JPH1099877A - Pressure downward injection type multistage ozone contact tank and its control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an actual scale corresponding pressure downward injection type multistage ozone contact tank enhanced in the absorbing efficiency of ozone gas to water to be treated without being scaled up and not generating an absorbing efficiency lowering phenomenon with the elapse of time and rpovide a control method therefor. SOLUTION: In this multistage ozone contact tank, a first pressure vortex pump 17 mixing ozone gas with water to be treated by providing a branch pipe 15a to the midway part of the inflow pipe 15 of water to be treated to an up and down opposed flow type multistage ozone contact tank 11 and the quick contraction valve 19 adjusting the pressure in the output pipe l7a of the pressure vortex pump are arranged and the output pipe 17a is connected to the downward injection pipe 21 vertically inserted and arranged in the first tank 11a of the multistage ozone contact tank 11 through a water sending pipe 16a while a second pressure vortex pump 22 mixing ozone gas with water to be treated and a quick contraction valve 24 are arranged to the branch pipe 15a and the output pipe 17a is connected to the downward injection pipe 25 inserted and arranged in the second tank 11b of the multistage ozone contact tank 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressurized downward injection type multistage ozone contact tank useful for application to an ozone treatment apparatus as a method for treating water and sewage and a control method therefor.

[0002]

2. Description of the Related Art Water pollution in rivers and lakes has been progressing with the deterioration of the water environment in urban areas in recent years. Raw water for tap water can be obtained only by the conventional combination of coagulation sedimentation, sand filtration and chlorination. There is a point where the chromaticity and odor removing action of the odor have a limit. In particular, about 70% of the water sources used as tap water in Japan depend on surface water, such as lakes, dams and river water, and these lakes and dams have active biological activities associated with eutrophication. There is a generation of mold odor and algae odor due to the formation of organic substances and ammonia nitrogen contained in various wastewater into the other river water,
It is impossible to completely purify these inflows by the natural purification action of rivers.

[0003] In order to cope with the deterioration of the water quality of the water source due to such high economic growth, pre-chlorination is generally adopted. Trihalomethane which is an organic chlorine compound generated in a water purification process employing pre-chlorination is used. (THM) is known to have carcinogenicity. Advanced water purification systems that introduce ozone treatment or a combined treatment of ozone treatment and activated carbon treatment during the water purification operation are being studied as measures to eliminate mold and algal odors from such water sources and to take measures against carcinogens such as trihalomethane. ing.

[0004] Ozone gas has an action of oxidizing and removing dissolved harmful substances dissolved in water by its own strong oxidizing power, and has recently been adopted not only for water supply but also for sewage treatment. However, the cost of ozone treatment is about twice as high as that of chlorination, and it is required to further enhance the effect of ozone gas treatment. Therefore, by forming countless fine ozone gas bubbles, water and ozone gas It is an essential requirement to increase the contact efficiency and to efficiently dissolve and absorb ozone gas in water.

Conventionally, as means for increasing the contact efficiency and absorption efficiency of ozone gas, a diffuser type ozone contact tank or a downward injection type ozone contact tank (U tube type ozone contact tank) is known. As an example of the above-mentioned aeration tube type ozone contact tank, for example, “Ozone water treatment technology” (Isao Soumiya,
The Pollution Control Technology Club, May 1989) discloses an example of a vertically opposed ozone contact tank as shown in FIG.

That is, in this example, partitions 2 and 2 rising from the bottom and partitions 3 and 3 suspended from the top are disposed inside the ozone contact tank 1, and the gas phase portion is formed by the partitions 2 and 3. A plurality of overflow-type reaction chambers which are separated and whose liquid phase portions communicate with each other are formed. An air diffusion pipe 4.4 made of ceramic or the like having fine holes of several tens of μm is arranged near the inner bottom surface of each chamber, and ozone gas obtained from an ozone generator (not shown) is sent into the air diffusion pipe 4.4. Then, the water to be treated flowing from the inlet 5 and the ozone gas come into contact with each other as a counterflow as shown by arrows A and A, so that the contact efficiency of the ozone gas is increased and the ozone gas flows out as the ozonized water 10.

[0007] The other downward injection type ozone reaction tank (U tube type ozone reaction tank) is also referred to as an injector type ozone contact tank, and as shown in FIG. Is disposed, and the ozone gas obtained by the ozone generator 7 is sent from the upper part of the inner pipe 6 through the gas discharge pipe 8. And the ozone gas contact tank 1
The water to be treated and the ozone gas flowing from the inlet 5 on the side of the inner pipe 6 continuously contact as a downward flow in the inner pipe 6 to perform a desired ozone treatment, and rise as it is along the outer wall surface of the inner pipe 6 Then, it flows out as ozonized water 10 from the upper part of the ozone contact tank 1. Unreacted ozone gas is discharged to the ozone treatment device 9
To be cleaned.

The vertical length of the ozone contact tank 1 is 20.
The water pressure in the inner tube 6 is maintained at a level of 2.0 to 2.5 (kgf / cm ² ).

This U-tube type ozone contact tank has an inner pipe 6
The gas-liquid contact effect between the ozone gas and the water to be treated is enhanced by the turbulent flow generated in the step, and the water pressure that increases as the ozone gas flows down in the inner pipe 6 promotes the dissolution of the ozone gas into the water. The ozone dissolution efficiency is improved by 5 to 10% compared to the system, the contact time between ozone gas and the water to be treated can be about 5 times or more, and the residence time in the reaction tank is reduced to 1/5 or less. It has the feature that it can be done. Further, since the ozone contact tank is vertically long, there is an advantage that the installation space of the ozone treatment facility is only 1/5 that of the air diffuser system.

[0010] By using such an ozone reaction tank,
Ozone gas, which has much more oxidizing power than chlorine, removes off-flavors and chromaticity of the water to be treated, and oxidizes and removes harmful substances. (For the U-tube type ozone treatment equipment, the 2nd Annual Ozone Association of Japan Research Lecture Series No. 7
Pages 6 to 77, see Toriyama et al., "Organic matter removal characteristics of U-tube ozone contact tank").

[0011]

However, the ozone contact tank employed in the above-mentioned advanced water purification system or the like does not have a control method for increasing the efficiency of absorbing ozone gas with respect to the water to be treated. In addition to the possibility that a reduction in efficiency may occur, the residence time of the ozone contact tank needs to be lengthened, resulting in a problem that the cost increases due to an increase in the size of the apparatus.

For example, in the diffuser type ozone contact tank shown in FIG. 9, iron or manganese oxidized by ozone gas adheres to the surface of the diffuser tube 4 as the treatment proceeds, and the diffuser tube 4
There is a concern that the ozone absorption efficiency may decrease over time due to clogging of the air, and there is a problem that it is necessary to replace the air diffuser itself in order to cope with the phenomenon. Furthermore, in order to take sufficient reaction time with ozone gas, the contact tank must be enlarged, which leads to an increase in equipment costs and the like, and also requires a large site area for installing the apparatus. It is difficult to adopt in areas where land is difficult to secure, such as water purification plants in urban areas.

