JP2001300552A - Dephosphorizing material and dephosphorizing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dephosphorizing material excellent in dephosphorizing performance and capable of restraining the pH when water is made to pass initially from being excessively raised and stably removing a phosphate ion over a long period of time and to provide a method for removing phosphorus from the wastewater containing the phosphate ion by using the dephosphorizing material. SOLUTION: This dephosphorizing material consists of a hydrate of calcium silicate subjected to carbonation treatment. This dephosphorizing method comprises making the wastewater containing the phosphate ion pass through a column packed with the dephosphorizing material and subjecting the wastewater thus treated to aeration treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a dephosphorizing material and a dephosphorizing method for removing phosphate ions in wastewater.

[0002]

2. Description of the Related Art Phosphate is a causative substance that causes eutrophication of water quality. Therefore, there is a demand for removing phosphorus from wastewater, and wastewater treatment using a septic tank is not an exception.
Some sewage treatment plants have already introduced a phosphorus removal process using a biological dephosphorization method.However, since this method assumes that sludge containing excessive phosphorus is frequently withdrawn, it takes more than several months. It cannot be applied to septic tanks that do not remove sludge.

On the other hand, as a method for removing phosphorus from wastewater, a coagulation sedimentation method and an adsorption method have been proposed. However, the coagulation sedimentation method requires a large amount of sludge and requires frequent extraction. There is a problem that the operation of replacing and regenerating the adsorbent must be performed frequently, and application to a septic tank is not practical.

[0004] On the other hand, the crystallization method is a method in which phosphate ions in the wastewater are removed by causing hydroxyapatite crystals to grow in the presence of seed crystals in the wastewater containing phosphate ions. Expected as almost no way.

For this reason, various seed crystals have been proposed.
Japanese Patent Application Laid-Open No. Hei 10-235344 proposes a method using calcium silicate hydrate obtained by mixing siliceous and calcareous materials and performing a hydrothermal reaction as a seed crystal. Although this seed crystal exhibits excellent dephosphorization performance, it is inevitable that unreacted raw materials remain in this method.
There was a problem that H was too high. If the pH is too high, the dephosphorization column may be clogged due to the agglutination reaction.In addition, the treated water cannot be discharged as it is, and even if some pH reduction measures are taken after the dephosphorization step, the initial It is difficult to respond to an excessive rise in

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above problems, and has excellent dephosphorization performance.
Provided are a dephosphorizing material capable of suppressing an excessive increase in pH at the beginning of water passage and capable of stably removing phosphate ions for a long period of time, and a method for dephosphorizing wastewater containing phosphate ions using the same. Things.

[0007]

The dephosphorizing material of the present invention is characterized in that it is made of carbonated calcium silicate hydrate.

The calcium silicate hydrate functions as a seed crystal on which hydroxyapatite is crystallized, and is composed of tobermorite, zonotlite, fillet brandite,
Affilite, gyrolite, wollastonite and the like may be mentioned, and a mixture thereof may be used.

Among the above-mentioned calcium silicate hydrates, tobermorite is particularly preferred in that it works well as a crystallization site.

The above-mentioned calcium silicate hydrate can be obtained by mixing siliceous and calcareous materials together with water and subjecting them to a hydrothermal reaction under high temperature and high pressure. As the siliceous and calcareous components, silica stone, diatomaceous earth, silicate clay, blast furnace slag, fly ash, cement, gypsum, quicklime and the like can be used. As a method of causing a hydrothermal reaction under the above high temperature and high pressure, a method using an autoclave is exemplified. In an autoclave, it is preferable to allow the hydrothermal reaction to proceed at 100 to 250 ° C. and 0.2 to 3 Mpa. The above pressure means a gauge pressure value.

The above carbonation treatment can be carried out by placing calcium silicate hydrate in a carbon dioxide atmosphere for a certain period of time. Further, the processing time can be shortened by performing the processing under a pressurized condition. The processing time is, for example, 2 hours or more under normal pressure, 1 Mpa under pressure,
The processing may be performed for 30 minutes or more. The upper limit of the treatment time is not particularly limited. For example, the calcium silicate hydrate may be left closed just before use in a state of being sealed in a carbon dioxide atmosphere, and may be opened at the time of use. In the above autoclave, by setting the atmosphere at the time of the hydrothermal reaction to carbon dioxide,
The hydrothermal reaction and the carbonation treatment may be performed simultaneously. The carbon dioxide atmosphere in which the carbonation treatment of the present invention is performed means an atmosphere in which carbon dioxide occupies at least 50% by volume or more.

The above calcium silicate hydrate is preferably granulated or pulverized to an appropriate particle size from the viewpoint of use as a dephosphorizing material. In addition, the carbonation treatment is preferably performed after granulation or pulverization to an appropriate particle size, since carbonation can be performed uniformly. If the particle size of the calcium silicate hydrate is less than 1 mm, clogging is likely to occur, and if it exceeds 30 mm, a large-volume column must be prepared to secure the surface area required for the crystallization reaction. Therefore, the thickness is preferably 1 to 30 mm. further,
The larger the surface area of calcium silicate hydrate is, the more preferable it is in terms of dephosphorization efficiency.

[0013] The dephosphorization method of the present invention is characterized in that aeration treatment is carried out after passing a wastewater containing phosphate ions through a column filled with the above dephosphorization material.

In the column, a supply material of calcium or hydroxyl ions may be used in combination with the phosphorus removal material.
Specifically as the above-mentioned supply material, cement hydrate, gypsum,
And minerals containing calcium oxide.

