JP2008006404A - Method for treating phosphorus-containing waste water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the production of a precipitate in regeneration, in desorbing a phosphorous component from an adsorbent adsorbed with the phosphorous component to regenerate the adsorbent for recycle, when removing a phosphorous component contained in phosphorous-containing waste water using the adsorbent. <P>SOLUTION: A method for treating phosphorus-containing waste water comprises: a removal step of removing the phosphorus component contained in phosphorus-containing waste water by using the adsorbent consisting of specific compound metal hydroxide; a desorption step of desorbing the adsorbed phosphorus component from the phosphorus component-adsorbed compound metal hydroxide; and a recovery step of recovering the capacity of the compound metal hydroxide for adsorbing the phosphorus component. After each of the desorption step and the recovery step is carried out, the resulting compound metal hydroxide is washed with water until the pH of the used washing water becomes 11 or less. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for treating phosphorus-containing wastewater that removes a phosphorus component contained in phosphorus-containing wastewater. More specifically, regarding wastewater treatment for human waste, sewage, food processing wastewater and factory wastewater, livestock manure, etc., the adsorbent that adsorbs the phosphorus component when removing the phosphorus component contained in the wastewater using the adsorbent. Thus, the present invention relates to a method for suppressing the generation of precipitates during regeneration when desorbing a phosphorus component to regenerate and reuse an adsorbent.

  In recent years, organic substances, nitrogen, phosphorus, etc. contained in large quantities in rivers, various industrial wastewater or domestic wastewater, are cited as factors of eutrophication that leads to water pollution of lakes and marshes that promote the generation of algae and red tide in the nearby sea. It has been. 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, it should be studied in the future, such as spillage of salt derived from the flocculant due to the addition of the flocculant, problems of sludge treatment and phosphorus component recovery / reuse, and insufficient phosphorus component removal at low concentrations. There are challenges. As a method other than the coagulation precipitation method, an adsorption treatment method of a phosphorus component using an adsorbent (for example, see Patent Document 1) has been attempted.

  In this adsorption treatment method, aluminum hydroxide gel, magnesium oxide, titanium oxide-activated carbon composite agent, zirconium oxide-activated carbon composite agent, volcanic ash soil, etc., or modified soils are used as the phosphorus adsorbent. However, it is essential that the adsorbent can be used repeatedly.

In this repeated use, it has been proposed to use a chemical such as an aqueous alkali solution, alkali metal salt, or alkaline earth metal salt as a regeneration treatment of the adsorbent (see, for example, Patent Document 2). Solids may precipitate during processing, causing increased pressure loss in the adsorbent column and drift in the column. If the pressure loss increases, the throughput will greatly drop below the economic process flow rate, and eventually the column will be completely removed. Will be blocked.
Increased pressure loss and drift in the column can no longer express the inherent ability of the phosphorus adsorbent in repeated continuous wastewater treatment, and therefore, establishment of a water washing method to avoid these problems has been required.

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

  The object of the present invention is to eliminate the problems of the above prior art and remove the phosphorus component contained in the phosphorus-containing wastewater by using the adsorbent. In order to regenerate and reuse the adsorbent by desorbing the adsorbent, it is to provide a method for suppressing the formation of precipitates during regeneration.

  The inventors of the present invention have reached 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 treatment of 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.
In each of the step of desorbing the phosphorus component from the composite metal hydroxide after adsorbing the phosphorus component and the step of regenerating the phosphorus component adsorption capacity of the composite metal hydroxide, the composite metal hydroxide is converted into a composite metal hydroxide after each step. On the other hand, it can be achieved by a waste water treatment method characterized by performing a water washing treatment until the pH of the water after washing becomes 11 or less.
[Chemical 1]
M _1-x ² + Mx ³⁺ (OH ⁻ ) _{2 + xy} (An ⁻ ) _{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 present invention, when removing the phosphorus component contained in the phosphorus-containing wastewater using the adsorbent, the phosphorus component is desorbed from the adsorbent that has adsorbed the phosphorus component, and the adsorbent is regenerated and reused. Since it is possible to suppress the formation of precipitates during regeneration, for example, it is possible to prevent an increase in pressure loss and a drift due to the formation of a column blockage when the column is filled with an adsorbent and wastewater treatment is performed. .

