JP2006159129A - Fluorine-containing water treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluorine-containing water treatment method using a calcium fluoride method which achieves a reduction in chemical consumption, reduction in the amount of generated sludge, and an improvement in quality of treated water. <P>SOLUTION: In the fluorine-containing water treatment method, after adding slaked lime to raw water, an aluminum chloride-based coagulant with high acidity is added, and the mixture is subjected to solid-liquid separation after neutralization. The addition of the aluminum chloride-based coagulant with high acidity can return water to be treated, alkalified by the addition of slaked lime, to the vicinity of neutral, which enables the reduction in the amount of used neutralizing agent, such as sulfuric acid. When an acidic AC-based coagulant is used, ionic fluorine is coprecipitated with its aluminum component and removed to improve the quality of treated water. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for treating fluorine-containing water, and more particularly to a method for obtaining high-quality treated water by performing efficient treatment with a small amount of chemical use in treatment of fluorine-containing water by the calcium fluoride method.

  Fluorine-containing wastewater discharged from silicon wafer manufacturing process in semiconductor parts manufacturing, pickling wastewater discharged from stainless steel plate manufacturing process, aluminum surface treatment wastewater, hydrofluoric acid manufacturing wastewater, fertilizer manufacturing wastewater, waste incineration wastewater, etc. Needs to be discharged after fluorine removal treatment to meet the drainage standards. Regarding fluorine-containing wastewater, the development of treatment technology that can further reduce the fluorine concentration of treated water is expected as the wastewater standard was strengthened from 15 mg / L to 8 mg / L in 2001. It is rare.

  Conventionally, calcium fluoride method and hydroxide coprecipitation method as advanced treatment are known as treatment methods for fluorine-containing water, and as shown in FIG. Thereafter, a two-stage treatment method is also known in which advanced treatment is performed by the hydroxide coprecipitation method in the second stage (Non-Patent Document 1). That is, in the calcium fluoride method, the fluorine concentration of the treated water cannot be reduced below the solubility of calcium fluoride, and the waste water standard cannot be satisfied, so such a two-stage treatment is adopted.

  In the calcium fluoride method, after adding a calcium compound to the raw water (fluorine-containing water) from the raw water tank 11 (first reaction tank 12), a neutralizer is added to adjust the pH to around neutral (second reaction) In the tank 13), an insoluble salt of calcium fluoride is produced by the reaction between fluorine and calcium, and a polymer flocculant is added to perform a coagulation treatment (coagulation tank 14), followed by solid-liquid separation (precipitation tank 15). is there. In this method, slaked lime is generally used as the calcium compound, and inexpensive sulfuric acid is usually used as the neutralizing agent, but hydrochloric acid may also be used.

The hydroxide coprecipitation method uses a coprecipitation action when aluminum is precipitated as aluminum hydroxide, and is generally used for advanced treatment. In this method, after adding polyaluminum chloride (PAC) to the raw water (the first-stage treated water in FIG. 4) (first reaction tank 16), it is neutralized with a neutralizing agent (second reaction tank 17). A molecular flocculant is added for agglomeration treatment (aggregation tank 18) and then solid-liquid separation (precipitation tank 19). In this method, the pH of the treated water becomes acidic by adding PAC, but caustic soda or the like is added as an alkali agent for neutralization because treatment near neutrality can be most efficiently performed.
“Pollution Prevention Technology and Regulations” pp. 288-289

  After adding slaked lime to fluorine-containing water, the calcium fluoride method, which uses a neutralizing agent such as sulfuric acid or hydrochloric acid to adjust the pH to neutral, increases the removability of fluorine and improves the quality of treated water. If a large amount is added, the amount of neutralizing agent necessary for neutralization increases, and the chemical cost is high. In addition, when sulfuric acid is used as the neutralizing agent, gypsum is produced by the reaction of slaked lime and sulfuric acid, and the slaked lime added to the fluorine-containing water is not effectively used for fluorine removal. There was also a problem that the amount of generated sludge increased.

