JPH11169864A - Treatment method of boron-containing water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high quality treated water by separating a boron-containing water into a condensed water and a concentrated material by evaporation concentration, bringing the condensed water into contact with an ion exchange resin to remove boron and returning a regeneration waste liquid generated by the regeneration of the ion exchange resin to an evaporation concentration process to efficiently remove boron. SOLUTION: The raw water from a raw water passage 5 and the regenerated waste liquid from a waste liquid supply passage 6 are introduced into an adjusting vessel 1, mixed with a stirrer 7 and adjusted pH to >= neutral by injecting a pH adjuster from a chemical injection passage 8. The mixed liquid in the adjusting vessel 1 is introduced into an evaporation condensation device 2, the condensed water is obtained by condensing the vapor and is sent to an ion exchange resin vessel 3. The ion exchange resin vessel 3 has a resin layer 12, boron is exchanged and adsorbed to be removed by passing the condensed water through the resin 12 in an ion exchange process and the treated water is taken out from a treated water passage 13. The resin layer 12 is regenerated by injecting a regenerating agent from the chemical injection passage 14 and the regenerated waste liquid is sent to a waste liquid storage vessel 4 from a line passage 15, mixed by a stirrer 16 and supplied to the adjusting vessel 1 from the waste liquid supply passage 6 at a homogenization flow rate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for treating boron-containing water, and more particularly to a method for treating boron-containing water by evaporation and concentration and ion exchange.

[0002]

2. Description of the Related Art Boron compounds are used in various fields, and some wastewaters generated from these fields and those discharged from other fields contain those containing boron compounds.
Since such compounds are considered harmful, treatments have been performed to remove boron from boron-containing water.

As a conventional method for treating boron-containing water, a method of separating and removing boron by coagulation precipitation using an aluminum compound and a calcium compound has been performed (Japanese Patent Publication Nos. 58-15193 and 59-24876).
issue). However, this method requires the use of a large amount of chemicals, generates a large amount of sludge, and has a problem that its treatment is difficult.

There is also known a method in which boron-containing water is ion-exchanged with an anion exchange resin to remove boron, and a regenerated effluent of the anion exchange resin is evaporated and concentrated (Japanese Patent Publication No. 43594/1994). However, since this method directly ion-exchanges raw water, it is necessary to use a large amount of ion-exchange resin, the frequency of regeneration is high, the amount of regenerant used is large, and the treatment of boron in condensed water generated by evaporation and concentration. Is not shown.

In addition, boron-containing water is subjected to reverse osmosis (hereinafter referred to as R
A method is disclosed in which a membrane is separated in a membrane apparatus, a concentrated solution is evaporated and concentrated, and a permeate of the RO membrane apparatus and a condensate obtained by evaporation and concentration are treated with an ion-exchange resin (Japanese Patent Laid-Open No. 59-1984). -49898). But with this method,
Since the boron removal rate of the RO film is as low as about 60% at the maximum, a large amount of resin and a large amount of chemicals are required.

According to this method, the regenerated effluent can be mixed with raw water for treatment.
When treated with a membrane device, the boron concentration of the permeate becomes about 1.5 times that of raw water, so a larger amount of resin and regenerant is required than when directly ion-exchanging raw water, and the frequency of regeneration is higher. There is a problem.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to reduce the amount of ion exchange resin and chemicals to be used and to efficiently remove boron at a high removal rate without draining the regenerated waste water of the ion exchange resin. To obtain high quality treated water,
An object of the present invention is to provide a method for treating boron-containing water that can reduce the amount of generated sludge.

[0008]

SUMMARY OF THE INVENTION The present invention provides an evaporative concentration step for separating boron-containing water into coagulated water and a concentrate by evaporative concentration, and an ion exchange step for bringing condensed water into contact with an ion exchange resin to remove boron. And a regeneration step of regenerating the ion exchange resin and returning the regenerated effluent to the evaporative concentration step.

The boron-containing water to be treated in the present invention is usually water containing boron in the form of orthoboric acid (H ₃ BO ₃ ), but it may be borate or other forms containing boron. Examples of such boron-containing water include manufacturing process wastewater, plating wastewater, radioactive wastewater generated from nuclear power plants, geothermal power generation wastewater, flue gas desulfurization wastewater, and waste incineration plants that use pharmaceuticals, cosmetics, soap, and other boron compounds. Smoke-wash drainage. In general, the boron-containing water containing 1000 to 10000 mg / l of boron is suitable as a target to be treated.

