FR2921651A1 - Treating organically polluted water e.g. domestic wastewater, by separating solid elements contained in water effluents, pretreating liquid flow and solid mass, and treating liquid flow and solid mass by intervention of earthworms - Google Patents

Abstract

The process for treating organically polluted water such as domestic and agro-industrial wastewater, comprises separating solid elements contained in water effluents to obtain a liquid flow in one part and a solid mass in other part, pretreating the liquid flow by ventilation and the solid mass by thermophilic activation, treating the pretreated liquid flow and solid mass by the intervention of earthworms, and post-treating the liquid flow using a filtration unit (4) having an ultrafiltration membrane, a lagoon unit and/or an ultraviolet treatment unit. The process for treating organically polluted water such as domestic and agro-industrial wastewater, comprises separating solid elements contained in water effluents to obtain a liquid flow in one part and a solid mass in other part, pretreating the liquid flow by ventilation and the solid mass by thermophilic activation, treating the pretreated liquid flow and solid mass by the intervention of earthworms, post-treating the liquid flow using a filtration unit (4) having an ultrafiltration membrane, a lagoon unit and/or an ultraviolet treatment unit before discharging or storing the liquid flow, and post-treating the solid mass using a dryer (7) followed by a screening unit (2) thus obtaining finally dried solid in one part and compost in other part. The liquid flow treatment is carried out by aspersion and percolation on a filter constituted by a substrate comprising the earthworms. The solid mass is treated by conversion assisted by the earthworms. The earthworms belong to the genus Eisenia. The solid mass is rehydrated before treating it by the intervention of earthworms. The aspersion is carried out in a discontinuous manner by maintaining the period of rest. The organically polluted water undergoes a desanding operation before separating the solid elements from the effluents. The solid elements are separated by passing the water to be treated through a sieve unit having a mesh of = 1 mm. An INDEPENDENT CLAIM is included for a device for treating organically polluted water.

Description

The invention relates to a method for treating organically polluted water and to a device for carrying out said method. The invention is in the field of domestic and agro-industrial wastewater treatment. The treatment of polluted water for their sanitation by ecological methods is expanding. Among the various techniques used, there are, for example, bacterial beds, biological disks, activated sludge during prolonged aeration, natural or aerated lagooning, infiltration-percolation on sand, or filters planted with reeds. While the bacterial beds have good overall performance, they nevertheless lead to the production of sludge and odors and require high investment costs while vulnerable to cold climates. Biological records are adapted to cold climates and even to seasonal variations of populations, but remain expensive to invest and always produce sludge and odors. Activated sludge with prolonged aeration also has high investment and operating costs, is ill-adapted to temporary hydraulic overloads and still produces sludge and odors. Although natural lagooning has relatively low investment and exploitation costs while being easy to exploit with excellent landscape integration, it still produces sludge, has very pronounced seasonal variations, is poorly adapted to cold climates, its efficiency with respect to the elimination of phosphorus decreases with the age of the installation and the delicate biological balance created remains sensitive to concentrated effluents. Aerated lagoons, on the other hand, always produce sludge and are very noisy, while requiring, like natural lagooning, a large footprint. Its operating costs are quite high.

Infiltration-percolation on sand is a rustic technique with low energy consumption and low cost, non-noisy but still producing sludge, presenting risks of clogging and odors, and poorly adapted for overloads. Reeds planted with reeds, quiet and aesthetic, however, also have high investment costs, and also require regular operation and maintenance, with a significant footprint and a recommended planting period between April and October. It is an object of the present invention to achieve an ecological solution for the treatment of organically polluted water, which produces neither sludge, odor nor is silent, has a low space constraint, also low operating cost , simple maintenance and adaptable to all types of climates. It is another object of the present invention to obtain a solution for the treatment of both organically polluted waters, but also solid residues that they may contain, with a view to optimal purification in quality and recovery. organic content of organically polluted waters. It is yet another object of the present invention that the treatment obtained is effective almost instantaneously.

It is thus within the framework of an inventive step that a method for treating organically polluted water has been devised, characterized in that the following steps are carried out: separating the effluent (s) from water with treating the solid elements contained in said effluent, so as to obtain on the one hand at least one liquid stream and on the other hand at least one solid mass, which are then treated in parallel; the liquid stream is aerated by aeration and the solid mass by thermophilic activation; the pretreated liquid flow and solid mass are treated by the intervention of earthworms; the liquid stream is post-treated by post-treatment means, such as filtration means, in particular of the type enabling membrane ultrafiltration, and / or lagooning means, and / or ultraviolet treatment means; , before rejection or storage of the liquid stream then depolluted thus obtained, and the solid mass is post-treated by drying means and then sieving means, in order to obtain, on the one hand, ultimate solid waste and on the other hand compost. According to another characteristic of the invention, the treatment of the liquid flow by spraying and percolation is carried out on a filter constituted by a substrate further comprising earthworms, and the treatment of the solid mass by composting assisted by earthworms. According to one embodiment of the invention, earthworms belonging to the genus Eisenia are used. Advantageously, after pretreatment of the solid mass, a step of rehydration of said solid mass is carried out before its treatment by the intervention of earthworms. According to another characteristic of the invention, during the treatment of the liquid flow by spraying and percolation on a filter, the sprinkling is performed discontinuously, reserving rest periods. According to another characteristic of the invention, prior to the separation step leading to a liquid flow and a solid mass to be treated, an operation is carried out for desanding the organically polluted waters to be treated.

Furthermore, the separation step leading to a liquid flow and a solid mass to be treated is advantageously carried out by passing the water to be treated through sieving means, especially at least mesh less than or equal to 1 millimeter.

The invention also relates to a device for carrying out said method, characterized in that it comprises at least: means for desilting effluent water, sieving means designed capable of separating said desiccated water in at least one part a solid flow, and on the other hand at least one solid mass, means for aeration of said liquid flow, means for the filtration on substrate comprising lombricians of said liquid stream, and at least means for treatment by thermophilic activation of said solid mass, means for the composting assisted by earthworms of said solid mass, means for drying and means for the final sieving of said solid mass. According to another characteristic, the device further comprises means for the post-treatment of the liquid flow, such as filtration means, in particular of the type enabling membrane ultrafiltration, and / or lagging means and / or treatment means by Ultra-Violets. We see that the present invention is part of an ecological logic, economic, respectful of the natural environment, and in a perspective of sustainable development. Other objects and advantages of the present invention will become apparent from the following description. The understanding of this description will be facilitated by reference to the accompanying drawings, in which: FIG. 1 is a diagrammatic representation, in sectional view and from above, of a device for carrying out the method according to FIG. invention; - Figure 2 corresponds to a sectional view along II-II of Figure 1; The present invention relates to the field of domestic and agro-industrial wastewater treatment and relates, more particularly, to a method of treating organically polluted water. The process according to the invention advantageously makes it possible to treat all of the used effluents, that is to say both their liquid and solid contents. In addition, the treatment of the solid content of said effluent partially allows the recovery of this content, in the form of compost.

To do this, the process according to the invention first requires a step of separating the solid elements contained in the effluents of water to be treated from said liquid effluents, so as to obtain on the one hand at least one liquid flow and on the other hand at least one solid mass, which are then processed in parallel. According to a preferred embodiment, the separation is carried out by at least one sieving operation with at least one sieve of mesh less than 2 millimeters, preferably less than or equal to one millimeter, of the water to be treated. According to an advantageous embodiment, it is carried out, prior to the separation step, a desanding operation of organically polluted water to be treated. At the end of these operations, one obtains on the one hand a liquid flow free of sand particles and comprising only particles with a maximum size of less than or equal to 2 millimeters, on the other hand a solid mass composed of rejections. sieve, comprising solid particles of larger size than the mesh of the sieve used, and finally sand to be evacuated. The liquid flow, thus obtained after grit removal and fine sieving of the starting effluents, is then pretreated by aeration, using aeration means such as hydro ejectors which mix water and air. During this operation, a continuous control of parameters such as the redox potential of the liquid stream and its dissolved oxygen level can advantageously be achieved. At the end of the aeration phase, the liquid stream is treated to be cleaned up on a filter constituted by by a substrate, including naturally comprising microorganisms, inoculated by earthworms. The whole, formed by this substrate colonized by microorganisms and earthworms, acts as a filter. The liquid flow through this filter to reach a drain, the filter retaining organic matter and some ions, which are then degraded by the work of ingestion-digestion of earthworms and microorganisms naturally present in the substrate. The substrate used is advantageously made of wood chips, pine bark and oak chips. The earthworms are inoculated with this substrate. The substrate is preferably arranged in a container over a thickness greater than 0.5 meters and less than 2 meters. Thanks to the burrowing of earthworms, mainly at the surface, the filter thus obtained does not get stuck.

