JPH11138183A - Ozone inject control method in water treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To treat organic matter containing sewage by effectively utiliying a generated ozone quantity and reducing a discharge ozone gas quantity. SOLUTION: As a combination treatment of a sand filtering tank 10 and an ozone reaction tank 11, the sand filtering tank 10 is installed at a front stage and the reaction tank 11 is at a post stage. In such a constitution, an SS(suspend solids) component in a secondary treatment is performed a sand filtering treatment at the front stage and then an ozone treatment is performed at the post stage, thus an ozone injection quantity can be to the absolute minimum and also the discharge ozone gas discharged from the ozone reaction tank 11 can be restrained at minimum.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the treatment of organic sewage, and more particularly to a method of treating suspended sewage secondary effluent to effectively remove suspended matter and organic matter and improve the quality of treated sewage. It relates to the treatment of sewage.

[0002]

2. Description of the Related Art Generally, a water treatment process in a sewage treatment plant basically includes a primary treatment plant having a sand basin and a primary sedimentation basin as basic facilities, a microbial reaction tank called an aeration tank or an aeration tank, and a final sedimentation basin. It consists of a secondary processing plant that is a facility. The function of the primary plant is to remove coarse impurities suspended in the influent and suspended substances that settle by gravity. The secondary treatment plant removes soluble organic matter in the sewage using a variety of microorganisms called activated sludge, and removes suspended substances that could not be removed by the primary treatment plant, making clear treated water. I have. Furthermore, there is a system in which a facility for ozone treatment or sand filtration is disposed after the secondary treatment plant in order to improve the quality of the secondary treatment water.

[0003] These facilities are called tertiary treatment or advanced treatment. An example of the ozone treatment will be described with reference to FIG. The water to be treated 30 is supplied from the upper part of the ozone reaction tank 10. On the other hand, the ozone gas 33 is injected from the lower part of the reaction tank, is brought into gas-liquid countercurrent contact in the ozone reaction tank, and the treated water 31 is withdrawn from the lower part of the reaction tank. Further, the injected ozone gas is not consumed in its entirety, but becomes unreacted ozone gas 34, and is discharged as a processing gas 42 to the atmosphere via the exhaust ozone gas processing device 18.

In such a configuration, the water quality value of the water to be treated 30, the dissolved ozone concentration of the treated water 31, and the ozone concentration of the unreacted ozone gas 34 are measured (a measuring instrument is not shown).
Generally, the amount of injected ozone is set.
(Cited document: Ozone treatment characteristics of secondary sewage water, No. 30
Proceedings of the Annual Conference on Sewerage Research, 1993)

[0005]

Among the conventional methods, the advanced treatment plant aims to remove the chromaticity and odor in the microorganism-treated water (secondary treated water) or the organic substances remaining in the secondary treated water. Ozone treatment and sand filtration treatment are regarded as effective as these removing methods. However, the ozone reaction reacts with non-oxidizing substances as soon as possible, and the suspended substance (S
The component (S), hereinafter referred to as SS component) and the soluble component react without distinction. Therefore, ozone is consumed by the SS component, so that the actual ozone consumption is increased, resulting in a low water quality improvement effect.

Further, ozone generation has a problem that power consumption is large, and it is important how to control the amount of ozone generated and use it efficiently, including the problem of SS.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned prior art, and an object of the present invention is to provide a water treatment method for effectively injecting and controlling ozone into secondary treated water to improve treated water quality. It is in.

[0008]

In order to achieve the above object, in the present invention, a combination of a sand filtration tank and an ozone reaction tank is employed, and the sand filtration tank is provided in the first stage and the ozone reaction tank is provided in the second stage. In such a configuration, the secondary treatment water S
By subjecting the S component to sand filtration and then ozone treatment in the subsequent stage, the amount of injected ozone can be minimized and the amount of exhausted ozone gas discharged from the ozone reaction tank can be minimized.

That is, in the above means constituting the present invention, the first stage is a sand filtration tank, and the second stage is an ozone reaction tank. In other words, when there is no sand filtration, the water to be treated contains a soluble organic substance (a chromaticity component is also a kind of organic substance) and an SS component.
And it is consumed by both, as if the soluble organic matter is in a large state. To improve the quality of treated water,
It is essential that soluble organic matter is oxidatively decomposed by ozone.

