JP3300852B2 - Method and apparatus for treating contaminated water - Google Patents

Description

The present invention relates to a method and an apparatus for treating an organic chlorine compound contained in groundwater or the like.

[Conventional technology]

As a technique for treating an organic chlorine compound contained in groundwater or the like, for example, trichloroethylene, tetrachloroethylene, 1,1,1-trichloroethane, etc., conventionally, a transpiration adsorption method combining a heated aeration method and an activated carbon method or potassium permanganate is used. An oxidative decomposition method using a Fenton reagent or the like is known, but a transpiration adsorption method combining a heated aeration method and activated carbon is mainly used at present.

[Problems to be solved by the invention]

However, in the respective heating and aeration methods and activated carbon methods that are the basis of the transpiration adsorption method, the activated carbon is wetted by the water generated during the aeration, and the ability of the activated carbon to adsorb organochlorine compounds is remarkably reduced. The amount of organochlorine compounds released to the atmosphere without being adsorbed increases, and these organochlorine compounds released to the atmosphere permeate underground again. In addition, it is necessary to treat the saturated activated carbon, and when this is left to the contractor, new costs are inevitable for the treatment. Furthermore, there are various problems such as clogging of pipes, heat exchangers, and air diffusers caused by the generation of bacteria after pumping groundwater and heating and aeration.
On the other hand, in the oxidative decomposition method using potassium permanganate, Fenton's reagent, etc., the amount of reagent used is large, the contamination load by the reagent is increased, and the heavy metal is contained in the reagent. Equipment is required.

An object of the present invention is to provide a method and an apparatus for treating contaminated water that solve the above problems.

[Means for solving the problem]

In order to achieve the above object, the method for treating contaminated water according to the present invention includes a sterilizing step, a suspended matter removing step, an organic chlorine compound decomposing step, and a residual oxidizing agent treating step,
A method of treating contaminated water as raw water, wherein the sterilization step supplies an oxidizing agent such as hydrogen peroxide or ozone into the raw water, sterilizes bacteria in the water, and uses a flow meter, a filter, This is a step to prevent clogging of the pipes with bacteria, and the amount of the oxidizing agent added to the raw water is set according to the bactericidal effect and the amount used to decompose organic substances in the organic chlorine compound decomposing step. The suspended matter removal step is a step of removing suspended matter in raw water by separation treatment including filtration and sedimentation. The organic chlorine compound decomposing step is a step of oxidization remaining in water after the treatment by the sterilization step and the suspended matter removal step. This is a step of irradiating the agent with ultraviolet rays to generate active oxygen, and oxidatively decomposing organic chlorine compounds in water by the generated active oxygen. The residual oxidizing agent treatment step is an organic chlorine compound decomposition step This is a step of reducing the oxidizing agent remaining in the water after the treatment with water. It is to adjust.

Further, the apparatus for treating contaminated water according to the present invention has a sterilizing apparatus, a filtering apparatus, an ultraviolet oxidative decomposition apparatus, a reducing apparatus, and an alkali agent adding apparatus, and treats contaminated water as raw water. The sterilizer is a device that supplies oxidizing agents such as hydrogen peroxide and ozone to raw water. The filtering device is a device that removes suspended matter contained in raw water, and the oxidizing agent added to raw water. The amount of is set according to the sterilizing effect and the amount used to decompose organic substances in the subsequent treatment with an ultraviolet oxidative decomposition device. The oxidizing agent is added to the ultraviolet oxidative decomposition device via a sterilizing device and a filtration device. Is a device that oxidizes and decomposes an organic chlorine compound contained in water by irradiating ultraviolet light onto water from which water has been removed and from which suspended matters have been removed. chlorine A device that reduces the oxidizing agent remaining in the water in which the compound has been decomposed.The alkali agent adding device is used in the water during the treatment with the ultraviolet oxidative decomposition device or during the treatment between the ultraviolet oxidative decomposition device and the reducing device. This is a device for adjusting the pH by adding an alkaline agent.

[Principle and operation]

The first step of the present invention is a sterilization step. The first step is a step of sterilizing bacteria growing by various organic substances contained in contaminated groundwater using an oxidizing agent such as hydrogen peroxide and ozone. Accordingly, clogging of the flow meter, filter, piping, and the like used in the processing apparatus by bacteria is eliminated. The oxidizing agent used in this step is not particularly limited. However, it is desirable to satisfy requirements such as high sterilizing ability, high ultraviolet absorbing ability, easy post-treatment, and no corrosion of piping. Ozone dissolves in a small amount in water and has very poor efficiency. In addition, ozone that does not dissolve in water is a source of malodor. In this regard, hydrogen peroxide is easy to handle, and even if it remains in water, it is easily decomposed with ultraviolet light, a reducing agent, or activated carbon into water and oxygen, and thus is effective without causing pollution. The amount of the oxidizing agent to be added is set in consideration of the bactericidal effect and the amount used for decomposing organic substances in the organic chlorine compound decomposition step to be introduced in the third step.

The second step is a step of removing suspended matter in the water by a filter or a coagulation sedimentation method.

