JPH091162A - High degree treating method for waste water and catalyst for oxidation treatment of waste water - Google Patents

Abstract

PURPOSE: To provide a high degree treating method capable of attaining a high treating effect at low cost with a small chemical consumption even if a COD concn. in waste water is remarkably high and to provide a catalyst for an oxidative decomposition by using an oxidizing agent. CONSTITUTION: In this high degree treating method of waste water in which an org. sludge component in waste water is decomposed oxidatively with the oxidizing agent by using a metal ion as the catalyst, an aluminum based compd. is added to a treating system at the time of the oxidative decomposition and the catalyst is incorporated with an iron compd. and the aluminum based compd..

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for advanced treatment of wastewater and a catalyst used in the oxidation treatment of wastewater, and more specifically to a advanced treatment of wastewater by a chemical oxidation method which can significantly reduce the amount of chemicals used and has an excellent treatment capacity. The present invention relates to a method and a catalyst used in the oxidation treatment of waste water.

[0002]

2. Description of the Related Art Conventionally, in the removal of organic pollutants in wastewater indicated by BOD, various biological treatment methods which have been put into practical use have achieved satisfactory results at a relatively low cost. . On the other hand, in order to remove organic pollutants existing as CODs (bio-degradable substances, bio-metabolized waste substances, etc.), activated carbon adsorption method, ozone oxidation method, reverse osmosis method, chemical oxidation using an oxidizing agent such as hydrogen peroxide Methods and physicochemical methods using various flocculants have been utilized. Among these physicochemical removal methods, hydrogen peroxide and first
The chemical oxidation method using an iron salt has an extremely strong treatment capacity, is effective as a method for decomposing and removing a wide range of COD components in wastewater, and is partially put into practical use (PPM-1986 / 10 3
(See ~ 16P).

[0003]

However, even in the above-described chemical oxidation method using hydrogen peroxide, a large amount of hydrogen peroxide, iron salts and other chemicals used are treated in organic wastewater having a relatively high concentration. Various problems remain in terms of cost. For example, in this chemical oxidation method, COD in wastewater
When hydrogen peroxide is added to the presence of an iron ion catalyst for oxidative decomposition, the following reaction is carried out. Fe ²⁺ + H ₂ O ₂ → Fe ³⁺ + HO ⁻ + HO. In this reaction, approximately equivalent mole of ferrous ion is required for 1 mole of hydrogen peroxide.

As the ferrous iron salt, ferrous sulfate heptahydrate (FeSO ₄ .7H ₂ O) is usually used, and therefore, for example, about 350 to 400 parts by weight per 100 parts by weight of 35% hydrogen peroxide aqueous solution is used. It becomes the ratio of part usage. This ferrous salt is relatively inexpensive, but the produced ferric salt is later coagulated and precipitated by neutralization with an alkali. Therefore, the amount of alkali such as caustic soda used and the use of a polymer coagulant are used. There is a drawback that the amount becomes large and the amount of sludge containing ferric hydroxide as a main component also becomes large, the treatment cost becomes large, and the total treatment cost becomes remarkably large.

Further, in the method using a coagulant, the COD of waste water can be reduced by using a large amount of the coagulant, but it is difficult to lower the COD below the treatment limit value, and a sludge treatment problem is caused. However, there is a problem similar to the above that the total processing cost becomes extremely large.

The cost problem described above is due to COD in wastewater.
The relatively low concentration of CO2 can be avoided to some extent by the method previously developed by the inventors, the A-Hipo® method, which causes a significant amount of COD to be agglomerated and precipitated before the oxidation treatment. Can be, but COD in the wastewater
The concentration is high, and a large amount of CO is generated even by the coagulation and precipitation in advance.
If D remains in the wastewater, the cost problem still remains and it is economically difficult to use.

The amount of hydrogen peroxide added is usually 0.01 to 2 times the COD amount in the waste water in terms of effective oxygen, but the COD concentration in the waste water is reduced to 50 to 60%. In many cases, even if hydrogen peroxide is added to further reduce COD, it is difficult to further reduce COD.
On the contrary, the residual hydrogen peroxide is apparent COD when measuring the COD concentration.
Is detected as the value of. For this reason, it is necessary to further add ferrous ions to remove residual hydrogen peroxide, and furthermore, there is a problem that the cost of chemicals such as the alkali and the polymer flocculant and the cost of sludge treatment increase.

