Sludge reduction method applied to wastewater treatment

Abstract

The invention discloses a sludge reduction method applied to wastewater treatment, belongs to the field of water treatment, and particularly relates to a method which comprises the following steps: adding a polyquaternium flocculant into water to form a flocculating liquid, and preparing a micro-nano air bag in the flocculating liquid to obtain an air bag grafted polyquaternium flocculating liquid; adding the air bag grafted polyquaternium flocculating liquid into wastewater for treatment, and separating to obtain treated water; the molar ratio of the polyquaternium flocculating agent to the micro-nano air bag is 1: (5-10), and the polyquaternium flocculating agent comprises cationic polyacrylamide. The sludge reduction method applied to wastewater treatment is good in sewage treatment effect, short in sewage treatment time, good in COD (Chemical Oxygen Demand) removal effect and high in sludge reduction amount.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, specifically relating to a sludge reduction method applied to wastewater treatment. Background Technology

[0002] The cost of sludge disposal is increasingly accounting for a significant portion of the overall cost of wastewater treatment plants, highlighting the crucial need for sludge reduction at its source. Coagulation sedimentation tanks are key equipment in wastewater treatment, separating suspended solids and sludge from wastewater through chemical coagulation and physical sedimentation. Sludge is also a major source of sludge in wastewater treatment plants. The sludge produced by coagulation sedimentation tanks typically contains organic matter, inorganic salts, and microorganisms, and the amount produced is related to the type, dosage, and efficiency of the coagulant, as well as the amount of sludge introduced by the coagulant itself. To reduce sludge volume at the source during wastewater treatment, it is possible to improve coagulation efficiency by selecting more efficient coagulants with lower dosages and employing physicochemical methods that do not increase sludge volume, while achieving the same coagulation effect. Summary of the Invention

[0003] The purpose of this invention is to provide a sludge reduction method for wastewater treatment that has good wastewater treatment effect, short wastewater treatment time, good COD removal effect, and high sludge reduction.

[0004] The technical solution adopted by the present invention to achieve the above objectives is as follows: A sludge reduction method for wastewater treatment includes: adding a polyquaternary ammonium salt flocculant to water to form a flocculant; creating micro-nano airbags in the flocculant to obtain an airbag-grafted polyquaternary ammonium salt flocculant; adding the airbag-grafted polyquaternary ammonium salt flocculant to wastewater for treatment; and separating the treated water. The molar ratio of the polyquaternary ammonium salt flocculant to the micro-nano airbags is 1:5-10. This invention employs a micro-nano airbag encapsulation technology to assist polyquaternary ammonium salt flocculants in replacing traditional polyaluminum or polyferric coagulants, which can significantly reduce the amount of coagulant used and substantially reduce the amount of subsequent sludge generated. Furthermore, because it does not use metal flocculants such as polyaluminum or polyferric coagulants, it avoids metal hydroxide sludge, improving the biodegradability of sludge for biological treatment. This significantly reduces the cost of subsequent sludge treatment, both in terms of sludge production and treatment difficulty.

[0005] Preferably, the polyquaternary ammonium salt flocculant includes cationic polyacrylamide; or, micro / nano airbags are grafted onto the chain of the polyquaternary ammonium salt flocculant.

[0006] More preferably, the cationic polyacrylamide is prepared from acrylamide, dimethyl diallyl ammonium chloride, and N-hydroxymethylacrylamide. This invention uses acrylamide, dimethyl diallyl ammonium chloride, and N-hydroxymethylacrylamide to prepare a cationic polyacrylamide with a specific structure. This cationic polyacrylamide is used as a polyquaternary ammonium salt flocculant. This invention has found that, under certain usage ranges, further grafting micro / nano air pockets onto the dimethyl diallyl ammonium chloride and N-hydroxymethylacrylamide monomers results in high COD removal rates and significantly reduced sludge production.

[0007] More preferably, the preparation of cationic polyacrylamide includes the preparation of dimethyl diallyl ammonium chloride, which is prepared from dimethylamine and acryloyl chloride.