The boron-containing water may be subjected to the treatment of the present invention as it is, or the treatment of the present invention may be carried out after the treatment for removing other components. When the raw water contains solids, other scale components and corrosive components, it is preferable to remove these other components by pretreatment such as coagulation sedimentation and filtration.

In the coagulation precipitation treatment, coagulation is performed by adding a coagulant such as an aluminum salt and an iron salt and, if necessary, an alkali agent such as calcium hydroxide, and solid-liquid separation is performed to remove solids and other coagulable components. Operation. Filtration includes coagulation filtration as well as general filtration for solids separation.

The pretreatment may be performed in such a range as to remove substances that inhibit evaporation and concentration, such as solid matter removal. However, if all components other than boron are removed, boron will be purified in a later step. Can be recovered in any form. In the pretreatment, boron may or may not be removed. As a pretreatment, a concentration operation for reducing the load of the evaporative concentration step may be performed.
Concentration is performed in the evaporative concentration step without performing a concentration operation in which boron separation is incomplete such as a membrane treatment.

In the evaporative concentration step, the boron-containing water is evaporated and concentrated together with the regenerated effluent of the ion-exchange resin to concentrate the boron compound. In the evaporative concentration step, any evaporating apparatus such as heating evaporation, vacuum evaporation, or a combination thereof can be employed, but heating evaporation is preferred. As the type of each evaporator, any type of evaporator such as a flash type or a film type can be used.

Into these evaporators, water to be treated such as boron-containing water, pretreatment water thereof, and regenerated wastewater of the ion exchange resin are introduced to evaporate the water and condense the steam to produce condensed water. By recovering heat using raw water as cooling water for condensation, evaporation and concentration can be performed efficiently with a small amount of heat. By evaporation of the water, the boron compound and other non-volatile components are concentrated on the liquid side to obtain a concentrate.

The concentration ratio at this time is determined in consideration of the concentration of the raw water and the disposal method of the concentrated liquid. The concentrate can be obtained in a solid or liquid state and can be collected or disposed of as it is, or can be disposed of after being hardened with cement or the like. Further, it can be obtained in the form of a concentrated liquid and can be subjected to post-treatment such as aggregation. In any case, when the boron compound is obtained in a pure form, it can be recovered and used.

Since the condensed water obtained in the evaporating and condensing step contains about 1 to 10 mg / l of boron transferred with the vapor, the condensed water is brought into contact with the ion exchange resin in the ion exchange step. To remove boron. Boron contained in condensed water is 1/100 to 1/10000 of raw water
Therefore, the amount of the resin and the amount of the regenerant used here can be reduced by the ratio in comparison with the case where the raw water is directly ion-exchanged.

As the ion exchange resin used in the ion exchange step, an anion exchange resin is used in order to remove boron, but when it is necessary to remove cations, a cation exchange resin can also be used. In this case, the treatment is preferably performed in a mixed bed.

The anion exchange resin for removing boron may be either weakly basic or strongly basic, but is preferably weakly basic because of its higher regeneration efficiency. In addition, when a chelate resin having an increased amount of adsorbed boron, for example, an N-methylglucamine type resin that selectively adsorbs boron, the removal rate of boron is increased and the purity of the recovered boron compound (boric acid) is increased. Get higher.

In the ion exchange step, condensed water is passed through the resin layer filled with the anion exchange resin to perform ion exchange to exchange and adsorb boron. Most of the boron contained in the condensed water is orthoboric acid, and it is considered that the boron is dissociated in water according to the formula (1).

Embedded image H ₃ BO ₃ + H ₂ O = B (OH) ₄ ⁻ + H ⁺ (1)

The equilibrium in the equation (1) changes depending on the pH, and the higher the pH, the more the equilibrium tends to shift to the right. In this case, when the anion exchange resin is SO _{4 type} , the treatment is difficult unless the pH is 9 or more. In the case of the OH type, the treatment can be carried out even near the neutrality. Is preferred.

In the ion exchange step, boron-containing water is brought into contact with an anion exchange resin to form the B (O)
H) ₄ ^- is exchange-adsorbed to the resin and removed. From the treated water, boron and other anions are removed, and high-purity treated water close to pure water is obtained and can be used as it is. If the condensed water contains cations, the cations can be removed by treating with a cation exchange resin as described above,
When the treatment is performed using a resin that also removes other anions as the anion exchange resin, pure water can be obtained as treated water.

When the anion exchange resin is saturated with boron, the process proceeds to a regeneration step, where the resin layer is backwashed, and a regenerant is passed through to elute the exchange-adsorbed boron. As the regenerating agent, a general regenerating agent such as an acid and an alkali can be used, but it is particularly preferable to use sulfuric acid, hydrochloric acid or nitric acid. Boron is eluted by the passage of the regenerant, and regenerated wastewater containing high-concentration boron is generated. After the boron has been eluted, the resin can be converted to the OH form with sodium hydroxide if necessary, and then used again for boron adsorption.

The regenerated effluent is returned as it is, or after adjusting the pH, mixed with raw water and returned to the evaporation and concentration step. In the evaporative concentration step, the lower the pH, the more easily the orthoboric acid moves to the vapor side. Therefore, it is preferable to introduce the orthoboric acid into the evaporative concentration step at a neutral or higher pH. If the raw water is acidic or alkaline, and the pH of the neutral water or higher is obtained by mixing the regenerated effluent,
They simply need to be mixed. If the mixture does not become neutral or more, it is preferable to add an acid or an alkali as a pH adjuster. When an acid and an alkali are used as the regenerant, they are mixed and returned to the evaporation and concentration step.

[0024] By concentrating the treated water obtained by mixing the regenerated effluent with the raw water in the evaporative concentration step, the concentrated boron and other substances contained in the regenerated effluent are concentrated and recovered or disposed of. Further, the concentration of boron to be treated increases due to the mixing of the regenerated effluent, and the amount of boron migrating to the condensed water side increases accordingly, but these are removed in the ion exchange step.

It is preferable for the operation of the evaporative concentration step that the quality of the water to be treated supplied to the evaporative concentration step is as stable as possible. For this purpose, the regenerated wastewater discharged intermittently is stored in a storage tank. It is preferable to return to the evaporative concentration step by a fixed amount at a time. In addition, the operation of the evaporative concentration process is continued during the regeneration of the ion exchange resin, so the condensed water generated during the operation is stored to homogenize the treatment amount, or the treatment is continued by switching over by installing multiple ion exchange devices. It is preferable to perform it in an appropriate manner.

In the above treatment, boron is previously concentrated by evaporative concentration, and only the condensed water having a low boron content is ion-exchanged. Therefore, the amounts of the ion-exchange resin and the regenerant are small and the boron removal rate is increased. It is possible to obtain treated water of high quality and close to pure water. Also, in order to return the regenerated effluent of the ion exchange resin to the evaporative concentration step and evaporate and concentrate,
The treatment of the regenerated effluent is easy, and the amount of generated sludge is reduced.

[0027]

According to the present invention, the amount of ion exchange resin and chemicals used is reduced, and boron is efficiently removed at a high removal rate without draining the regenerated effluent of the ion exchange resin. Treated water can be obtained, and the amount of generated sludge can be reduced.

[0028]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a system diagram showing a method for treating boron-containing water according to an embodiment of the present invention. In FIG. 1, 1 is an adjustment tank, 2 is an evaporating and concentrating device, 3 is an ion exchange tank, and 4 is a drainage storage tank.

The method of treating the boron-containing water by the above-described apparatus is as follows. First, raw water is introduced into the adjusting tank 1 from the raw water channel 5, regenerated effluent is introduced from the effluent supply channel 6, stirred and mixed by the stirrer 7, and a pH adjuster is injected from the chemical injection channel 8 as necessary. Adjust the pH to neutral or higher. The mixed liquid in the adjusting tank 1 is introduced into the evaporating and concentrating apparatus 2 from the system line 9 as a liquid to be treated.

The evaporating and concentrating apparatus 2 is of a heating and evaporating type, in which the supplied liquid to be treated is heated and evaporated, and the generated steam is condensed to obtain condensed water. The concentrate is sent to the tank 3, while the concentrate is removed from the concentrate path 11. Here, the boron is concentrated by evaporation to the concentrate side, and a part of the boron moves to the condensate side. Although the steam is configured to be cooled by the liquid to be treated and recover heat, detailed illustration is omitted.

The ion exchange tank 3 has a resin layer 12 filled with an anion exchange resin. In the ion exchange step, condensed water is passed through the resin layer 12 to remove and remove boron by exchange and adsorption. From the treated water channel 13. By providing a plurality of ion exchange tanks 3, when the ion exchange step is completed and the process proceeds to the regeneration step, the ion exchange tank 3 is switched to perform continuous processing.

