A seawater circulating aquaculture water treatment system with simultaneous nitrogen and phosphorus removal and its start-up operation

Abstract

A seawater circulating aquaculture water treatment system with simultaneous nitrogen and phosphorus removal and its startup and operation relate to the field of aquaculture water treatment. The system consists of an aquaculture pond, a precipitator, a circulation pump, a carbon source filter, a biological filter, an ultrafiltration filter, a backwash water tank, and a backwash pump. The system uses a separate startup method for the autotrophic nitrification system and the simultaneous nitrification and denitrification system, avoiding the accumulation of ammonia nitrogen and nitrite nitrogen during the startup of the simultaneous nitrification and denitrification system. Ultrafiltration is used to rapidly enrich high-concentration nitrifying bacteria, significantly shortening the startup time of the autotrophic nitrification system. The combination of the carbon source filter, biological filter, and ultrafiltration filter fully utilizes the slow-release properties of the solid carbon source for organic carbon, the long-term enrichment and retention of aerobic simultaneous nitrification and denitrification bacteria by the biological filler, and the efficient interception and removal of inorganic and organic particles and pathogenic microorganisms in the water by the ultrafiltration membrane. This allows for rapid startup of the simultaneous nitrification and denitrification system and long-term stable operation, ensuring the safety of the system's water quality.

Description

Technical Field

[0001] The present invention belongs to the technical field of aquaculture water treatment, and in particular relates to a seawater circulating aquaculture water treatment system with simultaneous nitrogen and phosphorus removal and its startup operation. Background Art

[0002] Seawater recirculating aquaculture systems are an environmentally friendly, intensive aquaculture model that efficiently utilizes water resources and produces high aquaculture yields. Due to their advantages of water and land conservation, high-density intensive production, and controlled emissions, they have rapidly developed and been applied both domestically and internationally. A comprehensive water treatment system is crucial to the success of seawater recirculating aquaculture. Through a series of water treatment processes, including sedimentation, flotation, microfiltration, and biological purification, they effectively remove particulate pollutants such as feces and leftover bait, as well as dissolved organic matter, and convert the highly toxic ammonia nitrogen and nitrite nitrogen in the water into less toxic nitrate nitrogen. However, due to the lack of further nitrate and phosphorus removal capabilities, recirculating aquaculture systems often accumulate large amounts of nitrate nitrogen and reactive phosphate. High concentrations of nitrate nitrogen can lead to slow fish growth, reduced survival rates, and decreased immunity. Current aquaculture practices primarily rely on water exchanges to reduce nitrate and phosphate concentrations in the circulating water. This not only results in significant waste of water resources and energy, but the discharge of high-concentration nitrogen and phosphorus wastewater can also easily lead to eutrophication of nearshore waters. Furthermore, under high-density, intensive aquaculture conditions, potentially pathogenic microorganisms (such as Vibrio and neuronecrosis virus) are highly susceptible to fish diseases. Aquaculture companies typically administer antibiotics to control disease outbreaks, which not only increases drug costs but also induces the development of antibiotic-resistant genes, leading to increased antibiotic resistance in pathogenic bacteria and the spread of resistant bacteria. Therefore, there is an urgent need to develop a water treatment system suitable for seawater recirculating aquaculture systems that can simultaneously remove nitrogen and phosphorus while efficiently separating and removing pathogens. Summary of the Invention

[0003] The present invention provides a seawater circulating aquaculture water treatment system with simultaneous denitrification and phosphorus removal and its start-up operation, which can not only efficiently separate and remove particulate pollutants such as feces and leftover bait and pathogenic microorganisms continuously generated in the aquaculture water, but also has the function of simultaneous denitrification and phosphorus removal, and can remove pollutants such as nitrogen, phosphorus and other pollutants continuously generated in the aquaculture water online.

[0004] To achieve the above object, the technical solutions adopted by the present invention are as follows:

[0005] The present invention provides a seawater circulating aquaculture water treatment system with simultaneous denitrification and dephosphorization, which is composed of a culture pond, a precipitator, a circulation pump, a carbon source filter, a biological filter, an ultrafiltration filter, a backwash water tank, and a backwash pump;

[0006] The top of the side wall of the breeding pond is connected to the water inlet pipe, and an overflow pipe of the breeding pond is set 20 cm downward from the top of the side wall of the breeding pond. An aerator is set inside the breeding pond and connected to an aeration pump. The bottom of the breeding pond is connected to the water inlet area of ​​the sedimentation tank through a connecting pipe, and the top of the breeding pond and the sedimentation tank are set at the same elevation;

[0007] The precipitator is used to quickly separate and remove particulate pollutants such as feces and leftover bait that are constantly generated in the aquaculture pond. The interior of the precipitator is sequentially provided with a sludge settling area, a water inlet area, an inclined pipe settling area, and a clear water area from bottom to top. The bottom of the sludge settling area is connected to a sludge discharge pipe, and an electric sludge discharge valve is provided on the sludge discharge pipe of the precipitator. The side wall of the clear water area is connected to the water suction pipe of the circulation pump.

