WO2007088138A1 - Procede de traitement d'une boue - Google Patents

Procede de traitement d'une boue Download PDF

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Publication number
WO2007088138A1
WO2007088138A1 PCT/EP2007/050769 EP2007050769W WO2007088138A1 WO 2007088138 A1 WO2007088138 A1 WO 2007088138A1 EP 2007050769 W EP2007050769 W EP 2007050769W WO 2007088138 A1 WO2007088138 A1 WO 2007088138A1
Authority
WO
WIPO (PCT)
Prior art keywords
iron
sludge
trivalent iron
trivalent
filtration
Prior art date
Application number
PCT/EP2007/050769
Other languages
English (en)
Inventor
Stefan JÄFVERSTRÖM
Kjell Stendahl
Hans David Ulmert
Original Assignee
Feralco Ab
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
Application filed by Feralco Ab filed Critical Feralco Ab
Publication of WO2007088138A1 publication Critical patent/WO2007088138A1/fr

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Classifications

    • 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
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F9/00—Multistage treatment of water, waste water or sewage
    • 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
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • 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
    • C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
    • 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
    • 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
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/72—Treatment of water, waste water, or sewage by oxidation
    • 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
    • C02F1/72—Treatment of water, waste water, or sewage by oxidation
    • C02F1/76—Treatment of water, waste water, or sewage by oxidation with halogens or compounds of halogens
    • 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
    • C02F1/72—Treatment of water, waste water, or sewage by oxidation
    • C02F1/78—Treatment of water, waste water, or sewage by oxidation with ozone
    • 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
    • C02F2101/20—Heavy metals or heavy metal compounds
    • C02F2101/203—Iron or iron compound
    • 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
    • C02F2103/26—Nature of the water, waste water, sewage or sludge to be treated from the processing of plants or parts thereof
    • C02F2103/28—Nature of the water, waste water, sewage or sludge to be treated from the processing of plants or parts thereof from the paper or cellulose industry

Definitions

  • TITLE METHOD FOR TREATMENT OF SLUDGE
  • the invention relates to treatment of sludge from waterworks, and similar sludge from industrial processes, such as paper industry. More specifically, the invention relates to a method for recycling of iron from a sludge, which sludge includes trivalent iron.
  • a separation of suspended matter lowers the turbidity of the water and a separation of humus reduces the discoloration of the water.
  • inorganic chemical coagulants such as trivalent metallic salts of iron and aluminium.
  • metallic ions formed in this connection during mild stirring, flocks of hydroxide, that encase and adsorb the suspended material and the in water solved organic substances.
  • the formed flocks are separated in different ways, such as flotation/sandfiltra- tion, sedimentation/sandfiltration, or merely sandfiltra- tion.
  • the separated flocks are pumped as thin sludge out from the construction, directly back to the recipient or to a sludge lagun.
  • the sludge is dewatered, for example in a centrifuge, to be deposited thereafter. In warm countries the sludge may be laid on drying beds, to be deposited thereafter.
  • Another alternative method to take care of the thin sludge is to add acid, preferably sulphuric acid.
  • the metallic hydroxide which was obtained during the flocculation process, is dissolved in such way that metallic ions are obtained, mainly Fe 3+ and Al 3+ .
  • metallic ions mainly Fe 3+ and Al 3+ .
  • a sludge mixture with low pH is thus obtained, that includes suspended matter, organic substances and inorganic ions.
  • This sludge mixture may then be filtrated in a membrane filtration process, in such way that a concentrate and a permeate are obtained.
  • said permeate includes mainly the inorganic chemical coagulants in solution.
  • membranes with large pores are used (for example micro filtration)
  • the membranes in other processes have small pores (for example reversed osmosis) .
  • Some processes are based on the fact that the membranes are charged (for example nano filtration) , while the possible charge of the membranes does not affect the main separation mechanism in other processes (for example micro filtration) .
  • the sludge mixture is led to a first construction for membrane filtration, which may be a construction for ultra filtration or a construction for micro filtration.
  • UF ultra filtration
  • the size of the particles mainly decides what will be separated and what will pass through the membrane.
  • the sieving mechanism dominates, but diffusion and interaction between membrane and the dissolved substances are also of importance.
  • the separation with micro filtration (MF) is totally based on a sieving mechanism, and the size of the pores is the decisive factor in respect of what will pass through the membrane .
  • the sludge mixture is pumped through a MF con- struction or a UF construction.
  • the MF construction sepa- rates mainly suspended substances and colloids, but not dissolved organic substances, while the UF construction also separates bigger organic molecules.
  • a permeate including mainly water with inorganic ions, such as Fe 3+ and Al 3+ , which pass through said filter.
  • inorganic ions such as Fe 3+ and Al 3+
  • the permeate may therefore be used as chemical coagulant in both wastewater treatment plants and waterworks.
  • the permeate will also include dissolved organic substances with low molecu- lar weight and such heavy metals that, just as aluminium and iron ions, have been dissolved during the acid treatment. This is a disadvantage. Both heavy metals and organic substances will therefore accumulate in the system and constantly increase in respect of concentration, which may result in a deteriorating quality on the treated water.
  • a concentration process may be performed in a nano filtration construction (NF) , or in a reversed osmosis construction (RO) .
  • NF nano filtration construction
  • RO reversed osmosis construction
  • US 5,674,402 describes a process wherein the concentration is obtained by precipitation of Al, in form of alunite, which means that alunite on one hand has to be reprocessed, by dissolving the alunite in acid, to obtain a water soluble chemical coagulant, and on the other hand has to be calcinated, to get rid of co-precipitated organic matter. Furthermore, precipitation of alunite does not give a product that is free from heavy metals, which results in that it may be difficult to fulfil the demands on chemical substances in drink-water by this process.
  • the present invention preferably seeks to mitigate, alleviate or eliminate one or more of the above-identified deficiencies in the art and disadvantages singly or in any combination and solves at least the above mentioned problems by providing a method and a chemical coagulant according to the appended patent claims.
  • An aspect of the present invention is to provide a method for recycling iron from a sludge, which sludge has been obtained from waterworks, or similar sludge from industrial processes, such as paper industry.
  • FIG. 1 is a flow chart of an embodiment of the present invention.
  • a sludge 11, containing iron hydroxide (Fe(OH) 3 ) formed during flocculation in flocculation basins in waterworks, or similar sludge from industrial processes, such as paper industry, is led to an acid dissolution step A.
  • This iron hydroxide is formed from trivalent iron (Fe 3+ ) that is added in said flocculation basin as a chemical coagulant.
  • an acid 12 is added to the sludge.
  • This acid may for example be sulphuric acid, but other acids, which are known to the person skilled in the art may also be used.
  • the iron hydroxide Fe(OH) 3
  • the present inventors have found that the divalent iron ions (Fe 2+ ) formed in this acid dissolution step do not react with the organic substances, which will be shown to be very favourable later in the process, as seen below. Therefore, by in this step maximizing the reduction of trivalent iron to divalent iron a condition is obtained in which the separation between iron and organic substances is optimized.
  • a reduction agent 13 is added to further improve the transformation of trivalent iron ions to divalent iron ions.
  • this reduction agent 13 is at least one reduction agent selected from the group comprising sodium bisulphite and metallic iron powder.
  • the acidified sludge, containing the divalent iron ions (Fe + ) formed in the acid dissolution step is transported to a membrane filtration step B.
  • Said membrane filtration step B may be an ultra filtration step, a nano filtration step, or a combination of an ultra filtration step and a nano filtration step.
  • organic substances are separated as an organic concentrate 14, while the permeate comprises the divalent iron, which was formed in the acid dissolution step A.
  • the permeate leaving the membrane filtration step B is of course still of a low pH.
  • said permeate has a pH of 2. Since the separation between iron (divalent iron) and organic substances were optimized in the dissolution step A, the separation of iron (divalent iron) and organic substances is also optimized in this filtration step B.
  • Said organic concentrate 14 may be used or deposited 15.
  • the further improvement of the reduction of the trivalent iron by addition of a reduction agent 13 is performed after said membrane filtration step B.
  • the only limitation in this respect is to perform the reduction before a precipitation step C, further described below.
  • the separation is obtained by a driving force, in form of a difference in chemical potential over the membrane.
  • This driving force may be an applied pressure, a difference in concentration or in temperature, or a difference in electric potential.
  • the separation mechanism is based on a solution theory, in which the solubility of the dissolved substances and the diffusivity in the membrane are decisive.
  • a precipitation step C wherein divalent iron is precipitated as iron hydroxide (Fe(OH) 2 ).
  • This precipitation is accomplished by adding a suitable alkali 16, whereupon the pH naturally is increased. This increase of pH makes the pH rise from 2 to neutral. The increase of pH may of course vary somewhat, but normally it results in a pH of 7 to 8.
  • This alkali 16 may be selected from the group comprising potassium hydroxide, sodium hydroxide, sodium carbonate, magnesium hydroxide, potassium carbonate, magnesium carbonate, and/or magnesium oxide.
  • a separation step D the iron hydroxide (Fe(OH) 2 ) is separated from the solution (i.e. the permeate from the membrane filtration step, which has been exposed to the precipitation step C) , since this solution still contains a degree of organic substances.
  • This separation may be performed by any kind of filtration, which filtration is obvious to the person skilled in the art. Examples of such separation methods are filtration, sedimentation, flotation/sandfiltration, sedimentation/sandfiltration, or merely sandfiltration . Therefore, a filtrate 17 is obtained in said separation step D. In one embodiment of the present invention this filtrate 17 is exposed to a nanofiltration step G, from which water 18 of neutral water and an organic concentrate.
  • This organic concentrate may be combined with the organic concentrate 14 obtained in the membrane filtration step B. Said organic concentrate, or combined organic concentrate, 14 may then be used or deposited 15.
  • the iron hydroxide (Fe (OH) 2) is then exposed to an oxidation step E.
  • said divalent iron hydroxide (Fe (OH) 2) is oxidized to the trivalent form of iron hydroxide (Fe(OH) 3 ).
  • This oxidation is accomplished by adding a suitable oxidation agent 19.
  • said oxidation agent is oxygen in air or concentrated oxygen.
  • said oxidation agent may be selected from the group consisting of ozone and hydrogen peroxide, or active chlorine, such as chlorine gas, chlorate, and sodium hypochlorite.
  • active chlorine such as chlorine gas, chlorate, and sodium hypochlorite.
  • oxidising compounds including active oxygen are preferred, since chlorine together with organic substances may form toxic and carcinogenic organochlorines .
  • the iron hydroxide (Fe(OH) 3 ) is exposed to an acid dissolution step F.
  • an acid 20 is added.
  • trivalent iron ions (Fe 3+ ) 20 are obtained.
  • Said trivalent iron ions 21 may thereafter be reused as chemical coagulant in waterworks, or similar sludge from industrial processes, such as paper industry.

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  • Life Sciences & Earth Sciences (AREA)
  • Hydrology & Water Resources (AREA)
  • Engineering & Computer Science (AREA)
  • Environmental & Geological Engineering (AREA)
  • Water Supply & Treatment (AREA)
  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)

Abstract

L'invention concerne un procédé pour le traitement d'une boue (11) comprenant du fer trivalent, ladite boue (11) étant soumise à une dissolution acide (A), puis à au moins une filtration sur membrane (B), un perméat comprenant du fer trivalent étant obtenu. Le fer trivalent est réduit en fer bivalent avant de précipiter (C) ledit fer bivalent.
PCT/EP2007/050769 2006-01-31 2007-01-26 Procede de traitement d'une boue WO2007088138A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE0600206 2006-01-31
SE0600206-7 2006-01-31

Publications (1)

Publication Number Publication Date
WO2007088138A1 true WO2007088138A1 (fr) 2007-08-09

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PCT/EP2007/050769 WO2007088138A1 (fr) 2006-01-31 2007-01-26 Procede de traitement d'une boue

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2012146324A1 (fr) * 2011-04-29 2012-11-01 Feralco Ab Procédé de traitement de boues provenant d'installations de traitement de l'eau et des eaux usées utilisant un traitement chimique

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4680126A (en) * 1986-02-18 1987-07-14 Frankard James M Separation and recovery of reusable heavy metal hydroxides from metal finishing wastewaters
WO1996020894A1 (fr) * 1994-12-30 1996-07-11 Kemira Chemicals Oy Procede de traitement de boues d'eaux residuaires
WO1998041479A1 (fr) * 1997-03-14 1998-09-24 Kemira Kemi Ab Procede de traitement des boues resultant d'un traitement des eaux de decharge
WO2005037714A1 (fr) * 2003-10-17 2005-04-28 Feralco Ab Procede de traitement des boues
US20050145569A1 (en) * 2002-05-28 2005-07-07 Ulmert Hans D. Method for treatment of sludge from waterworks and wastewater treatment plants

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4680126A (en) * 1986-02-18 1987-07-14 Frankard James M Separation and recovery of reusable heavy metal hydroxides from metal finishing wastewaters
WO1996020894A1 (fr) * 1994-12-30 1996-07-11 Kemira Chemicals Oy Procede de traitement de boues d'eaux residuaires
WO1998041479A1 (fr) * 1997-03-14 1998-09-24 Kemira Kemi Ab Procede de traitement des boues resultant d'un traitement des eaux de decharge
US20050145569A1 (en) * 2002-05-28 2005-07-07 Ulmert Hans D. Method for treatment of sludge from waterworks and wastewater treatment plants
WO2005037714A1 (fr) * 2003-10-17 2005-04-28 Feralco Ab Procede de traitement des boues

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2012146324A1 (fr) * 2011-04-29 2012-11-01 Feralco Ab Procédé de traitement de boues provenant d'installations de traitement de l'eau et des eaux usées utilisant un traitement chimique

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