A microalgae-bacteria coupled bioreactor and synergistic purification process for high-salt antibiotic-containing aquaculture wastewater treatment

Abstract

This invention discloses a microalgae-bacteria coupled bioreactor and synergistic purification process for treating high-salt, antibiotic-containing aquaculture wastewater, belonging to the field of wastewater treatment technology. The reactor body is vertically divided into a light zone and a dark zone. The light zone is a translucent structure for microalgae photosynthetic oxygen production, while the dark zone provides a low-light / no-light environment for bacterial facultative / anaerobic metabolism. The reactor is equipped with an external LED light source system, a mixing system, a gas exchange system, a bottom water inlet system, and an online monitoring and automatic control system. The synergistic purification process includes steps such as algae and bacteria inoculation and acclimatization, wastewater pretreatment, bottom-inlet and top-outlet, dark-then-light water inlet treatment, photosynthetic oxygen production and pollutant degradation, online feedback control, and sludge-water separation and disinfection. This invention achieves simultaneous and efficient removal of carbon, nitrogen, phosphorus, and antibiotics through a light-dark partition structure and complementary algae and bacteria metabolism, with low energy consumption and strong resistance to shock loads.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a microalgae-bacteria coupled bioreactor and synergistic purification process for treating high-salt, antibiotic-containing aquaculture wastewater. Background Technology

[0002] High-salinity, antibiotic-containing aquaculture wastewater mainly originates from mariculture, tidal flat aquaculture, and some high-salinity freshwater aquaculture processes. This type of wastewater not only contains high concentrations of salt, organic matter, and nitrogen and phosphorus nutrients, but also commonly retains various antibiotics (such as sulfonamides, fluoroquinolones, and tetracyclines). With the intensive and large-scale development of aquaculture in my country, antibiotics are used extensively as feed additives and disease treatment drugs, leading to increasingly prominent antibiotic residue problems in aquaculture wastewater. These antibiotic residues enter the environment with wastewater discharge, not only stressing aquatic ecosystems but also inducing and spreading antibiotic resistance genes (ARGs), posing a potential threat to public health. Therefore, developing efficient, economical, and stable technologies for treating high-salinity, antibiotic-containing aquaculture wastewater has significant environmental and social value.

[0003] Currently, the mainstream technologies for treating high-salt, antibiotic-containing aquaculture wastewater include the following categories: (1) Physicochemical methods: such as advanced oxidation methods (Fenton oxidation, ozone oxidation, photocatalytic oxidation, etc.), adsorption methods (activated carbon adsorption, resin adsorption, etc.) and membrane separation methods (nanofiltration, reverse osmosis, etc.). These methods can effectively remove some antibiotics and organic matter, but they have problems such as high operating costs, large reagent consumption, and easy generation of secondary pollution (such as concentrated waste liquid and waste adsorbent). In addition, they have limited adaptability to high-salt environments, making it difficult to promote and apply them on a large scale.

[0004] (2) Traditional activated sludge process and its variants: As the most widely used biological treatment technology, the traditional activated sludge process is suitable for the treatment of general organic wastewater. However, in a high-salt environment, the osmotic pressure regulation mechanism of ordinary microorganisms is difficult to adapt, and cell dehydration leads to a significant inhibition of metabolic activity; at the same time, antibiotic residues will exert selective pressure on functional flora, destroying the flora structure and ecological niche balance, resulting in low treatment efficiency, and the system is prone to sludge bulking or even collapse.

[0005] (3) Single microalgae treatment system (such as microalgae pond, photobioreactor, etc.) or single bacterial treatment system (such as MBR membrane bioreactor, biofilter, etc.): Microalgae treatment system can remove nitrogen, phosphorus and some organic matter through photosynthesis, but it has poor tolerance to antibiotics. High concentrations of antibiotics will inhibit the electron transfer efficiency of photosystem II and reduce photosynthetic performance. Although single bacterial system can degrade some antibiotics through specific strains, it requires continuous external oxygen supply, has high energy consumption, and is sensitive to carbon-nitrogen ratio fluctuations, resulting in insufficient system stability.

[0006] In recent years, microalgae-bacteria coupling technology has attracted increasing attention from researchers. This technology utilizes the photosynthetic oxygen production of microalgae to provide electron acceptors for bacteria, while the CO2 produced by bacterial metabolism can be utilized by microalgae, forming a carbon-oxygen complementary cycle. This not only reduces the energy consumption of external aeration but also achieves synergistic removal of antibiotics through the adsorption and biotransformation of antibiotics by microalgae and the enzymatic degradation by bacteria. However, most existing algae-bacteria coupling systems are designed for freshwater or low-salinity wastewater and lack specialized reactor structure design for environments under dual stress from high salinity and antibiotics. Specifically, existing research still has the following shortcomings: First, there is a lack of dedicated reactor configuration designs for high-salinity antibiotic-containing wastewater. Traditional algae-bacteria reactors are mostly single-light structures, which cannot achieve functional zoning and synergistic control of light and dark zones; second, there is a lack of systematic control methods for regulating the dynamic ratio of bacteria and algae within the reactor, making it difficult to maintain a stable symbiotic relationship in the long term; third, while existing literature reports the removal efficiency of algae-bacteria systems for conventional pollutants, insufficient consideration is given to controlling antibiotic degradation pathways and the risk of resistance gene transmission; fourth, the shock load resistance and abnormal operating condition recovery strategies of algae-bacteria coupling systems have not yet been systematically addressed.

