JPH09192680A - Treatment of water with ozone and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately control an ozone pour by calculating an ozone consumption by injecting ozone to a part of a treated water and deciding the ozone injection amount from a flow rate of a water to be treated and an ozone absorption efficiency in a water treatment in which the water to be treated is introduced to an ozone contact pond. SOLUTION: A part of the water to be treated is introduced to an ozone contact reaction tank 23, and a gaseous ozone G having a prescribed concn. is injected from an ozonizer 25. An ozone concentration meter 29 is disposed at an outlet side of the ozonizer 25 to measure a concn. of an injected gaseous ozone. A dissolved gaseous ozone concentration meter 35 is disposed at the outlet side of the ozone contact reaction tank 23 to measure a dissolved ozone concn. in a treated water. Moreover, the ozone concn. in a discharged gaseous ozone discharged from the ozone contact reaction tank 23 is measured with the ozone concentration meter 43. Then the ozone consumption of the treated water is calculated from these ozone concentration and a flow rate measured with a flow meter 34. Then a required ozone injection amount is obtained from this absorption efficiency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ozone treatment method and an ozone treatment apparatus which are used in a water purification plant or a sewage treatment plant to remove organic substances such as humic substances which are precursors of trihalomethane generation and odorous substances. Staff,
In particular, the present invention relates to an ozone injection control method and an ozone injection control device suitable for appropriately controlling the amount of ozone injection without excess or deficiency.

[0002]

2. Description of the Related Art In recent years, the off-flavor of tap water and organic chlorine compounds such as trihalomethane contained in tap water have become a problem. The offensive odor has come to be felt as a result of the contamination of water sources such as rivers and lakes by domestic wastewater and the breeding of cyanobacteria. Further, the organic chlorine compound is generated by the reaction of chlorine injected for the purpose of removing ammoniacal nitrogen in the raw water or sterilization with the corrosive substance in the raw water. Since the organic chlorine compound has carcinogenicity, the chlorine injection amount tends to be reduced.

From such a background, so-called advanced water purification treatment, which performs ozone treatment and biological activated carbon treatment, has been attracting attention. Ozone treatment is intended to decompose substances that cause off-flavors due to the strong oxidizing power of ozone, and to reduce decolorization and deodorization as well as generation of organic chlorine compounds. The biological activated carbon treatment is a process in which ammonia nitrogen and the like are decomposed by the action of microorganisms attached to activated carbon, and by-products produced by the reaction between ozone and organic substances are adsorbed and removed or decomposed by microorganisms. Regarding this type of advanced water purification treatment, JP-A-58-174288 and JP-A-2-2
It is disclosed in Japanese Patent No. 33197, Japanese Unexamined Patent Publication No. 4-281893, and the like.

In ozone treatment, the ozone generation efficiency of the ozonizer is very low, and the power consumption rate is about 20 kW.
Since it is very high at h / kg · O ₃ , it is required to minimize the ozone injection amount.

The injection amount of ozone in the ozone treatment changes depending on the water quality. Therefore, originally, the ozone injection amount should be controlled using the odor concentration or the organic substance concentration as a control index, but there is no suitable sensor that can immediately measure the odor concentration or the organic substance concentration. Therefore, ozone injection control is performed using the concentration of exhaust ozone discharged from the ozone contact pond in the gas phase or the concentration of dissolved ozone remaining in the liquid phase as a control index.

[0006]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention As can be seen from the current mainstream, the dissolved ozone concentration constant control for keeping the dissolved ozone concentration constant or the exhaust ozone constant control for keeping the discharged ozone concentration constant has become the mainstream at present. It is effective as it is.
However, each of these ozone injection control methods is nothing but feedback control. If the concentration of organic substances in the water to be treated is rapidly increasing, it is too late because ozone treatment is already proceeding in the ozone contact pond when controlling the ozone injection rate according to the flow rate of the water to be treated. . As a result, the off-flavor of tap water is not completely removed. Further, when the concentration of organic substances in the water to be treated was significantly reduced, it means that ozone was injected more than necessary. This means that ozone, which has a high power consumption rate, was wasted.

[0007] The concentration of organic substances in the water to be treated rapidly increases due to the organic matter flowing from the fields into the river due to heavy rain, and also because the mud deposited on the river bottom during heavy rain is mixed up into the water. To increase.

