KR20150020435A - Landfill leachates treatment method - Google Patents

Abstract

The present invention relates to a method for producing landfill leachate, comprising passing landfill leachate through a blast furnace slag filling column; Passing the leachate having passed through the blast furnace slag filling column to a pH adjusting tank containing an exhaust gas containing carbon dioxide, and passing the leachate passing through the pH adjusting tank to an activated carbon filling column . According to the present invention, it is possible to treat the landfill leachate in a stable pH state by using the flue gas containing the blast furnace slag and the carbon dioxide as a neutralizer, and to remove heavy metal ions and chromaticity of the landfill leachate.

Description

Landfill leachates treatment method

The present invention relates to a method of treating landfill leachate which removes heavy metal ions and chromaticity in leachate. More specifically, leachate generated in a landfill is neutralized by using blast furnace slag, which is a byproduct generated in a steel process, And a method for adsorbing and removing chromaticity by passing an exhaust gas containing carbon dioxide to neutralize leachate and passing through an activated carbon filling column.

The leachate generated in the landfill is a malicious wastewater containing various organic substances, heavy metal ions and other inorganic substances.

So far, the most well-known landfill leachate treatment method is biological treatment after being collected through porous layer, but chemical precipitation method is mainly used for removing heavy metal ions.

However, recently, a method of fundamentally reducing environmental risks by adsorbing pollutants in landfill leachate to clay or soil for landfill, and a method for stabilizing landfill by recycling leachate have been actively studied have. As described above, the conventional methods have many problems from the technical point of view. The chemical precipitation method using chemicals has a problem in that the chemical cost is high and the sludge generation amount is large and also the generated sludge treatment is difficult.

The present invention attempts to treat landfill leachate at a stable pH by using a flue gas containing blast furnace slag and carbon dioxide as a neutralizer to remove heavy metal ions and chromaticity of the landfill leachate.

The present invention relates to a method for producing landfill leachate, comprising passing landfill leachate through a blast furnace slag filling column; Passing the leachate having passed through the blast furnace slag filling column through a pH adjusting tank containing carbon dioxide-containing flue gas, and passing the leachate passing through the pH adjusting tank through an activated carbon filling column .

The blast furnace slag may contain 35 to 45 wt% of CaO.

The blast furnace slag may contain at least one or more selected from the group consisting of Al ₂ O ₃ , MnO, and SiO ₂ .

The blast furnace slag may have a size of 10 to 100 mesh.

The space velocity of the landfill leachate in the blast furnace slag filling column is preferably 4 to 6 L / h.

Preferably, the carbon dioxide is contained in the pH adjustment tank at 15 to 25% based on the volume of the exhaust gas.

According to the present invention, it is possible to treat the landfill leachate in a stable pH state by using the flue gas containing the blast furnace slag and the carbon dioxide as a neutralizer, and to remove heavy metal ions and chromaticity of the landfill leachate.

1 is a schematic diagram of a process for treating landfill leachate in accordance with the present invention.
FIG. 2 is a graph showing the removal efficiency of heavy metal ions according to contact time of landfill leachate and a blast furnace slag packed column according to the present invention.
FIG. 3 is a graph showing changes in pH of the landfill leachate and the pH adjusting tank according to the present invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. Further, the embodiments of the present invention are provided to more fully explain the present invention to those skilled in the art. The shape and size of elements in the drawings may be exaggerated for clarity.

Conventional landfill leachate treatment methods include a biological treatment after being collected through a porous layer and a chemical precipitation method. However, the conventional biological treatment methods have many problems from the technical point of view, and the chemical precipitation method is difficult to treat the sludge which is generated due to the high cost of the drug and the large sludge generation amount.

Thus, the present invention provides a method of treating landfill leachate, comprising: passing landfill leachate through a blast furnace slag filling column; Passing the leachate having passed through the blast furnace slag filling column through a pH adjusting tank containing carbon dioxide-containing flue gas, and passing the leachate passing through the pH adjusting tank through an activated carbon filling column .

1 is a schematic diagram of a process for treating landfill leachate in accordance with the present invention.

