JP6344587B1 - Soil purification system - Google Patents

Abstract

[PROBLEMS] To recover a chelating agent accompanying sand and the like and reduce the site area of the chelating agent recovery facility for a soil purification system that classifies while cleaning contaminated soil with cleaning water containing a chelating agent. Provide a means to A soil purification system (1) includes a soil washing classification unit (2), a chelating agent regeneration unit (3), a chelating agent recovery unit (4), a rinse water generation unit (5), and a washing water supply unit (7). The chelating agent recovery unit 4 removes and recovers the chelating agent adhering to the sand and the like by washing the sand and the like discharged from the soil washing and classifying unit 2 with rinse water. The rinse water generator 5 generates rinse water by removing the chelator from a part of the wash water discharged from the chelator regenerator 3 and supplies the rinse water to the chelator recovery unit 4. The rinse water production | generation part 5 has a reverse osmosis membrane separation apparatus which isolate | separates wash water into permeated water (rinse water) and concentrated water with a reverse osmosis membrane. [Selection] Figure 1

Description

  The present invention purifies soil containing gravel, sand and fine-grained soil and contaminated with harmful metals and / or compounds thereof with washing water containing a chelating agent and cleaning the gravel, sand and fine-grained soil. The present invention relates to a soil purification system classified into soil.

  In recent years, sites of production facilities that use harmful metals such as chromium, lead, cadmium, selenium, mercury and / or their compounds (hereinafter collectively referred to as “hazardous metals”) as raw materials or materials, or the vicinity thereof The problem is soil contamination due to illegal soil dumping of industrial waste containing toxic metals and the like. Then, the soil contaminated with toxic metal (hereinafter referred to as “toxic metal-contaminated soil”) is insolubilized, for example, toxic metal at the position where the toxic metal-contaminated soil actually exists (hereinafter referred to as “original position”). Effective purification, such as by containment or electrical repair, is quite difficult. For this reason, the toxic metal-contaminated soil is generally removed from the original position by excavation and purified at an external soil purification facility.

  Conventionally, as a method for purifying toxic metal-contaminated soil at such off-site soil purification facilities, a cleaning method that removes toxic metals by washing toxic metal-contaminated soil with washing water or washing liquid has been widely used. Yes. Thus, the applicant of the present application removes harmful metals by washing the contaminated soil contaminated with harmful metals with washing water containing a chelating agent, while using a solid-phase adsorbent from the washed water after washing. Various types of closed system type soil purification facilities that regenerate and repeatedly use washing water or chelating agents by removing etc. and do not discharge washing water outside the facility have been proposed (see Patent Documents 1 to 5).

Japanese Patent No. 576094 Japanese Patent No. 5771342 Japanese Patent No. 5771343 Japanese Patent No. 6022102 Japanese Patent No. 6026700

  By the way, in the soil remediation facilities disclosed in Patent Documents 1 to 3 according to the applicant of the present application, the soil contaminated with harmful metals and the like and the washing water containing the chelating agent are mixed and stirred, and adhered to the soil. Hazardous metals and the like are separated from the soil and captured by the chelating agent, and the soil is classified to generate sand and the like, which are reused as civil engineering and building materials.

  And the washing | cleaning water containing a chelating agent has adhered to the sand produced | generated in this way, but the sand containing a chelating agent is not so preferable as civil engineering, a building material, etc. In addition, the chelating agent in the soil purification facility is reduced by the amount taken away by the sand. Therefore, even if the chelating agent is repeatedly used while being regenerated, it is necessary to replenish the chelating agent in an amount corresponding to the chelating agent carried away by the sand. For this reason, in a soil remediation facility that purifies a large amount of contaminated soil (for example, 1000 tons / day), a considerable amount of chelating agent must be constantly replenished, resulting in high soil treatment costs. .

  By the way, in the soil remediation facilities disclosed in Patent Documents 4 to 5 related to the applicant of the present application, the sand discharged from the liquid cyclone to which the cleaning liquid containing the chelating agent is attached is washed with rinse water to remove the chelating agent from the sand. Try to remove. Then, the cleaning wastewater containing the chelating agent is evaporated to the atmosphere by the evaporating sand in the sand container, the chelating agent is left and accumulated in the evaporating sand, and the evaporating sand containing the chelating agent is introduced into the soil treatment system. Thus, the chelating agent is recovered (so-called Shioda method). However, since a large amount of rinsing water is required to clean the sand to which the cleaning liquid containing the chelating agent is attached, a very large area sand container is required to evaporate a large amount of the cleaning wastewater generated. For this reason, there exists a problem that a large site is required for installation of the collection | recovery equipment of a chelating agent.

  The present invention has been made to solve the above-described conventional problems, and purifies soil contaminated with harmful metals with washing water containing a circulating chelating agent, while separating sand and the like from the soil. In addition to preventing or reducing chelating agent from being taken away by sand, the site area of the facility for recovering chelating agent is greatly reduced for closed system type soil remediation facilities that have been reused. It is an object to be solved to provide a means that enables to do so.

  A soil purification system according to the present invention made to solve the above-described problems includes a soil washing classification unit, a chelating agent regeneration unit, a chelating agent recovery unit, a rinse water generation unit, and a washing water supply unit. Yes. Here, the soil washing classifying unit contains soil containing gravel, sand and fine-grained soil and contaminated with harmful metals or the like (hazardous metal and / or compound thereof) or these ions with washing water containing a chelating agent. Wash and purify and classify into gravel, sand and fine-grained soil. The chelating agent regeneration unit regenerates the chelating agent by removing harmful metals and the like or these ions from the chelating agent capturing the harmful metals and the like in the wash water discharged from the soil washing and classifying unit. The chelating agent recovery unit removes and recovers the chelating agent adhering to the sand by washing the sand discharged from the soil washing classification unit with rinse water.

  The rinse water generating part introduces a part of the washing water discharged from the chelating agent regeneration part and separates the concentrated water in which the chelating agent is concentrated by the reverse osmosis membrane and the permeated water not containing the chelating agent. It has a separation device and supplies permeate as rinse water to the chelating agent recovery section. The cleaning water supply unit includes cleaning water other than the cleaning water introduced into the rinsing water generation unit out of the cleaning water discharged from the chelating agent regeneration unit, concentrated water discharged from the rinsing water generation unit, and a chelating agent recovery unit. It receives and mixes with the washing waste water of sand discharged from the water, and supplies (returns) the mixed water as washing water to the soil washing classification unit.

  In the soil purification system according to the present invention, the washing water supply unit may include, for example, a mixing tank, a pump, and a pipeline. In this case, the mixing tank includes cleaning water other than the cleaning water introduced into the rinsing water generation unit out of the cleaning water discharged from the chelating agent regeneration unit, concentrated water discharged from the rinsing water generation unit, and recovery of the chelating agent. Accepts and mixes with waste washing wastewater discharged from the section. In addition, the pump and the pipe supply (return) the mixed water in the mixing tank to the soil washing classification unit as washing water.

