FR2929608A1 - Device for sanitizing wastewater originating from houses or small and medium-sized communities, comprises first and second filters for treating wastewater comprising filtration medium and plants, a body for settling materials, and a wall - Google Patents

Abstract

The device comprises a first filter (2) and a second filter (4) for treating wastewater, each comprising a filtration medium and plants e.g. reeds planted in the filtration medium, a body (3) for settling materials suspended in wastewater, receiving water from the first filter, sending back the suspended material settled in the first filter and conducting water purified in the second filter, and a wall surrounding an inlet of wastewater in the tank. The settling body comprises a reservoir arranged in the center of the second filter. The second filter has a circular shape. The device comprises a first filter (2) and a second filter (4) for treating wastewater, each comprising a filtration medium and plants e.g. reeds planted in the filtration medium, a body (3) for settling materials suspended in wastewater, receiving water from the first filter, sending back the suspended material settled in the first filter and conducting water purified in the second filter, and a wall surrounding an inlet of wastewater in the tank. The settling body comprises a reservoir arranged in the center of the second filter. The second filter has a circular shape surrounding the reservoir. The wall has an opening in its bottom part contacting the tank. The inlet of wastewater in the tank is an opening for outlet of a pipe, where the opening is directed upwards. A pump is arranged for sucking the settled suspended material and driving them back into the first filter. The tank is surrounded by the wall guiding the water discharged by the overflow towards the bottom of the second filter. The filter medium mainly comprises a particulate material. The bottom of the second filter is waterproof and tilted downward starting from its center towards its periphery. The second filter has an outlet of treated water laid at the periphery of the filter medium. The outlet comprises a peripheral channel separated from the filtration medium of the second filter, where the water present in the second filter flows into the peripheral channel when it rises over the overflow wall. The outlet comprises a first pipe around the filtration medium of the second filter, has openings in its upper part to receive water obtained from the filter medium. A second pipe is placed in the first pipe contacting with a volume of air above the filtration medium.

Description

The invention relates to the treatment of wastewater, particularly wastewater treatment devices comprising a layer of particulate material in which plants are planted to degrade pollutants.

In order to reduce the concentration of organic matter in discharged water by non-collective or privately managed habitats, such as single-family dwellings, or by small and medium-sized communities managed by public bodies, it is known to place a sanitizing device by filtration and organic degradation. The devices described in the prior art for the treatment of wastewater consist essentially of two distinct filters operating in series, respectively constituting a first and a second treatment stage, the different layers of which have an increasing grain size from top to bottom (cf. Bibliographic study RMC water agency 1999, Document n ° 22 of the FNDAE). The filters are powered by tarpaulin. The first stage type filter makes it possible to combine a primary treatment with a start of secondary treatment. Primary treatment consists of physical filtration and aerobic stabilization (on the surface) of suspended solids. Secondary treatment consists of a degradation of the dissolved pollution inside the filter. The first stage type filter consists of layers of different successive granulometries increasing from the top (the surface of the filter) to the bottom (the bottom of the filter). It generally comprises an upper layer of gravel with a particle size of 1/10 mm and 0.40 m to 1 m thick. This layer sometimes includes an intermediate ventilation consisting of drains with slots facing down. Below the first layer described above are arranged a succession of one or more layers of increasing particle size (gravel layer of particle size of 10/20 mm or 15/25 mm for example and about 0.2 m thick ). This filter finally comprises, beneath the previous layers, a layer of gravel with a particle size of 20/40 to 30/60 mm. A drainage system communicates with the atmosphere through a system of chimneys rising to the surface of the filter.

The second stage type filter makes it possible to improve the rejection quality at the outlet of the first stage type filter. The second floor consists of layers of finer grain size. A first sand layer with a particle size of 0/6 mm or 1/6 mm, and 0.20 to 0.40 m thick, is always placed on the surface, in the open air, so as to have maximum oxygenation. filter mass and aerobic degradation of organic deposits not retained on the filter type first stage. It is on this layer of sand that most of the additional filtration takes place. Intermediate aeration (drains with slits facing downwards) is sometimes located between the sand layer and a lower layer of gravel with a larger grain size than sand. This layer of gravel, generally of 1/10 mm granulometry, has a thickness of 0.10 m to 0.40 m. Below this last layer are arranged a succession of one or more layers of increasing particle size (layer of gravel particle size 10/20 mm or 15/25 mm), and, below the previous layers, a layer of gravel granulometry 20/40 to 30/60 mm. A drainage system communicates with the atmosphere through chimneys rising to the surface of the filter. French patent applications FR2801805 and international WO 00/10927 describe examples of such filters used in the prior art.

Sometimes, for lack of oxygen, a part of the bacterial population in the filter of the first stage decays. The water discharged into the second stage filter may then comprise a bacterial film called zooglea, having an excessive viscosity and leading to the clogging of this second stage filter. The water discharged can then also present an excessive level of pollution. In addition, the discharge of water into the second stage filter requires complex dispersion devices. In addition, the second stage filter requires a large filtration area in order to remove a sufficient amount of suspended solids. The invention aims to solve one or more of these disadvantages. The invention thus relates to a sewage treatment device, said wastewater from a collective or non-collective wastewater network, preferably collective and preferably managed by a public body, comprising

a first wastewater treatment filter comprising a filtration medium and comprising plants planted in this filtration medium; a second wastewater treatment filter comprising a filtration medium and comprising plants planted in this filtration medium; - A settling member of the suspended matter in the wastewater, receiving water from the first filter, returning the decanted suspended matter in the first filter and conducting purified water in the second filter. According to a variant, the settling member comprises a reservoir disposed in the center of the second filter and the overflow of which flows into the second filter. According to another variant, the second filter has a circular shape surrounding said reservoir. According to another variant, the device comprises a wall surrounding a wastewater inlet in the tank, said wall having an opening in its lower part communicating with the tank. According to yet another variant, the entry of wastewater into the reservoir is an outlet of a pipe, this orifice being directed upwards. According to a variant, the device comprises a pumping device sucking up the suspended solids present in the tank and discharging them into the first filter. According to another variant, said tank is surrounded by a wall guiding the water discharged by the overflow to the bottom of the second filter. According to another variant, said plants are reeds. According to yet another variant, the filtration medium essentially comprises a particulate material. According to one variant, the bottom of the second filter is inclined downwards from its center towards its periphery. According to another variant, the bottom of the second filter is sealed.

According to another variant, the second filter has a treated water outlet disposed at the periphery of its filtration medium. According to yet another variant, the outlet comprises a peripheral channel separated from the filtration medium of the second filter by an overflow wall, the water present in the second filter flowing into the peripheral channel when it exceeds the wall too much. -full. According to a variant, the outlet comprises a first conduit surrounding the filtration medium of the second filter, advantageously having openings in its upper part for receiving water from said filtration medium, the device further comprising a second conduit putting the first conducts in communication with a volume of air above said filtration medium. The invention also relates to a wastewater treatment process comprising the steps of: - discharging wastewater comprising suspended matter into a first filter comprising a filtration medium in which plants are planted; - decant the suspended matter in the filtered water by the first filter

- Conducting purified water by decantation in a second filter 20 comprising a filtration medium in which plants are planted; - Return the suspended solids in the first filter.

Other features and advantages of the invention will emerge clearly from the description which is given below, by way of indication and in no way limitative, with reference to the accompanying drawings, in which: - Figure 1 is a sectional view of a collective sanitizing device according to a first embodiment of the invention; - Figure 2 is a top view of the sanitizer of Figure 1; FIG. 3 is a sectional view of a sanitizing device according to a second embodiment of the invention; FIG 4 is a sectional view of a sanitation device according to a third embodiment of the invention.

The invention proposes to dispose a settling member of suspended matter between first and second wastewater filters comprising a filtration medium in which plants are planted. The suspended solids are returned to the first filter, the purified water being conducted or discharged into the second filter.

Figure 1 shows a wastewater treatment device 1 according to a first embodiment of the invention. The device 1 comprises a first filter 2. The first filter 2 typically receives wastewater from a collective wastewater network via a pipe 21. The filter 2 comprises a filtration medium 23 in which plants 22 are planted.

After passing through the filter 2, the wastewater is drained by a pipe 24. The pipe 24 transports the drained wastewater to a settling member 3. The settling member 3 thus separates the wastewater into a sludge containing the materials in question. suspension (especially in the form of biomass) and in purified water. The settling member returns the suspended solids settled in the first filter 2 and conducts or discharges the purified water into a second filter 4. The purified water is discharged into the second filter 4. The filter 4 comprises a filtration medium 42 in which plants 41 are planted. Thus, during a possible bacterial step leading to a zooglea, the settling member 3 protects the second filter 4 against clogging. The sludge loaded with suspended matter being returned to the first filter 2, the water quality at the outlet of the second filter 4 is also greatly improved. To satisfy given discharge levels, the floor area required for the second filter 4 is thus reduced.

In the illustrated example, the settling member 3 comprises a tank 31 placed in the center of the second filter 4. When the water level 5 in the tank 31 exceeds an overflow threshold, these waters 5 (purified water) poured into the second filter 4. The overflow of the tank 31 flowing in the center of the second filter 4, the water distribution in the filter is optimized and allows to use a filter 4 of a reduced surface for a filtration level given. Moreover, this distribution is obtained without resorting to a complex structure. Advantageously, the filter 4 has a circular shape, as illustrated by the top view of FIG. 2. The settling member 3 comprises a wall 32 surrounding the inlet of the wastewater in the tank 31. This wall 32 has an opening in its lower part in communication with the tank 31. Thus, the incoming water can not directly pour through the overflow threshold in the filter 4 and are thus previously decanted. Advantageously, the entry of wastewater into the tank 31 is formed by an outlet 25 of the pipe 24. This orifice 25 is preferably oriented upwards in order to increase the settling time of the wastewater. This orifice 25 is preferably arranged in a median position with respect to the wall 32. The wall 32 will advantageously have a circular section. The water issuing from the orifice 25 is decanted. The decanted suspended solids follow the path represented by the dotted arrow towards the bottom of the tank 31. The purified water from the settling back to the overflow threshold as illustrated by the arrows in broken lines. A circuit 33 recovers the suspended solids at the bottom of the tank and returns them or delivers them to the first filter 2. The circuit 33 preferably comprises a non-illustrated pumping device enabling the suspended matter to be brought back into the first filter 2.

In the example, the peripheral wall of the reservoir 31 has an upper edge forming the overflow threshold disposed above the level of the filtration medium 42 of the filter 4. The reservoir 31 has a circular section. The bottom of the tank 31 is inclined downward from its peripheral portion to its central portion. Thus, the suspended solids are channeled towards this central part which is in communication with the circuit 33.

Access to the settling member being easy, it is possible to add chemicals such as iron sulfate in the tank 31 to treat phosphorus. The bottom of the filter 4 is advantageously sealed in order to drain the water during filtration to an outlet. The seal may for example be provided by a synthetic membrane or a filter bottom 4 made of concrete. The bottom of the second filter 4 is inclined downwards from the decanting member 3 towards the periphery of this filter 4. Thus, the water will flow by gravity towards the periphery of the filter 4, an area in which an outlet evacuation is advantageously arranged. In the example, the second filter 4 has a conduit 43 surrounding the filtration medium 42, totally or partially immersed. This duct 43 is provided with openings, for example located in its upper part or in a lateral part, to receive water from the filtration medium 42. This duct 43 communicates with an outlet pipe 47 discharging the cleaned water. The duct 43 may also be in communication with at least one other non-illustrated duct, placing the duct 43 in communication with a volume of air above the filtration medium 42. A glance may be provided at the level of the duct. exit 47 to inspect the flow of purified water.

The filter 2 is typically supplied with wastewater by successive sheeting. A sequential sheeting feed, known per se, advantageously allows to better impregnate the filtration medium 23, and thus optimize the efficiency of filtration and aerobic degradation of bacteria wastewater for a given volume of medium filtration. The flow of water between the first filter 2 and the second filter 4 is advantageously provided by gravity, in order to avoid the maintenance of a pumping device. Filters 2 and 4 can be configured to achieve vertical or horizontal wastewater flow as required. In this case, the filter 4 is a horizontal flow filter.

The plants 22 and 41 will for example be reeds. Plants 22 and 41 make it possible to improve the decomposition of certain pollutants in wastewater. Plants 22 and 41 make it possible to use a particulate material having a reduced particle size, insofar as they participate in themselves in reducing the risk of clogging of the filter medium with wastewater. The plants may for example be Phragmitis Australis, which maintain the hydraulic conductivity in the filtration medium. Filtration media 23 and 42 may comprise essentially a particulate material. The particulate material may comprise in a manner known per se sand or gravel, to a thickness of 0.3 to 1 m. For example, it is possible to use a gravel having a grain size of between 1 and 10 mm for the filtration media 23 or 42.

FIG. 3 represents a second embodiment of a sanitizing device 1 according to the invention. In this example, the exhaust outlet of the second filter 4 comprises a peripheral channel separated from the filtration medium 42 by an overflow wall 45. When the water present in the filtration medium 42 exceeds the upper edge of the wall 45, it flows into the channel 44. The upper edge of the wall 45 is disposed below the overflow threshold of the reservoir 31, so that the water will pass through the filtration medium 42 before reaching the channel 44. The overflow threshold of the wall 45 may also be fixed by V-shaped notches made in the wall 45. Such V-shaped notches may be distributed around the periphery of the wall 45, in order to distribute and channel the flow at desired locations over the entire periphery of the wall 45. The lower part of the slots of course defines the threshold of the overflow. FIG. 4 represents a third embodiment of a sanitizing device 1 according to the invention. In this example, the device 1 comprises a wall 46 surrounding the tank 31. This wall 46 reaches the level of the overflow threshold of the tank 31. The wall 46 guides the water discharged by the tank 31 to the bottom of the second filter 4. The wall 46 thus forces the spilled water to pass through the filtration medium 42 before reaching the peripheral outlet. In the example, the second filter 4 also has a wall 45 separating the filtration medium 42 from the pipe 44. Thus, the liquid must flow from bottom to top through the filtration medium 42 before reaching the outlet peripheral, which guarantees a long filtering course through the filtration medium 42.

Claims (15)

REVENDICATIONS1. Sanitizing device (1) for wastewater, characterized in that it comprises: a first filter (2) for treating wastewater, comprising a filtration medium (23) and comprising plants (22) planted in this filtration medium; a second filter (4) for treating wastewater, comprising a filtration medium (42) and comprising plants (41) planted in this filtration medium; - a settling member (3) of the suspended matter in the wastewater, receiving water from the first filter (2), returning the suspended solids settled in the first filter and conducting purified water in the second filter (4). 2. sanitation device according to claim 1, wherein the decanting member (3) comprises a reservoir (31) disposed in the center of the second filter (4) and whose overflow flows into the second filter. 3. Sanitizing device according to claim 2, wherein the second filter (4) has a circular shape surrounding said reservoir (31). 4. sanitation device according to claim 2 or 3, comprising a wall (32) surrounding an inlet (25) of wastewater in the tank, said wall having an opening in its lower part communicating with the reservoir. 5. Sanitizing device according to claim 4, wherein the entry of wastewater into the reservoir (31) is an orifice (25) for the exit of a pipe (24), this orifice being directed upwards. 6. Sanitizing device according to any one of claims 2 to 5, comprising a pumping device sucking the suspended solids and discharging in the first filter (2). 7. Sanitizing device according to any one of claims 2 to 6, wherein said reservoir (31) is surrounded by a wall (46) guiding the water discharged from the overflow to the bottom of the second filter. 8. Sanitizing device according to any one of the preceding claims, wherein said plants (22,41) are reeds. The sanitation device of any preceding claim, wherein the filtration medium (23,42) comprises substantially particulate material. 10. Sanitizing device according to any one of the preceding claims, wherein the bottom of the second filter (4) is inclined downwards from its center to its periphery. 20 11. Sanitizing device according to claim 10, wherein the bottom of the second filter (4) is sealed. 12. Sanitizing device according to any one of the preceding claims, wherein the second filter (4) has a treated water outlet disposed at the periphery of its filtration medium. The sanitation device according to claim 12, wherein the outlet comprises a peripheral channel (44) separated from the filtration medium of the second filter by an overflow wall (45), the water present in the second filter. flowing into the peripheral channel as it passes the overflow wall (45). 14. Sanitizing device according to claim 12, wherein the outlet comprises a first conduit (43) surrounding the filtration medium of the second filter, having openings in its upper part to receive water from said filter medium, the device further comprising a second conduit placing the first conduit in communication with a volume of air above said filtration medium. 15. A wastewater treatment process comprising the steps of: discharging wastewater comprising suspended matter into a first filter comprising a filtration medium in which plants are planted; - decant the suspended matter in the filtered water by the first filter; - Conducting purified water by decantation in a second filter comprising a filtration medium in which plants are planted; - return the suspended solids in the first filter.