WO2003097534A2

WO2003097534A2 - Effluent treatment method and installation

Info

Publication number: WO2003097534A2
Application number: PCT/FR2003/001524
Authority: WO
Inventors: Pierre Sabalcagaray
Original assignee: Pierre Sabalcagaray
Priority date: 2002-05-22
Filing date: 2003-05-20
Publication date: 2003-11-27
Also published as: FR2839965A1; FR2839965B1; WO2003097534A3

Abstract

The invention concerns the treatment of effluents essentially by mixed microbiological process. More particularly, the invention concerns the treatment of highly biodegradable liquid effluents derived in particular from agricultural activity (dairy cattle breeding, soilless breeding, winemaking), industrial activity (small agri-food industries) or urban (small townships or isolated hamlets). Therefor, it consists in causing the effluents to flow successively in different zones of bioconversion comprising in particular: a solution (1') consisting of liquid to be treated; a bacterial support including a plurality of panels (3) made of synthetic materials arranged adjacent and spaced apart from one another, at least substantially vertically, such that each panel (3) has at least one non-immersed aerial part (3a) extending above the solution (1') and at least one part immersed (3b) in said solution (1').

Description

EFFLUENT TREATMENT PROCESS AND INSTALLATION.

The invention relates to the treatment of effluents by an essentially mixed microbiological route, that is to say by degradation of organic pollutants by means of bacterial systems, both with aerobic and anaerobic metabolism. It is more particularly aimed at the treatment of highly biodegradable liquid effluents which come in particular from agricultural activity (dairy farming, above-ground farming, wine-growing operations ...), industrial (small food industries) or even urban (from small towns or isolated hamlets).

Throughout the text, the following terminology is adopted:

- effluent: aqueous liquid composition comprising pollutants, biodegradable or not, essentially soluble or in the form of small particles responsible for turbidity,

- liquid composition: any essentially liquid composition which may be a raw effluent which has not yet undergone any purification treatment, an effluent during treatment, or a mixture of effluents at different stages of treatment, - aerobic treatment: biotransformation of organic compounds of effluents, essentially produced by bacteria (or any other micro-organism) with aerobic metabolism,

- anaerobic treatment: biotransformation of the organic compounds of the effluents, essentially carried out by bacteria (or any other micro-organism) with anaerobic metabolism,

- anoxia: is said to be a condition in which free oxygen is substantially absent, but where different elements are found in oxidized form (for example, nitrites and nitrates),

- biofilm: thin film formed by microorganisms, in particular bacteria, which develop on the surface of a culture support, - biological sludge: mixture of muddy appearance of microorganisms and residual sediments essentially resulting from an aerobic type treatment.

For a few years now, livestock farms as well as small communities and small agrifood companies have been concerned with the application of regulatory texts relating to the preservation of the environment which require them to treat the effluents from their activities, before any rejection in the natural environment. There is thus a need for these small structures to be able to have treatment means, both adapted to the nature of their effluents, to the production rate of these effluents, and which take into account the lack of space of these small structures as well only financial constraints.

Among the methods of effluent treatment by mixed microbiological route, lagooning processes have been known for a long time. These so-called rustic methods are based on the use of one or more retention tanks left in the open air, into which the effluents to be treated are routed. Lagooning is available in two main variants, called non-aerated or aerated, depending on whether the oxygenation of the basin takes place naturally in contact with atmospheric air and especially by algae which produce oxygen by photosynthesis, or mechanically, for example by means of air diffusers arranged at the bottom of the basins or, more often, surface aerators.

In non-aerated lagooning, at the level of the effluent surface of the basin occurs mainly an aerobic type treatment with degradation of organic compounds by oxygenation. At the bottom of the tank, away from oxygen, an anaerobic digestion of particles and decanted biological sludge occurs essentially.

In aerated lagooning, a better yield is obtained thanks to a mechanical oxygenation and mixing of the liquid composition of the basin allowing the maintenance of a dissolved oxygen concentration favorable to an aerobic mechanism. In addition, the stirring is deliberately low enough to allow the settling of biological sludge at the bottom of the basin and the anaerobic digestion of these. A performance clearly superior to that of aerobic aerated lagoon is thus obtained in return for heavy equipment resulting in additional and high expenses, both technically and in terms of operating energy consumption. In both cases, an improvement in yield is obtained by immersing, in the bath of the basin, directly in contact with the effluents, structures acting as supports for bacterial systems which adhere to it. This attachment to a support increases the amount of biomass within the system, enriches the composition of this biomass (more diverse bacteria) and promotes exchanges between microorganisms and organic matter to be degraded.

However, the yield from these lagooning processes remains relatively low and the purification requires a hydraulic residence time of several months. These processes thus prove to be unsuitable for small structures such as farms, small industries or small municipalities, which for lack of space, cannot envisage an accumulation and storage of their effluents.

More intensive treatment methods involve compact installations with a partitioned enclosure, more or less hermetically closed. These space-saving systems but with a high processing capacity are commonly called bioreactors. In these bioreactors, which can be aerobic, anaerobic or mixed, the effluents are treated with different bacterial systems, most often immersed inside the effluents and under optimal conditions of temperature, oxygenation or non-oxygenation. , pH in order to accelerate their metabolism and the processes of degradation of organic impurities.

DE 35 03 723 describes a bioreactor with mixed treatment comprising, inter alia, a leaf-filled biofilter with an aerial part and a part immersed in a bath of liquid composition. The aerial part of the biofilter is supplied with a liquid composition to be treated which then flows by gravity, inside the biofilter, as far as the bath. The liquid composition of the bath can be reintroduced again into the aerial part of the biofilter. To maintain for this bioreactor to function properly, an addition of reagents is necessary to correct the pH of the liquid composition to be treated. In addition, in the aerial part of the biofilter, mechanical ventilation and mechanical removal of C0 ₂ are necessary. Apart from the cost of these bioreactors, partly justified by the technology used, and the operating costs, in particular to maintain optimal conditions, these bioreactors have many disadvantages and impose many constraints on their owners. The complexity of these bioreactors is generally not compatible with their technical skills. Also, in the event of a complication, the owners often prove to be powerless in the face of the situation and the accumulation of their effluents, until the intervention of a specialist.

Finally, these bioreactors require regular maintenance (periodic washing and unclogging, control of operation, etc.) generating significant operating constraints for their owners.

The object of the present invention is to overcome these drawbacks by proposing a method and an individual installation for treating effluents essentially by microbiological means, the yield of which is sufficiently high to avoid any risk of accumulation of effluents while having a sufficiently small bulk. with, however, a treatment capacity adapted to the production of effluents from a dominated agricultural, urban or industrial structure.

Another object of the invention is to provide a simple and rapid construction installation, operation and maintenance compatible with the technical skills of non-specialized owners - notably free of clogging. Furthermore, the invention aims to propose an installation which generates only minimal operating constraints so that its owner can normally go about his business.

The invention therefore aims to propose an alternative (in terms of purification efficiency, size and maintenance constraint) to lagoon systems (the advantage of which is to require minimal constraints maintenance and operation, but in return offer only a very low yield resulting in considerable treatment times and tank sizes) and to bioreactors (whose advantage is to offer intensive treatment for a very small footprint, in return for a significant operating cost, due to the technical nature of the device and the obligation to maintain optimal treatment conditions, in particular temperature, pH, oxygenation and / or non-oxygenation ...).

The present invention therefore relates to an effluent treatment process in which the effluents are circulated successively in different biotransformation zones comprising:

- a bath of liquid composition to be treated,

- A bacterial support comprising a plurality of plastic panels arranged adjacent and spaced from each other, at least substantially vertically so that each panel has at least one non-submerged aerial part extending above the bath and at at least one part immersed in said bath, each panel having a structure adapted to form a bacterial support and to allow:

- each panel to withstand its weight and the weight of the materials it carries, - a gravity runoff, of liquid composition over at least part of the height of the panel into the bath,

- a flow by gravity of the biological sludge formed, over at least part of the height of the panel into the bath.

In an effluent treatment method according to the invention: - the aerial part of each panel is supplied with a liquid composition to be treated, coming from the bath,

the panels are placed in relation to each other, and the circulation of the liquid composition and the aeration in the installation are adapted so as to bring about an essentially aerobic treatment in the aerial part of the panels and an essentially anaerobic treatment in the bath. According to the invention, the bacterial support and the bath are placed in contact with ambient atmospheric air so that the aerial part of the panels is aerated by natural convection, and that the oxygenation of the bath is based exclusively on solubilization of the oxygen from the ambient air on the surface of the bath. Furthermore, the circulation of the liquid composition is adapted and the panels are placed in relation to each other to allow:

- in the aerial part of the panels, circulation and renewal of the ambient air between each panel, spontaneous fixation and the development of an essentially aerobic bacterial system and an essentially aerobic treatment,

- in the lower part of the panels immersed in the liquid composition bath, spontaneous fixation and the development of a bacterial system essentially of the anaerobic type and an essentially anaerobic treatment.

A method according to the invention thus advantageously combines a substantially aerobic treatment (in the panels) and a substantially anaerobic treatment (in the bath) which, in terms of purification, are complementary. It is thus possible to define, in an installation allowing the implementation of a method according to the invention, at least substantially two types of zones for successive treatment of effluents, aerobic or anaerobic. The aerobic treatment zone corresponds to the aerial part of each of the panels serving as culture supports for bacterial systems of aerobic type. As for the anaerobic treatment zone, it corresponds to the lower part of the pelvis, in particular the submerged part of the panels which acts as a culture support for bacterial systems essentially of anaerobic type. The combination of these two types of treatment thus makes it possible to minimize the formation of sludge at the outlet of the installation, unlike an installation with exclusively aerobic operation. It also makes it possible to work over a very wide temperature range, from the lowest temperatures of substantially aerobic operation to the maximum temperatures of substantially anaerobic operation. In addition, at the interface of the aerobic and anaerobic treatment zones, anoxia zones are also created at the level of which particular bacteria, also fixed to the panels, carry out a denitrification (passage of nitrates to nitrogen gas) . This is in addition to the great adaptability of the operation of the installation in relation to the different characteristics (temperature, pH, COD ...) of the liquid effluents to be treated and the evolution of COD (chemical oxygen demand) over time .

In practice, it is possible to use panels made of any type of synthetic material, such as, for example, polyvinyl chloride, polypropylene, carbon fiber, polyamides ... according to a structure capable of exhibiting permeability to liquids and air permeability, at least perpendicular to their thickness. Such a panel structure thus allows good attachment of the bacterial systems and good circulation of air between the panels and through, hence a large specific treatment surface. Advantageously and according to the invention, panels of grid structure are chosen with a vacuum index at least equal to 70%, preferably at least of the order of 90%.

These grid structure panels can have a three-dimensional structure, for example consisting of a tangle of synthetic fibers possibly reinforced by means of a main lattice around which the fibers can also be wound. It is thus advantageously possible to use, within the framework of the invention, products of the geogrid type used to combat surface erosion on slopes and banks, and to promote the rooting of plants. The panels according to the invention can also have very varied structures, different from a grid structure, and however meeting the characteristics already mentioned (in particular, highly permeable culture support and sufficiently resistant to traction).

When these panels are supplied with raw effluents, or any other liquid composition to be treated, the bacteria naturally present in these effluents can adhere to these panels. Thus fixed, the bacteria to aerobic metabolism can grow abundantly by capturing organic compounds from effluents, which they degrade by oxidation. Biofilms from this oxidative degradation, or increasingly thick biological sludge appear on the panels, partly aerial, and reach by gravity, the anaerobic treatment zone. In this region of the bath, which is very poor in free oxygen, the anaerobic metabolic bacterial systems, fixed to the culture support and therefore immersed in a very rich culture broth, develop by digestion of organic pollutants, made up in part by the biological sludge produced. at the level of the aerial part and falling into the anaerobic treatment zone.

The liquid composition flowing all along and in the panels allows an almost optimal bacterial population of the panels, in all corners. In addition, by their distribution and their high permeability, these panels constitute a considerable gas exchange surface, allowing bacteria, fixed in the aerial part of the panels, to be in permanent, almost direct, contact with the air and thus have an abundant source of oxygen for their metabolism. Consequently, without additional mechanical means being necessary for the aeration of the aerial part of the panels, the aerobic treatment presents a high efficiency thanks to aeration by natural convection. The size of the gaps left between the panels considerably influences the efficiency and the yield of the treatment process according to the invention. It is adjusted in particular according to the permeability (vacuum index) and the thickness of the panels used. One can also take into consideration the nature of the effluents to be treated and their concentration. This consideration is based on the compromise between the overall dimensions of the panels, i.e. the number of panels for a given volume, which reflects the specific treatment surface of the entire installation, and the spacing between each panel serving as a ventilation chimney ensuring the diffusion of air through the installation. Advantageously and according to the invention, the panels are arranged so that the gap left between two adjacent panels is at less equal to 5 cm at the level of the aerial part-notably at least of the order of 10 cm-.

According to the invention, each of the panels acting as a culture support can be arranged within the installation both vertically and at a certain inclination. The panels according to the invention have, when inclined, a face facing the bath so that any liquid composition or biological mud falling from these panels, falls directly into the bath, that is to say without falling on another panel. The inclination applied to the panels makes it possible to slow the runoff of liquid compositions in the aerated zone and to obtain a more intense aerobic treatment.

Advantageously and according to the invention, the panels are placed in the installation so that the lower edges of the panels and the bottom of the basin define a non-zero volume. In other words, the panels are held above the basin with their lower edges at a distance above the bottom of the basin.

According to a particular embodiment of the method according to the invention, each panel is suspended by two opposite sides so as to form, inside the bath, a culture support for a curved lower part. In this particular configuration of the panels, the submerged lower part advantageously forms a filtering structure allowing the retention of part of the sludge formed in the aerial part. Some of the thickest sludge, which requires a long digestion time, can thus be retained in the folds of the panels. The clogging of the sludge in the bottom of the basin is thus limited, as is the risk of obstruction of the means of supplying the aerial part of the panels with liquid composition coming from the bath.

According to another particular embodiment of a method according to the invention, two adjacent panels are attached by their lower edges. In doing so, a slight inclination of the panels is advantageously obtained, resulting in a slowing down of the speed of flow of the liquid compositions along the panels. It is possible to attach the panels over the entire extent of the lower edge of the panels in order to obtain a structure filtering comparable to that obtained according to the previous embodiment variant. It is also possible to attach the lower edges of the panels in a punctual manner and more or less spaced depending on the desired filtration capacity.

According to the invention, repeated recirculation of a liquid composition from the bath to the aerated part of the panels advantageously allows a progressive and looping purification thereof which, successively and repeatedly, undergoes treatments of anaerobic, aerobic and denitrification. After an adapted number of treatment cycles, which varies according to the nature of the effluents and their concentration, the liquid compositions reach an acceptable COD according to the legislation and can then be rejected outside the installation.

Advantageously and according to the invention, the means for supplying the panels thus comprise means adapted to allow the circulation of a liquid composition contained in the basin towards at least part of the height of the panels, partly aerated. These supply means, by way of nonlimiting examples, may include sprinkler, sprinkler, immersion systems of the aerial part of the panels in order to soak them ...

In practice, as a means of supplying the panels, a system of sprinkling networks is used, operating with the aid of a pumping system, and connected to sprinkling systems such as diffusers, spray nozzles or vaporization, regularly distributed above the panels, so as to disperse a liquid composition in more or less fine droplets.

Advantageously and according to the invention, the aerial part of the panels is supplied by pumping the liquid composition contained in the bath, in particular the pumping is also controlled in order to carry out a predefined number of treatment cycles before rejecting the liquid compositions outside the 'installation.

Advantageously and according to the invention, the raw effluents are introduced at the level of an introduction compartment adapted to allow the retention, inside this compartment, of fats by flotation, and of the densest materials by decantation, and to allow the rest of the raw effluent to pass through the basin. Advantageously, said introduction compartment is separated from the rest of the basin by means of a vertical wall of height at least substantially identical to that of the basin and perforated at mid-height. This compartment advantageously extends over at least part of the width or the length of the basin. An introduction compartment according to the invention can also be a separate compartment from the basin. In this case, an installation according to the invention comprises two tanks advantageously of different dimensions. The raw effluents arrive in the first tank, corresponding to the introduction compartment, in which the grease and decantable matter are trapped. Generally, less bulky than the main tank, the first tank is advantageously higher so that the liquid composition of the latter can pour into the main tank by an overflow arranged below the level of fat flotation.

When an introduction compartment is used to prevent the introduction of grease and decantable matter from raw effluents into the main tank, these grease and decantable matter are retained in the introduction compartment where they undergo a slow transformation, before to reach, in the form of an essentially aqueous composition, the main basin where they continue their treatment with the rest of the effluents. The content of the basin, apart from the biological mud at the bottom of the basin, is essentially aqueous. The evacuation of the essentially aqueous treated compositions contained in the basin can be done in a simple manner by an overflow.

Advantageously and according to the invention, the installation comprises means allowing the recirculation of at least part of the liquid composition from the bath of the basin (main basin) to the introduction compartment. This reduces the residence time of the various liquid compositions in the introduction compartment so as to avoid the development of strictly anaerobic type fermentations. In addition, at the bottom of this compartment will be able to accumulate excess biological sludge. So if necessary, the evacuation of excess sludge from the station will be facilitated. It will suffice to empty the introduction compartment after removing the surface grease. According to a variant of the invention, the raw effluents are introduced directly into the installation basin. Consequently, in this basin, the fats float on the surface of the bath, and the decantable matters are distributed in the bottom of the basin. The complete degradation of these fats and these settlable materials requires a longer treatment time than the aqueous compositions of the raw effluents. Under these conditions, the treated compositions are removed from the basin by means of an outlet pipe, arranged opposite the introduction of the raw effluents, immersing under the surface of the bath and kept at a distance from the bottom of the basin. The fats and decantable materials remain inside the tank and thus continue their treatment while only the treated compositions, essentially aqueous, are removed from the tank.

Advantageously and according to the invention, each of the stages of the treatment is carried out inside a shelter of closed but not hermetic structure, in which there is effective ventilation by natural convection. Advantageously and according to the invention, a shelter with lateral and / or upper partitions is used, at least partly made of windbreak net.

According to another alternative embodiment, it is also possible to use a shelter of closed, non-hermetic structure having lateral and / or upper partitions adapted to create a greenhouse effect inside said shelter - in particular a greenhouse -.

Many greenhouse models are already commercially available and advantageously offer great variability in dimensions, in ventilation and air renewal systems, by natural convection. Shelters of this type are perfectly suitable for the production of an effluent treatment installation according to the invention. In addition to a purifying yield which can be significantly improved, since it is thus possible to control the climatic conditions - in particular of temperature -, the invention thus allows treatment of effluents of controlled odor nuisance. The methane and the highly foul-smelling volatile fatty acids produced and released by anaerobic digestion are at least partially retained inside the installation. In addition, the aerial part of the panels works advantageously in the greenhouse like a tower deodorization; aerobic bacteria attached to it capture and then metabolize these smelly molecules to finally release carbon dioxide into the environment.

Optionally, the fat retention volume or the installation introduction compartment can be covered, by means forming a cover or cover in order to at least partially retain the biogas formed, and these biogas are distributed at the level of the towers of deodorization that constitutes the aerial part of the panels. This controlled release of volatile fatty acids directly in contact with bacteria, essentially aerobic metabolism, improves the efficiency of their elimination.

In the case of an installation incorporating a greenhouse or any shelter of comparable structure, part of the frame is advantageously used as a frame, for hanging the panels, for example, horizontal reinforcing rods keeping the walls vertical. said greenhouse or said shelter, and / or spacers used to reinforce the structure of the assembly.

In general, it is not necessary to seed, the different treatment zones, of microorganisms -in particular bacteria-. Naturally present in the effluents, which constitute very favorable culture broths, large varieties of microorganisms, both with essentially aerobic metabolism and with essentially anaerobic metabolism, are transported inside the installation where they go. ability to attach themselves to the culture media of the different treatment areas.

Of course, to optimize the yield of the treatment, it is possible to seed bacteria periodically in order to increase their concentration, directly in the bath and / or directly at the level of the aerial part of the panels.

One can also consider seeding with particular strains of bacteria depending on the nature of the pollutants to be treated.

The invention extends to an installation allowing the implementation of an effluent treatment method according to the invention.

An installation according to the invention comprises: - a basin adapted to contain a bath of liquid composition to be treated,

a bacterial support comprising a plurality of panels of synthetic material arranged adjacent and spaced apart from one another, at least substantially vertically, so that each panel has at least one non-submerged aerial part extending above the bath, and at least one part immersed in the bath, each panel having a structure adapted to form a bacterial support and to allow:

a flow by gravity of the biological sludge formed, over at least part of the height of the panel as far as the bath, the relative arrangement of each of the panels allowing a circulation of the liquid composition and aeration of the installation adapted to cause a essentially aerobic treatment in the aerial part of the panels and an essentially anaerobic treatment in the bath,

means for supplying the aerial part of each panel with a liquid composition to be treated coming from the bath. According to the invention, in the operating state of said installation, the bacterial support and the bath are placed in contact with ambient atmospheric air so that the aerial part of the panels is aerated by natural convection, and that the oxygenation of the bath relies exclusively on a solubilization of oxygen from the ambient air on the surface of the bath. Advantageously and according to the invention, the panels have a grid structure with a vacuum index at least equal to 70% - in particular of the order of 90% -.

Advantageously and according to the invention, the panels are arranged so that the gap left between two adjacent panels is at least of the order of 5 cm - in particular at least of the order of 10 cm -. Advantageously, the lower edges of the panels and the bottom of the basin define a non-zero volume. In other words, the panels are immersed in the liquid composition bath by their lower part and are kept with their lower edges at a distance above the bottom of the basin. According to a particular embodiment of an installation according to the invention, each panel is suspended by two opposite sides so as to form, inside the bath, a culture support for the curved lower part.

According to another particular embodiment of the invention, the adjacent panels are attached in pairs by their lower edges, with attachment points more or less close together, more or less regularly distributed.

Advantageously and according to the invention, the means for supplying the aerial part of the panels comprise means for pumping the liquid composition contained in the basin and means for automatically controlling said pumping in order to carry out a predefined number of treatment cycles before to reject the liquid compositions outside the installation.

Advantageously, an installation according to the invention advantageously comprises an introduction compartment adapted to receive raw effluents and to allow the retention of greases by flotation, and of the densest materials by decantation, and to allow the passage of the rest of the raw effluents in the basin. Advantageously, said introduction compartment is separated from the rest of the basin by means of a vertical wall of height at least substantially identical to that of the basin and perforated at mid-height.

Advantageously, said installation comprises an overflow making it possible to evacuate treated compositions from the basin. According to another alternative embodiment, an installation according to the invention comprises means for introducing the raw effluents directly into the basin and an outlet pipe plunging under the surface of the bath and kept at a distance from the bottom of the basin, adapted to evacuate treated aqueous compositions of the basin. An installation according to the invention can advantageously be a covered installation by means of a closed structure shelter but not airtight, in which there is effective ventilation by natural convection.

It can be a shelter with lateral and / or upper partitions at least partly made of windbreak net. It can also be a shelter of closed, non-hermetic structure having lateral and / or upper partitions adapted to create a greenhouse effect inside said shelter - in particular a greenhouse -.

Optionally, the fat retention volume of the supply line or the installation introduction compartment can be covered by means forming a cover or cover in order to at least partially retain the biogas formed. According to the invention, suitable means then make it possible to redistribute these biogas at the level of the deodorization towers that constitute the aerial part of the panels.

The invention also relates to a process for the treatment of effluents by an essentially microbiological route, as well as an installation allowing the implementation of a process according to the invention, characterized, in combination, by all or some of the characteristics mentioned above. above or below.

Other objects, characteristics and advantages of the invention will appear on reading the following description which refers to the appended figures, in which:

- Figure 1 is a general view, in cutaway perspective, of an exemplary embodiment of an effluent treatment installation according to the invention, - Figure 2 is a schematic sectional view describing the arrangement of the elements constituting an installation according to the invention and the operation of the assembly,

- Figure 3 shows a schematic side view of an installation according to the invention, showing in detail the arrangement of the panels within the installation ,. FIG. 4 illustrates a particular mode enabling the treated effluents to be removed from the installation,

- Figures 5 and 6 illustrate two particular configurations of the panels according to the invention. According to the preferred embodiment, shown in Figure 1, the installation according to the invention is carried out in a greenhouse, that is to say comprises a greenhouse structure. In the figures, the relative dimensions - in particular the relative thicknesses - are not represented in a realistic manner, for purposes of illustration. Under the greenhouse, whose frame 2 alone is shown, for reasons of clarity, a sealed basin 1 of rectangular shape is adapted to contain a bath of liquid composition to be treated. In the figures, the basin 1 is shown with a side wall and a bottom wall. It can rest on the ground or be buried in whole or in part. The side walls delimit an upper opening of the basin 1. In a variant not shown, this basin 1 can be manufactured using a waterproof cover covering an excavation made in the ground. The height of the basin 1 is for example of the order of 1 m. The capacity of the basin 1 can be very variable; its surface being at least equal to the area projected on the ground of the zone equipped with panels, which is itself adapted to the load to be treated. The capacity of the basin 1 is above all chosen as a function of the rate of production of the effluents and the biodegradability of the latter.

In the lengthwise direction of the basin 1, panels 3, for example from 2 to 3 m in height, are suspended from horizontal reinforcing rods 2a of the frame 2 of the greenhouse and extend at least substantially vertically, adjacent and parallel to each other.

The lower part 3b of these panels 3 plunges inside the bath the liquid composition. About 60 cm of panels 3 are thus immersed, leaving a height of about 40 cm between the bottom of the basin 1 and the bottom of the panels 3. The panels 3 used can be made of a synthetic material (polyvinyl chloride, polypropylene, fiber carbon, polyamides, etc.) chosen for its ability to fix bacterial systems. Preferably, the panels 3 have a more or less complex grid structure, which forms a considerable specific treatment surface, of great permeability, at least perpendicular to their thickness, to liquids and to air. These panels 3 are spaced from each other by a gap, for example of the order of 5 cm.

Still for reasons of clarity, in FIG. 1, only a very small number of panels 3 is shown, and the thickness of these panels 3 is deliberately exaggerated. In order to facilitate the attachment of the panels 3 to the horizontal reinforcing rods 2a, a mesh 5 of the conventional type, preferably made of synthetic material, is deployed and fixed on these reinforcements 2a. Advantageously, there are therefore multiple attachment points for the panels 3, over the entire extent of the grid 5 (partially shown in FIG. 1). The raw effluents are conveyed inside the installation by a supply duct 6 of the installation, emerging at the level of the introduction compartment 4 located inside the basin 1. This compartment 4, as shown in FIG. 1, is rectangular in shape and extends over a whole width of the basin 1. It is separated from the rest of the basin by a vertical wall of height identical to that of the basin 1. This wall is perforated in the middle part of its height allowing communication between compartment 4 and basin 1, as well as the retention of grease and settlable matter inside this compartment 4.

Equivalently, this compartment can also extend over the entire length of the basin 1, or only part of its length or width.

Not shown in FIG. 1, but appearing in FIG. 2, a waterproof cover plate 10 makes it possible to cover the introduction compartment 4. Similarly, at the level of the upper part of the wall of this compartment 4, a duct 11 makes it possible to recover the gases formed in this compartment 4, and in particular the volatile fatty acids, and to release them at the level of the lower part of the aerial part 3 has panels 3, by perforations made in this duct 11.

The installation also includes means for supplying the aerial part of the panels with liquid composition to be treated. A submerged pump system 7a, allows the pumping of a flow of liquid composition from the lower part of the basin, on the side opposite the inlet (supply conduit 6) of the raw effluents, to a distribution network 7b placed at above and at a distance from the panels 3 and from the mesh 5. This distribution network 7b is connected to a set of spraying devices which, in the embodiment shown, are preferably diffusers 7c regularly distributed above the panels 3. This type of device advantageously produces a ring for spraying liquids into fine droplets, or even in the form of a mist, and this over a radius of the order of 1 m, depending on the pressure applied.

To optimize the efficiency of the installation, the distribution of these diffusers 7c above the panels, the power and the orientation of the spraying are adjusted so that a maximum of panel surface 3 can be humidified and that each jet, drop or droplet, of the liquid composition falls on at least part of the height of the aerial part 3 a of these panels 3 and does not fall directly into the bath. Bypassing the distribution network 7b and connected to the submerged pump 7a, means 9 make it possible to recirculate part of the liquid composition of the bath 1 'to the introduction compartment 4. A mixing valve 7d advantageously allows a continuous supply of the aerial part 3a of the panels 3 in liquid composition coming from the bath l ', with an adjustable flow rate, and a recirculation of part of this liquid composition towards the introduction compartment 4, also continuously but with a flow rate generally more low.

On the side opposite the inlet (supply conduit 6) of the raw effluents, the installation has an overflow 8 allowing the contents of the basin 1 to be gradually removed from the installation. According to an alternative embodiment, an installation according to the invention does not include a compartment 4 allowing the introduction, into the basin 1, of raw effluents freed of grease and settling materials. The raw effluents are directly introduced into the tank 1, without there being any prior retention of its fats and of its settling matter. Consequently, in the basin 1, the fats float on the surface of the bath l ', and the decantable matters are distributed in the bottom of the basin. By means of an outlet pipe 8 ′, disposed opposite the introduction of the raw effluents, plunging below the level of flotation of the fats and kept at a distance from the bottom of the basin, as shown in FIG. 4, of the basin the essentially aqueous phase of the basin. The fats and decantable matter remain inside the tank and thus continue their treatment.

The treatment of effluents in an installation according to the invention as described, can be described as follows. The raw effluents enter the installation through the introduction compartment 4. A fraction of the effluents, greases and settlable matter, remain inside this compartment 4. Another part of the effluents, entrained by the current generated by the operation of the pump 7a, crosses the perforated wall of the compartment 4 to reach the bath. At the lower zone of the submerged part 3b of the panels 3, a substantially anaerobic treatment zone, the organic impurities undergo digestion, that is to say mineralization by anaerobic fermentation accompanied by a release of methane which can freely diffuse out of the greenhouse, and from a production of foul-smelling volatile fatty acids which will be captured then metabolized by aerobic bacteria from the aerial part 3 has panels 3.

At the bottom of the basin, an anaerobic treatment zone, there is essentially a digestion of the biological sludge mainly fallen from the panels 3.

Overall, during the transit from the introduction compartment 4 (or from the downstream end of the supply line 6 ') to the pumping system 7a, the liquid composition undergoes a gradual dilution of its COD. It is then pumped from the basin 1 to the distribution network 7b located above the panels 3. By means of the diffusers 7c connected to the distribution system 7a, the composition of liquid is sprayed on the aerial part 3a of the panels 3. That -this then flows, generally parallel to the main faces of the panels 3, along the aerobic treatment zone of the panels 3. As this flow takes place, it discharges organic impurities captured by the bacteria with aerobic metabolism, fixed along the network of synthetic fibers of the panels 3 in almost direct contact with the ambient air. It is obviously possible to envisage placing the panels 3, not vertically, but slightly inclined, of the order of a few degrees. The composition of liquid sprayed on the aerial part 3 has panels 3, then rather flows through the thickness of the panels 3, with a lower speed. Thus, depending on the fluidity of the liquid composition of the bath, it is preferable to incline the panels 3 or not. Similarly, aerobic treatment may or may not be favored.

A simple way to slightly tilt the panels 3 consists in attaching the adjacent panels in pairs by their bottom edges as illustrated in FIG. 6.

On the aerial part of the panels 3, biofilms appear illustrating the growth of aerobic bacterial systems. These develop both inside the panels 3 and outside. Given the small thickness of the panels 3, when the biofilms reach a certain dimension, they find themselves dripping outside the panels 3 and end up falling, under their weight, into the basin 1. Thus, in particular , by the small thickness and by the high vacuum index of the supports used, any problem of clogging of the panels 3 is avoided.

Furthermore, in the case of an installation according to the invention, the risk of clogging of the culture supports, both at the level of the anaerobic treatment zone and at the level of the aerobic treatment zone, is extremely rare. In fact, unlike the culture media of bioreactors which make also as a filter, the panels 3 only fulfill a role of culture media.

However, depending on the nature of the liquids to be treated, their initial COD and their speed of flow along the panels, it can happen that the aerobic production speed of sludge is much higher than that of their anaerobic digestion so that there is a risk of clogging of the supply means of the aerial part 3 has panels 3 in liquid composition coming from the bottom of the bath. To overcome this, and as illustrated in FIG. 5, the panels 3 are used in a particular configuration, suspended by two opposite sides so as to form, inside the bath, culture supports of curved lower part. . In this particular configuration, the panels 3 make it possible, on the one hand, to limit the deposition of sludge at the bottom of the basin 1 and, on the other hand, to extend the residence time of the sludge in the lower part 3b of the panels 3, zone conducive to their anaerobic digestion. Similarly, this filtration and retention effect of part of the sludge can be obtained by the submerged lower part of the panels 3 by attaching the adjacent panels by two at their lower edges, as illustrated in FIG. 6, with more or less close attachment points depending on the desired retention capacity.

An installation according to the invention does not require regular washing of the culture supports, as is for example the case in most bioreactors. In addition to the advantage represented by the absence of frequent washing, a panel 3 according to the invention allows a high and very constant yield treatment, insofar as washing the panels necessarily leads to a stall of the bacterial systems. Added to this is the fact that washing generates significant water consumption.