The regenerant is injected from the chemical injection path 14 to form the resin layer 1
2 is regenerated, and the regenerated effluent is sent from the system path 15 to the effluent storage tank 4. Regeneration efficiency can be increased by sequentially flowing an acid and an alkali as a regenerating agent. In this case, these waste liquids are collected in the waste liquid storage tank 4 and agitated by the stirrer 16 to perform neutralization, and are supplied from the waste liquid supply path 6 to the adjustment tank 1 at a homogenized flow rate.

[0033]

Example 1 Examples and comparative examples of the present invention will be described below.

Example 1 Raw water having a pH of 7.0 and containing 2500 mg / l of boron was heated to 100 ° C. in an evaporator and concentrated by a factor of 15 to evaporate and condense condensed water having a boron concentration of 7.1 mg / l. Obtained. This condensed water is subjected to N-methylglucamine-type boron selective adsorption resin (Mitsubishi Chemical's Diaion CRB-02,
(Trademark) was passed through the resin layer of SV2 hr ^-1 to find that 44
Processed water of 1 mg / l or less boron was obtained up to 0 BV.

When the resin layer was regenerated with 100 g / l sulfuric acid, a regenerated wastewater having a boron concentration of 2450 mg / l was obtained. When the regenerated effluent was mixed with the raw water without neutralization, the pH of the reclaimed effluent was adjusted to pH 3. When the regenerated effluent was concentrated to a concentration multiple of 15 times using an evaporator, the boron concentration of the condensed water was 2%.
It became 6 mg / l. When the condensed water was passed through the resin layer in the same manner as described above, the boron concentration was 1 mg / l up to 120 BV.
The following treated water was obtained.

Example 2 In Example 1, sodium hydroxide was added to the regenerated effluent to adjust the pH to 7.0, and neutralized regenerated effluent was mixed at a ratio of 3 ml with 1 liter of raw water to evaporate. After concentration, the boron concentration of the condensed water at a concentration ratio of 15 was 6.
It became 9 mg / l. When this condensed water was subjected to an ion exchange treatment in the same manner as in Example 1, the boron concentration was 1 to BV440.
mg / l or less of treated water was obtained. The solid obtained by drying the concentrated liquid in the above-mentioned evaporation and concentration step is the same as raw water 1
The weight was 25 g per liter.

Comparative Example 1 The same waste water as in Example 1 was passed through a boron-selective resin at SV 2 hr ^-1 to obtain treated water of 1 mg / l or less up to 1.5 BV. In addition, 100 g /
When regenerated with 1 sulfuric acid, a regenerated effluent containing 2480 mg / l of boron was obtained. In this case, the amount of the required resin was about 300 times that of Example 1, and the amount of the regenerant and the amount of the alkali for neutralizing the regenerated effluent was about 300 times that of the Example. For this reason, the amount of regenerated effluent was almost equal to the amount of raw water, and the capacity of the evaporator was equal to that in Example 1 when the regenerated effluent was evaporated and concentrated.

Comparative Example 2 The regenerated effluent obtained in Comparative Example 1 was added with 45 g / l of a sulfuric acid band and 150 g / l of slaked lime (pH 12.4), stirred for 30 minutes, and then subjected to solid-liquid separation. The boron content was 180 mg / l.
Of treated water was obtained. 220 g of solid matter generated at that time
/ L-raw water. On the other hand, the solid matter produced in Example 2 is only 25 g / l-raw water, which is greatly reduced.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a method for treating boron-containing water according to an embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Adjustment tank 2 Evaporative concentration apparatus 3 Ion exchange tank 4 Drainage storage tank 5 Raw water channel 6 Drainage supply channel 7, 16 Stirrer 8, 14 Chemical injection channel 11 Concentrated liquid channel 13 Treatment water channel

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI C02F 1/42 C02F 1/42 B 9/00 502 9/00 502B 502J 503 503G 504 504B 504E

Claims (1)

[Claims] 1. An evaporative concentration step of separating boron-containing water into condensed water and a concentrate by evaporative concentration, an ion exchange step of contacting the condensed water with an ion exchange resin to remove boron, and regenerating the ion exchange resin. And a regenerating step of returning the regenerated effluent to the evaporative concentration step.