JPH0663570A - Method for determining and controlling ozone injection quantity and purified water treatment device - Google Patents

Abstract

PURPOSE:To always inject a proper quantity by calculating the injection quantity of ozone by setting an ultraviolet ray absorbance quantity of water to be treated having high correlation to a decrease quantity of a very small quantity of organic matter, as an index, in a device which eliminates a very small quantity of organic matter contained in water to be treated by using ozone. CONSTITUTION:In an ozone contact pond 1 into which water 2 to be treated flows, ozonized air 4 generated by an ozone generating device 13 is injected from its bottom part through a duct line in which flowmeters 14, 15 are provided, and exhaust gas is exhausted from duct line in which a flow rate system 16 and an ozone meter 17 are equipped. In a supply duct line of the sater 2 to be treated, a flowmeter 6, a UV meter 7 and a thermometer 8 for detecting ultraviolet ray absorbance are provided, and also, in a discharge duct line of treatment water 3 discharged from the ozone contact pond 1, a UV meter 11 and a dissolved ozone meter 12 are provided. Also, in a computer 9 for inputting output signals of each above detecting means, inflow concentration of a very small quantity of organic matter is predicted, and the injection quantity of ozone is calculated by setting the ultraviolet absorbance decrease quantity having high correlation to its decrease quantity, as an index.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ozone injection method for removing trace organic substances contained in raw water in a water purification system using ozone, a method for controlling the same, and a water purification apparatus.

[0002]

2. Description of the Related Art Current water treatments are systems centered on rapid filtration. That is, raw water → coagulation (chemical addition)
→ Precipitation → Filtration → Sterilization (chlorination) → Tap water. However, as is well known, the water quality has recently deteriorated with the progress of pollution of tap water, and raw water contains odorous substances that generate odors and toxic substances such as pesticides. We are in a situation where we cannot respond. As a result, it is difficult to make so-called "delicious water" without these trace amounts of organic substances.

Therefore, in order to decompose or adsorb and remove odorous substances and toxic substances contained in raw water for tap water, an advanced water purification system in which a treatment process of ozone → activated carbon is installed in the latter stage of the precipitation or filtration process of the water treatment system is proposed. It is being adopted rapidly. Many studies have demonstrated that ozone water purification uses the extremely strong oxidizing power of ozone to decompose odorous substances and toxic substances.
In order to carry out this ozone treatment, ozone gas electrically generated using an ozone generator is injected as fine bubbles from the bottom of a contact tank, which is a reaction device for dissolving ozone gas and for subsequent reaction.

[0004]

Since ozone gas can be generated electrically, it has the advantage that the injection amount can be easily adjusted and controlled, but on the other hand, it has the following problems. In carrying out water purification treatment using ozone, if economic efficiency and treated water quality are taken into consideration, there are many operating factors such as ozone gas concentration and ozone injection rate. However, for the purpose of removing odorous substances and toxic substances, because there is no method and device for monitoring the concentration of these trace organic substances in water online, at present, automatic control cannot be performed and the ozone injection rate cannot be controlled. Only when it is constant or the concentration becomes high,
The empirical method of manually increasing the injection rate of ozone is the mainstream. Therefore, under the present circumstances, a means capable of adjusting the ozone injection rate more precisely, that is, a support system capable of controlling is desired.

The present invention has been made in view of the above points, and an object thereof is to make it possible to determine the amount of injected ozone online by using an alternative characteristic that has a high correlation with the ozone removal characteristic of trace organic substances. A method, a control method thereof, and a water purification apparatus to which the method is applied.

[0006]

In order to solve the above problems, the method for determining the ozone injection amount of the present invention predicts the concentrations of odorous substances and toxic substances, and as an alternative index thereof, decreases the ultraviolet absorbance. The amount of water is calculated and the control is performed by first calculating the target value of the alternative index, and then correcting the treated water and the raw water. In addition to the equipment, flow meter for treated water, UV meter, thermometer, UV meter for treated water, dissolved ozone meter, flow meter for ozonized air, ozone meter for measuring the amount of ozonized air, flow meter for ozone exhaust gas Control that inputs the measured values of the ozone meter that measures the ozone concentration in the ozone exhaust gas and the measuring instruments described above, and feeds back the calculation results to the ozone generator to adjust the amount of ozonized air generated. A storage device for storing computer as calculation results.

