JPH11207369A - Ozone injection controlling method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To establish an optimum ozone injection controlling method injecting a desired ozone by grasping the removing effect of an objective material to be removed by an ozone treatment. SOLUTION: In the ozone injection treatment so that an ozone treated water 3 is obtained by treating a water 1 to be treated with an injected ozone concn. controlling device 7 at an ozone contract pond 2, the UV absorbance of the water 1 to be treated is measured with a UV meter 4, also the dissolved ozone concn. of the ozone treated water 3 is measured with a DO3 meter 5 provided with a UV absorbance measuring function, the feedback controlling of the injected ozone concn. controlling device 7 is executed by an arithmetic processor 8 so that the UV residual ratio of the ozone treated water 3 to the UV value of the water 1 to be treated is constant and the ozone injection controlling method is made as a basic method so that gaseous ozone is injected into the ozone contact pond 2 based on the obtained ozone concn. A UV residual ratio setting function, a THMFP residual ratio setting function, a KMnO4 consumption setting function and the upper limit setting function of the dissolved ozone concn. DO3 are provided at the arithmetic processor 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ozone injection control method using an ultraviolet absorbance meter and a dissolved ozone concentration meter with an ultraviolet absorbance measurement function in advanced water and sewage water purification treatment.

[0002]

2. Description of the Related Art In order to purify raw water taken from a river or the like, a suspension is aggregated and precipitated and separated by a coagulant pouring, mixing, stirring and retaining treatment in a coagulation sedimentation tank. This process incorporates algal killing and chlorination to remove chromatic components such as iron and manganese. However, in recent years, rivers are very polluted in the suburbs of large cities, and the content of chromaticity components including ammonia and humic substances, which are precursors of the carcinogen trihalomethane, is high. As a result of producing chloramine by reaction and consuming more chlorine than necessary, there is a problem that a chlorine injection rate is increased and THM is increased.

In recent years, a method of incorporating an advanced water purification system into a water purification process has been used for the purpose of removing the above-mentioned substances. This advanced water treatment method includes ozone treatment and biological activated carbon treatment.For example, ozone treatment is performed by an ozone contact pond as an alternative to chlorination treatment, and chromaticity components are removed by activated carbon treatment or biological filtration treatment. After filtering in a pond etc., chlorination is performed and water is sent to a water purification pond. In particular, by performing the ozone treatment before the biological activated carbon treatment, it is possible to improve the tolerance to load fluctuation and the life of the activated carbon.

[0004] The purpose of the ozone treatment is to decompose and remove odorous substances such as musty odor and the like and chromatic components composed of humic substances, to reduce organic chlorine compounds, to oxidize iron and manganese, and to decompose organic substances. In the case of advanced sewage treatment, COD removal is also one of the objectives.

[0005] Known methods of controlling ozone treatment include constant control of ozone injection rate, constant control of exhausted ozone concentration, constant control of dissolved ozone concentration, and control of UV value (ultraviolet absorbance). This is described above. However, this method is not a method of directly grasping the quality of treated water, but a control of grasping the treatment effect indirectly from the ozone index.

[0006]

At present, energy saving and reduction of CO ₂ gas emission are required in order to prevent global warming. In ozone treatment, a desired treatment effect is maintained and power consumption is reduced. There is a need for a means to adopt a method that saves as much as possible. For that purpose, it is necessary to establish a method of controlling the amount of ozone injection by grasping the removal effect of the target substance to be removed by ozone treatment, that is, "optimal ozone amount injection control" that injects only the optimum amount of ozone. It is considered.

Based on such a concept, the above-described constant control of the ozone injection rate cannot completely grasp the ozone treatment effect, so that the optimum ozone injection control cannot be performed.
In the control of the concentration of the dissolved ozone with the control of the concentration of the exhausted ozone, the effect of the ozone treatment is not directly grasped from the quality of the treated water.

[0008] Therefore, in the above-mentioned method, there is a concern that excessive injection of ozone may cause waste of ozone and electric power, and conversely, a target ozone treatment effect may not be obtained due to insufficient ozone injection. Conceivable.

On the other hand, with the improvement of analysis technology, it has become possible to measure substances which could not be measured conventionally, and one of them is bromate ion. In particular, potassium bromate has been shown to be carcinogenic, and the WHO (World Health Organization)
Bromate ion concentration according to the drinking water guidelines of
(Μg / l) The following have been proposed.