First, the leachate generated in the landfill is collected in the landfill leachate collection tank 100. Typically, the landfill leachate exhibits an acidity of pH 3-6. The landfill leachate showing acidity is passed through a blast furnace slag filling column 110. The landfill leachate having passed through the blast furnace slag filling column 110 is converted to an alkaline pH of 8 to 9 by blast furnace slag showing alkalinity. The pH of the landfill leachate having passed through the blast furnace slag filling column 110 is 8 to 9 and shows a color.

The blast furnace slag charged in the blast furnace slag charging column 110 is not particularly limited as long as it is a commonly used blast furnace slag. As a representative example thereof, blast furnace slag having the chemical composition shown in Table 1 below can be used.

ingredient CaO SiO ₂ Al ₂ O ₃ T-Fe MgO MnO Furtherance 39.5 to 43.4 32.5 to 35.0 12.9 to 15.2 0.3 to 0.76 3.5 to 6.8 0.38 to 0.74

(Unit: wt%)

The blast furnace slag may contain 35 to 45 wt% of CaO, as shown in Table 1 above. Since CaO is alkaline, it reacts with acidic landfill leachate and acts as a neutralizing agent. When the content of CaO in the blast furnace slag is less than 35% by weight, the landfill leachate can not be sufficiently neutralized. When the CaO content exceeds 45% by weight, the leachate passing through the blast furnace slag filling column 110 is alkaline.

In order to remove heavy metal ions such as iron, manganese, zinc, and copper contained in the acidic landfill leachate, the blast furnace slag was treated with Al ₂ O ₃ , an adsorbing material, and MnO, SiO _2, and the like.

Secondary contamination of landfill leachate by the blast furnace slag does not occur, and the blast furnace slag can be used as a neutralizer of landfill leachate.

Specifically, the concentration of heavy metal ions in the permeate water by the blast-furnace slag elution test was analyzed in order to determine whether secondary leakage of landfill leachate was caused by the blast furnace slag, as shown in Table 2 below.

ingredient F CD Pb Mn Cr Emission Standards (Clean Area) 2 or less 0.02 or less 0.1 or less 2 or less 0.5 or less content 0 to 0.01 0 0 to 0.01 0 0 to 0.01

(Unit: mg / L)

As can be seen from the above Table 2, the concentration of each pollutant eluted from the blast furnace slag is significantly lower than the discharge allowance criterion, which means that there is no problem in using it as a neutralizing agent for landfill leachate.

The blast furnace slag may have a size of 10 to 100 meshes. The particle size of blast furnace slag has the greatest influence on the adsorption capacity. The smaller the blast furnace slag particle, the more surface area increases and the adsorption capacity increases.

The results of analyzing the specific surface area of the blast furnace slag by the particle size are shown in Table 3 below.

Particle size (mesh) 18-20 20 to 28 28 ~ 42 60 to 80 Specific surface area (m ² / g) 0.72 to 0.74 0.74 to 0.76 0.77-0.79 0.84 to 0.86

As shown in Table 3, the specific surface area of the blast furnace slag increases with the increase of the particle size of the blast furnace slag, and thus the adsorption capacity is slightly improved. However, all of the above particle sizes have a specific surface area of 0.70 m ^{2 /} g or more and have a sufficient specific surface area for use in the blast furnace slag filling column 110.

However, when the particle size of the blast furnace slag is less than 10 meshes, the blast furnace slag has a large particle size, which results in poor adsorption capability. When the blast furnace slag has a particle size exceeding 100 mesh, the size of the particles to fill the column is small.

The space velocity of the landfill leachate in the blast furnace slag filling column 110 is preferably 4 to 6 L / h. When the space velocity is less than 4 L / h, the contact time between the blast furnace slag filling column 110 and the landfill leachate is short, neutralization and heavy metal ion removal can not be sufficiently performed. When the space velocity is less than 6 L / h, There is a problem that the landfill leachate has a strong alkalinity because the contact time between landfill leachates is long.

