Method for improving sludge activity and heat production performance by stripping or adding extracellular polymeric substances

Abstract

A method for improving sludge activity and heat production performance by stripping or adding an extracellular polymeric substance (EPS) comprises the following steps: in a sewage treatment system, adding equipment for stripping the EPS on the way that sludge in a secondary sedimentation tank flows back to a biochemical tank, and stripping a mucus layer of the floc sludge to improve the activity of the floc sludge; the loose binding layer extracellular polymeric substance (LB-EPS) of the granular sludge is stripped, so that the activity of the granular sludge is improved; the LB-EPS after the floc sludge is stripped is fed back, so that the heat yield of the floc sludge is improved; a mucus layer and LB-EPS which are stripped from the granular sludge are fed back, so that the heat production rate of the granular sludge is increased; the EPS is stripped, so that the activity of the sludge is improved, and the treatment capacity of a sewage treatment system is improved; the stripped EPS is fed back, so that the heat production capacity or the heat production rate of the sludge is improved, the heat production performance of the sludge is improved, meanwhile, EPS resource recycling is facilitated, and therefore the purposes of improving the activity of heterotrophic bacteria in sewage treatment and the heat production capacity of the sludge and improving the heat energy recycling efficiency are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage treatment, and in particular relates to a method for stripping or adding extracellular polymers to improve sludge activity and heat generation performance. Background Art

[0002] Energy recovery and resource recycling have become a consensus and a key focus in the wastewater treatment industry. During biological wastewater treatment, microorganisms release a certain amount of heat energy during the metabolic transformation of organic pollutants. Efficiently utilizing this heat energy can contribute to the low-carbon operation of wastewater treatment systems. Research is also targeting increasing heat production in wastewater treatment using relatively simple operations, or enhancing the activity of heterotrophic bacteria in sludge treatment to improve wastewater treatment capacity.

[0003] Patent application publication number CN114573095A describes stripping the slime layer and loosely bounded layer (LB-EPS) from the extracellular polymeric substances (EPS) of flocculent sludge. After stripping the slime layer, the ammonia nitrogen half-saturation coefficient drops sharply, indicating a higher affinity for ammonia nitrogen in the sludge, enhancing the nitrification capacity of the activated sludge. After stripping the LB-EPS, kinetic parameters such as the yield coefficient indicate that stripping the EPS can reduce sludge production and increase heat production. The stripped EPS is then recovered.

[0004] The drawbacks of this technical solution are that there are no direct parameters to characterize the heat production of flocculent sludge, and instead the improved heat production is inferred indirectly through kinetic parameters. It also fails to explain whether EPS continues to affect heat production after being separated from the sludge. No new uses for EPS are proposed, and only recycling is permitted. No method is proposed for improving the heat production of EPS in the emerging granular sludge. Summary of the Invention

[0005] In order to overcome the deficiencies of the above-mentioned prior art, the object of the present invention is to provide a method for stripping or adding extracellular polymers to improve sludge activity and heat production performance. This method targets the dual action mechanism of EPS components in flocculent sludge or granular sludge in maintaining sludge structural stability and metabolic activity, combined with the sludge metabolic behavior during actual operation, and quantitatively strips off different levels of components in EPS (such as mucus layer and LB-EPS) to break its restrictions on microbial biomass transfer and metabolic activity. At the same time, specific EPS components can be returned under appropriate conditions to induce microorganisms to produce stress responses and improve intracellular energy metabolism levels and material circulation efficiency. This method can, on the basis of not relying on additional nutrient sources or energy input, achieve the improvement of microbial respiratory activity and heat release efficiency in flocculent sludge and granular sludge by precisely adjusting the EPS content and composition, thereby improving the overall heat production performance of the sludge, and providing technical support for sludge stabilization treatment, energy recovery and system operation optimization.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for improving sludge activity and heat production by stripping or adding extracellular polymers comprises the following steps:

[0008] Step 1: The sewage to be treated enters the biochemical tank 1 through the water inlet pipe 7. After the sewage from the biochemical tank 1 enters the secondary sedimentation tank 2, the mud and water are separated, and the supernatant is discharged. A portion of the sludge at the bottom is returned to the biochemical tank 1 through the tenth pipe 16 to maintain the sludge volume of the biochemical tank 1. A portion of the excess sludge is discharged through the first pipe 3 for dehydration treatment.

