KR19990067585A - High performance polymer flocculant - Google Patents

Abstract

Water soluble branched high molecular weight cationic polymer flocculants, methods for their preparation and methods for dehydrating suspended solids using the same are described.

Description

High performance polymer flocculant

Agglomeration is a method of dehydrating suspended solids by aggregating solids. Agglomeration substantially improves the dehydration rate of many types of suspended solids, including those used in mineral, paper, wastewater treatment and oil field applications.

Synthetic polymer flocculants have been used in the industry as flocculants for the treatment of suspended solids since the 1950s. However, due to modern concerns regarding environmental protection, sludge incineration, transport and disposal costs, the performance of conventional linear polymer flocculants by providing flocculants that achieve greater dehydration at a given polymer dose, or equivalent dehydration at a lower polymer dose, It has become very desirable to improve.

The present invention provides compositions and methods for dewatering suspended solids, including those frequently occurring in wastewater treatment, mining and paper industry, using high molecular weight water soluble or water-expandable branched cationic polymer flocculants, and methods of making the compositions. to provide. The compositions and methods of the present invention provide better dehydration compared to those previously used in the art.

Linear polymeric flocculants have been "constituted" in the art via branching agents or crosslinkers. Polymer constructions are described in J.E. Morgan et al., Adv. Chem. Ser., Vol. 187, pp. 235-52 (1980). US Pat. Nos. 4,720,346 and 4,943,378 describe the use of crosslinked cationic polymer particles having a dry particle size of 10 μm or less. US Pat. Nos. 5,152,903 and 5,340,865 describe agglomeration using cationic polymer microparticles crosslinked. US Pat. No. 3,235,490 describes agglomeration processes using crosslinked polyacrylamides. US Pat. No. 3,968,037 teaches a method of releasing water from activated sewage sludge using a crosslinked cationic emulsion polymer. Methods and compositions useful for enriching aqueous media are described in US Pat. Nos. 4,059,522 and 4,172,066. Cationic high molecular weight water soluble side chains in co-pending applications 08 / 028,916, 08 / 028,001, 07 / 437,258, 08 / 454,974 and 08 / 455,419, assigned to the assignee of the present invention and incorporated herein by reference. A process for agglomeration of suspended solids using a polymeric polymer is described.

The water soluble polymer is characterized by measuring the solution viscosity of the polymer solution in diluents such as 0.05 to 1%, distilled water and salt solutions. All percentages are given herein in weight percent based on total weight. Diluent viscosity of the internal cationic high molecular weight water soluble polymer is typically much higher in clean water than, for example, in a 1 M NaCl solution. For the purpose, the "bulk viscosity" of a polymer is defined as the viscosity of a 0.2% solution in clean water measured using a rotating cylinder viscometer, for example a Brookfield viscometer, under the conditions described in the Examples. As used herein, “standard viscosity” is the viscosity of a 0.1% polymer solution in 1M NaCl solution. Bulk Viscosity: The standard viscosity ratio, BV / SV, is likely to change as a function of the structural diagram present in the polymer.

The "sedimentation value" also changes as a function of the schematic diagram present in the polymer. "Sedimentation value" is a sensitive indicator of the settling rate of a water-soluble or water-expandable polymer in a salt solution. A sedimentation value of 10% or less means that the polymer has little or no tendency to settle in the salt solution. The sedimentation value produced a 0.05% solution of a specific polymer in 1.001 M NaCl, and a portion of the solution was centrifuged at about 18,000 XG (gravity) at 22 ° C. for about 60 minutes and 215 nm of the supernatant of the noncentrifuge and centrifuge sections This is determined by measuring the ultraviolet absorbance at. The absorbance of the supernatant of the centrifuge compared to the absorbance of the noncentrifuge is calculated as [ΔA (noncentrifuged)-ΔA (centrifuged) / ΔA (noncentrifuged)]], where ΔA = A (polymer solution) A is water and A is the UV absorbance measured at 215 nm. This multiplies the calculated value by 100 to get the settling value expressed as a percentage.

Surprisingly, it has been found that water-soluble polymers with BV / SV of about 300-500 and up to 10% sediment are good flocculants for suspended solids. In particular, such polymers produce more rapid dewatering of waste activated sludges, especially extended ventilated activated sludges, than polymers of similar molecular weight and cation without BV / SV and sedimentation described above.

According to the invention, an effective amount of a cationic water-soluble or water-expandable polymer having a bulk viscosity: standard viscosity ratio of about 300 to 500 and a sedimentation value of about 10% or less is added to the dispersion to form a mixture of the dispersion and the polymer, and then the mixture A process for dewatering a dispersion of suspended solids is provided, including dehydrating a.

The present invention more preferably uses a copolymer of acrylamide and quaternized dialkylaminoalkyl (alk) acrylate having at least about 20 mol% cationic units based on the total moles of repeat units of the polymer. A method of dewatering a dispersion of suspended solids is provided.

In a preferred embodiment, a copolymer of acrylamide and acryloxyethyltrimethylammonium chloride having at least about 30 mole percent of cationic units based on the total moles of repeat units of the polymer is used to dehydrate the dispersion of suspended solids. A method is provided.

