JP2009101262A - Method and apparatus for water treatment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water treatment method which employs a small amount of activated carbon, and can treat raw water containing COD components while suppressing the amount of generated sludge. <P>SOLUTION: The water treatment method comprises a first Fenton treatment process performing a first Fenton treatment of the raw water containing COD components, a biological treatment process performing biological treatment of the treated water subjected to the first Fenton treatment, and a second Fenton treatment process performing second Fenton treatment of the biologically treated water, and reduces the COD concentration of the treated water to equal to or lower than 20 mg/L. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a water treatment method and a water treatment apparatus for oxidizing and decomposing raw water containing a COD component.

  In many cases, the wastewater containing highly COD-containing wastewater containing COD components is disposed as industrial waste through operations such as concentration as waste liquid. In that case, a high processing cost is cited as a drawback.

On the other hand, as a wastewater treatment method, a method of biodegrading COD components in wastewater by biodegradation by combining ozone oxidation and Fenton treatment has been proposed. Here, the Fenton treatment is a method in which organic substances are oxidatively decomposed by hydroxy radicals generated by reacting hydrogen peroxide (H ₂ O ₂ ) and Fe ²⁺ under acidic conditions.

  In recent years, when treated as wastewater in this way, due to the COD total amount regulation, there is an increasing need for the COD concentration in the final treated water to be 10 to 20 mg / L or less even for raw water containing high-concentration COD components.

Japanese Patent No. 3139337 Japanese Patent Publication No. 4-080758 JP 59-000375 A

  However, in the conventional Fenton treatment-biological treatment method, it is difficult to set the COD concentration in the final treated water to 10 to 20 mg / L or less. That is, it is empirically known that in the biological treatment in the conventional technology, even if it can be ideally treated, about 10% of the COD component remains in the treated water with respect to the COD concentration of the inflowing raw water. For example, when raw water having a COD concentration of 1000 mg / L or more is easily biodegraded by Fenton treatment and treated with about 50 to 95% of the COD component, the COD component of about 50 mg / L to 300 mg / L is usually present. In order to reduce the COD concentration in the final treated water to 10 to 20 mg / L or less, the treated water thus obtained must be further treated by adsorption with an activated carbon tower, and the amount of activated carbon used. Increases the processing cost.

  The present invention is a water treatment method and a water treatment apparatus capable of treating raw water containing a COD component while suppressing the amount of generated sludge while using a small amount of activated carbon.

  The present invention provides a first Fenton treatment step in which a first Fenton treatment is performed on raw water containing a COD component, and a biological treatment in which a biological treatment is performed on the first Fenton treated water that has been subjected to the first Fenton treatment. And a second Fenton treatment step of performing a second Fenton treatment on the biologically treated water that has been subjected to the biological treatment, wherein the COD concentration of the treated water is 20 mg / L or less. is there.

  Moreover, in the said water treatment method, when the COD density | concentration of the said raw | natural water is 1000 mg / L or more and 6000 mg / L or less, this invention can be applied more suitably and an effect is high.

  In addition, it is preferable to perform the treatment by adding activated carbon in at least the first Fenton treatment step of the water treatment method.

  Moreover, in the said 2nd Fenton process process of the said water treatment method, it is preferable to add activated carbon and process and to return the generated sludge to the said 1st Fenton process process.

  In the water treatment method, the biological treatment is preferably a floating biological treatment or a fixed bed biological treatment.

  Moreover, it is preferable to perform a batch process in the first Fenton process of the water treatment method.

  The present invention also provides a first Fenton treatment means for performing a first Fenton treatment on raw water containing a COD component, and a biological treatment on the first Fenton treated water subjected to the first Fenton treatment. And a second Fenton treatment means for performing a second Fenton treatment on the biologically treated water subjected to the biological treatment.

  In the present invention, the raw water containing the COD component is subjected to biological treatment after performing Fenton treatment, and then further Fenton treatment, so that the amount of activated carbon used in the subsequent stage of those treatments is small, and the amount of generated sludge It is possible to provide a water treatment method and a water treatment apparatus capable of treating raw water containing a COD component while suppressing the above.

