JP2000033384A - Water treatment by flocculation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the amt. of sludge generated by flocculation. SOLUTION: The suspended matter in the water to be treated is flocculated in a flocculation basin 11 by injecting a fluocculant to form a flock, and the flock is settled in a settling basin 12 to form a deposit. In this case, a granular material coated with a thin film of titanium dioxide positively charged through electrical processing is used as the flocculant, and the titanium dioxide of the flocculant with the suspended matter flocculated thereon is irradiated with the UV from a UV lamp 13 in the water in the settling basin 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water treatment method by coagulation and sedimentation, and more particularly, to a water treatment method applied in a step of coagulating and suspending suspended matter in treated water by injecting a coagulant in water and sewage treatment. .

[0002]

2. Description of the Related Art For example, in water treatment in a water purification facility, treated water (raw water) taken from a river or the like flows into a landing well to calm and stabilize the level of treated water, and the amount of water is regulated. Above, inorganic substances contained in the treated water,
It removes suspended matter such as organic matter, bacteria and microorganisms.

[0003] The removal of suspended matter in the treated water is performed by a coagulation pond 1 installed at the latter stage of the landing well as shown in FIG.
It is general that the suspended solids contained in the treated water are agglomerated by a chemical and then precipitated in the sedimentation basin 2. As a chemical used in this coagulation precipitation step, there has been a coagulant such as aluminum sulfate (sodium sulfate) or polyaluminum chloride (PAC).

[0004] In the above-mentioned flocculation basin 1, suspended matter in the treated water is flocculated by rapid and slow stirring by injecting a flocculant to form massive flocs, and sediment is formed by the flocculation in the sedimentation basin 2. After that, the treated water is discharged to the filtration pond. On the other hand, the sediment generated in the sedimentation basin 2 is discarded as sludge.

[0005]

However, in the conventional method, as described above, a coagulant such as aluminum sulfate (sodium sulfate) or polyaluminum chloride (PAC) is used. The sediment produced by flocculation in the sedimentation basin 2 is simply discarded as sludge, having only the function of simply aggregating suspended matter in water. As a result, the amount of the sludge becomes large, causing a problem in the disposal.

Accordingly, the present invention has been proposed in view of the above-mentioned problems, and an object of the present invention is to provide a water treatment method capable of reducing the amount of sludge generated by coagulation and sedimentation. is there.

[0007]

Means for Solving the Problems As a technical means for achieving the above-mentioned object, the present invention relates to a method of coagulating suspended matter in treated water in a coagulation pond by injecting a coagulant to form flocs, and then forming a floc. In the flocculation and sedimentation process where sedimentation of flocs in the pond produces sediment, titanium dioxide positively charged by electrical treatment is used as a flocculant, and the suspended flocculant is treated with ultraviolet light on the flocculant titanium dioxide. It is characterized by irradiation in water.

In the method of the present invention, by using titanium dioxide positively charged by electric treatment as a coagulant, the coagulant of titanium dioxide injected into the treated water is:
Floating matter negatively charged in the treated water of the flocculation pond is adsorbed by electrostatic force. After that, by irradiating titanium dioxide of the flocculant which flocculated the suspended matter with ultraviolet rays in the precipitation tank, the titanium dioxide was activated and the suspended matter attached to the surface was oxidized and decomposed, and the amount of sludge was reduced. Can be achieved. still,
Both titanium dioxide and ultraviolet irradiation also exert a bactericidal action.

Specifically, the coagulant is preferably a granular material in which a thin film of titanium dioxide is coated on the surface of a nucleus having a specific gravity greater than that of water. Recovery and reuse of titanium dioxide are facilitated.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail. In the following embodiments, a water treatment will be described, but the present invention is not limited to this, and is applicable to other water treatments such as a sewer treatment using a coagulant.

When the embodiment of the present invention is applied to the coagulation sedimentation step of the water supply treatment in a water purification facility, as shown in FIG.
Upstream, a coagulant of titanium dioxide positively charged by an electric treatment is injected. The amount of the coagulant to be injected may be appropriately set according to the quality of the treated water. In this flocculation pond 11, the flocculent is formed by injecting a flocculant of the treated water by injecting a flocculant of titanium dioxide.

In a sedimentation basin 12 installed at a stage subsequent to the coagulation basin 11, an ultraviolet lamp 13 is provided in the stored treated water.
Are disposed in a predetermined number, and a precipitate is generated by sedimentation of flocs while irradiating ultraviolet rays in the treated water. On the other hand, the sediment generated in the sedimentation basin 12 is discarded as sludge.

