JP2014233692A - Treatment method and treatment device for hard-biodegradable organic matter-containing water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain treatment water of high quality reducing the using amount of an iron medicine and a sludge generation amount in a Fenton oxidation treatment for hard-biodegradable organic matter-containing water, and further, improving the dewaterability of sludge.SOLUTION: Hydrogen peroxide and an iron medicine by 0.005 to 0.2 molar time quantity of the amount of the hydrogen peroxide are added to hard-biodegradable organic matter-containing water, reaction is caused at pH 2 to 4 for 1 hr or more, thereafter, an alkali agent is added to oxidation treatment water to generate an insolubilization material, and the produced insolubilization material is subjected to solid-liquid separation. Alkali mixed sludge obtained by adding and mixing the alkali agent into a part of the separated sludge obtained in the solid-liquid separation stage is added at least as a part of an alkali agent added to oxidation treatment water in an insolubilization stage.

Description

  The present invention relates to a treatment method and a treatment apparatus for water containing hardly biodegradable organic matter, which efficiently treats water containing hardly biodegradable organic matter by Fenton oxidation treatment.

  The reaction mechanism of Fenton oxidation treatment, which is a method for treating hardly biodegradable organic substances, is to oxidize and decompose organic substances by generating OH radicals, which are strong oxidizing agents, by the reaction of iron chemicals and hydrogen peroxide. The Fenton oxidation treatment is a treatment consisting of two steps of an oxidation step and a subsequent aggregation step because it is necessary to remove the added iron agent.

  The Fenton oxidation treatment has a first problem that the amount of iron agent used as a catalyst is large, which affects the chemical cost. In addition, the amount of iron sludge generated is very large, and there is a second problem that dewatering costs and sludge transportation / disposal costs associated with the sludge dewatering increase.

  Conventionally, in order to solve the first problem, a small amount of iron agent is added and a Fenton oxidation treatment is performed by reacting at a pH of 1.0 to 2.0 for 3 to 8 hours. The proposal (patent document 1) of making it biologically process without producing | generating sludge by forming is made | formed. However, according to the study by the present inventors, the COD decomposition rate is very slow at a pH of 1.0 to 2.0, and sludge is finally produced after biological treatment.

Further, in order to solve the second problem, in the flocculation treatment of the wastewater, the alkali mixed sludge obtained by adding the alkali agent to a part of the flocculated separation sludge is used as the flocculant of the metal salt added to the wastewater as the flocculant. For example, a proposal has been made to reduce the amount of generated sludge and improve sludge dewaterability while returning to the agglomeration reaction tank so that the metal amount is 2 to 50 times the amount. (Patent Documents 2 and 3). However, as a result of studies by the present inventors, it has been found that when this method is applied to Fenton oxidation treatment to reduce the amount of iron agent added, the sludge dewaterability is not improved.
Furthermore, it has been proposed that a divalent iron chemical is added to the oxidized water to form a mixed sludge of divalent and trivalent iron (green last and iron ferrite), and the separated sludge is returned (Patent Document 4). . However, in this method, it is necessary to generate sludge having a ratio of divalent iron to total iron of 0.4 to 0.8, and the amount of divalent iron chemical added is large and the chemical cost is excessive.

Japanese Patent Publication No. 4-80758 Japanese Patent No. 2601441 Japanese Patent No. 2910346 JP 2009-148749 A

  The present invention solves the above-mentioned conventional problems, and in the Fenton oxidation treatment of water containing hardly biodegradable organic matter, reduces the amount of iron chemicals used and the amount of sludge generated, and improves the dewaterability of sludge. It is another object of the present invention to provide a treatment method and a treatment apparatus for water containing hardly biodegradable organic matter to obtain treated water with good water quality.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have conducted hydrogen peroxide and hydrogen peroxide addition amount of 0.1% in the oxidation step in the Fenton oxidation treatment of water containing a hardly biodegradable organic substance. After adding 005-0.2 mol times the amount of iron drug and reacting under conditions of pH 2-4 for 1 hour or longer to obtain oxidized water, a part of the sludge obtained by solid-liquid separation is used. By adding alkaline mixed sludge to which alkaline agent is added to this oxidized treated water, it is possible to obtain good treated water quality, reduce the amount of iron chemicals, and at the same time reduce the amount of iron sludge produced. It has been found that high iron sludge can be obtained, and further, hydrogen peroxide remaining by oxidation treatment can be decomposed by adding alkali mixed sludge.