  In the soil purification system according to the present invention, it is preferable that the soil washing classification unit includes a mixing device, a first classification device, a second classification device, a sedimentation separation device, and a filtration device. In this case, the mixing device mixes and stirs the soil containing the gravel, sand and fine-grained soil and the washing water, and removes the harmful metals adhering to the soil or these ions from the soil to chelate. Let the agent trap. The first classifying device receives a mixture containing soil and washing water discharged from the mixing device, and separates gravel from the mixture. The second classifying device receives a mixture containing sand, fine soil, and washing water discharged from the first classifying device, and separates the sand from the mixture. The sedimentation separator separates the mixture containing the fine-grained soil discharged from the second classifier and the washing water into supernatant water and sludge containing the fine-grained soil by sedimentation. The filtering device filters sludge discharged from the sedimentation separator to produce a filtrate and a filter cake.

  Further, in this case, the chelating agent regeneration unit has a higher complexing power than the chelating agent and, when contacting with the supernatant water discharged from the sedimentation separator, adsorbs harmful metals or the like in the supernatant water. It has a phase adsorbent, and has a chelating agent regenerator that regenerates the chelating agent by removing harmful metals and the like ions from the chelating agent in the supernatant water. The chelating agent recovery unit has a sand rinsing device that sprays or jets rinsing water on the sand separated by the second classifying device to wash away the chelating agent held in the sand.

  According to the soil purification system according to the present invention, the sand discharged from the soil washing classification unit is washed with the permeated water (rinse water) generated by the reverse osmosis membrane separation device in the chelating agent recovery unit, and adheres to the sand. The chelating agent is removed and collected. Therefore, high-quality sand containing no chelating agent can be obtained. The cleaning wastewater containing the chelating agent generated by the sand cleaning in the chelating agent recovery unit is returned to the soil cleaning classification unit via the cleaning water supply unit, and is not discharged outside the soil purification system. Loss outside the soil purification system is reliably prevented.

  On the other hand, the installation area of the reverse osmosis membrane separation device constituting the rinse water generator is very small. The washing water supply unit that mixes washing water, concentrated water and washing waste water and supplies (returns) the washing water to the soil washing classification unit is, for example, a mixing tank such as a simple concrete pit, a pump, a pipe line, etc. The installation area that can be configured is very small. Therefore, the installation of the chelating agent recovery facility does not require a large site such as the sand container disclosed in Patent Documents 4 to 5, for example. Therefore, the chelating agent can be prevented from being taken out of the soil purification system by the sand, and the site area of the facility for recovering the chelating agent can be extremely reduced.

It is a block diagram which shows the structure of the soil purification system which concerns on this invention. It is a block diagram which shows the structure of the soil washing classification | category part which is a component of the soil purification system shown in FIG. It is a typical elevation which shows the structure of the chelating agent reproduction | regeneration part which is a component of the soil purification system shown in FIG. It is a typical side view of the gravel rinse apparatus which is a component of a chelating agent collection | recovery part. It is a typical side view of the sand rinse apparatus which is a component of a chelating agent collection | recovery part. It is a typical side view of the fine-grain soil rinse apparatus which is a component of a chelating agent collection | recovery part. It is a typical elevation view of the rinse water production | generation part of the soil purification system shown in FIG. 1, and the apparatus around it. It is a figure which shows an example of the flow volume of the soil in the important point of a soil purification system, water, and a chelating agent. It is a figure which shows an example of the flow volume of a soil, water, a chelating agent, and a chelating agent density | concentration in the key point of a chelating agent collection | recovery part and a rinse water production | generation part.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
First, the whole structure of the soil purification system 1 which concerns on this invention is demonstrated, referring FIG. The soil purification system 1 includes a soil washing classification unit 2, a chelating agent regeneration unit 3, a chelating agent recovery unit 4, a rinsing water generation unit 5, a chelating agent supplement unit 6, and a washing water supply unit 7. Yes.

  Here, the soil washing classifying unit 2 is a washing water containing a chelating agent containing soil including gravel, sand and fine-grained soil and contaminated with harmful metals or the like (hazardous metals and / or compounds thereof) or these ions. Wash and purify, and classify into gravel, sand and fine-grained soil. The chelating agent regeneration unit 3 regenerates the chelating agent by removing the harmful metal from the chelating agent capturing the harmful metal in the wash water discharged from the soil washing classification unit 2. The chelating agent recovery unit 4 is configured to wash the gravel, sand and / or fine soil discharged from the soil cleaning classification unit 2 with rinse water, thereby adhering to the gravel, sand and / or fine soil. Remove and recover. The rinsing water generating unit 5 introduces a part of the washing water discharged from the chelating agent regeneration unit 3 and reversely separates the concentrated water in which the chelating agent is concentrated by the reverse osmosis membrane and the permeated water not containing the chelating agent. The osmotic membrane separation device 110 (see FIG. 7) is provided, and the permeated water is supplied to the chelating agent recovery unit 4 as rinse water.

  When the chelating agent decreases, the chelating agent replenishing unit 6 replenishes and supplies the reduced amount of the chelating agent to the washing water returned to the soil washing classifying unit 2, and the chelating agent concentration of the washing water is a preset value. To maintain. The cleaning water supply unit 7 includes cleaning water other than the cleaning water introduced into the rinsing water generation unit 5 among the cleaning water discharged from the chelating agent regeneration unit 3, concentrated water discharged from the rinsing water generation unit 5, and Gravel, sand and / or fine soil washing wastewater discharged from the chelating agent collection unit 4 is received and mixed, and the mixed water is supplied as washing water to the soil washing classification unit 2 (returned).

  If it demonstrates in detail, the soil washing classification part 2 has the mixing apparatus 11, the 1st classification apparatus 12, the 2nd classification apparatus 13, the sedimentation-separation apparatus 14, and the filtration apparatus 15. FIG. Here, the mixing device 11 mixes and stirs the soil containing gravel, sand and fine-grained soil and the washing water containing the chelating agent, and removes harmful metals adhering to the soil or these ions. Separated from the soil and captured by chelating agent. The first classifying device 12 receives the mixture of soil and washing water discharged from the mixing device 11 and separates gravel from this mixture. The second classifier 13 receives a mixture of sand, fine-grained soil, and washing water discharged from the first classifier 12, and separates the sand from this mixture. The sedimentation separator 14 separates the wash water containing fine-grained soil discharged from the second classifier 13 into supernatant water and sludge containing fine-grained soil by sedimentation. The filtration device 15 filters the sludge discharged from the sedimentation separation device 14 to generate a filtrate and a filter cake (separate fine-grained soil).

  The chelating agent regeneration unit 3 has a solid-phase adsorbent that adsorbs harmful metals, etc. in the supernatant water or these ions when it comes into contact with the supernatant water having a higher complexing power than the chelating agent and discharged from the sedimentation separator 14. And a washing water regeneration device 41 (see FIG. 3) for removing harmful metals from the chelating agent in the supernatant water and regenerating the supernatant water as washing water. The solid-phase adsorbent has a multipoint interaction by coordinating bonds and hydrogen bonds in which a cyclic molecule is supported on a carrier and a chelate ligand is modified on the cyclic molecule, and harmful metals, etc. or these ions are selectively selected. It is something to capture. In addition, since the harmful metals adsorbed on the solid phase adsorbent or these ions can be removed by an acid solution (for example, dilute nitric acid or dilute sulfuric acid), the solid phase adsorbent can be easily regenerated.

