JP2001205276A - Dephosphorization material and method for dephosphorizing wastewater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dephosphorization material capable of stably developing an excellent phosphate ion removing function (dephosphorizing function) over a long period of time without requiring the addition of calcium ions or the adjustment of pH and a method for dephosphorizing wastewater using the same. SOLUTION: The dephosphorization material 2 comprises a composite of a calcium silicate compound and a cement hydrate. In the method for dephosphorizing wastewater, phosphate ion-containing wastewater is passed through a dephosphorization column 1 filled with the dephosphorization material 2 to be subjected to dephsphorization treatment and the treated water is aerated in an aeration tank 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Since phosphates cause eutrophication of water, it is strongly required to remove phosphorus from wastewater, and wastewater treatment in a septic tank is no exception.

[0003] As a method for removing phosphorus from wastewater, there are a biological dephosphorization method, a coagulation sedimentation dephosphorization method, an adsorption dephosphorization method, and a crystallization dephosphorization method. A phosphorus removal step by a phosphorus removal method has been introduced.

[0004] However, the biological dephosphorization method is based on the assumption that sludge containing excessive phosphorus is frequently extracted, and therefore cannot be applied to a septic tank in which sludge is not extracted for more than several months. There is a problem.

Further, the coagulation sedimentation dephosphorization method has a problem that frequent sludge extraction is required as in the case of the biological dephosphorization method because the amount of generated sludge is large. In addition, there is a problem that the operation of replacing and regenerating the adsorbent must be performed frequently, and it is difficult to apply any of these to the septic tank.

On the other hand, the crystallization dephosphorization method is a method of removing phosphate ions from wastewater by growing hydroxyapatite crystals by allowing seed crystals to exist in wastewater containing phosphate ions. It is expected as a method having the advantage of almost no occurrence.

However, in order to generate hydroxyapatite, it is necessary to adjust the pH of the water to be treated (drainage) and the calcium ion concentration to a certain range, so that calcium ions are added by chemical injection before the crystallization step. In general, methods such as pH adjustment and pH adjustment by chemical injection after the crystallization step are adopted, but this method is applied to septic tanks where frequent maintenance cannot be expected. There is a problem that it is difficult to do.

In order to cope with such a problem, for example, Japanese Patent Application Laid-Open No. 9-308889 discloses a "reaction tank filled or fluidized with a dephosphorizing material mainly composed of calcium silicate hydrate, Or an addition means for adding calcium ions to raw water containing phosphorus supplied to the reaction tank ".

[0009] However, in the case of the phosphorus removal method using the phosphorus removal apparatus disclosed in the above disclosure, calcium silicate hydrate initially elutes calcium ions and hydroxyl ions satisfactorily. Apatite crystallizes and coats the surface of calcium silicate hydrate, and the amount of calcium and hydroxide ions eluted decreases with time, so it is necessary to add calcium and hydroxide ions by chemical injection. There is a problem, that is, the sustainability of the dephosphorization function is insufficient.

[0010]

SUMMARY OF THE INVENTION In view of the above-mentioned conventional problems, an object of the present invention is to provide an excellent phosphate ion removing function (phosphorus removing function) without the necessity of adding calcium ions by chemical injection or adjusting pH. The present invention is to provide a dephosphorizing material capable of stably expressing) over a long period of time, and a method for dephosphorizing waste water using the dephosphorizing material.

[0011]

The dephosphorizing material according to the first aspect of the present invention (hereinafter referred to as "the present invention 1") comprises a composite of a calcium silicate compound and a cement hydrate. And

The dephosphorizing material according to the second aspect of the present invention (hereinafter referred to as "the present invention 2") is the dephosphorizing material according to the first aspect, wherein the calcium silicate compound is wollastonite and / or tobermorite. It is characterized by being.

Further, the invention according to claim 3 (hereinafter referred to as “the invention”)
In the method for dephosphorizing wastewater according to the “present invention 3”), the wastewater containing phosphate ions is treated with the present invention 1 or 2
After passing through a dephosphorization column filled with a dephosphorization material by the above, the dephosphorization treatment is performed, and then the aeration treatment is performed in an aeration tank.

The calcium silicate compound used in the dephosphorizing material of the present invention 1 functions as a seed crystal on which hydroxyapatite is crystallized, and includes, for example, wollastonite, tobermorite, zonotlite, hilletbrandite,
Affilite, gyrolite and the like are mentioned, and are preferably used. Among them, wollastonite and tobermorite which are excellent in the function as a seed crystal for crystallizing hydroxyapatite are more preferably used. These calcium silicate compounds may be used alone or in combination of two or more.

Since the calcium silicate compound has a higher function as a seed crystal as the surface area is larger, it is preferable to use the calcium silicate compound having a fine particle diameter and a fine irregular shape on the surface.

