JP2008049240A - Phosphorus recovery and phosphorus adsorbent disattacment measure in treatment for wastewater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a detachable regeneration method which enables an enhancement in the detachable recovery efficiency of phosphorus in waste water treatment for removing phosphorous in waste water by an adsorbent. <P>SOLUTION: The detachment treatment of an adsorbed phosphorous component is carried out by bringing into contact with an alkaline aqueous solution prepared by dissolving an alkali metal salt except carbonate having temperatures of 40°C to 100°C. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to wastewater treatment for human waste, sewage, food processing wastewater and factory wastewater, livestock manure, etc., and improves phosphorus desorption recovery efficiency in wastewater treatment that removes phosphorus in wastewater with an adsorbent. The present invention relates to a desorption method that can be performed.

  In recent years, as a cause of eutrophication phenomenon, organic substances, nitrogen, phosphorus, etc. contained in large quantities in rivers, various industrial effluents or domestic effluents cause water pollution in lakes that promote the generation of algae and red tides in the near sea. Are listed. Establishing advanced water treatment technology capable of removing nitrogen and phosphorus from high to low concentrations, which are said to be 0.15ppm and 0.02ppm of phosphorus as the limiting concentrations of nitrogen and phosphorus that cause eutrophication. Is strongly desired.

Methods for removing phosphorus in waste water are roughly classified into two methods, biological treatment methods and physicochemical treatment methods. Among the physicochemical treatment methods, a coagulation precipitation method is generally used in which a phosphorus component is removed as a poorly soluble phosphate using a flocculant from the viewpoint of economy, treatment efficiency, and the like.
However, there are issues that should be studied in the future, such as spillage of salts derived from the flocculant due to the addition of flocculant, problems of sludge treatment and phosphorus recovery / reuse, and insufficient phosphorus removal in low concentrations. Can be mentioned.

  As a method other than the coagulation precipitation method, an adsorption treatment method of a phosphorus component using a phosphorus adsorbent (see, for example, Patent Document 1) has been attempted. In the adsorption method, aluminum hydroxide gel, magnesium oxide, titanium oxide-activated carbon composite agent, zirconium oxide-activated carbon composite agent, volcanic ash soil, etc. and those modified soil are used as the phosphorus adsorbent, A regeneration method for improving the number of times the adsorbent is used and a desorption method for desorbing and collecting adsorbed phosphorus with high efficiency have been problems in practical use.

Chemical composition formula (1): M _1-x ²⁺ M _x ³⁺ (OH ⁻ ) _{2 + xy} (A ⁿ⁻ ) _{y / n} (where M ²⁺ is Mg ²⁺ , Ni ²⁺ , Zn ²⁺ , Fe ²⁺ , Ca ^At least one divalent metal ion selected from the group consisting of ²⁺ and Cu ²⁺ , M ³⁺ represents at least one trivalent metal ion selected from the group consisting of Al ³⁺ and Fe ³⁺ , and ^{An -} represents a n-valent anion is 0.1 ≦ x ≦ 0.5, a 0.1 ≦ y ≦ 0.5, the composite metal hydroxide where n is represented by 1 or 2). As a method for regenerating a phosphate desorbent relating to the phosphate ion adsorbent, for example, although described in Patent Document 2, further improvement in efficiency has been a problem.

Japanese Patent No. 3131183 JP-A-2005-305343

  The objective of this invention is providing the desorption method which can improve the desorption recovery efficiency of phosphorus in the waste_water | drain process which removes the phosphorus in waste_water | drain with an adsorption agent.

The inventor of the present invention has arrived at the present invention as a result of further intensive studies in view of the above prior art.
That is, the object of the present invention is to
In the method for treating phosphorus-containing wastewater, the removal of the phosphorus component in the phosphorus-containing wastewater is performed using the composite metal hydroxide represented by the following chemical composition formula (1) as an adsorbent for the phosphorus component.
After the phosphorus component is adsorbed on the adsorbent, the adsorbed phosphorus component is desorbed by contacting the adsorbent with an alkaline aqueous solution in which an alkali metal salt excluding carbonate is dissolved at a temperature of 40 to 100 ° C. This can be achieved by the method of desorbing the adsorbent.
[Chemical 1]
M _1-x ²⁺ M _x ³⁺ (OH ⁻ ) _{2 + xy} (A ⁿ⁻ ) _{y / n} (1)
( ^Wherein M ²⁺ represents at least one divalent metal ion selected from the group consisting of Mg ²⁺ , Ni ²⁺ , Zn ²⁺ , Fe ²⁺ , Ca ²⁺ and Cu ²⁺ , and M ³⁺ represents Al ³⁺ and Fe ^3+. At least one trivalent metal ion selected from the group consisting of: An ⁿ⁻ represents an n-valent anion, 0.1 ≦ x ≦ 0.5, and 0.1 ≦ y ≦ 0.5 And n is 1 or 2.)

