JPH1076296A - Treatment method for drainage containing poorly decomposable organic substance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To convert poorly decomposable substances in raw water into highly coagulation-separable substances by a method in which raw water, after being treated by a modification process and a coagulation-separation process, is returned to the modification process, and part of water discharged from the modification process or part of water discharged from the coagulation-separation process is made treated water. SOLUTION: Treated water is circulated between a modification process 2 and a coagulation separation process 3, part of water discharged from the process 3 is made treated water 12. The process 2 has a modification treatment tank 4 and supplies hydrogen perioxide water 5 and ozone 6 for generating active seeds to the inlet of the tank and into the tank, respectively. Raw water which was treated in the process 2 and contains organic substances which can be coagulated and separated easily is introduced into a mixing tank 7 in the process 3. and mixed with a coagulant 8. A coagulated product, which is formed in a coagulation tank 9 installed downstream from the tank, is separated into solid and liquid by a solid-liquid separating tank 10. Treated water containing residual organic substances difficult to be coagulation- separated which failed to be modified in the process 2 is circulated to the process 2.

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 containing hardly decomposable organic substances, and more particularly to a method for treating effluent containing hardly decomposable organic substances at a high degree of physicochemical properties.

[0002]

2. Description of the Related Art As a conventional method for treating wastewater containing hardly decomposable organic substances, a coagulation sedimentation treatment, a Fenton treatment utilizing a Fenton reaction, an ozone treatment utilizing a strong oxidizing power of ozone, and the like are known. Further, there is known a treatment method in which active species such as hydroxyl radicals are generated by a photochemical reaction or a chemical reaction to oxidatively decompose an organic substance. However, the coagulation-sedimentation method has the property that the amount of organic substances that can be removed per unit sludge amount is small, and there is a drawback that the amount of sludge generated for treating a large amount of organic substances 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 species generated by the Fenton method is partially used for oxidizing ferrous ions, there is a disadvantage that the reaction efficiency of the active species is low.

Further, in a method of generating an active species such as a hydroxyl radical by a photochemical reaction or a chemical reaction, the cost for irradiating an oxidizing agent or an ultraviolet ray is expensive, and it is difficult to put it to practical use. There are drawbacks. In the ozone treatment, a treatment target portion is limited to an unsaturated bond portion and cannot be applied to a hardly decomposable substance having various structures. Furthermore, these treatment methods do not have a high level of organic substance removal capability in terms of cost, and thus, in many cases, activated carbon adsorption treatment is provided in the post-treatment.However, since organic substances are not highly removed, activated carbon is not removed. However, there is a disadvantage that the replacement cost is high.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a process for treating wastewater containing hardly decomposable organic substances, which enables efficient and sophisticated treatment without the high treatment cost and large amount of sludge in the prior art. It is an object to provide a method.

[0005]

In order to solve the above-mentioned problems, the present invention provides a method for treating wastewater containing a hardly decomposable organic substance to a high degree, comprising the steps of: After the treatment in the coagulation / separation step of coagulation / separation of the reformed wastewater, the water is returned to the reformation step, and a part of the water in the reformation step or a part of the water in the coagulation / separation step is treated water. This is a method for treating wastewater containing a hardly decomposable organic substance, characterized by the following. Further, according to the present invention, in the method for highly treating wastewater containing hardly decomposable organic matter, the wastewater is treated by a flocculation separation step of flocculating and separating the wastewater, and a reforming step of generating and treating the flocculated and separated water by active species. Thereafter, while returning to the coagulation / separation step, a method for treating the hardly decomposable organic matter-containing wastewater, wherein a part of the effluent of the coagulation / separation step or the effluent of the reforming step is treated water. Things.

In the above-mentioned method for treating hardly decomposable organic matter-containing wastewater, an agglomeration / separation step may be further provided in a preceding stage, and an oxidative decomposition step or an activated carbon treatment step in which active species are generated and treated in a later stage. It can also be provided. In the above treatment method, the generation of the active species can be performed by using one or more of ozone, hydrogen peroxide, light, and a heterogeneous catalyst or a homogeneous catalyst.

