CA2470270A1 - Method and facility for processing contaminated liquids - Google Patents

Abstract

A method of purifying contaminated liquids that combines chemical flocculation treatment and electrochemical treatment to achieve a synergistic effect on the consumption of chemicals and energy because the integration of the two treatment stages consume in total fewer chemicals and more energy than if they were done individually, to give the same purification performance. Installation for implementing the new method for purifying contaminated liquids based on the synergistic effect resulting from the integration of the chemical flocculation treatment and the electrochemical treatment, optionally comprising a treatment tank and a filtration or ultrafiltration system and at least one device for dosing and injecting coagulant into the effluent to be treated, a static mixer and an electrochemical reactor equipped with one or more electrochemical cells, including at least one electrocoagulation cell.

Description

METHOD AND INSTALLATION FOR TREATMENT
CONTAMINATED LIQUIDS
S
DESCRIPTION
Field of the invention The present invention relates to a method and an installation for the purification of contaminated liquids and, more method and a facility for the treatment of wastewater in general and water residual of domestic, industrial, agri-food and agricultural origin in particular.
The invention can be used for the purification of liquids polluted by Contents organic and inorganic dissolved or suspended, but it applies all particularly for the removal of phosphorus (P) and heavy metals, nitrogen (TKN), for the reduction of the chemical oxygen demand (COD and DBOS) and for the destruction of the microorganisms contained in the effluents to be treated.
Description of the prior art The purification of the contaminated liquids can be carried out by a a multitude of physical, chemical, biological and electrochemical methods.
Chemical coagulation (CC) is one of the treatment methods the most common contaminated fluids. It ensures a lowering of content in organic compounds, dissolved P and suspended particles. The coagulation chemical is generally accomplished by (addition of chemical coagulants and by bring necessary energy (mechanical agitation). Chemical coagulants used are especially the aluminum and iron sulphates III: Alz (SO4) 3 and Fe2 (SO4) 3, the aluminum chlorides and iron III: AlCl3 and FeCl3, sulphate mixtures and of lime: M2 (SO4) 3 + Ca (OH) Z and mixed products Al3 + / Fe3 +.
The major drawbacks of CC methods are: transport and storage of large quantities of chemicals, the management of volumes of mud important, generated during treatment, the difficulty of adapting the concentration of coagulants to random variations in the pollutant load, the variation considerable pH, the poor homogenization of the mixtures and the residual salinity of the processed solutions.
Synthetic organic coagulants can completely replace or partially the mineral coagulants. They present (advantage of reducing the volume of sludge produced but in many cases they are less efficient.
Joint use of two or more types of coagulant allows some decrease in the amount of mineral coagulant needed all in ensuring a lower volume of sludge produced. US Patent 4,450,092 (Huang-1984) and 4,582,627 (Carlsson-1986) propose the use of a combination of soluble inorganic chemical compounds (ferric chloride, chloride aluminum, aluminum sulphate) with polymers or a mixture of polymers.
Some chemical treatments exploit the synergy due to the combined use of ferric salts and cationic polymers, method who 1 S offers superior purification performance that the use of both compounds individually in chemical coagulation treatments (US Patents 5,035,808, Hassick-1991 and 5,171,453, Communal.-1992).
Despite these improvements, the amount of coagulant needed is the volume of sludge generated during treatment with chemical coagulation, the treatment efficiency is satisfactory only for a limited number of applications and for good operating conditions accurate.
To remedy some of these disadvantages, methods that significantly reduce the consumption of chemicals or do not require at all their use have been developed: flotation, electroflotation, electrocoagulation.
Flotation is used as a liquid purification treatment contaminated and is carried out either by dissolved air flotation (FAD), in the case where air is injected into fine bubbles in the effluent, either by electroflotation (EF), by generating fine bubbles of hydrogen and oxygen by electrolysis with electrodes insoluble. In both cases, gas bubbles cause agglomeration of the

-2-pollutants and their separation by flotation. These treatments have a efficiency purification equipment, significant energy consumption and usually be combined with chemical flocculation. In the case of electroflotation (EF), the anodes are very sensitive to corrosion and cathodes to (scaling by decarbonization.
Electrocoagulation (EC) is an electrode electrolysis process soluble solution of a metal cation (Fe3 +, A13 + or others) causing the coagulation of colloids. Obtained without mechanical agitation and without products floc is more compact and stable than in the case of treatment by CC. Electrocoagulation gives, under certain conditions, good results for the effluents mainly loaded with colloidal materials or suspension and also kill bacteria and viruses.
Electrocoagulation purification applications have been developed for wastewater treatment in the pasta industry and papers, 1 S the mining industry and the metal processing industry, for the purification waste water from the food industry, water containing oils, dyes, organic materials, particles in suspension, for the decontamination of effluents containing synthetic detergents and of the heavy metals.
To perform the electrocoagulation treatment (EC) several Solutions for installations and appliances have been proposed: reactors Electrochemicals that use plate-shaped electrodes rectangular parallel steel or aluminum (Okert-1975, Herbst-1991, Powell-1999, Markovsky-2001) or perforated plates with steel anode (Harms, 1976) or tubular plates (Herbst-1989), electrochemical cells with cathodes stainless steel and aluminum anodes (Sundel-1993).
French patent FR 2 707 282 (Cognot-1993) presents a solution improved for an electrocoagulation cell with shaped electrodes of sheet of steel sheets compactly grouped by strapping means insulating.
A system of separators in the form of vertical bars made of material

-3-insulation provides spacing between electrodes and a connector system in isolated copper in relation to the liquid to be treated distributes the current in the electrodes connected. The cell is installed in a tubular housing. These solutions have the disadvantage that the separator and connector systems are position with difficulty compared to the cell, the bulk assembly of elements of the cell limits the realization of cells of industrial dimensions to cause of difficulty handling this type of cells for mounting, repair and the replacement of the electrodes. The clamping system for assembling the cell, as proposed, is rudimentary, difficult to control and can not be ensure suitably its role in improving electrical contacts between connectors and the electrodes.
Despite the large number and diversity of solutions proposed since the 1900s, the research findings point to the fact that the process electrocoagulation is poorly known, that the life of the electrodes limited, that there risk of clogging of the electrolytic cells and that the variation of the conductivity and pH of the liquid to be treated limits the performance of the treatment.
The addition in the liquid to be treated of additives, catalysts, flocculants or coagulants, before, during or after electrochemical treatments is often used to increase the electrical conductivity of the effluent, to adjust pH, to amplify the oxidation phenomena or to help flocculation.
In Canadian Patent Application CA 2 316 446 - 1999, Powell proposes a method and apparatus for electrocoagulation (EC) and provides for possibility of adding an additive to promote coagulation.
In the case of electroflotation (EF) treatment, it is the addition of certain metal or polymer salts which improves the purification efficiency.
This improvement is explained by the complex interaction between the added additive, the colloidal particles of the pollutants in the liquid to be treated and the microparticles bubbles electrolytically generated hydrogen and oxygen (Baer, US Patent 3,347,786, Ramirez - US Patents 3,975,269, - 3969,203, - 3969,245 and 4,012,319, Huang, patent US 6,126,838). The disadvantages that characterize the treatments electroflotation

-4-in general are only partially eliminated: the effectiveness of the test is limited, the energy consumption is important and methods can apply only for the removal of certain pollutants.
US Patents 5,611,907 (Herbst-1997) and European Patent EP
0749 157 (Lee-1997) exploit the polarization effect to agglomerate the particles pollutants and separate them as part of an electrolytic treatment with adding of additives before and after treatment.
Ichiki (US Patent 3,816,276 -1974) proposes a method of purification using an electrocoagulation (EC) treatment followed by adding a anionic polymer and finally the effluent to be treated is subjected to a treatment electroflotation (EF).
Brewser (US Patent 5,368,703-1994), Cole (US Patent 5,531,865-1996) and Morkovsky (US Patent 6,294,061-2001), Cognot (French patent FR 2 282-1993) use wastewater purification processes based on a treatment electrocoagulation (EC) followed by chemical coagulation (CC) treatment.
Canadian patent CA 2 298 122 (Stephenson-2000) proposes a succession of physical, chemical and electrochemical treatments for the purification of water and wastewater, according to a complex scheme that includes a large number of devices and equipment: decanters, filters, cell electrochemical, flotation cell, filter press, hydrocyclone, mixers, coagulant dosers. According to this method, it would be advantageous to achieve a injecting compressed air and an anionic polymer into the fluid to be treated just before applying the electrocoagulation treatment. The same technique is applied before the flotation treatment that follows.
Canadian Patents CA 2,409,573 (2002) and CA 2,447,333 (2002) present a process for the treatment of phosphatic waters in which the precipitation of P is caused by the diffusion of Ca2 + ions during a treatment electrocoagulation or the anode is a source of calcium ions. The method requires the manufacture of a special electrode and operating costs are high.

-5-Despite all these improvements, energy consumption and chemical substances remains important and the costs of manufacturing and replacement electrodes of the electrochemical cells are high. In addition, the configuration Electrochemical cell mechanics lacks flexibility to adapt easily their configuration to the chemical changes of the effluent, especially those caused by the addition of chemicals.
The devices for performing these electrochemical treatments have a limited number of adjustment possibilities to adapt them to the conditions industrial. This lack of flexibility is evident especially in cell current electrochemicals. Indeed, for a given device it is very difficult or impossible to change the number of electrode plates, the distance between plates, The thickness of plates, the configuration of electrical connections (bipolar plates / monopolar plates). The setting possibilities of the regime of operation of the device are limited: we can change the parameters electrical supply of the cell (current, voltage), the flow of liquid in circulation and duration of treatment. Powell (Canadian Patent CA 2 316 446 - 1999) adds the possibility of modifying the active surface of the electrodes by making it change their position in the reactor, but the solution is complicated and difficult to use.
The poor performances in the electrical efficiency of the electrochemical cells are due in part to a poor distribution of the current in the electrode plates. Indeed, the electrical contacts between connectors power supply and the electrode plates are made punctually and cause a local increase in the current density. Current leaks are frequency and corrosion of the electrode in the contact zone is amplified.
Circulation of the liquid to be treated in the electrolytic cells current is inappropriate because the flow is vertical upward or horizontal between parallel plates or through narrow spaces (cutouts, orifices) where he undergoes frequent changes of direction, which favors the clogging of cell in the dead zones by the solids that are coagulating and getting decant during treatment. This effect is magnified by the trend of contaminants at quickly form deposits on the electrode plates. These deposits determine

-6-also a reduction in the energy performance of the treatment and impose of the long and frequent cleaning of the electrodes.
Due to the constructive complexity of electrochemical reactors, their manufacture and maintenance are expensive, especially at the industrial. The majority of current achievements are small devices with some reduced treatment capabilities.
The present invention overcomes these disadvantages, both on the chemical and electrical aspects through optimization reducing costs energy and consumables, than on mechanical aspects by reducing maintenance and improving flexibility. In addition, the method and The proposed installation has several other advantages that will be discussed in detail in the detailed description of the invention.
SUMMARY OF THE INVENTION
One of the objectives of the invention is to provide a method for purification of contaminated liquids and, more specifically, a method for treatment of wastewater in general and wastewater of origin domesticated, industrial and agricultural sectors in particular, while avoiding the disadvantages of other methods mentioned above.
Another object of the invention is a method for producing simultaneously effective removal of pollutants such as heavy metals, the reduction of chemical oxygen demand (COD and DBOS), total nitrogen Kjeldahl (TKN) and suspended solids (MES) and the destruction of microorganisms contained in the effluents to be treated.
The present invention relates to a purification method contaminated liquids that combines chemical flocculation treatment realized by the addition of one or more specific coagulants, in particular salts ferric, aluminum salts or other salts with the electrochemical treatment by electrocoagulation which causes the generation in situ of coagulating ions over there electrolytic dissolution of consumable electrodes and optionally with the electro-chemical treatment by electroflotation which allows the separation into continued at least a portion of the flocculated contaminants. In addition, these techniques combined are simultaneously highlighted in an innovative mechanical configuration who promotes the desired reactions. More precisely, the invention sets worth a synergistic effect of these integrated techniques on product consumption chemical and energy. Indeed, according to the new purification method, the integration of two or three of these processing stages consumes less than chemicals and energy that if they were realized individually, for give the same purification performance.
Another object of the invention is to provide a method and a liquid purification facility that reduces the number of treatments necessary to achieve the required treatment efficiency and thus achieve a simple treatment facility with a reduced number of devices, equipment and accessories, easy to operate and maintain.
Another main aspect of the invention is to carry out an installation to implement the new liquid purification method contaminated based on the synergistic effect resulting from the integration of the treatment of flocculation chemical and electrochemical treatment by electrocoagulation and electroflotation, while avoiding the disadvantages of the other installations mentioned above. More specifically, the facility for the treatment of contaminated liquids a realization is preferably designed to achieve successively the injection of coagulants and electrochemical treatment. The installation consists of minimum a device for dosing and injecting coagulant into the effluent to treat, a static mixer and an electrochemical reactor equipped with one or many electrochemical cells including at least one electrocoagulation cell.
According to another preferred embodiment, the installation comprises a treatment tank, optionally a filtration system or ultrafiltration, a device for dosing and injecting coagulant in the effluent treat, a static mixer and an electrochemical reactor provided with one or more cell electrochemical cells including at least one electrocoagulation cell. According to this preferential configuration, it is possible to carry out a succession of treatments filtration, coagulant injections, electrocoagulation, electroflotation and _boy Wut_ separation of solids by flotation and decantation, by recirculating the effluent to be treated from the treatment tank. This type of recirculation determines a decrease considerable deposits on the plates of electrochemical cells, reduced the risk of clogging of the cell, prolongs the life of the electrodes, facilitates the maintenance and increases the purification efficiency and energy efficiency of installation. Indeed the liquid that comes from the treatment tank is optionally filtered and then the coagulant is injected, First by a dosing system and secondly during the passage of the liquid into the electrochemical reactor. Following the phenomena of flocculation-coagulation-flotation, the pollutants of the liquid have the tendency to agglomerate and to separate.
The installation is designed to allow a first settling of sludge while the passage of the liquid in the electrochemical cells and a second decantation in the settling tank of the electrochemical reactor. A scraping system is capable of removing floating foam formed during processing electrochemical pollutants. But the flocculation-coagulation-flotation effect and the separation by decantation of pollutants takes place mostly in the treatment tank of way more accelerated and with superior purification and energy efficiency by report to traditional methods. During the progress of the treatment, the liquid recirculated in the installation that comes from the tank clarified liquid zone of treatment is less and less loaded with pollutants (the liquid is more "clean").
This type of recirculation thus makes it possible to reduce the quantity of contaminants who pass through the equipment of the installation (filtration system, reactor electrochemical) while in traditional systems that use Ie continuous treatment or partial recirculation, the entire pollutants contained by the liquid to be purified passes through the installation.
Another object of the invention is to provide a cell very flexible electrochemical, able to adapt to a wide range applications, easy to install, modify and maintain. More specifically, the cell is provided electrodes made in the form of rectangular metal plates, parallel, arranged vertically and spaced apart by removable separators. At least two plates are connected to a DC power source (plates monopolar).

Removable connectors with special shape ensure contact electric improved and uniform electric current distribution in connected electrodes. Electrode plates, separators and connectors are assembled to form a sandwich structure using a pressure plate and tightening screws. This configuration facilitates assembly and disassembly and allows to perform various configures of the cell (by changing the number of plates, their thickness, electrical configuration, etc.).
According to another object of the invention, the electrodes, the connectors and separators are very easy to manufacture and assemble to achieve a cell electrolytic.
According to another aspect of the invention, the flow of the effluent contaminated in the electrochemical reactor is characterized by a circulation fluid in order to promote coagulation reactions and of decanting. Thus, the effluent to be treated has a vertical flow down in the first electrolytic cell, in the same direction as the movement of particles coagulating and decanting to the base of the cell, where the speed fluid is decreased. Ensuring a sufficiently high fluid velocity between plaques-electrodes of the cell it is possible to create a cleaning effect and thus to limit the formation of deposits on these plates. This effect is amplified by performing periodically a change of polarity of the electric supply current of the electrode plates, according to the prior art in the art of electrocoagulation. A
space is provided at the base of the cell to house the separated solids in this first stage of decantation. This space promotes the decantation of particles by its higher traffic volume compared to the previous section of the reactor.
Subsequently, in the following compartment which optionally houses a second electrolytic cell, the flow becomes vertical ascending. This flow is in the same sense as the movement of gas bubbles that cause other contaminating particles in flotation so that they are immediately separated in the form of foams. The scraping area of the foams is also a second zoned slowing of the fluid which favors the settling of the particles having no not been recovered by flotation before discharging the effluent.

Another object of the invention is to provide an installation for the multipurpose contaminated fluid purification, with treatments high, preferably from effluent flow rates of 20 m3 per day and more, with a purification efficiency that can reach more than 95% for the elimination of P, of the suspended matter (MES) and heavy metals, more than 60% for lowering the Nitrogen (TKN), Chemical Demand for Oxygen and Biological Demand in oxygen (COD and DBOS) and more than 99% for the destruction of microorganisms contained in the effluents to be treated.
Another object of the invention is to provide a method and a liquid purification plant for use in the production of polishing treatment after biological treatment or after others treatments purification of contaminated fluids (primary treatments example).
According to another aspect of the invention, the liquid thus purified can be reused as washing liquid, irrigation water or for any other use that can ensure water saving in domestic, industrial applications or agricultural or it can be disposed in the natural environment if the purification has been accomplished up to the level of specific environmental standards.
Another object of the invention is to use the solids recovered under the form of sludge and foam after treatment lice preparation fertilizer.
BR ~ VE DESCRIPTION OF THE DRAWINGS
Fig. 1 is a schematic diagram of the installation to put in the new method of purifying contaminated liquids based on the effect synergistic resulting from the integration of chemical flocculation treatment and electrocoagulation treatment according to one of the preferred embodiments of the invention;
Fig. 2 is a vertical section of a schematic view of the installation for the purification of contaminated liquids according to one of the embodiments preferential of the invention;
-ll-Fig. 3 is a perspective view of a mounting detail of the cells electrolytics within the electrochemical reactor;
Fig. 4 shows a perspective view of a connector of the cell electrolytic, according to a preferred embodiment of the invention; and Fig. 5 shows a perspective view of a separator of the cell electrolytic, according to a preferred embodiment of the invention.
DESCRIPTION OF PREFERENTIAL ACHIEVEMENTS
Research on the mechanisms that govern the electrocoagulation phenomena are fairly recent. It is considered now that it is a complex process with a multitude of mechanisms that interact to remove pollutants from the liquid to be treated (Holt-2002).
Got without mechanical agitation and without the addition of external products, the floc is more compact and the volume of sludge is much lower than with a coagulation chemical flocculation.
If in chemical coagulation the addition of coagulant is discrete, with a balance given by the evolution of the pH, for the electrocoagulation, the bill The coagulant is a function of the applied current and the time.
Numerous scientific works have analyzed the treatment of chemical coagulation versus electrocoagulation treatment (Holt 1999 and Powell Water Systems Inc.-2000, Hicham-2002, Jiang-2002). The researches demonstrated the many benefits of electrocoagulation compared to the coagulation chemical. A direct comparison between the two treatments is not possible because the bases of operation are different.
We discovered an unexpected synergistic effect, especially for elimination of P, using the combination of flocculation treatment chemical (the addition in the effluent to be treated of one or more coagulants specific: salts ferns, aluminum salts or others) and electrocoagulation treatment.
The new method of purifying contaminated liquids is thus based on integrating the two treatment steps that consume fewer substances chemicals and energy that if performed individually, lice give the same purification performance.
According to a main aspect of the invention, the purification method contaminated liquids is based on a synergistic effect of consumption of chemicals and energy achieved by integrating a treatment of chemical flocculation and electrocoagulation treatment. To put in evidence this synergistic effect, the procedure described in this invention has been validated in three 3 steps - test jars performed on coagulants alone, - electrochemical tests alone (without addition of chemical coagulants), - electrochemical tests combined with the addition of chemical coagulants.
The test jars are carried out on I.0 L of liquid sample to be treated.
The chemical coagulant (the quantity of which is previously determined) is added gradually and the mixture is stirred continuously for 1 hour.
The sample is then decanted for half an hour. The supernatant is separated from the decanted phase and analyzed for environmental parameters (MES, COD, Total coliforms, total P).
Electrochemical tests are performed by applying a current density of 50 to 1000 A / m2, preferably between 100 and 300 A / m2, a quantity of electricity of 10 to 500 Ah / m3, preferably between 20 and 50 Ah / m3.
Example -1 The initial characteristics of the liquid to be treated is described in Table 1. The pH of the liquid is maintained between 3 and 14, preferably between 6 and 8.
Coagulant used is fernic chloride (FeCl3-40%). The mass ratio of the iron total on the initial phosphorus is maintained around 3 kg iron / kg P in this example. The results are shown in Table 1.

Table 1 Parameter Unit InitiaFinal Efficiency (%) s 1 EC oagulanE.C EC CoagulaE.C
+ +

(only) t oagulanseule) t Coagula (alone) t (alone) t pH - 8.2 8.56 7.41 7.79 +4.4 -9.6 -5.0 MES mg / L 250 60 60 30 76.0 76 88 COD totalmg / L 510 I00 272 270 80.4 46.7 47.1 P total mg / L 34.0 4.8 14.7 3.3 85.9 56.8 90.3 ColiformsUFC / 1 430009000 45000 8100 79.1 0 81.1 fcaux OOmL

Thanks to the method described in this invention, the performances related to electrochemical dephosphatation and purification are clearly improved. In effect, total phosphorus conversion is 46.7% for coagulant alone and 80.4% for the electrochemical alone to 90.3% for the combination electrochemical and addition of the chemical coagulant. The purification also undergoes the effect synergistic, both on suspended solids (MES) and on coliforms totals.
Example -2 The experiment described in Example 1 is renewed but this time it is to achieve a total conversion rate of P greater than or equal to 90%. The report mass Fe / P (kg Fe / kg P removed), energy consumption and chemical coagulant are determined to show the synergistic effect of the process electrochemical with the addition of chemical coagulant. The results are reported to table 2.

Table 2 Procds Fe / Consumption Consumption of (g / g) Energy Coagulant Cot CE CC

kWh / m3 kWh / kg-kg-Fe / kg-P ($ CE

(kg-P Fe / m3 removed + $ CC) /

removed) kg-P removed EC only 4.0 6.0 142 - - 8.S

EC + 3.5 1.6 50.6 0.061 2.0 5.7 Coagulant Coagulant 6.0 - - 0.204 6.6 8.9 alone CE: 0.06 $ lkWh, CC = 0.185 $ lkg- (FeCl3-40%) The synergistic effect of the addition of a chemical coagulant on the process electrochemical is further highlighted by the fact that a report relatively low Fe / P is required to obtain phosphorus conversion superior or equal to 90%. This translates into an energy cost and a consumption of less chemical coagulant.
The invention is characterized by the following steps - make an injection of coagulant (ferric salts, aluminum salts or other) in the liquid to be treated by means of a dosing system and ensure the homogenization of the liquid through a static mixer or by a mechanical agitation, - direct the liquid through an electrochemical reactor to initiate the flocculation-coagulation phenomena and achieve a separation of 1 S solid agglomerated by settling and by flotation, In accordance with FIG. 1, the liquid to be treated is subjected to a succession of treatments consisting of the injection of a coagulant (salts fernques, aluminum salts or the like) produced by a metering device 23 provided with a 24. The uniformization of the liquid is carried out during the passage of the liquid in a static mixer 25 from which it is sent to an electrochemical reactor 1 . This configuration allows the continuous treatment of the liquid to be purified according to a procedure very simple but it can also be easily integrated into treatments complexes that require in advance, for example, a biological treatment, a filtration or ultrafiltration and / or in treatment regimens that require after separation treatments, filtration, etc.
According to another main aspect of the invention, the method of purification of contaminated liquids is carried out according to the following steps - fill the treatment tank with the liquid to be treated, - deliver liquid from this tank to a filtration system or ultrafiltration and perform a first purification step (Optionally), - make an injection of coagulant (ferric salts, aluminum salts or other) in the liquid to be treated by means of a dosing system and ensure the homogenization of the liquid through a static mixer or by a mechanical agitation, - direct the liquid through an electrochemical reactor to start flocculation-coagulation phenomena and realize a first separation of the agglomerated solids by settling and by flotation, - return the liquid thus treated in the treatment tank where the flocculation-coagulation process is accomplished under the effect of coagulants added in the previous steps; agglomerated solids settle quickly and accumulate in the form of sludge at the bottom of this tank, - recirculate the liquid to be treated to resume the treatment sequence presented above until the degree of purification is reached longed for, - remove the sludge accumulated by settling and the foam formed by electrochemical flotation in the electrochemical reactor and in the treatment tank, in continuous mode or at the end of treatment and - Empty the liquid treatment tank thus purified.

In accordance with FIG. 2, the liquid is recirculated using a pump 22 in the installation and subjected to a succession of treatments of filtration, coagulant and electrocoagulation injections, flotation separation and by decanting. The first step according to the proposed treatment method, consists of fill the treatment tank 21 with the liquid to be treated by the connection input 30, then filtration is applied using a filtration system 28.
A
connection 29 connected to a pump 19 serves for the evacuation of solids separated by filtration and / or for the periodic washing of the filter. The next step consists in the injection of a coagulant (ferric salts, aluminum salts or other) carried out by a metering device 23 provided with a pump 24. The uniformization of the liquid is during the passage of the liquid in a static mixer 25. The reactor electrochemical 1 is made in the form of a sealed tank made of plastic or, preferably, of stainless steel plasticized inside and. The reactor has several compartments: a compartment 2 for the entry of the liquid at treat, a compartment 3 which houses an electrocoagulation cell 8a, the compartment 4, which can house a second electrochemical cell 8b, a tank primary settling chamber 6, a settling tank S and an evacuation tank of the 7. The effluent to be treated enters the electrochemical reactor 1 through the connection input 9 according to an upward vertical flow through the compartment 2 and then enters by pouring into the compartment 3 according to a flow vertical descending among the electrodes of the electrocoagulation cell 8a. This flow promotes effective entrainment of a significant portion of the particles that begin to separate during the passage in the cell 8a, towards the tank of decantation 6. A sufficiently high fluid displacement velocity favors also a cleaning effect of the electrodes and decreases the formation trend of the chemical deposits. This effect is amplified by periodically performing a change of polarity of the supply electric current of the electrode, according to the art known in the technique of electrocoagulation. The accumulated solids in the tank 6 are removed periodically or continuously by an outlet fitting 20 and a pump 19.
Then the liquid to be treated passes through the compartment 4 to go through dumping in the settling tank 5, where the separation of contaminants continues through decantation or flotation. A scraper system (mechanical, pneumatic or further) discharges the formed foam to a tank 7 provided with an outlet pipe 17.
The The sludge formed in the settling tank 5 is removed periodically or in continuously through the outlet connection 18 and the pump 19. The effluent leaves the reactor electrochemical 1 through a spillway pipe 16 to the treatment tank 21. One cover 26 ensures the safe protection of the device. A system of ventilation 27 allows the dilution of the gases formed during the electrolysis and their evacuation.
This system also performs the function of moving the foam formed in the compartment 3 to compartment 4 and thus to tank 5 to enter the area Action Plan 15. Between inlet compartment 2 and compartment 3 is located a plate 10 which is fixed with respect to the electrochemical reactor. A system of vertical plates 11 and 12, movable relative to the electrochemical reactor is used to transmit a clamping pressure necessary for mounting the cells electrolytic, pressure created using a clamping system composed by the screws 35 and the frame 13 which is, in turn, integral with the reactor vessel electrochemical 1. The plates 10, 11 and 12 are made of an insulating material, preference in polypropylene. Following the addition of coagulant by direct injection and during the treatment in the electrochemical reactor the flocculation process-coagulation and the separation by settling of pollutants takes place accelerated especially in the treatment tank 21. Solids in the form of sludge are evacuated the end treatment by the connection 33 and the pump 34. The reservoir 21 is provided with a zoned K, which allows, by the recirculation of the effluent to be treated, of reintroduce an increasingly decontaminated liquid into the installation. The treatment continues until the desired degree of purification is achieved.
achieved.
Once the recirculation is stopped, the purified liquid is evacuated using the pump 31 through the fitting 32.
In accordance with Fig.3, the electrolytic cell 8a (or 8b) is provided with several electrodes 81 made in the form of metal sheets rectangular, parallel, vertically arranged and spaced apart by separators removable 83 made of insulating material, preferably polypropylene. At at least two plates of each cell are connected (monopolar plates) to a DC power source (not shown). The feeding of each plate monopolar is performed by a removable connector 82, preferably performs in stainless steel. The electrode plates 81, the separators 84 and the connectors 83 are assembled successively to form a sandwich structure using of the mobile pressure plate 12 and the movable plate 11, thanks to a system of Tightening composed by the screws 35 and the clamping frame 13. This solution facilitates the editing and rapid disassembly of the cell for cleaning, repairs or replacement fast plates and in addition provides increased flexibility to achieve a big diversity of electrochemical cell configurations as it is explain more far. The plate 10 and the plate 12 are provided with a series of vertical channels made by machining to allow the insertion of connectors 82 and avoid so the formation of an unnecessary space between the electrode plate at the end of the cell and the plates 10 and respectively 12. The electrode plates 81 are supported by a frame 14 fixed in the tank 6 of the electrochemical reactor; he is covered by an insulating material to prevent any electrical contact between the electrodes 81. Two side plates 84, made of insulating material, solidarity with the electrochemical reactor vessel support the separators 82 and the connectors 83. To connect the connectors 82 to the source of current (not shown) standardized connection parts 85 are used which allow to attach the electric cables according to the desired configuration.
The invention provides increased flexibility in the configuration of the cell 8a (8b), because it is possible to realize various configurations by changing the number of 81 plates, the thickness of the plates, the distance between the plates (in using different thicknesses for separators 82). The electrical configuration of the Cell 8a (8b) can be easily modified by varying the number of plates mono-polar (using multiple connectors 83).
In concordance with a preferred embodiment of the invention the Electrochemical reactor 1 can be configured according to several variants, function treatment conditions to achieve - first, it is possible to install a single cell electrocoagulation 8a while the compartment 4 which contains only a number of separators 82 serves to direct the liquid to the settling tank 5, - secondly, it is possible to install two cells identical electrocoagulation 8a and 8b or two cells different electrochemicals, depending on the number of plates 81, the distance between the plates, the nature of the plates (soluble electrodes or insoluble), depending on the electrical configuration (number of bipolar and monopolar).
By this flexibility in the configuration of the reactor electrochemical the method of treatment according to the invention proves to be a method versatile to adapt the treatment to various types applications. In effect it is possible to use a single electrocoagulation cell with a big number of electrodes, for example, two electrocoagulation cells but with different configurations at the electrodes, connections electric or current parameters, ie a first electrocoagulation cell and a second electroflotation cell, etc. The variation of the parameters of the current supply of electrochemical cells also remains another means of setting operating regimes of the electrochemical reactor. The source of current ensures the possibility to adjust the amperage, the applied voltage and the change periodic polarity according to the known art in the technology of Electrochemical.
In accordance with FIG. 4 the connector 82 is made from a corrosion-resistant metal sheet, preferably a steel sheet stainless laser cut or made by welding to obtain a part 821 which includes a horizontal bar Al and a minimum of 2 vertical bars C1 provided for ensure a electrical contact along the entire length of the electrode plates 81 of the cell electrochemical 8a (8b). At each end of the horizontal bar A1 there is a shoulder B 1 which serves to position the connector 82 relative to the plates during assembly of the cell 8a (8b). A tab D is provided for ensure the assembly of the electrical connection parts 85. The vertical bars C 1 are covered with an insulating material 822 (by gluing, laminating or other method) on one of the vertical surfaces, preferably a rubber bar type nitrite.

The connector 82 is installed in the electrochemical cell 8a (8b) of such way that the electrical contact is ensured with an electrode plate 81 located non-rated isolated from vertical bars C1, while the next plate is isolated by report to connector.
The role of the connector is to ensure good electrical contact while along each connected plate, on both lateral sides and possibly at center and thus determine a uniform distribution of electric current. The connector also plays the role of separator between the electrodes 81 and it ensures the transmission of the pressure force created by the screws 35 to the assembly of the cell.
In accordance with FIG. The separator 83 is made in a insulating material, preferably polyethylene and it has substantially the same form that the connector 82 having a horizontal bar H2 and minimum 2 bars verticals C2. At each end of the horizontal bar V2 there is a shoulder B2 which serves to position the separator 83 relative to the plates 84 during the assembly of the cell 8a (8b). The separator 83 is installed in the cell electrochemical 8a (8b) for the purpose of achieving the required spacing between electrodes 81 and to ensure the transmission of the pressure force created at mounting by the screws 35.

Claims (20)

1. Purification method for contaminated liquids characterized by an effect synergy on the consumption of chemicals and energy by the integration of a chemical flocculation treatment and a treatment electrocoagulation and accomplished by the following steps:
- convey the liquid to a filtration or ultrafiltration system and carry out a first purification step, - make an injection of coagulant (ferric salts, aluminum salts or other) in the liquid to be treated by means of a dosing system and ensure the homogenization of the liquid through a static mixer or by a mechanical agitation, - direct the liquid through an electrochemical reactor to start flocculation-coagulation phenomena and realize a first separation of the agglomerated solids by settling and by flotation, 2. Method of purifying contaminated liquids characterized by a Synergistic effect on the consumption of chemicals and energy produced by the integration of a chemical flocculation treatment and a treatment, electrocoagulation and accomplished by the following steps:
- deliver the liquid to be treated to a filtration system or ultrafiltration and perform a first purification step, - make an injection of coagulant (ferric salts, aluminum salts or other) in the liquid to be treated by means of a dosing system and ensure the homogenization of the liquid through a static mixer or by a mechanical agitation, - direct the liquid through an electrochemical reactor to start flocculation-coagulation phenomena and realize a first separation of the agglomerated solids by settling and by flotation, - convey the liquid thus treated to a treatment tank where the flocculation-coagulation process is accomplished under the effect of coagulants added in the previous steps; agglomerated solids settle quickly and accumulate in the form of mud at the bottom of this tank, - remove the sludge accumulated by settling and the foam formed by flotation in the treatment tank, in continuous mode or at the end of the treatment and - evacuate the liquid thus treated. 3. Purification method for contaminated liquids characterized by a Synergistic effect on the consumption of chemicals and energy produced by the integration of a chemical flocculation treatment and a treatment electrocoagulation and accomplished, by the following steps:

- fill the treatment tank with the liquid to be treated, - deliver liquid from this tank to a filtration system or ultrafiltration and perform a first purification step, - make an injection of coagulant (ferric salts, aluminum salts or other) in the liquid to be treated by means of a dosing system and ensure the homogenization of the liquid through a static mixer or by a mechanical agitation, - direct the liquid through an electrochemical reactor to start flocculation-coagulation phenomena and realize a first separation of the agglomerated solids by settling and by flotation, - return the liquid thus treated in the treatment tank where the flocculation-coagulation process is accomplished under the effect of coagulants added in the previous steps; agglomerated solids settle quickly and accumulate in the form of mud at the bottom of this tank, - recirculate the liquid to be treated to resume the treatment sequence above until the degree of purification is reached longed for, - remove the sludge accumulated by settling and the foam formed by electrochemical flotation in the electrochemical reactor and in the treatment tank, in continuous mode or at the end of treatment and - empty the treatment tank 4. Purification method according to claims 1, 2 or 3 characterized in that it is accomplished without using the filtration step or ultrafiltration. 5. purification method according to one of claims 1 to 4 characterized in that instead of a coagulant a mixture of coagulants or a mixture of coagulants and polymers. 6. purification method according to one of claims 1 to 5, characterized in that it is used for the treatment of wastewater in general and residual waters of domestic, industrial, agri-food and agricultural particular. 7. purification method according to one of claims 1 to 6, characterized in that it is used for the purification of polluted liquids by organic and inorganic matter dissolved or suspended and any particularly for the simultaneous removal of P and heavy metals, nitrogen (TKN), for the reduction of the chemical oxygen demand (COD or BOD5) and for the destruction of the microorganisms contained in the effluents to be treated. 8. purification method according to one of claims 1 to 7, characterized in that it is used as a polishing treatment after a biological treatment or after other purification treatments fluid including a primary separation. 9. Purification method according to one of claims 1 to 8, characterized by producing a purified liquid that can be used as a liquid washing, irrigation water or any other application that can ensure the economy in domestic, industrial, food and agricultural or it can be dumped in the natural environment if the purification has been completed until level of specific environmental standards. 10. Purification method according to any one of claims 1 to 5, characterized in that the recovered solids in the form of sludge and foams after the treatment are used for the preparation of fertilizer. 11. Installation to implement the method of purification of contaminated liquids according to claim 1 and one of claims 4 to characterized in that it comprises a filtration system or ultrafiltration, and less a device for dosing and injecting coagulant into the effluent treat, a mixing system and an electrochemical reactor equipped with one or many electrochemical cells of which at least one is a cell electrocoagulation. 12. Installation to implement the method of purification of contaminated liquids according to claim 2 and one of claims 4 to characterized in that it comprises a filtration system or ultrafiltration, and less a device for dosing and injecting coagulant into the effluent treat, a mixing system an electrochemical reactor equipped with one or more electrochemical cells of which at least one is a cell electrocoagulation and a treatment tank. 13. Installation according to claim 3 and one of the claims from 4 to 10, characterized in that it carries out a succession of treatments of filtration, of coagulants and electrocoagulation and electroflotation in the goal of carry out the separation of solids by flotation and decantation, in recirculating the effluent to be treated with a recirculation pump from a zone of clarification in the treatment tank. 14. Installation according to claims 11, 12 and 13, characterized in that that it is equipped with an electrochemical reactor which is produced under the form a sealed plastic or stainless steel tank interior and which has several compartments including a first compartment for the entrance of the liquid to be treated, a second compartment which houses a cell electrocoagulation, a third compartment that can house, optionally, a second electrochemical cell, a settling tank located at the base of the electrochemical cells, a foam evacuation tank and optionally a main settling tank. 15. Electrochemical reactor according to claim 14, characterized what the effluent to be treated has an upward vertical flow through the first compartment and enters by spill into the second compartment according to a descending vertical flow among the electrodes of the cell electrocautery, then it passes through the third compartment equipped or no of a second electrochemical cell, to pass by spilling into the tank of main decantation, where the separation of contaminants continues through decantation or by flotation and finally the effluent comes out of the electrochemical reactor by a pipe spillway to the treatment tank or the flocculation process-coagulation and separation by settling takes place in an accelerated manner. 16. Electrochemical reactor according to claim 15, characterized in that it is provided with a scraper system (mechanical, pneumatic or else) for evacuate the foam formed during the treatment, to a tank equipped with a pipe of exit. 17. Electrochemical reactor according to one of claims 14 to 16, characterized in that the sludge accumulated in the tanks is eliminated periodically or continuously through outlet fittings and a pump. 18. Electrochemical reactor according to one of claims 14 and 17, characterized in that the electrochemical reactor is provided with a lid which assures safe protection for electrochemical cells. 19. Electrochemical reactor according to one of claims 14 and 18 characterized in that it is provided with a ventilation system with a double function: firstly the dilution of the gases formed during the electrolysis and their evacuation and secondly the transfer of the foam formed on the surface of the liquid in the electrochemical cells to the main cell in the zone Action Plan scraper. 20. Electrochemical reactor according to one of claims 14 to 19, characterized in that the electrochemical cells use as electrodes of the rectangular, parallel metal plates arranged vertically and spaced by removable separators made of insulating material and connectors removable provide electrical contact with connected electrode plates, and assembly is realized in the form of a sandwich structure by the alternation of electrodes, separators and connectors that are clamped between a fixed plate and a plate made of insulating material, under the effect of the pressure created at using a clamping system composed by several screws and a frame which is, in turn, solidary with the electrochemical reactor vessel21. Electrochemical cell according to 20, characterized in that the electrode plates are supported by a frame covered by an insulating material.
22. Electrochemical cell according to claims 20 and 21, characterized in that the fixed plate and the movable plate located at the end of the cell are equipped with a series of vertical channels made by machining to enable the insertion removable connectors to prevent the formation of unnecessary space between the-electrodes located at the end and these plates.
23. Electrochemical cell according to claims 20 to 22, characterized in that at least two plates of each cell are connected (plates monopolar) to a DC power source using the connectors removable.
Electrochemical cell according to claims 20 to 23, characterized in that the removable connector is made from a sheet of metal resist corrosion, preferably a laser cut stainless steel sheet or realized by welding to get a piece that has a horizontal bar and minimum 2 vertical bars provided to ensure electrical contact throughout the length electrode plates. At each end of the horizontal bar there is a shoulder that serves to position the connector in the cell relative both insulating material plates attached to the side walls of the reactor. The bars are covered with insulating material (by gluing, laminating, painting or other method) on one of the vertical surfaces, preferably a bar in nitrile rubber.

Electrochemical cell according to claims 20 to 25, characterized in that the connector has a triple role, firstly to ensure a good contact electrical connection throughout each connected electrode plate, on both rated lateral and possibly in the center, if it has three bars vertical secondly also plays the role of separator between the electrode plates and thirdly it ensures the transmission of the pressure force created by the screw tightening when mounting the cell.
Electrochemical cell according to claims 20 to 26, characterized in that the separator is made of insulating material, preferably polyethylene and it has substantially the same shape as the connector in with a horizontal bar and minimum 2 vertical bars. At each end of the closed off horizontal there is a shoulder that serves to position the separator by report two insulating boards attached to the side walls of the reactor.
Electrochemical cell according to claims 20 to 27, characterized in that the separator has a dual function. First, he plays the role of separator between the electrode plates and secondly, it ensures the transmission of the forced pressure created by the clamping screws when mounting the cell.
28. The method according to claims 1, 2 and 3 characterized in that that the flow of the contaminated effluent that is vertical down into the first electrochemical cell, followed by a settling zone, a flow vertical ascending and optionally at least one other settling zone, created from better kinetic conditions for flocculation and separation of particles at course of the process.
29. Installation according to claim 14 which uses a reactor electrochemical device according to claims 15 to 20, characterized in that is operated without using the step of adding additive.