Process and five-in-one reactor for water treatment

Abstract

A reactor for water treatment is provided together with a water treatment plant and a process for treating water. The reactor comprises a tank for receiving water to treated, wherein the tank is equipped with an outlet for treated water, wherein the tank comprises a flocculant and a fibrous treatment agent, wherein the flocculant and the fibrous treatment agent cause the formation of fiber-based flocs in the water to be treated, wherein the flocs contain contaminants to be removed from the water to be treated; and a porous means for compressing the flocs, wherein, in use, the porous means for compressing the flocs: compresses the flocs, thus forming and dewatering a compressed sludge made of the flocs, and allows through treated water towards said outlet for treated water of the tank, wherein said treated water has a reduced floc content when compared to the water to be treated.

Description

PROCESS AND FIVE-IN-ONE REACTOR FOR WATER TREATMENT CROSS REFERENCE TO RELATED APPLICATIONSThis application claims benefit, under 35 U.S.C. § 119(e), of U.S. provisional application Serial No. 63 / 745,897, filed on January 16, 2025. All documents above are incorporated herein in their entirety by reference.FIELD OF THE INVENTION

[0001] The present invention relates to a five-in-one reactor and a process for water treatment. More specifically, the present invention is concerned with a reactor that allows 1) coagulation, 2) flocculation, 3) sedimentation / settling, 4) filtration, and 5) sludge dewatering and a process that accomplishes 1) to 5) in a few steps.BACKGROUND OF THE INVENTION

[0002] Many populations around the globe still lack access to safe drinking water and proper infrastructure for wastewater treatment and management1’2. In industrialized countries, urban systems for water transit and sanitation are sewer-based and supported by advanced technologies involving chemistry, microbiology, physical and bioprocess engineering, as well as significant investments from high-income governments. The United Nations Sustainable Development Goals report that more than half of the global population cannot afford proper sanitation and drinking water systems.3This global issue is exacerbated in low- and middle-income countries, where infrastructure dedicated to water management (treatment and transit) is often prohibitively expensive.4Consequently, several developing countries and regions, as well as remote and marginalized communities would greatly benefit from a non-sewered sanitation system combined with decentralized, simple, robust, and inexpensive water treatment processes.

[0003] Drinking water, wastewater, and sludge management applications must all be prioritized to ensure public health in these regions and to reduce endemic disease.5For many small and remote communities in Africa and North America, the high cost of centralized treatment infrastructure limits access to drinking water.67In Canada, drinking water primarily comes from treated surface water (> 70 %)8, which generally requires extensive and costly treatment to sufficiently reduce the microbiological and toxicological risks. The issue of water access primarily affects remote and Indigenous communities.

[0004] Conventional treatment for drinking water production via surface water involves coagulation-flocculation and chemicals such as metal salts, which require careful monitoring for proper operation. The performance of coagulation requires constant monitoring and qualified operators and is sensitive to pH, temperature, dose, and mixing time / intensity, among other factors. Consequently, metal-based coagulants cannot be easily implemented in decentralized systems for remote communities.

[0005] Decentralized, simpler, smaller, more autonomous, and more robust processes could be cheaper than centralized water treatment plants in the long term and could be democratized for drinking water production9to beaccepted and used by communities in need that are currently affected by water scarcity and untreated wastewater.SUMMARY OF THE INVENTION