On the other hand, the U-tube type ozone contact tank shown in FIG. 10 has improved ozone dissolution efficiency by about 5 to 10% as compared with the diffuser type ozone contact tank, and also has a high efficiency of ozone gas and water to be treated. The contact time can be increased by 5 times or more, and the residence time in the contact tank can be reduced to 1/5 or less. However, as described above, the water depth of the ozone contact tank is 20 to 30 meters. The construction of the facility is more complicated than the air diffuser method, and the removal of sediment stored in the contact tank and the cleaning of the tank cannot be performed easily. However, there is a disadvantage that even if some trouble occurs near the bottom of the contact tank, it cannot be immediately treated.

Considering the reaction process of ozone from another point of view, the ozone reaction process can be roughly classified into an initial stage in which the diffusion of ozone is rate-limiting and a late stage in which the ozone reaction is rate-determining. . Therefore, it is ideal that the gas-liquid reaction contact tank is also a device based on these characteristics.For example, at the beginning of the ozone reaction, it has a large contact area and a strong stirring mechanism to increase the diffusion efficiency, and Sometimes it is desirable to have a device that ensures a residence time for obtaining a sufficient reaction.

Considering the reaction processes of the two types of ozone contact tanks, a U-tube type ozone contact tank is suitable at the beginning of the ozone reaction, and a diffuser ozone contact tank is suitable at the latter stage of the ozone reaction. I can say.

According to Japanese Patent Application No. 8-42257, the applicant of the present invention is provided with a pressurized vortex pump for gas-liquid mixing of water to be treated and ozone gas and a variable speed device for adjusting the amount of inflow of the water to be treated. The lower injection pipe into which the gas-liquid mixed water to be treated falls as a downward flow is discharged from a tip opening formed at a portion facing the bottom wall of the ozone contact tank, and the pressure in the pipe is adjusted near the tip opening. We have proposed a pressurized downward injection type ozone contact tank with a rapid contraction part for use, but this time we have proposed a pressurized downward injection type multi-stage ozone contact tank for real scale, without increasing the size of special equipment It is an object of the present invention to provide a pressurized downward injection type ozone contact tank in which the absorption efficiency of ozone gas with respect to the water to be treated is increased and the absorption efficiency does not decrease with time, and a control method therefor.

[0017]

In order to achieve the above object, according to the present invention, first, according to claim 1, a branch pipe is provided in the middle of an inflow pipe for feeding water to be treated into a multistage ozone contact tank of a vertically opposed flow type. And a first pressurized vortex pump for gas-liquid mixing of the water to be treated and the ozone gas and a rapid reduction valve for adjusting the pressure in the output pipe of the first pressurized vortex pump are provided in the branch pipe. Then, the output pipe is connected to a lower injection pipe vertically inserted and disposed in the first tank of the multi-stage ozone contact tank via a water pipe for the water to be treated, and the branch pipe is connected to the water to be treated. A second pressurized vortex pump for gas-liquid mixing of ozone gas and the second
Of the pressurized vortex pump of the present invention is provided with a rapid reduction valve for adjusting the pressure in the output pipe, and the output pipe is connected to a lower injection pipe vertically inserted and disposed in the second tank of the multistage ozone contact tank. A pressurized downward injection type multistage ozone contact tank is provided.

According to a second aspect of the present invention, there is provided a method for controlling the pressurized downward injection type multistage ozone contact tank, wherein a treated water amount controller is provided in an inflow pipe of the water to be treated, and an ozone injection rate controller and an injected ozone concentration controller are installed in the ozone generator. And a generated ozone concentration meter, and determines the target value of the treated water amount from the treated water amount set value and the treated water flow signal input to the treated water amount controller. An injection ozone concentration target value is determined from the ozone injection rate set value and output to the injection ozone concentration controller. The injection ozone concentration controller controls the driving state of the ozone generator based on the injection ozone concentration target value and the generated ozone concentration. A signal is output to supply ozone gas to the first and second pressurized vortex pumps. And using a method of performing emission infusion rate constant control.

According to a third aspect of the present invention, the exhaust ozone concentration controller, the injection ozone concentration controller and the generated ozone concentration meter are provided in the ozone generator, and the exhaust ozone concentration meter is provided in the multi-stage ozone contact tank and the ozone is discharged from the contact tank. The exhaust ozone concentration of the exhausted ozone gas is measured and input to the exhaust ozone concentration controller. The exhaust ozone concentration controller obtains the injected ozone concentration target value from the exhaust ozone concentration set value and the exhaust ozone concentration signal and outputs the target value to the injected ozone concentration. The injected ozone concentration controller outputs a signal for controlling the driving state of the ozone generator based on the injected ozone concentration target value and the generated ozone concentration to supply ozone gas to the first and second pressurized vortex pumps. A method of controlling the concentration of exhausted ozone by using the method described above is used.

By using a dissolved ozone concentration controller instead of the above-mentioned exhaust ozone concentration controller and disposing a dissolved ozone concentration meter in the multi-stage ozone contact tank, a method for controlling the dissolved ozone concentration constant is provided. Thus, a control method of using a UV value controller and disposing a low-concentration UV meter in a multi-stage ozone contact tank to realize constant ultraviolet absorbance control is realized.

Further, an injection ozone concentration controller and a generated ozone concentration meter are provided in the ozone generator, and a discharged ozone concentration controller and a discharged ozone concentration meter are provided in the multi-stage ozone contact tank. A pressure gauge and a valve opening controller are provided between the valves to measure the exhaust ozone concentration of the exhaust ozone gas discharged from the contact tank. Is measured, and when the pressure value is within a predetermined range,
After the variable valve is controlled by the control output of the variable valve opening controller, when the exhausted ozone concentration is high, the pressure is increased by reducing the valve opening of the variable valve while the exhausted ozone concentration is low. We propose a method to control the pressure to decrease by increasing the opening of the quick-reduction valve. Further, a method is proposed in which a dissolved ozone concentration controller or a UV value controller is used instead of the exhaust ozone concentration controller.

According to the ninth aspect, the flock flotation tank is provided in the front part of the multi-stage ozone contact tank, and the output pipe of the water supply pump for inflowing the water to be treated is inserted and arranged in the flock flotation tank vertically. A pressurized downward injection type multi-stage ozone contact tank which is connected to the lower injection pipe, and is provided with an injection port for a flocculant in the middle of the output pipe so that soluble organic molecules are aggregated and floated and separated as flocs. Provide configuration.

