FR3025510A1 - PROCESS FOR TREATING INDUSTRIAL WASTE WATER BY COUPLING A BIOLOGICAL REACTOR BY CULTURE FIXED ON MOBILE MEDIA AND A MACROPHYTE FILTER - Google Patents

Abstract

Wastewater treatment plant (1, 21) comprising: - a buffer tank (2) containing a system for aeration and agitation; a biological reactor (8) containing mobile supports with fixed cultures capable of developing a biofilm on their surface positioned downstream of said buffer pool; and a filter planted with macrophytes (13, 14, 24, 25, 26 and 27) positioned downstream of said biological reactor (8).

Description

FIELD OF THE INVENTION The present invention belongs to the field of wastewater treatment that is evacuated, in particular to the treatment of industrial wastewater by the coupling of a biological reactor by a culture fixed on mobile supports and of a macrophyte filter. , industrial infrastructures.

Treatment plants attached to industrial complexes are often saturated and fail to treat wastewater in accordance with the requirements of developed country regulations. In order to have facilities that comply with industrial effluent treatment standards, it is customary to use channels incorporating "activated sludge", using an aeration tank that operates with a downstream clarifier, from which the activated sludge is reinjected into the aeration basin. Such a method of treatment is described in application WO2011033476.

This method of treatment using activated sludge is expensive to set up and the operation of the activated sludge die requires the presence of a clarifier with upstream sludge recirculation, and, as a result, it is complex as well. to implement, to maintain in operation. The present application aims to remedy the disadvantages of the prior art. The present invention relates to a wastewater treatment plant comprising: - a buffer tank containing a system for aeration and agitation; a biological reactor containing mobile supports with fixed cultures 3025510 2 capable of developing a biofilm on their surface, positioned downstream of the buffer tank; and a filter planted with macrophytes, positioned downstream of the biological reactor.

The wastewater treatment plant according to the invention is inexpensive to set up, install and is easy maintenance, while maintaining, or even improving, the performance obtained in the context of activated sludge. The production of sludge is lower in volume compared to the purification plants which operate with activated sludge. In addition, the sludge produced is more mineralized and more stable, which makes it possible to value it, particularly in the horticulture sector. Unlike activated sludge, it is not essential to carry out a continuous evacuation of the sludge, which makes the installation more efficient in terms of sludge management to be evacuated. For industrial effluents charged with large size solid waste, a screening and / or sieving device is advantageously provided upstream: it protects the rest of the device with respect to the risks of clogging and wear of the equipment. The system intended to aerate and stir the effluent in the buffer tank is advantageously a stirring aerator comprising a helical screw. The power of such a helical screw stirrer aerator is for example at least 5.5 kW for a buffer pool of the order of 80 m3. When the water that is discharged at the outlet of the plant has a high temperature, as in the case of a chocolate factory, the buffer tank advantageously comprises a cooling system sufficient for the water leaving the said basin to be cooled to a lower temperature. at 30 ° C. The cooling system is advantageously a buffer watering system on the surface, and comprises a pump for collecting water in the bottom of the buffer tank. Said pump has for example a flow rate of at least 40 m3 / h.

The wastewater treatment plant advantageously comprises a degreasing device capable of causing the flotation of grease, positioned directly downstream of the buffer tank. The degreasing device is advantageously a degreaser provided with a bubbling device for accelerating the flotation of greases. The degreasing device is advantageously coupled to a physicochemical treatment device allowing the formation of flocs by coagulation-flocculation and then their separation by direct or indirect injection of pressurized water. The degreaser advantageously comprises a surface scraping device which allows the evacuation of the floated greases to a specific pit. The bottom of the degreaser advantageously comprises a drain valve to allow the evacuation of settled materials to a specific pit. The water thus degreased is directed downstream. A device 20 for neutralizing the effluent is advantageously provided at the outlet of the degreasing device. Alternatively or in combination with the above, a nutrient injection device is advantageously provided at the outlet of the degreasing device.

The biological reactor used in the context of the invention is advantageously an aerated biological reactor, that is to say that at least one air injection means is integrated in the reactor. The air injection means advantageously comprises a booster. The injected air is advantageously enriched with oxygen. Such an aerated reactor promotes the oxidation of organic matter; Nitrogen treatment, and therefore nitrification, are not specifically targeted in this context.

The aerated biological reactor contains movable supports homogeneously suspended in suspension, said movable supports are preferably plastic objects kept in homogeneous suspension in the reactor. Said mobile supports are capable of developing a biofilm on their surface (fixed cultures). This reactor advantageously allows a removal of at least 80% of the load in BOD5 (biological oxygen demand in five days). Such a reactor is for example a cylindrical reactor of 50 m.sup.3 of useful volume, which is advantageously filled with at least 25%, more advantageously at least 30%, or even at least 40% by volume of material offering a surface area. specific less than 1200 m2 / m3. Said specific surface is advantageously between 100 and 600 m 2 / m 3, or even between 140 and 370 m 2 / m 3.

The water treatment plant according to the invention comprises a sludge separation and process finishing system comprising a filter planted with macrophytes. The filter planted with macrophytes is, for example, a filter planted with reeds (especially Phragmites australis (Cav.) Trin. Ex Steud.), Cattails, rushes, irises and / or elephant grasses (in Particularly Pennisetum purpureum Schumach.). Advantageously, the treatment plant in the context of the invention does not resort to the use of hydroponics, that is to say, agriculture above ground (sometimes qualified in English by the term " hydroponic reactor "), and is therefore less restrictive than this one in terms of the cost and maintenance of the 25 installations, since in cultivation above ground it is essential to maintain a close monitoring of the various parameters which condition the state of plant health. The macrophyte filter system advantageously comprises two macrophyte filters arranged in parallel. The macrophyte filters are operated alternately, preferably weekly. Such alternation allows a rest period for filters planted for several weeks, for example three weeks.

Each filter planted with macrophytes advantageously comprises the following strata: A concrete or earthen basin covered with a geomembrane (such as that defined by the AFNOR standard NFP 84-500); - a filtering floor or a drains device for aeration of the filter and the collection of treated effluents; at least two layers of gravel of different diameters; - a layer of sand or compost; and 10 - the aerial part of the plants. A geogrid (better known by the term "geogrid") may alternatively be provided, or in combination, with the gravel layers. Such a geogrid is advantageously composed of a perforated material made of polyamide or polypropylene, and at least 2 cm thick. The effluents treated at the outlet of the macrophyte filter can be discharged into the natural environment.

The installation advantageously comprises an infiltration network, for example composed of an infiltration well or a point of discharge towards a watercourse. The present invention also relates, in another aspect, to a process for treating industrial wastewater by coupling at least one biological reactor by mobile support culture with at least one macrophyte filter. The process according to the invention is advantageously carried out, but not exclusively, by means of an installation as described in the description of the invention which precedes.

The present invention will be better understood on reading the following detailed description of which the embodiments and the figures are only given by way of illustration and can in no way be regarded as limiting. The figures which illustrate the embodiments are as follows: FIGS. 1 and 2 schematically represent two embodiments of installations according to the invention comprising two and four filters planted with reeds in parallel.

FIG. 1 shows an embodiment of an installation 1 according to the invention, comprising a buffer tank 2 upstream collecting the water leaving the plant after passing through a lifting station 3, which allows the smoothing of the polluting loads. and flow rates. The basin 2 of cylindrical shape and minimum useful height of 4.5 m (5 m in all), has a useful volume of 80 m3, this volume includes a "dead" volume of 20 m3, the basin has a surface area of soil will be approximately 18 m2 (inner diameter of 4.75 m). The contents of basin 2 are aerated and stirred. Aeration and mixing allow better homogeneity of the effluents and limit the emission of odors by maintaining a sufficient level of ventilation. This aeration and stirring are provided by a floating brewer 4 (helical screw type) having a power of at least 5.5 kW. A cooling system 5 (by "sprincklage"), fed by a bottom pump 6, allows sufficient cooling (temperature below 30 ° C) of effluents from the industrial site 9D nt hot. The pump 6 submerged sprincklage has a flow rate of at least 40 m3 / h. The cooled and buffered effluents then feed, at a constant rate, a degreaser 7 with the aid of a pumping device equipped with an electromagnetic flowmeter for the regulation of the pumps. In parallel, an overflow of the buffer tank 2 directly feeds the degreaser 7.

The degreaser 7 comprises an air injection device in the form of microbubbles for accelerating the flotation of grease and a float grease recovery device (surface scraping). The degreaser is cylindro-conical in shape, its grease flotation surface has a diameter of at least 1 m. The scraping device allows the evacuation of the floated fats to a specific pit. The bottom of the degreaser 7 comprises a drain valve for discharging the settled material to a specific pit. The defatted water will be gravity directed to a biological reactor 8. The transfer line is equipped with a pH measurement and a control system (injection of soda) to neutralize the effluent to be treated (effluent having a acid character, conversely acid treatment can be done for basic effluents). In addition, this pipe is equipped with a nutrient injection device (nitrogen and phosphorus) 15 to rebalance the effluent. The water leaving the degreaser 7 is injected into the biological reactor 8 with culture fixed on mobile supports which are homogeneously suspended and which are capable of developing a biofilm on their surface (fixed cultures). This reactor makes it possible to fix the purifying biomass on mobile supports and to cause a removal of at least 80% of the charge in BOD5. This cylindrical reactor 8 of 50 m3 useful, has a useful height of at least 3.4 m, and is filled to 40% of material with a specific surface of 220 m 2 / m3. The floor area of reactor 8 is 15 m 2 (internal diameter 4.4 m).

This reactor 8 is equipped with an aeration device consisting of two boosters 9 and 10 and a submerged network of air diffusion. Each booster will be able to provide 180 kg 02 / day (with 4 m of water column). The boosters operate alternately. The reactor 8 supplies a lifting station 12 with gravity, which itself feeds two macrophyte filters 13 and 14 per 5 m3 sheet.

The macrophyte filters 13 and 14 operate alternately weekly (a three-filter option is possible). Each bed has a surface of 205 m2. Each bed is installed on a filtering floor allowing a natural ventilation of the massif and the evacuation of the filtered water. These beds allow a first filtration on the first centimeters, the residual pollution of carbon, nitrogen and phosphorus is oxidized and retained by the bacteria present in the massif about 1 m thick. The water from each bed having drilled through the filter bed and the floor are sent to a final counting channel equipped with a venturi threshold and a height measurement (ultrasonic measurement). After counting, these treated waters join an infiltration network 15. FIG. 2 shows another embodiment of an installation 21 according to the invention, comprising a buffer tank 2 upstream collecting water 15 at the end of the plant after passage in a lifting station 3, which allows the smoothing of polluting loads and flows. The basin 2 of cylindrical shape and minimum useful height of 4.5 m (5 m in all) has a useful volume of 80 m3, this volume includes a "dead" volume of 20 m3, the basin has a floor area will be approximately 18 m2 (inside diameter 4.75 m). The contents of basin 2 are aerated and stirred. Aeration and mixing allow a better homogeneity of the effluents and limit their degradation by maintaining a sufficient level of ventilation. This aeration and stirring are provided by a floating brewer 4 (helical screw type) having a power of at least 5.5 kW. A cooling system 5 (by "sprincklage"), fed by a bottom pump 6, allows sufficient cooling of the effluents from the industrial site which are hot (temperature below 30 ° C). The pump 6 submerged sprincklage has a flow rate of at least 40 m3 / h. The cooled and buffered effluents then supply, at a constant rate, a pressurized water float 22 with the aid of a pumping device equipped with an electromagnetic flowmeter for regulating the pumps. In parallel, an overflow of the buffer tank 2 feeds the float 22 directly. The float 22 operates in indirect pressurization. Pressurization is provided by a dissolution tube equipped with its own compressor.

Float 22 is cylindrical and has a flotation area of 1.2 m2. A scraping system allows the evacuation of fat to a specific storage. A purge device is used to evacuate decantable materials to a lifting station placed upstream of macrophyte filters. The defatted water is gravitarily directed to a biological reactor 8. The transfer line is equipped with a pH measurement and a control system (injection of soda) to neutralize the effluents to be treated (effluent having an acidic character ). In addition, this pipe is equipped with a nutrient injection device (nitrogen and phosphorus) to rebalance the effluent.

The water at the outlet of the float 22 is injected into the biological reactor 8 with culture fixed on mobile supports which are homogeneously suspended. and which are likely to develop a biofilm on their surface (fixed cultures). This reactor makes it possible to fix the purifying biomass on mobile supports, and to cause a removal of at least 80% of the charge in BOD5. This cylindrical reactor 8 of 50 m3 useful, has a useful height of at least 3.4 m, and is filled to 40% of material with a specific surface of 220 m 2 / m3. The floor area of reactor 8 is 15 m 2 (internal diameter 4.4 m). This reactor 8 is equipped with an aeration device consisting of two boosters 9 and 10 and a submerged network of air diffusion. Each booster will be able to provide 180 kg 02 / day (with 4 m of water column). The boosters operate alternately. The reactor 8 feeds overflow a lifting station 23 which itself feeds a system of macrophyte filters. This overflow is equipped with a protective grid 30 for retaining the support material.

The macrophyte filter system is composed of four macrophyte filters 24, 25, 26 and 27 operate alternately weekly (a three-filter option is possible). Each bed has a surface of 70 m2. Each bed is installed on a filtering floor 5 allowing natural ventilation of the massif and the evacuation of filtered water. These beds allow a first filtration on the first centimeters, the residual pollution of carbon, nitrogen and phosphorus is oxidized and retained by the bacteria present in the massif about 1 m thick. The water from each bed that has percolated through the filter bed and the floor is sent to a final counting channel equipped with a Venturi Threshold and a height measurement (ultrasonic measurement). After counting, these treated waters join an infiltration network 15.

Claims (8)

REVENDICATIONS1. Wastewater treatment plant (1, 21) comprising: - a buffer tank (2) containing a system for aeration and agitation; a biological reactor (8) containing mobile supports with fixed cultures capable of developing a biofilm on their surface positioned downstream of said buffer pool; and a filter planted with macrophytes (13, 14, 24, 25, 26 and 27) positioned downstream of said biological reactor (8). 2. Installation according to claim 1, wherein the system for aerating and stirring said buffer pool is a spiral screw stirrer aerator (4). 3. Installation according to one of claims 1 or 2, wherein the buffer pool (2) comprises a cooling system. 4. Installation according to one of claims 1 to 3, wherein a degreasing device capable of causing the flotation of grease is positioned directly downstream of said buffer pool. 5. Installation according to one of claims 1 to 4, wherein the biological reactor (8) comprises an air injection means. 6. Installation according to one of claims 1 to 5, wherein the movable supports fixed cultures capable of developing a biofilm on their surface occupy at least 25% of the volume of said reactor (8) and have a specific surface area of less than 1200 m2 / m3. 3025510 12 7. Installation according to one of claims 1 to 6, wherein said installation comprises two filters planted macrophytes (13, 14, 24, 25, 26 and 27) arranged in parallel. 5 8. Installation according to one of claims 1 to 7, wherein the filter planted macrophytes (13, 14, 24, 25, 26 and 27) comprises the following layers: - A concrete basin or earth covered with geomembrane; - A filtering floor or a drain device for aeration of the filter and the collection of treated effluent; at least two layers of gravel of different diameters; - a layer of sand or compost; and - the aerial part of the plants. Installation according to one of claims 1 to 8, comprising an infiltration network (15) or spillway to a watercourse. Process for the treatment of industrial wastewater by coupling at least one biological reactor by a culture fixed on mobile supports with at least one macrophyte filter. 10 159. 10. 20