  In addition, the quality of the treated water can be improved by two-stage treatment of the calcium fluoride method and the hydroxide coprecipitation method. In this case, however, the equipment becomes larger and two precipitation tanks with particularly large installation areas are required. It requires a tank and is not preferred.

  The present invention solves the above-mentioned conventional problems and provides a method for treating fluorine-containing water that reduces the amount of chemical used, reduces the amount of generated sludge, and improves the quality of treated water in the treatment of fluorine-containing water by the calcium fluoride method. The purpose is to do.

  In the method for treating fluorine-containing water of the present invention (Claim 1), in the method for treating fluorine-containing water, after adding slaked lime to raw water, an aluminum chloride flocculant having high acidity is added, and after neutralization, It is characterized by solid-liquid separation.

  The method for treating fluorine-containing water according to claim 2 is characterized in that, in claim 1, the aluminum chloride flocculant having a high acidity has a pH of 4 or less.

  The fluorine-containing water treatment method according to claim 3 is characterized in that, in claim 2, the aluminum chloride-based flocculant having high acidity is LAC.

  The method for treating fluorine-containing water according to claim 4 is the method according to any one of claims 1 to 3, wherein the aluminum chloride flocculant having high acidity is diluted with dilute waste water having a fluorine concentration of 15 mg / l or less, and then slaked lime. It is characterized by being added to the raw water to which is added.

  The method for treating fluorine-containing water according to claim 5 is characterized in that in any one of claims 1 to 4, the separated sludge obtained by solid-liquid separation is mixed with the slaked lime and added to the raw water.

  In the present invention, by adding an aluminum chloride-based flocculant having high acidity (hereinafter sometimes referred to as “acidic AC-based flocculant”), the water to be treated that has become alkaline by the addition of slaked lime is neutral to It can return to weak alkalinity, and this can reduce the usage-amount of neutralizing agents, such as a sulfuric acid. In addition, when sulfuric acid is used as the neutralizing agent, as described above, there are problems of consumption of slaked lime due to the formation of gypsum and an increase in the amount of sludge. In the present invention, the neutralizing agent is added by adding an acidic AC flocculant. Since the amount used can be reduced, the amount of sulfuric acid added without causing such problems can be adjusted to a sufficient pH neutrality, and the problems of consumption of slaked lime due to gypsum formation and increase in the amount of sludge are prevented. The

  And if it is an acidic AC type coagulant | flocculant, the water quality can also be improved by coprecipitating and removing ionic fluorine with the aluminum component. Therefore, it is possible to eliminate the need for advanced treatment by the conventional hydroxide coprecipitation method. In this case, the processing efficiency is improved and the settling tank for advanced treatment is reduced to greatly increase the equipment installation area. Can be reduced.

  Therefore, according to the present invention, it is possible to efficiently treat fluorine-containing water with a small amount of chemical use, reduce the amount of generated sludge, and to remove fluorine to a high degree to obtain high-quality treated water.

  In the present invention, the acidic AC flocculant is preferably a flocculant having a pH of 4 or less (Claim 2), and in particular, LAC: Liquid Aluminum Chloride produced from electrolytic aluminum waste is preferred (Claim 3). .

  Such an acidic AC flocculant may be diluted with diluted wastewater having a fluorine concentration of 15 mg / l or less and then added to raw water to which slaked lime has been added. In this case, other diluted wastewater is simultaneously treated. In addition, a good treatment effect can be obtained (claim 4).

  In addition, slaked lime may be mixed with a part of the separated sludge obtained by solid-liquid separation and added to the raw water. In this case, the crystallinity of the sludge is improved, the sedimentation is improved, and the water content is reduced. As a result, the quality of treated water can be further improved, and the amount of generated sludge can be reduced (claim 5).

