A filtering device and a method for removing contaminants from a contaminated fluid

Abstract

A filtering device for removing contaminants from a contaminated fluid, wherein said filtering device comprising at least one cellulose-based filtering material comprising cellulose fibers and a positively charged polyelectrolyte adsorbed on said cellulose fibers, at least one filtering material comprising an adsorbing agent, and wherein said at least one cellulose-based filtering material and said at least one filtering material comprising said adsorbing agent being arranged for series flow therethrough; at least one filter housing arranged to house at least one of said at least one cellulose-based filtering material and said at least one filtering material comprising said adsorbing agent, and wherein said at least one filter housing comprising at least one inlet for inflow of contaminated fluid or filtered fluid and at least one outlet for outflow of filtered fluid.

Description

[0001] A FILTERING DEVICE AND A METHOD FOR REMOVING CONTAMINANTS

[0002] FROM A CONTAMINATED FLUID

[0003] FIELD OF THE INVENTION

[0004] The present invention relates to the area of removing contaminants from fluids by filtering, more specifically to filtering hazardous substances such as per- and polyfluoroalkyl substances, hydrocarbons, heavy metals, chlorine dioxide, chlorine and drug rests from different contaminated fluids, such as contaminated ground water and waste water.

[0005] The invention describes a filtering device, a method and a filtering system for cleaning contaminated fluid by filtration.

[0006] BACKGROUND INFORMATION

[0007] Per- and polyfluoroalkyl substances (PFASs) are a large class of thousands of synthetic chemicals with varying properties that are used throughout society. However, they are increasingly detected as harmful to the environment and several of them are also linked to negative effects on human health. All PF AS are man-made synthetics that do not occur naturally in the environment.

[0008] PF AS substances are synthetic organofluorine chemical compounds that have multiple fluorine atoms attached to an alkyl chain, i.e. hydrogen atoms in a carbon chain are entirely or partly replaced by fluorine atoms. These carbon-fluorine bonds are one of the strongest chemical bonds in organic chemistry.

[0009] This means that PFASs are very difficult to break down and hence resist degradation when used and also in the environment. Most PFASs are also easily transported in the environment covering long distances away from the source of their release. PFASs have been frequently observed to contaminate groundwater, surface water and soil. Cleaning up polluted sites is technically difficult and costly. If releases continue, they will continue to accumulate in the environment, drinking water and food.

[0010] Due to the PF AS being extremely persistent in themselves and as degradation products, they therefore accumulate in the environment. PFOA is an example of a persistent, bioaccumulative and toxic substance (PBT). PF AS may be released into the environment at any time during their lifecycle: from the manufacture of the substance, to the use of the products that contain PFAS, to the point of disposal as waste. As long as we manufacture and use PFAS, these substances will, in some form or other, accumulate over time in the environment.

[0011] One thing that all PFASs have in common is the ability to disperse over long distances through air and water, meaning that they can be detected far from any areas of manufacture or use - for example, in arctic environments - making PFAS very much a global problem. Different PFAS disperse in the environment in different ways. Volatile variants, such as fluorotelomers, can be dispersed over large areas in the air. Less volatile, ionised forms are largely dispersed in water and bound to particles of organic matter, soil particles for example, or through absorption into living organisms.

[0012] PFAS have a wide range of applications, including waterproof and dirt-repellent fabrics. PFAS occur everywhere in the environment and are present in the bodies of almost every human being. Local exposure to significantly high levels occurs in areas where drinking water has been contaminated with PFAS, for example by firefighting foam at fire drill sites.

[0013] The difficulty involved in breaking down PFAS, combined with the fact that many of the substances are water-soluble and mobile in soil, means that there is a risk that drinking water supplies will continue to be contaminated for many years to come. The dispersal of and exposure to PFAS takes place throughout the substance’s lifecycle, from manufacture to waste management.

[0014] Conventional systems and methods for PFAS capture are hitherto ineffective and / or extremely expensive and as such not relevant for capturing large amounts of PFAS. Moreover, water sources contaminated with PFAS may also be contaminated with other hazardous components such as heavy metals and hydrocarbons. Few systems, if any, are capable of simultaneously capturing not only PFAS but also heavy metals and hydrocarbons.

[0015] Hence, there is a great need for an unexpensive, easy to produce and easy to use technology that effectively captures PFAS and possibly also heavy metals and hydrocarbons, in different contaminated water systems and water-based systems such as groundwater, waste water, used firefighting foams on site, waste water from fire drill sites etc. Often, there is also a need to simultaneously capture chlorine dioxide, chlorine, and drug rests.

[0016] SUMMARY OF THE INVENTION

[0017] It is an object of the present invention to obviate at least some of the disadvantages in the prior art and to provide a filtering device for removing contaminants from a contaminated fluid as defined in claim 1.

[0018] The invention further provides a method for removing contaminants from a contaminated fluid and a filtering system for removing contaminants from a contaminated fluid.

[0019] In a first aspect of the invention, said filtering device comprises:

[0020] - At least one cellulose-based filtering material comprising cellulose fibers and a positively charged polyelectrolyte adsorbed on said cellulose fibers,

[0021] - At least one filtering material comprising an adsorbing agent,

[0022] - Said at least one cellulose-based filtering material and said at least one filtering material comprising said adsorbing agent being arranged for series flow through them,

[0023] - At least one filter housing arranged to house at least one of said at least one cellulose- based filtering material and said at least one filtering material comprising said adsorbing agent, and wherein

[0024] - Said at least one filter housing comprising at least one inlet for inflow of contaminated fluid or filtered fluid and at least one outlet for outflow of filtered fluid.

[0025] Thanks to the invention an efficient and cheap filtering device is provided wherein contaminated fluids are efficiently filtered even though the contaminants may comprise compounds that are known to be difficult to filter away, e.g. perfluoroalkyl substances, polyfluoroalkyl substances and drug residues.

[0026] Said cellulosic material has improved hydrophobicity thanks to the modification of the cellulose fibers by the positively charged polyelectrolyte to be less negatively charged, or even positively charged, and preferably uncharged. A hydrophobic fiber structure is preferred because a hydrophobic cellulosic material will not absorb water in such a high content as a hydrophilic fiber would while the absorption capacity of hydrophobic substances such as hydrocarbons, e.g. grease, oils, oil mists, fats, non-polar particles, and carbon compounds, is highly improved. Said at least one cellulose-based filtering material comprising cellulose fibers and the positively charged polyelectrolyte adsorbed on said cellulose fibers efficiently removes long-chained molecules, while said at least one filtering material comprising an adsorbing agent efficiently removes short-chained molecules and molecules having chains of moderate lengths.

[0027] Said filtering device has good capacity for also removing heavy metals, hydrocarbons, chlorine dioxide and chlorine from contaminated fluids.

[0028] In one embodiment of the invention, said cellulose-based filtering material is arranged upstream of said filtering material comprising said adsorbing agent for said series flow through said filtering materials. Thanks to this aspect, said at least one cellulose-based filtering material comprising cellulose fibers and a positively charged polyelectrolyte adsorbed on said cellulose fiber will remove long-chained molecules and larger, nonpolar substances meaning that these long-chained molecules and nonpolar substances do not need to pass said at least one filtering material comprising said adsorbing agent thereby minimizing the risk of clogging said at least one filtering material comprising said adsorbing agent. A lifespan thus increases for said at least one filtering material comprising said adsorbing agent.

[0029] In another embodiment, said filtering device comprises at least one cellulose-based filtering material comprising cellulose fibers and a positively charged polyelectrolyte adsorbed on said cellulose fibers is arranged as a last filtering material downstream of said at least one filtering material comprising said adsorbing agent. Any remaining residue of adsorbing agent and / or any PF AS may be captured by said at least one cellulose-based filtering material as the last filtering material.

[0030] In yet another embodiment of the invention, said at least one filter housing is selected from a tank, an intermediate bulk container (IBC), a cistern, a tub, a hose, a load changer bed, and / or a pipe making the filtering device very flexible and easy to tailor to any available space.

[0031] In still an embodiment of the invention, said at least one cellulose-based filtering material and said at least one filtering material comprising said adsorbing agent are arranged in a common filter housing thereby providing a compact, small, but still highly efficient filtration device suitable for e.g. small scale filtration plants. In another embodiment of the invention, said at least one cellulose-based filtering material and said at least one filtering material comprising said adsorbing agent are arranged in separate filter housings, said separate filter housings are connected by connecting means for said series flow therethrough. Thanks to this aspect, a housing having a poor filtering capacity can easily be replaced, or at least the filtering material inside the housing may easily be replaced, without having to replace the other housing or the other filtering material still having a good enough capacity.

[0032] In yet an embodiment of the invention, two or more cellulose-based filtering materials are connected in series and / or in parallel; and / or two or more filtering materials comprising said adsorbing agent are connected in series and / or in parallel. Thanks to this aspect the filtering device may be tailored for the specific needs, e.g. filtration capacity or available space at the site to be used at. A further advantage is that when any one of the filtering materials has got reduced filtering capacity the filtering material having reduced capacity can easily be replaced. Further, a filtering material having poor capacity can easily be removed when the filtering materials are arranged in series / parallel relation. A filtering material downstream of the removed filtering material having poor capacity can be moved upstream and connected with the filtering material upstream of the removed filtering material having poor capacity. Repositioning a filtering material that still has good enough filtering capacity from a position downstream to a position upstream and replacing the repositioned filtering material with a clean and fresh filtering material downstream gives the advantage that the cleanest water meets the cleanest filter or put the other way around, the most contaminated fluid meets the more contaminated filtering material. As the contaminated fluid flows in the downstream direction, both the fluid and the filtering materials get cleaner and cleaner if removing, repositioning and replacing the filtering materials.

[0033] In another embodiment of the invention, said device further comprises at least one polishing filter. Preferably said at least one polishing filter is arranged downstream of said at least one filtering material comprising said adsorbing agent and arranged in a direct or indirect contact with said at least one filtering material comprising said adsorbing agent. Preferably, said polishing filter comprises a granular filtering material and / or a fibrous filtering material. Thanks to this aspect, any remining residue of adsorbing agent and possibly adsorbing agent comprising adsorbed contaminants may be trapped by the granular particles and removed from the filtered fluid. In one embodiment said fibrous filtering material comprises a cellulose-based filtering material comprising cellulose fibers and a positively charged polyelectrolyte adsorbed on said cellulose fibers.

[0034] In yet another embodiment of the invention, said positively charged polyelectrolyte comprises at least one of polyvinylamine (PVAm), polyacrylamide, polyacrylic acid (PAA), polymethacrylic acid, chitosan, cationic gelatin, polydiallyldimethylammonium chloride (polyDADMAC), polyallylamine, polyethylenimine, anionic nanocellulose, sodium lignin sulfonate, sodium polyacrylate, anionic polyacrylamide, anionic glyoxalated polyacrylamide, poly-(sodium styrene sulphonate) and poly(vinylphosphonic acid), or a mixture of two or more thereof.