  The present invention has been achieved on the basis of such findings, and the gist thereof is as follows.

[1] In the method of Fenton oxidation treatment of water containing a hardly biodegradable organic substance, hydrogen peroxide and 0.005 to 0.2 mol times the hydrogen peroxide addition amount to the water containing the hardly biodegradable organic substance A Fenton oxidation process in which an amount of iron agent is added and reacted for 1 hour or more under the condition of pH 2 to 4, and an insolubilization that generates an insolubilized product by adding an alkaline agent to the oxidized water obtained in the oxidation process An alkali mixed sludge obtained by adding and mixing an alkali agent to a part of the separated sludge obtained in the solid-liquid separation step. A method for treating water containing hardly biodegradable organic substances, which is added as at least part of an alkaline agent added to oxidation-treated water in the insolubilization step.

[2] In [1], the solid content of the alkali mixed sludge added to the insolubilization step is 20 to 500 times the amount of the insolubilized product generated by the reaction of the oxidation-treated water and the alkali agent. A method for treating water containing hardly biodegradable organic matter.

[3] In [1] or [2], the insolubilization step adjusts the oxidation-treated water to pH 3.5 to 4.5 and the pre-neutralization treatment water to pH 5 to 12. And a neutralizing step. A method for treating water containing a hardly biodegradable organic substance.

[4] In an apparatus for Fenton oxidation treatment of water containing a hardly biodegradable organic substance, the water containing the hardly biodegradable organic substance is added to hydrogen peroxide and 0.005 to 0.2 mol times the hydrogen peroxide addition amount. Fenton oxidation means for adding an amount of iron agent and reacting for 1 hour or more under the conditions of pH 2 to 4, and insolubilization for generating an insolubilized product by adding an alkaline agent to the oxidized water obtained by the oxidation means And an alkali mixing means for adding and mixing an alkaline agent to a part of the separated sludge obtained by the solid-liquid separation means, and a solid-liquid separation means for solid-liquid separation of the generated insolubilized material. An apparatus for adding water containing hardly biodegradable organic matter, comprising: means for adding alkali mixed sludge as at least part of an alkali agent added to oxidation-treated water by the insolubilizing means.

[5] In [4], the solid content of the alkali mixed sludge added to the insolubilization means is 20 to 500 times the amount of the insolubilized product produced by the reaction of the oxidation-treated water and the alkali agent. Equipment for treating water containing hardly biodegradable organic substances.

[6] In [4] or [5], the insolubilizing means adjusts the oxidation-treated water to a pH of 3.5 to 4.5 and a preliminary neutralization-treated water to a pH of 5 to 12. A treatment apparatus for water containing hardly biodegradable organic substances, comprising a neutralization tank.

  According to the present invention, in the Fenton oxidation treatment of water containing a hardly biodegradable organic substance, an alkaline agent is added to a part of the solid-liquid separation sludge after controlling the pH, the amount of iron agent added and the reaction time in Fenton oxidation. By adding the added alkaline mixed sludge to the oxidized water, a good quality of treated water is obtained, and the amount of iron chemicals is reduced and at the same time the amount of iron sludge produced is reduced to obtain a concentrated and highly dewatering iron sludge. Further, by adding alkali mixed sludge, it becomes possible to decompose and remove hydrogen peroxide remaining in the oxidation treatment, and an efficient treatment can be performed.

It is a systematic diagram which shows an example of embodiment of the processing apparatus of the hardly biodegradable organic substance containing water of this invention. It is a systematic diagram which shows the other example of embodiment of the processing apparatus of the hardly biodegradable organic substance containing water of this invention. It is a systematic diagram which shows another example of embodiment of the processing apparatus of the hardly biodegradable organic substance containing water of this invention. It is a systematic diagram which shows another example of embodiment of the processing apparatus of the hardly biodegradable organic substance containing water of this invention.

  Hereinafter, embodiments of the present invention will be described in detail.

