A recovery system and method for a composite carrier for sludge reduction and application
By employing static settling, cyclone separation, and dual-circulation reflux technology with composite BARMS microcarriers, the problem of high carrier loss rate was solved, achieving efficient sludge reduction and improved system stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NANJING PUBLIC WATER CO LTD
- Filing Date
- 2026-04-15
- Publication Date
- 2026-06-09
AI Technical Summary
In existing technologies, composite carriers have a loss rate of 30-45% in activated sludge reduction technology, which leads to increased operating costs, cannot effectively remove sand and gravel, and affects biofilm activity and separation efficiency.
By employing composite BARMS microcarriers and combining static sedimentation, cyclone separation, and dual-circulation reflux channel units, efficient separation and recovery of carriers are achieved through gravity sedimentation, cyclone separation, and low-shear reflux, thereby improving separation accuracy and recovery rate.
The system achieved a carrier recovery rate of over 80%, which reduced sludge treatment costs, decreased secondary pollution, and improved system stability and denitrification efficiency.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of sludge treatment technology, specifically relating to a sludge reduction composite carrier recycling system, method, and application. Background Technology
[0002] In activated sludge reduction technologies, composite carriers (such as BARMS) can significantly reduce sludge yield by providing a biofilm attachment interface. However, the lack of carrier recovery devices severely limits the techno-economic viability—in conventional processes, approximately 30-45% of the carrier is permanently lost with the excess sludge, forcing the system to continuously add new carriers to maintain effectiveness, leading to a substantial increase in costs. Current technologies cannot simultaneously achieve efficient sand and gravel removal, precise carrier-sludge separation, and biofilm activity protection, resulting in a carrier loss rate exceeding 30% and a surge in operating costs. Summary of the Invention
[0003] Based on the above-mentioned technical deficiencies, the present invention provides a recycling system, method and application of a composite carrier for sludge reduction, which can eliminate the interference of sand and gravel on separation equipment and processes; improve the separation accuracy of carrier-highly active sludge composite (recovery rate >80%); block the damage of turbulence to biofilm and maintain carrier activity.
[0004] This invention provides a recycling system for a composite carrier used in sludge reduction, comprising, in sequence: 1) Composite BARMS microcarrier unit: composed of 85%-95% inorganic biological carrier and 5%-15% microbial strain, with a particle size of 80-120μm and a true density of 2.00-2.20g / cm³; 2) Static settling unit: The bottom is equipped with a sand collection hopper with a cone angle ≥65°, the top has an overflow port, and the side wall is equipped with an ultrasonic mud level gauge connected to an automatic sand discharge valve; 3) Cyclone Separation Unit: The feed inlet is connected to the overflow port of the settling unit via a booster pump. The cylinder diameter is 50-80mm, and the cone angle is 8°-12°. A turbulence suppression grid is installed at the feed inlet. A flexible guide ring is added inside the cyclone separation unit. It is made of food-grade silicone material, with a ring spacing of 4-6mm. The inner diameter of the ring shrinks synchronously with the cone angle, and the surface of the ring is densely covered with micro-protrusions with a height of 0.4-0.6mm. 4) Dual circulation reflux channel unit: The dual circulation reflux channel unit includes a main channel and a bypass channel. The main channel is a corrosion-resistant pipe that directly connects the underflow port of the hydrocyclone separator to the bioreactor. The bypass channel has a built-in ultrasonic activator with a frequency of 25-30kHz. When the carrier is refluxed, the flow rate is through the bypass channel.
[0005] Furthermore, the inorganic biological carrier contains silica, alumina, and quorum sensing signal molecules; the surface of the inorganic biological carrier contains nano-titanium dioxide, zwitterionic polymer brushes, and cationic polymer segments.
[0006] Preferably, the inorganic biological carrier contains, by mass ratio, 65-75 parts silica, 24.9-34.9 parts alumina, and 0.1-1 parts quorum sensing signal molecules; The inorganic biological carrier surface is first uniformly loaded with 2-8% nano-titanium dioxide using a sol-gel method; then, 2-5% zwitterionic polymer brushes and 2-5% cationic polymer segments are covalently grafted onto it.
[0007] Preferably, the quorum sensing signal molecule is C12-acylhomoserine lactone; The zwitterionic polymer brush is a polysulfobetaine (pSBMA) brush; The cationic polymer segment is a polydiallyl dimethylammonium chloride (pDADMAC) segment; The microbial strains include at least one or more functional groups among nitrifying bacteria, denitrifying bacteria, and polyphosphate-accumulating bacteria.
[0008] Furthermore, the length-to-diameter ratio of the feed inlet is (3-5):1, and the diameter of the underflow outlet is 0.12-0.15 times the diameter of the cylinder.
[0009] Furthermore, the ultrasonic mud level gauge triggers automatic sand discharge when the sand layer thickness is ≥15cm, with the discharged sand having a solid content >25% and a sludge loss rate <0.8%.
