JP2002066573A - Method for removing manganese ion in wastewater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently remove a manganese ion in wastewater discharged from a wet stack gas desulfurizing device or the like by using a small amount of permanganate in a neutral range. SOLUTION: Slurry or a granular material containing a hydrated manganese dioxide generated by the reaction of a manganese ion and a permanganate is mixed with wastewater, which contains the manganese ion and the permanganate. Thereby, in nearly neutral range, with addition of a small amount of permanganate, the manganese is oxydized and it can be efficiently removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing manganese ions in wastewater which poses a problem on environmental protection.
The present invention particularly relates to a method for removing manganese ions in wastewater of an oil-fired boiler, which is suitable for treating wastewater containing ammonium ions and found in flue gas desulfurization wastewater of flue gas from an oil-fired boiler.

[0002]

2. Description of the Related Art Methods for removing manganese ions include a hydroxide method, a sulfide method, a contact filtration method, an ion exchange method and an adsorption method. Among them, the hydroxide method is a method in which an alkaline agent such as sodium hydroxide or slaked lime is added to wastewater containing manganese ions, and manganese ions are removed in the form of hydroxide in an alkaline region. One of the most representative methods will be described with reference to FIG.

First, waste water 1 containing manganese ions Mn ²⁺ is introduced into a pH adjusting tank 13. A pH adjuster 2 such as sodium hydroxide, slaked lime, or an acid is added thereto, and the wastewater is p
By adjusting to H9 to 10, a reaction is performed as in the following formula (1) to precipitate a manganese hydroxide precipitate. At this time, if necessary, the polymer coagulant 5 may be added to coarsen the precipitate and facilitate precipitation.

[0004]

Embedded image

[0005] The reaction solution is introduced into a sedimentation tank 14 for sedimentation. The supernatant water is discharged as treated water 11, and the precipitate is carried out of the system as a slurry 18a. In addition,
Part of the precipitate is returned to the pH adjusting tank 13 as a circulating slurry 18b, and is added to the pH adjusting tank 13 together with the wastewater 1.

As a method for oxidizing manganese ions and separating them as manganese dioxide MnO _2, there are methods such as an oxidation method using chlorine and an oxidation method using permanganate.
Among these, the oxidation method using permanganate involves adding permanganate to wastewater containing manganese ions and adding pH to the wastewater.
Has been proposed to adjust manganese to near neutrality and to separate manganese in the form of manganese dioxide (JP-A-7-10828).
No. 1).

[0007]

However, the above-mentioned conventional method has the following problems. That is, in the method of precipitating manganese as a hydroxide, the wastewater is adjusted to an alkaline region having a pH of 9 to 10. Therefore, when metal ions, particularly magnesium ions, are present in the wastewater, a large amount of the alkaline agent is consumed. In addition, a large amount of magnesium hydroxide precipitate is generated, and the amount of sludge increases significantly. Further, when the slurry is brought to a neutral pH range,
There was a problem of redissolving as Mn ²⁺ .

In the method of oxidizing using chlorine, when high-concentration ammonium ions are contained as in desulfurization wastewater from oil-fired boiler flue gas, chlorine added to the wastewater first reacts with ammonia, so manganese ions are oxidized. There is a problem that the amount of added chlorine must be significantly increased as compared with the amount of chlorine required to perform the process.

