GB2151153A

GB2151153A - Filter bed cleaning

Info

Publication number: GB2151153A
Application number: GB08428295A
Authority: GB
Inventors: Dr Ing Peter Ott; Reinhold Feller; Alfred Feller; Christian Puschel; Armin Bunger
Original assignee: PROJEKT WASSERWIRTSCHAFT VEB
Current assignee: PROJEKT WASSERWIRTSCHAFT VEB
Priority date: 1983-11-11
Filing date: 1984-11-08
Publication date: 1985-07-17
Also published as: FR2554736B3; DE3439547A1; FR2554736A1; DE3439547C2; GB8428295D0; GB2151153B

Abstract

Water is filtered through a sand bed 11 whose surface layer is progressively cleaned within the confines of a chamber which moves across the bed, while the rest of the bed continues to filter. The chamber includes an outlet 4, through which dirty water is sucked away, and a device for agitating the sand, which may be a rotating drum, as shown, or a grid which is submerged in the sand and is vibrated or supplied with compressed air which it injects into the sand. Flocculant or adsorption media may be added to the water upstream of the bed. <IMAGE>

Description

SPECIFICATION Process and Apparatus for Filtering Liquids The invention relates to a process and an apparatus for filtering via a granular filter layer. It finds particular application in the water-supply and effluent disposal sectors, as well as in the recovery of useful substances and the recirculation of water.

For filtration of liquids, it is quite common to use granular filter layers, e.g. sand. In water treatment, two filtration methods are widely used: The slow sand filters, used mainly for ground water purification, function by virtue of their fine grain as surface filter. Since in this case, a colmation layer forms very rapidly, an average filterthroughput of 4 . . . 6 m/d is only achieved, even with the hitherto possible regeneration intervals of 14 days. A more frequent regeneration is not possible with known types of equipment, since the filters have to be put out of action during regeneration.

Various methods are known for cleaning the uppermost sand layer in percolation basins or slow sand filters. These function either by means of mechanical scraper devices or hydromechanically.

With one known mechanism, the sand is picked-up with water jet pumps over the whole width of the basin, separated within the equipment, by means of a centrifugal separator to remove the sludge water, and then integrated. The sludge water is piped to waste. This mechanism is very expensive and complicated. It is not possible to purify the water while the plant is in operation.

Another system is known whereby the upper sand layer is disturbed by water jets, and deposited in a settling tank, while the specific lighter weight contaminants are removed from the filter sector with the water current. The whole process takes place beneath the filter overflow (head of water above the filter).

The disadvantages of this system are seen in that due to the hydraulic disturbance, the danger of deeper contamination of the filter bed is not excluded, with the result of an uneven surface being formed, which would have to be compensated by other means. The already concentrated sludge will be further diluted, necessitating expensive aftertreatment. For the extraction of the flushing water from the filter overflow (head of water above filter), this must not fall below a certain minimum depth.

Other systems are known in which an openbottom box is placed on the filter bed, through which the hydraulically disturbed soil-substance is extracted. More water is withdrawn from the box than is fed in for the hydraulic agitation. The contaminated water is extracted, for example, by vacuum. A major disadvantage is the high water consumption for the hydraulic vortexing and the small concentration of flushing water.

Since the fine grain slow sand filters achieve a far better cleansing effect than the high-speed filters of conventional design, it is often not possible to do without them. To achieve a high filter performance, predominantly high speed filters are used which can be re-flushed (backwashed) from below with water or with water and air. These function as deep-bed filters with filter speeds in excess of 4 m/h. The degree of purification attainable with these highspeed filters, which operate with coarse sand or gravel filter layers, is lower than slow sand filters with fine sand filter layers. The cost for re-flushing (backwashing) is very high. Moreover, it is necessary to use a narrow filter grain spectrum, otherwise the finer grain will become deposited on the filter surface, and a high pressure loss will be incurred.Furthermore, these filters are not particularly suitable for removing fibrous or pulverous substances.