[0007]

Next, the present invention will be described in detail.
As described above, the method for treating the hardly decomposable organic matter-containing wastewater according to the present invention is a method for physicochemically treating the hardly decomposable organic matter-containing wastewater. Note that the former stage of the coagulation / separation step is referred to as a first coagulation / separation step, and the latter stage of the coagulation / separation step is referred to as a second coagulation / separation step. In the present invention, by performing the above treatment, the target of the coagulation / separation step can be only the easily coagulable / separable substance, so that the amount of the coagulant required per the amount of the removed organic substance is reduced, and the amount of generated sludge is reduced. I do. In addition, since the treated water circulates between the coagulation separation step and the reforming step, the amount of active species required to reform the hardly coagulable and separable substance into the easily coagulable and separable substance is included in the raw water. It can be suitable for organic substances having various properties, and a suitable amount of active species can be applied to these substances to introduce and remove them in the coagulation separation step. Further, it is possible to further reduce the amount of the oxidizing agent used in the reforming step and the amount of the ultraviolet irradiation.

Further, by providing the first coagulation separation step,
When raw water, which contains relatively large amounts of organic substances that are easily aggregated and separated, can be removed in advance. Also, by dividing the coagulation / separation step into two, a coagulant suitable for each of the coagulation / separation substance previously contained in the raw water and the coagulation / separation substance generated in the reforming step. , A coagulation separation method can be employed. Further, the safety and purification of the treated water can be improved by subjecting the treated water to the treatment of residual organic substances by oxidative decomposition and activated carbon treatment and the removal of the residual oxidizing agent. That is, by using the method for treating the hardly decomposable organic matter-containing wastewater according to the present invention, the organic matter in the wastewater is low in cost, low in generated sludge,
And highly processed. Also, in the reforming step, the amount of oxidizing agent required to reform the hardly cohesive and separable substance into the easily coagulable and separable substance, and the amount of ultraviolet irradiation, up to the treated water quality required for the organic matter in the raw water, The amount is extremely small as compared with the case of completely decomposing, and the processing cost in the reforming step is not high. Further, the processing cost in the reforming step can be further reduced by circulating the treated water between the reforming step and the coagulation separation step.

Further, some organic substances are oxidatively decomposed into water and carbon dioxide gas along with the reforming. 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. In short, according to the method for treating hardly decomposable organic matter-containing wastewater according to the present invention, low-cost, low-sludge generation amount and advanced treatment are possible, which greatly contributes to the world. The active species used in the present invention means a radical having an oxidizing power or a reducing power and capable of reacting with a portion other than an unsaturated bond in an organic substance. There is no particular limitation as long as it has the ability to modify the decomposable organic substance into an organic substance having easy aggregation and separation. The generation of the active species can include those generated by one or a combination of two or more of ozone, hydrogen peroxide, light, and a catalyst. In the present invention, preferably, the generation of the active species is ozone and hydrogen peroxide, ozone and ultraviolet, ozone and catalyst, hydrogen peroxide and ultraviolet, hydrogen peroxide and catalyst, catalyst and ultraviolet, ozone and hydrogen peroxide. And an ultraviolet ray, an ultraviolet ray and an ozone and a catalyst, an ultraviolet ray and a hydrogen peroxide and a catalyst, and an ozone, a hydrogen peroxide and an ultraviolet ray and a catalyst. As a means for dissolving O ₃ ,
AC or cocurrent contact type bubble columns, injectors, and the like can be used.

The coagulant used in the coagulation / separation step, the first coagulation / separation step, and the second coagulation / separation step is an inorganic coagulant such as aluminum sulfate, ferric sulfate, ferrous sulfate, sodium aluminate, and ferric chloride. , Ferrous chloride, 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, electrolytic iron hydroxide, etc. Metal electrolyte, activated silicic acid, etc., and organic, for example,
Anionic surfactants such as sodium laurate, sodium stearate, sodium oleate, sodium dodecylbenzenesulfonate, sodium rosinate,
Cationic surfactants such as dodecylamine acetate, octadecylamine acetate, rosinamine acetate, octadecyltrimethylammonium chloride, octadecyldimethylbenzylammonium chloride, sodium alginate, water-soluble aniline resin hydrochloride, polyvinylbenzyltrimethylammonium chloride, starch, water-soluble Polymeric substances such as soluble urea resin, gelatin, sodium polyacrylate, maleic acid copolymer salt, polyacrylamide partially hydrolyzed salt, polyethyleneimine sulfate, vinylpyridine copolymer salt, polyacrylamide, polyoxyethylene, etc. Yes, these can be used alone or in combination. Further, the same flocculant may be used in the first flocculation / separation step and the second flocculation / separation step, or different flocculants may be used.