Non-biodegradable organic substance-containing water to be treated in the present invention is refractory biodegradation of dimethyl sulfoxide (DMSO), ethylenediaminetetraacetic acid (EDTA), phenols, organochlorine compounds, environmental hormones, surfactants, biometabolites, etc. a water containing sex organics, usually the organic content is about 50~1,000mg / L at _{COD Cr} concentration. Moreover, the pH of these hardly biodegradable organic substance containing water is about 1-9.

  In the present invention, when such a hardly biodegradable organic substance-containing water is used as a raw water, a predetermined amount of hydrogen peroxide and an iron agent are added, and an acid such as sulfuric acid is added if necessary. In the process of adjusting the pH to oxidatively decompose the hardly biodegradable organic substance by the Fenton oxidation reaction under a predetermined pH condition, neutralize the oxidized water to produce an insolubilized substance, and separate the insolubilized substance into solid and liquid. A part of the separated sludge obtained by liquid separation is added to the oxidation-treated water in the neutralization treatment as an alkali mixed sludge obtained by adding and mixing an alkali agent to this sludge.

As described above, the Fenton oxidation treatment includes an oxidation process and an aggregation process.
The Fenton reaction in the oxidation process generates OH radicals by the reaction of hydrogen peroxide and divalent iron, but iron repeatedly divalent and trivalent catalytically as shown in the following reaction formula 1. Therefore, it is not necessary to add equimolar amounts of iron to hydrogen peroxide.
<Reaction Formula 1>
Fe (II) + H ₂ O ₂ → Fe (III) + OH ⁻ + · OH
Fe (III) + H ₂ O ₂ → Fe (II) + H ⁺ + · OOH
Fe (III) +. OOH → Fe (II) + H ⁺ + O ₂

Since iron acts as a catalyst, the amount of iron affects the reaction time. Conventionally, the amount of iron has been determined so that it can be generally processed in a reaction time of about 15 to 60 minutes. However, as a result of investigations by the present inventors, it was found that the COD concentration of treated water deteriorates when iron is added so that it can be treated within a reaction time of 60 minutes or less. This is presumably because the reaction with hydrogen peroxide proceeds rapidly because the iron concentration is high, and the self-decomposition of hydrogen peroxide proceeds as shown in the following reaction formula 2.
<Reaction Formula 2>
2Fe (II) + 2H ₂ O ₂ → 2Fe (III) + 2OH ⁻ + 2 · OH
・ OH + ・ OH → H ₂ O ₂

  For these reasons, the present inventors have determined that it is not preferable to set a large amount of iron addition to shorten the reaction time.

  In the present invention, the amount of iron agent added is 0.005 to 0.2 mole times the amount of hydrogen peroxide added, which is less than the conventional amount, thereby suppressing hydrogen peroxide self-decomposition. As a result, the amount of hydrogen peroxide added can also be reduced as compared with the prior art. Moreover, reaction time is made into 1 hour or more by reducing the addition amount of an iron chemical | medical agent, Preferably it is 1-3 hours. The amount of iron agent added is particularly preferably 0.02 to 0.1 mol times the amount of hydrogen peroxide added.

  Iron agents added to raw water include ferrous sulfate (Fe (II)) compounds such as ferrous sulfate and ferrous chloride, ferric sulfate such as ferric sulfate and ferric chloride (Fe (III) ) One or more of compounds can be used. That is, as shown in the above reaction formula 1, in the oxidation process, iron repeats bivalent and trivalent continuously. Therefore, in the present invention, the iron agent to be added is either Fe (II) compound or Fe (III) compound. Is also possible. However, since the OH radical used for oxidative decomposition is produced by reaction with divalent iron, it is preferably a divalent iron compound.

The amount of hydrogen peroxide added is preferably 0.5 to 3 mol times, particularly 0.7 to 2 mol times with respect to COD _{Cr of} raw water.
Moreover, pH in an oxidation process shall be 2-4. If the pH is less than 2, the amount of iron dissolved is large, but the reactivity with hydrogen peroxide is poor, and if it exceeds 4, iron precipitates. Preferably, iron needs to be in an ionic state at the entrance of the solid-liquid separation step after the oxidation step, and therefore the optimum pH is determined based on the reaction time, iron concentration, water temperature, and raw water composition.