[0008] More preferably, the amount of dimethyl diallyl ammonium chloride used is 10-30 wt% of acrylamide; or, the amount of N-hydroxymethyl acrylamide used is 10-30 wt% of acrylamide.

[0009] Preferably, the diameter of the micro / nano airbag is 200 nm-50 μm; or, the micro / nano airbag is generated by ultrasonic cavitation, electrode electrolysis, pressurized gas dissolution, impeller shearing, hydraulic cavitation or membrane method.

[0010] More preferably, the diameter of the micro-nano airbag with the largest volume fraction is 40 μm; or, the micro-nano airbag is generated by hydrocavitation.

[0011] Preferably, the content of polyquaternary ammonium salt flocculant in the flocculant is 5-20 wt%; or, the airbag-grafted polyquaternary ammonium salt flocculant is added to the wastewater, and the amount of polyquaternary ammonium salt flocculant used is 50-800 mg / L.

[0012] More preferably, the wastewater is dyeing and printing wastewater, dye-containing sewage, or a mixture thereof.

[0013] More preferably, the molar ratio of polyquaternary ammonium salt flocculant to micro / nano airbags is 1:5; or, the molar ratio of polyquaternary ammonium salt flocculant to micro / nano airbags is 1:8.

[0014] Preferably, in the preparation of dimethyl diallyl ammonium chloride, dimethylamine solution and allyl chloride are mixed at 20-30°C, then an alkaline reagent is added, and the mixture is refluxed at 30-40°C for 2-6 hours. After the reaction is completed, the product is separated to prepare dimethyl diallyl ammonium chloride.

[0015] More preferably, in the preparation of dimethyl diallyl ammonium chloride, the dimethylamine solution is a mixture of dimethylamine and water, the content of dimethylamine in the dimethylamine solution is 30-50 wt%, and the amount of allyl chloride used is 5-15 wt% of dimethylamine, measured by the dimethylamine in the dimethylamine solution.

[0016] More preferably, in the preparation of dimethyl diallyl ammonium chloride, the alkaline reagent is sodium hydroxide, and the amount of sodium hydroxide used is 2-6 wt% of dimethylamine.

[0017] Preferably, in the preparation of cationic polyacrylamide, acrylamide, dimethyl diallyl ammonium chloride and N-hydroxymethylacrylamide are added to deionized water, then urea is added, and an initiator is added under a nitrogen atmosphere. The reaction is carried out at 40-80°C for 1-8 hours. After the reaction is completed, acetone is added to precipitate the precipitate, which is then filtered and dried to obtain cationic polyacrylamide.

[0018] More preferably, in the preparation of cationic polyacrylamide, the amount of acrylamide used is 10-30 wt% of deionized water.

[0019] More preferably, in the preparation of cationic polyacrylamide, the amount of dimethyl diallyl ammonium chloride used is 10-30 wt% of acrylamide.

[0020] More preferably, in the preparation of cationic polyacrylamide, the amount of N-hydroxymethylacrylamide used is 10-30 wt% of acrylamide.

[0021] More preferably, in the preparation of cationic polyacrylamide, the amount of urea used is 0.5-2 wt% of acrylamide.

[0022] More preferably, in the preparation of cationic polyacrylamide, the initiator is ammonium persulfate, and the amount of ammonium persulfate used is 0.1-0.8 wt% of acrylamide.

[0023] More preferably, in the preparation of cationic polyacrylamide, acetone is used in an appropriate amount to precipitate the product.

[0024] Preferably, acetylacetone acrylamide can also be added during the preparation of cationic polyacrylamide, with the amount of acetylacetone acrylamide being 3-15 wt% of acrylamide. When preparing cationic polyacrylamide using dimethyl diallyl ammonium chloride and N-hydroxymethyl acrylamide, acetylacetone acrylamide can be further added to prepare a cationic polyacrylamide containing the structures of dimethyl diallyl ammonium chloride, N-hydroxymethyl acrylamide, and acetylacetone acrylamide. This cationic polyacrylamide structure, when grafted with micro / nano airbags, forms an airbag-grafted polyacrylamide flocculant, which can improve the COD removal rate in wastewater and significantly reduce sludge production.