[0007] Therefore, developing a microalgae-bacteria coupled reactor and its supporting purification process with high tolerance, synergistic and efficient degradation capabilities, stable operation and low energy consumption is of great practical significance for solving the problem of treating high-salt and antibiotic-containing aquaculture wastewater. Summary of the Invention

[0008] This invention aims to solve the problems of low microbial activity, poor resistance, system instability, low treatment efficiency, and high energy consumption in the current treatment of high-salt and antibiotic-containing aquaculture wastewater, and provides a microalgae-bacteria coupled bioreactor with high tolerance and synergistic and efficient degradation capabilities and its synergistic purification process.

[0009] To achieve the above objectives, the present invention is implemented through the following technical solution: In a first aspect, the present invention provides a microalgae-bacteria coupled bioreactor for treating high-salt, antibiotic-containing aquaculture wastewater, comprising: The reactor body has a light zone and a dark zone arranged vertically from top to bottom. The light zone is a light-transmitting structure, and the dark zone is a weak light or no light environment. The light zone is used for photosynthetic oxygen production by microalgae, and the dark zone is used for facultative / anaerobic metabolism of bacteria. A light source system is located outside the reactor body at a position corresponding to the light zone, and is used to provide the light zone with the light required for photosynthesis; A mixing system, located between the light zone and the dark zone, is used to achieve mixing and circulation of materials within the reactor; A gas exchange system is used to replenish CO2 into the reactor and remove excess gas. The inlet system is located at the bottom of the reactor body and is used to allow wastewater to flow in a bottom-in, top-out, dark-first-light flow pattern through the dark zone and the light zone, and then be discharged from the top of the reactor body. In addition, an online monitoring and automatic control system is used to monitor the reactor's operating parameters in real time and to coordinate and control the light source system, mixing system, and gas exchange system.

[0010] As a further optimization of the present invention, the effective volume ratio of the light area to the dark area is (1.2~1.5):1; And / or, the dark area is filled with suspended biological packing material, which is selected from Pall rings or multifaceted hollow spheres made of polyethylene or polypropylene, and the filling rate is 25% to 35% of the effective volume of the dark area.

[0011] As a further optimization of the present invention, the light source system adopts an external LED light panel, which is arranged in a longitudinal array along the outer wall of the reactor body corresponding to the light area, and the distance between the LED light panel and the outer wall of the reactor body is 50~100mm.

[0012] As a further optimization of the present invention, the mixing system includes a stirrer, the blade diameter of which is 1 / 3 to 1 / 2 of the inner diameter of the reactor, and is installed at the junction of the light zone and the dark zone, with a rotation speed range of 20 to 60 rpm; And / or, the mixing system includes an air-lift circulation device, wherein the riser of the air-lift circulation device is located at the center of the reactor body, and compressed air is introduced from the bottom of the riser at a velocity of 0.5~1.5 L / (L·min), and the circulation flow rate is 2~5 times the effective volume of the reactor / h.

[0013] As a further optimization of the present invention, the CO2 replenishment port of the gas exchange system is located at the junction of the bottom of the light zone and the dark zone, and adopts an annular perforated aeration pipe with a gas flow rate adjustment range of 0.1~0.5L / (L·min).

[0014] As a further optimization of the present invention, the water inlet system includes a water inlet pipe and an annular perforated water distribution pipe, wherein the water inlet pipe extends into the lower end of the dark area at the bottom of the reactor body and is connected to the annular perforated water distribution pipe.

[0015] As a further optimization of the present invention, the top of the reactor body is provided with an inclined plate sedimentation zone, an exhaust pipe and a drain pipe, the inclined plate sedimentation zone being located below the effluent weir; the bottom of the reactor body is provided with a sludge discharge pipe.

[0016] As a further optimization of the present invention, the online monitoring and automatic control system includes a pH sensor, a DO sensor, a salinity sensor, a temperature sensor, and a turbidity sensor. The online monitoring and automatic control system automatically adjusts the light intensity, stirring speed, and CO2 supply based on the feedback signals from each sensor.

[0017] Secondly, the present invention provides a synergistic purification process using the aforementioned microalgae-bacteria coupled bioreactor, comprising the following steps: (1) Inoculation and acclimatization of bacteria and algae: Salt-tolerant and antibiotic-resistant microalgae and bacteria are inoculated into the reactor for salinity acclimatization and antibiotic tolerance acclimatization. (2) Wastewater pretreatment: High-salt aquaculture wastewater containing antibiotics is filtered to remove large particulate suspended solids and the pH is adjusted to 7.0~8.5; (3) Inlet water treatment: The pretreated wastewater is fed into the reactor from the bottom. The wastewater flows through the dark zone and the light zone in sequence, with the wastewater entering from the bottom and exiting from the top, and flowing through the dark zone first and then the light zone. (4) Photosynthetic oxygen production and pollutant degradation: Microalgae use light and CO2 to perform photosynthesis in the light zone to produce O2 and absorb nitrogen and phosphorus nutrients. Aerobic bacteria use the O2 produced by microalgae to degrade organic matter and antibiotics. Facultative / anaerobic bacteria carry out denitrification in the dark zone. (5) Online control: The operating parameters in the reactor are monitored in real time through the online monitoring system, and the light intensity, stirring speed and CO2 supply are controlled in conjunction to maintain the metabolic activity of bacteria and algae and the stability of the system. (6) Sludge-water separation and effluent treatment: The reactor effluent is discharged or reused after sedimentation, filtration and disinfection.

