JP2017094234A - Polluted soil purification method and purification system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polluted soil purifying method and purification system in which the saving space of installation can be achieved.SOLUTION: Provided is a polluted soil purification method in which, to a mud water in which a heavy metal-containing polluted soil and a water are mixed, an adsorbent for adsorbing the heavy metal is added and the heavy metal is removed by separating the adsorbent that adsorbed the heavy metal, in a separation unit 40 from the mud water. The separation unit includes a separation tank 30 in which the mud water is circulated by up-flow, and the up-flow is performed at a flow velocity faster than the settlement velocity of the mud particle and slower than the settlement velocity of the adsorbent.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a purification method and a purification system for contaminated soil containing heavy metals.

  When excavated soil generated in tunnel construction, etc. contains heavy metals, such as arsenic, selenium, hexavalent chromium, cadmium, lead, etc., when the excavated soil is disposed as construction generated soil, contamination containing heavy metals It is desirable to detoxify the construction soil by properly removing heavy metals from the soil.

  As a technology to purify contaminated soil containing such heavy metals, an adsorbent for adsorbing the heavy metals is added to the mud mixed with contaminated soil and water in a reaction tank and adsorbed by stirring them. A technique is known in which heavy metal is adhered to the agent, and then the adsorbent that has adsorbed the heavy metal from the muddy water is separated using a separator (for example, Patent Document 1).

  Further, in Patent Document 2, iron-containing particles are used as an adsorbent, and a magnetic separation device is used as a separation device. Mud water containing contaminated soil is supplied from a mud storage tank to a reaction tank, and iron is contained in the reaction tank. The particles are added and stirred, and then the iron-containing particles having adsorbed heavy metals are separated from the muddy water by magnetic force in a magnetic separator. The separated iron-containing particles further remove air using a gas-liquid separator, and then are returned to the reaction tank via the return path and reused as an adsorbent.

JP 2000-51835 A JP 2011-56482 A

  In shield construction methods used in tunnel construction, for example, in the muddy water type shield construction method, mud water mixed with excavated soil and water is filled into the chamber of the shield machine, and a predetermined pressure is applied to the muddy water to make the face of the shield machine. We are trying to stabilize. In some cases, surplus water generated by such a construction method contains naturally-derived heavy metals in excavated soil, and in recent years, a technique for purifying heavy metals contained in the surplus mud water at a construction site is required.

  However, in the purification processing techniques described in Patent Documents 1 and 2, a magnetic separation device is used for separating the adsorbent, and this magnetic separation device is expensive, and if the processing capacity is increased, the device becomes larger. There was a problem that it was easy. At the construction site of the shield construction method, it is necessary to carry out purification treatment in a limited space, so that space saving and power saving of the purification equipment have been demanded.

  This invention is made | formed in view of the said subject, The objective is to provide the purification method and purification system of the contaminated soil which can aim at the space saving of an installation, and power saving.

  In order to achieve the above object, the method for purifying contaminated soil according to claim 1 adds an adsorbent for adsorbing the heavy metal to mud mixed with contaminated soil containing heavy metal and water, and a separation device. In the method for purifying contaminated soil in which the adsorbent that has adsorbed the heavy metal is separated from muddy water to remove the heavy metal, the separation device includes a separation tank for circulating the muddy water in an upflow, and the upflow includes: It is characterized by being carried out at a flow rate that is faster than the sedimentation rate of the soil particles and slower than the sedimentation rate of the adsorbent.

  According to this configuration, in the separation tank, the adsorbent that has adsorbed heavy metal is separated in the separation tank by upflowing the muddy water at a flow rate that is faster than the sedimentation speed of the mud soil particles and slower than the sedimentation speed of the adsorbent. And can be separated from the muddy water. Such sedimentation separation can be achieved by changing the flow direction and flow velocity of the muddy water in the separation tank, so that it is not necessary to use an expensive and large-sized device such as a magnetic separation device, thereby saving space. be able to. Furthermore, the power consumption can be suppressed as compared with the magnetic separation device.

