MX2010011908A - Method for removing inorganic contaminants from soils via a physicochemical extraction technique. - Google Patents

Method for removing inorganic contaminants from soils via a physicochemical extraction technique.

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Publication number
MX2010011908A
MX2010011908A MX2010011908A MX2010011908A MX2010011908A MX 2010011908 A MX2010011908 A MX 2010011908A MX 2010011908 A MX2010011908 A MX 2010011908A MX 2010011908 A MX2010011908 A MX 2010011908A MX 2010011908 A MX2010011908 A MX 2010011908A
Authority
MX
Mexico
Prior art keywords
effluent
fines
order
soils
fractions
Prior art date
Application number
MX2010011908A
Other languages
Spanish (es)
Other versions
MX343510B (en
Inventor
Marie Josee Lamothe
Claude Gauthier
Marc Andre Bergeron
Katheen Dube
Original Assignee
Northex Environnement Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to CA 2630894 priority Critical patent/CA2630894A1/en
Application filed by Northex Environnement Inc filed Critical Northex Environnement Inc
Priority to PCT/CA2009/000601 priority patent/WO2009132464A1/en
Publication of MX2010011908A publication Critical patent/MX2010011908A/en
Publication of MX343510B publication Critical patent/MX343510B/en

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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B09DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
    • B09CRECLAMATION OF CONTAMINATED SOIL
    • B09C1/00Reclamation of contaminated soil
    • B09C1/02Extraction using liquids, e.g. washing, leaching, flotation
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B09DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
    • B09CRECLAMATION OF CONTAMINATED SOIL
    • B09C1/00Reclamation of contaminated soil
    • B09C1/002Reclamation of contaminated soil involving in-situ ground water treatment
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B09DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
    • B09CRECLAMATION OF CONTAMINATED SOIL
    • B09C1/00Reclamation of contaminated soil
    • B09C1/08Reclamation of contaminated soil chemically

Abstract

A method for decontaminating soils that are contaminated with an inorganic contaminant, comprising: screening the contaminated soils in order to obtain coarse and fine fractions; sieving the screened soils in order to retain therefrom the coarse fractions and, concurrently, washing the screened soils in order to obtain a first effluent comprising the washing liquid and the fine fractions flowing from the sieve and comprising fines and particles with dimensions greater than those of the fines; separating the fines from the first effluent in order to recirculate fresh water and thus obtain a second effluent; ensuring the supply of the washing operation; and conveying the contaminated fines separated from the first effluent to a chemical chamber where a portion of the first effluent and a chemical solution are added in order to produce a third effluent (acid), the latter containing metals dissolved in the fines that it is necessary to separate. The fourth effluent comprises the fines and a precipitation of this effluent is produced in order to extract the precipitated contaminants, so as to obtain a fifth effluent, whereby the inorganic contaminant is extracted and it is possible to reuse the fifth effluent for recirculation in the treatment process.

Description

METHOD FOR REMOVING INORGANIC SOIL POLLUTANTS THROUGH A PHYSICOCHEMICAL EXTRACTION TECHNIQUE REFERENCE TO RELATED REQUESTS The present patent application claims the priority of the Canadian patent application No. 2,630,894 filed on May 2, 2008, incorporating it by reference in the present application.
FIELD OF THE INVENTION The present invention relates to a method for removing inorganic contaminants from soils through a physicochemical extraction technique in an aqueous phase. The present invention consists in concentrating, in an aqueous solution, the inorganic contaminants amalgamated in fine fractions of the soils, in order to extract them.
TECHNOLOGICAL BACKGROUND The purpose of the techniques to decontaminate soils through physicochemical treatments is to reduce or even eliminate the concentration of pollutants at a level comparable to the environment of natural soils. Industrial inorganic contaminants that are not related to natural elements must necessarily be eliminated for reasons of human health, animal health or environmental reasons. The decontamination techniques for physicochemical treatments are currently increasing disproportionately, given the - - economic costs resulting from concentrations of pollutants that have been exceeded beyond acceptable or permitted standards; This is particularly true in the countries of Northern Europe.
A contaminant present in soils can be of the organic, inorganic or mixed type, that is, organic / inorganic. Inorganic contaminants are generally present in soils in solid form. The size of the inorganic contaminants in solid form can be of the order of one miera (μp?). These metal contaminants, called "heavy metals" or "trace metal elements" are typically found in the form of angular particles whose diameter does not generally exceed? Μ. Zinc, lead, cadmium and copper are some examples of inorganic contaminants.
DESCRIPTION OF THE INVENTION The object of the present invention is therefore to develop a method and treatment system for extracting inorganic contaminants from soils.
Therefore, according to the present invention, a method for removing inorganic contaminants from soils is proposed, the method comprising: selecting contaminated soils in order to obtain coarse and fine fractions; wash and select the soils with a washing effluent in order to obtain a first effluent comprising the - - washing liquid and the floors that flow in the screen and screening the floors in order to retain the coarse fractions thereof and, concurrently, retain the fractions that flow from the screen and that comprise the fines and particles with larger dimensions than the fines, subjecting the washing effluent to an extraction of the particles whose dimensions are greater than those of the fines, and thus obtaining a second effluent that is returned to the washing unit | and / or a fraction that can be returned to a chemical chamber; producing in the chemical chamber, an extraction of the second effluent containing the contaminated fines to dissolve the metals thereof in order to obtain a third effluent; and producing a precipitation and / or neutralization of the third effluent and extracting it from them by filtering the precipitate in order to obtain a fourth effluent, whereby the inorganic contaminants are precipitated in a fourth effluent.
Also according to the present invention, a method for removing inorganic contaminants from soils is proposed, the method comprising: a) washing a contaminated soil with a washing effluent in order to obtain a first effluent comprising the washing effluent and the fines, by which particles of larger dimensions are retained than those of fines; b) submit the first effluent to an extraction of the larger particles to those of the fines and thus obtain a second effluent that is returned to the washing unit and / or a fraction that is passed to stage c); c) produce the extraction of the second effluent containing the contaminated fines to dissolve the metals thereof, in order to obtain a third effluent and extract, by filtration, the precipitate thereof in order to obtain a fourth effluent, by means of which the inorganic contaminants for extraction in a fourth effluent.
Also, according to the present invention, a method for removing inorganic contaminants from soils is proposed, the method comprising: a) submitting a first effluent containing inorganic contaminants to filtration in order to extract the larger particles from those of the fines and thus obtain a second effluent; c) produce an extraction of the second effluent containing the contaminated fines to dissolve the metals thereof, thus obtaining a third effluent; and d) producing a precipitation and / or neutralizing the third effluent and extracting the precipitate therefrom by filtration. to obtain a fourth effluent, through which inorganic contaminants are precipitated for extraction in a fourth effluent.
The foregoing, as well as other objects, advantages and features of the present invention will be apparent to Starting from the non-limiting description of an embodiment, provided in order to exemplify the present invention and given only by way of example, with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS Having generally described the nature of the invention, a preferred embodiment of the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a schematic diagram showing one embodiment of a method for decontaminating soils of an inorganic contaminant according to the present invention; Y Figure 2 is a schematic representation of a decontamination plant according to the method of the present invention shown in Figure 1.
DETAILED DESCRIPTION OF THE INVENTION Therefore, according to the present invention, a method 100 for extracting inorganic contaminants from soils is presented. The method 100 comprises a dry selection 102 in order to extract the coarse fractions from the soils, the fractions thus removed being valued according to their potential reuse. The method 100 also comprises a wet selection 104 that separates the average fractions from the fines. Soils are selected so Mechanical using a washing liquid that generates an effluent that comprises the washing liquid and fractions of fines that flow from the screen, that is, the effluent # 1. The average fractions that are removed are valued according to their quality. The method 100 also comprises a magnetic selection 106 to which the fine fractions and the effluent 1 are subjected, in order to recover the magnetic fractions that are reusable.
Then, with the method 100, the effluent 1 passes to the unit for the separation by filtration and cyclone 108 distributed in four sizes and, at the outlet of the last unit, the effluent is returned either to the selection by washing (effluent # 2) for reuse or to the chemical area for the treatment of fines. After this, the method 100 proposes a chemical extraction 110 which consists in placing the fines of the metallic contaminants contained in the soils in a solution with an acid and effluent # 3. At the end of this stage, the effluent # 3 is separated from these acid sludges and the latter will be conditioned in step 114, in order to neutralize them and make them valuable according to their potential. In method 100, effluent # 3, almost free of solids, undergoes, at 112, basic conditions, and generates effluent # 4. Step 114 makes it possible to generate, treat and condition the sludge; the lumps (metallic) can then be extracted. After, a The fifth and last effluent is neutralized at 116 (effluent # 5), and returns to the wet selection unit or chemical unit and starts the cycle in the process again.
Therefore, the method 100 which is the subject of the invention can be used in general to extract inorganic contaminants from the soils. The term "Inorganic contaminants" is used herein in a broad sense, which means that inorganic contaminants can be single or multiple, comprising more than one element, compound or inorganic substance. In terms of granulometric, the soils to be "decontaminated" can contain variable proportions from rocks, pebbles, gravel, gravel to fine sands, silts or clays. The pH of the soils is generally within the range that varies from 6.0 to 8.0. The method 100 makes it possible to concentrate the inorganic contaminants in the fractions of the fines of the soil to be decontaminated, the fines of which have a dimension of approximately ??? μ ?? or less.
In the present descriptive summary, the term "effluent" refers to a liquid that originates from a stage or sub-stage of a treatment.
Method 100 will now be described for extracting inorganic contaminants from soils, according to a non-limiting mode, given by way of example, and - - refers to an inorganic contaminant of the metallic type, that is, a metal contaminant. However, it should be understood that persons of ordinary skill in the art can apply this method to other inorganic contaminants, other than those of a metallic nature.
The method 100 will now be described generally, with reference to Figure 1.
The first stage of method 100 is a stage 102 of dry selection of soils. The floors to be decontaminated are loaded in a bucket that directs the floors towards a rotating screen with metal screens, whose function is to carry out a selection of gravel from contaminated soils. The sieve separates fractions greater than 75.0mm comprising rocks, stones and residues. The fractions equal to or less than 75.00 are homogenized. The drum of the rotating screen is configured to retain the components whose dimensions are greater than 75.00mm, while the components of 0-75. Omm pass through the wire mesh. This dry method makes it possible to select clays and silts whose consistency is smooth without the latter blocking the selection drum.
The second stage of the method 100 is a wet selection step 104. The fractions of 75.Omm and below are introduced into the wet selection unit through - - a receiving tray combined with a conveyor. This wet selection unit washes and separates fractions from 5.00mm to 75.0mm, from 2.50mm to 4.99mm, from 2.00mm to 2.49mm and from 1.99mm and smaller. The components of 0-75. Omm are subjected to a washing liquid in order to concentrate the contaminants that are to be extracted in fine fractions, that is, fractions that have a dimension of 1.99mm or less, while the coarse fractions, that is, those greater than 2.00 mm are retained by means of the selection. The washing liquid can be simply water or water enriched with surfactants and / or chemical reagents. According to the wet selection 104, two products are obtained. Valuable inert materials that vary between 2.00mm and 75. Omm are subjected to a ferrous separator. The second product is an effluent (effluent # 1) that contains fractions of 1.99mm and smaller (which means less than 2. OOmm) as well as the metal fractions that are to be extracted.
The effluent # 1 passes from the wet selection unit 104 to the magnetic unit 106 (third stage of the method 100), which recovers the magnetic fractions and their alloys. The wet selection step 104 is operated continuously, in order to recover in a given batch the fines fractions which will be subsequently treated in a chemical chamber.
The fourth step of method 100 is separation by filtration and cycloning step 108. The effluent # 1 that leaves the magnetic unit 106 and which accumulates in the primary tank can be subjected, depending on the situation, to a light oxidation phase in an aqueous medium. Effluent # 1 is introduced into the primary reservoir, where it resides for approximately fifteen minutes. At the exit of the primary deposit, the effluent is subjected to a first filtration and cyclone that retains the fractions from 0.2mm (200μp?) To 2.00mm. Depending on the results, these fractions are available for evaluation.
Effluent # 1 goes to the secondary storage tank where it also resides for fifteen minutes. At the outlet of the secondary tank, the effluent is subjected to filtration and secondary cyclonation where the fractions are separated from 80μp? up to 199μp ?.
The effluent # 1 passes to the tertiary deposit, where it also resides for fifteen minutes. Separation and cyclonation in the tertiary tank separate the fractions from 25μp? until Effluent # 1 Finishes its course in the fourth tank. After residence for fifteen minutes, the effluent is subjected to separation and cyclonation where the fractions are retained from 5μ? up to 24μp ?.
The filters use centrifugal force to separate - 1 - and make possible the withdrawal from the effluent # 1 of the fines fractions whose size is from approximately 0.005mm (5μ ??) to 2.00mm, while the fractions of fines that have a dimension of less than 5μ? t ?, ie the fines remain in suspension in the effluent # 1 obtained after the separation stage by the filter 108. The effluent # 1 is loaded more or less with fines and, according to the quality of the water, the latter will be recirculated towards the selection by washing 104 (effluent # 2) or towards the chemical chamber (effluent # 3) to chemically treat the soils.
The fifth stage of the method 100 is a step to place the fines of the metal contaminant 110 in a solution. The effluent # 1, which results from the final separation stage 108, contains the fractions of 5μp? or less and part of this effluent is directed towards a chemical conditioning tank and becomes effluent # 3 when the chemical products and the soils to be treated have been added. In this stage acids are added and the metals associated with the fines and receptive to the acids become soluble. Effluent # 3, acidic, resides in the acidification tanks for approximately 30 to 40 minutes and is then filtered. The residual filtration (acid sludge) is neutralized (step 114) in a precipitation and neutralization tank, dehydrated, if necessary, and available for evaluation as a function thereof. - - properties. The effluent # 3 passes to other precipitation and neutralization deposits, for the purpose of neutralizing by means of the addition of bases, coagulants, coagulation aids and it becomes effluent # 4 of stage 112.
Step 112 consists of precipitating the metal ions from effluent # 4 in order to cause flocculation and neutralization of the metal contaminant that is in the suspension with the fines of effluent # 4. Flocculation produces lumps, which decant, thus forming a neutralized sludge in the effluent. The effluent # 4 resulting from the metal precipitation step 112 is subjected to a filtration step to collect the neutralized sludge 114 and allow recirculation in the process of the effluent # 5, conditioned in step 116.
The step of precipitating metal ions 112 comprises the addition of bases, coagulants and coagulation aids, if necessary, to effluent # 3 resulting from step 110, in order to cause precipitation of the metallic contaminant located therein. . The resulting precipitate is decanted and forms a sludge through a filter.
The method 100 further comprises a step to treat the sludge 114 produced by steps 110 and 112, as well as a step to condition the effluent # 116.
The method 100 will now be described in more detail, - - with reference to Figure 2.
Dry selection stage 102 The contaminated soils are first loaded in a receiving tray where they undergo a dry selection consisting of subjecting the contaminated soils to the action of a rotating screen. The material travels inside the container; each steel bar separates less than 15 cm. Due to the rotation, the floors are distributed over the entire surface of the container, and the coarse fractions retained in the screen are expelled on one side and fractions of 75.0mm or less are passed through the screen mesh and this material It is directed towards a wet selection unit for its treatment. The contaminated soils are subjected to dry selection, which are homogenized and fragmented into coarse fragments; the stones and waste are reused.
The rotating screen has a circumference of more than one (1) meter and a length of more than 3 (3) meters. Steel wire cloths are tensioned over the entire length of the drum and separated by less than 15cm. The metallic fabrics are configured in order to retain the fragments that have a dimension greater than 75.0mm. The fragments whose dimension is greater than 75.0mm are sampled and analyzed, in order to verify their quality. Depending on the results of the analyzes, they can be either directly assessed or - - directed towards a mobile washing area. The components of contaminated soils that have a dimension between Omm and 75.0mm, that is, the components of 0-75. Omm are directed towards the reception cell 1 (Figure 2) of the treatment plant.
Wet selection stage 104 With reference to Figure 2, the components of 0-75. Omm are loaded in the cuvette 1 for the wet selection step 104. The cuvette 1 may comprise a grid in order to limit the size of the components in the outlet of the cuvette. At the exit of cuvette 1, the components of 0-75. Omm are directed by means of a dry conveyor 6 to the wet selection unit 104 comprising a washing screen 10, which itself comprises three levels of horizontal selection. The washing screen 10 is provided with pressure injectors that allow the injection of the washing liquid. Submit the components 0-75. Omm to the washing liquid under pressure allows to separate the components from 0-99. Omm and the coarse particles, that is to say, those whose dimension is greater than 2.00mm. In effect, while the fine particles pass through the three horizontal levels 10, the coarse particles are retained therein; concurrently, as a result of pressure washing, the particles of the metallic contaminant located on the surface of the coarse particles flow with the - - fine particles in the washing liquid.
In the present embodiment, the washing liquid may be aqueduct water or water enriched with surfactants and / or reagents. The rate of circulation of soil materials by the dry conveyor 6, which is typically a conveyor device, varies between 40 and 100 tons (metric) / hour, considering that the maximum flow of the washing liquid is 1890 liters per hour. minute (500 USGPM (gallons per minute of the EU)), that is, 31.5 liters per second (1 / s). Typically, the three horizontal levels of the screen 10 comprise different sizes of mesh, in order to retain in three different stages the pebbles, gravel and finally the coarse sand with grains larger than 2.00mm in diameter.
Conventionally, coarse particles contain pebbles, gravel, sands and in general, particles whose diameters are greater than 2.00mm. These are directed towards a ferrous and non-ferrous separator 9 by means of the dry conveyor 6 '. The coarse particles are thus directed towards the ferrous and non-ferrous separator 9. The ferrous materials are stored in a storage container 18 in order to make possible its recovery. Clean non-ferrous materials, ie thick non-ferrous particles larger than 2.00mm free of contaminants are directed to a storage area 14. The fractions are separated from the next way to make possible its verification in view of an assessment: fractions from 5.00mm to 75.0mm, fractions from 2.50mm to 4.99mm and fraction from 2.00mm to 2.49mm.
Thus separated from the coarse particles as a result of the wet selection step 104, the washed fine particles (0-1.99mm) and the washed metal contaminant end up in suspension in the wash liquid, thus forming the effluent # 1 resulting from , step 104. The effluent from step 104 is directed through the conduit to the magnetic unit 5 of step 106.
Magnetic selection stage 106 Thus separated from the coarse particles as a result of the wet selection step 104, the fine particles as well as the metal contaminant end in suspension in the effluent # 1 and is directed through the conduit to the magnetic unit 5, step 106. Magnetic separation allows to retain the magnetic components included in the floors. Then, the effluent # 1 continues its course towards the storage tank 15 for specific storage and filtration purposes 108.
Separation stage by filtration and cyclone 108 At the exit of step 106, effluent # 1 proceeds to the storage tanks of 15-1 to 15-4 for storage and filtration purposes Specifies 108. Storage tanks 15 (here 15-1 to 15-4), which typically have a capacity from 30,283 to 37,854 liters (8,000 to 10,000 US gallons), are provided with agitators (mechanical or air) to Keep the fine particles in suspension.
The effluent # 1 from step 106 is then pumped and accumulated in the primary reservoir 15-1, where the effluent # 1 can be subjected, depending on the situation, to a light oxidation phase in an aqueous medium. The effluent # 1 is then introduced into the primary reservoir 15-1 and resides therein for approximately fifteen minutes. At the outlet of the primary reservoir 15-1, the effluent # 1 is subjected to a first filtration and cyclone 11-1 (dehydration), which retains the fractions from 0.2mm (200μ ??) to 2.00mm Depending on the results of the analysis , this fraction is available for evaluation.
The effluent # 1 is moved to the secondary storage tank 15-2 where it also resides for approximately fifteen minutes. At the outlet of reservoir 15-2, effluent # 1 is subjected to filtration and secondary cycloneage 11-2, whereby fractions are separated from 80 μp? up to 199μ? t ?.
Effluent # 1 travels to the tertiary deposit 15-3, and the residence period is also fifteen minutes. Separation and cycloneage 11-3 in the tank - - tertiary 15-3 separates the fractions from 25μ ?? up to 79μ ?? Effluent # 1 ends its course in tank four 15-4 and, after 15 minutes of residence, the effluent is subjected to separation and cycloneage 11-4 whereby fractions are retained from up to 24μ ?? The filters used to decant effluent # 1 use centrifugal force and allow the removal of fine fractions from effluent # 1 whose dimension is approximately 0.005mm (5μt?) To 2.00mm while fine fractions that have one dimension less than that is, the fines, remain in suspension in the effluent # 1 obtained after the separation step by the filter 108. The effluent # 1 is loaded more or less with the fines and, according to the quality of the latter, is recirculated to the wash screen (effluent # 2) or to the chemical chamber to treat the fines.
The fourth storage tank 15 is provided with a filtration and cycloning system (11) and is installed in parallel. They are designed to operate at the maximum flow provided at the entrance, that is, 1,890 liters per minute (500 USGPM). Each filter is used to remove fractions of fines that have variable sizes from the effluent. The filtration and cyclone system 11 allows extracting from the effluent # 1 of stage 106 the particles whose diameter is approximately between 5μ? and 2.00mm, which means to form sludge resulting from step 108. Depending on the analyzes, these soils are treated in a chemical chamber or are evaluated depending on their quality. On the other hand, the particles having a smaller diameter at 5μp ?, referring to the lighter ones, remain in suspension in the washing liquid and constitute the effluent of step 108.
The sludge resulting from stage 108, which contains fractions of fines that measure between 5μp? and 200μp? and between 200μp? and 2.00mm are transported through the conveyor 6"to a storage area at a downstream point 14. The effluent # 1 that flows from the fractions when stored in the storage area can be recovered by means of drains and water. go back to a conditioning line.
Typically, the wash effluent from step 108 has a maximum flow of 500 USGPM. This effluent (effluent # 2) is returned to the wet selection unit 10 so that the soils and / or part of this water (effluent # 3) can be used to treat the fines in the chemical chamber. This is made up of the following elements: • the washing effluent, neutral, or with the possibility of surfactants, oxidants or others. • soil particles that have a diameter of less than 5μp? • an amount of metallic contaminant, either in the form of particles that have a diameter of. less than 5μp, or dissolved in the washing liquid.
The concentration of suspended matter (MIS) in the effluent from step 108 depends on the nature of the soils that are treated by the method 100. For example, when the soils are essentially made up of sands, the effluent from step 108 it tends to be preferably liquid due to the low concentration of MIS, including the metal contaminant particles. Conversely, a soil constituted by a clayey matrix may result in an effluent from step 108 whose concentration of MIS may be higher.
Stage of placement of metal contaminant fines in a solution 110 The fines of 5 to 200μ ?? from step 108 are analyzed and, depending on the results, are evaluated or treated in the chemical chamber to reduce the concentration of metals. The step of placing the fines of the metallic contaminant 110 in a solution comprises the sub-stages: • acid dosage • a mixture of the acid with the effluent • coagulant and coagulant auxiliary dosing (if necessary) • decanting the MIS (if necessary), and • a filtration Acid dosage The acid dosage is carried out as a function of the nature of the metal contaminant, that is, according to the types and concentrations of metals that are contained therein, to be placed in a solution and of the pH decisions to be fulfilled. to get this placement in the solution. Measuring the pH by means of pH meters makes it possible to follow the reaction. The acid dosage is carried out while part of the effluent # 1 of step 108 is directed through the conduit to the mixing tanks 16 (with mechanical or air agitation), ie, the tanks of 16-1 to 16- 3, adapt to place the metals in a solution. The dehydrated fines from 5 to 200μp? they are incorporated with effluent # 1 and mixed with the acid. The amount of water to be added is determined according to the percentage of fines to be treated, the type and concentration of contaminants that are present.
Mixing the acid with the effluent Mix the acid with the effluent # 1 and the fines to produce the acidic effluent # 3.
Depending on the dosage, an acid solution such as hydrochloric, sulfuric or nitric acid is injected into a conduit when the effluent # 1 from step 108 is directed - - to the mixing tanks 16. Each of the mixing tanks 16 typically has a capacity of 30,283 to 37,854 liters (8,000 to 10,000 gallons of E.ü.) and is provided with an agitator, with which the effluent # 1 of Stage 108 and the injected acid solution are mixed to produce effluent # 3. The retention time in the mixing tanks 16 is typically in the order of 40 minutes for a continuous mode of feeding. The mixing tanks 16 can also be operated in a batch mode, ie in batch mode, for example in the case where a reaction time of more than 40 minutes is necessary.
Dosage of coagulant and coagulant auxiliary Then, if necessary, a coagulant, for example alum, ferric sulfate, or an equivalent, a coagulant or flocculant auxiliary in the conduit can be added to the effluent at the outlet of the acid mixing tanks 16.
Decantation of MIS If necessary, adding the coagulant and the coagulant auxiliary serves to cause the coagulation of the MIS in the effluent at the outlet of the mixing tanks 16 and then allow the decantation. The contact tanks 16 have a double purpose: to serve as a contact deposit to ensure the coagulation of MIS and then allow a static decantation in order that the acid sludge thus formed settle in the lower part of the deposits.
Filtration Typically, at the outlet of the contact tank or acid mixture 16, the effluent # 3 loaded with acidified metals and fines (5 μ ?? to 200 μp) is pumped and should be filtered 11-5 by means of a filter for Separate the following products: • Effluent # 3 loaded with dissolved metals containing fines (0-25 microns); must be neutralized in step 112 (precipitation of metals) • Acid sludge from 25 to 200 microns The treated fines must be neutralized and handled in the stage for sludge treatment 114 Typically, effluent # 3 loaded with metals at the outlet of filter 11-5 has a maximum flow of 80 USGPM. The pH of effluent # 3 is less than 5.0 and depends on the nature of the metals to be placed in a solution. It contains fines of 25 micras and minors (0-25 micras), which must be neutralized and filtered.
Precipitation of metal ions in step 112 The acidic effluent # 3 (0 to 25 μp?) At the outlet of the filter 11-5 generally contains dissolved ions of the metal contaminant.
- - The metal ion precipitation stage 112 of effluent # 3 comprises: • dose and mix the base- with effluent # 3 • decant MIS · filter Dosing and mixing the base with the effluent The acidic effluent # 3 (0 to 25 μp?) At the outlet of the filter 11-5 is collected through a conduit and directed towards the deposits for the precipitation of metal ions 17-2 and 17-3. A basic solution, for example sodium hydroxide or other equivalent bases, is injected into the conduit between the filter 11-5 and the deposit for the precipitation of the metal ions in order to precipitate the metals or neutralize the effluent # 3 and its content. Then, if necessary, a coagulant, for example alum, ferric sulfate or an equivalent, and a coagulation aid can be added through the conduit to the effluent.
This effluent # 4 is basic or neutral depending on the metals to be precipitated. The precipitation reservoir (s) 17 of the effluent # 4 is provided with a stirrer in order to carry out the mixing. The method of operation of the system for precipitating metals, that is, continuously or in batches, is determined by the steps previously described, as well as by the reaction time, the - - pH required to form the metal precipitates. The dosage of the basic solution depends on the nature of the metal ions in solution in the acidic effluent # 3 at the outlet of the filter 11-5 and under the pH conditions to be achieved in order to cause the precipitation of the metal ions. For this purpose, pH measurements are made by means of pH meters and allowing monitoring Decantation of MIS If necessary, adding the coagulant, the coagulant auxiliary and the flocculants serves to originate the decanting of the MIS in the effluent at the outlet of the mixing tanks 17. The deposits have a double purpose, that is, to serve as a contact deposit to ensure the coagulation and flocculation of the MIS as well as to subsequently allow a static decanting of the lumps formed by the flocculation, so that the neutralized or basic sludge thus formed is deposited in the lower part of the deposits.
Filtration According to the mixing, the neutralized effluent # 4 at the outlet of the deposit for the precipitation of the metal ions 17 is directed towards the filtration and separation unit 11-7 to separate the precipitates formed subsequent to the injection of the base. This stage allows the separation of the effluent containing metals - - precipitates of 0-25 microns. The filter unit allows to filter at 5 microns. Having like this: • Neutralized effluent The neutralized effluent that flows at the outlet of the filter has a maximum flow equivalent to that of the inlet. The pH of the effluent is between 6.0 and 8.0.
• Neutralized fines from 5 to 25 microns The neutralized fines are directed to the unit to treat the sludge 114 by dehydration and, subsequently, an outflow conveyor is used to be analyzed before handling.
Stage to treat sludge 114 The activities that constitute this stage of treatment include the dehydration of the sludge generated in the different stages of the chemical treatment process (stages 110 and 112) and the management of the latter. There are two (2) types of sludge: • Acidic sludge from 25 to 200 microns (stage 110) • The neutralized sludge from 5 to 25 microns (step 112) At the outlet of filter 11-5, the acidic sludge of 25 to 200 microns should be neutralized so that they can be handled. These are pumped to a deposit (or equivalent) 17-1 and neutralization products are injected into the latter. The conditioned sludge is directed towards the unit of dehydration of centrifugal filter type 11-6, in order to increase the dryness of the latter. At the exit of the dehydration unit, the material at the exit of the conveyor (or equivalent) is cleaned and neutralized. It will be sampled to determine the final management mode.
The neutralized sludge from 5 to 25 microns is directed towards the dehydration unit of the centrifugal filter 11-7, in order to increase the dryness of the latter and to use an output conveyor (or equivalent) to be analyzed before the final handling. The neutralized effluent extracted from the sludge is recovered and returned to the storage and neutralization tanks to recirculate the water in the process 116.
Stage to condition the effluent after the precipitation of the metal ions 116 The effluent collected at the exit of the chemical chamber is reused as process water. The activities that constitute this stage of the treatment are the following: • adjust the pH (if necessary and store the water) • recirculation Water for surface drainage can also be integrated into this conditioning line.
PH adjustment The neutralized effluent that originates from the precipitation unit 112 passes to the neutralization and storage area 4. An acid or a base can be injected at the entrance of the first reservoir if the water is not neutral for recirculation. The minimum retention time in a deposit is in the order of 40 minutes for a continuous feeding mode. The system will be operated in a discontinuous mode "(batch)", if the reaction time is longer. The target pH to be met must be between 6.0 and 8.0 before recirculation in the process. The continuous measurements of the pH by means of pH meters allow to follow the established points.
Recirculation When the quality of this water is acceptable to allow its reuse as process water within the treatment line, it is pumped into the distribution conduit.
The method 100 may further comprise the handling and treatment aspects of the gaseous effluents.
Control and analysis of treated soils Different fractions of soil resulting from the application of method 100 are stored in special areas. In summary, these fractions are the following: • pebbles • gravel • Thick and fine sands - - • fine particles (200μ ?? to 2.00mm in diameter); Y • sludges containing fines whose dimension is less than 200 μ.
These different fractions are characterized and analyzed in order to determine their level of contamination. If, for a given fraction, the contamination rate remains high, it can be returned to undergo method 100 again, possibly with an adjustment as a consequence of the operating parameters. Soils will be ordered later as a function of the quality criteria and the management methods that will be applied to contaminated soils. Depending on the results of the analyzes obtained, these different soil fractions can be reused for different uses, that is, assessed as a function of their characteristics with respect to the applicable criteria.
In Figure 2, it is noted that reference 3 refers to "dosing" tanks and pumps; reference 7 refers to a receiving cuvette; reference 8 refers to a return to water treatment; reference A refers to tanks for storing water; reference B refers to a water / oil separator; Reference C refers to filters under pressure; reference D refers to tanks for storing clean water; and the DP reference refers to a - - level drainage.
Although the present invention has been described in the foregoing by means of a non-limiting modality for the purpose of explanation, this modality may be modified at will, within the scope of the invention, without departing from the spirit and nature of the subject which is the object of the invention.

Claims (21)

1. A method for removing inorganic contaminants from soils, the method comprising: select contaminated soils to obtain coarse fractions and fine fractions; wash the selected soils with a washing effluent in order to obtain the first effluent that comprises the washing liquid and the floors that flow in the screen; and screening the soils in order to retain the coarse fractions and, concurrently, retain the fractions that flow from the screen and that comprise fines and particles with dimensions greater than those of the fines; subjecting the washing effluent to an extraction of the particles whose dimensions are greater than those of the fines, and thus obtaining a second effluent that is returned to the washing unit and / or a fraction that can be returned to the chemical chamber; produce in the chemical chamber, the extraction of the second effluent containing the contaminated fines to dissolve the metals thereof in order to obtain a third effluent; Y produce the precipitation and / or neutralization of the third effluent and extract the precipitate by filtration, in order to obtain a fourth effluent; whereby the inorganic contaminant is precipitates for extraction in a fourth effluent.
2. The method of claim 1, whereby the inorganic contaminant contains a metal contaminant.
3. The method of claim 2, whereby the metal contaminant contains more than one metal element.
4. The method of claim 2, whereby the metal contaminant is selected from the group consisting of aluminum, arsenic, silver, barium, cadmium, chromium, cobalt, copper, tin, iron, manganese, magnesium, mercury, molybdenum, nickel, lead, sulfur, selenium, sodium, zinc, and any combination of the above.
5. The method of claim 1, whereby the production of an extraction of the third effluent comprises the addition of an acid to the first effluent.
6. The method of claim 1, whereby the production of the flocculation of the third effluent comprises the addition of a coagulant, a coagulation aid or a flocculant.
7. The method of claim 1, whereby the production of a precipitation of the fourth effluent comprises the addition of a base, coagulant or flocculant to the third effluent.
8. The method of claim 1, by the wherein the extraction of the particles having a dimension greater than that of the fines comprises a filtration of the particles having a dimension greater than that of the fines.
9. The method of claim 1, whereby washing the floors comprises the addition of surfactants, of oxidants, to the first effluent.
10. The method of claim 1, whereby an effluent substantially free of contaminants becomes a fifth effluent.
11. The method of claim 10, whereby the fifth effluent is recirculated in the treatment process.
12. The method of claim 1, whereby after the selected soils have been washed, the first effluent is subjected to a magnetic effect in order to remove the magnetic fractions therefrom.
13. The method of claim 1, whereby in the step of subjecting the washing effluent to an extraction, this extraction of fine fractions is carried out by means of filtration and cycloning separation, the finest particles remaining in suspension in the first effluent after this stage, thus becoming the first effluent in the second effluent.
14. The method for removing inorganic contaminants from soils, the method comprising: a) washing a contaminated soil with a washing effluent in order to obtain a first effluent comprising the washing effluent and the fines, whereby particles of larger dimensions are retained than those of the fines; b) subjecting the first effluent to an extraction of the particles of larger dimensions than those of the fines and thus obtaining a second effluent that is returned to the washing unit and / or a fraction that can be moved to stage c); c) produce the extraction of the second effluent containing the contaminated fines to dissolve the metals thereof, in order to obtain a third effluent; Y d) producing the precipitation and / or neutralization of the third effluent and extracting the precipitate by filtration, in order to obtain a fourth effluent; whereby the inorganic contaminant is precipitated by extraction in a fourth effluent.
15. The method of claim 14, whereby prior to step a), there is a step to separate contaminated soil into coarse fractions and fine fractions.
16. The method of claim 15, whereby the separation is carried out by selection.
17. The method of claim 14, wherein step a) is carried out by wet selection.
18. The method of claim 14, by the which before step b), there is a stage in which the first effluent is subjected to a magnetic effect in order to remove the magnetic fractions thereof.
19. The method of claim 14, whereby, after step d), the effluent substantially free of contaminants becomes the fifth effluent.
20. The method of claim 19, whereby the fifth effluent is recirculated in the treatment process.
21. A method for removing inorganic contaminants from soils, the method comprising: a) submit a first effluent containing inorganic contaminants to filtration in order to extract larger particles from the fines and obtain a second effluent; b) produce the extraction of the second effluent containing the contaminated fines to dissolve the metals thereof, thus obtaining a third effluent; Y c) producing the precipitation and / or neutralization of the third effluent and extracting, by filtration, the precipitate, in order to obtain a fourth effluent; whereby the inorganic contaminant is precipitated by extraction in a fourth effluent.
MX2010011908A 2008-05-02 2009-05-04 Method for removing inorganic contaminants from soils via a physicochemical extraction technique. MX343510B (en)

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CN102601106B (en) * 2012-03-08 2014-12-24 中国科学院过程工程研究所 Ectopic leaching restoring device and restoring method for chromic slag polluted soil
CN104190701A (en) * 2014-09-19 2014-12-10 中节能六合天融环保科技有限公司 Leaching method for remediation of arsenic polluted soil by using magnetic separation
CN104249077B (en) * 2014-10-10 2016-05-11 福建农林大学 A kind of leaching repairing method of molybdenum polution soil
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