[0007]

[Function] Since there is a high correlation between the decrease amount of trace organic substances contained in water and the decrease amount of ultraviolet absorbance, the concentration of trace organic substances should be set and directly measured by reflecting the condition of water quality. It is possible to determine the ozone injection amount and control it online by calculating each measured value and the correction amount by using the above-mentioned device as an alternative index, which is the decrease amount of the ultraviolet absorbance.

[0008]

EXAMPLES The present invention will be described below based on examples. Dimethylisoborneol (hereinafter referred to as 2-MIB) and diosmin have been identified as odor substances of tap water sources, and the odor of each water source is often caused by any one of them or a combination thereof. . As the toxic substance, various agricultural chemicals for golf courses and organic solvents such as tetrachloroethylene are known. However, there is no technology to measure these odorous substances and toxic substances online. Therefore, at present, it is impossible to control odorous substances and toxic substances, but the present inventors have achieved the present invention by focusing on making it possible by using other indicators. Hereinafter, for convenience of description, a case of measuring an odor substance using an alternative index will be described.

The material balance in the contact pond of the water purification device can be expressed by equation (1). M ₀ = M ₁ + M ₂ + M ₃ (1) However, M ₀ : Generated ozone amount M ₁ : Emitted ozone amount M ₂ : Residual ozone amount M ₃ : Ozone consumption due to reaction (1) Like

Amount of generated ozone M ₀ [g / h] = A _IN × Z _IN (2) where A _IN : injected ozonized air amount [m ³ / h] Z _IN : ozonized air concentration [g / m ³ (gas)] Emission ozone amount M ₂ [g / h] = A _OUT × Z _OUT (3) where A _OUT : Exhaust gas amount [m ³ / h] Z _OUT : Exhaust ozone concentration [g / m ³ ( gas)] Residual ozone amount M ₃ [g / h] = Q _W × O _Z (4) where Q _W : treated water flow rate [m ³ / h] O _Z : dissolved ozone concentration [g / m ³ ( water)] ozone by reaction consumption M _3: ozone is consumed by the decomposition of ozone itself in addition to the reaction (autolysis),
This is also included in the amount M ₃ consumed by the reaction.

Ozone injection, which is generally used as an index of operation
Rate O_DOSE[G / m³(water)] is expressed as in equation (5).
To be done. O_DOSE= (A_IN× Z_IN) / Q_W (5) When formula (1) is rewritten using formula (5), (A)_IN× Z_IN) / Q_W = [(A_OUT× Z_OUT) / Q_W] + O_Z+ M₃/ Q_W (6) Below, M₃/ Q_W[G / m³(water)]
The amount of ozone is called ΔO ₃I will write. this is,
It represents the amount of ozone consumed in the reaction.

When considering the control considering the reaction, ΔO ₃
Is the most important, and to calculate this, A _IN , Z
_IN , A _OUT , Z _OUT , and O _Z data are required. Further, since the reaction rate is directly related to the temperature, it is of course important to monitor the water temperature. Using a certain river water,
From the water treatment experiment by ozone of the present inventors over a long period of time, 2-MIB decrease amount and ultraviolet absorbance (hereinafter, E260
It is clear that there is a correlation shown in the diagram of FIG.

The reduction amount is expressed by the following equation. Reduction amount of a certain water quality item = measured value of treated water−measured value of treated water (7) In the water used by the present inventors for the experiment and having the relationship shown in FIG. -It is possible to approximate the correlation between the MIB reduction amount and the E260 reduction amount. 2-MIB decrease (μg / l) = 1.125 × E260 decrease (8) On the other hand, ΔO ₃ and E260 decrease generally have a strong correlation. For example, with this water, the relationship shown in the diagram of FIG. 2 was obtained. That is, it can be approximated by the functional relationship of E260 decrease amount = 0.05 × ΔO ₃ (9).

