Cationic emulsion terpolymer for increasing solids content of filter cake

Abstract

The present disclosure is generally directed to dewatering aqueous sludge produced by wastewater or sewage treatment facilities, such as municipal and industrial processes. The method comprises treating an aqueous sludge with a cationic polyacrylamide polymer comprising the reaction product of: an acryloyl monomer comprising a nonionic amide; a cationic monomer; and a vinyl monomer.

Description

Technical Field

[0001] This disclosure generally relates to compositions and methods for dewatering water-containing sludge generated from wastewater or sewage treatment facilities (e.g., municipal and industrial processes). The method includes treating the water-containing sludge with a cationic polyacrylamide polymer comprising an acrylic monomer; a cationic monomer; and a vinyl monomer comprising a second nonionic group different from a nonionic amide group, and dewatering the treated water-containing sludge. Background Technology

[0002] The wastewater stream from the aforementioned processes typically contains solid waste that cannot be directly recycled and is transported to wastewater treatment plant facilities via a sludge discharge system. Depending on the specific industry and the configuration of the wastewater treatment facility, the wastewater stream undergoes a series of operations to concentrate and remove moisture from the solid waste, thereby producing sludge. Finally, the industrial wastewater stream passes through a filter press (e.g., chamber filter press, plate and frame filter press, frame filter press, membrane filter press, screw filter press, and belt filter press) or a centrifuge, where the solid waste is concentrated into primary sludge or filter cake, while the wastewater filtered from the filter press or centrifuge is further treated until it is suitable for discharge or reuse.

[0003] A typical wastewater treatment plant receives raw wastewater and produces solids and clarified water. Typically, raw wastewater is treated in a primary sedimentation stage to form primary sludge and supernatant. The supernatant undergoes biological treatment and then enters a secondary sedimentation stage to form secondary sludge and clarified water. The clarified water usually requires further treatment before being discharged.

[0004] The standard practice involves mixing a specific amount of polymeric flocculant into the sludge at the feeding point, followed by near-immediate dewatering of the sludge to form a filter cake and waste liquid. This dewatering process can be centrifugal dewatering, or it can be achieved through processes such as filter press or belt filter press.

[0005] In many countries, due to regulatory reasons, most sludge filter cake is landfilled. For landfilling, the filter cake must be dry to 40% (i.e., dry solids content greater than 40%), and the amount of sludge entering any landfill must not exceed 8% (mixing ratio). Therefore, it is desirable (i) to increase the separated dry matter (OS) content to more than about 40% by weight, i.e., to maintain the moisture content of the sludge filter cake below about 60% by weight using existing processes.

[0006] In conventional or standard processes for dewatering aqueous sludge, various ionic, anionic, and cationic polymers have been added as polymeric flocculants to induce flocculation of solids in the sludge. Other methods include adding quicklime (CaO) to the aqueous sludge to increase the dry matter content (OS). However, adding quicklime is both expensive and labor-intensive. Therefore, a simple sludge dewatering process capable of achieving high solids content is needed. Specifically, the objectives are to increase the residual dry matter in the dewatered sludge filter cake and reduce the moisture content in the filter cake.

[0007] Therefore, the object of the present invention is to provide copolymer compositions that improve the performance of sludge dewatering aids in wastewater and sewage treatment.

[0008] The currently produced compositions use cationic polyacrylamide terpolymers, which offer improved performance in the dewatering of aqueous sludge. While not wishing to be bound by theory, the second nonionic monomer is believed to exhibit vinyl polymerizable groups directly attached to the polymer backbone. This provides a monomer with less steric hindrance, greater rotatability and flexibility, and enables the polymer to have conformations different from conventional or standard CPAM polymers. Summary of the Invention

[0009] This disclosure relates to a method for dewatering aqueous sludge. The method involves treating or adding an aqueous sludge to a cationic polyacrylamide polymer comprising the following reaction products: an acryloyl monomer comprising a nonionic amide; a cationic monomer; and a nonionic vinyl monomer. The treated aqueous sludge is then dewatered.

[0010] A method for dewatering water-containing sludge and improving the cake size of filter cake during sludge dewatering is also disclosed. The method involves treating or adding a cationic polyacrylamide polymer comprising the reaction product of: an acrylic monomer containing a nonionic amide; a cationic monomer; and a nonionic vinyl monomer. The treated water-containing sludge is then dewatered to produce a filter cake, which can be disposed of accordingly.

[0011] This overview is intended to introduce a series of concepts in a simplified form, which will be further described in the specific embodiments below. This overview is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid to determining the scope of the claimed subject matter. Detailed Implementation

[0012] The following detailed description (specific implementation) is exemplary in nature and is not intended to limit the invention or its applications and uses. As used herein, the term "exemplary" means "serving as an example, instance, or illustration." Therefore, any embodiment described herein as "exemplary" is not necessarily to be construed as superior to or better than other embodiments. All embodiments described herein are exemplary embodiments intended to enable those skilled in the art to make or use the invention, and not to limit the scope of the invention as defined by the claims. Furthermore, there is no intention to be bound by any express or implied theory set forth in the foregoing technical field, background art, summary of the invention, or the following detailed description.

[0013] Unless otherwise expressly stated or obvious from the context, the term "about" as used herein shall be understood to mean within normal tolerances in the art, such as within two standard deviations of the mean. "About" can be understood as within 10%, 5%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. "About" may also be understood to mean the exact value stated. All numerical values ​​provided herein are modified by the term "about" unless the context clearly indicates otherwise.

[0014] The water-containing sludge to be dewatered according to the method of the present invention is not particularly limited. The water-containing sludge used as the starting material can be derived from, for example, mining sludge, municipal sludge, papermaking sludge, and industrial sludge. It can be digested sludge, activated sludge, coarse sludge, raw sludge, and mixtures thereof.

[0015] A cationic polyacrylamide (cPAM) polymer is provided, comprising a reaction product of: an acryloyl or acrylic monomer containing a nonionic amide; a cationic monomer; and a vinyl monomer.

[0016] In some aspects of the polymer, the acryloyl monomer may be selected from free radical polymerizable cationic monomers, specifically from: trimethylammonium halide-C2-C6-alkyl(meth)acrylate, trimethylammonium halide-C2-C6-alkyl(meth)acrylamide, (meth)acrylamide, or combinations thereof.

[0017] In other aspects of the polymer, the acryloyl monomer may be selected from [(acryloyloxy)alkyl]trialkyl, (acryloylaminoalkyl)trialkyl, or ammonium halide, such as [2-(acryloyloxy)ethyl]trimethylammonium chloride (AETAC), acryloyloxyethyltrimethylammonium chloride, 3-acryloylaminopropyltrimethylammonium chloride (APTAC, DiMAPA-Q), and combinations thereof.

[0018] In some aspects of the polymer, the vinyl monomer may be selected from vinyl formamide, vinyl acetate, vinyl alcohol, vinylpyrrolidone, and combinations thereof.

[0019] In other respects of the polymer, the vinyl monomer is vinylformamide.

[0020] In some aspects of the polymer, the vinyl monomer is present in amounts of about 0.2% to about 20% by weight, or 0.3% to about 15% by weight, or 0.5% to about 10% by weight, based on the total weight of the cationic polyacrylamide polymer.

[0021] In some aspects of this polymer, the weight ratio of acryloyl monomer, cationic monomer and vinyl monomer present in the cationic polyacrylamide polymer is from about 49.9:50:0.1 to about 1:90:9.

[0022] In other aspects of the polymer, the total charge density may be from about 50% to about 100% by weight, or from 60% to 75% by weight.

[0023] A method for dewatering water-containing sludge is also provided, comprising adding a cationic polyacrylamide polymer to the water-containing sludge and dewatering the treated water-containing sludge, wherein the polymer comprises a reaction product of the following substances: an acryloyl or acrylic monomer containing a nonionic amide; a cationic monomer; and a vinyl monomer containing a second nonionic group different from the nonionic amide group.

[0024] In some aspects of the method, the acryloyl monomer may be selected from free radical polymerizable cationic monomers, which are selected from: trimethylammonium halide-C2-C6-alkyl(meth)acrylate, trimethylammonium halide-C2-C6-alkyl(meth)acrylamide, (meth)acrylamide or combinations thereof.

[0025] In other aspects of the method, the acryloyl monomer is selected from [(acryloyloxy)alkyl]trialkyl, (acryloylaminoalkyl)trialkyl and / or ammonium halide.

[0026] In other aspects of the method, the acryloyl monomer is selected from [2-(acryloyloxy)ethyl]trimethylammonium chloride (AETAC), acryloyloxyethyltrimethylammonium chloride, 3-acryloylaminopropyltrimethylammonium chloride (APTAC, DiMAPA-Q), or a combination thereof.

[0027] In some aspects of the method, the vinyl monomer is selected from vinyl formamide, vinyl acetate, vinyl alcohol, vinylpyrrolidone, and combinations thereof.

[0028] In other aspects of the method, the vinyl monomer is vinylformamide.

[0029] In some aspects of the method, the cationic polyacrylamide polymer is added to the water-containing sludge in an amount of about 5 kg of active material per ton of dry sludge to about 20 kg of active material per ton of dry sludge, or about 8 kg of active material per ton of dry sludge to about 15 kg of active material per ton of dry sludge, based on the weight of the water-containing sludge.

[0030] In some aspects of this method, dehydration is carried out through a centrifugation process.

[0031] In other aspects of the method, the dewatering step is carried out in a chamber filter press, plate and frame filter press, frame filter press, membrane filter press, screw filter press and / or belt filter press.

[0032] In some aspects of the method, the water-containing sludge originates from municipal, industrial, papermaking wastewater, or mining processes.

[0033] In other aspects of the method, a filter cake is produced from dewatered sludge, wherein the filter cake solids content of the treated sludge is increased by at least 10% compared to the filter cake solids content of sludge treated with conventional polymers under the same conditions. Example

[0034] Preparation of comparative compositions

[0035] An aqueous phase was prepared by adding 276 g of acrylamide (50 wt%), 0.6 g of Trilon C, 394 g of ADAME Quat (80 wt%), 90 g of water, and 2 ppm of N,N'-methylenebisacrylamide to a 2 L beaker. While stirring, the pH was adjusted to 3 using sulfuric acid. An organic phase was prepared in a second 2 L beaker by mixing 20 g of Zephrym 7053, 3 g of Degacryl 3059L, 12.7 g of Intrasol FA1218 / 5, and 247 g of paraffin oil. See Table 1.

[0036] The aqueous phase was then added to the oil phase under vigorous stirring, followed by homogenization to obtain a stable water-in-oil reverse emulsion. The reverse emulsion was added to a 2-liter glass reactor equipped with an anchor stirrer, thermometer, and distillation apparatus, and the emulsion was evacuated. The emulsion temperature was adjusted to 63 ± 1°C, and polymerization was initiated by initially adding 1% by weight of V-65 (dissolved in oil) based on the total weight of the emulsion after purging with air or distillation for 30 minutes to remove any volatile organic compounds (VOCs). The distillate volume under negative pressure was 110 ml. After distillation, the vacuum was removed. The residual monomer reacted adiabatically, typically reaching a maximum temperature of approximately 70°C. The emulsion was stirred for another 15 minutes, and vacuum was applied again until the reactor cooled to 40°C. Vacuuming was stopped, and two grams of sodium persulfate (25% by weight) and eleven grams of sodium bisulfite (25% by weight) were added to the reactor to reduce the monomer content. Finally, an activator is added to the reactor containing the final product under stirring to facilitate the inversion of the inverted emulsion in water. If the inverted emulsion is added to water, the polymer dissolves in the water after inversion.

[0037] Preparation of new compositions The new composition was prepared in the same manner as the standard composition, except that vinyl formamide was added as a third monomer to the aqueous phase—237 g acrylamide (50 wt%), 394 g ADAME Quat (80 wt%), 19 g vinyl formamide (100 wt%), and 0 ppm N,N'-methylene.

[0038] Table 1 - Preparations

[0039] The water-containing sludge samples were obtained from a wastewater treatment plant in Cologne, Germany. Two 500 mL sludge samples were treated with two different dosages of standard drainage aids used as a baseline in this study. The sludge was treated at two different dosage levels, as shown in Table 2. The samples were sheared with a four-finger stirrer at 1000 rpm for 10–20 seconds to simulate the centrifuge used in the dewatering facility. The water-containing sludge was dewatered using a 315-micron metal sieve. The dewatering time of 300 mL of filtrate was measured, and the clarity of the filtrate was determined using a graduated measuring wedge.

[0040] Cover the filter cake remaining in the sieve with an acrylic disc, and place a 10 kg weight on top of the disc for 1 minute. At this point, visually assess the cake compaction to determine its pressability as good, fair, or poor. Next, place a portion of the pressed cake (weighed) in a heated oven at 105°C overnight. Weigh the dried cake and record the total solids content (TS).

[0041] Dehydration time and clarity Table 2 - KA Köln-Langel

[0042]

[0043] Dehydration (time required to collect 300 ml of filtrate): the lower the better.

[0044] Clarity (filtrate in a turbidity wedge): the higher the better.

[0045] Filter cake solids content TS (105°C, overnight): the higher the better.

[0046] As can be seen from Table 2, the terpolymer compositions containing acryloyl monomers and vinyl monomers exhibit improved efficacy compared to the standard formulation. Table 2 also shows that only specific combinations can provide the desired results.

[0047] While at least one exemplary embodiment has been presented in the foregoing detailed description of the subject matter of the invention, it should be understood that numerous variations exist. It should also be understood that the exemplary embodiments are merely illustrative and are not intended to limit the scope, applicability, or configuration of the subject matter of the invention in any way. Rather, the foregoing detailed description provides those skilled in the art with a convenient roadmap for implementing exemplary embodiments of the subject matter of the invention. It should be understood that various changes can be made to the function and arrangement of the elements described in the exemplary embodiments without departing from the scope of the subject matter set forth in the appended claims.

Claims

1. A cationic polyacrylamide polymer comprising the reaction product of: an acryloyl monomer comprising a nonionic amide; a cationic monomer; and a nonionic vinyl monomer.

2. The cationic polyacrylamide polymer according to claim 1, wherein the acryloyl monomer comprises a radical polymerizable cationic monomer selected from: trimethylammonium halide-C2-C6-alkyl(meth)acrylate, trimethylammonium halide-C2-C6-alkyl(meth)acrylamide, (meth)acrylamide, or a combination thereof.

3. The cationic polyacrylamide polymer according to claim 1, wherein the acryloyl monomer comprises [(acryloyloxy)alkyl]trialkyl, (acryloylaminoalkyl)trialkyl, or ammonium halide.

4. The cationic polyacrylamide polymer according to claim 1, wherein the acryloyl monomer comprises [2-(acryloyloxy)ethyl]trimethylammonium chloride (AETAC), acryloyloxyethyltrimethylammonium chloride, 3-acryloylaminopropyltrimethylammonium chloride (APTAC, DiMAPA-Q), and combinations thereof.

5. The cationic polyacrylamide polymer according to any one of claims 1 to 4, wherein the vinyl monomer is selected from vinyl formamide, vinyl acetate, vinyl alcohol, vinylpyrrolidone, and combinations thereof.

6. The cationic polyacrylamide polymer according to claim 5, wherein the vinyl monomer is vinylformamide.

7. The cationic polyacrylamide polymer according to any one of claims 1 to 6, wherein the content of the vinyl monomer is from about 0.2% to about 20% by weight, or from about 0.3% to about 15% by weight, or from about 0.5% to about 10% by weight, based on the total weight of the cationic polyacrylamide polymer.

8. The cationic polyacrylamide polymer according to any one of claims 1 to 7, wherein the acryloyl monomer, cationic monomer and vinyl monomer are present in the cationic polyacrylamide polymer in a weight ratio of about 49.9:50:0.1 to about 1:90:

9.

9. The cationic polyacrylamide polymer according to any one of claims 1 to 8, wherein the total charge density is about 50% to about 100% by weight.

10. Methods for dewatering water-containing sludge, including: a) Adding a cationic polyacrylamide polymer to the aqueous sludge, the polymer comprising a reaction product of an acryloyl monomer containing a nonionic amide; cationic monomers; and nonionic vinyl monomers; and b) Dewater the water-containing sludge obtained in step a).

11. The method of claim 10, wherein the acryloyl monomer comprises a radical polymerizable cationic monomer selected from: trimethylammonium halide-C2-C6-alkyl(meth)acrylate, trimethylammonium halide-C2-C6-alkyl(meth)acrylamide, (meth)acrylamide, or a combination thereof.

12. The method according to claim 11, wherein the acryloyl monomer is selected from [2-(acryloyloxy)ethyl]trimethylammonium chloride (AETAC), acryloyloxyethyltrimethylammonium chloride, 3-acryloylaminopropyltrimethylammonium chloride (APTAC, DiMAPA-Q), and combinations thereof.

13. The method according to any one of claims 10 to 12, wherein the vinyl monomer is selected from vinyl formamide, vinyl acetate, vinyl alcohol, vinylpyrrolidone, and combinations thereof.

14. The method of claim 13, wherein the vinyl monomer is vinylformamide.

15. The method according to any one of claims 10 to 14, wherein the cationic polyacrylamide polymer is added to the aqueous sludge in an amount of about 5 kg of active ingredient per ton of dry sludge to about 20 kg of active ingredient per ton of dry sludge or about 8 kg of active ingredient per ton of dry sludge to about 15 kg of active ingredient per ton of dry sludge, based on the weight of the aqueous sludge.

16. The method according to any one of claims 10 to 15, wherein dehydration is carried out by a centrifugation process.

17. The method according to any one of claims 10 to 16, wherein the dewatering step is carried out in a chamber filter press, plate and frame filter press, frame filter press, membrane filter press, screw filter press and / or belt filter press.

18. The method according to any one of claims 10 to 17, wherein the water-containing sludge is derived from municipal, industrial, papermaking wastewater or mining processes.

19. The method according to any one of claims 10 to 18, wherein the filter cake is produced from the dewatered sludge.

20. The method of claim 19, wherein the filter cake solids content of the treated aqueous sludge is increased by at least 10% compared to the filter cake solids content of aqueous sludge treated with conventional polymers under the same conditions.

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