JP4640149B2 - Fluorine-containing water treatment method - Google Patents

Description

  The present invention relates to a method for stably and efficiently agglomerating fluorine-containing water mixed with aluminum-containing water together with aluminum-containing water.

  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. After treatment with calcium fluoride method in the first stage, the second stage In addition, a two-stage treatment method in which advanced treatment is performed by a hydroxide coprecipitation method (hereinafter referred to as “aluminum adsorption method”) is also known (Non-Patent Document 1). That is, in the calcium fluoride method, since the theoretical solubility of calcium fluoride is 8 mg / L, the fluorine concentration of the treated water cannot satisfy the drainage standard, and thus such a two-stage treatment is adopted.

  In the calcium fluoride method, after adding a calcium compound to raw water (fluorine-containing water), a neutralizing agent is added to adjust the pH to near neutral, and an insoluble salt of calcium fluoride is generated by the reaction between fluorine and calcium. In this method, a polymer flocculant is added and agglomeration treatment is performed, followed by solid-liquid separation. On the other hand, the aluminum adsorption method uses a coprecipitation action when aluminum precipitates as aluminum hydroxide, that is, an adsorption action, and is generally used for advanced treatment. In this method, polyaluminum chloride (PAC) or aluminum sulfate (sulfuric acid band) is added to raw water, then neutralized with a neutralizing agent, a polymer flocculant is added for aggregation treatment, and then solid-liquid separation is performed.

  FIG. 4 is a system diagram showing a conventional two-stage processing method.

Fluorine-containing wastewater is introduced from the raw water tank 1 to the first pH adjustment tank 2 and the second pH adjustment tank 3 together with other wastewater, and calcium compounds such as slaked lime (Ca (OH) ₂ ) are added and sulfuric acid (H ₂ By adding an acid such as SO ₄ ) and processing at a predetermined pH, fluorine in the waste water is insolubilized as calcium fluoride (CaF ₂ ). The treated water in the second pH adjusting tank 3 that has been finely adjusted with slaked lime and sulfuric acid is added to the first flocculating tank 4 by adding a polymer flocculant (polymer), and the flocculated treated water is the first settling tank 5. Solid-liquid separation. The treatment pH by the calcium fluoride method is selected from any pH of 5 to 10, preferably pH 6 to 7. In general, inexpensive slaked lime is used as the calcium compound, but when pH is adjusted to pH 6-7, if sufficient calcium is not secured for fluorine, an acid, generally inexpensive sulfuric acid, is injected into the raw water in advance. Thus, it is adjusted so as to secure calcium necessary for the precipitation of CaF ₂ .

  Since the fluorine concentration of the treated water obtained by this calcium fluoride method (separated water from the first sedimentation tank 5) is about 10 to 20 mg / L, further advanced treatment is performed by the second-stage aluminum adsorption method. That is, the separated water in the first precipitation tank 5 is introduced into the reaction tank 6 and an aluminum salt such as a sulfuric acid band is added, and a pH adjuster such as sodium hydroxide (NaOH) is added as necessary to adjust the pH to 6 to 6. PH is adjusted to 7 and fluorine is adsorbed by an aluminum salt adsorbing action and precipitated together with aluminum hydroxide. Then, the polymer is added in the second agglomeration tank 7 and agglomerated, and then the solid liquid is obtained in the second precipitation tank 8. To separate. The separated water in the second sedimentation tank 8 is filtered by a filter 9 to further improve the water quality, and the filtered water is discharged out of the system as treated water.

  In the treatment by the first-stage calcium fluoride method, the separated sludge obtained from the first precipitation tank 5 and the separation sludge obtained in the second precipitation tank 8 in the treatment by the second-stage aluminum adsorption method are the dehydrator 10. And dehydrated cake is discharged out of the system. On the other hand, the dehydrated filtrate (dehydrated desorbed water) is fed to the storage tank 11. Further, backwash wastewater discharged by backwashing of the filter 9 is also fed to the storage tank 11. These wastewaters are stored in the storage tank 11, then returned to the raw water tank 1 by the metering pump P, and processed together with the fluorine-containing wastewater that is raw water.

