JP2001321763A - Method and device for treating dioxins in wastewater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently decompose dioxins in wastewater by uniformly irradiating the wastewater with ultraviolet rays so as to reach the dioxins sufficiently. SOLUTION: The wastewater is made to flow down in a film form along flow walls 1 consisting of a plurality of faces opposed to each other, and an ultraviolet light source 4 is disposed between the flow walls so as not to contact with wastewater films 3 and irradiates the wastewater film 3 to treat dioxins in the wastewater. Reflectors 6 that reflects the ultraviolet rays toward the falling wastewater film may be mounted to improve the irradiation efficiency of the ultraviolet rays, groove-like recessed and projecting parts may be formed on the flow walls to increase irradiation area, and a catalytic action may be added to the surfaces of the flow walls to promote a decomposition reaction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention effectively removes dioxins and other halogenated organic compounds (hereinafter referred to as dioxins) contained in various types of industrial wastewater, municipal sewage, wastewater from wastewater treatment plants, and landfill leachate. The present invention relates to a method and an apparatus for decomposing and removing the same.

[0002]

2. Description of the Related Art Conventionally, the above-mentioned wastewater has been treated alone or by appropriately combining various treatment apparatuses such as biological treatment, coagulation / precipitation, and activated carbon treatment. By the way, it has been found that dioxins, whose contamination has caused serious social problems in various places in recent years, have extremely low solubility in water, and most of them exist in a state of being adsorbed by organic substances and suspended solids (SS). ing. Therefore, conventionally, suspended solids have been separated and removed from the wastewater, and further subjected to a high-concentration treatment such as an activated carbon treatment.

[0003]

However, the above-described treatment method removes dioxins by adsorption or the like, and has a problem that an adsorbent containing concentrated dioxins is generated as waste. Was. Effective means for decomposing and removing dioxins include irradiation decomposition with ultraviolet rays, and more efficiently, combined use of ultraviolet irradiation with ozone, hydrogen peroxide, a catalyst and the like. However, when using these means to treat wastewater that is difficult to transmit ultraviolet light, using a conventional ultraviolet treatment device increases the transmission distance in the wastewater and reduces the irradiation effect. In addition, a dioxin treatment method and apparatus that can sufficiently reach dioxins in wastewater and can be decomposed efficiently can be required. The present invention has been completed as a result of research on the development of such a method and apparatus for treating dioxins.

[0004]

According to the present invention, as a means for solving the above-mentioned problems, a wastewater containing dioxins (hereinafter referred to as raw wastewater) is formed on a flowing wall (wet wall) composed of a plurality of opposing surfaces. ), And the dioxin in the wastewater is treated by irradiating the drainage film by arranging an ultraviolet light source between the downflow walls without contact with the drainage film and treating dioxins in the wastewater. And a method for treating dioxins.

[0005] Further, when dioxins are to be treated at a higher level, a method for treating dioxins in waste water by irradiating the raw waste water with ultraviolet rays and then oxidizing it with ozone, comprising the steps of: The film is caused to flow down in the form of a film along the flowing down wall composed of a surface, and a light source of ultraviolet light is disposed between the flowing down wall in a non-contact manner with the drainage film to irradiate the drainage film. Part of the wastewater) is sent to the ozone dissolution tank, and the rest is returned to the raw wastewater.
In the ozone dissolving tank, a method for treating dioxins in waste water, which comprises decomposing and treating dioxins by bringing ozone gas into gas-liquid contact with ultraviolet-treated waste water, is preferable. Preferably, part of the outlet wastewater of the ozone dissolving tank (hereinafter referred to as ozone treated wastewater) is led out of the system, and the remaining part is returned to the ultraviolet treated wastewater and circulated to the ozone dissolving tank.

