JP2015147154A - Treatment method and treatment apparatus for water containing heavy metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a treatment method and a treatment apparatus for water containing heavy metal, allowing for stable removal of heavy metals for a long period of time.SOLUTION: The treatment method of water containing heavy metal includes a pH adjustment step of adjusting the pH of water to be treated in a lime layer 12, a first separation step of insolubilizing heavy metals in the water to be treated in an iron-containing layer 13 containing an organic material to separate the heavy metals, a second separation step of reducing a sulfate ion in the water to be treated with a sulfuric acid reducing microbe in a sulfuric acid reduction layer 14 and forming sulfides of the heavy metals followed by separating them, and a third separation step of forming insoluble matters derived from an iron ion and insolubilizing the heavy metals by setting the water to be treated having passed through the second separation step, under an aerobic condition.

Description

  The present invention provides a treatment method and treatment for removing heavy metals from water containing heavy metals (cadmium, iron, copper, lead, zinc, etc.), such as mine waste water, ground water, factory waste water, permeated water in a rubble deposit site, etc. Relates to the device.

Conventionally, the processing method which removes heavy metal from heavy metal containing water is proposed (for example, refer patent documents 1 and 2).
For example, Patent Document 1 discloses a method for immobilizing heavy metals by bringing heavy metal-containing water into contact with a purifier containing metallic iron, iron oxide, and calcium compounds.
Patent Document 2 discloses a method for insolubilizing heavy metals by bringing heavy metal-containing water into contact with a purifier containing iron composite particles.

JP 2004-243222 A Japanese Patent No. 4639029

However, the processing methods described in Patent Documents 1 and 2 are actually difficult to say that the processing performance of heavy metals (such as cadmium) is insufficient.
Moreover, when the pH of to-be-processed water (raw water) is low, iron elutes from the purification agent for heavy metal processing, and the iron concentration of treated water may become high. For this reason, it may be difficult to reduce both the concentration of iron and other heavy metals (such as cadmium).
When the pH of the water to be treated (raw water) is low, the treatment efficiency of heavy metals can be increased by increasing the pH by adding an alkali agent, but in that case, the use of the alkali agent increases the processing cost. become.
The present invention has been made in view of the circumstances described above, and provides a method and apparatus for treating heavy metal-containing water that can efficiently treat both iron and other heavy metals at low cost. Objective.

The present invention is a method for treating heavy metal-containing water that removes heavy metals from water to be treated containing heavy metals, the pH adjusting step for adjusting the pH of the water to be treated by bringing the water to be treated into contact with a lime material, and The first separation step of bringing the water to be treated that has undergone the pH adjustment step into contact with an iron-containing material containing an organic material, and insolubilizing the heavy metal together with the iron oxide derived from the iron-containing material, and the first separation A second separation step in which the water to be treated that has undergone the process is brought into contact with an organic material under anaerobic conditions, and sulfate ions in the treated water are reduced by the sulfate-reducing microorganisms in the organic material and the sulfide of the heavy metal is generated. And a third separation step of generating insolubilized substances derived from iron ions and insolubilizing the heavy metals by placing the water to be treated after the second separation step under an aerobic condition. processing The law provides.
In the third separation step, it is preferable to place the water to be treated under aerobic conditions by bringing air introduced from the outside into contact with the water to be treated.
The insolubilized material derived from iron ions is preferably composed mainly of trivalent iron hydroxide.
The present invention has an oxygen concentration adjustment step of adjusting the dissolved oxygen concentration of the water to be treated by microorganisms in the organic material by bringing the water to be treated into contact with the organic material prior to the pH adjustment step. It may be.

The present invention includes a lime material, a pH adjusting unit that adjusts the pH of water to be treated with the lime material, and an iron-containing material containing an organic material, and the heavy metal in the water to be treated that has passed through the pH adjusting unit. A first separation part that is insolubilized and separated together with the iron oxide derived from the iron-containing material, and an organic material, and sulfate ions in the water to be treated are subjected to anaerobic conditions by sulfate-reducing microorganisms in the organic material. The insolubilized substance derived from iron ions is generated by placing the second separation part that reduces and generates and separates the heavy metal sulfide and the water to be treated after the second separation step under aerobic conditions. There is provided a heavy metal-containing water treatment device having a third separation unit for insolubilizing heavy metals.
It is preferable that the third separation unit has an introduction unit that introduces air to be brought into contact with the water to be treated from the outside.
In the present invention, an oxygen concentration adjusting unit that has an organic material upstream of the pH adjusting unit and adjusts the dissolved oxygen concentration of the water to be treated by microorganisms in the organic material may be provided.

According to the present invention, a large amount of trivalent iron ions can be generated by placing the water to be treated in an aerobic condition in the third separation step. Therefore, the iron ion-derived insolubilized product can be generated and other heavy metals (Cd and the like) can be insolubilized under relatively low pH conditions.
Accordingly, even when the pH of the water to be treated (raw water) is low, both iron and other heavy metals can be efficiently treated.
Moreover, since heavy metal processing is possible even if it does not raise pH with an alkali agent, processing cost can be suppressed.

