JPH0760288A - Method and device for preventing calcium scalling caused by leaching water - Google Patents

Abstract

PURPOSE:To prevent scaling caused by calcium which becomes a problem in treatment of leaching water of the final disposal site of refuse or in the recent dumping site mainly used for incineration adhes and to prevent generation of trouble of calcium scaling in the subsequent treatment. CONSTITUTION:Attention is not paid to calcium ions between calcium ions and carbonate ions which produce scaling but is paid to removing treatment of carbonate ions. A pH regulation tank 5 and a decarboxylation tank 6 are provided in the front step of a sewage storage tank 7. Leaching water is regulated weakly acidic by an acidic liquid in the pH regulation tank 5 and also carbonate ions are removed by performing deaeration in the decarboxylation tank 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for preventing calcium scaling of leachate,
In particular, the present invention relates to a method for preventing calcium scaling in leachate capable of preventing calcium scaling by removing carbonate ions, and a device for preventing the same.

[0002]

2. Description of the Related Art Conventionally, salt from leachate, especially calcium, which has been a problem in recent landfills mainly consisting of incinerated ash, has a higher concentration than other salts. There is a problem that scaling due to calcium carbonate adheres to the inside of the sewage storage tank and other pumps for treating sewage and damages it.

In order to solve such a problem, as an additive for preventing scaling, a method for preventing the scaling or a coagulation-precipitation method of calcium carbonate using a chemical such as sodium carbonate is adopted. For example, JP-A-63-25
8692 and JP-A-63-258694.

In the calcium carbonate coagulation precipitation method, however, calcium in the leachate and an equivalent amount of sodium carbonate are added, the pH is adjusted to about 10 with an alkaline agent, and the precipitated calcium carbonate is coagulated with a polymer to perform a precipitation treatment. However, there is a problem that the production cost of sludge and the dehydration treatment are required, and the equipment cost and the maintenance cost increase.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has become a problem in the treatment of leachate at the final disposal site of refuse or the recent landfill mainly of incinerated ash. The method for preventing calcium scaling of leachate that prevents calcium scaling problems by preventing calcium scaling, especially by treating the leachate at the first stage when it flows out, so that calcium scaling trouble does not occur in the subsequent treatment. An object is to provide a prevention device.

[0006]

That is, the present invention focuses on the removal treatment of not the calcium but the carbonate ion among the calcium ion and the carbonate ion which generate scaling. The first invention is What is claimed is: 1. A calcium scaling prevention method for leachate that prevents scaling of calcium from carbonated leachate, wherein a pH adjusting tank and a decarboxylation tank are provided in the preceding stage of a wastewater storage tank, and an acid solution is used in the pH adjusting tank. Is a method for preventing calcium scaling of the leachate, characterized in that the carbonate ion is removed by degassing in the decarbonation tank while adjusting the leachate to be weakly acidic.

The above-mentioned acidic liquid may be sulfuric acid, or acidic coagulation-precipitated treated water having a pH of about 4 to 5 in a water treatment facility in the subsequent stage.

The range of pH adjustment in the pH adjusting tank can be adjusted to about pH 2-6.

The second invention is a calcium scaling preventing device for leachate which prevents scaling of calcium from leachate containing calcium and carbonate ions. A pH adjusting tank for adjusting the above-mentioned leachate to be weakly acidic,
A descaling tank for removing carbonate ions by degassing the liquid from the pH adjusting tank, and a calcium scaling prevention device for leachate.

[0010]

[Function] As described above, calcium in leachate reacts with carbonate ions in the same and produces scaling of calcium carbonate. The carbonate ion in the leachate increases as the organic matter content in the landfills increases,
On the other hand, as the amount of calcium ions contained in the incineration ash increases, the amount of calcium in the leachate increases. Scaling of calcium carbonate occurs in large amounts in the process of storing, sending water, aerating and stirring the leachate that flows out from the landfill, and causes damage to various treatment equipment, so it flows out from the landfill. It is important to take preventive measures in the first stage.

That is, in the method and apparatus for preventing calcium scaling of leachate according to the present invention, the liquid is adjusted to have an acidity of, for example, pH 2 to 6 before the various treatments for sewage or leachate, and is usually p.
Since it is possible to remove the carbonate ion that is ionized at H8 or higher, the calcium ion does not combine with the carbonate ion to generate calcium carbonate, that is, the scaling does not occur, and the various problems as described above in the related art are solved. can do.

If treated water of acidic coagulation and precipitation is used as the acid for adjusting the acidity, the amount of treatment chemicals can be reduced.

Further, as compared with the conventional scaling prevention method of removing calcium in the leachate, sludge is not generated, so that the processing equipment cost can be reduced.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a calcium scaling prevention apparatus 1 for carrying out the method for preventing calcium scaling of leachate according to the present invention will be described with reference to FIG.

