A method for treating antibiotic-containing aquaculture effluent using granular cyanobacterial sludge

Abstract

The application discloses a method for treating antibiotic-containing aquaculture tail water by using bacteria-algae granular sludge, which comprises the following steps: (1) bacteria-algae granular sludge domestication stage; (2) antibiotic-free exposure test stage; (3) low-concentration antibiotic exposure test stage; (4) high-concentration antibiotic exposure test stage; and (5) antibiotic exposure recovery test stage. By inoculating scenedesmus and aerobic granular sludge to form a symbiotic system, the application realizes low-energy-consumption operation, strengthens antibiotic degradation path by using algal photosynthesis to supply oxygen and bacterial metabolism to produce carbon source, and promotes simultaneous removal of nitrite nitrogen and antibiotics by combining with a reflux device. The application solves the problems of low concentration of nutrients in traditional aquaculture tail water, antibiotic residue inhibiting microbial activity, high concentration of nitrite in effluent water and low antibiotic removal efficiency, and is suitable for efficient treatment of antibiotic-containing aquaculture tail water.

Description

Technical Field

[0001] This invention relates to the field of wastewater biological treatment technology, and in particular to a method for treating antibiotic-containing aquaculture wastewater using bacterial and algal granular sludge. Background Technology

[0002] Aquaculture wastewater often contains residual antibiotics (such as doxycycline hydrochloride and oxytetracycline) and high concentrations of nitrite nitrogen. Traditional biological treatment technologies have two major problems: first, antibiotics inhibit microbial activity, resulting in a significant decrease in nutrient removal efficiency; second, antibiotics are difficult to degrade by conventional microorganisms and are easily accumulated through the food chain.

[0003] While existing microalgae treatment technologies can reduce energy consumption, they lack targeted antibiotic degradation mechanisms and the functional bacterial communities have insufficient synergistic removal capabilities for pollutants.

[0004] Chinese patent CN220449939U discloses a treatment tank for treating aquaculture wastewater using microalgae. In its microalgae reaction component system, the growth and metabolism of microalgae are relatively slow, requiring a long hydraulic retention time (HRT), making it difficult to meet the needs of large-scale rapid treatment. In contrast, conventional activated sludge systems have high nitrite nitrogen concentrations in the effluent due to the inhibitory effect of antibiotics, and the antibiotic residue rate is as high as 50% or more.

[0005] Therefore, providing a method that can tolerate antibiotics and simultaneously and efficiently remove nitrite nitrogen and degrade antibiotics with low energy consumption, and which is of great significance for ensuring the compliance of aquaculture wastewater discharge, is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] In view of this, the present invention provides a method for treating antibiotic-containing aquaculture wastewater using bacterial and algal granular sludge, in order to solve the problems of antibiotics inhibiting microbial activity and low efficiency in removing nutrients and antibiotics.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] A method for treating antibiotic-containing aquaculture wastewater using granular sludge made from bacteria and algae includes the following steps:

[0009] (1) Accommodation stage of bacterial and algal granular sludge: Aerobic granular sludge is inoculated into the reactor, the sludge concentration is controlled, and after the operation is stable, the inoculation solution of Scenedesmus is added. The reactor is exposed to light from the top light source for 28 days to form bacterial and algal symbiotic sludge. Artificial simulated aquaculture tailwater is added into the reactor, and sludge is discharged daily to control the sludge age to 14 days.

[0010] (2) Antibiotic-free exposure test stage: Based on the above step (1), mature algae-bacterial symbiotic aerobic granular sludge is placed in the SBR reactor. The reactor is operated in the mode of the above step (1) for 28 days to allow the algae-bacterial symbiotic aerobic granular sludge to adapt to the new reactor and environment. The effluent index is tested every 3 days and the sludge index is tested every week until the nutrient removal rate and sludge index of the reactor remain stable before proceeding to the next stage.

[0011] (3) Low concentration antibiotic exposure experiment stage: Based on the above step (2), add low concentration antibiotics to the reactor and run the reactor in the mode of the above step (1) for 42 days to allow the aerobic granular sludge of bacterial-algae symbiosis to adapt to the sudden disturbance environment of antibiotics. Detect the effluent index every 3 days and the sludge index every week until the nutrient removal rate and sludge index of the reactor remain stable and then proceed to the next stage.

