprises a solid-liquid separation means for separating large solids from the asbestos-contaminated water, and the asbestos-contaminated water after separation of the large solids by this solid-liquid separation means is sent to the reaction tank.

[0007] In the third aspect of the present invention, the supernatant liquid generated in the sludge collection vessel is sent to the reaction tank.

[0008] In a fourth aspect of the present invention, the residue from the dehydrator is collected in a collection vessel separate from the sludge collection vessel. [Effects of the Invention]

[0009] In this invention, a relay tank having a larger capacity than the reaction tank is provided between the reaction tank and the dehydrator, so that even if the processing capacity of the dehydrator is low, the reaction tank can be emptied and reaction processing in the reaction tank can be carried out continuously. Furthermore, even when the primary filtrate squeezed out by the dehydrator is sent to a fine filter, the fine filter is less likely to clog, and the number of times the filter needs to be replaced can be significantly reduced compared to when the turbid asbestos-contaminated water recovered from a structure is sent directly to the fine filter. Therefore, according to the present invention, it is possible to continuously treat asbestos-contaminated water and separate it into dischargeable water and sludge, thereby improving the workability of the asbestos-contaminated water treatment work and reducing costs.

[0010] According to the second invention, large solids in the asbestos-contaminated water are separated before being sent to the reaction tank, so that the coagulant, for example, does not adhere to the large solids, functions effectively, and coagulation and sedimentation can be carried out efficiently in the reaction tank.

[0011] According to the third aspect of the present invention, the volume of sludge in the sludge collection container can be reduced by reprocessing the water that has been collected once in the sludge collection container and separating the dischargeable water, thereby reducing the volume of waste and lowering its disposal costs.

[0012] According to the fourth invention, the volume of sludge to be disposed of can be efficiently reduced. The residue from the dehydrator originally has a low water content, but if it is mixed with the sludge recovered from the reaction tank, moisture will be added to the residue. However, if the residue from the dehydrator and the sludge recovered from the reaction tank are recovered separately, as in this invention, the volume of the sludge to be ultimately disposed of can be efficiently reduced. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram of a system for implementing an embodiment of the present invention. [Figure 2] 1 is a flow chart of a process according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] (Embodiment) An embodiment of the present invention will be described below. Fig. 1 is a schematic diagram of a system for treating asbestos-contaminated water according to this embodiment. Fig. 2 is a flow chart of the treatment according to this embodiment. In this embodiment, asbestos-containing wall materials are stripped from a structure, and the asbestos-contaminated water generated during the process is separated into dischargeable water and asbestos-containing sludge.

[0015] The system of the embodiment shown in Figure 1 comprises an ultra-high pressure washer 1 that sprays ultra-high pressure water to clean asbestos-containing surfaces to be treated, and a dumper vehicle 2 that collects and stores asbestos-contaminated water W1 that contains asbestos-containing material peeled off by the ultra-high pressure washing water from the ultra-high pressure washer 1. In addition, in the order of steps for treating the asbestos-contaminated water W1, a solid-liquid separation means 3, a reaction tank 4, a relay tank 5, a dehydrator 6, and a fine filter (filtration device) 7 are arranged, as well as a suction device 8 and a sludge collection container 9.

[0016] The solid-liquid separation means 3 is a cage-shaped member installed in the path that transports the asbestos-contaminated water W1 from the damper vehicle 2 to the reaction tank 4. This solid-liquid separation means 3 separates and recovers large solids, such as concrete shavings, in the asbestos-contaminated water W1 transported from the damper vehicle 2.

[0017] The reaction tank 4 is a tank that receives one unit of reaction treatment of asbestos-containing turbid water W1, from which large solids have been removed by solid-liquid separation means 3, and leaves it for a predetermined time to coagulate and settle asbestos-containing sludge SL. A coagulant such as polyaluminum chloride (PAC) is added to the reaction tank 4 to coagulate the fine particles in the asbestos-containing water and facilitate settling. The reaction tank 4 is also equipped with an agitator 4a. One unit of reaction treatment is an amount that corresponds to the capacity of the reaction tank 4.