Furthermore, thanks to a support of this type and to an arrangement as previously described, it is advantageously freed from any constraint linked to the sufficient oxygenation of the system. The gap left between each of the panels allows natural air diffusion adapted to high aerobic performance. Part of the bath l 'and the sludge deposited at the bottom of the basin 1 can be pumped so as to be able to be recirculated in the introduction compartment 4. In it, the excess sludge will accumulate and the quantity of mud in the basin 1. The disposal of sludge from the installation may advantageously be limited to the emptying of this small compartment 4.

Furthermore, the foul-smelling volatile fatty acids generated by anaerobic digestion at the bottom of this compartment and by the acid hydrolysis of the fats on the surface, are transported and then released on the aerial part 3 to panels in order to be degraded there by bacteria. aerobic fixed. As an example of operation, it is possible to envisage a continuous supply of the aerial part 3 to the panels 3, in liquid composition to be treated. The pumping of the bath is then done regularly with a constant flow. Depending on the nature of the raw effluents, their initial COD and the operating parameters of the installation (pumping rate), it is possible to assess the necessary treatment time.

One can also provide a discontinuous supply of the aerial part, for example with pumping cycles of a quarter of an hour every hour. And as before, it will also be possible to determine the number of treatment cycles necessary, that is to say the number of pumping cycles, to reach a desired COD.

In these two operating examples, the installation will be emptied once the COD of the bath has reached a certain value, a satisfactory value according to the legislation.

An installation as described above can also operate "on the fly" and according to the principle of "infinitely mixed" systems. The raw effluents enter the installation by gravity and the liquid is discharged, also by gravity, through an overflow 8. The discharge takes place here at the rate of the inlets. The raw effluents entering are diluted in the bath without significantly modifying the COD which, permanently, remains below the value considered acceptable by the legislation. Such an installation as well as the treatment method which are implemented in the invention have great flexibility of operation and adaptability. It is thus clearly understood that the invention is not limited to the exemplary embodiments which have just been described. Many other variants and modifications can be made without departing from the scope of the invention.

Faced with the needs of small farms (dairy farms, above-ground farms, wineries ...), industrial (small food industries) or small municipalities, the invention meets many of their requirements. effluent treatment material.

First of all, the invention proposes a process, the implementation of which results in installations of less bulk, of lower price and of simple and rapid construction. Indeed, the civil engineering works are limited to the minimum since they can be summed up as the realization of a level platform, on which is installed an installation according to the invention. All the elements necessary for the construction of the latter are already on the market.

Although compact, an installation according to the invention offers intensive purification with high capacity. The high efficiency is largely explained by:

- a combination of different types of treatment (aerobic, anaerobic and denitrification) allowing interesting treatment results whatever the COD of the effluent, - the use of culture supports allowing a large surface area for the development of bacteria, and therefore a high concentration of bacteria permanently placed in conditions conducive to rapid growth,

- long-term operation without interruption, in particular for washing cycles of culture media, - easy adaptation of the installation according to the nature of the effluents. In addition, an installation according to the invention has the advantage of imposing on its owner only minor and very occasional constraints, and no regular maintenance (exceptional washing, emptying of the rare and simple introduction compartment, etc.).

Finally, the technical nature of an installation according to the invention is perfectly within the reach of a person of average capacity. Also, any owner of such an installation will be able to intervene by himself in the event of a malfunction of the installation.

Claims

CLAIMS 1 / Effluent treatment process in which the effluents are circulated successively in different biotransformation zones comprising: - a bath (1 ′) of liquid composition to be treated,

- a bacterial support comprising a plurality of trays (3) of synthetic material arranged adjacent and spaced apart from each other, at least substantially vertically, so that each panel (3) has at least one aerial part (3a) not submerged extending above the bath (V) and at least one submerged part (3b) in said bath (1 '), each panel (3) having a structure adapted to form a bacterial support and to allow:

- each panel (3) to resist its weight and the weight of the materials it carries, - a gravity runoff, of liquid composition over at least part of the height of the panel (3) into the bath (1 '),

- a flow by gravity of the biological sludge formed, over at least part of the height of the panel (3) into the bath

in said process:

- the aerial part (3 a) of each panel (3) is supplied with a liquid composition to be treated, coming from the bath (1 ′),

- the panels (3) are placed in relation to each other, and the circulation of the liquid composition and the aeration in the installation are adjusted so as to bring about an essentially aerobic treatment in the aerial part (3a) of the panels ( 3) and an essentially anaerobic treatment in the bath (1 ′), characterized in that:

- the bacterial support and the bath (1 ') are placed in contact with the ambient atmospheric air so that the aerial part (3 a) of the panels (3) is aerated by natural convection, and that the oxygenation of the bath ( 1 ') rests exclusively on a solubilization of the oxygen of the ambient air on the surface of the bath (F),

- the circulation of the liquid composition is adapted and the panels (3) are arranged relative to each other to allow: - in the aerial part (3a) of the panels (3), circulation and renewal of the ambient air between each panel (3), spontaneous fixation and development of an essentially aerobic bacterial system, and an essentially aerobic treatment, - in the lower part (3b) of the panels (3) immersed in the bath (1 ') of composition fluid, spontaneous fixation and development of an essentially anaerobic type bacterial system, and essentially anaerobic treatment.

2 / A method according to claim 1, characterized in that one chooses panels (3) of grid structure with a vacuum index at least equal to 70%.

3 / A method according to claim 2, characterized in that the vacuum index of the panels (3) is at least of the order of 90%.

4 / Method according to one of claims 1 to 3, characterized in that the panels (3) are arranged so that the gap left between two adjacent panels (3) is at least equal to 5 cm at the level of the aerial part (3a).

5 / Method according to one of claims 1 to 4, characterized in that the panels (3) are arranged in the installation so that the lower edges of the panels (3) and the bottom of the basin (1) define a volume not zero. 6 / A method according to claim 5, characterized in that each panel (3) is suspended by two opposite sides so as to form, inside the bath (1 '), a culture support of curved lower part.

Il Method according to one of claims 1 to 5, characterized in that two panels (3) are attached adjacent by their lower edges. 8 / A method according to one of claims 1 to 7, characterized in that it supplies the aerial part (3a) of the panels (3) by pumping the liquid composition contained in the bath (1 ') and in that the pumping is controlled in order to carry out a predefined number of treatment cycles before discharging the liquid compositions out of the installation.

9 / Method according to one of claims 1 to 8, characterized in that the raw effluents are introduced into the installation by an introduction compartment (4) adapted to allow retention, inside this compartment, greases by flotation, and the densest materials by decantation, and to allow the passage of the rest of the raw effluents in the basin

(1). 10 / A method according to claim 9, characterized in that discharges from the basin (1) of the treated aqueous compositions by an overflow (8).

11 / A method according to one of claims 1 to 8, characterized in that the raw effluents are introduced directly into the basin (1) and in that the compositions treated are removed from the basin (1) outlet pipe (8 ') plunging under the surface of the bath (1') and kept away from the bottom of the basin

(1).

12 / Method according to one of claims 1 to 11, characterized in that each of the stages of treatment is carried out inside a shelter of closed structure but not hermetic, in which there is effective ventilation by natural convection.

13 / A method according to claim 12, characterized in that a shelter with lateral and / or upper partitions is used, at least partly made of windbreak net.

14 / A method according to claim 12, characterized in that one uses a non-hermetic closed structure shelter having lateral and / or upper partitions adapted to create a greenhouse effect inside said shelter.

15 / Method according to one of claims 12 or 14, characterized in that a greenhouse is used. 16 / Effluent treatment installation comprising: - a basin (1) adapted to contain a bath (1 ') of liquid composition to be treated,

- a bacterial support comprising a plurality of panels (3) of synthetic material arranged adjacent and spaced from each other, at least substantially vertically, so that each panel (3) has at least one aerial part (3a) not submerged extending above the bath (1 '), and at least one submerged part (3b) in the bath (1'), each strut (3) having a structure adapted to form a bacterial support and to allow: - each panel (3) to resist its weight and the weight of the materials it carries,

- a runoff by gravity, of liquid composition over at least part of the height of the panel (3) into the bath (1 '),

(1 ^* ), the relative arrangement of each of the panels (3) allowing a circulation of the liquid composition and aeration of the installation adapted to bring about an essentially aerobic treatment in the aerial part (3 a) of the panels (3) and essentially anaerobic treatment in the bath (1 '),

- means for supplying the aerial part (3 a) of each panel (3) with liquid composition to be treated coming from the bath (1 ′), characterized in that, in the operating state of said installation, the bacterial support and the bath (1 ') are placed in contact with the ambient atmospheric air so that the air part (3a) of the panels (3) is aerated by natural convection, and that the oxygenation of the bath (1') rests exclusively on a solubilization of the oxygen of the ambient air on the surface of the bath (1 ').

17 / Installation according to claim 16, characterized in that the panels (3) have a grid structure with a vacuum index at least equal to 70%. 18 / Installation according to claim 17, characterized in that the vacuum index of the panels (3) is at least of the order of 90%.

19 / Installation according to one of claims 16 to 18, characterized in that the panels (3) are arranged so that the gap left between two adjacent panels (3) is at least equal to 5 cm at the level of the part aerial (3 a).

20 / Installation according to one of claims 16 to 19, characterized in that the lower edges of the panels (3) and the bottom of the basin (1) define a non-zero volume. 21 / Installation according to claim 20, characterized in that each panel (3) is suspended by two opposite sides so as to form, inside the bath (1 '), a culture support of curved lower part.

22 / Installation according to one of claims 16 to 20, characterized in that the adjacent panels (3) are attached in pairs by their lower edges.

23 / Installation according to one of claims 17 to 22, characterized in that the means for supplying the aerial part (3a) of the panels (3) comprise means for pumping (7a) of the liquid composition contained in the basin (1) and means for automatically controlling said pumping in order to carry out a predefined number of treatment cycles before discharging the liquid compositions from the installation.

24 / Installation according to one of claims 16 to 23, characterized in that it comprises an introduction compartment (4) adapted to receive raw effluents and to allow the retention of fats by flotation, and the densest materials by decantation, and to allow the passage of the rest of the raw effluents in the basin (1).

25 / Installation according to claim 24, characterized in that ^• the introduction compartment (4) is separated from the rest of the basin (1) by means of a vertical wall of height at least substantially identical to that of the basin (1) and openwork halfway up. 26 / Installation according to one of claims 24 or 25, characterized in that it comprises an overflow (8) allowing to evacuate from the basin (1) of the treated aqueous compositions.

27 / Installation according to one of claims 16 to 23, characterized in that it comprises means for introducing the raw effluents directly into the basin (1) and an outlet pipe (8 ') plunging below the surface of the bath (1 ') and kept at a distance from the bottom of the tank (1), suitable for removing aqueous treated compositions from the tank (1).

28 / Installation according to one of claims 16 to 27, characterized in that it is a covered installation by means of a shelter of closed structure but not hermetic, in which there is effective ventilation by natural convection.

29 / Installation according to claim 28, characterized in that said shelter of closed, non-hermetic structure comprises lateral and / or upper partitions at least partly made of windbreak net.

30 / Installation according to claim 28, characterized in that said shelter of closed non-hermetic structure having lateral and / or upper partitions adapted to create a greenhouse effect inside said shelter.

31 / Installation according to one of claims 24 or 26, characterized in that said shelter is a greenhouse.