A DEVICE FOR PURIFICATION OF LIQUID MEDIA SUCH AS WASTE WATER

Abstract: A device for purification of liquid media such as waste water shows a housing in the form of a trough with an inlet (18) and three outlets (20, 19, 21) for screenings, a strained medium and thickened sludge, respectively. Between the inlet (18) and the first outlet (20) a strainer drum (25) is rotatably arranged, the inside of which is associated with the second outlet (19). On the strainer drum (25) radial screening members (35) are arranged which, on one hand, project during the rotation of the drum through a cleaning screen in order to bring along coarse impurities along this from the inlet (18) to the first outlet (20) and, on the other hand, serve to thicken sludge collected at the bottom of the housing which can then be removed through the third outlet (21).

Description: A device for purification of liquid media such as waste water This invention relates to a device for purification of liquid media such as waste water comprising a housing in the form of a trough with a rotating, driven strainer drum. In conventional sewage treatment plants purification, to begin with, is usually carried out in several steps different from each other, such as screening, straining, preliminary sedimentation and sludge thickening. A screen in the form of bars and cleaned by means of a machine can be arranged in a first stage to catch coarse solid im- purities which are removed from the screen by the aid of screening combs engaging between the screen bars. However, such a screen cannot have smaller openings than about 8 mm in view of the strength of the screening bars. If a finer mechanical purification is desired it is known as an alternative or as an additional step to strain the waste water, e.g. through a rotary strainer drum while the. impurities incapable of penetrating the strainer openings are brought along around the periphery of the drum to be scraped off the latter and, thus, be separated from the water. It is one object of this invention to provide a device of the kind indicated above, in which the purification steps screen cleaning, straining, sedimentation and also sludge thickening are combined with each other in one single compact unit. This is achieved by means of the characteristic features defined in the following claims. In a device according to the invention the strainer drum is covered with a cleaning screen which is closely connected to its upper side, is peripherally oriented and separates, on one hand, the strainer drum from the inlet at one side of the housing and, on the other hand, from a screen outlet at the opposite side of the housing. At the periphery of the strainer drum some sets of radial screen- ing bars are arranged which at the rotation of the drum project through the cleaning screen and bring along the coarse impurities caught on the screen to the screen out- _OiV.PI let. The medium passing the cleaning screen and filling up the interior of the housing is strained into the strainer drum and flows axially out of this through an outlet in a wall of the housing adjacent the end section of the drum. . The remaining medium incapable of passing the strainer drum is sedimented and forms sludge on the bottom of the housing. When the sludge level reaches the lower path of motion of the screening bars these will agitate during the rotation of the drum and- thicken the sludge. When the sludge has reached a desired thickening degree in this way it can be emptied from the device through one additional outlet at the bottom of the housing. Illustrative examples of the invention are described more in detail below with reference to the enclosed draw- ings, in which Fig. 1 shows partly in section and with parts broken away a lateral view of a device according to the invention, Fig. 2 a section along the line II-II in Fig. 1 , Fig. 3 a strainer drum, Fig. 4 schematically an alternative bearing of the strainer drum at the housing as seen from the inside of the housing, and Fig. 5 a device according to the invention in ross section provided with an arrangement for sludge separation. The device shown in Figs. 1 and 2 is enclosed in a housing substantially defined by plane plate walls, more specifically a rear wall 10 at the inlet side of the housing, a pair of opposite end walls 11, 12, a lower front wall 13, an upper front wall 14 spaced from the front wall 13 and a bottom wall 15 inclined from the rear wall to¬ wards the lower front wall 13. The upper side of the housing is covered by a pair of tops 16, 17 which can be opened. At the lower part of the rear wall 10 of the housing there is an inlet 18, which can be provided with a cylindrical pipe connection according to Fig. 1 but which can also extend across the whole width of the rear wall 10, if desired. Three outlets of the components to be separated from each other in the cleaning process, viz. an outlet 19 for strained water, an outlet 20 for screenings, and a sludge outlet 21 , are also arranged at the housing. The outlet 19 is made as an opening with a pipe connection at the right end wall 11. The outlet 20 for screenings is de¬ fined in the rectangular area between the two front walls 13, 14 and the adjacent parts of the end section. The sludge outlet 21 which is intended to be closed during the operation of the device and be opened at emptying of • collected sludge is shown as a pipe connection connected to the underside of the housing via an upwardly widened trough 22. Within the housing there is a cleaning screen 23 arranged between the end walls 11 and 12, which separates the inlet 18 and the outlet 20 for screenings from the out¬ let 19 for strained water and the sludge outlet 21. The cleaning screen 23 consists of a plurality of steel bows 24 arranged in an evenly spaced relationship to each other, which extend from the bottom wall 15 close to the inlet 18 to the upper edge of the lower front wall 13. Between the cleaning screen 23 and the sludge outlet 21 there is arranged a strainer drum 25 which, in its turn, separates the outlet ' 19 for strained water from the sludge 21. The strainer drum 25 extends axially between the end walls 11 and 12 in close connection with the cleaning screen 23 and comprises a pair of semi-cylindrical screen plates 26 (Fig. 3) with screen holes 27 of a suitable distribution and size. The axial ends of the semicylindrical strainer plates 26 are connected, e.g. screwed, with each their annular rim 28, which in their turn are connected via spokes 29 with each their hub 30 and 32 by means of shaft pins 31 and 33, respectively, which are mounted in a way not illustrated in detail at the end walls 11 and 12. The right shaft pin 31 in Fig. 3 is made hollow to receive a spray water tube 38 placed within the strainer drum which will be described further below while the left shaft pin 33 is connected with a drive unit 34 having an electric motor. A pair of diametrically opposed sets of screening rods 35 project between the peripheral ends of the strainer plates 26 across the whole length of the drum. In the example shown these are formed ' as combs on a pair of elongate plates 36, 36, the outer ends of which are e.g. welded onto the spokes 29 and the annular rims 28. The combs 35 have such an axial width, e.g. 20 mm, and are arranged at such a distance from each other that they fit exactly between the bows 24 of the cleaning screen 23. During the rotation of the drum 25 in the direction of the arrow 37 the combs 35 project through and past the screen 23 from a point somewhat in front of and below the inlet 18 to a point somewhat above the upper edge of the lower front wall 13, where the screen 23 is at some greater distance from the periphery of the drum 25. The spray pipe 39 mentioned above is intended to be connected with water under pressure and extends from the outside of the end wall 11 through the hollow shaft pin 31 radially obliquely upwards towards the inner periphery of the drum 25 and axially along this to end somewhat inside the opposite end of the drum where its " tube end is closed. The spray pipe 38 has along the inside of the drum a plurality of radial nozzles or openings not shown, through which water can be sprayed against the insides of the strainer plates 26 to prevent the s.trainer holes 27 from being clogged during the operation of the device. In Fig. 4 a vertical section from within the housing towards one end wall 11 of an alternatively mounted strainer drum is shown. The annular rim 28 of the strainer drum is in this case supported at its outer periphery by a plurality of wheels 40 which, in their turn, are mounted at the end wall 11 and of which one is connected at each end" section with a drive motor not shown. Through this arrange¬ ment the spray pipe 38 can be drawn without preventing spokes straight through one or both the end walls 11 and 10, respectively. If required, the wheels 40 can be re¬ placed by gears while the annular rims 28 are provided with external toothing. The device is preferably installed as downwardly re- cessed at the place of operation so that its upper side lies on a ievel with the support, e.g. a floor in a sewage treatment plant. At great sewage treatment plants the housing can consist of concrete cast in situ. The device described above -is intended to operate as follows. The medium to be purified enters the device through the inlet 18 and fills up the interior of the housing approx. to the level of the shaft of the strainer drum, coarse im¬ purities adhering to the strainer, drum 23 to be brought along by the screening bars 25 of the strainer drum to the opposite side of the screen 23, where they fall out through the outlet 20 for screenings. The medium screened in this way is then strained through the strainer holes 27 of the strainer drum and flow thereafter axially out of the open end section of the drum through the outlet 19 for strained water. The impurities not being capable to pass through the strainer drum 25, which is rinsed continuously by means of the spray pipe 38, fall down and are sedimented under formation of sludge on the bottom of the housing. When the sludge level reaches the lower path of motion of the bars 35 after some time these will agitate the sludge which will be successively thickened in this way. When the sludge has obtained the desired thickening degree it is removed from the housing through the sludge outlet 21; Fig. 5 shows an arrangement for separation of sludge from sand at the trough 22. In case the sludge contains sand 50 or the like this will sink down to the bottom of the trough 22 as a consequence of gravitation so that the sludge 51 will lie on top of the sand 50. In the arrangement according to Fig. 5 this condition is utilized in such a way that the sludge 51 is allowed to flow out through an opening 54 in the housing arranged at some distance above the bottom of the trough 22 and further up through a channel 55 arranged at the outside of the housing, which terminates in a spill- way overflow 56. The sludge 51 can run away continuously from the spillway overflow 56 through a vertical channel 57 and be collected. If the level of the sand 50 rises so much that the opening 54 is more or less clogged and/or if the level 52 of the sludge 51 rises too high in the trough 22 the level 53 of the medium to be purified will reach another spillway overflow 58. At this additional spillway overflow 58 a level indicator 59 is arranged which is adapted to open a valve 61 automatically via a singnal line 60 for a definite time in another sludge emptying channel 62 disposed at the opening 54 through which the sludge 51 O PI can be emptied more rapidly from the trough 22. The signal from the level indicator 58 can also - optionally after a certain time delay - be utilized to open the outlet 21 for emptying the sand 50. O

Claims: 1. A device for purification of liquid media such as waste water, comprising a housing in the form of a trough with a rotary driven horizontal strainer drum, c h a r a c¬ t e r i z e d by an inlet (18) and a first outlet (20) arranged in the housing, a plurality of screening members (35) projecting from the periphery of the strainer drum (25) and arranged at a reciprocally axial distance, a cleaning screen (23) defining the strainer drum (25) from the inlet (18) and the first outlet (20) and consisting of a plurality of screen members (24) arranged in spaced re¬ lationship from each other, between which the screening members (35) project during the rotation of the strainer drum (25), a second outlet (19) arranged in the housing at at least one of the two end sections of the strainer drum (25), and a third outlet (21) arranged in the lower part of the housing. 2. The device of claim 1, c h a r a c t e r i z e d in that the inlet (18) and the first outlet (20) are located on each side of the shaft of the strainer drum (25) and that the cleaning screen extends between these around the upper side of the strainer drum (25) . 3. The device of claim 1 or 2, c h a r a c t e r i z e d by a spray pipe (38;39) arranged at the inside of the strainer drum (25) for rinsing drainage holes (27) on the periphery of the drum by means of pressure fluid. 4. The device of any one of the foregoing claims, c h a r a c t e r i z e d by a fourth outlet (54) arranged somewhat above the third outlet (21) in the housing. - OREATΓ O PI

Inventors: HELLMAN BOERJE, HELLMAN, BOERJE
Applicants: HELLMAN BOERJE, HELLMAN, BOERJE
Application year: 1984
Main classification: C02F1
IPC codes: B01D29, B01D33, B03B7, B07B1