[0010] Bromate ions are easily formed by ozonating water in which bromide ions are present. Therefore, in water purification treatment, suppression of bromate ions is a very important issue in performing ozone treatment.

Although various proposals have been made as a method for suppressing the formation of bromate ions in the ozone treatment, after all, the ozone injection rate or the contact time with ozone is reduced, and an appropriate CT value (= CT,
Operation control at (C: dissolved ozone concentration, T: contact time) is a usual means.

From the viewpoint of suppressing the bromate ion in the ozone treatment, it is considered that CT control using the dissolved ozone concentration C and the contact time T is effective in the above-mentioned constant control of the dissolved ozone concentration. However, even with this control, the original purpose of ozone treatment is not understood,
It is necessary to establish an "optimal ozone injection control" method that enhances the ozone treatment effect, suppresses the production of bromate ions, and minimizes power consumption.

The present invention has been made in view of the above problems, and has as its object to establish "optimal ozone amount injection control" for injecting required ozone by grasping the removal effect of a target substance to be removed by ozone treatment. is there.

[0014]

According to the present invention, in order to achieve the above object, according to the present invention, the water to be treated is dissolved in water by injecting the water to be treated into an ozone contact pond by an ozone concentration control device. Injection treatment to remove ozone-treated water by removing trace organic substances in water, measure the UV absorbance of the water to be treated with a UV meter and measure the dissolved ozone concentration of the ozonated water with a UV absorbance measurement function DO Measured by _three meters, the feedback control of the injection ozone concentration control device is performed by the arithmetic unit so that the UV residual ratio of the ozone treated water to the UV value of the water to be treated becomes constant, and the inside of the ozone contact pond is determined based on the obtained ozone concentration. To provide an ozone injection control method for injecting ozone gas into the device.

The arithmetic unit is provided with a function for setting the residual UV ratio and a function for setting the upper limit of the dissolved ozone concentration DO ₃ .

According to a third aspect of the present invention, the dissolved ozone concentration of the ozonized water is measured by a DO ₃ meter having an ultraviolet absorbance measuring function, and a feedback control of the injected ozone concentration control device is performed by an arithmetic unit so that THMFP is removed.
An ozone injection control method for injecting ozone gas into an ozone contact pond based on the obtained ozone concentration is provided.

The arithmetic unit is provided with an upper limit setting function for trihalomethane generation capability and DO ₃ , which determines a THMFP target removal rate set value by ozone treatment at the time of execution, and calculates a THMF estimated value of the water to be treated and the ozonated water. THM in search
The FP removal rate is calculated, and the feedback control of the injected ozone concentration control device is performed so that the THMFP removal rate becomes the target removal rate.

According to a sixth aspect of the present invention, the dissolved ozone concentration of the ozonized water is measured by a DO ₃ meter equipped with an ultraviolet absorbance measuring function, and potassium permanganate (KMn) is calculated by an arithmetic unit.
An ozone injection control method is provided in which feedback control of the injection ozone concentration control device is performed so that O ₄ ) is removed, and ozone gas is injected into an ozone contact pond based on the obtained ozone concentration.

In the above-mentioned arithmetic unit, KMnO ₄ consumption and DO ₃
The upper limit setting function is provided to determine the KMnO ₄ target removal rate set value by ozone treatment at the time of implementation, and to obtain the KMnO ₄ consumption estimated value of the water to be treated and the ozonated water to obtain KMnO _4.
The nO ₄ removal rate is calculated, and feedback control of the injected ozone concentration control device is performed so that the KMnO ₄ removal rate becomes the target removal rate.

[0020] According to the ozone injection control method, and a UV meter for the treated water, using a UV absorbance measurement function DO ₃ meter for ozone treatment of water, the ozonated water to UV value of the water to be treated UV By performing feedback control of the injected ozone concentration so that the residual rate becomes constant, the removal rate of moldy odor and difficult-to-analyze such as pesticides from the UV residual rate is increased, and THMPF, KMn and the water to be treated and the ozonated water are removed.
A continuous estimation and elimination of O ₄ consumption is achieved.