The present invention also relates to a dioxin treatment apparatus for irradiating raw waste water with ultraviolet rays, wherein the waste water flows between a downflow wall composed of a plurality of opposed surfaces and a downflow wall. An apparatus for treating dioxins in water, characterized in that the membrane comprises an ultraviolet light source for irradiating a drainage membrane attached in a non-contact manner. In the above device, a reflector that reflects ultraviolet rays toward the falling drainage film may be attached. Further, the effect of dioxin treatment by ultraviolet rays can be promoted by using a falling wall provided with groove-shaped irregularities on the surface, or by adding a catalytic action to the surface of the falling wall.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION A dioxin processing method and a dioxin processing apparatus according to the present invention will be specifically described with reference to embodiments. FIG. 1 is a cross-sectional view of an apparatus according to an embodiment of the present invention, which is shown for explaining a basic configuration. In the present invention, a plurality of flowing down walls (wet walls) 1 having an overflow weir 2 on the upper side, in this example, 2
The raw waste water is caused to flow down from each overflow weir 2 along the flow-down wall surface 1 in the form of a film, and the ultraviolet light source 4 is disposed at a position where the raw waste water does not touch the drain water film 3 to flow down. To treat dioxins in raw wastewater. 7 is an overflow surface of the raw wastewater.

By mounting the ultraviolet light source 4 including the protective cover 5 and the like corresponding to the passage of the ultraviolet light at a position where the ultraviolet light source 4 does not touch the drainage film 3, it is possible to prevent the irradiation efficiency of the ultraviolet light from being reduced due to dirt and to spread the film. The ultraviolet rays efficiently and uniformly reach the dioxins in the raw wastewater 3 thus obtained. Although there is no particular limitation on the type of the ultraviolet light source 4 used in the present invention, a low-pressure mercury lamp having high ultraviolet irradiation efficiency is preferable. The number of the ultraviolet light sources used, the size per lamp, the arrangement of vertical and horizontal arrangements, and the intervals may be appropriately designed so as to enhance the utilization efficiency of ultraviolet light, and are not particularly limited. FIG. 1 illustrates the basic configuration of the device of the present invention, and a large number of this configuration can be used. The wastewater can be circulated and irradiated until the concentration of dioxins in the wastewater falls to a required level.

In the present invention, an ultraviolet reflector 6 can be provided in order to increase the utilization efficiency of the ultraviolet light. The reflector 6 reflects the ultraviolet light lost without directly irradiating the drainage film 3 in the direction of the drainage film 3 so as to effectively utilize the ultraviolet light. Although there is no particular limitation on the mounting position, shape, etc., it is desirable to use a reflecting surface that is less likely to be contaminated and has a high reflection efficiency in order to enhance the irradiation efficiency, and to design and arrange the drainage falling film surface so that it is evenly irradiated. FIG. 1 shows an example in which a plurality of ultraviolet lamps 4 and reflecting mirrors 6 are alternately arranged side by side.

The flow-down wall 1 is not limited to a vertical or flat surface. For example, the facing surface may be a slope or a curved surface, or the cross section of the facing downflow wall may be set to a rectangle, a rhombus, a polygon, or the like. Alternatively, grooves or banks may be appropriately provided on the surface of the falling wall to prevent drifting, and the drainage film 3 may be disturbed to renew the surface, enlarge the surface area, and increase the irradiation efficiency of ultraviolet rays. it can. Furthermore, the surface 1 of the downflow wall
Can be coated with a substance having a catalytic action, such as titanium oxide, to promote the decomposition of dioxins.

The present invention can be used for batch circulation irradiation, continuous circulation irradiation, or continuous supply / circulation / partial continuous extraction irradiation of ultraviolet rays. Further, not only the case where the waste water is subjected to the ultraviolet irradiation treatment alone, but also the case where the waste water is used in combination with the ozone treatment, the hydrogen peroxide treatment and the like, the decomposition of dioxins can be made efficient. When UV irradiation and hydrogen peroxide are used together, the required amount of hydrogen peroxide is injected into the wastewater at one time, or the hydrogen peroxide is divided or continuously divided into appropriate amounts in parallel with UV irradiation as the treatment proceeds. It can also be injected.

FIG. 2 shows an ultraviolet irradiation tank 11 and an ozone dissolving tank 1
2 schematically shows an example of a batch-type wastewater treatment apparatus in which No. 2 is combined. In the present embodiment, the ultraviolet lamps 14 horizontally arranged between two opposing falling walls 13 and the falling walls 13.
Are provided. The wastewater stored in the drainage circulation tank 15 is sent to the overflow weir 17 by the ultraviolet irradiation tank pump 16, forms a drainage film over the overflow weir 18, and forms the drainage wall 13.
And circulates and is stored in the drainage circulation tank 15.

