WO2023104580A1 - Procédé de traitement des eaux usées contenant de la triazine - Google Patents

Procédé de traitement des eaux usées contenant de la triazine Download PDF

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Publication number
WO2023104580A1
WO2023104580A1 PCT/EP2022/083582 EP2022083582W WO2023104580A1 WO 2023104580 A1 WO2023104580 A1 WO 2023104580A1 EP 2022083582 W EP2022083582 W EP 2022083582W WO 2023104580 A1 WO2023104580 A1 WO 2023104580A1
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Prior art keywords
triazine
wastewater
melamine
acid
treatment system
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PCT/EP2022/083582
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English (en)
Inventor
Rene Koenig
Frank NIED
Peter KREITMANN
Domnik Bayer
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Basf Se
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Publication of WO2023104580A1 publication Critical patent/WO2023104580A1/fr

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    • 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
    • C02F1/001—Processes for the treatment of water whereby the filtration technique is of importance
    • 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
    • C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
    • C02F1/5209—Regulation methods for flocculation or precipitation
    • 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
    • C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
    • C02F1/5272—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using specific organic precipitants
    • 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
    • C02F1/28—Treatment of water, waste water, or sewage by sorption
    • C02F1/283—Treatment of water, waste water, or sewage by sorption using coal, charred products, or inorganic mixtures containing them
    • 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
    • C02F1/38—Treatment of water, waste water, or sewage by centrifugal separation
    • C02F1/385—Treatment of water, waste water, or sewage by centrifugal separation by centrifuging suspensions
    • 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
    • C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
    • C02F1/5236—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents
    • C02F1/5245—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents using basic salts, e.g. of aluminium and iron
    • 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
    • C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
    • C02F1/54—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using organic material
    • C02F1/56—Macromolecular compounds
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F11/00—Treatment of sludge; Devices therefor
    • C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
    • C02F11/121—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering
    • C02F11/127—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering by centrifugation
    • 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
    • C02F2001/007—Processes including a sedimentation step
    • 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
    • C02F2101/30—Organic compounds
    • C02F2101/38—Organic compounds containing nitrogen
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/34—Nature of the water, waste water, sewage or sludge to be treated from industrial activities not provided for in groups C02F2103/12 - C02F2103/32
    • C02F2103/36—Nature of the water, waste water, sewage or sludge to be treated from industrial activities not provided for in groups C02F2103/12 - C02F2103/32 from the manufacture of organic compounds
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2209/00—Controlling or monitoring parameters in water treatment
    • C02F2209/001—Upstream control, i.e. monitoring for predictive control
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2209/00—Controlling or monitoring parameters in water treatment
    • C02F2209/003—Downstream control, i.e. outlet monitoring, e.g. to check the treating agents, such as halogens or ozone, leaving the process
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2301/00—General aspects of water treatment
    • C02F2301/04—Flow arrangements
    • C02F2301/043—Treatment of partial or bypass streams
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2301/00—General aspects of water treatment
    • C02F2301/04—Flow arrangements
    • C02F2301/046—Recirculation with an external loop
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D251/00—Heterocyclic compounds containing 1,3,5-triazine rings
    • C07D251/02—Heterocyclic compounds containing 1,3,5-triazine rings not condensed with other rings
    • C07D251/12—Heterocyclic compounds containing 1,3,5-triazine rings not condensed with other rings having three double bonds between ring members or between ring members and non-ring members
    • C07D251/26—Heterocyclic compounds containing 1,3,5-triazine rings not condensed with other rings having three double bonds between ring members or between ring members and non-ring members with only hetero atoms directly attached to ring carbon atoms
    • C07D251/40—Nitrogen atoms
    • C07D251/54—Three nitrogen atoms

Definitions

  • the present invention relates to a process for treating a triazine-containing wastewater, the process comprising separating triazine in form of a cyanurate or picrate with the aid of a treating system which contains a cationic (meth)acrylic polymer. Further, the invention relates to the use of said treatment system in a solid-liquid separation stage of a suspension containing a cyanurate or picrate, derived from triazine-containing wastewater.
  • Melamine is a compound which is of particular interest in many applications, for example, in the manufacture of high-end plastics, adhesives and industrial coatings, as well as in concrete additives or flame retardants.
  • Melamine is mainly produced on an industrial scale from urea, either without a catalyst under high pressure or with a catalyst in a low-pressure process. Each type includes three stages: synthesis, melamine recovery and purification, and off-gas treatment.
  • Crude melamine from the synthesis stage may be worked up in the presence of water.
  • wastewater contaminated with nitrogen-containing substances occur at various stages of a melamine plant.
  • the wastewater ingredients may mainly be triazines, like melamine, ureidomelamine or cyanuric acid, oxoamino-triazines (OATs) like ammelide or ammeline, urea, carbonate, sodium or ammonium ions.
  • triazine-containing or melamine-containing wastewater may be obtained when melamine production plants or melamine-formaldehyde resin production plants are purged and rinsed on a regular basis.
  • Melamine is poorly but soluble in water, i.e. , about 3 to 10 g/l of melamine may be dissolved in water dependent on the temperature (for example, 5 g/l at 30°C).
  • a wastewater contaminated with melamine and related triazine compounds must be treated to remove their ingredients, especially melamine, before they can be discharged.
  • Dissolved triazines are usually not decomposed in a sewage plant. There are various known ways of treating a triazine- or melamine-containing wastewater.
  • WO 2006/042760 A1 discloses a process for treating triazine-containing wastewater of a pH of 11 to 13 from a melamine production plant using a membrane filtration unit, wherein the wastewater is separated into a fraction rich of ionic triazines and a fraction rich of non-ionic triazines, followed by discharging the fraction rich in ionic triazines and recycling the fraction rich in non-ionic triazines into the melamine plant.
  • WO 2006/133966 A1 discloses a process for cleaning wastewater of a melamine production plant. First, the wastewater is subjected to a thermal pretreatment stage at a temperature of 180 to 220°C and a pressure of 15 to 30 bar to form a gas phase and a liquid phase.
  • the vapors from the gas phase are condensed, and the condensed vapors consist essentially of water, CO2 and NH 3 , which may be recycled after separation.
  • the liquid phase passes into a thermal hydrolysis stage, wherein, for example, the triazines are degraded with the aid of a high- pressure steam, followed by removing NH3 and CO2 from the aqueous phase.
  • WO 99/37628 A1 discloses a process for first recovering melamine from a wastewater obtained in a melamine production process and in a second step ammelide and ammeline.
  • the wastewater is contacted with an H-type weakly acidic cation exchange fiber to separate melamine from the resulting aqueous solution, the fiber is regenerated with a strong acid and neutralized to obtain a slurry of ammelide and ammeline, which may be recovered by a solidliquid separation step therefrom.
  • CN 1020700543 A discloses a process for recovering melamine from melamine production waste by treating wastewater with glacial acetic acid followed by filtering and recycling the filtrate to a melamine refining step.
  • CN 107441669 A discloses a process for catalytic hydrolysis of waste residues of melamine, cyanuric acid or OATs in a sealed pressure vessel at 190 to 240°C, wherein NH3 and CO2 are formed to be recycled.
  • PL 275892 A2 discloses a process for treating a gas waste and liquid waste from a melamine production plant, wherein after filtration, urea decomposition and ammonia recycling melamine and melamine derivatives are separated from the remaining liquid with sulfuric acid as melamine sulfate and/or sulfite to be used as fertilizer.
  • Triazine-containing wastewater may also be passed over one or more activated carbon adsorbent(s), wherein dissolved melamine is adsorbed.
  • activated carbon adsorbent(s) have limited capacity and must therefore be regularly exchanged and regenerated.
  • melamine As melamine is a weak base, it forms well-defined salts with both organic and inorganic acids.
  • Melamine cyanurate of formula (I) is very insoluble in water and therefore useful in quantitative analysis of melamine. The same applies to melamine picrate of formula (II) and triazine cyanurate and triazine picrate in general.
  • This concept may also be applied in treating wastewater containing triazine(s), especially melamine.
  • CN 104803531 A discloses a process for treating a trichloro-isocyanuric acid-containing wastewater in five purifying steps to yield water in a quality that can be discharged. After a first step of dechlorination and hypochlorite removal, cyanuric acid is recovered in a second step by precipitating and pumping out melamine cyanurate at a pH of 6.5 to 7.5 in a sedimentation tank.
  • CN 102898389 A discloses a process for recycling solid waste containing melamine, cyanuric acid and OATs, wherein cyanuric acid and water are added at a temperature of 90-95°C to prepare melamine cyanurate.
  • a good conversion rate is described with a slight excess of melamine-containing waste to cyanuric acid of 16:7, at a mass ratio of water to solid reactants of 9:1 and at a reaction time of 120 min.
  • JP S50-26553 B1 discloses a process for treating an ammonia- and urea-containing mother liquid, obtained in a melamine production process, with cyanuric acid and CO2, wherein the formed cyanurate is filtered off, in order to use the remaining liquid as a raw material for the synthesis of industrial urea.
  • CO2 neutralizes ammonia and accelerates the formation of cyanurate.
  • DE 1493041 discloses a process for removing a triazine from aqueous guanidium salts at 90- 95°C by adding cyanuric acid and filtering the obtained precipitate after cooling.
  • US 2011/0000854 A1 discloses a process for removing cyanuric acid through binding with melamine followed by treating first with a 1 wt% solution of xanthan and then with a 1 wt% solution of chitosan.
  • EP 3366650 A1 discloses a process for extracting isocyanuric acid of pool water, comprising the steps of adsorption, regeneration and filtration, wherein the regeneration medium is treated with melamine admixed with a filtering adjuvant, for example a 50% mixture with particles of natural diatomaceous earth, perlite or cellulose.
  • a filtering adjuvant for example a 50% mixture with particles of natural diatomaceous earth, perlite or cellulose.
  • US 4793935 discloses a process for removing cyanuric acid from bather water in swimming pools, etc., by adding melamine, optionally in combination with a flocculating agent to reduce the concentration of cyanuric acid to an acceptable limit of less than a maximum level of about 150 ppm.
  • the content of melamine in wastewater is usually analyzed from an environmental monitoring system, for example, by an ion chromatography tandem mass spectrometry (IC-MS/MS), prior to discharging. It is therefore desirable to reduce the amount of triazines including melamine to a minimum.
  • IC-MS/MS ion chromatography tandem mass spectrometry
  • the invention relates to a process for treating a wastewater containing one or more triazine(s) in dissolved form, the process comprising a) adding an organic acid, selected from cyanuric acid and picric acid, to form a suspension containing a cyanurate or picrate, and b) subjecting the suspension to a solid-liquid separation stage, wherein the solid-liquid separation stage is assisted by a treatment system, the treatment system contains a cationic (meth)acrylic polymer, and at least 90 wt% of the one or more triazine(s), based on the total weight of triazine(s), is melamine.
  • the invention relates to the use of a treatment system, as defined in any aspect herein, in a solid-liquid separation stage of a suspension containing a cyanurate or picrate, wherein the suspension is formed by adding an organic acid, selected from cyanuric acid and picric acid, to a wastewater containing one or more triazine(s) in dissolved form, the treatment system contains a cationic (meth)acrylic polymer, and at least 90 wt% of the one or more triazine(s), based on the total weight of triazine(s), is melamine.
  • a treatment system as defined in any aspect herein, in a solid-liquid separation stage of a suspension containing a cyanurate or picrate, wherein the suspension is formed by adding an organic acid, selected from cyanuric acid and picric acid, to a wastewater containing one or more triazine(s) in dissolved form, the treatment system contains a cationic (meth)acrylic polymer, and at least 90 w
  • Alkyl e.g., Ci-Cs-alkyl, Ci-Cs-alkyl, Ci-C4-alkyl or C2-C4-alkyl, may be within the given limits of carbon atoms linear or branched, where possible.
  • Examples are methyl (Me), ethyl (Et), n- propyl, isopropyl, n-butyl, 1-methylpropyl, 2-methylpropyl, t-butyl, n-pentyl, 2-pentyl, 3-pentyl, 2,2-dimethylpropyl, n-hexyl, n-heptyl, 1-methylhexyl, 1 ,1 ,3,3-tetramethylbutyl, n-octyl, 1 -methylheptyl, 3-methylheptyl or 2-ethylhexyl.
  • (meth)acrylic as used herein, or similar expressions, for example, (meth)acrylamide, means acrylic, methacrylic or mixtures thereof.
  • solids content in wt%, as used herein, means the ratio of the mass of a sample after drying to the mass of the sample before drying, multiplied by 100.
  • the solids content may be determined from a material sample, for example of an organic polymer by drying this sample in a circulating air drying cabinet at 140°C for 120 minutes.
  • a material sample for example of an organic polymer by drying this sample in a circulating air drying cabinet at 140°C for 120 minutes.
  • the sample 0.5 to 1.5 g
  • a metal lid for drying. Drying is carried out at ambient pressure, usually at 1013 mbar.
  • Figure 1 describes a calibration curve demonstrating the relationship between turbidity vs. melamine content per m 3 .
  • the turbidity is measured in nephelometric turbidity units (NTU).
  • the wastewater may contain one or more triazine(s), ammonia, carbon dioxide, urea and sodium hydroxide.
  • the wastewater contains one or more triazine(s), like melamine, ureidomelamine, ammelide, ammeline, cyanomelamine or melam, i.e. , triazines which may be form an insoluble complex with cyanuric acid or picric acid.
  • the triazines may be ionic or non-ionic.
  • Dependent on pH, concentration and temperature the one or more triazine(s) may be partially present in solid form and/or in dissolved form.
  • the wastewater contains mainly melamine as triazine in dissolved form, for example, in an amount of at least 90 wt%, based on the total weight of the triazines, preferably at least 95 wt%, more preferably at least 98 wt%.
  • the invention relates to a process for treating wastewater containing one or more triazine(s) in dissolved form, the process comprising a) adding an organic acid, selected from cyanuric acid and picric acid, to form a suspension containing a cyanurate or a picrate, and b) subjecting the suspension to a solid-liquid separation stage, wherein the solid-liquid separation stage is assisted by a treatment system, the treatment system contains a cationic (meth)acrylic polymer, and at least 95 wt% of the one or more triazine(s), based on the total weight of triazine(s), is melamine.
  • More preferred is a process, wherein at least 98 wt% of the one or more triazine(s), based on the total weight of triazine(s), is melamine.
  • the suspension formed in step a) of the process comprises a triazine cyanurate or a triazine picrate.
  • the suspension formed in step a) of the process comprises melamine cyanurate or melamine picrate in an amount of at least 90 wt%, based on the total weight of triazine(s).
  • the instant process may be applied to a wastewater containing one or more triazine(s) which is usually weakly acidic, neutral or alkaline, for example with a pH of about 5 to 14. Hence, generally no pH adjusting step is necessary.
  • the wastewater may have a higher pH when the rinsing process is performed with aqueous alkali.
  • the wastewater has a pH of > 6, more preferably > 7.
  • the wastewater may have a pH in the range of from 6 to 14, preferably 7 to 14.
  • the invention relates to a process for treating wastewater containing one or more triazine(s) in dissolved form, the process comprising a) adding an organic acid, selected from cyanuric acid and picric acid, to form a suspension containing a cyanurate or a picrate, and b) subjecting the suspension to a solid-liquid separation stage, wherein the solid-liquid separation stage is assisted by a treatment system, the treatment system contains a cationic (meth)acrylic polymer, at least 90 wt% of the one or more triazine(s), based on the total weight of triazine(s), is melamine, and the wastewater has a pH of > 6, preferably > 7.
  • the amount of one or more triazine(s) in the wastewater in solid or dissolved form may vary.
  • wastewater derived from a rinsing process of a melamine production plant or a melamine-formaldehyde resin production plant may include only a low amount of solid particles.
  • Solid particles may include melamine, melamine cyanurate, urea or other triazines like ammelide, ammeline, ureidomelamine, cyanomelamine or melam.
  • Suitable separating methods are known in the art.
  • the solid particles may be separated by filtering, sedimentation or centrifugation, either alone or in any combination.
  • the separating step is done by filtration.
  • Suitable filtration units include, for example, a filter press, a belt press or a screw press, preferably a filter press.
  • the invention relates to a process for treating wastewater containing one or more triazine(s) in dissolved form, the process comprising a) adding an organic acid, selected from cyanuric acid and picric acid, to form a suspension containing a cyanurate or a picrate, and b) subjecting the suspension to a solid-liquid separation stage, wherein the solid-liquid separation stage is assisted by a treatment system, the treatment system contains a cationic (meth)acrylic polymer, at least 90 wt% of the one or more triazine(s), based on the total weight of triazine(s), is melamine, and the wastewater is subjected to a solid-liquid separation stage prior to step a).
  • Wastewater typically contains triazines in dissolved form up to about 1 wt%, based on the total weight of the wastewater.
  • Melamine is usually the main component as triazine in dissolved form.
  • the wastewater contains one or more triazine(s) in dissolved form in an amount of from 1 to 5 g/l, preferably 1 to 4.5 g/l.
  • the invention relates to a process for treating wastewater containing one or more triazine(s) in dissolved form, the process comprising a) adding an organic acid, selected from cyanuric acid and picric acid, to form a suspension containing a cyanurate or a picrate, and b) subjecting the suspension to a solid-liquid separation stage, wherein the solid-liquid separation stage is assisted by a treatment system, the treatment system contains a cationic (meth)acrylic polymer, at least 90 wt% of the one or more triazine(s), based on the total weight of triazine(s), is melamine, and the wastewater contains one or more triazine(s) in dissolved form in an amount of from 3 to 5 g/l, preferably 3 to 4.5 g/l.
  • the wastewater may have a temperature of 10 to 70°C, preferably 15 to 50°C, more preferably 15 to 40°C.
  • the wastewater containing one or more triazine(s) in dissolved form is usually contacted with an organic acid which forms an insoluble salt with the one or more triazine(s) in the aqueous medium.
  • the organic acid is added to the wastewater at a temperature of from 10 to 70°C, preferably 15 to 50°C, more preferably 15 to 40°C or 20 to 40°C.
  • the organic acid may be added to the wastewater at ambient temperature, for example, at 15 to 25°C.
  • the invention relates to a process for treating wastewater containing one or more triazine(s) in dissolved form, the process comprising a) adding an organic acid, selected from cyanuric acid and picric acid, to form a suspension containing a cyanurate or a picrate, and b) subjecting the suspension to a solid-liquid separation stage, wherein the solid-liquid separation stage is assisted by a treatment system, the treatment system contains a cationic (meth)acrylic polymer, at least 90 wt% of the one or more triazine(s), based on the total weight of triazine(s), is melamine, and the addition of the organic acid is conducted at a temperature of from 10 to 70°C, preferably from 15 to 40°C.
  • the addition of the organic acid is usually carried out under stirring.
  • the amount of the organic acid is usually dependent on the amount of the dissolved triazine(s).
  • the amount of dissolved triazine(s) may be determined in a semi-quantitative analysis using a liquid sample of wastewater, for example, a filtered or otherwise generated liquid sample of wastewater.
  • a saturated solution of the organic acid is added to a liquid, preferably filtered, sample of wastewater until no further precipitation occurs. Based on the used amount of organic acid, the amount of triazine(s) can be determined.
  • an excess of organic acid is added to a liquid, preferably filtered, sample of wastewater, and the amount of triazine(s) can be determined gravimetrically as triazine salt of the organic acid.
  • the amount of triazine(s) can be determined by a combination of a qualitative and quantitative analysis.
  • the approximate amount of dissolved triazine(s) may be estimated for the total volume of the wastewater to be treated.
  • the amount of organic acid to be added may then be adjusted.
  • the invention relates to a process for treating wastewater containing one or more triazine(s) in dissolved form, the process comprising a) adding an organic acid, selected from cyanuric acid and picric acid, to form a suspension containing a cyanurate or a picrate, and b) subjecting the suspension to a solid-liquid separation stage, wherein the solid-liquid separation stage is assisted by a treatment system, the treatment system contains a cationic (meth)acrylic polymer, at least 90 wt% of the one or more triazine(s), based on the total weight of triazine(s), is melamine, and the amount of the one or more triazine(s) in dissolved form is determined by a semi-quantitative analysis.
  • the amount of the one or more triazine(s) in dissolved form is determined by a semi-quantitative analysis, which is based on an analysis of a sample of wastewater, whereon the approximate amount of the total volume of wastewater to be treated is estimated, wherein the analysis of a sample of wastewater is especially performed by titration or gravimetrically, in particular gravimetrically.
  • the organic acid is typically used in an approximately equimolar amount, based on the value as determined by semi-quantitative analysis of the triazine(s).
  • the organic acid is added in an amount approximately of from 0.8 to 1.2 equivalents, based on 1 equivalent of triazine(s) determined by a semi-quantitative analysis, preferably 0.85 to 1.15 equivalents.
  • the organic acid is added in an amount of from 0.75 to 1.25 equivalents, based on 1 equivalent of triazine(s) determined by a semi-quantitative analysis, preferably 0.78 to 1.15 equivalents.
  • organic acid can be controlled, usually when at least 70 wt%, based on the estimated amount, is added.
  • the content of triazine(s) can be determined, for example, after the addition of 70 wt%, 80 wt% or 90 wt%.
  • the organic acid may be added to the main container, where the wastewater is collected, or to a reaction space, which is separated from the main container, for example a container integrated in a side stream.
  • the organic acid is added to a reaction space, which is separated from the main container and contains a partial amount of wastewater, for example, at most 10 wt%, preferably at most 5 wt%, based on the total weight of the wastewater.
  • the reaction space may be arranged as a side stream to a main container, wherein the wastewater may be pumped in a circle.
  • the total amount of organic acid may be added into the side stream, while the wastewater is continuously re-circulated to the main container.
  • the organic acid may be added in portions or continuously.
  • the invention relates to a process for treating wastewater containing one or more triazine(s) in dissolved form, the process comprising a) adding an organic acid, selected from cyanuric acid and picric acid, to form a suspension containing a cyanurate or a picrate, and b) subjecting the suspension to a solid-liquid separation stage, wherein the solid-liquid separation stage is assisted by a treatment system, the treatment system contains a cationic (meth)acrylic polymer, at least 90 wt% of the one or more triazine(s), based on the total weight of triazine(s), is melamine, and the organic acid is added to a reaction space which contains at most 10 wt% of the wastewater, based on the total weight of the wastewater.
  • an organic acid selected from cyanuric acid and picric acid
  • the invention relates to a process for treating wastewater containing one or more triazine(s) in dissolved form, the process comprising a) adding an organic acid, selected from cyanuric acid and picric acid, to form a suspension containing a cyanurate or a picrate, and b) subjecting the suspension to a solid-liquid separation stage, wherein the solid-liquid separation stage is assisted by a treatment system, the treatment system contains a cationic (meth)acrylic polymer, at least 90 wt% of the one or more triazine(s), based on the total weight of triazine(s), is melamine, the organic acid is added to a reaction space which contains at most 10 wt% of the wastewater, based on the total weight of the wastewater, and the reaction space is arranged as a side stream to a main container, wherein the wastewater is re-circulated.
  • the amount of triazine(s) in dissolved form may also be determined by an online measurement. This type
  • a liquid sample of the wastewater of the side stream is provided, optionally by separating solids from the sample, in order to provide a predefined amount of liquid to be analyzed.
  • the amount of liquid may, for example, be 0.1 ml to 10 ml.
  • the solids may be separated by filtering the sample of wastewater.
  • the analysis is usually done in a suitably diluted sample with deionized water or a suitable solvent dependent on the analytical method. The analysis may be carried out by a suitable analytical method.
  • Suitable analytical methods for triazine(s), preferably melamine include titration, high performance liquid chromatography optionally combined with mass spectrometry (HPLC/MS), gas chromatography optionally combined with mass spectrometry, and UV/VIS-spectrometry.
  • An example of the analytical method is titration to determine the content of triazine(s) and to automatically regulate the dosing of the organic acid.
  • titration may be carried out using an acid, for example with a pH electrode or a photometer.
  • a suitable acid is, for example, hydrochloric acid.
  • the titrant (acid) is usually metered automatically into the analyte (diluted sample containing the triazine(s)) and the titration curve is simultaneously recorded with a sensor.
  • the equivalence point of the titration is automatically determined from the titration curve.
  • the concentration of the analyte is calculated from the volume of titrant used up to the achievement of the respective equivalence point.
  • the amount of organic acid needed for precipitation of the salt of the organic acid may be calculated and automatically dosed.
  • the organic acid is dosed in solid form.
  • the calculation of the amount of organic acid may be based on a calibration curve based on comparative titration measurements.
  • the organic acid is usually dosed continuously via a suitable dosing means, for example, a metering screw, into the side stream or in an integrated separate container within said side stream, if present.
  • a suitable dosing means for example, a metering screw
  • the sample taking is generally done periodically, i.e., in predefined time intervals, until the triazine(s), preferably melamine, could not be detected.
  • the dosing amount of organic acid may be calculated and automatically dosed, in a continuous manner, desirably a part, preferably, 70 to 80 wt%, of the calculated amount of organic acid.
  • the triazine amount is measured online again, and the dosing step is repeated based on the new value, until the triazine(s) may no longer be detected.
  • the dosing amount of organic acid may be calculated, automatically dosed in a continuous manner and after a specific time interval the amount is analyzed continuously.
  • suitable time intervals may be about 5 min at dosage rate of from 40 to 170 g/s, preferably at a circulation rate of about 130 to 140 l/min.
  • a system for carrying out the process using online measurement may comprise an automatic sample taking, an analyzer close to the side stream, a device for evaluating the data and automatic regulating the dosing based on said data.
  • the invention relates to a process for treating wastewater containing one or more triazine(s) in dissolved form, the process comprising a) adding an organic acid, selected from cyanuric acid and picric acid, to form a suspension containing a cyanurate or a picrate, and b) subjecting the suspension to a solid-liquid separation stage, wherein the solid-liquid separation stage is assisted by a treatment system, the treatment system contains a cationic (meth)acrylic polymer, at least 90 wt% of the one or more triazine(s), based on the total weight of triazine(s), is melamine, the organic acid is added to a reaction space which contains at most 10 wt% of the wastewater, based on the total weight of the wastewater, and the organic acid to be added is automatically regulated, based on online measurement of the amount of one or more triazine(s).
  • the amount of triazine(s) is determined by titration or spectrometry, more preferably by titration.
  • the invention relates to a process for treating wastewater containing one or more triazine(s) in dissolved form, the process comprising a) adding an organic acid, selected from cyanuric acid and picric acid, to form a suspension containing a cyanurate or a picrate, and b) subjecting the suspension to a solid-liquid separation stage, wherein the solid-liquid separation stage is assisted by a treatment system, the treatment system contains a cationic (meth)acrylic polymer, at least 90 wt% of the one or more triazine(s), based on the total weight of triazine(s), is melamine, the organic acid is added to a reaction space which contains at most 10 wt% of the wastewater, based on the total weight of the wastewater, the organic acid to be added is automatically regulated, based on online measurement of the amount of one or more triazine(s), and the amount of triazine(s) is determined by spectrometry or titration
  • the organic acid may be cyanuric acid or picric acid.
  • the organic acid is cyanuric acid.
  • the invention relates to a process for treating wastewater containing a triazine in dissolved form, the process comprising a) adding an organic acid, which is cyanuric acid, to form a suspension containing a cyanurate, and b) subjecting the suspension to a solid-liquid separation stage, wherein the solid-liquid separation stage is assisted by a treatment system, the treatment system contains a cationic (meth)acrylic polymer, and at least 90 wt% of the one or more triazine(s), based on the total weight of triazine(s), is melamine.
  • the treatment system is usually applied to the solid-liquid separation stage to cause flocculation of the precipitate containing a salt of the organic acid.
  • the treatment system is usually added under stirring, whereby the flocculated solids may be granulated.
  • the treatment system may be a water-soluble or water-swellable polymer, optionally in combination with an inorganic material.
  • the treatment system contains a cationic (meth)acrylic polymer as organic polymer.
  • the cationic organic polymer may be derived from one or more ethylenically unsaturated cationic monomers, optionally in combination with one or more ethylenically unsaturated nonionic monomers.
  • the cationic (meth)acrylic polymer is a synthetic polymer, formed from an ethylenically unsaturated water-soluble monomer or a blend of such monomers.
  • the water-soluble monomers have a solubility in water of at least 5 g / 100 ml at 25°C.
  • the weight average molecular weight of the cationic organic polymer i.e., the cationic (meth)acrylic polymer, is preferably at least 500,000 g/mol, more preferably at least 1 ,000,000, most preferably at least 5,000,000, as determined by Gel permeation chromatography (GPC), using appropriate standards, for example polystyrene.
  • GPC Gel permeation chromatography
  • the treatment system may further include one or more high molecular weight polymer(s) that is/are non-ionic, anionic or amphoteric.
  • the further organic polymer may be a non-ionic, anionic or amphoteric polymer, typically formed from at least one ethylenically unsaturated monomer.
  • a non-ionic polymer the polymer may be derived from at least one non-ionic ethylenically unsaturated monomer.
  • an anionic polymer the polymer may be derived from at least one anionic ethylenically unsaturated monomer, optionally including at least one ethylenically unsaturated non-ionic monomer.
  • the polymer may be derived from one or more ethylenically unsaturated anionic monomers and one or more ethylenically unsaturated cationic monomers, optionally in combination with one or more ethylenically unsaturated non-ionic monomers.
  • the further organic polymer is a synthetic polymer, formed from an ethylenically unsaturated water-soluble monomer or a blend of such monomers.
  • the water-soluble monomers have a solubility in water of at least 5 g / 100 ml at 25°C.
  • the weight average molecular weight of the further organic polymer is preferably at least 500,000 g/mol, more preferably at least 1 ,000,000, most preferably at least 5,000,000, as determined by Gel permeation chromatography (GPC), using appropriate standards, for example polystyrene.
  • GPC Gel permeation chromatography
  • a preferred anionic polymer is formed from at least one monomer selected from an ethylenically unsaturated carboxylic acid, a sulphonic acid monomer and any combination thereof, preferably selected from (meth)acrylic acid, allyl sulphonic acid and 2-acrylamido-2-methyl propane sulphonic acid, and their salts, optionally in combination with at least one non-ionic monomer, preferably selected from (meth)acrylamide, a hydroxy C2-C4-alkyl ester of (meth)acrylic acid, a Ci-Cs-alkyl ester of (meth)acrylic acid, vinyl acetate, vinyl alcohol, allyl Ci-Cs-alkyl ether, styrene, and N-vinyl pyrrolidone.
  • Especially preferred polymers include the homopolymer of sodium acrylate, the homopolymer of acrylamide and the copolymer of sodium acrylate with acrylamide.
  • a preferred non-ionic polymer is formed from at least one ethylenically unsaturated monomer selected from (meth)acrylamide, a hydroxy C2-C4-alkyl ester of (meth)acrylic acid, N-vinyl pyrrolidone and any combination thereof.
  • the cationic (meth)acrylic polymer is preferably formed from at least one cationic monomer selected from a quaternary ammonium salt of di(Ci-C3-al kyl) amino Ci-C4-alkyl (meth)acrylate, such as methyl chloride quaternary ammonium salt of dimethylaminoethyl acrylate (DMAEA-q) or the methyl chloride quaternary ammonium salt of dimethyl amino ethyl methacrylate (DMAEMA-q), or a quaternary ammonium salt of di(Ci-C3-alkyl)amino-Ci-C4-alkyl (meth)acrylamide, such as acrylamido propyl trimethylammonium chloride (APTAC) or methacrylamido propyl trimethylammonium chloride (MAPTAC), optionally in combination with one or more non-ionic monomers, preferably selected from (meth)acrylamide, a hydroxy-
  • the cationic (meth)acrylic polymer may further contain a unit derived from diallyl dimethyl ammonium chloride (DADMAC).
  • the treatment system may further contain a cationic organic polymer based on diallyl dimethyl ammonium chloride (DADMAC).
  • polyamines for example partially or fully hydrolyzed polyvinyl formamides containing repeating vinyl amine units
  • polyethyleneimines polymers of alkyl amines with formaldehyde and/or epichlorohydrin
  • polycyandiamides include polycyandiamides.
  • polymeric flocculants may be used, for example, polymers commercially available under the trade names HIMOLOC, ZETAG, MAGNOFLOC or REIFLOCK.
  • the treatment system may comprise one or more cationic (meth)acrylic polymers, optionally in combination with an inorganic coagulant.
  • the inorganic coagulant may be ferric chloride, ferric sulfate, aluminum sulfate, polyaluminum chloride or other forms of iron or aluminum. If used, the inorganic coagulant may be added prior to the polymer(s). The inorganic coagulant is generally added as an aqueous formulation.
  • polymers In case two polymers are used, they may be used sequentially, preferably the cationic polymer followed by the anionic polymer.
  • the treatment system comprises a (meth)acrylamide-based cationic polymer.
  • the invention relates to a process for treating wastewater containing one or more triazine(s) in dissolved form, the process comprising a) adding an organic acid, selected from cyanuric acid and picric acid, to form a suspension containing a cyanurate or a picrate, and b) subjecting the suspension to a solid-liquid separation stage, wherein the solid-liquid separation stage is assisted by a treatment system, the treatment system contains a (meth)acrylamide-based cationic polymer, and at least 90 wt% of the one or more triazine(s), based on the total weight of triazine(s), is melamine.
  • the treatment system containing a cationic (meth)acrylic polymer, to be added may be used as dry particles, as an aqueous solution, as a reverse phase emulsion or as an aqueous dispersion.
  • the cationicity or anionicity of the polymers may be at least 10 mol%, preferably at least 20 mol%.
  • the weight average molecular weight of the polymers is preferably at least 1 ,000,000, more preferably at least 5,000,000.
  • the treatment system contains the cationic (meth)acrylic polymer, especially a (meth)acrylamide-based cationic polymer, in an amount of at least 60 wt%, based on the total weight of the treatment system, more preferably at least 80 wt%, especially 90 wt%, in particular at least 95 wt%.
  • the total weight of the treatment system corresponds to the solids content of the treatment system.
  • the acrylamide-based cationic polymer is a copolymer derived from (methacrylamide and a cationic monomer selected from a quaternary ammonium salt of di (Ci-Cs-alkyl) amino Ci-C4-alkyl (meth)acrylate, such as methyl chloride quaternary ammonium salt of dimethylaminoethyl acrylate (DMAEA-q) or the methyl chloride quaternary ammonium salt of dimethyl amino ethyl methacrylate (DMAEMA-q), or a quaternary ammonium salt of di(Ci-C3- alkyl)amino-Ci-C4-alkyl (meth)acrylamide, such as acrylamido propyl trimethylammonium chloride (APTAC) or methacrylamido propyl trimethylammonium chloride (MAPTAC).
  • the treatment system contains a cationic acrylamide-based polymer.
  • the cationicity may be at least 10 mol%, preferably at least 20 mol%.
  • the weight average molecular weight of the cationic polymer is preferably at least 1 ,000,000, more preferably at least 5,000,000.
  • the treatment system is added as a powder, as an aqueous dispersion or as a reverse emulsion, preferably suitably diluted with deionized water.
  • the treatment system may be added in an amount sufficient to effect flocculation.
  • the treatment system is added preferably in the reaction space, which contains at least at most 10 wt% of the wastewater, based on the total weight of the wastewater.
  • the amount of the treatment system, sufficient to induce flocculation would be usually at least 0.3 to 35 mg per liter wastewater to be treated, preferably 0.3 to 25 mg/l, more preferably 0.5 to 10 mg/l.
  • the amount of treatment system is less than 0.3 mg per liter wastewater, the formation of flocs is usually not sufficient. A higher amount than 35 mg per liter may lead to flocs floating at the surface, probably by entrapped air.
  • the treatment system may be added by a conventional dosing means, for example, by a chemical injection pump.
  • the solid product can be separated from the wastewater by mechanical means, for example, by filtration, centrifugation and/or sedimentation, preferably by sedimentation and filtration.
  • Suitable filtration units include a filter press, a belt press or screw press, preferably a filter press.
  • the mechanical solid-liquid separation stage is carried out by a temperature of 40°C or less, in order to achieve sufficient insolubility of the salt of the organic acid.
  • the invention relates to a process for treating wastewater containing one or more triazine(s) in dissolved form, the process comprising a) adding an organic acid, selected from cyanuric acid and picric acid, to form a suspension containing a cyanurate or a picrate, and b) subjecting the suspension to a solid-liquid separation stage, wherein the solid-liquid separation stage is assisted by a treatment system, the treatment system contains a cationic (meth)acrylic polymer, at least 90 wt% of the one or more triazine(s), based on the total weight of triazine(s), is melamine, and the solid-liquid separation stage is conducted by sedimentation, filtration and/or centrifugation, preferably at a temperature of ⁇ 40°C, preferably ⁇ 35°C,
  • the wastewater obtained has a sufficient purity which may be discharged.
  • the invention relates to a process for treating wastewater containing one or more triazine(s) in dissolved form, the process comprising a) adding an organic acid, selected from cyanuric acid and picric acid, to form a suspension containing a cyanurate or a picrate, and b) subjecting the suspension to a solid-liquid separation stage, wherein the solid-liquid separation stage is assisted by a treatment system, the treatment system contains a cationic (meth)acrylic polymer, at least 90 wt% of the one or more triazine(s), based on the total weight of triazine(s), is melamine, and the separated liquid of the solid-liquid separation stage is discharged.
  • an organic acid selected from cyanuric acid and picric acid
  • the wastewater obtained after the solid-liquid separation stage may be subjected to a further purification step, for example, passing over one or more activated carbon adsorbent(s).
  • the wastewater obtained in step c) may be recycled, optionally after a further purification step, for example to the urea plant, melamine plant or for any cleaning step.
  • the separated solids may also be discharged.
  • the instant process may be applied to any triazine-containing wastewater.
  • Examples may be wastewater derived from a melamine production process, a rinsing process of a melamine production plant or a melamine-formaldehyde resin production plant.
  • the invention relates to a process for treating wastewater containing one or more triazine(s) in dissolved form, the process comprising a) adding an organic acid, selected from cyanuric acid and picric acid, to form a suspension containing a cyanurate or a picrate, and b) subjecting the suspension to a solid-liquid separation stage, wherein the solid-liquid separation stage is assisted by a treatment system, the treatment system contains a cationic (meth)acrylic polymer, at least 90 wt% of the one or more triazine(s), based on the total weight of triazine(s), is melamine, and the wastewater is derived from a melamine production process, a rinsing process of a melamine production plant or a melamine-formaldehyde resin production plant.
  • the treatment system is used in a solid-liquid separation stage, as indicated herein-before.
  • the invention relates to the use of a treatment system, as defined in any aspect herein, in a solid-liquid separation stage of a suspension containing a cyanurate or picrate, wherein the suspension is formed by adding an organic acid, selected from cyanuric acid and picric acid, to a wastewater containing one or more triazine(s) in dissolved form, the treatment system contains a cationic (meth)acrylic polymer, and at least 90 wt% of the one or more triazine(s), based on the total weight of triazine(s), is melamine.
  • a treatment system as defined in any aspect herein, in a solid-liquid separation stage of a suspension containing a cyanurate or picrate, wherein the suspension is formed by adding an organic acid, selected from cyanuric acid and picric acid, to a wastewater containing one or more triazine(s) in dissolved form, the treatment system contains a cationic (meth)acrylic polymer, and at least 90 w
  • the instant process is applicable to any wastewater containing triazines, preferably melamine, which can then be discharged without any disadvantage to the environment.
  • Melamine as hazardous substance may easily and significantly be reduced to a value which is acceptable to be discharged. Also, only traces of dissolved triazines may be reliably removed.
  • the instant process is simple and easy to be used on a large scale, without any preconditioning steps, mainly for wastewaters deriving from rinsing processes of melamine production plants or melamine-resin production plants. Moreover, the process is flexible and can be quickly adjusted to achieve quantitative precipitation and minimizing triazine content in wastewater.
  • the instant process is less elaborate with respect to the equipment and steps.
  • the process using activated carbon requires more elaborate steps, generally containing removing the adsorber container from the process equipment, separating the used carbon material from said adsorber container, discharging, for example burning, the carbon material or regenerating the used carbon material, and refilling the adsorber container with fresh activated carbon or regenerated carbon material, which is then incorporated in the process again.
  • the instant process uses significantly less energy.
  • the action of the cationic polymeric treatment system greatly enhances the separation of the solids from the wastewater compared to separation using solely mechanical means.
  • the speed for the separation stage, especially the separation stage using mechanical means may be significantly increased. Further, the dewatering effect may be significantly enhanced.
  • the step of precipitating the insoluble salts with the organic acid may be desirably accelerated by treating the wastewater at elevated temperature.
  • Method 1 A 1 I sample of filtrated wastewater was mixed with an excess of cyanuric acid and stirred for 20 min at a specific temperature, for example at 30°C. Melamine cyanurate was precipitated, which was analyzed gravimetrically. The filtrate was analyzed by determining the residual turbidity (portable turbidimeter, HACH 2100Q IS).
  • Method 2 A 1 I sample of filtrated wastewater was mixed with a saturated solution of cyanuric acid (0.15 wt% in deionized water) under stirring at a specific temperature, for example at 30°C, while melamine cyanurate was precipitated, until no further precipitation occurs and no turbidity was determined (portable turbidimeter, HACH 2100Q IS).
  • Portions of 10 ml of treatment system (A) or (B) (1 ml diluted to 1000 ml deionized water) were added to a sample of 5 I wastewater under stirring, treated with the estimated equivalent amount of cyanuric acid, until flocculation occurs. Based on said determined amount, the amount of treatment system (A) or (B) was calculated for the total volume of the wastewater to be treated.
  • a filtrated sample to be analyzed is added to 200 ml of a saturated solution of cyanuric acid (0.15 wt% in deionized water) at 30°C. The solution remains clear, if no melamine is present. Quantitative analysis of melamine
  • Method a The turbidity was measured using a portable turbidimeter (HACH, 2100Q IS), using a pre-stirred/dispersed suspension. The content of melamine can be determined using the calibration curve shown in figure 1.
  • a filtrated sample to be analyzed is added to 200 ml of an aqueous melamine solution (1.5 g/l) at 30°C. The solution remains clear, if no cyanuric acid is present.
  • a total of 105 kg (813.5 mol, 0.98 eq.) of cyanuric acid were added in portions of 25 kg, while stirring for 35-40 min; melamine content was qualitatively regularly controlled during addition. Then 100 g of treatment system (B), diluted with 5 I of deionized water, were added while stirring for 5 min. After about 30 min allowing to stand, a clear supernatant was formed, which was analyzed by determining the residual turbidity.
  • the content of melamine was determined to 3.5 kg/m 3 (26.17 mol/m 3 ).
  • the wastewater was heated to a temperature of about 35°C.
  • a part (8 m 3 ) of the wastewater was removed from a main tank, pumped through a side stream via a separate container (250 I) and re-circulated with a continuous flow of 8 m 3 /h, wherein cyanuric acid was added to the separate container in portions of 25 kg within about 60 to 90 min, followed by re-circulating with a continuous flow of 45 m 3 /h for 4 hours (with regularly control of melamine content).
  • the supernatant could be discharged.
  • the sediment was filtered and separately discharged.
  • a content of melamine was determined at 30°C to 3.2 kg/m 3 (25.37 mol/m 3 ) by semi-quantitative analysis (method 1), corresponding to a need of cyanuric acid of 3.27 kg/m 3 .
  • the wastewater was heated to a temperature of about 35°C.
  • a part (8 m 3 ) of the wastewater was removed from the tank, pumped through a side stream via a separate container (250 I) and re-circulated with a continuous flow of 8 m 3 /h, wherein cyanuric acid was added to the side stream in portions of 25 kg within 60 to 90 min, followed by re-circulating with a continuous flow of 45 m 3 /h for 4 hours (with regularly control of melamine content).
  • the wastewater was heated to a temperature of about 35°C.
  • a part (8 m 3 ) of the wastewater was removed from the tank, pumped through a side stream via a separate container (250 I) and re-circulated with a continuous flow of 8 m 3 /h, wherein cyanuric acid was added to the side stream in portions of 25 kg within 60 to 90 min (with regular control of melamine content), followed by re-circulating with a continuous flow of 45 m 3 /h for 4 hours.
  • treatment system (A) 1 .6 kg of treatment system (A), diluted with 500 I of deionized water, were added to the separate container.
  • the supernatant could be discharged.
  • the sediment was filtered and separately discharged.

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  • Engineering & Computer Science (AREA)
  • Environmental & Geological Engineering (AREA)
  • Water Supply & Treatment (AREA)
  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Separation Of Suspended Particles By Flocculating Agents (AREA)

Abstract

L'invention concerne un procédé de traitement des eaux usées contenant une ou plusieurs triazines sous forme dissoute, le procédé comprenant a) l'ajout d'un acide organique, choisi parmi l'acide cyanurique et l'acide picrique, pour former une suspension contenant un cyanurate ou un picrate, et b) une étape de séparation solide-liquide de la suspension, l'étape de séparation solide-liquide étant assistée par un système de traitement, le système de traitement contenant un polymère (méth)acrylique cationique, et au moins 90 % en poids de la ou des triazines, par rapport au poids total de la ou des triazines, étant de la mélamine.
PCT/EP2022/083582 2021-12-09 2022-11-29 Procédé de traitement des eaux usées contenant de la triazine WO2023104580A1 (fr)

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