JP2001029751A - Separation apparatus and solid-liquid separation method - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To smoothly and efficiently filter and separate solids and liquids at a high water permeation rate even with biological treatment liquids containing activated sludge and having different properties. SOLUTION: A flat membrane-like separation membrane provided with a separation membrane (nonwoven fabric having an average pore diameter of about 1 to 300 μm) 17, a permeate port 18 for flowing out a permeate permeated into the flat membrane-like separation membrane, and Forming a cake layer of suspended particles on the surface of the separation membrane using a separation membrane element 14 having a washing port 21 for supplying a fluid into the flat membrane separation membrane to wash the separation membrane. Filter. Appropriate reference permeate volume F (m / da
y) and the suspension particle concentration C (mg / l) in the supernatant of the suspension adjusted to the activated sludge concentration of 3000 mg / l F = A × C ^−B (where A is 30 ~
50 and B indicate 0.8 to 1.0), and the control means controls the set amount of permeate and backwashing by the separation membrane based on the amount of permeate corresponding to the suspended particle concentration data. The solid-liquid separation is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating a liquid to be treated containing suspended particles such as activated sludge by forming a water-permeable porous membrane such as a nonwoven fabric as a separation membrane and forming a cake layer on the surface of the separation membrane. And a solid-liquid separation device and a solid-liquid separation method useful for obtaining a clean permeate.

[0002]

2. Description of the Related Art Separation membranes are used to obtain clean filtered water from treated water treated with biological treatment or activated sludge. For example, Japanese Patent Application Laid-Open No. 2-86893 discloses a solid-liquid separation device in which a filtration membrane device provided with a microfiltration membrane is immersed in purification water in an aeration tank, and an air diffuser is disposed immediately below the membrane to perform suction filtration. Is disclosed. Japanese Patent Application Laid-Open No. 5-185078 discloses filtration of an aeration tank using a filter in which two nonwoven fabrics each having a minimum retention particle size of 10 to 100 μm are formed into a bag and a porous material for maintaining a gap is inserted therein. An apparatus is disclosed.
In these apparatuses, a bag-shaped separation membrane element having a filtration membrane attached thereto is laminated on a frame provided with a water collection pipe, and the permeated water is taken out by the water collection pipe. In general, suspended particles (SS) such as suspended matter and activated sludge using these filtration membranes
When performing a solid-liquid separation treatment on a biological treatment liquid containing, the separation performance may greatly vary depending on the properties of the biological treatment liquid to be treated. Further, as the filtration proceeds, suspended particles SS and the like adhere to the membrane surface or inside the membrane, and the water permeation rate decreases. For this reason, usually, the operation is intermittently stopped, and the filtration membrane is backwashed with water or a chemical.

[0003] The phenomenon that suspended particles SS and the like adhere to the outer surface or inner surface of the membrane greatly depends on the filtration operation conditions, particularly, the set permeation flow rate. Consolidation causes a sharp decrease in the amount of permeated water and significant adhesion of suspended particles SS on the inner surface of the membrane.

[0004] Japanese Patent Application Laid-Open No. 10-286563 discloses that in an immersion tank containing water to be treated separated into activated sludge and a liquid phase containing a suspended substance existing thereon, the liquid sludge is mixed with the activated sludge. In the method of immersing the immersion type membrane separation means in the immersion tank and extracting the filtered water separated from the membrane separation means by suction to the outside of the immersion tank, the suspended substance concentration in the liquid phase is continuously determined, and the suspended substance concentration is determined. A membrane separation method for changing a membrane separation condition so that a value is maintained below a predetermined reference value is disclosed. This document measures at least one of turbidity, suspended solids (SS) concentration and evaporation residue (TS) concentration of liquid phase, intermittent operation stop, dilution of liquid phase, addition of flocculant A method for changing the membrane separation conditions by coagulation and sedimentation by pulling out activated sludge from the lower part of an immersion tank is described.

However, in this method, when the concentration of the suspended substance is high, the operation is stopped, the liquid phase is diluted,
A coagulation sedimentation operation using a coagulant or an operation for extracting activated sludge is required, and the concentration of suspended solids cannot be quickly reduced to a reference value or less. Moreover, since it is necessary to immerse the immersion type membrane separation means in the liquid phase separated from the activated sludge phase to separate the suspended substance, the above operation may cause the suspended substance to float in the liquid phase. Therefore, it is necessary to carefully perform operations such as dilution, which greatly reduces operability. In particular, the characteristics of not only activated sludge but also the treated liquid subjected to activated sludge treatment vary greatly depending on regions and facilities, so that the separation performance and separation efficiency of the separation membrane also vary greatly, making it impossible to perform smooth and efficient membrane separation.

[0006]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a solid-liquid separation apparatus and a solid-liquid separation method capable of filtering a liquid to be treated containing suspended particles smoothly and efficiently. is there.

Another object of the present invention is to provide a solid-liquid separation device and a solid-liquid separation method capable of efficiently treating water to be treated at a high water permeation rate.

[0008] Still another object of the present invention is to provide a solid-liquid separation apparatus and a solid-liquid separation apparatus capable of efficiently performing solid-liquid separation by controlling a set permeation flow rate in filtration and membrane washing conditions even for biological treatment liquids having different properties. It is to provide a method.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, the permeation rate of the separation membrane and the concentration of suspended particles in the supernatant are closely related. Using the concentration of suspended particles in the supernatant of the treatment liquid as an index, it has been found that solid-liquid separation can be performed smoothly and efficiently at an appropriate water permeation rate, and the present invention has been completed.