[0009] Step 2: When the sludge in the secondary sedimentation tank 2 is flocculent sludge and the heat production of the flocculent sludge needs to be increased, part of the flocculent sludge in the secondary sedimentation tank 2 is processed by the first slime layer stripping device 4. The flocculent sludge after the slime layer is stripped flows back to the biochemical tank 1 through the second pipe 8, and the stripped slime layer flows back to the biochemical tank 1 through the third pipe 9;

[0010] Part of the flocculent sludge in the secondary sedimentation tank 2 is processed in sequence by the second slime layer stripping device 5 and the LB-EPS device 6. The flocculent sludge after stripping the LB-EPS is returned to the biochemical tank 1 through the fourth pipe 10. At the same time, the stripped slime layer is returned to the biochemical tank 1 through the sixth pipe 12, and the stripped LB-EPS is returned to the biochemical tank 1 through the fifth pipe 11.

[0011] When the sludge in the secondary sedimentation tank 2 is flocculent sludge and the heat generation rate of the flocculent sludge needs to be increased, part of the flocculent sludge in the secondary sedimentation tank 2 is processed by the first slime layer stripping device 4. The flocculent sludge after the slime layer is stripped is returned to the biochemical tank 1 through the second pipe 8, and the stripped slime layer is recycled through the eighth pipe 14.

[0012] Part of the flocculent sludge in the secondary sedimentation tank 2 is processed in sequence by the second slime layer stripping device 5 and the LB-EPS device 6. The flocculent sludge after stripping the LB-EPS is returned to the biochemical tank 1 through the fourth pipe 10. The slime layer stripped by the second slime layer stripping device 5 is recycled through the ninth pipe 15. The LB-EPS stripped by the LB-EPS stripping device 6 is recycled through the seventh pipe 13.

[0013] When the sludge in the secondary sedimentation tank 2 is granular sludge and the heat generation rate of the granular sludge needs to be increased, part of the granular sludge precipitated in the secondary sedimentation tank 2 is processed by the first slime layer stripping device 4. The granular sludge after the slime layer is stripped is returned to the biochemical tank 1 through the second pipe 8. At the same time, the stripped slime layer is returned to the biochemical tank 1 through the third pipe 9.

[0014] Part of the granular sludge in the secondary sedimentation tank 2 is processed in sequence by the second slime layer stripping device 5 and the LB-EPS device 6. The flocculent sludge after stripping the LB-EPS is returned to the biochemical tank 1 through the fourth pipe 10. At the same time, the stripped slime layer is returned to the biochemical tank 1 through the sixth pipe 12, and the stripped LB-EPS is returned to the biochemical tank 1 through the fifth pipe 11.

[0015] When the sludge in the secondary sedimentation tank 2 is granular sludge and the heterotrophic activity of the granular sludge needs to be improved, part of the granular sludge precipitated in the secondary sedimentation tank 2 is processed by the first slime layer stripping device 4. The granular sludge after the slime layer is stripped is returned to the biochemical tank 1 through the second pipe 8, and the stripped slime layer is recycled through the eighth pipe 14.

[0016] Part of the granular sludge in the secondary sedimentation tank 2 is processed in turn by the second slime layer stripping equipment 5 and the LB-EPS equipment 6. The granular sludge after stripping the LB-EPS flows back to the biochemical tank 1 through the fourth pipe 10. The stripped slime layer is recycled through the ninth pipe 15, and the stripped LB-EPS is recycled through the seventh pipe 13.

[0017] In step 2, when there is granular sludge in the biochemical tank 1, the slime layer collected by the first slime layer stripping device 4 and the second slime layer stripping device 5 and the LB-EPS stripped by the LB-EPS stripping device 6 are added to the biochemical tank 1 when it is necessary to increase the heat production rate of the granular sludge.

