JPH11290878A - Control method for removing toc component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently remove a TOC component from TOC component- containing water while holding a desired ratio of ozone and hydrogen peroxide. SOLUTION: Ozone supply amt. is desirably controlled so as to cooperate with the TOC value of TOC component-containing water or treated water thereof and, by the monitoring of the treated water with an ORP monitor 160, a dissolved ozone monitor 167 or a hydrogen peroxide monitor (pref., ORP monitor), the supply amt. of hydrogen peroxide is controlled to supply ozone and hydrogen peroxide to the above-mentioned TOC component-containing water and the TOC component is oxidized and removed by hydroxyl free radicals generated from ozone and hydrogen peroxide to obtain treated water. The treated water is further treated by an ion removing device and residual org. acid components or the like are removed to produce pure water. For example, it is desirable to supply hydrogen peroxide so that ORP of treated water becomes 200-900 mV.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for controlling the removal of TOC components, and more particularly to a method for removing TOC components from water containing TOC components to produce, for example, clean water or industrial water.
Alternatively, the TOC component is removed from TOC component-containing water such as sewage or industrial wastewater containing a hardly decomposable TOC component, and water is recovered, or used in a washing process in a related electronic industry such as a semiconductor or a liquid crystal. The present invention relates to a method for controlling TOC component removal for producing and recovering (ultra) pure water.

[0002]

2. Description of the Related Art Properly combining ozone, hydrogen peroxide, ultraviolet light, various oxidation catalysts, and the like generates hydroxyl radicals having stronger oxidizing power than each of these individual oxidation means alone. Since these oxidizing means do not generate anything other than the oxygen element and the hydrogen element, there is little risk of secondary contamination, and the salt load in the subsequent treatment is very low.
Due to these characteristics, hydroxyl radicals are generated by an appropriate combination of the above-mentioned various oxidation means or a combination of ozone and an alkali (alkaline is not an oxidizing agent, but a hydroxyl radical is generated by this combination). The TOC component in the TOC component-containing water (hereinafter sometimes referred to as “raw water”) which is treated water is oxidatively decomposed to treat wastewater, produce pure water, ultrapure water, etc., and use pure water or ultrapure water after use. It is widely practiced to remove TOC components for water recovery from water.

[0003] As described above, by various combinations of the above-mentioned various oxidizing means and combinations of ozone and alkali,
Although hydroxyl radicals are commonly generated, each of these combinations has different characteristics.
For example, the combination of hydrogen peroxide and ultraviolet (UV) is a classic use, but usually requires a reaction time of several hours or more due to the slow reaction rate. The reaction rate of the combination of ozone and ultraviolet light (UV) is considerably high because the UV absorption by ozone is very high, but the initial cost and running cost (power cost and replacement cost of ultraviolet lamp) due to the ultraviolet irradiation device Both) will increase. The combination of ozone and alkali has a high reaction rate and low running cost, but it reacts on the alkali side, so when high-concentration TOC components are present in raw water, carbonate ions (CO ₃ ^2- ) and bicarbonate The reaction is inhibited by radical scavengers such as ions (HCO ₃ ⁻ ). (On the alkaline side, carbon dioxide, which is one of the decomposition products of the TOC component, exists as carbonate ions or bicarbonate ions. If present in raw water, the amount of carbon dioxide generated will also increase). on the other hand,
Although the combination of ozone and hydrogen peroxide is slightly inferior in reaction rate, it has a relatively wide range of use because it is less affected by radical scavengers and is economically advantageous. Note that carbonate ions have a greater effect as radical scavengers than bicarbonate ions.

Further, in any of the above-mentioned hydroxyl radical generating mechanisms, since an organic acid is generated as an intermediate product, the hydroxyl radical generating mechanism further substantially completely oxidizes and decomposes to carbon dioxide and water to obtain TO TO.
Rather than removing the C component substantially completely, as an economical method, a portion of the generated organic acid that is not decomposed into carbon dioxide and water is left, and the remaining portion of the organic acid is removed by ion removal provided in the subsequent stage. It may be removed using a mechanism (for example, an ion exchange device or an ion removal device such as a reverse osmosis membrane (RO) device).

[0005] Among the above various combinations, the combination of ozone and hydrogen peroxide (hereinafter referred to as the "ozone / hydrogen peroxide method") has little influence from the radical scavenger as described above, and Since the cost is relatively low and the economy is also advantageous, the most practical T
Because of these features, the ozone / hydrogen peroxide method decomposes hard-to-decompose organic substances in wastewater, decomposes trace organic matter in raw water such as clean water and industrial water, It is widely used for the purpose of decomposing and removing trace amounts of organic substances from (ultra) pure water.

In general, T by the ozone / hydrogen peroxide method
In the treatment of the water containing the OC component, first, a hydroxyl radical is generated by a reaction between ozone and hydrogen peroxide according to the following reaction formula. 2O ₃ + H ₂ O ₂ → 2OH · + 3O ₂

It is said that the decomposition of the TOC component, which is an organic substance, by the hydroxyl radical (OH.) Thus generated proceeds as follows. TOC component → alcohol → ketone → carboxylic acid → CO ₂
+ H ₂ O In each of the above steps, a hydroxyl radical (OH.) Is involved in the reaction. Of course, when the TOC component is originally an alcohol, it starts with conversion to ketone, and when the TOC component is originally a ketone, Starting from conversion to carboxylic acid, if the TOC component is originally a carboxylic acid, CO ₂ +
Proceed to conversion to H ₂ O.

Clogging, ozone is an oxidizing agent, and the role of hydrogen peroxide is to react with ozone to react with hydroxyl radicals (O
H.). Therefore, the efficiency of decomposition of the TOC component is related not only to the supply amount of ozone but also to the ratio of hydrogen peroxide to ozone.

[0009] In most cases of removing the TOC component from the water containing the TOC component, since the control of the amount of hydroxyl radical generation is not performed, the apparatus is operated on the safe side, so that the hydroxyl radical always becomes excessive. Also,
In the case where the ion removing mechanism is provided as described above, if the amount of hydroxyl radical generation is feedback-controlled based on the TOC value (TOC concentration) of the treated water obtained therefrom, it is inevitable that the time lag becomes long. The TOC component is adsorbed or released in the remaining oxidizing agent decomposition step (eg, activated carbon contacting step) before the mechanism, and it is difficult to ensure stable control.
Since the OC value is very low, it is difficult to secure a sufficient control width.
Therefore, it is desirable to control the amount of hydroxyl radicals generated by using feedforward control based on the TOC value of raw water or feedback control of TOC component oxidative decomposition treated water using hydroxyl radicals.