[0010] The present invention also provides a method for improving sludge reduction using a composite carrier recycling system for sludge reduction as described above, comprising the following steps: (i) The composite BARMS microcarrier is added to the bioreactor at a dosage of 3‰-5‰ of the bioreactor volume; (ii) Sedimentation and sand removal: In the static sedimentation unit, the returned sludge is allowed to stand for 20±5 minutes, and sand and gravel with a particle size >0.2mm are discharged; (iii) Cyclone Screening: In the cyclone separation unit, the desanded sludge enters the hydrocyclone at a pressure of 0.18-0.60 MPa, passes through the suppression grid and the guide ring, and is separated to obtain: Overflow liquid: containing low-active sludge with a density <1.10 g / cm³ and SOUR <8 mg O2 / g VSS·h; Underflow liquid: contains a composite of BARMS carrier and highly active sludge with a density >1.25 g / cm³ and a nitrification rate >0.15 kgN / kgVSS·d; (iv) Direct reflux of active components: The underflow is delivered directly to the head of the bioreactor without any treatment by a low-shear pump.
[0011] Furthermore, the feed velocity of the grid described in step (iii) is reduced to <1.5 m / s.
[0012] Furthermore, the zeta potential on the surface of the BARMS carrier in the underflow fluid is +15 to +25 mV.
[0013] Furthermore, the sludge concentration (X) in the bioreactor is monitored, and the reflux ratio of the underflow liquid is dynamically adjusted: When the sludge concentration X in the bioreactor is less than 3000 mg / L, the recirculation ratio should be increased by 30-40%. When the sludge concentration X in the bioreactor is greater than 8000 mg / L, the reflux ratio decreases by 10-15%.
[0014] Furthermore, the hydraulic residence time of the static settling unit is 1.8-4 hours.
[0015] The present invention also provides an application of the above-mentioned composite carrier recycling system for sludge reduction in the AAO wastewater treatment process, characterized in that the underflow liquid is connected to the head end of the anaerobic tank, thereby increasing the denitrification efficiency of the system by 40-60% and the sludge reduction rate by 35-45%.
[0016] Beneficial effects The recycling system of this invention uses BARMS microcarriers. This unique ratio and parameter setting, combined with the innovative process of "static sedimentation-cyclone separation-recirculation", allows the system to first use the static sedimentation unit to efficiently remove sand and gravel by utilizing the density difference between sand and gravel and other substances, simplifying the subsequent processing. Then, with the help of the cyclone separation unit, the system accurately separates the light sludge and the sludge complex containing BARMS carriers based on the principle of centrifugal force. This separation method has high separation accuracy and high efficiency, and the recovery rate can reach more than 90%.
[0017] From an overall application perspective, this invention not only achieves efficient microcarrier recycling, but also reduces sludge treatment costs, reduces secondary pollution, and improves system stability.
[0018] Specific implementation methods To make the objectives, technical solutions, and advantages of this application clearer, a more detailed description is provided below. However, it should be understood that the description herein is merely for explaining this application and is not intended to limit its scope.
[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. All reagents and instruments used herein are commercially available, and the characterization methods involved can be found in relevant descriptions in the prior art, and will not be repeated here.
[0020] To further understand this application, the following detailed description is provided in conjunction with the preferred embodiments.
[0021] Example 1 This embodiment provides a recycling system for a composite carrier used for sludge reduction, comprising, in sequence: 1) Composite BARMS microcarrier unit: composed of 85%-95% inorganic biological carrier and 5%-15% microbial strains, with a particle size of 80-120μm and an actual density of 2.00-2.20g / cm³. 2) Static settling unit: The bottom is equipped with a sand collection hopper with a cone angle ≥65°, the top has an overflow port, and the side wall is equipped with an ultrasonic mud level gauge connected to an automatic sand discharge valve; 3) Cyclone Separation Unit: The feed inlet is connected to the overflow port of the settling unit via a booster pump. The cylinder diameter is 50-80mm, and the cone angle is 8°-12°. A turbulence suppression grid is installed at the feed inlet. Preferably, the cylinder diameter is 60mm, the cone angle is 10°, and a flexible guide ring is added inside to reduce shear force and collision probability. It is made of food-grade silicone material, with a ring spacing of 4-6mm. The inner diameter of the ring shrinks synchronously with the cone angle, and the ring surface is densely covered with micro-protrusions with a height of 0.4-0.6mm.
[0022] 4) Dual-circulation reflux channel unit: The dual-circulation reflux channel unit includes a main channel and a bypass channel. The main channel is a corrosion-resistant pipe that directly connects the underflow port of the hydrocyclone separator to the bioreactor. The bypass channel has a built-in ultrasonic activator (frequency 25-30kHz). During carrier reflux, 30% of the total underflow volume flows through the bypass channel. This system effectively reduces biofilm damage, improves carrier circulation efficiency, and resolves the contradiction between separation efficiency and bioactivity protection in traditional processes.