That is, the separation apparatus (solid-liquid separation apparatus) of the present invention is an apparatus provided with a separation membrane element for filtering a liquid to be treated containing suspended particles, and a supernatant liquid of the liquid to be treated. Data input means for inputting data relating to the suspended particle concentration of the sample, and control means for controlling the permeate amount by the separation membrane element based on a reference permeate amount corresponding to the input data. ing. As the separation membrane, various separation membranes, for example, a water-permeable porous body in which fibers are entangled, for example, a separation membrane having an average pore diameter of about 1 to 300 μm, and a water permeability of the separation membrane with respect to pure water, a transmembrane pressure difference of 1 kPa And a separation membrane of about 10 to 10,000 m ³ / m ² · day can be used. The separation membrane element generally has a flat membrane separation membrane having separation membranes facing each other at a distance from each other, and a permeated liquid permeated into the flat membrane separation membrane flows out of the flat membrane separation membrane due to a pressure difference. And a washing port for introducing a washing solution into the flat membrane-shaped separation membrane and backwashing the separation membrane.

The liquid to be treated may be a biological treatment liquid or the like containing activated sludge, and when the liquid to be treated containing such suspended particles is treated, suspended components (suspended liquid) are formed on the outer surface of the separation membrane. Particles) can be formed and filtered.
In controlling the amount of permeate, the activated sludge concentration was 3000 m
The amount of permeated water corresponding to the concentration of suspended particles in the supernatant of the suspension adjusted to g / liter can be used as the reference amount of permeated liquid. The amount of permeated liquid is controlled by the following formula (i): F = A × C- ^B (i) (where F is the amount of permeate through the separation membrane (m / day), C is the concentration of suspended particles in the supernatant (mg / liter), and the coefficient A is 30 to
50, and coefficient B indicates 0.8 to 1.0).

When the amount of the permeated liquid by the separation membrane element reaches the lower limit of the reference permeated liquid amount corresponding to the data input by the data input means, the control means controls the cleaning liquid from the cleaning port into the flat membrane separation membrane. A chemical solution may be supplied to wash the separation membrane.

The method of the present invention is a method for filtering a liquid to be treated containing suspended particles through a separation membrane element,
The liquid to be treated is filtered by the separation membrane element while controlling the amount of permeate through the separation membrane based on the reference amount of permeate corresponding to the data on the suspended particle concentration of the supernatant of the liquid to be treated.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

FIG. 1 is a schematic configuration diagram of a solid-liquid separation device of the present invention, FIG. 2 is a schematic perspective view showing an example of a separation membrane element, and FIG. 3 is a separation membrane using the separation membrane element of FIG. It is a schematic perspective view which shows a module.

The separation apparatus includes a biological reaction tank 1 for treating raw water to be treated with activated sludge, and a filtration tank 11 for filtering a liquid to be treated supplied from the biological reaction tank.
And a water storage tank 31 for storing the filtrate from the filtration tank.
And The liquid to be treated supplied from the raw water supply line 2 is supplied to the biological reaction tank 1 by a valve 4a.
The liquid to be treated, which is treated with activated sludge while aeration is performed by adjusting the amount of air supplied from the air diffuser 3 and aerated in the biological reaction tank 1, is supplied by the pump 5 to the valve 4 b, the pressure gauge 6, and the flow meter 7. Is supplied to the filtration tank 11 through a supply line 8 provided with The supply line 8 connected to the filtration tank 11 has a valve 4c for discharging the processing liquid in the filtration tank 11.
Is provided.

In order to avoid the influence of the aeration in the biological reaction tank 11 and to perform stable filtration by the cake layer (flock layer) on the separation membrane surface, the filtration tank 1 independent of the biological reaction tank 1 is used.
1 is a membrane module. As shown in FIG. 3, this membrane module 11 constitutes a wall (wall) of a filtration tank 11 and has a housing (or casing) 12 connected to the supply line 8 at the bottom. And a separation membrane unit 13 that can be immersed in the liquid to be treated in the housing. The separation membrane unit 13 is formed by arranging a plurality of separation membrane elements (or flat membrane elements) 14 in parallel at intervals in the thickness direction (ie, laminating). An air diffuser 26 whose supply amount is adjustable by a valve 4d extends below the separation membrane unit 13 in the housing 12, and supplies air as needed from the air diffuser. The excessively thick cake formed on the surface of the separation membrane 17 is removed by utilizing the shearing force at the interface with the interface, and the thickness of the cake layer is adjusted to suppress a decrease in the water permeation rate. Note that an air diffuser is not necessarily required in the housing, and other means, for example, a stirring means for removing an excessive cake layer may be provided.

Further, on the side wall (upper side wall in this example) of the housing 12 on the side of the biological reaction tank 1, a liquid to be treated (a non-permeate liquid component containing suspended particles and the like) which has not been filtered by the separation membrane module 11 is provided. An opening window 27 for returning the wastewater to the biological reaction tank 1 by overflow is formed.

The air diffuser 3 of the biological reaction tank 1 and the air diffuser 26 of the membrane module 11 are connected to a single air supply line 38 via the valves 4a and 4d whose flow rates can be adjusted, respectively. I have.