More specifically, as the coagulant 14, FIG.
As shown in (a), the surface of a nucleus 15 (for example, a granular material such as glass or metal) having a higher specific gravity than water is coated with titanium dioxide 16 in the form of a thin film by vapor deposition or the like, and the surface is appropriately charged so as to be positively charged. It is preferable to use a granular material that has been subjected to the above electrical treatment. By forming the coagulant 14 into a granular material in this manner, the recovery and reuse of titanium dioxide can be easily realized.

As described above, the treated water flowing from the landing well contains suspended matter such as inorganic matter, organic matter, bacteria and microorganisms.
7 generally exists in a negatively charged state, the coagulation pond 11 is charged negatively in the treated water by the coagulant 14 of titanium dioxide 16 positively charged as shown in FIG. Floating matter 17 adheres by electrostatic force to form flocs.

Next, in the sedimentation basin 12, the flocculant 14 that has agglomerated the suspended matter 17 settles under its own weight, and sedimentation of the floc generates a sediment containing the flocculant 14 in which the suspended matter 17 is agglomerated. Is done. Simultaneously with the generation of the precipitate, as shown in FIG. 3, for example, ultraviolet rays are irradiated from an ultraviolet lamp 13 disposed below the sedimentation basin 12. The number, position and arrangement of the ultraviolet lamps 13 are determined according to the sedimentation basin 1.
The design can be changed as appropriate in accordance with the volume and shape of 2, for example. Further, when installing the ultraviolet lamp 13 at the bottom of the sedimentation basin 12, it is necessary to prevent the irradiation efficiency from decreasing due to the accumulation of sludge.

Titanium dioxide is an n-type semiconductor, and when irradiated with ultraviolet rays, electrons are generated in the conduction band and holes are generated in the valence band, and these holes have strong oxidizing power. Therefore,
As described above, when ultraviolet rays are irradiated by the ultraviolet lamp 13, the suspended matter 17 attached thereto is oxidized and decomposed due to the strong oxidizing power of the holes generated on the surface of the thin-film titanium dioxide 16 (reference numeral 17 in the figure). ), Organic substances are reduced in molecular weight and made inorganic, and hydrophobic substances are made hydrophilic. This float 1
Since the amount of sludge is reduced by the decomposition of 7, the recovery and reuse of titanium dioxide from the bottom of the sedimentation basin 12 are facilitated.

The titanium dioxide 16 of the coagulant 14 injected into the treated water in the coagulation pond 11 and the ultraviolet rays irradiated by the ultraviolet lamp 13 in the sedimentation pond 12 both have the effect of sterilizing the treated water. Demonstrate.

[0018]

According to the present invention, titanium dioxide positively charged by an electric treatment is used as a coagulant, and the coagulant of the titanium dioxide is injected into treated water and then irradiated with ultraviolet rays. The suspended matter aggregated by the coagulant titanium dioxide can be decomposed, the amount of sludge generated as a precipitate can be reduced, and the disposal of the sludge is facilitated. Further, sterilization of the treated water can be realized by the irradiation of the coagulant titanium dioxide and ultraviolet rays. Furthermore, if a granular material coated with a thin film of titanium dioxide is used as the coagulant, recovery and reuse of titanium dioxide can be easily realized.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a coagulation-sedimentation step in an embodiment of the present invention.

FIG. 2A is an enlarged view showing a flocculant used in the method of the present invention. FIG. 2B is an enlarged view showing a state where suspended matter adheres to the flocculant of FIG.

FIG. 3 is an enlarged view showing a state in which titanium dioxide as a coagulant decomposes suspended matter by irradiation with ultraviolet rays.

FIG. 4 is a schematic configuration diagram showing a coagulation-sedimentation step in a conventional example.

[Explanation of symbols]

 14 flocculant 15 nucleus 16 titanium dioxide 17 suspended matter

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C02F 1/72 101 C02F 1/72 101 F term (Reference) 4D015 BA03 BA08 BA23 BB05 CA14 DA30 DC04 EA32 FA03 FA11 FA23 4D037 AA11 AB02 BA18 BB09 CA06 CA08 4D050 AA12 AB11 AB31 BC06 BC09 BD02 CA16 4D062 BA03 BA08 BA23 BB05 CA14 DA30 DC04 EA32 FA03 FA11 FA23

Claims (2)

[Claims] 1. A flocculation process in which coagulation of suspended matter in treated water is performed in a flocculation pond by injection of a flocculant to form flocs. A water treatment method by coagulation sedimentation, comprising using positively charged titanium dioxide as a coagulant, and irradiating the coagulant titanium dioxide in which suspended matter is coagulated with ultraviolet light in the treated water of the precipitation tank. 2. The water treatment method according to claim 1, wherein the coagulant is a granular material obtained by coating a thin film of titanium dioxide on the surface of a nucleus having a specific gravity larger than that of water.