[0035] In still another embodiment of the invention, said positively charged polyelectrolyte comprises polyvinylamine (PVAm). PVAm has shown surprisingly good filtering effect together with cellulose fibers.

[0036] In yet another embodiment of the invention, a concentration of said positively charged polyelectrolyte comprising PVAm in said cellulose-based filtering material is preferably 0,001-30 wt-% of a dry weight of said cellulose fibers, preferably 0,005-20 wt-% and more preferred 0,01-10 wt-%. It has surprisingly been found that a specific concentration of PVAm provides the cellulose fibers with optimal adsorbing capacity for long-chained molecules.

[0037] In another embodiment of the invention, said adsorbing agent comprises at least one of activated carbon, graphene and carbon black. Activated carbon and carbon black both have high adsorption capacity, especially of moderately long-chained molecules or short-chained molecules, at low cost. Active carbon and carbon black effectively captures smaller PF As molecules, heavy metals, chlorine, chlorine dioxide, and drug rests.

[0038] In yet another embodiment of the invention, said cellulose fibers comprised in said at least one cellulose-based filtering material are selected from wood pulp, non-wood pulp, regenerated cellulose fibres, plant fibres such as fibres from bamboo, bagasse, cotton, hemp, flax, and jute, and / or mixtures thereof. Preferably, said wood pulp is selected from softwood pulp, hardwood pulp, High Yield Pulp (HYP), dissolving pulp, chemical pulp such as kraft pulp, sulphate pulp or sulphite pulp, recycled paper and board, broke, cellulose nano pulp, dissolving pulp, deinked pulp (DIP), straw pulps, hemp pulps, bagasse pulps, regenerated fibers or a combination of one or more of these. Cellulose fibers from these sources are common around the world and easily accessible.

[0039] In one embodiment of the invention, said High Yield Pulp (HYP) is selected from mechanical pulp, refiner mechanical pulp (RMP), thermomechanical pulp (TMP), chemi-thermomechanical pulp (CTMP), defibrated fiber-material, high temperature chemi-thermomechanical pulp (HTCTMP), chemi-mechanical pulp (CMP), stone groundwood pulp (SGW), pressure groundwood pulp (PGW) or a mixture thereof. These mechanical cellulose fibers have shown to be - in combination with positively charged polyelectrolytes - to be especially efficient in adsorbing contaminants.

[0040] In another embodiments of the invention, said filtering device further may comprise a pre-treatment filter and / or a post-treatment filter, said pre-treatment filter and / or said post-treatment filter comprising at least one of a granular filter, ion exchange resin and a pH-balancing filter, depending on the properties and degree of contamination of the contaminated fluid.

[0041] Further aspects and embodiments are defined in the appended claims, which are specifically incorporated herein by reference.

[0042] Compared to known methods the present filtering device is easy and efficient to use in a small scale set up as well as in a large scale set up. The filtering device may easily be adapted to different situations and can be scaled up and down to different sizes.

[0043] DETAILED AND EXEMPLIFYING DESCRIPTION OF THE INVENTION

[0044] Before the invention is disclosed and described in detail, it is to be understood that this invention is not limited to particular compounds, configurations, method steps, substrates, and materials disclosed herein as such compounds, configurations, method steps, substrates, and materials may vary somewhat. It is also to be understood that the terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting since the scope of the present invention is limited only by the appended claims and equivalents thereof.

[0045] It must be noted that, as used in this specification and the appended claims, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. The term “and / or”, e.g. “X and / or Y”, shall be understood to mean either “X and Y” or “X or Y” and shall be taken to provide explicit support for both meanings or either meaning.

[0046] If nothing else is defined, any terms and scientific terminology used herein are intended to have the meanings commonly understood by those of skill in the art to which this invention pertains.

[0047] The wording “cellulosic material” means a material comprising cellulose fibers. The cellulose fibers may be of any possible origin, e.g. virgin fibers, pulped fibers, recycled fibers etc and any mixture thereof.

[0048] The wording “fluid” shall be interpreted as a substance that flows and is not solid. An example is water or a mixture of water and other liquids.

[0049] The wording "filtering height" should be interpreted as the total height or length that the liquid or fluid to be filtered travels in the filter. It is commonly the distance between an inlet and an outlet of the filter or the distance between an upper surface and lower surface of a filtering material as seen in a direction of flow.

[0050] The wording “direct contact” shall be understood to mean a physical contact between two objects. A surface of one object and a surface of another object touches each other physically. An example of a direct contact is two filtering materials arranged such that a surface of one filtering material is touching a surface of another filtering material such that they are in a physical contact. A fluid may then enter a first filtering material, flow through the first filtering material and then exit the first filtering material while at the same time as exiting entering the second filtering material which is in said direct, physical contact with the first filtering material; said fluid then flow through the second filtering material.

[0051] The wording “indirect contact” shall be understood to mean that two objects are connected to each other but not in physical contact with each other. A separating means or a connecting means may be arranged between the objects and connecting the objects to each other. Said connecting means may comprise e.g. pipes or hoses. An example may be two filtering materials being connected to each other by a connecting means such that a fluid exiting the first filtering material flows through the connecting means and then enters the second filtering material. The wording “flow contact” includes direct contact flow and indirect flow contact.

[0052] Unless clearly indicated, all percentages are calculated by weight.

[0053] The term "about" as used in connection with a numerical value throughout the description and the claims denotes an interval of accuracy, familiar and acceptable to a person skilled in the art. Said interval is ± 5 %, and preferably within ±1%.

[0054] The term “PFAS” as used herein refers to per- and polyfluoroalkyl substances. Examples of PFAS include, but are not limited to, Perfluorobutanoic Acid (PFBA), Perfluoropentanoic Acid (PFPeA), 4:2 Fluorotelomer Sulfonic Acid (4:2 FTSA), Perfluorohexanoic Acid (PFHxA), Perfluorobutane Sulfonic Acid (PFBS), Perfluoroheptanoic Acid (PFHpA), Perfluoropentane Sulfonic Acid (PFPeS), 6:2 Fluorotelomer Sulfonic Acid (6:2 FTSA), Perfluorooctanoic Acid (PFOA), Perfluorohexane Sulfonic Acid (PFHxS), Perfluorohexane Sulfonic Acid-Linear (PFHxS-LN), Perfluorohexane Sulfonic Acid-Branched (PFHxS-BR), Perfluorononanoic Acid (PFNA), 8:2 Fluorotelomer Sulfonic Acid (8:2 FTSA), 10:2 Fluorotelomer Sulfonic Acid (10:2 FTSA), Perfluoroheptane Sulfonic Acid (PFHpS), Perfluorodecanoic Acid (PFDA), N-Methyl Perfluorooctane Sulfonamidoacetic Acid (N-MeFOSAA), N-Ethyl Perfluorooctane Sulfonamidoacetic Acid (EtFOSAA), Perfluorooctane Sulfonic Acid (PFOS), Perfluorooctane Sulfonic Acid-Linear (PFOS- LN), Perfluorooctane Sulfonic Acid-Branched (PFOS-BR), Perfluoroundecanoic Acid (PFUnDA), Perfluorononane Sulfonic Acid (PFNS), Perfluorododecanoic Acid (PFDoDA), Perfluorodecane Sulfonic Acid (PFDS), Perfluorotridecanoic Acid (PFTrDA), Perfluorooctane Sulfonamide (FOSA), N-Methyl Perfluorooctane Sulfonamide (Me-FOSA), N-Ethyl Perfluorooctane Sulfonamide (Et-FOSA), N-Methyl Perfluorooctane Sulfonamidoethanol (Me-FOSE), N-Ethyl Perfluorooctane Sulfonamidoethanol (Et-FOSE), Perfluorotetradecanoic Acid (PFTeDA), Nonafluoro- 3,5-dioxaheptanoic acid (NFDHA), Hexafluoropropylene oxide dimer acid (HFPO- DA), 11 -chi oroeicosafluoro-3 -oxaundecane- 1 -sulfonic acid (HCI-PF3OUds), 9- chlorohexadecafluoro-3-oxanone-l -sulfonic acid (9CI-PF3ONS), 4,8-dioxa-3H- perfluorononanoic acid (ADONA), and PolyTetraFluoroEthylene (PTFE, teflon). Salts and derivates are also included.

[0055] Perfluoroalkyl substances have a fully fluorinated carbon chain, while polyfluoroalkyl substances have a partially fluorinated carbon chain. Per- and polyfluoroalkyl substances are sometimes divided into short-chain and long- chain PF AS, based on the length of the fluorinated carbon chain. Among the long-chain PF AS are perfluorooctanoic acid (PFOA) and perfluorooctane sulphonate (PFOS), both of which consist of eight carbon atoms (sometimes referred to as C8 chemistry). Shortchain PF AS include perfluorohexanoic acid (PFHxA) and perfluorohexane sulfonate (PFHxS), both of which consist of six carbon atoms (C6 chemistry).

[0056] The molecular structure of most PF AS compounds can be broken into two functional units including the hydrophobic non-ionic "tail," comprised of the fluorinated carbon chain and the hydrophilic anionic "head," having a negative charge.

[0057] The term “heavy metal / -s” as used herein means metals with relatively high densities, atomic weights, or atomic numbers. Arsenic, cadmium, chromium, copper, nickel, lead and mercury are examples of the most common heavy metals which can pollute the environment. Other examples of heavy metals are iron, copper, lead, zinc, tin, silver, gold, and platinum, magnesium, aluminium, and titanium.

[0058] The term "hydrocarbon" shall be regarded broadly and include agents such as (a) alkanes, which either branched or straight, and optionally substituted, (b) aromatic hydrocarbons, preferably as benzene, toluene, ethylbenzene, xylene, benzoate, chlorobenzoate and p-hydrobenzoic acid, (c) polycyclic aromatic hydrocarbons (PAHs), preferably naphthalene, anthracene, fluorene, pyrene, benzopyrene, phenanthrene, (d) nitrogen compound, preferably ammonia, nitrite, nitrate as well as hydrocarbons containing nitrogen, and (e) hydrocarbons containing sulfur. Polycyclic aromatic hydrocarbon (PAH), petroleum, parabens, gasoline, kerosene. Liquid petroleum hydrocarbons, synthetic hydrocarbons and / or biological hydrocarbons are included as well. The hydrocarbons are hydrophobic, or at least a majority of them are.

[0059] The term “drug residue” shall be regarded broadly and refers to the presence of human and veterinary pharmaceutical products such as, but not limited to, antibiotics, antimicrobials, pain killers, antidepressants, and deworming products in meat or other animal products.

[0060] Adsorption is a process by which liquid or gaseous molecules are concentrated on a solid surface, e.g. on cellulose fibers, graphene, activated carbon or carbon black. The term "activated carbon" shall be regarded broadly and include extruded activated carbon (EAC), charcoal activated carbon cloth (ACC), powdered activated carbon (PAC) and granulated active carbon (GAC). Activated carbon is also known as activated charcoal.

