JP3496789B2 - Organic wastewater treatment method and treatment device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for treating organic sewage that purifies ammonia-containing sewage such as sewage to a high degree. The present invention relates to a method and an apparatus for treating organic sewage capable of reducing the amount of excess sludge generated as compared with the conventional method.

[0002]

2. Description of the Related Art Conventionally, various methods have been used as a method for removing nitrogen in wastewater such as sewage. Among them, the most representative technology is a nitrification solution circulation type biological nitrification denitrification method. is there. This wastewater treatment technology supplies organic wastewater to the biological denitrification section, supplies the denitrification solution to the nitrification section to nitrify ammonia, and circulates part of the nitrification solution to the denitrification section,
The other part is supplied to the settling tank to separate the activated sludge to obtain treated water. Recently, a technique of introducing a granular carrier in which nitrifying bacteria are immobilized into the nitrification section has been put into practical use.

In the above conventional sewage treatment method, a nitrogen removal rate of about 80% is obtained when treating sewage, and almost no ammonia remains in the treated water, and nitrate nitrogen and suspended matter in the aeration tank (hereinafter simply referred to as " A small amount of "SS") remains. However, in this sewage treatment method, since nitrate nitrogen remains in the treated water, it is impossible in principle to make the nitrogen removal rate 90% or more, and to prevent eutrophication in the discharge water area. It was very inadequate.

In order to increase the nitrogen removal rate in the conventional sewage treatment method, for example, as disclosed in Japanese Patent Laid-Open No. 8-190, a second denitrification section is provided after the nitrification section, and expensive methanol such as methanol is used. An organic carbon source must be added. However, with such a treatment method, the facility cost is extremely increased due to the large volume of the treatment tank, and the running cost is also greatly increased, which is unrealistic as a facility and is difficult to actually carry out. Met. Moreover, the amount of sludge generated was large, and sludge treatment and disposal became a major problem.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and solves the problems of the conventional biological nitrogen removal methods and obtains a very stable and high nitrogen removal rate. It is an object of the present invention to provide a method and an apparatus for treating organic sewage, which is capable of reducing the amount of sludge generated.

[0006]

Means for Solving the Problems The present inventor has changed the process constitution of the biological nitrification and denitrification method to produce an organic carbon source for denitrifying bacteria by ozone oxidation of activated sludge, and a packed bed of granular filter medium. It has been found that the above-mentioned object can be achieved by coupling the biological denitrification by P.

That is, the present invention provides a method for treating organic wastewater, which comprises treating organic wastewater by biological nitrification and denitrification and then subjecting the activated sludge to solid-liquid separation to obtain biologically treated water. A part of the sludge is subjected to ozone oxidation and then solid-liquid separated, and the separated liquid that has been solid-liquid separated is added to the biologically treated water and supplied to a granular filter medium filling tank in which denitrifying bacteria are immobilized, and biological It is a method for treating organic wastewater, which is characterized in that denitrification and SS filtration are performed simultaneously.

The present invention also provides a treatment tank for biological nitrification and denitrification of organic wastewater, a sedimentation tank for solid-liquid separation of biological sludge flowing out from the treatment tank, and an activity in the sedimentation tank. An ozone oxidation tank for oxidizing a part of sludge with ozone, a solid-liquid separation tank for performing solid-liquid separation of activated sludge treated in the ozone oxidation tank, and a separated liquid subjected to solid-liquid separation in the solid-liquid separation tank, A biological treatment water discharged from the settling tank and a denitrifying bacteria-immobilized granular filter medium filling tank are provided, and biological denitrification of the organic wastewater and SS filtration treatment are simultaneously performed. and configured this is a processing device organic wastewater characterized.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The configuration and operation of the present invention will be described in detail with reference to the preferred embodiment of the present invention shown in FIG. In the present embodiment, as shown in FIG. 1, a treatment tank 4 for biological nitrification and denitrification of organic wastewater, and a sedimentation tank 5 for solid-liquid separation of biological sludge flowing out from the treatment tank 4, An ozone oxidation tank 6 for ozone-oxidizing a part (sludge 60) of the activated sludge (return sludge 50) in the settling tank 5 is further provided, and the activated sludge treated in the ozone oxidation tank 6 is solid-liquid. A solid-liquid separation tank 7 for separating, a separation liquid 80 solid-liquid separated in the solid-liquid separation tank 7, and a granular filter medium filling tank 8 to which biologically treated water discharged from the precipitation tank 5 is supplied. The wastewater treatment device 100.