[0018] As a further optimization of the present invention, in step (1), the microalgae are selected from salt-tolerant Chlorella or Spirulina, and the bacteria are selected from salt-tolerant aerobic denitrifying bacteria Haloxylon ammodendron and antibiotic-degrading bacteria Pseudomonas ammodendron; the inoculation mass ratio of microalgae to bacteria is 1:1 to 3:1 on a dry weight basis.

[0019] Compared with the prior art, the present invention has the following significant advantages and beneficial effects: This invention utilizes a construction method that combines salt- and antibiotic-resistant functional microalgae and bacteria with stepwise salinity acclimation and antibiotic acclimation, enabling the coupled system to maintain high metabolic activity under the dual stress of high salt and high antibiotic levels. Through a metabolic complementarity mechanism between microalgae and bacteria, microalgae photosynthetically produce oxygen and provide electron acceptors for bacteria, while bacteria mineralize organic matter, releasing CO2 and inorganic nutrients for microalgae utilization. Facultative / anaerobic bacteria then perform denitrification in the dark zone, achieving simultaneous and efficient removal of carbon, nitrogen, phosphorus, and antibiotics. Furthermore, the partitioned structure of the upper and lower light zones allows for spatial separation of aerobic and facultative / anaerobic metabolism, while maintaining interconnection through hydraulic circulation, avoiding the problem of photosynthetic oxygen production inhibiting the denitrification process in a single-light reactor.

[0020] This invention maintains the algal-to-bacterial ratio within a stable range in real time through an online monitoring and automatic control system. It also features a three-level automatic control priority rule and a complete recovery plan for abnormal operating conditions, giving the system exceptional resistance to shock loads. This invention uses a combination of red and blue LED light sources to drive microalgae photosynthetic oxygen production, replacing traditional mechanical aeration with photosynthetic oxygen supply. CO2 injection ports are only located at the boundary between the light and dark zones for auxiliary pH and DO control. The stirring system operates at low speed intermittently or uses an airlift circulation method, avoiding high shear force damage to microalgae cells while significantly reducing power consumption.

[0021] This invention incorporates a process involving periodic sludge removal and microalgae harvesting, combined with quantitative real-time PCR (qPCR) monitoring of resistance gene abundance, aiming to control the relative abundance of resistance genes to ≤30% of the initial value. This design effectively reduces the accumulation and horizontal transfer risk of resistance genes within the system, avoiding the shortcomings of traditional microbial-algae systems that only focus on pollutant removal while neglecting the potential for resistance transmission. It embodies an upgrade in process philosophy from "pollutant removal" to "equal emphasis on pollutant removal and biosafety."

[0022] The integrated reactor structure of this invention integrates the light zone, dark zone, and inclined plate sedimentation zone into a single main body, occupying a small area. The light source module and reactor specifications can be flexibly configured according to the treatment scale, facilitating modular expansion and engineering promotion. The bottom inlet and top overflow hydraulic flow design allows wastewater to flow sequentially through the dark zone packing biofilm and the light zone microalgae suspension zone, achieving tiered utilization of functional zones and improving volume utilization. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the microalgae-bacteria coupled bioreactor of the present invention.

[0024] Figure 2 This is a flow chart of the synergistic purification process of the present invention.

[0025] Figure 3Line graph comparing the removal efficiency of multiple pollutants under different light intensities.

[0026] In the diagram: 1. Reactor body; 2. Light zone; 3. Dark zone; 4. Light source system; 5. Mixing system; 51. Agitator; 52. Air-lift circulation device; 6. Gas exchange system; 61. Annular perforated aeration pipe; 62. Exhaust pipe; 7. Water inlet system; 71. Water inlet pipe; 72. Annular perforated water distribution pipe; 8. Inclined plate sedimentation zone; 9. Water outlet pipe; 10. Sludge discharge pipe. Detailed Implementation

[0027] To enable those skilled in the art to better understand the technical solutions of the present invention, preferred embodiments of the present invention are described below in conjunction with specific examples. However, it should be understood that the accompanying drawings are for illustrative purposes only and should not be construed as limiting the present invention. For better illustration of this embodiment, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. For those skilled in the art, the omission of certain well-known structures and their descriptions in the drawings is understandable. The positional relationships described in the drawings are for illustrative purposes only and should not be construed as limiting the present invention.

[0028] like Figure 1 As shown, the microalgae-bacteria coupled bioreactor for treating high-salt, antibiotic-containing aquaculture wastewater according to the present invention includes a reactor body 1, a light source system 4, a mixing system 5, a gas exchange system 6, a water inlet system 7, and an online monitoring and automatic control system.

