JP2013017906A - Method for treating boron-containing waste water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating boron-containing waste water, capable of completely reducing the boron concentration in the waste water by generating good flock and conducting sedimentation treatment.SOLUTION: Boron-containing waste water is blended with an aluminum compound, calcium compound and sulphated compound, and the waste water treated in a high pH region is blended with a specific terpolymer and thus good flock is generated, and aggregated and settled as sedimentation with high filterability to remove the boron.

Description

  [Technical Field] The present invention is a technique relating to a treatment method using a high molecular weight polymer that can be aggregated in a high pH range in wastewater treatment containing boron generated at a high concentration in plating industry, semiconductor industry, hot spring wastewater, and the like.

  Boron is used for the production of electroplating industry, semiconductor industry, glass industry, raw materials for pharmaceuticals, etc., and wastewater generated in the process contains a lot of boron. Further, it is also discharged from flue gas desulfurization plants such as coal-fired power plants and hot springs. Based on the current situation, the drainage standard for boron is set to 10 mg / L or less outside the sea area based on the Water Pollution Control Law.

As a treatment technique for boron-containing wastewater, for example, a removal method using a boron-selective ion exchange resin and an inorganic adsorbent in combination is used as an adsorption treatment (for example, Patent Document 1). However, since a large amount of resin is required for boron adsorption, there still remains a problem in terms of economy in the treatment by this method. Moreover, since the adsorption method using such an ion exchange resin or chelate resin is applied to a dilute boron solution, there is a problem that it is not suitable for wastewater treatment containing high-concentration boron even compared with the conventional method.

In addition, a coagulation precipitation method is used as a treatment method instead of the above method, and the coagulation precipitation method of using aluminum sulfate and slaked lime, which are conventional techniques, and adjusting the pH to a high alkali side is often used. Yes. Various techniques related to the agglomeration treatment process using aluminum salt and calcium salt have been disclosed by applying this technique (for example, Patent Documents 2 to 7), and applied as a treatment process technique for removing boron in waste water. ing.

However, the current state of the art is that the conventional coagulation-precipitation technique cannot solve any starch treatment. In the coagulation precipitation method using aluminum salt and calcium salt used in the boron treatment, the amount of chemical used is very large, and the pK of boric acid is 9.18, so it is necessary to adjust the pH to a high alkali region. Produces a large amount of starch. No specific investigation has been made on effective treatment methods for these starches.

In the case of using a conventional treatment method, it is known that agglomeration with a flocculant is difficult in a high alkaline pH region which is generally optimal for the treatment of starch. The aggregating agent in the agglomeration-precipitation treatment is likely to produce good flocs in a neutral to weak alkaline range where charge neutralization between the starches is relatively easy, and is preferably used in the pH range. On the other hand, in the high alkaline pH region, the precipitation of boron-containing wastewater by the coagulation precipitation method is extremely difficult because the cohesiveness of precipitation by the polymer flocculant is generally poor.

JP 2006-263603 A JP 2010-269309 A JP 2010-269310 A JP 2009-233640 A JP 2009-233641 A JP 2004-000963 A Japanese Patent No. 3333483

  The object of the present invention is to solve the problems that occur in the conventional coagulation and precipitation treatment of boron-containing wastewater, and to generate a good floc for precipitation treatment, which reliably reduces the boron concentration in the wastewater. It is to provide a method for treating wastewater containing boron.

As a result of intensive investigations to achieve the above object, the inventors of the present invention have identified a ternary specific to wastewater containing boron and wastewater mixed with an aluminum compound, calcium compound and sulfuric acid compound and treated in a high pH region. It has been found that by mixing the polymer, a good floc is formed and boron in the waste water can be easily removed.

That is, this invention relates to the processing method of the boron containing waste water shown to the following <1>-<4>.
<1> A method for treating boron-containing wastewater, which comprises the following steps (a) and (b).
(A) The process which mixes an aluminum compound, a calcium compound, and a sulfuric acid compound with boron containing waste_water | drain, and processes this waste_water | drain at pH10.5-13.
(B) A terpolymer composed of the waste water of the step (a) and structural units represented by the following (I), (II) and (III), wherein x: y: z is 99.8: 0. The process of mixing and processing with the water-soluble polymer which has the range of 1: 0.1-75: 15: 10.