Therefore, it is an object of the present invention to provide an advanced wastewater treatment method which can achieve a high treatment effect at a low cost with a small amount of chemicals even if the COD concentration in the wastewater is extremely high. . Another object of the present invention is to provide a catalyst for oxidation treatment which enhances the efficiency of the wastewater oxidation treatment by the oxidizing agent.

[0009]

As a result of various studies to achieve the above object, the inventors of the present invention have found that in a chemical oxidation method for wastewater using an oxidizing agent, by adding a specific compound during the oxidation treatment, a remarkably small amount is added. The present invention has been completed by finding that an excellent treatment effect can be obtained depending on the amount of the metal ion used. That is, the present invention is an advanced treatment method for wastewater in which organic pollutant components in wastewater are oxidatively decomposed with an oxidant using metal ions as catalysts, in the wastewater characterized by adding an aluminum compound to the treatment system during oxidative decomposition. A catalyst for oxidation treatment of waste water, which comprises an advanced treatment method and an iron compound and an aluminum compound.

[0010]

According to the research conducted by the present inventors, in the chemical oxidation method using hydrogen peroxide and iron salt, by using an aluminum compound during the oxidation treatment, the decomposition and removal rate of COD can be achieved with the use of significantly less metal ions. It was confirmed that the aluminum compound also acts as a catalyst in the chemical oxidation method. It was also found that the metal and aluminum hydroxides deposited by the neutralization with alkali after the oxidation treatment easily aggregated and precipitated.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in more detail with reference to preferred embodiments. The wastewater to which the method of the present invention can be preferably applied includes human waste biological treatment water containing COD and chromaticity components, landfill leachate wastewater, waste incineration wastewater, fermentation and brewing wastewater, high-concentration organic wastewater, petroleum oil. , Coal chemical industry wastewater, dyeing wastewater, plating, surface treatment wastewater, soluble oil / fat wastewater, coating wastewater, and other wastewater containing organic substances such as COD, biodifficult-to-biodegradable substances and biometabolized waste substances. It can be applied to any conventionally known organic wastewater.
In particular, the wastewater in which the effect of the present invention remarkably appears is high in COD and chromaticity components, for example, COD of about 100 mg /
Wastewater with a concentration of 1 or more.

The oxidizing agent used in the present invention is an oxidizing agent used in a conventionally known chemical oxidation method, for example, hydrogen peroxide, calcium peroxide, ammonium persulfate, alkyl hydroperoxide, peracid ester, dialkyl peroxide. Alternatively, diacyl or the like is used, but hydrogen peroxide is most preferable in terms of cost and by-products. Hereinafter, hydrogen peroxide will be described as a representative example. The amount of hydrogen peroxide used is not particularly limited and varies depending on the content of the applied wastewater, but a preferable amount of hydrogen peroxide is about 1 to 200 mg / l (O, based on 100 mg / l of COD, hereinafter referred to as as O). ) Is the range.

The metal ions used in the present invention include iron, titanium, cerium, copper, manganese, cobalt,
Ions of vanadium, chromium, lead, and the like are used, and any of these metals, metal oxides, metal salts, complexes, and the like may be used. A particularly preferable metal ion in the present invention is iron ion, and therefore iron ion will be described below as a representative example.
As the iron ion to be used, ferrous ion was used in the prior art, but not only ferrous ion but also ferric ion is effective in the present invention, and further, metallic iron such as iron scraps and iron Fixed iron ions in which ions are fixed with an ion exchange resin or the like can also be used.

An important feature of the present invention is that by using an aluminum compound at the same time as iron ions during the oxidation treatment, the use amount of hydrogen peroxide and iron ions as a catalyst can be remarkably small as compared with the prior art. It is possible to obtain various effects, and the use ratio of hydrogen peroxide and ferrous ion to be used is the same as that of the conventional technique, but it is a point that a treatment effect more than conventional can be obtained with a small amount of these used. .

In the method of the present invention, the wastewater as described above is used by adding an aluminum compound to the treatment system when the organic pollutant components in the wastewater are oxidized and decomposed using the hydrogen peroxide and iron ions. Since the amounts of hydrogen peroxide and iron ions can be significantly reduced, the aluminum-based compound acts as a catalyst for oxidative decomposition together with iron ions. Further, the aluminum-based compound also has an effect of improving the cohesiveness of iron ions and hydroxides generated from aluminum ions precipitated by the alkali neutralization after the oxidation treatment and reducing the turbidity of the treated water. .

