JPH10202280A - Biological treatment of organic sewage using light weight activated carbon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily execute a separation of an activated sludge and an activated carbon and a regeneration of the activated carbon by charging a light weight activated carbon including spherical hollow particulates at inside and having a specified specific gravity into an aeration tank of a biological treating device for an org. sewage, subjecting the sludge to suspension fluidization with an aeration air and proceeding simultaneously biological treatment and COD adsorbing treatment. SOLUTION: The light weight activated carbon including the spherical hollow particulates at inside and having the specific gravity near 1 is charged into the aeration tank 2 together with the activated sludge, and a clear treated water 5 is obtained by precipitating only sewage 1 containing the activated sludge particles small in grain size at the sedimentation tank 4. In such a case, a prescribed amount of the granular activated carbon is discharged together with the activated sludge in the aeration tank 2 while continuing an operation of sewage treatment to separate to the granular activated carbon and the activated sludge with a screen 6. Then the classified activated sludge 12 is returned to the aeration tank 2, and the light weight activated carbon 7 is regenerated at an activated carbon regenerating stage 8 and charged into the aeration tank 2. And a part of the activated sludge precipitated at the sedimentation tank 4 is discharged out of system as a surplus sludge 11 and a part of others is charged into the aeration tank 2 as a return sludge 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a new technology for highly purifying organic wastewater, and more particularly, to a purification technology capable of highly removing hardly biodegradable COD by a very simple process.

[0002]

2. Description of the Related Art Conventionally, organic sewage such as sewage has been biologically purified by an activated sludge method and then discharged into public water bodies. However, in biological treatment such as activated sludge method, B
Although OD is highly removed, organic matter that cannot be separated biologically (refractory biodegradable COD) cannot be removed, and it is a serious problem when the water is discharged into a water body having a COD regulation of a closed water body. Conventionally, a coagulation sedimentation method and an activated carbon adsorption method have been known as methods for removing biodegradable COD, but they are not ideal methods due to the following problems.
That is, in the coagulation sedimentation method, since a large amount of hardly dewaterable sludge is generated, it is a problem that the disposal of the sludge is difficult. In addition, in the activated carbon adsorption method, after the treated water subjected to the activated sludge treatment is subjected to sand filtration, it must be further subjected to an adsorption treatment using an activated carbon adsorption tower. Therefore, a sand filtration facility and an activated carbon adsorption tower are required. Since the construction cost of the adsorption tower is expensive and a large installation area is required, it is not practical.

[0003]

Conventionally, there has been known a method in which powdered activated carbon is charged into an aeration tank for sewage activated sludge, and biological treatment and activated carbon treatment are performed simultaneously. Since the excess activated sludge was completely integrated and could not be separated, the activated carbon had to be discarded together with the excess sludge. Therefore, the activated carbon could not be recycled and reused, and the running cost was high, which was not practical. SUMMARY OF THE INVENTION An object of the present invention is to solve the disadvantages of the prior art, and it is not necessary to install a sand filtration device and an activated carbon adsorption tower, and it is easy to separate activated sludge and activated carbon and to regenerate activated carbon, and to use organic wastewater. It is to provide a new technology for purifying water.

[0004]

Means for Solving the Problems The object of the present invention is to provide:
(1) A lightweight activated carbon having a specific gravity close to 1 in which spherical hollow fine particles are contained therein is put into an aeration tank of a biological treatment apparatus for organic wastewater, and the lightweight activated carbon is suspended and fluidized by aerated air for biological treatment. A biological treatment method for organic wastewater using lightweight activated carbon, wherein the COD adsorption treatment is simultaneously performed. Preferably, (2) a part of the lightweight activated carbon is taken out of the biological treatment aeration tank and then regenerated, and the regenerated lightweight activated carbon is re-input into the biological treatment aeration tank. A biological treatment method for organic wastewater using activated carbon. More preferably, (3) the biological treatment method of organic wastewater using the lightweight activated carbon according to the above (1) or (2), wherein the specific gravity of the lightweight activated carbon is 0.9 to 1.1. It is.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the specific gravity is 0.9-1.
A lightweight activated carbon having a specific gravity close to that of 1 and water is prepared in advance by a method described later. The lightweight activated carbon of the present invention has a particle size of 1 to 3 m.
It is preferable that the particles have a particle size of about m. However, the light-weight activated carbon of the present invention has a particle size of 1 m as long as it has a particle size that can be classified with a mesh screen through which activated sludge can pass.
m or less. The light-weight activated carbon of the present invention, when put into an activated sludge treatment tank, has a property of suspending and flowing in the tank by riding on a water flow generated by aerated air without settling at the bottom of the tank. When light activated carbon having such flow characteristics is put into a sludge aeration tank and biologically treated, the BOD of wastewater is treated by living organisms,
The biodegradable COD is removed and adsorbed and removed by the granular activated carbon.

FIG. 1 shows an outline of the biological treatment apparatus of the present invention. However, the present invention is not limited to the biological treatment device shown in FIG. The outline of the biological treatment method for organic wastewater using the lightweight activated carbon of the present invention will be described with reference to FIG. In FIG. 1, the lightweight activated carbon of the present invention is charged in an aeration tank 2 together with activated sludge. At the outflow end of the aeration tank 2,
A screen 3 is provided to prevent the granular activated carbon from flowing out, and only the sewage 1 containing activated sludge particles having a small particle diameter flows into the sedimentation tank 4 and precipitates in the sedimentation tank 4 to obtain clear treated water 5. Is obtained. In such a state, if the operation of the sludge treatment is continued, the COD adsorption amount of the granular activated carbon reaches the limit, and the COD of the treated water is deteriorated. The granular activated carbon (light activated carbon) is pulled out together with the activated sludge in the aeration tank 2, supplied to a screen separation section, and separated by the screen 6 into granular activated carbon and activated sludge. The classified activated sludge 12 is returned to the aeration tank 2, and the lightweight activated carbon 7 is supplied to an activated carbon regeneration step 8. The regenerated granular activated carbon 7 is put into the aeration tank 2 again to remove COD. Part of the activated sludge settled in the settling tank 4 is excessive sludge 11.
And the other part is returned to the aeration tank 2 as returned sludge 10.

The following method can be recommended for producing lightweight granular activated carbon having a specific gravity close to 1. A method in which powdered activated carbon is mixed with hollow fine particles having closed cells such as shirasu balloon, and an appropriate binder is added to granulate the powder. The powdered carbon before activation is mixed with the hollow fine particles, granulated, and then activated to obtain a lightweight granular activated carbon. A plant powder such as sawdust powder and the hollow fine particles are mixed and granulated, carbonized and activated to produce a light-weight granular activated carbon. Specific examples of the binder include alumina cement, polyvinyl alcohol, and tar or pitch used in the production of activated carbon.
Or, gelatin, glue and the like can be mentioned.

The following effects are produced by the configuration of the present invention. (1) Since granular activated carbon and activated sludge can be easily classified and granular activated carbon does not flow out of the system, activated carbon is not disposable as in the activated sludge method with powdered activated carbon. Therefore, running costs are low. (2) Since the granular activated carbon is lightweight and has a specific gravity close to 1, there is no trouble that the granular activated carbon is easily suspended and flowed by the aerated air in the aeration tank, and the granular activated carbon is deposited on the bottom of the aeration tank. On the other hand, in the case of the conventional granular activated carbon, when the granular activated carbon is put into the aeration tank, the specific gravity of the activated carbon is as large as 1.8, so that the activated carbon is immediately deposited on the bottom of the aeration tank.

(3) Microorganisms such as nitrifying bacteria adhere to the surface of the charged granular activated carbon, and the effect of biological treatment is improved.
That is, the granular activated carbon functions not only as a COD adsorbing ability but also as a microorganism-immobilized carrier. (4) The contact time between the granular activated carbon and the sewage is the same as the residence time of the sewage in the aeration tank, and can be made extremely long.
Since it can be set as very small as 0.2 (1 / h), the COD adsorption capacity of the granular activated carbon can be used almost completely. On the other hand, SV is 3 to 5 (1
/ H) because it must be as large as
The D adsorption capacity could not be fully utilized.

[0010]

EXAMPLES The present invention will now be described specifically with reference to examples, but the present invention is not limited to these examples. Example 1 (1) Production of Light-Granular Activated Carbon Granules made of powdered activated carbon, shirasu balloon, and alumina cement had a bulk specific gravity (specific gravity when immersed in water) of 0.95 to 1. The resulting mixture was mixed at a ratio such that the mixture became 0.5, an aqueous polyvinyl alcohol solution was added, and the mixture was granulated and dried to produce a light-weight granular activated carbon having a particle size of 2 to 3 mm.

(2) Application to sewage treatment The light-weight granular activated carbon is activated sludge treatment tank (1) for sewage treatment.
(00 liters), the suspension was easily suspended and flowed when aerated, and did not sink to the bottom of the aeration tank. A mesh wedge wire screen was used to classify light-weight granular activated carbon and activated sludge. Activated sludge flowed easily under the screen, and granular activated carbon could be separated. The specifications of the sewage treatment experimental device are shown in Table 1 below.

[0012]

[Table 1]

Next, 200 cc of granular activated carbon was withdrawn per day from the aeration tank, heat-regenerated in a small activated carbon regeneration furnace (rotary kiln type), and the regenerated granular activated carbon was returned to the aeration tank. When such an operation was continued for 6 months and the water quality of the average treated water was measured, it was as shown in the first column of Table 2 (the treated water of the present invention).

Comparative Example 1 A parallel experiment was conducted under the same conditions as in Example 1 except that no light-weight granular activated carbon was added. As a result, the average value of the quality of the treated water was as shown in the second column of Table 2 (Comparative Example 1). (Treated water column)
It was as follows. From the results in Table 2, in the case of Comparative Example 1,
It is clear that the value of COD is significantly higher and the value of ammoniacal nitrogen is also much higher than in the case of Example 1 of the present invention. In the treated water of the present invention, the value of ammonia nitrogen is low because nitrifying bacteria are immobilized on the surface of activated carbon and the nitrification reaction has progressed well.

[0015]

[Table 2]

[0016]

According to the biological treatment method for organic sewage using the lightweight activated carbon of the present invention, biological treatment and COD can be carried out while suspending and flowing the lightweight activated carbon in the aeration tank with aerated air.
The adsorption treatment can proceed at the same time, and the lightweight activated carbon can be easily separated by separation by filtration. Therefore, biodegradable BOD and poor biodegradable COD
In the case of treating sewage containing water, the construction of sand filtration facilities and activated carbon adsorption towers is unnecessary and the equipment cost is low, as in the case of simultaneous treatment with conventional activated carbon and activated sludge. As a result, running costs can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an example of a flow of a biological treatment process of organic wastewater using the lightweight activated carbon of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sewage 2 Aeration tank 3 Screen 4 Sedimentation tank 5 Treated water 6 Screen 7 Activated carbon 8 Regeneration process 9 Regenerated activated carbon 10 Returned sludge 11 Excess sludge 12 Activated sludge

Claims (3)

[Claims] 1. A lightweight activated carbon having a specific gravity close to 1 and containing spherical hollow fine particles therein is charged into an aeration tank of a biological treatment apparatus for organic wastewater, and the lightweight activated carbon is suspended and fluidized by aerated air. A biological treatment method for organic wastewater using lightweight activated carbon, wherein the treatment and the COD adsorption treatment are simultaneously performed. 2. The lightweight activated carbon according to claim 1, wherein a part of the lightweight activated carbon is taken out of the biological treatment aeration tank and then regenerated, and the regenerated lightweight activated carbon is re-input into the biological treatment aeration tank. A biological treatment method for organic wastewater using activated carbon. 3. The lightweight activated carbon has a specific gravity of 0.9 to 1.1.
The biological treatment method for organic sewage using the lightweight activated carbon according to claim 1 or 2.