JPH11347592A - Method for treating sewage containing hardly decomposable organic matter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the subject method enabling high-degree treatment not accompanied by high treatment cost, a large amt. of sludge, a wide site area and complicated operation control. SOLUTION: Hardly decomposable waste water 1 is successively introduced into a flocculation process 2 performing treatment using a flocculant 9, a modifying process 3 performing solid-liquid separation by the treatment with active oxygens 6 and 7, and a flocculating separation process 4 performing solid-liquid separation of the waste water by the treatment of waste water with the flocculant 9 or introduced into the modifying process and a part of the outflow water of the flocculation process is introduced into the modifying process to perform the treatment with active oxygen to be circulated into a separation process performing the solid-liquid separation of the residual part of the outflow water of the flocculation process to be treated. The above mentioned active oxygen is formed by a combination of two or more of ozone by hydrogen peroxide, ultraviolet rays and a catalyst.

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 wastewater, and more particularly to a method for treating wastewater containing hardly decomposable organic substances.

[0002]

2. Description of the Related Art As a conventional method for treating hardly decomposable organic matter-containing wastewater, coagulation sedimentation treatment, Fenton treatment, ozone treatment, and generation of active oxygen such as hydroxy radicals are performed.
A method of oxidatively decomposing organic matter is known. Also, there is known a treatment method in which a reforming step for improving the cohesion and separation properties of dissolved organic substances by active oxygen such as hydroxy radicals is provided, and then a coagulation separation step is provided, and a treatment method in which a coagulation separation step is provided before the reforming step. I have. However, the coagulation sedimentation method
It has the property that the amount of organic matter that can be removed per unit amount of sludge is small, and there is a disadvantage that the amount of sludge generated by treating a large amount of organic matter becomes enormous. In the Fenton method, the cost related to hydrogen peroxide and ferrous salt necessary for the Fenton reaction is expensive, and a large amount of sludge is generated as in the coagulation sedimentation method to recover the iron ions used in the Fenton reaction. Occur. In addition, since the active oxygen generated by the Fenton method is partially used for oxidizing ferrous ions, there is a disadvantage that the reaction efficiency of the active oxygen is low.

[0003] By photochemical or chemical reaction,
The method of generating active oxygen such as hydroxy radical has a disadvantage that the cost for irradiating an oxidizing agent or an ultraviolet ray is high, and it is difficult to put it to practical use. In addition, as a method of solving the above-mentioned disadvantages of the processing method,
A treatment method in which a hardly decomposable organic substance in wastewater is oxidatively decomposed by active oxygen such as hydroxy radicals, and is introduced into a reforming step to improve the cohesive and separable properties of the hardly decomposable organic substance, and then coagulated and separated. There is a processing method in which a coagulation separation step is provided before the step. However, also in this method, in order to maximize the effect of the reforming step, it is necessary to provide an agglomeration / separation step before the reforming step, and it is necessary to perform solid-liquid separation twice in total. Solid-liquid separation has a large site area in the case of precipitation separation, and complicated equipment is involved in membrane separation and filtration separation. Therefore, performing solid-liquid separation twice is not preferable in terms of equipment and operation management.

[0004]

SUMMARY OF THE INVENTION In view of the above-mentioned prior art, the present invention provides a hard-to-disassemble method which enables high-level processing without high processing costs, large amounts of sludge, large site area and complicated operation management. An object of the present invention is to provide a method for treating wastewater containing a toxic organic matter.