A third stage is provided at the front of the flock flotation tank.
And a rapid reduction valve for adjusting the pressure in the pipe is provided in the middle of the output pipe of the pressurized vortex pump, and the other end of the output pipe is connected to the output pipe of the water supply pump. By injecting water containing fine bubbles of air or ozone gas into the water to be treated, simultaneously injecting the coagulant from the coagulant inlet and flowing it into the floc flotation / separation tank as a multiphase flow to generate microfloc, and float It is configured as a multi-stage ozone contact tank for separation.

According to the pressure-type downward injection type ozone contact tank according to the first aspect and the control method according to the second aspect, the water to be ozone-treated is supplied from the water supply pump via the branch pipe to the first water supply. The ozone gas and the water to be treated, which have been fed into the pressure vortex pump and injected through the ozone injection pipe, are mixed and finely bubbled by the first pressure vortex pump to become high-concentration dissolved ozone water, and the pressure is reduced by the rapid reduction valve. Merges with the water to be treated flowing through the output pipe while being pumped through the adjusted output pipe, and the ozone gas and the water to be treated fall in the lower injection pipe while gas-liquid contacting the lower injection pipe to form a turbulent flow state. And the efficiency of contact with the water to be treated is increased. The water to be treated that has flowed into the first tank flows upward and flows into the second tank.

In parallel with this operation, the water to be treated in the branch pipe is also fed to the second pressurized vortex pump, and the injected ozone gas and the water to be treated become high-concentration dissolved ozone water in the same manner as described above. While being pressure-fed in the output pipe, the pressure of which is adjusted by the pressure reducing valve, the gas and liquid descend and come into contact with the inside of the lower injection pipe arranged in the second tank of the multistage ozone contact tank.
The water to be treated that has flowed into the second tank becomes an upward flow and flows into the retention tank.

The injection ozone concentration controller issues a control signal to the ozone generator based on the injection ozone concentration target value and the generated ozone concentration to control the driving state of the ozone generator, and the ozone gas generated from the ozone generator is It is fed to the first and second pressurized vortex pumps, and the ozone injection rate constant control is performed. Hereinafter, constant control of exhausted ozone concentration, constant control of dissolved ozone concentration, and constant control of ultraviolet light absorbance are similarly performed.

Further, by disposing a flock flotation / separation tank, a third pressurized vortex pump and a rapid reduction valve in the front part of the multistage ozone contact tank, water containing fine bubbles generated by the action of the pressurized vortex pump is provided. Is injected into the water to be treated, and the air of the fine bubbles and the coagulant are mixed by the injection of the coagulant from the injection port, and flows into the floc flotation tank as a multiphase flow, and the microfloc in the growth period is generated. It flows into the flock flotation tank and is separated by flotation. By using ozone gas instead of air, the floc generation effect is significantly improved.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Various embodiments of a pressurized downward injection type multistage ozone contact tank and a control method thereof according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view of a first embodiment showing a basic configuration of a pressurized down-injection type multistage ozone contact tank corresponding to a real scale used in the present invention, in which 11 is a multistage ozone contact tank. The multi-stage ozone contact tank 11 includes a plurality of stages including a first tank 11a, a second tank 11b, and a retention tank 11c. Reference numeral 13 denotes an exhaust pipe for exhaust ozone gas. Therefore, the basic configuration of the multi-stage ozone contact tank 11 is a vertical counterflow type.

Reference numeral 15 denotes an inflow pipe for the water to be treated 20 fed into the multi-stage ozone contact tank 11. The inflow pipe 15 is connected to a water feed pump 16 and is connected to a branch connected to a middle portion of the inflow pipe 15. The pipe 15a is the first pressurized vortex pump 1
7 is connected. An ozone injection pipe 18 for feeding ozone gas from an ozone generator (not shown) into the water 20 to be treated is connected to a stage preceding the first pressurized vortex pump 17. The pressurized vortex pump 17 has three functions of “mixing / fine-bubbling / pressurizing” the ozone gas and the water 20 to be treated.

Output tube 1 of first pressurized vortex pump 17
A rapid-reduction valve 19 for adjusting the pressure in the output pipe 17a is provided in the middle of the pipe 7a. The valve 19
Is constituted by an orifice having a shape in which the diameter of the output tube 17a is partially reduced to a small diameter.

The other end of the output pipe 17a is connected to the water pump 1
6 is connected to an output pipe 16a, which is connected to a lower injection pipe 21 inserted vertically in the first tank 11a of the multi-stage ozone contact tank 11. The opening at the distal end of the lower injection pipe 21 is introduced to a position near the bottom wall of the first tank 11a.

On the other hand, the branch pipe 15a of the inflow pipe 15 for the water to be treated 20 is also connected to a second pressurized vortex pump 22. An ozone injection pipe 23 for feeding ozone gas into the water to be treated 20 is connected. A rapid contraction valve 24 for adjusting the pressure inside the output pipe 22a of the second pressurized vortex pump 22 is provided in the middle of the output pipe 22a. It is connected to the lower injection pipe 25 inserted and arranged in the vertical direction in the two tanks 11b. The opening at the distal end of the lower injection pipe 25 is introduced to a position near the bottom wall of the second tank 11b.

The operation and principle of operation of the pressure-type, downward-injection, multistage ozone contact tank 11 according to the first embodiment, which is applicable to a real scale, will be described below. First, as a basic operation, the water 20 to be ozone-treated is sent to the water supply pump 16, and at the same time, is sent from the branch pipe 15 a to the first pressurized vortex pump 17 and injected through the ozone injection pipe 18. The ozone gas and the water to be treated 20 are mixed and finely bubbled by the impeller portion of the first pressurized vortex pump 17 to become high-concentration dissolved ozone water, and the inside of the output pipe 17 a whose pressure is adjusted by the rapid reduction valve 19 is controlled. The water to be treated 20 flowing through the output pipe 16a of the water supply pump 16 while being pressure-fed merges with the water to be treated, and the ozone gas of the microbubbles and the water to be treated 20 descend in the lower injection pipe 21 while gas-liquid contacting the inside of the lower injection pipe 21 to cause the first tank It hits the bottom wall of 11a and becomes turbulent. Thereby, the contact efficiency between the ozone gas and the water to be treated 20 is increased.

By setting the flow rate of the output pipe 16a of the water supply pump 16 to 2 (m / sec) or less, the effect of staying in the pipe (abbreviated as hold-up) is generated, and the action of dissolving ozone gas is enhanced. In addition, the water 20 to be treated that has flowed into the first tank 11a flows upward and flows into the second tank 11b.