  Hereinafter, embodiments of the method for treating fluorine-containing water of the present invention will be described in detail.

  First, the acidic AC flocculant used in the present invention will be described.

  The acidic AC flocculant used in the present invention has a pH of 4 or less, particularly 2.5 or less, particularly 1.5 or less, and preferably pH 4 or less, particularly 2.5 or less, especially pH 1 under the condition that the aluminum concentration is 8% by weight or less. It is preferably a strongly acidic aluminum chloride-based flocculant of .5 or less. If this pH value exceeds 4, the neutralization effect due to the addition of this cannot be sufficiently obtained, and the effect of reducing the acid addition amount as a neutralizing agent after the addition of slaked lime is sufficiently obtained. I can't. Further, when the pH exceeds 4, the aluminum ions take a polymer-like form, whereas when the pH is 4 or less, the aluminum ions are dispersed. Dispersed aluminum ions aggregate in a network at the time of addition, so that the processing efficiency is improved. Here, the pH of the acidic AC-based flocculant is a value measured immediately before the acidic AC-based flocculant is added to the raw water. In the present invention, the pH is 4 or less at an aluminum concentration of 8% by weight or less. It is preferable that it is shown.

  The acidic AC flocculant used in the present invention is also preferably one that does not contain a large amount of anions that form insoluble salts with calcium, and particularly contains no sulfuric acid and has a sulfuric acid content of 2000 mg / L or less, What the ratio of the sulfuric acid in components other than is 50 weight% or less is preferable. This is a reaction between slaked lime and sulfuric acid in an acidic AC flocculant. As slaked lime is consumed for the production of gypsum, the reaction between slaked lime and fluorine is inhibited, and the amount of generated sludge increases due to the production of gypsum. This is to prevent this. In the present invention, “aluminum chloride-based” means that the proportion of aluminum chloride in components other than water is 50% by weight or more.

  The acidic AC flocculant used in the present invention is preferably LAC containing about 10% aluminum chloride and having high acidity.

  Polyaluminum chloride (PAC) generally used as an inorganic flocculant also corresponds to the acidic AC flocculant according to the present invention, but PAC exhibits a pH of 4 to 5 under the condition of an aluminum concentration of 8% by weight. On the other hand, LAC has a lower proportion of aluminum hydroxide than PAC, almost 100% is aluminum chloride, and the pH when diluted with water to an aluminum concentration of 8% by weight is about 0.5. Since it is strongly acidic, it is effective in the present invention. However, even in the case of PAC, by adding mineral acids such as hydrochloric acid and sulfuric acid, and adjusting the aluminum concentration to 8 pH or less, pH 4 or less, particularly pH 2.5 or less, especially pH 1.5 or less. Thus, it can be suitably used in the present invention. Alternatively, LAC and PAC may be mixed to form an acidic AC-based flocculant.

  Such an acidic AC flocculant may be diluted and added for handling. Here, the water used for the preparation of the aqueous solution may be city water, industrial water, or treated water obtained by the treatment according to the present invention, and may be other waste water as described later. It is preferable to add as an aqueous solution in order to obtain a high neutralizing action.

  In the present invention, after adding slaked lime to fluorine-containing water, such an acidic AC flocculant is added, and neutralized by adding a neutralizing agent (acid) as necessary, and then preferably a polymer After the coagulant is added and coagulated, solid-liquid separation is performed.

  The amount of slaked lime added is determined by the fluorine concentration in the raw water (fluorine-containing water), and is preferably 1 to 10 times the reaction equivalent to the fluorine concentration of the raw water, particularly about 1.1 to 3 times. If the amount of slaked lime added is too small, the fluorine in the raw water cannot be removed sufficiently, and if it is too large, not only slaked lime but also the amount of acid added for subsequent neutralization will increase. In the present invention, as described above, the addition amount of the acid as the neutralizing agent can be reduced by the addition of the acidic AC flocculant. For this reason, there is no problem of wasteful consumption of slaked lime due to the formation of gypsum when sulfuric acid is used as a neutralizing agent, so that the amount of slaked lime added is not excessively larger than the reaction equivalent, and fluorine in fluorine-containing water is efficiently used. Can be removed.

