Mineral-based activated sludge conditioner and sludge deep dehydration method

Abstract

The invention relates to the technical field of sludge reduction, in particular to a mineral-based activated sludge conditioner and a sludge deep dehydration method. The activated sludge conditioner comprises PAC and modified mineral-PAM with positive charges on the surface, and when activated sludge is conditioned by the activated sludge conditioner, on one hand, the sedimentation and flocculation performance of the activated sludge can be improved through the combined effect of the modified mineral with the positive charges on the surface, PAC and sludge, and on the other hand, the sedimentation and flocculation performance of the activated sludge can be improved; on the other hand, the filtering property of the sludge can be improved, release of extracellular polymeric substances is facilitated, and the dehydration performance is improved. The method disclosed by the invention is simple and controllable in process flow, can effectively improve the sludge settling effect and the dewatering performance, and has a wide application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of sludge reduction, and in particular to a mineral-based activated sludge conditioner and a sludge deep dehydration method. Background Art

[0002] Activated sludge is a general term for microbial communities and the organic and inorganic substances they are attached to. It contains a large amount of water, with a moisture content of up to 99%. Therefore, sludge dehydration is a necessary step before the treatment and disposal of excess sludge. Activated sludge dehydration is one of the most costly steps in the water treatment process.

[0003] Mechanical dewatering is the most widely used technology at present, but the organic matter and microbial cells in the residual sludge make dehydration difficult, so the sludge needs to be conditioned before mechanical dehydration. Chemical conditioning has been widely used in sludge conditioning due to its simple operation. Currently, chemical agents such as polyacrylamide, polyaluminum chloride, and calcium oxide are commonly used to condition the sludge structure, promote the rapid separation of water and sludge solid components, and increase the sludge dewatering performance. Subsequently, plate and frame filter press, mechanical centrifugation and other means are usually used to further mechanically dehydrate the conditioned sludge.

[0004] Since sludge particles are usually soft, they will be tightly combined together under the action of external force. At the same time, when the sludge particles are compressed to a certain extent, the particles are all negatively charged, and the repulsion is much greater than the attraction when the distance is too close, which hinders the further progress of deep dehydration. In addition, the extracellular polymers (EPS) in the sludge can combine with the water in the sludge to form hydrogen bonds, thereby affecting the existence form of water in the sludge. Most of the water in the sludge is combined in the EPS. EPS is one of the important factors affecting the sludge dewatering performance.

[0005] Therefore, although the dewatering performance of sludge can be increased by sludge conditioning methods, due to the special physical properties of sludge, sludge dewatering is still quite difficult. Therefore, the present invention proposes a mineral-based activated sludge conditioner, which can significantly improve the dewatering performance of sludge by conditioning the activated sludge with the activated sludge conditioner, which has positive significance for sludge reduction treatment. Summary of the invention

[0006] The purpose of the present invention is to provide a mineral-based activated sludge conditioner and a sludge deep dehydration method, so as to condition the sludge and further enhance the sludge dehydration performance.

[0007] To achieve the above object, the present invention adopts the following technical scheme: a mineral-based activated sludge conditioner, comprising component A, component B and component C, wherein component A is PAC, component B is a modified mineral with a positive charge on the surface, and component C is PAM;

[0008] The mass ratio of the A component, the B component and the C component is 20-40:1-5:0.1-3; each component is added quantitatively based on the absolute dry sludge in the activated sludge;

[0009] The mineral is one or more of zeolite, kaolinite and bentonite.

[0010] Furthermore, the mineral modification method is as follows: grinding the mineral and then sieving it, taking a certain mass of the sieved mineral and evenly dispersing it in a sulfuric acid solution, and then drying it, so as to obtain a modified mineral with a positive charge on the surface.

[0011] Furthermore, the particle size of the mineral is 60 to 300 meshes.

[0012] Furthermore, the concentration of sulfuric acid in the sulfuric acid solution is 3-4M.

[0013] Furthermore, the mass volume ratio of the sieved mineral to the sulfuric acid solution is 1:5-10.

[0014] Furthermore, when the sieved mineral is dispersed in the sulfuric acid solution, the stirring intensity is 200 to 400 rpm and the dispersion time is 10 to 30 minutes.

[0015] Furthermore, the drying temperature is 105-120°C.

[0016] The sludge deep dehydration method of the activated sludge conditioner comprises the following steps:

[0017] S1. Take a certain amount of activated sludge, measure its moisture content, and stir it for homogenization;

[0018] S2. Under stirring conditions, add component A, component B and component C to the activated sludge in sequence to condition the activated sludge;

[0019] S3. Dewatering the conditioned activated sludge.

[0020] Furthermore, in the S2, after adding component A, the stirring intensity is 80-100 rpm, and the stirring time is 10-15 min; after adding component B, the stirring intensity is 80-100 rpm, and the stirring time is 5-10 min; after adding component C, the stirring intensity is 20-50 rpm, and the stirring time is 10-15 min.

[0021] Furthermore, in the above-mentioned S3, when the sludge is dehydrated, the pressure is first maintained at 0.8 MPa for 10 minutes, and then maintained at 1.2 MPa for 10 minutes; the water content of the obtained dehydrated sludge can be reduced to below 50%.

[0022] Beneficial effects of the present invention:

[0023] 1. The method of the present invention utilizes calcination and acid leaching treatment to further optimize the pore structure of the mineral-based conditioning agent, and can achieve good treatment effects when a small amount of addition is added; more importantly, the calcination and acid leaching treatment can regulate the surface properties of the mineral-based conditioning agent, so that it has a net positive charge, which can neutralize part of the negative charge, reduce the repulsion between particles, and increase the probability of particle collision to promote flocculation; in addition, the calcination treatment activates the hydroxyl groups on the surface of the mineral, which can enhance the interaction between it and high molecular weight flocculants such as polyacrylamide (PAM), thereby promoting PAM and the mineral-based conditioning agent to form a spatial capture net, which can capture tiny flocs in the water and further enhance the flocculation effect;

[0024] 2. The minerals after acid leaching according to the method of the present invention have positive charges, which can compress the double electric layer, mainly the diffusion layer, reduce the ζ potential, make the destabilization and coagulation of the colloid easy to occur, and improve the dehydration performance. In addition, the acid-modified minerals can puncture the sludge bacteria, release the extracellular polymers, promote the discharge of bound water, and improve the dehydration performance of the sludge. DETAILED DESCRIPTION

[0025] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0026] Mineral materials such as zeolite, kaolinite, bentonite, etc. have rich pore structures. After calcination and acid leaching, not only can their strength be improved, but also their pore distribution can be further optimized. After adding sludge, they can serve as a transmission channel for water molecules, provide a spatial skeleton structure, enhance the filtration properties of activated sludge, and promote the discharge of free water; moreover, mineral materials have adjustable surface charges. After surface treatments such as calcination and acid leaching, they can generate a net positive charge on the surface. After adding sludge, part of the negative charge can be neutralized to reduce the repulsion between particles, increase the probability of particle collision, and thus promote flocculation; moreover, when the sludge particles are compressed to a certain extent, because the particles are all negatively charged, the repulsion is much greater than the attraction when the distance is too close, which hinders the further progress of deep dehydration; therefore, the present invention can promote the dehydration performance of sludge by electrical neutralization and compression of the double electric layer.

[0027] In addition, mineral materials usually have good adsorption properties and can change the flocculation structure of sludge through specific adsorption of organic matter in sludge flocs. Calcination treatment activates the hydroxyl groups on the surface of minerals, which can enhance their interaction with high molecular weight flocculants such as polyacrylamide (PAM), thereby promoting the formation of a spatial capture net between PAM and mineral-based conditioning agents, which can capture tiny flocs in the water and further enhance the flocculation effect. At the same time, minerals can also puncture the bacterial structure in the sludge and / or promote the release of extracellular polymers, accelerating the discharge of bound water.

[0028] Therefore, by using surface modification to optimize the surface charge characteristics and pore structure of minerals and compounding them with residual sludge in a certain proportion, it is possible to provide a spatial skeleton structure, enhance the filtration properties of activated sludge, improve the flocculation effect, and accelerate the discharge of bound water, further reducing the moisture content of residual sludge after mechanical dehydration, and significantly reducing subsequent disposal costs.

[0029] In the method of the present invention, minerals such as zeolite, kaolinite, bentonite, etc. are ground to a particle size of less than 60 meshes, then acid-leached and modified with sulfuric acid, and then ground again after drying to obtain modified minerals; the modified minerals are mixed with polyaluminium chloride (PAC) and polyacrylamide (PAM) in a proportioned manner and added into a conditioning process.

[0030] The minerals after acid leaching can produce a net positive charge on the surface. After being added to the sludge, they can be strongly adsorbed on the negatively charged residual sludge particles, neutralizing part of the negative charge, reducing the repulsive force between the particles, making it easier for the particles to approach each other and adsorb together, thus promoting the coagulation of sludge flocs. In addition, the modified minerals can further promote the formation of a network structure by adsorbing organic matter in the sludge, and can capture tiny flocs in the water, further improving the flocculation effect.

[0031] At the same time, since the minerals after acid leaching have positive charges, the double electric layer can be compressed, mainly the diffusion layer, which reduces the ζ potential, makes the destabilization and coagulation of the colloid easier to occur, and improves the dehydration performance. In addition, the acid-modified minerals can puncture the sludge bacteria, release extracellular polymers, and promote the discharge of bound water; therefore, the dehydration performance of the sludge is improved.

[0032] Example 1

[0033] In this example, zeolite was modified.

[0034] The zeolite is ground and passed through a 100-mesh sieve, and the sieved zeolite is taken and dispersed in a sulfuric acid solution, the concentration of the sulfuric acid solution is 4M, the mass volume ratio (g / mL) of the zeolite to the sulfuric acid solution is 1:8, and the dispersion is carried out at a stirring intensity of 300 rpm for 20 minutes; the suspension is placed in an oven and dried at 110° C. to obtain the modified zeolite with a positive charge on the surface of the present invention, which is collected and used for later use.

[0035] Example 2

[0036] Take the activated sludge from a sewage treatment plant, stir it and homogenize it. After measurement, the moisture content is 98.4%.

[0037] Take 1L of the activated sludge, the absolute dry mass of the sludge is 16g; under the stirring condition of 100rpm, add 5g of PAC to the activated sludge, and continue stirring for 15min, then add 0.5g of modified zeolite with positive charge on the surface of Example 1 to the activated sludge, and continue stirring at 100rpm for 10min; at this time, continue to add 0.2g of PAM to the activated sludge, and continue stirring at 50rpm for 15min; observe the sludge sedimentation time.

[0038] The sludge after flocculation and sedimentation was placed in a laboratory filter press, and the pressure was maintained at 0.8 MPa for 10 minutes, and then at 1.2 MPa for 10 minutes; the moisture content of the dehydrated mud cake was tested, and the moisture content of the dehydrated sludge was 48.8%.

[0039] Comparative Example 1

[0040] In this comparative example, unmodified zeolite sieved through a 100-mesh sieve was added to the activated sludge, and the rest was the same as in Example 2.

[0041] Comparative Example 2

[0042] In this comparative example, only PAC and PAM were added to the activated sludge, and no modified zeolite with positive charges on the surface was added. Other details were the same as in Example 2.

[0043] Table 1 Comparison of flocculation and sedimentation time and dewatering performance of activated sludge after conditioning

[0044]

[0045] It can be clearly seen that by adding the modified zeolite with positive charge on the surface of the present invention, the sedimentation efficiency after sludge flocculation is significantly improved, which helps to improve the sludge dewatering efficiency; and the moisture content in the mud cake finally obtained is significantly reduced to less than 50%, which significantly improves the sludge dewatering effect.

[0046] Example 3

[0047] Take the same batch of activated sludge as in Example 2; place the activated sludge in four conical flasks respectively, and add 200 mL to each conical flask.

[0048] The activated sludge in three conical flasks was conditioned by the steps of Example 2 and Comparative Examples 1-2, respectively, and the remaining conical flask was used as a blank reference without conditioning; after conditioning and filtration, the sludge after filtration was mixed with a NaCl solution with a mass fraction of 0.05%, and the extracellular polymers were extracted by heat extraction at 80° C. for 45 min; the protein and polysaccharide in each extract were measured, and the content of protein and polysaccharide relative to the absolute dry sludge was calculated, and the results are shown in the following table:

[0049] Table 2 Comparison of protein and polysaccharide contents in activated sludge heat extract after conditioning

[0050]

[0051] It can be clearly seen that after conditioning with the activated sludge conditioner of the present invention, the extracellular polymers in the activated sludge are released, which plays a positive role in improving the dewatering performance of the sludge.

[0052] The present invention is not limited to the above-mentioned optimal implementation mode. Anyone can derive other various forms of products under the inspiration of the present invention. However, no matter what changes are made in the shape or structure, all technical solutions that are the same or similar to those of the present application fall within the protection scope of the present invention.

Claims

1. A mineral-based activated sludge conditioner, characterized in that: It includes component A, component B and component C, wherein component A is PAC, component B is a modified mineral with positive charge on the surface, and component C is PAM; The mass ratio of the A component, the B component and the C component is 20-40:1-5:0.1-3; each component is added quantitatively based on the absolute dry sludge in the activated sludge; The mineral is one or more of zeolite, kaolinite and bentonite.

2. A mineral-based activated sludge conditioner according to claim 1, characterized in that: The mineral modification method is as follows: grinding the mineral and then sieving it, taking a certain mass of the sieved mineral and evenly dispersing it in a sulfuric acid solution, and then drying it, so as to obtain a modified mineral with a positive charge on the surface.

3. A mineral-based activated sludge conditioner according to claim 2, characterized in that: The particle size of the mineral is 60 to 300 meshes.

4. A mineral-based activated sludge conditioner according to claim 2, characterized in that: The concentration of sulfuric acid in the sulfuric acid solution is 3-4M.

5. A mineral-based activated sludge conditioner according to claim 4, characterized in that: The mass volume ratio of the sieved mineral to the sulfuric acid solution is 1:5-10.

6. A mineral-based activated sludge conditioner according to claim 2, characterized in that: When the sieved mineral is dispersed in the sulfuric acid solution, the stirring intensity is 200-400 rpm and the dispersion time is 10-30 minutes.

7. A mineral-based activated sludge conditioner according to claim 2, characterized in that: The drying temperature is 105-120°C.

8. The method for deep dehydration of sludge using an activated sludge conditioner according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. Take a certain amount of activated sludge, measure its moisture content, and stir it for homogenization; S2. Under stirring conditions, add component A, component B and component C to the activated sludge in sequence to condition the activated sludge; S3. Dewatering the conditioned activated sludge.

9. The method for deep dehydration of sludge using an activated sludge conditioner according to claim 8, characterized in that: In the S2, after adding component A, the stirring intensity is 80-100 rpm and the stirring time is 10-15 min; after adding component B, the stirring intensity is 80-100 rpm and the stirring time is 5-10 min; after adding component C, the stirring intensity is 20-50 rpm and the stirring time is 10-15 min.

10. The method for deep dehydration of sludge using an activated sludge conditioner according to claim 8, characterized in that: In the above-mentioned S3, when the sludge is dehydrated, the pressure is first maintained at 0.8Mpa for 10 minutes, and then maintained at 1.2Mpa for 10 minutes; the moisture content of the obtained dehydrated sludge can be reduced to below 50%.

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