JPH10286597A - Method for wastewater purification treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently capture and remove even a trace amount of dioxins by flocculating and precipitating raw water containing dioxins, then filtering the resultant raw water through a microfiltration membrane, adding hydrogen peroxide to the wastewater filtered through the filtration membrane, and radiating ultraviolet rays while stirring and mixing the wastewater. SOLUTION: Wastewater (raw water) W1 containing dioxins is introduced into a flocculation precipitation tank 1 to precipitate and remove suspended solid with large particle size. After a prescribed sludge treatment is carried out, the precipitated suspended solid is dewatered. Then, the wastewater which is treated by precipitation treatment is filtered by a microfiltration membrane 20 in a filtration tank 2 to filter and remove suspended solid with smaller particle size and dioxins. Further, the wastewater which passes through the microfiltration membrane 20 is mixed with hydrogen peroxide and then radiated with ultraviolet rays from an ultraviolet lamp 30 in a LUV radiation water route 3 while being stirred and mixed by a stirring and mixing apparatus 40 to oxidize and decompose dioxins. Consequently, the obtained water from which dioxins are removed can be released as purified water W2 .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for purifying wastewater containing dioxins, which is applied to wastewater treatment of waste incinerators and industrial waste incinerators and wastewater treatment of landfills.

[0002]

2. Description of the Related Art Dioxins in exhaust gas have been regarded as important, and regulations and guidelines have been established in Japan and overseas to improve exhaust gas treatment equipment. Dioxins in wastewater will be regulated in the future. It is presumed that is provided. In particular, in the waste incineration process, dioxins are easily generated, and the suppression of generation by combustion technology and the collection and removal by exhaust gas treatment technology have been widely performed.

[0003]

The exhaust gas generated in a waste incinerator can be treated by a dry method, a semi-dry method, a wet cleaning method, or the like. The wet cleaning method ｛caustic soda (neutralizing agent) NaOH) and calcium carbonate (CaC)
If the method using O ₃ ) is adopted, dioxins in the exhaust gas are suspended in the cleaning solution, and the waste liquid is contaminated with dioxins. Such a wastewater treatment technology containing dioxins has not yet been put into practical use as a well-studied effective facility because there is no regulation yet.

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, an object of the present invention is to provide a wastewater purification method capable of effectively collecting and removing even a small amount of dioxins from wastewater containing dioxins.

[0005]

The process leading to the present invention will be described step by step. Almost all dioxins in wastewater obtained by the wet washing method and the like are submicron-sized fine particles, and a part of the dioxins is present by being adsorbed to a suspension.
Therefore, in order to treat dioxins in wastewater, it is necessary to collect and remove particulate or suspended substances.
Therefore, the present invention provides wastewater (raw water) containing dioxins,
The first feature is that a coagulation sedimentation step of first coagulating and sedimenting to remove a suspension and a large suspension of particles adsorbing dioxins is provided.

[0006] Further, dioxins themselves are organic compounds, and since they are harmful in a very small amount, dioxins leaking in a very small amount must be completely removed from the drain side. Therefore, the present invention provides, as a second feature, a step of filtering a small suspension of dioxin-adsorbed particles or dioxin particles from the wastewater by passing the wastewater after the precipitation removal through a microfiltration membrane. . Further, in the present invention, in order to remove dioxins that have passed through the microfiltration membrane, ultraviolet light (UV) is irradiated after or with stirring and mixing with hydrogen peroxide solution (H ₂ O ₂ ). The third feature is that a step of disassembly is provided.

That is, the present invention relates to a method for purifying wastewater containing dioxins, wherein the raw water containing dioxins is coagulated and settled, filtered through a microfiltration membrane, and then discharged through the filtration membrane. We propose a purification method capable of effectively collecting and removing even trace amounts of dioxins contained in wastewater by irradiating ultraviolet rays after adding or stirring and mixing aqueous hydrogen peroxide into the wastewater.

[0008]

The dioxins contained in the waste water obtained by the wet washing method or the like are present as fine particles, and some dioxins are present in a suspension. Some of them are present as ultra-fine particles. To collect and remove these dioxins from the wastewater, a treatment method suitable for each property is required. Therefore, the present invention can be achieved smoothly by performing collection and removal according to the procedure described in the section of the above-mentioned solution means, but the procedure is as follows.