  An alkaline agent is added to the oxidized water obtained in the above oxidation step to insolubilize it, and the insolubilized product is separated into solid and liquid. In the present invention, an alkali agent is added to a part of the separated sludge obtained by the solid-liquid separation to obtain an alkali mixed sludge, and the alkali mixed sludge is added to the oxidation-treated water for insolubilization treatment. In this way, by adding alkali mixed sludge to the oxidized water, iron ions in the oxidized water react with the hydroxide adsorbed on the sludge surface of the alkali mixed sludge and precipitate on the sludge surface. Sludge with high density and excellent dewaterability can be obtained.

As described above, the process of returning part of the separated sludge is a known process as described in Patent Documents 2 and 3, but the sludge return method is used for Fenton-oxidized water having a low iron concentration. It was found that even when applied, the dewaterability of sludge was not improved.
That is, the amount of sludge returned in Patent Documents 2 and 3 is such that the amount of metal in the returned sludge is 2 to 50 times, preferably 15 to 40 times the amount of metal added as a flocculant. Under the conditions, the sludge was not densified or the solid-liquid separation was unstable in the Fenton oxidation treatment.

  According to the study by the present inventors, the solid content of sludge added to the oxidized water is determined based on the amount of insolubilized product produced by the reaction of the oxidized water and the alkaline agent (only the alkaline agent is added to the oxidized water to be insolubilized. 20 to 500 times, preferably 50 to 200 times the amount of the insolubilized product produced when the slag is produced, the aggregate floc size is coarse and the sludge has excellent dewatering properties. It has been found that liquid separation can be stabilized. If the amount of returned sludge is less than 20 times the amount, the amount of returned sludge is small, so precipitation of iron ions on the sludge surface does not proceed, and the sludge tends not to be densified. Since the sludge concentration is high, the sludge is not enlarged and becomes in a dispersed state, and easily leaks from the solid-liquid separation settling tank.

The insolubilization process in the present invention is preferably carried out by a two-stage treatment of preliminary neutralization and neutralization. That is, it is preferable to carry out in a first-stage neutralization tank and a second-stage neutralization tank.
Since the oxidation-treated water contains an acid component such as an organic acid, in one-step neutralization treatment, iron may not be sufficiently precipitated and may be partially dissolved. For this reason, it is preferable to carry out neutralization in two stages of preliminary neutralization and neutralization. In this two-step neutralization, the alkali mixed sludge may be added to the preliminary neutralization tank or may be added to the neutralization tank. Moreover, you may add to both a preliminary | backup neutralization tank and a neutralization tank, and the sludge which is not mixing the alkaline agent can also be added as it is. For example, the following neutralization treatment forms can be employed.
(1) Add sludge and an alkaline agent to the preliminary neutralization tank, and add the alkali mixed sludge to the neutralization tank.
(2) Add alkali mixed sludge to the preliminary neutralization tank, and add sludge and alkaline agent to the neutralization tank.
(3) Add alkali mixed sludge to the preliminary neutralization tank, and add an alkali agent to the neutralization tank.
(4) Add alkali mixed sludge to the preliminary neutralization tank and the neutralization tank, respectively.

  Among these, particularly as described in (4) above, by adding alkali mixed sludge to each of the preliminary neutralization tank and the neutralization tank, it is possible to obtain a sludge having higher density and excellent dewaterability.

As described above, when the separated sludge is returned in this manner, the return amount of the sludge is 20% of the amount of insolubilized matter generated by the reaction between the oxidized water and the alkaline agent as the solid content of the returned sludge added to the oxidized water. It is preferable that the amount is about 500 times.
In the following, the ratio of the solid content of the returned sludge to the amount of insolubilized product generated by the reaction between the oxidized water and the alkaline agent is referred to as “sludge return ratio”. By making this sludge return ratio 20 times or more, the sludge obtained by solid-liquid separation can be sufficiently densified to obtain a sludge excellent in dewaterability. However, if the sludge return ratio is excessively high, the processing efficiency is lowered, and a large-capacity tank is required as a preliminary neutralization tank or neutralization tank. Therefore, the sludge return ratio is preferably 500 times or less. From the viewpoint of processing efficiency and sludge densification, the sludge return ratio is particularly preferably 50 to 200 times.

