Gel aerobic granules based on sludge immobilization, and preparation method and application thereof

Abstract

The application provides a sludge immobilization-based gel aerobic particle and a preparation method and application thereof, and belongs to the field of sewage treatment.The method comprises the following steps: 1, uniformly dispersing sEPS powder in a sodium alginate solution to obtain a composite gel; 2, filtering, centrifuging and removing supernatant of activated sludge in an aerobic tank to obtain concentrated bacteria solution; 3, adding the concentrated bacteria solution into the composite gel, uniformly mixing, dropping into a cross-linking solution, and then solidifying to obtain the gel aerobic particle.The sludge immobilization-based gel aerobic particle is prepared by using structural extracellular polymeric substances in activated sludge and sodium alginate to prepare a composite gel, and using a multivalent metal ion cross-linking agent to immobilize concentrated activated sludge, so that the gel aerobic particle with similar chemical composition, mechanical strength and biological performance to natural aerobic particles is prepared, and rapid granulation of sludge and rapid start-up operation of a granular system are realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of sewage treatment, and particularly relates to a gel aerobic granule based on sludge immobilization and a preparation method and application thereof. BACKGROUND

[0002] Sludge immobilization technology is an important means to accelerate sludge granulation and aerobic granular sludge (AGS) formation, but existing sludge immobilization technologies are mostly based on embedding active sludge in high-molecular gel materials. Since natural aerobic granular sludge does not contain such high-molecular gel materials, it is difficult to prepare gel aerobic granules with similar chemical composition, mechanical strength and biological activity as aerobic granular sludge.

[0003] Existing sludge immobilization technologies use single or composite high-molecular gel materials to embed sludge to prepare sludge aggregates or gel granules, which are difficult to balance the relationship between rapid sludge granulation, regeneration after gel granule disintegration and efficient and synergistic removal of pollutants. On the one hand, the chemical composition of existing high-molecular gel materials is different from that of the gel materials in aerobic granular sludge, resulting in significant differences in chemical structure, biological activity and mechanical strength between the prepared sludge aggregates and gel granules and aerobic granules. On the other hand, swelling and microbial metabolism during long-term operation of gel granules lead to gradual degradation of the performance and disintegration of the structure of gel granules, but the existing technologies lack a gel granule disintegration-aerobic granule regeneration mechanism, and artificial replacement of gel granules or addition of reagents is required, which is difficult to maintain the long-term stable treatment efficiency of the aerobic granule system.

[0004] Therefore, in order to achieve rapid sludge granulation, efficient and synergistic removal of pollutants and regeneration of gel granules into aerobic granules after disintegration, it is urgent to develop a gel aerobic granule preparation and application method based on sludge immobilization. SUMMARY

[0005] In view of this, the present application aims to overcome the defects in the prior art and proposes a gel aerobic granule based on sludge immobilization and a preparation method and application thereof.

[0006] To achieve the above-mentioned purpose, the technical solution of the present application is as follows:

[0007] The present application provides a preparation method of a gel aerobic granule based on sludge immobilization, comprising the following steps:

[0008] Step 1 is to prepare a composite gel: uniformly disperse sEPS powder in a sodium alginate solution to obtain the composite gel;

[0009] Step 2 is to prepare a concentrated bacterial solution: filter, centrifuge and remove the supernatant of the aerobic tank active sludge to obtain the concentrated bacterial solution;

[0010] Step 3 is to prepare the gel aerobic granules: the concentrated bacterial solution is added to the composite gel, mixed uniformly, dripped into the cross-linking solution, and then solidified to obtain the gel aerobic granules.

[0011] Further, the mass concentration of the sodium alginate solution in step 1 is 1-3%; the solid-liquid ratio of the sEPS powder to the sodium alginate solution in step 1 is 1g:300-1000mL.

[0012] Further, the MLSS of the aerobic tank activated sludge in step 2 is 4-6g / L, the VSS:MLSS is 0.6-0.7, the SVI 30 is 80-120mL / g; the MLSS concentration of the concentrated bacterial solution in step 2 is 10-30g / L. The concentrated bacterial solution mainly contains the following aerobic microorganisms which play a key role in pollutant removal: Bacillus (Bacillus sp.), ammonia-oxidizing bacteria (AOB), nitrite-oxidizing bacteria (NOB), and common aerobic bacteria with carbon and / or nitrogen and phosphorus removal potential, such as Pseudomonas (Pseudomonas sp.) and Acinetobacter (Acinetobacter sp.). Bacillus spp. Ammonia-Oxidizing Bacteria, AOB Nitrite-Oxidizing Bacteria, NOB Pseudomonas spp. Acinetobacter spp.

[0013] Mixed liquor suspended solids (MLSS): refers to the mass of suspended solids contained in unit volume of mixed liquor, unit: g / L;

[0014] Volatile suspended solids (VSS): refers to the mass concentration of organic part that can be decomposed by burning in MLSS, unit: g / L;

[0015] 30-minute sludge volume index (SVI 30 ): refers to the volume occupied by per gram of dry sludge after the mixed liquor in the aeration tank is left for 30 minutes, unit: mL / g.

[0016] Further, the mesh number of the screen used in the filtration step in step 2 is 100-200 mesh; the speed of the centrifugation step in step 2 is 3000-5000r / min, and the time is 5-10min.

[0017] Further, the volume ratio of the concentrated bacterial solution, the composite gel and the cross-linking solution in step 3 is 1:2-1:5; the temperature of the solidification step in step 3 is 4-10℃, and the time is 6-12h; the particle size of the gel aerobic granules in step 3 is 1-3mm.

[0018] ​​​​​Further, the molar concentration of the metal ions in the cross-linking solution in step 3 is 0.25-0.30 mol / L; the metal ions are at least one of calcium ions, iron ions, magnesium ions or zinc ions; the cross-linking solution in step 3 comprises the following components with the following molar concentrations: Ca 2+ : 0.10-0.20 mol / L, Fe 3+ : 0.03-0.08 mol / L, Mg 2+ : 0.02-0.05 mol / L, Zn 2+ : 0.01-0.03 mol / L.

[0019] The application further provides a sludge immobilization-based gel aerobic particle prepared by the preparation method.

[0020] The application further provides an application of the sludge immobilization-based gel aerobic particle, and the sludge immobilization-based gel aerobic particle is applied to preparation of a sequencing batch bioreactor.

[0021] Further, the addition amount of the gel aerobic particle is 5-10% of the effective volume of the reactor.

[0022] Further, the sewage treatment process parameters of the reactor are as follows: periodic operation of water inflow, standing, aeration, sedimentation and water drainage, hydraulic retention time is 8-12 hours, operation cycle is 4-6 hours, and the operation cycle sequentially comprises water inflow for 10-15 minutes, aeration for 2-3 hours, sedimentation for 5-10 minutes and water drainage for 5-10 minutes; the inflow and outflow volume replacement rate is 50%; and the rising gas speed is 0.6-1.2 cm / s.

