FR2548167A1 - Process and device for the treatment of aqueous liquids, industrial and agri-foodstuff effluents, for the production of sterile or drinking water and their reuse or recycling - Google Patents

Abstract

An ultrafiltration of the liquid is carried out on mineral membranes 6d in which the pore diameters are sufficiently small to prevent the passage of microorganic particles and a treatment of the ultrafiltrate is performed in an electrolysis cell 15.

Description

Process and device for the treatment of aqueous liquids, industrial and food-processing effluents, for obtaining sterile or drinkable water and their reuse or recycling.

 The present invention relates to a process and a device for treating liquids and industrial and food-processing effluents, for obtaining sterile or drinkable water and their reuse or recycling.

 The water treatment devices intended for water purification are relatively varied. They are generally characterized by a significant investment in equipment or by the implementation of very complex processes adapted to the properties of the water source, in particular fresh water, which must be purified.

 It is recalled that, in general, apart from toxic industrial compounds, such as heavy metals, which are encountered in certain industrial effluents, the constituents of waste water, stagnant water, or of sources, in particular of fresh water. , contain suspended particles, microorganisms and dissolved ions. Depending on these different constituents, different techniques are currently used, namely lamellar decantation, flocculation and decantation with the aid of chemical agents, filtration in particular on sand, chlorination. The equipment used is bulky, not very mobile and frequently requires unclogging.

 One of the difficult problems to solve resides in the elimination of microorganisms, which must be rigorous, in particular when it is a question of obtaining drinking water or recycling effluents from agro-food or other industries.

 The present invention proposes to provide an effective and safe method and device for the treatment of water, stagnant water, used water, industrial or not, for obtaining drinking or sterile water.

 Another object of the invention is to provide such a device which is light, compact, energy efficient and which, therefore, is suitable for transport and mobility.

 Another objective of the invention is to provide a device which allows the treatment of very diverse waters or effluents, including industrial effluents, in particular from the food industry.

 Another object of the invention is to provide a device allowing pre-treatment before reverse osmosis or other desalination treatment for obtaining drinking water from brackish or saline water.

 Another object of the invention is to allow the purification of water from different sources, including polluted sources, to obtain drinking water without adding chemicals.

 The subject of the invention is a process for treating an aqueous liquid, characterized in that the ultrafiltration of the liquid is carried out on one or more mineral membranes whose pore diameters are sufficiently small to prevent passage. micro-organic particles and an electrolytic treatment of the ultrafiltrate is then carried out.

 Another objective of the invention is to provide water treatment which makes it possible to store the drinking water obtained without adding additional preservatives.

 The subject of the invention is a device for treating aqueous liquids having ultrafiltration means, characterized in that it comprises an ultrafiltration station equipped with mineral membranes whose pore diameters are small enough to prevent passage micro-organic particles and, downstream of said ultrafiltration station, an electrolytic treatment station for the ultra-filtered effluent.

 The ultrafiltration station includes one or more filter elements with mineral membranes, composed of a macro-porous support ensuring mechanical strength and one or more fine mineral layers allowing ultra-filtration.

 It should be understood that the size of the pores of the ultra-filtering membrane is greater than that allowing reverse osmosis but sufficiently small to retain at least all bacterial particles, leaven, organic materials of low molecular weight.

 The diameter of the pores of the mineral filtering layer is advantageously less than 1000 Angstroms.

 The thickness of the layer is between 1 and 15 microns.

 The device comprises means for allowing the circulation of the liquid to be purified so as to obtain a component of tangential velocity suitably high relative to the wall of the ultra-filtering membrane, which can advantageously be obtained by recycling the retentate to which one integrates, continuously, the volume corresponding to the filtrate discharged.

 Also advantageously, the device can include unclogging means, making it possible to pass purified liquid, which can be ultrafiltrate, in the opposite direction, through the ultra-filtering mineral membrane and this under the effect of overpressure.

 It is found and checked that it is possible, thanks to the invention, to obtain, in a single pass, potable water from various highly polluted aqueous liquids.

 An electrolytic treatment station can advantageously be produced using a stack of electrodes of opposite or bi-polar polarities having percolation properties produced for example from percolating conductive materials.

 It may be advantageous, in the case of liquids loaded with very large particles, to have, upstream of the device itself, a pre-treatment station for example by filtration or decantation. In most cases, this station is not essential and it is "possible to treat liquids to obtain drinking water directly using the device which can, due to its small size and low consumption energy, be designed as an easy-to-transport unit capable of immediately treating the water on site.

Other advantages and characteristics of the invention will appear on reading the following description, given by way of nonlimiting example and referring to the attached drawing in which
FIG. 1 schematically represents a device according to the invention.

 FIG. 2 schematically represents a view of the electrolysis station of the device.

 The device shown is connected to a source of fresh water 1, for example river fresh water, standing water, washing water or an effluent from an agrifood or other industry. This liquid is taken up by a pipe 2 by means of a pump 3. The discharge pipe 4 of the pump opens into the inlet pipe 5 of the ultrafiltration station 6. This comprises, in a hermetically closed enclosure 6a, an inlet chamber 6b and an outlet chamber 6c, between which are arranged the elements with ultra-filtering mineral membranes, parallel to each other, 6d.

 The mineral membrane proper is placed on a macro-porous support, ceramic or derivatives, of the composite type, in which the ultra-filtrate moves and is easily evacuated. The inside diameter of the support tube is between 2 and 15 millimeters, the thickness of the membrane is between 1 and 15 microns. The pore diameter is less than 1000 Angström.

 The outlet chamber 6c, connected to the inlet of the chamber 6b by the various tubular channels, is connected by an outlet pipe 7 to a recirculation pipe 8 which, via a pump 9, also opens into the inlet pipe 5.

Furthermore, this outlet pipe 7 is connected via a valve 10 to a discharge pipe 11 leading to a discharge pipe 12 to which the pipe 5 is also connected via a valve 13 The ultra-filtrate, which has passed through the filtration device and which circulates in the porous block, leaves the enclosure 6a by a conduit 14 leading to an electrolytic treatment station 15 supplied by an electrical source 16, for example a autonomous generator. The outlet 17 of the electrolytic treatment station 15 reaches a vertical tank 18 in the lower part of which opens the pipe 19 for evacuating drinking water, provided with a valve 20. In the upper part of the tank 18, there opens a compressed air supply line 21, normally closed by a valve 22.

The operation is as follows
First of all, the valves 10 and 20 are open and the valves 13 and 22 closed. Pump 3 is started. The pumped liquid fills then passes through the station 6 and, when it reaches the level of the valve 10, the latter closes, so that only the valve 20 remains open.

At this time, the pump 9 is also started.

 Consequently, the liquid continuously traverses the channels which extend between the chambers 6b and 6c, the membranes of which are thus traversed at high speed by a tangential flow, preferably in turbulent flow. Part of this flow is ultra-filtered and collected in line 14. Most of the flow circulating through the channels exits through line 7. It is recycled through line 8 and the pump 9 to be passed again to the through the ultrafiltration station 6. The pump 3 is therefore adjusted so as to supply to the device 6 a flow rate equal to the flow rate of the ultrafiltrate discharged through the pipe 14.

 The ultra-filtrate then passes through the electrolytic treatment station 15, the electrodes of which are subjected to a potential difference such that the intensity of the current is of the order of 500 mA.

 In this device is located a stack of bi-polar electrodes 23 separated by insulating plies. The electrodes are constituted by graphite felt discs having a thickness of 9 mm and a porosity sufficient to be percolated by water without clogging. The electrodes 23 can be isolated at their periphery in contact with the wall of the casing 15. The electrodes 23 are separated from each other by discs 24 made up of very fine nylon screens, which form a very good electronic insulator but which lets the ions through well. The thickness of the sieve is 0.08 mm.

 In the two extreme electrodes 23, two carbon electrodes 25 were inserted, one forming a positive electrode and the other a negative electrode, these electrodes being isolated with respect to the casing 15. The two electrodes 25, produced in stick to charton, are connected to a low voltage generator a6 capable of establishing and maintaining a current of a given intensity. The aqueous liquid is brought in the direction of the arrow by the nozzle 15a inside the envelope 15 and it emerges through the nozzle 15b after percolating through the various layers contained in the envelope.

 The mesh of the filters forming the sheets is preferably 15 microns.

 Preferably in the method according to the invention, the generator is adjusted so as to ensure the passage of a current intensity fixed at a desired value, for example 500 mA for a device having 8 cm in diameter and two bi-polar electrodes only. The resulting voltage was 5 volts.

 The flow of liquid through the device is ensured so as to obtain a sufficient speed for the electric field variations (positive on one side of each electrode and negative on the other side) to be fairly rapid.

 In the case of a device 8 cm in diameter, the flow rate can advantageously be of the order of 4 1 / hour.

For example, a device 8 cm in diameter with two percolating bi-polar electrodes 9 mm thick, an imposed current of 500 mA at a resulting voltage of 5 volts, with a flow rate of 4 1 / hour a allowed, from waste water with an extremely high number of bacteria, to obtain an almost totally disinfected water containing less than 3 bacteria per 1.

The ultra-filtrate used leaving the electrolytic treatment station via line 17 is
strictly potable water. This drinking water accumulates
first in tank 18 then out through the pipeline
19. At the end of the cycle, a decolma operation is carried out
floor. For this, the valve 20 closes, the pump 3 stops,
valve 10 opens, pump 9 stops, and the valves
13 and 22 open. The compressed air then delivers the electrolyzed ultrafiltrate located in the reservoir 18, against the current to the enclosure 6a. The ultra-filtrate then crosses the porous mineral membranes which are unclogged and the liquid is then evacuated through the pipe 12. At the end of this operation, which lasts a few minutes, the device is restarted as before.

 It is also possible, in this device, to unclog without using compressed air, by closing the valve 20 ,. opening the valve 10, stopping the pump 9, then opening the valve 13.

 The unclogging control can be carried out either from a timer, or by means of a pressure gauge 23 located on the pipe 8, this pressure gauge being sensitive to a slight increase in pressure which occurs when the membrane begins to patch up.

 It is remarkable to be able to obtain, thanks to such an extremely simple device, compact and easily transportable, drinking water from sources of extremely polluted fresh water.

 In addition, there is a obtaining of a residual effect on drinking water, allowing its storage for a long period without any chemical treatment. The bactericidal effect of the electrolytic treatment is superimposed on the ultrafiltration effect of the mineral membranes.

Claims (9)

 1. Process for the treatment and purification of aqueous liquids, agrifood or industrial effluents, in particular for obtaining sterile or drinkable water and their reuse or recycling, characterized in that the ultra-filtration of the liquid is carried out on one or more mineral membranes whose pore diameters are small enough to prevent the passage of micro-organic particles and that an electrolytic treatment of the ultra-filtrate is then carried out.  2. Device for the treatment and purification of aqueous liquids, agrifood or industrial effluents, in particular for obtaining sterile or drinkable water and their use or recycling from an ultra-filtration device, characterized by a station ultrafiltration with a mineral membrane whose pore diameters are small enough to prevent the passage of micro-organic particles and, downstream of said station, an electrolytic treatment station for ultra-filtered water.  3. Device according to claim 2, characterized in that the diameter of the pores of the ultrafiltration membranes is less than 1000 Angstroms.  4. Device according to any one of claims 2 and 3, characterized in that the thickness of the mineral ultra-filtering layer is between 1 and 15 microns.  5. Device according to any one of claims 2 to 4, characterized in that it comprises means (8, 9) for allowing the circulation of the liquid in the filters with a component of high tangential speed relative to the wall of the ultra-filtering membrane.  6. Device according to any one of claims 2 to 5, characterized in that it comprises unclogging means (21, 22, 17) making it possible to pass the purified liquid in the opposite direction through the ultra-filtering membrane under the effect of an overpressure.  7. Device according to any one of claims 2 to 6, characterized in that the electrolytic treatment station comprises a plurality of electrodes of opposite polarities and bipolar electrodes having percolation properties and made of percolating conductive materials.  8. Device according to claim 7, characterized in that the percolating electrodes are separated by thin sheets of electrically insulating material.  9. Device according to any one of claims 2 to 8, characterized in that said flow establishment means comprise means for the recirculation of the part of the non-ultra-filtered flow.