JPS61197094A - Treatment of waste water - Google Patents

Abstract

PURPOSE:To treat effectively waste water contg. hydrogen peroxide and high- concn. org. matter by using a simple method wherein a flocculation and separation vessel, sludge treating equipment, etc., have been dispensed with. CONSTITUTION:A ferrous salt, 1/70-1/7 of the amt. of COD and Mn to be removed (expressed in terms of ferrous salt), is added to waste water contg. hydrogen peroxide and high-concn. org. matter. The waste water is then regulated at 1.0-3.0pH, oxidized at 5-95 deg.C for 3-8hr, neutralized with an alkali and then treated with activated sludge. By this method, waste water contg. high-concn. org. matter can be treated even by addition of a small amt. of a ferrous salt. Moreover, since the sludge of iron salts is not generated during the treatment, a flocculation and separation vessel, sludge treating equipment, etc., can be dispensed with and the waste water can be effectively treated by the simple method.

Description

[Detailed Description of the Invention] [Industrial Application g′f] The present invention relates to a method for treating wastewater, and more specifically,
By adding a small amount of ferrous salt, il! The present invention relates to a wastewater treatment method that allows wastewater containing S hydrogen oxide and organic matter to be treated through a simple process.

[Prior art and its problems] Conventionally, as a method for treating wastewater containing organic matter, there are, for example, an activated carbon adsorption method, an activated sludge method, and the like.

However, industrial wastewater discharged from synthesis processes that use large amounts of iM hydrogen oxide contains hundreds of ppm of hydrogen peroxide and organic matter, and if such wastewater is treated as activated sludge, The sludge itself becomes oxidized, making effective wastewater treatment impossible. Therefore, in order to treat wastewater containing a large amount of hydrogen peroxide with activated sludge, it is necessary to decompose the hydrogen peroxide in the wastewater, and for this purpose, pretreatment such as addition of a reducing agent or alkali is required. It becomes inevitable. On the other hand, for example 1. The COD concentration of wastewater containing OOOppm or more is high, and it is difficult to directly treat such wastewater with an activated sludge method. This is because the organic compounds contained in the wastewater significantly weaken the activity of microorganisms in the activated sludge. Therefore, in order to treat wastewater containing organic matter with activated sludge, pretreatment is required.

The Fenton oxidation method is known as a pretreatment method, but this oxidation method generally requires the addition of large amounts of hydrogen peroxide and iron salts, and also because iron salts precipitate after the neutralization treatment. 1. Separation and removal operations are required. Therefore,
The wastewater treatment method that uses the Fenton oxidation method as a pretreatment requires the installation of a coagulation separation tank, sludge treatment equipment, etc., making the treatment process large-scale.

This invention was made based on the above circumstances. That is, the purpose of this invention is to reduce the amount of iron salt added,
The objective is to provide a wastewater treatment method that can effectively treat wastewater containing hydrogen peroxide and high concentrations of organic matter through a simple process that does not require the installation of coagulation separation tanks, sludge treatment equipment, etc. It is something to do.

[Means for solving the above-mentioned problems] The outline of the present invention for achieving the above-mentioned object is to add ferrous salt to waste water containing hydrogen peroxide and organic matter,
1/70 to 1/7 of n removal amount (ferrous ion equivalent amount)
Add in the amount of addition, adjust the pH to 1.0 to 3.0,
This wastewater treatment method is characterized by oxidizing the wastewater at a temperature range of ~95°C for 3 to 8 hours, neutralizing it with an alkali, and then treating it with activated sludge.

There are no particular restrictions on the wastewater to which the treatment method of the present invention can be applied, as long as it contains hydrogen peroxide and organic matter; for example, in the rubber industry where rubber is synthesized using a redox catalyst containing hydrogen peroxide.

Examples include wastewater discharged from the pulp industry, where pulp is bleached with hydrogen peroxide, and the organic synthesis industry, where various organic chemicals are synthesized using hydrogen peroxide as an oxidizing agent.