[0012] (4) High concentration antibiotic exposure experiment stage: Based on the above step (3), add high concentration antibiotics and run the reactor in the mode of the above step (1) for 42 days to allow the aerobic granular sludge of bacterial-algae symbiosis to adapt to the sudden disturbance environment of antibiotics. Detect the effluent index every 3 days and the sludge index every week until the nutrient removal rate and sludge index of the reactor remain stable and then proceed to the next stage.

[0013] (5) Antibiotic exposure recovery experiment stage: Based on the above step (4), stop adding antibiotics to test whether the damage of antibiotics to the aerobic granular sludge exposure experiment of bacterial-algae symbiosis can be recovered. The reactor is operated in the mode described in step (1) for 28 days, and the effluent index is tested every 3 days and the sludge index is tested every week until the nutrient removal rate and sludge index of the reactor remain stable.

[0014] Preferably, in step (1), the sludge concentration is controlled at 4500 mg / L, the concentration of the added Scenedesmus inoculum is 5000-7000 mg / L, and the ratio is 1:400-1:600; before addition, the Scenedesmus needs to be acclimated in the effluent containing 50-100 μg / L of antibiotics for 14 days, during which the DO is controlled at <0.2 mg / L in the anaerobic stage and DO = 8 mg / L in the aerobic stage. The reactor is subjected to 24h light intensity of 6000 lm for 28 days to form a symbiotic sludge of bacteria and algae.

[0015] Preferably, in step (1), during the entire 28-day operation period, the reactor operates according to a set cycle every day. The operation process of each cycle includes water inlet, anaerobic, aerobic, settling and drainage. Artificial simulated aquaculture tailwater is added to the reactor, and 1 / 14 of the sludge is discharged daily to control the sludge age to 14 days.

[0016] Preferably, the reactor operates in the following mode according to a set cycle each day: one hydraulic retention cycle is 6 hours, and the reactor operates for 4 cycles per day; one cycle includes five stages: 3 minutes of influent, 90 minutes of anaerobic reaction, 260 minutes of aerobic reaction, 4 minutes of settling, and 3 minutes of effluent discharge; synthetic wastewater is added for aeration, and the dissolved oxygen range during the aeration stage is controlled at 8 mg / L; the temperature is maintained at 25±1℃ and the pH is maintained at 7.5-8.5 throughout the entire operation.

[0017] Preferably, the synthetic wastewater contains a nitrogen source, a phosphorus source, a carbon source, magnesium chloride, ferrous sulfate, CaCl2, and NaHCO3; wherein the nitrogen source is provided by ammonium chloride, the phosphorus source by KH2PO4, the carbon source by sodium acetate, NaHCO3 is used to buffer the pH of the reactor, and CaCl2, ferrous sulfate, and magnesium chloride are required to maintain the particle structure and microbial growth; the initial concentration of nitrogen source in the wastewater is 20 mg / L, the initial concentration of phosphorus source is 2 mg / L, the initial concentration of COD is 140 mg / L, the initial concentration of NaHCO3 is 100 mg / L, the initial concentration of Mg is 2 mg / L, the initial concentration of Fe is 2 mg / L, and the initial concentration of Ca is 4 mg / L; the pH of the wastewater is adjusted to about 7.5 using NaHCO3.

[0018] Preferably, in step (1), the trace element composition and content of the simulated aquaculture wastewater are as follows: Na2EDTA 4.29 g / L, FeCl2·4H2O 1.99 g / L, MnCl2·2H2O 0.08 g / L, NiCl2·6H2O 0.02 g / L, CoCl2·6H2O 0.02 g / L, CuCl2·H2O 0.02 g / L, ZnCl2 0.02 g / L, NaMoO4·2H2O 0.02 g / L, Na2WO4·2H2O 0.03 g / L, and H3BO3 0.06 g / L.

[0019] Preferably, in step (1), the light is provided in a 24-hour continuous light mode, which aims to accelerate the formation and growth of bacterial and algal granular sludge; in steps (2)-(5), the light and dark alternation cycle strategy is adopted, which specifically means that the continuous light time is 12 hours per day and the continuous dark time is 12 hours per day, that is, the light-dark ratio is 12:12 and the light intensity is 6000lm, so as to simulate the day-night cycle in the natural environment.