The supply of ozone involved in the hydroxyl radical generation reaction can be controlled relatively easily, and the amount of ozone supplied to raw water or water treated with hydroxyl radicals can be controlled.
The C concentration may be measured, and the feedforward control method or the feedback control method may be performed according to the measurement position (raw water or treated water). However, there is no established method for controlling the supply amount of hydrogen peroxide. Generally, the optimum supply amount of hydrogen peroxide is a stoichiometric relationship with the supply amount of ozone, and the theoretical amount, that is, the weight ratio of hydrogen peroxide / ozone is 0.354 /
It is said that the amount is one. It is generally said that the pH during the reaction may be around neutral.

Further, when the TOC concentration in the raw water as the water to be treated is high or when the ozone remaining in the exhaust gas is reused, the water to be treated is treated twice or more by the ozone / hydrogen peroxide method. Has also been proposed. Also, when recovering (ultra) pure water from used (ultra) pure water, after decomposing the TOC component by the ozone / hydrogen peroxide method, it is possible to remove the ionic components in the decomposed water by the ion removal mechanism. Is being done.

[0012]

As described above, the ozone / hydrogen peroxide method is the most practical method for removing TOC components. However, in the ozone / hydrogen peroxide method, the reaction between ozone and hydrogen peroxide is performed. The generated hydroxyl radical and TOC
In addition to the reaction with the components, there is also the possibility of a direct reaction between the ozone and the TOC component, and there is also a reaction between the hydroxyl radical and the ozone and a reaction between the hydroxyl radical and the hydrogen peroxide. The (addition) amount is not always a theoretical amount in relation to the supply amount of ozone. Also, no effective control means has been found for the control means of the supply amount of hydrogen peroxide. Even if an attempt is made to control the supply amount of hydrogen peroxide in proportion to the supply amount of ozone, for example, the input signal value input to the ozone generator and the output (generation amount) of ozone from the ozone generator are non-linear. (That is, usually, the frequency of the ozone generator is controlled, but the input amount is not proportional to the amount of ozone actually generated, and the generated ozone may be immediately decomposed.) It is difficult to perform accurate control. When the amount of hydrogen peroxide is insufficient, the reaction efficiency becomes poor, and the ozone cannot be used effectively. On the other hand, if the amount of hydrogen peroxide becomes excessive, the generated hydroxyl radical reacts with the excess hydrogen peroxide, resulting in waste.

Accordingly, the present invention provides an effective means for controlling the supply of hydrogen peroxide to efficiently remove TOC components from water containing TOC components while maintaining a desired ratio of ozone to hydrogen peroxide. It is intended to provide a method for controlling the removal of the TOC component that enables the above.

[0014]

In order to solve the above-mentioned problems, the present inventor has developed a model TOC in which isopropyl alcohol (IPA) or the like is dissolved in ultrapure water as a model TOC component.
Using the C component-containing water (raw water), the TOC component is removed at various hydrogen peroxide supply amounts and ozone supply amounts (the amount of ozone absorbed in the water), and the dissolved ozone concentration of the treated water, ORP (Oxidation-reduction potential
potential), the concentration of residual hydrogen peroxide was monitored and shown in a graph. The inflection point appeared when the weight ratio of supplied (added) hydrogen peroxide / ozone absorbed in water was around 0.15. Was found. The position of such an inflection point fluctuates slightly depending on the conditions such as the type of the TOC component to be decomposed and removed, the treatment temperature, the pH of the raw water, and the hydraulic retention time, but the change is slight. there were. Moreover,
Even if the above weight ratio is increased after the inflection point, the TOC
The removal efficiency of the components was almost unchanged, and the TOC concentration of the treated water /
It was found that an inflection point also appeared in the graph showing the relationship between the ratio of the TOC concentration of the raw water (representing the TOC component residual ratio) and the ratio of the hydrogen peroxide supply amount / ozone supply amount ratio. Considering the reaction formula of hydrogen peroxide and ozone, when the supplied hydrogen peroxide and the ozone absorbed in the water are the same equivalent, the hydroxyl radical generation efficiency should be the best, but actually, Since the raw molecules of the TOC component and some of its decomposition intermediates may be directly oxidized by the ozone molecules, hydrogen peroxide which is actually required to correspond to such ozone consumption is required. The amount is less than the stoichiometric value (theoretical, ie, stoichiometric hydrogen peroxide / ozone weight ratio = 0.354). Clogging, the gap between the above weight ratio = 0.15 and the stoichiometric hydrogen peroxide / ozone weight ratio = 0.354, suggests this.

That is, the present inventor has determined that the TOC concentration of the treated water /
The ORP and dissolved ozone concentrations are located at the positions of the hydrogen peroxide supply amount / ozone supply amount ratio substantially corresponding to the inflection point of the graph showing the relationship between the raw water TOC concentration ratio and the hydrogen peroxide supply amount / ozone supply amount ratio. It was found that there is an inflection point in the graph showing the relationship between the hydrogen peroxide supply amount and the ozone supply amount ratio.
On the other hand, as compared with the case of the ORP or the dissolved ozone concentration of the treated water, the change in the hydrogen peroxide concentration due to the change in the hydrogen peroxide supply amount / ozone supply amount ratio becomes slightly gentle, but the residual amount in the treated water becomes small. Hydrogen peroxide is 100 μg / L (liter)
-2000 μg / L (ppb), stable TO
It was found that C removal could be performed.

