Water treatment system and method

Abstract

To provide highly efficient water treatment by using an appropriate amount of oxidation accelerator.SOLUTION: A water treatment system includes a treatment tank into which water to be treated is introduced, an oxidation promoter injection part that injects an oxidation promoter into the water to be treated, an ozone injection part that brings ozone into contact with the water to be treated containing the oxidation promoter flowing in the treatment tank, an oxidation promoter concentration measuring part that measures the concentration of the oxidation promoter in the water to be treated between the time when the ozone contact starts and before the time when the contact ends, and a control part that controls at least one of the injection amount of the oxidation accelerant and the ozone injection amount by the ozone injection part based on the injection amount of the oxidation accelerant by the oxidation accelerant injection part and the concentration of the oxidation accelerant in the water to be treated measured by the oxidation accelerant concentration measurement part.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE Embodiments of the present invention relate to a water treatment system and a water treatment method. [Background technology]

[0002] Conventionally, in the fields of drinking water, sewage, industrial wastewater, swimming pools, and the like, water treatment using a combination of ozone and a pro-oxidant such as hydrogen peroxide has been considered for the purpose of oxidative decomposition, sterilization, deodorization, and other treatment of organic matter in water. It is said that the highly oxidizing OH radical generated from a pro-oxidant and ozone is effective in the oxidative decomposition of difficult-to-decompose organic matter such as dioxin and 1,4-dioxane, which cannot be inorganicized by ozone alone. In addition, the method of using hydrogen peroxide as a pro-oxidant is said to be effective in suppressing the generation of bromate ions, which are a by-product of oxidative decomposition, due to the reducing action of hydrogen peroxide.

[0003] Therefore, in water treatment using ozone and hydrogen peroxide in combination, many proposals have been made regarding the use of pro-oxidants and methods for controlling the amount of ozone injected in order to promote the oxidative decomposition of organic matter and to suppress the production of bromate ions. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-181386 A [Patent Document 2] JP 2020-22971 A [Patent Document 3] JP 2020-124655 A Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a water treatment system and a water treatment method capable of performing highly efficient water treatment using an appropriate amount of a pro-oxidant. [Means for solving the problem]

[0006] The water treatment system according to the embodiment includes a treatment tank into which water to be treated is introduced, an oxidant pro-injection unit that injects an oxidant into the water to be treated, an ozone injection unit that brings ozone into contact with the water to be treated containing the oxidant flowing in the treatment tank, an oxidant pro-concentration measuring unit that measures the concentration of the oxidant in the water to be treated between the start of contact with the ozone and the end of contact, and a control unit that controls at least one of the amount of the oxidant pro-injected and the amount of ozone injected by the ozone injection unit based on the amount of the oxidant injected by the oxidant pro-injection unit and the concentration of the oxidant in the water to be treated measured by the oxidant pro-concentration measuring unit. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic configuration diagram of a water treatment system according to an embodiment. [Diagram 2] FIG. 2 is an exemplary schematic graph showing the relationship between the ratio of the injection amounts of ozone and hydrogen peroxide and the dissolved concentration of musty odor substances. [Diagram 3] FIG. 3 is an exemplary schematic graph showing the relationship between the ratio of the injection amounts of ozone and hydrogen peroxide and the bromate ion concentration. [Figure 4] FIG. 4 is an exemplary schematic graph showing the relationship between the amount of ozone injected and the dissolved concentration of musty odor substances. [Diagram 5] FIG. 5 is an exemplary schematic graph showing the relationship between the amount of ozone injected and the concentration of bromate ions. [Figure 6] FIG. 6 is an exemplary schematic graph showing the relationship between the ratio of the injection amounts of ozone and hydrogen peroxide and the concentrations of ozone and hydrogen peroxide dissolved in the water to be treated. [Figure 7] FIG. 7 is an exemplary schematic graph showing the relationship between the ratio of the injection amounts of ozone and hydrogen peroxide and the consumption amounts and consumption rates of ozone and pro-oxidant. [Figure 8]FIG. 8 is a flow chart showing the flow of water treatment according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] [Embodiment] Hereinafter, embodiments will be described with reference to the drawings.

