JP3418550B2 - Method and equipment for decomposing and removing dioxins in sewage - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for decomposing and removing dioxins in wastewater such as leachate at a final waste disposal site.

[0002]

2. Description of the Related Art Dioxins (PCDD), such as leachate from the final landfill of landfills of general waste and industrial waste
s, PCDFs) for purifying the waste water is, for example, as shown in FIG.

That is, wastewater is subjected to coagulation treatment 1 to remove heavy metals such as calcium and manganese, and biological treatment 2
Then, the BOD substance and TN are decomposed, and the coagulation treatment 3 is performed to CO.
D substances, suspended substances, TP, etc. are removed, sand filtration 4 is used to remove fine suspended substances, and then ozone / ultraviolet treatment 5 is carried out, in addition to residual dioxins, COD substances and chromaticity. The components are decomposed, and the product is discharged after being treated with activated carbon 6.

[0004]

However, even if the sand filtration treated water 4a after the sand filtration 4 is subjected to the ozone / ultraviolet treatment 5 as described above, dioxins (PCDDs, PCDDs) can be obtained.
Most (99% or more) of DFs) are removed in the form of being accumulated in microorganisms or SS in biological treatment 2 and coagulation treatments 1 and 3 before and after it, so the decomposition effect by ozone and ultraviolet rays is small, and each treatment It is included in the sludge generated in and discharged.

Even if the sand-filtered water 4a is S
S, COD such as humic substances, Ca ions, NH ₄ —N, C
l Ions, etc. remain, and these reduce the irradiation efficiency of ultraviolet rays and generate O from ozone and ultraviolet rays.
It acts as a scavenger for H radicals and inhibits the decomposition of dioxins.

The present invention solves the above problems, and an object of the present invention is to provide a decomposition removal method and a decomposition removal equipment capable of decomposing and removing dioxins in wastewater.

[0007]

In order to solve the above problems, the method for decomposing and removing dioxins in wastewater according to the present invention is a wastewater containing at least one of biological treatment and coagulation treatment of wastewater containing dioxins. Processing in the processing step,
In addition to obtaining purified treated water, sludge containing dioxins generated by the biological treatment or coagulation treatment is washed with fresh water, and the washed sludge is mixed with a dioxin extract solution to extract dioxin in the sludge. The dioxin is extracted in a liquid, the dioxin extract is separated from the sludge, filtered, and then treated with ozone and ultraviolet rays to decompose and remove dioxins.

The facility for decomposing and removing dioxins in sewage of the present invention is equipped with at least one of a biological treatment device for purifying sewage and a coagulation sedimentation treatment device, and is capable of removing sludge generated in the biological treatment device or the coagulation sedimentation treatment device. A sludge treatment device for processing, the sludge treatment device has a fresh water supply means, a sludge cleaning tank for cleaning the sludge, and a dioxin extract supply means, in the sludge transferred from the sludge cleaning tank A dioxin extraction tank for extracting dioxins,
A dioxin decomposition tower having a filtering means for filtering the dioxin extract transferred from the dioxin extraction tank, an ozone supply means, and an ultraviolet irradiation means, for decomposing dioxins in the dioxin extract transferred from the filtering means; Is provided with.

As the dioxin extract, acetone,
Acetonitrile, benzene, DMSO, chlorobenzene, o-dichlorobenzene, LAS (sodium linear alkylbenzene sulfonate) and the like can be used.

According to the above construction, by cleaning the sludge with fresh water, the water on the surface of the sludge is replaced with fresh water, and C such as SS and humic substances which become an obstructive factor for ozone / ultraviolet treatment.
OD, Ca ion, NH ₄ -N, Cl It is possible to reduce the concentration of scavengers such as ions, and the dioxin extract solution obtained by extracting dioxin from such sludge is filtered and then treated with ozone and ultraviolet rays, so that dioxins can be efficiently decomposed and removed.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. Figure 1 shows dioxins (PCDDs) such as leachate treatment plants at final waste disposal sites.
s, PCDFs) showing a schematic overall structure of a sewage treatment plant for treating sewage, including a regulating tank 11 into which sewage sequentially flows, a calcium removal facility 12, a biological treatment facility 13, a coagulation sedimentation facility 14, a sand filtration tower 15. , Activated carbon adsorption tower 16
Is equipped with.

