JP2023010383A - Leachate treatment system and leachate treatment method - Google Patents

Abstract

To provide an exudation water treatment system and an exudation water treatment method that enable smooth treatment without adding a chemical such as sodium carbonate that reacts with calcium in exudation water treatment.SOLUTION: In order to solve the above problems, an exudation water treatment system having a reaction tank that adjusts a Langelier index of exudation water to 1.5 or less, and an exudation water treatment method using the system are provided. According to the system and the method, by adjusting the Langelier index of the exudation water within a specific range, calcium precipitation (scale formation) in the exudation water is suppressed, it is possible to smoothly treat the exudation water by taking measures against scale without generating and removing calcium compounds by adding the chemical that reacts with calcium (such as sodium carbonate) in exudation water treatment, and it is possible to significantly reduce running costs in the exudation water treatment.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a leachate treatment system and a leachate treatment method.

Leachate generated from final landfill disposal sites often contains various chemical substances (salts, organic matter, heavy metals, etc.) resulting from the waste itself and additives added during the waste treatment process. Appropriate treatment is required before discharging into water. At this time, it is known that the calcium contained in the leachate adheres to the equipment as scale, which causes a problem that the safe operation of the treatment system is hindered. Therefore, in the treatment of leachate, scale countermeasures using calcium are being studied.

For example, in Patent Document 1, sodium carbonate is added to the leachate, the precipitated calcium carbonate is separated, and then the pH is adjusted to prevent redissolution of the precipitated calcium and remove calcium from the leachate. mentioned to be removed.

JP 2016-16341 A

As described in Patent Document 1, it is known to add a chemical such as sodium carbonate to the leachate to precipitate and precipitate calcium carbonate to remove calcium and take measures against scale. However, in order to precipitate calcium in the leachate as calcium carbonate, it is necessary to add sodium carbonate in an amount equivalent to calcium. For this reason, the higher the concentration of calcium contained in the leachate, the more sodium carbonate is required, which in turn increases the cost of the chemicals. In addition, there is the problem that the treatment of the sediment generated by the addition of the chemicals is costly. There is

Accordingly, an object of the present invention is to provide a leachate treatment system and a leachate treatment method that enable smooth treatment without adding a chemical that reacts with calcium, such as sodium carbonate, in the treatment of leachate. be.

As a result of intensive studies on the above-mentioned problems, the present inventors found that when treating leachate, by adjusting the Langelier index, which is known as an index of water corrosivity, it reacts with calcium like sodium carbonate. We have found that scale countermeasures can be taken without adding chemicals, and smooth processing is possible.
That is, the present invention is the following leachate treatment system and leachate treatment method.

A leachate treatment system of the present invention for solving the above problems is a leachate treatment system for treating leachate, characterized by comprising a reaction tank for adjusting the Langelier index of leachate to 1.5 or less. do.
According to this leachate treatment system, by adjusting the Langelier index of the leachate to within a specific range, conditions are established in which calcium deposition (scale formation) in the leachate is suppressed, and calcium ions in the leachate are removed. Therefore, it is possible to smoothly treat the leachate. In other words, scale countermeasures can be taken without the need to generate and remove calcium compounds by adding chemicals that react with calcium (sodium carbonate, etc.) in leachate treatment, and the running costs in leachate treatment can be greatly reduced. is possible.

Further, as an embodiment of the leachate treatment system of the present invention, it is provided with pH adjusting means for adjusting the pH of the leachate, and the pH adjusting means adjusts the pH in the reaction tank to be greater than 6.0. Characterized by
According to this feature, by providing a means for adjusting the pH that makes a large contribution to the Langelier index, it becomes easy to adjust the Langerier index so that it falls within an appropriate numerical range. In addition, by adjusting the pH to be higher than 6.0, it is possible to suppress the Langelier index from becoming a large negative value, and to maintain a state in which both scale countermeasures and corrosion tendency suppression are possible. At the same time, there is an effect that it becomes possible to suppress the cost related to pH adjustment.