(1) Wastewater containing dioxins (raw water)
Agglomerated sedimentation step By this step, a large suspension of particles adsorbing dioxins is precipitated and removed. (2) Microfiltration step By this step, a small suspension of dioxin-adsorbed particles and dioxin particles are filtered. (3) Addition of Hydrogen Peroxide Water and Stir Mixing / UV Irradiation Step Dioxins of more ultrafine particles that have passed through the microfiltration membrane are reacted with hydrogen peroxide water, oxidatively decomposed, and rendered harmless. Stirring and UV irradiation serve to accelerate the reaction at that time.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, and are merely illustrative examples. Only. FIG. 1 shows a schematic configuration diagram of a wastewater treatment as an embodiment of the present invention. Here, W ₁ is waste water (raw water) containing dioxins, W ₂ is purified water treated according to the present embodiment, 1 is a coagulation sedimentation tank, for example, aluminum sulfate (Al ₂ (SO ₄ )) as a coagulation precipitant ₃ ) a filtration tank 2 having a microfiltration membrane (MF membrane) 20; 3 an ultraviolet (UV) irradiation channel or an ultraviolet irradiation tank; After adding (H ₂ O ₂ ), ultraviolet irradiation is performed by the ultraviolet irradiation lamp 30 while stirring and mixing by the stirring mixer 40.

Next, the operation of the embodiment will be described. First, waste water containing dioxins (raw water) W ₁ is introduced into the coagulating sedimentation tank 1, precipitating and removing large suspension particles.
The precipitated suspension is subjected to a predetermined sludge treatment such as a contact explosion or activated sludge method in a sludge treatment tank (not shown), and then subjected to a dehydration treatment by a dehydrator (not shown). Next, the sediment-removed wastewater is passed through a microfiltration membrane (MF membrane) 20 in the filtration tank 2 to filter a suspension of smaller particles and dioxins.
Remove. Further, after adding aqueous hydrogen peroxide (H ₂ O ₂ ) to the wastewater that has passed through the microfiltration membrane 20, the dioxins are oxidatively decomposed while being stirred and mixed by the stirring mixer 40 in the UV irradiation water channel 3. .

[0012] subjected to oxidative decomposition while irradiating ultraviolet rays UV lamp 30 in the UV irradiation waterway 3 to accelerate the oxidative decomposition, it may thereby discharged as clean water W ₂ after treatment dioxins are removed I can do it.
It is not necessary to perform the ultraviolet irradiation and the stirring and mixing at the same time,
As shown in FIG. 2, a stirring / mixing tank 4 is provided in front of the ultraviolet irradiation tank 3 ', and after stirring and mixing while adding hydrogen peroxide solution (H ₂ O ₂ ), the ultraviolet irradiation tank 3' The oxidative decomposition may be performed while irradiating the lamp 30 with ultraviolet rays.

[0013]

EXAMPLES The effects of the present invention were confirmed as follows using the apparatus shown in FIG. Waste incinerator smoke washing wastewater (raw water) having a dioxin concentration (total of dibenzodiomosine and dibenzofuran) of 4.5 mg / l was treated by the wastewater treatment system shown in FIG. First, raw water was put into a coagulation sedimentation tank, coagulated and precipitated with aluminum sulfate (sulfuric acid band), then introduced into a filtration tank, and subjected to solid-liquid separation through a microfiltration membrane (MF membrane).

Next, 1 ppm of hydrogen peroxide solution was added to the treated water after passing through the microfiltration membrane (MF membrane), and the mixture was passed through a water channel 3 provided with an ultraviolet lamp (UV lamp) while stirring and mixing. As a result, the concentration of dioxins during the final treatment could be reduced to 0.01 mg / l or less.

[0015]

As described above, according to the present invention, it is possible to efficiently collect and remove trace amounts of dioxins from wastewater containing dioxins, and thereby purify without dioxins and suspended matter. You can get water.

[Brief description of the drawings]

FIG. 1 shows a schematic configuration diagram of a wastewater treatment as an embodiment of the present invention.

FIG. 2 shows a schematic configuration diagram of a wastewater treatment according to a modification of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Coagulation sedimentation tank 2 Filtration tank 3 Ultraviolet (UV) irradiation water path 3 'Ultraviolet irradiation tank 4 Stir-mixing tank 20 Microfiltration membrane (MF membrane) 30 Ultraviolet irradiation lamp 40 Stir-mixer

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C02F 9/00 504 C02F 9/00 504D 1/32 ZAB 1/32 ZAB 1/44 1/44 F 1/52 1/52 K 1/58 1/58 A 1/72 1/72 Z 101 101

Claims (1)

[Claims] 1. A method for purifying wastewater containing dioxins, comprising coagulating and sedimenting raw water containing dioxins.
A method for purifying waste water, comprising filtering through a microfiltration membrane, and then irradiating with ultraviolet light after stirring or mixing with hydrogen peroxide water added to the waste water passing through the filtration membrane.