JPH05277475A - Treatment method for water containing organic substance - Google Patents

Abstract

PURPOSE:To improve ozone processing efficiency by ensuring that the pH value in an ozone reaction tower is controlled more stably than ever. CONSTITUTION:Untreated water containing an organic substance is first biologically treated, then is subjected to ozone oxidation process, or is first subjected to ozone oxidation process, and is biologically treated. Next, at least, part of an effluent from a biological treatment stage is conducted to an ozone oxidation stage, and at least, part of the effluent from the ozone oxidation stage is conducted to the biological treatment stage, thus treating the water containing organic. The pH value of the untreated water in an ozone reaction tower 1 is adjusted to 7 to 9 by monitoring the pH value using a sensor 3, and supplying alkali using an alkali supply device 4, if necessary. Consequently, the untreated water in the ozone reaction tower 1 is always maintained at an appropriate alkali side for triggering an ozone oxidation reaction. Therefore, it is possible to achieve high organic substance-removal efficiency using a small ozone injection amount.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating organic matter-containing water, and particularly to the biological treatment of organic matter-containing water, which is capable of obtaining treated water of high quality with a small ozone injection amount. Regarding the method.

[0002]

2. Description of the Related Art Conventionally, there is a method of increasing the biodegradation rate of organic matter by using ozone in biologically treating organic matter-containing water such as biologically treated water of polluted river water or human waste. That is, the raw water such as polluted river water to be treated and biologically treated water of human waste is
Although it contains organic substances that are more or less biologically persistent, it is possible to increase the biodegradability by oxidizing these organic substances by applying ozone treatment.

Conventionally, as a method of applying ozone treatment, a method of introducing raw water into an ozone treatment tower to oxidize it and then performing a biodegradation in the biological treatment tower or a method of directly blowing ozone gas into the biological treatment tank ( JP-A-59-46679
No.) is taken.

By applying ozone treatment, biologically hardly decomposable organic substances (hereinafter referred to as "biodegradable organic substances") are oxidized and their biodegradability is enhanced. High organic matter (hereinafter referred to as "biodegradable organic matter") is easily mineralized by ozone. When a large amount of biodegradable organic matter is contained in the water to be treated, ozone is excessively consumed in the mineralization reaction of the biodegradable organic matter, which makes it relatively biodegradable. The proportion of ozone used to oxidize organic substances decreases.

That is, the mechanism of biological treatment to which ozone treatment is applied is as follows, and the [I] reaction of ozone oxidation and
It consists of [II] reactions in which ozone oxidation and biological oxidation are competing.
In general, the reaction rate of the [I] reaction is higher, so when the concentration of organic substances is high or when organic substances that are particularly easily oxidized are included, the ozone oxidation reaction is terminated at the gas-liquid interface,
I] Reactions can be biologically driven.

[0006]

[Chemical 1]

However, the organic matter concentration (DOC) 200
In human waste water of about ppm or polluted river water having only DOC of about 1 ppm, ozone is consumed in the mineralization of organic substances, that is, the above reaction [II], and the oxidation rate of bio-degradable organic substances is low. Moreover, in the conventional method, even if the ozone injection amount is increased, the oxidation rate of the above-mentioned [I] reaction cannot be improved by the increase of the ozone injection amount, and the effect of improving the biodegradability reaches a ceiling.

In the conventional method, when ozone is blown directly into the biological treatment tower, it is necessary to prevent ozone from deteriorating the biological activity of raw water having a low organic matter concentration. That is, in raw water having a low organic matter concentration, particularly in river water and lake water that are used for treatment of tap water, under normal ozone treatment conditions (ozone gas concentration several mg / l), the ozone concentration in the liquid is It becomes an obstacle, and there is a risk that the organism will die.

As a method for treating organic matter-containing water, which is capable of obtaining high-quality treated water with a small amount of injected ozone, in the method of solving such problems and performing biological treatment by ozone-oxidizing organic matter, the present applicant Is a method for treating raw water containing organic matter in the steps A and B (one of the steps A and B is a biological treatment step and the other is an ozone oxidation step), and at least one of the effluents of the step A is treated. Part B
A method for treating organic-containing water, which is introduced into the process and at least a part of the effluent water of the process B is introduced into the process A, was found, and a patent application was previously filed (JP-A-2-203598).

In the method of Japanese Patent Laid-Open No. 2-203598, at least a part of the water discharged from the ozone treatment step is introduced into the biological treatment step, and at least a part of the water discharged from the biological treatment step is introduced into the ozone treatment step. Therefore, 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 above [I
I] Oxidation of ozone acts only on biodegradable organic matter because the water to be treated, which has undergone biodegradation of biodegradable organic matter that undergoes the reaction in advance and is removed, will be supplied to the ozone treatment process. Like

According to this method, [transformation of bio-hardly-degradable organic matter into easily bio-degradable organic matter by ozone treatment] →
It is possible to perform treatment by repeating the treatment cycle of [mineralization of easily biodegradable organic matter by biological treatment] → [reoxidation of residual organic matter by ozone treatment] → [mineralization by biological treatment].

