JP2001096284A - Water treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently and economically make sewage incorporating a low concentration of dioxines like water leached from rubbish harmless. SOLUTION: Water incorporating a low concentration of dioxines to be treated is treated with ozone, UV rays and hydrogen peroxide in a three dimensional reaction tank 2. As the gaseous ozone, gaseous ozone of a >=200 mg/Nm3 high concentration and under >=2 kg/cm2 high pressure is used. Gaseous ozone dissolves into the water to be treated to nearly saturated concentration in a short time. The dioxines and an aromatic organic chlorine compound in the water to be treated are dechlorinated with irradiation of UV rays and the dechlorinated products are effectively decomposed by a large amount of ozone and a lot of hydroxy radicals generated from the ozone and hydrogen peroxide with irradiation of UV rays.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating water with ozone, and more particularly, to a method for treating dioxins (including PCBs and Co planar PCBs) at a low concentration, such as leachate of garbage and fly ash washing wastewater of incinerators. Specifically, 1000 pg
The present invention relates to a wastewater treatment method suitable for treating wastewater containing TEQ / L or less.

[0002]

2. Description of the Related Art As is well known, dioxins which are highly toxic and hardly decomposed are contained in large amounts in incineration ash discharged from garbage incineration plants. Although this incineration ash is disposed of at the final disposal site, there is a risk that dioxins gradually ooze out of the incineration ash due to rainfall and the like and are mixed into groundwater or the like. For this reason, contamination of groundwater and soil by dioxins contained in leachate leachate has become a serious problem in recent years.

Methods of decomposing dioxins to make them harmless include thermal decomposition in an incinerator, decomposition with supercritical water, photolysis (ultraviolet light, sunlight), chemical decomposition (ozone, hydrogen peroxide), microorganisms As a method of treating dioxin-containing sewage, a ternary treatment combining ultraviolet, ozone and hydrogen peroxide is currently considered to be the most effective method (for example, JP 7
-108285, JP-A-11-33570, etc.).

[0004] In photodecomposition by ultraviolet rays, dioxin molecules are converted into ozone-sensitive compounds which are susceptible to oxidative decomposition by chemical reaction with ozone by dechlorination. When the ether bond is cleaved by the action of ultraviolet rays, a chlorinated biphenyl compound is generated, but the dechlorination of dioxin molecules proceeds by irradiation with ultraviolet rays. In addition, the reaction of ozone with hydrogen peroxide, which has a high oxidizing power, generated by the combined use of ozone and hydrogen peroxide, opens the dechlorinated aromatic nucleus and converts it into a less toxic biodegradable substance. Be transformed into

[0005]

In the ternary treatment using a combination of ultraviolet light, ozone and hydrogen peroxide, the harmlessness is obtained at a relatively high reaction rate when the concentration of dioxins is high due to the complex treatment as described above. Conversion processing is performed.

[0006] However, in the case of leachate leachate, the concentration of dioxin contained therein is usually 1000 pg.
-On the order of several tens of pg-TEQ / L from TEQ / L,
Very sparse. Since the reaction efficiency is proportional to the concentration, in the conventional ternary treatment, the progress of the reaction is extremely slow even if the reaction rate constant is large, and a long time is required to complete the reaction. In addition, the scale of the equipment and the amount of use of the chemicals required for the treatment become enormous.

[0007] In addition, leachate leachate contains turbid and large amounts of CO.
Contains D component, inorganic salts and the like. Generally, ultraviolet rays, ozone, and hydrogen peroxide do not react selectively with dioxins, and are therefore mostly consumed for the decomposition of these substances other than dioxins. For this reason, an increase in reaction time, an increase in equipment scale, and an increase in the amount of drug used are further accelerated.

[0008] Therefore, even though it is a ternary treatment using a combination of ultraviolet light, ozone and hydrogen peroxide, sewage containing dioxins at a low concentration such as leachate from garbage can be used.
It is practically difficult to efficiently and economically detoxify on an industrial scale.