  Embodiments of the present invention will be described below. This embodiment is an example for carrying out the present invention, and the present invention is not limited to this embodiment.

  Conventionally, the COD component remaining when the raw biodegradable raw water containing highly biodegradable high-concentration COD is treated with Fenton has been considered as “a hardly decomposable COD component that could not be decomposed even in the previous Fenton treatment”. . Therefore, when further reducing COD in raw water that has been subjected to biological treatment after Fenton treatment, it has been considered unsuitable for Fenton treatment. Furthermore, since the production of sludge that requires industrial disposal is relatively large, the Fenton treatment has been refrained from performing the Fenton treatment twice individually in one treatment system. Therefore, as described above, adsorption treatment using an activated carbon tower has been mainly proposed for the final treated water. However, in order to treat raw water having a COD of about 50 to 300 mg / L to 20 mg / L or less, the replacement frequency of activated carbon is high. The processing cost was enormous.

  As a result of intensive studies, the inventors have determined that the residual COD component when the biological treatment is performed after the non-biodegradable high-concentration COD-containing raw water is subjected to the biological treatment is further degraded by the Fenton treatment due to the change in properties due to the biological treatment. It was found that the COD in the final treated water could be reduced to 20 mg / L or less by performing the Fenton treatment again after the biological treatment.

  In addition, regarding the amount of sludge generated at this time, it seems that the amount of sludge generated by Fenton treatment is increased considerably by applying the Fenton treatment twice, but the amount of sludge generated by Fenton treatment is mainly proportional to the COD concentration to be treated. Therefore, the amount of sludge generated in the Fenton treatment for the relatively low concentration COD component in the latter stage after the Fenton treatment-biological treatment is compared with the amount of sludge generated for the high concentration COD component in the Fenton treatment in the former stage. Then, it is only about a dozen percent, and it was found that there was no significant difference from the conventional Fenton treatment-biological treatment system, and the present invention was achieved.

  An outline of an example of the water treatment apparatus according to the present embodiment is shown in FIG. 1 and the configuration thereof will be described. The water treatment apparatus 1 includes a first Fenton treatment apparatus 10 that is a first Fenton treatment means, a biological treatment apparatus 12 that is a biological treatment means, and a second Fenton treatment apparatus 14 that is a second Fenton treatment means.

  In the water treatment apparatus 1, first, the first Fenton treatment is performed on the raw water containing the COD component (first Fenton treatment step). Next, biological treatment is performed on the first Fenton treated water that has been subjected to the first Fenton treatment (biological treatment step). Then, a second Fenton treatment is further performed on the biologically treated water that has been subjected to the biological treatment (second Fenton treatment step). Thereby, the COD concentration of the final treated water can be reduced to 20 mg / L or less.

  Moreover, as shown in FIG. 2, the activated carbon treatment apparatus 16 which is an activated carbon treatment means is provided in the back | latter stage of the 2nd Fenton treatment apparatus 14, and activated carbon treatment may be performed in consideration of safety with respect to the final treated water. Examples of the activated carbon treatment means include an activated carbon tower. Naturally, the replacement frequency of the activated carbon is much smaller than the conventional method of Fenton treatment-biological treatment-activated carbon treatment.

  Hereinafter, each device and each process will be described. FIG. 3 shows a schematic configuration diagram of an example of the first Fenton processing device 10 and the second Fenton processing device 14. In addition, the structure of the 1st Fenton processing apparatus 10 and the 2nd Fenton processing apparatus 14 is not restricted to this, Moreover, the same structure or a different structure may be sufficient. The 1st Fenton processing apparatus 10 and the 2nd Fenton processing apparatus 14 are the reaction tank 18 (the reaction tank 28 in the 2nd Fenton processing apparatus 14), the neutralization tank 20 (the neutralization tank 30), and the reduction tank 22 ( The reduction tank 32), the coagulation tank 24 (the coagulation tank 34), and the precipitation tank 26 (the same precipitation tank 36) which is a solid-liquid separation means are provided. In the first Fenton treatment apparatus 10 and the second Fenton treatment apparatus 14, the outlet of the reaction tank 18 (28) and the inlet of the neutralization tank 20 (30), the outlet of the neutralization tank 20 (30) and the reduction tank 22 (32) , The outlet of the reduction tank 22 (32) and the inlet of the agglomeration tank 24 (34), and the outlet of the agglomeration tank 24 (34) and the inlet of the sedimentation tank 26 (36) are connected by piping or the like.

