JP7178833B2 - Hydrogen peroxide-containing water treatment equipment - Google Patents

Description

TECHNICAL FIELD The present invention relates to a treatment apparatus for hydrogen peroxide-containing water, and more particularly to a treatment apparatus for adding a chemical for reduction treatment to hydrogen peroxide-containing water.

Hydrogen peroxide is widely used for cleaning and sterilization, and waste water containing hydrogen peroxide is discharged from processes such as cleaning and sterilization. Wastewater containing hydrogen peroxide cannot be discharged to the outside as it is, and it is necessary to remove the hydrogen peroxide in the wastewater. In some cases, waste water contains other components besides hydrogen peroxide, such as organic matter. Components will be removed. As a method for removing hydrogen peroxide contained in the hydrogen peroxide-containing water, which is the water to be treated, a method of adding a chemical for reduction treatment to decompose the hydrogen peroxide, thereby removing the hydrogen peroxide, platinum For example, a method of introducing water to be treated into a decomposition tower filled with a decomposition catalyst such as hydrogen peroxide to decompose and remove hydrogen peroxide, and a method of decomposing and removing hydrogen peroxide using a catalytic reaction with activated carbon are known. there is

Among these methods for removing hydrogen peroxide, the method of adding a chemical for reduction treatment can be broadly divided into the addition of a reducing agent such as sodium hydrogen sulfite (NaHSO ₃ ) to reductively decompose hydrogen peroxide. and a method of adding a hydrogen peroxide decomposition catalyst to accelerate the reduction of hydrogen peroxide by disproportionation. A typical method using a hydrogen peroxide decomposition catalyst is a method in which catalase, which is a hydrogen peroxide decomposition enzyme, is added to decompose hydrogen peroxide into water and oxygen. In the method of adding a reducing agent such as sodium bisulfite, it is necessary to add a reducing agent that is stoichiometrically equal to or greater than the amount of hydrogen peroxide. When the concentration of hydrogen peroxide in the water to be treated is high, the cost increases. On the other hand, the method of adding catalase can reduce the amount of chemicals used because catalase functions as a catalyst. Patent Document 1 describes an example of adding catalase to decompose hydrogen peroxide in the water to be treated. When catalase is added to decompose hydrogen peroxide, a relatively long reaction time (residence time in the reaction tank) is required, and in order to lengthen the reaction time, it is preferable to enlarge the reaction tank. However, there are cases where the reactor cannot be made large due to space constraints. Therefore, in Patent Document 2, in order to increase the efficiency of the decomposition treatment, the water to be treated is continuously supplied to a multi-stage reaction tank having a reaction zone divided into a plurality, and the water to be treated is supplied first. It discloses adding catalase to the region.

JP-A-8-132063 Japanese Patent Application Laid-Open No. 2009-269002

The method of adding catalase, which is a hydrogen peroxide degrading enzyme, disclosed in Patent Documents 1 and 2 to decompose hydrogen peroxide in the water to be treated has a wide range from extremely low concentrations close to 0 mg / L to high concentrations such as 50 g / L. It is an excellent method that is adaptable to a range of hydrogen peroxide concentrations and can treat water to be treated over a wide pH range. However, since the hydrogen peroxide concentration fluctuates, there is a problem that it is difficult to add an appropriate amount of catalase according to the hydrogen peroxide concentration in the water to be treated. If the amount of catalase added is excessive, the running cost will increase. On the other hand, if the amount of catalase added is too small, hydrogen peroxide may remain in the treated water, degrading the quality of the treated water. For the same reason, the method of adding a reducing agent such as sodium hydrogen sulfite also has the problem that it is difficult to determine the optimum amount to be added.

SUMMARY OF THE INVENTION An object of the present invention is to provide a treatment apparatus capable of optimizing the amount of chemical added when adding a chemical for reduction treatment to hydrogen peroxide-containing water to decompose and remove hydrogen peroxide. It is in.

The hydrogen peroxide-containing water treatment apparatus of the present invention is a treatment apparatus for decomposing and removing water to be treated containing hydrogen peroxide, and is connected to a raw water tank for temporarily storing the water to be treated and an outlet of the raw water tank. A pH adjusting tank for adjusting the pH of the water to be treated by supplying a pH adjusting agent together with the pH adjusting tank, a hydrogen peroxide concentration sensor provided at a position where the hydrogen peroxide concentration in the water to be treated can be measured, and an outlet of the pH adjusting tank and a supply means for supplying a reduction treatment chemical containing catalase to the reaction vessel in an amount controlled based on the measurement result of the hydrogen peroxide concentration sensor. The hydrogen peroxide concentration sensor has a first electrode as a working electrode and a second electrode as a counter electrode and a reference electrode, and a DC voltage is applied between the first electrode and the second electrode. It detects the current generated by the reduction of hydrogen peroxide when applied , is provided in the circulation pipe connected to the raw water tank, and reduces the hydrogen peroxide in the water to be treated by chemicals in the reaction tank. process.