[0012] Further, sludge cleaning tanks 17 and 18 for treating sludge generated in the calcium removal equipment 12, the biological treatment equipment 13, and the coagulation sedimentation equipment 14, a dioxin extraction tank 19, a filtration device 20, a dioxin decomposition device 21, Two
2. The sludge dehydrator 23 is provided.

The sludge cleaning tanks 17 and 18 are the fresh water supply means 1
7a and 18a, mixing tanks 17c and 18c equipped with stirring means 17b and 18b, and precipitation tanks 17d and 18d. The dioxin extraction tank 19 has a dioxin extract supply means 19a and is capable of shaking the contents,
The dioxin decomposers 21 and 22 have ultraviolet lamps 21b and 22b arranged at the axial center positions of the cylindrical tanks 21a and 22a, respectively, which are passed upward, and ozone supply pipes 21c and 22c arranged at the lower part of the tank. There is. The sludge dewatering machine 23 has a dewatering auxiliary agent supply means 23a at the inflow portion.

The treatment of wastewater in the above treatment plant will be described. The water quality and flow rate of the sewage 10 are adjusted in the adjusting tank 11, heavy metals such as calcium and manganese are aggregated and precipitated by the Na ₂ CO ₃ aggregating agent in the calcium removal facility 12, and the BOD substance and TN are decomposed in the biological treatment facility 13. Then, in the coagulation-sedimentation treatment facility 14, the COD substance, the suspended matter, T-P, etc. are coagulated and precipitated by the coagulant, and the remaining S
COD substances such as S, TN, humic substances and chromaticity components are removed by the sand filtration tower 15 and the activated carbon adsorption tower 16, and treated water 24
To be released as.

Calcium removal facility 12 and biological treatment facility 1
3 and the sludge 25 generated in the coagulation sedimentation treatment facility 14 contain dioxins, the mixing tank 1 of the sludge cleaning tank 17
7c, and in the clean water supplied from the fresh water supply means 17a, while stirring and washing with the stirring means 17b, it is transferred to the settling tank 17d for sedimentation separation, and then the sludge cleaning tank 1
Then, it is transferred to the mixing tank 18c of No. 8 and washed in the same manner, and then transferred to the precipitation tank 18d for sedimentation separation. For cleaning, Ca ions and NH ₄ − contained in the separated water separated from the sludge 25
N, Cl It is performed plural times as necessary until the amount of ions and the like is reduced to about 1/10 or less.

Then, the cleaning sludge 26 is taken out from the settling tank 18d and transferred to the dioxin extraction tank 19, and the dioxin extraction solution such as DMSO is injected from the dioxin extract supply means 19a and shaken for 1 hour or more to wash the sludge 2
The dioxins in 6 are extracted into the dioxin extract.

Next, the dioxin extract liquid 27 from which dioxins have been extracted is taken out, filtered by the filter device 20, and then passed through the dioxin decomposing devices 21, 22 in order, and inside the tank 21a (22a) of each device, OH radicals generated from ozone supplied through the ozone supply pipe 21c (22c) and the ultraviolet light emitted from the ultraviolet lamp 21b (22b) act to decompose dioxins.

The sludge 28 remaining in the dioxin extraction tank 19 is dehydrated in the sludge dehydrator 23 after adding a dehydration aid from the dehydration aid supply means 23a, and the dehydrated cake 2
9 is put into a cake hopper (not shown), then appropriately carried out, and incinerated and melted and disposed.

The desorbed liquid 30 in the sludge dewatering machine 23, the cleaning drainages 31 and 32 generated in the sludge cleaning tanks 17 and 18,
The dioxin extraction waste liquid 33 flowing out from the dioxin decomposition device 22 is returned to the adjusting tank 11 and a series of wastewater treatment is performed.

By cleaning the sludge 25 in clear water in this manner, the concentration of the sludge 25 is increased and the dioxins extraction efficiency is improved, and the sludge 2
The separated water on the surface of No. 5 is replaced with fresh water, and the dioxin extract liquid 27 is passed through the dioxin decomposers 21 and 22.
CO, such as SS and humic substances, Ca ions, NH ₄ −
N, Cl The concentration of ions etc. decreases.

