JP2019042723A - Soil purification system - Google Patents

Abstract

To provide, in a soil purification system that classifies contaminated soil while purifying the same with washing water containing a chelating agent, a means that can recover a chelating agent accompanying gravel and the like and enables reduction of lot area of a chelating agent recovery facility.SOLUTION: The soil purification system 1 comprises a soil washing and classifying part 2, a chelating agent regeneration part 3, a chelating agent removal part 4, and a rinse water generation part 5. The chelating agent removal part 4 removes the chelating agent adhering to gravel and the like discharged from the soil washing and classifying part 2 by washing the gravel and the like with rinse water. The rinse water generation part 5 generates rinse water by removing the chelating agent from a portion of washing water discharged from the chelating agent regeneration part 3 and supplies the rinse water to the chelating agent removal part 4. The rinse water generation part 5 has a reverse osmosis membrane separation device, a concentrated water merging means, a permeated water supply means, and a washing wastewater merging means.SELECTED DRAWING: Figure 1

Description

  The present invention cleans soil containing gravel, sand and fine-grained soil and contaminated with a toxic metal or a compound thereof with washing water containing a chelating agent, as well as gravel, sand and fine-grained soil. The present invention relates to a soil purification system that is classified into two categories.

  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 soil contamination or industrial waste disposal including hazardous metals. 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 present inventor 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 gravel and the like.

  And the washing water containing a chelating agent adheres to the gravel generated in this way, but the gravel containing the chelating agent is not preferable as a civil engineering / building material. In addition, the chelating agent in the soil remediation facility is reduced by the amount taken away by the gravel. 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 gravel. 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. .

  Therefore, in the soil purification facilities disclosed in Patent Documents 4 to 5 related to the applicant of the present application, the gravel discharged from the trommel and attached with the cleaning liquid containing the chelating agent is washed with rinse water to remove the chelating agent from the gravel. Like to do. 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 gravel to which the cleaning liquid containing the chelating agent adheres, a very large area sand container is required to evaporate a large amount of cleaning wastewater. 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-mentioned conventional problems, and purifies soil contaminated with harmful metals with washing water containing a circulating chelating agent, while separating gravel from the soil. For the closed system type soil remediation facilities that are reused, the chelating agent can be prevented or reduced from being taken away by gravel, and the site area of the facility for recovering the chelating agent can be reduced. It is an object to be solved to provide a means that enables a significant reduction.

  The soil purification system according to the present invention made to solve the above problems includes a soil washing classification unit, a chelating agent regeneration unit, a chelating agent removal unit, and a rinse water generation unit. Here, the soil washing classifying unit contains a soil containing gravel (coarse aggregate), sand, and fine-grained soil and contaminated with a toxic metal or the like (a toxic metal and / or a compound thereof or ions thereof), and a chelating agent. It is cleaned and cleaned with water containing water and classified into gravel, sand, and fine-grained soil. The chelating agent regeneration unit regenerates the chelating agent by removing the harmful metal from the chelating agent that captures the harmful metal in the washing water discharged from the soil washing classification unit, and the washing water is supplied to the soil washing classification unit. Return it. The chelating agent removing unit removes the chelating agent adhering to the gravel by washing the gravel discharged from the soil washing and classifying unit with rinse water. The rinsing water generating unit generates rinsing water by removing the chelating agent from a part of the washing water discharged from the chelating agent regeneration unit, and supplies the rinsing water to the chelating agent removing unit.

  In this soil purification system, the rinse water generator has a reverse osmosis membrane separation device (reverse osmosis membrane filtration device), concentrated water merging means, permeated water supply means, and washing wastewater merging means. Here, the reverse osmosis membrane separation device accepts a part of the washing water discharged from the chelating agent regeneration unit, the concentrated water in which the chelating agent is concentrated by the reverse osmosis membrane, the permeated water not containing the chelating agent, To separate. The concentrated water joining means joins the concentrated water to the washing water returned from the chelating agent regeneration unit to the soil washing classification unit. The permeated water supply means supplies the permeated water as rinse water to the chelating agent removing unit. The washing waste water merging means merges the washing waste water generated by the gravel washing in the chelating agent removing unit with the washing water supplied from the chelating agent regeneration unit to the reverse osmosis membrane separation device.