In the coagulation / separation step, usually, sedimentation separation using a sedimentation tank or the like is preferable, but filtration, membrane, centrifugation, etc. are also effective depending on the application. Further, the same solid-liquid separation method may be used in the first aggregation separation step and the second aggregation separation step, or different solid-liquid separation methods may be used. Visible light, ultraviolet light, and the like can be used as the light beam used to generate the active species in the reforming step. Examples of the light source for supplying the light include a low-pressure mercury lamp, an excimer laser, and the like, which can irradiate ultraviolet rays having a relatively low wavelength, a fluorescent lamp, natural light, and the like, but are not limited thereto. Further, these light beams may be directly or indirectly irradiated, or may be introduced by a light guide (such as an optical fiber). The catalyst used in the reforming process is a catalyst that promotes the generation of active species from the oxidizing agent, such as manganese dioxide, activated carbon, precious metal-containing solids, metal-containing solids, and metal ions. For example, there is a titanium dioxide-containing solid or the like, and an effective catalyst can be used regardless of whether the catalyst is a homogeneous or heterogeneous catalyst. Further, by treating the treated water according to the present invention with activated carbon, the quality of the treated water can be further improved.

In the present invention, the type and amount of active species in the reforming step are determined by the properties of the raw water to be treated, for example, TOC
Various selections can be made depending on the (total organic carbon) concentration and the like. For example, the case where the TOC of raw water is about 200 mg / liter and hydrogen peroxide and ozone are used as active species is described below. The injection amount of hydrogen peroxide in the reforming step is generally 10 to 5000 mg / liter, preferably 1 to 5000 mg / liter.
0 to 1000 mg / liter, and the ozone injection amount is usually 50 to 10,000 mg / liter, preferably 200
It is selected from the range of ３3000 mg / liter. The reaction time in the raw water reforming step is usually 0.1 to 6 hr, preferably 0.2 to 1 hr when a bubble column is used in the reforming treatment tank. When ultraviolet rays are used as the light beam, the output of the low-pressure mercury lamp is usually 6 to 200 W,
Preferably, it is 10 to 200 W. When a titanium dioxide solid catalyst is used as the heterogeneous catalyst, the concentration of the titanium dioxide solid catalyst is usually 10 to 10 as the titanium dioxide concentration.
5000 mg / liter, preferably 100 to 1000
mg / liter. When using FeCl ₃ as a coagulant in the first coagulation / separation step and the second coagulation / separation step,
The injection amount is usually 10-5000 mg / l, preferably 100-2000 mg / l, and the pH is usually 5-12, preferably 5-11.

Next, the present invention will be described with reference to the drawings. FIG. 1 is a flowchart showing an example of a specific configuration of the present invention, which will be described with reference to FIG. In FIG. 1, raw water 1
The organic substance contained in the above is treated with an active species, thereby modifying the organic substance into an organic substance having easy aggregation and separation, and the organic substance having easy aggregation and separation obtained in the modification step 2 is subjected to an aggregation separation treatment. The treatment water is circulated between the reforming step 2 and the coagulation / separation step 3, and a part of the water discharged from the coagulation / separation step becomes the treated water 12. The reforming step 2 has a reforming tank 4 into which the raw water 1 flows, and hydrogen peroxide 5 and ozone 6 for generating active species are supplied to the inlet and the tank, respectively. The raw water that is treated in the reforming step 2 and contains an organic substance having easy coagulation / separation is introduced into the mixing tank 7 in the coagulation / separation step 3, mixed with the added coagulant 8, and then provided in the coagulation tank provided downstream of the tank. Aggregates are generated in 9 and solid-liquid separated in the solid-liquid separation tank 10, and the treated water in which the hardly cohesive and separable organic matter which has not been modified in the reforming step 2 remains is circulated to the reforming step 2 Is done. In addition, treated water 12 with reduced TOC is obtained from a part of the effluent of the coagulation separation step.