An object of the present invention is to solve the above problems and provide an ozone treatment method and an ozone treatment apparatus capable of appropriately controlling the ozone injection amount without excess or deficiency even when the organic substance concentration changes rapidly. is there.

[0009]

The present invention provides a method for introducing ozone into a water to be treated by introducing water to be treated into the ozone contact pond.
A part of the water to be treated before being introduced into the ozone contact pond is extracted as sample water, and ozone is injected into this sample water. At this time, the injected ozone amount, the discharged ozone concentration and the dissolved ozone concentration, and the sample water flow rate The ozone consumption of the sample water is calculated from the calculated ozone consumption, and the ozone injection amount to the treated water is determined from the calculated ozone consumption, the flow rate of the treated water introduced into the ozone contact pond, and the ozone absorption efficiency. The ozone treatment is carried out in the ozone contact pond according to the ozone injection amount.

In order to carry out the ozone treatment according to the present invention, a means for extracting a part of the water to be treated flowing into the ozone contact pond into sample water, a means for injecting ozone into the sample water, and an injection at that time Ozone amount, exhaust ozone concentration,
Means for detecting the dissolved ozone concentration and the flow rate of the sample water are provided. Then, the ozone consumption amount of the sample water is calculated from the injected ozone amount into the sample water, the exhaust ozone concentration, the dissolved ozone concentration and the sample water flow rate, and further, the ozone consumption amount of the sample water, the treated water flow rate and the ozone amount. Means are provided for calculating the ozone injection amount into the water to be treated from the absorption efficiency.

The ozone injection amount in the ozone injection amount calculation means is obtained as follows. (1) Calculation of ozone consumption (Oc) of sample treated water Oc = [{G (Cg1-Cg2)} / L] -CW1 (1) where G: flow rate of ozone-containing gas (l / min) Oc: Ozone consumption amount of treated water (mg / l) Cg1: Ozone-containing gas ozone concentration before injection into sample water (mg / l) Cg2: Exhaust ozone concentration discharged to gas phase (mg / l) L: Sample Flow rate of water (l / min) CW1: Dissolved ozone concentration (mg / l) (2) Calculation of liquid phase ozone absorption efficiency Ozone absorption efficiency (η) = {(Cg1-Cg2) / Cg1} × 100 (%) (2) (3) Calculation of ozone injection amount into ozone contact pond Ozone injection amount (Io) = (Oc × Q) / η (3) where Q: treated water flow rate (m ³ / h) The ozone injection rate into the water to be treated is calculated by the following equation (4).

Ozone injection rate = Io / Q (4) When ozone is injected into the ozone contact pond with the ozone injection amount obtained by the equation (3), this ozone injection amount is the minimum necessary ozone injection amount. Therefore, dissolved ozone may not be detected. Even so, there is no problem in ozone treatment, but if the dissolved ozone concentration is not actually detected, it is uncertain whether ozone treatment is actually performed without problems. Therefore, in the actual ozone treatment, the target value of the dissolved ozone concentration is set within a certain range, the set value of the dissolved ozone concentration is added to the ozone consumption amount Oc, and the ozone is calculated by the following equation (5). The injection volume should be determined.

Ozone injection amount = {(Oc + Ko) × Q} / η (5) Here, Ko: set value of dissolved ozone concentration (mg / l) In performing ozone treatment by the method of the present invention, ozone contact is performed. It is recommended to monitor the dissolved ozone concentration from the pond and, if the dissolved ozone concentration is out of the allowable range, increase or decrease the ozone injection amount so as to be within the allowable range.

If the ozone injection amount is increased or decreased and the dissolved ozone concentration is still out of the allowable range, it means that the ozonizer is out of order, or the pipe or diffuser leading from the ozonizer to the ozone contact pond. Is either clogged or the dissolved ozone concentration meter is out of order. Therefore, the cause should be investigated and remedied, or the operation of the ozonizer should be stopped.

In the case where a plurality of ozonizers are provided and ozone is injected into the ozone contact basin from the ozonizers, if any of the ozonizers fails because the dissolved ozone concentration does not recover within the allowable range, the remaining ozonizers are not recovered. Should provide ozone injection.

