Method for promoting continuous flow sludge granulation by adopting induction particles

Abstract

The invention relates to a method for promoting continuous flow sludge granulation by adopting induction particles, which comprises the following steps: taking an SBR (sequencing batch reactor) as a granulation unit, and directionally culturing aerobic granular sludge with the particle size of 150-200mu m as the induction particles; adding the induction particles into the continuous flow reactor, and accelerating the granulation speed of the aerobic granular sludge in the continuous flow reactor; according to the speed condition of granulation in the continuous flow reactor, in combination with the daily sludge discharge amount of the continuous flow reactor, the adding mass ratio of the induced particles is 2-10%, and the adding frequency is once a day, so that the particle size of the granular sludge in the system is kept stable in the optimal interval; based on the idea of making and using separation, the concept of'inducing particles' is provided and utilized, that is, early-stage particles with the particle size in a particle formation acceleration interval are selected as a structure inducing core for floc aggregation and are added into the continuous flow reactor, so that the structure inducing core is added into the continuous flow reactor on the premise of not sacrificing the system load; the rapid granulation of the floc sludge and the stable operation of the system are realized.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage treatment, and in particular relates to a method for promoting continuous flow sludge granulation by using inducing particles. Background Art

[0002] With the tightening of discharge standards for wastewater treatment plants, particularly stringent requirements for nutrients like total nitrogen and total phosphorus, traditional activated sludge processes are struggling to meet these new demands. Furthermore, limited land resources and capital investment have made large-scale new wastewater treatment facilities difficult to build. Therefore, in-situ capacity expansion—increasing the treatment capacity of existing wastewater treatment facilities through process optimization or equipment upgrades without significantly increasing civil engineering costs—has become a pressing issue for the industry.

[0003] Aerobic granular sludge (AGS), an intensive and efficient biological treatment method, has been widely recognized in recent years as a key technology path for upgrading and expanding wastewater treatment plants due to its excellent settling performance, high biomass concentration, high reactor volume load, strong shock load resistance, and ability to simultaneously achieve organic matter removal, nitrification, denitrification, and biological phosphorus removal. Compared to traditional flocculent activated sludge technology, AGS significantly improves the system's volume load and sludge-water separation performance, effectively reducing hydraulic retention time (HRT), making it suitable for upgrading existing wastewater plants and increasing their efficiency without changing the civil engineering structure.

[0004] However, the application of AGS technology is still mainly limited to sequencing batch reactors (SBR). In actual engineering applications, especially in the widely used continuous flow reactors (such as oxidation ditch, A 2 / O, A / O, UCT processes, etc.), its promotion and application still faces many difficulties and bottlenecks:

[0005] (1) Lack of effective aerobic granular sludge selection and retention mechanism. Due to the continuous and stable process characteristics and the lack of obvious periodic sedimentation-elution stages, the continuous flow system is difficult to effectively screen the sludge, making the formation of aerobic granular sludge difficult and slow.

[0006] (2) Poor particle structure stability. The granular sludge formation process often goes through the floc-particle formation period-optimal particle size particles-abnormal particle growth-particle hollowing-particle disintegration process. Even if aerobic granular sludge is formed in a continuous flow reactor, it will grow excessively due to the lack of effective control measures, resulting in problems such as excessive particle size, loose structure, hollowing, and even disintegration, resulting in poor system operation stability.

[0007] (3) Existing granulation methods in the laboratory are difficult to replicate directly in actual projects. In the laboratory, “enhanced hydraulic selection mechanism” is widely used, such as shortening the sedimentation time to promote the formation of aerobic granular sludge in continuous flow. However, in actual projects, due to the limitations of process characteristics and equipment conditions, it is difficult to achieve large-scale application and stable operation.

[0008] (4) Traditional aerobic granular sludge control strategies usually sacrifice treatment efficiency. For example, the widely adopted “fed-starved” influent strategy can control the growth rate of particles, but this strategy will lead to a reduction in the system treatment load and is sensitive to influent water quality, carbon source composition, and carbon-nitrogen ratio, limiting its scope of application.