Next, an example of a specific configuration of the present invention is shown in FIG.
It will be described based on. In FIG. 2, a reforming step 2 in which an organic substance contained in the raw water 1 is treated with an active species to thereby convert the organic substance into an easily flocculated and separable organic substance, and the easily flocculated and separable property obtained in the reforming step 2 It comprises a coagulation / separation step 3 for coagulation / separation of an organic substance, wherein treated water circulates between the reforming step 2 and the coagulation / separation step 3, and a part of the effluent of the reforming step becomes treated water 12. is there. The reforming step 2 has a reforming treatment tank 4 into which the raw water 1 flows, and hydrogen peroxide 5 and ozone 6 for generating active species are supplied to the inlet of the tank and the inside of the tank, respectively. Raw water 1 which is treated in the reforming step 2 and contains an organic substance having easy coagulation / separation is introduced into the mixing tank 7 in the coagulation / separation step 3, mixed with the added coagulant 8, and then coagulated in the downstream of the tank. Aggregate is generated in the tank 9, and solid-liquid separation is performed in the solid-liquid separation tank 10, and the treated water in which the hardly-coagulable and separable organic matter which has not been modified in the reforming step remains is circulated to the reforming step. . Further, treated water 12 having a reduced TOC is obtained from a part of the effluent of the reforming process.

Next, an example of a specific configuration of the present invention will be described with reference to FIG. In FIG. 3, an organic substance contained in the raw water 1 is coagulated and separated, and a modification step 2 is performed by treating with an active species to convert the organic substance into an easily coagulated and separable organic substance. Treated water circulates between the separation step 3 and the reforming step 2, and a part of the effluent of the reforming step becomes treated water. The reforming step 2 has a reforming treatment tank 4 into which the raw water 1 flows, and hydrogen peroxide 5 and ozone 6 for generating active species are supplied to the inlet and the tank of the tank, respectively. Ultraviolet light is emitted from an ultraviolet lamp. In the coagulation / separation step, the raw water in which the easily coagulable / separable substances are removed, and the hardly coagulable / separable organic matter remains is introduced into the reforming step 2,
It is modified into an organic substance that is easily aggregated and separated. The treated water mainly composed of the organic substance having easy aggregation / separation is circulated to the aggregation / separation step 3. Further, the treated water 12 having a reduced TOC is obtained from a part of the effluent of the reforming process.

Next, an example of a specific configuration of the present invention will be described with reference to FIG. In FIG. 4, an organic substance contained in the raw water 1 is composed of an aggregation / separation step 3 for coagulation / separation treatment, and a modification step 2 for treating the organic matter with an active species to convert the organic matter into an organic substance having easy aggregation / separation. Treated water is circulated between the separation step 3 and the reforming step 2, and a part of the effluent of the coagulation separation step becomes treated water. The reforming step 2 has a reforming treatment tank 4 into which the raw water 1 flows, and hydrogen peroxide 5 and ozone 6 for generating active species are supplied to the inlet of the tank and the inside of the tank, respectively. In the coagulation / separation step, easily coagulated / separable organic matter is removed, and raw water mainly composed of hardly coagulated / separable organic matter is
In the reforming step 2, the treated water reformed into an organic substance having easy aggregation and separation, and mainly composed of the organic substance having easy aggregation and separation, is circulated to the aggregation and separation step 3. Further, the treated water 12 having a reduced TOC is obtained from a part of the effluent of the coagulation separation step.

Next, an example of a specific configuration of the present invention will be described with reference to FIG. In FIG. 5, a first coagulation / separation step 3a is provided in the preceding stage of the present invention to remove easily coagulable / separable organic substances contained in the raw water 1 by coagulation / separation in advance.
The raw water 1 mainly containing an organic substance which is hardly decomposable and hardly coagulated and separated is subjected to the flow shown in FIGS. The first coagulation / separation step 3a includes a mixing tank 7 in which the raw water 1 and the coagulant 8 are mixed, a coagulation tank 9 in which coagulates are generated, and a solid-liquid separation tank 10 in which coagulates are separated into solid and liquid. In the solid-liquid separation tank 10, the sludge 11 containing the easily coagulated and separable organic matter that has been coagulated and separated is removed, and the liquid part is subjected to the same processing steps as in FIGS. The aggregation / separation step 3 in FIGS. 1 to 4 corresponds to the second aggregation / separation step 3b in FIG. In FIG. 5, since the first coagulation / separation step 3a is provided, the efficiency of reforming the hardly decomposable and hardly coagulable / separable organic substance into the easily coagulable / separable organic substance in the reforming step 2 is higher than in FIGS. It has the effect of improving. Further, the coagulant and the solid-liquid separation method can be optimized for each of the easily coagulable and separable substances previously contained in the raw water and the easily coagulable and separable substances generated in the reforming step.