[0020] Preferably, in steps (1)-(5), the reactor is an SBR bioreactor. The aerobic granular sludge with algae symbiosis in the reactor is mainly composed of Scenedesmus and bacteria in the granular sludge. The algae grow on the outside of the granular sludge, wrapping the granular sludge. The inside of the granular sludge is bacteria. The functional bacteria in the reactor are denitrification and phosphorus removal bacteria. The reactor uses a peristaltic pump to control the inlet and outlet water, with water entering from the bottom and exiting from the middle. The exchange volume is 50%. The inlet water system includes an inlet pipe, an inlet tank, and an inlet water pump. The outlet water system includes an outlet water pipe, an outlet tank, and an outlet water pump. The inlet tank and the reactor body are connected by the inlet water pipe. The inlet water valve and the inlet water pump are located on the inlet water pipe. The reactor body and the outlet tank are connected by the outlet water pipe. The outlet water pump is located on the outlet water pipe. Both the inlet water system and the outlet water system are equipped with sampling valves and sampling pipes. The reactor body is made of acrylic. The inlet water pump and the outlet water pump are peristaltic pumps.

[0021] Preferably, in steps (2)-(5), the MLSS of the aerobic granular sludge with bacterial-algae symbiosis in the reaction system is 2.8-4.2 g / L, the MLVSS / MLSS is 0.72-0.83, and the mass ratio of C:N:P is 70:10:1.

[0022] Preferably, in steps (3)-(4), the added contaminant is doxycycline hydrochloride; in step (3), a low concentration of 1 mg / L antibiotic is added; in step (4), a high concentration of 10 mg / L antibiotic is added; in step (3), the concentration of doxycycline hydrochloride added is 1 mg / L, and the reactor is run for 42 days; in step (4), the concentration of doxycycline hydrochloride added is 10 mg / L, and the reactor is run for 42 days; wherein, the antibiotic is not limited to doxycycline hydrochloride.

[0023] The present invention achieves the following technical effects compared to the prior art:

[0024] (1) The method of the present invention can realize the start-up and stable operation of the aerobic granular sludge system with bacterial and algal symbiosis suitable for aquaculture tailwater containing antibiotics, and at the same time realize the stable removal of antibiotics and the simultaneous removal of nutrients.

[0025] (2) The present invention first uses antibiotic stress with appropriate concentration gradient to drive the aerobic granular sludge of bacteria and algae symbiosis to generate stress memory, so that it can adapt to the aquaculture tailwater containing antibiotics. This avoids the irreversible damage of high concentration antibiotics to aerobic granular sludge of bacteria and algae symbiosis and improves the tolerance of aerobic granular sludge of bacteria and algae symbiosis to antibiotics.

[0026] (3) This invention provides a new way for the system to remove nitrogen and phosphorus through the synergistic effect between algae and bacteria. At the same time, the aerobic granular sludge of algae-bacteria symbiosis has a significant improvement in the removal of nitrite nitrogen. Algae use photosynthesis to supply oxygen to the granular sludge, which can reduce energy consumption. The aerobic granular sludge of algae-bacteria symbiosis has excellent settling performance, strong resistance to shock load, and will not cause sludge bulking when stimulated by antibiotics.

[0027] (4) Compared with the traditional multi-stage coupled denitrification process for municipal wastewater, the bacterial-algae symbiotic granular denitrification system of the present invention has significant engineering application prospects and is a new method for treating antibiotic-containing aquaculture wastewater with low energy consumption, high efficiency and stability.

[0028] (5) This invention optimizes the efficiency of nutrient removal and improves the overall stability of the system through the synergistic effect of antibiotic concentration gradient stress and aerobic granular sludge with bacterial-algae symbiosis. It has significant innovation and practical application value. Attached Figure Description

[0029] Figure 1 This is a diagram of the operating apparatus of the SBR reactor of the present invention;

[0030] Figure 2 This is a graph showing the changes in COD, ammonia nitrogen, and phosphorus concentrations during the operation of the bacterial and algal granular sludge system in the SBR reactor of this invention.