Hereinafter, the present invention will be described in detail.
The phosphorus adsorbent in the present invention is the following chemical composition formula (1)
[Chemical 2]
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.), for example,
[Chemical formula 3]
Mg ²⁺ _0.665 Fe ³⁺ _0.335 OH ⁻ _2.099 Cl ⁻ _0.124 (CO ₃ ²⁻ ) _0.056
Or
[Chemical formula 4]
^{_{Mg 2+ 0.683 Al 3+ 0.317 OH -}} 2.033 Cl - 0.238 (CO 3 2-) 0.023
The composition such as can be taken.

  The adsorbent having an average particle size of 0.01 to 500 μm can be used as the above inorganic material or supported on a polymer, and the polymer is an aramid type that can be porously formed by wet coagulation. Resin, acrylic resin, vinyl alcohol resin, cellulose resin, and the like are used, but the type of 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 step of desorbing the phosphorus component after adsorbing the phosphorus component to the adsorbent and the step of regenerating the phosphorus component adsorption capacity of the composite metal hydroxide, after each step, the composite metal hydroxide It is necessary to perform a water washing treatment until the pH of the water after washing becomes 11 or less. In the case where water washing is not performed until the pH of the water after washing becomes 11 or less, precipitates are generated during the subsequent adsorbent regeneration treatment, further regeneration treatment and re-adsorption treatment. Column clogging is generated when the agent is filled in the column and wastewater treatment is performed, and the pressure loss increases.

  Here, the water washing may be performed under any conditions as long as the alkaline aqueous solution or the alkaline earth metal salt aqueous solution existing in or on the surface of the adsorbent can be removed. For example, it may be removed by washing with water vapor.

  The pH of the water after washing is preferably 11 or less, more preferably 10.5 or less. In addition, in order to prevent decomposition | disassembly of adsorption agent, it is necessary to be pH1.5 or more, However As long as it is washed with water, there is no possibility of becoming this pH.

Hereinafter, it demonstrates further concretely along a process based on 1 aspect of this invention.
In the present invention, the phosphorus component in the phosphorus waste water is adsorbed to the adsorbent, and then the phosphorus component is desorbed from the adsorbent. The phosphorus component desorbed liquid from the adsorbent is excluded from carbonate. An alkaline aqueous solution in which an alkali metal salt is dissolved can be preferably used. Preferred alkali metal salts include sodium hydroxide, potassium hydroxide, sodium chloride, potassium chloride, sodium fluoride, potassium fluoride, sodium bromide, odor Potassium fluoride, sodium sulfate, potassium sulfate, sodium sulfite, potassium sulfite and the like can be mentioned, and sodium chloride is more preferable.

  The desorption operation can be easily performed by bringing the adsorbent into contact with an alkaline 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.

  Further, desorption is preferably performed in an alkaline atmosphere having a pH of 11 or more, and sodium hydroxide or potassium hydroxide is used as the alkaline agent, but sodium hydroxide is preferably used.

  After the desorption regeneration treatment with the alkali metal salt aqueous solution, the adsorbent is washed with water. As described above, the water washing needs to be performed until the pH of the treated washing water after contacting the adsorbent becomes 11 or less. When washing with water is completed at pH 11 or higher, precipitates are generated during the subsequent regeneration treatment with the alkaline earth metal salt aqueous solution. Therefore, particularly when the column is filled with an adsorbent and wastewater treatment is performed, column clogging is generated. Pressure loss increases.

  Subsequently, in order to regenerate the composite metal hydroxide after completion of the water washing, it can be easily performed by bringing it into contact with an alkaline earth metal salt aqueous solution excluding carbonate, and an alkaline earth metal salt aqueous solution. Preferred examples include aqueous solutions of magnesium chloride, calcium chloride, magnesium sulfate, magnesium bromide, calcium bromide, etc., more preferred examples include magnesium chloride and aqueous magnesium sulfate solution, and more preferred examples include magnesium chloride.

  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.

  After the regeneration treatment with the alkaline earth metal salt, the adsorbent is washed with water, and as described above, washing with water is necessary until the pH of the treated washing water after contacting the adsorbent becomes 11 or less. When washing with water is completed at a pH of 11 or more, precipitates are generated during the subsequent adsorption treatment of the phosphorus component. In particular, when the column is filled with an adsorbent and wastewater treatment is performed, column clogging is generated and pressure loss increases. .

  After completion of washing with water, the phosphorus component adsorption in the wastewater is resumed, and by repeating the above adsorption, desorption regeneration with an aqueous alkali metal salt solution, washing with water, and regeneration with an alkaline earth metal salt aqueous solution, the phosphorus component adsorbent is not changed each time. It becomes possible to treat waste water.