Furthermore, the method of oxidizing using a permanganate requires a permanganate in an equivalent amount or more to Mn ²⁺ . That is, theoretically, 1 mg of Mn is obtained from the equation (2).
^When KMnO ₄ is used as a permanganate for ²⁺ ,
The equivalent value of 1.92 mg or more of KMnO ₄ is required. In this case, since there is an excess of permanganate, a heavy metal chelating agent must be added to remove it. The permanganates and heavy metal chelators are rather expensive, which has led to the problem of being extremely uneconomical.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has the following structure. That is, the present invention provides an oxidation step of adding permanganate to treated wastewater containing manganese ions to produce hydrated manganese dioxide, and treating the produced wastewater containing hydrated manganese dioxide with treated water by precipitation. A method for removing manganese ions in wastewater, comprising: a step of separating the slurry into a slurry having an increased hydrated manganese dioxide concentration; and a step of returning a part of the slurry to an oxidation step.
The method of the present invention preferably includes a step of adding and mixing a permanganate in advance to the slurry obtained by the precipitation, and adding the mixture to the wastewater to be treated. It is preferable that the method further comprises a step of solid-liquid separating the slurry obtained by the precipitation, mixing the obtained granular manganese dioxide and permanganate in advance, and adding the mixed manganese dioxide to the waste water to be treated. Further, the present invention is characterized in that it comprises a step of adding permanganate, a flocculant and a polymer flocculant to the treated wastewater containing manganese ions, stirring and granulating the produced hydrated manganese dioxide. Provided is a method for removing manganese ions in wastewater. In the method of the present invention, the amount of manganese dioxide MnO _{2 to be} added is 20 or more by weight based on the amount of manganese ions Mn ²⁺ contained in the effluent to be treated, and It is preferable to add the manganate (MnO ₄ ⁻ ) so that the amount thereof is equal to or less than the theoretical equivalent value of the manganese ion Mn ^{2+ in} the wastewater. Further, manganese sand is previously added to the treated wastewater, and the manganese sand has a particle size of 200 μm.
m or less. In addition, the configuration of the present invention can effectively treat wastewater containing manganese ions that is also wastewater containing ammonia ions, and is also suitable for treating desulfurization wastewater from a large amount of oil-fired boiler combustion exhaust gas. is there.

[0011]

Next, an embodiment of the present invention will be described with reference to the drawings. Note that these embodiments are merely examples, and do not limit the present invention.

The type of waste water is manganese ion Mn.
The method of the present invention can be applied without any particular limitation as long as the wastewater is dissolved as ²⁺ . When the content of manganese ions is extremely large, it is economically preferable to perform another treatment in advance.

In FIG. 1, waste water 1 containing manganese ions is introduced into a reaction tank 8. If the wastewater is not near neutral, a pH adjuster 2 is injected to adjust the wastewater to pH 6 to 8, and a chelating agent 3 for insolubilizing heavy metal ions in the water in advance is added.

As a pH adjuster, sodium hydroxide,
Examples thereof include alkali agents such as slaked lime, and acids such as hydrochloric acid and sulfuric acid. When the wastewater is flue gas desulfurization wastewater, it is preferable to use sodium hydroxide, hydrochloric acid, or the like in order to prevent gypsum from forming and increasing the amount of sludge.

As the chelating agent, a commercially available heavy metal chelating agent can be used. The amount of the chelating agent to be added depends on the amount of heavy metal ions in the waste water, but it is usually appropriate that the amount is about several mg / L to several tens mg / L.

Then, the reaction solution is led to the oxidation tank 9 and permanganate (MnO ₄ ⁻ ) 4 is added. As the permanganate, potassium permanganate, sodium permanganate, ammonium permanganate, or the like can be used. Most commonly used is potassium permanganate KMnO _4, which is also used in this treatment example, but the present invention is not limited to this. By adding permanganate, the manganese ion Mn ²⁺ contained in the reaction solution becomes insoluble hydrated manganese dioxide Mn as shown in the following equation (2).
O ₂ · nH ₂ O. Equation (2) shows the reaction when potassium permanganate is used as the permanganate.

[0017]

Embedded image

From equation (2), theoretically, manganese ion 1
The equivalent value is 1.92 mg of potassium permanganate per mg, but in the method of the present invention, it is not more than the theoretical equivalent value, for example, 0.1 mg of potassium permanganate per 1 mg of manganese ion.
It is only necessary to add about 7 to 0.8 mg. because,
The hydrated manganese dioxide contained in the slurry adsorbs unreacted manganese ions in the liquid, and also promotes the reaction when manganese ions are oxidized to form manganese dioxide as in the above formula (2). This is because it is considered that there is an action as Although the behavior is not yet clear, by the action of such hydrated manganese dioxide,
Manganese ions can be efficiently removed without adding a permanganate to an equivalent amount, which can contribute to improvement of the quality of treated water.