  According to the desorption method of the present invention, the desorption recovery efficiency of the adsorbed phosphorus component can be improved.

Hereinafter, the present invention will be described in detail.
The present invention improves the desorption recovery efficiency of phosphorus when desorbing the adsorbed phosphorus component in the wastewater treatment in which the phosphorus component which is a eutrophication product in the wastewater is removed by the phosphorus component adsorbent. It is.

Here, the phosphorus adsorbent in the present invention is
Chemical composition formula (1):
M _1-x ²⁺ M _x ³⁺ (OH ⁻ ) _{2 + xy} (A ⁿ⁻ ) _{y / n} (1)
( ^Wherein M ²⁺ represents at least one divalent metal ion selected from the group consisting of Mg ²⁺ , Ni ²⁺ , Zn ²⁺ , Fe ²⁺ , Ca ²⁺ and Cu ²⁺ , and M ³⁺ represents Al ³⁺ and Fe ^3+. At least one trivalent metal ion selected from the group consisting of: An ⁿ⁻ represents an n-valent anion, 0.1 ≦ x ≦ 0.5, and 0.1 ≦ y ≦ 0.5 And n is 1 or 2.), and specifically, for example, can have the following composition.
[Chemical 2]
Mg ²⁺ _0.665 Fe ³⁺ _0.335 OH ⁻ _2.099 Cl ⁻ _0.124 (CO ₃ ²⁻ ) _0.056
[Chemical formula 3]
^{_{Mg 2+ 0.683 Al 3+ 0.317 OH -}} 2.033 Cl - 0.238 (CO 3 2-) 0.023

  As the adsorbent, one having a thickness of 0.01 to 500 μm is used as it is, or supported on a polymer. As the polymer, an aramid resin, an acrylic resin, a vinyl alcohol resin, a cellulose resin, or the like that can be porously formed by wet coagulation is used, but the type of the polymer is not particularly limited. Further, the shape of the adsorbent and the adsorbent-supported polymer molded body is not limited to a circular shape, for example, and can take various shapes.

  In the present invention, after the phosphorus component in the phosphorus-containing wastewater is adsorbed to the adsorbent, the phosphorus component is subsequently desorbed from the adsorbent. As the phosphorus component desorbing liquid from the adsorbent, carbonate is used. An aqueous alkali metal salt solution is used. Here, preferable alkali metal salts include sodium hydroxide, potassium hydroxide, sodium chloride, potassium chloride, sodium fluoride, potassium fluoride, sodium bromide, potassium bromide, sodium sulfate, potassium sulfate, sodium sulfite, and sulfurous acid. Potassium etc. are mentioned, More preferably, sodium chloride is mentioned.

It is characteristic in the present invention that the temperature during this desorption operation is 40 ° C. or more and less than 100 ° C.
Here, “Fifth Amendment Pollution Prevention Technology and Regulations (Water Quality)”, 9th edition, Japan Industrial Environment Management Association, published on April 18, 2003 (first edition, May 20, 1995), 168th Page 2.2.8. In the section of activated carbon adsorption, as it is stated that “the influence of temperature is large in gas-phase adsorption, but the influence of temperature is small enough to be ignored in ordinary water treatment”, in activated water and other normal wastewater treatment. In adsorption and ion exchange, the effect of temperature is negligible. However, when the composite metal hydroxide used in the present invention is used as an adsorbent, it is possible to dramatically increase the phosphorus component desorption recovery rate by specifically raising the phosphorus component desorption liquid temperature. Become. A preferable desorption liquid temperature is 40 ° C. or more and less than 100 ° C. If the temperature is lower than 40 ° C., the effect of improving the phosphorus component desorption / recovery rate due to the temperature swing is not seen so much. If the temperature is 100 ° C. or higher, not only the equipment cost is wasted, but also the improvement in the desorption rate corresponding to the increase in power cost cannot be expected.

  This desorption operation is as described above with respect to the temperature at the time of contact, but the pressure can be employed under any conditions as long as the aqueous solution maintains a liquid phase within the above temperature range. From the viewpoint of stability, cost, etc., it may be set to about 0.1 to 0.5 MPa.

The contact time may be set in any way as long as the phosphorus component can be desorbed. For example, when the contact is performed batchwise, the contact time is about 0.5 to 24 hours. About 0.5 to 6 hours. Examples of the contact method include, but are not particularly limited to, a method of immersing the adsorbent in the alkaline aqueous solution, a method of introducing the alkaline aqueous solution into the tower filled with the adsorbent, and the like.
As for the purity of the alkali metal salt, for example, an industrial salt with a purity standard of 95% can be used, but it is preferable to use a highly pure alkali metal salt because the phosphorus component desorption recovery rate is high.