Thus, the ozone ΔO used in the reaction
_{The fact that 3} has a high correlation with the amount of decrease in E260 indicates that it is appropriate to use E260 as an index of the reactant to be decomposed. Further, the finding obtained from the experiments by the present inventors that the E260 decrease amount in the diagram of FIG. 1 has a high correlation with the 2-MIB decrease amount, although the absolute amount is considered to be different, the amount of ozone consumed in the reaction ΔO ₃
Indicates that each is constant with respect to the amount of decomposition. As is clear from these results, ΔO ₃ and 2-M
Of course, the amount of IB reduction is also correlated, but to control the amount of ozone injection, it is possible to directly measure it and conclude that it is better to use E260, which reflects the water quality situation at that time. Obtained.

On the other hand, the odor concentration TO (determined by the degree of human perception: according to the sensitivity test method) and the 2-MIB concentration of the odor concentration of the river water in which 2-MIB is the odor source should be approximated by the following functional relationship. You can TO = 79.8 × 2-MIB concentration (10) Therefore, in order to reduce the odor of tap water, it is sufficient to assume the inflow concentration of a certain odorous substance and consider the removal amount based on the E260 reduction amount. . The assumed inflow odor substance concentration can be determined from past data.

The method of the present invention will be described below by way of specific examples. FIG. 3 is a schematic system diagram in which ozone and water flows are indicated by solid arrows and electric signals are indicated by dotted arrows in an apparatus to which the method of the present invention is applied. In FIG. 3, the water 2 to be treated flows into the ozone contact pond 1 and becomes treated water 3 and flows out. The ozone contact pond 1 is supplied with ozonized air 4 from the bottom and discharged as exhaust gas 5. Treated water 2
The flow rate is measured by the flow meter 6, and the UV absorbance is measured by the UV meter 7 and the water temperature is measured by the thermometer 8 as the water quality items of the water 2 to be treated. All of these measured values are input to the computer 9 online. The computer 9
A storage device 10 for storing data and calculation results is attached. The ultraviolet absorbance of the treated water 3 is UV as in the case of the treated water 2.
The dissolved ozone is measured by a total of 11, and the dissolved ozone is measured by a dissolved ozone meter 12. All these measured values are also input to the computer 9 online.

As described above, the ozone contact basin 1 is provided with the UV meter 7 and the UV meter 11 for measuring the water temperature and the dissolved ozone meter 12 for measuring the dissolved ozone as a measuring device.

Similarly, all measured values are calculated by the computer 9.
Input to. The signal of the measured value to be processed and the control signal from the computer 9 to the ozone generator 13 are transmitted by a cable. The flow rate of the ozonized air 4 from the ozone generator 13 is measured by the flow meter 14, and the ozone concentration thereof is measured by the ozone meter 15. The flow rate of the exhaust gas 5 is measured by the flow meter 16, and the ozone concentration in the exhaust gas 5 is measured by the ozone meter 17. These measured values are input to the control computer 9, and the control computer 9 operates based on the following calculation method and adjusts the ozone generator 13 so as to change the ozone generation amount. The ozone injection amount can be controlled. The calculation method is performed by "calculation of alternative target value", "correction of treated water", and "correction of raw water". The main points are as follows.

First, an "alternative target value" is calculated. Odorants are caused by the metabolic products of algae that live in eutrophic lakes and marshes. Therefore, the timing of occurrence is clearly seasonally dependent, and the occurrence in summer is overwhelmingly large. In addition, the amount generated varies from year to year and varies considerably.
Therefore, Table 1 shows the basic pattern of the generation of odorous substances.
On the street.

[0020]

[Table 1] Patterns 1 to 3 are cases where the raw water contains a large amount of odorous substances or some organic matter. At this time, the set value of the inflowing odorant concentration (differs in the three cases) and the ultraviolet absorbance (E260) The target value of the E260 reduction amount is determined from the correlation formula of the reduction amount.

