Wastewater treatment system using a planted filter equipped with a bacteria injection device in a pretreatment structure such as a flushing or pumping station

Abstract

The invention relates to a wastewater treatment device (1) using a planted filter, preferably of the reed type, comprising at least one first stage (FP1) of planted filter including a plurality of filter layers based on a mineral substrate, including an upper layer of fine gravel intended to accommodate the plants, a transition layer just below the upper layer made of rather fine filter gravel with a larger grain size than the upper layer, and at least one bottom layer, known as a drainage layer, of the coarse gravel type, characterized in that it further comprises, upstream of said filter,at least one first feed structure (20) of the flushing or storage tank type, equipped with a fully submerged device (100) for injecting microbubbles of air, creating aeration and mixing of the wastewater, allowing for superoxygenation before its passage through the first stage (FP1) of the planted filter, and a device for injecting nitrifying and / or dephosphatizing bacteria, constituting a preliminary biological treatment reactor. Figure for the abbreviation: Fig. 1,

Description

Title of the invention: Wastewater treatment device using a planted filter equipped with a bacteria injection device in a flushing or pumping-type pretreatment structure. Technical field of the invention

[0001] The present invention relates to a wastewater treatment device using reed bed filters, that is to say, a wastewater treatment device comprising at least one gravel and sand filter using common reed (Phragmites australis) plants to promote, in particular, the infiltration of the wastewater to be treated. The invention relates more specifically to vertical flow filters, variably saturated or not. Previous technique

[0002] Developed in France in the 1980s, treatment using vertical flow filters planted with macrophytes such as reeds (VF) has seen increasing growth since the late 1990s. This simple, reliable, and environmentally friendly process relies on natural mechanisms for the purification of domestic wastewater from public sewer systems, such as filtration, microorganism activity, and plant assimilation.

[0003] Particularly popular with elected officials and suitable for collective sanitation in small municipalities (between 30 and 2000 population equivalents - PE), this system, now recognized by decision-making and regulatory bodies, offers numerous advantages: - Very low production of residual sludge, - No risk of odors, - Noise pollution is virtually non-existent, - No development of mosquito larvae, - Perfect integration into the landscape, - Very good acceptance from the locals. - Easy and inexpensive maintenance, - Very good purification performance, and - Good adaptation.

[0004] This technique is carried out according to the principle of primarily aerobic biological purification in granular media ranging from fine to coarse particle size. More specifically, this type of device generally comprises at least one filter stage filled with different layers of mineral substrate and in which are planted Plants are used, the most common being reeds of the Phragmites Australis type. The system is often complemented by drains to collect the treated water.

[0005] Usually, the successive layers from the bottom of the filter to the top of the filter consist of a layer of large diameter gravel, a layer of coarse gravel (medium grain size), and a layer of fine gravel or sand in which the reeds are planted.

[0006] The layer of coarse gravel or sand in which the plant root system is located is an aerated zone, serving as a substrate for aerobic bacteria that will decompose the organic matter. Since the reeds also have very well-developed rhizomes, they contribute, to a limited extent, to this supply of oxygen for the bacteria. Furthermore, the reeds, through their naturally oscillating movement (due to a north wind or breeze), have a fragmenting effect on the layer of sludge formed on the surface of the filter, preventing clogging and ensuring the continuous infiltration of the effluent.

[0007] In summary, the operation of such a device is as follows: wastewater is discharged onto the surface of the filter (what is commonly referred to as the "overflow"), bacteria carry out the degradation of the organic matter in the wastewater, the effluent flows by vertical percolation through the granular layers to the drainage system which collects the filtered / treated water for discharge from the drain outside the filter at the end of the treatment process. The overflow generally infiltrates through the plant bed in just a few minutes.

[0008] The root development of the plants used increases the surface area available for the development of microorganisms. This increase in active surface area is further stimulated by the activity, diversity, and density of microorganisms, as plant root tissues provide more hospitable niches than inert mineral substrates. Finally, plant metabolism also influences the treatment to varying degrees depending on the surface area involved.

[0009] According to a widespread but not necessary practice, it is known to use two consecutive vertical flow filters to achieve adequate treatment. This is referred to as a two-stage wastewater treatment plant. The surface area of ​​the filters normally depends on the number of inhabitants. Generally, a usable surface area of ​​between 1.2 and 1.5 m² / inhabitant is required for the first filter, and between 0.8 and 1 m² / inhabitant for the second filter, i.e., between approximately 2 and 2.5 m² / inhabitant (and between 4 and 8 m² of total surface area, the usable surface area of ​​a filter often being equal to about half of the total surface area used). The second filter, placed at an altitude lower than or equal to that of the first filter, allows for treatment that meets a more stringent regulatory standard, primarily by retaining and degrading ammonia nitrogen, which is only partially or minimally retained by the first filter. higher. Consequently, relatively large treatment areas can be utilized quickly, reaching, for example, 1000 to 1500 m² for a wastewater treatment plant with a capacity of 500 population equivalents. It should also be noted that the gross floor area of ​​a two-story plant varies according to the plant's capacity and stabilizes at approximately 4 m² / inhabitant for populations of 500 or more.

[0010] However, since the performance of the conventional process is now well known and decades of experience have made it possible to offer a range of solutions guaranteeing adequate discharge levels according to the specifics of each project, the treatment by vertical flow filters planted with reeds described above has limitations, both from the point of view of the elimination of major pollutants and the ground areas required for its installation.

[0011] In particular, the removal of the main nutrients (nitrogen, phosphorus) remains a constant concern for all relevant public and private stakeholders. Nitrogen removal is therefore a major avenue for optimization in terms of achievable performance, due to the biological mechanisms involved and the associated limiting parameters (bacterial competition, oxygen requirements). At the same time, phosphorus removal proves more complex since the biological (limited within reed bed filters) or physicochemical removal mechanisms are known but poorly controlled, and the intrinsic performance of the treatment system is very limited.

[0012] Nitrogen problem

[0013] The "nitrogen" parameter remains a major element among the avenues for optimizing purification performance, as it appears to be sensitive to external parameters and to heterotrophic bacterial competition (particularly carbon degradation).

[0014] The main nitrogen elimination mechanisms have both aerobic and anoxic components: - Ammonification: aerobic transformation of organic N into N-NH4, - Nitrification: aerobic transformation of N-NH4 into nitrates N-NO3, sensitive to dissolved oxygen concentrations as well as redox conditions, temperature and pH, - Denitrification: anoxic transformation of N-NO3 into N2, requiring the absence of dissolved oxygen and residence times of several hours within a water-saturated zone.

[0015] However, achieving high performance levels in terms of minimum yield, whether for total nitrogen (NGL), ammoniacal nitrogen (N-NH4) or Kjeldahl nitrogen (NTK), cannot be effective without the implementation of complex processes composed of several treatment stages associated with specific sizing (recirculation, partial or total saturation of a bed, use of specific filter materials).

[0016] These high treatment levels are therefore often associated with a large land area and the installation of specific equipment, materials or structures which are costly in terms of investment, operation and renewal (recirculation station, specific adsorbent materials, etc.).

[0017] The philosophy of the present invention therefore aims at the development of treatment systems that are both more compact, simpler in design and maintenance, and more efficient in terms of yields obtained.

[0018] Current research issues therefore concern in particular: - Improving nitrification to achieve emission levels of NTK < 5 mg / L and N-NH4 < 3 mg / L, and - The improvement of denitrification within a saturated zone combining the absence of dissolved oxygen, a high concentration of nitrates N-NO3 and a sufficient amount of available carbon, in order to achieve an outlet concentration N-NO3 < 10 mg / l.

[0019] The treatment objective targeted within the framework of this project is NGL < 15 mg / l at the station outlet.

[0020] Phosphorus problem

[0021] Moreover, since the implementation of the "planted filters" sector within the French park, the "phosphorus" parameter has been identified as the one on which the levers of elimination are limited, most of the time to physicochemical retention phenomena strongly linked to hydraulics and the mineralogical characteristics of the materials.

[0022] The different components of phosphorus in wastewater are summarized below: - Inorganic phosphorus: primarily polyphosphates, as well as orthophosphates P-PO4 (majority), some of which comes from the hydrolysis of the former, - Organic phosphorus: phospholipids, esters, polynucleotides, ATP, ADP, etc.

[0023] The main mechanisms for phosphorus removal within the process are as follows: - Plant assimilation, at a rate of 30 to 150 kg of phosphorus per inhabitant per year, i.e. a negligible removal compared to the input concentrations (1 to 2% of the Pt eliminated), - Adsorption of phosphorus on filter materials (specific and non-specific), - Precipitation of phosphorus on the surface of the grains (main phenomenon).

[0024] In this context, planted filters remain a reliable and sustainable solution when the receiving environment requires the following discharge levels at the wastewater treatment plant outlet: Pt < 10 mg / l OR Efficiency > 30%

[0025] In the context of higher performance requirements, other systems are preferred (bio-discs, activated sludge), despite the notable interest of planted filters in rural or semi-urban areas, because long-term performance is quite limited.

[0026] Therefore, a reflection is necessary with regard to the evolution of regulatory discharge standards, in order to sustain the sector among the leading sectors within the framework of the French territorial network.

[0027] Ongoing development projects concerning the "phosphorus and FPR" problem are primarily based on optimizing the physicochemical retention of phosphorus. This has resulted in numerous studies on specific materials designed to maximize contact surfaces and physicochemical reactions.

[0028] Although interesting, these approaches raise the question of the lifespan of the materials and their subsequent use when they need to be replaced.

[0029] The present project aims to investigate the possibility of biological phosphorus removal, which would provide a virtually inexhaustible resource. The combination of specific bacteria, microalgae, and various microorganisms, placed in a suitable environment (temperature, pH, applied hydraulic head), appears to be a promising approach.

[0030] The treatment objective targeted in the context of this project is Pt < 2 mg / l at the station outlet.

[0031] Current research on the treatment process therefore aims to improve performance with respect to nitrogen and phosphorus parameters, through the development of additional treatments to be combined with the various single- or two-stage planted filter systems. Presentation of the invention

[0032] The present invention aims to remedy these drawbacks with a totally innovative approach, more efficient than prior art solutions, without increasing gross / useful surface area, and significantly improving the quality of treated water.

[0033] More specifically, the object of the present invention relates to the improvement of the purification treatment by injection of specific bacteria targeting the elimination of dissolved pollutants such as nitrogen and phosphorus.

[0034] To this end, according to a first aspect, the present invention relates to a wastewater treatment device using a planted filter, preferably of the type reeds, said device comprising at least a first stage of planted filter comprising a plurality of filter layers based on mineral substrate including an upper layer of fine gravel intended to accommodate the plants, a transition layer of medium grain size gravel arranged below the upper layer, and a drainage bottom layer of coarse gravel, characterized in that it further comprises, upstream of said filter, at least a first feed structure of flushing type or station in the form of a storage tank equipped with a device for injecting nitrifying and / or dephosphatizing bacteria constituting a preliminary treatment biological reactor.

[0035] The solution is therefore to consider the feed structures for the filter beds (flushing points, injection stations) not only as storage and containment structures, but also as pretreatment structures. For this reason, they must be considered as biological reactors, within which the processes of degradation of organic matter and various nutrients present in the wastewater take place, prior to its conveyance to the filter beds.

[0036] It is therefore a question of acting on the effluent upstream of the main treatment within the filter beds, via a preliminary treatment acting as a catalyst and complementing the reactions already known.

[0037] The invention is implemented according to the embodiments and variants set out below, which are to be considered individually or according to any technically feasible combination.

[0038] Advantageously, the preliminary treatment biological reactor includes at least one reservoir of strictly aerobic bacteria, a dosing pump and a pipeline for transporting the bacteria from the reservoir to the flushing or station type feed structure.

[0039] Preferably, the preliminary treatment biological reactor includes at least one concentrate mixing element interposed between the reservoir and the pump.

[0040] According to a particular embodiment of the present invention, the preliminary treatment biological reactor is placed within a valve chamber adjacent to the flush or station type feed tank.

[0041] According to an alternative design, the preliminary biological treatment reactor is placed on a slab overlooking the flush or post type feed tank.

[0042] According to a preferred embodiment of the present invention, the bacteria are chosen from pure nitrifying bacteria or a combined mixture of nitrifying and dephosphatizing bacteria, with a proportion of 20% to 80% nitrifying bacteria.

[0043] Preferably, the strains of bacteria used in the nitrifying formulation are of the Nitrobacter and / or Nitrosomonas type.

[0044] For the phosphate control formulation, a Bacillus "consortium" preferably produced exclusively by HTS bio will be used. This consortium jointly sequesters nitrogen and phosphorus through the assimilation of organic matter and may also sequester free nitrogen and phosphorus. The dosage can be adjusted according to the performance observed in the system concerned, until all objectives are met.

[0045] Advantageously, the first supply structure of the flushing type or station in the form of a storage tank is further provided with a first totally submerged device for injecting microbubbles of air creating aeration and mixing of the wastewater allowing superoxygenation before its passage into the first stage of planted filter.

[0046] According to a specific embodiment of the present invention, the device comprises: - a second stage of planted filter similar to the first stage of planted filter and placed downstream and at a level lower than or equal to it, depending on the direction of flow of the water to be treated, and - a second flushing or station type feed structure in the form of a storage tank similar to the first flushing or station type feed structure, said second flushing or station type feed structure being interposed between the outlet of the first stage of planted filter and the inlet of the second stage of planted filter and equipped with a second device for injecting nitrifying and / or dephosphatizing bacteria constituting a second preliminary biological treatment reactor.

[0047] Advantageously, the flushing or tank-shaped supply structure is further equipped with a second totally submerged device for injecting microbubbles of air, creating aeration and mixing of the wastewater, allowing for superoxygenation before its passage into the second stage of the planted filter.

[0048] According to a complementary aspect, each totally immersed air microbubble injection device comprises at least one diffusion ramp pierced with microperforations and connected to an air production device such as a compressor or a blower. Brief description of the figures

[0049] Other advantages, purposes and features of the present invention will become apparent from the following description, given for explanatory purposes and in no way as a limitation, with reference to the accompanying drawings, in which:

[0050] [Fig-1] [Fig.1] is a cross-sectional view of a water treatment device worn in accordance with this standard, comprising a planted filter stage and a structure a flushing-type feeder or station in the form of a storage tank equipped with a micro-aeration device and a device for injecting nitrifying and / or denitrifying bacteria constituting a preliminary biological treatment reactor,

[0051] [Fig.2] [Fig.2] is a view similar to [Fig.1] but with two floors a planted filter and two feed structures of the flushing or station type in the form of a storage tank, each equipped with a micro-aeration device and a device for injecting nitrate-based bacteria constituting a preliminary biological treatment reactor,

[0052] [Fig.3] [Fig.3] is a perspective view of a first embodiment of a a post-type feed unit in the form of a storage tank equipped with a preliminary biological treatment reactor,

[0053] [Fig.4] [Fig.4] is a perspective view of a second embodiment of a flushing-type supply structure in the form of a storage tank equipped with the preliminary biological treatment reactor,

[0054] [Fig.5] [Fig.5] is a variant embodiment of [Fig.3],

[0055] [Fig.6] [Fig.6] is an alternative embodiment of [Fig.4],

[0056] [Fig.7] [Fig.7] is a detailed view of the biological treatment reactor preliminary,

[0057] [Fig.8] [Fig.8] is a detailed view of the micro-aeration device,

[0058] [Fig.9] [Fig.9] is a detailed view of a fully immersed injection device of microbubbles of air implanted at the bottom of a feeding structure such as a hunting or hunting station,

[0059] [Fig. 10] [Fig. 10] is a variant of [Fig. 9], and

[0060] [Fig.11] [Fig.11] is a variant view of [Fig.10]. Description of the implementation methods

[0061] The present description is given by way of non-limiting attribution, each feature of one embodiment being able to be combined with any other feature of any other embodiment.

[0062] It is noted from the outset that the figures are not necessarily to scale, without this affecting their understanding.

[0063] In the following description, the term "height", the qualifiers "upper", "lower", "top" and "bottom" of an element or layer are used in the context of a normal installation of the device, that is to say, relating to a vertical notion in relation to a ground in which the filter is arranged to achieve vertical percolation.

[0064] Figure 1 represents a device 1 according to the present invention for the treatment of domestic wastewater mainly from collective networks unitary or separate. The values ​​and dimensions given here are only arbitrary and may vary depending on the terrain on which the device is installed (slope in particular), the number of inhabitants whose wastewater must be treated with the device, the latitude of installation, the outside temperature / humidity, the type of plants chosen, etc.

[0065] This domestic wastewater treatment device 1 comprises, according to the direction of flow of the effluents to be treated between the high point of entry and the low point of exit, an inlet 10 of untreated effluents, coming for example from the wastewater network of dwellings, a first supply structure 20 of the flushing or station type, a first pipe 30 of effluent circulation to a first stage FP1 of reed bed filter (RDF), a pipe 40 of exit of the effluents treated by the first stage FP1 of reed bed filter (RDF) and a manhole 50 communicating with this exit pipe 40.

[0066] The first stage FP1 of the reed bed filter is designed to filter wastewater using a vertical percolation process, variably saturated or unsaturated. This first stage FP1 comprises layers, each composed of a mineral substrate, arranged one above the other, drainage and discharge means, aeration means, and outlet 40 for conveying the filtered water out of the filter.

[0067] The different layers arranged in the first stage FP1 of the filter, planted from top to bottom, are for example: - An upper filter layer composed of fine gravel, for example with a grain size between approximately 2 and 4 mm, this layer is intended to ensure fine filtration of the wastewater and also serves as the site for the reeds to take root. This upper filter layer aims to retain the majority of suspended solids and break down most of the organic matter. The thickness of this layer is typically between approximately 30 and 40 cm. The effluent is discharged into the filter in a known manner via the outlet pipe 30 (which may divide into several sub-pipes distributed across the width of the filter) and possibly water distribution jets; - A lower filter layer composed of gravel with a grain size of approximately 2 to 6.3 mm. This lower filter layer aims to remove residual organic matter and ammoniacal nitrogen. It also contains the tidal zone which promotes the retention of nitrogen pollutants. The thickness of this layer is typically between approximately 30 and 40 cm; - An intermediate layer composed of coarse gravel with a grain size between approximately 4 and 20 mm. The thickness of this layer is preferably approximately 20 cm; - A drainage layer of gravel with a grain size of approximately 20 to 40 mm. The thickness of this layer is approximately 20 cm. The intermediate and drainage layers correspond to the saturated zone (constantly saturated) at the bottom of the structure, the site of anoxic reactions. The water saturation of these layers and the tidal effect, depending on the thickness of the zeolite layer, are made possible by the flow regulation structure 20.

[0068] A zeolite layer composed of materials with a particle size between approximately 2 and 5 mm can be placed between the lower filter layer and the intermediate layer. This zeolite layer is only installed in the optimized nitrogen treatment configuration and preferably has a thickness between approximately 5 and 15 cm. In this specific case, it is the site of the temporary saturation.

[0069] The drainage layer includes drainage means known per se and comprising, for example, a plurality of spaced drains distributed over the entire bottom surface of the filter and a collector drain connected to the other drains and conveyed to the outlet 40 of the first stage FP1 of the planted filter.

[0070] The ventilation means comprise chimneys 95 and conveying means 90 which are connected to said chimneys, and deliver outside air within the upper and lower filter layers, as well as for the zeolite layer when present.

[0071] The conveying means are, for example, drains with a diameter of 100 mm. They pass through the upper layer and are positioned on the surface of the lower filter layer. In the variant for optimized nitrogen treatment, the zeolite layer, which corresponds to the tidal zone, particularly requires oxygen (O2) inputs so that the ammonia nitrogen (NH4), which adsorbs onto the zeolite, degrades with oxygen to transform into nitrates (NO3). The chimneys 95 are regularly distributed on the outer surface of the FPL filter. They are generally paired, being located at both ends of a drain. Finally, according to the invention, the device includes the structure 20 for regulating the flow rate of the treated water discharged from the filter, described below.

[0072] This first supply structure 20, of the flushing or pumping type, is structural and comprises a semi-buried concrete tank 21 covered by a top slab 22 and a valve chamber 24, forming a reservoir connected to the inlet pipe 10 and the outlet pipe 30 supplying the planting beds. This first structure 20 constitutes a structural means of regulating the flow of water conveyed to the first stage of the planted filter bed (FPL).

[0073] The concrete tank 21 is closed at least at its bottom and along its vertical peripheral walls. This tank 21 contains a set of pumps 25 of effluent circulation or a flushing drainage device 26 entering via the inlet pipe 10 and exiting towards the first stage FP1 of planted filter via the outlet pipe 30.

[0074] The tank 21 also contains a fully submerged microbubble air injection device 100 (see [Fig. 8]) which aerates and mixes the wastewater, providing superoxygenation before it passes through the first stage FP1 of the planted filter. This microbubble air injection device 100 comprises at least one diffusion ramp perforated with micro-perforations and connected to an air generation device such as a compressor or a blower of a known type.

[0075] As illustrated in [Fig. 8], the micro-perforated diffusion ramp 110 is attached to a weight 140 and has a multitude of micro-perforations 120, for example in the form of parallel rows. The ramp is connected to an air production device 130 such as a compressor or a blower of a known type, for example of the BIBUS® brand.

[0076] The air flow rate of the air microbubble injection device is between approximately 2.5 and 50 liters / minute / meter of diffuser / tube, and preferably between approximately 5 and 20 liters / minute / meter of diffuser / tube. The oxygen transfer rate of the air microbubble injection device is between approximately 0.04 and 0.08 kg Ck / hour / meter of diffuser / tube, and preferably between approximately 0.05 and 0.07 kg Ck / hour / meter of diffuser / tube.

[0077] The greater the height of the water column, the greater the oxygen transfer rate will be. Similarly, the greater the volume of air injected into the micro-perforated diffusion ramp 110, the greater the mixing will be.

[0078] The micro-perforated diffusion boom 110, for example, has the shape of a flexible tube reinforced with an internal braided polyester sheath, enabling it to resist bursting and maintain its shape, and is equipped with orifices 120. A self-supporting reinforced tube, resistant to UV rays, a wide range of chemicals, salinity, pH variations, and temperature, is preferably chosen. The thick wall of the tube helps prevent perforation, stretching, and kinking, and contributes to its weighting.

[0079] In accordance with the present invention, the first supply structure 20 is further provided with a device 200 for injecting nitrifying and / or dephosphatizing bacteria comprising a pipe 203 plunging towards the bottom of said structure and constituting a preliminary treatment biological reactor.

[0080] More specifically, as illustrated in [Fig.3] showing in more detail a substation-type feed structure 20, the preliminary treatment biological reactor 200 is placed on the upper slab 22 of the latter.

[0081] Fig. 4 illustrates an alternative in which the preliminary treatment biological reactor 200 for injecting nitrifying and / or dephosphatizing agents is placed on the upper slab 22 of a flushing-type supply structure 20.

[0082] In [Fig.5], the preliminary treatment biological reactor 200 is placed in the valve chamber 24 of the substation-type supply structure 20.

[0083] In [Fig.6], illustrating an alternative embodiment, the preliminary treatment biological reactor 200 is placed in the valve chamber 24 of the flush-type supply structure 20.

[0084] Figure 7 shows the nitrifying and / or dephosphatizing bacteria injection device 200, which mainly comprises a strictly aerobic bacteria reservoir 201 and a dosing pump 202 connected to the bacteria transport pipeline 203 from the reservoir 201 to the feed point 20, which is of the pumping or flushing type. A concentrate mixing unit 205 is interposed between the reservoir 201 and the dosing pump 202 for improved homogenization of the bacterial solution. The preliminary treatment biological reactor 200 also includes a timer / programmer 206 connected to the concentrate mixing unit 205 and a power supply 207 connected to the latter and to the dosing pump 202.

[0085] The dosing pump 202 is, for example, an electromagnetic diaphragm pump with a power rating of approximately 25W, operating at a pressure of approximately 16 bar and with a flow rate of approximately 3.6 l / h. The reservoir 201 is, for example, made of a plastic material such as translucent polyethylene, with a volume of several tens of liters.

[0086] The nature of the concentrate is preferably specific to each case (number of inhabitants, type of effluent treated, effective treatment area, volume to be treated, terrain elevation, etc.), and depends on the objectives for nitrogen and phosphorus parameters. The injected bacteria, which are non-pathogenic to humans and the environment, may be of two types: - Either pure nitrifying agents, in the case of specific nitrogen treatment without constraints on the phosphorus parameter, - Either a combined mixture of specific composition (nitrifying bacteria and dephosphatizing bacteria) in the case of combined nitrogen / phosphorus treatment with additional removal of carbonaceous organic matter, with a rate of approximately 20 to 80% nitrifying bacteria.

[0087] The strains of bacteria used in the nitrifying formulation are of the Nitrobacter and / or Nitrosomonas type.

[0088] For the phosphate-resistant formulation, a Bacillus "consortium" is used, preferably produced exclusively by HTS bio, which jointly sequesters nitrogen and phosphorus via the assimilation of organic matter, and which may be accompanied by the sequestration of free nitrogen and phosphorus. In this case, the dosage is adjusted based on the performance observed in the system concerned, until all objectives are achieved.

[0089] Current bacterial synthesis techniques offer the possibility of modulating the composition of the bacterial mixture in order to obtain a tailor-made concentrate, adapted to each project (nature and quantities of bacteria in the concentrate).

[0090] Regardless of the nature of the concentrate, a dissolved oxygen concentration of 4 to 6 mg / l is ensured within the storage tank 20 using in particular the submerged device 100 for injecting microbubbles of air in order to maximize aerobic bacterial growth.

[0091] Finally, whatever concentrate is used, it will also have an influence on the elimination of carbonaceous organic matter.

[0092] The operation of the wastewater treatment device 1 is as follows: Wastewater from the dwellings enters the first inlet 20, a flushing-type inlet pipe, via the inlet pipe 10. This wastewater is aerated by the submerged microbubble injection device 100, which creates continuous mixing, resulting in increased oxygenation (O2 saturation level) before it passes, via the outlet pipe 30, into the first stage FP1 of the planted filter. The operation of this first stage FP1 is known and will not be described here (see the introductory section). The treated wastewater from this first stage FP1 of the planted filter exits through the outlet pipe 40.

[0093] The effect of micro-aeration promotes aerobic processes, by considering the flushing structures or pumping stations not only as storage structures but also as biological reactors for preliminary treatment. This phenomenon induces the degradation of organic matter (COD, BOD5) as soon as the raw effluent arrives at the treatment plant within the feed structure 20, and no longer solely within the filter beds FPL.

[0094] The impact of this solution allows for optimization of nitrification (aerobic transformation of ammonium ions NH4+ into nitrate ions NO3) from the first stage of planted filter FP1 and optimization of phosphorus removal (orthophosphates PO43 and organic phosphorus), with, in particular, an improvement in biological treatment (overaccumulation within the biomass).

[0095] In addition, superoxygenation promotes the completion of aerobic processes for optimized performance on both organic matter and nutrients.

[0096] According to an alternative embodiment illustrated by [Fig.2], the domestic wastewater treatment device 1 comprises, depending on the direction of flow of the effluent to be treated between the upper inlet point and the lower outlet point: - an inlet of untreated effluent, originating for example from the residential wastewater network, - a first supply structure 20 of the flushing or station type, consisting of at least one semi-buried concrete tank 21 covered with a top slab 22 and comprising a valve chamber 24, - a first 30mm pipe for circulating effluents to a first stage FP1 of a reed bed filter (FPR), - a 40 outlet pipe for the effluents treated by the first stage FP1 of the reed bed filter (FPR), - and a second supply structure 60 of the flushing type or station identical to structure 20 and installed at the outlet of the treated effluent outlet pipe 40, and a second outlet pipe 70 for the circulation of treated effluents towards a second stage FP2 of a reed bed filter (FPR).

[0097] In this variant, the effluents therefore pass through two stages FP1 and FP2 of reed bed filters (RDF), arranged at different altitudes or not, and two feed structures of the flushing or station type 20 and 60, which will be described in more detail below.

[0098] More specifically, wastewater from the dwellings enters the first supply structure 20, a flushing or pumping station type, via the inlet pipe 10. This water is aerated by the first submerged microbubble injection device 100, which creates continuous or regulated mixing, allowing for superoxygenation of the wastewater before it passes, via the outlet pipe 30, into the first stage FP1 of the planted filter, the operation of which is described previously. The water treated by this first stage FP1 of the planted filter exits through the outlet pipe 40 and flows directly into the second supply structure 60, a flushing or pumping station type.These waters, already filtered once, are aerated again thanks to the 100 submerged microbubble air injection device which creates a permanent or regulated mixing allowing super-oxygenation of the wastewater before it passes, via the outlet pipe 70, into the second stage FP2 which operates in the same way as the first reed bed filter FPL. The wastewater is therefore filtered twice vertically (from upstream to downstream) and also passes through two feed structures of the flushing or pumping station type where it is super-oxygenated and mixed.

[0099] Of course, each time the wastewater passes through one and then the other of the inlet structures 20 and 60 of the pumping or flushing type, the nitrifying and / or dephosphatizing bacteria of the preliminary treatment biological reactor 200 act to significantly reduce dissolved pollutants (nitrogen, phosphorus), this action being further amplified (without this being necessary) by the creation of bubbles from the micro-perforated diffusion ramp 110 which allow better oxygenation (O2 saturation rate).

[0100] Bubbling allows a minimum oxygen saturation level of 40% to be achieved, which improves the dispersion and therefore the growth of nitrifying and / or dephosphatizing bacteria. This solution consequently reduces the required bacterial dosage and therefore the cost of treatment. For example, it is possible to obtain a bacterial injection rate of 35 ml / h with an oxygen saturation level of 40%, but 70 ml / h with an oxygen saturation level of 16%.

[0101] This solution also improves treatment performance in terms of BOD, COD, and TKN.

[0102] As shown in Figures 9 to 11, the air microbubble injection device 100 has a semi-rigid grid shape 150 with an external contour substantially identical to that of the bottom or wall of the tank 21 of the flushing or pumping station-type supply structure 20 in which it is located. As can also be seen in these figures, the grid 150 is provided with a multitude of parallel micro-perforated diffusion ramps 110.

[0103] The semi-rigid flat grid thus has a shape adapted to the supply structure 20 of the flushing or post type, for example rectangular ([Fig.9]) or circular ([Fig. 10]), and can include several distinct zones of different shapes, each equipped with micro-perforated diffusion ramps 110 parallel and / or perpendicular to each other ([Fig. 11]), some ramps being able to be rounded while others are straight.