The object of the invention is to develop a filter of granular material which will combine the high loading capacity of the known reversible flow filter with the good cleansing performance of fine sand filters.

The object of the invention is to develop a method of filtration through a fine grained filter layer, with this filter layer being cleanable without interrupting the operation, the cleaning action taking place superficially below the filter overflow. The envisaged means will achieve a smooth surface by mechanical and hydraulic means, will ensure a reliable cleansing effect with highly concentrated suspensions, and at the same time, avoid lower depth soiling. Different regeneration depths should be possible, as well as equally good cleansing performances in both flow directions.

The problems are solved by the characteristics described in the invention claim.

The function is as follows. During the filtration process, the laterally enclosed, open-bottom box is moved over the filter. The cleaning device gives rise to a disturbance of the filter layer up to a predetermined depth. The agitation is achieved either mechanically by the rotation of the wash drum, through the ascending gas bubbles, or through the transmitted vibrations. It is also possible to combine the gas injection with the transmission of vibrations.

Advantageously, the filter layer is excited to a resonance state, i.e. to the inherent frequency of the liquid V2 w0=- 2 with V=32g to the mean inherent frequency of the flow pipe system between the filter grains Vreai W1= 2R.

pipes orto the mean inherent frequency of the filter grain c W2= m with E F I Through the removal of the sludge from the enclosed compartment, the level of the liquid is reduced, thus causing a pressure drop relative to the remaining surface of the filter. If the medium in the filter water head is very concentrated, a higher liquid level is created in the washing compartment, due to a separate washing water infeed. As a result of the pressure drop and the sealing of the enclosed compartment relative to the filter, the liquid which has seeped in the filter through the filter layer, reaches the region of the vortexing, and then flows from there upwards. In this manner, the released contaminants are extracted upwards, thereby avoiding lower-depth soiling. The disturbed filter sand quickly settles.

For the separation of detached and colloidal water constituents, flocculation can be carried out in the filter head water. It is also possible to remove certain constituents with the aid of adsorption substances, such as activated carbon. In this case, the adsorption agent, contrary to known methods, may comprise any grain spectrum. The pulverous fraction remains in suspension in the filter head water, while the coarser fraction is deposited on the filter layer.

For the separation of finely dispersed water constituents, e.g. mono-cell algae, it is envisaged to introduce a filter ancillary into the filter head water.

After vortexing, this will settle more quickly than the substance to be filtered-off, and superficially seals the filter layer.

In the case of highly concentrated suspensions and sludges, provision can be made for feeding washing water to a compartment which is open towards the filter layer, and located in the flow direction, downstream of the enclosed compartment of the cleansing device. This second compartment will have a higher water level compared with that in the enclosed compartment.

Compared to the medium present in the filter basin, the water infiltrated alongside the wash drum generates a more intensive upwards current in the filter layer beneath the vortexing.

For the media concentrated during filtration, it is necessary to reduce the time interval between two regeneration operations. Due to the more frequent passage of the vortexing device, there is only a slightly concentrated sludge which requires an expensive aftertreatment. To overcome this disadvantage, it has been found advantageous to carry out the cleansing with two vortexing devices arranged in series in one appliance. The first device in the flow direction, disturbs the filter layer to a slight depth, as the result of which, a concentrated sludge can be extracted. The second device operates to a greater depth and enables a more intensive cleansing of the filter layer. With this arrangement, it is expedient to locate the openbottom compartment for the wash water infeed between the two devices.

The possibility of using the cleaning device in filter basins with high head water is achieved according to the invention by the fact that the laterally enclosed compartment is also closed at the top, and the sludge water infeed is fed into an extraction device, which is in the form of a pipe or trunking, extending above the water level of the basin.

In a separate embodiment of the invention, the washing water infeed in the upper section, is also in the form of a pipe or trunking extending above the water level of the basin. According to the invention, the pipe or the duct of the extraction device can be designed as one structural unit together with the pipe or duct of the washing water infeed. It is also possible to design this arrangement for deep basins with two vortexing devices with intermediate washing facility.