The present invention has been completed based on the above findings. That is, the present invention relates to T
TOC by supplying hydrogen peroxide and ozone to water containing OC component
ORP monitor (ORP meter, ORP sensor), dissolved ozone monitor (dissolved ozone meter, dissolved ozone sensor) or hydrogen peroxide monitor (hydrogen peroxide meter, hydrogen peroxide sensor) It is another object of the present invention to provide a TOC component removal control method, wherein the supply amount of hydrogen peroxide is controlled by monitoring the treated water. In this case, in addition to controlling the supply amount of the hydrogen peroxide, the raw water or treated water
It is preferable to measure the C concentration and control the supply amount of ozone so as to be linked with the measured value of the TOC concentration of the raw water or the treated water. It should be noted that the feedback control, which controls the supply amount of ozone in conjunction with the measured value of the TOC concentration of the treated water, is more effective than the feedforward control, which controls the supply amount of ozone in conjunction with the measured value of the TOC concentration of the raw water. Is preferable because it is less susceptible to the effect of the TOC source (the type of organic substance as the TOC component) in the raw water that is the target of decomposition and removal, and is more accurate. In some cases, the above-described feedforward control and feedback control May be used in combination.

More specifically, the control of the supply amount of hydrogen peroxide according to the method of the present invention will be described. When the supply amount of hydrogen peroxide is controlled by an ORP monitor based on the above experimental results, the ORP of the treated water becomes 200 mV or more. 900 mV, preferably 220 mV to 850 mV, more preferably 220 mV
Hydrogen peroxide is desirably supplied so as to be from mV to 400 mV. When the supply amount of hydrogen peroxide is controlled by a dissolved ozone monitor, the dissolved ozone concentration of the treated water is 10 μg.
/ L to 2000 µg / L (ppb), preferably 50 µg
It is desirable to supply hydrogen peroxide so as to be in the range of g / L to 500 μg / L. When the supply amount of hydrogen peroxide is controlled by a hydrogen peroxide monitor, the concentration of hydrogen peroxide in the treated water is 100 μg / L or less. It is desirable to supply hydrogen peroxide at 2000 μg / L (ppb), preferably 200 μg / L to 1000 μg / L.

By controlling the ratio between the supplied hydrogen peroxide and the ozone absorbed in the water within an appropriate range before and after the inflection point, good efficiency of the TOC component decomposition reaction can be ensured and the treatment efficiency can be improved. The concentration of residual hydrogen peroxide in water can also be kept within a reasonable range. By controlling the rate of addition of hydrogen peroxide to ozone to such an extent that each monitored value falls within the above range, the utilization efficiency of ozone and hydrogen peroxide will be substantially the best, and the peroxide remaining in the treated water will be substantially improved. The concentration of hydrogen is also low, and adverse effects such as high load at the subsequent stage due to excessive residual hydrogen peroxide when recovering water are reduced.

In treating the water containing the TOC component by the method of the present invention, it is preferable to supply hydrogen peroxide and ozone while maintaining the pH value of the water containing the TOC component near neutrality. Here, “near neutral” usually means 6.
PH value in the range of 0 to 8.0, preferably 6.5 to
PH value in the range of 7.8. In general, when treated on the acidic side, the reaction by ozone molecules becomes dominant and the reaction rate slows down.On the other hand, when treated on the alkaline side, the reaction inhibiting action of the radical scavenger increases, and self-decomposition of ozone occurs. As a result, the reaction efficiency with the TOC component deteriorates.

As a method for generating ozone, a silent discharge method,
Various methods such as a water electrolysis method can be used.

Further, according to the present invention, the treated water obtained by treating the TOC component-containing water by the ozone / hydrogen peroxide method under the above-mentioned control is further treated by an ion removing device, and the residual organic acid in the treated water is treated. Also provided is a method for producing pure water by removing ionic components such as components.

When such an ion removing step is performed, the treated water obtained by the ozone / hydrogen peroxide method of the present invention comprises:
In order to avoid the adverse effect that the remaining oxidant causes deterioration of the material such as the ion exchange resin and the reverse osmosis membrane used in the subsequent ion removing device, it is usual to remove the remaining oxidant prior to the ion removal. . Examples of the method for removing the residual oxidant include activated carbon treatment, injection of a reducing agent (for example, sodium sulfite), ultraviolet irradiation, contact with a reduction catalyst (for example, a palladium-based catalyst), and the like.
Activated carbon treatment is preferred because of low cost and simple equipment.

According to the results of experiments conducted by the present inventor, if the TOC value of the treated water obtained from the ion removal step is 0.3 mg / L or less, preferably 0.2 mg / L or less, the above ion When the purified water, which is the treated water from the removal device, is sent to the ultrapure water production process to produce ultrapure water, UV (ultraviolet) oxidation, RO treatment (reverse osmosis membrane treatment), etc. in the subsequent ultrapure water production device To further increase the TOC value by 0.02 mg
/ L or less (Japanese Patent Application No. 9-236492).
issue).

Generally, TO by hydroxyl radical
Although the decomposition route (a series of reactions) of the C component varies depending on the type of the substance to be decomposed, most of the organic substances are converted into carbon dioxide and water via low-molecular organic acids such as propionic acid, acetic acid, and formic acid in the final stage. Therefore, even if the TOC value of the raw water (TOC component-containing water) and the TOC source (the type of organic substance as the TOC component) are different, most of the TOC component was converted to at least a low molecular weight organic acid by the oxidation treatment with the hydroxyl radical. In the stage, since the amount converted to carbon dioxide and water is no longer a TOC component, the TOC value in the treated water after the treatment with the hydroxyl radical falls within a considerably narrow range. In the treatment by the ozone / hydrogen peroxide method, the TOC value range of the treated water is approximately 0.5 to 2.5 mg / L.
become. If the treated water obtained in this way is further subjected to ion removal, the TOC value in the treated water after ion removal becomes 0.3 mg / L or less, and in most cases, 0.2 mg / L or less.

In this case, in addition to the above-described control by the method of the present invention, the TOC of the treated water
The value may be monitored and the operation of controlling the amount of hydroxyl radicals generated so that the TOC value of the treated water after ion removal becomes 0.3 mg / L or less may be added as an auxiliary. The TOC value of the treated water after the removal can be more reliably reduced to 0.3 mg / L or less.

As described above by way of example, the TOC value of the treated water obtained by the ozone / hydrogen peroxide method of the present invention has a certain correlation with the TOC value of the treated water from the subsequent ion removing device. When the amount of hydroxyl radical generation is controlled so that the TOC value of the treated water from the hydroxyl radical generating / treating device (reactor, reactor) becomes a predetermined value, the ion removing device corresponding to the TOC value of the treated water from the reactor can be obtained. Is obtained.