[0008] The breeding pond and the sedimentation tank are further integrated. The bottom of the breeding pond is a conical structure. An isolation device is used on the side of the breeding pond to isolate a part of the space to prepare the clear water area and the inclined tube sedimentation area of ​​the sedimentation tank, so that the upper part of the entire sedimentation tank is an upright spatial structure as the clear water area, and the middle and lower parts of the sedimentation tank correspond to the side of the bottom of the conical structure of the sedimentation tank. The middle and lower parts of the sedimentation tank are an inclined space as the inclined tube sedimentation area. The lower part of the inclined sedimentation area is an upright water inlet area, and the water inlet area is connected to the bottom of the breeding pond by a gap; the lower part of the water inlet area is a conical mud settling area, and the lower part of the mud settling area is a mud discharge pipe with an electric mud discharge valve; the lower part of the above-mentioned isolation device is isolated to the inclined tube sedimentation area.

[0009] The clear water area (24) of the precipitator is connected to the circulation pump water suction pipe (31), the circulation pump (3), and the circulation pump pressure water pipe (32) in sequence. The outlet of the circulation pump pressure water pipe (32) is divided into two branches. One branch is connected to the carbon source filter transcending pipe (45), the carbon source filter transcending electric valve (47), and the biological filter water inlet pipe (53) in sequence. The other branch is connected to the carbon source filter water inlet pipe (42) and the carbon source filter water inlet electric valve (46) corresponding to the carbon source filter (4). The carbon source filter outlet pipe (43) corresponding to the carbon source filter (4) is connected to the biological filter water inlet pipe (53).

[0010] The carbon source filter (4) is a multi-media filter, which uses a carbon source filter run-in valve (40) to automatically control filtration, backwashing and forward washing. The interior is filled with solid carbon source particles (41) with a filling degree of 50%. The water inlet, water outlet and drain outlet of the carbon source filter run-in valve (40) are respectively connected to the carbon source filter water inlet pipe (42), the carbon source filter water outlet pipe (43) and the carbon source filter drain pipe (44);

[0011] The biofilter (5) is a multi-media filter, which uses a biofilter run-in valve (50) to automatically control filtration, backwashing and forward washing. The interior is filled with biological fillers (51) and granular activated carbon (52) from bottom to top, with a filling degree of 60%. The water inlet, water outlet and drain outlet of the biofilter run-in valve (50) are respectively connected to the biofilter inlet pipe (53), the biofilter outlet pipe (54) and the biofilter drain pipe (55); the biofilter outlet pipe (54) is connected to the ultrafiltration filter inlet pipe (61) corresponding to the ultrafiltration filter (6);

[0012] A hollow fiber ultrafiltration membrane assembly (60) is placed inside the ultrafiltration filter (6). The lower part of the ultrafiltration filter (6) is connected to an ultrafiltration filter water inlet pipe (61) and an ultrafiltration filter drain pipe (63), and the upper part is connected to an ultrafiltration filter outlet pipe (62) and an ultrafiltration filter backwash pipe (64). An ultrafiltration filter water inlet valve (65) and a pressure gauge (69) are sequentially arranged on the ultrafiltration filter water inlet pipe (61); the outlet of the ultrafiltration filter outlet pipe (62) is divided into two branches, one of which is connected to the backwash water tank (7) via the ultrafiltration filter outlet valve (66), and the other is connected to the backwash water tank (7) via the ultrafiltration filter backwash valve (68), the ultrafiltration filter backwash pipe (64), the backwash pump outlet pipe (82), the backwash pump (8), and the backwash pump inlet pipe (81); an ultrafiltration filter drain valve (67) is provided on the ultrafiltration filter drain pipe (63).

[0013] The backwash water tank (7) is used to store backwash water for the ultrafiltration filter (6). A backwash water tank overflow pipe (71) is provided on the upper portion of the backwash water tank (7). The outlet of the backwash water tank overflow pipe (71) is placed above the culture pond (1) so that the outflowing water falls into the culture pond (1). The lower portion of the backwash water tank (7) is connected to the backwash pump (8) through the backwash pump inlet pipe (81), and the backwash pump outlet pipe (82) is connected to the ultrafiltration filter backwash pipe (64).

[0014] The biological filler (51) is one or more of ceramsite, ceramic rings or volcanic rocks.

[0015] The solid carbon source particles (41) can be one or more of polyhydroxyalkanoate (PHA), polycaprolactone (PCL), polylactic acid (PLA), polybutylene succinate (PBS), polyβ-hydroxybutyrate (PHB / PHBV), aliphatic polyester (Bionolle) and starch-based blends, with a filling degree of 50%.

[0016] The volume ratio of the biological filler to the granular activated carbon is 2:1-5:1, and the filling degree is 60%.

[0017] The present invention also provides a start-up operation of a seawater circulating aquaculture water treatment system with simultaneous denitrification and phosphorus removal, characterized in that the start-up operation is divided into two stages: an autotrophic nitrification system start-up stage and a simultaneous nitrification and denitrification start-up operation stage, wherein:

