JPH06126292A - Sewage treatment equipment - Google Patents

Abstract

(57) [Summary] [Purpose] To reduce the processing time for sewage. [Structure] The activated sludge mixed solution 6 is treated with the immobilized denitrifying bacteria 9 in a denitrification tank 21 which performs biological denitrification under anoxic conditions, and the denitrified activated sludge mixed solution 6 is denitrified. 21. Immobilization comprising a fixed denitrifying bacteria flow container 5 that overflows and separates into 21 and a flow means 12 that supplies the activated sludge mixed liquid 6 in the tank 21 in a fluid state toward the inside of the fixed denitrification bacteria flow container 5. The denitrifying bacteria flow apparatus 1 is installed. Supplying air or oxygen to the immobilized nitrifying bacteria flow container and flow means similar to the denitrification tank, and the activated sludge mixed liquid and immobilized nitrifying bacteria in the nitrification tank that biologically nitrifies under aerobic conditions. The immobilized nitrifying bacteria flow device is installed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sewage treatment apparatus for treating sewage, industrial wastewater and the like.

[0002]

2. Description of the Related Art Conventionally, sewage is first introduced into a denitrification tank and then into a nitrification tank, and a part of the nitrification tank mixture is circulated in the denitrification tank and the rest is introduced into a sedimentation tank. At this time, organic substances such as BOD and nitrogen are removed in the denitrification tank, and Kjeldahl nitrogen containing ammoniacal nitrogen is oxidized to nitric acid or nitrous acid in the nitrification tank. In this process, a method of removing nitrogen by performing nitrification / denitrification by the action of floating activated sludge is a general nitrogen removal technology.

[0003]

However, in the above-mentioned nitrogen removal technique, the total residence time in the nitrification tank and the denitrification tank is 1
It takes 2 to 16 hours, and it is not applicable to ordinary existing sewage treatment plants that are designed and operated with aeration tank residence time of 6 to 8 hours because it is difficult to secure new land. I want to.

Therefore, in order to shorten the retention time of waste water in the reaction tank, application of a microorganism immobilization technique for increasing the nitrification or denitrification rate is being studied. However, in order to realize it, at the same time, it is necessary to devise a device for sufficiently exerting the nitrification or denitrification performance of the immobilized microorganisms.

That is, the immobilized denitrifying bacterium, which denitrifies under anoxic conditions, is made to flow uniformly in the denitrification tank in order to enhance the efficiency of the denitrification reaction, and then nitric acid or nitrite nitrogen and BO are added.
It is necessary to increase the chance of contact with the mixed solution containing D.

However, in general, the stirring operation with a propeller or the like can fluidize the immobilized denitrifying bacteria, but at the same time, abrades the immobilized denitrifying bacteria, resulting in a decrease in the amount of the immobilized denitrifying bacteria.
Further, there is a method in which the mixed liquid in the denitrification tank is agitated and circulated by circulating it through a pump, but in this case, the immobilized denitrifying bacteria are sucked into the pump suction portion, and the fluidized state cannot be maintained. Furthermore, in the actual reaction tank, there is a flow from the sewage inflow side to the outflow side, so the concentration of immobilized denitrifying bacteria on the outflow side of the reaction tank becomes higher than that on the inflow side, and as a result, on the inflow side of the reaction tank. There is also a problem that the reaction efficiency of is decreased.

Similarly, the immobilized nitrifying bacterium that nitrifies under aerobic conditions uniformly flows in the nitrification tank in order to increase the efficiency of the nitrification reaction, thereby increasing the chance of contact with the mixed liquid containing Kjeldahl nitrogen. There is a need. However, also in this case, there are problems that the concentration of the immobilized nitrifying bacteria becomes higher on the outflow side of the reaction tank than on the inflow side, and it is difficult to uniformly flow all the immobilized nitrifying bacteria.

The present invention solves the above-mentioned problems, and allows immobilized denitrifying bacteria, immobilized nitrifying bacteria, and the like to uniformly flow in the reaction tank, and at the same time, to suppress the abrasion thereof, thereby increasing the reaction efficiency. It is an object to provide a device that can be enhanced.