[0005]

In order to solve the above-mentioned problems, the present invention provides a coagulation step of treating a hardly decomposable organic matter-containing wastewater with a coagulant, a reforming step of treating the same with active oxygen, and a coagulant. This is a method for treating hardly decomposable organic matter-containing wastewater, which is successively introduced into a coagulation separation step of performing treatment and solid-liquid separation. In the present invention, the hardly decomposable organic matter-containing wastewater is introduced into a coagulation step of treating with a coagulant, and then introduced into a reforming step of treating at least a part of the effluent of the coagulation step with active oxygen. A method for treating hardly decomposable organic matter-containing wastewater, wherein the wastewater is circulated to the flocculation step and the remaining part of the effluent of the flocculation step is introduced and treated in a separation step for solid-liquid separation. In the treatment method, active oxygen can be generated by a combination of any two or more of ozone, hydrogen peroxide, and ultraviolet light.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, the present invention is an invention in which the respective steps of the aggregation step, the reforming step, and the separation step are combined, and these steps have the following actions.
In the coagulation step, a coagulant is added to the raw water, and among the organic substances in the raw water, organic substances that easily react with the coagulant and are easily coagulated and separated react with the coagulant to generate coagulated flocs. Next, in the reforming step, the flocculated floc generated in the preceding flocculating step was produced by a reaction of a combination of any two or more of ozone gas, ultraviolet rays, and hydrogen peroxide in a suspended state. By the active oxygen such as radicals, the hardly separable organic matter which has not reacted with the flocculant in the flocculation step is modified. The term “modification” as used herein means a partial increase in hydrophilicity caused mainly by the action of active oxygen on hardly cohesive organic substances. Thereby, the ionicity of the hardly coagulating organic substance increases, and the reactivity with the coagulant increases. Due mainly to the above-mentioned actions, in the reforming step, the hardly-coagulable and separable organic substance is reformed into the easily-coagulable and separable organic substance.

Finally, in the coagulation / separation step, a coagulant is added, and the easily coagulated / separated organic substance modified in the modification step is:
Reacts with the flocculant to form floc. Further, the flocculated floc generated in the flocculating step and the flocculated floc generated in the flocculating separation step are subjected to solid-liquid separation. The action as described above is introduced into the coagulation step of treating the hardly decomposable organic matter-containing wastewater with a coagulant, and then at least a part of the water discharged from the coagulation step,
It can also be achieved by a method of circulating in a reforming step of treating with active oxygen such as hydroxy radicals, and introducing the remainder of the effluent of the flocculation step to a separation step of performing solid-liquid separation. The active oxygen used in the present invention mainly has an oxidizing power and means a radical capable of reacting with a portion other than an unsaturated bond in an organic substance, and as described above, an organic substance, particularly a hardly decomposable organic substance. There is no particular limitation as long as it has the ability to be reformed into an organic substance that is easily aggregated and separated. The active oxygen is produced by a combination of two or more of ozone, hydrogen peroxide, and ultraviolet light. In the present invention, the preferred generation of active oxygen is a combination of ozone and hydrogen peroxide, ozone and ultraviolet light, hydrogen peroxide and ultraviolet light, ozone, hydrogen peroxide and ultraviolet light, etc., thereby efficiently generating active oxygen. Can be done.

The coagulant used in the coagulation step or coagulation separation step is, for example, an inorganic one such as aluminum sulfate, ferric sulfate, ferrous sulfate, sodium aluminate, ferric chloride, and ferrous chloride. Iron, inorganic salts such as PAC, sulfuric acid, hydrochloric acid, carbon dioxide, acids such as sulfur dioxide, alkalis such as sodium carbonate, sodium hydroxide, calcium hydroxide, electrolytic aluminum hydroxide, metal electrolytic products such as electrolytic iron hydroxide, Activated silicic acid, etc.
For example, anionic surfactants such as sodium laurate, sodium stearate, sodium oleate, sodium dodecylbenzenesulfonate, sodium rosinate, dodecylamine acetate, octadecylamine acetate, rosin amine acetate, octadecyltrimethylammonium chloride, octadecyl Cationic surfactants such as dimethylbenzylammonium chloride, sodium alginate, water-soluble aniline resin hydrochloride, polyvinylbenzyltrimethylammonium chloride, starch, water-soluble urea resin, gelatin, sodium polyacrylate, maleic acid copolymer salt, Polyacrylamide partial hydrolyzate salt, polyethyleneimine sulfate,
Examples thereof include polymer substances such as vinylpyridine copolymer salts, polyacrylamide, and polyoxyethylene, and these can be used alone or in combination. The same flocculant may be used in the flocculation step and the flocculation separation step, or different flocculants may be used.