In the present embodiment, a part of the wastewater stored in the wastewater circulation tank 15 is fed into the ozone dissolution tank 12 by the ozone dissolution tank pump 19, and the ultraviolet irradiation and the ozone treatment are performed simultaneously. Ozone gas is blown from the ozone generator 20 into the bottom of the ozone dissolving tank 12, and the ozone dissolving tank 12 is brought into contact with the wastewater in the countercurrent gas-liquid state. Reference numeral 21 denotes an ozone gas concentration meter. The duration of ultraviolet irradiation and ozone treatment of the wastewater varies depending on the type and concentration of dioxins in the wastewater, but is generally about 0.1 to 4 hours.

[0014]

EXAMPLE In order to confirm the effect of the present invention, an experiment was conducted using an apparatus having the same flow as that illustrated in FIG. 2 described above, and the details thereof will be specifically described below. The flow-down wall of the ultraviolet irradiation tank was composed of two opposing surfaces having a width of 2,000 and a height of 1,500 mm, and three low-pressure mercury lamps of 500 W were horizontally arranged as light sources of ultraviolet light. The analysis of dioxins was carried out according to the standard measurement manual for dioxins (Ministry of Health and Welfare), and the toxicity equivalent coefficient of WHO / IPCS was applied.

Example 1 After dioxins in fly ash were extracted with toluene, methanol-substituted extract was subjected to BOD 90 mg / l, COD
A test wastewater having a dioxin concentration of 4000 pg / L was prepared by adding to 210 mg / l of leachate raw water, and was subjected to an implementation test of the present invention. Using 150 liters of the test drainage described above, the circulation amount of the test drainage by the ultraviolet irradiation tank pump was adjusted to 1000 liters per hour, and ozone gas whose ozone concentration was adjusted to 5 g / Nm3 or more was blown into the ozone dissolution tank. The ozone dissolution tank was operated for 60 minutes at a circulation rate of 5400 liters per hour by a circulation pump. After the operation, the concentration of dioxins in the test wastewater was measured. As a result, the removal rate of dioxins as a whole in the test wastewater was 88%, and 75% or more of each homologue was removed.

Example 2 Four aluminum reflectors having the same arrangement as shown in FIG. 1 and having the same arrangement as shown in FIG. 1 and having a length of 2000 mm and a cross section of 50 mm on a side were attached. An experiment for treating the test wastewater was performed under the same conditions as in Example 1 except for the above. After the experiment, the concentration of dioxins in the test wastewater was measured. As a result, the removal rate of dioxins in the test wastewater was 92%, and 78% for each homologue.
These were removed.

Example 3 The surface has a length of 2000 mm at intervals of 30 mm and a side length of 5 mm.
Using the same apparatus as that used in Example 1 except that the regular triangular saw-tooth irregularities of mm were attached to the downflow wall, a treatment experiment of the test wastewater was performed under the same conditions as in Example 1. After the experiment, the concentration of dioxins in the test wastewater was measured. as a result,
The removal rate of dioxins as a whole in the test wastewater was 91%, and 76% or more of each homologue was removed.

Example 4 An experiment for treating a test wastewater under the same conditions as in Example 1 using the same apparatus as used in Example 1 except that a falling wall coated with titanium oxide having a photocatalytic action on the surface was used. Was done. After the experiment, the concentration of dioxins in the test wastewater was measured. As a result, the removal rate of dioxins as a whole in the test wastewater was 95%, and 80% or more of each homologue was removed.

Comparative Example 1 The same apparatus as used in Example 1 was used, except that a conventional immersion type apparatus equipped with the same ultraviolet light source as in Example 1 was used instead of the ultraviolet irradiation tank of the present invention. An irradiation treatment experiment was performed on the same amount of test wastewater under the same conditions and for the same time as in Example 1. After the experiment, the concentration of dioxins in the test wastewater was measured. As a result, the removal rate of the entire dioxins in the test wastewater was 81%, and each homolog was 60 to 60%.
The removal rate was 90%.

