DE20121465U1 - Device for separating a permeate - Google Patents

Description

Device for separating a permeate

The invention relates to a device for separating a permeate, in particular process water from waste water, wherein a membrane module such as a cassette with membranes is immersed in a solid/liquid mixture from which the permeate can be separated.

Such devices are used, for example, to purify municipal and/or industrial wastewater, i.e. to separate biomass from wastewater, which can also be referred to as permeate, using membranes. The biologically completely purified and membrane-filtered wastewater or permeate can be reused as process water due to the high quality that can be achieved with the device according to the invention.

The so-called aeration process, which includes an aeration tank and a secondary clarifier, is often used for the biological purification of wastewater. The biological purification of the wastewater is carried out by suspended microorganisms, which are supplied with oxygen in the aeration tank by blowing in air and are simultaneously kept in suspension. The microorganisms are separated from the purified wastewater by sedimentation in the secondary tank and kept in the system. The purified wastewater is fed back into the water cycle.

However, the separation of the activated sludge in secondary clarifiers is often incomplete. As a result, suspended matter enters the effluent, which significantly worsens the effluent values

and reuse of the effluent as process water is generally ruled out. In particular, germs and viruses - potential pathogens - cannot be retained in conventional secondary settling tanks. 5

This conventional process technology with aeration tanks and secondary clarification tanks is described, for example, in the patent specification DE-OS 44 15 637 (Process and device for cleaning and treating washing water from vehicle washing systems). In this biological cleaning process, the microorganisms are retained by sedimentation in the secondary clarification tank. A disadvantage of this process is that it is complex, as the secondary clarification tanks take up a lot of space and the construction of these tanks is expensive. In addition, the cleaning is not sufficiently thorough, so that the water returned to the water cycle can often only be used as poor quality process water.

An improvement to this process variant of separating the activated sludge in secondary clarifiers by means of a sedimentation process is the separation using membranes, i.e. by means of membrane filtration. Membrane filtration is a separation process in which the various ingredients can be separated using a selectively permeable membrane. In membrane filtration, the separation takes place mainly through a sieve effect. This means that all ingredients that are larger than the pore diameter of the membrane (e.g.

0 microorganisms) are retained, and only substances that can flow through the pores (e.g. liquids such as water) pass through the membrane. The water that passes through the membrane is called permeate.

A biological process and a device for purifying water, particularly from a composting process, are also known from the prior art (DE-OS 44 12 890). The purification process takes place in a bioreactor. To retain the microorganisms in the bioreactor, the water is then filtered, particularly ultrafiltered. The pressures required for this are in the range of 5 to 10 bar. The separation of the microorganisms from the purified water is made possible by a membrane with a suitable pore size. For aeration, the mixture is gassed with oxygen and stirred. A disadvantage of this process is that the high pressures require a corresponding pumping capacity, which in turn makes the process expensive and complex.

EP 0662341 describes a membrane module which can also be used for wastewater treatment and consists of parallel plates. The module is, however, permanently mounted in a container and the membrane module is subjected to uniform aeration to clean off the solids retained on the outside or surface of the membrane. Uniform air distribution under the module is achieved by maintaining a distance of more than 500 mm between the air outlet and the lower edge of the module. In addition, the plates are made of a rigid plastic material with the membranes welded on both sides and which is elaborately designed by adding recesses in the rigid plastic plate on the inside to enable the permeate to be drained off.

Furthermore, EP 0510328 A2 describes a process using a membrane module for filtering waste water. However, here the membrane is cleaned of the retained substances by installing a stirring unit under the membrane module, which forces an upward flow between the membrane cassettes and thus cleans the membrane surface.

The manufacture of membrane plates and in particular the fastening of the membranes to rigid plates is described in EP 653 240 A1. The membranes are fastened directly to the plastic plates in the edge area by gluing or ultrasonic welding. This manufacturing process is also discussed in EP 0662341. It also specifies that the support plates are made of plastic and that the permeate is removed inside the cassette through channels.

Another patent (US5248424) describes hollow fiber membranes and a method for keeping these fibers clean during the filtration of a substrate and the removal of permeate. Flexible hollow fibers with a length of more than 0.5 m are glued into permeate collectors at both ends. The hollow fibers have an external diameter of between 20 μm and 3 mm and a wall thickness of between 5 μm and 2 mm. The separation limit of the membrane, i.e. the size of the particles that can still be retained, is given as 0.001 /xm to 1.0 μm. According to this description, the hollow fibers are cleaned by blowing 0 air under the module and the rising air bubbles set the fibers in motion. The membrane module is immersed in a basin and does not move; only the fibers are set into vibration.

The known processes all have the disadvantage that they either require uneven cleaning of the membrane surfaces, which may require the filtration to be stopped for cleaning, or they require increased pressure, temperature and/or a pump. In addition, they do not offer any flexibility in terms of the number of membrane modules used depending on the degree of contamination of the wastewater.

The object of the invention is to provide a device for separating a permeate from a liquid/solid mixture, which operates continuously and without external influences such as pressure, pumping power and/or temperature at high performance and can be flexibly adapted to the respective content of solids to be separated.

The invention relates to a device for separating a permeate from a liquid/solid mixture, characterized in that at least one membrane module with integrated permeate discharge is immersed in the liquid/solid mixture and fastened in such a way that it can carry out at least one pendulum and/or rotary movement. The permeate is separated from the liquid/solid mixture via a membrane module, the membrane module being immersed in the liquid/solid mixture during operation and carrying out at least one pendulum and/or rotary movement. The device can be used to separate a permeate for wastewater treatment.

By means of the device according to the invention, the membrane of the membrane module can be continuously or discontinuously

Solids that have deposited on the membrane can be cleaned. This means that the separation process can be operated continuously without the need for an interruption to clean the membrane.

A membrane module is any type of component that can be used to separate solid and liquid components of a solid/liquid mixture using a membrane that acts as a sieve. Membrane modules of this type are well known.

The membrane that can be used according to the invention is, according to one embodiment, a flat structure for material separation and is configured for use in modules. Various variants have been developed here, of which the conventional tube module (internal flow), the externally coated tube membrane (external flow), the plate module with flat membrane and the hollow fiber module are common variants.

With flat membranes, membrane coatings are usually applied to both sides of a thin plate, also known as a cassette or support plate. A support fleece can also be arranged between the membrane and the plate. Filtration takes place from the outside to the inside, the permeate flows out and the solids stick to the outside. The plate can have a structure, such as channels, or be smooth. A plate that has no structures is preferred.

The individual flat membranes are arranged parallel at a distance along a permeate collector or a permeate collection line. The plate thus simultaneously takes over the

1 :

Draining the permeate to one or more outlets or holes along the permeate collector. The flat membranes are prefabricated and then stacked with suitable spacers in a housing with a permeate collector. The housing is preferably designed so that individual membranes can be added and/or removed. It is particularly preferred if this can be done without interrupting the process. Applying membrane coatings to both sides of a plate creates a closed space on all sides that is accessed through one or more openings. The permeate can flow out through these openings.

The hollow fiber module consists of thin, hollow fibers with an inner diameter of 0.2 to 6 mm. The fibers, which are usually flexible, are glued into permeate collectors at the top and bottom. Filtration in the hollow fiber module takes place from the outside to the inside and the permeate flows through the front-side permeate collectors into a drain line.

The membrane can be cleaned by a stream or jet of a medium directed at the module, e.g. in a point-like manner, which can reach all parts of the membrane where solids may be deposited due to the movement of the module. The stream or jet can be continuous or discontinuous; e.g. it can be bubbles, etc. Preferably, the jet, the stream or the bubbles hit the module from below and preferably rise up the membrane. A cleaning effect can also be caused by the movement of the module in the liquid.

Preferably, the membrane module is suspended as a pendulum module on a pivot bearing and is capable of a rotational movement around at least one axis in addition to the pendulum movement. The rotational movement ensures that, for example, a medium blown in from a point source beneath the module, such as a gas, e.g. air, does not rise at just one point on the membrane, which is covered with solids on the outside, and causes uneven cleaning of the membranes (in particular flat or tubular membranes) of retained particles, but that the same cleaning effect occurs across the entire membrane surface. This advantageous design of the pendulum module, which is mounted on a pivot, for example, means that the otherwise required large distance between the air inlet and the lower edge of the membrane, e.g. the flat membrane, can be avoided.

The pendulum movement of the membrane module occurs due to the turbulently rising air/sludge mixture even without external intervention. However, it is also or additionally possible to impose a defined oscillation on the membrane module using an exciter. The excitation can be carried out using an externally mounted device, by periodically blowing in air pockets attached to the side or by periodically blowing a liquid jet onto the membrane or by any combination of these measures. In addition to the aforementioned even distribution of the air/sludge mixture under the membranes, the pendulum movement causes an additional speed component on the membrane surface. This also leads to effective cleaning of the membrane surface and to long-term and efficient operation of the filtration unit.

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Advantageously, the pendulum and/or rotational movement is carried out in such a way that the membrane module does not collide with the container walls.

The membrane module advantageously comprises a housing that is open at the top and/or bottom and has membranes therein. The membranes are preferably designed as flat membranes or as tubular membranes.

The tubular membranes with an external diameter of 4 to 13 mm and a length of 350 to 3000 mm are preferably coated on the outside so that the filtration process takes place from the outside to the inside. These tubular membranes are attached at one or both ends to a permeate collector, in which the permeate is drained. If the tubular membranes are attached at only one point, the free end of the tubular membranes is preferably closed. The tubular membranes in a permeate collector are advantageously arranged in a row with up to 100 tubular membranes next to one another.

The permeate collectors are designed with a flow channel on the inside, which allows the permeate to be drained from the tubular membranes to an outlet point. The individual permeate collectors are arranged parallel to one another with a distance of between 3 and 15 mm from one another.

The permeate collectors can be mounted at the top or bottom of the housing.

The flat membranes advantageously consist of flexible and smooth plates, e.g. a thin stainless steel sheet, a thin plastic plate and/or foil, which is covered on both sides with a flat membrane. The flat membranes are preferably attached to the thin and flexible support plates using a simple clamping mechanism.

This avoids complicated gluing and/or welding techniques. The support plates are preferably smooth and, also preferably, have no channels for permeate drainage. The permeate is drained from the plates, for example, through two outlets. The permeate is guided to the plate and from there to the permeate outlets through a thin support fleece on the back of the membrane. The permeate outlets of the individual plates are connected to one another, for example, by a square permeate collector (square tube). The support plates are advantageously rounded at the corners, which makes it easier to attach the clamping mechanism all the way around.

Further advantages and advantageous embodiments of the invention can be found in the following description, the drawings and the claims.

The drawing shows embodiments of a device according to the invention and describes them in more detail below. They show:

Fig. 1 shows the device according to the invention suspended in a container;

Fig. 2 the device according to the invention arranged floating in a container,

Fig. 3 two cross sections of an externally coated tubular membrane (longitudinal and transverse view),

Fig. 4 the arrangement of the externally coated tubular membranes in a row
0 Fig. 5 the schematic structure of a cassette with tubular membranes,

Fig. 6 a partial section through the edge area of the plates

Fig. 7 shows a partial section through the membrane plates in the area of the permeate discharge.

The device shown in Fig. 1 shows the membrane module (1) suspended in a container (2). The container (2) is filled with a mixture of substances (e.g. activated sludge) (4) up to a liquid level (3) and is fed with inflow (5). A compressed gas (7), preferably air, is fed directly under the membrane module (1) through an aeration device (6). The gas inlet of the aeration device (6) is preferably fixed, but can also be flexible.

The gas/liquid mixture produced here rises upwards through the membrane module (1) and leads, on the one hand, to the cleaning of the membrane surface of retained substances and, on the other hand, to vibration excitation. This allows the membrane module (1) to move about at least one axis (8). By applying a transmembrane pressure difference, preferably by means of a negative pressure on the permeate side, permeate

(9) is removed from the system through the membrane. All particles (e.g. bacteria) that are larger than the pore diameter of the membrane are retained on the membrane surface. The pore diameter of the membrane can, for example, be in the range of 0.01 to λΩ. The substances that do not pass through the pores adhere to the outside of the membrane and are cleaned off by the rising gas/liquid mixture. The vibrations of the membrane module (1) caused by the turbulent gas injection can be further amplified by a vibration exciter (10). The dotted line that crosses the membrane module (1) diagonally indicates that a flat membrane with a support plate and double-sided

Membrane coating is shown schematically. The double arrow under the membrane module (1) shows the direction in which the membrane module (1) swings. The direction of rotation of the membrane module (1) around the axis (8) runs perpendicular to it. The suspension of the membrane module (1) can be designed as a simple pivot bearing or as a point suspension.

The device shown in Fig. 2 differs from that shown in Fig. 1 only in that the membrane module (1) is mounted floating in the container by means of a suitable floating body (11).

Fig. 3 shows the structure of an externally coated tubular membrane with an external membrane or separating layer (12) and an internal supporting fleece (13), once in longitudinal cross-section and once in plan view.

Fig. 4 shows the row-like arrangement of the tubular membranes on a permeate collector (14). Up to 100 tubular membranes can be attached close to one another in a row on a permeate collector (14) and have a closure at the free end. A permeate collector (14) can also be attached at both ends. A closure (15) is then omitted.

