JP2000051875A - Control of water treatment operation by ozone and ultraviolet rays - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water treatment method performing ultraviolet treatment after ozone treatment, adaptable even with respect to fluctuations in the quality of raw water and capable of reducing the operation cost of a system. SOLUTION: The injection of ozone and the irradiation with ultraviolet rays are properly performed by controlling the ozone generation amt. of an ozone generator 6 from the measured value due to a water quality meter 11 of treated water and controlling the output of an ultraviolet lamp from the measured value of the ultraviolet intensity meter 12 provided in the wall surface of an ultraviolet treatment reaction tank and the measured value of a dissolved ozone meter 14 provided before and after ultraviolet treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to water treatment for the purpose of oxidatively decomposing pollutants contained in water.

[0002]

2. Description of the Related Art Water treatment methods using the strong oxidizing power of ozone include the decomposition of musty odor substances and trihalomethane precursors in clean water, reuse of treated water in sewage by decolorization and sterilization, and chemical oxygen in industrial wastewater. It is used in a wide range of fields, such as reducing demand. The reaction of ozone in water is roughly classified into two types: direct oxidation by ozone molecules, and oxidation by hydroxy radicals having stronger oxidizing power than ozone generated by the self-decomposition of ozone in water. Therefore, as one means of enhancing the oxidizing power by the reaction of ozone in water, a method of irradiating ozone with ultraviolet rays to promote self-decomposition of ozone and generate hydroxyl radicals has been devised. It has been put to practical use in research on the oxidative decomposition of hard-to-decompose organic substances, and in pure water production equipment.

[0003] As an example, FIG.
FIG. 1 shows a schematic diagram of a control method in a “sterilization method for a high-purity water supply system” described in JP-A-433-433. Here, the following treatment is proposed as a sterilization method at the latter stage of the highly pure water production process. First, the raw water 1 flows into a water treatment system including an ozone injector 2, a reservoir 3, an ultraviolet treatment reaction tank 4, a dissolved ozone meter 5, an ozone generator 6, and a controller 7. Next,
Ozone from the ozone generator 6 is injected into the system based on the measured value of the dissolved ozone meter 5, and after a certain period of treatment, the ozone injection is stopped. Further, an ultraviolet irradiator provided in the ultraviolet treatment reaction tank 4 is operated to decompose dissolved ozone. The purpose of this ultraviolet irradiation is to remove ozone, but at the same time, the oxidation of organic substances is promoted by the generation of hydroxy radicals.

[0004] In the "method of removing organic substances in water" described in Japanese Patent Application Laid-Open No. 8-89976, an organic substance is oxidized by repeating a combination step of addition of ozone and subsequent ultraviolet irradiation a plurality of times. A method for disassembly is presented. Furthermore, in the "water treatment apparatus" described in JP-A-6-277660, there is proposed a method of sequentially performing ozone treatment and ultraviolet irradiation using an ultraviolet lamp for generating ozone.

[0005]

However, in the above-mentioned water treatment method using ozone and ultraviolet light, although a method for controlling the operation of the ozone generator based on the measured value of the dissolved ozone meter is shown, the control of the ultraviolet light is carried out. The method is not clear, and no method has been proposed for appropriately controlling both the amount of injected ozone and the amount of ultraviolet irradiation in order to obtain the target treated water quality.

[0006] Therefore, in the case of treating raw water whose water quality fluctuates greatly, simply controlling the ozone injection rate causes an excess or deficiency in the amount of ultraviolet irradiation, and not only does not make it possible to obtain the target treated water quality, but also The problem that processing cost becomes high arises.

[0007]

According to the present invention, there is provided a water treatment method for performing an ultraviolet treatment after an ozone treatment in a water treatment method provided by a water quality meter provided in a flow path after the ultraviolet treatment. Based on the difference from the value, the ozone generation amount from the ozone generator is controlled to a predetermined value, and at the same time, the difference between the measured value of the ultraviolet intensity meter provided on the wall of the ultraviolet treatment reaction tank and the set value, and before and after the ultraviolet treatment. Based on the difference between the measured value of the dissolved ozone meter provided and the set value, the output of the ultraviolet lamp is controlled by an ultraviolet dimmer, and the ozone injection and the irradiation of the ultraviolet light are carried out with respect to the fluctuation of the raw water quality. I do.

