KR100940286B1 - Acid Mine Drainage Natural Purification System Using Floating Body - Google Patents

Abstract

The present invention relates to an acid mine drainage natural purification system for naturally purifying the acid mine drainage discharged from the abandoned mine without using power.

The acid mine drainage natural purification system according to the present invention is disposed on the discharge path of acid mine drainage containing a large amount of iron ions discharged from the abandoned mine to neutralize the acid mine drainage and precipitate heavy metal contained therein, Treatment tank for temporarily receiving and purifying acid mine drainage, limestone layer for neutralizing acid mine drainage, upper part of limestone layer to be disposed upstream of limestone layer on discharge path of acid mine drainage It is stacked on the substrate and contains sulfate reducing bacteria that can reduce sulfate ions, and is suspended in an acid mine drainage housed in an organic material layer and a treatment tank made of organic matter, so that oxygen in the air comes into contact with the acid mine drainage to increase the amount of dissolved oxygen in the acid mine drainage. It is characterized by having a plurality of air barriers to prevent The.

Description

Passive treatment system for acid mind drainage using floating materials

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an acid mine drainage natural purification system for purifying acid mine drainage discharged from waste mines, and in particular, to naturally purify water without using power.

Environmental pollutions caused by mines and abandoned mines include ground subsidence, river burial due to loss of waste-rock and tailings, heavy metal contamination of soils, and water pollution by shaft runoff and waste-rock leachate. In particular, the problem of water pollution by acid mine drainage from underground coal mine waste-rock piles has started to be serious since the mid-1990s.

Acid mine drainage is formed when sulfide minerals such as pyrite (FeS ₂ ) and ferrite (FeS) exposed to the atmosphere are oxidized by reaction with oxygen and water, and have a low pH, resulting in acidity, iron, aluminum, and manganese sulfate. It is characterized by high metal content.

The oxidation of pyrite is given by the following equations.

FeS ₂ + 7 / 2O _{2 ^{+ H 2 O → Fe 2 +}} + 2SO 4 2 - + 2H +

Fe ^{2 +} + 1/4 O ₂ + H ⁺ → Fe ^{3 +} + 1/2 H ₂ O

Fe ^{3 +} + 3H ₂ O → Fe (OH) ₃ (s) + 3H ⁺

_{^{FeS 2 + Fe 3 + + 8H}} 2 O → 15Fe 2 + + 2SO 4 2 - + 16H +

As shown in the above equation, pyrite is oxidized to generate iron ions and sulfate ions and to be acidified by hydrogen ions. The acid mine drainage has high mobility of toxic heavy metals due to low pH, contaminating surrounding surface water and groundwater and destroying aquatic ecosystems. In addition, metal ions are oxidized and precipitated with metal hydroxides such as Fe (OH) 3. Reddish brown or white precipitates are generated (yellow boy phenomenon) to harm the aesthetics.

This acid mine drainage purification method is largely divided into active treatment (active treatment) and passive treatment (passive treatment). Active treatment methods include pH adjustment using ionizing agents, ion exchange and adsorption, flocculation, and filtration. Representative active treatment methods include reverse osmosis, ion exchange, and electrodialysis. However, this active treatment method has a high treatment efficiency but requires a high amount of equipment, chemicals, human resources, and power. Therefore, the maintenance cost is expensive. Therefore, the passive treatment method that requires very little facility investment and maintenance cost than the active treatment method, namely Natural purification is widely used.

Such passive treatments include neutralization treatment using limestone, such as ALDs (anoxic limestone drains) and OLD (oxic limestone drains), aerobic and anaerobic artificial marshes, and advanced alkalinity-producing systems (SAPS) or RAPS that have developed them. There is this. The structure of SAPS among these passive treatment methods is shown in FIG.

Referring to Figure 1, the SAPS forms a large pond-like tank (2, 상 에) on the discharge path of the acid mine drainage, laid a limestone layer (L) in the lower part of the tank (2) and this limestone layer (L) The organic material layer (O) is laminated on the top. The organic material layer (O) is filled with an organic material consisting of CH ₂ O. Such organic materials are used as mushroom compost, sawdust or sewage sludge.