[0009]

In order to solve the above problems, the sewage treatment apparatus of the present invention has a denitrification tank for biologically denitrifying under anoxic conditions. The activated sludge mixture can be treated by the immobilized denitrifying bacteria because it can flow with the denitrifying bacteria, and the immobilized denitrifying bacteria that settle the denitrified activated sludge mixed liquid overflow into the denitrification tank. A fixed denitrifying bacteria flow container that can be separated, and a flow means that can supply the activated sludge mixed liquid in the tank in a fluidized state toward the inside of the fixed denitrification bacteria flow container are provided. Is an outer cylinder that constitutes the outer wall of the container and through which the liquid flows from the upper end into the tank, and is provided in this outer cylinder and opened at the top and bottom, and is supplied from the flow means to the inside of the flow container in an upward flow state from the flow means. Immobilized denitrification with mixed liquid in tank and liquid in outer cylinder Preparative a first inner cylinder enter is provided outside the upper portion of the first inner cylinder, at least the lower is opened, the first
The second inner cylinder is configured to receive the liquid flowing out from the upper end of the inner cylinder and send the liquid from the lower opening to a position apart from the liquid outflow portion at the upper end in the outer cylinder.

Further, the sewage treatment apparatus of the present invention immobilizes the activated sludge mixed solution and the immobilized nitrifying bacteria in a nitrification tank that biologically nitrifies under aerobic conditions by allowing them to flow inside. A fixed nitrifying bacteria flow container capable of treating the activated sludge mixed liquid with nitrifying bacteria and allowing overflow separation from the immobilized nitrifying bacteria that precipitates the nitrified activated sludge mixed liquid into the nitrification tank, and this immobilization A flow means capable of supplying the activated sludge mixed liquid in the tank in a fluid state toward the inside of the nitrifying bacteria flow container,
Either in the nitrification tank or in the fixed nitrifying bacteria flow container or in the vicinity of the flow means, a means for supplying air or oxygen to the activated sludge mixture and the fixed nitrifying bacteria is provided, and the fixed nitrification bacteria flow container is , An outer cylinder that constitutes the outer wall of the container and through which liquid flows from the upper end into the tank, and is provided in this outer cylinder and has an opening at the top and bottom, and is supplied in an upward flow state from the flow means to the flow container from the flow means. A first inner cylinder into which the mixed liquid in the tank, the liquid in the outer cylinder, and the immobilized nitrifying bacteria enter, and an outer upper portion of the first inner cylinder, at least a lower portion of which is open,
The second inner cylinder is configured to receive the liquid flowing out from the upper end of the inner cylinder and send the liquid from the lower opening to a position apart from the liquid outflow portion at the upper end in the outer cylinder.

Further, the sewage treatment apparatus of the present invention has the above-mentioned second aspect.
An inclined plate or a group of inclined plates for improving the settling property of the immobilized denitrifying bacteria or the immobilized nitrifying bacteria is provided between the inner cylinder and the outer cylinder.

Further, the sewage treatment apparatus of the present invention is characterized in that the fixed denitrifying bacterium flow container or the fixed nitrifying bacterium flow container has a bottom portion,
A device for preventing falling of immobilized denitrifying bacteria or immobilized nitrifying bacteria is installed.

[0013]

In the above-described structure, the immobilized denitrifying bacteria having sedimentation property, that is, the immobilized and immobilized denitrifying bacteria, the entrapped immobilized denitrifying bacteria, and the self-immobilized denitrifying bacteria are immobilized in the denitrifying tank. Since the denitrifying bacterium is housed in a fluid container and the fluidizing means is installed outside the vessel, the immobilized denitrifying bacteria do not come into contact with the fluidizing means, and its abrasion is prevented. Further, in a state where the immobilized denitrifying bacteria are held inside the container, by flowing the activated sludge mixed liquid by the flow means, the activated sludge mixed liquid and the immobilized denitrifying bacteria are sufficiently stirred and mixed inside the container,
The efficiency of denitrification of the liquid to be treated by the immobilized denitrifying bacteria is increased.

In the nitrification tank, the immobilized nitrifying bacteria having a sedimentation property, that is, the binding-immobilized nitrifying bacteria, the entrapped and immobilized nitrifying bacteria, the self-immobilized nitrifying bacteria, etc., are placed in the immobilized nitrifying bacteria flow container. By accommodating and installing the flow means outside the container, the immobilized nitrifying bacteria do not come into contact with the flow means, and their abrasion is prevented. Further, while the immobilized nitrifying bacteria are held inside the container, the activated sludge mixed liquid is caused to flow by the flowing means, while the air is removed either in the nitrification tank or in the immobilized nitrifying bacteria flow container or near the flowing means. Alternatively, by supplying air or oxygen with an oxygen supply device, aerobic conditions are maintained and the activated sludge mixed solution and the immobilized nitrifying bacteria are sufficiently agitated and mixed in the container, and the liquid to be treated by the immobilized nitrifying bacteria is treated. Nitrification treatment efficiency increases.

