JP3250042B2 - 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 a fluidized bed type wastewater treatment apparatus for purifying organic wastewater with aerobic microorganisms.

[0002]

2. Description of the Related Art Conventionally, organic wastewater treatment apparatuses include:
BACKGROUND ART A so-called fluidized bed type processing apparatus has been widely used, in which a processing liquid in which microorganism-adhered particles are scattered is circulated and fluidized by aeration to reduce organic substances in the processing liquid. FIG. 6 shows an example of such a wastewater treatment apparatus, and reference numeral 1 in the figure denotes a wastewater treatment apparatus. This wastewater treatment device 1
The processing tank 2, a draft tube 3 erected in the center of the processing tank 2, an overflow part (extraction part) 4 formed on the upper inner wall of the processing tank 2, and an upper part of the processing tank 2. It comprises an installed solid-liquid separation cylinder 5, a diffuser 6, and an introduction pipe (inflow section) 7 for introducing waste liquid to be treated into the treatment tank 2. The processing tank 2 holds the processing liquid A and the microorganism-adhered particles, and is a container having an inverted pyramid bottom. The draft tube 3 is used for efficiently circulating the processing solution A and the microorganism-adhered particles in the processing tank 2, and is a substantially cylindrical body vertically installed at the center of the processing tank 2, and the lower end thereof is used for processing. Some are located above the bottom of the tank 2 and the top is below the water surface. The overflow portion 4 is a portion in which the processing liquid A that has flowed and purified in the processing tank 2 overflows, and is formed on an inner wall near the upper end of the processing tank 2. The solid-liquid separation cylinder 5 is a cylindrical one that keeps the microorganism-adhered particles in the treatment liquid A from moving to the overflow section 4 side by keeping it inside. The air diffuser 6 releases air from the lower center of the processing tank 2 to increase the dissolved oxygen of the processing liquid A. The introduction pipe 7 is provided with the processing solution A
Is introduced into the processing tank 2. Treatment solution A is an organic wastewater, which is a nutrient for aerobic microorganisms C, H, N
Are oxidatively decomposed and reduced. The microorganism-adhered particles are composed of a carrier made of diatomaceous earth or the like and a biofilm around the carrier.

In the wastewater treatment apparatus 1 having such a structure, the treatment liquid A is discharged by the air emitted from the air diffuser 6 in the lower center of the treatment tank 2.
The microorganism-adhered particles rise in the draft tube 3, descend outside the draft tube 3, and circulate in the treatment tank 2.
Then, while the treatment liquid A circulates in the treatment tank 2, the treatment liquid A is mainly purified by the biofilm of the microorganism-attached particles, and the purified treatment liquid A flows over the overflow section 4 and flows out.

In such a wastewater treatment apparatus 1, when the surface area of the carrier in the treatment tank 2 is compared with a certain volume of the treatment tank, for example, the surface area of the contact material used in the wastewater treatment apparatus of the contact aeration method is 20%. It is extremely large, twice or more, and has a large biofilm area per fixed volume. Incidentally, as shown in FIG. 7, when the dissolved oxygen concentration (DO) is 2 ppm or less, diffusion of DO in the biofilm is rate-limiting. Therefore, for high-efficiency purification, it is necessary to reduce the film resistance between the biofilm and the treatment liquid, and to bring the biofilm and the treatment liquid into sufficient contact. In the fluidized-bed wastewater treatment apparatus 1 as described above, oxygen and organic substances come into contact with the surface of the microorganism-attached particles efficiently, and the purification action is performed efficiently. For these reasons, as shown in Table 1, the above wastewater treatment apparatus 1 has a BOD volume load of 3 to 3 times as compared with wastewater treatment apparatuses of other methods (standard activated sludge method, long-time aeration method, contact aeration method). Wastewater can be treated 10 times more efficiently, and the treatment tank can be made smaller.