  The separated sludge obtained by the second-stage aluminum adsorption method is aluminum hydroxide sludge precipitated together with fluorine. Therefore, the dehydrated filtrate obtained by dehydrating it contains aluminum. Further, the filter 9 captures SS containing aluminum hydroxide mixed in the separated water without being separated in the second settling tank 8, and therefore backwash wastewater obtained by backwashing of the filter 9 is obtained. Also contains aluminum. Therefore, the mixed waste water returned from the storage tank 11 to the raw water tank 1 is waste water containing aluminum.

  Conventionally, the amount of treated water is made as constant as possible by returning the waste water of the storage tank 11 to the first stage treatment system, and the sedimentation state in the settling tank 5 is stabilized. At this time, the wastewater collected in the storage tank 11 contains aluminum hydroxide, and on the other hand, the aluminum salt has a fluorine adsorbing action, so that it is conventionally returned to the raw water tank 1. Therefore, the aluminum-containing wastewater from the storage tank 11 was returned to the raw water tank 1.

  When such a two-stage treatment method is adopted, if the amount of aluminum salt such as a sulfuric acid band added in the second-stage aluminum adsorption method is large, not only the chemical cost but also the sludge treatment cost due to the increase in the amount of generated sludge. Since it is expensive, it is desired to reduce the amount of aluminum salt added in the second stage treatment.

The amount of aluminum salt added in the treatment in the second-stage aluminum adsorption method is such that the fluorine concentration in the first-stage treated water, that is, the separated water in the first settling tank 5, is reduced to a concentration at which the target water quality can be obtained. It corresponds to the amount to be made. This target water quality has a fluorine concentration of 8 mg / L or less according to water quality standards. Therefore, since an aluminum salt is always required such that the fluorine concentration of the second stage treated water is 8 mg / L or less, in order to reduce the amount of aluminum salt added in the second stage treatment, In the first stage treatment, it is necessary to stabilize the fluorine concentration of the treated water at a low value. That is, if the fluorine concentration in the first-stage treated water is high, naturally the amount of aluminum salt added in the second-stage treatment increases, but even if the average fluorine concentration in the first-stage treated water is low However, when this fluorine concentration fluctuates, the amount of aluminum salt added is the variation in the fluorine concentration of the first-stage treated water in order to ensure that the treated water fluorine concentration is the target value in the second-stage treatment. Since the amount added corresponds to the upper limit of the width, it is necessary not only to lower the average fluorine concentration of the treated water but also to reduce the fluctuation of the fluorine concentration to stabilize the treatment in the first stage treatment. There is.
“Pollution Prevention Technology and Regulations” pp. 288-289

  However, in the conventional two-stage treatment method, the average fluorine concentration of the first-stage treated water is high and the fluorine concentration is unstable, so that the maximum fluctuation value can be accommodated in the second-stage treatment. Since the addition amount of the aluminum salt is set, the addition amount of the aluminum salt cannot be reduced.

  As a result of examining the cause of the fluctuation in the fluorine concentration of the first-stage treated water, the present inventors have found that the main cause is aluminum in the raw water.

  That is, as described above, in the two-stage treatment of fluorine-containing wastewater, the aluminum-containing wastewater generated in the treatment step of the second-stage aluminum adsorption method is returned to the raw water tank 1 and the first-stage calcium fluoride together with the fluorine-containing wastewater. Processed by law. The raw water tank 1 may also be introduced with other waste water, and the waste water may contain aluminum. That is, for example, conventionally, the raw water tank 1 is mixed with wastewater containing aluminum such as backwash wastewater of a filter in the pressurized flotation or coagulation sedimentation process of water, or regeneration wastewater of ion exchange resin. And, by introducing these aluminum-containing wastewater into the raw water tank 1, an aluminum salt of about several to several tens mg / L coexists in the raw water subjected to the treatment by the first-stage calcium fluoride method. Become.

  Although the aluminum salt has an ability to adsorb fluorine, according to the study by the present inventors, an aluminum salt mixed at a low concentration of several to several tens mg / L in raw water is a fluorine by the calcium fluoride method. In the treatment, it became a factor that deteriorated the treatment efficiency, and as a result, it was found that the fluorine concentration of the treated water obtained by the treatment by the first-stage calcium fluoride method was unstable.