Here, a circulating slurry 7b from a sedimentation tank 10 described later is added to the oxidation tank 9. In this slurry, hydrated manganese dioxide MnO _2.
In addition to nH ₂ O, gypsum, heavy metals, etc. are included when flue gas desulfurization wastewater is treated. The order of addition of the permanganate and the addition of the circulating slurry or granulated material may be simultaneous or before or after each other, and both have the same effect.

Next, the oxidized solution is led to the precipitation tank 10. If necessary, a polymer flocculant 5 is added in the sedimentation tank 10 or a stage before the sedimentation tank 10, and the precipitate is coarsened and separated by settling. As the polymer flocculant 5, a commercially available anionic flocculant can be used. For example, a polyacrylamide-based flocculant may be added at about 1 to 10 mg / L. Thus, the supernatant water is discharged or reused as the treated water 6. Further, the precipitate is returned to the oxidation tank 9 as a circulating slurry 7b, and a part of the remaining is discharged to the outside as a slurry 7a.

The processing step shown in FIG. 2 is almost the same as that of FIG. 1, but in the course of returning from the precipitation tank 10 to the oxidation tank 9, the circulating slurry 7b contains, for example, potassium permanganate. The location where permanganate is added is different.

Incidentally, when the manganese ions in the waste water and the hydrated manganese dioxide MnO ₂ .nH ₂ O in the circulating slurry 7b are kept in contact without adding an oxidizing agent such as potassium permanganate, MnO ₂ · MnO · H ₂ O
Is generated. This substance cannot oxidize and adsorb manganese ions in wastewater.

[0023]

Embedded image

Therefore, in the method of the present invention shown in FIG. 2, the permanganate 4 and the circulation slurry 7b are mixed in advance. Thus, the inert slurry in the circulating slurry 7b is
MnO ₂ · MnO · H ₂ O the active hydrated manganese dioxide MnO ₂ · nH ₂ O
To restore the oxidizing and adsorbing power of manganese ions in wastewater. In the oxidizing tank 9, the hydrated manganese dioxide in the circulating slurry 7b effectively acts as a catalyst, so that the processability is greatly improved as will be seen in the examples described later.

In the processing step shown in FIG. 3, when adding the permanganate 4 in the oxidizing tank 9, manganese sand is added to the oxidizing tank 9 in advance. As the manganese sand, a manganese filter medium used for water supply, industrial water, and the like can be used, but is not limited thereto. By the addition of manganese sand, manganese ions in the wastewater are adsorbed and insolubilized by MnO ₂ · H ₂ O on the surface of the manganese sand. It is not necessary to continuously add the manganese sand, but only to add the manganese sand as needed when starting up the treatment. Thereafter, the circulating slurry 7 containing the manganese sand discharged from the sedimentation tank 10 is used.
The same treatment can be performed by adding b.

As shown in FIG. 3, the oxidizing tank 9 is provided with a partition wall in the tank to separate a region to which the polymer flocculant 5 is added. It is preferred that the reaction product be easily coarsened. To the oxidized solution after the reaction, a polymer flocculant 5 is added in a later region to coarsen the particles, and then sedimentation and separation are performed in a sedimentation tank 10 to discharge the treated water 6 and a slurry 7b containing manganese sand. Is used as a circulation slurry.

The concentration of manganese sand and reaction products in the slurry 7b discharged from the sedimentation tank is 20000-4.
0000 mg / L, the particle size is 20-200 μm, MnO ₂
The amount is about 500-3000 mg / L. The circulating slurry 7b is introduced into a cyclone 9a provided in a return line reaching the oxidation tank 9 and classified, and the circulating slurry 7d containing particles having a large particle diameter of 50 μm or more is returned to the oxidation tank 9 and is classified. The slurry 7c containing particles of 50 μm or less is discharged out of the system as a surplus. Classify like this 50 ~
By returning 200 μm particles, the subsequent settling tank 1
The sedimentation separation performance at 0 can be greatly improved.

