JP3388892B2 - Wastewater treatment method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of treating wastewater containing dyes, dyeing assistants, pigments, nitrogen compounds, etc., which is difficult to decompose in the dyeing industry.

[0002]

2. Description of the Related Art Wastewater containing suspended solids, COD and BOD components is generally discharged after being subjected to coagulation sedimentation treatment, activated sludge treatment, activated carbon adsorption treatment, oxidation treatment, etc.
Of these, if the waste water contains coloring substances or hardly decomposable components such as nitrogen compounds, it cannot be treated by such a single treatment in many cases, and a trace amount of the coloring component remains in the treated water, which may be noticeable. It is not preferable from the above point. In addition, the types of coloring components in colored waste liquids discharged from various industries vary widely depending on the emission source, and even if the same emission source is merged from multiple wastewater routes, there are many types of coloring components. May be mixed,
Particularly, when a coloring component having high chemical stability is contained, it is extremely difficult to treat.

[0003]

The conventional wastewater treatment methods have the following problems. (1) In addition to requiring a large amount of oxidizing agent, it takes a long time to perform the treatment, and especially when a suspended substance or an organic substance coexists, the decolorizing effect is likely to decrease. (2) The oxidizing agents used, such as chlorine gas, bleaching powder, sodium hypochlorite, ozone, etc., are generally expensive, and the treatment cost when used in large amounts alone is considerably high.

(3) Generally, the colored waste water often contains pollutant components other than the coloring component, and in particular, when the dyeing waste water and the waste water from other processes are mixed, it is expected to be treated by a single treatment. Therefore, it was necessary to combine a plurality of processing methods without obtaining the processing effect. That is, in order to achieve a sufficient decolorizing effect while achieving the wastewater standard, it is inevitable that the treatment method becomes very complicated and the treatment cost becomes high.

The present invention is intended to provide a method for treating wastewater which can solve the above problems.

[0006]

In order to solve the above-mentioned problems in the method for treating wastewater, the present invention adjusts the pH of the seawater component-containing liquid to 1 to 5 with mineral acid, electrolytically treats it, and leaves it at rest. 0.5 to 20 v / lower electrolyte for electrolyte
v% amount (volume / volume percentage) was fractionated and neutralized to pH 5 to 9 with an alkaline agent, and the neutralized water was adjusted to 0.
A method is provided in which 1 to 1 volume is mixed and subjected to an oxidation treatment, and the oxidation treatment liquid is adjusted to pH 9 or higher with an alkaline agent to separate an aggregated product.

In the above method of the present invention, the separated lower electrolytic solution is neutralized to pH 5 to 9 with an alkaline agent as it is, and the upper electrolytic solution is extracted and a seawater component-containing solution is newly mixed and then electrolyzed again. After the treatment, it may be similarly subjected to a step of neutralizing with an alkaline agent. in this case,
The effect of improving the oxidizing effect by recovering the amount of chlorine-based oxidizer such as sodium hypochlorite, which has disappeared due to the change with time after electrolysis, and also the lower electrolytic solution is constantly accumulated in the electrolytic cell, and the required amount is taken out in succession. The effect of enabling continuous processing is additionally exerted by supplying to the process. In the above-mentioned method of the present invention, since the pH of the treated water from which the agglomerated product is separated exhibits an alkalinity of 9 or more, a neutralizing agent is appropriately added or mixed with other waste water, and the neutralized water is adjusted to near neutrality for discharge. It will be possible.