[0029] In some embodiments, the reactor body 1 is a vertical, closed column structure made of acrylic or plexiglass material with good light transmittance and corrosion resistance. It can be designed with different specifications with an effective volume of 5L to several cubic meters, depending on the processing scale. The reactor body 1 is provided with a light zone 2 and a dark zone 3 from top to bottom in the vertical direction. The light zone 2 is a light-transmitting structure used for photosynthetic oxygen production and aerobic metabolism of microalgae; the dark zone 3 is a weak light or no light environment used for facultative anaerobic / anaerobic metabolism of bacteria.

[0030] The effective volume ratio of light zone 2 to dark zone 3 is (1.2~1.5):1, corresponding to a height ratio of (1.1~1.3):1. The effective volume of the light zone accounts for 50%~60% of the total effective volume of the reactor, while the dark zone accounts for 40%~50%. This ratio ensures that photosynthetic oxygen production matches bacterial oxygen consumption. For example, in a small-scale reactor with an effective volume of 10L, the height of the light zone is 600mm and the height of the dark zone is 400mm; in a pilot-scale reactor with an effective volume of 100L, the height of the light zone is 1000mm and the height of the dark zone is 800mm. The scale can be linearly scaled up proportionally. Dark zone 3 is filled with suspended biological packing material, selected from polyethylene or polypropylene Pall rings or multifaceted hollow spheres, with a diameter of 25~50mm and a filling rate of 25%~35% of the effective volume of dark zone 3. The surface of the packing material allows facultative / anaerobic bacteria to attach and grow, forming a biofilm, enhancing denitrification and antibiotic degradation.

[0031] The reactor body 1 is equipped with an inclined plate sedimentation zone 8, an exhaust pipe 62, and an outlet pipe 9 at its top. The inclined plate sedimentation zone 8 is located below the outlet weir, with an inclination angle of 60°, a plate spacing of 50~80mm, and a surface load of ≤0.5m². 3 / (m 2 •h), used to achieve mud-water separation of bacterial-algae mixture; the bottom of the reactor body 1 is equipped with a sludge discharge pipe 10, used to periodically discharge excess sludge and aged biofilm.

[0032] In some embodiments, the light source system 4 is located outside the reactor body 1 at a position corresponding to the light zone 2, and adopts an external LED light panel, which is arranged in a longitudinal array along the outer wall of the reactor body 1 corresponding to the light zone 2. The LED light panel adopts a red and blue light combined light source, with a red light wavelength of 660nm±10nm and a blue light wavelength of 450nm±10nm. The ratio of red to blue LED beads is (3~5):1, preferably 4:1, which can efficiently match the absorption spectrum of microalgae photosynthesis.

[0033] The power density of each LED panel is 30~50W / m². 2 (Based on the reactor's projected area), the LED spacing is 100-150mm, and the uniformity of light intensity within the illuminated area is ≤±15%. The distance between the LED light panel and the outer wall of reactor body 1 is 50-100mm, ensuring both uniform illumination and preventing heat dissipation from the light panel from affecting the reactor's internal temperature. The light source system supports PWM dimming, enabling continuous adjustment of light intensity within the range of 2000-8000 lux, and the light-dark cycle can be set as needed. No light source is arranged on the outer wall of the reactor corresponding to dark area 3 to maintain a low-light / no-light environment in the dark area.

[0034] In some embodiments, the mixing system 5 is located at the junction of the light zone 2 and the dark zone 3 to achieve mixing and circulation of materials in the reactor, and may take the form of mechanical stirring, air stripping circulation or a combination of both.

[0035] When mechanical stirring is used, the mixing system includes a stirrer 51. The stirrer is either a slanted blade impeller (45° tilt angle) or a propeller impeller. The blade diameter is 1 / 3 to 1 / 2 of the reactor's inner diameter. The installation position is 40% to 50% of the total height of the reactor from the bottom. The rotation speed range is 20 to 60 rpm, with an upper limit of 80 rpm to avoid shear force damage to microalgae cells. The operation mode can be intermittent stirring (stirring for 10 minutes, then pausing for 5 to 10 minutes) or continuous low-speed stirring.

[0036] When using an air-lift circulation system, the mixing system includes an air-lift circulation device 52. The riser of the air-lift circulation device is located at the central axis of the reactor body 1. The inner diameter of the riser is 1 / 10 to 1 / 8 of the reactor's inner diameter, the bottom end is 50 to 100 mm from the bottom, and the top end extends into the upper part of the light zone 2. Compressed air is introduced from the bottom of the riser at a velocity of 0.5 to 1.5 L / (L·min) (based on the effective volume of the reactor), and the circulation flow rate is 2 to 5 times the effective volume of the reactor / h. The air-lift action drives the liquid in the reactor to circulate up and down, achieving material mixing.

[0037] In some embodiments, the gas exchange system 6 is used to replenish CO2 into the reactor and discharge excess gas, including a CO2 supply component and an exhaust component.

[0038] The CO2 inlet is located at the junction of the bottom of the light zone 2 and the dark zone 3, using a ring-shaped perforated aeration pipe 61 with a diameter of DN10~DN25. The pipe wall has uniformly distributed 1~2mm aeration micropores with a spacing of 50~100mm. The bubble diameter is ≤3mm, and the gas flow rate is adjustable from 0.1~0.5L / (L·min) (based on the effective volume of the light zone). The CO2 source is industrial-grade CO2 from a cylinder (purity ≥99.5%). The gas supply is automatically adjusted via a mass flow meter and a solenoid valve, providing a carbon source for microalgae photosynthesis and also regulating the pH value within the reactor.