[0061] Both carbon black and activated carbon have a high surface area compared to their volume, which allows the substance to adsorb as much as it can. They are examples of paracrystalline carbon compounds.

[0062] Activated carbon may preferably be produced from environmental wastes with high carbon content. Lignocellulosic and coal materials are often used as raw materials for manufacturing of activated carbons. Examples of raw materials, but not limited to, are coal, coconut shells, wood and wood rest materials, e.g. branches and tree tops. The raw material has a very large influence on the characteristics and performance of the activated carbon.

[0063] Activated carbon has good potential for adsorbing heavy metals because of its greater surface area, microporous ability, and chemical complexity of its external area. Activated carbon capture natural organic compounds, taste and odour compounds, and synthetic organic chemicals by adsorption of molecules to the surface of the activated carbon. Activated carbon is an effective adsorbent because it is a highly porous material and provides a large surface area to which contaminants may adsorb.

[0064] The term “polyelectrolyte” as used herein shall be regarded as polymers whose repeating units bear an electrolyte group. Polycations and polyanions are polyelectrolytes. These groups dissociate in aqueous solutions (water), making the polymers charged. Polyelectrolyte properties are thus similar to both electrolytes (salts) and polymers (high molecular weight compounds) and are sometimes called polysalts. Like salts, their solutions are electrically conductive.

[0065] The polyelectrolyte concerned in the present invention is preferably a positively charged polyelectrolyte. Said positively charged polyelectrolyte adsorbs to the surface of the cellulosic material, probably to the surface of the negatively charged cellulose fibers of the cellulosic material.

[0066] A positively charged polyelectrolyte adsorbed to the cellulose fibers of the cellulosic material affects the negative charge of the cellulose fibers by modifying the negative charge of the fibers to be less negative, or even change the fiber charge to a net zero charge of the cellulosic material.

[0067] Furthermore, the cellulosic material has improved lipophilicity thanks to the modification to less negative charges of the cellulose fibers. The cellulosic material will have an improved absorption capacity for lipids and lipid particles.

[0068] In addition, also bacteria and / or viruses - if any present - may be captured and bound to the cellulosic material, probably again due to the fact that the positively charged polymer adsorbed to the cellulosic material attract the negatively charged bacteria and / or viruses.

[0069] The positively charged polyelectrolyte of the present invention is preferably selected from at least one of polyvinylamine (PVAm), polyacrylamide, polyacrylic acid (PAA), polymethacrylic acid, chitosan, cationic gelatin, polydiallyldimethylammonium chloride (polyDADMAC), polyallylamine, polyethylenimine, anionic nanocellulose, sodium lignin sulfonate, sodium polyacrylate, anionic polyacrylamide, anionic glyoxalated polyacrylamide, poly-(sodium styrene sulphonate) and poly(vinylphosphonic acid).

[0070] A combination of two or more of the above mentioned positively charged polyelectrolytes may in some embodiments be preferred.

[0071] In one preferred embodiment, the polyelectrolyte preferably comprises polyvinylamine (PVAm) including unmodified PVAm or PVAm modified with straight or branched and optionally substituted alkyl chains. PVAm has a very high content of primary amine functional groups and is one of the technical polymers having the highest charge density.

[0072] It may in some embodiments be preferred that said PVAm is unmodified.

[0073] In some embodiments said polyvinylamine (PVAm) may be used as the only positively charged polyelectrolyte. Embodiments are however conceivable said PVAm may be used in a combination with one or more other positively charged polyelectrolyte / -s.

[0074] Said cellulosic material comprising cellulose fibers may preferably be selected from wood pulp, non-wood pulp, regenerated cellulose fibres, plant fibres such as fibres from bamboo, bagasse, cotton, hemp, flax, and jute, and / or mixtures thereof. Said cellulosic material may be selected from non-wood pulps, e.g. straw pulps, hemp pulps, bagasse pulps etc., or mixtures thereof.

[0075] Said cellulosic material may be selected from wood pulp, e.g. softwood pulp, hardwood pulp, High Yield Pulp (HYP), dissolving pulp, chemical pulp such as kraft pulp, sulphate pulp or sulphite pulp, recycled paper and board, broke, nanopulp, dissolving pulp, deinked pulp (DIP), regenerated fibers or a combination of one or more of these; or mixtures thereof.

[0076] Said cellulosic material preferably comprises High Yield Pulps (HYP), where single cellulose fibers are separated from the wood raw material, defibrated, as a result of mechanical treatments of chips in disc refiners or of logs in wood grinders after softening of the wood lignin at enhanced temperature and / or with chemical pretreatments, such as mechanical pulp, refiner mechanical pulp (RMP), thermomechanical pulp (TMP), chemi-thermomechanical pulp (CTMP), defibrated fiber-material, high temperature chemi-thermomechanical pulp (HTCTMP), chemimechanical pulp (CMP), stone groundwood pulp (SGW) and pressure groundwood pulp (PGW) or a mixture thereof. The wood yield in these types of pulping processes is high, typically over 90%.

[0077] The present invention may further make use of and comprise microorganisms selected from bacteria, fungi and archaea, preferably the microorganisms comprise archaea.

[0078] Some examples of bacteria which may be used are selected from Pseudomonas putida, Pseudomonas oleovorans, Dechloromonas aromatic, Nitrosomonas europaea, Nitrobacter hamburgensis, Paracoccus denitrificans, Deinococcus radiodurans, Methylibium petroleiphilum and / or Alcanivorax borkumensis. Halophile bacteria such as Salinibacter ruber, Chromohalobacter salexigens, Halothermothrix orenii and / or Halorhodospira halophile may also be used.

[0079] Some examples of fungi which may be used are selected from Aureobasidium pullulans, Myrothecium verrucaria, Cladosporium cladosporioides , Saccharomyces cerevisiae, Aspergillus, Rhodotorula, brown-rot fungi and / or white-rot fungi. Some examples of white-rot fungi which may be used are Phanerochaete chrysosporium, Pleurotus ostreatus, Bjerkandera adjusts and Trametes versicolor. More generally, white-rot fungus from the Phanerochaete, Phlebia, Trametes, Pieurotus and / or Bjerkandera genera may also be used.

[0080] Some examples of archaea which may be used are selected from Archaeoglobus fulgidus and / or halophilic archaea such as haloarchaea strains belonging to the genus Halobacterium (e g. Hatoferax volcanii), Haloferax (e.g. Haloferax denitrificans), Haloarcula (e.g. Haloarcula marismortui and Haloarcula quadrata ) and / or Halococcus. Archaea such as Halogeometricum borinquense, Haloquadratum walsbyi Hatothermothrix oreni Natronobacterium magadii, Natronobacterium gregoryi and Natronomonas pharaonis may also be used. Further preferred archaea are sulfatereducing archaea and / or hyperthermophilic archaea.

[0081] The invention concerns in a first aspect a filtering device for removing contaminants from a contaminated fluid and in a second aspect a method for removing contaminants from a contaminated fluid. In a third aspect the invention concerns a filtering system for removing contaminants from a contaminated fluid.

[0082] Now to the first aspect of the invention, i.e. the filtering device for removing contaminants from a contaminated fluid, e.g. a source of contaminated water.

[0083] Said filtering device comprises at least one cellulose-based filtering material comprising cellulose fibers and a positively charged polyelectrolyte adsorbed on said cellulose fibers.

[0084] Said at least one cellulose-based filtering material comprising cellulose fibers and a positively charged polyelectrolyte adsorbed on said cellulose fibers may preferably be manufactured as described below.

[0085] The process for manufacturing said at least one cellulose-based filtering material comprising cellulose fibers and a positively charged polyelectrolyte adsorbed on said cellulose fibers preferably starts with choosing the starting materials; the raw materials.

[0086] A source of cellulose fibers is chosen. Said cellulose fibers are preferably selected from wood pulp, non-wood pulp, regenerated cellulose fibres, plant fibres such as fibres from bamboo, bagasse, cotton, hemp, flax, and jute, and / or mixtures thereof. Said wood pulp may preferably be selected from softwood pulp, hardwood pulp, High Yield Pulp (HYP), dissolving pulp, chemical pulp such as kraft pulp, sulphate pulp or sulphite pulp, recycled paper and board, broke, cellulose nano pulp, dissolving pulp, deinked pulp (DIP), straw pulps, hemp pulps, bagasse pulps, regenerated fibers or a combination of one or more of these.

[0087] Said High Yield Pulp (HYP) is preferably selected from mechanical pulp, refiner mechanical pulp (RMP), thermomechanical pulp (TMP), chemi-thermomechanical pulp (CTMP), defibrated fiber-material, high temperature chemi-thermomechanical pulp (HTCTMP), chemi-mechanical pulp (CMP), stone groundwood pulp (SGW), pressure groundwood pulp (PGW) or a mixture thereof.

[0088] If the chosen cellulose fibers are in dry form the process preferably comprises a step of mixing the cellulose fibers with an appropriate amount of water; with e.g. fresh water, raw water, cleaned industrial water etc to a mixture, and in the forthcoming termed a stock, comprising cellulose fibers.

[0089] In some embodiments, the mixing occurs in a batch mixing in a tank or cistern or the like.

[0090] In other embodiments, the mixing takes place in said tank or cistern or the like and in a continuously arranged process.

[0091] A suitable device, e.g. a rotor, may be used for performing the mixing.

[0092] An appropriate amount of water in relation to an amount of added cellulose fibers to the tank or cistern may be such that a dry weight of cellulose fibers in the stock is equal to or more than 0,1 wt-% of the total weight of the stock.

[0093] Said dry weight of cellulose fibers in the stock is equal to or less than 30 wt-%.

[0094] A dry weight of the cellulose fibers comprised in the stock is 0,1-30 wt-% of the total weight of the stock, preferably 0,5-10 wt-%, and more preferred 1-5 wt-%.

[0095] A control of pH in the stock is preferably performed. A suitable pH may be pH 7 or higher, preferably pH 8 or higher, and even more preferred pH 9 or higher. It may be preferred that pH in some embodiments are pH 9,5 or higher.

[0096] The step of adjusting pH may be performed by adding a water solution of sodium hydroxide (NaOH) to the mixture.

[0097] A positively charged polyelectrolyte is chosen. Said positively charged polyelectrolyte is preferably selected from polyvinylamine (PVAm), polyacrylamide, polyacrylic acid (PAA), polymethacrylic acid, chitosan, cationic gelatin, polydiallyldimethylammonium chloride (polyDADMAC), polyallylamine, polyethylenimine, anionic nanocellulose, sodium lignin sulfonate, sodium polyacrylate, anionic polyacrylamide, anionic glyoxalated polyacrylamide, poly-(sodium styrene sulphonate) and / or poly(vinylphosphonic acid).

