JP2000189714A - Flocculated floc storing and recovering device and flocculating filter and method of catching and recovering flocculated floc - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve catching efficiency of flocculated flocs in the device in which treated water is passed through a tank filter provided with a filter bed packed with filter medium in a upflow by installing a partition net for catching and storing flocculated flocs in the lower position of the tank filter and installing a floc storage chamber on the upper part side thereof. SOLUTION: When in mid-way of an inflow pipe 5 of raw water, secondary treated water to which a flocculant from a flocculant tank 8 has been added is caused to flow in a flocculating tank A, by aeration from a diffuser 10, it is subjected to bubbling to uniformly agitate and mix it. This liquid mixture is subjected to flocculation by gradually taking in SS in the secondary treated water and phosphorus components in the treated water in a process in which it is caused to flow down in the flocculating tank A. The liquid mixture containing flocculated flocs X is caused to flow in a bottom chamber B1 of the tank filter B and is turned in an upflow and is raised, and when it is passed through the partition net 13, flocs are caught. When a part thereof is floated in a floc chamber B2, it is flocculated and turned into floc lumps, which are precipitated and stored on the partition net 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a coagulation filtration apparatus suitable for adding a flocculant to secondary treatment water and removing suspended matters and the like in the secondary treatment water, and capturing and collecting the flocculated floc. About the method.

[0002]

2. Description of the Related Art Conventionally, when a flocculant is added to secondary treatment water to remove suspended matter (hereinafter referred to as SS) in the secondary treatment water and a phosphorus component contained in the secondary treatment water, usually, coagulation and sedimentation are performed. Solid-liquid separation by the method. This coagulation / sedimentation apparatus is a combination of a coagulation tank having a two-chamber structure including a rapid stirring chamber and a slow stirring chamber, and a coagulation precipitation tank. First, raw water and a coagulant are mixed in the rapid stirring chamber of the coagulation tank. Next, flocs are grown in the slow stirring chamber of the flocculation tank, and the flocs are sedimented by gravity in the flocculation settling tank.

[0003] Therefore, in addition to requiring a separate processing tank,
Since the solid-liquid treatment is performed by sedimenting the floc that has been subjected to the coagulation treatment in the coagulation sedimentation tank over time, it is necessary to incorporate a coagulation sedimentation tank having a large tank capacity.

[0004] In this regard, in the case of the coagulation biological filtration device described in Japanese Patent No. 2653086, raw water to which a coagulant has been added is caused to flow from a lower portion of the filtration tank based on a filtration tank filled with a filtering material. In addition, a drainage device for treated water is provided at the upper part of the filter layer, and water is passed upward from the lower part, and biological filtration is performed by performing aeration with diffused air.
It satisfies the demand for downsizing with a single tank structure.

[0005]

However, in the case of the biological filtration apparatus described above, in order to recover the flocs trapped in the filter layer, aeration is performed by backwashing air supplied from the lower part of the filtration tank. By supplying backwashing water from the lower part, the backwash sludge drainage is discharged from the upper part of the filter layer.

[0006] Therefore, it is necessary to inject backwashing water every time backwashing is performed. In this case, the discharged backwashed sludge treated water is diluted and increased in volume, and the sludge concentration in the post-treatment tank is increased. Increasing the capacity of the storage tank, increasing the load in the post-treatment tank, or returning the desorbed liquid more than necessary to the previous process for reprocessing, which lowers the efficiency of sewage treatment. There is an adverse effect.

Further, since the flocs trapped in the filter layer are subjected to biological treatment by aeration with air for aeration, the flocs which have been formed into flocs and flowed into the filter tank are dispersed by aeration from a diffuser, thereby destroying the flocs. Will be invited.

Therefore, in the present invention, the formation of flocs and the destruction of the formed flocs can be efficiently performed without causing the flocs to be formed in a single tank. The present invention has invented a coagulation filtration device which does not require backwashing water by providing a tank structure capable of efficiently recovering wastewater and enabling backwashing by only air backwashing.

[0009]

More specifically, the present invention relates to a coagulation filtration apparatus in which treated water flows upward in a filtration tank provided with a filter layer filled with a filter medium. A partition net for capturing and storing the flocculated floc is provided at a lower position of the filtration tank, and a floc storage chamber for forming and flocculating the fine flocs floating to the sediment particle size is provided on the upper side thereof, so that the partition net is formed as a core. Agglomerated flocs are efficiently captured, and fine flocs that escape through the partitioning net and float to the floc storage chamber are re-agglomerated with each other to settle as floc with a sediment particle size. The sludge cake is layered and stored on the partitioning net.

[0010] Further, the fine flocs which have slipped out of the partitioning net and floated are finally caught by the filter layer in the upper part of the filtration tank and subjected to the filtration treatment. It greatly reduces the number of washes and contributes to a reduction in operating costs.

According to the second aspect of the invention, the sludge cake stored around the partition net as a nucleus and the mixed solution containing the floc captured in the filter layer are pumped downflow by the discharge pump.

[0012] Therefore, in addition to the above usefulness,
Collection of the mixed liquid containing the sludge cake captured in the partitioning net and stored in layers, that is, the mixed liquid containing a large amount of flocculated floc is returned to the flow control tank in the previous process and subjected to reprocessing, Alternatively, the solid-liquid separation efficiency can be remarkably improved by being sent to a sludge concentration storage tank in a post-process and subjected to solid-liquid separation by gravity sedimentation or the like,
Contribute to downsizing of sludge concentration storage tank.

According to the third aspect of the present invention, a plurality of partitioning nets are provided at a lower position of the filtration tank with a vertical interval therebetween.
The efficiency of capturing flocculated flocs with the partition net at the core is improved, and the storage property of sludge cake is further improved.

According to a fourth aspect of the present invention, the raw water to which the flocculant has been added is stirred by bubbling, and is allowed to flow downward in a downward flow, thereby promoting the formation of flocculated flocs. A filter tank for the mixed liquid containing the flocculated floc is provided, which rises as an upward flow from the filter tank, and a partition net for preventing filter medium sedimentation is provided at an upper position of the filter tank. Formed, provided in multiple stages a partition net for capturing and storing the flocculated floc at a lower position of the filtration tank, and providing a backwashing device at a lower position of the partition net and the partition net for preventing filter medium sedimentation,
In addition, a coagulation filtration device is used in which a mixed liquid containing sludge cake is pumped by a discharge pump.

According to a fifth aspect of the present invention, a flocculation tank having a bottom opening at the center of the tank is provided, an upward filtration tank is provided at an outer position of the flocculation tank, and the filtration tank is vertically spaced by a partition net. By separating and forming the filtration tank, the filtration tank is divided into chambers from a tank bottom to a bottom chamber, a plurality of floc storage chambers, a filter layer chamber, and a supernatant fluid outlet chamber, thereby improving the storage and filtration efficiency of floc. ing.

According to a sixth aspect of the present invention, the raw water to which the coagulant has been added is subjected to coagulation treatment by bubbling and stirring, followed by downflow, and the surface water is raised by an upward flow. Is a filtration treatment by passing the solution through a filter layer, and discharging the supernatant liquid out of the tank, wherein the flocculation floc rising by the upward flow is captured by the partition net, and the partition net is sludge. The method is to capture and store coagulated flocs that store cakes.

Further, in the present invention, by operating the discharge pump, the partition net, the sludge cake stored on the partition net, or the mixed liquid containing the floc trapped in the filter layer is pumped downward. For efficient recovery and reduce the frequency of backwashing.

According to the present invention, at the time of backwashing, the filtering material filled in the partitioning net and the filter layer is washed by aeration treatment from a backwashing device provided below the partitioning net and the partitioning net for preventing the settling of the filter material. After the treatment, the backwashed sludge mixture is pumped down by the operation of the discharge pump and collected.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a coagulation filtration tank S according to the present invention will be described.
1 will be described with reference to a longitudinal sectional view of FIG. 1 showing a state of being buried in the ground and a plan view of FIG. Coagulation filtration tank S
Consists of a cylindrical coagulation tank A vertically supported at the center of the tank, and a flat donut-shaped filtration tank B on the outer periphery thereof.

Reference numeral 1 denotes a main body wall of the coagulation filtration tank S, which is made of a ready-made concrete product molded into a cylindrical shape. However, it can be made into a bottomed rectangular tube shape or made of FRP. . Reference numeral 2 denotes a bottom wall of the coagulation filtration tank S, which has a hopper shape having a downward slope toward the center of the tank, and a discharge pump 4 is installed in a recess 3 which is recessed at the center thereof.

Reference numeral 5 denotes an inflow pipe for secondary treated water, which is raw water. An injection pipe 6 for a coagulant is provided in the middle of the pipe, and a pipe joint 7 at the end of the advection pipe 5 is connected to a coagulation tank. It faces the upper end of A. Reference numeral 8 denotes a coagulant tank, 9 denotes an air supply pipe attached to the upper edge of the coagulation tank A, and a diffuser 10 formed at the lower end thereof is submerged in the liquid in the surface layer of the coagulation tank A. .

The coagulation tank A is formed of a hollow tube made of FRP or vinyl chloride, and has a lower end opening 11 facing a position directly above the depression 3 in the center of the coagulation filtration tank S. Reference numeral 12 denotes a latent outlet of the treated water containing the flocculated floc that penetrates from the lower edge of the flocculation tank A to the filtration tank B.

Numerals 13 and 14 denote partition nets which perform the function of capturing and storing the flocculated floc X which has been flocculated in the flocculation tank A and flows upward from the submerged opening 12 and has a mesh size of about # 20 to # 30. At a position below the filtration tank B corresponding to a lower outside position of the coagulation tank A, it is stretched and supported at intervals vertically. The partitioning nets 13 and 14 and a partitioning net for filter medium settling described later are a rectangular inner frame 21 at an inner position and a polygonal outer frame 2 at an outer position shown in the plan view of FIG.
2 is attached to the upper part of a frame F formed of a frame by a radial connection frame 23. Reference numeral 15 denotes a backwashing device, and a frame F supporting the partitioning nets 13 and 14 is provided.
It is piped in a rectangular shape at the lower position of.

Numeral 16 denotes a partition net for preventing the settling of the filter medium. The partition net 16 is formed in a filter tank B corresponding to a height above the intermediate portion of the coagulation tank A.
Is filled with a filter medium Z. In this embodiment, as the filter medium Z, a plastic hollow container having a capacity of about several tens of cc and a specific gravity slightly larger than a specific gravity of water of 1 is adopted. 20 is a partition net 1 for preventing filter media from settling.
6 is a backwashing device in which a rectangular pipe is provided at a lower position of a gantry F that supports the gantry 6.

Numeral 17 denotes a tubular water collecting device, which is provided in a polygonal shape in the water of the supernatant flowing out of the surface layer of the filter medium Z, and has an overflow port 18 for the supernatant in all directions of the water collecting device 17. The opening is upward. Reference numeral 19 denotes a drain pipe for the supernatant liquid flowing from the overflow port 18 into the water collecting device 17.

Therefore, in the filtration tank B partitioned and formed as described above, the bottom chamber B1 is provided between the bottom wall 3 and the lowermost partitioning net 13, and the first-stage partitioning net 13 and the upper first partitioning net 13 are provided. A first floc storage chamber B2 is provided between the two-stage partition net 14 and a second floc storage chamber B3 is provided between the second-stage partition net 14 and a filter medium sedimentation preventing partition net 16 above the second net. However, a filter layer chamber B4 in which a filter medium Z is filled on a partition net 16 is provided above the partition net 16, and a supernatant liquid discharge chamber B5 is provided above the filter layer chamber B4.

Next, the processing steps of the coagulation filtration in the present invention will be described. (Coagulation treatment) First, the secondary treatment water to which the coagulant is added from the coagulant tank 8 flows into the coagulation tank A in the middle of the raw water inflow pipe 5. Then, the inflowing secondary treatment water and the coagulant are bubbled by the blast from the diffuser 10, so that the mixed liquid is uniformly stirred, and the coagulation processing on the mixed liquid is promoted. In the process of slowly flowing down the coagulation tank A as a downward flow, the SS in the secondary treated water
And the floc formation by gradually taking in the phosphorus component in the treated water proceeds.

The mixed liquid containing the flocculated floc X subjected to the flocculation treatment is supplied to the latent flow port 12 at the lower end opening 11 of the flocculation tank A.
, Flows into the bottom chamber B1 of the filtration tank B, turns to upward flow, and rises up the filtration tank B.

The floating and sedimentation states of flocculated flocs X of various sizes contained in the mixed liquid ascending in the filtration tank B will be described with reference to the enlarged schematic diagram of FIG.

(First Stage Filtration Process) First, the lowermost stage (first stage filtration process)
When the flocculated floc X passes through the partition net 13, that is, the mesh of the partition net 13 is
When escaping, the sludge attached to the mesh of the partitioning net 13 is trapped by entangled as a seed,
In addition, a part thereof passes through the partitioning net 13 to
The flock chamber B2 floats slowly. Along with this floating, a part of the fine floc X is re-aggregated with each other to form floc lumps having a sedimented particle diameter, so that the fine floc X is gradually settled, and the first floc X is first settled.
It is settled and stored on the upper part of the partitioning net 13, and a layered sludge cake layer Y <b> 1 is formed on the partitioning net 13.

Further, the flocculated flocs X that float one after another from the bottom chamber B1 pass through the mesh of the partitioning net 13, and
In addition, the sludge cake layer Y1 deposited thereon takes in the flocculated flocks X that are going to sink and float and are coalesced and integrated to be captured. In other words, the sludge cake layer Y1 having the partition net 13 as a nucleus is bonded while performing a filtering function as a filter of the flocculated floc X which is going to float and pass. In addition, a part of the fine floc X passes or is separated without being captured by the sludge cake layer Y1, and the first floc storage chamber B2 is formed in the same manner as described above.
Are floated or floated, and at this time, the fine flocs X are re-agglomerated into flocs having a settled particle size and settle, and are deposited on the sludge cake layer Y1.

(Second-stage filtration process) Next, when a part of the fine floc X floating in the first floc storage chamber B2 escapes through the mesh of the second-stage partition net 14, the partition net 14 The sludge adhering to the mesh is trapped by entanglement as a seed, and a part of the sludge passes through the partitioning net 14 and slowly floats in the second floc chamber B3. Along with the floating, a part of the fine floc X is re-agglomerated with each other to form floc having a sedimented particle diameter, sedimented, and settled and stored on the upper part of the second stage partition net 14. Eventually, a layered sludge cake layer Y2 is formed on the partition net 14.

Further, the flocculated floc X floating in the first floc storage chamber B2 passes through the mesh of the partitioning net 14, and the sludge cake layer Y deposited on the flocculated floc X tends to pass through and float. X is taken in, coalesced and integrated and captured. In other words, the flocculated floc X where the sludge cake layer Y2 is going to float and pass through
It is filtered and coalesced by functioning as a filter. In addition, a part of the fine floc X passes or is separated without being caught by the sludge cake layer Y2, and floats in the second floc storage chamber B3 in the same manner as described above, or floats or sinks after floating. It is settled by being re-agglomerated into floc lumps having a particle size, and is deposited on the sludge cake layer Y2.

(Third-stage Filtration Process) A part of the fine floc X floating to the second floc storage chamber B3 passes through the mesh of the partition net 16 for preventing the filter material from settling, and the filter material Z filled in the filter layer B4. And is captured in the filter medium Z and subjected to a filtration process. The tertiary treated water filtered in this way flows out into the supernatant chamber B5 of the supernatant liquid in the surface layer, flows into the water collecting device 17 from the overflow port 18, and is drained.

As the above-mentioned coagulation filtration process is repeated, the sludge cake layer Y stored above the first-stage partition net 13 and the second-stage partition net 14 is formed.
1. The increase in the thickness of Y2 further causes the filter effect to gradually decrease due to the flocculated floc X trapped between the filter medium sedimentation preventing partitioning net 16 and the filter medium Z, or the trapped floc X Efficiency and storage efficiency gradually decrease.

(Sludge Collection Process) At this stage, the discharge pump 4 is operated to cause the flocculated floc in the flocculated filtration tank S and the mixed liquid containing the stored sludge cake to flow downward at an appropriate suction speed. , 1/2 to 2/3 of tank capacity
The degree is extracted. Then, the sludge deposited in the bottom chamber B1 and the sludge of the sludge cake layers Y1 and Y2 having the partition nets 13 and 14 as nuclei are withdrawn in a downward flow, returned to the flow control tank in the previous process, and subjected to reprocessing. Alternatively, or by being sent to a sludge sedimentation storage tank in a later step, it is subjected to solid-liquid treatment of a mixed liquid containing the flocculated floc X.

In the case of floc X captured by the filter medium Z in the filter layer chamber B4, the floc X is pumped toward the lower second floc storage chamber B3 or the first floc storage chamber B2.
The sludge cake Y2 in the second floc storage room B3 is
It is pumped out to the floc storage chamber B2 and the bottom chamber B1, and is used for capturing and filtering the floc from the next time. Further, in the case of the sludge cake Y1 in the first floc storage chamber B2 and the accumulated sludge in the bottom chamber B1, the entire amount thereof is pumped out and sent out to the flow control tank or the sludge sedimentation storage tank.

(Backwashing treatment) As the above-mentioned treatment for recovering the mixed solution containing sludge is repeated several times a day, the recovery efficiency gradually decreases, and the filtration efficiency is reduced once a week. It becomes necessary to backwash tank B. In such a case, after the backwashing air is jetted from the backwashing devices 15 and 20 to perform a cleaning treatment by aerating and stirring the inside of the tank, the entire amount of the backwashing sewage is pumped out by the discharge pump 4, and the flow control tank and the like are discharged. Send to sludge concentration storage tank.

[0039]

[Modification] In the above-described embodiment, the two partitioning nets 13 and 14 are formed at a lower position of the filtration tank B with a vertical interval therebetween. By adjusting the trapping efficiency of the aggregated floc X by making three or more sheets or increasing or decreasing the vertical interval, or
The sludge cake extraction efficiency can also be adjusted. Of course, this depends on the size of the meshes of the partitioning nets 13, 14, and 16, so that the size of the meshes can be a large, medium, and small mesh structure for each of the partitioning nets 13, 14, and 16.

In the case of the above-described embodiment, the discharge pump 4 is installed in the recess 3. However, the discharge pump 4 is installed outside the tank, and the suction hose or suction pipe (not shown) of the suction pump is connected. The depression 3 can also be exposed.

Further, in the case of the above-mentioned embodiment, the water collecting device 17 for the supernatant liquid is piped to the discharge chamber B5 with a polygonal pipe, but it may be used as a water collecting gutter or the discharge chamber B5. A water collecting gutter can be provided on the inner peripheral portion of the main body wall 1 at the outer peripheral position.

In the above embodiment, the supply pipe 6 for the coagulant is provided in the middle of the inflow pipe 5 of the raw water, but the lower supply port of the supply pipe 6 is connected to the upper opening of the coagulation tank A. Or the pipe joint 7 can be directly faced.

[0043]

According to the present invention, there is provided an agglomeration method in which treated water flows upward in a filtration tank provided with a filter layer filled with a filter medium. In the filtration device, a partition net for capturing and storing the flocculated floc is provided at a lower position of the filter tank, and a floc storage chamber for forming the floating floc to a sediment particle size and settling on the upper side thereof is provided. Agglomerated flocs with the partition net as the nucleus are efficiently captured, and fine flocs that escape through the partition net and float to the floc storage chamber are re-agglomerated with each other to settle as floc clumps. Then, the sludge cake can be stored in layers on the partitioning net and stored. In addition, the fine flocs that escaped from the partitioning net and floated are finally captured by the filter layer in the upper layer of the filtration tank and subjected to the filtration treatment.
The number of backwashing to prevent clogging of the filter layer is greatly reduced, contributing to a reduction in operating costs.

According to the second aspect of the present invention, the sludge cake stored with the partitioning net as a core and the mixed solution containing the floc trapped in the filter layer are pumped down by a discharge pump. In addition to the above-mentioned usefulness, the recovery of the mixed liquid containing the sludge cake captured in the partitioning net and stored in layers, that is, the mixed liquid containing a large amount of flocculent flocs is returned to the flow rate adjusting tank and reprocessed. Or sent to a sludge concentration storage tank and subjected to solid-liquid separation by gravity sedimentation, etc., thereby significantly improving the solid-liquid separation efficiency.

According to the third aspect of the present invention, the plurality of partitioning nets are provided at the lower position of the filtration tank with a vertical interval therebetween, so that the efficiency of capturing and storing flocculated flocs having the plurality of partitioning nets as nuclei is improved. As well as improving the storage properties of the sludge cake.

According to a fourth aspect of the present invention, the raw water to which the coagulant is added is stirred by bubbling, and is caused to flow down in a downward flow, thereby promoting the formation of flocculated flocs. A filter tank for the mixed liquid containing the flocculated floc is provided, which rises as an upward flow from the filter tank, and a partition net for preventing filter medium sedimentation is provided at an upper position of the filter tank. Formed and provided in multiple stages a partition net for capturing coagulated floc at a lower position of the filtration tank, a backwashing device is provided at a lower position of the partition net and the filter material sedimentation preventing partition nut, and a mixed solution containing sludge cake is provided. The coagulation filtration device is pumped up by a discharge pump. Further, in claim 5, a coagulation tank having a bottom opening at the center of the tank is provided, an upward filtration tank is provided at an outer position of the coagulation tank, and the filtration tank is partitioned vertically by a partition net at intervals. Since the filtration tank is formed and divided into the chambers from the tank bottom to the bottom chamber, a plurality of floc storage chambers, a filter layer chamber, and a supernatant liquid spouting chamber, the tank structure for the tertiary treatment is significantly reduced in size and size. And other effects.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a coagulation filtration tank according to the present invention.

FIG. 2 is a plan view of a coagulation filtration tank.

FIG. 3 shows a flocculated floc captured by two partition nets partitioned at a lower position of a filtration tank, a stored sludge cake layered on the net, and a floc storage by passing the net in an upward flow. FIG. 4 is a schematic view showing a situation where fine flocs floating or floating in a chamber are reagglomerated into flocs having a settling particle size and settle.

[Explanation of symbols]

 S Coagulation filtration tank A Coagulation tank B Filtration tank B1 Bottom chamber B2 First floc storage chamber B3 Second floc storage chamber B4 Filter layer chamber B5 Spring chamber F Mounting base 1 Main body wall 2 Bottom wall 3 Depression 4 Discharge pump 5 Inflow pipe 6 Injection Pipe 7 Pipe joint 8 Coagulant tank 9 Air supply pipe 10 Air diffuser 11 Lower end opening 12 Submerged outlet 13, 14, 16 Partition net 15, 20 Backwashing device 17 Water collector 18 Overflow port 19 Drain pipe 21 Inner frame 22 outer frame 23 connecting frame

Claims (8)

[Claims] 1. A filter tank provided with a filter layer filled with a filter medium,
In the flocculation filtration device configured to flow the treated water in the upward flow, a partition net for capturing and storing the flocculated floc is provided at a lower position of the filtration tank, and on the upper side of the partition net, A flocculation floc storage device comprising a floc storage chamber for forming floating fine flocs to a settling particle size and for sedimentation. 2. The flocculated floc storage and recovery device according to claim 1, wherein the mixed liquid containing the sludge cake stored in the partitioning net and the floc trapped in the filter layer is pumped downward by a discharge pump. 3. The storage and recovery device for flocculated flocs according to claim 1, wherein a plurality of partitioning nets are provided at a lower position of the filtration tank at an interval vertically. 4. A coagulation tank for promoting the formation of coagulated flocs by bubbling raw water to which a coagulant has been added and flowing down in a downward flow, and an upward flow from a latent flow port of the coagulation tank. Providing a filtration tank for the mixture containing the rising flocculent floc, providing a partition net for preventing filter medium sedimentation at the upper position of the filter tank, forming a filter layer filled with filter medium on the partition net for preventing filter medium sedimentation, A partition net for capturing and storing the flocculated floc is provided at a lower position of the filtration tank, and a backwashing device is provided at a lower position of the partition net and the partition net for preventing the settling of the filter medium to discharge the mixed liquid containing the floc. A coagulation filtration device characterized by being configured to be pumped up by a pump. 5. A coagulation tank having an open bottom at the center of the tank, an upward-flow filtration tank provided outside the coagulation tank, and the filtration tank formed by a partition net at intervals vertically. 5. The coagulation filtration apparatus according to claim 4, wherein the filtration tank is divided into a bottom chamber, a bottom chamber, a plurality of floc storage chambers, a filtration layer chamber, and a supernatant fluid discharge chamber. 6. A raw water to which a coagulant has been added is bubbling and stirred, and then subjected to a coagulation treatment by flowing down the water, raised by an upward flow, and passed through a filter layer in a surface layer to perform a filtration treatment. A coagulation filtration method comprising discharging the supernatant liquid out of the tank, wherein the coagulation floc rising by the upward flow is captured by a partition net, and the flocculated floc is stored in the partition net. Capture and storage method. 7. By operating a discharge pump, a partition net, a sludge cake stored on the partition net, or a mixed solution containing floc captured in a filter layer is recovered by being pumped downward. A method for collecting flocculated flocs according to claim 6. 8. During backwashing, the filtering material filled in the partitioning net and the filter layer is washed by aeration treatment from a backwashing device provided below the partitioning net and the partitioning net for preventing settling of the filter medium. The method for recovering a mixed sludge liquid according to claim 7, wherein the mixed liquid for washing sludge is pumped up and recovered in a downward flow by operating a discharge pump.