The arithmetic unit has a UV residual ratio setting function, T
By providing the HMFP residual rate setting function or the KMnO ₄ consumption setting function and the dissolved ozone concentration DO ₃ upper limit setting function, the U set even if the UV value of the water to be treated increases.
When the UV value does not decrease to the V residual ratio, control is performed so as not to adversely affect the ozone excess injection and the activated carbon treatment to the subsequent stage, and by setting the upper limit of DO ₃ , bromate ion generation is reduced. Can be suppressed.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, various specific embodiments of an ozone injection control method according to the present invention will be described with reference to the drawings. In the various embodiments described below, the basic means is a method of controlling ozone injection by an ozone generator using an ultraviolet absorbance meter and a dissolved ozone concentration meter with an ultraviolet absorbance measurement function.

FIG. 1 is a schematic diagram showing a first embodiment of the present invention, wherein 1 is water to be treated, 2 is an ozone contact pond, 3 is ozonized water, 4 is an ultraviolet absorbance meter (hereinafter referred to as UV meter 4). 5 is a dissolved ozone concentration meter (hereinafter abbreviated as DO ₃ meter 5), 6 is an ozone generator, 7 is an injection ozone concentration control device, and 8 is a calculation device. DO ₃ meter 5 is provided with an ultraviolet absorbance measurement function. Further, the arithmetic unit 8 is provided with a UV residual ratio setting function UV Co / Ciset and an upper limit setting function for the dissolved ozone concentration DO ₃ .

The basic operation of this embodiment is as follows. According to the normal operation mode, the water to be treated 1 flows into the ozone contact pond 2, the ozone gas obtained by the ozone generator 6 is injected, a predetermined ozone treatment is performed, and the treated water 1 flows out as ozonized water 3. In this process, first, the ultraviolet absorbance (UV value) of the water 1 to be treated is measured by the UV meter 4 and input to the arithmetic unit 8. Further, the dissolved ozone concentration of the ozonized water 3 is set to DO ₃
It is measured by a total of 5, and is similarly input to the arithmetic unit 8.

The arithmetic unit 8 has a DO ₃ total of 5 for the ozonized water 3.
The UV value is obtained from the measured value, and the injection ozone concentration control device 7 performs feedback control so that the UV residual ratio of the ozonized water 3 with respect to the UV value of the water 1 to be treated becomes constant, based on the obtained ozone concentration. Ozone gas is injected from the ozone generator 6 into the ozone contact pond 2.

The DO ₃ meter 5 has a function of correcting the turbidity of the visible light absorbance.
It is better to use the turbidity-corrected UV value than the value. Briefly explaining this, the absorbance at 253.7 nm of ultraviolet light (E
253.7) and visible light 5 highly correlated with suspended solids and turbidity
In order to overcome the "weak to turbidity" point, which is a drawback of the absorptiometry method, the signal of the absorbance at 46 nm (E546) is used to subtract E546 from E253.7 in the detection unit to obtain E253. 7 is added. This enables measurement even if the sample contains a moderate turbidity. UV and visible light absorbance (VI
The measurement principle of S) is described in Japanese Patent Application No.
No. -103071.

In the case of the first embodiment, the ozone treatment effect of the water to be treated 1 is evaluated by the UV value obtained from the dissolved ozone concentration of the ozonated water 3, and the ozone treatment water 3 is compared with the UV value of the water 1 to be treated. It is a great feature in operation that feedback control is performed so that the UV residual ratio of the LED becomes constant.

Here, focusing on the treatment of musty odor substances and pesticides as examples of ozone treatment target substances, the analysis of these musty odor substances and pesticides themselves generally takes a long time, and it cannot be measured online. Therefore, when the musty odor substance or the pesticide is detected by the analysis, the ozone-treated water 3 has already been transferred to the next-stage water purification treatment step, and there is a possibility that the ozone-treated water 3 may be mixed into the tap water without treatment.

On the other hand, in the case of the first embodiment, injection control of ozone is performed so that the UV residual ratio of the ozone-treated water 3 with respect to the UV value of the water 1 to be treated becomes a constant level, so that the musty odor substance is controlled. Or pesticides can be almost completely removed. Figure 2 shows ozone contact time (min) and musty odor substances,
It is a graph which shows the relationship of the residual rate of a pesticide etc., when the mold odor residual rate set value is set to c and the pesticide 1 residual rate set value is set to d, when the ozone treatment is performed until the UV residual rate becomes a, the musty odor substance is set. It has been removed up to the residual ratio c. Also, the pesticide 1 can be treated by ozone treatment until the UV residual ratio becomes b.
Can be removed up to the set residual rate d. Therefore, a desired removal result can be obtained by setting a target residual rate of the musty odor substance and the pesticide, that is, a removal rate, and obtaining an appropriate UV residual rate and performing ozone treatment.

The arithmetic unit 8 has a UV residual ratio setting function UV Co /
The reason why the upper limit setting function of Ciset and DO ₃ is provided is that, when the UV value of the water 1 to be treated rises and the UV value does not decrease to the set UV residual ratio, it is necessary to prevent excessive ozone injection. This is for preventing an adverse effect on the activated carbon treatment and the like in the subsequent stage, and for maintaining the upper limit of DO ₃ in order to suppress the formation of bromate ions.

FIG. 3 shows the CT value (mg / l · min, C: dissolved ozone concentration, T: contact time) and the amount of bromate ion generated (mg).
/ L) is a graph showing the relationship, where assuming that the bromate ion concentration upper limit set value is a, the CT value may be set to b or less in order to keep the bromate ion concentration at or below a. Here, assuming that the residence time of the ozone contact pond 1 is t (minutes), the DO ₃ upper limit setting can be obtained by b / t (mg / l). Therefore, by creating a control set value for each ozone contact pond in which the present control is performed, an action of suppressing the generation of bromate ions is achieved.

FIG. 4 is a schematic diagram showing a second embodiment of the present invention. Since the basic configuration is the same as that of the first embodiment, the same components are denoted by the same reference numerals. Is displayed. 1 water to be treated, 2 ozone contact basin, 3 ozonated water, 5 DO ₃ meters, 6 ozone generator, 7 is injected ozone concentration control device, 8 is a computing device. Arithmetic unit 8
Is provided with a trihalomethane generating ability (THMFP) and an upper limit setting function of DO ₃ .

The basic operation of this embodiment is as follows. The water 1 to be treated flows into the ozone contact pond 2 and the ozone generator 6
The ozone gas obtained in step (1) is injected to perform predetermined ozone treatment, and flows out as ozonized water 3. The dissolved ozone concentration of the ozonized water 3 is measured by the DO ₃ meter 5 and input to the arithmetic unit 8.

The arithmetic unit 8 obtains a UV value from the dissolved ozone concentration of the ozonated water 3, and calculates one of the substances removed by the ozone treatment.
Feedback control of the injection ozone concentration control device 7 is performed so that one of the THMFPs is removed, and ozone gas is injected into the ozone contact pond 2 from the ozone generator 6 based on the obtained ozone concentration.

Generally, the UV value and THMFP have a high correlation, and can be expressed as THMFP = a.UV + b (1). Here, a and b are coefficients.
THMF is calculated from the UV value of the ozonized water 3 using the equation (1).
The abundance of P can be estimated with high accuracy.

In this example, first, the THMFP set value (THMF
Pset). Next, TH is calculated by the following equation (2).
UV set value of the ozonated water 3 (UVs
et).

UVset = (THMFPset−b) / a (2) Then, the feedback control of the injection ozone concentration control device 7 is performed so that the UVset is constant.

A more specific control example will be described with reference to the control flow chart of FIG. 5. The correlation between the UV value and the THMFP (Y
= AX + b). In step 101, the UV value and DO ₃ of the ozonized water 3 are measured, and in step 102, coefficients a and b are determined by a correlation test between the UV value and THMFP.
Then, in step 103, the THMFP in the ozonized water 3 is estimated using the above equation (1).

In step 104, the T of the ozonized water 3 is determined in advance.
HMFP setting and DO ₃ upper limit setting are performed. In step 105, the injection ozone concentration is calculated from the THMFP setting value by the above equation (2) so that UVset is constant, and the feedback control of the injection ozone concentration control device 7 is performed. I do.