The injection of ozone into the sample water and the calculation of equations (1) to (3) should be performed continuously while the ozone treatment is being performed in the ozone contact pond. Then, the value of the ozone consumption calculated based on the equation (1) is compared with the previous value, and if the deviation is within the set value range of the dissolved ozone concentration, the ozone injected into the ozone contact pond It is better not to control the injection amount of. If the injection amount of ozone is changed frequently, the hunting phenomenon is likely to occur. Therefore, in order to avoid this, it is desirable not to change the injection amount of ozone when the deviation from the previous value of the ozone consumption amount is small. As described above, in the present invention, before the water to be treated is introduced into the ozone contact pond, a part of the water is extracted as sample water to inject ozone, and the amount of ozone injection required for ozone treatment of the water to be treated is adjusted. Since it is calculated, it is possible to deal with a sudden change in the quality of the treated water.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

First, the overall construction of a water treatment plant water treatment system to which the present invention is applied will be described with reference to FIG. In FIG. 3, the raw water RW taken from a river or the like goes to a sand basin (not shown) via a water pipe (not shown), and after the sand with a large particle size is removed, the landing well ( (Not shown). The raw water RW is then guided to the chemical mixing pond 1,
Here, after being rapidly mixed with a flocculant 2 such as a sulfuric acid band or PAC (polyaluminum chloride), and further with an alkali agent 3 serving as a flocculation aid, it is sent to a floc formation pond 4.

In the floc formation pond 4, the microflocs in which the fine particles in the raw water RW are aggregated are agitated by the flocculator 5 to promote their growth. After that, the flocculated water containing flocs having a large particle size is guided to the settling tank 6, where the flocs are separated by sedimentation.

The settling water SW from which flocs have been settled and separated through the above-described process is then introduced into the ozone contact pond 7 as the water to be treated Wo to be subjected to the ozone injection treatment. Ozone gas OG is injected from the ozonizer 8 into the ozone contact pond 7. More specifically, the raw material gas R
Moisture in A (air or oxygen) is removed by the dehumidifier 9 and then supplied to the ozonizer 8. A blower 10 supplies the raw material gas RA to the ozonizer 8. Ozonizer 8
Oxygenates the oxygen in the vent pipe 1 as ozone-containing gas.
Air diffuser 12 having a large number of small holes (not shown) through
Is introduced into the ozone contact pond 7.

The concentration of ozone gas from the ozonizer 8 is controlled by the controller 13, high frequency inverter 14 and high voltage converter 15. That is, a high frequency high voltage is applied from the power source to the discharge unit (not shown) via the high frequency inverter 14 and the high voltage transformer 15. When the flow rate of the gas supplied to the ozonizer 8 is constant, the ozone gas concentration to be generated is determined by the discharge power in the discharge section. Therefore, the ozone gas concentration is increased by increasing the applied voltage or frequency. Further, when the applied voltage and the frequency are constant, the ozone gas concentration is determined by the gas flow rate supplied to the discharge part, and the ozone gas concentration increases when the gas flow rate is reduced. Therefore, in this embodiment, the applied voltage is kept constant and the frequency is controlled by the high-frequency inverter 14 to control the ozone generation amount, but the flow rate of the feed material gas may be controlled. The control method of is not particularly limited.

A mist separator 16 for removing water in the ozone-containing exhaust gas EG discharged from the ozone contact pond 7 is disposed above the ozone contact pond 7, and on the downstream side of the mist separator 16. Ozone decomposition tank 17
Are arranged. The processing tank 17 is filled with an ozone decomposition catalyst 18. As the ozone decomposition catalyst 18, MnO ₂ , activated carbon, at least one element such as Ni or Fe, an oxide or a composite oxide can be used. However, the catalyst used is not particularly limited.

A blower 19 for sucking and exhausting the ozone-containing exhaust gas EG is provided at the subsequent stage of the ozone contact reservoir 7.

A biological activated carbon pond 20 is disposed downstream of the ozone contact pond 7. The biological activated carbon pond 20 is filled with activated carbon 21, and the treated water TW that has passed through the ozone contact pond 7 and the ozone retention pond 7A is introduced. Initially, the activated carbon 21 is filled with water to pass water, but few microorganisms are present on the surface or inside of the activated carbon 21, but with the passage of time, acclimated and propagated microorganisms are present on the surface or inside of the activated carbon 21. . Pseudomo as the dominant microbial species
Examples include nas.

In the treated water TW from the ozone contact pond 7, ammonia nitrogen which cannot be removed by the ozone treatment is nitrified and removed by the action of the microorganisms described above, and dissolved organic substances whose molecular weight is lowered by the ozone treatment are metabolically removed. It The treated water AW from the biological activated carbon pond 20 thus treated is then sent to a distribution reservoir (not shown) or the like. Although not shown in the present embodiment, the biological activated carbon pond 20 is a microorganism that has been backwashed with a part of the treated water from the biological activated carbon pond 20 as necessary and excessively attached to the surface of the activated carbon or the like. Are removed.