  When adding the return sludge to each of the pre-neutralization tank and the neutralization tank or the alkali mixed sludge mixed with the alkali agent in the return sludge, the ratio of the solid content of the sludge added to the pre-neutralization tank and the neutralization tank Although there is no particular limitation, it is preferable that the return sludge is added to at least the pre-neutralization tank, and when the return sludge and / or alkali mixed sludge is added to both the pre-neutralization tank and the neutralization tank, the return sludge is returned. It is preferable to add 20 to 80% to the pre-neutralization tank and the remainder to the neutralization tank.

When the treatment is performed at a suitable sludge return ratio as described above, the concentration (solid content concentration) of the separated sludge, that is, the returned sludge is usually a high concentration of 10 to 30%.
In addition, caustic soda (sodium hydroxide), slaked lime, etc. can be used as an alkaline agent added to sludge, a preliminary neutralization tank, and a neutralization tank.

  The treatment in the preliminary neutralization tank is preferably carried out at a pH of 3.5 to 4.5, particularly 3.8 to 4.2. The residence time in the preliminary neutralization tank is preferably about 5 to 20 minutes.

  In the preliminary neutralization tank, hydrogen peroxide remaining in the oxidation step is also decomposed. Since hydrogen peroxide is decomposed by hydroxide and iron (Reference 1: Paper Partnership Magazine Vol. 49, No. 4, the following reaction formula 3), the sludge return ratio is 20 to 500 times in the present invention. It is considered that hydrogen peroxide is decomposed by the high concentration alkaline agent adsorbed on the surface of iron and sludge contained in the sludge. In order to promote the decomposition of hydrogen peroxide, a reducing agent such as sodium bisulfite can be supplementarily added to the preliminary neutralization tank or the neutralization tank.

Moreover, it is preferable to perform the process in the neutralization tank after preliminary neutralization by pH 5-12. As mentioned above, in the pre-neutralization tank, iron may not be sufficiently precipitated and may partially dissolve. In this case, crystallization is promoted by adding separated sludge or alkali mixed sludge to the neutralization tank. Can do. Even when metals other than iron are contained in the wastewater, it is possible to select the optimum pH according to the metal components in the wastewater and add the separated sludge or the alkali mixed sludge. When iron is the main component of the metal in the oxidation treated water, the treatment in the neutralization tank is preferably carried out at a pH of 6.0 to 8.5.
The residence time of this neutralization tank is preferably about 5 to 20 minutes.

The neutralized water is then agglomerated by adding a flocculant to form agglomerated flocs.
As the flocculant, a polymer flocculant is used, and one kind of anionic polymer, cationic polymer, amphoteric polymer, and nonionic polymer is used alone or in combination of plural kinds depending on the properties of raw water. The anionic polymer is preferable. The amount of these flocculants added is usually 1 to 5 mg / L.

  The agglomerated treated water is then subjected to solid-liquid separation to separate the treated water and sludge. Any solid-liquid separation means may be used as long as it can perform solid-liquid separation, and a precipitation tank, a membrane separation device, a filter, and the like can be applied. Part of the separated sludge is sent to a preliminary neutralization tank, a neutralization tank, or an alkali mixing tank, and the remainder is discharged out of the system as excess sludge.

  In the alkali mixing tank, the sludge is mixed with an alkali agent to form an alkali mixed sludge. In order to transfer the alkali mixed sludge to the preliminary neutralization tank or the neutralization tank, the alkali mixed sludge may be continuously overflowed from the alkali mixing tank. The amount of the alkali agent added to the alkali mixing tank is controlled based on the pH fluctuation of the preliminary neutralizing tank or the neutralizing tank.

