JPH0741252B2 - Wastewater treatment method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a wastewater treatment method for purifying wastewater by using a microbial carrier, and in particular, it has excellent filtration efficiency of wastewater and continuously for a long period of time. The present invention relates to an inexpensive wastewater treatment method capable of treating wastewater.

“Prior art and its problems” Conventionally, as a wastewater treatment method, for example, there is a method of passing wastewater through a filtration layer and filtering. The filter layer used in this method is composed of a filter material (hereinafter referred to as a microbial carrier) having a surface on which a microbial membrane that decomposes contaminants such as suspended solids (SS content) in wastewater is attached. There is. As such a wastewater treatment method, a method using a microbial carrier having a specific gravity of 1 or less and a method using a microbial carrier having a specific gravity of more than 1 are known.

In the former method, first, a microbial carrier having a specific gravity of 1 or less is stored in a treatment tank, and then the upper part of the microbial carrier that floats by buoyancy is pressed downward by a screen such as a wire mesh to form a densely packed filtration layer. Then, waste water is supplied from the upper part of this filter layer through a screen to remove contaminants such as suspended solids (SS content) in the waste water, and treated water is obtained from below the filter layer. However, in this method, since the wastewater is supplied to the filtration layer through the screen, contaminants in the wastewater are easily trapped by the screen and the screen is easily clogged, resulting in poor filtration efficiency for the wastewater and wastewater. There were problems such as continuous processing being difficult.

Further, in the latter method, first, a microorganism carrier having a specific gravity of more than 1 is densely packed in a treatment tank to form a filter layer at the bottom of the treatment tank. It removes pollutants such as SS and obtains treated water from below the filtration layer. In this method, since it is necessary to form the filtration layer as a fixed layer on the inner bottom of the treatment tank, a microorganism carrier having a specific gravity much larger than 1 and an outer dimension of mainly 1 mm or less and having a uniform grain size. Is preferably used. However, in this method, since the microbial carrier is heavy and small in diameter, the gap between the microbial carriers in the filtration layer becomes narrower due to its own weight, etc., and in the upper layer of the filtration layer, which is the starting end of the filtration channel. There is a problem that clogging easily occurs, pressure loss increases, the filtration speed of the wastewater decreases, and the filtration efficiency decreases, such as a longer processing time.

Therefore, in such a method, in order to eliminate clogging of the filtration layer, water or air is sent into the filtration layer to remove contaminants trapped on the surface of the microorganism carrier or in the spaces between the microorganism carriers to remove the microorganism carrier. It was necessary to frequently carry out a backwash operation for regenerating.

However, if the backwashing operation is frequently performed on the microbial carrier as described above, the microbial film adhering to the surface of the carrier will be peeled off together with the pollutants, and therefore, adsorption by the microbial film carried on the surface of the microbial carrier will occur. There was a problem of losing all filtering functions. Further, in this backwashing operation, since the specific gravity of the microbial carrier is large, in order to flow backwash the microbial carrier into the treatment tank by the water flow and the air flow, a large amount of energy is required and the operating cost is increased. There was also a problem. Furthermore, the wash water for washing must be stored in advance, so various facilities such as a water tank for wash water and a water pump for supplying water into the treatment tank are required, which also leads to construction costs and operating costs. There was a problem of rising prices.

"Object" The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an excellent wastewater filtration efficiency and an inexpensive wastewater treatment that can continuously perform wastewater treatment over a long period of time. To provide a wastewater treatment method.

"Means for Solving Problems" A feature of the first invention of the present invention is that a specific gravity is provided in a processing tank having a bottomed cylindrical outer cylinder and a cylindrical inner cylinder erected in the outer cylinder. A filtration layer composed of a microbial carrier having a particle size distribution of less than 1 and having a particle size in the range of 0.5 to 8.0 mm is formed such that the upper part of the filter layer is exposed from the water level and the lower part is separated from the bottom of the treatment tank and the whole is dense. Then, the waste water is directly supplied into the filtration layer inside the inner cylinder.

Further, the second aspect of the present invention is characterized in that, after carrying out the first aspect, only the air is supplied from the bottom of the treatment layer to circulate and wash the microbial carrier forming the filtration layer. Especially.

Furthermore, the feature of the third invention of the present invention is that a microbial carrier having a particle size distribution with a specific gravity of 1.05 to 1.6 and a particle size of 0.5 to 8.0 mm is provided below the filtration layer used in the first invention. To form a sedimentary layer and to use this sedimentary layer together with the filtration layer for wastewater treatment.