[0039] The exhaust assembly includes an exhaust pipe 62 located at the top of the reactor. A baffle-type gas-liquid separator or a wire mesh demister is installed at the inlet of the exhaust pipe to prevent the mixed liquid from overflowing with the gas. The separated gas is discharged through a pipeline or introduced into the tail gas treatment device, and the liquid phase is returned to the reactor.

[0040] In some embodiments, the water inlet system 7 is located at the bottom of the reactor body 1, and includes an inlet pipe 71 and an annular perforated water distribution pipe 72. The inlet pipe 71 extends from the outside of the reactor into the lower end of the dark area 3 at the bottom of the cylinder, and its end is connected to the annular perforated water distribution pipe 72. The entire water distribution pipe is submerged in the reactor mixture. The annular water distribution pipe has a diameter of DN15~DN25, and water distribution holes of φ4~φ6mm are evenly opened on the pipe, with the holes facing downwards and the hole spacing of 50~100mm. The outflow velocity of the water distribution holes is controlled at 0.5~1.0m / s.

[0041] After the wastewater is pumped in, it is evenly distributed through the bottom distribution pipe. The wastewater flows through the dark zone 3 and the light zone 2 in sequence, with the flow pattern of bottom inlet and top outlet, and dark zone first and then light zone. Finally, it is discharged from the top of the reactor through the outlet pipe 9, ensuring that the wastewater is first degraded by facultative / anaerobic processes and then deeply treated by photosynthetic aerobic processes.

[0042] In some embodiments, the online monitoring and automatic control system includes a pH sensor, a DO sensor, a salinity sensor, a temperature sensor, and a turbidity sensor installed inside the reactor, as well as a PLC control cabinet and actuators. Each sensor collects operating parameters from the reactor in real time and transmits them to the PLC control cabinet. The system, based on preset control thresholds, adjusts the light intensity of the light source system, the stirring speed / gas lift rate of the mixing system, and the CO2 replenishment amount of the gas exchange system to achieve closed-loop automatic control of the system.

[0043] The regulatory rules are as follows: When DO ≤ 2.0 mg / L, increase light intensity by 10%~20%; when DO ≥ 8.0 mg / L, decrease light intensity by 10%~20% or start CO2 supplementation. When pH < 7.0, reduce or stop CO2 injection; when pH > 8.5, start CO2 injection at a rate of 0.1~0.3 L / (L·min). When turbidity > 300 NTU, start sludge removal or microalgae harvesting; when turbidity is below 50 NTU, reduce the influent flow or supplement with bacteria and algae. When the temperature exceeds the range of 25~35℃, the heating or cooling device will be activated, and if the temperature exceeds the limit severely, a shutdown alarm will be triggered.

[0044] The synergistic purification process for treating high-salt, antibiotic-containing aquaculture wastewater using the above-mentioned microalgae-bacteria coupled bioreactor includes the following steps: Step (1) Inoculation and acclimatization of bacteria and algae Screening of algae and bacteria: Salt-tolerant and antibiotic-resistant microalgae and functional bacteria were selected. Microalgae were selected from salt-tolerant Chlorella vulgaris or Spirulina platensis; bacteria were selected from salt-tolerant aerobic denitrifying bacteria Halomonas sp. and antibiotic-degrading bacteria Pseudomonas sp. All of the above strains could be obtained publicly from the China General Microbiological Culture Collection (CGMCC) or the American Type Culture Collection (ATCC).

[0045] Microalgae culture: A modified BG11 medium with high salt content was used. The culture temperature was 25-30℃, the light intensity was 3000-5000 lux, the light-dark cycle was 12h:12h, and the shaking speed was 120-150 rpm. Culture was continued for 7-10 days until the late logarithmic growth phase (OD). 680 (≈1.0~1.5), after centrifugation, the sample was resuspended and washed with sterile artificial seawater for later use.

[0046] Bacterial culture: Salt-tolerant denitrifying bacteria were cultured on high-salt LB medium, while antibiotic-degrading bacteria were cultured on LB medium with the target antibiotic added for targeted acclimatization. The culture temperature was 28–32°C, the shaking speed was 150–180 rpm, and the culture time was 24–48 hours until the logarithmic growth phase (OD200). 600 (≈1.0~1.5), collected by centrifugation and resuspended for later use.

[0047] Inoculation and acclimatization: Microalgae and bacteria were inoculated into the reactor at a dry weight ratio of 1:1 to 3:1 (preferably 2:1). The initial inoculation concentrations were: 5-10 mg / L for microalgae chlorophyll a and 200-500 mg / L for bacteria MLSS. The inoculation sequence was as follows: first, add the microalgae solution, turn on the light and stir for 12-24 hours, and then add the bacterial solution after the microalgae had adapted to the environment.