[Table 1]

In the fluidized-bed type wastewater treatment apparatus 1 as described above, when the load of the wastewater is within a certain range and the operation is performed properly, organisms grow and the thickness of the biofilm increases. Is increased, and the amount of decrease in the thickness of the biofilm due to separation due to the shear force of the water flow is the same, and a film thickness with good purification efficiency can be maintained. Also,
On the other hand, the wastewater treatment apparatus 1 of the other method requires return sludge, whereas the wastewater treatment apparatus 1 described above does not require return sludge, so that bulking of sludge does not occur and attention must be paid to the sedimentation of sludge. Operation is easy.

[0006]

However, the wastewater treatment apparatus 1 having such a configuration has a problem in that the microorganisms are changed due to a change in the amount of wastewater, a variation in the concentration of organic substances, an increase in organic substances having a high sludge conversion rate, and a poor aeration operation. There is a problem that the attached particles are enlarged and flow out. For example, in the treatment of domestic wastewater, the bulk specific gravity of the carrier is set to 2 in consideration of fluidity.
Hereinafter, the carrier particle diameter is 0.4 mm or less, and the BOD volume load is 2K.
At g / m ³ / day, 40 to 50% of microorganism-adhered particles flow out in one year. As the biofilm area decreases due to the outflow of the microorganism-adhered particles, the purification ability decreases. If the carrier is replenished so that the purification ability does not decrease, the running cost increases. Further, in the aerobic treatment, the effective function is 100 to 150 μm from the surface of the biofilm due to the rate of diffusion of oxygen into the biofilm. Therefore, when it enlarges, the part which does not work effectively increases. In addition, as the thickness of the microorganism increases, the sedimentation speed of the microorganism-adhered particles decreases as shown in FIG. 8, and it becomes difficult to separate the microorganism-adhered particles by the solid-liquid separation cylinder 5. By the way, in the wastewater treatment apparatus 1 using such aerobic microorganisms, the suspended sludge from which a part of the biofilm of the microorganism-attached particles has separated is treated in the treatment tank 2.
It is sent to the next sedimentation tank along with the processing liquid A overflowing from the tank, and is extracted from the sedimentation tank as excess sludge. In order to solve the above problem, it is conceivable to collect the microorganism-adhered particles flowing out of the treatment tank 2 from the sedimentation tank.
In such a case, since the microorganism-adhered particles and a large amount of sludge are mixed, an enormous cost is required for the recovery operation, which is not practical. On the other hand, protozoa as well as bacteria play an important role in aerobic microorganisms involved in the purification of organic wastewater. In order to solve the above problem, all the microorganism-adhered particles in the treatment tank 2 are treated at once by a water ejector or the like, and a part of the biofilm of the microorganism-adhered particles is peeled off. Is considered to be reduced from 6000 mg / l to 4000 mg / l as MLVSS. However, in this case, all the protozoa fixed and living on the surface of the biofilm of the microorganism carrier are detached, which is extremely undesirable.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fluidized bed type wastewater treatment apparatus capable of suppressing the growth and outflow of microorganism-adhered particles. It is in.

[0008]

In order to solve the above-mentioned problems, a wastewater treatment apparatus according to the present invention has an inflow portion of wastewater to be treated and a takeout portion of a treatment liquid, in which microorganism-adhered particles are contained. A treatment tank configured to hold the scattered treatment liquid, an air diffuser for aerating the inside of the treatment tank, and a biofilm of the microorganism-attached particles by introducing the microorganism-adhered particles and the treatment liquid in the treatment tank. A biological film thickness determination device that determines the thickness and returns the microorganism-adhered particles and the processing liquid having a biological film thickness less than a certain thickness to the processing tank through the determination particle return unit, and a biological film thickness determined by the biological film thickness determination device. A biofilm peeling device that removes a biofilm of the microorganism-adhered particles by introducing a microorganism-adhered particle and a treatment liquid having a certain thickness or more, Liquid into the processing tank Those formed by and a to recovery means.