  Since the liquid after adding slaked lime to the raw water is usually alkaline with a pH of about 10.0 to 13.0, an acidic AC flocculant and an acid as a neutralizing agent are then added to this liquid to a pH of 6.0 to 6.0. The pH is adjusted to a neutral value of 7.5, preferably about 7.0.

  Here, if the addition amount of the acidic AC flocculant is too small, the effect of the present invention by adding the acidic AC flocculant cannot be sufficiently obtained, and if it is too much, the amount of sludge increases, Since the pH of the treated water is too low, the addition amount of the acidic AC flocculant is 5 to 100 times, particularly about 5 to 20 times the fluorine concentration (mg / L) before the addition of the acidic AC flocculant. It is preferable to do.

  As the acid as the neutralizing agent, mineral acids such as hydrochloric acid and sulfuric acid, preferably sulfuric acid are used, and the acid is added in such an amount that the liquid pH becomes neutral.

  Note that the acidic AC-based flocculant and the acid may be added simultaneously or separately. Moreover, an acidic AC type flocculant and an acid can be mixed and added in advance. When added separately, it is preferable to adjust the pH by adding an acid after the addition of the acidic AC flocculant.

  After the addition of the acidic AC type flocculant, it is preferable to agglomerate by stirring for a predetermined time, for example, about 5 to 20 minutes.

  After adjusting to pH neutrality by adding an acidic AC-based flocculant and an acid, and aggregating for a predetermined time, preferably, a polymer flocculant is further added for aggregating. As the polymer flocculant, one or more of polyacrylamide partial hydrolyzate, sodium polyacrylate, polyvinylamidine and the like can be used, and the amount added is the quality of raw water to be treated and the polymer used. Although it varies depending on the flocculant, it is usually about 0.1 to 5 mg / L.

  The coagulation treatment liquid is then subjected to solid-liquid separation to obtain treated water. For this solid-liquid separation, a precipitation tank, a membrane separation device, or the like can be used.

  In the present invention, the acidic AC flocculant can be added after dilution as described above, but this water does not necessarily have to be neutral in pH, and may be drainage from other systems. However, this diluted water needs to have a pH and an amount so as not to impair the neutralization effect by the acidic AC flocculant in a state in which the acidic AC flocculant is dissolved, and depends on the amount of wastewater used. However, it is preferable that the wastewater has a pH of 10 or less, and the pH of the acidic AC flocculant solution dissolved in such wastewater is preferably 6 or less, and preferably about pH 4. Moreover, although this waste water may contain a fluorine, it is preferable that the content is a diluted waste water of 15 mg / L or less. By mixing an acidic AC flocculant with such a diluted wastewater, the aggregating action of the acidic AC flocculant can be applied to the diluted wastewater. Can be processed.

  In addition, a part of the sludge obtained by solid-liquid separation can be returned to the raw water side, and the crystallinity of the sludge can be improved, the water content can be reduced, and the sedimentation can be improved by the seed crystal effect of the returned sludge. In this case, the returned sludge can be mixed with slaked lime, and the mixture (hereinafter sometimes referred to as “modified sludge”) can be added to the raw water, thereby further improving the quality and generation of treated water. The amount of sludge can be reduced.

  In addition, if the amount of returned sludge in this case is too small, the above-described effect by performing sludge return cannot be sufficiently obtained. If the amount is too large, the load on the settling tank increases. About 30 times, especially when slaked lime and return sludge are mixed, it is preferable to set the amount so that the pH of the modified sludge is 10 or more.