According to a preferred embodiment, the earthworms used belong to the genus Eisenia. By way of non-limiting example, it is possible to use earthworms of the species Eisenia andrei. The filter is also advantageously contained in a covered structure so as to protect earthworms from extreme temperatures, that is to say negative temperatures or above 35 ° C, and to limit photosynthesis. In particular, the spraying of the liquid flow on the same filter is carried out, according to an example given by way of indication and not limitation, over a cycle of 120 minutes, counting 20 minutes of spraying for 100 minutes of rest. In this case, the parallel use of several filters, in several separate containers receiving the substrate and the earthworms, may advantageously allow treatment over the water of the liquid stream, without prior storage or decantation zone. At the end of the colonized substrate treatment phase of earthworms, the liquid stream is post-treated by filtration means, in particular of the type allowing ultrafiltration membrane filtration, and / or by natural processes such as lagooning, filtration on a filtered plant or sand filter, and / or physicochemical processes such as treatment with ultraviolet radiation, possibly preceded by a dephosphatation, before discharge or storage of the liquid stream then cleared. Indeed, the water resulting from this post-treatment can be reused in an agricultural use.

The solid mass resulting from the rejections of sieves during the previous step of separation previously mentioned, is, parallel to the execution of the treatment in three stages (pretreatment, treatment, post-treatment) of the liquid flow as previously described, pretreated by thermophilic activation. This step is also called biohygenization, and corresponds to a natural thermophilic activation process, conducted at temperatures up to 75 ° C, using the properties of thermophilic bacteria to spontaneously heat the solid mass. This step constitutes a phase of disinfection and disinsection and a first step of decomposition of the organic matter. This operation lasts at least fifteen days, and requires aeration and riddling of the solid mass at least once a day to avoid anaerobiosis.

After rehydration of the remaining density, the pretreated mass is treated with earthworms for up to three months. This stage is composting assisted by earthworms. At the end of composting, the resulting organic substrate also has many inert materials or bodies. A post-treatment, or refining, is still needed to produce compost of excellent quality and eliminate the ultimate waste. To do this, the solid mass is post-treated by drying then sieving, in order to obtain on the one hand final solid waste and on the other hand compost. The drying consists in spreading out in thin layer, after elimination of the earthworms, the solid mass resulting from the step of composting with earthworms. At the end of the three months of composting, the volume of the solid mass was reduced by 60% compared to that of the starting solid mass. By eliminating earthworms, it is understood that these are removed from the solid mass from the composting step, but according to an advantageous embodiment, they can be recovered for the seeding of another pretreated solid mass, and thus recycled.

The sieving is carried out on the dried solid mass, in an automatic sieve with three types of mesh, as the cascade sieving progresses. As a non-limiting example, the successive meshes used may be 5, then 3, then 2 millimeters. The different fractions obtained between the sieves are recovered. The last two fractions, in the case of cascade sieving on three different types of meshes, correspond to more or less fine compost, and the first two fractions to ultimate waste, to be treated as household waste or possibly still partly value. The treatment of the solid mass according to the invention ultimately allows the recycling, and therefore the recovery, of 2/3 of said mass as compost, for 1/3 of this mass to be considered as ultimate waste, of the household waste type. , devoid of any organic matter. In this way, the invention makes it possible to treat domestic and agro-industrial wastewater without the production of sludge, with a parallel treatment by contact with earthworms of a liquid flow and a solid mass initially contained in the effluents of water. water to be treated. The goal of the most complete decomposition of organic matter from the wastewater, on site, is thus achieved.

The invention also relates to a device for implementing the method as described above, for treating organically polluted water. As can be seen in FIGS. 1 and 2, the device comprises at least: means 1 for degreasing the effluent water, screening means 2 designed for separating said dewatered water into at least one liquid stream and a solid mass, means aeration 3 of said liquid stream, means 4 for substrate filtration comprising earthworms of said liquid stream, and at least 5 means for treatment by thermophilic activation of said solid mass, means 6 for composting assisted by earthworms of said solid mass, means 7 for drying and means 8 for the final sieving of said solid mass. Thus, the organically polluted water to be treated enters the device through an arrival view capable of collecting one or more flows supplied by one or more of the pipes E1, E2 or E3. According to the particular embodiment illustrated in FIGS. 1 and 2, the collected water then passes through an automatic screen 100, at least consisting of a grid of wide mesh, for example 30 millimeters, capable of eliminating water bulky waste as branches that can be carried by the waters to be treated. Furthermore, a channel 101 with an irregular bottom, and placed downstream of this grid, can complement the action of this screen 100 further optimizing the removal of heavy waste carried by water, such stones or rubble , which, by gravity, may be retained in the irregularities of the surface forming the bottom of said channel 101. The flow of water to be treated is then brought to a pumping station defined by a tank 102 having at least one pump, the the capacity of said tank 102 further allowing a buffer zone to the treatment device according to the invention. According to a particular embodiment, a sample sampler 103 may be associated with the tank 102 in order to analyze the quality of the water to be treated. A nonreturn valve 104 is provided after the pumping station. The water to be treated then passes through the desanding means 1, able to remove the sand contained in the water to be treated. This sand is destined to be evacuated. The desalinated water then passes through the sieving means 2, capable of separating said dewatered water into at least one liquid stream and a solid mass. These sieving means 2 are advantageously constituted by at least one sieve 20 having a mesh size of less than 2 millimeters, preferably less than or equal to one millimeter.

According to an advantageous embodiment, a second mesh sieve 21 calibrated between 0.50 and 0.25 millimeters, second the first sieve 20. The liquid stream is directly conveyed by pipes to the aeration means 3 of said liquid stream, the solid mass being recovered by the means 5 for treatment by thermophilic activation of said solid mass. The recovery of the solid mass is advantageously done in at least one chamber 50 called biohygenerator or thermophilic-mesophilic composter. The transfer of the solid mass discharged from the sieves 20 and / or 21 to the biohygenerator 50 can be done manually or by an automated treadmill system 51. According to a particular embodiment, this automated treadmill system is also transferred 51 the sand, evacuated from the degreasing means 1, to the biohygenerator 50, according to the desired composition of the biohygéniser mass in said biohygéniseur 50. It is in this biohygienizer 50 that the thermophilic activation of the solid mass, through a process natural heat production by thermophilic bacteria, up to temperatures of 75 ° C, will be able to unfold. This step constitutes a phase of disinfection and disinsection and a first step of decomposition of the organic matter. It lasts at least fifteen days, and requires aeration and riddling of the solid mass at least once a day to avoid anaerobiosis. The aeration means 3 of the liquid flow consist of hydro-ejectors 30, which bring air into the liquid flow. According to one embodiment, the hydro-ejectors 30 are arranged in a lifting station 31 further comprising pumps 32 for circulating the liquid flow in the device. According to another particularity of the embodiment illustrated in FIGS. 1 and 2, valves 33 or else measurement and / or flow control means 34 may be arranged at the output of said raising station 31.

At the end of its passage through the aeration means 3, the liquid flow is led to the means 4 for its filtration on inoculated substrate of earthworms. In particular, the liquid flow is sprayed, via irrigation ramps 40, onto bins, constituting as many filters 41 composed of substrate inoculated with earthworms. Advantageously, the dimensions of the irrigation ramps 40 will be adapted so that they can cover the width of a tray. The bins serving as the filter container 41 may, without limitation, be made of reinforced concrete. Naturally, the number of filters 41 may vary according to need. If a filter 41 at least is required, the device according to the invention may advantageously understand more. Indeed, the spraying of the liquid flow on the same filter 41 being carried out on a cycle of 120 minutes, counting 20 minutes of spraying for 100 minutes of rest, the parallel use of several filters 41, in several tanks distinct, can allow a treatment over the water of the liquid flow, without storage area or prior decantation. The use of several bins, such as for example four bins according to the embodiment illustrated in FIGS. 1 and 2, and therefore as many separate filters 41, naturally gives more flexibility in the management of the liquid flow. According to another particularity of the invention, and in order not to flood the substrate, the irrigation ramps 40 may be mounted movably along the tanks and filters 41, the spraying then being carried out by reciprocating said Ramps 40. By way of non-limiting example, four round trips can be envisaged by filter 41 during the 20 minutes of spraying, for an instantaneous flow of the ramps 40 from 5 to 20 m 3 of liquid per hour, the nozzles with a square dispersion providing a solid cone spray with a square impact surface and a dispersion angle of 40 ° to 105 °. In any case, it will be possible to adjust the number of bins and filters 41 in use as required, in particular according to the quantity of wastewater to be treated each day.

Thus, according to a first exemplary embodiment, it is possible to treat up to 60 m 3 of liquid flow per day with two rectangular filters 41 of 10 meters in length and 5 meters in width, thus 50 m 2 each.

According to a second exemplary embodiment, the use of two rectangular filters 41 of 12 meters in length and 9 meters in width, and therefore of 100 square meters each, makes it possible to treat up to 120 cubic meters of liquid flow per day. With four of these filters 41 thus sized, it is possible to reach up to 240 m3 per day, and 360 m3 for six filters 41. The filter substrate 41 is to air, including digging, at least once a week within the limit of once a day. Such digging should be done avoiding damage to the population of earthworms, and therefore to a maximum depth of 15 centimeters. After percolation of the liquid flow through these filters 41, it is evacuated by gravity and / or pumping, and collected in a pipe to post-processing means 9. According to the method according to the invention, the post-treatment can be carried out by filtration means, in particular of the type allowing a membrane ultrafiltration finish, and / or by natural processes such as lagooning, filtration on a filtered plant or sand filter, and / or physicochemical processes. -chemicals such as a dephosphatation followed by ultraviolet radiation, before release into the natural environment or storage of the liquid stream then cleared. After post-treatment, the liquid stream may be stored in a tank 90. A circuit 91 for the reuse of the post-treated stream 30 may also be provided. To return to the treatment of the solid mass, at the end of the thermophilic activation period in the biohygienizer (s) 50, the biohygenized solid mass is recovered, rehydrated and disposed in means 6 for composting 35 assisted by earthwomen. of said solid mass.

The transfer of the biohygenized solid mass to the means 6 for composting can be done manually or automatically, the container or containers of the solid mass for said transfer may advantageously be in the form of one or more rectangular perforated plastic containers 52, whose bottom and side walls are covered with a geotextile cover. As illustrated in FIG. 1, the means 6 for composting consist of one or more containers 6 that are suitable for carrying out composting, the solid mass to be composted constituting the nutrient medium necessary for earthworms. Thus, after inoculation by earthworms of the solid mass disposed in the container or containers 6, the solid mass is left to compost for at most three months.

The composting assisted by earthworms requires the control and regulation of the humidity of the composting medium. According to a particular embodiment of the invention, the rectangular perforated tanks 52 with their geotextile cover can directly constitute such containers 6 conducive to the realization of composting. The solid mass resulting from this composting step is then conveyed to the means 7 for drying and the means 8 for the final sieving of said solid mass. The means 7 for drying advantageously allow thin layer spreading of the solid mass resulting from the composting step, for drying by evaporation or the like. In particular, the solid mass is dried in a few hours on a platform with hot circulation.

Naturally, the transfer of the solid mass resulting from the composting step to the drying means 7 requires the elimination, in particular by migration to another container, of the earthworms before drying. This migration may advantageously be performed to the means 6 for composting on substrate comprising earthworms, in order to recycle the earthworms.

The means 8 for sieving the dried solid mass are advantageously constituted by an automatic screen with three types of mesh, for a cascade sieving. According to one embodiment, the successive meshes used may be 5, then 3, then 2 millimeters. The different fractions obtained between the sieves are recovered, corresponding according to their granulometry to more or less fine compost or ultimate waste. The sieve used may be vibrator or rotary drum.

According to another embodiment, the device according to the invention may further comprise means 9 for the post-treatment of the liquid flow. The post-treatment can thus be carried out, preferably by membrane ultrafiltration finish, or by any other means of conventional additional filtration, and / or by lagooning and / or UV treatment and optionally dephosphatation before discharge or storage of liquid flow then cleared . In fact, if the treated liquid stream, at the outlet of the filters 41, is very lightly charged and of clear appearance, it may still contain some earthworms escaping from the filters 41 in the outlet pipes, or organic particles, as for example example of orthophosphates, or bacteria. Microorganisms and macromolecules can be retained by means of membrane ultrafiltration, which is why, depending on the quality of the liquid flow targeted at the outlet, such post-treatment can be envisaged. The means used to carry out such an ultrafiltration membrane comprise, at least, on the one hand an aeration system in order to maintain the treated flow in oxygen saturation, and on the other hand a series of membranes whose total area accumulated will be sized according to the flow rate of the flow to be treated. The ultrafiltration means may also include means for backwashing, allowing less maintenance. The objectives of such a membrane ultrafiltration are thus to recover the large particles and / or the few earthworms that may have escaped from the filters 41, and to propose a liquid flow of such quality that it can directly reach the natural environment. If the membrane ultrafiltration has the advantage of being a compact and effective post-treatment solution, requiring for its implementation a little ground surface, and can take place in a reduced volume such as an output station of the treated liquid stream, the post-treatment may also be carried out by any other conventional filtration means, such as filters planted with reeds and / or sand filters, and / or by lagooning.

Claims (9)

1) A method for treating organically polluted water, characterized in that the following steps are carried out: the solids contained in said effluents are separated from the effluent (s) from the water to be treated, so as to obtain, on the one hand, at least one liquid stream and secondly at least one solid mass, which are then processed in parallel; - On the one hand pretreat the liquid flow by aeration, and secondly the solid mass by thermophilic activation; the pretreated liquid flow and solid mass are treated by the intervention of earthworms; the liquid flux is post-treated by post-treatment means (9), such as filtration means, in particular of the type enabling membrane ultrafiltration, and / or lagooning means, and / or treatment means by means of Ultra-Violets, before rejection or storage of the liquid stream then depolluted thus obtained, and the solid mass is post-treated by drying means (7) and then sieving means (8), in order to obtain, on the one hand, final solid waste and compost. 2) Process according to claim 1, characterized in that one carries out the treatment of the liquid flow by spraying and percolation on a filter (4,41) constituted by a substrate further comprising earthworms, and the treatment of the solid mass composting assisted by earthworms. 3) Method according to one of claims 1 or 2, characterized in that one uses earthworms belonging to the genus Eisenia. 4) Method according to one of claims 1 to 3, characterized in that at the end of the pretreatment of the solid mass is carried out a step of rehydration of said solid mass before treatment by the intervention of earthworms. 5) Method according to one of claims 2 to 4, characterized in that during the treatment of the liquid flow by sprinkling and percolation on a filter (4,41), sprinkling is performed discontinuously, reserving periods of rest. 6) Method according to one of claims 1 to 5, characterized in that prior to the separation step leading to a liquid flow and a solid mass to be treated, it performs a desanding operation of organically polluted water to be treated. 7) Method according to one of claims 1 to 6, characterized in that the separation step leading to a liquid flow and a solid mass to be treated is conducted by passing water to be treated through sieving means (2) , in particular at least one sieve (20) of mesh less than or equal to 1 millimeter. 8) Device for carrying out the process according to claims 1 to 7, for treating organically polluted water, characterized in that it comprises at least: means for desanding (1) effluent water, sieving means (2) designed to separate said dewatered water in at least one solid stream, and secondly at least one solid mass, aeration means (3) of said liquid stream, means (4) for substrate filtration comprising earthworms of said liquid stream, and at least means (5) for treatment by thermophilic activation of said solid mass, means (6) for the composting assisted by earthworms of said solid mass, means (7) for drying and means (8) for final sieving of said solid mass. 9) Device according to claim 8, characterized in that it further comprises means (9) for the post-treatment of the liquid flow, such as filtration means, in particular of the type allowing membrane ultrafiltration, and / or Lagooning means and / or ultraviolet treatment means.