JP3155457B2 - Wastewater treatment equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the removal of nitrogen contained in wastewater, particularly to the removal of nitrogen in general sewage, and more particularly to a wastewater treatment apparatus using a fluidized bed system utilizing a biological carrier. I do.

[0002]

2. Description of the Related Art Conventionally, as one of the microbiological treatment methods of wastewater containing nitrogen, there is a nitrification liquid circulation method using suspended microorganisms suspended in wastewater. An example will be described with reference to FIG. 4. The first half of the reaction tank 1 for performing biological treatment is an anaerobic tank 11 for stirring without blowing air, and the second half is a diffuser 13.
An aerobic tank 12 for injecting air from the tank, a part of the aerobic treatment liquid (nitrification liquid) is circulated from the end of the aerobic tank 12 to the anaerobic tank 11 (nitrification liquid circulation), and most of the aerobic treatment liquid is removed. Activated sludge is settled and separated by leading to the next settling tank 2. The sludge settled here is withdrawn from the lower part of the sedimentation tank 2, and one part thereof is returned to the anaerobic tank 11 (sludge return). Thus, in the first half of the anaerobic tank 11, the nitric acid component in the nitrification liquid is removed by the denitrifying bacterium while utilizing the organic component in the wastewater, and in the second half of the aerobic tank 12, the remaining organic component is removed by the nitrifying bacterium. After oxidizing ammonia nitrogen to remove organic matter and nitrogen components, microorganisms are separated as sludge from the reaction solution in the next settling tank 2, and the final solution is discharged out of the system.

In a treatment method using such a microorganism,
Although the treatment speed is in principle proportional to the amount (concentration) of the microorganism, the concentration of the microorganism in the reaction solution is adjusted to the concentration in the next settling tank 2.
The concentration could not be increased to exceed the separation capacity of To overcome this problem, a method using a biological carrier carrying a microorganism at a high concentration has been developed. In this method, the number m of particles carrying microorganisms
By loading a support made of a high-molecular-weight hydrogel having a specific gravity of m and being slightly heavier than water into the reaction tank 1, the advantage that the processing speed can be dramatically increased in addition to the conventional suspended microorganisms is obtained. Was.

In order to continue such a treatment, it is necessary to keep a predetermined amount of the carrier in the reaction tank 1 at all times. For this purpose, the biological carrier is subjected to the denitrification and nitrification treatment. Is set up so that it can be collected and recycled. Therefore, in order to separate the biological carrier from the processing solution,
For example, in FIG. 4 , at the end of the aerobic tank 12, a screen 14 having openings that can prevent the outflow of biological carriers is arranged.

[0005] On the other hand, in this treatment method using a biological carrier, the larger the specific surface area of the carrier itself and the amount of the carrier, the greater the processing speed. Therefore, as many small carriers as possible are loaded. However, the smaller the size of the carrier, the more difficult the separation operation from the processing solution becomes. Therefore, from the viewpoint of the processing efficiency and the separation characteristics, the size of the carrier is a particle having a particle size of about 2 to 3 mm to 10 mm. Has been adopted.

As described above, since the screen 14 has a relatively narrow opening, the screen 14 is clogged by flocculent microorganisms (for example, calcium bacterium) grown in the reaction tank 1 or mixed with raw water. The screen 14 is also clogged by contaminant solids in the coming processing liquid, for example, debris of synthetic resin articles, wood chips, food residue, hair, etc., and by increasing while they stay in the reaction tank 1, In some cases, the operation of the biological treatment apparatus was significantly obstructed. In order to prevent the inflow of such contaminant solids, measures such as providing a contaminant removal tank 15 in which a scooping screen 16 is disposed at the inlet of the reaction tank 1 are taken. However, even if it is removed, there is a problem that it cannot be completely removed and that it must be cleaned frequently.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and has made it possible to separate a biological carrier without using a screen device as described above.
To provide a wastewater treatment apparatus.

[0008]

Means for Solving the Problems To solve the above problems,
The wastewater treatment apparatus of the present invention made for
Biological denitrification or coexistence of specific gravity biological carrier and wastewater
The terminal end of the reactor for nitrification is separated by a partition.
To form an inlet for wastewater containing biological carriers
At the same time, wastewater introduced from the introduction channel is
Flow to the upward flow and decelerate to reduce the biological burden
A rectification path to lift the body and a speed lower than the ascent rate of the biological carrier
Carrier separation section consisting of a slow flow path with
It is characterized by having been formed .