  According to such a method of the present invention, the acidic AC flocculant can provide not only a neutralizing action but also an aggregating action, and as described above, a fluorine removing effect by a coprecipitation action can also be obtained. Can do. For this reason, the treated water obtained by the above-mentioned solid-liquid separation is one from which fluorine has been removed to a high degree, and without performing the advanced treatment by the hydroxide coprecipitation method as in the conventional method, FIG. It is possible to obtain treated water having a water quality equivalent to or higher than the treated water by the conventional two-stage treatment shown.

  In the method of the present invention, although the amount of acid such as sulfuric acid can be greatly reduced as compared with the conventional calcium fluoride method, an acidic AC-based flocculant is required, but thus two-stage treatment is not required. Therefore, a flocculating agent such as PAC used in the second stage treatment is not required, and the amount of acidic AC type flocculant is smaller than that of the PAC added in the second stage. As a result, the total chemical use amount is greatly increased. It is possible to obtain good treated water after reducing the amount of generated sludge.

  Next, a specific treatment method of the fluorine-containing water treatment method of the present invention using such an acidic AC flocculant will be described with reference to the drawings. 1 to 3 are system diagrams showing an embodiment of the method for treating fluorine-containing water of the present invention.

  In the method of FIG. 1, the raw water in the raw water tank 1 is introduced into the first reaction tank 2, slaked lime is added and reacted, and then introduced into the second reaction tank 3 to introduce an acidic AC flocculant and a neutralizing agent. (Acid) is added and coagulation treatment is performed for a predetermined time. Next, a polymer flocculant is added in the flocculation tank 4 for flocculation treatment, and the flocculation treatment liquid is solid-liquid separated in the precipitation tank 5, and the supernatant is discharged out of the system as treated water and the separated sludge is discharged. .

  The method of FIG. 2 uses an acidic AC-based flocculant mixed with dilute waste water of another system, and is the same as the method shown in FIG. 1 except that this mixed solution is added to the first reaction tank 2. Processing is performed.

  The method of FIG. 3 is a method in which a part of the separated sludge in the settling tank 5 is mixed with slaked lime, and the modified sludge is added to the raw water. The adjusting tank 6 is provided, and a part of the separated sludge is added to the adjusting tank 6. The treatment is performed in the same manner as in the method of FIG. 1 except that the slaked lime is added and mixed and reformed, and the modified sludge is injected into the raw water introduction pipe to the first reaction tank 2. The modified sludge from the adjustment tank 6 may be added directly to the first reaction tank 2.

  The method shown in FIGS. 1-3 is an example of embodiment of this invention, Comprising: This invention is not limited to the method of illustration at all unless the summary is exceeded. For example, the acidic AC type flocculant and the neutralizing agent (acid) may be added in separate reaction tanks, and reaction tanks therefor may be provided separately.

  Such a method for treating fluorine-containing water of the present invention includes fluorine-containing wastewater discharged from a silicon wafer manufacturing process in semiconductor component manufacturing, pickling wastewater discharged from a stainless steel plate manufacturing process, aluminum surface treatment wastewater, and hydrofluoric acid manufacturing. It is effective for the treatment of various fluorine-containing water such as wastewater, fertilizer manufacturing wastewater, and waste incineration wastewater.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. In the following, the measurement of the fluorine concentration was performed according to JIS K0102 34.1. A polyacrylamide partial hydrolyzate was used as the polymer flocculant.

Example 1
The processing was carried out by the method shown in FIG. 1 using the waste water from the electronic industry containing 130 mg / L of fluorine as raw water.

  First, slaked lime 550 mg / L was added to raw water, and then LAC (pH 1.5) 300 mg / L was added and sulfuric acid was added to adjust to pH 7. After stirring for 30 minutes for aggregation treatment, 1 mg / L of a polymer flocculant was added for aggregation treatment, followed by solid-liquid separation in a precipitation tank.

  While measuring the fluorine concentration and sulfuric acid concentration in the obtained treated water (supernatant water), the amount of generated sludge was examined, and the results are shown in Table 1. In Table 1, the amount of chemicals other than the polymer flocculant is also shown.