It is a schematic explanatory drawing of the processing apparatus of the heavy metal containing water which is the 1st Embodiment of this invention. It is a flowchart of the processing method of heavy metal containing water using the processing apparatus of a previous figure. It is a schematic explanatory drawing of the processing apparatus of the heavy metal containing water which is the 2nd Embodiment of this invention. It is a schematic explanatory drawing of the processing apparatus of the heavy metal containing water which is the 3rd Embodiment of this invention. It is a schematic explanatory drawing of the processing apparatus of the heavy metal containing water which is the 4th Embodiment of this invention. (A) It is a schematic explanatory drawing of the processing apparatus of the heavy metal containing water which is the 5th Embodiment of this invention. (B) It is a figure which shows the structure of one layer of the processing apparatus shown to (a). It is a schematic explanatory drawing of the processing apparatus of the heavy metal containing water which is the 6th Embodiment of this invention. It is a test result which shows pH of to-be-processed water. It is a test result which shows the oxidation-reduction potential of to-be-processed water. It is a test result which shows Cd density | concentration of to-be-processed water. It is a test result which shows Fe concentration of to-be-processed water. It is a test result which shows Cu density | concentration of to-be-processed water.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is a diagram illustrating the configuration of a heavy metal-containing water treatment apparatus 1 according to the first embodiment of the present invention. FIG. 2 is a flowchart of a processing method using the processing apparatus 1.

The object of treatment of the present invention is water containing heavy metals, such as mine wastewater, groundwater, factory wastewater, permeated water in a rubble deposit site, and the like. These (for example, mine wastewater) usually contain sulfate ions.
Examples of heavy metals to be treated include cadmium (Cd), iron (Fe), copper (Cu), lead (Pb), and zinc (Zn). The present invention can also treat aluminum (Al).
The pH of the water to be treated is 3 to 6, for example.

As shown in FIG. 1, the heavy metal-containing water treatment apparatus 1 is connected to the first reaction tank 10 via a first reaction tank 10 and a pipe line 16 from the upstream side to the downstream side in the flow direction of the water to be treated. Second reaction tank 20.
Reference numeral 2 denotes a water tank to be treated for storing the water to be treated 3 (raw water), and is connected to the first reaction tank 10 via a pipe line 5.
The oxidation-reduction potential is at sampling points P1-1 (lower end of the oxygen concentration adjustment layer 11), P1-2 (lower end of the sulfate reduction layer 14), and P2 (lower end of the aerobic treatment layer 21) of the first reaction tank 10. Measured. It was confirmed that P1-1 and P1-2 were in a reduced state and P2 was in an oxidized state.

The first reaction tank 10 is a bottomed cylindrical body, and from the upstream side to the downstream side, the oxygen concentration adjustment layer 11 (oxygen concentration adjustment unit), the lime layer 12 (pH adjustment unit), and the iron-containing layer 13. (First separation part), a sulfate reduction layer 14 (second separation part), and a support layer 15.
The oxygen concentration adjustment layer 11, the lime layer 12, the iron-containing layer 13, the sulfate reduction layer 14, and the support layer 15 are arranged in this order from the upper layer side to the lower layer side in the first reaction tank 10.

  The pipeline 5 can supply the treated water 3 (raw water) of the treated water tank 2 to the oxygen concentration adjusting layer 11 of the first reaction tank 10. The pipe line 16 can supply the water to be treated that has passed through the support layer 15 to the aerobic treatment layer 21 of the second reaction tank 20. The pipe line 17 can discharge the treated water 63 that has passed through the aerobic treatment layer 21 to the outside of the system.

The oxygen concentration adjusting layer 11 is a layer for adjusting the dissolved oxygen concentration in the water to be treated, and contains a biodegradable organic material.
Organic materials include humus, bark compost, charcoal, oil cake, chicken manure, cow dung, pig manure, compost, peat, rice cracker, peat moss, coco pate, eggplant, crushed wood, oat flour, rice straw, wood chips, rapeseed Examples include salmon, bagasse, okara, fish salmon, fish meal, and food residues. As the organic material, one of these may be used, or two or more may be used in combination.
Since a biodegradable organic material is used for the oxygen concentration adjusting layer 11, aerobic microorganisms (aerobic bacteria) can grow when the dissolved oxygen concentration of the water to be treated is sufficiently high.

The oxygen concentration adjusting layer 11 may contain a lime material. The lime material is preferably composed mainly of calcium carbonate (CaCO ₃ ). For example, limestone (limestone, crystalline limestone (marble), calcite, aragonite, etc.) can be used.
As a lime material, for example, when a granular material (or powdery material) having an average particle size of about 0.1 to 10 mm (for example, an average particle size of 0.3 to 0.6 mm) is used, the gap between the lime materials is increased, Water permeability can be increased. The amount of lime material used (bulk capacity) can be, for example, 1/10 or less of the bulk capacity of the organic material.

The amount of lime added is preferably set such that the pH of the water to be treated (the pH of the outlet water of the oxygen concentration adjusting layer 11) is 4.5 to 6.5, preferably 5 to 6.
By using the lime material, iron ions (Fe ³⁺ ) and aluminum ions are deposited and removed as oxides or hydroxides, so that it is possible to prevent the formation of fixed matter (scale) in the lime layer 12.
Moreover, the use of lime material can prevent the decrease in the activity of microorganisms in the oxygen concentration adjusting layer 11 by suppressing the decrease in pH, and maintain an oxygen-free state. For this reason, the oxidation (Fe ^< 2 ⁺ >-> Fe ^<3+ >) of an iron ion can be suppressed and the production | generation of the fixed substance (scale) in the lime layer 12 can be prevented. Unlike other alkaline agents, lime has the advantage that an excessive increase in pH is unlikely to occur even if the amount added is large.
The addition amount of lime material is good, for example as 5-100 mass parts (preferably 25-50 mass parts) with respect to 100 mass parts of organic materials.
Since the lime material suppresses a decrease in pH, it is possible to prevent the iron-containing material from being eluted and to reduce the Fe concentration in the water to be treated.

The oxygen concentration adjusting layer 11 may include a contact material (iron-containing material) containing iron.
The iron-containing material is made of a material containing iron (metal iron, iron oxide, etc.), and for example, iron powder, iron fine particles, iron pieces, iron cutting waste, and the like can be used.
The addition amount of the iron-containing material may be, for example, 5 to 100 parts by mass (preferably 5 to 25 parts by mass) with respect to 100 parts by mass of the organic material.
By adding the iron-containing material, the redox potential of the water to be treated can be lowered. For this reason, it can prevent that the iron oxide etc. which originate in iron in to-be-processed water adhere to the lime layer 12. FIG. The iron-containing material also has an action of suppressing a decrease in pH.

  The distribution of the iron-containing material and the lime material in the oxygen concentration adjusting layer 11 is not particularly limited, but it is desirable that the iron-containing material and the lime material are uniformly mixed with the organic material.

If the water to be treated with a high metal concentration is treated for a long period of time, the treatment performance of the first reaction tank 10 is lowered, the oxidation-reduction potential cannot be kept low, and the problem of iron oxide sticking occurs and the treatment performance is lowered. However, by using an iron-containing material and a lime material for the oxygen concentration adjusting layer 11, even when the metal concentration of the water to be treated is high, the oxidation-reduction potential can be lowered over a long period of time and the treatment performance can be maintained.
In addition, when the dissolved oxygen concentration of to-be-processed water is low enough, the oxygen concentration adjustment layer 11 is not necessary.

The lime layer 12 (pH adjusting unit) is a layer that adjusts the pH of the water to be treated, and includes a lime material. The lime material is preferably composed mainly of calcium carbonate (CaCO ₃ ). For example, limestone (limestone, crystalline limestone (marble), calcite, aragonite, etc.) can be used.
When the lime material which is a granular material (or powdery material) having an average particle diameter of about 10 to 100 mm made of calcium carbonate or the like is used as the lime layer 12, the gap between the lime materials can be increased and water permeability can be increased. . The lime material preferably has an average particle size larger than that used for the oxygen concentration adjusting layer 11.

The addition amount of the lime material is preferably set so that the pH of the water to be treated (the pH of the outlet water of the lime layer 12) is 5 to 7, and preferably 5.5 to 6.5.
Since the lime material suppresses a decrease in pH, it is possible to prevent the iron-containing material from being eluted in the iron-containing layer 13 and to reduce the Fe concentration in the treated water.
By suppressing the decrease in pH, the lime material can suppress the precipitation of metal hydroxide and prevent a situation where water flow is hindered. Unlike other alkaline agents, lime materials (particularly limestone) have the advantage that an excessive increase in pH is unlikely to occur even if the amount added is large.
In the present specification, as the average particle size, for example, a 50% cumulative particle size, a mode particle size, or the like may be adopted. The average particle size can be measured on a volume basis or a mass basis. Moreover, a main component means containing the said component exceeding 50 mass%.

The iron-containing layer 13 includes a contact material (iron-containing material) containing iron.
The iron-containing material is made of a material containing iron (metal iron, iron oxide, etc.), and for example, iron powder, iron fine particles, iron pieces, iron cutting waste, and the like can be used.
By adding the iron-containing material, the redox potential of the water to be treated can be lowered. For this reason, it can prevent that the iron oxide etc. which originate in iron in to-be-treated water adhere to the sulfate reduction layer 14. The iron-containing material also has an action of suppressing a decrease in pH.
The iron-containing layer 13 may contain an organic material. As the organic material, those listed as organic materials that can be used for the oxygen concentration adjusting layer 11 (humus, bark compost, etc.) can be used.

The sulfate reduction layer 14 includes an organic material. As the organic material, those listed as organic materials that can be used for the oxygen concentration adjusting layer 11 (humus, bark compost, etc.) can be used.
As will be described later, since the sulfate reduction layer 14 is under anaerobic conditions, sulfate-reducing microorganisms (sulfur-reducing bacteria) grow.
Examples of sulfate-reducing bacteria include Desulfovibrio, Desulfomicrobium, Desulfobacula, and Desulfobacter. The sulfate-reducing bacteria are not limited to these.
For the sulfate reduction layer 14, a filler (carrier) made of plastic (for example, biodegradable plastic) or ceramic may be used.

  The support layer 15 is made of gravel sand or the like. The support layer 15 can prevent the filler and suspended substances in the first reaction tank 10 from flowing out.

  The water surface 18 of the water to be treated in the first reaction tank 10 is desirably higher than the upper end surface of the oxygen concentration adjusting layer 11.

  The second reaction tank 20 has an aerobic treatment layer 21 (third separation part) and a support layer 22 made of gravel sand from the upstream side to the downstream side. The support layer 22 is provided on the lower layer side of the aerobic treatment layer 21.

For the aerobic treatment layer 21, an organic material may be used as a filler. As the organic material, those listed as organic materials that can be used for the oxygen concentration adjusting layer 11 (humus, bark compost, etc.) can be used.
The aerobic treatment layer 21 may contain a lime material as a filling material. As the lime material, those mentioned as the lime material that can be used for the lime layer 12 (for example, those mainly composed of calcium carbonate) can be used.
As the lime material, for example, when a granular material (or powdery material) having an average particle size of about 0.1 to 10 mm (for example, an average particle size of 0.6 to 2 mm) is used, the gap between the lime materials is increased, and water permeability is increased. Can be increased. The amount of lime material used (bulk capacity) can be, for example, 1/10 or less of the bulk capacity of the organic material.
By using the lime material, it is possible to prevent a decrease in the activity of microorganisms in the aerobic treatment layer 21 by suppressing a decrease in pH and maintain an oxygen-free state. For this reason, oxidation of iron ions (Fe ²⁺ → Fe ³⁺ ) can be suppressed, and the generation of fixed matter (scale) can be prevented.