[0023] The static settling unit analyzes sand, activated sludge, and microcarriers through gravity settling, trapping sand and gravel impurities in the returned sludge and protecting the sludge-reducing microcarriers through a density screening mechanism. The cyclone separation unit recovers the microcarrier-highly-active sludge composite through a shallow cone-angle flow field design and turbulence-suppressing grid. A carrier circulation channel connects the cyclone separation unit to the bioreactor.
[0024] The above system can perform shallow cone vortex precise density separation on the sludge after pre-settling, enrich the carrier-highly active sludge composite at the bottom flow port, implement low-shear direct transport of the vortex bottom flow liquid, dynamically sense and adjust the sludge concentration of the system, and match the reflux ratio (10-40%) with MLSS fluctuations in real time to improve the ability to resist shock loads.
[0025] The aforementioned sludge reduction microcarrier system is suitable for wastewater treatment plants that use activated sludge processes and add sludge reduction microcarriers.
[0026] As a further preferred embodiment, the inorganic biological carrier contains silica, alumina, and quorum sensing signal molecules; the surface of the inorganic biological carrier contains nano-titanium dioxide, zwitterionic polymer brushes, and cationic polymer segments.
[0027] Preferably, the inorganic biological carrier contains, by mass ratio, 65-75 parts silica, 24.9-34.9 parts alumina, and 0.1-1 parts quorum sensing signal molecules; The inorganic biological carrier surface is first uniformly loaded with 2-8% nano-titanium dioxide using a sol-gel method; then, 2-5% zwitterionic polymer brushes and 2-5% cationic polymer segments are covalently grafted onto it.
[0028] Preferably, the quorum sensing signal molecule is C12-acylhomoserine lactone; The zwitterionic polymer brush is a polysulfobetaine (pSBMA) brush; The cationic polymer segment is a polydiallyldimethylammonium chloride (pDADMAC) segment.
[0029] The inorganic biological carrier is mainly composed of silica and alumina, and encapsulates quorum sensing signal molecules internally. Nano-titanium dioxide is first uniformly loaded onto the surface of the inorganic biological carrier using a sol-gel method, and then zwitterionic polymer brushes and cationic polymer segments are covalently grafted onto the surface. The zwitterionic polymer brushes provide anti-bioadhesion properties, preventing non-specific adhesion of activated sludge flocs; the cationic polymer segments act as "tentacles," preferentially and rapidly adsorbing negatively charged dissolved organic matter in wastewater; the quorum sensing signal molecules are acylhomoserine lactones, which are slowly released in the wastewater environment to activate the activity of functional microorganisms, promote the secretion of extracellular polymers by functional microorganisms, and enhance the aggregation effect of the inorganic biological carrier.
[0030] Titanium dioxide is used to connect the internal and external components, and can efficiently combine with zwitterionic polymer brushes and cationic polymer segments, preventing the polymer brushes from peeling off from the carrier surface during sewage hydraulic mixing and biofilm growth, thus significantly improving the long-term cycling stability of the functionalized carrier.
[0031] The microbial strains include at least one or more functional groups among nitrifying bacteria, denitrifying bacteria, and polyphosphate-accumulating bacteria.
[0032] Compared to microcarriers commonly found in other patents, the BARMS microcarriers in this invention consist of 85%-95% inorganic biological carriers and 5%-15% microbial strains. The inorganic biological carriers are uniformly loaded with nano-titanium dioxide via a sol-gel method. The content of nano-titanium dioxide relative to the inorganic biological carrier is 2-8%, with its particle size precisely controlled at 80-100 micrometers and its actual density at 2.00-2.20 g / cm³. 3 The inorganic biological carrier surface employs surface-initiated atom transfer radical polymerization (SI-ATRP) technology, covalently grafting polysulfobetaine (pSBMA) and polydiallyldimethylammonium chloride (pDADMAC) segments onto its surface, and physically adsorbing trace amounts of C12-acylhomoserine lactone (AHL). This unique ratio and parameter setting allows the BARMS microcarrier to fully mix with water during plug flow or aeration in the biochemical system, enabling bacteria to colonize its surface more efficiently and form a dense biofilm structure. This significantly alters the microbial community structure, reduces cell proliferation rate, and achieves sludge reduction effects far exceeding those of other ordinary microcarriers.
[0033] In the system of this invention, the carrier and sludge work synergistically, meaning that the BARMS microcarriers continuously function in the bioreactor. The generated biofilm carrier functions include: a specific surface area ≥15 m² / g, and a biomass loading of 8-12 g VSS / L carrier; a microbial screening function: a surface zeta potential of +15 to +25 mV, specifically adsorbing nitrifying bacteria; and an activity maintenance function: the complex reflux stabilizes the proportion of nitrifying bacteria in the system at 25-35%. As a further preferred embodiment, the length-to-diameter ratio of the feed inlet is (3-5):1, preferably 4:1; and the diameter of the underflow outlet is 0.12-0.15 times the diameter of the cylinder.