However, R in the structural units (I), (II) and (III) represents hydrogen or a methyl group, respectively.
<2> The processing method according to <1>, wherein x: y: z of the terpolymer is 99.8: 0.1: 0.1 to 85: 10: 5.
<3> The aluminum compound is at least 2 moles as aluminum with respect to 1 mole of boron in the wastewater, the calcium compound is at least 6 moles as calcium with respect to 1 mole of boron in the wastewater, and the sulfuric acid compound is at 1 mole of boron in the wastewater. On the other hand, the treatment method according to <1> or <2>, wherein at least 3 mol of sulfuric acid is mixed.
<4> The processing method according to any one of <1> to <3>, wherein the pH for treating the waste water in the step (a) is 10.5 to 12.

  According to the present invention, with respect to a large amount of starch produced by boron treatment in a high alkali region, good flocs are generated and aggregated while maintaining the pH in the high alkali region using a specific terpolymer. It is possible. Therefore, the wastewater containing boron can be more efficiently removed by using the coagulation precipitation method, and the resulting starch can be easily treated.

  The aluminum compound used in the present invention is not particularly limited, and examples thereof include aluminum sulfate, aluminum nitrate, aluminum hydroxide, aluminum chloride, polyaluminum chloride, aluminum oxide, sodium aluminate, and potassium aluminate. The calcium compound of the present invention is not particularly limited, and examples thereof include calcium chloride, calcium hydroxide (slaked lime), calcium nitrate, calcium carbonate, calcium hydrogen carbonate, calcium sulfate and the like. Further, the sulfuric acid compound of the present invention is not particularly limited, and examples thereof include sodium sulfate, sodium hydrogen sulfate, potassium sulfate, calcium sulfate, magnesium sulfate, aluminum sulfate, and ammonium sulfate.

  Among the above aluminum compounds, calcium compounds and sulfuric acid compounds, preferred combinations in the wastewater treatment of the present invention include aluminum chloride, calcium chloride and sodium sulfate. A plurality of salts may be used as one compound, and examples of such agents include aluminum sulfate, calcium sulfate, calcium aluminate and the like.

  In practicing the present invention, since the pK of borate ions is 9.18, boron is ionized into borate ions toward the higher pH region, and a boron-containing precipitate is reliably generated by reaction with the mixed drug. It is thought that the boron removal rate becomes high. On the other hand, as the coagulation effect by the terpolymer, the better the coagulation action is, the more neutral the treatment pH is. Accordingly, in the step (a) of the present invention, the waste water mixed with the aluminum compound, the calcium compound and the sulfuric acid compound is preferably treated at pH 10.5 to 13, more preferably pH 10.5 to 12. By treating in the above pH range, it is thought that Charlesite, which is a boron-containing compound, and similar compounds are formed, and further, flocs that can be easily separated into solid and liquid are formed by the action of the terpolymer mixed in the waste water. . These flocs can be easily separated from the wastewater by a general filtration method, and the boron and fluorine concentrations in the wastewater can be simultaneously reduced. On the other hand, when the wastewater is treated at a pH of 10 or less, the generation of boron-containing precipitates becomes insufficient, and good flocs cannot be generated. Therefore, the boron and fluorine concentrations in the wastewater are effectively reduced. It cannot be reduced.

  The pH adjustment when treating the waste water in the step (a) of the present invention may be adjusted using a known pH adjuster after mixing the aluminum compound, the calcium compound and the sulfuric acid compound. Using slaked lime, the pH may be set to 10.5 or more simultaneously with mixing of the boron-containing wastewater with slaked lime, an aluminum compound, and a sulfuric acid compound. Although it does not specifically limit as a pH adjuster, Alkalis, such as sodium hydroxide (caustic soda), potassium hydroxide, slaked lime, acids, such as hydrochloric acid and a sulfuric acid, are mentioned.

In the step (a) of the present invention, the mixing amount of the aluminum compound mixed in the boron-containing wastewater is preferably a molar ratio of 2 or more, more preferably a molar ratio of 3 or more, as aluminum with respect to 1 mole of boron in the wastewater. The mixing amount of the calcium compound is preferably a molar ratio of 6 or more, and more preferably a molar ratio of 9 or more, with respect to 1 mol of boron in the waste water as calcium. The mixing amount of the sulfuric acid compound is preferably 3 or more, and more preferably 4.5 or more as sulfuric acid with respect to 1 mol of boron in the waste water.
The upper limit of the mixing amount of the drug in the step (a) is not particularly limited, and the effect of the present invention can be obtained even when added in a large amount, but from an economical viewpoint, 1 mol of boron in the wastewater. The aluminum compound preferably has a molar ratio of 6 or less as aluminum, the calcium compound has a molar ratio of 18 or less as calcium, and the sulfuric acid compound preferably has a molar ratio of 9 or less as sulfuric acid.