Example 2
In Example 1, instead of LAC, treatment was performed in the same manner except that 300 mg / L of PAC adjusted to pH 3 using hydrochloric acid was added, and the fluorine and sulfuric acid concentrations of the treated water and the amount of sludge were examined. The results are shown in Table 1 together with the chemical usage.

Example 3
In Example 1, instead of LAC, treatment was performed in the same manner except that 300 mg / L of PAC adjusted to pH 3 using sulfuric acid was added, and the fluorine and sulfuric acid concentrations of the treated water and the amount of sludge were examined. The results are shown in Table 1 together with the chemical usage.

Comparative Example 1
In Example 1, after adding slaked lime, LAC was not added, and the treatment was performed in the same manner except that the pH was adjusted to 7 only with sulfuric acid, and the fluorine and sulfuric acid concentrations of the treated water and the amount of sludge generated were examined. Is shown in Table 1 together with the amount of chemical used.

Comparative Example 2
In Example 1, slaked lime was added, LAC was not added, the pH was adjusted to 7 only with sulfuric acid, the mixture was stirred for 30 minutes and agglomerated, then 450 mg / L of 10 wt% PAC was added, and then sodium hydroxide After adjusting the pH to 7, the same treatment was performed except that it was subjected to a flocculation treatment with a polymer flocculant, and the fluorine and sulfuric acid concentrations of the treated water and the amount of sludge generated were examined. The results are shown in Table 1.

Comparative Example 3
In Example 1, treatment was performed in the same manner except that 300 mg / L (converted to FeCl ₃ ) of 10 wt% aqueous ferric chloride solution was added instead of LAC, and the fluorine and sulfuric acid concentrations of the treated water and the amount of sludge generated were determined. The results are shown in Table 1 together with the amount of chemical used.

Comparative Example 4
In Example 1, the treatment was performed in the same manner except that 300 mg / L (converted to MgCl ₂ ) of a 10 wt% magnesium chloride aqueous solution was added instead of LAC, and the fluorine and sulfuric acid concentrations of the treated water and the amount of sludge generated were examined. The results are shown in Table 1 together with the amount of chemical used.

  From Table 1, it can be seen that the addition of an acidic AC flocculant can reduce the amount of chemical used, improve the quality of treated water, and reduce the amount of generated sludge.

  That is, in Comparative Example 1 treated with slaked lime and sulfuric acid, the amount of generated sludge is small, but the quality of the treated water is poor. Moreover, in the comparative example 2, although the advanced process which adds PAC with respect to this comparative example 1 is performed and the quality of treated water is improved, the amount of generated sludge increases remarkably in this case. In addition, as in Comparative Examples 3 and 4, the effect is not obtained even if an iron-based or magnesium-based flocculant is added.

  On the other hand, in Example 1 using LAC, the treated water quality of 8 mg-F / L or less was achieved by one-stage treatment without performing advanced treatment, and the amount of sulfuric acid used in Comparative Examples 1 and 2 was About 1/5 is sufficient, and chemical usage and sludge generation are small. As in Examples 2 and 3, the same effect can be obtained by using PAC whose pH is lowered with an acid instead of LAC.

Example 4
There are two types of wastewater: wastewater containing 300 mg / L of fluorine (hereinafter referred to as “hydrofluoric acid wastewater”) and wastewater of pH 4 containing phosphoric acid 100 mg / L (hereinafter referred to as “phosphoric acid wastewater”). The electronic industrial wastewater was treated by the method shown in FIG.

  After adding 2200 mg of slaked lime (addition amount of 733 mg / L of slaked lime to the total wastewater) to 2 L of hydrofluoric acid wastewater, add 1 L of phosphoric acid wastewater to which 900 mg of LAC was added (pH after addition of LAC is 3.5) (LAC addition amount of 300 mg / L with respect to the total waste water), and then sulfuric acid was added to adjust the pH to 7. After stirring for 30 minutes for aggregation treatment, 1 mg / L of polymer flocculant was added for aggregation treatment, followed by solid-liquid separation in a precipitation tank.