Fig. 5 shows the structure of the membrane cassettes with flat membranes, consisting of two membranes (12) with supporting fleece (13) and a thin, smooth plate (16) with a thickness of less than or equal to 2 mm. The corners of the plate and the membranes are rounded so that the 0 adhesive/clamping mechanism can be attached to them.

Fig. 6 shows a section through the edge area of a flat membrane. In addition to the elements already shown in Figure 5,

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known parts, the two membranes (12), the supporting fleece (13) arranged centrally between them and the thin, smooth plate (16), also the clamping profile (17) with which the membranes (12) are attached to the thin, smooth plate (16).

The clamping device such as this clamping profile (17) makes it possible to dispense with complex gluing and welding methods for mounting the flat membrane and to easily replace faulty membranes.

Fig. 7 shows a section through the membrane module with the permeate discharge (18). This consists of a square tube with holes (20) on all sides for the discharge of the permeate. The permeate is passed through one of the two membranes (12) via the support fleece (13) to the thin plate (16) and from there the permeate passes through spacer and discharge discs (19) into the space outside the square tube and from there through the holes (20) into the square tube. The permeate is then attracted to one or both sides of the square tube. The individual flat membranes are fixed against each other with spacers (21). In this preferred embodiment of the flat membrane, it is not necessary to structure the thin plate to discharge the permeate (for example by forming channels), but simply a smooth plate is sufficient so that the permeate can drain off.

The invention relates to a device for separating a permeate, whereby a membrane module such as a cassette with 0 membranes is immersed in a liquid mixture from which the permeate can be separated. The membrane module can carry out at least one rotary and/or pendulum movement so that a

uniform flow to the membrane module from a fixed gas inlet is ensured.

All features presented in the description, the following claims and the drawings can be essential to the invention both individually and in any combination with one another.

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List of reference symbols

1 pendulum module

2 containers

3 Liquid level

4 Mixture of substances

5 Wastewater

6 Ventilation device

7 Gas

8 Axis

9 Permeate

10 Vibration exciter 11 Floating body

12 Membran

13 Support fleece

14 Support plate

15 clamping profile

0 16 Permeate discharge from square tube

17 spacers

18 holes

19 Space

Claims (18)

1. Device for separating a permeate from a liquid/solid mixture, characterized in that at least one membrane module with permeate discharge is immersed in the liquid/solid mixture and attached in such a way that it can carry out at least one pendulum and/or rotary movement. 2. Device according to claim 1, wherein the membrane module is completely immersed in the liquid/solid mixture. 3. Device according to claim 1 or 2, wherein the membrane module is attached to a holder in such a way that, in addition to a pendulum movement, it can also perform a rotary movement about at least one axis and/or can be raised or lowered. 4. Device according to one of the preceding claims, wherein the holder is a rotary bearing. 5. Device according to one of the preceding claims, in which the holder is arranged floating in the liquid/solid mixture. 6. Device according to one of the preceding claims, in which the holder is arranged above the liquid/solid mixture so that at least one membrane module can be added or removed during operation of the device. 7. Device according to one of the preceding claims, wherein the membrane module has an integrated permeate discharge. 8. Device according to one of the preceding claims, in which the membrane module is connected to a permeate collection line via at least one opening and/or is held together by means of a clamping device. 9. Device according to one of the preceding claims, in which the permeate collection line is a square tube. 10. Device according to one of the preceding claims, in which an exciter is provided by which the membrane module is movable. 11. Device according to one of the preceding claims, wherein the exciter comprises a medium such as a gas and/or a liquid. 12. Device according to one of the preceding claims, in which the introduced medium sets the membrane module in motion and/or cleans the membrane of adhering solids. 13. Device according to one of the preceding claims, wherein the exciter is a mechanical vibration exciter. 14. Device according to one of the preceding claims, wherein the membrane module comprises at least one flat membrane, a tubular membrane and/or a hollow fiber module. 15. Device according to one of the preceding claims, wherein the membrane module comprises at least one membrane with a separation limit between 0.01 and 10 µm. 16. Device according to one of the preceding claims, wherein the membrane module comprises at least one tubular membrane having an outer diameter of 4 to 13 mm and/or a length of 300 to 3000 mm. 17. Device according to one of the preceding claims, in which the membrane module comprises at least two tubular membranes arranged parallel to one another, which are connected at one end or at both ends to a permeate collector, wherein in the case of one-sided attachment to the permeate collector, the free end of the tubular membrane is closed. 18. Device according to one of the preceding claims, in which the at least two membranes are arranged parallel and at a distance of 3 to 15 mm from each other.