[0025] Preferably, the airbag-grafted polyquaternary ammonium salt flocculant includes an airbag-grafted polyacrylamide flocculant.

[0026] Preferably, in the preparation of the airbag-grafted polyacrylamide flocculant, cationic polyacrylamide is added to water to form a flocculant, and micro / nano airbags are generated using a hydraulic cavitation method to form the airbag-grafted polyacrylamide flocculant. The diameter of the micro / nano airbags is 200 nm-50 μm.

[0027] More preferably, in the preparation of the airbag-grafted polyacrylamide flocculant, the content of cationic polyacrylamide in the airbag-grafted polyacrylamide flocculant is 5-20 wt%.

[0028] More preferably, in the preparation of the airbag-grafted polyacrylamide flocculant, the molar ratio of micro / nano airbags to cationic polyacrylamide is 1:5-10. The micro / nano airbags are wrapped and grafted onto the cationic polyacrylamide chain, which increases the charge density and adsorption capacity of the cationic polyacrylamide.

[0029] More preferably, in the preparation of the airbag-grafted polyacrylamide flocculant, the micro-nano airbags are prepared by the hydrocavitation method, and the diameter of the obtained micro-nano airbags is concentrated in the range of 200nm-50μm.

[0030] Preferably, in the wastewater treatment, the pH of the dyeing and printing wastewater is adjusted to neutral, airbag-grafted polyacrylamide flocculant is added, stirred for 2-10 minutes, allowed to stand for 10-60 minutes, and the sediment is separated to obtain the treated water.

[0031] More preferably, in the treatment of wastewater, the pH adjuster includes calcium hydroxide, sodium hydroxide, or potassium hydroxide.

[0032] More preferably, in the treatment of wastewater, the amount of airbag-grafted polyacrylamide flocculant used is measured according to the amount of cationic polyacrylamide, and the amount of cationic polyacrylamide added to the dyeing and printing wastewater is 50-800 mg / L.

[0033] This invention discloses the use of airbag-grafted polyquaternary ammonium salt flocculant in water treatment and / or wastewater treatment and / or dyeing wastewater. The airbag-grafted polyquaternary ammonium salt flocculant contains polyquaternary ammonium salt flocculant and micro / nano airbags. The polyquaternary ammonium salt flocculant includes cationic polyacrylamide.

[0034] This invention utilizes cationic polyacrylamide as a polyquaternary ammonium salt flocculant, then generates micro / nano airbags in situ. Leveraging the high specific surface area and strong charge of these airbags, they are grafted onto the polyquaternary ammonium salt flocculant chains. This increases the charge density and adsorption capacity of the flocculant, thereby improving flocculation speed and efficiency. Under the same flocculation effect, the flocculant dosage can be significantly reduced, achieving a good COD removal rate while reducing sludge production. Therefore, it offers the following advantages: shorter wastewater treatment time, better COD removal, and higher sludge reduction. Thus, this invention is a sludge reduction method for wastewater treatment that offers excellent wastewater treatment results, shorter treatment time, better COD removal, and higher sludge reduction. Attached Figure Description

[0035] Figure 1 This is an infrared spectrum.

[0036] Figure 2 This is a graph showing the COD removal rate.

[0037] Figure 3 This is a graph showing the reduction in sludge volume. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] The concepts involved in this application will first be described with reference to the accompanying drawings. It should be noted that the following descriptions of various concepts are only for the purpose of making the content of this application easier to understand and do not constitute a limitation on the scope of protection of this application; furthermore, the embodiments and features in the embodiments of this application can be combined with each other unless otherwise specified. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0040] Micro- and nano-sized airbags can be generated using the hydrocavitation method, a technique that generates micro- and nano-sized bubbles through hydraulic shearing. This method utilizes a high-speed flowing liquid to generate high pressure in a localized area, followed by a sudden decompression in a low-pressure area, causing the dissolved gas in the liquid to become supersaturated and rapidly released, forming tiny bubbles.

[0041] The fabrication of micro / nano airbags involves the following process: First, a liquid containing dissolved gas is introduced into a specially structured channel or cavity, a process achieved using a pump or a specific hydrodynamic system. As the liquid passes through narrow channels or elements with specific geometries, it experiences acceleration and intense shear forces, increasing the kinetic energy and turbulence within the liquid. At certain points in the flow channel, such as the expansion region after a narrowing, the fluid pressure drops rapidly. This pressure surge causes the dissolved gas to become supersaturated and rapidly precipitate from the solution, forming tiny gas nuclei. With further pressure reduction, these gas nuclei can rapidly expand into tiny bubbles, known as cavitation bubbles. In some cases, these cavitation bubbles may undergo periodic generation, growth, and interaction with the surrounding liquid, including potential violent collapse. This process can further refine the bubble size, generating even smaller micro / nano bubbles.

[0042] Grafting generally refers to the reaction in which appropriate branches or functional side groups are chemically bonded to a macromolecular chain. However, this invention uses the term grafting because micro / nano airbags, especially at the nanoscale, become an unstable and high-energy state with high surface energy. The process of binding with polymeric flocculants is not a simple charge adsorption but is closer to valence bond bonding, hence the term grafting.

[0043] Example 1: A sludge reduction method applied to wastewater treatment Preparation of dimethyl diallyl ammonium chloride: Dimethylamine solution and allyl chloride were mixed at 25°C, then an alkaline reagent was added, and the mixture was refluxed at 35°C for 4 hours. After the reaction was complete, the product was separated to obtain dimethyl diallyl ammonium chloride. The dimethylamine solution was prepared by mixing dimethylamine and water, with a dimethylamine content of 35 wt%. The amount of allyl chloride used was 8 wt% of the dimethylamine, and the alkaline reagent was sodium hydroxide, with an amount of sodium hydroxide of 4 wt% of the dimethylamine.

[0044] Preparation of cationic polyacrylamide: Acrylamide, dimethyl diallyl ammonium chloride, and N-hydroxymethylacrylamide were added to deionized water, followed by urea. Under a nitrogen atmosphere, an initiator was added, and the reaction was carried out at 60°C for 4 hours. After the reaction was complete, acetone was added to precipitate the product. The precipitate was filtered and dried to obtain cationic polyacrylamide. The amount of acrylamide used was 20 wt% of deionized water, 25 wt% of dimethyl diallyl ammonium chloride, 25 wt% of N-hydroxymethylacrylamide, and 1 wt% of urea. The initiator was ammonium persulfate, and the amount of ammonium persulfate was 0.5 wt% of acrylamide. Acetone was used in appropriate amounts to precipitate the product.

[0045] Preparation of airbag-grafted polyacrylamide flocculant: Cationic polyacrylamide was added to water to prepare a flocculant. Micro-nano airbags were generated using a hydrocavitation method, forming the airbag-grafted polyacrylamide flocculant. The diameter of the micro-nano airbags ranged from 200 nm to 50 μm. The cationic polyacrylamide content in the airbag-grafted polyacrylamide flocculant was 10 wt%. The molar ratio of micro-nano airbags to cationic polyacrylamide was 1:5. The micro-nano airbags encapsulated the cationic polyacrylamide chains, increasing the charge density and adsorption capacity of the cationic polyacrylamide. The micro-nano airbags were prepared using a hydrocavitation method, and the diameters of the obtained micro-nano airbags were concentrated in the range of 200 nm to 50 μm.

[0046] Wastewater treatment: Adjust the pH of the dyeing and printing wastewater to neutral, add air-filled grafted polyacrylamide flocculant, stir for 2 minutes, let stand for 10 minutes, separate the sediment, and obtain the treated water. pH adjusters include calcium hydroxide, sodium hydroxide, or potassium hydroxide. The amount of air-filled grafted polyacrylamide flocculant used is measured based on the cationic polyacrylamide content; the amount of cationic polyacrylamide added to the dyeing and printing wastewater is 150 mg / L. The COD of the dyeing and printing wastewater is 500 mg / L.

[0047] Example 2: A sludge reduction method applied to wastewater treatment The difference between this embodiment and Example 1 lies in the preparation of cationic polyacrylamide.

[0048] Preparation of cationic polyacrylamide: Acrylamide, dimethyl diallyl ammonium chloride, and N-hydroxymethylacrylamide were added to deionized water, followed by urea. Under a nitrogen atmosphere, an initiator was added, and the reaction was carried out at 60°C for 4 hours. After the reaction was complete, acetone was added to precipitate the product. The precipitate was filtered and dried to obtain cationic polyacrylamide. The amount of acrylamide used was 20 wt% of deionized water, 12 wt% of dimethyl diallyl ammonium chloride, 12 wt% of N-hydroxymethylacrylamide, and 1 wt% of urea. The initiator was ammonium persulfate, which was used at a concentration of 0.5 wt% of acrylamide. Acetone was used in appropriate amounts to precipitate the product.

[0049] Example 3: A sludge reduction method applied to wastewater treatment The difference between this embodiment and Example 1 lies in the preparation of cationic polyacrylamide.

[0050] Preparation of cationic polyacrylamide: Acrylamide, dimethyl diallyl ammonium chloride, N-hydroxymethylacrylamide, and acetylacetone acrylamide were added to deionized water, followed by urea. Under a nitrogen atmosphere, an initiator was added, and the reaction was carried out at 60°C for 4 hours. After the reaction was complete, acetone was added to precipitate the product. The precipitate was filtered and dried to obtain cationic polyacrylamide. The amount of acrylamide used was 20 wt% of deionized water, 25 wt% of dimethyl diallyl ammonium chloride, 25 wt% of N-hydroxymethylacrylamide, 12 wt% of acetylacetone acrylamide, and 1 wt% of urea. The initiator was ammonium persulfate, and the amount of ammonium persulfate was 0.5 wt% of acrylamide. Acetone was used in appropriate amounts to precipitate the product.

[0051] Example 4: A sludge reduction method applied to wastewater treatment The difference between this embodiment and Example 1 lies in the preparation of cationic polyacrylamide.

[0052] Preparation of cationic polyacrylamide: Acrylamide, dimethyl diallyl ammonium chloride, N-hydroxymethylacrylamide, and acetylacetone acrylamide were added to deionized water, followed by urea. Under a nitrogen atmosphere, an initiator was added, and the reaction was carried out at 60°C for 4 hours. After the reaction was complete, acetone was added to precipitate the product. The precipitate was filtered and dried to obtain cationic polyacrylamide. The amount of acrylamide used was 20 wt% of deionized water, 25 wt% of dimethyl diallyl ammonium chloride, 25 wt% of N-hydroxymethylacrylamide, 5 wt% of acetylacetone acrylamide, and 1 wt% of urea. The initiator was ammonium persulfate, which was used at a concentration of 0.5 wt% of acrylamide. Acetone was used in appropriate amounts to precipitate the product.

[0053] Comparative Example 1: A sludge reduction method applied to wastewater treatment The difference between this comparative example and Example 1 lies in the preparation of the cationic polyacrylamide.

[0054] Preparation of cationic polyacrylamide: Acrylamide, dimethyl diallyl ammonium chloride, and N-hydroxymethylacrylamide were added to deionized water, followed by urea. Under a nitrogen atmosphere, an initiator was added, and the reaction was carried out at 60°C for 4 hours. After the reaction was complete, acetone was added to precipitate the product. The precipitate was filtered and dried to obtain cationic polyacrylamide. The amount of acrylamide used was 20 wt% of deionized water, 5 wt% of dimethyl diallyl ammonium chloride, 5 wt% of N-hydroxymethylacrylamide, and 1 wt% of urea. The initiator was ammonium persulfate, which was used at 0.5 wt% of acrylamide. Acetone was used in appropriate amounts to precipitate the product.

[0055] Comparative Example 2: A sludge reduction method applied to wastewater treatment The difference between this comparative example and Example 1 lies in the preparation of the cationic polyacrylamide.

[0056] Preparation of cationic polyacrylamide: Acrylamide, dimethyl diallyl ammonium chloride, and N-hydroxymethylacrylamide were added to deionized water, followed by urea. Under a nitrogen atmosphere, an initiator was added, and the reaction was carried out at 60°C for 4 hours. After the reaction was complete, acetone was added to precipitate the product. The precipitate was filtered and dried to obtain cationic polyacrylamide. The amount of acrylamide used was 20 wt% of deionized water, 25 wt% of dimethyl diallyl ammonium chloride, 5 wt% of N-hydroxymethylacrylamide, and 1 wt% of urea. The initiator was ammonium persulfate, which was used at 0.5 wt% of acrylamide. Acetone was used in appropriate amounts to precipitate the product.

[0057] Comparative Example 3: A sludge reduction method applied to wastewater treatment The difference between this comparative example and Example 1 lies in the preparation of the cationic polyacrylamide.

[0058] Preparation of cationic polyacrylamide: Acrylamide, dimethyl diallyl ammonium chloride, and N-hydroxymethylacrylamide were added to deionized water, followed by urea. Under a nitrogen atmosphere, an initiator was added, and the reaction was carried out at 60°C for 4 hours. After the reaction was complete, acetone was added to precipitate the product. The precipitate was filtered and dried to obtain cationic polyacrylamide. The amount of acrylamide used was 20 wt% of deionized water, 5 wt% of dimethyl diallyl ammonium chloride, 25 wt% of N-hydroxymethylacrylamide, and 1 wt% of urea. The initiator was ammonium persulfate, which was used at a concentration of 0.5 wt% of acrylamide. Acetone was used in appropriate amounts to precipitate the product.

[0059] Comparative Example 4: A sludge reduction method applied to wastewater treatment The difference between this comparative example and Example 1 lies in the preparation of the cationic polyacrylamide.

[0060] Preparation of cationic polyacrylamide: Acrylamide, dimethyl diallyl ammonium chloride, and N-hydroxymethylacrylamide were added to deionized water, followed by urea. Under a nitrogen atmosphere, an initiator was added, and the reaction was carried out at 60°C for 4 hours. After the reaction was complete, acetone was added to precipitate the product. The precipitate was filtered and dried to obtain cationic polyacrylamide. The amount of acrylamide used was 20 wt% of deionized water, 0.01 wt% of dimethyl diallyl ammonium chloride, 0.01 wt% of N-hydroxymethylacrylamide, and 1 wt% of urea. The initiator was ammonium persulfate, which was used at 0.5 wt% of acrylamide. Acetone was used in appropriate amounts to precipitate the product.

[0061] Comparative Example 5: A sludge reduction method applied to wastewater treatment The difference between this comparative example and comparative example 4 is that the airbag-grafted polyacrylamide flocculant was replaced with cationic polyacrylamide flocculant in the wastewater treatment.

[0062] Preparation of cationic polyacrylamide flocculant: Cationic polyacrylamide was added to water to prepare a flocculant, resulting in cationic polyacrylamide flocculant. The content of cationic polyacrylamide in the cationic polyacrylamide flocculant was 10 wt%. The cationic polyacrylamide was obtained by the preparation method of Comparative Example 4.

[0063] Comparative Example 6: A sludge reduction method applied to wastewater treatment The difference between this comparative example and comparative example 4 is that the airbag-grafted polyacrylamide flocculant was replaced with micro-nano airbag liquid in the wastewater treatment.

[0064] Preparation of micro / nano airbag fluid: Micro / nano airbags were generated using a hydrocavitation method to obtain the micro / nano airbag fluid. The diameter of the micro / nano airbags ranged from 200 nm to 50 μm.

[0065] Experimental example: The infrared spectrum of the cationic polyacrylamide prepared in Example 1 of this invention is as follows: Figure 1 As shown, at 3382cm ~1 The infrared absorption peak for hydroxyl groups is at 2968 cm⁻¹. ~1 The infrared absorption peak of methyl is at 2872 cm⁻¹. ~1 The methylene infrared absorption peak is located at 1682 cm⁻¹. ~1 The infrared absorption peak at the carbonyl group indicates that cationic polyacrylamide has been obtained.

[0066] The COD removal rates of the airbag-grafted polyacrylamide flocculants in the various embodiments and comparative examples of this invention are as follows: Figure 2 As shown, S1 is Example 1, S2 is Example 2, S3 is Example 3, S4 is Example 4, D1 is Comparative Example 1, D2 is Comparative Example 2, D3 is Comparative Example 3, D4 is Comparative Example 4, D5 is Comparative Example 5, and D6 is Comparative Example 6. Comparative Example 6, using only micro / nano airbags without cationic polyacrylamide, could not remove COD, resulting in a COD removal rate of 0%. This invention prepares dimethyl diallyl ammonium chloride by reacting dimethylamine with allyl chloride, and then reacts it with acrylamide and N-hydroxymethylacrylamide to prepare cationic polyacrylamide. The cationic polyacrylamide is then used to make a flocculant, which is then grafted onto micro / nano airbags, resulting in a high COD removal rate for wastewater. However, if only cationic polyacrylamide flocculant or micro / nano airbag solution is used, the COD removal effect on wastewater is significantly lower. Relatively poor performance is observed when using airbag-grafted polyacrylamide flocculants containing cationic polyacrylamide and micro / nano airbags. Only when the cationic polyacrylamide, specifically dimethyl diallyl chloride and N-hydroxymethylacrylamide, is used in appropriate amounts can the resulting cationic polyacrylamide effectively remove COD from wastewater. The amounts of dimethyl diallyl chloride and N-hydroxymethylacrylamide must be within a certain range; if only dimethyl diallyl chloride or N-hydroxymethylacrylamide is used within this range, it cannot effectively remove COD from the wastewater. Furthermore, when using dimethyl diallyl chloride and N-hydroxymethylacrylamide, acetylacetone acrylamide can be added to produce cationic polyacrylamide, which, when then applied to the airbag-grafted polyacrylamide flocculant, can further improve COD removal in the wastewater.

[0067] The reduction in sludge after treatment of dyeing and printing wastewater by the airbag-grafted polyacrylamide flocculant in the various embodiments and comparative examples of this invention is as follows: Figure 3As shown, S1 is Example 1, S2 is Example 2, S3 is Example 3, S4 is Example 4, D1 is Comparative Example 1, D2 is Comparative Example 2, D3 is Comparative Example 3, D4 is Comparative Example 4, D5 is Comparative Example 5, and D6 is Comparative Example 6. Comparative Example 5, which uses only cationic polyacrylamide without micro / nano airbags, is used as a reference. The sludge reduction in Comparative Example 5 is 0%, while in Comparative Example 6, using only micro / nano airbags without cationic polyacrylamide, no sludge is generated, resulting in a sludge reduction of -100% for Comparative Example 5. This invention prepares dimethyl diallyl ammonium chloride by reacting dimethylamine with allyl chloride, and then reacts it with acrylamide and N-hydroxymethylacrylamide to prepare cationic polyacrylamide. After the cationic polyacrylamide is made into a flocculant, micro / nano airbags are then grafted onto the cationic polyacrylamide, which can effectively reduce the amount of sludge generated by wastewater flocculation. However, if only cationic polyacrylamide is used… Flocculants or micro / nano-inflatable blister solutions are relatively ineffective at reducing the amount of flocculated sludge in wastewater. When using blister-grafted polyacrylamide flocculants containing cationic polyacrylamide and micro / nano-inflatable blister cells, the cationic polyacrylamide, specifically dimethyl diallyl chloride and N-hydroxymethylacrylamide, must be used in appropriate amounts to effectively reduce the amount of flocculated sludge. The amounts of dimethyl diallyl chloride and N-hydroxymethylacrylamide must be within a certain range. If only dimethyl diallyl chloride or N-hydroxymethylacrylamide is used within this range, it will not effectively reduce the amount of flocculated sludge. When using dimethyl diallyl chloride and N-hydroxymethylacrylamide, acetylacetone acrylamide can be further added to produce cationic polyacrylamide, which can then be applied to the blister-grafted polyacrylamide flocculant to further reduce the amount of flocculated sludge in wastewater.

[0068] The embodiments and / or implementation methods described above are merely preferred embodiments and / or implementation methods for implementing the technology of the present invention, and are not intended to limit the implementation methods of the technology of the present invention in any way. Any person skilled in the art can make some modifications or alterations to other equivalent embodiments without departing from the scope of the technical means disclosed in the content of the present invention, but they should still be regarded as the technology or embodiments that are substantially the same as the present invention.

[0069] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. The above descriptions are only preferred embodiments of this application. It should be noted that due to the limitations of written expression, while there are objectively infinite specific structures, those skilled in the art can make several improvements, modifications, or changes without departing from the principles of this application, and can also combine the above technical features in an appropriate manner. These improvements, modifications, changes, or combinations, or the direct application of the inventive concept and technical solution to other situations without modification, should all be considered within the scope of protection of this application.

Claims

1. A method for reducing sludge volume in wastewater treatment, comprising: Polyquaternary ammonium salt flocculant is added to water to form flocculent liquid, and micro-nano airbags are made in the flocculent liquid to obtain airbag-grafted polyquaternary ammonium salt flocculent liquid. The polyquaternary ammonium salt flocculant grafted with airbags was added to the wastewater for treatment, and the treated water was obtained by separation; the molar ratio of polyquaternary ammonium salt flocculant to micro-nano airbags was 1:5-10.

2. The sludge reduction method for wastewater treatment according to claim 1, characterized in that: The polyquaternary ammonium salt flocculant includes cationic polyacrylamide; or, micro-nano airbags are grafted onto the chain of the polyquaternary ammonium salt flocculant.

3. The sludge reduction method for wastewater treatment according to claim 2, characterized in that: The cationic polyacrylamide was prepared from acrylamide, dimethyl diallyl ammonium chloride and N-hydroxymethylacrylamide.

4. The sludge reduction method for wastewater treatment according to claim 2, characterized in that: The preparation of the cationic polyacrylamide includes the preparation of dimethyl diallyl ammonium chloride, which is prepared from dimethylamine and acryloyl chloride.

5. A sludge reduction method for wastewater treatment according to any one of claims 3-4, characterized in that: The amount of dimethyl diallyl ammonium chloride used is 10-30 wt% of acrylamide; or, the amount of N-hydroxymethylacrylamide used is 10-30 wt% of acrylamide.

6. The sludge reduction method for wastewater treatment according to claim 1, characterized in that: The diameter of the micro-nano airbag is 200nm-50μm; or, the micro-nano airbag is generated by ultrasonic cavitation, electrode electrolysis, pressurized gas dissolution, impeller shearing, hydraulic cavitation or membrane method.

7. A sludge reduction method for wastewater treatment according to claim 6, characterized in that: The diameter of the micro-nano airbag with the largest volume fraction is 40 μm; or, the micro-nano airbag is generated by hydrocavitation.

8. The sludge reduction method for wastewater treatment according to claim 1, characterized in that: The content of polyquaternary ammonium salt flocculant in the flocculant is 5-20 wt%; or, the airbag-grafted polyquaternary ammonium salt flocculant is added to the wastewater, and the polyquaternary ammonium salt flocculant content is used for measurement, with the amount of polyquaternary ammonium salt flocculant used being 50-800 mg / L.

9. A method for reducing sludge volume in wastewater treatment according to claim 1, characterized in that: The wastewater is dyeing and printing wastewater, dye-containing sewage, or a mixture thereof.

10. Use of airbag-grafted polyquaternium salt flocculant in water treatment and / or wastewater treatment and / or dyeing wastewater, wherein the airbag-grafted polyquaternium salt flocculant contains polyquaternium salt flocculants and micro / nano airbags, the polyquaternium salt flocculants including cationic polyacrylamide.

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