JPS59150593A - Catalytic dephosphorization - Google Patents

Abstract

PURPOSE:To efficiently remove phosphoric acid while enhancing the power of a dephosphorizing agent, by circulating a liquid to be treated into a packed column packed with the dephosphorizing agent containing a phosphate mineral after being catalytically treated with an aqueous alkali solution in which an oxidizing agent is coexistent. CONSTITUTION:After a calcium agent is optionally added to raw water, from which floating substance is previously removed by the operation of pretreatment, in response to the concentration of a soluble phosphate in said raw water, a pH is adjusted to 6.0-11.0. Then, the raw water is introduced through an inflow pipe 1 for raw water into the upper part of a dephosphorizing column 2. The dephosphorizing column 2 is packed with a crushed phosphate mineral containing calcium phosphate as a catalytic dephosphorizing agent 3. The raw water flowing in contact with the catalytic dephosphorizing agent 3 is discharged through an outflow pipe 4. The catalytic dephosphorizing agent 3 in the column is continuously or intermittently introduced into a reaction tank 6 and catalytically treated by agitating it with an aqueous alkali solution, in which an oxidizing agent is coexistent, supplied from a tank 14 by an agitator 8.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for removing acid salts present in tap water, sewage, human waste water, industrial water, factory wastewater, boiler water, and all other liquids, specifically catalytic dephosphorization. This invention relates to a method for improving the ability of a catalytic dephosphorization material used when removing soluble phosphoric acid groups using a catalytic dephosphorization material.

In general, the above-mentioned heavy liquids discharged into natural water systems contain inorganic phosphates, various condensed phosphates, and organic phosphates in various states. The presence of these phosphates is a factor that induces the occurrence of "blue water" and "red tide" in closed or stagnant waters such as lakes, inland seas, and inner bays. Biological slime and chemical scale are formed in the pipes, which is a major cause of accidents.

-3- Therefore, various phosphorus removal methods are being considered in order to remove the phosphates present in these liquids. A cylindrical or conical dephosphorization tower is filled with a catalytic dephosphorization material containing calcium phosphate having a certain particle size, and the pH of the liquid to be treated is adjusted to a range of 6 to 11. Calcium hydroxyapatite is added to the surface of the catalytic dephosphorization material by adding a calcium agent such as calcium chloride in accordance with the concentration of soluble phosphates contained in the catalytic dephosphorization material and bringing it into contact with the catalytic dephosphorizer at a constant flow rate. We proposed a method to remove soluble phosphates by crystallizing and fixing the crystals.

A typical chemical reaction on the surface of the catalytic dephosphorizing material in this method is as follows.

If such a dephosphorization/method is applied, it is extremely easy to separate and dewater the catalytic dephosphorization material to which calcium hydroxyapatite is fixed. 59-150593(
2) It is an excellent dephosphorization technology that not only does not require conventional sludge treatment facilities such as thickeners, dehydrators, and dryers, but also can recover phosphorus as a resource.

However, when the conventional catalytic dephosphorization method is applied to various types of wastewater, there are the following drawbacks.

In other words, when the liquid to be treated contains many highly adsorbable substances such as chromaticity components and organic substances, these substances adhere to the surface of the dephosphorizing material at the same time as apatite crystallizes, inhibiting the phosphorus removal reaction. There were cases where it was significantly inhibited.

The catalytic dephosphorization method is a method in which a calcium agent is added under appropriate pH conditions, and the soluble phosphates contained in the solution are fixed as calcium hydroxyapatite crystals on the surface of the dephosphorization material. The surface condition greatly affects the crystallization reaction. Therefore, the coating of the surface of the furnace material with the adsorbed substance causes a decrease in the dephosphorization activity and the rate of apatite formation, resulting in the loss of the initial dephosphorization performance. Adsorbed substances are concentrated in the liquid to be treated 5
- If operation is continued that deviates from the optimal pH adjustment and calcium addition conditions for apatite formation, the coating of the surface of the dephosphorizing material with adsorbed substances will be further promoted, significantly interfering with the crystallization reaction. , which would have a fatal impact on the functionality of the catalytic dephosphorization method.

As a solution to this problem, it has been confirmed that cleaning the catalytic dephosphorizing material with a reduced phosphorus removal ability with an alkaline aqueous solution is effective, but subsequent research has shown that If certain organic substances are present in the solution, even if the above method is applied, no significant effect may be obtained, and it has not been a satisfactory solution.

It is an object of the present invention to provide a method that eliminates the above-mentioned problems in the catalytic dephosphorization method and more effectively improves the dephosphorizing ability of a dephosphorizing material to remove phosphorus.