[0018] The operation method of the autotrophic nitrification system startup phase is as follows: close the carbon source filter inlet valve (46), open the carbon source filter overrun valve (47), the seawater circulating water aquaculture water treatment system at this stage consists of a breeding pond, a precipitator, a circulation pump, a biological filter, an ultrafiltration filter, a backwash tank and a backwash pump. The fully aerated and oxygenated aquaculture water in the breeding pond passes through the precipitator, the biological filter, the ultrafiltration filter in sequence under the drive of the circulation pump and enters the backwash tank, and finally returns to the breeding pond through the backwash tank overflow pipe. The particulate pollutants such as leftover bait and feces in the aquaculture water are removed by the silt settling device, and the fine inorganic and organic particles and pathogenic microorganisms in the water are completely intercepted and removed under the combined filtration of the biological filter and the ultrafiltration filter. Dissolved organic carbon in the water is removed through physical adsorption by granular activated carbon and the subsequent biodegradation of the formed biochar. In addition, the hollow fiber ultrafiltration membrane assembly, as an attachment carrier for microorganisms, is used in combination with granular activated carbon and biological fillers to enrich high-concentration nitrifying bacteria, significantly shortening the startup time of the autotrophic nitrification system, quickly establishing a mature nitrification system, and achieving efficient removal of ammonia nitrogen and nitrite nitrogen. The startup progress of the autotrophic nitrification system is judged by continuously monitoring ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen in the water outlet of the backwash tank overflow pipe. When the ammonia nitrogen and nitrite nitrogen in the water are both stably below 0.3 mg / L, the autotrophic nitrification system is started and enters the synchronous nitrification and denitrification startup operation stage;

[0019] The operation method of the synchronous nitrification and denitrification startup operation stage is as follows: open the carbon source filter inlet valve (46), close the carbon source filter overflow valve (47), the seawater circulating water aquaculture water treatment system at this stage consists of a breeding pond, a precipitator, a circulation pump, a carbon source filter, a biological filter, an ultrafiltration filter, a backwash water tank and a backwash pump. The aquaculture water in the aquaculture pond passes through the precipitator, the carbon source filter, the biological filter, the ultrafiltration filter in sequence under the drive of the circulation pump and enters the backwash water tank, and finally returns to the aquaculture pond through the backwash water tank overflow pipe. In the synchronous nitrification and denitrification startup operation stage, the particulate pollutants such as leftover bait and feces in the aquaculture water are removed by the silt collector, and the fine inorganic and organic particles and pathogenic microorganisms in the water are removed by the biological filter. The dissolved organic carbon in the water is removed by physical adsorption and biodegradation of granular activated carbon. At the same time, the slow-release characteristics of organic carbon in seawater, a solid carbon source, are used to induce the production of biological flocs to provide a suitable carbon-nitrogen ratio, which promotes the rapid start-up of simultaneous nitrification and denitrification. The start-up process of simultaneous nitrification and denitrification is judged by continuously monitoring the nitrogen and phosphate content in the water outlet of the overflow pipe of the backwash tank. When the total inorganic nitrogen and phosphate content in the water are stably lower than 2.0 mg / L and 0.5 mg / L, it indicates that the start-up of simultaneous nitrification and denitrification is completed and the simultaneous nitrification and denitrification enters the long-term stable operation stage, which can simultaneously remove nitrogen and phosphorus and other pollutants continuously produced in the aquaculture water online.

[0020] Furthermore, the operation of the carbon source filter includes filtration, backwashing and forward washing processes, and the operation method is as follows: the carbon filter run-in valve is adjusted to the filtration state, and the water entering the carbon source filter is filtered from top to bottom through the filter layer. When the filtration time reaches 12 hours, the carbon filter run-in valve is adjusted to the backwash state, and the water entering the carbon source filter is backwashed from top to bottom on the filter layer. The backwash time is 3 to 5 minutes, and then the carbon filter run-in valve is adjusted to the forward washing state. The forward washing time is 1 minute. After the forward washing is completed, the filtration process is entered again.

[0021] Furthermore, the operation of the biofilter includes filtration, backwashing and forward washing processes, and the operation method is as follows: the biofilter conditioning valve is adjusted to the filtration state, and the water entering the biofilter is filtered from top to bottom through the filter layer. When the filtration time reaches 24 hours, the biofilter conditioning valve is adjusted to the backwash state, and the water entering the biofilter is backwashed from top to bottom on the filter layer. The backwash time is 1 to 2 minutes. Then, the biofilter conditioning valve is adjusted to the forward washing state. The forward washing time is 1 minute. After the forward washing is completed, the filtration process is entered again.

[0022] Furthermore, the operation of the ultrafiltration filter includes two processes: filtration and backwashing. The operation method of the filtration process is as follows: close the ultrafiltration filter drain valve and the ultrafiltration filter backwash valve, open the ultrafiltration filter water inlet valve and the ultrafiltration filter outlet valve, and the water from the biological filter enters the hollow fiber ultrafiltration membrane component of the ultrafiltration filter at a rate of 10 to 25 L / (m 2h) Flux filtration: When the filtration time reaches 6h or the pressure before the membrane rises to 0.1MPa, the ultrafiltration system enters the backwash process; the backwash process is operated as follows: close the ultrafiltration filter inlet valve and ultrafiltration filter outlet valve, open the ultrafiltration filter drain valve and ultrafiltration filter backwash valve, and start the backwash pump at the same time to backwash the hollow fiber ultrafiltration membrane assembly. The backwash intensity is 60~80L / (m 2 ·h), backwash time 1 to 2 minutes. After the backwash is completed, close the ultrafiltration filter drain valve and ultrafiltration filter backwash valve, open the ultrafiltration filter inlet valve and ultrafiltration filter outlet valve, and resume filtration.

