JPH0871579A - Wastewater treatment apparatus - Google Patents

Abstract

PURPOSE: To obtain a high nitrogen removing rate by a method in which a support fluidized aeration tank is filled with synthetic resin porous supports with a cylindrical shape and a specified size in a specified packing ratio, the aeration drift velocity of the porous supports is reduced, and the anaerobic area in the porous support is increased. CONSTITUTION: In a wastewater treatment apparatus composed of an conditioning tank 1, a support fluidized aeration tank 2, a sedimentation tank 3, a disinfection tank 4, a sludge returning apparatus 5, a discharge tank 6, a sludge concentration storage tank 7, etc., an air diffusion pipe is installed in the bottom part of the tank 2, and wastewater and porous supports in the tank 2 are circulated by air ejected from a compressor. In this process, the air diffusion pipe is filled with the cylindrical porous supports 300-600mm in length, 30-50mm in diameter or diagonal length in the cross section in a packing rate of 20-40vol.%. Part of sludge separated in the sedimentation-separation tank 3 is returned to the aeration tank 2 and/or the conditioning tank 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is used for the purification of human waste and household wastewater, and is mainly a carrier aeration tank, and is capable of simultaneously removing BOD and nitrogen components in wastewater. It relates to an improvement of the device.

[0002]

2. Description of the Related Art The applicant first found that the length of one side is 10 to 15
mm prismatic polyurethane porous carrier 20 to 30 mm
We developed a wastewater treatment method that enables simultaneous removal of BOD and nitrogen components of the wastewater by aeration-treating the wastewater in an aeration tank filled with about VOL%.
It is open to the public as issue 5. That is, in the sewage treatment method, as shown in FIG. 6, the ammonia nitrogen and the organic nitrogen in the sewage W flowing into the carrier flow aeration tank C are added to the outer layer portion of the porous carrier under the aerobic environment. While contacting with nitrifying bacteria in sludge and converting it to nitrate nitrogen or nitrite nitrogen, the nitrate nitrogen or nitrite nitrogen after nitrification is continuously applied to the inner layer of the porous carrier under anaerobic environment. The nitrogen in the wastewater is removed by bringing it into contact with denitrifying bacteria in the sludge and converting it into nitrogen gas. Incidentally, in FIG. 7, D
Is a settling tank, E is a sludge return passage, F is a sludge measuring device, and G is a sludge concentration storage tank.

The sewage treatment method disclosed in Japanese Patent Laid-Open No. 4-66195 is capable of simultaneously removing BOD and nitrogen components in sewage with a very simple treatment system that combines a carrier flow aeration tank and a precipitation tank. It has been widely put to practical use as it has excellent practical utility.

However, the sewage treatment method disclosed in JP-A-4-66195 still has many problems to be solved. The first problem is that the denitrification performance decreases with the lapse of operating time. For example, 12 mm x 12 mm
A BOD load of 0.8 to ³ kg BOD / m ³ · day, using a carrier flow aeration tank (effective volume 1 m ³ ) filled with a urethane porous carrier of × 12 mm at a filling rate of 30 VOL%,
Amount of activated sludge returned 5.0 kg / m ³ / day, average total inflowing nitrogen 0.04 kg / kg (activated sludge) and 0.2 kg or less / m ³ (tank volume), aeration strength 9.0 m ³ / m ³ Hr
When the sewage treatment was carried out under the conditions described above, the removal rate of BOD in the sewage was about 90% and the total nitrogen removal rate was about 70% or more in the initial operation of the sewage treatment apparatus. The total nitrogen removal rate drops to about 40%. By the way, it is assumed that the reason for the decrease in the nitrogen removal rate is that the continuous aeration treatment causes the anaerobic region of the porous carrier to be sequentially decreased and the nitrification function and denitrification function to be decreased. Therefore, in reality, the continuous aeration process is intermittently aerated, or the amount of aeration is appropriately adjusted to prevent the decrease in the nitrogen removal capability, but it is troublesome to manage the operation of the processing device. Moreover, it becomes extremely difficult to keep the nitrogen removal rate close to the maximum value (about 70% or more).

The second problem is that it takes too much time and labor to put the porous carrier into the tank. When a porous carrier such as urethane is put into the carrier flow aeration tank,
As the sludge adheres to it, the porous carrier sinks into the wastewater. Therefore, a predetermined amount (filling rate of about 30
%) Of the porous carrier cannot be charged into the tank. Usually, it is divided into 3 times, and about 30 to 50 days are required to fill a predetermined amount of the porous carrier into the tank. Therefore, it takes a lot of trouble to fill the porous carrier.