[0009] 1 is a schematic configuration diagram of a water treatment system 1 according to an embodiment. The water treatment system 1 of the present embodiment is used for water purification treatment (hereinafter, water purification treatment may be referred to as "water treatment"), for example, in a water purification plant.

[0010] As shown in FIG. 1, a water treatment system 1 of this embodiment includes a treatment tank 2, an oxidant pro-injector section 3, an ozone injector section 4, and a control device 11.

[0011] In the following description, the water to be treated is referred to as "raw water" or "water to be treated", with "raw water" referring to the water to be treated before being introduced into the treatment tank 2, and "water to be treated" referring to the water to be treated regardless of whether it is before or after being introduced into the treatment tank 2. In particular, the term "water to be treated" is used to refer to the water to be treated both before and after being introduced into the treatment tank 2. The water to be treated contains mold odor substances as the substances to be treated. An example of a mold odor substance is an organic substance called 2-MIB. The substances to be treated may be trihalomethane precursors in addition to mold odor substances.

[0012] The treatment tank 2 is a tank into which the water to be treated is introduced. The water to be treated in this embodiment is, for example, water from which turbid components have been removed in a sedimentation tank at a water purification plant. The treatment tank 2 has an inflow section 2a into which the water to be treated flows, an outflow section 2b into which the water to be treated flows, two divided treatment tanks 2c and 2d, and a connection flow path 2e between the two divided treatment tanks 2c and 2d. The connection flow path 2e is partitioned from the divided treatment tanks 2c and 2d by a partition wall 2f. The water to be treated introduced into the treatment tank 2 from the inflow section 2a flows through the divided treatment tank 2c, the connection flow path 2e, and the divided treatment tank 2d, and is then discharged from the outflow section 2b to the outside of the treatment tank 2. The inflow section 2a and the outflow section 2b refer to the connection section of the piping through which the water to be treated flows with the treatment tank 2, respectively, but may also refer to the connection section of the piping through which the water to be treated flows with the treatment tank 2 and the vicinity of this connection section.

[0013] The pro-oxidant injection unit 3 is installed near the inflow unit 2a, and injects hydrogen peroxide into the water to be treated (raw water) before it is introduced into the treatment tank 2. The pro-oxidant injection unit 3 transmits the amount of hydrogen peroxide injected to the control device 11. The pro-oxidant injection unit 3 also adjusts the amount of hydrogen peroxide injected into the water to be treated (raw water) based on instructions from the control device 11. Hydrogen peroxide is an example of a pro-oxidant.

[0014] The ozone injector 4 is installed in the treatment tank 2, and brings ozone into contact with the water to be treated containing hydrogen peroxide flowing in the treatment tank 2. Specifically, the ozone injector 4 is installed below each of the two divided treatment tanks 2c, 2d, and introduces ozone-containing gas bubbles into the water to be treated via an air diffuser, an air diffuser plate, or an injector.

[0015] The ozone injection unit 4 is also connected to an ozone generator 4b. The ozone generated by the ozone generator 4b is sent to the ozone injection unit 4 through a pipe 4a. The ozone generator 4b adjusts the amount of ozone injected into the water to be treated by the ozone injection unit 4 based on an instruction from the control device 11.

[0016] With the above-mentioned configuration, the water to be treated comes into contact with ozone in the separate treatment tank 2c, and then comes into contact with ozone in the separate treatment tank 2d. As a result, hydrogen peroxide and ozone react in the water to generate OH radicals.

[0017] In this embodiment, the time when the water to be treated first comes into contact with ozone in the split treatment tank 2c is defined as the start of ozone contact, and the time when the water to be treated no longer comes into contact with ozone in the split treatment tank 2d is defined as the end of ozone contact.

[0018] The control device 11 has a dissolved ozone measuring unit 12 , a pro-oxidant concentration measuring unit 13 , a raw water measuring unit 14 , a treated water measuring unit 15 , and a control unit 16 .