In the first Fenton treatment apparatus 10, raw water (treated water) containing a COD component is sent to the reaction tank 18, and hydrogen peroxide, a decomposition catalyst containing at least a ferrous salt, and the like are added to the reaction tank 18. The COD component is decomposed by oxidation (decomposition step). At this time, the acid condition is adjusted with an acid such as sulfuric acid. After the oxidation treatment, the reaction solution is sent to the neutralization tank 20, where an alkali agent is added in the neutralization tank 20, and the pH is adjusted to 6 to 10.5 (neutralization step). Thereafter, the neutralized neutralized liquid is sent to the reduction tank 22, a reducing agent is added to reduce the residual hydrogen peroxide (reduction process), and the residual hydrogen peroxide is removed. The reducing solution from which the residual hydrogen peroxide has been removed is sent to the agglomeration tank 24 where a flocculant is added to grow flocs and agglomerate (aggregation step). The agglomerated liquid containing the grown floc is sent to the precipitation tank 26, and is solid-liquid separated into sludge containing ferric ions (Fe ³⁺ ) and the treated water by natural sedimentation separation (solid-liquid separation step). . At least a part of the sludge may be returned to the reaction tank 18 by a return means (not shown) and added again to the reaction tank 18 together with hydrogen peroxide, a decomposition catalyst, and the like. Further, at least a part of the sludge may be extracted and discharged out of the system as sludge. On the other hand, the first Fenton-treated water that has been subjected to solid-liquid separation contains a readily biodegradable COD component, and is sent to the next biological treatment apparatus 12.

  As the biological treatment in the biological treatment apparatus 12, a general biological treatment is used, and a floating type, a fluidized bed type in which efficiency is increased by adding a carrier, a fixed bed type in which water is supplied to the packing, and the like are used. Thereafter, by performing the Fenton treatment again, final treated water having a COD concentration of 20 mg / L or less is obtained.

  FIG. 4 shows a general schematic configuration of the biological treatment apparatus 12. The biological treatment apparatus 12 includes a biological treatment tank 38 and a sedimentation tank 40. The first Fenton-treated water is sent to a biological treatment tank (aeration tank) 38. The biological treatment tank 38 is supplied with return sludge, and the inside of the tank is aerated and agitated by the air from the blower 42 to be in an aerobic condition. Therefore, organic substances in the first Fenton-treated water are decomposed by aerobic microorganisms in the sludge. The biological reaction water from the biological treatment tank 38 flows into the sedimentation tank 40, where the sludge is settled and separated, and the supernatant is sent to the second Fenton treatment apparatus 14 as biological treatment water. Further, at least a part of the sedimented sludge in the sedimentation tank 40 may be returned to the biological treatment tank 38 as the returned sludge by the return sludge pump 44. At least a part of the precipitated sludge may be discharged as excess sludge. The configuration shown in FIG. 4 is an example, and the present invention is not limited to this.

Next, in the second Fenton treatment device 14 of FIG. 3, the biologically treated water from the biological treatment device 12 is sent to the reaction vessel 28, and in the reaction vessel 28, a decomposition catalyst containing hydrogen peroxide and at least a ferrous salt. Etc. are added, and the remaining COD components are decomposed by oxidation (decomposition step). At this time, the acid condition is adjusted with an acid such as sulfuric acid. After the oxidation treatment, the reaction solution is sent to the neutralization tank 30, where an alkali agent is added in the neutralization tank 30, and the pH is adjusted to 6 to 10.5 (neutralization step). Thereafter, the neutralized neutralized solution is sent to the reduction tank 32, a reducing agent is added to reduce the residual hydrogen peroxide (reduction step), and the residual hydrogen peroxide is removed. The reducing solution from which the residual hydrogen peroxide has been removed is sent to the agglomeration tank 34 where a flocculant is added to grow flocs and agglomerate (aggregation step). The agglomerated liquid containing the grown floc is sent to the precipitation tank 36, and is solid-liquid separated into sludge containing ferric ions (Fe ³⁺ ) and the treated water by natural sedimentation separation (solid-liquid separation step). . At least a part of the sludge may be returned to the reaction tank 28 by a return means (not shown) and added to the reaction tank 28 together with hydrogen peroxide, a decomposition catalyst, and the like. Further, as described later, at least a part of the sludge may be returned to the reaction tank 18 of the first Fenton treatment apparatus 10. Further, at least a part of the sludge may be extracted and discharged out of the system as sludge. On the other hand, the second Fenton treated water subjected to the solid-liquid separation is discharged out of the system as final treated water.