  The method for purifying contaminated soil according to claim 2 is the method for purifying contaminated soil according to claim 1, wherein the upflow is carried out on the upstream side of the separation tank, and the settling rates of the adsorbent and the soil particles, respectively. It is characterized by being performed at a faster flow rate.

  According to this configuration, the muddy water to which the adsorbent is added is stirred on the upstream side by upflowing the muddy water at a flow rate faster than the settling rate of the adsorbent and the soil particles on the upstream side of the separation tank. Can adsorb heavy metals. Thereby, agitation time can be secured and purification performance can be improved, and muddy water agitation and subsequent separation of the adsorbent can be performed in one tank to save space.

  In addition, by controlling the flow rate of the upflow in this way, it is possible to perform the muddy water agitation and the separation of the adsorbent in a state where the adsorbent is kept in the separation tank. In order to reuse it, a recovery device for returning the adsorbent separated from the muddy water to the reaction tank again becomes unnecessary, and the equipment can be miniaturized to save power.

  The method for purifying contaminated soil according to claim 3 is the method for purifying contaminated soil according to claim 2, wherein the muddy water is circulated through the separation tank a plurality of times.

  According to this configuration, by allowing the muddy water to flow through the separation tank a plurality of times, the stirring time can be extended and the heavy metal can be sufficiently adsorbed by the adsorbent. In addition, by increasing the stirring time, it is possible to reduce the amount of adsorbent added necessary for the removal of heavy metals and to reduce costs.

  The method for purifying contaminated soil according to claim 4 is the method for purifying contaminated soil according to any one of claims 1 to 3, further comprising a mud storage tank for storing the mud water flowing into the separation tank. And the mud water added with the adsorbent is stirred in the mud storage tank.

  According to this configuration, the agitation time can be lengthened and the heavy metal can be sufficiently adsorbed to the adsorbent.

  Moreover, in order to achieve the said objective, the purification system of the contaminated soil of Claim 5 is a mixture of the muddy water which mixed the contaminated soil containing heavy metal, and water, and the adsorption agent for making the said heavy metal adsorb | suck. From the contaminated soil purification system comprising a separation device for separating the adsorbent adsorbing the heavy metal, the separation device comprises a separation tank for circulating the muddy water in an upflow, and the upflow comprises soil particles. It is characterized by being carried out at a flow rate that is faster than the settling rate and slower than the settling rate of the adsorbent.

  According to this configuration, in the separation tank, the adsorbent that has adsorbed heavy metal is separated in the separation tank by upflowing the muddy water at a flow rate that is faster than the sedimentation speed of the mud soil particles and slower than the sedimentation speed of the adsorbent. And can be separated from the muddy water. Such sedimentation separation can be achieved by changing the flow direction and flow velocity of the muddy water in the separation tank, so that it is not necessary to use an expensive and large-sized device such as a magnetic separation device, thereby saving space. be able to. Furthermore, the power consumption can be suppressed as compared with the magnetic separation device.

  The polluted soil purification system according to claim 6 is the polluted soil purification system according to claim 5, wherein the upflow is performed on the upstream side of the separation tank, and the settling rates of the adsorbent and the soil particles are set. It is characterized by being performed at a faster flow rate.

  According to this configuration, the muddy water to which the adsorbent is added is stirred on the upstream side by upflowing the muddy water at a flow rate faster than the settling rate of the adsorbent and the soil particles on the upstream side of the separation tank. Can adsorb heavy metals. Thereby, agitation time can be secured and purification performance can be improved, and muddy water agitation and subsequent separation of the adsorbent can be performed in one tank to save space.

  In addition, by controlling the flow rate of the upflow in this way, it is possible to perform the muddy water agitation and the separation of the adsorbent in a state where the adsorbent is kept in the separation tank. In order to reuse it, a recovery device for returning the adsorbent separated from the muddy water to the reaction tank again becomes unnecessary, and the equipment can be miniaturized to save power.