Furthermore, the feature of the fourth invention of the present invention is that after carrying out the third invention, only the air is supplied from the bottom of the treatment tank to circulate and wash the microbial carrier that forms the filtration layer and the deposition layer. I have tried to do it.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an example of a processing tank suitably used for carrying out the first and second inventions of the present invention, and reference numeral 1 in the drawing is a processing tank. The processing tank 1 is generally composed of an outer cylinder 2 and an inner cylinder 3 which is erected coaxially inside the outer cylinder 2.

The outer cylinder 2 is a processing tank having a bottomed cylindrical shape, and an air diffuser 4 for backwashing is arranged below the inner cylinder 3 at the bottom of the outer cylinder 2, and further this air diffuser 4 Similar diffusers 5 and 6 are provided on the outer sides of, respectively. And these air diffusers 4-6 are connected to the blower 7 for backwash, and the blower 7 blows air etc. at a predetermined flow rate in the processing tank 1 through these air diffusers 4-6. It is designed to supply gas. Further, on the upper side wall of the outer cylinder 2, the processing tank 1
A discharge pipe 9 having a solenoid valve 8 for discharging the treated water treated in 1. and adjusting the discharge amount of the treated water is attached, and the discharge port 9a of the discharge pipe 9 is provided with the treated water and the microorganism carrier. A separating screen 9b is provided. Furthermore, a discharge pipe 11 having a solenoid valve 10 and a discharge pipe 13 having a solenoid valve 12 are provided at the bottom of the outer cylinder 2. The discharge pipe 11 is fried to the same height as the upper end portion of the inner cylinder 3 so that potential energy can be secured when the treated water is sent to the next process.

Inside such an outer cylinder 2, a cylindrical inner cylinder 3 coaxial with the outer cylinder 2 is provided. The upper end of the inner cylinder 3 is located above the discharge port 9a of the outer cylinder 2, and the lower end of the inner cylinder 3 extends near the upper portions of the air diffusers 4 to 6 of the outer cylinder 2,
The waste water flowing down in the inner cylinder 3 is bent obliquely outward in the radial direction of the inner cylinder 3 so that the flow direction of the waste water can be easily reversed at the bottom of the outer cylinder 2. Inside the upper part of the inner cylinder 3, a waste water supply pipe 14 for supplying waste water into the treatment tank 1 is suspended. The lower end portion 14a of the waste water supply pipe 14 extends from the upper end portion of the inner cylinder 3 to a position below the discharge port 9a of the outer cylinder 2, and connects the lower end portion 14a of the waste water supply pipe 14 and the upper end of the inner cylinder 3 to each other. The distance is about 20% of the length of the inner cylinder 3 in the up-down direction, but is not limited to this. Furthermore, inside the upper part of the inner cylinder 3, the processing tank 1
A water level gauge 15 is provided for measuring the water level inside.
The water level gauge 15 is interlocked with the solenoid valves 8, 10 and 12 and is opened / closed as appropriate according to the water level measured by the water level gauge 15.

Next, an example of a wastewater treatment method using the treatment tank 1 having such a configuration will be described. First, as described above, this wastewater treatment method captures SS components in the wastewater, colloidal substances, and partially pollutants such as partially soluble organic substances, BOD due to SS components, and partially soluble BOD. A microbial carrier that decomposes is used. This microbial carrier is, for example, a particulate filter material that carries microorganisms as a microbial membrane, and its specific gravity is 1 or less, preferably in the range of about 0.5 to 0.95.
The microbial carrier has a particle size distribution of about 0.5 to 8.0 mm, preferably about 1.5 to 5.0 mm. And, the carrier of the microbial carrier used here has excellent adhesion to the microbial membrane,
The shape of the carrier is not limited to spherical particles, and may be, for example, a long shape such as a cylinder, a prism, a cylinder, or a cylinder, or an irregular shape such as a star or an ellipse.

Then, such a microbial carrier is filled in a predetermined amount in the outer cylinder 2 and the inner cylinder 3 in the treatment tank 1 shown in FIG.
Becomes Since the filtration layer 16 is composed of a microbial carrier having a specific gravity of 1 or less, its upper part is partially exposed from the water surface of the water stored in the treatment tank 1 before operation and its lower part is an outer cylinder due to buoyancy. It is formed so as to be spaced apart from the bottom portion of 2 and be dense as a whole. The thickness of the filtration layer 16 is in the range of about 60 to 90% of the depth of the outer cylinder 2. If it is less than 60%, the filtration layer 16 is too small compared to the size of the outer cylinder 2, making the facilities such as the outer cylinder 2 uneconomical, and the amount of microorganisms retained by the filtration layer 16 is small, and therefore the wastewater treatment It causes inconvenience such as low ability. If it exceeds 90%, although there is no problem in removing pollutants in the wastewater, the filtration layer 16 is too large to sufficiently fluidize the microbial carrier during the backwashing operation on the filtration layer 16, and therefore the microbial carrier The contaminants trapped on the surface or in the gaps between the microbial carriers cannot be removed, which causes a problem that the adsorptive filtration function of the microbial carrier by the microbial membrane is deteriorated. In addition, this filter layer 16 is
Since the microbial carrier forming 16 has a particle size distribution,
The filtration layer 16 is filled so that the particle size becomes smaller from the upper layer to the lower layer due to the difference in the floating speed due to the difference in the particle size distribution during the accommodation in the treatment layer 1 or the backwashing described later. Furthermore, in the filtration layer 16, since the microorganism carrier is densely packed, it does not flow or float due to the waste water supplied into the treatment layer 1 during the treatment of the waste water, and the microorganism carrier does not move. Becomes

Waste water is supplied through the waste water supply pipe 14 into the treatment tank 1 in which the filter layer 16 is formed. This wastewater is
As shown by the solid line arrow in FIG. 1, first, from the lower end portion 14a of the wastewater supply pipe 14 hanging down to the inside of the filtration layer 16 to the filtration layer 16
The flow is reversed at the bottom of the outer cylinder 2, and the filtration layer 16 between the inner and outer cylinders 3 and 2 is raised. The wastewater that has risen in the filtration layer 16 between the inner and outer cylinders 3 and 2 is purified by trapping contaminants such as SS by the adsorption filtration function on the surface of the microbial carrier forming the filtration layer 16 or between the microbial carriers. The treated water becomes treated water, which is then sent to the next process or the like through the discharge pipe 9 through the screen 9b by opening the solenoid valve 8. Here, as shown in FIG. 1, the water level of the treatment tank 1 during treatment is set to the same water level A as the height of the discharge port 9a of the discharge pipe 9. The amount of waste water supplied to the treatment tank 1 is determined in consideration of the treatment capacity of the filtration layer 16 and the like, and the amount of supply per hour is usually within about 6 times the capacity of the filtration layer 16. When this supply amount exceeds 6 times the capacity of the filtration layer 16, the supply amount becomes so large that the filtration treatment of the wastewater becomes insufficient and a part of the filtration layer 16 collapses. Then, the supply of the waste water to the treatment tank 1 is appropriately continuously or intermittently performed depending on the concentration of pollutants in the waste water, the treatment capacity of the treatment tank 1, and the like.

When the microbial treatment of the wastewater is continuously performed in the treatment tank 1 in this manner, the filter layer 16 in the inner cylinder 3 below the lower end portion 14a of the wastewater supply pipe 14 is gradually clogged and the pressure loss of this portion is lost. And the flow of wastewater is restricted. Even in this case, it is possible to continue the supply of the waste water, and in this case, the waste water is allowed to flow over the upper end portion of the inner cylinder 3 at the water level B as shown by the broken line arrow in FIG. Further, it rises above the water level B and is made to flow down between the inner and outer cylinders 3 and 2 through the portion exposed from the water surface above the filtration layer 16. Here, the portion of the filter layer 16 exposed from the water surface above the inner cylinder 3 is pushed upward by buoyancy and the like as the water level of the wastewater rises, so the gap between the microbial carriers in this portion is appropriate. The capacity for capturing pollutants in wastewater in this part has been increased.

Then, when the filtering operation for the waste water is continued, the filtration tank 16 between the inner and outer cylinders 3 and 2 is gradually clogged, and the water level of the waste water rises above the water level B. At this time, in the exposed filtration layer 16, the three forces of adhesive force between the microbial membrane of the microbial carrier and the contaminants captured by the microbial membrane, buoyancy, and gravity applied to the particles are in an equilibrium state, It is subjected to a filtration treatment while being floated.

The rise of the water level due to the clogging of the filter layer 16 and the overflow of water from the upper end of the inner cylinder 3 are monitored by the water level gauge 15, and an electric signal from the water level gauge 15 is accompanied by the change of the water level. Solenoid valve 8 is closed by solenoid valve 10
Is released. At this time, the treated water is discharged from the discharge pipe 11 in which the solenoid valve 10 is opened.

Then, in the above-mentioned wastewater filtration channel, the period during which the wastewater flows through the channel indicated by the broken line arrow in FIG. 1 is about 2 to 3 times longer than the period during which it flows through the channel indicated by the solid line arrow. That is,
The flow path indicated by the broken line arrow has a particle size of a microbial carrier forming the filter layer 16 from the part exposed from the water surface above the inner cylinder 3 toward the filter layer 16 between the inner and outer cylinders 3, 2. Since it is filled so as to become gradually smaller, when, for example, wastewater with variations in the size of pollutants is flowed through this flow path, among the pollutants in the wastewater, the smallest one is the gap between the microbial carriers. It passes through a large upper layer and is captured by a lower layer having a small gap, and a large one is captured by an upper layer. Further, even when a wastewater having a uniform size of the pollutant is flowed, the pollutant in the wastewater is efficiently transferred to the entire filtration layer 16 without causing pressure loss due to extreme clogging at the beginning of the filtration layer. Filtered. Furthermore, the same can be said in common when any wastewater is targeted.However, the gap between the microbial carriers is larger toward the top, and pollutants are not captured at the beginning of the filtration layer, and vice versa. Due to the adsorbing power of the microbial membrane and the trapping power of the filtered pollutant itself, the pollutant that physically passes is also trapped at the upper part to some extent (so-called filter cake filtration) in terms of particle size. ing. In this way, in the wastewater treatment in this flow path, since the filtration layer 16 is welted by the microbial carrier having a particle size distribution, the backwashing operation described below gradually increases the particle size from large particles to small particles. Since it is stratified to have a diameter, it is less likely to be clogged at the beginning of the dotted flow path, and in addition to that, the beginning of filtration, that is, the filtration layer
Of the 16 parts, the part exposed from the water surface is less likely to be clogged, and pressure loss at this part is less likely to occur, so that continuous operation can be performed over a long period of time.

On the other hand, the flow path indicated by the solid arrow is a portion where the gap of the upper layer microbial carrier is larger than that of the lower layer, that is, the portion having excellent filterability is only the filtration layer 16 below the lower end portion 14a of the wastewater supply pipe 14. Since it is short, the wastewater treatment period is shorter than that of the flow path indicated by the dashed arrow.

Then, when the filtering operation is further continued, the entire filter layer 16 gradually becomes clogged. In this case, a backwashing (washing) operation is performed in order to remove contaminants such as SS components trapped on the surface of the microbial carrier forming the filtration layer 16 or in the spaces between the microbial carriers. In this backwash operation, first,
The water in the treatment tank 1 is added so that the water level in the treatment tank 1 is above the water level B, and then the inside of the treatment tank 1 is blown by the blower 7 through the air diffusers 5 and 6 provided at the bottom of the outer cylinder 2. A gas such as air is supplied to the inner and outer cylinders 3, 2 by this gas for a predetermined time.
The filter layer 16 in between is collapsed. Subsequently, the gas is supplied from the blower 7 through the air diffuser 4 only for a predetermined time to collapse the filter layer 16 in the inner cylinder 3 and circulate and fluidize it. Next, the electromagnetic valve 12 of the discharge pipe 13 at the bottom of the outer cylinder 2 is opened to discharge the cleaning water in the processing tank 1 and the pollutants such as SS suspended in the cleaning water to the outside. Next, washing water is supplied from the upper part into the treatment tank 1 until the water level A is reached, and the backwashing operation is repeated again using the above-mentioned air diffusers 4 to 6. This backwashing operation is slightly different depending on the concentration of pollutants such as SS in wastewater and the concentration of microorganisms carried by the microbial carrier, but for example, if the pollutant concentration is about the secondary treatment of general domestic wastewater, Sufficient effect can be obtained about twice including the first time. Also, in this backwash operation,
The treatment water in the treatment tank 1 may be discharged from the bottom of the treatment tank 1, while the cleaning water may be supplied into the treatment tank 1 from the upper portion of the treatment tank 1. In this case, the effect that the treated water in the treatment tank 1 can be efficiently pushed out by the wash water is obtained.

According to the first aspect of the invention, the following excellent effects of the embodiment can be obtained.

[1] The particle size of the microbial carrier forming the filtration layer 16 is 0.5 to 8.0.
By setting the distribution range of about mm, preferably about 1.5 to 5.0 mm, during cleaning, due to the difference in the floating speed due to the difference in the particle size distribution, the filtration layer 16 has a large microbial carrier in the upper part and a particle size in the lower part. Since the microbial carriers having a small size are distributed respectively, the upper layer of the filtration layer 16 has a larger gap between the microbial carriers than the lower layer. This distribution effect is further promoted by using a material having a smaller specific gravity as the particle size becomes larger. Therefore, in such a filter layer 16, when treating wastewater having variations in the size of pollutants, small pollutants such as SS components pass through the upper layer of the filter layer 16 and are captured in the lower layer, Even when treating a wastewater in which large ones are trapped in the upper layer and the size of the pollutants is uniform, the pollutants are efficiently trapped in the entire filtration layer 16, so pressure loss at the beginning of filtration is less likely to occur. The occurrence of clogging is small, and wastewater treatment can be continuously performed over a long period of time.