[0006] In accordance with the present invention, there is provided:1. A reactor for water treatment, the reactor comprising:a tank for receiving water to treated,wherein the tank is equipped with an outlet for treated water,wherein the tank comprises a flocculant and a fibrous treatment agent,wherein the flocculant and the fibrous treatment agent cause the formation of fiber-based flocs in the water to be treated, andwherein the flocs contain contaminants to be removed from the water to be treated; and a porous means for compressing the flocs, wherein, in use, the porous means for compressing the flocs: compresses the flocs, thus forming and dewatering a compressed sludge made of the flocs, and allows through treated water towards said outlet for treated water of the tank,wherein said treated water has a reduced floc content when compared to the water to be treated.2. The reactor of embodiment 1, wherein the flocculant is a cationic flocculant, an anionic flocculant, or a mixture thereof.3. The reactor of embodiment 1 or 2, wherein the flocculant is a cationic flocculant.4. The reactor of embodiment 3, wherein the cationic flocculant is:a cationic polyacrylamide (PAM), such as poly(acrylamide-co-diallyldimethylammonium chloride), poly(acrylamide-co-acryloyloxyethyltrimethylammonium chloride), poly(acrylamide-co- methacryloyloxyethyltrimethylammonium chloride), and poly(acrylamide-co-dimethylaminoethyl methacrylate);a polyamine, such as ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), and polyethylenimine (PEI);polyDADMAC (polydiallyldimethylammonium chloride);chitosan;a quaternary ammonium compound such as cetyltrimethylammonium bromide (ctab), cetyltrimethylammonium chloride (ctac), alkyl trimethylammonium chlorides, and alkyl benzyl dimethylammonium chlorides; and / orsaccharine-based, and / or a polysaccharide-based polymer, and is another organic polymer, preferably a polyacrylamide (PAM),more preferably poly(acrylamide-co-diallyldimethylammonium chloride), poly(acrylamide-co-acryloyloxyethyltrimethylammonium chloride), poly(acrylamide-co-methacryloyloxyethyltrimethylammonium chloride), or poly(acrylamide-co-dimethylaminoethyl methacrylate).The reactor of embodiment 3 or 4, wherein the cationic flocculant has a charge density of at least about 10%, preferably at least about 15%, more preferably at least about 20%, yet more preferably at least about 25%, even more preferably at least about 30%, and most preferably at least about 35%.The reactor of any one of embodiments 3 to 5, wherein a concentration of the cationic flocculant is between about 0.1 and about 5 mg / L, preferably between about 0.4 and about 3 mg / L of water to be treated; most preferably, the concentration of the cationic flocculant is about 1.2 mg / L of water to be treated, preferably when a polyacrylamide is used as the flocculant.The reactor of embodiment 1 or 2, wherein the flocculant is an anionic flocculant.The reactor of embodiment 7, wherein the anionic flocculant is:an anionic polyacrylamide (PAM) such as poly(2-propenamide-co-2-propenoic acid), sodium polyacrylate, poly(acrylamide-co-acrylic acid), or poly(acrylamide-co-maleic acid);a sulfonated polymer such as:a polystyrene sulfonate e.g., sodium polystyrene sulfonate (poly(styrene-4-sulfonic acid), sodium salt), potassium polystyrene sulfonate;calcium polystyrene sulfonate; ora sulfonated polyacrylamide e.g. poly(acrylamide-co-sodium acrylate-co-sodium 2- acrylamido-2-methylpropane sulfonate) and poly(acrylamide-co-sodium 2-acrylamido-2- methylpropane sulfonate); ora lignosulfonate such as calcium lignosulfonate, sodium lignosulfonate, or ammonium lignosulfonate,preferably an anionic polyacrylamide (PAM) such as poly(2-propenamide-co-2-propenoic acid), sodium polyacrylate, poly(acrylamide-co-acrylic acid), or poly(acrylamide-co-maleic acid).9. The reactor of embodiment 7 and 8, wherein a concentration of the anionic flocculant is between about 0.05 and 5 mg / L, preferably between about 0.1 and 1 mg / L of water to be treated.10. The reactor of any one of embodiments 7 to 9, wherein, when a concentration of the flocculant is below about 0.2 mg / L of water to be treated, a porous means for compressing the flocs with a smaller mesh size, for examples about 50 pm mesh size, or smaller is used.11. The reactor of any one of embodiments 1 to 10, wherein the fiber-based flocs are at least about 1000 pm in size.12. The reactor of any one of embodiments 1 to 11, further comprising a coagulant.13. The reactor of embodiment 12, wherein the coagulant is:an inorganic coagulant such as :an aluminum-based coagulant e.g., aluminum sulfate (alum), aluminum chlrohydrate (ACH), or polyaluminum chloride (PAC);an iron-based coagulant e.g., ferric chloride, ferric sulfate, or ferrous sulfate;another inorganic coagulant e.g., sodium aluminate; oran organic coagulant (typically used for applications where the water to be treated has a low concentration or organic contaminants) such as:a polyamine e.g., ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), or polyethylenimine (PEI);polydiallyldimethylammonium chloride (polyDADMAC);chitosan; ora quaternary ammonium compound e.g., cetyltrimethylammonium bromide (CTAB), cetyltrimethylammonium chloride (CTAC), alkyl trimethylammonium chloride, or an alkyl benzyl dimethylammonium chloride.14. The reactor of embodiment 12 or 13, wherein the coagulant is an inorganic coagulant, more preferably an aluminum-based coagulant, and most preferably aluminum sulfate.15. The reactor of embodiment 12 or 13, wherein the coagulant is a prehydrolyzed coagulant such as aluminum chlorohydrate (ACH) or polyaluminum chloride (PAC)..16. The reactor of any one of embodiments 12 to 15, wherein a concentration of the coagulant is between about 0.5 and about 1500 mg / L, preferably between about 10 and about 50 mg / L of water to be treated.17. The reactor of any one of embodiments 1 to 11, being free of alum, preferably free of aluminum-based coagulants, more preferably free of aluminum-based coagulants or iron-based coagulants, yet more preferably free of inorganic coagulants, and most preferably free of any coagulant.18. The reactor of any one of embodiments 1 to 17, wherein the flocculant is an anionic flocculant, preferably an anionic polyacrylamide (PAM).19. The reactor of any one of embodiments 1 to 18, wherein when the reactor comprises an inorganic coagulant, for example a metallic coagulant, the flocculant is an anionic flocculant.20. The reactor of any one of embodiments 1 to 19, wherein the fibrous treatment agent is made of fibers having an average length of at least about 100 pm and an average diameter of at least about 5 pm.21. The reactor of any one of embodiments 1 to 20, wherein the fibrous treatment agent is in the form of single fibers, or fibers assembled in particles (such as microparticles), flakes, aggregates, hydrogels, sponge materials, and / or any other fiber-based materials.22. The reactor of any one of embodiments 1 to 21 , wherein the fibrous treatment agent comprises:cellulosic fibers comprising e.g., cellulose, hemicellulose, and / or lignin,textile fibers such as cotton, polyester, other natural or synthetic textile fibers, and their mixture, and / orkeratin-based fibers.23. The reactor of any one of embodiments 1 to 22, wherein the fibrous treatment agent comprises fibers are recovered from:wastewater from water treatment plants, from the pulp and paper industry (e.g., paper mill sludge), from the textile industry, or from other industries,residues and waste materials, for example:agricultural residues such as straw, bagasse, fibers extracted from agriculture residues (maize and soy), rice husk, and hemp hurds as well as keratin-based fibers from wool and feathers),wood processing residues such as sawdust and wood chips, and Kraft pulp residues, orrecycled materials.24. The reactor of any one of embodiments 1 to 23, wherein the fibrous treatment agent comprises virgin fibers.25. The reactor of any one of embodiments 1 to 24, wherein the fibrous treatment agent comprises pristine fibers, functionalized fibers, or a mixture thereof.26. The reactor of embodiment 25, wherein the functionalized fibers are functionalized with an oxide; an hydroxide; a metal oxide; a metal hydroxide; a metallic element; a carboxyl group; a sulfonyl group; a phosphoryl group; an amine group, such as a quaternary amine group; a coagulant; a flocculant; a polymer; another polar or nonpolar group; and / or another hydrophobic or hydrophilic moiety.27. The reactor of embodiment 25 or 26, wherein the functionalized fibers are functionalized with iron oxide and / or iron hydroxide groups.28. The reactor of any one of embodiments 1 to 27, wherein the fibrous treatment agent is already present in the water to be treated.29. The reactor of any one of embodiments 1 to 28, wherein the fibrous treatment agent is added to the water to be treated, either entirely or to increase the concentration of the fibrous treatment agent.30. The reactor of any one of embodiments 1 to 29, wherein a concentration of the fibrous treatment agent is between about 10 and about 500, preferably between about 50 and about 250 mg / L of water to be treated.31. The reactor of any one of embodiments 1 to 30, wherein the porous means for compressing flocs is a porous medium, for example a sieve, a screen, a mesh, a membrane, or any other porous media, preferably a sieve, a screen, or a mesh, more preferably a screen.32. The reactor of any one of embodiments 1 to 31 , wherein the porous means for compressing flocs is:configured to compress the flocs against a solid surface, for example against a wall of the tank, preferably the bottom of the tank while allowing through treated water; orplaced in a flow path of water to be treated, allowing through treated water towards the outlet for treated water of the tank and catching the flocs, and accompanied by a pump that draws the treated water through said outlet, whereby the negatively pressurized flow of water through the means for compressing flocs compresses the flocs against said means for compressing flocs. 33. The reactor of any one of embodiments 1 to 32, wherein the porous means for compressing flocs divides the tank into a water-to-be-treated section and a treated-water section; is fitted in or next to the outlet for treated water; or is removable, for example being inserted in the tank to compress the flocs when desired.34. The reactor of any one of embodiments 1 to 32, wherein the porous means for compressing flocs is perpendicular to a flow path of water to be treated or inclined with regard to said flow path of water to be treated.35. The reactor of any one of embodiments 1 to 34, wherein the porous means for compressing flocs is flat, tubular, or flexible.36. The reactor of any one of embodiments 1 to 35, wherein the porous means for compressing flocs has a nominal mesh size between about 10 pm and about 10000 pm, preferably a mesh size of about 500 pm and 2000 pm.37. The reactor of any one of embodiments 1 to 36, wherein the outlet for treated water is an opening at the top of the tank, for example the tank has an open top, or an opening on a treated-water side of the means for compressing the flocs, for example an opening at the bottom of the tank, or an opening in a side wall of the tank.38. The reactor of any one of embodiments 1 to 37, further comprising an inlet for water to be treated.39. The reactor of embodiment 38, wherein inlet for water to be treated is an opening at the top of the tank, for example the tank has an open top, or an opening on the water-to-be-treated side of the means for compressing the flocs, for example an opening in a side wall of the tank.40. The reactor of any one of embodiments 1 to 39, further comprising a stirrer or a static mixer.41. The reactor of any one of embodiments 1 to 40, being configured for use in batch mode or in continuous mode.42. The reactor of any one of embodiments 1 to 41 , further comprising a scraper to remove the compressed sludge off the means for compressing flocs and / or from the reactor.43. The reactor of any one of embodiments 1 to 42, further comprising a means for cleaning the means for compressing flocs, for example a waterjet, an air jet, a brush, a scraper, or a combination thereof.44. The reactor of any one of embodiments 1 to 43, being configured for recovering reactants from the flocs or from the compressed sludge or being connected to a second tank for the recovery of reactants from the flocs or from the compressed sludge.45. The reactor of any one of embodiments 1 to 44, the pH in the tank of the reactor or in the second tank is adjusted to fragment the flocs or to remove contaminants from the flocs, for example, increased to 8.5, thus producing contaminant-free flocs.46. The reactor of any one of embodiments 1 to 45, the pH in the tank of the reactor or in the second tank is adjusted to resolubilize the flocculant and coagulant from the contaminant-free flocs.47. The reactor of any one of embodiments 1 to 46, wherein the water to be treated is surface water;groundwater; domestic sewage; industrial effluents; water originating from industrial processes; mining wastewaters; water originating from tailing ponds; water from cooling towers, boilers, and the like); water / sludge originating from agri-food processes; rainwater runoff from urban areas; irrigation runoff; water used in livestock operations; water from coastal areas, or estuaries; seawater; and already treated wastewater.48. The reactor of any one of embodiments 1 to 47, wherein the treated water is drinking water, reclaimed water for non-potable applications, industrial water, treated stormwater, recycled agricultural water, reclaimed water for non-potable applications, and desalinated water for drinking or non-potable applications.49. The reactor of any one of embodiments 1 to 48, wherein the compressed sludge is to be used in feeding livestock.50. The reactor any one of embodiments 1 to 49, being fluidly connected, via a treated water pipe, to a downstream water treatment unit, preferably a disinfection unit, a water softening unit, and / or a tertiary treatment unit, preferably without intervening coagulation unit, flocculation unit, settling unit, or filtration unit.51. The reactor any one of embodiments 1 to 50, being fluidly connected, via a pipe for water to be treated, to an upstream screening unit and / or aeration unit, preferably without intervening coagulation unit, flocculation unit, settling unit, or filtration unit.52. The reactor any one of embodiments 1 to 51 , being configured such that the treated water is treated two or more times in the reactor.53. The reactor any one of embodiments 1 to 52, wherein the reactor is connected in series, downstream from one another, to one or more other reactor as defined in any one of embodiments 1 to 52, so that water treatment in a first reactor is fed to a second reactor and so on.54. The reactor any one of embodiments 1 to 53, being equipped with a recycling loop to feed part of or all the treated water back in the reactor.55. The reactor any one of embodiments 1 to 54, being fluidly connected to a tank for fibrous treatment agent preparation.56. A water treatment plant comprising the reactor of any one of embodiments 1 to 55.57. The water treatment plant of embodiment 56, being free of :a coagulation unit, such as e.g., a coagulation tank,a flocculation unit, such as e.g., a flocculation basin,a settling unit, such as e.g., a settling tank or basin for sedimentation of the flocs,a filtration unit, such as e.g., a granulation or membrane filter for filtration of the flocs and / or other particles, and / ora sludge dewatering unit such as e.g., a centrifuge, a belt filter press, and / or a rotary drum thickener.58. The water treatment plant of embodiment 56 or 57, further comprising, one or more of the following:a screening unit, comprising for example, coarse and fine screen(s) for removing large objects and debris,an aeration unit, such as e.g. a spray or cascading steps,a stabilisation unit (e.g. for pH adjustment),an oxidation unit,a disinfection unit,a water softening unit, orone or more tertiary treatment unit.59. The water treatment plant of any one of embodiments 56 to 58, wherein the reactor is fluidly connected, via a treated water pipe, to a downstream disinfection unit, a water softening unit, and / or a tertiary treatment unit, preferably without intervening coagulation unit, flocculation unit, settling unit, or filtration unit.The water treatment plant of any one of embodiments 56 to 59, wherein the reactor is fluidly connected, via a pipe for water to be treated, to an upstream screening unit and / or aeration unit, preferably without intervening coagulation unit, flocculation unit, settling unit, or filtration unit.A process for treating water using the reactor of any one of embodiments 1 to 55, the process comprising the steps of:adding water to be treated, the flocculant, and the fibrous treatment agent to the tank of the reactor,allowing formation of the fiber-based flocs,using the porous means for compressing the flocs to compress the flocs, thus forming and dewatering the compressed sludge, while allowing treated water through the porous means for compressing the flocs towards said outlet for treated water of the tank.The process of embodiment 61, being free from:a coagulation step other than any coagulation happening in the reactor, such as e.g., using a coagulation tank,a flocculation step other than any flocculation happening in the reactor, such as e.g., using a flocculation basin,a settling step other than that any settling happening in the reactor, such as e.g., using a settling tank or basin for sedimentation of the flocs,a filtration step other than any filtration happening in the reactor, such as e.g., using a granulation or membrane filter for filtration of the flocs and / or other particles, and / ora sludge dewatering step other than any sludge dewatering happening in the reactor, such as e.g., using a centrifuge, a belt filter press, and / or a rotary drum thickener.The process of embodiment 61 or 62, further comprising one or more of the following steps:using a screening unit, comprising for example, coarse and fine screen(s) for removing large objects and debris,using an aeration unit, such as e.g. a spray or cascading steps,using a stabilisation unit (e.g. for pH adjustment),using an oxidation unit,using a disinfection unit,using a water softening unit, orusing one or more tertiary treatment unit.64. The process of any one of embodiment 61 to 63, further comprising a step of treating again water that has already been treated in the reactor.65. The process of any one of embodiment 61 to 64, comprising:using the porous means for compressing flocs to compress the flocs against a solid surface, for example against a wall of the tank, preferably the bottom of the tank; orusing a pump to draw water to be treated through the porous means for compressing flocs, allowing through treated water and catching the flocs, and to draw the treated water through the outlet for treated water, whereby the negatively pressurized flow of water through the means for compressing flocs compresses the flocs against said means for compressing flocs.66. The process of any one of embodiment 61 to 65, wherein the reactor is used in batch mode or in continuous mode.67. The process of any one of embodiment 61 to 66, further comprising a step of recovering the compressed sludge from the means for compressing flocs and / or from the reactor.68. The process of any one of embodiment 61 to 67, further comprising a step of cleaning the means for compressing flocs.69. The process of any one of embodiment 61 to 68, further comprising a step of recovering the fibrous treatment agent, the flocculant and / or the coagulant from the compressed sludge and reusing the fibrous treatment agent, the flocculant and / or the coagulant in the reactor.70. The process of any one of embodiment 61 to 69, further comprising a step of adjusting the pH in the tank to fragment the flocs or to remove contaminants from the flocs, for example, increasing the pH to 8.5 and recovering the contaminant-free flocs.71. The process of any one of embodiment 61 to 70, further comprising a step of adjusting the pH is adjusted to resolubilize the flocculant and coagulant from the contaminant-free flocs, for example decreasing the pH to s 5.5.72. The process of any one of embodiment 61 to 71 , further comprising a step of recovering the fibrous treatment agent for example using a screen (for example, the means for compressing flocs), thus isolating the fibrous treatment agent from a solution of flocculant and coagulant.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] In the appended drawings:Fig. 1 Contaminant removal improvement using fibers, a, Conventional treatment combining polyacrylamide and screening: the flocs formed are too small to be screened and filter press can’t be used to dewater the sludge, b, Fiber-based treatment combining polyacrylamide, fibers, and screening (filter press): the flocs formed are very large and are screenable (filter presses; tested mesh sizes of 20 - 5000 pm), while filter press can be used to dewater the sludge, c, Impact of fibers on the removal of total organic carbon and turbidity after screening, d, Impact of fibers on the removal of nanoplastics, polyester fibers, and polyethylene beads after screening. Treatment conditions (c and d): 0.4 - 3.0 mg c-PAM 3 / L, 200 mg fibers / L, 4 minutes of flocculation at pH 7.0 ± 0.3, temperature of 21 °C, flocs were removed during pressing with a 500 pm screen mesh (lab-scale press filter). Raw water turbidity: 6.0 ± 0.5 NTU. Colored areas (orange and green) are included as eye guides showing the minimal and maximal values (triplicate experiments). The difference between fibrous and conventional treatment (no fibers) was statistically significant (p-value < 0.05; c and d). Tested waters: St Lawrence River (c) and synthetic water (d).Fig. 2 Performance of fibers on different water types, a, c, Impact of fibers on turbidity removal after 3 min of settling (synthetic water (a); DRC B water (c); cfTable 2). b, d, Impact of fibers on turbidity removal after pressing (synthetic water (b); DRC B water (d)). A 500 pm and a 200 pm screen mesh size were used for synthetic water and DRC B water, respectively. Aggregation conditions: 0.4-3.0 mg c-PAM 3 / L, 200 mg fibers / L, 4 minutes of flocculation at pH 7.0 ± 0.3, temperature of 21 °C (a-d). Synthetic water turbidity: 6 NTU (a,b). DRC B water turbidity: 589 NTU (c,d). Dashed lines are included as eye guides connecting average values obtained from duplicate experiments. Grey areas show the industry standard after treatment: < 1.5 NTU after settling and < 0.3 UTN after pressing (screened-based press filter used as an alternative to membrane or granular filtration). The difference between fibrous and conventional treatment (no fibers) was statistically significant (p-value < 0.05; a-d).Fig. 3 Process optimization to reduce the residual turbidity, a, b, Impact of fibers concentration on settled turbidity (a, 3 min of settling) and pressed turbidity (b, 500 pm screen mesh), c, Impact of the screen mesh size (100, 300, 500, 1000, and 2000 pm) on pressed turbidity. Settled turbidites (no screen was used, grey bars) are shown as a reference, d, Impact of smaller screen mesh size (20, 50, and 100 pm) on pressed turbidity. Aggregation conditions (a-d): 1.2 mg C-PAM3 / L, 4 minutes of mixing, pH 7 ± 0.5, temperature of 21°C. Turbidity of synthetic water (a-d): 6.0 ± 0.5 NTU.Fig. 4 Fibers used with physicochemical treatments, a, Impact of polyacrylamide type (cfTable 1) onsettled and pressed turbidity. Paired t-test between c-PAM 3 and c-PAM 4: p-value < 0.05. b, Impact of polyacrylamide charge density on settled and pressed turbidity. Dashed lines are included as eye guides connecting average values obtained from duplicate experiments (b). c,d, Different physicochemical treatments combining alum, c-PAM 3, and a high molecular weight anionic flocculant (a-PAM) for highly and moderately turbid water. Synthetic water: 6 NTU, at pH 7.0 (a,b). DRC B water: 589, at pH 6.1 (c,d). DRC A water: 78 NTU, at pH 6.7 (d). Aggregation conditions: 4 minutes of mixing at 21 °C. Floc separation: 3 minutes of settling or press filtering with a 200 pm screen mesh (a-d). Grey areas show the industry standard after treatment: < 1.5 NTU after settling and < 0.3 UTN after press-filtering (a-d). e, Image of DRC B river (high turbidity and low pH and alkalinity), f, Image of the St. Lawrence River (low turbidity and high pH and alkalinity).Fig. 5 Limiting the use of synthetic flocculant for flocs separation via screening. a,b,c, Pressed turbidity with different screen mesh sizes with 0.2 mg c-PAM / L (a), 0.35 mg c-PAM / L (b), and 1.2 mg c-PAM / L (c). d, Pressed turbidity obtained with different c-PAM concentrations and screen mesh sizes. Settled turbidities in d are shown as a reference (no pressing was performed). Conditions for a-d: 4 minutes of mixing, pH 7 ± 0.5, temperature of 21 °C, 3 minutes of settling (if any), tested screen mesh size: 100, 300, 500, 1000, and 2000 pm. Type of PAM: c-PAM 3. Fiber concentration: 200 mg / L. Turbidity of raw water: 6 ± 0.5 NTU. Dashed lines are included as eye guides connecting average values obtained from duplicate experiments. Fig. 6 Improving sludge dewatering with fibrous agents, a, Impact of fibers and treatment conditions on the sludge solid content (%) without pressing (grey) vs with pressing (green), b, Pressed sludge after the fibrous aggregation treatment (left) and microscope image of the 200 pm screen mesh (right), c, Schematic diagram showing the compression of the fibers-based. DRC B raw water conditions: 589 NTU, pH 7.0, temperature of 21°C. Error bars correspond to the standard deviation calculated from triplicate experiments (a).Fig. 7 shows a reactor according to an embodiment of the invention.Fig. 8 shows a reactor according to another embodiment of the invention.Fig. 9 shows a reactor according to yet another embodiment of the invention.Fig. 10 shows a porous means to compress flocs according to an embodiment of the invention a) installed perpendicular to water flow and b) installed at an angle of the water flow.Fig. 11 shows a porous means to compress flocs according to another embodiment of the invention. Fig. 12 shows a porous means to compress flocs according to yet another embodiment of the invention.DETAILED DESCRIPTION OF THE INVENTION

[0008] Turning now to the invention in more details, there is provided a five-in-one reactor for water treatment. There is also provided a water treatment plant that comprises this reactor. The reactor of invention comprises:a tank for receiving water to treated,o wherein the tank is equipped with an outlet for treated water,o wherein the tank comprises a flocculant and a fibrous treatment agent,o wherein the flocculant and the fibrous treatment agent cause the formation of fiber-based flocs in the water to be treated, ando wherein the flocs contain contaminants to be removed from the water to be treated; and a porous means for compressing the flocs, wherein, in use, the porous means for compressing the flocs:o compresses the flocs, thus forming and dewatering a compressed sludge made of the flocs, and o allows through treated water towards said outlet for treated water of the tank,wherein said treated water has a reduced floc content when compared to the water to be treated.