The volume of the wastewater containing phosphate ions that passes through the column preferably has a space velocity (SV) of 0.5 to 3 [/ h] in consideration of the crystallization reaction speed. In consideration of the phosphate ion concentration and the flow rate of the wastewater, the column length and the packing amount of the complex may be set so as to satisfy the above SV. In addition, the SV
May be achieved.

In the dephosphorization method of the present invention, aeration treatment is performed after passing the wastewater containing phosphate ions through the column filled with the dephosphorization material. By performing the aeration treatment, carbon dioxide in the air is dissolved in the treated water, and the pH of the discharged water can be suppressed. Usually, in the case of a septic tank, there is an aerobic tank and an aeration equipment is provided, so if the aeration tank of the aerobic tank is diverted and guided immediately before discharge, the pH is required without increasing the equipment in particular. It is possible to lower to the level.

The method for removing phosphorus according to the present invention is not particularly limited, and can be applied to septic tanks, sewage treatment plants, rivers, industrial wastewater treatment facilities, and the like, which are objects requiring removal of phosphate ions. In particular, it is preferable to be used for a septic tank because the equipment is simple and has a configuration suitable for small-scale processing. When used as a septic tank, after the biological treatment step, after passing through the column filled with the dephosphorizing material, it may be subjected to aeration treatment and discharged. The biological treatment step is not particularly limited, and examples thereof include an activated sludge method and a contact aeration method used in a general septic tank.

(Action) In the present invention, calcium silicate hydrate is carbonated to have excellent dephosphorization performance, and at the same time as the initial pH of water flow derived from the raw material of calcium silicate hydrate. The excessive rise of
The clogging of the column due to the coagulation reaction of the dephosphorizing material can be eliminated. Therefore, by using the dephosphorization material of the present invention packed in a column, dewatering treatment of wastewater can be performed stably for a long period of time. Furthermore, in the dephosphorization method of the present invention, a stable pH state can be maintained and the water can be discharged by performing aeration treatment after passing through the column.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to embodiments. (Example 1) Tobermorite (manufactured by Kamishima Chemical Co .; particle size 1-2)
mm, produced by hydrothermal reaction of siliceous and calcareous substances)
In a container, carbon dioxide gas is introduced into the container at a rate of 1 liter (hereinafter referred to as L) / min, and a carbonation treatment is carried out at atmospheric pressure for 20 hours so that excess gas leaks from the container. went.

A column having an inner diameter of 20 mm was packed with 60 g of the above-carbonated tobermorite to prepare a 140-ml column filled with a dephosphorizing material.

Water discharged from the septic tank (BOD: 20 mg / L)
In addition, disodium hydrogen phosphate 12 water (Na ₂ HPO ₄
12H ₂ O) was added to adjust the phosphorus concentration to 5 mg / L, and the solution was passed through the dephosphorization column at a water flow rate of 84 ml / h, and the pH and the phosphorus concentration at the outlet of the dephosphorization column were measured. did. Phosphorus concentration is determined according to JIS K0102.
It measured according to.

Example 2 A column filled with a dephosphorizing material was prepared in the same manner as in Example 1 except that the carbonation time was changed to 1 hour.

Comparative Example 1 A column filled with a dephosphorizing material was prepared in the same manner as in Example 1 except that the carbonation treatment was not performed.

Table 1 shows the results of pH, Ca concentration, and phosphorus concentration in Examples 1, 2 and Comparative Example 1 after the initial 7 days and 2 months. Also, the pH for the first 7 days,
FIG. 1 shows the change in Ca concentration and Ca concentration.

[0025]

[Table 1]

From the above results, it was found that the initial p
It can be seen that H is suppressed. In each of Examples 1 and 2 and the comparative example, the phosphorus concentration achieved 1 mg / L or less until 4 months after the start of water supply, and the amount of calcium required for the dephosphorization reaction was maintained regardless of the initial suppression. It can be seen that the supply of alkali and the supply of alkali continue.

(Example 3) In Example 1, the treated water after passing through the column containing the dephosphorizing material was led as shown in FIG. 2 and the pump was operated to perform aeration at 400 ml / min, and not performed. In each case, the pH was measured.
The following are the average values for the first seven days. When aeration is performed 8.03 When aeration is not performed 9.81

[0028]

As described above, the dephosphorizing material of the present invention exhibits excellent dephosphorizing performance and can suppress an excessive increase in pH at the initial stage of passing water. Furthermore, after passing the wastewater containing phosphate ions through the column filled with the dephosphorizing material of the present invention, the aeration treatment is carried out, so that the pH can be suppressed to a range that can be discharged.
Therefore, the column filled with the dephosphorizing material of the present invention, after allowing the wastewater containing phosphate ions to pass therethrough, by performing aeration treatment, while suppressing an increase in the initial pH, was stabilized over a long period of time. A phosphorus removal treatment can be performed.

[0029]

[Brief description of the drawings]

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a graph showing changes in pH and Ca concentration in Examples 1, 2 and Comparative Example over the passage of water days.

FIG. 2 is a diagram illustrating an experimental apparatus according to a third embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Dephosphorization column 2 Dephosphorization material of this invention 3 Aeration tank 4 Air stone 5 Blower

Claims (4)

[Claims] 1. A dephosphorizing material comprising a carbonated calcium silicate hydrate. 2. The phosphorus-removing material according to claim 1, wherein the calcium silicate hydrate is tobermorite. 3. The dephosphorizing material according to claim 1, wherein the calcium silicate hydrate is obtained by mixing siliceous and calcareous materials together with water and performing a hydrothermal reaction under high temperature and high pressure. 4. A phosphoric acid characterized by subjecting waste water containing phosphate ions to a column filled with the dephosphorizing material according to any one of claims 1 to 3, followed by aeration treatment. A method for removing phosphorus from wastewater containing ions.