[0009]

[0010]

Next, an embodiment of the present invention will be described. In the present invention, in one or both of the anaerobic tank and the aerobic tank, wastewater containing a nitrogen component and an organic component is subjected to a biological treatment by coexisting with a biological carrier carrying a denitrifying or nitrifying microorganism. In the purification, a biological carrier having a specific gravity smaller than that of the treatment liquid is used . Further, in order to return the biological carrier after the treatment to the previous biological treatment step, the biological carriers are floated and aggregated, and separated from the processing solution .
You.

According to the present invention, since the specific gravity of the biological carrier is set to be slightly smaller than that of the processing liquid, the processing liquid is uniformly mixed as it flows in the reaction tank, so that the biological processing is improved. At the same time as proceeding, if the flow rate of the processing solution is adjusted to an appropriate slow speed, the biological carrier floats by its own buoyancy, so that it can be collected and easily separated from the processing solution.

In this case, the specific gravity of the biological carrier is 1
The smaller the particle size, the greater the buoyancy, so that flotation becomes easier. On the other hand, uniform mixing with the processing solution becomes difficult, and biological treatment is hindered. FIG. 1 shows such a relationship in a graph. The relationship between the specific gravity of the carrier and the residual ratio of the carrier in the processing solution after separation and the carrier concentration at the bottom of the reaction tank (average carrier concentration: 10%, aeration intensity: 1m ³ Air /
m ³ Hr, separation time: 1 minute).

In this wastewater treatment method, after the biological treatment, it is most preferable that no carrier is present in the treatment liquid from which the carrier has been separated, that is, the residual ratio is 0, as shown in FIG. When the specific gravity of the carrier is 0.99 or less, the specific gravity of 0.99 or less is preferable so that the residual ratio is 0.1% or less, and 0.9% or less is 0%.
It is understood that a specific gravity of 0.98 or less is particularly preferable.

Further, in the wastewater treatment method of the present invention, a graph of FIG. 2 (reactor water temperature: 2) showing the relationship between the nitrification rate of the reactor and the floating speed of the carrier with respect to the particle size of the carrier.
0 ° C., NH ₄ concentration: 25 mg / liter, carrier concentration set value: 10%) shows that it is preferable to set the size of the biological carrier to 2 mm or more and 10 mm or less.

[0015] From the viewpoint of the effect of the particle size of the carrier on the biological treatment speed, a small particle size having a large specific surface area is preferred.
4 m / min, and there is almost no difference as compared with the practical flow velocity of the processing solution, which is not preferable from the point of separation efficiency. When it exceeds 10 mm, the desirable practical nitrification rate of 80 mg / liter carrier hr is used. It is not preferable because it will be less than 2 mm from this point.
It is particularly preferable that the thickness be 7 mm or less. The particle size in this case means that the shape of the carrier can be various other than spherical, such as cubic, cylindrical, amorphous solid, etc. It is assumed that.

Further, the above-mentioned wastewater treatment method may be a wastewater treatment method for performing the biological treatment in an aerobic tank, or introducing wastewater into an aerobic tank via an anaerobic tank. Wastewater treatment method of performing biological treatment and returning the separated biological carrier to the inflow end of the aerobic tank,
Or a wastewater treatment method of introducing wastewater into an aerobic tank via an anaerobic tank, performing the biological treatment in the anaerobic tank and the aerobic tank, and returning the separated biological carrier to the anaerobic tank inflow end. It can be embodied as follows.

In the wastewater treatment method described above, the biological carrier is floated by buoyancy to separate it from the treatment liquid, and therefore, the conventional biological carrier separation screen device provided at the outlet of the reaction tank is not necessary. In addition, the treatment is hardly hindered by contaminant solids flowing from the undiluted solution, and the contaminant solids flowing in can be treated together with surplus sludge in the final settling tank at the next stage, etc. There are advantages that do not even require.

Next, an embodiment of the waste water treatment apparatus of the present invention
It will be described with reference to FIG. FIG. 3 shows a region where the biological carriers float and assemble and are separated from the processing solution.
1 is an embodiment arranged inside the first embodiment. In the wastewater treatment apparatus of this embodiment, a reaction tank 31 for biologically treating wastewater containing a nitrogen component and an organic component and a sedimentation basin (not shown) for sedimenting and separating activated sludge from the treatment liquid are arranged. 31
Is provided as a region for performing biological denitrification or nitrification treatment by coexisting the biological carrier 4 with a specific gravity smaller than the wastewater and the wastewater. At the end of the reaction tank 31, the biological carrier 4 is floated. A carrier separation unit 32 as a region to be collected and separated from the processing liquid, and a carrier return device for collecting the separated biological carrier 4 and transferring the collected biological carrier 4 to the reaction tank 31 which is the biological treatment region is provided. Have been.