[0034] As a further preferred embodiment, the ultrasonic mud level gauge triggers automatic sand discharge when the sand layer thickness is ≥15cm, the discharged sand solid content is >25% and the sludge loss rate is <0.8%.
[0035] Example 2 Based on the sludge reduction composite carrier recycling system described in Example 1, this embodiment provides a method for improving sludge reduction efficiency, comprising the following steps: (i) The composite BARMS microcarrier is added to the bioreactor at a dosage of 3‰-5‰ of the bioreactor volume.
[0036] (ii) Sedimentation and sand removal: In the static sedimentation unit, the returned sludge is allowed to stand for 20±5 minutes, and sand and gravel with a particle size >0.2mm are discharged; (iii) Cyclone Screening: In the cyclone separation unit, the desanded sludge enters the cyclone separator at a pressure of 0.18-0.30 MPa. A turbulence suppression grid is installed at the inlet. A flexible guide ring made of food-grade silicone is added internally, with a ring spacing of 4-6 mm. The inner diameter of the ring contracts synchronously with the cone angle, and the ring surface is densely covered with 0.5 mm micro-protrusions. The separated sludge yields: Overflow liquid: contains low-activity sludge with density <1.10g / cm³, SOUR <8mgO2 / gVSS·h, of which floc particle size <50μm and SVI>150mL / g; Underflow liquid: contains a BARMS carrier and highly active sludge composite with a density >1.25 g / cm³ and a nitrification rate >0.15 kgN / kgVSS·d, wherein the floc particle size is >100 μm and SVI <80 mL / g; (iv) Dual-circulation active component reflux: The underflow liquid is refluxed through the dual-circulation reflux channel unit. The main channel is a corrosion-resistant pipeline that directly delivers the underflow liquid to the head end of the bioreactor. The bypass channel has a built-in ultrasonic activator with a frequency of 28kHz. 30% of the flow rate is treated through the bypass channel when the carrier is refluxed.
[0037] As a further preferred embodiment, the suppression grid feed velocity in step (iii) is reduced to <1.5m / s.
[0038] As a further preferred embodiment, the surface zeta potential of the BARMS carrier in the underflow fluid is +15 to +25 mV.
[0039] Nano-TiO2 loading enhances the Zeta potential (+22mV) on the carrier surface, promotes the specific adsorption of nitrifying bacteria, increases the density gradient of the carrier-sludge complex, and significantly improves the accuracy of cyclone separation.
[0040] As a further preferred embodiment, the sludge concentration (X) in the bioreactor is monitored, and the reflux ratio of the underflow is dynamically adjusted: When the sludge concentration X in the bioreactor is less than 3000 mg / L, the recirculation ratio should be increased by 30-40%. When the sludge concentration X in the bioreactor is greater than 8000 mg / L, the reflux ratio decreases by 10-15%.
[0041] As a further preferred embodiment, the hydraulic residence time of the static settling unit is 1.8-4 hours.
[0042] Example 3 This embodiment is based on the application of the sludge reduction composite carrier recovery system described in Embodiment 1 in the AAO wastewater treatment process. The underflow liquid is connected to the head end of the anaerobic tank, which improves the denitrification efficiency of the system by 40-60% and the sludge reduction rate by 35-45%.
[0043] The recycling system of this invention first uses a static settling unit to efficiently remove sand and gravel by utilizing the density difference between sand and gravel and other substances, simplifying the subsequent processing flow; then, with the help of a cyclone separation unit, it accurately separates light sludge and sludge complex containing BARMS microcarriers based on the principle of centrifugal force. This separation method has high separation accuracy and high efficiency, and the recovery rate can reach more than 90%.
[0044] AAO treatment process, short for Anaerobic-Anoxic-Oxic, is a commonly used secondary wastewater treatment process that simultaneously removes nitrogen and phosphorus. It can be used for secondary or tertiary wastewater treatment. After further advanced treatment, it can be reused as reclaimed water, exhibiting excellent nitrogen and phosphorus removal effects.
[0045] Example 4 The sludge reduction and microcarrier recovery system of this invention was applied in the biochemical treatment system of a large municipal wastewater treatment plant. This wastewater treatment plant has a daily wastewater treatment capacity of 10,000 m³ / d and a biochemical tank volume of 8,640 m³. 3 The designed influent water quality indicators are: chemical oxygen demand (COD) 300 mg / L, five-day biochemical oxygen demand (BOD5) 150 mg / L, ammonia nitrogen (NH3-N) 30 mg / L, and total phosphorus (TP) 3 mg / L.