As a solid-liquid separation means that can be employed in the coagulation separation step or the separation step, a sedimentation basin is usually used, but a method using filtration, membrane, centrifugation or the like is also effective. In the reforming step, ultraviolet rays having a wavelength of 170 to 380 nm can be used as the ultraviolet rays used to generate active oxygen. Low-pressure mercury lamps,
Examples thereof include a medium-pressure mercury lamp, a high-pressure mercury lamp, an excimer laser, and the like, which can irradiate ultraviolet rays having a relatively low wavelength, natural light, and the like, but are not limited thereto.
When a protective tube is used to prevent damage to the ultraviolet lamp, the material is desirably quartz or synthetic quartz having a high ultraviolet transmittance of 170 to 380 nm. As a method of installing ultraviolet rays, there is a method in which the flow method of the ultraviolet lamp is arranged vertically or horizontally with respect to the flow of water or ozone gas, but when considering the contact efficiency between water and ozone gas and ultraviolet rays,
A method of arranging in the vertical direction with respect to the flow of water and ozone gas is preferable because unevenness in contact efficiency is reduced.

[0010] As a stirring method in the reaction tank in the reforming step,
In addition to ozone bubbles or stirring by a stirring blade, a method in which the upper and lower ends, left and right ends, or front and rear ends of the reaction tank are connected by piping and circulated by a pump is also possible. In particular, when a complex ultraviolet lamp is installed in the reaction tank and the distance between the lamps is increased,
It is effective to perform strong agitation to stabilize the treatment.
Each reaction tank in the reforming step may be composed of a plurality of reaction tanks. In this case, the configuration in which a plurality of reaction vessels are connected in series allows the flow of water to be a plug flow, and the processing is performed more reliably. Further, each reaction tank in the reforming step may be a different active species generation method. In particular, when the former reactor is an active species generation method using ozone or ozone and hydrogen peroxide, and the latter is an active species generation method using ultraviolet and ozone, or ultraviolet, ozone and hydrogen peroxide, In the first-stage reaction vessel, the ultraviolet transmittance of the water to be treated can be improved by the action of ozone or active species, and the irradiation efficiency of ultraviolet rays in the second-stage reaction vessel can be improved.

As a method for injecting ozone gas, a diffuser method, an ejector method, a U-tube method, a method of dissolving ozone gas under a pressurized state of 0.5 to 10 kg / cm ² , a method of using an underwater stirring type air diffuser, and the like are used. Examples include, but are not limited to: It is also possible to generate ozone gas by applying electric energy to the oxygen-containing gas injected into the reaction tank. Hydrogen peroxide can be injected into the inflow pipe of the inflow water of the oxidation treatment step, directly into the reaction tank of the oxidation treatment step, or injected into the inflow pipe of the ejector water into which the ozone gas is injected or into the ejector. And a method of injecting into the inside of a submerged stirring type air diffuser. In these cases, it is also possible to inject hydrogen peroxide from a plurality of locations. By subjecting the treated water according to the present invention to biological treatment, activated carbon treatment and the like, the treated water quality can be further improved. In addition, by circulating the treated water according to the present invention to the reforming step, it is possible to further improve the treated water quality.
In addition, by providing a deoxidizing step after the reforming step, it is also possible to stabilize the subsequent processing.