In factories for manufacturing electronic components such as semiconductors and liquid crystals, organic reagents such as isopropyl alcohol (IPA) and dimethyl sulfoxide (DMS) are used for various purposes.
O) etc.], for example, such organic reagents remaining on the surface of a wafer or the like are washed and removed with ultrapure water.
TO in the resulting ultrapure water containing organic matter
Those having a relatively low C concentration are usually subjected to a water recovery treatment. For example, water recovered by removing the TOC component and the ionic component from the used ultrapure water is used for producing ultrapure water. The control method for removing TOC components by the ozone / hydrogen peroxide method of the present invention can be used for removing TOC components from such used ultrapure water.

Of course, besides the removal of the TOC component in the production of ultrapure water, the method of the present invention is also applicable to the purpose of, for example, decomposing and removing trace organic contaminants in water treatment and advanced treatment of various wastewater and sewage. be able to. In such a case, it is often unnecessary to perform the ion component removing step.

That is, in the method of the present invention, the above-mentioned spent ultrapure water, tap water containing a small amount of organic contaminants (particularly organic contaminants which are difficult to decompose by biological treatment), industrial water, industrial waste water, The treated water, sewage treated water, etc. can be used as raw water.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

In the method of the present invention, by measuring and using the dissolved ozone concentration of the treated water, it is possible to control the ratio of the amount of hydrogen peroxide supplied / the amount of ozone absorbed in the water to a desirable range. it can. As a dissolved ozone monitor (dissolved ozone meter, dissolved ozone sensor), for example, an electrode type or an ultraviolet (UV) absorption type may be used, but when there is a complex organic component such as a surfactant in water, the UV absorption type may be used. The electrode type is preferable in order to ensure accurate measurement because interference by organic components is considered.

In the method of the present invention, the ORP of the treated water is
The amount of hydrogen peroxide supplied can also be controlled by measuring and utilizing. As an ORP monitor (ORP meter, ORP sensor) used for ORP measurement, for example,
Most commercially available ORP monitors have a combined platinum-silver chloride electrode, but have the advantage of being less expensive than dissolved ozone monitors.

In the method of the present invention, the supply amount of hydrogen peroxide can be controlled by measuring and using the concentration of hydrogen peroxide in the treated water. An advantage of the control using the hydrogen peroxide concentration is that the concentration of the hydrogen peroxide in the treated water is always measured, so that it is convenient when there is a hydrogen peroxide removal step at the subsequent stage. Measurement of hydrogen peroxide concentration
For example, it can be carried out using an automatic hydrogen peroxide monitor (hydrogen peroxide meter, hydrogen peroxide sensor) using the phenolphthaline method described in JP-B-56-54582.

As described above, the ozone / hydrogen peroxide method is
High TO with little effect from radical scavenger
A relatively high reaction rate can be obtained in the C concentration region, and the economy is good. Therefore, it is an excellent TOC component removal method. However, the reaction rate is low particularly at a low TOC concentration. Requires a large hydroxyl radical generation / treatment device (reaction tank, reactor), and this method has a relatively poor ozone absorption efficiency into a hydrogen peroxide-containing water system. Process, a decomposition process using a metal catalyst, or an ultraviolet irradiation process). Therefore, for example, the TO
When the C load is high, the following preferred embodiment (I) or (II) can be adopted.

The combination of (I) the ozone / hydrogen peroxide method according to the present invention and (1) an ozone treatment under an alkaline condition and / or (2) an ozone treatment under ultraviolet irradiation, which has a high reaction rate. it can. That is, the water containing the TOC component is treated by the ozone / hydrogen peroxide method according to the present invention, and T
Subsequent to the first step in which most of the OC component is decomposed, the treated water obtained in the first step is further subjected to (1) ozone treatment under alkaline conditions and / or (2) ozone treatment under ultraviolet irradiation. May be performed to perform a second step of ionizing at least substantially all of the remaining TOC components,
By doing so, effective TOC component removal can be achieved with a more compact apparatus at a reasonable processing cost, and, if necessary, ozone / peroxidation as part of ozone in the second step. The waste ozone gas from the hydrogen treatment device can be reused as an ozone source to improve the ozone utilization rate and reduce the load on the waste ozone gas treatment system (Japanese Patent Application No. 9-236493). In the case of this embodiment, according to the results of experiments performed by the present inventors, the TOC value of the treated water in the ozone / hydrogen peroxide method was 2.5 mg / L.
(Liter) or less, it is known that the reaction rate becomes extremely low. Therefore, the target value of the TOC value of the treated water from the ozone / hydrogen peroxide treatment system is, for example, 1.0 to 3.
It may be set to about 0 mg / L, preferably about 1.5 to 2.5 mg / L. When (1) the ozone treatment under alkaline conditions and (2) the ozone treatment under ultraviolet irradiation are used in combination, it is sufficient to perform the treatment in two stages.
What is necessary is just to provide in a step.

(II) Further, when the TOC load of raw water is high or when ozone in exhaust ozone gas is reused, the TOC component is decomposed with hydroxyl radicals by the most practical ozone / hydrogen peroxide method. A plurality of reaction tanks using the ozone / hydrogen peroxide method may be provided in multiple stages. In this case, a plurality of reactors for decomposing the TOC component with hydrogen peroxide and ozone are used in multiple stages, preferably, the supply amount of ozone to each reactor is reduced sequentially, and the total supply amount of ozone is reduced from the final stage reactor. The supply amount of the pH adjuster is controlled by the pH value of the treated water in the first-stage reaction tank, and the supply amount of hydrogen peroxide to at least the first-stage reaction tank is controlled by ORP. It is preferable to adopt a method of controlling by a measured value of the treated water in the reaction tank by a monitor, a dissolved ozone monitor or a hydrogen peroxide monitor (particularly, an ORP monitor).
This method is characterized in that the supply amount of the pH adjusting agent is controlled only by the pH value of the treated water in the first-stage reaction tank.
This is because when the water containing the TOC component is treated only in the one-stage reaction tank, the ozone supply amount control, the hydrogen peroxide supply amount control, and the pH adjusting agent supply amount control are each performed substantially optimally.
While the total number of parameters for these controls is relatively small, it is relatively easy. On the other hand, when the treatment by the ozone / hydrogen peroxide method is performed a plurality of times in a multi-stage reaction tank, the treatment for each parameter is performed. This is because if the control is performed for the number of times, the processing device becomes too complicated and practical use becomes difficult. This is a method obtained as a result of studying a simple system control method in this case from various angles. This will be described in detail below.