  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 metal adhering to the soil from the soil and captures it by the chelating agent. . The first classifier receives a mixture of soil and washing water discharged from the mixing device, and separates gravel from the mixture. The second classifier receives a mixture of sand, fine soil, and washing water discharged from the first classifier, and separates the sand from the mixture. The sedimentation separation device separates the wash water containing fine-grained soil discharged from the second classification device into supernatant water and sludge containing fine-grained soil by sedimentation separation. The filtration device separates the fine-grained soil by filtering the sludge discharged from the sedimentation separation device.

  The chelating agent regeneration unit has a solid-phase adsorbent that adsorbs harmful metals and the like in the supernatant water when coming into contact with the supernatant water discharged from the sedimentation separator having a higher complexing power than the chelating agent, It is preferable to provide a washing water regeneration device for removing harmful metals from the chelating agent in the supernatant water and regenerating the supernatant water as washing water. Moreover, it is preferable that the chelating agent removing unit includes a gravel rinsing device that sprays or jets rinsing water on the gravel separated by the first classifier and removes the chelating agent held by the gravel.

  In the soil purification system according to the present invention, the concentrated water joining means receives and mixes the cleaning water discharged from the chelating agent regeneration unit and returned to the soil cleaning classification unit and the concentrated water discharged from the reverse osmosis membrane separation device. It is preferable to include a concentrated water mixing tank and a pump that supplies a mixed liquid of the cleaning water and the concentrated water in the concentrated water mixing tank to the soil cleaning classification unit. The washing waste water merging means includes a washing waste water mixing tank that receives and mixes the washing water discharged from the chelating agent regeneration unit and supplied to the reverse osmosis membrane separator and the washing waste water discharged from the chelating agent removal unit, It is preferable to provide a high-pressure pump for supplying the cleaning water in the waste water mixing tank and the mixed solution of the cleaning waste water to the reverse osmosis membrane separation device.

  According to the soil purification system of the present invention, the gravel discharged from the soil washing classification unit is washed with the permeated water (rinse water) separated by the reverse osmosis membrane separator in the chelating agent removing unit, and adhered to the gravel. The chelating agent is removed. Therefore, high-quality gravel that does not contain a chelating agent can be obtained. The cleaning wastewater containing the chelating agent generated by the gravel cleaning in the chelating agent removing unit is merged with the cleaning water supplied to the reverse osmosis membrane separation device and is not discharged outside the system. Loss to is reliably prevented. On the other hand, the installation area of the reverse osmosis membrane separation device is very small, and the installation area of the washing wastewater merging means that joins the washing wastewater generated in the chelating agent removal unit with the washing water supplied to the reverse osmosis membrane separation device is also very large Small. Therefore, a very large site is not required for the installation of the chelating agent recovery facility. Therefore, the chelating agent can be prevented from being taken out of the system by gravel, and the site area of the facility for collecting the chelating agent can be made very small.

FIG. 1 is a block diagram showing a configuration of a soil purification system according to the present invention. FIG. 2 is a block diagram illustrating a configuration of a soil washing classification unit that is a component of the soil purification system illustrated in FIG. 1. FIG. 3 is a schematic elevation view showing a configuration of a chelating agent regeneration unit that is a component of the soil purification system shown in FIG. 1. FIG. 4 is a schematic side view of a gravel rinsing device that is a component of the chelating agent removing unit. FIG. 5 is a schematic side view of a sand rinsing apparatus that is a component of the chelating agent removing unit. FIG. 6 is a schematic side view of a fine-grain soil rinsing device that is a component of the chelating agent removing unit. FIG. 7 is a schematic elevation view showing a configuration of a rinse water generating unit that is a component of the soil purification system shown in FIG. 1. FIG. 8 is a diagram showing the flow rates of soil, water, and chelating agent at key points of the soil purification system. FIG. 9 is a diagram showing the flow rate of the soil, water and chelating agent and the chelating agent concentration at the key points of the chelating agent removing unit and the rinse water generating unit.