In this device 100, sewage 1 such as sewage is first supplied to a denitrification tank 2 together with a nitrification slurry (circulation liquid 40) which is circulated from a biological nitrification tank 3 through a circulation liquid passage 20. . Nitrate nitrogen in the nitrifying slurry is biologically denitrified by utilizing the BOD of wastewater 1. Since nitrate nitrogen remains in the slurry flowing out from the nitrification tank 3 to the settling tank (final settling tank 5), nitrate nitrogen also remains in the outflow water from the final settling tank 5.

In order to remove this nitrate nitrogen, the present invention applies the following solution means.
That is, a part of the sludge 60 of the activated sludge of the biologically treated water (returned sludge 50 returned to the denitrification layer 2 through the sludge return passage 21) is passed through the appropriately branched sludge passage 22 and the ozone oxidation tank 6 To dissolve the soluble BOD component by ozone-oxidizing and solubilizing the sludge 60 (for example, the appropriate ozone addition amount for ozone oxidation is 5 per 1 kg of activated sludge SS).
0-100 g ozone. ), In the solid-liquid separation unit 7, the sludge is subjected to solid-liquid separation by a method such as membrane separation or sedimentation separation.

After the solid-liquid separation, the separated liquid 80 contains 20 soluble BOD (organic carbon source) which is easily utilized by denitrifying bacteria.
About 0 mg / liter is included. The separated liquid 80 is added to the outflow water from the final settling tank 5 via the separated liquid passage 24, and is supplied to the granular filter medium filling tank 8 in which the denitrifying bacteria are fixed. As a result, the biological denitrification reaction proceeds at high speed in the granular filter medium filling tank 8 without using expensive chemicals such as methanol, and at the same time, SS contained in the water discharged from the final settling tank 5 is also filtered. Clear, nitrogen, SS 1m
Highly treated water 1A of g / liter or less is obtained. In addition,
The solid content after solid-liquid separation is returned to the denitrification layer 2 as the solubilized sludge 70 via the solubilized sludge return passage 23.

As shown in FIG. 2, a filling layer 8a made of a granular filter medium is appropriately formed in the granular filter medium filling tank 5.
The particle size of the filter medium filled in the granular filter medium filling tank 5 and the thickness of the packed layer are not particularly limited, but for example, 2
It is appropriate that the particle size is ˜3 mm and the layer thickness L of the packed layer 8a is about 2 m, and the water flow rate to the packed tank is 100 to 15
It is preferably 0 m / d. In addition, as shown in FIG. 2, the granular filter medium filling tank 5 is provided with an aeration member 9 at an intermediate portion in the height direction of the filter medium filling layer 8a, a lower portion thereof is a denitrification portion 18, and an upper portion thereof is left by an aerobic biofilm. A method in which the BOD removing unit 19 is operated in an upward flow is a very preferable embodiment.

Although the granular filter medium is not particularly limited, for example, in addition to sedimentary filter medium such as anthracite and ceramics, floating filter medium such as expanded polystyrene, polypropylene and polyethylene can be applied.

When sewage treatment is performed using the above-described treatment apparatus of the present invention, extremely effective sewage treatment can be performed. That is, according to the present invention, the activated sludge is solubilized by ozone, converted into the activated sludge substrate (food of microorganisms) again, and returned to the biological treatment tank so that it is usually disposed of outside the wastewater treatment system. Since undesired sludge can be biologically decomposed into carbon dioxide and water in the aeration tank, chemicals such as methanol are unnecessary, and it is not necessary to add a second denitrification tank to the activated sludge treatment system. Further, since SS filtration is also performed in the granular filter medium filling tank 8 at the same time, a separate filtration tank for SS removal is not required. Further, the sludge is solubilized with ozone and then solid-liquid separated, and the separated sludge is supplied again as a substrate for the activated sludge to biologically reduce the amount of the sludge.

[0016]

Example According to the experiments conducted by the present inventor, the amount of BOD eluted from sludge by ozone oxidation was 40 per 1 kg of activated sludge.
Was ~ 50 g BOD. Further, the flow rate of addition of the sludge solubilizing solution due to ozone to the final settling tank outflow water is set so that the BOD is about 3 kg per 1 kg of nitrate nitrogen. As a method of preventing BOD from remaining in the water discharged from the denitrification tank by the granular filter medium (which causes such an excessive amount of the ozone solubilizing solution), as shown in FIG. An aeration member 9 is provided at an intermediate portion in the height direction of the packed bed 8a, and the lower portion of the aeration member 9 is provided with the denitrification unit 1.
8. Residual BOD removal part 1 with aerobic biofilm on top of it
It was set to 9 and it was the method of operating by an upflow.

As a result, it was confirmed that the sludge generation amount was significantly reduced. The reason for this is that activated sludge is solubilized by ozone, and the activated sludge substrate (microorganism food) is reused.
This is because sludge, which normally has to be discarded outside the system, can be biologically decomposed into carbon dioxide gas and water in the aeration tank by converting to sludge and returning it to the biological treatment tank. According to a test for the sewage of the present inventor, using the treatment apparatus of FIG. 1, treatment conditions other than the above are: -Treatment amount of sewage is 100 liters / d-Granular filter medium material is granular sponge , Its particle size is 10
〜15mm ・ When the layer thickness L of the filter medium filling layer is 2m, the amount of sludge generated is larger than the amount of excess sludge generated by the conventional activated sludge method (that is, a treatment device that does not use a granular filter medium filling tank). It decreased to about 1/6.

[0018]

INDUSTRIAL APPLICABILITY As described above, the present invention provides a method for treating organic sewage obtained by treating organic sewage by a biological nitrification denitrification method, and then subjecting activated sludge to solid-liquid separation to obtain biologically treated water. ,
After a part of the activated sludge in the biological treatment process is subjected to ozone oxidation, it is subjected to solid-liquid separation, and the separated liquid obtained by the solid-liquid separation is added to the biologically treated water and supplied to a granular filter medium filling tank in which denitrifying bacteria are immobilized. Thus, it is a method for treating organic wastewater that simultaneously carries out biological denitrification and SS filtration, and an apparatus capable of carrying out the treatment method. Therefore, the following effects are exhibited. 1. The sludge is solubilized with ozone to elute BOD, and then solid-liquid separation is performed.
Since it is used as an organic carbon source in the denitrification section of the filter medium filling tank , a chemical such as methanol is unnecessary, and running costs can be suppressed. Further, since it is not necessary to add a second denitrification tank to the activated sludge treatment system, it is possible to avoid an increase in equipment size. 2. In a granular filter medium filling tank in which denitrifying bacteria are fixed , S
Since S filtration is also performed at the same time, a separate filtration tank for SS removal is not required, and the processing apparatus can be simplified. 3. Since the sludge is solubilized with ozone and then solid-liquid separated, the separated sludge is supplied again as a substrate for the activated sludge to biologically reduce the amount of the sludge, so that the amount of excess sludge generated can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an embodiment of a processing apparatus of the present invention.

FIG. 2 is a schematic view of a main part of the treatment apparatus of the present invention.

[Explanation of symbols]

1 dirty water 1A advanced treated water 2 denitrification tank 3 Biological nitrification tank 4 processing tanks 5 Settling tank (final settling tank) 6 Ozone oxidation tank 7 Solid-liquid separation tank 8 Granular filter medium filling tank 8a packed bed 9 Aeration member 18 Denitrification part 19 Residual BOD removal section 100 Sewage treatment equipment

Claims (2)

(57) [Claims] 1. A method for treating organic wastewater, which comprises treating biological wastewater by biological nitrification and denitrification and then subjecting the activated sludge to solid-liquid separation to obtain biological treated water. Part is subjected to ozone oxidation and then subjected to solid-liquid separation, and the separated liquid subjected to the solid-liquid separation is added to the biologically treated water to remove it.
A method for treating organic sewage, which comprises supplying a nitrogen-containing bacteria-immobilized granular filter medium tank and simultaneously performing biological denitrification and SS filtration. 2. A treatment tank for biologically nitrifying and denitrifying organic sewage, a sedimentation tank for solid-liquid separation of biological sludge flowing out from the treatment tank, and a part of activated sludge in the sedimentation tank. An ozone oxidation tank for ozone-oxidizing, a solid-liquid separation tank for performing solid-liquid separation of the activated sludge treated in the ozone oxidation tank, a separation liquid subjected to solid-liquid separation in the solid-liquid separation tank, and the precipitation tank The denitrifying bacteria supplied with the discharged biologically treated water
And a immobilized particulate filter material filling tank, processor Organic wastewater characterized that it has been configured to perform biological denitrification and SS filtration of the organic wastewater simultaneously.