According to the present invention, the addition amount of the reduction treatment chemical to the water to be treated is controlled based on the measurement result of the hydrogen peroxide concentration, so the addition amount of the reduction treatment chemical can be optimized.

1 is a flow sheet showing the configuration of a processing apparatus according to one embodiment of the present invention; It is a flow sheet which shows the structure of the processing apparatus of another embodiment.

Preferred embodiments of the present invention will now be described with reference to the drawings. FIG. 1 shows a processing apparatus according to one embodiment of the present invention. In this treatment apparatus, water containing hydrogen peroxide (H ₂ O ₂ ) is treated as water to be treated, and a chemical for reduction treatment is added to the water to be treated to reduce and decompose the hydrogen peroxide. A treated water from which hydrogen has been removed is obtained.

A raw water tank 11 for temporarily storing water to be treated is provided, and a pump 13 is provided at the outlet of the raw water tank 11. led to. A pH adjuster is also supplied to the pH adjustment tank 15 from a storage tank 17 . The pH adjustment tank 16 is provided to adjust the pH of the water to be treated to a value suitable for hydrogen peroxide reduction treatment. A pH sensor (not shown) for measuring the pH of the water to be treated in the pH adjusting tank 16 may be provided, and the amount of pH adjusting agent supplied to the pH adjusting tank 16 may be controlled based on the measured value of the pH sensor. good. The outlet of the pH adjustment tank 16 is connected to the reaction tank 21 through the pipe 18 . When the pH of the water to be treated supplied to the raw water tank 11 is already at a value suitable for reduction treatment, the pH adjustment tank 16 may not be provided. The water to be treated may be directly supplied to the reaction tank 21 .

Furthermore, a circulation pipe 12 is connected to the pipe 15 to return at least part of the water to be treated discharged from the pump 13 to the raw water tank 11 . The circulation pipe 12 is for adjusting the amount of the water to be treated supplied to the pH adjusting tank 16, and also prevents the water to be treated in the raw water tank 11 from remaining even when the treatment is stopped. and is provided as necessary. The circulation pipe 12 is provided with a hydrogen peroxide concentration meter 14 for online measurement of the hydrogen peroxide concentration in the water to be treated. The hydrogen peroxide concentration meter 14 may be installed in the raw water tank 11 as long as it can measure the concentration of hydrogen peroxide in the water to be treated. The concentration of hydrogen oxide may not be uniform, and it may be provided on the pipe 15. It is preferable to install it in the circulation pipe 12 because it becomes large and has a large influence on the piping design considering the maintenance of the hydrogen peroxide concentration meter 14 . As described above, the circulation pipe 12 is provided to adjust the amount of water to be treated supplied to the pH adjustment tank 16, so the flow rate is small and the pipe diameter of the pipe 15 is small, so the hydrogen peroxide concentration meter 14 The impact on piping design is also small. Further, since the water to be treated in the raw water tank 11 circulates, the concentration of hydrogen peroxide in the water to be treated in the circulation pipe 12 becomes uniform, and measurement errors are less likely to occur.

In the reaction tank 21, a reduction treatment chemical, that is, a hydrogen peroxide decomposing agent, is added to the water to be treated supplied through the pipe 18, and the chemical reduces and decomposes the hydrogen peroxide in the water to be treated to remove it. be done. The water in which the hydrogen peroxide concentration has been reduced in this manner is discharged from the reaction tank 21 through the pipe 24 as treated water. A stirring device (not shown) may be attached to the reaction tank 21 . In order to supply the chemical for reduction treatment to the reaction tank 21, a storage tank 22 for temporarily storing the chemical for reduction treatment in the form of an aqueous solution, and an injection pump 23 for injecting the chemical from the storage tank 22 into the reaction tank 21. and are provided. A relay tank 31 is provided to temporarily store the treated water discharged through the pipe 24. A pipe 32 is connected to the outlet of the relay tank 31, and the treated water is supplied to the pipe 32. A pump 33 is provided for this purpose. The treated water is sent through a pipe 32 to post-stage equipment that removes organic matter, nitrogen, fluorine, and the like, for example.