[0031] The components include: external water distribution tank 1, inlet peristaltic pump 2, inlet 3, outlet 4, outlet peristaltic pump 5, external outlet tank 6, reactor body 7, aeration head 8, gas flow meter 9, and aeration pump 10. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] This invention discloses a method for treating antibiotic-containing aquaculture wastewater using bacterial and algal granular sludge, comprising the following steps:

[0034] (1) Accommodation stage of bacterial and algal granular sludge: Aerobic granular sludge is inoculated into the reactor, the sludge concentration is controlled, and after the operation is stable, the inoculation solution of Scenedesmus is added. The reactor is exposed to light from the top light source for 28 days to form bacterial and algal symbiotic sludge. Artificial simulated aquaculture tailwater is added into the reactor, and sludge is discharged daily to control the sludge age to 14 days.

[0035] (2) Antibiotic-free exposure test stage: Based on the above step (1), mature algae-bacterial symbiotic aerobic granular sludge is placed in the SBR reactor. The reactor is operated in the mode of the above step (1) for 28 days to allow the algae-bacterial symbiotic aerobic granular sludge to adapt to the new reactor and environment. The effluent index is tested every 3 days and the sludge index is tested every week until the nutrient removal rate and sludge index of the reactor remain stable before proceeding to the next stage.

[0036] (3) Low concentration antibiotic exposure experiment stage: Based on the above step (2), add low concentration antibiotics to the reactor and run the reactor in the mode of the above step (1) for 42 days to allow the aerobic granular sludge of bacterial-algae symbiosis to adapt to the sudden disturbance environment of antibiotics. Detect the effluent index every 3 days and the sludge index every week until the nutrient removal rate and sludge index of the reactor remain stable and then proceed to the next stage.

[0037] (4) High concentration antibiotic exposure experiment stage: Based on the above step (3), add high concentration antibiotics and run the reactor in the mode of the above step (1) for 42 days to allow the aerobic granular sludge of bacterial-algae symbiosis to adapt to the sudden disturbance environment of antibiotics. Detect the effluent index every 3 days and the sludge index every week until the nutrient removal rate and sludge index of the reactor remain stable and then proceed to the next stage.

[0038] (5) Antibiotic exposure recovery experiment stage: Based on the above step (4), stop adding antibiotics to test whether the damage of antibiotics to the aerobic granular sludge exposure experiment of bacterial-algae symbiosis can be recovered. The reactor is operated in the mode described in step (1) for 28 days, and the effluent index is tested every 3 days and the sludge index is tested every week until the nutrient removal rate and sludge index of the reactor remain stable.

[0039] In step (1), the sludge concentration is controlled at 4500 mg / L, and the concentration of the added Scenedesmus inoculum is 5000-7000 mg / L, with a ratio of 1:400-1:600. Before addition, the Scenedesmus needs to be acclimated in the effluent containing 50-100 μg / L of antibiotics for 14 days. During this period, the DO is controlled to be <0.2 mg / L in the anaerobic stage and DO = 8 mg / L in the aerobic stage. The reactor is subjected to a top light source for 24 hours of light cultivation at an intensity of 6000 lm for 28 days to form a symbiotic sludge of bacteria and algae.

[0040] In step (1), during the entire 28-day operation phase, the reactor operates according to the set cycle every day. The operation process of each cycle includes water inlet, anaerobic, aerobic, settling and drainage. Artificial simulated aquaculture tailwater is added to the reactor, and 1 / 14 of the sludge is discharged daily to control the sludge age to 14 days.

[0041] The reactor operates daily according to the following mode based on a set cycle: one hydraulic retention cycle is 6 hours, and the reactor operates for 4 cycles per day; one cycle includes five stages: 3 minutes of influent, 90 minutes of anaerobic reaction, 260 minutes of aerobic reaction, 4 minutes of settling, and 3 minutes of effluent discharge; synthetic wastewater is added for aeration, and the dissolved oxygen level is controlled within the range of 8 mg / L during the aeration stage; the temperature is maintained at 25±1℃ and the pH is maintained at 7.5-8.5 throughout the entire operation.

[0042] The synthetic wastewater contains nitrogen, phosphorus, carbon, magnesium chloride, ferrous sulfate, CaCl2, and NaHCO3. The nitrogen source is provided by ammonium chloride, the phosphorus source by KH2PO4, and the carbon source by sodium acetate. NaHCO3 is used to buffer the reactor pH. CaCl2, ferrous sulfate, and magnesium chloride are necessary to maintain particle structure and support microbial growth. The initial concentrations of nitrogen, phosphorus, COD, NaHCO3, Mg, Fe, and Ca in the wastewater are 20 mg / L, 2 mg / L, 140 mg / L, 100 mg / L, 2 mg / L, 4 mg / L, and NaHCO3 is used to adjust the pH of the wastewater to approximately 7.5.