An embodiment of the present invention will be described below with reference to the flow sheet of FIG. Waste water 11 discharged from each process in the factory is put into the mixing tank 3. On the other hand, liquid containing seawater component 1
2 into the electrolytic cell 1 and pour mineral acid 13a such as hydrochloric acid into the p
H1 to 5 preferably adjusted to pH 3 or less and subjected to electrolytic treatment to generate a halogen-based oxidant and allowed to stand,
0.5 to 20 v / v% of lower electrolytic solution to this electrolytic solution
Amount, preferably 2-10 v / v%, more preferably 0.
An amount of 5 to 1 v / v% or less is sampled, and the pH of the neutralizing tank 2 is adjusted to 5 to 9, preferably 6 to 8 by the alkaline agent 14a.
Neutralize to. Next, 0.1 to 1 volume of the neutralization liquid is mixed with 1 volume of the waste water 11 stored in the mixing tank 3 to perform oxidation treatment. Further, this oxidation treatment liquid is transferred to the pH adjusting tank 4 or the separating tank 5 and the alkali agent and 14b are added to adjust the pH to 9 or more, preferably 10 to 12. At this time, the alkaline agent 14b does not need to be added in the separation tank 5 when it is added in the pH adjustment tank 4, and the separation tank 5 is bypassed when the oxidation treatment liquid is transferred to the separation tank 5 by bypassing the pH adjustment tank 4. Is added at the stage (in FIG. 1, the case where the pH adjusting tank 4 is bypassed is indicated by a broken line).

Further, during pH adjustment, flocs of magnesium hydroxide are produced, and most of the remaining unreacted components are adsorbed by this precipitate and discharged as sludge 16, and treated water 15
These components are removed from the inside. By adding an organic polymer flocculant during the formation of the flocs, sludge precipitation can be promoted and a further separation effect can be obtained. The treated water whose pH has been adjusted in the separation tank 5 has a high pH exceeding the release standard.
In this case, if necessary, it can be neutralized with the mineral acid 13b, or acidic wastewater discharged from other steps, and then discharged. In this case, hydrochloric acid, sulfuric acid or the like is used as the mineral acid 13b, but when a calcium compound is used during neutralization, a mineral acid such as hydrochloric acid that does not produce a sludge component is preferable.

The seawater component-containing liquid 12 may be natural seawater or artificial seawater obtained by dissolving a commercially available powdery material containing a seawater component in an arbitrary concentration. The material of the electrode used in the electrolytic cell 1 is sufficient to be made of carbon, but it can be appropriately selected and used from other commonly used materials. The voltage during electrolysis is around 10V DC and the current density is 1
It is preferable that the distance between the electrodes is about ^{2 A} / dm ² , and the short distance between the electrodes is about 5 to 10 mm.

[0011]

[Action] In the processing method of waste water according to the present invention, the seawater is 20000 mg / l approximately chloride - reacts as follows: When the electrolyte due to the presence of salts containing ^(Cl).

Embedded image [Anode side] 2Cl ⁻ → Cl ₂ + 2e 4OH ⁻ → O ₂ + 2H ₂ O + 4e [Cathode side] 2H ₂ O + 2e → H ₂ + 2OH ⁻ Na ⁺ + OH ⁻ → NaOH Here, the NaOH generated on the cathode side is , Reacts immediately in an acidic solution as follows to produce Na salt [the following formula is obtained when hydrochloric acid is acidified].

Embedded image NaOH + HCl → NaCl + H ₂ O On the other hand, Cl ₂ generated on the anode side is M coexisting in seawater.
By reacting with gBr ₂ as follows, Br ₂ is released, and upon standing, supersaturated Br ₂ is precipitated.

Embedded image Cl ₂ + MgBr ₂ → MgCl ₂ + Br ₂

That is, in the electrolytic solution obtained by the above operation, Br ₂ is diluted in the upper portion of the electrolytic solution and Br ₂ is concentrated in the lower portion of the electrolytic solution. Therefore, the upper portion of the electrolytic solution is discharged by decantation after standing for a predetermined time. , Or by collecting only the zone below the electrolytic solution, an electrolytic solution rich in Br ₂ can be obtained. When an alkaline agent such as NaOH is added to the thus obtained Br ₂ -rich electrolytic solution and the mixture is neutralized to pH 5 to 9, the reaction proceeds as follows to form a bromine salt, and the chlorine-based oxidizing agent (for example, NaOCl) remaining A part becomes a brominated oxidant (for example, NaOBr).