Compared with the currently used arrangements, the main advantages are: ~Increasing the filter speed from 5 to above 20-70 m/d, ~no interruption of the filter operation, ~energy saving about 90%, hence power supply possible via drag cable, ~low weight-transportable designs possible, - higher cleansing performance with highly concentrated suspensions, ~no operation disturbances due to stones in the filter bed, ~lower level of manning-automation simple to introduce, ~higher concentration of resulting sludge water, ~full operational effectiveness in both flow directions.

The design of the cleaning equipment also enables construction not necessarily bound to tracks.

Embodiment Examples The invention will be described below in conjunction with 9 typical embodiments with reference to the accompanying diagrammatic drawings, in which: Fig. 1: Apparatus for cleaning filter sand in filter basins with slight damming with one wash drum; Fig. 2: Apparatus for cleaning filter sand in filter basins with two-direction flow facility; Fig. 3: Apparatus for cleaning filter sand in filter basins with high damming in two-way flow directions; Fig. 4: Apparatus with flocculation in the filter head water; Fig. 5: Apparatus with adsorption in the filter head water; Fig. 6: Apparatus for cleaning filter sand with two aeration grids; Fig. 7: Apparatus for cleaning filter sand with aeration grids in deep basins; Fig. 8: Apparatus for cleaning filter sand with two vibration grids; Fig. 9: Apparatus for cleaning filter sand with vibration grids in deep basins.

In all the examples, the cleaning apparatus is used to treat fine-grain sand filter layers 11 with a grain size of 0.4 to 0.63 mm. Beneath the sand filter layers 11 there are support layers 12, provided with drainage. Through the constant cleaning of the upper region of the fine grain filter layer 11, there is a considerable improvement in performance. The attainable filter speed is 0.5 m/h for example, when flocculation of severely soiled surface water is carried out directly in the filter head water, and up to 5 m/h with pre-cleansed waters from coarse purification plants. The attained water quality is much better than with the known backwashing high-speed filters.

EXAMPLE 1 The equipment shown in Fig. 1 comprises a basic frame 5 and is moved via running wheels 6 on rails or concrete tracks in the basin length direction. The wash drum 1 is fitted to the basic frame 5, and depending on the required depth of regeneration (3 to 25 cm), can be lowered. From the basic frame 5, and in parallel to the rails 7, side walls 14 extend as far as the filter sand. Viewed in the travel direction, the rearward demarcation of the enclosed working compartment 8 is formed by a resultant sand wall.

The front seal is formed mechanically by a sealing strip 9. The sludge trough 2 is secured to the basic frame 5. The overflow edge 13 of the sludge trough 2 is adjustable in height, so that the necessary outflow volume can be adjusted. The wash drum 1 rotates at a speed of 30 to 40 rpm, while the whole apparatus moves forwards at a speed of 0.25 to 0.42 m/min. The sludge water discharge is 60 to 100 I/min, based on a 1 metre wash drum. Behind the enclosed working compartment 8 is an open-bottom tank 3 for the introduction of washing water. This washing water is in the form of pre-cleaned waste water. Due to the increased water level in the washing water tank 3, an upward current is produced in the region of the washing drum 1 in the filter layer 11, as the result of which, deposited solids can be removed.

EXAMPLE 2 The apparatus shown in Fig. 2 comprises a basic frame 5 which moves in the basin length direction by means of crawler track chains 6. In the case of highly concentrated suspensions, the wash drum 1 is arranged axially symmetric two-fold and driven in both directions. The forward wash drum in the travel direction is lowered to a regeneration depth of 3~9 cm; the rearward wash drum is lowered to a regeneration depth of 6~15 cm.