1 to 4 are system diagrams showing an example of an embodiment of the apparatus for treating water containing hardly biodegradable organic substances of the present invention. In FIGS. 1 to 4, 1 is a Fenton oxidation reaction tank, and 2 is pre-neutralization Tank 3, neutralization tank 4, coagulation tank 5, precipitation tank 5, 6, 6 A and 6 B are alkali mixing tanks, and in either apparatus, hydrogen peroxide and sulfuric acid were added to the raw water in the Fenton oxidation reaction tank 1. An iron agent such as ferrous iron (FeSO ₄ ) and, if necessary, an acid such as sulfuric acid (H ₂ O ₂ ) are added, and Fenton oxidation is carried out for 1 hour or more under pH 2 to 4 conditions. The oxidized water in tank 1 is then neutralized in order in pre-neutralizing tank 2 and neutralizing tank 3, and the neutralized water is agglomerated by adding a polymer flocculant (polymer) in agglomeration tank 4, and agglomerated. The treated water is solid-liquid separated in the precipitation tank 5. Part of the separated sludge is fed to one of the preliminary neutralization tank 2, the neutralization tank 3, and the alkali mixing tank 6, 6A, 6B, and the alkali mixed sludge or the separated sludge is supplied to the preliminary neutralization tank 2 and / or neutralization. Added to tank 3.

  FIG. 1 shows the sludge return form of (1) above. Part of the separated sludge is transferred to the preliminary neutralization tank 2, and the other part is transferred to the alkali mixing tank 6. Alkaline mixed sludge mixed with an alkali agent such as is added to the neutralization tank 3. FIG. 2 shows the sludge return form of (2) above, in which part of the separated sludge is transferred to the neutralization tank 3 and the other part is transferred to the alkali mixing tank 6, such as NaOH in the alkali mixing tank 6. The alkali mixed sludge to which the alkali agent is added and mixed is added to the preliminary neutralization tank 1. FIG. 3 shows the sludge return form of (3) above, in which a part of the separated sludge is transferred to the alkali mixing tank 6 and the alkali mixed sludge to which the alkali agent is added and mixed in the alkali mixing tank 6 is in reserve. An alkali agent such as NaOH is added to the neutralization tank 3. FIG. 4 shows the sludge return form of (4) above, in which part of the separated sludge is transferred to the alkali mixing tank 6A, and the other part is transferred to the alkali mixing tank 6B, and the alkali mixing tanks 6A and 6B respectively. The alkali mixed sludge mixed with an alkali agent such as NaOH is added to the preliminary neutralization tank 2 and the neutralization tank 3, respectively.

  Thus, in the present invention, the amount of iron chemical added to the Fenton oxidation reaction tank, the pH condition, and the reaction time are controlled, and a part of the separated sludge obtained by solid-liquid separation is used as alkali mixed sludge to treat Fenton oxidation treated water. The amount of iron chemicals required is reduced and the amount of sludge produced is reduced, and concentrated dewatered sludge is obtained. Further, by adding alkali mixed sludge, Fenton The remaining hydrogen peroxide by the oxidation treatment can be decomposed, and an efficient treatment can be performed.

Hereinafter, the present invention will be described more specifically with reference to examples.
In the following Examples and Comparative Examples, treatment was performed using simulated raw water prepared as follows as the raw material containing hardly biodegradable organic matter-containing water.
<Preparation of simulated raw water>
After biologically treating synthetic wastewater containing 100 mg / L of isopropyl alcohol (IPA), dimethyl sulfoxide (DMSO), and tetramethylammonium hydroxide (TMAH), concentrated water obtained by coagulation treatment and reverse osmosis membrane separation treatment is used. Furthermore, COD _Cr 600 mg / L water containing hardly biodegradable organic matter was prepared by evaporating and concentrating.

In addition, COD _Cr of treated water obtained in the following examples, comparative examples and reference examples was measured after decomposing residual hydrogen peroxide with sodium bisulfite. Further, the hydrogen peroxide concentration of the treated water was measured with a hydrogen peroxide test paper “Checkle KS” (measurement lower limit 3 mg / L) manufactured by Kurita Kogyo Co., Ltd.