On the other hand, the organic material layer (O) is supported on the sulfate reducing bacteria (SRB: surfate reducing bacteria, not shown). The sulfate reducing bacterium is a microorganism commonly found in a reducing environment in which sulfates and organic matters around us are sufficient, and disulfate bacters (acetate oxidizers) that use fatty acids, especially acetic acid, as a carbon source while reducing sulfates to hydrogen sulfide ( Desulfabactor, Desulfosarcina, Desulfonema, etc. Desulfovibrio as a non-acetate oxidizers group using lactate, pyruvate, ethanol, etc. , Desulfomonas, Desulfotomaculum and the like.

In the SAPS of the above configuration, the acid mine drainage is discharged from the tunnel to the outside and flows into the upper portion of the SAPS system and flows downward along the vertical direction. That is, the acid mine drainage flows into the limestone layer L through the organic material layer O, and is discharged along the conduit T connected to the limestone layer L. By the metabolic action of the sulfate reducing bacterium during the acid mine drainage through SAPS, the sulfate in the acid mine drainage is reduced to hydrogen sulfide and generates alkalinity, and the metal ions in the acid mine drainage are combined with hydrogen sulfide to precipitate. Thereby purifying.

However, in the conventional SAPS, since the acid mine drainage is exposed to the atmosphere, oxygen is dissolved so that much oxygen is contained in the acid mine drainage. This dissolved oxygen forms iron hydroxide by oxidizing iron in acid mine drainage. The scheme is shown below.

4Fe ^{2 +} + O ₂ + 4H ⁺ → 4Fe ^{3 +} + 2H ₂ O

Fe ^{3 +} + 3H ₂ O → Fe (OH) ₃ (s) + 3H ⁺

That is, iron is oxidized and iron hydroxide precipitates. The iron hydroxide forms a sludge layer (s) on the organic material layer (O). As the sludge layer (s) becomes thick, the permeability becomes poor, and acid mine drainage does not flow into the limestone layer (L). If the permeability is poor, since the acid mine drainage system discharged from the abandoned mine overflows, acid mine drainage passes through the organic material layer (O) and limestone layer (L), there is a problem that can not be purified. In addition, the maintenance work to remove the sludge layer (s) due to the iron hydroxide on a regular basis had a problem that the economic efficiency is also reduced.

The present invention is to solve the above problems, by reducing the amount of dissolved oxygen in the acid mine drainage induced by the air contact so that the sludge caused by the iron hydroxide does not occur so that the permeability of the acid mine drainage can be kept constant The purpose is to provide an acid mine drainage purification system with improved structure.

The acid mine drainage natural purification system according to the present invention for solving the above object is disposed on the discharge path of the acid mine drainage discharged from the abandoned mine containing a large amount of iron ions to neutralize the acid mine drainage and contained therein. A treatment tank for precipitating heavy metals, for temporarily receiving and purifying acid mine drainage, Laminated in a lower portion of the treatment tank, a limestone layer for neutralizing acid mine drainage, and a limestone layer on the discharge path of acid mine drainage. Stacked on top of the limestone layer so as to be located upstream, containing sulfate reducing bacteria capable of reducing sulfate ions and floating in the organic material layer made of organic matter and the acid mine drainage contained in the treatment tank, oxygen in the air is acid mine drainage. To prevent dissolved oxygen from increasing in acid mine drainage It is characterized in having a plurality of air shields.

According to the present invention, it is preferable that the air blocking material is suspended floating in the acid mine drainage so as to reduce the contact area between the acid mine drainage and the air, and the plurality of floating balls are formed in different sizes. It is more desirable to reduce the porosity between the floating balls.

In addition, according to the present invention, the air barrier material preferably comprises a decomposable organic material decomposed using oxygen, and a floating means capable of floating in an acid mine drainage in a state in which the decomposable organic material is accommodated.

In addition, according to the present invention, the floating means comprises a plurality of receptors formed in a network to accommodate the degradable organic matter, and floating around the respective receptors and floating in the acid mine drainage, It is preferable that the receptor containing the degradable organic matter is suspended together by the buoyancy of the float, and the float is more preferably wood or plastic.

In addition, the plurality of receptors are connected to each other, the degradable organic material is preferably at least one of mushroom compost, coconut fiber, food sludge, oak sawdust.