Next, an example of a specific configuration of the present invention will be described with reference to FIG. In FIG. 6, the treated water of the present invention is used as raw water, and an oxidative decomposition step of treating with the active species is provided to further oxidatively decompose organic substances remaining in the treated water.
It improves the safety and purification of treated water. The oxidative decomposition step has an oxidative decomposition tank into which raw water 1 flows, and hydrogen peroxide 5 and ozone 6 for generating active species are supplied to the inlet and the tank, respectively. FIG.
The treated water is used as raw water, and an activated carbon treatment step is provided. 1. adsorption and removal of organic substances remaining in the treated water; By decomposing and removing the remaining oxidizing agent, the safety and purification of treated water are improved.

[0019]

Hereinafter, specific examples of the present invention will be described.
The present invention is not limited to this. Example 1 Wastewater from litter landfill leachate having a TOC of 150 mg / liter was treated according to the flow shown in FIG. 1 under the following conditions. Reforming step Oxidizing agent used: hydrogen peroxide, ozone Hydrogen peroxide injection amount: 300 to 500 mg / liter Ozone injection amount: 850 to 1400 mg / liter Residence time: 1 hr Aggregation / separation step Coagulant used: FeCl ₃ coagulant injection amount: 700 mg-Fe / liter pH: 5.0 Raw water flow rate: 1.0 liter / min Circulation rate: 0, 2.0

Table 1 shows the results of processing under the above conditions.

[Table 1]

From Table 1, when comparing the case where the circulation rate is 0 and 2.0, the treated water D-TOC under the condition of the circulation rate = 2.0
Was found to be lower. In addition, even when the amount of the oxidizing agent added in the reforming step was reduced under the condition of the circulation rate = 2.0, treated water having the same water quality as the case of the circulation rate = 0 was obtained. From this, it was recognized that the oxidizing agent consumption in the reforming step can be reduced by circulating the treated water between the reforming step and the coagulation separation step. Tables 2 and 3 show the results of coagulation and sedimentation of the raw water and oxidative decomposition using ozone and hydrogen peroxide.

[Table 2]

[0022]

[Table 3] Here, from Tables 1, 2 and 3, in the method for treating the hardly decomposable organic matter-containing wastewater according to the present invention, the D-TOC removal amount is larger than the sum of each of the coagulation sedimentation treatment and the oxidative decomposition treatment. It was recognized that the cohesive separation property was improved.

Example 2 Water treated for coagulation and sedimentation of leachate from landfills having a TOC of 150 mg / liter was treated according to the flow shown in FIG. 2 under the following conditions. Reforming step Oxidizing agent used: hydrogen peroxide, ozone Hydrogen peroxide injection amount: 400 to 600 mg / liter Ozone injection amount: 1100 to 1700 mg / liter Residence time: 1 hr Aggregation / separation step Coagulant used: FeCl ₃ coagulant injection amount: 700 mg-Fe / liter pH: 5.0 Raw water flow rate: 1.0 liter / min Circulation rate: 2.5, 5.0

Table 4 shows the results of processing under the above conditions.

[Table 4] Thus, even when comparing the case where the circulation rate to the coagulation / separation step = 2.5 and 5.0, under the condition where the circulation rate = 5.0, the amount of the oxidizing agent added in the reforming step is small. It was found that the treated water D-TOC could be reduced. It was found that by increasing the circulation rate, the amount of organic substances removed in the coagulation separation step was increased and the oxidant consumption in the reforming step could be reduced.