[0009]

According to the wastewater treatment apparatus of the present invention, the microorganism-adhered particles in the treatment tank and the treatment liquid are introduced into the biofilm judging device, and the thickness of the biofilm is judged. Then, the microorganism-adhered particles having a biological film thickness of a certain thickness or more are introduced into the biofilm peeling device, subjected to the peeling treatment, and the microorganism-adhered particles subjected to the peeling treatment are returned to the treatment tank. Therefore, loss of the microorganism-adhered particles from within the treatment tank can be suppressed.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The wastewater treatment apparatus of the present invention will be described below in detail with reference to embodiments. FIGS. 1 to 3 show an embodiment of a wastewater treatment apparatus according to the present invention. In this figure, reference numeral 11 denotes a wastewater treatment apparatus. This wastewater treatment device 11
Is a processing tank 12 holding the processing liquid A and the microorganism-adhered particles.
A draft tube 13 erected in the center of the processing tank 12, an overflow section (extraction section) 14 formed on an upper inner wall of the processing tank 12, and a solid-liquid installed at an upper part of the processing tank 12. A separation cylinder 15, an aeration device 16, an introduction pipe (inflow portion) 17 for introducing waste liquid to be treated into the treatment tank 12, and a biological film thickness determination device 18 ((recovery means)). ), A biofilm stripping device 19 (hereinafter, abbreviated as a stripping device), and a water storage container 20a, a water pipe 20b, a water pipe 20c, and a pump 20d which constitute the recovery means 20.

The wastewater treatment apparatus 11 includes a treatment tank 12, a draft tube 13, an overflow section 14, a solid-liquid separation cylinder 15,
The air diffuser 16 and the introduction pipe 17 are the same as those of the conventional wastewater treatment apparatus 1. Further, similarly to the conventional example, the treatment liquid A is one in which C, H, N, etc., which are nutrients for aerobic microorganisms, are oxidized and decomposed and reduced. , And a biofilm around the carrier.

The judging device 18 is installed above the processing tank 12, and as shown in FIG.
, A liquid collecting unit 22, a determination particle returning unit 23, and an introducing unit 24.
And a re-introduction section 25 and a perforated plate 26. The determination device 18 uses a pump 24b as a power source, and a processing tank 12 through a water supply pipe 24a including an introduction portion 24.
A part of the processing solution is introduced therein. The determination device main body 21 collects only the microorganism-attached particles B having a high sedimentation speed at the lower portion, and includes an upper body portion 21a and a lower particle collecting portion 21b. Body part 21a
Is a cylindrical shape, is filled with the microorganism-attached particles B ... and the treatment liquid A, has a rising water flow, and drops only the microorganism-adhered particles having a high sedimentation speed. The particle collecting portion 21b collects microorganism-adhered particles having a high sedimentation speed at a lower portion thereof, and has a funnel shape. The liquid collecting part 22 collects the microorganism-attached particles B flowing over from the judging device main body 21 and the processing liquid A and sends out the processing liquid A to the peeling device 19 as shown in FIGS. The body has a feed portion 22a formed downward from the lower end of the inclined bottom. The determination particle return portion 23 is located above the processing tank 12 so as to face the solid-liquid separation cylinder 15, and as shown in FIG. 2, a valve 23 a and a valve 23 a attached to a lower end portion of the determination device main body 21. And a particle return pipe 23b attached below the bottom of the container. The valve 23a is opened when returning the microorganism-adhered particles B collected in the lower part of the particle collecting section 21b to the processing tank 12. The introduction unit 24 introduces the microorganism-attached particles B ... pumped from the treatment tank 12 by the pump 24b and the treatment liquid A into the determination device main body 21. ... and the processing liquid A is emitted in a substantially horizontal radial direction. The re-introduction section 25 is a part of a water pipe 20c for introducing the microorganism-attached particles B and the treatment liquid A treated by the peeling apparatus 19 into the determination apparatus main body 21, and the end thereof is located above the particle collection section 21b. It is provided with a large number of holes for releasing the microorganism-attached particles B and the treatment liquid A toward the upper body 21a. The perforated plate 26 prevents the drift in the body 21 a due to the introduction of the microorganism-attached particles B and the treatment liquid A that have been treated by the peeling device 19. It is attached above.