As described above, the acid mine drainage natural purification system according to the present invention can reduce the content of dissolved oxygen in the acid mine drainage, thereby preventing the occurrence and precipitation of iron hydroxide, and thus, the permeability of the acid mine drainage is constant. The advantage is that it can be maintained.

In addition, as the transmittance of the acid mine drainage becomes constant, there is an advantage that the system can be operated economically.

In addition, as the dissolved oxygen content in the acid mine drainage is reduced, the inside of the system can maintain anaerobic conditions, so that the purification of sulfate reducing bacteria can be performed very smoothly.

Hereinafter, with reference to the accompanying drawings, it will be described in more detail with respect to the acid mine drainage natural purification system according to a preferred embodiment of the present invention.

Figure 2 is a schematic configuration diagram of the acid mine drainage natural purification system according to a preferred embodiment of the present invention, Figure 3 is a plan view of the acid mine drainage natural purification system shown in FIG.

2 and 3, the acid mine drainage natural purification system 100 according to a preferred embodiment of the present invention includes a treatment tank 10, a limestone layer 20, an organic material layer 30, and an air barrier. .

The treatment tank 10 is disposed on the discharge path of the acid mine drainage w to temporarily receive the acid mine drainage w. In the treatment tank 10, the acid mine drainage w is neutralized by the limestone layer 20 and the organic material layer 30 which will be described later, and the dissolved heavy metal is purified by precipitation.

The limestone layer 20 is for neutralizing the acid mine drainage w and is formed by being laminated under the treatment tank 10. Limestone layer 20 is filled with limestone (CaCO ₃ ). Since the limestone layer 20 is disposed downstream of the organic layer 30 to be described later on the discharge path of the acid mine drainage w, the acid mine drainage w is introduced into the limestone layer 20 through the organic layer 30. . When the limestone packed in the limestone layer 20 is dissolved, the acid mine drainage (w) is neutralized by consuming protons and generating HCO ₃ ⁻ ions. Expressed by the chemical formula is as follows.

_{^{CaCO 3 + H + → Ca 2}} + + HCO 3 -

The organic material layer 30 is for neutralizing the acid mine drainage w and precipitating the metal in the acid mine drainage w. The organic layer 30 is stacked on the limestone layer 20. That is, it is disposed upstream of the limestone layer 20 on the discharge path of the acid mine drainage w. The organic material layer 30 is filled with an organic material, which is represented by the chemical formula CH ₂ O. As organic matter, mushroom compost, a mixture of rice straw and manure, sawdust, oak compost, oak bark, pine needles, sewage sludge, paper sludge, dairy waste and mixtures thereof may be used. In this example, mushroom compost was used as organic matter.

The organic material layer 30 contains sulfate reducing bacteria. The sulfate reducing bacterium undergoes metabolic reaction by feeding organic material consisting of CH ₂ O. In this metabolic reaction, the organic material charged in the organic material layer 30 becomes an electron donor, and the sulfate ion (SO) in acid mine drainage (w) ₄ ^{2 -)} is an electron acceptor. In this metabolic reaction, sulfates are reduced to produce hydrogen sulfide (H ₂ S) and alkaline (HCO ₃ ⁻ ). Sulfate reduction reaction is represented by the following formula.

_{^{2CH 2 O + SO 4 2 -}} → H 2 S + 2HCO 3 -

This sulfate with hydrogen sulfide (H ₂ S) produced by the metabolic reactions of the reducing bacteria and alkalinity (HCO ₃ ^-) is an acid mine drainage metal ions present in the (w) (M ^{2 +)} reacts with the metal sulfide (MS) Precipitate. The chemical equation is:

_{^{M 2 + + H 2 S +}} 2HCO 3 - → MS (↓) + 2H 2 O + 2CO 2

On the other hand, the proton (H ⁺ ) in the acid mine drainage (w) is neutralized by alkalinity (HCO ₃ ⁻ ), resulting in an increase in the pH of the acid mine drainage (w).

In the acid mine drainage natural purification system 100 according to the present invention, a plurality of air barriers are provided. The air barrier material floats on the surface of the acid mine drainage w accommodated in the treatment tank 10, so that oxygen in the air contacts the acid mine drainage w and increases the amount of dissolved oxygen in the acid mine drainage w. It is to prevent.

