JP2861045B2 - Treatment of water containing organic matter - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for treating organic matter-containing water, and particularly to biological treatment of organic matter-containing water, in which high-quality treated water is obtained with a small ozone injection amount. To a method for treating organic-containing water.

[Prior Art] Conventionally, there is a method of increasing the biodegradation rate of organic substances by using ozone when biologically treating water containing organic substances such as polluted river water and biologically treated human waste water. In other words, raw water such as polluted river water to be treated and biologically treated human waste water contains organic substances that are more or less biologically hardly decomposable, but are subjected to ozone treatment to oxidize these organic substances. Biodegradability can be increased.

Conventionally, methods of applying ozone treatment include a one-time method in which raw water is introduced into an ozone treatment tower to oxidize the water, and then biodegraded in a biological treatment tower, or a method in which ozone gas is directly blown into a biological treatment tank (Japanese Unexamined Patent Publication No. No. 59-46679).

[Problems to be Solved by the Invention] By applying ozone treatment, biologically hardly decomposable organic matter (hereinafter referred to as “biodegradable organic matter”) is oxidized to increase its biodegradability. On the other hand, organic substances having a high component decomposability (hereinafter referred to as “biodegradable organic substances”) are easily mineralized by ozone. When a large amount of biodegradable organic matter is contained in the water to be treated, ozone is consumed by the mineralization reaction of the biodegradable organic matter, and the biodegradable organic matter is relatively insoluble. The proportion of ozone used for the oxidation of organic matter is reduced.

That is, the mechanism of the biological treatment to which the ozone treatment is applied is as follows, and includes the [I] reaction of ozone oxidation and the [II] reaction in which ozone oxidation and biological oxidation compete. In general, the reaction rate of the [I] reaction is higher than that of the [I] reaction. Therefore, when the concentration of the organic substance is high or the organic substance contains a particularly easily oxidizable substance, the oxidation reaction of ozone ends at the gas-liquid interface, and
The reaction can proceed on a biological basis.

However, in human wastewater with an organic matter concentration (DOC) of about 200 ppm or in polluted river water with only about 1 ppm of DOC, the organic matter is mineralized, that is, ozone is consumed in the above [II] reaction, and the oxidation rate of the biodegradable organic matter is reduced. Is low. Moreover, in the conventional method, even if the amount of injected ozone is increased, the oxidation rate of the above-mentioned [I] reaction cannot be improved by the increased amount of injected ozone, and the effect of improving the biodegradability is leveled off.

In the conventional method, when ozone is directly blown into the biological treatment tower, it is necessary to prevent ozone from lowering the biological activity of raw water having a low organic matter concentration. That is, among raw water with low organic matter concentration, especially in river water and lake water used for water treatment, under normal ozone treatment conditions (ozone gas concentration of several mg /), the ozone concentration in the liquid inhibits organisms. Organisms may die.

The present invention solves the above-mentioned conventional problems, and provides a method for treating organic matter-containing water that can obtain high-quality treated water with a small amount of ozone in a method for treating organic matter by ozone oxidation treatment and biological treatment. The purpose is to do.

[Means for Solving the Problems] The method for treating organic matter-containing water according to claim 1, wherein the first treatment step (i) comprises one of biological treatment and ozone oxidation treatment, and the second treatment comprises the other. In the method for treating raw water containing an organic substance by the step (ii),
A part of the treated water from the step (ii) is returned to the step (i).

The method for treating organic-containing water according to claim 2 is a method for treating raw water containing organic matter by performing biological treatment after performing ozone oxidation treatment, wherein the treatment step comprising the ozone oxidation treatment and biological treatment is performed. It is characterized in that it is repeated at least twice.

[Action] In the present invention, the ozone oxidation treatment and the biological treatment are repeated twice for at least a part of the raw water.

For this reason, at least a part of the water to be treated introduced into the ozone treatment step has undergone biological treatment, and at least a part of the water to be treated introduced into the biological treatment step has undergone ozone treatment. Therefore, the water to be treated, which is obtained by previously decomposing and removing the biodegradable organic matter that undergoes the [II] reaction in which ozone oxidation and biological oxidation compete with each other by biological treatment, is supplied to the ozone treatment step. Ozone oxidation acts only on biorefractory organic matter.