Next, the wastewater treatment apparatus 1 having the above configuration
1 will be described. A part of the processing liquid in the processing tank 12 is pumped up by the pump 24b, and is introduced into the determination device main body 21 of the determination device 18 from the introduction portion 24 of the water pipe 24a. In the determination device 18, a rising water flow is generated in the body 21 a by the processing liquid A introduced by the introduction unit 24 and a reintroduction unit 25 described below. Then, the microorganism-attached particles B having a low sedimentation speed move to the liquid collecting portion 22 together with the processing liquid A flowing from the upper end of the body portion 21a, and the microorganism-attached particles B having a fast sedimentation speed are moved to the lower portion of the particle collecting portion 21b. Gather in Then, the microbe-attached particles B in the particle collecting part 21b ...
Is returned to the processing tank 12 by the determination particle return unit 23. In addition, as can be seen from FIG. 8, the microorganism-adhered particles have a greater water resistance as the biofilm is thicker, and the specific gravity of the biofilm is smaller than the specific gravity of the carrier. The speed becomes slow. Therefore, judging the sedimentation velocity means judging the biological film thickness.

On the other hand, the microorganism-adhered particles B and the treatment liquid A in the liquid collecting section 22 of the judging device 18 are introduced into a peeling device 19, in which the biofilm of the microorganism-adhered particles B is peeled. In this case, as the peeling device 19, a water ejector in which the internal pressure is reduced by driving water to mix the internal chamber, a stirrer in which the stirring blade rotates at a high speed, and the like are used.

The microorganism-adhered particles B and the treatment liquid A, which have been treated by the detaching device 19 and from which the biofilm has been detached, are supplied to the water pipe 20b.
Through the water storage container 20a. Water storage container 20a
And the treatment liquid A are pumped up by a pump 20d and introduced into the judging device 18 through the re-introduction section 25 of the water pipe 20c, where the microorganism adhering particles B ... Redetermination is performed.

According to the wastewater treatment apparatus 11 as described above,
A judging device 18 for introducing the microbe-attached particles B ... in the treatment tank 12 to determine the biological film thickness of the microbe-adhered particles B by introducing the treatment liquid A; A first collecting means 20 for introducing the microorganism-attached particles B treated by the stripping device 19 back into the judging device 18, and a microorganism-adhered particle B having a biofilm of a certain thickness or less.
Is provided with a particle return portion 23 for returning only the microorganisms B into the processing tank 12, so that the microorganism-attached particles B having a low sedimentation speed are introduced from the determination device 18 into the separation device 19, subjected to the separation processing, and returned to the processing tank 12. As a result, it does not flow out of the processing tank 12. For this reason, there is no reduction in the processing capacity due to the decrease in the biofilm area in the processing tank 12, and the running cost is reduced because there is no need to replenish the carrier. In addition, since only the microorganism-attached particles B having a low sedimentation speed are introduced into the peeling device 19, the peeling treatment is rational and economical, and the microorganism system in the treatment tank 12 can be maintained. Also,
Since the outflow of the microorganism-attached particles B can be suppressed and the biofilm can be controlled to a certain thickness or less, the amount of microorganisms in the treatment tank 12 can be effectively controlled.
In addition, since the thickness of the biofilm, which is one of the two factors of the dispersion of the sedimentation speed of the microorganism-adhered particles B, can be reduced to a certain thickness or less, the allowable range of the dispersion of the particle size of the carrier, which is another factor, is expanded. In addition, carrier procurement costs are reduced. In addition, the microbe-adhered particles B are small particles in which the biofilm is not dense and the purification action is small, and the biofilm has a high purification action attached to the carrier. sell. Further, the microorganism B is re-introduced from the stripping device 19 to the determination device 18 and the biofilm is attached to the microorganism-adhered particles B having a certain thickness or less.
.. Are returned to the processing tank 2, the determination becomes strict, and the operation becomes easy because the microorganism-attached particles B are collected in one place. Further, since the determination particle return unit 23 of the determination device 18 is disposed above the processing tank 12,
The microorganism-adhered particles B can be introduced into the treatment tank by gravity, and the microorganism-adhered particles B do not stay in the piping or the pump. Further, when the determination of the microorganism-adhered particles and the peeling operation are performed simultaneously to perform continuous operation, the operation labor is greatly reduced, and the driving operation is easy.

