GB2195327A - Fluid processing medium - Google Patents

Abstract

Media assembly for providing a large surface area in the processing of fluids, particularly the biological treatment of sewage or the like as in RBC plant, comprises primary medium plates 10, typically vacuum formed sheet plastics, having corrugations 14 providing complementary uniform ridge and valley formations of its opposite faces; the plates may be stacked with the formations of alternate sheets crossed over each other and/or have flatter secondary plates 12 interposed between them. Further uses envisaged include air precipitation, heat exchange and settling of solids. <IMAGE>

Description

SPECIFICATION Fluid processing medium This invention relates to media for use in the processing of fluids as by inter-action between the fluid and a surface or surfaces of the medium itself exposed thereto and/or an agent carried on said surface or surfaces of carried or embodied in the medium or in chambers, channels or passages defined by said surfaces.

It is to be understood that the invention may have application in a wide range of processes for gaseous, vapour or liquid fluids including those having a content of dispersed or other solids, as in the bacterial or other purification or treatment of liquids such as sewage or other effluents; purifying, clarifying, filtration, aeration, oxidation or like treatment of water, effluent or other liquids; precipitating or separating solid constituents such as sludge in the case of liquids or dust in the case of air or other gases; and/or heating or cooling of fluids by heat exchange.

The object of the invention is to provide a medium for fluid processing which is simple and economical to manufacture; adaptable to a wide range of applications: readily stored, transported, assembled and installed; and which is durable and effective in use.

According to one aspect of the invention a media assembly for fluid processing includes a plurality of primary medium plates each being a sheet of material corrugated to provide complementary uniform ridge and valley formations of its opposite faces, said plates being arranged in a stack with the formations of alternate sheets crossed over each other.

According to another aspect of the invention a media assembly for fluid processing includes a plurality of primary plates as defined above and one or more secondary medium plates, each of sheet material which is planar or has a much flatter profile than the primary plates and each interposed between a respective pair of adjacent primary plates.

Preferably, in the latter assembly, the primary plates are still arranged with the formations of alternate sheets crossed to add to the rigidity of the assembly, and the secondary plates may be provided with dimples, projections or other shallow formations to aid in location of the primary plates in the stack.

Preferably the corrugations of the primary plates are of V cross-section and it is further preferred that the faces defining each ridge/valley are angled at 600 to each other, i.e. are pitched in planes inclined at 300 from the vertical when the plate is horizontal.

It is further preferred that the sheet is formed to include a series of buttress formations spaced at intervals along each valley/ridge of the corrugations by portions of the sheet material being displaced to project above the general level of the valley bottoms and correspondingly below the level of the ridge crests and extending at least part-way along the flanks of the corrugations to provide added rigidity to the latter and at the same time to facilitate the cross-cross location of the abutting ridges or the engagement of those ridges with a dimpled or otherwise formed secondary plate.

The invention further resides in apparatus for the purification or other treatment of water, effluent or sewage incorporating media according to one or more of the above definitions.

The invention is particularly applicable to media serving as the vehicle for carying an active bacterial film for the biological treatment of sewage, for example using a rotary biological contactor ("R.B.C.") or as a basis for a static bacterial treatment bed.

In the latter applications the plates are preferably formed from polyethylene or polypropylene materials which may include inhibitors to increase their resistance to degrading or deterioration in service, e.g. carbon black to inhibit degradation due to exposure to sunlight and/or a bacterial, fungicidal or insecticidal inhibitor for resisting bacteriological erosion of the media and/or the growth of undesirable organisms thereon or therein or in the fluids under treatment, e.g. to reprepress the breeding of mosquitoes in water under treatment.

Examples of the invention and its application are now more particularly described with reference to the accompanying drawings wherein: Figure 1 is a perspective view of part of a primary medium plate; Figure 2 is a like view of part of a secondary medium plate.

Figure 3 is a perspective view of part of a pack built up from said plates, and Figure 4 is a section of part of said pack.

The drawings show a media assembly primarily intended for use in an R.B.C. for sewage treatment. Primary plates 10 and secondary plates 12 are vacuum formed from sheet polyethylene or polypropylene containing carbon black as an inhibitor against degradation due to sunlight.

The primary plates 10 are each formed to have corrugations 14 forming ridges and valleys extending across or diagonally of the whole area of the sheet. The crests of the ridges on each side of the sheet occupy respective common planes in spaced parallel relationship and, in this example, the flanks of the corrugations are generally planar and meet at said crests at an included angle of around 600. Thus each flank is inclined at an angle of about 300 to a plane normal to said parallel planes and intersecting the respective crest as shown in Fig. 4.

Portions of the sheet at regular intervals along each valley/crest are displaced to form buttress formations 16 (Fig. 1), each said for mation projecting upwardly of the floor of each valley and extending part-way up the pair of flanks defining the valley and, conversely, forming a corresponding depression or notch in the crests of the ridges extending down the associated flanks. The adjacent formations 16 along each valley/ridge extend past each other transversely of the flanks.

These buttress formations add considerably to the rigidity of the plates 10 as they resist any tendency for the areas of the sheet forming the flanking walls of the valleys/ridges to buckle or deform, thus pressures which would otherwise tend to flatten the corrugations are resisted.

When a number of plates 10 are aligned with their corrugations running in the same direction they will nest with each other so that a large number of plates can be contained in a small volume for storage or transport until required for use.

Buttress formations 16 also facilitate the location together and assembly of the plates as referred to hereafter.

The secondary medium plates 12 (Fig. 2) are generally planar except that, in this example, they are formed with a chequer board pattern of shallow pyramid shaped projections and dimples or depressions.

A number of plates 10 and 12 are formed into a stack as shown in Fig. 3 to provide a media assembly for fluid processing in its operational form. Sector shaped stacks may be assembled on a rotatably driven horizontal shaft with suitable supporting spokes framework in the construction of an R.B.C. for sewage treatment as described and claimed in our co-pending patent application number of even date herewith.

The stack consists of alternate primary plates 10 and secondary plates 12 sandwiched together. Preferably the adjacent primary plates 10 are arranged so that their respective corrugations 14 cross each other which adds to the rigidity and integrity of the stack, and the slight projections on the opposite faces of the secondary sheets 12 co-act with at least some of the notches in the crests of the ridges of plates 10 to locate said plates positively in place.

It should be mentioned that many of the plastics materials most suited for such applications as sewage treatment due to their high resistance to corrosion and chemical action cannot be reliably bonded together using adhesives, nor is it practicable or economical to secure the stacked plates together by welding.

The shaping and arrangement above described dispenses with the need for such securing together of the plates, they are adequately held in place on assembly by appropriate clamping of the opposing faces stack e.g., in the case of an R.B.C. by tie rods or the like extending through the stack or pack in an axial direction.

For some applications the secondary plates 12 may be dispensed with and the stack or assembly may consist solely of primary plates 10. In this case the ridges on the opposite faces of the adjacent plates are disposed so that they cross over each other to keep them apart, and again location and integrity of the stack so formed is provided by inter-engagement of the notched portions of the crests of the ridges provided by the buttress formations 16.

One of the important advantages of the invention, particularly in the form utilising the secondary plates 14, is that a very large surface area can be provided for interaction with the fluids being processed or treated within a compact overall volume or envelope.

With the 60 included angle between the flanks of the ridges/valleys each valley defines a passage which is an equilateral triangle in cross-section. As both sides of the primary plates 10 are exposed to the fluid for most applications, e.g. in an R.B.C. the ratio of effective area (E.A.) to projected area (P.A.) is 2: 1, i.e. the E.A. is twice the area of a flat plate. With the inclusion of the secondary plates 12, which, in effect, adds a further flat surface the E.A./P.A. ratio allowing for loss at the local areas of contact between the plates 10 and 12 at the crests of the ridges) is increased to about 2.85:1. For biological applications the E.A. is referred to as the effective biological area (E.B.A).

The E.A. can also be considered in relationship to the volume occupied by a pack or assembly of the media, the E.A. to volume ratio. In defining this it is imagined that a cube of assembled plates has a projected area equivalent to the area of the two sides of a flat plate of unit area e.g. 1m2, i.e. 2m2. The E.A.

is hence 2x2.85 (assuming that secondary plates 12 are incorporated, i.e. 5.7 m2. In the example shown in the drawings the spacing between centres of adjacent secondary plates 12 of the sandwiched assembly is 37.5 mm, thus in the 1000 mm thickness of a 1 m cube the number of plates 12 would be 26 and the nominal E.A. per cubic meter volume would be 150 m2. If secondary plates 12 were not incorporated the ratio would be 100 m2 per cubic meter.

Where square or other rectangular plates are used it is preferred that the corrugations extend at an angle of 45 to the plate edges to maximise the length of the through passages so defined and thus the contact time of fluids therein. Thus with coordinates along x and y axes at the plate edges of 1 the length of the diagonal passages would be 1.4142.

However other angles may be used. With the plates vertical or near vertical laminar flow conditions will be created as the fluid passes along the inclined apertures which will enhance settlement of solid content at theoretical retention periods so that pollutants can be effectively separated from liquids in a minimum overall volume.

Some of the various practical applications of the invention, by way of example, are as follows:a) R.B.C. applications.

As referred to above the invention has particular application to R.B.C. for sewage and effluent purification and it is contemplated that various sizes of R.B.C. unit may be provided depending on the capacity required. The assembly of disc or sector shaped media packs may be from 1 m up to 6m in diameter and may be rotatably driven at speeds from 10 r.p.m. down to 0.5 r.p.m. or less depending on the overall diameter as the desirable peripheral speed of the rotor assembly should be around 0.35m per second for this biological application. As indicated above the E.B.A. of the sandwiched medium is 2.85 x the projected area giving an effective biological area to volume ratio of at least 150:1.

b) Conventional biological filtration.

In conventional bacteria beds or the like where previously settled effluent is spread onto a bed of media or is cascaded by means of a revolving or rectangular distributor device, or is flowed through the media in a flooded upward or downward flow arrangement conventional media beds are made frrom washed anthracite, washed stone or various plastics substitutes. In conventional applications vertical depths of up to 3m are usual. It is also known to provide packed media towers so as to reduce the overall service area either because of restriction in the space available or because of the need to have high rate filtration but such towers may have to be up to 6m in height.The use of the invention, as referred to above, gives the substantial increase of the E.P.A./P.A. ratio and, if the through passages defined in the stacked media are inclined at 45 the length of the vertical travel through the stack is substantially increased, e.g. from the height of the stack alone to its heightx 1.4142. Thus, the media of the invention is far more effective than conventional media for this type of application.

c) Aeration plant.

Similar considerations as in paragraph b) apply to the aeration of effluents or the like, e.g.

to provide oxidation. Conventional methods include the provision of fine, medium or coarse bubble means; or use of mechanical vertical or horizontal aerators. It is proposed that a sub merged module being an assembly of the media of the invention, is used covering the com plete area of the tank. This will increase the actual aeration time without having to increase the power requirements for oxidation pur poses, thus producing a high rate aeration plant. Such plants are particularly suitable for industrial waste treatment, for-example waste from cellulose paper production and chemical processes, enabling the water to be re-used if sufficiently purified.

d) Cooling towers and other heat exchange apparatus.

Known cooling towers use a series of plastics or other elements such as trays or troughs, the water or other fluid cascading from one to the other with fan or natural ventilation.

The media of the invention can be employed, preferably with the passages defined by the primary plates arranged to cross each other diagonally to produce a more tortuous path. It is believed this will provide for effective operation without getting the build-up of re-calcified salts which can ultimately block some types of conventional media used at present.

e) Parallel plate separators.

Known apparatus of this type uses spaced flat plates supported at an angle to the vertical in a tank for primary or final settling or clarification of sewage, water or industrial effluent. The retention period within the tank is intended to provide quiescent conditions allowing the solids to settle to the bottom while the clear effluent is discharged over a weir. It is contemplated that submerged modules assembled from the plates of the invention would be suspended above floor level but well below the weir level to form a type of stratifying element. The liquid under treatment would have to find its way upwardly through the passages through the media assembly with laminar rather than turbulent flow.This enables the retention period and hence the volume of tank required to be reduced considerably and/or enables the parallel plate arrangement to be considered as a "roughing" unit for primary settlement with the further treatment in the media modules giving finished effluent of very high standard. It is believed this application has particula#r merit for water treatment where precipitators or clarifiers are normally the first treatment stage with chemicals such as alum added to enhance settlement out of the solids before the water goes on for filtration, chlorination etc. The plastics material preferred for the invention has high resistance to most chemicals though it may be need to be further treated to withstand some chemicals used in this type of application.

f) Air precipitators.

It is contemplated that the media of the in vention might be used in air precipitators of the dry and wet type.

Claims (20)

1. A media assembly for fluid processing including a plurality of primary medium plates each being a sheet of material corrugated to provide complementary uniform ridge and valley formations of its opposite faces.

2. An assembly as- in Claim 1 wherein the plates are arranged in a stack with the formations of alternate sheets cross over eache other.

3. An assembly as in Claim 1 or 2 including one or more secondary medium plates, each of sheet material which is planar or has a much flatter profile than the primary plates and each interposed between a respective pair of adjacent primary plates.

4. An assembly as in Claim 2 wherein the secondary plates are provided with dimples, projections or other shallow formations to aid in location of the primary plates in the stack.

5. An assembly as in Claim 1, 2 or 3 wherein the corrugations of the primary plates are of V cross section.

6. An assembly as in Claim 5 wherein the faces defining each ridge/valley are. angled at 60 degrees to each other so as to be pitched in planes inclined at 30 degrees from the vertical when the plate is horizontal.

7. An assembly as in any preceding claim wherein each primary medium plate includes a series of buttress formations spaced at intervals along each of valley/ridge formation by portions of the sheet material being displaced to project above the general level of the valley bottoms and correspondingly below the level of the ridge crests and extending at least partway along the flanks of said corrugations.

8. An assembly as in any preceding claim wherein the plates are formed from sheet plastics material.

9. An assembly as in Claim 8 wherein the sheets are vacuum formed.

10. An assembly as in Claim 8 or 9 wherein the plastics material is polyethylene or polypropylene.

11. An assembly as in Claim 10 wherein said material includes one or more inhibitors to increase resistance to degrading or deterioration in use.

12. A media assembly substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

13. Apparatus for the purification or other treatment of water, effluent or sewage incorporating a media assembly as in any preceding claim.

14. Apparatus as in Claim 13 wherein the apparatus includes a rotary biological contactor having a pack or packs of said media assembly as a vehicle for carrying an active bacterial film in use.

15. Apparatus as in Claim 13 including one or more static beds or stacks of media comprising said media assembly.

16. Apparatus as in Claim 13 including a tank for settling or clarification having a said assembly positioned to act as a stratifying element to assist settlement of solids.

17. Heat exchange apparatus including a media assembly as in any one of Claims 1 to 12.

18. Apparatus as in Claim 17 in the form of a cooling tower.

19. An air precipitator including a media assembly as in any one of Claims 1 to 12.

20. A rotary biological contactor for sewage treatment substantially as hereinbefore described with reference to the accompanying drawings.