Since the amount of generated hydroxyl radicals depends on the amount of ozone supplied, control of the amount of ozone supplied is the most important. From the viewpoint of minimizing the control time lag, it is better to control the ozone supply amount based on the water quality data of the treated water obtained from the first treatment step (that is, the first-stage reaction tank), but it should be a target. Since the water quality is the quality of the final treated water of the ozone / hydrogen peroxide method from the final reaction tank, the total ozone supply amount is controlled by the target water quality value of the final treated water.

The water quality target value of the final treated water can be a desired value such as a TOC concentration (TOC value), an absorbance or a concentration of a specific organic substance depending on the purpose of the treatment. For example, when the purpose of the treatment is to remove humic substances (one TOC component and a colored component) in the raw water (such as decolorization), 25
0 to 265 nm (preferably 254 nm or 260 n
m) The absorbance of the final treated water in the UV absorption at the wavelength of m) may be measured. If the purpose of the treatment is to remove all organic substances (all TOC components) in the raw water, the TOC concentration of the final treated water may be measured. Should be measured. In the ozone / hydrogen peroxide method, as described above, organic substances are decomposed while generating organic acids in the reaction process. When the organic acid is generated, the alkalinity component in the water is consumed and the pH is lowered. On the other hand, when the organic acid is decomposed, the pH rises, and carbon dioxide is generated as a product of the decomposition of the organic acid. The generated oxygen dioxide is present in water as bicarbonate ions and the like, and acts as a radical scavenger that consumes hydroxyl radicals.

Therefore, if organic matter is decomposed in one continuous reaction tank for continuously supplying raw water, all organic substances will react in the direction of decomposing into carbon dioxide and water in the end. In two continuous reactors, a large amount of bicarbonate ions and the like as radical scavengers are generated, which lowers the effective utilization rate of ozone. On the other hand, if there are a plurality of reaction vessels, the influence of the radical scavenger is reduced at least in the last reaction vessel,
The total ozone utilization can be increased.

In this embodiment (II), a large amount of organic acid is generated in the first first-stage reaction tank, and in the subsequent reaction tanks, the generation of organic acid and the decomposition of organic acid occur simultaneously. Fluctuation is small. Therefore, according to the embodiment (II), if the pH in the first-stage reaction tank is set to a neutral range of pH = 6.0 to 8.0 with good treatment efficiency, the pH in the second-stage reaction tank is substantially reduced. To be kept in the neutral region
There is no need to adjust the pH in the subsequent reaction tank. It is desirable to sequentially reduce the amount of ozone supplied to each stage of the reaction tank. In this case, as much organic acid as possible can be generated in the first stage of the first stage reaction tank. If the pH is sufficiently adjusted in the tank, the fluctuation of the pH in the second-stage reaction tank is very small, and the ozone gas discharged from the first-stage reaction tank can be used for the second-stage reaction tank.
This is also advantageous in that the waste ozone gas can be used more effectively. According to the result of the experiment of the embodiment (II) by the inventor, if the pH is adjusted with the pH adjuster in the neutral region in the first-stage reaction tank, the pH is not adjusted after the second-stage reaction tank. It was confirmed that the pH of the solution also reached the neutral range.

On the other hand, the amount of hydrogen peroxide supplied to each reaction tank depends on the amount of ozone supplied, and therefore, an ORP monitor, a dissolved ozone monitor or a hydrogen peroxide monitor (particularly preferably an ORP monitor) in each reaction tank. Is preferably controlled by the measured values according to However, when the supply amount of ozone in the first-stage reaction tank accounts for most of the total supply amount of ozone, in order to simplify the control system, supply of hydrogen peroxide to the second-stage reaction tank is not performed. Even if a simple fixed amount of hydrogen peroxide is supplied to the reaction tank,
Hydrogen peroxide in an amount proportional to the amount of ozone supplied to the (respective) post-reaction tank may be supplied to the (respective) post-reaction tank.

In this embodiment (II), the exhausted ozone gas of the ozone gas supplied to the first-stage reaction tank as at least a part of the ozone supplied to the second-stage reaction tank and / or the subsequent-stage reaction tank, if present, is used. Supplying is preferable because the ozone utilization rate can be increased. In general, the ozone absorption efficiency largely depends on the supply amount of ozone gas. However, when the reaction tank is, for example, a bubble column having a water depth of 3 m or less, the ozone absorption efficiency is 70 to 80% at an ozone-containing gas blowing speed of about 10 m / hr. become. Clogging, 20 to 30% of ozone is discharged as waste ozone gas without being used. Therefore, if this exhausted ozone gas is supplied as at least a part of ozone to be supplied to the second-stage reaction tank and / or a further-stage reaction tank if present, the ozone utilization rate can be remarkably improved.

Further, according to the method of the present invention, the TOC component is not substantially completely removed from the water containing the TOC component by the treatment with the hydroxyl radical generated by hydrogen peroxide and ozone. The organic acid residue can be removed using an ion removal mechanism provided at a later stage, leaving a small amount that is not decomposed into carbon dioxide and water, and pure water can be produced economically. Examples of the removal mechanism include an ion exchange device and a reverse osmosis membrane (R
O) An ion removing device such as a device can be used. The pure water obtained in this case can be sent to the ultrapure water production process, and such a means can be suitably used for the recovery of used (ultra) pure water. It is also effective to further treat the treated water from which the residual organic acid has been removed in this way by at least one of the above-mentioned oxidizing means for generating hydroxyl radicals, and to further remove the remaining TOC component other than the organic acid. It is.

When an ion exchange apparatus is used to remove the remaining organic acid generated by the decomposition of the TOC component, at least an anion exchange resin is used. In order to produce pure water by removing various ionic components including residual organic acids, it is preferable to use an anion exchange resin and a cation exchange resin in combination. It can be used in a system such as a tower system. The timing of regeneration of the ion exchange resin can be determined based on the electrical conductivity of the ion exchange treated water flowing out of the ion exchange device.