Further, by installing the inclined plate or the inclined plate group between the second inner cylinder and the outer cylinder, it is possible to improve the sedimentation property of the immobilized denitrifying bacteria and the immobilized nitrifying bacteria. Furthermore, by installing a device for preventing falling of immobilized denitrifying bacteria or immobilized nitrifying bacteria from the bottom of the immobilized denitrifying bacteria flowing container or immobilized nitrifying bacteria flowing container, contact with these flowing means is avoided, and wear is prevented. It is possible to prevent the concentration of immobilized microorganisms from decreasing.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction and operation of a sewage treatment apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment in which the immobilized denitrifying bacteria flow apparatus is immersed in a denitrification tank. Reference numeral 1 is an immobilized denitrifying bacterium flow apparatus, and 5 is an immobilized denitrifying bacterium flow container. The flow container 5 is composed of an outer cylinder 2 forming an outer wall of the container, a first inner cylinder 3 installed inside the outer cylinder 2, and a second inner cylinder 4 installed on an upper outer side of the first inner cylinder 3. The lower portion of the outer cylinder 2 has a structure in which the cross section gradually decreases toward the bottom. First
The inner cylinder 3 and the second inner cylinder 4 are open at both upper and lower ends,
The upper end of the outer cylinder 2 is open. The first inner cylinder 3 is the denitrification tank 2
When soaked in the activated sludge mixed liquid 6 in 1, the whole is installed so as to be located below the liquid surface, and the second inner cylinder 4 has the lower end located below the liquid surface and the upper end located above the liquid surface. Is installed as. The upper end portion 7 of the outer cylinder 2 has an outward inclination as necessary to facilitate the outflow of the activated sludge mixed liquid 6 to the outside of the outer cylinder 2. Further, there is a gap 8 between the lower end of the first inner cylinder 3 and the bottom of the outer cylinder 2 so that the activated sludge mixed liquid 6 and the immobilized denitrifying bacteria 9 can pass through. An opening 10 is provided at the bottom of the outer cylinder 2, and the opening 10 is connected to a flow means 12 such as an external pump via a pipe 11. With this configuration, the activated sludge mixed liquid 6 in the tank 21 flows into the flow means 1
2 is fed from the bottom of the container 5 through the pipe 11,
After ascending within the first inner cylinder 3, the first inner cylinder 3 is crossed over the upper end thereof to descend between the inner cylinder 3 and the second inner cylinder 4, and then the second inner cylinder 4 and the outer cylinder 2 are connected. Between the outer cylinder 2 and the upper end 7 of the outer cylinder. At this time, a part of the immobilized denitrifying bacteria 9 having gravity settling property in water and the activated sludge mixed liquid 6 in the container 5 rises in the first inner cylinder 3 and exceeds the upper end of the first inner cylinder 3. After descending between the inner cylinder 3 and the second inner cylinder 4 and further falling inside the outer cylinder 2, the first inner cylinder 3 again passes through the gap 8 between the lower end of the first inner cylinder 3 and the bottom of the outer cylinder 2, and then the first cylinder again. It is possible to return to the bottom of the inner cylinder 3.

The operation of the above configuration will be described below.
First, the liquid to be treated 30 from the settling tank is introduced into the denitrification tank 21 in which the immobilized denitrifying bacteria flow apparatus 1 is installed, and the activated sludge existing in the tank 21 and the circulating liquid from the nitrification tank are mixed with each other. Use liquid 6. In the denitrification process, the liquid to be treated 30 continuously flows in, and the denitrification-treated activated sludge mixed liquid continuously flows out. Immobilized denitrifying bacteria 9 having gravity settling property in water or an activated sludge mixed liquid 6 in the outer cylinder 2 of the flow container 5.
Then, the activated sludge mixed liquid 6 and the immobilized denitrifying bacteria 9 are caused to flow by using a flow means 12 such as a pump.

Then, the activated sludge mixed liquid 6 is supplied to the pipe 1 by the flow means 12 as shown by a dotted arrow in FIG.
After being sent from the bottom of the container 5 through 1 and rising in the first inner cylinder 3, it evenly descends between the inner cylinder 3 and the second inner cylinder 4 over the upper end thereof, and most of them subsequently. Second inner cylinder 4
Between the outer cylinder 2 and the outer cylinder 2 and rises over the upper end 7 of the outer cylinder 2 to the outside of the outer cylinder 2.

