JP6612177B2 - Water treatment system and water treatment method - Google Patents

Description

  The present invention relates to a water treatment system and a water treatment method.

In general, water to be treated such as waste water contains a substance having a pH buffering action such as carbonate ions. If carbonate ions are present in the water to be treated, the pH is buffered even when an acid agent or an alkali agent is added, and thus the amount of the drug for adjusting to a predetermined pH for treating the target substance increases. Further, when the pH is adjusted to the alkali side, metal ions such as Ca ²⁺ existing in the water to be treated are likely to precipitate as carbonates, which hinders the operation of the facility such as an increase in the differential pressure of the subsequent filter. In addition, when draining water into a river after treating factory wastewater, etc., it is necessary to comply with the wastewater standards set by the government under the Water Pollution Control Law. Therefore, finally, it is necessary to control pH near neutrality. Here, pH is a hydrogen ion index.

  There are several methods for adjusting the pH, but a method of adjusting to a predetermined pH by injecting an acid agent or an alkali agent is mainly used. Examples of the acid agent used include hydrochloric acid and sulfuric acid, and examples of the alkali agent include sodium hydroxide. Moreover, when controlling pH to neutral vicinity finally, sodium carbonate etc. may be used. Further, there is a method using solid carbonate mineral as a pH buffering agent.

  Patent Document 1 describes a method for treating agricultural chemical wastewater in which agricultural chemical wastewater is contacted with a carbonate mineral that acts as a pH buffering agent, and then the agricultural chemical is removed with a biological carrier.

  Non-patent document 1 discloses that Mg-Al oxide is obtained by calcining hydrotalcite, which is an Mg-Al oxide incorporating carbonate ions, at 500 ° C. for application of hydrotalcite to water environment conservation and purification. The principle of regeneration, the removal of metal ions from an aqueous solution using hydrotalcite, and the like are described.

JP-A-6-15285

The Chemical Times 2005 No.1 (Vol.195) pp.10-16

  In Patent Document 1 described above, carbonate mineral is used to adjust the pH of the agricultural chemical wastewater to a pH suitable for the subsequent biological treatment. The pH adjustment method using carbonate mineral is different from the method of injecting acid agent or alkali agent, and the advantage that the pH control is not hindered due to mechanical trouble such as pump, and the pH of treated water is carbonate mineral Since it depends on the equilibrium pH of the solution, unlike the injection of the drug, local high or low pH is unlikely to occur, and there is an advantage of preventing the precipitation of carbonate. However, if the carbonate mineral continues to be used, the ability to adjust the pH will decrease, so it will eventually be necessary to replace it with a new carbonate mineral.

  In the above-mentioned Non-Patent Document 1, the main purpose is to remove carbonate ions (or other metal ions or the like) with Mg—Al oxide, and it is necessary to provide another means when adjusting the pH. An object of the present invention is to use an Mg / Al-based layered compound as a carbonate mineral and to be able to be used repeatedly as a pH buffer material while taking advantage of the pH adjustment of the carbonate mineral.

  The water treatment system of the present invention comprises a plurality of adsorption towers having an Mg / Al-based layered compound or a hydrotalcite-like compound, a target substance removal means for removing the target substance from the treated water, and a hydrotalcite-like compound to be coated. And a regeneration treatment means for regenerating the hydrotalcite-like compound by supplying carbonate ions when carbonate ions are released into the treated water and partially become Mg / Al-based layered compounds. The removal and desorption of carbonate ions from the water to be treated by the layered compound and the hydrotalcite-like compound were made possible.

  According to the present invention, since the hydrotalcite-like compound that is a carbonate mineral can be repeatedly used for decarboxylation and pH control, decarboxylation and rapid alkali injection are not necessary, and the local pH is high or low. It is difficult to occur, and carbonate precipitation in the water to be treated can be suppressed, the subsequent filter can be prevented from being clogged with carbonate, and an increase in the differential pressure of the filter can be suppressed.

It is a schematic block diagram which shows the water treatment system of Example 1. FIG. It is a figure which shows the reaction cycle of Mg / Al type | system | group layered compound. It is a flowchart which shows the process of the to-be-processed water of a pH control system. It is a flowchart which shows operation after reproduction | regeneration processing. It is a schematic block diagram which shows the water treatment system of Example 2. FIG. It is a schematic block diagram which shows the water treatment system of Example 3. It is a schematic block diagram which shows the water treatment system of Example 4.

  The present invention relates to a method and system for adjusting pH in water treatment for treating wastewater and the like.