From the base frame 5, side walls extend parallel to the rails 7, 10 cm deep into the filter sand 11. The demarcation of the two enclosed working compartments 8 relative to the intermediate washing water inlet, is formed by the resultant sand walls. The rearward and forward seal is effected by sealing rails 9. As the result of the washing water infeed 3, a higher cleansing performance is achieved for very fine grain fractions. Withdrawal of the sludge water is effected both sides via the adjustable height-overflow edges 13. The wash drums 1 rotate at a speed of 30~40 rpm, while the whole apparatus travels forwards at a speed of 0.25--0.42 m/min. The sludge water outflow can be set differently for both working compartments.

By means of this arrangement, the apparatus can also be used for further concentration of highlyconcentrated suspensions (sludge) and for separating certain grain fractions from the suspension.

EXAMPLE 3 The apparatus shown in Fig. 3, for use in deep basins, is made up of a basic frame 5 (as Example 2) and moves along running wheels 6 on rails or concrete tracks 7 along the basin length. In the case of highly concentrated suspensions, the wash drum 1 is arranged axially symmetrical two-fold, and driven in both directions. The leading wash drum in the travel direction is lowered to a regeneration depth of 3 to 9 cm; the rear wash drum is lowered to a regeneration depth of 6 to 15 cm.

From the basic frame 5, and in parallel to the rails 7, side walls extend 10 cm deep into the filter sand 11. The demarcation of the two sealed working compartments 8 to the intermediately arranged washing water infeed 3 is formed by the resultant sand walls. The rearward and forward seal is effected by sealing rails 9. As the result of the washing water infeed 3, a higher cleansing efficiency is achieved for very fine grain fractions. In the working compartments 8, sludge water inlets 2 are provided. The washing water infeed 3 between the working compartments 8, is in the form of an open-bottom box which extends upwards to a pipe or shaft extending above the surface of the water level in the basin 10. Around this pipe or shaft, an extraction means 4 is provided, having sludge water inlets 2 in the working compartments 8.The extraction means 4 and the washing water infeed 3 are directed upwards as a common structural unit, as a result of which the equipment can be used in deep basins. Through the washing drums 1, the solids deposited in the filter layer 11, are flushed out together with the upwardly enforced current in the filter layer. This upwards current is caused by the infiltration of washing water in the region of the open-bottom box 3.

EXAMPLE 4 (Fig. 4) In a filter basin 10, equipped with a partially open filter base 16 for the purpose of seeping a fraction of the water into the underground, there is a drainage system 15 for removal of cleaned water, the drainage 15 is enveloped by a support layer on which the fine grain filter layer 11 rests. The crude water with the flocculation agents, is fed via the infeed 17 to the filter basin. Immediately at the infeed, there is the mixing and distribution device 18. This comprises a roller, made up of rods 19, rotating about a horizontal axis. Alternatively, two rollers of different diameter can be fitted one inside the other. The apparatus is driven at a filter speed of 0.6 to 2.8 m/h.In the case of lightly soiled waters, far higher filter speeds are possible, up to the region of known open high-speed filters, although the method according to the present invention achieves a superior water quality by virtue of the small filter grain, for example, of 0.4 to 0.63 mm. The high performance of the filter layer 11 is achieved through constant regeneration with the rotating wash drum 1. This is located within one of the compartments 8, enveloped by the encompassing walls 14, and from which, the disturbed sludge is extracted. Like the mixing and distributor mechanism 18, the drum 1 is made up of rods 19.

With a regeneration depth of 10 cm, the drum or cylinder diameter is 40 cm, for example. The overall cleaning apparatus is mounted on wheels at the edge of the basin.

EXAMPLE 5 (Fig. 5) In a filter basin 10, equipped with a partially open filter floor 16, for the purpose of percolating a portion of the water in the underground, there is a drainage system 15 for disposing of the purified water. The drainage 15 is enveloped in a support layer 12 on which rests the fine grain filter layer 11, which has a grain size of 0.4 to 0.63 mm. The water, containing activated carbon of high, fine-grain fraction, is fed into the filter basin. This is operated at a filter speed of 2 m/h at 6 minute intervals in the filter head compartment 7. The coarser fraction of the charcoal 21 with grain diameter above 0.15 0.25 mm, is deposited on the filter layer 11.

Consequently, the layer grows constantly during the process. Extraction takes place when regeneration becomes necessary.

The high performance rate of the filter layer 11 is achieved through the constant cleansing with the rotating wash drum 1. This is located within a compartment 8, enveloped by the encompassing walls 14, and from which the fine grain fraction disturbed by the drum 1, is extracted. The whole cleaning apparatus is mounted on wheels on the basin edge.

EXAMPLE 6 (Fig. 6) The apparatus shown in Fig. 6 comprises a basic frame 5 and is moved on rollers 6 in the basin length direction. For the filtration of concentrated suspensions, two series-arranged aeration grids are fitted with jets 1 in enclosed compartments 8. The aeration grids 1 comprise horizontally arranged, perforated or porous pipes. The air supply is via a pipe 22. The first grid 1 is lowered to a depth of 5 cm in the filter sand, and the following grid is lowered to a depth of 10 cm into the filter sand 11. Between the two aeration grids 1 is the washing water infeed 3. Because of the difference in water levels between the enclosed compartments 8, sealed off by rails 9, and the washing compartment 3, upward currents are caused in the region of the aeration grids 1.The air escape from the filter surface causes a breakingup of the colmation layer, while the washing water carries the contaminants upwards and out. The sludge water is discharged via sludge channels 2 with vertically adjustable overflow edges 13, to be discharged from the basin 10 via the pump 4. From the leading enclosed compartment 8 a relatively concentrated sludge is obtained, whereas with the second aeration grid 1, a much higher level of cleaning by the filter layer 11 is achieved.

In a not further described embodiment, the grid 1 is caused to vibrate. By this means, a more uniform breaking-up of the filter layer 1 is achieved.

EXAMPLE 7 (Fig. 7) The apparatus shown in Fig. 7, for use in deep basins, comprises, like the apparatus in Example 5, a basic frame 5 and moves along the basin length on rollers 6 along the concrete edge 7. Here too, two aeration grids 1 are fitted with interlying washing water inlet 3. The washing water infeed takes the form of an open-bottom box, extending upwards to a shaft reaching above the water level of the basin 10. About this shaft is the extraction device 4 with sludge water inlets 2 into the enclosed compartments 8. The extraction device 4 and the washing water infeed 3 are directed upwards as a common structural component. As in Example 6, the aeration grids 1 are fitted and are subject to compressed air supplies.

EXAMPLE 8 (Fig. 8) The apparatus shown in Fig. 8 consists of a basic frame 5, moving along the basin length on rollers 6.

For the filtration of concentrated suspensions, two series arranged vibration grids 1 are fitted in enclosed compartments 8. The first grid 1 is lowered into the filter sand 11 to a depth of 5 cm; the following grid is lowered to a depth of 1S20 cm.

The vibration grids 1 are excited by oscillators 23 via vibration transmitter 24 to the inherent frequency of the water, i.e. about 220 S~1 (forT=1O5C). Between the two vibration grids 1, is the washing water infeed 3. Due to the difference in water level between the enclosed compartments 8, sealed-off by sealing strips 9, and the washing compartment 3, upward currents are formed in the region of the vibration grids 1. The vibration in the resonance region causes a break-up of the colmation layer, while the washing water carries the contaminants upwards and away.

Sludge water is discharged via the sludge channel 2 with adjustable height overflow edge 13, and conveyed via the pump 4from the basin 10. From the leading enclosed compartment 8, a relatively concentrated sludge is obtained, while at the second vibration grid 1, a much greater degree of cleansing of the filter layer 11 is achieved.

EXAMPLE 9 (Fig. 9) The apparatus shown in Fig. 9, for use in deep basins, consists of a basic frame like that in Example 8, and moves along the concrete edges 7 in the basin length direction on rollers. Here to, there are two vibration grids 1 with interlying washing water infeed 3. The washing water infeed is in the form of an open-bottom box, extending upwards into a shaft, reaching above the water level of the basin 10.

Around this shaft is the extraction device having sludge water inlets 2 in the enclosed compartments 8. The extraction device 4 and the washing water infeed 3 form a common structural component in the upper section. As in Example 8, vibration grids 1 are fitted, excited by oscillators 23 via vibration transmitters 24.

Claims

CLAIMS 1. Process of filtration of liquids, in which the liquids are passed through a granular filter layer which functions as a surface filter, wherein the granular filter layer (11) is superficially agitated (1) at predetermined intervals within a laterally enclosed compartment (8) moved over the filter layer (11), during which time, in the region of agitation (8) an upwards current is created in the granular filter layer (11), with the agitation (1) of the granular filter layer (11) taking place without interruption of the filtration process in the remaining filter area. 2. Process according to Claim 1, wherein the upwards current in the granular filter layer (11) is created by lowering the liquid level within the enclosed compartment (8) relative to the surrounding liquid level. 3. Process according to Claim 1, wherein the upwards current in the granular filter layer (11) is created by setting a higher liquid level in the area (3) alongside the agitation (1). 4. Process according to Claim 1, wherein the agitation of the granularfilter layer (11) is caused by a rotating wash drum (1) with horizontal axis, located within the compartment (8) enclosed from the remaining filter surface, such that the wash drum (1) is moved continuously at right angles to its axis, over the filter, and the sludge is withdrawn continuously from the enclosed compartment (8). 5. Process according to Claim 1, wherein the agitation of the granular filter layer (11) is effected by introducing a gas via a number of jets (1 ) penetrating into the filter layer (11), said jets being within a compartment (8) sealed-off from the remaining filter surface, said jets (1) being continuously moved over the filter, and the sludge being continuously withdrawn from the enclosed compartment (8). 6. Process according to Claim 1, wherein the agitation of the granular filter layer (11) being effected by inducing mechanical vibrations (1) within the compartment (8), sealed-off from the remaining filter surface, such that the zone in which vibration is induced is moved continuously over the filter, and the sludge is continuously withdrawn from the enclosed compartment (8). 7. Process according to Claim 1, wherein flocculation agents are added to the liquids prior to filtration. 8. Process according to Claim 1, wherein the liquids, prior to filtration, have adsorption agents added in any grain size range and fine grain fraction, such that the coarser fraction is deposited on the filter layer (11), and the pulverous fraction being held in suspension in the filter liquid head (7). 9. Process according to Claim 1, wherein a finely dispersed filter additive is floated on the filter layer (11). 10. Process according to Claim 6, wherein the filter layer (11 ) is excited by mechanical vibrations (1 ) to the inherent frequency of the liquid, to the mean inherent frequency of the flow pipe system or to the mean inherent frequency of the filter grain. 11. Apparatus for carrying out the process according to Claim 1, wherein a filter basin (10) contains a granular filter layer (11 ) with support layer (12) and drainage (15), or a filter base (16), having a rotating washing drum (1) with horizontal axis, attached to a basic frame, said drum partly dipping into the granularfilter layer (11), and caused to move over the granular filter layer (11), said rotating washing drum (11) being encompassed by enveloping walls (14) which make up a sealed-off compartment (8) which is provided with a sludge extraction means (2). 12. Apparatus according to Claim 11, wherein the rotating washing drum (1) can be adjusted in height and is fitted to the basic frame (5). 13. Apparatus according to Claim 11, wherein the rotating washing drum (1) has horizontal rods about its perimeter. Apparatus according to Claim 4, wherein the sludge extraction (2) consists of a horizontal channel which is adjustable in the direction of the rotating wash drum (1), and having an adjustable height overflow lip (13). 14. Apparatus for carrying out the process according to Claim 1, wherein a filter basin (10) contains a granular filter layer (11) with support layer (12) and drainage (17), or a filter base (18), and a number of jets (1 ) penetrating into the filter granular layer (11 ) for injecting gas, said jets being connected to a gas supply line (15), such that the jets are located within a compartment (8) sealed-off by lateral walls (14), said compartment (8) having a sludge extraction means (2) above the jets (1). 15. Apparatus according to Claim 14, wherein the jets (1) andlor the sludge extraction (4) being adjustable in height. 16. Apparatus according to Claim 14, wherein the jets (1) for feeding-in gas are fitted on a grid (18) of horizontally arranged tubes, with the grid (10) being connected to a gas supply line (15). 17. Apparatus for carrying out the process according to Claim 1, wherein a filter basin (10) contains a granular filter layer (11) with support layer (12) and drainage (16), or a filter base (17), with a vibration grid (1) located on the granular filter layer (11) and immersing into same, said vibration grid (1) being connected with an oscillator (15) located above the water level, such that the vibration grid is located within a compartment (8) sealed off by side walls (14) and being equipped with a sludge extractor (2) above the vibration grid (1). 18. Apparatus according to Claim 17, wherein the sludge extractor (2) is adjustable in height. 19. Apparatus according to Claims 11, 14 or 17, wherein downstream of the agitation device (1) and parallel thereto, a second agitation device (1) is fitted within a second enclosed compartment (8). 20. Apparatus according to Claim 19, wherein the compartment (3) which is open towards the filter layer (11) and is envisaged for feeding washing water, is located between the two enclosed compartments (8) equipped with agitation devices (1). 21. Apparatus according to Claims 11, 14 or 17, wherein the compartment (8) sealed-off by side walls (14), is also enclosed at the top, and the outlet for the sludge water from the sludge water inlet (2) is located in an extraction device (4), which is designed as a pipe or shaft extending above the water level of the basin (10). 22. Apparatus according to Claim 21, wherein the washing water supply (3) is in the form of a pipe or shaft extending above the water level of the basin (10). 23. Apparatus according to Claim 21 or 22, wherein the pipe or shaft of the extraction device (4), and the pipe or shaft of the washing water infeed (3) are constructed as a common structural unit. 24. Process of filtration of liquids substantially as herein described. 25. Apparatus for the filtration of liquids, constructed, arranged and adapted to operate subsantially as herein described with reference to, and as shown in, the accompanying drawings. 26. Liquid filtered by an apparatus according to any one of Claims 11 to 23 or 25. New Claims or Amendments to Claims Filed on 8th February 1985 Superseded Claims 1 to 26 New or Amended Claims:~1 to 27

1. Process of filtration of liquids, in which the liquids are passed through a granular filter layer which functions as a surface filter, wherein the granular filter layer is superfically agitated at predetermined intervals within a laterally enclosed compartment moved over the filter layer, during which time, in the region of agitation an upwards current is created in the granular filter layer, with the agitation of the granular filter layer taking place without interruption to the filtration process in the remaining filter area.

2. Process according to Claim 1, wherein the upwards current in the granular filter layer is created by lowering the liquid level within the enclosed compartment relative to the surrounding liquid level.

3. Process according to Claim 1, wherein the upwards current in the granular filter layer is created by setting a higher liquid level in the area alongside the agitation.

4. Process according to Claim 1, wherein the agitation of the granular filter layer is caused by a rotating wash drum with horizontal axis, located within the compartment enclosed from the remaining filter surface, such that the wash drum is moved continuously at right angles to its axis, over the filter, and the sludge is withdrawn continuously from the enclosed compartment.

5. Process according to Claim 1, wherein the agitation of the granular filter layer is effected by introducing a gas via a number of jets penetrating into the filter layer, said jets being within a compartment sealed-off from the remaining filter surface, said jets being continuously moved over the filter, and the sludge being continuously withdrawn from the enclosed compartment.

6. Process according to Claim 1, wherein the agitation of the granular filter layer being effected by inducing mechanical vibrations within the compartment, sealed-off from the remaining filter surface, such that the zone in which vibrations is induced is moved continuously over the filter, and the sludge is continuously withdrawn from the enclosed compartment.

7. Process according to Claim 1, wherein flocculation agents are added to the liquids prior to filtration.

8. Process according to Claim 1, wherein the liquids, prior to filtration, have adsorption agents added in any grain size range and fine grain fraction, such that the coarser fraction is deposited on the filter layer, and the pulverous fraction being held in suspension in the filter liquid head.

9. Process according to Claim 1, wherein a finely dispersed filter additive is floated on the filter layer.

10. Process according to Claim 6, wherein the filter layer is excited by mechanical vibrations to the inherent frequency of the liquid, to the mean inherent frequency of the flow pipe system or to the mean inherent frequency of the filter grain.

11. Apparatus for carrying out the process according to Claim 1, wherein a filter basin contains a granular filter layer with support layer and drainage, or a filter base, having a rotating washing drum with horizontal axis, attached to a basic frame, said drum partly dipping into the granular filter layer, and caused to move over the granular filter layer, said rotating washing drum being encompassed by enveloping walls which make up a sealed-off compartment which is provided with a sludge extraction means.

12. Apparatus according to Claim 11, wherein the rotating washing drum can be adjusted in height and is fitted to the basic frame.

13. Apparatus according to Claim 11, wherein the rotating washing drum has horizontal rods about its perimeter.

14. Apparatus according to Claim 4, wherein the sludge extraction consists of a horizontal channel which is adjustable in the direction of the rotating wash drum, and having an adjustable height overflow lip.

15. Apparatus for carrying out the process according to Claim 1, wherein a filter basin contains a granular filter layer with support layer and drainage, or a filter base, and a number of jets penetrating into the filter granular layer for injecting gas, said jets being connected to a gas supply line, such that the jets are located within a compartment sealed-off by lateral walls, said compartment having a sludge extraction means above the jets.

16. Apparatus according to Claim 15, wherein the jets and/orthe sludge extraction being adjustable in height.

17. Apparatus according to Claim 15 or 16, wherein the jets for feeding-in gas are fitted on a grid of horizontally arranged tubes, with the grid being connected to a gas supply line.

18. Apparatus for carrying out the process according to Claim 1, wherein a filter basin contains a granular filter layer with support layer and drainage, or a filter base, with a vibration grid located on the granular filter layer and immersing into same, said vibration grid being connected with an oscillator located above the water level, such that the vibration grid is located within a compartment sealed off by side walls and being equipped with a sludge extractor above the vibration grid.

19. Apparatus according to Claim 18, wherein the sludge extractor is adjustable in height.

20. Apparatus according to Claims 11,15Or 18, wherein downstream of the agitation device and parallel thereto, a second agitation device is fitted within a second enclosed compartment.

21. Apparatus according to Claim 20, wherein the compartment which is open towards the filter layer and is envisaged for feeding washing water, is located between the two enclosed compartments equipped with agitation devices.

22. Apparatus according to Claims 11, 15 or 18, wherein the compartment sealed-off by side walls, is also enclosed at the top, and the outlet for the sludge water from the sludge water inlet is located in an extraction device, which is designed as a pipe or shaft extending above the water level of the basin.

23. Apparatus according to Claim 22, wherein the washing water supply is in the form of a pipe or shaft extending above the water level of the basin.

24. Apparatus according to Claim 22 or 23, wherein the pipe or shaft of the extraction device, and the pipe or shaft of the washing water infeed are constructed as a common structural unit.

25. Process of filtration of liquids substantially as herein described.

26. Apparatus for the filtration of liquids, constructed, arranged and adapted to operate substantially as herein described with reference to, and as shown in, the accompanying drawings.

27. Liquid filtered by an apparatus according to any one of Claims 11 to 24 or 26.