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 which concerns on this invention is demonstrated, referring FIG. As shown in FIG. 1, the soil purification system 1 includes a soil washing classifying unit 2, a chelating agent regeneration unit 3, a chelating agent removing unit 4, a rinse water generating unit 5, and a chelating agent supplementing unit 6. 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 metals from the chelating agent that captures the harmful metals in the washing water discharged from the soil washing classification unit 2 and classifies the washing water into the soil washing classification. Return to part 2. The chelating agent removing unit 4 is configured to wash the gravel, sand and / or fine soil discharged from the soil washing and classifying unit 2 with rinsing water, thereby adhering to the gravel, sand and / or fine soil. Is removed (collected). 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 remover 4. 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.

  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 apparatus 11 mixes and stirs the soil containing gravel, sand, and fine-grained soil and washing water, and removes harmful metals attached to the soil from the soil and traps them in the chelating agent. Let The first classifier 12 receives a mixture of soil and washing water discharged from the mixing device 11 and separates gravel from the mixture. The second classifier 13 receives the mixture of sand, fine soil, and washing water discharged from the first classifier 12, and separates the sand from the 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 separate the fine-grained soil.

  The chelating agent regeneration unit 3 has a solid-phase adsorbent that adsorbs harmful metals and the like in the supernatant water when it comes into contact with the supernatant water discharged from the sedimentation separator 14 having a higher complexing power than the chelating agent, A washing water regeneration device 41 (see FIG. 3) is provided 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 removing unit 4 includes a gravel rinsing device 16 that sprays or jets rinsing water on the gravel separated by the first classifying device 12 and removes the chelating agent held in the gravel, and a second classifying device 13. After the rinsing water 17 is sprayed or sprayed on the separated sand to remove the chelating agent held in the sand, the finely divided soil (filter cake) separated by the filtration device 15 is crushed. And a fine-grain soil rinsing device 18 for removing the chelating agent held in the fine-grained soil by spraying or spraying rinse water.

  In the soil purification system 1, the rinse water generator 5 includes a reverse osmosis membrane separation device 110 (see FIG. 7), a concentrated water merging means, a permeate supply means, and a washing wastewater merging means, as will be described in detail later. And have. Here, the reverse osmosis membrane separation device 110 receives a part of the washing water discharged from the chelating agent regeneration unit 3 and the permeated water containing the chelating agent concentrated by the reverse osmosis membrane and the permeation containing no chelating agent. Separate into water. The concentrated water joining means joins the concentrated water to the washing water returned from the chelating agent regeneration unit 3 to the soil washing classification unit 2. The permeated water supplying means supplies the permeated water to the chelating agent removing unit 4 as rinse water. The washing wastewater merging means uses the reverse osmosis membrane separation device 110 (see FIG. 7) for washing wastewater generated by washing (rinsing) of gravel, sand and / or fine soil in the chelating agent removing unit 4 from the chelating agent regenerating unit 3. To the washing water supplied to the.

  Hereinafter, the specific configuration and function of the soil washing classification unit 2 will be described with reference to FIG. As shown in FIG. 2, in the soil washing classifying unit 2, it is contaminated with harmful metals or the like (toxic metals and / or compounds thereof) or these ions, and in some cases, other pollutants (for example, fluorine, boron, cyanide). The soil (contaminated soil) collected by excavation of the ground contaminated with the second type specific harmful substance (such as the second type specific harmful substance) 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 and 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, etc. to gravel or sand. At that time, harmful metals or other contaminants adhering to or contained in the gravel or sand are peeled off or removed and separated into the washing water. Harmful metals and other contaminants or ions of these released from the soil surface are captured by the chelating agent in the wash 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 captures (chelates) toxic metals or the like ions adhering to the soil. 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, soil particles in the soil / washing water mixture rub against each other, so that toxic metals and other contaminants remaining on or adhered to the surface of the soil particles or other contaminants are peeled off and separated into the wash water. Harmful metals and the like or other contaminants or these ions released in the washing water are trapped by the chelating agent in the washing 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.