The third problem is the sludge holding ability of the porous carrier and the wear due to friction. About 15mm x 15mm x
A porous carrier having a size of about 15 mm has a filling rate of 20 to 40 VO.
When L% is around 60 to 100 cm / s due to airflow
It circulates in the tank at a relatively high flow rate of about ec. Therefore, not only the sludge that has adhered is separated and dropped off relatively easily, but also the porous carrier itself is worn out relatively early due to the collision of the porous carriers, which requires replacement. Incidentally, in order to prevent sludge from falling off and abrasion of the porous carrier, if the aeration amount is reduced and the circulation flow rate of the carrier is reduced, there arises a problem that the removal rate of BOD in the wastewater is reduced. Will be done.

[0007]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention The present invention has the above-mentioned problems in the conventional wastewater treatment apparatus mainly composed of a carrier flow aeration tank, that is, the denitrification performance decreases with the lapse of operating time, and It is intended to solve problems such as the time and effort required to load the carrier into the tank, the separation and removal of sludge adhering to the porous carrier, and the wear of the carrier, and the relatively high denitrification performance. The present invention provides a sewage treatment apparatus capable of stably and continuously holding the porous carrier, facilitating the filling of the porous carrier into the tank, and improving the sludge holding capability of the carrier and reducing wear. .

[0008]

According to the present invention, there is provided a diffuser tube 8 having a length of 300 to 600 mm and a diameter of a cross section or a diagonal length of 30 to 50 mm, which is cylindrical or cylindrical or prismatic. Filling ratio of quality carrier B is 20-40VOL%
The carrier flow aeration tank 2 filled with the above, the settling separation tank 3 that receives the treated wastewater from the carrier flow aeration tank 2 and separates the sludge in the wastewater, and a part of the separated sludge is the carrier flow aeration tank. 2 or the carrier flow aeration tank 2 and the sludge returning device 5 for returning to either one or both of the adjusting tank 1 provided on the upstream side of the carrier flowing aeration tank 2 is a basic configuration of the invention.

[0009]

[Function] Ammonia nitrogen and organic nitrogen in the sewage flowing into the carrier flow aeration tank come into contact with the nitrifying bacteria in the sludge in the outer layer of the porous carrier under aerobic environment, resulting in nitrification. It is converted to nitrate nitrogen and nitrite nitrogen. The converted nitrate nitrogen or the like is subsequently contacted with the denitrifying bacteria in the sludge in the inner layer portion of the porous carrier under an anaerobic environment, so that the nitrogen is removed by the denitrifying action. Further, the BOD component in the sewage is decomposed and removed by aerobic bacteria by being subjected to so-called aeration treatment.

The sewage treated in the carrier flow aeration tank is transferred to a settling tank, where sludge is precipitated and separated, and then discharged to the outside through treatment such as disinfection. Further, a part of the sludge that has been separated by settling is returned to either or both of the carrier flow aeration tank or the carrier flow aeration tank and the adjustment tank provided upstream thereof, and is adsorbed by the flowing porous carrier. . by this,
The amount of sludge in the carrier aeration tank is always maintained at a predetermined value.

In the present invention, since the outer diameter of the flowing porous carrier is considerably large with a diameter of 30 to 50 mmφ and a length of 300 to 700 mm, the anaerobic region in the deep part of the carrier is expanded, and as a result, nitrogen is increased. The removal action is increased. Also,
Since the outer diameter of the porous carrier is large, the flow rate in the tank becomes relatively slow, and as a result, the sludge that has adhered to the carrier and the wear of the carrier itself are significantly reduced.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a basic configuration of a sewage treatment apparatus according to the present invention, which includes an adjustment tank 1, a carrier flow aeration tank 2, a precipitation tank 3, a disinfection tank 4, a sludge returning device 5, a discharge tank 6, and a sludge concentration storage tank. The processing device is composed of 7 or the like. Incidentally, the sewage treatment system itself is the same as that of the above-mentioned JP-A-4-66195.

2 to 5 show a tank body A used in the sewage treatment apparatus of the present invention. The tank body A
The adjusting tank 1, the main processing tank 2, the disinfecting tank 4, and the discharge tank 6 are provided inside.
Etc. are integrally formed, and the sedimentation tank 3, the sludge concentration storage tank 7, and the sludge returning device 5 are provided separately from the tank body A. 2 to 6, 8 is an air diffusing tube, 9 is an air diffusing tube fixing base, 10 is an air feeding valve, 11 is an advection tube, 12 is an air escape tube, 13 is an advancing tube, 14 is a screen portion, 15
Is a discharge pump, 16 is a disinfection device, 17 is a partition wall, 18 is an advection wall, 19 is a medicine cylinder, and 20 is an advection tube. Further, in the present embodiment, the settling tank 3 and the sludge concentration storage tank 7 are separate from the tank main body A and the like, but the settling tank 3 and the like can be formed integrally with the tank main body A. Further, although the adjusting tank 1 is provided in the present embodiment, it may be omitted.

With reference to FIGS. 3 and 4, an air diffuser 8 is provided at the bottom of the carrier flow aeration tank 2, and air supplied from a compressor (not shown) is jetted out, Sewage in the tank 2 and the porous carrier B circulate and circulate in the direction of the arrow. The external dimensions of the tank 2 are 30m.
A polyurethane porous carrier B having a rectangular parallelepiped shape of m × 30 mm × 300 mm is filled so that the volume occupancy rate becomes about 30%.

It is desirable that the porous carrier B has a specific gravity of about 1 and a cylindrical shape, a cylindrical shape or a prismatic shape having a diameter or diagonal length dimension of 30 to 50 mm and a length dimension of about 300 to 600 mm. This is because if the specific gravity deviates greatly from 1, or if the diameter or diagonal length or length dimension exceeds each of the above numerical values, the fluidity due to the aeration deteriorates, and the outer mold dimension of the carrier becomes less than each of the above numerical values. Then, the anaerobic region of the porous carrier B, which will be described later, is reduced, and the denitrification ability is reduced. When the carrier has a cylindrical shape, its inner diameter is preferably about 15 to 25 mm. Further, the porous carrier B needs to have abrasion resistance, and in the case of the polyurethane porous carrier B, ether-based open-cell polyurethane is preferable.

The optimum filling rate of the porous carrier B is about 20 to 35%. When the filling rate is 20% or less, the denitrification effect is sharply reduced, and when the filling rate is 35% or more, the flow due to the air becomes difficult, and when the amount of the air is increased to increase the fluidity. This is because the denitrification effect is offset on the contrary, and these are all confirmed by the denitrification test.

As described above, in the porous carrier B, it is necessary that the outer layer portion acts as an aerobic region and the inner layer portion acts as an anaerobic region. From this point, it is simply continuous foaming, or Even if the BOD can be removed only by having a high bubble ratio, it is impossible to exert an excellent nitrogen removing action. That is, when the air bubbles of the porous carrier are large and most of the air bubbles are continuous bubbles, the air bubbles easily pass through the inside of the carrier together with water, and the anaerobic region becomes almost zero and denitrification occurs. No effect is obtained. On the contrary, if the voids are not open cells, no matter how large the porosity is, the anaerobic region increases, but the water permeability becomes poor, and the denitrifying action cannot be obtained. Therefore, it is essential that the porous carrier B has an appropriate pore size and an appropriate open cell ratio (desirably, the open cell ratio in the outer layer region is relatively small). From a sample thickness of 30 mm (plate shape) and a filtration resistance of about 15 to 45 mm H ₂ O at a wind velocity of 2 m / sec, a length of 300 to 60 cut from a polyethylene or polyurethane plate body.
A 0 mm columnar carrier was found to be optimal in maintaining high nitrogen removal rates.

The sludge returning device 5 is composed of an automatic sludge metering device, a sludge returning pump, etc. The sludge separated in the settling tank 3 is calculated by the automatic metering device, and a predetermined amount of sludge is adjusted. 1 or the adjusting tank 1 and the carrier flow tank 2.

Next, the wastewater removing process according to the present invention will be described. The water to be treated W first enters the carrier-flow aeration tank 2 from the adjusting tank 1 through the advection pipe 13, and together with the porous carrier B and floating activated sludge holding activated sludge therein, the tank is driven by the air flow ejected from the air diffusion pipe 8. Circulate in 2 About 90% of the BOD in the wastewater is removed by biological treatment with activated sludge while circulating in the tank 2.

Further, the wastewater comes into contact with the aerobic region of the outer layer of the porous carrier B and the nitrifying bacteria in the floating sludge, whereby nitrification treatment of ammonia nitrogen and the like is performed. Further, in the anaerobic region of the inner layer of the porous carrier, the nitrified nitrate nitrogen or nitrite nitrogen is contacted with the denitrifying bacteria in the sludge to perform denitrification treatment, About 70% or more is removed. In this example, the BOD load was 0.8 to ³ kg BOD / m ³ · day, and the amount of activated sludge was 5.0.
More than kg / m ³ , daily, average inflow total nitrogen 0.04 kg / k
g (activated sludge) and 0.2 kg or less / m ³ (tank volume),
The aeration intensity is set to 9.0 m ³ / m ³ · Hr, respectively. Further, the porous carrier B has a size of 30 mm × 30 mm × 30
A 0 mm prismatic urethane porous body (air filtration resistance P =
18 mmH20) is used at a filling rate of 30 VOL%, and the flow velocity in the vicinity of the inner peripheral surface of the tank 2 is 30 to
50 cm / sec, the flow velocity in the center of tank 2 is 2
It is about 6 cm / sec.

The mixed liquid of activated sludge and treated sewage from the carrier flow tank 2 is taken out through the screen portion 14 and sent to the settling tank 3 through the advection pipe 11, where the sludge is separated and settled. The treated water Wb from which the sludge has been separated is returned to the disinfection tank 4 through the advection pipe 20 and is disinfected.
Is discharged to the outside of the tank by the discharge pump 15 via the discharge tank 6. The sludge separated in the settling tank 4 is automatically weighed by the sludge returning device 5, and a necessary amount is returned to the adjusting tank 1 or the carrier flowing tank 2 through the sludge returning pipe. The amount of activated sludge in 2 is adjusted to the set value.

[0022]

According to the present invention, the carrier flow aeration tank 2 which is the main part of the sewage treatment apparatus has a columnar shape, a cylindrical shape or a prismatic shape having a length of 300 to 600 mm and a cross sectional diameter or a diagonal length of 30 to 50 mm. 20 to 4 of synthetic resin porous carrier
A carrier flow aeration tank having a structure filled with 0 VOL% is used to slow the aeration flow rate of the porous carrier and increase the anaerobic region of the porous carrier. As a result, unlike the conventional sewage treatment apparatus using this type of carrier flow aeration tank, the phenomenon that the nitrogen removal rate decreases with the passage of operating time does not occur, and under a predetermined amount of continuous aeration operation. However, the total nitrogen removal rate of almost 70% or more can be always maintained, and a high nitrogen removal rate can be stably obtained without trouble.

Further, in the present invention, since the outer dimensions of the synthetic resin porous carrier are made considerably larger than those of the conventional porous carrier, the carrier flow rate in the tank is greatly reduced. As a result, the sludge that adheres and falls off and the wear of the carrier itself is reduced, and the purification process of the sewage can be performed stably, and the life of the carrier can be extended.

Further, even when the porous carrier is filled, the number of the filled carrier itself may be small, and the large size of the carrier makes it easier to put it in the wastewater, and the time required for filling the carrier can be greatly reduced. it can. As described above, the present invention has excellent practical utility.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a wastewater treatment system according to the present invention.

FIG. 2 is a cross-sectional view with a part of the wastewater treatment device according to the present invention omitted.

FIG. 3 is a sectional view taken along line I-I of FIG.

FIG. 4 is a sectional view taken along line II-II of FIG.

5 is a sectional view taken along line III-III in FIG.

FIG. 6 is a processing system diagram of a nitrogen removal method using a carrier flow aeration tank.

[Explanation of symbols]

A is a tank body, B is a porous carrier, 1 is an adjustment tank, 2 is a carrier flow aeration tank, 3 is a precipitation tank, 4 is a disinfection tank, 5 is a sludge returning device, 6 is a discharge tank, and 7 is a sludge concentration storage tank. , 8 is an air diffuser, 9
Is an air diffuser fixing base, 10 is an air feeding valve, 11 is an advection pipe, 1
2 is an air escape pipe, 13 is an advection pipe, 14 is a screen part, 15 is a discharge pump, 16 is a disinfection device, 17 is a partition wall, 18 is an advection wall, 19 is a medicine cylinder, and 20 is an advection pipe.

Claims (4)

[Claims] 1. An air diffuser (8) is provided and has a length of 3 inside.
00-600 mm, cross-section diameter or diagonal length 30-
Carrier flow aeration tank (2) formed by filling 50 mm cylindrical or prismatic porous carrier (B) at a filling rate of 20 to 40 (VOL%), and treated wastewater from the carrier flow aeration tank (2) Settling tank (3) for receiving sludge and separating sludge in sewage
And a sludge returning device for returning a part of the separated sludge to either or both of the carrier flow aeration tank (2) or the carrier flow aeration tank (2) and the adjusting tank (1) provided upstream thereof. A sewage treatment apparatus composed of (5). 2. The sewage treatment apparatus according to claim 1, wherein the porous carrier (B) is an open-cell urethane resin or polyethylene resin porous carrier (B). 3. The sewage treatment according to claim 1, wherein the adjusting tank (1), the carrier flow aeration tank (2) and the precipitation tank (3) are integrally formed in one tank body A. apparatus. 4. The outer diameter of the cylindrical porous carrier (B) is 30.
The sewage treatment apparatus according to claim 1, wherein the sewage treatment apparatus has a diameter of -50 mm and an inner diameter of 15-25 mm.