In the present invention, the type and amount of active oxygen in the reforming step depend on the properties of the raw water to be treated, for example, TO
Various selections can be made according to the C (total organic carbon) concentration and the like. As an example, the case where the TOC of raw water is about 200 mg / l and hydrogen peroxide and ozone are used as active oxygen is described below. The injection amount of hydrogen peroxide in the reforming step is usually 10 to 5000 mg / l, preferably 10 to 5000 mg / l.
1000 mg / l, and the ozone injection amount is usually 50 to 1
0000 mg / l, preferably 200-3000 mg /
1 range. The reaction time in the raw water reforming step is usually 5 to 60 when a bubble column is used.
min, preferably 10 to 20 min. Separately, when using ultraviolet light, the output of a low-pressure mercury lamp is usually 6
It is -200W, preferably 10-200W. When PAC is used as the flocculant in the flocculation step and the flocculation separation step, the injection amount is usually 10 to 5000 mg · Al / l,
It is preferably 100 to 1000 mg · Al / l, and p
H is usually 5-7.

By using the above-described method for treating wastewater containing hardly decomposable organic matter according to the present invention, the organic matter in the wastewater is treated with low cost, low generated sludge and highly. That is,
First, in the aggregating step, by adding an aggregating agent, among the organic substances in the raw water, those that are easily aggregated and separated selectively generate aggregated flocs. Second, in the reforming step, the hardly flocculable and separable material that did not become flocculated floc in the flocculation step is reformed into an easily flocculated and separable material by active oxygen such as hydroxy radical. Third,
In the aggregating / separating step, by adding the aggregating agent, the material which has been modified in the reforming step and has an easily aggregating / separating property reacts with the aggregating agent to generate an aggregated floc. Further, the flocculated floc generated in the flocculating step and the flocculated floc generated in the flocculating separation step are separated and removed from water.

As described above, by performing the first to third steps, the substance to be treated in the aggregating step and the aggregating / separating step can be made only of the easily aggregating / separating substance. However, the amount of generated sludge decreases and the cost related to the flocculant decreases. In addition, since only one flocculation floc separation facility is required, the operation of the facility is simple. The effects as described above are produced as a result of reforming in the reforming step even when at least a part of the effluent of the flocculation step is circulated to the reforming step and the remainder of the effluent of the flocculation step is introduced to the separation step. An easily coagulable and separable organic substance can be subjected to a coagulation treatment in the coagulation step, and the same effect can be obtained. Also, in the reforming process, the amount of oxidizing agent and the amount of UV irradiation required to reform the hard-to-aggregate separable organic matter to the easily-separable sedimentable organic matter are completely decomposed to the required treated water quality of the organic matter in the raw water. The amount is extremely small as compared with that required for the process, and the processing cost in the reforming process is not high.

Further, with the reforming, some organic substances are oxidized and decomposed into water and carbon dioxide gas. However, even with such an auxiliary effect, the concentration of the organic substances in the waste water is reduced, and a necessary coagulant is required. The amount is reduced. As described above, there has been no report on the improvement of the cohesion and separability of dissolved organic matter in the presence of coagulated flocs, and an intensive study on the present invention has confirmed for the first time an effect that cannot be simply confirmed. In short, according to the method for treating hardly decomposable organic matter-containing wastewater according to the present invention, advanced treatment is possible with low cost, low sludge generation amount, and easy operation.

Next, the present invention will be described in detail with reference to the drawings. FIG. 1 is an explanatory diagram showing an example of a specific configuration of the present invention. In FIG. 1, an organic substance in raw water is treated with a flocculant, and a dissolved organic substance remaining in the flocculation step 2 is treated with active oxygen in the presence of flocculants to convert the organic substance into an easily flocculated and separable organic substance. Quality reforming process 3
And an aggregation separation step 4 in which the easily aggregated and separable organic matter obtained in the reforming step 3 is aggregated and the aggregated flocs are separated.
It consists of The coagulation step 2 includes raw water 1 and coagulant 9
And a coagulation tank 10 in which coagulated flocs are generated. The reforming step 3 has a reforming treatment tank 5 into which the coagulation step effluent flows, and hydrogen peroxide 6 and ozone 7 for generating active oxygen are supplied to the inlet of the tank and the inside of the tank, respectively. The water that is treated in the reforming step 3 and contains the easily coagulable and separable organic substance flows into the mixing tank 8 in the coagulation / separation step, is mixed with the added coagulant 9, and then the coagulation tank 10 provided downstream of the tank. To form flocculated floc, and the solid-liquid separation is performed in the solid-liquid separation tank 13 to obtain treated water 11.

