FR2483799A1 - Lamellar flow decantation plant to clarify treated waste water etc. - has simplified, more compact construction for given treatment capacity - Google Patents

Abstract

Process and installation for the sepn. of materials in suspension by decantation in lamellar flow between plates inclined to the horizontal. Incoming liq. flows first along a horizontal inlet leg. At the end of this first leg, the horizontal component of the flow path is changed in direction pref. through a U-turn of 180 deg. to flow along a second leg. In progressing along the first leg, the flow direction has a vertical component which is opposite to that of the flow direction of liq. progressing along the second leg. The decantation plane is used to clarify a suspension by sepn. of solid inclusion, esp. to clarify a treated waste water by removal of floccules. For a given tank vol., a predetermined treatment rate is now obtainable from a tank of reduced depth. The construction of the lamellar flow tank is simple and inexpensive.

Description

 The invention relates to a method and a device for the treatment of liquids, with the aim of separating therefrom, by gravity, suspended materials, such as flocculates resulting from the treatment of waste water.

 The separation of such materials can be carried out by decantation towards the bottom, when the sludge is heavier than the liquid, or by decantation towards the surface, generally called flotation, when the sludge is lighter and in particular charged with gas bubbles t these can have been created artificially to accelerate the phenomenon, by various means such as injection of compressed air, pressure reduction of pressurized water or electrolysis: one speaks then about aero-flotation zutou of electro-flotation.

The process is carried out in tanks fitted with scrapers or squeegees intended to collect and extract the sludge, while a pipe with overflow discharges the treated water. If we refer to the case where decantation takes place downwards, that is to say that of the devices generally called decanters, the member which allows the collection of sludge and their extraction is of course placed at the lower part of the tank. In the apparatuses for separating light sludges, generally called floats, the settling tank works in the opposite direction, so that the extracting member is then placed at its upper part, but the sequence of the segregation phenomenon is quite similar to what happens in the previous case.

 In general, the relative slowness of the process requires devices of a fairly large volume, inside which a stream of purified liquid and a thickened stream of sludge are gradually formed. The segregation time is proportional to the height of the fluid stream, so that there is no need to increase it and it is therefore impossible to increase the maximum admissible flow without correspondingly increasing the installation floor area.

 It is thus realized that there is interest in superimposing several tanks of low height, insofar as it is possible to collect the solid matter decanted in the form of sludge in each of them. This is why various types of "lamellar" separators have been developed, each element of which is intended to treat a more or less wide, but thin, liquid vein. These separators therefore consist of one or more batteries of closely spaced plates, possibly corrugated or ribbed, or of stacks of honeycomb shelving, organs mounted between vertical walls which generally serve as a support, to form series of more or less flattened parallel tubes.

 To allow the evacuation of sludge, these various elements are arranged obliquely, at a sufficiently low slope so as not to prevent the formation of two flows, one purified, the other, along one of the inclined walls, gradually laden with sludge t this slope, however, must be sufficient to allow the decanted materials to slide progressively along this wall to separate at one of the ends. Unless a transverse decantation is accepted, with the disadvantage of an inconsistent treatment , the arrangement, preferably, is such that the movement of the solid materials takes place in the opposite direction to the general direction of flow of the liquid, so that the separation which precedes the extraction takes place in a collecting zone opposite to that where there is the line for removing the purified liquid.

 In practice, the ideal slope, limited both by the vertical size and the corresponding decrease in efficiency of the device, is between around thirty degrees, in co-current devices, and around sixty degrees, in counter-current devices, more efficient as regards final purification, but more bulky in height, which can constitute a notable drawback.

The design of decanters comes up against an important difficulty, since one of the connections, that intended for the evacuation of the purified liquid or, preferably, that intended for the supply of liquid to be treated, must be made in the region of "separation", where the sludge leaves the inclined elements, before, if they are heavy, to fall towards the bottom. This requires, in practice, a purely lateral supply of each battery of plates and therefore leads to placing laterally, by interposing them consequently between the successive batteries, more or less complex systems of supply and transfer conduits avoiding creating turbulence likely to resuspend solids.

 The difficulty encountered on lamellar flotation devices, at their upper part this time, is quite similar.

 The invention aims to allow the construction of devices free of these difficulties, which will therefore be simpler to manufacture and more economical to use. Their structure will also give them, at equal volume, a higher extraction yield for a reduced vertical size.

 To this end, the subject of the invention is a method of separation by decantation of solid matter suspended in a lamellar liquid vein in movement along an inclined path relative to the horizontal. OO imposes on said liquid vein an elbow reversing its vertical movement, the segregation of the suspended solids being carried out co-current in the first part of the path, then against the current in its second part, the separation of the sludges obtained with a view to their extraction occurring at the external part of the elbow, after a transverse settling phase.

 The liquid vein is therefore folded in its middle part and, typically, this liquid vein is made to follow, descending on the heavy sludge settling tanks during the first part of the treatment, and rising in the second, two successive directions of circulation inverses, by folding it entirely to 1800, into a hairpin whose two branches, located side by side and as a rule of neighboring or even equal lengths, are advantageously arranged symmetrically with respect to a vertical plane. The flow of the settled solid matter is thus carried out along one of the inclined faces of the pin and their separation outside the elbow which connects the two branches.

For the sake of clarity of the explanations, the remainder of this description will mainly refer to the settlers for heavy sludge, it being understood that the explanations given are immediately applicable to the floats.

 On such a decanter, the liquid, to pass from the vein to go to the corresponding return vein, placed side by side, turns from 1800 to the lower part, around an axis located in a vertical plane, while the solid matters continue to be decanted towards the lower face of the pin, to separate vertically from the lower end of the turn in the direction of a collecting zone from which their extraction can take place.

Advantageously, a succession of pin circuits are superimposed along the same vertical plane, to form a row of which all the homologous openings are located at the same level. Each settling channel has a more or less rectangular flat section, the width of which is not excessive.

The implementation device therefore consists of one or more batteries of tubular passages conjugated in series of two contiguous inclined channels, interconnected and arranged so as to form a hairpin path, one of the branches of which is in communication with the supply of liquid charged with suspended matter and the other with the evacuation of clarified liquid, this at neighboring levels, the pin formed by two contiguous communicating channels, in the vicinity of its elbow and at the end of the wall of solid matter sliding, with a collecting basin provided with a means of extraction of the settled solid matter.

Advantageously, the bend of the pin can be, on the part of its external or peripheral face opposite to said sliding wall, closed by a wall insulating to a large extent the liquid current in circulation from the collecting basin with which the pin now communicates only through a relatively narrow slot
Each hairpin circuit is thus well isolated.

The upstream channel and the corresponding downstream channel being placed side by side, the successive rows generate superimposed oblique layers, the pins of which draw the lines of greatest slope. The successive layers emerging at the same level, both at their lower part than at their upper part generally embedded in the liquid, a battery of tubes is therefore, in a way, in the form of an oblique bundle of tubular passages, sectioned along two horizontal planes. These passages are connected separately in the vicinity of the first of these planes to two circuits for circulating the liquid and, in the vicinity of the second plane, at their outlet on the collecting basin provided for example with a sludge scraper, communicate on the contrary two by two,
The entire apparatus will advantageously consist of a battery of lamellar channels of rectangular section generated by a network consisting of parallel walls superposed obliquely, forming the roof and the floor of each element and cut transversely, at regular intervals, from vertical partitions. .The latter are shortened, half of the time, so as to draw several superimposed layers of similar pins, the channels of the same kind will preferably be aligned in vertical planes and connected to one another to feeder channels, the others to liquid discharge channels.

 It is also possible to form the channels or tubular passages using removable sliding elements, inserted for example between parallel vertical walls spaced by a distance corresponding to the width of one or more pins.

One can also consider using networks of more or less flattened hexagonal or triangular shape to drain the sludge along a line of the bottom wall of each tube. Due to the flat shape of the channels, this solution is however relatively unattractive: it results in complicating the construction of the device; on the other hand, it generally leads to staggered staggering of the separation openings, which may tend to increase the disturbance caused to the flow of sludge leaving a pin by the proximity of the elbows belonging to the neighboring pins.

Finally, the direction of circulation of the liquid in two successive pins of the same sheet will advantageously be reversed. Each outward or return tube will then be able to communicate at the same time with the two neighboring tubes, except of course at the ends of the apparatus, thus grouping in a way two juxtaposed channels which it has become unnecessary to separate by a wall.

 In an advantageous variant, the layout of the pins is gaucho: their descending branches and their ascending branches, always aligned respectively in parallel vertical planes, remain inclined in the same direction, but according to different slopes, adapted one for decantation at co-current, the other with settling against the current.

 We realize that the floor area of a device according to the invention is somewhat greater than that of a conventional type of device, but that its vertical size is greatly reduced, which may constitute a very significant advantage.

The structure of such a device will be explained below in detail in its application to decanters with parallel plates. In this description, reference will be made to the accompanying drawings, in which
Figures 1 and 2 are two schematic perspective views illustrating the process of the invention in its application to two types of decanters with parallel plates t
Figures 3 and 4 show the plates used in the decanter of Figure 1;
Figures 5 and 6 are views, respectively from above and in longitudinal section along the line VI-VI of Figure 5, of a settling tank comprising several batteries of parallel plates;
Figures 7 and 8 are views, respectively from above and in longitudinal section along the line Vili-Vili of Figure 7, of another type of decanter comprising several batteries of parallel plates;
FIG. 9 is a partial cross section illustrating the evacuation of the decanted solids in a hopper decanter 2
FIG. 10 illustrates another mode of lateral supply, with liquid to be clarified, of a decanter according to the invention:
FIG. 1a is a section along the line Xl-Xl of FIG. 10.

We will first refer to Figure 1, which represents, in schematic form, a settling tank 1, equipped with a single series of parallel plates 2 which, in this example, are flat plates, shown in detail on the figure 30
These plates 2 are inclined relative to the horizontal horizon and they have a notch 3, in which is engaged a partition 4, which divides the basin 1 into two parallel reaches, one 5, connected to the supply of liquid containing suspended solids, waste water for example, the other 6, connected to the discharge of the clarified liquid.

The liquid to be clarified therefore flows according to the arrow
F1, in the reach 5, and enters the tubular passages defined by the different plates 2, the partition 4 and the side wall 7 of the basin 1, in which it flows downward, along arrow F2, while the the solid particles it contains also flow towards the bottom, therefore co-current, along the inclined plates.

Arrival at the base of the partition 4, the liquid to be clarified passes into the reach 6, where it rises according to the arrow
F3 in the tubular passages formed by #laques 2, the partition 4 and the side wall 8 of the basin 1 parallel to the wall 7, while, in these passages, the solid products continue to descend towards the bottom, the separation therefore performing against the tide. The clarified liquid then flows along arrow F4 towards the discharge, in the direction of any other device, while the solids thus separated, sludge for example, are taken up by a scraping system such as a pallet conveyor 9 , which drives them to an extraction set.

 As explained above, the veins of liquid flowing between the plates 2 therefore undergo a change of direction at 1800 and follow a hairpin path, the elbow of which is located at the base of the partition 4 , the solid materials separating, by gravity, first by co-current, then against the current of the liquid to be clarified, after a transverse settling phase.

The plates 2 can be supported by tabs fixed on the side walls 7 and 8. The partition 3 will be removable and may be made of any material0
The plates 2 may advantageously include, at their lower part, set back on the nose of the plates, a projecting part 10, forming a deflector and iaisg only a narrow passage pcssr the flow of solid materials,
The two parts 2a and 2b of the plates 2, separated by the notch 3, can be in the same plane or not, depending on whether one wants to give or not the same inclination to the plates in the two reaches 5 and 6. If the 'desired inclination must be different, we will advantageously use a plate such as plate 12, shown in Figure 4, wherein the parts 123 and possibly l2b1 separated by the notch 13, are warped relative to the part 12c which corresponds to the elbow 0
FIG. 2 illustrates another form of implementation of the invention. In this embodiment, plates are precisely used comprising parts of different inclination, that is to say not coplanar.

These plates 13, arranged as previously in parallel in a settling tank 14, equipped in its lower part with a scraper 15, have two notches, in which partitions 16 are engaged, parallel to the side walls 11 of the tank la with which they define a central reach 17arelié to the supply of the liquid comprising particles in suspension, and two lateral reach 17bwreliás to the evacuation of the clarified liquid.The central part 13a of the plates 13 has an inclination, relative to the bottom of the basin, different that of the side portions 13b and a greater length.

 The liquid to be clarified first flows to the upper part of the reach 17a in the central channel 18a, along arrow F'1, and enters the tubular passages defined by the parts 13a of the plates 13 and the partitions 16, in which it heads towards the bottom, the solid particles flowing co-current in the same direction.

The veins of liquid circulating in the various passages then undergo a deflection at the base of the partitions 16, where they divide in two, according to the arrows F'2 and
F'3, to pass through the side reaches 17b and go up, in the opposite direction to their previous direction, in the tubular passages defined by the parts 13b of the plates 13, the partition 16 and the side walls Il of the basin 14, after having been deflected by the deflectors 19, provided at the base of the plates 13. The solid particles continue to descend towards the bottom, beyond the nose of the plates, in the direction of the scraper 15, which drives them towards the extraction members. For their part, the clarified water is finally evacuated according to arrows F'4 to an evacuation collector, by the channels 18b, located at the upper part of the reaches 17b.

 Many modifications can naturally be made to the systems which have just been described, without departing from the scope of the invention.

 Thus, FIGS. 5 and 6 represent a settling tank 21, comprising a plurality of longitudinal partitions 22a, 22b parallel to the side walls 23 of the basin and defining a plurality of reaches 24a and 24b furnished with inclined plates 25. The reaches 24 # are closed at their downstream end and open at their upstream end, through which they communicate with a liquid supply channel 26 charged with suspended solid particles. The diversion bays 24b, on the contrary, are closed at their upstream end, but open at their downstream end, through which they communicate with a channel 27 for discharging clarified water. The plates 223 are interrupted at their lower part before the plates 22b for forming passages by which the liquid which circulates between the inclined plates 25 arranged in two contiguous reaches is transferred from each lamellar channel 28a into the corresponding channel 28b, passing under the partitions 223, at the level of which, preferably guided by deflectors 29 between the partitions 22b, it undergoes an inversion at 1800 of its direction a of flow.

The scraper 30 routes the settled solid particles, sludge for example, to a hopper 31, from which they are extracted by a nozzle 32.

 Figures 7 and 8 show a variant of the decanter according to Figures 5 and 6 In this variant, longitudinal partitions 33 always divide the basin 34 into a plurality of parallel reaches 35a and 35b cut respectively from plates 36a and 36b and communicating respectively with a channel 37 for supplying liquid to be treated and with a channel 38 for discharging clarified water, but the series of plates of each reach, upstream and downstream, have different inclinations, for example 300 with respect to the vertical for the plates 36a of the upstream channels 39a and 60Q for the plates 36b of the downstream channels 39b and are put in place through hoppers offset longitudinally so as to correspond to their lower parts e Finally, all the partitions 33 are interrupted at the same height so that each lamellar channel communicates with the corresponding neighboring channels of two rows, the circulation of the liquid taking place up to a weir 40, as the e schematically show the arrows.

 In this variant also, the scraper 41 routes the decanted solid matter to a hopper 42, where it is taken up by a nozzle 43.

 As shown in FIG. 9, the same basin 44 may include a plurality of hoppers 45 each equipped with an independent suction system 46.

 FIGS. 10 and finally illustrate a decanter 50 divided longitudinally, by a partition 51, into two parts 52 and 53, each provided with inclined plates 54, the upstream part 52 being supplied laterally with liquid to be treated by a chute 55, provided with 'a weir 56, while the clarified liquid is discharged laterally from the part 53 to a chute 57 by a second weir 58, the inclined plates rising at least up to the level thereof. With such a system, it can be said that each tubular space formed by two parallel contiguous plates is supplied independently, or is independently connected to the evacuation system, which ensures a great regularity of the flow.

We could of course make other modifications to the systems which have just been described and in particular, possibly providing a system for rain-spraying the channels or chutes for supplying the liquid to be treated. It seems particularly superfluous to describe in detail the structure. a float, structure which is simply inverted compared to the previous ones, except of course with regard to the supplies, raised to the level of the free surface of the liquid.

Claims (13)

XEVEEDICATIONS l.- Method of gravity separation of solid matter suspended in a lamellar liquid vein in movement according to an inclined path relative to the horizontal, characterized in that an elbow is imposed on said liquid vein, the displacement of the liquid stream thus taking place successively in two directions having opposite vertical components, the segregation of the suspended matter occurring co-current along the first part of the path, and counter-current following the second, the separation of the materials with a view to their extraction taking place at the outer part of the elbow after a transverse segregation phase0 2.- Method according to claim 1, characterized in that the path of the fluid stream forms a pin, the two branches of which are located in parallel vertical planes and inclined in the same direction.  3.- Method according to one of claims 1 and 2, characterized in that the path of the liquid stream is folded back to 1800, the two branches of the pin having substantially equal lengths. 4.- Method according to one of claims 1 to 3, characterized in that the two branches of the pin are symmetrical relative to a vertical plane0 5.- Method according to one of claims l to 3, characterized in that the pin is gauchiea the branch co-current being longer and less inclined than the branch against the current. 6.- Method according to one of claims 1 to 5, characterized in that the liquid borrows in parallel several hairpin paths.  7.- Device for the separation by lamellar settling of solid matter suspended in a liquid, comprising one or more batteries of tubular passages connected to a supply system (5) in liquid charged with suspended particles, an evacuation system (6) clarified liquid and a collecting basin provided with means for extracting (9) the decanted solid particles, characterized in that said tubular passages are conjugated in series of two inclined channels, connected together so as to form a hairpin path, one of the branches of which is in communication with the supply (5) of charged liquid and the other with the discharge (6) of clarified liquid, this at neighboring levels, the hairpin communicating, in the vicinity of his elbow, with the collecting basin. 8.- Device according to claim 7, characterized in that the path of the liquid along each of the branches of a pin is defined by two plates parallel to each other, inclined relative to the horizontal, the parallel plates (2a, 12a) of one of the branches being separated from the plates (2b, 12b) of the other branch, parallel or not to the previous ones, by a vertical partition (3, 13) interrupted at one end and the edge of which thus defines the internal part of the elbow of said hairpin path.  9.- Device according to claim 8, characterized in that the bend of the pin is closed, on the part of its external or peripheral face opposite to the sliding wall of solid materials, by a wall (10) isolating the current liquid circulating in the extraction means (9).  10.- Device according to one of claims 8 and 9, characterized in that it comprises a battery of tubular passages with rectangular section generated by a network consisting of parallel walls (2) superposed obliquely, forming the roof and the floor of each element and cut transversely, at regular intervals, with vertical partitions (4), shortened once in two at least at the same end, so as to draw several layers superimposed with similar pins, the passages of the same nature, connected some to supply channels, others to liquid discharge channels, are aligned in vertical planes. llo Device according to claim PO, characterized in that all the intermediate vertical partitions (33) are shortened, each channel except the end channels thus communicating with two neighboring channels  12.- Device according to one of claims 7 to 11, characterized in that the channels connected to the aeration system have a lower slope than that of the channels connected to the evacuation system0  13.- Device according to l9une of claims 10 to 12, characterized in that the tubular passages are delimited at least partially by removable sliding elements (2-4, 13-16), inserted between parallel vertical walls (7, 8 ), spaced by a distance corresponding to the width of one or more pins. 14.- Application of the method and the device according to one of claims 1 to 13 to the settling of heavy sludge. 15.- Application of the method and the device according to one of claims 1 to 13 to the flotation of light sludge.