An object of the present invention is to provide a water treatment method that can efficiently and economically detoxify wastewater containing dioxins at a low concentration, such as leachate leachate.

[0010]

The performance of an ozone generator (ozonizer) used for ozone treatment of sewage water including ternary treatment has been based on the use of high-purity oxygen gas as a raw material gas. Even several tens of ozone concentration generated
１２０120 g / Nm ³ , and as a result, the concentration of ozone that can be dissolved in the water to be treated was also limited to about several ppm to about 20 ppm.

The present applicant has been conducting research on ozonation of sewage, but at the same time is also a manufacturer of ozonizers used for the ozonation, and is also conducting research for improving the performance of the ozonizer. . This time, as a result of the research, a high-performance ozonizer capable of generating a much higher concentration and higher pressure of ozone gas than before has been successfully developed (Japanese Patent Application No. 10-346049).

Various experiments were performed on the decomposition behavior of organic substances under high-concentration and high-pressure ozone using this high-performance ozonizer for water treatment.
By using a high-concentration ozone gas of at least 00 g / Nm ³ , preferably a high-concentration and high-pressure ozone gas having a pressure of at least 2 kg / cm ^2, leaching water that has been considered extremely difficult to detoxify until now Thus, the present inventors have found that sewage containing dioxins at a low concentration can be treated very efficiently and economically in detoxification, and have completed the present invention.

The water treatment method of the present invention is a water treatment method using ozone, in which ozone gas is injected into water to be treated containing organic substances to decompose and remove organic substances in the water to be treated, wherein the ozone gas has an ozone concentration of 200 g / Nm ^3. The above-mentioned high concentration ozone gas is used.

Although the upper limit of the ozone concentration is not particularly specified from the viewpoint of treatment efficiency, it is not easy to stably obtain an ultra-high concentration exceeding 400 g / Nm ³ , so that the upper limit is not more than 400 g / Nm ^3. Is a realistic level.

The high-concentration ozone gas has a pressure of 2 kg / cm.
It is preferable to use ^two or more high-pressure ozone gases. The upper limit of the pressure does not need to be particularly specified in terms of processing efficiency, but 5 kg /
cm ² or less is preferred.

The water treatment with ozone is preferably a binary treatment combined with irradiation of ultraviolet rays, and more preferably a ternary treatment combined with the addition of hydrogen peroxide. Dioxins need to be dechlorinated prior to decomposition by ozone, and photodecomposition with ultraviolet light is effective for this dechlorination, so irradiation of treated water containing dioxins with ultraviolet irradiation is also used. Binary processing or ternary processing is particularly effective.

The lamp used for irradiating ultraviolet rays in binary or ternary processing has a UV-C output of 0.4 W /
cm high power UV lamp is preferable, and 0.5 W /
cm or more are particularly preferred. For treated water containing dioxins, the use of a high-power ultraviolet lamp is particularly effective for dechlorination of dioxins.

The amount of hydrogen peroxide added in the ternary treatment is 30.
mg / L or more is preferred.

According to the water treatment method of the present invention, sewage containing dioxins at a low concentration, such as leachate leachate, is extremely efficiently and economically detoxified. The mechanism is as follows. Similarly, other harmful organic substances are efficiently and economically detoxified.

The use of high-concentration ozone gas allows the ozone to be dissolved in the water to be treated to near the saturation concentration (about 100 ppm) in a short time. By increasing the pressure of the ozone gas, the ozone dissolving efficiency is improved. Can be further enhanced. In combination with the irradiation of strong ultraviolet light, the dechlorination reaction of dioxins proceeds by photoreaction by ultraviolet light, and the dechlorinated product is efficiently decomposed by high-concentration ozone, and the ozone is reacted by ultraviolet light. The decomposition reaction of the dechlorinated product proceeds also by the hydroxy radical generated from. If hydrogen peroxide is added under irradiation of strong ultraviolet rays, the concentration of hydroxyl radicals generated by the decomposition of hydrogen peroxide by ultraviolet rays also increases dramatically.

When the ozone concentration in the water to be treated is low, even if the binary treatment is performed by irradiating strong ultraviolet rays, or the ternary treatment is performed using a large amount of hydrogen peroxide, the low ozone concentration is low. Efficient treatment of dioxins contained in a concentration is not performed. In other words, by increasing the ozone concentration in the water to be treated, the irradiation of strong ultraviolet rays and the use of a large amount of hydrogen peroxide are effectively used without wasting, and the processing efficiency of dioxins is dramatically improved. I do.

The ozone treatment of the water to be treated can be carried out after the organic substances such as dioxins contained in the water to be treated are concentrated in advance. For this concentration, for example, a synthetic polymer adsorbent such as crosslinked polystyrene having a porous structure, activated carbon, zeolite, silica, etc. can be used, but the use of a crosslinked polystyrene adsorbent having a porous structure is particularly preferable. .

That is, the crosslinked polystyrene adsorbent having a porous structure selectively adsorbs an aromatic organic chlorine compound represented by dioxins. In particular, only dioxins can be selectively adsorbed and removed with high efficiency from wastewater containing other large amounts of organic substances and inorganic salts.

In addition, in the crosslinked polystyrene-based adsorbent,
The adsorbed hydrophobic dioxins and organic chlorine compounds can be easily and completely eluted with a polar organic solvent such as alcohol or acetone. In particular, alcohol is inexpensive, easy to recover and reuse, and also functions as a hydrogen donor when dechlorinating dioxins, thereby promoting the dechlorination reaction. For this reason, it can be said that the adsorption treatment with the crosslinked polystyrene adsorbent is particularly effective in combination with the dechlorination by irradiation with ultraviolet rays. That is,
It is effective to use alcohol as an eluent and perform dechlorination by irradiation with ultraviolet light in the presence of the alcohol.

In the water treatment method of the present invention, wastewater containing dioxins at a low concentration, specifically, a low concentration of 1000 pg-TEQ / L or less, such as leachate leachate or fly ash washing water of a garbage incinerator. It is especially effective for the treatment of sewage, but also for other sewage treatment such as treatment of wastewater containing aromatic and heterocyclic organochlorine pesticides and pesticides, and aliphatic organochlorine compounds (trichlene, etc.). It goes without saying that it is effective.

[0026]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a system diagram of a water treatment system showing a first embodiment of the present invention.

The water to be treated here is leachate leachate containing, for example, dioxins at a low concentration. This water to be treated is first sent to the filtration device 1 to reduce the load at the subsequent stage, where it is subjected to a two-layer filtration treatment with sand / anthrasant or the like to remove SS and the like.

The treated water subjected to the filtration treatment is sent to the three-way reaction tank 2. The three-way reaction tank 2 is equipped with an ozone injecting device 3 such as a diffuser at the lower part in the tank, and a plurality of ultraviolet lamps 4, 4,. The ozone injector 3 is connected to a high-performance ozonizer 5 for generating a high-concentration / high-pressure ozone gas having an ozone concentration of 200 mg / Nm ³ or more and a pressure of 2 kg / cm ² or more. The UV lamps 4, 4,... Are of a high output type having a UV-C output of 0.5 W / cm or more, and a high output power source 6 capable of driving the UV lamps.
Is connected to In addition, 30 mg / L or more of hydrogen peroxide is added to the water to be treated in the tank.

In the three-way reaction tank 2, high-concentration and high-pressure ozone gas is injected into the water to be treated introduced into the tank, so that the ozone can reach a high concentration close to the saturation concentration in the water to be treated in a short time. Dissolve. In this state, when strong ultraviolet rays are irradiated to the water to be treated, dioxins in the water to be treated are dechlorinated with high efficiency by the irradiation of the ultraviolet rays. at the same time,
Due to the irradiation of the ultraviolet rays, a large amount of hydroxyl radicals are generated from high concentration dissolved ozone in the water to be treated, and a large amount of hydroxyl radicals are also generated from hydrogen peroxide added to the water to be treated. And, by a large amount of dissolved ozone and a large amount of hydroxyl radical generated from this,
The dechlorinated products of dioxins are efficiently opened and converted to biodegradable substances.

