JPH1119689A - Water purifier and water purifying method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the consumption of a flocculant and the generation amt. of sludge by providing a fluocculator for fluocculating and enlarging suspended matter in raw water in which the flocculant is added, a pretreating device for removing the flocks, etc. in the raw water and a membrane filter for removing the remaining flocks, etc. SOLUTION: A flocculant is added to the raw water of city water introduced into a feed pipe 1 and after the both are mixed by an in-line mixer 2, the mixture is introduced into a downflow packed-bed follculator 6. The flocculator 6 is provided with a packed bed 3 with which a pipe 5 is provided for sending the water and air to backwash the packed bed at the lower part and the suspended matter in the raw water is flocculated and enlarged into flocks. When the flocks are passed successively through a downflow biologically treating filter 11 and a membrane filter 12, the flocks are removed. The biologically treating filter 11 is furnished with a biological filter bed 7 in which a pipe 9 is provided for sending the backwashing water and air to the lower part so that the waste water at the backwashing time is discharged from a discharge pipe 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water purification apparatus and a water purification method mainly used for removing pollutants from raw tap water. In the present invention, a stirrer for mixing raw water tap water and a flocculant, a downflow packed bed type floc forming device capable of efficiently performing floc formation, and a device having a high level of filtration and biological purification functions Because the downflow biological filtration treatment device as the treatment device and the membrane filtration treatment device are used in combination in the same order in series, it is possible to remove suspended substances particularly in comparison with the prior art,
Another object of the present invention is to provide a water purification treatment apparatus capable of stably obtaining treated water having good water quality because it can remove a part of soluble pollutants. Further, the present invention provides a water purification treatment method using the water purification treatment device, which is economical by returning washing wastewater generated at the time of cleaning the biological filtration treatment device and the membrane filtration treatment device to stirring equipment and using it as raw water. Things.

[0002]

2. Description of the Related Art Conventionally, in water purification treatment, an apparatus which combines treatment techniques such as coagulation, sedimentation and sand filtration as shown in FIG. 3 is used. That is, as shown in the figure, the floc is formed by adding a flocculant to flowing tap water and then rapidly stirring in a stirring tank 21 and slowly stirring in a floc forming tank 22, as shown in FIG. After the floc containing most of the turbid matter is settled and removed as sludge, the remaining turbid matter is removed by filtration in the sand filter tank 24.

[0003] However, such a water purification apparatus is
In particular, there is a problem that the area and volume required for the floc forming tank 22 and the settling tank 23 are large, and a large site area is required for installing the apparatus. In addition, when using the water purification apparatus, it is necessary to frequently control the apparatus in accordance with changes in operating conditions such as the quality of raw water or the amount of treated water in order to perform stable water purification processing. There was also a problem that it required. In some cases, proper operation and maintenance that follows changes in the quality of raw water or operating conditions cannot be performed, and the quality of purified water as treated water temporarily deteriorates. In addition, in performing stable water purification treatment using such a device,
Depending on the quality of raw water, it is necessary to add an excessive coagulant, and there is a problem that the amount of sludge generated as a result increases.

As one means for solving such a problem, Japanese Patent Application Laid-Open No. Hei 9-131598 (Japanese Patent Application No.
As seen in -290168), there is a water purification treatment apparatus in which a fixed-bed type multi-layer biological contact filtration treatment apparatus is arranged in two tanks in series, and a sand filtration treatment apparatus or a membrane filtration treatment apparatus is provided at a subsequent stage. The water purification apparatus will be described below with reference to the drawings.