Since the organic acid component generated by the decomposition of the TOC component is basically biodegradable, the regenerated wastewater generated by the regeneration of the ion-exchange resin and the reject water generated by the reverse osmosis membrane treatment are not used. , Activated sludge method and other biological treatment methods to make organic acid components inorganic (CO ₂ , H
₂ O).

The method of the present invention can be applied not only to the above-mentioned pure water production but also to water treatment. In the case of water treatment, drinking water is provided downstream of the ozone / hydrogen peroxide treatment apparatus. Activated carbon treatment equipment is almost always installed for the purpose of ensuring safety (removal of undesired by-products) and removing residual oxidant. Therefore, the organic acid component generated by the decomposition of the TOC component is easily biodegraded by microorganisms that have settled on the surface of the activated carbon in the activated carbon treatment device.

Next, this embodiment (II) will be described with reference to FIG. 4 which is a system flow diagram showing an example of a TOC component removing apparatus for carrying out the above-mentioned preferred embodiment (II) of the present invention. Will be described in detail. Raw water (TOC component-containing water) is introduced into a bubble column first reactor (reaction tank) 201 via a raw water line 205 in a downward flow manner. The ozonized gas generated by the ozone generator 230 is supplied from the lower part of the first reactor 201 via the ozonized gas line 231, and after the reaction, is sent to the second reactor 261 via the exhausted ozone gas line 233. The treated water obtained from the lower part of the bubble column first reactor 201 is supplied to the second reactor 261 via the first reactor treated water line 202. First reactor treated water line 2
02 pH monitor 203, ORP monitor 20
4 are respectively attached. Generally, such monitors can be attached to the reactor body, but from the viewpoint of maintenance of the monitors, it is more convenient to attach them to the treated water line.

The pH signal 240 of the treated water of the first reactor obtained from the pH monitor 203 is a pH controller (p
H controller) 241 and the pH controller 241
Is sent to a pH adjusting agent (usually an alkaline agent) injection pump 243, and a pH adjusting agent supply line 244 is provided as necessary so that the pH of the treated water becomes a predetermined value.
To control the supply rate of the pH adjusting agent supplied via the control unit.

On the other hand, the ORP signal 250 from the first reactor treated water from the ORP monitor 204 is input to an ORP controller (ORP controller) 251, and the output signal 252 from the ORP controller 251 is sent to a hydrogen peroxide supply pump 253. The supply rate of the hydrogen peroxide supplied via the hydrogen peroxide supply line 254 is controlled so that the ORP of the first reactor treated water becomes a predetermined value.

In the ozone / hydrogen peroxide method, there is a substantially optimum ratio of addition (supply) of hydrogen peroxide and ozone. As can be seen from FIGS. 2 and 3 obtained in the following examples, the addition ratio of hydrogen peroxide and ozone was
Affects RP value, residual hydrogen peroxide concentration value and residual ozone concentration value. Therefore, the supply amount of hydrogen peroxide can be controlled using the ORP of the treated water. Of course, the residual hydrogen peroxide concentration value or the residual ozone concentration value of the treated water can be used in place of the ORP, but the inflection point of the ORP is most remarkable and the ORP monitor is the most affordable of these monitors. Considering that the price is high, control using ORP is desirable.

On the other hand, in the second reactor 261, a part of the water treated by the second reactor is circulated by the circulation pump 262 via the circulation line 263.
Ejector 26 that absorbs exhausted ozone gas near the exit
The gas-liquid mixture from the ejector 265 is sent to the second reactor 261. You can also use a blower or in-linemixer instead of an ejector. Further, in this embodiment, the whole ozone gas used in the second reactor is the ozone gas discharged from the first reactor, but a part or all of the ozone gas is branched from the ozone generator 230 and sent. Can be replaced by The discharged ozone gas from the second reactor 261 is discharged via a discharged ozone gas line 264. Normal,
The exhausted ozone gas is once treated with an ozone decomposition catalyst or the like and then released into the atmosphere.

The treated water from the second reactor is supplied to a second reactor treated water discharge line 26 having a branch line 266.
The ORP signal 281 is transmitted by another ORP monitor 280 attached on the way, and the output signal 28 transmitted from the ORP controller 282 to which the ORP signal 281 is inputted.
3 is sent to the hydrogen peroxide supply pump 284, and the supply rate of hydrogen peroxide sent via the hydrogen peroxide supply line 285 is controlled so that the ORP in the second reactor becomes a predetermined value.

The second reactor treated water flowing into the branch line 266 is sent to a TOC meter 267 to measure the TOC concentration. The TOC signal 220 from the second reactor treated water from the TOC meter 267 is input to the TOC controller (TOC controller) 221, and the output signal 222 from the TOC controller 221 is output from the ozone generator 23.
The ozone generation amount (usually, the ozone concentration) is controlled so that the TOC concentration of the second reactor treated water becomes a predetermined value. Here, the TOC concentration is used to control the ozone supply amount, but another input signal may be used depending on the decomposition target. For example, when the object to be decomposed is humic substance in water, it is 250 to 265 nm (preferably 254 nm or 2 nm).
It is also possible to use the absorbance at ultraviolet light (UV) having a wavelength of 60 nm) or, when the decomposition target is another specific organic substance, the absorbance at a UV absorption wavelength specific to the organic substance.

Most of the second reactor treated water is supplied to the activated carbon tower 270 via the second reactor treated water line 268.
After removing the residual oxidizing agent (ozone and hydrogen peroxide) in the water, the ionic component, especially the organic acid component, is removed by the ion removing mechanism 271, and the final treated water (final treated by this device) is supplied from the final treated water line 272. Meaning treated water,
When used for production of ultrapure water or the like, it is natural that it is further processed. Of course, the ion removing mechanism 271 may not be necessary depending on the purpose. Even when the ion removal mechanism is omitted, the activated carbon tower 270 may be provided. In this case, the activated carbon tower is a biofilm reactor (a reactor in which a microorganism is formed on the surface of activated carbon to form a biofilm). ) Is often used.

Further, in the above embodiment, the TOC component removal is performed in a two-stage reaction tank.
If necessary, the treatment can be performed in three or more reaction vessels.