Example 3 Water treated for coagulation and sedimentation of leachate from a landfill having a TOC of 150 mg / liter was treated according to the flow shown in FIG. 3 under the following conditions. Reforming process Oxidizing agent used: hydrogen peroxide, ozone Hydrogen peroxide injection amount: 500 mg / liter Ozone injection amount: 1400 mg / liter Low-pressure mercury lamp input power: 200 W Residence time: 40 min Coagulation separation process Coagulant: FeCl ₃ coagulant Injection amount: 700 mg-Fe / liter pH: 5.0 Raw water flow rate: 1.0 liter / min Circulation rate: 3.0, 5.0

Table 5 shows the results of processing under the above conditions.

[Table 5] From Table 5, when comparing the case where the circulation rate to the coagulation separation step is 3.0 and 5.0, it is recognized that the treated water D-TOC can be reduced under the condition of the circulation rate = 5.0. Was. From this, it was recognized that, even in the flow as shown in FIG. 3, by increasing the circulation rate, the amount of organic substances removed in the coagulation / separation step was increased, and the consumption of the oxidizing agent in the reforming step could be reduced.

Example 4 Water treated for coagulation and sedimentation of leachate from a landfill having a TOC of 150 mg / liter was treated according to the flow shown in FIG. 4 under the following conditions. Reforming step Oxidizing agent used: hydrogen peroxide, ozone Hydrogen peroxide injection amount: 500 mg / liter Ozone injection amount: 1,400 mg / liter Residence time: 1 hr Aggregation separation step Coagulant used: FeCl ₃ coagulant injection amount: 700 mg-Fe / 1 liter pH: 5.0 Raw water flow rate: 1.0 liter / min Circulation rate: 3.0, 5.0

Table 6 shows the results of processing under the above conditions.

[Table 6] From Table 6, when comparing the case where the circulation rate to the coagulation separation step is 3.0 and 5.0, it was recognized that the treated water D-TOC can be reduced under the condition of the circulation rate = 5.0. . From this, it was recognized that by increasing the circulation rate also in the flow as shown in FIG. 4, the amount of organic substances removed in the coagulation / separation step was increased, and the consumption of the oxidizing agent in the reforming step could be reduced.

Example 5 Water treated for coagulation and sedimentation of leachate from garbage landfill having a TOC of 150 mg / liter was treated according to the flow shown in FIG. 5 under the following conditions. First coagulation separation step Coagulant used: FeCl ₃ coagulant injection amount: 200 mg-Fe / liter pH: 5.0 Reforming step Oxidant used: ozone titanium dioxide solid catalyst: 400 mg / l Ozone injection amount: 1400 mg / l low pressure Mercury lamp input power: 200 W Residence time: 1 hr Second coagulation / separation step Coagulant used: FeCl ₃ Coagulant injection amount: 700 mg-Fe / liter pH: 5.0 Raw water flow rate: 1.0 liter / min Circulation rate: 0, 1.5

Table 7 shows the results of processing under the above conditions.

[Table 7] From Table 7, when comparing the case where the circulation rate to the coagulation separation step is 0 and 1.5, the treated water D-
It has been found that TOC can be reduced. From this, it was recognized that by increasing the circulation rate also in the flow as shown in FIG. 5, the amount of organic substances removed in the coagulation / separation step was increased, and the consumption of the oxidizing agent in the reforming step could be reduced.

Example 6 Biologically treated water having a TOC of 200 mg / liter was treated according to the flow shown in FIG. 6 under the following conditions. First flocculation / separation step Flocculant: Ferric chloride Flocculant injection amount: 200 mg-Fe / L pH: 5.0 Reforming process Oxidant used: Hydrogen peroxide, ozone Hydrogen peroxide injection amount: 400-500 mg / L Ozone injection amount: 1100 to 1400 mg / liter Residence time: 1 hr

Second coagulation separation step Coagulant used: FeCl ₃ coagulant injection amount: 700 mg-Fe / liter pH: 5.0 Oxidative decomposition step Oxidizer used: hydrogen peroxide, ozone Hydrogen peroxide injection amount: 300 mg / l Ozone injection amount: 1000 mg / liter Residence time: 1 hr Raw water flow rate: 1.0 liter / min Circulation rate: 0, 1.5

Table 8 shows the results of processing under the above conditions.