The reduction reaction rate of hydrogen peroxide in the reaction tank 21 increases as the residence time or reaction time increases, as the concentration of hydrogen peroxide increases, and as the concentration of the chemical for reduction treatment increases. Therefore, in the present embodiment, as described in Patent Document 2, as the reaction vessel 21, a structure in which a plurality of (for example, two) partitioned reaction zones are connected in series is used. It is also possible to use one configured so that the water to be treated and the chemicals for reduction treatment are supplied from the pipe 18, and the treated water is discharged from the reaction zone at the final stage.

In the present embodiment, a reducing agent such as an aqueous solution of sodium sulfite or sodium hydrogen sulfite can be used as a chemical for reduction treatment (that is, a hydrogen peroxide decomposing agent), but the consumption of this reducing agent tends to be large. Therefore, it is preferable to use catalase, which is a hydrogen peroxide degrading enzyme. Catalase is an enzyme that exists widely and commonly in the living world. Catalase produced by microorganisms is readily available, for example, in the form of an aqueous solution. Examples of catalase produced from microorganisms include catalase produced from microorganisms belonging to the genus Aspergillus, catalase produced from microorganisms belonging to the genus Thermomyces, catalase produced from microorganisms belonging to the genus Micrococcus, and the like. be. Catalase derived from these microorganisms is known to have different properties depending on the type of microorganism. Among them, catalase derived from microorganisms of the genus Aspergillus is less likely to be deactivated by high-concentration hydrogen peroxide, so that the amount to be added can be reduced, so it is used as a chemical for reduction treatment in this embodiment. preferred. Examples of catalase that can be used as a chemical for reduction treatment in the present embodiment include Orsorb EZ-800H (main component: Aspergillus-produced catalase) manufactured by Organo Corporation.

In this treatment apparatus, the operation of the injection pump 23 is controlled based on the measurement output signal from the hydrogen peroxide concentration meter 14 in order to optimize the addition amount of the chemical for reduction treatment to the water to be treated. Based on the result of measurement by the densitometer 14, the amount of chemical for reduction treatment to be added to the reaction tank 21 is adjusted to be the optimum amount. Even if the concentration of hydrogen peroxide in the supplied water to be treated fluctuates, the treatment apparatus maintains the concentration of hydrogen peroxide in the treated water discharged from the reaction tank 21 to a predetermined level or less. is decomposed and removed. Therefore, in the control of the operation of the injection pump 23 based on the measurement output signal from the hydrogen peroxide concentration meter 14, control is performed so that the concentration of hydrogen peroxide in the treated water is below a predetermined level. If the volume of the reaction tank 21 and the flow rate of the water to be treated to the reaction tank 21 are known, the residence time (reaction time) ensured in the reaction tank 21 can be calculated. Assuming that the temperature is constant, the reaction rate constant (or reaction rate formula) of the decomposition reaction of hydrogen peroxide by the chemical for reduction treatment may vary depending on the type of chemical (for example, the difference in species of microorganisms that produce catalase). However, it can be said that it is uniquely determined once the type of drug is determined. When the concentration of hydrogen peroxide in the water to be treated is given as a measurement result, the concentration of hydrogen peroxide at the outlet of the reaction vessel 21 is calculated by reaction rate calculation based on the residence time in the reaction vessel 21 and the reaction rate constant. It is possible to calculate the amount of chemical to be added so as to achieve a predetermined level. In view of safety, the actual addition amount of the chemical for reduction treatment may be slightly larger than the addition amount calculated here. Although not shown in the figure, a calculation unit may be provided for calculating the addition amount of the chemical for reduction treatment from the reaction rate calculation, and the injection pump may be controlled by the calculation unit.

Next, the hydrogen peroxide concentration meter 14 will be explained. Methods for measuring hydrogen peroxide concentration include a titration method using potassium permanganate or iodine, a voltammetry method, a post-column HPLC method using a chemiluminescence detector, and a method using a sensor and a detector. The hydrogen peroxide concentration meter 14 has a hydrogen peroxide concentration sensor, measures the concentration of hydrogen peroxide on-line, and outputs a measurement output signal for controlling the addition amount of the reduction treatment chemical based on the measurement result. It is. Since online measurement is performed and used to control the amount of chemicals added, the hydrogen peroxide concentration sensor provided in the hydrogen peroxide concentration meter 14 should be capable of continuous analysis and have a fast response speed. is required. From this point of view, it is preferable to use a two-electrode sensor based on current measurement as the hydrogen peroxide concentration sensor.