Further, one embodiment of the leachate treatment system of the present invention is characterized in that the leachate contains calcium and suspended solids, and a coagulation sedimentation tank is provided after the reaction tank.
According to this feature, unlike the conventional leachate treatment in which a calcium compound (calcium carbonate) is precipitated by adding a chemical that reacts with calcium, there is no need to perform a coagulating sedimentation treatment related to the calcium compound. Therefore, in addition to eliminating the need to add chemicals that react with calcium, it is also possible to reduce the amount of coagulant to be added. As a result, there is an effect that it is possible to smoothly proceed with scale countermeasures and coagulation sedimentation treatment in leachate treatment without incurring running costs.

In one embodiment of the leachate treatment system of the present invention, a biological treatment tank is provided after the reaction tank or the coagulating sedimentation tank.
According to this feature, unlike conventional leachate treatment in which a calcium compound (calcium carbonate) is precipitated by adding a chemical that reacts with calcium, without removing calcium and after taking measures against scale, It is possible to smoothly perform leachate treatment for discharging leachate into public water areas. In particular, there is no need to add chemicals that react with calcium and there is no need to treat calcium compounds, so compared to conventional leachate treatment, it is possible to significantly reduce running costs. Play.

In addition, a leachate treatment method of the present invention for solving the above problems is a leachate treatment method for treating leachate, comprising a Langelier index adjustment step of adjusting the Langelier index of the leachate to 1.5 or less. It is characterized by
According to this leachate treatment method, by adjusting the Langelier index of the leachate within a specific range, calcium precipitation (scale formation) in the leachate is suppressed, and calcium ions in the leachate are removed. Therefore, it is possible to smoothly treat the leachate. In other words, scale countermeasures can be taken without the need to generate and remove calcium compounds by adding chemicals that react with calcium (sodium carbonate, etc.) in leachate treatment, and the running costs in leachate treatment can be greatly reduced. is possible.

According to the present invention, it is possible to provide a leachate treatment system and a leachate treatment method that enable smooth treatment without adding a chemical such as sodium carbonate that reacts with calcium in the treatment of leachate.

1 is a schematic diagram showing the configuration of a leachate treatment system according to a first embodiment of the present invention; FIG. 4 is a graph showing an example of calculation results of the Langelier index for standard leachate. 4 is a graph showing an example of the result of adjusting the Langelier index of standard leachate by the leachate treatment system according to the first embodiment of the present invention; 5 is a graph showing an example of the result of adjusting the Langelier index of standard leachate by another aspect of the leachate treatment system according to the first embodiment of the present invention; FIG. 2 is a schematic diagram showing the configuration of a leachate treatment system according to a second embodiment of the present invention; FIG. 3 is a schematic diagram showing the configuration of a leachate treatment system according to a third embodiment of the present invention;

Preferred embodiments of the present invention will be described below with reference to the drawings. The leachate treatment method of the present invention will be replaced with the description of the configuration and operation of the leachate treatment system below. Also, this embodiment does not limit the invention.

The leachate treatment system of the present invention is for use in treatment of leachate from a landfill final disposal site for waste.
Here, the "leaching water" in the present invention refers to the water derived from the waste landfilled in the final landfill disposal site, rainwater that has fallen in the final landfill disposal site, etc. that has passed through the waste layer. In particular, it refers to those containing calcium (calcium ions) that cause scale. Examples of the leachate to be treated in the present invention include those having a calcium concentration of 1 mg/L or more. As a result, it is possible to sufficiently exhibit the effect of the present invention that suppresses the influence of scale generation on leachate treatment.
Other components contained in the leachate are not particularly limited, but examples thereof include suspended solids (hereinafter referred to as "SS"), heavy metals, and the like.
As will be described later, one aspect of the leachate treatment system of the present invention is particularly useful in treatment of leachate containing calcium and SS.