[0056]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples, but it goes without saying that the present invention is not limited to the examples.

FIG. 1 shows an apparatus used in the embodiment. A 30 liter reactor (reaction tank) 101 treats TOC component-containing water as raw water and oxidizes and decomposes the TOC component in raw water with hydrogen peroxide and ozone. Raw water is supplied to the reactor 101 from a raw water line 141 by a raw water pump 140. Part of the treated water from the reactor 101 is TO
The TOC value is measured by the C meter 120, and based on the TOC value, the ozone generator control signal 12 is output from the PID controller 121.
2 is transmitted to control the ozone generator 130, and another part of the treated water is OR-monitored by the ORP monitor 160.
P, dissolved ozone concentration, pH with dissolved ozone monitor 161
The pH is measured on the monitor 170. In an actual apparatus, it is sufficient to provide one of the ORP monitor and the dissolved ozone monitor. A hydrogen peroxide pump control signal 163 is transmitted from the PID controller 162 based on the measured value of the ORP or dissolved ozone concentration, and controls the hydrogen peroxide pump 150. The ozonized gas generated by the ozone generator 130 is
The gas is injected into the reactor 101 through the ozonized gas line 131. In the embodiment and the comparative example, the ozone dissolution in the reactor 101 was performed through a diffuser (a diffuser plate), but other means such as an ejector or an in-line mixer can be used. Hydrogen peroxide is supplied to the reactor 101 through the hydrogen peroxide supply line 151 by the hydrogen peroxide supply pump 150. Further, a signal 172 for controlling the pH adjusting agent injection pump is transmitted from the PID controller 171 based on the measured value of the pH, and controls the pH adjusting agent injection pump 173, and adjusts the pH through the pH adjusting agent injection line 174 as necessary. The agent is injected into the reactor 101. Reactor 10
Most of the treated water from 1 is sent to the activated carbon tower 111 through the treated water line 110, where the remaining oxidizing agent (hydrogen peroxide, ozone) is decomposed, and the activated carbon treated water is converted into ionized water. Water is sent to the exchange resin tower 112, where organic acids and the like are removed by ion exchange, and flows out to the ion exchange treated water line 113 as treated water after ion exchange. In addition, 133 is a reactor exhaust gas discharge pipe.

Example 1 In the apparatus shown in FIG.
At a flow rate of hr and a hydraulic residence time of 1.8 hr, water containing various TOC components is supplied as raw water by a raw water pump 140 via a raw water line 141 while being generated by an ozone generator 130 by silent discharge. The ozonized gas is sent to the reactor 101 via the ozonized gas line 131 at an ozone / TOC concentration ratio of 20 to 30/1, and is dissolved in raw water by a diffuser plate (not shown) installed below the reactor. Hydrogen peroxide was continuously supplied to the reactor 101 via the hydrogen peroxide supply line 151 by the hydrogen oxide supply pump 150. T in each TOC component-containing water
OC source is IPA (isopropyl alcohol), DMSO
Such TOC source is dissolved in ultrapure water with (dimethylsulfoxide) or NMP (N-methylpyrrolidone) so that the TOC concentration becomes 7 mg / L, to prepare TOC component-containing water. In the apparatus of FIG. 1, the TOC value of the treated water after being treated with hydroxyl radicals in the reactor 101 is measured online by a Seabus 810 TOC meter (manufactured by Seabass (USA)) 120, and T
Although a measurement signal from the OC meter 120 is sent to the PID controller 121 to control the amount of ozone generation to a predetermined value, in each experiment of this embodiment, the TO
Since the C value was constant, the amount of ozone generated was kept constant. In the apparatus shown in FIG. 1, the dissolved ozone concentration and the ORP value of the treated water after the treatment with hydroxyl radicals in the reactor 101 are respectively measured by a dissolved ozone monitor 16.
1 and the ORP monitor 160 to measure online, send a measurement signal from the dissolved ozone monitor 160 or the ORP monitor 161 to the PID controller 162, and output the output of the pump 150 for supplying hydrogen peroxide to the dissolved ozone concentration or ORP.
Although it is configured so that the value can be controlled to be within a predetermined range, in the case of each experiment of this embodiment, the ratio relationship between the amount of hydrogen peroxide supplied and the amount of ozone absorbed in water was examined. Therefore, the experiment was conducted by changing the supply amount of hydrogen peroxide stepwise. The pH of the water in the reactor 101 was kept constant at around 7.0. The treated water from the reactor 101 decomposes the oxidizing agent (hydrogen peroxide and ozone) with the activated carbon of the activated carbon tower 111, and then degrades the ion exchange resin (H type strongly acidic cation exchange resin and OH type) in the ion exchange resin tower 112. Ion exchange was carried out using ultra-pure water “Amberlite ESG-1” (sold by Organo Corporation) mixed with a strongly basic anion exchange resin at a volume ratio of 1: 1 to remove ionic organic substances. . The results of each experiment are summarized in FIGS.

FIG. 2 shows the weight ratio of hydrogen peroxide / ozone absorbed in raw water (hereinafter referred to as “H ₂ O ₂ / O ₃ weight ratio”) when IPA-containing water is treated as raw water. Dissolved ozone concentration in the treated water (measured with the dissolved ozone monitor 161), hydrogen peroxide concentration (phenol phthalin added to the sampled treated water, and colorimetric analysis using a colorimetric method [spectrophotometric method] [phenol phthalin method ] And ORP (measured by the ORP monitor 160). In FIG. 2, ○ indicates the dissolved ozone concentration,
Represents hydrogen peroxide concentration, and ● represents ORP. As can be seen from FIG. 2, the inflection point of the dissolved ozone concentration and the ORP appeared in the treated water when the weight ratio of H ₂ O ₂ / O ₃ was around 0.15. Before and after the inflection point, the OPR of the treated water becomes about 200 with a change of the H ₂ O ₂ / O ₃ weight ratio of only about 0.04.
changes rapidly over the range of mV to 900 mV, and
The dissolved ozone concentration of the treated water also changed rapidly over the range of about 1 mg / L to 3 mg / L. Meanwhile, the inflection point of the hydrogen peroxide concentration remaining in the treated water is the clear did, H ₂
O from ₂ / O ₃ weight ratio of 0.3 around, significantly hydrogen peroxide concentration with increasing H ₂ O ₂ / O ₃ weight ratio was increased.
When the DMSO-containing water and the NMP-containing water were treated as raw water, there was a slight difference from the case where the IPA-containing water was treated, but they showed almost the same tendency.