Thus, refuse leachate containing dioxins at a low concentration can be efficiently detoxified by ternary treatment with ozone, ultraviolet light and hydrogen peroxide. The waste ozone generated in the three-way reaction tank 2 is decomposed by an ozone killer (not shown) and released into the atmosphere.

When the water to be treated which has been subjected to the ternary treatment with ozone, ultraviolet rays and hydrogen peroxide in the ternary reaction tank 2 clears the discharge standard value, the water to be treated is discharged as it is. If the discharge reference value is not satisfied, the water to be treated is sent to the biodegradation treatment device 7, detoxified by the decomposition treatment by biofilm filtration, and discharged.

In the three-way reaction tank 2, the water to be treated can be circulated. Further, pressure treatment can be performed using a closed container. These can further increase the efficiency of the decomposition reaction.

FIG. 2 is a system diagram of a sewage treatment system showing a second embodiment of the present invention.

In the present embodiment, litter leachate as the water to be treated is first sent to a filtration device 11 to reduce the load at a later stage, where it is subjected to a two-layer filtration treatment with sand / anthracite, etc. Minutes are removed.

The treated water subjected to the filtration treatment is supplied to the selective adsorption tower 1
Passed through 8. The selective adsorption tower 18 is filled with a crosslinked polystyrene adsorbent having a porous structure showing a high degree of selective adsorption to non-polar aromatic organic compounds as an adsorbent. By passing the treated water through this, aromatic organic chlorine compounds such as dioxins in the treated water are selectively adsorbed and removed.

The crosslinked polystyrene adsorbent having a porous structure includes Amberlite manufactured by Rohm and House.
(Trade name), and HP series manufactured by Mitsubishi Chemical Corporation. Regarding the specification of the adsorbent, the pore diameter suitable for adsorbing dioxins is 10 to 100 Å, and the surface area is 300 to 80.
Those having 0 m ² / g are suitable.

The treated water that has passed through the selective adsorption tower 18 contains almost no dioxins. If the treated water has cleared the discharge standard value, it can be discharged as it is. If the discharge reference value has not been cleared, for example, it is mixed with a residue of an eluent described later, and further detoxification processing is performed.

The cross-linked polystyrene in the column to which the aromatic organochlorine compound containing dioxins has been adsorbed is treated with alcohol (IPA or ethanol) as an eluent at a predetermined cycle, whereby the adsorbed substance is eluted. Crosslinked polystyrene is regenerated. Dioxins are highly concentrated in the eluent (for example, about 1000 times or more).
And concentrated.

The eluent containing a high concentration of dioxins is sent to an eluent recovery device 19, where 95% or more of the alcohol is separated and recovered by vacuum distillation. The recovered alcohol is sent to the selective adsorption tower 18 and reused as an eluent.

The residue of the eluate generated in the separation and recovery of alcohol is obtained by concentrating the eluate several tens or more times. This residue is diluted with water and sent to the three-way reaction tank 12. As the dilution water, for example, treated water that has passed through the selective adsorption tower 18 and that does not clear the drainage standard value can be used.

The ternary reaction tank 12 is equipped with an ozone injection device 13 and a plurality of ultraviolet lamps 14, 14,... Like the ternary reaction tank 2 in the first embodiment. The ozone injector 13 is connected to a high-performance ozonizer 15 for generating a high-concentration / high-pressure ozone gas having an ozone concentration of 200 mg / Nm ³ or more and a pressure of 2 kg / cm ² or more. UV lamps 14, 14,... Have a UV-C output of 0.55 W
/ Cm or more, and is connected to a high-output power supply 16 capable of driving the same. In addition, 30 mg / L or more of hydrogen peroxide is added to the water to be treated in the tank.

Also in the three-way reaction tank 12, dioxins in the water to be treated are efficiently decomposed by high-concentration / high-pressure ozone gas, high-output ultraviolet light and high-concentration hydrogen peroxide. In particular, in the present embodiment, since the dioxins in the water to be treated are concentrated at a high concentration, and the water to be treated is an aqueous alcohol solution, higher treatment efficiency can be obtained.

When the water to be treated which has been subjected to the ternary treatment with ozone, ultraviolet rays and hydrogen peroxide in the ternary reaction tank 12 clears the discharge standard value, the water to be treated is discharged as it is. If the discharge reference value is not satisfied, the water to be treated is sent to the biodegradation treatment device 17 and detoxified by the decomposition treatment by biofilm filtration and discharged. The exhausted ozone generated in the three-way reaction tank 12 is decomposed by an ozone killer (not shown) and released into the atmosphere.

In the three-way reaction tank 12, the water to be treated can be circulated. Further, pressure treatment can be performed using a closed container. These can further increase the efficiency of the decomposition reaction.

As described above, according to the water treatment method of the present invention, dioxins contained at extremely low concentrations in leachate leachate are detoxified with high reaction efficiency. Reduced to a realistic level.

[0046]

EXAMPLE 1 The following describes the results of actual ternary treatment of raw water assuming dust leachate using the experimental apparatus of the water treatment system (first embodiment) shown in FIG.

Total dioxin concentration 10,000 pg /
L, high-concentration, high-pressure ozone gas of ² kg / cm ² at 300 g / Nm ³ was supplied to raw water of 250 pg-TEQ / L using a high performance ozonizer. The ozone concentration in the raw water reached 80-100 ppm. In conjunction with this, high-power UV lamps (UV-C output 0.55W)
/ Cm), and hydrogen peroxide was added.

The ozone injection amount was 500 mg / L, the ultraviolet irradiation amount was 10 Whr / L, and the hydrogen peroxide addition amount was 50 mg / L.
L.

After a reaction time of 30 minutes, the total concentration of dioxins in the treated water became 10 pg / L or less, and TEQ / L fell below the detection limit. Dioxin decomposition rate of 9
9.9% or more was obtained, and almost complete detoxification treatment was performed.

[0050]

Example 2 In Example 1, the injection amount of high-concentration and high-pressure ozone gas and the addition amount of hydrogen peroxide were reduced. That is, the ozone injection amount is 50 mg / L and the ultraviolet irradiation amount is 10
Whr / L, and the amount of hydrogen peroxide added was 10 mg / L.
Others are the same as the first embodiment.

In the case of the same reaction time of 30 minutes as in Example 1, the total dioxin concentration in the treated water was 400 pg / L or less, and the TEQ / L was 10 pg / L. Despite the reduced ozone injection and hydrogen peroxide addition, the decomposition rate of dioxins was 96%.

When the treated water after the ternary treatment is treated with a biofilm, the total dioxin concentration becomes 200 pg / L, TEQ /
L was reduced to 5 pg / L. The degradation rate by biofilm treatment was 50%.

[0053]

[Comparative Example 1] Total dioxin concentration of 10,000 pg /
L, 1 kg / cm ² of ozone gas at 120 g / Nm ³ was supplied to raw water of 250 pg-TEQ / L using a normal ozonizer. Ozone concentration in raw water is 10pp
m. At the same time, the raw water was irradiated with ultraviolet rays from a general ultraviolet lamp (UV-C output: 0.2 W / cm), and hydrogen peroxide was added.

The ozone injection amount was 500 mg / L, the ultraviolet irradiation amount was 10 Whr / L, and the hydrogen peroxide addition amount was 50 mg / L.
L, the level of Example 1 was secured.

In the case of the same reaction time of 30 minutes as in Example 1, the total dioxin concentration in the treated water was 4300 pg / L,
The EQ / L was only 110 pg / L, and the decomposition rate of dioxins was as very low as 57%.

[0056]

Comparative Example 2 In Comparative Example 1, the reaction time was increased by 10 times to 3
It was extended to 00 minutes. Nevertheless, the total dioxin concentration in the treated water is 1000 pg / L and TEQ / L is 25 pg / L.
L, and the decomposition rate of dioxins was 90%.