[First Embodiment]
FIG. 1 is a schematic diagram showing the configuration of a leachate treatment system according to a first embodiment of the present invention.
A leachate treatment system 1A of this embodiment is for treating leachate W, and as shown in FIG. It has In addition, a line L1 for supplying the leachate W to the reaction tank 2 and a line L2 for discharging the leachate W1 adjusted for the Langelier index from the reaction tank 2 are provided. In FIG. 1, arrows indicate the flow of water.

The reaction tank 2 is a tank for storing the leachate W, and is a tank for adjusting the Langelier index of the leachate W to be within a specific range. Further, the reaction tank 2 is provided with a Langelier index adjusting means 3 for adjusting the Langelier index of the leachate W. As shown in FIG. Then, as shown in FIG. 1, the leachate W is supplied into the reaction tank 2 via the line L1.
The reaction tank 2 is not particularly limited as long as the leachate W is stored and the Langelier index can be adjusted by the Langelier index adjusting means 3 . In addition, although one tank is shown as the reaction tank 2 in FIG. 1, a combination of a plurality of tanks may be used.

The Langelier index is an index used as an index relating to water corrosiveness, and is a numerical value that indicates the tendency of calcium carbonate to precipitate (film formation) in water. When the Langelier exponent is positive and the absolute value is large, the precipitation of calcium carbonate tends to occur. more prone to corrosion.

As shown in Equation 1 below, the Langerier index (LI) is the actual pH of water and the pH when calcium carbonate in water is in an equilibrium state where neither dissolution nor precipitation (theoretical pH: hereinafter referred to as “pHs” ) and is affected by the water temperature (T (unit: °C)).

ここで、［Ｃａ^２＋］はカルシウムイオン濃度（単位：ｍｅｑ／Ｌ）、[Ａ]は総アルカリ濃度（単位：ｍｅｑ／Ｌ）を示す。なお、［Ｃａ^２＋］（ｍｅｑ／Ｌ）＝［Ｃａ^２＋］（ｍｇ／Ｌ）÷（４０．１÷２）、［Ａ］（ｍｅｑ／Ｌ）＝［Ａ］（ｍｇ／Ｌ）÷（１００÷２）が成り立つ。
また、Ｓは補正値で、以下の式３により求められる。

ここで、Ｓｄは蒸発残渣濃度（単位：ｍｇ／Ｌ）を示す。 In addition, pHs is calculated|required by the following formula 2.

Here, [Ca ²⁺ ] indicates calcium ion concentration (unit: meq/L), and [A] indicates total alkali concentration (unit: meq/L). Incidentally, [Ca ²⁺ ] (meq/L) = [Ca ²⁺ ] (mg/L) ÷ (40.1 ÷ 2), [A] (meq/L) = [A] (mg/L) ÷ (100 ÷2) holds.
Also, S is a correction value, which is obtained by the following equation 3.

Here, Sd indicates evaporation residue concentration (unit: mg/L).

Calculation of the Langelier index based on the above formulas 1 to 3 will be described below using specific examples.
Here, as an object for calculation of the Langelier index, leachate having a general property of being highly alkaline and containing a certain amount of calcium ions (hereinafter referred to as "standard leachate") will be described as an example.

FIG. 2 is a graph showing the calculation results of the Langelier index for standard leachate. More specifically, FIG. 2 is a graph showing the contribution of each parameter to the Langelier index in standard leachate.
The properties of the standard leachate in FIG. 2 are pH 11.0, calcium ion concentration 1,500 mg/L (=74.8 meq/L), total alkali amount The evaporation residue concentration is 14,600 mg/L, and the water temperature is 20°C.
As shown in FIG. 2, the Langerier index of the standard leachate taken as an example is 3.83 as a result of calculations by formulas 1 to 3 based on each parameter of the standard leachate. The inventors of the present invention have confirmed that scale is generated in leachate treatment using the Langelier index.

On the other hand, in the reaction tank 2 of this embodiment, the Langelier index is adjusted to fall within a specific range.
More specifically, the Langelier index of the leachate W in the reaction tank 2 is preferably adjusted to 1.5 or less. As a result, the conditions for suppressing calcium precipitation (scale formation) in the leachate W can be set, and the treatment of the leachate W can proceed smoothly without removing the calcium ions in the leachate W. It becomes possible. In other words, scale countermeasures can be taken without the need to generate and remove calcium compounds by adding chemicals that react with calcium (sodium carbonate, etc.) in leachate treatment, and the running costs in leachate treatment can be greatly reduced. becomes possible.

Furthermore, the upper limit of the Langelier index of the leachate W in the reaction tank 2 is more preferably 1.0 or less, more preferably 0.5 or less. This makes it possible to further enhance the effect of suppressing scale generation.
On the other hand, when the Langelier index becomes a negative value, the tendency of water corrosion increases. This can prevent corrosion of the leachate treatment system 1A.
In particular, by setting the Langelier index to around 0, it is possible to suppress both scale generation and corrosion tendency.

The Langelier index adjusting means 3 is for performing a Langelier index adjusting step of adjusting the Langelier index of the leachate W in the reaction tank 2 .
Here, as shown in Equations 1 to 3, the pH value of water, calcium ion concentration, total alkali concentration, evaporation residue concentration, and water temperature are parameters in the Langerier index. Moreover, as shown in FIG. 2, the pH value of water particularly greatly contributes to the Langelier index.
For this reason, as the Langelier index adjusting means 3 in this embodiment, various means for adjusting parameters related to the Langelier index based on Equations 1 to 3 above may be provided.

An example of the Langelier index adjusting means 3 in this embodiment is to provide means for adjusting the pH value of water, which is a parameter that contributes highly to the Langelier index. That is, a pH adjusting means 30 for adjusting the pH value of the leachate W in the reaction tank 2 may be provided.

The pH adjusting means 30 is not particularly limited as long as it can adjust the pH value of the leachate W.
As an example of the pH adjusting means 30, for example, as shown in FIG. In addition, this aeration device 31 may also function as a stirring means in the reaction tank 2 .

By performing air aeration with the aerator 31, components contained in the air (especially carbon dioxide) are dissolved in the leachate W. At this time, the carbon dioxide dissolved in the leachate W exhibits acidity. As described above, the leachate W is mainly highly alkaline, and a neutralization reaction occurs due to the dissolution of carbon dioxide, and the pH of the leachate W decreases. Thereby, the pH value of the leachate W can be adjusted. The range of pH adjustment by the aerator 31 depends on the solubility of carbon dioxide in the leachate W, and the pH of the leachate W is in the range of about 7-9.

Further, when the pH is adjusted by the aeration device 31, control means for adjusting the amount of aeration by the aeration device 31 may be provided. At this time, it is preferable to provide a pH meter (pH sensor) in the reaction tank 2 and control the amount of aeration while monitoring the pH. This makes it easy to adjust the pH value of the leachate W so as to satisfy the predetermined Langerier index.

FIG. 3 is a graph showing the result of adjusting the Langelier index by adjusting the pH of the standard leachate shown in FIG. More specifically, FIG. 3 is a graph showing the contribution of each parameter related to the Langelier index in pH-adjusted leachate.
As shown in FIG. 3, when the aeration device 31 sets the pH value of the standard leachate (leakage W) to 8.0, the Langelier index decreases to 0.83. The present inventors have confirmed that the Langelier index suppresses scale formation in leachate treatment. As a result, calcium deposition (scale generation) in the leachate treatment system 1A can be suppressed without using chemicals that react with calcium, and leachate treatment can be performed smoothly.

Moreover, as another example of the pH adjusting means 30, as shown in FIG.
The pH adjuster addition part 32 is not particularly limited as long as it can add the pH adjuster to the reaction tank 2 . For example, one having a storage tank 32a for storing the pH adjuster and a pipe 32b for adding the pH adjuster to the reaction tank 2 from the storage tank 32a may be used. In addition, in order to adjust the addition amount of the pH adjuster, it is preferable to provide an addition amount adjustment mechanism such as a valve in the pipe 32b.

The pH adjuster is not particularly limited as long as it can adjust the pH of the leachate W. Note that the leachate W is mainly highly alkaline, and the pH of the leachate W must be lowered in order to adjust the Langelier index within a predetermined range. Therefore, it is preferable to use an acid as the pH adjuster in this embodiment, but depending on the properties of the leachate W, an alkali may be used.
An example of the pH adjuster in this embodiment is the use of an inorganic acid in view of its influence on leachate treatment and ease of availability and handling. More specific examples include sulfuric acid.

FIG. 4 is a graph showing the result of adjusting the Langelier index by adjusting the pH of the standard leachate shown in FIG. More specifically, FIG. 4 is a graph showing the contribution of each parameter related to the Langelier index in pH-adjusted leachate.
As shown in FIG. 4, an inorganic acid (sulfuric acid) was added as a pH adjuster by the pH adjuster addition unit 32 to set the pH value of the standard leachate (leakage W) to 7.1. At this time, the addition of the inorganic acid also changed the value of the total alkali concentration (0.4 meq/L (=22 mg/L)), and the Langelier index decreased to -0.52. The present inventors have confirmed that the Langelier index suppresses scale formation in leachate treatment. As a result, calcium deposition (scale generation) in the leachate treatment system 1A can be suppressed without using chemicals that react with calcium, and leachate treatment can be performed smoothly.

When the pH adjuster addition unit 32 is provided as the pH adjuster 30 and the pH of the leachate W is adjusted by the pH adjuster, the pH of the leachate W can easily be made more acidic. However, as described above, it is not preferable from the viewpoint of corrosion tendency that the Langelier index becomes a large negative value by making the pH of the leachate W more acidic. Moreover, using the pH adjuster more than necessary is not preferable from the viewpoint of running costs.
Therefore, the pH adjustment by the pH adjustment means 30 preferably includes adjustment so that the pH of the leachate W is higher than 6.0. More preferably, the pH of the leachate W is adjusted to 7.0 or higher.

In addition, although FIG. 1 shows that the pH adjusting means 30 is provided with the aeration device 31 and the pH adjusting agent adding section 32, any device that can perform necessary pH adjustment may be used. It is not limited. For example, either one of the aeration device 31 and the pH adjuster addition section 32 may be provided. This makes it possible to simplify the structure of the leachate treatment system 1A and reduce the running cost.

The Langelier index adjusting means 3 in this embodiment is not limited to providing means for adjusting pH. For example, a water temperature adjusting means for adjusting the water temperature in the reaction tank 2 and a calcium concentration adjusting means that does not rely on the addition of a chemical that reacts with calcium to form a precipitate may be provided. More specifically, a cooling device for lowering the temperature of the water in the reaction tank 2 or a means for introducing diluent water into the reaction tank 2 may be provided.

Further, as one of the Langelier index adjusting means 3, a measuring device for acquiring numerical values relating to each parameter for calculating the Langelier index may be provided. For example, in addition to the pH meter (pH sensor) described above, a thermometer, a calcium concentration meter, and the like can be used. At this time, the timing of measurement by each measuring device is not particularly limited, and in addition to constant (real-time) measurement, measurement may be performed periodically or at arbitrary timing.
At this time, the measurement by each measuring device may be performed within the reaction tank 2 or may be performed on a part of the leachate W in the reaction tank 2 that is sampled.

In the reaction tank 2, the leachate W1 adjusted to a predetermined Langelier index is discharged out of the system through the line L2.
If the leachate W1 does not contain components (organic substances, heavy metals, etc.) related to wastewater standards and meets the water quality that can be discharged into public waters, it can be discharged directly into public waters through line L2. becomes.

With the leachate treatment system 1A in this embodiment, the Langelier index of the leachate W is adjusted within a specific range, so that calcium precipitation (scale formation) in the leachate W is suppressed, and the leachate W It is possible to smoothly treat the leachate W without removing the calcium ions therein.
In the leachate treatment system 1A of this embodiment, the Langelier index of the leachate W in the reaction tank 2 is within a specific range, so that calcium precipitation is suppressed. , calculation of the Langelier index during treatment in the leachate treatment system 1A is not an essential requirement.