As shown in FIGS. 2 and 3, each separation membrane element 14 has a rectangular frame (or support) 15.
And a solid-liquid separation membrane 17 stretched on both sides of the frame via a liquid-permeable spacer 16 such as a metal mesh and opposed to each other at a distance from each other. ) Is formed. A pair of frame portions of the frame body 15 facing each other have a water collecting pipe 19 forming a permeate liquid port 18 and an introduction pipe forming a cleaning liquid port 21 for introducing a cleaning liquid into the element (cavity). 22.

More specifically, a permeate flow path 20 through which a permeate (permeate) permeating the solid-liquid separation membrane 17 flows is formed in the cavity between the solid-liquid separation membranes 17 facing each other. The permeate flow path 20 communicates with a permeate port 18 formed in the frame 15. Therefore, the permeated liquid permeated through the permeated liquid flow path 20 in the flat membrane-shaped (bag-shaped) separation membrane by utilizing the pressure difference (the pressure difference between the membranes of the separation membrane element (internal and external pressure difference)) is transmitted to the permeated liquid port 18. Element 1 through
4 can be taken out. Further, the separation membrane element 14 is provided with a washing liquid flow path 23 for introducing a washing liquid into the cavity inside the element 14 independently of the permeate liquid flow path 20.
And the introduction pipe 2 constituting the cleaning liquid flow path 23.
The cleaning liquid port 21 is formed in communication with the port 2.
From a plurality of locations in the axial direction of the introduction pipe 22, a plurality of thin tubes 24 are combed in a direction crossing the hollow portion in the element 14 (in this example, a direction toward the water collection pipe 19 in the permeate flow path 20). It extends in communication with teeth. A plurality of blowing holes (blowing holes) 25 for blowing out the cleaning liquid are formed at predetermined intervals along the axial direction in these thin tubes 24, the tip ends are closed, and the blowing holes 6 are fixed. The opening is provided in a direction substantially perpendicular to the surface of the liquid separation membrane 17. That is, the cleaning liquid flow path 23 is also configured by a thin tube 24 and also has a tubular flow path in which the blowout hole 25 is formed.

In such a separation membrane element 14, since the permeate flow path 20 and the cleaning liquid flow path 23 are formed independently of each other in the element, the suspension or sludge can be filtered with high efficiency, and The permeate that has passed through the liquid separation membrane 17 can be taken out through the permeate port 18 stably at a high water permeation rate. Further, the cleaning liquid introduced from the cleaning liquid port 21 does not flow out through a short path to the permeation liquid port 18 and can be uniformly dispersed in the cavity in the element, so that the solid-liquid separation membrane 17 can be efficiently cleaned. it can. In particular, when the cleaning liquid channel 23 is formed by the thin tube 24,
The cleaning liquid introduced from the cleaning liquid port 21 can be blown out toward the solid-liquid separation membrane surface at a high pressure through the outlet 25 of the thin tube 24, and the suspended particles adhered (or deposited) on the solid-liquid separation membrane surface can be highly formed. Can be washed off. The plurality of outlets 25 can be formed at substantially equal intervals or at random intervals in the axial direction of the thin tube so that the cleaning liquid can be uniformly sprayed onto the solid-liquid separation membrane surface.

In the membrane module 11, the permeate port 18 of each separation membrane element 14 is connected to and joined to a permeate line 32. The permeate from the permeate line 32 is supplied to the water storage tank 31, The flow rate of the permeate line 32 is detected by a flow meter 33. In the water storage tank 13, the height of the liquid surface is set lower than the height of the liquid surface of the filtration tank 12, so that the difference in the height of the liquid surface (water head difference) is handled by the principle of siphon. Pressure (suction force)
Thus, the permeate can be smoothly discharged from the permeate port 18.

By adjusting the mounting height of the drainage line 39 with respect to the side wall of the water storage tank 31, excessive filtered water can be discharged from the discharge line 39, and the head difference and the transmembrane pressure can be adjusted. In order to obtain a pressure difference or a transmembrane pressure difference, a drainage line may be provided below the water storage tank 31 and drainage may be performed from the drainage line to increase the head difference. Further, the permeated liquid is not limited to the method using the head difference due to gravity as described above, but may be a means for generating various pressure differences, for example, pressurization of the liquid surface in the membrane module 11 or coating of the membrane module 11 with the liquid. The processing liquid can be taken out by using a method such as pressurization by circulation of the pump 5 or suction by a suction pump provided in the permeated liquid line 32.

On the other hand, the cleaning liquid port 21 of each of the separation membrane elements 14 joins with the cleaning liquid supply line 34 for cleaning the solid-liquid separation membrane 17 using the permeated liquid of the water storage tank 31. That is, one end of the cleaning liquid supply line 34 is connected to the cleaning liquid port 2 of the separation membrane element 14.
1 and the other end is immersed in the liquid phase of the water storage tank 31. The cleaning liquid supply line 34 is provided with a backflow cleaning pump 35 for supplying a permeated liquid into the separation membrane element 14, a flow rate adjusting valve 4e, a pressure gauge 36, and a flow meter 37.

Even if solid-liquid separation treatment is performed using such a separation device, the properties of the activated sludge vary greatly depending on the region, facility, timing, time, etc., so that the operating conditions vary greatly and the efficiency and stability are improved. Solid-liquid separation becomes impossible. On the other hand, the concentration of suspended particles in the supernatant (particularly, activated sludge concentration of 3000 m
A close relationship is observed between the suspension (concentration of suspended particles in the supernatant liquid adjusted to g / liter) and the water permeation rate through the separation membrane. For this reason, in the present invention, data relating to the concentration of suspended particles in the supernatant of the liquid to be treated is measured in advance, and the measured value is used as an index to control the filtration conditions (particularly, the set amount or flow rate of the permeate) or to perform backwashing. By doing so, the filtration treatment is performed smoothly and efficiently while preventing the amount of the permeated liquid from becoming excessively large and suppressing the adhesion of the suspended particles SS to the membrane surface and the compaction of the cake layer.

More specifically, the permeated liquid amount (m / da) of the separation membrane
y) The following relational expression (i) is observed between F and the suspended particle concentration (mg / liter) C in the supernatant of the suspension adjusted to the activated sludge concentration of 3000 mg / liter.

F = A × C ^-B (i) (where the coefficient A is 30 to 50 and the coefficient B is 0.8 to 1.0
The preferable coefficient A is about 35 to 45, and the preferable coefficient B is 0.85 to 1.0 (especially 0.88 to 0.9).
9) about.

Therefore, the concentration of suspended particles in the supernatant (mg
By using the reference permeate amount (reference permeation flow rate) F related to C as an index or a reference to control the permeate amount by the separation membrane element in operation, filtration can be performed under appropriate conditions. .

The reference amount of permeate (reference permeation flow rate) refers to the suspended particles SS adhering to the separation membrane surface (outer or inner surface).
Means a reference value with which a permeate can be obtained smoothly while preventing the compaction of the solution, and can be selected according to the type of the separation membrane. For example, when a porous membrane (such as a nonwoven fabric) in which fibers are entangled is used as a separation membrane, water having a suspended particle concentration of 20 mg / liter or less is applied to a transmembrane pressure difference of 0.5 to 5 kPa (particularly 1 to 5 kP).
The permeated liquid amount (permeation flow rate) after filtration in a) can be used as the reference permeated liquid amount.

FIG. 4 is a flow chart showing an example of the solid-liquid separation device of the present invention.
Data input means for inputting data on the concentration of suspended particles (mg / liter) in the supernatant of the suspension adjusted to 00 mg / liter, and a reference permeate volume corresponding to the input data, Control means for controlling the set amount of permeate by the separation membrane. That is, in the control means, based on the data input in the input step 41, in the reference flow rate calculating step 42, the reference permeate corresponding to the input data relating to the suspended particle concentration is utilized by using the relational expression (i). In the comparison step 43, the reference flow rate data and the amount of permeate from the separation membrane element 14 or the module 11 are detected by a flow meter (flow sensor) 33 provided in the permeate line 32. By comparing the detected flow rate data with the detected flow rate data, it is determined whether or not the detected flow rate data is within the threshold range of the reference flow rate data. If the detected flow rate data is within the threshold range of the reference flow rate data, the comparison determination is repeated.

If the detected flow rate data is outside the threshold value of the reference flow rate data, the control means calculates the control of the permeated liquid quantity by the calculating means based on the deviation data from the reference flow rate data in a control amount calculating step 44. The amount data is calculated, and in a control step 45, the membrane pressure difference of the separation membrane is controlled by the drive control means based on the calculated control amount data. This membrane pressure difference is adjusted by adjusting the water head difference by the supply amount of the liquid to be treated by the pump 5 of the supply line 8, adjusting the water head difference by drainage from the drain line below the water storage tank 31, and by the suction pump of the permeate line 32. It can be controlled by suction, pressurization of the liquid level of the membrane module 11 by a pressure pump, or the like.

In the present invention, even if the average pore size of the separation membrane 17 of the separation membrane element 14 is slightly larger than the particle size of the minimum suspended particles SS, the suspended particles SS accumulate on the surface of the separation membrane 17, The activated sludge layer (cake layer or dynamic layer) formed on 17 functions as a kind of separation membrane,
Moreover, it can be operated at a predetermined low transmembrane pressure. Therefore, by such an operation, these elements act synergistically to suppress the intrusion of the suspended particles SS into the separation membrane 17 and the inside of the membrane element 14. Separation performance for SS can be exhibited in a well-balanced manner.

On the other hand, when such a solid-liquid separation treatment is continued for a long time, the suspended particles SS excessively adhere to the surface of the separation membrane 17, and the amount of the permeated liquid is reduced. In such a case, it is possible to remove the suspended particles SS that have excessively adhered by stopping the filtration operation or applying an external force to the separation membrane 17 by supplying gas or stirring from the air diffuser 6. However, when the suspended particles further accumulate in association with the solid-liquid separation treatment, the amount of the permeated liquid is significantly reduced.

Then, when the control step 45 is completed,
In the comparison determination step 46, the separation membrane element 14
Alternatively, the permeated liquid amount by the membrane module 11 is compared with the lower limit (allowable lower limit) of the reference permeated liquid amount corresponding to the input data by the data input means, and it is determined whether or not the lower limit has been reached. Flow sensor 33 in permeate line 32
When the permeation flow rate data reaches the lower limit value, in the backflow cleaning step 47, the cleaning liquid is supplied from the cleaning liquid supply line 34 into the separation membrane element 14 by the drive control means, and the separation membrane 17 is subjected to cleaning processing. The backflow cleaning of the separation membrane by the drive control means is performed by the cleaning liquid supply line 34.
The cleaning can be performed by controlling at least one factor selected from the flow rate of the cleaning liquid, the operation time (cleaning time), the frequency of cleaning (the number of times of cleaning), the cleaning pressure, and the like. When the cleaning operation is performed a plurality of times, the subsequent cleaning conditions may be stricter than the preceding cleaning conditions.