In parallel with the above operation, the water 20 to be treated in the branch pipe 15a is sent to a second pressurized vortex pump 22,
The ozone gas injected through the ozone injection pipe 23 and the water 20 to be treated are mixed and finely bubbled by the impeller of the second pressurized vortex pump 22 in the same manner as described above to become a high-concentration dissolved ozone water, The multi-stage ozone contact tank 1 is pressure-fed in the output pipe 22a whose pressure is adjusted by the valve 24.
The gas and liquid descend while contacting the inside of the lower injection pipe 25 arranged in the first second tank 11b, and hit the bottom wall to be in a turbulent state. The to-be-processed water 20 that has flowed into the second tank 11b becomes an upward flow and overflows into the retention tank 11c.

The water to be treated 20 mixed with the ozone gas flows upward from below the first tank 11a, the second tank 11b, and the retaining tank 11c constituting the multi-stage ozone contact tank 11, and flows at a predetermined rate. Ozonated water 1 after the residence time
It flows out as 0 and is temporarily stored in an ozonated water tank (not shown) to prepare for the next step. The unreacted ozone gas is sent from the exhaust pipe 13 to an exhaust ozone treatment device (not shown), and is decomposed into harmless gas by well-known thermal decomposition, decomposition using a catalyst, soil decomposition, chemical liquid cleaning treatment, or activated carbon treatment, and is discharged into the atmosphere. Will be released. That is, since ozone gas has a strong oxidizing power next to fluorine and is a harmful substance to the human body, it is indispensable to decompose the ozone gas with an exhaust ozone treatment device.

By the contact between the ozone gas and the water 20 to be treated, deodorization, decolorization, oxidative removal of iron manganese, polycyclic compounds and organic substances, sterilization, algicidal action and removal of off-flavor are performed.

In the above operation, the ratio of the flow rate of the water to be treated / the flow rate of the ozone gas (abbreviated as L / G ratio) by driving the first and second pressurized vortex pumps 17 and 22 is 5 or more, and the pressure in the pipe is It is necessary to be 1.5 (kgf / cm ² ) or more. That is, FIG. 2 is a graph showing the relationship between the dissolved ozone concentration (mg / l) and the residence time (min) when the pipe pressure P is changed, and FIG. 3 is a graph showing the dissolved ozone concentration when the L / G ratio is changed. It is a graph which shows the relationship between ozone concentration and residence time. Note that η shown in the figure is the ozone absorption efficiency (%).

As shown in FIG. 2, when the ozone injection rate is constant, the dissolved ozone concentration increases as the pipe pressure P increases, and as shown in FIG. 3, the dissolved ozone concentration increases as the L / G ratio decreases. Therefore, it can be seen that a high concentration of dissolved ozone water can be obtained under high pressure. From the viewpoint of energy cost, it is appropriate to set the pressure in the pipe to 4.0 (kgf / cm ² ) at the maximum.

Further, the amount of water to be treated 20 and the first and second
(Lm / Lk)
(Abbreviated as) depends on the maximum dissolved ozone concentration target value in the multi-stage ozone contact tank 11, but the maximum dissolved ozone concentration is 0.5.
(Mg / l), it is appropriate to set Lm / Lk in the range of 15 to 30. Therefore, the injection rate of the pressurized vortex pumps 17 and 22 is set so that the ozone absorption efficiency η is 95
%, It is about 8 to 16 (mg / l).

Next, a control example 1 in this embodiment will be described with reference to FIG. Since the basic configuration of the device itself is the same as that of the first embodiment shown in FIG. 1, it is denoted by the same reference numerals in the figure.

In the control example 1, the pressure of the first and second pressurized vortex pumps 17 and 22 is kept constant, and the control for changing the ozone injection rate is performed. In the figure, 27 is a treated water amount controller, 28 is an ozone injection rate controller, 29 is an injected ozone concentration controller, 30 is an exhaust ozone concentration meter,
1 is an ozone generator, 32 is a generated ozone concentration meter, 33 is a waste ozone decomposing device, 34 and 35 are pressure gauges, 36, 37, and
38, 39, 40, 41 are flow meters, 42 is a blower, 43
Is a dissolved ozone concentration meter.

According to the first control example, as described above, the water to be treated 20 is supplied to the first and second pressurized vortex pumps 17 and 2.
Since the flow is branched into two, the sum of the flow rates of the two pressurized vortex pumps 17 and 22 and the flow rate of the water supply pump 16 coincides with the overall processing amount. Also, the first and second pressurized vortex pumps 17,
The rotation speed of the pump 22 is not changed and is constant, and the flow rate of the ozone gas to both the pressurized vortex pumps 17 and 22 is not changed as a fixed amount. Therefore, the L / G ratio of the two pressurized vortex pumps 17 and 22 is also constant, and only the injected ozone gas concentration is variably controlled.

More specifically, a treated water amount set value 44 and a flow rate signal of the treated water 20 measured by the flow meter 38 are input to the treated water amount controller 27, and the treated water amount output from the treated water amount controller 27. The target value 45 is input to the water pump 16. Further, the flow rate signal of the water to be treated 20 measured by the flow meter 38 is input to the ozone injection rate controller 28, and the ozone injection rate controller 28 calculates the injected ozone concentration from the ozone injection rate set value 46 and the flow rate signal of the water to be treated. The target value 47 is obtained and output to the injected ozone concentration controller 29.

The injected ozone concentration controller 29 issues a control signal 48 for the ozone generator 31 based on the injected ozone concentration target value 47 and the generated ozone concentration obtained from the generated ozone densitometer 32 to drive the ozone generator 31 in the driving state. Is controlled. The normal control signal 48 is input to the ozone generator 31 as a power value,
Ozone gas generated from 1 is sent to first and second pressurized vortex pumps 17 and 22 via ozone injection pipes 18 and 23. The amount of ozone gas generated from the ozone generator 31 is measured by the flow meter 40 and fed back to the generated ozone concentration meter. Further, the dissolved ozone concentration after the ozone treatment is measured and monitored by the dissolved ozone concentration meter 43 provided in the retention tank 11c. Therefore, the control example 1 is based on the constant ozone injection rate control.

The exhausted ozone gas discharged from the exhausted ozone gas discharge pipe 13 is guided to the exhausted ozone concentration meter 30 via the flow meter 39 to measure the exhausted ozone concentration, and the exhausted ozone gas is decomposed by driving the blower 42. It is sent to the device 33 and decomposed.

This control example 1 is controlled by a flow rate of the water to be treated, an ozone injection rate and an ozone concentration controller.
It is characterized in that the ozone injection rate is variably controlled by detecting a change in water supply amount or a change in setting based on a signal from the flow meter 38, and performing a comparison calculation process with a set value. Assuming that the ozone injection rate is D, D = aX ± b (1) Here, a is a set coefficient, and b is a correction coefficient.

Next, referring to FIG. 5, a control example 2 in this embodiment will be described.
Will be described. In the control example 2, a waste ozone concentration controller 50 is used instead of the ozone injection rate controller 28 in the control example 1, and the treated water amount controller 27 is used.
Is not installed. Other configurations are the same as in the control example 1.