[0019] The dissolved ozone measuring unit 12 measures the ozone concentration dissolved in the water to be treated. Specifically, the dissolved ozone measuring unit 12 is installed in the connection flow path 2e and is configured to be able to measure the dissolved ozone concentration of the water to be treated flowing through the connection flow path 2e. The dissolved ozone measuring unit 12 transmits the measured dissolved ozone concentration to the control unit 16.

[0020] The pro-oxidant concentration measuring unit 13 measures the hydrogen peroxide concentration in the water to be treated. Specifically, the pro-oxidant concentration measuring unit 13 is installed in the connection flow path 2e and is configured to be able to measure the concentration of hydrogen peroxide dissolved in the water to be treated flowing through the connection flow path 2e. The pro-oxidant concentration measuring unit 13 transmits the measured hydrogen peroxide concentration in the water to be treated to the control unit 16.

[0021] By providing the dissolved ozone measuring unit 12 and the pro-oxidant concentration measuring unit 13 in the connecting flow path 2e, it is possible to measure the dissolved ozone concentration and hydrogen peroxide concentration in the water to be treated from the start of contact with ozone to the end of contact with ozone. This makes it possible to speed up the control response by controlling the injection amounts of ozone and hydrogen peroxide, and to improve the tracking ability to the control target value.

[0022] The timing of measuring the dissolved ozone concentration and the hydrogen peroxide concentration is not particularly limited. For example, the measurements may be continuous, or water may be collected and measured at time intervals using a portable water quality meter.

[0023] The raw water measuring unit 14 measures the fluorescence intensity of the water to be treated (raw water). The fluorescence intensity is an index showing the concentration of mold odor substances in the water to be treated, and is, for example, the intensity of fluorescence with an excitation light wavelength of 320 to 360 nm and a fluorescence intensity of 400 to 450 nm. Specifically, the raw water measuring unit 14 is installed in the inflow unit 2a, and is configured to be able to specify the concentration of mold odor substances in the water to be treated (raw water) before being introduced into the treatment tank 2. The raw water measuring unit 14 transmits the specified concentration of mold odor substances in the water to be treated (raw water) before being introduced to the control unit 16. Note that by installing the raw water measuring unit 14 in the inflow unit 2a, controllability can be improved when treating water with large fluctuations in the inflow water quality.

[0024] The treated water measuring unit 15 measures the fluorescence intensity of the water to be treated. Specifically, the treated water measuring unit 15 is installed in the connection flow path 2e and is configured to be able to identify the concentration of mold odor substances in the water to be treated flowing through the connection flow path 2e. The treated water measuring unit 15 transmits the identified concentration of mold odor substances in the water to be treated to the control unit 16.

[0025] Control unit 16 controls the amount of hydrogen peroxide injected based on the information received from each unit. Specifically, control unit 16 controls the amount of hydrogen peroxide injected based on the amount of hydrogen peroxide injected received from pro-oxidant injection unit 3 and the concentration of hydrogen peroxide received from pro-oxidant concentration measurement unit 13. The specific operation of control unit 16 will be described later in the explanation of the water treatment method.

[0026] Next, prior to describing the water treatment method in the above-mentioned water treatment system 1, a method for controlling the injection amounts of ozone and hydrogen peroxide will be described using the research results by the inventors shown in FIGS.

[0027] First, the effect of reducing moldy odor substances in the water to be treated and the effect of suppressing the production of bromate ions when the injection amount of hydrogen peroxide is changed will be described with reference to Figs.

[0028] Fig. 2 is an exemplary schematic graph showing the relationship between the ratio of the injection amounts of ozone and hydrogen peroxide and the dissolved concentration of mold odor substances. In the graph shown in Fig. 2, the horizontal axis corresponds to the injection amount ratio (molar ratio) of hydrogen peroxide / ozone, and the vertical axis corresponds to the dissolved concentration of mold odor substances in the water to be treated.