[Example 1]
Continuous water treatment with a water flow rate of 1 L / hr was performed with the apparatus shown in FIG.
In the Fenton oxidation reactor 1, hydrogen peroxide was added in an amount of 1500 mg / L and ferrous sulfate was added in an amount of 100 mg / L as Fe, and the conditions were pH 3, residence time 2 hours, and 25 ° C. ([Fe] / _{[H 2 O 2] = 0.04} ).
Next, while separating and adding the separated sludge of the precipitation tank 5 in the preliminary neutralization tank 2, NaOH was added so that the pH was 4.2 ± 0.1. The residence time in the preliminary neutralization tank 2 was 0.2 hours.
Next, in the neutralization tank 3, the alkali mixed sludge from the alkali mixing tank 6 was added so that the pH was 8.0 ± 0.1. The residence time of this neutralization tank was 0.4 hours.
The return sludge concentration at this time was 12%. The return sludge ratio was 80, and the sludge was returned to the preliminary neutralization tank 2 and the alkali mixing tank 6. That is, since the SS concentration generated from the oxidized water is 190 mg / L in terms of Fe (OH) ₃ , the return ratio is 80, and the sludge is returned at a sludge return rate of 127 mL / hr (sludge concentration 12%). In addition, it adjusted so that 70% might be added to the preliminary | backup neutralization tank 2 and 30% might be added to the neutralization tank 3 among returned sludge.
In the aggregating tank 4, 3 mg / L of an anionic polymer “PA331” manufactured by Kurita Kogyo Co., Ltd., a polymer aggregating agent, was added, and the agitation was performed at 100 rpm and agglomeration was performed for a residence time of 0.1 hour. .
In the next settling tank 5, the coarse floc produced by the coagulation treatment was settled and separated, and the supernatant water that overflowed the trough in the water tank was used as the treated water of Example 1.
The treated water after performing this operation for 2 weeks was analyzed. The results are shown in Table 1. Table 1 shows the water content of the dewatered sludge obtained by dewatering the sludge discharged from the settling tank 5.

[Example 2]
The treated water was obtained under the same reaction time, chemical injection conditions, and sludge return conditions as in Example 1 with continuous water flow of 1 L / hr with the apparatus of FIG. Table 1 shows the analysis results of the treated water and the moisture content of the dewatered sludge.

[Example 3]
The treated water was obtained under the same reaction time, chemical injection conditions, and sludge return conditions as in Example 1 with continuous water flow of 1 L / hr with the apparatus of FIG. However, the return sludge was added to the preliminary neutralization tank 2 in its entirety as alkali mixed sludge. Table 1 shows the analysis results of the treated water and the moisture content of the dewatered sludge.

[Example 4]
The treated water was obtained under the same reaction time, chemical injection conditions, and sludge return conditions as in Example 1 with continuous water flow of 1 L / hr with the apparatus of FIG. Table 1 shows the analysis results of the treated water and the moisture content of the dewatered sludge.

[Comparative Example 1]
Tests by Fenton oxidation and coagulation sedimentation treatment were carried out.
Under conditions of pH 3, the raw water was added with 1500 mg / L of hydrogen peroxide and 200 mg / L as Fe of ferrous sulfate, reacted at 25 ° C. for 0.5 hours, then adjusted to pH 9 and stirred for 10 minutes. Then, 3 mg / L of an anionic polymer “PA331” manufactured by Kurita Kogyo Co., Ltd. was added, and the generated coarse floc was settled and separated, and the supernatant water was used as the treated water of Comparative Example 1.

[Comparative Example 2]
The test was carried out in the same manner as in Comparative Example 1 except that the ferrous sulfate addition amount in Fenton oxidation was 100 mg / L as Fe, and the reaction time was 2 hours, and the supernatant water obtained by sedimentation separation was compared. The treated water of Example 2 was used. Table 1 shows the analysis results of the treated water and the moisture content of the dewatered sludge.

[Reference Example 1]
The test was carried out under the same conditions as in Example 1 except that the sludge return ratio was set to 20, and the supernatant water of the sedimentation tank 5 was used as the treated water of Reference Example 1. The return sludge concentration at this time was 5.5%. That is, since the SS concentration generated from the oxidized water is 190 mg / L in terms of Fe (OH) ₃ , sludge was returned with a return ratio of 20 and a sludge return amount of 69 mL / hr (sludge concentration 5.5%). Table 1 shows the analysis results of the treated water and the moisture content of the dewatered sludge.