[0098] Said positively charged polyelectrolyte may in some embodiments be only one of the above listed positively charged polyelectrolytes while in other embodiments a mixture of two or more of the above mentioned polyelectrolytes are preferred.

[0099] A concentration of the positively charged polyelectrolyte in the stock is preferably equal to or greater than 0,01 wt-% of a dry weight of cellulose fibers in the stock, more preferred equal to or greater than 0, 1 wt-%, and most preferred equal to or greater than 0,5 wt-%.

[0100] In order not to overdose the use of positively charged polyelectrolyte but rather to optimize the use, an upper limit of positively charged polyelectrolyte in the stock may be equal to or lower than 30 wt-% of a dry weight of cellulose fibers in the stock, preferably equal to or lower than 20 wt-%, and more preferred equal to or lower than 10 wt-%.

[0101] A concentration interval of positively charged polyelectrolyte in the stock may be within the interval of 0,01 - 30 wt-% positively charged poly electrolyte, preferably 0,1 - 20 wt-% positively charged poly electrolyte, and more preferred 0,5 - 10 wt-% positively charged polyelectrolyte.

[0102] Depending on the cellulose fibers chosen the process may comprise addition of salt to the stock. An example of a salt is sodium chloride (NaCl). It has been discovered that for some cellulose fibers, e.g. mechanical pulps such as CTMP, addition of NaCl may lower a needed concentration of positively charged polyelectrolyte / -s in the stock. In embodiments where salt is to be added to the stock, said salt addition is preferably performed before addition of the chosen polyelectrolyte / - s.

[0103] A suitable amount of salt added to the stock may be 10-90 wt-% salt of a dry weight of cellulose fibers comprised in the stock, preferably 20-80 wt-%, and more preferred 40- 70 wt-%.

[0104] The stock now comprising cellulose fibers, NaOH, the positively charged polyelectrolyte and possibly salt and additives such as complexing agents is preferably agitated or stirred for 1-120 minutes, preferably 5-60 minutes, and more preferred 20-40 minutes. It has been found that agitation seems to create good contact between especially the cellulose fibers and the positively charged polyelectrolyte thereby enhancing the adsorption of the polyelectrolyte to the cellulose fibers.

[0105] A temperature of the stock during agitation may preferably be lower than 100°C, preferably 1-75°C, and more preferred 3-35°C.

[0106] Water to be added to the tank may be preheated to the chosen temperature and / or the stock in the tank may be heated to the chosen temperature by making use of suitable heating means, e.g. heating spirals or coils or the like.

[0107] After having performed the agitation step the stock is dewatered in a dewatering equipment, e.g. one or more screw press / -es or chamber filter press / -es.

[0108] Dewatering is performed until a dryness of 10-70 wt-% solid content of the stock has been reached, preferably 20-60 wt-% and more preferred 30-50 wt-%. The stock may now be termed a dewatered pulp.

[0109] If salt has been added to the stock in the tank, it may be preferred to wash the fiber cake after the dewatering to wash away the salt and then to repeat the dewatering step once more to the desired dryness of the fiber cake. Washing water may be fresh water or water withdrawn from the stock during the dewatering step. A step of drying is preferably performed after the dewatering step. Drying may preferably be performed until a dryness of 90 wt-% or more of solid material has been reached. Suitable drying techniques may involve hot air, infrared radiation (IR) drying, microwave drying, flake drying etc.

[0110] For fiber cakes that are found to be too dense a step of adding fluffmess to the fiber cake may preferably be performed, e.g. by a refiner. A higher degree of fluffmess means more air and space between the fibers and it has been found that a higher fluffmess of the filter cake improves adsorption of hydrocarbons. This step may be performed before and / or after said drying step.

[0111] A cellulose-based filtering material comprising cellulose fibers and a positively charged polyelectrolyte adsorbed on said cellulose fibers has now been produced and is ready to be used in the inventive filtering device.

[0112] Said positively charged polyelectrolyte adsorbed on said cellulose fibers is preferably 0,001-30 wt-% of a dry weight of said cellulose fibers, more preferred 0,005-20 wt-% and most preferred 0,01-10 wt-%.

[0113] In some embodiments, said positively charged polyelectrolyte adsorbed on said cellulose fibers is 0,2-8 wt-%.

[0114] Said filtering device further comprises at least one filtering material comprising an adsorbing agent.

[0115] Said adsorbing agent preferably comprises at least one of an activated carbon, graphene and a carbon black and having a specific surface area within an interval of 350-750 m2 / g, preferably 450-650 m2 / g, and more preferred 500-600 m2 / g.

[0116] Said at least one cellulose-based filtering material and said at least one filtering material comprising said adsorbing agent are preferably arranged for series flow therethrough.

[0117] The filtering device is arranged such that a flow of contaminated fluid, e.g. contaminated water, comprising contaminants to be filtered is allowed to enter a first one of the filtering materials and to pass / flow through that first one of the filtering materials. When the water has passed through the first one of the filtering materials and thereby has been filtered from at least some of the contaminants, the filtered water is arranged to exit the first one of the filtering materials and to flow into and through a second one of the filtering materials. Hence, a series flow has been performed through said at least one cellulose-based filtering material and said at least one filtering material comprising said adsorbing agent.

[0118] Preferably, said filtering device comprises at least one filter housing arranged to house at least one of said at least one cellulose-based filtering material and said at least one filtering material comprising said adsorbing agent.

[0119] Said at least one filter housing comprises at least one inlet for inflow of said contaminated water or already filtered water that needs to be further filtered, and at least one outlet for outflow of filtered water.

[0120] Said at least one filter housing may e.g. be a barrel, a cistern, a tank, an intermediate bulk container (IBC), a tub, a hose, a load changer bed, and / or a pipe or combinations thereof.

[0121] Said filtering device may further comprise at least one polishing filter for final cleaning of the filtrated fluid / water before discharging the filtrate to a recipient.

[0122] Said at least polishing filter is preferably arranged downstream of the filtering material comprising said adsorbing agent. Said at least one polishing filter may be arranged in a same filter housing as the filtering material comprising said adsorbing agent or arranged in another filter housing downstream.

[0123] Any contaminant residue still left in the already filtered water may be captured by said at least one polishing filter.

[0124] Thanks to said polishing filter arranged downstream of said at least one filtering material comprising said adsorbing agent, any adsorbing agent comprising adsorbed PF AS, hydrocarbon, heavy metal, chlorine dioxide, chlorine and / or drug residues will be captured by the filter.

[0125] Said polishing filter preferably comprises a granular filtering material and / or a fibrous filtering material. Said granular filtering material preferably comprises at least one of silica sand, garnet sand, gravel, silicon dioxide, ceramic, coal, clay and graphene.

[0126] Said fibrous filtering material preferably comprises fibers selected from plant fibers, bast fibers, wood fibers, recycled fibers, cellulose fibers and a positively charged polyelectrolyte adsorbed on said cellulose fibers, or a mixture thereof.

[0127] Said fibrous filtering material may be a woven or non-woven filtering material comprising unprocessed or processed fibers of natural origin. Said woven or non-woven filtering material may also comprise polypropylene and / or polyethylene.

[0128] In one preferred embodiment, said polishing filter comprises a cellulose-based filtering material comprising cellulose fibers and a positively charged polyelectrolyte adsorbed on said cellulose fibers.

[0129] An example of one preferred embodiment is a cellulose-based filtering material comprising cellulose fibers and PVAm adsorbed on said cellulose fibers.

[0130] Said cellulose-based filtering material may in some preferred embodiments preferably be CTMP.

[0131] It is conceivable to mix said cellulose-based filtering material comprising cellulose fibers and PVAm adsorbed on said cellulose fibers with graphene in some preferred embodiments of the polishing filter.

[0132] Downstream of said at least one inlet for inflow of contaminated fluid, e.g. contaminated water, or already filtered fluid to be filtered again, spreading means may be arranged for spreading the inflowing contaminated or already filtered water over a whole or a substantially whole upper surface of at least one of said filtering materials for better utilization of a filtering capacity of said filtering materials. Said spreading means may e.g. be a spray nozzle. The spreading means may in its simplest form be a layer of a granular material, e.g. sand, on top and spread over all or at least over substantially said upper surface of at least one of said filtering materials.

[0133] Any one or all of the filtering materials may be arranged in at least one pouch of a permeable material such that the filtering material is kept in place in the pouch while fluid to be filtered may flow through the pouch from an inlet to an outlet and further through the next-coming pouch and through its filtering material and then to leave the filtering device. Examples of suitable permeable materials may e.g. be woven or nonwoven materials made of polyester, cotton, wool, viscose etc. Preferably the pouch comprises fibers of natural origin. Said pouch is preferably used in combination with said at least one filter housing such that said at least one pouch is arranged inside said at least one filter housing.

[0134] An advantage of arranging at least one of said filtering materials in one or more pouch / - es may be that when the filtering capacity of any of the filtering materials has reached a critical lower limit the pouch comprising that filtering material with poor remaining filtering capacity can easily be removed from the filter housing and be replaced with a pouch comprising a fresh filtering material.

[0135] It may be preferred to arrange said at least one cellulose-based filtering material as a first filtering material in said filtering device and to let a flow of contaminated fluid to first enter and flow through said at least one cellulose-based filtering material and to thereafter enter and flow through said at least one filtering material comprising said adsorbing agent. Long-chained PF AS molecules, hydrocarbons and drug residues will be efficiently trapped in said at least one cellulose-based filtering material and filtered out from the contaminated water before the next-coming filtering step comprising said at least one filtering material comprising said adsorbing agent. Said at least one filtering material comprising said adsorbing agent will then not be blocked by said long-chained PF AS molecules and hydrocarbons but can efficiently trap and filter out PF AS molecules, hydrocarbons and drug residues having shorter chains. It is believed that also chlorine dioxide and chlorine will, if not already filtered out, be trapped and filtered out by said at least one filtering material comprising said adsorbing agent.

[0136] Said filtering device may further comprise a pre-treatment filter and / or a post-treatment filter, said pre-treatment filter and / or said post-treatment filter comprising at least one of a granular filter, a fibrous filter, ion exchange resin and a pH-balancing filter.

[0137] Said filtering device comprises a filtering height that in this context is a sum of the filtering height of said at least one cellulose-based filtering material and the filtering height of said at least one filtering material comprising said adsorbing agent. Said filtering height of said at least one cellulose-based filtering material is within an interval of 10-90% of a total filtering height of said filtering device. Preferably, said filtering height is 10-50% of said total filtering height, and more preferred 15-40%.

[0138] The filtering height of said at least one filtering material comprising said adsorbing agent is preferably within an interval of 10-90% of said total filtering height of said filtering device. Preferably, said filtering height is 50-90% of said total filtering height, and more preferred 60-85%.

[0139] In a first embodiment of the first aspect of the invention, said cellulose-based filtering material is preferably arranged upstream of said filtering material comprising said adsorbing agent and said two filtering materials are arranged for said series flow.