Treated water TW supplied to the biological activated carbon pond 20
The dissolved ozone concentration is measured by the dissolved ozone concentration meter 61, and this measured value is input to the ozone injection control device 60. The ozone injection control device 60 is configured to control the ozone injection amount according to the measurement value from the ozone consumption measuring device 22 for measuring the ozone consumption amount consumed in the ozone contact pond 7 and the measurement value of the dissolved ozone concentration meter 61. Has been done.

Reference numeral 22 is an ozone consumption measuring device, which measures the ozone consumption amount Oc of the water Wo to be treated flowing into the ozone contact basin 7.

The details will be described with reference to FIG. Into the ozone contact reaction tank 23, part of the water to be treated Wo to be subjected to the ozone injection treatment, which is sampled by the sampling pump 24 from the outlet of the sedimentation tank 6 or the like, is introduced as the sample water S.
Further, the ozone contact reaction tank 23 has an ozonizer 25.
Ozone gas G having a concentration set to a predetermined concentration is injected from. A dehumidifier 26 is arranged on the inlet side of the ozonizer 25. The dehumidifier 26 removes moisture in the raw material gas (air or oxygen) supplied to the ozonizer 25,
The dry raw material gas having a low dew point is supplied to the ozonizer 25. In this embodiment, the air pump 28 supplies air as a raw material gas to the ozonizer 25 through the filter 27. In this case, oxygen or oxygen-enriched air may be used as the raw material gas, and the raw material gas is not particularly limited.

An ozone concentration meter 29 is disposed on the outlet side of the ozonizer 25. The ozone concentration meter 29 measures the concentration Cg of the ozone gas G injected into the ozone contact reaction tank 23.
Measure 1. The ozone densitometer 29 measures the concentration of the ozone gas G by, for example, a method using a diaphragm type polarographic electrode or a method using an ultraviolet absorption method, but the measuring principle of the ozone densitometer is not limited.

A controller 30 for controlling the ozone generation concentration is connected to the ozonizer 25, and in the present embodiment, the generation concentration is adjusted by adjusting the voltage applied to a discharge part (not shown) constituting the ozonizer 25. Have control.

The flow rate G of the ozone gas injected into the ozone contact reaction tank 23 is adjusted by the constant flow valve 31, and the ozone gas set to a predetermined flow rate is passed through the flow meter 32 to the diffusing pipe 4.
Injected from 0A. The flow rate of the sample water S sampled by the sampling pump 24 is adjusted by the constant flow rate adjusting valve 33. Then, the sample water S set to a predetermined flow rate is supplied to the ozone contact reaction tank 23 via the flow meter 34.
Is supplied to. The sample water S introduced into the ozone contact reaction tank 23 becomes a counterflow to the gas flow of the ozone gas introduced at the same time, comes into contact with ozone and flows down.

A dissolved ozone concentration meter 35 is disposed on the outlet side of the ozone contact reaction tank 23, and this dissolved ozone concentration meter 35 measures the dissolved ozone concentration CW1 in the treated water TW1 after the ozone gas has been injected. To do. As the dissolved ozone densitometer 35, an ozone densitometer of the diaphragm type polarographic electrode method or the ultraviolet absorption type is used as described above.
The method is not particularly limited. In the present embodiment, the dissolved ozone concentration CW1 is measured at the outlet of the ozone contact reaction tank 23, but the dissolved ozone concentration in the ozone contact reaction tank 23 may be measured and after the ozone is injected into the sample water S. If so, it may be measured anywhere.

The treated water TW1 containing dissolved ozone from the ozone contact reaction tank 23 is then dissolved in the dissolved ozone removing tank 36.
Flows into. Air is introduced and diffused from the air pump 28 into the dissolved ozone removing tank 36 in order to remove dissolved ozone. That is, the air from the air pump 28 is introduced into the dissolved ozone removing tank 36 from the air diffuser 40B through the ventilation pipe 37, the flow rate control valve 38, and the flow meter 39. In the embodiment of the present invention, the air pump 28 shares the source gas source for the ozonizer 25 and the supply gas source for removing dissolved ozone, but it may be provided independently, and the number of pumps, etc. It is not limited.