[0010] Therefore, by removing the SS content by the sand filtration provided in the preceding stage of the present invention, ozone may be injected into the subsequent ozone reaction tank with respect to the soluble organic matter. However, it is impossible to always remove 100% of the SS content in the sand filtration tank, and the setting of the amount of ozone injected into the ozone reaction tank takes into account the ozone consumption of suspended substances not captured in the sand filtration tank. Driving is required. Further, in the ozone reaction tank, the entire amount of the injected ozone is not reacted and consumed with the water to be treated, but is discharged as unreacted exhaust ozone gas.
Since ozone gas itself is harmful, it cannot be released to the atmosphere, and an exhaust ozone gas treatment device such as a catalyst is required.

The amount of exhausted ozone gas is proportional to the amount of injected ozone. If the amount of ozone is adjusted to the minimum necessary in the ozone reaction tank as described above, the amount of exhausted ozone gas is reduced, and the load of exhaust gas treatment is reduced. Is reduced.

From the above, it is possible to obtain the water quality value to be set by measuring the SS content as the water quality value in the sand filtration tank and the chromaticity as the water quality value in the ozone reaction tank, and calculating the water quality value. Required ozone amount can be controlled. Specifically, in the first stage, the required ozone amount is calculated from the comparison of the chromaticity of the ozone reaction treated water and the set chromaticity of the treated water, and in the second stage, the first-stage ozone injection amount is corrected by the SS content in the sand filtration treated water. I do.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention realizes an ozone injection method in sand filtration and ozone treatment for advanced treatment of treated water such as municipal sewerage and industrial wastewater. Hereinafter, the configuration of the altitude processing will be described based on the embodiment shown in FIG.
In the sand filtration tank 10 and the ozone reaction tank 11, the inflow raw water (secondarily treated water) 20 flows in from the upper part of the sand filtration tank 10 and flows out from the lower part. Next, the sand filtration treatment water 21 flows in from the upper part of the ozone reaction tank 11 and is taken out as treatment water 22 from the lower part.

On the other hand, ozone gas 23 from the ozone generator 12 is injected from the lower part of the ozone reaction tank 11 through the diffuser 14. After the gas-liquid contact in the ozone reaction tank 11, the ozone gas 24 remaining unreacted is discharged to the ozone gas treatment apparatus 1.
After that, the gas is released to the atmosphere as the processing gas 25.

Next, the operation of the embodiment configured as described above will be described. The SS component in the raw water 20 flowing from the upper part of the sand filter tank 10 is captured in the filter layer by a sedimentation action and separated and removed. Next, the sand filtration treated water 21 from which the SS component was removed.
Flows down into the ozone reaction tank 11, where the ozone gas 23 injected from the lower part of the ozone reaction tank 11 is brought into countercurrent gas-liquid contact, and organic substances are removed or reduced by an oxidation reaction with ozone. However, the entire amount of the ozone gas injected into the ozone reaction tank 11 is not consumed, and a part of the ozone gas remains as unreacted exhaust ozone gas 24. For this reason, the exhausted ozone gas 24 is decomposed into oxygen through the exhausted ozone gas treatment device 13 filled with a catalyst such as a manganese-based catalyst, and then released into the atmosphere as a treated gas 25.

Next, a description will be given of a method of controlling ozone injection in the water treatment having the above-described construction. In the present invention, ozone injection control is corrected by SS using chromaticity as a basic index. In FIG. 1, water quality measuring devices 30, 31
(As an example, each measurement is an SS densitometer and a chromaticity meter), an arithmetic processing unit 50, a sand filtration water quality signal 40, and an ozone reaction water quality signal 41. In the above configuration, the SS concentration of the water quality value signal 40 measured by the water quality measurement devices 30 and 31 and the chromaticity of the water quality value signal 41 are transmitted to the arithmetic processing device 50.

The arithmetic processing unit 50 first compares the chromaticity set value with the chromaticity input value of the ozone reaction tank treated water 22, and calculates the first stage ozone injection rate based on the difference. Next, the SS concentration input value of the water quality value signal 40 of the sand filtration treatment water 21 is used as a correction value of the ozone injection rate.