  The second reaction tank 20 is a bottomed cylindrical body whose upper opening 20a is released to the atmosphere. Outside air is introduced into the tank through the upper opening 20a (introduction section), and water to be treated is treated in the aerobic treatment layer 21. Can be contacted. A space inside the second reaction tank 20 and above the upper end surface 21a of the aerobic treatment layer 21 is referred to as an upper space 20b.

  It is desirable that the supply end 16 a of the pipe line 16 (path) for sending the water to be treated from the first reaction tank 10 to the second reaction tank 20 is higher than the upper end surface 21 a of the aerobic treatment layer 21. As a result, the water to be treated can come into contact with the air in the upper space 20b before it is dropped from the supply end 16a and reaches the aerobic treatment layer 21.

Since the upper end surface 21a of the aerobic treatment layer 21 is in contact with the air in the upper space 20b, the aerobic treatment layer 21 is in an aerobic condition.
The water surface 23 of the water to be treated in the second reaction tank 20 is desirably located at a position lower than the upper end surface 21 a of the aerobic treatment layer 21. In the illustrated example, the water surface 23 is substantially at the same height as the lower end of the aerobic treatment layer 21.
When the position of the water surface 23 in the second reaction tank 20 is lower than the upper end surface 21a, in the region above the water surface 23, the filler 24 (24a, 24b) (organic material, lime material) of the aerobic treatment layer 21 is used. And the like, the water to be treated flowing on the surface of the filling 24 can be brought into contact with air over a large area.

The illustrated aerobic treatment layer 21 includes a first layer 21A made of a first filler 24a (organic material, lime material, etc.), and a second filler 24b having an average particle size smaller than that of the first filler 24a. And a second layer 21B made of (organic material, lime material, etc.).
The first layer 21A is located on the upstream side (upper layer side in the illustrated example) of the second layer 21B.

In the first layer 21 </ b> A in which the average particle size of the filler 24 is large, it is easy to ensure a contact opportunity between the flowing water on the surface of the filler 24 and the air in the gaps between the fillers 24. For this reason, the efficiency of the oxidation reaction can be increased.
In the second layer 21B in which the average particle size of the filler 24 is small, suspended substances such as hydroxides and oxides generated in the aerobic treatment layer 21 and fragments of the filler 24 are captured, and these are aerobic. Outflow from the treatment layer 21 can be prevented.

For the aerobic treatment layer 21, a filler (carrier) (not shown) made of plastic (for example, biodegradable plastic) or ceramic may be used. The filler may be spherical, cylindrical, rectangular parallelepiped, string, spiral (coiled), or the like.
Since the filler is less likely to be deformed or broken, a void can be secured in the aerobic treatment layer 21 for a long period of time, and the contact area between the water to be treated and air can be increased. For this reason, the efficiency of the oxidation reaction in the aerobic treatment layer 21 can be increased.
Even in the case of using a filler, as shown in FIG. 1, the aerobic treatment layer 21 includes a first layer 21 </ b> A having a large average particle diameter of the filler (fillers 24, 24 a) and a filler (filler 24). , 24b) and the second layer 21B having a small average particle size.

  The aerobic treatment layer 21 may be aerobic by aeration of the water to be treated stored in the second reaction tank 20.

Next, with reference to FIG. 1 and FIG. 2, the processing method of the heavy metal containing water using the processing apparatus 1 is demonstrated.
The treated water 3 (raw water) in the treated water tank 2 is supplied to the first reaction tank 10 through the pipe line 5 (path) by the liquid feed pump 4.
In the 1st reaction tank 10, to-be-processed water is supplied to the oxygen concentration adjustment layer 11, and contacts the organic material which comprises the oxygen concentration adjustment layer 11 (oxygen concentration adjustment process). Thereby, the dissolved oxygen of the water to be treated is consumed by the aerobic microorganisms in the organic material, and the concentration thereof decreases.
Since the dissolved oxygen concentration of the water to be treated is lowered by passing through the oxygen concentration adjusting layer 11, the generation of a fixed substance (scale) made of iron oxide (or iron hydroxide) in the lime layer 12 on the downstream side is generated. Can be suppressed.
In addition, since the organic material is biodegradable and can serve as a nutrient source for aerobic microorganisms, the oxygen concentration adjusting layer 11 is suitable for the growth of aerobic microorganisms.

The organic material constituting the oxygen concentration adjusting layer 11 includes a substance having pH buffering ability such as humic acid (humic acid). Humic acid (humic acid) and the like include a carboxyl group (—COOH), a hydroxyl group (—OH), an amino group (—NH ₂ ), and the like, and these functional groups can be ion-exchanged with metals.

As an example of the pH buffering ability of the organic material, an acid and alkali neutralization reaction is shown below.
R ₁ ⁻ Na ⁺ + H ⁺ + Cl ⁻ → R ₁ H + Na ⁺ + Cl ⁻
R ₁ H + Na ⁺ + OH ⁻ + Cl ⁻ → R ₁ ⁻ Na ⁺ + H ₂ O
(R ₁ is a functional group contained in the organic material and is a cation exchange group having high selectivity for H ⁺ )

The pH of the water to be treated is adjusted by the pH buffering ability of the organic material. The pH of the water to be treated rises from 3-4 to 5-6, for example.
Moreover, the density | concentration in some to-be-processed water falls in the metal of some to-be-processed water by reaction with an organic material.
For example, the concentration of Al and Zn decreases in the water to be treated due to a reaction with an organic material (for example, the aforementioned humic acid).

The treated water that has passed through the oxygen concentration adjusting layer 11 is supplied to the lime layer 12.
In the lime layer 12, the water to be treated comes into contact with the lime material (pH adjustment step). The pH of water to be treated rises when calcium carbonate or the like constituting the lime material is dissolved in the water to be treated. The pH of the water to be treated is increased to 5 to 7, for example.

The example of the reaction at the time of melt | dissolution of a lime material (calcium carbonate) is given. When the pH is lower than 5, the following reaction proceeds mainly.
CaCO ₃ + 2H ⁺ → Ca ²⁺ + H ₂ O + CO ₂
When the reaction proceeds and the pH is 5 or more, the next reaction mainly proceeds.
CaCO ₃ + H ₂ CO ₃ → Ca ²⁺ + 2HCO ₃ ⁻
Due to the production of hydrogen carbonate ions having a pH buffering action, even if iron ions are oxidized in the iron-containing layer 13, the pH is hardly lowered.
For this reason, if the thing which has calcium carbonate as a main component is used as a lime material, it will become easy to adjust pH to neutral vicinity (for example, 5-7).
By making the pH of the water to be treated near neutral, it is possible to suppress an excessive amount of iron elution from the iron-containing layer 13.

  The treated water is preferably in an oxygen-free state (or a state close thereto) at the inlet of the lime layer 12. For example, the redox potential at the inlet of the lime layer 12 is preferably 0 mV or less. The oxidation-reduction potential can be a measured value converted to a hydrogen reference electrode using an Eh meter (Fujiwara Seisakusho).

  The treated water that has passed through the lime layer 12 is supplied to the iron-containing layer 13 (first separation step). In the iron-containing layer 13, the dissolved oxygen concentration of the water to be treated is further lowered by the aerobic microorganisms in the organic material.

When the water to be treated is supplied to the iron-containing layer 13 (first separation step), part of the iron contained in the iron-containing material is ionized as shown in the following formula.
Fe ⁰ + 2H ₂ O → Fe ²⁺ + H ₂ + 2OH ⁻
According to this reaction, since hydrogen and hydroxide ions are generated, the pH of the water to be treated rises and the water to be treated is in a strong reduced state.
The oxidation-reduction potential of the water to be treated at the iron-containing layer 13 outlet can be set to −100 mV or less (for example, −600 to −100 mV), for example. The oxidation-reduction potential of the water to be treated in the iron-containing layer 13 is preferably −200 mV or less because the sulfuric acid reduction reaction in the sulfuric acid reduction layer 14 is promoted.

The produced iron ions are insolubilized as oxides. Since this oxide has an action of adsorbing heavy metals (Cd, Fe, Cu, Pb, Zn, etc.), it becomes insoluble with the heavy metals.
For this reason, the heavy metal density | concentration in to-be-processed water falls. The insolubilized heavy metal is captured by the iron-containing layer 13 and separated from the water to be treated.

The organic material contained in the iron-containing layer 13 has an effect of suppressing excessive elution of iron from the iron-containing material of the iron-containing layer 13.
The reason why organic materials can suppress iron elution is that the organic material covers the surface of the iron-containing material, the chance of contact between the iron-containing material and water is reduced, and the dissolved iron is adsorbed and co-precipitated on the organic material. Therefore, it can be estimated that iron ion elution is less likely to occur.
In addition, since the organic material has a pH buffering ability, it is possible to prevent a decrease in pH of the water to be treated and suppress iron elution.

The treated water that has passed through the iron-containing layer 13 is supplied to the sulfate reduction layer 14 in a reduced state, and comes into contact with the organic material under anaerobic conditions (second separation step).
Sulfate ions in the water to be treated are reduced by sulfate-reducing bacteria in the sulfate reduction layer 14 to generate sulfide ions (S ²⁻ ).
The sulfide ion and heavy metal react to generate the heavy metal sulfide. Since most of the heavy metal sulfides are hardly soluble, most of them are insolubilized and captured by organic materials. For this reason, it is separated from the water to be treated.

For example, cadmium (Cd) reacts with sulfide ions to produce cadmium sulfide (CdS). Since cadmium sulfide is hardly soluble in water, it is separated from the water to be treated as an insolubilized product.
The reaction formula from the production of sulfide ions to the production of cadmium sulfide by sulfate-reducing bacteria is shown below.
2CH ₂ O + SO ₄ ²⁻ → H ₂ S + 2HCO ³⁻
H ₂ S + Cd ²⁺ → CdS ↓ + 2H ⁺

It is considered that Fe in the water to be treated reacts with sulfide ions and is insolubilized as iron sulfide (FeS) or the like.
Since the inside of the sulfuric acid reduction layer 14 is in a reduced state, it is possible to suppress the generation of fixed matter (scale) made of iron oxide.
The treated water that has passed through the sulfate reduction layer 14 is supplied to the upper part of the second reaction tank 20 through the pipe line 16.

In the second reaction tank 20, since the upper opening 20a is open to the atmosphere, outside air is introduced into the upper space 20b through the upper opening 20a, and the aerobic treatment layer 21 is in an aerobic condition.
The water to be treated is dropped from the supply end 16 a of the pipe line 16 and comes into contact with the air in the upper space 20 b until reaching the aerobic treatment layer 21.
When the water surface 23 in the second reaction tank 20 is lower than the upper end surface 21a, at least a part of the surface of the filler 24 (organic material, lime material, etc.) of the aerobic treatment layer 21 is exposed. The water to be treated flows down while the surface of the filling 24 is in contact with air.