  On the other hand, 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). These sands are used as recycled sand or sold.

  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 into 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 accumulating in the lower part of the thickener 30 is extracted 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 cake or fine-grained soil discharged from the filter press 32 can be reused or sold. 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 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. As shown in FIG. 3, the chelating agent regeneration unit 3 has a solid phase adsorbent particle or a packing (packing) in which the solid adsorbent is fixed as a means for regenerating washing water or chelating agent. A packed tower type washing water regenerating device 41 (chelating agent regenerating 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 line 52 are provided for returning the washing water stored in the regenerated washing water storage tank 43 to the soil washing classification unit 2 (see FIG. 1).

  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.

  Solid-phase adsorbents with higher complexing power than chelating agents are solid, such as gels, and generally coordinate with chelating agents when they come into contact with aqueous solutions containing chelating agents that capture metals. It has a strong binding force other than a covalent bond to such an extent that the bonded metal ion can be released 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 removing 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 removing 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 little chelating agent and contaminants is stored in the gravel storage (not shown).

  As shown in FIG. 5, the sand rinsing device 17 that forms a part of the chelating agent removing unit 4 includes a belt conveyor 84, a sand supply device 85, a rinsing water spraying device 86, and a washing 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, a sand storage (not shown) stores clean sand that is substantially free of chelating agents and contaminants.

  As shown in FIG. 6, the fine-grain soil rinsing device 18 that forms a part of the chelating agent removing 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 soil containing no chelating agent is stored in a fine soil reservoir (not shown).

  Hereinafter, the specific configuration and function of the rinse water generator 5 will be described with reference to FIG. As shown in FIG. 7, the reverse osmosis membrane separation device 110 (RO separation device) that forms a part of the rinse water generation unit 5 basically has a part of the wash water discharged from the chelating agent regeneration unit 3. It receives and isolate | separates into the concentrated water with which the chelating agent was concentrated, and the permeate which does not contain a chelating agent by a reverse osmosis membrane. However, in order to reduce the load on the reverse osmosis membrane, the cleaning wastewater discharged from the chelating agent removal unit 4 and having a lower chelating agent concentration than the cleaning water is transferred from the chelating agent regeneration unit 3 to the reverse osmosis membrane separation device 110. Means for merging with the supplied wash water (washing wastewater merging means) are provided.

  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 operating conditions such as the supply flow rate and supply pressure (operating pressure) of washing water or washing waste water, and the discharge flow rate of concentrated water are 30 to 30 times the supply flow rate of washing water or washing waste water. It is set to produce permeate with a flow rate of 50%. That is, concentrated water having a flow rate of 50 to 70% of the supply flow rate of cleaning water or cleaning wastewater is generated, and this concentrated water is combined with the cleaning water returned to the soil cleaning classification unit 2. That is, the chelating agent contained in the concentrated water is returned to the washing water returned to the soil washing classification unit 2 and is not discharged outside the soil purification system.

  The permeated water not containing the chelating agent discharged from the reverse osmosis membrane separation device 110 is supplied to the chelating agent removing 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 removing unit 4 is introduced into the cleaning wastewater tank 83 and temporarily stored. As described above, in the chelating agent removing 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).

  Moreover, the rinse water production | generation part 5 is discharged | emitted from the reverse osmosis membrane separator 110, the concentrated water whose chelating agent density | concentration is higher than washing water, and the washing water returned to the soil washing classification | category part 2 from the chelating agent reproduction | regeneration part 3 And a pump 112 that supplies the washing water (including the concentrated water) in the concentrated water mixing tank 111 to the soil washing classification unit 2. doing. The washing water returned from the chelating agent regeneration unit 3 to the soil washing classification unit 2 is introduced from the regeneration washing water storage tank 43 into the concentrated water mixing tank 111 via the pump 51 and the conduit 52. The concentrated water discharged from the reverse osmosis membrane separation device 110 is introduced into the concentrated water mixing tank 111 via the pipe 109. Here, when it becomes necessary to increase the chelating agent concentration of the cleaning water for some reason, the chelating agent is supplied (supplemented) from the chelating agent supplementing unit 6 to the concentrated water mixing tank 111.