For _{example, HF50mg / L, H 2 SO} 4 200mg / L, and synthetic waste water A of CaCl ₂ 250mg / L (as Ca), HF100mg / L, H 2 SO 4 200mg / L, CaCl 2 250mg / L ( as Ca) 0 to 6000 mg / L of a commercially available liquid sulfuric acid band for each of the synthetic waste water B and HF 200 mg / L, H ₂ SO ₄ 200 mg / L, and CaCl ₂ 250 mg / L (as Ca). As can be seen from FIG. 5 showing the result of adjusting the pH to 6.1 to 6.3 by adding Ca (OH) ₂ , in the raw water containing the aluminum salt, the processing characteristics of fluorine are significantly deteriorated. However, this tendency is greater when the fluorine concentration is lower. However, as the amount of sulfuric acid band added is increased and the sulfuric acid band / fluorine ratio increases, the sulfuric acid band functions as a fluorine adsorbent, and the processing characteristics are restored. Since the liquid sulfuric acid band used here has an Al ₂ O ₃ content of 8% by weight, 8 × ₂ Al / Al ₂ O ₃ = 4.2 mg / L of Al by adding 100 mg / L of the liquid sulfuric acid band. Corresponds to the content. Therefore, from this result, in raw water with a low fluorine concentration, the treatment characteristics deteriorate due to mixing of 1 to 2 mg / L as aluminum, and the mixing of a small amount of aluminum salt is an obstacle to fluorine treatment by the calcium fluoride method. It became clear that

  Therefore, the present invention solves the problem of instability of treatment characteristics when treating fluorine-containing water together with aluminum-containing water, and performs stable and efficient agglomeration treatment so that fluorine is sufficiently removed. The object is to provide a method of obtaining

The fluorine-containing water treatment method of the present invention (Claim 1) is a method of coagulating fluorine-containing water and aluminum-containing water, wherein the fluorine-containing water and aluminum-containing water are separated, and the aluminum-containing water is treated with fluorine coagulation. A method for treating fluorine-containing water to be added to a treatment step under neutral conditions of pH 6 or higher in the step , wherein the aluminum-containing water is a dehydrated filtrate, pressurized flotation of water, or backwashing of a filter in a coagulation sedimentation step Wastewater, wastewater from other processes including aluminum, which is recycled wastewater from ion-exchange resin; solid-liquid separation sludge of adsorption-treated water obtained by adsorbing flocculated and solid-liquid separation treated water with aluminum salt Dehydrated and desorbed water; or backwash drainage obtained by backwashing a filter that filters the adsorption-treated water; A first-stage treatment step of adding a compound to insolubilize fluorine as calcium fluoride, and a second-stage treatment step of adding an aluminum salt to the treated water of the first-stage treatment step to agglomerate the aluminum-containing water. Is added to the first-stage treatment step in which the calcium fluoride insolubilized product is produced .

Processing method of the fluorine-containing water 請 Motomeko 2 Oite to claim 1, wherein the receiving aluminum-containing water tank was neutralized to pH5 or higher, adding to the processing steps of the neutral condition of the pH6 more It is characterized by doing.

The method for treating fluorine-containing water according to claim 3 is the first pH adjusting step according to claim 1 or 2, wherein the first stage treatment step adjusts the pH to pH 6 to 8 by adding a calcium compound to the fluorine-containing water. And a second pH adjustment step of adjusting the pH to pH 6 to 8 by further adding a calcium compound to the treated water of the first pH adjustment step, and the aluminum-containing water added to the first step treatment step is a first pH adjustment It is added to the treated water of a process or a 2nd pH adjustment process .

  According to the present invention, aluminum-containing water is added to a step under neutral conditions at a pH of 6 or more in the fluorine aggregation treatment step, thereby preventing an interference effect of fluorine aggregation treatment with an aluminum salt, and being stable and efficient. Agglomeration treatment can be performed.

  That is, as described above, when aluminum is mixed into fluorine-containing water, the processing characteristics of fluorine differ depending on the amount of the mixed water, that is, when the Al / F ratio is large, aluminum functions as an adsorbent, and fluorine In contrast, when the Al / F ratio is small, the reason for the deterioration of the fluorine treatment characteristics due to the hindering action of aluminum is as follows.