The arithmetic unit 8 has a trihalomethane forming ability (TH
The reason why the MFP ₃ ) and the DO ₃ upper limit setting function are provided is that when the UV value of the water 1 to be treated rises as in the first embodiment,
If the UV value does not decrease to the set UV residual ratio, the upper limit of DO ₃ is maintained to prevent bromine ion generation, because it does not adversely affect the ozone excess injection and the activated carbon treatment in the subsequent stage. To do that. As a specific method for suppressing the formation of bromate ions, the method described with reference to FIG. 3 is used.

FIG. 6 is a schematic diagram showing a third embodiment of the present invention. Since the basic configuration is the same as that of the first embodiment, the same components are denoted by the same reference numerals. Is displayed. 1 water to be treated, 2 ozone contact basin, 3 ozonated water, 4 UV meter, 5 DO ₃ meters, 6 ozone generator, 7 is injected ozone concentration control device, 8 is a computing device. The arithmetic unit 8 is provided with a THMFP residual ratio setting function and an upper limit setting function of the dissolved ozone concentration DO ₃ .

The present embodiment is characterized in that a stable THMFP removal rate can be obtained even with respect to the THMFP fluctuation of the water 1 to be treated. Normally, ozone treatment involves a qualitative change in organic matter, so the relationship between UV value and THMFP may differ before and after ozone treatment. Therefore, a correlation equation between UV value and THMFP is created separately before and after ozone treatment.

Before ozone treatment: THMFP1 = a1 · UV1 + b1 (3) After ozone treatment: THMFP2 = a2 · UV2 + b2 (4) THMFP Removal rate = 1−THMFP2 / THMFP1 (5) where a1, a2, b1, and b2 are coefficients and THMF
P1 and THMFP2 are the T of the water 1 to be treated and the ozonated water 3
This is the HMFP estimation value.

As a basic operation of the third embodiment, the water to be treated 1 flows into the ozone contact pond 2 and the ozone gas obtained by the ozone generator 6 is injected to perform a predetermined ozone treatment. Outflow as 3. In this process, the UV value of the water to be treated 1 is measured by the UV meter 4 and input to the arithmetic unit 8. Furthermore, the dissolved ozone concentration DO _{3 of the} ozonized water ₃
Is measured by the DO ₃ meter 5 and input to the arithmetic unit 8 in the same manner.

The arithmetic unit 8 obtains a UV value from the dissolved ozone concentration of the ozonated water 3 and performs feedback control of the injected ozone concentration control unit 7 so that THMFP, which is one of the substances removed by the ozone treatment, is removed. Then, ozone gas is injected into the ozone contact pond 2 from the ozone generator 6 based on the obtained ozone concentration.

In this example, a target removal rate set value (THMF removal rate set) by the ozone treatment of the THMFP is determined.
Next, THMF1 and THMFP2, which are THMF estimated values of the to-be-treated water 1 and the ozone-treated water 3, are obtained from Expressions (3) and (4), and the THMFP removal rate is calculated by Expression (5). Then, feedback control of the injected ozone concentration control device 7 is performed so that the THMFP removal rate becomes the target removal rate set value (THMF removal rate set).

A more specific control example will be described with reference to the control flow chart of FIG. 7. The UV value before ozone treatment and the THMF
Correlation formula of P (Y = a1X + b1) and UV after ozone treatment
A correlation equation (Y = a2X + b2) between the value and the THMFP is created. Next, in step 201, the UV value of the ozone-treated water 3 and the DO ₃ and the UV value of the water to be treated 1 are measured, and in step 202, the coefficients of the equations (3) and (4) are determined by a correlation test between the UV value and THMFP. . Then, in step 203, the THMFP in the ozonized water 3 is estimated by using the equation (4), and the THMFP of the water 1 is estimated by the equation (3).

In step 204, the T of the ozonized water 3 is
The HMFP residual ratio Co / Ci is obtained by calculation, and in step 205, the THMFP residual ratio Co / Ci is set and the upper limit of DO ₃ is set.
In step 206, feedback control of the injected ozone concentration control device 7 is performed so that the THMFP removal rate of the equation (5) becomes the target removal rate set value (THMF removal rate set).

The remaining ratio of THMFP and DO ₃
The reason for providing the upper limit setting function is to prevent excessive ozone injection and activate carbon treatment to the subsequent stage when the UV value of the water 1 to be treated rises and the UV value does not decrease to the set UV residual ratio. This is because the upper limit of DO ₃ is maintained so as not to have an adverse effect and to suppress the production of bromate ions. The specific method for suppressing the formation of bromate ions uses the method described with reference to FIG. 3, which is the same as in the second embodiment.