That is, the present invention provides a method for removing phosphates present in a solution by passing a solution to be treated through a catalytic dephosphorizing material containing calcium 9/acid. It is characterized in that the dephosphorization ability of the catalytic dephosphorization material is improved by contact treatment with a coexisting alkaline aqueous solution.

An embodiment of the present invention will be described below based on the drawings.
First, if there is a large amount of suspended solids in the liquid to be treated,
This floating material is removed in advance through a sedimentation tank or offshore filter tank.

The raw water from which suspended solids have been removed in advance through pretreatment is treated with an acidic or alkaline pH adjuster, after which a calcium agent is added according to the concentration of soluble phosphate in the raw water as necessary. The pH is adjusted to 6.0 to 11.0, and the raw water is introduced from the inlet pipe 1 to the upper part of the dephosphorization tower 2. In this dephosphorization tower 2, a catalytic dephosphorization material 6 is prepared by crushing and sieving phosphate minerals containing calcium phosphate to a certain particle size.
The raw water descends while coming into contact with this catalytic dephosphorization material 6, and is led out of the tower from the treated water outflow pipe 4.

Instead of phosphate minerals as the catalytic dephosphorization material 3, materials such as carmacium phosphate supported on the surface of bone char, coral sand, sand, etc. can also be used.

In such a dephosphorization operation, impurities such as chromaticity and organic matter in the raw water are adsorbed to the catalytic dephosphorizing material 6, which deteriorates the surface activity of the catalytic dephosphorizing material 60 and reduces the dephosphorizing function. Simultaneously with the passage of raw water to the phosphor tower 2 or after a certain period of time, the catalytic dephosphorizing material 3 in the tower is continuously or intermittently fed into the reaction tank 6 from the take-out pipe 5. In the reaction tank 6, the alkali aqueous solution in which the oxidizing agent coexists is supplied from the tank 14 by the pump 7, and is occasionally stirred by the stirrer 8 for contact treatment. After this contact treatment has been completed, the alkaline aqueous solution containing the oxidizing agent is discharged from the drain pipe 9.

The alkaline agent used in the above contact treatment may be caustic soda, potassium hydroxide, slaked lime, or magnesium hydroxide. Further, the oxidizing agent may be H2O, O3, or Na01O, and these can also be used in combination.

Next, treated water is introduced into the reaction tank 6 as cleaning water from the treated water introduction pipe 10, and the catalytic dephosphorization material 6 is
50593(3) After the wastewater is washed until I)H no longer rises, it is returned to the dephosphorization tower 2 by the pump 11, and the washed wastewater is discharged from the drain pipe 9. However, this washing step may be omitted depending on the type of raw water to be dephosphorized.

Furthermore, the dephosphorization ability of the catalytic dephosphorizing material 3 can be increased by performing the same operation as the contact treatment outside the tower in the dephosphorizing tower 2 without leading the catalytic dephosphorizing material 6 outside the tower. can. In this case, the alkaline aqueous solution containing the oxidizing agent used in the contact treatment is passed through the dephosphorization tower 2 in an upward flow from the inflow pipe 12 to the outflow pipe 16, so that the catalytic dephosphorization material 6 expands and becomes fluidized. It is more effective if the contact is made under suitable conditions.

As described above, according to the present invention, the dephosphorizing effect of the catalytic dephosphorizing material is extended by contacting the catalytic dephosphorizing material with an alkaline aqueous solution in which an oxidizing agent coexists as necessary during the dephosphorizing operation. It was possible to maintain a good condition for a long period of time, making it possible to perform stable dephosphorization treatment.

Next, examples of the present invention will be shown.

Example (1) Phosphate rock was crushed and sieved in a cylindrical dephosphorization tower with an inner diameter of 100 mm and an effective depth of 2.5 m (effective diameter of 0.5 m).
For 44 hours, a uniformity factor of 1.4) was filled with a thickness of 1000.

Secondary treated water obtained by treating food factory wastewater with coarse solids separated by the activated sludge method was used as the liquid to be treated, and the pH of the liquid to be treated was adjusted to around 9.0 with caustic soda, and calcium chloride was added as a calcium agent. is used, and the weight ratio of Oa/P04 is adjusted to 1 depending on the concentration of soluble phosphates in the liquid to be treated.
．． It was added in a range of 0 to 15. This liquid to be treated is introduced into the dephosphorization tower and is passed downward from above to LV=2.
Water was passed through at a flow rate of 0 m/H.