[0140] In said first embodiment said cellulose-based filtering material and said filtering material comprising said adsorbing agent are arranged in a common filter housing.

[0141] Said two filtering materials may be arranged in a direct contact or an indirect contact with each other inside said filter housing.

[0142] Said filter housing further comprises at least one inlet for inflow of contaminated fluid or already filtered fluid and at least one outlet for outflow of filtered fluid.

[0143] Said at least one inlet for inflow is arranged upstream of said cellulose-based filtering material; and said at least one outlet for outflow is arranged downstream of said filtering material comprising said adsorbing agent.

[0144] A perforated separating means, e.g. a perforated disc, may be arranged between said cellulose-based filtering material and said filtering material comprising said adsorbing agent to separate the filtering materials from each other but still allowing fluid to flow from one filtering material to the next filtering material arranged downstream.

[0145] At least one polishing filter may be arranged downstream of said filtering material comprising said adsorbing agent, either in the same housing or in another housing.

[0146] An alternative of the first embodiment may be a filtering device wherein said cellulose- based filtering material and said filtering material comprising said adsorbing agent are comprised in separate filter housings meaning that said cellulose-based filtering material is arranged in one filter housing and said filtering material comprising said adsorbing agent is arranged in another filter housing, and said two filter housings are connected to each other by connecting means for said series flow through said filtering materials.

[0147] Said connecting means may comprise at least any one of a pipe, a tube, a hose and a coupling device or other therefore suitable equipment.

[0148] A second alternative of the first embodiment may be to arrange said filtering material comprising said adsorbing agent upstream of said cellulose-based filtering material comprising cellulose fibers and the positively charged polyelectrolyte adsorbed on said fiber. There may be a risk that larger PF AS molecules will clog said filtering material comprising said adsorbing agent in filtering devices having a filtering material comprising said adsorbing agent as the first filtering material meeting the contaminated fluid. However, for certain types of contaminated fluids, this solution may be preferable. The filtering device in this second alternative may further comprise at least one cellulose-based filtering material arranged as a last filtering material downstream of said at least one filtering material comprising said adsorbing agent.

[0149] In this second alternative it is conceivable that said cellulose-based filtering material comprising cellulose fibers and the positively charged polyelectrolyte adsorbed on said fiber is a polishing filter when being arranged as a last filtering material.

[0150] The filtering height of said polishing filter may in this example be 1-15%, preferably 5- 10%.

[0151] Said at least one polishing filter may be arranged in a same filter housing as said filtering material comprising said adsorbing agent or be arranged in a separate filter housing and connected to the other filter housing / -s by connecting means for said series flow.

[0152] In a second embodiment of the first aspect of the invention, said filtering device as described in relation to the first embodiment comprises two or more of said cellulose- based filtering material and / or two or more of said filtering material comprising said adsorbing agent.

[0153] Said two or more cellulose-based filtering materials are arranged for a series flow therethrough and being arranged in any one of a direct contact and an indirect contact. A flow of a contaminated fluid or a volume of already filtered fluid enters a first cellulose-based filtering material, flows through said first cellulose-based filtering material, exits first cellulose-based filtering material and enters a second cellulose-based filtering material, flows through said second cellulose-based filtering material and exits second cellulose-based filtering material.

[0154] Two or more cellulose-based filtering materials may further be arranged for a parallel flow, each of said two or more cellulose-based filtering materials receiving an amount of said flow of contaminated fluid or already filtered fluid.

[0155] It is to be understood that said two or more cellulose-based filtering materials may be housed in one and the same filter housing or in separate filter housings.

[0156] As disclosed above said filtering device may in the second embodiment comprise two or more filtering materials comprising said adsorbing agent; and wherein said two or more filtering materials comprising said adsorbing agent are arranged for a series flow therethrough and being arranged in any one of a direct contact and an indirect contact.

[0157] When said filtering device comprises two or more filtering materials comprising said adsorbing agent, said adsorbing agent may be of a same kind in said two or more filtering materials or of different kinds. It is e.g. conceivable to use activated carbon as adsorbing agent in one of the filtering materials and carbon black as adsorbing agent in another one of the filtering materials and graphene as adsorbing agent in still another one of the filtering materials, or to use a mixture of them.

[0158] A flow of a contaminated fluid or an already filtered fluid enters a first filtering material comprising said adsorbing agent, flows through said first filtering material comprising said adsorbing agent, exits said first filtering material comprising said adsorbing agent and then enters a second filtering material comprising said adsorbing agent. The filtered fluid then flows through said second filtering material comprising said adsorbing agent and exits said second filtering material comprising said adsorbing agent.

[0159] Two or more filtering material comprising said adsorbing agent may further be arranged for a parallel flow, each of said two or more filtering materials comprising said adsorbing agent receiving an amount of said flow of contaminated fluid or filtered fluid. It is to be understood that said two or more filtering materials comprising said adsorbing agent may be housed in one and the same filter housing or in separate filter housings.

[0160] Said first and second embodiment may be combined in any possible way and still be within the scope of the invention.

[0161] The filtering device may e.g. comprise one cellulose-based filtering material and two filtering materials comprising said adsorbing agent arranged downstream of said one cellulose-based filtering material.

[0162] Another example may be a filtering device comprising two or more cellulose-based filtering materials arranged for parallel flow therethrough and one filtering material comprising said adsorbing agent arranged downstream of said two or more cellulose- based filtering materials. Said one filtering material comprising said adsorbing agent receives flows of filtered fluid from the two or more cellulose-based filtering materials.

[0163] In still another example, said filtering device comprises said at least one cellulose-based filtering material comprising cellulose fibers and a positively charged polyelectrolyte adsorbed on said cellulose fibers upstream of said at least one filtering material comprising said adsorbing agent. In this example, at least one cellulose-based filtering material comprising cellulose fibers and a positively charged polyelectrolyte adsorbed on said cellulose fibers is / are also arranged downstream of said at least one filtering material comprising said adsorbing agent. This means that the first and last filtering material comprised in the filtering device both are cellulose-based filtering materials comprising cellulose fibers and a positively charged polyelectrolyte adsorbed on said cellulose fibers.

[0164] The second aspect of the invention, i.e. the method for removing contaminants from a source of a contaminated fluid by making use of the above disclosed filtering device is now to be described.

[0165] In the description below said source of a contaminated fluid is a source of a contaminated water but it is to be understood that the inventive method concerns any contaminated fluid, not only contaminated water.

[0166] Said method for removing contaminants from a contaminated water, comprises the steps of a) providing at least one cellulose-based filtering material, said at least one cellulose- based filtering material comprising cellulose fibers and a positively charged polyelectrolyte adsorbed on said cellulose fibers, b) providing at least one filtering material comprising an adsorbing agent, c) arranging said at least one cellulose-based filtering material and said at least one filtering material comprising said adsorbing agent to be in a series flow with each other, d) allowing a flow of contaminated water to first flow through one of said at least one cellulose-based filtering material and said at least one filtering material comprising said adsorbing agent, and then to flow through the other one of said at least one cellulose- based filtering material and said at least one filtering material comprising said adsorbing agent.

[0167] Preferably, said at least one filtering material comprising said adsorbing agent is positioned downstream of said at least one cellulose-based filtering material. The flow of contaminated water first enters and flows through said at least one cellulose-based filtering material and then exits said at least one cellulose-based filtering material. The now - at least partly - filtered water continues to flow further downstream and enters and flows through said at least one filtering material comprising said adsorbing agent.

[0168] In some embodiments, at least one cellulose-based filtering material comprising cellulose fibers and a positively charged polyelectrolyte adsorbed on said cellulose fibers is / are arranged as a last filtering material downstream of said at least one filtering material comprising said adsorbing agent such that the filtered water is finally filtered through said at least one cellulose-based filtering material before being discharged to the recipient.

[0169] Said method may further comprise the step: e) allowing at least a partial flow of filtered water from at least one of said at least one cellulose-based filtering material and said at least one filtering material comprising said adsorbing agent to flow through at least one polishing filter.

[0170] Preferably, said at least one polishing filter is arranged downstream of said at least one filtering material comprising said adsorbing agent - or said cellulose-based filtering material as the last filtering material downstream of said adsorbing agent - allowing the filtered water to flow through said at least one polishing filter for capturing and filtering out any residue of adsorbing agent comprised in the water. Said residue of adsorbing agent may have a contaminant adsorbed to it. In some embodiments it may be advantageous to add a pre-treatment filtering step and / or a post-treatment filtering step; said pre-treatment filtering step and / or said posttreatment filtering step may comprise at least one of a granular filter, ion exchange resin, photochemical treatment, and a pH-balancing filter.

[0171] It is to be pointed out that although it may be preferred to work in a direction of gravity for the flowing water, it is however conceivable to use pressurized / forced systems such that the direction of flow is in a direction not coinciding with the direction of gravity. Pumping equipment may then be needed.

[0172] The filtering device can be scaled in size ranging from small passive systems for personal use to large scale, high flow-rate systems.

[0173] The contaminated water to be filtered may be a batch source of contaminated water comprised in e.g. a barrel, a tank or a cistern or the like.

[0174] The contaminated water may also be a continuous source of contaminated water, e.g. from a groundwater source.

[0175] EXAMPLES

[0176] EXAMPLE 1

[0177] In a preferred embodiment for manufacturing said at least one cellulose-based filtering material comprising cellulose fibers and a positively charged polyelectrolyte adsorbed on said cellulose fibers, the stock comprises cellulose fibers from mechanical pulp. Said mechanical pulp may preferably be CTMP, and possibly mixed with other kinds of HYPs.

[0178] The positively charged polyelectrolyte comprises PVAm.

[0179] 400 kg CTMP is mixed with 12 m3water thereby forming a stock comprising 3 wt-% cellulose fibers.

[0180] Salt may be added to the stock. In this example 12 wt-% NaCl of the dry weight of cellulose fibers in the stock was added. A concentration of the PVAm in the stock is preferably equal to or greater than 0,01 wt- % PVAm of a dry weight of cellulose fibers in the stock.

[0181] Preferably, the concentration of PVAm in the stock is equal to or greater than 0,1 wt-% PVAm, and more preferred equal to or greater than 0,5 wt-% PVAm.

[0182] In order not to overdose the use of PVAm but rather to optimize the use, an upper limit of PVAm in the stock may be equal to or lower than 30 wt-% of a dry weight of cellulose fibers in the stock, preferably equal to or lower than 20 wt-%, and more preferred equal to or lower than 10 wt-%.

[0183] A concentration interval of PVAm in the stock may be within the interval of 0,05 - 10,0 wt-% PVAm of a dry weight of cellulose fibers in the stock, preferably 0,1 - 6,0 wt-% PVAm, and more preferred 0,5 - 2,0 wt-% PVAm.