[0023] Extracellular polymeric substances (EPS) are a kind of complex mixture secreted by microorganisms, and can be divided into gel-forming EPS (also known as structural extracellular polymeric substances, sEPS) and non-gel-forming EPS (also known as dissolved EPS, dEPS) according to whether they have the ability to form hydrogel. The unpurified EPS contains a large amount of dEPS existing in the liquid phase, and the main components are small molecular proteins (molecular weight <10 kDa), nucleic acids and monosaccharides; such dEPS will make the immobilization efficiency below the practical threshold, and it is difficult to meet the actual process requirements of sludge immobilization. Specifically, dEPS will competitively bind the coordination sites of metal ions (such as the phosphate groups of nucleic acids chelate Ca 2+ ), and at the same time, destroy the ordered arrangement of beta-glucan fibers, finally leading to the instability of the gel network structure. As shown in Figure 1 , sEPS is a biological macromolecular complex secreted by microorganisms, and is rich in hydroxyl groups (-OH), carboxyl groups (-COOH), amino groups (-NH2) and phosphate groups (-PO4 3-SA is a linear polysaccharide composed of β-D-mannuronic acid (M unit) and α-L-guluronic acid (G unit) linked by 1,4-glycosidic bonds. Its molecular chain contains numerous free carboxyl groups (-COOH), which readily dissociate into negatively charged -COO groups in solution. - Both achieve composite cross-linking with complex metal ions through multi-dimensional intermolecular interactions: the G unit carboxyl group of SA interacts with Ca... 2+ Adjacent SA chains are connected via bidental coordination, each Ca 2+ Simultaneously, the carboxyl groups of the two G units chelate to form a rigid six-membered ring backbone similar to "egg-box chimerism"; the carboxyl group of the M unit then binds with Mg... 2+ Single-tooth coordination is formed, and the network flexibility is adjusted through weaker bonding, avoiding pure Ca... 2+ Brittleness caused by cross-linking; hydroxyl, amino and Fe groups in sEPS 3+ It can form strong coordination bonds, and its carboxyl and phosphate groups can be further strengthened through polydentate coordination, constructing a dense secondary network that surrounds the SA main framework; Zn 2+ It can selectively bind to the imidazole and thiol groups in sEPS proteins and form a weak interaction with the carboxyl group of SA, acting as a "molecular bridge" between the two phases; at the same time, the amino group of sEPS interacts with the -COO group of SA. - Initial cross-linking is formed through electrostatic attraction, and the hydroxyl and amino groups on the molecular chains are further strengthened by hydrogen bonds. The physical entanglement of the branched structures of the two increases the spatial complexity of the network. This three-dimensional network formed by multi-level synergistic effects makes the final gel aerobic particles similar to natural AGS in terms of chemical composition, mechanical strength, and bioactivity.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] The sludge-immobilized gel aerobic particles of this invention are prepared by using structural extracellular polymers (sEPS) from activated sludge and sodium alginate (SA) to prepare a composite gel, and using multivalent metal ions (Ca) 2+ Mg 2+ Fe 3+ Zn 2+ Crosslinking agents are used to fix and concentrate activated sludge, producing gel aerobic granules with chemical composition, mechanical strength, and biological properties similar to natural aerobic granules. This enables rapid sludge granulation and quick start-up of the granular system. The gel aerobic granules can be gradually regenerated into natural aerobic granular sludge in the reactor, thereby achieving efficient and stable operation of the aerobic granular sludge system.

[0026] The sludge immobilization-based gel aerobic granule has similar chemical composition, mechanical strength and biological performance to natural AGS; the sEPS and the composite metal ion crosslinking agent are highly similar to the organic and inorganic chemical composition of the natural AGS, the sEPS, the SA and the metal ion composite crosslinking form a three-dimensional network gel structure, the gel structure and the mechanical strength are similar to those of the natural AGS, the embedded sludge can maintain high biological activity, and efficient removal of pollutants is realized.

[0027] The sludge immobilization-based gel aerobic granule can be directly added into an SBR reactor for operation, and stable operation can be realized without long-term domestication, and the system start-up period is shortened to 2-7 days (more than 30 days is required for the traditional aerobic granular sludge technology).

[0028] The sludge immobilization-based gel aerobic granule can be regenerated into AGS, and long-term stable operation of the system is ensured; in the operation process, the gel aerobic granule is gradually disintegrated, the fragments can be used as the core carrier of the natural AGS, microorganisms are planted and aggregated on the surface of the fragments, the natural AGS is formed, and the process of “gel aerobic granule-gel aerobic granule / natural AGS coexistence-natural AGS” is experienced, the system collapse caused by sudden disintegration of the granule in the traditional technology is avoided, and long-term stable operation of the system is ensured.

[0029] The raw materials used in the sludge immobilization-based gel aerobic granule have significant availability and economic advantages, the alginate and various composite crosslinking metal salts (such as calcium chloride, ferrous sulfate, magnesium chloride, zinc sulfate and the like) are widely used in water treatment and food, medicine and other fields, and the source is stable and the industrialization condition is mature; the sEPS can be extracted from the biological sludge produced in the conventional sewage treatment system through centrifugation, heat extraction and chemical dissolution, and the existing sludge byproduct resources can be fully utilized; the whole system does not depend on expensive functional polymers or exogenous microbial strains, the preparation cost is significantly reduced while the performance of the granule is ensured. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The figure is a schematic diagram of the combination of the sludge immobilization-based gel aerobic granule;

[0031] Figure 2 The figure is an electron microscope photograph of the surface of the granule described in Example 1 of the present application; wherein, A is a photograph taken at 7 days of operation, and B is a photograph taken at 14 days of operation;

[0032] Figure 3 The figure is a line graph of the change of the pH value of the reactor with time described in Example 1 of the present application. DETAILED DESCRIPTION

[0033] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art. Unless otherwise specified, the experimental reagents used in the following embodiments are conventional biochemical reagents; and the experimental methods described are conventional methods.

[0034] The method for preparing sEPS according to the embodiments of the present invention includes the following steps:

[0035] 50g (wet weight) of aerobic granular sludge (MLSS=6g / L, VSS / MLSS=0.7, SVI) 30 =30mL / g) was added to 500mL of 0.5% (w / v) Na2CO3 solution and magnetically stirred at 400 r / min for 3 h in a 90℃ water bath. After naturally cooling to room temperature, it was centrifuged at 10000 rpm for 15 min at 4℃, and the supernatant was collected and the precipitate was discarded. 1 mol / L HCl was added dropwise to the supernatant to adjust the pH to 2.2, and a flocculent precipitate was formed. The precipitate was then centrifuged at 10000 rpm for 15 min at 4℃, and the precipitate was collected and the supernatant was discarded. The precipitate was dissolved in 1 mol / L NaOH and the pH was adjusted to 8.5. It was then separated by ultrafiltration membrane with a molecular weight cutoff of 10 kDa. The filtrate was frozen and then freeze-dried under vacuum at -40℃ for 24 h before being ground into powdered SEPS.

[0036] The present invention will be described in detail below with reference to embodiments.

[0037] Example 1

[0038] A method for preparing gel aerobic particles based on sludge immobilization includes the following steps:

[0039] (1) Take 500 mL of ultrapure water and place it in a 60℃ constant temperature water bath and stir (magnetic stirrer, speed 200 r / min). Slowly add 10 g of food grade SA and continue stirring for 3 h until completely dissolved to form an SA solution with a mass volume concentration of 2%. After cooling to room temperature, add 1 g of sEPS powder, adjust the stirring speed to 400 r / min, and stir at room temperature for 1.5 h until the sEPS is evenly dispersed to obtain a composite gel solution with a sEPS concentration of 2 g / L. Let it stand for 30 min to remove air bubbles for later use.

[0040] (2) Collect samples from municipal wastewater treatment plant A 2 / O process aerobic tank activated sludge (MLSS=5g / L, VSS / MLSS=0.65, SVI) 30 =100mL / g), filtered through a 200-mesh nylon screen to remove fibrous impurities; 100mL of the filtered sludge was placed in a centrifuge tube and centrifuged at 5000r / min for 10min at 4℃, the supernatant was discarded, and concentrated bacterial solution (MLSS=20g / L) was obtained.

[0041] (3) Preparation of composite cross-linking solution: 22.05 g of CaCl2·2H2O, 13.51 g of FeCl3·6H2O, 6.10 g of MgCl2·6H2O, and 2.73 g of ZnCl2 were weighed and dissolved in 1 L of deionized water, and stirred until completely dissolved to obtain a cross-linking solution with ion concentrations of Ca 2+ 0.15 mol / L, Fe 3+ 0.05 mol / L, Mg 2+ 0.03 mol / L, and Zn 2+ 0.02 mol / L, and the pH was adjusted to 7.0 with 0.1 mol / L HCl;

[0042] (4) The concentrated bacterial solution (30 mL) was mixed with the sEPS-SA composite gel solution (90 mL) at a volume ratio of 1:3, and a motor stirrer (speed 200 r / min) was used to stir for 10 min to form a uniform gel aerobic granule system. The gel aerobic granule system was dropped into the cross-linking solution, and then solidified at 4°C for 12 h to obtain the gel aerobic granules;

[0043] (5) The obtained gel granules were added to the SBR reactor (inner diameter 10 cm, height 100 cm) at 10% of the effective volume of the reactor, and the operation cycle was set to 4 hours, including: water feeding for 10 min, standing for 50 min, aeration for 170 min, sedimentation for 5 min, and water drainage for 5 min (volume replacement rate 50%); the water temperature of the reactor was controlled at 25°C±1°C, the rising gas velocity was controlled at 0.8 cm / s, the water inlet and outlet were quantitatively controlled by a peristaltic pump, the water inlet was simulated municipal wastewater with a COD concentration of 600 mg / L, ammonia nitrogen of 35 mg / L, total phosphorus of 5 mg / L, and pH=7.0±0.2.