[Second embodiment]
FIG. 5 is a schematic diagram showing the configuration of a leachate treatment system according to a second embodiment of the present invention.
In the leachate treatment system 1B of the second embodiment, as shown in FIG. 5, a coagulating sedimentation tank 4 is provided after the reaction tank 2 in the first embodiment. The reaction tank 2 and the coagulating sedimentation tank 4 are connected by a line L3, and the leachate W1 adjusted for the Langelier index is supplied from the reaction tank 2 to the coagulating sedimentation tank 4 via the line L3. Furthermore, the coagulating sedimentation tank 4 is provided with a line L4 and a line L5 for discharging the separated solid content S and liquid content (treated water W2) out of the system, respectively. The description of the same configuration as that of the first embodiment will be omitted.

If the leachate W contains calcium and SS, it cannot be discharged into public waters while still containing SS. Moreover, as will be described later, when biological treatment is applied as one of the leachate treatments, it is known that SS is an obstacle to the biological treatment. Therefore, in order to perform the leachate treatment smoothly, it is necessary to suppress the precipitation of calcium in the leachate W and to separate the SS.

Here, in the leachate treatment system 1B in this embodiment, the reaction tank 2 and the coagulating sedimentation tank 4 are provided separately, and the reaction tank 2 is arranged upstream of the coagulating sedimentation tank 4. As a result, it is possible to perform the process of adjusting the Langelier index of the leachate W in advance and independently, and the coagulation sedimentation process is performed on the leachate W1 in which the calcium deposition is maintained. Therefore, unlike conventional leachate treatment in which a calcium compound (calcium carbonate) is precipitated by adding a chemical that reacts with calcium, the coagulation sedimentation tank 4 in this embodiment performs coagulation sedimentation treatment related to calcium compounds. There is no need, and only the SS coagulation sedimentation treatment is performed. Therefore, in addition to eliminating the need to add chemicals that react with calcium, it is also possible to reduce the amount of coagulant to be added. As a result, it is possible to smoothly proceed with scale countermeasures and SS treatment in leachate treatment without incurring running costs.

Examples of the leachate W to be treated by the leachate treatment system 1B according to this embodiment include those having a calcium concentration of 1 mg/L or higher and an SS concentration of 100 mg/L or higher. As a result, the effects of the leachate treatment system 1B according to the present embodiment can be fully exhibited.

The coagulation-sedimentation tank 4 in this embodiment is not particularly limited as long as it can perform coagulation-sedimentation treatment related to SS in the leachate W1. For example, the coagulant sedimentation tank 4 may be provided with a coagulant addition unit for adding a coagulant and a stirring unit for stirring and mixing the coagulant and the leachate W1. In addition, the coagulant addition section may be provided in the reaction tank 2, and the adjustment of the Langelier index and the mixing of the coagulant may be performed in the reaction tank 2 at the same time.

Moreover, the coagulant added in the coagulating sedimentation tank 4 is not particularly limited. The flocculant used in this embodiment may be either an inorganic flocculant or a polymer flocculant, and depending on the components in the leachate W1 and the aggregation state, the inorganic flocculant and the polymer flocculant may be used in combination. may For example, inorganic flocculants include polyferric sulfate, ferric chloride, polysilica iron, aluminum sulfate, and polyaluminum chloride. Cationic polymer flocculants such as diallyl ammonium, chitosan, urea-formalin resin, sodium polyacrylate, polyacrylamide partial hydrolyzate, partially sulfomethylated polyacrylamide, poly(2-acrylamide)-2-methylpropane sulfate, etc. nonionic polymer flocculants such as polyacrylamide and polyethylene oxide; and amphoteric polymer flocculants such as copolymers of acrylamide, aminoalkyl methacrylate and sodium acrylate. It is preferable to use at least an inorganic flocculant because the flocculation state can be maintained well.

The solid content S and the liquid content (treated water W2) separated by the coagulating sedimentation tank 4 are discharged outside the system through lines L4 and L5, respectively.

