JP3373138B2 - Organic wastewater treatment method and apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to the treatment of organic wastewater containing organic chlorine compounds such as dioxins, and more particularly to the treatment of organic wastewater that can be used for leachate or industrial wastewater treatment.

[0002]

2. Description of the Related Art Conventionally, as a main treatment method for organic wastewater such as leachate, a treatment method mainly for removing organic substances has been used. Main treatment methods include biological treatment for the purpose of removing BOD and nitrogen, coagulation sedimentation treatment for the purpose of removing chromaticity, COD, SS, etc., sand filtration treatment for the purpose of removing suspended matter such as SS, etc. There is. Further, activated carbon treatment may be used as the advanced treatment method. However, none of the above treatment methods has the effect of decomposing and removing a small amount of organic chlorine compounds such as dioxins in the organic waste water, and the organic chlorine compounds such as dioxins often remain in the discharged water. Furthermore, organic chlorine compounds such as dioxins are almost insoluble in water, and even if the organic chlorine compounds such as dioxins decrease in each treatment step, most of them are contained in the sludge generated from the treatment steps, and after dehydration treatment, The content of organic chlorine compounds such as dioxins in the cake is high, and it is considered that the effect of decomposing and removing organic chlorine compounds such as dioxins in the entire system is not so great. As a recent technology for decomposing organic chlorine compounds such as dioxins, it is known to decompose and remove organic chlorine compounds such as dioxins dissolved in water to be treated by dechlorination reaction by ultraviolet irradiation and oxidation reaction by ozone injection. .

[0003]

However, when ultraviolet irradiation or ozone injection is introduced into organic wastewater having a high concentration of suspended solids, chromaticity components, and organic substances, the ultraviolet transmittance is low, which causes a decrease in reaction efficiency. It is considered that most of injected ozone is consumed for decomposition and removal of organic substances other than soluble dioxins. Furthermore, there is almost no treatment that combines decomposition treatment of organic chlorine compounds such as dioxins accumulated in sludge with water treatment process, and even if organic chlorine compounds such as dioxins are removed in the water treatment process, high concentration of dioxins etc. in sludge Organochlorine compounds often accumulate.

The present invention solves the above problems,
Removal of organic pollutants and suspended substances from the treated water in the pretreatment process and sludge treatment process, which mainly consist of biological treatment of the treated water, and in the subsequent treatment, dissolved chlorine dioxide compounds such as dioxins in the treated water. Efficiently decomposes and removes dioxin and other organochlorine compounds in sludge generated from the previous treatment process, and decomposes and removes dioxin and other organochlorine compounds in the treatment system at a high removal rate
And to provide a device .

[0005]

The above-mentioned problems can be solved by the following constitutions. (1) A method of treating organic wastewater, wherein water to be treated is treated by a pretreatment mainly consisting of biological treatment, and sludge generated from the pretreatment is treated with ozone or ozone and hydrogen peroxide. A method for treating organic wastewater containing an organic chlorine compound such as dioxin, which is carried out and returns the supernatant water to the treated water inflow section. (2) An organochlorine compound such as dioxin according to (1), characterized in that the treated water of the preceding stage treatment is subjected to a subsequent stage treatment in which waste ozone from the sludge treatment is used and combined with hydrogen peroxide or ultraviolet rays. A method for treating organic wastewater containing. (3) Biological treatment device for biologically treating water to be treated, the organism
Coagulation sedimentation treatment equipment for coagulating sedimentation of treated water from treatment equipment
From the biological treatment device and the coagulation sedimentation treatment device.
Decompose sludge with ozone or ozone and hydrogen peroxide
Sludge decomposition treatment device, supernatant in the sludge decomposition treatment device
An arrangement for returning the water to the inflow part of the treated water of the biological treatment device.
Organic chlorination such as dioxins characterized by having a tube
A device for treating organic wastewater containing compounds.