In the control example 2, the exhaust ozone concentration is basically constant, and the exhaust ozone gas discharged from the exhaust ozone gas discharge pipe 13 is guided to the exhaust ozone concentration meter 30 via the flow meter 39 to measure the exhaust ozone concentration. The exhaust ozone concentration signal 51 is input to the exhaust ozone concentration controller 50. The exhaust ozone concentration controller 50 has an exhaust ozone concentration set value 52.
From the ozone concentration signal 51 and the ozone concentration target value 4
7 is output to the injected ozone concentration controller 29. The injected ozone concentration controller 29 issues a control signal 48 to the ozone generator 31 based on the injected ozone concentration target value 47 and the generated ozone concentration obtained from the generated ozone concentration meter 32, and the driving state of the ozone generator 31 is controlled. . Other control modes correspond to the control example 1.

Next, a control example 3 in this embodiment will be described. Although the control example 3 is not shown, it is characterized in that a dissolved ozone concentration controller is used in place of the exhaust ozone concentration controller 50 in the control example 2. Other configurations are the same as those of the control example 2.

In the control example 3, the dissolved ozone concentration is basically constant, and the dissolved ozone concentration after the ozone treatment is measured by the dissolved ozone concentration meter 43 provided in the retention tank 11c. Will be fed back. The dissolved ozone concentration controller obtains the injection ozone concentration target value from the preset dissolved ozone concentration set value and the measured dissolved ozone concentration signal and outputs the target value to the injection ozone concentration controller. A driving signal of the ozone generator 31 is controlled by issuing a control signal 48 to the ozone generator 31 based on the generated ozone concentration obtained from the ozone generator 32.

Next, a control example 4 in this embodiment will be described. Although not shown in the control example 4, the control example 3 is omitted.
Is characterized in that a UV value controller is used instead of the dissolved ozone concentration controller and a low concentration UV meter is provided instead of the dissolved ozone concentration meter 43 provided in the retention tank 11c. Other configurations are the same as those of the control example 3.

In the control example 4, the UV value (ultraviolet absorbance) is basically constant, and the UV value after the ozone treatment is measured by the UV meter provided in the retention tank 11c, and this UV value is fed back to the UV value controller. You. The UV value controller obtains the injection ozone concentration target value from the preset UV setting value and the measured UV value signal and outputs the target value to the injection ozone concentration controller, which is obtained from the generated ozone concentration meter 32 as in the control example 2. The control signal 48 for the ozone generator 31 is issued based on the generated ozone concentration, and the driving state of the ozone generator 31 is controlled.

Next, FIG. 6 shows a control example 5 in this embodiment.
Will be described. 50 in the figure is an exhaust ozone concentration controller,
53 is a pressure gauge provided between the second pressurized vortex pump 22 and the rapid-contraction valve 24, 54 is a rapid-contraction valve opening controller,
The arrangement of the pressure gauge 53 and the rapid-decrease valve opening degree controller 54 is a feature of the configuration of the control example 5.

According to the control example 5, the discharged ozone gas discharged from the discharged ozone gas discharge pipe 13 is guided to the discharged ozone concentration meter 30 via the flow meter 39 to measure the discharged ozone concentration at the same time as the pressure. The pressure between the second pressurized vortex pump 22 and the rapid reduction valve 24 is measured by the meter 53, and each measured value is input to the determination means 100. When the pressure value P is within a predetermined range, for example, 2 (kgf / cm ² ) <P <4 (kg
f / cm ² ) (YES), the rapid output valve 24 is controlled by the control output of the rapid valve opening controller 54.
When the exhausted ozone concentration measured by the exhausted ozone concentration meter 30 is high, the opening degree of the rapid contraction valve 24 is decreased to increase the pressure P, while when the exhausted ozone concentration is low, the rapid contraction valve is increased. The pressure P is decreased by increasing the opening degree of the valve 24.

If the measured value of the pressure gauge 53 is out of the predetermined range (No), the exhaust ozone concentration controller 5
0 is a target value 47 of the injected ozone concentration obtained from the set value 52 of the exhausted ozone concentration and a signal from the determination means 100 and output to the injected ozone concentration controller 29. The injected ozone concentration controller 29 sets the target value 47 of the injected ozone concentration and the generated ozone concentration. Based on the generated ozone concentration obtained from the total 32, a control signal 48 for the ozone generator 31 is issued to control the driving state of the ozone generator 31.

In the control example 5, the state of pressurization between the second pressurizing vortex pump 22 and the rapid compression valve 24 is measured by the pressure gauge 53 simultaneously with the measurement of the exhausted ozone concentration, and the variable control of the rapid compression valve 24 is performed. It is characterized by doing.

Next, a control example 6 in this embodiment will be described. In the case of the control example 6, although not shown, a feature is that a dissolved ozone concentration controller is provided in place of the exhaust ozone concentration controller 50 of the control example 5. Other configurations are substantially the same as those of the control example 5.

According to the control example 6, in consideration of the fact that the dissolved ozone concentration also changes with the change in pressure, the measured value of the dissolved ozone concentration meter 43 installed in the storage tank 11c is measured at the same time as the measured value. The pressure between the second pressurized vortex pump 22 and the rapid reduction valve 24 is measured by the pressure gauge 53, and each measured value is input to the determination means 100. As in the control example 5, the pressure value P falls within a predetermined range. For example, 2 (kgf / cm ² ) <
When P <4 (kgf / cm ² ) (YE
In S), the rapid-contraction valve 24 is made variable by the control output of the rapid-contraction valve opening degree controller 54. When the dissolved ozone concentration measured by the dissolved ozone concentration meter 43 is high, the rapid constriction valve 24
The pressure P is decreased by increasing the opening of the valve, while the pressure P is increased by decreasing the opening of the rapid contraction valve 24 when the dissolved ozone concentration is low. When the measured value of the pressure gauge 53 is out of the predetermined range (No), the dissolved ozone concentration controller obtains the injected ozone concentration target value 47 from the dissolved ozone concentration set value and the signal from the determination means 100. A control signal 48 for the ozone generator 31 is output to the injected ozone concentration controller 29 based on the injected ozone concentration target value 47 and the generated ozone concentration obtained from the generated ozone concentration meter 32.
And the driving state of the ozone generator 31 is controlled.

FIG. 7 is a graph showing the correlation between the residence time when the pressure is varied and the residual ratio (Co / Ci) of E260 (ultraviolet absorbance at a wavelength of 260 nm), which is an index of an organic substance. As a result, the removal rate of organic substances also changes in proportion. The following control example 7 was realized using this characteristic.