Next, the leachate having passed through the blast furnace slag filling column 110 is passed through a pH adjustment tank 120 containing an exhaust gas containing carbon dioxide. In the pH regulator 120, alkaline colored landfill leachate and flue gas containing carbon dioxide react with each other to form H ⁺ ions and HCO ₃ ^- ions through H ² CO ₃ to increase the hydrogen ion concentration, thereby reducing the pH to 6 to 7.

In addition, the colored leachate which has reacted with carbon dioxide in the pH adjusting tank 120 and becomes neutral has a brown chromaticity.

The carbon dioxide is not particularly limited as long as it is commonly used, but carbon dioxide discharged together with the blast furnace slag at the steel mill can be supplied to the pH adjusting tank 120 for utilization.

Preferably, the carbon dioxide is contained in the pH adjusting tank 120 at 15 to 25% based on the volume of the exhaust gas. If the volume of the carbon dioxide is less than 15% based on the volume of the flue gas, neutralization of the landfill leachate does not occur sufficiently. If the carbon dioxide is more than 25%, neutralization of the landfill leachate is excessive and acidic.

And passes through the pH adjustment tank 120 to pass neutral colored leachate to the activated carbon filling column 130. When the neutral colored leachate is passed through the activated carbon filling column 130 filled with activated carbon to make the neutral colorless leachate, acidic landfill leachate is finally treated as safe neutral leachate.

Hereinafter, the present invention will be described more specifically by way of specific examples. The following examples are provided to aid understanding of the present invention, and the scope of the present invention is not limited thereto.

Example

The landfill leachate was charged with 322 g and 470 mm of 50-mesh blast furnace slag into a column having an inner diameter of 26 mm and a height of 600 mm, and contacted with an upward flow for 5 hours at a space velocity of 4 L / h. The heavy metal ions such as chromium, zinc, and lead were precipitated as hydroxide by passing through the blast furnace slag filling column 110, and the heavy metal removal rate with time was shown in FIG. As can be seen from FIG. 2, when the contact time between the blast furnace slag filling column 110 and the landfill leachate was more than 2 hours, it was confirmed that the heavy metal removal rate was 90% or more.

The landfill leachate having passed through the blast furnace slag filling column 110 is passed through the pH adjusting tank 120. The pH adjusting tank 120 contains 20% of carbon dioxide based on the volume of the exhaust gas. FIG. 3 shows changes in pH depending on the contact time between the leachate passing through the blast furnace slag filling column 110 and the pH adjusting tank 120. The leachate having passed through the blast furnace slag filling column 110 should be neutralized as it passes through the pH adjusting tank 120 and should therefore exhibit a pH of 6 to 7 after passing through the pH adjusting tank 120. 3, the contact time between the leachate passing through the blast furnace slag filling column 110 and the pH adjusting tank 120 was 6 to 7 at 30 to 60 seconds, indicating that the leachate was properly neutralized .

The leachate having passed through the pH adjusting tank 120 was passed through a column having an inner diameter of 26 mm and a height of 600 mm, filled with 322 g of active carbon and 470 mm, to obtain neutral colored leachate of transparent color.

100: Landfill leachate collection tank
110: Blast furnace slag charging column
120: pH adjusting tank
130: activated carbon filling column

Claims (7)

Passing landfill leachate through a blast furnace slag filling column;
Passing the leachate having passed through the blast furnace slag filling column to a pH adjusting tank containing an exhaust gas containing carbon dioxide; And
And passing the leachate having passed through the pH adjusting tank to an activated carbon filling column.
The method according to claim 1, wherein the blast furnace slag includes at least one or more selected from the group consisting of Al ₂ O ₃ , MnO, and SiO ₂ .
The method of claim 1, wherein the blast furnace slag comprises 35 to 45 wt% of CaO.
The method of claim 1, wherein the blast furnace slag is 10 to 100 mesh in size.
The method according to claim 1, wherein the space velocity of the landfill leachate in the blast furnace slag packed column is 4 to 6 L / h.
The method according to claim 1, wherein the carbon dioxide is contained in the pH adjustment tank at 15 to 25% based on the volume of the exhaust gas.
The method according to claim 1, wherein the carbon dioxide is contained in the pH adjustment tank at 15 to 25% based on the volume of the exhaust gas.

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