[0050] Figure 8 is a schematic diagram showing a fourth embodiment of the present invention, 1 is the water to be treated, 2 ozone contact basin, 3 ozonated water, 5 DO ₃ meters, 6 ozone generator , 7 is an injection ozone concentration control device, and 8 is an arithmetic device. Arithmetic unit 8
Is provided with a potassium permanganate (KMnO ₄ ) consumption setting function and a DO ₃ upper limit setting function.

The basic operation of this embodiment is the same as in each of the above embodiments, except that the water 1 to be treated flows into the ozone contact pond 2 and the ozone generator 6
The ozone gas obtained in step (1) is injected to perform predetermined ozone treatment, and flows out as ozonized water 3. The dissolved ozone concentration of the ozonized water 3 is measured by the DO ₃ meter 5 and input to the arithmetic unit 8.

The arithmetic unit 8 obtains a UV value from the dissolved ozone concentration of the ozonated water 3, and calculates 1
The ozone gas is injected into the ozone contact pond 2 from the ozone generator 6 based on the obtained ozone concentration based on the feedback control of the injection ozone concentration control device 7 so that KMnO ₄ is removed.

Based on the correlation between the UV value and KMnO4, it can be expressed as: KMnO4 consumption = a.UV + b (6). Here, a and b are coefficients.
From the UV value of the ozonized water 3 using the equation (6),
₄ can be estimated with high accuracy.

In this example, first, the KMnO ₄ consumption set value (K
MnO ₄ consumption set) is determined. Next, a UV set value (UVset) of the ozonized water 3 corresponding to the KMnO4 consumption amount set is obtained by the following equation (7).

UVset = (KMnO4 consumption amount set-b) / a (7) Then, feedback control of the injection ozone concentration controller 7 is performed so that the UVset is constant.

A more specific control example will be described with reference to the control flow chart of FIG. 9. First, a correlation equation (Y = aX + b) between the UV value and the KMnO ₄ consumption is created. In step 301, the UV value and DO ₃ of the ozonized water ₃ are measured.
At 02, the coefficients a and b of the equation (6) are determined by a correlation test between the UV value and the KMnO ₄ consumption. Then, in step 303, the KMnO ₄ consumption amount in the ozonized water 3 is estimated using the equation (6).

In step 304, the K of the ozonized water 3 is determined in advance.
Set MnO ₄ consumption and DO ₃ upper limit
In step 305, the injected ozone concentration is calculated from the set value of the KMnO ₄ consumption by the above equation (7) so that UVset is constant.
The feedback control of the injection ozone concentration control device 7 is performed.

The KMnO ₄ consumption setting and DO ₃
The reason for providing the upper limit setting function is that when the UV value of the water to be treated 1 rises, as in the first embodiment, the set UV
The reason is to prevent excessive ozone injection when the UV value does not decrease to the residual ratio, not to have an adverse effect on the activated carbon treatment in the subsequent stage, and to maintain the upper limit of DO ₃ to suppress the formation of bromate ions. As a specific method for suppressing the formation of bromate ions, the method described with reference to FIG. 3 is used.

FIG. 10 is a schematic view showing a fifth embodiment of the present invention. The basic structure is the same as that of each of the above embodiments. ozonated water, the 4 UV meter, 5 DO ₃ meters, 6 ozone generator, 7 is injected ozone concentration control device, 8 is a computing device. The arithmetic unit 8 is provided with a function for setting the remaining KMnO ₄ consumption rate and an upper limit for the dissolved ozone concentration DO ₃ .

The present embodiment is characterized in that a stable KMnO ₄ removal rate can be obtained even when the KMnO ₄ consumption of the water to be treated 1 fluctuates. As described above, since the ozone treatment involves a qualitative change in organic matter, the relationship between the UV value and the KMnO ₄ consumption may differ before and after the ozone treatment. Therefore, the UV value and the KMnO ₄ consumption are divided before and after the ozone treatment. Create a quantity correlation equation.