FIGS. 4 and 5 are diagrams showing another example of the determination apparatus of the wastewater treatment apparatus according to the present invention. In FIG. 4, reference numeral 30 denotes a determination device. The determination device 30 includes a determination device main body 31, a liquid collecting unit 32, a determination particle return unit 33, an introduction unit 34, a reintroduction unit 35, a perforated plate 36, and side cut tubes 37, 37. The difference from the determination device 18 is that side cut tubes 37, 37 are attached.

The side cut pipes 37, 37 extract the microorganism-attached particles B... And the processing solution A in the judging device main body 31 and send them to the processing tank 12, so that the flow velocity in the body 31a is made lower as going upward. , Each end is a body part 31
A valve is arranged at a substantially central portion of a at a distance in the vertical direction, and a valve for adjusting a withdrawal amount is attached. The number of the side cut pipes 37 is not limited to two, and a valve provided with a sensor that senses the flow velocity in the body 31a by a sensor and automatically adjusts the extraction amount by the side cut pipes. It may be.

In the determination device 30 having such a configuration, only the microorganism-attached particles B having a low flow velocity in the body 31a and having a low sedimentation velocity are collected together with the processing liquid A flowing over the upper end of the body 31a. The microorganism-attached particles B having a high sedimentation speed move to the portion 32 and collect at the lower portion of the particle collecting portion 31b.

The judging device 40 shown in FIG.
, A liquid collecting section 42, a determination particle returning section 43, and an introducing section 44.
It consists of: The judging device main body 41 is filled with the microorganism-attached particles B and the treatment liquid A therein, and collects the microorganism-attached particles B having a high sedimentation speed at a lower portion thereof.
It is a substantially conical shape that is formed thicker from the lower end to the upper end. The liquid collecting part 42 has the same structure as the liquid collecting part 22 of the judging device 18, and collects the microorganism-attached particles B flowing from the judging device main body 41 and the treatment liquid A and sends them to the peeling device 19. . The determination particle return unit 43 has the same structure as the determination particle return unit 23 of the determination device 18, and includes a valve 43 a attached to the lower end of the determination device main body 41 and a particle return tube 43 b attached below the valve 43 a. It consists of The introduction unit 44 introduces the microorganism-attached particles B and the processing liquid A pumped from the processing tank 2 by the pump into the determination device main body 41, and has an end portion thereof.
1 and has a structure in which the shape of the end is such that the microorganism-attached particles B and the treatment liquid A are emitted in a substantially horizontal radial direction.

In the judging device 40 having such a configuration, the upward water flow in the judging device main body 41 is slower as going upward. Therefore, only the microorganism-attached particles B having a low sedimentation speed move to the collecting section 42 together with the processing liquid A flowing from the upper end of the determination device main body 41, and the microorganism-adhered particles B having a fast sedimentation speed are removed from the determination device main body. 41 gather at the bottom.

[0022]