  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%) was filled in a 48 mL column with 18 g of the hydrotalcite weight, and a phosphorous concentration of 5 mg. The solution of / L was passed at 4 mL / min until the phosphorus concentration in the treatment solution after passing through the column reached 1 mg / L or more.
Here, the Mg-Al-Cl type hydrotalcite adsorbent is an adsorbent of phosphate ions, and the phosphorus concentration is determined by quantifying the phosphate ion concentration using the molybdenum blue method, and the value is converted to the phosphorus concentration. Measured.

Next, sodium chloride: sodium hydroxide: water = 34 wt: 1 wt: 100 wt alkali metal salt aqueous solution was passed through the column at 4 mL / min for 120 minutes.
After 120 minutes, ion exchange water was passed at 8 mL / min until the pH of the rinsing water after passing through the column was 11 or less. The washing time was 90 to 120 minutes.

Next, magnesium chloride hexahydrate: water = 74.9 wt: 100 wt. Alkaline earth metal salt aqueous solution was passed through the column at 4 mL / min for 120 minutes.
After 120 minutes, ion exchange water was passed through the column at 8 mL / min. In the case of a magnesium chloride aqueous solution, the pH of the rinsing water in the treated water did not become 11 or more, so the rinsing was completed in 60 minutes.

  The operations of adsorption, desorption regeneration with alkali metal salt, water washing, regeneration with alkaline earth metal salt, and water washing were repeated five times. The column pressure loss average value and the adsorption capacity at each number of adsorption are shown in FIG. The adsorption capacity is converted to a phosphorus adsorption amount (mg) per 1 g of hydrotalcite.

[Comparative Example 1]
Phosphorus adsorption and alkali metal were carried out in the same manner as in Example 1 except that the washing time after passing the aqueous alkali metal salt solution was 30 minutes and the washing was terminated when the pH of the treated washing water was 12 to 12.7. The operations of desorption regeneration with salt, water washing, regeneration with alkaline earth metal salt, and water washing were repeated 5 times. The column pressure loss average value and the adsorption capacity at each number of adsorption are shown in FIG. The adsorption capacity is converted to a phosphorus adsorption amount (mg) per 1 g of hydrotalcite.

The present invention relates to wastewater treatment for human waste, sewage, food processing wastewater and factory wastewater, livestock manure, etc., adsorbing phosphoric acid in the wastewater by the adsorbent, desorbing phosphoric acid from the adsorbent and regenerating the adsorbent Thus, in the continuous drainage treatment using a column that is repeatedly reused for adsorption, it is possible to prevent an increase in column pressure loss and a drift due to the formation of a column blockage.
As a result, it is possible to prevent a decrease in the amount of wastewater treatment due to an increase in pressure loss, to prevent an increase in equipment due to an increase in the required pump capacity, and to prevent a phosphorus adsorbent capacity from being suppressed due to drift.

It is a graph of the pressure loss fluctuation | variation at the time of the repetition phosphorus adsorption | suction at the time of the water washing method implementation by this invention, and adsorption capacity fluctuation | variation, and comparative evaluation.

Claims (3)

In the treatment of 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.
In each of the step of desorbing the phosphorus component from the composite metal hydroxide after adsorbing the phosphorus component and the step of regenerating the phosphorus component adsorption capacity of the composite metal hydroxide, the composite metal hydroxide is converted into a composite metal hydroxide after each step. On the other hand, the waste water treatment method characterized by performing a water washing process until the pH of the water after washing becomes 11 or less.
[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 wastewater treatment method according to claim 1, wherein the process of regenerating the desorption and adsorption capacity of the phosphorus component from the composite metal hydroxide is performed by sequentially passing the following steps.
Step (1): A step of bringing the composite metal hydroxide into contact with an alkaline aqueous solution in which an alkali metal salt excluding carbonate is dissolved.
Step (2): Step of washing the composite hydroxide after passing through step (1) until the pH of the washed water becomes 11 or less.
Step (3): A step of bringing the composite metal hydroxide after the water washing into contact with an alkaline earth metal salt aqueous solution excluding carbonate.
Step (4): Step of washing the composite hydroxide after passing through step (3) until the pH of the washed water becomes 11 or less.   The wastewater treatment method according to claim 2, wherein the pH of the alkaline aqueous solution is 11 or more.

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