JPH05261394A - Treatment of high-concentration organic waste liquid - Google Patents

Abstract

PURPOSE:To stably treat waste liquid such as excretions without performing advanced waste water treatment and to efficiently obtain treated water high in water quality at low cost by performing biological treatment in pressurization when high-concentration organic waste liquid is oxidized by a wet catalyst and thereafter the residual COD component is biologically treated. CONSTITUTION:Excretions and/or sludge of a septic tank 1 is firstly ground and treated. Then as a result, waste water containing organic substance at high concentration is obtained. The waste water is used as raw liquid and oxidized by a wet catalyst and treated. Successively the obtained reacted liquid is biologically filtered and thereby the residual organic acid low in molecular weight is decomposed and removed. At that time, biological filtration is performed is performed under Further alkali such as calcium hydroxide is added to one part of the treated liquid oxidized by the wet catalyst. The liquid regulated to weak acidity of about pH5 is preferably used for biological filtration. In other words, pH is regulated and the concentration of PO4 phosphorus is regulated for the treated liquid oxidized by the wet catalyst. The water treated by biological filtration is furthermore filtered in accordance with necessity and thereafter discharged to the outside of the system.

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 high-concentration organic waste liquor, and more particularly to a method for treating CO2 and chromaticity by high-concentration organic waste liquor such as human waste by wet catalytic oxidation. The present invention relates to a method for treating a high-concentration organic waste liquid which can be efficiently processed at low cost using a small reaction tank without requiring a process.

[0002]

2. Description of the Related Art Conventionally, as a method for treating high-concentration organic waste liquid such as human waste fluid, there is a wet oxidation process by heat treatment of human waste, which is a ginpro method (Japanese Patent Laid-Open No. 97160/1975).
Known as. In this process, as shown in FIG. 2, the raw solution containing human waste or septic tank sludge is crushed, heat-treated and wet-oxidized, and the treated liquid is subjected to solid-liquid separation to obtain a separated liquid, which is then subjected to activated sludge treatment and then subjected to solid-liquid separation again. Then, advanced treatment such as activated carbon treatment or ozone treatment is performed to obtain final treated water.
The solid content obtained by the solid-liquid separation after the wet oxidation is dehydrated, while the solid content obtained by the solid-liquid separation after the activated sludge treatment is circulated and reprocessed.

Such a wet oxidation process has the following drawbacks. Wet oxidation has an oxidative decomposition rate of about 50% due to efficiency problems.
Therefore, activated sludge treatment is essential. Moreover, since nitrogen remains in the form of ammonia, a biological nitrification denitrification method is required. Organic substances that are decomposed to organic acids in the heat treatment stage of wet oxidation are decomposed in the next biological treatment (activated sludge treatment), but high molecular colored components with a molecular weight cutoff of about 500 or more cannot be removed. .. Therefore, the biological treated water is about 2
It exhibits a chromaticity of about 500 to 5500 degrees, and further undergoes advanced treatment such as activated carbon treatment or ozone treatment to reduce CO
It is necessary to remove D and chromaticity. Since the oxidative decomposition waste gas is a strong malodorous gas, it is necessary to perform a deodorizing process, but the deodorizing is not easy, and combustion deodorizing or activated carbon adsorption is used.

On the other hand, as another method of the Zinpro method, a wet catalytic oxidation process has been proposed in which an oxidation catalyst is used in the heat treatment portion (Japanese Patent Laid-Open No. 55-152591).

According to the wet catalytic oxidation process, by using a catalyst, the oxidative decomposition rate is 5
Since it is improved from 0% to about 99.8% and most of the organic substances and total nitrogen in the liquid to be treated are decomposed, the subsequent activated sludge treatment process becomes unnecessary. Since NOx, SOx, CH compounds, etc. are not contained in the oxidative decomposition waste gas, no bad odor is generated from the oxidation reaction process. Therefore, the deodorizing process becomes unnecessary. Since the oxidative decomposition rate is high and decolorization is sufficient,
It does not require advanced processing for chromaticity removal. 99% or more of TN (total nitrogen) can also be removed. And so on.

However, in the above-mentioned wet catalytic oxidation process, the reaction time depends on the organic matter concentration of the stock solution which enters the heat treatment step, and when the treatment is actually carried out, it is not necessarily advantageous in cost as compared with the wet oxidation process. There was a drawback.

That is, in the case of treating a stock solution containing an organic substance at a high concentration by a wet catalytic oxidation process, it is necessary to considerably lengthen the reaction time in order to obtain treated water of high water quality. If the reaction time is made sufficiently long, the concentration of organic substances in the treated water can be reduced to an extremely low concentration.However, making the reaction time longer directly leads to an increase in the tank capacity and the amount of catalyst, which causes a rise in the treatment cost. ..

By solving the above-mentioned conventional problems and performing stable and efficient treatment in the wet catalytic oxidation process of high-concentration organic waste liquid, it becomes possible to obtain treated water of high quality at low cost. As a method of treating a high-concentration organic waste liquid, the present applicants perform high-concentration organic waste liquid by wet-catalytic oxidation, and then cool and depressurize the remaining COD components, and then gas-liquid separation and biological filtration to remove the high-concentration organic waste liquid. A method for treating organic waste liquid has been proposed (JP-A-3-26399).

According to the method disclosed in JP-A-3-26399, it is possible to significantly reduce the reaction time of wet catalytic oxidation. Therefore, the capacity of the wet catalytic oxidation tower and the amount of catalyst can be reduced. TN, COD _Cr, and chromaticity are efficiently removed, and high-level post-treatment is not required. No odor is generated. Energy efficient. Excellent operational efficiency is achieved, and both initial cost and running cost are reduced.

[0010]

However, the size of the biological filtration tank used in the method of Japanese Patent Laid-Open No. 3-26399 affects the amount of dissolved air as an oxygen source supplied from the lower part of the tank. Miniaturization was left as a future task.

An object of the present invention is to provide a method for treating a high-concentration organic waste liquid, which is capable of improving the dissolution efficiency of oxygen and enabling downsizing of a biological filtration tank in the method disclosed in Japanese Patent Laid-Open No. 3-26399.

[0012]

The method for treating a high-concentration organic waste liquid according to the present invention comprises:
A method for biologically treating a residual COD component is characterized in that the biological treatment is carried out under pressure.

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

FIG. 1 is a system diagram showing an embodiment of a method for treating a high-concentration organic waste liquid according to the present invention.

In the present invention, waste water containing organic matter at a high concentration obtained by finely crushing human waste and / or septic tank sludge is used as a stock solution, which is first subjected to a wet catalytic oxidation process.

The wet catalytic oxidation process will be described below with reference to FIG. FIG. 3 is a system diagram showing an embodiment of a wet catalytic oxidation treatment method suitable for carrying out the present invention.

In FIG. 3, the undiluted solution is introduced into the storage tank 1 through the pipe 11 and then into the wet catalytic oxidation tower 2 through the pipe 12 by the pump P.

The wet catalytic oxidation tower 2 has a catalyst layer 2a formed by filling a high-pressure container with a catalyst to be described later, and the stock solution flows upward or downward in the catalyst layer 2a (see FIG. 3). Is flown upward and is subjected to oxidation treatment under high temperature and high pressure. That is, a pipe 12 for introducing an undiluted solution to the wet catalytic oxidation tower 2 is connected to a pipe 13 for supplying an oxygen-containing gas such as the atmosphere, which is equipped with a compressor C, and an oxygen-containing gas such as air is blown into the undiluted solution. After that, it is introduced into the wet catalytic oxidation tower 2 and subjected to oxidation treatment in the presence of a catalyst. Wet catalytic oxidation tower 2
The treated water and treated gas are taken out from the pipe 14, cooled, gas-liquid separated (not shown) or not separated, and the treated liquid is neutralized in the neutralization tank 15 and then the pressurized biological filtration tower. 3 is supplied.

In the present invention, preferred catalysts to be packed in the wet catalytic oxidation tower are iron, manganese, cobalt, nickel, ruthenium, rhodium, palladium, iridium, platinum, copper, gold and tungsten, and these. Oxides, chlorides such as ruthenium dichloride and platinum dichloride, ruthenium sulfide, sulfides such as rhodium sulfide, and other insoluble or sparingly soluble compounds in water are listed. These may be used alone or in combination. The above can be used in combination.

The catalyst composed of these metals or compounds may be titania (titanium oxide), zirconia (zirconia oxide), alumina, silica, silica-alumina, or the like according to a conventional method.
Activated carbon, or nickel, nickel-chromium, nickel-chromium-aluminum, nickel-chromium-iron is preferably used by being supported on a carrier such as a porous metal body.
The loading amount is usually 0.05 with respect to the weight of the carrier.
It is suitable to be -25%, preferably 0.5-3%.

The catalyst may be used in various forms such as granular form, pellet form, columnar form, crushed piece form, honeycomb form or powder form.

The reaction temperature in the wet catalytic oxidation tower is 20
The reaction pressure is preferably 0 to 300 ° C., particularly 250 to 300 ° C., and the reaction pressure is, for example, 40 to 95 kg / c under pressure such that the stock solution retains the liquid phase even under such high temperature.
It is preferably m ² and particularly preferably 70 to 95 kg / cm ² .

The stock solution flow rate in the wet catalytic oxidation tower is preferably set so that the reaction time (residence time in the tower) is 40 to 90 minutes.

As the oxygen-containing gas, it is preferable to use a gas having an oxygen concentration of 21% or more in addition to air. In the case of a gas containing oxygen at a concentration higher than 21%, the amount of blown gas can be reduced. Further, the heat loss amount is decreased and the reaction rate is increased, so that the treatment efficiency can be improved. As a gas having an oxygen concentration of 21% or more, an oxygen-enriched air obtained by a selective oxygen permeable membrane method, a method of mixing pure oxygen with air, a pressure swing adsorption (PSA) method, or the like,
Pure oxygen obtained by vaporizing liquid oxygen can be used.

Blowing the oxygen-containing gas into the stock solution is the third step.
As shown in the figure, a pipe 1 for supplying the undiluted solution to the wet catalytic oxidation tower 2
In addition to supplying to the wet catalytic oxidation tower 2, it may be directly supplied to the wet catalytic oxidation tower 2.

When the stock solution is supplied to the wet catalytic oxidation tower via the heat exchanger, the oxygen-containing gas can be supplied to the stock solution supply pipe before or after the heat exchanger.

The amount of oxygen supplied by the oxygen-containing gas may be set so that the amount of oxygen is larger than the amount of oxygen necessary for the amount of organic matter and N in the stock solution supplied to the wet catalytic oxidation tower 2. In general, the gas: liquid flow ratio (volume ratio at normal pressure) between the oxygen-containing gas containing the malodorous gas and the stock solution is 100.
It is preferably about 200: 1.

In the present invention, the heat consumption can be reduced by exchanging heat between the treated water from the wet catalytic oxidation tower and the stock solution supplied to the wet catalytic oxidation tower to recover heat.

In the present invention, the COD _Cr removal rate (decomposition rate) in such a wet catalytic oxidation treatment is 95%.
Above all, it is particularly preferable to be 95 to 98%. 95% or more of COD _Cr is reduced to CO
Decomposes TN and chromaticity of 99% or more into ₂ , H ₂ O.

Then, the treatment liquid obtained by such a wet catalytic oxidation treatment is subjected to biological filtration to decompose and remove the remaining low molecular weight organic acids and the like. In the present invention, this biological filtration is carried out under pressure. Do in.

Preferably, in biological filtration, an alkali such as calcium hydroxide or sodium hydroxide is added to a portion of the wet catalytic oxidation treatment liquid under a predetermined pressure to adjust the pH to 5
It is desirable to use a slightly acidified liquid for biological filtration. It is also possible to add Ca (OH) ₂ or the like to the wet catalytic oxidation treatment liquid to adjust the pH to 9 or more, to solid-liquid separate the produced calcium phosphate, and then subject it to pressurized biological filtration.

Wet catalytic oxidation treatment liquid or preferably the above p
Biological filtration of the wet catalytic oxidation treatment liquid (hereinafter referred to as "biological filtration stock solution") after H adjustment and PO ₄ -P concentration adjustment is preferably performed as shown in FIG. 3, for example. That is, using a pressurized biological filtration tower 3 equipped with an inlet pipe 16 and an outlet pipe 17 for a biological filtration stock solution and an air diffusing pipe, and filled with a granular medium layer 19 and a support material layer 20 for supporting the granular medium layer, The filtered stock solution is introduced into the pressurized biological filtration tower 3 through the introduction pipe 16 and is passed together with the gas (air) from the diffuser pipe 18 through the layer 19 of the aerobically maintained granular medium in an upward flow. At this time, the biological filtration stock solution is subjected to aerobic microbial treatment by the microbial membrane adhering to the surface of the granular medium and is subjected to a filtering action, and the resulting treated water of high quality is taken out from the discharge pipe 17.

As the granular medium to be filled in the pressurized biological filtration tower 3, one or more types of granular medium such as gravel, sand, activated carbon, anthracite and plastic material can be used.

In the present invention, such a biological filtration treatment is carried out at a pressure of 50 kg / cm ² or less, preferably 3 to 5 kg.
In / cm ² about pressure, hereinafter COD _Cr load 10 kg / m ³ · day pressurized圧生was filtered tower, ^3-preferably 5 kg / m
It is preferable to do it on a daily basis.

The treated water obtained by biological filtration is optionally filtered and then discharged to the outside of the system.

In such biological filtration, surplus biological sludge in the biological filtration tower and biological sludge separated by the subsequent filter can be returned to the fine crushing step and treated together with the stock solution such as human waste. ..