[When Al / F ratio is small]
By the following reaction, an aluminum fluoride complex is generated and adsorbed on the calcium fluoride insolubilized material, thereby causing colloidal dispersion of calcium fluoride and deteriorating the aggregation property of calcium fluoride. However, in the following reaction formula, x> 3.
Al ³⁺ + xF ⁻ → AlF _x ^(3-x)
nCaF ₂ (precipitation) + AlF _x ^(3-x) → (CaF ₂ ) _n AlF _x ^(3-x) (dispersion to dissolution)

[When Al / F ratio is large]
An aluminum fluoride complex is not formed, and fluorine is adsorbed and precipitated by aluminum hydroxide according to the following reaction formula.
nAl ³⁺ + F ⁻ → [Al (OH) ₃ ] _n · F (precipitation)

  Aluminum fluoride complexes are likely to be produced under acidic conditions of pH 3 or lower, but conventionally, as shown in FIG. 4, in raw water tank 1, aluminum-containing water is usually added and mixed with acidic fluorine-containing water of pH 3 or lower. In order to carry out the treatment, an aluminum fluoride complex has already been generated in the raw water tank 1, and even in the next step, a calcium compound is added to convert the fluorine to calcium fluoride. The aluminum complex is adsorbed and colloidal dispersion occurs.

  In the present invention, since the aluminum-containing water is added in the fluorine aggregation treatment step under neutral conditions at pH 6 or higher where it is difficult to form an aluminum fluoride complex, the inhibition of fluorine aggregation due to the formation of the aluminum fluoride complex is suppressed. .

In the present invention, as the aluminum-containing water, dehydration / desorption water of solid-liquid separation sludge obtained by adsorption treatment of waste water from other processes, coagulation / solid-liquid separation treatment water of fluorine-containing water using an aluminum salt. or strainer Ru include backwash effluent obtained by backwashing the filtration process the adsorption-treated water. The aluminum-containing water may be a mixed water of these two or more aluminum-containing wastewaters.

In addition, when the pH of the aluminum-containing water to be added is excessively low acidic or excessively alkaline, it can be added even if it is added to the fluorine flocculation treatment step under neutral conditions of pH 6 or higher as described above. In this case, after receiving the aluminum-containing water in the storage tank and neutralizing to pH 5 or higher, neutral conditions of pH 6 or higher are required. It is preferable to add to the treatment step (Claim 2 ).

More specifically, the method for treating fluorine-containing water according to the present invention includes an aluminum-containing water in the step of coagulating fluorine by a calcium fluoride method in which a calcium compound is added to fluorine-containing water to insolubilize fluorine as calcium fluoride. a fluorine-containing water insolubles calcium fluoride is generated, Ru is carried out by the addition without mixing with the fluorine-containing water.

  Embodiments of a method for treating fluorine-containing water according to the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is a system diagram showing an embodiment of a method for treating fluorine-containing water according to the present invention. In FIG. 1, members having the same functions as those shown in FIG.

  In the method of FIG. 1, aluminum-containing wastewater from the storage tank 11 is injected into the inlet side of the second pH adjustment tank 3 instead of the raw water tank 1; pH adjustment is performed in the storage tank 11; The treatment is performed in the same manner as in the conventional method shown in FIG. 4 except that the wastewater is divided into wastewater containing aluminum and wastewater containing no aluminum, the wastewater containing aluminum is introduced into the storage tank 11, and the wastewater containing no aluminum is introduced into the raw water tank 1. .

That is, the fluorine-containing waste water is extracted through the raw water tank 1 together with the waste water not containing aluminum from other processes, and an acid such as sulfuric acid (H ₂ SO ₄ ) is injected into the first pH adjusting tank 2. Then, a calcium compound such as slaked lime (Ca (OH) ₂ ) is added to adjust the pH to pH 6 to 8, preferably pH 6.0 to 6.5. As a result, the fluorine in the raw water is insolubilized as calcium fluoride. The treated water in the first pH adjusting tank 2 is then introduced into the second pH adjusting tank 3 after the aluminum-containing wastewater from the storage tank 11 is quantitatively injected while being transferred to the second pH adjusting tank 3. A calcium compound such as slaked lime (Ca (OH) ₂ ) is added and an acid such as sulfuric acid (H ₂ SO ₄ ) is added to finely adjust the pH to pH 6 to 8, preferably pH 6.0 to 6. The pH is adjusted to 5 neutral, and further insolubilization of fluorine is performed.