  The polluted soil purification system according to claim 7 is the polluted soil purification system according to claim 6, further comprising a circulation path through which the muddy water is circulated a plurality of times in the separation tank.

  According to this configuration, by allowing the muddy water to flow through the separation tank a plurality of times through the circulation path, the agitation time can be extended and the heavy metal can be sufficiently adsorbed by the adsorbent. In addition, by increasing the stirring time, it is possible to reduce the amount of adsorbent added necessary for the removal of heavy metals and to reduce costs.

  The polluted soil purification system according to claim 8 is the polluted soil purification system according to any one of claims 5 to 7, further comprising: a mud storage tank for storing the mud water flowing into the separation tank. And the mud storage tank has stirring means for stirring the mud water to which the adsorbent is added.

  According to this configuration, the muddy water can be stirred in the mud storage tank by the stirring means, and the stirring time can be made longer and the heavy metal can be sufficiently adsorbed by the adsorbent.

  According to the present invention, space saving of equipment can be achieved.

The figure which shows the outline | summary of the purification system of the contaminated soil in 1st Embodiment of this invention. The figure which shows the outline | summary of a muddy water type shield method. The figure which shows the flow of the excavation soil which generate | occur | produces in a muddy water type shield method. The figure which shows the outline | summary of the purification process of the contaminated soil which generate | occur | produced in the muddy water type shield method. The figure which shows the outline | summary of the purification process of the conventional contaminated soil. The figure which shows the outline | summary of the purification system of the contaminated soil in 2nd Embodiment of this invention.

(First embodiment)
FIG. 1 is a diagram showing an outline of a contaminated soil purification system 1 according to the first embodiment of the present invention. In the present embodiment, an example will be described in which the contaminated soil purification system 1 is applied to a purification process of excavated soil (contaminated soil) containing heavy metals, which is generated in a muddy water type shield method that is an example of a shield method. The purification system 1 includes a mud storage tank 20 and a reaction / separation tank (separation tank) 30.

  FIG. 2 is a diagram showing an outline of the muddy water type shield construction method. The muddy water type shield method is a method in which the inside of the chamber of the shield machine 11 is filled with muddy water, and the muddy water is kept at a sufficient pressure to resist the earth pressure and water pressure of the ground, thereby stabilizing the face. The excavated soil is mixed with muddy water and discharged to the outside of the mine.

  The excavated soil generated by the shield method may contain naturally-derived heavy metals such as arsenic, selenium, hexavalent chromium, cadmium, and lead. The purification system 1 of this embodiment can be suitably used as a system for purifying excavated soil containing such heavy metals at an excavation site. Here, the contaminated soil purification system 1 containing arsenic, which is an example of heavy metal, will be described.

  FIG. 3 is a diagram showing a flow of excavated soil generated in the muddy water type shield method. The excavated soil treatment system in the muddy water shield method includes a shield machine 11 and a treatment facility 12, and the treatment facility includes a primary treatment machine 13 and a secondary treatment machine 14.

  The shield machine 11 excavates the face by rotating the cutter head. The excavated soil cut by the cutter head is mixed with muddy water and conveyed to the ground processing facility 12 (see FIG. 2) using a mud pump.

  The primary processing machine 13 is a device that classifies the muddy water discharged from the shield machine into a coarse particle having a particle size of 75 μm or more and a fine particle having a particle size of less than 75 μm. Combinations of these can be used. In many cases, the coarse particles (primary treated soil) classified by the primary treatment machine 13 can be disposed as construction generated soil (concentration of arsenic is 0.01 mg / L or less) in which heavy metals conform to environmental standard values. it can.

  A portion of the mud that is fine is supplied to the chamber of the shield machine for use as pressurized mud used in the shield machine. The remaining muddy water (excess muddy water) for the fine particles is conveyed to the secondary processor 14.