According to the method of JP-A-2-203598, it is possible to divide a treatment area for producing biodegradable organic matter by ozone treatment and a treatment area for biological treatment of biodegradable organic matter, and use ozone. It is possible to allow the oxidation reaction to be carried out only by the biodegradable organic matter.
Moreover, the reaction efficiency can be kept high by repeating the treatment steps in this manner. As a result, more organic matter is biodegraded with a smaller ozone injection amount.

[0013]

According to the method of JP-A-2-203598, in which such ozone treatment-biological treatment is repeated several times, ozone is consumed for mineralizing the biodegradable organic matter as described above. In addition to preventing this, the organic acid generated by ozone treatment is decomposed by biological treatment, which has the effect of preventing the pH of the ozone treatment tank from leaning toward the acid side, which is unsuitable for the reaction. The pH control of the ozone treatment tank by biological treatment is often insufficient or unstable, and new measures are needed.

The present invention solves the above-mentioned conventional problems, and in a method of treating organic substance-containing water by a combined treatment of ozone treatment and biological treatment, the pH of the ozone treatment tank is controlled more stably and surely to perform ozone treatment. It is intended to provide a method of increasing efficiency.

[0015]

The method for treating organic matter-containing water according to the present invention is a method of subjecting raw water containing an organic matter to biological treatment followed by ozone oxidation treatment, or a method of performing biological treatment after ozone oxidation treatment, In the method for treating organic matter-containing water, wherein at least a part of the effluent water of the biological treatment step is introduced into the ozone oxidation step, and at least a part of the effluent water of the ozone oxidation step is introduced into the biological treatment step, the pH in the ozone oxidation step Is adjusted to 7-9.

[0016]

In the method of the present invention, in the combined treatment of ozone treatment and biological treatment, the pH in the ozone treatment step is
Therefore, the ozone treatment step is always maintained on the alkali side suitable for the ozone oxidation reaction. Therefore, a high ozone removal efficiency can be achieved with a small ozone injection amount.

[0017]

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a system diagram showing a method of one embodiment of the method for treating organic matter-containing water of the present invention.

The method shown in FIG. 1 is a method of circulating treated water by using one ozone reaction tower 1 and one biological treatment tower 2. That is, from the introduction pipe 11 to the ozone reaction tower 1
The raw water introduced into the column 1 is contacted with ozone supplied to the ozone reaction tower 1 from the ozone supply pipe 12 in the tower 1 to be oxidized, ozone is discharged from the discharge pipe 13, and ozone-treated water is discharged from the pipe 14 to the living organisms. It is sent to the processing tower 2. Biological treatment tower 2
The treated water biologically treated in is extracted from the pipe 15,
A part is returned to the ozone reaction tower 1 through the pipe 15A, and the rest is discharged as treated water out of the system through the pipe 15B.

In the present invention, however, in such a treatment, the pH sensor 3 is provided in the ozone reaction tower 1, and the measured value is transmitted to the alkali supplying device 4 such as NaOH, and the alkali supplying device 4 P in the ozone reaction tower 1
NaOH as needed so that H is in the range of 7-9
And the like are supplied to the raw water introduction pipe 11 via the pipe 16.

In the method shown in FIG. 1, the raw water to which the alkali has been supplied as described above has a pH of 7-9.
Since it is returned to the ozone reaction tower 1 again through the ozone reaction tower 1 and the biological treatment tower 2 maintained at 1, and then further circulated to the biological treatment tower 2, biodegradation in raw water by ozone oxidation in the ozone reaction tower 1 is difficult. A series of treatment cycles of conversion of organic matter to bio-degradable organic matter, mineralization of bio-degradable organic matter in biological treatment tower 2, ozone oxidation of remaining organic matter in ozone reaction tower 1, and mineralization in biological treatment tower 2. Can be repeated. At that time, since the inside of the ozone reaction tower 1 is maintained at a pH of 7 to 9 suitable for ozone oxidation by supplying alkali with the alkali supply device 4 according to the monitoring result by the pH sensor 3, The reaction efficiency is remarkably high, and organic substances can be efficiently removed with a small ozone injection amount.