[0023] The advantages of a seawater circulating aquaculture water treatment system with simultaneous nitrogen and phosphorus removal are:

[0024] 1. The present invention connects the bottom of the aquaculture pond and the water inlet area of ​​the sedimentation tank through a connecting pipe, and the top is set at the same elevation. Only one circulation pump can drive the filtration of the entire synchronous denitrification and phosphorus removal seawater circulating water aquaculture water treatment system, as well as the backwashing and forward washing of the carbon source filter and the biological filter. During operation, it is only necessary to pre-set the operating status of the carbon source filter run-in valve and the biological filter run-in valve to realize the automatic operation of filtration-backwash-forward washing-filtration of the carbon source filter and the biological filter.

[0025] 2. The present invention starts autotrophic nitrification and simultaneous nitrification and denitrification separately, avoiding the local nitrite accumulation during the startup of simultaneous nitrification and denitrification, as well as the accumulation of ammonia nitrogen and nitrite nitrogen caused by the process of nitrate reduction to ammonia, thereby ensuring the water quality safety of the seawater circulating aquaculture water treatment system in the initial startup.

[0026] 3. During the startup phase of the autotrophic nitrification system, the combination of a biofilter and an ultrafiltration filter can not only rapidly enrich high-concentration nitrifying bacteria using the ultrafiltration membrane, significantly shortening the startup time of the nitrification system, but also promptly and efficiently convert the highly toxic ammonia nitrogen and nitrite continuously produced in the fish farming water into less toxic nitrates. Furthermore, the system can efficiently intercept and remove inorganic and organic particles, algae, and pathogenic microorganisms in the water, thereby improving the clarity of the aquaculture water and ensuring its biological safety.

[0027] 4. During the startup phase of simultaneous nitrification and denitrification, the carbon source filter, biological filter and ultrafiltration filter are combined to give full play to the advantages of the solid carbon source's slow-release properties of organic carbon, the biological filler's long-term enrichment and retention of aerobic simultaneous nitrification and denitrification bacteria, and the ultrafiltration membrane's high-efficiency interception and removal of inorganic and organic particles and pathogenic microorganisms in the water. This allows for online and simultaneous removal of nitrogen, phosphorus and pathogenic microorganisms from the circulating aquaculture water, overcoming the defects of large-scale accumulation of nitrate nitrogen and active phosphate and long-term enrichment of potential pathogenic microorganisms in conventional recirculating aquaculture systems. This ensures the water quality safety of the seawater recirculating aquaculture system and achieves efficient recycling of aquaculture water. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the structure of a seawater circulating aquaculture water treatment system with simultaneous nitrogen and phosphorus removal;

[0029] Figure 2 This is the startup and operation parameter diagram of the autotrophic nitrification system of the seawater circulating aquaculture water treatment system;

[0030] Figure 3 This is the startup and operation parameter diagram of the simultaneous nitrification and denitrification of the seawater circulating aquaculture water treatment system.

[0031] Reference numerals:

[0032] 1. Breeding pond; 10. Connecting pipe; 11. Water inlet pipe; 12. Breeding pond overflow pipe; 13. Aeration stone; 14. Aeration pump; 2. Sedimentation tank; 21. Mud settling area; 22. Water inlet area; 23. Inclined tube sedimentation area; 24. Clear water area; 25. Mud discharge pipe; 26. Electric mud discharge valve; 3. Circulating pump; 31. Circulating pump suction pipe; 32. Circulating pump pressure pipe; 4. Carbon source filter; 40. Carbon filter lubrication valve; 41. Solid carbon source particles; 42. Carbon source filter inlet pipe; 43. Carbon source filter outlet pipe; 44. Carbon source filter drain pipe; 46. Carbon source filter inlet valve; 47. Carbon source filter override valve; 5. Biofilter; 50. Biofilter lubrication valve; 51. Biological filler; 52. Granular activated carbon; 53. Biofilter inlet pipe; 54. Biofilter outlet pipe; 55. Biofilter drain pipe; 6. Ultrafiltration filter; 60. Hollow fiber ultrafiltration membrane assembly; 61. Ultrafiltration filter inlet pipe; 62. Ultrafiltration filter outlet pipe; 63. Ultrafiltration filter drain pipe; 64. Ultrafiltration filter backwash pipe; 65. Ultrafiltration filter inlet valve; 66. Ultrafiltration filter outlet valve; 67. Ultrafiltration filter drain valve; 68. Ultrafiltration filter backwash valve; 69. Pressure gauge; 7. Backwash water tank; 71. Backwash water tank overflow pipe; 8. Backwash pump; 81. Backwash pump inlet pipe; 82. Backwash pump outlet pipe. DETAILED DESCRIPTION

[0033] The present invention will be described in detail below with reference to the accompanying drawings.

[0034] In order to more clearly illustrate the purpose, technical solutions and advantages of the present invention, the present invention is described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0035] Example 1

[0036] like Figure 1As shown, the seawater circulating aquaculture water treatment system for simultaneous denitrification and phosphorus removal of the present invention comprises a culture pond 1, a precipitator 2, a circulation pump 3, a carbon source filter 4, a biological filter 5, an ultrafiltration filter 6, a backwash water tank 7, and a backwash pump 8, wherein:

[0037] The top of the side wall of the culture pond 1 is connected to the water inlet pipe 11, and a culture pond overflow pipe 12 is set 20 cm away from the top of the side wall of the culture pond 1. An aerator 13 is set inside the culture pond 1 and connected to an aeration pump 14 to provide a dissolved oxygen concentration in the culture pond of ≥6 mg / L. The bottom of the culture pond 1 is connected to the water inlet area 22 of the sedimentation tank 2 through a connecting pipe 10. The top of the culture pond 1 and the sedimentation tank 2 are set at the same elevation;

[0038] The interior of the precipitator 2 is sequentially provided with a sedimentation area 21, a water inlet area 22, an inclined tube sedimentation area 23 and a clear water area 24 from bottom to top. The bottom of the sedimentation area 21 is connected to a mud discharge pipe 25, and an electric mud discharge valve 26 is provided on the sedimentation pipe 25. The side wall of the clear water area 24 is connected to the circulation pump suction pipe 31.