  The present invention is characterized in that an Mg / Al-based layered compound is used as a carbonate mineral and can be used repeatedly while taking advantage of the pH adjustment of the carbonate mineral.

  In the present invention, when removing anions derived from organic matter, carbonate ions that cause a buffering action that inhibits a decrease in pH even when an acidic solution is added are removed in advance, and the adsorbent that adsorbs carbonate ions is treated. It is related with the technology of regenerating with hydrogen ion of water.

  The present invention comprises an adsorption tower packed with an Mg / Al-based layered compound used for decarboxylation, an adsorption tower filled with a hydrotalcite-like compound used for pH control, a means for removing a target substance, Regenerative treatment means that converts hydrotalcite-like compounds whose pH is controlled by ion desorption into Mg / Al-based layered compounds, a valve that controls the flow of treated water, and a pH meter that measures the pH of treated water Water treatment system.

  The pH control in the water treatment system described above is based on the order of water flow between the adsorption tower filled with the Mg / Al-based layered compound used for decarboxylation and the adsorption tower filled with the hydrotalcite-like compound used for pH control. This is done by reversing, enabling repeated use.

  Embodiments will be described below with reference to the drawings.

  In this embodiment, an example of pH control in the water treatment system will be described.

  FIG. 1 shows a configuration example of a water treatment system that performs pH control.

  In this figure, the water treatment system includes a first adsorption tower 110 (adsorption tower A), a second adsorption tower 120 (adsorption tower B), a target substance removal means 200, a regeneration treatment means 300, valves 410 to 480, The pipe 500 includes a pH measuring unit 1000. The pH control is performed by a configuration in which the pH measuring unit 1000 and a control unit (not shown) are connected by a network (not shown). In addition, measuring instruments, pumps, etc. for measuring the target substance, temperature, water pressure, etc. are installed as necessary.

The first adsorption tower 110 and the second adsorption tower 120 are filled with a Mg / Al-based layered compound for decarboxylation of treated water and pH control of treated water. The Mg / Al-based layered compound has a chemical formula of [Mg ²⁺ _8-x Al ³⁺ _x (OH) ₁₆ ] [A ^n- _{x / n} · yH ₂ O] (2 ≦ x ≦ 5, 0 ≧ y, A is It is an interlayer anion, and Cl ⁻ or PO ₄ ³⁻ is common.

  It is desirable that either one of the first adsorption tower 110 and the second adsorption tower 120 is filled with a hydrotalcite-like compound that is an Mg / Al-based layered compound incorporating carbonate ions. After filling the Mg / Al-based layered compound, it may be changed to a hydrotalcite-like compound by contacting with an aqueous solution containing carbonate ions.

  Here, decarboxylation means removing carbonate ions contained in the water to be treated.

The target substance removing unit 200 is composed of an apparatus for removing a target substance that is to be removed from the water to be treated. For example, when the target substance is a metal ion such as Sr ²⁺ or Cs ⁺ , ion exchange using a cation exchange resin or a chelate resin is possible, so an adsorption tower filled with these resins is installed. Cation exchange resins (for example, UBK10 manufactured by Mitsubishi Chemical Corporation) and chelate resins (for example, CRB05 manufactured by Mitsubishi Chemical Corporation) are generally set to the optimum pH (or pH range) for use. It is. Therefore, an acid agent or alkali agent injection means is also installed in the front stage of the adsorption tower filled with the resin as necessary in order to adjust the pH.

  In the present invention, since the decarboxylation is performed before the target substance removing unit 200, the pH buffering ability of the water to be treated is lowered, and the necessary acid agent or alkali agent is reduced and the pH is easily adjusted. It becomes possible to do.

  Here, hydrochloric acid (HCl) etc. are mentioned as an acid agent. Examples of the alkali agent include sodium hydroxide (NaOH).

  The regeneration treatment means 300 is used for controlling the pH of the hydrotalcite-like compound to release carbonate ions and converting them into Mg / Al-based layered compounds to return them to the hydrotalcite-like compounds. Device. When the hydrotalcite-like compound deteriorates, carbonate ions are removed by heating, and the treatment amount and usable time can be extended when used in decarboxylation of water to be treated. The heating means may be any method, but here, the hydrotalcite-like compound is taken out from the adsorption tower and heated by a heating apparatus not directly connected to the system. As an example, when treating wastewater from a factory or the like, there is a method of making heated dry air (200 to 500 ° C.) using heat discharged from the factory and heating the hydrotalcite-like compound. In this embodiment, when the regeneration process is being performed, water treatment cannot be performed at the same time. However, by using two systems, other systems can be operated during the regeneration process, and water treatment can be performed continuously.