In this embodiment, the floating ball 40 is used as the air barrier. Since the floating ball 40 is spherical and hollow inside, it floats on the surface of the acid mine drainage w by buoyancy. When the plurality of balls 40 are suspended, the contact area between the air and the acid mine drainage w is reduced to reduce the dissolved oxygen in the air in the acid mine drainage w. In addition, in order to further reduce the contact area between the atmosphere and the acid mine drainage w, the floating balls 40 are formed in different sizes (different diameters) as shown in FIG. That is, the porosity between the pores 40 is reduced to prevent contact between the atmosphere and the acid mine drainage w. When the acid mine drainage (w) is reduced in exposure to the atmosphere to reduce the amount of dissolved oxygen, iron in the acid mine drainage (w) can be greatly reduced since iron is formed of iron hydroxide and precipitated. As described above, it is possible to solve the problem that the precipitate is accumulated in the organic layer to reduce the permeability.

So far, the air blocking material has been described as a floating official, but the air blocking material is not limited thereto, and various forms may be used. 4 and 5 show an embodiment using different types of air barriers.

4 is a schematic perspective view of an air blocker employed in an acid mine drainage natural purification system according to another embodiment of the present invention, and FIG. 5 is a view for explaining a state in which the air blocker shown in FIG. 4 is suspended in an acid mine drainage. Schematic drawing. 4 and 5, only the air blocker is different from the above-described embodiment, and all other configurations are the same. Therefore, only the air blocker will be described in detail.

The air barrier used in this sealing example is provided with a decomposable organic substance 70 and floating means for suspending the degradable organic substance 70.

The degradable organic material 70 is a material decomposed using oxygen by a biochemical action, and any one or a mixture of mushroom compost, coconut fiber, food sludge, oak sawdust, and pine sawdust may be used. In this embodiment, mushroom compost is used. This degradable organic matter 70 does not float on the surface when it contains water in the acid mine drainage w, but floats on the surface of the acid mine drainage w by the floating means described later. As described above, the degradable organic material 70 serves to prevent the acid mine drainage w from being in contact with the air, thereby preventing an increase in the dissolved rate of oxygen in the acid mine drainage w. In addition, the degradable organic material 70 decomposes itself by using dissolved oxygen in the acid mine drainage w to perform an active action of removing oxygen in the acid mine drainage w. That is, the decomposable organic matter 70 is suspended on the surface of the acid mine drainage w to physically block the inflow of oxygen into the acid mine drainage w, as well as physically blocking dissolved oxygen in the acid mine drainage w. By actively consuming the decomposition, the amount of dissolved oxygen in the acid mine drainage w is reduced. Accordingly, the iron in the acid mine drainage w is oxidized and precipitated in the organic material layer 20, thereby preventing the permeability from being lowered.

As described above, in order to float the degradable organic material 70 on the surface of the acid mine drainage w, the floating means is required. In the present embodiment, the floating means includes a plurality of receptors 51 and a floating body 52. It is done by

The receptor 51 is formed of a lattice-shaped box to accommodate the degradable organic material 70 therein. Floating body 52 is to provide a buoyancy to float the receptor 51 containing the degradable organic material 70, in this embodiment a hollow cylindrical plastic material is used. Plastics, by themselves, are floating, but are hollow and generate large buoyancy in acid mine drainage (w). A plurality of floating bodies 52 are provided, and are connected to each other by a rope 53 to enclose the container 51. In addition, a plurality of receptors 51 floating in the state in which the decomposable organic matter 70 is accommodated are provided in plural so as to cover most of the surface of the acid mine drainage w. They are connected to each other by a rope. Since the receptors 51 are connected to each other, it is possible to prevent the receptors 51 from being lost or separated from the acid mine drainage w due to unwanted external force such as wind. On the other hand, the float 52 has been described as a hollow plastic material, but can be configured in various forms, such as wood having excellent floating performance in addition to this form.