[0039] The circulating pump pressure water pipe 32 of the circulating pump 3 is connected to the carbon source filter water inlet pipe 42 and the carbon source filter transcending pipe 45 at the same time;

[0040] The carbon source filter 4 is a multi-media filter, which uses a carbon source filter run-in valve 40 to automatically control filtration, backwashing and forward washing. It is filled with polyhydroxyalkanoate (PHA) as solid carbon source particles 41 with a filling degree of 50%. The water inlet, water outlet and drain of the carbon source filter run-in valve 40 are respectively connected to the carbon source filter inlet pipe 42, the carbon source filter outlet pipe 43 and the carbon source filter drain pipe 44. The carbon source filter inlet pipe 42 and the carbon source filter transcending pipe 45 are respectively provided with a carbon source filter inlet electric valve 46 and a carbon source filter transcending electric valve 47. The carbon source filter outlet pipe 43 is simultaneously connected to the carbon source filter transcending pipe 45 and the biological filter inlet pipe 53;

[0041] The biofilter 5 is a multi-media filter that uses a biofilter run-in valve 50 to automatically control filtration, backwashing, and forward washing. The interior is filled with biological filler 51 (ceramsite) and granular activated carbon 52 in order from bottom to top, with a volume ratio of 3:1 and a filling degree of 60%. The water inlet, water outlet, and drain outlet of the biofilter run-in valve 50 are respectively connected to the biofilter inlet pipe 53, the biofilter outlet pipe 54, and the biofilter drain pipe 55. The biofilter outlet pipe 54 is connected to the ultrafiltration filter inlet pipe 61.

[0042] A hollow fiber ultrafiltration membrane assembly 60 is placed inside the ultrafiltration filter 6. The lower part of the ultrafiltration filter 6 is connected to the ultrafiltration filter inlet pipe 61 and the ultrafiltration filter drain pipe 63, and the upper part is connected to the ultrafiltration filter outlet pipe 62 and the ultrafiltration filter backwash pipe 64. An ultrafiltration filter inlet valve 65 and a pressure gauge 69 are sequentially provided on the ultrafiltration filter inlet pipe 61. An ultrafiltration filter outlet valve 66, an ultrafiltration filter drain valve 67 and an ultrafiltration filter backwash valve 68 are respectively provided on the ultrafiltration filter outlet pipe 62, the ultrafiltration filter drain pipe 63 and the ultrafiltration filter backwash pipe 64. The water outlet of the ultrafiltration filter outlet pipe 62 is connected to the top of the backwash water tank 7;

[0043] The backwash water tank 7 is used to store backwash water for the ultrafiltration filter 6. A backwash water tank overflow pipe 71 is provided on the upper part of the backwash water tank 7. The outlet of the backwash water tank overflow pipe 71 is placed above the breeding pond 1 so that the outflowing water falls into the breeding pond 1. The lower part of the backwash water tank 7 is connected to the backwash pump 8 through the backwash pump inlet pipe 81, and the backwash pump outlet pipe 82 is connected to the ultrafiltration filter backwash pipe 64.

[0044] The startup and operation of the seawater circulating aquaculture water treatment system with simultaneous denitrification and phosphorus removal of the present invention is divided into two stages: the autotrophic nitrification system startup stage and the simultaneous nitrification and denitrification startup and operation stage, wherein:

[0045] The operation method of the autotrophic nitrification system startup stage is as follows: close the carbon source filter inlet valve 46, open the carbon source filter override valve 47, and the seawater circulating water aquaculture water treatment system at this stage consists of a culture pond 1, a precipitator 2, a circulation pump 3, a biological filter 5, an ultrafiltration filter 6, a backwash tank 7 and a backwash pump 8. The aquaculture water in the culture pond 1 is driven by the circulation pump 3 and passes through the precipitator 2, the biological filter 5, the ultrafiltration filter 6 in sequence to enter the backwash tank 7, and finally returns to the culture pond 1 through the backwash tank overflow pipe 71. Particulate pollutants such as leftover bait and feces in the aquaculture water are removed by the silt collector 2, and fine inorganic and organic particles and pathogenic microorganisms in the water are filtered by the combination of the biological filter 5 and the ultrafiltration filter 6. The dissolved organic carbon in the water is completely intercepted and removed, and the dissolved organic carbon in the water is removed by physical adsorption of granular activated carbon and the biodegradation of the biochar formed thereafter. In addition, the hollow fiber ultrafiltration membrane assembly 60 is used as an attachment carrier for microorganisms in combination with the granular activated carbon 51 and the biological filler 52 to enrich high-concentration nitrifying bacteria, significantly shortening the startup time of the autotrophic nitrification system, quickly establishing a mature nitrification system, and achieving efficient removal of ammonia nitrogen and nitrite nitrogen. By continuously monitoring the ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in the water effluent from the backwash tank overflow pipe 71, the startup progress of the autotrophic nitrification system is judged. When the system is running for 20 days, the ammonia nitrogen and nitrite nitrogen in the water are both stable below 0.3 mg / L (see Appendix Figure 2 ), indicating that the autotrophic nitrification system has been started and entered the synchronous nitrification and denitrification start-up operation stage;

[0046] The operation method of the synchronous nitrification and denitrification startup operation stage is as follows: open the carbon source filter inlet valve 46, close the carbon source filter override valve 47, and the seawater circulating water aquaculture water treatment system at this stage consists of aquaculture pond 1, precipitator 2, circulation pump 3, carbon source filter 4, biological filter 5, ultrafiltration filter 6, backwash water tank 7 and backwash pump 8. The aquaculture water in the aquaculture pond 1 is driven by the circulation pump 3 and passes through the precipitator 2, carbon source filter 4, biological filter 5, ultrafiltration filter 6 in sequence to enter the backwash water tank 7, and finally returns to the aquaculture pond 1 through the backwash water tank overflow pipe 71. During the synchronous nitrification and denitrification startup operation stage, the residual bait, Particulate pollutants such as feces are removed by the sedimentation device 2, and fine inorganic and organic particles and pathogenic microorganisms in the water are completely intercepted and removed by the combined filtration of the biological filter 5 and the ultrafiltration filter 6. The dissolved organic carbon in the water is removed by physical adsorption and biodegradation of the granular activated carbon. At the same time, the slow-release characteristics of organic carbon in the seawater of the solid carbon source 41 are used to induce the production of biological flocs, providing a suitable carbon-nitrogen ratio and promoting the rapid start-up of simultaneous nitrification and denitrification. When the system is running for 5 days, the phosphate content in the water is stable below 0.3 mg / L, and when the system is running for 12 days, the total inorganic nitrogen in the water is stable below 2.0 mg / L (see attached). Figure 3 ), and remain stable in the subsequent long-term operation, marking the completion of the startup of synchronous nitrification and denitrification, and entering the long-term operation stage of synchronous nitrification and denitrification, which can simultaneously remove pollutants such as nitrogen, phosphorus and other pollutants continuously produced in the aquaculture water online.

[0047] In actual operation, the operation of the carbon source filter 4 includes filtration, backwashing and forward washing processes, and the operation method is as follows: adjust the carbon filter run-in valve 40 to the filtering state, and the water entering the carbon source filter 4 is filtered from top to bottom through the filter layer. When the filtration time reaches 12 hours, adjust the carbon filter run-in valve 40 to the backwash state, and the water entering the carbon source filter 4 is backwashed from top to bottom on the filter layer. The backwash time is 5 minutes, and then adjust the carbon filter run-in valve 40 to the forward washing state. The forward washing time is 1 minute. After the forward washing is completed, enter the filtration process again;

[0048] In actual operation, the operation of the biofilter 5 includes filtration, backwashing and forward washing processes, and the operation method is as follows: the biofilter conditioning valve 50 is adjusted to the filtration state, and the water entering the biofilter 5 is filtered from top to bottom through the filter layer. When the filtration time reaches 24 hours, the biofilter conditioning valve 50 is adjusted to the backwash state, and the water entering the biofilter 5 is backwashed from top to bottom on the filter layer. The backwash time is 2 minutes. Then the biofilter conditioning valve 50 is adjusted to the forward washing state. The forward washing time is 1 minute. After the forward washing is completed, the filtration process is entered again.

[0049] In actual operation, the operation of the ultrafiltration filter 6 includes two processes: filtration and backwashing. The operation method of the filtration process is as follows: close the ultrafiltration filter drain valve 67 and the ultrafiltration filter backwash valve 68, open the ultrafiltration filter water inlet valve 65 and the ultrafiltration filter outlet valve 66, and the water from the biological filter 5 enters the hollow fiber ultrafiltration membrane assembly 60 of the ultrafiltration filter 6 at a rate of 20L / (m 2 h) flux filtration. When the filtration time reaches 6 h or the pressure before the membrane rises to 0.1 MPa, the ultrafiltration system enters the backwash process. The backwash process is operated as follows: close the ultrafiltration filter inlet valve 65 and the ultrafiltration filter outlet valve 66, open the ultrafiltration filter drain valve 67 and the ultrafiltration filter backwash valve 68, and start the backwash pump 8 at the same time to backwash the hollow fiber ultrafiltration membrane assembly 60. The backwash intensity is 60 L / (m 2 ·h), backwash time 2min, after the backwash is completed, close the ultrafiltration filter drain valve 67 and the ultrafiltration filter backwash valve 68, open the ultrafiltration filter water inlet valve 65 and the ultrafiltration filter outlet valve 66, and resume filtration.

