FR2796305A1 - Perforated base of biological filter which is adjustable to give flat horizontal surface so liquid does not stagnate - Google Patents

Abstract

The base of a biological filter is made of prefabricated square or rectangular sheets of reinforced concrete (1) with a pattern of perforations (3). The sheets are supported on conical feet (10), the height of which can be adjusted. There is a water tight seal between adjacent sheets.

Description

The invention relates to the technical field of water treatment facilities.

The invention relates more particularly to a method for producing draining filter floors.

The invention also relates to a new filter floor structure as well as to water treatment installations comprising such floors.

Some filtration operations in the field of water treatment are carried out on filters of granular material, contained in a structure generally made of reinforced concrete, casing, provided with a raft supported on the peripheral walls or any other concrete foundation armed consisting of a solid slab spread over the company's structure, a perforated floor supporting the filter material.

As granular filter materials, activated carbon, calcined clay sands, shales, glazed terracotta, expanded polymers for example could be used.

Such filters are in particular used for the purification of industrial effluents and wastewater with selected microorganisms or microbial consortia immobilized, for the degradation of xenobiotic or recalcitrant compounds present in many effluents.

These filters are sometimes referred to as immobilized biomass bioreactors, as opposed to conventional flocculation-free flotation activated activated sludge basins.

The Biofor® process of the Dégremont company implements such filters. This bioprocess for the treatment of urban wastewater or industrial wastewater by fixed biomass uses a biofilter, a fixed bed column packed with a granular support composed of Biolite spheres.

A feed of methanol for the heterotrophic bacteria fixed on the granules of Biolite allows, for example, a denitrification of the effluents.

The filter is fed continuously by an ascending cocurrent of air or oxygen and effluents to be treated and periodically undergoes washing of the filtering mass. It should be noted that the Biolite spheres, which are not very compressible, serve as both a filter and a support surface for the action of microorganisms and that the most important part of the biological activity occurs in the lower part of the filter.

This not only results in an attenuation of odors in the upper free surface of the granular filter, but also a need for perfect control of the co-current of effluent air at the bottom of the filter, and in particular between the slab and the perforated floor, and directly above the perforated floor.

In this respect, excellent flatness of the perforated floor is imperative, to avoid stagnation of effluents, and this for floor surfaces sometimes very large, of the order of 200 m2.

The perforated floor, in addition to its role of supporting the filter material, contributes to the homogeneity of the distribution of fluids within the filter mass, both during filtration and during filter washing.

Another process, called Biostyr, uses a particle filter in two zones: a lower anoxic zone with heterotrophic flora and a fluidized bed and an upper zone with an autotrophic flora and a fixed bed. The support for microorganisms is formed by spherical granules of two to four millimeters, made of polystyrene or any other equivalent polymer, with a density lower than the effluents to be treated. For this Biostyr® process, reference can be made to FR-A-2 741 872 and EP-A-0 347 296, for example.

There are also various methods of biomass filtering fixed on embossed supports, corrugated or on fabrics such as geotextiles.

For this type of process, reference may be made, for example, to the following documents: FR-A-2 531 099, FR-A-2 639 342 and FR-A-2 565 223.

The first perforated floors for activated biomass filter fixed or not were most often made by assembling prefabricated concrete slabs.

Reference may be made, in this regard, to the following documents: US-A-4,096,068, US-A-4,064,050, US-A-3,762,559, FR-A-2,596,385, WO-A-97 40,907.

Alternatively, a pouring of beams or concrete posts was made in the casing of the filters, a reinforced concrete slab being cast on a lost formwork previously installed on the beams constituting the floor support structure.

For this type of process, reference can be made to EP-A-0 324 673.

US-A-4 925 556 discloses a method of making a perforated floor for biomass filters.

According to this method, in a first step, a predalle thickness less than or equal to half the thickness of the finished floor first put in place. Then, in a second step, concrete is poured at one time over the entire surface of the predalle, so as to avoid differential settlements.

For this type of perforated floor installation, reference may also be made to US-A-5,087,361. There are also processes for pouring concrete in a single phase, for the entire support structure I slab. monolithic, this technique using several types of formwork lost for the realization of the beams and the slab respectively.

Document FR-A-2 759 720 describes a process for producing a filter floor in which concrete is poured directly into the casing of the filter, following the following steps: - making the casing of the filter; - Establishment of beam reinforcement of the support structure of the filter; - positioning and fixing of lost formwork; - Mounting rings protected by caps, on lost formwork, at the locations provided for the strainers; - realization of the reinforcement of the upper part of the slab; pouring the concrete to make the support structure and the slab, in one or two steps; removing the caps protecting the rings and mounting strainers on said rings.

The aim of the invention is to provide a simplified method of producing perforated floors which support filter media, this method making it possible both to avoid, unlike traditional methods, the assembly of a large number of prefabricated elements, such assembly resulting in a site by - a flatness of the floor difficult to ensure; - significant handling of parts both too heavy for transport by force of man and too light for the use of lifting cranes conventionally encountered on the site; - to limit the use of lost formwork; - to ensure an even distribution of plaster or burrs; - To avoid, by a better control of the flatness, in particular the formation in the dead zones of bacterial colonies harmful to the quality of the filtration. The implementation of the method according to the invention also allows the realization of perforated floors filters large areas on the ground, cheaper and faster than by the methods of the state of the art.

To this end, the invention relates, according to a first aspect, to a method of producing a perforated floor supporting vertical loads, in particular for fixed or non-fixed biomass water treatment filters, this process comprising the steps of: prefabrication of flat plates, holes through the thickness of said plate; prefabrication of support leg pieces for said flat plates; placing at least one flat plate on its support feet on the bottom wall of a structure such as a casing of effluent treatment biofilter; - Adjusting the distance between each flat plate and the bottom wall of the structure, by actuating means forming struts; - fixing by sealing of each flat plate on the bottom wall of the structure; - Sealing between flat plates placed edge to edge and making seals between flat plates and side walls of the structure; - withdrawal of props after waiting time necessary for good rigidity of the entire floor.

Flat plates and support feet are made of concrete, reinforced concrete or prestressed concrete.

In one embodiment, the prefabrication of the support legs and the prefabrication of the flat plates is simultaneous, elementary parts each comprising a flat plate and support feet being obtained by this prefabrication.

In another embodiment, the prefabrication of the support legs is carried out independently of the prefabrication of the flat plates, the elementary parts each comprising a flat plate and waiting frames for fixing the support legs being obtained on the one hand, and support feet being obtained on the other hand at the end of these prefabrications.

The method according to the invention may have the following other characters, taken alone or in combination - the planar plates used are not all of the same dimension in a first direction D1; the flat plates are of two types, namely square plates of a given first surface and rectangular plates of a given second surface; the means forming struts each comprise a bar passing through one of the through holes; the support feet comprise an internal frame capable of being sealed in a reservation of the bottom wall of the structure; - Is provided an additional step of introducing a lattice of continuity between the side edges of the flat plates opposite, during the production of seals; - The seals comprise a keying, the common part cast in place being made of fiber concrete without shrinkage; - the keying concrete is a concrete of metal fibers; - is also provided for the establishment of a bank bench between the bottom of the structure and the lower lateral surface of the flat plates placed near the side walls of the structure, these bench seats, pressed against the walls side of the structure, forming an additional support for the free edges of said flat floor edge plates; an additional step is provided for placing a hydro-swelling seal in a reservation of the side walls of the structure, at the edge of the lateral edge of the flat floor edge plates.

The invention relates, in a second aspect, to a perforated floor obtained by the implementation of the above method.

This floor has the following characters, taken alone or in combination - it includes through holes arranged on the nodes of a network; - The network of arrangement of the through holes is square mesh, rectangular or diamond; the support feet are arranged on the nodes of a network; - The network of arrangement of the support legs is square mesh, the flat plates being square or rectangular; - The support legs are frustoconical.

Other objects and advantages of the invention will become apparent in the course of the following embodiment of embodiments, a description which will be made with reference to the accompanying drawings in which - Figure 1 is a plan view, from above, of a first prefabricated elementary piece for the realization, by the method according to the invention, of a perforated filter media support floor, this first elementary part being of substantially square contour; - Figure 2 is a view similar to Figure 1 of a second prefabricated elementary part, substantially rectangular contour; FIG. 3 is a detail view of FIG. 1; FIG. 4 is a detail view of FIG. 2; - Figure 5 is a sectional view along the line V-V of Figure 3 or Figure 4; - Figure 6 is a detail view in vertical section, the assembly area edge to edge of two prefabricated elementary parts; - Figure 7 is a detail view in vertical section, of the junction zone between a side edge of a prefabricated elementary part and a side wall of the filter basin.

In the following text, for the sake of simplicity, the term "filter" will mean indifferently - the mass of filter material, for example granular, monolayer or multilayer, for example aerated anoxic bilayer; - The filter basin itself, that is to say in particular the tank made of reinforced concrete or metal, provided with a casing. The dimensions by weight which are mentioned in the following description are given for information only.

They correspond to a dimensioning obtained using a concrete type B40 steel reinforcement type E500.

We first refer to Figure 1.

A first prefabricated elementary piece 1, designated first piece in the rest of the text, is shown in plan view and from above.

This first piece 1 is substantially square contour and is prefabricated concrete.

The first part 1 has an upper surface 2 substantially flat and parallel to the plane P of Figure 1, plane P defined by two perpendicular directions D1 and D2.

A third direction D3, elevation, perpendicular to the plane of Figure 1, forms with the directions D1 and D2 a trihedron.

Holes 3, with axes substantially parallel to the elevation direction D3, pass through the first part 1.

These holes 3 are intended, as it will appear more fully in the following, to form support of upward injection nozzles of fluids in the filter.

These holes 3 are, in the embodiment shown, substantially identical to each other.

In other embodiments, not shown, the through holes are not all identical, so for example to establish a different injection regime in the vicinity of the side edges 4, 5, 6, 7 of the first part 1. The through holes 3 are arranged aligned in columns parallel to two first lateral edges 4, 5 of the first part 1, these columns being regularly spaced, in the embodiment shown.

The through holes 3 are, in the embodiment shown, also arranged in lines, parallel to the other two opposite side edges 6, 7 of the first part 1, these lines being regularly spaced from each other. So that, in the embodiment considered in Figure 1, the holes 3 are placed on the nodes of a square mesh grid.

In other embodiments, not shown, the holes 3 are arranged in staggered rows, or on the nodes of a rectangular mesh network or rhombus. The first piece 1 is provided with a reinforcement formed, in the embodiment in question, of steel sections of type HA8, HA12, HA14.

Thus, for a first piece of 2160 mm side and 150 mm in height, thirty six bars HA8, divided into an upper layer 8a of eighteen bars and a lower layer 8b of eighteen bars extend in the first direction D1 , thirty six bars extending similarly in the second direction D2 in a first layer 9a and a second layer 9b.

Four feet 10 form a support for the first part 1, the reinforcement associated with these feet 10 being represented in FIG.

These four legs 10, seen in the plane of Figure 1, are arranged at the corners of a square of sides parallel to the directions D1 and D2 and on the diagonals of the first part 1.

For the first piece dimensions given above, a reinforcement weight of 95 Kg is obtained.

Referring now to FIG. 2, a second prefabricated elementary part 11, designated second part in the remainder of the text, is shown in plan view and from above.

This second piece 11 is substantially rectangular in outline and is made of concrete.

The second part 11 has an upper surface 12 substantially flat and parallel to the plane P 'of FIG. 2, plane P' defined by two perpendicular directions D'1 and D'2.

A third direction D'3, of elevation, perpendicular to the plane of FIG. 2, forms with the directions D'1 and D'2 a trihedron.

Holes 13, with axes substantially parallel to the elevation direction D'3, pass through the second part 11.

These holes 13 are similar to the holes 3 of the first piece 1.

These holes 13 are, in the embodiment shown, substantially identical to each other.

In other embodiments, not shown, the through holes are not all identical, so for example to establish a different injection regime in the vicinity of the side edges 14, 15, 16 and 17 of the second part 11.

The through holes 13 are arranged aligned in columns parallel to two first side edges 14, 15 of the second part 11, these columns being evenly spaced, in the embodiment shown.

The through holes 13 are, in the embodiment shown, also arranged in lines, parallel to two other opposite lateral edges 16, 17 of the second part 11, these lines being regularly spaced from each other.

So that, in the embodiment considered in Figure 2, the holes 13 are placed on the nodes of a squared grid square.

In other embodiments, not shown, the holes 13 are arranged in staggered rows, or on the nodes of a rectangular mesh network or rhombus. The second piece 11 is provided with a reinforcement formed, in the embodiment in question, of steel sections of type HA8, HA12, HA14.

Thus, for a second piece of 2160 mm by 3240 mm side and 150 mm high, fifty four bars HA8, divided into an upper layer 18a of twenty seven bars and a lower layer 18b of twenty seven bars extend according to the first direction D'1, thirty six bars extending similarly in the second direction D'2 in a first layer 19a of eighteen bars and a second layer 19b of eighteen bars.

Six feet 20 form a support for the second piece 11.

These feet are placed in two lines of three, substantially parallel to the direction D'1.

The distances between the feet 20 of the second piece, measured in the direction D'1 or the direction D'2 are substantially identical to the distances between the feet 10 of the first piece, measured along the directions D1 or D2.

For the second piece dimensions given above, a reinforcement weight of 146 Kg is obtained.

We now refer to Figures 3 and following. Each elementary part 1, 11 is provided with reservations 21 for the introduction of height adjustable struts 22.

In the embodiment considered, the reservations 21 are placed on the nodes of the grid formed by the through holes 3, 13 so that, when the struts are removed after consolidation of the perforated floor formed by the assembly of the elementary parts 1, 11, injection nozzles can be placed in the reservations 21, as in all other through holes 3, 13 of the elementary parts.

As their name suggests, the struts 22 are elongate members, of adjustable length, for temporarily supporting and transmitting a load, namely here the weight of the elementary parts assembled together to form the perforated floor.

Each strut 22 comprises, in the embodiment considered, a bar 23 at least partially threaded in the upper part 24, the lower end portion of said bar being supported on the bottom 25 of the casing.

A threaded bush 26 cooperating with the upper portion 24 of the bar 23 allows the adjustment of the flatness of each prefabricated element of the floor. This flatness is, as has been said above, of great importance to prevent gravity stagnation of effluents in dead zones of the filter.

A coupler 37 inserted in each leg 10, 20 allows the end-to-end connection of a steel bar 27, internal to the parts 1, 11, with at least one steel bar 36 of sealing, said sealing bar 36 being placed in a reservation 28 formed in the casing floor.

In another embodiment, the steel bars 27 and 36 form a single bar, the lower portion of this bar protruding from the lower portion of the support leg 10, 20, to allow sealing in the reservation 28. Straight and in line with this reservation 28, the casing comprises a frustoconical bowl 29, opening upwards, allowing reception with functional clearance of the lower part 30 of each support leg 10, 20.

In the embodiment considered, each support leg 10, 20 is frustoconical, of straight axis, and tapers towards its lower part 30.

Each through hole forms a strainer nozzle support.

The strainers may be provided with a slotted head laterally for the diffusion of the fluids, the lateral slits preventing any passage of the filter mass, their width being less than the lower limit of the grain size curve of the filter material.

The strainers may be provided with a tubular lower part fixed in the through holes 3, 13 by means of polypropylene inserts or any other equivalent material.

The tightness between two elementary pieces assembled on their contiguous side edges will now be described.

In another general manner, this seal can be obtained by a plastic seal covered by a mortar key which maintains a good flatness between the elementary parts 1, 11.

In the embodiment considered in FIG. 6, a continuity lattice 31 is disposed between the lateral edges of the parts 1, 11 facing each other, these lateral edges being provided with a groove 32 in which a non-shrink fiber-reinforced concrete 33 is placed.

For example, class 32.5 metal fiber concrete can be used. The seal can be reinforced by the introduction of a flat gasket 35 between two lateral faces facing assembled elementary elements 1, 11, as well as by the installation of sealing strips 38, placed horizontally and parallel to the side edges 4, 5, 6, 7 or 14, 15, 16, 17, parts 1, 11, and incorporated for half of their width in parts 1, 11, and for the other half in fiber concrete 33 , thus ensuring a continuity of sealing between the parts 1, 11 and fiber concrete 33.

It should be noted that both the upper face of the perforated floor and its lower face (with the exception of course of the support legs 10, 20) are substantially flat, so that no significant area of retention or inconvenience to the Fluid flow does not exist.

Claims (19)

claims 1. A method of producing a perforated floor supporting vertical loads, in particular for fixed or non-fixed biomass water treatment filters, characterized in that it comprises the steps of prefabrication of flat plates, holes (3, 13), ) passing through the thickness of said plate; prefabrication of the support leg pieces (10, 20) for said flat plates; placing at least one flat plate on its support feet on the bottom wall of a structure such as a casing of effluent treatment biofilter; - Adjusting the distance between each flat plate and the bottom wall of the structure, by actuating means forming struts (22); - fixing by sealing of each flat plate on the bottom wall of the structure; - Making seals between the flat plates placed edges to edges and making seals between flat plates and side walls of the structure; - withdrawal of struts after waiting time necessary for good rigidity of the entire floor; 2. Method according to claim 1, characterized in that the flat plates and the support legs are prefabricated concrete. 3. Method according to claim 2, characterized in that the flat plates and the support legs are prefabricated reinforced concrete or prestressed concrete. 4. Method according to any one of claims 1 to 3, characterized in that the prefabrication of the support legs (10, 20) and the prefabrication of the flat plates are simultaneous, elementary parts (1, 11) each comprising a flat plate and support feet being obtained by this prefabrication. 5. Method according to any one of claims 1 to 3, characterized in that the prefabrication of the support legs (10, 20) is performed independently of the prefabrication of the flat plates, the elementary parts (1, 11) each comprising a plate plane and waiting frames for fixing the support legs being obtained on the one hand, and support feet being obtained on the other hand, at the end of these prefabrications. 6. Method according to any one of claims 1 to 5, characterized in that the planar plates used are not all the same dimension in a first direction D1. 7. Method according to claim 6, characterized in that the flat plates are of two types, namely square plates of a given first surface and rectangular plates of a given second surface. 8. Method according to any one of claims 1 to 7, characterized in that the means forming struts (22) each comprise a bar passing through one of the through holes. 9. Method according to any one of claims 1 to 8, characterized in that the support legs comprise an internal frame capable of being sealed in a reservation (28) of the bottom wall of the structure. 10. Method according to any one of claims 1 to 9, characterized in that it comprises a further step of introducing a trellis of continuity (31) between the side edges of the flat plates opposite, during the realization seals. 11. Method according to any one of claims 1 to 10, characterized in that the seals comprise a keyway, the common part cast in place being made of fiber concrete without shrinkage. 12. The method of claim 11, characterized in that the keying concrete is a concrete de-metal fibers. 13. Method according to any one of claims 1 to 12, characterized in that it further comprises the establishment of a bank bench between the bottom of the structure and the lower lateral surface of the flat plates placed at proximity of the side walls of the structure, these bench seats, pressed against the side walls of the structure, forming an additional support for the free edges of said flat floor edge plates. 14. Method according to any one of claims 1 to 13, characterized in that it comprises an additional step of placing a hydro-swelling seal in a reservation of the side walls of the structure, to the right of the lateral edge of the flat floor edge plates. 15. Perforated floor obtained by the implementation of the method according to any one of claims 1 to 14, characterized in that it comprises through holes arranged on the nodes of a network. 16. Floor according to claim 15, characterized in that the network of arrangement of the through holes is square mesh, rectangular or diamond. 17. Floor according to claim 15 or 16, characterized in that the support legs are arranged on the nodes of a network. 18. Floor according to claim 17, characterized in that the network of arrangement of the support legs is square mesh, the flat plates being square or rectangular. 19. Floor according to claim 18, characterized in that the support legs are frustoconical.