Examples of organic substances contained in wastewater include lower alkyl alcohols such as methanol, ethanol, n-propyl alcohol, and isopropyl alcohol, diols such as glycerin, ethylene glycol, propylene glycol, butanediol, and butynediol, and other triols. alcohols such as tetraols and polyols; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and isophorone; aldehydes such as formaldehyde, acetaldehyde, and acrolein; formic acid, acetic acid, and propionic acid.

Examples include carboxylic acids such as maleic acid and acrylic acid 5, ethols such as methyl ether, ethyl ether, methyl cellosolve, ethyl cellosolve, and isopropyl cellulose, and cellulose. The treatment method of the present invention can suitably treat wastewater containing the hydrogen peroxide and the various organic substances.

In the method of the present invention, it is believed that when ferrous salts are added to the wastewater, the Fenton oxidation reaction proceeds between hydrogen peroxide and ferrous salts in the wastewater, and the generated OH radicals oxidize the organic matter in the wastewater. It will be done.

As the ferrous salt, ferrous sulfate or ferrous chloride is used. The amount of ferrous salt added is 1/7 of the amount of COD Mn removed.
0 to 1/7 (ferrous ion equivalent), preferably 1/65 to 1/20, and usually 1100 pp or less. The amount of ferrous salt added is 1/7 of the amount of COD Mn removed.
Exceeding this is effective in reducing CO, but increases the cost of wastewater treatment, generates sludge containing iron hydroxide, requires equipment to remove this sludge, and complicates operation. It will be a huge process.

In this invention, a ferrous salt is added to the wastewater in the amount described above, the pH of the wastewater after addition is adjusted to 1.0 to 3.0, preferably about 1.5, and the temperature is adjusted to 5 to 95°C. , preferably 40~
It is important to carry out the oxidation treatment at 70°C for 3 to 8 hours.

When the pH of the wastewater is higher than 3.0, the decomposition of hydrogen peroxide in the wastewater becomes too fast, and the generated OH radicals do not contribute to the oxidation of organic matter in the wastewater. If it is also small, hydrogen peroxide becomes stable and OH radicals are less likely to be generated.

The pH can be adjusted by adding an acid such as sulfuric acid or hydrochloric acid. These acids may be added, for example, before or after the ferrous salt is added.

Moreover, if the temperature during the oxidation treatment is lower than 5°C.

Iron salts precipitate during the neutralization process after oxidation treatment, making it impossible to avoid the generation of sludge. Also, if the temperature is higher than 95°C, hydrogen peroxide decomposes too quickly, resulting in OH radicals being generated in the wastewater. will no longer contribute to the oxidation of organic matter.

The oxidation treatment of the wastewater can be carried out by adding the hydrogen peroxide and ferrous salt, adjusting the pH to the range described above, and then stirring the wastewater at the temperature range for the period described above.

After the oxidation treatment, alkali is added to neutralize it.

Examples of the alkali include one or a mixture of two or more selected from sodium hydroxide, potassium hydroxide, and slaked lime.

The amount of alkali added is determined when the pH of the liquid after oxidation treatment is 7.0~
8.0. Preferably, it is determined to be 7.5 to 8.5.

Since the amount of ferrous salt added to the solution after neutralization is small and the ferrous salt and the organic matter in the wastewater form a complex salt, there is no sludge of iron salts and the solution is not in a solution state. It has become.

The solution after the neutralization treatment is subjected to activated sludge treatment. As this activated sludge, for example, sludge containing organic matter can be used, and the composition of the sludge, its proportion, etc. can be appropriately determined as necessary.

Next, an example of the method of the present invention will be explained with reference to the drawings.

The waste water is introduced into mixing tank l. After adding acid to this mixing tank 1 to adjust the pH of the waste water to 1.0 to 3.0, ferrous salt is supplied and mixed. The wastewater containing hydrogen peroxide, organic substances, ferrous salts, and acids is transferred from the mixing tank 1 to the oxidation tank 2, where it is oxidized at a temperature in the range of 5 to 95°C for 3 to 8 hours with stirring. The solution after the oxidation treatment is transferred to the neutralization tank 3, and an alkali is added to the neutralization tank 3 while stirring to bring the pH to 7.0.
Adjust to ~9.0. The pH-adjusted solution is transferred to the activated sludge device 4 and subjected to biological treatment.