  The chelating agent recovery unit 4 includes a gravel rinsing device 16 that sprays or jets rinsing water on the gravel separated by the first classifying device 12 to remove the chelating agent held in the gravel, and a second classifying device 13. The sand rinsing device 17 that removes the chelating agent held in the sand by spraying or spraying the separated sand with rinsing water and the filter cake (fine-grained soil) separated by the filtering device 15 are crushed. And a fine-grain soil rinsing device 18 for removing the chelating agent held in the fine-grained soil by spraying or spraying rinsing water.

  The rinse water production | generation part 5 has the reverse osmosis membrane separator 110 (refer FIG. 7) so that it may demonstrate in detail later. The reverse osmosis membrane separation device 110 introduces (accepts) a part of the washing water discharged from the chelating agent regeneration unit 3 and includes the concentrated water in which the chelating agent is concentrated by the reverse osmosis membrane and the chelating agent. Not separated into permeate.

  Hereinafter, the specific configuration and function of the soil washing classification unit 2 will be described with reference to FIG. In the soil washing and classifying unit 2, toxic metals or the like (toxic metals and / or compounds thereof) or soil (contaminated soil) collected by excavation of the ground contaminated with these ions is received by the input hopper 21. Then, the soil in the charging hopper 21 is introduced into the mixer 22 and is mixed with the cleaning water containing the chelating agent in the mixer 22. Here, the soil includes gravel, sand, and fine-grained soil (silt or clay having a particle size of 0.075 mm or less). In the mixer 22, harmful metals or the like adhering to the soil are separated from the soil and captured by the chelating agent.

  A mixture of soil and washing water generated by the mixer 22 (hereinafter referred to as “soil / washing water mixture”) is transferred to a wet mill breaker 23. As the mill breaker 23, for example, a rod mill can be used. The mill breaker 23 applies impact force, shear force, friction force and the like to gravel and sand. At that time, harmful metals attached to or contained in the gravel and sand are peeled off or removed and separated into the washing water. Hazardous metals and the like released from the soil surface or these ions are captured by the chelating agent in the wash water. Further, harmful metals or the like adsorbed on or adhering to the fine-grained soil or these ions are also released from the fine-grained soil and captured by the chelating agent in the washing water. The mixer 22 and the mill breaker 23 correspond to the mixing device 11 in FIG.

  Examples of the chelating agent include EDTA (ethylenediaminetetraacetic acid), HIDS (3-hydroxy-2,2′-iminodisuccinic acid), IDS (2,2′-iminodisuccinic acid), MGDA (methylglycine diacetic acid), EDDS ( Ethylenediaminediacetic acid) or sodium salt of GLDA (L-glutamic acid diacetic acid) can be used. The chelating agent is adsorbed on the soil or captures (chelates) toxic metals or these ions adhering thereto. When treating the soil, a chelating agent suitable for the treatment is selected according to the type of harmful metal or the like contained in the soil. The higher the concentration of the chelating agent in the washing water, the higher the trapping amount of harmful metals or these ions, but practically the range of 0.005 to 0.1 mol / liter, preferably 0.01 to 0. .05 mol / liter is set.

  The soil / washing water mixture discharged from the mill breaker 23 is introduced into the trommel 24. Although not shown in detail, the trommel 24 is a wet sieving device having a receiving tank capable of storing cleaning water, and a substantially cylindrical drum screen arranged to be inclined with respect to a horizontal plane. The drum screen can be rotated around its central axis by a motor. Further, the cleaning water can be sprayed into the drum screen. The trommel 24 corresponds to the first classifying device 12 in FIG.

  When the mixture of soil and washing water flows through the rotating drum screen of the trommel 24, the soil particles finer than the mesh of the drum screen pass through the mesh of the drum screen together with the washing water, and go out of the drum screen to the receiving tank. Get inside. On the other hand, soil particles coarser than the mesh of the drum screen are discharged out of the drum screen via the opening end on the lower side of the drum screen. In the trommel 24, the soil particles in the soil / washing water mixture rub against each other, so that harmful metals remaining on and adhered to the surface of the soil particles are peeled off and separated into the washing water. Harmful metals and the like released from the wash water or these ions are captured by the chelating agent in the wash water.

  In this embodiment, the mesh diameter (opening) of the drum screen of the trommel 24 is set so that soil particles having a particle diameter of less than 2 mm pass through the mesh of the drum screen. Therefore, in the trommel 14, soil particles having a particle diameter of 2 mm or more, that is, gravel is separated or collected from the soil / wash water mixture. The gravel separated by the trommel 24 is transferred to the gravel rinsing device 16 (see FIGS. 1 and 4). Note that the mesh size (opening) of the drum screen of the trommel 24 is not limited to the above, and is arbitrarily set according to the particle size of the relatively large particle of the particle to be obtained. be able to.

  A soil / washing water mixture containing soil particles having a particle size of less than 2 mm and washing water contained in a receiving tank of the trommel 24 is introduced into a cyclone 25 (liquid cyclone). The cyclone 25 includes a soil / wash water mixture, a mixture of fine soil having a relatively small particle size (for example, less than 0.075 mm) and wash water, and soil particles having a relatively large particle size (for example, 0.075 mm or more). To separate. A mixture of fine-grained soil and washing water (hereinafter referred to as “fine-grained soil-containing water”) is discharged from the upper end of the cyclone 25, and soil particles having a relatively large particle size are discharged from the lower end of the cyclone 25. . The fine-grained soil contained in the fine-grained soil-containing water is, for example, silt or clay having a particle diameter of less than 0.075 mm. The cyclone 25 corresponds to the second classifier 13 in FIG.

  Soil particles having a relatively large particle size discharged from the lower end of the cyclone 25 are introduced into a sand clean 26 (rinse washing device). The soil particle having a relatively large particle size is, for example, sand having a particle size of 0.075 to 2 mm. The sand clean 26 causes the washing water to flow at a predetermined pressure and an amount of water to perform a rinsing washing process on soil particles having a relatively large particle size, that is, sand, and remove remaining floating matters or foreign matters. Soil particles having a relatively large particle size, that is, sand subjected to the rinsing treatment, are transferred to the sand rinsing device 17 (see FIGS. 1 and 5).

  The fine-grained soil-containing water discharged from the cyclone 25 is introduced into the PH adjustment tank 27. Further, the washing water discharged from the sand clean 26 is also introduced into the pH adjusting tank 27 and mixed with the fine-grained soil-containing water. In the pH adjusting tank 27, the pH (hydrogen index) of the fine-grained soil-containing water uses a pH adjusting agent such as an acidic liquid (for example, sulfuric acid, hydrochloric acid, etc.) and an alkaline liquid (for example, an aqueous sodium hydroxide solution). Thus, the pH is adjusted to be almost neutral or a predetermined pH (for example, pH 7 to 8).