Before ozone treatment: KMnO ₄ consumption 1 = a1 · UV1 + b1 (8) After ozone treatment: KMnO ₄ consumption 2 = a2 · UV2 + b2 (9) KMnO ₄ removal rate = 1−KMnO ₄ consumption 2 / KMnO ₄ consumption 1 (10) where a1, a2, b1, and b2 are coefficients and KMnO 4
₄ Consumption 1 and KMnO ₄ consumption 2 are estimated values of the water 1 to be treated and the ozone-treated water 3.

As a basic operation of the third embodiment, first, the water 1 to be treated flows into the ozone contact pond 2 and the ozone generator 6
The ozone gas obtained in step (1) is injected to perform predetermined ozone treatment, and flows out as ozonized water 3. In this process, the UV value of the water to be treated 1 is measured by the UV meter 4 and input to the arithmetic unit 8. Further, the dissolved ozone concentration of the ozonized water 3 is measured by the DO ₃ meter 5 and is similarly input to the arithmetic unit 8.

The arithmetic unit 8 calculates the UV value from the dissolved ozone concentration of the ozonated water 3 by calculation, and the feedback of the injected ozone concentration control unit 7 so that KMnO ₄ which is one of the substances removed by the ozone treatment is removed. Control is performed, and ozone gas is injected into the ozone contact pond 2 from the ozone generator 6 based on the obtained ozone concentration.

In this example, the target value of the KMnO ₄ consumption target removal rate set by the ozone treatment (KMnO ₄ removal rate set) is determined. Next, THMFP1 and THM, which are estimated values of KMnO ₄ consumption of the water 1 to be treated and the ozone-treated water 3 from the equations (8) and (9), respectively.
Seeking MFP 2, and calculates the KMnO ₄ removal rate by the equation (10). Then, feedback control of the injected ozone concentration control device 7 is performed so that the KMnO ₄ removal rate becomes the target removal rate set value (KMnO ₄ removal rate set).

A more specific control example will be described with reference to the control flow chart of FIG.
Correlation formula of O ₄ consumption (Y = a1X + b1) and correlation formula of UV value and KMnO ₄ after ozone treatment (Y = a2X + b2)
Create Next, in step 401, the UV value of the ozonized water 3 and the UV value of DO ₃ and the water 1 to be treated are measured. In step 402, the coefficient of the formulas (8) and (9) is obtained by a correlation test between the UV value and the consumption of KMnO _4. To determine. Then, in step 403, the KMnO ₄ consumption amount in the ozonized water 3 is estimated by using the equation (9), and the THMFP of the water 1 is estimated by the equation (8).

In step 404, the K of the ozone-treated water 3 is previously determined.
The MnO ₄ residual ratio Co / Ci is obtained by calculation, and in step 405, the KMnO ₄ residual ratio Co / Ci is set and the upper limit of DO ₃ is set.
In step 406, the feedback control of the injected ozone concentration controller 7 is performed so that the KMnO ₄ removal rate of the equation (10) becomes the target removal rate set value (KMnO ₄ removal rate set).

The setting of KMnO ₄ consumption and DO ₃
The reason why the upper limit setting function is provided is as described in the fourth embodiment, and a specific method for suppressing the formation of bromate ions uses the method described with reference to FIG.

[0068]

As described above in detail, according to the present invention, the UV absorbance of the water to be treated in the ozone injection treatment is measured by a UV meter, and the dissolved ozone concentration of the ozonized water is measured by a DO with ultraviolet absorbance measurement function. _The basic means is to perform feedback control of the injected ozone concentration control device so that the UV residual ratio of the ozone-treated water to the UV value of the water to be treated is kept constant by the arithmetic unit. From the residual rate, it is possible to grasp the contamination of a difficult-to-analyze substance such as musty odor substance or pesticide, and it can be continuously removed.

Further, a UV residual ratio setting function, T
By providing the HMFP residual ratio setting function or the KMnO ₄ consumption setting function and the dissolved ozone concentration DO ₃ upper limit setting function, THMPF, KM
Continuous estimation and removal of the residual rate of nO ₄ consumption can be performed. Ozone, especially when the provision of the UV residual rate setting function and capping function of the concentration of dissolved ozone DO ₃ to the arithmetic unit, UV value does not decrease until the UV residual rate of UV value of the water to be treated is set when elevated Control is performed so as not to adversely affect the excess injection and the activated carbon treatment in the subsequent stage, and it is possible to suppress bromate ions generated when ozone treatment is performed on water containing bromide ions.