Desorption is preferably carried out in an alkaline atmosphere of pH 8 or higher, more preferably in an alkaline atmosphere of pH 11 or higher. As the alkaline agent, sodium hydroxide or potassium hydroxide is used, preferably sodium hydroxide is used. Used.
After recovering the alkaline aqueous solution after contact with the adsorbent and adjusting the pH to be in the range of 8 to 11, ammonium ions and magnesium ions are further added to remove phosphorus components as precipitates (phosphorus). It is also possible to reuse the alkaline aqueous solution after removal as the magnesium acid ammonium salt as a desorption liquid or as an alkaline earth metal salt aqueous solution in the regeneration step described later.

Further, after adjusting the recovered alkaline aqueous solution so that the pH is in the range of 4.5 to 13.5, further adding calcium ions to remove the phosphorus component as a precipitate (hydroxyapatite), Since it contains magnesium ion as the alkaline aqueous solution in the step (A), it can be reused as the alkaline earth metal salt aqueous solution in the later-described step (B).
Here, the agent used for the pH adjustment is not particularly defined, but hydrochloric acid, sulfuric acid, etc. can be used as the acid, but hydrochloric acid is preferred. Sodium hydroxide or potassium hydroxide can be used as the alkali.

In the present invention, after the phosphorus component adsorbent is brought into contact with an alkaline aqueous solution and subjected to desorption treatment, the adsorbent is washed with water and brought into contact with an alkaline earth metal salt aqueous solution in order to improve the adsorbent regeneration rate. It is preferable to perform a regeneration process.
Here, the washing with water may be performed under any conditions as long as the alkaline aqueous solution existing inside or on the surface of the adsorbent can be removed. For example, the alkaline aqueous solution may be removed by washing with water vapor.

Next, the alkaline earth metal salt aqueous solution excluding the carbonate for performing the regeneration treatment is preferably an aqueous solution of magnesium chloride, calcium chloride, magnesium sulfate, magnesium bromide, calcium bromide, etc., more preferably magnesium chloride. And magnesium sulfate aqueous solution, more preferably magnesium chloride.
There is no restriction | limiting with respect to purity about an alkaline-earth metal salt, For example, the thing of the purity specification 95% currently sold as an industrial salt can be used.

  The regeneration operation can be easily performed by bringing the adsorbent after washing with water into contact with the alkaline earth metal salt aqueous solution. Any temperature and pressure at the time of contact can be adopted as long as the aqueous solution maintains a liquid phase, but from the viewpoint of process stability, cost, etc., 10 to 40 ° C., 0.1 to 0. What is necessary is just to set to about 5 MPa.

  The contact time may be set as long as the adsorbent can be regenerated. For example, when the contact is performed in a palindromic manner, the contact time is about 0.5 to 20 hours. Is about 0.5 to 5 hours. Examples of the contact method include a method of immersing the adsorbent in the alkaline earth metal salt aqueous solution, a method of charging the alkaline earth metal salt aqueous solution into the tower filled with the adsorbent, and the like. It is not limited.

Further, the phosphorus component in the phosphorus adsorbent is recovered as a water-soluble phosphorus component by desorption of the phosphorus component from the adsorbent with an alkaline earth metal salt aqueous solution and regeneration treatment of the adsorbent.
Therefore, as long as the alkaline aqueous solution is used without being exchanged, the adsorption / desorption operation is a concentration operation of the phosphorus component, that is, the concentration of the phosphorus component in the alkaline aqueous solution can be made much higher than the drainage liquid, and the concentration can be increased. Since it can be removed from the aqueous solution containing the phosphorus component, it can be efficiently recovered.

  In addition, the alkaline earth metal salt aqueous solution is repeatedly used as it is, and when the phosphorus component concentration becomes a certain level or more, the same operation as the removal of the phosphorus component from the alkaline earth metal salt aqueous solution is performed, and the alkaline earth metal again. It can be reused as a metal salt aqueous solution.

  Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto.