  The valves 410 to 480 are installed to control the flow order of the water to be treated to the first adsorption tower 110, the second adsorption tower 120, and the target substance removing unit 200. These are controlled by being connected to the control means by a network (not shown).

  The pipe line 500 is connected to each facility for passing water to be treated.

  The pH measuring unit 1000 (pH meter) is installed to measure the pH of the treated water, is connected to the control unit via a network (not shown), and transmits pH data to the control unit. If the pH control ability of the hydrotalcite-like compound decreases and the pH of the treated water falls below the set value, an alarm is output from the control means and the operation of the system is changed.

  FIG. 2 shows the reaction cycle of the Mg / Al-based layered compound.

  In the reaction cycle shown in this figure, neutralization and regeneration are repeated. Here, neutralization means that the hydrotalcite-like compound incorporating carbonate ions raises the pH of water by releasing carbonate ions or elution of the hydrotalcite-like compound itself. Regeneration is to recapture carbonate ions by bringing the hydrotalcite-like compound used for the neutralization into contact with an aqueous solution containing carbonate ions. Therefore, regeneration is to fill the Mg / Al-based layered compound with carbonate ions. This is different from “reproduction” described in Non-Patent Document 1.

As shown in FIG. 2, the Mg / Al-based layered compound packed in the first adsorption tower 110 and the second adsorption tower 120 in FIG. 1 takes in an anion between layers when an anion such as carbonate ion is present. Intercalation occurs. Thereby, a hydrotalcite-like compound (an example of a chemical formula: Mg ₆ Al ₂ (OH) ₁₆ CO ₃ .yH ₂ O) is generated. Conversely, a hydrotalcite-like compound that has incorporated carbonate ions raises the pH of the water by releasing carbonate ions or elution of the hydrotalcite-like compound itself, particularly when it comes into contact with an aqueous solution having a pH of 7 or less. Has a neutralizing effect. The hydrotalcite-like compound used for neutralization can be regenerated to a form incorporating carbonate ions when it comes into contact with an aqueous solution containing carbonate ions again.

  In this embodiment, the removal of carbonate ions of the water to be treated and the pH control of the water to be treated are carried out using these phenomena.

  Specifically, carbonate ions contained in the water to be treated are gradually taken into the Mg / Al-based layered compound together with water molecules by the Mg / Al-based layered compound. Thereby, a hydrotalcite-like compound is produced. By subjecting this hydrotalcite-like compound to a regeneration treatment such as heating, carbonate ions and water molecules are desorbed and returned to the Mg / Al-based layered compound. In this manner, the hydrotalcite-like compound is generated from the Mg / Al-based layered compound, and the process for regenerating the Mg / Al-based layered compound is repeated.

  FIG. 3 is a flowchart showing a treatment process of water to be treated in a water treatment system with pH control.

  In the operation shown in the figure, the valve state immediately after the operation is open between a and b shown in FIG. In the following description, components corresponding to the reference numerals shown in FIG. 1 may be described using the reference numerals.

  In FIG. 3, in S <b> 1, carbonate ions are removed from the water to be treated by the first adsorption tower 110 filled with the Mg / Al-based layered compound into which carbonate ions have not been taken in. When the use of the Mg / Al-based layered compound is continued, it gradually changes to a hydrotalcite-like compound incorporating carbonate ions.

  In S2, the target substance is removed by the target substance removing unit 200.

  In S3, the second adsorption tower 120 is filled with a hydrotalcite-like compound into which carbonate ions have been taken in, and the pH of the water from which the target substance has been removed is controlled.

  In S4, the pH of the treated water is measured by the pH measuring means 1000. When the pH of the treated water becomes lower than the set value, an alarm is output by the control means, the valves 410 to 480 are closed, the operation is stopped, and the regeneration process of the second adsorption tower 120 is started.

  When the regeneration treatment of the hydrotalcite-like compound packed in the second adsorption tower 120 (conversion to the Mg / Al layered compound) is completed, the operation is resumed.

  FIG. 4 is an operation flow after the regeneration process. Valves 410 to 480 are opened and closed by a control means (not shown), and the space between a and c is opened. The treated water first passes through the second adsorption tower 120.

  In S5, carbonate ions are removed from the water to be treated by the second adsorption tower 120 filled with the Mg / Al-based layered compound into which the regenerated carbonate ions have not been taken in. This is because the order of water flow through the first adsorption tower 110 and the second adsorption tower 120 is reversed before the regeneration treatment.