[2] From a microbial carrier having physical properties that can form the filtration layer 16 in the treatment tank 1 in a state where the upper portion is partially exposed from the water surface and the lower portion is separated from the bottom portion of the treatment tank 1 and the whole is densely packed. Since the microbial carrier can be fixed in the treatment tank 1 without being fluidized by the supply of waste water, the microbial carrier can be easily fluidized with a small amount of energy during backwashing.

[3] By setting the supply position of the waste water in the treatment tank 1 inside the filtration layer 16 inside the inner cylinder 3, the filtration layer 16 inside the inner cylinder 3 flows down and is inverted at the bottom of the outer cylinder 2, A flow path (indicated by a solid arrow in FIG. 1) rising between 3 and 2, and a filtration layer in the inner cylinder 3.
After the clog 16 is clogged, the filter layer 16 in the inner cylinder 3 is raised from the waste water supply position, and flows down between the inner and outer cylinders 3 and 2 through a part of the filter layer 16 that is partially exposed from the water surface. 2) (shown by the broken line arrow in FIG. 1). Of the filtration layer 16 of such a flow path, the part that is partially exposed from the water surface in particular is pushed upward by buoyancy and the like as the water level of the wastewater rises, so that the gap between the microbial carriers can be appropriately expanded. The capability of capturing pollutants in the lever area is increased. Therefore, by using such two filtration channels, it is possible to continuously perform wastewater treatment for a long period of time, and therefore it is possible to prolong the interval between backwashing operations, and thus backwashing. It is possible to suppress the peeling of the microbial membrane from the surface of the microbial carrier caused by the operation, and to keep the adsorption filtration function of the microbial carrier by the microbial membrane. In addition, since the number of backwash operations is reduced, it is possible to significantly reduce power energy such as blower consumed in the backwash operation and return water, and circulate the microbial carrier in the conventional backwash operation. It is possible to eliminate the need for the water (treated water) used for the conversion.

According to the second invention, the filtration layer 16 has a particle size of 0.5 to 8.0.
mm, preferably composed of a microbial carrier having a distribution range of about 1.5 to 5.0 mm, to lighten the filtration layer itself,
In the backwash operation, only the air from the bottom of the treatment tank can be used to easily collapse the filter bed with a small amount of energy, and it can be circulated and fluidized for cleaning, and the operating cost associated with the circulatory fluidization is low. Can be suppressed.

FIG. 2 shows an example of a processing tank which is preferably used for carrying out the third and fourth inventions of the present invention.
In the third invention, the specific gravity is 1 or less and the particle size is 0.5 to 8.0.
Filtration layer consisting of microbial carrier with particle size distribution in mm range
In addition to 16, below the filtration layer 16 in a specific gravity range of 1.05 to 1.6, preferably in a specific gravity range of 1.05 to 1.3 and a particle size of 0.5 to 8.
It is characterized in that a sediment layer 17 made of a microbial carrier having a particle size distribution in the range of 0 mm, preferably in the range of 1.5 to 5.0 mm is formed, and the waste water is directly supplied into the filtration tank 16 in the inner cylinder. Therefore, in the vicinity of the bottom of the outer cylinder 2 of the processing tank 1 and the air diffuser 4
On the lower side of ~ 6, the specific gravity is in the range of 1.05 to 1.6, preferably in the range of 1.05 to 1.3 and the particle size is in the range of 0.5 to 8.0 mm,
Preferably, a microbial carrier having a particle size distribution in the range of 1.5 to 5.0 mm is settled and deposited on the screen 18 to form a deposition layer 17.

According to such a third invention, the deposition layer is formed on the bottom of the outer cylinder 2.
Since 17 is provided, the wastewater flowing down in the filtration layer 16 in the inner cylinder 3 passes through the sedimentary layer 17 formed at the bottom of the outer cylinder 2, and again, the pollutants such as SS components in the wastewater are also present. Since it is filtered, pollutants can be removed from the wastewater with high efficiency, and further, an excellent effect such as a long filtration duration can be obtained.

In addition, in the fourth invention, after carrying out the third invention, air is supplied into the processing tank 1 by the blower 7 via the air diffusers 4 to 6 provided at the bottom of the processing tank 1. By doing so, the microbial carrier forming the filtration tank 16 and the deposition tank 17 is circulated and fluidized to wash the microbial carrier.

And according to this 4th invention, the specific gravity of the microorganisms carrier which forms the sedimentary layer 17 is 1.05 to 1.6, Preferably it is 1.0.
Since the range of 5 to 1.3 is set, the sedimentary layer 17 can be made relatively light like the filtration layer 16, so that the microorganism carriers of the filtration layer 16 and the sedimentary layer 17 can be easily circulated with a small amount of energy during the backwash operation. Can be fluidized,
The operating cost associated with the circulation and fluidization can be kept low.

Hereinafter, the working effects of the present invention will be clarified by showing examples.

(Embodiment 1) An inner cylinder is erected inside as shown in FIG. 1, the effective water depth is about 1 m, and the treatment tank 1 having an inner diameter of 10 cm has a particle size distribution in the range of 0.5 to 3.0 mm. In addition, a microbial carrier having a specific gravity of 0.5 to 0.95 is densely packed to a thickness of about 90 cm and the filtration layer
16 formed. Then, the secondary treatment of general domestic wastewater was supplied into the filtration layer 16 using the wastewater supply pipe 14 so that the following SV value became 3.

SV = (waste water supply amount; m ³ / Hr) / (microbial carrier filling amount; m ³ ) The SS concentration in the waste water to be treated above is about 15 mg / l, and the BOD concentration is about 14 mg / l Met.

Then, in the above treatment tank 1, the waste water is obtained by tracing the filtration flow path that rises from the lower part of the filter layer 16 in the inner cylinder 3 to the bottom of the outer cylinder 2 and ascends the filter layer 16 between the inner and outer cylinders 3 and 2. In the treated water, the SS concentration was less than 1 mg / l, and the average BOD concentration was about 5.5 mg / l, indicating that pollutants were removed from the wastewater at a high rate.

Then, when the waste water was continuously supplied for 3 days as described above, the lower part of the filtration layer 16 in the inner cylinder 3 was clogged and the waste water overflowed the upper end of the inner cylinder 3. This rise in the water level of the wastewater was detected by the water level gauge 15, and immediately the solenoid valve 8 linked to this water level gauge was closed and the bottom solenoid valve 10 was opened. The wastewater rises from the water level B, passes through the portion exposed from the water surface, and passes through the filtration layer between the inner and outer cylinders 3 and 2.
After gradually flowing down 16, the water was discharged to the outside through the discharge pipe 11 as treated water. When the SS concentration of this treated water was measured, it was 1 mg / l or less, and the average concentration of BOD was about 6.2 mg / l.
It was found that pollutants were removed from wastewater at a high rate in all cases such as l.

Further, when the supply of the waste water was continued for 12 days, the whole filter layer 16 began to be clogged, so the filter layer 16 was backwashed here. First, a gas such as air was supplied from the blower 7 into the processing tank 1 through the air diffusers 5 and 6 for about 1 minute to collapse the filtration layer 16. The amount of gas supplied from the blower 7 at this time was about 0.5 l per minute, which was sufficient. Then, 2 l / min of gas was supplied from the blower 7 through the air diffuser 4 into the treatment tank 1 for about 5 minutes in the same manner as described above to circulate and fluidize the microbial carrier in the same manner as described above. Then, the electromagnetic valve 12 was opened to discharge the cleaning water in the processing tank 1 through the discharge pipe 13. Then, such an operation was repeated twice to almost completely eliminate the contaminants trapped by the microbial carrier. The time required for this backwashing operation was about 15 minutes, which was not much different from the conventional method,
It was found that the duration of filtration operation was 15 days, which was about 15 times longer than that of the conventional method (1 day).

Next, when the secondary treated water of domestic treated water was treated using a full-scale treatment tank with a diameter of 1.5 m and a filtration layer formed inside with a thickness of 1.5 m, it was operated continuously for 15 days. The amount of air used during backwashing was about 3.5 m ³ / hr. On the other hand, when the wastewater treatment (rapid filtration treatment) with the conventional filter layer consisting of sand particles was performed using a treatment tank of the same scale, clogging occurred in one day, and the amount of air and water during backwashing was All required about 56 m ³ / hr.
From this result, this method was able to reduce the amount of air to about 1/240 [3.5 / 56] x (1/15)] compared to the conventional method. In addition, the backwashing operation of this method does not require water to circulate and fluidize the microbial carrier, and the amount of about 3 m ³ (the backwashing time is about the same as the content integral of the treatment tank to fill the treatment tank after discharge). 15 minutes) of water was needed. On the other hand, the conventional method required about 14 m ³ of water during backwashing. Therefore, the amount of water used during backwashing was reduced by about 1/70 [3/14] x (1/15)] compared with the conventional method.

In this way, the fact that the filtration operation duration can be lengthened leads to a reduction in the number of times of backwashing operation, so that the separation of the microbial membrane of the microbial carrier generated by the backwashing operation is suppressed and the microorganisms of the microbial carrier are suppressed. This means that the adsorption and filtration function of the membrane can be maintained and continued, and the kinetic energy such as the blower consumed in the backwash operation and the return water can be greatly reduced. Also, regarding the regeneration efficiency of the microbial carrier (pressure loss after backwashing / initial pressure loss), an excellent result of about 99% was obtained.