Through this kind of wastewater treatment, CO in wastewater containing organic matter is reduced.
The D concentration can be reduced from about 3,500 to 1,000 ppm.

Although the wastewater treatment method shown in FIG. 1 uses a continuous device, it goes without saying that a batch-type device can also be used.

[Effects of the Invention] According to the present invention, even if the amount of ferrous salt added is small, wastewater containing organic matter and having a high COD concentration can be treated. Moreover, since iron salt sludge is not generated during treatment, there is no need to install a coagulation separation tank, sludge treatment equipment, etc., and wastewater can be effectively treated with a simple process.

[Example] Next, examples and comparative examples of the present invention will be shown.

(Example 1) Using the continuous wastewater treatment equipment shown in Figure 1, industrial wastewater containing high concentrations of hydrogen peroxide and organic matter [hydrogen peroxide 3,200 ppm, CODMn concentration (excluding hydrogen peroxide)] 1) 3,500ppm, COD Mn concentration is JIS
[measured according to KO102] was introduced into a mixing tank, and ferrous sulfate 100 p p
m (ferrous ion equivalent amount) and 98% sulfuric acid to adjust the pH! . Adjusted to 5. The adjusted liquid was transferred to an oxidation tank and subjected to fermentation treatment for 4 hours while being heated to 60°C. The liquid after the oxidation treatment was transferred to a neutralization tank, and the pH was adjusted to 8.5 by adding sodium chloride. After the neutralization treatment, the COD Mn concentration in the wastewater was 950 ppm, and the hydrogen peroxide concentration was reduced to 10 ppm. Further, the wastewater after this neutralization treatment did not contain any sludge and was homogeneous because iron formed an organic complex salt.

The wastewater after the neutralization was transferred to an activated sludge treatment device and subjected to activated sludge treatment. When the flow rate of the liquid after medium treatment was 10 t/H, the load in activated sludge treatment was 228 Kg/D.

As a precaution, the wastewater treatment conditions and treatment results are shown in Table 1.

(Example 2) Using the continuous wastewater treatment equipment shown in Figure 1.

Industrial wastewater containing high concentrations of hydrogen peroxide and organic matter [
Hydrogen peroxide 3,000 ppm, CODMn concentration (excluding hydrogen peroxide) 3,000 ppm.

COD Mn concentration was measured according to JIS KO102], the pH was adjusted to 2.0 by adding 98% sulfuric acid, and the oxidation treatment was performed while heating to 50°C. It was carried out in The results are shown in Table 1.

(Comparative Example 1) The same wastewater as in Example was introduced into the first tank, and the pH was adjusted to 8.5 by adding sodium hydroxide to this first tank.Then, this wastewater with a pH of 8.5 was introduced into the first tank. was transferred to a second tank, and 105 kg/h of sodium sulfite was added to decompose hydrogen peroxide in the waste water. Furthermore, the liquid after decomposition was transferred to a third tank, water was added at 30 t/h to dilute the liquid, and the liquid was then transferred to an activated sludge treatment apparatus for activated sludge treatment. The load in activated sludge treatment was 840 K g-COD/It. As a precaution, the wastewater treatment conditions and treatment results are shown in Table 1.

In this wastewater treatment operation, the liquid after decomposition with hydrogen peroxide is
Sludge was generated.

(Hereafter, margin) Table 1

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of an apparatus for carrying out the method of the present invention. 1.φ mixing tank, 2. oxidation tank, 3. Neutralization tank, 4 buildings
・Activated sludge equipment.

Claims (1)

[Claims] (1) Add ferrous salt to waste water containing hydrogen peroxide and organic matter in an amount of 1/70 to 1/7 of the amount of CODMn removed (ferrous ion equivalent amount), and adjust the pH to 1.0 to 1/7 (ferrous ion equivalent amount). 3.0, oxidize for 3 to 8 hours at a temperature of 5 to 95°C, neutralize with alkali, and then treat with activated sludge.