[0029] Fig. 3 is an exemplary schematic graph showing the relationship between the ratio of the injection amounts of ozone and hydrogen peroxide and the bromate ion concentration. In the graph shown in Fig. 3, the horizontal axis corresponds to the injection amount ratio (molar ratio) of hydrogen peroxide / ozone, and the vertical axis corresponds to the bromate ion concentration in the water to be treated. In the examples of Fig. 2 and Fig. 3, the injection amount of ozone is constant at 1.5 mg / L.

[0030] As shown in Figure 2, when the ratio of hydrogen peroxide to ozone is greater than 0.5, there is no significant difference in the dissolved concentration of mold odor substances. In other words, even if the amount of hydrogen peroxide injected is reduced to an injection ratio of approximately 0.5, a sufficient decomposition effect of mold odor substances can be obtained.

[0031] However, as shown in Figure 3, increasing the ratio of the amount of hydrogen peroxide injected to the amount of ozone decreases the concentration of bromate ions in the water to be treated. Increasing the amount of hydrogen peroxide injected can suppress the generation of bromate ions.

[0032] Next, the effect of reducing moldy odor substances in the water to be treated and the effect of suppressing the production of bromate ions when the amount of ozone injected is changed will be described with reference to FIG. 4 and FIG.

[0033] Fig. 4 is an exemplary schematic graph showing the relationship between the injection rate (concentration) of ozone and the dissolved concentration of mold odor substances. In the graph shown in Fig. 4, the horizontal axis corresponds to the amount of ozone injected, and the vertical axis corresponds to the dissolved concentration of mold odor substances.

[0034] 5 is an exemplary schematic graph showing the relationship between the ozone injection rate (concentration) and the bromate ion concentration. In the graph shown in FIG. 5, the horizontal axis corresponds to the ozone injection amount, and the vertical axis corresponds to the bromate ion concentration.

[0035] In Figures 4 and 5, the values ​​plotted with squares indicate the dissolved concentration of mold odor substances and the bromate ion concentration when both hydrogen peroxide and ozone are included. For comparison, the values ​​plotted with diamonds indicate the concentration of mold odor substances and the bromate ion concentration when ozone is injected alone. In Figures 4 and 5, the injection ratio (molar ratio) of ozone to hydrogen peroxide is fixed at 1.

[0036] As shown in FIG. 4, whether both ozone and hydrogen peroxide were injected or ozone was injected alone, the dissolved concentration of moldy odor substances decreased as the amount of ozone injected increased.

[0037] Furthermore, as shown in FIG. 5, it can be seen that the bromate ion concentration increases as the amount of ozone injected increases, both when both ozone and hydrogen peroxide are injected and when ozone is injected alone.

[0038] From the research results shown in FIGS. 2 to 5, the inventors have found that it is preferable to select different control methods for controlling the injection amounts of ozone and hydrogen peroxide depending on the purpose.

[0039] For example, in case 1, it is desired to lower the dissolved concentration of mold odor substances in the water to be treated. For this purpose, it is advisable to control the amount of ozone injected to be increased. This is because the dissolved concentration of mold odor substances decreases as the amount of ozone injected is increased (for example, FIG. 4). The control of the amount of ozone injected in case 1 can be performed, for example, based on the decomposition rate of mold odor substances obtained by dividing the concentration of mold odor substances acquired in treated water measurement unit 15 by the concentration of mold odor substances acquired in raw water measurement unit 14. Ozone injection unit 4 controls the amount of ozone injected so that the decomposition rate reaches a predetermined target decomposition rate. This method makes it possible to improve controllability, for example, when treating water with large fluctuations in inflow water quality. Note that when treating water with small fluctuations in inflow water quality, the amount of ozone added may be adjusted manually as needed.

[0040] Case 2 is when it is desired to suppress the generation of bromate ions. For this purpose, it is advisable to control the injection amount of hydrogen peroxide to be increased. This is because the higher the injection amount ratio of hydrogen peroxide to ozone is, the lower the bromate ion concentration in the water to be treated (e.g., FIG. 3). Specifically, for example, the injection amount of hydrogen peroxide is controlled based on the injection amount of hydrogen peroxide relative to the injection amount of ozone that is predetermined according to the risk of generation of bromate ions.

[0041] And, for example, in case 3, there is a case where it is not necessary to suppress the generation of bromate ions. This case includes, for example, cases where there are no water quality standards regarding bromate ions, and even if there are, cases where there is no need to control the concentration of bromate ions due to the properties of the raw water. In such cases, it is possible to reduce the amount of hydrogen peroxide injected. This is because even when the amount of hydrogen peroxide injected is small, a sufficient decomposition effect of moldy odor substances can be obtained (for example, Figure 2). This makes it possible to obtain the effect of oxidative decomposition of moldy odor substances while reducing the amount of hydrogen peroxide used.

[0042] A more detailed method of controlling the injection amount of hydrogen peroxide in the case 3 will be described below with reference to FIGS.

[0043] Fig. 6 is an exemplary schematic graph showing the relationship between the ratio of the injection amounts of ozone and hydrogen peroxide and the ozone concentration and hydrogen peroxide concentration dissolved in the water to be treated. In the graph shown in Fig. 6, the horizontal axis corresponds to the injection amount ratio (molar ratio) of hydrogen peroxide / ozone, the vertical axis (left) corresponds to the ozone concentration dissolved in the water to be treated, and the vertical axis (right) corresponds to the hydrogen peroxide concentration dissolved in the water to be treated.

[0044] In addition, in Fig. 6, values ​​plotted with black squares indicate dissolved ozone concentrations, and values ​​plotted with black diamonds indicate hydrogen peroxide concentrations. In the example of Fig. 6, the amount of ozone injected is constant at 1.5 mg / L.

[0045] As shown in Figure 6, when the injection rate ratio of hydrogen peroxide to ozone is increased, the dissolved ozone concentration decreases, and approaches zero when the injection rate ratio exceeds 0.5. This is because the injected ozone reacts with hydrogen peroxide to generate OH radicals, which are consumed for the oxidative decomposition of moldy odor substances, etc.

[0046] The dissolved ozone concentration and hydrogen peroxide concentration values ​​shown in FIG. 6 are converted into their respective consumption amounts and consumption rates and are shown in FIG.

[0047] 7 is an exemplary schematic graph showing the relationship between the ratio of the injection amounts of ozone and hydrogen peroxide and the consumption amounts and consumption rates of ozone and pro-oxidant. In the graph shown in FIG. 7, the horizontal axis corresponds to the injection amount ratio (molar ratio) of hydrogen peroxide / ozone, the vertical axis (left) corresponds to the consumption rates of ozone and hydrogen peroxide, and the vertical axis (right) corresponds to the consumption amounts of ozone and hydrogen peroxide.

[0048] In Fig. 7, the values ​​plotted with black ◇ indicate the consumption rate of ozone, the values ​​plotted with black □ indicate the consumption amount of ozone, the values ​​plotted with ◇ indicate the consumption rate of hydrogen peroxide, and the values ​​plotted with □ indicate the consumption amount of hydrogen peroxide. For both hydrogen peroxide and ozone, the consumption amount is calculated by subtracting the amount dissolved in the water to be treated from the amount injected, and the consumption rate is calculated by dividing the consumption amount by the amount injected. The amount dissolved in the water to be treated is calculated from the concentration.

[0049] As shown in Fig. 7, when the injection ratio of hydrogen peroxide to ozone is increased, both the consumption amount and the consumption rate of ozone increase, and when the injection ratio exceeds 0.5, the consumption rate approaches 100%. As described above with reference to Fig. 6, this is because the injected ozone is consumed by the generation of OH radicals, reactions with moldy odor substances in the treated water, self-decomposition reactions, etc.

[0050] In addition, the consumption of hydrogen peroxide increases as the ratio of hydrogen peroxide to ozone is increased. However, the consumption rate of hydrogen peroxide increases rapidly from an injection ratio of approximately 0.2, reaches a maximum at approximately 0.5, and does not change significantly when the injection ratio exceeds 0.5.