In the case of this control example 7, although not shown, the dissolved ozone concentration controller of control example 6 is replaced with U
It is characterized in that a V value controller is provided, and a low concentration UV meter is provided in place of the dissolved ozone concentration meter 43 also in the retention tank 11c. Other configurations are the same as those of the control examples 5 and 6.

According to the control example 7, the E260 absorbance is measured by the UV meter installed in the retention tank 11c, and at the same time, the second pressurized vortex pump 2 is measured by the pressure gauge 53.
The pressure between the valve 2 and the squeeze valve 24 is measured, and each measured value is input to the determination means 100. This pressure value P is within a predetermined range,
For example, 2 (kgf / cm ² ) <P <4 (kgf / cm ² )
(YES), the rapid reduction valve 24 is made variable by the control output of the rapid reduction valve opening degree controller 54,
When the E260 absorbance measured by the UV meter is high, the opening degree of the rapid contraction valve 24 is increased to decrease the pressure P, while when the E260 absorbance is low, the opening degree of the rapid contraction valve 24 is decreased to reduce the pressure. Increase P. If the measured value of the pressure gauge 53 is out of the predetermined range (No), the UV value controller obtains the injection ozone concentration target value from the UV set value and the signal from the determination means 100, and obtains the control example 6 described above. In the same manner as described above, a control signal 48 for the ozone generator 31 is issued based on the injected ozone concentration target value 47 and the generated ozone concentration obtained from the generated ozone concentration meter 32, and The driving state is controlled.

FIG. 8 is a schematic view of a second embodiment of a pressurized, downward-injection, multistage ozone contact tank applicable to a real scale used in the present invention, and has the same configuration as that of the first embodiment shown in FIG. The parts are indicated by the same reference numerals.

In the second embodiment, a floc flotation tank 60 for the purpose of agglomeration and separation is provided at the front stage of the multistage ozone contact tank 11 disclosed in the first embodiment. Reference numeral 61 denotes a water supply pump for flowing the water to be treated 20 into the floc flotation / separation tank 60, and an output pipe 6 of the water supply pump 61.
1a is connected to a lower injection pipe 65 inserted and arranged in the flock flotation tank 60 in the vertical direction. The output tube 61a
An injection port 64 for a coagulant is provided in the middle of the section.

Reference numeral 62 denotes a third pressurized vortex pump, and 63 denotes a third
The pressure reducing valve is provided in the middle of the output pipe 62 a of the pressurized vortex pump 62 for adjusting the pressure in the pipe. The other end of the output pipe 62 a is connected to the output pipe 61 a of the water supply pump 61.

An injection pipe 66 for feeding air or ozone gas into water is connected to a stage preceding the third pressurized vortex pump 62. The third pressurized vortex pump 62 is connected to a pipe 67 drawn from the retention tank 11c of the ozone multi-stage contact tank 11, so that once treated ozone-treated water is re-used for mixing ozone gas and water. It is used. or,
The piping 68 led out of the retention tank 11c is also connected to the first and second pressurized vortex pumps 17 and 22.

In the vicinity of the water surface of the flock flotation / separation tank 60, a rotary scraper 70 and a scraper 71 are provided. An air outlet 73 is opened.

The structure of the multi-stage ozone contact tank 11, the first and second pressurized vortex pumps 17, 22 and the rapid reduction valves 19, 24
Is basically the same as that of the first embodiment, and the description will not be repeated.

The operation of the pressurized downward injection type multistage ozone contact tank 11 of the second embodiment during operation will be described below. First, when air is used as the gas to be injected into the injection pipe 66, the third
The water containing fine bubbles generated by the action of the pressurized vortex pump 62 and the rapid contraction valve 63 is output from the output pipe 61 a of the water supply pump 61.
Is injected into the water to be treated 20 flowing through
By injecting the coagulant from the inlet 64 opened in the middle of 1a, the air of the fine bubbles and the coagulant are mixed in the output pipe 61a and flow into the floc flotation tank 60 as a multiphase flow.

Then, microflocs in the growth period are generated in the water 20 to be treated by the air of the fine bubbles and the coagulant, and flow into the flock floatation / separation tank 60 from the lower injection pipe 65 inserted and arranged in the vertical direction. At this time, fine air bubbles adhere to the flocs of several tens of microns, and act to reduce the apparent density of the micro flocs.

The micro flocs to which the fine bubbles adhere are floated in the floc flotation / separation tank 60, are scraped by a rotary scraper 70 provided near the water surface, and are scraped by the scraper 71 to remove the system. It is discharged outside.

The water to be treated, from which flocs have been removed in the floc flotation / separation tank 60, is sent to the first tank 11a of the ozone multistage contact tank 11, and the first and second waters are used as described in the first embodiment. Pressurized vortex pumps 17 and 22 and rapid reduction valve 1
The desired ozone treatment is performed in conjunction with the operations of 9, 24.

Next, a third embodiment of the present invention will be described. In the third embodiment, the injection pipe 66 of the second embodiment shown in FIG.
It is characterized in that ozone gas is used as the gas to be injected into the gas.

The following items can be considered as factors for improving the floc cohesion by the coagulant. That is, (1) reduction of the molecular weight of the organic polymer substance, (2) aggregation and precipitation of soluble organic substance molecules, (3) increase in the polarity of the organic molecules, and (3) further conversion of organic substances into polyelectrolyte and floating. Improvement of the adsorptivity to the substance, increase of the chemical cross-linking function between the viscous colloid and the micro floc by chemical aggregation are mentioned.

The ozone gas and dissolved ozone have an action of oxidizing and reacting with soluble organic matter molecules to reduce the molecular weight, thereby reducing disinfection by-products.

Therefore, in the third embodiment, since the ozone gas is used as the gas to be injected into the injection pipe 66, the injection port 6
Floc coagulability by the coagulant injected from No. 4 is improved, and the ozone contact effect thereafter can be enhanced.

[0077]

As described in detail above, according to the pressurized downward injection type multistage ozone contact tank of the present invention and the control method therefor, the water to be ozone-treated is first discharged after passing through the branch pipe. And is mixed with the injected ozone gas and made into fine bubbles to become a high-concentration dissolved ozone water, which is pressure-fed through the output pipe whose pressure has been adjusted by the rapid-reduction valve and merges with the water to be treated. The contact efficiency can be enhanced by the ozone gas of the fine bubbles and the water to be treated descending while the gas-liquid contacts the lower injection pipe, so that the residence time is equivalent to the residence time of the conventional diffusion tube type ozone contact tank, which is shorter than the residence time Can be obtained.

Further, in parallel with the above operation, the water to be treated in the branch pipe is also sent to the second pressurized vortex pump, and the injected ozone gas and the water to be treated become high-concentration dissolved ozone water in the same manner as described above. While being pressure-fed in the output pipe whose pressure has been adjusted by the squeeze valve, it is fed into the second tank of the multi-stage ozone contact tank to increase ozone treatment efficiency.