  The order in which the aluminum compound, calcium compound, and sulfuric acid compound are mixed with the boron-containing wastewater is not particularly limited, and the aluminum compound, calcium compound, and sulfuric acid compound may be separately mixed into the wastewater, and the aluminum compound, calcium compound may be mixed. Further, two or more kinds of sulfuric acid compounds may be mixed in advance and then mixed with waste water. In addition, the mixed form of the drug may be solid or liquid, and all or part of the drug previously made water-soluble may be added.

  In the step (a) of the present invention, the mixing time after adding the drug is preferably 5 minutes or more, more preferably 10 minutes or more, and it is preferable that the drug is completely dissolved. Further, the stirring time after pH adjustment is preferably 5 minutes or more, more preferably 10 minutes or more, and further preferably 30 minutes or more. The mixing method is not particularly limited as long as the waste water and the chemical can be mixed or uniformly mixed so as not to be non-uniform.

In the present invention, the boron-containing wastewater is mixed with an aluminum compound, a calcium compound and a sulfuric acid compound, and the wastewater is treated at pH 10.5 to 13, and then treated with a terpolymer represented by the following structural unit. Therefore, it is possible to generate good flocs and efficiently and easily remove boron in the waste water.

However, R in the structural units (I), (II) and (III) represents hydrogen or a methyl group, respectively.

  The terpolymer used in the present invention comprises (I) a unit having acrylamide or methacrylamide, (II) a unit having acrylic acid or methacrylic acid, and (III) 2-acrylamido-2-methylpropanesulfonic acid. Or a water-soluble polymer having a unit having 2-methacrylamide-2-methylpropanesulfonic acid as a constituent unit. The content ratio of each structural unit is 99.8: 0.1: 0.1 to 75:15:10, preferably 99.8: 0.1: 0.1 to 80: 15: 5, as a polymerization ratio. More preferably, it is 99.8: 0.1: 0.1-85: 10: 5. If the content ratio of each structural unit is within the above range, good floc can be generated in the waste water, so that solid-liquid separation can be easily performed in a short time without introducing a special separation device. The boron concentration in the waste water can be efficiently reduced.

  Although the addition form of the terpolymer used in the step (b) of the present invention is not limited, it is preferably added in a water-soluble state. By using a water-soluble terpolymer, a large agglomeration effect can be obtained by adding a small amount. The terpolymer may be used alone or in combination of two or more terpolymers. For example, several nonionic and anionic terpolymers having the same structure within the scope of the present invention may be used. When several types of terpolymers are used, several types of terpolymers may be added to the wastewater separately, or the terpolymers may be mixed in advance and then added to the wastewater. Such a terpolymer is available as a commercial product, and examples thereof include Akofloc A-243, N-225, A-95, and A-245H (all manufactured by MT Aqua Polymer Co., Ltd.). The molecular weight of the terpolymer of the present invention is not particularly limited as long as good flocs can be generated. For example, the weight average molecular weight of a terpolymer easily available as a commercial product is about 1 million to 50 million. .

  The addition amount of the terpolymer used in the step (b) of the present invention is not particularly limited in order to produce a good floc even with a small addition, but preferably 1 to 100 mg / L for waste water, More preferably, it is desirable to add in the range of 1-50 mg / L, more preferably 3-20 mg / L, and most preferably 5-20 mg / L.

  The mixing container and the mixing apparatus in the step (b) of the present invention can be the same as those in the step (a). In the step (b), the mixing time is preferably 30 seconds or longer, more preferably 1 minute or longer, and a desired amount of floc starts to be generated in several seconds to several tens of seconds after the required amount is added. The mixing method is not particularly limited as long as the waste water and the chemical can be mixed or uniformly mixed so as not to be non-uniform.