The gas phase portions of the tanks 23 and 36 are communicated with each other through an exhaust ozone discharge pipe 41. The ozone-containing exhaust gas Eg discharged from the liquid phase of each of the tanks 23 and 36 to the gas phase is discharged to the outside of the system through the discharge pipe 41. When the ozone-containing exhaust gas Eg is discharged to the outside of the system, it is discharged via the ozone decomposition catalyst 42 arranged in the discharge pipe 41, and the ozone is decomposed by passing through the catalyst 42.

An ozone concentration meter 43 measures the ozone concentration Cg2 in the exhaust ozone gas discharged from the ozone contact reaction tank 23. Although not shown in this embodiment, the exhaust ozone gas Eg from the ozone contact reaction tank 23 flows into the ozone concentration meter 43 after the moisture in the gas is removed by the mist separator.

Reference numeral 50 is an ozone injection amount O into the ozone contact pond 7.
This is an ozone injection amount calculation means for calculating c, and this calculation means is configured as follows.

To explain the structure, 51 is an arithmetic unit, to which the concentration Cg1 of the ozone gas injected into the ozone contact reaction tank 23 is measured by the ozone concentration meter 29 and input. Further, the ozone concentration Cg2 in the exhaust ozone gas Eg discharged from the ozone contact reaction tank 23 is measured by the ozone concentration meter 43 and input to the calculator 51. Further, the flow rate G of the ozone gas injected into the ozone contact reaction tank 23 is measured by the flow meter 32 and input. Further, the flow rate L of the sample water S to the ozone contact reaction tank 23 measured by the flow meter 34 is input to the calculator 51. Further, the dissolved ozone concentration CW1 in the treated water TW1 from the ozone contact reaction tank 23 measured by the dissolved ozone concentration meter 35 is input to the calculator 51. As a result, the calculator 51 obtains the ozone consumption amount Oc (mg / l) of the water to be treated Wo sampled according to the following equation (6).

Oc = {G (Cg1-Cg2) / L} -CW1 (6) 52 is a calculator, to which the ozone consumption amount Oc obtained by the calculator 51 is input. Then, the deviation ± ΔOc from the held ozone consumption amount Oc ′ obtained last time (hereinafter,
ΔOc) is obtained based on the following equation (7).

ΔOc = Oc′−Oc (7) Reference numeral 53 is a judging device, and the deviation ΔOc of the ozone consumption amount calculated by the arithmetic unit 52 is inputted to the judging device. Further, the discriminator 53 includes a deviation range De (-ΔOc, + ΔO
c) is input and set. As a result, the deviation ΔOc input to the determiner 53 is set in the setting range De (−ΔOc <ΔOc <+
ΔOc) It is determined whether it is inside or outside, and if it is within the range, the ozone consumption amount Oc ′ obtained last time which is separately input is separately input.
Is selected. On the other hand, when it is out of the range, the newly obtained ozone consumption amount Oc is selected and output.

Reference numeral 54 is a calculator, which calculates the ozone absorption efficiency η. That is, the ozone concentration Cg1 to the ozone contact reaction tank 23 measured by the ozone concentration meter 29 is input to this arithmetic unit, and the ozone contact reaction tank 2 is further supplied.
Ozone concentration Cg in the exhaust ozone gas Eg discharged from No. 3
2 is input. As a result, the calculator 54 calculates the ozone absorption efficiency η based on the following equation (8).

Η (%) = {(Cg1−Cg2) / Cg1} × 100 (8) 55 is an arithmetic unit for obtaining the required ozone injection amount to the water Wo to be treated, and this arithmetic unit is the above-mentioned arithmetic unit The ozone consumption amount Oc (or O
c ', and Oc for convenience) is input. Further, the flow rate Q of the water to be treated Wo to be ozone-treated which flows into the ozone contact pond 7 measured by the flow meter 56 is input to the calculator 55. Further, the ozone absorption efficiency η obtained by the arithmetic unit 54 is input. As a result, this calculator 55
Then, the required ozone injection amount Io required for injection into the ozone contact pond 7 is obtained based on the following equation (9).

