METHOD FOR REMOVING DISSOLVED ORGANIC COMPOUNDS FROM WASTEWATER

Abstract

This invention relates to a treatment system comprising wood-based organic material and its use in wastewater treatment, and a method for removing dissolved organic compounds from wastewater. It is a treatment system for removing dissolved organic compounds from wastewater, comprising a water-soluble cationic polymer and wood-based organic material with an average particle size < 10 mm. The invention also relates to the use of said treatment system for COD removal in wastewater treatment and a method for removing dissolved organic compounds from wastewater.

Description

Descriptive Report of the Invention Patent for "METHOD FOR REMOVING DISSOLVED ORGANIC COMPOUNDS FROM "OF WASTEWATER". FIELD OF THE INVENTION

[0001] The present invention relates to a treatment system and its use for COD removal in the treatment of wastewater from pulp and / or paper mills, according to the independent claims set forth below. The present invention also relates to a method for removing dissolved organic compounds from wastewater from pulp and / or paper mills. BACKGROUND OF THE INVENTION

[0002] Pulp and paper production is one of the most water-intensive industrial processes, generating large quantities of highly contaminated wastewater per ton of paper or cardboard produced. The chemical oxygen demand (COD) in pulp and paper wastewater can reach up to 40,000 mg / l. Conventionally, wastewater treatment plants for such effluents include primary clarifiers, which remove all suspended solids and other particulate matter; biological treatment, which removes most of the dissolved organic matter; secondary clarifiers for activated sludge separation; and tertiary treatment in the form of coagulation-flocculation processes with a solid-liquid separation unit, or zonation, adsorption, and others for the removal of biologically recalcitrant soluble organic compounds, such as lignin.Conventionally, coagulation with salts or compounds of inorganic metals based on Al and Fe is used in the treatment of tertiary wastewater for the removal of residual COD. Due to the high volumes of wastewater produced in the pulp and paper industry, treatment with inorganic metal salts generates large quantities. Petition 870240086596, dated 09 / 10 / 2024, page 8 / 71 2 / 26 of wastewater is inorganic sludge during wastewater treatment. Landfill disposal is the common method for sludge disposal. However, current landfills reach their capacity quickly, and due to stricter environmental legislation, it is difficult to build new ones. Therefore, it is necessary to find new ways to reduce the volume of sludge for disposal. Many plants choose sludge incineration as a solution to the problem. However, this in turn leads to the formation of large quantities of ash, which need to be subsequently landfilled.

[0003] In addition, the use of inorganic metal salts based on Al and Fe in coagulation pollute the water with counterions, such as sulfate and chlorides, which can cause scaling and corrosion in distribution systems, especially in closed-loop systems where the accumulation of these ions is occurring.

[0004] There is a constant need to find an innovative solution for the removal of biologically recalcitrant soluble organic compounds from pulp and paper mill wastewater in tertiary treatment facilities, whose solutions meet environmental licenses and safety levels and reduce the ash content in sludge incineration. SUMMARY OF THE INVENTION

[0005] It is an objective of the present invention to reduce or even eliminate the aforementioned problems that appear in the prior art.

[0006] It is especially an objective of the present invention to provide innovative compositions for use in wastewater treatment for COD removal that would reduce the inorganic metal coagulant load in sludge formation in wastewater treatment plants of pulp and paper mills, and further reduce ash generation during sludge combustion. Petition 870240086596, dated 09 / 10 / 2024, page 9 / 71 3 / 26 are generated during wastewater treatment. Reducing ash production in sludge incineration is one of the objectives.

[0007] In order to achieve, among others, the objectives presented above, the invention is characterized by what is presented in the characterization parts of the appended independent claims.

[0008] Some preferred embodiments of the invention will be described in the other claims.

[0009] The features and advantages mentioned in this text refer, where applicable, to the treatment system, the method and the uses according to the invention, although this is not always specifically mentioned.

[0010] Typical treatment system according to the present invention for the treatment of wastewater from a pulp and / or paper mill comprises

[0011] - a water-soluble cationic polymer,

[0012] - Al and / or Fe-based inorganic metal coagulant, and

[0013] - Wood-based organic material with an average particle size < 10 mm, wherein the treatment system comprises an Al and / or Fe-based inorganic metal coagulant and a combination of wood-based organic material and the cationic polymer in a weight ratio of 4:1-1:10. The treatment system according to the present invention is typically used in the treatment of wastewater from pulp and / or paper mills for the efficient removal of COD.

[0014] A typical method according to the invention for removing dissolved organic compounds from wastewater, preferably wastewater from a pulp and / or paper mill, comprises

[0015] - obtain wastewater from a pulp and / or paper mill comprising dissolved organic compounds, Petition 870240086596, dated 09 / 10 / 2024, page 10 / 71 4 / 26

[0016] - add a coagulant to wastewater to precipitate dissolved organic compounds,

[0017] - remove precipitated organic substances from wastewater and form organic sludge,

[0018] wherein the coagulant comprises the treatment system according to the present invention.

[0019] It has been found that wood-based organic material in the form of powder, flakes, shavings and / or other particles in combination with a cationic polymer is efficient in the coagulation and flocculation process for COD removal in wastewater treatment. Therefore, Al and / or Fe-based inorganic metal coagulants conventionally used in tertiary wastewater treatment can be partially replaced by a treatment system comprising wood-based organic material and a cationic polymer in order to provide treatment efficiency at least similar to conventional inorganic metal coagulants alone.According to the present invention, the dose of Al and / or Fe-based inorganic metal coagulant can be reduced when used in combination with wood-based material and cationic polymer; for example, the dose of Al and / or Fe-based inorganic metal coagulant can be reduced by about 50% while maintaining COD removal effectiveness. When using cationic polymer and wood-based material, the coagulation effectiveness with an active inorganic metal coagulant is increased, and therefore a similar degree of COD removal can be achieved with a much lower total dose of inorganic metal coagulants, or COD removal can be improved by at least 20% compared to adding the inorganic metal coagulant alone.