[0018] In the step 2, the first slime layer peeling device 4 and the second slime layer peeling device 5 adopt a peeling method of centrifuging the sludge with a centrifugal force of 1600-2500g, a temperature of 1-10°C, and a time of 1-10min to obtain a slime layer and the sludge after the slime layer is peeled off; the peeling LB-EPS device 6 adopts a method of first ultrasonically crushing the sludge after the slime layer is peeled off with a power of 3-15W, a frequency of 10-50kHz, and a time of 1-10min, and then performing high-speed centrifugation treatment with a centrifugal force of 8000-15000g, a temperature of 1-10°C, and a time of 10-30min.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. Improving the activity of activated sludge. After the flocculent sludge is treated by the first slime layer stripping device 4, the respiration rate of heterotrophic bacteria in the flocculent sludge increases after the slime layer is stripped, and the activity of heterotrophic bacteria is enhanced, which can improve the activity of the flocculent sludge and the sewage treatment effect. After the LB-EPS is stripped from the granular sludge, the respiration rate of heterotrophic bacteria increases, and the activity of heterotrophic bacteria is enhanced, which can improve the activity of the granular sludge.

[0021] 2. Increase the heat production of activated sludge and reduce sludge production. The flocculent sludge is stripped by the LB-EPS equipment and then returned to the biochemical pool 1 to increase the heat production of the flocculent sludge. From the perspective of energy conservation, it can be seen that the increase in sludge heat production will lead to a decrease in energy in other aspects, such as growth and proliferation, thereby reducing sludge production and reducing sludge treatment costs.

[0022] 3. Increase the heat production rate of activated sludge. The granular sludge is processed by the first slime layer stripping device 4 or the second slime layer stripping device 5 and the LB-EPS stripping device. The stripped granular sludge, the stripped slime layer and the LB-EPS are returned to the biochemical tank 1. This can increase the heat production rate of the granular sludge, release heat faster during the heat production process of the granular sludge, and improve the energy conversion rate of the granular sludge system. This provides a method for situations where the sewage temperature needs to be increased quickly.

[0023] In summary, the present invention processes flocculent sludge and granular sludge through a first slime layer stripping device 4, a second slime layer stripping device 5, or an LB-EPS stripping device 6, then recycles the stripped sludge and recycles or recycles the stripped slime layer and LB-EPS. This simple operation, without the need for an external carbon source, increases sludge heat production and enhances heterotrophic bacterial activity. This facilitates heat recovery, reduces excess sludge generation, enhances heterotrophic bacterial activity, improves sewage treatment performance, and reduces operating costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural diagram of the device of the present invention.

[0025] Figure 2 This is the change of respiration spectrum after the EPS of floc sludge is removed.

[0026] Figure 3 This is the respiration spectrum of granular sludge after stripping EPS.

[0027] In the figure: 1. Biochemical pool; 2. Second sedimentation tank; 3. First pipeline; 4. First slime layer stripping equipment; 5. Second slime layer stripping equipment; 6. LB-EPS stripping equipment; 7. Water inlet pipe; 8. Second pipeline; 9. Third pipeline; 10. Fourth pipeline; 11. Fifth pipeline; 12. Sixth pipeline; 13. Seventh pipeline; 14. Eighth pipeline; 15. Ninth pipeline; 16. Tenth pipeline. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The following embodiments are used to illustrate the present invention.

[0029] The present invention provides a method for improving sludge activity and heat production performance by stripping or adding extracellular polymers, comprising the following steps:

[0030] Step 1: The sewage to be treated enters the biochemical tank 1 through the water inlet pipe 7. After the sewage from the biochemical tank 1 enters the secondary sedimentation tank 2, the mud and water are separated, and the supernatant is discharged. A portion of the sludge at the bottom is returned to the biochemical tank 1 through the tenth pipe 16 to maintain the sludge volume of the biochemical tank 1. A portion of the excess sludge enters the sludge treatment workshop of the sewage treatment plant through the first pipe 3 and is dehydrated and then treated;