When the treated water after the ternary treatment is treated with a biofilm, the total dioxins concentration is 500 pg / L, TEQ /
L was reduced to 12.5 pg / L. The degradation rate by biofilm treatment was 50%.

[0058]

Comparative Example 3 In Comparative Example 1, a high-power ultraviolet lamp (UV-C output: 0.55 W / cm) was used. The ozone injection amount is 500 mg / L and the ultraviolet irradiation amount is 10 Whr /
L, the amount of hydrogen peroxide added was 50 mg / L.

In the case of a reaction time of 30 minutes, the total dioxin concentration in the treated water is 2900 pg / L, and the TEQ / L is 7
5 pg / L. Since a normal ozonizer was used, the decomposition rate of dioxins was only 71% despite the use of a high-power ultraviolet lamp.

As can be seen from these results, high concentration
The method of rapidly increasing the ozone concentration in the water to be treated to almost the saturation concentration by injecting high-pressure ozone gas is very effective in improving the efficiency of decomposing dioxins. By generating a large amount of hydroxy radicals at once in combination with the addition, particularly high decomposition efficiency can be ensured, and it is also effective for improving the decomposition efficiency in biofilm treatment following ozone treatment.

[0061]

As described above, the sewage treatment method of the present invention uses high-concentration ozone gas, preferably high-concentration ozone gas.
The use of high-pressure ozone gas, and more preferably the combined use of a high-power ultraviolet lamp, makes it possible to perform detoxification with high reaction efficiency even when dioxins are contained at a low concentration such as leachate leachate. It has a great effect on reducing time, reducing the scale of equipment, reducing the amount of drug used, etc., and makes it possible to carry out practical processing on an industrial level.

[Brief description of the drawings]

FIG. 1 is a system diagram of a water treatment system showing a first embodiment of the present invention.

FIG. 2 is a system diagram of a water treatment system showing a second embodiment of the present invention.

[Explanation of symbols]

 1,11 Filtration device 2,12 Three-way reaction tank 3,13 Ozone injection device 4,14 High power ultraviolet lamp 5,15 High performance ozonizer 6,16 High power supply 7,17 Biodegradation treatment device 18 Selective adsorption tower 19 Elution Agent recovery device

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) C02F 1/72 101 C02F 1/72 101 F term (Reference) 2E191 BA12 BB01 BC01 BD11 BD20 4D037 AA11 AB14 BA18 BB01 CA01 CA02 CA07 CA11 CA12 4D038 AA08 AB14 BA02 BA04 BA06 BB06 BB07 BB16 BB17 BB19 4D050 AA12 AB19 BB02 BB09 BC02 BC09 BD02 BD03 BD08 CA06 CA15 CA17

Claims (7)

[Claims] 1. A water treatment method using ozone in which ozone gas is injected into water to be treated containing organic matter to decompose and remove organic matter in the water to be treated, wherein the ozone gas has a high concentration ozone gas having an ozone concentration of 200 g / Nm ³ or more. A water treatment method characterized by being used. 2. The high-concentration ozone gas has a pressure of 2 kg.
The water treatment method according to claim 1, wherein the ozone gas is a high-pressure ozone gas of not less than / cm ² . 3. The water treatment method according to claim 1, wherein the water treatment with ozone is a binary treatment combined with irradiation of ultraviolet rays. 4. A lamp used for irradiating ultraviolet rays,
The water treatment method according to claim 3, wherein a high-output ultraviolet lamp having a UV-C output of 0.4 W / cm or more is used. 5. The water treatment method according to claim 3, wherein the water treatment with ozone is a ternary treatment combined with irradiation of ultraviolet rays and addition of hydrogen peroxide. 6. The amount of the hydrogen peroxide to be added is 30 mg / L.
The water treatment method according to claim 5, wherein: 7. The organic matter contained in the water to be treated contains dioxins.
The water treatment method according to 4, 5, or 6.