  The water treatment method according to this embodiment includes organic substances such as dimethyl sulfoxide (DMSO), ethylenediaminetetraacetic acid (EDTA), phenols, organochlorine compounds, environmental hormones, biologically treated water, pumped contaminated groundwater, surfactants, and the like. Used for oxidative degradation or biodegradation of hardly biodegradable organic substances. The concentration of the COD component in the raw water is effective by optimizing the drug concentration at any concentration, but this embodiment relates to the raw water having a COD of 1000 mg / L or more and 6000 mg / L or less. It is preferable to apply a water treatment apparatus and a water treatment method. When the COD of raw water is less than 1000 mg / L, COD of 10 to 20 mg / L or less is often achieved after Fenton treatment-biological treatment. In addition, when the COD of raw water exceeds 6000 mg / L, the cost may increase due to the cost of chemicals such as hydrogen peroxide.

  Moreover, the water treatment apparatus and water treatment according to the present embodiment for the raw water containing hardly biodegradable high-concentration COD having a BOD / COD value of raw water of preferably 0.4 or less, more preferably 0.1 or less It is preferable to apply the method. When the value of BOD / COD of raw water exceeds 0.4, it may be more efficient to perform a decomposition treatment by biological treatment-activated carbon treatment. When the value of BOD / COD of raw water is 0.4 or less and the COD of raw water is less than 1000 mg / L, COD of 10 to 20 mg / L or less is often achieved after Fenton treatment-biological treatment. Therefore, the water treatment method according to this embodiment can be particularly suitably applied when the raw water BOD / COD value is 0.4 or less and the raw water COD is 1000 mg / L or more. By performing Fenton treatment on such hardly biodegradable high-concentration COD-containing raw water, and further performing Fenton treatment on the biologically treated water, a COD of 20 mg / L or less is obtained. Water quality can be obtained. Examples of such raw water containing hardly biodegradable high-concentration COD include substrate waste water, paint and dye waste water in the electronics industry.

  Here, the COD value can be analyzed according to JIS-K0102 (1998) -17, and the BOD value can be analyzed according to JIS-K0102 (1998) -21.

  In the first Fenton treatment step and the second Fenton treatment step, ferrous ions and hydrogen peroxide generated from the decomposition catalyst containing at least a ferrous salt may be simultaneously present in the reaction tank 18 (28). Here, at least in the first Fenton treatment step, it is preferable to perform the treatment by adding activated carbon to the reaction tank 18. Addition of activated carbon improves the efficiency of the Fenton reaction itself, and can also remove hydrophobic non-biodegradable substances that are difficult to decompose with hydroxy radicals by adsorption, so it is applicable to raw water containing highly biodegradable high-concentration COD. If you do so, you will have a double desired effect. Of course, in the second Fenton treatment step, the treatment may be performed by adding activated carbon.

The activated carbon used in the present embodiment is not particularly limited, but is preferably pulverized coal in order to ensure a specific surface area. Activated carbon mainly plays a role of increasing the catalytic activity of ferric ions (Fe ³⁺ ) generated in the decomposition step and promoting the decomposition reaction. The reaction promoting effect of the activated carbon depends to some extent on the activated carbon raw material, but there is no significant difference. In view of cost and versatility, coal-based or wood-based activated carbon is preferably used. The activated effect of the Fenton method with activated carbon is due to the action of activating Fe ³⁺ present in the reaction system, so the iron salt to be added is not suitable for use in the normal Fenton method in addition to the ferrous salt A ferric salt can also be used. As the ferrous salt and ferric salt, sulfates, hydrochlorides, nitrates and the like thereof can be used, and iron sulfate and iron chloride are particularly preferably used.