The third step is a step of irradiating the residual oxidant after the first step and the second step with ultraviolet rays to oxidatively decompose the organic chlorine compound. In the oxidative decomposition reaction, active oxygen is first generated by irradiating the residual oxidizing agent with ultraviolet rays, and the organic chlorine compound is oxidatively decomposed by the active oxygen. As the ultraviolet oxidation apparatus, either a cylinder type or a tank type may be used, but a cylinder type is advantageous in terms of installation space, maintenance and ultraviolet irradiation efficiency. As the UV lamp, either a high-pressure mercury lamp or a low-pressure mercury lamp may be used. The low-pressure mercury lamps provided are more advantageous.

The fourth step is a step of reducing the oxidant remaining in the third step with a reducing agent, activated carbon, a catalyst resin, or the like.

In addition, in the third step, when the organic chlorine compound is oxidatively decomposed, hydrochloric acid is generated. Particularly, when the concentration of the organic chlorine compound is high, the pH is significantly lowered. In this case, an alkaline agent is added in the third step to carry out oxidative decomposition while adjusting the pH, or an alkaline agent is added between the third step and the fourth step to adjust the pH. Good. The alkaline agent used here may be potassium hydroxide or calcium hydroxide, or any of sodium hydroxide and sodium carbonate, but sodium hydroxide is the most easily used in operation.

According to the treatment method of the present invention, the treatment of the organic chlorine compound in the contaminated water is easier than in the conventional method, the generation of bacteria is prevented, and the clogging of the piping due to the generation can be prevented.

〔Example〕

Hereinafter, an example of the present invention will be described using a treatment example of wastewater containing trichloroethylene. At the time of processing, the test apparatus shown in FIG. 1 was used. Table 1 shows the specifications of the test apparatus.

Dissolve a special grade reagent of trichlorethylene in a volumetric flask in advance, put it in tank 1 and dilute with pure water.
And The trichlorethylene concentration at that time is 5.0 to 0.0
The range is 5 mg / m, and the viable cell count is 100 cells / m. This was used as a test solution.

The test liquid is pumped up by the pump 2, filtered by the cartridge filter 3, and stored in the tank 4. On this occasion,
Hydrogen peroxide is supplied from a hydrogen peroxide storage tank 9 to the tank 1 by a pump 10. The concentration of hydrogen peroxide in the tank 4 at that time is about 300 mg /.

The test liquid containing hydrogen peroxide stored in the tank 4 is sent to the ultraviolet oxidative decomposition device 7 through the flow meter 6 by the pump 5. Then, the trichlorethylene is oxidatively decomposed here. FIG. 2 shows the measurement results when the initial concentration of trichlorethylene was 5.0 mg /, and FIG. 3 shows the measurement results when the concentration was 0.05 mg /.

In any of the tests, residual hydrogen peroxide in the test solution is reduced with sodium bisulfite. Sodium bisulfite is pumped from sodium bisulfite storage tank 11
It is supplied to the tank 8 by 12. At the same time, sodium hydroxide was supplied to the tank 8 and decreased by oxidative decomposition.
The pH is adjusted. Sodium hydroxide is supplied from a sodium hydroxide storage tank 13 to a tank 8 by a pump 14.

Regarding viable bacteria which is one of the effects of the present invention,
When the number of viable bacteria in the test solution sampled from the tank 4 was measured and examined, it was 0 cells / m, and the bactericidal effect of hydrogen peroxide was confirmed in each case. The hydrogen peroxide concentration in the examples was 300 mg /, but the same experiment was performed by adjusting the hydrogen peroxide concentration to 1000 mg /, 500 mg /, and 100 mg /. I was not able to admit.

Also, regarding the decomposition of trichlorethylene, see FIG.
As shown in FIG. The concentration of trichlorethylene in the treated water is based on provisional water quality standards for tap water (February 18, 1984
The target was 0.03mg / or less. Fig. 2 shows the change of trichlorethylene concentration in water when decomposed by the UV + H ₂ O ₂ method according to the present invention using the trichlorethylene concentration of 5.0 mg / at the start as raw water.
H / M ³ ) is the experimental data shown. That is, the concentration of trichlorethylene in the water after the treatment when the UV irradiation amount was 0.18 KWH / M ³ was 0.5 mg /, and the UV irradiation amount was 0.37,
Trichlorethylene concentration with increasing the 0.77,1.35,2.03KW · H / M ³ is decreased to 0.04,0.01,0.004,0.003mg /,
It is clear that the method of the present invention is effective when the irradiation amount is about 0.4 KW · H / M ³ or more. FIG. 3 shows the results when the initial trichlorethylene concentration was 0.05 mg /. According to this example, when the irradiation amount is 0.2 KW · H / M ³ or more, the concentration of trichlorethylene in the water after treatment is 0.03 mg / or less, and it is clear that the method of the present invention is effective. In particular, when the irradiation dose was 0.77 KW · H / M ³ or more, the concentration of trichlorethylene in the treated water was less than 0.001 mg /.