When the backwashing is completed, in a concentration determination step 48, the concentration of suspended particles in the supernatant of the liquid to be treated is calculated as follows:
It is determined whether there is no change from the suspended particle concentration corresponding to the input data (preset input data), and the suspension particle concentration corresponding to the input data in the supernatant of the liquid to be treated is compared with the suspended particle concentration. When the concentration of the repellent particles is out of the reference value, an input step 41 for inputting data again.
The input data relating to the concentration of suspended particles in the supernatant of the liquid to be treated is updated (reset), and the above operation is repeated.

On the other hand, when the concentration of repellent particles in the supernatant of the liquid to be treated is within the range of the reference value with respect to the concentration of suspended particles corresponding to the input data in the concentration determination 48 step, It is determined whether a predetermined amount of the liquid to be processed has been processed. If the predetermined amount of the liquid to be processed has not been processed, the process returns to the comparison determination step 43,
When a predetermined amount of the liquid to be treated is filtered, the above operation is completed.

The amount of permeated liquid (permeation flow rate) in the above apparatus
Can be controlled using the concentration of suspended particles in the supernatant as an index, and the amount of permeate (permeate flow rate) can be easily controlled by the transmembrane pressure difference of the separation membrane. Further, the control may be performed by automatic control or program control in various modes. For example, the input data on the concentration of suspended particles in the supernatant is supplied to an automatic measuring device for the concentration of suspended particles (for example, a turbidimeter or a transmittance measurement unit capable of optically measuring the concentration of suspended particles in the supernatant). Automatically and continuously and continuously at intervals or with data from a device provided. The control of the permeate amount by the transmembrane pressure may be controlled by a single control object, or may be controlled by combining a plurality of control objects. In addition, backwashing is performed without performing determination based on whether the flow rate has reached a predetermined reference value.
It may be repeated every predetermined time set in the timer.
Further, in the backwashing, the flow rate (flow velocity), pressure, etc. of the washing solution may be controlled based on the deviation between the predetermined reference value and the amount of the permeate, and a switching step is employed in addition to the backwashing step. In the switching step, the separation liquid may be cleaned by switching the cleaning liquid to the chemical liquid. This switching step can be performed based on whether or not the number of times of cleaning has reached a predetermined reference number, or may be performed based on whether or not the permeation flow rate has excessively decreased below the reference value.

In the separation apparatus and the separation method of the present invention, a high water permeation rate can be maintained for a long period of time by washing the separation membrane and adjusting the thickness of the cake layer by the above-mentioned operation. The water permeation rate can be maintained at a high level even when continuously operated for preferably 200 hours or more, more preferably 500 hours or more.

The apparatus and method of the present invention can be used for filtration of various liquids containing suspended particles (mud water, polluted water, sludge, etc.), particularly for biological treatment liquid containing activated sludge. .

In the separation apparatus and method of the present invention, the separation membrane may be a microfiltration membrane (MF) or an ultrafiltration membrane, but in order to obtain a treatment liquid (flux) at a high water permeation rate, It is advantageous to use a separation membrane (water-permeable porous membrane) having a high water permeation rate, particularly a water-permeable porous body (woven cloth, nonwoven cloth, etc.) in which fibers are entangled. That is, by forming a cake layer (or a floc layer or a dynamic layer) of the suspended component on the outer surface of the separation membrane, the suspended particles can be separated and removed by using the filter function of the cake layer. A membrane is available. A preferred solid-liquid separation membrane is a non-woven fabric. As the nonwoven fabric, for example, a nonwoven fabric having at least one of the following characteristics can be selected. (1) Weight per unit area: about 10 to 1,000 g / m ² , preferably about ²⁰ to 900 g / m ² (2) Air permeability: about 0.1 to 200 cm ³ / cm ² · s
Preferably about 0.2 to 150 cm ³ / cm ² · s (3) Average fiber diameter: 0.5 to 30 μm, preferably about 1 to 10 μm (4) Fabric thickness: about 30 to 5,000 μm, preferably Is about 100 to 2,000 μm The non-woven fabric is made of fibers (natural fibers, regenerated fibers, semi-synthetic fibers, etc.), and is formed by a conventional method (a method of forming fibers into a web and bonding by thermocompression bonding or an adhesive, a needle punching method). Such)
Can be manufactured. Natural fibers include cotton, hemp, wool,
Cellulose fibers and the like can be exemplified. Regenerated fibers include rayon (such as viscose rayon). Examples of the semi-synthetic fibers include cellulose ester fibers (such as cellulose acetate fibers) and cellulose ether fibers (such as methyl cellulose fibers). Synthetic fibers include polyester (polyethylene terephthalate, polybutylene terephthalate, etc.), (meth) acrylic resin (poly (meth) acrylate, polyacrylonitrile, etc.), polycarbonate, polyether, polyetherester, polyamide (nylon 6, Nylon 66, etc.), polyimide, polyamide imide, polyolefin (polyethylene, polypropylene, etc.), halogen-containing vinyl resins (polyvinyl chloride, polyvinylidene chloride, etc.), thermoplastic resins such as polystyrene, etc. Fibers obtained from polymers, crosslinked products, and mixtures are included. Preferred fibers include polyester fibers (such as polyethylene terephthalate fibers and polybutylene terephthalate fibers) and polyolefin fibers (such as polyethylene fibers and polypropylene fibers), especially polyester fibers.

