JPH0249798B2 - JUKIKAGOBUTSUGANJUSUINOSHORIHOHO - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an improvement in a method for treating water containing organic compounds, particularly organic compounds that are difficult to decompose or are harmful to the human body. More specifically, the present invention relates to a method for efficiently treating and rendering harmless water and wastewater containing persistent organic compounds such as organic chlorine compounds and various organic compounds that are harmful to the human body.

[Conventional technology]

Cleaning industry or high-tech related industry,
Particularly in the semiconductor manufacturing industry and the machinery industry, various organic solvents such as trichlorethylene that are harmful to the human body are used as solvents, and the treatment of wastewater discharged from these industries has become a problem.
In addition, contamination of groundwater and river water by wastewater containing various harmful natural or synthetic organic compounds discharged from various chemical factories has become a problem.Furthermore, in the process of chlorinating drinking water, The formation of trihalomethanes due to the reaction of dissolved organic compounds with chlorine has become a problem.

Conventionally, such organic compounds have been treated by (1) ozone treatment, (2) activated carbon treatment, (3) volatilization treatment, (4) reduction treatment using semiconductor photocatalysts, and (5) reduction using metals or alloys thereof. Treatment methods such as the treatment method (Patent Application No. 62-182016) have been attempted and adopted. Among these treatment methods, method (1) selectively reacts with organic compounds with double bonds and decomposes them, so it has been put into practical use for deodorization and decolorization. Since many compounds are difficult to decompose with ozone, this method is not only limited in its applicability, but also consumes a large amount of energy to generate ozone, making it not an economically effective method.

Furthermore, method (2) above is currently the most effective method and is widely used. However, this method has a small adsorption capacity for organic compounds such as trihalomethane, requires a high frequency of regeneration of the activated carbon, and has problems in terms of treatment costs, similar to the method (1) above. Method (3) above is used as a treatment method for volatile and difficult-to-decompose substances, but it is difficult to completely remove harmful organic compounds by aeration treatment alone, and it is not effective for non-volatile substances. There is no. Furthermore, if exhaust gas is released into the atmosphere untreated, harmful substances will simply be transferred from the water to the atmosphere, so it is necessary to treat the exhaust gas using methods such as activated carbon treatment or combustion. . Method (4) is a method that uses an N-type semiconductor such as titanium dioxide as a catalyst to oxidize and reductively decompose various organic compounds using solar energy.It uses natural energy and is economical. Although this seems like a reasonable method, it is difficult to irradiate light all over a highly concentrated photocatalyst suspension, and so far no practical scale device has been produced.

Method (5) is a method proposed by the present inventors to improve the drawbacks of these conventional methods, and is also effective in detoxifying harmful organic compounds in the water. However, when the temperature of the water is low or when oxidizing substances such as nitrate ions and dissolved oxygen are present, it takes a long time to process the substances to a predetermined standard concentration, and the reaction temperature is 40°C. At temperatures above ℃, a large amount of hydrogen gas is generated.

[Problem that the invention seeks to solve]

The present invention overcomes the drawbacks of such conventional techniques and provides a method for efficiently and economically treating and rendering harmless water and wastewater containing various organic compounds such as organic chlorine compounds that are harmful to the human body. It was done for the purpose of

[Means for solving problems]

As a result of extensive research to achieve the above object, the present inventors have found that after adjusting the water to be treated to a predetermined pH, the oxidation-reduction potential progresses to a reaction that renders harmful components in the water harmless. A reducing substance is added to reduce the PV to 300 mv or less, oxidizing components such as dissolved oxygen are removed, and if necessary, an electrolyte is added to increase the electrical conductivity of the water, and then a metal reducing agent is used. method (6) (patent application 62-
182016), it was discovered that the reaction time could be shortened to 1/3 or less, and that the side reaction that generated hydrogen gas was also suppressed by shortening the reaction time.Based on this knowledge, the present invention was developed. I was able to complete it.

That is, the present invention is characterized in that the water to be treated containing organic compounds is adjusted to a pH value of 6.5 or higher, and after adding a reducing substance, the water is treated using a metal reducing agent. The present invention provides a water treatment method.

The present invention will be explained in detail below.

The water to be treated in the method of the present invention includes, for example, municipal water and wastewater containing persistent organic compounds such as organochlorine compounds such as trichlorethylene and trihalomethane, and natural and synthetic organic compounds discharged from factories manufacturing dyes, pharmaceuticals, and agricultural chemicals. Examples include wastewater containing compounds.

Normally, the water to be treated is in contact with air, so
ppm of oxygen is dissolved. It also sometimes contains nitrate ions. Since the reaction between these oxidizing substances and the metal reducing agent is slow, it takes a long time to lower the potential of the water to the redox potential at which a detoxifying reaction occurs. Therefore, reducing substances such as sodium sulfite are added to reduce these oxidizing substances (1).
When removed by the reaction shown in the formula, the redox potential rapidly decreases and a reaction to detoxify the refractory organic compound begins.

Na _z SO ₃ ＋O ₂ →Na _z SO ₄ (1) Regarding the reaction mechanism for detoxification of harmful organic compounds, for example, an organic chlorine compound is given as an example of a persistent organic compound, and it is subjected to metal reduction. In the case of treatment using an agent, the reaction proceeds as shown below, and the refractory organic compound is rendered harmless.