FIG. 2 is an explanatory diagram showing another example of a specific configuration of the present invention. FIG. 2 shows a configuration in which the flocculated floc and water are separated by the membrane 17 in the coagulation / separation step 4, and the ultraviolet lamp 14 is additionally used in the modification step 3. The rest is the same as the configuration shown in FIG. FIG.
FIG. 4 is an explanatory diagram showing another example of a specific configuration of the present invention. In FIG. 3, the aggregation step 2 is configured by an aggregation mixing tank 16. In the reforming step 3, ozone 7, hydrogen peroxide 6, and ultraviolet light 14 are used together. The rest is the same as the configuration shown in FIG. FIG. 4 is an explanatory diagram showing another example of a specific configuration of the present invention. FIG. 4 shows that at least a part of the effluent of the coagulation step 2 is circulated to the reforming step 3 and the coagulation step 2
The remaining part of the effluent is introduced into the separation step 15. In the reforming step 3, ozone 7 and hydrogen peroxide 6 are used in combination.

[0018]

EXAMPLES The present invention will be described below in more detail with reference to examples, but the present invention is not limited to these examples. Example 1 Wastewater from litter landfill leachate having a TOC of 300 mg / l was used as raw water, and the raw water flow rate was 0.1 liter / mi.
n was processed according to the flow shown in FIG. 1 under the following conditions. Coagulation process-Coagulant used: PAC-Coagulant injection amount: 500 mg Al / l-pH: 6.0 Reforming process-Oxidant used: hydrogen peroxide, ozone-Hydrogen peroxide injection amount: 300 mg / l-ozone Injection amount: 1000 mg / l ・ Ozone injection method: diffuser ・ Residence time: 30 min

Coagulation separation step Coagulant used: PAC Coagulant injection amount: 100 to 400 mg Al / l pH: 6.0 The result of treatment under the above conditions is a comparative example without modification step 1 and Table 1 are shown. FIG. 5 shows the relationship between the PAC injection amount and the D-TOC removal amount in the aggregation separation step. In FIG. 5, Example 1 is indicated by -O-, and Comparative Example 1 is indicated by -X-. Thus, the DT in the coagulation separation step of the present example
The OC removal amount is higher than that in the case where the reforming is not performed in the reforming step, and in the present invention, the flocculation and separability of the dissolved organic matter is improved even under the condition where the flocculated floc generated in the flocculation step exists. Was recognized.

[0020]

[Table 1]

Example 2 The biologically treated water of leachate from garbage landfill having a TOC of 300 mg / l was used as raw water, and the raw water flow rate was 0.1 liter / min.
The process was performed according to the flow shown in FIG. 3 under the following conditions. Coagulation process • Coagulant used: PAC • Coagulant injection amount: 500 mg · Al / l • pH: 6.0 Reforming process • Oxidant: hydrogen peroxide, ozone • Ultraviolet light: 25 W low-pressure mercury lamp • Hydrogen peroxide injection amount : 50 mg / l ・ Ozone injection amount: 500 mg / l ・ Ozone injection method: diffuser ・ Dwell time: 30 min

Coagulation separation step • Coagulant used: PAC • Coagulant injection amount: 100 to 400 mg • Al / l • pH: 6.0 • Membrane pore size: 0.1 μm Comparison of the treatment results without the modification step The results are shown in Table 2 together with Example 2. Thereby, the same result as in Example 1 was recognized.