Comparative Example A microbial carrier having a specific gravity of 1 or less was filled in the treatment tank 1 shown in FIG. 1 to form a filtration layer having a thickness of about 90 cm. Next, a screen having a diameter of about 2 mm was provided by pushing the entire filter layer downward from the top of the filter layer to the same height as the water level. Due to the downward pressing force of the screen and the buoyancy of the microorganism carrier, the filter layer was densely formed.

Then, using this filter layer, the secondary treated water of domestic wastewater was treated under the same conditions as in Example 1, and it was found that
The screen was clogged in 1.2 days and a backwash operation was required, and continuous operation of this filter layer was almost impossible.

(Example 2) In a treatment tank 1 having an effective water depth of about 1 m and an inner diameter of 10 cm as shown in FIG. 2, a microbial carrier having a particle size of 0.5 to 3.0 mm and a specific gravity of 0.5 to 0.95 and a particle size of 0.5 to 3.0 mm and a specific gravity of Each of the 1.3 microbial carriers was densely packed to form a filtration layer 16 having a thickness dimension of about 60 cm and a deposition layer 17 having a depth dimension of about 20 cm. Then, the secondary treated water of the general domestic wastewater similar to that of Example 1 was supplied into the treatment tank 1 to treat the wastewater.

The supply position of the waste water and the flow direction of the waste water after that were the same as in Example 1, and the filtration layer 16 in the inner cylinder 3
The SS concentration of the treated water before clogging the lower part of the and the treated water after clogging was 1 mg / l or less, and the average concentration of each BOD was about 5.3 mg / l or less. .

(Example 3) A microbial carrier having a specific gravity of 1 or less and having a uniform particle size (particle size 1.
8 mm) and those with a distribution in particle size (particle size 1.5 to 4.0 mm)
Was used for wastewater treatment, and the degree of clogging by pollutants contained in the wastewater was investigated, and the results are shown in the graph of FIG. In this graph, the vertical axis represents pressure loss, which is a measure of clogging, and the horizontal axis represents the number of days of wastewater treatment. Then, those having uniform particle diameters are shown by the broken line (a), and those having a distribution of particle diameters are shown by the solid line (b). The thickness of both of the above filtration layers was 90 cm, and the waste water used was secondary treated water having an SS concentration of about 7 to 18 mg / l.

As is clear from the graph of FIG. 3, in the filtration layer (solid line) made of a microbial carrier having a distribution in particle size, there is no part where the pressure loss is high in the filtration layer, and the pressure loss tends to increase as a whole. Since it is small and therefore has little clogging over a long period of time, it can be seen that wastewater treatment can be continuously performed.

"Effect of the Invention" As described above, according to the first invention of the present invention, the particle size distribution of the microorganism carrier forming the filtration layer is about 0.5 to 8.0 mm, preferably about 1.5 to 5.0 mm. By doing
Since the filtration layer is configured such that the microbial carrier having a large particle size is distributed in the upper layer and the microbial carrier having a small particle size is distributed in the lower layer, the upper layer of the filtration layer has a larger gap between the microbial carriers than the lower layer. Pressure loss does not increase locally,
Wastewater treatment can be performed continuously without clogging for a long period of time. Further, according to this method, the filtration layer is partially exposed from the water surface in the treatment tank in the treatment tank. Since the lower part was separated from the bottom of the treatment tank and the whole was densely packed, the microbial carrier forming the filtration layer was not fluidized by the supply of the waste water, and the microbial carrier was treated in water in the treatment tank. It can be fixed on water, and the microorganism carrier can be easily fluidized with a small amount of energy during backwashing. Furthermore, since the waste water supply position is set inside the inner cylinder, the flow path inside the inner cylinder flows down, is reversed at the bottom of the outer cylinder, and rises between the inner and outer cylinders. After the lower part of the inner filter layer is clogged, it is possible to take two filter channels, that is, a channel that rises from the supply position of the waste water and flows down between the inner and outer cylinders through the portion exposed from the water surface of the filter layer. Of the filtration layer 16 of such a flow path, the part that is partially exposed from the water surface in particular is pushed upward by buoyancy and the like as the water level of the wastewater rises, so that the gap between the microbial carriers can be appropriately expanded. The capability of capturing pollutants in the lever area is increased. Therefore, by using these two filtration channels, it is possible to continuously perform wastewater treatment for a long period of time, so that it is possible to lengthen the interval between backwash operations, and thus the backwash operation can be performed. It is possible to suppress the peeling of the microbial membrane from the surface of the microbial carrier that occurs and to maintain the adsorption filtration function of the microbial carrier by the microbial membrane. In addition, since the number of backwash operations is reduced, it is possible to significantly reduce power energy such as blower consumed in the backwash operation and return water, and circulate the microbial carrier in the conventional backwash operation. It is possible to eliminate the need for the water (treated water) used for the conversion.