The driving state of the ozone generator is controlled by the injected ozone concentration controller based on the target value of the injected ozone concentration and the generated ozone concentration, and the generated ozone gas is supplied to the first and second pressurized vortex pumps. It is possible to perform injection rate constant control, exhaust ozone concentration constant control, dissolved ozone concentration constant control, and ultraviolet absorbance constant control. At the beginning of the ozone reaction, the diffusion efficiency is sufficiently increased based on the downward injection method. The removal of highly reactive substances is performed, thereby promoting the reaction process in the initial stage in which the diffusion of ozone gas is rate-determined, and the removal of less reactive substances even in a short residence time in the late stage of the ozone reaction, The effect is obtained that the reaction in the latter stage in which the ozone reaction is rate-determined is promoted.

Further, by disposing a floc flotation / separation tank, a third pressurized vortex pump and a rapid reduction valve in the front part of the multistage ozone contact tank, fine bubbles can be formed by the action of the pressurized vortex pump and the action of injecting the flocculant. Air and coagulant mix and flow into the flock flotation tank, allowing microfloc in the growing season to flotate in the flock flotation tank,
In particular, the use of ozone gas instead of air can significantly enhance the floc generation effect.

In the case of the conventional deep U-tube type ozone contact tank, the processing characteristics vary when the flow rate varies, whereas the control example of the present embodiment provides stable processing characteristics. In particular, it becomes possible to control the ozone injection rate optimally in response to fluctuations in the amount of water. Further, by performing the constant control of the exhausted ozone concentration, the constant control of the dissolved ozone concentration, and the constant control of the ultraviolet absorbance, the effect of shortening the time required to reach the target water quality as compared with the diffuser system can be obtained.

The multi-stage ozone contact tank according to the present embodiment does not need to be formed to have a length of 20 to 30 meters unlike the conventional U-tube reaction tank, so that the water to be treated can be treated without increasing the size of the apparatus. Ozone gas absorption efficiency can be increased. Further, it is possible to prevent a phenomenon of a decrease in absorption efficiency over time due to clogging or the like due to adhesion of iron or manganese oxidized by ozone gas.

Further, there is no problem that the construction work of the facility is complicated as in the case of the U tube type ozone reaction tank, the construction cost can be reduced, and the sediment stored in the reaction tank can be removed or the inside of the tank can be removed. Cleaning can be easily performed, and even if a failure occurs near the bottom of the reaction tank, it is possible to immediately take measures.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing the entire first embodiment of a pressurized downward injection multistage ozone contact tank according to the present invention.

FIG. 2 is a graph showing the relationship between the dissolved ozone concentration and the residence time when the pressure in the pipe is changed.

FIG. 3 is a graph showing the relationship between dissolved ozone concentration and residence time when the L / G ratio is changed.

FIG. 4 is a schematic diagram for explaining a control example 1 in the embodiment.

FIG. 5 is a schematic diagram for explaining a control example 2 in the embodiment.

FIG. 6 is a schematic diagram for explaining a control example 5 in the embodiment.

FIG. 7 is a graph showing the correlation between the residence time and the E260 residual ratio when the pressure is changed.

FIG. 8 is a schematic diagram showing an entirety of a second embodiment of a pressurized downward injection type multistage ozone contact tank according to the present invention.

FIG. 9 is a sectional view of a main part showing an example of a normal diffuser ozone reaction tank.

FIG. 10 is a schematic view showing the structure of a normal U-tube type ozone contact tank.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Multi-stage ozone contact tank 11a ... 1st tank 11b ... 2nd tank 13 ... Discharge pipe (of waste ozone gas) 15 ... Inflow pipe (water to be treated) 16, 61 ... Water supply pump 17 ... 1st pressurized vortex pump 18, 23 ozone injection pipes 19, 24, 63 ... rapid reduction valve 20 ... water to be treated 21, 25, 65 ... lower injection pipe 22 ... second pressurized vortex pump 27 ... treated water amount controller 28 ... ozone injection rate controller 29 ... Injection ozone concentration controller 30 ... Exhaust ozone concentration meter 31 ... Ozone generator 32 ... Emission ozone concentration meter 33 ... Exhaust ozone decomposer 34,35.53 ... Pressure gauge 43 ... Dissolved ozone concentration meter 50 ... Exhaust ozone concentration controller 54 ... Rapid opening valve controller 60... Flock floating separation tank 62. Third pressurized vortex pump 70.

Claims (10)

