SETTLEMENT TANKS

Abstract: A settlement tank has a lower region defining a series of conical chambers (10) and an upper region having a portion (18') separating the upper region into inlet and outlet chambers both lying above and communicating with the conical chambers (10). The outlet chamber contains plastics settlement media (14) which encourages sedimentation. The conical chambers (10) are provided by connecting modular components defining two half cones extending back to back together in a row. Adjacent conical chambers (10) intersect oe another at the upper ends without deviating from the conical profile to define a channel of communication between the cones to allow a substantially even distribution of water throughout the tank.

Description: SETTLEMENT TANKS The present invention relates to a modular settlement tank used for the removal of suspended solids from a liquid such as use in a waste water treatment plant . A modular settlement tank for use in the treatment of waste water has been disclosed in co-pending international patent application PCT/GB 96/01435. This prior art settlement tank is formed of a series of inverted cone-like settlement chambers provided with ground engaging support legs. Plastics settlement media in the form of an array of inclined parallel tubular members are supported above the settlement chambers on perimeter walls formed by the truncated walls of the chambers. The plastics media is surrounded by modular support panels resting on the perimeter walls with deflector plates dividing the interior of the tank between the panels so that incoming waste water is guided through the media towards an outlet so provided above the settlement media. The plastics settlement media encourages suspended solids in the liquid passing through to collect into clumps which then fall under gravity as sediment into the settlement chambers for subsequent removal to a de- sludging apparatus in the normal way. In the prior art settlement tank, the perimeter walls of the base of the settlement chambers all lie in the same plane so that there is no possibility of intercommunication between the chambers when the plastics settlement media is in place. There is an evident problem with this arrangement which occurs when the deposited material in some of the settlement chambers is evacuated faster than that in other chambers as a result of which, the settlement media can become blocked. This leads to an imbalancing effect which reduces the operating efficiency of the system. Furthermore, solid material deposited in the settlement chambers is prone to adhere to the corners of the settlement chambers rather than flowing smoothly towards their vertices, this being due in part to the configuration of the quasi cone shaped chambers brought about by the need to form a common flat perimeter between them while maintaining individuality. It is an object of the present invention to overcome the disadvantages of the prior art modular settlement tank as explained above. This is achieved by designing the internal surfaces of the settlement chambers so that collection of solid material in the chambers for efficient disposal is not impeded and at the same time providing for limited communication between individual settlement chambers so that evacuation of the chambers substantially occurs at a uniform rate as between the individual chambers in the settlement tank. According to one aspect of the invention there is provided a modular settlement tank for use in waste water treatment comprising two or more cone shaped settlement chambers for settled material, a series of interconnected modular panels for housing plastics settlement media erected around an outer planar perimeter formed by the assembled settlement chambers, means for passing waste water through the settlement media thereby to remove solid residue contained therein for subsequent collection in the settlement chambers, characterised in that the walls of the settlement chambers intercept in advance of the planar perimeter on circular cross sections of the cones to provide intercommunicating overflow openings between the settlement chambers positioned at the upper part of the settlement chambers and beneath said planar perimeter. According to another aspect of the present invention there is provided a modular settlement tank comprising a linearly extending array of similar modular sections connected end to end between two end sections, each said similar section comprising a component defining two inverted half cones connected back to back and intersecting one another at their upper ends to define a channel of communication between the half cones, each half cone being sealingly connected to an adjacent half cone of an adjacent section to define a conical chamber having a wall whose internal surface does not deviate substantially from the conical. The openings between the adjacent cones, where all the vertical axes of the cones are made parallel and the intersection of the walls are on circular cross sections of the cones, will thus be defined by a base edge of parabolic curvature formed along the line of intersection with the line joining the parabolic part lying in a plane containing the planar perimeter of the assembled cones for supporting the settlement media. Since the walls of the cones intercept in advance of the planar perimeter, there is no need to introduce discontinuities in the slope of the walls which would provide preferential sites for accumulation of solid residue as with the prior art. Settlement tanks embodying the present invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a perspective view of a modular settlement tank according to the prior art; Figure 2 is a perspective view of a modular settlement tank incorporating an embodiment of the invention; Figure 3 is a perspective view of a further form of modular settlement tank incorporating the invention; Figure 4 is a transverse section through a pair of settlement tanks each according to Figure 2 linked by a common walkway; Figure 5 is a transverse section through a pair of settlement tanks one of which corresponds to the tank of Figure 3 and the other of which is a modification of the tank of Figure 3; Figure 6 is a transverse section of the tank of Figure 2 incorporating a modification; and Figure 7 is an enlarged detail of Figure 6. The modular settlement tank 1 shown in Figure 1 according to the prior art, is formed of a series of inverted generally cone-shaped chambers 2 supported on the ground by depending legs 3. Any number of these cone- shaped chambers 2 may be joined together to provide the required base area of the settlement tank. The perimeter wall of the assembled settlement chambers 2 is formed with standard vertical panels 4 joined and sealed to the base and to each other as shown. Plastic settlement media 5 are supported within the perimeter walls on the top of the settlement chambers 2 and modular panels 4, or deflector plates 6, divide the interior of the tank so that incoming liquid, such as from a waste water filter, through inlet pipe 7 is guided upwardly through the settlement media towards the outlet 8. Suspended solids in the waste water removed during passage through the settlement media 5 thereafter collect in the settlement chambers 2, the vertices of which are connected via piping 9 to de-sludging apparatus (not shown) . The generally cone-shaped chambers 2 have a portion thereof extending from their vertices which is of the form of a true circular cone. Over a final upper portion, however, the chambers depart from true circularity so as to achieve the formation of a rectangular support rim 2' as shown. Thus the slope of the interior surface of the chamber 2 is not within a preferred range having regard to the need for rapid settlement in the chambers and subsequent de-sludging. The structure of the modular settlement tank as above described is such that a modular filter housing of the type described in my co-pending international application PCT/GB 96/01435 may be constructed on the tank to form a complete modular waste water treatment plant. Settled liquid from the tank may be re-circulated through the filter enhancing the process without increasing the floor plan. This system, while being generally effective, suffers certain disadvantages which the present invention seeks to overcome. Thus in the first place there is no overflow provision for the settlement chambers leading to blockage in the settlement media and the creation of imbalancing effects in the system. Secondly, and as mentioned above, the configuration of the internal surfaces of the settlement chambers leads to preferential settlement of solid residue so that a de-sludging process is needed. Thirdly, the design lacks versatility and cannot be adapted readily to accommodate settlement media of differing depth to suit user requirements. A settlement tank according to an embodiment of the invention and as illustrated in Figures 2 and 3 comprises a row of settlement chambers 10 formed by joining two twinned half cone sections 13 together by any suitable means such as nuts and bolts. Any number of twinned half cone section 12 can be coupled together to increase the length and therefore the capacity of the settlement tank as desired. Each settlement chamber 10 is in the form of an inverted true circular hollow cone having a surface slope at a predetermined angle with no detrimental discontinuities and within a preferred range of inclination having regard to the requirements of efficient settlement and disposal of solid residue, ie sludge, including from a cost point of view. To achieve this, the walls of adjoining settlement chambers 10 intersect on circular cross sections of the individual cones, the line of intersection thus following a parabolic curve 11, the ends of which terminate at a perimeter frame 12 of the settlement chambers 10, having a flat horizontal surface 12' for supported settlement media 14. By this means, intercommunicating overflow passages are formed between the settlement chambers 10 and beneath the perimeter frame 12. Two closure half-cone sections 40 complete the opposite ends of the row. Modular wall panels 15 for defining a chamber to contain settlement media 14 are mounted on top of the flat perimeter supporting surface 12'. To improve the operational versatility oi " the settlement tank the design of the modular wall panel 15 and its other operative component parts may be designed to accommodate settlement media 14 of differing depths. Thus the form of settlement tank shown in Figure 2 is designed to cater for greater depth settlement media 14 than that shown in Figure 3 which size differential will vary according to user requirements. Parts in Figure 3 similar to those in Figure 2 are similarity referenced. In Figure 2, the greater depth settlement media 14 rests directly on the flat perimeter surface 12' and cross members 16 extending across the width of the frame 12, while the settlement media 14 of lesser depth shown in Figure 3 is supported on the cross members 17 arranged between the modular wall panels 15 above the frame 12. The type of plastics settlement media 14 shown in the drawings and sold under the trade mark TUBE Dek ® , is composed of individual blocks provided with internal passageways inclined at 60° to the vertical and to the horizontal top and bottom surfaces. However, other proprietary lamella media could be used to encourage sedimentation . Accordingly the individual blocks of settlement media 14 are bounded on their inclined sides 14' and 14" by modular panels 18, 18' composed of a sloping section 20 to correspond to the inclined sides 14' and 14" of the blocks 14, and an upper vertical section 21 which extends to the top of the settlement tank. A series of such modular panels 18 forms one outer wall of the settlement tank shown in Figures 2 and 3, while another series of modular panels 18' form internal deflector plates for incoming waste water from inlet pipes 23. These deflector plates 18' form a partition which divides the upper part of the tank into two separate chambers each of which communicate with chambers 10. The three other outer sides of the settlement tank are formed of flat modular wall panels 24 all connected one to the other and resting on the flat perimeter surface 12' of the rectangular frame 12. In Figure 2, the blocks of settlement material 14 extend substantially across the whole width of the perimeter frame 12 such that an internal chamber 25 for receiving waste water from inlet 23 is formed between the modular panels 18' forming the deflector plates and the flat modular panels 24 forming the sides of the settlement tank. The chamber 25 is in communication with the settlement chambers 10 through a narrow opening 26 formed between the bottom edge of the sloping section 20 and the outer modular wall panels 24. In Figure 3 the deflector plates 18' are so positioned between the sloping walls 20 of modular panels 18 and the flat modular outer wall panels 24 that a larger receiving chamber 27 for waste water from inlets 23 is formed and leaving a wider communicating opening 28 to the settlement chambers 10 than in the Figure 2 embodiment. The waste water in both the Figure 2 and Figure 3 settlement tanks is directed to the receiving chambers 25 and 27, through inlets 23, collects in the settlement chambers 10 which then gradually fill up, the waste water eventually rising through the tubes of the settlement media 14 to the top of the settlement tank. Solid residue in the waste water is encouraged to collect in the tubing of the settlement media 14 thereafter to fall under gravity back into the settlement chamber 10. The thusly treated waste water rising to the top of the settlement tank is borne away through outlet weir 29. It will be appreciated that the two half cone sections 13 can be formed from a single moulding which is provided along the perimeter of each half cone with a flange 42 extending outwardly and at right angles to the adjacent surface so that it can be clamped to a corresponding flange of an adjacent half cone section 13 by fastening means such as nuts and bolts. A sealant or gasket may be supplied between abutting flanges 10 to achieve a watertight seal. Similarly, the flanges along the upper perimeter of each half cone section can be secured to corresponding flanges on the panels 15, 18 and 24. It will be appreciated that by using the modular construction of two half cone sections, a linear series of settlement chambers 10 can be produced to cover as great an area as is required. Also, because of the parabolic recess formed by the intersecting walls of adjacent settlement chambers, there is a free flow of water between the chambers 10 to ensure greater uniformity in the flow of water through the different blocks of settlement media. This ensures a more uniform and trouble free settlement action. Instead of having a single long run of settlement chambers 10, two separate runs 60 and 62 of settlement chambers can be located side by side (see Figure 4) . The chambers 10, as in the case of the prior art arrangement of Figure 1, are supported by legs 64. Also, a further leg 66 is used to support the upper part of the panel 18. By arranging the direction of the run 62 to extend in the opposite direction of the run 60, the legs 66 of the two runs will lie adjacent one another. By arranging the two sets of legs 66 to be spaced say a meter apart, a raised walkway 68 can be suspended between the two runs to extend the full length of the two runs. This walkway 68 will provide access for personnel to the upper regions of the settlement tanks of servicing or maintenance and carry the inlet and outlet pipes and other equipment. Since servicing sometimes involves unclogging the tubes of the settlement media with water or air jets, it is particularly advantageous for the tubes of the two rows of runs 60 and 62 to be inclined in a direction in which the upper ends lie closest to the walkway 68 and extend in a direction away from the walkway 68. A ladder (not shown) may provide access to the walkway. In the arrangement shown in Figure 5, two runs 70 and 72 of settlement chambers are provided. The first run uses settlement chambers similar to those described in Figure 3. The run 72 uses settlement chambers which are a modification of the chambers of Figure 3. In Figure 5, each chamber of the run has two sets of settlement media 14 located on opposite sides of the settlement chamber 10. Two modular panels 18 define opposite outer walls and two modular panels 18' define internal deflector plates for incoming waste water from pipe 23. The two inner walls 18' define a receiving chamber 37 which converges towards a narrower communicating opening 39 to the settlement chambers . Outlet weirs 29, on opposite sides of the tank, carry away treated waste water rising to the top of the settlement tank. In this arrangement, as with the arrangement of Figure 4, the adjacent spaced legs 66 carry a walkway 68 to enable servicing and maintenance of the tanks. When three rows of settlement tanks are required, it will be appreciated that a third row can be provided similar to the row 70 but running in the opposite direction on the opposite side of the row 72. This will allow a further walkway to be supported between the row 72 and the further row. In the arrangement of Figure 6, parts similar to those in Figure 2 are similarly referenced. In this arrangement, the inlet pipes 23 dispensing incoming water into the settlement tanks are omitted and instead incoming water to be treated is admitted through an opening 80 in the wall 15 at a level below the upper water level in the tanks at a location adjacent the side panel 24. The panels 24 and 18 are bridged by a series of "U" shaped cross members 82 which have a slight degree of flexibility. A partition 84 comprising an elongate member of curved cross-section is supported to extend the length of the receiving chamber 25 with its upper end being supported by the cross-members 82 at a position slightly spaced from the wall 20 and its lower end actually engaging the inner face of the wall 20. The partition 84 together with the wall 20 forms a trough for receiving the incoming water from the inlet orifice 80. The partition 84, at locations between the cross members 82, is provided with recesses 86 which define a series of weirs to allow water to pass from the trough into the receiving chamber proper. This arrangement of the inlet introduces less turbulence in the tank and therefore encourages settlement to take place more efficiently. In the event of the level of the water in the receiving chamber 24 dropping significantly, the weight of the water left in the trough will bear heavily on the partition 84. This in turn will apply a bending movement to the beans 82 which will then flex sufficiently for the lower end 84' of the partition to be disengaged from the wall 20. The water in the trough will then escape through the resulting gap flushing out with it any material which has in the meantime settled in the bottom of the trough. As can be seen in Figure 7, the upper end of the trough 84 has a horizontal extending flange 84" which is secured to the cross-members 82.

Claims: CLAIMS 1. A modular settlement tank comprising a linearly extending array of similar modular sections connected end to end between two end sections, each said similar section comprising a component defining two inverted half cones connected back to back and intersecting one another at their upper ends to define a channel of communication between the half cones, each half cone being sealingly connected to an adjacent half cone of an adjacent section to define a conical chamber having a wall whose internal surface insofar as it extends does not deviate substantially from the conical. 2. A tank according to Claim 1, wherein said array has an upper perimeter wall supported on the upper perimeter of the array, and a partition extending longitudinally of the array to divide the space bounded by the perimeter wall into first and second processing chambers, both lying directly above and communicating with the conical chambers, the first processing chamber being arranged to receive water to be treated and the second processing chamber containing plastics settlement media through which the water from the first chamber must flow before being discharged from the second chamber. 3. A tank according to Claim 2 , wherein the lower end of the partition lies substantially level with the upper extent of the conical chambers. 4. A tank according to Claim 2, wherein the lower end of the partition lies spaced above the upper extent of the conical chambers. 5. A tank according to Claim 2 or to Claim 3, including pipe means having a plurality of outlets for discharging water to be treated into said first chamber. 6. A tank according to Claim 2 or to Claim 3, including a curved element which is urged against a wall of the first chamber to define a trough for receiving water to be treated and providing a weir over which water from the trough can pass to the first chamber, the trough, when not supported by water within the first chamber, being arranged to be displaced by the weight of water in the trough, away from the wall of the chamber to release the water from the trough through the resulting gap into the first chamber. 7. A tank according to Claim 6, wherein the curved element is secured to cross members extending across the first chamber, the flexibility of the cross members being such as to normally urge the element against the wall of the first chamber, but allowing it to become spaced from the first chamber in response to pressure. 8. A pair of modular settlement tanks each according to any preceding claim, supported in side by side parallel but spaced relationship by ground engaging legs, and a raised walkway extending between the two tanks substantially along the length thereof, the walkway being supported by adjacent legs of the two tanks. 9. A pair of modular settlement tanks according to Claim 8, each having inclined lamella media for encouraging sedimentation, the inclinature of the lamella media of the two tanks being downwardly from the top of each tank and away from the walkway. 10. A modular settlement tank for use in waste water treatment comprising two or more cone shaped settlement chambers for settled material, a series of interconnected modular panels for housing plastics settlement media erected around an outer planar perimeter formed by the assembled settlement chambers, means for passing waste water through the settlement media thereby to remove solid residue contained therein for subsequent collection in the settlement chambers, characterised in that the walls of the settlement chambers intercept in advance of the planar perimeter on circular cross sections of the cones to provide intercommunicating overflow openings between the settlement chambers positioned at the upper part of the settlement chambers and beneath said pianar perimeter.

Inventors: SINGLETON MARK JAMES, SINGLETON, MARK, JAMES
Applicants: BIORIGINAL LTD, SINGLETON MARK JAMES, BIORIGINAL LIMITED, SINGLETON, MARK, JAMES
Application year: 1997
Main classification: B01D21
IPC codes: B01D21