In the two-electrode type hydrogen peroxide concentration sensor, for example, a first electrode serving as a working electrode is provided at the tip of a rod-shaped member, and a second electrode serving as both a counter electrode and a reference electrode is provided on the side surface of the member. The area of the second electrode is sufficiently larger than that of the electrodes. The first electrode is, for example, an electrode made of gold (Au) or platinum (Pt), and the second electrode is, for example, a silver/silver chloride (Ag/AgCl) electrode, as disclosed in JP-A-9-178700. It is an electrode made of a metal that can be deactivated. The hydrogen peroxide concentration sensor may be separated from the liquid to be measured by a diaphragm that is permeable to hydrogen peroxide. It is filled with an electrolytic solution (for example, a potassium chloride (KCl) solution of a predetermined concentration). In such a hydrogen peroxide concentration sensor, hydrogen peroxide receives electrons and is reduced by applying a predetermined DC voltage between the first electrode and the second electrode. Since the current flowing between the electrodes at this time is proportional to the concentration of hydrogen peroxide, the hydrogen peroxide concentration meter 14 outputs a measurement output signal corresponding to the current flowing between the electrodes. A hydrogen peroxide concentration sensor that can be used in this embodiment includes, for example, PER1 or PEROX manufactured by Prominent of Germany.

In the configuration shown in FIG. 1, a hydrogen peroxide concentration meter 14 is connected to a circulation pipe 12 connected to a raw water tank 11 in which water to be treated is temporarily stored, and circulates through the circulation pipe 12 to the raw water tank 11. It measures the concentration of hydrogen peroxide in the water to be treated. However, the installation position of the hydrogen peroxide concentration meter 14 is not limited to this, and the water to be measured by the hydrogen peroxide concentration meter 14 is not limited to water to be treated. The hydrogen peroxide concentration meter 14 can be provided at any position in the treatment apparatus if the addition amount of the reduction treatment chemical can be optimized based on the hydrogen peroxide concentration.

FIG. 2 shows a processing device of another embodiment of the invention. This treatment apparatus is the same as the treatment apparatus shown in FIG. 1, except that an activated carbon packed tower 40 is arranged after the relay tank 31 for temporarily storing the treated water discharged from the reaction tank 21 . The activated carbon packed tower 40 is provided at the tip of the pipe 32 extending from the outlet of the relay tank 31 . The inside of the activated carbon packed tower 40 is filled with activated carbon to form an activated carbon layer, and the treated water that has passed through this activated carbon layer is sent from the outlet of the activated carbon packed tower 40 to the subsequent equipment. In this treatment apparatus, the hydrogen peroxide concentration in the treated water at the outlet of the reaction tank 21 should be low enough to be treated by the activated carbon packed tower 40, specifically, 50 mg / L or less. Therefore, compared with the treatment apparatus shown in FIG. 1, the injection amount of chemicals for reduction treatment into the reaction tank 21 can be reduced, and the running cost can be greatly reduced. The activated carbon-filled tower 40 further decomposes and removes hydrogen peroxide in the treated water discharged from the reaction tank 21 to reduce the concentration of hydrogen peroxide in the treated water sent to the subsequent equipment to a predetermined value or less. The activated carbon packed tower 40 may be either a pressurized type or an open type, and may be either downward flowing water or upward flowing water. The invention is more effective in the case of packed columns.

11 raw water tank 13, 33 pump 14 hydrogen peroxide concentration meter 16 pH adjustment tank 21 reaction tank 23 injection pump 31 relay tank 40 activated carbon packed tower

Claims (3)

A treatment apparatus for decomposing and removing water to be treated containing hydrogen peroxide,
a raw water tank for temporarily storing the water to be treated;
a pH adjusting tank connected to the outlet of the raw water tank and supplied with a pH adjusting agent to adjust the pH of the water to be treated;
a hydrogen peroxide concentration sensor provided at a position where the hydrogen peroxide concentration in the water to be treated can be measured;
a reaction tank connected to the outlet of the pH adjusting tank and supplied with the water to be treated;
supply means for supplying a reduction treatment chemical containing catalase to the reaction vessel in an amount controlled based on the measurement result of the hydrogen peroxide concentration sensor ;
with
The hydrogen peroxide concentration sensor has a first electrode serving as a working electrode and a second electrode serving as both a counter electrode and a reference electrode. It detects the current generated by the reduction of hydrogen peroxide when is applied , and is provided in the circulation pipe connected to the raw water tank ,
A treatment apparatus for reducing hydrogen peroxide in the water to be treated with the chemical in the reaction tank. 2. The process according to claim 1, wherein the addition amount of said chemical is calculated using a residence time of said water to be treated in said treatment apparatus and a reaction rate constant of a reductive decomposition reaction of hydrogen peroxide by said chemical. Device. 3. The processing apparatus according to claim 1, further comprising an activated carbon packed tower connected to the outlet of said reactor.

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