Examples of the aluminum-based compound used in the present invention include aluminum salts such as aluminum chloride and aluminum nitrate, aluminum alum, and all conventionally used aluminum-based coagulants such as aluminum sulfate and sulfuric acid band. Sodium aluminate, polyaluminum chloride, etc. can be used. The amount of aluminum compound used is 1/3 of the weight of metal ions used as a catalyst for oxidative decomposition of aluminum (as Al).
An amount of 0 or more is preferable. When the amount is less than 1/30, the COD of wastewater is treated as a treatment limit value (for example, in the wastewater of the embodiment, COD
It is difficult to reduce the removal rate to 80% or less. However, if the amount of aluminum compound used exceeds twice the weight of metal ions as aluminum, the COD will increase even if used more than that.
Is not reduced, and the amount of hydrogen peroxide or metal ions used cannot be further reduced, which is not preferable.

As described above, since the metal compound (ion) and the aluminum compound (ion) are present at the same time during the oxidation treatment of waste water, the efficiency of the oxidation treatment is improved, and the aluminum compound also acts as a catalyst for the oxidation reaction. To do. The catalytic effect is remarkable, and it is particularly preferable to use an aluminum compound and iron compound in combination. Iron compounds (as Fe) and aluminum compounds (as A
When l) is used as a catalyst for wastewater oxidation treatment,
A mixed aqueous solution of both compounds may be added to the oxidation treatment system (oxidation reaction tank), or an aluminum compound may be added to the treatment system to which the iron compound has been added as described above. Iron compound (as
The use ratio of Fe) and the aluminum compound (as Al) is the same as the above, and the aluminum compound (as Al) is used at a ratio of 1/30 (weight) or more of the iron compound (as Fe). It is preferable. When the proportion of aluminum compound used exceeds twice the weight of iron as aluminum, no further improvement in treatment efficiency can be seen, and it is not uneconomical, but for treating sludge mainly composed of aluminum hydroxide. Expensive and unfavorable.

The wastewater treatment method of the present invention will be described with reference to FIG. 1 showing the flow of treatment. The wastewater to be treated is guided to an oxidation tank, where the amount of iron ion catalyst 1, hydrogen peroxide 2 and aluminum-based compound 4 in an amount corresponding to the COD concentration in the wastewater to be treated, and if necessary, the pH of the wastewater is adjusted to about 2. Mineral acid 3 such as sulfuric acid is added and mixed to adjust to 4 to 4. When an aluminum compound is added during the oxidation treatment, the same treatment effect can be obtained even if the amount of hydrogen peroxide used is reduced to about 1/5 and the amount of iron ion is reduced to about 1/5 as compared with the case where it is not added. Is obtained.

By carrying out oxidative decomposition while stirring in this oxidizing tank, the organic pollutant components in the waste water are oxidatively decomposed to complete the reaction. In the present invention, the temperature during the oxidation treatment is not particularly limited, but it is preferable that the temperature of the waste water is high because the oxidation efficiency can be increased. The reaction time is about 0.01 to 5 hours at room temperature.

When the treated water subjected to the oxidation treatment is neutralized with an alkali 5 such as caustic soda in a neutralization tank to adjust the pH to about 4 or more, iron ions (mainly ferric ion) as a catalyst and The aluminum-based compound added during the oxidation treatment precipitates in the form of flocs. This is introduced into a coagulation tank, and, for example, a polymer coagulant 6 is added to cause precipitation in the precipitation tank. Since the used aluminum-based compound also acts as a coagulant, the above-mentioned precipitate can be precipitated by using a remarkably small amount of the polymer coagulant. The precipitate is collected as sludge from the bottom of the tank. Since this sludge contains ferric hydroxide and aluminum hydroxide as main components, by dissolving this in acid, the ferric hydroxide and aluminum hydroxide can be reused as the iron ion catalyst and aluminum compound. It is possible. The supernatant is discharged as treated water or passed to another treatment system, eg biological treatment.