  The aluminum-containing wastewater added here is neutralized to pH 5-9, preferably pH 5.5-8 by adding a pH adjuster as necessary in the storage tank 11 as described later. There is no problem of the formation of an aluminum fluoride complex in the second pH adjusting tank 3, and therefore, the inhibition of fluorine aggregation by the aluminum fluoride complex is suppressed, and it is excellent as in the case of treatment of fluorine-containing wastewater in which no aluminum salt is present. Processing effects can be obtained.

  The treated water in the second pH adjusting tank 3 is then subjected to a coagulation treatment by adding a polymer as a coagulant in the first coagulation tank 4, and then solid-liquid separated in the first precipitation tank 5. The separated water (first stage treated water) in the first settling tank 5 is fed to the reaction tank 6, and the separated sludge is dehydrated by the dehydrator 10.

  In the reaction vessel 6, an aluminum salt such as a sulfuric acid band or PAC is added to the first stage treated water, and a pH adjuster such as sodium hydroxide (NaOH) is added as necessary to adjust the pH to pH 6-7. Then, fluorine is adsorbed by the adsorption action of aluminum salt and precipitated together with aluminum hydroxide, and then polymer is added in the second agglomeration tank 7 and agglomerated, and then solid-liquid separation is performed in the second precipitation tank 8. The separated water in the second sedimentation tank 8 is filtered by a filter 9 to further improve the water quality, and the filtered water is discharged out of the system as treated water.

  The separated sludge obtained in the second settling tank 8 is dehydrated by the dehydrator 10 together with the separated sludge in the first settling tank 5, and the dehydrated cake is discharged out of the system. On the other hand, the dehydrated filtrate is fed to the storage tank 11. Further, backwash wastewater discharged by backwashing of the filter 9 is also fed to the storage tank 11.

The storage tank 11 is introduced with aluminum-containing wastewater discharged from other processes. Further, means for adding an acid such as sulfuric acid (H ₂ SO ₄ ) and means for adding an alkali such as slaked lime Ca (OH) ₂ are provided. The pH of the waste water is adjusted to pH 5-9, preferably pH 5.5-8 neutral.

  Then, the aluminum-containing wastewater whose pH is adjusted to neutral in the storage tank 11 is fed by the pump P to the raw water introduction line to the second pH-adjusting tank 3 and coagulated with the fluorine-containing wastewater.

  According to the present invention, aluminum-containing wastewater is thus added to a stage where the wastewater is adjusted to neutral pH 6 or more in the flocculation treatment step of fluorine-containing wastewater, thereby enabling stable and efficient treatment. Yes.

  The method shown in FIG. 1 is an embodiment of the method for treating fluorine-containing water of the present invention, and the present invention is not limited to the illustrated method. For example, the location where the aluminum-containing wastewater is added from the storage tank 11 is The first flocculating tank 4 or the upstream side of the first flocculating tank 4 may be used, and it is added to the first pH adjusting tank 2, the second pH adjusting tank 3, the introduction line to the first flocculating tank 4, or the first flocculating tank 4. You can also. In order to perform sufficient agglomeration treatment for the aluminum-containing wastewater, the location where the aluminum-containing wastewater is added is preferably a location where a sufficient agglomeration treatment time can be secured after the addition of the aluminum-containing wastewater. It is preferable to add in the middle of the tank or its introduction line, in particular, a pH adjusting tank arranged in two stages in series as shown in FIG.

In FIG. 1, Ca (OH) ₂ is used as an alkali for adjusting the pH of the waste water in the storage tank 11, but this alkali may be NaOH. However, the addition of Ca (OH) ₂ here is advantageous because it can be effectively used as a calcium compound in the first stage treatment.

For the same purpose, Ca (OH) ₂ may be added instead of NaOH in the reaction vessel 6.

In the present invention, the calcium compound added to the fluorine-containing water is not particularly limited, but slaked lime (Ca (OH) ₂ ) is usually used. However, it is not limited to slaked lime at all, and calcium chloride, calcium carbonate, or the like may be used. However, when these calcium compounds are used, an alkali for pH adjustment is additionally used. These calcium compounds may be used individually by 1 type, and may use 2 or more types together.

  Moreover, as a polymer added in the aggregation tanks 4 and 7, 1 type (s) or 2 or more types, such as a polyacrylamide partial hydrolyzate, sodium polyacrylate, polyvinylamidine, can be used, and the addition amount is raw water to be processed. Although it varies depending on the water quality and the polymer used, it is usually about 0.1 to 5 mg / L.