[0104] According to an example embodiment, the pipe will have the following characteristics:

[0105] - Outer diameter: 2.54 cm,

[0106] - Inner diameter: 1.27 cm,

[0107] - Weight: 0.32 kg / m,

[0108] - Normal air flow rate: 37 liters / minute / meter,

[0109] - Transfer rate: 0.061 kg of O2 / hour / meter,

[0110] - Bursting pressure: 5.5 bar,

[0111] - Recommended cleaning: with clean water.

[0112] After comparative studies between the device of the present invention and devices of the prior art, the following improvements were noted: - Custom design, - Easy and permanent installation, - Very high oxygen transfer (fine bubbles), - Low operating cost (low-consumption compressor), - No electrical source in the water, - Soundproofed.

[0113] It must be clearly understood that the detailed description of the object of the Invention, given solely by way of illustration, does not in any way constitute a limitation, technical equivalents also being included in the scope of the present invention.

[0114] Thus, a third circulation structure of the flushing or post type coupled with a third stage of reed-planted filter could also be considered in particularly complex filtration cases.

Claims

Demands

1. A wastewater treatment device (1) using a planted filter, preferably of the reed type, said device comprising at least: - a first stage (FP1) of planted filter comprising a plurality of filter layers based on a mineral substrate, including an upper layer of fine gravel with a grain size of between approximately 2 to 4 mm intended to accommodate the plants, a transition layer of gravel with a medium grain size of between approximately 4 and 20 mm arranged below the upper layer, and a drainage bottom layer of coarse gravel with a grain size of between approximately 20 and 40 mm, and - upstream of said filter, at least one first feed structure (20) of the flushing type or station in the form of a storage tank equipped with a device (200) for injecting nitrifying and / or dephosphatizing bacteria constituting a preliminary treatment biological reactor,characterized in that it further comprises: - a second stage (FP2) of planted filter similar to the first stage (FP1) of planted filter and placed downstream and at a level lower than or equal to it, depending on the direction of flow of the water to be treated, and - a second feed structure (60) of the flushing or station type in the form of a storage tank similar to the first feed structure (20) of the flushing or station type, said second feed structure (60) of the flushing or station type being interposed between the outlet of the first stage (FP1) of planted filter and the inlet of the second stage (FP2) of planted filter and equipped with a second injection device (200) of nitrifying and / or dephosphatizing bacteria constituting a second preliminary biological treatment reactor.

2. Wastewater treatment device (1) according to claim 1, characterized in that each preliminary biological treatment reactor (200) comprises at least one reservoir (201) of strictly aerobic bacteria, a metering pump (202), a pipeline (203) transporting the bacteria from the reservoir (201) to the flushing or pumping type supply structure (20).

3. A wastewater treatment device (1) according to claim 2, characterized in that the preliminary biological treatment reactor (200) includes at least one concentrate mixing element (205) interposed between the reservoir (201) and the pump (202).

4. Wastewater treatment device (1) according to any one of the preceding claims, characterized in that the preliminary treatment biological reactor (200) is placed within a valve chamber (24) adjacent to the flushing or post type supply structure (20).

5. Wastewater treatment device (1) according to any one of claims 1 to 3, characterized in that the preliminary treatment biological reactor (200) is placed on an upper slab (22) overhanging the flushing or post type supply structure (20).

6. Wastewater treatment device (1) according to any one of the preceding claims, characterized in that the bacteria are selected from pure nitrifying bacteria or a combined mixture of nitrifying and dephosphatizing bacteria, with a proportion of 20% to 80% nitrifying bacteria.

7. Device (1) according to any one of the preceding claims, characterized in that the first supply structure (20) of the flushing or storage tank type is further provided with a first totally submerged device (100) for injecting microbubbles of air creating aeration and mixing of wastewater allowing superoxygenation before its passage into the first stage (FP1) of planted filter.

8. Device (1) according to any one of the preceding claims, characterized in that the supply structure (60) of the flushing or station type in the form of a storage tank is further provided with a second totally submerged device (100) for injecting microbubbles of air creating aeration and mixing of the wastewater allowing superoxygenation before its passage into the second stage (FP2) of planted filter.

9. Device (1) according to any one of the preceding claims, characterized in that each totally immersed air microbubble injection device (100) comprises at least one diffusion ramp (110) pierced with microperforations (120) and connected to an air production device (130) such as a compressor or a blower.

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