  In S6, the target substance is removed by the target substance removing unit 200 in the same manner as in S2.

  In S7, the pH of the water that has passed through the target substance means 200 is controlled by the first adsorption tower 110 filled with the hydrotalcite-like compound that has taken in carbonate ions in the water treatment before the regeneration treatment.

  In S8, the pH of the treated water is measured by the pH measuring unit 1000 in the same manner as in S4. When the pH of the treated water becomes equal to or lower than the set value, an alarm is output by the control means, the operation is stopped, and the regeneration process of the first adsorption tower 110 is started.

  In the present embodiment, the Mg / Al layered compound, which is a carbonate mineral, is repeatedly used in the operation flow as described above. Thereby, decarboxylation and rapid alkali injection can be prevented, carbonate precipitation in the water to be treated can be suppressed, and an increase in the differential pressure of the subsequent filter can be suppressed.

  In the second embodiment, in the water treatment system of the first embodiment, when there are a plurality of target substances to be removed and the optimum pH for treatment is different, that is, a plurality of means for removing the target substances (target substance removing means) are provided. This shows the case.

  FIG. 5 is a configuration example of a water treatment system according to the second embodiment.

  This figure is different from the first embodiment in that it has a plurality of target substance removing means. That is, the target substance removing means 210 (target substance removing means A) and the target substance removing means 220 (target substance removing means B) are provided, and the pH of the water to be treated is controlled before the target substance removing means B. , Pass water. Example 2 is established when the optimum pH in the latter target substance removal means B is near the pH controlled by the hydrotalcite-like compound, and uses an acid agent or an alkali agent necessary for the removal of the target substance. There is an advantage of not having to.

  In the target substance removing unit A, boron ions, iodine ions, ruthenium ions, and the like can be removed with an appropriate adsorbent. Here, zeolite or the like is desirable as the adsorbent. Further, as the adsorbent used for the target substance removing means B, an alkaline and high performance material is desirable, and silicotitanate and the like can be mentioned.

  Example 3 shows the case where the water treatment system of Example 1 is provided with a carbonic acid supply means for supplying carbonated water to the adsorption tower used in decarboxylation.

  FIG. 6 is a configuration example of a water treatment system according to the third embodiment.

  In this figure, a carbonic acid supply means 600 is attached. As an example of the carbonic acid supply means 600, a tank configured to store carbonated water (carbon dioxide aqueous solution) and a pump for injecting carbonated water and connected to the adsorption towers 110 and 120 using pipes is used. is there.

  Compared with Example 1, by carrying out carbonate ion supply treatment (conversion to hydrotalcite-like compound) to Mg / Al-based layered compound, throughput and use of adsorption tower used for pH control The possible time can be extended and the operating rate of the system can be improved.

  When processing by the carbonic acid supply means 600 (carbonic acid supply processing) is added, there is a possibility that the stop time of the system may become long. By carrying out the filling process of carbonate ions into the compound, the treatment can be performed without extending the stop time.

  Example 4 shows the case where the water treatment system of Example 1 has a configuration for performing carbonate precipitation treatment of water to be treated.

  Carbonate precipitation treatment is a treatment that precipitates carbonate by adding carbonate to the water to be treated, adding sodium hydroxide (NaOH), etc., and making the pH of the water to be treated alkaline. It is. At this time, it is generally desirable to add carbonic acid in excess so that a sufficient amount of carbonate is generated. As a result, the amount of carbonate ions in the water to be treated after the carbonate precipitation treatment increases.

  FIG. 7 is a configuration example of the water treatment system according to the fourth embodiment.

  In this figure, the water to be treated is once stored in the tank 700. Carbonate addition means 800 is attached to the tank 700, and carbonate precipitation treatment is performed in the tank 700. At this time, it is desirable to attach an agitator or the like to the tank 700. Thereby, when chemical | medical agents, such as carbonated water and sodium hydroxide, are inject | poured into the tank 700, it fully stirs and mixing of a chemical | medical agent and to-be-processed water can be accelerated | stimulated.

  The carbonic acid addition means 800 is used to inject carbonate ions into the tank 700. As an example, a tank for storing an aqueous sodium carbonate solution, a pump for supplying the aqueous sodium carbonate solution to the tank 700, a tank for storing an alkaline agent for making the pH alkaline, and an alkaline agent to the tank 700. And a pump for supplying for supplying.