[0020] According to one embodiment of the invention, the system of Petition 870240086596, dated 09 / 10 / 2024, page 11 / 71 The 5 / 26 treatment is designed for use with a solid-liquid separation system for the removal of biologically recalcitrant soluble organic compounds, such as lignin, from wastewater, i.e., the so-called hard COD. The treatment system according to the invention is particularly suitable for use in the treatment of tertiary wastewater in pulp and / or paper mills, but the treatment system can also be dosed before primary and / or secondary clarifiers. The tertiary treatment can be a conventional coagulation-flocculation process with a solid-liquid separation unit. Conventionally, coagulation with salts or inorganic metal compounds based on Al and / or Fe is used in the treatment of tertiary wastewater for the removal of residual COD.According to the present invention, the use of cationic polymer and wood-based material in combination with Al and / or Fe-based inorganic metal coagulants for the precipitation of organic substances, such as lignin, notably reduces the amount of Al and / or Fe-based inorganic metal coagulants added to achieve the desired COD removal. Due to the high volumes of wastewater produced in the pulp and paper industry, the reduced amount of Al and / or Fe-based inorganic metal coagulants also reduces the amounts of salts or inorganic compounds in the resulting sludge. Therefore, the present invention allows for the removal of biologically recalcitrant soluble organic compounds with minimized inorganic sludge production in the treatment of pulp and / or paper mill wastewater.

[0021] The combination of cationic polymer and wood-based material has synergistic effects, as the wood-based material acts as a coagulant and the cationic polymer assists in coagulation by attracting suspended solids and forming larger flakes for faster precipitation. Larger flakes can be Petition 870240086596, dated 09 / 10 / 2024, page 12 / 71 6 / 26 removed more easily and efficiently from wastewater.

[0022] Furthermore, it was observed that adjusting the pH of wastewater before tertiary treatment can further improve COD removal. When the pH is adjusted in the range of 3-6, preferably in the range of about 4-5, the same COD reduction can be obtained with doses of inorganic metal coagulant up to twice as low as without pH adjustment.

[0023] The wood-based organic material (or materials) used in the present invention is highly available from pulp and paper mills, making it an economical product for use in wastewater treatment in pulp and paper mills. The wood-based organic material may comprise wood flour, sawdust, wood powder, wood chips or flakes, wood bark, other wood particles, or the like. It is economically and logistically beneficial to use said wood-based organic materials in the on-site wastewater treatment process as at least a partial replacement for Al and / or Fe-based inorganic metal coagulants. Typically, they do not require any separate treatment or handling before use, but can be used in the form in which they are available from the pulp and paper mill.Furthermore, commercial wood-based material products comprising particles with an average particle size < 10 mm can also be used as an organic wood-based coagulant in the treatment system, according to the present invention.

[0024] The treatment system according to the present invention does not noticeably affect the pH of the wastewater as the use of inorganic metal coagulants alone does. DESCRIPTION OF THE DRAWINGS

[0025] The invention will be described in more detail with reference Petition 870240086596, dated 09 / 10 / 2024, page 13 / 71 7 / 26 to the attached drawings, in which

[0026] Figure 1 shows the COD removal efficiency when using the iron sulfate coagulant Ferix-3 alone without (784 ppm points) and with pH adjustment (202-358 ppm points; pH = 4),

[0027] Figure 2 shows the soluble (filtered) COD removal efficiency when using the iron sulfate coagulant Ferix-3 alone without (784 ppm points) and with pH adjustment (202-358 ppm points; pH = 4),

[0028] Figure 3 shows the UVabS254nm removal efficiency when using the iron sulfate coagulant Ferix-3 alone (784 ppm points) and with pH adjustment (202-358 ppm points; pH = 4).

[0029] Figures 4 and 5 show COD removal efficiency and Soluble COD from wastewater from bleached softwood kraft pulp manufacturing, using a combination of Ferix-3 iron sulfate coagulant and FennoFloc C50 cationic polyamine-enhanced Vemissa E150 surface adsorbent with pH adjustment (pH = 4).

[0030] Figures 6-8 show COD removal efficiency, Soluble COD and UVabS254nm from wastewater from bleached softwood kraft pulp manufacturing, using a combination of Ferix-3 iron sulfate coagulant and FennoFloc C50 cationic polyamine-enhanced pine bark surface adsorbent with pH adjustment (pH = 4), and

[0031] Figures 9-11 show COD removal efficiency, Soluble COD and UVabS254nm from wastewater from bleached softwood kraft pulp manufacturing, using a combination of Ferix-3 iron sulfate coagulant and FennoFloc C50 cationic polyamine-enhanced sawdust surface adsorbent with pH adjustment (pH = 4). Petition 870240086596, dated 09 / 10 / 2024, page 14 / 71 8 / 26 DETAILED DESCRIPTION OF THE INVENTION

[0032] A treatment system or treatment composition, according to the present invention, comprises at least wood-based organic material with an average particle size < 10 mm and a water-soluble cationic polymer. Furthermore, the treatment system according to the present invention comprises Al and / or Fe-based inorganic metal coagulants in combination with wood-based organic material and a cationic polymer, wherein wood-based organic material with an average particle size < 10 mm and a water-soluble cationic polymer is used to partially replace conventional Al and / or Fe-based inorganic metal coagulants in wastewater treatment.

[0033] In the present invention, the wood-based material acts as an adsorption surface and the cationic polymer in combination with the Al and / or Fe-based inorganic metal coagulant provides the required charge for the flocculation treatment system. Therefore, the treatment system, according to the present invention, provides efficient precipitation of dissolved organic compounds.

[0034] According to the present invention, the wood-based organic material can be any wood-based material with an average particle size < 10 mm. The average particle size refers to the average particle size distribution value of the wood-based material. The wood-based organic material can be in the form of powder, flakes, chips, sticks and / or other particles. In one embodiment of the present invention, the particles of the wood-based organic material can be, for example, crushed or refined. According to one embodiment of the present invention, the wood-based material comprises sawdust, wood bark, mechanically ground wood particles, wood flour, wood powder or any combination thereof. The wood-based material Petition 870240086596, dated 09 / 10 / 2024, p. 15 / 71 9 / 26 Wood can comprise coarse and / or fine particles. According to the present invention, the average particle size of the wood-based material is < 10 mm, preferably < 5 mm to allow for coagulation and flocculation efficiency to precipitate dissolved organic compounds from wastewater. According to one embodiment of the present invention, the average particle size of the wood-based organic material is in the range of 0.010-10 mm and preferably in the range of 0.050-5 mm. The smaller particle size of the wood-based material increases the specific surface area of ​​the wood-based material and therefore improved performance can be seen at even lower dosage amounts.

[0035] According to one embodiment of the present invention, the wood-based material may comprise sawdust or wood dust. Sawdust or wood dust are common residues from wood products. Sawdust or wood dust is a typical byproduct or residue of woodworking operations, such as sawing. It is mainly composed of fine wood particles. Wood dust is a form of particulate material or particles. The wood-based material may also be any other unrefined wood material in particle form.

[0036] According to one embodiment of the present invention, the wood-based material may comprise wood bark. Wood bark is also a common material in the by-flow of pulp and paper mills. Wood bark comprising bark flakes or chips and / or bark mulch may be used in the treatment system according to the present invention. The particle size of the husk-based material may vary. It can be used in the present invention without any further processing and / or it can be treated, for example, crushed, to smaller particulate matter before being used in the treatment of... Petition 870240086596, dated 09 / 10 / 2024, page 16 / 71 10 / 26 wastewater.

[0037] According to one embodiment of the present invention, the wood-based material in a fine particle form may be wood powder, wood flour, or the like. The wood flour may be a lignocellulosic adsorbent, comprising micronized softwood and / or hardwood powder, also called wood flour. According to one embodiment of the present invention, the wood flour / wood powder may comprise wood particles with 95% grain size < 150 µm and 80% grain size > 10 µm. According to one embodiment of the present invention, the wood-based material may be a mixture of finely divided wood powder / wood flour and coarse particles, such as wood chips and / or tree bark or other particulate material and / or sawdust.

[0038] According to the present invention, the wood-based material can originate from any wood species. It can be softwood and / or hardwood.

[0039] According to one embodiment of the present invention, the treatment system comprises wood-based organic material and the cationic polymer in a weight ratio of 0.5:1-5:1, preferably 1:1-3:1 and, more preferably, 1:1-2:1, calculated using the active quantity of the cationic polymer. The benefits of flocculation for COD removal can be achieved even with small quantities of wood-based material, but the effect is improved by increasing the amount of wood-based material relative to the cationic polymer. The appropriate ratio depends on the wood-based material and its absorbent surface area and charge density of the cationic polymer.

[0040] The treatment system, according to the present invention, comprises at least one cationic polymer soluble in Petition 870240086596, dated 09 / 10 / 2024, page 17 / 71 11 / 26 water to increase the size of the floc to be formed and to improve the separation of precipitated organic substances from wastewater. To achieve improved flocculation, the cationic polymer has a net cationic charge. According to one embodiment of the present invention, the cationic polymer comprises a synthetic cationic polymer and / or a bio-based cationic polymer. The water solubility of the cationic polymer means that the cationic polymer is substantially soluble in water in an aqueous medium. The aqueous medium may, for example, comprise acid to achieve dissolution.

[0041] According to one embodiment of the present invention, the cationic polymer comprises polyamine, polyvinylamine, polyethyleneimine, polydicyandiamide (polyDCD), polydiallyldimethylammonium chloride (polyDADMAC), poly(acryloyloxyethyl trimethylammonium chloride) (polyADAM-CI), poly(methacryloyloxyethyl trimethylammonium chloride) (polyMADAM-CI), poly(acrylamido-N-propyltrimethylammonium chloride) (polyAPTAC), poly(methacrylamidopropyltrimethylammonium chloride) (polyMAPTAC) and / or a copolymer of (meth)acrylamide and cationic monomers selected from diallyldimethylammonium chloride (DADMAC), acryloyloxyethyl chloride (ADAM-CI), methacryloyloxyethyl chloride (MADAM-CI), acrylamido-N-propyltrimethylammonium chloride. (APTAC) and / or methacrylamidopropyltrimethylammonium chloride (MAPTAC). According to a preferred embodiment of the present invention, a cationic polymer comprises polyamine and / or polyDADMAC, preferably polyamine.Polyamines typically have higher cationicity, such as polyDADMAC, and therefore provide the same efficiency at lower dosages. Polyamines are organic compounds with two or more primary amino groups. PolyDADMAC is a homopolymer of diallyldimethylammonium chloride (DADMAC). Petition 870240086596, dated 09 / 10 / 2024, page 18 / 71 12 / 26

[0042] According to one embodiment of the present invention, a cationic polymer may comprise a bio-based cationic polymer comprising a cationic polysaccharide, such as starch, cellulose, guar gum, dextran or the like, and / or chitosan.

[0043] In one embodiment according to the present invention, the cationic polymer comprises cationic starch with a degree of substitution (DS) value of at least 0.3, preferably at least 0.4, to provide the cationicity required for flocculation. In the context of the present application, the term cationic starch means starch that has been modified by cationization.

[0044] Cationic starches, which have a degree of substitution, DS, > 0.3 starches are considered highly cationic in this application. The highly cationic starch is preferably only slightly degraded or not degraded and modified only by cationization. More preferably, the starch used is not degraded and not cross-linked. There are several derivatizing agents that can be used to provide a positive charge density to the starch. A cationic starch may have quaternary ammonium, quaternary phosphonium, tertiary sulfonium or other corresponding substituent(s). Particularly preferred is a cationic charge that is derivatized to contain a quaternary ammonium ion, for example, by etherification of hydroxyl groups with a suitable etherifying agent having a cationic character, such as the quaternary methyl chloride salt of N(2,3-epoxypropyl)dimethylamine or N-(2,3-epoxypropyl)dibutylamine or N(2,3-epoxypropyl)methylaniline.Suitable highly cationic starches are of natural origin, for example, potato, rice, corn, waxy maize, wheat, barley, sweet potato or tapioca starch, with potato starch being preferred.

[0045] The cationicity of cationic starch can be defined using the degree of substitution (DS). The degree of substitution defines how many Petition 870240086596, dated 09 / 10 / 2024, page 19 / 71 13 / 26 substituted groups are contained in cationic starch, calculated per unit of starch anhydroglucose. The degree of substitution of cationic starch, which is cationized with 2,3-epoxypropyltrimethylammonium chloride, is typically calculated using the nitrogen content of pure dry cationic starch, which contains no other nitrogen source besides quaternary ammonium groups. The nitrogen content is typically determined using the commonly known Kjeldahl method. The degree of substitution of cationic starch, which is cationized with 2,3-epoxypropyltrimethylammonium chloride, can be calculated using the following equation:

[0046] DS = (162 x N-%) / (1400 - (N-% x 151.6),

[0047] where 162 is the molecular weight of an anhydroglucose (AHG) unit, N-% is the nitrogen value in %, 1400 is the molecular weight of nitrogen multiplied by 100, and 151.5 is the molecular weight of 2,3-epoxypropyltrimethylammonium chloride.

[0048] According to the present invention, wood-based organic material and cationic polymer are used in combination with Al and / or Fe-based inorganic metal coagulant(s). The present invention allows for a reduction in the amount of Al and / or Fe-based inorganic metal coagulants used per kg of organic compounds in wastewater. According to one embodiment of the present invention, the treatment system comprises an Al and / or Fe-based inorganic metal coagulant and a combination of wood-based organic material and the cationic polymer in a weight ratio of 4:1-1:10, preferably 4:1-1:4, and more preferably 1:1-1:4, calculated using the active metal content and the active quantity of the cationic polymer. Improved COD removal efficiency, for example, COD removal of up to more than 80%, is achieved by decreasing the dosage of inorganic coagulant by Petition 870240086596, dated 09 / 10 / 2024, page 20 / 71 14 / 26 comparison with the use of inorganic metal coagulants alone.

[0049] According to one embodiment of the present invention, the Al and / or Fe-based inorganic metal coagulant comprises aluminum sulfate, polyaluminum chloride, iron sulfate, ferric chloride, or any combination thereof. According to one embodiment of the present invention, the treatment system may also comprise other multivalent compounds in addition to the Al and / or Fe-based inorganic metal coagulant to enhance the effect of the coagulants. According to one embodiment of the present invention, the multivalent compound may be zirconium, calcium, and / or magnesium-based.

[0050] In one embodiment according to the present invention, an addition of Al and / or Fe-based inorganic metal coagulant can be carried out simultaneously with the addition of wood-based organic material and cationic polymer, or they can be added sequentially to the wastewater.

[0051] The treatment system according to the present invention is preferably used to remove recalcitrant biologically soluble organic substances, such as lignin, from wastewater, the removal of which can be observed as reduced COD. The treatment system according to the present invention is especially used in the treatment of wastewater from pulp and / or paper mills. The method according to the invention can be used to remove dissolved lignin, for example, from wastewater from a chemical pulp bleaching plant. Therefore, according to a preferred embodiment of the present invention, the dissolved organic compounds to be precipitated from wastewater are understood to be organic substances, such as lignin originating from pulp and / or paper manufacturing processes. Petition 870240086596, dated 09 / 10 / 2024, page 21 / 71 15 / 26 for example, from the chemical pulping process of cellulosic fiber material. Organic compounds refer to, for example, lignin, lignin-like substances or compounds and their decay products, as well as other organic compounds present in wastewater from pulp and paper processes. In the present context, the term recalcitrant soluble organic substances is understood as organic substances or compounds that resist microbial degradation, are difficult to oxidize biochemically and / or are not readily biodegradable. Examples of such compounds are humic substances, such as wood-based lignin and its degradation products, large aromatic compounds and phenolic compounds, such as polyphenols.

[0052] A typical method, according to the present invention, for removing dissolved organic compounds from wastewater, especially from wastewater originating from a pulp and / or paper mill, comprises

[0053] - obtain wastewater comprising dissolved organic compounds,

[0054] - add the treatment system, according to the present invention, as a coagulant for wastewater to precipitate dissolved organic compounds, and

[0055] - remove precipitated organic substances from wastewater and form organic sludge.

[0056] The treatment system according to the present invention can be added to wastewater at any suitable point for the removal of dissolved organic compounds. The separation of dissolved organic compounds from precipitated organic compounds can be carried out using any suitable solid-liquid separation system. The precipitated compounds can be separated from the wastewater in primary clarifiers, secondary clarifiers Petition 870240086596, dated 09 / 10 / 2024, page 22 / 71 16 / 26 and / or in tertiary treatment after biological treatment.

[0057] According to one embodiment of the present invention, the treatment system is added to the wastewater after biological treatment of the wastewater, where particularly recalcitrant soluble organic substances can be precipitated from the wastewater.

[0058] In one embodiment of the present invention, the treatment system is added to the wastewater after biological wastewater treatment and before tertiary treatment, where precipitated organic substances can be removed from the wastewater in the solid-liquid separation unit of the tertiary treatment. This application is especially valuable in the treatment of wastewater from pulp and / or paper mills. In one embodiment according to the present invention, at least part of the treatment system can also be added to the tertiary treatment. According to one embodiment of the present invention, the tertiary treatment comprises the dissolved air flotation (DAF) step, wherein the treatment system of the present invention is preferably added to the wastewater before transporting the wastewater to the DAF flotation tank.In one embodiment of the present invention, the treatment system can be dosed into the feed water of the DAF flotation tank to coagulate the colloidal particles and / or conglomerate the particles into larger clusters.

[0059] Precipitated solids can also be removed from wastewater using a disc filter, settling tank, or membrane filtration, where the treatment system is added before the separation stage. The reject, i.e., an organic sludge comprising the precipitated organic substances, can be transported to the incinerator. The sludge produced by the method of Petition 870240086596, dated 09 / 10 / 2024, page 23 / 71 17 / 26 according to the invention is highly organic and therefore final disposal can be done with existing incinerators.

[0060] According to one embodiment of the present invention, the pH of the wastewater is adjusted to be < 7, preferably in the range of 3-6 and, more preferably, in the range of about 4-5 depending on the use of inorganic metal coagulant. In a preferred embodiment according to the present invention, the pH is adjusted before the addition of the treatment system, according to the present invention. The pH adjustment can be carried out using conventional pH adjusting chemicals, such as H2SO4. It has been observed that COD removal with the treatment system, according to the present invention, can be improved with pH adjustment. pH adjustment is especially used when the treatment system is dosed for wastewater after biological treatment, where it does not impair the operation of the biological treatment.

[0061] The appropriate amount of treatment system components to be added depends on the wastewater to be treated. EXPERIMENTAL

[0062] A better understanding of the present invention can be obtained through the following examples which are presented for illustrative purposes only, but should not be interpreted as limiting the present invention. Flocculation Method and COD Analysis

[0063] Flocculation and coagulation experiments in Example of Reference and Application Examples 1-5 below are conducted using the “Flocculator 2000” mini-flocculator. Approximately 30 liters of water is collected to perform all tests using the same water sample. The water is stored in a cold chamber before testing begins. The entire sample batch is... Petition 870240086596, dated 09 / 10 / 2024, page 24 / 71 18 / 26 homogenized and 1 l samples are taken for coagulation tests.

[0064] The sample is mixed (rapid mixing 400 rpm 30 s) and 0.1 M H2SO4 is used as a pH adjustment chemical, and the treatment chemical(s) specified in the following examples are added to the sample. After treatment, the mixing of the chemical additions (slow mixing at 40 rpm for 10-20 min) is continued to encourage floc formation and accumulation. The pH is measured at this stage. After mixing, the sample is held for approximately 10-30 min to settle.

[0065] After sedimentation, samples are removed from the supernatant with a pipette approximately 3 cm below the liquid level. The effect of the treatment chemical (or chemicals) on COD removal and UV absorbance reduction is determined. Chemical oxygen demand (COD) is used as an indicative measure of the amount of oxygen that can be consumed by reactions in a measured solution. It is commonly expressed as the mass of oxygen consumed over the volume of solution, which in SI units is milligrams per liter (mg / l). A COD test can be used to easily quantify the amount of organic matter in water or wastewater. The most common application of COD is in quantifying the amount of oxidizable pollutants found in wastewater. COD samples are analyzed using Hach Lange kit tubes and a DR390 photometer. UV absorbance measurements at 254 nm are conducted using a Unicam SN024 spectrophotometer.The filtered samples are removed by filtering the decanted supernatant. Sample filtration prior to COD analysis is performed with a pre-washed 0.45 µm cellulose acetate (CA) membrane filter. EXAMPLES Petition 870240086596, dated 09 / 10 / 2024, page 25 / 71 19 / 26

[0066] The wastewater used in the following reference example and in application examples 1-5 originates from the manufacture of bleached softwood kraft pulp and the sample was taken after biological treatment of the wastewater. The dissolved organic compounds are precipitated as described in more detail in the following Examples.

[0067] EXAMPLE OF REFERENCE: REMOVAL EFFICIENCY COD REMOVAL EFFICIENCY FROM WASTEWATER USING FERROUS SULFATE COAGULANT FERIX-3 ALONE

[0068] The COD removal efficiency from wastewater using ferrous sulfate coagulant Ferix-3 (Kemira Oyj) alone is shown in Figure 1. Figure 1. COD removal efficiency is tested using Ferix-3 coagulant alone (dosage of 784 ppm of said product) without pH adjustment and with pH adjustment (dosages of 202, 224, 269, 314 and 358 ppm of said product; pH = 4). As seen in Figure 1, 90% COD removal can be achieved without pH adjustment at a coagulant dose of 784 ppm. By adjusting the pH of wastewater to a value of 4, the same reduction in COD can be achieved with Ferix-3 doses of 314 and 358 ppm, meaning the coagulant dose is reduced more than twice.This means that the amount of incinerated ash produced after combustion of wastewater sludge is half that when pH adjustment is used in wastewater treatment compared to the amount of sludge generated in water treatment without pH adjustment. Therefore, in order to achieve a reduction in ash content, the experiments were conducted at a fixed pH of 4.

[0069] A similar trend is observed in the reduction values ​​of soluble COD (filtered) and UVabS254nm as shown in Figures 2 and 3. A coagulant dose of 224 ppm and pH adjustment up to 4 allows for a 60% reduction in total COD and approximately 80% reduction in soluble COD and removal of Petition 870240086596, dated 09 / 10 / 2024, page 26 / 71 20 / 26 UVabs. A pH of 4 and a Ferix-3 dose of 358 ppm allowed for approximately 90% removal of filtered COD and UVabs versus 91% and 94% removal of filtered COD and UVabs, respectively, when 758 ppm of Ferix-3 was used without pH adjustment. As seen in Figures 13, coagulation with the iron sulfate coagulant Ferix-3 alone, with pH adjustment up to 4, does not work with iron doses below 200 ppm. APPLICATION EXAMPLE 1: GROUND LIGNOCELLULOSIC ADSORBENT AND CATIONIC POLYMER FLOCCULANT

[0070] Precipitation of dissolved organic compounds was conducted using a mixture of lignocellulosic adsorbent and cationic polyamine flocculant FennoFloc C50 alone or in combination with the iron sulfate coagulant Ferix-3 (Kemira Oyj), at pH = 4.

[0071] The ground lignocellulosic adsorbent comprises micronized wood-based powder (wood flour) with 95% grain size < 150 µm and 80% grain size > 10 µm (product code Vemissa E150, manufacturer SPPS, France). The dosage quantities shown in the Figures are provided as dosages of said product.

[0072] FennoFloc C50 (Kemira Oyj) is a polyamine with a typical active polymer content of 50% and a typical Brookfield viscosity of 500-1000 mPas at 25 °C.

[0073] The COD and soluble (filtered) COD removal efficiency from wastewater using a combination of lignocellulosic adsorbent and cationic polyamine flocculant is shown in Figures 4 and 5. The cationic polyamine flocculant Fennofloc C50 (Figures referred to as “C 50”) can be used to aid coagulation by attracting suspended solids and forming larger flocs for faster precipitation. Test results Petition 870240086596, dated 09 / 10 / 2024, p. 27 / 71 Studies 21 / 26 showed that the lignocellulosic adsorbent “Vemissa” can reduce the use of inorganic metal salts in wastewater treatment by precipitation. A mixture of the lignocellulosic adsorbent “Vemissa” and the polyamine flocculant FennoFloc C50 can remove up to 30% of COD from wastewater when used alone, thus preventing the formation of inorganic sludge. When combined with the iron sulfate coagulant Ferix-3, the maximum COD removal efficiency can reach over 80%. This example shows that the lignocellulosic adsorbent mixed with the polyamine flocculant requires much smaller amounts of iron and aluminum salts for sufficient COD removal in the coagulation process. In most cases, a reduction of almost 50% in metallic coagulant was observed when conducting the treatment process with a mixture of lignocellulosic adsorbent and polyamine flocculant while maintaining the same level of removal efficiency.

[0074] Figure 4 shows the COD removal efficiency when assisting coagulation with lignocellulosic adsorbent mixed with the cationic polyamine flocculant FennoFloc C50. Over 60% total COD removal can be achieved with a Ferix3 coagulant dose of 224 ppm and pH 4. When using a 230 ppm dose of Ferix-3 coagulant together with 45 ppm of organic lignocellulosic adsorbent mixed with 45 ppm of polyamine flocculant Fennofloc C50, over 80% total COD reduction was achieved. As seen in Figure 4, a 67% reduction in COD was observed when the Ferix-3 dose was reduced from 224 ppm to 120 ppm and with the use of 91 ppm of lignocellulosic adsorbent mixed with 91 ppm of FennoFloc C50 flocculant. The reduction in filtered COD (Figure 5) showed similar behavior to total COD removal. Further decreases in the metal coagulant dose require increased dosages of lignocellulosic adsorbent and polyamine flocculant to maintain COD removal efficiency. Petition 870240086596, dated 09 / 10 / 2024, p. 28 / 71 22 / 26 filtered to a sufficient level. For example, a 70% reduction in soluble COD requires a dose of 120 ppm metal coagulant assisted by 91 ppm of lignocellulosic adsorbent which, in turn, is mixed with 91 ppm of FennoFloc C50 polyamine flocculant. It is important to note that 91 ppm of lignocellulosic adsorbent in combination with 91 ppm of FennoFloc C50 polyamine flocculant used alone without metal coagulant at pH 4 allows for the removal of approximately 20% of the total COD and 30% of the soluble COD from the wastewater. APPLICATION EXAMPLE 2: WOOD BARK AND Cationic Polymer Flocculant

[0075] The precipitation of dissolved organic compounds was conducted using a mixture of pine bark material (average particle size < 10 mm) and cationic polyamine flocculant FennoFloc C50 alone or in combination with ferrous sulfate coagulant Ferix-3 (Kemira Oyj). The dosage amounts shown in the Figures are provided as dosages of said product.

[0076] FennoFloc C50 (Kemira Oyj) is a polyamine with a typical active polymer content of 50% and a typical Brookfield viscosity of 500-1000 mPas at 25 °C.

[0077] Figures 6-8 show the performance of pine bark material modified with the cationic polyamine flocculant FennoFloc C50 in removing COD, soluble COD, and UVabS254nm values ​​at pH = 4. When using a dose of 230 ppm of Ferix-3 iron sulfate coagulant and adding 91 ppm of pine bark adsorbent mixed with 91 ppm of polyamine flocculant, COD removal was improved by more than 20% and was equal to 85%. Lower doses of Ferix-3 coagulant below 200 ppm combined with the pine bark and polyamine flocculant mixtures allowed for the removal of organic matter from the wastewater, which was not Petition 870240086596, dated 09 / 10 / 2024, p. 29 / 71 23 / 26 observed when the iron sulfate coagulant Ferix-3 was used alone (see reference example). For example, when 120 ppm of Ferix-3 coagulant was dosed into wastewater along with a mixture of pine bark and polyamine flocculant (91 ppm, 1:1 ratio), 60-70% removal of COD and UVabS254nm was achieved. The use of a mixture of pine bark and polyamine flocculant alone (91 ppm, 1:1 ratio) without inorganic metal coagulant removes approximately 30% of COD and 40% of UVabs from wastewater. APPLICATION EXAMPLE 3: SAWDUST AND CATIONIC POLYMER FLOCCULANT

[0078] The precipitation of dissolved organic compounds was conducted using a mixture of sawdust (average particle size < 5 mm) and cationic polyamine flocculant FennoFloc C50 alone or in combination with ferrous sulfate coagulant Ferix-3 (Kemira Oyj). The dosage amounts shown in the Figures are provided as dosages of said product.

[0079] FennoFloc C50 (Kemira Oyj) is a polyamine with a typical active polymer content of 50% and a typical Brookfield viscosity of 500-1000 mPas at 25 °C.

[0080] Figures 9-11 show the performance of sawdust material modified with the polyamine flocculant FennoFloc C 50 in removing COD, soluble COD, and UVabS254nm values ​​at pH = 4. When using a dose of 230 ppm of Ferix-3 iron sulfate coagulant and adding 45 ppm of sawdust adsorbent mixed with 45 ppm of polyamine flocculant, COD removal was improved by 20% and reached 80%, but there was no improvement in soluble COD and UVabs removal. However, lower doses of Ferix-3 coagulant below 200 ppm combined with the sawdust and polyamine flocculant mixtures allowed for the removal of organic compounds from Petition 870240086596, dated 09 / 10 / 2024, page 30 / 71 24 / 26 wastewater, which was not observed when the Ferix-3 coagulant was used alone. For example, when 120 ppm of Ferix-3 iron sulfate coagulant was dosed into wastewater together with a sawdust-polyamine mixture (91 ppm, 1:1 ratio), 60-70% removal of COD and UVabs was achieved. APPLICATION EXAMPLE 4: GROUND LIQNOCELLULOSIC ADSORBENT AND CATIONIC POLYIDADMAC FLOCCULANT

[0081] Precipitation of dissolved organic compounds was conducted using a lignocellulosic adsorbent and a cationic polyDADMAC flocculant FennoFloc C40 alone or in combination with iron sulfate coagulant Ferix-3 (Kemira Oyj).

[0082] The ground lignocellulosic adsorbent comprises micronized wood-based powder (wood flour) with 95% grain size < 150 µm and 80% grain size > 10 µm (product code Vemissa E150, manufacturer SPPS, France). The dosage quantities shown in the Figures are provided as dosages of said product.

[0083] FennoFloc C40 (Kemira Oyj) is a poly(diallyldimethylammonium chloride) (polyDADMAC) with a typical active polymer content of 40% and a typical Brookfield viscosity of 1000-4000 mPas at 25 °C.

[0084] Table 1 shows the performance of the sawdust material modified with poliDADMAC FennoFloc C40 in removing COD, soluble COD and UVabS254nm values, at pH = 4 and 21 °C. TABLE 1. Ferix-3 ppm C40 ppm Vemissa ppm Turbidity NTU Uvabs (254 nm) 1 / cm COD mg / l COD filt (0.45 pm) mg / l 2.5 4.6 387 379 171 91 91 1.1 1.0 77 70.5 85 91 91 9.2 2.0 220 165 0 91 91 15 2.9 359 290 Petition 870240086596, dated 09 / 10 / 2024, page 31 / 71 25 / 26

[0085] As shown in the Reference Example above, the dosages of Ferix-3 used in this experiment are ineffective for COD removal on their own. A mixture of the lignocellulosic adsorbent and the cationic flocculant provides efficient COD removal, even at small dosages of Ferix-3 iron sulfate. The lignocellulosic adsorbent in combination with the cationic flocculant used alone without the addition of Ferix-3 also reduces COD from wastewater. APPLICATION EXAMPLE 5: SAWDUST AND CATIONIC STARCH

[0086] Precipitation of dissolved organic compounds was conducted using a mixture of sawdust (average particle size < 5 mm) and cationic starch flocculant in combination with Ferix-3 iron sulfate coagulant (Kemira Oyj). One test point was as in Application Example 3 using sawdust and FennoFloc C50 cationic polyamine flocculant in combination with Ferix-3.

[0087] The cationic starch used was highly cationic dry starch powder with a charge density of 4.0 meq / g at pH 7.5 and a Brookfield viscosity of 471 mPas as a 3% water solution at 25 °C.

[0088] Table 2 shows the performance of sawdust material modified with cationic starch in removing COD, soluble COD, and UVabS254nm values ​​at pH = 4 and 21 °C. As shown in the results, COD can be efficiently removed. COD removal of around 90% can be achieved with a combination of sawdust and cationic starch with a reduced dosage of Ferix-3 compared to the reference sample. TABLE 2. Ferix-3 ppm H2SO4 ppm Sawdust m ppm Cationic starch ppm C-50 ppm Turbidity NTU UVabs (254nm) 1 / cm COD mg / l filtered COD (0.45μm) mg / l 3.9 5.3 392 380 Petition 870240086596, dated 09 / 10 / 2024, page 32 / 71 26 / 26 245 345 No removal 245 348 40 40 7.1 0.72 54 49 245 342 30 30 81 0.77 189 45 273 336 30 30 8.1 0.61 46 35 273 336 20 20 24 0.66 67 38 CONCLUSION OF APPLICATION EXAMPLES

[0089] The results of the application examples showed that wood-based organic material can reduce the amount of inorganic metal salt used in wastewater treatment. When a mixture of wood-based organic material and cationic polymer with Ferix-3 iron sulfate coagulant is used, the maximum COD removal efficiency can reach more than 80%.

Claims

1. A method for removing dissolved organic compounds from wastewater from a pulp and / or paper mill, characterized in that it comprises: - obtaining wastewater from the pulp and / or paper mill containing dissolved organic compounds; - adding a coagulant to the wastewater to precipitate dissolved organic compounds; and - removing precipitated organic substances from the wastewater and forming organic sludge, wherein the coagulant comprises a treatment system comprising: - a water-soluble synthetic cationic polymer and / or a bio-based cationic polymer; - wood-based organic material in the form of powder, flakes, shavings, sticks and / or other particles with an average particle size < 10 mm; and - an Al and / or Fe-based inorganic metal coagulant.and wherein the treatment system comprises an Al and / or Fe-based inorganic metal coagulant and a combination of wood-based organic material and cationic polymer in a weight ratio of 4:1 - 1:10, and wherein the coagulant is added to the wastewater after the biological wastewater treatment stage and before tertiary treatment.

2. Method according to claim 1, characterized in that the wood-based organic material comprises sawdust, wood bark, mechanically crushed wood particles, wood flour, wood powder or any combination thereof. Petition 870240086596, dated 09 / 10 / 2024, p. 34 / 71 2 / 3 3. Method according to claim 1 or 2, characterized in that the average particle size of the wood-based organic material is <5 mm.

4. A method, according to any of the preceding claims, characterized in that the average particle size of the wood-based organic matter is in the range of 0.010-10 mm and, preferably, in the range of 0.050-5 mm.

5. A method, according to any of the preceding claims, characterized in that the treatment system comprises wood-based organic material and cationic polymer in a weight ratio of 0.5:1-5:1, preferably 1:13:1 and, more preferably, 1:1-2:1, calculated using the active quantity of the cationic polymer.

6. A method, according to any of the preceding claims, characterized in that the treatment system comprises an Al and / or Fe-based inorganic metal coagulant and a combination of wood-based organic material and the cationic polymer in a weight ratio of 4:1-1:4 and, more preferably, 1:1-1:4, calculated using the active metal content and the active quantity of the cationic polymer.

7. Method, according to any of the preceding claims, characterized in that the cationic polymer comprises polyamine, polyvinylamine, polyethyleneimine, polydicyandiamide (polyDCD), polydiallyldimethylammonium chloride (polyDADMAC), poly(acryloyloxyethyl trimethylammonium chloride) (polyADAMCI), poly(methacryloyloxyethyl trimethylammonium chloride) (polyMADAM-CI), poly(acrylamido-N-propyltrimethylammonium chloride) (polyAPTAC), poly(methacrylamidopropyltrimethylammonium chloride) (polyMAPTAC) and / or a copolymer of (meth)acrylamide and cationic monomers selected from diallyl dimethylammonium chloride (DADMAC), Petition 870240086596, dated 09 / 10 / 2024, p. 35 / 71 3 / 3 acryloyloxyethyl trimethylammonium chloride (ADAM-CI), methacryloyloxyethyl trimethylammonium chloride (MADAM-CI), acrylamide-N-propyltrimethylammonium chloride (APTAC) and / or methacrylamidopropyltrimethylammonium chloride (MAPTAC).

8. A method, according to any of the preceding claims, characterized in that the cationic polymer comprises polyamine and / or polydiallyldimethylammonium chloride (polyDADMAC).

9. A method, according to any of the preceding claims, characterized in that the cationic polymer comprises cationic starch with a degree of substitution (DS) value of at least 0.3, preferably at least 0.

4.

10. A method, according to any of the preceding claims, characterized in that the Al and / or Fe-based inorganic metal coagulant comprises aluminum sulfate, polyaluminum chloride, iron sulfate, ferric chloride, or any combination thereof.

11. A method, according to any of the preceding claims, characterized in that the pH of the wastewater is adjusted to < 7, preferably in the range of 3-6, before the addition of the coagulant.

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