At this time, the solid content S is mainly derived from SS, and is preferably further treated as necessary. More specifically, the solid content S can be supplied to the dehydration equipment via the line L4. The dehydration equipment may include one or a plurality of devices related to the dehydration treatment of the solid content S. Examples of such devices include concentration tanks, storage tanks, chemical introduction devices, dehydrator, and the like. is mentioned.
As described above, in the leachate treatment system 1B of this embodiment, treatment is performed without causing calcium in the leachate W to precipitate. Therefore, compared to conventional leachate treatment in which calcium compounds are precipitated by adding chemicals that react with calcium, it is possible to reduce the amount of solid content S precipitated and discharged in the coagulation sedimentation tank 4. Therefore, the amount of solid content S supplied to the dehydration equipment is also reduced, so that it is possible to reduce the processing cost for dehydration.

On the other hand, the liquid portion (treated water W2) contains components other than SS (calcium and other components) among the components contained in the leachate W1. For this reason, if the treated water W2 does not contain components (organic substances, heavy metals, etc.) related to the wastewater standards and meets the water quality that can be discharged to the public water area, it can be discharged to the public water area as it is via the line L5. It becomes possible.

[Third Embodiment]
FIG. 6 is a schematic diagram showing the configuration of a leachate treatment system according to a third embodiment of the present invention.
In the leachate treatment system 1C of the third embodiment, as shown in FIG. 6, a biological treatment tank 5 is provided after the coagulating sedimentation tank 4 in the second embodiment. The coagulating sedimentation tank 4 and the biological treatment tank 5 are connected by a line L6, and the liquid (treated water W2) separated in the coagulating sedimentation tank 4 is supplied to the biological treatment tank 5 via the line L6. . Further, the biological treatment tank 5 is equipped with a line L7 for discharging the treated water W3 that has undergone biological treatment to the outside of the system. The description of the same configuration as that of the second embodiment will be omitted.

If the leachate W contains calcium and SS as well as nitrogen-containing compounds and organic substances subject to discharge standards, the coagulation-sedimentation treatment alone cannot treat all of them, so the treated water W2 is directly discharged into public waters. you can't. Therefore, in addition to the coagulation-sedimentation treatment, it is necessary to further apply a treatment means for treating the treated water W2 to a quality that allows it to be discharged into public waters.

Here, in the leachate treatment system 1C in this embodiment, the biological treatment tank 5 is provided after the reaction tank 2 and the coagulating sedimentation tank 4 . Accordingly, after adjusting the Langerier index, the treated water W2 subjected to the coagulation-sedimentation treatment is subjected to biological treatment.
For this reason, unlike conventional leachate treatment that precipitates calcium compounds (calcium carbonate) by adding chemicals that react with calcium, leachate treatment is performed without removing calcium and after taking measures against scale. It becomes possible to perform the whole smoothly. In particular, there is no need to add chemicals that react with calcium, and there is no need to treat calcium compounds, so it is possible to significantly reduce running costs compared to conventional leachate treatment.
In addition, by providing the biological treatment tank 5 after the coagulating sedimentation tank 4, the treated water W2 from which the SS, which is a hindrance to the biological treatment, has been removed in advance can be subjected to the biological treatment. Smoother process progress is possible without reducing efficiency.

The biological treatment tank 5 in this embodiment is not particularly limited as long as it can treat nitrogen-containing compounds and organic substances in the leachate W (treated water W2). For example, a nitrification tank into which activated sludge containing nitrifying bacteria is introduced and a denitrification tank into which activated sludge containing denitrifying bacteria is introduced can be used. The nitrification tank oxidizes ammonium nitrogen to oxidized nitrogen by nitrifying bacteria in an oxidizing (aerobic) atmosphere. In addition, the denitrification tank reduces oxidized nitrogen to nitrogen gas by denitrifying bacteria in a reducing (anaerobic) atmosphere. These biological treatment tanks 5 may be used alone, or may be a combination of a plurality of tanks.

