EP1042231A1 - Procede permettant d'extraire la silice des eaux usees - Google Patents

Procede permettant d'extraire la silice des eaux usees

Info

Publication number
EP1042231A1
EP1042231A1 EP98952200A EP98952200A EP1042231A1 EP 1042231 A1 EP1042231 A1 EP 1042231A1 EP 98952200 A EP98952200 A EP 98952200A EP 98952200 A EP98952200 A EP 98952200A EP 1042231 A1 EP1042231 A1 EP 1042231A1
Authority
EP
European Patent Office
Prior art keywords
silica
process according
coagulant
range
membrane
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP98952200A
Other languages
German (de)
English (en)
Other versions
EP1042231A4 (fr
Inventor
Stephen D. Allen
Leonard R. Lyman
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Microbar Inc
Original Assignee
Microbar Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US08/965,574 external-priority patent/US5965027A/en
Application filed by Microbar Inc filed Critical Microbar Inc
Publication of EP1042231A1 publication Critical patent/EP1042231A1/fr
Publication of EP1042231A4 publication Critical patent/EP1042231A4/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/14—Ultrafiltration; Microfiltration
    • B01D61/147—Microfiltration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/14—Ultrafiltration; Microfiltration
    • B01D61/16—Feed pretreatment
    • 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
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/444—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by ultrafiltration or microfiltration
    • 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
    • C02F1/58—Treatment of water, waste water, or sewage by removing specified dissolved compounds
    • C02F1/583—Treatment of water, waste water, or sewage by removing specified dissolved compounds by removing fluoride or fluorine compounds
    • 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
    • C02F2103/346—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 semiconductor processing, e.g. waste water from polishing of wafers

Definitions

  • the present invention relates to the high flow treatment and purification of wastewater containing silica. More particularly, the present invention relates to process and apparatus for removing silica from large quantities of wastewater using a combination of filter membranes and organic polymers.
  • CMP chemical mechanical polishing
  • silica is a scale forming material commonly found in cooling water which can foul heat exchangers, pipes, valves, pumps, and boilers. No known inhibitor, chelating agent or dispersant exists which will significantly control silica's tendency to form scale. When the silica concentration in a cooling water system exceeds its solubility limit of roughly about 150 to about 200 milligrams per liter, silica polymerizes to form scale. It may also react with multivalent cations, such as magnesium and calcium, to form scale.
  • Microfiltration systems have been considered to remove silica contaminants from wastewater.
  • traditional microfiltration membranes having a pore size of about 0.5 microns rapidly clog with silica that was precipitated with conventional inorganic coagulants.
  • Such particulates are consistently less than 1.0 micron in size.
  • the inorganic coagulants cannot aid in the precipitation of microfine colloidal silica.
  • the partially formed floe will also deform and block the membrane pores, preventing flow.
  • the present invention is directed to a process for removing silica from large volumes of wastewater.
  • a wastewater stream containing silica is treated with an organic polymer.
  • the coagulant reacts with the silica to form spherical particulates which agglomerate into clusters having a size greater than about 5 ⁇ .
  • a wastewater stream includes raw water containing silica as well as process water streams containing silica.
  • Organic and polymeric coagulants which can be used to achieve the desired particulate formation, such as polyacryl- amides (cationic, nonionic, and anionic) , epi-dma's (epichlo- rohydrin/dimethyla ine polymers having a molecular weight from in the range from 25,000 to 1.5 million, preferably greater than 100,000, and more preferably between 100,000 and 300,000),
  • DADMAC's polydiallydimethylammonium chlorides
  • copolymers of acrylamide and DADMAC natural guar, etc.
  • the stoichiometric ratio of coagulant to silica is preferably optimized to result in acceptable silica removal at minimum coagulant cost.
  • the required coagulant concentration will depend on several factors, including silica contaminant influent concentration, wastewater flow rate, silica contaminant effluent compliance requirement, coagulant/contaminant reaction kinetics, etc.
  • the ratio of silicon to coagulant contaminant is typically in the range from 20:1 to 50:1, depending on the system, an preferably about 40:1.
  • the ratio of silicon to coagulant can be 120:1 or even higher.
  • the optimum mole ratio will also vary depending on the coagulant used. For instance, low molecular weight epi-dma and very high molecular weight epi- dma require from 3 to 5 times the dose to flocculate the silicon.
  • organic coagulants cause the silica to form well defined spherical particles which agglomerate to form particles having a size in the range from about 10 ⁇ to 90 ⁇ .
  • the silica particles are easily separated from microfiltration membranes enabling efficient silica removal without membrane degradation.
  • Small amounts of a supplemental coagulant can optionally be used in combination with the organic and polymeric coagulant to optimize the silica removal.
  • typical supplemental coagulants include, aluminum chlorohydrate ("ACH,” Al n 0H 2n .
  • m Cl m e.g., Al 4 OH 6 Cl 2 with a typical A1:C1 ratio of 2:1
  • sodium aluminate NaA10 2
  • aluminum chloride A1C1,
  • polyaluminum chloride (“PAC,” A1 6 0C1 5 )
  • the typical mole ratio of silica to inorganic coagulant is about 25:1.
  • Treated wastewater is passed through a microfiltration membrane which physically separates the silica contaminant from the wastewater.
  • Suitable microfiltration membranes are commercially available from manufacturers such as W.L. Gore, Koch, and National Filter Media (Salt Lake City, Utah) .
  • one GOR-TEX® membrane used in the present invention is made of polypropylene felt with a sprayed coating of teflon. The teflon coating is intended to promote water passage through the membrane.
  • Such microfiltration membrane material has been found to be useful for many wastewater treatment systems. However, when used in a system for removing fluoride or silica, it has been observed that the coagulated particles adhere to the exterior and interior surface and plug the membrane. Back- flushing was not effective in such cases.
  • the microfiltration membranes are used in a tubular "sock" configuration to maximize surface area.
  • the membrane sock is placed over a slotted tube to prevent the sock from collapsing during use.
  • a net material is placed between the membrane sock and the slotted tube to facilitate flow between the membrane and the slots in the tube.
  • a large number of membrane modules, each containing a number of individual filter socks, are used.
  • the microfiltration membranes preferably have a pore size in the range from 0.5 micron to 5 micron, and preferably from 0.5 micron to 1.0 micron. By controlling the ratio of coagulant to silica contaminant, 99.99% of the precipitated contaminant particles can be greater than 5 microns. This allows the use of larger pore size microfiltration membranes. It has been found that the treated wastewater flow rate through 0.5 to 1 micron microfiltration membranes can be in the range from 150 gallons per square foot of membrane per day ("GFD") to 600 GFD.
  • Solids are preferably removed from the membrane surface by periodically backflushing the microfiltration membranes and draining the filtration vessel within which the membranes are located. The periodic, short duration back flush removes any buildup of contaminants from the walls of the microfiltration membrane socks. The dislodged solid material within the filtration vessel is flushed into a holding tank for further processing of the solids.
  • Wastewater pretreatment chemistry creates insoluble silica contaminant particulates which are efficiently removed by the microfiltration membranes.
  • Figure 1A is a photomicrograph of the precipitated silica particles produced in Example 3 at 24,000x magnification.
  • Figure IB is a photomicrograph of the precipitated silica particles produced in Example 3 at 49,000x magnification.
  • Figure 2A is a photomicrograph of the precipitated silica particles produced in Example 4 at 20,000x magnification.
  • Figure 2B is a photomicrograph of the precipitated silica particles produced in Example 4 at 40,000x magnification.
  • Figure 3 is a schematic representation of one wastewater pretreatment system.
  • FIG. 4 is a schematic representation of one wastewater microfiltration apparatus for high flow impurity removal.
  • the present invention is directed to a process for removing silica contaminants from large volumes of wastewater.
  • the wastewater is collected and pretreated with one or more organic polymer coagulants such that the silica reacts with the coagulant (s) to form spherical particulates which agglomerate into clusters having a size greater than 5 ⁇ .
  • the chemical coagulants are preferably mixed with the wastewater using reaction vessels or static in-line mixers, although other mixing methods can be used.
  • the treated wastewater is then passed through a microfiltration membrane having a pore size in the range from 0.5 ⁇ to 5 ⁇ to remove the silica contaminant particulates.
  • wastewater flow rates in the range from 150 gallons per square foot of membrane per day ("GFD") to 600 GFD are possible.
  • the microfiltration membrane is periodically backflushed to remove solids from the membrane surface.
  • the rejected solids are gravity collected in the filter vessel bottom and time cycle discharged to a settling tank for further sludge processing.
  • the microfiltration membranes are preferably provided in a cassette arranged module.
  • the microfiltration membranes provide a positive particle separation in a high recovery dead head filtration array.
  • the dead head filtration operates effectively at low pressures (4 psi to 15 psi, preferably 5 psi to 10 psi) and high flow rates, allowing 100% discharge of the supplied water with no transfer pumps needed. Solids which settle on the wall of the membrane during filtration are periodically backflushed away (and gravity settled) from the membrane surface to ensure a continuously clean filtration area.
  • the individual cassette module design allows for easy replacement of the membrane modules.
  • filter socks useful with the present invention contain a teflon coating on a polypropylene or polyethylene felt backing material. Such socks are available from W.L. Gore.
  • Another presently preferred filter sock manufactured by National Filter Media, Salt Lake City, Utah consists of a polypropylene membrane bonded to a polypropylene or polyethylene felt backing. Membrane "failure" is due primarily to flux loss, not mechanical failure. Many operations deem it more cost-effective to replace the membrane socks instead of cleaning contaminants from the membrane.
  • the membrane life is important to the continuous operation and operational cost of the filtration system.
  • the membranes manufactured by W.L. Gore and National Filter Media have been found to be robust and free of catastrophic failures at a temperature of 160°F and a pH greater than 13.
  • Anticipated operating conditions for the present invention are ambient temperature and pH between 5 and 11.
  • a currently preferred operating pH range is between about 7.3 and 9.3, although good results are obtained ⁇ 1.0 pH unit from the optimum pH. It is presently preferred to adjust the pH before adding the organic coagulant. It is expected that membranes used according to the present invention will have a life equal to or greater than 18 months.
  • the filtration system operates at a low pressure, preferably between 4 and 15 psi.
  • Example 1 A 15 gpm pilot scale system was used to process wastewater containing fluoride and a combined flow of fluoride and silica. A 38% sodium aluminate solution at a ratio of 0.23:1 A1:F and 50% aluminum chlorohydrate at a dose of 35 ppm to aid in the removal of the fluoride, total dissolved solids (TDS) , total suspended solids (TSS) , and some of the other present salt forms.
  • TDS total dissolved solids
  • TSS total suspended solids
  • the precipitate was flocculated with a medium charge (25 ⁇ 5 mole percent) , medium molecular weight anionic polyacrylamide polymer for ease of filtering or settling. This yielded very low to non-detectable effluent values of fluoride and Silt Density Indices (SDI) below 3.0.
  • the filtration membrane was a 0.5 ⁇ polypropylene bonded membrane obtained from National Filter Media. The membrane flux was measured at 650 to 800 GFD at a vessel operating pressure less than 9 psi. The results are reported below in parts per million.
  • the filtration membrane was a 0.5 micron polypropylene felt with a PTFE (polytetrafluoroethylene) coating obtained from W.L. Gore.
  • the membrane flux ranged from 175 GFD to 400 GFD at a vessel operating pressure less than 15 psi. The results are reported below in parts per million. Time
  • Example 3 A 3-5 gpm bench scale system was used to process wastewater containing silica.
  • the silica-containing waste stream was obtained from a commercially available CMP slurry sold by Rodel, known as ILD 1300.
  • the ILD 1300 slurry was diluted according to manufacturer's instructions, and it was found to contain about 1380 ppm Si, measured by graphite furnace atomic absorption, and about 70 ppm ammonium (NH 4 ) , measured by ion chromatography .
  • One liter of the waste stream weighted about 993.7 grams.
  • the silicon was present in the waste stream as dissolved and colloidal silica.
  • the waste stream was adjusted to a pH of about 8.58 by adding small amounts of sodium hydroxide and sulfuric acid.
  • the waste stream was mixed for about 3 minutes while the pH was adjusted. 2.09 g of a 20% by weight solution of epi-DMA, an epichlorohydrin/dimethylamine polymer having an average molecular weight of 250, 000 ⁇ 50, 000 (EnChem Lot I- 1396/423/MIC) and 0.19 g of dry aluminum chlorohydrate were added to one liter of the waste stream and mixed for about 20 minutes .
  • the reaction mixture was pumped at a pressure of about 6 psi through a two foot long filter sock having a diameter of about 3.5 inches.
  • the membrane flux was estimated at 189 GFD.
  • the filter sock contained a GOR-TEX® membrane (Lot. No. 66538-3- 786) obtained from W.L. Gore.
  • the membrane had a PTFE (polytetrafluoroethylene) coating on polypropylene felt having a 0.5 ⁇ pore size (1.5 ⁇ absolute).
  • the filter membrane effluent was collected, and it was found to contain about 15.5 ppm Si, measured by graphite furnace atomic absorption, and about 70 ppm ammonium (NH 4 ) , measured by ion chromatography .
  • the solids were collected from the filter surface and air dried for 24 hours.
  • the recovered solids formed well defined spherical particles which were easily removed from the filter membrane surface.
  • the dried and ground solids were analyzed, and the results are reported below in weight percent.
  • Figure 1A is a scanning electron micrograph (SEM) of the resulting spherical silica particles taken at 24,000x magnifi- cation.
  • Figure IB is a SEM of the product of Figure 1A taken at 49,000x magnification.
  • the particles had a typical particle size in the range from 0.05 ⁇ to 0.15 ⁇ .
  • the spherical particles are smaller than the membrane pore size, it has been found that the particles agglomerate to form large clusters that do not pass through the membrane.
  • the clusters have an average size in the range from 10 ⁇ to 300 ⁇ .
  • EDX analysis of the sample indicated the presence of silicon and aluminum in the sample, wherein the concentration of silicon was much greater than the concentration of aluminum.
  • a 3-5 gpm bench scale system was used to process wastewater containing silica.
  • the silica-containing waste stream was obtained from a commercially available CMP slurry sold by Hoescht, known as KLEBOSOL.
  • the KLEBOSOL slurry was diluted according to manufacturer's instructions, and it was found to contain about 4474 ppm Si and about 3.2 ppm aluminum by graphite furnace atomic absorption.
  • One liter of the waste stream weighed about 998.4 grams.
  • the silicon was present in the waste stream as dissolved and colloidal silica.
  • the waste stream was adjusted to pH 9.84 by addition of small amounts of NaOH and
  • the reaction mixture was pumped through the filter sock of Example 3 at a pressure of about 6 psi.
  • the filter membrane effluent was collected, and it was found to contain about 8.32 ppm Si and ⁇ 0.1 ppm aluminum by graphite furnace atomic absorption.
  • Figure 2A is a scanning electron micrograph (SEM) of the resulting spherical silica particles taken at 20,000x magnification.
  • Figure 2B is a SEM of the product of Figure 2A taken at 40,000x magnification.
  • EDX analysis of the sample indicated the presence of silicon and aluminum in the sample, wherein the concentration of silicon was much greater than the concentration of aluminum.
  • the silica particles of Figures 2A and 2B are remarkably similar to the silica particles of Figures 1A and IB.
  • Figure 3 illustrates one possible wastewater pretreatment system 10 within the scope of the present invention.
  • the illustrated wastewater pretreatment system 10 includes a plurality of pretreatment reactor vessels 12, 14, and 16 which enable the wastewater feed stream 18 to chemically react with one or more chemical coagulants.
  • Chemical coagulants which react with contaminants in the wastewater feed stream 18 are introduced into the pretreatment reactor vessels via chemical coagulant feed streams 20, 22, and 24.
  • the pH within the pretreatment reactor vessels is preferably monitored with a pH sensor 26. Acid or base can be added to the pretreatment reactor vessels, if necessary, to adjust the pH via acid/base feed stream 28.
  • the number of pretreatment reactor vessels can vary depending on the number of chemical coagulants being used and the reaction chemistry used to form the waste particulates.
  • the size of the reactor vessels can be varied to provide different reaction times.
  • the wastewater feed stream flows into a feed tank 30 for holding the pretreated wastewater. Additional chemical coagulants can be added directly to the feed tank 30, if necessary, via a chemical coagulant feed stream 31.
  • the pretreated wastewater is directed to one or more filtration vessels 32, 34, and 36 via filtration vessel feed stream 38.
  • the size of feed stream 38 will depend on the designed flow rate of the filtration vessel. For example, in a system having 5 filtration vessels, each handling 2500 gpm, a 24 inch feed line to the system is suitable.
  • Each filtration vessel 32, 34, and 36 is a stand alone filtration device. The number and size of each filtration vessel can vary depending on the system capacity requirements.
  • the filtrate is removed from each filtration vessel via a filtrate stream 40.
  • Each filtration vessel preferably provides a mounting platform for from 9 to 49 filter cassette modules.
  • One currently preferred filter cassette module contains 16 individual sock filters configured with 0.5 micron filtration membranes. The rated flow rate is 0.9 gpm per square foot of membrane area.
  • Each full cassette module has 64 square feet of membrane area and is rated at 58 gpm with a differential pressure less than 15 psi.
  • a lifting mechanism is preferably included to allow removal and replacement of the membrane cassette modules.
  • the filtration membranes are periodically backflushed with filtrate to remove solids from the membrane surface.
  • the filtration vessel is taken off line and wastewater is drained from the filtration vessel via a backflush exit stream 42 to a backflush tank 44.
  • the backflush tank 44 provides temporary storage before the backflushed wastewater is conveyed to the feed tank 30 via backflush return stream 46. It is estimated that 400-500 gallons of water will be used during a typical back flush cycle for a 2500 gpm filtration vessel.
  • a vacuum breaker 48 is preferably provided to allow equalization of pressure within the respective filtration vessel 32, 34, or 36 during the backflush procedure.
  • a vent/relief stream 49 is provided to allow venting or release of excess or over- pressurized wastewater.
  • the filtrate side of the filtration vessel 32, 34, 36 is open to the atmospheric pressure.
  • the filtrate is collected in the top of the filtration vessel and allowed to drain into the filtrate stream 40.
  • This volume of water provides the positive head which, when coupled with the negative head of draining the pressure side of the vessel via backflush exit stream 42, produces enough positive pressure gradient to backflush the filtration membrane.
  • the sludge is removed via a sludge discharge stream 50. While the sludge is removed, the filtration membranes are preferably rinsed with water from a water rinse stream 52. The collected sludge is removed from the system for further processing or storage.
  • the membranes may require soaking to remove trace amounts of organics. Cleaning preferably occurs as needed or as part of a regular maintenance program.
  • the vessel drain opens to remove all contaminant via the sludge discharge stream 50.
  • the cleaning solution is introduced into each filtration vessel through cleaning supply stream 54. Typical cleaning solutions include acids, bases, and surfactants.
  • the filtration vessel can be returned to operation without draining and rinsing the filtration membranes. If membrane rinsing is necessary, the contents of the filtration vessel 32, 34, 36 are removed via cleaning discharge stream 56 for further processing.
  • multiple filtration vessels are preferably used, in parallel, to provide for the required flow rate.
  • the filtration vessels can be operated in series to provide primary filtration and secondary filtration. Because filtration vessels are taken off line during the backflushing, additional filtration vessels and capacity are preferably used to ensure that the require discharge flow is maintained. An additional filtration vessel may be supplied to provide for offline maintenance while the remainder of the system meets the flow rate requirements.
  • the wastewater treatment system preferably includes access to the various process streams to allow for sampling and analysis.
  • the valves, pumps, and sensors customarily used in the art to safely control the described fluid flow to and from the filtration vessels are preferably provided. Such valves, pumps, and sensors also allow for automation of the process. From the foregoing, it will be appreciated that the present invention provides a process for removing contaminants from wastewater utilizing a positive physical barrier to precipitated particles.
  • the positive separation barrier permits discharge having lower concentration limits than conventional clarifier/sand filter systems.

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  • Engineering & Computer Science (AREA)
  • Water Supply & Treatment (AREA)
  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Hydrology & Water Resources (AREA)
  • Environmental & Geological Engineering (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)
  • Separation Of Suspended Particles By Flocculating Agents (AREA)

Abstract

L'invention concerne un procédé et un système permettant d'extraire la silice de volumes importants d'eaux usées. Dans ce procédé on traite un flux d'eaux usées contenant de la silice avec un coagulant chimique tel qu'un polymère épichlorhydrine/diméthylamine, de manière à former des particules sphériques qui s'agglomèrent en paquets d'un diamètre supérieur à 5 microns. On passe ensuite les eaux usées traitées à travers une membrane de microfiltration qui sépare physiquement les particules contaminantes de silice des eaux usées. On peut utiliser à cette fin des membranes de microfiltration disponibles dans le commerce comprenant des pores d'une dimension comprise entre 0,5 microns et 5 microns. La vitesse d'écoulement des eaux usées traitées à travers les membranes de microfiltration peut aller de 150 à 600 gallons par pied carré de membrane par jour. Les solides sont éliminés de la surface de la membrane par un rinçage périodique à courant inverse des membranes de microfiltration et les solides sont drainés à intervalles minutés de la cuve de filtration contenant les membranes. Le matériau solide délogé de la cuve de filtration est déversé dans une cuve de rétention pour être soumis à des traitements complémentaires.
EP98952200A 1997-11-06 1998-10-09 Procede permettant d'extraire la silice des eaux usees Withdrawn EP1042231A4 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US965574 1997-11-06
US08/965,574 US5965027A (en) 1996-11-26 1997-11-06 Process for removing silica from wastewater
PCT/US1998/021337 WO1999024364A1 (fr) 1997-11-06 1998-10-09 Procede permettant d'extraire la silice des eaux usees

Publications (2)

Publication Number Publication Date
EP1042231A1 true EP1042231A1 (fr) 2000-10-11
EP1042231A4 EP1042231A4 (fr) 2002-07-17

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP98952200A Withdrawn EP1042231A4 (fr) 1997-11-06 1998-10-09 Procede permettant d'extraire la silice des eaux usees

Country Status (6)

Country Link
EP (1) EP1042231A4 (fr)
JP (1) JP3470130B2 (fr)
KR (1) KR100385706B1 (fr)
AU (1) AU9795498A (fr)
TW (1) TW425376B (fr)
WO (1) WO1999024364A1 (fr)

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JPH1076277A (ja) * 1996-09-04 1998-03-24 Lion Corp 水処理用薬剤組成物およびそれを用いた水処理方法
JPH10118665A (ja) * 1996-10-15 1998-05-12 Kurita Water Ind Ltd Ｎｈ４系ｃｍｐ廃液の処理方法
JPH10180008A (ja) * 1996-12-26 1998-07-07 Kurita Water Ind Ltd 膜分離装置

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KR20010031846A (ko) 2001-04-16
KR100385706B1 (ko) 2003-05-27
WO1999024364A1 (fr) 1999-05-20
TW425376B (en) 2001-03-11
EP1042231A4 (fr) 2002-07-17
AU9795498A (en) 1999-05-31
JP3470130B2 (ja) 2003-11-25
JP2001522720A (ja) 2001-11-20

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