[0037]

The present inventors have obtained the following findings as a result of examining the removal characteristics in the wet catalytic oxidation process.

That is, in the wet catalytic oxidation process, if it is attempted to reduce the residual COD _Cr after the treatment as much as possible, the reaction time per removed weight of contaminants becomes very long, which is inefficient and uneconomical. Therefore, in the wet catalytic oxidation process, CO is generated by the wet catalytic oxidation.
Without highly remove D _Cr, it is effective to a state of leaving a residual COD _Cr.

By the way, the residual C contained in this low concentration is
OD _Cr is mainly composed of a low molecular weight organic acid,
When the activated sludge method is applied as in the conventional method, the biodegradability is relatively good, but there are disadvantages such that bulking easily occurs and the aeration tank capacity and sedimentation basin area are large.

On the other hand, by adopting the biological filtration, it becomes possible to perform an efficient treatment, and in particular, the biological filtration under pressure significantly improves the dissolution efficiency of oxygen, and It is possible to reduce the size.

In the present invention, the COD _Cr removal rate in wet catalytic oxidation is set to 95 to 98% in order to perform efficient wet catalytic oxidation and to obtain treated water of high water quality by biological filtration under pressure. Is preferred. By such treatment, BOD: 5 mg / liter or less COD _Cr : 10 mg / liter or less SS: 10 mg / liter or less Chromaticity: 30 degrees or less TN: 10 mg / liter or less It can be obtained by high load operation using a pressure biological filtration tank.

[0042]

EXAMPLES The present invention will be described in more detail with reference to the following examples.

Example 1 According to the method shown in FIGS. 1 and 3, the water quality shown in Table 1 was treated as human waste. The conditions of the wet catalytic oxidation treatment and the biological filtration treatment were as follows. In addition, the biological filtration process is under atmospheric pressure (case No. 1) or under pressure (case No. 2 and 3).
Was carried out in three ways.

Table 1 shows the water quality of the treated water obtained by the wet catalytic oxidation treatment and each biological filtration treatment.

Wet catalytic oxidation treatment Temperature: 250 ° C. Pressure: 70 kg / cm ² Liquid flow rate (residence time in the column): 90 minutes Gas / liquid flow ratio (volume ratio): 150/1 Oxidative decomposition rate (to stock solution): 96 % Biological filtration treatment Case No. 1 (comparative example): pressure = atmospheric pressure COD _Cr load = 2 kg / m ³ · day Case No. 2 (Example of the present invention) Pressure = 5 kg / cm ² COD _Cr load = 2 kg / m ³ · day Case No. 3 (Example of the present invention): Pressure: 5 kg / cm ² COD _Cr load = 5 kg / m ³ · day

[0046]

[Table 1]

As is clear from Table 1, Case No. carried out at atmospheric pressure. 1 (method of JP-A-3-26399), C
Good results are obtained with an OD _Cr load of 2 kg / m ³ · day, but case No. 2, a better result was obtained, and therefore, the COD _Cr load was 5 kg / m ³ ·
Case No. increased on the day Also in case 3, Results equal to or better than 1 were obtained.

That is, according to the method of the present invention, the COD _Cr load of the pressurized biological filtration tower can be set to about 5 kg / m ³ · day or more, and a compact pressurized biological filtration tower is used. It is possible to obtain treated water of high water quality under high load operation.

[0049]

As described in detail above, according to the method for treating a high-concentration organic waste liquid of the present invention, a waste liquid containing a high-concentration organic substance such as human waste can be stably treated without requiring advanced treatment, resulting in high water quality. It is possible to efficiently obtain the treated water at low cost. Moreover, according to the method of the present invention, the device can be downsized, which is extremely advantageous industrially.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of a method for treating a high-concentration organic waste liquid according to the present invention.

FIG. 2 is a system diagram showing a conventional method.

FIG. 3 is a system diagram showing an example of a wet catalytic oxidation treatment method suitable for carrying out the present invention.

[Explanation of symbols]

 1 Storage Tank 2 Wet Catalytic Oxidation Tower 3 Pressurized Biological Filtration Tower P Pump C Compressor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Noboru Yamada 3-4 Nishi-Shinjuku, Shinjuku-ku, Tokyo Kurita Industries Co., Ltd. (72) Inventor Tadashi Takadoi 3-4 Nishi-Shinjuku, Shinjuku-ku, Tokyo No. Kurita Industry Co., Ltd.

Claims (1)

[Claims] 1. After wet-type catalytic oxidation of a high-concentration organic waste liquid,
A method for biologically treating residual COD components, wherein the biological treatment is carried out under pressure.