JP2001113291A - Apparatus for treating organic matter-containing water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably and efficiently decompose and remove organic matter by ozone without being affected by the quality of water to be treated. SOLUTION: Organic matter-containing water the pH of which is adjusted to 4-6 is subjected to degassing treatment in a degassing treatment apparatus 1 before subjected to ozone oxidizing decomposition treatment in a reaction tower. Ozone treatment efficiency is enhanced and stabilized by preliminarily removing a carbonic acid component obstructing ozone oxidation or dissolved gas exerting effect on ozone dissolving quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic substance-containing water treatment apparatus for efficiently decomposing and removing organic substances in organic substance-containing water with ozone.

[0002]

2. Description of the Related Art Conventionally, as a method for removing organic substances in water containing organic substances, a method of oxidizing and decomposing organic substances with ozone has been known. When such organic substances are decomposed by ozone, hydrogen peroxide (H ₂ It is also known that by using O ₂ ) addition, catalyst filling, ultraviolet (UV) irradiation or pH adjustment by alkali addition, the oxidizing action of ozone is improved to promote decomposition.

[0003]

In the oxidative decomposition of organic substances by ozone, the decomposition efficiency of organic substances can be increased by adding H ₂ O ₂ , filling the catalyst, irradiating UV or adding alkali as described above. Depending on the quality of the water to be treated, organic substances may not be sufficiently removed,
In some cases, the amount of the supplied ozone dissolved in the water to be treated was not stable, and organic substances remained in the treated water.

[0004] For these reasons, there is a demand for the development of a technology that can always obtain a stable treatment effect without being affected by the quality of the water to be treated.

The present invention solves the above-mentioned conventional problems and provides an organic matter-containing water treatment apparatus capable of decomposing and removing organic matter stably and efficiently without being affected by the quality of the water to be treated. With the goal.

[0006]

According to the present invention, there is provided a treatment apparatus for treating organic-containing water, which adjusts the pH of the organic-containing water to 4 to 6.
H adjusting means, a degassing device for separating a dissolved gas from water whose pH has been adjusted by the pH adjusting means under reduced pressure, and supplying ozone to the water degassed by the degassing device to ozone decompose organic substances. And an organic matter decomposer.

The present inventor has studied the quality of the water to be treated when the organic substances cannot be sufficiently removed by the conventional ozone treatment. As a result, the following two points impair the ozone utilization efficiency in the ozone treatment. I learned. When the treated water contains carbonate ions or bicarbonate ions. That is, in ozone oxidation, hydroxyl radicals (.OH) are generated, and these radicals act on decomposition of organic substances. However, when carbonate ions or bicarbonate ions are present in the water to be treated, these radicals consume hydroxy radicals, Inhibits the decomposition of organic matter. When the treated water contains dissolved gas. That is,
The amount of supplied ozone dissolved in the water to be treated fluctuates according to the amount of dissolved gas in the water to be treated, so that a sufficient amount of dissolved ozone cannot be obtained, and the ozone treatment cannot be performed stably.

In the present invention, prior to the ozone treatment, the water to be treated is adjusted to a pH of 6 or less, and the dissolved gas in the water is separated and removed by a reduced pressure treatment or the like. By adjusting the pH of the water to be treated to 6 or less, the carbonate ions and bicarbonate ions in the water become carbon dioxide. By degassing, the carbon dioxide component in the form of carbon dioxide and other dissolved gases are removed from the water to be treated. Can be removed efficiently.

Therefore, in the organic matter-containing water treatment apparatus of the present invention, the water to be subjected to the ozone treatment has been subjected to removal of the carbonate ions and the bicarbonate ions in advance, so that the hydroxyl radicals generated during the ozone treatment are not included in the water. It is not consumed and can contribute to the oxidation of organic matter without being affected by water quality. Further, since other dissolved gases are also removed, when ozone is supplied, the supplied ozone is easily dissolved in water, and a desired amount of ozone can be dissolved. Therefore, the amount of dissolved ozone does not fluctuate due to the amount of dissolved gas, the amount of dissolved ozone can be stabilized, and the ozone treatment can be stably performed.

As described above, in the treatment apparatus for water containing organic matter according to the present invention, prior to ozone treatment, the use of ozone to remove carbonic acid components and dissolved gas in the water to be treated, which is a factor inhibiting the efficiency of use of ozone, is performed. Efficiency can be increased to perform stable and efficient ozone treatment.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a system diagram showing an embodiment of the apparatus for treating organic matter-containing water of the present invention.

In the apparatus for treating organic matter-containing water of the present invention, the organic matter-containing water as the water to be treated is not particularly limited, and any water that requires removal of organic substances can be used as the water to be treated. For example, when processing water with relatively low organic matter content such as city water, industrial water, well water, and process wastewater to perform process water, pure water, and ultrapure water, or factory wastewater, sewage The present invention can be suitably applied to various organic substance treatments, for example, when performing sewage treatment for treating water having a relatively high organic substance content.