  Further, the rinsing water generation unit 5 receives and mixes the cleaning water discharged from the chelating agent regeneration unit 3 and supplied to the reverse osmosis membrane separation device 110 and the cleaning waste water discharged from the chelating agent removal unit 4. The high pressure pump 114 that supplies the reverse osmosis membrane separation device 110 with the raw water to be subjected to reverse osmosis membrane separation (hereinafter referred to as “mixed raw water”) as a raw water to be subjected to reverse osmosis membrane separation (hereinafter referred to as “mixed raw water”). And a pipe line 115. The high-pressure pump 114 pressurizes the mixed raw water to, for example, 0.5 to 1.5 MPa and supplies it to the reverse osmosis membrane separation device 110. The cleaning wastewater in the cleaning wastewater tank 83 is introduced into the cleaning wastewater mixing tank 113 through the pump 116 and the pipe line 117. The cleaning water (part) in the regenerated cleaning water storage tank 43 is introduced into the cleaning waste water mixing tank 113 via the pump 118 and the pipe line 119.

  In the rinse water generating unit 5, all the washing wastewater discharged from the chelating agent removing unit 4 is returned to the reverse osmosis membrane separation device 110, while all the concentrated water discharged from the reverse osmosis membrane separation device 110 is returned to the soil washing classification unit 2 Since it is combined with the wash water that is returned to the plant, water is not discharged outside the soil purification system. In addition, since the raw mixed water having a lower chelating agent concentration than the wash water is supplied to the reverse osmosis membrane separation device 110, the load on the reverse osmosis membrane is reduced, and the discharge pressure of the high pressure pump 114 is lowered accordingly. Or the total surface area of the reverse osmosis membrane can be reduced. The installation of the reverse osmosis membrane separation device 110, the concentrated water mixing tank 111, the washing waste water mixing tank 113, and the like constituting the rinse water generating unit 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. Specific examples of water and chelating agent flow rates are 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 returned to the wash water by the chelating agent removing unit 4 and the rinse water generating unit 5, and are not discharged outside the soil purification system.

FIG. 9 shows specific examples of flow rates and chelating agent concentrations of the washing water, the rinsing water, the washing waste water, the chelating agent, etc. in the chelating agent removing unit 4 and the rinsing water generating unit 5 in the case of FIG. In this example, it is set to generate permeate having a flow rate (50 m ³ / hr) of 50% of the flow rate of the mixed raw water supplied at a pressure of about 1 MPa. 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 mentioned above, according to the soil purification system 1 which concerns on embodiment of this invention, the gravel, sand, and / or fine-grained soil discharged | emitted from the soil washing classification | category part 2 of the reverse osmosis membrane separation apparatus 110 by the chelating agent removal part 4 are carried out. The chelating agent adhering to the gravel, sand and / or fine-grained soil is removed by washing with permeated water (rinse water). Therefore, high-quality gravel, sand and / or fine-grained soil containing no chelating agent can be obtained. And the washing waste water containing the chelating agent produced by washing the gravel, sand and / or fine-grained soil in the chelating agent removing unit 4 is merged with the washing water supplied to the reverse osmosis membrane separation device 110, and the soil purification system. Since it is not discharged | emitted outside, the loss of a chelating agent can be prevented reliably. On the other hand, the installation area of the reverse osmosis membrane separation device 110 is very small, and the installation area of the facility for merging the washing waste water generated in the chelating agent removing unit 4 with the washing water supplied to the reverse osmosis membrane separation device 110 is also very large. Small. Therefore, a very large site is not required for the installation of the chelating agent recovery facility. 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 removal part, 5 Rinsing water production | generation part, 6 Chelating agent replenishment part, 11 Mixing device, 12 1st classification device, 13 2nd classification device , 14 Sedimentation separator, 15 Filtration device, 16 Gravel rinsing device, 17 Sand rinsing device, 18 Fine-grain soil 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 tanks, 46 pumps, 47-50 pipes, 51 pumps, 52 pipes, 53 pumps, 54 pipes , 55 pipes, 56 pumps, 57 pipes, 58 pipes, 61-68 valves, 74 belt conveyors, 75 gravel feeders, 76 rinsing water sprayers, 77 washing wastewater receiving tanks, 78 drive rollers, 78a shafts, 79 driven Roller, 79a shaft, 80 conveyor 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 Crushing machine, 94 Crushing soil washing machine, 95 blade, 96 Belt conveyor, 97 Crushing soil receiving part, 98 Rinsing water spray device, 99 Washing waste water receiving tank, 100 Drive roller , 100a shaft, 101 driven roller, 101a Yaw, 102 Conveyor belt, 103 Support roller, 104 Guide plate, 109 Pipe, 110 Reverse osmosis membrane separator, 111 Concentrated water mixing tank, 112 pump, 113 Washing waste water mixing tank, 114 High pressure pump, 115 pipe, 116 pump 117 lines, 118 pumps, 119 lines.