If the wastewater to be treated contains a large amount of organic pollutant components which can be separated by a coagulant such as a polymer coagulant, a pretreatment step should be provided before carrying out the method of the present invention. By removing a part of the organic pollutant components and then subjecting to an oxidation treatment, the amount of the chemical agent used in the present invention can be further saved.

In the wastewater treatment method of the present invention, the batch process and the oxidation tank are continuous reaction towers (or reaction tubes),
The catalyst carrier supporting the iron ion catalyst is fixed or flowed in the reaction tower, and if necessary, a predetermined amount of hydrogen peroxide, an aluminum compound and a mineral acid are continuously added to the wastewater heated by a heat exchanger or another heat source. It is possible to use a continuous process in which the compound is sent to the reaction tower while being injected, and then oxidized.

[0023]

Next, the present invention will be described more specifically with reference to examples and comparative examples. Example 1 Hydrogen peroxide 20 mg / l (as O) and ferrous salt (3 from Ferrocut FI: FeCl ₂ manufactured by Environmental Engineering Co., Ltd.)
0 wt% aqueous solution) 100 mg / l (as Fe) was used, and a sulfuric acid band (Al ₂ O ₃ content 8 wt%) was added in a variable amount,
2 of waste water with the composition shown in Table 1 below adjusted to pH 3 with dilute sulfuric acid
It was oxidatively decomposed at 5 ° C for 15 minutes. There was no turbidity in the treated water after neutralization, and the iron hydroxide agglomerated state was good. 1/5 or less of the amount of hydrogen peroxide and 1 of the amount of ferrous salt in Comparative Example 2 described below.
It was possible to make the COD below the treatment limit value (COD removal rate 80%) by using / 4 and a sulfuric acid band of 500 mg / l. The relationship between the COD and BOD of the treated water and the amounts of hydrogen peroxide, ferrous salt and sulfuric acid band added is shown in FIG.

[0024]

[Table 1] Soluble concentration is shown in parentheses.

Comparative Example 1 The effluent whose pH was adjusted to 7 with dilute sulfuric acid was subjected to coagulation treatment at 25 ° C. for 15 minutes while varying the sulfuric acid band. 2 sulfuric acid bands
Even if 000 mg / l or more is used, COD has a treatment limit value (C
The OD removal rate could not be reduced below 80%). The relationship between the COD and BOD of the treated water and the addition amount of the sulfuric acid band is shown in FIG.

Comparative Example 2 The amount of hydrogen peroxide (mg / l as O) and the amount of the ferrous salt used which was four times the amount of hydrogen peroxide were varied, and the pH of the waste water adjusted to 3 with diluted sulfuric acid was adjusted to 25. It was oxidatively decomposed at 15 ° C. for 15 minutes. Hydrogen peroxide 100 mg / l (as O) and ferrous salt 400 mg
The COD can be lowered to the treatment limit value (COD removal rate of 80%) by using / l (as Fe) or more. FIG. 4 shows the relationship between the COD and BOD of the treated water and the addition amounts of hydrogen peroxide and ferrous salt.

Examples 2 and 3, Comparative Examples 3 and 4 Using secondary treated water from a paper mill having a BOD of 18 mg / l and a COD of 95 mg / l, the pH was adjusted to 3 with dilute sulfuric acid, and at 25 ° C. Oxidative decomposition was performed for 15 minutes. The chemicals used and the amounts used are shown in Table 2. The same compound as in Example 1 was used as the ferrous salt. The results are also shown in Table 2.

[0028]

[Table 2] (*) Ferrous salt and hydrogen peroxide are not used.

Even if the concentration of organic pollutants is comparatively low, it is necessary to reduce the load of organic pollution even if the removal rate is low, as in the case of secondary treated water such as wastewater from paper mills where the amount of wastewater is enormous. If this is not the case, it will be necessary to reprocess some of the remaining BOD and COD components to achieve the process goal. However, in the conventional chemical oxidation method, when the amount of iron ion catalyst used is small, hydrogen peroxide may be consumed before being used for the original oxidative decomposition reaction, or aggregation failure may occur in the catalyst recovery step. . In the method of the present invention, not only the treatment effect is remarkably improved as shown in Table 2, but
The stable aggregation of hydroxides such as iron enabled easy and stable catalyst recovery.

