EP2148840A2

EP2148840A2 - Water treatment device having discs and a rotary drum filter, and corresponding process

Info

Publication number: EP2148840A2
Application number: EP08759896A
Authority: EP
Inventors: Patrick Exposito; Jacques Debuire
Original assignee: OTV SA
Current assignee: Veolia Water Solutions and Technologies Support SAS
Priority date: 2007-05-23
Filing date: 2008-05-21
Publication date: 2010-02-03
Also published as: WO2008142128A2; WO2008142128A3; FR2916436A1; FR2916436B1

Abstract

The technique proposed here relates to a water treatment device comprising raw water inlet means (24), treated water discharge means (17, 28) and an essentially parallelepipedal frame (10) having a bottom and a cover element (11), said frame (10) defining at least: a biological treatment zone (12) accommodating a plurality of biological discs (16); and a filtration zone (13) accommodating at least one drum filter (21), at least one part of which has perforations, and sludge collecting means (33), said biological discs (16) and said drum filter (21) both being mounted essentially on the same axis (X) and having approximately the same outside diameters, the device further including means (22) for conveying a partly biologically purified flow coming from said biological treatment zone (12) within said drum filter (21). According to the technique proposed here, such a device includes means for declogging said perforations of said drum filter (21) which comprise at least means for blowing pressurized air on the periphery of said drum filter (21).

Description

Disk water treatment device and rotating drum, and corresponding method

1. Domain

The field of technology proposed here is that of biological wastewater treatment facilities.

More specifically, this technique relates to a wastewater treatment plant specially adapted for use by small communities of, for example, between 500 and 5000 inhabitants, and implementing a biomass fixed on rotating disks. 2. Prior Art

The patent number FR-B-2 166 129 describes an installation of this type, which comprises a frame delimiting a biological treatment zone and a raw water filtration zone. The biological treatment zone accommodates a rotating bacterial bed and the filtering zone accommodates a closed filtering drum with orifices.

According to this technique, the logically treated water flows inside the filter drum and is recovered at its center by means of pipe elements. The water is filtered from the outside to the inside of the drum.

As logically bio-treated water flows into the filter drum, the holes in the filter drum become clogged progressively, resulting in increased water in the filtration zone.

A declogging device, implementing a pump immersed in the filtration zone, is provided to suck the sludge present on the surface of the drum, when the water level present in the filtration zone exceeds a certain threshold.

3. Disadvantages of prior art

A disadvantage of this technique of the prior art is related to the fact that it is relatively bulky. In particular, the diameter of the bacterial bed is much greater than the diameter of the filter drum. Therefore, this installation according to the prior art implements a relatively large frame size.

In addition, the space available inside such an installation according to the prior art is not used in its entirety and there remain many empty spaces.

In particular, this technique involves filtration from the outside of the drum inwards. This results in the implementation of a suction unclogging device on the surface of the drum, which occupies a large space in the filtration zone.

Another disadvantage of this technique of the prior art is that the motor used to rotate the bacterial bed and the filter drum is placed outside the frame, which reduces the compactness of such a device. installation. This technique of the prior art also has the disadvantage of implementing a complex declogging device including the fact that it involves the integration of a pump immersed in the liquid to be treated and that its operating principle requires measurement the level of water present in the filtration zone. In addition, such a declogging device, the operation of which consists in generating a vacuum in order to suck the sludge at the surface of the drum, tends to accelerate the degradation of the filter drum, and thus to reduce the service life thereof.

In addition, the sludge harvested by means of such a declogging device are directly discharged into the liquid to be treated. This limits the thickening of the sludge, and induces water losses because the sludge harvested is loaded.

Another disadvantage of this technique of the prior art comes from the fact that the axis of rotation on which the bacterial bed is mounted and the filter drum is immersed in whole or in large part in the water, and is thus subjected to fouling, corrosion phenomena. Such an architecture therefore requires frequent maintenance operations, which can be long and therefore represent a significant cost item.

Such a technique according to the prior art also has the disadvantage of providing a processing capacity limited to a community size for which it was designed, without being easily adapted to other needs. It therefore has a modularity almost inextensible.

4. Objectives of the technique proposed here

The technique proposed here is intended to overcome these disadvantages of the prior art.

Specifically, an objective of this technique is to provide a water treatment device that has a relatively small footprint, with equal capacity, compared to the techniques of the prior art.

Another objective of this technique is to make it possible to optimize the use of available space in order to improve the filtration capacity for a given volume.

Another objective of this technique is to improve the life of such a device while facilitating and limiting the frequency and duration of maintenance operations it may be required to undergo. The technique proposed here again aims to simplify and facilitate unclogging while improving the drying of harvested sludge.

The present technique also aims to be flexible and in particular to present a processing capacity that can, to a certain extent, be easily adapted to the needs, without the need for major modification of its architecture.

5. Presentation of the technique proposed here

These objectives, as well as others which will appear later, are achieved by means of the technique proposed here which concerns a water treatment device comprising raw water supply means, evacuation means of treated water, and a substantially parallelepipedic frame having a bottom and a cover member, said frame defining at least:

a biological treatment zone accommodating a plurality of biological disks, and

a filtration zone accommodating at least one filter drum element, at least one part of which has perforations, and sludge collecting means, said biological disks and said filtering drum being mounted substantially in the same axis and having external diameters of substantially equal value; the device further comprising means for conveying a logically partially purified flow from said biological treatment zone into said filter drum member.

According to the technique proposed here, such a device comprises means for unclogging said perforations of said filter drum element comprising at least pressurized air diffusion means at the periphery of said filter drum element.

This technique is based on an innovative approach to regularly clean the filter drum in order to maintain its level of efficiency.

In addition, the diffusion of pressurized air on the surface of the filter drum makes it possible to effectively unclog the perforations provided on its surface, while limiting the hydration of the harvested sludge. The collected sludge can therefore be drained with greater ease, and the treated water losses reduced.

Furthermore, it is also provided according to the present technique that filtration by the filter drum is from the inside to the outside of it, the flow partially biologically purified logically being injected into the filter drum and passing through its surface when it is rotated.

Such an approach makes it possible to avoid the implementation of means for conveying the partially biologically purified flow logically to the outer surface of the drum. This also makes it possible to avoid the use of means of unclogging and sludge recovery, of substantial size, to the outer surface of the filter drum. As a result, the filtration zone accommodating the filter drum may have a reduced volume compared to the prior art.

The proposed technique also provides for the implementation of biological disks and a filter drum of substantially equal diameters. This approach makes it possible to optimize the use of the available space while increasing the filtration surface and consequently the filtration capacity of the device for a given volume.

According to such a characteristic, the volume of the biological treatment zone can be optimized while allowing the biological treatment zone and the filtration zone to be relatively compact.

In addition, such a device according to the technique proposed here is flexible in that its filtration capabilities can easily be varied by simply adding or removing biological disks, without major modification of the overall architecture of the device, that is to say by re-using the main elements that make it up.

According to an advantageous characteristic of the present technique, said axis extends at a distance from said bottom of said frame, said distance being greater than the maximum height of water likely to be reached in said device during the implementation of a treatment method of passing water to be treated therein.

Thus, the guide elements of the biological disks and the filter drum, for example bearings, are permanently out of water. Their life is therefore improved. Preferably the device according to this technique, comprises motorization means included in said frame and provided in said axis.

Providing that the motorization means are included in the frame increases the compactness of the treatment device. In addition, the motorization means extending in said axis, they are also out of water. Besides the fact that this makes it possible to increase their lifespan, this makes it possible to facilitate their maintenance insofar as access to motorization means does not require in particular drain the installation.

Advantageously, said biological disks and said one or more filter drums are mounted on the same shaft which can be rotated by said motorization means.

Such an approach makes it possible to reduce the number of parts involved in producing such a treatment device.

According to an advantageous characteristic, the device presented here comprises a treated water retention zone which extends essentially in the lower part of said filtration zone.

After being treated, the treated water flows by simple gravity into such a retention zone.

Advantageously, said unclogging means comprise pressurized water diffusion means at the periphery of said filter drum element.

The projection of pressurized water ensures good loosening of the sludge closing the perforations in the filter drum.

Preferably, said water diffusion means are connected to sensing means communicating with said treated water retention zone. Treated water can thus be used to unclog the filter drum. A certain amount of the water projected on the filter drum flows along the latter before finishing its course in the treated water retention zone. The projection of treated water has the particular advantage of preventing a degradation of the quality of the treated water contained in the retention zone. According to a preferred aspect of the technique described herein, said collection means comprises a chute member which extends within said filter drum member substantially opposite said unclogging means.

The implementation of such a chute ensures efficient recovery of sludge that peel off the filter drum. Moreover, the provision that this chute is housed inside the filter drum makes it possible to increase the space available for its implantation in the chassis. It is then possible to implement a filter drum having, for a given volume of installation, a larger diameter. An installation according to the invention therefore has a relatively large processing capacity and compactness compared to the techniques of the prior art.

Preferably, a water treatment device according to this technique comprises means for raising said treated water.

The implementation of such lifting means may allow, depending on the configuration of setting up a treatment device in its environment, to raise the level of the water treat so that it is removed from the water. installation by simple gravity flow.

Preferably, said lifting means comprise a trough wheel mounted on said shaft, and in that said means for discharging treated water comprise a trench element capable of collecting the treated water contained in said troughs and which extends above said tree.

The implementation of such a trough wheel makes it possible simply and effectively to evacuate the treated water from the gravity flow treatment device by pouring it into a channel provided for this purpose, without requiring the use of complex means such as, for example, a lift pump.

According to a preferred embodiment of the present technique, said frame further delimits a screening area upstream of said biological treatment zone, said screening area receiving a rotary screen element mounted on said shaft.

Pretreatment of the raw water is used to remove a portion of particles of relatively large size, which may be in suspension. This makes it possible to improve the effectiveness of the subsequent biological treatment. Advantageously, the diameter of the holes of said sieve element rotating to a value between 1 and 10 millimeters.

Preferably, the diameter of said perforations of said filter drum is between 10 and 40 micrometers.

According to a preferred feature of the technique proposed here, said frame further delimits a dewatering zone of said sludge placed downstream of said filtration zone, said dewatering zone accommodating at least one roller element mounted on said shaft and whose at least one portion has a plurality of orifices.

Sludge collected in the filtration zone is dehydrated, at least in part, in the dewatering zone. This makes it possible to limit the losses in treated water and to facilitate the storage and / or subsequent treatment (s) of the sludge (s).

Advantageously, the diameter of said orifices of said roll has a value between 20 and 200 microns. Preferably, said means for collecting said sludge communicate with said roller element.

The sludge collected in the filtration zone can be directly and simply introduced inside the roll in order to be dried.

According to an advantageous characteristic of this embodiment of the present technique, the installation comprises first means for compaction of residues of said screening and / or second means of compaction of said sludge from said drying zone.

These compaction means make it possible to dehydrate the sludge and / or the screening residues further and to reduce their volume so as to facilitate their storage and / or handling.

The technique presented here also relates to a method of water treatment consisting of passing water in a water treatment device according to the present technique, and admitting water to be treated in the biological treatment zone of to remove certain pollutants, and then admit said partially purified flow from said treatment zone biologically in said filtration zone so as to filter it from the inside of said filter drum member outwardly therefrom and to separate said sludge from said biologically partially purified flow.

According to the present technique, such a method comprises a step of unclogging said filter drum element, said unclogging step of implementing said air diffusion means alone or in combination with said water diffusion means.

Preferably, the implementation of said air diffusion means is permanent, and the implementation of said water diffusion means is intermittent.

This approach allows for an efficient unclogging while reducing the declogging phases with water. The hydration rate of the collected sludge and the losses in treated water are reduced accordingly. In addition, the subsequent treatment that the sludge can undergo is also simplified. 6. List of figures

Other characteristics and advantages of the technique proposed here will appear more clearly on reading the following description of preferred embodiments, given as simple illustrative and non-limiting examples, and the appended drawings, among which: FIG. 1 shows a perspective view of a water treatment device according to a first embodiment of the present technique; Figure 2 illustrates a side view of the water treatment device illustrated in Figure 1; Figure 3 is a perspective view of the device of Figure 1 in which the cover and the frame are not shown; Figure 4 is a top view of a water treatment device according to a second embodiment of this technique; Figure 5 is a side view of the water treatment device shown in Figure 4. 7. Description of embodiments of the technique proposed here

7.1. Recall of the principle

The general principle of the technique proposed here is based on the implementation of the unclogging means of the perforations of the filter drum element comprising at least air diffusion means under pressure at the periphery of the filter drum element.

In addition, the diffusion of pressurized air on the surface of the filter drum makes it possible to effectively unclog the perforations provided on its surface, while limiting the hydration of the harvested sludge. The collected sludge can therefore be drained with greater ease, and the treated water losses reduced. The present technique also relates to the implementation of means for conveying the logically purified biological flow directly inside the filtering drum so that it undergoes filtering from the inside to the outside of the drum. filter.

This particular approach of the technique proposed here makes it possible in particular to avoid the implementation of means for conveying the purified flow to the surface of the filtering drum. It also makes it possible, because the deposition of sludge is formed on the inner surface of the filtering drum and not on its outer surface, to avoid the use of non-suction declogging means and sludge recovery means. outside the drum. This frees space to implant the drum inside the treatment device.

The technique proposed here provides that the biological disks and the rotary drum have a diameter of the same value, and are mounted substantially in the same axis.

This notably makes it possible to improve the filtering capacity of the treatment device according to the technique proposed here in a relatively compact size. reduced, especially in comparison with the techniques of the prior art, which gives it a good compactness.

Moreover, the axis in which the biological disks and the rotating drum are essentially mounted extends above the maximum level of water that can be reached inside the device during the implementation of a method of water treatment using a device according to the technique proposed herein. This makes it possible to limit the wear, for example at the level of the shaft and its bearings, in particular because of the reduction of the risk of fouling and corrosion that they can undergo when they are immersed. The longevity of the treatment device according to the technique proposed here is therefore increased while limiting the frequency of maintenance operations. The out of water of these parts making up the treatment device also makes it possible to facilitate the maintenance operations when they are necessary, and consequently to reduce their duration and their cost.

7.2. Example of an architecture of a water treatment device according to a first embodiment of the present technique

In relation to FIGS. 1 to 3, a first embodiment of a water treatment device according to the technique proposed herein is presented.

As it appears, this water treatment device comprises a substantially parallelepipedal frame 10 whose side faces and the bottom face (also called bottom) are formed by not shown casing elements, so as to define a tank that may contain some water. This frame 10 can be closed in its upper part not a lid 11 secured to the frame 10 by means of hinges not shown. He is destined to be buried. The frame 10 delimits a biological treatment zone 12 and a filtration zone 13 separated by a substantially vertical wall 14. The upstream face of the frame 10 has water inlet means in the form of an inlet pipe. water to be treated 24 in the biological treatment zone 12. The biological treatment zone 12 accommodates at least one batch 15 of a plurality of biological disks 16. In this embodiment, three batches of biological disks 16 are implemented. In variants of this embodiment, a variable number of batches 15 may be implemented, their number being chosen according to the biological load contained in the water to be treated, that is to say according to the capacity or equivalent inhabitants of the treatment device. A treatment device according to the technique proposed here thus has a capacity that can vary between 500 and 5000 population equivalents by simply adding lots 15 of biological disks 16, without requiring significant modification of its architecture, which gives it a good modularity.

The biological disks 16 are mounted on a single shaft 17 guided in rotation relative to the chassis 10 by means of bearings 18, and rotated by an electric motor 19. This motor 19 is secured to a platform 20 integral with the chassis 10. In a variant of this embodiment, it can be provided that the electric motor 19 is powered by renewable energy. Such a configuration has the particular advantage of being able to have a completely autonomous water treatment device that can for example be implemented, without particular difficulty, in areas without an electricity generating facility.

Providing for the implementation of the single shaft 17 makes it possible to limit the number of parts and to use only one motor to drive all the moving parts in rotation.

The filtration zone 13 accommodates a filter drum element 21 mounted on the shaft 17. The biological disks 16 and the filter drum 21 are thus mounted in the same axis X, which is in this case that of the shaft 17. The periphery of the filter drum 21 is covered with a filter cloth (also called mass or filter material) and is traversed by a plurality of perforations whose diameter is advantageously between ten and forty micrometers. The outer diameter of the biological disks 16 and the filter drum 21 are substantially equal.

The biological treatment zone 12 communicates with the filtration zone 13 by means of conveyance in the form of a pipe 22 which opens into the rotating drum 21. The upstream end of this pipe 22 is placed at a distance of level N that can be reached by the water to be treated in the biological treatment zone 12. This level N is greater than the level n of treated water contained in a retention zone 23 which extends essentially in a lower part of the zone The water level in the biological treatment zone 12 is greater than the water level in the filtration zone 13 so that the logically partially purified biological flow from the biological treatment zone 12 flows. by gravity in the pipe 22 towards the filter drum 21.

The water levels N and n are less than a distance d between the axis X of the shaft 17 of the bottom of the frame 10. The shaft 17, the bearings 18 and the motor 19 are therefore permanently out of water .

In addition, the downstream face of the frame 10 has a channel forming overflow 25, which extends at a distance L from the bottom of the frame 10. This distance L is less than the distance d so that the water level in the frame 10 can not reach the shaft 17. This distance L is also lower than the level N of water in the biological treatment zone 12 so as to prevent a return of treated water from the filtration zone 13 to the zone of filtration. biological treatment 12.

The filtration zone 13 also accommodates lifting means in the form of a trough wheel 26 mounted on the shaft 17. The treated water contained in the retention zone 23 can thus be raised by means of the impeller. troughs 26 to be discharged into treated water recovery means in the form of a channel 27, which extends near the trough wheel 26, in an upper part of the filtration zone 13 of the frame 10. The channel 27 is connected to a treated water discharge pipe 28 which allows to convey the treated water outside the treatment device. In a variant of this embodiment, the pipe 28 can communicate directly with the retention zone 23. Such a variant can be implemented when it is not necessary to raise the treated water to ensure its gravity flow. outside the treatment device. The filtration zone 13 also accommodates means for unclogging the perforations provided at the periphery of the filtering drum 21.

These unclogging means comprise a ramp 29 provided with a plurality of diffusers 291 of pressurized water facing the periphery of the filtering drum 21. The ramp 29 is connected by a pipe 30 to means of capture taking the form of a strainer 31 dipped in the treated water retention zone 23. A pump 32, joining the pipe 30 and the ramp 29, makes it possible to draw treated water into the retention zone 23 and to diffuse it to the surface filter drum 21 by the diffusers 291, at a pressure of the order of one bar.

Sludge collection means, taking the form of a chute 33, make it possible to recover the sludge formed on the inner surface of the filtering drum 21. This chute 33 extends substantially horizontally inside the filtering drum 21 opposite the 291 diffusers, and is connected to a pipe 34 which can convey the sludge outside the treatment device, for example towards a treatment zone. In a variant of this embodiment (not shown), the unclogging means also implement a ramp provided with pressurized air diffusers, connected to means for producing air, which may for example comprise a compressor. As will be explained in more detail later, these air diffusers can be permanently activated, while the water diffusers 291 can be activated intermittently, in order to avoid loading sludge water and to promote accordingly their thickening.

7.3. Example of an architecture of a water treatment device according to a second embodiment of the present technique FIGS. 4 and 5 show a second embodiment of a water treatment device according to the technique proposed here.

This second embodiment shares a number of elements in common with the first embodiment described above. Only the major structural differences between these two embodiments will be described here.

In this second embodiment, the frame 10 further delimits a screening zone 34 placed upstream of the biological treatment zone 12 and separated therefrom by a substantially vertical partition 35. The screening zone 34 accommodates a forming element rotary screen 36, mounted on the shaft 17, and whose periphery has a plurality of holes whose diameter is advantageously between one and ten millimeters. Furthermore, in this embodiment, the water introduction pipe 24 to be treated opens into the rotary screen member 36. As will be explained in more detail later, the rotary screen 36 allows coarse filtering of the water to be treated in order to remove some solids that may be in suspension.

As it appears in FIG. 4, the inlet of a screening compactor 41 is housed inside the rotary screen element 36. This screening compactor 41 comprises a hollow part which incorporates a worm of which the pitch decreases and one end stops before a dispensing nozzle 42, so as to compress and dehydrate the screening residues. The water separated from the screening residues flows in the lower zone of the screening zone 34 (this makes it possible in particular to limit the losses of water), whereas the compacted screening residues are collected at the level of a spout. distribution 42.

Furthermore, the frame 10 also defines a sludge dewatering zone 37, placed downstream of the filtration zone 13, and separated from the latter by a partition 38. This dewatering zone 37 accommodates a roller element 39 mounted on the shaft 17, and whose surface has a plurality of orifices whose diameter is between 20 and 200 microns. The trough 33 inside which the sludge present on the surface of the filter drum 21 is collected is connected to a duct 40 which opens into the interior of the roll 39.

The inlet of a sludge compactor 43 opens into the roll 39. This compactor 43 makes it possible to harvest the dried sludge. It comprises a hollow portion inside which is rotatably mounted a worm whose pitch decreases, and one end of which stops at a certain distance from a spout 44. This screw makes it possible to compact the dried sludge and to dehydrate them even more. The compacted sludge is recovered at the spout 44 while the water separated from the compacted sludge flows into the retention zone which extends below the dewatering zone 37.

7.4. Method of water treatment according to the technique proposed here

A method of water treatment by the implementation of a treatment device according to the technique proposed here will now be described. The water treatment method described below consists of passing water to be treated in a water treatment device according to the second embodiment.

Such a water treatment method consists in introducing water to be treated in the screening zone 34, more precisely inside the rotary screen element 36, by means of the water introduction pipe. to be treated 24.

The motor 19 is supplied with electrical energy so that it rotates the shaft 17, at a speed of the order of five tr.mn ^-1 , and all the elements connected to it, such as the sieve. rotary disk 36, the biological disks 16, the filter drum 21, the bucket wheel 26, the roller 39. The rotation of the rotary sieve element 36 makes it possible to screen the water to be treated, treatment which is from the inside to the outside of the rotary screen member 36.

The refusals of the screening gradually come to cover the inner wall of the rotary screen member 36. These screening refusals can be detached from this inner wall by the implementation of means of unclogging with treated water (not shown), substantially similar to those used for unclogging the filter drum 21. These screening refusals fall at the entrance of the screening compactor 41 and are compacted by the screw that it houses before being recovered at spout 42. The partially purified flow from screening area 34 then flows into biological treatment zone 12 for aerobic and anoxic biological treatment. Carbon pollution and nitrogen pollution are treated by rotating the biological discs 16 on which biomass develops. Indeed, because the biological discs 16 are rotatable and partially immersed, the biomass therein is alternately immersed and emerged. During its emergence phases, the biomass takes the oxygen necessary for breathing. During its immersion phases, biomass absorbs some of the dissolved pollution it feeds on.

The logically partially purified flow then flows, by gravity, into the interior of the pipe 22, into an inner region of the filter drum 21. The logically partially purified flow then flows through the filter material (not shown). covering the periphery of the filter drum 21 driven by a rotational movement. In this way, the sludge formed during the biological treatment, and essentially composed of excess biomass from the biological disks 16, separate from the treated liquid by settling on the inner wall of the filter drum 21. The treated liquid flows in the treated water retention zone 23.

The fact that the logically partially purified flow is injected directly into the filter drum 21 induces filtration of this flow from the inside of the filter drum 21 towards the outside thereof. It is therefore not necessary to provide for the implementation of means of admission of the partially biologically purified flow logically to the surface of the filtering drum 21. This characteristic makes it possible to increase the diameter of the filtering drum 21 because it can occupy the maximum space available in the treatment device. The filtration surface is therefore increased. This has the advantage of increasing the filtering capabilities of the device for a given volume.

In addition, this principle of filtration from the inside towards the outside makes it possible to avoid the use of suction means so that the partially biologically purified flow logically passes through the surface of the filtering drum 21. the technique proposed here, the flow partially biologically purified flows by gravity, without suction means housed inside the filter drum 21, and then passes through the surface of the filter drum 21 because it rotates. This implementation is therefore greatly simplified. According to this principle of filtration from the inside to the outside, the sludge is deposited on the inner face of the filter drum 21. This makes it possible to avoid the use of sludge suction means on the outside of the filter drum. ci, and increase the space available for its implementation in the treatment device. The treated liquid accumulated in the retention zone 23 is then caught by the troughs of the trough wheel 26. The contents of each of the troughs are discharged, at each rotation of the trough wheel 26, in the channel 27, then flows into the treated water discharge line 28, for example towards a storage area. As the sludge is separated from the logically partially purified flow by being deposited on the filtering mass (or filter cloth) covering the periphery of the filter drum 21, the perforations it presents clog. The declogging means are thus activated, preferably intermittently, in order to loosen the sludge covering the inner surface of the filtering drum 21.

For this purpose, the pump 32 is started to collect treated water in the retention zone 23 by means of the strainer 31, and then to diffuse it at a pressure of about one bar, on the surface of the drum filtering 21 via the diffusers 291. Under the action of the pressure of the diffused water, the sludge is detached from the filter drum, collected inside the trough 33, and then discharged out of it by the pipe 40.

In a variant of the technique proposed here, in which the unclogging means further comprise pressurized air diffusers, these are permanently activated so as to prevent the perforations of the filtering drum 21 from being plugged. In parallel, pressurized water diffusers 291 are activated intermittently. Such an implementation makes it possible to limit the hydration of the sludge, to facilitate its drying, and to reduce the losses in treated water.

The sludge is then directed to the dewatering zone 37 and open into the interior of the roller 39 which is rotated. Due to the rotation of the roller 39, the sludge, which has slightly loaded with water during the projection of water necessary for their separation from the filter drum 21, is dried. The collected water flows into the retention zone 23. Such an approach not only allows drying the collected sludge, but also to harvest a portion of the water they contain. This makes it possible to increase the quantity of treated water recovered and to reduce the losses of treated water accordingly. The dried sludge then falls to the inlet of the sludge compactor 43 and then enter and are compressed under the action of the worm it incorporates. The sludge is thus dehydrated further. The water separated from the dried and then compacted sludge flows into the retention zone under the dewatering zone. The compacted sludge is recovered at the spout 44 so as to be processed or stored.

In order to promote the separation of dried sludge agglomerated on the roller 39, additional declogging means may be provided. These advantageously comprise means for diffusing air under pressure on the surface of the roller 39. If, during the implementation of the water treatment method just described, the flow of raw water (also called water to be treated) introduced into the device is greater than the treated water flow rate. is evacuated, resulting in an increase in the level of treated water in the retention zone 23, the excess treated water can flow through the overflow 25 so that the shaft 17, the bearings 18 and the engine 19 are perpetually out of water. A water treatment method according to the technique proposed here may also consist of passing raw water through a water treatment device according to the first embodiment. Such a water treatment method shares a number of steps in common with the treatment method described above. Only the differences between a water treatment method implementing a treatment device according to the second embodiment or according to the first embodiment will be detailed later.

In such a water treatment method of passing raw water inside a treatment device according to the first embodiment, the raw water is directly introduced into the biological treatment zone 12 via the pipe 24. It therefore undergoes no screening in the water treatment device.

The sludge collected in the trough 33, after activation of the unclogging means, flows into a pipe 34 which makes it possible to route the sludge outside the treatment device, for example in the direction of a treatment zone. The sludge is therefore not dried in the water treatment device.

The water treatment devices described in the first and second embodiments of the technique proposed herein are adapted respectively to small communities of 500 and 1000 population equivalents. Several devices can be coupled in order to conjugate and increase their capacity. The capacity of these water treatment devices can also be increased by increasing the number of biological disks they contain. The capacity these devices can thus be brought to values of between 2000 and 5000 equivalent inhabitants.

Claims

A water treatment device comprising raw water supply means (24), treated water discharge means (27, 28), and a substantially parallelepipedal frame (10) having a bottom and a cover member (11), said frame (10) defining at least:

a biological treatment zone (12) accommodating a plurality of biological disks (16), and

- a filtration zone (13) accommodating at least one filter drum element (21) at least a portion of which has perforations, and sludge collecting means (33), said biological disks (16) and said filtering drum ( 21) being mounted substantially in the same axis (X) and having outer diameters of substantially equal value; the apparatus further comprising means (22) for conveying a biologically partially purified flow logically from said biological treatment zone (12) into said filter drum member (21); characterized by comprising means for unclogging said perforations of said filter drum member (21) comprising at least pressurized air diffusion means at the periphery of said filter drum member (21).

2. A water treatment device according to claim 1, characterized in that said axis (X) extends at a distance (d) from said bottom of said frame (10), said distance (d) being greater than the height of said maximum water (N) likely to be reached in said device during the implementation of a treatment process of passing water to be treated therein.

3. Water treatment device according to any one of claims 1 to 2, characterized in that it comprises motorization means (19) included in said frame (10) and provided in said axis (X).

4. A water treatment device according to claim 3, characterized in that said biological disks (16) and said one or more filter drums (21) are mounted on the same shaft (17) capable of being rotated by said motor means (19).

5. Water treatment device according to any one of claims 1 to 4, characterized in that it comprises a treated water retention zone (23) which extends essentially in the lower part of said zone of water filtration (13).

6. A water treatment device according to any one of claims 1 to 5, characterized in that said unclogging means comprise pressurized water diffusion means (291) at the periphery of said filter drum member (21). ).

7. Water treatment device according to claim 6, characterized in that said water diffusion means (291) are connected to sensing means (31) communicating with said treated water retention zone (23). .

The water treatment device according to any one of claims 1 to 7, characterized in that said collection means comprises a chute member (33) which extends inside said filter drum member (21). ) substantially opposite said unclogging means.

9. Water treatment device according to any one of claims 1 to 8, characterized in that it comprises means for lifting said treated water.

10. Processing device according to claim 9, characterized in that said lifting means comprise a trough wheel (26) mounted on said shaft (17), and in that said means for discharging treated water comprise an element forming a channel (27) capable of collecting the treated water contained in said troughs and which extends above said shaft (17).

11. A water treatment device according to any one of claims 1 to 10, characterized in that said frame (10) further delimits a screening area (34) upstream of said biological treatment zone (12), said screening area (34) accommodating a rotary screen member (36) mounted on said shaft (17).

The water treatment device according to claim 11, characterized in that the diameter of the holes of said rotary screen member (36) has a value of between 1 and 10 millimeters.

13. A water treatment device according to any one of claims 1 to 12, characterized in that the diameter of said perforations of said filter drum (21) to a value between 10 and 40 micrometers.

14. Processing device according to any one of claims 1 to 13, characterized in that said frame (10) further delimits a dewatering zone (37) of said sludge placed downstream of said filtration zone (13), said dewatering zone (37) accommodating at least one roller element (39) mounted on said shaft (17) and at least a portion of which has a plurality of orifices.

15. Water treatment device according to claim 14, characterized in that the diameter of said orifices of said roller (39) has a value between 20 and 200 micrometers.

16. Water treatment device according to any one of claims 14 and 15, characterized in that said means for collecting said sludge communicate with said roller member (39).

17. A water treatment device according to at least one of claims 11 and 14, characterized in that it comprises first means for compacting residues of said screening (41) and / or second compaction means (43). said sludge from said dewatering zone (37).

18. A water treatment method of passing water in a water treatment device according to any one of claims 1 to 17, and to admit water to be treated in the biological treatment zone. (12) to remove certain pollutants therefrom and then admit said partially purified flow from said biological treatment zone (12) to said filtration zone (13) so as to filter it from within said filter drum member (21) to the outside thereof and to separate said sludge from said logically partially purified flow, characterized in that it comprises a step of unclogging said filter drum member (21), said unclogging step of implement said air diffusion means alone or in combination with said means for water diffusion (291).

19. A method of water treatment according to claim 17, characterized in that the implementation of said air diffusion means is permanent, and in that the implementation of said water diffusion means (291) is intermittent.