On the other hand, the immobilized denitrifying bacteria 9 and a part of the activated sludge mixed liquid 6 in the container 5 rise inside the first inner cylinder 3 as shown by the solid arrow in FIG. And descends between the inner cylinder 3 and the second inner cylinder 4 to reach the outer cylinder 2
After descending inside, it returns to the bottom of the first inner cylinder 3 again through the gap 8 between the first inner cylinder 3 and the bottom of the outer cylinder 2.

In this way, the immobilized denitrifying bacteria 9 and the activated sludge mixed liquid 6 flow in the immobilized denitrifying bacteria flowing container 5 and are sufficiently mixed, and the immobilized denitrifying bacteria 9 are retained in the container 5. The activated sludge mixed liquid 6 flows inside and outside the container 5. In this way, the liquid to be treated 30 not only comes into sufficient contact with floating denitrifying bacteria existing inside and outside the container 5 while flowing in the denitrifying tank 21, but also sufficiently with the immobilized denitrifying bacteria 9 in the container 5. They will come into contact and will be effectively denitrified,
The denitrification processing time is shortened.

The undissolved part of the gas such as nitrogen gas generated by the action of the denitrifying bacteria is naturally discharged from the inside of the immobilized denitrifying bacteria flow container 5 to the outside air. The first inner cylinder 3, the second inner cylinder 4, and the outer cylinder 2 may be circular or rectangular when viewed from above, but are preferably concentric.

Further, between the second inner cylinder 4 and the outer cylinder 2 in the flow container 5, there is a rising liquid flow, a descending liquid flow and a falling immobilized denitrifying bacterium 9 flow. 2 A turbulent zone occurs near the lower end of the inner cylinder 4, and the larger the rising linear velocity of the liquid in the first inner cylinder 3, the larger this turbulent zone,
The settling property of the immobilized denitrifying bacteria 9 is likely to decrease. Therefore, in order to enhance the sedimentation property of the immobilized denitrifying bacteria 9, an inclined plate or a group of inclined plates 13 is installed as shown in FIG. 2, and the activated sludge mixed liquid 6 is allowed to flow out of the flow container 5, The immobilized denitrifying bacteria 9 may be retained in the flow container 5 by enhancing the sedimentation property of the nitrifying bacteria 9.

As shown in FIG. 3, a lid 14 is provided on the upper end of the second inner cylinder 4, and a gas vent 15 is provided in a part of the lid 14,
It is also possible to prevent the ejection of the liquid when the rising linear velocity of the liquid in the first inner cylinder 3 becomes large.

At the bottom of the outer cylinder 2, for example, as shown in FIG. 4, at the bottom of the outer cylinder 2, a device 16 for preventing drop of carriers such as a wire net, a screen, a check valve, etc. is installed, and the operation is stopped. Alternatively, the backflow of the immobilized denitrifying bacteria 9 to the flow means 12 during operation may be prevented. The fall prevention device 16 may be provided between the outer cylinder 2 and the flow device 12.

As the immobilized denitrifying bacterium 9, various ones such as bond immobilized denitrifying bacterium, entrapment immobilized denitrifying bacterium, and self-immobilized denitrifying bacterium can be used. In the case of a carrier that binds and immobilizes denitrifying bacteria, the denitrifying bacteria may be immobilized in advance and then charged into the fluid container 5, but the carrier is fluidized in the fluid container 5 in the presence of the activated sludge mixed liquid 6. Since the denitrifying bacteria are adhered and immobilized in accordance with the above, it suffices to put the carrier on which the denitrifying bacteria are not adhered and immobilized into the fluid container 5. When such a carrier that binds and immobilizes denitrifying bacteria is used, the carrier having gravity settling property in water or an activated sludge mixed liquid in a state where the denitrifying bacteria are not immobilized or immobilized is used and has a pore size of 2 mm. It is desirable that the carrier has less than 4 cells at least in the surface layer portion or has open cells having a pore size of less than 2 mm. When the water temperature is relatively high in summer and the concentration of BOD organic matter in the inflow sewage is low, thread earthworms with a thickness of 0.1 to 0.3 mm are likely to occur,
Since it will interfere with the intended treatment, such as eating up microorganisms, it has air bubbles with a pore size of less than 0.1 mm in at least the surface layer, or has a pore size of 0.1 mm.
Carriers with less than open cells may be used to prevent the generation of unwanted organisms.

When a carrier for entrapping immobilization of denitrifying bacteria is used, entrapping immobilization of denitrifying bacteria is carried out in advance and the fluid container 5 is used.
Throw in. When using the self-immobilizing denitrifying bacterium, it is not necessary to put the carrier in the flow container 5, and it is sufficient to operate the activated sludge mixed liquid 6 in the container 5 so that the carrier has the self-immobilizing ability. Pellets of nitrifying bacteria are generated and accumulated, and flow in the container 5.

FIG. 5 shows an embodiment in which the immobilized nitrifying bacteria flow device is immersed in a nitrification tank. Reference numeral 17 is a fixed nitrifying bacteria flow apparatus, 18 is a fixed nitrifying bacteria flow container, 19 is fixed nitrifying bacteria, and 22 is a nitrification tank. Since the structure of the immobilized nitrifying bacteria flow device 17 is almost the same as that of the immobilized denitrifying bacteria flow device 1 shown in FIG. 1, parts having the same functions are designated by the same reference numerals and the description thereof will be omitted. Alternatively, it differs from the immobilized denitrifying bacteria flow apparatus 1 in that a means for supplying oxygen or the like is provided. Suction side A of the flow means 12, between the discharge side of the flow means 12 and the immobilized nitrifying bacteria flow container 18,
Air, oxygen or the like can be supplied by a general air diffuser or the like at C in the immobilized nitrifying bacteria flow container 18 or at least one position in the other nitrification tanks. Alternatively, in either or both of the sections A and B, a part of the pipe may be a pipe 20 having fine holes for allowing bubbles to pass as shown in FIG. 6, and air or oxygen may be supplied from there. .

In this way, the activated sludge mixed liquid 6, that is, the denitrification-treated liquid from the denitrification tank 21 and the activated sludge are caused to flow in the nitrification tank 22 while sufficiently supplying air or oxygen. The mixed liquid is a floating nitrifying bacterium existing inside and outside the container 18 and the immobilized nitrifying bacterium 1 in the container 18.
9 is brought into sufficient contact, and nitrification is efficiently performed, and the nitrification treatment time is shortened.

The slant plate or slant plate group 13, the lid 14 and the device 16 for preventing drops of the carrier and the like described in the treatment in the denitrification tank 21 are all applicable to the nitrification tank 22 and are used for immobilizing denitrifying bacteria. Can also be applied to a method for immobilizing nitrifying bacteria.

[0031]

As described above, according to the present invention, the immobilized denitrifying bacterium or the immobilized nitrifying bacterium can be held in the immobilized denitrifying bacterium flow container or the immobilized nitrifying bacterium flow container and uniformly flowed. it can. At this time, since the immobilized denitrifying bacteria and the immobilized nitrifying bacteria are cut off from the stirring device portion, it is prevented that these are worn in the stirring device portion, and thus the concentration of the immobilized bacterial cells is reduced. Furthermore, by using a microbial immobilization carrier having gravity sedimentation property and self-immobilized bacterial cells, immobilized denitrifying bacteria or immobilized cells can be obtained without providing a screen etc. to prevent these from flowing out of the container. Nitrifying bacteria can be retained in the container.

As a result of the above, the chances of contact of the liquid to be treated with the immobilized denitrifying bacteria or the immobilized nitrifying bacteria are increased, so that the denitrification efficiency or the nitrification efficiency can be greatly increased, and the denitrification reaction or the nitrification reaction can be improved. The time required can be greatly reduced.

Further, since the apparatus is simple, it is possible that fibers and the like in the inflowing sewage accumulate in the immobilized denitrifying bacteria flow apparatus or the immobilized nitrifying bacteria flow apparatus or cause clogging of these apparatuses. Absent.

When the sewage treatment apparatus of the present invention is applied to the removal of biological pollutants such as the removal of organic substances such as BOD and COD, the same effects as above can be obtained.

[Brief description of drawings]

FIG. 1 is a view showing an example of an immobilized denitrifying bacteria flow apparatus applied to a sewage treatment apparatus of the present invention.

FIG. 2 is an enlarged view of a main part of the immobilized denitrifying bacteria flow apparatus of FIG.

FIG. 3 is an enlarged view of another main part of the immobilized denitrifying bacteria flow apparatus of FIG. 1.

FIG. 4 is an enlarged view of still another main part of the immobilized denitrifying bacteria flow apparatus of FIG. 1.

FIG. 5 is a diagram showing an example of an immobilized nitrifying bacteria flow apparatus applied to the wastewater treatment apparatus of the present invention.

6 is an enlarged view of a main part of the immobilized nitrifying bacteria flow device of FIG.

[Explanation of symbols]

 1 immobilized denitrifying bacteria flow device 2 outer cylinder 3 first inner cylinder 4 second inner cylinder 5 immobilized denitrification bacteria flow container 6 activated sludge mixed liquid 9 immobilized denitrification bacteria 12 flow device 13 slant plate or slant plate group 16 fall prevention Equipment 17 Fixed nitrifying bacteria flow device 18 Fixed nitrifying bacteria flow container 19 Fixed nitrifying bacteria 21 Denitrification tank 22 Nitrification tank 30 Liquid to be treated

Claims (6)

[Claims] 1. A method of mixing activated sludge with immobilized denitrifying bacteria by allowing the activated sludge mixed solution and the immobilized denitrifying bacteria to flow inside a denitrifying tank for biologically denitrifying under anoxic conditions. Of the immobilized denitrifying bacteria flow container that can process the liquid and overflow and separate from the immobilized denitrifying bacteria that settles the denitrifying activated sludge mixed liquid into the denitrification tank, and An external cylinder which is provided with a flow means capable of supplying the activated sludge mixed liquid in the tank in a fluidized state toward the inside, forms the outer wall of the fixed denitrifying bacteria flow container, and causes the liquid to flow from the upper end into the tank. And, provided in this outer cylinder, the upper and lower sides are opened, and the mixture solution in the tank, the liquid in the outer cylinder, and the immobilized denitrifying bacteria, which are supplied in the upward flow state from the flow means into the flow container, enter through the lower opening. At least the first inner cylinder and the outer upper part of the first inner cylinder are provided. The lower part also opens, receives the liquid flowing out from the upper end of the first inner cylinder, and sends this liquid from the lower opening to a position away from the liquid outflow part at the upper end in the outer cylinder.
A wastewater treatment device comprising an inner cylinder. 2. The activated sludge mixed solution by the immobilized nitrifying bacteria by allowing the activated sludge mixed solution and the immobilized nitrifying bacteria to flow inside the nitrification tank for biologically nitrifying under aerobic conditions. In addition to being able to treat the same, the immobilized nitrifying bacteria flow container that can separate and overflow the immobilized nitrifying bacteria that settles the nitrification-treated activated sludge mixture into the nitrification tank, and the inside of this immobilized nitrifying bacteria flow container And a flow means capable of supplying the activated sludge mixed solution in a tank in a flowing state, and the activated sludge mixed solution and the immobilized nitrifying bacteria either in the nitrification tank or in the fixed nitrifying bacteria flow container or near the flowing means. Means for supplying air or oxygen to the fixed nitrifying bacteria flow container, the outer cylinder constituting the outer wall of the container and the liquid flowing out from the upper end into the tank, and the upper and lower parts provided in the outer cylinder. Open and open from the lower opening A first inner cylinder into which the mixed liquid in the tank, the liquid in the outer cylinder, and the immobilized nitrifying bacteria, which have been supplied in an upwardly flowing state into the fluid container from the first inner cylinder, are provided on the outer upper portion of the first inner cylinder, and at least the lower portion is open. And a second inner cylinder which receives the liquid flowing out from the upper end of the first inner cylinder and sends the liquid from the lower opening to a position apart from the liquid outflow portion at the upper end in the outer cylinder. Sewage treatment equipment. 3. An inclined plate or a group of inclined plates for improving the settling property of the immobilized denitrifying bacteria or the immobilized nitrifying bacteria is installed between the second inner cylinder and the outer cylinder. The sewage treatment apparatus according to claim 1 or claim 2. 4. A device for preventing fall of immobilized denitrifying bacteria or immobilized nitrifying bacteria is installed at the bottom of the immobilized denitrifying bacteria flowing container or immobilized nitrifying bacteria flowing container.
4. The sewage treatment apparatus according to claim 3. 5. The carrier for immobilized denitrifying bacteria or immobilized nitrifying bacteria has a pore having a pore size of less than 2 mm at least in the surface layer portion, or a bound immobilization carrier having continuous pores having a pore size of less than 2 mm. Claim 1 characterized by
5. The sewage treatment apparatus according to claim 4. 6. The carrier has pores having a pore size of less than 0.1 mm in at least the surface layer, or has a pore size of 0.1 mm.
The sewage treatment apparatus according to claim 5, wherein the sewage treatment apparatus is a bonded immobilization carrier having less than continuous pores.