The dephosphorizing material of the present invention 2 requires that wollastonite and / or tobermorite be used as the calcium silicate compound in the dephosphorizing material of the present invention 1. The wollastonite and tobermorite may be used alone or in combination.

By using wollastonite and / or tobermorite as the calcium silicate compound, it is possible to obtain a dephosphorizing material having a more excellent function as a seed crystal.

The cement hydrate used in the dephosphorizing material of the present invention refers to a material obtained by hydrating and hardening hydraulic cement.

Examples of the hydraulic cement include ordinary Portland cement, early-strength Portland cement,
Medium heat Portland cement, sulfate resistant Portland cement, white Portland cement, oil well Portland cement, colloid cement, blast furnace cement, fly ash cement, silica cement, ultra low heat cement,
High-strength cement, geothermal well cement, alumina cement, ultra-rapid hardening cement, low alkali cement for GRC, and the like are preferably used, and among them, ordinary Portland cement, which has an excellent balance between performance and cost, is more preferably used. . These hydraulic cements may be used alone or in combination of two or more.

The above cement hydrate functions as a calcium and alkali supplier required for the crystallization reaction. By using cement hydrate as the above-mentioned feeder, it becomes possible to stably supply calcium having a concentration of several tens of mg / liter, which is necessary and sufficient for the crystallization reaction, for a long period of time.

The dephosphorizing material of the present invention comprises a composite of the calcium silicate compound and the cement hydrate. The composite refers to a material obtained by mixing and integrating a calcium silicate compound and a cement hydrate.

As a method for producing the above-mentioned composite, for example, the particles of the calcium silicate compound and the particles of the hydraulic cement before hydration are mixed and then water is added to hydrate and harden the hydraulic cement. Examples of the method include a method of preparing a composite, and a method of preparing a composite by integrating particles of a calcium silicate compound and particles of a hydraulic cement after hydration and curing using a binder such as an organic resin. However, since the function of the calcium silicate compound as a seed crystal is activated in the presence of an alkali, direct contact between the calcium silicate compound and the hydraulic cement is advantageous, and therefore, the former method is more preferable. preferable.

The mixing ratio of the calcium silicate compound and the cement hydrate in the composite is not particularly limited, but the weight ratio is calcium silicate compound / cement hydrate = 0.5 to 5. And more preferably, calcium silicate compound / cement hydrate = 1 to 1
2. In other words, calcium silicate compound 1
The cement hydrate is preferably 20 to 200 parts by weight, more preferably 100 parts by weight, and more preferably 100 parts by weight of the calcium silicate compound.
１００100 parts by weight.

The amount of water used for preparing the above-mentioned composite is not particularly limited.
Hydraulic cement = 0.25-3, and total amount of water / hydraulic cement and calcium silicate compound = 0.2
~ 2 is preferred.

If the amount of water is less than the respective lower limit values, the hydration reaction and the hardening reaction of the hydraulic cement may not proceed sufficiently. Conversely, if the amount of water exceeds the respective upper limit values. In some cases, the mixed composition becomes a slurry and a good solid composite cannot be obtained.

In addition to the calcium silicate compound and the cement hydrate, which are essential components, the above-mentioned composite may contain, if necessary, calcium oxide, calcium carbonate, calcium sulfate, carbonate apatite as long as the object of the present invention is not hindered. In addition, one or more of natural minerals and the like containing these may be added and mixed.

After the hydraulic cement has been hydrated and hardened, the above-described composite is pulverized, and the obtained pulverized composite is packed in a column, and the dephosphorization column is subjected to wastewater containing phosphate ions (treatment water). By passing the water, the dephosphorization treatment of the wastewater can be effectively performed.

The particle size of the above-mentioned pulverized composite material is not particularly limited, but is preferably from 0.3 to 30 mm. If the particle size of the composite ground material is less than 0.3 mm, clogging may easily occur in the water flow. Conversely, if the particle size of the composite ground material exceeds 30 mm, the particle size required for the crystallization reaction may increase. In order to secure the surface area, it may be necessary to prepare a column with a large volume.

The column used for the dephosphorization column has a space velocity (SV) of 0.5 in consideration of the crystallization reaction speed.
〜3 / hour. The length of the column and the amount of the crushed composite material charged into the column may be set so as to satisfy the preferred space velocity (SV) in consideration of the phosphate ion concentration in the wastewater and the flow rate of the wastewater. Further, the preferable space velocity (SV) may be satisfied by using a plurality of columns.

Since the pH of the waste water (water to be treated) after passing through the thus prepared dephosphorization column is high, it is preferable to discharge the waste water after performing aeration treatment. By performing the aeration treatment, carbon dioxide in the air is dissolved in the wastewater (water to be treated), and the pH of the wastewater (water to be treated) can be easily and easily lowered.