[0043] In step (1), the trace element composition and content of the simulated aquaculture wastewater are as follows: Na2EDTA 4.29g / L, FeCl2·4H2O 1.99g / L, MnCl2·2H2O 0.08g / L, NiCl2·6H2O 0.02g / L, CoCl2·6H2O 0.02g / L, CuCl2·H2O 0.02g / L, ZnCl2 0.02g / L, NaMoO4·2H2O 0.02g / L, Na2WO4·2H2O 0.03g / L, and H3BO3 0.06g / L.

[0044] In step (1), the light is provided in a 24-hour continuous light mode, which aims to accelerate the formation and growth of bacterial and algal granular sludge. In steps (2)-(5), the light and dark alternation cycle strategy is adopted, which specifically means that the continuous light time is 12 hours and the continuous dark time is 12 hours per day, that is, the light-dark ratio is 12:12 and the light intensity is 6000lm. This alternation cycle is used to simulate the day-night cycle in the natural environment.

[0045] In steps (1)-(5), the reactor is an SBR bioreactor. The aerobic granular sludge with algae symbiosis in the reactor is mainly composed of Scenedesmus and bacteria in the granular sludge. The algae grow on the outside of the granular sludge and wrap around it. The inside of the granular sludge is bacteria. The functional bacteria in the reactor are denitrification and phosphorus removal bacteria. The reactor uses a peristaltic pump to control the inlet and outlet water, with water entering from the bottom and exiting from the middle. The exchange volume is 50%. The inlet water system includes an inlet pipe, an inlet tank, and an inlet pump. The outlet water system includes an outlet pipe, an outlet tank, and an outlet pump. The inlet tank and the reactor body are connected by the inlet pipe. The inlet valve and the inlet pump are located on the inlet pipe. The reactor body and the outlet tank are connected by the outlet pipe. The outlet pump is located on the outlet pipe. Both the inlet water system and the outlet water system are equipped with sampling valves and sampling pipes. The reactor body is made of acrylic. The inlet pump and the outlet pump are peristaltic pumps.

[0046] In steps (2)-(5), the MLSS of the aerobic granular sludge with bacterial-algae symbiosis in the reaction system is 2.8-4.2 g / L, the MLVSS / MLSS is 0.72-0.83, and the mass ratio of C:N:P is 70:10:1.

[0047] In steps (3)-(4), the added contaminant is doxycycline hydrochloride. In step (3), a low concentration of 1 mg / L antibiotic is added, and in step (4), a high concentration of 10 mg / L antibiotic is added. In step (3), the concentration of doxycycline hydrochloride added is 1 mg / L, and the reactor is run for 42 days. In step (4), the concentration of doxycycline hydrochloride added is 10 mg / L, and the reactor is run for 42 days. The antibiotic is not limited to doxycycline hydrochloride.

[0048] The above-mentioned method for treating antibiotic-containing aquaculture wastewater using aerobic granular sludge with symbiotic bacteria and algae shows that the granular sludge's performance is almost unaffected under 1 mg / L doxycycline hydrochloride stress, achieving a COD removal rate of approximately 92%, an ammonia nitrogen and nitrite nitrogen removal rate of approximately 99%, a total phosphorus removal rate of approximately 75%, and an antibiotic removal rate of approximately 99%.

[0049] like Figure 1 As shown, the method of treating antibiotic-containing aquaculture wastewater using aerobic granular sludge with bacterial-algae symbiosis of the present invention uses an SBR reactor as the main body of the reactor with a working volume of 500 ml. A microporous aeration head is placed at the bottom of the SBR reactor for aeration. The MLSS concentration of the inoculated bacterial-algae granular sludge is maintained at 3500 mg / L, and the exchange volume is 50%.

[0050] The reactor body includes an inlet 3 and an outlet 4. The inlet 3 of the reactor body 7 is connected to the external water distribution tank 1 through an inlet peristaltic pump 2. The outlet 4 of the reactor body 7 is connected to the external outlet tank 6 through an outlet peristaltic pump 5. Aeration of the reactor body 7 is achieved by an aeration pump 10, which is controlled by a gas flow meter 9 and released through an aeration head 8 at the bottom of the reactor body 7.

[0051] The hydraulic retention time is 6 hours per cycle, the SBR reactor exchange volume is 50%, and it runs for 4 cycles per day. One cycle includes five stages: 3 minutes of influent, 90 minutes of anaerobic reaction, 260 minutes of aerobic reaction, 4 minutes of settling, and 3 minutes of effluent discharge. During the entire operation, the temperature is maintained at 25±1℃ and the pH is maintained at around 7.5.

[0052] Example 1:

[0053] The influent to the SBR reactor has an ammonia nitrogen concentration of 20 mg / L, an influent COD concentration of 140 mg / L, a total phosphorus concentration of 2 mg / L, and a nitrite nitrogen concentration of 14 mg / L. In addition, the influent to the reactor also contains other elements, including 2 mg-Mg / L, 2 mg-Fe / L, 4 mg-Ca / L, and sodium bicarbonate of 1.5 g / L.

[0054] The concentrations of trace elements are as follows: Na₂EDTA 4.29 g / L, FeCl₂·4H₂O 1.99 g / L, MnCl₂·2H₂O 0.08 g / L, NiCl₂·6H₂O 0.02 g / L, CoCl₂·6H₂O 0.02 g / L, CuCl₂·H₂O 0.02 g / L, ZnCl₂ 0.02 g / L, NaMoO₄·2H₂O 0.02 g / L, Na₂WO₄·2H₂O 0.03 g / L, H₃BO₃ 0.06 g / L. After weighing, the trace elements are dissolved in 1 L of deionized water to make a concentration of 1 ml / L.

[0055] 500 mL of bacterial and algal granular sludge was inoculated into the SBR reactor. The initial mixed liquor suspended solids (MLSS) concentration of the inoculated sludge was 3500 mg / L, the temperature was controlled at 25±1℃, the dissolved oxygen (DO) was 8 mg / L, and the pH was maintained at 7.5.

[0056] Synthetic wastewater was added for aeration. The effluent quality indicators of the reactor were tested every three days, and the sludge indicators in the reactor were tested every seven days. The granular sludge was taken from a laboratory of a university in Nanjing.

[0057] After the SBR reactor has been running stably for more than 4 weeks, synthetic wastewater with 1 mg / L antibiotic was added and the reactor was run for 42 days. The specific efficiency of the entire reactor process is as follows: Figure 2 As shown.

[0058] The final reactor maintained the concentrations of ammonia nitrogen and nitrite nitrogen in the effluent below 0.1 mg / L, with a removal rate of 100% for both. The COD removal rate remained at around 92% without significant fluctuations. The total phosphorus removal rate initially decreased after antibiotic stress, then increased, and finally stabilized at around 75%, making it suitable for establishing a high-efficiency treatment system for aquaculture wastewater containing antibiotics.

[0059] After the low-concentration exposure test phase, the operating conditions of the sequencing batch reactor remained unchanged, and the SBR reactor was operated for 42 days with synthetic wastewater containing a high concentration (10 mg / L) of antibiotics.

[0060] The final ammonia nitrogen concentration in the effluent from the reactor was maintained below 1 mg / L, with an ammonia nitrogen removal rate of 100%. The nitrite nitrogen in the effluent decreased from the initial 14 mg / L to about 0.2 mg / L. The TP removal rate stabilized at over 75% after the antibiotic cyclic gradient stress strategy, making it suitable for treating aquaculture wastewater containing antibiotics.

[0061] As can be seen from the figure, compared with the changes in the system diagram without antibiotic addition, in the bacterial and algae granular sludge system, the removal rate of both is 100% under both low and high concentrations, demonstrating good denitrification capabilities.

[0062] As can be seen from the embodiments, the method of the present invention can obtain an efficient denitrification system for aerobic granular sludge suitable for antibiotic-containing aquaculture tailwater. It solves the technical bottleneck of over-reliance on the coupling and superposition of multiple wastewater treatment processes in aquaculture tailwater treatment, realizes the establishment of an efficient aerobic granular sludge denitrification system in a single structure, reduces the difficulty of developing efficient and stable treatment processes for antibiotic-containing aquaculture tailwater, reduces construction and maintenance management costs, alleviates difficulties such as land resource scarcity, and improves the feasibility of engineering applications.