[0023]

[Table 2]

Example 3 Wastewater from litter landfill leachate having a TOC of 300 mg / l was used as raw water, and the flow rate of raw water was 0.05 l / m2.
In was processed according to the flow shown in FIG. 4 under the following conditions. Coagulation process-Coagulant used: PAC-Coagulant injection amount: 1000 mg Al / l-pH: 6.0 Reforming process-Oxidizer: hydrogen peroxide, ozone-Hydrogen peroxide injection amount: 50 mg / l-Ozone injection Amount: 500 mg / l ・ Ozone injection method: Diffuser ・ Residence time: 30 min ・ Circulation rate of effluent of coagulation process to reforming process: 100% (relative to raw water flow rate)

The result of processing under the above conditions is shown in FIG.
Shown in FIG. 7 shows the result of Comparative Example 3 in which ozone and hydrogen peroxide were not injected in the reforming step. From these, the amount of D-TOC removed in the aggregation step was 70 mg / l in this example and 50 mg / l in comparative example 3, which was greater in this example. From this, also in this embodiment,
It was found that the cohesive separation of dissolved organic matter was improved. As described above, even when at least a part of the effluent of the flocculation step is circulated to the reforming step, and the remaining part of the effluent of the flocculation step is introduced into the separation step, the effect of the present invention remains unchanged.

[0026]

According to the present invention, the object to be treated in the aggregating step and the aggregating / separating step can be made of only an easily aggregating / separating substance.
The amount of generated sludge decreases, and the cost related to the flocculant decreases. In addition, since only one flocculation floc separation facility is required, the operation of the facility is simple. Also, in the reforming process, the amount of oxidizing agent and the amount of UV irradiation required to reform the hard-to-aggregate separable organic matter to the easily-separable sedimentable organic matter are completely decomposed to the required treated water quality of the organic matter in the raw water. The amount is extremely small as compared with that required for the process, and the processing cost in the reforming process is not high. In addition, some organic substances are oxidatively decomposed into water and carbon dioxide gas due to the reforming. However, such auxiliary effects also lower the concentration of organic substances in the wastewater and reduce the amount of required coagulant. Be transformed into

[Brief description of the drawings]

FIG. 1 is a flow diagram illustrating a method for treating wastewater containing hardly decomposable organic substances according to the present invention.

FIG. 2 is a flowchart illustrating another embodiment of the present invention.

FIG. 3 is a flowchart illustrating another embodiment according to the present invention.

FIG. 4 is a flowchart illustrating another embodiment of the present invention.

FIG. 5 is a graph showing the relationship between the PAC injection amount and the D-TOC removal amount in the aggregation separation step in Example 1.

FIG. 6 is a view showing a processing result of the third embodiment.

FIG. 7 is a view showing a processing result of Comparative Example 3.

[Explanation of symbols]

1: raw water, 2: coagulation step, 3: reforming step, 4: coagulation separation step, 5: reforming tank, 6: hydrogen peroxide, 7: ozone,
8: mixing tank, 9: flocculant, 10: flocculation tank, 11: treated water, 12: sludge, 13: solid-liquid separation tank, 14: ultraviolet lamp, 15: separation step, 16: flocculation mixing tank, 17: membrane

Continued on the front page (51) Int.Cl. ⁶ Identification code FI C02F 1/32 C02F 1/32 1/52 1/52 K 1/72 1/72 Z 101 101 1/78 ZAB 1/78 ZAB

Claims (3)

[Claims] 1. A wastewater containing a hardly decomposable organic substance is sequentially introduced into a coagulation step of treating with a coagulant, a reforming step of treating with active oxygen, and a coagulation / separation step of treating with a coagulant and performing solid-liquid separation. A method for treating wastewater containing a hardly decomposable organic substance, comprising: 2. The method according to claim 1, wherein the wastewater containing the hardly decomposable organic substance is introduced into a coagulation step of treating with a coagulant, and then introduced into a reforming step of treating at least a part of the water discharged from the coagulation step with active oxygen. A method for treating hardly decomposable organic matter-containing wastewater, wherein the wastewater is circulated to a coagulation step and the remaining part of the effluent of the coagulation step is introduced into a separation step for solid-liquid separation for treatment. 3. The active oxygen includes ozone, hydrogen peroxide,
The method according to claim 1, wherein the wastewater is generated by a combination of two or more of ultraviolet rays.