  Other processing conditions in the Fenton treatment may be almost the same in the first Fenton treatment step and the second Fenton treatment step.

  The pH in the reaction tank 18 (28) may be an acidic condition. However, in consideration of maintaining the dissolved iron concentration in the system, the pH is in the range of 2 to 3, particularly in the range of pH 2.4 to 2.6 (2.5 Near) is suitable for the reaction. Acids such as sulfuric acid, hydrochloric acid, acetic acid, phosphoric acid and nitric acid are used to adjust the pH, but it is preferable to use sulfuric acid. Nitric acid is expensive and leads to a subsequent increase in nitrogen load, and hydrochloric acid is not preferred because the reaction with chloride ions acts as a radical scavenger.

The addition concentration of the chemical in the reaction tank 18 (28) varies depending on the COD concentration of the raw water to be treated, but the addition amount of Fe ²⁺ is generally 0.05 to 0. 0 in terms of the chemical equivalent to the COD concentration of the raw water. It is preferably 25 times (that is, Fe ²⁺ / COD (chemical equivalent ratio) = 0.05 to 0.25). When the amount of Fe ²⁺ added exceeds 0.25 times the COD concentration of raw water, a large amount of sludge may be generated. Moreover, when the added amount of Fe ²⁺ is less than 0.05 times the COD concentration of raw water, a good COD decomposition rate may not be obtained. Fe ²⁺ / COD (chemical equivalent ratio) is more preferably in the range of 0.05 to 0.15. Further, the addition amount of Fe ²⁺ is preferably 0.05 to 1 times as much as the chemical equivalent ratio with respect to the addition amount of hydrogen peroxide.

  The amount of hydrogen peroxide added is preferably about 0.8 to 3 times the chemical equivalent ratio of the raw water COD (that is, hydrogen peroxide / COD (chemical equivalent ratio) = 0.8 to 3). If the amount of hydrogen peroxide added exceeds 3 times the COD of the raw water, the residual hydrogen peroxide concentration may increase and the cost of hydrogen peroxide reduction may increase. If the amount of hydrogen peroxide added is less than 0.8 times the COD of raw water, a good COD decomposition rate may not be obtained. Further, hydrogen peroxide / COD (chemical equivalent ratio) = 1 to 2 is more preferable.

The addition amount of the activated carbon is 1 to 20 times by weight with respect to Fe ^{2+ of the} ferrous salt added in the reaction tank 18 (28) (that is, activated carbon / Fe ²⁺ (weight ratio) = 1 to 20). It is preferable that Even if the addition amount of the activated carbon exceeds 20 times with respect to Fe ²⁺ , the COD decomposition rate does not greatly improve, and agglomeration failure tends to occur. When the added amount of activated carbon is less than 1 time with respect to Fe ²⁺ , a good COD decomposition rate may not be obtained. Further, activated carbon / Fe ²⁺ (weight ratio) = 1 to 10 is more preferable.

  Moreover, the addition amount of activated carbon is 0.1-1 times by weight ratio with respect to the hydrogen peroxide added in the reaction tank 18 (28) (that is, activated carbon / hydrogen peroxide (weight ratio) = 0.1-1). ) Is preferable. Even if the addition amount of activated carbon exceeds 1 time with respect to hydrogen peroxide, the COD decomposition rate is not greatly improved, and if it is less than 0.1 times, a good COD decomposition rate may not be obtained. Moreover, it is more preferable that the range is activated carbon / hydrogen peroxide (weight ratio) = 0.1 to 0.5.

When the COD component, which is the substance to be treated, is a substance that is adsorbed on activated carbon, the Fe ²⁺ / COD (chemical equivalent ratio) for the concentration obtained by adding the COD value adsorbed on the activated carbon to be added to the initial COD value It is sufficient to apply within the range.