[0051] Hydrogen peroxide injected into the water to be treated is consumed to generate OH radicals while ozone remains in the water to be treated. That is, hydrogen peroxide is consumed to generate OH radicals within a range where the hydrogen peroxide injection amount ratio does not exceed 0.5. Therefore, for example, in a range where the hydrogen peroxide consumption rate changes significantly (for example, the injection amount ratio range of 0.2 to 0.5 in FIG. 7), it is considered that a large amount of hydrogen peroxide is consumed and a large amount of OH radicals is generated.

[0052] At this time, the concentration of hydrogen peroxide remaining in the water to be treated is 0.2 to 0.5 mg / L (FIG. 6).

[0053] On the other hand, when there is little ozone remaining in the water, hydrogen peroxide injected into the water to be treated is consumed in the decomposition reaction of OH radicals, reactions with other radical components, and reduction reactions of reaction by-products caused by ozone. This is because hydrogen peroxide in the water to be treated cannot promote the decomposition reaction of mold odor substances in the water by itself, and the self-decomposition reaction does not proceed in a short time. In other words, in the range where the hydrogen peroxide injection amount ratio exceeds 0.5, hydrogen peroxide is consumed in reactions other than the generation of OH radicals. Therefore, in the range where there is no significant change in the consumption amount of hydrogen peroxide, it is considered that the generation of OH radicals is not progressing.

[0054] In this way, by controlling the injection amount of hydrogen peroxide based on the consumption rate of hydrogen peroxide, it becomes possible to efficiently generate OH radicals with a smaller injection amount of hydrogen peroxide. Next, the water treatment method of the present invention capable of carrying out the above-mentioned control will be described with reference to FIG.

[0055] 8 is a flow chart showing the flow of water treatment according to the embodiment. The water treatment method according to the present embodiment includes a pro-oxidation step, a pro-oxidant measurement step, and a control step. The amount of ozone injected in this embodiment is assumed to be 1.5 mg / L.

[0056] In the accelerated oxidation step, the control unit 16 controls the oxidation promoter injection unit 3 to inject hydrogen peroxide into the water to be treated (raw water) introduced into the treatment tank 2 from the inlet 2a (S101). The water to be treated into which hydrogen peroxide has been injected is injected into the divided treatment tank 2c from the inlet 2a of the treatment tank 2. The control unit 16 receives the injection amount of hydrogen peroxide from the oxidation promoter injection unit 3.

[0057] Next, the control unit 16 controls the ozone generator 4b to inject ozone from the ozone injector 4 into the water to be treated flowing through the treatment tank 2 (S102). This causes the water to be treated containing hydrogen peroxide flowing through the treatment tank 2 to come into contact with the ozone.

[0058] In the pro-oxidant measurement step, the pro-oxidant concentration measurement unit 13 measures the concentration of hydrogen peroxide dissolved in the water to be treated (S103). Specifically, in the pro-oxidant measurement step, the pro-oxidant concentration measurement unit 13 measures the concentration of hydrogen peroxide in the water to be treated from the start of contact with ozone to the end of the contact. The pro-oxidant concentration measurement unit 13 transmits the hydrogen peroxide concentration as the measurement result to the control unit 16.

[0059] Next, in a control step, the control unit 16 controls the injection amount of the pro-oxidant based on the injection amount of hydrogen peroxide received from the pro-oxidant injection unit 3 and the concentration of hydrogen peroxide received from the pro-oxidant concentration measurement unit 13 (S104). Specifically, the control unit 16 calculates the consumption rate of hydrogen peroxide in the water to be treated based on the injection amount of the pro-oxidant received from the pro-oxidant injection unit 3 and the hydrogen peroxide concentration received from the pro-oxidant concentration measurement unit 13. The control unit 16 controls the pro-oxidant injection unit 3 based on the consumption rate to adjust the injection amount of hydrogen peroxide.

[0060] As described above, the consumption rate is calculated by subtracting the amount of hydrogen peroxide dissolved in the water to be treated from the amount of hydrogen peroxide injected, and dividing the result by the amount injected. The control unit 16 calculates the amount of hydrogen peroxide dissolved in the water to be treated from the concentration of hydrogen peroxide dissolved in the water to be treated, and calculates the consumption rate based on the dissolved amount.

[0061] More specifically, the control unit 16 controls the amount of hydrogen peroxide injected so that the consumption rate of hydrogen peroxide in the water to be treated exceeds a first threshold value of 20%. More preferably, the control unit 16 controls the amount of hydrogen peroxide injected so that the consumption rate of hydrogen peroxide in the water to be treated exceeds 23%.

[0062] For example, when the consumption rate is less than 20%, the control unit 16 can adjust the amount of hydrogen peroxide injected by controlling the pro-oxidant injection unit 3. This increases the amount and rate of hydrogen peroxide consumption and generates OH radicals, which promotes the oxidative decomposition of moldy odor substances.

[0063] As shown in Figure 7, in water treatment using ozone and hydrogen peroxide, the consumption rate of hydrogen peroxide is less likely to increase than that of ozone, and is a maximum of about 30%. By controlling the injection amount of hydrogen peroxide so that the consumption rate of hydrogen peroxide exceeds 20%, a constant amount of OH radicals can be generated, making it possible to stably maintain the mold odor decomposition effect.

[0064] Furthermore, the control unit 16 controls the amount of hydrogen peroxide injected so that the concentration of hydrogen peroxide in the water to be treated is between 0.2 and 0.5 mg / L.

[0065] [Summary] The water treatment system 1 of this embodiment includes a pro-oxidant injection unit 3 that injects hydrogen peroxide into the water to be treated that contains a mold odor substance, an ozone injection unit 4 that brings ozone into contact with the water to be treated that contains hydrogen peroxide, a pro-oxidant concentration measurement unit 13 that measures the concentration of hydrogen peroxide dissolved in the water to be treated, and a control unit 16. The control unit 16 controls the injection amount of hydrogen peroxide based on the injection amount of hydrogen peroxide and the concentration of hydrogen peroxide. Specifically, the control unit 16 controls the injection amount of the pro-oxidant based on the consumption rate of hydrogen peroxide.

[0066] This makes it possible to efficiently generate OH radicals with a smaller amount of hydrogen peroxide injected. As a result, it is possible to promote the oxidative decomposition of moldy odor substances with high efficiency using an appropriate amount of hydrogen peroxide. In addition, by reducing the amount of hydrogen peroxide injected, ozone can be left in the water to be treated, so that the treated water with dissolved ozone can be passed through the subsequent treatment stage. As a result, it is possible to suppress the proliferation of microorganisms in the subsequent treatment stages such as activated carbon treatment.

[0067] In addition, the control unit 16 controls the amount of hydrogen peroxide injected so that the consumption rate of hydrogen peroxide exceeds 20%. By maintaining the consumption rate of hydrogen peroxide within a certain range, it is possible to stably promote the oxidative decomposition of mold odor substances.

[0068] [Other embodiments] In the above embodiment, the control unit 16 controls the amount of hydrogen peroxide injected based on the amount of hydrogen peroxide injected received from the pro-oxidant injection unit 3 and the measurement result in the pro-oxidant concentration measurement unit 13, but the control target is not limited to the amount of hydrogen peroxide injected. For example, the control unit 16 may control the amount of ozone injected based on the amount of hydrogen peroxide injected and the hydrogen peroxide concentration. The consumption rate of hydrogen peroxide is determined by an appropriate injection rate ratio of ozone and hydrogen peroxide. Therefore, for example, even if the injection amount of ozone is controlled so that the consumption rate of hydrogen peroxide exceeds a 20% value, the same effect as in the above embodiment can be obtained.

[0069] Furthermore, for example, the control unit 16 may control the amount of hydrogen peroxide injected based on the dissolved ozone concentration identified by the dissolved ozone measuring unit 12. Specifically, the control unit 16 may control the amount of pro-oxidant injected so that the dissolved ozone concentration received from the dissolved ozone measuring unit 12 becomes greater than zero. In this way, by controlling the amount of hydrogen peroxide injected so that ozone remains in the water to be treated, it is possible to promote the oxidative decomposition of moldy odor substances with a small amount of hydrogen peroxide used.