[0046] The biochemical system was operating stably. BARMS microcarriers were added to the system at a rate of 3‰ of the tank volume, amounting to 26 tons. The BARMS microcarriers consisted of 90% inorganic biological carriers (mainly composed of 70% silica and 29.5% alumina) and 10% microbial strains (including 34% nitrifying bacteria, 33% denitrifying bacteria, and 33% polyphosphate-accumulating bacteria). The particle size was 100 micrometers, and the actual density was 2.20 g / cm³. The inorganic biological carrier surface was loaded with 5% nano-titanium dioxide, uniformly loaded onto the surface using a sol-gel method. The inorganic biological carrier surface was then subjected to surface-initiated atom transfer radical polymerization (SI-ATRP) technology, with 3% polysulfobetaine (pSBMA) and 4% polydiallyldimethylammonium chloride (pDADMAC) segments covalently grafted onto its surface, and 0.5% C12-acylhomoserine lactone (AHL) physically adsorbed. The recycling system is started, and each unit operates as follows: 1) Settling Unit: Dimensions: 10m long, 5m wide, 3m high, with an effective volume of 120m³. The mixed liquor flows slowly into the settling tank through a pipe at a flow rate of 0.5m³ / min, with a hydraulic retention time of 2 hours. The bottom of the settling tank features a conical sand collection hopper with a 65° cone angle to facilitate sand and gravel accumulation. A 200mm diameter sand discharge port is installed at the bottom, controlled by an electric gate valve. An ultrasonic mud level gauge is installed on the side wall, with a sand discharge threshold of 15cm. The sand discharge frequency is set twice daily, at 8:00 AM and 4:00 PM, with each discharge lasting 10 minutes. During the settling process, the sand and gravel quickly settle to the bottom of the tank under gravity. Testing shows that after 2 hours of settling, the sand and gravel removal rate reaches over 95%. 2) Cyclone Separation Unit: The separator has a processing capacity of 500 m³ / h and a maximum processing pressure of 0.6 MPa. The mixed liquid enters the tangential inlet of the cyclone separator through a pipeline with a cylinder diameter of 600 mm and a cone angle of 10°. A turbulence suppression grid is installed at the inlet, with a feed velocity of 1.3 m / s, a length-to-diameter ratio of 4:1, and a bottom outlet diameter of 90 mm. The separator is internally equipped with flexible guide rings made of food-grade silicone, with a ring spacing of 5 mm. The inner diameter of the rings contracts synchronously with the cone angle, and the ring surface is densely covered with 0.5 mm micro-protrusions. The mixed liquid rotates at high speed within the separator, with a centrifugal force set at 1500 g. Light sludge, due to its lower density, moves towards the center of the separator under centrifugal force and rises along the central overflow pipe, eventually exiting from the top 150 mm diameter light sludge outlet. The sludge complex containing BARMS microcarriers moves towards the outside of the separator, settles downwards along the inner wall, and exits from the bottom 90 mm diameter outlet. Analysis of the discharged mixed liquor revealed that the overflow contained low-activity sludge with a density <1.10 g / cm³ and a solubility urinate (SOUR) <8 mg O₂ / g VSS·h; the underflow contained a complex of BARMS carrier and highly active sludge with a density >1.25 g / cm³ and a nitrification rate >0.15 kg N / kg VSS·d. The Zeta potential of the BARMS carrier surface in the underflow was 20 mV. The separation efficiency between the light sludge and the sludge complex containing the BARMS carrier exceeded 90%. 3) Dual-circulation reflux channel unit: The reflux anti-corrosion pipeline is 50m long and directly connected to the anaerobic tank, forming the main channel. A bypass channel is also added, equipped with a 28kHz ultrasonic activator. During the reflux process, 30% of the underflow liquid is treated through the bypass channel and then merges with the underflow liquid in the main channel for reflux. A single-stage, single-suction horizontal centrifugal pump with a power of 5kW, a rated flow rate of 50m³ / h, and a head of 32m is installed on the reflux pipeline as the reflux pump. Meanwhile, an electromagnetic flowmeter is installed to monitor the return flow rate. The return flow rate is adjusted to 100 m³ / h via an electric regulating valve. The sludge concentration of the return liquid is checked every 12 hours. If the sludge concentration of the return liquid is less than 3000 mg / L, the return ratio is increased to 130 m³ / h. If the sludge concentration of the return liquid is greater than 8000 mg / L, the return ratio is reduced to 85 m³ / h. This ensures that the mixed liquid containing the sludge and carrier complex can be smoothly returned to the anoxic section of the biological system. During three months of continuous operation, the system underwent comprehensive monitoring weekly. Monitoring included indicators such as microcarrier recovery rate, sludge production, and effluent quality. Microcarrier recovery rate was calculated using a combination of sieving and weighing; a certain volume of the mixed liquor was sieved through a screen with a specific aperture to separate the microcarriers, which were then dried, weighed, and the recovery rate was calculated. Sludge production was calculated by measuring the sludge volume and concentration in the sludge thickening tank. Effluent quality was tested using national standard testing methods.