As a reaction method in the reaction tank 18 (28), either batch processing or continuous processing is possible. In the case of batch processing, after acidifying the pH in the reaction tank 18 (28) system, a decomposition catalyst, activated carbon, return sludge, etc. are added until hydrogen peroxide reaches a predetermined addition amount within a predetermined reaction time. It is preferable to gradually add hydrogen in terms of suppressing the self-decomposition of hydrogen peroxide. Furthermore, with respect to hydrogen peroxide, an equimolar amount of Fe ²⁺ is added in the initial stage, and then the remaining amount is gradually added within a predetermined reaction time in that the self-decomposition of hydrogen peroxide can be suppressed. preferable. In addition, it is possible to reduce the concentration of hydrogen peroxide in the treated water by decomposing hydrogen peroxide by adding about 10-20% of the reaction time and adding the stirring time without adding chemicals after adding hydrogen peroxide. Is preferable. Further, by providing such a stirring time, it is possible to prevent the sludge once precipitated by the oxygen generated by the self-decomposition of the remaining hydrogen peroxide in the solid-liquid separation step.

  In the case of continuous processing, the reaction tank 18 (28) in this embodiment may be divided into two or more and arranged in series from the viewpoint of reaction kinetics. The number of reaction vessels 18 (28) is not particularly limited, but is preferably divided into 2 to 10 from the viewpoint of reaction kinetics, and more preferably divided into 2 to 4. Moreover, the addition of each chemical when the reaction tank 18 (28) is divided may be divided and added to each tank. At this time, the addition of hydrogen peroxide brings about a desirable effect that the self-decomposition of hydrogen peroxide can be suppressed if the reaction tank 18 (28) is divided and added to each tank. There is no particular limitation on the method of adding activated carbon, decomposition catalyst, and circulated sludge to the divided reaction tank, but from the viewpoint of cost and simplicity of the apparatus shape, it is added to the first reaction tank among the tanks arranged in series. It is preferable. The reaction tank 18 (28) may be divided into two or more and arranged in parallel.

Hydrogen peroxide is added separately to each reaction tank arranged in series, and the decomposition rate is further improved by adding a decomposition catalyst to the first stage of the divided reaction tank and activated carbon and return sludge to the second stage of the reaction tank. It has the desired effect. This is because the decomposition reaction proceeds more efficiently when the decomposition reaction is performed with Fe ²⁺ in the first stage of the reaction tank and the Fe ³⁺ generated in the second stage of the reaction tank is activated with activated carbon. Thus, when adding the decomposition catalyst to the first stage of the reaction tank and the activated carbon and the return sludge to the second stage of the reaction tank, the volume after the second stage is made larger than that of the first stage reaction tank, The abundance of ³⁺ may be increased, or the volume of the first-stage reaction tank may be made larger than the second and subsequent stages to increase the residence time of Fe ²⁺ in the first-stage reaction tank. . By these, the decomposition rate can be further improved.

  In the present embodiment, the Fenton treatment in the first Fenton treatment step is preferably performed by batch processing. Thereby, it is possible to efficiently decompose a high concentration of the hardly biodegradable COD component. In the second Fenton treatment step, since the concentration is low, the Fenton treatment can be performed by continuous treatment.

  As the flocculant used in the flocculation step, a polymer flocculant or the like is used. The kind of the polymer flocculant at this time is not particularly limited, and anionic and nonionic ones are preferably used.

  The solid-liquid separation in the solid-liquid separation step may be performed by a separation method such as membrane separation or pressurized flotation in addition to sedimentation separation.

  In the present embodiment, when activated carbon is added in the second Fenton treatment step, the sludge generated in the second Fenton treatment step is returned to the first Fenton treatment step by the return means as shown in FIG. It is preferable to reuse the first Fenton treatment because the performance of the first Fenton treatment is improved. The return sludge at this time is preferably free from impurities other than iron and activated carbon, and therefore, it is preferred that the SS component in the biologically treated water flowing from the biological treatment step to the second Fenton treatment step is small. Biological treatment methods that have a small amount of SS components in the biologically treated water include: a floating type provided with a sedimentation tank; treated water for membrane-separated activated sludge; a fibrous filler and a plastic filler in which SS is captured by the filler. Fixed bed type filled with The fluidized bed type without a settling tank tends to have a relatively high outflow SS.