Once a month + H2ot for 100m in the catalytic dephosphorization tower
A caustic soda solution adjusted to a pH of 1 liter and containing 100 g/g/g was introduced, and the catalytic dephosphorizing material was immersed in the solution for about 24 hours for contact treatment. Approximately 1 hour while periodically performing the above contact treatment operation.
A water flow experiment was conducted for two months. The results are shown in Table-1.

-10- Table-1 As is clear from Table-1, the filled catalytic dephosphorization material was
Even after 12 months, the phosphorus concentration of the treated water passed through the alkali contact treatment in the coexistence of 2O, 2mg/
1 was maintained, and no decrease in dephosphorization performance was observed. On the other hand, as a comparative example, when a catalytic dephosphorization material was contacted with only alkali and the treatment was continued for 12 months under the same conditions, the results were also shown in Table 1. The quality of the treated water deteriorated significantly compared to the initial stage of water flow, and the performance was close to that of untreated reactor material.

Example (2) Raw water prepared under the same conditions as Example (1) was passed through the water for 12 months, and the catalytic dephosphorization material with decreased phosphorus removal performance was extracted from the dephosphorization tower, and 100 mg/H2O was added. , pH
A contact treatment was carried out by immersing the sample in an alkaline water bath liquid whose pH was adjusted in the range of 8.5 to 12 for about 24 hours. In this case, 630 CC of contact dephosphorization material was used, and the contact treatment was performed with a bee force of 1 t.

After washing with water, the dephosphorization materials contact-treated under each I)H condition were packed in a dephosphorization tower with an inner diameter of 40 m and packed with a thickness of about 50 m (1 m thick).
LV = 1.0 m/l under the same conditions as Example (1)
(Water was passed through the tubes for about one month, and the phosphorus removal performance was compared. The results are shown in Table 2.

The following margin is JP-A-59-150593 (4) Table 2 As is clear from Table 2, when the catalytic dephosphorization material is treated with alkali in the coexistence of Hlo, the higher the pH of the alkaline aqueous solution, the better the cleaning effect. There is a tendency that pH9,
For those treated with 5 or more, stable treated water was obtained even after passing 1 ton of water for a month, confirming the effect of the present invention.

Example (3) Raw water prepared under the same conditions as Example (1) was passed through for 12 months, and the catalytic dephosphorization material with reduced phosphorus removal performance was extracted from the dephosphorization tower. , O5°Na01O were added at 100 mg/l each, and the sample was immersed in a solution adjusted to pH 11 with caustic soda for about 24 hours for contact treatment. In this case, the catalytic dephosphorization material is 630cc
The contact treatment was carried out using a bead force of 1 t.

After washing with water, the dephosphorization material contact-treated with each cleaning solution was packed into a dephosphorization tower with an inner diameter of 40 mm to a thickness of about 50 m + LV.
= 1.0 m/)l and the other conditions were the same as in Example (1) for about one month, and the phosphorus removal performance was compared. Display the results -
Shown in 3.

Table 3 -14- As is clear from Table 3, the water quality after 1 ton of treatment was stable regardless of whether H, 0, O, or Na01O was used as the oxidizing agent added to the alkali. I was able to confirm that it was obtained.

[Brief explanation of the drawing]

The drawing is a flow sheet of one embodiment of the invention. 1... Raw water inflow pipe, 2... Dephosphorization tower, 3... Catalytic dephosphorization material, 4... Treated water outflow pipe, 5... Takeout pipe, 6
・・・Reaction tank, 7... Pump, 8... Stirrer, 9...
... Drain pipe, 10 ... Treated water introduction pipe, 11 ... Pump, 12 ... Inflow pipe, 13 ... Outflow pipe, 14 ...
tank.

Claims (1)

[Scope of Claims] 1. In a method for removing phosphorus from a liquid to be treated by passing a liquid to be treated through a tank filled with a dephosphorizing material containing a phosphate mineral, the dephosphorizing material is oxidized. A catalytic dephosphorization method characterized in that the dephosphorization ability of the dephosphorization material is improved by contact treatment with an alkaline aqueous solution in which a dephosphorization agent coexists. 2. The method according to claim 1, wherein the pH of the alkaline aqueous solution is 9.5 or higher. 3. The method according to claim 1, wherein the oxidizing agent is at least one of H, 0, 03, and Na01O. 4. After the dephosphorization material is continuously or intermittently taken out of the filling tank and subjected to contact treatment with the aqueous alkali solution,
The method according to claim 1, 2 or 3, wherein the material is returned to the filling tank. 2-5. Contact treatment of the dephosphorizing material with an alkaline aqueous solution,
The method according to claim 1, 2 or 3, wherein the method is carried out in the filling tank.