APPARATUS FOR PURIFICATION OF WATER BY FLOCULATION

Abstract: Apparatus for purification of waste water or untreated (raw) water by a floculation method, comprising a container (1) having an inlet (2) for untreated water and an outlet (3) for floculated water, and having means (4) for stirring the water during its passage through the floculation container, and in which the floculation contaitner (1) contains partition walls (8, 9) forming concentric floculation chambers (10-12), and in which each partition wall (8, 9) and the wall (6) into the outlet (3) has passageway openings (13-15) for bringing the flow of water to pass successively inwards or outwards through the several floculations chambers (10-12) from the inlet (2) to the outlet (3), and in which a flexible or resilient deflection wall (16) is arranged in each floculation chamber adjacent the flow openings (13-15) thereof for directing the flow of water into the succeeding floculation chamber (11, 12) and for allowing a stirring means (19) to pass said deflection wall (16) in the floculation chamber (10-12).

Description: APPARATUS FOR PURIFICATION OF WATER BY FLOCULATION The present invention generally relates to an apparatus, in the following referred to as floculator, for purification of waste water or any other untreated (raw) water, or emulsions or mixtures of water and oil or oil-like products by a floculation method, and the invention is more particularly concerned with such an apparatus which comprises a container having an inlet for untreated water and an outlet for floculated water, and which has or not has means for stirring of the water during its passage through the floculation container, and which apparatus is simple and effective, has small dimensions, which can be connected to practically any existing purification plant or another equipment, which as a complete can be operated by one single motor and which can be manufactured at low cost. FLOCULATION Under favourable electrostatic conditions it is possible, by stirring the water, to make microscopically small particles grow to particle aggregates, generally referred to as floes, of such size that the said aggregates may flotate of sediment. For making the the particle aggregates build up to floes which can be separated it is necessary that the stirring is arranged so that the shearing forces do not become so high that the growing floes break. Normally this has been achieved by directing the masses of water under decreasing stirring speeds through a series of successive floculation chambers, generally 2-4 chambers. Since there are only 2-4 stirring speed levels there will be a coarse control of the floe growth. Irrespective of the size of the particle aggregates said floes are subjected to the same stirring intensity. When a plant is being dimensioned the considerations are based on a balancing between a quick groowth of the floes and the size of the floes. It is posible by a so called tube floculation to provide a quick and very effective floculation. By said method the particle containing water is passed through a tube in a predetermined speed, whereby the floculation follows spontaneously depending on the turbulence which appears in the tube and which is momentarily and uniformly distributed throughout the water mass. The method is disadvantageious in that an optimum floculation follows within a very narrow flow interval. According to the invention there is suggested a floculation apparatus comprising a series of concentrically placed floculation chambers which are connected to each other in a special formation, so that the water with the particles carried thereby moves successively through all of said floculation chambers without the use any particular stirring means, and whereby any eventual stirring follows continuously or stepwise decreasing. All of the intermediate partition walls of the floculation chambers preferably are cylindrical, and the water is, especially, allowed to move through the floculations chambers from the outermost to the innermost of the concentrically arranged floculation chambers. In said apparatus the volume between the chamber cylinder surfaces corresponds to that of the chambers of a convention floculator. By arranging an end wall in each separate cyllinder chamber and a flow passageway or opening in the inner wall, which inner wall is at the same time is the outer wall of the adjacent cylinder chamber formed radially inside of said first chamber, the said several concentric cylinder chambers form a continuous long floculation chamber. A long continuous floclation chamber is good is making a so called "plug flow" possible, which in turn allows a control of the continuously decreasing stirring operation, whereby each particle aggregate can be given such stirring intensity which is useful for th quickest possible and best possible floe formation and/or for a uniform stirring during the entire "water way". The stirring can be follow spontaneously during the passage of the water through the concentric cylinder chambers, or by means of a stirring apparatus arranged for this purpose. In the most simple embodiment of the floculation apparatus the water is introduced in the outermost cylinder chamber and is drained through the central cylinder. The kinetic energy of the water itself is allowed to provide the necessary stirring turbulence. In an alternative embodiment the floculation chamber can be formed as a uniform spiral chamber. Said two simple embodiments, however, are sensitive to varying flows, and it is necessary to manually clean same at even intervals, especially in case of large flow variations. For providing a more flow insensitive and self cleaning floculator a mechanical stirring or a stirring by means of air is necessary. The kinetic energy thereby supplied must be arranged so that the said mechanically supplied stirring dominates the stirring operation which the water flow itself gives in order to make the system flow-independent. Contrary to what is said above it is, alternatively, possible to let the water enter in the central cylinder and to be drained from the outermost cylinder. It is also possible to arrange the water inlet so that eventually supplied chemicals like floculation chemicals, e.g. lime, aluminum sulphate, ferric chloride etc. can be supplied at the inlet part, whereby an effective admixture of the chemicals, if needed, can be made at this place. In an alternative embodiment of the apparatus it is possible to introduce two flows of water at different places. The flows may for instance have different supplies of chemicals, and/or each flow may be more or less difficult to floculate. The different flows meet in some of the intermediate chambers for being floculated in common and for being drained through the outlet in common. STIRRING The stirring, which is necessary for an effective floculation, can be made in three different ways, namely by the kinetic energy of the water itself, by air stirring or by mechanical stirring. When stirring by means of the kinetic energy of the water itself the necessary turbulence is created at the contact surface between the liquid and the floculator walls and within the water mass depending on the curvature of the chamber or chambers. If the walls are "naked" the floculation is very depending on the flow conditions. The system can be made more insensitive of the flow in that turbulence-creating-obstacles, like screens or similar means, are provided for instance on the walls of the chamber. In case providing the stirring operation by means of air the aeration is arranged point-wise or along the entire chamber bottom with decreasing intensity in the flow direction. Also in this case turbulence-creating screens can be used. It is, however, recommended that the stirring is made mechanically. This makes it possible to arrange a floculator which is independent of the flow intensity and which is self-cleaning, and this is very essential in practical operation. In the apparatus described in the following the mechanical stirring means is formed so that one single, integral stirring unit can be used for stirring of the water in all part chambers. DESCRIPTION OF THE INVENTION Now the invention is to be described more closely with reference to the accompanying drawings, in which figure 1 shows a cross section through an apparatus according to the invention, and in which figure 2 shows a side view of the apparatus of figure 1 , partly in a cut open view. The illustrated apparatus mainly comprises a cylindrical container 1 having an inlet 2 for waste water or another untreated - raw - water and an outlet 3 for floculated water, and further having a stirring means 4 for the water. The container 1 is substantially cylindrical and can have any desired dimensions and any relationship between the diameter and the height. The container is closed at the bottom 5, and the bottom is sealed against the outlet 3 which is formed as a tube 6 which is open at the bottom and which is mounted concentrically inside the container 1. In case the apparatus is arranged for operating with a "reversed" flow direction, i.e. whereby the flow of water enters at the center and leaves in the direction outwards from the center, it is of course necessary that the outlet tube 6 is formed with a bottom. Between the outer wall 7 of the container 1 and the outlet tube 6 there are several, in the illustrated case two, inner partition walls 8, 9 of cylindrical shape which are mounted concentrically inside the main container 1 , thereby forming a first, a second and a third inner chamber 10, 1 1 and 12 resp. inside the main container 1. The number of intermediate partition walls and concentrical chambers can be varied according to need and special circumstances. Also the volume of the inner chambers 10-12 can be varied mutually, for instance so that all chambers have substantially the same volume, or so that the volume is successively increased from the outermost chamber 10 to the innermost chamber 12. In said last mentioned case there is achieved the advantage, which is important in some cases, that the flow speed of the passing water is successively reduced during the passage of water from the inlet 2 to the outlet 3. It is also possible, for other special conditions, to form the chambers oppositely, i.e. so that the flow speed is successivly increases. It should be pointed out that it is also possible to arrange the flow through the floculator with a "reversed" flow direction, i.e. so that the water enters at the central cylinder 6 and leaves from the outermost floculation chamber 10, whereby the central cylinder 6, as mentioned above, must be formed with a sealed bottom. In the illustrated case the inlet 2 is formed by a tube which is preferably fixedly mounted on the outer surface of the container 1. The container may have several inlets, or the inlet may be split like a cascade inlet at the casing of the main cylinder 1. The water also may be introduced in the first cylinder chamber via a bottom inlet, or from above. In the latter case there is no need for any special inlet means. All intermediate walls 8, 9 and the wall to the inner cylinder 6 are formed with through flow passageways 13, 14, 15, for instance axially extending flow passageways for intake of water from the adjacent outer cylinder chamber. The passageways may extend along the entire height of the wall or only along a part thereof, whereby short circuit flows are counteracted. For this purpose it is for instance possible to arrange a first passageway on a low level and the succeeding passageway on a high level and vice versa. Sediments are more quickly discharged from the floculator if passageways are provided adjacent the bottoms between all chambers or compartments and into the central cylinder 6. If there are passageways both at the bottom and at the surface, at least at the central cylinder 6, or, in case of "reversed" flow, at the outermost part chamber 10 it is possible to handle particles which easily sediment and particles which are difficultly sedimentable, respectively, in different basins. In order to both prevent a back flow in the cylinder chambers provided in several turns outside or inside each other, and also for providing a deflection of the water flow from one cylinder chamber into the succeeding inner cylinder chamber a flexible deflection wall 16 is mounted behind and close to the respective flow opening 13-15 as seen in the flow direction. For reasons which will be evident from the following description the deflection walls ought to be formed so as to deflect depending on a mechanical pressure thereby allowing the stirring rods to pass, for instance so that said deflection walls are being folded, rotated, offset or rotated. It is, however, important that said deflection walls are stiff enough to withstand a deflection depending on a pressure from the water flow, so that said water flow is directed from one floculation chamber, through the flow opening 13-15 and into the succeeding inner (or outer) floculation chamber. In a simplified embodiment of the invention the floculator can be designed without any deflection walls, whereby the water has the possibility of flowing several turns in circle in the same chamber before finding its way into the succeeding chamber. As mentioned above, it is important that the water in the floculation chambers 10-12 is being stirred, and to this end there is used a stirring device 4 which, in the illustrated case, is driven by a motor 17. One or more cross arms 18 are mounted on the rotating shaft of said motor 17, and each said arm 18 carries a stirring rod 19 having a stirring paddle blade 20 for each individual floculation chamber. The paddle blades 20 can be fixedly mounted on the stirring rods, or they can be free hanging. The paddle blades 20 also can be formed so that said blades, at the same time as providing a stirring of the water, provides a scraping of sediment along the bottom of the chamber for removing such sediment from the floculator. The stirring device with the stirring rods 19 is provided concentrically with respect to the floculation chambers, so that the stirring rods 19 can be rotated reciprocally and/or rotating about a vertical shaft in the floculation chambers 10-12. The stirring rods 19 can pass the deflection walls 16 in that said walls, elastically or resiliently, deflect when the stirring rods 19 pass same, whereupon each said wall rotate or flex back and closes the floculation chamber so that the water is directed into the succeeding inner chamber 1 1 or 12 respectively through the openings 13, 14. In the above mentioned simplified embodiment of the invention the deflection walls may be fixed and can thereby be formed with a vertical slot through which the stirring rods 19 can pass. The narrow vertical ribs on opposite sides of said vertical slot contribute to an increased turbulence in the flow of water and to a deflection of the water into, or out of, the succeeding floculation chamber. The stirring device preferably can be arranged speed-controlled, so that the stirring intensity is maintained constant at increasing and decreasing water flows respectively. For increasing the turbulence in the floculation chambers said chambers can be formed with turbulence increasing means like wings 21 which are secured to the cylinder chamber walls as indicated in chamber 12 in figure 2. The wings 21 can be provided for speeding up a vertical stirring of the water, and the wings can be mounted angularly in relation to the horisontal plane for intensifying the stirring effect. The shaft of the stirring motor 17 is preferably formed so long as to extend some distance underneath the bottom edge of the outlet tube 6, and the projecting part of the said shaft can have an assymetrically formed cone 22 with the point thereof facing upwardly. Said cone 22 has two functions: it prevents an erosion of a sludge mass existing under said cone, and it also spreads the water in the separation basin so as to avoid the appearance of short circuit flows. The centrally mounted motor 17 and the drive shaft thereof also can be used for performing two further functions in the case that the floculator is installed in, for instance, small waste water plants, namely both for driving a bottom scraper and also for driving the spreader arms in a biological bed provided above said waste water plant. If it is considered neccessary to maintain a lower speed of rotation for said last mentioned functions it is possible to increase the number of support arms and the number of stirring rods in the floculator for providing a sufficiently effective stirring operation therein. Thus, the the floculator designed as mentioned above excellently can form basis for savings of drive units in small plants and for providing a very compact plant. In connection to the inlet, or outside the floculator there may be provided known means for supply and admixture of floculation substances or any other chemicals. It is also possible to form the floculator with a square, oval or any other regular polygonal cross section shape and, upon need, to form the stirring device coulisse guided for moving same in a coresponding square or polygonal movement. In some cases it may both be functional and may save work to foresee an "automatic cleaning" of the floculator. One such case in when sludge mixed in water, which is insufficiently cleaned from sludge, is directly precipitated, or when the floculator is used for precipitating and floculating a completely untreated waste water. For this purpose the apparatus may, at the bottom thereof, be formed with one, or eventually several radially arranged, narrow cleansing slots 23 which are covered by a bottom lid which is spring biassed in the direction upwards.The cleansing slot or slots is/are opened at the same time as the stirring device 4 is rotated. Such cleansing operation may be useful, in particular in small plants, which can thereby be operated without special de-sludging or coarse separation apparatus. The cleansing can be made by manually opening the cleasing lid, for instance a few times every week, but it can also be automatically-operated by a timer. There is also a possibility of arranging a central cleansing lid by forming the stirring rods 19 so that they continuously scrape sediment towards the centre of the floculator, where such sediment is drained through a bottom lid which can be opened and which is arranged for this purpose. The bottom opening alternatively can be the above mentioned outlet tube opening 15.

Claims: C L A I M S 1. Apparatus for purification of waste water and other untreated (raw) water or emulsions or mixtures of water and oil or oil like products by a floculation method, comprising a container (1 ) having an inlet (2) for untreated water and an outlet (3) for floculated water, and in which the floculation container (1 ) contains several concentric intermediate walls (8, 9) therein which define several concentric floculation chambers (10-12) which are substantially closed at the bottom thereof, characterized in that - each intermediate wall (8, 9) and the wall (6) to the outlet (3) is formed with flow openings or slots (13-15) extending along the entire height of the wall or parts thereof, - and which are arranged so that the flow of water can pass succesively inwards or outwards through the several floculation chambers (10-12) from the inlet (2) to the outlet (3), - and in that the floculation chambers (10-12) have one or more means (16) for positively directing the flow of water from one floculation chamber (10), through the respective flow opening or slot (13-15) to the succeeding floculation chamber (11) or to the outlet (3) respectively and to positively prevent a flow in a direction which is opposite to the intended flow direction. 2. Apparatus according to claim 1 , characterized in that the means for positively directing the flow of water from one floculation chamber to the succeeding floculation chamber (10-12) is a deflection wall (16) which is arranged substantially transversally of the floculation chamber downstream of and adjacent the flow opening or slot (13-15) of the succeeding floculation chamber, as seen in the flow direction. 3. Apparatus according to claim 2, which is formed with means (4) for stirring the water while the water is passing through the floculation container, and in which the stirring means (4) is driven by a motor (17) for providing an oscillating and/or rotating movement in the respective floculation chamber (10-12), and in which the stirring means comprises one or more stirring rods (19) for each individual floculation chamber (10-12), and in which each stirring rod (19) can be formed with, for instance, one or more paddle blades (20) for incresing the stirring effect and/or with wings (21) mounted along the stirring rods (19) for increasing the turbulence in the flow of water, characterized in that the deflection wall (16) is arranged so that the stirring rods (19) may pass said walls (16), or so that said walls (16) can be temporarily opened mechanically. 4. Apparatus according to claim 3, characterized in that the deflection walls (16) are flexible or resilient, so that said walls are being opened if mechanically acted on, for instance by a passing stirring means (19), whereupon the walls are automatically being closed. 5. Apparatus according to claim 3, characterized in that each floculation chamber (10-12) has a deflection wall which is only partially closing the chamber, and which is formed as a narrow vertical slot through which stirring rods (19) can pass and which leaves a narrow edge adjacent at least one of the walls, which edge contributes to increasing the turbulence in the flow of water and to direct the water into (or out of) the succeeding floculation chamber (10-12). 6. Apparatus according to any of the preceding claims, characterized in that each intermediate wall (8-9) and the outlet wall (6) has two or more flow openings (13-15) which are distributed along the height of the wall, or has one flow opening adjacent the top and/or one flow opening adjacent the bottom thereof. 7. Apparatus according to claim 5, in which the stirring rods (19) are formed with paddle blades (20), characterized in that one or more of the paddle blades (20) extends angularly to the horizontal plane for providing a vertical stirring component in the flow of water and/or are formed for providing a scraping of sludge along the bottom (through 23) of the floculation chamber (10-12). 8. Apparatus according to claims 5 and 7, characterized in that the shaft of the stirring motor (17) extends to a level underneath the outlet (6) of the floculator, and in that said shaft at the bottom end thereof carries an non-symetrical cone (22) having the point thereof facing upwards and arranged to prevent erosion of a sludge mass existing underneath said cone (22), and to spread the water flowing into the sedimentation basin existing thereunder. 9. Apparatus according to any of the preceding claims, characterized in that the floculation container (1 ) and all concentrically arranged floculation chambers (10-12) are cylindrical having a circular, square, oval or regularly polygonal cross section shape, and in that the flow of water through the concentrical floculation chambers (10-12) is arranged to follow from an inlet (2) provided in the outermost floculation chamber (10) and successively through the succeeding inner floculation chambers (11 , 12) to a central outlet tube (6) from which the floculated water is drained into a lower sedimentation basin or a similar receptacle. 10. Apparatus according to any of the preceding claims, characterized in that it is formed with two or more inlets opening into different floculation chambers, whereby the different flows of water can be of different kind and/or can have different admixtures of chemicals, and in which the respective flows of water meet in the second or any succeeding floculation chamber (11 , 12).

Inventors: LARSSON FOLKE, LARSSON, FOLKE
Applicants: AQUA PROCESSOR AB, LARSSON FOLKE
Application year: 1993
Main classification: C02F1
IPC codes: C02F1