According to the method of the present invention, [conversion of biodegradable organic substance to biodegradable organic substance by ozone treatment] → [mineralization of biodegradable organic substance by biological treatment] → [ozone treatment of remaining organic substance The treatment can be carried out by repeating a treatment cycle of [reoxidation] → [mineralization by biological treatment].

As described above, according to the method of the present invention, it is possible to divide the treatment area for producing the biodegradable organic substance by the ozone treatment and the treatment area for the biological treatment of the biodegradable organic substance, and to carry out the oxidation reaction by ozone. It can be carried out only for biodegradable organic matter. Moreover, the reaction efficiency can be kept high by repeating the processing steps in this manner. As a result, more organic matter is biodegraded with a smaller amount of injected ozone.

Example An example of the present invention will be described below in detail with reference to the drawings.

FIG. 1 and FIG. 2 are system diagrams each showing an embodiment of a method for treating organic-containing water of the present invention.

The method shown in FIG. 1 is a method of circulating treated water using one ozone contact tower 1 and one biological treatment tower 2 each. That is, in the method shown in FIG. 1, the raw water introduced into the ozone contact tower 1 from the introduction pipe 11 is oxidized by contact with ozone supplied from the ozone supply pipe 12 to the ozone contact tower 1 in the tower 1. The ozone is discharged from the discharge pipe 13, and the ozonated water is supplied to the biological treatment tower 2 from the pipe 14. A part of the treated water biologically treated in the biological treatment tower 2 is returned to the ozone contact tower 1 from the pipe 15, and the remainder is discharged out of the system through the pipe 16 as treated water.

In the method shown in FIG. 1, raw water is returned to the ozone contact tower 1 again through the ozone contact tower 1 and the biological treatment tower 2,
After that, since it is further circulated to the biological treatment tower, conversion of the hardly biodegradable organic matter in the raw water into biodegradable organic matter by ozone oxidation in the ozone contact tower 1 and mineralization of the biodegradable organic matter in the biological treatment tower 2 The treatment can be performed by repeating a series of treatment cycles in which the remaining organic matter is oxidized with ozone in the ozone contact tower 1 and mineralized in the biological treatment tower 2.

The method shown in FIG. 2 is a method in which an ozone contact tower and a biological treatment tower are provided in multiple stages. That is, in the method shown in FIG. 2, the raw water introduced into the ozone contact tower 1A from the introduction pipe 21 comes into contact with the ozone supplied from the ozone supply pipe 12 to the ozone contact tower 1A in the tower 1A and is oxidized. Is done. The ozone discharged from the tower 1A is sent to the ozone contact tower 1B downstream of the pipe 23, and the ozonated water of the tower 1A is sent to the biological treatment tower 2A from the pipe 24. The treated water subjected to the biological treatment in the biological treatment tower 2A is supplied from the pipe 25 to the ozone contact tower 1B, and comes into contact with the ozone supplied from the pipe 23 to be oxidized again with ozone. The ozone discharged from the ozone contact tower 1B is discharged from the discharge pipe 26. Tower
The ozone-treated water 1B is supplied from the pipe 27 to the biological treatment tower 2B and subjected to biological treatment again, and the treated water is discharged from the discharge pipe 28 to the outside of the system.

In the method shown in FIG.
A, biological treatment tower 2A, ozone contact tower 1B, biological treatment tower 2B to be processed in this order, by the ozone oxidation in the ozone contact tower 1A, the conversion of biodegradable organic matter in raw water to biodegradable organic matter, The treatment can be performed by repeating a series of treatment cycles of mineralizing the biodegradable organic matter in the biological treatment tower 2A, oxidizing the remaining organic matter in the ozone contact tower 1B with ozone, and mineralizing the biological treatment tower 2B.

The treated water circulation system shown in FIG. 1 and the multistage treatment tower system shown in FIG. 2 do not limit the method of the present invention at all,
The circulation process and the grounding mode of the processing tower can adopt other types. Further, the circulation system and the multistage system can be used in combination. Generally, in the case of the circulation system, the size of the equipment can be reduced, and in the case of the multistage system, the processing efficiency can be improved. In particular, in the case of the multi-stage system, the second
As shown in the figure, by introducing the ozone discharged from the ozone contact tower in the former stage into the ozone contact tower in the latter stage, the effective utilization rate of ozone can be increased.