[0018] The relay tank 5 is a tank for storing the supernatant liquid W2 sent from the reaction tank 4 after the treatment in the reaction tank 4 is completed. The capacity of the relay tank 5 is set to be sufficiently larger than the capacity of the reaction tank 4.

[0019] The dehydrator 6 is connected to the relay tank 5 via a liquid pressure-transfer means (not shown) and is a device that squeezes water out of the supernatant liquid W2 that has been pumped from the relay tank 5. Specifically, the dehydrator 6 has branched flow paths formed therein, each of which is provided with a filtration chamber, and the supernatant liquid W2 flowing in from each flow path is filtered using the filter material provided in each chamber. During this process, pressure is applied to the supernatant liquid W2 as it passes through the filter material provided in each chamber, so that the water in the supernatant liquid W2 is sufficiently squeezed out. In this dehydrator 6, the filter material is removable from the dehydrator 6, and residue can be collected from the removed filter material, which can then be washed.

[0020] The fine filter 7 is a filter capable of capturing particles of a few μm or less, and is a device that filters the primary filtrate W3 squeezed out by the dehydrator 6 and discharges the secondary filtrate W4 as dischargeable water. The drain outlet of the dehydrator 6 is connected to the fine filter 7 via a pipe, so that the primary filtrate W3 discharged from the dehydrator 6 is automatically supplied to the fine filter 7. The suction device 8 is a device for sucking sludge SL, which is sediment accumulated at the bottom of the reaction tank 4, and transferring it to a sludge recovery container 9. The sludge collection container 9 is a drum or the like, and is a container for collecting sludge SL containing asbestos to be disposed of as industrial waste.

[0021] (Actions, effects, etc.) The procedure for treating asbestos-contaminated water in this embodiment will be described with reference to FIG. First, a worker cleans the surface to be treated with the ultra-high pressure washer 1, while sucking up the turbid asbestos water that is generated (step S1), and storing it in a dumper truck (step S2). These steps S1 and S2 can be carried out continuously until the capacity of the dumper truck 2 is filled with the turbid asbestos water W1. However, this may be temporarily interrupted once the dumper truck 2 has stored one unit of the turbid asbestos water W1 for reaction treatment in the reaction tank 4 or more.

[0022] After the asbestos-contaminated water W1 is stored in the dumper truck 2, in step S3, the worker operates the liquid transport means to transport the asbestos-contaminated water W1 to one unit of reaction treatment in the reaction tank 4, here, approximately 4 [m] depending on the capacity of the reaction tank 4. 3 ] is sent to the reaction tank 4. The asbestos-contaminated water W1 from which large solids have been removed by the solid-liquid separation means 3 is sent to the reaction tank 4.

[0023] In step S4, a coagulant such as polyaluminum chloride (PAC) is added to the reaction vessel 4, stirred and dissolved by the stirring device 4a, and then left for a predetermined time to coagulate and settle the fine particles. The treatment time required in the reaction vessel 4 varies depending on the solid concentration and the volume, but it is assumed that the standard concentration of asbestos-contaminated water W1 is approximately 4 [m 3 ], leave it for 5 to 10 minutes. After a predetermined processing time has elapsed, in step S5, the operator operates the water conveying means to send the supernatant liquid W2 from the reaction tank 4 to the relay tank 5. When the entire amount of the supernatant liquid W2 has been sent to the relay tank 5, the process proceeds to step S6.

[0024] In step S6, the worker uses the suction device 8 to suck up the sludge SL, which is the sediment that has accumulated at the bottom of the reaction tank 4, and transfers it to a sludge collection container 9 such as a drum. Once all the sludge SL has been transferred to the sludge collection container 9 and the reaction tank 4 is empty, the process returns to step S3, and the asbestos-contaminated water W1 is sent from the dumper truck 2 to the reaction tank 4 again. The processes from step S3 to step S6 are repeated until the asbestos-contaminated water W1 stored in the dumper truck 2 is empty.

[0025] On the other hand, when the supernatant liquid W2 of the reaction tank 4 is sent to the relay tank 5 in the above step S5, the relay tank 5 receives the supernatant liquid W2 (step S7). In other words, step S5 and step S7 are performed at almost the same time. Once the supernatant liquid W2 has been stored in the relay tank 5, in step S8, the worker activates the pressure-transfer means to pressure-transfer the supernatant liquid W2 to the dehydrator 6. At this time, the worker can also activate the pressure-transfer means to pressure-transfer the supernatant liquid W2 to the dehydrator 6 at the time when storage of the supernatant liquid W2 in the relay tank 5 begins. In step S9, the sent supernatant liquid W2 is filtered in the dehydrator 6, and the primary filtrate W3 is sent to the fine filter 7. In step S10, the secondary filtrate W4 that has been filtered through the fine filter 7 and discharged is discharged.

[0026] Steps S7 to S10 are continued until the supernatant liquid W2 stored in the relay tank 5 is depleted. Furthermore, if the sludge collection container 9 containing the collected sludge SL is left as it is, a supernatant liquid W5 will seep out. This supernatant liquid W5 is returned to the reaction tank 4 and coagulated and precipitated together with the asbestos-contaminated water W1 in step S4.

[0027] By performing the above steps S1 to S10, the asbestos-contaminated water can be separated into secondary filtrate W4, which is dischargeable water, and sludge SL. The residue from the dehydrator 6 has had the water sufficiently squeezed out, so it is collected in a collection container (for example, a burlap bag) separate from the sludge collection container 9 and disposed of.

[0028] In this embodiment, a relay tank 5 is provided between the reaction tank 4 and the dehydrator 6. This allows the supernatant liquid W2 to be sent from the reaction tank 4 to the relay tank 5, and while the dehydrator 6 is starting the dehydration process, the reaction tank 4 can also start the coagulation and precipitation process of the newly sent asbestos-contaminated water W1. If the relay tank 5 were not provided, the supernatant liquid W2 would have to be sent directly from the reaction tank 4 to the dehydrator 6, and the supernatant liquid W2 would remain in the reaction tank 4 while the dehydrator 6 is performing the dehydration process. Therefore, the dehydration process in the dehydrator 6 and the reaction process in the reaction tank 4 cannot be performed simultaneously. In contrast, by providing the relay tank 5 between the reaction tank 4 and the dehydrator 6, the dehydration process in the dehydrator 6 and the reaction process in the reaction tank 4 can be performed simultaneously.

[0029] In particular, when the processing capacity of the dehydrator 6 is low, that processing capacity becomes a bottleneck, significantly affecting the upstream processes such as reaction treatment, etc. In response to this, by providing the relay tank 5 between the reaction tank 4 and the dehydrator 6, even when the processing capacity of the dehydrator 6 is low, the impact on the upstream processes such as reaction treatment can be suppressed.

[0030] Furthermore, because the capacity of the relay tank 5 is larger than the capacity of the reaction tank 4, even if the processing capacity of the dehydrator 6 is low and supernatant liquid W2 remains in the relay tank 5, new supernatant liquid W2 can be sent from the reaction tank 4 to the relay tank 5. Then, each time the transport of supernatant liquid W2 is completed, sludge SL can be recovered from the reaction tank 4. Therefore, regardless of the progress of the processing in the dehydrator 6, once the reaction processing is completed, the reaction tank 4 can be emptied and the asbestos-contaminated water W1 can be sent to the reaction tank 4 again, and the reaction processing of coagulation and sedimentation can be carried out continuously.

[0031] As described above, in this embodiment, the processing of steps S3 to S6 and the processing of steps S7 to S10 in FIG. 2 are executed in parallel, thereby improving the overall processing efficiency. Furthermore, since the fine filter 7 is supplied with the primary filtrate W3 squeezed out by the dehydrator 6, the fine filter 7 is less likely to clog, and the number of times the filter needs to be replaced can be significantly reduced compared to when, for example, the asbestos-contaminated water W1 is sent directly to the fine filter 7. This not only improves the workability of the processing work but also reduces the cost of the filters.

[0032] Although the solid-liquid separation means 3 is not essential, in this embodiment, the solid-liquid separation means 3 separates large solids from the asbestos-contaminated water W1 before sending it to the reaction tank 4. Therefore, in this embodiment, for example, the flocculant does not adhere to the large solids, functions effectively, and flocculation and sedimentation in the reaction tank 4 is also carried out efficiently.

[0033] Furthermore, by returning the water (supernatant W5) in the sludge collection container 9 from which the sludge SL has been collected back to the reaction tank 4, the water content in the sludge collection container 9 can be reduced and the proportion of solids in the sludge collected in the sludge collection container 9 can be increased. Furthermore, the water in the sludge collection container 9 can be subjected to a reaction treatment again to separate it into coagulated and settled sludge and dischargeable water.

[0034] Furthermore, if the residue from the dehydrator 6, which originally has a low water content, is mixed with the sludge SL recovered from the reaction tank 4, moisture will be added to the residue. However, in this embodiment, the residue from the dehydrator 6 is recovered separately from the sludge recovery container 9, so that the volume of the waste can be efficiently reduced by reducing the moisture content.

[0035] The cost of disposing of industrial waste depends on the volume of sludge and the number of sludge collection containers, but in this embodiment, the water can be sufficiently separated from asbestos-containing sludge, thereby reducing disposal costs. For example, when sludge containing a lot of water is collected, a large number of drums serving as collection containers are required, but if the water content of the sludge is reduced as much as possible, fewer drums (sludge collection containers) are required, resulting in a significant difference in disposal costs. In this embodiment, it is possible to dispose of drums containing sludge from which as much water as possible has been removed, thereby significantly reducing disposal costs compared to conventional methods. [Industrial Applicability]

[0036] It is useful at demolition sites where asbestos-containing structures are used. [Explanation of symbols]

[0037] 3 Solid-liquid separation means 4 Reactor 5 Relay tank 6 Dehydrator 8 Suction device 9 Sludge collection container W1 Asbestos-contaminated water W2 supernatant W3 Primary filtrate W5 Supernatant liquid (from sludge collection vessel) SL (Sludge) Sediment

Claims

1. A method for treating asbestos-contaminated water, which contains asbestos peeled from a structure, is separated into dischargeable water and sludge, The asbestos-contaminated water generated in the process of removing asbestos from the structure is sent to a reaction tank in a unit amount for reaction treatment, The asbestos-containing water is left in the reaction tank for a predetermined treatment time to coagulate and precipitate the solids in the water, and then The entire amount of the supernatant liquid from the reaction tank is sent to a relay tank having a larger capacity than the reaction tank, Every time the transfer of the supernatant to the relay tank is completed, the precipitate in the reaction tank is transferred to a sludge recovery container, The method for treating turbid asbestos-contaminated water includes a process of pumping the supernatant stored in the relay tank to a dehydrator and squeezing out a primary filtrate in the dehydrator.

2. a solid-liquid separation means for separating large solids from the asbestos-contaminated water; After separating the large solids with this solid-liquid separation means, the asbestos-containing turbid water is sent to the reaction tank.

2. The method for treating asbestos-contaminated water according to claim 1.

3. The supernatant liquid generated in the sludge collection vessel is sent to the reaction tank.

3. The method for treating asbestos-contaminated water according to claim 1 or 2.

4. The method for treating turbid asbestos water according to any one of claims 1 to 3, wherein the residue from the dehydrator is collected in a collection container separate from the sludge collection container.

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