[Table 8]

From Table 8, it can be seen that the circulation rate to the coagulation / separation step = 0,
In comparison with the case of 1.5, when the circulating rate = 1.5, the treated water D-
It has been found that TOC can be reduced. From this, it was recognized that the oxidizing agent consumption in the reforming step can be reduced by circulating the treated water between the reforming step and the coagulation separation step also in the flow as shown in FIG.
When oxidative decomposition treatment using ozone and hydrogen peroxide as oxidizing agents was performed using the treated water in the first coagulation separation process as raw water, hydrogen peroxide consumption = 3000 mg / liter, ozone consumption = 9200 mg / liter. Under the condition
Treated water D-TOC = 40 mg / liter. From this, it was recognized that the method for treating the hardly decomposable organic matter-containing wastewater according to the present invention can reduce the oxidant consumption even under conditions where circulation is not performed.

As a target experiment, the same raw water was treated under the following experimental conditions in accordance with the flow shown in FIG. 8, and as a result, the treated water D-TOC = 60 mg / liter.
In Table 8, the water quality was lower than that of the treated water with the circulation rate = 0. From this, it was recognized that the method for treating the hardly decomposable organic matter-containing wastewater according to the present invention has improved the coagulation / separation property of the raw water, and can perform advanced treatment with a small amount of oxidizing agent. Experimental Conditions Coagulation Separation Step 1 Coagulant: Ferric chloride Coagulant injection amount: 200 mg-Fe / liter pH: 5.0 Coagulation separation step 2 Coagulant used: Ferric chloride Coagulant injection amount: 700 mg-Fe / Liter pH: 5.0

Oxidative decomposition step 1 Oxidant used: hydrogen peroxide, ozone Hydrogen peroxide injection amount: 500 mg / liter Ozone injection amount: 1400 mg / liter Residence time: 1 hr Oxidative decomposition step 2 Oxidizer used: hydrogen peroxide, Ozone Hydrogen peroxide injection amount: 300 mg / liter Ozone injection amount: 1000 mg / liter Residence time: 1 hr Raw water flow rate: 1.0 liter / min Circulation rate: 0

Example 7 Biologically treated water having a TOC of 200 mg / liter was treated according to the flow shown in FIG. 7 under the following conditions. First coagulation separation step Coagulant: ferric chloride Coagulant injection amount: 200 mg-Fe / liter pH: 5.0 Reforming step Oxidant used: hydrogen peroxide, ozone Hydrogen peroxide injection amount: 500-600 mg / liter Ozone injection amount: 1100 to 1400 mg / liter Residence time: 40 min

Second coagulation separation step Coagulant used: PAC Coagulant injection amount: 500 mg-Al / liter pH: 5.0 Activated carbon treatment step Activated carbon amount: 500 mg / L Raw water flow rate: 1.0 L / min Circulation rate: 0 , 1.5

Table 9 shows the results of processing under the above conditions.

[Table 9]

According to Table 9, the circulation rate to the coagulation / separation step = 0,
In comparison with the case of 1.5, it was recognized that the treated water D-TOC can be reduced under the condition of the circulation rate = 1.5 under the condition that the amount of the oxidizing agent added in the reforming step is small. From this, it was recognized that the oxidizing agent consumption in the reforming step can be reduced by circulating the treated water between the reforming step and the coagulation separation step. In addition, when the hydrogen peroxide concentration of the inflow water and the outflow water of the activated carbon treatment step was measured, the inflow water was 50 mg / liter and the outflow water was 1 mg / liter or less. From this, it was confirmed that in the activated carbon treatment step, not only the removal of organic substances but also the removal of hydrogen peroxide were carried out, and the treated water was highly purified and the safety was enhanced.

[0041]

According to the method for treating wastewater containing hardly decomposable organic matter according to the present invention, the organic matter in the wastewater is treated at low cost, with low sludge generation and at a high level. That is,
In the reforming step, the hardly decomposable substance in the raw water is reformed into a substance having high aggregating and separating properties by active species such as hydroxy radicals. The modification here mainly means (1) a partial increase in anionic and cationic properties due to the action of the active species, (2) a change in molecular weight due to the action of the active species,
Alone or in synergy. Mainly due to these effects, the reactivity of the substance with the coagulant is increased, and the substance in the raw water is reformed into a substance having a high coagulation separation property. In the aggregating / separating step, the substance having a high aggregating / separating property that has been modified in the modifying step is removed.

