Method for strengthening dewatering of aerobic granular sludge by coupling mechanical crushing with persulfate conditioning

Abstract

The invention discloses a method for strengthening dewatering of aerobic granular sludge by coupling mechanical crushing with persulfate conditioning. According to different structural characteristics and extracellular polymeric substance content of the aerobic granular sludge and traditional floc activated sludge, a physical method of filter cloth filtration and mechanical crushing is combined on the basis of chemical conditioning, so that the dewatering capacity of the aerobic granular sludge is effectively improved, and the method is a practical and feasible aerobic granular sludge dewatering means; the popularization and application prospects are realized.

Description

Technical Field

[0001] The invention belongs to the technical field of sludge treatment, and in particular relates to a method for mechanical crushing coupled with persulfate conditioning to enhance aerobic granular sludge dehydration. Background Art

[0002] Sludge dehydration is a necessary step in the treatment of excess sludge in the activated sludge process. The excess sludge in the traditional activated sludge process has a high moisture content, large volume, and poor dehydration, which greatly increases the cost of transportation and treatment of activated sludge. Currently, the management cost of sludge in sewage treatment plants accounts for 30-60% of the total operating cost of sewage treatment plants. Sludge dehydration has been proven to be one of the effective measures to reduce the moisture content of sludge. Therefore, reducing the moisture content of excess sludge is of great significance to sludge reduction and reducing the operating costs of sewage treatment plants.

[0003] Aerobic granular sludge is an emerging treatment technology in wastewater biological treatment technology. Its essence is a special biofilm formed by the self-agglomeration of activated sludge microorganisms. Since its first report in 1997, aerobic granular sludge has been widely studied and applied in municipal wastewater treatment, industrial wastewater treatment and high value-added product recovery. At present, with the large-scale engineering application of aerobic granular sludge technology, the treatment and disposal of residual aerobic granular sludge has received more extensive attention and attention, and the efficient dehydration of aerobic granular sludge is imminent.

[0004] Aerobic granular sludge has a complete and dense spatial structure and a high content of extracellular polymers, which makes it have completely different dewatering characteristics from traditional floc activated sludge. Aerobic granular sludge has excellent sedimentation performance and lower surface charge, which means that the free water on the surface of aerobic granular sludge is easier to remove, while its internal water is more tightly bound to the particle structure through extracellular polymers and is relatively difficult to remove. At the same time, the dense structure of aerobic granular sludge makes traditional sludge conditioning methods less efficient and unable to release a large amount of internal bound water. This feature also seriously hinders the dewatering efficiency of the remaining aerobic granular sludge. Summary of the invention

[0005] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a method for strengthening the dehydration of aerobic granular sludge by mechanical crushing coupled with persulfate conditioning. The present invention aims at the different structural characteristics and extracellular polymer content of aerobic granular sludge and traditional floc activated sludge, and combines the physical methods of filter cloth filtration and mechanical crushing on the basis of chemical conditioning, thereby effectively improving the dehydration capacity of aerobic granular sludge. It is a practical and feasible aerobic granular sludge dehydration method with prospects for promotion and application.

[0006] To achieve the above objectives, the present invention provides the following technical solutions:

[0007] A method for mechanical crushing coupled with persulfate conditioning to enhance aerobic granular sludge dehydration, comprising the following steps:

[0008] S1. The remaining aerobic granular sludge is quickly filtered through a filter cloth to remove most of the free water to obtain concentrated aerobic granular sludge;

[0009] S2. placing a submersible pump into the concentrated aerobic granular sludge for mechanical crushing to obtain crushed aerobic granular sludge;

[0010] S3. adding persulfate to the broken aerobic granular sludge, stirring for a period of time, and then adding ferrous chloride solution, stirring for a period of time, to complete the conditioning of the broken aerobic granular sludge;

[0011] S4. The conditioned sludge is centrifugally dehydrated to complete the dehydration of the aerobic granular sludge.

[0012] Preferably, the concentration of the residual aerobic granular sludge in S1 is 6-15 g / L.

[0013] Preferably, the filter cloth in S1 is a polyester filter cloth with a pore size of 0.18-0.43 mm (35-80 mesh).

[0014] Preferably, the concentrated aerobic granular sludge obtained in step S1 has a concentration of 30-60 g / L and a moisture content of 91-96%.

[0015] Preferably, the power of the submersible pump used in S2 is 100-2200 W, the crushing time is 30-60 min, and the average particle size of the obtained crushed aerobic granular sludge is 0.1-0.5 mm.