  Fluorine and sulfuric acid concentrations of the treated water (supernatant water) and the amount of sludge generated were examined, and the results are shown in Table 2 together with the amount of chemicals other than the polymer flocculant.

Comparative Example 5
The same electronic industrial wastewater treatment as in Example 4 was performed.

  1 L of phosphoric acid waste water was mixed with 2 L of hydrofluoric acid waste water, 2200 mg (733 mg / L) of slaked lime was added thereto, and then sulfuric acid was added to adjust to pH 7. After flocculation treatment with stirring for 30 min, PAC 900 mg (300 mg / L) is added, sodium hydroxide is added to adjust to pH 7, and then the polymer flocculant 1 mg / L is added for flocculation treatment, and then the precipitation tank And solid-liquid separation.

  Fluorine and sulfuric acid concentrations of the treated water (supernatant water) and the amount of sludge generated were examined, and the results are shown in Table 2 together with the amount of chemicals other than the polymer flocculant.

  From Table 2, it can be seen that even when LAC is added to dilute wastewater, a remarkably good treatment water quality improving effect is recognized, and the amount of generated sludge is almost the same, but the amount of chemicals used can be reduced.

Example 5
Electronic industrial wastewater similar to that treated in Example 1 was treated by the method shown in FIG.

Separation sludge (1% by weight with respect to the raw water) of the settling tank and slaked lime (550 mg / L with respect to the raw water) are mixed, and the modified sludge (pH 12.2) is added to the raw water, and then pH 3. 300 mg / L (converted to Al ₂ O ₃ ) of 10 wt% aluminum chloride aqueous solution adjusted to 0 was added, and sulfuric acid was added to adjust to pH 7. After stirring for 30 minutes for aggregation treatment, 1 mg / L of a polymer flocculant was added for aggregation treatment, followed by solid-liquid separation in a precipitation tank.

  Fluorine and sulfuric acid concentrations of the treated water (supernatant water) and the amount of sludge generated were examined, and the results are shown in Table 3 together with the amount of chemicals other than the polymer flocculant.

  In Table 3, the results of Example 1 are also shown.

  From Table 3, it can be seen that the quality of treated water can be further improved and the amount of generated sludge can be reduced by returning the separated sludge and adding it to the raw water.

It is a systematic diagram which shows embodiment of the processing method of the fluorine-containing water of this invention. It is a systematic diagram which shows embodiment of the processing method of the other fluorine-containing water of this invention. It is a systematic diagram which shows embodiment of the processing method of another fluorine-containing water of this invention. It is a systematic diagram showing a conventional method.

Explanation of symbols

1 Raw water tank 2 First reaction tank 3 Second reaction tank 4 Coagulation tank 5 Precipitation tank

Claims (5)

  A method for treating fluorine-containing water, comprising adding slaked lime to raw water, then adding an aluminum chloride-based flocculant having high acidity, neutralizing, and solid-liquid separation.   The method for treating fluorine-containing water according to claim 1, wherein the aluminum chloride flocculant having a high acidity has a pH of 4 or less.   The method for treating fluorine-containing water according to claim 2, wherein the aluminum chloride-based flocculant having a high acidity is LAC.   The aluminum chloride flocculant having high acidity according to any one of claims 1 to 3, wherein the aluminum chloride flocculant is diluted with dilute waste water having a fluorine concentration of 15 mg / l or less, and then added to the raw water to which slaked lime is added. Treatment method for fluorine-containing water.   The method for treating fluorine-containing water according to any one of claims 1 to 4, wherein the separated sludge obtained by solid-liquid separation is mixed with the slaked lime and added to the raw water.

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