Io = (Oc × Q) / η (9) Inputting the ozone absorption efficiency η to obtain the required ozone injection amount Io is because all of the ozone injected into the water Wo to be treated is not absorbed and This is because the part is discharged to the gas phase as exhaust ozone gas, and the amount is compensated. In the embodiment of the present invention, the ozone concentration C injected into the ozone contact reaction tank 23 is as described above.
It is calculated from the difference between g1 and the exhaust ozone concentration Cg2. In this case, the ozone absorption efficiency η may be obtained from the difference between the concentration of ozone injected into the ozone contact pond 7 and the concentration of exhausted ozone from the ozone contact pond 7 according to the equation (8), and may be input to the calculator 55. . Further, the ozone absorption efficiency η of a predetermined value may be input, and the present invention is not limited to the embodiment of the present invention.

Reference numeral 57 is an arithmetic unit to which the required ozone injection amount Io obtained by the arithmetic unit 55 is input. Further, the target value Ko of the dissolved ozone concentration after the ozone injection processing is input. Further, the ozone absorption efficiency η and the flow rate Q of the water to be treated are input. As a result, this calculator 57
Then, the ozone injection amount Ij in which the target value Ko of the dissolved ozone is added is calculated based on the following equation (10).

Ij = Io + (Ko × Q) / η (10) The ozone injection amount Ij in consideration of the dissolved ozone concentration Ko may be calculated based on the following equation (11), The method of obtaining the ozone injection amount in consideration of the target value Ko is not limited to this embodiment.

Ij = {(Oc + Ko) Q} / η (11) When the ozone injection amount Ij obtained by the calculator 57 is corrected based on the output of the corrected ozone injection amount Ia described later,
The corrected ozone injection amount Ic is input to the calculator 58 as shown in FIG. On the other hand, the ozone injection amount Ij
If there is no correction in, the ozone injection amount Ij is directly input. Further, the gas flow rate F of the ozonizer 8 measured by the flow meter 59 is input to the calculator 58,
The generated ozone concentration Gc generated by the ozonizer 8 is obtained based on the following equation (12).

Gc = Ij / F (12) The generated ozone concentration Gc obtained by the calculator 58 is input to the controller 13 of the ozonizer 8. The controller 13 of the ozonizer 8 controls the high frequency inverter 14 and the like based on the input generated ozone concentration Gc to control the ozone gas concentration Cg from the ozonizer 8. Ozonizer 8
The ozone gas concentration Cg is measured by the ozone concentration meter 60, and the measured value is fed back to the controller 13 so that the ozone gas concentration Cg becomes a predetermined value. Then, the ozone gas OG having a predetermined concentration is injected into the water to be treated Wo introduced into the ozone contact pond 7.

Reference numeral 61 is a dissolved ozone concentration meter for measuring the dissolved ozone concentration DO3 in the treated water TW after the ozone has been injected into the treated water Wo. This dissolved ozone concentration meter indicates whether or not dissolved ozone is contained in the treated water TW. To monitor.

Reference numeral 62 denotes a dissolved ozone concentration controller, which controls when the dissolved ozone concentration is out of the allowable range.
The ozone injection amount is controlled so that it is within the allowable range.

As shown in FIGS. 4 and 5, the dissolved ozone concentration controller 62 includes comparators 63, 65, a calculator 64,
It is composed of 66 and an arithmetic unit 67.

The dissolved ozone concentration D measured by the dissolved ozone concentration meter 61 will be described with reference to FIGS. 4 and 5.
O3 is input as an output value to the comparator 63 that constitutes the controller 62. Then, it is compared whether or not the lower limit value Dn is satisfied among the preset allowable upper and lower limit values Ds (upper limit value Dm, lower limit value Dn) of the dissolved ozone concentration, and if the lower limit value Dn or less, the calculator 64 Then, the deviation + ΔDO3 between the dissolved ozone concentration DO3 and the lower limit value Dn is obtained.

On the other hand, when the dissolved ozone concentration DO3 is equal to or higher than the lower limit value, the dissolved ozone concentration DO3 is determined by the other comparator 6
5, the dissolved ozone concentration DO3 is compared with the upper limit value Dm or less. Dissolved ozone concentration DO
When 3 is equal to or more than the upper limit value Dm, the calculator 66 calculates the deviation −ΔDO3 between the dissolved ozone concentration DO3 and the upper limit value Dm.

Deviation of each dissolved ozone concentration described above ± ΔDO
3 is input to a computing unit 67 that constitutes the dissolved ozone concentration controller 62, and the computing unit 67 further includes an ozone contact tank 7
Flow rate Q of treated water Wo and ozone absorption efficiency η
Is input, and the corrected ozone injection amount Ia is obtained based on the following equation (13).