Me+H ₂ O+RX→RH+Me ⁺⁺ +OH ^- +X ^- (2) Here, Me is a metal reducing agent and RX is an organic chlorine compound. That is, organic chlorine compounds are dehalogenated and converted into harmless hydrocarbons. In addition, at this time, the following side reactions occur,
Hydrogen is generated.

Me+2H ₂ O→2HO ^- +Me ⁺⁺ +H _z (3) In the method of the present invention, the above detoxification reaction is
Since the redox potential occurs when the redox potential is around -300mv or less, in order to promote the reaction, it is preferable to quickly reduce the redox potential in the water to about -300mv or less. This can be done, for example, by injecting about 0.08 kg of sodium sulfite per 1 m ³ of water to be treated. As a result, the oxidation-reduction potential in the water becomes -300mv or less, which is a favorable condition for the detoxification reaction of the organic chlorine compound. In addition, the pH of the water to be treated
A score of 6.5 or higher is selected. If the pH value is less than 6.5, a large amount of the metal reducing agent is dissolved and a large amount of hydrogen gas is generated, which is disadvantageous.

The oxidation-reduction potential regulator used in the method of the present invention is not particularly limited as long as it exhibits a regulating ability in water with the above-mentioned pH, but from the economical point of view sodium sulfite and thiosulfate are used. Sodium is preferably used. In addition, the amount used varies depending on the amount of oxidizing substances dissolved in the water to be treated and cannot be determined unconditionally, but it is usually 0.04 per 1 ^m3 .
Selected in the range of ~0.1Kg.

If the water to be treated is, for example, washing wastewater using ion-exchanged water or distilled water, add an electrolyte such as sodium phosphate or sodium sulfate at 0.05 to 0.1 per ^m3 of water.
The reaction can be accelerated by adding Kg and adjusting the electrical conductivity to 100 μmho/cm or more to promote the anodic reaction at the metal reducing agent interface. The electrolyte to be added is not particularly limited as long as it is oxidizing or produces chlorine ions, but phosphates and the like are preferably used.

The metal-based reducing agent used in the method of the present invention is not particularly limited, but from the viewpoint of economy, metals, alloys, or compounds of metals such as iron and zinc are preferably used.

The amount of this metal-based reducing agent to be used varies depending on the amount of persistent organic compounds dissolved in the water to be treated and cannot be determined unconditionally, but it is usually used for 1 m ³ of the water to be treated.
It is in the range of 1×10 ^-3 to 5×10 ^-3 Kg per unit.

Further, the treatment temperature is preferably a high temperature in order to promote the reduction reaction, but consuming energy for heating is not so desirable from an economic standpoint, and is usually selected in the range of 0 to 30°C.

〔Effect of the invention〕

According to the method of the present invention, it is possible to efficiently and economically treat water and wastewater containing persistent organic compounds such as organic chlorine compounds and nitrogen-containing organic compounds that are harmful to the human body and render them harmless.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 Here, the effects of electrolytes and reducing agents are shown. A 1/100 molar solution of sodium sulfate was used as the electrolyte.
Sodium sulfite was used as a reducing agent. each about 10% of 1,1,2,2-tetrachloroethane
The sample water prepared to have a concentration of mg/ml was placed in a 5 ml vial, 1 g of iron powder was added, and then detoxified while shaking in a constant temperature bath at 20°C. The results are shown in FIG. Here, A is pure water, B is when sodium sulfite is dissolved in pure water, C is when sodium sulfite is dissolved in pure water, D is when sodium sulfate and sodium sulfite are dissolved in pure water, and sodium sulfate is When ion-exchanged water is dissolved, the reaction is faster and the effect of adding sodium sulfite is also higher than when using only ion-exchanged water.

Example 2 To ion exchange water whose pH was adjusted to 7.0 using Michaelis' phosphate buffer, 1,
Take the test water in which 1,2,2-tetrachloroethane has been dissolved into a 5 ml vial, and add 100 g/sodium sulfite solution to 20 μ (2
mg), and after adding 1 g of iron powder, 10
A reduction test of 1,1,2,2-tetrachloroethane was carried out while shaking in a constant temperature oven maintained at 20°C, 30°C, 40°C, and 50°C. The second result is
As shown in the figure. Figure 2 is a graph showing the relationship between the treatment time and the residual rate of 1,1,2,2-tetrachloroethane at each temperature, where A is 10°C and B is 20°C.
℃, C is 30℃, D is 40℃, and E is 50℃. As can be seen from this figure, at a treatment temperature of 50°C, the residual rate of 1,1,2,2-tetragloloethane becomes 0% within 30 minutes, and at 30°C, the residual rate reaches 0% within 1 hour and 30 minutes. %.

[Brief explanation of drawings]

FIG. 1 is a graph showing the effect of adding a reducing substance and an electrolyte in the present invention. Figure 2 shows the processing time at each processing temperature of the present invention and 1, 1, 2,
It is a graph showing the relationship with the residual rate of 2-tetrachloroethane.

Claims (1)

[Claims] 1. The PH value of water to be treated containing organic compounds is 6.5.
The redox potential in the water is adjusted to about -
Organic compound-containing water characterized by adding a reducing substance that lowers the PV to 300mv or less, removing oxidizing substances such as dissolved oxygen, and making the organic compound harmless using a metal reducing agent. Processing method. 2. If the electrical conductivity of the water to be treated containing the organic compound is 100 μmho/cm or less, add an electrolyte that does not contain chlorine ions and oxidizing ions in order to promote the anodic reaction at the metal interface, and then A method for performing the process according to claim 1.