The processing step shown in FIG.
In the line from the lower part of a to the oxidation tank 9, permanganate 4
Is different from the processing step shown in FIG.
The other steps are the same as the processing steps shown in FIG.
The effect is, as shown in the processing step of FIG. 2 above, that inactive MnO ₂ .MnO.H ₂ O generated on the surface of manganese sand is converted into hydrated manganese dioxide MnO ₂ .nH ₂ O
To restore the oxidizing and adsorbing power of the manganese ions in the wastewater, which has the effect of greatly improving the processability.

Further, in the processing step shown in FIG.
The mixing of the wastewater 1 with the pH adjuster 2 and the chelating agent 3 is the same as the treatment step shown in FIG. After adding the permanganate 4 and the flocculant 15 to this mixed solution, the polymer flocculant 5 is added, and the mixture is introduced into the oxidizing granulation tank 16. The injection rate of the permanganate 4 at this time is the same as that of the processing step shown in FIG.

The coagulant 15 is preferably an aluminum salt or a ferric salt. As the aluminum salt, polyaluminum chloride and aluminum sulfate can be used, and as the ferric salt, ferric chloride can be used, but not limited thereto. The injection rate of the coagulant 15 is 50 to 500 m as a solution.
g / L is preferable. If it is 50 mg / L or less, granulation of hydrated manganese dioxide in the oxidation granulation tank 16 described below will be insufficient, and if it is 500 mg / L or more, the chemical cost will be excessive.

As the polymer flocculant 5, a commercially available anionic flocculant can be used as in the treatment step shown in FIG. 1, and the injection rate is 0.5 to 10 mg / L. If the injection rate is 0.5 mg / L or less, the formation of particulate matter in the granulation tank 16 described below is insufficient, and if the injection rate is 10 mg / L or more, the chemical cost becomes excessive.

The polymer coagulant 5 is preferably added within 30 seconds to 90 seconds after injection of the coagulant 15 in order to form particles in the oxidation granulation tank 16 described later.

The wastewater to which the coagulant 15 and the polymer coagulant 5 have been added flows into the lower part of the oxidation granulation tank 16. The tip peripheral speed of the impeller is 0.1 to 0.5 m /
s is equipped with a stirrer 17 that rotates to
The rolling motion of the agglomerates in the oxidizing granulation tank 16 caused by the impeller forms a zone of hydrated manganese dioxide granules. The concentration is 5 to 10% by weight, and the particle size of the hydrated manganese dioxide granules is 2 to 2.5 m.
m. The manganese dioxide concentration in the granules is 5000
２０20,000 mg / L, which is 20 times or more by weight relative to the manganese ion concentration in the wastewater. Excess particulate matter is discharged from the oxidizing granulation tank 16 above the stirrer 17 as a particulate matter-containing slurry 12a. Since the sedimentation velocity of the particulate matter is high, the upward flow velocity of the drainage water in the oxidation granulation tank 16 can be as high as 0.2 to 2 m / s. According to this method, there is an effect that separation of the hydrated manganese dioxide granules is easy and the apparatus becomes smaller.

The supernatant water separated from the particulate zone is discharged from the oxidizing granulation tank 16 as treated water 11. Also,
The granular material-containing slurry 12a is discharged out of the system as it is or after being dehydrated.

The processing step shown in FIG.
The processing steps shown in FIG. 5 are the same as those shown in FIG.
The action is similar to the treatment step shown in FIG. 2 in that the inactive MnO ₂ .MnO.H ₂ O generated by the contact between the waste water and the particulate matter of hydrated manganese dioxide is converted into the active hydrated manganese dioxide MnO _2.
- it has an effect of converting nH to ₂ O. This has the effect of significantly improving the processing capacity.

The particulate matter in the oxidizing granulation tank 16 and the concentration of manganese dioxide contained therein are the same as in the treatment step shown in FIG.
More than double.