[0048] After inoculation, salinity acclimatization and antibiotic tolerance acclimatization were carried out sequentially: Salinity acclimatization: A gradual increase in salinity is adopted, with each level increasing by 5‰ and each level lasting 3-5 days, progressively increasing from the initial salinity to the target salinity (35-50‰). Successful acclimatization is determined by stable chlorophyll a content in the microalgae and a specific growth rate ≥ 0.2 days. -1 The bacterial MLSS concentration was stable and the COD degradation rate was ≥50%.

[0049] Antibiotic tolerance acclimatization: This is conducted after salinity acclimatization. The antibiotic concentration is gradually increased from 0.5 mg / L to 2 mg / L and then to 5 mg / L, with each acclimatization cycle lasting 5-7 days. Acclimatization success is determined by: COD removal rate ≥60% and ammonia nitrogen removal rate ≥50% at the target antibiotic concentration, with continuous and stable operation for 7 days without significant fluctuations.

[0050] Step (2) Wastewater pretreatment Pretreatment of high-salt, antibiotic-containing aquaculture wastewater involves the following steps: First, a rotary drum screen or vibrating screen with a gap of 1-3 mm is used to remove large suspended solids such as feed residue and feces. Then, a dilute hydrochloric acid or sodium hydroxide solution is added via an automatic dosing system to adjust the wastewater pH to 7.0-8.5. If the influent salinity is higher than 50‰, it needs to be diluted with fresh water to a suitable range of 35-40‰. The pretreated wastewater is temporarily stored in an equalization tank and then pumped into the reactor.

[0051] Step (3) Inlet water treatment Pretreated wastewater is fed into the reactor through the inlet system at the bottom. The wastewater flows from bottom to top, first entering the dark zone and passing through the packing layer for anaerobic / facultative reactions. It then flows upward into the light zone, where it undergoes photosynthetic aerobic reactions under illumination. Finally, the treated wastewater overflows from the top of the reactor. The system reflux ratio is controlled at 50%–100%, and the hydraulic retention time (HRT) is adjusted to 24–72 hours based on the influent water quality.

[0052] Step (4) Photosynthetic oxygen production and pollutant degradation During the process of wastewater flowing through the reactor, the synergistic degradation of multiple pollutants occurs simultaneously: Within the light zone, microalgae utilize light and supplemented CO2 for photosynthesis, absorbing nitrogen and phosphorus nutrients from wastewater for their own growth, while releasing oxygen; aerobic bacteria utilize the oxygen produced by microalgae photosynthesis to degrade organic matter in wastewater and decompose antibiotic pollutants through enzymatic reactions. Within the dark zone, facultative / anaerobic bacteria use organic matter in the wastewater as electron donors to carry out denitrification, reducing nitrate nitrogen to nitrogen gas; at the same time, anaerobic bacteria can further degrade recalcitrant antibiotic intermediates through cometabolism.

[0053] Microalgae and bacteria form a metabolic complementarity: microalgae produce oxygen for aerobic bacteria to use, and the CO2 produced by bacterial metabolism can serve as a carbon source for microalgae. The two work together to achieve the simultaneous removal of carbon, nitrogen, phosphorus and antibiotics.

[0054] Step (5) Online control The reactor's pH, DO, salinity, temperature, and turbidity are collected in real time by an online monitoring system. The control system then adjusts the light intensity, stirring speed, and CO2 supply according to preset thresholds to maintain the metabolic activity of bacteria and algae and the stability of the system. Simultaneously, COD, ammonia nitrogen, total phosphorus, antibiotic concentrations, and bacterial and algal biomass are periodically monitored offline. The hydraulic retention time, influent flow rate, and sludge discharge cycle are dynamically adjusted to maintain the bacterial-algae biomass ratio (chlorophyll a / MLSS) within the optimal range of 0.3–0.8 mg / g.

[0055] Step (6) Sludge-water separation and effluent treatment The reactor effluent first enters the inclined plate sedimentation zone at the top for sludge-water separation. Part of the settled sludge is returned to the reaction zone, while the remaining sludge is periodically discharged through the bottom sludge discharge pipe. The supernatant after sedimentation is then filtered sequentially through quartz sand filtration and bag filtration to remove residual suspended solids, and finally disinfected with ultraviolet light (irradiation dose ≥40 mJ / cm³). 2 After a contact time of ≥10s, the waste is discharged in compliance with standards or reused in the aquaculture process.

[0056] The system has a sludge removal cycle of 5 to 10 days per cycle, with a single sludge removal volume accounting for 10% to 20% of the effective reactor volume; the microalgae harvesting cycle is 7 to 14 days per cycle, with a harvesting ratio of 20% to 30% of the microalgae biomass in the light zone, and the harvested microalgae can be recycled as biomass resources.

[0057] Specific embodiments and comparative examples Example 1: Low-salt, low-antibiotic operating conditions A column reactor with an effective volume of 10L is used, with a light zone height of 600mm and a dark zone height of 400mm, resulting in a light-to-dark effective volume ratio of 1.5:1. The dark zone is filled with polypropylene multifaceted hollow sphere packing material, with a filling rate of 30%. The light source consists of four external LED red and blue light panels with a red-to-blue light ratio of 4:1, and the light panels are 80mm away from the reactor wall. The mixing system uses mechanical stirring, with the stirring paddle diameter being 1 / 3 of the reactor's inner diameter and a rotation speed of 30rpm. CO2 supplementation is achieved using an annular perforated aeration pipe with an adjustable flow rate range of 0.1~0.3L / (L·min).