[0008] According to this method, if the raw water quality load gradually increases, the set value of the water quality meter provided after the ultraviolet treatment may exceed the target water quality value. I do. First, the amount of ozone generated from the ozone generator is increased to a predetermined value. Next, it is measured whether or not the whole of the water to be treated is irradiated with the ultraviolet ray by the measured value of the ultraviolet intensity meter provided on the wall surface of the ultraviolet ray treatment reaction tank. To increase. At this time, the amount of ultraviolet irradiation is controlled so that the measured value of the dissolved ozone meter provided in the flow path after the ultraviolet treatment becomes zero. This is repeated a plurality of times to achieve the target water quality value.

On the other hand, if the raw water quality load gradually decreases, the set value of the water quality meter provided after the ultraviolet treatment may be lower than the target water quality value. Therefore, the following control is performed. First, the amount of ozone generated from the ozone generator is reduced to a predetermined value. Next, it is measured whether or not the whole of the water to be treated is irradiated with the ultraviolet ray by the measurement value of the ultraviolet intensity meter provided on the wall surface of the ultraviolet treatment reaction tank. Decrease the amount. At this time, the amount of ultraviolet irradiation is controlled so that the measured value of the dissolved ozone meter provided in the flow path after the ultraviolet treatment becomes zero. This is repeated a plurality of times to achieve the target water quality value.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a description will be given based on an embodiment using a schematic diagram of a water purification treatment flow used to demonstrate the present invention. FIG. 1 shows a flow diagram of a water purification apparatus used to prove the effect of the method of the present invention.

As raw water 1, sodium humate (A
ldrich) was dissolved in tap water, and a solution having a TOC (total organic carbon) concentration of 1.3 to 2 mg / L and a pH of about 7 was used. This humic acid solution is 1 L / min
At a flow rate of 5 l, and then treated in an ultraviolet treatment reaction tank 9 having a volume of 1 L and a lamp output of 5 W. Ozone gas has a maximum ozone generation concentration of 200
A 5 L volume ozone treatment reaction tank 8 was injected at a flow rate of 0.1 L / min from an ozone generator 6 having a g / m ³ and a maximum ozone generation amount of 25 g / hr.

The concentration of ozone gas is measured by a gas phase ozone meter 16 and is controlled by a controller 7 according to a difference between a measured value of TOC by a water quality meter (TOC meter) 11 and a set value (TOC 1.5 mg / L). Adjusted. The ozone gas not absorbed in the water was decomposed in the exhaust ozone decomposition tower 17. The dissolved ozone concentration was measured by dissolved ozone meters 14 and 5 provided before and after the ultraviolet treatment reaction tank 9. The output of the ultraviolet lamp is measured by an ultraviolet intensity meter 12 through a quartz glass ultraviolet radiation intensity measurement window 13 provided on the side surface of the ultraviolet treatment reaction tank 9.
And the controller 7 adjusted the ultraviolet light controller 15 according to the measured value of the dissolved ozone concentration.

The set value of each parameter in this control is as follows:
It is as follows. 1) TOC set value of treated water when TOC of raw water is 2 mg / L: 1.5 mg / L, 2) Ozone gas concentration set value: 80 g / m ³ , 3) UV lamp output set value: 4 W, 4) UV irradiation intensity measurement window setting: 0.01 mW
/ Cm ² , 5) Set value of dissolved ozone concentration before ultraviolet rays: 0.5 mg / L.

There are three control methods: (a) constant ozone and ultraviolet (hereinafter referred to as UV) constant, (b) ozone control and constant UV, and (c) ozone control and UV control. The processing results of the cases were compared. (A) In the case of constant ozone and constant UV: FIG. 2 shows the change over time in the TOC concentration. As can be seen from this figure, the raw water T
If the OC concentration exceeds 2 mg / L, the treated water TOC concentration exceeds 1.5 mg / L as shown by the broken line, and the target treated water quality cannot be obtained. Furthermore, raw water TOC
Even when the concentration is 1.5 mg / L or less, the processing proceeds similarly, so that the TOC concentration as the target treated water quality is 1.5 mg / L.
This results in lowering than L.

This phenomenon is shown in FIG. 3 which shows the change with time of the dissolved ozone concentration before the ultraviolet treatment when the raw water concentration is high.
The dissolved ozone concentration falls below the set value, the dissolved ozone becomes insufficient, and the water quality cannot be sufficiently improved. As a result, the measured value of the ultraviolet lamp output shown in FIG. 4 becomes zero. On the other hand, when the concentration of raw water is low, as shown in FIG.
The dissolved ozone concentration rises above the set value, the dissolved ozone becomes excessive, and the amount of ultraviolet transmission in water increases with the improvement of the water quality more than necessary. As a result, as shown in FIG. The set value is exceeded, and the ultraviolet rays are wasted. (B) Ozone control / UV constant: As shown by the dashed line in FIG. 2, since the ozone injection amount is controlled,
The target treated water quality is satisfactory all the time. But,
Even when the raw water TOC concentration is 1.5 mg / L or less, the process proceeds in the same manner, and the TOC concentration as the target treated water quality is lower than 1.5 mg / L.