  Furthermore, it is possible to add a certain amount of the terpolymer of the present invention used in the step (b) in advance together with the drug in the step (a). In that case, the total addition amount of the terpolymer used in the step (a) and the step (b) is preferably 1 to 100 mg / L, more preferably 1 to 50 mg / L, further preferably 3 to the waste water. It is desirable to be in the range of 20 mg / L, most preferably 5-20 mg / L.

  In the present invention, since the generated floc is separated from the waste water after the step (b), it is possible to obtain the waste water in which the boron in the waste water is reliably reduced to 10 mg / L or less which is the waste water reference value. It is possible to process at low cost without performing processing steps such as two-stage processing. According to the treatment method of the present invention, a floc that can be separated into solid and liquid can be generated. Therefore, the method for separating the floc from the wastewater is not particularly limited. For example, filtration using a general filter paper or sedimentation tank It is possible to separate and remove the floc by discharging it from the lower sludge discharge hole.

  Examples of the present invention will be specifically described below. However, the present invention is not limited to the following examples.

  Table 1 shows the chemicals and amounts used in this test, Table 2 shows the polymerization ratio of each structural unit of the terpolymer used in the examples, and polymerization of each structural unit of the terpolymer used in the comparative example. The ratio is shown in Table 3. As an addition form of the ternary polymer, 0.1 g of each polymer was weighed and dissolved in 100 mL of pure water while gradually stirring to make a 0.1% (w / w) solution.

Example 1
0.572 g of boric acid (Wako Pure Chemicals, reagent grade) was accurately sampled and dissolved in 1 L of 1N HCl / NaOH electrolyte solution to obtain 100 mg / L boron simulated waste water. To this, as shown in Table 1 (1), the aluminum salt (aluminum chloride) corresponding to a molar ratio of 3 to boron as an aluminum compound is added, and the molar ratio of 9 as a calcium compound to boron. After adding a corresponding calcium salt (calcium chloride) and a sulfate (sodium sulfate) corresponding to a molar ratio of 4.5 to boron as a sulfate compound and stirring for 10 minutes (= added drug is completely dissolved) The pH was adjusted to 12 with sodium hydroxide and stirred for 30 minutes. 40 mL of this solution was fractionated with a graduated cylinder, transferred to a 50 mL screw tube, and the terpolymer (A) shown in Table 2 (each constituent unit was (I) acrylamide / (II) acrylic acid / (III) 2 -Acrylamide-2-methylpropanesulfonic acid) was added and stirred for 1 minute and allowed to stand for 30 seconds, and then the state of the generated floc was confirmed. The floc (polymer addition amount: 10.0 mg / L) was again stirred for 1 minute to disperse, then transferred to a 40 mL graduated cylinder, and the interface height of the precipitate after standing for 5 minutes was confirmed. Then, no. Filtration was performed with 2 qualitative filter paper (manufactured by ADVANTEC), and the amount of filtrate after 10 minutes was confirmed with a graduated cylinder scale. Further, the residue on the filter paper was collected, and the moisture content was measured using a halogen moisture meter (HR73 manufactured by METTLER TOLEDO). The results are shown in Table 4.

Examples 2-4
Instead of the terpolymer (A) of Example 1, the terpolymers (B) to (D) in Table 2 (each constituent unit is (I) acrylamide / (II) acrylic acid / (III) 2− Except for using acrylamido-2-methylpropanesulfonic acid, the treatment was performed in the same manner as in Example 1 to confirm the state of floc formation. Further, as in Example 1, the interface height of the precipitate when 10.0 mg / L of each polymer was added was measured. Filtration was performed with 2 qualitative filter paper (manufactured by ADVANTEC), and the amount of filtrate after 10 minutes was confirmed with a graduated cylinder scale. And the residue on a filter paper was collect | recovered, and the moisture content was measured using the halogen moisture meter (HR73 by METTLER TOLEDO). The results are shown in Table 4.

Comparative Examples 1-5
Instead of the terpolymer (A) of Example 1, the terpolymers (E) to (H) shown in Table 3 (each structural unit is (I) acrylamide / (II) acrylic acid / (III) 2 -It is an acrylamido-2-methylpropane sulfonic acid), or the treatment was performed in the same manner as in Example 1 except that the terpolymer was not added, and the floc formation state was confirmed. Further, as in Example 1, the interface height of the precipitate when 10.0 mg / L of each polymer was added was measured. Filtration was performed with 2 qualitative filter paper (manufactured by ADVANTEC), and the amount of filtrate after 10 minutes was confirmed with a graduated cylinder scale. And the residue on a filter paper was collect | recovered, and the moisture content was measured using the halogen moisture meter (HR73 by METTLER TOLEDO). The results are shown in Table 4.

* Evaluation of the state of floc formation A: Large flocs with good sedimentation are generated, and there is a clear supernatant.
○: Medium-sized flocs are generated and solid-liquid separation is possible.
Δ: Fine flocs are generated, but solid-liquid separation is not completed or insufficient.
X: Flock is not formed.

From the results of Table 4, the terpolymers (A) to (D) used in the present invention clearly form good flocs with respect to boron single simulated drainage and have good cohesiveness and filterability. Became clear. Moreover, also about the moisture content of the residue after filtration, it became clear by the ternary polymer used for this invention that the moisture content has fallen compared with the other polymer.

Examples 5-6
0.572 g of boric acid reagent was sampled and dissolved in 1 L of 1N HCl / NaOH electrolyte solution to obtain 100 mg / L boron simulated waste water. To this, as shown in Table 1 (2), the aluminum salt (aluminum chloride) corresponding to a molar ratio of 4 with respect to boron is added as an aluminum compound, and the molar ratio is 12 with respect to boron as a calcium compound. Corresponding calcium salt (calcium chloride) and sulfate (sodium sulfate) corresponding to a molar ratio of 6 to boron as a sulfate compound are added and stirred for 10 minutes (= added drug is completely dissolved), and then hydroxylated. The pH was adjusted to 12 with sodium and stirred for 30 minutes. 40 mL of this solution was fractionated with a graduated cylinder, transferred to a 50 mL screw tube, and the terpolymers (A) or (C) shown in Table 2 (each constituent unit was (I) acrylamide / (II) acrylic acid / (III) 2-acrylamido-2-methylpropanesulfonic acid) was added, stirred for 1 minute, allowed to stand for 30 seconds, and then the state of floc formation was confirmed. Further, a certain amount of supernatant was collected, filtered through a 0.22 μm pore size membrane filter, and the residual boron concentration was measured by ICP emission spectroscopic analysis (ICP-7500, manufactured by Shimadzu Corporation). The results are shown in Table 5.

Comparative Examples 6-8
Instead of the terpolymer (A) of Example 5, the terpolymer (E) or (G) shown in Table 3 was added, or except that the terpolymer was not added. Similarly, the flock generation state was confirmed. Further, a certain amount of supernatant was collected, filtered through a 0.22 μm pore size membrane filter, and the residual boron concentration was measured by ICP emission spectroscopic analysis (ICP-7500, manufactured by Shimadzu Corporation). The results are shown in Table 5.

* Evaluation of the state of floc formation A: Large flocs with good sedimentation are generated, and there is a clear supernatant.
○: Medium-sized flocs are generated and solid-liquid separation is possible.
Δ: Fine flocs are generated, but solid-liquid separation is not completed or insufficient.
X: Flock is not formed.

From the results of Table 5, even if the amount of the drug added was changed, a good floc was formed by adding the terpolymer used in the treatment method of the present invention, and the supernatant was compared with the polymer shown in the comparative example. It became clear that boron was also removed.

Examples 7-12
0.572 g of boric acid (Wako Pure Chemicals, reagent grade) was accurately sampled and dissolved in 1 L of 1N HCl / NaOH electrolyte solution to obtain 100 mg / L boron simulated waste water. To this, as shown in Table 1 (1), the aluminum salt (aluminum chloride) corresponding to a molar ratio of 3 to boron as an aluminum compound is added, and the molar ratio of 9 as a calcium compound to boron. Corresponding calcium salt (calcium chloride) and a sulfate (sodium sulfate) corresponding to a molar ratio of 4.5 to boron as a sulfate compound were added and stirred for 10 minutes (= added drug was completely dissolved). Then, it adjusted to pH12.0, 11.0, or 10.5 with sodium hydroxide, and stirred for 30 minutes. 40 mL of this solution was fractionated with a graduated cylinder, transferred to a 50 mL screw tube, and the terpolymer (A) or (C) shown in Table 2 (each constituent unit was (I) acrylamide / (II) acrylic acid / (III) 2-acrylamido-2-methylpropanesulfonic acid) was added, stirred for 1 minute, allowed to stand for 30 seconds, and then the state of flocs produced was confirmed. The floc (polymer addition amount: 10.0 mg / L) was again stirred for 1 minute to disperse, then transferred to a 40 mL graduated cylinder, and the interface height of the precipitate after standing for 5 minutes was confirmed. Then, no. Filtration was performed with 2 qualitative filter paper (manufactured by ADVANTEC), and the amount of filtrate after 10 minutes was confirmed with a graduated cylinder scale. Further, the residue on the filter paper was collected, and the moisture content was measured using a halogen moisture meter (HR73 manufactured by METTLER TOLEDO). The results are shown in Table 6.