That is, the present invention has found that the SS concentration and the organic matter concentration are in a proportional relationship, and adjusts the ozone injection rate according to the fluctuation of the SS concentration. Therefore,
As a second step, a correction value is calculated from the SS concentration of the sand filtration treatment water and the consumption constant k, and the ozone injection rate based on the chromaticity is corrected. Finally, the ozone generation amount 44 is calculated by the injection ozone controller 51 from the corrected ozone injection rate 42 and the filtered flow rate 43, and this value is transmitted to the ozone generator 12. Accordingly, the required ozone amount 23 is blown into the ozone reaction tank from the ozone generator 12.

Next, the effectiveness of the present invention will be described based on specific demonstration data. First, FIG. 3 shows a decrease in the concentration of the organic matter in the treated water with respect to the ozone injection rate when the sand filtration tank is installed and when the sand filtration tank is not installed. As a result, in the raw water (organic matter concentration BOD: 13 mg / L, SS concentration: 5 mg / L
The ozone injection for obtaining the same treated water organic matter concentration by removing the SS component in L) can be reduced by about 30 to 40% by installing a sand filtration tank. However, in the sand filter tank, 100% of SS is not always removed.
Some SS enters the ozone reactor.

Next, FIG. 4 shows the relationship between the chromaticity and the ozone injection rate. It can be seen that the chromaticity is greatly reduced by ozone injection. The required ozone injection rate for the set chromaticity can be calculated from FIG. FIG. 5 shows the relationship between the SS content and the organic substance concentration, and FIG. 6 shows the relationship between the organic substance concentration and the ozone injection rate. From FIG. 5, the SS concentration and the organic matter concentration are in a proportional relationship,
Therefore, from the SS concentration measurement in the sand filtration treated water,
FIG. 7 shows the relationship between the concentration and the ozone injection rate. As described above, in the present invention, FIGS.
The ozone injection rate is set based on the relationship shown in FIG.

[0021]

As is apparent from the above description, according to the present invention, by efficiently injecting ozone used for advanced treatment of sewage secondary treatment water, the amount of generated ozone can be efficiently used and the ozone can be introduced into the atmosphere. It is possible to reduce the amount of exhaust gas. In addition, it leads to the improvement of the quality of treated effluent water, which is effective in improving the aquatic environment.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an entire ozone treatment apparatus according to an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a part of a conventional ozone treatment apparatus.

FIG. 3 is a characteristic diagram showing a relationship between an ozone injection rate and an organic matter concentration in treated water.

FIG. 4 is a characteristic diagram showing a relationship between chromaticity and an ozone injection rate.

FIG. 5 is a characteristic diagram showing a relationship between an SS concentration and an ozone injection rate.

FIG. 6 is a characteristic diagram showing a relationship between an organic substance concentration and an ozone injection rate.

FIG. 7 is a characteristic diagram showing a relationship between an SS concentration and an ozone injection rate.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Sand filtration tank, 11 ... Ozone reaction tank, 12 ... Ozone generator, 13 ... Exhaust ozone treatment apparatus, 14 ... Aeration tube, 20 ...
Raw water, 21: sand filtration treated water, 22: ozone treated water, 23
... ozone gas, 24 ... exhaust ozone gas, 25 ... processing gas,
30, 31: water quality measuring instrument, 40: sand filtration treated water quality signal, 41: ozone reaction treated water quality signal, 42: ozone injection rate, 43: filtered water flow, 44: ozone generation, 50
... arithmetic processing unit, 51 ... injection ozone controller.

Claims (1)

[Claims] 1. A method for treating wastewater containing an organic substance and a floating substance through a sand filtration layer in a first stage and treating the wastewater with injected ozone in an ozone reaction tank in a second stage. The respective water quality value and the set water quality value are transmitted to the arithmetic processing device, and the ozone treatment water quality value and the set water quality value are compared and calculated by the arithmetic processing device to calculate an ozone injection rate suitable for the set water quality value, An ozone injection control method in water treatment, wherein the ozone injection rate is corrected based on the water quality value of the sand filtration treatment water.