Ia = (± ΔDO3 × Q) η (13) The corrected ozone injection amount Ia obtained by the arithmetic unit 67 is input to the arithmetic unit 68, and the ozone injection amount Ij described above is input.
Is corrected based on the following equation (14).

Ic = Ia + Ij (14) Here, Ic is an ozone injection amount 68 corrected by the corrected ozone injection amount Ia is a comparator, and this comparator has a dissolved ozone concentration measured by the dissolved ozone concentration meter 61. DO3 is input, and the allowable upper and lower limit value Ds of the dissolved ozone concentration is also input. In the comparator 68, the allowable upper and lower limit value Ds is compared with the dissolved ozone concentration DO3, and even if the dissolved ozone concentration controller 62 controls the dissolved ozone concentration, the dissolved ozone concentration is outside the allowable upper and lower limit value Ds. In this case, the output for stopping the operation of the ozonizer 8 is issued. The stop of the ozonizer 8 may be automatic or manual.

Next, the operation of the apparatus having the above configuration will be described.

First, a part of the water Wo to be treated which is the object of ozone injection treatment is introduced into the ozone consumption measuring device 22 by the sampling pump 24. Where the ozonizer 2
By injecting ozone gas having a predetermined concentration Cg1 and a flow rate G from 5, the ozone consuming component in the water Wo to be treated is oxidized by ozone.

On the other hand, the treated water TW1 after ozone injection is then introduced into the dissolved ozone removing tank 36. Here, the dissolved ozone contained in the treated water TW is released from the liquid phase to the gas phase by the air introduced from the air pump 28, and the treated water TW containing no dissolved ozone is discharged out of the system.

When ozone is injected into the water Wo to be treated as described above, the ozone concentration C injected into the sample water S is C.
Exhaust ozone gas Eg discharged from g1 and sample water S
The ozone concentration Cg2, the injection ozone gas flow rate G, and the sample water S flow rate L are measured. Further, the dissolved ozone concentration CW1 in the treated water TW1 after ozone injection is measured. As a result, the ozone consumption amount Co of the water to be treated Wo sampled based on the above equation (6) is obtained by the calculator 51 constituting the ozone injection amount calculation means 50. Then, this ozone consumption amount Co is input to the calculator 55, and from the relationship of the flow rate Q of the treated water Wo to be subjected to the ozone injection treatment, the required ozone injection amount into the treated water Wo in which the ozone absorption efficiency η is taken into consideration. Io is calculated based on the equation (9).

The required ozone injection amount obtained as described above is Io, and then the ozone generation concentration Gc in the ozonizer 8 is obtained.
Is input to a calculator 58 for calculating the generated ozone concentration Gc to be injected into the water Wo to be treated in relation to the gas flow rate F.
Is controlled by the controller 13, and the ozone gas OG having the necessary ozone concentration and gas flow rate G is the treated water W.
will be injected into the o.

When the required ozone injection amount is injected into the water to be treated Wo as described above, the measured ozone consumption amount Oc
When the deviation from the previous measurement value is within the set deviation De, the required ozone injection amount Io is obtained based on the ozone consumption amount Oc of the previous measurement value. On the other hand, the set deviation D
If it is outside e, the newly measured ozone consumption Co
The required ozone injection amount Io is calculated based on

When the required ozone injection amount Io into the water to be treated Wo is obtained as described above, the ozone injection amount Ij in which the target value Ko of the dissolved ozone concentration is added to the required ozone injection amount Io is given by the above formula. Operation unit 5 based on (10)
The water is obtained in step 7 and injected into the water to be treated Wo.

On the other hand, in the dissolved ozone concentration controller 62, the dissolved ozone concentration DO3 in the treated water TW after the ozone injection treatment is performed.
Is measured, and the corrected ozone injection amount Ia is obtained so that the dissolved ozone concentration falls within the allowable upper and lower limit value Ds. The corrected ozone injection amount Ia is added to the separately obtained ozone injection amount Ij, and ozone is injected into the water to be treated Wo based on the corrected ozone injection amount.

[0063]

As described above, according to the present invention, the ozone consumption of the water to be treated which is the object of the ozone injection treatment is obtained in advance, and the ozone injection amount to the water to be treated obtained from this ozone consumption is calculated. Since it is injected into the water to be treated,
Even if the concentration of the organic substance, which is an ozone consuming component, in the water to be treated changes abruptly, the ozone injection amount can be appropriately injected without excess or deficiency.