  In FIG. 1, a part of the separated sludge obtained in the first sedimentation tank 5 may be returned to the first pH adjustment tank 2 and / or the second pH adjustment tank 3, and in this case, the calcium compound is returned in advance. It may be mixed with sludge and added to the pH adjustment tank. By doing so, it is possible to improve the sludge cohesiveness, lower the moisture content, and improve the sedimentation property by the seed crystal effect of the returned sludge. . Further, by adding the return sludge mixed with the calcium compound, it is possible to further improve the quality of the treated water and reduce the amount of sludge generated.

  As fluorine-containing water to be treated in the present invention, 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, hydrofluoric acid manufacturing wastewater, fertilizer Various fluorine-containing waters such as production wastewater and waste incineration wastewater are listed.

  On the other hand, examples of the aluminum-containing water that is coagulated with such fluorine-containing water include backwash waste water from a filter and dehydrated filtrate that are generated by the above-described second-stage aluminum adsorption method. In addition, aluminum-containing wastewater generated in other systems, such as dewatered filtrate, backwash wastewater of the filter in the pressurized flotation or coagulation sedimentation process of water, miscellaneous wastewater containing aluminum such as regeneration wastewater of ion exchange resin, etc. It is done.

  Such a method for treating fluorine-containing water according to the present invention is particularly suitable for the treatment by the aluminum adsorption method in the latter stage in the treatment by the two-stage treatment method in which the treatment by the aluminum adsorption method as the advanced treatment is carried out after the calcium fluoride method. The required amount of aluminum salt used can be greatly reduced to reduce processing costs and the amount of sludge generated, which is extremely advantageous industrially.

  Hereinafter, the present invention will be described in more detail with reference to experimental examples, examples and comparative examples.

[Experimental Example 1]
After adding a liquid sulfuric acid band (Al ₂ O ₃ content 8% by weight) to raw water containing fluorine of the following water quality, neutralize to pH 6.1 to 6.3 by adding slaked lime (Ca (OH) ₂ ). Case (No. 1) and liquid sulfuric acid band previously neutralized to pH 7.0 to 7.2 after neutralization to pH 6.1 to 6.3 by adding slaked lime (Ca (OH) ₂ ) to raw water When No. 2 was added (No. 2), an experiment was conducted to examine the effect of the amount of sulfuric acid band added on the fluorine concentration of the treated water.
<Raw water quality>
F: 100 mg / L
H ₂ SO ₄ : 200 mg / L
CaCl ₂ (Ca conversion): 250 mg / L

As a result, as shown in FIG. 2, even if the sulfuric acid band was mixed with the raw water and then neutralized with Ca (OH) ₂ , good treatment results could not be obtained, and the treatment water fluorine concentration increased as the amount of sulfuric acid band added increased. However, when the raw water is neutralized by adding Ca (OH) ₂ and then a pre-neutralized sulfuric acid band is added, good treatment results can be obtained regardless of the amount of sulfuric acid band added. confirmed.

[Examples 1-3, Comparative Examples 1-3]
The following water quality semiconductor manufacturing waste water (fluorine-containing water) and mixed water (aluminum-containing water) of the backwash waste water of the filter generated by the aluminum adsorption method and the sludge dehydrated filtrate were treated by the method shown in FIG. 3, members having the same functions as those in FIG. 1 are denoted by the same reference numerals.
<Fluorine-containing water>
pH: 2.7
F: 89.5 mg / L
NH ₄ -F: 18.4 mg / L
<Aluminum-containing water quality>
pH: 6.5
SS: 280 mg / L
T-PO ₄ : 15 mg / L
F: 42 mg / L
T-Al: 25 mg / L

The capacity of each tank was as follows, and the raw water treatment amount was 2 L / hr. The mixing ratio of fluorine-containing water and aluminum-containing water was fed from the storage tank at 200 mL / hr so that the flow rate ratio was fluorine-containing water / aluminum-containing water = 2 / 0.2.
Raw water tank: 100L
First pH adjustment tank: 0.8L
Second pH adjustment tank: 0.8L
Coagulation tank: 0.8L
Settling tank: 10L

Raw water was introduced from the raw water tank 1 into the first pH adjustment tank 2 at 2 L / hr. The raw water was added with 200 mg / L of H ₂ SO ₄ in this introduction line. After adding Ca (OH) ₂ to the predetermined pH in the first pH adjusting tank 2, necessary amounts of Ca (OH) ₂ and H ₂ SO ₄ are added to the predetermined pH in the second pH adjusting tank 3. Then, 2 mg / L of polyacrylamide polymer ("PA331" manufactured by Kurita Kogyo Co., Ltd.) was added in the coagulation tank 4 for coagulation treatment, and the coagulation treated water was solid-liquid separated in the precipitation tank 5.