In the above examples, the case where the initial trichloroethylene concentration was 5.0 mg /, 0.05 mg / was described.However, in any case where the initial concentration was 5.0 mg / or more and 0.05 mg / or less, after the treatment according to the method of the present invention, The trichlorethylene concentration in water could easily achieve the target value of less than 0.03mg /.
Further, as organic chlorine compounds contained in water, there are tetrachloroethylene and 1,1,1-trichloroethane in addition to trichlorethylene, and these have caused a problem of groundwater pollution. Therefore, 0.1-100 mg of tetrachloroethylene
/, 1,1,1-Trichloroethane 1.0 ~ 100mg / solution containing 1.0 ~ 100mg / as a raw water as a result of decomposition experiments under the same method and conditions as in the case of the above trichlorethylene, each concentration in the treated water 0.01mg / or less , 0.3 mg / or less. In addition, tetrachloroethylene,
With regard to the concentration of 1,1,1-trichloroethane in the treated water, the provisional water quality standard for tap water (targeted by the Ministry of Health and Welfare on February 18, 1984) was targeted.

〔The invention's effect〕

As described above, according to the present invention, sterilization of bacteria in groundwater and decomposition of organochlorine compounds contained in water by ultraviolet irradiation following the addition of an oxidizing agent to contaminated water, Only reduction treatment is sufficient, and contaminated water can be treated effectively and economically easily. Bacteria are sterilized by adding an oxidizing agent. By introducing only, it is possible to treat a large amount of water without causing clogging of pipes, heat exchangers, etc., which has the effect of effectively utilizing contaminated water, including groundwater. .

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a processing apparatus of the present invention, and FIGS. 2 and 3 are diagrams each showing the relationship between the concentration of trichloroethylene and the amount of ultraviolet irradiation in each embodiment. 1,4,8, ... tank, 2,5,10,12,14 ... pump 3 ... cartridge filter, 6 ... flow meter 7 ... ultraviolet oxidative decomposer, 9 ... hydrogen peroxide storage tank 11 ... … Sodium bisulfite storage tank 13 …… Sodium hydroxide storage tank

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI C02F 9/00 503 C02F 9/00 503Z 504 504E 1/32 1/32 1/50 510 1/50 510A 520 520Z 531 531Q 531R 560 560C 560Z 1/52 1/52 Z 1/58 1/58 A 1/66 510 1/66 510Z 521 521B 521C 540 540B 540G 540H 540Z 1/70 1/70 Z 1/72 101 1/72 101 1/78 1/78 (56) References JP-A-1-218676 (JP, A) JP-A-63-236593 (JP, A) JP-A-63-218293 (JP, A) JP-A-59-39386 (JP, A) A) JP-A-52-35445 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C02F 1/32 C02F 1/50 C02F 1/52 C02F 1/58 C02F 1/66 C02F 1/70 C02F 1/72 C02F 1/78 C02F 9/00 WPI (DIALOG)

Claims (2)

(57) [Claims] 1. A method for treating contaminated water as raw water, comprising a sterilizing step, a suspended matter removing step, an organochlorine compound decomposing step, and a residual oxidizing agent treating step, wherein the sterilizing step comprises hydrogen peroxide. , An oxidizing agent such as ozone into the raw water to sterilize the bacteria in the water and prevent clogging of the flow meter, filter, piping, etc. used in the treatment equipment by the bacteria. The amount of the oxidizing agent is set according to the sterilizing effect and the amount used to decompose the organic matter in the organic chlorine compound decomposing step, and the suspended matter removing step is to separate suspended matter in the raw water by filtration and sedimentation. In the organic chlorine compound decomposition step, active oxygen is generated by irradiating the oxidizing agent remaining in the water after the treatment in the sterilizing step and the suspended matter removing step with ultraviolet rays to generate active oxygen. Te,
The step of oxidatively decomposing the organic chlorine compound in the water, and the step of treating the residual oxidant is a step of reducing the oxidant remaining in the water after the treatment in the organic chlorine compound decomposing step. A method for treating contaminated water, comprising adding an alkaline agent to water and adjusting the pH between the compound decomposition step and the residual oxidizing agent treatment step. 2. An apparatus for treating contaminated water as raw water, comprising a disinfection device, a filtration device, an ultraviolet oxidative decomposition device, a reduction device, and an alkali agent addition device, wherein the disinfection device is a peroxidation device. A device that supplies oxidizing agents such as hydrogen and ozone into raw water. A filtration device is a device that removes suspended matter contained in raw water. Is set according to the amount used for decomposing organic substances in the treatment with an ultraviolet oxidative decomposer. The oxidant is added to the ultraviolet oxidative decomposer via a sterilizer and a filtration device, and suspended matter is removed. It is a device that oxidizes and decomposes organic chlorine compounds contained in water by active oxygen generated by irradiating the water with ultraviolet rays. Remain in The alkaline agent addition device adjusts the pH by adding an alkaline agent to water during the treatment with the ultraviolet oxidation decomposition device or between the treatment with the ultraviolet oxidation decomposition device and the reduction device. An apparatus for treating contaminated water, the apparatus comprising: