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WO2019115884A1 - Procédé pour la déshydratation de boues biologiques - Google Patents

Procédé pour la déshydratation de boues biologiques Download PDF

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Publication number
WO2019115884A1
WO2019115884A1 PCT/FI2018/050924 FI2018050924W WO2019115884A1 WO 2019115884 A1 WO2019115884 A1 WO 2019115884A1 FI 2018050924 W FI2018050924 W FI 2018050924W WO 2019115884 A1 WO2019115884 A1 WO 2019115884A1
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WIPO (PCT)
Prior art keywords
polymer
sludge
mol
cationic
dewatering
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Ceased
Application number
PCT/FI2018/050924
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English (en)
Inventor
Joonas LIKANDER
Rosa Carceller
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.)
Kemira Oyj
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Kemira Oyj
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Filing date
Publication date
Application filed by Kemira Oyj filed Critical Kemira Oyj
Publication of WO2019115884A1 publication Critical patent/WO2019115884A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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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
    • 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
    • B01D21/00—Separation of suspended solid particles from liquids by sedimentation
    • B01D21/01—Separation of suspended solid particles from liquids by sedimentation using flocculating agents
    • 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
    • C02F11/14—Treatment of sludge; Devices therefor by de-watering, drying or thickening with addition of chemical agents
    • C02F11/147—Treatment of sludge; Devices therefor by de-watering, drying or thickening with addition of chemical agents using organic substances

Definitions

  • the present invention relates to a method for dewatering of biological sludge according to preambles of the enclosed independent claim.
  • Biological sludge contains mass of aerobic bacteria and other aquatic organisms, which are suspended and mixed with wastewater in an aerated tank. Excess sludge is removed from the process for post-treatment of sludge. Typically, large quantities of wet sludge are formed, which must be dewatered before it can be disposed. Dewatering can be done by using gravity, filtering, pressing or centrifugal force. The sludge is exposed to various forces, e.g. high shear forces, during the dewatering and other post-treatment steps.
  • Biological sludges are often difficult to dewater.
  • Sludges may be conditioned before dewatering by addition of chemicals, such as inorganic compounds of iron and lime, or organic compounds, such as polymer coagulants and flocculants.
  • the chemicals are added to improve the sludge handling, to coagulate and/or flocculate the suspended matter into larger agglomerates and to increase dewatering effect.
  • the formed floes should resist various forces, e.g. shear forces, without breaking of the floe. This would ensure that high quality water phase with low turbidity is obtained from the dewatering step and that the solids content of the sludge is high after dewatering.
  • An object of this invention is to minimise or even eliminate the disadvantages existing in the prior art.
  • An object is also to provide a polymer composition which provides an effective dewatering of biological sludge.
  • a further object of this invention is to provide a polymer composition which is provides improved sludge performance during dewatering, especially under high- shear conditions.
  • Typical method according to the present invention for dewatering of biological sludge comprises
  • a flocculant to a biological sludge, which comprises an aqueous phase and suspended solid organic material, and flocculating the sludge
  • the flocculant comprises a polymer composition, which comprises
  • a cationic linear first polymer which is obtained by polymerising diaiiyidimethylammonium chloride (DADMAC), and
  • a cationic second polymer which is a copolymer obtained by polymerisation of (meth)acrylamide and at least one cationic monomer, the second cationic polymer being polymerised in presence of the cationic first polymer.
  • the polymer composition which is formed from a combination of the first polymer comprising diailyidimethyi- ammonium chloride (DADMAC) and the second polymer comprising cationic copolymer of (meth)acrylamide and cationic monomer, provides the flocculant with properties, with which an improved dewatering rate, filtrate quality, shear resistance and dry solids content can be achieved for the biological sludge. It is speculated that the polymer composition is able to interact with the solid constituents of the biological sludge in a manner that generates more robust floes and enhances the dewatering performance. Furthermore, the flocculant comprising the defined polymer composition tolerates well process variations.
  • DADMAC diailyidimethyi- ammonium chloride
  • cationic copolymer of (meth)acrylamide and cationic monomer provides the flocculant with properties, with which an improved dewatering rate, filtrate quality, shear resistance and dry solids content can be achieved for the biological s
  • biological sludge denotes a sludge originating from a biological treatment process of wastewater and/or sewage.
  • Biological sludge comprises an aqueous phase and suspended solid organic material, and it is typically rich in material of bacterial origin as well as other aquatic organisms.
  • the biological sludge may have a biological oxygen demand (BOD) > 50 mg/I, and/or a dry solids content in the range of 5 - 80 g/l, preferably 10 - 40 g/l.
  • BOD biological oxygen demand
  • the biological sludge to be dewatered originates from a process treating municipal or agricultural wastewater.
  • the biological sludge may thus be municipal wastewater sludge or agricultural sludge.
  • the biological sludge may originate from an industrial process, especially from wastewater treatment or from food or beverage production or from food or beverage processing.
  • Dewatering of biological sludge comprises an addition of a flocculant to the biological sludge for flocculating the biological sludge before the dewatering of the biological sludge.
  • the flocculant is added immediately before the dewatering.
  • the flocculant is added 30 s, preferably 20 s, more preferably 15 s before start of the dewatering.
  • the flocculant can be added directly to a pipeline or the like where the biological sludge is transported to the dewatering.
  • Dewatering of the biological sludge may be performed by using mechanical dewatering means, such as centrifuge(s), belt press or chamber press, preferably centrifuge(s).
  • the flocculant comprises a polymer composition, which comprises a first polymer, which is obtained by polymerising dia!ly!dimethylammonium chloride, DADMAC.
  • a polymer composition which comprises a first polymer, which is obtained by polymerising dia!ly!dimethylammonium chloride, DADMAC.
  • the first polymer functions as a polymerisation medium for the second polymer, i.e. the monomers of the second polymer are added to a polymer solution of the first polymer and polymerisation of the second polymer is conducted in the presence of the first polymer.
  • the first and second polymers become inseparable from each other without breaking of the polymer chains, i.e.
  • the polymer chains of the first polymer and the second polymer are physically entangled and inseparably entangled in during the polymerisation of the second polymer.
  • the first polymer is preferably free of reactive polymerizable groups, such as double carbon-carbon bonds, in its structure.
  • the monomers of the second polymer when polymerised in the presence of the first polymer, are reacting with each other and not forming covalent bonds with the first polymer, which is present as polymerisation medium.
  • the first polymer is preferably present essentially only as polymerisation medium.
  • Covalent bonds between the first and the second polymer are not requisite for providing the three-dimensional structure to the polymer composition, as the first and second polymer are physically entangled, and their polymer chains are inseparably intertwined or interlaced with each other.
  • the first polymer and the second polymer are fully miscible and compatible with each other.
  • the obtained polymer composition is not in form of an emulsion or dispersion. This means that the obtained polymer composition does not contain two or more phases of different polymers.
  • the polymer composition is also preferably free from polymer particles comprising mostly (>40 %) of only one polymer.
  • the polymer composition is water-soluble.
  • the first polymer is obtained by polymerising diailyldimethylammonium chloride, DADMAC.
  • the first polymer is diailyldimethylammonium chloride (DADMAC) homopolymer.
  • DADMAC diailyldimethylammonium chloride
  • the first polymer comprises a small amount of other second monomers, as long as the second monomers are non-ionic, such as acrylamide, and their total amount is low, preferably ⁇ 10 weigh-%, more preferably ⁇ 5 weight- %, calculated from the weight of monomers used for obtaining the first polymer.
  • the first polymer may have a weight average molecular weight at least 10 000 g/mol, preferably in the range of 10 000 - 750 000 g/mol, more preferably 50 000 - 450 000 g/mol, even more preferably 75 000 - 400 000 g/mol.
  • the first polymer may have a weight average molecular weight in the range of 120 000 - 450 000 g/mol, preferably 125 000 - 400 000 g/mol, more preferably 135 000 - 350 000 g/mol.
  • the first polymer preferably has a molecular weight, which has been observed to improve the performance of the polymer composition and its flocculation ability.
  • the first polymer may preferably be obtained by radical polymerisation.
  • the polymer composition may comprise at least 1 weight-%, preferably 1 - 30 weight-%, more preferably 2 - 20 weight-%, even more preferably 2 - 15 weight-%, of the first polymer, calculated from the total dry polymeric material weight of the composition.
  • the amount of first polymer provides suitable viscosity, when it acts as polymerisation medium for the second polymer while simultaneously providing the final polymer composition with an efficient interaction with the constituents of the biological sludge and good flocculation ability.
  • the polymer composition which is used as flocculant, comprises further a cationic second polymer, which is a copolymer obtained by polymerisation of (meth)acrylamide and at least one cationic monomer.
  • the second cationic polymer is polymerised in presence of the cationic first polymer.
  • the polymerisation medium for the second polymer thus comprises an aqueous, preferably particle- free, solution of the first polymer.
  • the polymerisation medium preferably is free from any oil phase.
  • the polymerisation medium does not comprise high concentration of any inorganic salt, either.
  • the amount of inorganic salt is less than 5 weight-%, preferably less than 2.5 weight-%, more preferably less than 1.5 weight-%. It has been observed that the second polymer improves the robustness of the formed floes.
  • the second polymer is obtained by free radical polymerisation.
  • the second polymer may be obtained by gel polymerisation, e.g. by adiabatic gel polymerisation. It is possible to obtain a polymer composition having a higher polymer content by gel polymerisation, which makes the composition more cost efficient in view of the logistics. A high polymer content has the additional benefit of improved microbial stability.
  • the polymer composition may preferably be in form of a dry powder or particulate material or particulate product, and it is dissolved into the water and diluted to desired appropriate feed concentration before its use.
  • the obtained polymer composition may be dried and optionally milled to a suitable particle size.
  • the dry polymer composition in form of particulate product or particulate material or powder may have a solids content of at least 80 weight-%, preferably at least 85 weight-%, more preferably at least 90 weight-%. Dry particulate polymer composition is easy and cost-efficient to transport and store, it remains stable for long periods of time and is resistant towards microbiological degradation.
  • the cationic monomer for the second polymer may be selected from group consisting of 2-(dimethylamino)ethyl acrylate (ADAM), [2-(acryloyloxy)ethyl] trimethylammonium chloride (ADAM-CI), 2-(dimethylamino)ethyl acrylate benzylchloride, 2-(dimethylamino)ethyl acrylate dimethylsulphate, 2- dimethylaminoethyl methacrylate (MADAM), [2-(methacryloyloxy)ethyl] trimethylammonium chloride (MADAM-CI), 2-dimethylaminoethyl methacrylate dimethylsulphate, [3-(acryloylamino)propyl] trimethylammonium chloride (APTAC), [3-(methacryloylamino)propyl] trimethylammonium chloride (MAPTAC), and diaiiyldimethylammonium chloride (
  • the cationic monomer is [2-(acryloyloxy)ethyl] trimethylammonium chloride (ADAM-CI) or diaiiyldimethyl ammonium chloride (DADMAC).
  • ADAM-CI [2-(acryloyloxy)ethyl] trimethylammonium chloride
  • DMDMAC diaiiyldimethyl ammonium chloride
  • the cationicity is not pH dependent, which is a preferable feature.
  • the second polymer may be obtained by copolymerisation of (meth)acrylamide and at least 10 mol-% of cationic monomer(s), preferably 10 - 90 mol-%, more preferably 20 - 70 mol-%, even more preferably 30 - 60 mol-%, of cationic monomer(s), calculated from amount of monomers used for second polymer.
  • the second polymer may be a linear polymer.
  • the second polymer is a crosslinked copolymer.
  • the crosslinked second polymer may be obtained by polymerising (meth)acrylamide and cationic monomers in the presence of at least one crosslinking agent. It has been observed that when the second polymer is crosslinked, the formed floes of biological sludge are very robust, and resist well high-shear forces.
  • Suitable crosslinking agent may be selected from methylenebis- acrylamide, ethylene glycol divinyl ether, di(ethylene glycol) divinyl ether and tri- (ethylene glycol) divinyl ether. Methylenebisacrylamide is being preferred as crosslinking agent.
  • the amount of crosslinking agent may be, for example, in the range of 0.25 - 100 mg/kg monomers, preferably 0.5 - 10 mg/kg monomers, more preferably 0.75 - 5 mg/kg monomers.
  • the polymer composition which is used as a flocculant for the biological sludge, may have a standard viscosity SV of 3.5 - 5 mPas, preferably 3.8 - 4.8, measured at 0.1 weight-% solids content in an aqueous NaCI solution (1 M), at 25 °C, using Brookfield DVII T viscometer with UL adapter.
  • the flocculant comprising the polymer composition may be added in amount of 1 - 40 kg/ton dry sludge, preferably 2 - 30 kg/ton dry sludge, preferably 4 - 20 kg/ton dry sludge, given as active polymer.
  • composition C1 comprised as first polymer linear homopolymer of dialiyldimethyl- ammonium chloride (DADMAC), having weight average molecular weight ca. 300 000.
  • DMDMAC dialiyldimethyl- ammonium chloride
  • the second polymer which was polymerised in the presence of the first polymer was a copolymer of acrylamide and 30 mol-% of [2-(acryloyloxy)ethyl] trimethylammonium chloride (ADAM-CI).
  • the amount of first polymer was 9 weight-%, as active, based on monomers of the second polymer.
  • Composition C2 comprised as first polymer linear homopolymer of dial!y!dimethyl- ammonium chloride (DADMAC), having weight average molecular weight ca. 300 000.
  • the second polymer which was polymerised in the presence of the first polymer was a copolymer of acrylamide and 30 mol-% of [2-(acryloyloxy)ethyl] trimethylammonium chloride (ADAM-CI). Methylenebisacrylamide was used as crosslinker in the polymerisation.
  • the amount of first polymer was 9 weight-%, as active, based on monomers of the second polymer.
  • Polymer R1 was used as reference in the Examples. Polymer R1 was a copolymer of acrylamide and 30 mol-% of [2-(acryloyloxy)ethyl] trimethylammonium chloride (ADAM-CI). Methods Used in the Examples
  • Table 1 Apparatuses and methods used in sludge dewatering examples.
  • Gravity dewaterability of sludge was tested with Polytest.
  • the sludge samples were filtered with Polytest cylinder of 10 cm diameter using in bottom a wire cloth having air permeability of 5400 m 3 /m 2 h. Treads/cm was 13.0/5.9.
  • the sludge sample amount was 200 - 400 g, but always identical between samples compared.
  • Mixing of the polymer composition was done with motor stirrer in baffled mixing vessel. Mixing speed was 1000 rpm and mixing time was 10 - 30 seconds, but always identical between samples compared.
  • Sludge dry solids content after centrifugation was tested with Heraeus laboratory centrifuge. For this test, sludge sample was taken from Polytest wire after gravity dewaterability testing.
  • Sludge sample of about 6 grams was measured to a 50 mesh plastic filter that was placed on upper part of centrifuge tube. Centrifugation time was 60 seconds and rotation rate 1000 rounds per minute (rpm). After the centrifugation, reject water was collected from bottom of the centrifuge tube and centrifuged sludge from plastic filter.
  • Example simulates dewatering of biological sludge after anaerobic digestion process in a wastewater treatment plant with biological phosphorus removal. Dry solids content of the biological sludge was 29 g/l before dosage of the polymer composition. Polymer compositions were diluted to 0.1 % concentration before dosing to the sludge. Dewatering rate was tested with Polytest as described above. Polymer doses were 5, 6 and 6.5 kg/ton dry sludge. Mixing time was 10 seconds. Amount of drained water was measured after 60 seconds. Turbidity was measured from the drained reject water. Results are presented in Table 2.
  • This example simulates centrifugation of biological sludge after anaerobic digestion process in municipal wastewater treatment plant with biological phosphorus removal. Dry solids content of the biological sludge was 29 g/l before dosage of the polymer composition.
  • Polymer compositions were diluted to 0.1 % concentration before dosing to the sludge.
  • Sludge dry solids after centrifugation was tested with table centrifuge as described above. Polymer doses were 5, 6 and 6.5 kg/ton dry sludge with mixing time 10 seconds and 6, 7 and 8 kg/ton dry sludge with mixing time 20 seconds. Dry solids content of the sludge was measured after 60 second centrifugation at 1000 rpm. Results are presented in Table 3. Table 3 Dry solids content results after centrifugation in Example 2.
  • This example simulates dewatering of biological sludge after anaerobic digestion process in municipal wastewater treatment plant with chemical phosphorus removal. Dry solids content of the biological sludge was 25 g/l before dosage of the polymer composition.
  • Polymer compositions were diluted to 0.1 % concentration before dosing to the sludge. Dewatering rate was tested with Polytest as described above. Polymer doses were 7, 8 and 9 kg/ton dry sludge with mixing time 10 seconds and 9, 10 and 11 kg/ton dry sludge with mixing time 30 seconds. Amount of drained water was measured after 10 seconds. Turbidity was measured from the drained reject water. Results are presented in Table 4. Table 4 Results for drainage and reject water turbidity in Example 4.
  • polymer composition C2 According to the invention provided better performance than the reference polymer R1. Polymer composition C2 produced faster dewatering and better reject water quality than the reference polymer R1. Polymer composition C2 did also have much better shear resistance, which was seen in the experiments with longer mixing time causing more shear forces to the floes. All of these factors are important for economical sludge dewatering.

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

Abstract

L'invention concerne un procédé de déshydratation de boues biologiques. Il comprend l'addition d'un floculant à une boue biologique, composée d'une phase aqueuse et d'un matériau organique solide en suspension, la floculation et la déshydratation des boues. Le floculant comprend une composition polymère, composée d'un premier polymère linéaire cationique, qui est obtenu par polymérisation de DADMAC, et un second polymère cationique, qui est un polymère obtenu par polymérisation de (méth)acrylamide et de monomères cationiques, le second polymère cationique étant polymérisé en présence du premier polymère cationique.
PCT/FI2018/050924 2017-12-15 2018-12-14 Procédé pour la déshydratation de boues biologiques Ceased WO2019115884A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI20176123 2017-12-15
FI20176123 2017-12-15

Publications (1)

Publication Number Publication Date
WO2019115884A1 true WO2019115884A1 (fr) 2019-06-20

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0479616A1 (fr) * 1990-10-04 1992-04-08 Ciba Specialty Chemicals Water Treatments Limited Compositions et procédés pour la déshydratation
WO2002081384A2 (fr) * 2001-04-05 2002-10-17 Ciba Specialty Chemicals Water Treatments Limited Procede de floculation de suspensions
US20070187330A1 (en) * 2004-03-12 2007-08-16 Tony Whittaker Dewatering process
WO2017142827A2 (fr) * 2016-02-18 2017-08-24 General Electric Company Concentration de solides de distillation

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0479616A1 (fr) * 1990-10-04 1992-04-08 Ciba Specialty Chemicals Water Treatments Limited Compositions et procédés pour la déshydratation
WO2002081384A2 (fr) * 2001-04-05 2002-10-17 Ciba Specialty Chemicals Water Treatments Limited Procede de floculation de suspensions
US20070187330A1 (en) * 2004-03-12 2007-08-16 Tony Whittaker Dewatering process
WO2017142827A2 (fr) * 2016-02-18 2017-08-24 General Electric Company Concentration de solides de distillation

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