[0184] In this example the concentration of PVAm is 0,2 gram / of a dry weight of cellulose fibers in the stock; and the PVAm is Xelorex™ RS 1300.

[0185] Possibly, at least one additional positively charged polyelectrolyte other than PVAm may be added.

[0186] In the above example, a cellulose-based filtering material comprising cellulose fibers from mechanical pulp and a positively charged polyelectrolyte comprising PVAm adsorbed on said cellulose fibers has now been produced.

[0187] EXAMPLE 2

[0188] A source of a contaminated water comprising a variety of PFAS compounds was filtered by the inventive method and by making use of the inventive filtering device.

[0189] In the example, the filtering device comprised a dry cellulose-based filtering material comprising cellulose fibers and a positively charged polyelectrolyte adsorbed on said cellulose fibers.

[0190] Said cellulosic material comprised cellulose in the form of a chemi-thermomechanical pulp, CTMP. Said positively charged polyelctrolyte comprised PVAm and in an amount of approx. 0,5-1% as calculated on a dry content of said cellulose fibers.

[0191] Downstream of said cellulose-based filtering material said filtering device further comprised three filtering materials comprising an adsorbing agent; a first filtering material comprising an adsorbing agent, a second filtering material comprising an adsorbing agent and a third filtering material comprising an adsorbing agent. Said second filtering material was positioned downstream of said first filtering material and said third filtering material was positioned downstream of said second filtering material. The three filtering materials were arranged in a series flow relation for series flow through them.

[0192] Said adsorbing agent comprised commercial granular activated carbon GAC. A same type of GAC was used as adsorbing agent in all three filtering materials comprising said adsorbing agent.

[0193] Said device further comprised a polishing filter arranged downstream of said third filtering material comprising said adsorbing agent and arranged in a series flow relation.

[0194] Said filtering device further comprised four filter housings. Said four filter housings were in the form of tanks which each comprised an inlet for inflow of contaminated fluid or filtered fluid and an outlet for outflow of filtered fluid. The tanks were connected to each other by connecting means for said series flow.

[0195] A first filter housing was arranged to house said cellulose-based filtering material while a second, a third and a fourth filter housing were arranged to respectively house said first, said second and said third filtering materials comprising said adsorbing agent.

[0196] Said polishing filter was in this example a filter sock comprising cotton fibers. Said filter sock was arranged on the outlet of the last tank comprising the adsorbing agent.

[0197] A total filtering height of said filtering device was 140 cm.

[0198] About 3 kg of said cellulose-based filtering material was arranged in a first tank. A density of said dry cellulose-based filtering material was about 0,05 g / cm3. Said cellulose-based filtering material was arranged uncompacted in said first tank and the - uncompacted - filtering height was about 35 cm. i.e. 25% of the total filtering height. On an upstream surface of said cellulose-based filtering material, close to an inlet for inflow into said first tank, a spreading means was arranged.

[0199] Said spreading means comprised a permeable woven cloth comprising non-adsorbing threads and a layer of about 2 cm of a silica sand on an upstream surface of said cloth.

[0200] Upstream of said silica sand was said inlet arranged on the first tank.

[0201] Said first tank further comprised a stainless net in a bottom portion of said first tank and downstream of said cellulose-based filtering material such that said cellulose-based filtering material rested on said stainless net. Said stainless net did not add any filtering properties to the filtering device but only served as a bottom rest for the cellulose-based filtering material. The size of the openings of the net was large enough for any contaminant to pass through the net and continue to flow in the downstream direction.

[0202] An outlet of said first tank was arranged downstream of said stainless net.

[0203] Said three filtering materials comprising said GAC were arranged in three tanks downstream of said first tank. Said three tanks were connected to each other by connecting means in the form of hoses and hose connections for series flow therethrough.

[0204] Each of the tanks comprising said GAC had a filtering height of dry GAC of about 35 cm. The filtering height of the three filtering materials was 105 cm constituting 75% of the total filtering height of the filtering device.

[0205] A density of said GAC was about 0,23 g / cm3and a specific surface area of said GAC was approx. 576 m2 / g.

[0206] On top of an upstream surface of each adsorbing agent - the GAC - the same kind of spreading means as in the first tank was used. The same kind of stainless net as in the first tank was arranged in a bottom portion of each of the three tanks and downstream of said GAC such that said GAC rested on said stainless net. The three tanks each comprised an outlet arranged downstream of said stainless net. The contaminated water entered the inlet of said first tank and was spread out by the spreading means over substantially a hole of said upstream surface of said dry cellulose- based filtering material comprising cellulose fibers and a positively charged polyelectrolyte comprising PVAm adsorbed on said cellulose fibers. Said contaminated water flowed into and through said cellulose-based filtering material, and further through said stainless mesh and to the outlet of said first tank where a second sample for analysis was taken of the filtered water. The cellulose-based filtering material became wet and compacted by the through-flowing contaminated water and the filtering height decreased significantly due to compaction.

[0207] The filtered water from the first tank continued to flow through the connecting means to the inlet of said second tank for further filtration. The filtered water flowed into said second tank and was spread out by the spreading means over substantially a hole of said upstream surface of said first filtering material comprising GAC. Said filtered water flowed into and through said first filtering material comprising GAC, and further through said stainless mesh and to the outlet of said second tank where a third sample for analysis was taken of the filtered water.

[0208] The filtered water from the second tank continued to flow through the connecting means to the inlet of said third tank, i.e. the second filter material comprising GAC. The filtered water flowed into said third tank and was spread out by the spreading means over substantially a hole of said upstream surface of said filtering material comprising carbon black. Said filtered water flowed into and through said filtering material comprising GAC, and further through said stainless mesh and to the outlet of said third tank where a fourth sample for analysis was taken of the filtered water.

[0209] The filtered water from the third tank continued to flow through the connecting means to the inlet of said fourth tank, i.e. the third filter material comprising GAC. The filtered water flowed into said fourth tank and was spread out by the spreading means over substantially a hole of said upstream surface of said filtering material comprising GAC. Said filtered water flowed into and through said filtering material comprising GAC, and further through said stainless mesh and to the outlet of said fourth tank where a fifth sample for analysis was taken of the filtered water.

[0210] The filtered water from the third filtering material comprising GAC continued to flow through the polishing filter. Said filtered water flowed into and through said polishing filter and to the outlet of said polishing filter where a sixth sample for analysis was taken of the filtered water. This is end of filtration.

[0211] As mention above, six samples were taken out for analysis. A first sample was taken on unfiltered contaminated water and is presented under Contamin. Water in Table 1. A second sample was taken after the first filtering step comprising CTMP and PVAM adsorbed on the cellulose fibers (presented under Cellulose / PVAM in Table 1), and a third, fourth and fifth sample was taken after each of the three filtering steps comprising GAC (presented under GAC1, GAC2 and GAC3 in Table 1). Finally, a sixth sample was taken out after the polishing step comprising the cotton sock (presented under Polishing step in Table 1).

[0212] For all analyzes the following applies: Test was performed by Eurofins Food & Feed Testing Sweden ISO / IEC 17025:2017 SWEDAC 1977.

[0213] Symbol description: The laboratory / laboratories are accredited by the respective national accreditation body. Non-accredited tests are marked *. ** The information has been provided by the customer.

[0214] Sum PF AS (TOP), Sum PF AS, Sum PF AS 4, SUM PF AS SLV 11 and PFBA were analyzed and the results are presented in Table 1 below. Three of the samples were analysed on Sum PF AS (TOP) and Sum PF AS 4 while all six samples were analysed on Sum PF AS, Sum PF AS SLV 11 and PFBA.

[0215] Table 1 Analysis results

[0216]

[0217] As shown in table 1, the contaminated water before filtration had a sum of PF AS being 360000 ng / 1 and a sum of PF AS SLV 11 being 350000 ng / 1. In summary, by making use of the inventive method and filtering device, the sum of PF AS and the sum of PF AS SLV 11 of the incoming contaminated water were reduced with more than 99,99%.

[0218] As can be seen in Table 1, both the sum of PF AS and the sum of PF AS SLV 11 were 12 ng / 1 in the filtered and polished water leaving the filtering device.

[0219] PFBA was 1100 ng / 1 in the incoming contaminated water and only 4,1 ng / 1 in the filtered water which is a reduction of 99,6%.

[0220] The first filtering step comprising said cellulose-based filtering material reduced the Sum of PF AS in the contaminated water from 360000 to 120000 ng / 1, i.e. a reduction of about 67%.

[0221] The sum of PFAS and the sum of PFAS SLV 11 after the GAC3 step was 570 ng / 1 and 550 ng / 1 respectively. The following polishing filter step reduced the respective sums to 12 ng / 1 for each. This means that the polishing filter reduced sum of PFAS and sum of PFAS SLV 11 with more than 97% by capturing free activated carbons comprising adsorbed PFAS in the filtered water.

[0222] By using the inventive filtering device the filtered water leaving said filtering device was almost totally free from PFAS-compounds. Said at least one cellulose-based filtering material comprising cellulose fibers and a positively charged polyelectrolyte adsorbed on said cellulose fibers may after use preferably be sent to a destruction facility.

[0223] The third aspect of the invention, i.e. the filtering system for removing contaminants from a source of a contaminated fluid is now to be described.

[0224] Said filtering system for removing contaminants from a contaminated fluid comprises:

[0225] - At least one cellulose-based filtering material comprising cellulose fibers and a positively charged polyelectrolyte adsorbed on said cellulose fibers,

[0226] - At least one filtering material comprising an adsorbing agent; and

[0227] - At least one pouch comprising at least one of said at least one cellulose-based filtering material and said at least one filtering material comprising an adsorbing agent,

[0228] - Said at least one pouch comprising an inlet upstream of said at least one of said at least one cellulose-based filtering material and said at least one filtering material comprising an adsorbing agent and an outlet downstream of said at least one of said at least one cellulose-based filtering material and said at least one filtering material comprising an adsorbing agent.

[0229] Preferably, said positively charged polyelectrolyte adsorbed on said cellulose fibers is selected from polyvinylamine (PVAm), polyacrylamide, polyacrylic acid (PAA), polymethacrylic acid, chitosan, cationic gelatin, polydiallyldimethylammonium chloride (polyDADMAC), polyallylamine, polyethylenimine, anionic nanocellulose, sodium lignin sulfonate, sodium polyacrylate, anionic polyacrylamide, anionic glyoxalated polyacrylamide, poly-(sodium styrene sulphonate) and / or poly(vinylphosphonic acid), or a mixture of two or more thereof.

[0230] Preferably, a concentration interval of said positively charged poly electrolyte is 0,001- 30 wt-% of a dry weight of said cellulose fibers, preferably 0,005-20 wt-% and more preferred 0,01-10 wt-%.

[0231] Said cellulose fibers comprised in said at least one cellulose-based filtering material are selected from wood pulp, non-wood pulp, regenerated cellulose fibres, plant fibres such as fibres from bamboo, bagasse, cotton, hemp, flax, and jute, and / or mixtures thereof.

[0232] Said wood pulp is preferably selected from softwood pulp, hardwood pulp, High Yield Pulp HYP, dissolving pulp, chemical pulp such as kraft pulp, sulphate pulp or sulphite pulp, recycled paper and board, broke, cellulose nano pulp, dissolving pulp, deinked pulp DIP, straw pulps, hemp pulps, bagasse pulps, regenerated fibers or a combination of one or more of these.

[0233] Preferably, said High Yield Pulp HYP is selected from mechanical pulp, refiner mechanical pulp RMP, thermomechanical pulp TMP, chemi-thermomechanical pulp CTMP, defibrated fiber-material, high temperature chemi-thermomechanical pulp HTCTMP, chemi-mechanical pulp CMP, stone groundwood pulp SGW, pressure groundwood pulp PGW or a mixture thereof.

[0234] Said adsorbing agent preferably comprises activated carbon and / or carbon black and / or graphene and as mentioned in relation to the first and second aspects of the invention.

[0235] Said pouch comprises at least one side wall, a bottom portion attached to said at least one wall and an opening which serves as an inlet and arranged opposite to the bottom portion. Said bottom portion comprises an outlet.

[0236] Preferably, said filtering system further comprises at least one polishing filter arranged as a last filter downstream of said at least one cellulose-based filtering material and said at least one filtering material comprising an adsorbing agent and upstream of said outlet.

[0237] Said at least one polishing filter is of a kind as described in relation to the first and second aspects of the invention.

[0238] Preferably said at least one polishing filter comprises a cellulose-based filtering material comprising cellulose fibers and a positively charged polyelectrolyte adsorbed on said cellulose fibers.

[0239] In one preferred embodiment of said at least one polishing filter, said cellulose-based filtering material comprising cellulose fibers is a mechanical pulp, e.g. CTMP, and said positively charged polyelectrolyte adsorbed on said cellulose fibers is PVAm.

[0240] Preferably, said pouch further comprises at least one handle. Said at least one handle may preferably be arranged in vicinity to said opening. Said handlers may also function, when needed, as a closing means for closing the opening and hence closing an entrance to an inside of the pouch where said at least one of said at least one cellulose- based filtering material and said at least one filtering material comprising an adsorbing agent is arranged.

[0241] Said at least one side wall is essentially impermeable to fluids while said bottom portion is permeable to fluids.

[0242] Said side wall may be a woven or a non-woven tube or e.g. be comprised of one or more pieces of fabric sewn or laminated thereby forming said at least one wall.

[0243] Said opening is arranged to receive a flow of contaminated fluid entering into the pouch. Said contaminated fluid flows downstream to said at least one cellulose-based filtering material and / or said at least one filtering material comprising an adsorbing agent and through said filtering material / -s to said bottom portion comprising said outlet of the pouch. In some embodiments the bottom portion is the outlet.

[0244] An example of use of said filtering system may be inside a drain well at fire drill sites. The pouch is positioned inside the drain well and is arranged to receive contaminated water comprising e.g. different PFAS compounds and / or drug residues. Preferably said pouch has connecting means for connecting to the place / site of use, e.g. the drain well or / pipes / holes / inlets in which said pouch is to be removably arranged. Said at least one handle may be used for positioning the filtering system inside the drain well and for lifting out said filtering system e.g. when its filtering capacity is too low.

[0245] Said bottom portion and said at least one side wall may be press-formed from one single piece of material.

[0246] Said at least one side wall is essentially impermeable to fluids thanks to being laminated and / or impregnated and / or tightly woven / having a high thread density.

[0247] Said bottom portion and said at least one side wall may have a same or a different thread density.

[0248] Preferably, said pouch is made of a biobased material and is at least partly made from a non-woven or a woven material comprising fibers of natural origin, a biobased plastic, compacted and impregnated saw dust, board and moulded pulp. However, synthetic fibers, e.g. polyester, elastane and acrylic, may be used in some embodiments.

[0249] Also steel or cast iron may be used. If used in said bottom portion, said steel or cast iron is made permeable in said bottom portion by arranging holes or grids or the like at an area of said outlet of said bottom portion.

[0250] Said at least one side wall and said bottom portion may preferably be made of a same material.

[0251] Said fibers of natural origin are selected from plant fibres such as fibres from jute, bamboo, bagasse, cotton, hemp, flax, wheat, or mixtures thereof.

[0252] Said at least one side wall of the pouch comprises fibers of natural origin and a positively charged polyelectrolyte adsorbed on said fibers.

[0253] In one preferred embodiment, said filtering system comprises one pouch. Said pouch comprises at least one side wall wherein said at least one side wall comprises jute fibers and PVAm adsorbed on said jute fibers. Also said bottom portion comprises said jute fibers.

[0254] Inside said pouch is arranged a cellulose-based filtering material comprising HYP and wherein said positive polyelectrolyte adsorbed on the cellulose fibers comprises PVAm. Downstream of said cellulose-based filtering material, and closer to said outlet of the pouch, is a filtering material comprising a granulated activated carbon GAC arranged.

[0255] In this embodiment, a polishing filter may be comprised downstream the filtering material comprising GAC. Said polishing filter preferably comprises a cellulose-based filtering material comprising HYP and wherein said positive polyelectrolyte adsorbed on the cellulose fibers comprises PVAm.

[0256] Said filtering system may be manufactured in different sizes and shapes so as to fit in any kind of drain pipes, escape pipes, discharge pipes, drain wells, street drainwell inlets, surface water manholes, floor drains indoors and outdoors. The pouch may have a square, rectangular or circular cross section in relation to a direction of flow therethrough. The invention is however not limited to a shape of the cross section of the pouch. The present inventive filtering device and / or filtering system may further make use of and comprise microorganisms selected from bacteria, fungi and archaea, preferably the microorganisms comprise archaea.

[0257] In preferred embodiments of said filtering device and / or filtering system, said positively charged polyelectrolyte comprises PVAm and said PVAm in said cellulose-based filtering material is 0,001-30 wt-% of a dry weight of said cellulose fibers, preferably 0,005-20 wt-% and more preferred 0,01-10 wt-%.

[0258] Preferably, said cellulose-based filtering material comprising cellulose fibers and a positively charged polyelectrolyte adsorbed on said cellulose fibers further comprises at least one of said bacteria, fungi and archaea.

[0259] As will be understood by those skilled in the present field of art, numerous changes and modifications may be made to the above described and other embodiments of the present invention, without departing from the scope of the present invention as defined in the appending claims.

[0260] It should be noted that the above described aspects may be the subject for its own protection, as such in a separate divisional application. Hence, it is foreseen that this aspect of the invention may require a protection by its own, e.g. since it may be applicable per se also in other concepts than that defined by the independent claim in this application.

[0261] It is conceivable that only some of the total amount of positively charged polyelectrolyte / -s to be added to the cellulose fibers are added to the stock. A part of the total amount of the polyelectrolyte / -s to be added may be added at other positions during a production of the cellulosic material comprising said positively charged polyelectrolyte / -s adsorbed to the cellulose fibers of the cellulosic material. The polyelectrolyte / -s may e.g. be sprayed onto surfaces of said cellulosic material and / or said cellulosic material may be dipped into a solution comprising said positively charged polyelectrolyte / -s.

[0262] It is conceivable to use a mixture of said cellulose-based filtering material and said filtering material comprising said adsorbing agent such that said at least one cellulose- based filtering material further comprises said adsorbing agent and / or wherein said at least one filtering material further comprises said adsorbing agent further comprising cellulose fibers and positively charged polyelectrolytes adsorbed on said cellulose fibers. One example may be a mixture comprising graphene and cellulose fibers comprising PVAm adsorbed on said cellulose fibers.

[0263] It is conceivable that tubes, pipes, hoses etc are used as the filter housings such that said tubes, pipes, hoses both provides filtration and provides connection between the filtering materials comprised in said tubes, pipes, hoses. Embodiments are conceivable where the pouch is the housing.

[0264] Additional embodiments are conceivable where the polishing filter is comprised in a bottom portion of the last housing downstream below the adsorbing agent, or where the polishing filter may be a filter sock arranged on a bottom portion of said last housing such that treated water leaving the adsorbing agent enters the filter sock at the same time. Said filter sock may be made of synthetic fibers. Preferably, said fiber sock comprises fibers of natural origin, e.g. cotton, viscose, hemp, flax etc.

Claims

CLAIMS1. A filtering device for removing contaminants from a contaminated fluid, wherein said filtering device comprising:- At least one cellulose-based filtering material comprising cellulose fibers and a positively charged polyelectrolyte adsorbed on said cellulose fibers,- At least one filtering material comprising an adsorbing agent,- Said at least one cellulose-based filtering material and said at least one filtering material comprising said adsorbing agent being arranged for a series flow therethrough,- At least one filter housing arranged to house at least one of said at least one cellulose-based filtering material and said at least one filtering material comprising said adsorbing agent, and wherein- Said at least one filter housing comprising at least one inlet for inflow of contaminated fluid or filtered fluid and at least one outlet for outflow of filtered fluid.

2. The filtering device according to claim 1, wherein said at least one cellulose- based filtering material being arranged upstream of said at least one filtering material comprising said adsorbing agent for said series flow through said filtering materials.

3. The filtering device according to any one of the preceding claims, wherein said at least one cellulose-based filtering material and said at least one filtering material comprising said adsorbing agent are arranged in a common filter housing, or wherein said at least one cellulose-based filtering material and said at least one filtering material comprising said adsorbing agent are arranged in separate filter housings, said separate filter housings being connected by connecting means for said series flow.

4. The filtering device according to any one of the preceding claims, wherein two or more cellulose-based filtering materials are connected in series and / or in parallel; and / or wherein two or more filtering materials comprising said adsorbing agent are connected in series and / or in parallel.

5. The filtering device according to any one of the preceding claims, wherein said device further comprises at least one polishing filter; preferably said polishingfilter is arranged downstream of said at least one filtering material comprising said adsorbing agent and arranged for series flow in a direct or indirect contact with said at least one filtering material comprising said adsorbing agent.

6. The filtering device according to claim 5, wherein said polishing filter comprising a granular filtering material comprising at least one of silica sand, garnet sand, gravel, silicon dioxide, ceramic, coal, clay; and / or a fibrous filtering material, wherein said fibrous filtering material is preferably a woven or a nonwoven filtering material comprising fibers selected from plant fibers, bast fibers, wood fibers, recycled fibers, polypropylene, polyethylene or a mixture thereof, preferably said fibrous filtering material comprises a cellulose-based filtering material comprising cellulose fibers and a positively charged polyelectrolyte adsorbed on said cellulose fibers.

7. The filtering device according to any one of the preceding claims, wherein said positively charged polyelectrolyte comprises at least one of polyvinylamine (PVAm), polyacrylamide, polyacrylic acid (PAA), polymethacrylic acid, chitosan, cationic gelatin, polydiallyldimethylammonium chloride (polyDADMAC), polyallylamine, polyethylenimine, anionic nanocellulose, sodium lignin sulfonate, sodium polyacrylate, anionic polyacrylamide, anionic glyoxalated polyacrylamide, poly-(sodium styrene sulphonate) and poly(vinylphosphonic acid), or a mixture of two or more thereof.

8. The filtering device according to claim 7, wherein a concentration of said positively charged polyelectrolyte in said cellulose-based filtering material is 0,001-30 wt-% of a dry weight of said cellulose fibers, preferably 0,005-20 wt- % and more preferred 0,01-10 wt-%.

9. The filtering device according to any one of the preceding claims, wherein said positively charged polyelectrolyte comprises polyvinylamine (PVAm).

10. The filtering device according to any one of the preceding claims, wherein said adsorbing agent comprises activated carbon and / or carbon black and / or graphene.

11. The filtering device according to any one of the preceding claims, wherein a filtering height of said at least one cellulose-based filtering material is within aninterval of 10-90% of a total filtering height of said filtering device, preferably 10-50% and more preferred 15-40%; and wherein a filtering height of said at least one filtering material comprising said adsorbing agent is within an interval of 10-90%, preferably 50-90% and more preferred 60-85% of a total filtering height of said filtering device.

12. The filtering device according to any one of the preceding claims, wherein said at least one cellulose-based filtering material and / or said at least one filtering material comprising said adsorbing agent is / are comprised in at least one pouch at least partly made from a biobased material comprising natural fibers and / or a plastic material, preferably a biobased plastic material; preferably said natural fibers comprises hemp fibers, bast fibers, flax fibers, bagasse fibers, jute fibers, cellulose fibers, processed cellulose fibers, recycled fibers.

13. The filtering device according to any one of the preceding claims, wherein said cellulose fibers comprised in said at least one cellulose-based filtering material are selected from wood pulp, non-wood pulp, regenerated cellulose fibres, plant fibres such as fibres from bamboo, bagasse, cotton, hemp, flax, and jute, and / or mixtures thereof.

14. The filtering device according to claim 13, wherein said wood pulp is selected from softwood pulp, hardwood pulp, High Yield Pulp (HYP), dissolving pulp, chemical pulp such as kraft pulp, sulphate pulp or sulphite pulp, recycled paper and board, broke, cellulose nano pulp, dissolving pulp, deinked pulp (DIP), straw pulps, hemp pulps, bagasse pulps, regenerated fibers or a combination of one or more of these.

15. The filtering device according to claim 14, wherein said High Yield Pulp (HYP) is selected from mechanical pulp, refiner mechanical pulp (RMP), thermomechanical pulp (TMP), chemi-thermomechanical pulp (CTMP), defibrated fiber-material, high temperature chemi-thermomechanical pulp (HTCTMP), chemi-mechanical pulp (CMP), stone groundwood pulp (SGW), pressure groundwood pulp (PGW) or a mixture thereof.

16. The filtering device according to any one of the preceding claims, wherein said contaminants comprising at least one of a perfluoroalkyl substance, a polyfluoroalkyl substance, a heavy metal, a hydrocarbon, a drug residue,chlorine dioxide and chlorine.

17. The filtering device according to any one of the preceding claim, wherein said filtering device further comprising a pre-treatment filter and / or a post-treatment filter, said pre-treatment filter and / or said post-treatment filter comprising at least one of a granular filter, ion exchange resin and a pH-balancing filter.

18. The filtering device according to any one of the preceding claims, wherein said filtering device comprises at least one cellulose-based filtering material being arranged as a last filtering material downstream of said at least one filtering material comprising said adsorbing agent; preferably said last filtering material is arranged as a polishing filter.

19. A method for removing contaminants from a contaminated fluid, said method comprising the steps of a) providing at least one cellulose-based filtering material, said at least one cellulose-based filtering material comprising cellulose fibers and a positively charged polyelectrolyte adsorbed on said cellulose fibers, b) providing at least one filtering material comprising an adsorbing agent, c) arranging said at least one cellulose-based filtering material and said at least one filtering material comprising said adsorbing agent to be in a series flow with each other, d) allowing a flow of contaminated fluid to first flow through one of said at least one cellulose-based filtering material and said at least one filtering material comprising said adsorbing agent, and then to flow through the other one of said at least one cellulose-based filtering material and said at least one filtering material comprising said adsorbing agent.

20. The method according to claim 19, wherein said at least one filtering material comprising said adsorbing agent is positioned downstream of said at least one cellulose-based filtering material.

21. The method according to any one of claims 19-20, wherein said method further comprising the step: e) allowing at least a partial flow of filtered fluid from at least one of said at least one cellulose-based filtering material and said at least one filtering material comprising said adsorbing agent to flow through at least onepolishing filter; said polishing filter preferably comprising a granular filtering material comprising at least one of silica sand, garnet sand, gravel, silicon dioxide, ceramic, coal, clay; and / or a fibrous filtering material, wherein said fibrous filtering material is a woven or a non-woven filtering material comprising fibers selected from plant fibers, bast fibers, wood fibers, recycled fibers, polypropylene, polyethylene or a mixture thereof, preferably said fibrous filtering material comprises a cellulose-based filtering material comprising cellulose fibers and a positively charged polyelectrolyte adsorbed on said cellulose fibers.

22. The method according to any one of claims 19-21, wherein said method further comprising a pre-treatment filtering step and / or a post-treatment filtering step, said pre-treatment filtering step and / or said post-treatment filtering step comprising at least one of a fibrous filter, a granular filter, ion exchange resin and a pH-balancing filter.

23. The method according to any one of claims 19-22, said cellulose fibers comprised in said at least one cellulose-based filtering material are selected from wood pulp, non-wood pulp, regenerated cellulose fibres, plant fibres such as fibres from bamboo, bagasse, cotton, hemp, flax, and jute, and / or mixtures thereof.

24. The method according to claim 23, wherein said wood pulp is selected from softwood pulp, hardwood pulp, High Yield Pulp (HYP), dissolving pulp, chemical pulp such as kraft pulp, sulphate pulp or sulphite pulp, recycled paper and board, broke, cellulose nano pulp, dissolving pulp, deinked pulp (DIP), straw pulps, hemp pulps, bagasse pulps, regenerated fibers or a combination of one or more of these.

25. The method according to claim 24, wherein said High Yield Pulp (HYP) is selected from mechanical pulp, refiner mechanical pulp (RMP), thermomechanical pulp (TMP), chemi-thermomechanical pulp (CTMP), defibrated fiber-material, high temperature chemi-thermomechanical pulp (HTCTMP), chemi-mechanical pulp (CMP), stone groundwood pulp (SGW), pressure groundwood pulp (PGW) or a mixture thereof.

26. The method according to any one of claims 19-25, wherein said positively charged polyelectrolyte comprises at least one of polyvinylamine (PVAm), polyacrylamide, polyacrylic acid (PAA), polymethacrylic acid, chitosan, cationic gelatin, polydiallyldimethylammonium chloride (polyDADMAC), polyallylamine, polyethylenimine, anionic nanocellulose, sodium lignin sulfonate, sodium polyacrylate, anionic polyacrylamide, anionic glyoxalated polyacrylamide, poly-(sodium styrene sulphonate) and poly(vinylphosphonic acid), or a mixture of two or more thereof; preferably said positively charged polyelectrolyte comprises PVAm.

27. The method according to any one of claims 19-26, wherein a concentration of said positively charged polyelectrolyte in said cellulose-based filtering material is 0,001-30 wt-% of a dry weight of said cellulose fibers, preferably 0,005-20 wt-% and more preferred 0,01-10 wt-%.

28. The method according to claim 19-27, wherein at least one cellulose-based filtering material comprising cellulose fibers and a positively charged polyelectrolyte adsorbed on said cellulose fibers is arranged as a last filtering material positioned downstream of said at least one filtering material comprising said adsorbing agent.

29. A filtering system for removing contaminants from a contaminated fluid, wherein said filter system comprising:- At least one cellulose-based filtering material comprising cellulose fibers and a positively charged polyelectrolyte adsorbed on said cellulose fibers,- At least one filtering material comprising an adsorbing agent; and- At least one pouch comprising at least one of said at least one cellulose-based filtering material and said at least one filtering material comprising an adsorbing agent,- Said at least one pouch comprising an inlet upstream of said at least one of said at least one cellulose-based filtering material and said at least one filtering material comprising an adsorbing agent and an outlet downstream of said at least one of said at least one cellulose-based filtering material and said at least one filtering material comprising an adsorbing agent.

30. The filtering system according to claim 29, wherein said positively charged polyelectrolyte is selected from polyvinylamine (PVAm), polyacrylamide,polyacrylic acid (PAA), polymethacrylic acid, chitosan, cationic gelatin, polydiallyldimethylammonium chloride (polyDADMAC), polyallylamine, polyethylenimine, anionic nanocellulose, sodium lignin sulfonate, sodium polyacrylate, anionic polyacrylamide, anionic glyoxalated polyacrylamide, poly- (sodium styrene sulphonate) and / or poly(vinylphosphonic acid), or a mixture of two or more thereof.

31. The filtering system according to claim 29-30, wherein said cellulose fibers comprised in said at least one cellulose-based filtering material are selected from wood pulp, non-wood pulp, regenerated cellulose fibres, plant fibres such as fibres from bamboo, bagasse, cotton, hemp, flax, and jute, and / or mixtures thereof.

32. The filtering system according to any one of claims 29-31, wherein said pouch comprises at least one side wall and bottom portion attached to said at least one wall; said at least one side wall is essentially impermeable to fluids while said bottom portion is permeable to fluids.

33. The filtering system according to claim 32, wherein said at least one side wall and said bottom portion preferably are made of a same material; said material comprising synthetic fibers and / or fibers of natural origin and wherein said synthetic fibers are selected from polyester, elastane and acrylic, and wherein said fibers of natural origin are selected from plant fibres such as fibres from jute, bamboo, bagasse, cotton, hemp, flax, wheat, or mixtures thereof.

34. The filtering system according to any one of claims 32-33, wherein said at least one side wall is essentially impermeable to fluids thanks to being laminated and / or impregnated and / or tightly woven.

35. The filtering system according to any one of claims 32-34, wherein said at least one side wall comprising fibers of natural origin and a positively charged polyelectrolyte adsorbed on said fibers.

36. The filtering system according to any one of claims 29-35, wherein said filtering system further comprising at least one polishing filter upstream of said outlet, preferably said polishing filter comprises a cellulose-based filtering material comprising cellulose fibers and a positively charged polyelectrolyte adsorbed onsaid cellulose fibers; and / or wherein said adsorbing agent comprising at least one of activated carbon, carbon black and graphene.

37. Use of a filtering device as defined in claims 1-18.

38. Use of a filtering system as defined in claims 29-35.

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