[0070] Furthermore, the control unit 16 may control the amount of ozone injected based on the dissolved ozone concentration received from the dissolved ozone measurement unit 12 so that the dissolved ozone concentration becomes greater than zero.

[0071] In the above embodiment, the pro-oxidant injection unit 3 is configured to be able to inject hydrogen peroxide into the water to be treated before it is introduced into the treatment tank 2 (FIG. 1), but the configuration of the pro-oxidant injection unit 3 is not limited to this. For example, the pro-oxidant injection unit 3 may be configured to be able to inject hydrogen peroxide into the water to be treated after it has been introduced into the treatment tank 2.

[0072] In the above embodiment, the dissolved ozone measuring unit 12 and the pro-oxidant concentration measuring unit 13 are installed in the connecting flow path 2e (FIG. 1), but the locations are not limited to this. For example, the dissolved ozone measuring unit 12 and the pro-oxidant concentration measuring unit 13 may be provided near the outflow portion 2b.

[0073] The water treatment system 1 in the above-described embodiment can be applied not only to the treatment of drinking water but also to the treatment of sewage, industrial wastewater, swimming pools, and the like.

[0074] The embodiments of the present invention are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents as described in the claims, as well as the scope and spirit of the invention. [Explanation of symbols]

[0075] 1...water treatment system, 2...treatment tank, 2c, 2d...divided treatment tanks, 2e...connecting flow path, 3...pro-oxidant injection section, 4...ozone injection section, 11...control device, 12...dissolved ozone measurement section, 13...pro-oxidant concentration measurement section, 14...raw water measurement section, 15...treated water measurement section, 16...control section.

Claims

1. a treatment tank into which the water to be treated is introduced; An oxidation promoter injection unit that injects an oxidation promoter into the water to be treated; an ozone injection unit that brings ozone into contact with the water to be treated that contains the pro-oxidant and flows through the treatment tank; a pro-oxidant concentration measuring unit that measures the concentration of the pro-oxidant in the water to be treated from the start of contact with the ozone to the end of contact; a control unit that controls at least one of the injection amount of the pro-oxidant by the pro-oxidant injection unit and the injection amount of ozone by the ozone injection unit based on the injection amount of the pro-oxidant by the pro-oxidant injection unit and the concentration of the pro-oxidant in the water to be treated measured by the pro-oxidant concentration measurement unit; A water treatment system comprising:

2. The control unit is A consumption amount of the pro-oxidant is calculated from the injection amount of the pro-oxidant and the concentration of the pro-oxidant in the water to be treated, and at least one of the injection amount of the pro-oxidant and the injection amount of the ozone is controlled based on a consumption rate which is a value obtained by dividing the calculated consumption amount of the pro-oxidant by the injection amount of the pro-oxidant. The water treatment system of claim 1 .

3. The control unit is controlling at least one of the injection amount of the pro-oxidant and the injection amount of the ozone so that the consumption rate exceeds a first threshold value; The water treatment system of claim 2 .

4. A dissolved ozone measuring unit that measures a dissolved ozone concentration in the water to be treated from the start of contact with the ozone to the end of contact; Further equipped with The control unit is At least one of the injection amount of the pro-oxidant and the injection amount of the ozone is controlled so that the dissolved ozone concentration is greater than zero. The water treatment system of claim 1 .

5. A water treatment method carried out in a water treatment system including a treatment tank into which water to be treated is introduced, injecting a pro-oxidant into the water to be treated; contacting the water to be treated containing the pro-oxidant flowing in the treatment tank with ozone; measuring a concentration of the pro-oxidant in the water to be treated between the start of contact with the ozone and the end of the contact; A step of controlling at least one of the injection amount of the pro-oxidant and the injection amount of the ozone based on the injection amount of the pro-oxidant and the concentration of the pro-oxidant in the water to be treated; A water treatment method comprising:

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