According to the second invention, the filtration layer has a particle size of 0.5 to 8.0.
mm, preferably composed of a microbial carrier having a particle size distribution of about 1.5-5.0 mm, because the filtration layer itself is lightened,
In the backwash operation, only the air from the bottom of the treatment tank can be used to easily collapse the filter bed with a small amount of energy, and it can be circulated and fluidized for cleaning, and the operating cost associated with the circulatory fluidization is low. Can be suppressed.

Furthermore, according to the third invention, in addition to the excellent effect of the first invention, by passing the wastewater into the sedimentary layer, the pollutants in the wastewater can be removed with higher efficiency. Further, it is possible to obtain an excellent effect such as a longer filtration duration.

According to the fourth aspect of the invention, since the deposition layer is configured to be almost the same as the filtration layer, it is possible to easily supply the filtration layer and the deposition layer with a small amount of energy by supplying only air from the bottom of the treatment layer in the backwashing operation. It is possible to disintegrate and circulate them to circulate and fluidize them for cleaning, and it is possible to reduce the operating cost associated with the circulatory fluidization.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a processing tank used in the first and second inventions of the present invention, and FIG. 2 is a third diagram of the present invention.
And FIG. 3 is a schematic configuration diagram showing a treatment tank used in the fourth invention, and FIG. 3 is a graph showing changes over time in pressure loss of the filtration layer used in the first to fourth inventions of the present invention.

Claims (4)

[Claims] 1. A method for treating wastewater, which comprises filtering wastewater by passing it through a filtration layer composed of a microbial carrier, which has a bottomed cylindrical outer cylinder and a cylindrical inner cylinder erected inside the outer cylinder. In the tank, a filter layer composed of a microbial carrier having a specific gravity of 1 or less and a particle size distribution in the range of 0.5 to 8.0 mm is provided. The upper part of the filter layer is exposed from the water level and the lower part is separated from the bottom of the processing tank. A method for treating wastewater, characterized in that the whole is formed to be dense together with the whole, and then the wastewater is directly supplied into the filtration layer inside the inner cylinder. 2. A method for treating wastewater, which comprises filtering wastewater by passing it through a filtration layer comprising a microbial carrier, which has a bottomed cylindrical outer cylinder and a cylindrical inner cylinder erected inside the outer cylinder. In the tank, a filter layer composed of a microbial carrier having a specific gravity of 1 or less and a particle size distribution in the range of 0.5 to 8.0 mm is provided. The upper part of the filter layer is exposed from the water level and the lower part is separated from the bottom of the processing tank. And then form a dense whole, and then directly supply the wastewater into the filter layer inside the inner cylinder, then circulate and fluidize the microbial carrier that forms the filter layer by supplying only air from the bottom of the treatment tank. A method for treating wastewater, which comprises: 3. A method for treating wastewater, which comprises filtering wastewater by passing it through a filtration layer composed of a microbial carrier, which has a bottomed cylindrical outer cylinder and a cylindrical inner cylinder erected inside the outer cylinder. In the tank, a filter layer composed of a microbial carrier having a specific gravity of 1 or less and a particle size distribution in the range of 0.5 to 8.0 mm is provided. The upper part of the filter layer is exposed from the water level and the lower part is separated from the bottom of the processing tank. Along with this, it is formed so that the whole becomes dense, and below this filtration layer, a sedimentary layer consisting of a microbial carrier having a particle size distribution with a specific gravity of 1.05 to 1.6 and a particle size of 0.5 to 8.0 mm is formed. Then, the wastewater treatment method is characterized in that wastewater is directly supplied into the filtration layer inside the inner cylinder. 4. A method for treating wastewater, which comprises filtering wastewater by passing it through a filtration layer composed of a microbial carrier, which comprises a bottomed cylindrical outer cylinder and a cylindrical inner cylinder erected inside the outer cylinder. In the tank, a filter layer composed of a microbial carrier having a specific gravity of 1 or less and a particle size distribution in the range of 0.5 to 8.0 mm is provided. The upper part of the filter layer is exposed from the water level and the lower part is separated from the bottom of the processing tank. Along with this, it is formed so that the whole becomes dense, and below this filtration layer, a sedimentary layer consisting of a microbial carrier having a particle size distribution with a specific gravity of 1.05 to 1.6 and a particle size of 0.5 to 8.0 mm is formed. Then, after supplying the waste water directly into the filtration layer inside the inner cylinder, the microbial carrier forming the filtration layer is circulated and fluidized by supplying only air from the bottom of the treatment tank to wash the waste water. Processing method.