FIG. 3 shows the H ₂ O ₂ / O ₃ weight ratio when the IPA-containing water was treated as raw water and the TOC concentration of the treated water /
The relationship of the ratio of the TOC concentration of the raw water (representing the residual ratio of the TOC component, hereinafter referred to as “TOC / TOC ₀ concentration ratio”) is shown. As is clear from FIG. 3, an inflection point of the TOC / TOC ₀ concentration ratio appears when the H ₂ O ₂ / O ₃ weight ratio is around 0.15, and the H ₂ O ₂ / O ₃ weight ratio is 0.1%. Even if the supply amount of hydrogen peroxide is increased from 15, TOC / TOC ₀
The concentration ratio hardly changed, and it was found that there was almost no effect in removing the TOC component. On the other hand, as is clear from FIG. 2, since the residual hydrogen peroxide concentration increased remarkably from the H ₂ O ₂ / O ₃ weight ratio of around 0.3, the H ₂ O ₂ / O ₃ weight ratio was 0.1 to 0. It can be seen that it is preferable to set the supply amount of hydrogen peroxide so as to fall within the range of 0.25. IPA is also available when DMSO-containing water and NMP-containing water are treated as raw water.
Although there is some difference from the case where the contained water is treated, it shows almost the same tendency, and the H ₂ O ₂ / O ₃ weight ratio = 0.1 to 0.1.
It has been found that it is preferable to set the supply amount of hydrogen peroxide so as to fall within the range of 25.

[0061]

According to the present invention, by using an ORP monitor, a dissolved ozone monitor or a hydrogen peroxide monitor as an effective control means of the hydrogen peroxide supply amount, the hydrogen peroxide supply amount and the ozone supply amount (water (Amount of ozone absorbed) while maintaining the desired ratio of TOC
It is possible to efficiently remove the OC component.

When the TOC component is decomposed and removed in multiple stages using a plurality of reactors by the ozone / hydrogen peroxide method, only the pH value of the treated water in the first stage reactor is measured. If necessary, the pH of the first-stage reaction tank may be controlled to be around neutral with a pH adjuster.
In the reaction vessel (1), the organic acid is decomposed and generated, and is maintained at a pH value near neutrality. Therefore, control for pH adjustment is not particularly required.

[Brief description of the drawings]

FIG. 1 is a system flow diagram showing a configuration of a TOC component removing device used in an embodiment.

FIG. 2 shows the weight ratio of hydrogen peroxide / ozone absorbed in raw water (H ₂ O ₂ / O ₃ weight ratio) and the dissolved ozone of treated water when IPA-containing water is treated as raw water. It is a graph which shows the relationship between a density | concentration, hydrogen peroxide density | concentration, and ORP.

FIG. 3 shows the weight ratio of hydrogen peroxide / ozone absorbed in raw water (H ₂ O ₂ / O ₃ weight ratio) and the TOC concentration of the treated water when IPA-containing water is treated as raw water. / raw TOC concentration ratio of a graph showing the relationship between (TOC / TOC ₀ concentration ratio).

FIG. 4 is a system flow diagram showing an example of a TOC component removing apparatus for implementing a preferred embodiment (II) of the present invention.

[Explanation of symbols]

101 reactor 110 treated water line 111, 270 activated carbon tower 112 ion exchange resin tower 113 ion exchange treated water line 120, 267 TOC meter 121, 162, 171 PID controller 122, 222 Ozone generator control signal (output signal) 130, 230 Ozone generator 131, 231 Ozonated gas line 133, 233, 264 Waste ozone gas line 140 Raw water pump 141, 205 Raw water line 150, 253, 284 Hydrogen peroxide supply pump 151, 254, 285 Hydrogen peroxide supply line 160, 204 280 ORP monitor 161 Dissolved ozone monitor 163, 252, 283 Hydrogen peroxide pump control signal (output signal) 170, 203 pH monitor 172, 242 pH control agent injection pump control signal (output signal) 173 243 pH adjusting agent injection pump 174 pH adjusting agent injection line 201 First reactor 202 First reactor treated water line 241 pH controller 251, 282 ORP controller 261 Second reactor 262 Circulation pump 263 Circulation line 263 265 Ejector 265 266 Branch line 268 Second reactor treated water discharge line 271 Ion removal mechanism 272 Final treated water line

Claims (5)

[Claims] 1. To supply hydrogen peroxide and ozone to water containing a TOC component as raw water to decompose the TOC component to obtain treated water, the treated water is measured by an ORP monitor, a dissolved ozone monitor, or a hydrogen peroxide monitor. A method for controlling the removal of TOC components, comprising controlling a supply amount of hydrogen peroxide by monitoring. 2. In addition to controlling the supply amount of hydrogen peroxide, further measuring the TOC concentration of raw water or treated water and supplying ozone so as to interlock with the measured value of the TOC concentration of the raw water or treated water. 2. The method according to claim 1, wherein the amount is controlled. 3. A pH adjuster in which a plurality of reactors for decomposing TOC components with hydrogen peroxide and ozone are used in multiple stages, and the total ozone supply amount is controlled by a target water quality value of treated water from the final stage reactor. Is controlled by the pH value of the treated water in the first-stage reaction vessel, and the amount of hydrogen peroxide supplied to at least the first-stage reaction vessel is controlled by an ORP monitor, a dissolved ozone monitor, or a hydrogen peroxide monitor. The method for controlling the removal of TOC components according to claim 1 or 2, wherein the control is performed based on a measured value of the treated water in the tank. 4. An exhaust ozone gas, which is an exhaust gas of ozone supplied to the first-stage reaction tank, as at least a part of ozone supplied to the second-stage reaction tank and / or a further-stage reaction tank if present. 4. The T according to claim 3, wherein
Control method of OC component removal. 5. A method for producing pure water by further treating treated water obtained by decomposing TOC components in raw water by an ion removing device to remove ionic components such as organic acid components remaining in the treated water. The method of controlling TOC component removal according to any one of claims 1 to 4, wherein: