EP0518938A1

EP0518938A1 - Apparatus for separating liquids and solids

Info

Publication number: EP0518938A1
Application number: EP91905585A
Authority: EP
Inventors: Gunther Abel
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-03-06
Filing date: 1991-03-06
Publication date: 1992-12-23
Also published as: WO1991013672A3; CA2077687A1; AU7457891A; WO1991013672A2

Abstract

Dans un appareil de traitement d'eaux usées possédant un dispositif de séparation (12A, 12B) servant à séparer les matières solides d'un écoulement d'eau, le dispositif de séparation (12A, 12B) comprend des barres de filtrage (24) cylindriques qui entourent seulement une partie inférieure et un couvercle (25) cylindrique recouvrant les barres (24). Un râteau (26) évacue les matières filtrées dans un convoyeur à vis (14) situé latéralement par rapport au dispositif de séparation (12A, 12B), lequel peut être l'un d'une paire de dispositifs de séparation situés sur les côtés opposés du convoyeur à vis (14).In a wastewater treatment apparatus having a separation device (12A, 12B) for separating solids from a water flow, the separation device (12A, 12B) includes filter bars (24) cylindrical which surround only a lower part and a cylindrical cover (25) covering the bars (24). A rake (26) discharges the filtered material in a screw conveyor (14) located laterally relative to the separation device (12A, 12B), which can be one of a pair of separation devices located on opposite sides of the screw conveyor (14).

Description

APPARATUS FOR SEPARATING LIQUIDS AND SOLIDS

The present invention relates to apparatus for separating liquids and solids and is useful, for example, as waste water treatment apparatus for screening sewage, sludges and industrial effluents from waste water, It has previously been known to provide a waste water treatment apparatus with a separator device for receiving an inflow of waste water and for separating solid materials in the waste water from liquid, and a screw conveyor for conveying and compressing the thus- separated solid materials. In one such prior art apparatus (see German Patents Nos. 3,019,127 and 3,122,131 and European Patent No. 81 103 835) the separator device comprises an inclined, cylindrical screening basket into which waste water flows at one end in a waste water channel, the basket having axially spaced annular bars through which the water can flow from the basket. Screenings retained by the bars are collected by the teeth of a rake rotating within the basket and are thereby deposited into a screw conveyor, which is co-axial with the basket and which extends upwardly therefrom.

To assist in cleaning the teeth of the rake, the rotation of the rake is periodically reversed to pass the rake through a comb at the top of the basket, where screenings are combed from the rake. As the screenings are transported upwardly by the screw conveyor to a pressing chamber, they are compacted and dewatered.

This prior art device, therefore, combines the functions of mechanical screening of the waste water, washing of the screenings, removal of the screenings and dewatering of the screenings.

Since, however, the cylindrical basket is inclined, with the lower portion of the basket immersed in the waste water and an upper portion of the basket located above the waste water, only a small portion of the screening area of the bars in the lower portion of the basket is immersed and utilized. This prior apparatus, therefore, has the disadvantage that a considerable portion of the screening area is wasted. It is accordingly an object of the present invention to overcome this problem.

According to the present invention, this object is achieved in that the separator device comprises circularly curved, parallel screen bars extending around only a lower portion of the separator device and a cylindrically curved cover portion extending over the screen bars.

In order to enable the screw conveyor to be located outside of the separator device, an embodiment of the invention is characterized by an opening between the cover portion and the screen bars and a rake for discharging screenings laterally from the separator device through the opening.

To provide an increased throughput using only one screw conveyor, a further embodiment is characterized in that separator device is one of a pair of separator devices and in that the screw conveyor is positioned to receive the screenings from both of the separator devices through the openings thereof.

In order to enable the apparatus also to pick up sand or other grit separately from the bottom of a waste water channel, a further embodiment of the invention is characterized in that the screw conveyor is an outer one of a pair of co-axial inner and outer screw conveyors, in that the outer screw conveyor receives the screenings from the separator devices and in that the inner screw conveyor projects axially downwardly from the outer screw conveyor for receiving material and conveying the material upwardly through the interior of the outer screw conveyor. A still further embodiment of the invention, in order to enable the additional treatment of further waste liquid, for example a slurry, is characterized by a third separator device located between opposite ends of the screw conveyor for feeding the additional material into the screw conveyor.

In order to adjust the apparatus to the dimensions of its location and/or to locate the separator device in a first position for screening operation and a different, second position for discharging the screenings from the separator device into the screw conveyor, another embodiment is characterized in that the separator device is adjustable by vertical tilting movement relative to the screw conveyor.

It is a further disadvantage of the above- discussed prior art apparatus that, since the auger conveyor is coaxial with the cylindrical screenings basket, and since the latter must be disposed at a relatively low inclination in order to utilize the maximum area of the basket for screening, the auger must consequently be disposed at the same low angle of inclination. This prior art system is therefore bulky.

It is accordingly a further object of the present invention to provide a novel and improved apparatus for separating liquids and solids, in which, in order to save space, the solids can be removed along a path extending at a greater inclination than was possible with the above-described prior art apparatus. According to another aspect of the present invention, there is provided apparatus for separating liquids and. solids which comprises a separator for removing and separating the solids and liquids, the separator means comprising a cylindrically curved screening basket, and conveyor means for feeding the separated solids upwardly from the separator. A compactor is provided for compacting the solids, and the - o - conveyor means comprises a first conveyor extending at a first upward inclination through the separator and a second conveyor extending further upwardly, and at a greater inclination than the first conveyor means. Preferably, the compactor is interposed between the first and second conveyors for feeding the solids in a compacted state to the second conveyor.

The apparatus may also be provided with means, for example cutter means or pelletizer means, between the compacting means and the second conveyor for reducing the compacted solids to separate or readily conveyable pieces, "to thereby facilitate conveyance of the solids by the second conveyor.

The invention will be more readily apparent from the following description thereof when taken in conjunction with the accompanying drawings, in which:-

Figure 1 shows a partially broken-away view in perspective of a screening apparatus according to a first embodiment of the present invention;

Figure 1A shows a diagrammatic view in end elevation of a modification of the apparatus of Figure 1;

Figure 2 shows a view corresponding to Figure 1 but of a modified screening apparatus; Figure 3 shows a diagrammatic view of in side elevation of a modification of the screening apparatus of Figure 2;

Figure 4 shows a view in transverse cross-section through a screenings pelletizer for use in the apparatuses of Figures 1 to 3;

Figure 5 shows a broken-away view in longitudinal vertical cross-section through the pelletizer of Figure 4 and a part of the screw conveyor of Figure 1;

Figure 6 shows a view in longitudinal cross-section through a different form of pelletizer for use in the screening apparatuses of Figures 1 to 3 ; and

Figure 6A shows a view in longitudinal vertical cross- section through the pelletizer of Figure 5;

Figure 7 shows a view in side elevation of a modified screen provided with a heater; and

Figure 8 and 9 show a diagrammatic view in side elevation of the different pivotable separator device arrangements.

Figure 10 shows a view taken in vertical cross-section through a screening apparatus according to a further embodiment of the present invention; Figure 10a shows a view taken in cross-section along the line lOa-lOa of Figure 10;

Figure 10b shows a view taken in cross-section along the line lOb-lOb of Figure 10;

Figure 10c shows a view taken in section along the line lOc-lOc of Figure 10;

Figure lOd shows a view taken in section along the line lOd-lOd of Figure 10c and showing a portion only of the apparatus shown in Figure 10c;

Figure lOe shows a view corresponding to Figure 10a but taken in cross-section through a modification of the apparatus of Figure 10;

Figure 11 shows a view in vertical cross-section through a different screening apparatus according to the present inventioni in vertical cross section;

Figure 11a shows a view taken in transverse cross-section along the line 12a-12a of Figure 11;

Figure lib shows a view taken in transverse cross-section along the line 2b-2b of Figure lie; Figure lie shows a broken-away view, in longitudinal cross-section, through parts of the apparatus of Figure

U;

Figure lid shows a view corresponding to Figure to 2a, but of a modification of a pelletizer forming part of the apparatus of Figure 11;

Figure lie shows a broken-away view of part of the apparatus shown in Figure lid;

Figure ϊlf shows a broken-away view taken in cross- section along the line 2f-2f of Figure lie;

Figure llg shows a broken-away view in end elevation, of an extrusion formed by the apparatus of Figures 2d-2f;

Figure 12 shows a view in vertical cross-section through a screening apparatus according to a third embodiment of the present invention;

Figure 12a shows a broken-away view taken in longitudinal cross-section through parts of Figure 12;

Figure 12b shows a view corresponding to that of Figure 12a but of a modified apparatus; Figure 12c shows a view taken in transverse cross-section along the line 3c-3c of Figure 12a;

Figure 13 shows a modification of the screening apparatus of Figure 12;

Figure 14 shows a view in side elevation, partly broken- away in longitudinal cross-section, of a further screening apparatus according to the present invention;

Figure 15 shows a broken-away view in side elevation of a still further screening apparatus according to the present invention;

Figure 16 shows an end view taken in the direction of arrow A of Figure 15;

Figure 17 shows a broken away view in side elevation of a scoop chain forming part of the apparatus of Figures 6 and 7;

Figure 18 shows a broken-away view in side elevation, and on a larger scale, of parts of the chain of Figure 17;

Figure 19 shows a broken-away view taken in section along the line 10-10 of Figure 18; Figure 20 shows a view in elevation of a screening element for use in a modified separator screen basket;

Figure 21 shows a part of the screening element being cut from a metal strip;

Figure 22 shows a broken-away view in side elevation of a separator screen incorporating screen elements such as that of Figure 11;

Figure 23 shows a side view of a further screening apparatus;

Figure 24 shows an end view of the screening apparatus of Figure 23; and

Figure 25 shows a diagrammatic view in longitudinal cross-section through a screening apparatus according to a still further embodiment of the present invention. In Figure 1 of the drawing there is shown a waste water treatment apparatus indicated generally by reference numeral 10, which has a pair of separation devices, indicated generally by reference numerals 12A and 12B, arranged at opposite sides of a screw conveyor indicated generally by reference numeral 14.

The screw conveyor 14 has a cylindrical casing 16 containing a screw 18, which is rotated by a drive motor 20 through a reduction gearing indicated generally by reference numeral 22.

The separator devices 12A and 12B have axes A and B, which are parallel to the longitudinal axis C of the screw conveyor 14.

Each separator devices 12A and 12B is a basket which comprises a plurality of axially-spaced, semi¬ circular screen bars 24 through which the waste water passes. The screen bars 24 extend over only the lower half of each basket, the upper portion of which is formed by a cylindrically curved cover 25 of sheet metal. The separator devices 12A and 12B also comprise rakes 26, each Which is mounted on the outer ends of a pair of arms 28, of which only one is shown in each basket. The arms 28 are secured at their inner ends to a rotatable shaft 30.

Between the screen bars 24 and the cover portion 25 of each basket, there is left a gap or opening 31 for the discharge of the screenings by the rakes 26. Between the separator devices, 12A and 12B, the screw conveyor casing 16 is formed with an opening 32 through which screenings raked from the screen bars 24 by the rakes 26 and discharged through the openings 31 are deposited into the screw conveyor 14 for upward propulsion and compression by the screw 18.

An electric motor 33, through gears 35 and 37, rotates the shaft 30 of the separator device 12A, and through two further gears 39 and 41, rotates the shaft 30 of the separator device 12B.

In operation of this apparatus, the rakes 26 are rotated in opposite directions about their axes A and B to remove the screenings from the screen bars 24 into the screw conveyor 14. The direction of rotation of the rakes 26 is periodically reversed, to pass the rakes 26 through combs 34 for cleaning the rakes 26.

The apparatus shown in Figure 1 may be modified as shown in Figure 1A by the provision, in place of the screw conveyor 14 , of a third separator device indicated generally by reference numeral 12C, with an associated screw conveyor 15 extending axially through the third separator device 12C. In this case the separator device 12C has a top opening 36 through which the screenings from the separator devices 12A and 12B can fall into the screw conveyor 36.

In the embodiments of the invention illustrated in Figures 2 and 3, the two separator devices 12A and 12B are provided at opposite sides of a double screw conveyor indicated generally by reference numeral 40.

The double screw conveyor 40 comprises an outer screw conveyor indicated generally by reference numeral 41 and formed by a cylindrical sleeve 42 and by a screw 44 on the sleeve 42, and an inner screw conveyor indicated generally by reference numeral 45 and comprising a shaft 46 provided with a screw 48. The double screw conveyor 40 is provided in a cylindrical casing 50 formed with an opening 52 through which screenings can be deposited by the separator devices 12A and 12B into the outer screw conveyor 41, i.e. between the casing 50 and the sleeve 42.

The inner screw conveyor 45 projects axially downwardly beyond the outer screw conveyor 41 and through a tube 49 for picking up sand and other grit form the bottom of a waste water channel and for conveying the sand or other grit upwardly for discharge from the upper end of the double screw conveyor 40.

* The embodiment of Figure 3 is similar to that of Figure 2 except that there is in addition provided a microscreen, indicated generally by reference numeral 54, which is provided between the opposite ends of the screw conveyors and which serves to screen, for example, solid material from a slurry into an inlet hopper 56 opening into the outer conveyor.

Figures 4 and 5 show a transverse cross- sectional view and a longitudinal cross-sectional view, respectively, of a pelletizer indicated generally by reference numeral 60, which car be provided at the upper end of the screw conveyor 14 of igure 1 for forming the compressed screenings into pellets. This pelletizer 60 has a cam-shaped deflector 66, which s can be seen in Figure 4 is eccentrically mounted on shaft 67 of the conveyor screw 18 to which the screenings are fed by the screw 14 and which presents a convex outer surface 69 for pressing the screenings radially through openings 68 extending radially outwardly through a cylinder 70.

An outer screw conveyor indicated generally by reference numeral 71 extends around the sleeve 70 and comprises a screw 72 secured, at its outer periphery, to a cylindrical sleeve 74, which is rotatable in a cylindrical housing 76.

As the solid material formed from the screenings is extruded through the openings 68 in the form of rods, the rods are periodically broken-off by the inner periphery of the screw 72 into individual cylindrical pellets, which are then discharged axially from the pelletizer by the screw 72. In Figures 6 and 6A, there is shown a modified form of pelletizer, indicated generally by reference numeral 80, to which the screw conveyor 14 feeds the screenings.

The pelletizer 80 has a cylinder 82 formed with radial openings 84 and defining therein a cylindrical chamber 86. A compactor 88, which is eccentrically mounted on the shaft 67 of the screw conveyor 14, rotates in the chamber 86 and serves to press the screenings, fed into the chamber 86 by the screw 18, in a radially outwardly extending direction through the openings 84.

The shaft 67 is rotated by an electric motor 89 through a pinion 90 on the shaft of the motor 89 and a larger gear 92 mounted on a hub 94, which is journalled in a bearing 96.

An annular plate 98 is secured to the gear 92 for rotation therewith, by means of four connecting members 100 and, thus, rotates about the common axis of the shaft 67 and the gear 92.

The annular plate 98 is connected by means of four helically curved metal strips 101 to the respective four arms 102 of a spider indicated generally by reference numeral 104. The spider 104 has a central annular 106 which is rotatably mounted by means of a bearing "108 on the exterior of the screw conveyor 14 for rotation about the axis of the shaft 67.

The metal strips 101 thus rotate around the inner surface of a cylindrical housing 110, which defines an outlet chamber 112 at the left-hand side of the pelletizer as viewed in Figure 6, the outlet chamber 112 having an outlet opening defined by an inverted hopper 114. As can be seen in Figure 6, the metal strips 101 are spaced radially outwardly frorr the outer surface of the cylindrical member 82.

In operation of this pelletizer, the screenings are fed by the screw conveyor 14 into the chamber 86, from which they are pressed radially by the eccentrically mounted compactor member 88 through the openings 84. In this way, the screenings are formed into fairly rigid rods, which are extruded from the openings 84 and continued to advance radially outwardly from the openings 84, until they are broken off by the metal strips 101 into rod-shaped pellets. These pellets are then displaced to the left, as viewed in Figure 6, by the metal strips 101 until they tumble downwardly through the outlet chamber 112 and the inverted hopper 114.

Figure 7 diagrammatically illustrates a separator device indicated generally by reference numeral 12D, which may for example correspond to any one the separator devices 12A to 12C. The separator device 12D, however, is additionally provided with a heater element 120, which is wound helically around the separator device 12D and which may be used to heat the material flowing into the separator device in order to facilitate the flow of such material and the separation of the screenings therefrom. While the separator device 12D is illustrated in Figure 7 as being of a cylindrical shape, it is to be understood that the separator device is not, in fact, restricted to such a shape but may, for example, have a frusto-conical shape, as shown in broken lines and indicated generally by reference numeral 12E.

The or each separator device may be pivotally adjustable relative to the screw conveyor, for example upon installation of the apparatus in order to adapt the apparatus to the dimensions of a location in which the apparatus is being installed or to locate the separation device in different positions for screening and for discharge of the screenings. Thus, for example, with reference to Figure 8, in which the axis of the screw conveyor 14 is indicated by C, the separator device may be adjustable by vertical tilting movement, by pivotation about a pivot axis PI extending perpendicular to the plane of Figure 8, between a separator position shown in broken lines and indicated generally by reference numeral 12F and an a different separator position which is also shown in broken lines and which is indicated generally by reference numeral 12G.

Alternatively, as illustrated in Figure 9, the separator device may be adjusted by vertical tilting movement, by pivotation downwardly about a pivot point P2, at the front, bottom of the separator device, into a lowered position indicated generally by reference numeral 12H, for example to increase the amount of the area of the screen immersed in the water, and into a raised position indicated generally by reference numeral 121, for example to facilitate a discharge of the screenings from the separator device into the screw conveyor.

Referring firstly to Figures 10 through lOd of the accompanying drawings, reference numeral 110 indicates generally a screening apparatus, which comprises a separator section indicated generally by reference numeral 112, a compactor section indicated generally by reference numeral 114 and an output conveyor section indicated generally by reference numeral 116. The separator section 112 comprises a separator screen or basket indicated generally by reference numeral 118 (see Figure 10a), which comprises parallel, longitudinally extending screen bars 120 arranged in a generally cylindrically curved array about the periphery of a conveyor auger 122, with the bars 120 spaced laterally apart from one another. A hopper indicated generally by reference numeral 124 is upwardly open and has its bottom formed by the screen 118 and serves to receive a mixture of liquid and solids through the open top thereof_*

- The liquid can flow outwardly of the separator section 112 through the gaps between the bars 120, but the solids are displaced upwardly along the bars 120 by rotation of the auger 122.

The compactor section 114 has a compactor auger 126, which forms an extension of the conveyor auger 122 and which serves to compact the separate pieces of solid material advanced from the separator section 112 into a solid mass. The auger 126 rotates within longitudinal, stationery bars 127 (Figure 10b), which allow water to escape and prevent, at least to some extent, rotation of the solid material compacted by the auger 126.

The bars 127 are mounted on the inner surface of cylinder 129 enclosing the auger 126. At the upper, outlet end of the compactor section 114, there is provided a cutter device indicated generally by reference - 19 - numeral 128, by means of which the solid, compacted mass of material is sliced into pieces.

These pieces of solid material then drop from the cutter device 128 into the lower, input end of the 5 conveyor section 116.

A second conveyor auger 130 in the conveyor section 116 then conveys these pieces of the solid material upwardly along the output conveyor section 116 for discharge into a suitable container (not shown). The 10 lower end of the auger 130 includes a shaft 131, which extends through only two turns of the auger 130, the remainder of which has no shaft.

On the compactor section 114, there is mounted an electric drive motor 132, having an output gear 134 which 15 meshes with a ring gear 136.

The ring gear 136 is mounted on a shaft 138, which is common to the conveyor auger 122 and the compactor auger 126. More particularly, the ring gear 136 has a hub 140 fixed to the shaft 138. The cutter device 20 128 comprises four arms 142 connecting the ring gear 136 to the hub 140 and each provided with a cutter blade 144, as shown in Figures 10c and lOd. The arrangement is such that, as the compacted .___.. _>s of solid materials is forced through the spaces between the arms 142 by the compactor 25 auger 126, the cutter blades 144 slice this material, which is thus broken into separate pieces. These separate pieces of solid material then drop downwardly to the second conveyor section 116. The auger 130 of the output conveyor section 116 is driven by means of a gear 146, which is mounted on the shaft 131 of the conveyor auger 130 and which meshes with the ring gear 136 so as to be driven thereby. The motor 132 and the gears 134 and 136 are enclosed in a housing indicated generally by reference numeral 150.

This housing defines an outlet chute 152 extending downwardly from the cutter device 134 to the inlet end of the output conveyor section 116 for guiding the sliced pieces of solid material to the latter. The gear 146 is enclosed in a separate housing indicated generally by reference numeral 154.

Figure lOe shows a separator screen or basket indicated generally by reference numeral 118a, which is identical to that shown in Figure 10a in that the screen 118a is formed by the bars 120 and the hopper 124. In addition, however, the screen 118a of Figure lOe is provided with a microscreen 121 at the interior of the array of bars 120 and between the latter and the auger

122. This microscreen 121 may be made of metal or fabric mesh, perforated sheet metal, woven fabric or woven or mesh plastics material and is useful, in particular, in applications which require relatively small pieces of solid material to be conveyed upwardly by the auger 122 rather than being discharged through the bars 120 with the escaping water. Turning now to Figures 11 and 11a of the drawings, which show a second screening apparatus indicated generally by reference numeral 300, it can be seen that the screening apparatus 300 has a separator section indicated generally by reference numeral 302, a compactor section indicated generally by reference numeral 304 and an output conveyor section indicated generally by reference numeral 306.

The separator section 302 has a cylindrical screening basket indicated generally by reference numeral 308, which comprises annular screening bars or rings 310 extending coaxially about a first conveyor auger 312, which has a shaft 314, the lower end of which is carried by a support plate 311. A stationary hopper 307 is provided at the upper end of the screen 308. The hopper 307 has an outlet communicating with an inlet opening 309 in a circular plate 311, which forms the upper end of the screen 308. Through the hopper 307 and the inlet opening 309, substances may be introduced into the interior of the screen 308 of mixing with and treating the waste material in the screen 308.

The cylindrical screening basket 308 has an open lower end, through which a mixture of liquid and solids can enter in the direction indicated by arrows 315. The lower end of the screening basket 308 is carried on a support roller 317, which is rotatably mounted on a support bracket 319. The liquids leave the cylindrical basket 308 through the gaps between the bars 310, while the solids are raised by radially inwardly extending arms 316 (Figure 11a) and dropped into the upwardly-open top of a cylindrically curved hopper 318 containing the conveyor auger 312. Bars 319 are interposed between the inner surface of the hopper 318 and the periphery of the auger 312 to allow liquid to drain from the solids removed by the auger 312. These solids are conveyed upwardly by the auger

312 to a compactor auger 320, which forms an extension of the conveyor auger 312.

The material compressed by the compactor auger 320 is discharged into a pelletizer indicated generally by reference numeral 321.

The pelletizer 321 has an eccentric rotor 322 (Figures lib and lie), which with the compactor auger 320 is mounted on the shaft 314, and which forces the compacted material radially outwardly through openings 324 in a cylindrical wall 326, through outwardly- convergent frusto-conical openings 323 in a cylindrical wall 325 and through cylindrical extrusion passages 327 in a cylindrical extrusion block 329.

Solid compacted material forced into the pelletizer 321 by the compactor auger 312 is pressed radially outwardly by the eccentric rotor 322 through the openings 323 and is thus extruded as rods from the extrusion passages 327. Plates 328 rotating about the exterior of the cylindrical extrusion block 329 and within a cylindrical housing 333 break the rods of extruded, compacted solid materials which exit the openings 324, and the broken pieces of rod fall downwardly through an outlet opening 335 in the housing 333 and into the lower, inlet end of the output conveyor section 306. The radial plates 328 extend from plates 331 at right angles to the plates 328, so that plates 328 and 331 together form spaced T-shaped members.

An electric drive motor 330, through an output gear 332^' on the shaft of the motor 330, and through a ring gear 334 coaxial with the shaft 314, rotates a gear 336. The ring gear 334 also rotates the plates 328 and 331 and, through a cylindrical housing 337 rotates the screening basket 308.

The output conveyor section 306 has an output auger 340 having a shaft 342, which is connected to and driven by the gear 336. The shaft 342 extends through only the first two turns of the auger 340, the remainder of which has no shaft.

The drive motor 330 has a second output gear 344, which meshes with and drives a gear 346.

The gear 346, in turn, drives the shaft 314 and, therewith, the pelletizer rotor 322, the first conveyor auger 312 and the compactor auger 320 in a direction opposite to the direction of rotation of the screening basket 308. As can be seen from Figure 11, the inclination of the axis of_. the shaft 314 is such as to substantially optimize the screening area of the cylindrical screening basket 308, which is immersed in the mixture of liquid and solids to be separated.

The angle of inclination of the shaft 342 of the second conveyor auger 340 of the output conveyor 306, however, is disposed at a substantially steeper angle of inclination. Figures lld-f show a modification of the pelletizer 321 of Figures lib and lie. The pelletizer illustrated in Figures lld-2f is indicated generally by reference numeral 321a and, instead of the cylindrical walls 325 and 326 and the extrusion block 329 of Figures lib, has a cylindrical wall 326a formed with outlet slots 324a and a cylindrical extrusion block 329a at the exterior of the wall 326a. The extrusion block 329a is formed with extrusion slots 327a having outwardly convergent inner portions 323a (Figure llf). The remainder of each slot 327a is defined by a pair of parallel, generally flat surfaces 330a, which are interrupted by opposed pairs of radial ribs 332a.

Figures llg shows a broken-away end view of a piece of solid material extruded from one of the slots 327a and indicated generally by reference numeral 332a. The solid material piece 332a has V-shaped indentations 334a which extend longitudinally thereof and are formed by the ribs 332a, and also fissures 336a, which are formed on expansion of the solid material as it leaves the slot 324a. The indentations 334a and the fissures 336a serve to enable moisture to penetrate into the interior of the extended solid material in order to soften the material and to promote biological action when the material is used for compost.

Referring now to Figures llh which shows in greater detail components of the basket 308, it will be seen that the basket 308 is formed by rings 350a, 350b and 350c, which are connected together by rods 352 to form the cylindrical basket 308. The rings 350a, 350b and 350c are each formed by flat metal annuler, the rings 350a having the greatest radial dimensions, the rings 350c having the least radial dimensions and the rings 350b having radial dimensions intermediate those of the rings 350a and 350c.

Arms 354 are interposed between the rings 350a and 350b. The arms 354 serve as spacers and project radially inwardly, beyond the rings, where they are connected together by a further metal rod 356. Spacers 358, located radially inwardly of the rings 350a, 350b and 350c, are interposed between the arms 354 and are likewise secured by the rod 356.

At the radially innermost ends of the arms 354, a longitudinally extending strip-shaped member 359 is mounted at opposite ends thereof on a pair of arms 360 which, in turn, are pivotally mounted on the rod 356 for pivotation about the axis of the latter under the action of a spring 362 interconnecting the strip-shaped member 359 and one of the arms 354. The spring 362 is a tension spring and, thus, biases the strip-shaped member 359 for pivotation in a clockwise direction, as viewed in Figure 11a, about the rod 356.

One of the arms 360 carries a roller 364 which, as the basket 308 rotates, rolls against a fixed guide plate 366 located at the upper end of the basket 308. This guide plate 366 deflects the roller 364 radially inwardly, thus deflecting the strip-shaped member 359 so as to align it with the lengths of the arms 354. In this way, solid material picked up by the arms 354 and the strip-shaped member 359, as the latter travels through the lowermost portions of its path of travel on rotation of the basket 308, is deposited onto the auger 312. The dropping of this solid material from the strip-shaped member 359 and the associated arms 354 into the auger 312 is facilitated by an overhead spray 368.

Figure Hi shows a modification of the basket which in this case comprises single radially wide rings 350d separated by pairs of rings 350e of intermediate radial width, which in turn are separated by three narrow rings 350f.

When it is required to clean or service the apparatus shown in Figure 11, the entire apparatus may be pivoted upwardly, in a clockwise direction as viewed in Figure 11, about a pivotal support indicated generally by reference numeral 360. Figure 12 shows a separator apparatus indicated generally by reference numeral 400, which has a separator section indicated generally by reference numeral 402, a compactor section indicated generally by reference numeral 404 and an output conveyor section indicated generally by reference numeral 406.

The separator section 402 has a cylindrical separator basket, indicated generally by reference numeral 408, which is similar to the separator basket 308 of Figure 11 and which, therefore, will not be described in further detail. A shaft 410 is provided with a first conveyor auger 412, within the separator section 402 and a compactor auger 414, which forms an extension of the first conveyor auger 412. A cutting device 416 which is similar to the cutting device 128 of Figure 10, is fixed to the compactor auger 414 at the upper, outer end thereof for slicing the compacted solids into pieces which drop into the second conveyor 444.

An electric drive motor 418 has an output gear 420 which meshes with and rotates a ring gear 422.

The ring gear 422 is fixedly connected to a sleeve 424, which is rotatably mounted in bearings 426.

Four annular members 428 (Figure 12A) are provided within the sleeve 424 and are fixedly connected by welding to the latter and, also, to the outer periphery of the compactor auger 414 for imparting drive to the latter and, thus, to the shaft 410 and the first conveyor auger 412. Through meshing gears 430 and 432, and through a pinion 434 which meshes with an internally toothed ring gear 436 at the lower, input end of the screenings basket 408, the latter is rotated about an upwardly open hopper 438 containing the first conveyor auger 412. In this way, the solid material picked up by the rotating screening basket is deposited into the first conveyor auger 412 in the same manner as that described above in connection with the embodiment of Figure 11. Longitudinal metal strips 439 are spaced around the auger 412 and 414.

^• The ring gear 422 meshes with a further gear 440 on the' lower end of a shaft 442 of a second conveyor auger 444, within the output conveyor section 406, for rotating the second conveyor auger 444 and, thus, removing in an upward direction the cut pieces of solid material dropping from the cutting device 416. The slot 442 extends through only the first two turns of the auger 444. As will be apparent from Figure 12, the angle of inclination of the second conveyor auger, which in this case is the auger 444, is once again substantially- greater than that of the first conveyor auger.

The arrangement shown in Figure 12a may be modified by replacing the four annular members 428 by a single helical member 450, which is fixed, by welding, to the periphery of the auger 414 and to the inner surface of the sleeve 424. The entire apparatus of Figure 12 can be pivoted upwardly in a clockwise direction as viewed in Figure 12, about a support pivot indicated generally by reference numeral 452, for cleaning and/or servicing of the apparatus.

Figure 13 shows a further separator device indicated generally by reference numeral 500.

The separator device 500 has a separator section 502 and a compactor section 504 , which are similar to the separator section 402 and the compactor section 404 of Figure 12 and which, therefore, are not described in further detail.

In this embodiment, however, the output of the compactor is not provided with a cutting device for cutting the compacted solid material, nor a pelletizer device such as that of Figure 11 for pelletizing the solid material.

Instead, the compactor auger, which in this embodiment is indicated by reference numeral 506 and which is mounted on an auger shaft 508, is extended as a conveyor auger 51C

The shaft 08 is connected through a universal joint 511 to a fu„ ,ner auger shaft 512, which extends upwardly at an inclination greater than that of the shaft 508 and which is provided with a second or output conveyor auger 514. The auger 514 terminates in a radial plate 516, which serves to retain the solid material which has been forced beyond the plate 516. The solid material is at least partly prevented from rotating by means of a plurality of stationary metal strips 518, which are spaced around the augers 510 and 514.

Figure 14 shows a separator apparatus which is designed to separate solid materials floating in a liquid in a channel and, in addition, to pick up settlings, i.e. sediment such as sand, mud and sludge, and other objects such as stones and gravel from the bottom of the channel. The apparatus shown in Figure 14 is indicated generally by reference numeral 600, and has at its lower end an auger indicated generally by reference numeral 602 for removing the settlings from a recess 604 formed in the bottoπ of a channel containing a liquid 606, in which waste material floats. _ The apparatus 600 also has a cylindrical screen indicated generally by reference numeral 608, an outer auger indicated generally by reference numeral 610, which is co-axial with and extends around the auger 602, an inlet indicated generally by reference numeral 612, a compactor and pelletizer unit indicated generally by reference numeral 614 and two outlet conveyors indicated generally by reference numerals 616 and 618. The inlet 612 has a hopper 619 through which substances may be introduced into the outer auger 610 for conditioning the solids conveyed by the latter.

The screen 608 is constructed similarly to the scree* 508 of Figure 11 and, therefore, will not be described in greater detail. However, the screen 608 is provided with a heater element 620, which is wound in a helical fashion around the periphery of the cylindrical screen 608 and serves to heat the latter and the waste material within the screen 608. The mixture of liquid and floating solid material travelling along the channel 606 enters the lower end of the screen 608, in the manner described above, and the solid material is then removed from the liquid and deposited into the outer auger 610, which extends through the screen 608 and upwardly therefrom to the compactor and pelletizer unit 614.

^• At the opening 612, additional substances can, if required, be added to the solid material being conveyed upwardly by the outer conveyor 610, for the purpose of treating the solid material before it is compacted. The inner conveyor 602 extends through the compactor and pelletizer unit 614 and is connected, through a universal joint (not shown) in a manner similar to that described above with reference to Figure 13, to an outlet auger (not shown) in the outlet conveyor 618.

The compactor and pelletizer unit 614 is similar to that shown in Figure 11 and, therefore, will not be described in greater detail.

The outlet conveyor 616, which corresponds to the conveyor 606 of Figure 11, serves to convey upwardly the pellets produced by the compacting and pelletizing unit 614. The outlet conveyors 616 and 618 have an inclination substantially greater than the inclination of the inner and outer augers 602 and 610, so as to save space. Figures lδ through 19 show a different type of apparatus for picking up sediment from the bottom of a channel in front of a separator screen. More particularly, in Figure lδ there is shown a duct, indicated generally by reference numeral 700, which may, for example, be a concrete trough, defining a channel for flow of waste water or sewage 902 in the direction of arrow A."

A cylindrical separator screen, indicated generally by reference numeral 704 , forms part of a separating apparatus such as those described above with reference to Figures 10 to 13, and a sediment pick-up mechanism indicated generally by reference numeral 706 is provided upstream from the separator screen 704.

The sediment pick-up mechanism, as shown in Figure 16, comprises a rectangular front portion 708, formed with an opening 710 through which the waste water can flow to the screen 704. The front portion 708 is spaced upstream from a rear portion 712, which likewise has an opening (not shown) through which the waste water can flow to the screen 704. The front and rear portions 708 and 712 are formed of sheet metal. The rear portion 712 extends downwardly to the bottom of the channel defined by the duct 700, whereas the bottom of the front portion 708 is formed with a horizontally elongate opening 713, through which sediment, indicated generally by reference numeral 714, can travel along the bottom of the duct 700 into the space between the front and rear portions 708 and 712. A drive chain indicated generally by reference numeral 716 in Figure 17 and driven by a motor 717 is provided for driving scoops, one of which is indicated by reference numeral 718, and plates 720 along the bottom of the duct 700 between the front and rear portion 708 and 712 so as to pick up the sediment, which is then deposited from the scoops 718 through a hopper 722 into an outlet duct 724.

Alternatively, the sediment picked up by the bucket 718 may be deposited into laterally offset outlet ducts, shown in broken lines in Figure 16 and indicated by reference numerals 726 and 728, or may be carried laterally for discharge into any suitable container, for example a truck 729, also shown in broken lines in Figure 16. The drive chain 716 is illustrated in greater detail in Figures 18 and 19 and travels along a track formed by a pair of L-section metal channels 730 and 732. The drive chain comprises links 734 and 736, connected by pins 738, which extend through ball bearings 740 between the plates 734. The pins 738 project laterally into connecting members 742 which, in turn, carry the plates 720, as shown in Figures 18 and 19, and the scoops 718. The cylindrical screens described above and illustrated in Figures 10 to 15 of the drawings are formed by a plurality of ring-shaped or annular members.

Referring now to Figures 20 through 22, reference numeral 800 indicates generally a screen element which may advantageously be employed instead of the annular screen bars of the separator sections of Figures 10 through 14.

The screen element 800 comprises a metal strip 801 which is formed in a meander or serpentine shape having a plurality of radially inwardly open concavities or loop-shaped formations 802 alternating with radially outwafdly open concavities or loop-shaped formations 803. Annular radially outwardly extending projections 805 in the interiors of the formations 803 define circular openings 806, the projections 805 being formed in one piece with the strip 801.

As illustrated in Figure 21, the screen element 800 is cut in one piece from a metal strip 808, with slots 809 having convergent opposite sides 810 extending into the openings 806 from the opposite sides of the strip 801.

After the strip 801 has cut from the strip 810, the opposite ends of the strip 801 are drawn together and welded together to form the endless screen element 800 extending symmetrically about a central point P as shown in Figure 11. This deformation of the strip 801 causes the opposite sides 810 of the slots 809 to be drawn - 3δ - together into abutment with one another, thus closing the slots 809.

A plurality of such screen elements, indicated by reference numerals 812 in Figure 22, are then secured together by connecting or securing rods, one of which is shown in Figure 22 and indicated by reference numeral 814, to form a separating screen. Spacers 816 are provided on the securing rods for maintaining drainage gaps or spacings between the separating elements 812. By forming the separating elements in the endless meander or serpentine shape shown in Figure 11, the separator screen or section is provide with an internal peripheral length which is much greater than that of a separating screen having substantially the same diameter but formed of annular screen elements or bars.

Thus, the separator screen formed by the screen elements 812 has a substantially larger effective area than a cylindrical screen of the same diameter, resulting in a substantially more efficient utilization of space. Figures 23 and 24 show a modification of the apparatus of Figure 15, in which the sediment pick-up mechanism 706 of Figure lδ has been omitted and has been replaced by an auger 950 for removing sediment, for example sand, from the bottom of the duct 900. The auger 950 extends forwardly, i.e. upstream, of the separator screen 904. In this case, the bottom of the duct 900 is formed with a recess 952 for receiving a lower end 954 of the auger 950.

The inclination of the auger 950 is such that the axes of the auger 9δ0 and the cylindrical separator screen 904 are parallel to one another, the auger 950 being almost level with the top of the separator screen 904 and extending between the separator screen 904 and a side wall 954 of the concrete duct 900. The auger 950, as viewed in Figure 15, is located at the left-hand side of the separator screen 904, but may alternatively be provided at the opposite side of the separator screen 904, as shown in broken lines in Figure 15 and indicated by reference numeral 950a.

The auger 950a is also parallel to the axis of the separator screen 904.

Furthermore, the augers 950 and 950a may be replaced by a different auger, which is shown in broken lines in Figure 24 and indicated by reference numeral

950b, and which has a substantially steeper inclination than the augers 950 and 950a.

Figure 25 shows a compact, combined separator screen, pelletizer, microscreen and sediment auger apparatus, indicated generally by reference numeral 1000, according to a further embodiment of the invention.

The apparatus 1000 is contained in a tank 1002, which is supported on a foundation 1004 by means of jacks 1006. By adjustment of the jacks 1006, the bottom of the tank 1002 can be tilted so as to be downwardly inclined to the right, as viewed in Figure 25.

An upwardly open inlet 1008 is provided at one end of the tank 1002 for receiving a flow of waste water containing sludge and sediment, e.g. stones and/or sand, mixed with a liquid.

A sediment removal auger 1010 has one end located in the inlet 1008 and is upwardly inclined from that end. The auger 1010 serves to remove sediment from the bottom of the inlet. Lighter material, for example paper, which can float in the liquid, and sludge are kept above the bottom of the inlet 1010 by means of an annular air duct 1012, to which compressed air is supplied. The compressed air is discharged from the annular duct 1012 in directions inclined upwardly and inwardly with respect to the annular duct 1012 by spaced air discharge nozzles 1014 at the inner side of the annular duct 1012. The thus-suspended material floats into the tank 1002 and enters a cylindrical separator screen or basket 1016, which is similar to the screen 308 of Figure 11 and is co-axial with the auger 1010.

Instead of employing compressed air to keep the floating material in suspension, a pump or other type of agitation may be employed for that purpose.

The separator screen 1016 removes paper and other floating material from the liquid and the thus-removed material is deposited, through a hopper 1018, into an auger 1019, which extends co-axially around the auger 1010 and is driven in a manner analogous to the driving of the auger 410 of Figures 12 - 12C.

The auger 1019 has a compactor section 1017, immediately following the hopper 1018, at which the pitch of the auger is reduced in order to compact and at least partially dewater the material conveyed by the auger

1019. This has the advantage that the addition of material subsequently into the auger 1019, beyond the compactor section 1017 at a location where the pitch of the auger 1019 is increased, is facilitated and also travel of such additional material downwardly along the auger 1019 is counteracted.

The liquid itself, with entrained fine solid material and sludge, passes radially outwardly from the screen into the interior of a cylindrical microscreen

1020, which is also co-axial with the auger 1010.

The microscreen 1020 is formed of a plurality of endless serpentine screen elements 1021, which are similar to the screen elements 800 of Figure 20 but which are spaced apart from one another by a greater spacing, e.g. 20 cms. The screen elements 1021 are covered, at the interior of the thus-formed cage or basket, by a metal screen 1023. For convenience of illustration, the screen elements 1021 and the screen 1023 have been shown broken-away in Figure 26.

Water sprinkler or compressed air nozzles (not shown) may be provided above the microscreen 1020 to assist in removal of sludge from the interior surface of the screen 1023.

The microscreen 1020 removes the sludge and fine solid material from the liquid and deposits them through a hopper 1022 into the auger 1019.

Additional material may also be deposited into the auger 1019 through the hopper 1022 in order to facilitate disposal of such additional material and/or to condition the material already in the auger 1019.. For example, microsludge or biologically treated sludge may in this way be added to the auger 1019.

The sediment conveyed by the auger 1010 is transferred from the ipper end of the latter to the lower end of a further auger 1024, which is upwardly inclined at an angle greater than that of the auger 1010. The upper end of the auger 1024 may, for example, discharge this material into a suitable container, truck or the like (not shown) for transport to a disposal site.

The material conveyed by the auger 1019 is fed by the auger 1019 into a compactor 1025 and a pelletizer 1026 which, in a manner analogous to that of the compactor 304 and pelletizer 306 of Figure 11, form this material into pellets.

The thus-formed pellets drop into the lower end of an auger 1028, which is parallel to the auger 1024 and which deposits the pellets into a suitable container (not shown), e.g. for transportation. The augers 1010 and 1019, the separator screen 1016 and the microscreen 1020 are all rotated about their common axis by a drive motor 1030, acting through transmission gearing 1032, and for cleaning and other servicing can be pivoted upwardly about a pivot 1034, for example by use of a hoist indicated generally by reference numeral 1031.

In a modified embodiment of the invention, which is not illustrated in the drawings, the separator screen 1016 and the microscreen 1020 are driven by separate drive motors. This has the advantage that the separator screen 1016 and the microscreen 1020 can be driven at different speeds and/or at different times.

The liquid which passes through the microscreen 1020 leaves the tank 1002 through an outlet pipe 1036, the tank 1002 being provided near its bottom with another outlet pipe 1038 through which the tank 1002 may be drained, when required.

Claims

PATENT CLAIMS

1. A waste water treatment apparatus comprising a separator device for receiving an inflow of waste water and for separating solid materials in the waste water from liquid, and a screw conveyor for conveying and compressing the thus-separated solid materials, characterized in that the separator device (12A, 12B) comprises circularly curved, parallel screen bars (24) extending around only a lower portion of the separator devices^" (12A, 12B), and a cylindrically curved cover portion (25) extending over the screen bars (24).

2. A waste water treatment apparatus according to claim 1, characterized by an opening (31) between the cover portion (25) and the screen bars (24) and a rake (26) for discharging screenings laterally from the separator device (12A, 12B) through the opening (31).

3. A waste water treatment apparatus according to claim 2, characterized in the separator device is one of a pair of separator devices (12A, 12B), and in that the screw conveyor (14, 40) is positioned to receive the screenings from both of the separator devices (12A, 12B) through the openings (31) thereof. 4. A waste water treatment apparatus according to claim 3, characterized in that the screw conveyor (40) is an outer one of a pair of co-axial inner and outer screw conveyors (41, 45), in that the outer screw conveyor (41) δ receives the screenings from the separator devices (12A, 12B) and in that the inner screw conveyor (45) projects axially downwardly from the outer screw conveyor (41) for receiving material and conveying the material upwardly through the interior of the outer screw conveyor (41).

0 5. A waste water treatment apparatus according to any of claims 1 to 4 , characterized by a third separator device (54) located between opposite ends of the screw conveyor (40) for feeding additional material into the screw conveyor (40).

5 6. A waste water treatment apparatus according to any of claims 1 to 5 , characterized in that the separator device (Fig. 8 or 9 ) is adjustable by vertical tilting movement relative to the screw conveyor (14).

7. Apparatus for separating liquids and solids, 0 comprising a separator screen for receiving and separating the solids and liquids, a conveyor for feeding the separated solids upwardly from the separator screen and a compactor for compacting the solids, characterized in that the conveyor comprises a first 5 conveyor (222) extending at a first upward inclination through the separator screen (220) and a second conveyor (230) extending further upwardly and at a greater inclination than the first conveyor (222).

8. Apparatus as claimed in claim 7, characterized in that the compactor (214) is interposed between the first and second conveyors (222, 220) for feeding the solids in a compacted state to the second conveyor (220).

9. Apparatus as claimed in claim 8, characterized by a cutter (228) between the compactor (214) and the second conveyor' (220) for cutting the compacted solids into pieces.

10. Apparatus as claimed in claim 9, characterized in that the cutter (228) comprise a cutter blade (244) mounted for rotation with the compactor (214) at an outer end of the compactor (214) for slicing through compacted solid material discharged from the compactor (214).

11. Apparatus as claimed in claim 10, characterized in that the compactor (214) comprise a compactor auger (226) and the cutter blade (244) extends radially of the axis of rotation of the compactor auger (226). 12. Apparatus as claimed in claim 7, characterized in that the separator screen ( 302 ) comprises a cylindrical screen (308) formed by a plurality of co-axial ring members (310) and means (330) for rotating the cylindrical screen (308), the first conveyor (312) extending co-axially through the cylindrical screen (308) and comprising an auger and means extending around the first conveyor (312) for retaining solid material and the cylindrical screen (308) having means (354) for lifting solid material caught by the screen (308) and depositing the lifted solid material into the first conveyor (312).

13. Apparatus as claimed in claim 7, characterized by a pelletizer (321) for converting the compacted solids into pellets, the pelletizer (321) being located between the compactor (324) and the second conveyor (306).

14. Apparatus as claimed in claim 7, characterized in that the pelletizer (321) comprises a cylindrical housing (325), an eccentric rotor (322) within the cylindrical housing (325), outlet openings (323) for the extrusion of the compacted solids from the cylindrical housing (325) by the rotation of the rotor (322) and means (328) at the exterior of the cylindrical housing (325) for breaking into pieces the compacted solids extruded through the outlet openings (323). - 4 δ -

lδ. .Apparatus as claimed in claim 14, characterized in that the outlet openings (323) are cylindrical.

16. Apparatus as claimed in claim 14, δ characterized in that the outlet openings (327a) are slot-shaped and provided with projections (332a) extending into the outlet openings (327a) for forming indentations in the compacted solids extruded through the outlet openings (327a).

10 17. Apparatus as claimed in claim 8, characterized in that the compactor comprises a compactor auger (414), a cylindrical member (424) surrounding and co-axial with the compactor auger (414); the compactor auger (414) being connected to the cylindrical member lδ (424), and means for rotating the cylindrical member (424) and the compactor auger (414).

18. Apparatus as claimed in claim 17, characterized in that the first conveyor comprises a conveyer auger (412) co-axial with and fixed relative to

20 the compactor auger (414), whereby the rotation of the compactor auger (414) rotates the conveyer auger (412).

19. Apparatus as claimed in claim 17, characterized in that the compactor auger (414) is connected to the cylindrical member (424) by a plurality of ring members (428) spaced apart form one another along the compactor auger (414) and interposed between and fixedly connected to the compactor auger (414) and the cylindrical member (424).

20. Apparatus as claimed in claim 17, characterized in that the compactor auger (414) is connected to the cylindrical member (424) by a helical member (460) extending co-axially around the compactor auger (414).

21. Apparatus as claimed in claim 7, characterized by a universal joint (510) connecting the compactor auger shaft (508) to the second conveyor auger (514).

22. Apparatus as claimed in claim 7, characterized in that the first conveyor comprises an outer auger (610) extending around an inner auger (602) for conveying settlings from the bottom of a channel served by the apparatus.

23. Apparatus as claimed in claim 7, characterized by a heater (620) for the separator screen (608). 24. Apparatus as claimed in claim 7, characterized by means (619) for adding substances to the solids conveyed by the first conveyor (610).

2δ. Apparatus as claimed in claim 7, δ characterized by a sediment conveyor (706) for removing sediment from a location upstream of the separator screen, the sediment conveyor (706) comprising an endless drive chain (716), means (717) for driving the endless drive chain (716) around an endless path and scoops 10 (718) on the drive chain (716) for scooping up sediment.

26. A method of constructing a separator screen for use in separating liquids and solids, characterized by cutting a plurality of serpentine-shaped strips (801) of metal; deforming each of the strips (801) to lδ bring opposite ends thereof together and thereby to transform the strips into a corresponding number of endless strip-shaped members; and arranging the strip- shaped endless members side by side in succession along a common axis.

20 27. A method as claimed in claim 26, characterized by providing spacers (816) between the strip-shaped endless members to form drainage gaps therebetween. 28. A screen element for use in a separator screen for separating solids and liquids, characterized by an elongate strip of material (801) extending around a central point and having opposite ends thereof connected to one another, the strip (801) being shaped to form a plurality of alternately radially inwardly and outwardly open formations (802) distributed around and spaced radially outwardly from the central point.

29. A screen element as claimed in claim 28, characterized in that the strip (801) has an endless serpentine shape.

30. A screen element as claimed in claim 29, characterized by means (805) defining an array of openings (806) distributed around the central point for receiving connecting rods (814) for securing together a plurality of such screen elements.

31. A screen element as claimed in claim 30, characterized in that the opening defining means (805) comprise radially projecting formations formed in one piece with the strip.

32. Apparatus for separating liquids and solids, comprising a separator screen for receiving and separating the liquids and solids, the apparatus being characterized by a sediment pick-up device (602) for removing sediment from a location upstream of the separator screen.

33. Apparatus as claimed in claim 32, characterized in that the sediment pick-up device δ comprises an auger (602) projecting beyond the separator screen (608) .

34. Apparatus as claimed in claim 33, characterized in that the separator screen (608) and the auger (602) are co-axial.

0 35. Apparatus as claimed in any of claims 32 to

34, characterized by means (1016) for removing sludge from the liquid.

36. Apparatus as claimed in claim 32, characterized by a pelletizer (1026) for compacting the 5 solids removed from the liquid and forming the compacted material into pellets.

37. Apparatus as claimed in claim 34, characterized in that the means for removing sludge comprise a cylindrical microscreen (1026) coaxial with 0 the separator screen (1016) and the auger (1019) for removing sludge from the liquid. 38. Apparatus as claimed in claim 37, characterized by a pelletizer (1026) coaxial with the separator screen (1016) and the auger (1019) for compacting and pelletizing the solids separated from the liquid.

39. Apparatus as claimed in claim 38, characterized by a conveyor (1028) for removing the pelletized solids, the common axis of the separator screen (1016) and the auger (1019) being upwardly inclined and the conveyor (1028) extending upwardly at a greater inclination than such axis.