[0009] A conventional water treatment plant typically comprises equipment to carry out the following treatments:a) Screening: This step removes large objects and debris (such as leaves, branches, or trash) from the contaminated water typically using coarse and fine screens. This prevents damage to the equipment and pipes in the later stages.b) Aeration: This step exposes the water to air typically by spraying or cascading it over cascading steps. This helps to remove dissolved gases (such as carbon dioxide or hydrogen sulfide) that can cause corrosion or bad taste. It also helps to oxidize iron and manganese, which can stain clothes or plumbing fixtures, and to kill some microorganisms.c) Coagulation: In this step, typically carried out in a coagulation tank with rapid mixing, chemicals called coagulants are added to the water to neutralize the charges on suspended particles. This allows the particles to come together and form small clumps known as microflocs. Common coagulants include metal salts such as aluminum sulfate (alum), ferric chloride, and ferric sulfate, and organic polymers such as poly- DADMACs and cationic PAM.d) Flocculation: Flocculation follows coagulation and involves gentle mixing to encourage the microflocs to combine into larger, more easily removable flocs. This process uses flocculants, which can be synthetic polymers (e.g., polyacrylamides), or natural polymers (e.g., starch derivatives, chitosan). The gentle mixing is typically done in flocculation basins with paddle mixers or other slow-mixing devices to ensure the formation of larger flocs that can settle out in the subsequent sedimentation step.e) Sedimentation (settling): The flocs formed in the previous step are easier to remove by sedimentation or filtration than the original small particles. The sedimentation step consists of allowing the water to settle, typically in large settling tanks or basins, such as circular or rectangular clarifiers, where the heavier flocs sink to the bottom and are removed as sludge. The clear water on top is then transferred to the next stage. i. Sludge dewatering: The goal of this step is to reduces the volume of sludge collected from thesettling tanks. It typically uses centrifuges, belt filter presses, and / or rotary drum thickeners to do so.f) Filtration: This step passes the water through a filter that trap any remaining particles or microorganisms.The filters are periodically cleaned by backwashing with air and / or water. Granular filtration systems use rapid sand filters or slow sand filters whereas membrane filtration systems use microfiltration, ultrafiltration, or reverse osmosis systems.g) Disinfection: This step kills any harmful bacteria, viruses, or parasites that may still be present in the water.This is typically done by adding chlorine, chloramine, ozone, or ultraviolet light. The disinfectant also provides residual protection against recontamination during distribution.h) Water softening: This step reduces the hardness of the water by removing calcium and magnesium ions that can cause scaling or interfere with soap action. This is typically done by adding lime or soda ash, which precipitate the hardness ions, or by using ion exchange resins, which replace them with sodium ions. i) Tertiary treatment: Depending on the quality of the raw water and the desired standards of the treated water, some additional methods may be used, such as activated carbon adsorption (to remove organic compounds or taste and odor), reverse osmosis (to remove salts or contaminants), or fluoridation (to prevent tooth decay).

[0010] Very advantageously, the reactor of the invention allows 1) coagulation, 2) flocculation, 3) sedimentation / settling, 4) filtration, and 5) sludge dewatering in a single unit. The reactor of the invention could serve as an alternative to complex and expensive conventional physicochemical treatments, which involve a coagulant, a flocculant, a settling tank, and granular or membrane filtration.

[0011] As will be explained in more details below, the reactor of the invention improves water treatment and sludge dewatering. Firstly, the presence of the fibrous treatment agent allows for the formation of large fiber-based flocs that are at least 5 times larger (up to 32 times larger) in volume than conventional flocs formed without fibrous treatment agent. This allows:• efficient floc separation using the porous means for compressing the flocs (e.g., a screen) without the need for settling or a filtration system,• sludge dewatering using the same porous means for compressing the flocs without further chemical addition, and• when the reactor comprises a means porous means for compressing the flocs based on centipede force, such as a rotary press filter, the fibrous treatment increases sludge dewatering.

[0012] More specifically, the reactor of the invention allows for in situ sludge dewatering, that is sludge dewatering where the sludge itself is formed (or where its components e.g., the flocs, are formed). Indeed, as noted above, the porous means for compressing the flocs compresses the flocs, thus forming and dewatering a compressed sludge made of the flocs and allows through treated water towards said outlet for treated water of thetank. That is to say that the both the treated water and the compressed (dewatered) sludge are formed in said tank. In situ sludge dewatering is not possible in the absence of the fibrous treatment agent. Comparing the two methods (with and without the porous means for compressing the flocs), the differences are noticeable, compressing the flocs yielding an 11 -fold higher solid content in sludge: from 0.3% for the conventional treatment to 3.5% (Figures 6a and 7a).

[0013] In addition, the flocs are so big that the coarseness of the porous means for compressing the flocs (e.g., a screen) has, in many cases, a limited impact on floc removal as the flocs are caught even by relatively coarse screens e.g., 2000 pm mesh size. However, smaller mesh sizes (e.g., 500 pirn and even, in some cases, 50 and 20 pm) are preferred for improved removal of e.g., colloids not captured in the flocs.

[0014] Furthermore, compared to settling, compressing the flocs using the porous means for compressing the flocs of the reactor of the invention allows recovery of more solid matter e.g., up to 11 times more. Such increase could considerably reduce the overall costs associated with sludge treatment, such as reducing the amount of sludge transported and the energy input during thermal drying, among others. Such applications could benefit both centralized and decentralized wastewater systems by offering significant advantages in terms of public health, environmental sustainability, and operational efficiency.

[0015] Notably, sludge dewatering account for a significant portion of the total operating costs in a water treatment plant. In fact, it can range from 30 to 40% of the total costs, depending on the size of the plant and the characteristics of the wastewater being treated.

[0016] Very low turbidities were measured after floc separation in this manner with no need for membrane or granular filtration systems. The addition of fibrous treatment agent drastically improved the floc removal (from 39% to 94%). In fact, the reactor of the invention produced treated water with turbidity levels below 0.2 NTU, thereby complying with drinking water regulations in North America. The drinking water minimal standard (< 0.5 NTU) was not achieved when screens were used with flocculant in the absence of the fibrous treatment agent. The replacement of membrane or granular filtration systems with a simple porous means for compressing the flocs (e.g., a screen) is quite remarkable.

[0017] Quite remarkably, the reactor of the invention allows producing drinking water according to the strictest standards (those of USEPA), without using granular or membranar filtration, just by using a coarse screen.

[0018] Advantageously, except in very challenging cases, the reactor of the invention does not require a coagulant, such as metal-based coagulant, e.g., alum. In contrast, conventional treatment requires large amounts of both metal-based coagulants (e.g., alum) and synthetic flocculants.

[0019] Synthetic polymers flocculants, such as acrylamide-based polymers, have faced criticism for their i) potential toxicity (group 2A), ii) clogging effect, and Hi) cost. For implementation in marginalized communities and developing countries, the reactor should be operated at low cost (low OPEX), and systemic / heavy reactor maintenance (to avoid clogging) must be avoided. As such it is advantageously to be able to reduce polymers flocculant concentration when desired. Interestingly, in cases when a minimal concentration of the flocculant isdesired, the undesirably effect of a suboptimal concentration of flocculant (e.g., the formation of smaller and / or more fragile flocs) can be easily compensated, up to a point, by using a finer means for compressing the flocs (e.g., a finer screen).

[0020] The addition of the fibrous treatment agent significantly improved the removal of regulated and emerging contaminants. Indeed, the use of fibrous treatment agent also significantly improved the removal of total organic carbon, nanoplastics (from 20% to 72%), and microplastics (from 49 % to 91 % for polyethylene and from 64 % to 95 % for polyester). Since microplastic and nanoplastics can be used to model and predict virus removal during filtration, the reactor of the invention could be used for drinking water application to offer some protection against viruses and other pathogens. For drinking water applications, the reactor of the invention could be combined with a disinfection unit, for example using chlorine. Advantageously, optimizing the flocculant and fibrous treatment agent selection and concentration as well as the mesh size of the porous means for compressing the flocs would allow reducing the amount of disinfectant needed for providing safer drinking water, thus reducing disinfection by-product formation. This could be especially helpful in marginalized communities and developing countries.

[0021] The reactor of the invention is thus suitable for producing safer drinking water, wastewater applications, and sludge dewatering. It offers a cost-effective solution compared to granular or membrane filtration systems, which require qualified operators and more maintenance.

[0022] Because of these good performances, the reactor could be used in situ for decentralized water treatment in drinking water and wastewater applications in small cities, marginalized communities, and developing countries. The reactor, which also performs in situ sludge dewatering, would reduce the risks associated with mismanaged sludge to the environment and human health.

[0023] The reactor of the invention is thus efficient, compact, and affordable, in particular affordable enough for small, remote, or marginalized communities, as well as an alternative to conventional centralized water treatment plants that use sequential tanks for 1) coagulation, 2) flocculation, 3) sedimentation / settling, and 5) sludge dewatering as well as 4) a filtration system for the treatment of surface water.

[0024] Finally, the fiber-based floc in the compressed sludge produced by the reactor of the invention can be treated as explained below, to recover the flocculant, the coagulant (if any), the contaminants (for disposal). The recovered fibrous treatment agent thus regenerated can be reused in the reactor of the invention. All of this reduces costs as well as the environmental impact of water treatment. In fact, the fibrous treatment agent can even be reused without prior cleaning up to the point where it is saturated in contaminant.The reactor of the invention in the context of a water treatment plant

[0025] Because the reactor of the invention allows 1) coagulation, 2) flocculation, 3) sedimentation / settling, 4) filtration, and 5) sludge dewatering in a single unit, the water treatment plant of the invention is preferably free of the conventional equipment for carrying any one of (preferably all of) 1) to 5). In embodiments, the water treatment plant is free of :1) a coagulation unit, such as e.g., a coagulation tank,2) a flocculation unit, such as e.g., a flocculation basin,3) a settling unit, such as e.g., a settling tank or basin for sedimentation of the flocs,4) a filtration unit, such as e.g., a granulation or membrane filter for filtration of the flocs and / or other particles, and / or5) a sludge dewatering unit such as e.g., a centrifuge, a belt filter press, and / or a rotary drum thickener.

[0026] In embodiments, the water treatment plant of the invention could comprise in addition to the reactor of the invention, one or more of the following:optionally a screening unit, comprising for example, coarse and fine screen(s) for removing large objects and debris,optionally, an aeration unit, such as e.g. a spray or cascading steps,optionally, a stabilisation unit (e.g. for pH adjustment),optionally, an oxidation unit,optionally, a disinfection unit,optionally, a water softening unit, oroptionally, one or more tertiary treatment unit.

[0027] In embodiments, the reactor of the invention is fluidly connected, via a treated water pipe, to a downstream water treatment unit, preferably a disinfection unit, a water softening unit, and / or a tertiary treatment unit, preferably without intervening coagulation unit, flocculation unit, settling unit, or filtration unit. For drinking water applications, a disinfection unit is preferred, alone or with a water softening unit, and / or a tertiary treatment unit.

[0028] In embodiments, the reactor of the invention is fluidly connected, via a pipe for water to be treated, to an upstream screening unit and / or aeration unit, preferably without intervening coagulation unit, flocculation unit, settling unit, or filtration unit.

[0029] In embodiments, the reactor of the invention is connected to next conventional step for such sludge. For example, the sludge can be used as a fertilizer in agriculture, sent to a landfill, or incinerated. When the sludge originates from agri-food processes, it can be reused as dry food for livestock.

[0030] As noted above, the treated water has a reduced floc content when compared to the water to be treated. In preferred embodiments, the treated water is free of flocs.

[0031] In embodiments, the treated water can be treated again in the reactor of the invention. In such embodiments, the reactor is configured such that the treated water is treated two or more times in the reactor of the invention. In embodiments, two of more reactors of the invention are connected in series, downstream from one another, so that water treatment in a first reactor of the invention is fed to a second reactor of the invention and soon. Alternatively, or additionally, the reactor of the invention may be equipped with a recycling loop to feed part of or all the treated water back in the reactor of the invention.

[0032] In embodiments, the reactor of the invention is fluidly connected to a tank for fibrous treatment agent preparation. Dry fibers can be added to this tank, wetted, hydrolyzed, and dispersed (forming a suspension), for example using a blender.The water to be treated

[0033] The reactor of the invention can treat any type of water. In embodiments, the water to be treated is surface water (from rivers, lakes, and reservoirs); groundwater; domestic sewage; industrial effluents; water originating from industrial processes; mining wastewaters; water originating from tailing ponds; water from cooling towers, boilers, and the like); water / sludge originating from agri-food processes; rainwater runoff from urban areas; irrigation runoff; water used in livestock operations; water from coastal areas, or estuaries; seawater; and already treated wastewater.

[0034] The treated water produced by the reactor can be of various natures depending on the water to be treated used. In embodiments, the treated water is drinking water, reclaimed water for non-potable applications, industrial water, treated stormwater, recycled agricultural water, reclaimed water for non-potable applications, and desalinated water for drinking or non-potable applications.

[0035] Each of the water to be treated can be treated for various purposes and to produce various treated waters. The table below list the most common purpose for treating each type of water.

[0036] In the embodiments in which the compressed sludge is to be used in feeding livestock. Food grade reactant should be used. Corn residues could be used as the fibrous treatment agent and saccharine-based flocculant could be used.The flocculant, fiber-based flocs, fibrous treatment agent, and others

[0037] As noted above, the reactor of the invention comprises a flocculant, this flocculant can be a cationic flocculant, an anionic flocculant, or a mixture thereof. Such flocculants are well known to the skilled person. They carry a positive or a negative charge and are used to aggregate and settle suspended particles in water by neutralizing the negative or the positive charges on the particles, which helps them clump together into larger flocs that can be more easily removed through sedimentation or filtration.

[0038] In preferred embodiments, the flocculant is a cationic flocculant. In alternative embodiments, the flocculant is an anionic flocculant.