When the dephosphorizing material of the present invention is applied to a septic tank, an aerobic tank is generally provided in the septic tank and aeration is always performed. By adopting a method of introducing into wastewater (water to be treated), the pH of the wastewater (water to be treated) can be reduced to a necessary level without providing a new aeration pump.

When the dephosphorizing material of the present invention is applied to a septic tank, the wastewater (water to be treated) after the biological treatment step is introduced into a dephosphorizing column, and after performing the dephosphorizing treatment, the wastewater is treated in an aeration tank. It is preferable to adopt a step of performing aeration treatment at, and discharging the obtained treated water.

The biological treatment step is not particularly limited, and may be after any of the steps such as an activated sludge method and a contact aeration method used in a general septic tank.

Next, the method for dephosphorizing waste water of the present invention 3 will be described with reference to the drawings. FIG. 1 is a schematic diagram showing an example of a wastewater treatment device that can be used in the above-mentioned method for removing phosphorus from wastewater.

The wastewater treatment apparatus shown in FIG. 1 comprises a dephosphorization column 1 in which a dephosphorizing material 2 of the present invention is filled in a column, and an aeration tank 3. The aeration tank 3 supplies air into the tank. It has a blower 5 for supplying and an air stone 4 for diffusing the supplied air.

As shown in FIG. 1, first, waste water (water to be treated) is introduced into a dephosphorization column 1 filled with a dephosphorizing material 2 of the present invention, and phosphoric acid in the waste water (water to be treated) is discharged. The phosphorus removal treatment is performed by adsorbing the ions to the phosphorus removal material 2.

Next, waste water after dephosphorization (water to be treated)
Into the aeration tank 3, and the air supplied from the blower 5 into the aeration tank 3 is diffused by the air stone 4,
Perform aeration treatment of waste water (water to be treated).

The treated water after the dephosphorization treatment and the aeration treatment is overflowed or discharged to the outside of the aeration tank 3 by a discharge device such as a discharge pipe, thereby dephosphorizing the wastewater according to the present invention 3. The method is complete.

The dephosphorizing material of the present invention and the method of dephosphorizing waste water of the present invention can be suitably applied particularly to a septic tank, but it is needless to say that the method is not limited to a septic tank. The present invention can be suitably applied to, for example, a sewage treatment plant, a river, a factory wastewater treatment facility, and the like that need to effectively remove phosphate ions in (treated water).

[0040]

The dephosphorizing material of the present invention has a calcium silicate compound exhibiting a function as a seed crystal on which hydroxyapatite crystallizes, and a function of stably supplying calcium and alkali required for the crystallization reaction over a long period of time. Consists of a complex that is used in combination with a hydrated cement hydrate, so that excellent phosphate ion removal function (phosphorus removal function) is stable over a long period of time without adding calcium ions or pH adjustment by chemical injection. It can be expressed in a specific way. In particular, by using wollastonite and / or tobermorite as the calcium silicate compound, the above-mentioned properties are significantly improved.

Further, since the method for dephosphorizing waste water of the present invention is carried out using the above-mentioned dephosphorizing column filled with the dephosphorizing material of the present invention, complicated operations such as addition of calcium ions by chemical injection and pH adjustment are performed. It is possible to stably remove phosphorus from wastewater at a high level for a long period of time without any need.

[0042]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In the examples, “parts” means “parts by weight”.

(Example 1) (1) Preparation of phosphorus removal material and phosphorus removal column Ordinary Portland cement (manufactured by Taiheiyo Cement Corporation) 10
0 parts and fibrous wollastonite (trade name “Kemolit A-60”, average fiber diameter: 1 μm, manufactured by Sumitomo Chemical Co., Ltd.)
After uniformly mixing 100 parts, 100 parts of water was added and mixed to hydrate and harden the ordinary Portland cement. Removed on the third day after curing, pulverized to a particle size of 1.4
A dephosphorizing material of ~ 3.3 mm was produced.

A column having an inner diameter of 25 mm was filled with 56 g of the dephosphorizing material obtained above to prepare a dephosphorizing column having a volume of 140 cm ³ .

[0045] (2) dephosphorization treatment water discharged embodiment septic tank (BOD: about 20mg / l) to disodium hydrogenphosphate · 12 Water (Na ₂ HPO ₄ · 12
H ₂ O) was added to adjust the phosphorus concentration to 5 mg / liter, and the wastewater (water to be treated) was passed through the dephosphorization column obtained above at a flow rate of 80 ml / hour for 10 days. At this point, wastewater (water to be treated) was sampled (sampling A).