The average pore size of the separation membrane such as a nonwoven fabric can be selected within a range that does not impair the water permeation rate and the separation performance, and is, for example, about 1 to 300 μm (for example, about 1 to 200 μm), preferably about 10 to 300 μm (for example, 10
~ 200 µm), more preferably 15-300 µm
m (for example, about 15 to 200 μm). The average pore size was 100 times the surface of the separation membrane and 1
It can be calculated by taking an electron microscope photograph at a magnification of 0000 and processing with an image processing device.

The water permeation rate of the solid-liquid separation membrane with respect to pure water is, for example, 10 to 10 at a transmembrane pressure difference of 1 kPa.
About 000 m ³ / m ² · day, preferably 50 to 5,000
About 0 m ³ / m ² · day, more preferably 100 to 1,
It may be about 000 m ³ / m ² · day.

The apparatus and method of the present invention may be applied directly to a biological treatment liquid for treating sludge with aeration using activated sludge by immersion in a biological reaction tank. In the case of performing dynamic filtration using the method, when the separation membrane element is immersed in the biological reaction tank, formation of a cake layer or a dynamic layer is inhibited by aeration for sludge treatment. Therefore, it is advantageous to supply the treatment liquid of the biological reaction tank containing the activated sludge to the filtration tank (membrane module), and to filter the sludge in the filtration tank (membrane module). Instead of forming the filtration tank with a membrane module, the liquid to be treated may be filtered by immersing the separation membrane element or the separation membrane unit in a filtration tank independent of the biological reaction tank.

The separation membrane element is not limited to the above structure, and various elements can be used. For example, a separation membrane element is provided on both sides of a frame (or a support) and separated from each other and opposed to each other, and an outflow port or an outflow line for allowing permeated liquid permeated between the separation membranes to flow out. When a separation membrane is regenerated by backwashing, a supply port or a supply line for supplying a washing liquid between the separation membranes may be provided. Further, the water collection pipe for the permeated liquid and the introduction pipe for the cleaning liquid are formed at appropriate places of the frame (or the support), for example, at the same side or the frame, at the opposite side or the frame, or at the adjacent side or the frame. It can be formed in a portion facing each other or a non-facing portion. When the washing liquid port is arranged at the upper part and the permeate liquid port is arranged at the lower part, solid-liquid separation is performed, so that the filtrate (permeate) can be smoothly taken out from the lower part in the separation membrane element and suspended in the element. Particles can be prevented from accumulating.

Further, various structures can be adopted for the membrane module. Usually, a housing to which a supply liquid line for supplying the liquid to be treated is connected, and at least one separation membrane element which can be accommodated in the housing. And a permeate line for allowing the permeate to flow out of the separation membrane element, and in the case of backwashing, a washing line connected to the separation membrane element is provided, and an overflow port or the like is not necessarily required. Absent. The separation membrane unit can be formed by arranging a plurality of separation membrane elements in various forms in which the separation membrane does not contact, and it is not necessary to arrange the separation membrane elements in parallel in the thickness direction.

In the above-mentioned apparatus, the biological reaction tank and the filtration tank are made independent, but the biological reaction tank is divided into a biological reaction section and a filtration section by a partition plate having a liquid passing section. Filtration may be performed using an element or a separation membrane module. In addition, the liquid-passing part of the partition plate can be formed at an appropriate part between the biological reaction part and the filtration part. For example, at least one of the lower part and the upper part can pass the biological reaction part and the filtration part. May be communicated with.

In the present invention, the transmembrane pressure can be appropriately selected according to the type of the liquid to be treated and the type of the separation membrane.
For example, about 1 cm to 1 m, preferably 10 to 50 cm
Degree. The pressure acting on the separation membrane surface corresponding to the head difference (transmembrane pressure) is, for example, about 0.1 to 5 kPa, preferably 0.5 to 5 kPa (for example, 1 to 3 kP).
a).

The amount of permeate (water permeation rate) can be appropriately selected according to the type of the separation membrane. When a separation membrane having a large average pore diameter such as a nonwoven fabric is used, the average permeate water amount is, for example, 0.5%.
５5 m ³ / m ² · day, preferably 0.8 to ³ m ³ / m
^It may be about ² days. The concentration of suspended particles in the permeate (the permeate SS concentration) also greatly depends on the type of separation membrane, and when a nonwoven fabric is used as the separation membrane, for example, 0 to 30 m
g / liter (weight basis), usually 1-10 mg /
It is about liter (weight basis). The concentration of the permeate SS was determined by removing insoluble components contained in the permeate by a pore diameter of 0.4 μm.
Can be determined by collecting on a glass filter, drying the whole glass filter, and measuring the weight after drying.