Since the aerobic treatment layer 21 is under aerobic conditions, a part of the divalent iron ions (Fe ²⁺ ) contained in the water to be treated is oxidized to become trivalent iron ions (Fe ³⁺ ). For this reason, the ratio of the trivalent iron ion to the whole iron ion increases.
Divalent iron ions (Fe ²⁺ ) are not insolubles such as hydroxides (Fe (OH) ₂ etc.) and oxides unless they have relatively high pH conditions (7 to 8). The iron ions (Fe ³⁺ ) become insolubilized substances such as hydroxides (Fe (OH) ₃ etc.) and oxides even under relatively low pH conditions (for example, 4 or less).
For this reason, the insolubilized material derived from iron ions is mainly composed of an insolubilized material derived from trivalent iron ions (for example, iron hydroxide).

Since the insolubilized material derived from iron ions has an action of adsorbing heavy metals (Cd, Fe, Cu, Pb, Zn, etc.), the heavy metals are also insolubilized as hydroxides.
Since the iron ion-derived insolubilized material and the insolubilized material containing heavy metal are captured by the filler 24 of the aerobic treatment layer 21, the concentrations of iron and other heavy metals (Cd and the like) in the water to be treated are reduced (third separation). Process).
The treated water that has passed through the aerobic treatment layer 21 is discharged out of the system through the pipe line 17 as treated water 63.

According to the method for treating heavy metal-containing water of the present embodiment, a large amount of trivalent iron ions can be generated by placing the water to be treated in the aerobic treatment layer 21 under aerobic conditions. Therefore, an iron ion-derived insolubilized product can be generated and other heavy metals (Cd and the like) can be insolubilized under relatively low pH conditions.
Accordingly, even when the pH of the water to be treated (raw water) is low, both iron and other heavy metals can be efficiently treated.
Moreover, since heavy metal processing is possible even if it does not raise pH with an alkali agent, processing cost can be suppressed.

FIG. 3 is a schematic explanatory diagram of a treatment apparatus for heavy metal-containing water according to the second embodiment of the present invention. Hereinafter, the same reference numerals are assigned to components common to the processing apparatus 1 of the first embodiment, and the description thereof is omitted or simplified.
The processing apparatus 31 shown here has an oxygen concentration adjusting layer 11, a lime layer 12, an iron-containing layer 13, a sulfate reduction layer 14, and an aerobic processing layer 21 from the upstream side to the downstream side.
The aerobic treatment layer 21 can introduce outside air through the opening 20a (introduction portion) and can be brought into contact with the water to be treated.

  In the processing apparatus 31, the plurality of layers (layers 11 to 21) are integrated. For example, it is possible to provide a structure in which these plural layers are provided and integrated in the exterior body, and a water-permeable partition is provided between adjacent layers.

FIG. 4 is a schematic explanatory diagram of a treatment apparatus for heavy metal-containing water according to the third embodiment of the present invention.
The treatment apparatus 41 shown here has an oxygen concentration adjustment layer 11, a lime layer 12, an iron-containing layer 13, a sulfate reduction layer 14, and a water storage section 64 (for storing treated water) from the upstream side to the downstream side. Aerobic treatment layer).
The oxygen concentration adjustment layer 11, the lime layer 12, the iron-containing layer 13, and the sulfate reduction layer 14 are installed inside a downflow type constructed wetland 62.
The water reservoir 64 is open on the upper surface side (that is, has an upper surface open portion 64a). The upper surface side opening part 64a functions as an introduction part for bringing air into contact with the water to be treated in the water storage part 64. For this reason, the water surface 64b is open to the atmosphere and is in contact with the atmosphere over a wide area. Thus, the water to be treated is placed in an aerobic condition.

In the treatment apparatus 41, by placing the water to be treated in the water storage section 64 under an aerobic condition, a large amount of trivalent iron ions can be generated. Therefore, an iron ion-derived insolubilized product can be generated and other heavy metals (Cd and the like) can be insolubilized under relatively low pH conditions.
In the treatment apparatus 41, the treated water that has passed through the artificial wetland 62 can be jetted into the atmosphere from the jet pipe 65 and supplied to the water storage section 64. Therefore, the contact efficiency between the treated water and the air is increased, and the treated water The metal oxidation reaction can be promoted. For example, manganese (Mn) can be insolubilized as an oxide.

FIG. 5 is a schematic explanatory diagram of a treatment apparatus for heavy metal-containing water according to the fourth embodiment of the present invention.
The treatment apparatus 51 shown here includes a water passage main body 73 having a groove-like space 72, a supply portion 74 of water to be treated 3 provided at one side edge of the water passage main body 73, and a water passage main body 73. An aerobic treatment part 75 provided on the other side edge of the gas and a discharge path 79.
The groove-like space 72 inside the water passage main body 73 is partitioned by a partition wall 76 into a treatment space 77 and a lead-out passage 78 that guides the water to be treated to the aerobic treatment part 75.
The oxygen concentration adjustment layer 11, the lime layer 12, the iron-containing layer 13, and the sulfate reduction layer 14 are provided in the processing space 77.
The aerobic treatment layer 21 is provided in the aerobic treatment part 75. The aerobic treatment part 75 can introduce outside air into the aerobic treatment layer 21 through the upper opening 75a (introduction part).

The treated water 3 from the supply unit 74 flows into the groove-like space 72 of the water passage main body 73 and is introduced into the layers 11 to 14 while flowing in the groove-like space 72 in the longitudinal direction. The water to be treated that has passed through the layer 14 is introduced into the aerobic treatment layer 21 of the aerobic treatment unit 75 through the outlet path 78.
The treated water 63 that has passed through the aerobic treatment layer 21 is introduced into the discharge unit 79 and discharged out of the system.
In the treatment apparatus 51, a large amount of trivalent iron ions can be generated by placing the water to be treated in the aerobic treatment layer 21 under aerobic conditions. Therefore, an iron ion-derived insolubilized product can be generated and other heavy metals (Cd and the like) can be insolubilized under relatively low pH conditions.

FIG. 6 is a schematic explanatory diagram of a treatment apparatus for heavy metal-containing water according to the fifth embodiment of the present invention.
In the processing apparatus 61 shown in FIG. 6A, the oxygen concentration adjusting layer 11, the lime layer 12, the iron-containing layer 13, the sulfate reduction layer 14, and the aerobic processing layer 21 are each formed into a cartridge, and can be attached and removed.
FIG. 6B is a configuration diagram showing an example of the structure of each layer (in this example, the oxygen concentration adjusting layer 11). The oxygen concentration adjusting layer 11 is formed of an organic material or the like in a rectangular cylindrical outer casing 11a. The layer main body 11b filled with, and a holding net 11c that covers the openings at both ends.
The holding net portion 11c can pass the water to be treated and can prevent the filler (organic material or the like) in the exterior body 11a from dropping off. Similarly, the other layers (layers 12, 13, 14, and 21) can also have a structure in which both end openings of the layer main body filled with the contents are covered with the holding net.
The holding net part of the aerobic treatment layer 21 functions as an introduction part that introduces air into the aerobic treatment layer 21 and makes it contact with the water to be treated.
For this reason, a large amount of trivalent iron ions can be generated by placing the water to be treated in the aerobic treatment layer 21 under aerobic conditions. Therefore, an iron ion-derived insolubilized product can be generated and other heavy metals (Cd and the like) can be insolubilized under relatively low pH conditions.

  As shown in FIG. 6A, when a part of the layers 11, 12, 13, 14, 21 is deteriorated, the layer can be replaced with a new one. In the illustrated example, the deteriorated oxygen concentration adjusting layer 11 (11A) is taken out and replaced with a new oxygen concentration adjusting layer 11 (11B).

FIG. 7 is a schematic explanatory diagram of a treatment apparatus for heavy metal-containing water according to the sixth embodiment of the present invention.
The processing apparatus 71 shown here has layers 11, 12, 13, 14, 21. The ventilation part 21b of the aerobic treatment layer 21 functions as an introduction part that introduces air into the aerobic treatment layer 21 and makes it contact with the water to be treated.
In the processing apparatus 71, as a path for connecting adjacent layers to each other, a lower path for connecting lower layers and an upper path for connecting upper layers are alternately secured from the upstream side to the downstream side.

In the illustrated example, partition walls 67 (67A and 67B) are provided between the layers 12 and 13 and between the layers 14 and 21. The partition wall 67 is erected from the installation surface 66. The height of the partition wall 67 is set lower than each layer.
Reference numeral 68 denotes a separator having a top plate portion 69 and a partition wall 70 depending from the lower surface thereof.
As for the 1st separator 68 (68A), the top-plate part 69 (69A) covers the upper surface of the layers 11 and 12, and the partition 70 (70A) is provided between the layers 11 and 12. As for the 2nd separator 68 (68B), the top-plate part 69 (69B) covers the upper surface of the layers 13 and 14, and the partition 70 (70B) is provided between the layers 13 and 14. FIG.
The partition wall 70 has a length that does not reach the installation surface 66 at the lower end.

The water to be treated that flows into the layer 11 flows from the upper part toward the lower part in the layer 11, passes through the gap (lower path 91 (91 </ b> A)) between the lower end of the partition wall 70 </ b> A of the separator 68 </ b> A and the installation surface 66. To be introduced. The water to be treated flows in the layer 12 from the lower part to the upper part, and is introduced into the upper part of the layer 13 through a gap (upper path 92 (92A)) between the upper end of the partition wall 67A and the top plate part 69B.
The water to be treated that flows into the layer 13 flows from the upper part toward the lower part in the layer 13, passes through the gap (lower path 91 (91 </ b> B)) between the lower end of the partition wall 70 </ b> B of the separator 68 </ b> B and the installation surface 66. To be introduced. The water to be treated flows in the layer 14 from the lower part to the upper part, and is introduced into the upper part of the layer 21 through a gap (upper path 92 (92B)) between the upper end of the partition wall 67B and the top plate part 69B.
The treated water that has flowed into the layer 21 flows in the layer 21 from the upper part toward the lower part, and flows out of the system through the lower path 91 (91C).
The layer 21 can introduce outside air through the ventilation part 21b (introduction part), and can be made to contact with to-be-processed water.

The treatment device 71 can generate a large amount of trivalent iron ions by placing the water to be treated in the aerobic treatment layer 21 under aerobic conditions. Therefore, an iron ion-derived insolubilized product can be generated and other heavy metals (Cd and the like) can be insolubilized under relatively low pH conditions.
In the treatment apparatus 71, since the lower path 91 (91A, 91B, 91C) and the upper path 92 (92A, 92B) are alternately used from the layer 11 to the layer 21, the water to be treated is supplied to each layer while having a simple structure. Can be passed through. Therefore, the processing efficiency can be improved. Further, since the structure is simple, the cost can be reduced and the apparatus can be downsized.

Example 1
The processing apparatus 1 shown in FIG. 1 was produced.
For the oxygen concentration adjustment layer 11 of the first reaction tank 10 (capacity 500 mL), 20 g of organic material (humus), 5 g of lime (limestone), and 5 g of iron-containing material (iron powder) were used. The average particle size of the humus was 0.106 to 0.3 mm. The average particle size of limestone was 0.3 to 0.6 mm.
For the lime layer 12, 200 g of limestone was used. The average particle size of limestone was 20 to 47 mm.
For the iron-containing layer 13, 5 g of an iron-containing material (iron powder) and 30 g of an organic material (humus) were used. The average particle size of the humus was set to 0.3 to 0.6 mm.
For the sulfate reduction layer 14, 20 g of organic material (humus) was used. The average particle diameter of humus was 0.6-2 mm.

The aerobic treatment layer 21 includes a first layer 21A composed of 30 g of a first organic material (humus) (average particle size 20 to 47 mm), and a second organic material (humus) (average particle size 0.6 to 2 mm). And a second layer 21B made of 40 g. The first layer 21A and the second layer 21B1 contained lime material (limestone) (average particle size 0.6 to 2 mm) (total 10 g).
The average porosity of the layers 11 to 21 is about 50%.

The flow rate of the water to be treated was about 0.5 L / day, and continuous water flow was performed until the total water flow amount reached 45.4 L. The residence time of the processing apparatus 1 was about 1.1 days.
The measurement results of the water to be treated are shown in FIGS. The sampling point P1 of the water to be treated is the outlet of the first reaction tank 10, and the sampling point P2 is the outlet of the second reaction tank 20. The sampling location P1-1 is the lower end of the oxygen concentration adjusting layer 11 of the first reaction tank 10, and the sampling location P1-2 is the lower end of the sulfate reduction layer 14.
Table 1 shows the components contained in the treated water 3 (raw water) in the treated water tank 2 and their concentrations. The water temperature of the water to be treated 3 was 17.2 ° C., the pH was 4.0, and the ORP was 444 mV.

From FIG. 8, the pH was in the neutral region (6 to 8) in both the collection point P1 (exit of the first reaction tank 10) and P2 (exit of the second reaction tank 10).
From FIG. 9, the oxidation-reduction potential is lower than 0 in most of the periods at the sampling point P1-1 (the lower end of the oxygen concentration adjustment layer 11) and P1-2 (the lower end of the sulfate reduction layer 14) of the first reaction tank 10. The value was higher than 0 at the collection point P2 of the water tank 2 to be treated.
From FIG. 10, the Cd concentration was generally lower than 0.005 mg / L at the sampling point P1 of the first reaction tank 10 and further lower at the sampling point P2 of the second reaction tank 20.
From FIG. 11, the Fe concentration was slightly high at the sampling point P <b> 1 of the first reaction tank 10, but was sufficiently low at the sampling point P <b> 2 of the second reaction tank 20.
As shown in FIG. 12, the Cu concentration was sufficiently low at both the sampling points P1 and P2.

  The lime material includes calcium carbonate, calcium oxide, calcium hydroxide and the like, and calcium carbonate is particularly preferable.

1, 31, 41, 51, 61, 71 Treatment apparatus for heavy metal-containing water 10 First reaction tank 11 Oxygen concentration adjusting layer (oxygen concentration adjusting unit)
12 Lime layer (pH adjuster)
13 Iron-containing layer (first separation part)
14 Sulfuric acid reduction layer (second separation part)
20 2nd reaction tank 20a, 75a Upper opening (introduction part)
21 Aerobic treatment layer (3rd separation part)
21b Ventilation part (introduction part)
64 Water storage part (aerobic treatment layer, third separation part)
64a Upper surface side open part (introduction part)

Claims (7)

A method for treating heavy metal-containing water that removes heavy metal from water to be treated containing heavy metal,
A pH adjusting step of bringing the water to be treated into contact with the lime material and adjusting the pH of the water to be treated;
A first separation step of bringing the water to be treated that has undergone the pH adjustment step into contact with an iron-containing material containing an organic material, and insolubilizing the heavy metal together with the iron oxide derived from the iron-containing material;
The water to be treated that has undergone the first separation step is brought into contact with an organic material under anaerobic conditions, and sulfate ions in the treated water are reduced by the sulfate-reducing microorganisms in the organic material, and the heavy metal sulfide is generated. A second separation step;
A third separation step of generating insolubilized material derived from iron ions and insolubilizing the heavy metal by placing the water to be treated through the second separation step under aerobic conditions;
A method for treating heavy metal-containing water, comprising:   The treatment of heavy metal-containing water according to claim 1, wherein in the third separation step, the water to be treated is placed under aerobic conditions by bringing air introduced from the outside into contact with the water to be treated. Method.   3. The method for treating heavy metal-containing water according to claim 1, wherein the insolubilized material derived from the iron ions contains a trivalent iron hydroxide as a main component.   Prior to the pH adjustment step, the method includes an oxygen concentration adjustment step of adjusting the dissolved oxygen concentration of the water to be treated by microorganisms in the organic material by bringing the water to be treated into contact with the organic material. The processing method of the heavy metal containing water of any one of Claims 1-3. A pH adjusting unit having a lime material and adjusting the pH of the water to be treated by the lime material;
A first separation unit that has an iron-containing material containing an organic material and insolubilizes and separates the heavy metal in the water to be treated through the pH adjusting unit together with the iron oxide derived from the iron-containing material;
A second separation unit that has an organic material, reduces sulfate ions in the water to be treated under anaerobic conditions by sulfate-reducing microorganisms in the organic material, and generates and separates the heavy metal sulfide;
A heavy metal content, comprising: a third separation unit that generates insolubilized matter derived from iron ions and insolubilizes the heavy metal by placing the water to be treated that has undergone the second separation step under aerobic conditions Water treatment equipment.   The apparatus for treating heavy metal-containing water according to claim 5, wherein the third separation unit includes an introduction unit that introduces air to be brought into contact with the water to be treated from the outside.   6. An oxygen concentration adjusting unit that has an organic material upstream of the pH adjusting unit and adjusts the dissolved oxygen concentration of the water to be treated by microorganisms in the organic material. Or the heavy metal containing water processing apparatus of 6.

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