[0063] The comparison shows that the effluent from the reactor meets the Class A discharge standard of the "Discharge Standard of Pollutants for Urban Wastewater Treatment Plants".

[0064] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the technical scope of the present invention. Therefore, any minor modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for treating antibiotic-containing aquaculture wastewater using bacterial and algal granular sludge, characterized in that, Includes the following steps: (1) Accommodation stage of bacterial and algal granular sludge: Aerobic granular sludge is inoculated into the reactor, the sludge concentration is controlled, and after the operation is stable, the inoculation solution of Scenedesmus is added. The reactor is then exposed to light from the top light source for 28 days to form bacterial and algal symbiotic sludge. Artificial aquaculture wastewater was added to the reactor, and sludge was discharged daily to control the sludge age to 14 days. (2) Antibiotic-free exposure test stage: Based on the above step (1), mature algae-bacterial symbiotic aerobic granular sludge is placed in the SBR reactor. The reactor is operated in the mode of the above step (1) for 28 days to allow the algae-bacterial symbiotic aerobic granular sludge to adapt to the new reactor and environment. The effluent index is tested every 3 days and the sludge index is tested every week until the nutrient removal rate and sludge index of the reactor remain stable before proceeding to the next stage. (3) Low concentration antibiotic exposure experiment stage: Based on the above step (2), add low concentration antibiotics to the reactor and run the reactor in the mode of the above step (1) for 42 days to allow the aerobic granular sludge of bacterial-algae symbiosis to adapt to the sudden disturbance environment of antibiotics. Detect the effluent index every 3 days and the sludge index every week until the nutrient removal rate and sludge index of the reactor remain stable and then proceed to the next stage. (4) High concentration antibiotic exposure experiment stage: Based on the above step (3), add high concentration antibiotics and run the reactor in the mode of the above step (1) for 42 days to allow the aerobic granular sludge of bacterial-algae symbiosis to adapt to the sudden disturbance environment of antibiotics. Detect the effluent index every 3 days and the sludge index every week until the nutrient removal rate and sludge index of the reactor remain stable and then proceed to the next stage. (5) Antibiotic exposure recovery experiment stage: Based on the above step (4), stop adding antibiotics to test whether the damage of antibiotics to the aerobic granular sludge exposure experiment of bacterial-algae symbiosis can be recovered. The reactor is operated in the mode described in step (1) for 28 days, and the effluent index is tested every 3 days and the sludge index is tested every week until the nutrient removal rate and sludge index of the reactor remain stable. In step (1), the sludge concentration is controlled at 4500 mg / L, the concentration of the added Scenedesmus inoculum is 5000-7000 mg / L, and the ratio is 1:400-1:

600. Before addition, the Scenedesmus needs to be acclimated in the effluent containing 50-100 μg / L of antibiotics for 14 days. During this period, the DO is controlled to be <0.2 mg / L in the anaerobic stage and DO = 8 mg / L in the aerobic stage. The reactor is subjected to a top light source for 24 hours of light cultivation at an intensity of 6000 lm for 28 days to form a symbiotic sludge of bacteria and algae. In steps (2)-(5), the MLSS of the aerobic granular sludge with bacterial-algae symbiosis in the reaction system is 2.8-4.2 g / L, the MLVSS / MLSS ratio is 0.72-0.83, and the mass ratio of C:N:P is 70:10:

1.

2. The method for treating antibiotic-containing aquaculture wastewater using bacterial and algal granular sludge according to claim 1, characterized in that, In step (1), during the entire 28-day operation phase, the reactor operates according to a set cycle every day. The operation process of each cycle includes water inlet, anaerobic, aerobic, settling and drainage. Artificial simulated aquaculture tailwater is added to the reactor, and 1 / 14 of the sludge is discharged daily to control the sludge age to 14 days.

3. The method for treating antibiotic-containing aquaculture wastewater using bacterial and algal granular sludge according to claim 1, characterized in that, The reactor operates daily according to a set cycle in the following mode: one hydraulic retention cycle is 6 hours, and the reactor operates for 4 cycles per day; one cycle includes five stages: 3 min of influent, 90 min of anaerobic reaction, 260 min of aerobic reaction, 4 min of settling, and 3 min of effluent discharge; synthetic wastewater is added for aeration, and the dissolved oxygen range during the aeration stage is controlled at 8 mg / L; the temperature is maintained at 25±1℃ and the pH is maintained at 7.5-8.5 throughout the entire operation.