[0044] During the continuous operation of the reactor, it was divided into four stages: start-up stage (1-5 days): the gel aerobic granules gradually recovered activity, the effluent COD gradually decreased to below 50 mg / L, the ammonia nitrogen removal rate reached more than 85%, and there was no granule disintegration and sludge loss; temporary stable stage (6-15 days): the structure and performance of the gel aerobic granules remained stable, the effluent COD remained below 50 mg / L, the ammonia nitrogen removal rate remained above 85%, and there was no granule disintegration and sludge loss; transition stage (16-30 days): the gel aerobic granules gradually began to disintegrate, microbial colonization appeared on the surface of the fragments, and primary natural AGS with a particle size of 1-2 mm gradually formed; long-term stable stage (after 31 days): the proportion of natural AGS reached 100%, and the SVI 30At concentrations below 50 mL / g, the average removal rates of COD, ammonia nitrogen, and total phosphorus were 91%, 98.4%, and 92.1%, demonstrating that the method of this invention can achieve rapid start-up and long-term stable operation.

[0045] like Figure 2 As shown, compared to 7 days of operation (Figure A), after 14 days of operation (Figure B), the particle surface changed from a dense, wrinkled layered structure to a rough, porous structure, with microcracks enlarging and becoming interconnected; and colloid-like deposits appeared on the surface. These changes indicate that microorganisms colonized the particle surface and secreted EPS, causing gel cortex rearrangement and pore enlargement, which facilitates mass transfer, and the particle integrity decreased as this process continued.

[0046] like Figure 3 As shown, in the initial stage of operation (0-4d), the pH rapidly increased from 7.1 to 7.9 due to CO2 removal and the release of weak alkali from the system; it stabilized at 7.85 from 5 to 10d, with slight fluctuations consistent with the SBR cycle; subsequently, it slowly decreased to around 7.7 as nitrification intensified, and was generally within the suitable nitrification range, which is consistent with the expected start-up to stabilization process of the example.

[0047] Comparative Example 1

[0048] The only difference from Example 1 is that sEPS is replaced with an equal amount of ungraded total EPS.

[0049] The EPS extraction method includes the following steps: 50g (wet weight) of aerobic granular sludge (MLSS=6g / L, VSS / MLSS=0.7, SVI... 30 =30mL / g) was added to 500ml of 0.5% (w / v) Na2CO3 solution and magnetically stirred at 400r / min for 3h in a 90℃ water bath. After naturally cooling to room temperature, it was centrifuged at 10000rpm for 15min at 4℃. The supernatant was collected, frozen, and then freeze-dried under vacuum at -40℃ for 24h before being ground into powdered EPS.

[0050] When the "EPS-SA mixture" was dropped into the composite metal ion crosslinking solution, the droplets significantly diffused and tailed in the crosslinking solution, forming spherical particles that dispersed and disintegrated under stirring with a glass rod. After curing at 4℃ for 12 hours, the resulting product was in a viscous fluid state and could not maintain its self-supporting structure after being lightly scooped through a filter, exhibiting a lack of macroscopic self-supporting gel. Small-amplitude oscillatory rheological tests (25℃, parallel plates Φ40mm, gap 2mm, strain 1%, frequency 1Hz) recorded a storage modulus G′ < 50Pa (no repeatable effective curves were obtained in three tests, and the limit was recorded). Immersion in deionized water for 4 hours resulted in continuous swelling and disintegration. The results show that, under the same SA concentration and composite metal ion crosslinking system, simply replacing sEPS with ungraded EPS leads to the inability to form gel particles.

[0051] Comparative Example 2

[0052] The difference between Example 1 and Comparative Example 2 is only that the cross-linking solution is 0.275 mol / L CaCl2 solution with the same total metal positive charge concentration as Example 1 (charge concentration in equivalent concentration Eq·L-1); the curing time is 12 h at 4 ℃, and the wet-based particle size swelling rate is 28% after the particles are immersed in deionized water for 4 h. The storage modulus G' measured by small amplitude oscillatory rheological test (25 ℃, parallel plate Φ40 mm, gap 2 mm, strain 1%, frequency 1 Hz) is 640 Pa. -1

[0053] The reactor is put into operation, and after 5 days, the effluent COD is maintained below 50 mg / L, and the ammonia nitrogen removal rate is stably above 85%, which is not significantly different from Example 1. The particle integrity rate is 65% after 20 d. The results show that only replacing the calcium-iron-zinc-magnesium composite ion cross-linking solution with a single calcium ion cross-linking solution, the initial strain shear stiffness of the formed gel particles (G' = 640 Pa, compared with G' = 980 Pa of Example 1), water resistance (wet-based particle size swelling rate is 28% after curing and immersing in deionized water for 4 h, compared with 15% of Example 1), and 20 d running stability (integrity rate is 65%, compared with 88% of Example 1) are all significantly worse than those of the particles obtained in Example 1, indicating that the hydrolysis resistance and anti-swelling ability of the gel particles formed by the composite ion cross-linking system are higher than those of the single calcium ion cross-linking system.

[0054] Comparative Example 3

[0055] The difference between Example 1 and Comparative Example 3 is only that only 2% (w / v) SA solution is used as the gel matrix, and no sEPS is added.

[0056] Particles can be formed after the SA solution is dropped into the cross-linking solution, but the particle size distribution is different; the wet-based particle size swelling rate is 35% after the particles are cured at 4 ℃ for 12 h and immersed in deionized water for 4 h. The storage modulus G' measured by small amplitude oscillatory rheological test (25 ℃, parallel plate Φ40 mm, gap 2 mm, strain 1%, frequency 1 Hz) is 460 Pa.

[0057] The particles are added to the SBR reactor for continuous operation for 7 d, and the particle integrity rate is only 50%, the effluent COD is maintained above 50 mg / L, and the ammonia nitrogen removal rate is 72%, which are all significantly worse than those of Example 1. The results show that the anti-swelling, hydrolysis resistance, and pollutant removal capacity of the gel particles formed without adding sEPS are all worse than those of the particles formed in Example 1.

[0058] Comparative Example 4

[0059] The difference between Example 1 and Comparative Example 4 is only that the curing time of the gel aerobic granular system dropped into the cross-linking solution is 24 h.​

[0060] After curing at 4 °C for 24 h, the granules were immersed in deionized water for 4 h, and the wet-based particle size swelling rate was 12%. The storage modulus G' measured by small amplitude oscillatory rheometry (25 °C, parallel plate Φ40 mm, gap 2 mm, strain 1%, frequency 1 Hz) was 1.15 kPa. When the granules were added to the SBR reactor for continuous operation for 7 d, the granule surface was observed to be broken and peeled off, the granule integrity rate was 80%, the effluent COD was greater than 50 mg / L in the short term, and the ammonia nitrogen removal rate was 80%, indicating that the excessive curing time increased the strain shear stiffness and reduced the swelling, but introduced the brittleness and diffusion limitation caused by the excessive cross-linking of the shell layer, thereby showing a decrease in integrity rate and impaired purification efficiency in actual operation, which is not conducive to the rapid regeneration of natural AGS.

[0061] Comparative Example 5

[0062] Compared with Example 1, the only difference is that the cross-linking solution is changed to a solution with an ion concentration of Ca 2+ 0.22 mol / L, Fe 3+ 0.09 mol / L, Mg 2+ 0.06 mol / L, and Zn 2+ 0.04 mol / L.

[0063] After curing at 4 °C for 12 h, the granules were immersed in deionized water for 4 h, and the wet-based particle size swelling rate was 8%. The storage modulus G' measured by small amplitude oscillatory rheometry (25 °C, parallel plate Φ40 mm, gap 2 mm, strain 1%, frequency 1 Hz) was 1.45 kPa.

[0064] When the granules were added to the SBR reactor for continuous operation for 7 d, the effluent COD remained above 50 mg / L, the ammonia nitrogen removal rate was 80%, and the granule disintegration time was observed to be delayed, with the granule edge cracking phenomenon occurring around the 20th day of reactor operation, and the stable aerobic granular sludge with an average particle size of 1.8-2.4 mm was formed on the 40th day. The results show that increasing the ion concentration of the cross-linking solution can improve the initial strain shear stiffness and reduce the swelling, but it causes the long-term purification efficiency to deteriorate and the granule disintegration time to be delayed, which is not conducive to the engineering operation stability of the granules and the regeneration process of natural AGS.

[0065] Comparative Example 6

[0066] Compared with Example 1, the only difference is that the solid-liquid ratio of sEPS powder to sodium alginate solution is 5 g:1000 mL.

[0067] After 12h curing at 4℃, the granules were immersed in deionized water for 4h, and the wet-based particle size swelling rate was 8%. The storage modulus G′ measured by small amplitude oscillatory rheometry (25℃, parallel plate Φ40mm, gap 2mm, strain 1%, frequency 1Hz) was 900Pa.

[0068] The granules were added to the SBR reactor for continuous operation for 7d, and the effluent COD was less than 50mg / L, and the ammonia nitrogen removal rate was 78%; the results showed that the anti-swelling ability of the gel granules formed when the sEPS was excessive was slightly enhanced, but the pollutant removal efficiency and strain shear stiffness were reduced, which was not conducive to the stable and rapid operation in actual application.

[0069] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing gel aerobic particles based on sludge immobilization, characterized in that: Includes the following steps: Step 1 is to prepare the composite gel: the sEPS powder is uniformly dispersed in a sodium alginate solution to obtain the composite gel; Step 2 is to prepare concentrated bacterial solution: the activated sludge from the aerobic tank is filtered, centrifuged, and the supernatant is removed to obtain the concentrated bacterial solution; Step 3 is to prepare aerobic gel particles: the concentrated bacterial solution is added to the composite gel, mixed evenly, and then dropped into the crosslinking solution, and then solidified to obtain the aerobic gel particles. The mass concentration of sodium alginate solution in step 1 is 1-3%; the solid-liquid ratio of sEPS powder to sodium alginate solution in step 1 is 1g:300-1000mL. The volume ratio of concentrated bacterial solution, composite gel and crosslinking solution in step 3 is 1:2-1:5; the curing temperature in step 3 is 4-10℃ and the time is 6-12h; the particle size of aerobic gel particles in step 3 is 1-3mm. The molar concentration of metal ions in the crosslinking solution in step 3 is 0.25-0.30 mol / L; the crosslinking solution in step 3 includes the following components with the following molar concentrations: Ca 2+ 0.10-0.20 mol / L, Fe 3+ 0.03-0.08 mol / L, Mg 2 + 0.02-0.05 mol / L, Zn 2+ : 0.01-0.03mol / L.

2. The method for preparing gel aerobic particles based on sludge immobilization according to claim 1, characterized in that: In step 2, the MLSS of the activated sludge in the aerobic tank is 4-6 g / L, the VSS:MLSS is 0.6-0.7, and the SVI is... 30 The concentration of MLSS in the concentrated bacterial solution in step 2 is 80-120 mL / g; the concentration of MLSS in the concentrated bacterial solution is 10-30 g / L.

3. The method for preparing gel aerobic particles based on sludge immobilization according to claim 1, characterized in that: The filtration step in step 2 uses a sieve with a mesh size of 100-200; the centrifugation step in step 2 has a speed of 3000-5000 r / min and a time of 5-10 min.

4. A sludge-immobilized gel aerobic particle prepared by the preparation method according to any one of claims 1-3.

5. The application of the sludge-immobilized gel aerobic particles according to claim 4, characterized in that: The application of the sludge-immobilized gel aerobic particles in the preparation of sequencing batch bioreactors.

6. The application of the sludge-immobilized gel aerobic particles according to claim 5, characterized in that: The amount of the gel aerobic particles added is 5-10% of the effective volume of the reactor.

7. The application of the sludge-immobilized gel aerobic particles according to claim 5, characterized in that: The specific wastewater treatment process parameters of the reactor are as follows: it operates cyclically with influent, settling, aeration, sedimentation, and drainage, with a hydraulic retention time of 8-12 hours and an operating cycle of 4-6 hours, including 10-15 minutes of influent, 2-3 hours of aeration, 5-10 minutes of sedimentation, and 5-10 minutes of drainage; the influent and effluent volume replacement rate is 50%; and the rising air velocity is 0.6-1.2 cm / s.

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