In addition, as the cleaning liquid, in addition to the permeated liquid of the water storage tank, water or a chemical solution (an aqueous solution of hypochlorous acid, an aqueous solution of sodium hydroxide, etc.) can be used. Water or chemicals can be supplied to the separation membrane element through the cleaning liquid line or through another line. When using a large separation membrane with an average pore size such as a nonwoven fabric, the feed rate of the solid-liquid separation membrane 1 m ² per wash, for example, 1~100m ³ / m ² · day, preferably about 5~701~100m ³ / m ² · day, more preferably about 10 to 50 m ³ / m ² · day.

The separation apparatus and the separation method of the present invention can be suitably used as wastewater treatment of various facilities, for example, a sludge treatment apparatus using activated sludge in a sludge treatment plant. It can also be used for purification of rivers and lakes.

[0052]

According to the present invention, since the set amount of permeate is controlled by using the concentration of suspended particles in the supernatant as an index, even a liquid to be treated containing suspended particles can be filtered smoothly and efficiently. . Further, the water to be treated can be efficiently treated at a high water permeation rate by utilizing the dynamic filtration. Furthermore, even for biological treatment liquids having different properties, solid-liquid separation can be performed efficiently by controlling the set permeation flow rate and membrane washing conditions in filtration.

[0053]

The present invention will be described below in more detail with reference to Examples, but the present invention is not limited to these Examples.

The following numerical values were obtained by the following methods. (1) Electron micrographs of the surface of the filtration membrane were taken at an average pore diameter of 100 times and 10,000 times, and a total of three photographs (2 cm × 2 cm area) were obtained.
Was processed by an image processing apparatus to calculate an average pore diameter. (2) SS concentration The solid concentration contained in a predetermined volume of the liquid is determined by measuring the pore diameter to 0.4 μm.
After filtration through a glass filter of m and drying, measurement was performed by weighing. (3) Supernatant liquid SS concentration The biological treatment liquid was diluted with water so that the SS concentration became 3,000 mg / liter, and allowed to stand in a 1-liter measuring cylinder for 2 hours. Thereafter, the liquid at the center of the supernatant was taken out and the SS concentration was measured. (4) Water Permeation Rate The water permeation rate was determined from the effective membrane area of the filter and the amount of permeate in a certain period of time. [Relationship between Average Permeation Rate and Supernatant SS Concentration] Using a nonwoven fabric H8007 (a nonwoven fabric made of polyester fiber having a fiber diameter of 10 μm; manufactured by Japan Vilene Co., Ltd.) as a filter,
A filtration membrane element having an effective membrane area of 0.05 m ² shown in FIG. 2 was produced. A module shown in FIG. 3 was prepared using the two obtained filtration membrane elements, and solid-liquid separation was performed using the apparatus shown in FIG.

As a liquid to be treated, a biological treatment liquid containing activated sludge collected at a sewage treatment plant and a human waste treatment plant is used. The pump circulation linear velocity is 1 cm / s, the transmembrane pressure is 1.2 kPa, and the temperature of the treatment liquid is 18 Solid-liquid separation was performed at ２３23 ° C. 2 L / min of air was supplied from below the membrane through an air diffuser. The SS concentration of the biological treatment liquid was 7,000 to 14,000 mg / liter, and the supernatant liquid SS concentration c was 20 to 642 mg / liter. The average amount of permeated water was the average permeation rate for 12 hours after the start of filtration.

FIG. 5 shows the relationship between the average amount of permeated water and the concentration of the supernatant liquid SS. As is clear from FIG. 5, there is a relational expression F = A · C between the average permeated water amount F and the supernatant SS concentration c.
^-B (A = 39.0, B = 0.935) was observed.

Example 1 A membrane module shown in FIG. 3 was prepared by using two non-woven fabrics H8007 as filtration bodies and ^two filtration membrane elements having an effective membrane area of 0.05 m 2 shown in FIG. 2 and an apparatus shown in FIG. To perform solid-liquid separation.

As a liquid to be treated, a biological treatment liquid containing activated sludge collected at a sewage treatment plant (SS concentration 10,000 mg / l, SS concentration c of the supernatant liquid = 20 mg / l) was used, and the initial set permeate water amount was 2 m. / Day, and the solid-liquid separation was performed at a transmembrane pressure of 1.2 kPa and a temperature of the liquid to be treated of 18 to 23 ° C. Air at a rate of 2 l / min was supplied from below the membrane through an air diffuser. In addition, 30m of water backwash once every 12 hours.
^This was performed for 1 minute under the condition of ³ / (m ² · day). Immediately after the start of the filtration, c was 20 mg / L, but one month after the start of the filtration, c increased to 60 mg / L. Therefore, the set permeated water amount was set to 1 m / day, and two months later,
= 100 mg / liter, so the set permeate flow rate was set to 0.5 m / day. FIG. 6 shows the change over time in the transmembrane pressure difference.

Example 2 An experiment was carried out using the same apparatus and conditions as in Example 1. Water backwashing was performed once every 12 hours under the condition of 30 m ³ / (m ² · day) for 1 minute. Immediately after the start of the filtration, c was 20 mg / L, but one month after the start of the filtration, it was increased to c = 60 mg / L.
Performed for 1 minute under the condition of m ³ / (m ² · day). In addition, 2
After months, since c = 100 mg / liter, the water backwash was performed once every 6 hours at a rate of 30 m ³ / (m ² · da).
y) is performed for 1 minute under the conditions of (1) and backwashing with 100 ppm sodium hypochlorite is performed once every 12 hours.
The test was performed for 1 minute under the condition of 30 m ³ / (m ² · day). FIG. 6 shows the change over time in the transmembrane pressure difference.