3 (a) to 3 (e) are schematic diagrams showing specific examples of the method of implementing the present invention. For convenience of explanation, FIG.
In (e), A is an ozone contact tower, and B is a biological treatment tower. FIG. 3 (a) schematically shows the method shown in FIG. In the method shown in FIG. 3 (b), a part of the treated water of the ozone contact tower A is supplied to the biological treatment tower, and the remaining part is discharged as treated water. A is returned to A. FIG. 3 (c),
The method shown in (d) is obtained by replacing the ozone contact tower and the biological treatment tower in the method shown in FIGS. 3 (a) and 3 (b), respectively. The method shown in FIG. 3 (e) is an example in which two stages of the ozone contact tower A and the biological treatment tower B are installed in this order, and corresponds to the method shown in FIG.

In the method of the present invention, the ozone injection rate in the ozone oxidation step varies depending on the DOC concentration of the raw water, the absorption efficiency of the ozone contact tower, and the like. For example, when river water (DCO 1 to 2 ppm) is used as the raw water, 2mg-O ₃ / mg-DOC about,
When using human waste water (DOC 30ppm) as raw water,
Preferably between 10mg-O ₃ / mg-DOC about. actually,
Perform a batch test in advance to determine the optimum value.

On the other hand, as a biological treatment tower in the biological treatment step, a floating activated sludge treatment device including an aeration tank and a sedimentation tank, and a fixed bed or a fluidized bed activated sludge treatment device in which microorganisms are adhered to a carrier may be adopted. However, it is preferable to use a filtration tank provided with an inlet and an outlet for the liquid to be treated and a diffuser tube, and filled with a granular medium layer and a support material layer for supporting the granular medium layer. The liquid to be treated is introduced into the filtration tank from the inflow port, and passes through the tank of the aerobicly maintained granular medium together with gas (air) from the air diffuser in an upward flow or a downward flow. Aerobic microbial treatment by the microbial membrane adhering to the surface of the granular medium and filtration are performed, and high-quality treated water is taken out from the outlet.

In this case, as the granular medium to be filled in the biological filtration tank,
One or more of granular media such as gravel, sand, activated carbon, anthracite, and plastic materials can be used.

In the present invention, such a biological filtration treatment is carried out in a biological filtration tank with a DOC load of 0.5 kg / m ³ day or less, preferably 0.2 to 0.05.
It is preferable to carry out at about kg / m ³ · day.

The treated water obtained by the method of the present invention is discharged out of the system after being subjected to further filtration treatment or other treatment as necessary.

In such a biological filtration, the excess biological sludge in the biological filtration tank and the biological sludge separated by the subsequent filter can be treated together with a stock solution such as human waste.

Since the method of the present invention is a method applied to a flow for oxidizing organic substances and performing biological treatment, it can be applied to advanced treatment of water containing various organic substances such as wastewater and clean water. In particular,
It is effective for advanced treatment of colored biological treatment liquid of night soil and polluted river water.

Hereinafter, the present invention will be described more specifically with reference to experimental examples.

Experimental Example 1 (Example of the Present Invention)
Processing was performed by the method shown in the figure. The specifications of each tower,
The processing conditions were as follows.

Ozone contact tower column: 40 cm (height) × 4 cmφ column Ozone concentration at the inlet of the ozone contact tower: 20 mg / ozone injection rate: 8 mg-O ₃ / mg-DOC Biological treatment tower column: Apparent volume 1 Biological treatment tower Microbial carrier: 4 mmφ Ceramic beads of the raw water and the liquid circulation ratio of the biological treatment tower: 10 The residence time of the biological treatment tower: 15 minutes In such treatment, the ozone concentration discharged from the ozone contact tower is 10 mg / and the treated water quality (DOC) is 4 ppm. And the DOC removal rate was 80%.

Experimental Example 2 (Example of the Present Invention) Using the same ozone contact tower and biological treatment tower as those used in Experimental Example 1, two experimental towers were used in the method shown in FIG.
The processing was performed in the same manner as described above. However, the residence time of the biological treatment tower was 15 minutes in total for the two towers.

