HU0105236A2

HU0105236A2 - Immersed membrane filtration system and overflow process

Info

Publication number: HU0105236A2
Application number: HU0105236A
Authority: HU
Inventors: Nicholas Adams; Jason Cadera; Pierre Cote; Arnold Janson; Steven Kristian Pedersen
Original assignee: Zenon Environmental Inc.
Priority date: 1999-11-18
Filing date: 2000-11-15
Publication date: 2002-04-29
Also published as: AU1376701A; AU777485B2; JP2003513784A; AT286777T; JP2003513785A; CA2360425A1; US6790360B1; DE60017360T2; DE60017360D1; ES2235983T3; AU1376401A; KR20010092783A; PL348909A1; HU0105236A3; WO2001036075A1; WO2001036074A1; HK1045471A1; EP1146954B1; JP4713801B2; CN1143725C

Abstract

A lot of filtering equipment is available for filtering water. One filter module (10) is provided with a filter membrane immersed in a water tank (36) in one of the v 's openings (12) according to the above conditions. (10) provides a filtration residue (22) from the reservoir (20), (i) introducing a certain amount of water into the reservoir (12), and (ii) filtering the total amount of water in the given amount through one module (10) of legal bb. When the water is filtered, the water is shaken, the bladder is staged periodically and the concentration is driven by the modules (10) to provide cleaning bubbles, and (I) to control. carrying (12) one or more of the modules (10) from the introduction of the t ram ram or all of these processes; and discharging water containing the retained silica material through the filtration residue stream (22). A plurality of filter cycles of the same type are included in the filter cycle, where the water (1) is extracted (12) in the solid state step and (ii) (12), whereby the concentration "in the step (iii), through the modules (10), leads to cleaning bubbles from the bottom upwards, (iv) the filter membranes. and (v) the water containing the sinter material is discharged through the modules (10) and discharged from the reservoir (12). A further variation according to step (iv) of the previous variant (12) from the modules (10) dampens water from the modules (10). The filter apparatus comprises an open holder (12), a module (10) for extracting a filtered filtrate formed from suction suction filter membranes arranged in the holder (12); the first one (10) of the module (10) is provided with a water inlet (30) formed in the supply (12), and at least one (10) f of the filter material containing water retained from the holder (12). residual effluent (22); and (b) a vent (14) arranged under a module (10). HE

Description

DISCLOSURE

COPIES

Processes for filtering water and filtering equipment

FIELD OF THE INVENTION The present invention relates to a filtering apparatus using suction filter membranes operating on the principle of suction for filtering water, for example for the production of drinking water, and to a method for operating such a filtering apparatus.

Figure 1 illustrates a submerged membrane water filter assembly used today, in which an open container is provided with a membrane module b immersed in tank water c. The feed water to be filtered flows into the container, typically continuously. The suction force at the inner surface of the filter membranes arranged in the membrane module b passes through the filtrate through the membrane wall. The filter membranes filter out the solids, which thereby accumulate in tank water c. The solids-rich filtration residue is emptied continuously or periodically from the container.

The membrane module b is partially cleaned by countercurrent washing and aeration. During countercurrent washing, washing fluid (typically filtrate or filtrate containing some chemical additive) is pumped into the compartments inside the filter membranes, which flows into the tank water c. During aeration, the aeration d of the diaphragm, mounted under module b, creates air bubbles. The air bubbles shake and clean the filter membranes and exert an air lifting effect. As a result of the air lifting action, the tank water c enters this circulation with upward flow through module b and downward flow f through portions between the circumference of module b and the walls of the tank. The tank water c circulating in the circulation e further physically cleans the filter membranes and distributes the water rich in solids near the membrane module b.

94821 -3126 / SZT / GL

It is an object of the present invention to further develop the solutions used today, that is, to develop improved filtration procedures and to provide an improved filtration apparatus for their implementation.

It is a first object of the present invention to provide a filtration process comprising (a) providing at least one module of filter membranes immersed in container water in a container open to the environment; (b) providing a filter residual outflow from the region of the container above the at least one module; (c) (i) introducing a predetermined amount of water into the container, and (ii) filtering the filtered water through the at least one module to recover substantially all of the water; (d) periodically stopping the leakage and performing a concentration-reducing step comprising providing cleaning bubbles under the modules, and (I) backwash and (II) at least one or both of these processes introducing a feed stream from the modules. is performed; and (e) removing excess water containing the retained solids during the concentration reduction step through the residual filtration stream.

The modules preferably cover a greater portion of the horizontal cross-sectional area of the container, more preferably at least 90% of the horizontal cross-sectional area of the container, and more preferably substantially all of the horizontal cross-sectional area of the container.