Comparative Example 1 Water backwashing was performed once every 12 hours at a rate of 30 m ³ / (m ² · da).
Solid-liquid separation was performed under the same conditions as in Example 1 except that the reaction was performed for 1 minute under the condition of y).

Comparative Example 2 Solid-liquid separation was carried out under the same conditions as in Example 1 except that the initially set water permeability was 5 m / day. However, water backwashing was performed once every 12 hours under the condition of 30 m ³ / (m ² · day) for 1 minute.

As is apparent from FIG. 6, by setting an appropriate amount of permeate and selecting washing conditions according to the concentration of sludge supernatant SS, a high amount of permeate can be maintained over a long period of time.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a solid-liquid separation device of the present invention.

FIG. 2 is a schematic perspective view showing an example of a separation membrane element.

FIG. 3 is a schematic perspective view showing a separation membrane module using the separation membrane element of FIG.

FIG. 4 is a flowchart showing an example of the solid-liquid separation device of the present invention.

FIG. 5 is a graph showing the relationship between the average amount of permeated water and the supernatant SS concentration.

FIG. 6 is a graph showing the change over time in the SS concentration and the transmembrane pressure in the supernatant in Examples and Comparative Examples.

[Explanation of symbols]

 14: Separation membrane element 17: Separation membrane 18: Permeate liquid port 21: Washing port

Continued on the front page F-term (reference) 4D006 GA02 GA06 GA07 HA42 HA93 JA04A JA04C JA08A JA16A JA25A JA30A JA39A KA02 KA13 KA43 KA63 KB22 KC03 KC13 KC16 KD17 KD24 KE01Q KE02P KE03Q KE05P12 KE12P23 KE06PKE MA40 MB02 MC11 MC14 MC18 MC19 MC22 MC23 MC24 MC26 MC27 MC37 MC39 MC45 MC48X MC49 MC54 MC55 MC58 PA01 PB04 PB08 PC62 4D028 BC17 BD16 CA00 CB02 CC05

Claims (12)

[Claims] 1. An apparatus provided with a separation membrane element for filtering a liquid to be treated containing suspended particles, comprising: data for inputting data relating to the concentration of suspended particles in a supernatant of the liquid to be treated. A separation apparatus comprising: input means; and control means for controlling a permeate amount by the separation membrane element based on a reference permeate amount corresponding to input data. 2. The separation device according to claim 1, wherein the separation membrane is a water-permeable porous body in which fibers are entangled. 3. The separation device according to claim 1, wherein the average pore size of the separation membrane is 1 to 300 μm. 4. The water permeation rate of the separation membrane with respect to pure water is 10 to 10,000 m ³ / m ² · day at a transmembrane pressure of 1 kPa.
The separation device according to claim 1, wherein 5. A separation membrane element comprising a flat membrane separation membrane having a water-permeable porous membrane opposed to each other at a distance from each other, and a permeated liquid permeating the flat membrane separation membrane is separated by a pressure difference by a flat membrane separation. 2. The separation device according to claim 1, further comprising a permeate port for flowing out of the membrane. 6. The separation apparatus according to claim 1, wherein the liquid to be treated is a biological treatment liquid containing activated sludge. 7. The standard amount of permeate is 3000 when the activated sludge concentration is 3000.
The separation device according to claim 1, wherein the amount of permeated water corresponds to the concentration of suspended particles in the supernatant of the suspension adjusted to mg / liter. 8. The following formula (i): F = A × C ^−B (i) (where F is the amount of permeated liquid through the separation membrane (m / day), and C is the concentration of suspended particles in the supernatant liquid (mg / day). Liter), coefficient A is 30 ~
The separation apparatus according to claim 1, wherein the control means controls the amount of the permeated liquid of the separation membrane by using a control means (50, coefficient B indicates 0.8 to 1.0). 9. A control means for calculating control amount data relating to the amount of permeate based on deviation data between the amount of permeate by the separation membrane and a reference amount of permeate corresponding to the input data; 2. The separation apparatus according to claim 1, further comprising control means for controlling a transmembrane pressure of the separation membrane based on the control amount data. 10. A separation membrane element comprising a flat membrane-like separation membrane having a water-permeable porous membrane which is separated from and opposed to each other, and a permeated liquid permeated into the flat membrane-like separation membrane is flattened by a pressure difference. It has a permeate port for allowing the liquid to flow out of the separation membrane, and a washing port for supplying fluid into the flat membrane-shaped separation membrane to wash the separation membrane. 2. The separation device according to claim 1, further comprising a control unit for supplying a cleaning solution or a chemical solution from the cleaning port into the flat membrane-shaped separation membrane when the lower limit of the reference permeate amount corresponding to the input data from the input unit is reached. apparatus. 11. A method for filtering a liquid to be treated containing suspended particles through a separation membrane element, based on a reference permeate amount corresponding to data relating to the concentration of suspended particles in the supernatant of the liquid to be treated. And separating the liquid to be treated by a separation membrane element while controlling the amount of permeate through the separation membrane. 12. The separation method according to claim 11, wherein a cake layer of the suspended component is formed on the outer surface of the separation membrane, followed by filtration.