[0058] The system was inoculated with salt-tolerant Chlorella, Halomonas, and Pseudomonas schrenckii at a dry weight ratio of 2:1. After acclimatization, the system adapted to water conditions with a salinity of 20‰ and sulfadiazine concentration of 1 mg / L.

[0059] Influent water quality: COD 800 mg / L, NH4 + -N 80mg / L, TP 15mg / L, salinity 20‰, sulfadiazine 1mg / L.

[0060] Operating parameters: HRT 36h, light intensity 3000 lux, light-dark cycle 16h:8h, temperature 28℃, stirring speed 30 rpm.

[0061] After 60 days of continuous operation, the effluent quality remained stable: COD 80 mg / L (removal rate 90%), NH4 + -N 8 mg / L (removal rate 90%), TP 1.5 mg / L (removal rate 90%), sulfadiazine 0.05 mg / L (removal rate 95%), effluent quality fluctuation ≤ ±10%, unit water treatment energy consumption 0.45 kWh / m³ 3 .

[0062] Example 2: High-salt, high-antibiotic working conditions The reactor structure is the same as in Example 1.

[0063] Influent water quality: COD 1500 mg / L, NH4 + -N 150mg / L, TP 30mg / L, salinity 35‰, sulfadiazine 5mg / L.

[0064] Operating parameters: HRT 60h, light intensity 6000 lux, light-dark cycle 18h:6h, temperature 30℃, stirring speed 40 rpm.

[0065] After 45 days of continuous operation, the effluent quality was: COD 180 mg / L (removal rate 88%), NH4 + -N 18mg / L (removal rate 88%), TP 3.6mg / L (removal rate 88%), sulfadiazine 0.15mg / L (removal rate 97%), effluent water quality fluctuation ≤±15%.

[0066] Example 3: Impact Load Condition Based on the stable operation in Example 2, on the 30th day, the concentration of sulfadiazine in the influent was instantaneously increased to 10 mg / L and maintained for 24 hours to simulate an antibiotic shock load. After the shock occurred, the system automatically reduced the influent flow rate to 50% of the original design, added sodium acetate to supplement the carbon source (based on C / N=5), and maintained operation with light and stirring.

[0067] The system recovered to normal removal levels within 48 hours, and the sulfadiazine removal rate rebounded from an instantaneous 72% to over 90%, verifying that the system has good resistance to shock loads and self-recovery capabilities.

[0068] Comparative Example 1: Single Microalgae Treatment System A reactor of the same specifications was used, but only salt-tolerant Chlorella was inoculated, without functional bacteria. The other operating conditions were the same as in Example 1.

[0069] Results: COD removal rate 40%, NH4 + -N removal rate 55%, TP removal rate 70%, sulfadiazine removal rate 35%, continuous stable operation days ≤20 days, unit energy consumption 0.30kWh / m³ 3 .

[0070] Comparative Example 2: Single Bacterial Treatment System Using a reactor of the same specifications, the light source was turned off, and only Halomonas and Pseudomonas were inoculated. External aeration was used to supply oxygen, and the other influent conditions were the same as in Example 1.

[0071] Results: COD removal rate 55%, NH4 removal rate 55%. +-N removal rate 60%, TP removal rate 25%, sulfadiazine removal rate 60%, continuous stable operation days ≤15 days, unit energy consumption 0.80kWh / m³ 3 .

[0072] Comparative Example 3: Conventional algae and bacteria reactor without light and dark partitions The reactor of the same specifications was used, and light sources were provided throughout the entire section with no dark areas. The inoculation and operation conditions for bacteria and algae were the same as in Example 1.

[0073] Results: COD removal rate 65%, NH4 removal rate 65%. + -N removal rate 70%, TP removal rate 65%, sulfadiazine removal rate 70%, continuous stable operation days ≤30 days, unit energy consumption 0.60kWh / m³ 3 .

[0074] As can be seen from the above embodiments and comparative examples, the present invention, through a reactor structure with light and dark partitioning, a salt-tolerant and antibacterial algae coupling system, and a synergistic control process, can achieve efficient and stable treatment of high-salt and antibiotic-containing aquaculture wastewater. The pollutant removal rate, operational stability, and energy consumption indicators are all significantly better than those of the comparative system.

[0075] Based on the description and accompanying drawings of this invention, those skilled in the art can readily manufacture or use the microalgae-bacteria coupled bioreactor and synergistic purification process for treating high-salt, antibiotic-containing aquaculture wastewater, and can achieve the positive effects described in this invention.

[0076] Unless otherwise specified, in this invention, terms such as "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe orientation or positional relationships in this invention are for illustrative purposes only and should not be construed as limiting this invention. For those skilled in the art, the specific meaning of the above terms can be understood in conjunction with the accompanying drawings and according to the specific circumstances.