With respect to these three patterns, the estimated value MB of the inflowing odorous substance concentration is determined by, for example, the concept of cumulative probability.
To decide. Figure 4 shows 60-day 2-MIB in summer
FIG. 6 is a diagram showing the relationship between the relative frequency of occurrence and the cumulative probability (cumulative relative frequency) from the low concentration side, which is the measured value when acquired at a frequency of 1 sample / day. The relative frequency means each section shown on the horizontal axis of FIG. 4 (for example, 2-MIB concentration 0.02 to 0.04).
μg / l) is the number of data divided by the total number of data, and the cumulative probability is an integrated value of these.

For example, when it is desired to set the desired odorous substance concentration to 80% of the total probability, the cumulative probability is 80%, that is, the interval 0.12 to 0.14 μg / l in FIG.
The average value of 0.13 μg / l is set as the inflow water value. When the 2-MIB concentration of treated water is 0.04 μg / l,
From equation (7), the target value for E260 removal is (0.13-
0.04) /1.125=0.08, and in order to obtain this value, the ozone injection amount is adjusted according to the present invention. The method using this cumulative probability is an extremely useful method because it is possible to accumulate unique data at the water treatment plant and utilize it.

On the other hand, the water quality may vary considerably,
There may be situations where odorous substances are contained in clean water. In this case, the water quality is considerably different from the water quality for which the above correlation formula was created, and therefore ozone is excessively injected to achieve the ultraviolet absorbance removal amount. That is, when the water quality is good, the amount of ΔO ₃ does not easily increase, so the ozone injection rate is increased more than necessary. To avoid this, as a control stopper, the maximum ozone injection rate MO
Set _DOSE or maximum dissolved ozone concentration MO _Z and enter it first.

In Pattern 4, it is expected that the quality of the inflowing water is clean and the odorous substance concentration is obviously low.
In this case, it is possible to inject a constant amount of low-concentration ozone or determine a certain E260 removal rate, and control the ozone injection amount based on this. It is the measurements of water temperature and their trends that the computer recognizes the seasons. This makes it possible to roughly distinguish between two types of recognition, summer and winter.

The input functional relationship is equation (8). Although the linear relationship is shown in FIG. 1 in the present embodiment, it may be an exponential function, for example, as long as the correspondence relationship between the 2-MIB decrease amount and the E260 decrease amount is clear. . Next, "treatment water correction" is to correct the substitute target value. This is done based on the following four conditions and judgments.

Condition 1) When the water temperature in winter is low, raw water is good and ozone is easily dissolved. Therefore, dissolved ozone is controlled within a range of 0.05 to 0.15 mg / l. Condition 2) Dissolved ozone concentration is controlled at 0.15 mg / l ( _NOZ ) or less in consideration of the influence of the activated carbon adsorption basin at all times. Condition 3) The exhaust ozone concentration is always 0.3 to 1.0 g / Nm.
Control within ³

Condition 4) If the above conditions are satisfied, E
The 260 reduction amount is set so as to reach the target value. However,
Maximum injection rate MO _DOSE or less. The actual operation method using these is as shown in Table 2, for example.

[0028]

[Table 2] Next, "raw water correction" is to calculate the correction amount from the change amount of each data under the following conditions.

When the pH is acidic → The reaction becomes slow. When the pH is alkaline → The reaction becomes faster. Residual salt → ozone is decomposed. Turbidity → Ozone is consumed. However, these corrections shall be made when there is a significant change in the exhaust ozone concentration due to the change in each water quality data.

An actual operation method using these is as shown in Table 3, for example.

[0031]

[Table 3] Fuzzy inference or the like is used to calculate each correction value.

The method for determining the ozone injection amount in the water purification method using ozone, its control method, and the water purification apparatus have been described above. In particular, although the case where the odorous substance is removed has been described in the examples, the present invention is also applicable to the various agricultural chemicals on the golf course as described above and the toxic substance that is an organic solvent such as tetrachloroethylene.