Furthermore, the monomer component of an ethylenically unsaturated cationic monomer sufficient to form a water soluble or water-expandable cationic polymer having a bulk viscosity ratio of about 300 to about 500 and a settling ratio of about 10% or less, an effective amount of a chain transfer agent, and Provided are methods of making a cationic polymer comprising polymerizing or copolymerizing a mixture of effective amounts of branching agents.

In a more preferred embodiment, the present invention provides acrylamide and acryloxyethyltrimethylammonium to form water soluble cationic polymers containing at least about 30 mole% of acryloxyethyltrimethylammonium chloride based on the total moles of repeat units in the cationic polymer. A molecular viscosity of at least 1,000,000, bulk viscosity ranging from about 300 to about 400, comprising copolymerizing monomer components of a mixture of chloride, an effective amount of isopropanol or lactic acid as a chain transfer agent and an effective amount of methylenebisacrylamide as a branching agent: Provided are methods of making cationic polymers having a viscosity ratio and a settling value of about 5% or less.

In another embodiment, a mixture of monomeric components of acrylamide, an effective amount of a chain transfer agent, and an effective amount of a branching agent is polymerized or copolymerized to form a water soluble or water-expandable precursor polymer, and the precursor of the polymer is formed from an effective amount of formaldehyde and secondary Mannich acrylamide polymers comprising reacting with an amine or a complex thereof to form a water soluble or water-expandable Mannich acrylamide polymer having a bulk viscosity in the range of about 300 to about 500 and a settling ratio of about 10% or less. A method for producing is provided.

Also provided are water soluble or water-expandable cationic polymers having a bulk viscosity: standard viscosity ratio of about 300 to about 500 and a settling value of about 10% or less.

In a more preferred embodiment, the invention consists of repeating units of acrylamide and quaternized dialkylaminoalkyl (alk) acrylate units, and based on the total moles of repeating units in the cationic copolymer, at least about 30 mole% of 4 Cationic air having a weight average molecular weight of at least about 1000,000, a bulk viscosity in the range of about 300 to about 400: a standard viscosity ratio, and a sedimentation value of about 5% or less, containing a rapid dialkylaminoalkyl (alk) acrylate repeat unit Provide coalescence.

In a more preferred embodiment, the invention contains at least about 30 mole percent of acryloxyethyltrimethylammonium chloride based on the total moles of repeat units in the cationic copolymer, and has a weight average molecular weight of at least about 1,000,000, in the range from about 300 to about 400 Provided is a cationic copolymer consisting of repeating units of acrylamide and acryloxyethyltrimethylammonium chloride having a bulk viscosity: standard viscosity ratio and a settling value of about 5% or less.

Additionally, in the present invention, an effective amount of a cationic water soluble or water-expandable polymer having a bulk viscosity: standard viscosity ratio in the range of about 300 to about 500 and a sedimentation value of about 10% or less is added to the sludge to form a mixture of sludge and polymer. Thereafter, there is provided an extended vented sludge dewatering method comprising the step of dewatering the mixture.

The present invention provides, in a preferred embodiment, having at least about 20 mole percent cationic units, a bulk viscosity in the range of about 300 to about 500, a standard viscosity ratio and no more than about 5% settling value, based on the total moles of repeat units in the polymer. Extended aerated sludge dewatering process comprising adding an effective amount of an aqueous copolymer of acrylamide and quaternized dialkylaminoalkyl (alk) acrylate to the sludge to form a mixture of sludge and copolymer, followed by dehydrating the mixture. This is provided.

The present invention also provides, in a more preferred embodiment, at least about 30 mole% of acryloxyethyl trimethylammonium chloride units based on the total moles of repeat units in the polymer, bulk viscosity: standard viscosity ratio and about 5% in the range of about 300 to about 400. An extended aeration sludge dewatering method comprising the steps of adding an effective amount of an aqueous copolymer of acrylamide and acryloxyethyl trimethylammonium chloride to the sludge to form a mixture of sludge and copolymer, and then dehydrating the mixture. To provide.

The present invention relates to a high performance polymer flocculant.

High molecular weight, cationic water soluble or water-expandable polymer flocculants of the present invention are formed by polymerization of cationic ethylenically unsaturated monomers alone or with comonomers in the presence of an optimal ratio of branching agent and chain transfer agent. High molecular weight cationic water soluble or water-expandable polymers are also polymers which can polymerize or copolymerize and quaternize nonionic monomers such as acrylamide to form nonionic polymers such as polyacrylamide. And, preferably, by functionalizing the nonionic polymer to impart a cationic group to the tertiary aminomethyl group.

Cationic monomers useful in the practice of the present invention include diallyldimethylammonium chloride; Acryloxyethyltrimethylammonium chloride; Methacryloxyethyltrimethylammonium chloride; Dialkylaminoalkyl (alk) acrylate compounds; And quaternary products and salts thereof, such as N, N-dimethylaminoethylmethacrylate methylchloride salt; Monomers of N, N-dialkylaminoalkyl (meth) acrylamide; And quaternaries and salts thereof, such as N, N-dialkylaminoethylacrylamide; Methacrylamidopropyltrimethylammonium chloride; 1-methacryloyl-4-methyl piperazine and the like. Quaternized dialkylaminoalkyl (alk) acrylate monomers are preferred, with acrylicoxyethyltrimethylammonium chloride and methacryloxyethyltrimethylammonium chloride being most preferred. Cationic monomers generally have Formula 1:

In the above formula,

R ₁ is hydrogen or methyl;

R ₂ is C ₁ to C ₄ lower alkyl;

R ₃ is C ₁ to C ₄ lower alkyl;

R ₄ is hydrogen, C ₁ to C ₁₂ alkyl, aryl or hydroxyethyl;

R ₂ and R ₃ or R ₂ and R ₄ may be bonded to form a cyclic ring containing one or more hetero atoms;

X is a conjugate base of acid;

A is oxygen or -NR _{1-, wherein} R ₁ is as described above;

B is an alkylene group of C ₁ to C ₁₂ or a compound of Formula 2;

R ₅ and R ₆ are hydrogen or methyl;

R ₇ is hydrogen, C ₁ to C ₁₂ alkyl, benzyl or hydroxyethyl.

Nonionic monomers suitable for the practice of the invention generally include acrylamide; Methacrylamide; And N-alkylacrylamides such as N-methylacrylamide; And N, N-dialkylacrylamides such as N, N-dimethylacrylamide. Acrylamide and methacrylamide are preferred. Small amounts, for example up to 10 mol%, of weakly water-soluble nonionic monomers, such as methyl acrylate, methyl methacrylate, ethyl acrylate, acryl, based on the total moles of repeat units in the polymer Nitrile and the like may also be suitable.

Cationic homopolymers having repeat units of at least one nonionic monomer may be used in the present invention. Preferably, one or more nonionic monomers such as acrylamide may be copolymerized with one or more cationic monomers such as acryloxyethyltrimethylammonium chloride to produce a cationic copolymer. Preferably, the cationic copolymer consists of at least about 20 mole percent cationic monomer based on the total moles of repeat units in the polymer. As used herein, when referring to mole percent of repeat units in a polymer, all mole percentages are based on the total moles of repeat units in the copolymer. More preferably, the copolymer consists of at least about 25 mole percent of the repeat units of the cationic monomer; Most preferably, the copolymer consists of at least about 30 mole percent of the repeat units of the cationic monomer.

Cationic charges can also be imparted to the polymer by functionalizing the nonionic repeat units of the polymer. For example, acrylamide units in the polymer backbone are reacted with effective amounts of formaldehyde and secondary amines or complexes thereof in a known manner to form Mannich acrylamides having pendant tertiary aminomethyl groups which are cations at low pH. Or tertiary aminomethyl groups can be quaternized according to procedures known to those skilled in the art of US Pat. Nos. 5,037,881, 4,956,399 and 4,956,400, which are incorporated herein by reference to form cationic pendant groups. Formaldehyde useful in the practice of the present invention is selected from formaldehyde, paraformaldehyde, trioxane, aqueous formalin and the like. Useful secondary amines are selected from dimethylamine, methylethylamine, diethylamine, amylmethylamine, dibutylamine, dibenzylamine, piperidine, morpholine, ethanolmethylamine, diethanolamine or mixtures thereof. Particular preference is given to the process wherein formaldehyde comprises formalin and the secondary amine comprises dimethylamine. It is also contemplated to use formaldehyde-secondary amine complexes such as N, N-dimethylaminomethanol.

Skeletal polymers containing nonionic groups may consist entirely of nonionic groups prior to functionalization reactions imparting cationic groups, or may consist of partially nonionic groups and partially cationic groups. Preferably, the polyacrylamide emulsion or microemulsion polymer is introduced into Mannich reaction conditions as described in US Pat. Nos. 5,037,881, 4,956,399 and 4,956,400, which are incorporated herein by reference, to form an optionally quaternized precursor polymer. In order to polymerize in a known manner. Preferably, at least about 20 mole% of repeat units are charged with cations. More preferably, at least about 30 mole% of repeat units are charged with cations.

Polymerization of the monomers is generally carried out in the presence of branching or crosslinking agents to form branched or crosslinked homopolymers or copolymers. Branching agents generally include compounds having at least two double bonds, or at least a double bond and a reactive group, or at least two reactive groups. Multifunctional branching agents should have at least some water solubility. Preferred multifunctional branching agents include compounds containing at least two double bonds, for example methylenebisacrylamide; Methylenebismethacrylamide; Polyethylene glycol diacrylate; Polyethylene glycol dimethacrylate; N-vinyl acrylamide; Divinylbenzene; Triallyl ammonium salt; N-methylallyl acrylamide and the like. Also preferred are multifunctional branching agents containing at least one reactive group including at least one double bond and acrolein methylolacrylamide and the like. Multifunctional branching agents containing at least two reactive groups include aldehydes such as glyoxal; Diepoxy compounds, epichlorohydrin and the like.

The presence of optimal concentrations of molecular weight regulators or chain transfer agents is essential to the practice of the present invention to provide a suitable polymer structure. In the absence of chain transfer agents, even the incorporation of even minor amounts, for example 10 parts of branching agent per million parts, will result in extensive crosslinking which makes the polymer less effective as a flocculant. However, branched cationic polymers are obtained according to the invention when chain transfer agents are used in optimal concentrations in parallel with branching agents. Many such chain transfer agents are well known in the art. Alcohols such as lactic acid and isopropyl alcohol; Mercaptans such as 2-mercaptoethanol; Thio acid; Although phosphites and sulfites such as sodium hypophosphite are included, many different chain transfer agents can be used. Preferred chain transfer agents are isopropyl alcohol and lactic acid.

The weight average molecular weight of the polymer of the invention is generally at least 500,000, preferably at least 1,000,000. The weight average molecular weight can be measured by light scattering methods well known in the art.

The polymers of the present invention are characterized by a BV / SV of at least about 300, preferably at least about 320, and the BV / SV generally does not exceed about 500, preferably about 450 or less, more preferably at least about 400 to be.

Optimal concentrations of chain transfer agent and branching agent are employed to produce a polymer having a BV / SV of about 300 to about 500, preferably about 300 to about 400, and a sediment of about 10% or less, preferably about 5% or less. It is important to use. The optimum amount of chain transfer agent and branching agent will depend on the relative efficiency of the particular chain transfer agent and branching agent and will vary depending on the polymerization conditions. Therefore, it is difficult to set specific amounts of chain transfer agents and crosslinkers for all polymers and types of chain transfer agents and crosslinkers. Routine experimental methods are particularly useful for determining the optimal levels of branching agents and chain transfer agents since polymerization conditions will obviously affect branching and molecular weight. It is known that customary components of polymerization, such as surfactants, polymers, monomers, solvents, can act as chain transfer agents, and impurities in monomers can act as branching agents or crosslinkers. Therefore, it is difficult to define suitable amounts of added chain transfer agent and branching agent to produce a polymer having the desired BV / SV and sedimentation without knowing the polymer conditions. Nevertheless, for the purposes of the present invention, a general range of chain transfer agent concentrations may range from 0.01% to 5% and branching agents may range from 0.001% to 0.1%.

In the polymer, polymerization conditions, chain transfer agent and branching agent, the optimum ratio of the chain transfer agent to the branching agent tends to be in a rather small range. For example, in the emulsion copolymerization of acrylamide and acryloxyethyltrimethylammonium chloride using branching agent MBA and chain transfer agent lactic acid, the weight ratio of lactic acid to MBA is preferably from about 40 to about 90, preferably from about 50 to about 80, Most preferably in the range of about 60 to 70. When more efficient chain transfer agents are used, for example 2-mercaptoethanol, the ratio is more likely to vary. Optimal levels of chain transfer agents and branching agents can be determined for each type of cationic polymer by routine experimental methods known to those skilled in the art. For example, a matrix of polymerization comprising different combinations of different levels of chain transfer agent and branching agent can be performed, and then the BV / SV and settling values of each resulting polymer are measured.

The bulk viscosity (BV) of the polymer is determined by diluting the polymer or polymer emulsion to a concentration of 0.2% in clean water using a rotary cylinder viscometer, especially a Brookfield LVT viscometer, at 30 rpm with a # 2 spindle. The standard viscosity of the polymer dissolves the polymer or polymer emulsion in deionized water, adds NaCl solution to produce a polymer concentration of 0.1% and a NaCl concentration of 1.0 M, and rotates a rotary cylinder viscometer, especially a Brookfield LVT viscometer, at 60 rpm. It is measured by measuring the viscosity of the polymer solution by using it with a # 00 spindle. If the dissolution time is long, the pH may need to be adjusted in the range of about 3 to about 4 to stabilize the polymer.

The sedimentation value is measured by first separating the polymer by precipitating the polymer emulsion or polymer solution with an organic solvent such as acetone to remove the ultraviolet absorbing material such as the surfactant, and then collecting and drying the polymer. The polymer solution is then prepared by stirring the separated polymer in deionized water until dissolved and adding NaCl solution to produce a polymer solution having a polymer concentration of 0.05% and a NaCl concentration of 0.001 M. Some of the polymer solution is then centrifuged at about 18,000 × G (gravity), 22 ° C. for about 60 minutes and the UV absorbance at 215 nm of the supernatant of the noncentrifuge and centrifuge is measured. The sedimentation value is equal to ΔΔA / ΔA and equals [ΔA (non-centrifugation) -ΔA (centrifugation) / ΔA (centrifugation)]] (ΔA = A (polymer solution) -A (water) and A measured at 215 nm. UV absorbance). A convenient centrifuge is a Labnet ZK380 centrifuge spinning with a fixed angle rotor at a constant temperature of 13,000 rpm and 22 ° C. Ultraviolet absorbance measurements can be performed using a flow-through ultraviolet detector (ABI Model 875A) using a Harvard syringe pump in a 0.5 ml recovery form per minute to draw the solution through the detector. Other types of devices substantially the same as used herein are well known in the art.

The polymerization can be carried out using microemulsion or emulsion polymerization techniques. Such techniques are well known to those skilled in the art. For example, emulsion polymerization procedures generally involve the preparation of two phases as described in US Pat. No. 2,384,393, which is incorporated herein by reference. The aqueous phase consists of monomers, branching agents and chain transfer agents dissolved in deionized water, other additives well known in the art, such as stabilizers and pH adjusters. The oily phase usually comprises a water-insoluble hydrocarbon solution of a surfactant. The aqueous and oil phases are mixed and homogenized in a conventional apparatus to form an emulsion and sparged with inert gas or otherwise deoxygenated and then polymerization is initiated in a conventional manner. Polymerizations are also described in US Pat. No. 5,037,881, incorporated herein by reference; 4,956,399; This can be accomplished by using microemulsion techniques well known in the art, such as in 4,956,400 and 4,521,317.

The polymerization can also be carried out by solution polymerization techniques. Monomers, branching agents, and chain transfer agents are added to the deoxygenated water described above and polymerized by conventional initiators. When the amount and type of branching agent and chain transfer agent are selected by routine experiments to produce a viscous solution of the constructed polymer useful in the present invention having a BV / SV of about 300 to 500 and a settling value of about 10% or less. Is generated.

Conventional additives may be used for stabilization. Suitable additives include ammonium sulfate, ethylene diaminetetraacetic acid (disodium salt) and diethylene triaminepentaacetate (odium salt). (See Modern Plastics Encyclopedia / 88, McGraw Hill, October 1987, pp. 147-8)

Conventional initiators can be used to initiate the polymerization, including heat, redox and ultraviolet radiation. Azobisisobutyronitrile; Sodium sulfite; Sodium metabisulfite; 2,2'-azobis (2-methyl-2-amidinopropane) dihydrochloride; Ammonium persulfate and ferrous ammonium sulfate hexahydrate and the like are suitable for use in the present invention. Organic peroxides can also be used to polymerize ethylenically unsaturated monomers. Particularly preferred initiators for the purposes of the present invention are sulfur dioxide / sodium bromate. (See Modern Plastics Encyclopedia / 88, McGraw Hill, October 1987, pp. 165-168)

The products thus prepared are generally cationic high molecular weight polymers that are soluble in clean water. In water typically generated in the application, for example, hard water or water containing various amounts of minerals, the polymer may be water-expandable. The polymers of the present invention are particularly useful as chemical flocculants.

In order to release water from a dispersion of suspended solids, the flocculation and dehydration steps of the present invention add a cationic side chain high molecular weight water soluble or water-expandable polymer flocculant to the solid suspended in solution or directly as a emulsion or microemulsion. The solids and polymers are mixed to agglomerate the solids and then preferably dewatered using conventional dehydration devices, such as centrifuges, belt presses, piston presses, filters, etc. to remove water from the suspension. . The products of the present invention promote a wide range of solid / liquid separations, including industrial sludge, and dehydrate suspended solids in wastewater treatment applications for drainage of cellulose suspensions, such as those found in paper products, and for precipitation of various inorganic suspensions. useful.

Optimal doses of polymers are determined by routine experimentation well known to those skilled in the art. Cationic water soluble or water-expandable branched polymers of the invention having a BV / SV of about 300 to about 500 and no more than 10% sedimentation perform substantially better than polymers having no BV / SV and no sedimentation. For example, FIG. 1 shows the results of experiments tested on suspended solids in the form of waste activated sewage sludge. In this test, the dehydration rate of the sludge after aggregation with the polymer flocculents A to G is illustrated as a function of the polymer capacity. The BV / SV values of the flocculants are shown in Table 1. It is noted that the sludge agglomerated with polymers B, C and G having a BV / SV of 300 or more dehydrated much faster than the sludge treated with polymers A, D, E and F. Sludge treated with Polymer C is dehydrated at a rate very similar to sludge treated with Polymers G and B, but much higher capacity of polymer is required. The settling values of polymers B, C and G are illustrated in Table 2. It is noted that Polymer C has a sedimentation value of at least 10%. Thus, the polymers that produce the highest rate of dehydration, namely polymers B, C and G, all have BV / SV values in the range of 300 to 500. Dehydrated polymers B and G at a much lower capacity than polymer C also have sedimentation rates of 10% or less. These results show that polymers having a BV / SV in the range of about 300 to about 500 and having a sediment of less than 10% perform much better than polymers having no BV / SV and sediment.

The present invention is suitable for the dewatering of sludge, especially sludge comprising biologically treated suspensions. Generally, sludge is a thick viscous material, usually sediment or filtered waste. Waste activated sludge means sludge that undergoes aerobic suspended growth and biological treatment using microbial metabolism to produce high quality wastewater waste by converting and removing materials with high oxygen demand. The present method for producing waste activated sludge reduces the concentration of dissolved particulate and colloidal organic contaminants in wastewater. In addition, this method also reduces the ammonia concentration in the wastewater (nitrification). Ammonia is an inorganic pollutant that is toxic to aquatic life at high concentrations and exerts oxygen demands on the receiving water.

Extended aeration is a waste activated sludge method that works in a medium that holds wastewater for at least 18 hours in a venting tank and removes enough food from the microorganisms to support them all. Therefore, microorganisms actively compete for limited food supply and even use their cellular material in place of food. Highly competitive situations lead to highly treated wastewater waste with low sludge production. (See Operation of Municipal Wastewater Treatment Plants, Manual of Practice, MOP 11, Vol 11, 1990, pp. 418-419 and 501-516, herein incorporated by reference.) The extended aerated sludge used herein is extended aeration. It means waste activated sludge put into. In contrast, for the purposes of the present invention, extended vented sludge means sludge which typically has similar chemical and / or physical properties associated with the extended vented sludge.

Embodiments of the present invention relate to a method for dewatering sludge. More preferably, the present invention relates to a method of dewatering waste activated sludge. More preferably, the present invention relates to a method of dewatering extended vented sludge.

The following examples illustrate the invention. They do not intend to limit the scope of the claims in any way.

Polymers A, C, D, E and R are considered copolymers of acrylamide and cationic monomers and are all commercially available. Polymer A is SD-2081 ^™, available from Cytec Industries, Inc. Polymer C is EM840TPD ^™ commercially available from SNF Floerger. Polymer D is Percol 778FS25 ^™ , Polymer E is Percol 778FS40 ^™ and Polymer F is Percol 775FS25 ^™ , all available from Allied Colloids, Inc.

Example 1

Preparation of Polymer G: The following components are mixed together to prepare an aqueous phase: 210 parts of 50% aqueous acrylamide, 238.74 parts of 80% acryloxyethyltrimethylammonium chloride, 120 parts of deionized water, 17.76 parts of citric acid, 0.74 parts of 40% di Ethylenetriaminepentaacetic acid, a sodium salt (chelating agent), 0.67 parts of 89% lactic acid (chain transfer agent), 0.0089 parts of methylenebisacrylamide (branching agent), and 0.015 parts of sodium bromate. The pH is adjusted to about 3.5 with 2.3 parts of 29% aqueous ammonia and then deionized water is added to give a total of 612 parts.

10.29 parts of nonionic surfactant, HLB = 12.0, prepared from 11.13 parts of sorbitan monooleate and ethoxylated linear alcohol, 148.58 parts of paraffinic solvent (mixture of side chain and cyclic hydrocarbon, boiling point 408 to 442 ° F) Range) to prepare an oil phase. Adding the aqueous phase to the oil phase with mixing; The crude emulsion is then mechanically homogenized to give a monomer emulsion. Transfer the monomer emulsion to a suitable reaction vessel equipped with agitation means, gas dip tube, exhaust line and thermometer; The mixed vessel is washed with 10 parts of paraffinic solvent and it is also added to the emulsion. The mixture is sparged with nitrogen for 30 minutes.

Polymerization was initiated at 24 ° C. using sulfur dioxide gas (4000 ppm in nitrogen); The flow rate is adjusted such that the mixture exotherms to 40 ° C. over 35 minutes; The sulfur dioxide flow rate is then gradually increased over 20 minutes to maintain a temperature of 40-42 ° C. by active cooling of the reaction vessel. After the exothermic reaction is completed, the temperature is maintained at 40 to 42 ° C. for 3.5 hours by heating. After the polymerization is completed, the injection of nitrogen and sulfur dioxide is stopped. About 8.0 parts of a nonionic surfactant, HLB = 12.0, made from an ethoxylated straight chain alcohol was added over 15 minutes; The emulsion is mixed for 1.5 hours and then cooled to ambient temperature.

Example 2

Preparation of Polymer B: The following components are mixed together to prepare an aqueous phase: 13413 parts of 52.5% aqueous acrylamide, 13200 parts of 80% acryloxyethyltrimethylammonium chloride, 7643 parts of deionized water, 151 parts of 17% sulfuric acid, 18 parts of 40 % Ethylenediaminetetraacetic acid, disodium salt, 650 parts isopropanol (chain transfer agent), 0.44 parts methylenebisacrylamide, and 1 part 70% t-butylhydroperoxide.

572 parts of surfactant, mainly containing dihydroxyethyl oleamide and 308 parts of polyoxyethylene monooleate, HLB = 11.4 in 12814 parts of a paraffinic solvent (mixture of side chain and cyclic hydrocarbon, boiling point 408 to 442 ° F) in a mixing vessel Range) to prepare an oil phase. Adding the aqueous phase to the oil phase with mixing; The crude emulsion is then homogenized to give a monomer emulsion. The monomer emulsion is transferred to a suitable reaction vessel equipped with agitation means, gas dip tube, exhaust line and thermometer. The mixture is sparged with nitrogen for 30 minutes.

Polymerization was initiated at 24 ° C. using sulfur dioxide gas (4000 ppm in nitrogen); The flow rate is adjusted such that the mixture exotherms to 40 ° C. over 35 minutes; The sulfur dioxide flow rate is then gradually increased over 20 minutes to maintain a temperature of 40-42 ° C. by active cooling of the reaction vessel. After the exothermic reaction is completed, the temperature is maintained at 40 to 42 ° C. for 3.5 hours by heating. After the polymerization is completed, the injection of nitrogen and sulfur dioxide is stopped. About 940 parts of polyoxyethylene monooleate, HLB = 11.4 was added over 15 minutes; The emulsion is mixed for 1.5 hours and then cooled to ambient temperature.

Examples 3-16

The bulk viscosity of polymers A to G is determined as follows: Dilute the polymer or polymer emulsion in deionized water and stir until the polymer is dissolved to bring the polymer concentration to 0.2%. Bulk viscosity (BV) is measured at 30 rpm with a # 2 spindle using a Brookfield viscometer (LVT model) at 25 ° C ± 1 ° C.

The standard viscosity (SV) of polymers A to G is determined as follows: The polymer or polymer emulsion is diluted in deionized water and stirred until the polymer is dissolved, then NaCl solution is added to give a polymer concentration of 0.1% and a NaCl concentration. Is 1.0M. The standard viscosity (SV) is measured with a # 00 spindle at 60 rpm using a Brookfield viscometer (LVT model) at 25 ° C ± 1 ° C. BV, SV and BV / SV of polymers A through G are shown in Table 1. For long periods of dissolution, for example overnight, the pH is adjusted in the range of about 3 to about 4 to stabilize the polymer.

polymer BV, Sentipoise SV, centipoise BV / SV A ^* 453 3.32 136 B 708 2.09 339 C ^* 585 1.53 382 D ^* 284 2.37 120 E ^* 411 2.29 179 F ^* 397 2.42 164 G 705 1.94 363 ^* Comparative Example

Examples 17-19

Settling values of polymers B, C and G are determined as follows:

Hydrocarbon oil is added to the polymer emulsion to reduce the viscosity of the emulsion and the emulsion is added dropwise to excess acetone under stirring to precipitate the polymer. The polymer is collected and dried. The polymer solution is prepared by stirring the dry polymer until dissolved in deionized water and adding NaCl solution to obtain a polymer solution having a polymer concentration of 0.05% and a NaCl concentration of 0.001 M. When dissolved for a long time, for example overnight, the pH is adjusted to a range of about 3 to about 4 to stabilize the polymer. A portion of the solution is centrifuged at about 18,000 × G and 22 ° C. for about 60 minutes. Ultraviolet (UV) absorbance at 215 nanometers (nm) of the supernatant of the non-centrifuged and centrifuged portions is measured. The settling value is ΔΔA / ΔA corresponding to [ΔA (non-centrifugation)-ΔA (centrifugation)] / ΔA (non-centrifugation), where ΔA = A (polymer solution)-A (water) and A at 215 nm. Absorption value measured by UV absorption. The Labnet ZK380 centrifuge with a fixed angle roto is used and rotated at a constant temperature of 13,000 rpm and 22 ° C. UV absorption measurements are performed using a flow-through UV detector (ABI model 875A) and withdrawing the solution through the detector using a Harvard syringe pump at a draw rate of about 0.5 ml per minute. The settling values of polymers B, C and G are shown in Table 2.

polymer Sediment B 0 C ^* 23 G 3 ^* Comparative Example

Examples 20-26

Solutions of polymers A to G are prepared at a polymer concentration of 0.2%. Various amounts of polymer solution are mixed with a 200 g sample of suspended solids (waste activated sewage sludge, about 1.2% solids) to achieve a polymer "dose" range. The polymer / sludge mixture is vigorously stirred and filtered through a funnel equipped with a 35 mesh stainless steel screen. The volume (ml) of water drained through the screen during the first 10 seconds of filtration is recorded as drain volume. The doses and drainage volumes for each polymer are listed in Table 3. The drainage volume of each sample of each polymer is plotted in FIG. 1 as a function of polymer capacity, where the capacity is in pounds of polymer per tonne of sludge solid dry weight. High drainage volume means that the sludge is dewatered quickly. Figure 1 shows that polymers B and G both aggregate suspended sewage sludge solids more efficiently than other polymers, thus giving higher dehydration rates than polymers A, D, E and F, and substantially equivalent to polymer C. Imparts performance, but much lower polymer capacity than polymer C.

polymer Capacity (lbs / dry tons) Drainage volume (ml) A ^* 3.4 89 6.7 109 10.1 107 13.4 112 16.8 108 B 10.1 125 13.4 154 16.8 154 20.2 165 C ^* 13.4 117 16.8 160 20.2 166 23.5 168 26.9 166 D ^* 6.7 114 10.1 122 13.4 127 16.8 133 23.5 132 E ^* 6.7 101 10.1 114 13.4 119 16.8 124 26.9 109 ^* Comparative Example

F ^* 3.4 82 6.7 124 10.1 128 16.8 120 G 6.7 87 10.1 140 13.4 161 16.8 165 ^* Comparative Example

Examples 27-33

Solutions of polymers A to G are prepared at a polymer concentration of 0.2%. Various amounts of polymer solution are mixed with a 200 g sample of suspended solids (extended aeration sewage sludge) to achieve a polymer “dose” range. The polymer / sludge mixture is vigorously stirred and filtered through a funnel equipped with a 35 mesh stainless steel screen. The volume (ml) of water drained through the screen during the first 10 seconds of filtration is recorded as drain volume. Both polymers B and G agglomerate suspended and extended aerated sewage sludge solids more efficiently than other polymers, thus giving a higher dehydration rate than polymers A, D, E and F and giving substantially equivalent performance to polymer C. However, it is a much lower polymer capacity than polymer C.

Claims (20)

An effective amount of water-soluble or water-expandable polymer of the cation, having a bulk viscosity of about 300 to about 500, and a sedimentation value of about 10% or less, is added to the dispersion to form a mixture of the dispersion and the polymer, followed by dehydration of the mixture. Dehydration method of suspended solid dispersion comprising the step. The method of claim 1 wherein the polymer contains at least about 20 mole percent cationic units based on the total moles of repeat units in the polymer. The method of claim 1 wherein the polymer contains repeatable (meth) acrylamide units. The process of claim 1 wherein the polymer contains at least about 30 mole percent quaternized dialkylaminoalkyl (alk) acrylate units based on the total moles of repeat units in the polymer. Acrylamide and quaternized dialkyl having at least about 20 mole percent of cationic units, a bulk viscosity of from about 300 to about 400: standard viscosity, and a sedimentation value of about 5% or less, based on the total moles of repeat units in the polymer A method of dewatering sewage sludge, comprising the step of adding an effective amount of water-soluble copolymer of aminoalkyl (alk) acrylate to the sludge to form a mixture of sludge and copolymer, and then dehydrating the mixture. Bulk viscosity of about 300 to about 500 by polymerizing or copolymerizing monomer components of a mixture consisting of an ethylenically unsaturated cationic monomer, an effective amount of a chain transfer agent and an effective amount of a branching agent: a water-soluble or water having a standard viscosity ratio and a settling value of about 10% or less. -Forming a expandable cationic polymer. 7. The process of claim 6 wherein the cationic polymer contains repeatable (meth) acrylamide units. 7. The method of claim 6, wherein the cationic polymer contains at least about 20 mole percent cationic units based on the total moles of repeat units in the polymer. 7. The process of claim 6 wherein the cationic polymer contains at least about 30 mole percent quaternized dialkylaminoalkyl (alk) acrylate units based on the total moles of repeat units in the polymer. The monomer component of the mixture consisting of acrylamide, effective amount of chain transfer agent and effective amount of branching agent is polymerized or copolymerized to form a water-soluble or water-expandable precursor polymer, and then the precursor polymer is combined with an effective amount of formaldehyde and secondary amine or complex thereof. Reacting to form a water-soluble or water-expandable Mannich acrylamide polymer having a bulk viscosity of about 300 to about 500: standard viscosity and a settling value of about 10% or less. The method of claim 10, further comprising quaternizing the water-soluble or water-expandable Mannich acrylamide polymer containing at least about 20 mole percent cationic units based on the total moles of repeat units in the polymer. At least about based on the total moles of repeating units in the cationic polymer by copolymerizing monomer components of a mixture of acrylamide and acryloxyethyltrimethylammonium chloride, an effective amount of isopropanol or lactic acid as a chain transfer agent and an effective amount of methylenebisacrylamide as a branching agent Forming a water soluble cationic polymer containing 30 mol% of acryloxyethyltrimethylammonium chloride, wherein the copolymer has a weight average molecular weight of at least about 1,000,000, a bulk viscosity in the range of about 300 to about 400: standard viscosity ratio and about 5 A process for producing a cationic polymer having a sedimentation value of less than or equal to%. Bulk Viscosity of about 300 to about 500: A water soluble or water-expandable cationic polymer or copolymer having a standard viscosity ratio and no more than about 10% sedimentation value. The composition of claim 13 wherein the cationic polymer contains at least about 30 mole percent quaternized dialkylaminoalkyl (alk) acrylate units based on the total moles of repeat units in the polymer. Consisting of repeating units of acrylamide and quaternized dialkylaminoalkyl (alk) acrylate units, and at least about 30 mol% of the quaternized dialkylaminoalkyl (alk) acrylate repeats based on the total moles of repeating units in the polymer A cationic copolymer containing units and having a weight average molecular weight of at least about 1,000,000, a bulk viscosity of from about 300 to about 400: standard viscosity and no more than about 5% sedimentation value. A bulk viscosity of about 300 to about 500: an effective amount of a water-soluble or water-expandable polymer of a cation having a standard viscosity ratio and a settling value of about 10% or less is added to the sludge to form a mixture of sludge and polymer, and then dewatering the mixture. A method of dewatering sludge extended by aeration. The method of claim 16, wherein the polymer contains at least about 20 mole percent cationic units based on the total moles of repeat units in the polymer. The method of claim 16 wherein the polymer contains repeatable quaternized dialkylaminoalkyl (alk) acrylate units. The method of claim 16, wherein the sludge comprises a biological treatment suspension. Acrylamide and acrylic having at least about 20 mole% of acrylicoxyethyl trimethylammonium chloride units, bulk viscosity of about 300 to about 500, based on the total moles of repeating units in the polymer: A method for dewatering extended aeration sludge, comprising adding an effective amount of a water-soluble copolymer of oxyethyl trimethylammonium chloride to the sludge to form a mixture of sludge and copolymer, and then dehydrating the mixture.