4. The method for treating antibiotic-containing aquaculture wastewater using bacterial and algal granular sludge according to claim 3, characterized in that, The synthetic wastewater contains nitrogen, phosphorus, carbon, magnesium chloride, ferrous sulfate, CaCl2, and NaHCO3. The nitrogen source is provided by ammonium chloride, the phosphorus source by KH2PO4, and the carbon source by sodium acetate. NaHCO3 is used to buffer the reactor pH. CaCl2, ferrous sulfate, and magnesium chloride are necessary to maintain particle structure and support microbial growth. The initial concentrations of nitrogen, phosphorus, COD, NaHCO3, Mg, Fe, and Ca in the wastewater are 20 mg / L, 2 mg / L, 140 mg / L, 100 mg / L, 2 mg / L, 2 mg / L, and 4 mg / L, respectively. The pH of the wastewater is adjusted to approximately 7.5 using NaHCO3.

5. The method for treating antibiotic-containing aquaculture wastewater using bacterial and algal granular sludge according to claim 1, characterized in that, In step (1), the trace element composition and content of the simulated aquaculture wastewater are: Na2EDTA 4.29 g / L, FeCl2 2· 4H₂O 1.99 g / L, MnCl₂ 2· 2H₂O 0.08 g / L, NiCl 2· 6H₂O 0.02 g / L, CoCl 2· 6H₂O 0.02 g / L, CuCl 2· H2O 0.02 g / L, ZnCl2 0.02 g / L, NaMoO 4· 2H₂O 0.02 g / L, Na₂WO₃ 4· 2H2O 0.03g / L, H3BO3 0.06 g / L.

6. The method for treating antibiotic-containing aquaculture wastewater using bacterial and algal granular sludge according to claim 1, characterized in that, In step (1), the light is provided in a 24-hour continuous light mode, which aims to accelerate the formation and growth of bacterial and algal granular sludge. In steps (2)-(5), the light and dark alternation cycle strategy is adopted, which specifically means that the continuous light time is 12 hours and the continuous dark time is 12 hours per day, that is, the light-dark ratio is 12:12 and the light intensity is 6000 lm. This alternation cycle is used to simulate the day-night cycle in the natural environment.

7. The method for treating antibiotic-containing aquaculture wastewater using bacterial and algal granular sludge according to claim 1, characterized in that, In steps (1)-(5), the reactor is an SBR bioreactor. The aerobic granular sludge with algae symbiosis in the reactor is mainly composed of Scenedesmus and bacteria in the granular sludge. The algae grow on the outside of the granular sludge and wrap around it. The inside of the granular sludge is bacteria. The functional bacteria in the reactor are denitrification and phosphorus removal bacteria. The reactor uses a peristaltic pump to control the inlet and outlet water. Water enters from the bottom and exits from the middle. The exchange volume is 50%. The inlet water system includes an inlet pipe, an inlet tank, and an inlet pump. The outlet water system includes an outlet pipe, an outlet tank, and an outlet pump. The inlet tank and the reactor body are connected by the inlet pipe. The inlet valve and the inlet pump are located on the inlet pipe. The reactor body and the outlet tank are connected by the outlet pipe. The outlet pump is located on the outlet pipe. Both the inlet water system and the outlet water system are equipped with sampling valves and sampling pipes. The reactor body is made of acrylic. The inlet pump and the outlet pump are peristaltic pumps.

8. The method for treating antibiotic-containing aquaculture wastewater using bacterial and algal granular sludge according to claim 1, characterized in that, In steps (3)-(4), the added contaminant is doxycycline hydrochloride. In step (3), a low concentration of 1 mg / L antibiotic is added, and in step (4), a high concentration of 10 mg / L antibiotic is added. In step (3), the concentration of doxycycline hydrochloride added is 1 mg / L, and the reactor is run for 42 days. In step (4), the concentration of doxycycline hydrochloride added is 10 mg / L, and the reactor is run for 42 days. The antibiotic is not limited to doxycycline hydrochloride.

Images