Embedded image Br ₂ + 2NaOH → 2NaBr + 2OH ^-- NaBr + NaOCl → NaOBr + NaCl

Here, the dissolved chlorine-based oxidizer (NaOC
1) and the bromine-based oxidant (NaOBr) are gradually decomposed to generate atomic oxygen (O), and due to its strong oxidizability, a specific component which is easily oxidized in the waste water is decomposed. Thus, after electrolysis, many components involved in redox are decomposed by adding the seawater component-containing liquid at the time when the activity does not disappear into the wastewater, but the residual components not involved in the reaction are separated by the treatment described below. . That is, an alkaline agent such as sodium hydroxide, sodium carbonate or potassium hydroxide is added to the wastewater containing the seawater component-containing liquid to adjust the pH to 9 or more, preferably 10 to 12. By this pH adjustment, magnesium in the seawater component becomes a hydroxide and aggregates. At that time, the residual substance which is solubilized or colloidally dispersed in the liquid is adsorbed on magnesium hydroxide and removed together with the precipitate. INDUSTRIAL APPLICABILITY The present invention can be applied not only to wastewater containing dyes, dyeing assistants, pigments, nitrogen compounds and the like in the dyeing industry, but also to wastewater such as lignin, caramel and lanolin that is difficult to decompose by biological treatment only, wastewater containing heavy metals and the like.

[0014]

EXAMPLES The present invention will now be described in more detail with reference to examples. Table 1 below shows the composition of seawater used as a raw material for additives used in the oxidation treatment of colored wastewater. In the following Examples 1 to 6, all seawater refers to the seawater. Although this seawater is artificial seawater obtained by dissolving commercially available crystal powder for artificial seawater in pure water, the content of each component is almost equivalent to natural seawater.

[Table 1]

Example 1 As a coloring substance, a reactive dye was dissolved in pure water in the following proportions, heated in a hot bath at 70 ° C. for 30 minutes and then allowed to cool to prepare simulated waste water. Reactive dye 2g / l Sodium carbonate (Na ₂ CO ₃ ) 20g / l Sodium sulphate (Na ₂ SO ₄ ) 50g / l Here, 2 kinds of reactive dyes are used, and 2 kinds of reactive dyes are mixed. Different kinds of simulated wastewater were prepared. Sample (1): Reactive dye [Sumitomo Chemical, trade name: Sumifix Su
pra Red 3BF] Sample (2): Reactive dye [Ciba Chemical, trade name: Cibacron R
ed FB] Colored wastewater in Examples 1 to 6 below refers to the simulated wastewater.

Hydrochloric acid (0.
1N HCl) to adjust the pH to 0.5, 1,
After adjusting to 1.5, 2, 3, 4, 5 and put in an electrolysis device, electrolysis was performed under the conditions of the following Table 2.

[Table 2]

Immediately after electrolysis, the electrolytic solution was gently moved so as not to rock, transferred to a separating funnel, and allowed to stand for 20 minutes.
A lower electrolyte solution (10 v / v%) was collected from the electrolyte solution and neutralized to pH 8.0 with sodium hydroxide (0.1 N NaOH). 10 v / v% was mixed and stirred for 5 minutes for reaction, and this solution was used as an oxidation treatment liquid. Most of the coloring components in the wastewater are decolorized by the treatment, but some coloring components not involved in the redox remain in the treatment liquid. As Comparative Example 1, after electrolyzing seawater in the same manner as above without adjusting the pH, an electrolytic solution taken out from any portion without standing and fractionation was added to each of the colored wastewaters.
v / v% was mixed, and the mixture was stirred for 5 minutes for reaction to obtain an oxidation treatment liquid. Table 3 shows the transmittances of the respective oxidation treatment liquids treated in Example 1 and Comparative Example 1 at a wavelength of 540 nm.

[0018]

[Table 3] (Note) * 1 pH is seawater pH (adjusted with 0.1N HCl)

As a result, it was found that a good decolorizing effect can be obtained in this example as compared with the comparative example 1. In particular, when the electrolysis treatment is performed with seawater at a pH of 3 or less, the effect becomes remarkable. Therefore, when the electrolysis treatment is allowed to stand still, free bromine (Br ₂ ) precipitates in the lower part of the electrolysis treatment liquid to form a rich zone. It is considered that this is because the bromine compound and the hypobromite are produced by neutralizing this, and the oxidative action of the chlorine-based oxidizing agent such as hypochlorite is promoted.