[0077] Unless otherwise explicitly specified and limited, the terms "set up," "connected," and "linked" in this invention should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0078] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A microalgae-bacteria coupled bioreactor for treating high-salt, antibiotic-containing aquaculture wastewater, characterized in that, include: The reactor body has a light zone and a dark zone arranged vertically from top to bottom. The light zone is a light-transmitting structure, and the dark zone is a weak light or no light environment. The light zone is used for photosynthetic oxygen production by microalgae, and the dark zone is used for facultative / anaerobic metabolism of bacteria. A light source system is located outside the reactor body at a position corresponding to the light zone, and is used to provide the light zone with the light required for photosynthesis; A mixing system, located between the light zone and the dark zone, is used to achieve mixing and circulation of materials within the reactor; A gas exchange system is used to replenish CO2 into the reactor and remove excess gas. The inlet system is located at the bottom of the reactor body and is used to allow wastewater to flow in a bottom-in, top-out, dark-first-light flow pattern through the dark zone and the light zone, and then be discharged from the top of the reactor body. In addition, an online monitoring and automatic control system is used to monitor the reactor's operating parameters in real time and to coordinate and control the light source system, mixing system, and gas exchange system.

2. The microalgae-bacteria coupled bioreactor according to claim 1, characterized in that, The effective volume ratio of the light area to the dark area is (1.2~1.5):1; And / or, the dark area is filled with suspended biological packing material, which is selected from Pall rings or multifaceted hollow spheres made of polyethylene or polypropylene, and the filling rate is 25% to 35% of the effective volume of the dark area.

3. The microalgae-bacteria coupled bioreactor according to claim 1, characterized in that, The light source system uses an external LED light panel, which is arranged in a longitudinal array along the outer wall of the reactor body corresponding to the light area. The distance between the LED light panel and the outer wall of the reactor body is 50~100mm.

4. The microalgae-bacteria coupled bioreactor according to claim 1, characterized in that, The mixing system includes a stirrer, the blade diameter of which is 1 / 3 to 1 / 2 of the inner diameter of the reactor, and is installed at the junction of the light zone and the dark zone, with a rotation speed range of 20 to 60 rpm; And / or, the mixing system includes an air-lift circulation device, wherein the riser of the air-lift circulation device is located at the center of the reactor body, and compressed air is introduced from the bottom of the riser at a velocity of 0.5~1.5 L / (L·min), and the circulation flow rate is 2~5 times the effective volume of the reactor / h.

5. The microalgae-bacteria coupled bioreactor according to claim 1, characterized in that, The CO2 supply port of the gas exchange system is located at the junction of the bottom of the light zone and the dark zone, and adopts an annular perforated aeration pipe with a gas flow rate adjustment range of 0.1~0.5L / (L·min).

6. The microalgae-bacteria coupled bioreactor according to claim 1, characterized in that, The water inlet system includes an inlet pipe and an annular perforated water distribution pipe. The inlet pipe extends into the lower end of the dark area at the bottom of the reactor body and is connected to the annular perforated water distribution pipe.

7. The microalgae-bacteria coupled bioreactor according to claim 1, characterized in that, The reactor body is equipped with an inclined plate sedimentation zone, an exhaust pipe, and a drain pipe at the top, with the inclined plate sedimentation zone located below the effluent weir; the reactor body is equipped with a sludge discharge pipe at the bottom.

8. The microalgae-bacteria coupled bioreactor according to claim 1, characterized in that, The online monitoring and automatic control system includes a pH sensor, a DO sensor, a salinity sensor, a temperature sensor, and a turbidity sensor. The online monitoring and automatic control system automatically adjusts the light intensity, stirring speed, and CO2 supply based on the feedback signals from each sensor.

9. A synergistic purification process using the microalgae-bacteria coupled bioreactor as described in any one of claims 1-8, characterized in that, Includes the following steps: (1) Inoculation and acclimatization of bacteria and algae: Salt-tolerant and antibiotic-resistant microalgae and bacteria are inoculated into the reactor for salinity acclimatization and antibiotic tolerance acclimatization. (2) Wastewater pretreatment: High-salt aquaculture wastewater containing antibiotics is filtered to remove large particulate suspended solids and the pH is adjusted to 7.0~8.5; (3) Inlet water treatment: The pretreated wastewater is fed into the reactor from the bottom. The wastewater flows through the dark zone and the light zone in sequence, with the wastewater entering from the bottom and exiting from the top, and flowing through the dark zone first and then the light zone. (4) Photosynthetic oxygen production and pollutant degradation: Microalgae use light and CO2 to perform photosynthesis in the light zone to produce O2 and absorb nitrogen and phosphorus nutrients. Aerobic bacteria use the O2 produced by microalgae to degrade organic matter and antibiotics. Facultative / anaerobic bacteria carry out denitrification in the dark zone. (5) Online control: The operating parameters in the reactor are monitored in real time through the online monitoring system, and the light intensity, stirring speed and CO2 supply are controlled in conjunction to maintain the metabolic activity of bacteria and algae and the stability of the system. (6) Sludge-water separation and effluent treatment: The reactor effluent is discharged or reused after sedimentation, filtration and disinfection.

10. The synergistic purification process according to claim 9, characterized in that, In step (1), the microalgae are selected from salt-tolerant Chlorella or Spirulina, and the bacteria are selected from salt-tolerant aerobic denitrifying bacteria Haloxylon ammodendron and antibiotic-degrading bacteria Pseudomonas aeruginosa; the inoculation mass ratio of microalgae to bacteria is 1:1 to 3:1 on a dry weight basis.

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