[Example 1]
Mg-Al-Cl type hydrotalcite adsorbent with an average particle size of 10 μm (Tonda Pharmaceutical Co., Ltd., TPEX standard product) supported on a meta-aramid polymer (manufactured by Teijin Techno Products Limited, CONEX powder) A spherical molded body having a diameter of 0.5 to 1.0 mm (hydrotalcite: meta-aramid polymer = 90 wt%: 10 wt%), and a molded body having a hydrotalcite weight of 31.8 g with a phosphorus concentration of 933 mg / L It was immersed in 1 L of the solution and stirred at 200 rpm using a propeller blade to adsorb phosphorus for 3 hours. The amount of phosphorus adsorbed was 27.1 mg per 1 g of hydrotalcite.
Here, the Mg-Al-Cl type hydrotalcite adsorbent is a phosphate ion adsorbent, and the phosphorus concentration in FIG. 1 is determined by quantifying the phosphate ion concentration using the molybdenum blue method, It is converted into concentration.
Next, 5.3 g by weight of hydrotalcite was adsorbed with phosphorus adsorbed into 100 mL of 49 ° C. desorption solution in which 34 g of sodium chloride having a purity of 99% or more and 1 g of sodium hydroxide were dissolved in 100 g of water, and 60 minutes. Stir.
Every predetermined time, the phosphorus concentration in the aqueous solution was measured, and the phosphorus desorption rate was evaluated. The result is shown in FIG.

[Example 2]
Adsorption and desorption were carried out in the same manner as in Example 1 except that the sodium chloride used in the desorption solution was industrial sodium chloride having a purity of 98.6%, and the phosphorus desorption rate was evaluated. The result is shown in FIG.

[Example 3]
Adsorption / desorption was carried out in the same manner as in Example 2 except that the temperature of the desorption solution was set at 76 ° C., and the phosphorus desorption rate was evaluated. The result is shown in FIG.

[Comparative Example 1]
Adsorption and desorption were carried out in the same manner as in Example 1 except that the temperature of the desorption solution was 19 ° C., and the phosphorus desorption rate was evaluated. The result is shown in FIG.

[Comparative Example 2]
Adsorption / desorption was carried out in the same manner as in Example 2 except that the temperature of the desorption solution was 19 ° C., and the phosphorus desorption rate was evaluated. The result is shown in FIG.

It is a graph of the desorption performance evaluation of the desorption reproduction | regeneration method by this invention, and comparative evaluation.

Claims (7)

In the method for treating phosphorus-containing wastewater, the removal of the phosphorus component in the phosphorus-containing wastewater is performed using the composite metal hydroxide represented by the following chemical composition formula (1) as an adsorbent for the phosphorus component.
After the phosphorus component is adsorbed on the adsorbent, the adsorbed phosphorus component is desorbed by contacting the adsorbent with an alkaline aqueous solution in which an alkali metal salt excluding carbonate is dissolved at a temperature of 40 to 100 ° C. , Adsorbent desorption method.
[Chemical 1]
M _1-x ²⁺ M _x ³⁺ (OH ⁻ ) _{2 + xy} (A ⁿ⁻ ) _{y / n} (1)
( ^Wherein M ²⁺ represents at least one divalent metal ion selected from the group consisting of Mg ²⁺ , Ni ²⁺ , Zn ²⁺ , Fe ²⁺ , Ca ²⁺ and Cu ²⁺ , and M ³⁺ represents Al ³⁺ and Fe ^3+. At least one trivalent metal ion selected from the group consisting of: An ⁿ⁻ represents an n-valent anion, 0.1 ≦ x ≦ 0.5, and 0.1 ≦ y ≦ 0.5 And n is 1 or 2.)   The desorption method according to claim 1, wherein the pH of the alkaline aqueous solution is 8 to 14.   After bringing the adsorbent into contact with the alkaline aqueous solution, the alkaline aqueous solution is recovered and adjusted so that the pH is in the range of 8 to 13. Further, ammonium ions and magnesium ions are added to remove phosphorus components as precipitates. The desorption method according to claim 1, wherein the desorption method is reused as an alkaline aqueous solution.   After contacting the adsorbent with the alkaline aqueous solution, the alkaline aqueous solution is recovered, adjusted to have a pH in the range of 4.5 to 13.5, and further added with calcium ions as a phosphorus component as a precipitate. The desorption method according to claim 1, wherein the method is removed and reused as an alkaline aqueous solution.   A method for regenerating an adsorbent, wherein the adsorbent after contacting with the alkaline aqueous solution according to claim 1 is further washed with water and contacted with an alkaline earth metal salt aqueous solution excluding carbonate.   After bringing the adsorbent into contact with the alkaline aqueous solution, the alkaline aqueous solution is recovered and adjusted so that the pH is in the range of 8 to 13. Further, ammonium ions and magnesium ions are added to remove phosphorus components as precipitates. The recycling method according to claim 5, wherein the regeneration method is reused as an aqueous alkali metal salt solution excluding carbonate.   After contacting the adsorbent with the alkaline aqueous solution, the alkaline aqueous solution is recovered, adjusted to have a pH in the range of 4.5 to 13.5, and further added with calcium ions as a phosphorus component as a precipitate. The regeneration method according to claim 5, wherein the regeneration method is removed and reused as an aqueous alkali metal salt solution excluding carbonate.

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