As a result, it is possible to efficiently decompose and remove the dioxins extracted in the dioxin extraction liquid 27 in a state where the ultraviolet irradiation efficiency is high and the wasteful ozone consumption by the scavenger is small. Moreover, since the dehydrated cake 29 has a low Cl content, the amount of dioxin generated during incineration / melting is small.

As the dioxin extract, the above-mentioned D
In addition to MSO, LAS (sodium linear alkylbenzene sulfonate), benzene, acetone, chlorobenzene, acetonitrile, o-dichlorobenzene and the like can be used. For example, in the case of DMSO, the concentration of 10 to 20 w / v% DMSO is added to a sludge of 2 w / v% concentration (dry basis) in an amount equal to or more than the amount of sludge, and benzene (or acetone, chlorobenzene, acetonitrile, o −
In the case of (dichlorobenzene), 20 w / v% concentration is added in an amount equal to or more than the sludge amount.

As the fresh water, it is convenient to use the treated water 24 obtained in the sewage treatment step. In addition, the above-described embodiment can be appropriately changed based on the property of sewage.
For example, in the sewage treatment step, calcium removal treatment and biological treatment may be performed to omit the coagulation-sedimentation treatment, or biological treatment and coagulation-sedimentation treatment may be performed to omit the calcium removal treatment, or a chelate treatment, Ion exchange treatment or the like may be added. In the sludge treatment process,
A sludge concentration step may be added, or the dehydrated cake may be landfilled.

[0024]

As described above, according to the present invention, by washing sludge with fresh water before extraction of dioxins, NH ₄ -N, Cl, which becomes an obstructive factor for ozone / ultraviolet treatment, can be obtained.
It is possible to reduce the concentration of ions, Ca ions, etc., to achieve high ultraviolet irradiation efficiency, reduce unnecessary ozone consumption, and efficiently decompose and remove dioxins. In addition, since the Cl content remaining in the sludge is reduced, it is possible to reduce the generation of dioxins when the sludge is incinerated or melted and disposed.

[Brief description of drawings]

FIG. 1 is a schematic overall configuration diagram of a wastewater treatment plant for decomposing and removing dioxins in wastewater in an embodiment of the present invention.

FIG. 2 is a flowchart showing a conventional wastewater treatment method.

[Explanation of symbols]

10 dirty water 12 Calcium removal equipment 13 Biological treatment equipment 14 Coagulation sedimentation treatment equipment 17,18 Sludge cleaning tank 19 Dioxin extraction tank 19a Dioxin extract supply means 20 Filtration device 21,22 Dioxin decomposition device 24 Treated water 25 sludge 26 Washing sludge 27 Dioxin extract

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI C02F 11/00 ZAB C02F 11/00 ZABC (56) References JP-A-11-309499 (JP, A) JP-A-11-33570 (JP, A) JP-A-11-5099 (JP, A) JP-A-10-296299 (JP, A) JP-A-7-108285 (JP, A) (58) Fields investigated (Int. Cl. ⁷⁾ , DB name) C02F 1/00-1/78 C02F 3/00-3/34 101 C02F 11/00-11/20

Claims (2)

(57) [Claims] 1. A sewage containing dioxins is treated in a sewage treatment step in which at least one of biological treatment and coagulation treatment is performed to obtain purified treated water, and dioxin generated by the biological treatment or coagulation treatment. The sludge containing the substances is washed with fresh water, the dioxin extract is mixed with the washed sludge to extract the dioxins in the sludge into the dioxin extract, and the dioxin extract is separated from the sludge, filtered and then ozone. A method for decomposing and removing dioxins in wastewater, which comprises decomposing and removing dioxins by treating with ultraviolet light. 2. A biological treatment device for purifying sewage and / or a coagulation sedimentation treatment device, and a sludge treatment device for treating sludge generated in the biological treatment device or the coagulation sedimentation treatment device. , Having a fresh water supply means, a sludge cleaning tank for cleaning sludge, and a dioxin extract supply means, a dioxin extraction tank for extracting dioxins in the sludge transferred from the sludge cleaning tank,
A dioxin decomposition tower having a filtering means for filtering the dioxin extract transferred from the dioxin extraction tank, an ozone supply means, and an ultraviolet irradiation means, for decomposing dioxins in the dioxin extract transferred from the filtering means; A facility for decomposing and removing dioxins in sewage characterized by being equipped with.