[0009] Chinese invention application number CN202310022363.4 proposes a method, stripping modification device, and system for promoting sludge granulation by stripping the slime layer of treated sludge. This method involves stripping and modifying the slime layer of sludge discharged from a bioreactor, recycling the modified activated sludge back into the bioreactor, and promoting sludge granulation in the reactor. However, this method relies on a relatively complex centrifugation step and is more suitable for smaller-scale sewage treatment systems. Summary of the Invention

[0010] In order to overcome the problems of slow startup, unstable structure and difficult to control operation of aerobic granular sludge in continuous flow sewage treatment systems, the present invention proposes a method for promoting the granulation of continuous flow sludge by using inducing particles. This method is based on the idea of ​​"separation of formation and use" and proposes and utilizes the concept of "induced particles", that is, early particles with a particle size in the accelerated range of particle formation (about 150-200μm) are selected as the structural inducing core of floc aggregation, and added into the continuous flow reactor, thereby achieving rapid granulation of floc sludge and stable operation of the system without sacrificing the system load.

[0011] In order to achieve the above object, the technical solution adopted by the present invention is:

[0012] A method for promoting continuous flow sludge granulation by using inducing particles comprises the following steps:

[0013] Step 1: Using the SBR reactor as a granulation unit, aerobic granular sludge with a particle size of 150-200 μm is cultured as inducing particles;

[0014] Step 2: Add the inducing particles obtained by culture in step 1 to the continuous flow reactor to accelerate the granulation rate of the aerobic granular sludge in the continuous flow reactor; according to the granulation rate in the continuous flow reactor and the daily sludge discharge of the continuous flow reactor, the mass ratio of the inducing particles is 2-10%, and the addition frequency is once a day to keep the particle size of the granular sludge in the system stable in the optimal range, i.e., 150-200 μm.

[0015] The continuous flow reactor includes but is not limited to oxidation ditch, A 2 / O, A / O, UCT.

[0016] In step 2, according to the daily sludge discharge of the continuous flow reactor, the mass ratio of the inducing particles is 2%, and the addition frequency is once a day to keep the particle size of the granular sludge in the system stable in the optimal range, i.e., 150-200 μm.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) The present invention utilizes inducing particles in the accelerated particle growth stage to guide the aggregation of flocculent microorganisms in the system, thereby achieving rapid establishment of particle structure and effectively overcoming the problem of difficult and slow formation of aerobic granular sludge in continuous flow reactors.

[0019] (2) By adding inducing particles with a particle size distribution in the range of 150-200 μm, problems such as excessive particle size, loose structure, hollowing, and even disintegration in the continuous flow reactor can be effectively avoided, maintaining good particle structure strength and optimizing system stability.

[0020] (3) The present invention does not require structural modification of the existing continuous flow reactor. Instead, it can be implemented by simply connecting a small or medium-sized SBR reactor as a granulation unit. It is suitable for various sewage treatment plants to carry out low-cost, fast-response in-situ upgrading and granulation upgrades. It has good engineering adaptability and easy operation.

[0021] (4) The present invention is based on the monitoring feedback of the average particle size of the activated sludge in the continuous flow reactor to control the frequency and proportion of the addition of induced particles, thereby achieving efficient particle structure control without sacrificing treatment efficiency, and has stronger system adaptability, regulation flexibility and application universality.

[0022] In summary, the present invention breaks through the limitations of slow granulation speed and poor system stability in the continuous flow reactor by constructing a synergistic mechanism of "induced particles-continuous flow system", realizes the rapid start-up and stable operation of aerobic granular sludge in the continuous flow reactor, and significantly improves the treatment capacity and effluent stability of the continuous flow reactor. It is suitable for in-situ upgrading of existing sewage treatment plants and the engineering promotion of AGS technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a process flow chart of a continuous flow reactor in an embodiment of the present invention.

[0024] Figure 2 Graph showing particle size distribution according to an embodiment of the present invention.

[0025] Figure 3 The content changes in the examples of the present invention.

[0026] Among them, 1. Aeration pump; 2. Peristaltic pump; 3. Electric valve; 4. Microporous aeration head; 5. Flow pusher; 6. Inclined baffle; 7. Outlet weir; 8. Inlet pipe; 9. PLC controller; 10. Residual sludge; 11. Secondary sedimentation tank; 12. Return sludge; 13. Ditch A; 14. Ditch B; 15. Outlet pipe. DETAILED DESCRIPTION

[0027] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The exemplary embodiments and descriptions of the present invention are used to explain the present invention but are not intended to limit the present invention.

[0028] A method for promoting continuous flow sludge granulation by using inducing particles, specifically comprising the following steps:

[0029] Step 1: The existing SBR for cultivating AGS is used as a granulation unit, and aerobic granular sludge with a particle size of 150-200 μm is directed to be cultivated as inducing particles;

[0030] The particle size of the inducing particles is controlled within a range of 150-200 μm, so as to keep the particles in an accelerated formation period and enhance their structural induction effect.

[0031] The continuous flow reactor is used as a particle unit to achieve the target sewage treatment function and also as a receiving system for induced particles;

[0032] The continuous flow reactor refers to a reactor in which sewage flows continuously and undergoes biochemical reactions in the reactor, and the treated water flows out of the reactor continuously. Common continuous flow reactors in water treatment include but are not limited to oxidation ditches, A 2 / O, A / O, UCT or other continuous inlet and outlet type activated sludge reactors.

[0033] Step 2: Add the inducing particles obtained by culture in step 1 to the continuous flow reactor to accelerate the granulation rate of the aerobic granular sludge in the continuous flow reactor; according to the granulation rate in the continuous flow reactor and the daily sludge discharge of the continuous flow reactor, the mass ratio of the inducing particles is 2-10%, and the addition frequency is once a day to keep the particle size of the granular sludge in the system stable in the optimal range, i.e., 150-200 μm.

[0034] In step 2, according to the daily sludge discharge of the continuous flow reactor, the mass ratio of the inducing particles can be 2%, and the addition frequency is once a day to keep the particle size of the granular sludge in the system stable in the optimal range, i.e., 150-200 μm.

[0035] The present invention constructs a "granulation-use" dual system, and directionally cultivates induced particles with a particle size of 150-200μm and in the accelerated particle formation stage in a sequencing batch reactor (SBR). As the structural core of floc aggregation, they are added to the continuous flow reactor, thereby guiding the rapid transformation of floc sludge in the system into stable particles. The added mass of the induced particles is 2%-10% of the sludge discharge of the continuous flow system, and the addition frequency is once a day. This method can effectively improve the formation rate and structural stability of granular sludge, avoid problems such as abnormal particle enlargement and hollowing, and enhance the system's impact resistance and operational stability. Compared with traditional production and use separation strategies, the present invention proposes the concept and application mechanism of "induced particles" for the first time. It has the advantages of clear structural induction, controllable operation, and strong engineering adaptability. It is suitable for in-situ upgrading of sewage treatment plants and large-scale promotion of granular sludge technology.

[0036] Example

[0037] This embodiment provides a method for promoting continuous flow sludge granulation using inducing particles, which specifically includes the following steps:

[0038] First, using the SBR reactor as a granulation unit, the formation of aerobic granular sludge was promoted by gradually shortening the settling time and increasing the hydraulic selective pressure within the SBR reactor. The average particle size and particle size distribution of the aerobic granular sludge within the SBR reactor were monitored, and induced particles with a particle size controlled within the range of 150-200μm were targeted for cultivation, causing them to enter the accelerated granulation stage. After the average particle size was controlled within the range of 150-200μm, the settling time was increased to slow the particle size growth rate within the SBR reactor.

[0039] Secondly, the continuous flow reactor is used as the particle unit. In this embodiment, a DE-type oxidation ditch system is selected to carry out a continuous flow aerobic granular sludge system cultivation experiment, and the induced particles cultivated in the SBR reactor are adopted.

[0040] The initial inoculum sludge was obtained from return sludge from a municipal wastewater treatment plant. Its sludge concentration (MLSS) was approximately 8817 mg / L, and its sludge settling volume (SVI) was 104.35 mL / g. The inoculum sludge was screened to remove impurities, aerated for 24 hours, and diluted to 3000 mg / L before being introduced into a DE oxidation ditch system for acclimatization.

[0041] The DE oxidation ditch adopts a four-stage double-ditch alternating operation mode. The operating conditions are shown in Table 1. Figure 1The process flow chart is shown below. The sum of the time for Stages 1 and 2 is the ditch reversal time, which is the time it takes to switch ditch water inflow. By controlling the alternating time and alternating operation sequence of the DE-type oxidation ditch, different denitrification requirements can be met. In this example, the ditch reversal time is 4 hours, and four alternating operations are set in a single cycle.

[0042] Table 1 DE type oxidation ditch operating conditions

[0043]

[0044] like Figure 1 As shown, wastewater is delivered through inlet pipe 8 via peristaltic pump 2 to the currently operating inlet ditch. The inlet path is switched and controlled by electric valve 3, and the ditch cycle is coordinated by PLC controller 9 to achieve alternating operation. The reactor operation process is divided into four stages. In stage I, water enters ditch A 13 and exits ditch B 14. During this period, ditch A 13 is not aerated, while ditch B 14 is aerated. In stage II, water enters ditch A 13 and exits ditch B 14. During this period, ditch A 13 and ditch B 14 are aerated. In stage III, water enters ditch B 14 and exits ditch A 13. During this period, ditch B 14 is not aerated, while ditch A 13 is aerated. In stage IV, water enters ditch B 14 and exits ditch A 13. During this period, ditch B 14 and ditch A 13 are aerated. Each ditch is equipped with a microporous aeration head 4 connected to an aeration pump 1 to provide dissolved oxygen, and a flow propeller 5 maintains the thrust of the water flow within the ditch. After the sewage undergoes biochemical reactions in the ditch, it is initially settled through the inclined baffle 6 at the end of the ditch, and the mud-water mixture is discharged from the outlet weir 7. Part of the mud-water mixture is discharged as residual sludge 10, and the rest of the mud-water mixture enters the secondary sedimentation tank 11 at the end. In the secondary sedimentation tank 11, the mud-water mixture undergoes further mud-water separation. The precipitated sludge is returned to the head section of the ditch as return sludge 12, mixed with the inlet water through the inlet pipe 8, and the supernatant is discharged from the outlet pipe 15.

[0045] After the inoculated sludge is acclimated in the DE oxidation ditch, the inducing particles are added at a mass ratio of 2% and the frequency of addition is once a day. Figure 2As shown in the figure, in the initial stage of operation (days 0-31), the sludge in the system is still mainly composed of small-particle flocs. The proportion of sludge with a particle size of less than 50μm and 50-100μm is always above 80%, of which the proportion of <50μm is 45-60%, and the average particle size is maintained in the range of 54-65μm. Particles have not yet formed significantly. On the 36th day of operation, the average particle size of the system rose to 75.58μm, and the proportion of particles with a particle size of 100-150μm and 150-200μm increased to 8.24% and 3.86% respectively. The total proportion of particles >200μm exceeded 6% for the first time, and the system began to granulate. By the 44th day, the average particle size exceeded 100μm, reaching 105.7μm. At this point, the particle size distribution shifted significantly, with the proportion of particles in the 50-100μm range dropping to 53.36%, while the proportions of particles in the 100-150μm, 150-200μm, 200-300μm, and >300μm ranges were 11.6%, 6.8%, 7.29%, and 6.07%, respectively. The proportion of medium and large particles increased significantly. The average particle size of the system continued to increase thereafter, remaining between 105-110μm from the 55th to the 73rd day of operation. Particles in the 150-300μm range gradually became dominant, and the proportion of particles >300μm also continued to increase, indicating that the particle population structure within the system was gradually stabilizing. By the 85th day of operation, the average particle size of the system had risen significantly to 121.3μm, with particles of 200-300μm accounting for 9.24% and particles >300μm accounting for 7.10%. By the 101st day, the average particle size reached 165.3μm, the proportion of particles with a size >300μm further increased to 14.21%, and the proportion of particles between 200-300μm was as high as 13.62%. A large particle group with stable structure and excellent sedimentation performance has been formed in the system. At the same time, the proportion of flocculent sludge continued to decline, and the proportion of sludge <50μm dropped from 45.81% in the initial stage to 18.97%. The particle size distribution results clearly verified the effectiveness of the method described in the present invention. By continuously and quantitatively adding inducing particles in the accelerated particle formation period, the flocculent sludge in the continuous flow DE oxidation ditch system is gradually transformed into granular sludge with stable structure, and the average particle size and the proportion of large-size particles are significantly increased, indicating that the system has achieved rapid granular startup and stable operation.

[0046] To further reveal the bioaggregation mechanism during particle formation, Figure 3The changing trends of the protein (PN) and polysaccharide (PS) content in the extracellular polymeric substances (EPS) and their ratio (PN / PS) during the operation of the system are shown. In the initial operation period (days 0-6), the PN content in the system increased from 90.78 mg / gVSS to 106.11 mg / gVSS, and the PS content decreased from 30.57 mg / gVSS to 22.21 mg / gVSS. The PN / PS ratio increased significantly to 4.78, indicating that in the early stage of particle formation, protein-based polymers were predominant in the system, which was conducive to the adhesion of microbial flocs and the formation of preliminary aggregate structures. In the subsequent operation period (days 24-31), both PN and PS contents decreased, and the PN / PS ratio fell back to 2.45-3.63, reflecting that the system entered a relatively stable bioaggregation state. However, the overall EPS content was low, the particle structure was not yet compact, and the granulation process was still in a slow progress stage. By day 39, the total EPS content rose rapidly, with the PN content jumping to 181.23 mg / gVSS and the PS content reaching 105.19 mg / gVSS, among the highest values ​​during the entire operation cycle. During this period, the PN / PS ratio dropped to 1.72, reflecting a significant increase in polysaccharide content, which facilitated the compaction and stabilization of the particle structure during particle formation, and the system granulation entered an accelerated phase. By day 46, the PN content rose further to 209.15 mg / gVSS, while the PS content dropped to 66.16 mg / gVSS, and the PN / PS ratio rebounded to 3.16. At this point, the particle structure was further compacted, the particle interface was dominated by protein, and adhesion was enhanced, helping to maintain particle shape and strength. Subsequently, from days 63 to 78, the total EPS content remained at a high level (200-220 mg / gVSS), and the PN / PS ratio remained stable between 1.7 and 1.74, indicating that the system particle structure was in a relatively stable stage, with a dense structure and good adhesion. By day 86-100, the PN and PS contents showed a synchronous downward trend, but the PN / PS ratio increased again to 2.63-3.76, indicating that the outer layer of the granules once again showed protein-dominated structural characteristics, which may be related to granule self-stabilization or granule renewal.

[0047] In summary, the results of the examples clearly demonstrate the effectiveness of the method of the present invention. By continuously and quantitatively dosing induced particles with an accelerated particle size, flocculent sludge within a continuous flow system can be transformed into a structurally stable granular sludge population in a relatively short period of time, significantly increasing the system's average particle size and particle ratio, promoting rapid granular startup and maintaining steady-state conditions. This strategy is suitable for the in-situ construction and enhanced operation of aerobic granular sludge in continuous flow reactors and has significant technical promotion value.

Claims

1. A method for promoting continuous flow sludge granulation using induced particles, characterized in that: The following steps are involved: Step 1: Using the SBR reactor as a granulation unit, aerobic granular sludge with a particle size of 150-200 μm is cultured as inducing particles; Step 2: Add the inducing particles obtained by culture in step 1 to the continuous flow reactor to accelerate the granulation rate of the aerobic granular sludge in the continuous flow reactor; according to the granulation rate in the continuous flow reactor and the daily sludge discharge of the continuous flow reactor, the mass ratio of the inducing particles is 2-10%, and the addition frequency is once a day to keep the particle size of the granular sludge in the system stable in the optimal range, i.e., 150-200 μm.

2. The method of promoting continuous flow sludge granulation by using inducing particles according to claim 1, characterized in that: The continuous flow reactor includes but is not limited to oxidation ditch, A 2 / O, A / O, UCT.

3. The method of promoting continuous flow sludge granulation by using inducing particles according to claim 1, characterized in that: In step 2, according to the daily sludge discharge of the continuous flow reactor, the mass ratio of the inducing particles is 2%, and the addition frequency is once a day to keep the particle size of the granular sludge in the system stable in the optimal range, i.e., 150-200 μm.

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