According to the present invention, by subjecting the water to be treated to the pretreatment mainly consisting of biological treatment, most of the insoluble suspended solids and organic substances in the water to be treated can be removed and separated, and almost all the water can be treated. Insoluble organic chlorine compounds such as dioxins can be reduced together with a decrease in SS and organic matter concentrations. The treated water obtained by the above-mentioned pretreatment process is organic matter and S.
Since S was also highly removed, the concentration of organic chlorine compounds such as dioxins dissolved in water became extremely small,
In the subsequent treatment step for decomposing organic chlorine compounds such as dioxins, the organic chlorine compounds such as dioxins can be decomposed and removed with high efficiency by the ozone discharged from the sludge treatment and a small amount of ultraviolet irradiation or the amount of hydrogen peroxide added.

On the other hand, in the sludge treatment step, the sludge generated by the ozone or the hydroxyl radicals produced by the injection of ozone and hydrogen peroxide is used for the high-concentration organic chlorine compounds such as dioxins contained in the sludge generated from the preceding treatment step. Dioxin in the sludge can be decomposed and removed, and some organic matter in the sludge can be decomposed to reduce the sludge volume.
By returning the supernatant water after sludge treatment to the inflow part of the previous stage treatment, for some organic substances and organic chlorinated compounds such as dissolved dioxins that have been eluted from the sludge, the organic substances can be removed in the previous stage of the treatment process, and the dissolved dioxins and other organic substances can be removed. Since chlorine compounds can be decomposed and removed in the subsequent organic chlorine compound decomposition treatment step such as dioxins, there is no residue of dioxins or other organic chlorine compounds in the discharged water, and the amount of organic chlorine compounds such as dioxins in sludge discharged to the outside of the system is considerably reduced. Inorganic chlorine compounds such as inflowing dioxins can be decomposed and removed at a high removal rate in the treatment system.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the drawings showing an example of an embodiment. FIG. 1 is a flow sheet showing an example of the processing method according to the present invention. As shown in FIG. 1, the water 1 to be treated is subjected to a biological treatment step 2 to remove biologically removable organic substances, SS, etc.
Part of the organic chlorine compounds such as dioxins in the water to be treated are removed, and the sludge 6 generated from the biological treatment step 2 is sent to the sludge decomposition treatment step (also simply referred to as sludge treatment step) 11 to decompose and remove dioxin in the sludge and to remove sludge. Reduce the volume. The treated water of the biological treatment step 2 is further subjected to coagulation-sedimentation treatment step 3 to remove chromaticity, organic contaminants and SS, and also to remove organic chlorine compounds such as residual dioxins. The sludge 7 from the coagulation-sedimentation step 3 is sent to the sludge decomposition treatment step 11 similarly to the sludge 6 of the biological treatment step 2 to decompose and remove organic chlorine compounds such as dioxins in the sludge and reduce the volume of the sludge.

The coagulated sedimentation treated water is further subjected to a sand filtration treatment step 4
Residual SS and organochlorine compounds such as SS dioxins are removed by. The sand filtration backwash drainage 14 is returned to the coagulation sedimentation treatment step 3 to separate and remove SS and the like. In the dioxin decomposition step 5, the waste ozone 15 from the sludge decomposition processing step 11 was introduced into the sand filtration treated water in which the concentration of organic chlorine compounds such as dissolved dioxin was considerably reduced, and the organic chlorine compounds such as dissolved dioxin were completely decomposed and removed. The treated water is discharged as discharged water 10 to the outside of the system.

In the sludge decomposition treatment step 11, the mixed sludge of the biological treatment sludge 6 and the coagulation sedimentation sludge 7 is added with the addition of hydrogen peroxide 13 and at the same time, ozone gas 12 is injected from the bottom of the sludge to cause organic chlorine such as dioxins in the sludge. The compound is dissolved by the decomposition or elution of the organic substance by the hydroxy radical having strong oxidizing power, and a part thereof is oxidatively decomposed. The sludge having a reduced concentration of organic chlorine compounds such as dioxins is discharged to the outside of the system as discharged sludge 9. Further, the supernatant water 8 after the sludge decomposition treatment is returned to the inflow part of the water to be treated 1.

In the above treatment flow, the biological treatment step 2, the coagulation sedimentation treatment step 3, and the sand filtration treatment step 4 which are the preceding treatments
Is an example of removing organic matter and SS from the water to be treated,
Depending on the properties of the water to be treated, the coagulation-sedimentation treatment step 3 may be provided first, and the combination includes biological treatment + filtration treatment, biological treatment + coagulation-sedimentation filtration treatment, and the like. The biological treatment method may be any of a catalytic oxidation method, a rotating disk method, a biological nitrification denitrification method, and the like. The flocculation treatment and the filtration treatment may be flocculation membrane filtration, flocculation sedimentation and sand filtration.

[0012]

EXAMPLE An organic wastewater containing an organic chlorine compound such as dioxin was treated by the method shown in the flow sheet of FIG. Table 1 shows the water quality of each treatment step obtained by this method, and Table 2 shows the water quality before and after sludge decomposition treatment. Table 3 shows the conditions for decomposing organic chlorine compounds such as dioxins and the conditions for decomposing sludge.

[0013]

[Table 1]

As shown in Table 1, the water to be treated has a chromaticity of 600.
In contrast to COD 200 mg / liter, BOD 150 mg / liter, SS 30 mg / liter, treated water after biological treatment has a chromaticity of 300 degrees, COD 80 mg / liter, BOD 10 mg / liter, SS 15 mg / liter I was able to remove it. Similarly, total dioxin could be reduced from 1900 pg / liter of treated water to about 500 pg / liter. Furthermore, the treated water that has been subjected to coagulation treatment and sand filtration treatment has a chromaticity of 80 degrees and COD3
It became 5 mg / liter, BOD, and SS for all 1 mg / liter or less.

As a result, total dioxin is also 150 pg /
Liter, dioxin TEQ is 2.5 pg / liter, dioxin decomposition process, ozone discharged from sludge treatment 10 mg / liter, UV irradiation amount 0.25
W ・ hr / liter, reaction time was only 2.5 minutes, dioxins in treated water were below the detection limit, chromaticity, CO
The effect of removing D was also obtained, and the chromaticity was reduced to 5 degrees and COD to 10 mg / liter. In addition, TEQ is 2, 3, 7, 8
-TCDD (chlorotetradipenzoparadioxin tetrachloride) toxicity equivalent conversion concentration is shown.

[0016]

[Table 2]

As shown in Table 2, sludge before decomposition is SS
7,000mg / liter, total dioxin 35,000p
g / liter and dioxin TEQ 450 pg / liter, whereas ozone injection rate 100 mg / liter, H ₂ O ₂ addition amount 50 mg / liter, residence time about 60
Under the condition of minutes, the sludge after the decomposition treatment was reduced to SS 5000 mg / liter, total dioxin 10000 pg / liter, and dioxin TEQ 120 pg / liter. As a result, dioxin of SS was 5.0 ng before decomposition treatment.
/ G to 1.3 ng / g. On the other hand, the sludge filtrate had a chromaticity of 100 degrees, COD of 200 mg / liter, BOD of 80 mg / liter, and total dioxin of 30 before being decomposed.
0 pg / liter and dioxin TEQ 5.0 pg / liter, whereas the filtrate after the decomposition treatment had a chromaticity of 50.
0 degree, COD 600mg / liter, BOD 300mg
/ L, and decomposition and elution of organic substances was observed with the decomposition treatment.

As a result, the total dioxin and dioxin TEQ in the filtrate became higher than those before the decomposition treatment, and
It became 3500 pg / liter and 50 pg / liter. However, if these are returned to the pretreatment process of the water to be treated, organic substances and dioxins can be surely removed in each treatment process. In this way, about 70% or more of the total dioxins in the sludge decomposition treatment step can be decomposed and removed in the inflowing dioxin, and the removal rate in the system becomes at least 70% or more when the amount of decomposed and removed dissolved dioxin is combined. .

[0019]

[Table 3]

[0020]

As shown in the examples, according to the present invention, organic wastewater containing an organic chlorine compound such as dioxin is subjected to a preliminary treatment mainly for biological treatment, and insoluble suspended substances and a part of organic substances are treated. It is also possible to remove the concentration of organic chlorine compounds such as dioxins in the water to be treated which is almost insoluble in water by removing and separating the water. The treated water that has undergone the treatment steps as described above was able to highly remove both organic matter and SS,
The concentration of organic chlorine compounds such as dioxins dissolved in water becomes extremely small, and the waste ozone from sludge treatment is used in the subsequent dioxin decomposition treatment process, resulting in high efficiency of dioxins, etc., by irradiating ultraviolet rays or adding hydrogen peroxide. Organic chlorine compounds can be decomposed and removed, and organic chlorine compounds such as dioxins in discharged water can be reduced to below the detection limit.

On the other hand, with respect to high-concentration organic chlorine compounds such as dioxins contained in the sludge generated from the pretreatment process, sludge is generated in the sludge treatment process by hydroxy radicals generated by injection of ozone or ozone and hydrogen peroxide. It is possible to decompose and remove organic chlorine compounds such as dioxins, and also to elute and decompose some of the organic substances in the sludge, thus reducing the sludge volume. By returning the supernatant water after sludge treatment to the inflow part of the previous stage treatment, for some organic substances and organic chlorinated compounds such as dissolved dioxins that have been eluted from the sludge, the organic substances can be removed in the previous stage of the treatment process, and the dissolved dioxins and other organic substances can be removed. Since chlorine compounds can be decomposed and removed in the subsequent dioxin decomposition treatment step, there are no residual organic chlorine compounds such as dioxins in the discharged water, and the concentration of organic chlorine compounds such as dioxins in sludge discharged to the outside of the system is considerably reduced, and inflow dioxins, etc. The organic chlorine compound can be decomposed and removed at a high removal rate in the treatment system.

[Brief description of drawings]

FIG. 1 is a flow sheet diagram showing an example of a processing method according to the present invention.

[Explanation of symbols]

1 treated water 2 biological treatment process 3 Coagulation sedimentation process 4 sand filtration process 5 Dioxin decomposition process 6 biological treatment sludge 7 Coagulation sedimentation sludge 8 Sludge decomposition treatment Clear water 9 discharged sludge 10 Discharged water 11 Sludge decomposition process 12 Ozone gas 13 Hydrogen peroxide 14 Backwash drainage 15 Exhausted ozone

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI C02F 9/00 503 C02F 9/00 503C 504 504A 11/06 ZAB 11/06 ZABA (72) Inventor Souta Nakagawa Fujisawa Ichimoto, Kanagawa 4-2-1 Fujisawa, Ebara Research Institute Co., Ltd. (56) References JP-A-9-99292 (JP, A) JP-A-9-122678 (JP, A) International Publication 96/9987 (WO, A2) (58) Fields surveyed (Int.Cl. ⁷ , DB name) C02F 3/00-3/34 C02F 9/00 C02F 11/00-11/20

Claims (3)

(57) [Claims] 1. A method of treating organic wastewater, wherein water to be treated is treated by a pretreatment mainly consisting of biological treatment, and sludge generated from said pretreatment is ozone or ozone and hydrogen peroxide sludge. A method for treating organic wastewater containing an organic chlorine compound such as dioxin, which comprises performing treatment and returning the supernatant water to the treated water inflow section. 2. The organochlorine compound such as dioxin according to claim 1, wherein the treated water of the pretreatment is subjected to posttreatment of a combination of ozone discharged from the sludge treatment and hydrogen peroxide or ultraviolet rays. A method for treating organic wastewater containing. 3. A biological treatment apparatus for biologically treating water to be treated,
Coagulation sedimentation for coagulating sedimentation of treated water from the biological treatment equipment
Treatment device, biological treatment device, and coagulation sedimentation treatment device
Sludge from the plant is separated by ozone or ozone and hydrogen peroxide.
Sludge decomposition treatment device for decomposing, with the sludge decomposition treatment device
Return the supernatant water to the inflow part of the treated water of the biological treatment equipment
Organic such as dioxins characterized by having piping
A treatment device for organic wastewater containing chlorine compounds.