[0016] Preferably, the persulfate in S3 is sodium persulfate or potassium persulfate.

[0017] Preferably, the dosage of persulfate in S3 is 50.0-200.0 mg / g dry sludge, and the dosage of ferrous chloride solution is 15-30 mg FeCl 2 / g dry sludge.

[0018] Preferably, the stirring time for adding persulfate and ferrous chloride in S3 is 10-30 min, and the stirring speed is 100-300 r / min.

[0019] Preferably, the rotation speed of the centrifugal dehydration in S4 is 2000-4000 r / min, and the centrifugal time is 5-10 min.

[0020] Preferably, the moisture content of the sludge after dehydration treatment in S1-S4 is 80%-83%.

[0021] The beneficial effects of the present invention are:

[0022] The present invention uses filter cloth filtration to quickly remove most of the free water in aerobic granular sludge. The free water in aerobic granular sludge is easier to be separated than that in traditional floc activated sludge. Therefore, through the filter cloth, most of the free water can be removed simply and at low cost, reducing the sludge moisture content, laying a good foundation for subsequent treatment.

[0023] The present invention uses a submersible pump to efficiently mechanically crush aerobic granular sludge. Without destroying the microbial cell structure, the granular spatial structure is destroyed and a small amount of tightly bound extracellular polymers are released, becoming loose and dissolved extracellular polymers. This process is conducive to removing part of the released internal bound water and a large amount of free water, and is also conducive to subsequent sludge conditioning, further improving the dehydration efficiency.

[0024] The present invention uses a persulfate advanced oxidation method to condition the broken aerobic granular sludge. Persulfate destroys the extracellular polymers and decomposes organic matter in the sludge through persulfate ions, thereby releasing a large amount of interstitial water and bound water, improving the dehydration efficiency. At the same time, persulfate ions also have a relatively long life and can oxidize organic components in the sludge under a wider range of pH conditions. In addition, the present invention also uses Fe 2+ As a catalyst to further activate the free radicals in the reaction, the Fe 3+ The mechanically broken aerobic granular sludge makes it easier for active free radicals such as persulfate to contact the sludge, thereby increasing the release efficiency of extracellular polymers and thus improving the conditioning effect of persulfate. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 They are aerobic granular sludge (A) which has not been dehydrated by the present invention and aerobic granular sludge (B) which has been dehydrated by the present invention. DETAILED DESCRIPTION

[0026] 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.

[0027] Example 1

[0028] Take the remaining aerobic granular sludge to be treated, such as Figure 1As shown in (A), the sludge concentration is 8g / L, the average sludge particle size is 854μm, and the moisture content is 96.3%. The above-mentioned remaining aerobic granular sludge is loaded into a 80-mesh polyester filter cloth, and most of the free water is removed by gravity compression and extrusion to obtain concentrated aerobic granular sludge with a sludge concentration of 30g / L and a sludge moisture content of 94%. A submersible pump with a power of 100W is placed in the concentrated aerobic granular sludge and mechanically crushed for 60 minutes to obtain crushed aerobic granular sludge. The average particle size of the crushed sludge is 325μm. 50.0mg / g of sodium persulfate of dry sludge is added to the above-mentioned mechanically crushed aerobic granular sludge, and the reaction is stirred at a speed of 180r / min for 10 minutes, and then 15mgFeCl is added. 2 / g dry sludge ferrous chloride solution, stirring at a speed of 150r / min for 15min to complete the sludge dehydration conditioning process. The above conditioned aerobic granular sludge is placed in a centrifugal dehydrator for centrifugal dehydration at a speed of 2000r / min for 5min. Figure 1 (B) is the morphology of aerobic granular sludge after dehydration treatment. It can be seen that the particle size of aerobic granular sludge after dehydration treatment of the present invention is significantly reduced. In addition, after mechanical crushing coupled with persulfate conditioning and centrifugal dehydration, the moisture content of the sludge cake is reduced to 82.9%, which is 6% lower than that of aerobic granular sludge without mechanical crushing and persulfate conditioning, and the indicators characterizing the sludge dehydration efficiency such as sludge specific resistance and capillary water absorption time are not affected.

[0029] Example 2

[0030] Take the remaining aerobic granular sludge to be treated, the sludge concentration is 15g / L, the average sludge particle size is 623μm, and the moisture content is 95.2%. The above-mentioned remaining aerobic granular sludge is loaded into a 35-mesh polyester filter cloth, and most of the free water is removed by gravity compression and extrusion to obtain concentrated aerobic granular sludge, the sludge concentration is 60g / L, and the sludge moisture content is 92%. Put a submersible pump with a power of 2200W into the concentrated aerobic granular sludge and mechanically crush it for 30 minutes to obtain crushed aerobic granular sludge. The average particle size of the crushed sludge is 108μm. Add 200.0mg / g of sodium persulfate to the above-mentioned mechanically crushed aerobic granular sludge, stir and react at a speed of 180r / min for 30 minutes, and then add 30mg FeCl 2 / g dry sludge with ferrous chloride solution, stirred at a speed of 150r / min for 30min to complete the sludge dehydration conditioning process. The above-mentioned conditioned aerobic granular sludge was placed in a centrifugal dehydrator for centrifugal dehydration at a speed of 4000r / min for 10min. After mechanical crushing coupled with persulfate conditioning and centrifugal dehydration, the moisture content of the sludge cake dropped to 82.3%, which was 6% lower than that of aerobic granular sludge without mechanical crushing and persulfate conditioning, and the indicators characterizing the sludge dehydration efficiency, such as sludge specific resistance and capillary water absorption time, were not affected.

[0031] Example 3

[0032] Take the remaining aerobic granular sludge to be treated, the sludge concentration is 10g / L, the average sludge particle size is 810μm, and the moisture content is 93.8%. The above-mentioned remaining aerobic granular sludge is loaded into a 60-mesh polyester filter cloth, and most of the free water is removed by gravity compression and extrusion to obtain concentrated aerobic granular sludge, the sludge concentration is 35g / L, and the sludge moisture content is 92%. Put a submersible pump with a power of 1000W 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 210μm. Add 100.0mg / g of sodium persulfate to the above-mentioned mechanically crushed aerobic granular sludge, stir and react at a speed of 180r / min for 15min, then add 23.5mg FeCl2 / g of ferrous chloride solution of dry sludge, stir and react at a speed of 150r / min for 10min, and complete the sludge dehydration conditioning process. The aerobic granular sludge that has been conditioned as described above was placed in a centrifugal dehydrator for centrifugal dehydration at a speed of 4000r / min for 10 minutes. After mechanical crushing coupled with persulfate conditioning and centrifugal dehydration, the moisture content of the sludge cake dropped to 80.0%, which was 8% lower than that of the aerobic granular sludge that had not been mechanically crushed and conditioned with persulfate, and the indicators characterizing the sludge dehydration efficiency, such as the sludge specific resistance and capillary water absorption time, were not affected.

[0033] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for mechanical crushing coupled with persulfate conditioning to enhance aerobic granular sludge dehydration, characterized in that: The following steps are involved: S1. The remaining aerobic granular sludge is quickly filtered through a filter cloth to remove most of the free water to obtain concentrated aerobic granular sludge; S2. placing a submersible pump into the concentrated aerobic granular sludge for mechanical crushing to obtain crushed aerobic granular sludge; S3. adding persulfate to the broken aerobic granular sludge, stirring for a period of time, and then adding ferrous chloride solution, stirring for a period of time, to complete the conditioning of the broken aerobic granular sludge; S4. The conditioned sludge is centrifugally dehydrated to complete the dehydration of the aerobic granular sludge.

2. The method according to claim 1, characterized in that The concentration of residual aerobic granular sludge in S1 was 6-15 g / L.

3. The method according to claim 1, characterized in that The filter cloth in S1 is polyester filter cloth with a pore size of 35-80 mesh.

4. The method according to claim 1, characterized in that: The concentrated aerobic granular sludge obtained in step S1 has a concentration of 30-60 g / L and a moisture content of 91-96%.

5. The method according to claim 1, characterized in that The power of the submersible pump used in S2 is 100-2200W, the crushing time is 30-60min, and the average particle size of the obtained crushed aerobic granular sludge is 0.1-0.5mm.

6. The method according to claim 1, characterized in that The persulfate in S3 is sodium persulfate or potassium persulfate.

7. The method according to claim 1, characterized in that The dosage of persulfate in S3 is 50.0-200.0 mg / g dry sludge, and the dosage of ferrous chloride solution is 15-30 mg FeCl2 / g dry sludge.

8. The method according to claim 1, characterized in that The stirring time for adding persulfate and ferrous chloride in S3 is 10-30 minutes, and the stirring speed is 100-300r / min.

9. The method according to claim 1, characterized in that: The speed of centrifugal dehydration in S4 is 2000-4000r / min, and the centrifugal time is 5-10min.

10. The method according to claim 1, characterized in that The moisture content of the sludge after S1-S4 dehydration treatment is 80%-83%.

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