[0047] Experimental results: Monitoring showed that the microcarrier recovery rate remained stable at around 92%. The sludge production of the biological system was reduced by 40% compared to when the recovery system was not used. The effluent quality consistently met the Class A standard of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" (GB18918-2002), specifically COD < 50 mg / L, BOD5 < 10 mg / L, NH3-N < 5 mg / L, and TP < 0.5 mg / L, as detailed in Table 1. Example 5 The recycling system of this invention has been applied to an industrial wastewater treatment plant in a chemical industrial park. This industrial wastewater treatment plant has a daily wastewater treatment capacity of 5000 m³. 3 / d, biological treatment tank volume is 11666m³ 3 The influent water quality is complex, containing a large amount of organic pollutants (such as benzene series compounds, phenols, etc.) and heavy metal ions (such as copper, zinc, cadmium, etc.). The COD is 800 mg / L, BOD5 is 300 mg / L, ammonia nitrogen is 40 mg / L, total phosphorus is 4 mg / L, copper ion concentration is 2 mg / L, zinc ion concentration is 3 mg / L, and cadmium ion concentration is 0.1 mg / L. BARMS microcarriers were added to the biochemical system at a dosage of 5‰, totaling 59 tons. The composition, particle size, and density of the microcarriers were the same as in Example 4. The recovery system was started, and the operating parameters of each unit were as follows: 1) Settling Unit: The settling tank measures 8m long, 4m wide, and 2.5m high, with an effective volume of 72m³. The mixed liquor enters the settling tank at a flow rate of 0.3m³ / min, with a hydraulic retention time of 1.5 hours. The bottom of the settling tank features a conical sand collection hopper with a 60° cone angle. The sand discharge outlet at the bottom of the settling tank has a diameter of 150mm and is controlled by a pneumatic butterfly valve. Sand discharge occurs three times daily at 7:00 AM, 12:00 PM, and 5:00 PM, with each discharge lasting 8 minutes. Testing shows that the sand and gravel removal rate reaches over 90%. 2) Cyclone Separation Unit: 600mm cylinder diameter, 12° cone angle; turbulence suppression grid installed at the inlet; feed velocity 3.2m / s; inlet length-to-diameter ratio 4:1; underflow diameter 80mm; processing capacity 300m³ / s. 3 The flow rate is [ / h], with a maximum processing pressure of 0.5 MPa. The separator is internally equipped with flexible guide rings made of food-grade silicone, with a ring spacing of 5 mm. The inner diameter of the rings contracts synchronously with the cone angle, and the ring surface is densely covered with 0.5 mm micro-protrusions. After the mixed liquid enters the hydrocyclone separator, the centrifugal force is set to 1200 g. Light sludge is discharged from the top outlet with a diameter of 120 mm, while the sludge complex containing BARMS carriers is discharged from the bottom outlet with a diameter of 80 mm. The separated mixed liquor was tested. By sampling and analyzing the discharged mixed liquor, the overflow liquid contained low-activity sludge with a density <1.10 g / cm³ and SOUR <8 mgO2 / gVSS·h; the underflow liquid contained a complex of BARMS carrier and high-activity sludge with a density >1.25 g / cm³ and a nitrification rate >0.15 kgN / kgVSS·d. The surface zeta potential of the BARMS carrier in the underflow liquid was +18 mV. The separation effect between the light sludge and the sludge complex containing BARMS carrier was good, with a separation efficiency of over 88%. 3) Dual-circulation reflux channel unit: The reflux pipeline is 30m long, with the main channel being a corrosion-resistant pipe directly connected to the front end of the biological contact oxidation tank. A bypass channel is also added, equipped with a 28kHz ultrasonic activator. During the reflux process, 30% of the underflow liquid is treated through the bypass channel and then merges with the underflow liquid from the main channel for reflux. The reflux pump is a corrosion-resistant centrifugal pump with a power of 3kW, a rated flow rate of 25m³ / h, and a head of 20m. The reflux flow rate is controlled at 60m³ / h using a rotor flow meter and a manual regulating valve. The sludge concentration in the reflux liquid is monitored every 12 hours. If the sludge concentration is less than 3000mg / L, the reflux ratio is increased to 80m³ / h; if the sludge concentration is greater than 8000mg / L, the reflux ratio is reduced to 50m³ / h, ensuring that the mixed liquor containing sludge and carrier composites can be smoothly refluxed to the front end of the biological contact oxidation tank.
[0048] During the two-month operation period, the system was monitored every five days. In addition to monitoring the microcarrier recovery rate, sludge production, and routine effluent quality indicators, the heavy metal ion removal rate was also tested, and the concentration of heavy metal ions was determined by atomic absorption spectrophotometry.
[0049] The results showed that the microcarrier recovery rate reached 90%, and organic pollutants and heavy metal ions in industrial wastewater were effectively removed. The COD removal rate reached 85%, the BOD5 removal rate reached 90%, the ammonia nitrogen removal rate reached 95%, the total phosphorus removal rate reached 92%, and the removal rates of copper ions, zinc ions, and cadmium ions reached 90%, 85%, and 95%, respectively. The amount of sludge generated was reduced by 35%, achieving good wastewater treatment and microcarrier recovery effects.
[0050] Comparative Example 1 The sludge reduction microcarrier recovery system of this invention was applied to the biochemical treatment system of a large municipal wastewater treatment plant (same as Example 4). After the biochemical system was running stably, unmodified BARMS microcarriers were added to the system. The BARMS microcarriers consist of 90% inorganic biological carriers (mainly composed of 70% silica and 30% alumina) and 10% microbial strains (including 34% nitrifying bacteria, 33% denitrifying bacteria, and 33% polyphosphate-accumulating bacteria), with a particle size of 100 micrometers, an actual density of 2.20 g / cm³, and an addition amount of 3‰ of the tank volume, which is 26 tons.
[0051] Start the recycling system, which is exactly the same as in Example 4, with all unit devices and operating parameters kept consistent.
[0052] During the continuous operation for 3 months, the same monitoring method as in Example 1 was used to comprehensively monitor indicators such as microcarrier recovery rate, sludge production, and effluent quality every week, as detailed in Table 1.
[0053] Comparative Example 2 The sludge reduction microcarrier recovery system of the present invention was applied to the biochemical treatment system of a large municipal wastewater treatment plant (same as in Example 4). After the biochemical system was running stably, the same BARMS microcarriers as those added in Example 4 were added to the system.
[0054] The recycling system was started, and the operating parameters of each unit were as follows: there was no static settling unit, and all other settings were the same as in Example 4. The experimental results are shown in Table 1.
[0055] Comparative Example 3 The sludge reduction microcarrier recovery system of this invention was applied to the biochemical treatment system of a large municipal wastewater treatment plant (same as in Example 4). After the biochemical system was running stably, the same BARMS microcarriers as those in Example 4 were added to the system, and the experimental results are shown in Table 1.
[0056] The recovery system was started, and the operating parameters of each unit were as follows: the cone angle of the cyclone separation unit was 18°, and other settings were the same as in Example 4. The experimental results are shown in Table 1.
[0057] Comparative Example 4 The sludge reduction microcarrier recovery system of this invention was applied to the biochemical treatment system of a large municipal wastewater treatment plant (same as in Example 4). After the biochemical system was running stably, the same BARMS microcarriers as those in Example 4 were added to the system, and the experimental results are shown in Table 1.
[0058] The recycling system was started, and the operating parameters of each unit were as follows: the sand-removed sludge entered the hydrocyclone at a pressure of 0.8 MPa, and the other settings were the same as in Example 4. The experimental results are shown in Table 1.
[0059] Comparative Example 5 The sludge reduction microcarrier recovery system of this invention was applied to the biochemical treatment system of a large municipal wastewater treatment plant (same as in Example 4). After the biochemical system was running stably, the same BARMS microcarriers as those added in Example 4 were added to the system. The experimental results are shown in Table 1.
[0060] The recycling system was started, and the operating parameters of each unit were as follows: when the sludge concentration in the returned liquid was less than 3000 mg / L, the return ratio was increased to 125 m³ / h; when the sludge concentration in the returned liquid was greater than 8000 mg / L, the return ratio was reduced to 75 m³ / h, ensuring that the mixed liquor containing the sludge and carrier complex could be smoothly returned to the anoxic section of the biological system. All other settings were the same as in Example 4, and the experimental results are shown in Table 1.
[0061] Table 1 Comparison of results from Example 4 and Comparative Examples 1-5
[0062] The comparison results clearly show that, under the same wastewater treatment plant environment, the same recycling system equipment, and operating parameters, the recovery rate of the modified microcarriers was significantly higher than that of the unmodified microcarriers, with the former remaining stable at around 92% and the latter only at 78%. This increased microcarrier recovery rate ensured the effective amount of microorganisms involved in sludge reduction within the biological system, thereby increasing the sludge production reduction ratio from 28% to 40%, and significantly improving the wastewater treatment effect. All effluent quality indicators were superior to those without microorganism modification. This fully demonstrates that carrier modification plays a crucial role in improving the microcarrier recovery rate and sludge reduction effect. Nano-TiO2 loading, by enhancing the zeta potential on the carrier surface (+22mV), promotes the specific adsorption of nitrifying bacteria (Example 4), increases the density gradient of the carrier-sludge complex (1.28 vs 1.10 g / cm³), significantly improves the cyclone separation accuracy (recovery rate 92% vs 78%), and significantly enhances the treatment efficiency of this recycling system.
[0063] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this application should be included within the protection scope of this application.
Claims
1. A sludge reduction composite carrier recycling system, characterized in that, In order, they include: 1) Composite BARMS microcarrier unit: composed of 85%-95% inorganic biological carrier and 5%-15% microbial strain, with a particle size of 80-120μm and a true density of 2.00-2.20g / cm³; 2) Static settling unit: The bottom is equipped with a sand collection hopper with a cone angle ≥65°, the top has an overflow port, and the side wall is equipped with an ultrasonic mud level gauge connected to an automatic sand discharge valve; 3) Cyclone Separation Unit: The feed inlet is connected to the overflow port of the settling unit via a booster pump. The cylinder diameter is 50-80mm, and the cone angle is 8°-12°. The feed inlet is equipped with a turbulence suppression grid and a flexible guide ring is added inside. The ring is made of food-grade silicone material, with a ring spacing of 4-6mm. The inner diameter of the ring shrinks synchronously with the cone angle, and the surface of the ring is densely covered with micro-protrusions with a height of 0.4-0.6mm. 4) Dual circulation reflux channel unit: The dual circulation reflux channel unit includes a main channel and a bypass channel. The main channel is a corrosion-resistant pipeline that directly connects the underflow port of the hydrocyclone separator to the bioreactor. The bypass channel has a built-in ultrasonic activator with a frequency of 25-30kHz. When the carrier is refluxed, the flow rate is through the bypass channel.
2. The recycling system according to claim 1, characterized in that, The inorganic biological carrier contains silica, alumina, and quorum sensing signal molecules; the surface of the inorganic biological carrier contains nano-titanium dioxide, zwitterionic polymer brushes, and cationic polymer segments.
3. The recycling system according to claim 2, characterized in that, The inorganic biological carrier contains, by mass ratio, 65-75 parts silica, 24.9-34.9 parts alumina, and 0.1-1 parts quorum sensing signal molecules; The inorganic biological carrier surface is first uniformly loaded with 2-8% nano-titanium dioxide using a sol-gel method; then, 2-5% zwitterionic polymer brushes and 2-5% cationic polymer segments are covalently grafted onto it.
4. The recycling system according to claim 3, characterized in that, The quorum sensing signal molecule is C12-acylhomoserine lactone; The zwitterionic polymer brush is a polysulfobetaine (pSBMA) brush; The cationic polymer segment is a polydiallyl dimethylammonium chloride (pDADMAC) segment; The microbial strains include at least one or more functional groups among nitrifying bacteria, denitrifying bacteria, and polyphosphate-accumulating bacteria.
5. The recycling system according to claim 1, characterized in that, The length-to-diameter ratio of the feed inlet is (3-5):1, and the diameter of the underflow outlet is 0.12-0.15 times the diameter of the cylinder. The ultrasonic mud level gauge triggers automatic sand discharge when the sand layer thickness is ≥15cm.
6. A method for improving sludge reduction using a composite carrier recovery system according to any one of claims 1-5, characterized in that, Includes the following steps: (i) The composite BARMS microcarrier is added to the bioreactor at a dosage of 3‰-5‰ of the bioreactor volume; (ii) Sedimentation and sand removal: In the static sedimentation unit, the returned sludge is allowed to stand for 20±5 minutes, and sand and gravel with a particle size >0.2mm are discharged; (iii) Cyclone Screening: In the cyclone separation unit, the desanded sludge enters the hydrocyclone at a pressure of 0.18-0.60 MPa, passes through the suppression grid and the guide ring, and is separated to obtain: Overflow liquid: containing low-active sludge with a density <1.10 g / cm³ and SOUR <8 mg O2 / g VSS·h; Underflow liquid: contains a composite of BARMS carrier and highly active sludge with a density >1.25 g / cm³ and a nitrification rate >0.15 kgN / kgVSS·d; (iv) Direct reflux of active components: The underflow is delivered directly to the head of the bioreactor without any treatment by a low-shear pump.
7. The method according to claim 6, characterized in that, The feed velocity of the suppression grid is reduced to <1.5m / s.
8. The method according to claim 6, characterized in that, The surface zeta potential of the BARMS carrier in the underflow fluid is +15 to +25 mV. The hydraulic retention time of the static settling unit is 1.8-4 hours.
9. The method according to claim 6, characterized in that, Monitor the sludge concentration (X) in the bioreactor and dynamically adjust the reflux ratio of the underflow liquid: When the sludge concentration X in the bioreactor is less than 3000 mg / L, the recirculation ratio should be increased by 30-40%. When the sludge concentration X in the bioreactor is greater than 8000 mg / L, the reflux ratio decreases by 10-15%.
10. The application of a sludge reduction composite carrier recovery system according to any one of claims 1-5 in the AAO wastewater treatment process, characterized in that, Introducing the underflow liquid into the head end of the anaerobic tank increases the system's nitrogen removal efficiency by 40-60% and reduces sludge volume by 35-45%.