As a result, the DOC concentration of the effluent of the first stage biological treatment tower was 1
5 ppm (DOC removal rate 25%) The DOC concentration of the effluent of the second stage biological treatment tower, that is, the final treated water, is 5 ppm (DOC removal rate 75%).
Met.

The concentration of ozone discharged from the second-stage ozone contact tower is 1 m
g /, and the total absorption efficiency of ozone was 95%. That is, the ozone contact tower was twice as large as that of Experimental Example 1, but the ozone absorption efficiency (ozone utilization efficiency) was ten times.

Experimental Example 3 (conventional example: one-pass type) The treatment was performed in the same manner as in Experimental Example 1 except that the liquid circulation in the biological treatment tower was not performed.

As a result, the concentration of exhausted ozone from the ozone contact tower was 8 mg /, but the DOC concentration of the obtained treated water was 20 ppm,
The removal rate was as low as 30%.

Experimental Example 4 (Conventional example: injection of ozone into biological treatment tower) Ozone gas was blown into a column of 20 cm high and 10 cmφ packed with microbial carriers at a rate of 1 vvm, and the same raw water treatment as in Experimental Example 1 was performed. . The residence time of the raw water was 15 minutes. The concentration of the ozone gas to be blown was 3 mg /.

As a result, the DOC concentration of the obtained treated water was 30 ppm. On the other hand, the number of organisms in the column was 5 × 10 ³ cel before the start of the experiment.
It was 1 / ml, but dropped sharply to 1 cell / ml 24 hours after the start of the experiment. This was determined to be due to the toxicity of dissolved ozone since the ozone concentration in the liquid was 0.5 ppm. Therefore, it was recognized that the removal of DOC in this method was not due to organisms but to a mineralization reaction by ozone.

Experimental Example 5 An ozone contact tower and a biological treatment tower were alternately provided in multiple stages, and the ozone injection rate of each ozone contact tower was 1 mg-O ₃ / mg-DOC, and raw water having a DOC concentration of 3 mg / was used in the same manner as in Experimental Example 2. Was performed.

As a result, as shown by the curve I in FIG. 4, each time the ozone injection rate increases, that is, the more the effluent from the later biological treatment tower,
Improved DOC treatment rate, total ozone injection rate 4mg-O ₃ / mg-DOC
The DOC removal rate reached 90% in (treated water obtained by biologically treating the effluent of the fourth-stage ozone contact tower). From this,
It is clear that according to the method of the present invention, by increasing the ozone injection rate, it is possible to obtain DOC removal efficiency according to the injection rate.

On the other hand, when the raw water having a DOC concentration of 3 mg / was treated in the same manner as in Experimental Example 3 while changing the ozone injection rate, as shown in a curve II in FIG. The improvement was lower than in the method of the present invention.

When the same treatment was performed using only the ozone contact tower, the DOC removal rate was only 30% even when the ozone injection rate was increased, as shown by the curve III in FIG.

[Effects of the Invention] As described in detail above, according to the method for treating organic matter-containing water of the present invention, it is possible to improve the effective utilization rate of ozone and perform advanced DOC removal with a small amount of injected ozone. Is done. Therefore, according to the method of the present invention, it is possible to efficiently obtain high-quality treated water at low cost.

[Brief description of the drawings]

FIG. 1 and FIG. 2 are system diagrams showing one embodiment of the method for treating the organic matter-containing water of the present invention, and FIG. 3 (a) to FIG.
(E) is a schematic diagram showing one embodiment of the method for treating organic-containing water of the present invention, and FIG. 4 is a graph showing the results of Experimental Example 5. 1,1A, 1B …… Ozone contact tower, 2,2A, 2B …… Biological treatment tower.

Claims (2)

(57) [Claims] 1. A method for treating raw water containing organic matter in a first treatment step (i) comprising one of biological treatment and ozone oxidation treatment and a second treatment step (ii) comprising the other. In the method for treating organic-containing water, a part of the treated water from the step (ii) is returned to the step (i). 2. A method for treating raw water containing organic matter by performing biological treatment after performing ozone oxidation treatment, wherein the treatment step comprising the ozone oxidation treatment and biological treatment is performed in two steps.
A method for treating organic-containing water, wherein the method is repeated at least twice.