Table 1 shows the following.
In Comparative Example 1, the amount of iron agent added is 200 mg-Fe / L, which is twice that of Examples 1 to 4, so that hydrogen peroxide undergoes autolysis in the Fenton oxidation reaction, and the treated water COD _Cr is high. Sludge has poor dewaterability. In addition, since Comparative Example 2 has the same amount of iron chemical addition as Example 1, the treated water COD _Cr concentration is equivalent, but since the sludge is not densified, the moisture content of the dewatered sludge is 79%. high. Reference Example 1 performs sludge return for densification as in Example 1, and the treated water COD _Cr is slightly higher than Example 1, but the sludge return ratio is as low as 20. The density of the sludge is insufficient, and the moisture content of the dewatered sludge is as high as 68%. Moreover, since the sludge return ratio is low and the reaction between the alkali mixed sludge and hydrogen peroxide is insufficient, hydrogen peroxide remains in the treated water.
On the other hand, in Examples 1 to 4, the moisture content of the dewatered sludge is as low as 51 to 56%. In particular, in Example 4 in which alkali mixed sludge is added to the preliminary neutralization tank and the neutralization tank, the moisture content is the lowest. High density sludge can be obtained.
From the above results, according to the present invention, the Fenton oxidation reaction is carried out with a small amount of iron agent added, the alkali agent is added to the sludge obtained by solid-liquid separation, and the alkali mixed sludge is returned. It can be seen that water quality can be obtained, iron agent addition amount, sludge generation amount, sludge dewaterability can be improved, and residual hydrogen peroxide can be decomposed and removed.

1 Fenton oxidation reaction tank 2 Preliminary neutralization tank 3 Neutralization tank 4 Coagulation tank 5 Precipitation tank 6 Alkali mixing tank

Claims (6)

In a method for Fenton oxidation treatment of water containing a non-biodegradable organic substance,
Add hydrogen peroxide and 0.005 to 0.2 mol times the amount of the hydrogen peroxide to the water containing the hardly biodegradable organic substance, and add 1 hour under conditions of pH 2 to 4 The Fenton oxidation process to be reacted as described above, the insolubilization process for generating an insolubilized product by adding an alkaline agent to the oxidized water obtained in the oxidizing process, and the solid-liquid separation process for solid-liquid separation of the generated insolubilized product. And
Adding an alkali mixed sludge obtained by adding and mixing an alkali agent to a part of the separated sludge obtained in the solid-liquid separation step as at least a part of the alkali agent added to the oxidized water in the insolubilization step; A method for treating non-biodegradable organic substance-containing water, characterized by:   In Claim 1, the solid content amount of the alkali mixed sludge added to the insolubilization step is 20 to 500 times the amount of the insolubilized product produced by the reaction of the oxidation-treated water and the alkali agent. For treatment of water containing organic substances.   3. The insolubilization step according to claim 1 or 2, wherein the insolubilization step adjusts the oxidation-treated water to pH 3.5 to 4.5 and a neutralization step to adjust the pre-neutralization treatment water to pH 5-12. A method for treating water containing hardly biodegradable organic matter, comprising: In an apparatus that includes a non-biodegradable organic substance and fenton-oxidizes water,
Add hydrogen peroxide and 0.005 to 0.2 mol times the amount of the hydrogen peroxide to the water containing the hardly biodegradable organic substance, and add 1 hour under conditions of pH 2 to 4 Fenton oxidation means for reaction, an insolubilization means for generating an insolubilized product by adding an alkaline agent to the oxidized water obtained by the oxidizing means, and a solid-liquid separation means for solid-liquid separation of the generated insoluble material. And
Alkali mixing means for adding and mixing an alkali agent to a part of the separated sludge obtained by the solid-liquid separation means, and at least a part of the alkali agent for adding the obtained alkali mixed sludge to the oxidized water by the insolubilization means And a means for adding as a non-biodegradable organic substance-containing water treatment apparatus.   In Claim 4, the solid content amount of the alkali mixed sludge added to the insolubilization means is 20 to 500 times the amount of the insolubilized product produced by the reaction of the oxidation-treated water and the alkali agent. Equipment for water containing organic substances.   In Claim 4 or 5, the said insolubilization means is a pre-neutralization tank which adjusts said oxidation treatment water to pH 3.5-4.5, and a neutralization tank which adjusts pre-neutralization treatment water to pH 5-12. An apparatus for treating water containing hardly biodegradable organic substances, comprising:

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