WO2011127425A1

WO2011127425A1 - Systems and methods for sludge processing

Info

Publication number: WO2011127425A1
Application number: PCT/US2011/031820
Authority: WO
Inventors: Gangadhar Jogikalmath; Lynn Reis; David Soane
Original assignee: Nanopaper, Llc
Priority date: 2010-04-09
Filing date: 2011-04-08
Publication date: 2011-10-13

Abstract

Systems include a sludge fluid stream containing fines, an activator polymer that associates with the fines, an anchor particle bearing a tether polymer that is capable of interacting with the activator polymer, wherein the anchor particle is mixed into the sludge fluid stream so that the tether polymer interacts with the activator polymer, forming a sludge complex comprising the fines and the anchor particle and a separation system that removes the sludge complex from the sludge fluid stream. Methods include steps: adding an activator polymer to the sludge fluid, preparing a tether-bearing anchor particle by associating a tethering polymer to an anchor particle, wherein the tethering polymer is capable of interacting with the activator polymer; contacting the activator-fines complex with the tether-bearing anchor particle to form an activator-tether-anchor complex comprising the fines and the anchor particle; and removing the activator- tether-anchor complex from the sludge fluid, thereby removing the fines.

Description

SYSTEMS AND METHODS FOR SLUDGE PROCESSING

RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Application No.

61/322,597, filed April 9, 2010. The entire teachings of the above-referenced application are incorporated herein by reference.

FIELD OF THE APPLICATION

[0002] This application relates to processing of waste sludge produced by paper mills and paper/pulp production facilities. BACKGROUND

[0003] Paper and pulp production facilities such as such as Kraft mills, office paper production facilities and recycled fiber processing facilities produce a large amount of sludge which is usually discarded or sold at low costs to industries such as pet bedding manufacturers and mulch producers. The sludge, depending on the source, contains cellulosic fines, clay, precipitated calcium carbonate (PCC), carbon black and/or pigments from ink. Such components of sludge are typically characterized by high surface area, small size and surface functionalities amenable to chemical modification. The cellulose content of the sludge entraps a large amount of water so that dewatering the sludge is difficult, impairing compression of the sludge into solid masses for efficient transportation.

[0004] A typical sludge processing system involves use of a flocculating polymer used to create flocculant complexes ("floes") suspended in the aqueous fluid stream. The stream containing the floes is then fed onto a gravity filtration unit (e.g., a screen or wire belt) that drains free water. The partially dewatered sludge is then fed to a compressor section (e.g., screw or belt press) to concentrate the solids. Despite this processing, the pressed sludge product from paper and pulp mills still contains about 60% water. By reducing the water content of this sludge, the gross tonnage of material to be removed from the mill could be reduced. With effective dewatering, the sludge could be further processed to yield commercially valuable products. There remains a need, therefore, for an effective and efficient system to permit the faster settling of flocculated sludge, and the more complete dewatering of sludge during gravity filtration, to yield sludge-derived materials with higher solids content. SUMMARY

[0005] Disclosed herein are systems for removing fines from a sludge fluid, comprising a sludge fluid stream containing the fines, an activator polymer that associates with the fines, and an anchor particle bearing a tether polymer that is capable of interacting with the activator polymer, wherein the anchor particle is mixed into the sludge fluid stream so that the tether polymer interacts with the activator polymer, forming a sludge complex comprising the fines and the anchor particle, and further comprising a separation system that removes the sludge complex from the sludge fluid stream. In embodiments, the anchor particle comprises sand. In embodiments, the separation system comprises gravity filtration. In embodiments, the sludge complexes that are removed from the sludge fluid are consolidated to form a consolidated material. In embodiments, the sludge complexes are treated with a surface-modifying agent. In embodiments, the surface-modifying agent comprises a polyamine. In other embodiments, the surface-modifying agent comprises a hydrophobicizing agent.

[0006] Also disclosed herein are methods for removing fines from a sludge fluid, comprising adding an activator polymer to the sludge fluid, wherein the activator polymer associates with the fines to form an activator-fines complex, preparing a tether-bearing anchor particle by associating a tethering polymer to an anchor particle, wherein the tethering polymer is capable of interacting with the activator polymer, contacting the activator- fines complex with the tether-bearing anchor particle to form an activator- tether-anchor complex comprising the fines and the anchor particle; and removing the activator-tether-anchor complex from the sludge fluid, thereby removing the fines. In embodiments, the step of removing the activator-tether-anchor complex further comprises consolidating a plurality of anchor-tether-activator complexes to form a consolidated sludge complex. In embodiments, the method further comprises treating the consolidated sludge complex with a surface-modifying agent.

[0007] In certain aspects of the systems and methods disclosed herein, the sludge fluid is produced during paper or pulp production. In additional aspects, the sludge fluid comprises fines selected from the group consisting of cellulosic fines, clay, precipitated calcium carbonate, carbon black, ink pigments, and combinations thereof. DETAILED DESCRIPTION

[0008] Disclosed herein are systems and methods for enhancing the settlement rate of dispersed fine materials suspended in the fluid stream of papermaking sludge. As disclosed herein, the fine materials (cellulose, cellulosic fines, clay, precipitated calcium carbonate (PCC), carbon black and/or pigments from ink, and the like, hereinafter

"fines") can be incorporated within a coarser particulate matrix, so that the fines can be removed from aqueous suspension as a material having mechanical stability. The systems and methods disclosed herein involve three components: activating the fines in the sludge by mixing them with a flocculating polymer, preparing an attachment particle (an "anchor") by associating it with a polymer capable of complexing with the flocculated fines (a "tether") and mixing the activated fines with the tether-bearing anchor particles to form durable complexes that can be separated from the fluid stream in a free-draining filtration step. As used herein, the term "ATA Process" refers to the process, described in more detail below, whereby the fines are activated by mixing them with a flocculating polymer, and then the activated fines are mixed with a tether-bearing anchor particle to form durable complexes. The application of the ATA process to the fines produced during the papermaking process can yield a material comprising sludge complexes having a higher solids content than the untreated sludge.

1. Activation

[0009] As used herein, the term "activation" refers to the interaction of an activation material, such as a polymer, with suspended particles in a liquid medium, such as fines in a sludge fluid stream. An "activator" polymer carries out this activation. In

embodiments, high molecular weight polymers can be introduced into the particulate dispersion as activator polymers, so that these polymers interact, or complex, with fines. The polymer-particle complexes (the activated fines) interact with other similar complexes, or with other fines, to form agglomerates.

[0010] This "activation" step can function as a pretreatment to prepare the surface of fine particles for further interactions in the subsequent phases of the disclosed system and methods. For example, the activation step can prepare the surface of the fines to interact with other polymers that have been rationally designed to interact therewith in a subsequent "tethering" step, as described below. Not to be bound by theory, it is believed that when the fines are coated by an activating material such as a polymer, these coated materials can adopt some of the surface properties of the polymer or other coating. This altered surface character in itself can be advantageous for sedimentation, consolidation and/or dewatering. In another embodiment, activation can be accomplished by chemical modification of the particles. For example, oxidants or bases/alkalis can increase the negative surface energy of particulates, and acids can decrease the negative surface energy or even induce a positive surface energy on suspended particulates. In another embodiment, electrochemical oxidation or reduction processes can be used to affect the surface charge on the particles. These chemical modifications can produce activated fines that have a higher affinity for tethered anchor particles as described below.

[0011] Fines suitable for modification or activation can include organic or inorganic particles, or mixtures thereof. Fine particle sizes can range from a few nanometers to few hundred microns. Under certain conditions, macroscopic particles in the millimeter range may be appropriate for activation. In embodiments, fines may comprise materials such as lignocellulosic material, cellulosic material, carbonaceous materials, or the like.

Cellulosic and lignocellulosic materials for activation may include wood materials such as wood flakes, wood fibers, wood waste material, wood powder, lignins, or fibers from woody plants.

[0012] The "activation" step may be performed using flocculants or other polymeric substances. Preferably, the polymers or flocculants can be charged, including anionic or cationic polymers. In embodiments, anionic polymers can be used, including, for example, olefmic polymers, such as polymers made from polyacrylate, polymethacrylate, partially hydrolyzed polyacrylamide, and salts, esters and copolymers thereof (such as sodium acrylate/acrylamide copolymers), sulfonated polymers, such as sulfonated polystyrene, and salts, esters and copolymers thereof. In embodiments, suitable polycations include: polyvinylamines, polyallylamines, polydiallyldimethylammoniums (e.g., the chloride salt), branched or linear polyethyleneimine, crosslinked amines (including epichlorohydrin/dimethylamine, and epichlorohydrin/alkylenediamines), quaternary ammonium substituted polymers, such as

(acrylamide/dimethylaminoethylacrylate methyl chloride quat) copolymers and trimethylammoniummethylene- substituted polystyrene, and the like. Nonionic polymers suitable for hydrogen bonding interactions can include polyethylene oxide, polypropylene oxide, polyhydroxyethylacrylate, polyhydroxyethylmethacrylate, and the like. In embodiments, an activator such as polyethylene oxide can be used as an activator with a cationic tethering material in accordance with the description of tethering materials below. In embodiments, activator polymers with hydrophobic modifications can be used. Flocculants such as those sold under the trademark MAGNAFLOC® by Ciba Specialty Chemicals can be used. In embodiments, activators such as polymers or copolymers containing carboxylate, sulfonate, phosphonate, or hydroxamate groups can be used. These groups can be incorporated in the polymer as manufactured; alternatively, they can be produced by neutralization of the corresponding acid groups, or generated by hydrolysis of a precursor such as an ester, amide, anhydride, or nitrile group. The neutralization or hydrolysis step could be done on site prior to the point of use, or it could occur in situ in the process stream.

[0013] In embodiments, an activated fine particle can also be an amine functionalized or modified particle. As used herein, the term "modified particle" can include any particle that has been modified by the attachment of one or more amine functional groups as described herein. The functional group on the surface of the particle can be from modification using a multifunctional coupling agent or a polymer. The multifunctional coupling agent can be an amino silane coupling agent as an example. These molecules can bond to a particle surface and then present their amine group for interaction with the particulate matter. In the case of a polymer, the polymer on the surface of the particles can be covalently bound to the surface or interact with the surface of the particle and/or fiber using any number of other forces such as electrostatic, hydrophobic, or hydrogen bonding interactions. In the case that the polymer is covalently bound to the surface, a multifunctional coupling agent can be used such as a silane coupling agent. Suitable coupling agents include isocyano silanes and epoxy silanes as examples. A polyamine can then react with an isocyano silane or epoxy silane for example. Polyamines include polyallyl amine, polyvinyl amine, chitosan, and polyethylenimine.

[0014] In embodiments, polyamines (polymers containing primary, secondary, tertiary, and/or quaternary amines) can also self-assemble onto the surface of the fines to functionalize them without the need of a coupling agent. For example, polyamines can self-assemble onto the surface of the particles through electrostatic interactions. They can also be precipitated onto the surface in the case of chitosan for example. Since chitosan is soluble in acidic aqueous conditions, it can be precipitated onto the surface of fines by suspending the particles in a chitosan solution and then raising the solution pH.

[0015] In embodiments, the amines or a majority of amines are charged. Some polyamines, such as quaternary amines are fully charged regardless of the pH. Other amines can be charged or uncharged depending on the environment. The polyamines can be charged after addition onto the particles by treating them with an acid solution to protonate the amines. In embodiments, the acid solution can be non-aqueous to prevent the polyamine from going back into solution in the case where it is not covalently attached to the particle. The polymers and particles can complex via forming one or more ionic bonds, covalent bonds, hydrogen bonding and combinations thereof, for example. In a preferred embodiment, the polymers and particles form a complex via ionic

complexing.

[0016] To obtain activated fines, the activator can be introduced into the liquid sludge medium through a variety of mechanisms, as would be apparent to those of ordinary skill in the art. As an example, a large mixing tank can be used to mix the activating material with the sludge. As another example, the activating material can be added along a transport pipeline bearing the sludge, with the mixing taking place, for example, by the turbulence encountered in fluid transport, optionally aided by a static mixer or series of baffles.

2. Tethering

[0017] As used herein, the term "tethering" refers to an interaction between an activated fine particle and an anchor particle (as described below). The anchor particle can be treated or coated with a tethering material. The tethering material, such as a polymer, forms a complex or coating on the surface of the anchor particles such that the tethered anchor particles have an affinity for the activated fines. In embodiments, the selection of tether and activator materials is intended to make the two solids streams complementary so that the activated fine particles become tethered, linked or otherwise attached to the anchor particle. When attached to activated fine particles via tethering, the anchor particles enhance the rate and completeness of sedimentation or removal of the fine particles.

[0018] In accordance with these systems and methods, the tethering material acts as a complexing agent to affix the activated particles to an anchor material. In embodiments, sand can be used as an anchor material, as may a number of other substances, as set forth in more detail below. In embodiments, a tethering material can be any type of material that interacts strongly with the activating material and that is connectable to an anchor particle. [0019] As used herein, the term "anchor particle" refers to a particle that facilitates the separation of fine particles. Generally, anchor particles have a density that is greater than the liquid process stream. For example, anchor particles that have a density of greater than about 1.3 g/cc can be used. Additionally or alternatively, the density of the anchor particles can be greater than the density of the fine particles or activated particles.

Alternatively, the density is less than the dispersal medium, or density of the liquid or aqueous stream. Alternatively, the anchor particles are simply larger than the fine particles or the activated fine particles. A difference in density or particle size facilitates separating the solid complexes from the fluid medium.

[0020] For example, for the removal of particulate matter with an approximate mean diameter less than about 50 microns, anchor particles may be selected having larger dimensions, e.g., a mean diameter of greater than about 70 microns. An anchor particle for a given system can have a shape adapted for easier settling when compared to the target particulate matter: spherical particles, for example, may advantageously be used as anchor particles to remove particles with a flake or needle morphology. In other embodiments, increasing the density of the anchor particles may lead to more rapid settlement. Alternatively, less dense anchors may provide a means to float the fine particles, using a process to skim the surface for removal. In this embodiment, one may choose anchor particles having a density of less than about 0.9 g/cc, for example, about 0.5 g/cc, to remove fine particles from an aqueous process stream.

[0021] Advantageously, anchor particles can be selected that are indigenous to a particular geographical region where the particulate removal process would take place. In embodiments, suitable anchor particles can be formed from organic or inorganic materials, or any mixture thereof. Inorganic particles can include one or more materials such as calcium carbonate, dolomite, calcium sulfate, kaolin, talc, titanium dioxide, sand, diatomaceous earth, aluminum hydroxide, silica, other metal oxides and the like. Organic particles can include one or more materials such as starch, modified starch, polymeric spheres (both solid and hollow), and the like. Particle sizes can range from a few nanometers to few hundred microns. In certain embodiments, macroscopic particles in the millimeter range may be suitable.

[0022] In embodiments, an anchor particle may comprise materials, such as

lignocellulosic material, cellulosic material, minerals, vitreous material, cementitious material, carbonaceous material, plastics, elastomeric materials, and the like. In embodiments, cellulosic and lignocellulosic materials may include wood materials such as wood flakes, wood fibers, wood waste material, wood powder, lignins, or fibers from woody plants.

[0023] Examples of inorganic anchor particles include clays such as attapulgite and bentonite. In embodiments, the inorganic compounds can be vitreous materials, such as ceramic particles, glass, fly ash and the like. The particles may be solid or may be partially or completely hollow. For example, glass or ceramic microspheres may be used as particles. Vitreous materials such as glass or ceramic may also be formed as fibers to be used as particles. Cementitious materials may include gypsum, Portland cement, blast furnace cement, alumina cement, silica cement, and the like. Carbonaceous materials may include carbon black, graphite, carbon fibers, carbon microparticles, and carbon nanoparticles, for example carbon nanotubes.

[0024] In embodiments, plastic materials may be used as anchor particles. Both thermoset and thermoplastic resins may be used to form plastic anchor particles. Plastic anchor particles may be shaped as solid bodies, hollow bodies or fibers, or any other suitable shape. Plastic anchor particles can be formed from a variety of polymers. A polymer useful as a plastic anchor particle may be a homopolymer or a copolymer.

Copolymers can include block copolymers, graft copolymers, and interpolymers. In embodiments, suitable plastics may include, for example, addition polymers (e.g., polymers of ethylenically unsaturated monomers), polyesters, polyurethanes, aramid resins, acetal resins, formaldehyde resins, and the like. Addition polymers can include, for example, polyolefms, polystyrene, and vinyl polymers. Polyolefms can include, in embodiments, polymers prepared from C2-C10 olefin monomers, e.g., ethylene, propylene, butylene, dicyclopentadiene, and the like. In embodiments, poly( vinyl chloride) polymers, acrylonitrile polymers, and the like can be used. In embodiments, useful polymers for the formation of particles may be formed by condensation reaction of a polyhydric compound (e.g., an alkylene glycol, a polyether alcohol, or the like) with one or more polycarboxylic acids. Polyethylene terephthalate is an example of a suitable polyester resin. Polyurethane resins can include, e.g., polyether polyurethanes and polyester polyurethanes. Plastics may also be obtained for these uses from waste plastic, such as post-consumer waste including plastic bags, containers, bottles made of high density polyethylene,

polyethylene grocery store bags, and the like. [0025] Anchor particles (as measured as a mean diameter) can have a size up to few hundred microns, preferably greater than about 70 microns. In certain embodiments, macroscopic anchor particles up to and greater than about 1 mm may be suitable.

[0026] As an example of a tethering material used with an anchor particle in accordance with these systems and methods, chitosan can be precipitated upon a selected anchor particle, for example, via pH-switching behavior. The chitosan can have affinity for anionic systems that have been used to activate fine particles. In one example, partially hydrolyzed polyacrylamide polymers can be used to activate particles, resulting in an activated fine particle with anionic charge properties. The cationic charge of the chitosan will attract the anionic charge of the activated particles, to attach the anchor particles to the activated fine particles.

[0027] In embodiments, various interactions such as electrostatic, hydrogen bonding or hydrophobic behavior can be used to affix an activated particle or particle complex to a tethering material complexed with an anchor particle. In the foregoing example, electrostatic interactions can govern the assembly of the activated fine particle complexes bearing the anionic partially-hydrolyzed polyacrylamide polymer and the cationic anchor particles bearing the chitosan tethering material.

[0028] In embodiments, polymers such as linear or branched polyethyleneimine can be used as tethering materials. It would be understood that other anionic or cationic polymers could be used as tethering agents, for example polydiallyldimethylammonium chloride poly(DADMAC). In other embodiments, cationic tethering agents such as

epichlorohydrin dimethylamine (epi/DMA), styrene maleic anhydride imide (SMAI), polyethylene imide (PEI), polyvinylamine, polyallylamine, amine-aldehyde condensates, poly(dimethylaminoethyl acrylate methyl chloride quaternary) polymers and the like can be used. Advantageously, cationic polymers useful as tethering agents can include quaternary ammonium or phosphonium groups. Advantageously, polymers with quaternary ammonium groups such as poly(DADMAC) or epi/DMA can be used as tethering agents. In other embodiments, polyvalent metal salts (e.g., calcium, magnesium, aluminum, iron salts, and the like) can be used as tethering agents. In other embodiments cationic surfactants such as dimethyldialkyl(C₈-C22)ammonium halides, alkyl(C₈-

C22)trimethylammonium halides, alkyl(C₈-C22)dimethylbenzylammonium halides, cetyl pyridinium chloride, fatty amines, protonated or quaternized fatty amines, fatty amides and alkyl phosphonium compounds can be used as tethering agents. In embodiments, polymers having hydrophobic modifications can be used as tethering agents.

[0029] The efficacy of a tethering material, however, can depend on the activating material. A high affinity between the tethering material and the activating material can lead to a strong and/or rapid interaction there between. A suitable choice for tether material is one that can remain bound to the anchor surface, but can impart surface properties that are beneficial to a strong complex formation with the activator polymer. For example, a polyanionic activator can be matched with a polycationic tether material or a polycationic activator can be matched with a polyanionic tether material. In one embodiment, a poly(sodium acrylate-co-acrylamide) activator is matched with a chitosan tether material.

[0030] In hydrogen bonding terms, a hydrogen bond donor should be used in

conjunction with a hydrogen bond acceptor. In embodiments, the tether material can be complementary to the chosen activator, and both materials can possess a strong affinity to their respective deposition surfaces while retaining this surface property. In other embodiments, cationic-anionic interactions can be arranged between activated fine particles and tether-bearing anchor particles. The activator may be a cationic or an anionic material, as long as it has an affinity for the fine particles to which it attaches. The complementary tethering material can be selected to have affinity for the specific anchor particles being used in the system. In other embodiments, hydrophobic interactions can be employed in the activation-tethering system.

[0031] The anchor particle material is preferably added in an amount that permits a flowable slurry. For example, the particle material can be added in an amount greater than 1 gram/liter but less than the amount which results in a non- flowable sludge or slurry, amounts between about 1 to about 1000 grams/liter (g/1), preferably about 5 to about 100 g/1 are often suitable. In some embodiments, it may be desirable to maintain the concentration of the anchor particles to about 20 g/1 or higher. The anchor particles may be fresh (unused) material, recycled, cleaned ballast, recycled, uncleaned ballast, and the like. In embodiments, for example when sand is chosen as an anchor particle, higher amounts of the particle material may be added. For example, sand can be added in a range between about 1 to about 300 gm/1, preferably between about 50 to about 300 gm/1, for example at a dosage level of about 240 gm/1. 3. ATA Complex Recovery

[0032] It is envisioned that the complexes formed from the anchor particles and the activated particulate matter can be recovered from the fluid stream containing them using a separation system. In embodiments, the complexes thus removed can be used for other applications. In embodiments, the interactions between the activated fine particles and the tether-bearing anchor particles can enhance the mechanical properties of the complex that they form. For example, an activated fine particle or collection thereof can be durably bound to one or more tether-bearing anchor particles, so that they do not segregate or move from the position that they take on the particles. This property of the complex can make it mechanically more stable.

[0033] A variety of separation systems are available for removing the complexes comprising activated fines associated with tether-bearing anchor particles from the fluid stream. For example, the tether-bearing anchor particles can be mixed into a stream carrying activated fine particles, and the complexes can then separated via a settling process such as gravity or centrifugation. In another method, the process stream carrying the activated fine particles could flow through a bed or filter cake of the tether-bearing anchor particles. In any of these methods, the modified particles interact with the fine particulates and pull them out of suspension so that later separation removes both modified particles and fine particulates.

4. Sludge Treatment

[0034] In embodiments, the systems and methods described herein use a flocculating polymer that is mixed with the sludge to yield activated fines, followed by the

introduction of a heavier particle tethered to one or more polymers capable of interacting with activated fines to produce a complex. This complex comprises activated fines and tether-bearing anchor particles associated with each other. The sludge complexes produced by the ATA Process, as disclosed herein, can be removed from the fluid stream by filtration or other removal methods, for example, free-draining filtration.

[0035] The sludge complexes produced by the ATA Process, thus consolidated, can then be converted into a variety of useful products by further modifying the surfaces of sludge complexes with other materials that would enable specific functionalities. As an example, the consolidated sludge complexes can be converted into an odor absorbent material, useful for example as cat litter or as an additive thereto. [0036] In an embodiment, a polyamine, such as chitosan or branched PEI (bPEI), can be used as a surface modification agent for the sludge complexes. After ATA Process treatment, the ensuing sludge complexes can then be dried and converted into uniform- sized particles capable of absorbing body fluids and odors. Not to be bound by theory, it is believed that the amine moieties from the surface-modifying agent can neutralize odorific agents such as butyric acid (a component of the body odor of mammals), resulting in an odor-absorbing product when supported by the sludge-derived substrate. In another embodiment, porous particles such as diatomaceous earth or zeolite could be added to the sludge as anchor particles that would act as absorbent centers for odorific substances, for example, urea.

[0037] In another embodiment, a hydrophobicizing agent can be used as the surface- modifying agent for sludge complexes to impart oleophilic properties to them. For example, the consolidated sludge complexes can be treated with a hydrophobicizing agent such as a quaternary ammonium aliphatic compound (such as debonders used in fluff pulp industry), or rosin size or stearic acid or its derivatives such as sodium or aluminum salt of stearic acid. Such hydrophobic sludge-based material could be used as an oil absorption medium.

[0038] In another embodiment, consolidated sludge complexes can be dried and subsequently modified with sustained release formulations to effect sustained release of a substance into an area of interest, for example, to release fertilizer or pesticide into the soil on a time-controlled basis. In this embodiment, fertilizer formulations could be coated with a polymeric coating such as a wax to release the fertilizer into the

surrounding soil. As an example, a wax coating for fertilizer compounds (such as ammonium compounds, nitrates, phosphates and the like) could be designed such a way that the wax melts when the temperature of the surrounding soil is suitable for seeding, thereby increasing the rate of release of the water-soluble fertilizer formulation while minimizing its run-off Other examples of sustained, timely release in accordance with these systems and methods can be envisioned by those of ordinary skill, where loss of a topically-applied agent in an area of interest due to run-off or dilution would be minimized. EXAMPLES

[0039] MATERIALS

Magnafloc LT30 anionic polyacrylamide Ciba Chemicals

DCF 55 Cationic polyacrylamide from Polymer Ventures

Chitosan CG10, Primex, Siglufjordur, Iceland

Sand 40 mesh from Sigma- Aldrich

Lupasol bPEI from BASF

Stearic Acid Sodium salt

Beeswax

Slurry comprising 50% ash and 50% cellulose fines to simulate sludge from typical deinking plant or paper mill (hereinafter "sludge")

PROSOFT® TQ2021 NE quaternary ammonium aliphatic compound.

[0040] EXAMPLE 1 : Sand as tether-bearing anchor particle

[0041] Sand, an anchor particle, was treated with 30 ppm by weight of sand using 200 ppm of DCF 55 polymer as a tethering agent. The tether-bearing sand was then diluted with water to 2% consistency.

[0042] EXAMPLE 2: Activated sludge preparation

[0043] A 2%> slurry of sludge was treated with 30 ppm (by solids weight) of 250 ppm solution of LT30 polymer to produce an activated sludge.

[0044] EXAMPLE 3 : Complexing tether-bearing sand with activated sludge

[0045] The activated sludge prepared in Example 2 was immediately mixed with 10% (by weight of solids) of tether-bearing sand prepared in accordance with Example 1. The resulting sludge mixture was then filtered using a 100 mesh screen, and then solids content of the filtrate was measured. The filtrate comprised sludge complexes containing activated sludge fines associated with tether-bearing sand anchor particles.

[0046] EXAMPLE 4: Preparation of Chitosan solutions

[0047] A chitosan solution of CG10 was prepared by dispersing CG10 in deionized water and adding 1M HC1 until the chitosan was dissolved. The final pH was approximately 3.5. Chitosan solutions prepared as above were then further diluted with deionized water to obtain the concentrations set forth in the Examples below. [0048] EXAMPLE 5 : Preparation of treated sludge using bPEI to produce odor- absorbing material

[0049] A 10% suspension of diatomaceous earth (DE) was treated with a 1% solution of bPEI. The treated DE was then complexed with DCF 55 polymer as a tethering agent, using the protocol of Example 1. Activated sludge was prepared in accordance with Example 2. The tether-bearing treated DE was then combined with the activated sludge in accordance with Example 3, using DE in the amount of 10% by weight of the solids in the activated sludge. The mixture was then pressed and dried to form particles of uniform size and consistency that could be used, e.g., for an odor-absorbent medium for acidic odorifacient molecules such as butyric acid.

[0050] EXAMPLE 6: Preparation of treated sludge using chitosan to produce odor- absorbing material

[0051] A 10% suspension of DE can be treated with a 1% solution of a chitosan formulation prepared in accordance with Example 4. The treated DE can then be complexed with DCF 55 polymer as a tethering agent, using the protocol of Example 1. Activated sludge can be prepared in accordance with Example 2. The tether-bearing treated DE can then be combined with the activated sludge in accordance with Example 3, using DE in the amount of 10%> by weight of the solids in the activated sludge. The mixture was then pressed and dried to form particles of uniform size and consistency that could be used, e.g., for an odor-absorbent medium for acidic odorifacient molecules such as butyric acid.

[0052] EXAMPLE 7: Preparation of oil-absorbing sludge-based hydrophobic material using quaternary aliphatic compounds

[0053] PROSOFT® TQ2021 NE was dissolved in water to create a 1 % solution. This quaternary aliphatic solution was added at 30 ppm loading by solids weight to the sludge complexes that had been prepared in accordance with Example 3. The quaternary aliphatic solution was stirred for five minutes with the sludge complex solution, then filtered, pressed and dried. The resulting solid was hydrophobic and showed significantly improved capacity for absorbing oils as compared to sludge that did not contain the quaternary ammonium compound. [0054] EXAMPLE 8: Preparation of oil-absorbing sludge-based hydrophobic material using soluble salts of stearic acid

[0055] A sodium salt of stearic acid was made into a 1% solution in water. This sodium stearate solution was used to treat sludge in accordance with the protocol of Example 7. The resulting solid was hydrophobic and showed improved capacity for absorbing oils as compared to sludge that did not contain the sodium stearate solution.

[0056] EXAMPLE 9: Preparation of encapsulated fertilizers for sustained delivery

[0057] Beeswax can be used as an encapsulant for fertilizer compounds such as ammonium nitrate. Beeswax that melts at temperatures around 50°C can be melted and combined with a 1% by weight composition of ammonium nitrate. The molten wax/fertilizer suspension can then be cooled, and the resulting mass ground to obtain encapsulated fertilizers. This product can be added to the dried and pressed sludge in a mixer to produce granulated sludge with fertilizer encapsulated particles.

While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.

Claims

CLAIMS What is claimed:

1. A system for removing fines from a sludge fluid, comprising:

a sludge fluid stream containing the fines;

an activator polymer that associates with the fines;

an anchor particle bearing a tether polymer that is capable of interacting with the activator polymer, wherein the anchor particle is mixed into the sludge fluid stream so that the tether polymer interacts with the activator polymer, forming a sludge complex comprising the fines and the anchor particle;

and a separation system that removes the sludge complex from the sludge fluid stream.

2. The system of claim 1, wherein the anchor particle comprises sand.

3. The system of claim 1, wherein the separation system comprises gravity filtration.

4. The system of claim 1, wherein the sludge complexes removed from the sludge fluid are consolidated to form a consolidated material.

5. The system of claim 4, wherein the sludge complexes are treated with a surface- modifying agent.

6. The system of claim 5, wherein the surface-modifying agent comprises a polyamine.

7. The system of claim 5, wherein the surface-modifying agent comprises a

hydrophobicizing agent.

8. A method for removing fines from a sludge fluid, comprising:

adding an activator polymer to the sludge fluid, wherein the activator polymer associates with the fines to form an activator-fines complex; preparing a tether-bearing anchor particle by associating a tethering polymer to an anchor particle, wherein the tethering polymer is capable of interacting with the activator polymer;

contacting the activator- fines complex with the tether-bearing anchor particle to form an activator-tether-anchor complex comprising the fines and the anchor particle; and removing the activator-tether-anchor complex from the sludge fluid, thereby removing the fines.

9. The method of claim 8, wherein the step of removing the activator-tether-anchor complex further comprises consolidating a plurality of anchor-tether-activator complexes to form a consolidated sludge complex.

10. The method of claim 9, further comprising treating the consolidated sludge complex with a surface-modifying agent.

11. The system of any one of claims 1 to 7, wherein the sludge fluid is produced in the production of paper or pulp.

12. The system of any one of claims 1 to 7 and 11, wherein the sludge fluid comprises fines selected from the group consisting of cellulosic fines, clay, precipitated calcium carbonate, carbon black, ink pigments, and combinations thereof.

13. The method of any one of claims 8 to 10, wherein the sludge is produced in the production of paper or pulp.

14. The method of any one of claims 8 to 10 and 13, wherein the sludge fluid comprises fines selected from the group consisting of cellulosic fines, clay, precipitated calcium carbonate, carbon black, ink pigments, and combinations thereof.