  The sedimentation processing means 900 is disposed on the downstream side of the tank 700. The precipitation processing means 900 is for removing the precipitated carbonate from the water to be treated. The supernatant liquid is sent to the first adsorption tower 110 or the second adsorption tower 120. On the other hand, the precipitated carbonate is discharged from a discharge port (not shown).

  In Example 4, compared with Example 1, by reducing the metal ion concentration in the water to be treated as carbonate, it becomes easier to remove the target substance (Sr and the like) thereafter. Moreover, there exists an advantage which becomes a hydrotalcite-like compound easily because the amount of intercalation in a layered compound increases by increasing the amount of carbonate ions in the water to be treated.

  In the above description, the example using the valve and the pH measuring means has been described. However, the present invention is not limited to this, and the water flow path may be switched without using the valve. You may control by processing time, for example, without using a measurement means.

  110: first adsorption tower, 120: second adsorption tower, 200: target substance removing means, 210, 220: target substance removing means, 300: regeneration processing means, 410, 420, 430, 440, 450, 460, 470, 480: valve, 500: conduit, 600: carbonic acid supply means, 700: tank, 800: carbonic acid addition means, 900: precipitation treatment means, 1000: pH measurement means.

Claims (15)

A plurality of adsorption towers having Mg / Al-based layered compounds or hydrotalcite-like compounds;
Target substance removing means for removing the target substance from the water to be treated;
Regeneration treatment for regenerating the hydrotalcite-like compound by supplying carbonate ions when the hydrotalcite-like compound releases carbonate ions into the water to be treated and partially becomes a Mg / Al layered compound Means, and
A water treatment system capable of repeatedly removing and desorbing carbonate ions from the water to be treated by the Mg / Al-based layered compound and the hydrotalcite-like compound. The water treatment system according to claim 1,
Furthermore, the water treatment system provided with the pH measurement means which measures pH of treated water. The water treatment system according to claim 1,
Carbonate ions are removed by the adsorption tower having the Mg / Al-based layered compound installed before the target substance removing means,
A water treatment system for controlling pH by desorbing carbonate ions in the adsorption tower having the hydrotalcite-like compound installed downstream from the means for removing the target substance. The water treatment system according to claim 2 ,
A water treatment system in which the hydrotalcite-like compound is converted into the Mg / Al-based layered compound by the regeneration treatment means when the pH of the treated water is lower than a set value. The water treatment system according to claim 1 ,
Before SL hydrotalcite like compound, when degradation is that to remove the carbonate ions upon heating, the water treatment system. The water treatment system according to claim 2,
And a valve for controlling the flow of the water to be treated.
When the pH of the treated water detected by the pH measuring unit is lower than a set value, the water treatment system reverses the order of water flow in the plurality of adsorption towers by opening and closing the valve. The water treatment system according to claim 1,
A water treatment system in which another target substance removing unit is attached to a downstream stage of the downstream adsorption tower among the plurality of adsorption towers. The water treatment system according to claim 1,
The water treatment system which attached the carbonic acid supply means which supplies carbonated water to the Mg / Al type | system | group layered compound of the said adsorption tower. The water treatment system according to claim 1,
Furthermore, a tank for storing the treated water;
Carbonate addition means for adding carbonate ions to the tank;
A precipitation removing means for removing the precipitated carbonate by precipitation;
A water treatment system configured to send the supernatant of the sediment removal means to the adsorption tower. The water treatment system according to claim 1,
The water treatment system, wherein the target substance is a radionuclide. Decarboxylation using Mg / Al-based layered compound,
Remove the target substance from the treated water,
Including a step of regenerating the hydrotalcite-like compound by supplying carbonate ions when the hydrotalcite-like compound partially releases a carbonate ion into the treated water to partially become a Mg / Al layered compound. ,
A water treatment method capable of repeatedly removing and desorbing carbonate ions from the treated water with the Mg / Al-based layered compound and the hydrotalcite-like compound. The water treatment method according to claim 11,
A water treatment method for controlling pH by supplying carbonate ions to a liquid from which the target substance has been removed from the hydrotalcite-like compound. The water treatment method according to claim 11,
A water treatment method for regenerating the hydrotalcite-like compound when the pH of the treated water is lower than a set value. The water treatment method according to claim 11 ,
Before SL hydrotalcite-like compound, when degradation removes carbonate ions by heating, the water treatment method. The water treatment method according to claim 11,
A water treatment method in which carbonate is precipitated and removed by adding carbonate ions to the water to be treated, and the supernatant is decarboxylated.

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