[0031] Step 2: When the sludge in the secondary sedimentation tank 2 is flocculent sludge and the heat production of the flocculent sludge needs to be increased, part of the flocculent sludge in the secondary sedimentation tank 2 is processed by the first slime layer stripping device 4. The flocculent sludge after the slime layer is stripped flows back to the biochemical tank 1 through the second pipe 8, and the stripped slime layer flows back to the biochemical tank 1 through the third pipe 9;

[0032] Part of the flocculent sludge in the secondary sedimentation tank 2 is processed in sequence by the second slime layer stripping device 5 and the LB-EPS device 6. The flocculent sludge after stripping the LB-EPS is returned to the biochemical tank 1 through the fourth pipe 10. At the same time, the stripped slime layer is returned to the biochemical tank 1 through the sixth pipe 12, and the stripped LB-EPS is returned to the biochemical tank 1 through the fifth pipe 11.

[0033] When the sludge in the secondary sedimentation tank 2 is flocculent sludge and the heat generation rate of the flocculent sludge needs to be increased, part of the flocculent sludge in the secondary sedimentation tank 2 is processed by the first slime layer stripping device 4. The flocculent sludge after the slime layer is stripped is returned to the biochemical tank 1 through the second pipe 8, and the stripped slime layer is recycled through the eighth pipe 14.

[0034] Part of the flocculent sludge in the secondary sedimentation tank 2 is processed in sequence by the second slime layer stripping device 5 and the LB-EPS device 6. The flocculent sludge after stripping the LB-EPS is returned to the biochemical tank 1 through the fourth pipe 10. The slime layer stripped by the second slime layer stripping device 5 is recycled through the ninth pipe 15. The LB-EPS stripped by the LB-EPS stripping device 6 is recycled through the seventh pipe 13.

[0035] When the sludge in the secondary sedimentation tank 2 is granular sludge and the heat generation rate of the granular sludge needs to be increased, part of the granular sludge precipitated in the secondary sedimentation tank 2 is processed by the first slime layer stripping device 4. The granular sludge after the slime layer is stripped is returned to the biochemical tank 1 through the second pipe 8. At the same time, the stripped slime layer is returned to the biochemical tank 1 through the third pipe 9.

[0036] Part of the granular sludge in the secondary sedimentation tank 2 is processed in sequence by the second slime layer stripping device 5 and the LB-EPS device 6. The flocculent sludge after stripping the LB-EPS is returned to the biochemical tank 1 through the fourth pipe 10. At the same time, the stripped slime layer is returned to the biochemical tank 1 through the sixth pipe 12, and the stripped LB-EPS is returned to the biochemical tank 1 through the fifth pipe 11.

[0037] When the sludge in the secondary sedimentation tank 2 is granular sludge and the heterotrophic activity of the granular sludge needs to be improved, part of the granular sludge precipitated in the secondary sedimentation tank 2 is processed by the first slime layer stripping device 4. The granular sludge after the slime layer is stripped is returned to the biochemical tank 1 through the second pipe 8, and the stripped slime layer is recycled through the eighth pipe 14.

[0038] Part of the granular sludge in the secondary sedimentation tank 2 is processed in turn by the second slime layer stripping equipment 5 and the LB-EPS equipment 6. The granular sludge after stripping the LB-EPS flows back to the biochemical tank 1 through the fourth pipe 10. The stripped slime layer is recycled through the ninth pipe 15, and the stripped LB-EPS is recycled through the seventh pipe 13.

[0039] In step 2, when there is granular sludge in the biochemical tank 1, the slime layer collected by the first slime layer stripping device 4 and the second slime layer stripping device 5 and the LB-EPS stripped by the LB-EPS stripping device 6 are added to the biochemical tank 1 when it is necessary to increase the heat production rate of the granular sludge.

[0040] In the step 2, the first slime layer peeling device 4 and the second slime layer peeling device 5 adopt a peeling method of centrifuging the sludge with a centrifugal force of 2000g, a temperature of 4°C, and a time of 5 minutes to obtain the slime layer and the sludge after the slime layer is peeled off; the peeling LB-EPS device 6 adopts a method of first ultrasonically crushing the sludge after the slime layer is peeled off with a power of 5W, a frequency of 20kHz, and a time of 5 minutes, and then performing high-speed centrifugation treatment with a centrifugal force of 10,000g, a temperature of 4°C, and a time of 15 minutes.

[0041] As a preferred embodiment of the present invention, part of the flocculent sludge is subjected to a slime layer stripping treatment; part of the flocculent sludge in the secondary sedimentation tank 2 is treated by the first slime layer stripping device 4, and the flocculent sludge after the slime layer is stripped is returned to the biochemical tank 1 through the second pipe 8, which can increase the respiration rate of heterotrophic bacteria in the flocculent sludge, increase the activity of heterotrophic bacteria, and improve the treatment capacity of the sewage system.

[0042] Experimental example

[0043] Two groups of reactors were cultured in the laboratory, one for flocculent sludge and the other for granular sludge. The control reactors were consistent, both with 1.5 kg COD / (m 3d), the aeration rate was controlled to be consistent at 4 L / min. The influent was artificially distributed to simulate domestic sewage. The inoculated sludge was taken from the regulating tank of a sewage treatment plant in Xi'an. The sludge samples were screened using 1 mm and 0.4 mm pore sieves. The sludge volume index was 62±3.31 mL / g, the sludge flocs were yellow-brown, and the sedimentation was normal. The suspended solids concentration of the mixed liquor of the original sludge was 10480±110 mg / L. The sludge was air-dried for 24 hours before inoculation and then inoculated into two reactors. The heat production of the sludge after 40 days of culture was measured. The sludge was subjected to operations such as EPS stripping and EPS reinjection. The heat production and heat production rate, as well as the kinetic parameters and respiratory spectrum, were also measured.

[0044] As shown in Table 1, after stripping LB-EPS from flocculent sludge and then reinjecting it, the heat production and heat production rate increased compared to the original flocculent sludge. Therefore, for flocculent sludge, the method of the present invention, i.e., stripping LB-EPS from flocculent sludge and then reinjecting it, can increase both heat production and heat production rate. For granular sludge, the additional addition of a slime layer and LB-EPS can also increase the heat production rate of the granular sludge.

[0045] Table 1. Heat generation characteristics of activated sludge after different treatments

[0046]

[0047]

[0048]

[0049] from Figure 2 It can be seen that the endogenous respiration rate (SOUR e ), autotrophic bacterial respiration rate (SOUR A ), there was no significant change after stripping the mucus layer and LB-EPS, and the heterotrophic bacterial respiration rate (SOUR H ) increased significantly after the floc sludge was stripped of the mucus layers. The increase in the respiration rate of heterotrophic bacteria indicated that the activity of heterotrophic bacteria increased. This showed that for floc sludge, stripping the mucus layer could increase the activity of heterotrophic bacteria in floc sludge and improve the overall activity of floc sludge. The total respiration rate (SOUR T ) also increased significantly.

[0050] from Figure 3 It can be seen that the endogenous respiration rate (SOURe) of granular sludge increased after stripping LB-EPS, and the autotrophic respiration rate (SOUR A ) There was no significant change in the heterotrophic bacterial respiration rate (SOUR H) increased slightly after stripping the mucus layer and significantly after stripping the LB-EPS.

Claims

1. A method for increasing sludge activity and heat production by stripping or adding extracellular polymers, characterized in that: The steps include: Step 1: The sewage to be treated enters the biochemical pool (1) through the water inlet pipe (7). After the sewage from the biochemical pool (1) enters the secondary sedimentation tank (2), the mud and water are separated, and the supernatant is discharged. A portion of the sludge at the bottom is returned to the biochemical pool (1) through the tenth pipe (16) to maintain the sludge amount in the biochemical pool (1). A portion of the remaining sludge is discharged through the first pipe (3) for dehydration treatment. Step 2: When the sludge in the secondary sedimentation tank (2) is flocculent sludge and the heat production of the flocculent sludge needs to be increased, a portion of the flocculent sludge in the secondary sedimentation tank (2) is processed by the first slime layer stripping device (4), and the flocculent sludge after the slime layer is stripped is returned to the biochemical tank (1) through the second pipe (8), and the stripped slime layer is returned to the biochemical tank (1) through the third pipe (9); Part of the flocculent sludge in the secondary sedimentation tank (2) is sequentially processed by the second slime layer stripping device (5) and the LB-EPS device (6), and the flocculent sludge after stripping the LB-EPS is returned to the biochemical tank (1) through the fourth pipe (10). At the same time, the stripped slime layer is returned to the biochemical tank (1) through the sixth pipe (12), and the stripped LB-EPS is returned to the biochemical tank (1) through the fifth pipe (11); When the sludge in the secondary sedimentation tank (2) is flocculent sludge and the heat generation rate of the flocculent sludge needs to be increased, part of the flocculent sludge in the secondary sedimentation tank (2) is processed by the first slime layer stripping device (4), and the flocculent sludge after the slime layer is stripped is returned to the biochemical tank (1) through the second pipe (8), and the stripped slime layer is recycled through the eighth pipe (14); Part of the flocculent sludge in the secondary sedimentation tank (2) is processed in sequence by the second slime layer stripping device (5) and the LB-EPS device (6); the flocculent sludge after stripping the LB-EPS is returned to the biochemical tank (1) through the fourth pipe (10); the slime layer stripped by the second slime layer stripping device (5) is recycled through the ninth pipe (15); and the LB-EPS stripped by the LB-EPS stripping device (6) is recycled through the seventh pipe (13); When the sludge in the secondary sedimentation tank (2) is granular sludge and the heat generation rate of the granular sludge needs to be increased, part of the granular sludge precipitated in the secondary sedimentation tank (2) is processed by the first slime layer stripping device (4), and the granular sludge after the slime layer is stripped is returned to the biochemical tank (1) through the second pipe (8), and at the same time, the stripped slime layer is returned to the biochemical tank (1) through the third pipe (9); Part of the granular sludge in the secondary sedimentation tank (2) is sequentially processed by the second slime layer stripping device (5) and the LB-EPS device (6), and the flocculent sludge after stripping the LB-EPS is returned to the biochemical tank (1) through the fourth pipe (10). At the same time, the stripped slime layer is returned to the biochemical tank (1) through the sixth pipe (12), and the stripped LB-EPS is returned to the biochemical tank (1) through the fifth pipe (11); When the sludge in the secondary sedimentation tank (2) is granular sludge and the heterotrophic activity of the granular sludge needs to be improved, part of the granular sludge precipitated in the secondary sedimentation tank (2) is processed by the first slime layer stripping device (4), and the granular sludge after the slime layer is stripped is returned to the biochemical tank (1) through the second pipe (8), and the stripped slime layer is recycled through the eighth pipe (14); Part of the granular sludge in the secondary sedimentation tank (2) is processed in turn by the second slime layer stripping device (5) and the LB-EPS device (6). The granular sludge after stripping the LB-EPS is returned to the biochemical tank (1) through the fourth pipe (10), the stripped slime layer is recycled through the ninth pipe (15), and the stripped LB-EPS is recycled through the seventh pipe (13).

2. The method of stripping or adding extracellular polymers to improve sludge activity and heat production according to claim 1, characterized in that: In step 2, when there is granular sludge in the biochemical tank (1), the slime layer collected by the first slime layer stripping device (4) and the second slime layer stripping device (5) and the LB-EPS stripped by the LB-EPS stripping device (6) are added to the biochemical tank (1) when it is necessary to increase the heat generation rate of the granular sludge.

3. The method of stripping or adding extracellular polymers to improve sludge activity and heat production according to claim 1, characterized in that: In the step 2, the first slime layer stripping device (4) and the second slime layer stripping device (5) adopt a stripping method of centrifuging the sludge with a centrifugal force of 1600-2500g, a temperature of 1-10°C, and a time of 1-10 minutes to obtain the slime layer and the sludge after the slime layer is stripped; the stripping LB-EPS device (6) adopts a method of first ultrasonically crushing the sludge after the slime layer is stripped with a power of 3-15W, a frequency of 10-50kHz, and a time of 1-10 minutes, and then performing high-speed centrifugation treatment with a centrifugal force of 8000-15000g, a temperature of 1-10°C, and a time of 10-30 minutes.

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