Patent Application
20240132382
The present disclosure generally relates to the field of water treatment, and more particularly to the separation step in a water treatment process.
Water treatment facilities are costly to construct and operate. Contaminant aggregation and settling of flocculated contaminants (flocs) add to these costs. Settling performance is highly dependent on the floc size and density, and requires costly, non-renewable, non-reusable (intended for landfilling), and/or toxic products; such as, metal-based coagulants (lost in sludge), and synthetic flocculants. It can also require ballast media which is an added cost, and often obtained in an unsustainable process. Indeed these currently used products often have significant environmental footprints. The floc size, that dictates contaminant removal during settling, is limited by the size of flocculant used i.e., that is less than 100 nm. The floc sizes generated with prior art technologies, do not permit floc removal through efficient screening, as flocs readily pass through coarse screens and clog smaller mesh sizes. Therefore, improvements are needed in water treatment processes particularly for separating flocs.
In one aspect there is provided a method of separating contaminants from contaminated water comprising: providing a fibrous treatment agent to the contaminated water, wherein the fibrous treatment agent has a length of at least 100 μm and a diameter of at least 5 μm; allowing the fibrous treatment agent to associate with the contaminants forming flocs comprising a size of at least 1000 μm; and physically separating the flocs from the contaminated water.
In one aspect, there is provided a method of separating contaminants from contaminated water comprising: providing the contaminated water comprising fibrous treatment agent; allowing the fibrous treatment agent to associate with the contaminants to form flocs; and physically separating the flocs from the contaminated water. In one embodiment, the fibrous treatment agent has a length of at least 100 μm and a diameter of at least 5 μm. In one embodiment, the floc has a size of at least 1000 μm.
In one embodiment, the fibrous treatment agent comprises at least one of fibers, microspheres, flakes (structures formed of at least two fibers linked together or more), hydrogels, frayed fibers, sponge materials, and other fibre based materials or porous structures.
In one embodiment, the fibers are pristine and/or functionalized.
In one embodiment, the fibrous treatment agent comprises functionalized fibers.
In one embodiment, the fibrous treatment agent comprises metal-grafted fibers or polymer-grafted fibers.
In one embodiment, the method further comprises washing and/or fragmenting the flocs to retrieve the fibrous treatment agent.
In one embodiment, a portion of the fibrous treatment agent provided includes recovered fibrous treatment agent obtained after physically separating the flocs from the contaminated water.
In one embodiment, physically separating includes one or more of sedimentation, decantation, aggregation, coagulation, flocculation, ballasted flocculation, settling, screening, sieving, adsorption, flotation, sludge blanket clarifiers, gravitational separation, and filtration.
In one embodiment, the filtration includes at least one of granular filtration, biofiltration, membrane filtration, and biosorption.
In one embodiment, the gravitational separation includes at least one of ballasted flocculation, flocculation, and flotation.
In one embodiment, the physical separation includes passing the contaminated water through a sieve, a screen, and/or a rotating drum.
In one embodiment, the fibrous treatment agent is a bridging agent, a ballasting agent, an adsorbent, a flocculant and/or a coagulation agent.
In one embodiment, the fibrous treatment agent comprises pristine fibers having a length of at least 1000 μm.
In one embodiment, the fibrous treatment agent comprises functionalized fibers.
In one embodiment, the functionalized fibers are functionalized with Si, Fe, Al, Ca, Ti, Zn (hydr)oxides, polymers, coagulants, flocculants, hydrophobic or hydrophilic entities, polar or non-polar groups, a carboxyl group, a sulfonated group, and/or a phosphoryl group.
In one embodiment, the fibrous treatment agent is iron grafted fibers.
In one embodiment, the fibrous treatment agent comprises microspheres having a diameter of at least 20 μm.
In one embodiment, the microspheres are functionalized with Si, Fe, Al, Ca, Ti, and Zn oxides and/or hydroxides, polymers, coagulants, flocculants, hydrophobic or hydrophilic entities, polar or non-polar groups, a carboxyl group, a sulfonated group, and/or a phosphoryl group.
In one embodiment, the fibrous treatment agent comprises flakes having a diameter of at least 20 μm.
In one embodiment, the flakes are functionalized with Si, Fe, Al, Ca, Ti, Zn (hydr)oxides, polymers, coagulants, flocculants, hydrophobic or hydrophilic entities, polar or non-polar groups, a carboxyl group, a sulfonated group, and/or a phosphoryl group.
In one embodiment, the fibrous treatment agent comprises fibers from municipal wastewater treatment, industrial wastewater treatment, pulp and paper industry, agriculture waste, cotton, cellulose, lignin, maize, hemicellulose, polyester, polysaccharide-based fiber, keratin, and/or recycled cellulose.
In one embodiment, the method further comprises providing a bridging agent, a ballasting agent, an adsorbent, a coagulant and/or a flocculant to the contaminated water.
In one embodiment, the flocs have a diameter of at least 1000 μm.
In one embodiment, wherein the coagulant, the adsorbent, and/or the flocculant are recovered with the fibrous treatment agent and recirculated and/or reused during aggregation or for separating the contaminants.
In one embodiment, the method is free of any coagulant and/or flocculant additions.
In one embodiment, the flocs have a diameter of at least 2000 μm.
In one embodiment, the fibrous treatment agent is already present in the contaminated water.
In one embodiment, the physically separating step is a screening step with a mesh size of at least 100 μm.
In one embodiment, the physically separating step is a screening step with a mesh size of at least 500 μm.
In one embodiment, the fibrous treatment agent is iron grafted fibers having an aspect ratio of length over diameter of at least 10.
In one embodiment, the method further comprises the step of washing and/or fragmenting the flocs to retrieve and/or reuse the fibrous treatment agent. In some cases where coagulant, flocculant, ballast media, and/or adsorbent are employed in the method, these can also be recovered and/or reused with or without the fibrous treatment agent. In one embodiment of the method, a portion of the fibrous treatment agent provided includes recovered fibrous treatment agent, coagulant, flocculant, ballast media, and/or adsorbent obtained after physically separating the flocs from the contaminated water. In one embodiment, the fibrous treatment is used as a carrier to recover and/or reuse coagulant, flocculant, ballast media, and/or adsorbent that are employed in the method as described herein.
In one embodiment, physical separation includes one or more of sedimentation, decantation, aggregation, coagulation, flocculation, ballasted flocculation, settling, screening, three dimensional screening, three dimensional porous collector, sieving, adsorption, flotation, biological treatment, sludge blanket clarifiers, gravitational separation, press filtration, belt filtration, separation via a fluidized bed, and filtration.
In one embodiment, the physical separation step is a screening step with a mesh size of at least 500 μm, preferably at least 1000 μm.
In one embodiment, the fibrous treatment agent is pristine or iron grafted fibers having an aspect ratio of length over diameter of at least 10.
In yet a further aspect, there is provided a floc having a size of at least 1000 μm and comprising pristine, metal oxide and/or hydroxide functionalized fibers, and optionally at least one of a coagulant, a flocculant, a bridging agent, an adsorbent, a ballasting agent, and a contaminant, wherein the metal oxide and/or hydroxide functionalized fibers comprise fibers selected from the group consisting of cellulose, polyester, cotton, nylon, maize, polysaccharide-based, lignin, keratin and combinations thereof. In one embodiment, the floc comprises metal oxide and/or hydroxide functionalized fibers. In one embodiment, the oxide and/or hydroxide functionalized fibers are iron oxide and/or hydroxide fibers. In one embodiment, the contaminant is selected from the group consisting of phosphorus contaminants, natural organic matter, specific natural organic matter fraction, disinfection by-products, disinfection by-products precursors, soluble contaminants, particulate contaminants, colloidal contaminants, turbidity, total suspended solids (TSS), hardness, bacteria, viruses, pathogens, microorganisms, hydrocarbons, nanoplastics, microplastics, naphthenic acids, and metals.
In one aspect, there is provided the use formulations of fibers and polymers (or other chemicals such as coagulant, flocculant, and any other chemical, media, and adsorbent used in water treatment) in the methods described herein or the flocs described herein, for biological treatment (e.g., activated sludge), or any other aggregation and separation method that don't usually required metal-based coagulant such as alum or ferric sulfate. In one embodiment, the formulations of fibers and ballast media (e.g., silica sand and magnetite) increase the floc size and density. In one embodiment, the formulation comprises fibers of different lengths (e.g. around 1000 μm cellulose fibers and >10 000 μm cotton fibers). In one embodiment, the use of formulations is for biological treatment, to improve biofilm formation and growth during biofiltration, activated sludge system, or any other biological treatment. In one embodiment, the use of the formulation is for the treatment of domestic wastewater or other decentralized treatment applications. In one embodiment, the formulations further comprise granular media (such as sand, anthracite, granular activated carbon). In one embodiment, the use comprises a porous collector, for filtration applications.
Many further features and combinations thereof concerning the present improvements will appear to those skilled in the art following a reading of the instant disclosure. As would be understood by those skilled in the art, the aspects described herein may be combined with any of the embodiments described herein. Furthermore, the embodiments can also be combined with one or more other embodiments described herein.
), keratin fibers (∘), cotton fibers (⋄), and SiO2-microspheres (▪);
Stuffed flakes were filled with recycled crushed glass (density of 2.6) to increase the material density;
: 8 min of aggregation, ▴: 2 min of aggregation. Dashed line represents the average value obtained from triplicates;
The present disclosure concerns the treatment of water containing contaminants using a physical separation. The contaminants can be natural organic matter (NOM), specific NOM fractions, phosphorus and other soluble contaminants as well as particulate or colloidal contaminants (such as turbidity and total suspended solids (TSS)). The water provided to the present methods for treatment, in some embodiments, can be raw or pre-treated, to remove the macro and large contaminants (cellulose, polyester, cotton, nylon, keratin and the like). The term “physical separation” as used herein refers to a separation that relies on at least one physical characteristic such as the size and/or density of contaminant species to remove them from the contaminated water. In one embodiment, the physical separation is one or more of sedimentation, decantation, aggregation, settling, screening, sieving, adsorption, gravitational separation, flotation, sludge blanket clarifier, and filtration. For example, the filtration is at least one of granular filtration, membrane filtration, biofiltration, and biosorption. In another example, the gravitational separation is at least one of ballasted flocculation, flocculation, and air-dissolved flotation.
To achieve adequate physical separation and simultaneously achieve improved sustainability, cost and efficiency, fibrous treatment agents having a length of at least 100 μm and a diameter of at least 5 μm are used. The fibrous agents could be already present in the water to be treated (e.g., domestic wastewater that contains textile fibers, or wastewater from the pulp & paper industry containing cellulose/lignin fibers), or added to the water to improve treatment. These fibrous treatment agents can be engineered from fibers recovered from wastes from wastewater treatment plants, pulp and paper industry and from other industries; namely, cotton, cellulose, polyester, and keratin fibers, and other waste, recycled and pristine materials. The fibrous treatment agents, such as fibers, microspheres (
Referring to
Different exemplary flocs are illustrated in
As used herein the term “coagulant” refers to an agent that promotes the destabilization of a colloidal suspension and/or precipitates soluble contaminants. The coagulant can for example, neutralize the electrical charge on colloidal particles, which destabilizes the forces keeping the colloids apart. As used herein the term “flocculant” refers to an agent that promotes flocculation by increasing floc size and/or stabilizing the floc shape. For example, the flocculant can cause colloids or other suspended particles to aggregate and form a floc. Typically, a flocculant is used to increase the size of flocs, notably by aggregating the particles formed during coagulation. As used herein the terms “ballasting”, “ballasting agent” or “ballast media” refers to an agent that increases the size and/or the density of flocs. As used herein the term “adsorbent” refers to an agent that absorbs contaminants and thereby captures the contaminants within its fibrous matrix or on its surface. As used herein the term “bridging agent” refers to an agent or linear structure able to connect particles or flocs together, hence increasing the size of flocs. For example, fibers having a length larger than 100 μm are considered bridging agents.
To produce the flocs, a fibrous treatment agent comprising fibers in the form of free fibers can be used. In one example the free fibers are functionalized. In another example the free fibers are pristine. In a further example, the free fibers can be a mix of functionalized and pristine. In one embodiment, the fibrous treatment agent comprises pristine fibers having a length of at least 10 μm, at least about 100 μm, at least about 500 μm, at least about 1000 μm, at least about 2000 μm, at least about 3000 μm, at least about 4000 μm, or at least about 5000 μm, and a diameter of at least about 5 μm, at least about 6 μm, at least about 7 μm, at least about 8 μm, at least about 9 μm, at least about 10 μm, at least about 15 μm, at least about 20 μm, or at least about 50 μm. For example, the pristine fibers can have a length of between about 100 to about 15,000 μm, about 1000 to about 15,000 μm, about 2000 to about 15,000 μm, about 3000 to about 15,000 μm, about 4000 to about 15,000 μm, or about 5000 to about 15,000 μm. In one embodiment, the pristine fibers have an aspect ratio of length over diameter of at least about 10, at least about 15, at least about 20, or at least about 25. The density of the fibers depends on the type of fibers used during its synthesis (e.g., cellulose, cotton, polyester, keratin, nylon, etc. which can be pristine, waste or recycled). For example, the density of fibers that are not functionalized is between about 0.6 to about 1.5. In one embodiment, the fibrous treatment agent consists of pristine fibers as defined herein. In a further embodiment, the fibrous treatment comprising or consisting of pristine fibers is free of functionalized fibers. Pristine fibers according to the present disclosure are particularly suitable for use as super bridging agents. The effectiveness of pristine fibers as super bridging agents increases with size, for example a length of at least 1000 μm. The fibers used to obtain the pristine fibers of the fibrous treatment agent may be cellulosic fibers derived from wastewater fibers (such as bathroom tissue), and/or recycled cellulosic fibers (such as from blended domestic residues or pulp and paper industry wastes).
In one embodiment, the fibrous treatment agent comprises functionalized fibers. In one embodiment, the fibrous treatment agent comprises functionalized fibers having a length of at least about 100 μm, at least about 150 μm, at least about 200 μm, at least about 300 μm, at least about 400 μm, at least about 500 μm, at least about 1000 μm, or at least about 2000 μm, and a diameter of at least about 5 μm, at least about 6 μm, at least about 7 μm, at least about 8 μm, at least about 9 μm, at least about 10 μm, at least about 15 μm, at least about 20 μm, or at least about 50 μm. For example, the functionalized fibers can have a length of between about 100 to about 15,000 μm, about 200 to about 15,000 μm, about 300 to about 15,000 μm, about 400 to about 15,000 μm, about 500 to about 15,000 μm, about 1000 to about 15,000 μm, or about 2000 to about 15,000 μm. In one embodiment, the functionalized fibers have an aspect ratio of length over diameter of at least about 10, at least about 15, at least about 20, or at least about 25. The density of the fibers depends on the functionalization and on the type of fibers used during its synthesis (e.g., cellulose, cotton, polyester, keratin, nylon, etc. which can be pristine, waste or recycled). The density increases with increasing levels of functionalization. In one embodiment, the density is at least about 1.5. The term “functionalized” as used herein refers to a functionalization with metal ions, metal oxides and other hydroxides such as Si, Ca, Ti, Zn, Al and/or Fe oxides and hydroxides (monomeric or polymeric forms), and/or with organic polymers such as polyamines, polyacrylamides, polydiallyldimethylammonium chloride, epichlorohydrin/dimethylamine, polysaccharide-based polymers, and any other polymers with hydrophobic or hydrophilic entities, coagulants, flocculants, and/or fiber binding/linking agents. The functionalization grants the fibers increased interactions with contaminants. Functionalized fibers are particularly suitable to be used as a bridging agent, adsorbent and/or ballasting agent. In one embodiment, the surface area is estimated to be about 10 to 300 m2/g, 10 to 350 m2/g, 10 to 400 m2/g, or 10 to 500 m2/g. The fibers may be cellulosic fibers derived from wastewater fibers (such as bathroom tissue), and/or recycled cellulosic fibers (such as from blended domestic residues or pulp and paper industry wastes). Although more costly, it is also an option to produce the fibers from pristine cellulosic fibers. The use of fibers in the treatment agent allows for a reduction in the amounts of coagulant and flocculant needed, increases the floc settling velocity, and produces flocs that can be extracted by screening.
The fibrous treatment agent can include microspheres (
The fibrous treatment agent can include flakes (
In some embodiments, the fibrous treatment agent consists of functionalized fibrous components. In other embodiments, the fibrous treatment agent comprises or consists of functionalized fibrous components and is free of pristine fibers. In one example, the fibrous components comprise functionalized free fibers, microspheres and/or flakes. In one embodiment, the fibrous treatment agent is functionalized with amines (e.g. quaternary), coagulant, flocculant, with hydrophobic or hydrophilic entities, polar and/or non-polar groups, a carboxymethylation, a sulfonation and/or a phosphorylation. Functionalization can be performed as the agent is produced or subsequently. Functionalization can improve the removal of negatively and positively charged contaminants during water treatment (e.g., negatively charged nanoplastics). In one embodiment, to graft, functionalize or link fibers together, or to synthesize grafted fibers or fiber-based aggregates, oxides and hydroxides such as Al(OH)x, Fe(OH)x, Al2O3, Fe2O3, CaCO3, Fe3O4, FeOOH, SiO2, TiO2 and ZnO and any other monomeric or polymeric hydroxides or oxides can be used (alone or as a blend). Furthermore, in one embodiment, inorganic and organic (e.g. cationic) polymers such as polyamines (e.g. functionalized with quaternary amine group), polyacrylamides, polydiallyldimethylammonium chloride, epichlorohydrin/dimethylamine, polysaccharide-based polymers, and any other polymers with hydrophobic or hydrophilic entities, and/or fiber binding/linking agents can be used. To increase the mechanical resistance of the fibrous treatment agent, it can be reinforced 1) by adding high molecular weight polymers during synthesis promoting internal linkages or 2) by grafting Si (or other hydroxides or oxides) on the external structure of the materials. In one example, the concentration of Fe grafted on fibers of the fibrous treatment agent is about 0 or about more than 0, to about 90 w/w %, or higher (near 100). Similarly, in one example, the concentration of Si grafted on fibers of the fibrous treatment agent is about 0 or about more than 0, to about 90 w/w % or higher (near 100).
The following table presents exemplary components or precursor materials of the fibrous treatment agent.
Accordingly there is provided a method of treating water with the fibrous treatment agents of the present disclosure described above (pristine fiber, functionalized fiber, microsphere, and/or flake). The water suitable to be treated in the present methods includes “raw” water or previously treated water, for example to remove macro and large contaminants. Raw water can refer to water directly extracted from a natural body of water (river, lake, sea, ocean, ground water, etc.), or output water from an industrial plant (e.g., municipal wastewaters and sludge, steel and aluminum industries, food processing, pulp and paper, agriculture wastewaters/drainage water, pharmaceutical, mining, and petrochemical) or a tailings pond (naphthenic acids) or domestic wastewater or other decentralized treatment applications. The water may be treated before the present fibrous treatment agent is added to the water. Such treatments include but are not limited to removing at least a portion of the macro and large contaminants. The fibrous treatment can be implemented at the influent of the water treatment plant (e.g., before coagulation), in the coagulation tank, or injected later in the process (e.g., in the flocculation tank, in settling tank or during filtration). The fibrous treatment can also be used at the effluent of the plant, to treat, dewater and/or dehydrate sludge.
When the fibrous treatment agent is added to the contaminated water, the fibrous treatment agent will associate with the contaminants (soluble and/or colloidal) to form flocs. In one embodiment the flocs formed can remove turbidity and can capture at least one of soluble or insoluble particulates, NOM, phosphorus, nanoplastics, microplastics, total suspended solids (or any other types of soluble molecules, colloids or contaminants), hydrocarbons or other contaminants targeted by the municipal industry or issued from the petrochemical industry (e.g., naphthenic acids, heavy metals (
In some embodiments, the fibrous treatment agents according to the present disclosure, particularly the iron grafted fibers, can be used to recover coagulants, flocculants, polymers, and other products or media involved in water treatment such as activated carbon, adsorbent, sand, and ballast media, from sludge. This in turn allows the recirculation and reuse of those agents because they can be recycled along with the fibrous treatment agents as described herein. Consequently, the fiber recirculation can reduce the amount of sludge produced.
In one embodiment, the fibrous treatment agent can be added to the water to be at a concentration of at least about 1.0 mg/L, at least about 10.0 mg/L, at least about 100.0 mg/L, at least about 1.0 g/L, at least about 2.0 g/L, at least about 3.0 g/L, at least about 4.0 g/L, at least about 5.0 g/L, at least about 6.0 g/L, at least about 7.0 g/L, at least about 8.0 g/L, at least about 9.0 g/L, at least about 10.0 g/L, at least about 11.0 g/L, or at least about 12.0 g/L. The fibrous treatment agent concentration depends on the composition of the fibrous treatment agent. For example, fibrous treatment agent with a majority of microspheres and/or flakes may be effective with a smaller concentration than a fibrous treatment agent with a minority of microspheres and/or flakes. Optionally, a further coagulant and/or a further flocculant is added to the contaminated water to improve the aggregation, flocculation and/or coagulation thereby improving the floc size, density, and/or contaminant capture efficiency. However, in one embodiment the method according to the present disclosure reduces the demand in chemicals (coagulants and flocculants).
Once the flocs are formed, the flocs are separated by a physical separation step. In one embodiment, the physical separation step includes or is one or more of sedimentation, decantation, aggregation, settling, screening, sieving, adsorption, gravitational separation, flotation, sludge blanket clarifier, and filtration. For example, the filtration is at least one of granular filtration, membrane filtration, biofiltration, and biosorption. In the case of biofiltration the fibrous treatment agent can be used to form the biofilm on which the microorganisms will grow. The physical separation step can be composed of two or more consecutive or concurrent steps. For example, the physical step can include screening followed by settling. In one embodiment, the gravitational separation includes at least one of ballasted flocculation, flocculation, and air-dissolved flotation. In one embodiment, the physical separation includes passing the contaminated water through a sieve, a screen, and/or a rotating drum. In one example, a screen having pores of at least about 10 μm, 100 μm, at least about 200 μm, at least about 300 μm, at least about 500 μm, at least about 1000 μm, at least about 2000 μm, at least about 3000 μm, at least about 4000 μm, at least about 5000 μm, at least about 10 000 μm, at least about 20 000 μm, or at least about 50 000 μm.
The higher the size and/or density of the flocs, the faster and/or more efficient the physical separation becomes. The fibrous treatment agents according to the present disclosure produce an advantageously large particle/floc (and optionally dense) that improves physical separation in water treatment. In one embodiment, it can optionally allow for major changes in water treatment plant operations by removing the settling tank and relying on screening or sieving to remove the flocs. This can significantly reduce the process footprint, the operation time and costs as well as improve the sustainability of water treatment operations.
Furthermore, the flocs of the present disclosure can be optionally washed to recover and therefore reuse the fibrous treatment agent. After the physical separation step (e.g. settling and/or screening), the fibrous treatment agents are extracted from sludge or from the screen and can be reused several times. For example, i) flocs are fragmented and NOM and particles are partially desorbed and detached from the fibrous treatment agent, ii) cleaned fibrous treatment agent are separated from the sludge by screening, hydrocycloning or other suitable means, and iii) the recovered fibrous treatment agents are reinjected in the treatment tank (e.g. aggregation tank) after cleaning and extraction. Fragmented flocs, desorbed NOM and sludge can be sent for sludge dewatering and drying. The fibrous treatment agent could also be left in the settled/screened sludge to improve the sludge treatment, dewatering, dehydration, or other sludge conditioning.
The present method has many advantages including but not limited to reducing the demand in chemicals (additional coagulants, flocculants and ballasting agent), reducing the required settling time and improving the retention of flocs, allows the screening of flocs to be a self-sufficient separation step, optionally eliminating the settling tank, reusability, sustainability of source materials, reduced cost of materials and operation, improving aggregation kinetics and floc settling rate, improving contaminant adsorption and removal, and reducing alkalinity consumption (and other chemicals), thus sludge production/landfilling is expected to decrease proportionally as coagulant/flocculant usage is decreased. Furthermore, the fibrous treatment agents can be used to improve sludge dewatering, sludge drying, sludge purification, or other sludge treatments.
The fibrous treatment agent can be produced or fabricated from waste materials and resources from different industries (e.g., steel and aluminum industries, food processing, pulp and paper, pharmaceutical, mining and other industries). The fabrication method can optionally include the use of a catalyst, an alcohol and/or silica. The fabrication method can be modified to optimized the fibrous treatment agent's chemical composition, size, density, functional groups, shape, hydrophobicity, mechanical resistance, elasticity, or other physicochemical properties. The optimization can be tailored towards a specific type of contaminant that is generally expected to be present in the water (for example industrial contamination). Thus, the fibrous treatment agents can be modified so as to give specific surface affinities with contaminants, coagulants, flocculants, or other chemicals. In one embodiment, the fabrication method includes the use of dense fillers (e.g., sand, magnetite, recycled crushed glass, or other) to synthesize and to increase the density and/or the size of the fibrous treatment agent. Similarly, in one embodiment, light fillers (e.g., plastic, sugar, salts, anthracite, air, or other) can be used to synthesize, to modify the size, to modify the porosity, and/or to modify the density of the fibrous treatment agent. The fillers can be retrieved from the fibrous treatment agent either by heating and/or by solubilizing (e.g., salt and sugar) and washing (e.g. water). In one embodiment, the fibrous treatment agents are produced on site of the water treatment plant operation (e.g. municipal water treatment plant) using waste fibers (e.g. from bathroom tissue, or other fibers such as polyester, cotton, nylon, keratin).
Additional advantages of the fibrous treatment agent of the present disclosure include: (a) reducing the demand in coagulant and flocculant, (b) improve sludge dewatering, sludge drying, sludge purification, or other sludge treatments, (c) improve process sustainability, to reduce capital/operational expenditures or to reduce the process footprint, (d) reduce the concentration of contaminants in treated water.
1.1 SiO2-Fibers and SiO2-Microspheres Synthesis and Characterization
Different types of fibers were used for the grafting: cotton fibers (textile industry), polyester fibers (textile industry), nylon, keratin-based fibers, pristine fibers, low-cost recycled and deinked fibers from the pulp and paper industry, fibers (bathroom tissue) contaminated by municipal wastewater (influent from the city of Montreal, Canada), and other fibers. To simulate the fibers saturation with wastewater, 1 g of pristine fibers were soaked in 1 L of wastewater (city of Montreal) during 24 h at room temperature. Fibers were subsequently extracted from wastewater. Briefly, the solution was firstly screened with a 2000 μm (or more) nylon screen to remove larger aggregates and secondly intensively mixed at 1000 rpm (pH 4.5) with a magnetic stirrer to break aggregates attached to fibers into filterable particles. Fibers were subsequently collected using a 160 μm sieve, while the previously fragmented particles passed through the sieve. Using this technique, only long fibers with a high bridging potential are collected. Other fibre types such as cotton, polyester and keratin-based, all present in wastewater influent, were also used as bridging materials. Prior the grafting SiO2 procedure, all fiber types were washed in water and dried at 40° C. for 24 h prior to carrying out the Si grafting reaction described elsewhere. Tetraethoxysilane (TEOS) was used as the reagent, and phosphotungstic acid (H3PW12O40) as the catalyst were added to the pulp dispersion. The mixture was then vortexed to achieve a well-mixed dispersion before setting it to stir for 24 h at room temperature. The grafted SiO2-fibers were then separated from the solvent using a 160 μm sieve and rinsed twice with water to remove any residual unreacted reagent and catalyst.
During the synthesis, SiO2-fibers (used in
A three-in-one material (flakes, used as coagulant, flocculant and ballast medium;
Different type of fibers (cotton, keratin, cellulosic fibers and polyester, dryer lint, and other fibers from the textile, pulp and paper, food, mining, pharmaceutical industries, agriculture (
Water samples were first coagulated with alum (or other coagulants) and then flocculated with an organic polymer (or other chemicals). Fibers, SiO2-microspheres or flakes and other fiber/materials were injected at the onset of flocculation (i.e., after the coagulation). Turbidity measurements were assessed after sieving/screening using different nylon screens mesh sizes (100, 500, 1000, 2000 and 5000 μm). Other mesh sizes and other materials than nylon could be used. Turbidity measurements were also assessed after settling. All screened and settled samples were collected at a depth of 2 cm from the top of the water surface. Floc sizing was performed at the end of flocculation using a stereomicroscope (10×; Olympus, model SZX16). Aftertreatment, all materials were extracted from the screen or settled sludge, washed and reused several times in the processes (to reduce the operational expenditure). Jar test experiments were conducted using surface waters, wastewaters, municipal wastewaters, domestic wastewaters, and synthetic wastewaters. Screened and settled floc solutions were collected and adjusted at different pH to promote the floc fragmentation and NOM desorption. The solution was then mixed and the fibrous treatment agents were collected using different mesh sizes. Materials were then reused for subsequent jar tests.
The fibrous treatment agents, used as bridging agents during aggregation, were grafted with different (hydr)oxides (e.g., silica oxide (SiO2)) to increase the agent's specific gravity (density), to modify the fiber hydrophobicity/hydrophilicity and to modify affinities with contaminants or coagulants/flocculants (
Increasing the floc size by bridging particles together is a key element in water treatment as it determines the floc settling velocity and contaminant removal rates. The flocculant effective chain length or hydrodynamic volume (dictated by its molecular weight and architecture) are good indicators of a flocculant's potential in aggregation processes. Synthetic flocculants such as polyacrylamide (theoretical chain length<100 nm) are used worldwide to increase the floc size. For the tested water, a floc mean diameter of 520±50 μm was measured for conventional treatment (coagulant and flocculant, without fibers or fiber-based materials). However, when used as super-bridging agents and having a structure considerably longer than traditional flocculants, SiO2-fibers generated flocs with unprecedented size: 4950±480 μm (or larger), more than 10 times larger than flocs obtained with the conventional treatment. As shown in
In
Due to their super-bridging effect, the tested fibers and microspheres (or other fiber-based materials) also allowed a reduction in coagulant/flocculant demand. This translates into a reduction in sludge production, hence decreasing the burden of its physical transport to landfills. Finally, we showed that SiO2-fibers and SiO2-microspheres (or other fiber-based materials) can be extracted, washed and reused several times in the process (at least 20 times) without affecting the solids removal (
For decades, engineers and researchers have used a systematic approach to reduce the settling tank size, cost and footprint: increasing—as much as possible—the floc settling velocity. With the floc size according to the present disclosure that can be obtained with fibers, grafted fibers and fiber-based material (used as bridging agent), screening methods can be implemented as more sustainable and cost effective strategies for floc removal. A key advantage of screening versus settling is that floc removal is not controlled by the floc settling velocity, but rather by its size. The unprecedented size of the flocs formed by using SiO2-fibers and SiO2-microspheres (or other fibrous treatment agents according to the present disclosure) allows considerable increases in the screen mesh size (with lower risks of clogging) without affecting the floc removal by screening, while conventional flocs would readily pass through the same mesh size (
Water treatment using SiO2-fibers and SiO2-microspheres successfully reached 1 NTU event with large mesh size: 2000 and 5000 μm mesh (or other) were required for SiO2-fibers and SiO2-microspheres, respectively, while conventional treatment required a much finer mesh of 100 μm (
After being trapped, the aggregated fibers and microspheres were retrieved from the screen, cleaned and reinjected in the aggregation tank. Other types of fibers promoting aggregation such as keratin-based fibers (cotton and polyester (textile) and other fibers were used as alternatives to cellulosic fibers). All the tested fibers reached the −1 NTU target during screening (
The water treatment industry currently uses three classes of additives for high-rate clarification processes: coagulant, flocculant and ballast media. Technico-economically and for large water treatment plants, aggregation/settling is still the most efficient and common way to remove NOM from surface water, the coagulant concentration being in many cases driven by the residual NOM after treatment (or other target contaminants in wastewater). As a cheap and sustainable solution to existing practices, flakes (metal (hydr)oxides grafted on fibers), or other porous/filamentous fiber-based materials, can serve as a three-in-one coagulant/flocculant/ballast medium that can simultaneously remove soluble contaminants (e.g. NOM and P) by adsorption (
Finally, reinforced flakes can also be fabricated with either a high molecular weight polyacrylamide or SiO2 to improve the mechanical resistance over time and during high-shearing events (e.g. in mixing tank). Flakes were shown to be relatively resistant to shearing. The fiber-based aggregates' structure could also be grafted with other metal (hydr)oxides or polymers to increase the durability, to improve biofilm formation/attachment for biological treatment (
Dense media (e.g., sand, crushed glass, magnetite, or other) were also used as filler to increase the density and the settling velocity of fiber-based materials (
Chemicals were obtained from Sigma-Aldrich. 1 g of cellulose fibers (referred in the present and subsequent examples as “fibers”) (NISTRM8496 Sigma-Aldrich; fibers diameter: 4-40 μm; fibers length: 10-2000 μm) were added in 100 mL alum or ferric sulphate solution at pH 7 (iron concentration: 0.06-42 mM). Fibers were then removed from the solution using a 160 μm sieve and heated (50-150° C.) for 0.1-6 h to convert Fe(OH)3 into FeOOH/Fe2O3, or other oxides and/or hydroxides. After heating, the dried pulp iron-grafted fibers were mixed and re-dispersed in water, and then rinsed 3 times to remove the loosely bound metal or other (oxides and/or hydroxides.
Different concentrations of Fe-grafted fibers were tested: 0, 10, 20, 50, 100, 200, 350 and 500 mg/L. Screens with different mesh size (5000, 2000, 1000, 500 and 100 μm, Pentair™) were used to remove flocs from water. The turbidity was measured after screening or after 5, 10, 20, 60 and 180 sec of settling. After treatment, fibers were recovered from screened and settled water to be reused several times (at least 4).
As shown in
To reduce the operating expenditures (OPEX) and the water treatment plant footprint, Fe-grafted fibers coated with coagulant and flocculant were reused several times in the process to reduce the demand in coagulant and flocculant. Consequently, coagulant and flocculant previously added in the treatment can be extracted from sludge (after settling or screening) and be recirculated in the process via the fibers. Thus, the fibers act as carriers to recirculate chemicals used in water treatment (e.g., coagulant and flocculant). When Fe-grafted fibers were used in combination with alum in
The Fe-grafted fibers demonstrated an excellent performance at removing natural organic matter NOM, phosphorus (P) (
As shown in
Due to their high surface area, porosity and grafted metals/or functionalized groups, fibrous materials can also support and improve biofilm formation and biological growth. Moreover, as confirmed by high deposition rate measured by quartz-crystal microbalance (QCM) (
Fibrous materials could be tuned to promote the adsorption of specific contaminants for drinking and wastewater applications. For example, Fe-based surface better adsorbs different NOM fractions (protein and humics) compared to Si-based surface, as shown by deposition rates measured by QCM (
The amount of metal grafted on fibrous materials can be controlled by adjusting the metal concentration (
Benzene, toluene, ethybenzene, p-, m-xylene, and o-xylene (BTEX) removal was evaluated. The pristine and Fe-grafted fibers removed on average 88% and 80% of all the BTEX, respectively (
Removal via screening was shown to be efficient for the treatment of surface water for a drinking water application.
After 5 cycles of water treatment with fibers, the Fe-fibers were washed at pH 7 and 10 to remove contaminants (
Based on XPS analysis performed on fibers used 4 times (extracted at cycle 4), pristine and Fe-fibers have (positively charged) amine groups and aluminum (hydr)oxides attached to their surfaces that arise from cationic polymer (polyacrylamide) and alum, respectively (
A formulation of fibers and cationic polymers was used to treat a surface water in order to produce drinking water via a compact separation process (no settling was required;
When pristine fibers were used, sludge solid content was 20% after settling (3 min) and 37% after pressing (500 μm mesh size). The presence of the fibrous treatment improved sludge dewatering. Solids content of sludge without fibers could not be increased by pressing as flocs were too small and readily pass through the mesh structure.
Fibers from agriculture residues (e.g., maize) were successfully used as fibrous agents (data not shown). Such fibers were grafted with metal (6.5% Fe; obtained by XPS) to provide new adsorption sites for contaminants.
As seen therefore, the examples described above and illustrated are intended to be exemplary only. The scope is indicated by the appended claims.
The present application claims priority from: U.S. provisional application Ser. No. 63/147,289 filed on Feb. 9, 2021 which is incorporated herein by reference in its entirety, and from U.S. provisional application Ser. No. 63/221,978 filed on Jul. 15, 2021, which is also incorporated herein by reference in its entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CA2022/050160 | 2/4/2022 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63221978 | Jul 2021 | US | |
| 63147289 | Feb 2021 | US |
