Method for strengthening dewatering of aerobic granular sludge by combining mechanical crushing with macromolecular coagulant

Abstract

The invention discloses a method for strengthening dewatering of aerobic granular sludge by combining mechanical crushing with a high-molecular coagulant, which is characterized in that the granular structure is destroyed on the basis of removing most of free water through a physical method of filtering with filter cloth and mechanical crushing, and a large amount of combined water between cells and in the cells is released; then, hydrophilic functional groups on the surface of the sludge are destroyed by utilizing the coagulating sedimentation effect of the polymer coagulant to reduce the hydrophilicity of the surface of the sludge, so that the dehydration efficiency of the sludge cake is effectively improved. According to the method, the problem that water in the aerobic granular sludge cannot be released and removed is effectively solved, and an effective scheme is provided for treatment and disposal of the residual aerobic granular sludge.

Description

Technical Field

[0001] The invention belongs to the technical field of sludge treatment, and in particular relates to a method for strengthening aerobic granular sludge dehydration by combining mechanical crushing with a polymer coagulant. Background Art

[0002] With the rapid development of science and technology in today's society, the urbanization rate and people's living standards are constantly improving, and people's demand and consumption of water resources are increasing, which leads to increasingly prominent sewage discharge problems. At present, the activated sludge method in biological treatment technology is one of the most widely used wastewater treatment methods, and residual sludge is the main by-product in the activated sludge process. Sludge dehydration is the main means to achieve sludge reduction. The moisture content and volume of dehydrated sludge are greatly reduced, which can effectively reduce the cost of residual sludge transportation and subsequent treatment and disposal. The factors affecting sludge dehydration are mainly sludge particle size, extracellular polymer content and composition, sludge surface charge, sludge rheological properties, etc.

[0003] Aerobic granular sludge is a special biofilm formed by microbial self-agglomeration, with a regular and dense granular structure. At present, with the full range of engineering applications of aerobic granular sludge technology, the treatment and disposal of its residual sludge has become an important issue that cannot be ignored. Compared with traditional floc sludge, aerobic granular sludge has a very high content of extracellular polymers, and a large amount of bound water is stored in the extracellular polymers. Therefore, the large amount of extracellular polymers contained in aerobic granular sludge is one of the main factors hindering its dehydration efficiency.

[0004] The dense structure of aerobic granular sludge and its high extracellular polymer content make its dewatering characteristics significantly different from those of activated floc sludge. The free water of aerobic granular sludge is easier to remove, but the high extracellular polymer content makes it difficult to remove its bound water, resulting in low dewatering efficiency. At the same time, the dense structure of aerobic granular sludge also leads to the inability of the added polymer coagulant to produce a good coagulation effect with the granular sludge, and it is still impossible to remove the large amount of bound water present in the extracellular polymer, resulting in the low dewatering efficiency of aerobic granular sludge after traditional sludge conditioning methods. In addition, the viscosity of the granular sludge after the destruction of the extracellular polymers is greatly increased, which seriously affects the dewatering efficiency of the sludge. Therefore, it is urgent to study a new method for dewatering aerobic granular sludge. Summary of the invention

[0005] In view of the problems existing in the prior art, the purpose of the present invention is to provide a method for enhancing aerobic granular sludge dehydration by combining mechanical crushing with a polymer coagulant, which uses mechanical crushing combined with a polymer coagulant to release the bound water in the extracellular polymers of aerobic granular sludge, thereby improving the dehydration efficiency of aerobic granular sludge.

[0006] Mechanically destroying the extracellular polymer structure is one of the feasible ways to release the bound water inside aerobic granular sludge. In addition, the use of polymer coagulants has been applied to the dewatering treatment of traditional floc activated sludge. The polymer coagulant has strong hydrophilicity and strong adhesion to the sludge colloidal particles. It is easy to be adsorbed on the surface of the sludge colloidal particles, and can agglomerate a large number of fine floc sludge, greatly improving the sludge dewatering efficiency. The present invention uses polyferric chloride as a polymer coagulant. The iron ions in the polyferric chloride can form bonds with the sludge exopolymers. When small aggregates are formed in the mud-water mixture, they can further play a net-catching and sweeping role under the action of centrifugation, thereby improving the sludge dewatering efficiency.

[0007] To achieve the above purpose, this method is implemented through the following technical solutions: S1. The remaining aerobic granular sludge to be treated is filtered through a filter cloth to remove free water and obtain concentrated aerobic granular sludge; S2. The concentrated aerobic granular sludge in step S1 is mechanically crushed to obtain crushed aerobic granular sludge; S3. Adding a polymer coagulant to the broken aerobic granular sludge in step S2 and performing a short period of rapid stirring reaction; after the reaction is fully carried out, slowly stirring for a period of time to complete the sludge conditioning before dehydration; S4. The conditioned sludge in step S3 is centrifugally dehydrated to complete the dehydration process of the remaining aerobic granular sludge.

[0008] Preferably, the concentration of the remaining aerobic granular sludge in step S1 is 6-15 g / L, the filter cloth is preferably a polyester filter cloth with a pore size of 0.18-0.43 mm (35-80 mesh), and the concentration of the concentrated aerobic granular sludge obtained after filtration with the filter cloth is 30-60 g / L, and the moisture content is 92-98%.

[0009] Preferably, in step S2, a submersible pump is used to mechanically crush the aerobic granular sludge, the power of the submersible pump is 500-2000 W, and the crushing time is 30-60 min.

[0010] Preferably, the average particle size of the obtained broken aerobic granular sludge is 0.1-0.5 mm.

[0011] Preferably, the polymer coagulant added in step S3 is preferably polyferric chloride powder, and the addition amount is 50-200 mg / g dry sludge.

[0012] Preferably, in step S3, the rapid stirring speed is 150-300 r / min, the stirring time is 30-60 s, and the slow stirring speed is 50-100 r / min, and the stirring time is 5-15 min.

[0013] Preferably, centrifugal dehydration is adopted in step S4, the centrifugal speed is 2000-4000 r / min, and the centrifugal time is 5-10min; after mechanical crushing combined with high molecular coagulant conditioning and then centrifugal dehydration, the moisture content of the sludge cake after dehydration is 81-84%.

[0014] Compared with the prior art, the present invention has the following beneficial effects: (1) The mechanical crushing method adopted in this method can effectively destroy the dense structure and extracellular polymer structure of aerobic granular sludge, fully release the internal bound water present in the extracellular polymer, which is beneficial to the subsequent sludge conditioning and further improves the dehydration efficiency.

[0015] (2) The polymer coagulant used in this method plays a skeleton role in the sludge dewatering process and can effectively reduce the compressibility of the mud cake. In the present invention, since the viscosity of the aerobic granular sludge after mechanical crushing is greatly increased, which seriously affects the sludge dewatering efficiency, the method of adding a polymer coagulant is used to improve the dewatering efficiency without affecting the dewatering capacity.

[0016] (3) This method aims to address the drawback that mechanical crushing may reduce the dewatering efficiency of aerobic granular sludge. By adding high molecular weight flocculants, a large number of fine sludge flocs are re-aggregated to improve the sludge dewatering efficiency. Finally, the released bound water is removed by centrifugal dehydration, greatly improving the dewatering performance of aerobic granular sludge.

[0017] In summary, the present invention destroys the particle structure on the basis of removing most of the free water through the physical method of filter cloth filtration and mechanical crushing, releases a large amount of bound water between cells and within cells, and then uses the coagulation and precipitation effect of the polymer coagulant to destroy the hydrophilic functional groups on the sludge surface to reduce the hydrophilicity of the sludge surface, effectively improving the dehydration efficiency of the sludge cake. This method effectively solves the problem that the water inside the aerobic granular sludge cannot be released and removed, and provides an effective solution for the treatment and disposal of the remaining aerobic granular sludge. DETAILED DESCRIPTION

[0018] To make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention. Example 1

[0019] Take the remaining aerobic granular sludge to be treated, the sludge concentration is 6 g / L, the average sludge particle size is 589 μm, and the moisture content is 95.2%. The above-mentioned remaining aerobic granular sludge is loaded into a polyester filter cloth of 80 mesh, and most of the free water is removed by gravity compression and extrusion to obtain concentrated aerobic granular sludge, the sludge concentration is 30 g / L, and the sludge moisture content is 93%. Put a submersible pump with a power of 500 W into the concentrated aerobic granular sludge and mechanically crush it for 60 minutes to obtain crushed aerobic granular sludge, and the average particle size of the crushed sludge is 261 μm. Add 50 mg / g of polyferric chloride powder to the above-mentioned mechanically crushed aerobic granular sludge, stir and react at a speed of 200 r / min for 30 s, and then stir and react at a speed of 100 r / min for 15 min to complete the sludge dehydration conditioning process. The above-mentioned conditioned aerobic granular sludge is placed in a centrifugal dehydrator for centrifugal dehydration, and centrifuged at a speed of 2000 r / min for 5 minutes. After mechanical crushing coupled with high molecular coagulant conditioning and centrifugal dehydration, the sludge moisture content dropped to 83.6%. Example 2

[0020] Take the remaining aerobic granular sludge to be treated, the sludge concentration is 15 g / L, the average sludge particle size is 672 μm, and the moisture content is 97.1%. The above-mentioned remaining aerobic granular sludge is loaded into a polyester filter cloth with a mesh of 80, and most of the free water is removed by gravity compression and extrusion to obtain concentrated aerobic granular sludge, the sludge concentration is 60 g / L, and the sludge moisture content is 94%. Put a submersible pump with a power of 2000 W into the concentrated aerobic granular sludge and mechanically crush it for 30 minutes to obtain crushed aerobic granular sludge, and the average particle size of the crushed sludge is 125 μm. Add 200 mg / g of polyferric chloride powder to the above-mentioned mechanically crushed aerobic granular sludge, stir and react at a speed of 250 r / min for 60 s, and then stir and react at a speed of 100 r / min for 30 minutes to complete the sludge dehydration conditioning process. The aerobic granular sludge that has been conditioned is placed in a centrifugal dehydrator for centrifugal dehydration at a speed of 4000 r / min for 10 min. After mechanical crushing coupled with high molecular coagulant conditioning and centrifugal dehydration, the sludge moisture content is reduced to 82.8%. Example 3

[0021] Take the remaining aerobic granular sludge to be treated, the sludge concentration is 10 g / L, the average sludge particle size is 854 μm, and the moisture content is 96.3%. The above-mentioned remaining aerobic granular sludge is loaded into a polyester filter cloth with a mesh of 80, and most of the free water is removed by gravity compression and extrusion to obtain concentrated aerobic granular sludge, the sludge concentration is 40 g / L, and the sludge moisture content is 92%. Put a submersible pump with a power of 2000 W into the concentrated aerobic granular sludge and mechanically crush it for 30 minutes to obtain crushed aerobic granular sludge, and the average particle size of the crushed sludge is 125 μm. Add 100 mg / g of polyferric chloride powder to the above-mentioned mechanically crushed aerobic granular sludge, stir and react at a speed of 200 r / min for 60 s, and then stir and react at a speed of 100 r / min for 15 minutes to complete the sludge dehydration conditioning process. The aerobic granular sludge that has been conditioned is placed in a centrifugal dehydrator for centrifugal dehydration at a speed of 4000 r / min for 10 min. After mechanical crushing coupled with high molecular coagulant conditioning and centrifugal dehydration, the sludge moisture content is reduced to 81.2%.

[0022] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for mechanical crushing combined with polymer coagulant to enhance aerobic granular sludge dehydration, characterized in that: The steps include: S1. The remaining aerobic granular sludge to be treated is filtered through a filter cloth to remove free water and obtain concentrated aerobic granular sludge; S2. The concentrated aerobic granular sludge in step S1 is mechanically crushed to obtain crushed aerobic granular sludge; S3. Adding a polymer coagulant to the broken aerobic granular sludge in step S2, during which a short period of rapid stirring reaction is carried out; after the reaction is fully carried out, slowly stirring for a period of time to complete the sludge conditioning before dehydration; S4. The conditioned sludge in step S3 is centrifugally dehydrated to complete the dehydration process of the remaining aerobic granular sludge.

2. The method for strengthening aerobic granular sludge dehydration by mechanical crushing combined with polymer coagulant according to claim 1, characterized in that: The concentration of the remaining aerobic granular sludge in step S1 is 6-15 g / L, the filter cloth is preferably a polyester filter cloth with a pore size of 0.18-0.43 mm, and the concentration of the concentrated aerobic granular sludge obtained after filtration with the filter cloth is 30-60 g / L, and the moisture content is 92-98%.

3. The method for strengthening aerobic granular sludge dehydration by mechanical crushing combined with polymer coagulant according to claim 1, characterized in that: In step S2, a submersible pump is used to mechanically crush the aerobic granular sludge. The power of the submersible pump is 500-2000 W, and the crushing time is 30-60 min.

4. The method for strengthening aerobic granular sludge dehydration by mechanical crushing combined with polymer coagulant according to claim 3, characterized in that: In step S2, the average particle size of the obtained broken aerobic granular sludge is 0.1-0.5 mm.

5. The method for strengthening aerobic granular sludge dehydration by mechanical crushing combined with polymer coagulant according to claim 1, characterized in that: The polymer coagulant added in step S3 is polyferric chloride powder, and the addition amount is 50-200 mg / g dry sludge.

6. The method for strengthening aerobic granular sludge dehydration by mechanical crushing combined with polymer coagulant according to claim 5, characterized in that: In step S3, the fast stirring speed is 150-300 r / min, the stirring time is 30-60 s, and the slow stirring speed is 50-100 r / min, and the stirring time is 5-15 min.

7. The method for mechanical crushing combined with polymer coagulant to enhance aerobic granular sludge dehydration according to claim 1, characterized in that: In step S4, centrifugal dehydration is adopted, the centrifugal speed is 2000-4000 r / min, and the centrifugal time is 5-10 min; after mechanical crushing combined with high molecular coagulant conditioning and then centrifugal dehydration, the moisture content of the sludge cake after dehydration is 81-84%.