Comparative Examples 9-14
Flock generation state, filtrate in the same manner as in Example 7 or Example 8, except that the pH adjusted with sodium hydroxide in Example 7 or Example 8 was 10.0, 9.5, or 9.0. The height and the moisture content of the filtration residue were measured. The results are shown in Table 6.

* Evaluation of the state of floc formation A: Large flocs with good sedimentation are generated, and there is a clear supernatant.
○: Medium-sized flocs are generated and solid-liquid separation is possible.
Δ: Fine flocs are generated, but solid-liquid separation is not completed or insufficient.
X: Flock is not formed.

  From the results of Table 6, it was confirmed that in the treatment method of the present invention, good flocs were formed at a pH of 10.5 or higher, and precipitation interface height, filtrate height, and residual water content showed good values.

Examples 13-15
0.572 g of boric acid (Wako Pure Chemicals, reagent grade) was accurately sampled and dissolved in 1 L of 1N HCl / NaOH electrolyte solution to obtain 100 mg / L boron simulated waste water. To this, as shown in Table 1 (2), the aluminum salt (aluminum chloride) corresponding to a molar ratio of 4 with respect to boron is added as an aluminum compound, and the molar ratio is 12 with respect to boron as a calcium compound. Corresponding calcium salt (calcium chloride) and sulfate (sodium sulfate) corresponding to a molar ratio of 6 with respect to boron as a sulfate compound were added and stirred for 10 minutes (= added drug was completely dissolved). Then, it adjusted to pH12.0, 11.0, or 10.5 with sodium hydroxide, and stirred for 30 minutes. 40 mL of this solution was fractionated with a graduated cylinder, transferred to a 50 mL screw tube, and the terpolymer (A) shown in Table 2 (each constituent unit was (I) acrylamide / (II) acrylic acid / (III) 2 -Acrylamide-2-methylpropanesulfonic acid) was added and stirred for 1 minute, allowed to stand for 30 seconds, a certain amount of supernatant was collected, filtered through a 0.22 μm pore membrane filter, and then subjected to ICP emission spectroscopic analysis (ICP- 7500 (manufactured by Shimadzu Corporation) was used to measure the residual boron concentration. The results are shown in Table 7.

Comparative Examples 15-17
The residual boron concentration in the supernatant was measured in the same manner as in Example 13 except that the adjusted pH with sodium hydroxide in Example 13 was 10.0, 9.5, or 9.0. The results are shown in Table 7.

  From the results of Table 7, it was clarified that in the treatment method of the present invention, the boron removal rate in the wastewater was greatly improved at a pH of 10.5 or more, and was below the boron wastewater standard (10 mg / L or less).

Claims (4)

A method for treating boron-containing wastewater, which comprises the following steps (a) and (b):
(A) The process which mixes an aluminum compound, a calcium compound, and a sulfuric acid compound with boron containing waste_water | drain, and processes this waste_water | drain at pH10.5-13.
(B) A terpolymer composed of the wastewater treated in the step (a) and structural units represented by the following (I), (II) and (III), wherein x: y: z is 99.8. The process of mixing and processing with the water-soluble polymer which has the range of 0.1: 0.1-75: 15: 10.

However, R in the structural units (I), (II) and (III) represents hydrogen or a methyl group, respectively.   2. The processing method according to claim 1, wherein x: y: z of the terpolymer is 99.8: 0.1: 0.1 to 85: 10: 5.   The aluminum compound is at least 2 moles as aluminum per mole of boron in the wastewater, the calcium compound is at least 6 moles as calcium per mole of boron in the wastewater, and the sulfate compound is sulfuric acid per mole of boron in the wastewater. The processing method according to claim 1, wherein at least 3 moles are mixed. The treatment method according to any one of claims 1 to 3, wherein the pH for treating the waste water in the step (a) is 10.5 to 12.