The temperature of the water to be treated is not particularly limited, and may be in the range of room temperature to 70 ° C.

In the present invention, the pH is adjusted to pH 4 to 6, preferably pH 4.5 to 6, by adding an acid to such organic substance-containing water (water to be treated) as necessary. By setting the pH of the water to be treated to 6 or less, it is possible to form carbon dioxide and bicarbonate ions in the water in a form of carbon dioxide that can be removed by a degassing device at the subsequent stage, as described above. In addition, even if this adjusted pH is less than 4,
No improvement in degassing efficiency can be expected, and a large amount of acid for pH adjustment is required, and the oxidation reaction in the subsequent ozone treatment is impaired, which requires pH adjustment and equipment corrosion. This adjusted pH is set to 4 or more in order to cause or the like. The acid used for this pH adjustment is not particularly limited, and hydrochloric acid (HCl), sulfuric acid (H ₂ SO
Any one of ₄ ) and the like can be used.

In the apparatus for treating organic matter-containing water shown in FIG. 1, the pH is adjusted by adding an acid. However, in the present invention, the pH adjusting means is not limited to the addition of an acid, but may be an H-type cation exchange resin tower. The water may be passed through the water to be treated.

The water to be treated, whose pH has been adjusted to pH 4 to 6, is then degassed under reduced pressure by a degassing device such as a membrane degassing device 1 so that the carbonic acid component in the form of carbon dioxide is formed. , Remove other dissolved gases.

In the present invention, as the degassing device, any device can be used as long as the gas phase side is in a reduced pressure state. In addition to a film degassing device, a vacuum degassing device or the like can be used. In the vacuum deaerator, the dissolved gas in the water to be treated moves to the gaseous phase side when the gas phase in contact with the water to be treated is decompressed. Also in the membrane deaerator, one side of the membrane is a gas phase, and this gas phase side is sucked by a vacuum pump, and the dissolved gas in the water to be treated is sucked and removed through the membrane.

As a degassing device, other degassing devices, such as a decarbonation tower, heating degassing, and nitrogen degassing, can be applied. Can not be removed, the gas remains dissolved in the water to be treated, or the dissolved gas component is replaced by another gas and remains.
In the present invention, a degassing device that performs processing under reduced pressure, such as a vacuum degassing device or a film degassing device that can remove dissolved gas, is used.

The degassed water is then subjected to ozone treatment.

In the present invention, the type of the reaction tower of the organic substance decomposing apparatus for decomposing organic substances by reacting ozone with organic substances is not particularly limited, and a sufficient contact time (reaction time) between ozone and water can be secured. Anything is fine. Usually, a reaction tower in which water stays for a predetermined time is used. In the reaction tower, water in which ozone is dissolved may be introduced and stored, or water to be treated may be introduced into the reaction tower to supply ozone into the tower. Ozone may be supplied by dissolving ozone by bringing an ozone-containing gas into direct contact with the water to be treated, or preparing water in which ozone is dissolved in advance and mixing the ozone-dissolved water with the water to be treated. May be. Further, the reactor may be of a piping type having a contact time such as an ejector instead of a reaction tower type. Regardless of the type, the reactor is provided with means for separating excess ozone gas and gaseous reaction products from treated water.

This ozone treatment may be a single oxidation treatment of ozone or a combination of one or more other oxidation efficiency improving means. in this case,
Examples of the combined use method include the following known methods for promoting ozone oxidation, such as the following methods. In each case, it is effective to increase the amount of generated hydroxyl radicals and improve the oxidizing action of ozone. Of H ₂ O ₂ in combination: oxidizing power of the coexistence of a small amount of _H 2 _{O 2} Ozone is improved. In this case, H ₂ O ₂ is added before the ozone treatment, and the added amount is H ₂ O ₂ / O.
₃ (molar ratio) It is preferable to set the amount to be about 0.2 to 2. Addition of alkali: pH neutral to 11 by addition of alkali,
Preferably, when it is 9 to 11, the oxidation reaction can be promoted. In this case, the alkali is added before the ozone treatment. The alkali to be added is not particularly limited, and sodium hydroxide (NaOH), potassium hydroxide (KOH), or the like can be used. UV irradiation: An oxidation reaction can be promoted by irradiating a reaction tower with a UV lamp having a wavelength of 360 nm or less. Catalyst filling: An oxidation reaction can be promoted by filling a reaction tower with an oxidation-reduction catalyst. In addition, since excess dissolved ozone is also decomposed, it is possible to prevent ozone from remaining in the treated water. In addition to filling the catalyst into the reaction tower,
A catalyst packed tower may be installed and used at the subsequent stage of the reaction tower. Examples of the catalyst used include metal catalysts such as Pt, Ru, and Pd.