Therefore, according to the present invention, “optimal ozone injection control” that eliminates waste of electric power is established by grasping the residual ratio of the target substance to be removed by ozone treatment and controlling the amount of ozone injected. This has the effect that the management of processing conditions can be performed with high accuracy.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a first embodiment of an ozone injection method according to the present invention.

FIG. 2 is a graph showing the relationship between ozone contact time (minutes) and residual rates of musty odor substances, pesticides, and the like.

FIG. 3 is a graph showing the relationship between the CT value and the amount of bromate ion generated.

FIG. 4 is a schematic diagram showing a second embodiment of the present invention.

FIG. 5 is a control flowchart of the second embodiment.

FIG. 6 is a schematic diagram showing a third embodiment of the present invention.

FIG. 7 is a control flowchart of the third embodiment.

FIG. 8 is a schematic diagram showing a fourth embodiment of the present invention.

FIG. 9 is a control flowchart of the fourth embodiment.

FIG. 10 is a schematic diagram showing a fifth embodiment of the present invention.

FIG. 11 is a control flowchart of the fifth embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Treatment water 2 ... Ozone contact pond 3 ... Ozonated water 4 ... UV meter 5 ... DO ₃ meter 6 ... Ozone generator 7 ... Injection ozone concentration control device 8 ... Calculation device

Claims (8)

[Claims] 1. An ozone injecting process for injecting water to be treated into an ozone contact pond and performing ozone treatment by an ozone concentration control device to remove dissolved trace organic substances in the water to obtain ozonated water. , as well as determined by UV meter UV absorbance of the treatment water, the dissolved ozone concentration in the ozonated water was measured by UV absorbance measurement function DO ₃ meters, with an arithmetic device ozonated water to UV value of the water to be treated UV An ozone injection control method, comprising: performing feedback control of an injection ozone concentration control device so that a residual ratio becomes constant, and injecting ozone into an ozone contact pond based on the obtained ozone concentration. 2. The ozone injection control method according to claim 1, wherein the arithmetic unit is provided with a UV residual ratio setting function and a dissolved ozone concentration DO ₃ upper limit setting function. 3. An ozone injecting process for injecting water to be treated into an ozone contact pond and performing ozone treatment by an ozone concentration controller to remove dissolved trace organic substances in the water to obtain ozonated water. , the dissolved ozone concentration in the ozonated water was measured by UV absorbance measurement function DO ₃ meters, THMFP the arithmetic unit
An ozone gas injection control method, wherein feedback control of the injection ozone concentration control device is performed so that ozone gas is removed, and ozone gas is injected into the ozone contact pond based on the obtained ozone concentration. 4. The ozone injection control method according to claim 3, wherein the arithmetic unit is provided with a trihalomethane generating ability and an upper limit setting function of DO ₃ . 5. A THMFP target removal rate set value by ozone treatment is determined, a THMF estimation value is calculated by obtaining a THMF estimation value of the water to be treated and ozonized water, and the THMFP removal rate is set to the target removal rate. 4. The feedback control of the injection ozone concentration control device is performed.
3. The method for controlling ozone injection according to item 1. 6. An ozone injecting process for injecting water to be treated into an ozone contact pond by an ozone concentration control device to remove dissolved trace organic substances in the water to obtain ozonated water. the dissolved ozone concentration in the ozonated water was measured by UV absorbance measurement function dO ₃ meters, the arithmetic unit performs feedback control of the injection ozone concentration control device as potassium permanganate is removed, the ozone concentration determined An ozone injection control method characterized by injecting ozone gas into an ozone contact pond based on the above. 7. The arithmetic unit includes a KMnO ₄ consumption amount and a D
7. An O ₃ upper limit setting function is provided.
3. The method for controlling ozone injection according to item 1. 8. A KMnO ₄ target removal rate set value by the ozone treatment is determined, and the KMnO _{4 of the} water to be treated and the ozonized water are determined.
The KMnO ₄ removal rate is calculated by obtaining the estimated consumption amount, and KM
ozone injection control method according to claim 6 nO ₄ removal rate and performs feedback control of the injection ozone concentration control device so that the target removal rate.