Example 4 Dyeing plant wastewater (COD 88 mg / l, chromaticity 180 °)
Hydrogen peroxide (35% by weight aqueous solution) as an oxidant,
Mixed aqueous solution of ferrous chloride and aluminum sulfate as a catalyst (Fe content: 4% by weight, Al content: 1% by weight)
Was used to perform oxidation treatment using hydrogen peroxide and a catalyst in the proportions shown in Table 3. The oxidation reaction was carried out by adding hydrogen peroxide and a catalyst to the waste water, adjusting the pH to 3 with dilute sulfuric acid, and at 25 ° C. for 10 minutes. After adjusting the pH to 8 with a caustic soda solution, After filtering through 5A filter paper, the COD and chromaticity of the filtrate were measured. Table 3 shows the results. The COD was measured according to the sewage test method, and the chromaticity was measured according to the clean water test method. The same applies to the following examples.

Example 5 A mixed aqueous solution of ferrous chloride and polyaluminum chloride as a catalyst (Fe content: 4.5% by weight, Al content: 0.5)
The above waste water was oxidized in the same manner as in Example 4 except that (% by weight) was used. Table 3 shows the results.

Comparative Example 5 Ferrous chloride aqueous solution (Fe content: 5% by weight) as a catalyst
The wastewater was oxidized in the same manner as in Example 4 except that the above was used. Table 3 shows the results.

Comparative Example 6 Aluminum sulfate aqueous solution (Al content: 5% by weight) as a catalyst
The wastewater was oxidized in the same manner as in Example 4 except that the above was used. Table 3 shows the results.

[0034]

[Table 3]

[0035]

As described above, according to the present invention, high concentration C
In a chemical oxidation method for wastewater containing OD, treatment is carried out by adding an aluminum compound to the reaction system during the oxidation reaction, thereby reducing the amount of hydrogen peroxide, metal, especially iron catalyst and polymer flocculant used. Not only is efficiency improved, but significant processing cost savings are possible. Furthermore, after the treatment, the metal such as iron and the hydroxide of aluminum produced by the neutralization with alkali easily aggregate and precipitate, so that clear treated water without coloring can be obtained. Further, the amount of the polymer flocculant used for flocculating and precipitating the hydroxide can be very small. Therefore, it is possible to significantly reduce the processing cost,
It is possible to carry out the chemical oxidation treatment method industrially at a sufficient cost.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a wastewater treatment process of the present invention.

FIG. 2 is a diagram showing a result of wastewater treatment of Example 1. The dotted line indicates the level of the COD processing limit (COD removal rate 80%). The same applies to the following figures.

FIG. 3 is a diagram showing a result of wastewater treatment of Comparative Example 1.

FIG. 4 is a diagram showing a result of wastewater treatment of Comparative Example 2.

[Explanation of symbols]

 1: Metal Ion Catalyst 2: Hydrogen Peroxide (Oxidizer) 3: Mineral Acid 4: Aluminum Compound 5: Alkaline 6: Polymer Coagulant

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location C02F 1/52 C02F 1/52 Z (72) Inventor Ichiro Yamamoto 2-5 Higashikanda, Chiyoda-ku, Tokyo −12 Environmental Engineering Co., Ltd.

Claims (6)

[Claims] 1. A high-grade treatment method for wastewater, comprising the step of oxidatively decomposing organic pollutant components in the wastewater with an oxidizing agent using a metal ion as a catalyst, wherein an aluminum compound is added to the treatment system during oxidative decomposition. Processing method. 2. The advanced treatment method for wastewater according to claim 1, wherein the amount of the aluminum compound used is 1/30 or more of the weight of metal ions as aluminum. 3. The oxidizing agent is hydrogen peroxide, and the added concentration of hydrogen peroxide (as oxygen atoms) is 100 COD concentration.
The advanced treatment method for wastewater according to claim 1, wherein the range is 1 to 200 mg / l per mg / l. 4. The metal ions are ferrous ions and / or ferric ions, and the concentration of these iron ions (as Fe) is from 50 to 100 mg / l hydrogen peroxide (as O).
The advanced treatment method for wastewater according to claim 1, wherein the range is 800 mg / l. 5. A catalyst for oxidation treatment of waste water, comprising an iron compound and an aluminum compound. 6. The catalyst for oxidation treatment of waste water according to claim 5, wherein the amount of the aluminum compound (as Al) used is 1/30 or more of the weight of the iron compound (as Fe).