The processing step shown in FIG. 7 is a method in which manganese sand is added in advance to the oxidizing granulation tank 16 similarly to the processing step shown in FIG. The particle size of the manganese sand is 50-200 μm. As in the treatment step of FIG. 3, permanganate 4
Is added, the manganese ions in the wastewater are oxidized to manganese dioxide and flow into the oxidizing granulation tank 16.
In the oxidation granulation tank 16, manganese sand particles are flowing, and the generated manganese dioxide and manganese ions are adsorbed and insolubilized on the particle surfaces. Further, the particle size of the manganese sand grows and increases to be granular due to the polymer flocculant 5 added into the oxidation granulation tank 16 and the rolling motion by the stirrer 17. In this case, the particle size of the granular material is 2 to 2.5 mm.
It is.

The granular material-containing slurry 12a discharged from the oxidizing granulation tank 16 is a reaction product of manganese sand as in the processing step of FIG. Its concentration is 10,000-1
00000 mg / L, the particle size is 50 to 200 μm, and the manganese dioxide concentration in the granular material is 5,000 to 2,000.
0 mg / L, which is at least 20 times the weight of the manganese ion concentration in the wastewater. The granular material-containing slurry 12a in the oxidizing granulation tank 16 is introduced into the cyclone 9a and classified in the same manner as in the processing step shown in FIG. The operation and effect are the same as those in FIG.

The processing step shown in FIG.
Is the same as the processing step shown in FIG. 7 except that the part where the is injected is a circulation line of the granular material. The effect is similar to that of the treatment step shown in FIG. 2, and the inert MnO ₂ .MnO.H ₂ O generated by the contact between the waste water and the particulate matter of hydrated manganese dioxide.
Has the effect of converting into active hydrated manganese dioxide MnO ₂ · nH ₂ O. This has the effect of significantly improving the processing capacity.

[0040]

Next, embodiments of the present invention will be described based on examples. Example 1 The flue gas desulfurization effluent of an oil fired boiler was treated by the apparatus shown in FIG. That is, 40 mg / L of Mn ²⁺
Inject sodium hydroxide into the wastewater containing
While adjusting to 8.0, 30 mg /
After adding L, 30m of potassium permanganate KMnO ₄
Manganese ions were oxidized by adding g / L, and adjusted to pH 8 by injecting sodium hydroxide. Then, after adding the circulating slurry discharged from the subsequent settling tank so that the MnO ₂ concentration in the liquid becomes 0 to 1500 mg / L stepwise,
The quality of the supernatant water in the settling tank was compared. Table 1 shows the results.

[0041]

[Table 1]

From the above results, in order to satisfy Mn of 10 mg / L or less, which is the discharge standard stipulated in the Water Pollution Control Law, the circulating slurry discharged from the sedimentation tank should be MnO ₂ / Mn ²⁺
Was found to be effective so that the weight ratio became 12 or more. It was also found that the amount of potassium permanganate added was much lower than the equivalent value, and was 1 / 2.5 or less of the equivalent value. In addition, the concentration of heavy metals such as Ni in the above treated water satisfied the emission standard similarly to the above.

Example 2 The same waste water as in Example 1 was treated with the apparatus shown in FIG. That is, the chelating agent 30
mg / L and pH 8.0 with sodium hydroxide.
While adjusting to 0, a mixture of potassium permanganate (30 mg / L) was added to the circulating slurry from the precipitation tank, and oxidation treatment was performed in the same manner as described above. The amount of circulating slurry is MnO ₂
Was gradually adjusted to 0 to 1000 mg / L, and the quality of the supernatant water in the sedimentation tank was compared. Table 2 shows the results.

[0044]

[Table 2]

From the above results, in order to satisfy the above-mentioned Mn of 10 mg / L or less, the amount of the circulating slurry in which MnO ₂ / Mn ²⁺ becomes 6 or more by weight and potassium permanganate are mixed and added. It was found that, as in Example 1, even if the amount of potassium permanganate added was equal to or less than the equivalent value, good treatment results could be obtained. Also,
The concentration of heavy metals such as Ni in the above-mentioned treated water satisfied the emission standard as in Example 1.

