FR2929607A1 - Device for sanitizing wastewater, comprises inlet for overflowing wastewater, outlet for evacuation of wastewater, filter equipped with medium extending between inlet and outlet, and twining plants, nitrophilous plants or procumbent plants - Google Patents

Abstract

The device comprises an inlet for overflowing wastewater, an outlet for evacuation of wastewater, a filter equipped with a filtration medium (23) extending between the inlet and the outlet, twining plants (22), nitrophilous plants or procumbent plants with roots or rhizomes planted in the medium, and a trench having a sealed bottom. The filtration medium has an upper surface inclined towards bottom from the inlet to the outlet, and a thickness of 200 mm to 1 m. The sealed bottom of the trench is inclined towards the bottom direction from the inlet to the bottom, and comprises a geomembrane. The device comprises an inlet for overflowing wastewater, an outlet for evacuation of wastewater, a filter equipped with a filtration medium (23) extending between the inlet and the outlet, twining plants (22), nitrophilous plants or procumbent plants with roots or rhizomes planted in the medium, and a trench having a sealed bottom. The filtration medium has an upper surface inclined towards bottom from the inlet to the outlet, and a thickness of 200 mm to 1 m. The sealed bottom of the trench is inclined towards the bottom direction from the inlet to the bottom, and comprises a geomembrane on which the medium is present. The trench has a length that is ten times of its width. An INDEPENDENT CLAIM is included for a process for fabrication of a device for sanitizing wastewater.

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, part of the bacterial population in the first-stage filter 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. Maintenance operations must then be carried out. The spilled water may also present an excessive level of pollution, incompatible with new discharge standards. In addition, the discharge of water into the second stage filter requires complex dispersion devices. 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: - an inlet wastewater discharge; - a drain outlet of filtered water; a filtration medium extending between the inlet and the outlet and having an upper surface inclined downward from the inlet to the outlet; - voluble plants or plants with roots or rhizomes tracing, planted in the filtration medium. According to a variant, the device comprises a trench having a sealed bottom on which said filtration medium rests. According to another variant, the watertight trench has a bottom inclined downwards from the inlet to the outlet. According to another variant, the length of the trench is at least ten times greater than its width. According to yet another variant, said plants are creeping. According to yet another variant, said plants are nitrophilous. According to another variant, the sealed bottom comprises a geomembrane on which said filtration medium rests. According to another variant, said filtration medium is a particulate material. According to yet another variant, the thickness of said filtration medium is between about 200 mm and about 1 m. According to a variant, the device comprises a filter provided with a filtration medium in which plants are planted, the drained water of said filter being discharged at the sewage discharge inlet. The invention also relates to a method of manufacturing a sewage treatment device, comprising a step of planting voluble plants or root plants or rhizomes tracing in a filtration medium whose upper surface is inclined towards the bottom from a water discharge inlet to a water discharge outlet.

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 limiting, with reference to the accompanying drawings, in which: - Figure 1 is a longitudinal sectional view of an example of a filtration device 5 according to the invention; - Figure 2 is a cross sectional view of the filter device of Figure 1 at its filter ditch.

The invention provides a sanitizing device comprising a filtration medium 10 extending between a wastewater inlet and a filtered water outlet. The upper surface of this filter medium is tilted downward from the inlet to the outlet and twining plants or root plants or rhizomes tracing are planted in this filtration medium. Thus, when a zooglated bacterial film is spilled onto this filtration medium, the film is retained at the upper surface of the filtration medium by the voluble plants or by naturally extending rooting plants or rhizomes. on all this surface. The sludge then formed on the surface can easily be removed by tearing off the said plants: the roots of these plants will retain the sludge and the network formed by these plants will allow them to be pulled off by a simple pull during a maintenance operation. In addition, these surface sludges will not interfere with filtration in the filtration medium.

Figure 1 shows a wastewater treatment device 1 according to an exemplary implementation of the invention. The device 1 comprises in a manner known in itself 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 filter medium. filtration 23 in which plants 22 are planted, for example reeds. After having passed through the first filter 2, the wastewater is drained by a pipe 24. The outlet orifice of the pipe 24 forms an inlet for discharging wastewater into a filtration ditch 3. The filtration ditch 3 presents a filtration medium 33 extending between the wastewater discharge inlet 24 and a filtered water discharge outlet 35. The wastewater is advantageously poured continuously into the filtration medium 33 through the inlet 24 The upper surface of this filtration medium 33 is inclined starting from the inlet 24 to the outlet 35. Spiny plants or plants with roots or rhizomes tracing 31 are planted in this filtration medium 33. Their roots 32 thus extend to the upper surface of the filtration medium 33. The voluble plants or plants with roots or rhizomes tracing 31 are advantageously planted on the whole of the upper surface of the filter medium 33. The inclination of the upper face of the filtration medium 33 makes it possible to promote a runoff of the water at the upper surface of the filtration medium 33. The invention thus makes it possible to fix the zooglea discharged at the inlet 24 below. form of mud at the roots of voluble plants or rooting plants or rhizomes tracing. In addition, the voluble plants or plants with roots or rhizomes tracing 31 will naturally form a network of roots 32 interconnected. The presence of the aqueous medium in the ditch 3 will promote a rapid growth of these plants. Thus, a pulling step will allow the roots 32 to be pulled continuously by a simple traction while simultaneously carrying the sludge fixed at the level of the upper surface of the filtration medium 33. The manufacture and maintenance of such a ditch 3 are so particularly simple. The voluble plants as well as the plants with roots or rhizomes tracing 31 are advantageously adapted to wet areas. The plants 31 may advantageously be creeping. They can also advantageously be nitrophilous, in order to promote the degradation of nitrated compounds in the discharged water. The plants that can be used in the context of the invention are plants whose root system has a large surface area.

Voluble plants 31 may for example be plants of the Solenaceae family, such as nightshades, especially bittersweet nightshade or black nightshade.

Plants with roots or rhizomes tracing 31 may for example be grasses or reeds. Examples of grasses include grasses of the family Poaceae. In the family Poaceae, species such as Paturin (eg Poa Pratensis) or the ring (eg Oyat) can be used in the context of the present invention. The filtration medium 33 is advantageously made of a particulate material. The filtration medium 33 may consist of gravel having a particle size of between about 1 and about 10 mm. The filtration medium 33 may be formed of 2/6 mm granulates. The filtration medium 33 may have a thickness of about 300 mm. Advantageously, this thickness is between about 100 mm and about 1 m, preferably between about 200 mm and about 500, 600, 700, 800 or 900 mm, which promotes the runoff of wastewater at the roots of plants 31 and allows to fix the zooglée.

The filtration gap 3 forms a downstream filtration stage for the filter 2. The level of pollutant discharge in the drained water in the outlet 35 is thus substantially lowered. Those skilled in the art will be able to determine the length of the ditch 3 necessary to clean up a given wastewater flow rate in accordance with the rejection standards in force. Advantageously, the length of the ditch 3 will be at least ten times greater than its width. The filter ditch may for example have a length of 30 m. The filtration ditch 3 of the example is made in the form of a trench in the ground 38. This trench has a sealed bottom 37 on which the said filter medium 33 rests. The sealed bottom 37 can be made in the form of a geomembrane (polyethylene, polypropylene, elastomeric bitumen, etc.) deposited on an earth floor. The sealed bottom 37 may also be made of cement or any suitable materials. The bottom of the trench is also inclined downward from the inlet 24 towards the outlet 35. This inclination promotes the horizontal flow of water through the filtration medium 33. The inclination is advantageously between about 0.2 and about 5%, preferably between about 0.3 and about 3%, even more preferably between about 0.3% or about 0.5% and about 2%, in order to maintain the filtration medium 33 moist and to guarantee the thrust of voluble plants or plants with roots or rhizomes tracing 31. The trench performed has a trapezoidal cross section, as shown in Figure 2. The water is thus naturally driven to the bottom 37 and separated from the zooglée and suspended solids forming sludge. The large base of the trapezium (corresponding to the upper part of the trench) can measure between about 1 m and about 2m, its small base (corresponding to the lower part of the trench) can measure about 300 mm and about 1 m, for example 400 or 500 mm. The outlet 35, as a means of evacuation of the filtered water, can be made in the form of a manhole provided with a top surveillance cover 36. Thus, the quality of the water can be easily monitored by lifting cover 36. The view may be formed of standard concrete sections.

The entrance of the filtered water in the view 35 can be achieved by means of a grid 34 arranged in one of its lateral faces. The end of the filtration medium 33 is advantageously placed in contact with this gate 34 in order to drain the filtered water.

Claims (11)

REVENDICATIONS1. Sanitation device (1) wastewater, characterized in that it comprises: -a spill inlet (24) wastewater; an evacuation outlet (35) for filtered water; - a filtration medium (33) extending between the inlet (24) and the outlet (35) and having an upper surface inclined downwardly from the inlet to the outlet; - twining plants or plants with roots or rhizomes tracing (31), planted in the filtration medium (33). 2. Sanitizing device according to claim 1, comprising a trench having a sealed bottom (37) on which said filtration medium (33) rests. The sanitation device of claim 2, wherein the sealed trench has a downward inclined bottom (37) from the inlet to the outlet. 4. Sanitizing device according to claim 2 or 3, wherein the length of the trench is at least ten times greater than its width. Sanitizing device according to any one of the preceding claims, wherein said plants (31) are creeping. 6. Sanitizing device according to any one of the preceding claims, wherein said plants (31) are nitrophilous. 30 7. Sanitizing device according to any one of the preceding claims, wherein the sealed bottom comprises a geomembrane (37) on which said filtration medium. 20 8. Sanitizing device according to any one of the preceding claims, wherein said filter medium (33) is a particulate material. 9. Sanitizing device according to any one of the preceding claims, wherein the thickness of said filter medium is between about 200 mm and about 1 m. 10 10. Sanitizing device according to any one of the preceding claims, comprising a filter (2) provided with a filtration medium (23) in which plants (22) are planted, the water drained from said filter (2). being discharged at the spill inlet (24) of the wastewater. 15 11. A method of manufacturing a sewage treatment device, comprising a step of planting voluble plants or roots plants or rhizomes tracer in a filtration medium whose upper surface is inclined downwards from a water discharge inlet to a water discharge outlet. 20