[0020]

According to the present invention, since the wastewater containing dioxins is irradiated with ultraviolet light in a thin film form, the ultraviolet light can be evenly applied to the wastewater which is difficult to transmit ultraviolet light, and can efficiently reach the decomposition target. Let me know. Therefore, halogenated organic substances including dioxins are effectively dechlorinated. Further, the size and number of surfaces of the downflow wall can be appropriately changed according to installation conditions and processing conditions.

Further, in the present invention, if necessary, a reflector, a groove on the surface of the falling wall, a falling wall having a catalytic action, and the like can be provided. The reflector has the effect of increasing the utilization efficiency of ultraviolet rays, the grooves on the surface of the falling wall increase the irradiation surface area, and the turbulence of the drainage film is generated to increase the decomposition efficiency of dioxins. In addition, the surface of the downflow wall can be made of a substance having a catalytic action to promote the decomposition of dioxins.

[Brief description of the drawings]

FIG. 1 is a sectional view of an apparatus showing an embodiment of the present invention.

FIG. 2 is a diagram schematically illustrating an example of a batch type wastewater treatment apparatus in which the ultraviolet irradiation tank and the ozone dissolving tank are combined.

[Explanation of symbols]

1: Falling wall (surface) 2: Overflow weir 3: Drain film 4: Ultraviolet light source 5: Light source cover 6: Reflector 7: Drain overflow surface 11: Ultraviolet irradiation tank 12: Ozone dissolution tank 13: Downflow wall 14: UV lamp 15: Drain circulation tank 16: UV irradiation tank pump 17: Overflow weir 18: Overflow weir 19: Ozone dissolution tank pump 20: Ozone generator 21: Ozone gas concentration meter

Continued on front page F-term (reference) 2E191 BA12 BA15 BB00 BC01 BD11 BD17 4D037 AA11 AA13 AB14 BA18 CA12 4D050 AA12 AA13 AA15 AB19 BB02 BD02 BD03 BD06 BD08 CA07 4H006 AA05 AC13 AC26 BA10 BA30 BA95 BB14 BB31 BC18 BC19 BE19

Claims (7)

[Claims] 1. A wastewater containing dioxins is caused to flow down in a film form along a falling wall (wet wall) composed of a plurality of opposing surfaces, and ultraviolet light is discharged between the falling walls without contact with the drainage film. A method for treating dioxins in wastewater, comprising irradiating a wastewater film with a light source to treat dioxins in wastewater. 2. A method for treating dioxins in waste water, wherein the waste water containing dioxins is irradiated with ultraviolet rays and then oxidized with ozone, wherein the waste water is applied to a downstream wall composed of a plurality of opposing surfaces. Along the membrane, and irradiate the drainage film by arranging an ultraviolet light source between the downflow wall and the drainage film in a non-contact manner. A part of the wastewater irradiated with ultraviolet light (hereinafter referred to as ultraviolet treatment wastewater) A method for treating dioxins in waste water, comprising sending water to an ozone dissolution tank and returning the remainder to raw wastewater, and decomposing and treating dioxins in the ozone dissolution tank by bringing ozone gas into gas-liquid contact with ultraviolet-treated wastewater. . 3. An ozone dissolving tank outlet wastewater (hereinafter, referred to as ozone treatment wastewater) is partly taken out of the system, and the remainder is returned to ultraviolet treatment wastewater and circulated to the ozone dissolution tank. Item 6. The method for treating dioxins in wastewater according to Item 2. 4. A dioxin treatment apparatus for irradiating ultraviolet light to waste water containing dioxins, wherein a drain wall composed of a plurality of opposed surfaces and a drain film flowing down between the downstream walls. The apparatus for treating dioxins in water is characterized in that the apparatus comprises a non-contact ultraviolet light source for irradiating a drainage film. 5. The dioxins processing apparatus according to claim 4, wherein a reflector that reflects ultraviolet light is attached to the falling drainage film. 6. The dioxin processing apparatus according to claim 4, wherein a groove-like unevenness is provided on the surface of the falling wall. 7. The apparatus for treating dioxins according to claim 4, wherein a catalytic action is added to the surface of the falling wall.