According to the wastewater treatment apparatus of the first aspect of the present invention, the biological film thickness of the microorganism-adhered particles is determined by introducing the microorganism-adhered particles and the treatment liquid in the treatment tank, and the biological film thickness is kept constant. A biological film thickness judging device for returning the microorganism-adhered particles having a thickness smaller than the thickness to the treatment tank; A biofilm stripping device for stripping the biofilm of particles, and a collecting means for returning the microorganism-adhered particles and the treatment liquid treated by the biofilm stripping device to the treatment tank; By being introduced into the stripping device, being stripped, and returned to the processing tank, it is possible to suppress the outflow from the processing tank. As a result, there is no decrease in the processing capacity due to a decrease in the biofilm area, and there is no need to replenish the carrier, so that the running cost is reduced. Further, the outflow of the microorganism-adhered particles can be suppressed, and the thickness of the biofilm can be controlled, so that the amount of microorganisms in the treatment tank can be effectively controlled. In addition, since the thickness of the biofilm can be reduced to a certain thickness or less, the allowable range of the variation in the particle size of the carrier, which is another factor of the outflow of the microorganism-adhered particles, is widened, and the cost of procuring the carrier is reduced. In addition, the microorganism-adhered particles after the stripping treatment are returned to the treatment tank in which a biological system favorable for the purification action of the wastewater is maintained, whereby a favorable microorganism system can be recovered. Therefore, the microorganism system in the processing tank can be maintained. In addition, it is possible to make small particles in which only a biofilm having a high purification action adheres to the carrier, and the device can have a high biofilm area per volume.

[0023] Further , since the biofilm is introduced again into the judging device from the peeling device and only the microorganism-adhered particles having a biofilm of a certain thickness or less are returned to the treatment tank, the judgment becomes strict and the microorganism-adhered particles are collected at one place. This facilitates operation.

In the wastewater treatment apparatus according to the second aspect of the present invention, since the determination particle return portion of the determination device is disposed above the treatment tank, the microorganism-adhered particles are introduced into the treatment tank by gravity. It is easy to return the microorganism-adhered particles collected in the lower part of the determination device to the treatment tank.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a first embodiment of a wastewater treatment apparatus of the present invention.

FIG. 2 is an explanatory diagram of a determination device of the wastewater treatment device shown in FIG.

FIG. 3 is a plan view of the determination device shown in FIG.

FIG. 4 is a schematic diagram showing a second embodiment of the determination device.

FIG. 5 is a schematic diagram showing a third embodiment of the determination device.

FIG. 6 is a schematic diagram showing an example of a conventional wastewater treatment device.

FIG. 7 is a diagram showing a purification speed by a biofilm.

FIG. 8 is a graph showing the sedimentation speed of microorganism-adhered particles.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Wastewater apparatus 12 Treatment tank 13 Draft tube 14 Overflow part (extraction part) 16 Air diffuser 17 Inlet pipe (inflow part) 18 Biofilm thickness determination device (second recovery means) 23 Determination particle return part 19 Biofilm peeling Apparatus 20 First recovery means A Treatment liquid B Microorganism-adhered particles

Claims (2)

(57) [Claims] 1. A wastewater treatment apparatus for purifying organic wastewater with microorganisms, comprising a wastewater inflow part to be treated and a treatment liquid takeout part, in which microorganism-adhered particles are scattered. A treatment tank configured to hold the treated liquid, a diffuser for aerating the inside of the treatment tank, and introducing the microorganism-adhered particles and the treatment liquid in the treatment tank to determine the biological film thickness of the microorganism-adhered particles. A biological film thickness determining device for returning the microorganism-adhered particles and the treatment liquid having a biological film thickness less than a certain thickness to the treatment tank through a determination particle returning unit; and a biological film thickness determined by the biological film thickness determining device is a certain thickness. A biofilm peeling device for removing the biofilm of the microorganism-adhered particles by introducing the above-mentioned microorganism-adhered particles and a treatment liquid, and In processing tank Ri Na and and a to collecting means, said collecting means, microorganisms treated with the biofilm peeling device
The particles attached to the substance and the treatment liquid to the biological film thickness determination device
First collection means and sent by this first collection means
The microbe-adhered particles and the processing solution are judged again and the biofilm thickness is reduced.
The treatment tank is adapted to remove the microorganism-adhered particles and the treatment liquid having a thickness smaller than a certain thickness.
A second recovery means comprising the biological film thickness determination device
A wastewater treatment device comprising: 2. The wastewater treatment apparatus according to claim 1 ,
The wastewater treatment apparatus according to claim 1, wherein the determination particle return unit is disposed above the treatment tank.