  Hereinafter, although an example and a comparative example are given and the present invention is explained more concretely in detail, the present invention is not limited to the following examples.

(Examples 1-4)
COD value analyzed according to JIS-K0102 (1998) -17 and BOD value analyzed according to JIS-K0102 (1998) -21 are COD of 1890 mg / L and BOD of 2 mg / L or less (BOD / COD = about 0) .001), the first Fenton treatment-biological treatment-second Fenton treatment was performed.

The 1st Fenton process was performed by the semibatch process. To be treated raw water 8L, was added _{FeSO 4 · 7H 2 O 26000mg /} L condition (1), as the condition _{(2) FeSO 4 · 7H 2} O 2200mg / L and wood-based powdered activated carbon 2200 mg / L, respectively, sulfate After adjusting the pH to 2.5 ± 0.5, H ₂ O ₂ was continuously added to each to be 6700 mg / L over 1 hour with stirring, and then stirred for 0.5 hour. After completion of the reaction, the pH was adjusted to neutral (pH 6-8) with sodium hydroxide, 10 mg / L of a polymer flocculant (OA-23, manufactured by Organo) was added to form a floc and sedimented. When the COD concentration of each supernatant was analyzed according to JIS-K0102 (1998) -17, the condition (1) was 340 mg / L and the condition (2) was 103 mg / L. Further, the amount of SS generated was measured by sampling the suspension solution after treatment and measuring according to JIS-K0102 (1998) -14.2, under conditions (1) 17000 mg / L and (2) 4800 mg / L, respectively. there were.

  Next, the biological treatment was performed by batch processing about the supernatant (1st Fenton treated water) after the process of conditions (1) and (2). As biological treatment, using seed sludge conditioned by meat extract-peptone, it is added to 3000 mg / L with respect to 5 L of Fenton treated water of each condition, and DO (dissolved oxygen) is 4 mg / L in batch treatment. For 24 hours. The pH during the treatment was controlled using sodium hydroxide and a pH controller so as to maintain 7.0 ± 0.5. After the treatment, the treated water was filtered through filter paper 5A and the COD concentration was analyzed according to JIS-K0102 (1998) -17. As a result, condition (1) was 120 mg / L and condition (2) was 55 mg / L.

The 2nd Fenton process was performed using the biological treatment water filtered with the filter paper 5A of the conditions (1) and conditions (2) which implemented the 1st Fenton process and the biological process (Examples 1-4). The Fenton treatment is carried out as a batch treatment. The pH is adjusted to 2.5 ± 0.5 with sulfuric acid, and a predetermined amount of FeSO ₄ .7H ₂ O and wood-based powdered activated carbon are added to 300 mL of the water to be treated and stirred. A predetermined amount of hydrogen oxide was added and stirred for 1 hour. After completion of the reaction, the pH was adjusted to neutral (pH 6-8) with sodium hydroxide, 1 mg / L of a polymer flocculant (OA-23, manufactured by Organo) was added to form a floc and settled. The COD concentration of each supernatant was analyzed according to JIS-K0102 (1998) -17. In addition, the amount of SS generated was measured. The results are shown in Table 1.

(Comparative Examples 1-5)
Using biologically treated water filtered with the filter paper 5A under the same conditions (2) as in Examples 1 to 4, a comparison test with the adsorption treatment with activated carbon was performed. In the adsorption treatment with activated carbon, a predetermined amount of wood-based powdered activated carbon is added to 300 mL of water to be treated and stirred for 24 hours, and then the COD concentration of the filtrate filtered through a 0.1 μm filter is JIS-K0102 (1998) -17. According to the analysis. The amount of activated carbon used is 60 mg / L (Comparative Example 1), 100 mg / L (Comparative Example 2), 550 mg / L (Comparative Example 3), 1000 mg / L (Comparative Example 4), and 2000 mg / L (Comparative Example 5). The experiment was conducted. The results are shown in Table 1.

(Comparative Example 6)
Using biologically treated water filtered by the filter paper 5A under the same conditions (2) as in Examples 1 to 4, a comparative test with an acidic flocculation treatment was performed. In the flocculation treatment, 700 mg / L of 38% FeCl ₃ was added to 300 mL of the water to be treated under a fixed condition of pH 4 ± 0.1 with sulfuric acid and stirred for 5 minutes, and then pH 7 ± 0. Set to 5, 1 mg / L of a polymer flocculant (OA-23, manufactured by Organo Co., Ltd.) was added to form a floc and sedimented, and the COD concentration of each supernatant was analyzed according to JIS-K0102 (1998) -17 did. In addition, the amount of SS generated was measured. The results are shown in Table 1.

  From the comparison of Examples 1 to 4 and Comparative Examples 1 to 5, it is necessary to add 2000 mg / L or more of activated carbon in the activated carbon adsorption treatment in order to make the COD of the final treated water 10 mg / L or less. Therefore, it is easily guessed that the amount of activated carbon consumed is very large, and it can be seen that the second Fenton treatment is effective. Further, it can be seen from Comparative Example 6 that the treated water can hardly remove the COD component by the acidic coagulation treatment. Furthermore, the amount of SS generated from the Fenton treatment in the entire treatment flow is about 19000 mg / L (17000 mg / L + 1730 mg / L, in the present treatment method shown in Examples 1 and 2 while Fenton treatment-biological treatment is 17000 mg / L, The Fenton treatment with activated charcoal added to the biological treatment was 4800 mg / L, whereas the treatment method shown in Examples 3 and 4 was about 5800 mg / L (4800 mg / L + 880 mg / L, 840 mg / L). Therefore, it can be seen that the amount of sludge generated by this treatment method is not significantly different from the Fenton treatment-biological treatment. Further, by comparing Examples 1 and 2 with Examples 3 and 4, it can be seen that by adding activated carbon in the first Fenton treatment in the previous stage, the generated SS and the treated water COD value of the entire system are lowered. .

It is a schematic structure figure showing an example of the water treatment equipment concerning the embodiment of the present invention. It is a schematic block diagram which shows the other example of the water treatment apparatus which concerns on embodiment of this invention. It is a schematic block diagram which shows an example of the Fenton processing apparatus which concerns on embodiment of this invention. It is a schematic block diagram which shows an example of the biological treatment apparatus which concerns on embodiment of this invention. It is a schematic block diagram which shows the other example of the water treatment apparatus which concerns on embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Water treatment apparatus, 10 1st Fenton treatment apparatus, 12 Biological treatment apparatus, 14 2nd Fenton treatment apparatus, 16 Activated carbon treatment apparatus, 18, 28 Reaction tank, 20,30 Neutralization tank, 22,32 Reduction tank, 24, 34 Coagulation tank, 26, 36 Sedimentation tank, 38 Biological treatment tank, 40 Sedimentation tank, 42 Blower, 44 Return sludge pump.

Claims (7)

A first Fenton treatment step of performing a first Fenton treatment on raw water containing a COD component;
A biological treatment step of performing biological treatment on the first Fenton-treated water that has undergone the first Fenton treatment;
A second Fenton treatment step of performing a second Fenton treatment on the biologically treated water subjected to the biological treatment;
Including
A water treatment method, wherein the COD concentration of treated water is 20 mg / L or less. The water treatment method according to claim 1,
A COD concentration of the raw water is 1000 mg / L or more and 6000 mg / L or less. The water treatment method according to claim 1 or 2,
At least in the first Fenton treatment step, treatment is performed by adding activated carbon. The water treatment method according to claim 3,
In the second Fenton treatment step, activated water is added for treatment, and the generated sludge is returned to the first Fenton treatment step. The water treatment method according to claim 4,
The water treatment method, wherein the biological treatment is a floating biological treatment or a fixed bed biological treatment. The water treatment method according to any one of claims 1 to 5,
In the first Fenton treatment, a batch treatment is performed. A first Fenton treatment means for performing a first Fenton treatment on raw water containing a COD component;
Biological treatment means for performing biological treatment on the first Fenton treated water that has undergone the first Fenton treatment;
A second Fenton treatment means for performing a second Fenton treatment on the biologically treated water subjected to the biological treatment;
A water treatment apparatus comprising:

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