Example 3 The same waste water as in Examples 1 and 2 was treated with the apparatus shown in FIG. That is, after adding 30 mg / L of the chelating agent to the waste water, 30 mg / L of potassium permanganate was added while adjusting the pH to 8.0 with sodium hydroxide. At that time, the circulating slurry containing manganese sand returned from the precipitation tank was classified by a cyclone, and a slurry containing only particles of 50 μm or more was added. The amount of the circulating slurry was such that MnO ₂ was gradually reduced to 0 to 1000 mg / L with respect to the amount of wastewater, and the quality of the supernatant water in the sedimentation tank was compared. Table 3 shows the results.

[0047]

[Table 3]

From the above results, in order to satisfy the above-mentioned Mn of 10 mg / L or less, even in the case of a circulating slurry containing manganese sand, MnO ₂ / Mn ²⁺ is added so that the weight ratio of MnO ₂ / Mn ²⁺ becomes 6 or more. Even when the amount of potassium permanganate added was equal to or less than the equivalent value, effective treatment performance was obtained. In addition,
The concentration of heavy metals such as Ni in the above-mentioned treated water satisfied the emission standard similarly to the above.

Example 4 The same waste water as in Examples 1, 2 and 3 was treated with the apparatus shown in FIG. That is, while adjusting the pH to 8.0 by injecting sodium hydroxide into the wastewater,
After adding 30 mg / L of the chelating agent, a slurry obtained by adding 30 mg / L of potassium permanganate to a slurry containing only 50 μm particles classified by a cyclone was added in the same manner as in Example 3. The amount of the circulating slurry was such that MnO ₂ was gradually reduced to 0 to 1000 mg / L with respect to the amount of wastewater, and the quality of the supernatant water in the sedimentation tank was compared. Table 4 shows the results.

[0050]

[Table 4]

From the above results, in order to satisfy the above-mentioned Mn of 10 mg / L or less, even in the case of a circulating slurry containing manganese sand, MnO ₂ / Mn ²⁺ is added so that the weight ratio of MnO ₂ / Mn ²⁺ becomes 6 or more. Even when the amount of potassium permanganate added was equal to or less than the equivalent value, effective treatment performance was obtained. In addition,
The concentration of heavy metals such as Ni in the above-mentioned treated water satisfied the emission standard similarly to the above.

Example 5 The same waste water as in Examples 1 to 4 was treated with the apparatus shown in FIG. That is, while adjusting the pH to 8.0 by injecting sodium hydroxide into the wastewater, a chelating agent of 30 mg / L was added, and then potassium permanganate 3
0 mg / L was added. This solution contains 50 mg of ferric chloride.
L, and an anionic polymer flocculant 10 mg /
L was added. While the granules of hydrated manganese dioxide prepared in advance were allowed to flow in an oxidizing granulation tank so as to have a concentration of 0 to 50,000 mg / L, the mixed solution was introduced to about 3 mg.
Contact was made for 0 minutes. The quality of the supernatant water was compared. Table 5 shows the results.

[0053]

[Table 5]

From the above results, in order to satisfy the above-mentioned Mn of 10 mg / L or less, even in the case of granular material, it is necessary to add MnO ₂ / Mn ²⁺ to the oxidizing granulation tank so that the weight ratio becomes 10 or more. As a result, effective treatment performance was obtained even when the amount of potassium permanganate added was equal to or less than the equivalent value. The concentration of heavy metals such as Ni in the above treated water satisfied the emission standard as in the above.

Example 6 The same waste water as in Examples 1 to 5 was treated by the apparatus shown in FIG. That is, sodium hydroxide, a chelating agent, ferric chloride, and an anionic polymer flocculant were added in exactly the same manner as in Example 5.
This liquid was prepared in exactly the same manner as in Example 5, and the previously prepared granules of hydrated manganese dioxide were gradually reduced to 0 to 0.
While flowing in the oxidizing granulation tank so as to be 50,000 mg / L, the mixed solution was introduced and brought into contact for about 30 minutes. Table 6 shows the results of comparing the quality of the supernatant water.

[0056]

[Table 6]

From the above results, in order to satisfy the above-mentioned Mn of 10 mg / L or less, it is necessary to add permanganate by adding MnO ₂ / Mn ^{2+ so} that the weight ratio of MnO ₂ / Mn ²⁺ becomes 10 or more. Effective treatment performance was obtained even when the added amount of potassium was equal to or less than the equivalent value. In addition, Ni in the above treated water
Heavy metal concentrations satisfied the emission standards as described above.

Example 7 The same waste water as in Examples 1 to 6 was treated with the apparatus shown in FIG. That is, while adjusting the pH to 8.0 by injecting sodium hydroxide into the wastewater, a chelating agent of 30 mg / L was added, and then potassium permanganate 3
0 mg / L was added. Further, 10 mg / L of an anionic polymer flocculant was injected into the oxidation tank 9. Granules containing manganese sand discharged from the oxidation granulation tank 16 were classified by a cyclone, and granules having a particle size of 50 μm or more were added.
The concentration of the particulate matter in the oxidizing granulation tank 16 is gradually increased from 0 to 50.
000 mg / L, at which time the concentration of MnO ₂ is 0 to 20000 m
g for about 30 minutes. Table 7 shows the results of comparison of the quality of the supernatant water.

[0059]

[Table 7]

From the above results, in order to satisfy the above-mentioned Mn of 10 mg / L or less, it is necessary to add permanganate by adding MnO ₂ / Mn ²⁺ at a weight ratio of 10 or more even in the case of granular material. Effective treatment performance was obtained even when the added amount of potassium was equal to or less than the equivalent value. In addition, Ni in the above treated water
Heavy metal concentrations satisfied the emission standards as described above.

Example 8 The same waste water as in Examples 1 to 7 was treated with the apparatus shown in FIG. That is, sodium hydroxide, a chelating agent and an anionic polymer flocculant were added in the same manner as in Example 7. This liquid was classified in the same manner as in Example 7 to a particle size of 5
Granules containing manganese sand of 0 μm or more and 30 mg / L of potassium permanganate were added. The concentration of the particulate matter in the oxidizing granulation tank was gradually increased from 0 to 500, as in Example 7.
The contact was performed at 00 mg / L and the MnO ₂ concentration was 0 to 20000 mg / L for about 30 minutes. Table 8 shows the results of comparing the quality of the supernatant water.

[0062]

[Table 8]

From the above results, in order to satisfy the above-mentioned Mn of 10 mg / L or less, even in the case of granular materials, permanganate is added by adding so that the weight ratio of MnO ₂ / Mn ²⁺ becomes 10 or more. Effective treatment performance was obtained even when the added amount of potassium was equal to or less than the equivalent value.

[0064]

The present invention has the following effects by the above configuration. During the entire process, the treatment is carried out in the pH range from pH 6 to pH 8 near neutrality, so that no excessive pH adjuster is required, and it is not necessary to adjust the pH to near neutral when discharging the treated water. Therefore, cost and labor can be greatly reduced. In particular, in wastewater containing high-concentration ammonia, such as desulfurization wastewater from an oil-fired boiler, ammonia gas in the wastewater is generated according to the conventional method, but the method of the present invention does not have such a problem.

In the oxidation treatment, it is only necessary to add permanganate in an amount much smaller than the equivalent to manganese ions. In particular, even in wastewater containing high-concentration ammonia, such as desulfurization wastewater from an oil-fired boiler, the above-described reaction proceeds without being inhibited by ammonia, so that the cost of expensive chemicals can be significantly reduced.

Further, since the permanganate does not become excessive and does not flow out into the processing solution, it is not necessary to post-treat the excess permanganate by adding a heavy metal chelating agent or the like.

Further, by using the method of the present invention in which the granulated hydrated manganese dioxide is brought into contact with the wastewater together with the permanganate, the separation of the granules is facilitated, and the apparatus can be miniaturized. .

[Brief description of the drawings]

FIG. 1 is a process explanatory view showing a first embodiment of the present invention.

FIG. 2 is a process explanatory view showing a second embodiment of the present invention.