Next, after passing water for 30 days at a water flow rate of 320 ml / hour, the water flow rate was returned to 80 ml / hour again, and at this time, drainage (water to be treated) was again sampled (sampling B). .

(3) Evaluation The following evaluation results were as shown in Table 1.

Measurement of phosphorus concentration: The phosphorus concentration of the wastewater (water to be treated) collected in sampling A and sampling B was measured according to JIS K-0102.

Measurement of pH: After introducing the waste water (water to be treated) after the dephosphorization treatment into the aeration tank 3 shown in FIG. 1, the blower 5 is operated to supply air, and the air is diffused by the air stone 4. Aeration treatment was performed. Next, the pH of the wastewater (water to be treated) before and after the aeration treatment was measured. The pH value was shown as an average value for the first 10 days.

Example 2 The composition of the dephosphorizing material was 100 parts of ordinary Portland cement (manufactured by Taiheiyo Cement Co., Ltd.), 100 parts of tobermorite powder (trade name "11 @ tobamolite", manufactured by Kamishima Chemical Industry Co., Ltd.) and 100 parts of water. A phosphorus removal material and a phosphorus removal column were produced in the same manner as in Example 1 except for the above. Next, the dephosphorization treatment was performed in the same manner as in Example 1.

Comparative Example In the preparation of a dephosphorization column,
Example 1 was repeated except that 90 g of wollastonite (manufactured by Kakiuchi) having a particle diameter of 0.6 to 1.4 mm was used instead of using the dephosphorizing material produced in Example 1.
A dephosphorization column having a volume of 140 cm ³ was prepared in the same manner as in the above case. Next, the dephosphorization treatment was performed in the same manner as in Example 1.

[0052] The phosphorus concentration of the waste water (water to be treated) dephosphorized in Example 2 and Comparative Example was measured in the same manner as in Example 1. The results were as shown in Table 1.

[0053]

[Table 1]

As is clear from Table 1, the wastewater subjected to the dephosphorization treatment using the dephosphorization columns of Examples 1 and 2 filled with the dephosphorization material of Examples 1 and 2 according to the present invention ( The water to be treated) was passed for 10 days at a water flow rate of 80 ml / hour (sampling A), and after water flow under the above water flow conditions, and further for 30 days at a water flow rate of 320 ml / hour (sampling B). The phosphorus concentration is 1
It was less than mg / liter and was sufficiently low. This indicates that the dephosphorization columns of Example 1 and Example 2 had excellent dephosphorization ability and their durability and stability. The above results show that the dephosphorization treatment with a phosphorus concentration of 1 mg / liter or less under a water flow rate of 80 ml / hour {space velocity (SV) = 1.14 / hour} was achieved for at least 4 months. Shows what is possible.

On the other hand, the waste water (water to be treated) subjected to the dephosphorization treatment using the dephosphorization column of the comparative example filled with wollastonite alone as the dephosphorization material had a water flow rate of 80%.
After passing water for 10 days at a rate of 100 ml / hour (sampling A), the phosphorus concentration was 1 mg / liter or less, which was sufficiently low.
After passing water for 30 days at a ml / hour (sampling B), the phosphorus concentration was 2.4 mg / L, which was high. this is,
The results show that the dephosphorization column of the comparative example was excellent in the initial dephosphorization ability, but lacked the sustainability and stability of the dephosphorization ability.

[0056]

As described above, the dephosphorizing material of the present invention stably exhibits an excellent dephosphorizing function over a long period of time without the need of adding calcium ions by chemical injection or adjusting pH. Therefore, it is suitably used for dephosphorization treatment of various wastewaters such as wastewater from a septic tank, various domestic wastewaters, and industrial wastewaters.

Further, in the method for dephosphorizing waste water of the present invention, since the dephosphorization treatment is performed using the dephosphorization column filled with the dephosphorizing material of the present invention, it is necessary to add calcium ions by chemical injection, adjust pH, and the like. It is possible to stably remove phosphorus from various types of domestic wastewater and industrial wastewater at a high level for a long period of time, including drainage from a septic tank, without requiring complicated operations.

[0058]

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a wastewater treatment device that can be used in the method for removing phosphorus from wastewater according to the present invention.

[Description of Signs] 1 Dephosphorization column 2 Dephosphorization material of the present invention 3 Aeration tank 4 Airstone 5 Blower

Claims (3)

[Claims] 1. A dephosphorizing material comprising a composite of a calcium silicate compound and a cement hydrate. 2. The phosphorus removal material according to claim 1, wherein the calcium silicate compound is wollastonite and / or tobermorite. 3. A dephosphorization treatment is performed by passing a wastewater containing phosphate ions through a dephosphorization column filled with the dephosphorization material according to claim 1 or 2, and then performing aeration treatment in an aeration tank. A method for dephosphorizing wastewater, comprising: