JP3654579B2 - Wastewater purification method - Google Patents

Description

注：試験用原水の DXN濃度＝25,900 Pg-TEQ/L
膜ろ過 ：精密ろ過膜または限外ろ過膜によるろ過。
凝集剤 ：ポリ塩化アルミニウム、添加量 30mg/L
酸化処理 ：二酸化マンガン触媒とオゾンの併用。
排水規制値：１０ Pg-TEQ/L
【００１７】
【発明の効果】
本発明の排水の浄化処理方法は、以上に説明したように構成されているので、排水中の固形分を汚泥として再処理する必要がなくなり、焼却装置などに熱損失を与えることが少なく、かつ膜ろ過装置の寿命を大幅に延長して二次廃棄物の発生を抑制できる。そして、排水中のダイオキシン類を効果的に除去でき、排水の大部分は放流可能な低濃度にすることができるという優れた効果がある。よって本発明は従来の問題点を解消した排水の浄化処理方法として、その工業的価値は極めて大なるものがある。
【図面の簡単な説明】
【図１】本発明の排水の浄化処理方法の要部を示すシステムフロー図。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a treatment method for removing dioxins contained in waste water generated in incineration equipment and melting equipment, for example, waste water for washing exhaust gas.
[0002]
[Prior art]
Conventionally, incineration equipment, melting equipment, or industrial waste incineration equipment at nuclear facilities, the presence of dioxins in exhaust gas has been regarded as important, and remarkable progress has been made in combustion technology and exhaust gas treatment technology. As for dioxins, research is not progressing as in the case of exhaust gas.
[0003]
As a method for treating dioxins in waste water, a waste water purification treatment method disclosed in JP-A-10-286597 has been proposed. In this treatment method, raw water containing dioxins is agglomerated and precipitated, then passed through a microfiltration membrane, hydrogen peroxide water is added to the filtered wastewater, mixed, and irradiated with ultraviolet rays to dioxins in the filtered wastewater. Is to disassemble.
[0004]
However, when this treatment method is applied to a nuclear facility, it is necessary to treat the coagulated sediment sludge, and since it passes through a microfiltration membrane, secondary waste is easily generated. In addition, there are problems that the life of the ultraviolet irradiation lamp is short and the replacement frequency is high, and the waste sludge contaminated with dioxins and the reprocessing of the secondary waste are complicated.
[0005]
[Problems to be solved by the invention]
The present invention has been made to solve the above-mentioned problems, and it is not necessary to reprocess the solid content in the wastewater as sludge, and the lifetime of the filtration membrane is greatly extended to generate secondary waste. Provided is a waste water purification treatment method that can effectively remove dioxins in waste water while suppressing the above.
[0006]
[Means for Solving the Problems]
The above problem is that wastewater containing dioxins obtained by washing exhaust gas generated from an incinerator or melting device is circulated through a filtration device using a microfiltration membrane or an ultrafiltration membrane and subjected to crossflow filtration. The wastewater containing dioxins is reduced in volume as concentrated wastewater containing gaseous dioxins, and then returned to the incinerator or melting apparatus for incineration or melting treatment, and the wastewater purification method of the present invention is characterized in that Can be solved by.
Further, the present invention is preferably used as a method for purifying wastewater in such a form that the filtered water of the filtering device is passed through a reactor packed with a manganese dioxide catalyst in the presence of ozone to oxidatively decompose soluble dioxins. Can be
[0007]
According to the present invention, crossflow filtration is performed with a filtration device using a microfiltration membrane or an ultrafiltration membrane, and the volume is reduced to a concentrated wastewater containing particulate dioxins contained in the wastewater, which is then incinerated or melted. Since it is returned to the equipment, waste sludge contaminated with dioxins is not generated. Further, since the cross-flow filtration is performed, the microfiltration membrane or the ultrafiltration membrane is hardly clogged, and the life is extended.
In the present invention, dioxins are used as a generic term for polychlorinated dibenzodioxins, which are organochlorine compounds containing a large number of isomers depending on the number of chlorine, including tetrachlorodibenzodioxin (TCDD).
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment according to the method for purifying wastewater of the present invention will be described with reference to FIG.
Combustion exhaust gas generated from incinerators, melting devices, or industrial waste incinerators at nuclear facilities is freed of suspended solids by dust removal devices such as ceramic filters, bag filters, HEPA filters, etc., and then cleaned by cleaning devices. Water removes soluble components and fine solids that have passed through the dust remover. The exhaust gas that has passed through the dust removing device and the cleaning device is finally purified and exhausted by a dioxin (DXN) removing device.
In this case, the dioxins contained in the exhaust gas immediately before the cleaning device are transferred to the cleaning water side at the time of cleaning, and the amount that passes while remaining in the exhaust gas, according to the inventor's investigation, It was found that the amount of transition reached around 60% of the total.
[0009]
In the embodiment, the waste water containing dioxins obtained by washing the exhaust gas generated from the incinerator or the melting device is filtered by a membrane filtration device using a microfiltration membrane or an ultrafiltration membrane. However, in this case, the waste water is circulated on the stock solution side of the drain tank and the membrane filtration device so as to be subjected to cross flow filtration. Thus, the waste water containing dioxins is reduced in volume as concentrated waste water containing particulate dioxins. The concentrated waste water whose volume has been reduced in this way is returned to the incinerator or melting apparatus and incinerated or melted.
The degree of volume reduction is not limited, but reducing the volume to at least 1/100, preferably 1/1000 of the stock solution will affect the combustion state of the returned incinerator and the like. Since it does not give, it is preferable.
[0010]
Furthermore, in this embodiment, a process for passing the filtered water of the membrane filtration device through a catalyst filling device filled with a manganese dioxide catalyst and oxidizing and decomposing soluble dioxins so as to satisfy the discharge standard is added. . In this catalyst filling apparatus, ozone is introduced to promote the oxidative decomposition reaction, and the filtered water is effectively oxidatively decomposed by the action of the manganese dioxide catalyst in the presence of ozone.
[0011]
According to this embodiment of the present invention, first, cross flow filtration is performed with a membrane filtration device, and the concentrated wastewater containing particulate dioxins occupying most of the dioxins contained in the wastewater is returned to the incinerator or melting device. As a result, there is an advantage that waste sludge contaminated with dioxins is not generated. Further, since the cross-flow filtration is performed, the membrane filtration device is hardly clogged and the life is extended, so that the used waste membrane contaminated with dioxins is also reduced. Furthermore, since the waste water containing dioxins is concentrated to 1/100 to 1/1000 and returned to an incinerator for further processing, there is little heat loss because it does not place a load on the incinerator. There are also advantages such as easy maintenance of the high temperature required for decomposition.
Furthermore, the filtered water that has passed through the membrane filtration device is subjected to a final treatment with a manganese dioxide catalyst, and is purified to a discharge standard or lower as described later.
[0012]
Next, raw water for testing corresponding to the washing waste water of the present invention was prepared, and the dioxin removal performance by post-treatment shown below was investigated. The test results are shown in Table 1.
In the treatment system 1, the change in the concentration of dioxins (DXN concentration) was examined by filtering the raw water for testing with an MF membrane or UF membrane without oxidation treatment with a manganese dioxide catalyst, and the removal rate was 99.95%. However, in order to clear the regulation value 10 Pg-TEQ / L with certainty, it is desirable to dilute about 10 times by combining with other waste liquid.
[0013]
In this case, dioxins (DXN) concentration of 25,900 Pg-TEQ / L was used as test raw water. This is because the transfer rate of dioxins from exhaust gas to waste water was selected based on a preliminary test based on the fact that it was approximately 60% (weight ratio). However, the migration rate is the weight ratio of the total amount of dioxins in the washing wastewater to the total amount of dioxins in the exhaust gas immediately after the dust removal device, measured in unit time.
[0014]
In addition, the treatment system 2 is a method in which the flocculant polyaluminum chloride is added to the raw water for testing to increase the membrane filtration efficiency, and the removal efficiency is improved. The merging with the waste liquid is necessary as in the case of the processing system 1.
[0015]
The treatment system 3 is obtained by subjecting the treated water subjected to membrane filtration to an oxidation treatment using the manganese dioxide catalyst or the like of the present invention, and can remove the concentration to 1/10 or less of the regulation value. The process of merging with the waste liquid is also unnecessary.
[0016]
[Table 1]

Note: DXN concentration of raw water for test = 25,900 Pg-TEQ / L
Membrane filtration: Filtration using a microfiltration membrane or ultrafiltration membrane.
Flocculant: Polyaluminum chloride, added amount 30mg / L
Oxidation treatment: Combined use of manganese dioxide catalyst and ozone.
Drainage regulation value: 10 Pg-TEQ / L
[0017]
【The invention's effect】
Since the wastewater purification treatment method of the present invention is configured as described above, it is not necessary to reprocess the solid content in the wastewater as sludge, and less heat loss is caused to the incinerator, etc. The lifetime of the membrane filtration device can be greatly extended and the generation of secondary waste can be suppressed. And the dioxins in waste_water | drain can be removed effectively, and there exists the outstanding effect that most of waste_water | drain can be made into the low density | concentration which can be discharged. Therefore, the present invention has an extremely large industrial value as a wastewater purification treatment method that has solved the conventional problems.
[Brief description of the drawings]
FIG. 1 is a system flow diagram showing a main part of a method for purifying wastewater according to the present invention.

Claims (2)

Wastewater containing dioxins obtained by cleaning exhaust gas generated from an incinerator or melting device is circulated through a filtration device using a microfiltration membrane or ultrafiltration membrane and crossflow filtered to contain particulate dioxins A wastewater purification method comprising reducing the volume of the wastewater containing the dioxins as concentrated wastewater and then returning the wastewater to the incinerator or melting device to incinerate or melt the wastewater. The method for purifying wastewater according to claim 1, wherein the filtered water of the filtering device is passed through a reactor filled with a manganese dioxide catalyst in the presence of ozone to oxidatively decompose soluble dioxins.

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