The oxygen removal rate by the degradable organic material 70 was tested, and the result is shown graphically in FIG. 6. Figure 6 is a graph showing the experimental results of the oxygen removal rate of one embodiment of the present invention. 450 ml of acid mine drainage was put into three beakers of 1000 ml each, without degradable organic matter in the first beaker, 50g of mushroom compost as degradable organic matter in the second beaker, and 40g of mushroom compost and pine in the third beaker as degradable organic matter. A total of three samples were made by mixing 10 g of sawdust. After shaking all three samples, the amount of dissolved oxygen (DO) in the sample was measured in units of 6 hours after a certain time.

Referring to FIG. 6, the dissolved oxygen content of the acid mine drainage was 6.5 mg / l before the experiment, but in the case of Sample 2 and Sample 3 containing the decomposable organic matter, the dissolved oxygen amount was approximately 1 mg / l after about 80 hours. It confirmed that it fell below. On the other hand, in the sample 1 containing no degradable organic matter, no sharp decrease in dissolved oxygen was found.

That is, in the case of using the decomposable organic material as an air barrier, it was confirmed that the dissolved oxygen in the acid mine drainage (w) can be drastically reduced, and the amount of dissolved oxygen is reduced so that the iron in the acid mine drainage (w) is oxidized to iron hydroxide. It was confirmed that the precipitation can be prevented.

 The acid mine drainage (w) is discharged from the abandoned mine and introduced into the treatment tank, and then purified while passing through the organic material layer 30 and the limestone layer 20 along the downward direction, and finally discharged. By floating on the surface of the acid mine drainage (w) can solve the problem of poor permeability due to iron hydroxide precipitation, which has been pointed out as the biggest problem in natural purification facilities.

Although the present invention has been described with reference to one embodiment shown in the accompanying drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Could be. Accordingly, the true scope of protection of the invention should be defined only by the appended claims.

1 is a schematic configuration diagram of a conventional acid mine drainage natural purification facility.

2 is a schematic configuration diagram of an acid mine drainage natural purification system according to a preferred embodiment of the present invention.

3 is a plan view from above of the acid mine drainage natural purification system shown in FIG.

Figure 4 is a schematic perspective view of the air blocker employed in the acid mine drainage natural purification system according to another embodiment of the present invention.

FIG. 5 is a schematic view for explaining a state in which the air barrier shown in FIG. 4 is suspended in an acid mine drainage.

Figure 6 is a graph showing the experimental results of the oxygen removal rate of one embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

100 ... Acid Mine Drainage Natural Purification System 10 ... Treatment Tank

20 ... limestone layer 30 ... organic material layer

40 ... floating ball 51 ... receptor

52 ... suspended solids 70 ... degradable organics

Claims (8)

Is disposed on the discharge path of the acid mine drainage discharged from the abandoned mine containing a large amount of iron ions to neutralize the acid mine drainage and to precipitate the heavy metal contained therein, A treatment tank for temporarily receiving and purifying acid mine drainage; A limestone layer laminated on the bottom of the treatment tank to neutralize acid mine drainage; An organic material layer formed on an upper portion of the limestone layer so as to be disposed upstream of the limestone layer on an exhaust path of an acid mine drainage, and including sulfate reducing bacteria capable of reducing sulfate ions and comprising an organic material; And And a plurality of air blockers that float in the acid mine drainage accommodated in the treatment tank to prevent oxygen in the air from contacting the acid mine drainage and increasing the amount of dissolved oxygen in the acid mine drainage. And the air barrier material comprises a decomposable organic material decomposed using oxygen and a floating means capable of floating in an acid mine drainage in a state in which the decomposable organic material is accommodated. delete delete delete The method of claim 1, The floating means, It comprises a plurality of receptors formed in a network to accommodate the degradable organic matter, and a floating body surrounding the respective receptors and floating in an acid mine drainage, The acid mine drainage natural purification system, characterized in that the receptor containing the degradable organic matter is suspended together by the buoyancy of the floating body. The method of claim 5, The float is an acid mine drainage natural purification system, characterized in that the wood or plastic. The method of claim 5, The acid mine drainage natural purification system, characterized in that the plurality of receptors are connected to each other. The method of claim 1, The degradable organic material is acid mine drainage natural purification system, characterized in that at least any one of mushroom compost, coconut fiber, food sludge, oak sawdust, pine sawdust.

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