As described above, since the substance to be treated in the coagulation / separation step is a substance having a high coagulation / separation property, the amount of coagulant required per the amount of removed organic matter is reduced, and the amount of generated sludge is reduced.
In addition, some organic substances are decomposed into water and carbon dioxide gas due to the reforming. However, such an auxiliary effect also lowers the concentration of organic substances in the wastewater and reduces the required amount of coagulant. .
Further, by circulating the treated water between the coagulation separation step and the reforming step, the reforming efficiency in the reforming step is improved, and the amount of active species required for the reforming for organic substances having various properties is increased. It becomes possible to be suitable. Therefore, it is possible to further reduce the amount of the oxidizing agent used in the reforming step and the energy related to the ultraviolet irradiation. Accordingly, in the coagulation separation step, it is possible to further increase the organic substance removal amount per coagulant addition amount. Further, by providing the oxidative decomposition step and the activated carbon treatment step at the subsequent stage, the purification degree and safety of the treated water are improved. In short, according to the method for treating hardly decomposable organic matter-containing wastewater according to the present invention, advanced treatment can be performed with low cost and low sludge generation amount.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an example of a processing method of the present invention.

FIG. 2 is a flowchart showing an example of the processing method of the present invention.

FIG. 3 is a flowchart showing an example of the processing method of the present invention.

FIG. 4 is a flowchart showing an example of the processing method of the present invention.

FIG. 5 is a flowchart showing an example of the processing method of the present invention.

FIG. 6 is a flowchart showing an example of the processing method of the present invention.

FIG. 7 is a flowchart showing an example of the processing method of the present invention.

FIG. 8 is a flowchart used in the subject experiment.

[Explanation of symbols]

1: raw water, 2: reforming step, 3: coagulation separation step, 3a: first coagulation separation step, 3b: second coagulation separation step, 4: reforming treatment tank, 5: hydrogen peroxide, 6: ozone, 7 : Mixing tank, 8:
Coagulant, 9: Coagulation tank 10: Treated water, 11: Sludge, 1
2: solid-liquid separation tank, 13: ultraviolet lamp, 14: titanium dioxide solid catalyst, 15: sulfuric acid, 16: ferric chloride, 17:
Oxidative decomposition step, 18: oxidative decomposition tank, 19: activated carbon adsorption step, 20: activated carbon adsorption tank, 21: coagulation separation step 1,
22: Coagulation separation step 2, 23: Oxidative decomposition step 1, 24: Oxidative decomposition step 2,

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location C02F 9/00 504 C02F 9/00 504E 1/32 1/32 1/52 ZAB 1/52 ZABZ 1 / 72 1/72 Z 101 101 1/78 1/78

Claims (5)

[Claims] 1. A method for highly treating a wastewater containing hardly decomposable organic matter, wherein the wastewater is treated in a reforming step of generating and treating an active species and a coagulation separation step of coagulating and separating the modified wastewater. A method of treating the wastewater containing hardly decomposable organic matter, wherein the wastewater is returned to the reforming step and a part of the effluent of the reforming step or a part of the effluent of the coagulation / separation step is treated water. 2. A method for highly treating wastewater containing hardly decomposable organic matter, comprising: an agglomeration / separation step of aggregating / separating the wastewater; and a reforming step of generating and treating the agglomerated / separated water with active species. A method for treating the wastewater containing hardly decomposable organic matter, wherein the wastewater is returned to the coagulation / separation step and a part of the effluent of the coagulation / separation step or the effluent of the reforming step is treated water. 3. The method for treating hardly decomposable organic matter-containing wastewater according to claim 1 or 2, wherein a coagulation separation step is provided in a preceding stage. 4. The method for treating wastewater containing hardly decomposable organic matter according to claim 1, wherein an oxidative decomposition step or an activated carbon treatment step of generating and treating active species is provided at a subsequent stage. A method for treating wastewater containing persistent organic matter. 5. The method according to claim 1, wherein the generation of the active species is caused by one or a combination of two or more of ozone, hydrogen peroxide, light, and a heterogeneous catalyst or a homogeneous catalyst. The method for treating wastewater containing hardly decomposable organic matter according to any one of the above.