(Example 2) Next, seawater of the above composition was adjusted to pH 2 with hydrochloric acid and electrolyzed under the same conditions as in Example 1, and the lower electrolytic solution after standing for 20 minutes was replaced with the entire electrolytic solution. 0.5,1,2,5,10,20,50 v / v% equivalent amount was separately collected and neutralized, and then 10 v / v% of the neutralization liquid was added to each of the colored wastewaters for 5 minutes. The mixture was stirred to give an oxidation treatment liquid. In Comparative Example 2, the pH of seawater was adjusted to 2 with hydrochloric acid, electrolysis was performed under the same conditions as in Example 1, and after 20 minutes of standing, the electrolytic solution taken out from an arbitrary portion without preparative separation was neutralized,
10 v / v% was added to each of the colored wastewaters, and the mixture was stirred for 5 minutes to prepare an oxidation treatment liquid. Table 4 shows the transmittance of each oxidation treatment liquid treated in Example 2 and Comparative Example 2 at a wavelength of 540 mm.

[0021]

[Table 4] (Note) * 2: Horizontal column shows fractionation ratio of lower electrolyte (v / v%)

As a result, as compared with the comparative example, the influence of the fractionation ratio of the lower electrolytic solution added to the colored wastewater after standing in the present example on the decolorizing effect begins to appear from around 20 v / v%.
A sharp increase around 10v / v% and around 2v / v% or 1v
It was found that the upper limit was almost reached around / v%.

(Examples 3 to 4) A large amount of seawater having the above composition was used in an electrolytic cell having a slightly larger scale than that of Example 1 or 2, and the pH was adjusted to 2 with hydrochloric acid, and the same procedure as in Example 1 was performed. Electrolysis is performed under the conditions, and the lower electrolytic solution after 20 minutes of standing is
After collecting 10 v / v% of the total amount of the electrolytic solution and further neutralizing by electrolyzing again for 10 minutes under the same conditions, 10 v / v% of the neutralizing solution was added to the colored wastewater. The mixture was stirred for 5 minutes to obtain an oxidation treatment liquid. In Example 4, the same operation as in Example 3 was performed to neutralize without re-electrolyzing, and then 10 v / v% was added to each colored wastewater and stirred for 5 minutes to prepare an oxidation treatment liquid. Table 5 shows the transmittance at a wavelength of 540 nm of each oxidation treatment liquid treated in Example 3 and Example 4.

[0024]

[Table 5]

As a result, when the electrolytic treatment was carried out again, there was a further decolorizing effect as compared with the case where the electrolytic treatment was carried out once. It is considered that this is because the amount of chlorine-based oxidizer such as sodium hypochlorite, which has disappeared due to the change with time after electrolysis, is restored to some extent.

Example 5 The pH of seawater having the above composition was adjusted with hydrochloric acid.
2 was electrolyzed under the same conditions as in Example 1, and the lower solution after standing for 20 minutes was treated with 10 v /
An amount corresponding to v% was collected and neutralized, and then 10 v / v% was added to the coloring wastewater and the mixture was stirred for 5 minutes.
H) was added to adjust the pH to 10.5, and the mixture was stirred for 5 minutes. Here, the magnesium compound contained in seawater is precipitated as a hydroxide according to the following formula.

Embedded image Mg ²⁺ +2 (OH ⁻ ) → Mg (OH) ₂ Magnesium bromide contained in seawater also reacts according to the following formula.