1 (a) to 1 (c), the processing apparatus shown in FIG. 1 (a) uses an alkali addition.
The alkali is added to the degassed water of the membrane deaerator 1
After adjustment, add ozone and add static mixer 2
And then react in the reaction tower 3A. FIG.
(B) combines the addition of an alkali and the addition of H ₂ O _{2. The} pH is adjusted by adding an alkali to the degassed water of the membrane deaerator 1, and then the H ₂ O ₂ is added and a static mixer is added. 2 and then react in countercurrent contact with ozone in the reaction tower 3B. FIG. 1 (c) shows the addition of alkali and H
_The addition of ₂ O ₂ and the filling of the catalyst are used in combination. After the alkali is added to the degassed water of the membrane deaerator 1 to adjust the pH, H ₂ O ₂ is added and mixed with the static mixer 2, Thereafter, the reaction is performed by bringing the ozone countercurrently into contact with the reaction tower 3B filled with the catalyst 4.

The ozone reaction tower may be provided in multiple stages, and ozone may be added in each tower.

In such an ozone treatment, the residence time (HRT) of the reaction tower is appropriately determined according to the organic matter concentration of the water to be treated, and is usually about 15 to 120 minutes.

The dissolved concentration of ozone to be supplied to the water to be treated and dissolved in the water to be treated is determined as appropriate according to the content of organic substances in the water to be treated. It is preferable to supply them in the same amount to 10 times by weight.

Since the exhaust gas discharged from the reaction tower contains residual ozone, it is discharged outside the system after being treated by an ozone decomposer. Further, the treated water is discharged out of the system, and is further desalinated by a desalination device or the like as necessary.

[0028]

The present invention will be described more specifically below with reference to examples and comparative examples.

Example 1 City water and pure water (isopropyl alcohol as TOC was 3
1: 1 was used as the water to be treated and treated with the apparatus shown in FIG. 1A (however, H ₂ O ₂ was added instead of alkali). The quality of the water to be treated is as follows.

[Water quality of treated water] Conductivity: 70 μS / cm pH: 6.7 TOC: 1.9 ppm CO ₂ : 8.3 ppm HCl was added to the treated water to adjust the pH to 5.0, and then the membrane was treated. Deaerator (“Liqu Cel” 4 manufactured by Hoechst)
(1 inch) at 160 L / hr. The membrane degasifier, a _{N 2} gas as sweep gas 0.1N-
The mixture was ventilated at m ³ / hr and treated at a vacuum of 40 Torr.
The pH of the resulting degassed water was 6.1.

The degassed water contains H₂O₂50 ppm
After the addition, ozone gas is ₃/ Hr added,
The reaction was carried out in the tower. This reaction tower (560 mm diameter × 20
(HRT) is 60 minutes.
Was.

In this treatment, CO at the inlet water of the reaction tower
₂ and the TOC concentration and the TOC concentration of the outlet water (treated water) were examined. The results are shown in Table 1. Further, the TOC removal rate in the reaction tower was calculated, and the results are shown in Table 1.

Example 2 In Example 1, a 15-mesh wire mesh was used to form Pt in the reaction tower.
The same process was performed except that 100 L of the plated catalyst was charged and the reaction was performed, and the CO ₂ concentration, T
The OC concentration and the TOC removal rate were examined, and the results are shown in Table 1.

Comparative Examples 1 and 2 In Examples 1 and 2, treatment was carried out in the same manner as in Examples 1 and 2, except that the degassing treatment was not carried out in the membrane deaerator. The concentration was adjusted so that the CO ₂ concentration, TOC concentration, TOC
The removal rate was examined, and the results are shown in Table 1.

[0035]

[Table 1]

From Table 1, it can be seen that the efficiency of oxidative decomposition of organic substances by ozone can be increased by removing carbonic acid components and dissolved gases prior to ozone treatment by the apparatus for treating organic substance-containing water of the present invention.

[0037]

As described above in detail, according to the apparatus for treating organic substance-containing water of the present invention, organic substances can be decomposed and removed stably and efficiently without being affected by the quality of the water to be treated.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an embodiment of an organic matter-containing water treatment apparatus of the present invention.

[Explanation of symbols]

 1 membrane deaerator 2 static mixer 3A, 3B, 3C reaction tower

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D037 AA01 AA11 AB11 BA18 BA23 BB07 BB09 CA03 CA12 CA14 CA15 4D050 AA02 AA04 AA13 AA15 AB07 AB14 BB02 BB09 BC06 BC09 BC10 BD02 BD03 BD06 BD08 CA03 CA08 CA13

Claims (1)

[Claims] 1. A pH adjusting means for adjusting the pH of water containing organic matter to 4 to 6, a degassing device for separating a dissolved gas from water whose pH has been adjusted by said pH adjusting means under reduced pressure, and a degassing device. An organic matter decomposer for supplying ozone to the degassed water to decompose organic matter by ozonolysis.