The carrier separating section 32 here is constituted by a flow path separated by a partition wall 34 at the terminal end of the reaction tank 31, and the treatment liquid containing activated sludge and the biological carrier 4 is
The flow is guided from the introduction path 35 to the rectification path 36 in the carrier separation unit 32, is rectified into an upward flow, is decelerated, and is then guided to a slow flow path 37 of a downward flow, and is further decelerated. During this time, the biological carrier 4 floats by buoyancy and gathers on the upper part of the carrier separating section 32, while the processing liquid containing activated sludge is discharged from the outlet 39 through the outlet channel 38 and sent out to the sedimentation basin (not shown). It is done.

In order to cause the biological carrier 4 to float against the downward flow of the processing liquid in the slow passage 37, the downward flow speed may be set lower than the floating speed. This can be dealt with by determining the cross-sectional area by the difference in specific gravity between the biological carrier 4 and the processing liquid. For example, when the specific gravity of the biological carrier 4 is 0.95 and the treatment liquid is 1, the downward flow velocity is 1.0 m
/ Min may be selected so that the cross-sectional area of the slow path 37 is not more than / min.

As the carrier returning device for collecting the biological carrier 4 and transferring it to the biological treatment area, a return pump such as an air lift pump, a screw or a screw pump which is a transport driving device that does not damage the biological carrier. 33
Alternatively, a mechanical conveyor using a bucket can be used.

As described above, in the case of the wastewater treatment apparatus according to this embodiment, the biological carrier can be floated by buoyancy and separated from the treatment liquid. In addition, a scraping screen device or the like provided at the inlet of the reaction tank to prevent the inflow of the contaminant solids becomes unnecessary, and the inflowing contaminant solids can be treated together with excess sludge in the final sedimentation basin. Further, in this embodiment, since the water level of the floating biological carrier and the water level of the reaction tank 31 can be kept the same, there is an advantage that the carrier can be easily returned and a simple return device can be used.

[0023]

[0024]

[0025]

[0026]

[0027]

Since the wastewater treatment apparatus of the present invention is constructed as described above, a conventional screen apparatus for separating carriers and a screen apparatus for screening and preventing the inflow of contaminant solids are not required. The contaminated solids that have flowed into the final sedimentation basin can be discharged out of the system together with excess sludge. Therefore, since no screen equipment is required, maintenance is extremely easy, maintenance costs are reduced,
There is an excellent effect that labor saving can be expected, equipment can be simplified, and equipment cost can be reduced. Therefore, there is a wastewater treatment apparatus according to the present invention which has solved the conventional problems and has a very large industrial value.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the specific gravity of a carrier of the present invention and the carrier concentration at the bottom of a reaction tank and the carrier residual ratio in a processing solution.

FIG. 2 is a graph showing the relationship between the nitrification speed and the floating speed of the carrier with respect to the particle size of the carrier of the present invention.

FIG. 3 is a sectional view of a main part showing an embodiment of the wastewater treatment apparatus of the present invention.

FIG. 4 is an outline of a wastewater treatment apparatus to which a conventional biological carrier is applied.
FIG .

[Explanation of symbols]

2 sedimentation basin, 23 return pump, 27 carrier separation unit, 3
1 reaction tank, 32 carrier separation section, 33 return pump, 3
4 partition wall, 35 introduction path, 36 rectification path, 37 slow speed path,
4 biological carriers

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C02F 3/02-3/10 C02F 3/34 101

Claims (1)

(57) [Claims] 1. A wastewater containing a biological carrier having a specific gravity smaller than that of the wastewater.
Reaction for coexisting biological denitrification or nitrification
Separate the terminal end of the tank by a partition wall, and put a biological carrier on the partition wall.
Of wastewater containing wastewater, and inside the bulkhead
Rectifies wastewater introduced from the introduction channel into upward flow and decelerates
Rectification path for floating biological carriers in wastewater
And have a downward flow velocity less than the floating velocity of the biological carrier.
And a carrier separation section consisting of a slow path.
Wastewater treatment equipment.