Embedded image MgBr ₂ + 2NaOH → Mg (OH) ₂ + 2NaBr

The addition of a necessary amount of the organic polymer coagulant during the coagulation treatment is of great significance in coarsening the coagulated particles and promoting the precipitation. The suspension in which the precipitate was formed as described above was allowed to stand for about 20 minutes, the supernatant was filtered through filter paper (No. 5A), and the pH was adjusted to 8 with hydrochloric acid (0.1N HCl) as a mineral acid.
What was neutralized to be the coagulation treatment liquid. Further, as Comparative Example 3, an oxidation treatment liquid was used, which was subjected to electrolytic treatment by the same operation as in Example 5 above, fractionated, neutralized to pH 5 to 9, and then not subjected to aggregation treatment with an alkaline agent at pH 9 or higher. Example 5
And the wavelength of each oxidation treatment liquid treated according to Comparative Example 3 was 54
Table 6 shows the transmittance at 0 nm.

[0028]

[Table 6]

Example 6 Ammonium chloride as ammoniacal nitrogen was dissolved in pure water in the following proportions to prepare simulated waste water. Sample (1) Ammonium chloride (NH ₄ Cl) 250
g / l Sample (2) Ammonium chloride (NH ₄ Cl) 500
g / l Seawater having the above composition was adjusted to pH 2 with hydrochloric acid and electrolyzed under the same conditions as in Example 1, and the lower electrolytic solution after standing 20 minutes was collected in an amount equivalent to 10 v / v% of the entire electrolytic solution. After neutralization by addition, 5,10,20 v / v% of each simulated waste water was added and stirred for 5 minutes as an oxidation treatment liquid, and the oxidation treatment liquid was adjusted to pH 10.5 with an alkaline agent and allowed to stand for 20 minutes. Then, the supernatant was filtered through a filter paper (No. 5A), neutralized to pH 8, and stirred for 5 minutes to obtain an aggregation treatment liquid.

In Comparative Example 4, seawater was adjusted to pH 2 with hydrochloric acid and electrolysis was carried out under the same conditions as in Example 1, and after 20 minutes of standing, the electrolytic solution taken out from an arbitrary part without preparation was used. After the addition, 5,10,20 v / v% was added to each of the colored wastewaters to prepare an oxidation treatment liquid and an aggregation treatment liquid in the same manner. Table 7 shows the total nitrogen (TN) and ammonia nitrogen (NH ₄ -N) contained in each of the oxidation treatment liquids treated in Example 6 and Comparative Example 4, and the aggregation treatment liquid.

[0031]

[Table 7]

According to the experimental conditions of Example 5, when the electrolytic solution in which the bromine compound was concentrated was added to the waste water, the effect of removing nitrogen compounds such as ammonia nitrogen was dramatically improved, and In contrast, 10 to 20 v / v electrolytic solution
It has been found that the nitrogen compound can be almost completely removed by adding 100%. On the other hand, although the treatment effect of Comparative Example 5 is recognized to some extent, a bromine compound is separately added to the seawater before electrolysis in order to obtain a treatment effect equivalent to that of this example because the bromine compound in natural seawater is low. It is considered necessary to add. It should be noted that when the amounts of nitrogen compounds remaining in the oxidation treatment liquid and the aggregation treatment liquid are compared, there is no great difference, and it is considered that the nitrogen compounds are mainly decomposed during the oxidation treatment.

[0033]

As described above, the following effects can be obtained by using the method for treating wastewater according to the present invention. (1) Due to the synergistic effect of the chlorine-based oxidant and the bromine compound, the coloring components in the wastewater can be strongly oxidatively decomposed to almost completely decolorize, and subsequently the coagulation-precipitation treatment can be combined. Therefore, the remaining coloring component can be adsorbed to ensure the decolorization treatment. (2) Inexpensive and inexhaustibly existing seawater components can be effectively used, and not only an oxidizing agent such as sodium hypochlorite, which is necessary for decomposition of coloring components in wastewater, can be obtained.
Since an expensive bromine compound which can effectively accelerate the decolorization reaction by a synergistic effect with the same oxidizing agent is also obtained, the chemical cost can be remarkably reduced. (3) After the oxidation treatment, magnesium hydroxide is generated only by adjusting the pH and acts as a coagulant, so that it is not necessary to supply an inorganic coagulant from the outside, and the chemical cost can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a wastewater treatment method according to an embodiment of the present invention.