FIG. 1 is a schematic diagram of a treatment system 2 including the calcium scaling prevention device 1. The treatment system 2 includes, for example, a water collecting pipe 4 from a retaining wall 3 of a landfill and a pH adjusting tank 5. And the calcium scaling prevention device 1 having a decarbonation tank 6, a sludge storage tank 7,
It has a leachate treatment facility 8.

The pH adjusting tank 5 of the calcium scaling prevention apparatus 1 is provided with a pH sensor 9, a controller 10 such as a pH adjuster, and a stirring motor 11, and an acidic liquid such as sulfuric acid is supplied from an acidic liquid tank 12 to the acidic liquid tank 12. The pH can be adjusted by adding it.

In the pH adjusting tank 5, the controller 1
By controlling 0, the pH of carbonate ion in the liquid is adjusted to about 2 to 6, for example, a weak acidity of pH 5.5. Carbonate ions in the acidified leachate produce fine carbon dioxide gas bubbles.

In the decarbonation tank 6, air is blown from a diffusing pipe 13 having a hole in a vinyl chloride pipe or the like to carry out coarse bubble aeration so that the bubbles are easily deaerated and released into the atmosphere.

In the sludge storage tank 7, the decarbonated leachate flows in, is stirred and stored, and then is driven by the supply pump 14 to be treated in the leachate treatment facility 8 by a series of treatment steps.

That is, in the general treatment process in the leachate treatment facility 8, the biological treatment process 15 for decomposing and assimilating organic matters and nitrogen components using activated sludge and the biological treatment water from the biological treatment process 15 are aggregated. Acid coagulation sedimentation treatment process 16 and sand filtration that performs general filtration
It is the activated carbon adsorption process 17, and the leachate is discharged as treated water through these treatment steps.

In the acidic coagulation / precipitation treatment process 16, a coagulant such as ferric chloride is used to adjust the pH to about 4-5.
At agglomeration treatment is performed.

The pH of the treated water in the sedimentation tank (acidified coagulated treated water) from the acidic coagulated sedimentation treatment process 16 is about 4-5.
And part of it is used as a decarboxylation acid in the pH adjusting tank 5, and the rest is neutralized and treated in the sand filtration / activated carbon adsorption process 17.

Even when a large amount of calcium is contained in the liquid in the leachate treatment facility 8 and the sludge storage tank 7 described above, the carbonate ion itself is removed in the calcium scaling prevention device 1 which is the preceding stage. As such, it does not produce calcium carbonate scaling.

[0024]

As described above, according to the present invention, in the first stage of the outflow of leachate, the pH of the leachate is adjusted to be weakly acidic to remove carbonate ions in the leachate as carbon dioxide gas. Therefore, it is possible to solve the problem that calcium scaling occurs in various treatment processes in a sewage storage tank or a leachate treatment facility after that.

[0025]

[Brief description of drawings]

1 is a schematic view of a treatment system 2 including a calcium scaling prevention apparatus 1 for carrying out a method for preventing calcium scaling of leachate according to the present invention.

[Explanation of symbols]

1 Calcium Scaling Prevention Device 2 Treatment System Including Calcium Scaling Prevention Device 1 3 Landfill Retaining Wall 4 Water Collection Pipe 5 pH Adjustment Tank 6 Decarbonation Tank 7 Sludge Storage Tank 8 Leachate Treatment Facility 9 pH Sensor 10 pH Controller etc. Controller 11 Stirring motor 12 Acid solution tank 13 Air diffuser 14 Supply pump 15 Biological treatment process 16 Acidic coagulation sedimentation treatment process 17 Sand filtration and activated carbon adsorption process

Claims (5)

[Claims] 1. A method for preventing calcium scaling of leachate that prevents scaling of calcium from leachate containing calcium and carbonate ions, wherein a pH adjusting tank and a decarbonation tank are provided in the preceding stage of the wastewater storage tank, A method for preventing calcium scaling of leachate, wherein the leachate is adjusted to be weakly acidic with an acid solution in the pH adjusting tank, and the carbonate ions are removed by deaeration in the decarbonation tank. 2. The method for preventing calcium scaling of leachate according to claim 1, wherein the acidic liquid is sulfuric acid. 3. The method for preventing calcium scaling of leachate according to claim 1, wherein the acidic liquid is used as acidic coagulation sedimentation treated water having a pH of about 4 to 5 in a water treatment facility at a subsequent stage. 4. The method for preventing calcium scaling of leachate according to claim 1, wherein the range of pH adjustment in the pH adjusting tank is about 2 to 6. 5. A calcium scaling prevention device for leachate that prevents scaling of calcium from leachate containing calcium and carbonate ions, the device being provided in the preceding stage of a wastewater storage tank, wherein the leachate is weakened by an acidic liquid. A calcium scaling prevention device for leachate, comprising: a pH adjusting tank for adjusting to acidic, and a decarbonating tank for removing the carbonate ion by degassing the liquid from the pH adjusting tank.