FIG. 4 shows an example of an embodiment in Japanese Patent Application Laid-Open No. Hei 9-131598. In the figure, after adding a coagulant or an alkaline agent to raw water stored in a raw water tank 31, the raw water is supplied to a stirring pond 32 and rapidly stirred, and then supplied to a floc forming pond 33 to form flocs. Thereafter, the water to be treated is subjected to a filtration treatment in a first-stage fixed-layer-type multi-layer biological contact filtration device 34 in which an upper stage is filled with a hollow filter medium and a lower stage is filled with a ceramic filter medium. Then, filtration is performed in a second fixed-layer type multi-layer biological contact filtration device 35 in which a ceramic filter material is filled in a lower stage, and then filtration is performed in a sand filtration device 36.

[0006] On the other hand, a membrane filtration treatment device has been used as an alternative device to a combination treatment such as coagulation, sedimentation and sand filtration (JP-A-2-265628 and JP-A-6-296830). In this method, tap water is directly supplied to a membrane treatment apparatus to remove manganese and the like.

[0007]

However, in the case of using the processing apparatus disclosed in Japanese Patent Application Laid-Open No. Hei 9-131598, a means for washing the biological filtration layer for eliminating clogging of the biological filtration layer caused by the continuous water flow operation is provided. Because of the necessity, the height required for the apparatus is increased and the number of towers is increased, so that it is difficult to supply an inexpensive water purification apparatus. In addition, when a fixed-bed type multi-layer biological contact filtration treatment apparatus is provided as a single stage, problems such as the height required for the above-described apparatus and the number of towers are solved, but the fixed-bed type multi-layer biological contact filtration processing apparatus is solved. In order to improve the quality of the filtered water, it is necessary to reliably perform floc formation in the preceding floc formation pond, and it is necessary to take measures such as increasing the floc formation pond or increasing the amount of flocculant for floc formation. Therefore, there is a problem that it is difficult to supply an economical water purification treatment device.

On the other hand, in the above-mentioned membrane treatment apparatus, tap water is usually supplied directly to the membrane treatment apparatus, and as the continuous water flow operation is performed, iron, manganese, or some organic substances contained in the water to be treated are removed. Since the pores of the membrane are blocked by pollutants, lower the flux of the membrane filtration system and increase the frequency of cleaning such as physical cleaning or chemical cleaning for stable continuous operation. In addition, there is a problem that it is necessary to increase the frequency of replacing the membrane and the like, and it is difficult to provide an economical processing apparatus.

The present invention provides a technique for solving the above problems.

[0010]

The apparatus of the present invention comprises a stirring device for mixing raw tap water and a flocculant, and a floc forming device for flocculating and expanding suspended substances in the raw water to which the flocculant is added and mixed. , A pretreatment device for removing suspended substances, flocs and some soluble pollutants in raw water from water, and a membrane filtration device for removing remaining suspended substances and flocculated flocs from water. . In particular, the floc forming apparatus has a different effective diameter and a different sedimentation velocity, has a higher specific gravity than water, and has a downward flow packed layer type floc forming apparatus including a granular material packed layer filled with at least two or more types of porous granular materials. There is provided a water purification treatment device. Also,
The pretreatment device is a downflow biological filtration treatment device having a biological filtration layer filled with at least two or more types of porous granular filter media having different effective diameters and sedimentation speeds and a specific gravity greater than that of water. It is a water purification treatment device.

[0011] The method of the present invention is also directed to a method for temporarily removing a biological filtration washing wastewater generated by washing a biological filtration layer for eliminating clogging of a biological filtration layer contained in the biological filtration treatment apparatus. And the supernatant of the biological filtration washing wastewater obtained in the concentration tank is returned to the stirring device. Further, the membrane cleaning wastewater generated by physical cleaning of the membrane for eliminating clogging of pores of the membrane included in the membrane filtration processing apparatus is returned to the stirring apparatus. This is a water purification method using the method.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The stirring device may be any device capable of mixing raw tap water and a coagulant, and may be, for example, any of a stirrer, a turbine stirrer and a propeller stirrer, and these are installed in a tank and stirred. Alternatively, an in-line mixer may be used. In addition, it is also possible to use jet stirring and gas blowing stirring.

[0013] The floc forming apparatus may be a conventional floc forming pond, but it is provided with a granular material packed bed filled with at least two or more kinds of porous granular materials having different effective diameters and sedimentation velocities and having a specific gravity greater than that of water. It is preferable to use a counterflow packed bed type floc forming apparatus.

Here, the granular material packed layer included in the packed bed type floc forming apparatus does not unnecessarily restrain suspended substances in the packed bed during continuous water flow, and extremely reduces the water flow resistance in the packed bed. The structure is such that a stable continuous water flow operation can be performed without increasing the number of holes and an effective floc formation can be performed. In order to obtain such a structure, the effective diameter d is used for two or more types of porous granular materials constituting the packed bed.
_It is preferable to use the _{one in} which 10 mm ≦ d ₁ ≦ 100 mm. Here, the effective diameter indicates the particle size of the granular material as a filter medium for water supply, and for details, refer to the test method of filter medium for water supply (JWWA A103) formulated by the Japan Water Works Association.

Further, the filling layer has a sufficient space in the upper filling layer to obtain a gentle stirring effect, and further has a sufficient space in the lower filling layer to obtain a more gentle stirring effect. The structure is such that effective floc formation can be performed. For this reason, the effective diameter d ₁₁ of the upper filler among the porous granular materials constituting the packed layer is 10 mm ≦ d ₁₁ ≦ 8.
0 mm, preferably 15 mm ≦ d ₁₁ ≦ 50 mm, the effective diameter d ₁₂ of the lower filler is in the range of 20 mm ≦ d ₁₂ ≦ 100 mm, preferably 50 mm ≦ d ₁₂ ≦ 80 mm, and
The difference between the effective diameter of the upper filler and the lower filler is 10 mm or more,
Preferably, it should be 20 mm or more.

Further, even when the suspended solids are temporarily restrained in the packed bed during continuous water flow and the water flow resistance in the packed bed is increased, air and / or water are sent from the lower part of the packed bed. It is preferable to have a structure in which the filling layer can be effectively washed by being filled, and the layer can be easily formed by stopping the supply of air, water, or both. the specific gravity of the filler constituting the filling layer is greater than that of water, and it is preferable that the sedimentation rate v ₁₂ of the sedimentation rate v ₁₁ and the lower packing of the upper packing satisfies the relationship of v ₁₁ <v _12. Here, the sedimentation velocity indicates a length that the granular material can settle within the reference time when the granular material freely settles in the stationary water layer showing the reference water temperature (20 ° C.).

The material of the filler may be either inorganic or organic as long as it is porous. Examples of inorganic materials include porous ceramics, zeolite, granular anthracite, sand and the like. Examples thereof include foamed polypropylene, foamed polyethylene, and the like, in which an inorganic filler is blended to increase the specific gravity to 1 or more, and the surface is roughened. Preferred are porous ceramics and expanded polypropylene. The specific gravity is preferably about 1.1 to 3.0, particularly preferably about 1.3 to 2.5. In order to provide a difference in sedimentation speed, the upper layer packing material has a specific gravity of about 1.3 to 2.0, and the lower layer packing material has a specific gravity of about 1.3 to 2.0. It is preferable that the material has a specific gravity of about 1.5 to 2.5 and the difference in specific gravity of the refill material is 0.1 or more, particularly 0.5 or more. The shape is hollow cylindrical, twisted plate, channel,
A frame shape, a spiral shape, a saddle shape, and the like are preferable, and a hollow cylindrical shape is particularly preferable. The porosity of the filling layer is preferably such that the upper layer is about 30 to 70% and the lower layer is about 50 to 80%. The thickness of the upper layer is about 0.2 to 2.0 m, preferably 0.5 to 2.0 m.
About 1.0 m, the lower layer is about 0.2 to 2.0 m, preferably about 0.5 to 1.0 m, and the whole is about 0.4 to 4.0 m, preferably about 1.0 to 2.0 m. It is. The upper layer and the lower layer do not need to be clearly separated, and a layer structure or a middle layer that continuously changes from top to bottom is provided.
It may be a layer or more.

The pretreatment device is a device for adhering organisms to the porous granules to remove pollutants, flocs and some soluble pollutants in raw water by a filtering function of the granules and a purifying function by the organisms. The filtration layer may be a single layer, but has a different effective diameter and a different sedimentation velocity, a specific gravity larger than water, and a downward flow packed layer including a granular material packed layer filled with at least two or more types of porous granular materials. It is preferable to use a mold floc forming device.

The biological filtration device continuously feeds tap water in a downward flow through a filtration layer filled with a particulate filter medium (for example, ceramic-based porous granular material), and performs biological purification by a biofilm attached to the surface of the particulate filter medium. It is a device that removes sludge substances (for example, ammonia nitrogen, off-flavors, algae, etc.) contained in raw water with high efficiency by using both the function and the filtration function by a filter layer.

The biological filtration layer included in the biological filtration apparatus retains most of the flocs formed in the preceding floc forming apparatus in the upper layer of the biological filtration layer, and also retains a small amount of flocs and some suspensions. Suspended substances are also retained in the lower layer of the biological filtration layer, and good treatment is continuously performed while minimizing the rise in head loss caused by retaining suspended substances in the biological filtration layer during continuous water flow. A structure that can be used. The effective diameter d ₂₁ of the upper filter medium constituting the biological filtration layer is 2.0 mm <d ₂₁ ≦ 10 mm, preferably 4.0 mm ≦ d ₂₁ ≦ 6.0 mm, and the effective diameter d _{22 of the} lower filter medium.
Is 1.0 mm ≦ d ₂₂ ≦ 2.0 mm, preferably 1.1 m
It is preferable that m ≦ d ₂₂ ≦ 1.5 mm. Further, the difference between the effective diameters of the upper filter medium and the lower filter medium is 1.0 mm or more, preferably 2.0 mm or more.

Further, even if the biological filtration layer increases the water flow resistance in the biological filtration layer by retaining suspended substances in the biological filtration layer during continuous water flow, air or water, or both, are removed from the lower part of the biological filtration layer. It is preferable that the structure is such that the biological filtration layer can be effectively washed by feeding, and the biological filtration layer can be easily formed by stopping the supply of air, water or both. , specifically it is preferable to satisfy the relationship density of the filter medium is larger than that of water, and sedimentation rate v ₂₁ and the sedimentation rate v ₂₂ of the lower filter media of the upper filter media that v ₂₁ <v ₂₂ constituting the biological filtration layer.

The material of the filter medium can be selected from those listed above as the material of the filler in the floc forming apparatus. Preference is again given to porous ceramics and foamed polypropylene, and it is particularly preferred to use porous ceramics for both the upper and lower layers, or foamed polypropylene for the upper layer and porous ceramics for the lower layer. The specific gravity is preferably about 1.1 to 3.0, particularly preferably about 1.3 to 2.5. In order to provide a difference in sedimentation velocity, the specific gravity of the upper filter medium is about 1.3 to 2.0, and the specific gravity of the lower filter medium is about 1.3 to 2.0. The specific gravity is about 1.5 to 2.5, and the specific gravity difference between the two is 0.1 or more,
In particular, it is preferably 0.5 or more. The shape is not critical, and may be any shape such as a hollow cylindrical shape, a crushed shape, a spherical shape, and a dice shape. The thickness of the upper layer is 0.5 to 3.0.
m, preferably about 1.5 to 2.5 m, and the lower layer is 0.1 m.
About 2 to 1.5 m, preferably about 0.5 to 1.0 m,
As a whole, about 0.7 to 4.5 m, preferably 2.0 to 4.5 m
About 3.5 m is appropriate. The upper layer and the lower layer do not need to be clearly separated, and may have three or more layers by providing a layer configuration that changes continuously from top to bottom or an intermediate layer. In order to attach living organisms to this biological filtration device, the raw water to be treated may be passed through.

[0023] The membrane filtration treatment device has a composition of a membrane contained therein,
It is not limited by the type and the structure of the membrane module, but is applicable to any of polyester-based, cellulose-based, microfiltration membrane, ultrafiltration membrane, dead-end type or cross-flow type membranes and membrane modules.

At the time of the water flow operation using the apparatus of the present invention, the raw tap water is caused to flow into the stirring equipment via the raw water supply pipe.
At that time, a necessary coagulant is injected through the chemical injection equipment according to the turbidity concentration in the raw water, and rapid stirring is performed to mix the raw tap water with the coagulant. The water to be treated, which has been rapidly stirred, flows into a downward flow packed bed type floc forming apparatus, and when the water to be treated is passed downward through the granular material packed bed filled with the porous granular material, the filling material and the water to be treated are mixed. The collision effectively agitates to form flocculated flocs. Even when the continuous water supply operation is resumed immediately after washing the packed bed without discharging the suspended water, most of the suspended matter contained in the suspended water generated by washing the packed bed has a floc shape. As a result, most of the suspended solids are easily trapped and removed in the subsequent biological filtration apparatus. Thereafter, the water to be treated flows into the downflow biological filtration treatment device, and the suspended substance contained in the water to be treated is treated by the filtration function of the filter layer and the biological purification function of the biofilm attached to the surface of the porous granular filter medium. , Flocs and partially soluble pollutants (eg, ammonia nitrogen, off-flavor, etc.) and the like. After that, the water to be treated is flowed into the membrane filtration treatment device, and a part of the remaining suspended solids and flocculated floc are removed from the water to be treated. And then supply it as purified water.

Further, if necessary, the biological filtration washing wastewater generated by washing the biological filtration layer for eliminating clogging of the biological filtration layer contained in the biological filtration treatment apparatus is temporarily stored in a sludge concentration tank. Returning the supernatant water of the biological filtration washing wastewater obtained in the concentration tank to the stirring device and using it as raw water improved the recovery rate of water represented by the ratio of the total amount of raw water to the total amount of purified water, and collected water. It is economical because raw water can be used effectively. Further, it is possible to return the membrane cleaning wastewater generated by physical cleaning of the membrane for eliminating clogging of the pores of the membrane included in the membrane filtration processing device to the stirring device and use it as raw water if necessary. In addition, it is economical because the raw water from tap water can be effectively used.

According to the present invention, some of the soluble pollutants are removed in the biological filtration apparatus, and a small amount of suspended substances remaining in the water to be treated are completely removed in the membrane filtration apparatus. The quality of the treated water to be obtained is superior to the quality of the treated water of a conventional coagulation sedimentation / sand filtration treatment device. In addition, a uniform and good floc can be formed by the floc forming device, and there is no need to form a flocculant having a high sedimentation property unlike the conventional coagulating sedimentation treatment device, so that it is not necessary to excessively add a flocculant. It is economical because the amount of coagulant used can be reduced and the amount of generated sludge can be reduced. In addition, in order to perform stable water purification treatment, it is not necessary to frequently control the apparatus in accordance with changes in operating conditions such as the quality of raw water or the amount of treated water, so that it is possible to automate operation and maintenance and save labor.

Further, a water purification treatment comprising a stirring device, a downflow packed bed type floc forming device as a floc forming device, and a downflow biological high-speed filtration device and a membrane filtration processing device as a pretreatment device. Since it is an apparatus, it is more compact and economical than a conventional coagulation sedimentation / sand filtration apparatus.

In addition, most of the pollutants contained in the water to be treated, including iron, manganese, etc., which cause clogging of the membrane, are removed by the biological filtration apparatus, so that the membrane filtration apparatus is operated under high flux conditions. It is economical because it can be operated and the frequency of cleaning such as physical cleaning or chemical cleaning of the film can be reduced, and the life of the film can be extended accordingly.

In the apparatus of the present invention, when a two-stage biological filtration apparatus as disclosed in Japanese Patent Application No. 7-290168 is used in place of the combination of the packed bed type floc forming apparatus and the biological filtration apparatus, continuous water flow operation is required. It is necessary to provide a washing means for the biological filtration layer to eliminate clogging of the biological filtration layer caused by both in the device, because the height required of the device is increased and the number of towers is increased, It is not possible to exhibit the economics of an inexpensive water purification treatment apparatus such as the apparatus of the present invention.

[0030]

FIG. 1 shows a water purification apparatus according to an embodiment of the present invention.
Shown in

This apparatus comprises an in-line mixer 2 to which a raw water supply pipe 1 is connected, a downflow packed bed type floc forming apparatus 6, a downflow biological filtration apparatus 11, and a membrane filtration apparatus 12. .

The floc forming device 6 has an inner diameter of 0.4 mx 0.4 mm.
It is a 4 m box-shaped tank, and the layer thickness of the packed layer 3 is 1.0
m, the lower layer is 1.0 m, and therefore 2.0 m in total.
The upper layer packing has an effective diameter d ₁₁ of 20 mm (outer diameter 20 mm,
A hollow cylindrical porous polypropylene (inner diameter 16 mm, length 20 mm) (specific gravity 1.3) was used. Effective diameter d ₁₂ in the lower packings 50 mm (outer diameter 50 mm, inner diameter of 40 mm,
A hollow cylindrical porous polypropylene (specific gravity: 1.5) having a length of 50 mm) was used. Above and below the packed layer 3, nets 4 for preventing the outflow of the packed material are stretched, and below the lower net 4, supply pipes 5 for sending back water and air for back washing of the packed layer 3 are provided. A pipe is connected from the lower end of the floc forming device 6 to the upper portion of the biological filtration treatment device 11.

The biological filtration apparatus 11 has an inner diameter of 0.5 m ×
The thickness of the biological filtration layer 7 is 2.0 m for the upper layer, 0.5 m for the lower layer, and therefore 2.5 m as a whole. Effective diameter d ₂₁ in the upper layer filter medium 4.0 mm (outer diameter 4.
A hollow cylindrical porous polypropylene (specific gravity: 1.3) having a diameter of 0 mm, an inner diameter of 3.0 mm, and a length of 4.0 mm) was used. Effective diameter d ₂₂ was used silica sand spherical shape of 1.0mm in the lower layer filter medium. Below the biological filtration layer 7, a plate 8 supporting the biological filtration layer
A water and air supply pipe 9 for backwashing the biological filtration layer 7 is provided below the perforated plate 8. A washing drainage pipe 10 for extracting washing wastewater generated by back washing is attached to the upper part of the tank. Biological filtration treatment device 11
Is connected to the membrane filtration device 12 from the lower end.

The membrane filtration apparatus 12 has a pore diameter of 0.2 μm
And a microfiltration membrane treatment apparatus including a polypropylene hollow membrane having the following characteristics.

In the above-mentioned apparatus, the sludge concentration tank 13 for temporarily storing the washing wastewater from the biological filtration layer 7 to settle and concentrate the sludge contained in the washing wastewater and the membrane washing wastewater from the membrane filtration device 12 are supplied to the in-line mixer 2. FIG. 2 shows an example in which a return line 15 is provided for returning data to a computer. The supernatant water of the sludge thickening tank 13 is returned to the in-line mixer 2 via the return line 14, and the concentrated sludge is withdrawn from the bottom. As a result, it is possible to increase the recovery rate of the tap water and perform more economical operation.

Using the above apparatus, two river surface water purification operations were performed. Polyaluminum chloride was used as the coagulant. For comparison, a case where the treatment was performed using a conventional coagulation / sedimentation / sand filtration treatment apparatus (Comparative Example 1 (a,
b)), when the treatment was carried out using a two-stage fixed bed type multi-layer biological contact filtration treatment device (Comparative Example 2 (a, b)), and a one-stage fixed bed type multi-layer biological contact filtration treatment device was used. An experiment was also performed in the case where the processing was performed using this method (Comparative Example 3 (a, b)).

Tables 1 and 2 show examples of the processing results.

[0038]

[Table 1]

[0039]

[Table 2]

As shown in Tables 1 and 2, when water purification treatment was performed using the apparatus of the present invention, water purification treatment was performed using a conventional coagulation sedimentation / sand filtration treatment apparatus, As compared with the case where the water purification treatment was performed using a single-stage fixed-layer type multi-layer biological contact filtration treatment apparatus, high-quality treated water could be obtained although the apparatus was compact.

[0041]

According to the water purification apparatus of the present invention, which combines a stirrer, a downflow packed bed type floc forming apparatus, a downflow biological filtration apparatus and a membrane filtration apparatus, the quality of the treated water obtained is the same as that of the conventional coagulation apparatus. It is superior to the treated water quality of the sedimentation / sand filtration equipment, and reduces the amount of flocculant used.
It is economical because the amount of generated sludge can be reduced and the apparatus can be made compact. Further, the apparatus is compact and economical as compared with a conventional two-stage biological filtration apparatus.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a water purification apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of another water purification apparatus of the present invention.

FIG. 3 is a diagram showing a configuration of an example of a conventional water purification treatment device.

FIG. 4 is a diagram showing a configuration of another example of the conventional water purification treatment device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Raw water supply pipe 2 ... In-line mixer 3 ... Packing bed 4 ... Net 5 ... Backwashing water and air supply pipe 6 ... Flock forming apparatus 7 ... Biological filtration layer 8 ... Plate 9 ... Backwashing water and air supply pipe 10 ... Washing drainage pipe 11 ... Biological filtration treatment device 12 ... Membrane filtration treatment device 13 ... Sludge concentration tank 14 ... Return line 15 ... Return line

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C02F 3/06 ZAB C02F 3/06 ZAB (72) Inventor Takeshi Tsuji 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan 1-2 In company

Claims (5)

[Claims] 1. A stirrer for mixing raw tap water with a flocculant, a floc forming device for flocculating and expanding a suspended substance in raw water to which a flocculant is added and mixed, a suspended substance in raw water, floc and A water purification treatment device comprising a pretreatment device for removing some soluble pollutants from water, and a membrane filtration treatment device for removing remaining suspended substances and flocculants from water. 2. A downflow packed bed type wherein the floc forming apparatus includes a granular material packed layer filled with two or more kinds of porous granular materials having different effective diameters and sedimentation velocities, and having a specific gravity greater than that of water. The water purification device according to claim 1, wherein the water purification device is a floc forming device. 3. A downflow biofiltration, wherein the pretreatment device includes a biofiltration layer filled with two or more kinds of porous granular filter media having different effective diameters and sedimentation velocities, and having a specific gravity larger than that of water. The water treatment apparatus according to claim 1 or 2, wherein the water treatment apparatus is a treatment apparatus. 4. A biological filtration washing wastewater generated by washing a biological filtration layer for eliminating clogging of a biological filtration layer included in the biological filtration treatment device, is temporarily stored in a sludge concentration tank, and the concentration is performed. 4. The method of claim 3, wherein the supernatant of the biological filtration washing wastewater obtained in the tank is returned to the stirring device. 5. 5. A membrane cleaning wastewater generated by physically cleaning a membrane for eliminating clogging of pores of the membrane included in the membrane filtration treatment device, is returned to the stirring equipment. A water purification method using the water purification apparatus according to 1, 2, or 3.