[Explanation of symbols]

1. Electrolyzer 2. Neutralization tank 3. Mixing tank 4. pH adjusting tank 5. Separation tank 6. Treated water tank 11. Wastewater 12. Liquid containing seawater components 13a. 13b. Mineral acid 14a. 14b. Alkaline agent 15. Treated water 16. Sludge

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI C02F 9/00 502 C02F 9/00 502R 504B 504 1/46 101Z (72) Inventor Sadao Sato Kogomatsu, Hyogo-ku, Kobe-shi, Hyogo Inc. 1-16 Shinryo Hi-Tech Co., Ltd. (72) Inventor Masao Akimoto 5-16-16 Komatsu-dori, Koyo-ku, Kobe, Hyogo Pref. (56) Reference Kokai 7-299475 (JP, A) JP-A-7-299474 (JP, A) JP-A-2-290989 (JP, A) JP-A-62-182293 (JP, A) Actual development 3-41851 (JP, U) (JP, A) 58) Fields investigated (Int.Cl. ⁷ , DB name) C02F 1/52-1/56 C02F 1/46 C02F 1/76 C02F 9/00

Claims (6)

(57) [Claims] 1. A seawater component-containing liquid of natural seawater or artificial seawater is adjusted to pH 1 to 5 with a mineral acid, electrolyzed and allowed to stand, and then a lower electrolyte solution of 0.5 to 20 is added to this electrolyte.
An amount of v / v% was fractionated and neutralized to pH 5 to 9 with an alkaline agent, 0.1 to 1 volume of the neutralized water was mixed with 1 volume of waste water, and oxidation treatment was performed. A method for treating wastewater, which comprises adjusting the pH to 9 or more with an alkaline agent and separating a coagulation product. 2. The method for treating wastewater according to claim 1, wherein the seawater component-containing liquid contains a bromine compound and / or a magnesium compound. 3. The method for treating wastewater according to claim 1, wherein the amount of the lower electrolytic solution to be left to stand after the electrolytic treatment is 2 to 10 v / v% of the total amount of the electrolytic solution. 4. A seawater component-containing liquid of natural seawater or artificial seawater is adjusted to pH 1 to 5 with a mineral acid, electrolyzed and allowed to stand, and then 0.5 to 20 v of lower electrolyte is added to this electrolyte.
/ V% amount of the upper electrolyte solution is discharged, the remaining lower electrolyte solution is newly mixed with a seawater component-containing solution, and electrolytically treated again, and then neutralized to pH 5 to 9 with an alkaline agent. A method for treating wastewater, which comprises mixing 0.1 to 1 volume of wastewater to perform an oxidation treatment, further adjusting the pH of the oxidation treatment liquid to 9 or more with an alkaline agent, and separating an aggregated product. 5. A seawater component-containing liquid of natural seawater or artificial seawater is adjusted to pH 1 to 5 with a mineral acid, electrolyzed and allowed to stand, and then a lower electrolyte solution of 0.5 to 20 is added to this electrolyte.
An amount of v / v% was fractionated and neutralized to pH 5 to 9 with an alkaline agent, 0.1 to 1 volume of the neutralized water was mixed with 1 volume of waste water, and oxidation treatment was performed. A method for treating wastewater, which comprises adjusting pH to 10 to 12 with an alkaline agent, and adding an organic polymer coagulant to separate coagulation products. 6. A seawater component-containing liquid of natural seawater or artificial seawater is adjusted to pH 1 to 5 with a mineral acid, electrolyzed and allowed to stand, and then 0.5 to 20 parts of the lower electrolyte is added to this electrolyte.
An amount of v / v% was fractionated and neutralized to pH 5 to 9 with an alkaline agent, 0.1 to 1 volume of the neutralized water was mixed with 1 volume of waste water, and oxidation treatment was performed. A method for treating wastewater, which comprises adjusting pH to 10 to 12 with an alkaline agent, separating a coagulation product, and then performing neutralization treatment.