  The fine-soil-containing water whose pH has been adjusted in the pH adjustment tank 27 is introduced into the aggregation tank 28. In the agglomeration tank 28, a polyaluminum chloride liquid (PAC), a polymer flocculant, and a pH adjuster (an acidic liquid or an alkaline liquid) are added to fine-grained soil-containing water. As a result, a large number of flocs in which water-insoluble metal hydroxide and fine-grained soil are mixed are generated in the aggregation tank 28. At that time, water-polluting substances in the washing water are adsorbed on or attached to the floc. The polyaluminum chloride liquid and the polymer flocculant may be added to the fine-grained soil-containing water by the pH adjustment 27 instead of the flocculent tank 28.

  The fine-soil-containing water in the agglomeration tank 28 is introduced into the thickener 30 after the suspended matter is removed by the suspended matter collection device 29. The thickener 30 sinks water-insoluble flock or fine-grained soil by gravity in a state where the fine-grained soil-containing water is almost stationary, and has a sludge layer (solid content ratio: 5 to 10%) located at the bottom. It forms a supernatant water (wash water) which is located in the upper part and hardly contains flock or fine-grained soil. The floating oil floating on the surface of the supernatant water is removed by overflowing a small amount of the supernatant water from the upper part of the thickener 30. The thickener 30 corresponds to the sedimentation separator 14 in FIG.

  Sludge staying or precipitating in the lower portion of the thickener 30 is pulled out by a sludge pump or the like, transferred to the intermediate tank 31, and temporarily stored in the intermediate tank 31. The sludge in the intermediate tank 31 is transferred to the filter press 32 intermittently or continuously. The filter press 32 pressure-filters the sludge received from the intermediate tank 31, and produces | generates a filter cake and a filtrate. The filtration pressure of the filter press 32 is set so that the moisture content of the filter cake is 30 to 40%, for example. The filtrate of the filter press 32 is returned to the thickener 30. The filter press 32 corresponds to the filtration device 15 in FIG.

  On the other hand, the supernatant water (wash water) in the thickener 30 is introduced into the wash water tank 33 and temporarily stored. When the washing water tank 33 is full, the spare water tank 34 is used. The cleaning water stored in the cleaning water tank 33 is introduced into the chelating agent regeneration unit 3 (see FIGS. 1 and 3). When the cleaning water stored in the cleaning water tank 33 decreases due to evaporation or the like, the cleaning water tank 33 is appropriately replenished with tap water, industrial water or the like.

  Hereinafter, a specific configuration and function of the chelating agent regeneration unit 3 will be described with reference to FIG. The chelating agent regeneration unit 3 has a packed tower format in which solid phase adsorbent particles or packing (packing) in which the solid adsorbent is fixed is packed as a means for regenerating washing water or chelating agent. A washing water regeneration device 41 (chelating agent regeneration device) is provided. In addition, the chelating agent regeneration unit 3 is provided with a regenerated wash water storage tank 43 that stores the regenerated wash water, an acid solution storage tank 44 that stores an acid solution, and a water storage tank 45 that stores water.

  When the cleaning water (chelating agent) is regenerated, the cleaning water stored in the cleaning water tank 33 is transferred to the cleaning water regeneration device 41, while the cleaning water regenerated by the cleaning water regeneration device 41 is regenerated as a cleaning water storage tank. A pump 46 and a series of a plurality of pipes 47 to 50 for transferring to 43 are provided. Furthermore, a pump 51 and a pipe 52 for returning the cleaning water stored in the regenerated cleaning water storage tank 43 to the soil cleaning classification unit 2 (see FIG. 1) via the cleaning water supply unit 7 (see FIG. 1) are provided. Is provided.

  Further, the chelating agent regeneration unit 3 transfers the acid solution stored in the acid solution storage tank 44 to the washing water regeneration device 41 when the solid-phase adsorbent is regenerated, and the acid discharged from the washing water regeneration device 41. A pump 53 and a plurality of pipes 54 and 55 for returning the liquid to the acid liquid storage tank 44 are provided. In addition, when the solid phase adsorbent regenerated with the acid solution is washed with water, the chelating agent regeneration unit 3 transfers the water stored in the water storage tank 45 to the washing water regeneration device 41 while the washing water regeneration device 41. A pump 56 and a plurality of pipes 57 and 58 for returning the water discharged from the water storage tank 45 are provided.

  Valves 61, 62, 63, and 64 for opening and closing the corresponding pipes are provided in the pipes 47, 48, 54, and 57 for transferring the washing water, the acid solution, or the water to the washing water regenerating device 41, respectively. Has been. On the other hand, the pipes 49, 50, 55, 58 for discharging the washing water, the acid solution or the water from the washing water regenerating apparatus 41 have valves 65, 66, 67, 68 for opening and closing the corresponding pipe lines, respectively. It is installed. By switching the open / closed state of these valves 61 to 68, either the cleaning water, the acid solution, or the water can be supplied to and discharged from the cleaning water regenerating device 41. Note that the opening and closing of these valves 61 to 68 are automatically controlled by a controller (not shown).

  Hereinafter, an example of the operation method of the chelating agent regeneration unit 3 will be described. In addition, the driving | operation method demonstrated below is a mere illustration, and of course, the driving | running method of the chelating agent reproduction | regeneration part 3 which concerns on this invention is not limited to the following. When the cleaning water (chelating agent) is regenerated, the valves 61, 62, 65, 66 interposed in the pipe lines 47-50 are opened, while the other valves 63, 64, 67, 68 are closed, The pump 46 is operated. As a result, the cleaning water in the cleaning water tank 33 is circulated through the cleaning water regenerator 41 and transferred to the regenerated cleaning water storage tank 43.

  Thus, in the cleaning water regenerating apparatus 41, the cleaning water containing the chelating agent capturing toxic metals and the like is brought into contact with the solid phase adsorbent (solid phase adsorbent particles) having a higher complexing power than the chelating agent. As a result, harmful metals and the like captured by the chelating agent are separated from the chelating agent and adsorbed or extracted by the solid phase adsorbent. As a result, harmful metals and the like are removed and collected from the cleaning water, while the chelating agent is again in a state where it can capture the harmful metals and the cleaning water is regenerated. The washing water stored in the regenerated washing water storage tank 43 is returned to the soil washing classification unit 2 via the pipe line 52 by the pump 51.

  A solid-phase adsorbent having a higher complexing power than a chelating agent is a solid material such as a gel, and is generally coordinated with a chelating agent when contacted with an aqueous solution containing a chelating agent capturing a metal. It has a strong binding force other than a covalent bond to such an extent that the metal ions can be detached from the chelating agent and transferred to the solid phase adsorbent. Examples of such a solid-phase adsorbent include a material in which a cyclic molecule is densely supported on a carrier such as silica gel or a resin and a chelate ligand is modified on the cyclic molecule. When such a solid-phase adsorbent is used, a plurality of various bonds and interactions such as coordination bonds and hydrogen bonds occur due to adjacent cyclic molecules and chelate ligands, resulting in multipoint interactions, and metal ions In contrast to this, a chemical bond stronger than that of a chelating agent is generated, and metal ions can be selectively taken in by the properties of the cyclic molecule.

  Accompanying such regeneration of the washing water, the amount of adsorption of harmful metals and the like in the solid phase adsorbent increases with time, but there is an upper limit on the adsorption capacity of the solid phase adsorbent. For this reason, the solid phase adsorbent is regenerated when the amount of adsorption of harmful metals or the like in the solid phase adsorbent reaches a saturated state or the vicinity thereof. That is, an acid solution (for example, dilute nitric acid, dilute sulfuric acid, etc.) is flowed into the wash water regenerating device 41 with the wash water removed, and harmful metals adsorbed on the solid phase adsorbent are removed by the acid solution. Regenerate the solid-phase adsorbent. Thus, while the toxic metal and the like are recovered by the acid solution, the solid phase adsorbent is regenerated and becomes capable of adsorbing or extracting the toxic metal and the like or these ions again. The solid phase adsorbent is regenerated with an acid solution and then washed with water to remove a small amount of acid solution adhering to the solid phase adsorbent.

  When the amount of adsorption of toxic metal or the like of the solid phase adsorbent in the washing water regenerating apparatus 41 reaches a saturated state or in the vicinity thereof and the solid phase adsorbent is regenerated with an acid solution, the pipelines 54, 48, 49, 55 The valves 63, 62, 65, and 67 interposed in are opened, while the other valves 61, 64, 66, and 68 are closed, and the pump 53 is operated. As a result, the acid solution in the acid solution storage tank 44 flows through the cleaning water regenerator 41 and returns to the acid solution storage tank 44. Before starting the regeneration operation of the solid-phase adsorbent, the cleaning water in the cleaning water regeneration device 41 is removed. If a plurality of cleaning water regeneration devices 41 are arranged in parallel, the cleaning water can be continuously regenerated even when the supply of the cleaning water to some of the cleaning water regeneration devices 41 is stopped. . Whether or not the amount of harmful metal adsorption of the solid-phase adsorbent reaches a saturated state or the vicinity thereof can be determined by detecting the content of harmful metals or the like in the washing water discharged from the washing water regenerating device 41. it can.

  The time for which the acid solution is allowed to flow through the cleaning water regenerator 41 is preferably set according to the size or shape of the cleaning water regenerator 41, the size of the solid-phase adsorbent particles, and the like. The acid solution circulates through the acid solution storage tank 44 and the washing water regenerator 41. At that time, the solid phase adsorbent in the washing water regenerating apparatus 41 comes into contact with the acid solution, and harmful metals and the like adsorbed on the solid phase adsorbent are separated into the acid solution. That is, while the harmful metal and the like are recovered by the acid solution, the solid-phase adsorbent is regenerated to be able to adsorb the harmful metal and the like again.

  When the solid-phase adsorbent is washed with water after the regeneration of the solid-phase adsorbent with the acid solution, the valves 64, 62, 65, 68 provided in the pipes 57, 48, 49, 58 are opened. The other valves 61, 63, 66 and 67 are closed, and the pump 56 is operated. As a result, the water in the water storage tank 45 flows through the cleaning water regenerator 41 and returns to the water storage tank 45. Before starting the water washing operation of such a solid phase adsorbent, the acid solution in the washing water regenerating apparatus 41 is removed. The water circulates between the water storage tank 45 and the washing water regenerating device 41. At that time, the solid-phase adsorbent in the washing water regenerator 41 comes into contact with water, and the acid solution adhering to the solid-phase adsorbent is washed. Thereafter, the regeneration of the washing water is resumed.

Hereinafter, a specific configuration and function of the chelating agent recovery unit 4 will be described with reference to FIGS. 4 to 6.
As shown in FIG. 4, the gravel rinsing device 16 that forms a part of the chelating agent recovery unit 4 includes a belt conveyor 74, a gravel supply device 75, a rinse water spraying device 76, and a washing waste water receiving tank 77. .

  The belt conveyor 74 is a substantially cylindrical drive roller 78 coaxially attached to a shaft 78a that is rotationally driven by an electric motor (not shown), and a substantially coaxially attached shaft 79a that is not connected to a drive source. A cylindrical driven roller 79, a ring-shaped or endless conveying belt 80 wound around the driving roller 78 and the driven roller 79, a number of supporting rollers 81 for supporting or guiding the conveying belt 80, and the belt And a guide plate 82 for guiding gravel discharged from the conveyor 74. The gravel rinsing device 16 is sprayed or sprayed with rinsing water on the gravel discharged from the trommel 24 (see FIGS. 1 to 2) forming a part of the soil washing classifying unit 2, and is held or attached to the gravel. Wash away the chelating agent.

  The driving roller 78 and the driven roller 79 have the same diameter and are arranged at the same height. The conveyor belt 80 is formed of a porous material, mesh material, fibrous material, or cloth material that can be curved in a ring shape that allows rinsing water to pass but not gravel. The rinse water spraying device 76 sprays rinse water on the gravel transported by the transport belt 80 in an area having a predetermined length (for example, 1 to 2 m) in the moving direction of the transport belt 80. The amount of rinse water sprayed from the rinse water spray device 76 is preferably set so that almost all of the wash water adhering to the gravel can be washed away. For example, two to three times as much rinse water as the amount of washing water adhering to the gravel is sprayed. As a specific example, for example, when transporting gravel having a water content ratio of 15% at 20 tons per hour (dry basis), 6 to 9 tons of rinse water is sprayed per hour.

  The gravel supply device 75 supplies the gravel discharged from the trommel 24 at a predetermined flow rate on the conveyor belt 80 in the vicinity of the driven roller 79. The gravel supplied in this way is transported by the transport belt 80, falls downward via the guide plate 82 at a position corresponding to the drive roller 78, and is stored in a gravel storage (not shown). Rinsing water is sprayed from the rinse water spraying device 76 to the gravel transported by the transport belt 80, and the rinse water moves downward through the gaps between the gravel particles and passes through the transport belt 80 to be washed waste water receiving tank. Flow down to 77. At that time, the washing water containing the chelating agent adhering to the gravel is washed downward by the rinse water and falls or flows into the washing waste water receiving tank 77, but a part of the rinse water is held in the gap between the gravel particles. The That is, the washing water containing the chelating agent held or attached to the gravel is replaced with rinsing water that does not contain the chelating agent. That is, the chelating agent contained in or adhering to the gravel is washed away by the rinse water and accommodated in the washing waste water receiving tank 77 together with a part of the rinse water. The cleaning wastewater containing the chelating agent accommodated in the cleaning wastewater receiving tank 77 is introduced into the cleaning wastewater tank 83 (see FIG. 7). Thus, clean gravel containing almost no chelating agent and harmful metals is stored in the gravel storage (not shown).

  As shown in FIG. 5, the sand rinsing device 17 that forms part of the chelating agent recovery unit 4 includes a belt conveyor 84, a sand supply device 85, a rinsing water spray device 86, and a cleaning waste water receiving tank 87. . Here, the belt conveyor 84 is coaxially attached to a substantially cylindrical drive roller 88 that is coaxially attached to a shaft 88a that is rotationally driven by an electric motor (not shown), and a shaft 89a that is not connected to a drive source. A substantially cylindrical driven roller 89, a ring-shaped or endless conveying belt 90 wound around the driving roller 88 and the driven roller 89, and a number of supporting rollers 91 that support or guide the conveying belt 90. , And a guide plate 92 for guiding the sand discharged from the belt conveyor 84. The sand rinsing device 17 is sprayed or sprayed with rinsing water on the sand discharged from the sand clean 26 (see FIGS. 1 and 2) forming a part of the soil washing classifying unit 2, and is held by the sand. Wash off and remove the attached chelating agent.

  The driving roller 88 and the driven roller 89 have the same diameter and are disposed at the same height. The conveyor belt 90 is formed of a porous material, mesh material, fibrous material, or cloth-like material that can be curved in a ring shape that allows rinsing water to pass but not sand particles. The rinse water spraying device 86 sprays rinse water on the sand transported by the transport belt 90 in an area having a predetermined length (for example, 1 to 2 m) in the moving direction of the transport belt 90. The amount of rinse water sprayed from the rinse water spray device 86 is preferably set so that almost all of the wash water adhering to the sand can be washed away. For example, two to three times as much rinse water as the amount of washing water adhering to the sand is sprayed. As a specific example, for example, when sand having a water content of 20% is transported at 35 tons (dry basis) per hour, 14 to 21 tons of rinse water is sprinkled per hour.

  The sand supply device 85 supplies the sand discharged from the sand clean 26 onto the transport belt 90 in the vicinity of the driven roller 89 at a predetermined flow rate. The sand thus supplied is conveyed by the conveying belt 90, falls downward through the guide plate 92 at a position corresponding to the driving roller 88, and is stored in a sand storage (not shown). Rinsing water is sprayed from the rinsing water spraying device 86 onto the sand transported by the transport belt 90, and the rinsing water moves downward through the gaps between the sand particles, passes through the transport belt 90, and is a washing waste water receiving tank. Flow down to 87. At that time, the washing water containing the chelating agent adhering to the sand is washed down by the rinsing water and falls or flows into the washing waste water receiving tank 87, but a part of the rinsing water is held in the gap between the sand particles. The That is, the washing water containing the chelating agent held or adhered to the sand is replaced with rinsing water not containing the chelating agent. That is, the chelating agent contained in or adhering to the sand is washed away by the rinse water and accommodated in the washing waste water receiving tank 87 together with a part of the rinse water. The cleaning wastewater containing the chelating agent accommodated in the cleaning wastewater receiving tank 87 is introduced into the cleaning wastewater tank 83 (see FIG. 7). Thus, clean sand containing almost no chelating agent and harmful metals is stored in a sand storage (not shown).

  As shown in FIG. 6, the fine-grain soil rinsing device 18 that forms a part of the chelating agent recovery unit 4 includes a pulverizer 93 and a pulverized soil cleaner 94. The crusher 93 crushes the filter cake (fine-grained soil) discharged from the filter press 32 (see FIG. 2) to generate granular or powdery crushed soil (fine-grained soil). The crushed soil washing machine 94 sprays or sprays rinsing water on the crushed soil generated by the pulverizer 93 to remove (recover) the chelating agent held in the crushed soil.

  The crusher 93 crushes the filter cake discharged from the filter press 32 into a large number of filter cake pieces having a particle size of, for example, several mm (for example, 1 to 3 mm) by a blade 95 that rotates at high speed. As the crusher 93 for crushing the filter cake in this way, for example, a “dehydrated cake crusher” related to Taiheiyo Kiko Co., Ltd. it can.

  The crushed soil washing machine 94 includes a belt conveyor 96, a crushed soil receiving unit 97, a rinse water spraying device 98, and a washing waste water receiving tank 99. Here, the belt conveyor 96 is coaxially attached to a substantially cylindrical drive roller 100 that is coaxially attached to a shaft 100a that is rotationally driven by an electric motor (not shown), and a shaft 101a that is not connected to a drive source. A substantially cylindrical driven roller 101, a ring-shaped or endless conveying belt 102 wound around the driving roller 100 and the driven roller 101, and a number of supporting rollers 103 that support or guide the conveying belt 102. , And a guide plate 104 for guiding the crushed soil discharged from the belt conveyor 96.

  The driving roller 100 and the driven roller 101 have the same diameter and are arranged at the same height. The conveyor belt 102 is formed of a porous material, mesh material, fibrous material, or cloth material that can be curved in a ring shape that allows rinsing water to pass but does not allow pulverized soil particles to pass through. The rinsing water spraying device 98 sprays rinsing water onto the crushed soil transported by the transport belt 102 in an area having a predetermined length (for example, 1 to 2 m) with respect to the moving direction of the transport belt 102. The amount of rinse water sprayed from the rinse water spray device 98 is preferably set so that almost all of the wash water adhering to the crushed soil can be washed away. For example, two to three times as much rinse water as the amount of washing water adhering to the crushed soil is sprayed. As a specific example, for example, when transporting crushed soil having a water content ratio of 40% at 25 tons per hour (dry basis), 20 to 30 tons of rinse water is sprinkled per hour.

  The crushed soil receiving unit 97 supplies the crushed soil discharged from the pulverizer 93 onto the conveying belt 102 in the vicinity of the driven roller 101 at a predetermined flow rate. The crushed soil supplied in this way is transported by the transport belt 102, falls downward via the guide plate 104 at a position corresponding to the driving roller 100, and is stored in a fine grain soil storage (not shown). The Rinse water is sprayed from the rinse water spraying device 98 to the crushed soil transported by the transport belt 102, and the rinse water moves downward through the gaps between the particles of the crushed soil and passes through the transport belt 102 for cleaning. It flows down to the waste water receiving tank 99. At that time, the washing water containing the chelating agent adhering to the crushed soil is washed downward by the rinse water and flows down to the washing waste water receiving tank 99. Here, a part of rinse water is hold | maintained in the clearance gap between the particles of crushed soil. That is, the washing water containing the chelating agent held or attached to the crushed soil is replaced with rinsing water. That is, the chelating agent contained in or adhering to the crushed soil is washed away by the rinse water and accommodated in the washing waste water receiving tank 99 together with the rinse water (part). The cleaning wastewater containing the chelating agent accommodated in the cleaning wastewater receiving tank 99 is introduced into the cleaning wastewater tank 83 (see FIG. 7). Thus, a fine-grained soil storage (not shown) stores fine-grained soil that does not contain chelating agents and harmful metals.

  Hereinafter, with reference to FIG. 7, configurations and functions of the rinsing water generation unit 5 and the washing water supply unit 7 (mixing tank 111, pump 112, pipe 113, etc.) will be described. The rinse water generator 5 has a reverse osmosis membrane separator 110. A part of the washing water in the regenerated washing water storage tank 43 is introduced into the reverse osmosis membrane separation device 110 by a pump 118 and a pipe line 119. In this embodiment, the reverse osmosis membrane separation device 110 receives a part of the washing water discharged from the chelating agent regeneration unit 3 and pressurizes it with an attached high-pressure pump (not shown) (for example, 0. 5 to 1.5 MPa) A reverse osmosis membrane generates concentrated water in which the chelating agent is concentrated and permeated water not containing the chelating agent. That is, the reverse osmosis membrane separation device 110 separates the washing water into concentrated water in which the chelating agent is concentrated and permeated water that does not contain the chelating agent. Then, the concentrated water is introduced into the mixing tank 111 forming a part of the washing water supply unit 7 via the pipe 109. Of the washing water discharged from the chelating agent regeneration unit 3, the washing water other than the washing water introduced into the reverse osmosis membrane separation device 110 is supplied to a part of the washing water supply unit 7 by the pump 51 and the pipe 52. It is introduced into the mixing tank 111.

  The reverse osmosis membrane of the reverse osmosis membrane separation device 110 is, for example, a three-layer structure in which a polysulfone support layer and a crosslinked aromatic polyamide dense layer are laminated on the surface of a polyester nonwoven fabric (thickness: 100 to 120 μm). Can be used. The dense cross-linked aromatic polyamide layer has a large number of pores having a pore diameter of about 0.5 to 1.5 nm, and is very thin (for example, 0.2 to 0.25 μm) a semipermeable membrane. The polysulfone support layer is a relatively thick (for example, 40 to 50 μm) porous membrane for supporting or protecting a very thin crosslinked aromatic polyamide dense layer to prevent breakage thereof.

The reverse osmosis membrane separation device 110 is of a spiral type and has a plurality of reverse osmosis membrane elements in which a reverse osmosis membrane wound in a spiral shape is accommodated in a cylindrical container. It is practical that each reverse osmosis membrane element has, for example, a total length of about 1 to 2 m and an outer diameter of about 0.2 to 0.4 m. For example, the effective membrane area of a reverse osmosis membrane in a commercially available reverse osmosis membrane element of this type having a total length of about 1 m and an outer diameter of about 0.2 m (for example, manufactured by Authentec Co., Ltd., Nakatsugawa, Gifu Prefecture) is About 40 m ² . In the case of this reverse osmosis membrane element, it is estimated that the amount of permeated water produced when supplying cleaning water having a chelating agent concentration of about 1 mass% at a pressure of about 1 MPa is about 1.5 m ³ / hr. Therefore, for example, when generating permeated water of 60 m ³ per hour under the above conditions, 40 reverse osmosis membrane elements may be connected in parallel. When each reverse osmosis membrane element is horizontally arranged in multiple stages (for example, 8 rows and 5 stages), the area of the site required for the installation is about 10 to 20 m ² .

  The reverse osmosis membrane separation device 110 is a continuous type, and the operating conditions such as the supply amount and supply pressure (operating pressure) of washing water, the discharge amount of concentrated water or permeated water are 30 to 50% of the supply amount of washing water. It is set to generate a flow rate of permeate. That is, concentrated water having a flow rate of 50 to 70% of the supply amount of cleaning water is generated, and this concentrated water is introduced into the mixing tank 111 via the pipe 109. Thus, the chelating agent contained in the concentrated water is returned to the soil washing classification unit 2 via the mixing tank 111 and is not discharged outside the soil purification system.

  The permeated water discharged from the reverse osmosis membrane separation device 110 is supplied to the chelating agent recovery unit 4 as rinse water. Specifically, the permeated water is not shown in detail, but the rinse water spraying device 76 of the gravel rinsing device 16 and the rinsing water spraying of the sand rinsing device 17 are connected via a pump and a conduit (permeate water supply means). Rinsing water is supplied to the device 86 and the rinsing water spraying device 98 of the fine-grain soil rinsing device 18. The cleaning wastewater discharged from the chelating agent recovery unit 4 is introduced into the cleaning wastewater tank 83 and temporarily stored. As described above, in the chelating agent recovery unit 4, gravel, sand, or fine-grained soil adheres to these or is washed with 2 to 3 times the rinse water that is retained. The agent concentration is considerably lower than the wash water chelating agent concentration (approximately 1/2 to 1/3). The cleaning wastewater in the cleaning wastewater tank 83 is introduced into the mixing tank 111 forming a part of the cleaning water supply unit 7 by the pump 116 and the pipe line 117.

  Thus, to the mixing tank 111 which forms a part of the cleaning water supply unit 7, the cleaning water discharged from the cleaning water regeneration device 41 (see FIG. 3) other than the cleaning water introduced into the reverse osmosis membrane separation device 110. The cleaning water, the concentrated water discharged from the reverse osmosis membrane separation device 110, and the cleaning waste water discharged from the chelating agent recovery unit 4 are introduced, and these waters are mixed in the mixing tank 111. Then, the mixed water in the mixing tank 111 is supplied (returned) to the soil cleaning classification unit 2 as cleaning water by the pump 112 and the pipe 113. When it becomes necessary to increase the concentration of the chelating agent in the cleaning water for some reason, the chelating agent is supplied (supplemented) from the chelating agent supplementing unit 6 to the mixing tank 111. In addition, installation of the reverse osmosis membrane separation apparatus 110, the mixing tank 111, etc. which comprise the rinse water production | generation part 5 does not require a very large site.

  As described above, the soil purification system 1 is a completely closed system that circulates and uses wash water and does not discharge waste water outside the soil purification system. Moreover, in the soil purification system 1, the chelating agent contained in the washing water is not discharged outside the soil purification system but is repeatedly used while being regenerated. For this reason, the running cost of the soil purification system 1 can be made very low.

In FIG. 8, the soil at the main point of the soil purification system 1 when the soil cleaning classification unit 2 cleans and classifies 100 tons of soil per hour with, for example, cleaning water containing 1.0% by mass of a chelating agent. An example of the flow rates of water and chelating agent is shown. The total flow rate of the washing water supplied to the soil washing classification unit 2 is 450 m ³ / hr. In this example, 100 tons of soil includes 20 tons of gravel, 35 tons of sand, 25 tons of fine-grained soil, and 20 tons of water with a moisture content of 25%. The water content of gravel discharged from the trommel 24 is 15%, the water content of sand discharged from the sand clean 26 is 20%, and the fine-grained soil (filter cake) discharged from the filter press 32 is The water content is 40%. As is apparent from FIG. 8, in this example, 0.2 ton of chelating agent per hour is taken away from the soil washing classification unit 2 by gravel, sand and fine-grained soil. However, these chelating agents are recovered by the chelating agent recovery unit 4, introduced into the cleaning water supply unit 7 together with the cleaning waste water, and then returned to the soil cleaning classification unit 2, so that they are not discharged outside the soil purification system.

FIG. 9 shows an example of the flow rate and chelating agent concentration of the cleaning water, the rinsing water, the cleaning waste water, the chelating agent, etc. in the chelating agent recovery unit 4 and the rinsing water generation unit 5 in the case of FIG. In this example, set so as to produce a permeate 50% of the flow rate of the washing water supplied at a pressure of about 1MPa flow ^{(120m 3 / hr) (60m} 3 / hr). The total effective membrane area of the reverse osmosis membrane of the reverse osmosis membrane separator 110 is about 1600 m ² . Therefore, for example, 40 reverse osmosis membrane elements (length of about 1 m, outer diameter of about 0.2 m) having an effective membrane area of each reverse osmosis membrane of about 40 m ² may be connected in parallel. As is clear from FIG. 9, all the chelating agent (0.2 tons per hour) taken away from the soil washing classification unit 2 by gravel, sand and fine-grained soil is returned to the washing water and returned to the soil washing classification unit 2 Has been.

  As described above, according to the soil purification system 1 according to the embodiment of the present invention, the gravel, sand and / or fine soil discharged from the soil washing and classifying unit 2 is separated from the reverse osmosis membrane separation device 110 by the chelating agent recovery unit 4. Washing with permeated water (rinse water) removes and collects the chelating agent adhering to gravel, sand and / or fine-grained soil. Therefore, high-quality gravel, sand and / or fine-grained soil containing no chelating agent and harmful metals can be obtained. Then, the cleaning wastewater containing the chelating agent generated by the cleaning of gravel, sand and / or fine-grained soil in the chelating agent recovery unit 4 is returned to the soil cleaning classification unit 2 via the cleaning water supply unit 7 and soil purification. Since it is not discharged outside the system, the loss of the chelating agent outside the soil purification system is reliably prevented.

  On the other hand, the installation area of the reverse osmosis membrane separation device 110 constituting the rinse water generation unit 5 is very small. The washing water supply unit 7 that mixes washing water, concentrated water, and washing waste water and supplies (returns) the washing water to the soil washing classification unit 2 includes a mixing tank 11 such as a simple concrete pit, a pump 112, The installation area constituted by the pipe 113 or the like is very small. Therefore, the installation of the chelating agent recovery facility does not require a large site such as the sand container disclosed in Patent Documents 4 to 5, for example. Therefore, the chelating agent can be prevented from being taken out of the soil purification system by gravel, sand and / or fine-grained soil, and the site area of the facility for recovering the chelating agent can be extremely reduced.

  DESCRIPTION OF SYMBOLS 1 Soil purification system, 2 Soil washing classification part, 3 Chelating agent reproduction | regeneration part, 4 Chelating agent collection | recovery part, 5 Rinsing water production | generation part, 6 Chelating agent replenishment part, 7 Washing water supply part, 11 Mixing device, 12 1st classification device , 13 Second classifier, 14 Sedimentation separator, 15 Filtration device, 16 Gravel rinsing device, 17 Sand rinsing device, 18 Fine grain rinsing device, 21 Input hopper, 22 Mixer, 23 Mill breaker, 24 Trommel, 25 Cyclone , 26 Sand clean, 27 PH adjustment tank, 28 Coagulation tank, 29 Floating substance recovery device, 30 Thickener, 31 Intermediate tank, 32 Filter press, 33 Washing water tank, 34 Spare water tank, 41 Washing water regeneration device, 43 Recycled washing water storage tank , 44 Acid solution storage tank, 45 Water storage tank, 46 pump, 47-50 pipe line, 51 pump, 52 pipe line, 53 Pump, 54 pipelines, 55 pipelines, 56 pumps, 57 pipelines, 58 pipelines, 61-68 valves, 74 belt conveyor, 75 gravel supply device, 76 rinse water spray device, 77 washing waste water receiving tank, 78 drive roller, 78a shaft, 79 driven roller, 79a shaft, 80 conveying belt, 81 support roller, 82 guide plate, 84 belt conveyor, 85 sand supply device, 86 rinse water spray device, 87 washing waste water receiving tank, 88 drive roller, 88a shaft, 89 Driven roller, 89a shaft, 90 conveying belt, 91 support roller, 92 guide plate, 93 pulverizer, 94 crushed soil washing machine, 95 blade, 96 belt conveyor, 97 crushed soil receiving unit, 98 rinse water spraying device, 99 washing waste water Receiving tank, 100 drive roller, 100a shaft, 101 driven b , 101a shaft, 102 conveying belt, 103 support roller, 104 guide plate, 109 pipe, 110 reverse osmosis membrane separator, 111 mixing tank, 112 pump, 113 pipe, 116 pump, 117 pipe, 118 pump, 119 pipeline.

Claims (3)

Soil washing that includes gravel, sand, and fine-grained soil, and that is contaminated with harmful metals or compounds thereof, is cleaned with washing water containing a chelating agent, and is classified into gravel, sand, and fine-grained soil. A classification section;
A chelating agent regeneration unit that regenerates the chelating agent by removing the harmful metal or the compound from the chelating agent capturing the harmful metal or the compound in the washing water discharged from the soil washing classification unit;
A chelating agent recovery unit that recovers the chelating agent attached to the sand by washing the sand discharged from the soil cleaning classifying unit with rinse water;
A reverse osmosis membrane separation device that separates into a concentrated water in which the chelating agent is concentrated by a reverse osmosis membrane and a permeated water that does not contain the chelating agent by introducing a part of the washing water discharged from the chelating agent regeneration unit A rinse water generator that supplies permeate as rinse water to the chelating agent recovery unit;
Of the wash water discharged from the chelating agent regeneration unit, the wash water other than the wash water introduced into the rinse water generation unit, the concentrated water discharged from the rinse water generation unit, and the discharge from the chelating agent recovery unit A soil purification system comprising: a washing water supply unit that receives and mixes the washed waste water of sand and supplies the mixed water as washing water to the soil washing classification unit. The washing water supply unit
Of the wash water discharged from the chelating agent regeneration unit, the wash water other than the wash water introduced into the rinse water generation unit, the concentrated water discharged from the rinse water generation unit, and the discharge from the chelating agent recovery unit A mixing tank for receiving and mixing the waste sand washing wastewater,
The soil purification system according to claim 1, further comprising a pump and a pipe for supplying mixed water in the mixing tank as cleaning water to the soil cleaning classification unit. The soil washing classification unit is
A mixing device that mixes and agitate the soil containing gravel, sand, and fine-grained soil and washing water, separates the harmful metal adhering to the soil or a compound thereof from the soil, and captures the chelating agent;
A first classifying device for receiving a mixture containing soil and washing water discharged from the mixing device, and separating gravel from the mixture;
A second classifier for receiving a mixture containing sand, fine-grained soil and washing water discharged from the first classifier, and separating the sand from the mixture;
A sedimentation separator that separates a mixture containing fine-grained soil discharged from the second classifier and washing water into supernatant water and sludge containing fine-grained soil by sedimentation;
A filtration device for filtering sludge discharged from the sedimentation separator,
The chelating agent regeneration unit has a solid-phase adsorbent that has a higher complexing power than the chelating agent and adsorbs harmful metals or compounds thereof in the supernatant water when it comes into contact with the supernatant water discharged from the sedimentation separator. And having a chelating agent regeneration device for removing the harmful metal or its compound from the chelating agent in the supernatant water and regenerating the chelating agent,
The chelating agent recovery unit has a sand rinsing device that sprays or jets rinsing water on the sand separated by the second classifying device to wash away the chelating agent held in the sand. Item 3. The soil purification system according to Item 1 or 2.

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