[0033]

EFFECTS OF THE INVENTION Water purification treatment utilizing the strong oxidizing power of ozone is very effective, but the injection amount of ozone is changed according to the fluctuation of the inflow concentration of odorous substances and toxic substances contained in the water to be treated. Since it was empirically determined, it was impossible online, but in the present invention, as described in the examples, the concentrations of odorants and toxic substances are predicted, and as an alternative index to this, the ultraviolet absorption decrease amount is calculated. Is used to determine the ozone injection amount, and as a device for realizing this, an ozone contact basin, an ozone generator, a flow meter for the water to be treated, a UV meter, a thermometer, and a UV meter for the treated water are used. , Dissolved ozone meter, flow meter of ozonized air, ozone meter for measuring the amount of ozonized air, flow meter of ozone exhaust gas, ozone meter for measuring ozone concentration in ozone exhaust gas, and the measurement values of the above measuring instruments Input, The result of the above calculation is fed back to the ozone generator to adjust the amount of ozonized air generated, and the storage device for storing the calculation result is arranged. An online control process can be put into practical use for the removal of trace organic substances in treated water.

[Brief description of drawings]

FIG. 1 is a diagram showing a correlation between a 2-MIB decrease amount and an ultraviolet absorbance decrease amount.

FIG. 2 is a diagram showing the correlation between ΔO ₃ and the amount of decrease in ultraviolet absorbance.

FIG. 3 is a schematic diagram showing a water flow and an electric signal system of a water purification apparatus to which the method of the present invention is applied.

FIG. 4 is a diagram showing the relationship between 2-MIB occurrence relative frequency and cumulative probability.

[Explanation of symbols]

 1 Ozone Contact Pond 2 Treated Water 3 Treated Water 4 Ozoned Air 5 Exhaust Gas 6 Flowmeter 7 UV Meter 8 Thermometer 9 Computer 10 Storage Device 11 UV Meter 12 Dissolved Ozone Meter 13 Ozone Generator 14 Flowmeter 15 Flowmeter 16 Flowrate Total 17 Ozone meter

Claims (4)

[Claims] 1. A method for predicting the inflow concentration of trace organic matter in determining the injection amount of ozone in water purification treatment for removing trace organic matter contained in water to be treated using ozone, and correlating with the decrease amount instead of the inflow concentration. A method for determining the amount of injected ozone, which comprises calculating the amount of injected ozone using the highly-reduced amount of decrease in ultraviolet absorbance as an alternative index. 2. The method according to claim 1, wherein the inflow concentration of a trace amount of organic matter is determined from the concentration occurrence probability of the water treatment plant used. 3. When controlling the ozone injection amount using the method according to claim 1 or 2, the target value of the alternative index is first calculated, and the treated water correction and the raw water correction are further performed. How to control quantity. 4. The method according to claims 1 to 3 is applied,
The ozone contact pond (1) into which the water to be treated flows and injects ozone from the bottom to flow out the treated water, the ozone generator (13) to generate ozonized air to be injected into this contact pond, and the flow rate of the water to be treated A flow meter (6) for measuring, a UV meter (7) for measuring the ultraviolet absorbance of the treated water, a thermometer (8) for measuring the water temperature of the treated water, a UV meter (for measuring the ultraviolet absorbance of the treated water ( 11), a dissolved ozone meter (12) for measuring the amount of dissolved ozone, a flow meter (14) for measuring the amount of ozonized air sent from the ozone generator (13), and an ozone meter for measuring the ozone concentration of the ozonized air as well. (15), Flowmeter (16) that measures the amount of ozone exhaust gas discharged from the contact pond (1), Ozone meter (17) that also measures the ozone concentration in ozone exhaust gas, and the measurement values of the above-mentioned measuring instruments are input. The calculated result A control computer (9) for feeding back to the generator (13) to adjust the amount of ozonized air generated, and a storage device (10) connected to the computer (9) for storing the calculation result. Water purification equipment.