Classifications

• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F3/00—Biological treatment of water, waste water, or sewage
  • C02F3/30—Aerobic and anaerobic processes
  • C02F3/302—Nitrification and denitrification treatment
  • C02F3/305—Nitrification and denitrification treatment characterised by the denitrification
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F3/00—Biological treatment of water, waste water, or sewage
  • C02F3/34—Biological treatment of water, waste water, or sewage characterised by the microorganisms used
  • C02F3/346—Iron bacteria
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/70—Treatment of water, waste water, or sewage by reduction
  • C02F1/705—Reduction by metals
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2101/00—Nature of the contaminant
  • C02F2101/10—Inorganic compounds
  • C02F2101/16—Nitrogen compounds, e.g. ammonia
  • C02F2101/163—Nitrates
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2101/00—Nature of the contaminant
  • C02F2101/10—Inorganic compounds
  • C02F2101/16—Nitrogen compounds, e.g. ammonia
  • C02F2101/166—Nitrites
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F3/00—Biological treatment of water, waste water, or sewage
  • C02F3/28—Anaerobic digestion processes
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F3/00—Biological treatment of water, waste water, or sewage
  • C02F3/30—Aerobic and anaerobic processes
  • C02F3/302—Nitrification and denitrification treatment
  • C02F3/307—Nitrification and denitrification treatment characterised by direct conversion of nitrite to molecular nitrogen, e.g. by using the Anammox process

Definitions

• the present invention relates to a process for the treatment of nitrogenous materials, and in particular to a continuous process of biologically assisted inorganic denitrification in a liquid medium, without the production of ammonium, using a biogenic carbonated green rust and the use of such a green rust for the reduction of nitrite ions into nitrogenous gases.
• Nitrate ions exist in natural waters in the absence of pollution. Their concentration, then, does not exceed 3 to 5 mg / 1 in the surface waters of rivers, canals, lakes, ponds and some mg / 1 in groundwater. However, the levels of nitrate ions in these waters have been steadily increasing in recent years and reflect a pollution of the resource linked to human activities (industrial and domestic discharges from agriculture and livestock, effluents from livestock, food surface waters by polluted groundwater, "leakage” from industrial and inhabited areas) and in particular surface activities (dense urban and industrial occupancy and / or intensive agriculture, traditional medium intensity agriculture, dispersed rural housing).
• the concentrations of nitrate ions in the aquifers are generally all the higher as they are sensitive, poorly protected, influenced by urbanization, industrial sites and intensive agriculture or livestock farming. These concentrations also vary with the speed of circulation-renewal of water in the aquifers.
• the maximum permitted limit is 50 mg / l of nitrate ions in drinking water supplies.
• the upper limit of a "good ecological status" of water was set at 25 mg / 1 in the Water Framework Directive (WFD) of 23 October 2000.
• Nitrate ions are not toxic in themselves. It is their transformation into nitrite ions and nitroso compounds (nitrosamines and nitrosamides) which can cause characteristic disorders such as methemoglobinemia or cyanosis of the infant, reproductive disorders, endocrine or vitamin effects in animals and finally the occurrence of digestive cancers in humans. In addition, the high levels of nitrate ions are at the origin of the proliferation of macroscopic green algae throughout the Brittany region.
• nitrate ions consist of a process for the treatment of biologically or physicochemically polluted waters using ion exchange resins. These techniques are very effective in the short term, but expensive in investments and in operation.
• purely biological denitrification ie bacterial denitrification
• bacterial denitrification defined as the reduction of nitrate ions to gaseous nitrogen by means of denitrifying bacteria, has been massively studied in the context of wastewater treatment.
• Synthetic green rust such as GR S04 , GRci and GRco 3 , generally have a ratio of Fe (II) / Fe (III) molar concentrations ranging from 2 to 3 depending on the pennant used and it has been shown that the reduction of nitrate ions in The presence of such synthetic green rust leads to the exclusive formation of ammonium and magnetite (Hansen et al., Environ Science Sci., 1996, 30, 2053-2056 and Applied Clay Science, 2001, 18, 81-91).
• a carbonated Fe (II) -Fe (III) hydroxide also called ferrous-ferric hydroxycarbonate or ferrous-ferric oxyhydroxycarbonate or carbonated green rust, corresponding to Fe formula 6 n (i -X) m 6x Oi2H2 Fe (7- 3 X) CO 3, for the implementation of an oxidation-reduction process of the nitrate ions in the presence of ferric-reducing bacteria.
• x is defined as the ratio of Fe (III) / [Fe (III) + Fe (II)] molar concentrations.
• the ferrous-ferric hydroxycarbonate has a ratio of Fe (II) / Fe (III) molar concentrations ranging from 0.5 to 2 (corresponding to a value of x varying from 0.33 to 0.66) and oxide by reducing nitrate ions to gaseous nitrogen.
• the oxidized phase obtained having a ratio of Fe (II) / Fe (III) molar concentrations of less than 0.5 (x> 0.66), is in turn reduced in the presence of ferri-reducing bacteria to regenerate the hydroxycarbonate
• Ferrous-ferric starting material having a ratio of Fe (II) / Fe (III) molar concentrations ranging from 0.5 to 2 without substantial structural changes.
• Examples 1 and 2 describe, on the one hand, the preparation of a biogenic carbonaceous green rust (the ratio of Fe (II) / Fe (III) molar concentrations ranging from 0.5 to 2) by bacterial reduction of iron ( III) to iron (II) in a ferric oxyhydroxycarbonate, and secondly, the catalytic reduction of nitrate ions to gaseous nitrogen in the presence of this carbonated green rust.
• the inventors have set themselves the goal of providing a process for the treatment of nitrogenous materials, in particular for the treatment of nitrate / nitrite ions present in a liquid medium, which is simple and inexpensive to implement, usable at the scale industrial, for example in sewage treatment plants, without the production of ammonium.
• the subject of the present invention is therefore a biologically assisted inorganic denitrification method in a liquid medium, said process being characterized in that it comprises the following steps: i) a step of preparing a carbonated green rust by bioreduction of an Fe (III) oxyhydroxide under anaerobic conditions in the presence of a culture of at least one bacterium having a ferri-reducing activity until obtaining a carbonate green rust with a ratio of Fe (II) / Fe (III) molar concentrations ranging from 1 to 1.5;
• step iii) a step of bioreduction of said Fe (III) produced in step ii), in the presence of a culture of at least one bacterium having a ferri-reducing activity to obtain a carbonated green rust with a molar concentration ratio Fe (II) / Fe (III) ranging from 1 to 1.5.
• the nitrite ions could be reduced and converted into a gaseous mixture comprising N 2 O and N 2 and without generating ammonium, in the presence of a biogenic carbonate green rust having a ratio Fe (II) / Fe (III) molar concentrations typically vary from 1 to 1.5. Outside the value range [1-1,5] of the Fe (II) / Fe (III) molar concentration ratio, either the reduction of nitrite ions can lead to ammonium or the reduction kinetics is very low. slow and therefore unsuited to the use of this process on an industrial scale.
• said step ii) leads to the formation of one or more nitrogen gases, without production of ammonium, and to the production of Fe (III) associated with a solid phase comprising one or more Fe oxyhydroxides (III). and / or one or more carbonated Fe (II) -Fe (III) hydroxides.
• Carbonated Fe (II) -Fe (III) hydroxides means biogenic carbonate green rust obtained in step i) and which has not reacted in the following step ii), especially when this step is introduced in excess relative to the nitrite ions in said step ii).
• the Fe (III) oxyhydroxide used in the step i) of preparing a carbonated green rust having a ratio Fe (II) / Fe (III) molar concentrations ranging from 1 to 1.5 is chosen from lepidocrocite ( ⁇ -FeOOH), ferric green rust (Fe m 6 O 2 H 8 CO 3 ), ferrihydrite ( 5FeOOH.nH 2 O), in order to favor a complete bioreduction.
• steps i) and iii) can be independently carried out in the presence a pure culture of at least one bacterium with a ferri-reductive activity.
• the bacteria having a ferri-reducing activity that can be used during steps i) and iii) of the process according to the invention may be independently selected from the bacterial species of aquatic environments belonging to the genera Shewanella, Geobacter, Pseudomonas, Desulfovibrio, Geothrix and Pelobacter. . It is preferred to use the bacteria of the genus Shewanella and even more preferably the bacteria chosen from S. putrefaciens CIP 59.28, S. putrefaciens CIP 80.40 and S. oneidensis MR1.
• the bioreduction time during step i) is preferably at least about 20 hours.
• the bioreduction time during step iii) preferably varies from about 5 hours to about 5 days depending on the oxidation state of the system.
• the concentration of ferri-reducing bacterium during steps i) and iii) is preferably greater than 10 CFU / ml. Then, the concentration of Fe (III) during steps i) and iii) is preferably less than 400 mM.
• the contact time during step ii) is preferably less than 5 days, so as to avoid the formation of undesirable side products, such as for example magnetite.
• the contact time between the nitrite ions and the carbonated green rust during step ii) preferably varies from 1 hour to 48 hours approximately.
• step ii) The amount of green rust used in step ii) is advantageously such that the ratio of molar concentrations [Fe (II) ions present in the green carbonate rust] / [nitrite ions] is at least 3, in order to to favor a complete reduction of nitrite ions as well as the production of nitrogen gas as final product.
• steps ii) and iii) can be carried out simultaneously in one and the same step.
• the process is carried out continuously and said steps ii) and iii) can then be repeated until the total possible depletion of the nitrite ions in the starting liquid medium.
• the reduction of nitrite ions is rapid, of the order of a few hours, and reproducible with the assurance of never leading to the production of ammonium.
• the oxidation of biogenic carbonated green rust by nitrite ions leads to the production of one or more Fe (III) oxyhydroxides and / or one or more carbonated Fe (II) -Fe (III) hydroxides. , which in turn are new reducible by ferri-reductive bacteria.
• the process according to the invention operates from nitrite ions present in a liquid medium. Consequently, the nitrogenous materials present in said liquid medium, such as, for example, nitrate ions, must first be reduced to nitrite ions.
• the method further comprises a step ii 0 ) which is carried out prior to step ii) and during which the nitrate ions present in the liquid medium are reduced nitrite ions in the presence of a culture of at least one bacterium capable of reducing nitrate ions to nitrite ions.
• step ii 0 leads to nitrite ions only, without producing ammonium.
• step ii 0 leads to one or more nitrogen gases, without ammonium production.
• step ii 0) can lead to the production of ammonium.
• This step ii 0 ) of prior reduction of nitrate ions to nitrite ions can preferably be carried out using bacteria capable of reducing nitrate ions to nitrite ions chosen from the genera Alcaligenes, Paracoccus, Thiobacillus, Vibrio, Desulfovibrio, Shewanella, Micrococcus, Geobacter, Pseudomonas and Bacillus.
• bacteria capable of reducing nitrate ions to nitrite ions chosen from the genera Alcaligenes, Paracoccus, Thiobacillus, Vibrio, Desulfovibrio, Shewanella, Micrococcus, Geobacter, Pseudomonas and Bacillus.
• step ii 0 ) of prior reduction of nitrate ions to nitrite ions can be carried out in the presence of a culture of at least one strictly denitrifying bacterium, that is to say capable of reducing nitrate ions into nitrite ions without ammonium production.
• step ii 0 ) leads to one or more nitrogen gases without producing ammonium.
• Such a strictly denitrifying bacterium may be advantageously Paracoccus denitrificans.
• the reduction time during step ii 0 ) preferably varies from approximately 2 hours to 24 hours.
• the concentration of bacteria capable of reducing the nitrate ions to nitrite ions during stage ii 0 ) of the process according to the invention is preferably at least 10 'CFU / ml in order to favor a reaction time included in the range. of time mentioned above.
• the amount of green rust used during stage ii) is advantageously such that the ratio of the molar concentrations [Fe (II) ions present in green carbonate rust] / [ions nitrates] is at least 3, and this to favor a complete reduction as well as the production of nitrogen gas as final product.
• the steps ii 0 ) and ii) can be carried out simultaneously in one and the same step, that is to say that the nitrite ions generated in situ during step ii 0 ) are simultaneously reduced according to step ii).
• carbonated green rust with a ratio of Fe (II) / Fe (III) molar concentrations ranging from 1 to 1.5 obtained according to step i) is directly brought into contact with a liquid medium comprising nitrate ions. and culturing at least one bacterium capable of reducing nitrate ions to nitrite ions.
• the nitrite ions formed in situ in the liquid medium by contacting in step ii) with a green carbonate rust having a Fe (II) / Fe (III) molar concentration ratio varying from 1 at 1.5 lead to one or more nitrogen gases without ammonium production, in particular when step ii 0 ) uses one or more bacteria which allow bacterial denitrification and / or that they catalyze only the transformation of nitrate ions into nitrite ions.
• steps ii 0 ) and ii) are carried out simultaneously in one and the same step and that they use indigenous bacteria of a water when purified, ammonium production is completely avoided.
• step ii 0 When step ii 0 ) employs one or more bacteria resulting at least in part in a concealing reduction of ammonium nitrate ions, said step ii 0 ) can lead to the production of ammonium. However, the presence of green carbonate rust with a ratio of Fe (II) / Fe (III) molar concentrations varying from 1 to 1.5 in the liquid medium makes it possible to considerably reduce its production. Step ii 0 ) is then a concurrent step of step ii).
• identical bacteria may be used in steps ii 0 ) and iii) and the method according to the invention. They are selected from the genera Shewanella, Geobacter.
• the steps ii 0 ), ii) and iii) can then be advantageously performed simultaneously during a single step.
• the process is carried out continuously and said steps ii 0 ), ii) and iii) can then be repeated until any nitrate ions and nitrite ions in the liquid medium have been completely exhausted.
• step iii) of regeneration of the biogenic carbonated green rust it is preferable, however, to obtain a better yield, to decouple the step iii) of regeneration of the biogenic carbonated green rust, step ii 0 ) of reduction of the nitrate and nitrite ions.
• step iii 0 the step iii of regeneration of the biogenic carbonated green rust
• step ii 0 of reduction of the nitrate and nitrite ions.
• Step ii ( 0 ) represents bacterial denitrification and / or dissimilar reduction of ammonium nitrate ions. Since nitrite ions are systematic intermediates of microbial metabolisms of denitrification and dissimilar reduction of ammonium nitrate ions, step ii 0 ) can be divided into two sub-steps, a first sub-step ii 0 a) of ion transformation.
• Step i) represents the initial production of a carbonate green rust with a Fe (II) / Fe (III) molar ratio ratio varying from 1 to 1.5 of the process according to the invention, by bioreduction of an oxyhydroxide of Fe (III).
• Step ii) represents the abiotic denitrification by a carbonate green rust of Fe (II) / Fe (III) molar concentration ratio varying from 1 to 1.5 of the process according to the invention.
• Step iii) represents the dissimilatory reduction step of the Fe (III) of the process according to the invention allowing the regeneration of the green carbonate rust with a Fe (II) / Fe (III) molar concentration ratio ranging from 1 to 1.5.
• step ii the rate of abiotic reduction of nitrite ions by biogenic carbon green rust according to step ii) could compete with the bacterial reduction of nitrite ions corresponding to step ii 0 b), and thus take charge of this intermediary. It is then conceivable to couple the biological denitrification involving bacteria capable of reducing nitrate ions to nitrite ions (step ii 0 a)) and abiotic denitrification involving biogenic carbonated green rust capable of reducing nitrite ions to nitrogenous gases (step ii). )).
• the method according to the invention therefore has the advantage of being able to be carried out continuously and to lead to a denitrification of liquid media much faster than the known processes of the prior art (of the order of a few hours instead of Several weeks).
• the process is inexpensive, with autonomous regeneration involving low maintenance, ecological because based on natural processes, and adaptable to the concentration of nitrogenous material to be treated.
• nitrite ions occurs in the treatment plants whose operation is based on principles of biological nitrification / denitrification but also when mixed cultures are contained in the activated sludge.
• the intervention of biogenic carbon green rust on nitrite ions, whatever the metabolism present, prevents their accumulation and improve yields of nitrogen gas.
• the intervention of green rust during the reduction of nitrate ions can support about 50% of the nitrite ions present in the liquid medium. Ammonium production is not totally avoided but it is significantly reduced.
• the process according to the invention can be used in domestic and industrial wastewater treatment plants, in water purification plants and in manure treatment or sludge recycling plants.
• the invention also relates to the use of at least one carbonate green rust, of the formula II 6 Fe (i-X) Fe 2 m 6x Oi2H (7- 3x) CO3, wherein the ratio of Fe (II) / Fe (III) molar concentrations vary from 1 to 1.5 in order to catalyze, in a liquid medium, the nitrite ion reduction reaction without producing ammonium.
• Millipore Ultra-pure and oxygen-free distilled water (millipore water): Millipore, previously degassed water under N 2 (Alphagaz, impurities: H 2 O ⁇ 3 ppm, O 2 ⁇ 2 ppm C n H n ⁇ 0.5 ppm) and filtered using a sterile filter (filter pore diameter: 0.22 ⁇ )
• GR L or GR F biogenic carbonate green rust obtained by bioreduction of lepidocrocite (Lp) of formula ⁇ -FeOOH or by bioreduction of ferric green rust (RVF) of formula Fe m 6 (OH) 4 (OH) 4 CO 3 ) was ultrasonically dispersed in 59 mL of milliQ water and the pH was adjusted to 7.5 ⁇ 0.2 with 1M HCl solution. Two stock solutions of nitrite ions and Nitrate ions of 0.3 M concentration, oxygen-free were prepared.
• the initial concentration of nitrite ions or nitrate ions determined experimentally varies from about 4 mM to 7 mM. Indeed, in order to preserve the anaerobic conditions of the system, inaccuracy exists on the volume of the mother solution in nitrite ions actually injected into the closed bottles. This inaccuracy induces an initial concentration of experimentally calculated nitrite ions which may be slightly different from the theoretical initial concentration of nitrite ions.
• the concentration of Fe (II) to tai was determined after mixing 0.5 ml of a collected sample and 0.5 mL of a solution of HCl concentration of 1 M.
• the concentration of Fe (II) SO i u bi e was determined after filtering a sample on a Minisart brand cellulose membrane filter (filter pore diameter: 0.22 ⁇ ) and mixing 0.5 mL of the filtrate obtained and 0.5 mL of 1M HCl solution.
• the concentrations of Fe (II) to tai and Fe (II) n e i u bi were determined seconds after collection of each sample by the modified method of 1,10-phenanthroline (Fadrus and Maly, Analyst, 1975 , 100, 549-554).
• concentrations of nitrite ions, nitrate ions and ammonium were determined from the same filtered samples as those used for determining the concentration of Fe (II) solu bi e by ion chromatography with an apparatus sold under the trade name DIONEX ISC 3000.
• pH values in solution were determined using a pH meter sold under the trade name Consort C830 by Fisher Bioblock Scientific and calibrated at pH 4, 7 and 10 with Fisher Scientific standard solutions.
• the green carbonate rust obtained according to stage i) of the process according to the invention and the oxyhydroxides of Fe (III) (oxidized solid phases) obtained according to stage ii) of the process according to the invention were subjected to XRD analysis.
• the samples were taken under an argon atmosphere in a glove box (O 2 content of about 40 ppm) with a syringe and then placed directly on a silicon wafer. and dried in a vacuum desiccator.
• the pellet containing the dry sample was fixed in an anaerobic chamber.
• the green carbonate rust obtained according to step i) of the process according to the invention were subjected to analysis by transmission electron microscopy (TEM).
• TEM transmission electron microscopy
• a Philips CM 20 electronic microscope operating at 200 kV equipped with a dispersive energy spectrometer was used to observe the solid phases.
• a suspension of the green carbonate rust to be analyzed was rapidly dispersed in air on a grid covered with amorphous carbon and loaded into the microscope analysis support.
• the products were identified from selected area diffraction models and dispersive energy analysis.
• the green carbonate rust obtained according to stage i) of the process according to the invention was also subjected to transmission Mössbauer spectroscopy (SMT) analysis.
• SMT transmission Mössbauer spectroscopy
• Môssbauer spectroscopy in transmission was carried out from 8 K to 295 K with a Mössbauer cryostat with variable temperature close to the helium cycle, equipped with vibratory insulation manufactured by Cryo Industries of America, using a spectrometer sold under the trade name Môssbauer constant acceleration with a source of cobalt 57 embedded in a rhodium matrix and an activity of 50 mCi (millicuries) and calibrated with an iron sheet 25 ⁇ thick at room temperature.
• the spectra were adjusted using Lorentzian profile lines.
• inocula of strains of Shewanella putrefaciens bacteria CIP 59.28 equivalent to the Collection of American Type Cultures (ATCC) 12099 were prepared according to the method described in Ona-Nguema et al., Geochim. Cosmochim. Acta, 2009, 73, 1359-1381.
• the cell density of each inoculum was determined by the number of colony forming units (CFU).
• CFU colony forming units
• a ferri-reducing bacterium concentration of 5.75 ⁇ 10 9 CFU / ml was used in the following two bioreductions.
• the bioreduction of the RVF in biogenic green carbon rust GR F was carried out according to the procedure described as follows: an RVF suspension of concentration 80 mM and pH 7.5 ⁇ 0.2 was prepared in glove box under atmosphere N 2 in water and containers previously sterilized by autoclave for 20 minutes at a temperature of 120 ° C. Only RVF was not sterilized because heating at 120 ° C alters its structure. Sterility of the preparation environment was ensured with a Hofmann electric burner sold by Horo Dr. Hofmann GmbH. Then, a suspension of Shewanella putrefaciens bacteria CIP 59.28 was added.
• FIG. 3a shows a DRX analysis of the RVF (lower part) and of the biogenic carbonate green rust obtained GR F after 14 days of RVF bioreduction (characteristic peaks labeled GR, upper part).
• FIG. 3b shows a DRX analysis of the Lp (lower part), the biogenic carbonate green rust obtained GR L after 14 days of bioreduction of the Lp (intermediate part) and after 33 days of bioreduction of the Lp (characteristic peaks denoted GR , upper part).
• the intensity in arbitrary units, ua is a function of the angle 2 Theta (2 ⁇ ).
• green rust GR L and GR F respectively obtained after 33 days of bioreduction from Lp and 12 days of bioreduction from RVF were centrifuged in a glove box under nitrogen flow, washed twice. with milliQ water, and dried to be characterized by SMT and MET analyzes.
• FIGS. 4a and 4b respectively show the hexagonal form of the crystallites isolated from green carbonate rusts GR F and GR L observed by transmission electron microscopy (TEM).
• the average diameters were respectively measured on 8 and 10 crystallites of GR F and GR L and are respectively 2.29 ⁇ 0.42 ⁇ and 4.96 ⁇ 0.44 ⁇ .
• the Môssbauer spectra are shown in FIGS. 4c and 4d on which the transmittance (in%) is a function of the speed (in mm.s -1 ).
• the ratio of Fe (II) / Fe (III) molar concentrations in the GR F and GR L green carbonate rust can be determined from the D1 doublets (attributed to Fe (II) carbonate green rust), D2 (also attributed to Fe (II) of carbonate green rust) and D3 (attributed to Fe (III) of green carbonate rust) characteristic of a green rust spectrum and the ratio of relative areas corresponding [AR (D1) + AR (D2)] / [AR (D3)]
• the ratios of Fe (II) / Fe (III) molar concentrations of GR F and GR L are respectively 1 and 1.25.
• the ratios of Fe (II) / Fe (III) molar concentrations of GR F and GR L estimated according to this method are thus respectively 0.93 and 1.17. These theoretical ratios are slightly underestimated since they are calculated from the concentration values of Fe (II) to tai during the analysis of the last samples at 12 days for bioreduction of Lp and at 27 days for bioreduction. of the RVF and are not calculated from the actual Fe (II) to tai concentration values at the end of the experiments, ie 14 days for RVF bioreduction and 33 days for bioreduction of RVF. the Lp. EXAMPLE 2
• FIG. 6 shows the intensity (in arbitrary units, ua) as a function of the angle 2-Theta (in degrees).
• the oxidation of biogenic carbonate green rust by nitrite ions leads to the production of Fe (III) oxyhydroxides with no trace of magnetite.
• the oxidation of GR F and GR L leads to a mixture of goethite (characteristic peaks Gt) and lepidocrocite (characteristic peaks noted Lp) ( Figure 6, upper part: oxidation of GR F and lower part: oxidation of the GR L ).
• Bacterial nitrate ion reduction experiments involving model bacteria were conducted with 3 distinct strains of Shewanella species (S. putrefaciens CIP 59.28, S. putrefaciens CIP 80.40 and S. oneidensis MR1). Each strain (2.5 ⁇ 10 9 CFU / ml) was incubated with 5 to 6.5 mM nitrate ions or with 4 to 5 mM nitrite ions at pH 7.5.
• FIG. 7 shows the evolution of the concentrations of nitrate ions (in mM) (solid circles), nitrite ions (solid squares) and ammonium ions (solid triangles) as a function of time (in minutes) during the contacting of the ions nitrates (diagrams on the left) or nitrite ions (diagrams on the right) with the S. putrefaciens bacteria CIP 59.28 ( Figure 7a), with S. putrefaciens CIP 80.40 bacteria ( Figure 7b) and with bacteria S. oneidensis MR1 ( Figure 7c).
• strains S. putrefaciens CIP 59.28 and S. putrefaciens CIP 80.40 accumulate the nitrite ions in about 90 minutes and the production of ammonium appears after about 120 minutes.
• the strain S. oneidensis MR1 accumulates nitrite ions in only about 30 minutes and ammonium production appears more rapidly after about 90 minutes.
• FIG. 8 shows the evolution of the concentrations of nitrate ions (in mM) (solid circles), nitrite ions (solid squares), ammonium (solid triangles) and Fe (II) to tai (Fe (II) tot, solid diamonds ) versus time (in minutes) during contacting of 6 mM of nitrate ions with 0.1 g of GR F biogenic bacteria and S. putrefaciens CIP 59.28 (8a), S. putrefaciens CIP 80.40 ( FIG. 8b) and S. oneidensis MR1 (FIG. 8c) (3.75 ⁇ 10 9 CFU / ml).
• nitrate ions are rapidly reduced by the bacteria in 1 to 2 hours depending on the strain used. Nitrite ions are observed as intermediates. The results show that the bacteria first convert the nitrate ions to nitrite ions, and then the bacteria reduce some of these nitrite ions leading to the production of ammonium.
• Fe (II) ions of biogenic carbonate green rust are oxidized, demonstrating an intervention of green rust particles in the system.
• the ferri-reductive activity is put in question to produce Fe (II) again.
• FIG. 9 shows the accumulation of nitrite ions (in mM) when 6 mM nitrate ions are brought into contact with bacteria alone (2.5 ⁇ 10 9 CFU / ml) (solid line) or with bacteria ( 3.75 x 10 9 CFU / ml) and 0.1 g of GRp (dotted line) as a function of time (in minutes).
• bacteria alone 2.5 ⁇ 10 9 CFU / ml
• bacteria 3.75 x 10 9 CFU / ml
• 0.1 g of GRp dotted line
• Different strains of bacteria are used: S. putrefaciens CIP 59.28 (solid circles), S. putrefaciens CIP 80.40 (solid squares) and S. oneidensis MR1 (solid triangles).
• a synthetic green rust GR C i corresponding to the formula [Fe 4 n (i -X) m Fe 4x OH 8 Cl.nH 2 O] was prepared by air oxidation of ferrous hydroxide slurry in the presence a slight excess of dissolved ferrous chloride (Refait et al., Corrosion Science, 1997, 39, 539-553).
• FIG. 11 shows the DRX analysis of the GR C i synthetic green rust thus obtained (characteristic peaks denoted RV).
• the intensity in arbitrary units
• the ratio of Fe (II) / Fe (III) molar concentrations in GRci synthetic green rust is close to 3 (Genin et al., Solid State Sciences, 2004, 39, 705-718).
• FIG. 12a shows the changes in concentrations (in mM) nitrite ions (closed triangles), ammonium (closed diamonds), Fe (II) solu bi e (filled squares) and Fe (II) to tai (round full) as a function of time (in hours).
• the injection of 5 mM sodium nitrite results in a decrease in the concentration of Fe (II) to tai and Fe (II) so i u bi e and rapid consumption of nitrite ions.
• Figure 12b attached shows the concentrations (in mM) nitrite ions (1 black rectangles), nitrate ion (2 th gray rectangles), ammonium (3 rd rectangles having bias bars) and ions Fe 2+ (4 th rectangles comprising horizontal bars) in the four final mixtures I, II, III and IV respectively obtained after preparation of the starting mixtures I 0 , II 0 , IIIo and IV 0 and reaction for 48 hours.
• FIG. 11 also shows the DRX analysis of the product obtained after oxidation of the green green rust GR C i by nitrite ions.
• the product obtained comprises a mixture of magnetite (peaks characteristic Mt and residual green rust GRQ residual (characteristic peaks noted RV) .
• peaks characteristic Mt and residual green rust GRQ residual characteristic peaks noted RV
• RV residual green rust GRQ residual
• a GRC 03 synthetic carbonyl green rust having the formula Fe n 4 Fe m 2 (OH) 12 CO 3 .3H 2 O was prepared by co-precipitation of FeSO 4 .7H 2 O and Fe 2 SO 4 .5H 2 O in condition anoxia.
• the ratio of Fe (II) / Fe (III) molar concentrations in GRc 03 synthetic green carbon rust obtained was 2 (Bocher et al, Solid State Sciences, 2004, 6, 117-124).
• the green rust was then centrifuged, washed with degassed water and dried in a vacuum desiccator under anoxic conditions.
• the synthetic GRco 3 thus obtained (0.1 g of powder) was resuspended in the presence of 6.5 mM nitrite ions at pH 8 in a volume of 60 ml.
• the appended FIG. 13 shows the evolution of the concentrations (in mM) in nitrite ions (solid triangles) and in ammonium (solid diamonds) as a function of time (in hours).
• step iin) and ii) of the process according to the invention carried out simultaneously involving an aboriginal biological consortium of purified water comprising nitrite ions or nitrate ions
• this purified wastewater included approximately 60 mg / 1 ammonium prior to the experiments, likely due to a malfunction in the nitrification treatment used in the Rhysostep ® SAUR wastewater treatment plant in Douy-la- Ramée (77), from where it was taken.
• This station is of type filters planted with reeds.
• this purified wastewater was incubated with 76.4 mg / l N-NO 2 ⁇ approximately.
• FIG. 14 shows the evolution of concentrations (in mg-N / 1) of nitrite ions (solid triangles) and ammonium (solid diamonds) as a function of time (in days) in this purified wastewater comprising nitrite ions, in the absence of biogenic carbonate green rust (FIG. 14a), in the presence of GR L (FIG. 14b) or in the presence of GR F (FIG. 14c).
• biogenic carbonated green rust has a high reactivity vis-à-vis the nitrite ions (step ii) of the process according to the invention) even in a natural liquid medium comprising a natural biological consortium (ie a purified wastewater including an indigenous biological consortium).
• Biogenic carbonate green rust reduces nitrite ions to nitrogen gas without producing ammonium.
• This experiment shows the reactivity of biogenic carbonate green rust with respect to nitrite ions in purified wastewater.
• FIG. 15 shows the evolution of concentrations (in mg-N / 1) in nitrate (solid round), nitrite (full triangles) and ammonium (solid diamonds) ions as a function of time (in days) in this purified wastewater comprising nitrate ions, in the absence of biogenic carbonated green rust (FIG. 15a) or in the presence of GR L (FIG. 15b).
• Figure 15a shows that in purified wastewater incubated with 73 mg / l N-NO 3 ⁇ and in the absence of GR L , 28.6 mg / 1 N-NO 3 " are reduced on the first day with accumulation. maximum nitrite ion of 16.8 mg / 1 N-NO 2 ⁇ during the first hour and no ammonium production is observed.No further reduction of nitrate is observed the following days.
• Figure 15b shows that in purified waste water incubated with 83.9 mg / 1 N-NO 3 " in the presence of GR L ( Figure 2b), the nitrate ions are completely reduced in 4 days, still without ammonium production , with 47.1 mg / 1 N-NO 3 " reduced on the first day and a maximum nitrite ion accumulation of 24.4 mg / 1 N-NO 2 " .

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