If the amount of SS in the leachate W to be treated is less than 100 mg/L and the separation of SS is unnecessary, the coagulating sedimentation tank 4 in FIG. The tank 5 may be connected. This makes it possible to simplify the configuration of the leachate treatment system 1C.

After being treated in the biological treatment tank 5, the treated water W3 is discharged outside the system through the line L7. If the treated water W3 does not contain components (heavy metals, etc.) related to effluent standards and meets the water quality that can be discharged into public waters, it can be discharged directly into public waters through line L7.

On the other hand, if the treated water W3 does not satisfy the water quality that can be discharged into the public water area, an advanced treatment facility for treating the treated water W3 may be further provided after the biological treatment tank 5 in this embodiment. As the advanced treatment facility, one or a plurality of devices for treating substances that cannot be completely treated by the coagulation sedimentation treatment in the coagulation sedimentation tank 4 or the biological treatment in the biological treatment tank 5 may be provided. Examples thereof include a filtering device, an activated carbon adsorption tower, a chelate adsorption tower for collecting heavy metals, an ozonation device, an acidic coagulation sedimentation treatment tank, and the like.

At this time, part of the treated water discharged from the advanced treatment facility may be used as a pH adjuster. For example, the treated water in the acidic coagulation-sedimentation treatment tank has a pH of about 4-5. Therefore, as the Langerier index adjusting means 3 in this embodiment, instead of the pH adjusting agent addition unit 32, part of the treated water of the advanced treatment facility (acidic coagulation sedimentation treatment tank) is supplied to the reaction tank 2 in this embodiment. A line may also be provided. This makes it possible to further reduce the running cost of the leachate treatment system 1C.

The embodiment described above is an example of a seepage water treatment system and a seepage water treatment method using this system. The leachate treatment system and the leachate treatment method according to the present invention are not limited to the above-described embodiments. The water treatment method may be modified.

For example, as the leachate treatment system and the leachate treatment method according to the present invention, the configuration of the leachate treatment system of the present embodiment (reaction tank 2 and A Langelier index adjusting means 3) may be provided so that the operation (leachage treatment method) of the existing leachate treatment system and the present embodiment can be switched as needed. As a result, it is possible to recover calcium carbonate, etc. from the calcium contained in the leachate and remove the calcium contained in the leachate, and to enable discharge without removing the calcium contained in the leachate. It becomes possible. In other words, depending on the properties of the leachate (calcium content, types of components other than calcium, etc.), the running costs associated with the use of chemicals and the treatment efficiency required to make the water quality suitable for discharge should be considered. Processing systems and processing methods can be selected.

The leachate treatment system and the leachate treatment method of the present invention can be used for leachate treatment. In particular, it is suitable for treatment of leachate that requires measures against scale, such as leachate containing calcium.

1A, 1B, 1C... Leachate treatment system, 2... Reaction tank, 3... Langelier index adjusting means, 30... pH adjusting means, 31... Aerator, 32... pH adjusting agent addition section, 32a... Storage tank, 32b... Piping , 4... coagulation sedimentation tank, 5... biological treatment tank, L1 to L7... line, S... solid content, W... leachate, W1... leachate with adjusted Langelier index, W2, W3... treated water

Claims (5)

A leachate treatment system for treating leachate, comprising:
A leachate treatment system comprising a reaction tank for adjusting the Langelier index of said leachate to 1.5 or less. pH adjusting means for adjusting the pH of the leachate,
2. The leachate treatment system according to claim 1, wherein the pH adjusting means adjusts the pH in the reaction tank to be higher than 6.0. The leachate contains calcium and suspended solids,
3. The leachate treatment system according to claim 1, further comprising a coagulating sedimentation tank after said reaction tank. The leachate treatment system according to any one of claims 1 to 3, characterized by comprising a biological treatment tank after said reaction tank or said coagulating sedimentation tank. A leachate treatment method for treating leachate, comprising:
A leachate treatment method, comprising a Langelier index adjustment step of adjusting the Langelier index of the leachate to 1.5 or less.

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