Further, since the ozone consumption is obtained and the target value of the dissolved ozone concentration is added to this ozone consumption to obtain the ozone injection amount into the water to be treated, the treated water after the ozone injection treatment is performed. Since the dissolved ozone concentration is constantly detected, it is possible to easily determine whether or not the injected ozone is insufficient in the actual ozone contact pond.

[Brief description of the drawings]

FIG. 1 is a system flow diagram of an ozone consumption measuring apparatus showing an embodiment of the present invention.

FIG. 2 is a system flow chart of an ozone injection control method showing an embodiment of the present invention.

FIG. 3 is a flow chart of an ozone treatment system in a water purification plant showing an embodiment of the present invention.

FIG. 4 is a partial detailed view of the system flow diagram shown in FIG.

5 is a functional diagram of the partial detailed view shown in FIG. 4. FIG.

[Explanation of Codes] 5 ... Flocculator, 7 ... Ozone contact pond, 8 ... Ozonizer, 20 ... Bioactive carbon pond, 22 ... Ozone consumption measuring device, 23 ... Ozone contact reaction tank, 24 ... Sampling pump, 29, 43 ... Ozone concentration meter, 30 ... Controller, 35,
61 ... dissolved ozone concentration meter, 36 ... dissolved ozone removal tank, 5
0 ... Ozone injection amount calculation means, 62 ... Dissolved ozone concentration controller.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shoji Watanabe 7-1-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi Research Laboratory (72) Minoru Suzuki 1-chome, Kokubun-cho, Hitachi-shi, Ibaraki No. 1 inside the Kokubun Plant of Hitachi, Ltd. (72) Naoto Komatsu 1-1-1 Kokubuncho, Hitachi City, Ibaraki Prefecture Inside the Kokubun Plant of Hitachi, Ltd. (72) Naoki Hara Five Omika-cho, Hitachi City, Ibaraki Prefecture 2-2-1, Hitachi Ltd. Omika Plant (72) Inventor Nobuyoshi Yamakoshi 5-2-1 Omika-cho, Hitachi City, Ibaraki Prefecture Hitachi Ltd. Omika Plant

Claims (6)

[Claims] 1. In a method for performing ozone treatment by introducing treated water into an ozone contact pond, a part of the treated water before being introduced into the ozone contact pond is extracted as sample water and ozone is injected. At this time, the ozone consumption of the sample water is calculated from the amount of injected ozone, the concentration of exhausted ozone, the concentration of dissolved ozone, and the flow rate of the sample water, and the ozone consumption and the flow rate of the treated water flowing into the ozone contact pond and the ozone absorption efficiency are calculated. The ozone treatment method is characterized in that the ozone injection amount to the water to be treated is determined from the above, and the ozone treatment in the ozone contact pond is performed by the ozone injection amount. 2. The method according to claim 1, wherein the ozone injection amount obtained by injecting ozone into the sample water is added with an ozone injection amount considering the dissolved ozone concentration at the outlet of the ozone contact pond, and ozone is added. An ozone treatment method, which comprises injecting into a contact pond and monitoring whether or not dissolved ozone is contained in the treated water from the ozone contact pond. 3. The method according to claim 2, wherein if the dissolved ozone concentration of the treated water from the ozone contact pond is out of the set range, the ozone injection amount is corrected so as to fall within the range. An ozone treatment method characterized by the above. 4. The method according to claim 3, wherein the ozone treatment is stopped if the dissolved ozone concentration is still out of the set range even after the ozone injection amount is corrected. Ozone treatment method. 5. The method according to claim 2, wherein the deviation between the ozone consumption amount of the water to be treated obtained by injecting ozone into the sample water and the ozone consumption amount obtained last time is a set range of the dissolved ozone concentration. If it is within the range, the ozone treatment method is characterized in that the ozone injection amount to the ozone contact pond is not corrected. 6. An ozone treatment apparatus comprising means for introducing water to be treated into an ozone contact pond and means for injecting ozone into the ozone contact pond, wherein a part of the water to be treated flowing into the ozone contact pond is A means for extracting the sample water, a means for injecting ozone into the sample water, and a means for calculating the ozone consumption amount of the sample water from the injected ozone amount, the exhaust ozone concentration, the dissolved ozone concentration and the flow rate of the sample water at that time And an ozone treatment device for determining the ozone injection amount into the water to be treated from the obtained ozone consumption of the sample water, the flow rate of the water to be treated and the ozone absorption efficiency.