Claims

1. A seawater circulating aquaculture water treatment system with simultaneous denitrification and phosphorus removal, characterized in that: It consists of a breeding pond, a sedimentation tank, a circulation pump, a carbon source filter, a biological filter, an ultrafiltration filter, a backwash water tank, and a backwash pump; The top of the side wall of the breeding pond is connected to the water inlet pipe, and an overflow pipe of the breeding pond is set 20 cm downward from the top of the side wall of the breeding pond. An aerator is set inside the breeding pond and connected to an aeration pump. The bottom of the breeding pond is connected to the water inlet area of ​​the sedimentation tank through a connecting pipe, and the top of the breeding pond and the sedimentation tank are set at the same elevation; The precipitator is used to quickly separate and remove feces and leftover bait continuously produced in the aquaculture pond. The interior of the precipitator is sequentially provided with a mud settling area, a water inlet area, an inclined pipe sedimentation area and a clear water area from bottom to top. The bottom of the mud settling area is connected to a mud discharge pipe, and an electric mud discharge valve is provided on the mud discharge pipe of the precipitator. The side wall of the clear water area is connected to the water suction pipe of the circulation pump. The clear water area of ​​the precipitator is connected to the circulation pump suction pipe, the circulation pump, and the circulation pump pressure pipe in sequence. The circulation pump pressure pipe outlet is divided into two branches. One branch is connected to the carbon source filter transcending pipe, the carbon source filter transcending electric valve, and the biological filter inlet pipe in sequence. The other branch is connected to the carbon source filter inlet pipe and the carbon source filter inlet electric valve corresponding to the carbon source filter in sequence. The carbon source filter outlet pipe corresponding to the carbon source filter is connected to the biological filter inlet pipe. The carbon source filter is a multi-media filter, which uses a carbon source filter run-in valve to automatically control filtration, backwashing and forward washing. The interior is filled with solid carbon source particles with a filling degree of 50%. The water inlet, water outlet and drain outlet of the carbon source filter run-in valve are respectively connected to the carbon source filter water inlet pipe, carbon source filter water outlet pipe and carbon source filter drain pipe; The biofilter is a multi-media filter that uses a biofilter run-in valve to automatically control filtration, backwashing, and forward washing. The interior is filled with biological fillers and granular activated carbon in sequence from bottom to top, with a filling degree of 60%. The water inlet, water outlet, and drain outlet of the biofilter run-in valve are connected to the biofilter inlet pipe, biofilter outlet pipe, and biofilter drain pipe, respectively; the biofilter outlet pipe is connected to the ultrafiltration filter inlet pipe corresponding to the ultrafiltration filter; A hollow fiber ultrafiltration membrane assembly is placed inside the ultrafiltration filter, the lower part of the ultrafiltration filter is connected to the ultrafiltration filter inlet pipe and the ultrafiltration filter drain pipe respectively, and the upper part is connected to the ultrafiltration filter outlet pipe and the ultrafiltration filter backwash pipe, and an ultrafiltration filter inlet valve and a pressure gauge are sequentially arranged on the ultrafiltration filter inlet pipe; the water outlet of the ultrafiltration filter outlet pipe is divided into two branches, one of which is connected to the backwash water tank via the ultrafiltration filter outlet valve, and the other is connected to the backwash water tank via the ultrafiltration filter backwash valve, the ultrafiltration filter backwash pipe, the backwash pump outlet pipe, the backwash pump, and the backwash pump inlet pipe in sequence; the ultrafiltration filter drain pipe is provided with an ultrafiltration filter drain valve; The backwash water tank is used to store backwash water for the ultrafiltration filter. An overflow pipe is provided on the upper portion of the backwash water tank. The outlet of the overflow pipe is placed above the aquaculture pond so that the outflowing water falls into the aquaculture pond. The lower portion of the backwash water tank is connected to the backwash pump through the backwash pump inlet pipe, and the backwash pump outlet pipe is connected to the backwash pipe of the ultrafiltration filter. The breeding pond and the sedimentation tank are integrated. The bottom of the breeding pond is a conical structure. An isolation device is used on the side of the breeding pond to isolate a part of the space to prepare the clear water area and the inclined tube sedimentation area of ​​the sedimentation tank, so that the upper part of the entire sedimentation tank is an upright spatial structure as the clear water area. The middle and lower parts of the sedimentation tank correspond to the side of the bottom of the conical structure of the sedimentation tank. The middle and lower parts of the sedimentation tank are an inclined space as the inclined tube sedimentation area. The lower part of the inclined sedimentation area is an upright water inlet area, and the water inlet area is connected to the bottom of the breeding pond by a gap; the lower part of the water inlet area is a conical mud settling area, and the lower part of the mud settling area is a mud discharge pipe with an electric mud discharge valve; the lower part of the above-mentioned isolation device is isolated to the inclined tube sedimentation area.

2. A seawater circulating aquaculture water treatment system for simultaneous denitrification and phosphorus removal according to claim 1, characterized in that: The solid carbon source particles are polyhydroxyalkanoate (PHA).

3. A seawater circulating aquaculture water treatment system for simultaneous denitrification and phosphorus removal according to claim 1, characterized in that: The biological filler is one or more of ceramsite, ceramic ring or volcanic rock.

4. A seawater circulating aquaculture water treatment system for simultaneous nitrogen and phosphorus removal according to claim 1, characterized in that: The volume ratio of the biological filler to the granular activated carbon is 2:1 to 5:

1.