  In Examples 1 to 3, aluminum-containing water from the storage tank 11 is quantitatively injected into the introduction line of the second pH adjustment tank 3 (line II), and the adjusted pH values of the pH adjustment tanks 2 and 3 are the values shown in Table 1. did.

  On the other hand, in Comparative Examples 1 to 3, the aluminum-containing water from the storage tank 11 was added to and mixed with the raw water tank 1 (line I), and the adjusted pH values of the pH adjusting tanks 2 and 3 were as shown in Table 1.

  The fluorine concentration of the treated water (separated water in the precipitation tank 5) obtained in Examples 1 to 3 and Comparative Examples 1 to 3 was examined, and the results are shown in Table 1.

  From Table 1, when the aluminum-containing water is mixed with the fluorine-containing water in the raw water tank and coagulated, the fluorine concentration of the resulting treated water is very high, but the aluminum-containing water is not mixed with the fluorine-containing water. It can be seen that by adding to the neutralization step of pH 6 or higher in the fluorine aggregation treatment step, the inhibition of aggregation due to aluminum can be suppressed, and treated water with good water quality can be stably obtained.

It is a systematic diagram which shows embodiment of the processing method of the fluorine-containing water of this invention. 6 is a graph showing the results of Experimental Example 1. It is a systematic diagram which shows the processing method in Examples 1-3 and Comparative Examples 1-3. It is a systematic diagram which shows the conventional two-stage processing method. It is a graph which shows the relationship between the sulfuric acid band addition amount of the fluorine-containing water which added the sulfuric acid band, and the treated water fluorine concentration.

DESCRIPTION OF SYMBOLS 1 Raw water tank 2 1st pH adjustment tank 3 2nd pH adjustment tank 4 1st coagulation tank 5 1st sedimentation tank 6 Reaction tank 7 2nd aggregation tank 8 2nd sedimentation tank 9 Filter 10 Dehydrator 11 Storage tank

Claims (3)

In the method of coagulating fluorine-containing water and aluminum-containing water, the fluorine-containing water and the aluminum-containing water are separated, and the aluminum-containing water is added to a treatment step under neutral conditions of pH 6 or higher in the fluorine aggregation treatment step. A method for treating fluorine-containing water,
The aluminum-containing water is a dehydrated filtrate, a backwash drainage of a filter in the pressurization flotation or coagulation sedimentation process of water, and other process wastewater containing aluminum which is a regeneration wastewater of ion exchange resin; agglomeration and solid-liquid separation of fluorine-containing water Dehydrated and desorbed water of solid-liquid separation sludge obtained by further subjecting the treated water to an adsorption treatment using an aluminum salt; or backwash drainage obtained by backwashing a filter that filters the adsorption treated water ;
The fluorine agglomeration treatment step includes a first-stage treatment step in which a calcium compound is added to fluorine-containing water to insolubilize fluorine as calcium fluoride, and an aluminum salt is added to the treated water in the first-stage treatment step for agglomeration treatment. Including the stage treatment process,
The method for treating fluorine-containing water, wherein the aluminum-containing water is added to a first-stage treatment step in which the calcium fluoride insolubilized product is generated . 2. The method for treating fluorine-containing water according to claim 1 , wherein the aluminum-containing water is received in a storage tank, neutralized to a pH of 5 or higher, and then added to a treatment step under neutral conditions of the pH 6 or higher. 3. The first stage treatment step according to claim 1, wherein the first stage treatment step includes adding a calcium compound to the fluorine-containing water to adjust the pH to pH 6 to 8, and further adding calcium to the treated water in the first pH adjustment step. A second pH adjusting step of adjusting the pH to 6 to 8 by adding a compound, and the aluminum-containing water added to the first stage treatment step is added to the treated water of the first pH adjustment step or the second pH adjustment step A method for treating fluorine-containing water.

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