The method of the present invention may be any method as long as it can introduce the treated water that has undergone the ozone oxidation step into the biological treatment step and the treated water that has undergone the biological treatment step into the ozone oxidation step. The method of circulating the treated water is not limited at all, and a method of providing treatment towers in multiple stages may be used.
As the circulation process and the installation mode of the processing tower, any other mode can be adopted. Further, the circulation system and the multi-stage system can be used together. Generally, in the case of the circulation system, the equipment can be made compact, and in the case of the multi-stage system, the processing efficiency can be improved. In particular, in the case of a multi-stage system, it is possible to increase the effective utilization rate of ozone by introducing the exhaust ozone of the ozone reaction tower of the former stage into the ozone reaction tower of the latter stage.

In the method of the present invention, the ozone injection rate in the ozone oxidation step varies depending on the DOC concentration of raw water, the absorption efficiency of the ozone reaction tower, and the like.
0.1 to 2 ppm) as raw water
About 2 mg-O ₃ / mg-DOC, treated human waste water (DOC
2 to 10 mg-when raw water is about 30 ppm)
It is preferably about O ₃ / mg-DOC. In practice, a batch test is performed in advance to find the optimum value.

On the other hand, as the biological treatment tower in the biological treatment process, a floating activated sludge treatment device consisting of an aeration tank and a sedimentation tank, a fixed bed or fluidized bed activated sludge treatment device in which microorganisms are adhered to the carrier is adopted. However, it is preferable to use a filtration tank provided with an inlet and an outlet for the liquid to be treated and an air diffuser 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 through the inflow port and passes through the tank of the granular medium maintained aerobically with the gas (air) from the diffuser pipe in an upward flow or a downward flow. The microbial film adhering to the surface of the granular medium undergoes aerobic microbial treatment and is subjected to a filtering action, and treated water of high quality is taken out from the outlet.

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

When the ozone concentration in the ozone-treated water is high, the organisms in the biological treatment tower are adversely affected. Therefore, water is passed through an ozone decomposition carrier (activated carbon, manganese-based catalyst, etc.) before the biological treatment step, or A biological treatment tank is preferably a filtration tank partially or wholly filled with the decomposition carrier.

[0027] In the present invention, such biological filtration process, the following COD load 0.5 kg / m ³ · day biological filtration tank, that preferably at 0.2~0.05kg / m about ³ · day preferable.

The treated water obtained by the method of the present invention is, if necessary, further subjected to filtration treatment or other treatment,
It is discharged outside the system.

In the biological filtration as described above, 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 night soil.

Since the method of the present invention as described above is applied to a flow for oxidizing an organic substance for biological treatment,
It can be applied to advanced treatment of water containing various organic substances such as tap water, sewage, night soil, and industrial wastewater. In particular, it is effective for biological treatment liquid of colored human waste and advanced treatment of polluted river water.

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. Example 1 Human waste secondary treated water (TOC = 65 mg / l, pH = 7.
Using 2) as raw water, the treatment was carried out by the method shown in FIG. The specifications and processing conditions of each tower were as follows.

Ozone reaction tower HRT = 20 minutes O ₃ gas concentration = 20 mg / l O ₃ gas flow rate = 200 ml / min Liquid flow rate = 25 ml / min Circulation flow rate = 100 ml / min Control pH = 8.0 Biological treatment tower HRT = 30 Filler = activated carbon with an average particle size of 1 mm The continuous effluent passed through the activated carbon of the biological treatment tower, and the TOC of the treated water became almost steady. The results are shown in Table 1.

Comparative Example 1 Water was continuously passed through in the same manner as in Example 1 except that the pH of the ozone reaction tower was not controlled, the activated carbon in the biological treatment tower almost passed through, and the TOC of the treated water was almost steady. Table 1 shows the results of the examination of the water quality when it became.

[0034]

[Table 1]

From Table 1, according to the method of the present invention, TOC
It is clear that the removal rate is remarkably improved and a treated water of high quality can be obtained.

[0036]

As described in detail above, according to the method for treating organic matter-containing water of the present invention, the effective utilization rate of ozone and the efficiency of ozone oxidation reaction are improved, and a high ozone removal rate is achieved with a small ozone injection amount. It is possible to do. 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 drawings]

FIG. 1 is a system diagram showing an implementation method of an organic matter-containing water treatment method of the present invention.

[Explanation of symbols]

 1 Ozone Reaction Tower 2 Biological Treatment Tower 3 pH Sensor 4 Alkali Supply Device

Claims (1)

[Claims] 1. A method of biologically treating raw water containing organic matter and then performing ozone oxidation treatment, or performing biological treatment after ozone oxidation treatment, wherein at least a part of effluent water of the biological treatment process is subjected to ozone oxidation process. In the method for treating organic matter-containing water, which is introduced and at least a part of the effluent water of the ozone oxidation step is introduced into the biological treatment step, the pH in the ozone oxidation step is adjusted to 7 to 9, and the organic matter-containing water is adjusted. Processing method.