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;
The toxic agent or the compound is removed from the chelating agent capturing the toxic metal or the compound in the washing water discharged from the soil cleaning classifying unit to regenerate the chelating agent, and the washing water is supplied to the soil cleaning classifying unit. A chelating agent regeneration unit to be returned;
A chelating agent removing unit that removes the chelating agent adhering to the gravel by washing the gravel discharged from the soil washing classification unit with rinse water;
A soil purification system comprising a rinsing water generating unit that generates rinsing water by removing a chelating agent from a part of washing water discharged from the chelating agent regeneration unit and supplies the rinse water to the chelating agent removing unit. And
The rinse water generator is
A reverse osmosis membrane separation device that accepts a part of the washing water discharged from the chelating agent regeneration unit and separates the concentrated water in which the chelating agent is concentrated and the permeated water not containing the chelating agent by a reverse osmosis membrane;
Concentrated water merging means for merging concentrated water with the washing water returned from the chelating agent regeneration unit to the soil washing classification unit,
Permeated water supply means for supplying permeated water to the chelating agent removing unit as rinse water;
Washing wastewater merging means for merging the washing wastewater generated by the gravel washing in the chelating agent removing unit with the washing water supplied from the chelating agent regeneration unit to the reverse osmosis membrane separator. Purification system. 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 classification device for receiving a mixture of soil and washing water discharged from the mixing device and separating gravel from the mixture;
A second classifier for receiving a mixture of sand, fine-grained soil and washing water discharged from the first classifier and separating the sand from the mixture;
A sedimentation separator that separates wash water containing fine-grained soil discharged from the second classifier into supernatant water and sludge containing fine-grained soil by sedimentation;
A filtration device that separates fine-grained soil by filtering sludge discharged from the sedimentation separation device,
The chelating agent regeneration section 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 a washing water regeneration device that removes harmful metals or compounds thereof from the chelating agent in the supernatant water and regenerates the supernatant water as washing water. The chelating agent removal unit is separated by the first classification device. The soil purification system according to claim 1, further comprising a gravel rinsing device that sprays or jets rinsing water on the gravel to remove a chelating agent held in the gravel. The concentrated water merging means includes
Concentrated water mixing tank that receives and mixes the washing water discharged from the chelating agent regeneration unit and returned to the soil washing classification unit, and the concentrated water discharged from the reverse osmosis membrane separation device,
A pump for supplying the mixed solution of washing water and concentrated water in the concentrated water mixing tank to the soil washing classification unit;
The washing wastewater merging means is
A cleaning waste water mixing tank for receiving and mixing the cleaning water discharged from the chelating agent regeneration unit and supplied to the reverse osmosis membrane separation device, and the cleaning waste water discharged from the chelating agent removal unit,
3. The soil purification system according to claim 1, further comprising a high-pressure pump that supplies a cleaning liquid in the cleaning wastewater mixing tank and a mixed liquid of the cleaning wastewater to the reverse osmosis membrane separation device.

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