When the raw water TOC concentration is 1.5 mg / L or less, the water quality is good, but as shown in FIG. 4, the measured value of the UV lamp output exceeds the set value, and the UV light is wasted. It will be used. FIG. 6 shows the change over time of the generated ozone concentration. Compared with the case where the ozone concentration indicated by the broken line is constant, the ozone generator can be saved when the ozone concentration indicated by the solid line is controlled. I understand. (C) In the case of ozone control / UV control: As shown by the bold solid line in FIG. 2, since the ozone injection amount is controlled and the UV control is performed according to the treated water quality, the target treated water quality is satisfied at all times are doing. Raw water TOC concentration is 2mg / L
In the following cases, the ozone injection amount and the ultraviolet irradiation amount are reduced, and when the raw water TOC concentration is 1.5 mg / L or less, the operation is stopped.

FIG. 5 shows the change over time in the output of the ultraviolet lamp. It can be seen that energy is used more effectively than in the above-mentioned (a) or (b) constant UV operation method. FIG. 6 shows the change over time of the generated ozone concentration. It can be seen that the ozone generator can be saved in the case of the ozone concentration control shown by the solid line, compared to the case of the constant ozone concentration shown by the broken line. .

In the control method described above, a TOC meter is used as a water quality meter.
4, 260 nm), measurement control is performed, and similar results are obtained.

[0019]

As described above, according to the present invention, in the water treatment method for performing the ultraviolet treatment after the ozone treatment, the difference between the measured value of the water quality meter provided in the flow path after the ultraviolet treatment and the set value is obtained. The amount of ozone generated from the ozone generator is controlled to a predetermined value, and at the same time, the difference between the measured value of the UV intensity meter provided on the wall of the UV treatment reaction tank and the set value, and the measurement of the dissolved ozone meter provided before and after the UV treatment Based on the difference between the value and the set value,
The UV lamp output is controlled by a UV dimmer.
According to this control method, the operation of the ozone generator and the ultraviolet lamp is efficiently performed with respect to the fluctuation of the raw water quality, the power consumption can be reduced, and the running cost of the system can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a water purification treatment flow used to demonstrate the present invention.

FIG. 2 is a graph showing a change over time in TOC concentration.

FIG. 3 is a diagram showing a change with time of dissolved ozone concentration before ultraviolet treatment.

FIG. 4 is a diagram showing a change with time in measurement of the amount of ultraviolet irradiation.

FIG. 5 is a diagram showing a change with time of the intensity of an ultraviolet lamp.

FIG. 6 is a graph showing changes over time in the concentration of generated ozone.

FIG. 7 is a schematic diagram of a control method of the cited patent.

[Explanation of symbols]

 1: Raw water 2: Ozone injector 3: Storage tank 4: Ultraviolet treatment reactor 5: Dissolved ozone meter 6: Ozone generator 7: Control device 8: Ozone treatment reactor 9: Ultraviolet treatment reactor 10: Treated water 11: Water quality meter 12: Ultraviolet intensity meter 13: Ultraviolet irradiation intensity measurement window 14: Dissolved ozone meter 15: Ultraviolet light dimmer 16: Gas phase ozone meter 17: Waste ozone decomposition tower

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Ryutaro Takahashi 1-1-1, Tanabe-Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa F-term in Fuji Electric Co., Ltd. 4D037 AA11 AB01 AB02 AB03 AB04 AB05 BA18 BB01 CA12 4D050 AA03 AA15 AB03 AB04 AB06 AB07 AB17 BB02 BD06 BD08 CA07

Claims (1)

[Claims] In a water treatment method in which ultraviolet treatment is performed after ozone treatment, the amount of ozone generated from an ozone generator is determined based on a difference between a measured value of a water quality meter provided in a flow path after ultraviolet treatment and a set value. The difference between the measured value and the set value of the ultraviolet intensity meter provided on the wall of the ultraviolet treatment reaction tank at the same time, and the difference between the measured value and the set value of the dissolved ozone meter provided before and after the ultraviolet treatment, A water treatment operation control method using ozone and ultraviolet light, wherein an ultraviolet lamp output is controlled by an ultraviolet light dimmer.