  The secondary processor 14 is an apparatus that removes heavy metals from surplus mud water mixed with contaminated soil containing heavy metals. In the secondary processing machine 14, heavy metal is made to adhere to an adsorbent by adding and mixing an adsorbent to surplus muddy water. Thereafter, the heavy metal is removed by separating the adsorbent adsorbing the heavy metal from the muddy water. The purification system 1 is used as the secondary processor 14 and includes the mud storage tank 20 and the reaction / separation tank 30 as described above. As shown in FIG. Together with the flow generation means 41, the discharge path 42, and the adsorbent recovery means 43, a separation device 40 that separates the adsorbent adsorbing heavy metals from the muddy water is constituted.

  As an adsorbent that adsorbs heavy metals, for example, iron powder, activated carbon, zeolite, and the like can be used. In this embodiment, iron powder is used. As the adsorbent, an adsorbent having a sedimentation rate faster than the sedimentation rate of the soil particles based on the particle size and specific gravity of the soil particles of the contaminated soil to be purified is used. Here, iron powder having a sedimentation speed faster than that of soil particles having a particle size of about 75 μm and a specific gravity of about 2.6 μm classified by the primary processor (for example, a particle size of about 70 to 100 μm and a specific gravity of about About 7.85 iron powder). The sedimentation rate of the soil particles and the adsorbent can be calculated from the Stokes equation.

  The adsorbent is supplied into the reaction / separation tank 30 using the charging device 50. The charging device 50 is for charging a predetermined amount of adsorbent into the reaction / separation tank 30.

  The mud storage tank 20 is a tank for storing mud water, and here, excess mud water that has passed through the primary treatment machine 13 is stored in the mud storage tank 20 via the supply path 19. The mud storage tank 20 and the reaction / separation tank 30 are connected to each other by a first transport path 23 and a second transport path 24. At the lower part of the mud storage tank 20, an outflow port 21 for flowing out mud water is provided, and the first transport path 23 extends from the outflow port 21 to the reaction / separation tank 30.

  The reaction / separation tank 30 is a container for stirring the muddy water to which the adsorbent is added and separating the adsorbent from the muddy water, and an inflow portion 31 for allowing the muddy water to flow into the reaction / separation tank. And an outflow part 32 for allowing the muddy water to flow out of the reaction / separation tank, a reaction area part 35 located on the inflow part 31 side (upstream side), and a separation area part located on the outflow part 32 side (downstream side) 36. The inflow part 31 is connected to the first transfer path 23 extending from the discharge part of the mud storage tank, and the outflow part 32 is reacted / reacted so that the muddy water level is kept constant in the reaction / separation tank 30. It is located above the separation tank 30 and is connected to the second transport path 24 and the discharge path 42. The outflow part 32 is provided with a switching valve (not shown) for switching the muddy water outflow path to one of the second transport path 24 and the discharge path 42.

  The reaction area part 35 is a part that constitutes a function as a reaction tank for stirring the muddy water together with the flow generating means 41. The separation region part 36 is a part that constitutes a function as a separation tank that performs sedimentation separation of the adsorbent together with the flow generation means 41. The separation region portion 36 has a cylindrical shape formed so that the inner diameter is substantially constant, and the reaction region portion 35 has a smaller inner diameter than the separation region portion 36.

  In the present embodiment, a cylindrical column extending in the vertical direction is used as the reaction / separation tank 30. The inflow portion 31 is located at the bottom of the column, and the reaction region portion 35 is formed in a tapered shape so that the inner diameter gradually increases upward from the inflow portion 31. It is located above the separation region portion 36 and the reaction region portion 35, and has a cylindrical shape formed so that the inner diameter is constant in the vertical direction.

  The structure of the reaction / separation tank 30 is not limited to the above-described configuration, and the mud can be stirred in the reaction region 35 while the mud is circulated from the inflow portion 31 to the outflow portion 32, and in the separation region portion 36. Any configuration that can settle and separate the adsorbent is acceptable. For example, a stirring means such as a stirring blade is provided to stir the muddy water in the reaction region 35, or an inclined plate or a slanted tube is provided in the separation region 36 to keep the muddy water flow in a static laminar flow state. It is also possible to do.

  The flow generating means 41 generates a muddy water flow from the inflow portion 31 toward the outflow portion 32 in the reaction / separation tank 30. The flow generating means 41 forms an upflow so that the muddy water flows from the lower side to the upper side at least in the separation region portion 36 of the reaction / separation tank 30.

Further, the reaction / separation apparatus 40 is configured so that the flow velocity of the reaction region 35, particularly the flow velocity of the inflow portion 31, depending on the flow generating means 41 and the configuration of the reaction / separation tank 30, is the soil particle sedimentation rate and the adsorbent sedimentation rate. The flow rate of the muddy water is adjusted so that the first flow rate V ₁ is faster and the flow rate in the separation region is the second flow rate V ₂ that is faster than the sedimentation rate of the soil particles and slower than the sedimentation rate of the adsorbent. To do.

In the present embodiment, a pump is used as the flow generating means 41, and the pump is disposed in the first conveyance path 23 disposed between the mud storage tank 20 and the reaction / separation tank 30. Note that the position of the flow generation unit 41 is not limited to this, and may be configured to be provided in the reaction / separation tank 30 or the second transport path 24, for example. The flow generating means 41 and the cylindrical reaction / separation tank 30 form upflows with different flow velocities in the reaction region 35 and the separation region 36. Here, the flow velocity is the first flow velocity V ₁ at the end of the first transport path 23 on the reaction / separation tank 30 side, which has a flow channel cross-sectional area substantially equal to the flow path cross section of the inlet of the reaction / separation tank 30. As described above, the pressure and flow rate of the pump that is the flow generating means 41 are adjusted. Furthermore, as the flow rate in the separation region 36 is a second flow velocity V _2, and setting the flow path cross-sectional area of the isolation region 36 (i.e., the inner diameter of the column).

As an example of such a reaction / separation tank 30, for example, the inner diameter of the lowermost part (inlet) of the reaction region 35 is about 0.4 m, and the height of the reaction region 35 is about 0.6 m, A column having an inner diameter of the separation region portion of about 1.0 m and a height of the separation region portion of about 2.0 m can be used. As an example, the sedimentation rate of soil particles (maximum particle size 75 μm, specific gravity 2.6) is 0.49 cm / sec, and the sedimentation rate of iron powder (particle size 70 μm, specific gravity 7.85) as an adsorbent is 1 In the case of .8 cm / sec, the adsorbent can be precipitated by setting the first flow rate V ₁ to about 6 cm / sec and the second flow rate V ₂ to 1 cm / sec in this column. The size of the reaction / separation tank 30 and the flow rate of muddy water are not limited to this, and can be set as appropriate based on the amount of muddy water to be purified, the adsorbent used, and the like.

  The second conveyance path 24 is a flow path extending from the outflow portion 32 of the reaction / separation tank 30 to the mud storage tank 20. The second conveyance path 24, the mud storage tank 20, and the first conveyance path 23 are configured so that the muddy water flows through the reaction / separation tank 30 a plurality of times, and the outflow part 32 and the inflow part 31 of the reaction / separation tank 30 A circulation path that connects the two is formed.

  The discharge path 42 is a flow path for discharging the muddy water from which the adsorbent has been separated out of the reaction / separation tank 30, and extends from the outflow portion 32 to the outside of the reaction / separation tank 30.

  The recovery means 43 recovers the used adsorbent from the reaction / separation tank 30, and for example, a blower having a required suction force can be used.

  Next, the purification process of the contaminated soil by the purification system 1 described above will be described.

  As shown in FIG.1 and FIG.4, the surplus muddy water after classifying with the primary processor 13 is conveyed to the mud storage tank 20 using conveyance means, such as a pump. After a predetermined amount of mud is stored in the mud tank 20, the mud stored in the mud tank 20 is supplied to the reaction / separation tank 30 by the flow generation means 41.

  Before the muddy water flows into the reaction / separation tank 30, a predetermined amount of adsorbent is introduced by the charging device 50, and the muddy water flows into the reaction region 35 by the flow generating means 41, whereby the adsorbent is added to the muddy water. Is added (addition process).

Further, in the reaction region portion 35, the flow generation means 41 controls the mud water flow rate to the first flow rate V ₁ that is faster than the sedimentation rate of the soil particles and the adsorbent, thereby mixing and stirring the mud water and the adsorbent. (Stirring step).

The muddy water is moved from the reaction region portion 35 to the separation region portion 36 by the flow generation means 41. The isolation region 36, the flow rate of the mud to be upflow is faster than the settling velocity of the soil particles, is controlled by the second flow rate V ₂ slower than the settling velocity of the adsorbent, the adsorbent in mud, isolation region portion The muddy water that settles at 36 and contains soil particles flows out of the reaction / separation tank 30 from the outflow portion 32.

  In the outflow portion 32, the flow path is selected as the second transport path 24 by the switching valve, and the mud that has flowed out is flown by the flow generation means 41 to the second transport path 24, the mud tank 20, and the first It flows again into the reaction / separation tank 30 through one transport path 23. The reaction / separation device 40 repeats the stirring and separation of the muddy water in the reaction / separation tank 30 via such a circulation path a predetermined number of times.

  Thereafter, the flow path is switched from the second conveyance path 24 to the discharge path 42 by the switching valve. The muddy water separated in the separation region part 36 of the reaction / separation tank 30 is discharged from the discharge path 42 to the outside of the reaction / separation tank 30, and the adsorbent that has adsorbed heavy metals settles in the separation region part 36 and reacts. It remains in the separation tank 30. As a result, the adsorbent is separated from the muddy water (separation step).

  The muddy water from which the adsorbent has been separated is conveyed to a sludge treatment tank (not shown) using a conveying means such as a pump. In the sludge treatment tank, a flocculant is added to the mud water, and the mixture is stirred and subjected to a coagulation sedimentation treatment (coagulation sedimentation treatment step), and treated as sludge and treated water whose heavy metals have been purified to a specified value or less. The adsorbent in the reaction / separation tank 30 is carried out of the reaction / separation tank 30 by the recovery means 43 and treated as industrial waste. Before collecting the adsorbent by the collecting means 43, the soil particles may be washed by supplying water to the storage tank 20 or the reaction / separation tank 30.

In purification system 1 described above, the separation region 36 of the reaction and separation vessel 30, faster than the settling rate of the mud soil particles, and up flow muddy water at a slow first velocity V ₁ than the settling velocity of the adsorbent Thereby, the adsorbent which adsorb | sucked the heavy metal can be settled in a separation tank, and can be isolate | separated from muddy water. Therefore, it is not necessary to install an expensive and large-sized apparatus unlike the magnetic separation apparatus used in the conventional purification system, and the adsorbent is separated from the muddy water by changing the flow direction and flow velocity of the muddy water in the separation tank. Therefore, space saving can be achieved. In addition, the power consumption can be reduced as compared with the purification system using the magnetic separation device, and the adsorbent can be separated and collected with a simple configuration.

  As shown in FIG. 5, the conventional purification system includes a mud storage tank, a reaction device, a magnetic separation device, and a recovery device, and a reaction device that stirs mud water to which an adsorbent is added (that is, a reactor). The reaction tank having the stirring means) and the magnetic separation device for separating the adsorbent adsorbing heavy metal from the muddy water are separate devices, and thus it is necessary to secure a wide installation space.

In contrast, in the purification system 1 of this embodiment, the reaction zone 35 Oite located upstream of the reaction and separation vessel 30, the muddy water in the adsorbent and the second flow rate V ₂ higher than the settling velocity of the soil particles By upflowing, the muddy water can be agitated on the upstream side and the heavy metal can be adsorbed by the adsorbent. That is, in the purification system 1 of the present embodiment, heavy metals can be removed by one apparatus, that is, the separation apparatus 40 having a stirring function and a separation function in one container, so that the purification equipment can be made more compact. To save space. Further, in the reaction / separation tank 30, by changing the shapes of the reaction region portion 35 and the separation region portion 36, it is possible to obtain a stirring action and a separation action by driving the common flow generating means 41. A power effect can be obtained.

  Furthermore, by providing a circulation path and allowing the muddy water to flow through the reaction / separation tank 30 a plurality of times, the agitation time can be lengthened and the heavy metal can be sufficiently adsorbed to the adsorbent. The amount can be reduced to reduce the cost.

  Moreover, in the purification system 1, since the adsorbent can be reused in a state where the adsorbent remains in the reaction / separation tank 30, in order to reuse the adsorbent as in the conventional purification system, There is no need to provide a recovery device for returning the adsorbent separated from the muddy water by the separation device to the reaction tank again. In other words, the stirring process for stirring the muddy water, the separation process for separating the adsorbent from the muddy water, and the reuse of the separated adsorbent can be performed with a single device. Electric power and simplification of processing steps can be achieved.

  In the purification system 1 of the present embodiment, the adsorbent is added to the muddy water in the reaction / separation tank 30, but the site to which the adsorbent is added is not limited to this, and after the muddy water is classified by the primary processing machine. I just need it.

(Second Embodiment)
FIG. 6 is a view similar to FIG. 1 showing a second embodiment of the purification system 1. In the second embodiment, portions corresponding to those in the first embodiment are denoted by the same reference numerals, and details of the same configuration and the same purification treatment process are omitted here.

  In the second embodiment, the charging device 50 is connected to the mud tank 20 and feeds a predetermined amount of adsorbent into the mud tank 20. The mud storage tank 20 includes stirring means 25.

  The agitating means 25 is for agitating the muddy water stored in the mud storage tank 20, and for example, using an agitator provided with a motor as a drive source and agitating blades connected to the motor. it can.

  In the purification treatment of contaminated soil by the purification system 1 of the second embodiment, a predetermined amount of adsorbent is introduced into the mud tank 20 by the input device 50, and after a predetermined amount of mud water is stored in the mud tank 20, The muddy water to which the adsorbent is added is mixed and stirred by the stirring means 25 (addition step and stirring step).

Thereafter, mud is supplied from the mud storage tank 20 to the reaction / separation tank 30 by the flow generation means 41. In the reaction region portion 35 of the reaction / separation tank 30, the muddy water and the adsorbent are mixed and stirred by the flow generation means 41 controlling the muddy water flow rate to the first flow velocity V ₁ .

The muddy water that has moved from the reaction region portion 35 to the separation region portion 36 by the flow generation means 41 is controlled to the second flow velocity V _2, and the adsorbent in the muddy water settles in the separation region portion 36 to remove the soil particles. The contained mud flows out of the reaction / separation tank 30 from the outflow part 32.

  In the outflow part 32, the flow path is selected as the second transport path 24 by the switching valve, and the muddy water that has flowed out passes through the second transport path 24, the mud tank 20, and the first transport path 23 that serve as a circulation path. Then, it flows into the reaction / separation tank 30 again. After the agitation and separation of the muddy water in the reaction / separation tank 30 via the circulation path are repeated a predetermined number of times, the flow path is switched from the second transport path 24 to the discharge path 42 by the switching valve.

  Thereafter, the muddy water separated in the separation region part 36 of the reaction / separation tank 30 is discharged from the discharge path 42 to the outside of the reaction / separation tank 30, and the adsorbent adsorbing heavy metal settles in the separation region part 36. It remains in the reaction / separation tank 30. As a result, the adsorbent is separated from the muddy water (separation step).

  In the purification system 1 of the present embodiment, after mixing and stirring the muddy water to which the adsorbent is added in the mud storage tank 20, the muddy water can be further stirred in the reaction / separation tank 30. When a predetermined amount of adsorbent is added to a predetermined amount of mud containing a heavy metal, the purification effect becomes higher when the stirring time is longer. Therefore, in the purification system of the second embodiment, the purification time is increased by increasing the stirring time as compared to that of the first embodiment, or the number of times the reaction / separation tank 30 is circulated is reduced to shorten the processing time. You can do it.

  In the second embodiment, the second conveyance path 24 may not be provided. In this case, after stirring the muddy water to which the adsorbent is added in the mud storage tank 20, the adsorbent is separated from the muddy water in the reaction / separation tank 30. The muddy water is conveyed from the outflow part 32 of the reaction / separation tank 30 to the sludge treatment tank via the drainage channel 42. The adsorbent in the reaction / separation tank 30 is carried out of the reaction / separation tank 30 by the recovery means 43 and treated as industrial waste. Thus, when the 2nd conveyance path 24 is not arrange | positioned, an installation can be reduced more. Further, when the second transport path 24 is not provided, the reaction / separation tank 30 can be a separation tank having only a separation function (that is, not having a stirring function). Thus, the separation device 40 can be reduced in size.

  The present invention is not limited to the first and second embodiments described above, and various modifications can be made without departing from the spirit of the invention. For example, in the above-described embodiment, an example in which the purification system is applied to the muddy water type shield construction method is described. However, in the earth pressure type shield construction method, the purification treatment can be performed using the same purification system. Further, as the reaction / separation device, for example, a slurry circulation type precipitation device including a first stirring chamber and a second stirring chamber can be used. Moreover, it is good also as a structure which replaces with the 2nd conveyance path 24 and provides the circulation path which does not go through the storage tank 20 separately.

DESCRIPTION OF SYMBOLS 1 Purification system 20 Mud storage tank 23 1st conveyance path 24 2nd conveyance path 25 Stirring means 30 Reaction and separation tank (separation tank)
35 Reaction zone 36 Separation zone 40 Reaction / separation equipment (separation equipment)
41 Flow generation means

Claims (8)

Pollution that removes the heavy metal by adding an adsorbent for adsorbing the heavy metal to the mud mixed with contaminated soil containing heavy metal and water, and separating the adsorbent that adsorbed the heavy metal from the mud in a separator In the soil purification method,
The separation device includes a separation tank that circulates the muddy water in an upflow,
The method of purifying contaminated soil, wherein the upflow is performed at a flow rate faster than a sedimentation rate of soil particles and slower than a sedimentation rate of the adsorbent.   2. The method for purifying contaminated soil according to claim 1, wherein the upflow is performed at a flow rate faster than a settling velocity of each of the adsorbent and the soil particles on the upstream side of the separation tank.   The method for purifying contaminated soil according to claim 2, wherein the muddy water is circulated through the separation tank a plurality of times.   4. A mud storage tank for storing the mud water flowing into the separation tank is provided, and the mud water added with the adsorbent is stirred in the mud tank. The method for purifying contaminated soil according to item 1. In a purification system for contaminated soil, comprising a separation device for separating the adsorbent adsorbing heavy metal from a mixture of muddy water mixed with contaminated soil containing heavy metal and water and an adsorbent for adsorbing the heavy metal ,
The separation device includes a separation tank that circulates the muddy water in an upflow,
The purification system according to claim 1, wherein the upflow is performed at a flow rate that is faster than a sedimentation rate of soil particles and slower than a sedimentation rate of the adsorbent.   6. The contaminated soil purification system according to claim 5, wherein the upflow is performed at a flow rate faster than the settling rates of the adsorbent and soil particles on the upstream side of the separation tank.   The contaminated soil purification system according to claim 6, further comprising a circulation path through which the muddy water is circulated through the separation tank a plurality of times. A mud storage tank for storing the muddy water flowing into the separation tank;
The method for purifying contaminated soil according to any one of claims 5 to 7, wherein the mud storage tank has stirring means for stirring the mud water to which the adsorbent is added.

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