FIG. 3 is a process explanatory view showing a third embodiment of the present invention.

FIG. 4 is a process explanatory view showing a fourth embodiment of the present invention.

FIG. 5 is a process explanatory view showing a fifth embodiment of the present invention.

FIG. 6 is a process explanatory view showing a sixth embodiment of the present invention.

FIG. 7 is a process explanatory view showing a seventh embodiment of the present invention.

FIG. 8 is a process explanatory view showing an eighth embodiment of the present invention.

FIG. 9 is an explanatory view of a process according to a conventional method.

[Explanation of symbols]

 Reference Signs List 1 drainage 2 pH adjuster 3 chelating agent 4 permanganate 5 polymer flocculant 6 treated water 7a slurry 7b circulating slurry 7c slurry 7d circulating slurry 8 reaction tank 9 oxidation tank 9a cyclone 10 sedimentation tank 11 treated water 12a particulate matter Slurry 12b Granules 13 pH adjusting tank 14 Precipitation tank 15 Coagulant 16 Oxidizing granulation tank 17 Stirrer 18a Slurry 18b Circulating slurry

Continued on the front page (72) Inventor Hideki Kamiyoshi 5-1-1-16 Komatsudori, Hyogo-ku, Kobe-shi, Hyogo Prefecture Inside Shinryo High-Tech Co., Ltd. (72) Inventor Ken Terasaki 5-1-1 Komatsudori, Hyogo-ku, Kobe-shi, Hyogo No. 16 Shinryo Hitec Co., Ltd. F-term (reference) 4D015 BA04 BA05 BA19 BA25 BB09 CA17 DA13 DB03 DC02 DC08 EA02 EA14 EA32 4D038 AA08 AB66 BA04 BB13 BB16 BB18 4D050 AA13 AB55 BB11 BD06 CA13 CA16

Claims (10)

[Claims] An oxidation step of adding hydrated manganese dioxide by adding permanganate to wastewater to be treated containing manganese ions; and treating the wastewater containing hydrated manganese dioxide by treatment with treated water and water. A method for removing manganese ions from wastewater, comprising: a step of separating the slurry into a slurry having an increased concentration of manganese dioxide; and a step of returning a part of the slurry to an oxidation step. 2. The manganese ion in the wastewater according to claim 1, further comprising a step of adding and mixing a permanganate in advance to the slurry obtained by the precipitation, and adding the mixture to the wastewater to be treated. How to remove. 3. A step of solid-liquid separating the slurry obtained by the precipitation, mixing the obtained granular manganese dioxide and permanganate in advance, and adding the mixed manganese dioxide to the waste water to be treated. The method for removing manganese ions in wastewater according to claim 1. 4. A process for adding permanganate, a coagulant, and a polymer coagulant to treated wastewater containing manganese ions and stirring the mixture to granulate the produced hydrated manganese dioxide. To remove manganese ions in wastewater. 5. The method according to claim 1, wherein the amount of manganese dioxide MnO _{2 to be} added is at least 20 by weight based on the amount of manganese ions Mn ²⁺ contained in the waste water to be treated. The method for removing manganese ions in wastewater according to the above. 6. The amount of permanganate (MnO ₄ ⁻ ) to be added to the waste water to be treated containing manganese ions is not more than the theoretical equivalent value to the manganese ion Mn ²⁺ in the waste water to be treated. The method for removing manganese ions in wastewater according to any one of claims 1 to 4, wherein the manganese ions are added. 7. The method for removing manganese ions from wastewater according to claim 1, wherein manganese sand is added to the wastewater to be treated in advance. 8. The method according to claim 7, wherein the manganese sand has a particle size of 200 μm or less. 9. The method for removing manganese ions from wastewater according to claim 1, wherein the wastewater to be treated containing manganese ions is wastewater also containing ammonium ions. . 10. The method for removing manganese ions in wastewater according to claim 9, wherein the wastewater to be treated containing manganese ions and ammonium ions is desulfurization wastewater of oil-fired boiler combustion exhaust gas.