Further, prior to countercurrent washing, venting is preferably initiated.

Preferably, the filter membranes are formed as hollow fibers with a horizontal orientation.

On the other hand, we have achieved our object by a filtration process comprising repeating a filtration cycle consisting of a percolation step and a concentration-reducing step, wherein (i) feeding water to a container and (ii) exiting the container ; and wherein, in the concentration-reducing step (iii), the bottom-up cleaning bubbles are passed through the modules, (iv) the filter membranes are countercurrently washed, and (v) the solids-containing water is flushed up through the modules and emptied from the container.

In the process in question, the filter membranes are preferably formed in the form of horizontally directed hollow fibers and the feed water is preferably fed above the modules in the permeation step.

A further object of the present invention is to provide a new filtration process comprising repeating a filtration cycle consisting of a percolation step and a concentration-reducing step, wherein (i) feeding water to a container and (ii) suctioning the filter Who; and wherein, in the concentration-reducing step (iii), bottom-up cleaning bubbles are passed through the modules, (iv) feed water is fed from under the modules, and (v) water containing the solids is flushed through the modules and drained from the container.

A further object of the present invention is to provide a filtration apparatus comprising (a) a container open to the environment;

(b) at least one module provided in the container to obtain a filtered filtrate formed from suction membranes operating on the principle of suction;

(c) a first inflow from the at least one module into the tank by supplying feed water;

(d) a filter residual effluent formed to discharge water containing solids retained from the reservoir over the at least one module; and (e) an aerator arranged under the at least one module.

Preferably, the modules cover most of the horizontal cross-sectional area of the container, more preferably at least 90% of the horizontal cross-sectional area of the container, and more preferably substantially all of the horizontal cross-sectional area of the container.

Further, the filtration residual effluent preferably has an overflow or an overflow dam, and the filtration membranes are preferably hollow fibers with horizontal direction.

In summary, in accordance with the present invention, a filtration device with immersed suction membranes is provided for the filtration of water containing low solids suspended, for example in the preparation of drinking water, for surface water. Further, we have developed methods for operating such a filtration device.

Membrane modules are arranged in a top open container in contact with ambient air so as to cover most of the horizontal area of the containers. The upper area of the tank directly above the modules defines a space. This upper region of the tank is provided with a drainage drainage filter from the tank - through which the tank water not recovered as filtrate is discharged.

The filtrate is recovered by suction through the inner surface of the membranes, preferably at a flow rate of 10-60 l / m ² / h, more preferably 20-40 l / m ² / h. Feed water is introduced into the container at a flow rate substantially equal to that of the filtrate. As a result, during the filtration process, only a small amount of water, if any, is discharged through the filtration residue drain and the tank water level remains above the membrane modules at all times.

The filtration process is periodically stopped to perform a concentration reduction step. During the concentration reduction step, the filter membranes are subjected to counter-current washing, or subjected to feedwater flow from modules, or both processes are performed simultaneously. The membrane modules flow through the tank water, the water level in the tank rises, and the tank water containing the solids (hereinafter referred to as the filtration residue), discharging through the filtration residue drain, reduces the solids concentration in the tank water. During the concentration reduction step, purging bubbles are purged with air.

In the following, the present invention will be described in detail with reference to the accompanying drawings, in which:

Figure 1 schematically illustrates a filter assembly used today; the

Figure 2 schematically illustrates a filtering apparatus according to a preferred embodiment of the present invention; while the

Figure 3 is a cross-sectional view of another possible embodiment of a filtering apparatus in accordance with the present invention.

As shown in Fig. 2, three membrane modules 10 are numbered one above the other in a container 12. The container 12 is open from above, although in another embodiment

-5 in shape with 13 ventilated covers. The membrane modules 10 may comprise flat sheet or hollow fiber membranes having a pore size in the range of microfiltration or ultrafiltration, i.e. preferably 0.003 to 10 µm, more preferably 0.01 to 1.0 µm. The inner surface of the membranes is connected to one or more manifolds. Below the diaphragm modules 10, a vent 14 is provided which is connected via a feed pipe 16 to a source of air, nitrogen or other gas suitable for the present invention. The diaphragm modules 10 are provided with ducts to allow vertical flow of water and air bubbles through them in a horizontal cross section and thereby to allow shaking and cleaning of the membranes. When the membrane modules 10 are arranged one above the other, the modules 10 are superimposed so that water can flow vertically through a series of them.

The diaphragm modules 10 preferably consist of horizontally guided hollow fiber membranes, which are mounted in a slightly releasable position between planar pairs of vertically extending collector tubes spaced apart. Such a module 10 is one possible example! in its embodiment, it consists of a few members arranged side by side, each of which has a plurality of fibers having an outer diameter of between 0.2 and 1.0 mm and a length of between 0.2 m and 1.0 m (the shorter length for smaller diameter fibers, while the larger lengths belong to the larger diameter fibers) at both ends, placed in a collecting tube, so that the filtrate can be recovered in only one collecting tube. The individual members can be separated by vertical waterproofing plates. These membrane modules 10 provide a membrane surface area of 500 to 1500 m ² per square meter of horizontal cross-sectional area of commercially available or commercially available tanks of huge size and, in their case, minimal channel occupied or dead zone flow through the tank water modules.

The diaphragm modules 10 are dimensioned and positioned in the container 12 so as to cover a large portion of the horizontal cross-sectional area of said container 12, leaving only the necessary fittings and other equipment, as well as maintenance or commissioning procedures.

Outside the circumference of the diaphragm modules 10, there is no downstream flow

-6 seats and, if necessary, fittings etc. baffles are provided outside the periphery of the diaphragm modules to prevent flow through the left space. The diaphragm modules 10 preferably cover at least 90%, and more preferably substantially all, of the horizontal portion of the container 12.

Filtration tubes 18 of the diaphragm modules 10 are connected to filtration drainage tubes 18 by means of suction filtration at the inner surfaces of the membranes and counterflow washing unit. Such units are known to those of ordinary skill in the art and allow the filtrate drain tube 18 to be withdrawn through the membranes into the tank 12 either through the membranes to retrieve the filtrate from the container 12, or through a membrane (usually filtrate or filtrate mixed with a chemical additive). to stream. In such cases, the wash liquid becomes part of the tank water 36 in the tank 12.

The upper region 20 of the container 12 is provided with a filter residue outlet 22 having an overflow area 24 connected to the drain tube 26 for removing the filter residue from the container 12. Preferably, the filter residual outlet 22 is provided with an overflow or an overflow dam 28, which facilitates the flow of aerated foam to the overflow area 24 (which otherwise leads to purity, safety or volatile chemical release problems). Preferably, said filtration residue outlet 22 also has sufficient capacity to rapidly pass through the projected filtration residue currents to reduce the required free surface area of the container 12.

The feed water introduced into the tank 12 enters through a first inlet 30 or a second inlet 32 designated by the position of the supply valves 34. After the feed water has entered the tank 12, it is referred to as the tank water 36, which usually flows upwards or downwards through the membrane modules 10 ........

The filtration cycle consists of a percolation step and a concentration reduction step, and is repeated many times between significantly more intensive maintenance or refurbishing cleaning processes. The permeation step usually lasts about 15-60 minutes, preferably 20-40 minutes, and is carried out without aeration. Preferably, the filtrate has a flow rate of 10-60 l / m ² / h, more preferably 20-40 l / m ² / h, wherein the hollow fiber membranes have a surface defined by their outer diameter.

During the permeation step, feed water is introduced into the container 12 through one of the first inlet 30 and the second inlet 32 at a rate substantially equal to that of the filtrate. The tank water 36 flows through the membrane modules 10, thereby replacing the filtrate usually obtained continuously from the tank 12. Accordingly, during the permeation step, little, if any, of the tank water 36 is discharged through the filter residue 22, so that the level of the tank water 36 remains above the membranes at all times. If the diaphragm module 10 functions to some extent as a volumetric filter (as is the case with diaphragm modules 10 made up of dense, horizontally directed hollow fiber membranes), the feed water preferably enters the container 12 through the second inlet 32. In this way, the solids content of a portion of the feed water is preferably deposited in the upper membrane module 10, closer to the filtration residual outlet 22, and where the flow rate of the upstream tank water 36 during the concentration reduction step will be highest. The design in question is also advantageous for the assembly of sand filters, which are usually arranged in such a way that the feed water is received from above, while the counter-current washing is received from below. For other types of membrane modules 10, designs, or feedwater, the first inlet 30 may be used during the filtration step.

The concentration reduction step begins after the leakage is stopped and lasts for about 20-90 seconds, preferably 30-60 seconds. During the concentration-lowering step, aeration bubbles are formed at the aeration 14, which as they rise, pass through the membrane modules 10. In addition, countercurrent washing and / or rinsing with feed water is also performed. To rinse with the feed water, the feed water enters the tank 12 through the first inlet 30, increasing the amount of tank water 36 upwardly through the membrane modules 10. When flushing with feed water, the flow rate of the feed water is typically 0.5 to 2 times, preferably 0.7 to 1.5 times the flow rate of the feed water introduced during filtration. Whether countercurrent washing or flushing with feedwater inlet, tank water 36 is elevated, tank water 36 flows upwardly through membrane modules 10, and solid (

In order to reduce the solids content of the tank water 36 (referred to as -8 filter residues), the filter residue 22 is discharged from the tank 12 through a drain.

In some cases, the upwardly directed reservoir water 36 may exert a force greater than its tensile strength on the membranes, particularly in the case of strong feedwater rinsing and countercurrent washing. In these cases, the flow of feed water or washing liquid or both can be reduced to reduce the rate of upwardly flowing tank water 36. Alternatively, the supplied feedwater stream may be shut off during the countercurrent wash, and rinsed with any feedwater in the absence of the countercurrent wash, or vice versa. By way of example, the first part of the concentration reduction step may preferably consist of backwash with aeration, but without rinsing with feed water, and a second part preferably include aqueous rinsing in the presence of aeration but without backwash. Another possibility is that the concentration reduction steps in certain cycles are preferably effected by backwash washing with aeration without feed rinse, while in other cycles the concentration reduction steps consist of feed water rinsing preferably with aeration but without backwash washing. Other combinations of the above processes may also be advantageously employed.

In order to reduce the total time of the concentration reduction step, the aeration is usually performed simultaneously with the other steps. However, aeration may begin a few seconds before counter-flushing or rinsing with feed water (a few seconds is needed to allow a bubble from the aeration 14 to reach the surface of the tank water 36). This venting causes turbulence in the absence of flow of tank water 36 (since no space is left for downstream flow) which, prior to the start of filtration residue flow through filtration residue 22, facilitates loosening of some impurities and a portion of the solid 12 swim near her.

It is not necessary for the aeration in the concentration-lowering step to separate the solids from the membranes

-9 · exceeds the suction power for the purpose. The surface velocity of aeration (normal air velocity expressed in m ³ / hr over 1 m ² of cross-sectional area of membrane modules 10) ranges from 25 m / hr to 75 m / hr. Many, if not all, of the feedwater supplied, especially low-turbidity feeds with a solids concentration of up to about 500 mg / l, do not require additional venting. However, in the case of heavy feedwater, a weak venting is used in the permeation step to distribute the solids from the dead strips in the membrane module 10 and homogenize the tank water 36. For this purpose, the aeration is carried out at a surface speed of up to 25 m / h or periodically at said higher speed.

In the concentration-reducing step, the feed water or wash liquid introduced into the container 12 causes the container water 36 to flow upwardly through the membrane modules 10. The tank water 36 flowing through the membrane modules 10 facilitates the removal of solids loosened by the cleaning bubbles from the membrane modules 10 and has a direct effect on the surface of the membranes. Reservoir water 36 flows most rapidly near the top of reservoir 12, which helps to reduce the exceptional sludge of the upper membranes when the membrane modules 10 are superimposed, for example at least 2 m high. Some of the solids in the tank water 36 have a sedimentation rate higher than the upward flow rate and will thereby settle. However, such solids are small in volume and may be removed from time to time by partial emptying of the container 12 through a backup drain.

Based on a nominal filtrate throughput, the feed water rate required for the permeation step can be calculated and adjusted, typically through control of a feed pump or feed valve. The frequency and intensity of the concentration reduction steps are then selected so that, over time, the desired drop in membrane permeability is achieved. If the flow rate during suction is kept below about 60 l / m ² / h, preferably about 40 l / m ² / h, it is surprisingly found that slight contamination occurs and that periodic concentration reduction steps are generally sufficient prove. More surprising, however, is the low throughput and poor venting • ·

The cost of energy saved by operating at · · · exceeds the cost of covering the tank 12 with membrane modules 10. Despite the low flow rate (compared to the more common 50-100 l / m ² / hr flow rates), high tank speeds (the value of the molten flow rate in m ³ / h divided by the tank's horizontal area in m ² ), which is beyond the reach of sand filtering. Furthermore, the required frequency of refurbishing maintenance is generally the same as that observed with single stage filtration, and refurbishing maintenance, even in the case of aggressive concentration reduction, is typically sufficient only for the first stage of two-stage filtration (where the filtration residue is re-filtered).