5. The method for starting and operating a seawater circulating aquaculture water treatment system with simultaneous nitrogen and phosphorus removal according to any one of claims 1 to 4, characterized in that: The startup operation is divided into two stages: the autotrophic nitrification system startup stage and the synchronous nitrification and denitrification startup operation stage, in which: The operation method of the autotrophic nitrification system startup stage is as follows: close the carbon source filter water inlet electric valve, open the carbon source filter overrun electric valve, this stage of the seawater circulating water aquaculture water treatment system consists of aquaculture pond, sedimentation tank, circulation pump, biological filter, ultrafiltration filter, backwash water tank and backwash pump. The fully aerated and oxygenated aquaculture water in the aquaculture pond is driven by the circulation pump and passes through the sedimentation tank, biological filter, ultrafiltration filter into the backwash water tank in sequence, and finally returns to the aquaculture pond through the backwash water tank overflow pipe. The residual bait and feces in the aquaculture water are removed by the sludge collector, and the fine inorganic and organic particles and pathogenic microorganisms in the water are removed by the biological filter and ultrafiltration filter. The organic carbon in the water is completely intercepted and removed by the combined filtration of the filters, and the dissolved organic carbon in the water is removed by physical adsorption and biodegradation of granular activated carbon. In addition, the hollow fiber ultrafiltration membrane module, as an attachment carrier for microorganisms, is used in combination with granular activated carbon and biological fillers to enrich high-concentration nitrifying bacteria, significantly shortening the startup time of the autotrophic nitrification system, quickly establishing a mature nitrification system, and achieving efficient removal of ammonia nitrogen and nitrite nitrogen. The startup progress of the autotrophic nitrification system is judged by continuously monitoring ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in the water outlet of the backwash tank overflow pipe. When the ammonia nitrogen and nitrite nitrogen in the water are both stably lower than 0.3 mg / L, the startup of the autotrophic nitrification system is completed and the synchronous nitrification and denitrification startup operation stage is entered; The operation method of the synchronous nitrification and denitrification startup operation stage is as follows: open the carbon source filter water inlet electric valve, close the carbon source filter overrun electric valve, this stage of the seawater circulating water aquaculture water treatment system consists of aquaculture pond, sedimentation tank, circulation pump, carbon source filter, biological filter, ultrafiltration filter, backwash water tank and backwash pump. Driven by the circulation pump, the aquaculture water in the aquaculture pond passes through the sedimentation tank, carbon source filter, biological filter, ultrafiltration filter in sequence and enters the backwash water tank, and finally returns to the aquaculture pond through the backwash water tank overflow pipe. During the synchronous nitrification and denitrification startup operation stage, the residual bait and feces in the aquaculture water are removed. Through the removal of silt traps, tiny inorganic and organic particles and pathogenic microorganisms in the water are completely intercepted and removed by the combined filtration of biological filters and ultrafiltration filters. The dissolved organic carbon in the water is removed by physical adsorption and biodegradation of granular activated carbon. At the same time, the property of solid carbon sources to slowly release organic carbon in seawater is used to provide a suitable carbon-nitrogen ratio for the production of biological flocs, promoting the rapid start-up of simultaneous nitrification and denitrification. By continuously monitoring the nitrogen, nitrogen and phosphate in the water outlet of the backwash tank overflow pipe, the start-up progress of simultaneous nitrification and denitrification is judged. When the total inorganic nitrogen and phosphate in the water are stably lower than 2.0 mg / L and 0.5 mg / L, it indicates that the start-up of simultaneous nitrification and denitrification is completed and enters the long-term stable operation stage of simultaneous nitrification and denitrification, which can simultaneously remove nitrogen, nitrogen and phosphorus pollutants continuously produced in aquaculture water online.

6. The method according to claim 5, characterized in that The operation of the carbon source filter includes filtration, backwashing and forward washing processes. The operation method is as follows: adjust the carbon filter lubrication valve to the filtration state, and the water entering the carbon source filter is filtered from top to bottom through the filter layer. When the filtration time reaches 12 hours, adjust the carbon filter lubrication valve to the backwash state, and the water entering the carbon source filter is backwashed from top to bottom on the filter layer. The backwash time is 3 to 5 minutes, and then adjust the carbon filter lubrication valve to the forward washing state. The forward washing time is 1 minute. After the forward washing is completed, enter the filtration process again.

7. The method according to claim 5, characterized in that The operation of the biofilter includes filtration, backwashing and forward washing processes, and the operation method is as follows: adjust the biofilter lubrication valve to the filtration state, and the water entering the biofilter is filtered from top to bottom through the filter layer. When the filtration time reaches 24 hours, adjust the biofilter lubrication valve to the backwash state, and the water entering the biofilter backwashes the filter layer from top to bottom. The backwash time is 1 to 2 minutes, and then adjust the biofilter lubrication valve to the forward washing state. The forward washing time is 1 minute. After the forward washing is completed, the filtration process begins again.

8. The method according to claim 5, characterized in that The operation of the ultrafiltration filter includes two processes: filtration and backwashing. The operation method of the filtration process is as follows: close the ultrafiltration filter drain valve and the ultrafiltration filter backwash valve, open the ultrafiltration filter water inlet valve and the ultrafiltration filter outlet valve, and the water effluent from the biological filter enters the hollow fiber ultrafiltration membrane component of the ultrafiltration filter at a rate of 10~25L / (m 2 h) flux filtration. When the filtration time reaches 6 h or the pressure before the membrane rises to 0.1 MPa, the ultrafiltration system enters the backwash process. The backwash process is operated as follows: close the ultrafiltration filter inlet valve and ultrafiltration filter outlet valve, open the ultrafiltration filter drain valve and ultrafiltration filter backwash valve, and start the backwash pump at the same time to backwash the hollow fiber ultrafiltration membrane assembly. The backwash intensity is 60~80 L / (m 2 ·h), backwash time 1 ~ 2 min. After the backwash is completed, close the ultrafiltration filter drain valve and ultrafiltration filter backwash valve, open the ultrafiltration filter inlet valve and ultrafiltration filter outlet valve, and resume filtration.

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