[Claims] 1. A branch pipe is provided in a middle part of an inflow pipe for feeding water to be treated into a multistage ozone contact tank of a vertically opposed flow type, and a gas-liquid mixture of the water to be treated and ozone gas is provided in the branch pipe. A pressurizing vortex pump and a rapid-contraction valve for adjusting the pressure in the output pipe of the first pressurizing vortex pump are provided, and the output pipe is connected to the multistage ozone contact tank through a water supply pipe for the water to be treated. While connected to the lower injection pipe inserted and arranged vertically in one tank,
In the branch pipe, a second pressurized vortex pump for gas-liquid mixing of the water to be treated and the ozone gas and a rapid reduction valve for adjusting a pressure in an output pipe of the second pressurized vortex pump are provided. A pressurized downward injection type multistage ozone contact tank characterized in that the output pipe is connected to a lower injection pipe vertically inserted and arranged in a second tank of the multistage ozone contact tank. 2. A branch pipe is provided in a middle part of an inflow pipe for feeding water to be treated into a multistage ozone contact tank of a vertically opposed flow type, and a gas-liquid mixture of the water to be treated and ozone gas is provided in the branch pipe. A pressurizing vortex pump and a rapid-contraction valve for adjusting the pressure in the output pipe of the first pressurizing vortex pump are provided, and the output pipe is connected to the multistage ozone contact tank through a water supply pipe for the water to be treated. While connected to the lower injection pipe inserted and arranged vertically in one tank,
In the branch pipe, a second pressurized vortex pump for gas-liquid mixing of the water to be treated and the ozone gas and a rapid reduction valve for adjusting a pressure in an output pipe of the second pressurized vortex pump are provided. In a pressurized downward injection type multi-stage ozone contact tank in which the output pipe is connected to a lower injection pipe vertically inserted and disposed in a second tank of the multi-stage ozone contact tank, a treated water amount controller is provided in an inflow pipe of the water to be treated. At the same time, an ozone injection rate controller, an injection ozone concentration controller, and a generated ozone concentration meter are provided in the ozone generator, and the target value of the treated water amount is obtained from the set value of the treated water amount input to the treated water amount controller and the flow rate signal of the treated water. The ozone injection rate controller determines an injection ozone concentration target value from the flow rate signal of the water to be treated and the ozone injection rate set value, and outputs the target value to the injection ozone concentration controller. The ozone concentration controller outputs a signal for controlling the driving state of the ozone generator based on the above-mentioned injected ozone concentration target value and the generated ozone concentration, and supplies ozone gas to the first and second pressurized vortex pumps. A method for controlling a pressurized downward injection type multi-stage ozone contact tank, wherein constant injection rate control is performed. 3. A first branch, in which a branch pipe is provided in the middle of an inflow pipe for feeding water to be treated into a multistage ozone contact tank of a vertically opposed flow type, and the water to be treated and ozone gas are mixed in a gas-liquid manner in the branch pipe. A pressurizing vortex pump and a rapid-contraction valve for adjusting the pressure in the output pipe of the first pressurizing vortex pump are provided, and the output pipe is connected to the multistage ozone contact tank through a water supply pipe for the water to be treated. While connected to the lower injection pipe inserted and arranged vertically in one tank,
In the branch pipe, a second pressurized vortex pump for gas-liquid mixing of the water to be treated and the ozone gas and a rapid reduction valve for adjusting a pressure in an output pipe of the second pressurized vortex pump are provided. In a pressurized downward injection type multi-stage ozone contact tank in which the output pipe is connected to a lower injection pipe vertically inserted and disposed in a second tank of the multi-stage ozone contact tank, the ozone generator includes a discharged ozone concentration controller and an injected ozone concentration. A controller and a generated ozone concentration meter are provided, and an exhausted ozone concentration meter is provided in the multi-stage ozone contact tank. The exhausted ozone concentration of the exhausted ozone gas discharged from the contact tank is measured, and the measured ozone concentration is input to the exhausted ozone concentration controller. The ozone concentration controller obtains the injection ozone concentration target value from the exhaust ozone concentration set value and the exhaust ozone concentration signal and outputs the target value to the injection ozone concentration. A signal for controlling the driving state of the ozone generator is output based on the target ozone concentration and the generated ozone concentration, and the ozone gas is supplied to the first and second pressurized vortex pumps, thereby performing the constant control of the exhausted ozone concentration. A method for controlling a pressurized downward injection type multistage ozone contact tank characterized by the above-mentioned. 4. A constant dissolved ozone concentration control is performed by using a dissolved ozone concentration controller in place of the exhaust ozone concentration controller and disposing a dissolved ozone concentration meter in a multi-stage ozone contact tank. 4. The method for controlling a pressurized downward injection type multistage ozone contact tank according to item 3 or 3. 5. A constant UV absorbance control is performed by using a UV value controller instead of the exhaust ozone concentration controller and providing a low concentration UV meter in the multi-stage ozone contact tank. A method for controlling a pressurized downward injection type multistage ozone contact tank according to the above. 6. A branch pipe is provided in a middle part of an inflow pipe for feeding water to be treated into a vertically opposed multi-stage ozone contact tank, and a gas-liquid mixture of the water to be treated and ozone gas is provided in the branch pipe. A pressurizing vortex pump and a rapid-contraction valve for adjusting the pressure in the output pipe of the first pressurizing vortex pump are provided, and the output pipe is connected to the multistage ozone contact tank through a water supply pipe for the water to be treated. While connected to the lower injection pipe inserted and arranged vertically in one tank,
In the branch pipe, a second pressurized vortex pump for gas-liquid mixing of the water to be treated and the ozone gas and a rapid reduction valve for adjusting a pressure in an output pipe of the second pressurized vortex pump are provided. In a pressurized downward injection type multistage ozone contact tank in which the output pipe is connected to a lower injection pipe vertically inserted and disposed in a second tank of the multistage ozone contact tank, the ozone generator is filled with an ozone concentration controller and an ozone concentration generated. A multi-stage ozone contact tank is provided with an exhaust ozone concentration controller and an exhaust ozone concentration meter, and a pressure gauge and a rapid opening valve controller are provided between the second pressurized vortex pump and the rapid reduction valve. The pressure between the second pressurized vortex pump and the rapid compression valve is measured by a pressure gauge at the same time as measuring the exhausted ozone concentration of the exhausted ozone gas discharged from the contact tank, and the pressure value is within a predetermined range. In case, rapid opening of valve After the valve is made variable by the control output of the controller, if the exhausted ozone concentration is high, the opening of the valve is reduced to increase the pressure, while if the exhausted ozone concentration is low, the valve is opened. A method for controlling a pressurized downward injection type multi-stage ozone contact tank, wherein control is performed to increase pressure and decrease pressure. 7. A dissolved ozone concentration controller is used in place of the exhaust ozone concentration controller, and a dissolved ozone concentration meter is provided in the multi-stage ozone contact tank. The pressure between the pressurized vortex pump and the rapid-reduction valve is measured. If the pressure value is within a predetermined range, the rapid-reduction valve is made variable by the control output of the rapid-reduction valve opening controller, and then the dissolved ozone concentration is measured. If the pressure is high, the opening of the rapid-contraction valve is increased to reduce the pressure, while if the dissolved ozone concentration is low, the control is performed to decrease the opening of the rapid-contraction valve and increase the pressure. The method for controlling a pressurized downward injection type multistage ozone contact tank according to claim 6. 8. A multi-stage ozone contact tank provided with a low-concentration UV meter using a UV concentration controller instead of the exhaust ozone concentration controller, and simultaneously measuring the UV value of the contact tank with a second pressure meter using a pressure gauge. The pressure between the pressure vortex pump and the squeeze valve is measured, and when the pressure value is within a predetermined range, the squeeze valve is made variable by the control output of the squeeze valve opening controller, and then measured by the UV meter. When the E260 absorbance is high, the control is performed to increase the pressure by increasing the opening of the rapid-contraction valve to decrease the pressure while the E260 absorbance is low. The control method for a pressurized downward injection type multistage ozone contact tank according to claim 6 or 7, wherein 9. A flock flotation / separation tank is provided in the front part of the multi-stage ozone contact tank, and an output pipe of a water supply pump for inflowing water to be treated is vertically inserted into the flock flotation / separation tank. A pressurized downward injection type multistage ozone contact, characterized in that a coagulant injection port is provided in the middle of the output tube, and a soluble organic molecule is aggregated and floated and separated as a floc. Tank. 10. A third pressurized vortex pump is provided in a front part of the flock floatation / separation tank, and a rapid reduction valve for adjusting pressure in the pipe is provided in a middle part of an output pipe of the pressurized vortex pump. By connecting the other end of the output pipe to the output pipe of the water pump, water containing fine bubbles of air or ozone gas is injected into the water to be treated, and at the same time, the coagulant is injected from the coagulant injection port to achieve multiphase flow. The pressurized downward injection type multi-stage ozone contact tank according to claim 9, wherein microfloc is generated by flowing into a flock flotation tank and separated by flotation.