Figure 3 is a cross-sectional view of a larger filter apparatus than previously described. In this embodiment of the filtering device, a plurality of cassettes 220 are disposed in a container 200, each of which may contain a plurality of modules. Between adjacent cassettes 220 are provided open channels 202 for collecting tank water flowing out of cassettes 220 as described above. The channels 202 are slanted for drainage to a larger manifold 204, and the manifolds 204 are also inclined for drainage to a second outlet 206. The second outlet 206 is provided with an outlet box 208 to temporarily retain the emptying tank water prior to entering the discharge pipe 210. As illustrated in the embodiment shown in Figure 2, the feed water enters the tank 200 at a point deeper than the cassettes 220, but a plurality of second inlets 212 are connected to the inlet manifold 214 to distribute the feed water.

It is to be understood that the foregoing embodiments are merely a preferred example of a filter apparatus according to the invention. Embodiments are provided by way of example only and are not intended to limit the combination of features required to carry out the invention. It will be apparent to those skilled in the art that various modifications and other embodiments of the invention may be made without departing from the spirit and scope of the invention as set forth in the following claims.

Claims

PATENT CLAIMS

A method for filtering water, comprising: (a) providing at least one module (10) of filter membranes immersed in a container water (36) in an environmentally open container (12);

(b) providing a filter residual outlet (22) from the region (20) of the container (12) above the at least one module (10);

(c) (i) introducing a certain amount of water into the container (12), and (ii) filtering the filtered water through the at least one module (10) to recover substantially all of the water;

(d) periodically stopping the permeation and performing a concentration-reducing step to provide cleaning bubbles under the modules (10), and (I) countercurrent washing, and (II) feed water from the modules (10) to the container (12). performing at least one or all of these processes; and (e) removing the excess water containing the retained solids during the concentration reduction step through the filtration residue outlet (22).
Method according to Claim 1, characterized in that the modules (10) cover a larger part of the horizontal area of the container (12).
Method according to claim 1, characterized in that the modules (10) cover at least 90% of the horizontal cross-sectional area of the container (12).
The method according to claim 1, characterized in that the modules (10) cover substantially the entire horizontal area of the container (12).
The method of claim 1, wherein aeration is initiated prior to the backwash.
6. The method of claim 1, wherein the filter membranes are formed as hollow fibers with horizontal direction.
7. The method of claim 4, wherein the filter membranes are formed as horizontal hollow fibers.
8. A method for filtering water, comprising repeating a filtration cycle consisting of a percolation step and a concentration-reducing step, wherein the percolation step comprises

- (i) feeding water (12) into the vessel (12) and (ii) obtaining a filtrate of similar volume by suction on the inner surface of the submerged filter membranes (12); and wherein, in the concentration-reducing step (iii), the bottom-up cleaning bubbles are passed through the modules (10), (iv) the filter membranes are subjected to countercurrent washing, and (v) the solids-containing water is flushed through the modules (10); discharging from the container (12).
9. The method of claim 8, wherein the filter membranes are formed as horizontal hollow fibers.
A filtration apparatus, characterized in that it comprises (a) a container (12) open to the environment;

(b) providing at least one module (10) for recovering the filtered filtrate formed from the suction filter membranes arranged in the container (12);

(c) a first inlet (30) formed from the at least one module (10) to supply feed water to the container (12);

(d) a filtration residual drain (22) formed over the at least one module (10) to drain water containing solids retained from the container (12); and (e) an aerator (14) disposed beneath the at least one module (10).
Filtering device according to claim 10, characterized in that the modules (10) cover a larger part of the horizontal area of the container (12).
Filter device according to claim 10, characterized in that the modules (10) cover at least 90% of the horizontal cross-sectional area of the container (12).
A filtering device according to claim 10, characterized in that the modules (10) cover substantially the entire cross-sectional area of the container (12).
Filtering device according to claim 10, characterized in that the filtering residual outlet (22) has an overflow or an overflow dam (28).
The filter apparatus according to claim 10, characterized in that the filter membranes are hollow fibers of horizontal direction.

13 • · · ·
16. A filtering device according to claim 13, characterized in that the filtering membranes are hollow fibers of horizontal direction.
Method according to claim 8, characterized in that, in the permeation step, the feed water is supplied above the modules (10).
Method according to claim 9, characterized in that, in the permeation step, the feed water is supplied above the modules (10).
A method for filtering water, comprising repeating a filtration cycle consisting of a permeation step and a concentration-reducing step, wherein in the permeation step (i) feed water is supplied to the container (12) and (ii) the internal surface of the filter membranes submerged therefrom. obtaining a filtrate of a similar volume by suction; and wherein, in the concentration-reducing step (iii), bottom-up cleaning bubbles are passed through the modules (10), (iv) feed water is supplied to the container (12) from the modules (10), and (v) solids-containing water on the modules It is flushed upwards through (10) and emptied from the container (12).
20. The method of claim 19, wherein the filter membranes are formed as hori- zontally oriented hollow fibers.