[0039] In embodiments, the cationic flocculant is:a cationic polyacrylamide (PAM), such as poly(acrylamide-co-diallyldimethylammonium chloride), poly(acrylamide-co-acryloyloxyethyltrimethylammonium chloride), poly(acrylamide-co- methacryloyloxyethyltrimethylammonium chloride), and poly(acrylamide-co-dimethylaminoethyl methacrylate);a polyamine, such as ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), andpolyethylenimine (PEI);polyDADMAC (polydiallyldimethylammonium chloride);chitosan;a quaternary ammonium compound such as cetyltrimethylammonium bromide (ctab), cetyltrimethylammonium chloride (ctac), alkyl trimethylammonium chlorides, and alkyl benzyl dimethylammonium chlorides; and / orsaccharine-based, and / or a polysaccharide-based polymer, and is another organic polymer.

[0040] In preferred embodiments, the cationic flocculant is a polyacrylamide (PAM), such as poly(acrylamide-co-diallyldimethylammonium chloride), poly(acrylamide-co-acryloyloxyethyltrimethylammonium chloride), poly(acrylamide-co-methacryloyloxyethyltrimethylammonium chloride), and poly(acrylamide-co-dimethylaminoethyl methacrylate).

[0041] Preferred cationic flocculants have a charge density of at least about 10%, preferably at least about 15%, more preferably at least about 20%, yet more preferably at least about 25%, even more preferably at least about 30%, and most preferably at least about 35%. Indeed, it seems that these higher charge densities allowed increase colloid destabilization and attachment onto the fibrous treatment agent structure.

[0042] The concentration of the cationic flocculant will depend on the water to be treated and the nature of the flocculant. In embodiments, the cationic flocculant concentration is between about 0.1 and about 5 mg / L, preferably between about 0.4 and about 3 mg / L of water to be treated. Most preferably, the flocculant concentration is about 1.2 mg / L of water to be treated, especially for polyacrylamides.

[0043] In embodiments, the anionic flocculant is:an anionic polyacrylamide (PAM) such as poly(2-propenamide-co-2-propenoic acid), sodium polyacrylate, poly(acrylamide-co-acrylic acid), or poly(acrylamide-co-maleic acid);a sulfonated polymer such as:o a polystyrene sulfonate e.g., sodium polystyrene sulfonate (poly(styrene-4-sulfonic acid), sodium salt), potassium polystyrene sulfonate;o calcium polystyrene sulfonate; oro a sulfonated polyacrylamide e.g. poly(acrylamide-co-sodium acrylate-co-sodium 2-acrylamido-2- methylpropane sulfonate) and poly(acrylamide-co-sodium 2-acrylamido-2-methylpropane sulfonate); ora lignosulfonate such as calcium lignosulfonate, sodium lignosulfonate, or ammonium lignosulfonate.

[0044] Preferred anionic flocculants include anionic polyacrylamide (PAM) such as poly(2-propenamide-co-2-propenoic acid), sodium polyacrylate, poly(acrylamide-co-acrylic acid), or poly(acrylamide-co-maleic acid).

[0045] The concentration of the anionic flocculant will depend on the water to be treated and the nature of theflocculant. In embodiments, the anionic flocculant concentration is between about 0.05 and about 5 mg PAM / L, preferably between about 0.1 and about 1 mg / L of water to be treated.

[0046] In embodiments in which lower flocculant concentrations are used (e.g., below about 0.2 mg / L of water to be treated), a porous means for compressing the flocs with a smaller mesh size, for examples about 50 pm mesh size or smaller is advantageously used.

[0047] As noted above, the flocculant together with the fibrous treatment agent create fiber-based flocs. These are typically at least about 1000 pm in size. In contrast, in similar conditions but in the absence of the fibrous treatment agent, the flocs are smaller since their size is limited by the size of flocculant used i.e., that is less than about 100 nm. Further, these conventional flocs are not fiber-based but rather merely comprise the flocculant, the coagulant and the contaminants.

[0048] In embodiments, the reactor further comprises a coagulant. Coagulants are typically not needed but they can improve aggregation and lower turbidity of the treated water. Coagulants are better used for challenging waters to be treated.

[0049] In embodiments, the coagulant is:an inorganic coagulant such as :o an aluminum-based coagulant e.g., aluminum sulfate (alum), aluminum chlrohydrate (ACH), or polyaluminum chloride (PAC);o an iron-based coagulant e.g., ferric chloride, ferric sulfate, or ferrous sulfate;o another inorganic coagulant e.g., sodium aluminate; oran organic coagulant (typically used for applications where the water to be treated has a low concentration or organic contaminants) such as:o a polyamine e.g., ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), or polyethylenimine (PEI);o polydiallyldimethylammonium chloride (polyDADMAC);o chitosan; oro a quaternary ammonium compound e.g., cetyltrimethylammonium bromide (CTAB), cetyltrimethylammonium chloride (CTAC), alkyl trimethylammonium chloride, or an alkyl benzyl dimethylammonium chloride.

[0050] In preferred embodiments, the coagulant is an organic coagulant. In alternative preferred embodiments, the coagulant is an inorganic coagulant, preferably an aluminum-based coagulant, and most preferably aluminum sulfate. In alternative embodiments, the coagulant is a prehydrolyzed coagulant such as ACH or PAC.

[0051] The concentration of the coagulant will depend on the water to be treated and the nature of the coagulant.In embodiments, the coagulant concentration is between about 0.5 and about 1500 mg / L, preferably between about 10 and about 50 mg / L of water to be treated.

[0052] In preferred embodiments, the reactor is free of a coagulant, preferably free of inorganic coagulants, preferably free of aluminum-based coagulants or iron-based coagulants, more preferably free of aluminum-based coagulants, and most preferably free of alum. In such embodiments, the flocculant is preferably an anionic flocculant, most preferably an anionic polyacrylamide (PAM). These acts as flocculants because of their relatively high molecular weight, but also act as coagulants because of their charge.

[0053] Typically, when an inorganic coagulant, for example a metallic coagulant is used, an anionic flocculant is preferably used.

[0054] The fibrous treatment agent is made of fibers having an average length of at least about 100 pm and an average diameter of at least about 5 pm.

[0055] In preferred embodiments, the fibrous treatment agent is preferably as defined in WO 2022 / 170419, incorporated herein by reference.

[0056] In embodiments, the fibrous treatment agent is in the form of single fibers, or fibers assembled in particles (such as microparticles), flakes, aggregates, hydrogels, sponge materials, and / or any other fiber-based materials.

[0057] In embodiments, the fibrous treatment agent comprises:• cellulosic fibers comprising e.g., cellulose, hemicellulose, and / or lignin,• textile fibers such as cotton, polyester, other natural or synthetic textile fibers, and their mixture, and / or • keratin-based fibers.

[0058] In embodiments, the fibers are recovered from:• wastewater from water treatment plants, from the pulp and paper industry (e.g., paper mill sludge), from the textile industry, or from other industries,• residues and waste materials, for example:o agricultural residues such as straw, bagasse, fibers extracted from agriculture residues (maize and soy), rice husk, and hemp hurds as well as keratin-based fibers from wool and feathers), o wood processing residues such as sawdust and wood chips, ando Kraft pulp residues, or• recycled materials.In alternative embodiments, the fibers are virgin fibers, that is fibers made from raw, processed or unprocessed materials and have not been previously used or recycled.

[0059] Alternatively, the fibrous treatment agent can be obtained commercially in dry form or in wet form. Whenprovided in dry form, the above tank for fibrous treatment agent preparation can be used. Alternatively, the fibrous treatment agent could be already present in the water to be treated.

[0060] The fibers can be pristine or functionalized. Herein, the term “pristine” refers to fibers that are free of any functionalization or chemical modification. The fibers can be a mixture of pristine or functionalized fibers.

[0061] When functionalized, the fibers are preferably functionalized with oxides; hydroxides; metal oxides; metal hydroxides; metallic elements; carboxyl groups; sulfonyl groups; phosphoryl groups; amine group, such as quaternary amine groups; coagulants; flocculants; polymers; other polar and nonpolar groups; and / or other hydrophobic or hydrophilic moieties.

[0062] In preferred embodiments, the fibers are functionalized with iron oxide and / or iron hydroxide groups.

[0063] In embodiments, the fibrous treatment agent is already present in the water to be treated (e.g., domestic wastewater that contains textile fibers, or wastewater from the pulp & paper industry containing cellulose / lignin fibers). In alternative embodiments, the fibrous treatment agent is added to the water to be treated, either entirely or to increase the concentration of the fibrous treatment agent.

[0064] The fibrous treatment agent can be tuned in terms of size, density, surface area, and surface chemistry to be optimal to the specific type of contamination that needs to be treated.

[0065] The concentration of the fibrous treatment agent will depend on the water to be treated and the nature of the fibrous treatment agent. In embodiments, the fibrous treatment agent concentration is between about 10 and about 500, preferably between about 50 and about 250 mg / L of water to be treated.The porous means for compressing the flocs

[0066] In embodiments, the porous means for compressing flocs is a porous medium, for example a sieve, a screen, a mesh, a membrane, or any other porous media, preferably a sieve, a screen, or a mesh, more preferably a screen.

[0067] In embodiments, the porous means for compressing flocs is:a) configured to compress the flocs against a solid surface, for example against a wall of the tank, preferably the bottom of the tank (much like a French press for coffee) while allowing through treated water; orb) placed in the flow path of water to be treated, allowing through treated water towards the outlet for treated water and catching the flocs, and accompanied by a pump drawing treated water through said outlet, whereby the negatively pressurized flow of water through the means for compressing flocs compresses the flocs against said means for compressing flocs.

[0068] The porous means for compressing flocs can be positioned in different ways in the reactor. It can divide the tank into a water-to-be-treated section and a treated-water section (Figure 8); it can be fitted in or next to theoutlet for treated water (Figure 7), or it can be removable (Figure 9). In the latter case, it can be inserted in the tank to compress the flocs when desired.

[0069] The porous means for compressing flocs can be oriented in the reactor in various ways. The porous means for compressing flocs can be perpendicular to the flow path of water to be treated (Figure 10A) or it can be inclined with regard to this flow path (Figure 10B). The angle between the porous means for compressing flocs and the flow path of water to be treated is not particularly limited. Indeed, Figure 10A shows flat screen 30 that is perpendicular to the flow path of water to be treated (black arrow). Flocs accumulate and are compressed on top of flat screen 30 by virtue of the flow of water through the screen. Figure 8 shows a similarly arranged flat screen 26 that is vertical and perpendicular to the flow path of water to be treated (black arrow). The flocs accumulate on the side of flat screen 26. Figure 10B shows flat screen 30 inclined with regard to the flow path of water to be treated (black arrow). Flocs accumulate and are compressed on the side of flat screen 30 by virtue of the flow of water through the screen. The flocs are eventually dislodged by this flow of water falling and accumulating at the bottom of flat screen 30. This is useful when the reactor is in continuous mode.

[0070] The porous means for compressing flocs can adopt various configurations. The porous means for compressing flocs can be flat (Figure 10A and B), tubular (Figure 11) or flexible (Figure 12). Indeed, Figures 10A and B, already discussed, show flat screen 30. Figure 11 shows tubular sieve 32 longitudinally traversed by the flow path of water to be treated (black arrow). The water to be treated (white treated) crossed through tubular sieve 32. Tubular sieve 32 may rotate around its longitudinal axis, thus being a rotary sieve or rotary press filter. Figure 12 shows flexible mesh 34 draped as a continuous mesh around a pair of rollers 36. Scraper 38 lifts the flocs off tubular mesh 32.

[0071] In embodiments, the porous means for compressing flocs, whether it is a sieve, a screen, a mesh, a membrane, or any other porous media, has a nominal mesh size between about 10 pm and about 10000 pm, preferably a mesh size of about 500 pm and 2000 pm. The nominal mesh size being the width of an opening in the mesh as shows in Figure 6B.

[0072] It should be noted that the flocs accumulating on the porous means for compressing flocs will result in an effective mesh size that is smaller than the nominal mesh size. This phenomenon is illustrated in Figure 10A and 10B.

[0073] As explained above, the nominal mesh size can be adjusted as needed depending on the water to the treated and the reactants in the reactor. Typically, smaller mesh size (such as 20 and 50 pm) may remove more flocs than larger mesh size. Particularly, when the flocculant concentration is reduced, mesh size may advantageously be reduced as well. For example, a nominal mesh size of about 20 pm or about 50 pm can be used.

[0074] Furthermore, the pH in the reactor can be adjusted to optimize results.Reactor Configurations

[0075] As noted above, the tank of the reactor is equipped with an outlet for treated water. This outlet can belocated in various position depending on the exact design of the reactor. In embodiments, the outlet is an opening at the top of the tank, for example the tank has an open top, or an opening on the treated side of the means for compressing the flocs, for example an opening at the bottom of the tank, or an opening in a side wall of the tank.

[0076] In embodiments, the tank of the reactor is further equipped with an inlet for treated water. In embodiments, this inlet is an opening at the top of the tank, for example the tank has an open top, or an opening on the water-to-be-treated side of the means for compressing the flocs, for example an opening in a side wall of the tank.

[0077] In embodiments, the reactor further comprises a stirrer or a static mixer. Non-limiting examples of stirrers include: anchor agitators (resembles a ship's anchor), paddle agitators (flat blades attached to a central shaft), turbine agitators (multiple flat blades mounted on a central hub), propeller agitators (similar to a boat propeller), helical ribbon agitators (helical ribbons wrapped around a central shaft), magnetic stirrers (uses a magnetic field to rotate a stir bar), high-shear mixers, static mixers (fixed elements within a pipe), and vortex mixers. The mixing conditions (time and intensity) are ideally adjusted to minimize shear stress on flocs and prevent floc breakage.

[0078] The reactor can be configured to be used in batch mode, for example see figure 9, or in continuous mode, see for examples figures 7 and 8.

[0079] The size of the reactor is not particularly limited. It can be at laboratory scale (typically less than 1 liter in volume), bench scale (typically 1 to 10 liters in volume), pilot scale (typically 10 to 1,000 liters in volume), demonstration scale (typically 1,000 to 10,000 liters in volume), or commercial scale (typically greater than 10,000 liters in volume).

[0080] The aggregation time and settling time can be adjusted as needed. In batch mode, this can be done simply by waiting before using the porous means for compressing the flocs. In continuous mode, the flow rater of water to be treated in the reactor and treated water out of the reactor can be increased or decreased as needed.

[0081] In embodiments, the reactor is equipped with a scraper to remove the compressed sludge off the means for compressing flocs and / or from the reactor.

[0082] In embodiments, the reactor is equipped with a means for cleaning the means for compressing flocs. This can be a waterjet, an air jet, a brush, a scraper, or a combination thereof. In alternative embodiments, for example when using a rotary press filter, the flocs can fall off the means for compressing flocs by inertia. For example, in Figure 12, the scraper 38 would be eliminated and flexible mesh 34 would rotate fast enough for the flocs to “fly off” the mesh.

[0083] Figure 7 shows an embodiment of the reactor of the invention, comprising a tank 10 containing water to be treated up to a water level 12. The tank is equipped with a mechanical stirrer 14. The water to be treated is mixed with the flocculant and the fibrous treatment agent. The tank is equipped with means for compressing flocs in the tank, which in this case, is a screen 16 obstructing a treated water outlet located at the bottom of the tank. Treated water is drawn from the outlet using a pump (not shown). Thus located, screen 16 is in the flow path of water (blackarrow) out of the tank. The flow of the water out of the tank passes through screen 16 and drags the flocs toward the bottom of the tank, and compresses the flocs against screen 16. The tank 10 has an inlet at the top of the tank; this inlet is simply the open top of the tank.

[0084] Figure 8 shows another embodiment of the reactor of the invention, comprising a tank 10 containing water to be treated up to a water level 12. The tank is equipped with a mechanical stirrer 14. The tank is also equipped with an inlet 18 for water to be treated and an outlet 22 for treated water, each equipped with a valve 20, 24. The water to be treated is mixed with the flocculant and the fibrous treatment agent. The tank is equipped with means for compressing flocs in the tank, which in this case, is a screen 26 located between inlet 18 in a wall of the tank on a water-to-be-treated side of screen 26 and outlet 22 in a wall of the tank located on a treated water side of screen 26. Treated water is drawn from the outlet 22 using a pump (not shown). The screen 26 obstructs the flow path of treated water (black arrow) from inlet 18 toward outlet 22. The flow of the treated water passes through screen 26 and drags and compresses the flocs against screen 26. In alternative embodiments, screen 26 can be inclined rather than vertical as shown in Figure 8. Preferably, as illustrated in Figure 8, inlet 18 is toward to top of the wall while outlet 22 is towards the bottom of the wall.

[0085] Figure 9 shows yet another embodiment of the reactor of the invention, comprising a tank 10 containing water to be treated up to a water level 12. The tank is equipped with a mechanical stirrer 14. It has an inlet and an outlet at the top of the tank (open top). The tank is also equipped with an outlet 22 for treated water equipped with a valve 24. The water to be treated is mixed with the flocculant and the fibrous treatment agent. The tank is equipped with means for compressing flocs in the tank, which in this case, is a screen 28 mounted on a shaft that is pushed from top to bottom in the tank 10 (white arrow), compressing the flocs at the bottom of tank 10. The flow of treated water through screen 28 is shows as black arrows. The supernatant (treated water) is then collected from the top of the tank.Reactant recovery

[0086] The compressed sludge formed in the reactor is made of flocs comprising the fibrous treatment agent, the flocculant, the coagulant (if any was used), and contaminants.

[0087] Typically, the fibrous treatment agent (with flocculant, coagulant, and contaminants mixed in) can be reused as is in the reactor of the invention. For example, it can be reused 5 to 10 times.

[0088] However, once the fibrous treatment agent is saturated in contaminants, it should be either discarded or treated to remove the contaminants and thus recover the fibrous treatment agent, and preferably the flocculant and coagulant as well.

[0089] Therefore, in embodiments, the reactor being configured for recovering reactants from the flocs or from the compressed sludge or is connected to a second tank for the recovery of reactants from the flocs or from the compressed sludge. The fibrous treatment agent, the flocculant, the coagulant can thus be separated from the contaminant and, optionally, from each other and then reused. Indeed, once the contaminants are removed, thefibrous treatment agent (with flocculant and coagulant mixed in) can be reused in the reactor of the invention. Alternatively, the fibrous treatment agent can be further treated to separate the fibrous treatment agent, the flocculant, and the coagulant from each other. Then, each of them can be reused in the reactor of the invention.

[0090] In embodiments, the pH in the tank is adjusted to fragment the flocs or to remove contaminants from the flocs (i.e. by removing contaminants from the fibers), for example, increased to 8.5. At this pH, metallic hydroxides and resolubilized and contaminant desorb from the flocs. Clean flocs can then be recovered for example using a screen (for example, the means for compressing flocs).

[0091] In embodiments, the pH in the tank is adjusted to resolubilize the flocculant and coagulant from the contaminant-free flocs, for example decreased to s 5.5. The fibrous treatment agent can then be recovered for example using a screen (for example, the means for compressing flocs) and reused, while the solution of flocculant and coagulant can be reused.Process for treating water

[0092] There is also provided a process for treating water using this reactor. The process comprises the steps of:a) adding water to be treated, the flocculant, and the fibrous treatment agent to the tank of the reactor,b) allowing formation of the fiber-based flocs,c) using the porous means for compressing the flocs to compress the flocs, thus forming and dewatering the compressed sludge, while allowing treated water through the porous means for compressing the flocs towards said outlet for treated water of the tank.

[0093] In the process of the invention, the reactor, the water to be treated, the treated water, the flocculant, the coagulant, the fibrous treatment agent, the fiber-based flocs, etc. are as defined above.

[0094] In embodiments, the process is free from:a coagulation step other than any coagulation happening in the reactor, such as e.g., using a coagulation tank,a flocculation step other than any flocculation happening in the reactor, such as e.g., using a flocculation basin,a settling step other than that any settling happening in the reactor, such as e.g., using a settling tank or basin for sedimentation of the flocs,a filtration step other than any filtration happening in the reactor, such as e.g., using a granulation or membrane filter for filtration of the flocs and / or other particles, and / ora sludge dewatering step other than any sludge dewatering happening in the reactor, such as e.g., using a centrifuge, a belt filter press, and / or a rotary drum thickener.

[0095] In embodiments, the process further comprises a step of:optionally using a screening unit, comprising for example, coarse and fine screen(s) for removing large objects and debris,optionally, using an aeration unit, such as e.g. a spray or cascading steps,optionally, using a stabilisation unit (e.g. for pH adjustment),optionally, using an oxidation unit,optionally, using a disinfection unit,optionally, using a water softening unit, oroptionally, using one or more tertiary treatment unit (wherein the tertiary treatment unit is as described above).

[0096] In embodiments, the process further comprises a step of treating again treated water one or more times in the reactor of the invention.

[0097] In embodiments, the process of the invention comprises:using the porous means for compressing flocs to compress the flocs against a solid surface, for example against a wall of the tank, preferably the bottom of the tank (much like a French press for coffee); or using a pump to draw water to be treated through the porous means for compressing flocs, allowing through treated water and catching the flocs, and to draw the treated water through the outlet for treated water, whereby the negatively pressurized flow of water through the means for compressing flocs compresses the flocs against said means for compressing flocs.

[0098] In embodiments, the reactor is used in batch mode or in continuous mode.

[0099] In embodiments, the process further comprises recovering the compressed sludge from the means for compressing flocs and / or from the reactor.

[0100] In embodiments, the process further comprises cleaning the means for compressing flocs.

[0101] In embodiments, the process further comprises recovering the fibrous treatment agent, the flocculant and / or the coagulant from the compressed sludge and reusing the fibrous treatment agent, the flocculant and / or the coagulant in the reactor.

[0102] In embodiments, the process further comprises adjusting the pH in the tank to remove contaminants from the flocs, for example, increasing the pH to 8.5 and recovering the contaminant-free flocs.

[0103] In embodiments, the process further comprises adjusting the pH is adjusted to resolubilize the flocculant and coagulant from the contaminant-free flocs, for example decreasing the pH to s 5.5.

[0104] In embodiments, the process further comprises recovering the fibrous treatment agent for example using ascreen (for example, the means for compressing flocs), thus isolating the fibrous treatment agent from a solution of flocculant and coagulant.

[0105]

[0106] In embodiments, the process further comprises reusing the recovered fibrous treatment agent and / or reusing the solution of flocculant and coagulant.Definitions

[0107] The use of the terms "a" and "an" and "the" and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context.

[0108] The terms "comprising", "having", "including", and "containing" are to be construed as open-ended terms (i.e., meaning "including, but not limited to") unless otherwise noted. In contrast, the phrase “consisting of” excludes any unspecified element, step, ingredient, or the like. The phrase “consisting essentially of” limits the scope to the specified materials or steps and those that do not materially affect the basic and novel characteristic(s) of the invention.

[0109] Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All subsets of values within the ranges are also incorporated into the specification as if they were individually recited herein.

[0110] All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context.

[0111] The use of any and all examples, or exemplary language (e.g., "such as") provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed.

[0112] No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

[0113] Herein, the term "about" has its ordinary meaning. In embodiments, it may mean plus or minus 10% or plus or minus 5% of the numerical value qualified.

[0114] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0115] Other objects, advantages and features of the present invention will become more apparent upon reading of the following non-restrictive description of specific embodiments thereof, given by way of example only with reference to the accompanying drawings.DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0116] The present invention is illustrated in further details by the following non-limiting examples.Example 1 - Very compact five-in-one reactor for simultaneous sludge dewatering and improved contaminants removalAbstract

[0117] A compact five-in-one water treatment reactor, combining a flocculant, a fibrous super-bridging agent, and a screen-based floc retention system, simultaneously improves water treatment and sludge dewatering.

[0118] The presence of fibrous materials allows for the formation of very large flocs, efficient floc separation via screening (without the need for settling), and sludge dewatering through a compact press-filter system. The sludge containing fibers was subsequently dewatered using the screen-based press filter without further chemical addition. The implementation of this five-in-one reactor is possible due to the formation of fiber-based flocs that are 32 times larger in volume than conventional flocs formed without fibers.

[0119] The reactor was tested with four water samples: two from African surface waters (78-589 Nephelometric Turbidity Unit (NTU)), one from North American surface water (4.5 NTU), and one from synthetic surface water (6.0 NTU). For all the waters tested, very low turbidities were measured after floc separation via settling or screening (0.2-1.6 NTU), with no need for membrane or granular filtration systems. The use of fibers also significantly improved the removal of total organic carbon, nanoplastics, and microplastics.

[0120] This five-in-one reactor could be used in situ for decentralized water treatment in drinking water and wastewater applications in small cities, marginalized communities, and developing countries. The compact reactor, which also performs in situ sludge dewatering, would reduce the risks associated with mismanaged sludge to the environment and human health.Introduction

[0121] This work proposes a new decentralized water treatment reactor that combines fibers used as fibrous super-bridging agents, cationic flocculants, and screen-based press filters. The objective of this approach is to provide an efficient, compact, and affordable five-in-one reactor for small, remote, or marginalized communities, as well as an alternative to conventional centralized plants that require three or four sequential tanks (coagulation (1), flocculation (2), settling (3), sludge dewatering (4)) as well as granular filtration (5) for the treatment of surface water. This five-in-one reactor was used herein for both floc removal and sludge dewatering.

[0122] The combination of super-bridging agents with cationic flocculants1011 12improved the removal of contaminants present in water through a simple separation process using coarse screens. The optimal flocculant and super-bridging agent concentrations were first determined, as well as the optimal screen mesh size for flocseparation and sludge dewatering.

[0123] The turbidity was measured for each condition tested. The results showed that the addition of fibers drastically improved the floc removal13. No metal-based coagulants such as alum were employed14; the flocculant was synergistically combined with fiber-based super-bridging agents to ensure an efficient floc formation and separation via settling and screening (up to 99 % turbidity removal).

[0124] The impact of fibers was also evaluated on the removal of i) total organic carbon, ii) nanoplastics, and Hi) microplastics (polyethylene microbeads and polyester microfibers) all of which showed considerable improvement compared to the conventional treatment without fibers1516.

[0125] To evaluate the versatility and robustness of the five-in-one reactor, two water samples from the Democratic Republic of the Congo (DRC) were also tested. It is crucial to note that these surface water samples exhibited significantly higher turbidity levels than those in Canada.Materials and methodsChemicals and materials

[0126] Jar tests were conducted to simulate a low-cost compact five-in-one treatment reactor (e.g., without granular filtration) to assist isolated populations or those in developing countries that lack access to clean water. According to Health Canada, the United States Environmental Protection Agency (USEPA), and the Ministry of the Environment (Environmental Quality Act; EQA),30the turbidity after filtration in conventional treatment systems must be below 0.3 NTU.

[0127] The tested cationic polyacrylamides were supplied by Kemira Water Solution Canada Inc. and are listed in Table 1. The tested anionic polyacrylamide (a-PAM) was supplied by Hydrex.

[0128] Table 1: Properties of polyacrylamides<

[0129] All solutions and suspensions were prepared using reverse osmosis (RO) water.

[0130] As described elsewhere,25 42the fiber suspensions were prepared by blending 2.5 g of dried fibers in 500mL of RO water (Ninja blender, for 7 s). Pristine fibers (eucalyptus) were used as starting materials. The fibers were blended as is, or blended after being rinsed at pH 4 or 10. Brown fibers extracted from recycled cardboard box were also used as the starting material. The brown fibers were used as is, or prerinsed in hot water (55°C), at pH 4 or 10. H / aters characteristics

[0131] Several waters were used during jar tests, including two surface waters from Kinshasa, Africa (water characteristics are listed in Table 2). Another surface water sample was taken from the St. Lawrence River in Montreal, Canada (TOC (total organic carbon) of 3.2 ± 0.3 mg C / L (mg of carbon per liter of water); turbidity of 4.5 ± 0.4 NTU; pH 7.8 ± 0.2).

[0132] The synthetic water2646was composed of 250 mL of tap water stabilized at room temperature, 250 piL of a kaolin suspension (10 g / L), and 100 piL of a starch solution (500 mg / L). The kaolin suspension was made from fine white clay powder (Cattier®), and the starch solution was made from cornstarch powder (Selection®). To prepare the starch solution, 250 mg of corn starch was dissolved in 500 mL of water. For the kaolin suspension, 5 g of white clay powder was mixed with 500 mL of water. The turbidity and pH of the synthetic water were approximately 6 ± 0.5 NTU and 7 ± 0.5, respectively.

[0133] The jar tests were performed using a 250 mL volume of samples in a glass beaker agitated at 200 rpm with a cross-shaped magnetic stir bar (3.5 cm x 3.5 cm). The raw waters were all equilibrated at ~21 °C before each experiment.

[0134] Table 2: Location and characteristics of the 4 tested watersJar tests

[0135] Various concentrations of fibers, flocculant (PAM, 500 mg / L solution), and mesh sizes were tested during the jar tests.

[0136] Four types of cationic PAM were used: c-PAM 1, c-PAM 2, c-PAM 3, and c-PAM 4 (see Table 1). The PAM solutions were prepared by dissolving 50 mg of dried PAM in 100 mL of water and mixing with a magnetic stirrer for 15 minutes.

[0137] The turbidity objectives after settling and pressing were set to be below 1.5 NTU and 0.3 NTU, respectively (measurement range: 0.1 - 2000 NTU; turbidimeter Hach TL2350 model). Jar tests were performed using a Corning brand magnetic stirring plate. These objectives were used to determine the optimal doses of PAMand fiber, as well as other operational conditions under investigation (mixing time, mesh size, etc.).

[0138] The experiment began with the introduction of fibers into the tested water (fiber suspension dosed at 5 g / L). Fibers (initial fibers suspension 5 g / L) were added at a concentration of 200 mg fibers / L to the beaker 10 seconds before the first half of the PAM dose was added into the system. The second half of the PAM was added after two minutes of mixing to reduce the PAM chain desorption and reconfiguration leading to floc fragmentation.4741Subsequently, two minutes of mixing were followed by three minutes of settling. At this stage, an initial turbidity measurement was taken. A second turbidity measurement was performed after separating the flocs using a filter press, which kept the flocs at the bottom of the beaker (mesh size: approximately 200 pm).

[0139] Different concentrations of PAM were tested: 0.2, 0.4, 0.8, 1.2, 2.0, and 3.0 mg / L. These concentrations were tested in the presence of 200 mg of fibers / L as well as in the absence of fibers (i.e., conventional treatment). Once the optimal PAM concentration was determined, additional fiber concentrations were tested to optimize the aggregation system and ultimately reduce the operational costs for full-scale applications: 0, 25, 50, 100, 150, 175, 200, and 250 mg of fibers / L.

[0140] The impact of mesh size was also tested once the optimal fiber dose was found. Mesh opening sizes of 100, 300, 500, 1000, and 2000 pm were used. These different mesh sizes were also tested under suboptimal mixing conditions, with PAM doses of 0.2 mg PAM / L and 0.35 mg PAM / L. The quality of the treated water remained the same ?? when fibers were used, except when finer meshes were used to compensate for aggregation affected by lower PAM doses.

[0141] The measurements were conducted using a turbidimeter. An analysis vial was measured three times to minimize variability and device imprecision. For each tested treatment condition, replicates were performed in all jar tests.

[0142] For the highly turbid DRC A (78.1 ± 0.5 NTU) and DRC B surface water (589.0 ± 0.5 NTU), to achieve adequate residual turbidity after treatment, 50 - 100 mg alum / L had to be added, along with the optimal dose of c-PAM 3 (3 mg / L) and 200 mg / L of fibers. Alum was added at the onset of the jar test, with agitation maintained for 2 minutes, followed by the addition of c-PAM 3 and fibers according to the previously mentioned protocol.Total organic carbon, nanoplastics, and microplastics measurement

[0143] Fluorescent latex polystyrene nanoplastics were used (28 nm, carboxylate modified, FluoSpheres, ex / em: 365 / 415 nm).

[0144] Polyester microfibers (PEST) were produced by blending a textile (SanMar Canada, ATC, ATC3600Y)2425. The textile was blended in water for 5 minutes at room temperature using a Ninja blender (-1200 rpm).48

[0145] Polyethylene microspheres were obtained from Cospheric (140 pm, ex / em: 515 / 414 nm).

[0146] Jar test experiments were spiked with 0.8 mg / L of nanoplastics. Polyethylene microspheres and polyester microfibers were spiked at a concentration of 1000 microplastics / L.

[0147] The properties of the tested plastics are listed in Table 3.

[0148] Turbidity measurements were performed using Standard Method 2130B (Hach 2100N turbidimeter), and total organic carbon (TOC) measurements were performed using Standard Method 5310C (Sievers 5310c total organic carbon analyzer, GE Water).

[0149] Table 3: Properties of nanoplastics and microplasticsResults and DiscussionImpact of super-bridging agents on conventional and emerging contaminants

[0150] Conventional treatment required large amounts of both metal-based coagulants (e.g., alum) and synthetic flocculants (e.g., PAM) (Figure 1a; a1), whereas fiber-based treatment, in most cases, only required PAM (Figure 1b; b1).

[0151] In the context of decentralized water treatment, it is preferable to avoid the use of metal-based coagulants, which require monitoring, pH control, and precise dosage adjustment to maintain process performance. Herein, the separation process was designed to be more robust and simpler by using PAM without metal-based coagulant. Compared to conventional treatment (PAM, no fibers; Figure 1a), the flocs formed by combining fibers and PAM (Figure 1b) were approximately 7-10 times larger, depending on the concentration of PAM and fibers.1718

[0152] Figures 1c and 1d show the impact of fiber-based super-bridging agents on the removal of total organic carbon, turbidity, nanoplastics, and microplastics (after floc separation with a 500 pm screen mesh). When fibers were synergistically combined with a cationic flocculant (200 mg fibers / L and 1.2 mg C-PAM3 / L), the removal of all contaminants was drastically improved. For turbidity, removal increased from 39% without fibers to 94 % with fibers, while nanoplastic removal increased from 20 % to 72 %.

[0153] As described elsewhere,1920microplastic and nanoplastics can be used to model and predict virus removal during filtration. Consequently, based on the nanoplastic and microplastic removals shown in Fig 1 d, the screenbased separation method could be used in combination with fibers for drinking water application to offer some protection against viruses and other pathogens.21-23

[0154] For microplastics, the impact of fiber-based super-bridging agents was also noticeable and statistically significant: removal increased from 49 % to 91 % for polyethylene and from 64 % to 95 % for polyester. Such improvements using fibers have also been observed elsewhere24. Similar improvements in turbidity and microplastic removal were previously observed for settling treatment when fibers were used in the aggregation process.2526Robustness of super-bridging agents for different water types

[0155] The impact of PAM concentration was tested during floc separation via settling (3 min) versus pressing (500 pm screen mesh) (Figure 1b; b2). The screen-based pressing system replaced the settling unit and was also used as an alternative to membrane filters or granular filters for drinking water applications (objective < 0.3 NTU, as required by regulations in North America; Figure 1b; b5).

[0156] The replacement of membrane or granular filters with a coarse screen mesh was possible due to the formation of very large fiber-based flocs. The drinking water minimal standard (< 0.5 NTU) was not achieved when screens were used in combination with flocculant alone (conventional treatment; no fibers).

[0157] When the PAM concentration was insufficient to initiate aggregation (< 0.2 mg PAM / L), the impact of fibers was not noticeable, and both treatments provided low turbidity removal (< 8%).

[0158] However, at a concentration of 0.4 mg PAM / L, the presence of fibers significantly improved floc formation and turbidity removal up to 85%, compared to only 40% without fibers. This improvement with fibers was observed for both floc separation methods: settling (Figure 2a) and pressing (Figure 2b).

[0159] When the concentration of PAM was increased to 0.8 mg / L, both treatments resulted in slightly lower turbidity removal of 78% and 33%, with and without fibers, respectively. This decrease was attributable to temporary charge reversal caused by the cationic PAM27’2829.

[0160] At concentrations of 1.2, 2.0, and 3.0 mg PAM / L used with fibers, the residual turbidity after settling was 0.39, 0.46, and 0.39 NTU, respectively (93-94% removal). For the same respective PAM concentrations without fibers, turbidity removal drastically dropped to 41-45%.

[0161] Based on a paired t-test, there was no statistically significant difference between the settled and pressed turbidity values. For suboptimal PAM concentrations (< 0.4 mg / L), contrary to settling, the pressing system captured more (smaller) flocs and partially compensated for the poor aggregation due to insufficient PAM concentration in the system. The concentration of 1.2 mg PAM / L was chosen as the optimal value under which all contaminant removal curves reached a plateau.

[0162] The same steps were conducted on Democratic Republic of the Congo B (DRC B) water (Africa) to investigate the impact of PAM concentration during floc separation after settling (3 min) and pressing (200 pm screen mesh). At a lower PAM concentration (0.2 mg / L), the presence of fibers showed no significant impact, reducing turbidity by only 30% after 3 min of settling, indicating poor floc formation. Pressing only achieved a 24% reduction, suggesting that small flocs passed through the mesh. A noticeable impact of fibers was observed at 0.8 mg PAM / L or higher (Figures 2c and d). At 2 and 3 mg PAM / L, turbidity with fibers was 34 and 23 NTU after 3 min of settling, respectively, and 38 and 23 NTU after pressing. Differences between settling and screening were not statistically significant when fibers were used, as large flocs were effectively removed via both separation methods. Considerably higher turbidities were measured without fibers: 62 and 33 NTU after 3 min of settling, and 55 and 37 NTU after pressing, with 2 and 3 mg PAM / L, respectively. To reach the lowest residual turbidity, 3 mg PAM / L was selected forfurther investigations on DRC B water.Reducing the microbiological risk for decentralized applications

[0163] The optimal PAM concentration of 1.2 mg / L (synthetic water) was used to determine the optimal fiber concentration. The lowest turbidity (0.39 NTU) after settling and pressing was observed at 200 mg of fibers / L (Figures 3a and b). This value complies with North American standards for drinking water and the design guide for drinking water production facilities, which requires post-filtration turbidity to be less than 0.5 NTU. This suggests that further improvements to the system or the use of smaller screen mesh sizes (e.g., 50 or 100 pm) could potentially achieve higher drinking water quality (e.g., < 0.3 NTU for granular filtration, Surface Water Treatment Rules (SWTRs), USEPA) to reduce the microbiological risk for decentralized applications in marginalized communities and developing countries.

[0164] The mesh sizes were modified using the optimal concentrations of PAM and fibers (1.2 mg / L of PAM; 200 mg / L of fibers). The mesh size had minimal influence on turbidity (p-value: 0.37) (Figure 3c). This could be explained by the large size of the flocs formed, allowing separation even with larger screen mesh sizes (0.45 NTU with a 2000 pm screen).

[0165] For these tested conditions, screen mesh sizes of 50 and 20 pm reduced the turbidity to 0.32 NTU and 0.20 NTU respectively (Figure 3d). It is hypothesized that smaller meshes were required to remove colloids that were not aggregated into the large fiber-based flocs.

[0166] Optimization of mixing conditions (time and intensity) could also be performed to minimize shear stress on flocs and prevent floc breakage.

[0167] According to the USEPA, the RQEP (Regulation on the Quality of Drinking Water in Canada), and the drinking water design guide (Ministry of the Environment, Quebec, Canada), after filtration, each filter should have a turbidity of less than 0.5 NTU, and water entering the distribution network should have a value below 1 NTU.30Although the results are compliant, they do not qualify for all the removal credits for Giardia, Cryptosporidium, and viruses31. For granular filtration, it is advised to achieve a turbidity lower than 0.3 NTU for better removal credits from a safety standpoint, and ideally to achieve a turbidity below 0.15 NTU to obtain all removal credits.32

[0168] For drinking water applications, the fiber and screen-based separation reactor presented herein could be combined with disinfection to gain additional removal credits. Improving the PAM and fiber synergy and selecting the proper screen mesh size to achieve turbidity below 0.3 NTU would also be necessary to reduce the amount of chlorine needed for providing safer drinking water and reducing disinfection by-product formation3334in marginalized communities and developing countries.Performances of fibers with different physicochemical treatments

[0169] Different PAMs with varying charge densities and molecular weights were tested to determine the optimal flocculant properties for forming very large fiber-based flocs.

[0170] After settling, the turbidity was 0.7, 0.4, 0.7, and 9.9 NTU for c-PAM 4, c-PAM 3, c-PAM 2, and c-PAM 1, respectively (Figure 4a). No significant difference (<3%) was observed between the settled (3 min) and pressed turbidities (mesh size of 200 pm), except for c-PAM 1 , which showed lower final turbidity of 9.8 NTU and 7.3 NTU after settling and filter-pressing, respectively (Figure 4b). In contrast to c-PAM 2, c-PAM 3, and c-PAM 4, which have higher charge densities (35% or 55%), the charge density of c-PAM 1 (only 7%) was not sufficient to destabilize and aggregate colloids via electrostatic affinities.

[0171] Compared to c-PAM 3 without fibers, c-PAM 4 typically provides better floc formation and removal due to its higher molecular weight (cf. Table 1). However, when fibers are used as super-bridging agents— drastically promoting floc formation and size— the higher molecular weight provided by c-PAM 4 did not result in better turbidity removal compared to c-PAM 3.

[0172] Based on the settled and pressed turbidities in Figure 4b, a charge density of 35% (c-PAM 2) was sufficient to complete colloid destabilization and attachment onto the fiber structure. For the testes water, a charge density higher than 7 % was required.

[0173] Although fibers can be used in a very simple system combining only one flocculant with screen pressing (without settling and filtration), they can also be used in more advanced physicochemical treatments combining metal salts and PAM (both anionic and cationic) (Figures 4c and 4d).

[0174] The impact of alum concentration (0-100 mg dry alum / L) is shown in Figure 4c, while the impact of more advanced physicochemical treatments on low, moderate, and high turbidity water is shown in Figure 4d. Such advanced physicochemical treatment improved aggregation and allowed meeting turbidity objectives after settling (<1.5 NTU) for African waters with very high turbidity (589 NTU). Settled turbidities of 3.75 NTU (99.4% removal, raw water: 589 NTU) and 1.63 NTU (98.0% removal, raw water: 78 NTU) were measured for DRC B and DRC A waters, respectively.

[0175] As shown in Figure 4d, further optimization efforts may be envisioned to reach the target of 1.5 NTU for DRC B water; for example, pH adjustment, prehydrolyzed coagulants, optimal agitation intensity and / or aggregation time, optimal settling time, and smaller screen mesh sizes could be tested to achieve better water quality35-37Nonetheless, the fiber-based treatment considerably improved turbidity removal compared to conventional treatment, which resulted in a settled turbidity of 33 NTU.Reducing polyacrylamide concentrations for drinking water application

[0176] Synthetic polymers flocculants, such as acrylamide-based polymers, have faced criticism for their i) potential toxicity38(group 2A), ii) clogging effect in membrane / screen, and Hi) cost.39’4041For implementation in marginalized communities and developing countries, the reactor should be operated at low cost (low OPEX), and systemic / heavy reactor maintenance must be avoided. Consequently, the PAM concentration was reduced, and the inevitable formation of smaller flocs was compensated for by using a smaller screen mesh (Figure 5).

[0177] The 500 pm mesh size was effective for a PAM concentration of 0.2 mg / L. Additional tests wereconducted for different mesh sizes at both 0.2 mg / L and 0.35 mg / L PAM concentrations. At this concentration, the floc's size was visibly affected. Turbidity values measured after pressing decreased as the mesh size became finer (Figures 5a and b). When the PAM concentration was low, the bridging effect between fibers was diminished, leading to smaller and more fragile flocs, a phenomenon also reported in a previous study.2542However, at 1.2 mg PAM / L, turbidity removal was not noticeably impacted by the screen mesh size, as the flocs formed were very large and were intercepted by all the tested screen mesh sizes (100 - 2000 pm; Figure 5c).

[0178] The impact of the mesh size and PAM concentration on the turbidity is displayed in Figure 5d. As the measured turbidities after pressing were still very low, the reactor could also be used for sludge dewatering. As shown in Figure 5d, the pressed turbidities were < 0.5 NTU, even though the sludge was manually pressed at the bottom of the 250 mL reactor (200 mg fibers / L, 500 pm screen mesh, cf Figure 3b). The volume of sludge collected after pressing was < 5 mL for all the jar tests performed. Consequently, this five-in-one reactor is a promising compact technology for contaminant aggregation, floc separation, and sludge dewatering (as shown in Figure 1; b3). Sludge dewatering and management, in situ

[0179] To evaluate the solid content in African (DRC B) water samples, two concentrations of c-PAM 3 (2 mg / L and 3 mg / L) were assessed under two conditions (with and without fiber addition) and using two dewatering methods (with and without pressing). The solid content was measured by drying the recovered solids at 103°C for 1 hour to determine the dryness.

[0180] As illustrated in Figure 6, the flocs obtained without fibers could not be effectively recovered due to their small size. In contrast, the addition of fibers resulted in more visible floc formation, although the percentage of solids remained relatively low. This can be attributed to the inherent characteristics of the sludge, which may contain extracellular polymeric substances with hydrophilic functional groups. These groups play a crucial role in making i) solid-liquid separation more challenging, ii) the thermal drying process less efficient, Hi) the entire process more energy-consuming43.

[0181] Comparing the two methods (with and without pressing), the differences are noticeable, with pressing yielding an 11 -fold higher solid content in sludge: from 0.3% for the conventional treatment to 3.5% for the fibrous treatment (Figure 6a).

[0182] Increasing the solid content in sludge could considerably reduce the overall costs associated with sludge treatment, such as reducing the amount of sludge transported and the energy input during thermal drying, among others44. Such applications could benefit both centralized and decentralized wastewater systems by offering significant advantages in terms of public health, environmental sustainability, and operational efficiency.45Conclusion

[0183] A compact reactor using flocculants and fibrous super-bridging agents could serve as an alternative to complex and expensive conventional physicochemical treatments, which involve a coagulant, a flocculant, a settling tank, and granular or membrane filtration.

[0184] This compact reactor is suitable for producing safer drinking water, wastewater applications, and sludge dewatering. When combined with super-bridging agents, coarse screen-based filters offer a cost-effective separation solution compared to granular or membrane filters, which require qualified operators and more maintenance.

[0185] Various lab-scale experiments were conducted to determine the optimal PAM concentrations, fiber concentrations, and screen mesh sizes for floc separation and sludge dewatering. The addition of fibers significantly improved the removal of regulated and emerging contaminants, such as nanoplastics and microplastics. The optimized treatment achieved treated water with turbidity levels below 0.2 NTU, thereby complying with drinking water regulations in North America. The treated African waters also demonstrated significant reductions in turbidity, achieving 3.77 NTU with a 99.4% reduction for DRC B raw water, and 1.6 NTU with a 98.0% reduction for DRC A raw water.

[0186] This five-in-one reactor could also reduce i) the environmental and health risks associated with mismanaged sludge— potentially at low cost— and ii) the energy required for sludge transport and subsequent processing.

[0187] The scope of the claims should not be limited by the preferred embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole.REFERENCES

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The investigation of the specific behavior of a cationic block structure and its excellent flocculation performance in high-turbidity water treatment ... - RSC Advances (RSC Publishing) DOI: 10.1039 / C8RA02006J [Internet], [cite 17 nov 2023], Disponible sur: https: / / pubs.rsc.org / en / content / articlehtml / 2018 / ra / c8ra02006j 29. Gregory J, Barany S. Adsorption and flocculation by polymers and polymer mixtures. Adv Colloid Interface Sci. 14 nov 2011;169(1):1 -12.30. Recommandations pour la qualite de I’eau potable au Canada [Internet], [cite 13 juill 2023], Disponible sur: https: / / publications.gc.ca / collections / collection_2019 / sc-hc / H129-24-2019-fra.pdf31. Betancourt WQ, Rose JB. Drinking water treatment processes for removal of Cryptosporidium and Giardia. Vet Parasitol. dec 2004; 126(1 -2):219-34.32. Guide de conception des installations de production d’eau potable.33. Kim J, Chung Y, Shin D, Kim M, Lee Y, Lim Y, et al. Chlorination by-products in surface water treatment process. Desalination . janv 2003; 151 ( 1 ) : 1 -9.34. Grunwald A, St’astny B, Slavickova K, Slavicek M. Formation of Haloforms during Chlorination of NaturalWaters. Acta Polytech [Internet], 2 janv 2002 [cite 3 aout 2023];42(2). Disponible sur: https: / / ojs.cvut.cz / ojs / index.php / ap / article / view / 33435. Thomas DN, Judd SJ, Fawcett N. Flocculation modelling: a review. Water Res. mai 1999;33(7): 1579-92.36. Lapointe M, Papineau I, Peldszus S, Peleato N, Barbeau B. Identifying the best coagulant for simultaneous water treatment objectives: Interactions of mononuclear and polynuclear aluminum species with different natural organic matter fractions. J Water Process Eng. avr 2021 ;40: 101829.37. Tang H, Xiao F, Wang D. Speciation, stability, and coagulation mechanisms of hydroxyl aluminum clusters formed by PACI and alum: A critical review. Adv Colloid Interface Sci. dec 2015;226:78-85.38. Xiong B, Loss RD, Shields D, Pawlik T, Hochreiter R, Zydney AL, et al. Polyacrylamide degradation and its implications in environmental systems. Npj Clean Water. 7 sept 2018;1(1):1 -9.39. Rice JM. The carcinogenicity of acrylamide. Mutat Res Toxicol Environ Mutagen. 7 fevr 2005;580(1 ):3-20.40. Lapointe M, Barbeau B. Substituting polyacrylamide with an activated starch polymer during ballasted flocculation. J Water Process Eng. 1 avr 2019;28:129-34.41. Lapointe M, Barbeau B. Dual starch-polyacrylamide polymer system for improved flocculation. Water Res.1 nov 2017;124:202-9.42. Kurusu RS, Lapointe M, Tufenkji N. Sustainable iron-grafted cellulose fibers enable coagulant recycling and improve contaminant removal in water treatment. Chem Eng J. 15 fevr 2022;430: 132927.43. Hou J, Hong C, Ling W, Hu J, Feng W, Xing Y, et al. Research progress in improving sludge dewaterability: sludge characteristics, chemical conditioning and influencing factors. J Environ Manage, fevr 2024;351 : 119863.44. Rao B, Tu H, Jia H, Ding Z, Xu P, Zhang Y, et al. The cooperative effect of mechanical dewatering and thermal drying for activated sludge deep reduction. Process Saf Environ Prot. mai 2024;185:9-20.45. Mwamlima P, Njau KN, Rwiza M, Chacha N. Evaluating the performance of faecal sludge dewatering technologies in urban settings of developing African countries: a review. Int J Environ Health Res. 2 mai 2024; 1-13.46. Raissouni B, Benkara LM, Lapointe M. Fiber-based super-bridging agents improve flotation and settling during water treatment. J Water Process Eng. juin 2024;63: 105499.47. Lapointe M, Barbeau B. Selection of media for the design of ballasted flocculation processes. Water Res. 15 dec 2018;147:25-32.48. Lapointe M, Farner JM, Hernandez LM, Tufenkji N. Understanding and Improving Microplastic Removal during Water Treatment: Impact of Coagulation and Flocculation. Environ Sci Technol. 21 juill2020;54(14):8719-27.• Blancho et al., Demonstrating scale-up of a novel water treatment process using super-bridging agents,Water Research, 254 (2024) 121301• WO2022170419 FIBER-BASED MATERIALS FOR WATER TREATMENT (PCT / CA2022 / 050160;CA3210604; CN116888081; EP4291536; US2024 / 132382)

Claims

CLAIMS:

1. A reactor for water treatment, the reactor comprising:a tank for receiving water to treated,wherein the tank is equipped with an outlet for treated water,wherein the tank comprises a flocculant and a fibrous treatment agent,wherein the flocculant and the fibrous treatment agent cause the formation of fiber-based flocs in the water to be treated, andwherein the flocs contain contaminants to be removed from the water to be treated; anda porous means for compressing the flocs, wherein, in use, the porous means for compressing the flocs:compresses the flocs, thus forming and dewatering a compressed sludge made of the flocs, andallows through treated water towards said outlet for treated water of the tank,wherein said treated water has a reduced floc content when compared to the water to be treated.

2. The reactor of claim 1 , wherein the flocculant is a cationic flocculant, an anionic flocculant, or a mixture thereof.

3. The reactor of claim 1 or 2, wherein the flocculant is a cationic flocculant.

4. The reactor of claim 3, wherein the cationic flocculant is:a cationic polyacrylamide (PAM), such as poly(acrylamide-co-diallyldimethylammonium chloride), poly(acrylamide-co-acryloyloxyethyltrimethylammonium chloride), poly(acrylamide-co- methacryloyloxyethyltrimethylammonium chloride), and poly(acrylamide-co-dimethylaminoethyl methacrylate);a polyamine, such as ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), and polyethylenimine (PEI);polyDADMAC (polydiallyldimethylammonium chloride);chitosan;a quaternary ammonium compound such as cetyltrimethylammonium bromide (ctab), cetyltrimethylammonium chloride (ctac), alkyl trimethylammonium chlorides, and alkyl benzyl dimethylammonium chlorides; and / orsaccharine-based, and / or a polysaccharide-based polymer, and is another organic polymer, preferably a polyacrylamide (PAM),more preferably poly(acrylamide-co-diallyldimethylammonium chloride), poly(acrylamide-co- acryloyloxyethyltrimethylammonium chloride), poly(acrylamide-co-methacryloyloxyethyltrimethylammonium chloride), or poly(acrylamide-co-dimethylaminoethyl methacrylate).

5. The reactor of claim 3 or 4, wherein the cationic flocculant has a charge density of at least about 10%, preferably at least about 15%, more preferably at least about 20%, yet more preferably at least about 25%, even more preferably at least about 30%, and most preferably at least about 35%.

6. The reactor of any one of claims 3 to 5, wherein a concentration of the cationic flocculant is between about 0.1 and about 5 mg / L, preferably between about 0.4 and about 3 mg / L of water to be treated; most preferably, the concentration of the cationic flocculant is about 1.2 mg / L of water to be treated, preferably when a polyacrylamide is used as the flocculant.

7. The reactor of claim 1 or 2, wherein the flocculant is an anionic flocculant.

8. The reactor of claim 7, wherein the anionic flocculant is:an anionic polyacrylamide (PAM) such as poly(2-propenamide-co-2-propenoic acid), sodium polyacrylate, poly(acrylamide-co-acrylic acid), or poly(acrylamide-co-maleic acid); a sulfonated polymer such asa polystyrene sulfonate e.g., sodium polystyrene sulfonate (poly(styrene-4-sulfonic acid), sodium salt), potassium polystyrene sulfonate;calcium polystyrene sulfonate; ora sulfonated polyacrylamide e.g. poly(acrylamide-co-sodium acrylate-co-sodium 2- acrylamido-2-methylpropane sulfonate) and poly(acrylamide-co-sodium 2-acrylamido-2- methylpropane sulfonate); ora lignosulfonate such as calcium lignosulfonate, sodium lignosulfonate, or ammonium lignosulfonate,preferably an anionic polyacrylamide (PAM) such as poly(2-propenamide-co-2-propenoic acid), sodium polyacrylate, poly(acrylamide-co-acrylic acid), or poly(acrylamide-co-maleic acid).

9. The reactor of claim 7 and 8, wherein a concentration of the anionic flocculant is between about 0.05 and about 5 mg / L, preferably between about 0.1 and about 1 mg / L of water to be treated.

10. The reactor of any one of claims 7 to 9, wherein, when a concentration of the flocculant is below about 0.2 mg / L of water to be treated, a porous means for compressing the flocs with a smaller mesh size, for example about 50 pm mesh size or smaller, is used.

11. The reactor of any one of claims 1 to 10, wherein the fiber-based flocs are at least about 1000 pm in size.

12. The reactor of any one of claims 1 to 11, further comprising a coagulant.

13. The reactor of claim 12, wherein the coagulant is:an inorganic coagulant such as :an aluminum-based coagulant e.g., aluminum sulfate (alum), aluminum chlrohydrate (ACH), or polyaluminum chloride (PAC);an iron-based coagulant e.g., ferric chloride, ferric sulfate, or ferrous sulfate;another inorganic coagulant e.g., sodium aluminate; oran organic coagulant (typically used for applications where the water to be treated has a low concentration or organic contaminants) such as:a polyamine e.g., ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), or polyethylenimine (PEI);polydiallyldimethylammonium chloride (polyDADMAC);chitosan; ora quaternary ammonium compound e.g., cetyltrimethylammonium bromide (CTAB), cetyltrimethylammonium chloride (CTAC), alkyl trimethylammonium chloride, or an alkyl benzyl dimethylammonium chloride.

14. The reactor of claim 12 or 13, wherein the coagulant is an inorganic coagulant, more preferably an aluminum- based coagulant, and most preferably aluminum sulfate.

15. The reactor of claim 12 or 13, wherein the coagulant is a prehydrolyzed coagulant such as aluminum chlorohydrate (ACH) or polyaluminum chloride (PAC).

16. The reactor of any one of claims 12 to 15, wherein a concentration of the coagulant is between about 0.5 and about 1500 mg / L, preferably between about 10 and about 50 mg / L of water to be treated.

17. The reactor of any one of claims 1 to 11, being free of alum, preferably free of aluminum-based coagulants, more preferably free of aluminum-based coagulants or iron-based coagulants, yet more preferably free of inorganic coagulants, and most preferably free of any coagulant.

18. The reactor of any one of claims 1 to 17, wherein the flocculant is an anionic flocculant, preferably an anionic polyacrylamide (PAM).

19. The reactor of any one of claims 1 to 18, wherein when the reactor comprises an inorganic coagulant, for example a metallic coagulant, the flocculant is an anionic flocculant.

20. The reactor of any one of claims 1 to 19, wherein the fibrous treatment agent is made of fibers having an average length of at least about 100 pm and an average diameter of at least about 5 pm.

21. The reactor of any one of claims 1 to 20, wherein the fibrous treatment agent is in the form of single fibers, or fibers assembled in particles (such as microparticles), flakes, aggregates, hydrogels, sponge materials, and / or any other fiber-based materials.

22. The reactor of any one of claims 1 to 21, wherein the fibrous treatment agent comprises:cellulosic fibers comprising e.g., cellulose, hemicellulose, and / or lignin,textile fibers such as cotton, polyester, other natural or synthetic textile fibers, and their mixture, and / orkeratin-based fibers.

23. The reactor of any one of claims 1 to 22, wherein the fibrous treatment agent comprises fibers recovered from:wastewater from water treatment plants, from the pulp and paper industry (e.g., paper mill sludge), from the textile industry, or from other industries,residues and waste materials, for example:agricultural residues such as straw, bagasse, fibers extracted from agriculture residues (maize and soy), rice husk, and hemp hurds as well as keratin-based fibers from wool and feathers),wood processing residues such as sawdust and wood chips, and Kraft pulp residues, orrecycled materials.

24. The reactor of any one of claims 1 to 23, wherein the fibrous treatment agent comprises virgin fibers.

25. The reactor of any one of claims 1 to 24, wherein the fibrous treatment agent comprises pristine fibers, functionalized fibers, or a mixture thereof.

26. The reactor of claim 25, wherein the functionalized fibers are functionalized with an oxide; an hydroxide; a metal oxide; a metal hydroxide; a metallic element; a carboxyl group; a sulfonyl group; a phosphoryl group; an amine group, such as a quaternary amine group; a coagulant; a flocculant; a polymer; another polar or nonpolar group; and / or another hydrophobic or hydrophilic moiety.

27. The reactor of claim 25 or 26, wherein the functionalized fibers are functionalized with iron oxide and / or iron hydroxide groups.

28. The reactor of any one of claims 1 to 27, wherein the fibrous treatment agent is already present in the water to be treated.

29. The reactor of any one of claims 1 to 28, wherein the fibrous treatment agent is added to the water to be treated, either entirely or to increase the concentration of the fibrous treatment agent.

30. The reactor of any one of claims 1 to 29, wherein a concentration of the fibrous treatment agent is between about 10 and about 500, preferably between about 50 and about 250 mg / L of water to be treated.

31. The reactor of any one of claims 1 to 30, wherein the porous means for compressing flocs is a porous medium, for example a sieve, a screen, a mesh, a membrane, or any other porous media, preferably a sieve, a screen, or a mesh, more preferably a screen.

32. The reactor of any one of claims 1 to 31 , wherein the porous means for compressing flocs is:configured to compress the flocs against a solid surface, for example against a wall of the tank, preferably the bottom of the tank while allowing through treated water; orplaced in a flow path of water to be treated, allowing through treated water towards the outlet for treated water of the tank and catching the flocs, and accompanied by a pump that draws the treated water through said outlet, whereby the negatively pressurized flow of water through the means for compressing flocs compresses the flocs against said means for compressing flocs.

33. The reactor of any one of claims 1 to 32, wherein the porous means for compressing flocs divides the tank into a water-to-be-treated section and a treated-water section; is fitted in or next to the outlet for treated water; or is removable, for example being inserted in the tank to compress the flocs when desired.

34. The reactor of any one of claims 1 to 32, wherein the porous means for compressing flocs is perpendicular to a flow path of water to be treated or inclined with regard to said flow path of water to be treated.

35. The reactor of any one of claims 1 to 34, wherein the porous means for compressing flocs is flat, tubular, or flexible.

36. The reactor of any one of claims 1 to 35, wherein the porous means for compressing flocs has a nominal mesh size between about 10 pm and about 10000 pm, preferably a mesh size of about 500 pm and 2000 pm.

37. The reactor of any one of claims 1 to 36, wherein the outlet for treated water is an opening at the top of the tank, for example the tank has an open top, or an opening on a treated-water side of the means for compressing the flocs, for example an opening at the bottom of the tank, or an opening in a side wall of the tank.

38. The reactor of any one of claims 1 to 37, further comprising an inlet for water to be treated.

39. The reactor of claim 38, wherein inlet for water to be treated is an opening at the top of the tank, for example the tank has an open top, or an opening on the water-to-be-treated side of the means for compressing the flocs, for example an opening in a side wall of the tank.

40. The reactor of any one of claims 1 to 39, further comprising a stirrer or a static mixer.

41. The reactor of any one of claims 1 to 40, being configured for use in batch mode or in continuous mode.

42. The reactor of any one of claims 1 to 41 , further comprising a scraper to remove the compressed sludge off the means for compressing flocs and / or from the reactor.

43. The reactor of any one of claims 1 to 42, further comprising a means for cleaning the means for compressing flocs, for example a waterjet, an air jet, a brush, a scraper, or a combination thereof.

44. The reactor of any one of claims 1 to 43, being configured for recovering reactants from the flocs or from the compressed sludge or being connected to a second tank for the recovery of reactants from the flocs or from the compressed sludge.

45. The reactor of any one of claims 1 to 44, the pH in the tank of the reactor or in the second tank is adjusted to fragment the flocs or to remove contaminants from the flocs, for example, increased to 8.5, thus producing contaminant-free flocs.

46. The reactor of any one of claims 1 to 45, the pH in the tank of the reactor or in the second tank is adjusted to resolubilize the flocculant and coagulant from the contaminant-free flocs.

47. The reactor of any one of claims 1 to 46, wherein the water to be treated is surface water; groundwater; domestic sewage; industrial effluents; water originating from industrial processes; mining wastewaters; water originating from tailing ponds; water from cooling towers, boilers, and the like); water / sludge originating from agri-food processes; rainwater runoff from urban areas; irrigation runoff; water used in livestock operations; water from coastal areas, or estuaries; seawater; and already treated wastewater.

48. The reactor of any one of claims 1 to 47, wherein the treated water is drinking water, reclaimed water for non- potable applications, industrial water, treated stormwater, recycled agricultural water, reclaimed water for non- potable applications, and desalinated water for drinking or non-potable applications.

49. The reactor of any one of claims 1 to 48, wherein the compressed sludge is to be used in feeding livestock.

50. The reactor any one of claims 1 to 49, being fluidly connected, via a treated water pipe, to a downstream water treatment unit, preferably a disinfection unit, a water softening unit, and / or a tertiary treatment unit, preferably without intervening coagulation unit, flocculation unit, settling unit, or filtration unit.

51. The reactor any one of claims 1 to 50, being fluidly connected, via a pipe for water to be treated, to an upstream screening unit and / or aeration unit, preferably without intervening coagulation unit, flocculation unit, settling unit, or filtration unit.

52. The reactor any one of claims 1 to 51, being configured such that the treated water is treated two or more times in the reactor.

53. The reactor any one of claims 1 to 52, wherein the reactor is connected in series, downstream from one another, to one or more other reactor as defined in any one of claims 1 to 52, so that water treatment in a first reactor is fed to a second reactor and so on.

54. The reactor any one of claims 1 to 53, being equipped with a recycling loop to feed part of or all the treated water back in the reactor.

55. The reactor any one of claims 1 to 54, being fluidly connected to a tank for fibrous treatment agent preparation.

56. A water treatment plant comprising the reactor of any one of claims 1 to 55.

57. The water treatment plant of claim 56, being free of :a coagulation unit, such as e.g., a coagulation tank,a flocculation unit, such as e.g., a flocculation basin,a settling unit, such as e.g., a settling tank or basin for sedimentation of the flocs, a filtration unit, such as e.g., a granulation or membrane filter for filtration of the flocs and / or other particles, and / ora sludge dewatering unit such as e.g., a centrifuge, a belt filter press, and / or a rotary drum thickener.

58. The water treatment plant of claim 56 or 57, further comprising one or more of the following:a screening unit, comprising for example, coarse and fine screen(s) for removing large objects and debris,an aeration unit, such as e.g. a spray or cascading steps,a stabilisation unit (e.g. for pH adjustment),an oxidation unit,a disinfection unit,a water softening unit, orone or more tertiary treatment unit.

59. The water treatment plant of any one of claims 56 to 58, wherein the reactor is fluidly connected, via a treated water pipe, to a downstream disinfection unit, a water softening unit, and / or a tertiary treatment unit, preferably without intervening coagulation unit, flocculation unit, settling unit, or filtration unit.

60. The water treatment plant of any one of claims 56 to 59, wherein the reactor is fluidly connected, via a pipe for water to be treated, to an upstream screening unit and / or aeration unit, preferably without intervening coagulation unit, flocculation unit, settling unit, or filtration unit.

61. A process for treating water using the reactor of any one of claims 1 to 55, the process comprising the steps of:adding water to be treated, the flocculant, and the fibrous treatment agent to the tank of the reactor,allowing formation of the fiber-based flocs,using the porous means for compressing the flocs to compress the flocs, thus forming and dewatering the compressed sludge, while allowing treated water through the porous means for compressing the flocs towards said outlet for treated water of the tank.

62. The process of claim 61 , being free from:a coagulation step other than any coagulation happening in the reactor, such as e.g., using a coagulation tank,a flocculation step other than any flocculation happening in the reactor, such as e.g., using a flocculation basin,a settling step other than that any settling happening in the reactor, such as e.g., using a settling tank or basin for sedimentation of the flocs,a filtration step other than any filtration happening in the reactor, such as e.g., using a granulation or membrane filter for filtration of the flocs and / or other particles, and / ora sludge dewatering step other than any sludge dewatering happening in the reactor, such as e.g., using a centrifuge, a belt filter press, and / or a rotary drum thickener.

63. The process of claim 61 or 62, further comprising one or more of the following steps :using a screening unit, comprising for example, coarse and fine screen(s) for removing large objects and debris,using an aeration unit, such as e.g. a spray or cascading steps,using a stabilisation unit (e.g. for pH adjustment),using an oxidation unit,using a disinfection unit,using a water softening unit, orusing one or more tertiary treatment unit.

64. The process of any one of claim 61 to 63, further comprising a step of treating again water that has already been treated in the reactor.

65. The process of any one of claim 61 to 64, comprising:using the porous means for compressing flocs to compress the flocs against a solid surface, for example against a wall of the tank, preferably the bottom of the tank; orusing a pump to draw water to be treated through the porous means for compressing flocs, allowing through treated water and catching the flocs, and to draw the treated water through the outlet for treated water, whereby the negatively pressurized flow of water through the means for compressing flocs compresses the flocs against said means for compressing flocs.

66. The process of any one of claim 61 to 65, wherein the reactor is used in batch mode or in continuous mode.

67. The process of any one of claim 61 to 66, further comprising a step of recovering the compressed sludge from the means for compressing flocs and / or from the reactor.

68. The process of any one of claim 61 to 67, further comprising a step of cleaning the means for compressing flocs.

69. The process of any one of claim 61 to 68, further comprising a step of recovering the fibrous treatment agent, the flocculant and / or the coagulant from the compressed sludge and reusing the fibrous treatment agent, the flocculant and / or the coagulant in the reactor.

70. The process of any one of claim 61 to 69, further comprising a step of adjusting the pH in the tank to fragment the flocs or to remove contaminants from the flocs, for example, increasing the pH to 8.5 and recovering the contaminant-free flocs.

71. The process of any one of claim 61 to 70, further comprising a step of adjusting the pH is adjusted to resolubilize the flocculant and coagulant from the contaminant-free flocs, for example decreasing the pH to s 5.5.

72. The process of any one of claim 61 to 71, further comprising a step of recovering the fibrous treatment agent for example using a screen (for example, the means for compressing flocs), thus isolating the fibrous treatment agent from a solution of flocculant and coagulant.

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